- Email: [email protected]
Serum leptin and adiponectin levels in children with type 1 diabetes mellitus – Relation to body fat mass and disease course
Advances in Medical Sciences 61 (2016) 117–122
Contents lists available at ScienceDirect
Advances in Medical Sciences journal homepage: www.elsevier.com/locate/advms
Original Research Article
Serum leptin and adiponectin levels in children with type 1 diabetes mellitus – Relation to body fat mass and disease course Katarzyna Anna Majewska a,b,*, Dominik Majewski c, Bogda Skowron´ska b, Witold Stankiewicz b, Piotr Fichna b a b c
Department of Clinical Auxology and Pediatric Nursing, Poznan University of Medical Sciences, Poznan, Poland Department of Pediatric Diabetes and Obesity, Poznan University of Medical Sciences, Poznan, Poland Department of Rheumatology and Internal Medicine, Poznan University of Medical Sciences, Poznan, Poland
A R T I C L E I N F O
A B S T R A C T
Article history: Received 26 March 2015 Accepted 22 October 2015 Available online 3 November 2015
Purpose: Leptin and adiponectin are adipokines presenting a wide range of impacts, including glycemic balance regulations. Insulin is one of the main regulators of adipose tissue function. In type 1 diabetes mellitus (T1DM) endogenous insulin secretion is replaced by the exogenous supply, which is not regulated naturally. The aim of the study was to establish serum leptin and adiponectin levels, and their relations to body fat mass and disease course in children with T1DM. Material/methods: The study included 75 children with T1DM and the control group of 20 healthy coevals. All children had estimated serum leptin and adiponectin concentrations, lipid profile, and bioelectrical impedance analysis. Results: Serum leptin concentrations in children with T1DM were not significantly different from the control group (p = 0.067, mean values SD: 3.11 2.98 vs. 5.29 5.06 mg/l, respectively), and related positively to body fat mass in both groups. Adiponectin serum concentrations were significantly higher in children with T1DM than in the control group (p < 0.001; mean values: 18.82 9.31 vs. 12.10 5.53 mg/ml, respectively), and were not related to the body fat content in the study group. Both, leptin and adiponectin, showed no relation to any of the analyzed parameters of the disease course. Conclusions: Differences observed between children with T1DM and their healthy coevals, when similar in terms of age, body weight, and body fat mass, seem not to depend directly on the disease duration, its metabolic control or insulin supply. ß 2015 Medical University of Bialystok. Published by Elsevier Sp. z o.o. All rights reserved.
Keywords: Leptin Adiponectin Type 1 diabetes Adipose tissue Children
1. Introduction Leptin and adiponectin are among the best known adipokines, both presenting a wide range of impacts. Leptin is involved in various biological processes, including the regulation of appetite, energy expenditure, or certain neuroendocrine functions. Its impact on glucose homeostasis is generally anti-hyperglycemic, increasing insulin sensitivity of liver and muscle cells. Serum leptin concentrations closely correlate with the body fat mass – increase with increasing fat mass, and decrease with its loss during the calorierestricted diet [1–5]. Adiponectin exerts, inter alia, the antiinflammatory, antithrombotic and antiatherosclerotic effect. It is
* Corresponding author at: Department of Clinical Auxology and Pediatric Nursing, Poznan University of Medical Sciences, ul. Szpitalna 27/33, 60-572 Poznan, Poland. Tel.: +48 61 8491 265; fax: +48 61 8491 265. E-mail address: [email protected] (K.A. Majewska).
also involved in the stimulation of fatty acid oxidation and gluconeogenesis inhibition. Its higher concentrations are associated with increased insulin sensitivity and improved glucose tolerance. In contrast to leptin, the adiponectin secretion decreases in obesity, along with the growing fat mass, and increases along with its loss [1–3,6,7]. Insulin is one of the main factors regulating the adipose tissue function. It exerts an inhibitory effect on lipolysis, while stimulating on lipogenesis, and regulating on glucose transport into adipocytes in the postprandial period. Insulin stimulates adipogenesis. It is an important regulator of leptin secretion, as well as one of the factors stimulating adiponectin secretion [2,4,6,8]. The interaction between insulin and adipose tissue is not unidirectional. There are reports indicating that leptin is involved in the regulation of insulin secretion, and that between the adipose tissue and pancreatic islands, there is a feedback loop – two-way adipo-insular axis [1,4,5,9].
http://dx.doi.org/10.1016/j.advms.2015.10.002 1896-1126/ß 2015 Medical University of Bialystok. Published by Elsevier Sp. z o.o. All rights reserved.
K.A. Majewska et al. / Advances in Medical Sciences 61 (2016) 117–122
In type 1 diabetes mellitus (T1DM) endogenous insulin secretion is replaced by the exogenous supply, which is not regulated naturally. The question arises, how it affects the regulation of adipose tissue secretory function. As altered adipokines production may influence glucose homeostasis, it could also influence the risk of complications in diabetic children and adolescents [10,11]. The aim of the study was to establish serum leptin and adiponectin levels, and their relations to body fat mass and disease course in children with T1DM. 2. Material and methods The study was conducted in Poznan University of Medical Sciences. It was based on a group of 75 children (30 boys and 45 girls) with T1DM, recruited among the patients admitted to the Karol Jonscher Teaching Hospital for a routine medical check-up, with disease duration of at least 1 year, and no acute nor chronic complications of diabetes or additional diseases. They were treated with insulin by various methods: 35 with flexible intensive insulin therapy with multiple daily injections, 21 with continuous subcutaneous insulin infusion, and 19 with the conventional method with 2–3 daily injections of premixed insulin in fixed doses. Included patients had various levels of glycated haemoglobin (HbA1c). The control group involved 20 healthy, normal weight children (10 boys and 10 girls), who were admitted to the hospital for diagnostic reasons, but with no disease found. Detailed characteristics of the groups have been described previously [12]. Patients from both groups had following investigations, all at basic conditions – in the morning, fasting: - blood samples taken to establish leptin and adiponectin serum concentrations, as well as the levels of triglycerides, total cholesterol, and free fatty acids; - body weight and growth established accurate to 0.1 kg and 0.1 cm, respectively; - bioelectrical impedance analysis (BIA), as a method of evaluating body composition (tetrapolar system, Akern analyzer BIA-101, Bioresearch) [13]. Leptin serum concentrations were performed by immunoradiometric assay (Human Leptin IRMA DSL). Adiponectin serum concentrations were performed by radioimmunoassay (Human Adiponectin RIA Kit, Linco Research). In the statistical analysis Kolmogorov–Smirnov test was used in evaluating the compatibility of the variables with the normal distribution. Non-parametric methods: Mann–Whitney test and the Spearman correlation r were used for the variables not compatible with the normal distribution. Parametric methods: Levene’s test of homoscedasticity, t-test and Pearson correlations were used for normally distributed variables. The study protocol was approved by the local Ethics Committee at the Karol Marcinkowski University of Medical Sciences in Poznan´ (No. 187/05). Legal guardians of all participants gave informed consent. 3. Results The study and the control group did not differ statistically in terms of age (p = 0.944, mean values standard deviation (SD): 12.47 3.51 vs. 12.55 2.68 years, respectively), body weight (p = 0.597, mean values SD: 47.72 15.18 vs. 45.81 10.29 kg, respectively), and fat mass content – the total body fat mass (p = 0.445, mean values SD: 11.59 5.85 vs. 10.54 3.69 kg,
respectively), and the percentage value of the body fat mass (p = 0.601, mean values SD: 24.46 7.96 vs. 23.43 7.10%, respectively). In children with T1DM mean disease duration was 4.95 3.2 years (SD) [12]. 3.1. Leptin concentrations Statistical analysis showed no significant difference in serum leptin concentrations between the study and the control group (p = 0.067, mean values SD): 3.11 2.98 mg/l vs. 5.29 5.06 mg/l; median values: 1.80 vs. 4.25 mg/l, respectively) (Figs. 1–3). In both groups leptin levels demonstrated a strong, positive correlation with the total body fat mass (FM) and the percentage value of the body fat mass – as compared to the total body weight (FM%), resulting in the increasing leptin concentrations along with increase of both: the absolute and the percentage value of body fat mass. Leptinaemia showed a strong positive correlation with body weight in children with diabetes. This dependence was not observed in the control group. In both, diabetic and healthy children, a significant relation of leptin levels and gender (p < 0.001 and p = 0.026, respectively) was present. Higher values were found in girls. Leptin concentrations observed in the study group showed a positive correlation with age. This dependence was not observed in the control group. Duration of diabetes, or its metabolic control rated as glycated haemoglobin (HbA1c), did not show a significant correlation with leptinaemia. Analysis of serum leptin concentrations in relation to the applied insulin dose (Ins/day, Ins/kg) revealed no correlation. Children treated with insulin according to various methods did not differ significantly in terms of leptin levels. Evaluated serum lipid parameters, revealed no significant difference between the groups (Table 1) and there was no correlation of serum leptin with total cholesterol, triglycerides, and free fatty acids levels in both groups. Correlations of leptin concentrations with clinical data are presented in Table 2. 3.2. Adiponectin concentrations Adiponectin serum concentrations presented significant differences between the groups, and were significantly higher in diabetic children than in the control group (p < 0.001; mean values: 18.82 9.31 mg/ml vs. 12.10 5.53 mg/ml; median values: 16.89 vs. 12.26 mg/ml, respectively) (Figs. 4–6).
12
Leptin serum concentrations [mcg/L]
118
10 8 6 4 2 0 Type 1 diabetes
Control group
Fig. 1. Leptin serum concentrations (mcg/l) in children with type 1 diabetes and the control group: mean values SD.
K.A. Majewska et al. / Advances in Medical Sciences 61 (2016) 117–122
119
25
Number of children
20
15
10
5
0 0-1
1-2
2-3
3-4
4-5
5-6
6-7
7-8
8-9
above 9 mcg/L
Lepn serum concentraons Fig. 2. Histogram for leptin serum concentrations in children with type 1 diabetes (N = 75).
5
Number of children
4
3
2
1
0 0-1
1-2
2-3
3-4
4-5
5-6
6-7
7-8
8-9
above 9 mcg/L
Lepn serum concentraons Fig. 3. Histogram for leptin serum concentrations in the control group (N = 20).
Statistical analysis showed an inverse correlation of adiponectin concentrations with body weight in children with T1DM. In the control group this dependence was not observed. There was no significant association between serum adiponectin and the body fat content in diabetic children, while in the control group a positive correlation with the percentage value of the body fat mass was present, but not with the total body fat mass. In both groups, there was no correlation between adiponectin levels, and gender as well as age of children. Neither the duration of diabetes nor its metabolic control (HbA1c), was statistically related to adiponectin levels. Also the individual insulin dose, as well as the method of insulin therapy in
Table 1 Triglycerides, total cholesterol and free fatty acids serum levels in children with type 1 diabetes and in the control group.
TG (mg/dl) CHOL (mg/dl) FFA (mg/dl)
Type 1 diabetes (N = 75)
Control group (N = 20)
Mean SD
Mean SD
78.63 39.94 179.05 41.74 7.86 6.34
67.71 30.14 160.70 28.21 9.86 5.15
p-Value
0.258 0.067 0.199
TG, triglycerides levels; CHOL, total cholesterol levels; FFA, free fatty acids levels.
patients with diabetes showed no correlation. There was also no correlation with lipid parameters in both groups. Correlations of serum adiponectin concentrations with clinical data are presented in Table 3. Table 2 Correlations of leptin serum concentrations with the clinical data of patients with type 1 diabetes mellitus and the control group. Type 1 diabetes (N = 75)
Age (years) BW (kg) FM (kg) FM% (%) Diabetes duration (years) HbA1c (%) INS/day (units/day) INS/kg (units/kg) TG (mg/dl) CHOL (mg/dl) FFA (mg/dl)
Control group (N = 20)
R
p-Value
R
p-Value
0.247 0.342 0.755 0.595 0.088 0.016 0.278 0.152 0.012 0.052 0.033
0.033 0.003 <0.001 <0.001 0.452 0.891 0.664 0.192 0.916 0.661 0.781
0.006 0.071 0.691 0.748 – – – – 0.073 0.080 0.236
0.980 0.767 0.001 <0.001 – – – – 0.760 0.738 0.317
BW, body weight; FM, total body fat mass; FM%, percentage value of the body fat mass; INS/day, daily insulin dose; INS/kg, daily insulin dose per kg of body weight; TG, triglycerides levels; CHOL, total cholesterol levels; FFA, free fatty acids levels.
K.A. Majewska et al. / Advances in Medical Sciences 61 (2016) 117–122
120
Adiponectin serum concentrations [mcg/ml]
30
Table 3 Correlations of serum adiponectin concentrations with clinical data among the analyzed groups.
25
Type 1 diabetes (N = 75) 20
Age (years) BW (kg) FM (kg) FM% (%) Diabetes duration (years) HbA1c (%) INS/day (units/day) INS/kg (units/kg) TG (mg/dl) CHOL (mg/dl) FFA (mg/dl)
15
10
5
0
Type 1 diabetes
Control group (N = 20)
R
p-Value
R
p-Value
0.183 0.260 0.125 0.038 0.064 0.155 0.293 0.166 0.098 0.014 0.092
0.117 0.024 0.286 0.745 0.586 0.184 0.639 0.156 0.402 0.902 0.441
0.370 0.285 0.247 0.491 – – – – 0.349 0.325 0.228
0.108 0.223 0.294 0.028 – – – – 0.132 0.162 0.334
Control group
Fig. 4. Adiponectin serum concentrations (mcg/ml) in children with type 1 diabetes and the control group: mean values SD.
4. Discussion Serum leptin concentrations in children with newly diagnosed T1DM present reduced values, but increase significantly after initiation of insulin therapy [14,15]. For the current study only
BW, body weight; FM, total body fat mass; FM%, percentage value of the body fat mass; INS/day, daily insulin dose; INS/kg, daily insulin dose per kg of body weight; TG, triglycerides; CHOL, total cholesterol; FFA, free fatty acids.
patients with disease duration of at least one year were qualified to unify the group. Studies assessing leptin concentrations in patients with longer T1DM duration compared with healthy people, do not give conclusive results. Some reports indicate increased leptinaemia
20
Number of children
15
10
5
0 0-5
5 - 10
10 - 15
15 - 20
20 - 25
25 - 30
30 - 35
35 - 40
40 - 45 above 45 mcg/ml
Adiponecn serum concentraons Fig. 5. Histogram for adiponectin serum concentrations in children with type 1 diabetes (N = 75).
Number of children
8
6
4
2
0 0-5
5 - 10
10 - 15
15 - 20
20 - 25
25 - 30
30 - 35
35 - 40
40 - 45 above 45 mcg/ml
Adiponecn serum concentraons Fig. 6. Histogram for adiponectin serum concentrations in the control group (N = 20).
K.A. Majewska et al. / Advances in Medical Sciences 61 (2016) 117–122
in these patients [14–17]. Other reports however indicate no differences between patients and healthy subjects [18]. In the present study, no significant differences in leptin levels between children with diabetes and the control group were found. Considering the stimulatory effect of insulin on the leptin secretion, peripheral insulin excess, that is commonly observed in patients with T1DM, should in theory result in elevated serum leptin levels. However, insulin excess may also cause adipocytes to develop insulin resistance, and then an insulin-stimulated increase in leptin secretion would not occur. This is particularly relevant in time preceding the next insulin dose injection, such as the morning after a night’s rest, when its serum levels are already reduced. The half-life of leptin is about 25 min [19], hence its reduced secretion will cause moderately fast reduction of its concentration. Numerous studies in both, children and adults, demonstrate a strong correlation between serum leptin levels, and parameters describing body mass, in particular the amount of body fat [18–20]. As confirmed by our study – positive dependencies were found between leptinaemia and body weight, as well as adipose tissue mass in diabetic children. In the control group leptin levels were not correlated with body weight, but in the presence of a significant association with the fat mass. There is a gender-depending dissociation in the range of leptin concentrations, with its higher values in girls, and this was confirmed in our study. These observations can be partly explained by differences in body fat content. Increase in fat mass during puberty is more significant in girls, while in boys relatively greater increase in muscle mass is observed. Variability of serum leptin presents also a relation to sex hormones levels [14,16–20]. Positive correlation of serum leptin concentrations and age observed in the group of children with T1DM might be related to the age progressive gradual weight gain and increase in fat mass. Studies analyzing the impact of diabetes metabolic control on the serum leptin levels, when correlating with HbA1c value, give ambiguous results. There are reports of both: a positive correlation between plasma leptin and poor metabolic control [15], and those indicating the absence of such a correlation [16,18]. Results obtained in our study suggest that diverse metabolic control, as well as diabetes duration, do not influence the adipose tissue leptin secretion in the developmental age. Regarding the relationship between leptin levels and the individual insulin dose, again the literature does not give a conclusive results [16–18]. The present study showed no effect of the individual insulin dose on the obtained values of serum leptin concentrations in children with diabetes, as no statistically significant differences resulting from the different methods of insulin therapy. Among the studies comparing serum adiponectin levels in patients with T1DM and healthy population, Galler et al. described its significantly higher values in diabetic children compared with healthy subjects. In the subgroup of patients with newly diagnosed diabetes, preceding insulin therapy, the obtained values of adiponectinaemia did not differ from the control group, but increased during follow-up [21]. Adiponectin concentrations in children and adolescents with diabetes in our study, compared to the control group, showed a significantly higher values. This observation may be a consequence of a common in T1DM peripheral insulin excess, as insulin is one of the factors stimulating adiponectin secretion. Here, however, raises the question about differences in concentrations of adiponectin and leptin, taking into account the stimulatory effect of insulin on both the adipokines secretion. The reason for this may be found in their half-lives. As mentioned previously, the half-life of leptin is about 25 min and is shorter than the half-life of adiponectin, which is approximately 2.5 h [22]. Despite the insulin excess during the day, in the early-morning hours, long after the last, evening dose of insulin, the concentrations of exogenous insulin are relatively
121
reduced, and often have lower efficiency. This may reduce secretion of both, adiponectin and leptin. However, the relatively longer half-life of adiponectin should result in more stable serum concentrations, while the half-life of leptin is relatively shorter, so its decreased secretion would reduce its serum concentrations more rapidly. Patients in this study, had the blood samples collected at basic conditions – in the morning, fasting, before administration of the morning dose of insulin. This time of the material collection may be of the importance for the present study results, despite the fact that the method of insulin-therapy or insulin dosage was not statistically related to the adiponectin level. Many authors point to a negative correlation between plasma adiponectin with body fat mass and obesity in children, adolescents, and adults [23–26]. In our study adiponectin serum concentrations demonstrated a negative correlation with body weight in children with T1DM, but not in the control group. In both groups, there was no relation to the absolute body fat mass, which may be explained by normal-weight children participating in the study, and the proper distribution of body fat. An interesting observation was a positive correlation of adiponectin levels with the percentage value of body fat mass in the control group, which may indicate different characteristics of adipose tissue secretion in healthy children of normal weight. In the adult population, a gender-depending differences in adiponectin concentrations are observed, with higher values in women [3]. In children and adolescents, these changes are not clearly marked. In our study, no significant differences between girls and boys in terms of adiponectin concentrations were found. Studies evaluating the impact of the metabolic control and the duration of T1DM for the adiponectin levels provide inconclusive results. Lindstrom et al. found a strong positive correlation of adiponectinaemia and a long diabetes duration, independent of metabolic control [27], while Celi et al. observed a positive correlation to glycated haemoglobin [17]. In turn, the study of Galler et al. did not confirm these results, indicating no significant difference dependent on the disease duration, and metabolic control [26], and so were the results of our study. Our research, however, was subject to certain limitations. The study group was based on patients admitted for a routine medical check-up, so it might not cover the potentially worst controlled patients, who do not attend regular visits. The control group was carefully selected to recruit only healthy, normal weight children, but as a consequence the size of a group was quite small, which could cause some relations not to reveal statistical significance. Cross-sectional study with enlarged both, the study, and the control group, with simultaneous determination of insulin and glucose serum concentrations would increase the understanding of adipokines regulations in patients with type 1 diabetes.
5. Conclusions Children with T1DM had significantly higher values of serum adiponectin levels, but did not statistically differ from their healthy coevals in terms of leptin levels. Leptin, but not adiponectin concentrations, are associated with body fat mass in diabetic children. Differences observed between children with T1DM and their healthy coevals – when similar in terms of age, body weight, and body fat mass – probably result from broken physiological adipoinsular regulations, independent of the disease duration, its metabolic control or insulin supply. Adipokines regulations in children with T1DM are still not well recognized. So far, obtained results are not conclusive, hence further research in this field should be conducted, including the issue of insulin resistance.
K.A. Majewska et al. / Advances in Medical Sciences 61 (2016) 117–122
122
Conflict of interests The authors declare no conflict of interests. Financial disclosure The study was financially supported by a grant from Poznan University of Medical Sciences (501-01-1104118-07914). References [1] Rosen ED, Spiegelman BM. Adipocytes as regulators of energy balance and glucose homeostasis. Nature 2006;444(7121):847–53. [2] Skowron´ska B, Fichna M, Fichna P. Rola tkanki tłuszczowej w układzie dokrewnym. Endokrynol Otyłos´c´ i Zaburzenia Przemiany Materii 2005;1(3):21–9. [3] Ahima RS, Lazar MA. Adipokines and the peripheral and neural control of energy balance. Mol Endocrinol 2008;22(5):1023–31. [4] Kieffer TJ, Habener JF. The adipoinsular axis: effects of leptin on pancreatic bcells. Am J Physiol Endocrinol Metab 2000;278(1):E1–4. [5] Tucholski K, Otto-Buczkowska E. The role of leptin in the regulation of carbohydrate metabolism. Endokrynol Pol 2011;62(3):258–61. [6] Kershaw EE, Flier JS. Adipose tissue as an endocrine organ. J Clin Endocrinol Metab 2004;89(6):2548–56. [7] Cieslak J, Skorczyk A, Stachowiak M, Szydlowski M, Grzes M, Paczynska P, et al. Polymorphisms in 50 -flanking regions of genes encoding adiponectin, leptin, and resistin are not associated with obesity of Polish children and adolescents. Mol Biol Rep 2011;38(3):1793–8. [8] Ishiki M, Klip A. Minireview: recent developments in the regulation of glucose transporter-4 traffic: new signals, locations, and partners. Endocrinology 2005;146(12):5071–8. [9] Otto-Buczkowska E, Chobot A. Role of ghrelin and leptin in the regulation of carbohydrate metabolism. Part II. Leptin. Postepy Hig Med Dosw 2012;66: 799–803 [online]. [10] Stankovic SM, Zivic SR, Saranac L, Cvetkovic V, Pesic M, Vasic K, et al. Determinants of atherosclerosis in children and adolescents with diabetes type 1. Endokrynol Pol 2012;63(6):414–9. [11] Nazim J, Fendler W, Starzyk J. Metabolic control and its variability are major risk factors for microalbuminuria in children with type 1 diabetes. Endokrynol Pol 2014;65(2):83–9. [12] Majewska KA, Majewski D, Skowronska B, Fichna P. Serum resistin concentrations in children with type 1 diabetes mellitus – negative relation to body fat mass. Endokrynol Pol 2014;65(5):342–7. [13] Lewitt A, Ma˛dro E, Krupienicz A. Podstawy teoretyczne i zastosowania analizy impedancji bioelektrycznej (BIA). Endokrynol Otyłos´c´ i Zaburzenia Przemiany Materii 2007;3(4):79–84.
[14] Kiess W, Anil M, Blum WF, Englaro P, Juul A, Attanasio A, et al. Serum leptin levels in children and adolescents with insulin-dependent diabetes mellitus in relation to metabolic control and body mass index. Eur J Endocrinol 1998; 138(5):501–9. [15] Soliman AT, Omar M, Assem HM, Nasr IS, Rizk MM, El Matary W, et al. Serum leptin concentrations in children with type 1 diabetes mellitus: relationship to body mass index, insulin dose, and glycemic control. Metabolism 2002;51(3): 292–6. [16] Szadkowska A, Wyka K, Młynarski W, Pietrzak I, Mianowska B, Bodalski J. Ste˛z˙enie leptyny a insulinowraz˙liwos´c´ u dzieci i młodziez˙y chorej na cukrzyce˛ typu 1. Pediatr Endocr Diabet Metab 2007;13(4):194–200. [17] Celi F, Bini V, Papi F, Santilli E, Castellani MS, Ferretti A, et al. Circulating adipocytokines in non-diabetic and type 1 diabetic children: relationship to insulin therapy, glycaemic control and pubertal development. Diabet Med 2006;23(6):660–5. [18] Myers SE, Albert SG, Haas MJ, Clifton D, Mooradian AD. Pubertal changes in serum leptin levels in adolescents with type 1 diabetes mellitus: a controlled longitudinal study. J Pediatr Endocrinol Metab 2004;17(12):1653–62. [19] Prolo P, Wong ML, Licinio J. Leptin. Int J Biochem Cell Biol 1998;30: 1285–90. [20] Blum WF, Englaro P, Hanitsch S, Juul A, Hertel NT, Muller J, et al. Plasma leptin levels in healthy children and adolescents: dependence on body mass index, body fat mass, gender, pubertal stage, and testosterone. J Clin Endocrinol Metab 1997;82(9):2904–10. [21] Galler A, Gelbrich G, Kratzsch J, Noack N, Kapellen T, Kiess W. Elevated serum levels of adiponectin in children, adolescents and young adults with type 1 diabetes and the impact of age, gender, body mass index and metabolic control: a longitudinal study. Eur J Endocrinol 2007;157(4): 481–9. [22] Hoffstedt J, Arvidsson E, Sjolin E, Wahlen K, Arner P. Adipose tissue adiponectin production and adiponectin serum concentration in human obesity and insulin resistance. J Clin Endocrinol Metab 2004;89(3):1391–6. [23] Cnop M, Havel PJ, Utzschneider KM, Carr DB, Sinha MK, Boyko EJ, et al. Relationship of adiponectin to body fat distribution, insulin sensitivity and plasma lipoproteins: evidence for independent roles of age and sex. Diabetologia 2003;46(4):459–69. [24] Huang KC, Lue BH, Yen RF, et al. Plasma adiponectin levels and metabolic factors in nondiabetic adolescents. Obes Res 2004;12(1):119–24. [25] Bacha F, Saad R, Gungor N, Arslanian S. Adiponectin in youth: relationship to visceral adiposity, insulin sensitivity, and b-cell function. Diabetes Care 2004;27(2):547–52. [26] Cieslak J, Bartz M, Stachowiak M, Skowronska B, Majewska KA, Harasymczuk J, et al. Effect of three common SNPs in 50 -flanking region of LEP and ADIPOQ genes on their expression in Polish obese children and adolescents. Mol Biol Rep 2012;39(4):3951–5. [27] Lindstrom T, Frystyk J, Hedman CA, Flyvbjerg A, Arnqvist HJ. Elevated circulating adiponectin in type 1 diabetes is associated with long diabetes duration. Clin Endocrinol (Oxf) 2006;65(6):776–82.
Contents lists available at ScienceDirect
Advances in Medical Sciences journal homepage: www.elsevier.com/locate/advms
Original Research Article
Serum leptin and adiponectin levels in children with type 1 diabetes mellitus – Relation to body fat mass and disease course Katarzyna Anna Majewska a,b,*, Dominik Majewski c, Bogda Skowron´ska b, Witold Stankiewicz b, Piotr Fichna b a b c
Department of Clinical Auxology and Pediatric Nursing, Poznan University of Medical Sciences, Poznan, Poland Department of Pediatric Diabetes and Obesity, Poznan University of Medical Sciences, Poznan, Poland Department of Rheumatology and Internal Medicine, Poznan University of Medical Sciences, Poznan, Poland
A R T I C L E I N F O
A B S T R A C T
Article history: Received 26 March 2015 Accepted 22 October 2015 Available online 3 November 2015
Purpose: Leptin and adiponectin are adipokines presenting a wide range of impacts, including glycemic balance regulations. Insulin is one of the main regulators of adipose tissue function. In type 1 diabetes mellitus (T1DM) endogenous insulin secretion is replaced by the exogenous supply, which is not regulated naturally. The aim of the study was to establish serum leptin and adiponectin levels, and their relations to body fat mass and disease course in children with T1DM. Material/methods: The study included 75 children with T1DM and the control group of 20 healthy coevals. All children had estimated serum leptin and adiponectin concentrations, lipid profile, and bioelectrical impedance analysis. Results: Serum leptin concentrations in children with T1DM were not significantly different from the control group (p = 0.067, mean values SD: 3.11 2.98 vs. 5.29 5.06 mg/l, respectively), and related positively to body fat mass in both groups. Adiponectin serum concentrations were significantly higher in children with T1DM than in the control group (p < 0.001; mean values: 18.82 9.31 vs. 12.10 5.53 mg/ml, respectively), and were not related to the body fat content in the study group. Both, leptin and adiponectin, showed no relation to any of the analyzed parameters of the disease course. Conclusions: Differences observed between children with T1DM and their healthy coevals, when similar in terms of age, body weight, and body fat mass, seem not to depend directly on the disease duration, its metabolic control or insulin supply. ß 2015 Medical University of Bialystok. Published by Elsevier Sp. z o.o. All rights reserved.
Keywords: Leptin Adiponectin Type 1 diabetes Adipose tissue Children
1. Introduction Leptin and adiponectin are among the best known adipokines, both presenting a wide range of impacts. Leptin is involved in various biological processes, including the regulation of appetite, energy expenditure, or certain neuroendocrine functions. Its impact on glucose homeostasis is generally anti-hyperglycemic, increasing insulin sensitivity of liver and muscle cells. Serum leptin concentrations closely correlate with the body fat mass – increase with increasing fat mass, and decrease with its loss during the calorierestricted diet [1–5]. Adiponectin exerts, inter alia, the antiinflammatory, antithrombotic and antiatherosclerotic effect. It is
* Corresponding author at: Department of Clinical Auxology and Pediatric Nursing, Poznan University of Medical Sciences, ul. Szpitalna 27/33, 60-572 Poznan, Poland. Tel.: +48 61 8491 265; fax: +48 61 8491 265. E-mail address: [email protected] (K.A. Majewska).
also involved in the stimulation of fatty acid oxidation and gluconeogenesis inhibition. Its higher concentrations are associated with increased insulin sensitivity and improved glucose tolerance. In contrast to leptin, the adiponectin secretion decreases in obesity, along with the growing fat mass, and increases along with its loss [1–3,6,7]. Insulin is one of the main factors regulating the adipose tissue function. It exerts an inhibitory effect on lipolysis, while stimulating on lipogenesis, and regulating on glucose transport into adipocytes in the postprandial period. Insulin stimulates adipogenesis. It is an important regulator of leptin secretion, as well as one of the factors stimulating adiponectin secretion [2,4,6,8]. The interaction between insulin and adipose tissue is not unidirectional. There are reports indicating that leptin is involved in the regulation of insulin secretion, and that between the adipose tissue and pancreatic islands, there is a feedback loop – two-way adipo-insular axis [1,4,5,9].
http://dx.doi.org/10.1016/j.advms.2015.10.002 1896-1126/ß 2015 Medical University of Bialystok. Published by Elsevier Sp. z o.o. All rights reserved.
K.A. Majewska et al. / Advances in Medical Sciences 61 (2016) 117–122
In type 1 diabetes mellitus (T1DM) endogenous insulin secretion is replaced by the exogenous supply, which is not regulated naturally. The question arises, how it affects the regulation of adipose tissue secretory function. As altered adipokines production may influence glucose homeostasis, it could also influence the risk of complications in diabetic children and adolescents [10,11]. The aim of the study was to establish serum leptin and adiponectin levels, and their relations to body fat mass and disease course in children with T1DM. 2. Material and methods The study was conducted in Poznan University of Medical Sciences. It was based on a group of 75 children (30 boys and 45 girls) with T1DM, recruited among the patients admitted to the Karol Jonscher Teaching Hospital for a routine medical check-up, with disease duration of at least 1 year, and no acute nor chronic complications of diabetes or additional diseases. They were treated with insulin by various methods: 35 with flexible intensive insulin therapy with multiple daily injections, 21 with continuous subcutaneous insulin infusion, and 19 with the conventional method with 2–3 daily injections of premixed insulin in fixed doses. Included patients had various levels of glycated haemoglobin (HbA1c). The control group involved 20 healthy, normal weight children (10 boys and 10 girls), who were admitted to the hospital for diagnostic reasons, but with no disease found. Detailed characteristics of the groups have been described previously [12]. Patients from both groups had following investigations, all at basic conditions – in the morning, fasting: - blood samples taken to establish leptin and adiponectin serum concentrations, as well as the levels of triglycerides, total cholesterol, and free fatty acids; - body weight and growth established accurate to 0.1 kg and 0.1 cm, respectively; - bioelectrical impedance analysis (BIA), as a method of evaluating body composition (tetrapolar system, Akern analyzer BIA-101, Bioresearch) [13]. Leptin serum concentrations were performed by immunoradiometric assay (Human Leptin IRMA DSL). Adiponectin serum concentrations were performed by radioimmunoassay (Human Adiponectin RIA Kit, Linco Research). In the statistical analysis Kolmogorov–Smirnov test was used in evaluating the compatibility of the variables with the normal distribution. Non-parametric methods: Mann–Whitney test and the Spearman correlation r were used for the variables not compatible with the normal distribution. Parametric methods: Levene’s test of homoscedasticity, t-test and Pearson correlations were used for normally distributed variables. The study protocol was approved by the local Ethics Committee at the Karol Marcinkowski University of Medical Sciences in Poznan´ (No. 187/05). Legal guardians of all participants gave informed consent. 3. Results The study and the control group did not differ statistically in terms of age (p = 0.944, mean values standard deviation (SD): 12.47 3.51 vs. 12.55 2.68 years, respectively), body weight (p = 0.597, mean values SD: 47.72 15.18 vs. 45.81 10.29 kg, respectively), and fat mass content – the total body fat mass (p = 0.445, mean values SD: 11.59 5.85 vs. 10.54 3.69 kg,
respectively), and the percentage value of the body fat mass (p = 0.601, mean values SD: 24.46 7.96 vs. 23.43 7.10%, respectively). In children with T1DM mean disease duration was 4.95 3.2 years (SD) [12]. 3.1. Leptin concentrations Statistical analysis showed no significant difference in serum leptin concentrations between the study and the control group (p = 0.067, mean values SD): 3.11 2.98 mg/l vs. 5.29 5.06 mg/l; median values: 1.80 vs. 4.25 mg/l, respectively) (Figs. 1–3). In both groups leptin levels demonstrated a strong, positive correlation with the total body fat mass (FM) and the percentage value of the body fat mass – as compared to the total body weight (FM%), resulting in the increasing leptin concentrations along with increase of both: the absolute and the percentage value of body fat mass. Leptinaemia showed a strong positive correlation with body weight in children with diabetes. This dependence was not observed in the control group. In both, diabetic and healthy children, a significant relation of leptin levels and gender (p < 0.001 and p = 0.026, respectively) was present. Higher values were found in girls. Leptin concentrations observed in the study group showed a positive correlation with age. This dependence was not observed in the control group. Duration of diabetes, or its metabolic control rated as glycated haemoglobin (HbA1c), did not show a significant correlation with leptinaemia. Analysis of serum leptin concentrations in relation to the applied insulin dose (Ins/day, Ins/kg) revealed no correlation. Children treated with insulin according to various methods did not differ significantly in terms of leptin levels. Evaluated serum lipid parameters, revealed no significant difference between the groups (Table 1) and there was no correlation of serum leptin with total cholesterol, triglycerides, and free fatty acids levels in both groups. Correlations of leptin concentrations with clinical data are presented in Table 2. 3.2. Adiponectin concentrations Adiponectin serum concentrations presented significant differences between the groups, and were significantly higher in diabetic children than in the control group (p < 0.001; mean values: 18.82 9.31 mg/ml vs. 12.10 5.53 mg/ml; median values: 16.89 vs. 12.26 mg/ml, respectively) (Figs. 4–6).
12
Leptin serum concentrations [mcg/L]
118
10 8 6 4 2 0 Type 1 diabetes
Control group
Fig. 1. Leptin serum concentrations (mcg/l) in children with type 1 diabetes and the control group: mean values SD.
K.A. Majewska et al. / Advances in Medical Sciences 61 (2016) 117–122
119
25
Number of children
20
15
10
5
0 0-1
1-2
2-3
3-4
4-5
5-6
6-7
7-8
8-9
above 9 mcg/L
Lepn serum concentraons Fig. 2. Histogram for leptin serum concentrations in children with type 1 diabetes (N = 75).
5
Number of children
4
3
2
1
0 0-1
1-2
2-3
3-4
4-5
5-6
6-7
7-8
8-9
above 9 mcg/L
Lepn serum concentraons Fig. 3. Histogram for leptin serum concentrations in the control group (N = 20).
Statistical analysis showed an inverse correlation of adiponectin concentrations with body weight in children with T1DM. In the control group this dependence was not observed. There was no significant association between serum adiponectin and the body fat content in diabetic children, while in the control group a positive correlation with the percentage value of the body fat mass was present, but not with the total body fat mass. In both groups, there was no correlation between adiponectin levels, and gender as well as age of children. Neither the duration of diabetes nor its metabolic control (HbA1c), was statistically related to adiponectin levels. Also the individual insulin dose, as well as the method of insulin therapy in
Table 1 Triglycerides, total cholesterol and free fatty acids serum levels in children with type 1 diabetes and in the control group.
TG (mg/dl) CHOL (mg/dl) FFA (mg/dl)
Type 1 diabetes (N = 75)
Control group (N = 20)
Mean SD
Mean SD
78.63 39.94 179.05 41.74 7.86 6.34
67.71 30.14 160.70 28.21 9.86 5.15
p-Value
0.258 0.067 0.199
TG, triglycerides levels; CHOL, total cholesterol levels; FFA, free fatty acids levels.
patients with diabetes showed no correlation. There was also no correlation with lipid parameters in both groups. Correlations of serum adiponectin concentrations with clinical data are presented in Table 3. Table 2 Correlations of leptin serum concentrations with the clinical data of patients with type 1 diabetes mellitus and the control group. Type 1 diabetes (N = 75)
Age (years) BW (kg) FM (kg) FM% (%) Diabetes duration (years) HbA1c (%) INS/day (units/day) INS/kg (units/kg) TG (mg/dl) CHOL (mg/dl) FFA (mg/dl)
Control group (N = 20)
R
p-Value
R
p-Value
0.247 0.342 0.755 0.595 0.088 0.016 0.278 0.152 0.012 0.052 0.033
0.033 0.003 <0.001 <0.001 0.452 0.891 0.664 0.192 0.916 0.661 0.781
0.006 0.071 0.691 0.748 – – – – 0.073 0.080 0.236
0.980 0.767 0.001 <0.001 – – – – 0.760 0.738 0.317
BW, body weight; FM, total body fat mass; FM%, percentage value of the body fat mass; INS/day, daily insulin dose; INS/kg, daily insulin dose per kg of body weight; TG, triglycerides levels; CHOL, total cholesterol levels; FFA, free fatty acids levels.
K.A. Majewska et al. / Advances in Medical Sciences 61 (2016) 117–122
120
Adiponectin serum concentrations [mcg/ml]
30
Table 3 Correlations of serum adiponectin concentrations with clinical data among the analyzed groups.
25
Type 1 diabetes (N = 75) 20
Age (years) BW (kg) FM (kg) FM% (%) Diabetes duration (years) HbA1c (%) INS/day (units/day) INS/kg (units/kg) TG (mg/dl) CHOL (mg/dl) FFA (mg/dl)
15
10
5
0
Type 1 diabetes
Control group (N = 20)
R
p-Value
R
p-Value
0.183 0.260 0.125 0.038 0.064 0.155 0.293 0.166 0.098 0.014 0.092
0.117 0.024 0.286 0.745 0.586 0.184 0.639 0.156 0.402 0.902 0.441
0.370 0.285 0.247 0.491 – – – – 0.349 0.325 0.228
0.108 0.223 0.294 0.028 – – – – 0.132 0.162 0.334
Control group
Fig. 4. Adiponectin serum concentrations (mcg/ml) in children with type 1 diabetes and the control group: mean values SD.
4. Discussion Serum leptin concentrations in children with newly diagnosed T1DM present reduced values, but increase significantly after initiation of insulin therapy [14,15]. For the current study only
BW, body weight; FM, total body fat mass; FM%, percentage value of the body fat mass; INS/day, daily insulin dose; INS/kg, daily insulin dose per kg of body weight; TG, triglycerides; CHOL, total cholesterol; FFA, free fatty acids.
patients with disease duration of at least one year were qualified to unify the group. Studies assessing leptin concentrations in patients with longer T1DM duration compared with healthy people, do not give conclusive results. Some reports indicate increased leptinaemia
20
Number of children
15
10
5
0 0-5
5 - 10
10 - 15
15 - 20
20 - 25
25 - 30
30 - 35
35 - 40
40 - 45 above 45 mcg/ml
Adiponecn serum concentraons Fig. 5. Histogram for adiponectin serum concentrations in children with type 1 diabetes (N = 75).
Number of children
8
6
4
2
0 0-5
5 - 10
10 - 15
15 - 20
20 - 25
25 - 30
30 - 35
35 - 40
40 - 45 above 45 mcg/ml
Adiponecn serum concentraons Fig. 6. Histogram for adiponectin serum concentrations in the control group (N = 20).
K.A. Majewska et al. / Advances in Medical Sciences 61 (2016) 117–122
in these patients [14–17]. Other reports however indicate no differences between patients and healthy subjects [18]. In the present study, no significant differences in leptin levels between children with diabetes and the control group were found. Considering the stimulatory effect of insulin on the leptin secretion, peripheral insulin excess, that is commonly observed in patients with T1DM, should in theory result in elevated serum leptin levels. However, insulin excess may also cause adipocytes to develop insulin resistance, and then an insulin-stimulated increase in leptin secretion would not occur. This is particularly relevant in time preceding the next insulin dose injection, such as the morning after a night’s rest, when its serum levels are already reduced. The half-life of leptin is about 25 min [19], hence its reduced secretion will cause moderately fast reduction of its concentration. Numerous studies in both, children and adults, demonstrate a strong correlation between serum leptin levels, and parameters describing body mass, in particular the amount of body fat [18–20]. As confirmed by our study – positive dependencies were found between leptinaemia and body weight, as well as adipose tissue mass in diabetic children. In the control group leptin levels were not correlated with body weight, but in the presence of a significant association with the fat mass. There is a gender-depending dissociation in the range of leptin concentrations, with its higher values in girls, and this was confirmed in our study. These observations can be partly explained by differences in body fat content. Increase in fat mass during puberty is more significant in girls, while in boys relatively greater increase in muscle mass is observed. Variability of serum leptin presents also a relation to sex hormones levels [14,16–20]. Positive correlation of serum leptin concentrations and age observed in the group of children with T1DM might be related to the age progressive gradual weight gain and increase in fat mass. Studies analyzing the impact of diabetes metabolic control on the serum leptin levels, when correlating with HbA1c value, give ambiguous results. There are reports of both: a positive correlation between plasma leptin and poor metabolic control [15], and those indicating the absence of such a correlation [16,18]. Results obtained in our study suggest that diverse metabolic control, as well as diabetes duration, do not influence the adipose tissue leptin secretion in the developmental age. Regarding the relationship between leptin levels and the individual insulin dose, again the literature does not give a conclusive results [16–18]. The present study showed no effect of the individual insulin dose on the obtained values of serum leptin concentrations in children with diabetes, as no statistically significant differences resulting from the different methods of insulin therapy. Among the studies comparing serum adiponectin levels in patients with T1DM and healthy population, Galler et al. described its significantly higher values in diabetic children compared with healthy subjects. In the subgroup of patients with newly diagnosed diabetes, preceding insulin therapy, the obtained values of adiponectinaemia did not differ from the control group, but increased during follow-up [21]. Adiponectin concentrations in children and adolescents with diabetes in our study, compared to the control group, showed a significantly higher values. This observation may be a consequence of a common in T1DM peripheral insulin excess, as insulin is one of the factors stimulating adiponectin secretion. Here, however, raises the question about differences in concentrations of adiponectin and leptin, taking into account the stimulatory effect of insulin on both the adipokines secretion. The reason for this may be found in their half-lives. As mentioned previously, the half-life of leptin is about 25 min and is shorter than the half-life of adiponectin, which is approximately 2.5 h [22]. Despite the insulin excess during the day, in the early-morning hours, long after the last, evening dose of insulin, the concentrations of exogenous insulin are relatively
121
reduced, and often have lower efficiency. This may reduce secretion of both, adiponectin and leptin. However, the relatively longer half-life of adiponectin should result in more stable serum concentrations, while the half-life of leptin is relatively shorter, so its decreased secretion would reduce its serum concentrations more rapidly. Patients in this study, had the blood samples collected at basic conditions – in the morning, fasting, before administration of the morning dose of insulin. This time of the material collection may be of the importance for the present study results, despite the fact that the method of insulin-therapy or insulin dosage was not statistically related to the adiponectin level. Many authors point to a negative correlation between plasma adiponectin with body fat mass and obesity in children, adolescents, and adults [23–26]. In our study adiponectin serum concentrations demonstrated a negative correlation with body weight in children with T1DM, but not in the control group. In both groups, there was no relation to the absolute body fat mass, which may be explained by normal-weight children participating in the study, and the proper distribution of body fat. An interesting observation was a positive correlation of adiponectin levels with the percentage value of body fat mass in the control group, which may indicate different characteristics of adipose tissue secretion in healthy children of normal weight. In the adult population, a gender-depending differences in adiponectin concentrations are observed, with higher values in women [3]. In children and adolescents, these changes are not clearly marked. In our study, no significant differences between girls and boys in terms of adiponectin concentrations were found. Studies evaluating the impact of the metabolic control and the duration of T1DM for the adiponectin levels provide inconclusive results. Lindstrom et al. found a strong positive correlation of adiponectinaemia and a long diabetes duration, independent of metabolic control [27], while Celi et al. observed a positive correlation to glycated haemoglobin [17]. In turn, the study of Galler et al. did not confirm these results, indicating no significant difference dependent on the disease duration, and metabolic control [26], and so were the results of our study. Our research, however, was subject to certain limitations. The study group was based on patients admitted for a routine medical check-up, so it might not cover the potentially worst controlled patients, who do not attend regular visits. The control group was carefully selected to recruit only healthy, normal weight children, but as a consequence the size of a group was quite small, which could cause some relations not to reveal statistical significance. Cross-sectional study with enlarged both, the study, and the control group, with simultaneous determination of insulin and glucose serum concentrations would increase the understanding of adipokines regulations in patients with type 1 diabetes.
5. Conclusions Children with T1DM had significantly higher values of serum adiponectin levels, but did not statistically differ from their healthy coevals in terms of leptin levels. Leptin, but not adiponectin concentrations, are associated with body fat mass in diabetic children. Differences observed between children with T1DM and their healthy coevals – when similar in terms of age, body weight, and body fat mass – probably result from broken physiological adipoinsular regulations, independent of the disease duration, its metabolic control or insulin supply. Adipokines regulations in children with T1DM are still not well recognized. So far, obtained results are not conclusive, hence further research in this field should be conducted, including the issue of insulin resistance.
K.A. Majewska et al. / Advances in Medical Sciences 61 (2016) 117–122
122
Conflict of interests The authors declare no conflict of interests. Financial disclosure The study was financially supported by a grant from Poznan University of Medical Sciences (501-01-1104118-07914). References [1] Rosen ED, Spiegelman BM. Adipocytes as regulators of energy balance and glucose homeostasis. Nature 2006;444(7121):847–53. [2] Skowron´ska B, Fichna M, Fichna P. Rola tkanki tłuszczowej w układzie dokrewnym. Endokrynol Otyłos´c´ i Zaburzenia Przemiany Materii 2005;1(3):21–9. [3] Ahima RS, Lazar MA. Adipokines and the peripheral and neural control of energy balance. Mol Endocrinol 2008;22(5):1023–31. [4] Kieffer TJ, Habener JF. The adipoinsular axis: effects of leptin on pancreatic bcells. Am J Physiol Endocrinol Metab 2000;278(1):E1–4. [5] Tucholski K, Otto-Buczkowska E. The role of leptin in the regulation of carbohydrate metabolism. Endokrynol Pol 2011;62(3):258–61. [6] Kershaw EE, Flier JS. Adipose tissue as an endocrine organ. J Clin Endocrinol Metab 2004;89(6):2548–56. [7] Cieslak J, Skorczyk A, Stachowiak M, Szydlowski M, Grzes M, Paczynska P, et al. Polymorphisms in 50 -flanking regions of genes encoding adiponectin, leptin, and resistin are not associated with obesity of Polish children and adolescents. Mol Biol Rep 2011;38(3):1793–8. [8] Ishiki M, Klip A. Minireview: recent developments in the regulation of glucose transporter-4 traffic: new signals, locations, and partners. Endocrinology 2005;146(12):5071–8. [9] Otto-Buczkowska E, Chobot A. Role of ghrelin and leptin in the regulation of carbohydrate metabolism. Part II. Leptin. Postepy Hig Med Dosw 2012;66: 799–803 [online]. [10] Stankovic SM, Zivic SR, Saranac L, Cvetkovic V, Pesic M, Vasic K, et al. Determinants of atherosclerosis in children and adolescents with diabetes type 1. Endokrynol Pol 2012;63(6):414–9. [11] Nazim J, Fendler W, Starzyk J. Metabolic control and its variability are major risk factors for microalbuminuria in children with type 1 diabetes. Endokrynol Pol 2014;65(2):83–9. [12] Majewska KA, Majewski D, Skowronska B, Fichna P. Serum resistin concentrations in children with type 1 diabetes mellitus – negative relation to body fat mass. Endokrynol Pol 2014;65(5):342–7. [13] Lewitt A, Ma˛dro E, Krupienicz A. Podstawy teoretyczne i zastosowania analizy impedancji bioelektrycznej (BIA). Endokrynol Otyłos´c´ i Zaburzenia Przemiany Materii 2007;3(4):79–84.
[14] Kiess W, Anil M, Blum WF, Englaro P, Juul A, Attanasio A, et al. Serum leptin levels in children and adolescents with insulin-dependent diabetes mellitus in relation to metabolic control and body mass index. Eur J Endocrinol 1998; 138(5):501–9. [15] Soliman AT, Omar M, Assem HM, Nasr IS, Rizk MM, El Matary W, et al. Serum leptin concentrations in children with type 1 diabetes mellitus: relationship to body mass index, insulin dose, and glycemic control. Metabolism 2002;51(3): 292–6. [16] Szadkowska A, Wyka K, Młynarski W, Pietrzak I, Mianowska B, Bodalski J. Ste˛z˙enie leptyny a insulinowraz˙liwos´c´ u dzieci i młodziez˙y chorej na cukrzyce˛ typu 1. Pediatr Endocr Diabet Metab 2007;13(4):194–200. [17] Celi F, Bini V, Papi F, Santilli E, Castellani MS, Ferretti A, et al. Circulating adipocytokines in non-diabetic and type 1 diabetic children: relationship to insulin therapy, glycaemic control and pubertal development. Diabet Med 2006;23(6):660–5. [18] Myers SE, Albert SG, Haas MJ, Clifton D, Mooradian AD. Pubertal changes in serum leptin levels in adolescents with type 1 diabetes mellitus: a controlled longitudinal study. J Pediatr Endocrinol Metab 2004;17(12):1653–62. [19] Prolo P, Wong ML, Licinio J. Leptin. Int J Biochem Cell Biol 1998;30: 1285–90. [20] Blum WF, Englaro P, Hanitsch S, Juul A, Hertel NT, Muller J, et al. Plasma leptin levels in healthy children and adolescents: dependence on body mass index, body fat mass, gender, pubertal stage, and testosterone. J Clin Endocrinol Metab 1997;82(9):2904–10. [21] Galler A, Gelbrich G, Kratzsch J, Noack N, Kapellen T, Kiess W. Elevated serum levels of adiponectin in children, adolescents and young adults with type 1 diabetes and the impact of age, gender, body mass index and metabolic control: a longitudinal study. Eur J Endocrinol 2007;157(4): 481–9. [22] Hoffstedt J, Arvidsson E, Sjolin E, Wahlen K, Arner P. Adipose tissue adiponectin production and adiponectin serum concentration in human obesity and insulin resistance. J Clin Endocrinol Metab 2004;89(3):1391–6. [23] Cnop M, Havel PJ, Utzschneider KM, Carr DB, Sinha MK, Boyko EJ, et al. Relationship of adiponectin to body fat distribution, insulin sensitivity and plasma lipoproteins: evidence for independent roles of age and sex. Diabetologia 2003;46(4):459–69. [24] Huang KC, Lue BH, Yen RF, et al. Plasma adiponectin levels and metabolic factors in nondiabetic adolescents. Obes Res 2004;12(1):119–24. [25] Bacha F, Saad R, Gungor N, Arslanian S. Adiponectin in youth: relationship to visceral adiposity, insulin sensitivity, and b-cell function. Diabetes Care 2004;27(2):547–52. [26] Cieslak J, Bartz M, Stachowiak M, Skowronska B, Majewska KA, Harasymczuk J, et al. Effect of three common SNPs in 50 -flanking region of LEP and ADIPOQ genes on their expression in Polish obese children and adolescents. Mol Biol Rep 2012;39(4):3951–5. [27] Lindstrom T, Frystyk J, Hedman CA, Flyvbjerg A, Arnqvist HJ. Elevated circulating adiponectin in type 1 diabetes is associated with long diabetes duration. Clin Endocrinol (Oxf) 2006;65(6):776–82.