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Evaluation of nitric oxide metabolites in a group of subjects with metabolic syndrome
Diabetes & Metabolic Syndrome: Clinical Research & Reviews 6 (2012) 132–135
Contents lists available at SciVerse ScienceDirect
Diabetes & Metabolic Syndrome: Clinical Research & Reviews journal homepage: www.elsevier.com/locate/dsx
Original article
Evaluation of nitric oxide metabolites in a group of subjects with metabolic syndrome Gregorio Caimi, Eugenia Hopps *, Maria Montana, Davide Noto, Baldassare Canino, Rosalia Lo Presti, Maurizio R. Averna Dipartimento di Medicina Interna e Specialistica, Universita` di Palermo, Italy
A R T I C L E I N F O
A B S T R A C T
Keywords: Nitric oxide metabolites Oxidative stress Metabolic syndrome
Aim: To evaluate the concentration of metabolites (NO2 , NO3 ) of nitric oxide (NO) in metabolic syndrome (MS). Materials and methods: We enrolled 106 subjects (45 women and 61 men) with MS of which 43 (14 women and 27 men) with diabetes mellitus and 63 (31 women and 32 men) without diabetes mellitus, and 54 subjects (19 women and 35 men) as control group. The nitric oxide metabolites (nitrite + nitrate = NOx) were evaluated employing the Griess reagent. Results: In the whole group of MS subjects was evident, in comparison with control group, a significant increase in NOx. The same finding was also present between control group and diabetic subjects with MS and between control group and nondiabetic subjects with MS. No difference was observed between the two subgroups (diabetic and nondiabetic subjects with MS) about NOx. Contrasting information were obtained examining the linear regression among NOx, age, anthropometric profile, blood pressure values and glycometabolic pattern of subjects with MS. Conclusions: In MS subjects we found a significant increase in NOx not influenced by diabetes mellitus. The NOx is a parameter that must be considered in MS keeping in mind that its behavior is related to chronic inflammation that accompanies this clinical condition. ß 2012 Diabetes India. Published by Elsevier Ltd. All rights reserved.
1. Introduction As it is known, a direct measurement of NO itself is difficult, but the plasma concentration of its more stable end products (nitrite + nitrate NOx) can be considered a marker of the total NO synthesis. Although, at baseline, the main source of plasma NO is related to the endothelial NO synthase (eNOS), during several clinical conditions the inducible NOS (iNOS) is activated. This activation is especially related to the increase of different inflammatory molecules observed also in metabolic syndrome (MS); this syndrome is today one of the major public healthy problems and its prevalence increases worldwide with a subsequent predisposition to the cardiovascular diseases. Many papers about NOx are available in the main components of MS. Up to now few are instead the information’s concerning the behavior of NOx in MS. This parameter examined in MS subjects has showed its increase, in comparison with normal controls, respectively in men and women with MS without any difference
* Corresponding author. E-mail address: [email protected] (E. Hopps).
between diabetic and nondiabetic subjects [1]. An increase of NOx was noted with the increment of the MS components in general population in Japan [2]; the NOx increase was also observed in postmenopausal women with MS [3]. Considering this preamble our goal was to examine the nitric oxide metabolites (NOx) in subjects with metabolic syndrome subdivided according to the presence or not of diabetes mellitus. 2. Subjects and methods We enrolled 106 subjects with MS (45 women and 61 men), defined following the International Diabetes Federation (IDF) criteria [4]. Subsequently MS subjects were subdivided in diabetics (14 women and 29 men) and in nondiabetics (31 women and 32 men). Means and S.D. of age, anthropometric profile, blood pressure values and glycometabolic pattern are shown in Table 1. The Study was approved by Ethical Committee and each subject gave informed consent. On fasting venous blood the NO production was evaluated by a micromethod which measures the concentration of NO metabolites: nitrite and nitrate (NOx). In vivo NO has a very short half-life (less than 0.1 s) and is converted into nitrite (NO2 ), which has a half-life of a few minutes, and the more stable nitrate (NO3 ). Then
1871-4021/$ – see front matter ß 2012 Diabetes India. Published by Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.dsx.2012.09.012
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Table 1 Mean S.D. of age, anthropometric profile, blood pressure values and metabolic pattern in MS subjects as a whole group and subdivided in diabetics and nondiabetics.
Age (years) Waist circumference (cm) Body mass index (kg/m2) Systolic blood pressure (mmHg) Diastolic blood pressure (mmHg) Fasting glucose (mg/dl) Total cholesterol (mg/dl) HDL cholesterol (mg/dl) LDL cholesterol (mg/dl) Triglycerides (mg/dl)
All MS subjects
Diabetic MS subjects
Non-diabetic MS subjects
53.5 8.9 106.7 11.2 32.21 4.53 132.1 16.3 81.2 9.9 114.3 44.3 213.9 53.0 40.4 10.8 133.2 46.5 220.2 147.8
58.9 6.0 114.4 11.7 33.2 5.0 136.0 20.5 79.6 11.4 147.5 54.2 193.1 53.1 41.4 12.8 112.8 39.7 204.2 150.9
49.7 8.6 102.8 8.8 31.5 4.2 130.0 13.3 82.2 8.9 92.2 10.3 228.0 48.3 39.7 9.3 147.9 45.8 231.0 145.9
NOx represents almost only the nitrate concentration. In the laboratory method adopted by us, at first nitrate was converted into nitrite by a nitrate reductase, then nitrite was assessed by spectrophotometry after addition of Griess reagent [5]. The same parameter was also examined in a group of 54 normal subjects (19 women and 35 men). 3. Statistical analysis The values were expressed as means S.D.; the differences between subjects with metabolic syndrome, diabetics and nondiabetics, and normal controls were evaluated using Student’s t test for unpaired data; the correlations were performed employing the linear regression test. The null hypothesis was rejected for p values less than 0.05. 4. Results From the obtained data it was evident that, in comparison with normal subjects, in whole group of MS subjects was present a significant increase in NOx (N = 28.07 18.83; MS = 79.82 29.22, p < 0.001). This datum was also evident between normal subjects and diabetics subjects with MS (N = 28.07 18.83; DMS = 78.10 20.76, p < 0.001) and between normal subjects and nondiabetic subjects with MS (N = 28.07 18.83; NDMS = 80.99 33.93, p < 0.001). Regarding the same parameter no difference was observed between diabetic and nondiabetic subjects with MS. Examining the linear regression between NOx, age, anthropometric profile, blood pressure values and glycometabolic pattern, we observed in the whole group of MS subjects a positive correlation between NOx and triglycerides (r = 0.344, p < 0.001), in the subgroup of diabetic subjects a positive correlation between NOx and total cholesterol (r = 0.442, p < 0.01) and between NOx and LDL-cholesterol (r = 0.441, p < 0.01), and in the subgroup of nondiabetic subjects a positive correlation between NOx and triglycerides (r = 0.413, p < 0.001) and a negative correlation between NOx and HDL-cholesterol (r = 0.287, p < 0.05). 5. Discussion In MS subjects an increase of NOx was found and this datum was similar in the two subgroups, diabetics and nondiabetics. These data agree with the observations of several authors that examined this parameter in MS or in each component of MS [1,6– 15]. We retained that in this clinical condition the NOx increase is related in particular to a nitric oxide overproduction by macrophages, in which the NOS activation is caused by cytokines such as TNFa, IL-1b and interferon [16–18]. It must be underlined also that some authors have noted a positive association between NOx concentration and the number of MS components [1,19]. Although by some authors [20] no significant correlation was observed between NOx and IL-1b or between NOx and TNFa, by others [13]
was observed a positive correlation between TNFa and NOx while by others [8] this significant correlation was present only when were examined obese women with BMI greater than 40 kg/m2; this point shows however contrasting results and in fact other authors found a negative correlation between NOx and TNFa in type 2 diabetics [10]. The NOx increase noted in diabetic and nondiabetic subjects with MS need to be marked as the insulin-resistance that characterizes MS is accompanied by elevated levels of asymmetric dimethylarginine (ADMA) [2,21], an inhibitor of all isoforms of NO synthase [22,23]. Recently it has been examined the correlation between ADMA and NO synthesis in obese subjects with and without MS [24] and, although the data of this study underline how the ADMA values are higher in obeses with MS in comparison with normal controls and with obeses without MS, no statistical correlation between ADMA and NO synthesis was observed. This finding is different from which observed by others [25] who described a negative correlation between ADMA and NOx in female subjects with uncomplicated type 1 diabetes mellitus. Another consideration might regard the possible future of NOx. Theorically the NOx increase found in MS might have a positive role considering that NO2 and NO3 can be reduced to nitric oxide again [26–29] and that the latter act as an endogenous antiatherogenic molecule. This hypothetical event does not induce therefore to consider the need to weigh a suitable treatment for interfering with the iNOS activity. At this regard in fact might be rational to follow two different indications. On the one hand the use of therapeutic agents able to inhibit the NO synthase in the three separate isoforms [30,31] and on the other hand the use of flavonoids, such as epicatechin [32] and quercetin [33], that reduces the IL-1b level that, as it is known, in animal models stimulates iNOS activity. It must be further considered that even if some authors [34] have demonstrated in animal models that the raised expression of iNOS might contribute to obesity-induced insulin-resistance, others [35,36] have demonstrated that iNOS knockout does not prevent some aspects related to the insulin-resistance, such as raised blood pressure values or oxidative stress, while it seems to have a protective role on the negative effects of obesity on glucoregulation. The study of the linear regression among NOx, age, anthropometric profile, blood pressure values and glycometabolic pattern needs future investigations although the correlations observed between NOx and each parameter of the glycometabolic pattern seems to take on a particular interest. At this regard we have not noted any correlation between NOx and age although we know that the literature data have demonstrated a positive association between these two parameters [37,38]. From this study does not emerge any correlation between NOx and anthropometric profile, such as waistline and BMI, and between NOx and blood pressure values. At this regard up to now a
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significant correlation between NOx and anthropometric profile has been observed in Iranian healthy subjects [38] while a statistical correlation with blood pressure values besides in Iranian healthy subjects [38] has been also noted in African Americans [39]. Our data show that in diabetic subjects with MS was evident a positive correlation between NOx and total and LDL-cholesterol while in nondiabetic subjects was noted a negative correlation between NOx and HDL-cholesterol. The literature data do not confirm these findings in aged 20 years healthy subjects [38] and in women with overweight and obesity [8] while NOx has been correlated positively to the total cholesterol and LDL-cholesterol and negatively to HDL-cholesterol in adolescent subjects [40]. We observed a positive correlation between NOx and triglycerides in whole group of MS subjects and in the subgroup of nondiabetic subjects. This datum, that agrees with those described by other authors in postmenopausal women with MS [3] and in a general health population [38], is different from which observed by other authors [20] in normal-weight obese syndrome; the positive correlation between NOx and triglycerides has been also found in adolescents [40]. In conclusion, the NOx is a parameter that must be considered in MS bearing in mind that its behavior might be related to chronic inflammation that accompanies this clinical condition. This last sentence assumes major value considering that some authors previously have retained the NOx as survival marker in the elderly patients [41] even comparing its trend to which of albumin levels [42]. It is not possible however to conclude this examination regarding the NOx in MS without to look out also the exogenous NO sources. As it is known these sources in the clinical practice are besides the diet, the NO donors (such as nitroglycerin) and the NOS activators (such as inhibitors of angiotensin converting enzyme) that must be well considered since they are employed in the treatment of some components of this syndrome. Conflict of interest
[11]
[12]
[13]
[14]
[15]
[16] [17]
[18]
[19]
[20]
[21]
[22]
[23]
[24]
[25]
The authors declare that there is no conflict of interest. [26]
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American Journal of Hypertension 2004;17:549–52. Caimi G, Mule` G, Hopps E, Carollo C, Lo Presti R. Nitric oxide metabolites and oxidative stress in mild essential hypertension. Clinical Hemorheology and Microcirculation 2010;46:321–5. Moncada S, Palmer RMJ, Higgs EA. Nitric oxide: physiology, pathophysiology and pharmacology. Pharmacological Reviews 1991;43:109–42. Forstermann U, Kleinert H, Gath I, Schwarz P, Closs EI, Dun NJ. Expression and expressional control of nitric oxide synthases in various cell types. Advances in Pharmacology 1995;34:171–86. Weinberg JB. Nitric oxide production and nitric oxide syntases type 2 expression by human mononuclear phagocytes – a review. Molecular Medicine 1998;4:557–91. Ueyama J, Kondo T, Imai R, Kimata A, Yamamoto K, Suzuki K. Association of serum NO(x) level with clustering of metabolic syndrome components in middle-aged and elderly general populations in Japan. Environmental Health and Preventive Medicine 2008;13(1):36–42. 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Metabolism Clinical and Experimental 2012;61(5):680–8. Pitocco D, Zaccardi F, Di Stasio E, Romitelli F, Martini F, Luca Scaglione G, et al. Role of asymmetric-dimethyl-L-arginine (ADMA) and nitrite/nitrate (NOx) in the pathogenesis of oxidative stress in female subjects with uncomplicated type 1 diabetes mellitus. Diabetes Research and Clinical Practice 2009;86:173–6. Millar TM, Stevens CR, Benjamin N, Eisenthal R, Harrison R, Blake DR. Xanthine oxidoreductase catalyses the reduction of nitrates and nitrite to nitric oxide under hypoxic conditions. FEBS Letters 1998;427:225–8. Modin A, Bjo¨rne H, Herulf M, Alving K, Weitzberg E, Lundberg JO. Nitritederived nitric oxide: a possible mediator of ‘acidic-metabolic’ vasodilation. Acta Physiologica Scandinavica 2001;171:9–16. Cosby K, Partovi KS, Crawford JH, Patel RP, Reiter CD, Martyr S, et al. Nitrite reduction to nitric oxide by deoxyhemoglobin vasodilates the human circulation. Nature Medicine 2003;9(12):1498–505. Lundberg JO, Govoni M. Inorganic nitrate is a possible source for systemic generation of nitric oxide. Free Radical Biology and Medicine 2004;37:395– 400. Ogden JE, Moore PK. Inhibition of nitric oxide synthase-potential for a novel class of therapeutic agent? Trends in Biotechnology 1995;13:70–8. Liu ZQ, Wildurth SM, Zhou HH. Specificity of inducible nitric-oxide synthase inhibitors: prospects for their clinical therapy. Acta Pharmacologica 1999;20:1052–6. Kim MJ, Ryu GR, Kang JH, Sim SS, Min DS, Rhie DJ, et al. Inhibitory effects of epicatechin on interleukin-1beta-induced inducible nitric oxide synthase expression in RINm5F cells and rat pancreatic islets by down-regulation of NF-kappaB activation. Biochemical Pharmacology 2004;68(9):1775–85. Cho JM, Chang SY, Kim DB, Needs PW, Jo YH, Kim MJ. Effects of physiological quercetin metabolites on interleukin-1b-induced inducible NOS expression. The Journal of Nutritional Biochemistry 2012;23(11):1394–402. Tsuchiya K, Sakai H, Suzuki N, Iwashima F, Yoshimoto T, Shichiri M, Hirata Y. Chronic blockade of nitric oxide synthesis reduces adiposity and improves insulin resistance in high fat-induced obese mice. Endocrinology 2007;148:4548–56. Noronha BT, Li JM, Wheatcroft SB, Shah AM, Kearney MT. Inducible nitric oxide synthase has divergent effects on vascular and metabolic function in obesity. Diabetes 2005;54:1082–9. Cha HN, Kim YW, Kim JY, Kim YD, Song IH, Min KN, Park SY. Lack of inducible nitric oxide synthase does not prevent aging-associated insulin resistance. Experimental Gerontology 2010;45(9):711–8.
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[40] Choi JW. Enhanced nitric oxide production is closely associated with serum lipid concentrations in adolescents. Clinica Chimica Acta 2004;347:151–6. [41] Hayashi T, Nomura H, Osawa M, Funami J, Miyazaki A, Iguchi A. Nitric oxide metabolites are associated with survival in older patients. Journal of the American Geriatrics Society 2007;55:1389–403. [42] Osawa M, Hayashi T, Nomura H, Funami J, Miyazaki A, Ignarro LJ, et al. Nitric oxide (NO) is a new clinical biomarker of survival in the elderly patients and its efficacy might be nearly equal to albumin. Nitric Oxide 2007;16:157–63.
Contents lists available at SciVerse ScienceDirect
Diabetes & Metabolic Syndrome: Clinical Research & Reviews journal homepage: www.elsevier.com/locate/dsx
Original article
Evaluation of nitric oxide metabolites in a group of subjects with metabolic syndrome Gregorio Caimi, Eugenia Hopps *, Maria Montana, Davide Noto, Baldassare Canino, Rosalia Lo Presti, Maurizio R. Averna Dipartimento di Medicina Interna e Specialistica, Universita` di Palermo, Italy
A R T I C L E I N F O
A B S T R A C T
Keywords: Nitric oxide metabolites Oxidative stress Metabolic syndrome
Aim: To evaluate the concentration of metabolites (NO2 , NO3 ) of nitric oxide (NO) in metabolic syndrome (MS). Materials and methods: We enrolled 106 subjects (45 women and 61 men) with MS of which 43 (14 women and 27 men) with diabetes mellitus and 63 (31 women and 32 men) without diabetes mellitus, and 54 subjects (19 women and 35 men) as control group. The nitric oxide metabolites (nitrite + nitrate = NOx) were evaluated employing the Griess reagent. Results: In the whole group of MS subjects was evident, in comparison with control group, a significant increase in NOx. The same finding was also present between control group and diabetic subjects with MS and between control group and nondiabetic subjects with MS. No difference was observed between the two subgroups (diabetic and nondiabetic subjects with MS) about NOx. Contrasting information were obtained examining the linear regression among NOx, age, anthropometric profile, blood pressure values and glycometabolic pattern of subjects with MS. Conclusions: In MS subjects we found a significant increase in NOx not influenced by diabetes mellitus. The NOx is a parameter that must be considered in MS keeping in mind that its behavior is related to chronic inflammation that accompanies this clinical condition. ß 2012 Diabetes India. Published by Elsevier Ltd. All rights reserved.
1. Introduction As it is known, a direct measurement of NO itself is difficult, but the plasma concentration of its more stable end products (nitrite + nitrate NOx) can be considered a marker of the total NO synthesis. Although, at baseline, the main source of plasma NO is related to the endothelial NO synthase (eNOS), during several clinical conditions the inducible NOS (iNOS) is activated. This activation is especially related to the increase of different inflammatory molecules observed also in metabolic syndrome (MS); this syndrome is today one of the major public healthy problems and its prevalence increases worldwide with a subsequent predisposition to the cardiovascular diseases. Many papers about NOx are available in the main components of MS. Up to now few are instead the information’s concerning the behavior of NOx in MS. This parameter examined in MS subjects has showed its increase, in comparison with normal controls, respectively in men and women with MS without any difference
* Corresponding author. E-mail address: [email protected] (E. Hopps).
between diabetic and nondiabetic subjects [1]. An increase of NOx was noted with the increment of the MS components in general population in Japan [2]; the NOx increase was also observed in postmenopausal women with MS [3]. Considering this preamble our goal was to examine the nitric oxide metabolites (NOx) in subjects with metabolic syndrome subdivided according to the presence or not of diabetes mellitus. 2. Subjects and methods We enrolled 106 subjects with MS (45 women and 61 men), defined following the International Diabetes Federation (IDF) criteria [4]. Subsequently MS subjects were subdivided in diabetics (14 women and 29 men) and in nondiabetics (31 women and 32 men). Means and S.D. of age, anthropometric profile, blood pressure values and glycometabolic pattern are shown in Table 1. The Study was approved by Ethical Committee and each subject gave informed consent. On fasting venous blood the NO production was evaluated by a micromethod which measures the concentration of NO metabolites: nitrite and nitrate (NOx). In vivo NO has a very short half-life (less than 0.1 s) and is converted into nitrite (NO2 ), which has a half-life of a few minutes, and the more stable nitrate (NO3 ). Then
1871-4021/$ – see front matter ß 2012 Diabetes India. Published by Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.dsx.2012.09.012
G. Caimi et al. / Diabetes & Metabolic Syndrome: Clinical Research & Reviews 6 (2012) 132–135
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Table 1 Mean S.D. of age, anthropometric profile, blood pressure values and metabolic pattern in MS subjects as a whole group and subdivided in diabetics and nondiabetics.
Age (years) Waist circumference (cm) Body mass index (kg/m2) Systolic blood pressure (mmHg) Diastolic blood pressure (mmHg) Fasting glucose (mg/dl) Total cholesterol (mg/dl) HDL cholesterol (mg/dl) LDL cholesterol (mg/dl) Triglycerides (mg/dl)
All MS subjects
Diabetic MS subjects
Non-diabetic MS subjects
53.5 8.9 106.7 11.2 32.21 4.53 132.1 16.3 81.2 9.9 114.3 44.3 213.9 53.0 40.4 10.8 133.2 46.5 220.2 147.8
58.9 6.0 114.4 11.7 33.2 5.0 136.0 20.5 79.6 11.4 147.5 54.2 193.1 53.1 41.4 12.8 112.8 39.7 204.2 150.9
49.7 8.6 102.8 8.8 31.5 4.2 130.0 13.3 82.2 8.9 92.2 10.3 228.0 48.3 39.7 9.3 147.9 45.8 231.0 145.9
NOx represents almost only the nitrate concentration. In the laboratory method adopted by us, at first nitrate was converted into nitrite by a nitrate reductase, then nitrite was assessed by spectrophotometry after addition of Griess reagent [5]. The same parameter was also examined in a group of 54 normal subjects (19 women and 35 men). 3. Statistical analysis The values were expressed as means S.D.; the differences between subjects with metabolic syndrome, diabetics and nondiabetics, and normal controls were evaluated using Student’s t test for unpaired data; the correlations were performed employing the linear regression test. The null hypothesis was rejected for p values less than 0.05. 4. Results From the obtained data it was evident that, in comparison with normal subjects, in whole group of MS subjects was present a significant increase in NOx (N = 28.07 18.83; MS = 79.82 29.22, p < 0.001). This datum was also evident between normal subjects and diabetics subjects with MS (N = 28.07 18.83; DMS = 78.10 20.76, p < 0.001) and between normal subjects and nondiabetic subjects with MS (N = 28.07 18.83; NDMS = 80.99 33.93, p < 0.001). Regarding the same parameter no difference was observed between diabetic and nondiabetic subjects with MS. Examining the linear regression between NOx, age, anthropometric profile, blood pressure values and glycometabolic pattern, we observed in the whole group of MS subjects a positive correlation between NOx and triglycerides (r = 0.344, p < 0.001), in the subgroup of diabetic subjects a positive correlation between NOx and total cholesterol (r = 0.442, p < 0.01) and between NOx and LDL-cholesterol (r = 0.441, p < 0.01), and in the subgroup of nondiabetic subjects a positive correlation between NOx and triglycerides (r = 0.413, p < 0.001) and a negative correlation between NOx and HDL-cholesterol (r = 0.287, p < 0.05). 5. Discussion In MS subjects an increase of NOx was found and this datum was similar in the two subgroups, diabetics and nondiabetics. These data agree with the observations of several authors that examined this parameter in MS or in each component of MS [1,6– 15]. We retained that in this clinical condition the NOx increase is related in particular to a nitric oxide overproduction by macrophages, in which the NOS activation is caused by cytokines such as TNFa, IL-1b and interferon [16–18]. It must be underlined also that some authors have noted a positive association between NOx concentration and the number of MS components [1,19]. Although by some authors [20] no significant correlation was observed between NOx and IL-1b or between NOx and TNFa, by others [13]
was observed a positive correlation between TNFa and NOx while by others [8] this significant correlation was present only when were examined obese women with BMI greater than 40 kg/m2; this point shows however contrasting results and in fact other authors found a negative correlation between NOx and TNFa in type 2 diabetics [10]. The NOx increase noted in diabetic and nondiabetic subjects with MS need to be marked as the insulin-resistance that characterizes MS is accompanied by elevated levels of asymmetric dimethylarginine (ADMA) [2,21], an inhibitor of all isoforms of NO synthase [22,23]. Recently it has been examined the correlation between ADMA and NO synthesis in obese subjects with and without MS [24] and, although the data of this study underline how the ADMA values are higher in obeses with MS in comparison with normal controls and with obeses without MS, no statistical correlation between ADMA and NO synthesis was observed. This finding is different from which observed by others [25] who described a negative correlation between ADMA and NOx in female subjects with uncomplicated type 1 diabetes mellitus. Another consideration might regard the possible future of NOx. Theorically the NOx increase found in MS might have a positive role considering that NO2 and NO3 can be reduced to nitric oxide again [26–29] and that the latter act as an endogenous antiatherogenic molecule. This hypothetical event does not induce therefore to consider the need to weigh a suitable treatment for interfering with the iNOS activity. At this regard in fact might be rational to follow two different indications. On the one hand the use of therapeutic agents able to inhibit the NO synthase in the three separate isoforms [30,31] and on the other hand the use of flavonoids, such as epicatechin [32] and quercetin [33], that reduces the IL-1b level that, as it is known, in animal models stimulates iNOS activity. It must be further considered that even if some authors [34] have demonstrated in animal models that the raised expression of iNOS might contribute to obesity-induced insulin-resistance, others [35,36] have demonstrated that iNOS knockout does not prevent some aspects related to the insulin-resistance, such as raised blood pressure values or oxidative stress, while it seems to have a protective role on the negative effects of obesity on glucoregulation. The study of the linear regression among NOx, age, anthropometric profile, blood pressure values and glycometabolic pattern needs future investigations although the correlations observed between NOx and each parameter of the glycometabolic pattern seems to take on a particular interest. At this regard we have not noted any correlation between NOx and age although we know that the literature data have demonstrated a positive association between these two parameters [37,38]. From this study does not emerge any correlation between NOx and anthropometric profile, such as waistline and BMI, and between NOx and blood pressure values. At this regard up to now a
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significant correlation between NOx and anthropometric profile has been observed in Iranian healthy subjects [38] while a statistical correlation with blood pressure values besides in Iranian healthy subjects [38] has been also noted in African Americans [39]. Our data show that in diabetic subjects with MS was evident a positive correlation between NOx and total and LDL-cholesterol while in nondiabetic subjects was noted a negative correlation between NOx and HDL-cholesterol. The literature data do not confirm these findings in aged 20 years healthy subjects [38] and in women with overweight and obesity [8] while NOx has been correlated positively to the total cholesterol and LDL-cholesterol and negatively to HDL-cholesterol in adolescent subjects [40]. We observed a positive correlation between NOx and triglycerides in whole group of MS subjects and in the subgroup of nondiabetic subjects. This datum, that agrees with those described by other authors in postmenopausal women with MS [3] and in a general health population [38], is different from which observed by other authors [20] in normal-weight obese syndrome; the positive correlation between NOx and triglycerides has been also found in adolescents [40]. In conclusion, the NOx is a parameter that must be considered in MS bearing in mind that its behavior might be related to chronic inflammation that accompanies this clinical condition. This last sentence assumes major value considering that some authors previously have retained the NOx as survival marker in the elderly patients [41] even comparing its trend to which of albumin levels [42]. It is not possible however to conclude this examination regarding the NOx in MS without to look out also the exogenous NO sources. As it is known these sources in the clinical practice are besides the diet, the NO donors (such as nitroglycerin) and the NOS activators (such as inhibitors of angiotensin converting enzyme) that must be well considered since they are employed in the treatment of some components of this syndrome. Conflict of interest
[11]
[12]
[13]
[14]
[15]
[16] [17]
[18]
[19]
[20]
[21]
[22]
[23]
[24]
[25]
The authors declare that there is no conflict of interest. [26]
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