- Email: [email protected]
Muscle and Fat Metabolism in Obesity After Kidney Transplantation: No Effect of Peritoneal Dialysis or Hemodialysis
ORIGINAL RESEARCH
Muscle and Fat Metabolism in Obesity After Kidney Transplantation: No Effect of Peritoneal Dialysis or Hemodialysis Vladimır Teplan, MD, PhD, DSc,*† Jan Maly, MD, PhD,*† Robert G€urlich, MD, PhD,‡ Vladimır Teplan, Jr., MD,‡ Michal Kudla,§ Jan Pit’ha, MD, PhD,{** enolt, MD, PhD,§§ Jaroslav Racek, MD, DSc,†† Martin Haluzık, MD, DSc,‡‡ Ladislav S tollova, DiS*† and Milena S Our prospective study analyzed selected adipocytokines: adiponectin (ADPN), leptin, visfatin, and asymmetric dimethylarginine (ADMA) in the plasma of renal transplant recipients previously treated by peritoneal dialysis and hemodialysis. A total of 70 patients were on follow-up for 12 months after transplantation. Of these, 30 patients (group I) developed obesity, and 40 patients were nonobese (group II). All were receiving standard immunosuppressive therapy (cyclosporine A or tacrolimus and mycophenolate mofetil, with prednisone added in the early posttransplant period) and did not differ statistically in HLA typing, age, sex, duration of previous dialysis, history of cardiovascular disease, and rate of rejection episodes. At the end of the study period, there were significant differences between groups I and II (t test, analysis of variance) in plasma: ADPN, 22.30 6 10.2 versus 14.3 6 7.2 mg/mL; visfatin, 1.7 6 0.1 versus 1.2 6 0.1 ng/mL; ADMA, 3.60 6 0.47 versus 2.10 6 0.36 mmol/L; P , .01; leptin, 55.6 6 10.2 versus 25.6 6 8.3 ng/L; P , .01 (P , .02). In conclusion, an increase of body fat after renal transplantation was associated with an increase of ADMA and leptin, TNF-a, MCP-1, and visfatin and decrease of adiponectin. Our study documented there was now long-term beneficial metabolic effect of peritoneal dialysis in developing posttransplant obesity. Ó 2012 by the National Kidney Foundation, Inc. All rights reserved.
O
BESITY IS ONE of the most common complications in renal transplant recipients and influences long-term outcome.1 It is characterized by the abdominal (visceral) type of obesity, which affects both men and women, with prevalence between 25% and 35% in the
first posttransplant year. A successful transplantation restores renal function as a major positive factor, but the administration of immunosuppressive agents (in particular, prednisone) and a generally increased dietary energy intake result in an increase in the incidence of obesity and
*Department of Nephrology, Transplant Centre, Institute for Clinical and Experimental Medicine, Prague, Czech Republic. †Institute for Postgraduate Education, Prague, Czech Republic. ‡Department of Surgery, Charles University, Prague, Czech Republic. §Department of Surgery, Transplant Centre, Institute for Clinical and Experimental Medicine, Prague, Czech Republic. {Laboratory for Atherosclerosis Research, Institute for Clinical and Experimental Medicine, Prague, Czech Republic. **Department of Experimental Medicine, Institute for Clinical and Experimental Medicine, Prague, Czech Republic. ††Institute of Clinical Biochemistry and Hematology, Charles University, Pilsen, Czech Republic. ‡‡3rd Department of Internal Medicine, Charles University, Prague, Czech Republic.
§§Department of Experimental and Clinical Rheumatology, Institute of Rheumatology, Charles University, Prague, Czech Republic. Funding Support: The study was supported by grant MS/105293/2009 awarded by the Internal Grant Agency of the Czech Republic; and Research Project MZO00023001 awarded by Ministry of Health of the Czech Republic. Address reprint requests to Vladimir Teplan, MD, PhD, DSc, Department of Nephrology, Transplant Centre, Institute for Clinical and Experimental Medicine, Videnska 1958/9, 140 21 Prague-4, Czech Republic. E-mail: [email protected] Ó 2012 by the National Kidney Foundation, Inc. All rights reserved. 1051-2276/$36.00 doi:10.1053/j.jrn.2011.10.016
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Journal of Renal Nutrition, Vol 22, No 1 (January), 2012: pp 166-170
ADIPOCYTOKINES AND ADMA IN OBESITY AFTER RENAL TRANSPLANTATION
even the development of metabolic syndrome in a number of cases.2 Obesity is accompanied by an increased local inflammatory response in adipose tissue, as measured by immunocompetent cell infiltration, that in turn leads to increased production of proinflammatory factors such as interleukin 6 (IL-6), tumor necrosis factor a (TNF-a), and monocyte chemoattractant protein-1 (MCP-1).3 Increased release of proinflammatory factors from adipose tissue may contribute to a systemic subclinical inflammatory response in patients with obesity and thus promote the development of insulin resistance and atherosclerosis in these patients.4 Vascular dysfunction may be linked to reduced nitric oxide (NO) bioactivity and increased circulating concentration of the endogenous NO synthase inhibitor, asymmetric dimethyl L-arginine (ADMA).5 It is currently not known whether increased ADMA levels depend only on renal function or constitute a feedback response to other metabolic disorders. Decreases of ADMA after renal transplantation were associated with improvements in endothelial function.6 In contrast, adiponectin (ADPN), the most abundant adipose-tissue protein, has antiatherosclerotic and anti-inflammatory functions.7 It decreases the expression of the adhesion molecules in endothelial cells and suppresses the cytokine production and foam cell transformation of macrophages, which indicates that ADPN is an essential protein for endothelial function. In nonobese renal transplant patients, ADPN increased immediately after transplantation, compared with the pretransplant period.8 Some studies in patients with chronic renal failure have confirmed that peritoneal dialysis (PD) predicts better patient survival compared with those on hemodialysis (HD) over the first 2 years. A beneficial effect of PD on early development of graft function has been reported after renal transplantation.9 However, some results of retrospective studies assessing the benefit of HD or PD on the posttransplant course are conflicting.10 In the present study, by comparing findings in obese and nonobese transplant patients, we tested the hypothesis whether there are differences between obese and nonobese transplant patients depending on previous PD or HD. We also evaluated how adipose tissue might contribute to the systemic inflammatory state through increased production of proinflammatory cytokines.
167
Patients and Methods The study was approved by the Human Ethical Review Committee, Institute for Clinical and Experimental Medicine, Prague, and complied with the Declaration of Helsinki, including the current revision and good Clinical Practice Guidelines. The procedures followed were in accordance with institutional guidelines. All patients gave written informed consent before being enrolled in the study. A total of 70 patients were on follow-up for 12 months. Of these, 30 patients (group I) developed obesity (before transplantation on PD and HD), and 40 patients were nonobese (group II). All were receiving standard immunosuppressive therapy (cyclosporine A or tacrolimus and mycophenolate mofetil, with prednisone added in the early posttransplant period) and did not differ statistically in HLA typing, age, sex, duration of previous dialysis, history of cardiovascular disease, and rate of rejection episodes. The patients were evaluated anthropometrically at basal state and after 12 months. All were weighed and measured and BMI calculated. An ADMA ELISA kit (DLD Diagnostic GmbH, Hamburg, Germany) and an AUTO-EIA II microplate reader (Labsystems Oy, Espoo, Finland) were used for ADMA quantification; this competitive method uses the microtiter plate format. Serum levels of adiponectin were measured using a commercial ELISA kit (BioVendor, Brno, Czech Republic; Linco Research, St. Charles, MI). Serum concentrations of IL-6, TNF-a, and MCP-1 were determined using a human serum adipokine LINCOplex kit on a Luminex 200 instrument (Linco Research). Serum concentrations of C-reactive protein (CRP) were measured using an ultrasensitive CRP ELISA kit (DSL, Oxon, United Kingdom). Serum visfatin levels were measured by enzyme immunoassay (ELISA) according to the manufacturer’s protocol (BioVision Research Products, Mountain View, CA). Glomerular filtration rates were estimated by inulin clearance. Inulin (polyfructosane S) was analyzed using anthrone on a spectrophotometer at wavelength 580 nm (Antelie Light Secoman, France). Serum albumin was determined using bromocresol purple in a routine procedure in the Department of Clinical Biochemistry. Total cholesterol, highdensity lipoprotein cholesterol, and triglycerides were determined using an enzymatic colorimetric method with an Olympus AU 600 analyzer and
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reagents from Olympus Diagnostics, GmbH (Hamburg, Germany). LDL cholesterol was calculated using Friedewald formula. Serum insulin concentrations were measured using a commercial RIA kit (CisBio International, Lyon, France); glycated hemoglobin (HbA1c) was analyzed using liquid chromatography on a Tosoh HLC-723 G7 (Shiba, Minato-Ku, Tokyo, Japan), and proteinuria per 24 hours was analyzed by photometry with pyrogallol red using an Olympus 800 system (Hamburg, Germany).
Statistical Analysis SigmaStat software (SPSS Inc., Chicago, IL) was used for the statistical analysis. A t test or Mann– Whitney rank sum test was used to compare data from the 2 groups of chronic kidney disease patients. The relations between respective variables were assessed using Pearson or Spearman correlation coefficient, as appropriate. Results were considered statistically significant at P ,.05.
Results Basic clinical characteristics of the 2 groups of transplant patients are listed in Table 1: the groups
did not differ significantly with respect to age, sex, or renal function measured by inulin clearance. Group I had significantly higher serum levels of ADMA, leptin, visfatin, TNF-a, MCP-1, IL-6, HbA1c, proteinuria, low-density lipoprotein cholesterol, triglycerides, blood pressure, and insulin and significantly lower adiponectin levels than group II, the control group. Group I also showed a significant increase in hsCRP levels compared with group II. With respect to lipid metabolism parameters, there were small but significant increases in the total serum cholesterol and lowdensity lipoprotein cholesterol levels in group I (6.1 6 1.2 vs. 5.8 6 2.2 and 3.9 6 1.2 vs. 3.6 6 1.0 mmol/L, P ,.02). More marked were changes in triglycerides in group I (3.9 6 1.6 vs. 2.8 6 1.0 mmol/L, P , .01). Similarly, group I showed an increase in HbA1c (5.3% 6 1.4% vs. 4.2% 6 0.9%, P , .02) and plasma insulin concentration (365.3 6 40.1 vs. 292.4 6 49.1 mU/L, P ,.02). Moreover, there were also differences between the 2 groups in proteinuria, which was significantly higher in group I (3.5 6 2.2 vs. 2.8 6 1.1 g/L, P , .02). A slight but significant difference was also found in systolic and diastolic blood pressures (P ,.02 for systolic and P ,.05 for diastolic
Table 1. Clinical and Biochemical Characteristics Group I (Obese Transplant Subjects) and Group II (Control, Nonobese Transplant Subjects) Parameter Cin (mL/minute/1.73 m2) BMI (kg/m2) WHR ADMA (mmol/L) ADPN (mg/mL) TNF-a (pg/mL) MCP-1 (pg/mL) Il-6 (pg/mL) Visfatin (ng/mL) HbA1c (%) Insulin (pg/mL) CRP (mg/L) Leptin (ng/L) Proteinuria (g/24 hour) Cholesterol (mmol/L) LDL cholesterol (mmol/L) Triglycerides (mmol/L) System BP (mm Hg) Diastolic BP (mm Hg)
Group I (n 5 30)
Group II (n 5 40)
Statistical Significance: Group I Versus Group II
69.7 6 9.9 32.2 6 3.3 0.88 6 0.05 3.6 6 0.4 14.3 6 4.2 8.6 6 2.3 195 6 53 14.8 6 4.2 1.7 6 0.1 5.3 6 1.4 365.3 6 40.1 14.9 6 4.5 55.6 6 10.2 3.5 6 2.2 6.1 6 1.2 3.9 6 1.2 3.9 6 1.6 135 6 10 90 6 9
71.2 6 9.7 25.1 6 4.0 0.81 6 0.04 2.1 6 0.3 22.3 6 7.1 5.3 6 1.7 112 6 40 9.0 6 3.1 1.2 6 0.1 4.2 6 0.9 292.4 6 49.1 7.4 6 2.5 25.6 6 8.3 2.3 6 2.1 5.8 6 2.2 3.6 6 1.0 2.8 6 1.0 125 6 7 82 6 7
NS P , .01 P , .02 P , .01 P , .01 P , .05 P , .05 P , .05 P , .05 P , .02 P , .02 P , .02 P , .01 P , .02 P , .02 P , .05 P , .01 P , .02 P , .05
Cin, inulin clearance; TNF-a, tumor necrosis factor a; BMI, body mass index; IL-6, interleukin 6; WHR, waist-to-hip ratio; MCP-1, monocyte chemoattractant protein; ADMA, asymmetric dimethylarginine; HbA1c, glycated Hb; ADPN, adiponectin; CRP, C- reactive protein; NS, nonsignificant. Statistical significance is from unpaired t test or Mann–Whitney rank sum test. Values are means 6 standard errors of the means.
ADIPOCYTOKINES AND ADMA IN OBESITY AFTER RENAL TRANSPLANTATION
blood pressure). As shown in Figure 1, levels of ADMA, IL-6, and TNF-a were significantly higher in group I.
Discussion Some studies in patients with chronic renal failure have confirmed that PD predicts better patient survival compared with those on HD over the first 2 years after renal transplantation. A beneficial effect of PD on early development of graft function and some metabolic parameters have been reported after renal transplantation.9 However, retrospective studies assessing the benefit of HD or CAPD on the posttransplant course are conflicting.10 In our study, we have analyzed posttransplant obesity in both groups 12 months after kidney transplantation. Adipose tissue has been recognized as an important endocrine organ producing numerous hormones and cytokines, including proinflammatory factors such as TNF-a and IL-6. Furthermore, production of proinflammatory cytokines is increased in obese patients, suggesting the pathogenetic contribution of these factors in the development of insulin resistance, vascular disease, and possibly other related pathologies.11 Experimental and clinical studies have shown that adipose tissue of obese individuals is characterized by increased infiltration by immunocompetent cells that become the most important producers of proinflammatory cytokines, which was also shown in our previous study.12 An increase in circulating levels of proinflammatory cytokines after transplantation is accompanied by increased levels of adiponectin,
169
an adipose tissue-derived hormone with antiinflammatory and antiatherogenic properties. In contrast, decreased adiponectin levels are normally found in nonrenal patients with obesity, atherosclerosis, insulin resistance, and type 2 diabetes mellitus, whereas leanness and increased levels of physical activity are accompanied by hyperadiponectinemia.13,14 The increased levels of ADMA in our patient could be attributed to renal impairment. Kidney transplantation normalizes symmetric dimethyl arginine, whereas ADMA levels remain elevated. Obesity and weight reduction have been shown to be associated with changes in endothelial function.15 Studies of kidney transplant recipients indicate that as renal function improves, the originally increased ADMA levels decline, but in spite of the presence of excellent kidney graft function, ADMA levels remain 2 to 3 times higher compared with those in healthy individuals. This finding may, in part, support our finding of weak correlation between ADMA and glomerular filtration rate. Visfatin is ubiquitously expressed in many tissues and was recently demonstrated to be an adipocytokine that is upregulated in visceral fat cells. Visfatin exerts insulin mimetic effects and plays a role in innate immunity and inflammation. In addition, visfatin has potent proinflammatory and destructive properties.16
Conclusion Our data show that expression of proinflammatory cytokines is increased in obese persons after kidney transplantation and is not dependent on previous pretransplant replacement therapy modality. Moreover, serum concentrations of several proinflammatory cytokines are higher, and insulin resistance is more pronounced in these patients. Preferential effect of previous PD was not confirmed when posttransplant obesity was developed.
Practical Application
Figure 1. Serum concentrations of asymmetric dimethylarginine, adiponectin, interleukin 6, and tumor necrosis factor a in obese transplant patients (group I, open bars) and in nonobese transplant patients (group II, filled bars).
Obesity after transplantation is a risk factor for cardiovascular complications. Our prospective study analyzed selected adipocytokines (adiponectin, leptin, visfatin) and asymmetric dimethylarginine. We did not confirm significant differences in these parameters in patients previously on peritoneal dialysis or hemodialysis.
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Acknowledgment The authors thank Ms V. Turkova, J. Skibova (Manager), and R. Prahl (Manager) for their technical assistance.
References 1. Gore JL, Pham PT, Danovitch M, et al. Obesity and outcome following renal transplantation. Am J Transplant. 2006;6:357-363. 2. Meier-Kriesche HV, Arndorfer JA, Kaplan B. The impact of body mass index on renal transplant outcomes: a significant independent risk factor for graft failure and patient death. Transplantation. 2002;73:70-74. 3. Kasap B, Soylu A, T€ urkmen M, Karakcu S, Bora S, G€ ulay H. Effect of obesity and overweight on cyclosporine blood levels and renal functions in renal adolescent recipients. Transplant Proc. 2006;38:463-465. 4. Armstrong KA, Campbell SB, Hawley CH, et al. Impact of obesity on renal transplant outcomes. Nephrology. 2005;10:405-413. 5. Kielstein JT, Fr€ ohlich JC, Haller H, Fliser D. ADMA: An atherosclerotic disease mediating agent in patients with renal disease? Nephrol Dial Transplant. 2001;16:1742-1745. 6. Yilmaz MI, Saglam M, Caglar K, et al. Endothelial functions improve with decrease in asymmetric dimethylarginine (ADMA) levels after renal transplantation. Transplantation. 2005;80:1660-1666. 7. Zoccali C, Mallamaci F, TripepiG, et al. Adiponectin, metabolic risk factors, and cardiovascular events among patients with end stage renal disease. J Am Soc Nephrol. 2005;13:134-141. 8. Chudek J, Adamczak M, Karkoszka H, et al. Plasma adiponectin concentration before and after successful kidney transplantation. Transplant Proc. 2003;35:2186-2189.
9. Van Biesen W, Vanholder R, Van Loo A, Van Der Vennet M, Lameire N. Peritoneal dialysis favorably influences early graft function after renal transplantation compared to hemodialysis. Transplantation. 2000;69:508-514. 10. Goldfarb-Rumyantzev AS, Hurdle JF, Scandling JD, Baird BC, Cheung AK. The role of pretransplantation replacement therapy modality in kidney allograft and recipient survival. Am J Kidney Dis. 2005;46:537-549. 11. Teplan V, Sch€ uck O, Racek J, et al. Asymmetric dimethylarginine in obesity after renal transplantation. J Ren Nutr. 2008;18:513-520. 12. Teplan V Jr, Vyhnanek F, G€ urlich R, et al. Increased proinflammatory cytokine production in adipose tissue of obese patients with chronic kidney disease. Wien Klin Wochenschr. 2010;122: 466-473. 13. Arita Y, Kihara S, Ouchi N, et al. Paradoxical decrease of an adipose-specific protein, adiponectin, in obesity. Biochem Biophys Res Commun. 1999;257:79-83. 14. Yang WS, Lee WJ, Funahashi T, et al. Weight reduction increases plasma levels of an adipose-derived anti-infl ammatory protein, adiponectin. J Clin Endocrinol Metab. 2001;86: 3815-3915. 15. Sciaqua A, Candigliota M, Ceravolo R, et al. Weight loss in combination in human obesity. Diabetes Care. 2003;26: 1673-1678. 16. Senolt L, Kryst ufkova O, Hulejova H, et al. The level of serum visfatin (PBEF) is associated with total number of B cells in patients with rheumatoid arthritis and decreases following B cell depletion therapy. Cytokine. 2011;55:116-121.
Muscle and Fat Metabolism in Obesity After Kidney Transplantation: No Effect of Peritoneal Dialysis or Hemodialysis Vladimır Teplan, MD, PhD, DSc,*† Jan Maly, MD, PhD,*† Robert G€urlich, MD, PhD,‡ Vladimır Teplan, Jr., MD,‡ Michal Kudla,§ Jan Pit’ha, MD, PhD,{** enolt, MD, PhD,§§ Jaroslav Racek, MD, DSc,†† Martin Haluzık, MD, DSc,‡‡ Ladislav S tollova, DiS*† and Milena S Our prospective study analyzed selected adipocytokines: adiponectin (ADPN), leptin, visfatin, and asymmetric dimethylarginine (ADMA) in the plasma of renal transplant recipients previously treated by peritoneal dialysis and hemodialysis. A total of 70 patients were on follow-up for 12 months after transplantation. Of these, 30 patients (group I) developed obesity, and 40 patients were nonobese (group II). All were receiving standard immunosuppressive therapy (cyclosporine A or tacrolimus and mycophenolate mofetil, with prednisone added in the early posttransplant period) and did not differ statistically in HLA typing, age, sex, duration of previous dialysis, history of cardiovascular disease, and rate of rejection episodes. At the end of the study period, there were significant differences between groups I and II (t test, analysis of variance) in plasma: ADPN, 22.30 6 10.2 versus 14.3 6 7.2 mg/mL; visfatin, 1.7 6 0.1 versus 1.2 6 0.1 ng/mL; ADMA, 3.60 6 0.47 versus 2.10 6 0.36 mmol/L; P , .01; leptin, 55.6 6 10.2 versus 25.6 6 8.3 ng/L; P , .01 (P , .02). In conclusion, an increase of body fat after renal transplantation was associated with an increase of ADMA and leptin, TNF-a, MCP-1, and visfatin and decrease of adiponectin. Our study documented there was now long-term beneficial metabolic effect of peritoneal dialysis in developing posttransplant obesity. Ó 2012 by the National Kidney Foundation, Inc. All rights reserved.
O
BESITY IS ONE of the most common complications in renal transplant recipients and influences long-term outcome.1 It is characterized by the abdominal (visceral) type of obesity, which affects both men and women, with prevalence between 25% and 35% in the
first posttransplant year. A successful transplantation restores renal function as a major positive factor, but the administration of immunosuppressive agents (in particular, prednisone) and a generally increased dietary energy intake result in an increase in the incidence of obesity and
*Department of Nephrology, Transplant Centre, Institute for Clinical and Experimental Medicine, Prague, Czech Republic. †Institute for Postgraduate Education, Prague, Czech Republic. ‡Department of Surgery, Charles University, Prague, Czech Republic. §Department of Surgery, Transplant Centre, Institute for Clinical and Experimental Medicine, Prague, Czech Republic. {Laboratory for Atherosclerosis Research, Institute for Clinical and Experimental Medicine, Prague, Czech Republic. **Department of Experimental Medicine, Institute for Clinical and Experimental Medicine, Prague, Czech Republic. ††Institute of Clinical Biochemistry and Hematology, Charles University, Pilsen, Czech Republic. ‡‡3rd Department of Internal Medicine, Charles University, Prague, Czech Republic.
§§Department of Experimental and Clinical Rheumatology, Institute of Rheumatology, Charles University, Prague, Czech Republic. Funding Support: The study was supported by grant MS/105293/2009 awarded by the Internal Grant Agency of the Czech Republic; and Research Project MZO00023001 awarded by Ministry of Health of the Czech Republic. Address reprint requests to Vladimir Teplan, MD, PhD, DSc, Department of Nephrology, Transplant Centre, Institute for Clinical and Experimental Medicine, Videnska 1958/9, 140 21 Prague-4, Czech Republic. E-mail: [email protected] Ó 2012 by the National Kidney Foundation, Inc. All rights reserved. 1051-2276/$36.00 doi:10.1053/j.jrn.2011.10.016
166
Journal of Renal Nutrition, Vol 22, No 1 (January), 2012: pp 166-170
ADIPOCYTOKINES AND ADMA IN OBESITY AFTER RENAL TRANSPLANTATION
even the development of metabolic syndrome in a number of cases.2 Obesity is accompanied by an increased local inflammatory response in adipose tissue, as measured by immunocompetent cell infiltration, that in turn leads to increased production of proinflammatory factors such as interleukin 6 (IL-6), tumor necrosis factor a (TNF-a), and monocyte chemoattractant protein-1 (MCP-1).3 Increased release of proinflammatory factors from adipose tissue may contribute to a systemic subclinical inflammatory response in patients with obesity and thus promote the development of insulin resistance and atherosclerosis in these patients.4 Vascular dysfunction may be linked to reduced nitric oxide (NO) bioactivity and increased circulating concentration of the endogenous NO synthase inhibitor, asymmetric dimethyl L-arginine (ADMA).5 It is currently not known whether increased ADMA levels depend only on renal function or constitute a feedback response to other metabolic disorders. Decreases of ADMA after renal transplantation were associated with improvements in endothelial function.6 In contrast, adiponectin (ADPN), the most abundant adipose-tissue protein, has antiatherosclerotic and anti-inflammatory functions.7 It decreases the expression of the adhesion molecules in endothelial cells and suppresses the cytokine production and foam cell transformation of macrophages, which indicates that ADPN is an essential protein for endothelial function. In nonobese renal transplant patients, ADPN increased immediately after transplantation, compared with the pretransplant period.8 Some studies in patients with chronic renal failure have confirmed that peritoneal dialysis (PD) predicts better patient survival compared with those on hemodialysis (HD) over the first 2 years. A beneficial effect of PD on early development of graft function has been reported after renal transplantation.9 However, some results of retrospective studies assessing the benefit of HD or PD on the posttransplant course are conflicting.10 In the present study, by comparing findings in obese and nonobese transplant patients, we tested the hypothesis whether there are differences between obese and nonobese transplant patients depending on previous PD or HD. We also evaluated how adipose tissue might contribute to the systemic inflammatory state through increased production of proinflammatory cytokines.
167
Patients and Methods The study was approved by the Human Ethical Review Committee, Institute for Clinical and Experimental Medicine, Prague, and complied with the Declaration of Helsinki, including the current revision and good Clinical Practice Guidelines. The procedures followed were in accordance with institutional guidelines. All patients gave written informed consent before being enrolled in the study. A total of 70 patients were on follow-up for 12 months. Of these, 30 patients (group I) developed obesity (before transplantation on PD and HD), and 40 patients were nonobese (group II). All were receiving standard immunosuppressive therapy (cyclosporine A or tacrolimus and mycophenolate mofetil, with prednisone added in the early posttransplant period) and did not differ statistically in HLA typing, age, sex, duration of previous dialysis, history of cardiovascular disease, and rate of rejection episodes. The patients were evaluated anthropometrically at basal state and after 12 months. All were weighed and measured and BMI calculated. An ADMA ELISA kit (DLD Diagnostic GmbH, Hamburg, Germany) and an AUTO-EIA II microplate reader (Labsystems Oy, Espoo, Finland) were used for ADMA quantification; this competitive method uses the microtiter plate format. Serum levels of adiponectin were measured using a commercial ELISA kit (BioVendor, Brno, Czech Republic; Linco Research, St. Charles, MI). Serum concentrations of IL-6, TNF-a, and MCP-1 were determined using a human serum adipokine LINCOplex kit on a Luminex 200 instrument (Linco Research). Serum concentrations of C-reactive protein (CRP) were measured using an ultrasensitive CRP ELISA kit (DSL, Oxon, United Kingdom). Serum visfatin levels were measured by enzyme immunoassay (ELISA) according to the manufacturer’s protocol (BioVision Research Products, Mountain View, CA). Glomerular filtration rates were estimated by inulin clearance. Inulin (polyfructosane S) was analyzed using anthrone on a spectrophotometer at wavelength 580 nm (Antelie Light Secoman, France). Serum albumin was determined using bromocresol purple in a routine procedure in the Department of Clinical Biochemistry. Total cholesterol, highdensity lipoprotein cholesterol, and triglycerides were determined using an enzymatic colorimetric method with an Olympus AU 600 analyzer and
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TEPLAN ET AL
reagents from Olympus Diagnostics, GmbH (Hamburg, Germany). LDL cholesterol was calculated using Friedewald formula. Serum insulin concentrations were measured using a commercial RIA kit (CisBio International, Lyon, France); glycated hemoglobin (HbA1c) was analyzed using liquid chromatography on a Tosoh HLC-723 G7 (Shiba, Minato-Ku, Tokyo, Japan), and proteinuria per 24 hours was analyzed by photometry with pyrogallol red using an Olympus 800 system (Hamburg, Germany).
Statistical Analysis SigmaStat software (SPSS Inc., Chicago, IL) was used for the statistical analysis. A t test or Mann– Whitney rank sum test was used to compare data from the 2 groups of chronic kidney disease patients. The relations between respective variables were assessed using Pearson or Spearman correlation coefficient, as appropriate. Results were considered statistically significant at P ,.05.
Results Basic clinical characteristics of the 2 groups of transplant patients are listed in Table 1: the groups
did not differ significantly with respect to age, sex, or renal function measured by inulin clearance. Group I had significantly higher serum levels of ADMA, leptin, visfatin, TNF-a, MCP-1, IL-6, HbA1c, proteinuria, low-density lipoprotein cholesterol, triglycerides, blood pressure, and insulin and significantly lower adiponectin levels than group II, the control group. Group I also showed a significant increase in hsCRP levels compared with group II. With respect to lipid metabolism parameters, there were small but significant increases in the total serum cholesterol and lowdensity lipoprotein cholesterol levels in group I (6.1 6 1.2 vs. 5.8 6 2.2 and 3.9 6 1.2 vs. 3.6 6 1.0 mmol/L, P ,.02). More marked were changes in triglycerides in group I (3.9 6 1.6 vs. 2.8 6 1.0 mmol/L, P , .01). Similarly, group I showed an increase in HbA1c (5.3% 6 1.4% vs. 4.2% 6 0.9%, P , .02) and plasma insulin concentration (365.3 6 40.1 vs. 292.4 6 49.1 mU/L, P ,.02). Moreover, there were also differences between the 2 groups in proteinuria, which was significantly higher in group I (3.5 6 2.2 vs. 2.8 6 1.1 g/L, P , .02). A slight but significant difference was also found in systolic and diastolic blood pressures (P ,.02 for systolic and P ,.05 for diastolic
Table 1. Clinical and Biochemical Characteristics Group I (Obese Transplant Subjects) and Group II (Control, Nonobese Transplant Subjects) Parameter Cin (mL/minute/1.73 m2) BMI (kg/m2) WHR ADMA (mmol/L) ADPN (mg/mL) TNF-a (pg/mL) MCP-1 (pg/mL) Il-6 (pg/mL) Visfatin (ng/mL) HbA1c (%) Insulin (pg/mL) CRP (mg/L) Leptin (ng/L) Proteinuria (g/24 hour) Cholesterol (mmol/L) LDL cholesterol (mmol/L) Triglycerides (mmol/L) System BP (mm Hg) Diastolic BP (mm Hg)
Group I (n 5 30)
Group II (n 5 40)
Statistical Significance: Group I Versus Group II
69.7 6 9.9 32.2 6 3.3 0.88 6 0.05 3.6 6 0.4 14.3 6 4.2 8.6 6 2.3 195 6 53 14.8 6 4.2 1.7 6 0.1 5.3 6 1.4 365.3 6 40.1 14.9 6 4.5 55.6 6 10.2 3.5 6 2.2 6.1 6 1.2 3.9 6 1.2 3.9 6 1.6 135 6 10 90 6 9
71.2 6 9.7 25.1 6 4.0 0.81 6 0.04 2.1 6 0.3 22.3 6 7.1 5.3 6 1.7 112 6 40 9.0 6 3.1 1.2 6 0.1 4.2 6 0.9 292.4 6 49.1 7.4 6 2.5 25.6 6 8.3 2.3 6 2.1 5.8 6 2.2 3.6 6 1.0 2.8 6 1.0 125 6 7 82 6 7
NS P , .01 P , .02 P , .01 P , .01 P , .05 P , .05 P , .05 P , .05 P , .02 P , .02 P , .02 P , .01 P , .02 P , .02 P , .05 P , .01 P , .02 P , .05
Cin, inulin clearance; TNF-a, tumor necrosis factor a; BMI, body mass index; IL-6, interleukin 6; WHR, waist-to-hip ratio; MCP-1, monocyte chemoattractant protein; ADMA, asymmetric dimethylarginine; HbA1c, glycated Hb; ADPN, adiponectin; CRP, C- reactive protein; NS, nonsignificant. Statistical significance is from unpaired t test or Mann–Whitney rank sum test. Values are means 6 standard errors of the means.
ADIPOCYTOKINES AND ADMA IN OBESITY AFTER RENAL TRANSPLANTATION
blood pressure). As shown in Figure 1, levels of ADMA, IL-6, and TNF-a were significantly higher in group I.
Discussion Some studies in patients with chronic renal failure have confirmed that PD predicts better patient survival compared with those on HD over the first 2 years after renal transplantation. A beneficial effect of PD on early development of graft function and some metabolic parameters have been reported after renal transplantation.9 However, retrospective studies assessing the benefit of HD or CAPD on the posttransplant course are conflicting.10 In our study, we have analyzed posttransplant obesity in both groups 12 months after kidney transplantation. Adipose tissue has been recognized as an important endocrine organ producing numerous hormones and cytokines, including proinflammatory factors such as TNF-a and IL-6. Furthermore, production of proinflammatory cytokines is increased in obese patients, suggesting the pathogenetic contribution of these factors in the development of insulin resistance, vascular disease, and possibly other related pathologies.11 Experimental and clinical studies have shown that adipose tissue of obese individuals is characterized by increased infiltration by immunocompetent cells that become the most important producers of proinflammatory cytokines, which was also shown in our previous study.12 An increase in circulating levels of proinflammatory cytokines after transplantation is accompanied by increased levels of adiponectin,
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an adipose tissue-derived hormone with antiinflammatory and antiatherogenic properties. In contrast, decreased adiponectin levels are normally found in nonrenal patients with obesity, atherosclerosis, insulin resistance, and type 2 diabetes mellitus, whereas leanness and increased levels of physical activity are accompanied by hyperadiponectinemia.13,14 The increased levels of ADMA in our patient could be attributed to renal impairment. Kidney transplantation normalizes symmetric dimethyl arginine, whereas ADMA levels remain elevated. Obesity and weight reduction have been shown to be associated with changes in endothelial function.15 Studies of kidney transplant recipients indicate that as renal function improves, the originally increased ADMA levels decline, but in spite of the presence of excellent kidney graft function, ADMA levels remain 2 to 3 times higher compared with those in healthy individuals. This finding may, in part, support our finding of weak correlation between ADMA and glomerular filtration rate. Visfatin is ubiquitously expressed in many tissues and was recently demonstrated to be an adipocytokine that is upregulated in visceral fat cells. Visfatin exerts insulin mimetic effects and plays a role in innate immunity and inflammation. In addition, visfatin has potent proinflammatory and destructive properties.16
Conclusion Our data show that expression of proinflammatory cytokines is increased in obese persons after kidney transplantation and is not dependent on previous pretransplant replacement therapy modality. Moreover, serum concentrations of several proinflammatory cytokines are higher, and insulin resistance is more pronounced in these patients. Preferential effect of previous PD was not confirmed when posttransplant obesity was developed.
Practical Application
Figure 1. Serum concentrations of asymmetric dimethylarginine, adiponectin, interleukin 6, and tumor necrosis factor a in obese transplant patients (group I, open bars) and in nonobese transplant patients (group II, filled bars).
Obesity after transplantation is a risk factor for cardiovascular complications. Our prospective study analyzed selected adipocytokines (adiponectin, leptin, visfatin) and asymmetric dimethylarginine. We did not confirm significant differences in these parameters in patients previously on peritoneal dialysis or hemodialysis.
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Acknowledgment The authors thank Ms V. Turkova, J. Skibova (Manager), and R. Prahl (Manager) for their technical assistance.
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