- Email: [email protected]
Tumor Necrosis Factor Alpha Promoter Polymorphism in Posttransplantation Diabetes Mellitus of Renal Transplant Recipients
Tumor Necrosis Factor Alpha Promoter Polymorphism in Posttransplantation Diabetes Mellitus of Renal Transplant Recipients C.-C. Kao, J.-D. Lian, M.-C. Chou, H.-R. Chang, and S.-F. Yang ABSTRACT Posttransplantation diabetes mellitus (PTDM) is a major complication in renal transplant recipients. Some studies have demonstrated that tumor necrosis factor alpha (TNF-␣) expression and its genetic polymorphism are associated with diabetes mellitus. We investigated this association in Asian renal transplant recipients. Polymerase chain reaction–restriction-fragment length polymorphism was used to measure TNF-␣ G-238A and G-308A gene polymorphisms among 241 nonposttransplantation diabetic subjects and 73 PTDM patients. PTDM patients showed higher values of body weight and body mass index (BMI) than the non-PTDM group. However, no significant association was observed between TNF-␣ G-238A and TNF-␣ G-308A polymorphisms with PTDM incidence, gender, age at transplantation, follow-up duration, BMI, or type of immunosuppression. umor necrosis factor ␣ (TNF-␣) is a proinflammatory cytokine produced by activated macrophages during the pathogenesis of diabetes mellitus (DM).1 Elevated TNF-␣ expression is associated with type 2 DM.2 TNF-␣ promoter gene polymorphisms (G-308A and G-238A) have been corelated with DM among nontransplant subjects.3,4 Posttransplantation diabetes mellitus (PTDM) is a serious metabolic complication. Risk factors for PTDM include type of immunosuppression, ethnicity, age, and body mass index.5,6 Gençtoy et al suggested that the TNF-␣ ⫺238 G/A genotype may contribute to insulin resistance among renal transplant recipients.7 Poli et al observed that TNF-␣ polymorphism was associated with differential TNF-␣ production which could relate to the clinical outcomes of kidney transplantation.8 However, associations between TNF-␣ promoter polymorphism and PTDM are unclear. Therefore, the objective of the present study was to evaluate whether the TNF-␣ promoter polymorphisms were associated with a risk of PTDM among Taiwanese subjects.
T
METHODS Subjects Among 379 recipients of kidney transplantations between February 1998 and January 2008, we included those with hemoglobin A1c (HbA1c) ⬎6.5 mg/dL on sequential blood samples or requiring insulin after transplantation who were diagnosed with PTDM, excluding 65 patients with DM before transplantation.
Genomic DNA Extraction and Polymerase Chain Reaction– Restriction-Fragment Length Polymorphism (PCR-RFLP) Venous blood from each subject drawn into Vacutainer tubes containing EDTA was stored at 4°C. Genomic DNA was extracted using QIAamp DNA blood mini kits (Qiagen, Valencia, CA, USA) according to the manufacturer’s instructions. TNF-␣ G-238A and G-308A polymorphisms were determined by PCR-RFLP assays.3
Statistical Analysis The distributions of genotype frequencies between PTDM and non-PTDM groups were analyzed by Fisher exact test. The MannWhitney U test was used to evaluate the two groups. A P value of ⬍.05 was considered to be significant. The data were analyzed using SPSS version 12.0 statistical software.
RESULTS
We enrolled 314 transplant recipients, including 241 nonPTDM (127 male and 114 female) and 73 PTDM (42 male and 31 female) patients. The mean ages at transplantation of non-PTDM and PTDM subjects were 47 years (range, From the Institute of Medicine (C.-C.K., M.-C.C., H.-R.C., S.-F.Y.), Chung Shan Medical University; and the Division of Nephrology (J.-D.L., H.-R.C.) and Department of Medical Research (S.-F.Y.), Chung Shan Medical University Hospital, Taichung, Taiwan. Address reprint requests to Horng-Rong Chang, MD, PhD and Shun-Fa Yang, PhD, Institute of Medicine, Chung Shan Medical University, 110, Section 1, Chien-Kuo N. Road, Taichung, Taiwan. E-mail: [email protected]
© 2010 by Elsevier Inc. All rights reserved. 360 Park Avenue South, New York, NY 10010-1710
0041-1345/–see front matter doi:10.1016/j.transproceed.2010.06.032
Transplantation Proceedings, 42, 3559 –3561 (2010)
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20 – 69) and 49.4 years (range, 15– 68), respectively. The mean posttransplant follow-ups among non-PTDM and PTDM subjects were 67.5 months (range, 15–216) and 67.1 months (range, 16 –202), respectively. There were significant differences between non-PTDM and PTDM subjects in weight (62.12 ⫾ 11.05 kg vs 65.84 ⫾ 13.48 kg; P ⫽ .017) and body mass index (BMI; 23.5 ⫾ 3.47 kg/m2 VS 25.36 ⫾ 4.44 kg/m2; P ⬍ .001), as well as in the percentage of tacrolimus use as an immunosuppressive agent (Table 1). The frequencies of TNF-␣ G-238A and G-308A genotypes associated with PTDM are shown in Table 2. They were not significantly different between the PTDM and non-PTDM groups, even when we furthermore classified the individuals as having ⱖ1 mutated A allele as one subgroup and homozygous GG alleles as another subgroup. As shown in Tables 3 and 4, there was no difference between TNF-␣ G-238A and G-308A genotypes regarding gender, age at transplantation, follow-up duration, height, weight, BMI, or immunosuppressive agent.
PTDM is a serious metabolic complication after kidney transplantation. Various risk factors have been reported: type of immunosuppression, ethnicity, age, and body mass index.5,6 However, there are few reports on genetic risks. Recently, elevated TNF-␣ expressions have been associated with type 2 DM.2 Furthermore, associations of TNF-␣ promoter gene polymorphisms (G-308A and G-238A) have been reported with DM.3,4 In vivo studies have shown mRNA and protein levels of TNF-␣ were higher in obese than in normal mice. Therefore a correlation between TNF-␣ and DM has become an important issue.9 We investigated genetic polymorphisms of TNF-␣ on the development of PTDM. TNF-␣, which located in the class III major histocompatibility complex region, includes several polymorphisms: G-308A and G-238A of the promoter region of the TNF-␣ gene are well known single-nucleotide polymorphisms (SNPs) Table 1. Comparison of Clinical Factors Between PTDM and non-PTDM Groups
Gender Male Female Age at transplantation (y) Follow-up duration (mo) Height (cm) Weight (kg) BMI (kg/m2) CsA FK506
Non-PTDM (n ⫽ 241)
PTDM (n ⫽ 73)
231 (95.9%) 10 (4.1%) 0 (0%) 231 (95.9%) 10 (4.1%) 472 (97.9%) 10 (2.1%)
71 (97.3%) 2 (2.7%) 0 (0%) 71 (97.3%) 2 (2.7%) 144 (98.6%) 2 (1.4%)
.444
190 (78.8%) 51 (21.2%) 0 (0%) 190 (78.8%) 51 (21.2%) 431 (89.4%) 51 (10.6%)
59 (80.8%) 13 (17.8%) 1 (1.4%) 59 (80.8%) 14 (19.2%) 131 (89.7%) 15 (10.3%)
.162
Variable
TNF-␣ ⫺238 G/G G/A A/A G/G G/A or A/A G A TNF-␣ ⫺308 G/G G/A A/A G/G G/A or A/A G A
P Value
.444 .445
.427 .528
P values were calculated from 2 test.
DISCUSSION
Variable
Table 2. TNF-␣ ⴚ238 and ⴚ308 Genotypes, Allele Frequencies, and the Risk of Developing PTDM
Non-PTDM (n ⫽ 241)
127 (52.7%) 114 (47.3%) 47 ⫾ 10.85 67.53 ⫾ 26.43 162.46 ⫾ 7.72 62.12 ⫾ 11.05 23.5 ⫾ 3.47 58 (24.1%) 183 (75.9%)
CsA, cyclosporine; FK506, tacrolimus. a P values were calculated from 2 test. b P values were calculated from t test.
PTDM (n ⫽ 73)
42 (57.5%) 31 (42.5%) 49.4 ⫾ 9.37
P Value
Table 3. Clinical Characteristics of PTDM Patients According to TNF-␣ ⴚ238 Genotype
.277a .089b
67.11 ⫾ 32.31 .91b 160.75 ⫾ 6.76 65.84 ⫾ 13.48 25.36 ⫾ 4.44 10 (13.7%) 63 (86.3%)
associated with DM. The TNF-␣ G-308A polymorphism at the 308 nucleotide upstream of the transcription start site was identified by Wilson et al.10 Furthermore, in vitro analysis revealed the A allele of TNF-␣ G-308A to show increased transcriptional activity compared with the G allele. Recently, Susa et al expanded the association study of the TNF-␣ gene with DM by examining several SNPs outside the promoter region. They showed a significant association of the SNP IVS1G⫹123A of the TNF-␣ gene with DM.11 Thus, an association between the TNF-␣ polymorphism outside of the promoter or even in the intronic region seemed to warrant further examination on the development of PTDM. To our knowledge, ours is the first study of TNF-␣ G-238A and G-308A gene polymorphism in a PTDM population in Taiwan. No significant differences were observed between TNF-␣ G-238A and G-308A genotypes and other clinical parameters in PTDM. There are some limitations in the interpretation of our data. First, patients with HbA1c ⬎6.5 mg/dL on sequential
.093b .017b .00026b .039a
Variable
Male (%) Age at transplantation (y) Follow-up duration (mo) Height (cm) Weight (kg) BMI (kg/m2) CSA (%) FK506 (%)
TNF-␣ ⫺238 G/G (n ⫽ 71)
TNF-␣ ⫺238 G/A (n ⫽ 2)
P Value
30 (42.3%) 49.35 ⫾ 9.49
1 (50%) 51 ⫾ 1.41
.672a .808b
66.89 ⫾ 32.57
75 ⫾ 28.28
.729b
160.65 ⫾ 6.7 66.08 ⫾ 13.6 25.47 ⫾ 4.44 10 (14.1%) 61 (85.9%)
P values were calculated from 2 test. P values were calculated from t test.
a
b
164 ⫾ 11.3 57.5 ⫾ 0.71 21.5 ⫾ 2.7 0 (0%) 2 (100%)
.494b .378b .216b .189a
TNF-␣ PROMOTER POLYMORPHISM AND DIABETES AFTER RENAL TRANSPLANTATION Table 4. Clinical Characteristics of PTDM Patients According to TNF-␣ ⴚ308 Genotype
Variable
Male (%) Age at transplantation (y) Follow-up duration (mo) Height (cm) Weight (kg) BMI (kg/m2) CSA (%) FK506 (%) a
TNF-␣ ⫺308 G/G (n ⫽ 59)
TNF-␣ ⫺308 G/A or A/A (n ⫽ 14)
P Value
26 (44.1%) 49.1 ⫾ 9.72
5 (35.7%) 50.64 ⫾ 7.87
.398a .583b
69.12 ⫾ 33.52
58.64 ⫾ 25.97
.279b
160.31 ⫾ 6.99 65.19 ⫾ 13.34 25.13 ⫾ 3.99 9 (15.3%) 50 (84.7%)
162.69 ⫾ 5.42 68.57 ⫾ 14.25 26.41 ⫾ 6.17 1 (7.1%) 13 (92.9%)
.254b .403b .35b .384a
P values were calculated from 2 test. P values were calculated from t test.
b
blood samples were diagnosed as having PTDM. However, diagnosing DM by HbA1c is not part of the World Health Organization or American Diabetes Association criteria. A better diagnostic criterion is a 2-hour postload glucose concentration ⱖ11.1 mmol/L (200 mg/dL) during an oral glucose tolerance test. Casual plasma glucose ⬎200 mg/dL or fasting plasma glucose ⬎126 mg/dL also are better diagnostic criteria for PTDM. Second, we recognize that our conclusions we based on a relatively small number of subjects that may be confounded by other potential risk factors. REFERENCES 1. Vassalli P: The pathophysiology of tumor necrosis factors, Annu Rev Immunol 10:411, 1992
3561
2. Pickup JC, Chusney GD, Thomas SM, Burt D: Plasma interleukin-6, tumour necrosis factor-a and blood cytokine production in type 2 diabetes. Life Sci 67:291, 2000 3. Shiau MY, Wu CY, Huang CN, et al: TNF-alpha polymorphisms and type 2 diabetes mellitus in Taiwanese patients. Tissue Antigens 61:393, 2003 4. Pérez C, González FE, Pavez V, et al: The ⫺308 polymorphism in the promoter region of the tumor necrosis factor-alpha (TNF-alpha) gene and ex vivo lipopolysaccharide-induced TNFalpha expression in patients with aggressive periodontitis and/or type 1 diabetes mellitus. Eur Cytokine Netw 15:364, 2004 5. Reisaeter AV, Hartmann A: Risk factors and incidence of posttransplant diabetes mellitus. Transplant Proc 33(suppl 5A):8S, 2001 6. Sumrani NB, Delaney V, Ding Z, et al: Diabetes mellitus after renal transplantation in the cyclosporine era-an analysis of risk factors. Transplantation 51:343, 1991 7. Gençtoy G, Kahraman S, Arici M, et al: The role of proinflammatory cytokine gene polymorphisms for development of insulin resistance after renal transplantation. Transplant Proc 38:521, 2006 8. Poli F, Boschiero L, Giannoni F, et al: Tumour necrosis factor-alpha gene polymorphism: implications in kidney transplantation. Cytokine 12:1778, 2000 9. Hofmann C, Lorenz K, Braithwaite SS, et al. Altered gene expression for tumor necrosis factor-alpha and its receptors during drug and dietary modulation of insulin resistance. Endocrinology 134:264, 1994 10. Wilson AG, Symons JA, McDowell TL, McDevitt HO, Duff GW. Effects of a polymorphism in the human tumor necrosis factor alpha promoter on transcriptional activation. Proc Natl Acad Sci USA 94:3195, 1997 11. Susa S, Daimon M, Sakabe J, et al: A functional polymorphism of the TNF-alpha gene that is associated with type 2 DM. Biochem Biophys Res Commun 369:943, 2008
T
METHODS Subjects Among 379 recipients of kidney transplantations between February 1998 and January 2008, we included those with hemoglobin A1c (HbA1c) ⬎6.5 mg/dL on sequential blood samples or requiring insulin after transplantation who were diagnosed with PTDM, excluding 65 patients with DM before transplantation.
Genomic DNA Extraction and Polymerase Chain Reaction– Restriction-Fragment Length Polymorphism (PCR-RFLP) Venous blood from each subject drawn into Vacutainer tubes containing EDTA was stored at 4°C. Genomic DNA was extracted using QIAamp DNA blood mini kits (Qiagen, Valencia, CA, USA) according to the manufacturer’s instructions. TNF-␣ G-238A and G-308A polymorphisms were determined by PCR-RFLP assays.3
Statistical Analysis The distributions of genotype frequencies between PTDM and non-PTDM groups were analyzed by Fisher exact test. The MannWhitney U test was used to evaluate the two groups. A P value of ⬍.05 was considered to be significant. The data were analyzed using SPSS version 12.0 statistical software.
RESULTS
We enrolled 314 transplant recipients, including 241 nonPTDM (127 male and 114 female) and 73 PTDM (42 male and 31 female) patients. The mean ages at transplantation of non-PTDM and PTDM subjects were 47 years (range, From the Institute of Medicine (C.-C.K., M.-C.C., H.-R.C., S.-F.Y.), Chung Shan Medical University; and the Division of Nephrology (J.-D.L., H.-R.C.) and Department of Medical Research (S.-F.Y.), Chung Shan Medical University Hospital, Taichung, Taiwan. Address reprint requests to Horng-Rong Chang, MD, PhD and Shun-Fa Yang, PhD, Institute of Medicine, Chung Shan Medical University, 110, Section 1, Chien-Kuo N. Road, Taichung, Taiwan. E-mail: [email protected]
© 2010 by Elsevier Inc. All rights reserved. 360 Park Avenue South, New York, NY 10010-1710
0041-1345/–see front matter doi:10.1016/j.transproceed.2010.06.032
Transplantation Proceedings, 42, 3559 –3561 (2010)
3559
3560
KAO, LIAN, CHOU ET AL
20 – 69) and 49.4 years (range, 15– 68), respectively. The mean posttransplant follow-ups among non-PTDM and PTDM subjects were 67.5 months (range, 15–216) and 67.1 months (range, 16 –202), respectively. There were significant differences between non-PTDM and PTDM subjects in weight (62.12 ⫾ 11.05 kg vs 65.84 ⫾ 13.48 kg; P ⫽ .017) and body mass index (BMI; 23.5 ⫾ 3.47 kg/m2 VS 25.36 ⫾ 4.44 kg/m2; P ⬍ .001), as well as in the percentage of tacrolimus use as an immunosuppressive agent (Table 1). The frequencies of TNF-␣ G-238A and G-308A genotypes associated with PTDM are shown in Table 2. They were not significantly different between the PTDM and non-PTDM groups, even when we furthermore classified the individuals as having ⱖ1 mutated A allele as one subgroup and homozygous GG alleles as another subgroup. As shown in Tables 3 and 4, there was no difference between TNF-␣ G-238A and G-308A genotypes regarding gender, age at transplantation, follow-up duration, height, weight, BMI, or immunosuppressive agent.
PTDM is a serious metabolic complication after kidney transplantation. Various risk factors have been reported: type of immunosuppression, ethnicity, age, and body mass index.5,6 However, there are few reports on genetic risks. Recently, elevated TNF-␣ expressions have been associated with type 2 DM.2 Furthermore, associations of TNF-␣ promoter gene polymorphisms (G-308A and G-238A) have been reported with DM.3,4 In vivo studies have shown mRNA and protein levels of TNF-␣ were higher in obese than in normal mice. Therefore a correlation between TNF-␣ and DM has become an important issue.9 We investigated genetic polymorphisms of TNF-␣ on the development of PTDM. TNF-␣, which located in the class III major histocompatibility complex region, includes several polymorphisms: G-308A and G-238A of the promoter region of the TNF-␣ gene are well known single-nucleotide polymorphisms (SNPs) Table 1. Comparison of Clinical Factors Between PTDM and non-PTDM Groups
Gender Male Female Age at transplantation (y) Follow-up duration (mo) Height (cm) Weight (kg) BMI (kg/m2) CsA FK506
Non-PTDM (n ⫽ 241)
PTDM (n ⫽ 73)
231 (95.9%) 10 (4.1%) 0 (0%) 231 (95.9%) 10 (4.1%) 472 (97.9%) 10 (2.1%)
71 (97.3%) 2 (2.7%) 0 (0%) 71 (97.3%) 2 (2.7%) 144 (98.6%) 2 (1.4%)
.444
190 (78.8%) 51 (21.2%) 0 (0%) 190 (78.8%) 51 (21.2%) 431 (89.4%) 51 (10.6%)
59 (80.8%) 13 (17.8%) 1 (1.4%) 59 (80.8%) 14 (19.2%) 131 (89.7%) 15 (10.3%)
.162
Variable
TNF-␣ ⫺238 G/G G/A A/A G/G G/A or A/A G A TNF-␣ ⫺308 G/G G/A A/A G/G G/A or A/A G A
P Value
.444 .445
.427 .528
P values were calculated from 2 test.
DISCUSSION
Variable
Table 2. TNF-␣ ⴚ238 and ⴚ308 Genotypes, Allele Frequencies, and the Risk of Developing PTDM
Non-PTDM (n ⫽ 241)
127 (52.7%) 114 (47.3%) 47 ⫾ 10.85 67.53 ⫾ 26.43 162.46 ⫾ 7.72 62.12 ⫾ 11.05 23.5 ⫾ 3.47 58 (24.1%) 183 (75.9%)
CsA, cyclosporine; FK506, tacrolimus. a P values were calculated from 2 test. b P values were calculated from t test.
PTDM (n ⫽ 73)
42 (57.5%) 31 (42.5%) 49.4 ⫾ 9.37
P Value
Table 3. Clinical Characteristics of PTDM Patients According to TNF-␣ ⴚ238 Genotype
.277a .089b
67.11 ⫾ 32.31 .91b 160.75 ⫾ 6.76 65.84 ⫾ 13.48 25.36 ⫾ 4.44 10 (13.7%) 63 (86.3%)
associated with DM. The TNF-␣ G-308A polymorphism at the 308 nucleotide upstream of the transcription start site was identified by Wilson et al.10 Furthermore, in vitro analysis revealed the A allele of TNF-␣ G-308A to show increased transcriptional activity compared with the G allele. Recently, Susa et al expanded the association study of the TNF-␣ gene with DM by examining several SNPs outside the promoter region. They showed a significant association of the SNP IVS1G⫹123A of the TNF-␣ gene with DM.11 Thus, an association between the TNF-␣ polymorphism outside of the promoter or even in the intronic region seemed to warrant further examination on the development of PTDM. To our knowledge, ours is the first study of TNF-␣ G-238A and G-308A gene polymorphism in a PTDM population in Taiwan. No significant differences were observed between TNF-␣ G-238A and G-308A genotypes and other clinical parameters in PTDM. There are some limitations in the interpretation of our data. First, patients with HbA1c ⬎6.5 mg/dL on sequential
.093b .017b .00026b .039a
Variable
Male (%) Age at transplantation (y) Follow-up duration (mo) Height (cm) Weight (kg) BMI (kg/m2) CSA (%) FK506 (%)
TNF-␣ ⫺238 G/G (n ⫽ 71)
TNF-␣ ⫺238 G/A (n ⫽ 2)
P Value
30 (42.3%) 49.35 ⫾ 9.49
1 (50%) 51 ⫾ 1.41
.672a .808b
66.89 ⫾ 32.57
75 ⫾ 28.28
.729b
160.65 ⫾ 6.7 66.08 ⫾ 13.6 25.47 ⫾ 4.44 10 (14.1%) 61 (85.9%)
P values were calculated from 2 test. P values were calculated from t test.
a
b
164 ⫾ 11.3 57.5 ⫾ 0.71 21.5 ⫾ 2.7 0 (0%) 2 (100%)
.494b .378b .216b .189a
TNF-␣ PROMOTER POLYMORPHISM AND DIABETES AFTER RENAL TRANSPLANTATION Table 4. Clinical Characteristics of PTDM Patients According to TNF-␣ ⴚ308 Genotype
Variable
Male (%) Age at transplantation (y) Follow-up duration (mo) Height (cm) Weight (kg) BMI (kg/m2) CSA (%) FK506 (%) a
TNF-␣ ⫺308 G/G (n ⫽ 59)
TNF-␣ ⫺308 G/A or A/A (n ⫽ 14)
P Value
26 (44.1%) 49.1 ⫾ 9.72
5 (35.7%) 50.64 ⫾ 7.87
.398a .583b
69.12 ⫾ 33.52
58.64 ⫾ 25.97
.279b
160.31 ⫾ 6.99 65.19 ⫾ 13.34 25.13 ⫾ 3.99 9 (15.3%) 50 (84.7%)
162.69 ⫾ 5.42 68.57 ⫾ 14.25 26.41 ⫾ 6.17 1 (7.1%) 13 (92.9%)
.254b .403b .35b .384a
P values were calculated from 2 test. P values were calculated from t test.
b
blood samples were diagnosed as having PTDM. However, diagnosing DM by HbA1c is not part of the World Health Organization or American Diabetes Association criteria. A better diagnostic criterion is a 2-hour postload glucose concentration ⱖ11.1 mmol/L (200 mg/dL) during an oral glucose tolerance test. Casual plasma glucose ⬎200 mg/dL or fasting plasma glucose ⬎126 mg/dL also are better diagnostic criteria for PTDM. Second, we recognize that our conclusions we based on a relatively small number of subjects that may be confounded by other potential risk factors. REFERENCES 1. Vassalli P: The pathophysiology of tumor necrosis factors, Annu Rev Immunol 10:411, 1992
3561
2. Pickup JC, Chusney GD, Thomas SM, Burt D: Plasma interleukin-6, tumour necrosis factor-a and blood cytokine production in type 2 diabetes. Life Sci 67:291, 2000 3. Shiau MY, Wu CY, Huang CN, et al: TNF-alpha polymorphisms and type 2 diabetes mellitus in Taiwanese patients. Tissue Antigens 61:393, 2003 4. Pérez C, González FE, Pavez V, et al: The ⫺308 polymorphism in the promoter region of the tumor necrosis factor-alpha (TNF-alpha) gene and ex vivo lipopolysaccharide-induced TNFalpha expression in patients with aggressive periodontitis and/or type 1 diabetes mellitus. Eur Cytokine Netw 15:364, 2004 5. Reisaeter AV, Hartmann A: Risk factors and incidence of posttransplant diabetes mellitus. Transplant Proc 33(suppl 5A):8S, 2001 6. Sumrani NB, Delaney V, Ding Z, et al: Diabetes mellitus after renal transplantation in the cyclosporine era-an analysis of risk factors. Transplantation 51:343, 1991 7. Gençtoy G, Kahraman S, Arici M, et al: The role of proinflammatory cytokine gene polymorphisms for development of insulin resistance after renal transplantation. Transplant Proc 38:521, 2006 8. Poli F, Boschiero L, Giannoni F, et al: Tumour necrosis factor-alpha gene polymorphism: implications in kidney transplantation. Cytokine 12:1778, 2000 9. Hofmann C, Lorenz K, Braithwaite SS, et al. Altered gene expression for tumor necrosis factor-alpha and its receptors during drug and dietary modulation of insulin resistance. Endocrinology 134:264, 1994 10. Wilson AG, Symons JA, McDowell TL, McDevitt HO, Duff GW. Effects of a polymorphism in the human tumor necrosis factor alpha promoter on transcriptional activation. Proc Natl Acad Sci USA 94:3195, 1997 11. Susa S, Daimon M, Sakabe J, et al: A functional polymorphism of the TNF-alpha gene that is associated with type 2 DM. Biochem Biophys Res Commun 369:943, 2008