Association of transforming growth factor-beta1 T29C polymorphism with the progression of diabetic nephropathy

TGFβ1 Induces Senescence and Attenuated VEGF Production in Retinal Pericytes

Diabetic retinopathy (DR) is a microvascular disease of the retina and a serious complication of type I and type II diabetes mellitus. DR affects working-age populations and can cause permanent vision loss if left untreated. The standard of care for proliferative DR is inhibiting VEGF. However, the mechanisms that induce excessive VEGF production in the retina remain elusive, although some evidence links elevated VEGF in the diabetic retina with local and systemic TGFβ1 upexpression. Here, we present evidence from animal models of disease suggesting that excessive TGFβ1 production in the early DR is correlated with VEGF mRNA and protein production by senescent pericytes and other retinal cells. Collectively, these results confirm that TGFβ1 is strongly implicated in the vascular complications of DR.

Study of the association of the T869C polymorphism of the transforming growth factor-β1 gene with polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is a common multifactorial disorder characterized by hyperandrogenism, insulin resistance and chronic oligoanovulation. In addition, a number of females with PCOS have ovaries with multiple cysts, an irregular or no menstrual cycle and an imbalance of female hormones compared with normal controls. The transforming growth factor β1 (TGF‑β1) gene is one of the genes associated with obesity and type 2 diabetes, which are characteristic symptoms of PCOS. The present study, therefore, investigated the association between the T869C polymorphism of the TGF‑β1 gene, a single nucleotide polymorphism (SNP) of TGF‑β1 and PCOS. The genomic DNA from 285 patients with PCOS and 129 healthy control individuals was used in the present study. P<0.05 was considered to indicate a statistically significant difference between the groups. The present study findings suggested that the frequency of genotypes provided no significant association between the T869C polymorphism in the TGF‑β1 gene and patients with PCOS. Although the present study concluded that the T869C polymorphism in the TGF‑β1 gene is not associated with the pathogenesis of PCOS, further studies regarding the correlation between other SNPs of the TGF‑β1 gene and PCOS are required.

The Role of Transforming Growth Factor-Beta in Diabetic Nephropathy

Several studies have demonstrated that chronic and low-grade inflammation is closely linked to type 2 diabetes mellitus. The associated mechanisms are related to synthesis and release of proinflammatory and anti-inflammatory cytokines, mainly by the adipose tissue. Moreover, there are evidences that cytokines and adhesion molecules are important for development of diabetic nephropathy. Among the cytokines associated with inflammatory responses in type 2 diabetes mellitus, the transforming growth factor-β (TGF-β) has been recognized as a central player in the diabetic nephropathy being involved in the development of glomerulosclerosis and interstitial fibrosis, as observed in the course of end-stage renal disease. Although TGF-β1 is classically an anti-inflammatory immune mediator it has been shown that in the presence of IL-6, which increases before the onset of T2D, TGF-β1 favors the differentiation of T helper 17 (Th17) cells that are activated in many pro-inflammatory conditions. Since TGF-β1 mRNA and consequently serum TGF-β1 levels are under genetic control, this review aims to discuss the relationship of TGF-β1 levels and polymorphisms in the development of nephropathy in type 2 diabetes mellitus.

Gene polymorphism of transforming growth factor-β1 in Egyptian patients with type 2 diabetes and diabetic nephropathy

Role of the transforming growth factor-β1 (TGF-β1) gene polymorphisms located at codons 10 and 25 in the genetic predisposition to type 2 diabetes (T2D) and in diabetic nephropathy (DN) in Egyptian patients was investigated. A case control study was done for 99 unrelated Egyptian patients with T2D (50 DN(-) and 49 DN(+)) and 98 age- and sex-matched healthy controls. TGF-β1 T869C (codon 10) and G915C (codon 25) polymorphism detection was done by amplification refractory mutation system method. DN(+) patients were younger, with higher body mass index, serum triglycerides, serum creatinine, and lower serum albumin than those in DN(-) patients. Moderate and bad grades of diabetic control were associated with DN (P < 0.001). The TGF-β1 (T869C) C allele, TC and TC + CC genotypes were significantly higher in patients; the T allele and TT genotype were significantly higher in controls (Pc < 0.001). The TGF-β1 TC genotype was associated with DN (Pc < 0.05). Non-significant differences were detected between T2D patients and controls in the frequencies of TGF-β1 (G915C) alleles and genotypes. In conclusion, these preliminary data showed that the TGF-β1 codon 10 C allele, and C allele-containing genotypes may be susceptible, and T allele/TT genotype may be protective factors for T2D and DN(+) complications.

Cytokines in diabetic nephropathy

Diabetic nephropathy (DN), the most common cause of end-stage renal disease (ESRD), is increasingly considered an inflammatory process characterized by leukocyte infiltration at every stage of renal involvement. Cytokines act as pleiotropic polypeptides that regulate inflammatory and immune responses, providing important signals in the pathologic and physiologic processes. Inflammation and activation of the immune system are closely involved in the pathogenesis of diabetes and its microvascular complications. Proinflammatory, Th1, Th2, and Th17 cytokines, as well as TGF-beta, all take part in the development and progression of DN. Gene polymorphism of cytokines and their receptors may have functional variations and can be applied to predict the susceptibility and progression to DN. Improved knowledge on recognizing cytokines as significant pathogenic mediators in DN leaves opens the possibility of new potential therapeutic agents for future clinical treatments.

Association between the T869C polymorphism of transforming growth factor-beta 1 and diabetic nephropathy: a meta-analysis

Accumulating evidence has suggested that transforming growth factor-beta 1 (TGF-β1) is a functional candidate for diabetic nephropathy (DN). However, association studies investigating the relationship of TGF-β1 gene T869C polymorphism and DN generate inconsistent results. To comprehensively clarify this issue, we performed a meta-analysis to evaluate the impact of the polymorphism on DN. We searched studies from PubMed and China National Knowledge Infrastructure (CNKI) through March 2011. Pooled ORs were calculated under allelic/additive/dominant/recessive/over-dominant genetic models. Nine studies with 1776 cases and 1740 controls were included. Our results indicated that C allele of T869C conferred a significantly increased risk of DN compared with T allele (OR = 1.25, 95% CI: 1.05-1.48) for allelic contrast. Similar results were also found under additive (OR = 1.57, 95% CI: 1.10-2.23) and dominant (OR = 1.40, 95% CI: 1.06-1.85) genetic models. However, subgroup analyses stratified by types of diabetes showed that significantly increased risks were only observed in type 2 diabetic patients, and the association persistently existed in further analysis for Asian populations. As for type 1 diabetic subjects, no significant association was detected under all the genetic models (P > 0.05). Our meta-analysis suggested that the TGF-β1 T869C polymorphism conferred an elevated risk of DN. However, significant associations were only observed in type 2 diabetic patients.

Tetrahydroxystilbene glucoside ameliorates diabetic nephropathy in rats: involvement of SIRT1 and TGF-β1 pathway

Oxidative stress caused by hyperglycaemia is believed to be a major molecular mechanism underlying diabetic nephropathy. 2,3,5,4'-tetrahydroxystilbene-2-O-β-d-glucoside (TSG), an active component extract from Polygonum multiflorum Thunb, exhibits antioxidative and anti-inflammatory effects. Possible protective mechanisms of TSG on diabetic nephropathy were investigated in rats and cultured rat mesangial cells. Total cholesterol and triglyceride levels of diabetic rats were clearly increased and these increases were diminished by treatment with TSG. Treatment of diabetic rats with TSG also significantly reduced blood urea nitrogen, creatinine, 24 h urinary protein levels, and kidney weight/body weight. The activities of superoxide dismutase and glutathione peroxidase in renal homogenate were increased markedly, whereas malonaldehyde levels were decreased significantly in TSG-treated diabetic rats. TSG dramatically inhibited diabetes-induced overexpression of TGF-β1 and COX-2, and restored the decrease of SIRT1 expression in diabetic rats. High glucose-induced overexpression of TGF-β1 in cultured mesangial cells was significantly inhibited, whereas the decease of SIRT1 expression was restored by pretreatment of TSG. Nicotinamide, the inhibitor of SIRT1, partially relieved the inhibitory effect of TSG on TGF-β1 expression under high glucose condition. These findings indicate that the protective mechanisms of TSG on diabetic nephropathy are involved in the alleviation of oxidative stress injury and overexpression of COX-2 and TGF-β1, partially via activation of SIRT1.

Common variants of inflammatory cytokine genes are associated with risk of nephropathy in type 2 diabetes among Asian Indians

Background

Inflammatory cytokine genes have been proposed as good candidate genes for conferring susceptibility to diabetic nephropathy. In the present study, we examined the combined effect of multiple alleles of pro inflammatory cytokine genes for determining the risk of nephropathy in type 2 diabetic patients.

Methodology/Principal Findings

Eight single nucleotide polymorphisms (SNPs) of pro-inflammatory cytokine genes (CCL2, TGFB1, IL8, CCR5, and MMP9) were genotyped in two independently ascertained type 2 diabetic cohorts with (DN) and without nephropathy (DM); consisting of patients from North India (n = 495) and South India (n = 188). Genotyping was carried out using PCR, allele specific oligonucleotide-PCR (ASO-PCR), PCR-RFLP and TaqMan allelic discrimination assays and the gene–gene interaction among genetic variants were determined by multi dimensional reduction (MDR) software. Serum high sensitive CRP (hs-CRP) levels were measured by ELISA. The hs-CRP levels were significantly higher in DN as compared to the DM group (p<0.05). The CCL2, IL8, CCR5 and MMP9 polymorphisms were found to be associated with the risk of diabetic nephropathy. Frequency of CCL2 II, IL8 -251AA, CCR5 59029AA and MMP9 279Gln/Gln genotypes were significantly higher in DN than in DM group (p<0.05) and associated with an increased risk of nephropathy in both North and South Indian cohorts. CCR5 DD and IL8 -251AA genotypes were more prevalent in North Indian DN group only. The co-occurrence of risk associated genotypes (II, -2518GG (CCL2), DD (CCR5) and 279Gln/Gln (MMP9) conferred a tenfold increased risk of nephropathy among type 2 diabetics (p<0.0002).

Conclusion

The present study highlights that common variants of inflammatory cytokine genes exert a modest effect on risk of DN and a combination of risk alleles confer a substantial increased risk of nephropathy in type 2 diabetes among Asian Indians.

Lack of association between TGF-beta-1 genotypes and microalbuminuria in essential hypertensive men

BACKGROUND

Polymorphisms within the gene for transforming growth factor (TGF)-beta-1, a pro-fibrogenic cytokine pathophysiologically involved in hypertension and hypertensive target damage, might modulate the biological activity of the encoded protein. Through that mechanism, they might contribute to microalbuminuria, a marker of subclinical renal damage and a correlate of systemic inflammation and endothelial dysfunction in hypertension, a possibility never before tested. For this reason, we assessed the association of four TGF-beta-1 polymorphic variants (C-509T, Leu(10)-->Pro, Arg(25)-->Pro, Thr(263)-->Ile) with albuminuria in uncomplicated essential hypertensive men, using (circulating active + acid-activatable latent) TGF-beta-1 levels as an indirect index of their in vivo biological activity. Because of the close pathophysiological link of TGF-beta-1 with the renin-angiotensin system, we also tested the behaviour of the angiotensin converting enzyme (ACE) deletion/insertion (D/I) polymorphism.

METHODS

Albuminuria (three overnight collections), office and 24-h BP, left ventricular mass index (LVMI), BMI, renal function, glucose, lipids, plasma TGF-beta-1 (n = 162, ELISA) were measured in 222 genetically unrelated, never-treated, uncomplicated Caucasian hypertensive men. ACE D/I polymorphisms were analysed by the polymerase chain reaction technique or a 5' nuclease assay with further restriction analysis when required.

RESULTS

Urine albumin levels or microalbuminuria (albuminuria > or =15 microg/min) did not differ by TGF-beta-1 genotypes, but both parameters were more frequent in ACE D/D homozygotes. Plasma TGF-beta-1 was similar across genetic backgrounds and was unrelated to albuminuria. Cardiovascular, renal, metabolic parameters were homogeneously distributed across genotypes.

CONCLUSIONS

In contrast to its link with the ACE D/I genotype, microalbuminuria was independent of TGF-beta-1 polymorphism in this group of never-treated, uncomplicated essential hypertensive men.

Transforming growth factor-beta1 SNPs: genetic and phenotypic correlations in progressive kidney insufficiency

Associations have been described between polymorphisms of cytokine and growth factor genes and susceptibility to, or progression of, an increasing number of diseases. TGF-beta1 plays an important role in the pathogenesis of experimental and clinical glomerulosclerosis and tubulointerstitial fibrosis. In this study, single nucleotide polymorphisms (SNPs) in the TGFbeta1 gene were investigated as possible markers for the progression of chronic kidney failure (CKF). 145 Caucasian patients with CKF were screened for four TGFbeta1 SNPs: T-509C in the promoter region; Arg25Pro and Leu10Pro in exon 1 and Thr263Ile in exon 5. There were significant differences between CKF patients and controls in allele frequencies of two of the SNPs, Leu10Pro (p = 0.038) and C-509T (p = 0.02) and in haplotype distributions (p = 0.0175), indicating an association with susceptibility to CKF. We also observed a significant association between progression of CKF and homozygosity for Arg25 (odds ratio 3.77, 95% confidence interval 1.57-9.04, p = 0.002). Homozygosity for Arg25 was also associated with severity of proteinuria at diagnosis (p = 0.038), plasma TGF-beta1 protein levels (p = 0.01), and severity of glomerulosclerosis (p = 0.04). Homozygosity for -509T was associated with severity of proteinuria at diagnosis (p = 0.0017), level of renal tubular TGF-beta1 immunostaining (p = 0.0006) and with severity of renal interstitial inflammatory cellular infiltration (p = 0.01). Tubular TGF-beta1 immunostaining was significantly higher in biopsies with inflammatory cellular infiltration compared those without inflammation (p = 0.0048). There was a significant difference in haplotype distributions between CKF patients with progressive, as opposed to non-progressive disease (p = 0.0484). TGFbeta1 SNPs may be useful prognostic indicators for the progression of CKF.

The role of the TSC-22 (-396) A/G variant in the development of diabetic nephropathy

TSC-22 is a leucine zipper transcriptional factor and expression of the TSC-22 gene is highly induced by TGF-beta treatment. We estimated the frequency of the -396 A/G polymorphism of the TSC-22 gene with an Alu I-Restriction fragment length polymorphism (RFLP) method in 498 Japanese subjects with type 2 diabetes mellitus. We also determined the promoter activity. The diabetic patients with the AA genotype had a significantly higher incidence of the diabetic nephropathy (vs. the AG genotype, P<0.05, odds ratio: 1.95; 95% confidence intervals 1.14-3.33). There was no significant difference in the promoter activity between the fragments with -396A and -396G. These findings suggest that the TSC-22 gene (-396) A allele is associated with an increasing risk of the diabetic nephropathy.

Association of transforming growth factor-beta (TGF-beta) T869C (Leu 10Pro) gene polymorphisms with type 2 diabetic nephropathy in Chinese

INTRODUCTION

Transforming growth factor-beta (TGF-beta) is known to play a pivotal role in the regulation of extracellular matrix (ECM) accumulation. Since diabetic nephropathy (DMN) is characterized by basement membrane thickening and mesangial expansion, control of ECM deposition is believed to be important in the pathogenesis of the disease. Recently, TGF-beta T869C (Leu 10Pro) gene polymorphism has been identified which may be associated with circulating TGF-beta levels.

METHODS

In order to examine the relationship between TGF-beta gene polymorphism with DMN in Chinese, we carried out a case-control study, which recruited 123 Chinese type 2 diabetic patients with an average duration of diabetes for 12 years. A total of 58 patients who developed DMN (micro- or macroalbuminuria, with or without renal impairment) were compared with 65 diabetic patients without DMN despite similar duration of disease (normoalbuminuric and creatinine <120 micromol/L). TGF-beta T869C (Leu 10Pro) gene polymorphism was determined by polymerase chain reaction (PCR).

RESULTS

Both groups of patients had similar baseline characteristics, including blood pressure, diabetic control, and duration of diabetes. Distribution of TGF-beta T869C (Leu 10Pro) genotype among the whole group is confined to Hardy Weinberg equilibrium. The DMN+ group has higher frequency of TGF-beta CC/CT genotypes than the DMN- group [CC, CT, TT = (DMN+) 46, 45, 9 (%) vs. (DMN-) 37, 37, 26 (%), P < 0.05]. C allele frequency is also higher in the DMN+ group than DMN- group (69% vs. 55%, P < 0.05). The adjusted odds ratio for TGF-beta CC/CT vs. TT genotype to develop DMN is 3.8 (3.2 to 4.4). Multivariate logistic regression analysis [hypertension, gender, age, duration of diabetes, hemoglobin (HbA1c), usage of angiotensin-converting enzyme (ACE) inhibitor, and cholesterol level] showed that TGF-beta genotype (P = 0.03) is an independent predictor for type 2 DMN. Among patients with DMN, those with TGF-beta CC/CT genotypes also had worse renal function and increased risk for macroalbuminuria.

CONCLUSION

Our results suggest that TGF-beta T869C (Leu 10Pro) gene polymorphism is associated with DMN in Chinese.

TGF-beta 1 as a genetic susceptibility locus for advanced diabetic nephropathy in type 1 diabetes mellitus: an investigation of multiple known DNA sequence variants

BACKGROUND

Transforming growth factor-beta1 (TGF-beta1) is a profibrotic cytokine suspected to be a crucial factor underlying glomerulosclerosis in advanced diabetic nephropathy. However, its potential role as a susceptibility gene for the development of this microvascular complication is unresolved.

METHODS

We examined whether DNA sequence variants in the TGF-beta1 gene are associated with advanced diabetic nephropathy among Caucasians with type 1 diabetes mellitus. These variants included three coding (Leu10Pro, Arg25Pro, and Thr263Ile) and two noncoding single-nucleotide polymorphisms (-800 and -509), as well as an insertion/deletion of a cytosine residue in intron 4. A large case-control study design was used in which cases were patients with type 1 diabetes with advanced diabetic nephropathy (presence of persistent proteinuria or end-stage renal disease [ESRD]; n = 298) and controls were patients who remained normoalbuminuric despite greater than 15 years of type 1 diabetes (n = 263).

RESULTS

Genotype frequencies for all polymorphisms were in Hardy-Weinberg equilibrium. Genotype distributions of all six DNA sequence variants were very similar between cases and controls (P = not significant). There was no significant difference in genotype distributions among cases regardless of whether these individuals with diabetes were proteinuric at the time of examination or had already developed ESRD secondary to diabetic nephropathy. Stratified analyses according to diabetes duration and glycemic control likewise did not detect an association between DNA sequence variants and advanced diabetic nephropathy.

CONCLUSION

Genetic variation at the TGF-beta1 locus is unlikely to confer significant susceptibility to advanced diabetic nephropathy in patients with type 1 diabetes mellitus.

RNA expression profiling as prognostic tool in renal patients: toward nephrogenomics

Damage to the kidney generally elicits tissue repair mechanisms, but these processes themselves conversely may result in the progression of chronic renal disease. In a majority of patients chronic renal insufficiency progresses to a common histological end point, marked by the presence of a vast amount of scar tissue, that is, glomerulosclerosis and interstitial fibrosis. These lesions are the result of an excessive production of extracellular matrix (ECM) components. Studies on RNA expression in experimental kidney disease have shown that renal mRNA levels for ECM components and cytokines can function as prognostic tools. This suggests that mRNA levels potentially predict outcome and reaction to therapy in patients with renal diseases. Timely detection of molecular alterations could allow early therapeutic intervention that slows down or even prevents the development of sclerotic and fibrotic lesions. This review first provides a short introduction on mechanisms of initiation and progression of renal disease. Molecular techniques are available to identify renal RNA sequences potentially involved in disease progression. We discuss several molecular techniques that are being used in kidney research for quantitation and detection of mRNA. This is followed by a brief overview of investigation in experimental renal diseases, which reveal that alterations in tissue ECM mRNA levels precede histological damage and can function as predictors of clinical outcome. In particular, studies in human kidney biopsies that evaluate the prognostic value of mRNA levels with respect to renal function are examined, paying special attention to the pitfalls that potentially are encountered when interpreting the results of such studies. Then, we elaborate on ways of optimal exploitation of mRNA quantification as a prognostic tool. The potential and limitations of microarray technology in the search for genes specifically involved in progression of renal disease are reviewed, including RNA expression profiling and large-scale DNA mutation screening. Finally, the future utilities of microarray in nephrology and renal pathology are discussed.