GENETICS OF DIABETIC NEPHROPATHY: STUDY OF TGF-1 GENE

Despite substantial progress in the clinical management of diabetes, diabetic nephropathy (DN) still occurs recurrently, implicating diabetes as the major underlying condition leading to the end stage renal disease. One of the main reasons is the influential role of genetic or inherited backgrounds of diabetics that are almost overlooked in daily practice. Owing to be orchestrated by the genetic makeup, cellular and molecular responses are different to similar metabolic disturbances. This in turn defines susceptibility/resistance state of the host to chronic diabetic complications, including DN. Separate analysis of every single gene that may be involved in genetics of a multi-factorial disease (such as DN) is the only available way to dissect the genetic basis of the disease and overcome its complexity. Among different genes accountable for DN, Transforming Growth Factor (TGF)-1 has an exceptional place. TGF-1 has profound impact on cell growth and proliferation, and in particular the regulation of extra cellular matrix deposition, branding it as a "pro-fibrotic" and "hypertrophic" mediator. By employing ARMS-PCR technique, the genetic susceptibility to DN was studied in 248 patients with T1DM (86 DN+, 162 DN−) and 113 healthy controls, all from British Caucasian origin. The analysis of two functional TGF-1 gene variations, which change codons 10 (+869*C/T) and 25 (+915*G/C) was carried out. There were some differences in alleles/genotypes distribution, but no significant association was apparent in patients as a whole or DN+/DN− subgroups and controls (P=NS). The negative result of this study may be false. As DN is a mortal disability, some fraction of risky genotypes associated with DN may previously be excluded by death. Such under-representation of the risky-genotypes (selective survivor effect) can be avoided by carrying out a prospective study. However, if the non-association result is true, it may question the functionality and reliability of the examined polymorphisms at least in the context of diabetes. Moreover, it does not underestimate the role of TGF-1 at the level of gene/protein themselves in development of DN.