The measurement of glomerular basement membrane components and glycated albumin as improved markers of incipient diabetic nephropathy.
MetadataShow full item record
Diabetes causes early structural changes to the glomerular basement membrane (GBM), which alters its function and leads to loss of protein in urine. Formation of advanced glycation endproducts (AGEs) is one mechanism proposed to be responsible for the structural changes to the GBM. AGEs are thought to affect blood flow i.e. glomerular filtration rate (GFR) and vascular permeability which over time manifests as overt proteinuria. The gradual loss of minute amounts of protein (albumin) is referred to as microalbuminuria (MA). Microalbuminuria is a dynamic process, with patients regressing to normoalbuminuria more often than progressing to overt proteinuria. Microalbuminuria is not specific to patients with diabetic nephropathy (DN) and new markers specific to DN are being sought. A prospective study was undertaken at the Inkosi Albert Luthuli Central Hospital (IALCH) to evaluate the relationship of serum glycated albumin, urinary and serum components of capillary basement membrane and DN in South African Black and Indian patients with type 1 diabetes. The study was undertaken with sampling of blood and urine at baseline, 6-months, 1 year and 2-year follow-up. Serum glycated albumin, urinary type IV collagen and plasma fibronectin were measured at each visit. Since correlations could be performed only at each time point individually, generalised estimating equation (GEE) regression models were constructed in SPSS (15.0) with time specified as a factor in order to take account of relationships among variables over time. The results of this study showed that serum percentage glycated albumin (PGA), plasma fibronectin (FN) and urinary type IV collagen were not better predictors of incipient impaired renal function than MA. Although previous authors have variously reported serum GA, plasma FN and urinary type IV collagen to be predictive of impaired renal function, these studies were conducted mainly in patients with overt DN. The present study suggest that markers of overt renal dysfunction are not necessarily useful predictors of incipient DN. Differences in predictive relationships point to a different disease processes in the two ethnic groups. Of particular note was the lack of a predictive relationship of either fasting plasma glucose (FPG) or glycated haemoglobin (HbA1c) with any of isotope GFR, estimated GFR and proteinuria in Black patients. The most significant finding of this study showed that combination of serum creatinine and MA provided broadest range of predictors of isotope GFR, estimated GFR and proteinuria.