Kidney function and glomerulopathy over 8 years in young patients with Type I (insulin-dependent) diabetes mellitus and microalbuminuria

Abstract

Aims/hypothesis. We aimed to investigate prospectively the interrelation between kidney function and glomerular morphological changes over 8 years in young patients with Type I (insulin-dependent) diabetes mellitus and microalbuminuria. Methods. Kidney biopsies were taken at baseline and after 8 years in 18 subjects who were 20 years of age (19-29 mean and range), had duration of diabetes for 11 years (7-18), and who had an albumin excretion rate of 45 μg/min (15-194). The glomerular ultrastructural parameters were analysed using stereological methods. Results. At the end of the study three patients had an increased albumin excretion rate of more than 25% a year, two of whom developed overt nephropathy. Glomerular filtration rate declined 2.3 ml/min·1.73 m-2·yr-1. Glomerular volume, volume fractions of matrix and mesangium, and basement membrane thickness showed an increase over the 8 years. Multiple regression analysis showed that mean 8-years HbA1c, matrix volume fractionbaseline and basement membrane thickness BMTbaseline accounted for 70% of the variation in AER at the end of the study. Mesangial volume fractionbaseline, glomerular filtration fractionbaseline, and mean 8-year HbA1c accounted for 73% of the change in glomerular filtration rate from baseline. Smoking was strongly associated with the glomerular filtration rate at baseline (r=0.65). When glomerular filtration ratebaseline was omitted from the equation, smoking was the only significant parameter linked to the change in glomerular filtration rate from the baseline. Conclusion/interpretation. In patients who had diabetes for 20 years, long-term hyperglycaemia and glomerulopathy found 8 years prior to the study, and possibly smoking, affected renal function (i.e. albumin excretion rate and glomerular filtration rate).