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 microg/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 x 1.73 m(-2) x 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 HbA(1 c), matrix volume fraction(baseline) and basement membrane thickness BMT(baseline) accounted for 70 % of the variation in AER at the end of the study. Mesangial volume fraction(baseline,) glomerular filtration fraction(baseline,) and mean 8-year HbA(1 c) 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 rate(baseline) 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).