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 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). [Diabetologia (2002) 45: 253–261]