Renal Structural-Functional Relationships at the Early Stage of Diabetic Nephropathy Among Types 1 and 2 Diabetes: Similarity and Difference

Details of renal structural changes and structural-functional relationships at the early stage of diabetic nephropathy in both types 1 and 2 diabetes are not well known. The present review focused on these topics from previous studies using light and electron microscopic morphometric analysis. Typical glomerular histological changes, glomerular basement membrane thickening, and mesangial expansion are already present in normoalbuminuric types 1 and 2 diabetic patients as a group. However, these parameters are similar between normo- and microalbuminuric type 2 diabetic patients, and therefore, relationships between renal structure and urinary albumin excretion cannot be seen in type 2 diabetic patients, and urinary albumin might not be an early reliable indicator for glomerular structural changes in type 2 diabetic patients. These phenomena might be due to histological heterogeneity in type 2 diabetic patients, which is not seen in type 1 diabetic patients. However, type 2 diabetic patients with typical diabetic glomerulosclerosis showed significant renal functional decline after 11 years observation. On the other hand, it is unclear whether lesions of diabetic nephropathy are concordant or discordant with diabetic retinopathy grade in type 2 diabetes. From above information, renal structural changes or structural-functional relationships in type 2 diabetic patients might be heterogeneous and different from those in type 1 diabetic patients. Careful longitudinal study of renal structure and function including serial renal biopsy at the early stage of diabetic nephropathy in patients with types 1 and 2 diabetes is necessary.