Glomerular basement membrane thickening and mesangial expansion are the main pathological features in diabetic nephropathy – glomerulosclerosis with the biochemical correlate of increased collagen accumulation. We studied a new principle to reduce collagen accumulation in the glomerulus: thiaproline, known to inhibit protein synthesis by blocking the elongation, led in our studies to a morphological reduction of the glomerular basement membrane thickening and to a decreased collagen content. As the thiaproline analogue is incorporated into collagen, the mechanism of increased degradation of the modified collagen is being discusse