Diabetic nephropathy refers to the kidney damage caused by both type I and type II diabetes.
Because of the growing number of people affected by diabetes, diabetic nephropathy is currently the leading cause of end-stage renal disease in most developed countries around the world.
Each kidney has millions of nephrons, each of which is served by a tiny capillary bed called a glomerulus.
The tiny arteriole that approaches the glomerulus is called the afferent arteriole - a for approaching, and the arteriole that exits the glomerulus is called the efferent arteriole - e for exits.
The glomeruli are a tiny cluster of capillaries that are physically supported by mesangial cells.
So when blood is filtered it moves through the endothelium lining the capillary, then through the basement membrane, and then through the epithelium lining the nephron, and finally into the nephron itself - at which point its called filtrate.
The endothelium has pores that keep cells from entering the filtrate, and the basement membrane is negatively charged and repels other negatively charged molecules and proteins, like the protein albumin.
The epithelium has of special cell type called a podocyte which looks like an octopus because it has foot processes that wrap around the basement membrane, leaving tiny gaps between its octopus-like projections called filtration slits.
In diabetes mellitus, there’s an excess of glucose in the blood, because it can’t get into cells, and when blood gets filtered through the kidneys, some of that excess glucose starts to spill into the urine, called glycosuria.
In addition, when there’s a lot of glucose in the blood, it also starts sticking to proteins in the blood — a process called non-enzymatic glycation because no enzymes are involved.
Because glucose can get through the endothelium, this process of glycation can also involve the basement membrane of small blood vessels making it thicken. The process particularly affects the efferent arteriole causing it to get stiff and more narrow - a process called hyaline arteriosclerosis.