Diabetic microangiopathy in KK mice. II. Suppression of Glomerulosclerosis by pyridinolcarbamate

Rodent animal models: from mild to advanced stages of diabetic nephropathy

Diabetic nephropathy (DN) is a secondary complication of both type 1 and type 2 diabetes, resulting from uncontrolled high blood sugar. 30-40% of diabetic patients develop DN associated with a poor life expectancy and end-stage renal disease, causing serious socioeconomic problems. Although an exact pathogenesis of DN is still unknown, several factors such as hyperglycemia, hyperlipidemia, hypertension and proteinuria may contribute to the progression of renal damage in diabetic nephropathy. DN is confirmed by measuring blood urea nitrogen, serum creatinine, creatinine clearance and proteinuria. Clinical studies show that intensive control of hyperglycemia and blood pressure could successfully reduce proteinuria, which is the main sign of glomerular lesions in DN, and improve the renal prognosis in patients with DN. Diabetic rodent models have traditionally been used for doing research on pathogenesis and developing novel therapeutic strategies, but have limitations for translational research. Diabetes in animal models such as rodents are induced either spontaneously or by using chemical, surgical, genetic, or other techniques and depicts many clinical features or related phenotypes of the disease. This review discusses the merits and demerits of the models, which are used for many reasons in the research of diabetes and diabetic complications.

Diabetic nephropathy: of mice and men

Accumulating evidence supports intrinsic genetic susceptibility as an important variable in the progression of diabetic nephropathy in people. Mice provide an experimental platform of unparalleled power for dissecting the genetics of mammalian diseases; however, phenotypic analysis of diabetic mice lags behind that already established for humans. Standardized benchmarks of hyperglycemia, albuminuria, and measurements of renal failure remain to be developed for different inbred strains of mice. The most glaring deficiency has been the lack of a diabetic mouse model that develops progressively worsening renal insufficiency, the sine qua non of diabetic nephropathy in humans. Differences in susceptibility of these inbred strains to complications of diabetes mellitus provide a possible avenue to dissect the genetic basis of diabetic nephropathy; however, the identification of those strains and/or mutants most susceptible to renal injury from diabetes mellitus is lacking. Identification of a mouse model that faithfully mirrors the pathogenesis of DN in humans will undoubtedly facilitate the development of new diagnostic and therapeutic interventions.

Mouse models of diabetic nephropathy

Mice provide an experimental model of unparalleled flexibility for studying mammalian diseases. Inbred strains of mice exhibit substantial differences in their susceptibility to the renal complications of diabetes. Much remains to be established regarding the course of diabetic nephropathy (DN) in mice as well as defining those strains and/or mutants that are most susceptible to renal injury from diabetes. Through the use of the unique genetic reagents available in mice (including knockouts and transgenics), the validation of a mouse model reproducing human DN should significantly facilitate the understanding of the underlying genetic mechanisms that contribute to the development of DN. Establishment of an authentic mouse model of DN will undoubtedly facilitate testing of translational diagnostic and therapeutic interventions in mice before testing in humans.

Diabetic microangiopathy in KK mice. VI. Effect of glycemic control on renal glycoprotein metabolism and established glomerulosclerosis

Twenty-three nonobese KK mice with abnormal tolerance to glucose, hyperinsulinemia with insulin resistance and human diabetic-like nephropathy were treated with either saline (12 mice) or glipizide, an oral hypoglycemic compound, 1 mg/kg, (11 mice) from 120 to 360 days of age. These mice develop significant increases in mesangial volume and matrix by 40 days of age. Oral glucose tolerance (OGTT), glucosyltransferase and N-acetyl-beta-glucosaminidase (enzymes involved in synthesis and degradation of kidney glycoproteins, respectively) in the kidney and serum, 24-hr proteinuria, and light microscopy studies of the kidney were performed. Glipizide-treated mice improved their OGTT. There was no difference in body weight; however, a 16% decrease (P less than 0.05) in kidney weight was observed in glipizide-treated mice. Both enzymes were significantly increased in the kidneys of mice treated with glipizide. No difference in serum enzymes was found between the two groups of mice. About 58% of the saline-treated mice had moderate glomerulosclerosis. By contrast, only 27% of glipizide-treated mice had moderate glomerulosclerosis. Also, a significant decrease in proteinuria was found in glipizide-treated mice. These data suggest that glipizide improves glucose metabolism, decreases kidney size, prevents kidney glycoprotein and mesangial matrix accumulation, and reduces proteinuria in type II diabetic KK mice. This indicates that good glycemic control prevents further progression of established diabetic nephropathy in animals.

Collagen metabolism in the retina of normal and diabetic rats

Glucosyltransferase, an enzyme involved in the synthesis of the carbohydrate portion of basement membranes and collagens, and collagen content were determined in the retina of normal and streptozotocin diabetic rats. No significant difference in glucosyltransferase activity was found at 4 weeks of diabetes. However, the enzyme activity was significantly increased in diabetic rats 12 and 48 weeks following the induction of diabetes. Similarly, a significant increase in collagen content was observed in diabetic retinas after 12 weeks of diabetes. Electron microscopy showed marked thickening of the retinal capillary basement membrane in long-term diabetic (48 weeks) rats. The data suggest that enhanced collagen synthesis and deposition occurs in the retina of diabetic rats, and with duration of diabetes this may result in thickening of the capillary basement membrane. These results are compatible with previously reported increases in kidney glucosyltransferase, collagen synthesis and thickening of the capillary basement membrane in diabetic rats.

Diabetic microangiopathy. I. Current status of the chemistry and metabolism of the glomerular basement membrane

In recent years, the nature of the renal glomerular basement membrane has been the subject of numerous investigations. In diabetes mellitus, the renal glomerulus is characterized primarily by thickening of the basement membrane and excessive accumulation of basement membrane-like material in the mesangial region. Compositional analyses have shown that basement membranes are glycoprotein in nature. Studies of the glomerular basement membranes in diabetes have indicated a change from normal chemical composition. Furthermore, studies of the metabolism of diabetic kidneys in experimental animals, using cortical homogenates and isolated glomeruli, have demonstrated higher anabolic and lower catabolic enzyme activities. However, contradictory data have been reported with regard to both the chemical composition and metabolism of the kidney in human and experimental diabetes. This review attempts to examine these reports in detail and discuss the possible causes for these discrepancies.