Vitamin D 3 improves lipophagy-associated renal lipid metabolism and tissue damage in diabetic mice.

Oxidative stress and abnormal lipid metabolism in diabetes can trigger renal lipotoxicity, extending to diabetic nephropathy. Vitamin D3 has been known to be involved in lipid metabolism as well as insulin secretion or inflammation. Therefore, we hypothesized that vitamin D3 supplementation attenuated hyperglycemia-induced renal damage in diabetic mice. Diabetes was induced by a 40% kJ high-fat diet with 30 mg/kg body weight of streptozotocin by intraperitoneal injection twice in male C57BL/6J mice. Among diabetic mice (fasting blood glucose > 140 mg/dL), mice were supplemented with 300 ng/kg body weight of vitamin D3 dissolved in olive oil for 12 weeks. Normal control and diabetic control mice were orally administrated with olive oil as a vehicle. Normal control mice were fed with an AIN-93G diet during the experiment. Vitamin D3 supplementation in diabetic mice improved glucose intolerance and kidney function, demonstrated by diminishing glomerular areas. Vitamin D3 supplementation in diabetic mice significantly reduced triglycerides and low-density lipoprotein cholesterol in plasma as well as triglycerides and total cholesterol in the kidney. Furthermore, vitamin D3 supplementation attenuated lipid synthesis, oxidative stress, and apoptosis, accompanied by activation of β-oxidation, antioxidant defense enzymes, and autophagy in diabetic mice. In conclusion, vitamin D3 supplementation ameliorates hyperglycemia-induced renal damage through the regulation of lipid metabolisms, oxidative stress, apoptosis, and autophagy in diabetes. Vitamin D3 could be a promising nutrient to weaken diabetic nephropathy.