Implication of insulin folate combined treatment on the relationship between hyperhomocysteinemia and nephropathy in STZ diabetic rats

ABSTRACT

To investigate the efficacy of folic acid supplementation and insulin administration as therapeutic intervention for hyperhomocysteinemia, nephropathy and hyperglycemic complications in streptozotocin diabetic nephrotic rats. Animals Male Wistar rats obtained from Veterinary animal farm. Setting: Department of Biochemistry, Faculty of Pharmacy, Zagazig University, Zagazig, Egypt. Design: Diabetes was induced in sixty male Wistar rats by single intraperitoneal [i.p.] STZ [50 mg/kg]. Diabetic rats were fed methionine overload diets for 30 days and subjected later to gradual doses of gentamycin [200 mg/kg] for 10 days for induction of nephrotoxicity. Diabetic methionine overload nephrotic rats [DMN] treated with insulin and/or folic acid [90 micro g] daily and orally for 4 weeks. Groups of age matched healthy animals [n = 10], diabetics [n = 8] and DMN rats [positive control, n =7] served as controls. At the end of the study, serum glucose, creatinine, insulin, folate, plasma tHcy, NO, lipid profile and the susceptibility of low density lipoprotein [LDL] to copper catalyzed oxidation were determined. Superoxide dismutase [SOD], reduced glutathione [GSH] and lipid peroxide expressed as malondialdehyde [MDA] were measured in kidney tissue homogenate. Histopathological examination of kidney slices were also determined. In DMN group, glucose, creatinine, tHcy, NO, susceptibility of LDL to oxidation, and renal MDA contents showed significant increase, whereas folate, renal GSH and SOD activities revealed marked reduction. Insulin treatment modulates the above mentioned parameters, however folic acid failed to affect serum glucose and lipid pattern. Combined form therapy has a better effect regarding reduction of tHcy as compared to insulin alone. Oxidative cell markers specifically oxidative susceptibility of LDL to oxidation, NO and SOD activities seemed to be greatly attenuated more than individual treatment. Finally, folic acid coadministration with insulin may limit the progression of the vascular nephropathy of kidney tissue and interstitial haemorrhage in comparison with diabetic and DMN rats. Hyperhomocysteinemia is mainly a consequence of renal insufficiency rather than diabetes and represents an inducer for vascular damage in respect to status and prognosis of renal failure. Folic acid may have a renoprotective effect augmenting the therapeutic efficiency of insulin through its effect on tHcy reduction and limitation of tissue toxicities originating from oxygen free radicals generation