Effects Of Rhein On Neuropeptide Y And Its Receptors Y1R, Y2R Expressions In Renal Tissue Of Streptozotocin-induced Diabetic Rats

Diabetic nephropathy (DN) occurs in 30% of patients with diabetic mellitus and is the leading cause of end-stage renal disease (ESRD).The pathophysiological mechanism for DN has not been fully understood yet, although previous studies have suggested that chronic hyperglycemia, dislipidemia and intrarenal blood flow distribution may play certain roles in the development of DN.Despite the renoprotective effects reported in recent years, there is still no drug that can completely prevent the progression of DN and delay the onset of ESRD.Therefore, a new drug for treatment of diabetic nephropathy based on a different mechanism of action is awaited with anticipation.Neuropeptide Y (NPY) is a 36 amino acid peptide widely distributed in the central and peripheral sympathetic nervous system, where it is co-localized with norepinephrine.It has been indicated that NPY, its receptors YIR and Y2R play an important role in the development of diabetes mellitus associated with its numerous secondary complications in mammalians.However, few studies have been done on renal NPY-Y1R/Y2R expression in diabetic conditions.Rhein, as the effective ingredient of rhubarb, has been found to have an effect on ameliorating glucolipid metabolism, controlling the symptoms of diabetes and delaying the progress of DN.This experiment was aimed to investigate the renal expression of NPY and its receptors Y1R/Y2R in diabetic conditions and explore the possible mechanism of rhein preventing and attenuating DN. Part one:Investigate the protective effect of rhein on kidneys in STZ-induced diabetic ratsObjective:To observe the effect of rhein on the glucolipid metabolism and the glomerular pathological change in the STZ-induced diabetic rats.Methods:Male Wister rats,8 weeks old and weighting 210±10 g, were housed under controlled temperature conditions with a 12-h light/12-h dark cycle.After 1 week, they were divided into three groups. Two groups received intravenous injection of streptozotocin(STZ) at 65 mg/kg dissolved in 1% citrate buffer into the femoral vein of fasted rats under pentobarbital anesthesia (30 mg/kg, i.p.).Control rats received a similar injection of the same volume of vehicle alone. Rhein was administrated orally in the rhein-treated group(100 mg·kg-1·d-1),and the other two groups were administrated with comparative solvent for 10 weeks.After 10 weeks of observation, rats were placed in metal metabolic cages for collection of 24-hour urine samples.After that, all animals were sacrificed.Blood was collected from the femoral vein of rats anesthetized with an injection of sodium pentobarbital (30 mg/kg, i.p.),and plasma samples, centrifuged at 4000g for 10 min,were stored at-70℃for further research. The hypothalamus and kidneys were immediately removed, frozen in liquid nitrogen and stored at-70℃for further studies.Results:Not only the elevated levels of fasting plasma glucose, TG, TC,24-hour urinary protein but also the glomerular pathological change in the diabetic rats were attenuated by rhein(P<0.01)Conclusion:Rhein posses an anti-diabetic property accompanied with amelioration of diabetic nephropathy in STZ-induced rats. Part two:Effects of rhein on neuropeptide Y and its receptors Y1R, Y2R expressions in renal tissues of streptozotocin-induced diabetic ratsObjective:To investigate the effects of rhein on NPY and its receptors YIR, Y2R expressions in the renal tissue of STZ-induced diabetic rats.Methods:The methods of modeling, diving group and administrating are the same as Part 1.The concentration of NPY was measured by radioimmunoassay. The mRNA expression of NPY and its receptors YIR and Y2R were determined by real-time RT-PCR. Protein expression of NPY receptors YIR and Y2R were detected by western blot.Results:The increased expressions of NPY in hypothalamic and renal tissues in STZ-induced diabetic rats were reduced by the treatment of rhein (P<0.01),and the increased mRNA and protein levels of NPY receptors YIR and Y2R in the kidney of diabetic rats were also attenuated by rhein (P<0.05)Conclusion:Rhein posses an anti-diabetic property accompanied with amelioration of diabetic nephropathy in STZ-induced diabetic rats, may partly through ameliorating the abnormality expression of NPY and its receptors Y1R and Y2R.