Abstract: TH-PO692

Insulin Prevents Bcl2 Modifying Factor-Induced Renal Proximal Tubular Cell Apoptosis via Stimulation of Heterogeneous Nuclear Ribonucleoprotein F and Sirtuin-1 Expression in Diabetic Akita Mice

Session Information

Category: Diabetes

  • 501 Diabetes Mellitus and Obesity: Basic - Experimental

Authors

  • Ghosh, Anindya, CRCHUM, University of Montreal, Montreal, Quebec, Canada
  • Lo, Chao-Sheng, CRCHUM, Universite de Montreal, Montreal, Quebec, Canada
  • Chenier, Isabelle, CHUM-Hotel Dieu Hosp, Montreal, Quebec, Canada
  • Abdo, Shaaban, CRCHUM, University of Montreal, Montreal, Quebec, Canada
  • Filep, Janos G., Maisonneuve-Rosemont Hosp., Montreal, Quebec, Canada
  • Ingelfinger, Julie R., The New England Journal of Medicine, Boston, Massachusetts, United States
  • Zhang, Shao-Ling, Research Center of Centre Hospitalier de l Universite de Montreal (CRCHUM), Montreal, Quebec, Canada
  • Chan, John S.D., CRCHUM,University of Montreal, Montreal, Quebec, Canada
Background

Tubular atrophy and tubulointerstitial fibrosis are closely associated with loss of renal function in diabetes. However, the underlying mechanisms are not fully understood. Here we investigated the role of the pro-apoptotic BH3-only protein, BCL2-modifying factor (Bmf), in renal proximal tubular cell (RPTC) apoptosis in mice and studied the effects of insulin on Bmf in rat immortalized RPTCs (IRPTCs) in vitro.

Methods

Non-transgenic (Tg) and Tg mice specifically overexpressing human Bmf in RPTCs were studied at 10 to 20 weeks of age. Non-Akita littermates and Akita mice (a type 1 diabetes model) +/- insulin implant from the age of 12 weeks were also studied until week 16. Blood glucose, systolic blood pressure (SBP), and urinary albumin creatinine ratio (ACR) were measured bi-weekly. Kidneys were processed for histology. RPTC apoptosis was evaluated by TUNEL assay. Freshly isolated RPTs were assessed for gene and protein expression by qPCR and Western blotting, respectively. Urinary cells were assessed by flow cytometry and then qunatified by qPCR for human Bmf transgene expression. Rat IRPTC stably transfected with a plasmid containing the full length Bmf promoter fused to luciferase reporter (pGL4.20 N-1370/+102) were cultured in normal glucose (5mM) or high glucose (HG, 25mM) medium +/- insulin.

Results

Bmf-Tg mice exhibited higher systolic blood pressure, ACR, RPTC apoptosis and more urinary RPTCs than non-Tg mice. Insulin treatment suppressed Bmf expression and tubular apoptosis and reduced urinary RPTCs in Akita mice. In vitro, insulin stimulated hnRNP F and sirtuin-1 expression and inhibited Bmf promoter activity in HG medium. Promoter DNA analysis identified putative responsive elements for hnRNP F, p53 and Foxo3 in rat Bmf promoter. Transfection of small interference RNA of hnRNP F or sirtuin-1 abrogated insulin inhibition of Bmf promoter activity.

Conclusion

Overexpression of Bmf in RPTCs induces RPTC apoptosis. Insulin prevents RPTC apoptosis via stimulation of hnRNP F and sirtuin-1 expression to inhibit Bmf gene expression in the diabetic kidney.

Funding

  • Government Support - Non-U.S.