Adjusting the 17b-etradiol-to-androgen ratio ameliorates diabetic nephropathy

Abstract

Diabetes is manifested predominantly in males in experimental models, and compelling evidence suggests that 17b-estradiol (E2) supplementation improves hyperglycemia in humans. We previously generated a severely diabetic transgenic (Tg) mouse model by b-cell-specific overexpression of inducible cAMP early repressor (ICER) and found that male but not female ICER-Tg mice exhibit sustained hyperglycemia and develop major clinical and pathologic features of human diabetic nephropathy (DN). Thus, we hypothesized that differences in circulating hormone levels have a key role in determining susceptibility to diabetes. Here, we examined whether DN inmale ICER-Tg mice is rescued by adjusting the androgen-to-E2 ratio to approximate that in normoglycemic female ICER-Tgmice. We treated hyperglycemic male ICER-Tgmice with orchiectomy (ORX), E2 pellet implantation, or both. E2 pellet implantation at an early stage of DN with or without ORX caused a rapid drop in blood glucose and a dramatic increase in b-cell number, and itmarkedly inhibited DNprogression [namely, E2 reduced glomerulosclerosis, collagen IV deposition and albuminuria, and prevented hyperfiltration]. Furthermore, E2 pellet implantation was more effective than ORX alone and induced a remarkable improvement, even when initiated at advanced-stage DN. In contrast, induction of normoglycemia by islet transplant in ICER-Tg mice eliminated albuminuria but was less effective than E2+ORX in reducing glomerulosclerosis or collagen IV deposition and hyperfiltration. These findings indicate that E2 treatment is effective, even after establishment of DN, whereas glucose normalization alone does not improve sclerotic lesions. We propose that E2 intervention is a potential therapeutic option for DN.