Renal Changes in the Early Stages of Diet-Induced Obesity in Ovariectomized Rats

Abstract

The relationship between obesity and renal lesions, especially in low estrogen levels, has been less documented. The aim of this study was to assess the renal changes in diet-induced obesity in ovariectomized rats. Wistar rats were ovariectomized or sham-operated and divided into four groups: sham-operated rats fed a standard diet (SSD); ovariectomized rats fed a standard diet (OSD); sham-operated rats fed a high-fat diet (SHFD); ovariectomized rats fed a high-fat diet (OHFD). Body weight and blood pressure were measured weekly. The rats were killed 24 weeks after initiation of standard or high-fat diet treatment, the kidneys were removed for immunohistochemical and histological studies. Blood and urine samples were collected to quantify sodium, potassium and creatinine. OHFD rats presented increases in visceral adipose tissue, serum insulin levels, blood pressure and proteinuria, and a decrease in fractional excretion of sodium as well. Histological and morphometric studies showed focal alterations in the renal cortex. Expression of macrophages, lymphocytes, nuclear factor-kappa B (NF-kB), Proliferating Cell Nuclear Antigen (PCNA), angiotensin II (ANG II) and vimentin was greater in OHFD rats than in control rats. Thus, these results demonstrate that the high-fat diet in ovariectomized rats promoted renal function and structure changes, renal interstitial infiltration of mononuclear cells and increased expression of ANG II and NF-kB.

Beneficial effects of previous exercise training on renal changes in streptozotocin-induced diabetic female rats

“…There are evidences suggesting an influence of gender on the incidence and progression of nondiabetic renal disease, and 17β-estradiol have been reported to exert renoprotective actions in both experimental animals and women of fertile age. 2–5 However, the influence of gender on diabetic renal disease is controversial. While some studies have demonstrated that diabetic nephropathy progress is faster in males, 29,30 others indicate the opposite, 31,32 suggesting that the renoprotection conferred to females is lost in the presence of DM, possibly due to a dysregulation of sex hormones.…”

“…Diabetic nephropathy is one of the most important clinical complications of diabetes mellitus (DM) and is the most common cause of end-stage renal disease. 1 Although evidences point the female sex as a renoprotective factor against the development of nondiabetic renal diseases, 2,3 several studies demonstrated that in DM this renoprotection appears to be lost, possibly due to dysregulation of the production of female sex hormones, which may be present in DM. 4–8…”

Ovariectomy exacerbates glycerol-induced acute kidney injury in rats

“…Before measurement, the animals were acclimated to the blood pressure recording. The average of five pressure readings was recorded for each measurement 18 .…”

“…The tubulointerstitial injury was defined as tubular necrosis, tubular lumen dilation, denuded basement membrane, intraluminal casts formation, swelling, and flattening of proximal tubular cells with brush border loss, inflammatory cell infiltrate or intratubular debris. A scale ranging from 0 to 4 was used to grade the renal damage 18 . Thirty-grid fields from the renal cortex measuring 0.245 mm 2 were evaluated in a section of each kidney.…”

“…The cells labeled positive for ED1 present in capillary lumens were not counted as infiltrating cells. To evaluate immunoperoxidase staining for nitrotyrosine and NF-κB, thirty consecutive grid fields of the renal cortex of each animal (measuring 0.245 mm2) were graded by score (ranging from 0 to IV) and provided an average score for each kidney 18 . The immunohistochemical analysis was performed by two independent observers who did not know the treatment groups.…”