Renal-Protective Effects of the Peroxisome Proliferator-Activated Receptor-γ Agonist Pioglitazone in ob/ob Mice

Abstract

BACKGROUND This study investigated the therapeutic effects of the peroxisome proliferator-activated receptor-γ (PPARγ) agonist pioglitazone in ob/ob mice with obesity-related glomerulopathy (ORG). MATERIAL AND METHODS A total of 24 mice were divided into 3 groups: wild-type C57BL/6 mice (n=8), ob/ob mice (n=8), and ob/ob mice receiving pioglitazone treatment (n=8). Body mass, blood glucose, serum adiponectin (ADP), and urine microalbumin (mALB) levels were determined. Renal histology was examined using light and electron microscopy. Wilms tumor 1 (WT1), Zonula occludens-1 (ZO-1), AMP activated protein kinase (AMPK), and NADPH oxidase-4 (NOX-4) expression were evaluated by immunohistochemistry and Western blot. RESULTS Serum ADP did not alter between weeks 0 and 12 in the control group, while the ob/ob mice showed a time-dependent decrease that was prevented by pioglitazone. Urinary mALB did not alter between week 0 and 12 in the control group, but was higher in week 0 and week 12 in the ob/ob group. Pioglitazone prevented the rise in urinary mALB in week 12. Histology revealed glomerulomegaly, mesangial proliferation, focal segmental glomerulosclerosis, and foot processes fusion in the ob/ob group, which were ameliorated by pioglitazone treatment. Compared to the control group, ob/ob mice had a higher kidney index and glomerular diameter, which were reduced by pioglitazone treatment. Immunohistochemical and Western blot experiments revealed lower expression levels of WT1, ZO-1, and AMPK and higher NOX-4 expression level in the ob/ob group, which was prevented by pioglitazone treatment. CONCLUSIONS Pioglitazone, a PPARγ agonist, can prevent ORG, probably by reducing oxidative stress.

Figure 1

Morphometric and biochemical measurements, including body mass (A), blood glucose (B), serum ADP (C), and urine mALB (D), in control (WT), ob/ob mice (ob/ob), and ob/ob mice receiving pioglitazone (ob/ob+PGZ). Data are displayed as mean. * P<0.05, ** P<0.01 compared to WT group at the same time; ^& P<0.05, ^&& P<0.01 compared to ob/ob group at the same time; ^# P<0.05, ^## P<0.01 compared to week 0 of the experiment at the same group.

Figure 2

Renal histology by light microscopy (LM, ×200, A) and electron microscopy (EM, ×10 000, B). Arrows point to podocyte foot processes. Kidney index (C) and glomerular diameter (D) in control (WT), ob/ob mice (ob/ob), and ob/ob mice receiving pioglitazone (ob/ob+PGZ). Data are displayed as mean and SD. ** P<0.01.

Figure 3

Immunohistochemical experiments showing the WT1, ZO-1, AMPK, and NOX-4 expression (IHC, ×200, A), with quantification (B). Data are displayed as mean and SD. * P<0.05; ** P<0.01.

Figure 4

Western blot experiments showing the WT1, ZO-1, AMPK, and NOX-4 expression (A), with quantification (B). Data are displayed as mean and SD. * P<0.05; ** P<0.01.