Uninephrectomy and class II PI3K-C2β inactivation synergistically protect against obesity, insulin resistance and liver steatosis in mice

Uninephrectomy (UNx) in living kidney donors for transplantation is now routine clinical practice. While chronic kidney disease, due to bilateral kidney dysfunction, is associated with insulin resistance, liver steatosis, and type 2 diabetes, the metabolic impact of UNx remains unclear. To better understand the crosstalk between the kidney and insulin target tissues, we studied the metabolic consequences of UNx and the potential involvement of class II PI3K-C2β, the inactivation of which has been reported to result in insulin sensitization. Mice underwent UNx or sham operation followed by either normal chow or high-fat diet (HFD). Seventeen weeks post-UNx, mice showed improved glucose tolerance, insulin sensitivity, and decreased HFD-induced liver steatosis. This was associated with an enhanced serum FGF21 and insulin-stimulated Akt signaling in the liver and muscle of both lean and obese mice. Remarkably, the combination of UNx and PI3K-C2β inactivation protected against HFD-induced obesity and further potentiated the metabolic improvement observed in WT UNx mice correlating with a synergistic increase in metabolic tissues of (1) insulin-stimulated Akt signaling (2) FGFR1 and βKlotho expression. We demonstrated a potential beneficial effect of kidney donation and more effectively with PI3K-C2β inactivation to protect against metabolic disorders through a mutual insulin/FGF21 sensitization.

Characterization of Enlarged Kidneys and Their Potential for Inducing Diabetes in DEK Rats

The kidneys participate in the regulation of systemic glucose metabolism via gluconeogenesis, insulin degradation, and the tubular reabsorption of glucose. The present study characterized rats from a strain of a novel type 2 diabetes model with enlarged kidneys (DEK). Histological and biochemical analyses of DEK rats were performed to assess the relationships between their kidneys and hyperglycemia. The kidney weight of diabetic DEK (DEK-DM) gradually increased over time from the onset of diabetes, with the glomerular number being higher in DEK-DM than in normal DEK (DEK-cont). A positive correlation between blood glucose level and kidney weight was observed in DEK-DM. The similar glomerular size and single glomerular creatinine clearance in DEK-cont and DEK-DM indicated that glomerular hypertrophy and hyperfiltration were not involved in the renal enlargement. Uninephrectomy (1/2Nx) in DEK-DM resulted in a reduction in blood glucose level at 7-28 post-operation days, with this concentration remaining lower than in Sham group until 84 days post-operation. 1/2Nx also improved systemic conditions, including reduced body weight gain, polyuria, polydipsia, and hyperphagia. Plasma concentrations of Na, total cholesterol, albumin, and total protein were higher, and urinary excretion of glucose, urea nitrogen, and proteins were lower, in the 1/2Nx than in the Sham group. Remnant kidney weight was two-fold higher in the 1/2Nx than in the Sham group 84 days later. In addition, 1/2Nx resulted in renal tubular dilatation but not in the progression of fibrosis or glomerular lesions. Taken together, these findings indicate that enlarged kidneys were associated with the onset of diabetes and with the resistance to diabetic nephropathy in DEK-DM.