Leptin-dependent gene expression and function in mouse kidney

Abstract

Objective: Leptin regulates energy balance via leptin receptor expressed in central and peripheral tissues. Little is known about leptin receptor (Lepr)-mediated kidney gene expression and function. Here, we determined kidney gene expression of Lepr splice variants, leptin-sensitive kidney gene expression, and the role of Lepr in renal tubular cells for the response to a high fat diet. Methods: A) Four groups of male mice were used for urine/plasma analysis, and kidney cortex RNA-seq and quantitative RT-PCR (qPCR) analysis: BTBR wild-type, BTBR ob/ob-vehicle (BTBR background in ob/ob promotes diabetic kidney disease), BTBR ob/ob-chronic leptin replacement [6 days via osmotic mini-pump, 4.7 μg/day], and BTBR ob/ob-acute leptin replacement [single dose of 5 mg/kg body weight i.p. and analysis after 7 hours]; all 12-19 weeks old; n=4~15/group. B) Tubular Lepr knockdown (Pax8-Lepr KO) mice were generated by the Pax8-Cre/loxP system, and 5-week old male Pax8-Lepr KO and littermate control mice (n=8-12/group) were fed either control diet or high fat diet (60 kcal% fat) for 35 weeks. Lepr in situ hybridization and qPCR were performed in kidney tissue, and physiological parameters and urinary albumin to creatinine ratio (UACR) were determined. Results: qPCR analysis of Lepr splice variants A, B and C in BTBR mouse kidney revealed a ratio of ~100:10:1 in cortex and medulla with medullary levels being ~10x higher vs cortex with little effects of leptin deficiency (ob/ob)/or replacement. Chronic leptin replacement in ob/ob mice reduced hyperphagia, hyperglycemia and albuminuria, associated with normalization of kidney mRNA expression of molecular markers of glycolysis, gluconeogenesis, amino acid synthesis and megalin. Acute leptin replacement was ineffective implicating indirect metabolic effects for albuminuria in leptin deficiency. Tubular knockdown of Lepr and in situ hybridization indicated that a minor fraction of kidney Lepr mRNA is expressed by tubular cells compared with interstitial or endothelial cells. Nonetheless, Pax8-Lepr KO mice had 13% lower kidney weight (P=0.038). Moreover, they presented similar high fat diet-induced increases in plasma leptin levels, body and kidney weight, and GFR vs controls but a 50% reduced rise in UACR (P=0.0005). Two additional leptin or tubular Lepr-sensitive genes were identified: Leptin deficiency and tubular Lepr knockdown reduced renal expression of acetoacetyl-CoA synthetase (AACS) and increased expression of gremlin 1 (Grem1), while leptin replacement in ob/ob induced opposite effects. Conclusions: Leptin deficiency may increase albuminuria via systemic metabolic effects that impinge on kidney megalin expression. Hyperleptinemia-induced albuminuria may involve direct effects via tubular Lepr. Implications of the novel tubular Lepr/AACS/Grem1 axis and of Lepr variants remain to be determined. This study was supported by Janssen Pharmaceuticals, Inc. This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.