12248 Leptin Signaling Deficiency At The Central Nervous System Reduces Hepatic Glucagon Sensibility Disturbing Liver Amino Acid Metabolism Leading To Hyperaminoacidemia And Hyperglucagonemia In Male Adult Rats

Abstract

Abstract Disclosure: C. Pintado Losa: None. L. Mazuecos Fernández-Pacheco: None. Ó. Gómez Torres: None. S. Artigas Jerónimo: None. E. Burgos Ramos: None. I. Ramos: None. J. Poveda Colado: None. C. Arribas Mocoroa: None. A. Andres: None. N. Gallardo: None. Leptin regulates glucagon secretion, but the contribution of central leptin resistance to circulating glucagon levels and hepatic glucagon signaling is poorly studied. To analyze the effects of deficient hypothalamic leptin signaling on glucagon levels and hepatic glucagon signaling, we infused intracerebroventricularly a rat-specific leptin receptor antagonist SLA (0,2 µg/day) for 21 days to male 3-month-old Wistar rats (n=12) or PBS (n=12). At day 21 of treatment and 30 min before sacrifice, a glucagon challenge (100 µg/kg) was performed in 16h fasted rats. After sacrifice, blood and liver samples were collected for analysis. Serum hormones, urea, and total and branched-chain amino acids (BCAA) levels were determined using commercial kits and by RP-HPLC. Hepatic neutral lipid was extracted and quantified using an enzymatic kit and the hepatic content of mRNA and proteins involved in lipid and amino acid metabolism were measured by RT-PCR and Western-Blot. Additionally, the HOMA-IR and glucagon-alanine index were determined in all rats. Blocking central leptin signaling led to impaired fat oxidation and triglyceride export capacity in the liver, resulting in a 50% increase in hepatic triglyceride content in SLA-treated rats. Glucagonemia increased in SLA-treated rats, indicating impaired hepatic glucagon sensitivity. In fact, in response to exogenous glucagon, the hepatic phosphorylation of CREB was reduced by 55% in SLA-infused compared to control rats. Importantly, SLA treatment significantly decreases the expression and the activity of BCKDH (branched-chain alpha-keto acid dehydrogenase) in the liver, leading to a reduction in the BCAA degradation in SLA-treated rats, hyperaminoacidemia, and decreased serum urea levels. In conclusion, deficient hypothalamic leptin signaling alters glucose, lipid, and amino acid homeostasis, highlighting the relevance of central leptin action in the control of peripheral metabolism and glucagon sensitivity. Funding: Work supported by Ministerio de Ciencia, Innovación y Universidades under project grants RTI2018-098643-B-I00, PID2021-128243OB-I00, and from the University of Castilla-La Mancha and the European Regional Development Fund (FEDER) under project grant 2023- GRIN-34280. Presentation: 6/1/2024