Insulin Signaling in the Hypothalamic Pro-opiomelanocortin (POMC) Neuronal Cell Model, mHypoA-POMC/GFP-1: Effects of Insulin Resistance

Program: Late-Breaking Abstracts
Session: MON-LB-Late-Breaking Poster Session 3
Bench to Bedside
Monday, June 17, 2013: 1:45 PM-3:45 PM
Expo Halls ABC (Moscone Center)

Poster Board MON-LB-07
Claire B Lee*, Anaies Nazarians-Armavil, Jennifer A Chalmers and Denise D Belsham
University of Toronto, Toronto, ON, Canada
Neurons in the hypothalamus expressing the prohormone proopiomelanocortin (POMC) and its anorexigenic derivative, alpha-melanocyte stimulating hormone (α-MSH), are responsible for appetite suppression.  The proper regulation of POMC and α-MSH levels by metabolic hormones, such as insulin, is critical in the maintenance of energy homeostasis and warrants thorough investigation.  Using the newly generated mHypoA-POMC/GFP-1 cell line, our laboratory investigated insulin-mediated changes in POMC mRNA levels by quantitative real-time RT-PCR, and also examined activation of insulin receptor-mediated downstream signaling molecules by Western blot analysis, before and after the induction of cellular insulin resistance.  The treatment of mHypoA-POMC/GFP-1 neurons with 10 nM insulin for 4 h significantly upregulated POMC mRNA levels by 38%, and reduced insulin receptor (IR) mRNA levels by 17% compared to vehicle-treated controls. Insulin also induced phosphorylation of AKT, ERK1/2 and FOXO1 compared to time-matched controls.  Next, insulin resistance was induced in the mHypoA-POMC/GFP-1 neurons via 24 h pre-treatment with 100 nM insulin.  Subsequent re-challenge with 10 nM insulin failed to cause the increase in POMC mRNA and the decrease in IR mRNA levels observed in insulin-sensing neurons.  Additionally, phosphorylation of AKT and FOXO1 were significantly attenuated, and total protein levels of IR were reduced.  Our findings provide evidence substantiating the existence of a cellular phenotype of insulin resistance in POMC neurons.  Furthermore, the mHypoA-POMC/GFP-1 cell line will serve as a representative POMC neuronal cell model to delineate the molecular mechanisms involved in hypothalamic control of energy regulation and metabolic disorders.

Funding sources: CIHR, NSERC, CRC, and CFI to DDB; NSERC and BBDC to CBL; CIHR and BBDC to AN-A.

Nothing to Disclose: CBL, AN, JAC, DDB

*Please take note of The Endocrine Society's News Embargo Policy at http://www.endo-society.org/endo2013/media.cfm

Sources of Research Support: Canadian Institutes of Health Research (CIHR); Natural Sciences and Engineering Research Council of Canada (NSERC); Canada Research Chair (CRC); and Canada Foundation for Innovation (CFI) to DDB. NSERC; Banting and Best Diabetes Centre (BBDC) to CBL. CIHR; BBDC to AN-A.