The metabolic syndrome is characterized by visceral obesity, hypertension, hyperlipidemia, and insulin resistance. Whole body energy balance is maintained through the integration of nutritional and hormonal information by two distinct neuronal populations in the mediobasal hypothalamus, the agouti-related peptide (AgRP) and the proopiomelanocortin (POMC) neurons. The hypothalamic POMC neurons express POMC that is processed to generate -melanocyte stimulating hormone (-MSH), which promotes energy expenditure. Macroautophagy (MA) is an essential mechanism that maintains cellular homeostasis by degrading proteins and organelles in lysosomes. Our published results have shown a role for MA in hypothalamic AgRP neurons in control of food intake. We have found that MA proteins are required for POMC processing and -MSH production as rodents lacking MA in hypothalamic POMC neurons display reduced -MSH, increased adiposity and glucose intolerance. Decreased MA activity has been described in different organs in old organisms, and we have now demonstrated a similar decrease in hypothalamic MA with age. The role of MA in hypothalamic -MSH production, and the mechanisms that reduce hypothalamic MA during aging are unknown. The overall goal of this proposal is to elucidate the contribution of failure of hypothalamic MA with age to the metabolic syndrome of aging. To that purpose we will: 1) determine whether nutrient, and hormonal activation of MA in POMC neurons mechanistically links -MSH production to peripheral energy expenditure, 2) characterize the neuron-intrinsic mechanisms that decrease MA in hypothalamic POMC neurons with age and in response to high fat feeding, and 3) examine whether restoration of hypothalamic MA using a novel scheduled-feeding intervention reverses or prevents the development of the metabolic syndrome of aging. These studies will be performed in primary hypothalamic neurons, hypothalamic cell lines, and in cohorts of different age control mice or those with the hypothalamic POMC-neuron specific ablation of the MA gene ATG7. Significance: The metabolic syndrome is a significant global health problem that affects greater than 44% of the U.S. population aged more than 50 years. The metabolic syndrome affects health span in the aging population through one of many adverse effects on cardio- and cerebrovascular health, locomotor activity, vision and cognition, as well as on the development of tumors. The current proposal will delineate a novel role for MA in hypothalamic regulation of energy homeostasis, setting the basis for therapeutic modulation of hypothalamic MA in preventing or treating the metabolic syndrome of aging, and in this way improving the quality of life and health-span in the aged.
The metabolic syndrome is a significant health problem affecting greater than 44% of the U.S. population of more than 50 years of age. Studies in this application will determine a new hypothalamic neuronal mechanism that controls whole body energy balance, and examine how the dysregulation of this mechanism with age promotes obesity and insulin resistance. These studies will be critical to the development of new strategies against the metabolic syndrome of aging.
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