CPT1A in AgRP neurons is required for sex-dependent regulation of feeding and thirst

Fatty acid metabolism in the hypothalamus has an important role in food intake, but its specific role in AgRP neurons is poorly understood. Here, we examined whether carnitinea palmitoyltransferase 1A (CPT1A), a key enzyme in mitochondrial fatty acid oxidation, affects energy balance. To obtain Cpt1a KO mice and their control littermates, Cpt1a (flox/flox) mice were crossed with tamoxifen-inducible AgRP CreERT2 mice. Food intake and body weight were analyzed weekly in both males and females. At 12 weeks of age, metabolic flexibility was determined by ghrelin-induced food intake and fasting-refeeding satiety tests. Energy expenditure was analyzed by calorimetric system and thermogenic activity of brown adipose tissue. To study fluid balance the analysis of urine and water intake volumes; osmolality of urine and plasma; as well as serum levels of angiotensin and components of RAAS (renin-angiotensin-aldosterone system) were measured. At the central level, changes in AgRP neurons were determined by: (1) analyzing specific AgRP gene expression in RiboTag- Cpt1a KO mice obtained by crossing Cpt1a KO mice with RiboTag mice; (2) measuring presynaptic terminal formation in the AgRP neurons with the injection of the AAV1 -EF1a-DIO-synaptophysin-GFP in the arcuate nucleus of the hypothalamus; (3) analyzing AgRP neuronal viability and spine formations by the injection AAV9 -EF1a-DIO-mCherry in the arcuate nucleus of the hypothalamus; (4) analyzing in situ the specific AgRP mitochondria in the ZsGreen- Cpt1a KO obtained by breeding ZsGreen mice with Cpt1a KO mice. Two-way ANOVA analyses were performed to determine the contributions of the effect of lack of CPT1A in AgRP neurons in the sex. Changes in food intake were just seen in male Cpt1a KO mice while only female Cpt1a KO mice increased energy expenditure. The lack of Cpt1a in the AgRP neurons enhanced brown adipose tissue activity, mainly in females, and induced a substantial reduction in fat deposits and body weight. Strikingly, both male and female Cpt1a KO mice showed polydipsia and polyuria, with more reduced serum vasopressin levels in females and without osmolality alterations, indicating a direct involvement of Cpt1a in AgRP neurons in fluid balance. AgRP neurons from Cpt1a KO mice showed a sex-dependent gene expression pattern, reduced mitochondria and decreased presynaptic innervation to the paraventricular nucleus, without neuronal viability alterations. Our results highlight that fatty acid metabolism a