Neonatal inhibition of androgen activity alters the programming of body weight and orexinergic peptides differentially in male and female rats.

The involvement of androgens in the regulation of energy metabolism has been demonstrated. The main objective of the present research was to study the involvement of androgens in both the programming of energy metabolism and the regulatory peptides associated with feeding. For this purpose, androgen receptors and the main metabolic pathways of testosterone were inhibited during the first five days of postnatal life in male and female Wistar rats. Pups received a daily s.c. injection from the day of birth, postnatal day (P) 1, to P5 of Flutamide (a competitive inhibitor of androgen receptors), Letrozole (an aromatase inhibitor), Finasteride (a 5-alpha-reductase inhibitor) or vehicle. Body weight, food intake and fat pads were measured. Moreover, hypothalamic Agouti-related peptide (AgRP), neuropeptide Y (NPY), orexin, and proopiomelanocortin (POMC) were analyzed by quantitative real-time polymerase chain reaction assay. The inhibition of androgenic activity during the first five days of life produced a significant decrease in body weight in females at P90 but did not affect this parameter in males. Moreover, the inhibition of aromatase decreased hypothalamic AgRP mRNA levels in males while the inhibition of 5α-reductase decreased hypothalamic AgRP and orexin mRNA levels in female rats. Finally, food intake and visceral fat, but not subcutaneous fat, were affected in both males and females depending on which testosterone metabolic pathway was inhibited. Our results highlight the differential involvement of androgens in the programming of energy metabolism as well as the AgRP and orexin systems during development in male and female rats.

Activity-based anorexia alters hypothalamic POMC and orexin populations in male rats.

The objective of this study was to investigate the orexin and POMC populations in the hypothalamic nuclei of male Wistar rats after the activity-based anorexia (ABA) procedure. Four groups were established based on food restriction and activity: activity (A), ABA, diet (D) and control (C). The ABA protocol consisted of free access to a running wheel for a period of 22 h and access to food for 1 h. When the animals in the ABA group reached the ABA criterion, were sacrificed, and their brains were collected and serially sectioned. The free-floating sections were processed for orexin and POMC immunostaining. The number of orexin A-ir cells in the perifornical-dorsomedial-hypothalamus continuum (PFD) and lateral hypothalamus (LH) and the number of POMC-ir cells in the arcuate nucleus (Arc) were estimated. Data on food intake, body weight and wheel turns were also analyzed. The ABA procedure caused a significant decrease in body weight along with a significant increase in activity. Moreover, at the end of the ABA procedure, the number of POMC-ir cells decreased in the Arc in the A group, and significantly more in the ABA group, and the number of orexin A-ir positive cells decreased in the LH in D and ABA groups. The differential decrease in POMC in the ABA group emphasizes the importance of the melanocortin system in the maintenance of ABA, but more research is needed to elucidate the involvement of this peptide in the mechanism that promotes and maintains anorexia nervosa and how increased activity may interact with all these processes.

Prenatal Low-Protein and Low-Calorie Diets Differentially Alter Arcuate Nucleus Morphology in Newborn Male Rats.

Background: Malnutrition during the early stages of development produces alterations that can compromise the functioning of the hypothalamic circuits that regulate food intake. The purpose of this study is to analyze the effects that a low-protein and low-calorie diet has on the morphology of the arcuate nucleus (ARC) of the hypothalamus in newborn male and female rats. Methods: On gestational day 6 (G6), six pregnant rats were divided into two groups. One group was made up of three pregnant rats, which were fed ad libitum with a control diet (20% casein), and the other one was made up of three pregnant rats, which were fed ad libitum with a low-protein diet (8% casein) and 30% of a calorie-restricted diet. On the day of birth, pups were sacrificed, resulting in four experimental groups: control male, control female, low-protein and low-calorie diet male, and low-protein and low-calorie diet female (n = 5 in each group). The volume and number of neurons, together with the neuronal density and number of apoptotic cells, were measured. Results: Males on a low-protein and low-calorie diet showed a significant increase in the number of neurons and in the neuronal density of the ARC with regard to the rest of the groups studied. These increases were also reflected in the posterior part of the nucleus. Although the existence of sexual dimorphism was not detected in any of the parameters studied in the control groups, the number of neurons and neuronal density showed differences between males and females fed with a low-protein and low-calorie diets due to the increase in the number of neurons shown by the male. No significant differences were found in the number of apoptotic cells. Conclusion: Our results show that a low-protein and low-calorie diet during the prenatal stage produces alterations in the ARC of the hypothalamus in newborn animals and, more importantly, that the effects of malnutrition are evident in males but not in females. Therefore, it is essential to follow a balanced diet during the early stages of life to ensure optimal development of the neural circuits that regulate eating.

Maternal hypercaloric diet affects factors involved in lipid metabolism and the endogenous cannabinoid systems in the hypothalamus of adult offspring: sex-specific response of astrocytes to palmitic acid and anandamide.

Aim: We aimed to investigate whether maternal malnutrition during gestation/lactation induces long-lasting changes on inflammation, lipid metabolism and endocannabinoid signaling in the adult offspring hypothalamus and the role of hypothalamic astrocytes in these changes.Methods: We analyzed the effects of a free-choice hypercaloric palatable diet (P) during (pre)gestation, lactation and/or post-weaning on inflammation, lipid metabolism and endogenous cannabinoid signaling in the adult offspring hypothalamus. We also evaluated the response of primary hypothalamic astrocytes to palmitic acid and anandamide.Results: Postnatal exposure to a P diet induced factors involved in hypothalamic inflammation (Tnfa and Il6) and gliosis (Gfap, vimentin and Iba1) in adult offspring, being more significant in females. In contrast, maternal P diet reduced factors involved in astrogliosis (vimentin), fatty acid oxidation (Cpt1a) and monounsaturated fatty acid synthesis (Scd1). These changes were accompanied by an increase in the expression of the genes for the cannabinoid receptor (Cnr1) and Nape-pld, an enzyme involved in endocannabinoid synthesis, in females and a decrease in the endocannabinoid degradation enzyme Faah in males. These changes suggest that the maternal P diet results in sex-specific alterations in hypothalamic endocannabinoid signaling and lipid metabolism. This hypothesis was tested in hypothalamic astrocyte cultures, where palmitic acid (PA) and the polyunsaturated fatty acid N-arachidonoylethanolamine (anandamide or AEA) were found to induce similar changes in the endocannabinoid system (ECS) and lipid metabolism.Conclusion: These results stress the importance of both maternal diet and sex in long term metabolic programming and suggest a possible role of hypothalamic astrocytes in this process.