Neuroscience
-
Review
POMC Neurons Dysfunction in Diet-induced Metabolic Disease: Hallmark or Mechanism of Disease?
One important lesson from the last decade of studies in the field of systemic energy metabolism is that obesity is first and foremost a brain disease. Hypothalamic neurons dysfunction observed in response to chronic metabolic stress is a key pathogenic node linking consumption of hypercaloric diets with body weight gain and associated metabolic sequelae. ⋯ However, whether such neuronal dysfunction represents a consequence or a mechanism of disease, remains a subject of debate. Here, we will review and highlight emerging pathogenic mechanisms that explain why POMC neurons undergo dysfunctional activity in response to caloric overload, and critically address whether these mechanisms may be causally implicated in the physiopathology of obesity and of its associated co-morbidities.
-
Maternal obesity plays a key role in the health trajectory of the offspring. Although research on this topic has largely focused on the potential of this condition to increase the risk for child obesity, it is becoming more and more evident that it can also significantly impact cognitive function and mental health. The mechanisms underlying these effects are starting to be elucidated and point to the placenta as a critical organ that may mediate changes in the response to stress, immune function and oxidative stress. ⋯ More recent evidence also indicates the gut microbiota as a potential mediator of these effects. Overall, understanding cause-effect relationships can allow the development of preventive measures that could rely upon dietary changes in the mother and the offspring. Addressing diets appears more feasible than developing new pharmacological targets and has the potential to affect the multiple interconnected physiological pathways engaged by these complex regulations, allowing prevention of both metabolic and mental disorders.
-
Amylin is co-secreted with insulin by pancreatic β-cells in response to a meal and produced by neurons in discrete hypothalamic brain areas. Leptin is proportionally secreted by the adipose tissue. Both hormones control food intake and energy homeostasis post-weaning in rodents. ⋯ Whether amylin and leptin interact during pregnancy and lactation remains to be assessed. Lastly, during brain development, amylin and leptin are major regulators of cell birth during embryogenesis and act as neurotrophic factors in the neonatal period. This review will highlight the role of amylin and leptin, and their possible interaction, during these dynamic time periods of pregnancy, lactation, and early development.
-
Cholecystokinin (CCK) released from the small intestine increases the activity of vagal afferents that relay satiety signals to the caudal nucleus of the solitary tract (cNTS). A caudal subset of A2 noradrenergic neurons within the cNTS that express prolactin-releasing peptide (PrRP) have been proposed to mediate CCK-induced satiety. However, the ability of exogenous CCK to activate cFos expression by PrRP neurons has only been reported in rats and mice after a very high dose (i.e., 50 μg/kg BW) that also activates the hypothalamic-pituitary-adrenal stress axis. ⋯ CCK-treated rats displayed increased numbers of cFos-positive cNTS neurons compared to non-injected and saline-injected controls, with no effect of diet. In chow-fed rats, a significantly larger proportion of PrRP neurons were activated after CCK treatment compared to controls; conversely, CCK did not increase PrRP neuronal activation in HFD-fed rats. Collectively, these results indicate that a relatively low dose of exogenous CCK is sufficient to activate PrRP neurons in chow-fed rats, and that this effect is blunted in rats maintained for several weeks on HFD.
-
Overweight and obesity are major risk factors for a number of chronic diseases, including diabetes, cardiovascular diseases, and cancer. Obesity rates are on the rise worldwide with women more frequently affected than men. Hedonic responses to food seem to play a key role in obesity, but the exact mechanisms and relationships are still poorly understood. ⋯ In contrast, among women with low ad libitum consumption levels, greater BMI was associated with less experienced pleasantness. At the neural level, satiety affected women with obesity to a lesser degree than women with healthy weight. Thus, having obesity was associated with altered relationships between food consumption and the hedonic responses to food rewards as well as reduced satiety effects in women.