Intermittent High-Fat Diet Intake Reduces Sensitivity to Intragastric Nutrient Infusion and Exogenous Amylin in Female Rats

The Impact of Binge-Like Palatable Food Intake on the Endogenous Glucagon-Like Peptide-1 System in Female Rats

Binge eating involves consumption of large amounts of food and a loss of control over the amount consumed. The incidence of binge eating disorder is higher in females than males, hinting at important sex differences in binge eating behavior, but the neural underpinnings of binge eating still remain unresolved. Recent work in male rats has shown that a history of binge-like palatable food intake suppresses hindbrain expression of preproglucagon (PPG), the precursor for glucagon-like peptide-1 (GLP-1). Given the roles of GLP-1 in reducing feeding and food reward, this could be a mechanism underlying binge-like eating in rodents. However, whether similar effects occur in female rats is unknown. Here, we tested the hypothesis that a history of binge-like palatable food intake in female rats would reduce PPG expression in the nucleus tractus solitarius (NTS), a key central site of GLP-1 production. Female rats given access to vegetable shortening every fourth day (4D) engaged in binge-like feeding, demonstrated by consuming significantly more shortening during the first hour of fat access compared to counterparts with ad libitum (AL) fat access. After several weeks of fat access under these schedules, PPG and GLP-1 receptor (GLP-1R) expression were measured in the NTS and ileum. Surprisingly, and in contrast to previous findings in male rats, there were no significant differences in expression of PPG or GLP-1R in either site in 4D versus AL rats, nor were there effects on plasma GLP-1 levels. These findings highlight key differences in the effects of binge-like intake on the central GLP-1 system in female compared to male rats.

Timosaponin alleviates oxidative stress in rats with high fat diet-induced obesity via activating Nrf2/HO-1 and inhibiting the NF-κB pathway

Anemarrhena asphodeloides originated from the rhizome of Liliaceae Anemarrhena asphodeloides. One of the active pharmacological components of Anemarrhena asphodeloides is timosaponin (TSA), which reduces blood lipids and shows antioxidation and anti-inflammatory effects, but its mechanism is unclear. The objective of this study was to investigate the effect of TSA on oxidative stress induced by a long-term high-fat diet in obese rats. Body weight and the obesity index of the rats were measured during the experiment. Total antioxidant capacity (T-AOC), malondialdehyde (MDA), and glutathione peroxidase (GSH-Px) were used to detect oxidative stress indexes in serum and liver tissue. To observe the effect of TSA on the liver and adipose tissue of rats with oxidative stress, hematoxylin & eosin (H&E) staining was used. The p-NF-κB, NAD(P)H: quinone oxidoreductase 1 (NQO-1), Heme oxygenase 1 (HO-1), and Nrf2 in Nrf2/HO-1 and NF-κB pathways were assayed by reverse transcription-polymerase chain reaction (RT-PCR) and Western blot. TSA was found to improve oxidative stress in obese rats by reducing MDA levels and increasing T-AOC and GSH-Px levels. Histological examination revealed that TSA effectively attenuated liver damage and improved obesity in rats. TSA was found to down-regulate the protein level of p-NF-κB and up-regulate the protein level of Nrf2/HO-1. These results suggested that TSA could effectively block inflammation and dyslipidemia in obese rats, thus improving oxidative stress, and its mechanism could be related to the Nrf2/HO-1 and NF-κB pathways.

Glucagon-Like Peptide-1 (GLP-1) in the Integration of Neural and Endocrine Responses to Stress

Glucagon like-peptide 1 (GLP-1) within the brain is produced by a population of preproglucagon neurons located in the caudal nucleus of the solitary tract. These neurons project to the hypothalamus and another forebrain, hindbrain, and mesolimbic brain areas control the autonomic function, feeding, and the motivation to feed or regulate the stress response and the hypothalamic-pituitary-adrenal axis. GLP-1 receptor (GLP-1R) controls both food intake and feeding behavior (hunger-driven feeding, the hedonic value of food, and food motivation). The activation of GLP-1 receptors involves second messenger pathways and ionic events in the autonomic nervous system, which are very relevant to explain the essential central actions of GLP-1 as neuromodulator coordinating food intake in response to a physiological and stress-related stimulus to maintain homeostasis. Alterations in GLP-1 signaling associated with obesity or chronic stress induce the dysregulation of eating behavior. This review summarized the experimental shreds of evidence from studies using GLP-1R agonists to describe the neural and endocrine integration of stress responses and feeding behavior.