L-Serine Supplementation Blunts Fasting-Induced Weight Regain by Increasing Brown Fat Thermogenesis.

Weight regain after fasting, often exceeding the pre-fasting weight, is a common phenomenon and big problem for the treatment of obesity. Thus, novel interventions maintaining reduced body weight are critically important to prevent metabolic disease. Here we investigate the metabolic effects of dietary L-serine supplementation, known to modulate various organ functions. C57BL/6N-Rj male mice were supplemented with or without 1% L-serine in their drinking water and fed with a chow or high-fat diet. Mice were fed either ad libitum or subjected to repeated overnight fasting. Body weight, body composition, glucose tolerance and energy metabolism were assessed. This was combined with a detailed analysis of the liver and adipose tissues, including the use of primary brown adipocytes to study mitochondrial respiration and protein expression. We find that L-serine supplementation has little impact on systemic metabolism in ad libitum-fed mice. Conversely, L-serine supplementation blunted fasting-induced body weight regain, especially in diet-induced obese mice. This reduction in body weight regain is likely due to the increased energy expenditure, based on elevated brown adipose tissue activity. Thus, L-serine supplementation during and after weight-loss could reduce weight regain and thereby help tackle one of the major problems of current obesity therapies.

Hypothalamic dopamine signaling regulates brown fat thermogenesis.

Dopamine signaling is a crucial part of the brain reward system and can affect feeding behavior. Dopamine receptors are also expressed in the hypothalamus, which is known to control energy metabolism in peripheral tissues. Here we show that pharmacological or chemogenetic stimulation of dopamine receptor 2 (D2R) expressing cells in the lateral hypothalamic area (LHA) and the zona incerta (ZI) decreases body weight and stimulates brown fat activity in rodents in a feeding-independent manner. LHA/ZI D2R stimulation requires an intact sympathetic nervous system and orexin system to exert its action and involves inhibition of PI3K in the LHA/ZI. We further demonstrate that, as early as 3 months after onset of treatment, patients treated with the D2R agonist cabergoline experience an increase in energy expenditure that persists for one year, leading to total body weight and fat loss through a prolactin-independent mechanism. Our results may provide a mechanistic explanation for how clinically used D2R agonists act in the CNS to regulate energy balance.

MCH Regulates SIRT1/FoxO1 and Reduces POMC Neuronal Activity to Induce Hyperphagia, Adiposity, and Glucose Intolerance.

Melanin-concentrating hormone (MCH) is an important regulator of food intake, glucose metabolism, and adiposity. However, the mechanisms mediating these actions remain largely unknown. We used pharmacological and genetic approaches to show that the sirtuin 1 (SIRT1)/FoxO1 signaling pathway in the hypothalamic arcuate nucleus (ARC) mediates MCH-induced feeding, adiposity, and glucose intolerance. MCH reduces proopiomelanocortin (POMC) neuronal activity, and the SIRT1/FoxO1 pathway regulates the inhibitory effect of MCH on POMC expression. Remarkably, the metabolic actions of MCH are compromised in mice lacking SIRT1 specifically in POMC neurons. Of note, the actions of MCH are independent of agouti-related peptide (AgRP) neurons because inhibition of γ-aminobutyric acid receptor in the ARC did not prevent the orexigenic action of MCH, and the hypophagic effect of MCH silencing was maintained after chemogenetic stimulation of AgRP neurons. Central SIRT1 is required for MCH-induced weight gain through its actions on the sympathetic nervous system. The central MCH knockdown causes hypophagia and weight loss in diet-induced obese wild-type mice; however, these effects were abolished in mice overexpressing SIRT1 fed a high-fat diet. These data reveal the neuronal basis for the effects of MCH on food intake, body weight, and glucose metabolism and highlight the relevance of SIRT1/FoxO1 pathway in obesity.

Beneficial Effects of Citrus Flavonoids on Cardiovascular and Metabolic Health.

The prevalence of cardiovascular disease (CVD) is increasing over time. CVD is a comorbidity in diabetes and contributes to premature death. Citrus flavonoids possess several biological activities and have emerged as efficient therapeutics for the treatment of CVD. Citrus flavonoids scavenge free radicals, improve glucose tolerance and insulin sensitivity, modulate lipid metabolism and adipocyte differentiation, suppress inflammation and apoptosis, and improve endothelial dysfunction. The intake of citrus flavonoids has been associated with improved cardiovascular outcomes. Although citrus flavonoids exerted multiple beneficial effects, their mechanisms of action are not completely established. In this review, we summarized recent findings and advances in understanding the mechanisms underlying the protective effects of citrus flavonoids against oxidative stress, inflammation, diabetes, dyslipidemia, endothelial dysfunction, and atherosclerosis. Further studies and clinical trials to assess the efficacy and to explore the underlying mechanism(s) of action of citrus flavonoids are recommended.

Obesity: Pathophysiology, monosodium glutamate-induced model and anti-obesity medicinal plants.

Obesity and overweight have increased at an alarming rate in the world during the last three decades. Obesity is a crucial factor in the development of metabolic abnormalities, including glucose intolerance, insulin resistance, metabolic syndrome, low-grade inflammation and oxidative stress. A similar scinario occurs during the aging process where alterations of the energetic metabolism homeostasis and a chronic systematic low-grade inflammation have been observed. Oxidative stress and poor physical performance can increase the risk of metabolic disease. Despite the diverse studies on the pathophysiological effects of obesity, its impact related to gender and through life, particularly during aging, hasn't received a reasonable attention. The purpose of this review is to outline the pathophysiological mechanisms and metabolic alterations associated with obesity, with an emphasis on the monosodium glutamate (MSG)-induced obese model. MSG-induced obesity associated inflammation and declined adiponectin were more obvious in male mice, while glucose tolerance, insulin sensitivity and the redox balance were altered with increased age of both male and female mice. These findings indicate that the metabolic alterations in MSG-induced obesity are associated with the gender as well as aging. Therefore, the MSG obesity model is of a resonable value to underlie the relationship between gender, aging and metabolic alterations in obesity. In addition, we reviewed the medicinal plants and their active constituents which have been used to treat MSG-induced obesity. Given the significat value of this model, studies are needed to scrutinize the benificial effects and underlying mechanisms of medicinal plants with proven anti-obesity activity.

p53 in AgRP neurons is required for protection against diet-induced obesity via JNK1.

p53 is a well-known tumor suppressor that has emerged as an important player in energy balance. However, its metabolic role in the hypothalamus remains unknown. Herein, we show that mice lacking p53 in agouti-related peptide (AgRP), but not proopiomelanocortin (POMC) or steroidogenic factor-1 (SF1) neurons, are more prone to develop diet-induced obesity and show reduced brown adipose tissue (BAT) thermogenic activity. AgRP-specific ablation of p53 resulted in increased hypothalamic c-Jun N-terminal kinase (JNK) activity before the mice developed obesity, and central inhibition of JNK reversed the obese phenotype of these mice. The overexpression of p53 in the ARC or specifically in AgRP neurons of obese mice decreased body weight and stimulated BAT thermogenesis, resulting in body weight loss. Finally, p53 in AgRP neurons regulates the ghrelin-induced food intake and body weight. Overall, our findings provide evidence that p53 in AgRP neurons is required for normal adaptations against diet-induced obesity.

Effect of fructooligosaccharides fraction from Psacalium decompositum on inflammation and dyslipidemia in rats with fructose-induced obesity.

Psacalium decompositum, commonly known as "Matarique," is a medicinal plant used in Mexico for diabetes mellitus empirical therapy. Previous studies have shown that the fructooligosaccharides (FOS) present in the roots of this plant exhibit a notable hypoglycemic effect in animal models; this effect might be associated with the attenuation of the inflammatory process and other metabolic disorders. In this study, we examined the effects of FOS fraction administration in a fructose-fed rat model for obesity. Phytochemical chromatographic studies (high performance thin layer chromatography and nuclear magnetic resonance) were performed to verify isolation of FOS. 24 male Wistar rats were maintained for 12 weeks on a diet of 20% HFCS in drinking water and chow. Glucose, cholesterol, triglycerides and liver transaminases levels were measured monthly, after administering FOS fraction intragastrically (150 mg/kg/day for 12 weeks), while the levels of inflammatory cytokines were only quantified at the end of the treatments. Rats treated with FOS fraction decreased body weight, cholesterol, triglycerides, and significantly reduced IL-6, IFN-γ, MCP-1, IL-1ß and VEGF levels (p < 0.05). These results suggest that P. decompositum has anti-inflammatory and hypolipidemic properties that might be used as an alternative treatment for the control of obesity.