A putative physiological role of hypothalamic CNTF in the control of energy homeostasis

Switching from high-fat diet to foods containing resveratrol as a calorie restriction mimetic changes the architecture of arcuate nucleus to produce more newborn anorexigenic neurons

PURPOSE

These days, obesity threatens the health for which one of the main interventions is calorie restriction (CR). Due to the difficulty of compliance with this treatment, CR mimetics such as resveratrol (RSV) have been considered. The present study compared the effects of RSV and CR on hypothalamic remodeling in a diet-switching experiment.

METHODS

C57BL/6 male mice received high-fat diet (HFD) for 4 weeks, subsequently their diet switched to chow diet, HFD + RSV, chow diet + RSV or CR diet for a further 6 weeks. Body weight, fat accumulation, hypothalamic apoptosis and expression of trophic factors as well as generation and fate specification of newborn cells in arcuate nucleus (ARC) were evaluated.

RESULTS

Switching diet to RSV-containing foods leading to weight and fat loss after 6 weeks. In addition, not only a significant reduction in apoptosis but also a considerable increase in production of newborn cells in ARC occurred following consumption of RSV-enriched diets. These were in line with augmentation of hypothalamic ciliary neurotrophic factor and leukemia inhibitory factor expression. Interestingly, RSV-containing diets changed the fate of newborn neurons toward generation of more proopiomelanocortin than neuropeptide Y neurons. The CR had effects similar to those of RSV-containing diets in the all-evaluated aspects besides neurogenesis in ARC.

CONCLUSIONS

Although both RSV-containing and CR diets changed the fate of newborn neurons to create an anorexigenic architecture for ARC, newborn neurons were more available after switching to RSV-enriched diets. It can be consider as a promising mechanism for future investigations.

Red pitaya juice supplementation ameliorates energy balance homeostasis by modulating obesity-related genes in high-carbohydrate, high-fat diet-induced metabolic syndrome rats

Background

Red pitaya (Hylocereus polyrhizus) or known as buah naga merah in Malay belongs to the cactus family, Cactaceae. Red pitaya has been shown to give protection against liver damage and may reduce the stiffness of the heart. Besides, the beneficial effects of red pitaya against obesity have been reported; however, the mechanism of this protection is not clear. Therefore, in the present study, we have investigated the red pitaya-targeted genes in obesity using high-carbohydrate, high-fat diet-induced metabolic syndrome rat model.

Methods

A total of four groups were tested: corn-starch (CS), corn-starch + red pitaya juice (CRP), high-carbohydrate, high-fat (HCHF) and high-carbohydrate, high-fat + red pitaya juice (HRP). The intervention with 5 % red pitaya juice was continued for 8 weeks after 8 weeks initiation of the diet. Retroperitoneal, epididymal and omental fat pads were collected and weighed. Plasma concentration of IL-6 and TNF-α were measured using commercial kits. Gene expression analysis was conducted using RNA extracted from liver samples. A total of eighty-four genes related to obesity were analyzed using PCR array.

Results

The rats fed HCHF-diet for 16 weeks increased body weight, developed excess abdominal fat deposition and down-regulated the expression level of IL-1α, IL-1r1, and Cntfr as compared to the control group. Supplementation of red pitaya juice for 8 weeks increased omental and epididymal fat but no change in retroperitoneal fat was observed. Red pitaya juice reversed the changes in energy balance homeostasis in liver tissues by regulation of the expression levels of Pomc and Insr. The increased protein expression levels of IL-6 and TNF-α in HCHF group and red pitaya treated rats confirmed the results of gene expression.

Conclusion

Collectively, this study revealed the usefulness of this diet-induced rat model and the beneficial effects of red pitaya on energy balance homeostasis by modulating the anorectic, orexigenic and energy expenditure related genes.

Role of BMP7 in appetite regulation, adipogenesis, and energy expenditure

Bone morphogenetic protein 7 (BMP7), also known as osteogenic protein-1 (OP-1) is a member of Transforming growth factor-β (TGF-β) family of proteins. Bone morphogenetic proteins were discovered in 1965 by Marshal Urist, of which BMP7 is of particular interest in this review being a leptin-independent anorexinogen and having role in energy expenditure in the brown adipose tissue, which makes it a potential target for preventing/treating obesity. As it has been established that Obesity displays a state of leptin-resistance, thus a protein-like BMP7 which acts through a leptin-independent pathway could give new therapeutic directions. This review will also discuss the synthesis and action of BMP7, along with its receptors and signal transduction. A brief note about BMP7-mediated brown fat development and energy balance is also discussed.

Opposite effects of a high-fat diet and calorie restriction on ciliary neurotrophic factor signaling in the mouse hypothalamus

In the mouse hypothalamus, ciliary neurotrophic factor (CNTF) is mainly expressed by ependymal cells and tanycytes of the ependymal layer covering the third ventricle. Since exogenously administered CNTF causes reduced food intake and weight loss, we tested whether endogenous CNTF might be involved in energy balance regulation. We thus evaluated CNTF production and responsiveness in the hypothalamus of mice fed a high-fat diet (HFD), of ob/ob obese mice, and of mice fed a calorie restriction (CR) regimen. RT-PCR showed that CNTF mRNA increased significantly in HFD mice and decreased significantly in CR animals. Western blotting confirmed that CNTF expression was higher in HFD mice and reduced in CR mice, but high interindividual variability blunted the significance of these differences. By immunohistochemistry, hypothalamic tuberal and mammillary region tanycytes stained strongly for CNTF in HFD mice, whereas CR mice exhibited markedly reduced staining. RT-PCR and Western blotting disclosed that changes in CNTF expression were paralleled by changes in the expression of its specific receptor, CNTF receptor α (CNTFRα). Injection of recombinant CNTF and detection of phospho-signal transducer and activator of transcription 3 (P-STAT3) showed that CNTF responsiveness by the ependymal layer, mainly by tanycytes, was higher in HFD than CR mice. In addition, in HFD mice CNTF administration induced distinctive STAT3 signaling in a large neuron population located in the dorsomedial and ventromedial nuclei, perifornical area and mammillary body. The hypothalamic expression of CNTF and CNTFRα did not change in the hyperphagic, leptin-deficient ob/ob obese mice; accordingly, P-STAT3 immunoreactivity in CNTF-treated ob/ob mice was confined to ependymal layer and arcuate neurons. Collectively, these data suggest that hypothalamic CNTF is involved in controlling the energy balance and that CNTF signaling plays a role in HFD obese mice at specific sites.

The cytokine ciliary neurotrophic factor (CNTF) activates hypothalamic urocortin-expressing neurons both in vitro and in vivo

Ciliary neurotrophic factor (CNTF) induces neurogenesis, reduces feeding, and induces weight loss. However, the central mechanisms by which CNTF acts are vague. We employed the mHypoE-20/2 line that endogenously expresses the CNTF receptor to examine the direct effects of CNTF on mRNA levels of urocortin-1, urocortin-2, agouti-related peptide, brain-derived neurotrophic factor, and neurotensin. We found that treatment of 10 ng/ml CNTF significantly increased only urocortin-1 mRNA by 1.84-fold at 48 h. We then performed intracerebroventricular injections of 0.5 mg/mL CNTF into mice, and examined its effects on urocortin-1 neurons post-exposure. Through double-label immunohistochemistry using specific antibodies against c-Fos and urocortin-1, we showed that central CNTF administration significantly activated urocortin-1 neurons in specific areas of the hypothalamus. Taken together, our studies point to a potential role for CNTF in regulating hypothalamic urocortin-1-expressing neurons to mediate its recognized effects on energy homeostasis, neuronal proliferaton/survival, and/or neurogenesis.

Fetal metabolic programming and epigenetic modifications: a systems biology approach

A growing body of evidence supports the notion that epigenetic changes such as DNA methylation and histone modifications, both involving chromatin remodeling, contribute to fetal metabolic programming. We use a combination of gene-protein enrichment analysis resources along with functional annotations and protein interaction networks for an integrative approach to understanding the mechanisms underlying fetal metabolic programming. Systems biology approaches suggested that fetal adaptation to an impaired nutritional environment presumes profound changes in gene expression that involve regulation of tissue-specific patterns of methylated cytosine residues, modulation of the histone acetylation-deacetylation switch, cell differentiation, and stem cell pluripotency. The hypothalamus and the liver seem to be differently involved. In addition, new putative explanations have emerged about the question of whether in utero overnutrition modulates fetal metabolic programming in the same fashion as that of a maternal environment of undernutrition, suggesting that the mechanisms behind these two fetal nutritional imbalances are different. In conclusion, intrauterine growth restriction is most likely to be associated with the induction of persistent changes in tissue structure and functionality. Conversely, a maternal obesogenic environment is most probably associated with metabolic reprogramming of glucose and lipid metabolism, as well as future risk of metabolic syndrome (MS), fatty liver, and insulin (INS) resistance.

The anorexigenic cytokine ciliary neurotrophic factor stimulates POMC gene expression via receptors localized in the nucleus of arcuate neurons

Ciliary neurotrophic factor (CNTF) is a neural cytokine that reduces appetite and body weight when administrated to rodents or humans. We have demonstrated recently that the level of CNTF in the arcuate nucleus (ARC), a key hypothalamic region involved in food intake regulation, is positively correlated with protection against diet-induced obesity. However, the comprehension of the physiological significance of neural CNTF action was still incomplete because CNTF lacks a signal peptide and thus may not be secreted by the classical exocytosis pathways. Knowing that CNTF distribution shares similarities with that of its receptor subunits in the rat ARC, we hypothesized that CNTF could exert a direct intracrine effect in ARC cells. Here, we demonstrate that CNTF, together with its receptor subunits, translocates to the cell nucleus of anorexigenic POMC neurons in the rat ARC. Furthermore, the stimulation of hypothalamic nuclear fractions with CNTF induces the phosphorylation of several signaling proteins, including Akt, as well as the transcription of the POMC gene. These data strongly suggest that intracellular CNTF may directly modulate POMC gene expression via the activation of receptors localized in the cell nucleus, providing a novel plausible mechanism of CNTF action in regulating energy homeostasis.

Bone morphogenetic protein 7 (BMP7) reverses obesity and regulates appetite through a central mTOR pathway

Body weight is regulated by coordinating energy intake and energy expenditure. Transforming growth factor β (TGFβ)/bone morphogenetic protein (BMP) signaling has been shown to regulate energy balance in lower organisms, but whether a similar pathway exists in mammals is unknown. We have previously demonstrated that BMP7 can regulate brown adipogenesis and energy expenditure. In the current study, we have uncovered a novel role for BMP7 in appetite regulation. Systemic treatment of diet-induced obese mice with BMP7 resulted in increased energy expenditure and decreased food intake, leading to a significant reduction in body weight and improvement of metabolic syndrome. Similar degrees of weight loss with reduced appetite were also observed in BMP7-treated ob/ob mice, suggesting a leptin-independent mechanism utilized by BMP7. Intracerebroventricular administration of BMP7 to mice led to an acute decrease in food intake, which was mediated, at least in part, by a central rapamycin-sensitive mTOR-p70S6 kinase pathway. Together, these results underscore the importance of BMP7 in regulating both food intake and energy expenditure, and suggest new therapeutic approaches for obesity and its comorbidities.

Thermogenesis and related metabolic targets in anti-diabetic therapy

Exercise, together with a low-energy diet, is the first-line treatment for type 2 diabetes type 2 diabetes . Exercise improves insulin sensitivity insulin sensitivity by increasing the number or function of muscle mitochondria mitochondria and the capacity for aerobic metabolism, all of which are low in many insulin-resistant subjects. Cannabinoid 1-receptor antagonists and β-adrenoceptor agonists improve insulin sensitivity in humans and promote fat oxidation in rodents independently of reduced food intake. Current drugs for the treatment of diabetes are not, however, noted for their ability to increase fat oxidation, although the thiazolidinediones increase the capacity for fat oxidation in skeletal muscle, whilst paradoxically increasing weight gain.There are a number of targets for anti-diabetic drugs that may improve insulin sensitivity insulin sensitivity by increasing the capacity for fat oxidation. Their mechanisms of action are linked, notably through AMP-activated protein kinase, adiponectin, and the sympathetic nervous system. If ligands for these targets have obvious acute thermogenic activity, it is often because they increase sympathetic activity. This promotes fuel mobilisation, as well as fuel oxidation. When thermogenesis thermogenesis is not obvious, researchers often argue that it has occurred by using the inappropriate device of treating animals for days or weeks until there is weight (mainly fat) loss and then expressing energy expenditure energy expenditure relative to body weight. In reality, thermogenesis may have occurred, but it is too small to detect, and this device distracts us from really appreciating why insulin sensitivity has improved. This is that by increasing fatty acid oxidation fatty acid oxidation more than fatty acid supply, drugs lower the concentrations of fatty acid metabolites that cause insulin resistance. Insulin sensitivity improves long before any anti-obesity effect can be detected.