Mouse Microglial Calcitonin Receptor Knockout Impairs Hypothalamic Amylin Neuronal pSTAT3 Signaling but Lacks Major Metabolic Consequences

Amylin and leptin synergistically interact in the arcuate nucleus of the hypothalamus (ARC) to control energy homeostasis. Our previous rodent studies suggested that amylin-induced interleukin-6 release from hypothalamic microglia may modulate leptin signaling in agouti-related peptide expressing neurons. To confirm the physiological relevance of this finding, the calcitonin receptor (CTR) subunit of the amylin receptor was selectively depleted in microglia by crossing tamoxifen (Tx) inducible Cx3cr1-CreERT2 mice with CTR-floxed mice. Unexpectedly, male mice with CTR-depleted microglia (KO) gained the least amount of weight of all groups regardless of diet. However, after correcting for the tamoxifen effect, there was no significant difference for body weight, fat mass or lean mass between genotypes. No alteration in glucose tolerance or insulin release was detected. However, male KO mice had a reduced respiratory quotient suggesting a preference for fat as a fuel when fed a high fat diet. Importantly, amylin-induced pSTAT3 was decreased in the ARC of KO mice but this was not reflected in a reduced anorectic response. On the other hand, KO mice seemed to be less responsive to leptin’s anorectic effect while displaying similar ARC pSTAT3 as Tx-control mice. Together, these data suggest that microglial amylin signaling is not a major player in the control of energy homeostasis in mice.

Efficacy and safety of the metformin-mazindol anorectic combination in rat

The current study investigates the anorectic interaction and safety of the mazindol-metformin combination in rats. Isobologram and interaction index were used to determine anorectic interaction between mazindol and metformin in the sweetened milk model. The safety profile of the mazindol-metformin combination was determined by measuring anxiety, blood pressure, hematic biometry and blood chemistry. An acute dose of mazindol and metformin administered per os, individually or as a mixture, has reduced the milk consumption in rats in a dose-dependent manner. Theoretical effective dose 40 (ED40t) did not differ from the experimental effective dose 40 (ED40e) obtained with the mazindol-metformin mixture in the anorexia experiments, by Student′s t-test. In addition, the interaction index confirmed the additive anorectic effect between both drugs. A single oral dose of ED40e mazindol-metformin mixture induced anxiolysis in the elevated plus-maze test. Moreover, oral administration of mazindol-metformin combination for 3 months significantly decreased glycemia, but not blood pressure nor other parameters of hematic biometry and blood chemistry. Results suggest that mazindol-metformin combination exerts an additive anorectic effect, as well as anxiolytic and hypoglycemic properties. Mazindol-metformin combination might be useful in obese patients with anxiety disorders or diabetes risk factors.

Peripheral Spexin Inhibited Food Intake in Mice

Spexin (SPX, NPQ), a novel endogenous neuropeptide, was firstly identified by bioinformatics. Spexin gene and protein widely distributed in the central nervous system and peripheral tissues, such as the hypothalamus and digestive tract. The role of spexin in appetite regulation in mammalian is still unclear. The present study was designed to investigate the mechanism and effect of peripheral spexin on food intake in mice. During the light period, an intraperitoneal (i.p.) injection of spexin (10 nmol/mouse) significantly inhibited cumulative food intake at 2, 4, and 6 h after treatment in fasted mice. During the dark period, spexin (1 and 10 nmol/mouse, i.p.) significantly suppressed cumulative food intake at 4 and 6 h after treatment in freely feeding mice. The GALR3 antagonist SNAP37889, not GALR2 antagonist, significantly antagonized the inhibitory effect on cumulative food intake (0–6 h) induced by spexin. Spexin significantly reduced the mRNA level of Npy mRNA, not Agrp, Pomc, Cart, Crh, Orexin, or Mch, in the hypothalamus. Spexin (10 nmol/mouse, i.p.) increased the number of c-Fos positive neurons in hypothalamic AHA and SCN, but not in ARC, DMN, LHA, PVN, SON, or VMH. The hypothalamic p-CaMK2 protein expression was upregulated by spexin. This study indicated that acute peripheral injection of spexin inhibited mouse food intake. The anorectic effect may be mediated by GALR3, and inhibiting neuropeptide Y (NPY) via p-CaMK2 and c-Fos in the hypothalamus.

mTOR signaling in the arcuate nucleus of the hypothalamus mediates the anorectic action of estradiol

Current evidence suggests that estradiol (E2), the main ovarian steroid, modulates energy balance by regulating both feeding and energy expenditure at the central level, through the energy sensor AMP-activated protein kinase (AMPK). We hypothesized that the hypothalamic mechanistic target of rapamycin (mTOR) pathway, a well-established nutrient sensor and modulator of appetite and puberty, could also mediate the anorectic effect of E2. Our data showed that ovariectomy (OVX) elicited a marked downregulation of the mTOR signaling in the arcuate nucleus of the hypothalamus (ARC), an effect that was reversed by either E2 replacement or central estrogen receptor alpha (ERα) agonism. The significance of this molecular signaling was given by the genetic inactivation of S6 kinase B1 (S6K1, a key downstream mTOR effector) in the ARC, which prevented the E2-induced hypophagia and weight loss. Overall, these data indicate that E2 induces hypophagia through modulation of mTOR pathway in the ARC.

The glucagon-like peptide-1 receptor in the ventromedial hypothalamus reduces short-term food intake in male mice by regulating nutrient sensor activity

Pharmacological activation of the glucagon-like peptide-1 receptor (GLP-1R) in the ventromedial hypothalamus (VMH) reduces food intake. Here, we assessed whether suppression of food intake by GLP-1R agonists (GLP-1RA) in this region is dependent on AMP-activated protein kinase (AMPK) and mammalian target of rapamycin (mTOR). We found that pharmacological inhibition of glycolysis, and thus activation of AMPK, in the VMH attenuates the anorectic effect of the GLP-1R agonist exendin-4 (Ex4), indicating that glucose metabolism and inhibition of AMPK are both required for this effect. Furthermore, we found that Ex4-mediated anorexia in the VMH involved mTOR but not acetyl-CoA carboxylase, two downstream targets of AMPK. We support this by showing that Ex4 activates mTOR signaling in the VMH and Chinese hamster ovary (CHO)-K1 cells. In contrast to the clear acute pharmacological impact of the these receptors on food intake, knockdown of the VMH Glp1r conferred no changes in energy balance in either chow- or high-fat-diet-fed mice, and the acute anorectic and glucose tolerance effects of peripherally dosed GLP-1RA were preserved. These results show that the VMH GLP-1R regulates food intake by engaging key nutrient sensors but is dispensable for the effects of GLP-1RA on nutrient homeostasis.

Evaluation of Anti Anorectic Activity of Zingiber officinale R. (Zingiberaceae)

A rhizome of Zingiber officinale R. commonly known as Ginger is one of the most popular anti-inflammatory drug in Indian traditional medicine. 6-gingerol is one of the constituent contributing in anti-inflammatory activity of Ginger. Ginger extract and 6-gingerol act as an anti inflammatory via inhibition of proinflammatory cytokines. Increase in proinflammatory cytokines is also responsible for the reduction in food intake resulting anorexia. The aim of the present study was thus to determine antianorectic activity of standardized hydroalcoholic extract of ginger and similarly the biomarker 6- gingerol was also studied to evaluate its contribution in antianorectic activity. Anorexia was induced by intraperitoneal administration of E.coli lipopolysaccharide (100µg/kg) and Fluoxetine (FLU 8mg/kg) in rats. The effect of same doses of the extract was also tested in freely feeding rats. Effect of ginger and 6- gingerol both were studied The results showed that at 200 and 400 mg/kg, ginger reversed the anorectic effect while 6- gingerol at 5mg/ kg require for the effect. Moreover the same doses did not modify the food intake in freely feeding rats. These findings provide strong evidence that ginger is ableto attenuate anorexia induced by proinflammatory cytokines mediators.