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GABA_B Receptor Signaling in the Mesolimbic System Suppresses Binge-like Consumption of a High-Fat Diet.

ABSTRACT: Binge eating could contribute to the development of obesity, and previous studies suggest that gamma-aminobutyric acid (GABA) type B receptor (GABA_BR) signaling is involved in the regulation of binge eating. Here, we show that time-restricted access to a high-fat diet (HFD) induces binge-like eating behavior in wild-type mice. HFD consumption during restricted time was significantly increased in corticostriatal neuron-specific GABA_BR-deficient mice compared with wild-type mice. Furthermore, the GABA_BR agonist baclofen suppressed HFD intake during restricted time in wild-type mice but not in corticostriatal or dopaminergic neuron-specific GABA_BR-deficient mice. In contrast, there were no significant differences in food consumption among genotypes under ad libitum access to HFD. Thus, our data show that the mesolimbic system regulates food consumption under time-restricted but not ad libitum access to HFD and have identified a mechanism by which GABA_BR signaling suppresses binge-like eating of HFD.

SUBMITTER: Tsunekawa T

PROVIDER: S-EPMC6817655 | biostudies-literature | 2019 Oct

REPOSITORIES: biostudies-literature

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GABAB Receptor Signaling in the Mesolimbic System Suppresses Binge-like Consumption of a High-Fat Diet.

Tsunekawa Taku T Banno Ryoichi R Yaginuma Hiroshi H Taki Keigo K Mizoguchi Akira A Sugiyama Mariko M Onoue Takeshi T Takagi Hiroshi H Hagiwara Daisuke D Ito Yoshihiro Y Iwama Shintaro S Goto Motomitsu M Suga Hidetaka H Bettler Bernhard B Arima Hiroshi H

iScience 20190926

Binge eating could contribute to the development of obesity, and previous studies suggest that gamma-aminobutyric acid (GABA) type B receptor (GABABR) signaling is involved in the regulation of binge eating. Here, we show that time-restricted access to a high-fat diet (HFD) induces binge-like eating behavior in wild-type mice. HFD consumption during restricted time was significantly increased in corticostriatal neuron-specific GABABR-deficient mice compared with wild-type m ...[more]

PMID: 31610370

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Project description:Binge drinking refers to a pattern of alcohol intake that raises blood alcohol concentration to or above legal intoxication levels. It is common among young adults and is associated with health risks that scale up with alcohol intake. Acute intoxication depresses neural activity via complex signaling mechanisms by enhancing inhibition mediated by gamma-amino butyric acid (GABA), and by decreasing excitatory glutamatergic effects. Evidence primarily rooted in animal research indicates that the brain compensates for the acute depressant effects under the conditions of habitual heavy use. These neuroadaptive changes are reflected in neural hyperexcitability via downregulated inhibitory signaling, which becomes apparent as withdrawal symptoms. However, human evidence on the compensatory reduction in GABA signaling is scant. The neurochemical aspect of this mechanistic model was evaluated in the present study with proton magnetic resonance spectroscopy (1H-MRS) which is sensitive to GABA plus macromolecule signal (GABA + ). Furthermore, we examined sex differences in GABA + levels as a function of a recent history of binge drinking, given interactions between endogenous neurosteroids, GABA signaling, and alcohol. The study recruited young adult women and men (22.2 ± 2.8 years of age) who were classified as binge drinkers (BDs, N = 52) if they reported ≥ 5 binge episodes in the previous six months. Light drinkers (LDs, N = 49) reported drinking regularly, but not exceeding ≤ 2 binge episodes in the past six months. GABA-edited 1H-MR spectra were acquired from the occipital cortex at 3 T with the MEGA-PRESS sequence. GABA + signal was analyzed relative to water and total creatine (Cr) levels as a function of binge drinking history and sex. Controlling for within-voxel tissue composition, both GABA + indices showed decreased GABA + levels in BDs relative to LDs. The reduced GABA + concentration was associated with occasional high-intensity drinking in the BD group. This evidence is consistent with compensatory GABA downregulation that accompanies alcohol misuse, tipping the excitation/inhibition balance towards hyperexcitability. Analysis of the time course of GABA + neuroplasticity indicated that GABA + was lowest when measured one day after the last drinking occasion in BDs. While the BD vs LD differences were primarily driven by LD women, there was no interaction between Sex and a history of binge drinking. GABA + was higher in LD women compared to LD men. Aligned with the allostasis model, the mechanistic compensatory GABA downregulation observed in young emerging adults engaging in occasional binge drinking complements direct neural measures of hyperexcitability in BDs. Notably, these results suggest that neuroadaptation to alcohol is detectable at the levels of consumption that are within a normative range, and may contribute to adverse health outcomes.

Project description:P2Y2, a G protein-coupled receptor (R), is expressed in all organs involved in the development of obesity and insulin resistance. To explore the role of it in diet-induced obesity, we fed male P2Y2-R whole body knockout (KO) and wild type (WT) mice (B6D2 genetic background) with regular diet (CNT; 10% calories as fat) or high-fat diet (HFD; 60% calories as fat) with free access to food and water for 16 weeks, and euthanized them. Adjusted for body weights (BW), KO mice consumed modestly, but significantly more HFD vs. WT mice, and excreted well-formed feces with no taint of fat or oil. Starting from the 2nd week, HFD-WT mice displayed significantly higher BW with terminal mean difference of 22% vs. HFD-KO mice. Terminal weights of white adipose tissue (WAT) were significantly lower in the HFD-KO vs. HFD-WT mice. The expression of P2Y2-R mRNA in WAT was increased by 2-fold in HFD-fed WT mice. Serum insulin, leptin and adiponectin levels were significantly elevated in the HFD-WT mice, but not in the HFD-KO mice. When induced in vitro, preadipocytes derived from KO mice fed regular diet did not differentiate and mature as robustly as those from the WT mice, as assessed by cellular expansion and accumulation of lipid droplets. Blockade of P2Y2-R by AR-C118925 in preadipocytes derived from WT mice prevented differentiation and maturation. Under basal conditions, KO mice had significantly higher serum triglycerides and showed slightly impaired lipid tolerance as compared to the WT mice. HFD-fed KO mice had significantly better glucose tolerance (GTT) as compared to HFD-fed WT mice. Whole body insulin sensitivity and mRNA expression of insulin receptor, IRS-1 and GLUT4 in WAT was significantly higher in HFD-fed KO mice vs. HFD-fed WT mice. On the contrary, the expression of pro-inflammatory molecules MCP-1, CCR2, CD68, and F4/80 were significantly higher in the WAT of HFD-fed WT vs. HFD-fed KO mice. These data suggest that P2Y2-R plays a significant role in the development of diet-induced obesity by promoting adipogenesis and inflammation, and altering the production of adipokines and lipids and their metabolism in adipose tissue, and thereby facilitates HFD-induced insulin resistance.

Dataset Information

GABA_B Receptor Signaling in the Mesolimbic System Suppresses Binge-like Consumption of a High-Fat Diet.

Publications

GABA<sub>B</sub> Receptor Signaling in the Mesolimbic System Suppresses Binge-like Consumption of a High-Fat Diet.

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