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Dietary triglycerides act on mesolimbic structures to regulate the rewarding and motivational aspects of feeding.

ABSTRACT: Circulating triglycerides (TGs) normally increase after a meal but are altered in pathophysiological conditions, such as obesity. Although TG metabolism in the brain remains poorly understood, several brain structures express enzymes that process TG-enriched particles, including mesolimbic structures. For this reason, and because consumption of high-fat diet alters dopamine signaling, we tested the hypothesis that TG might directly target mesolimbic reward circuits to control reward-seeking behaviors. We found that the delivery of small amounts of TG to the brain through the carotid artery rapidly reduced both spontaneous and amphetamine-induced locomotion, abolished preference for palatable food and reduced the motivation to engage in food-seeking behavior. Conversely, targeted disruption of the TG-hydrolyzing enzyme lipoprotein lipase specifically in the nucleus accumbens increased palatable food preference and food-seeking behavior. Finally, prolonged TG perfusion resulted in a return to normal palatable food preference despite continued locomotor suppression, suggesting that adaptive mechanisms occur. These findings reveal new mechanisms by which dietary fat may alter mesolimbic circuit function and reward seeking.

SUBMITTER: Cansell C

PROVIDER: S-EPMC4303340 | biostudies-literature | 2014 Oct

REPOSITORIES: biostudies-literature

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Dietary triglycerides act on mesolimbic structures to regulate the rewarding and motivational aspects of feeding.

Cansell C C Castel J J Denis R G P RG Rouch C C Delbes A-S AS Martinez S S Mestivier D D Finan B B Maldonado-Aviles J G JG Rijnsburger M M Tschöp M H MH DiLeone R J RJ Eckel R H RH la Fleur S E SE Magnan C C Hnasko T S TS Luquet S S

Molecular psychiatry 20140415 10

Circulating triglycerides (TGs) normally increase after a meal but are altered in pathophysiological conditions, such as obesity. Although TG metabolism in the brain remains poorly understood, several brain structures express enzymes that process TG-enriched particles, including mesolimbic structures. For this reason, and because consumption of high-fat diet alters dopamine signaling, we tested the hypothesis that TG might directly target mesolimbic reward circuits to control reward-seeking beha ...[more]

PMID: 24732670

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Project description:Current epidemic obesity levels apply great medical and financial pressure to the strenuous economy of obesity-prone cultures, and neuropeptides involved in body weight regulation are regarded as attractive targets for a possible treatment of obesity in humans. The lateral hypothalamus and the nucleus accumbens shell (AcbSh) form a hypothalamic-limbic neuropeptide feeding circuit mediated by Melanin-Concentrating Hormone (MCH). MCH promotes feeding behavior via MCH receptor-1 (MCH1R) in the AcbSh, although this relationship has not been fully characterized. Given the AcbSh mediates reinforcing properties of food, we hypothesized that MCH modulates motivational aspects of feeding.Here we show that chronic loss of the rat MCH-precursor Pmch decreased food intake predominantly via a reduction in meal size during rat development and reduced high-fat food-reinforced operant responding in adult rats. Moreover, acute AcbSh administration of Neuropeptide-GE and Neuropeptide-EI (NEI), both additional neuropeptides derived from Pmch, or chronic intracerebroventricular infusion of NEI, did not affect feeding behavior in adult pmch(+/+) or pmch(-/-) rats. However, acute administration of MCH to the AcbSh of adult pmch(-/-) rats elevated feeding behavior towards wild type levels. Finally, adult pmch(-/-) rats showed increased ex vivo electrically evoked dopamine release and increased limbic dopamine transporter levels, indicating that chronic loss of Pmch in the rat affects the limbic dopamine system.Our findings support the MCH-MCH1R system as an amplifier of consummatory behavior, confirming this system as a possible target for the treatment of obesity. We propose that MCH-mediated signaling in the AcbSh positively mediates motivational aspects of feeding behavior. Thereby it provides a crucial signal by which hypothalamic neural circuits control energy balance and guide limbic brain areas to enhance motivational or incentive-related aspects of food consumption.

Project description:Dietary fatty acids have myriads of effects on human health and disease. Many of these effects are likely achieved by altering expression of genes. Several transcription factors have been shown to be responsive to fatty acids, including SREBP-1c, NF-kB, RXRs, LXRs, FXR, HNF4Î±, and PPARs. However, the relative importance of these transcription factors in regulation of gene expression by dietary fatty acids remains unclear. Here, we take advantage of a unique experimental design using synthetic triglycerides composed of one single fatty acid in combination with gene expression profiling to examine the acute effects of individual dietary fatty acids on hepatic gene expression in mice. The dietary interventions were performed in parallel in wild-type and PPARÎ±-/- mice, enabling the determination of the specific contribution of PPARÎ±. Depending on chain length and degree of saturation, dietary fatty acids caused a statistically significant change in expression of over 400 genes. Surprisingly, the far majority of genes regulated by dietary fatty acids in wild-type mice were unaltered in mice lacking PPARÎ±, indicating PPARÎ±-dependent regulation. We conclude that the effects of dietary fatty acids on hepatic gene expression are almost entirely mediated by PPARÎ±, indicating that PPARÎ± dominates fatty acid-dependent gene regulation in liver. Experiment Overall Design: 2-6 months old male pure bred wild-type (129S1/SvImJ) and PPARÎ± -/- (129S4/SvJae) mice were used. Experiment Overall Design: Wild-type and PPARÎ± -/- mice fasted for 4 hours received a single dose of 400 Âµl synthetic triglyceride (tridecanoin â C10:0, triolein â C18:1, trilinolein â C18:2, trilinolenin â C18:3, trieicosapentaenoin â C20:5 or tridocosahexaenoin â C22:6), the synthetic PPARÎ± agonists WY14643 or fenofibrate (400 Î¼l of 10 mg/ml in 0.5% carboxymethyl cellulose, CMC) or control (400 Î¼l of 0.5% CMC). 6 hours after gavage, mice were killed and livers extracted. Experiment Overall Design: (Please note: Experiments with C10:0, C18:2 and C18:3 were carried out a few months later than the rest of the treatments. Therefore there is a second set of control arrays â named control2 â which belong to these three treatment groups.) Experiment Overall Design: Liver total RNA from biological replicates was hybridized onto Affymetrix mouse genome 430 2.0 GeneChip arrays. Five microgram total RNA was labelled according to the ENZO-protocol, fragmented and hybridized according to Affymetrix's protocols.

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Dietary triglycerides act on mesolimbic structures to regulate the rewarding and motivational aspects of feeding.

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Dietary triglycerides act on mesolimbic structures to regulate the rewarding and motivational aspects of feeding.

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