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Removing melatonin receptor type 1 signaling leads to selective leptin resistance in the arcuate nucleus.

ABSTRACT: Recent studies have highlighted the involvement of melatonin in the regulation of energy homeostasis. In this study, we report that mice lacking melatonin receptor 1 (MT1 KO) gained more weight, had a higher cumulative food intake, and were more hyperphagic after fasting compared to controls (WT). In response to a leptin injection, MT1 KO mice showed a diminished reduction in body weight and food intake. To evaluate hypothalamic leptin signaling, we tested leptin-induced phosphorylation of the signal transducer and activator of transcription 3 (STAT3). Leptin failed to induce STAT3 phosphorylation in MT1 KO mice beyond levels observed in mice injected with phosphate-buffered saline (PBS). Furthermore, STAT3 phosphorylation within the arcuate nucleus (ARH) was decreased in MT1 KO mice. Leptin receptor mRNA levels in the hypothalamus of MT1 KO were significantly reduced (about 50%) compared to WT. This study shows that: (a) MT1 deficiency causes weight gain and increased food intake; (b) a lack of MT1 signaling induces leptin resistance; (c) leptin resistance is ARH region-specific; and (d) leptin resistance is likely due to down-regulation of the leptin receptor. Our data demonstrate that MT1 signaling is an important modulator of leptin signaling.

SUBMITTER: Buonfiglio D

PROVIDER: S-EPMC6687516 | biostudies-literature | 2019 Sep

REPOSITORIES: biostudies-literature

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Removing melatonin receptor type 1 signaling leads to selective leptin resistance in the arcuate nucleus.

Buonfiglio Daniella D Tchio Cynthia C Furigo Isadora I Donato José J Baba Kenkichi K Cipolla-Neto José J Tosini Gianluca G

Journal of pineal research 20190429 2

Recent studies have highlighted the involvement of melatonin in the regulation of energy homeostasis. In this study, we report that mice lacking melatonin receptor 1 (MT<sub>1</sub> KO) gained more weight, had a higher cumulative food intake, and were more hyperphagic after fasting compared to controls (WT). In response to a leptin injection, MT<sub>1</sub> KO mice showed a diminished reduction in body weight and food intake. To evaluate hypothalamic leptin signaling, we tested leptin-induced ph ...[more]

PMID: 30968433

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Project description:Introduction:Accumulated evidence indicates that obesity is associated with enhanced sympathetic activation. Hypothalamic leptin-mediated signaling may contribute to the exaggerated sympathoexcitation of obesity. The goal of this study was to investigate the "neuron-astrocyte" interaction affecting leptin-mediated sympathoexcitation within the arcuate nucleus (ARCN) of the hypothalamus in obese rats. Methods and Results:Obesity was induced by high-fat diet (HFD, 42% of calories from fat) in Sprague Dawley rats. Twelve weeks of HFD produced hyperleptinemia, hyperlipidemia, and insulin resistance. In anesthetized rats, microinjections of leptin into the ARCN induced increases in heart rate (HR), renal sympathetic nerve activity (RSNA), and mean arterial pressure (MAP) in both control and HFD rats. However, microinjections of leptin in HFD rats elicited higher responses of RSNA and arterial pressure than control-fed rats. It also caused the inhibition of astrocytes within the ARCN using an astrocytic metabolic inhibitor, fluorocitrate, and reduced leptin-induced sympathetic activity and blood pressure responses. Moreover, the expression of the leptin receptor in the ARCN of HFD-fed rats was significantly increased compared to rats fed a control diet. Immunohistochemistry analysis revealed leptin receptor localization from both neurons and astrocytes of the ARCN. HFD rats exhibited increased protein expression of glial fibrillary acidic protein (GFAP) in the ARCN. We also found that the expression of astrocyte-specific glutamate transporters and excitatory amino acid transporter 1 (EAAT1) and 2 (EAAT2) were decreased within the ARCN of the HFD rats. In cultured astrocytic C6 cells, 24 h of leptin treatment increased the protein expression of GFAP and reduced the expression of EAAT1 and EAAT2. Conclusion:The results suggest that central leptin signaling occurs via neuron-astrocyte interactions in the ARCN and contributing to the exaggerated sympathoexcitation observed in obese rats. The effects may be mediated by the action of leptin on regulating astrocytic glutamate transporters within the ARCN of the hypothalamus.

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Removing melatonin receptor type 1 signaling leads to selective leptin resistance in the arcuate nucleus.

Publications

Removing melatonin receptor type 1 signaling leads to selective leptin resistance in the arcuate nucleus.

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