Abstract
cAMP responsive element binding protein (CREB)-regulated transcription coactivators (CRTCs) regulate gene transcription in response to an increase in intracellular cAMP or Ca2+ levels. To date, three isoforms of CRTC have been identified in mammals. All CRTCs are widely expressed in various regions of the brain. Numerous studies have shown the importance of CREB and CRTC in energy homeostasis. In the brain, the paraventricular nucleus of the hypothalamus (PVH) plays a critical role in energy metabolism, and CRTC1 and CRTC2 are highly expressed in PVH neuronal cells. The single-minded homolog 1 gene (Sim1) is densely expressed in PVH neurons and in some areas of the amygdala neurons. To determine the role of CRTCs in PVH on energy metabolism, we generated mice that lacked CRTC1 and CRTC2 in Sim1 cells using Sim-1 cre mice. We found that Sim1 cell-specific CRTC1 and CRTC2 double-knockout mice were sensitive to high-fat diet (HFD)-induced obesity. Sim1 cell-specific CRTC1 and CRTC2 double knockout mice showed hyperphagia specifically for the HFD, but not for the normal chow diet, increased fat mass, and no change in energy expenditure. Interestingly, these phenotypes were stronger in female mice than in male mice, and a weak phenotype was observed in the normal chow diet. The lack of CRTC1 and CRTC2 in Sim1 cells changed the mRNA levels of some neuropeptides that regulate energy metabolism in female mice fed an HFD. Taken together, our findings suggest that CRTCs in Sim1 cells regulate gene expression and suppress excessive fat intake, especially in female mice.
Highlights
The hypothalamus plays an important role in the energy metabolism
Pair-feeding abolished the difference in body weight gain between single-minded homolog 1 gene (Sim1)-CRTCDKO mice and control mice fed an high-fat diet (HFD). These results suggest that the significant body weight gain observed in Sim1-CRTCDKO mice may be caused by hyperphagia, not by reduced energy expenditure
Under HFD feeding, both male and female Sim1-CRTCDKO mice showed significant body weight gain, Disruption of CREB-regulated transcription coactivator (CRTC) in Sim1 cells increases high fat diet intake the difference in body weight between Sim1-CRTCDKO mice and control mice was more prominent in female Sim1-CRTCDKO mice than in male mice
Summary
Various transcription factors regulate gene expression in neuronal cells. Among these transcription factors, cAMP responsive element binding protein (CREB) plays an important role in regulating neuronal function and neuropeptide expression, affecting whole-body energy metabolism [3,4]. Sim haplodeficiency or postnatal deficiency of Sim causes early onset obesity with hyperphagia [13,14] Various neuropeptides such as corticotropin-releasing factor (CRF), arginine vasopressin (AVP), oxytocin (Oxt), and pituitary adenylate cyclase-activating polypeptide (PACAP) are expressed in PVH and regulate energy metabolism [15]. It is likely that the increase in cAMP by MC4R ligand binding may activate CREB and CRTCs. We previously investigated whether CRTC1 deficiency in PVH (Sim cells) could cause obesity. To block the compensatory action of CRTC2, in the present study, we generated mice that lacked both CRTC1 and CRTC2 in the PVH and evaluated the role of CRTCs in PVH in energy metabolism
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