Pennington Biomedical Research Center, Louisiana State University, 6400 Perkins Rd, Baton Rouge, LA, 70808, USA.
The Division of Endocrinology, Diabetes and Metabolism, Department of Medicine, The University of Illinois at Chicago, Chicago, IL, 60612, USA.
Mol Metab. 2021 Dec;54:101391. doi: 10.1016/j.molmet.2021.101391. Epub 2021 Nov 9.
Cav3.2, a T-type low voltage-activated calcium channel widely expressed throughout the central nervous system, plays a vital role in neuronal excitability and various physiological functions. However, the effects of Cav3.2 on energy homeostasis remain unclear. Here, we examined the role of Cav3.2 expressed by hypothalamic GABAergic neurons in the regulation of food intake and body weight in mice and explored the underlying mechanisms.
Male congenital Cana1h (the gene coding for Cav3.2) global knockout (Cav3.2KO) mice and their wild type (WT) littermates were first used for metabolic phenotyping studies. By using the CRISPR-Cas9 technique, Cav3.2 was selectively deleted from GABAergic neurons in the arcuate nucleus of the hypothalamus (ARH) by specifically overexpressing Cas9 protein and Cav3.2-targeting sgRNAs in ARH Vgat (Vgat) neurons. These male mutants (Cav3.2KO-Vgat) were used to determine whether Cav3.2 expressed by Vgat neurons is required for the proper regulation of energy balance. Subsequently, we used an electrophysiological patch-clamp recording in ex vivo brain slices to explore the impact of Cav3.2KO on the cellular excitability of Vgat neurons.
Male Cav3.2KO mice had significantly lower food intake than their WT littermate controls when fed with either a normal chow diet (NCD) or a high-fat diet (HFD). This hypophagia phenotype was associated with increased energy expenditure and decreased fat mass, lean mass, and total body weight. Selective deletion of Cav3.2 in Vgat neurons resulted in similar feeding inhibition and lean phenotype without changing energy expenditure. These data provides an intrinsic mechanism to support the previous finding on ARH non-AgRP GABA neurons in regulating diet-induced obesity. Lastly, we found that naringenin extract, a predominant flavanone found in various fruits and herbs and known to act on Cav3.2, decreased the firing activity of Vgat neurons and reduced food intake and body weight. These naringenin-induced inhibitions were fully blocked in Cav3.2KO-Vgat mice.
Our results identified Cav3.2 expressed by Vgat neurons as an essential intrinsic modulator for food intake and energy homeostasis, which is a potential therapeutic target in the treatment of obesity.
Cav3.2 是一种广泛存在于中枢神经系统中的 T 型低电压激活钙通道，在神经元兴奋性和各种生理功能中起着至关重要的作用。然而，Cav3.2 对能量平衡的影响尚不清楚。在这里，我们研究了下丘脑 GABA 能神经元表达的 Cav3.2 在调节小鼠摄食和体重中的作用，并探讨了其潜在机制。
首先使用雄性先天性 Cana1h（编码 Cav3.2 的基因）全局敲除（Cav3.2KO）小鼠及其野生型（WT）同窝仔鼠进行代谢表型研究。通过使用 CRISPR-Cas9 技术，特异性过表达 Cas9 蛋白和靶向 ARH Vgat（Vgat）神经元的 Cav3.2-sgRNA，选择性地从下丘脑弓状核（ARH）的 GABA 能神经元中删除 Cav3.2。这些雄性突变体（Cav3.2KO-Vgat）用于确定 Vgat 神经元表达的 Cav3.2 是否是适当调节能量平衡所必需的。随后，我们使用离体脑片的电生理膜片钳记录来探讨 Cav3.2KO 对 Vgat 神经元细胞兴奋性的影响。
与 WT 同窝仔鼠相比，雄性 Cav3.2KO 小鼠在给予正常饲料（NCD）或高脂肪饮食（HFD）时的食物摄入量明显减少。这种摄食减少的表型与能量消耗增加和脂肪量、瘦体重和总体重减少有关。选择性地从 Vgat 神经元中删除 Cav3.2 导致了类似的摄食抑制和瘦表型，而不改变能量消耗。这些数据为之前关于 ARH 非 AgRP GABA 神经元调节饮食诱导肥胖的发现提供了内在机制。最后，我们发现柚皮素提取物，一种存在于各种水果和草药中的主要黄烷酮，已知对 Cav3.2 起作用，可降低 Vgat 神经元的放电活动，减少食物摄入和体重。这些柚皮素诱导的抑制作用在 Cav3.2KO-Vgat 小鼠中完全被阻断。
我们的研究结果确定了 Vgat 神经元表达的 Cav3.2 是食物摄入和能量平衡的必需内在调节剂，这是肥胖治疗的一个潜在治疗靶点。
