下丘脑肉碱代谢整合营养和激素反馈以调节能量平衡。
Hypothalamic carnitine metabolism integrates nutrient and hormonal feedback to regulate energy homeostasis.
作者信息
Stark Romana, Reichenbach Alex, Andrews Zane B
机构信息
Department of Physiology, Monash University, Clayton, Victoria 3183, Australia.
Department of Physiology, Monash University, Clayton, Victoria 3183, Australia.
出版信息
Mol Cell Endocrinol. 2015 Dec 15;418 Pt 1:9-16. doi: 10.1016/j.mce.2015.08.002. Epub 2015 Aug 8.
The maintenance of energy homeostasis requires the hypothalamic integration of nutrient feedback cues, such as glucose, fatty acids, amino acids, and metabolic hormones such as insulin, leptin and ghrelin. Although hypothalamic neurons are critical to maintain energy homeostasis research efforts have focused on feedback mechanisms in isolation, such as glucose alone, fatty acids alone or single hormones. However this seems rather too simplistic considering the range of nutrient and endocrine changes associated with different metabolic states, such as starvation (negative energy balance) or diet-induced obesity (positive energy balance). In order to understand how neurons integrate multiple nutrient or hormonal signals, we need to identify and examine potential intracellular convergence points or common molecular targets that have the ability to sense glucose, fatty acids, amino acids and hormones. In this review, we focus on the role of carnitine metabolism in neurons regulating energy homeostasis. Hypothalamic carnitine metabolism represents a novel means for neurons to facilitate and control both nutrient and hormonal feedback. In terms of nutrient regulation, carnitine metabolism regulates hypothalamic fatty acid sensing through the actions of CPT1 and has an underappreciated role in glucose sensing since carnitine metabolism also buffers mitochondrial matrix levels of acetyl-CoA, an allosteric inhibitor of pyruvate dehydrogenase and hence glucose metabolism. Studies also show that hypothalamic CPT1 activity also controls hormonal feedback. We hypothesis that hypothalamic carnitine metabolism represents a key molecular target that can concurrently integrate nutrient and hormonal information, which is critical to maintain energy homeostasis. We also suggest this is relevant to broader neuroendocrine research as it predicts that hormonal signaling in the brain varies depending on current nutrient status. Indeed, the metabolic action of ghrelin, leptin or insulin at POMC or NPY neurons may depend on appropriate nutrient-sensing in these neurons and we hypothesize carnitine metabolism is critical in the integrative processing. Future research is required to examine the neuron-specific effects of carnitine metabolism on concurrent nutrient- and hormonal-sensing in AgRP and POMC neurons.
能量稳态的维持需要下丘脑对营养反馈信号进行整合,这些信号包括葡萄糖、脂肪酸、氨基酸等营养物质,以及胰岛素、瘦素和胃饥饿素等代谢激素。尽管下丘脑神经元对于维持能量稳态至关重要,但研究工作一直集中在孤立的反馈机制上,例如单独的葡萄糖、单独的脂肪酸或单一激素。然而,考虑到与不同代谢状态(如饥饿(负能量平衡)或饮食诱导的肥胖(正能量平衡))相关的营养和内分泌变化范围,这种观点似乎过于简单。为了理解神经元如何整合多种营养或激素信号,我们需要识别和研究潜在的细胞内汇聚点或共同分子靶点,这些靶点能够感知葡萄糖、脂肪酸、氨基酸和激素。在这篇综述中,我们聚焦于肉碱代谢在调节能量稳态的神经元中的作用。下丘脑肉碱代谢是神经元促进和控制营养及激素反馈的一种新方式。在营养调节方面,肉碱代谢通过肉碱棕榈酰转移酶1(CPT1)的作用调节下丘脑脂肪酸感知,并且在葡萄糖感知中具有未被充分认识的作用,因为肉碱代谢还能缓冲线粒体基质中乙酰辅酶A的水平,而乙酰辅酶A是丙酮酸脱氢酶的变构抑制剂,进而影响葡萄糖代谢。研究还表明,下丘脑CPT1活性也控制激素反馈。我们推测下丘脑肉碱代谢代表了一个关键的分子靶点,它能够同时整合营养和激素信息,这对于维持能量稳态至关重要。我们还认为这与更广泛的神经内分泌研究相关,因为它预测大脑中的激素信号会根据当前的营养状态而变化。事实上,胃饥饿素、瘦素或胰岛素在促黑素细胞激素(POMC)或神经肽Y(NPY)神经元上的代谢作用可能取决于这些神经元中适当的营养感知,并且我们推测肉碱代谢在整合过程中至关重要。未来需要开展研究,以检验肉碱代谢对AgRP和POMC神经元中同时进行的营养和激素感知的神经元特异性影响。