J Clin Invest. 2018 Jun 1;128(6):2626-2641. doi: 10.1172/JCI99350. Epub 2018 May 14.
In the brain, the ventral hypothalamus (VHT) regulates energy and bone metabolism. Whether this regulation uses the same or different neuronal circuits is unknown. Alteration of AP1 signaling in the VHT increases energy expenditure, glucose utilization, and bone density, yet the specific neurons responsible for each or all of these phenotypes are not identified. Using neuron-specific, genetically targeted AP1 alterations as a tool in adult mice, we found that agouti-related peptide-expressing (AgRP-expressing) or proopiomelanocortin-expressing (POMC-expressing) neurons, predominantly present in the arcuate nucleus (ARC) within the VHT, stimulate whole-body energy expenditure, glucose utilization, and bone formation and density, although their effects on bone resorption differed. In contrast, AP1 alterations in steroidogenic factor 1-expressing (SF1-expressing) neurons, present in the ventromedial hypothalamus (VMH), increase energy but decrease bone density, suggesting that these effects are independent. Altered AP1 signaling also increased the level of the neuromediator galanin in the hypothalamus. Global galanin deletion (VHT galanin silencing using shRNA) or pharmacological galanin receptor blockade counteracted the observed effects on energy and bone. Thus, AP1 antagonism reveals that AgRP- and POMC-expressing neurons can stimulate body metabolism and increase bone density, with galanin acting as a central downstream effector. The results obtained with SF1-expressing neurons, however, indicate that bone homeostasis is not always dictated by the global energy status, and vice versa.
在大脑中,腹下丘脑(VHT)调节能量和骨骼代谢。这种调节是否使用相同或不同的神经元回路尚不清楚。VHT 中 AP1 信号的改变会增加能量消耗、葡萄糖利用率和骨密度,但负责这些表型中的每一种或全部的特定神经元尚未确定。我们使用神经元特异性、基因靶向的 AP1 改变作为成年小鼠的工具,发现在 VHT 中的弓状核(ARC)中主要表达的刺鼠相关肽表达(AgRP 表达)或前阿黑皮素原表达(POMC 表达)神经元刺激全身能量消耗、葡萄糖利用率和骨形成和密度,尽管它们对骨吸收的影响不同。相比之下,在 VHT 中的甾体生成因子 1 表达(SF1 表达)神经元中改变 AP1 信号会增加能量但减少骨密度,表明这些影响是独立的。改变的 AP1 信号还增加了下丘脑神经递质甘丙肽的水平。下丘脑的全局甘丙肽缺失(使用 shRNA 沉默 VHT 甘丙肽)或药理学甘丙肽受体阻断拮抗了对能量和骨骼的观察到的影响。因此,AP1 拮抗作用表明 AgRP 和 POMC 表达神经元可以刺激身体代谢并增加骨密度,而甘丙肽作为中枢下游效应物起作用。然而,SF1 表达神经元的结果表明,骨稳态并不总是由全身能量状态决定,反之亦然。