Judd S J
Department of Medicine, Flinders Medical Centre, Bedford Park, SA, Australia.
Reprod Fertil Dev. 1998;10(1):65-72. doi: 10.1071/r98024.
Animal reproduction is impaired when intake of energy is so restricted that activities essential to life are threatened; this is seen as a homeostatic adjustment that restricts wasteful energy expenditure. Fasting or exercising to a degree requiring considerable energy expenditure has major effects on the hypothalamus, including activation of corticotrophin-releasing factor (CRF) neurons, suppression of thyrotrophin-releasing hormone synthesis, and increased growth hormone secretion; these are associated with increased concentrations of hypothalamic neuropeptide Y mRNA and are corrected by administration of leptin, an adipose-tissue protein with a tertiary structure similar to the cytokine interleukin-2. This response to fasting results from a disordered pattern of activity in the gonadotrophin-releasing hormone (GnRH) pacemaker, characterized by reduced luteinizing hormone pulsatility, particularly during daytime. Animal studies have suggested that the response depends on an intact afferent vagal system from the stomach and the presence of oestrogen. Noradrenergic neurons forming the A2 group increase the activity of CRF neurons that, in turn, inhibit GnRH pulsatility. Reproductive impairment due to fasting is reversed by leptin, and abnormalities of leptin are described in individuals who fast or who develop exercise-induced amenorrhoea. This paper discusses these changes induced by negative energy balance and speculates on the involvement of leptin as a contributor to these abnormalities.
当能量摄入受到严重限制，以至于生命必需活动受到威胁时，动物的繁殖能力会受到损害；这被视为一种稳态调节，可限制浪费性的能量消耗。禁食或进行需要大量能量消耗的运动对下丘脑有重大影响，包括促肾上腺皮质激素释放因子（CRF）神经元的激活、促甲状腺激素释放激素合成的抑制以及生长激素分泌的增加；这些变化与下丘脑神经肽Y mRNA浓度的增加有关，并且可通过给予瘦素得到纠正，瘦素是一种脂肪组织蛋白，其三级结构与细胞因子白细胞介素-2相似。这种对禁食的反应源于促性腺激素释放激素（GnRH）起搏器活动模式的紊乱，其特征是黄体生成素脉冲性降低，尤其是在白天。动物研究表明，这种反应取决于来自胃的完整传入迷走神经系统以及雌激素的存在。形成A2组的去甲肾上腺素能神经元会增加CRF神经元的活性，而CRF神经元又会抑制GnRH的脉冲性。禁食导致的生殖功能损害可通过瘦素逆转，并且在禁食或发生运动性闭经的个体中描述了瘦素异常。本文讨论了负能量平衡引起的这些变化，并推测了瘦素作为这些异常情况的促成因素的作用。
