Beverly J L, Martin R J
Department of Foods and Nutrition, University of Georgia, Athens 30602.
Am J Physiol. 1989 Jun;256(6 Pt 2):R1225-31. doi: 10.1152/ajpregu.1989.256.6.R1225.
Metabolic signals have been proposed as controls of energy balance. Glucose utilization for gamma-aminobutyric acid (GABA) synthesis was evaluated in diet-restricted and streptozotocin-diabetic rats. Rates for glucose flux through the GABA shunt and glutamate decarboxylase (GAD), the rate-limiting enzyme in GABA synthesis, were measured in ventro-medial nucleus (VMN) and lateral hypothalamic (LHA) homogenates. Rates of GAD activity were elevated in the VMN of both restricted and diabetic rats but did not change in the LHA of either model. The rate of glucose flux through the GABA shunt in the VMN was increased in restricted rats but were decreased in the VMN of diabetic rats. Restricted rats allowed to feed ad libitum initially ate 160% of the amount the control rats ate. GAD activity rates in the VMN returned to near control levels after 2 days of refeeding. Obese Zucker rats (fa/fa) also had higher rates of GAD activity and glucose flux through the GABA shunt in the VMN but not in the LHA. The increased rate of GABA synthesis may represent increased GABAergic activity in the VMN and may possibly be involved in feeding behavior and energy balance.
代谢信号被认为是能量平衡的控制因素。在饮食限制和链脲佐菌素诱导的糖尿病大鼠中，评估了用于γ-氨基丁酸（GABA）合成的葡萄糖利用情况。在腹内侧核（VMN）和下丘脑外侧区（LHA）匀浆中测量了通过GABA分流途径和谷氨酸脱羧酶（GAD，GABA合成中的限速酶）的葡萄糖通量率。在饮食限制和糖尿病大鼠的VMN中，GAD活性率均升高，但在两种模型的LHA中均未改变。在饮食限制的大鼠中，VMN中通过GABA分流途径的葡萄糖通量率增加，但在糖尿病大鼠的VMN中则降低。允许自由进食的饮食限制大鼠最初进食量是对照大鼠的160%。再喂食2天后，VMN中的GAD活性率恢复到接近对照水平。肥胖的 Zucker 大鼠（fa/fa）在VMN中也有较高的GAD活性率和通过GABA分流途径的葡萄糖通量率，但在LHA中则没有。GABA合成率的增加可能代表VMN中GABA能活性增加，并且可能参与进食行为和能量平衡。
