Salhanick A I, Chang C L, Amatruda J M
Department of Medicine, University of Rochester Medical Center, NY 14642.
Biochem J. 1989 Aug 1;261(3):985-92. doi: 10.1042/bj2610985.
Hormonal and substrate regulation of hepatic glycogen accumulation was evaluated in primary cultures of hepatocytes prepared from 1-day-fasted rats. Hepatocytes were cultured in media containing 5 mM-glucose and 10 mM-lactate and then exposed to 100 nM-dexamethasone for 4 h before an increase in glucose concentration and the addition of insulin. When this protocol was used to mimic the post-prandial state in vivo, net glycogen accumulation (over 2 h) and insulin (10 nM) effects were linear at physiological (5-10 mM) and supraphysiological (20-30 mM) glucose concentrations. To define the role of substrates in glycogen accumulation, hepatocytes were incubated in a buffered salt solution containing 10 mM-glucose and either 10 mM-lactate or 5 mM-glutamine, or both. In the absence of hormones, net glycogen accumulation was increased by 59%, 83%, and 127% by the addition of lactate, glutamine, and lactate plus glutamine respectively, compared with incubations with glucose alone, and 6-fold in the presence of substrates, insulin and dexamethasone. Labelling with [3-3H]glucose and [U-14C]glucose showed that in the absence of hormones approx. 50% of glycogen formation came from glucose via the direct pathway and the remainder from glucose via the indirect pathway or from non-glucose precursors, or both. Insulin-dependent enhancement of glycogen formation is through stimulation of both the direct and indirect pathways, and dexamethasone-dependent stimulation occurs through stimulation of both these pathways of glycogen formation from glucose as well as from non-glucose precursors. Lactate serves as a gluconeogenic C3 precursor for the observed enhanced glycogen formation, whereas glutamine-dependent enhancement of glycogen accumulation occurs primarily through a stimulation of the direct and indirect pathways of glycogen formation from glucose.
在从禁食1天的大鼠制备的原代肝细胞培养物中评估了肝糖原积累的激素和底物调节。将肝细胞培养在含有5 mM葡萄糖和10 mM乳酸的培养基中，然后在葡萄糖浓度增加和添加胰岛素之前，用100 nM地塞米松处理4小时。当使用该方案模拟体内餐后状态时，在生理（5 - 10 mM）和超生理（20 - 30 mM）葡萄糖浓度下，净糖原积累（超过2小时）和胰岛素（10 nM）的作用呈线性。为了确定底物在糖原积累中的作用，将肝细胞在含有10 mM葡萄糖和10 mM乳酸或5 mM谷氨酰胺或两者的缓冲盐溶液中孵育。在没有激素的情况下，与仅用葡萄糖孵育相比，添加乳酸、谷氨酰胺以及乳酸加谷氨酰胺后，净糖原积累分别增加了59%、83%和127%，在有底物、胰岛素和地塞米松存在的情况下增加了6倍。用[3 - 3H]葡萄糖和[U - 14C]葡萄糖标记表明，在没有激素的情况下，约50%的糖原形成来自通过直接途径的葡萄糖，其余来自通过间接途径的葡萄糖或来自非葡萄糖前体，或两者皆有。胰岛素依赖性糖原形成的增强是通过刺激直接和间接途径实现的，地塞米松依赖性刺激是通过刺激葡萄糖以及非葡萄糖前体形成糖原的这两条途径实现的。乳酸作为观察到的增强糖原形成的糖异生C3前体，而谷氨酰胺依赖性糖原积累的增强主要是通过刺激葡萄糖形成糖原的直接和间接途径实现的。
