Lietz T, Winiarska K, Bryła J
Institute of Biochemistry, Warsaw University, Poland.
Acta Biochim Pol. 1997;44(2):323-31.
In isolated rabbit renal kidney-cortex tubules 2 mM glycerol, which is a poor gluconeogenic substrate, does not induce glucose formation in the presence of alanine, while it activates gluconeogenesis on substitution of alanine by aspartate, glutamate or proline. The addition of either 5 mM 3-hydroxybutyrate or 5 mM acetoacetate to renal tubules incubated with alanine + glycerol causes a marked induction of glucose production associated with inhibition of glutamine synthesis. In contrast, the rate of the latter process is not altered by ketones in the presence of glycerol and either aspartate, glutamine or proline despite the stimulation of glucose formation. Acceleration of gluconeogenesis by ketone bodies in the presence of amino acids and glycerol is probably due to (i) stimulation of pyruvate carboxylase activity, (ii) activation of malate-aspartate shuttle as concluded from elevated intracellular levels of malate, aspartate and glutamate, as well as (iii) diminished supply of ammonium for glutamine synthesis from alanine resulting from a decrease in glutamate dehydrogenase activity.
在分离的兔肾皮质肾小管中，2 mM甘油是一种较差的糖异生底物，在丙氨酸存在时不会诱导葡萄糖生成，而当丙氨酸被天冬氨酸、谷氨酸或脯氨酸取代时，它会激活糖异生。向与丙氨酸+甘油一起孵育的肾小管中添加5 mM 3-羟基丁酸或5 mM乙酰乙酸会导致葡萄糖生成显著增加，同时谷氨酰胺合成受到抑制。相比之下，在甘油与天冬氨酸、谷氨酰胺或脯氨酸存在的情况下，酮类物质不会改变后者的反应速率，尽管会刺激葡萄糖生成。在氨基酸和甘油存在的情况下，酮体加速糖异生可能是由于：（i）刺激丙酮酸羧化酶活性；（ii）从细胞内苹果酸、天冬氨酸和谷氨酸水平升高得出，激活苹果酸-天冬氨酸穿梭；以及（iii）由于谷氨酸脱氢酶活性降低，从丙氨酸合成谷氨酰胺的铵供应减少。
