Effect of glucose on carbohydrate synthesis from alanine or lactate in hepatocytes from starved rats

Abstract

In hepatocytes from starved rats, 10mM-glucose suppressed in incorporation of 2mM labelled alanine into glucose+glycogen by more than 40%, whereas no inhibition was observed with labelled lactate as substrate. Addition of glycerol instead of glucose did not show this inhibition. The inhibitory effect could also be demonstrated in label-free experiments.

Gluconeogenesis and Related Aspects of Glycolysis

“…This is because in isolated liver preparations, the synthesis of glycogen is relatively deficient and hexose phosphates can be fo rmed fr om glucose faster than they are used. Accordingly, a 40%-50% inhibition by glucose of gluconeogenesis from alanine (255,256), or low concentrations of pyruvate (9 1) or lactate (257), has been observed with such preparations; this was, however, not the case in the presence of high concentrations of lactate (10-30 mM) (10,256), which are known to decrease fr uctose 2,6-bisphosphate levels in the hepatocytes. In vivo, glycogen metabolism is more sensitive to glucose, the administration of which causes a rapid inactivation of glycogen phosphorylase and sub sequent activation of glycogen synthase (2,3).…”

Stimulation of rat liver glycogen synthesis by the adenosine kinase inhibitor 5-iodotubercidin

“…Then (8)(9)(10)(11)(12)(13)(14)(15) x 106 cells were shaken under 02/C02 (19: 1) in stoppered 25 ml flasks at 37°C in Krebs bicarbonate buffer containing 0.5 % (w/v) BSA, defatted and dialysed by the method of Chen [17]. The cells were preincubated in the presence or absence of inhibitor or effector for 20 min before substrates were added.…”

“…As shown in Figures 3(a) and 3(c), glycogen formation was totally suppressed by 2-chloroadenosine, and this inhibition was accompanied by an increase in cyclic AMP. However, the inhibition of glycogen synthesis caused if the effects of ltu and amino acids It is well documented that amino acids stimulate glycogen synthesis from glucose and gluconeogenic precursors [7][8][9][10][11], and we determined whether Itu acts in a similar manner. Promotion of glycogen synthesis by added amino acids appears to be due to hepatocyte swelling after their uptake and the accumulation of intracellular catabolites such as glutamate and aspartate [34][35][36][37].…”

“…We had evidence that the known stimulating effect of amino acids on glycogen synthesis [7][8][9][10][11] may be due to a purine compound, since the increase in glycogen production by amino acids is strongly blocked by inhibitors of purine synthesis [8] and because this inhibition is correlated with a decrease of the formation of adenine nucleotides [12]. Adenosine has been reported to stimulate glycogen synthesis in vivo [13] and glycogen synthase activity in isolated liver preparations [1 1,14].…”

Regulation of Glycolytic Enzyme Phosphoglycerate Mutase-1 by Sirt1 Protein-mediated Deacetylation

“…Cell culture supernatants were collected and immediately frozen in liquid nitrogen. Glucose, lactate, and alanine were measured in the thawed supernatants as described previously (31).…”