Glucose-induced stimulation of human insulin-receptor mRNA and tyrosine kinase activity in cultured cells

Abstract

The effects of high glucose on insulin-receptor tyrosine kinase activity and gene expression were investigated in 3T3-HIR cells. Cells incubated for 48 h in the presence of 25 mM glucose showed a 5-fold increase in the amount of insulin receptors per cell, receptor autophosphorylation and phosphorylation of the exogenous substrate poly(Glu/Tyr) compared with cells grown in the absence of glucose but in the presence of 25 mM fructose. These effects were associated with a 4-fold stimulation in steady-state levels of insulin-receptor mRNA. Significant cellular glucose utilization and lactate production were observed in the presence of high glucose in the culture medium, indicating a functional glycolytic pathway in glucose-treated cells, but not in cells treated with fructose. Such a differential response to hexoses favours the hypothesis of a carbohydrate regulation via a glycolytic intermediate. This was further supported by a similar glucose-induced increase in mRNA levels of the enzyme glyceraldehyde-3-phosphate dehydrogenase. To test the hypothesis that the stimulatory effect of glucose on amount of insulin receptors and phosphorylation state could result from post-transcriptional modifications, cells exposed to glucose were incubated with actinomycin D, a potent inhibitor of gene transcription. In cells challenged with high glucose plus inhibitor, insulin-receptor mRNA half-life was increased from 1 to 3 h, indicating that posttranscriptional mechanisms are involved in these processes of glucose regulation. Inhibition of protein synthesis by cycloheximide induced an overexpression of insulin-receptor mRNA levels in the presence of glucose, suggesting that labile repressor protein(s) could be implicated in the effects of glucose. We conclude that (1) long-term culture with high glucose increases the amount of insulin receptors and their tyrosine kinase activity and (2) the glucose-induced increase in insulin-receptor mRNA levels can be accounted for, at least in part, by posttranscriptional events.

Altered expression and localization of insulin receptor in proximal tubule cells from human and rat diabetic kidney

“…This tandem system for insulin reabsorption may produce a great impact on the bioavailability of insulin at the level of PT and downstream nephron segments. Expression of several hepatic genes are controlled by metabolites rather than hormones [Dentin et al, 2012], and long‐term culture with high glucose has shown to increase IR and its kinase activity [Hauguel‐De‐Mouzon et al, 1995]. Nevertheless, renal proximal epithelial cells do not metabolize glucose efficiently [Bolon et al, 1997], which may explain why IR protein expression is reduced despite chronic hyperglycemia.…”

AMP-activated protein kinase is physiologically regulated by inositol polyphosphate multikinase

“…Mechanisms whereby glucose treatment stimulates tyrosine phosphorylation of IPMK are unknown. Tyrosine kinases regulated by glucose include focal adhesion kinase (FAK), insulin receptor kinase, and Src kinase (24)(25)(26). By phosphorylating a variety of targets, AMPK influences a wide range of signaling systems to mediate its pleiotropic cellular actions.…”

Treatment of streptozotocin-induced diabetic rats with vanadate and phlorizin prevents the over-expression of the liver insulin receptor gene

“…However, an increase in liver insulin receptor mRNA level has been observed both in hyperglycemic rodents, such as glucose-infused pregnant female rats (31) and genetically obese mice (33), and in hypoglycemic fasted rats (19,21). In addition, although reported to induce an increase in insulin receptor mRNA concentration in HepG2 hepatoma cells (34) and 3T3 fibroblasts over-expressing the human insulin receptor (35), high glucose levels did not significantly affect this mRNA in primary cultures of rat hepatocytes (C Mrejen & S Hauguel-de Mouzon, personal communication) and Fao hepatoma cells (28). Thus, vanadate and phlorizin treatments could lower insulin receptor gene expression in diabetic rats by reversing abnormalities other than hyperglycemia -perhaps hyperglucagonemia, as has been suggested for enzymes involved in carbohydrate metabolism (8,12).…”