Overexpression of regucalcin enhances glucose utilization and lipid production in cloned rat hepatoma H4‐II‐E cells: Involvement of insulin resistance

Abstract

The role of regucalcin, which is a regulatory protein in intracellular signaling pathway, in the regulation of glucose utilization and lipid production was investigated using the cloned rat hepatoma H4-II-E cells overexpressing regucalcin. The hepatoma cells (wild-type) and stable regucalcin/pCXN2-transfected cells (transfectant) were cultured for 72 h in a medium containing 10% fetal bovine serum (FBS) to obtain subconfluent monolayers. Cells with subconfluency were cultured for 24 or 72 h in medium containing either vehicle or insulin (10(-8) or 10(-7) M) with or without supplementation of glucose (10, 25, or 50 mg/ml of medium) in the absence of insulin. The production of triglyceride and free fatty acid was significantly increased in transfectants cultured without insulin and glucose supplementation as compared with that of wild-type cells. The supplementation of glucose (10, 25, or 50 mg/ml) caused a remarkable increase in medium glucose consumption, triglyceride, and free fatty acid productions in transfectants cultured without insulin. The presence of insulin (10(-7) M) caused a significant increase in medium glucose consumption, triglyceride, and free fatty acid productions in wild-type cells cultured with glucose supplementation. These increases were significantly prevented in transfectants cultured for 72 h. The expression of acetyl-CoA carboxylase, HMG-CoA reductase, glucokinase, pyruvate kinase, and glyceroaldehyde-3-phosphate dehydrogenase (G3PDH) mRNAs in wild-type cells was not significantly changed by culture with or without glucose supplementation in the presence of insulin. These gene expressions were not significantly changed in transfectants. The expression of glucose transporter 2 mRNA was significantly increased in transfectants as compared with that of wild-type cells. Such an increase was not seen in transfectants cultured in the presence of insulin with or without glucose supplementation. This study demonstrates that overexpression of regucalcin enhances glucose utilization and lipid production in the cloned rat hepatoma H4-II-E cells, and that it regulates the effect of insulin.

Overexpression of regucalcin suppresses gene expression of insulin signaling-related proteins in cloned rat hepatoma H4-II-E cells: Involvement of insulin resistance

“…From the proteome of H4-II-E cells exposed to insulin and TNF-α, it has been proposed that regucalcin has a role associated with proteins which are involved in insulin resistance (31). This was confirmed by our previous observations that overexpression of regucalcin plays a role in inducing insulin resistance in H4-II-E cells (24).…”

“…Overexpression of regucalcin has been shown to enhance glucose utilization and lipid production in cloned rat hepatoma H4-II-E cells, and to induce insulin resistance in the cells (24). Previous studies have shown that insulin resistance may be modeled in H4-II-E liver cells in tissue culture with the use of the cytokine tumor necrosis factor-α (TNF-α) and insulin (30).…”

“…Overexpression of regucalcin was found to enhance GLUT 2 mRNA in H4-II-E cells, although it failed to have a significant effect on Insr, PI3K, or G3PDH mRNA expression in the cells cultured in the absence of insulin. The expression of GLUT 2 mRNA in transfectants may be partly involved in the enhancement of glucose utilization in the H4-II-E cells overexpressing regucalcin (24).…”

“…Overexpression of regucalcin has been shown to enhance glucose utilization and lipid production in the cloned rat hepatoma H4-II-E cells in vitro, and to induce insulin resistance in the cells (24). This study was undertaken to determine whether overexpression of regucalcin has an inhibitory effect on gene expression of insulin signalingrelated proteins in the cloned rat hepatoma H4-II-E cells in vitro.…”

Identification of biomarkers associated with the development of hepatocellular carcinoma in CuZn superoxide dismutase deficient mice

“…How does a change in RGN level relate to the pathogenesis of HCC? RGN is a Ca binding protein and is important for intracellular Ca homeostasis and in signaling pathways controlling glucose utilization and lipid production [18][19][20]. RGN is sensitive to oxidative modification and a more than two-fold increase in the carbonyl content has been reported in old mice [21].…”