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SelS is a newly identi¢ed selenoprotein and its gene expression is up-regulated in the liver of Psammomys obesus after fasting. We have examined whether SelS is regulated by glucose deprivation and endoplasmic reticulum (ER) stress in HepG2 cells. Glucose deprivation and the ER stress inducers tunicamycin and thapsigargin increased SelS gene expression and protein content several-fold in parallel with glucose-regulated protein 78. The overexpression of SelS increased Min6 cell resistance to oxidative stress-induced toxicity. These results indicate that SelS is a novel member of the glucose-regulated protein family and its function is related to the regulation of cellular redox balance. ß 2004 Published by Elsevier B.V. on behalf of the Federation of European Biochemical Societies.

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Increased hepatic glucose output and decreased glucose utilization are implicated in the development of type 2 diabetes. We previously reported that the expression of a novel gene, Tanis, was upregulated in the liver during fasting in the obese/diabetic animal model Psammomys obesus. Here, we have further studied the protein and its function. Cell fractionation indicated that Tanis was localized in the plasma membrane and microsomes but not in the nucleus, mitochondria, or soluble protein fraction. Consistent with previous gene expression data, hepatic Tanis protein levels increased more significantly in diabetic P. obesus than in nondiabetic controls after fasting. We used a recombinant adenovirus to increase Tanis expression in hepatoma H4IIE cells and investigated its role in metabolism. Tanis overexpression reduced glucose uptake, basal and insulin-stimulated glycogen synthesis, and glycogen content and attenuated the suppression of PEPCK gene expression by insulin, but it did not affect insulin-stimulated insulin receptor phosphorylation or triglyceride synthesis. These results suggest that Tanis may be involved in the regulation of glucose metabolism, and increased expression of Tanis could contribute to insulin resistance in the liver. Diabetes 52:929 -934, 2003 A major factor that contributes to hyperglycemia in type 2 diabetes is excessive hepatic glucose production. Depending on the concentrations of insulin and glucagon in the portal blood and the level of glucose itself, the liver either stores glucose in the form of glycogen or, upon the depletion of glycogen, synthesizes glucose via the gluconeogenic pathway for export. In many subjects with type 2 diabetes, hepatic glucose utilization, associated with reduced glucokinase activity, is diminished (1). Furthermore, insulin is less effective in suppressing gluconeogenesis in these subjects, leading to elevated hepatic glucose output (2,3). The implication of these defects in the development of hyperglycemia has been supported by studies of transgenic mice that overexpress hepatic PEPCK or glucose-6-phosphatase. A modest increase in their activities (two-to threefold) caused hyperglycemia, hyperinsulinemia, impaired glucose tolerance, and decreased glycogen storage (4 -6). Conversely, increased hepatic glucose utilization through glucokinase overexpression lowered plasma glucose concentration, improved insulin sensitivity, and increased glycogen storage in rats (7,8). These findings strongly suggest a critical role of the liver in maintaining glucose homeostasis.As both genetic and environmental factors play a role in the development of type 2 diabetes (9), we have used a polygenic animal model, Psammomys obesus (Israeli sand rat), to identify genes that may contribute to its pathogenesis. When housed in the laboratory and maintained on an ad libitum diet of standard rodent food, a proportion of the animals spontaneously develop metabolic abnormalities, including obesity and type 2 diabetes (10 -12). The distributions of body weight, blood glucose, and...

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