Defective insulin action in fibroblasts from noninsulin-dependent diabetes mellitus patients with Gln1152 insulin receptor mutation.

Insulin action was investigated in cultured skin fibroblasts from two consanguineous patients with a heterozygous point mutation in the insulin receptor kinase (Arg1152-Gln). In spite of normal binding, Gln1152 insulin receptor exhibited 20% increased basal kinase activity, but significantly reduced insulin-dependent autophosphorylation and kinase activity compared to controls from either weight-matched noninsulin-dependent diabetic patients (n = 4) or normal subjects (n = 5). In fibroblasts from the mutant patients, basal alpha-aminoisobutyric acid and 2-deoxyglucose (2-DG) uptake, cytochalasin-B (CB) plasma membrane binding, and glycogen synthase activity were increased to levels similar to those in maximally insulin-stimulated control cells. No insulin stimulation of these metabolic effects was detected in the mutant cells. In spite of the high basal 2-DG uptake and CB binding and the lack of further insulin response, fibroblasts from the mutant patients responded to 12-O-tetradecanoylphorbol-13-acetate with a further 50% increase in 2-DG uptake and CB binding. The magnitude of the effects of insulin and 12-O-tetradecanoylphorbol-13-acetate in control cells were nearly identical. We conclude that the Gln1152 insulin receptor impairs insulin regulation of metabolic responses in patient cells. Its presence in fibroblasts from the mutant patients appears to be accompanied by an increased pool of glucose transporters.

Mutation in a conserved motif next to the insulin receptor key autophosphorylation sites de-regulates kinase activity and impairs insulin action.

We have recently reported two non-insulin-dependent diabetic patients exhibiting a heterozygous point mutation (R1152-Q) next to the key tyrosine autophosphorylation sites (Y1146, Y1150, Y1151) of the insulin receptor. In the present study, we demonstrate that the Q1152 mutation alters a previously unrecognized consensus sequence in the insulin receptor family of tyrosine kinases. To define the effect of this alteration on insulin receptor function, the mutant insulin receptor (Q1152) was constructed and overexpressed in NIH-3T3 cells. In spite of normal insulin binding, "in vivo" and "in vitro" autophosphorylation as well as transphosphorylation by the wild-type receptor (WT) were deficient in Q1152 as compared with the transfected WT receptors. Insulin-stimulated kinase activity toward poly(Glu, Tyr) 4:1 and the endogenous substrates p120 and p175 were also impaired in Q1152. However, insulin-independent kinase activity of Q1152 was 2-5-fold higher than that of WT. While insulin stimulated 2-deoxyglucose uptake and glycogen synthase activity in WT-transfected cells with a sensitivity proportional to receptor number, no insulin stimulation was observed in Q1152 cells. Similar to the kinase, insulin-independent glycogen synthase activity and 2-deoxyglucose uptake were 2-fold higher in Q1152 than in either WT or parental cells. We conclude that the Q1152 mutation deregulates insulin receptor kinase and generates insulin insensitivity in cells. Alterations in this highly conserved region of the insulin receptor may contribute to non-insulin dependent diabetes mellitin pathogenesis in humans.

Hepatitis B virus DNA in chronic HBsAg carriers: correlation with HBeAg/anti-HBe status, anti-HD and liver histology.

Hepatitis B virus DNA was determined in the sera of 198 chronic hepatitis B surface antigen (HBsAg) carriers by the spot hybridization technique. The results were correlated with hepatitis Be antigen (HBeAg) and antibody (anti-HBe), delta antibody (anti-HD) and liver histology. All subjects had a liver biopsy. The prevalence of HBV DNA was 63% in HBeAg-positive subjects and 8.8% in anti-HBe positives. HBV DNA was not found more frequently in chronic HBsAg carriers who had histological evidence of liver disease than in carriers without such evidence. Anti-HD was detected in 48.5% of subjects, with an increasing trend (p less than 0.001) according to the severity of liver disease. Among patients with more severe liver disease (CAH and cirrhosis), HBV DNA and HBeAg were detected less frequently in anti-HD-positive than in anti-HD-negative subjects (7% vs. 42.3%, p less than 0.001 and 7% vs. 34.4%, p less than 0.005, respectively). These findings indicate that HDV infection jointly affects both HBeAg status and HBV DNA.

Interaction between HDV and HBV infection in HBsAg-chronic carriers.

We studied the interaction between HBV and HDV infection in 149 consecutive subjects with HBsAg positive chronic hepatitis and in 22 chronic HBsAg healthy carriers. Liver HBcAg was detected in 52 (30.4%) of the 171 subjects. Of these 52, 35 were HBV-DNA and HBeAg positive, 11 HBV-DNA positive only; two HBeAg positive only and four were negative for both HBeAg and HBV-DNA. None of the 119 HBcAg-negative subjects had detectable HBV-DNA in serum. HD-Ag in hepatocytes was detected in 31 of the 171 subjects (18%); it was detectable in none of the 22 HBsAg healthy carriers, in four of the 56 patients with chronic persistent hepatitis (7.2%), in six of the 24 patients with chronic lobular hepatitis (25%), in 16 of the 40 patients with chronic active hepatitis (40%) and in five of the 29 with cirrhosis (17%). A presence of anti-HD in serum in the absence of liver HD-Ag was found in 54 of the 171 subjects (32%). This condition was observed not only in patients with a progressive disease (37.7% of chronic active hepatitis or cirrhosis and 33% of chronic lobular hepatitis), but also in healthy carriers (36%) and in chronic persistent hepatitis patients (21.4%). Liver HBcAg was detected in 6.4% of the 31 HD-Ag-positive patients, in 12.9% of the 54 HD-Ag-negative/anti-HD positive, but in 50% of the 86 with no marker of HDV infection. HDV appears to inhibit HBV genome and such inhibition may persist even when anti-HD is the only HDV marker detectable.