Pancreatic β-Cell-Specific Deletion of VPS41 Causes Diabetes Due to Defects in Insulin Secretion

Insulin secretory granules (SGs) mediate the regulated secretion of insulin, which is essential for glucose homeostasis. The basic machinery responsible for this regulated exocytosis consists of specific proteins present both at the plasma membrane and on insulin SGs. The protein composition of insulin SGs thus dictates their release properties, yet the mechanisms controlling insulin SG formation, which determine this molecular composition, remain poorly understood. VPS41, a component of the endolysosomal tethering homotypic fusion and vacuole protein sorting (HOPS) complex, was recently identified as a cytosolic factor involved in the formation of neuroendocrine and neuronal granules. We now find that VPS41 is required for insulin SG biogenesis and regulated insulin secretion. Loss of VPS41 in pancreatic β-cells leads to a reduction in insulin SG number, changes in their transmembrane protein composition, and defects in granule-regulated exocytosis. Exploring a human point mutation, identified in patients with neurological but no endocrine defects, we show that the effect on SG formation is independent of HOPS complex formation. Finally, we report that mice with a deletion of VPS41 specifically in β-cells develop diabetes due to severe depletion of insulin SG content and a defect in insulin secretion. In sum, our data demonstrate that VPS41 contributes to glucose homeostasis and metabolism.

Transforming growth factor-beta receptor type I gene is frequently mutated in ovarian carcinomas

Ovarian carcinomas (OCs), particularly recurrent OCs, are frequently resistant to transforming growth factor (TGF)-beta-mediated growth inhibition. Mutations in the TGF-beta receptor type II (TbetaR-II) gene are only evident in a minority of OCs, suggesting that other alterations of the TGF-beta signaling pathway may be involved in OC. Using PCR, cold single-strand conformation polymorphism, and DNA sequencing, we now show that 33% of primary OCs (10 of 30) harbor somatic changes in exons 2, 3, 4, and 6 of the TGF-beta receptor I (TbetaR-I) gene. Most of the changes are missense mutations and clustered largely in the catalytic domain of the receptor kinase. Interestingly, seven additional cases (23.3%) showed heterozygous carriers of an allelic variant [a 9-nucleotide deletion, del(GGC)(3)] in exon 1 of the TbetaR-I gene. This is in contrast with 10.6% of del(GGC)(3) heterozygous carriers in a recent report of a large normal population (n = 735; B. Pasche et al., Cancer Res., 59: 5678-5682, 1999). These results indicate that TbetaR-I is frequently mutated in OC and suggest that resistance to TGF-beta-mediated growth inhibition may frequently involve alterations of the TbetaR-I gene.

Disease progression, adherence, and response to protease inhibitor therapy for HIV infection in an Urban Veterans Affairs Medical Center

Indinavir therapy has demonstrated promise in the treatment of HIV-1 infection in clinical trials; however, its efficacy in a U.S. Veterans Affairs Medical Center, where access to therapy is generally unimpeded, is unknown. A review of the Miami cohort was conducted for the year beginning May 1996 to evaluate response to indinavir plus two nucleoside analogues. Of 483 HIV-1-positive patients (97% male; mean age, 46.7+/-9.7 years), 266 were offered indinavir based on their having CD4 counts <200 cells/microl or viral loads >10,000 copies/ml. Of these patients, 36% were adherent and experienced significant reductions in viral loads (-93,325+/-147,911 copies/ml) and elevations in CD4+ (111+/-103 cells/microl) and CD8+ (225+/-338 cells/microl) T cell counts. Adherent patients with baseline CD4 counts <100 cells/microl were 4.5 times more likely to have follow-up viral loads >10,000 copies/ml than those with CD4 >200 cells/microl. Adherent patients with CD4 counts <100 cells/microl did not show evidence of immune "exhaustion" because they were equal to those with CD4 counts >200 cells/microl in their capacity to replenish CD4 cells. Nonadherence to the regimen resulted in loss of therapeutic benefit and suggested that strategies to enhance adherence may become an essential component of treatment.

Epidemiology of diarrhoeal illness associated with coccidian-like organism among travellers and foreign residents in Nepal

A newly described organism called CLB (coccidian-like or cyanobacterium-like body) has been identified in cases of prolonged diarrhoea. To confirm an association of CLB with disease and identify risk factors for transmission, we conducted a case-control study of travellers and foreign residents at two outpatient clinics in Kathmandu, Nepal. Patients without diarrhoea were matched to CLB cases by clinic and date of visit. For comparison, patients with other causes of diarrhoea were also studied. Stools were examined for enteric pathogens with standard microbiological and molecular genetic techniques. CLB was identified in 108 (11%) of 964 individuals with gastrointestinal symptoms compared with only 1 (1%) of 96 symptom-free controls (p = 0.003). 7% of residents in the US Embassy community acquired the infection. The diarrhoeal illness associated with CLB lasted a median of 7 weeks (interquartile range 4-9) compared with 9 days (4-19) for individuals with other causes of diarrhoea (p < 0.0001). The prevalence of other enteric pathogens was no higher among CLB cases than among symptom-free controls. Patients with CLB infection were more likely than controls to report consumption of untreated water (odds ratio 3.98; 95% CI 1.29-13.14); organisms of the same appearance were identified in an epidemiologically implicated water sample. The significant association of CLB with prolonged diarrhoea, and the low rate of other enteropathogens in CLB cases, strongly supports the hypothesis that CLB is a new pathogen. Epidemiological and environmental data suggest that the organism is waterborne.

Automobile seat belt practices of pregnant women

Despite the fact that seat belts have been proved effective in reducing deaths and serious injuries, many pregnant women do not wear seat belts. A study was conducted to examine the seat belt practices of pregnant women. Of the 87 women who were interviewed, 40 reported using seat belts regularly during pregnancy. However, almost one-third of them did not adjust the belts properly for maximum protection. Older women and those with more education were more likely to use their seat belts routinely. Only 20 women recalled receiving information about seat belts during their pregnancies, but 48 women would have liked to receive more information.