Hepatitis C virus induces a prediabetic state by directly impairing hepatic glucose metabolism in mice.

Virus-related type 2 diabetes is commonly observed in individuals infected with the hepatitis C virus (HCV); however, the underlying molecular mechanisms remain unknown. Our aim was to unravel these mechanisms using FL-N/35 transgenic mice expressing the full HCV ORF. We observed that these mice displayed glucose intolerance and insulin resistance. We also found that Glut-2 membrane expression was reduced in FL-N/35 mice and that hepatocyte glucose uptake was perturbed, partly accounting for the HCV-induced glucose intolerance in these mice. Early steps of the hepatic insulin signaling pathway, from IRS2 to PDK1 phosphorylation, were constitutively impaired in FL-N/35 primary hepatocytes via deregulation of TNFα/SOCS3. Higher hepatic glucose production was observed in the HCV mice, despite higher fasting insulinemia, concomitant with decreased expression of hepatic gluconeogenic genes. Akt kinase activity was higher in HCV mice than in WT mice, but Akt-dependent phosphorylation of the forkhead transcription factor FoxO1 at serine 256, which triggers its nuclear exclusion, was lower in HCV mouse livers. These findings indicate an uncoupling of the canonical Akt/FoxO1 pathway in HCV protein-expressing hepatocytes. Thus, the expression of HCV proteins in the liver is sufficient to induce insulin resistance by impairing insulin signaling and glucose uptake. In conclusion, we observed a complete set of events leading to a prediabetic state in HCV-transgenic mice, providing a valuable mechanistic explanation for HCV-induced diabetes in humans.

Expression of the prion-like protein Shadoo in the developing mouse embryo.

The prion-like protein Shadoo has been suggested to compensate for the lack of PrP in Prnp-knockout mice, explaining their lack of extreme phenotype. In adult mice, both PrP and Shadoo have shown overlapping expression patterns and shared functions. Their expression in the mouse embryo has also been suggested to be complementary, as invalidation of both genes results in embryonic lethality. The developmental expression profile of PrP has been described from post-implantation stages up until birth. However the spatial expression pattern of Shadoo in the developing mouse embryo is not known. We previously described the expression profile of the prion-like protein Shadoo in adult mice using Sprn reporter mice (Sprn-GFP and Sprn-LacZ). Here we used these mice to describe the developmental expression of Shadoo between 10.5 and 14.5 dpc. The observed pattern in specific embryonic cell lineages and in extra-embryonic tissues is consistent with the previously reported phenotype resulting from its knockdown.

Phenotypic and Molecular Alterations in the Mammary Tissue of R-Spondin1 Knock-Out Mice during Pregnancy.

R-spondin1 (Rspo1) is a member of a secreted protein family which has pleiotropic functions in development and stem cell growth. Rspo1 knock-out mice are sex-reversed, but some remain sub-fertile, so they fail to nurse their pups. A lack of Rspo1 expression in the mammary gland results in an absence of duct side-branching development and defective alveolar formation. The aim of this study was to characterize the phenotypic and molecular alterations of mammary gland due to Rspo1 knock-out. Using the transcriptional profiling of mammary tissues, we identified misregulated genes in the mammary gland of Rspo1 knock-out mice during pregnancy. A stronger expression of mesenchymal markers was observed, without modifications to the structure of mammary epithelial tissue. Mammary epithelial cell immunohistochemical analysis revealed a persistence of virgin markers, which signify a delay in cell differentiation. Moreover, serial transplantation experiments showed that Rspo1 is associated with a regenerative potential of mammary epithelial cell control. Our finding also highlights the negatively regulated expression of Rspo1's partners, Lgr4 and RNF43, in the mammary gland during pregnancy. Moreover, we offer evidence that Tgf-ß signalling is modified in the absence of Rspo1. Taken together, our results show an abrupt halt or delay to mammary development during pregnancy due to the loss of a further differentiated function.

Overexpression of miR-30b in the developing mouse mammary gland causes a lactation defect and delays involution.

BACKGROUND: MicroRNA (miRNA) are negative regulators of gene expression, capable of exerting pronounced influences upon the translation and stability of mRNA. They are potential regulators of normal mammary gland development and of the maintenance of mammary epithelial progenitor cells. This study was undertaken to determine the role of miR-30b on the establishment of a functional mouse mammary gland. miR-30b is a member of the miR-30 family, composed of 6 miRNA that are highly conserved in vertebrates. It has been suggested to play a role in the differentiation of several cell types. METHODOLOGY/PRINCIPAL FINDINGS: The expression of miR-30b was found to be regulated during mammary gland development. Transgenic mice overexpressing miR-30b in mammary epithelial cells were used to investigate its role. During lactation, mammary histological analysis of the transgenic mice showed a reduction in the size of alveolar lumen, a defect of the lipid droplets and a growth defect of pups fed by transgenic females. Moreover some mammary epithelial differentiated structures persisted during involution, suggesting a delay in the process. The genes whose expression was affected by the overexpression of miR-30b were characterized by microarray analysis. CONCLUSION/SIGNIFICANCE: Our data suggests that miR-30b is important for the biology of the mammary gland and demonstrates that the deregulation of only one miRNA could affect lactation and involution.