The ubiquitously expressed G protein α-subunit Gsα mediates the intracellular cAMP response to glucagon-like peptide 1 (GLP1) and other incretin hormones in pancreatic islet cells. We have shown previously that mice with β-cell-specific Gsα deficiency (βGsKO) develop severe early-onset insulin-deficient diabetes with a severe defect in β-cell proliferation. We have now generated mice with Gsα deficiency throughout the whole pancreas by mating Gsα-floxed mice with Pdx1-cre transgenic mice (PGsKO). PGsKO mice also developed severe insulin-deficient diabetes at a young age, confirming the important role of Gsα signaling in β-cell growth and function. Unlike in βGsKO mice, islets in PGsKO mice had a relatively greater proportion of α-cells, which were spread throughout the interior of the islet. Similar findings were observed in mice with pancreatic islet cell-specific Gsα deficiency using a neurogenin 3 promoter-cre recombinase transgenic mouse line. Studies in the α-cell line αTC1 confirmed that reduced cAMP signaling increased cell proliferation while increasing cAMP produced the opposite effect. Therefore, it appears that Gsα/cAMP signaling has opposite effects on pancreatic α- and β-cell proliferation, and that impaired GLP1 action in α- and β-cells via Gsα signaling may be an important contributor to the reciprocal effects on insulin and glucagon observed in type 2 diabetics. In addition, PGsKO mice show morphological changes in exocrine pancreas and evidence for malnutrition and dehydration, indicating an important role for Gsα in the exocrine pancreas as well.
Tao Xie, Min Chen and Lee S Weinstein
Lili Chen, Xiaolong Jiang, Haiwei Feng, Hongjuan Shi, Lina Sun, Wenjing Tao, Qingping Xie and Deshou Wang
Estrogen, which is synthesized earlier in females than androgen in males, is critical for sex determination in non-mammalian vertebrates. However, it remains unknown that what would happen to the gonadal phenotype if estrogen and androgen were administrated simultaneously. In this study, XY and XX tilapia fry were treated with the same dose of 17α-methyltestosterone (MT) and 17β-estradiol (E2) alone and in combination from 0 to 30 days after hatching. Treatment of XY fish with E2 resulted in male to female sex reversal, while treatment of XX fish with MT resulted in female to male sex reversal. In contrast, simultaneous treatment of XX and XY fish with MT and E2 resulted in female, but with cyp11b2 and cyp19a1a co-expressed in the ovary. Serum 11-ketotestosteron level of the MT and E2 simultaneously treated XX and XY female was similar to that of the XY control, while serum E2 level of these two groups was similar to that of the XX control. Transcriptomic cluster analysis revealed that the MT and E2 treated XX and XY gonads clustered into the same branch with the XX control. However a small fraction of genes, which showed disordered expression, may be associated with stress response. These results demonstrated that estrogen could maintain the female phenotype of XX fish and feminize XY fish even in the presence of androgen. Simultaneous treatment with estrogen and androgen up-regulated the endogenous estrogen and androgen synthesis, and resulted in disordered gene expression and endocrine disruption in tilapia.