In pancreatic β cells, ABCA1, a 254 kDa membrane protein, affects cholesterol homeostasis and insulin secretion. Angiotensin II, as the main effector of the renin-angiotensin system, decreases glucose-stimulated insulin secretion (GSIS). We examined the effect of angiotensin II on ABCA1 expression in primary pancreatic islets and INS-1 cells. Angiotensin II decreased ABCA1 protein and mRNA; angiotensin II type 1 receptor (AT1R) blockade rescued this ABCA1 repression. In parallel, angiotensin II suppressed the promoter activity of , an effect that was abrogated by PD98095, a specific inhibitor of MAPK kinase (MEK). LXR enhanced promoter activity, and angiotensin II decreased the nuclear abundance of LXR protein. On a chromatin immunoprecipitation assay, LXR mediated the transcription of by directly binding to its promoter. Mutation of the LXR binding site on the promoter cancelled the effect of angiotensin II. Furthermore, angiotensin II induced cholesterol accumulation and impaired GSIS; inhibition of AT1R or MEK pathway reversed these effects. In summary, our study showed that angiotensin II suppressed ABCA1 expression in pancreatic islets and INS-1 cells, indicating that angiotensin II may influence GSIS by regulating ABCA1 expression. Additional research may address therapeutic needs in diseases such as diabetes mellitus.

BackgroundRecently, immune checkpoint inhibitors have widely been used for the management of advanced melanoma. However, high-grade immune-related adverse events can occur, particularly with combination immunotherapy. We report a case of a patient with melanoma who developed thyroid storm following treatment with ipilimumab and nivolumab.Case presentationAn 85-year-old Japanese man with a history of malignant melanoma presented to our department with severe thyrotoxicosis and poor blood glucose control. He was already being treated for Hashimoto’s disease and type 2 diabetes mellitus before the treatment for the melanoma. During admission, laboratory investigations revealed the following thyroid functions: thyroid-stimulating hormone below sensitivity, free triiodothyronine 31.7 pg/ml, and thyroglobulin 48,000 IU/ml. Thyroid-stimulating hormone receptor antibody was negative, and a 99mTc-labeled thyroid scan revealed a markedly decreased uptake. He was treated with beta-blocker, orally administered potassium iodine, a relatively low dose of prednisolone, and insulin injection therapy to control his blood glucose, resulting in an improvement in thyroid function and his symptoms.ConclusionIt might be important to be aware of the possibility of thyroid storm induced by immune checkpoint inhibitors.

Recently, several clinical studies have suggested that adult growth hormone deficiency that also has low concentration of IGF1 is associated with an increased prevalence of fatty liver (FL). ABCA1 is a pivotal regulator of lipid efflux from cells to apolipoproteins and play an important role on formation of FL. In this study, we determined the effects of IGF1 on ABCA1 expression in GH deficient mice to clarify its effects on FL. Western blotting, real-time PCR and a luciferase assay were employed to examine the effect of IGF1. The binding of FoxO1 to the ABCA1 promoter was assessed by ChIP assay. Cholesterol accumulation was analyzed by Oil-Red-O stain and cholesterol content measurement. We confirmed that IGF1 up-regulated the ABCA1 expression. The activity of a reporter construct containing the ABCA1 promoter was induced by IGF1, and this effect was blocked by LY294002, a specific inhibitor of PI3K. Constitutively active Akt stimulated the ABCA1 promoter activity, and a dominant-negative mutant of Akt or mutagenesis of the FoxO1 response element abolished the effect of IGF1. A ChIP assay indicated that FoxO1 mediated IGF1 transcriptional activity by directly binding to the ABCA1 promoter region. In vivo experiments, we used an inhibitor for the GH receptor (Pegvisomant) to reduce the IGF1 level. A HFD induced FL in mice (C57BL/6J) given Pegvisomant-treat. IGF1-treatment stimulated ABCA1 expression to improve cholesterol accumulation in these mice. These results show that the PI3K/Akt/FoxO1 pathway contributes to the regulation of ABCA1 expression in response to IGF1-stimulation that suppressed FL in GH-deficient mice.

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Thyroid stimulating hormone (TSH) stimulates the secretion of thyroid hormones by binding the TSH receptor (TSHR). TSHR is well-known to be expressed in thyroid tissue, excepting it, TSHR has also been expressed in many other tissues. In this study, we have examined the expression of TSHR in rat pancreatic islets and evaluated the role of TSH in regulating pancreas-specific gene expression. TSHR was confirmed to be expressed in rodent pancreatic islets and its cell line, INS-1 cells. TSH directly affected the glucose uptake in INS cells by up-regulating the expression of GLUT2, and furthermore this process was blocked by SB203580, the specific inhibitor of the p38 MAPK signaling pathway. Similarly, TSH stimulated GLUT2 promoter activity, while both a dominant-negative p38MAPK α isoform (p38MAPK α-DN) and the specific inhibitor for p38MAPK α abolished the stimulatory effect of TSH on GLUT2 promoter activity. Finally, INS-1 cells treated with TSH showed increased protein level of glucokinase and enhanced glucose-stimulated insulin secretion. Together, these results confirm that TSHR is expressed in INS-1 cells and rat pancreatic islets, and suggest that activation of the p38MAPK α might be required for TSH-induced GLUT2 gene transcription in pancreatic β cells.