Effects of 2-Methoxyestradiol, a Main Metabolite of Estradiol on Hepatic ABCA1 Expression in HepG2 Cells.

ATP-binding cassette transporter A1 (ABCA1) is a key regulator of lipid efflux, and the absence of ABCA1 induces hepatic lipid accumulation, which is one of the major causes of fatty liver. 2-Methoxyestradiol (2-ME2) has been demonstrated to protect against fatty liver. In this study, we investigated the effects of 2-ME2 on the hepatic lipid content and ABCA1 expression. We found that 2-ME2 dose-dependently increased ABCA1 expression, and therefore, the lipid content was significantly decreased in HepG2 cells. 2-ME2 enhanced the ABCA1 promoter activity; however, this effect was reduced after the inhibition of the PI3K pathway. The overexpression of Akt or p110 induced ABCA1 promoter activity, while dominant-negative Akt diminished the ability of 2-ME2 on ABCA1 promoter activity. Further, 2-ME2 stimulated the rapid phosphorylation of Akt and FoxO1 and reduced the nuclear accumulation of FoxO1. Chromatin immunoprecipitation confirmed that FoxO1 bonded to the ABCA1 promoter region. The binding was reduced by 2-ME2, which facilitated ABCA1 gene transcription. Furthermore, mutating FoxO1-binding sites in the ABCA1 promoter region or treatment with FoxO1-specific siRNA disrupted the effect of 2-ME2 on ABCA1 expression. All of our results demonstrated that 2-ME2 might upregulate ABCA1 expression via the PI3K/Akt/FoxO1 pathway, which thus reduces the lipid content in hepatocytes.

Oxidized LDL Downregulates ABCA1 Expression via MEK/ERK/LXR Pathway in INS-1 Cells.

Impaired insulin secretion is one of the main causes of type 2 diabetes. Cholesterol accumulation-induced lipotoxicity contributes to impaired insulin secretion in pancreatic beta cells. However, the detailed mechanism in this process remains unclear. In this study, we proved that oxidized low-density lipoprotein (OxLDL) reduced insulin content, decreased PDX-1 expression, and impaired glucose-stimulated insulin secretion (GSIS) in INS-1 cells, which were rescued by addition of high-density lipoprotein (HDL). OxLDL receptors and cholesterol content were increased by OxLDL. Consistently, OxLDL suppressed cholesterol transporter ABCA1 expression and transcription in a dose-dependent and time-dependent manner. Inhibition of MEK by its specific inhibitor, PD98059, altered the effect of OxLDL on ABCA1 transcription and activation of ERK. Next, chromatin immunoprecipitation assay demonstrated that liver X receptor (LXR) could directly bind to ABCA1 promoter and this binding was inhibited by OxLDL. Furthermore, OxLDL decreased the nuclear LXR expression, which was prevented by HDL. LXR-enhanced ABCA1 transcription was suppressed by OxLDL, and the effect was cancelled by mutation of the LXR-binding sites. In summary, our study shows that OxLDL down-regulates ABCA1 expression by MEK/ERK/LXR pathway, leading to cholesterol accumulation in INS-1 cells, which may result in impaired insulin synthesis and GSIS.

Nivolumab-induced hypophysitis followed by acute-onset type 1 diabetes with renal cell carcinoma: a case report.

BACKGROUND: Immune checkpoint inhibitors have recently become widely used for the management of advanced cancer patients. During the development of immune checkpoint inhibitors (ICPIs), it was quickly recognized that they are associated with autoimmune or autoinflammatory side effects. These toxicities are known as immune-related adverse events (irAEs): common endocrine irAEs include hypophysitis and thyroid dysfunction, and uncommon irAEs include type 1 diabetes mellitus (T1DM). CASE PRESENTATION: A 62-year-old Japanese man with metastatic renal cell carcinoma was treated with sunitinib followed by the 10th cycle of treatment with the ICPI nivolumab. He had already had thyroiditis and hypophysitis due to these anti-cancer drugs. On admission, he showed an extremely elevated plasma glucose level (601 mg/dl) and a low C-peptide level, and was diagnosed with acute T1DM. The patient was treated with intravenous fluid infusion and continuous insulin infusion. On the second day, he was switched to multiple daily injections of insulin therapy. Since these treatments, his blood glucose levels have been stable and he has been treated with an additional 10 ICPI treatments for renal cell carcinoma for over a year. CONCLUSIONS: Treatment with ICPIs is expected to increase in the future. There may be cases in which their use for cancer treatment is inevitable despite the side effects. As long as treatment with ICPI continues, multiple side effects can be expected in some cases. It is important to carefully observe the side effects that occur during ICPI treatment and to provide appropriate treatment for each side effect.

Successful Therapy Using Pasireotide Long-acting Release for Cushing's Disease Merged with Biochemical Acromegaly.

It is quite rare that Cushing's disease shows acromegaly, and no pharmacotherapy has yet been discussed. A 21-year-old woman was diagnosed with Cushing's disease and underwent trans-sphenoidal surgery. Five years later, she was diagnosed with recurrent Cushing's disease and biochemical acromegaly because of elevated levels of serum growth hormone (GH), plasma insulin-like growth factor-1, plasma adrenocorticotropic hormone (ACTH), and the 24-hour urinary excretion of free cortisol. After treatment initiation with pasireotide-long-acting release (LAR), both the ACTH and GH declined. Our case is the first to show the efficacy of pasireotide-LAR in controlling both Cushing's disease and acromegaly.

Ectopic Cortisol-producing Adrenocortical Adenoma Detected by 131I-6ß-iodomethyl-norcholesterol Scintigraphy.

A 50-year-old man was referred to our department for overt Cushing's syndrome (CS). His plasma cortisol concentrations were 314 µg/L, and his urinary cortisol concentrations were 431 µg/day. The plasma adrenocorticotropic hormone (ACTH) concentration was below the detectable limit. Computed tomography revealed atrophy of both adrenal glands and the presence of a left pararenal tumor. 131I-6ß-iodomethyl-norcholesterol scintigraphy showed an intense uptake by the left pararenal tumor. These findings suggested that the left pararenal tumor was ectopic cortisol-producing adrenocortical adenoma. This case serves as a reminder that 131I-6ß-iodomethyl-norcholesterol scintigraphy is an effective method for diagnosing ACTH-independent CS in which no adrenal tumor has been found.

Treatment with 2-methoxyestradiol increases endothelial nitric oxide synthase activity via scavenger receptor class BI in human umbilical vein endothelial cells.

Concentrations of 2-methoxyestradiol (2ME2), a principal metabolite of estradiol, are significantly lower in women with severe preeclampsia. Nitric oxide (NO) released by endothelial nitric oxide synthase (eNOS) plays an important role in regulating cardiovascular homeostasis. Importantly, high-density lipoprotein (HDL) stimulates eNOS activity via endothelial human scavenger receptor class B type I (hSR-BI/CLA-1). Here, we aimed to determine the effect of 2ME2 on hSR-BI/CLA-1 expression in human umbilical vein endothelial cells (HUVECs). hSR-BI/CLA-1 expression was measured by real-time PCR, western blotting and reporter gene assays; eNOS activity was assessed by the measurement of eNOS phosphorylation. Both the mRNA and protein concentrations of hSR-BI/CLA-1 were significantly increased by 2ME2 in HUVECs. 2ME2 also dose-dependently increased the transcriptional activity of the hSR-BI/CLA-1 promoter. The effect of 2ME2 treatment on the promoter activity of hSR-BI/CLA-1 was abrogated by treatment with LY294002, a specific inhibitor of phosphatidylinositol 3-kinase, as was the increase in HDL-induced eNOS activation. Notably, constitutively active Akt increased the activity of the hSR-BI/CLA-1 promoter, whereas dominant-negative Akt abolished the effect of 2ME2 treatment on hSR-BI/CLA-1 promoter activity. The nuclear Sp1 protein concentration was significantly increased by exposure to 2ME2 and Sp1 overexpression increased the promoter activity of the hSR-BI/CLA gene. Furthermore, knockdown of Sp1 inhibited the effect of 2ME2 treatment on hSR-BI/CLA-1 protein expression. These results indicate that 2ME2 treatment increases HDL-dependent eNOS phosphorylation by upregulating endothelial hSR-BI/CLA-1 expression, suggesting that 2ME2 has a potential therapeutic value in the treatment of preeclampsia.

Role of ATP-binding cassette transporter A1 in suppressing lipid accumulation by glucagon-like peptide-1 agonist in hepatocytes.

OBJECTIVE: Adenosine triphosphate (ATP)-binding cassette transporter A1 (ABCA1) influences hepatic cholesterol transportation. Accumulation of hepatic cholesterol leads to fatty liver disease, which is improved by glucagon-like peptide 1 (GLP-1) in diabetes. Therefore, we analyzed the molecular mechanism in the regulation of hepatic ABCA1 by GLP-1 analogue exendin-4. METHODS: Hepatic ABCA1 expression and transcription were checked by western blotting, real-time polymerase chain reaction (PCR), and luciferase assay in HepG2 cells. Chromatin immunoprecipitation (ChIP) and site-directed mutagenesis were employed to determine transcriptional regulation of the ABCA1 gene. Prolactin regulatory element-binding (PREB)-transgenic mice were generated to access the effect of exendin-4 on improving lipid accumulation caused by a high-fat diet (HFD). RESULTS: Exendin-4 stimulated hepatic ABCA1 expression and transcription via the Ca2+/calmodulin (CaM)-dependent protein kinase kinase/CaM-dependent protein kinase IV (CaMKK/CaMKIV) pathway, whereas GLP-1 receptor antagonist exendin9-39 cancelled this effect. Therefore, exendin-4 decreased hepatic lipid content. ChIP showed that PREB could directly bind to the ABCA1 promoter, which was enhanced by exendin-4. Moreover, PREB stimulated ABCA1 promoter activity, and mutation of PREB-binding site in ABCA1 promoter cancelled exendin-4-enhanced ABCA1 promoter activity. Silencing of PREB attenuated the effect of exendin-4 and induced hepatic cholesterol accumulation. Blockade of CaMKK by STO-609 or siRNA cancelled the upregulation of ABCA1 and PREB induced by exendin-4. In vivo, exendin-4 or overexpression of PREB increased hepatic ABCA1 expression and decreased hepatic lipid accumulation and high plasma cholesterol caused by a HFD. CONCLUSIONS: Our data shows that exendin-4 stimulates hepatic ABCA1 expression and decreases lipid accumulation by the CaMKK/CaMKIV/PREB pathway, suggesting that ABCA1 and PREB might be the therapeutic targets in fatty liver disease.

Bilateral Adrenocortical Adenomas along with Virilization and Cushing's Syndrome.

We herein present the case of a 27-year-old woman with clinical and biochemical features of virilism. Imaging studies revealed the presence of a bilateral adrenal tumor. Although the secretion of androgens was remarkable, the autonomous production of cortisol was also evident because of a loss of circadian rhythm and the absence of cortisol suppression by dexamethasone. The surgical excision of both adrenal tumors was performed, and the histological examination showed no malignancy. We also report the successful pregnancy and delivery of the patient who showed evolving adrenocortical insufficiency along with virilization and Cushing's syndrome and who continued to receive glucocorticoid replacement therapy during pregnancy.

Selective peroxisome proliferator-activated receptor-α modulator K-877 regulates the expression of ATP-binding cassette transporter A1 in pancreatic beta cells.

ATP-binding cassette transporter A1 (ABCA1) protein is a pivotal regulator of cholesterol and phospholipid efflux from cells to high-density lipoprotein (HDL) particles. Pancreatic ABCA1 functions in beta cell cholesterol homeostasis and affects insulin secretion. We investigated the effect of pemafibrate (K-877), a novel selective PPARα modulator (SPPARMα), on pancreatic ABCA1 expression. In vivo experiment, mice were divided into four treatment groups, namely, normal food plus placebo, high fat diet (HFD) plus placebo, normal food plus K-877 (0.3 mg/kg/day), or HFD plus K-877 (0.3 mg/kg/day), and treated for eight weeks. The results in vitro experiment indicate that K-877 treatment increased levels of ABCA1 mRNA, as well as protein, subsequently reduced the cellular cholesterol content in INS-1 cells. PPARα specific antagonist GW6471 attenuate K-877 induced ABCA1 expression in INS-1 cells. ABCA1 promoter activity increased with K-877 treatment at concentration 1 µM and 10 µM. Glucose-stimulated insulin secretion was ameliorated by K-877 treatment in INS-1 cells and isolated mouse islets. Although the expression of ABCA1 was reduced in mice with HFD treatment, both ABCA1 protein and mRNA levels were increased in mice with K-877 treatment. K-877 treatment improved glucose intolerance induced by HFD in mice. These findings raise the possibility that K-877 may affect insulin secretion by controlling ABCA1 expression in pancreatic beta cells.

Angiotensin II induces cholesterol accumulation and impairs insulin secretion by regulating ABCA1 in beta cells.

In pancreatic ß 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 ABCA1, an effect that was abrogated by PD98095, a specific inhibitor of MAPK kinase (MEK). LXR enhanced ABCA1 promoter activity, and angiotensin II decreased the nuclear abundance of LXR protein. On a chromatin immunoprecipitation assay, LXR mediated the transcription of ABCA1 by directly binding to its promoter. Mutation of the LXR binding site on the ABCA1 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.

Effect of TNF-α on the expression of ABCA1 in pancreatic ß-cells.

ATP-binding cassette transporter A1 (ABCA1), a 254-kD membrane protein, is a key regulator of lipid efflux from cells to apolipoproteins. ABCA1 in pancreatic ß-cells influences insulin secretion and cholesterol homeostasis. Tumor necrosis factor (TNF)-α is a pleiotropic cytokine that elicits a wide spectrum of physiological events, including cell proliferation, differentiation, and apoptosis, and is also known to decrease glucose-dependent insulin secretion in pancreatic islets. In the present study, we examined the role of TNF-α on ABCA1 expression in rat pancreatic islets and INS-1 cells. ABCA1 protein levels decreased in response to rising concentrations of TNF-α in pancreatic islets. Real-time polymerase chain reaction analysis showed a significant decrease in ABCA1 mRNA expression. In parallel with its effect on endogenous ABCA1 mRNA levels, TNF-α suppressed the activity of a reporter construct containing the ABCA1 promoter. This effect was abrogated by BIRB796, but not by SB203580 or PD98095. The constitutively active form of p38 mitogen-activated protein kinase (MAPK) γ suppressed ABCA1 promoter activity but not p38-MAPK (α, ß), while a dominant-negative mutant of p38-MAPK γ blocked the effect of TNF-α on ABCA1 promoter activity. BIRB796 inhibited the increased cholesterol ester content induced by TNF-α. However, BIRB796 had no effect on the decreased insulin content nor ABCA1 suppression caused by TNF-α in INS-1 cells. In summary, TNF-α suppressed the expression of endogenous ABCA1 in pancreatic islets and INS-1 cells. These findings raise the possibility that TNF-α may affect insulin secretion by controlling ABCA1 expression.

IGF1 suppresses cholesterol accumulation in the liver of growth hormone-deficient mice via the activation of ABCA1.

Recently, several clinical studies have suggested that adult growth hormone (GH) deficiency that also has low concentration of IGF1 is associated with an increased prevalence of fatty liver (FL). ATP-binding cassette transporter A1 (ABCA1) is a pivotal regulator of lipid efflux from cells to apolipoproteins and plays 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 chromatin immunoprecipitation (ChIP) assay. Cholesterol accumulation was analyzed by Oil Red O stain and cholesterol content measurement. We confirmed that IGF1 upregulated 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 phosphatidylinositol 3-kinase (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. For in vivo experiments, we used an inhibitor for the GH receptor (Pegvisomant) to reduce the IGF1 level. A high-fat diet induced FL in mice (C57BL/6J) given Pegvisomant treatment. 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.

Combination therapy of ipilimumab and nivolumab induced thyroid storm in a patient with Hashimoto's disease and diabetes mellitus: a case report.

BACKGROUND: Recently, 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 PRESENTATION: An 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. CONCLUSION: It might be important to be aware of the possibility of thyroid storm induced by immune checkpoint inhibitors.