The reversible effects of free fatty acids on sulfonylurea-stimulated insulin secretion are related to the expression and dynamin-mediated endocytosis of KATP channels in pancreatic ß cells.

Objective: Lipotoxicity-induced pancreatic ß cell-dysfunction results in decreased insulin secretion in response to multiple stimulus. In this study, we investigated the reversible effects of palmitate (PA) or oleate (OA) on insulin secretion and the relationship with pancreatic ß-cell ATP-sensitive potassium (KATP) channels. Methods: MIN6 cells were treated with PA and OA for 48 h and then washed out for 24 h to determine the changes in expression and endocytosis of the KATP channels and glucose-stimulated insulin secretion (GSIS) and sulfonylurea-stimulated insulin secretion (SU-SIS). Results: MIN6 cells exposed to PA or OA showed both impaired GSIS and SU-SIS; the former was not restorable, while the latter was reversible with washout of PA or OA. Decreased expressions of both total and surface Kir6.2 and SUR1 and endocytosis of KATP channels were observed, which were also recoverable after washout. When MIN6 cells exposed to free fatty acids (FFAs) were cotreated with 5-aminoimidazole-4-carboxamide ribonucleotide (AICAR) or dynasore, we found that endocytosis of KATP channels did not change significantly by AICAR but was almost completely blocked by dynasore. Meanwhile, the inhibition of endocytosis of KATP channels after washout could be activated by PIP2. The recovery of SU-SIS after washout was significantly weakened by PIP2, but the decrease of SU-SIS induced by FFAs was not alleviated by dynasore. Conclusions: FFAs can cause reversible impairment of SU-SIS on pancreatic ß cells. The reversibility of the effects is partial because of the changes of expression and endocytosis of Kir6.2 and SUR1 which was mediated by dynamin.

Compound heterozygosity of a novel Q73X mutation and a known R141X mutation in CYP11B1 resulting in 11ß-hydroxylase deficiency in a Chinese boy with congenital adrenal hyperplasia.

Steroid 11ß-hydroxylase deficiency (11ß-OHD), which is caused by mutations of the CYP11B1 gene, is the second leading cause of congenital adrenal hyperplasia (CAH), an autosomal recessive inherited disorder. Here, we report a case of classic 11ß-OHD in a Chinese boy characterized by hypertension, penile enlargement, skin pigmentation, and acne. Molecular analysis of CYP11B1 revealed that the patient was compound heterozygous for a c.217C > T (p.Q73X) mutation in exon 1 and a c.421C > T (p.R141X) mutation in exon 3. His parents carried the novel c.217C > T (p.Q73X) mutation and the prevalent c.421C > T (p.R141X) mutation. Furthermore, we identified a novel 217-bp substitution mutation (Q73X) in CYP11B1 that generates a truncated protein without biological activity, which is likely to be pathogenic. Pursuant to the phenotype of the proband and his family, the Q73X mutation is inferred to exacerbate the disease burden of the R141X mutation, a known pathogenic variant. To further explore this possibility, selecting the x-ray structure of human CYP11B2 as a template, we built three-dimensional homologous models of the normal and mutant proteins. In the mutant model, a change from a helix to terminal structure in amino acids 73 and 141 occurred that affected the binding capacity of CYP11B1 with heme and impaired 11ß-hydroxylase activity. Taken together, our findings expand the spectrum of known mutations leading to 11ß-OHD and provide evidence to study genotype-phenotype concordance, confirm early diagnosis and treatment of 11ß-OHD, and prevent most complications.

Comparison of biomarkers of endothelial dysfunction and microvascular endothelial function in patients with primary aldosteronism and essential hypertension.

INTRODUCTION: Studies have shown that primary aldosteronism (PA) has a higher risk of cardiovascular events than essential hypertension (EH). Endothelial dysfunction is an independent predictor of cardiovascular events. Whether PA and EH differ in the endothelial dysfunction is uncertain. Our study was designed to investigate the levels of biomarkers of endothelial dysfunction (Asymmetric dimethylarginine, ADMA; E-selectin, and Plasminogen activator inhibitor-1, PAI-1) and assess the microvascular endothelial function in patients with PA and EH, respectively. METHODS: The biomarkers of endothelial dysfunction were measured by enzyme-linked immunosorbent assay (ELISA). Microvascular endothelial function was evaluated by Pulse amplitude tonometry (PAT). RESULTS: Thirty-one subjects with EH and 36 subjects with PA including 22 with aldosterone-producing adenoma (APA) and 14 with idiopathic hyperaldosteronism (IHA) were enrolled in our study. The ADMA levels among the three groups were different (APA 47.83 (27.50, 87.74) ng/ml vs EH 25.08 (22.44, 39.79) ng/ml vs IHA 26.00 (22.23, 33.75) ng/ml; p = 0.04), however, when the APA group was compared with EH and IHA group, there was no statistical significance (47.83 (27.50, 87.74) ng/ml vs 25.08 (22.44, 39.79) ng/ml for EH, p = 0.11; 47.83 (27.50, 87.74) ng/ml vs IHA 26.00 (33.75) ng/ml, p = 0.07). The results of ADMA levels are presented as Median (p25, p75). Whereas, levels of PAI-1 and E-selectin, microvascular endothelial function were not significantly different between PA and EH subjects. CONCLUSIONS: Our study shows no significant differences between PA and EH in terms of biomarkers of endothelial dysfunction and microvascular endothelial function. The microvascular endothelial function of PA and EH patients is comparable.