Clinical characteristics of somatic mutations in Chinese patients with aldosterone-producing adenoma.

Recent studies have shown that somatic mutations in the KCNJ5, ATP1A1, ATP2B3, and CACNA1D genes are associated with the pathogenesis of aldosterone-producing adenoma. Clinical profile and biochemical characteristics of the mutations in Chinese patients with aldosterone-producing adenoma remain unclear. In this study, we performed DNA sequencing in 168 Chinese patients with aldosterone-producing adenoma and found 129 somatic mutations in KCNJ5, 4 in ATP1A1, 1 in ATP2B3, and 1 in CACNA1D. KCNJ5 mutations were more prevalent in female patients and were associated with larger adenomas, higher aldosterone excretion, and lower minimal serum K(+) concentration. More interestingly, we identified a novel somatic KCNJ5 mutation (c.445-446insGAA, p.T148-T149insR) that could enhance CYP11B2 mRNA upregulation and aldosterone release. This mutation could also cause membrane depolarization and intercellular Ca(2+) increase. In conclusion, somatic KCNJ5 mutations are conspicuously more popular than mutations of other genes in aldosterone-producing adenomas of Chinese patients. The T148-T149insR mutation in KCNJ5 may influence K(+) channel selectivity and autonomous aldosterone production.

Genipin stimulates glucose transport in C2C12 myotubes via an IRS-1 and calcium-dependent mechanism.

Genipin, a compound derived from Gardenia jasminoides Ellis fruits, has been used over the years in traditional Chinese medicine to treat symptoms of type 2 diabetes. However, the molecular basis for its antidiabetic effect has not been fully revealed. In this study, we investigated the effects of genipin on glucose uptake and signaling pathways in C(2)C(12) myotubes. Our study demonstrates that genipin stimulated glucose uptake in a time- and dose-dependent manner. The maximal effect was achieved at 2 h with a concentration of 10 µM. In myotubes, genipin promoted glucose transporter 4 (GLUT4) translocation to the cell surface, which was observed by analyzing their distribution in subcellular membrane fraction, and increased the phosphorylation of insulin receptor substrate-1 (IRS-1), AKT, and GSK3ß. Meanwhile, genipin increased ATP levels, closed K(ATP) channels, and then increased the concentration of calcium in the cytoplasm in C(2)C(12) myotubes. Genipin-stimulated glucose uptake could be blocked by both the PI3-K inhibitor wortmannin and calcium chelator EGTA. Moreover, genipin increases the level of reactive oxygen species and ATP in C(2)C(12) myotubes. These results suggest that genipin activates IRS-1, PI3-K, and downstream signaling pathway and increases concentrations of calcium, resulting in GLUT4 translocation and glucose uptake increase in C(2)C(12) myotubes.

Globular adiponectin inhibits GnRH secretion from GT1-7 hypothalamic GnRH neurons by induction of hyperpolarization of membrane potential.

Reproduction is accurately regulated by metabolic states in mammals. Adiponectin regulates luteinizing hormone (LH) secretion in the pituitary and energy homeostasis in the hypothalamus. We further investigated the gonadotropin-releasing hormone (GnRH) secretion regulation by adiponectin and its related molecular and electrophysiological mechanisms. The results showed that adiponectin receptors (AdipR1 and 2) were expressed in GT1-7 cells derived from hypothalamus neurons. GnRH secretion was inhibited via activation of AMP-activated protein kinase (AMPK). Moreover, we revealed that hyperpolarization of plasma membrane potentials and reduction of calcium influx was also caused by adiponectin.

[Effects of sodium metabisulfite on potassium currents in acutely isolated rat hippocampal CA1 neurons].

AIM: To investigate the effects of sodium metabisulfite (SMB), sulfur dioxide (SO2) and its derivatives in vivo, sodium bisulfite and sulfite on K+ channels of the central neurons and its mechanisms. METHODS: By using whole-cell patch-clamp technique, the effects of SMB on transient outward K+ (I(A)) and delayed rectifier K+ currents(IK) were observed. RESULTS: (1) SMB can increase the amplitudes of I(A) and I(K) in a dose-dependent and voltage-dependent manner. Their half-increase doses were 15.8 micromol/L and 11.5 micromol/L respectively. (2) SMB (10 micromol/L) significantly shifted the activation curves of I(A) and I(K) to more positive potentials. Before and after application of 10 micromol/L SMB, the half-activation voltages of I(A) and I(K) were (- 12.6 +/- 1.6) mV and (- 7.0 +/- 1.3) mV, (10.8 +/- 0.9) mV and (21.6 +/- 0.7) mV (P < 0.01, n = 8), respectively, but the slope factors were not changed. (3) The inactivation curve of I(A) was shifted to positive potentials, the half-inactivation voltage of I(A) were (- 97.0 +/- 1.1) mV and (- 84.4 +/- 3.3) mV (P < 0.01, n = 8) before and after application of SMB (10 micromol/L), without changing the slope factors. (4) SOD, CAT and GPx could partly inhibit the incremental effect of SMB on I(A) and I(K). CONCLUSION: SMB, SO2 and its derivatives in vivo, sodium bisulfite and sulfite have the damage effects on the central nervous system, and they can cause extracellular K+ increase and induce the disturbance of the central neuronal functions. Its mechanism may involve oxidation damage in the rat hippocampal CA1 neurons, caused by sulfur- and oxygen-centered free radicals formed in the process of sulfite or bisulfite oxidation.