OBJECTIVETo investigate the expression of GIRK4 gene in the kidney tissues of obese rats.

METHODSObese rat models were established using diet-induced method. The GIRK4 protein expression in kidney tissues was determined in 20 obese rats and 10 normal rats using Western blot analysis.

RESULTSThe relative expression level of GIRK4 protein in the kidney tissues of obese rat (1.75±0.42) was significantly lower than that in normal rats (3.37±0.68, P<0.05).

CONCLUSIONGIRK4 has a low protein expression in the kidney tissues of obese rat.

Animals ; Female ; Gene Expression ; Kidney ; metabolism ; Male ; Obesity ; genetics ; metabolism ; Potassium Channels, Inwardly Rectifying ; genetics ; metabolism ; Rats

OBJECTIVETo investigate the relationship between the G protein-gated inward rectifier K+ channel subunit 4 (GIRK4) gene polymorphism and the dyslipidemia among Uyghur residents in Xinjiang.

METHODSThe polymorphisms of rs2604204, rs4937391, rs6590357, and rs11221497 among the Uyghur residents were genotyped using Taqman polymerase chain reaction (PCR). Lipid levels were measured by conventional methods and were analyzed.

RESULTSIn the less-than-50-years population, the genotype distributions of the rs6590357 was statistically significant different in subjects with or without abnormal triglycerides (P=0.005). Aslo, the the genotype distributions of the rs11221497 also significantly differed in subjects with normal compared or abnormal TG (P=0.011). Logistic regression analysis suggested that rs6590357 still had positive association with TG abnormalities in subjects under 50 years (P=0.014). rs11221497 also had positive association with TC abnormalities. The TG levels of CT+TT genotypes were significantly higher than the CC group (P=0.006). Haplotype analysis found that the differences of H3 haplotype frequencies between the TG abnormal and normal groups were statistically significant (P=0.007).

CONCLUSIONThe polymorphisms of rs11221497 and rs6590357 of GIRK4 gene may play a role in the development of dyslipidemia in Uygur population.

China ; epidemiology ; Dyslipidemias ; epidemiology ; metabolism ; Genotype ; Humans ; Polymerase Chain Reaction ; Polymorphism, Single Nucleotide ; Potassium Channels, Inwardly Rectifying ; genetics ; Triglycerides

Inwardly rectifying potassium (Kir) channels exhibit an asymmetrical conductance at hyperpolarization (high conductance) compared to depolarization (low conductance). The KCNJ10 gene which encodes an inwardly rectifying K+ channel Kir4.1 subunit plays an essential role in the inner ear and hearing. Mutations or deficiency of KCNJ10 can cause hearing loss with epilepsy, ataxia, sensorineural deafness, and renal tubulopathy (EAST) or SeSAME (seizures, sensorineural deafness, ataxia, mental retardation, and electrolyte imbalance) syndromes. In this review, we mainly focus on the expression and function of Kir4.1 channels in the inner ear and mutation-induced EAST/SeSAME syndromes to provide insight for understanding the pathogenesis of deafness induced by KCNJ10 deficiency.
Deafness ; genetics ; metabolism ; Ear, Inner ; metabolism ; Hearing Loss, Sensorineural ; genetics ; metabolism ; Humans ; Intellectual Disability ; genetics ; metabolism ; Mutation ; Potassium Channels, Inwardly Rectifying ; genetics ; metabolism ; Seizures ; genetics ; metabolism

OBJECTIVETo compare the changes of both inward rectifying K(+) (Kir) current(I(k1)) density and mRNA expression level of Kir2.1, a major subfamily of Kir in chronic human atrial fibrillation (CAF) with those in normal sinus rhythm (NSR).

METHODSI(k1) density was measured with whole-cell patch clamp technique in single myocyte isolated by an enzymatic dissociation method from right atrial appendages in patients with CAF (n = 8) and those with NSR (n = 12). The mRNA expression levels of Kir2.1 was determined in right atrial appendages from CAF (n = 19) and NSR (n = 18) by semiquantitative reverse-transcription polymerase chain reaction (RT-PCR).

RESULTThe average resting membrane potentials were similar between CAF and NSR (-78.95 mV +/- 4.67 mV and -70.22 mV +/- 11.08 mV, P>0.05). I(k1) density in single myocyte significantly increased at hyperpolarized potential level (-100 mV) in CAF compared to that in NSR (-9.59 pA/pF +/- 2.47 pA/pF vs. -5.58 pA/pF +/- 2.52 pA/pF, P<0.01). The mRNA level of Kir2.1 was also significantly higher in CAF than that of NSR (0.50+/-0.16 vs. 0.34+/-0.09, P<0.05).

CONCLUSIONThe data suggest that Kir2.1 up-regulation and I(k1) current increase might contribute to the electrical remodeling in CAF patients.

Atrial Fibrillation ; genetics ; metabolism ; physiopathology ; Gene Expression ; Humans ; Myocytes, Cardiac ; metabolism ; physiology ; Patch-Clamp Techniques ; Potassium Channels, Inwardly Rectifying ; genetics ; metabolism ; RNA, Messenger ; genetics

OBJECTIVES: Epilepsy is a syndrome of central nervous system dysfunction caused by many reasons, which is mainly characterized by abnormal discharge of neurons in the brain. Therefore, finding new targets for epilepsy therapy has always been the focus and hotspot in neurological research field. Studies have found that 2-deoxy-D-glucose (2-DG) exerts anti-epileptic effect by up-regulation of K_ATP channel subunit Kir6.1, Kir6.2 mRNA and protein. By using the database of TargetScan and miRBase to perform complementary pairing analysis on the sequences of miRNA and related target genes, it predicted that miR-194 might be the upstream signaling molecule of K_ATP channel. This study aims to explore the mechanism by which 2-DG exerts its anti-epileptic effect by regulating K_ATP channel subunits Kir6.1 and Kir6.2 via miR-194. METHODS: A magnesium-free epilepsy model was established and randomly divided into a control group, an epilepsy group (EP group), an EP+2-DG group, and miR-194 groups (including EP+miR-194 mimic, EP+miR-194 mimic+2-DG, EP+miR-194 mimic control, EP+miR-194 inhibitor, EP+miR-194 inhibitor+2-DG, and EP+miR-194 inhibitor control groups). The 2-DG was used to intervene miR-194 mimics, patch-clamp method was used to detect the spontaneous recurrent epileptiform discharges, real-time PCR was used to detect neuronal miR-194, Kir6.1, and Kir6.2 expressions, and the protein levels of Kir6.1 and Kir6.2were detected by Western blotting. RESULTS: Compared with the control group, there was no significant difference in the amplitude of spontaneous discharge potential in the EP group (P>0.05), but the frequency of spontaneous discharge was increased (P<0.05). Compared with the EP group, the frequency of spontaneous discharge was decreased (P<0.05). Compared with the EP+miR-194 mimic control group, the mRNA and protein expressions of Kir6.1 and Kir6.2 in the EP+miR-194 mimic group were down-regulated (all P<0.05). Compared with the EP+miR-194 inhibitor control group, the mRNA and protein expressions of Kir6.1 and Kir6.2 in the EP+miR-194 inhibitor group were up-regulated (all P<0.05). After pretreatment with miR-194 mimics, the mRNA and protein expression levels of K_ATP channel subunits Kir6.1 and Kir6.2 were decreased (all P<0.05). Compared with the EP+2-DG group, the mRNA and protein expression levels of Kir6.1 and Kir6.2 in the EP+miR-194 mimic+2-DG group were down-regulated (all P<0.05) and the mRNA and protein expression levels of Kir6.1 and Kir6.2 in the EP+miR-194 inhibitor+2-DG group were up-regulated (all P<0.05). CONCLUSIONS The 2-DG might play an anti-epilepsy effect by up-regulating K_ATP channel subunits Kir6.1 and Kir6.2via miR-194.
Adenosine Triphosphate ; Anticonvulsants ; Deoxyglucose/pharmacology* ; Epilepsy/genetics* ; Glucose ; Humans ; MicroRNAs/genetics* ; Potassium Channels, Inwardly Rectifying/metabolism* ; RNA, Messenger/metabolism* ; Signal Transduction

A complete cDNA sequence encoding a pore-forming subunit (Kir6.2) of ATP-senstive potassium channel in the adult worm, Clonorchis sinensis, termed CsKir6.2, was isolated from an adult cDNA library. The cDNA contained a single open-reading frame of 333 amino acids, which has a structural motif (a GFG-motif) of the putative pore-forming loop of the Kir6.2. Peculiarly, the CsKir6.2 shows a lack-sequence structure, which deleted 57 amino acids were deleted from its N-terminus. The predicted amino acid sequence revealed a highly conserved sequence as other known other Kir6.2 subunits. The mRNA was weekly expressed in the adult worm.
Adenosine Triphosphate/metabolism ; Amino Acid Sequence ; Animals ; Base Sequence ; Cloning, Molecular ; Clonorchis sinensis/*genetics/metabolism ; Helminth Proteins/*genetics/metabolism ; Human ; Molecular Sequence Data ; Potassium Channels, Inwardly Rectifying/*genetics/metabolism ; RNA, Helminth/chemistry/genetics ; Sequence Alignment ; Support, Non-U.S. Gov't

PURPOSE: This study examined the expression and function of inward rectifier K+ channels in cultured rat hepatic stellate cells (HSC). MATERIALS AND METHODS: The expression of inward rectifier K+ channels was measured using real-time RT-PCR, and electrophysiological properties were determined using the gramicidin-perforated patch-clamp technique. RESULTS: The dominant inward rectifier K+ channel subtypes were K(ir)2.1 and K(ir)6.1. These dominant K+ channel subtypes decreased significantly during the primary culture throughout activation process. HSC can be classified into two subgroups: one with an inward-rectifying K+ current (type 1) and the other without (type 2). The inward current was blocked by Ba2+ (100micrometer) and enhanced by high K+ (140mM), more prominently in type 1 HSC. There was a correlation between the amplitude of the Ba2+-sensitive current and the membrane potential. In addition, Ba2+ (300micrometer) depolarized the membrane potential. After the culture period, the amplitude of the inward current decreased and the membrane potential became depolarized. CONCLUSION: HSC express inward rectifier K+ channels, which physiologically regulate membrane potential and decrease during the activation process. These results will potentially help determine properties of the inward rectifier K+ channels in HSC as well as their roles in the activation process.
Animals ; Barium/pharmacology ; Blotting, Western ; Cells, Cultured ; Electrophysiology ; Liver/cytology/*metabolism ; Male ; Membrane Potentials/drug effects ; Potassium/pharmacology ; Potassium Channels, Inwardly Rectifying/genetics/metabolism/*physiology ; Rats ; Rats, Sprague-Dawley ; Reverse Transcriptase Polymerase Chain Reaction

Dysfunction of the pancreatic beta-cell is an important defect in the pathophysiological changes of type 2 diabetes, and type 2 diabetes is evidently associated with obesity. But the role of the adipocyte in the dysfunction of the pancreatic beta-cell remains unknown. In the present study, we examined the direct effects of 3T3-L1 adipocytes on the expression of ATP-sensitive potassium channels (K(ATP) channels) in MIN6 insulin-secreting cells. MIN6 cells were divided into two groups as control group, where MIN6 cells were cultured in normal culture medium, and coculture group, where MIN6 cells were cocultured with differentiated 3T3-L1 adipocytes for 1 week. Semi-quantitative RT-PCR was employed to measure the expression of K(ATP) channel subunit Kir6.2 in MIN6 cells. Fura-2 was used to reflect changes in intracellular calcium concentration ([Ca(2+)](i)) in MIN6 cells. The secretary function of MIN6 cells from both groups was estimated by radioimmunoassay method. The results showed that the Kir6.2 cDNA levels corrected by GAPDH cDNA levels after densitometric analysis were 0.989+/-0.035 in control group and 0.726+/-0.087 in coculture group. The expression of Kir6.2 was significantly decreased in MIN6 cells in the coculture group as compared with that in control. MIN6 cells cocultured with 3T3-L1 adipocytes lost the ability to increase [Ca(2+)](i) when stimulated by tolbutamide (0.1 mmol/L), a highly selective KATP channel closer. In contrast, MIN6 cells in control group had typical responses to tolbutamide with a significant increase in [Ca(2+)](i). The magnitudes to basal levels of [Ca(2+)](i) after tolbutamide stimulation were 1.520+/-0.203 in control and 1.114+/-0.097 in coculture group (P<0.05, n=6). MIN6 cells in control showed a significant increase in insulin secretion from 0.38+/-0.099 mU/min to 2.87+/-0.248 mU/min after being stimulated by tolbutamide, whereas MIN6 cells in coculture group did not increase insulin secretion when stimulated by tolbutamide (0.21+/-0.055 mU/min to 0.22+/-0.082 mU/min). It is demonstrated that 3T3-L1 adipocytes decrease the expression of K(ATP) channels in MIN6 cells through secreting certain factors, which impair the secretary function of MIN6 cells. The present results indicate that adipocytes are directly involved in pancreatic beta-cell dysfunction, which may facilitate the development of type 2 diabetes.
3T3 Cells ; Adipocytes ; cytology ; Animals ; Cell Differentiation ; physiology ; Cells, Cultured ; Coculture Techniques ; Gene Expression ; Hypoglycemic Agents ; pharmacology ; Insulin ; biosynthesis ; Insulin Resistance ; Islets of Langerhans ; cytology ; metabolism ; Mice ; Potassium Channels, Inwardly Rectifying ; biosynthesis ; genetics ; physiology ; Tolbutamide ; pharmacology ; Transcription, Genetic ; drug effects

OBJECTIVETo investigate the regulation of leptin on insulin secretion and expression of ATP-sensitive potassium channel subunit sulfonulurea receptor 1 (SUR1) mRNA, and to determine whether the effects of leptin are mediated through known intracellular signaling transduction.

METHODSPancreatic islets were isolated by the collagenase method from male SD rats. The purified islets were incubated with different concentrations of leptin for 2 h in the presence of different concentrations of glucose. Insulin release was measured using radioimmunoassay. Expression of SUR1 mRNA was detected by RT-PCR.

RESULTSIn the presence of leptin 2 nmol/L, insulin release was significantly inhibited at either 11.1 or 16.7 mmol/L glucose concentration (both P < 0.05), but insulin release was not altered at glucose of 5.6 mmol/L physiological concentration. The dose-response experiment showed that the maximal effect of leptin on insulin secretion achieved at 2 nmol/L. Exposure of islets to 2 nmol/L leptin induced a significant increase of SUR1 transcription levels by 71% (P < 0.01) at 11.1 mmol/L glucose and by 56% (P < 0.05) at 16.7 mmol/L glucose concentration. Selective phosphatidylinositol 3-kinase (PI 3-kinase) inhibitor wortmannin significantly prevented the leptin effect on insulin secretion and SUR1 mRNA expression.

CONCLUSIONSRegulatory effects of leptin on insulin secretion could be biphasic at different concentrations of glucose and leptin. The stimulatory regulation of SUR1 transcription levels may be mediated through activation of PI 3-kinase pathway, which may be a possible mechanism of leptin in regulating insulin secretion.

Animals ; Butadienes ; pharmacology ; Cells, Cultured ; Dose-Response Relationship, Drug ; Insulin ; secretion ; Islets of Langerhans ; drug effects ; metabolism ; Leptin ; pharmacology ; Male ; Nitriles ; pharmacology ; Phosphatidylinositol 3-Kinases ; physiology ; Potassium Channels, Inwardly Rectifying ; genetics ; RNA, Messenger ; analysis ; Rats ; Rats, Sprague-Dawley

Age-related hearing loss (AHL) is one of the most common sensory disorders among elderly persons. The inwardly rectifying potassium channel 5.1 (Kir5.1) plays a vital role in regulating cochlear K(+) circulation which is necessary for normal hearing. The distribution of Kir5.1 in C57BL/6J mice cochleae, and the relationship between the expression of Kir5.1 and the etiology of AHL were investigated. Forty C57BL/6J mice were randomly divided into four groups at 4, 12, 24 and 52 weeks of age respectively. The location of Kir5.1 was detected by immunofluorescence technique. The mRNA and protein expression of Kir5.1 was evaluated in mice cochleae using real-time polymerase-chain reactions (RT-PCR) and Western blotting respectively. Kir5.1 was detected in the type II and IV fibrocytes of the spiral ligament in the cochlear lateral wall of C57BL/6J mice. The expression levels of Kir5.1 mRNA and protein in the cochleae of aging C57BL/6J mice were down-regulated. It was suggested that the age-related decreased expression of Kir5.1 in the lateral wall of C57BL/6J mice was associated with hearing loss. Our results indicated that Kir5.1 may play an important role in the pathogenesis of AHL.
Aging ; genetics ; metabolism ; Animals ; Cations, Monovalent ; Fluorescent Antibody Technique ; Gene Expression Regulation ; Ion Transport ; Mice ; Mice, Inbred C57BL ; Microtomy ; Potassium ; metabolism ; Potassium Channels, Inwardly Rectifying ; genetics ; metabolism ; Presbycusis ; genetics ; metabolism ; physiopathology ; RNA, Messenger ; genetics ; metabolism ; Spiral Ligament of Cochlea ; metabolism ; physiopathology ; ultrastructure