BACKGROUND: Sulfonylurea primarily stimulates insulin secretion by binding to its receptor on the pancreatic beta-cells. Recent studies have suggested that sulfonylureas induce insulin sensitivity through peroxisome proliferator-activated receptor gamma (PPARgamma), one of the nuclear receptors. In this study, we investigated the effects of sulfonylurea on PPARgamma transcriptional activity and on the glucose uptake via PPARgamma. METHODS: Transcription reporter assays using Cos7 cells were performed to determine if specific sulfonylureas stimulate PPARgamma transactivation. Glimepiride, gliquidone, and glipizide (1 to 500 microM) were used as treatment, and rosiglitazone at 1 and 10 microM was used as a control. The effects of sulfonylurea and rosiglitazone treatments on the transcriptional activity of endogenous PPARgamma were observed. In addition, 3T3-L1 adipocytes were treated with rosiglitazone (10 microM), glimepiride (100 microM) or both to verify the effect of glimepiride on rosiglitazone-induced glucose uptake. RESULTS: Sulfonylureas, including glimepiride, gliquidone and glipizide, increased PPARgamma transcriptional activity, gliquidone being the most potent PPARgamma agonist. However, no additive effects were observed in the presence of rosiglitazone. When rosiglitazone was co-treated with glimepiride, PPARgamma transcriptional activity and glucose uptake were reduced compared to those after treatment with rosiglitazone alone. This competitive effect of glimepiride was observed only at high concentrations that are not achieved with clinical doses. CONCLUSION: Sulfonylureas like glimepiride, gliquidone and glipizide increased the transcriptional activity of PPARgamma. Also, glimepiride was able to reduce the effect of rosiglitazone on PPARgamma agonistic activity and glucose uptake. However, the competitive effect does not seem to occur at clinically feasible concentrations.
Adipocytes ; Diabetes Mellitus, Type 2 ; Glipizide ; Glucose ; Insulin ; Insulin Resistance ; Peroxisome Proliferator-Activated Receptors ; Peroxisomes ; PPAR gamma ; Receptors, Cytoplasmic and Nuclear ; Sulfonylurea Compounds ; Thiazolidinediones ; Transcriptional Activation

OBJECTIVETo analyze the clinical characteristics of an infant with neonatal diabetes mellitus (NDM) and to sequence the ABCC8 gene of this family in order to provide a theoretical basis for the diagnosis and treatment.

METHODSThe clinical data of the patient was collected, and the proband and his direct relatives within three generations were sequenced.

RESULTSThe patient was 1-month-old, random blood glucose was more than 27.8 mmol/L, C-peptide was 33.8 pmol/L, blood gas analysis was pH 7.16, HCO3.9 mmol/L and urine alkone was 3+. Genetic testing revealed that the patient, his father, elder brother and grandmother have carried heterozygous mutation c.2690A>T(p.D897V) of the ABCC8 gene. Fluid infusion, intravenous administration of insulin and other supportive therapies were provided. After the correction of acidosis, subcutaneous insulin injection were uesd to control the blood glucose. Eight months later, blood glucose was pooly controlled. After combined with glibenclamide, blood glucose was under control.

CONCLUSIONThe patient carries a heterozygous mutation c.2690A>T(p.D897V) of ABCC8 gene, which is a novel mutation. Glibenclamide was partly effective for the patient.

Blood Glucose ; genetics ; Diabetes Mellitus ; genetics ; Follow-Up Studies ; Humans ; Infant ; Infant, Newborn ; Infant, Newborn, Diseases ; genetics ; Male ; Mutation ; genetics ; Sulfonylurea Receptors ; genetics

Neonatal diabetes mellitus (DM) is defined as insulin-requiring DM in the first six months of life. Unlike type 1 DM, it is a monogenic disorder resulting from a de novo mutation in the genes involved in the development of the pancreas, β-cell mass or secretory function. The majority of neonatal DM cases are caused by a heterozygous activating mutation in the KCNJ11 or ABCC8 genes that encode the Kir6.2 and SUR1 protein subunits, respectively, in the KATP channel. Sulphonylurea, a KATP channel inhibitor, can restore insulin secretion, hence offering an attractive alternative to insulin therapy. We report three cases of neonatal DM and their genetic mutations. Two patients were successfully switched over to sulphonylurea monotherapy with resultant improvement in the quality of life and a more stable blood glucose profile. Patients with neonatal DM should undergo genetic evaluation. For patients with KCNJ11 and ABCC8 gene mutation, oral sulphonylurea should be considered.
ATP-Binding Cassette Transporters ; genetics ; Blood Glucose ; metabolism ; Diabetes Mellitus ; genetics ; therapy ; Female ; Genotype ; Heterozygote ; Humans ; Infant ; Infant, Newborn ; Male ; Models, Biological ; Models, Genetic ; Molecular Biology ; Mutation ; Pancreas ; physiology ; Potassium Channels, Inwardly Rectifying ; genetics ; Quality of Life ; Receptors, Drug ; genetics ; Sulfonylurea Compounds ; therapeutic use ; Sulfonylurea Receptors

The ATP-sensitive potassium (KATP) channel is a member of inward rectifier potassium channel (Kir) that is inhibited by intracellular ATP and functions in close relation to sulfonylurea receptors (SUR). Although the molecular mechanism and physiological function of KATP channels are well understood, the expression pattern during development or treatment with the channel modulators such as glybenclamide is little known. In this work, we determined mRNA levels of a KATP channel (Kir6.2) and a sulfonylurea receptor (SUR2) in rat tissues by RNase protection assay. Levels of Kir6.2 and SUR2 mRNA in the rat brain and skeletal muscle were higher in adult (90-120 days) than in neonate (2-8 days), whereas those in the heart were not much different between neonate (2-8 days) and adult (90-120 days). In addition, none of KATP channel modulators (opener, pinacidil and nicorandil; blocker, glybenclamide) affected the Kir6.2 mRNA levels in the heart, brain and skeletal muscle. The results indicate that the expression of Kir and SUR genes can vary age-dependently, but the expression of Kir is not dependent on the long-term treatment of channel modulators. The effect of the channel modulators on mRNA level of SUR is remained to be studied further.
Adenosine Triphosphate ; Adult* ; Animals ; Brain ; Glyburide ; Heart ; Humans ; Infant, Newborn* ; KATP Channels ; Muscle, Skeletal ; Nicorandil ; Pinacidil ; Potassium Channels* ; Potassium Channels, Inwardly Rectifying ; Potassium* ; Rats* ; Ribonucleases ; RNA, Messenger ; Sulfonylurea Receptors

BACKGROUNDKCNJ11, ABCC8, PPARG, and HNF4A have been found to be associated with type 2 diabetes in populations with different genetic backgrounds. The aim of this study was to test, in a Chinese Han population from Beijing, whether the genetic variants in these four genes were associated with genetic predisposition to type 2 diabetes.

METHODSWe studied the association of four representative SNPs in KCNJ11, ABCC8, PPARG, and HNF4A by genotyping them using ABI SNaPshot Multiplex System in 400 unrelated type 2 diabetic patients and 400 unrelated normoglycaemic subjects.

RESULTSrs5219 (E23K) in KCNJ11 was associated with genetic susceptibility to type 2 diabetes (OR = 1.400 with 95% CI 1.117 1.755, P = 0.004 under an additive model, OR = 1.652 with 95% CI 1.086 2.513, P = 0.019 under a recessive model, and OR = 1.521 with 95% CI 1.089 2.123, P = 0.014 under a dominant model) after adjusting for sex and body mass index (BMI). We did not find evidence of association for ABCC8 rs1799854, PPARG rs1801282 (Pro12Ala) and HNF4A rs2144908. Genotype-phenotype correlation analysis revealed that rs1799854 in ABCC8 was associated with 2-hour postprandial insulin secretion (P = 0.005) after adjusting for sex, age and BMI. Although no interactions between the four variants on the risk of type 2 diabetes were detected, the multiplicative interaction between PPARG Pro12Ala and HNF4A rs2144908 was found to be associated with 2-hour postprandial insulin (P = 0.004 under an additive model for rs2144908; and P = 0.001 under a dominant model for rs2144908) after adjusting for age, sex and BMI, assuming a dominant model for PPARG Pro12Ala.

CONCLUSIONSOur study replicated the association of rs5219 in KCNJ11 with type 2 diabetes in Chinese Han population in Beijing. And we also observed that ABCC8 as well as the interaction between PPARG and HNF4A may contribute to post-challenge insulin secretion.

ATP-Binding Cassette Transporters ; genetics ; Adult ; Body Mass Index ; Diabetes Mellitus, Type 2 ; genetics ; Female ; Genetic Predisposition to Disease ; genetics ; Genotype ; Hepatocyte Nuclear Factor 4 ; genetics ; Humans ; Male ; Middle Aged ; PPAR gamma ; genetics ; Polymorphism, Single Nucleotide ; genetics ; Potassium Channels, Inwardly Rectifying ; genetics ; Receptors, Drug ; genetics ; Sulfonylurea Receptors

To study the effects of free fatty acids on insulin secretion and expression of SUR1 gene in rat pancreatic B cells in vitro, and to explore the molecular mechanisms in lipotoxicity inducing insulin secretion dysfunction, pancreatic islet cells were isolated and digested from male SD rats. Purified islets were incubated with either 0.25 mmol/L palmitate or 0.125 mmol/L oleate for 48 h in vitro. Then islets were stimulated with either 5.6 mmol/L or 16.7 mmol/L glucose for 1 h. Insulin release was measured by using radioimmunoassay, and the expression of SUR1 gene mRNA was quantified by reserve transcription-polymerase chain reaction (RT-PCR). The islets exposed to both palmitate and oleate for 48 h showed an increased basal and a decreased glucose-indused insulin release as compared with control islets. Palmitate increased basal insulin secretion by 110% (P< 0.01), decreased glucose stimulated insulin secretion by 43% (P<0.01); while oleate increased basal insulin secretion by 80% (P<0.01) and decreased glucose stimulated insulin secretion by 32 % (P<0.05). RT-PCR showed that oleate significantly suppressed SUR1 gene expression by 64 % (P<0.01) as compared with the control group, while palmitate group manifested a light decrease of 15% (P>0.05) of SUR1 gene expression. Our results suggested that chronic exposure to free fatty acids of pancreatic beta cells inhibited glucose stimulated insulin secretion. Regulation of SUR1 gene expression may be involved in such effects, which may also be one of the molecular mechanisms in lipotoxocity inducing beta cells secretion dysfunction.
ATP-Binding Cassette Transporters ; biosynthesis ; genetics ; Animals ; Cells, Cultured ; Fatty Acids ; pharmacology ; Insulin ; secretion ; Islets of Langerhans ; drug effects ; physiology ; Male ; Potassium Channels ; biosynthesis ; genetics ; Potassium Channels, Inwardly Rectifying ; biosynthesis ; genetics ; RNA, Messenger ; biosynthesis ; genetics ; Rats ; Rats, Sprague-Dawley ; Receptors, Drug ; biosynthesis ; genetics ; Sulfonylurea Receptors

This paper was aimed to investigate the effects of ATP-sensitive potassium channels on the proliferation and differentiation of rat preadipocytes. We examined the expression of sulphonylurea receptor 2 (SUR2) mRNA in preadipocytes and adipocytes obtained by inducing for 5 d and the effects of the inhibitor (glibenclamide) and opener (diazoxide) of ATP-sensitive potassium channels on the expression of SUR2 mRNA in preadipocytes by real-time PCR. Preadipocyte proliferation and cell cycle were measured by MTT spectrophotometry and flow cytometer. The content of intracellular lipid was measured by oil red O staining, cell diameter was determined by Image-Pro Plus 5.0 software and the expression of peroxisome proliferator-activated receptor-gamma (PPAR-gamma) mRNA was estimated by RT-PCR. SUR2 mRNA was expressed in both preadipocytes and adipocytes obtained by inducing for 5 d, and the expression in adipocytes was obviously higher than that in preadipocytes. Glibenclamide inhibited the expression of SUR2 mRNA in preadipocyte, promoted preadipocyte proliferation in a dose-dependent manner, increased the cell percentages in G(2)/M + S phase, increased lipid content, augmented adipocyte diameter, and promoted the expression of PPAR-gamma mRNA. But the actions of diazoxide were contrary to those of glibenclamide. These results suggest that ATP-sensitive potassium channels regulate the proliferation and differentiation of preadipocytes, and PPAR-gamma is probably involved in the effect of ATP-sensitive potassium channels.
ATP-Binding Cassette Transporters ; genetics ; metabolism ; Adipocytes ; cytology ; Animals ; Cell Differentiation ; physiology ; Cell Proliferation ; Cells, Cultured ; KATP Channels ; physiology ; Male ; Obesity ; pathology ; PPAR gamma ; metabolism ; Potassium Channels, Inwardly Rectifying ; genetics ; metabolism ; RNA, Messenger ; genetics ; metabolism ; Rats ; Rats, Sprague-Dawley ; Receptors, Drug ; genetics ; metabolism ; Sulfonylurea Receptors

BACKGROUNDType 2 diabetes mellitus (T2DM) results from the complex association of insulin resistance and pancreatic β-cell failure. Recent studies have shown that patients diagnosed with T2DM present with a significant decrease in β-cell function, which can be further compromised during the progression of the disease. Several mechanisms have been shown to play a role in this process such as glucotoxicity and lipotoxicity, which contribute to accelerating insulin secretion. In this regard, Chinese medicine has a certain advantage. This experiment was performed to observe the effect of a Chinese medicine named Kaiyuqingre formula (KYQRF) on β-cell function and its mechanisms of action therein.

METHODSHigh glucose was used to set up a model of β-cell function failure. At the same time, medicated serum of KYQRF with different doses were administered to the cells. Rosiglitazone was taken as a control to observe the changes in insulin secretion, ATP-sensitive K(+) channels (K(ATP) channel) and uncoupling protein-2 (UCP-2) in each group.

RESULTSKYQRF had some effects on the insulin secretion. In a low glucose environment, no effective change in insulin secretion was observed (P > 0.05). However, insulin levels increased significantly when INS-1 cells were exposed to a high glucose environment (P < 0.05). KYQRF could also enhance cell viability (P < 0.05) in an effect similar to rosiglitazone. Although KYQRF had no effect on inwardly rectifying potassium channels (Kir6.2) (P > 0.05), it could decrease the overexpression of both UCP-2 and sulfonylurea receptor 1 (P < 0.05).

CONCLUSIONKYQRF can protect islet function by decreasing UCP-2 and sulfonylurea receptor 1.

ATP-Binding Cassette Transporters ; genetics ; Animals ; Cell Survival ; drug effects ; Drugs, Chinese Herbal ; pharmacology ; Glucose ; pharmacology ; Insulin ; secretion ; Insulin-Secreting Cells ; cytology ; drug effects ; metabolism ; Ion Channels ; genetics ; Male ; Mitochondrial Proteins ; genetics ; Potassium Channels, Inwardly Rectifying ; genetics ; Rats ; Rats, Sprague-Dawley ; Receptors, Drug ; genetics ; Sulfonylurea Receptors ; Thiazolidinediones ; pharmacology ; Uncoupling Protein 2

ATP-sensitive potassium (K(ATP)) channels are widely distributed in vasculatures, and play an important role in the vascular tone regulation. The K(ATP) channels consist of 4 pore-forming inward rectifier K(+) channel (Kir) subunits and 4 regulatory sulfonylurea receptors (SUR). The major vascular isoform of K(ATP) channels is composed of Kir6.1/SUR2B, although low levels of other subunits are also present in vascular beds. The observation from transgenic mice and humans carrying Kir6.1/SUR2B channel mutations strongly supports that normal activity of the Kir6.1/SUR2B channel is critical for cardiovascular function. The Kir6.1/SUR2B channel is regulated by intracellular ATP and ADP. The channel is a common target of several vasodilators and vasoconstrictors. Endogenous vasopressors such as arginine vasopressin and α-adrenoceptor agonists stimulate protein kinase C (PKC) and inhibit the K(ATP) channels, while vasodilators such as β-adrenoceptor agonists and vasoactive intestinal polypeptide increase K(ATP) channel activity by activating the adenylate cyclase-cAMP-protein kinase A (PKA) pathway. PKC phosphorylates a cluster of 4 serine residues at C-terminus of Kir6.1, whereas PKA acts on Ser1387 in the nucleotide binding domain 2 of SUR2B. The Kir6.1/SUR2B channel is also inhibited by oxidants including reactive oxygen species allowing vascular regulation in oxidative stress. The molecular basis underlying such a channel inhibition is likely to be mediated by S-glutathionylation at a few cysteine residues, especially Cys176, in Kir6.1. Furthermore, the channel activity is augmented in endotoxemia or septic shock, as a result of the upregulation of Kir6.1/SUR2B expression. Activation of the nuclear factor-κB dependent transcriptional mechanism contributes to the Kir6.1/SUR2B channel upregulation by lipopolysaccharides and perhaps other toll-like receptor ligands as well. In this review, we summarize the vascular K(ATP) channel regulation under physiological and pathophysiological conditions, and discuss the importance of K(ATP) channel as a potentially useful target in the treatment and prevention of cardiovascular diseases.
ATP-Binding Cassette Transporters ; genetics ; physiology ; Animals ; Endotoxemia ; metabolism ; physiopathology ; Humans ; KATP Channels ; genetics ; physiology ; Mice ; Mice, Transgenic ; Muscle, Smooth, Vascular ; metabolism ; physiology ; Potassium Channels, Inwardly Rectifying ; genetics ; physiology ; Receptors, Drug ; genetics ; physiology ; Shock, Septic ; metabolism ; physiopathology ; Sulfonylurea Receptors ; Vasoconstriction ; physiology ; Vasodilation ; physiology ; Vasomotor System ; physiology

The aim of the present study is to investigate the expressions of ATP-sensitive K(+) channels (KATP) in pulmonary artery smooth muscle cells (PASMCs) and the relationship with p38 MAPK signal pathway in rats. Male SD rat PASMCs were cultured in vitro, and a model of hypoxia and hypercapnia was reconstructed. PASMCs were divided to normal (N), hypoxia-hypercapnia (H), hypoxia-hypercapnia+DMSO incubation (HD), hypoxia-hypercapnia+SB203580 (inhibitor of p38 MAPK pathway) incubation (HS) and hypoxia-hypercapnia+Anisomycin (agonist of p38 MAPK pathway) incubation (HA) groups. Western blot was used to detect the protein expression of SUR2B and Kir6.1; semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR) was used to detect the mRNA expression of SUR2B and Kir6.1. The results demonstrated that: (1) Compared with N, H, HD and HS groups, the expressions of Kir6.1 mRNA and protein in PASMCs of HA group were decreased significantly (P < 0.01), but there were no differences among N, H, HD and HS groups (P > 0.05); (2) Compared with N group, the expressions of SUR2B mRNA and protein in H, HD, HS and HA groups were increased significantly (P < 0.05), but there were no differences among H, HD, HS and HA groups (P > 0.05). The results imply that: (1) Hypoxia-hypercapnia, SB203580 didn't change the expressions of Kir6.1 mRNA and protein in PASMCs, but Anisomycin decreased the expressions of Kir6.1 mRNA and protein, so Kir6.1 may be regulated by the other subfamily of MAPK pathway; (2) Hypoxia-hypercapnia raised SUR2B mRNA and protein expressions in PASMCs, but SB203580 and Anisomycin did not affect the changes, so the increasing of SUR2B mRNA and protein induced by hypoxia-hypercapnia may be not depend on p38 MAPK pathway.
Animals ; Anisomycin ; pharmacology ; Cell Hypoxia ; Cells, Cultured ; Hypercapnia ; Imidazoles ; pharmacology ; KATP Channels ; metabolism ; MAP Kinase Signaling System ; Male ; Myocytes, Smooth Muscle ; metabolism ; Pulmonary Artery ; cytology ; Pyridines ; pharmacology ; Rats ; Rats, Sprague-Dawley ; Sulfonylurea Receptors ; metabolism ; p38 Mitogen-Activated Protein Kinases ; antagonists & inhibitors