ABSTRACT
Accumulating evidences showed metformin and berberine, well-known glucose-lowering agents, were able to inhibit mitochondrial electron transport chain at complex I. In this study, we aimed to explore the antihyperglycaemic effect of complex I inhibition. Rotenone, amobarbital and gene silence of NDUFA13 were used to inhibit complex I. Intraperitoneal glucose tolerance test and insulin tolerance test were performed in db/db mice. Lactate release and glucose consumption were measured to investigate glucose metabolism in HepG2 hepatocytes and C2C12 myotubes. Glucose output was measured in primary hepatocytes. Compound C and adenoviruses expressing dominant negative AMP-activated protein kinase (AMPK) α1/2 were exploited to inactivate AMPK pathway. Cellular NAD+ /NADH ratio was assayed to evaluate energy transforming and redox state. Rotenone ameliorated hyperglycaemia and insulin resistance in db/db mice. It induced glucose consumption and glycolysis and reduced hepatic glucose output. Rotenone also activated AMPK. Furthermore, it remained effective with AMPK inactivation. The enhanced glycolysis and repressed gluconeogenesis correlated with a reduction in cellular NAD+ /NADH ratio, which resulted from complex I suppression. Amobarbital, another representative complex I inhibitor, stimulated glucose consumption and decreased hepatic glucose output in vitro, too. Similar changes were observed while expression of NDUFA13, a subunit of complex I, was knocked down with gene silencing. These findings reveal mitochondrial complex I emerges as a key drug target for diabetes treatment. Inhibition of complex I improves glucose homoeostasis via non-AMPK pathway, which may relate to the suppression of the cellular NAD+ /NADH ratio.
Subject(s)
AMP-Activated Protein Kinases/metabolism , Electron Transport Complex I/metabolism , Glucose/metabolism , Animals , Apoptosis Regulatory Proteins/metabolism , Blood Glucose/metabolism , Cell Line , Cell Respiration/drug effects , Enzyme Activation/drug effects , Gluconeogenesis/drug effects , Glycolysis/drug effects , Humans , Insulin Resistance , Liver/drug effects , Liver/metabolism , Male , Mice, Inbred C57BL , Models, Biological , NAD/metabolism , NADH, NADPH Oxidoreductases/metabolism , Phosphorylation/drug effects , Rotenone/pharmacology , Signal Transduction/drug effectsABSTRACT
OBJECTIVE: To investigate the relationship between genetic polymorphisms of glucose transporter 4 (GLUT4) and hypoxia caused by obstructive sleep apnea syndrome (OSAS) as well as with related inflammatory factors. METHODS: Consecutive hypertension patients diagnosed at the People's Hospital of Xinjiang Uygur Autonomous Region were selected from January to December 2010. A total of 859 subjects with possible OSAS base on their histories and physical examination findings udner went the polysomnography and inflammatory factor determination, of whom 616 (72%) were diagnosed with moderate and severe hypoxia with OSAS (case group) and 243 (28%) without hypoxia or OASA (control group). Ninty-six patients from the case group underwent DNA sequencing at the functional domain of GLUT4 gene to screen for representative mutations. TaqMan PCR was used to genotyping then analyzed the relationship between locis of GLUT4 and hypoxia. RESULTS: GLUT4 genome sequencing was performed in 96 severe OSAS patients and 4 mutated sites were found, among which 3 mutated sites (rs5415, rs4517, and rs5435) were selected according to the principle of linkage disequilibrium (r² > 0.8) and minimum gene allele frequency > 5%. All of single nucleotide polymorphisms (SNP) satisfied Hardy-Weinberg equilibrium (P>0.05). A significant association of GLUT4 SNP rs5417 allele carried in control subjects, compared with moderate and severe hypoxia in OSAS patients (P<0.05); AA+AC genotype relative to CC with low oxygen levels in subjects significantly reduced. The difference existed in overweight and obese patients, as well as in those aged more than 50 years (P<0.05). AA was still an independent protective factor for hypoxia caused by OSAS (OR=0.385, 95%CI = 0.210-0.704, P=0.002). Male (OR=1.635, 95% CI=1.037-2.577, P=0.034) and total cholesterol (OR=1.600, 95% CI=1.287-1.987, P<0.001) were independent risk factors associated with hypoxia. Normal weight(OR=0.059, 95% CI=0.037-0.094, P<0.001) and high density lipoprotein cholesterol (OR=0.337, 95% CI=0.171-0.666, P=0.002)were independent protective factors for hypoxia. The levels of monocyte chemoattractant protein-1 and C-reaction protein above CC were significantly higher than AA+AC (P<0.05). CONCLUSION: Hypoxia caused by OSAS is associated with GLUT4 gene SNP rs5417.