Jin-Ho Koh

Association of angiotensin-converting enzyme I/D and α-actinin-3 R577X genotypes with metabolic syndrome risk factors in Korean children

OBJECTIVE This study analysed the risk factors associated with metabolic syndrome through the interaction between ACTN3 and ACE gene polymorphism in Korean children. METHODS The subjects of the study consisted of elementary school students (n=788, age 10.10±0.07 yr). The anthropometric parameters, blood lipid profiles, and metabolic markers were compared among groups of the ACE I/D or the ACTN3 R577X polymorphisms. RESULTS The subjects with the DD genotype showed significantly higher systolic blood pressure than the subjects with the II and ID genotype of the ACE gene polymorphism. XX genotype had significantly lower waist-hip ratio than those with RR genotype of the ACTN3 gene polymorphism. Also, the subjects with XX genotype exhibited significantly higher blood HDL cholesterol level than those with RR or RX genotype. The interaction of ACTN3 and ACE gene polymorphism in subjects having both ACE DD and ACTN3 RR genotypes demonstrated a significantly higher metabolic syndrome score than any other groups. CONCLUSION The children having both ACTN3 RR or RX genotype and ACE DD genotype showed high systolic blood pressure and low blood HDL cholesterol level, which may be considered a high-risk in metabolic syndrome.

Effect of Lithium on the Mechanism of Glucose Transport in Skeletal Muscles

While lithium is known to stimulate glucose transport into skeletal muscle, the mechanisms of the increased glucose transport by lithium in skeletal muscle are not well defined yet. We excised epitrochlearis muscles from male Wistar rats and measured the transport rates of a glucose analog into lithium-, insulin-, and muscular contraction-stimulated skeletal muscle tissue and we also analyzed the levels of cell surface glucose transport 4 using a photolabeling and multicolor immunofluorescence method. In addition, we generated a cell line that stably expresses myc-tagged GLUT4 to measure the rates of GLUT4 internalization and externalization. Lithium significantly increased 2-DG glucose transport rate in skeletal muscles; however, it was significantly lower than the stimulation induced by the maximum concentration of insulin or tetanic contraction. But co-treatment of lithium with insulin or tetanic contraction increased glucose transport rate by ∼200% more than lithium alone. When skeletal muscle tissues were treated with lithium, insulin, and muscular contraction, the levels of cell surface GLUT4 protein contents were increased similarly by ∼6-fold compared with the basal levels. When insulin or lithium stimuli were maintained, the rate of GLUT4myc internalization was significantly lower, and lithium was found to suppress the internalization of GLUT4myc more strongly. The lithium-induced increase in glucose uptake of skeletal muscles appears to increase in cell surface GLUT4 levels caused by decreased internalization of GLUT4. It is concluded that co-treatment of lithium with insulin and muscular contraction had a synergistic effect on glucose transport rate in skeletal muscle.