Relationship between sodium–lithium countertransport and insulin sensitivity in mild hypertension |
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Authors: | H. HERLITZ,K. LANDIN,& B. WIDGREN |
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Affiliation: | From the Departments of Nephrology, Endocrinology and Medicine, Göteborg University, Göteborg, Sweden |
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Abstract: | Objectives. To study the relationship between insulin sensitivity and sodium-lithium countertransport (Na+-Li+ CT) in mild, essential hypertension, and to investigate the effect of metformin and metoprolol, respectively. Design. A double-blind, triple cross-over, placebo-controlled study over a total period of 18 weeks. Setting. A hypertension out-patient clinic and research laboratory at Sahlgrenska University Hospital. Subjects. Seventeen non-obese men with mild essential hypertension and 17 weight-matched, healthy controls. Interventions. Metformin 850 mg b.i.d., metoprolol CR 100 mg once daily and placebo were given during 18 weeks. Each treatment period was 6 weeks. A euglycaemic clamp was performed and erythrocyte Na+-Li+ CT measured after each 6-week treatment period. Main outcome measures. Insulin sensitivity, erythrocyte Na+-Li+ CT, their interrelation, and the effect of metformin and metoprolol CR on both variables, respectively. Results. The hypertensive men tended to have an elevated Na+-Li+ CT compared with the control subjects (0.34±0.03 versus 0.26±0.02 mmol L-1 h-1, P<0.1). Glucose disposal rate was similar, but plasma insulin levels higher (P<0.05) among the hypertensives than the controls. Na+-Li+ CT exhibited a positive relationship to BMI (r=0.53, P=0.03) and a negative correlation to glucose disposal rate (r=-0.66, P=0.008) in the hypertensive subjects. In multiple regression analysis, Na+-Li+ CT showed a significant correlation to glucose disposal rate only. In the control subjects, there was no relation between glucose metabolism and Na+-Li+ CT. Neither metformin nor metoprolol influenced Na+-Li+ CT, glucose disposal rate or plasma insulin. Conclusion. Erythrocyte Na+-Li+ CT seemed to be closely related to insulin-glucose metabolism in mild hypertension, but was not influenced by metformin or metoprolol. |
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Keywords: | hypertension insulin insulin sensitivity euglycaemic clamp sodium-lithium countertransport metformin metoprolol |
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