Relationship between sodium-lithium countertransport and insulin sensitivity in mild hypertension.
OBJECTIVE
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.


METHODS
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.


METHODS
Seventeen non-obese men with mild essential -hypertension and 17 weight-matched, healthy controls.


METHODS
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.


METHODS
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.


CONCLUSIONS
Erythrocyte Na(+)-Li+ CT seemed to be closely related to insulin-glucose metabolism in mild hypertension, but was not influenced by metformin or metoprolol.
Herlitz
H
H
Department of Nephrology, Göteborg University, Sweden.
Landin
K
K
Widgren
B
B
D000959:Antihypertensive Agents / Q000627:therapeutic use*; D017920:Antiporters / Q000378:metabolism*; D001786:Blood Glucose / Q000378:metabolism; D001794:Blood Pressure; D015992:Body Mass Index; D018592:Cross-Over Studies; D004311:Double-Blind Method; D004912:Erythrocytes / Q000378:metabolism; D015309:Glucose Clamp Technique; D006801:Humans; D006973:Hypertension / Q000188:drug therapy* / Q000378:metabolism*; D007328:Insulin / Q000097:blood*; D008094:Lithium / Q000378:metabolism*; D008297:Male; D008687:Metformin / Q000627:therapeutic use*; D008790:Metoprolol / Q000627:therapeutic use*; D008875:Middle Aged; D012964:Sodium / Q000378:metabolism*
D000959:Antihypertensive Agents; D017920:Antiporters; D001786:Blood Glucose; D007328:Insulin; C045885:sodium-lithium countertransporter; D008687:Metformin; D008094:Lithium; D012964:Sodium; D008790:Metoprolol