title: Oral calcium supplementation reduces intraplatelet free calcium concentration and insulin resistance in essential hypertensive patients.
abstract: We evaluated the effect of oral calcium supplementation on blood pressure, calcium metabolism, and insulin resistance in essential hypertension. After receiving a standard diet with 500 mg of calcium per day during a 4-week period, 20 nondiabetic, essential hypertensive patients were randomized in a double-blind fashion to receive oral calcium supplementation (1500 mg of calcium per day) or placebo for 8 weeks. At the end of the 4-week period of low-calcium diet and after the 8-week period of intervention, we measured blood pressure (by both office and 24-hour ambulatory blood pressure monitoring), calcium-regulating hormones [urinary hydroxyproline and serum osteocalcin, parathormone, and 1,25(OH)2-vitamin D3], intraplatelet free calcium concentration, fasting plasma glucose and insulin levels, and the insulin-sensitivity index (euglycemic-hyperinsulinemic clamp). Compared with patients maintained at low calcium intake, essential hypertensive patients under oral calcium supplementation significantly reduced serum osteocalcin (from 22.2 +/- 1.9 to 17.9 +/- 2.0 micrograms/L; P = .0015), parathormone (from 4.20 +/- 0.38 to 3.30 +/- 0.36 pmol/L; P = .0003), and 1,25(OH)2-vitamin D3 (from 98.0 +/- 11.0 to 61.6 +/- 5.7 pmol/L; P = .0062). Likewise, we found a significant reduction in intraplatelet free calcium concentration (from 35.9 +/- 1.2 to 26.5 +/- 0.8 nmol/L; P = .0005) and fasting plasma insulin levels (from 71.8 +/- 5.9 to 64.6 +/- 6.2 pmol/L; P = .05) and a significant increase in the insulin-sensitivity index (from 2.89 +/- 0.77 to 4.00 +/- 0.95 mg.kg-1.min-1; P = .0007). None of these parameters were significantly modified in patients maintained at low calcium intake. Office and 24-hour mean values of systolic and diastolic blood pressure did not change after 8 weeks of oral calcium supplementation or placebo.
authors.affiliation: Department of Internal Medicine, Hospital Clínic, University of Barcelona, Spain.
authors.forename: M
authors.initials: M
authors.lastname: Sánchez
authors.forename: A
authors.initials: A
authors.lastname: de la Sierra
authors.forename: A
authors.initials: A
authors.lastname: Coca
authors.forename: E
authors.initials: E
authors.lastname: Poch
authors.forename: V
authors.initials: V
authors.lastname: Giner
authors.forename: A
authors.initials: A
authors.lastname: Urbano-Márquez
mesh_terms: D000284:Administration, Oral; D000328:Adult; D001792:Blood Platelets / Q000187:drug effects* / Q000378:metabolism; D001794:Blood Pressure / Q000187:drug effects*; D002118:Calcium / Q000008:administration & dosage / Q000378:metabolism* / Q000494:pharmacology*; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D006973:Hypertension / Q000378:metabolism* / Q000503:physiopathology; D007333:Insulin Resistance; D008297:Male; D008875:Middle Aged
chemical_list: D002118:Calcium