GenSalt: rationale, design, methods and baseline characteristics of study participants

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Abstract
Hypertension is a complex disorder influenced by genetic and environmental determinants and their interactions. The objectives of the Genetic Epidemiology Network of Salt Sensitivity (GenSalt) are to localize and identify genes related to blood pressure (BP) responses to dietary sodium and potassium intervention. GenSalt utilizes a family feeding-study design. Each family was ascertained through a proband with untreated prehypertension or stage-1 hypertension in rural China. A medical history, lifestyle risk factors and responses to cold pressor tests, were obtained at baseline visits while BP, weight, blood and urine specimens were collected at baseline and follow-up visits. The dietary intervention included a 7-day low-sodium feeding (51.3 mmol/day), a 7-day high-sodium feeding (307.8 mmol/day) and a 7-day high-sodium feeding with an oral potassium supplementation (60 mmol/day). Microsatellite markers for genome-wide linkage scan and single nucleotide polymorphism (SNP) markers in candidate genes will be genotyped. Overall, 3153 participants from 658 families were recruited for GenSalt. The mean systolic and diastolic BPs were 128.0 and 80.3, 111.6 and 71.0, 112.6 and 72.6, 106.6 and 65.3 and 136.7 and 75.0 mm Hg for probands, siblings, spouses, offspring and parents, respectively. The mean urinary excretion of sodium and potassium were 232.5 and 38.6, 222.9 and 38.2, 213.1 and 37.8 and 207.3 and 36.0 mmol/24-h for probands, siblings, spouses and offspring, respectively. Our study will identify novel genes that influence significantly the effect of dietary sodium and potassium intake on BP. This information is useful for development of targeted intervention for the prevention and treatment of hypertension.