Angiotensinogen levels and obesity in four black populations

BACKGROUND: The relationship between circulating levels of angiotensinogen and hypertension in the epidemiologic setting has not been studied much. Recent findings related to the association between hypertension and polymorphisms of the angiotensinogen gene have generated new interest in this potential pathway to hypertension. OBJECTIVES: To examine environmental factors associated with levels of circulating angiotensinogen as determinants of hypertension in populations of African origin. METHODS: We recruited 1557 participants from communities in Nigeria (n = 611), Zimbabwe (n = 161), Jamaica (n = 476), and Maywood, Illinois, USA (n = 309). RESULTS: Mean angiotensinogen levels varied widely across groups (Nigeria 1381 ng/ml angiotensin I generated, Zimbabwe 1638 ng/ml angiotensin I generated, Jamaica 1808 ng/ml angiotensin I generated, and Maywood 2039 ng/ml angiotensin I generated). Average body mass index was highly correlated to angiotensinogen level across the population samples, accounting for 90% of the between-sample variation. At the individual level the correlation between body mass index and angiotensinogen level was substantially smaller, in the range 0.04-0.15, although the association attained statistical significance for all but one of the populations. Women had higher levels of angiotensinogen and mean levels in subjects of both sexes declined in late middle age. Hypertensives also had significantly higher levels of angiotensinogen and we noted correlations to blood pressure for two of the four populations. CONCLUSION: Obesity, sex and age would all appear to be important modifiers of circulating angiotensinogen levels. The variation in level across populations was substantially larger than that which has been found previously in association with known genetic polymorphisms within populations, suggesting the possibility that environmental effects are more important than had previously been recognized.