The incidence of type 2 diabetes (T2D) continues to increase among African Americans (AA). However, a plateau has been observed among non-Hispanic whites (NHW). Furthermore, the mortality and morbidity associated with T2D has also been reported to be higher among AAs than NHWs. Thus, it is essential to examine novel factors to understand the disparities in TSD prevalence, incidence, and mortality among AAs.
One such risk factor is aldosterone which has been observed to be associated with increased incidences of cardiovascular disease (CVD), diabetes, and all-cause mortality among AAs. The American Heart Association introduced in 2010 a set of 7 cardiovascular health parameters, divided into 4 health behaviors (diet, physical activity, weight and smoking) and 3 health factors (glucose, total cholesterol and blood pressure). Stratification of individual components occurred into ideal, poor and intermediate levels, followed by their stratification into scoring systems.
The REFasoni for geographic Ana Racial ddifferences in Stexchange (GREETINGS), the Multi-Ethnic Study of Atherosclerosis and the Jackson Heart Study (JHS) reported an association of higher ICH (ideal cardiovascular health) metrics with a lower risk of diabetes incidence among AAs. Furthermore, higher ICH has been reported to be associated with lower aldosterone among AAs in the JHS. However, research on the potential mediating effect of aldosterone in the association of ICH with the incidence of T2D is limited. Aldosterone reductions may be the mechanism by which higher ICH reduces the incidence of T2D.
A new study in American Journal of Preventive Cardiology aimed to analyze the role of aldosterone as a mediator in the association of ICH with incidence of T2DF among AAs in JHS. The association of aldosterone with the incidence of T2D among AAs was also analyzed using glucose and blood pressure as mediators.
Study: The role of aldosterone and ideal cardiovascular health in incident diabetes: The Jackson heart study. Image Credit: Kateryna Kon / Shutterstock
About the study
The study involved 5,306 JHS AA adults aged 21 to 94 years. Baseline and enrollment exams were conducted between 2000 and 2004, and two in-person follow-up exams took place between 2005 and 2008, as well as 2009 and 2013. The primary exposure involved assessment of ICH using 5 of the 7 ICH metrics, total cholesterol, body mass index (BMI), physical activity (BP), diet, and cigarette smoking.
Total cholesterol was measured using the cholesterol oxidase method. Body mass index was calculated by dividing weight (kilograms) by the square of height (metres). Assessment of physical activity (PA) was assessed using an interviewer-administered BP questionnaire at baseline. Smoking was self-reported in which participants were asked about the duration and amount of smoking. Dietary assessment was performed using the Delta Nutrition Intervention Research Initiative Food Frequency Questionnaire. Each core metric was evaluated separately using ideal, poor, and intermediate categories.
Fasting blood samples were collected from all participants to measure aldosterone by radioimmunoassay. Blood pressure was measured twice at an interval of 5 minutes and fasting blood glucose was measured by the glucose oxidase colorimetric method. The definition of T2D included fasting blood glucose ≥ 126 mg/dL, HbA1c ≥ 6.5%, use of diabetes medications, or physician self-reported diagnosis. Information was also collected on education, occupation, demographics, current use of prescribed medications, alcohol consumption, and estimated glomerular filtration rate (eGFR).
Study results
Results indicated that a total of 2,791 participants were included in the study, of whom 2,364 had 0 to 2 ICH components while 427 had ≥3 ICH components. These latter participants were observed to have higher levels of education, kidney function, and professional occupational status, and lower levels of systolic blood pressure, fasting blood glucose, total cholesterol, and body mass index. Median serum aldosterone levels were reported as 4.00 ng/dL in ≥3 ICH participants and 4.3 ng/dL in 0 to 2 ICH participants. In addition, during the follow-up period, 447 cases of diabetes in the ICH categories 0 to 2 and 50 in the ICH ≥3 categories were reported.
Participants in the ≥3 ICH categories were reported to have a 37% lower risk of diabetes. 6.98% of the effect of the five ICH metrics was reported to be mediated by aldosterone. Increased aldosterone has been observed to be associated with a higher risk of diabetes. Furthermore, the effect of aldosterone on diabetes has been observed to be mediated by fasting glucose and blood pressure. Significant interactions of eGFR, age, and gender were observed for 3 ICH components with the incidence of diabetes. It was observed that participants with 2 ICH metrics had a 20% lower risk while participants with ≥3 ICH metrics had a 44% lower risk of diabetes than participants with 0-1 ICH metrics.
Thus, the current study demonstrates that aldosterone can mediate the association of ICH with incident diabetes among AAs. Thus, targeting aldosterone for primary prevention and introducing specific lifestyle interventions may reduce the risk of diabetes. More research is needed to evaluate aldosterone and other biological factors in the development of T2D.
Limitations
The study has some limitations. First, the results of the study are not generalizable. Second, no other racial/ethnic groups are included in the study for comparison. Third, the study could not include renin and other potential factors that could affect the RAAS system and aldosterone.