Objective: To examine the contribution of insulin related indices on the association between body fat and blood pressure among overweight adults.
Methods: From April to May 2014, based on convenience sampling, we recruited overweight and obese volunteer participants aged 20-55 years living in Beijing at least 1 year through a strict examination by doctors in a physical examination center. In this study, we excluded the participants who reported suffering from any severe heart, lung, liver or kidney organic diseases, and abnormal development, disabilities, and secondary obesity caused by other disease. Also participants with use of antihypertensive drugs, hypoglycemic drugs and lipid lowering drugs were excluded for this study. A total of 1 221 participants were investigated in this study. With a simple self-designed questionnaire, the birthdates, sex, drug use, and disease history were examined. Participants' blood pressure (BP), percentage of body fat (PBF), glucose and fasting insulin level were measured. Mediation analysis was used to analyze the total effect of PBF on BP (c), the association between PBF and insulin related indices (a), and the mediation effect of serum fasting insulin level/HOMA-IR/HOMA-%S on relation between PBF and systolic/diastolic blood pressure (SBP/DBP).
Results: PBF was positively associated with SBP (c=0.25 ± 0.05 and 0.19 ± 0.03 for male and female, respectively, P<0.001). In males, PBF was positively associated with fasting insulin level and HOMA-IR (a=0.28 ± 0.05 and 0.24 ± 0.05, P<0.001), and negatively associated with HOMA-%S (a=-0.29 ± 0.05, P<0.001); in females, PBF was positively associated with fasting insulin level, HOMA-IR (a=0.21 ± 0.04 and 0.20 ± 0.04, P<0.001), and negatively associated with HOMA-%S (a=-0.13 ± 0.04, P<0.001). In further mediation analysis for female participants, fasting insulin level/HOMA-IR/HOMA-%S played mediation roles in the relation between PBF and SBP, with ratio of mediation of 13.78%,18.3%, and 5.98%. Fasting insulin level/HOMA-IR also mediated the relation between PBF and DBP, with mediation ratio of 11.98% and 14.13%.
Conclusion: In overweight/obese female participants, insulin related indices mediated the relation between PBF and BP.