Insulin resistance in the adipose tissue predicts future vascular resistance: The Hiroshima Study on Glucose Metabolism and Cardiovascular Diseases.

Background And Aims: Diameter, plaque score, and resistance index (RI) in the common carotid artery (CCA) are indicators of arterial remodeling, atherosclerosis, and vascular resistance, respectively. This study investigated the longitudinal association between adipose tissue insulin resistance or serum free fatty acid (FFA) levels and the CCA parameters.

Methods: This retrospective cohort analysis included 1089 participants (mean age 57.6 years; 40.0 % women) with data on health checkups from January 1982 to March 2003 and carotid artery ultrasonography from January 2015 to June 2019. Baseline serum FFA and immunoreactive insulin levels were assessed before and 30, 60, and 120 min after glucose ingestion. Adipose insulin resistance index (Adipo-IR) was calculated as the product of fasting serum insulin and FFA levels. An RI value >0.75 was defined as high RI.

Results: A significant association was found between Adipo-IR and RI; however, Adipo-IR showed no association with CCA diameter or plaque score. The incidence of high RI increased with Adipo-IR quartile (Q) groups (47.3 % in Q1, 52.8 % in Q2, 53.3 % in Q3, 62.4 % in Q4; Cochrane-Armitage test for trend, p < 0.001). In multivariate analysis, Adipo-IR levels (Q4 vs. Q1 odds ratio: 1.67, 95 % confidence interval: 1.12-2.51) were positively associated with high RI incidence. Moreover, a significant association was found between RI and serum FFA levels after glucose intake, but not fasting FFA levels.

Conclusions: Future vascular resistance was predicted by insulin resistance in the adipose tissue. After glucose intake, serum FFA levels may significantly impact vascular resistance development.