Relationships between plasma apelin and adiponectin with normal weight obesity, body composition, and cardiorespiratory fitness in working adults

Abstract

Background: A significant proportion of adults have normal weight obesity (NWO), defined as a normal body mass index (BMI) but disproportionately high body fat percentage. Individuals with NWO may have increased risk of cardiometabolic disorders and lower exercise tolerance, but it is unclear if this obesity phenotype is linked with dysregulated production of adipokines or myokines such as adiponectin and apelin, respectively.

Methods: This cross-sectional, secondary analysis included 177 working adults (mean age 49.6 ± 9.9 yrs, 64% female). Plasma high-molecular weight adiponectin and apelin levels were measured by ELISA. Body composition and fat distribution were assessed using dual energy X-ray absorptiometry. Exercise tolerance (VO₂ maximum) was determined by treadmill testing. NWO was defined as a BMI <25 kg/m² and body fat >30% for women or >23% for men. Participants were categorized as lean, NWO, or overweight-obese.

Results: A total of 14.7% of subjects were categorized as lean, 23.7% as having NWO, and 61.6% as having overweight-obesity. Plasma adiponectin levels were elevated in the overweight-obesity group (P < 0.05) compared to the lean and NWO groups, which did not differ from each other (P > 0.05). Adiponectin concentrations were inversely associated with BMI, fat mass, fat mass percent, visceral fat, and trunk to leg fat ratio and positively associated with leg fat mass (all P < 0.001). Plasma apelin levels were similar between the three body composition groups (P < 0.05) and were not significantly associated with any body composition indices. Apelin concentrations were inversely related to VO₂ maximum (β = -0.03 ± 0.01, p = 0.002).

Conclusion: Plasma adiponectin and apelin levels did not distinguish between lean and NWO groups. Positive relationships with leg fat mass and adiponectin suggest the importance of assessing body composition and fat distribution when studying adipokines and cardiometabolic disorders. Further investigations are needed to understand relationships between exercise, body composition, and apelin secretion.

Keywords: Adipose; Cytokines; Fat distribution; Fitness; Metabolic; Obesity phenotype.

Fig. 1

Levels of plasma adiponectin between lean, normal weight obesity, and overweight-obesity groups. Geometric mean and 95% confidence interval are shown for each group. Groups connected with the same letters are statistically similar (P > 0.05), while groups with different letters are significantly different at P < 0.05 according to Tukey post-hoc comparisons.

Fig. 2

Levels of plasma apelin between lean, normal weight obesity, and overweight-obesity groups. Geometric mean and 95% confidence interval are shown for each group. Groups connected with the same letters are statistically similar (P > 0.05), while groups with different letters are significantly different at P < 0.05 according to Tukey post-hoc comparisons.

Fig. 3

Relationship between VO₂ maximum and log-transformed plasma apelin concentrations [−0.03 ± 0.01, p < 0.001, mean square error (MSE) = 0.699] adjusting for age, race, sex, and fat mass percent. A multiple linear regression model was fit to test the association between VO₂ maximum and log-transformed plasma apelin.