1 Department of Health, Kinesiology, and Applied Physiology, Concordia University, Montreal, QC, Canada.
2 Metabolism, Obesity, and Nutrition Lab, PERFORM Centre, Concordia University, Montreal, QC, Canada.
3 Institut Universitaire de Cardiologie et de pneumologie de Québec, Québec, QC, Canada.
4 Department of Health, Kinesiology, and Applied Physiology, Concordia University, Montreal, QC, Canada. s.santosa@concordia.ca.
5 Metabolism, Obesity, and Nutrition Lab, PERFORM Centre, Concordia University, Montreal, QC, Canada. s.santosa@concordia.ca.
6 Centre de recherche, Centre intégré universitaire de santé et de services sociaux du Nord-de-I'Île-de-Montréal, Hôpital du Sacré-Cœur de Montréal (CIUSS-NIM, HSCM), Montréal, QC, Canada. s.santosa@concordia.ca.

Background: The timing of obesity onset and age have been shown to affect the risk of obesity-related comorbidities, although the impact of each of these factors on markers of adipose tissue function remains unclear.

Objective: The aim of this study was to determine whether differences in regional adipose tissue characteristics vary with age and age of obesity onset, and whether these differences are associated with the markers of cardiometabolic health.

Methods: Adipose tissue samples were obtained from 80 female bariatric surgery candidates who were classified by age of obesity onset and age into 4 groups: (1) younger adults (<40 y) with childhood-onset obesity (<18 y) (Child-Young); (2) younger adults with adulthood-onset obesity (>18 y) (Adult-Young); (3) older adults (>55 y) with childhood-onset obesity (Child-Old); and (4) older adults with adulthood-onset obesity (Adult-Old). Adipocyte diameter, adipose tissue fibrosis, and macrophage infiltration were determined in subcutaneous (SAT) and visceral adipose tissue (VAT). Clinical parameters were obtained from participants' medical records.

Results: Visceral adipocyte size in the Child-Young group was the smallest of all the groups. Age affected visceral infiltration of M1-like cells with greater percent of M1-like cells in the Adult-Old and Child-Old groups. Though not significant, a stepwise increase in M2-like macrophages in VAT was observed with Adult-Young having the smallest followed by Adult-Old, Child-Young, and Child-Old having the greatest percent of M2-like macrophages. Pericellular fibrosis accumulation in SAT and VAT varied with both age and onset, particularly in the Child-Old group, which had the lowest fibrosis levels. Markers of cardiometabolic health (fasting glucose, glycated hemoglobin, total, HDL- and LDL-cholesterol and triglyceride concentrations) were positively and well-associated with adipose tissue characteristics of the Child-Old group but not of the Adult-Young group.

Conclusion: Older adults with childhood-onset obesity, who had the greatest duration of obesity exposure, were particularly vulnerable to the cardiometabolic effects associated with perturbations in adipose tissue characteristics. These results suggest that age and age of obesity onset may have independent and cumulative effects on obesity pathology.