Metabolic Outcomes of Aging and Obesity: A Longitudinal Study of the Dallas Heart Study Cohort

Sequestration of body fat into subcutaneous and intra- abdominal (visceral) compartments influences metabolic outcomes. Visceral fat contains more proinflammatory cytokines, and is more metabolically active, with a greater propensity for lipolysis. It is associated with hypertriglyceridemia, increased VLDL synthesis, liver insulin resistance, and reduced HDL cholesterol, and more strongly predicts mortality (Tchernof et al., 2013; Browning et al., 2004; Chalasani et al., 2018; Ibrahim, 2009). The purpose of this study is to examine adiposity in subjects of the Dallas Heart Study (DHS1 ran 1999-2000, DHS2 began shortly after) and extend the findings in the prospective, longitudinal Dallas Heart and Minds Study (2020- ), allowing the effects of changes in adiposity to be tracked over a nearly 20-year period. We hypothesize that visceral adiposity increases with age and predicts the development of cardiovascular disease and the metabolic syndrome. Adiposity analysis was undertaken on DHS subjects who completed an abdominal MRI in DHS1 and unique subjects who had completed a whole-body MRI in DHS2. DHMS subjects were former DHS subjects who had an abdominal MRI in DHS and whole-body MRI in DHMS. DHS subjects were scanned using a 1.5T MRI from diaphragm to pelvis with contiguous 10mm slices. Fat contouring was performed on a single slice at L2-L3 using Medis Mass software; DHMS subjects were scanned similarly. Adiposity segmentations in DHMS were performed on the slice corresponding with each subject's DHS segmentation. A prospective method of fat mass prediction from a single MRI slice was used to convert fat volumes to mass (Abate et al., 1997; Neeland et al., 2016). Changes in subcutaneous and visceral fat between DHS and DHMS were calculated to determine the effects on metabolic health. 135 of 254 contoured DHMS subjects had contours in DHS1/2. DHMS subjects had an average weight gain of 1.245kg, BMI increase of 0.792kg/m2, increase in subcutaneous adipose cross-sectional area of 67cm2, and increase in visceral adipose cross-sectional area of 31.102cm2. The change in weight was significantly correlated with changes in subcutaneous (r=0.74, p=0) and visceral adiposity (r=0.59, p=0). Changes in subcutaneous and visceral adiposity were significantly correlated (r=0.23, p=0.006). Finally, DHMS subjects with HOMA IR >2.73 during DHS1/2 had significant percent decreases in weight (p=0.003), subcutaneous adiposity (p<0.001), and visceral adiposity (p<0.001), in contrast to the trends described above.