Change in abdominal, but not femoral subcutaneous fat CT-radiodensity is associated with improved metabolic profile after bariatric surgery

Background and aims: Computed tomography (CT)-derived adipose tissue radiodensity represents a potential noninvasive surrogate marker for lipid deposition and obesity-relatedmetabolic disease risk.We studied the effects of bariatric surgery on CT-derived adipose radiodensities in abdominal and femoral areas and their relationships to circulating metabolites in morbidly obese patients. Methods and results: We examined 23morbidly obesewomenwho underwent CT imaging before and 6 months after bariatric surgery. Fifteen healthy non-obesewomen served as controls. Radiodensities of the abdominal subcutaneous (SAT)andvisceral adipose tissue(VAT),andthefemoral SAT, adipose tissue massesweremeasured in all participants. Circulatingmetabolites were measured by NMR. At baseline, radiodensities of abdominal fat depots were lower in the obese patients as compared to the controls. Surprisingly, radiodensity of femoral SAT was higher in the obese as compared to the controls. In the abdominal SAT depot, radiodensity strongly correlatedwith SATmass (rZ-0.72, p < 0.001). After surgery, the radiodensities ofabdominal fat increasedsignificantly (bothp<0.01),while femoral SATradiodensity remained unchanged. Circulating ApoB/ApoA-I, leucine, valine, and GlycA decreased, while glycine levels significantly increased as compared to pre-surgical values (all p < 0.05). The increase in abdominal fat radiodensitycorrelatednegativelywith thedecreasedlevels ofApoB/ApoA-I ratio, leucine and GlycA (all p < 0.05). The increase in abdominal SAT density was significantly correlated with the decrease in the fat depot mass (rZ-0.66, pZ0.002). Conclusion: Higher lipid content in abdominal fat depots, and lower content in femoral subcutaneous fat, constitute prominent pathophysiological features in morbid obesity. Further studies are needed to clarify the role of non-abdominal subcutaneous fat in the pathogenesis of obesity. Clinical trial registration number: NCT01373892. ª2020TheItalian Diabetes Society, the Italian Society for the StudyofAtherosclerosis, the Italian Society of Human Nutrition and the Department of ClinicalMedicine and Surgery, Federico II University. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http:// creativecommons.org/licenses/by-nc-nd/4.0/).