VALUTAZIONE CON METODICHE IMAGING DELLA DEPOSIZIONE ECTOPICA DEL TESSUTO ADIPOSO E SUE IMPLICAZIONI CLINICHE

In the last few decades there has been increasing focus on body fat distribution rather than on the degree of obesity. More recently great interest has been also focused on the ectopic fat deposition (i.e. deposition of triglycerides at the level of liver, muscle and pancreas). Weight loss improves metabolic complications of obesity through visceral fat reduction. However little is known about the effect of weight loss on various ectopic fat compartments and about the possible contribution of ectopic fat reduction on metabolic alterations of obese subjects. The purpose of this study was to compare liver and pancreas fat infiltration in men and women and determine the relationship between body fat distribution, adipocytokines, inflammatory markers, daily energy intake, dietary fat and lipid content of liver and pancreas, before and after weight loss. The study population underwent a weight-loss program designed to achieve a loss of 10% of initial weight. The caloric restriction was 500 kcal below the resting energy expenditure, as evaluated by indirect calorimetry. The present analyses were performed on 38 subjects (18 men and 20 women) with mean age 49.1 ± 13.0 years and mean body mass index (BMI) 34.9 ± 4.21 Kg/m. 24 subjects (13 men and 11 women) reached a >7% of initial weight and were therefore evaluated at follow-up. Weight, height, body mass index (BMI), waist circumference, fat mass and fat mass percentage as evaluated with DXA, as well as glucose, insulin, HOMA, cholesterol, triglycerides, HDL-Ch, Hs-CRP, daily energy and fat intake, leptin and adiponectin were evaluated before and after weight loss. Magnetic resonance was used to evaluate visceral, subcutaneous adipose tissue as well as liver and pancreas lipid content using in-phase and out-of-phase MRI sequence. Obese subjects had significantly higher weight, waist circumference, SCAT, Deep SCAT, VAT, liver and pancreatic lipid content than lean subjects. Obese women had significantly lower VAT, liver and pancreas lipid content regardless same BMI. In multiple regression analyses, the variance of liver lipid content explained by gender and VAT was 46%. When HOMA was added into a multiple regression a small increase in the proportion of variance explained was observed. A 59.2% of the variance of pancreas lipid content was explained by gender and VAT. After a mean body weight decrease of 8.9 %, BMI, Waist circumference, total and FM %, as well as all metabolic variables, ALT, Hs-CRP and adipokines but adiponectin and HDL-Ch, significantly decreased (all p<0.01). Visceral, subcutaneous and total abdominal adipose tissue significantly decreased (p<0.001), as well as liver and pancreas lipid content (p<0.001 and p=0.001 respectively). After weight loss, percentage of subjects with steatosis decreased from 75% to 12.5% and none of the subjects had grade 2 or 3 of steatosis. Visceral adipose tissue decrease was the best predictor of the reduction in liver and pancreas lipid content observed with weight loss. The insulin resistance improvement observed after weight loss is mainly independently related with liver lipid content decrease, waist circumference and systemic inflammation reduction.