Energy Metabolism Following High-Fat Diet and Bariatric Surgeries (Gastric Bypass, Sleeve Gastrectomy, Duodenal Switch and Ileum Transposition) in Rats
Yosuke Kodama*1, Helene Johannessen1, Marianne W. Furnes1, Chun-Mei Zhao1, Baard Kulseng1,2, Duan Chen1
1Dept. of Cancer Research and Molecular Medicine, Norwegian University of Science and Technology, Trondheim, Norway; 2Dept.of Surgery and Endocrinology, St. Olavs University Hospital, Trondheim, Norway
Background/aim: The role of energy metabolism in obesity aetiology as well as bariatric surgeries remains unclear. The aim of the present study was to examine the energy metabolism in rats fed with high-fat diet or underwent different surgical procedures that are currently used in obese patients.Methods: Male rats were fed with food containing either 60% or 10% fat (as controls) for 36 weeks, or subjected to gastric bypass (GB), sleeve gastrectomy (SG), duodenal switch (DS), SG + DS, ileum transposition (IT), or sham operation (SO) for 8-14 weeks follow-up.Energy metabolic parameters were measured by an open-circuit indirect calorimeter composed in comprehensive laboratory animal monitoring system. Results: During the course of high-fat diet-induced obesity, total energy expenditure (TEE kcal/h/rat), but not energy expenditure relative to body weight (EE kcal/h/100 g b.w.), was elevated at 3 and 20 weeks but not at 36 weeks compared with age-matched controls. Respiratory exchange ratio (RER) was reduced, due to low production of CO2 (VCO2 ml/kg/h), throughout the course. After GB, TEE was unchanged, but EE was increased at both 3 and 14 weeks postoperatively compared with SO. RER was unchanged at 3 weeks but reduced at 14 weeks. Oxygen consumption (VO2 ml/kg/h) was elevated at both 3 and 14 weeks, whereas VCO2 was unchanged at 3 weeks but increased at 14 weeks. After SG, neither TEE nor EE was changed neither 2 nor 11 weeks compared with preoperative levels. RER was increased only at 11 weeks during nighttime. After DS, TEE, but not EE, was reduced during both daytime and nighttime at 2 and 8 weeks compared with preoperative levels. RER was reduced at 2 weeks but increased at 8 weeks during daytime but unchanged during nighttime. After SG+DS, TEE was reduced at 2 weeks (both daytime and nighttime) and 8 weeks (both daytime and nighttime), whereas EE was increased only at 8 weeks (both daytime and nighttime). RER was unchanged neither at 2 nor 8 weeks. After IT, neither TEE nor EE was changed at 2 weeks. Resting VO2 and VCO2 (during 7-8 a.m.) were increased. RER was increased during both daytime and nighttime, due to higher VCO2. Conclusions: In high-fat diet-induced obese rats, TEE was increased initially and energy was provided mainly by fat metabolism. GB or SG+DS increased EE and the fat oxidation, whereas SG or IT was without effects on EE but increased the carbohydrate metabolism. The hypermetabolic state is likely to contribute to the metabolic benefits after IT procedure.
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