Subsarcolemmal and Intramyofibrillar Mitochondria And Lipids In Morbidly Obese Patients: Extreme Weight Loss And Exercise

Abstract

Gastric bypass surgery results in improved body composition, cardiovascular and metabolic profile. However, extreme weight loss in morbidly obese patients results in a large decrease in muscle mass. Mitochondria in skeletal muscle are known for their plasticity, subsarcolemmal mitochondria (mitoSS) seem to be important for cell signaling, on the other hand intramyofibrillar mitochondria (mitoIMF) are more involved in muscle contractions. PURPOSE: The effect of extreme weight loss and an exercise program on subsarcolemmal and intramyofibrillar mitochondria and lipid droplets in morbidly obese patients. METHODS: Four morbidly obese patients (study is still recruiting patients) were recruited for the study and followed an intensive strength and endurance exercise program during 12 weeks, starting 1 month after the operation. A muscle biopsy was taken and resting metabolic rate (oxygen uptake) was measured before, one month and four months after the operation. Electron microscopy and stereology was used to determine the density of mitoSS, mitoIMF and lipid droplets (lipidSS and lipidIMF). RESULTS: Extreme weight loss during 5 weeks (9% of body mass) had a pronounced effect on lipidSS (-32,7%), but no effect on mitoSS, mitoIMF and lipidIMF (mitoSS: pre: 15,7%±6,0 - post1m: 13,5%±6,5; mitoIMF: pre: 3,6%±1,5 - post1m: 2,9%±0,4; lipidIMF: pre: 1,2%±0,5 - post1m: 1,6%±1,1). A following exercise program of 12 weeks could significantly increase mitoSS and mitoIMF, with respectively 96,8% and 49,7% and further decreased lipidSS with 43,6%. Remarkably, lipidIMF was not influenced by extreme weight loss and exercise. Low resting metabolic rate of morbidly obese patients (2,59 ±0,48 ml/min/kg) did not improve after 5 weeks of extreme weight loss (2,09±0,76 ml/min/kg) or exercise during 12 weeks (2,23±0,90 ml/min/kg). CONCLUSIONS: Mitochondria in skeletal muscle of morbidly obese patients can only be improved by exercise. Furthermore, it is difficult to influence lipidIMF through weight loss and exercise.