Molecular Markers of Mitochondrial Metabolism are not Affected by the Chronic Influence of Caloric Restriction- or Exercise-Induced Weight Loss Robert H Coker, FACSM1, Rick H. Williams2, Philip A. Kern3 Center for Alaska Native Health Research1, Institute of Arctic Biology, University of Alaska-Fairbanks, Fairbanks, Alaska; Center for Translational Research in Aging and Longevity2, Reynolds Institute on Aging, University of Arkansas for Medical Sciences, Little Rock, AR; Department of Endocrinology and Molecular Medicine3, University of Kentucky, Lexington, KY Abstract PURPOSE: Variations in skeletal muscle peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1∝), adipose tissue triglyceride lipase (ATGL), carntine palmitoyltransferase (CPT-1) have been described to play important roles in the protection against metabolic disease. Under post-intervention conditions of weight stabilization, the influence of caloric restriction-induced weight loss (CRWL) versus exercise-induced weight loss (EXWL) on the above mentioned parameters and lipid accumulation were addressed. METHODS: Using controlled metabolic feeding and/or exercise training, we evaluated the influence of CRWL vs EXWL on markers of mitochondrial metabolism and lipid droplet size in overweight individuals. RESULTS: Under conditions of sustained weight loss and improved insulin sensitivity in CRWL and EXWL, there were no changes in PGC-1∝, ATGL, CPT-1 mRNA. There were no differences in the ΔPGC-1∝/18s (-0.11±0.10 and -0.02±0.08), ΔATGL/18s (-0.07±0.11 and 0.14±0.11), ΔCPT-1/18s (-0.11±0.20 and 0.18±0.11) mRNA or lipid droplet size within type 1 or type 2 skeletal muscle in CRWL (0.08±0.11; 0.20±0.10) or EXWL (0.01±0.10; 0.11±0.10) respectively. CONCLUSIONS: Most intervention-based studies have focused almost entirely on molecular endpoints collected during the immediate post-intervention terminus of the study. Under the conditions of chronic caloric balance following CRWL or EXWL, mediators of mitochondrial function and lipid droplet size were not affected. While studies are needed to compare acute versus chronic benefits of caloric deficit and/or exercise training, the long-term benefits of these interventions on skeletal muscle lipid metabolism in the post-absorptive state may be less than anticipated. Introduction Results Acute exercise and caloric restriction promotes an increase in skeletal muscle PGC-1∝ (1,2). Increased PGC-1 alpha and CPT-1 augment mitochondrial biogenesis and fat oxidation, respectively (1-3). ATGL lipase is a key regulator of in cellular lipid metabolism in skeletal muscle (4). Methods Subjects: Twelve middle aged individuals [55±1y (Ht), 86±2 kg (Wt), 31±1kg/m2(BMI)] participated in the current study. Utilizing metabolic feeding and supervised exercise training, each individual was randomly assigned to either CRWL or EXWL and lost 7% of their body weight over a 12 wk period. Study Paradigm: Muscle Tissue Collection and Analysis : Muscle samples were collected from the vastus lateralis under local anesthesia. Total RNA from muscle biopsies were isolated using an Ultraspec RNA isolation system kit (Biotex, Houston, TX). The quantity and quality of the isolated RNA were determined by Agilent 2100 Bioanalyzer (Palo Alto, CA) and expressed relative to 18s. Muscle lipid droplet size was determined using Oil Red O staining and images were analyzed using the NIH Image program v. 1.60. PGC-1α ATGL Weeks 0-------------------------5------------------6---------------------------------18-----------------------------------------24 Figure 1. Comparison of CRWL and EXWL on PGC-1α, ATGL, CPT-1, and lipid droplet size in skeletal muscle. Medical Screening Muscle Biopsy Exercise Training (2500 kcal/wk) or Caloric Restriction (2500 kcal/wk) 6 Wk Weight Stabilization Muscle Biopsy Conclusion In the context of caloric balance and chronic adaptations following weight loss, transcription of PGC-1α, ATGL and CPT-1 may return to baseline potentially lessening their influence on the lipid metabolism of skeletal muscle. 4 Week Weight Maintenance Body Comp Body Comp References Russell AP, et al., Skeletal muscle mitochondria: A major player in exercise, health and disease, Biochimica Biophysica Acta 2014 1840 1276-1284. Corton JC, Brown-Borg H, Peroxisome Proliferator-Activated Receptor gamma coactivator 1 in caloric restriction and other models of longevity. J Gerontol Biol Sci 2005 60A(12): 1492-1509. Schenk S, Horowitz JF, Coimmunoprecipitation of FAT/CD36 and CPTI in skeletal muscle increases proportionaly with fat oxidation after endurance exercise training. Am J Physiol Endocrinol Metab 2006 291(2): E254-260. Zechner R, et al., Adipose tissue triglyceride liipase and the lipolytic catabolism of cellular fat stores. J Lipid Res 2009 50: 3-21. We acknowledge the support of the National Institutes of Health, National Institute of Diabetes, Digestive and Kidney Diseases KO1 DK 64716- 01, and American Heart Association Grant 0335172N, and we also greatly appreciate the efforts of our participants in this study.