Calorie Restriction Does Not Increase Short-term or Long-term Protein Synthesis

Abstract

Increased protein synthesis is proposed as a mechanism of life-span extension during caloric restriction (CR). We hypothesized that CR does not increase protein synthesis in all tissues and protein fractions and that any increased protein synthesis with CR would be due to an increased anabolic effect of feeding. We used short- (4 hours) and long-term (6 weeks) methods to measure in vivo protein synthesis in lifelong ad libitum (AL) and CR mice. We did not detect an acute effect of feeding on protein synthesis while liver mitochondrial protein synthesis was lower in CR mice versus AL mice. Mammalian target of rapamycin (mTOR) signaling was repressed in liver and heart from CR mice indicative of energetic stress and suppression of growth. Our main findings were that CR did not increase rates of mixed protein synthesis over the long term or in response to acute feeding, and protein synthesis was maintained despite decreased mTOR signaling.

Assessment of protein synthesis in highly aerobic canine species at the onset and during exercise training

“…Skeletal muscle tissue was fractionated according to our previously published procedures (4,5,13,14). Muscle (15-50 mg) was homogenized 1:10 with a bead homogenizer (Next Advance, Averill Park, NY) in isolation buffer (100 mM KCl, 40 mM Tris HCl, 10 mM Tris Base, 5 mM MgCl2, 1 mM EDTA, 1 mM ATP, pHϭ7.5) with phosphatase and protease inhibitors (HALT, Thermo Scientific, Rockford, IL).…”

“…Muscle (15-50 mg) was homogenized 1:10 with a bead homogenizer (Next Advance, Averill Park, NY) in isolation buffer (100 mM KCl, 40 mM Tris HCl, 10 mM Tris Base, 5 mM MgCl2, 1 mM EDTA, 1 mM ATP, pHϭ7.5) with phosphatase and protease inhibitors (HALT, Thermo Scientific, Rockford, IL). After homogenization, subcellular fractions of mixed (Mixed, containing primarily contractile elements and nuclei), cytosolic (Cyto), and mitochondrial (Mito) proteins were isolated via differential centrifugation as previously described (4,5,13,14). After muscle fractions were isolated and purified, 250 l 1 M NaOH was added, and pellets were incubated for 15 min at 50°C and 900 rpm.…”

“…Determination of 2 H incorporation into purine deoxyribose (dR) of DNA was performed as previously described (4,5,14,15). Briefly, DNA isolated from whole tissue was hydrolyzed overnight at 37°C with nuclease S1 and potato acid phosphatase.…”

“…Longer periods of assessment are limited by the need to maintain a constant infusion of isotopes, thus restricting freeliving conditions. To address these limitations, we (4,5,13,14,19,22) and others (2,6,16,26) have employed stable isotope techniques that use deuterium oxide ( 2 H 2 O). By providing 2 H 2 O in the drinking water of humans (19,22) or rodents (4,5,13,14), we have assessed cumulative protein synthesis over the period of weeks, rather than hours.…”

Effect of L-carnitine Supplementation on Nutritional Status and Physical Performance Under Calorie Restriction

“…Declining food intake does not correlate with low serum protein levels and vice versa [37]. Miller et al [38] has demonstrated no effect of acute feeding (4 h) on protein synthesis. Decrease in plasma volume on a CR regime causes hypohydration, which thereby leads to an overall decrease in the blood volume.…”