Effects of slow- v. fast-digested protein supplementation combined with mixed power training on muscle function and functional capacities in older men.

Ageing leads to a progressive loss of muscle function (MF) and quality (MQ: muscle strength (MS)/lean muscle mass (LM)). Power training and protein (PROT) supplementation have been proposed as efficient interventions to improve MF and MQ. Discrepancies between results appear to be mainly related to the type and/or dose of proteins used. The present study aimed at determining whether or not mixed power training (MPT) combined with fast-digested PROT (F-PROT) leads to greater improvements in MF and MQ in elderly men than MPT combined with slow-digested PROT (S-PROT) or MPT alone. Sixty elderly men (age 69 (sd 7) years; BMI 18-30 kg/m2) were randomised into three groups: (1) placebo + MPT (PLA; n 19); (2) F-PROT + MPT (n 21) and (3) S-PROT + MPT (n 20) completed the intervention. LM, handgrip and knee extensor MS and MQ, functional capacity, serum metabolic markers, skeletal muscle characteristics, dietary intake and total energy expenditure were measured. The interventions consisted in 12 weeks of MPT (3 times/week; 1 h/session) combined with a supplement (30 g:10 g per meal) of F-PROT (whey) or S-PROT (casein) or a placebo. No difference was observed among groups for age, BMI, number of steps and dietary intake pre- and post-intervention. All groups improved significantly their LM, lower limb MS/MQ, functional capacity, muscle characteristics and serum parameters following the MPT. Importantly, no difference between groups was observed following the MPT. Altogether, adding 30 g PROT/d to MPT, regardless of the type, does not provide additional benefits to MPT alone in older men ingesting an adequate (i.e. above RDA) amount of protein per d.

Short-term Effects of Diet and Activity Changes on Inflammation and Insulin Resistance.

The present study focused on rapid responses of inflammation markers and insulin resistance to dietary restriction and exercise in inactive patients. 13 obese women were included during a 5-day time frame during which decreases in food intake (-1 378±298 kcal) were associated with 2 exercise sessions (80 and 40 min). Circulating inflammatory biomarkers, insulin resistance index and muscle soreness were measured in fasted conditions. Fasting plasma concentrations of CRP and insulin resistance index decreased over the period (respectively, p=0.02 and p=0.01), concentrations of IL-6 and TNF-α appeared unchanged (p>0.05). Changes in IL-6 (enhanced) and TNF-α (reduced) concentrations following the prolonged exercise differed compared to days with 40 min exercise and days without exercise (p<0.05). Muscle soreness appeared higher after the 80 min than after the 40-min exercise (p=0.01), and were related with IL-6 and CRP concentration changes. A 5-day period combining exercise and diet reduced the insulin-resistance index and the CRP fasting concentrations. The 80-min exercise enhanced IL-6 and lowered TNF-α concentration changes while days without exercise unaffected these cytokines. These exercise effects on cytokines may have benefited to the insulin resistance index. The duration and number of the exercise sessions appeared sufficient for inactive subjects to initiate health benefits without inducing negative effects on inflammation and muscle soreness.

Onset of exercise and diet program in obese women: metabolic and anorexigenic responses related to weight loss and physical capacities.

Perturbations of energy balance induce compensatory processes that may alter expected weight loss. In obese patients, our aim was to investigate the relationships that occurred between fasting plasma concentrations of anorexigenic peptides and metabolic parameters, appetite, physical capacity, and weight loss in the 5 first days of a program associating exercise and caloric reduction. Thirteen obese women were monitored from day 1 to day 5 with 2 exercise sessions in day 2 and day 4. We measured, in a fasted state, changes in body weight, hunger ratings, and plasma concentrations of fatty acids, triglycerides, leptin, insulin, amylin, peptide YY, and insulin-resistance index. Physical performance was assessed by a 6-min walking test. The program resulted in significantly reduced body weight (0.75±0.4 kg; p=0.001), of plasma concentrations of triglycerides, insulin, amylin, peptide YY, and the insulin-resistance index, and also increased fatty acids (p<0.05). Hunger ratings were increased (p<0.05). Program-induced changes in fatty acids, leptin, and insulin concentrations were related to physical performance (r(2)=0.45, 0.59, and 0.52; p<0.05, respectively) and to weight loss (r(2)=0.65, 0.57, 0.55; p<0.05, respectively). Five days of diet and exercise induced weight loss, improved lipid profile, and decreased insulin resistance while hunger ratings increased. Subjects with higher physical capacity lost more weight, presented higher increases in fatty acids and lower changes of leptin and insulin concentrations suggesting a better metabolic flexibility. To reduce the compensatory responses that can occur with energy imbalances, our study supports to account for individual activity level before prescribing weight-loss program associating diet and exercise.

Effect of citrulline on muscle functions during moderate dietary restriction in healthy adult rats.

Low calorie diets are designed to reduce body weight and fat mass, but they also lead to a detrimental loss of lean body mass, which is an important problem for overweight people trying to lose weight. In this context, a specific dietary intervention that preserves muscle mass in people following a slimming regime would be of great benefit. Leucine (LEU) and Citrulline (CIT) are known to stimulate muscle protein synthesis (MPS) in post-prandial and post-absorptive state, respectively. This makes them interesting bioactive components to test in the context of dietary restriction. We tested the concept of combining LEU and CIT in adult female rats. We postulated that the sequential administration of LEU (mixed in chow) and CIT (given in drinking water before a rest period) could be beneficial for preservation of muscle function during food restriction. Sixty female rats (22 weeks old) were randomized into six groups: one group fed ad libitum with a standard diet (C) and five food-restricted groups (60 % of spontaneous intake for 2 weeks) receiving a standard diet (R group), a CIT-supplemented diet (0.2 or 1 g/kg/day, CIT0.2 group and CIT1 group, respectively), a LEU-supplemented diet (1.0 g/kg/day) or a CIT + LEU-supplemented diet (CIT + LEU 1.0 g/kg/day each). At the end of the experiment, body composition, muscle contractile properties and muscle protein synthesis (MPS) rate were studied in the tibialis anterior muscle. Dietary restriction tended to decrease MPS (R: 2.5 ± 0.2 vs. C: 3.4 ± 0.4 %/day, p = 0.06) and decrease muscle strength (R: 3,045 ± 663 vs. C: 5,650 ± 661 A.U., p = 0.03). Only CIT administration (1 g/kg) was able to restore MPS (CIT1: 3.4 ± 0.3 vs. R: 2.5 ± 0.2 %/day, p = 0.05) and increase muscle maximum tetanic force (CIT1: 441 ± 15 vs. R: 392 ± 22 g, p = 0.05) and muscle strength (CIT1: 4,259 ± 478 vs. R: 3,045 ± 663 A.U., p = 0.05). LEU had no effect and CIT + LEU supplementation had few effects, limited to adipose mass and fatigue force. The results of this study highlight the ability of CIT alone to preserve muscle function during dietary restriction. Surprisingly, LEU antagonized some effects of CIT. The mechanisms involved in this antagonistic effect warrant further study.

Respective effects of anabolic/androgenic steroids and physical exercise on isometric contractile properties of regenerating skeletal muscles in the rat.

We examined the respective effects of anabolic-androgenic steroids and physical exercise on the contractile properties of regenerating fast and slow hindlimb skeletal muscles. Degeneration/regeneration of the left extensor digitorum longus muscles (EDL) and soleus of young Wistar male rats was induced by a snake venom (Notechis scutatus scutatus) injection. During muscle regeneration, experimental rats were either treated with nandrolone (NAN, nortestosterone, im, 2 mg X kg(-1) X week(-1), or endurance exercised on a treadmill (EXE, 60 min x day(-1), 10-40 m X min(-1). Twenty-one days after injury, isometric contractile properties of regenerating muscles were studied in situ. Neither the nandrolone treatment nor the physical exercise program was able to change significantly muscle contraction parameters both in twitch and tetanus in both regenerating EDL and soleus (p > 0.05). However, we observed a greater peak twitch tension in NAN versus grouped control and EXE EDL (p < 0.01). In conclusion, endurance exercise program or anabolic-androgenic steroid (nortestosterone) treatment did not significantly improve isometric contractile properties of regenerating slow and fast muscles in the male young rats.

Differential modification of myosin heavy chain expression by tenotomy in regenerating fast and slow muscles of the rat.

We have examined the effect of tenotomy on the expression of myosin heavy chains (MyHC) in regenerating fast and slow skeletal muscles. Degeneration/regeneration of the left soleus and plantaris of Wistar male rats was induced by an injection into the muscle belly of a myotoxin (snake venom: Notechis scutatus scutatus). MyHC isoform content of regenerating plantaris and soleus muscles were studied 21 days after muscle injury using an electrophoretic technique. Tenotomy of the regenerating plantaris (mechanical underload) did not alter its MyHC expression (P > 0.05). In contrast, tenotomy of the regenerating soleus increased its relative levels of MyHC-2b (P < 0.05) and MyHC-2x/d (P < 0.01), and decreased its relative level of MyHC-1 (P < 0.01). Tenotomy of the synergistic gastrocnemius (overload) tended to decrease the relative level of MyHC-2b in regenerating plantaris (P < 0.07). The effect of tenotomy of the synergistic gastronecmius on the regenerating soleus was different: a decrease in the relative levels of MyHC-1 (P < 0.05) and an increase in the relative level of MyHC-neonatal (P < 0.01). In conclusion, and in contrast to a regenerating slow muscle, a change of mechanical loading by tenotomy did not seem to markedly alter the expression of mature MyHC phenotype in a fast regenerating muscle.

Effect of anabolic/androgenic steroids on myosin heavy chain expression in hindlimb muscles of male rats.

We have examined the effect of male sex hormones on the myosin heavy chain (MHC) expression of the soleus and extensor digitorum longus (EDL) muscles. Young male adult Wistar rats were treated over a 25-day period with either oil (CON, n = 8), nandrolone (nortestosterone decanoate, NAN, n = 8), nandrolone combined with endurance exercise (treadmill running, NAN+EXE, n = 8), or were castrated (CAS, n = 8). The MHC composition of the soleus and EDL muscles was measured by electrophoresis. Castration and treatment with nandrolone had no effect (P > 0.05) on the relative levels of MHC in the soleus and EDL. In contrast, in NAN+EXE rats, the relative level of MHC-1 increased [slow isoform; mean (SD) 97.6 (4. 7)% in NAN+EXE rats, versus 86.5 (7.5)% in CON rats] and MHC-2a decreased [fast isoform; 2.4 (4.7)% in NAN+EXE, versus 13.5 (7.5)% in CON rats], only in the soleus (P < 0.05). In conclusion, it appears that endogenous anabolic/androgenic steroids are not essential for the maintenance of the MHC expression of fast- and slow-twitch muscles in the young adult male rat. In addition, nandrolone combined with endurance exercise induced a shift from a fast to a slower MHC phenotype of the slow-twitch muscle.

Effects of anabolic/androgenic steroids on regenerating skeletal muscles in the rat.

We have examined the effect of male sexual hormones on the regeneration of skeletal muscles. Degeneration/regeneration of the left soleus and extensor digitorum longus muscles (EDL) of Wistar male rats was induced by an injection of snake venom (2 microg, Notechis scutatus scutatus). During the muscle regeneration (25 days), rats were treated with either oil (CON), nandrolone (NAN), NAN combined with exercise (NAN + EXE) or were castrated (CAS). Muscle growth and myosin heavy chain (MyHC) isoform content of regenerating muscles were studied. Castration altered the concentrations of MyHC in venom-treated EDL (P < 0.01) and soleus (P < 0.05). NAN increased the mass (P < 0.01) of regenerating soleus and decreased the relative amount of fast MyHC protein (% of total, P < 0.05). The effect of NAN + EXE on the fast MyHC proteins of venom-treated soleus was opposite (P < 0.05). NAN and NAN + EXE were without effect on the regenerating EDL (P > 0.05). In conclusion, it is possible that male sexual hormones play a role in the growth (synthesis of contractile proteins) of regenerating muscles in rat. In addition, contrary to NAN + EXE, NAN could be beneficial to soleus regeneration.

Effect of increased physical activity on growth and differentiation of regenerating rat soleus muscle.

Our purpose was to determine the effect of physical exercise on growth and differentiation during regeneration of a slow-twitch muscle. Degeneration/regeneration of the left soleus muscles of Wistar female rats was induced by injection of a snake venom. Muscular differentiation was studied by monitoring the sequential expression of the various myosin heavy chain isoforms (MHCs). Rats were assigned to one of two groups: cage sedentary (n = 14) or exercised (n = 16). The exercise programme began 1-day post-injection and the rats ran 1 h/day on a motorized treadmill. Then, 9 and 25 days after venom treatment, the soleus MHC phenotype as determined by immunohistology, electrophoresis and immunoblotting, was studied. At 25 days the expression of MHCs by regenerating soleus was not changed by the increased level of physical activity (P > 0.05). Exercised and sedentary regenerating muscles contained similar numbers of type-I fibres (100% of total fibres), levels of MHC-1 (85.4 and 89.5% of total MHCs), MHC-2a and M/HC-2x/d and their fibres expressed MHC-1 (100% of total fibres) and MHC-2 (45-50%) in the same way. Moreover, the masses of regenerating and nonregenerating soleus were significantly increased by physical exercise (P < 0.02). At 9 days no effect of muscular exercise was found. In conclusion, endurance exercise did not alter differentiation of regenerating soleus. Moreover regenerating soleus can respond to increased physical activity by enhancing its mass in the same way as mature muscle.