B. Esmarck

1. Age-associated loss of skeletal muscle mass and strength can partly be counteracted by resistance training, causing a net synthesis of muscular proteins. Protein synthesis is influenced synergistically by postexercise amino acid supplementation, but the importance of the timing of protein intake remains unresolved. 2. The study investigated the importance of immediate (P0) or delayed (P2) intake of an oral protein supplement upon muscle hypertrophy and strength over a period of resistance training in elderly males. 3. Thirteen men (age, 74 +/- 1 years; body mass index (BMI), 25 +/- 1 kg m(-2) (means +/- S.E.M.)) completed a 12 week resistance training programme (3 times per week) receiving oral protein in liquid form (10 g protein, 7 g carbohydrate, 3 g fat) immediately after (P0) or 2 h after (P2) each training session. Muscle hypertrophy was evaluated by magnetic resonance imaging (MRI) and from muscle biopsies and muscle strength was determined using dynamic and isokinetic strength measurements. Body composition was determined from dual-energy X-ray absorptiometry (DEXA) and food records were obtained over 4 days. The plasma insulin response to protein supplementation was also determined. 4. In response to training, the cross-sectional area of m. quadriceps femoris (54.6 +/- 0.5 to 58.3 +/- 0.5 cm(2)) and mean fibre area (4047 +/- 320 to 5019 +/- 615 microm(2)) increased in the P0 group, whereas no significant increase was observed in P2. For P0 both dynamic and isokinetic strength increased, by 46 and 15 %, respectively (P < 0.05), whereas P2 only improved in dynamic strength, by 36 % (P < 0.05). No differences in glucose or insulin response were observed between protein intake at 0 and 2 h postexercise. 5. We conclude that early intake of an oral protein supplement after resistance training is important for the development of hypertrophy in skeletal muscle of elderly men in response to resistance training.

The extracellular matrix (ECM) of connective tissues enables linking to other tissues, and plays a key role in force transmission and tissue structure maintenance in tendons, ligaments, bone and muscle. ECM turnover is influenced by physical activity, and both collagen synthesis and metalloprotease activity increase with mechanical loading. This can be shown by determining propeptide and proteinase activity by microdialysis, as well as by verifying the incorporation of infused stable isotope amino acids in biopsies. Local tissue expression and release of growth factors for ECM such as IGF-1, TGF-beta and IL-6 is enhanced following exercise. For tendons, metabolic activity (e.g. detected by positron emission tomography scanning), circulatory responses (e.g. as measured by near-infrared spectroscopy and dye dilution) and collagen turnover are markedly increased after exercise. Tendon blood flow is regulated by cyclooxygenase-2 (COX-2)-mediated pathways, and glucose uptake is regulated by specific pathways in tendons that differ from those in skeletal muscle. Chronic loading in the form of physical training leads both to increased collagen turnover as well as to some degree of net collagen synthesis. These changes modify the mechanical properties and the viscoelastic characteristics of the tissue, decrease its stress-susceptibility and probably make it more load-resistant. The mechanical properties of tendon fascicles vary within a given human tendon, and even show gender differences. The latter is supported by findings of gender-related differences in the activation of collagen synthesis with exercise. These findings may provide the basis for understanding tissue overloading and injury in both tendons and skeletal muscle.

In addition to the well-documented loss of muscle mass and strength associated with aging, there is evidence for the attenuating effects of aging on the number of satellite cells in human skeletal muscle. The aim of this study was to investigate the response of satellite cells in elderly men and women to 12 weeks of resistance training. Biopsies were collected from the m. vastus lateralis of 13 healthy elderly men and 16 healthy elderly women (mean age 76+/-SD 3 years) before and after the training period. Satellite cells were visualized by immunohistochemical staining of muscle cross-sections with a monoclonal antibody against neural cell adhesion molecule (NCAM) and counterstaining with Mayer's hematoxylin. Compared with the pre-training values, there was a significant increase (P<0.05) in the number of NCAM-positively stained cells per fiber post-training in males (from 0.11+/-0.03 to 0.15+/-0.06; mean+/-SD) and females (from 0.11+/-0.04 to 0.13+/-0.05). These results suggest that 12 weeks of resistance training is effective in enhancing the satellite cell pool in skeletal muscle in the elderly.

We combined the interstitial sampling method of microdialysis with the natural tracer qualities (i.e. non-recyclability) of the amino acid 3-methylhistidine (3MH) to uniquely study in vivo degradation of the two most abundant skeletal muscle proteins, myosin and actin. Interstitial 3MH concentration was measured before and for 24 h following a single bout of resistance exercise in eight young (27 +/- 2 years) and eight old (75 +/- 4 years) men. The exercise bout consisted of four exercises (3 sets of 8 repetitions at 80% one-repetition maximum (1RM) per exercise) emphasizing the quadriceps. Interstitial 3MH concentration was calculated using the internal reference method from microdialysate samples that were obtained from two microdialysis probes placed in the vastus lateralis. Resting interstitial 3MH concentration was 44% higher (P < 0.05) in the old (6.16 +/- 0.56 nmol ml(-1)) as compared with the young (4.28 +/- 0.27 nmol ml(-1)). Interstitial 3MH was not different (P > 0.05) from preexercise at any time point within the 24 h following exercise in both the young and the old. Leg arteriovenous exchange measurements in a separate group of young subjects also showed no increase in 3MH release during the 4 h following a resistance exercise bout compared with a non-exercised control leg (control leg: -28 +/- 6, exercise leg: -28 +/- 11 nmol min(-1)). These results suggest that myosin and actin proteolysis are not increased in the first 24 h following a standard bout of resistance exercise, and this response is not altered with ageing. The higher interstitial 3MH concentration in the old suggests an increased proteolysis of the two main contractile proteins in the rested and fasted state, which is consistent with a decrease in muscle mass with ageing. Microdialysis is an appropriate methodology for use in ageing individuals and is compatible with high-intensity resistance exercise.

BACKGROUND: Pre-clinical data indicate enhanced anti-tumour activity when combining recombinant human interleukin-21 (rIL-21), a class 1 cytokine, with cetuximab, a monoclonal antibody, targeting the epidermal growth factor receptor. This phase 1 trial assessed the safety and tolerability of escalating doses of rIL-21 in combination with cetuximab in chemo-naïve patients with stage IV colorectal cancer. PATIENTS AND METHODS: Sequential cohorts of PS 0-1, asymptomatic patients, were treated weekly with cetuximab 250 mg m(-2) intravenously (i.v.) plus escalating i.v. doses of rIL-21 following an initial loading dose of cetuximab 400 mg m(-2). Initial treatment period was 8 weeks, with extension permitted in patients without disease progression. RESULTS: In all, 15 patients were included in this study. Adverse events related to rIL-21 or rIL-21 plus cetuximab included lethargy, nausea/vomiting, stomatitis, lymphopenia and pyrexia and were mainly ≤ grade 2. One dose limiting toxicity occurred (grade 3 diarrhoea). Maximum tolerated dose was not determined because of the premature study closure. Maximum administered dose was 100 μg kg(-1) rIL-21 weekly. In all, 60% of the patients had stable disease. Immune activation was confirmed by various T- and NK-cell activation biomarkers, including dose-dependent increases in serum sCD25. CONCLUSION: rIL-21 weekly combined with cetuximab is well tolerated at doses up to 100 μg kg(-1) and results in activation of immune response biomarkers.