Aims/hypothesis Brain-derived neurotrophic factor (BDNF) is produced in skeletal muscle, but its functional significance is unknown. We aimed to determine the signalling processes and metabolic actions of BDNF. Methods We first examined whether exercise induced BDNF expression in humans. Next, C2C12 skeletal muscle cells were electrically stimulated to mimic contraction. L6 myotubes and isolated rat extensor digitorum longus muscles were treated with BDNF and phosphorylation of the proteins AMP-activated protein kinase (AMPK) (Thr 172 ) and acetyl coenzyme A carboxylase β (ACCβ) (Ser 79 ) were analysed, as was fatty acid oxidation (FAO).Finally, we electroporated a Bdnf vector into the tibialis cranialis muscle of mice. Results BDNF mRNA and protein expression were increased in human skeletal muscle after exercise, but muscle-derived BDNF appeared not to be released into the circulation. Bdnf mRNA and protein expression was increased in muscle cells that were electrically stimulated. BDNF increased phosphorylation of AMPK and ACCβ and enhanced FAO both in vitro and ex vivo. The effect of BDNF on FAO was AMPK-dependent, since the increase in FAO was abrogated in cells infected with an AMPK dominant negative adenovirus or treated with Compound C, an inhibitor of AMPK. Electroporation of a Bdnf expression

Contracting human skeletal muscle is a major contributor to the exercise-induced increase of plasma interleukin-6 (IL-6). Although antioxidants have been shown to attenuate the exerciseinduced increase of plasma IL-6, it is unknown whether antioxidants inhibit transcription, translation or translocation of IL-6 within contracting human skeletal muscle. Using a singleblind placebo-controlled design with randomization, young healthy men received an oral supplementation with either a combination of ascorbic acid (500 mg day −1 ) and RRR-α-tocopherol (400 i.u. day −1 ) (Treatment, n = 7), or placebo (Control, n = 7). After 28 days of supplementation, the subjects performed 3 h of dynamic two-legged knee-extensor exercise at 50% of their individual maximal power output. Muscle biopsies from vastus lateralis were obtained at rest (0 h), immediately post exercise (3 h) and after 3 h of recovery (6 h). Leg blood flow was measured using Doppler ultrasonography. Plasma IL-6 concentration was measured in blood sampled from the femoral artery and vein. The net release of IL-6 was calculated using Fick's principle. Plasma vitamin C and E concentrations were elevated in Treatment compared to Control. Plasma 8-iso-prostaglandin F 2α , a marker of lipid peroxidation, increased in response to exercise in Control, but not in Treatment. In both Control and Treatment, skeletal muscle IL-6 mRNA and protein levels increased between 0 and 3 h. In contrast, the net release of IL-6 from the leg, which increased during exercise with a peak at 3.5 h in Control, was completely blunted during exercise in Treatment. The arterial plasma IL-6 concentration from 3 to 4 h, when the arterial IL-6 levels peaked in both groups, was ∼50% lower in the Treatment group compared to Control (Treatment versus Control: 7.9 pg ml −1 , 95% confidence interval (CI) 6.0-10.7 pg ml −1 ,versus 19.7 pg ml −1 ,CI13.8-29.4 pg ml −1 ,at3.5 h,P < 0.05betweengroups). Moreover, plasma interleukin-1 receptor antagonist (IL-1ra), C-reactive protein and cortisol levels all increased after the exercise in Control, but not in Treatment. In conclusion, our results show that supplementation with vitamins C and E attenuated the systemic IL-6 response to exercise primarily via inhibition of the IL-6 protein release from the contracting skeletal muscle per se.

No abstract

To characterize the physiological role of metallothioneins I and II (MT-I+II) in the brain, we have examined the chronological effects of a freeze injury to the cortex in normal and MT-I+II null mice. In normal mice, microglia/macrophage activation and astrocytosis were observed in the areas surrounding the lesion site, peaking at approximately 1 and 3 d postlesion (dpl), respectively. At 20 dpl, the parenchyma had regenerated. Both brain macrophages and astrocytes surrounding the lesion increased the MT-I+II immunoreactivity, peaking at approximately 3 dpl, and at 20 dpl it was similar to that of unlesioned mice. In situ hybridization analysis indicates that MT-I+II immunoreactivity reflects changes in the messenger levels. In MT-I+II null mice, microglia/macrophages infiltrated the lesion heavily, and at 20 dpl they were still present. Reactive astrocytosis was delayed and persisted at 20 dpl. In contrast to normal mice, at 20 dpl no wound healing had occurred. The rate of apoptosis, as determined by using terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling, was drastically increased in neurons of ipsilateral cortex of the MT-I+II null mice. Our results demonstrate that MT-I+II are essential for a normal wound repair in the CNS, and that their deficiency impairs neuronal survival.

The cytokine interleukin-15 (IL-15) has been demonstrated to have anabolic effects in cell culture systems. We tested the hypothesis that IL-15 is predominantly expressed by type 2 skeletal muscle fibres, and that resistance exercise regulates IL-15 expression in muscle. Triceps brachii, vastus lateralis quadriceps and soleus muscle biopsies were obtained from normally physically active, healthy, young male volunteers (n = 14), because these muscles are characterized by having different fibre-type compositions. In addition, healthy, normally physically active male subjects (n = 8) not involved in any kind of resistance exercise underwent a heavy resistance exercise protocol that stimulated the vastus lateralis muscle and biopsies were obtained from this muscle pre-exercise as well as 6, 24 and 48 h post-exercise. IL-15 mRNA levels were twofold higher in the triceps (type 2 fibre dominance) compared with the soleus muscle (type 1 fibre dominance), but Western blotting and immunohistochemistry revealed that muscle IL-15 protein content did not differ between triceps brachii, quadriceps and soleus muscles. Following resistance exercise, IL-15 mRNA levels were up-regulated twofold at 24 h of recovery without any changes in muscle IL-15 protein content or plasma IL-15 at any of the investigated time points. In conclusion, IL-15 mRNA level is enhanced in skeletal muscles dominated by type 2 fibres and resistance exercise induces increased muscular IL-15 mRNA levels. IL-15 mRNA levels in skeletal muscle were not paralleled by similar changes in muscular IL-15 protein expression suggesting that muscle IL-15 may exist in a translationally inactive pool.

No abstract

The beta-site APP-cleaving enzyme (BACE1) is a prerequisite for the generation of beta-amyloid peptides, which give rise to cerebrovascular and parenchymal beta-amyloid deposits in the brain of Alzheimer's disease patients. BACE1 is neuronally expressed in the brains of humans and experimental animals such as mice and rats. In addition, we have recently shown that BACE1 protein is expressed by reactive astrocytes in close proximity to beta-amyloid plaques in the brains of aged transgenic Tg2576 mice that overexpress human amyloid precursor protein carrying the double mutation K670N-M671L. To address the question whether astrocytic BACE1 expression is an event specifically triggered by beta-amyloid plaques or whether glial cell activation by other mechanisms also induces BACE1 expression, we used six different experimental strategies to activate brain glial cells acutely or chronically. Brain sections were processed for the expression of BACE1 and glial markers by double immunofluorescence labeling and evaluated by confocal laser scanning microscopy. There was no detectable expression of BACE1 protein by activated microglial cells of the ameboid or ramified phenotype in any of the lesion paradigms studied. In contrast, BACE1 expression by reactive astrocytes was evident in chronic but not in acute models of gliosis. Additionally, we observed BACE1-immunoreactive astrocytes in proximity to beta-amyloid plaques in the brains of aged Tg2576 mice and Alzheimer's disease patients.

Interleukin-6 (IL-6) is produced by many different cell types. Human skeletal muscles produce and release high amounts of IL-6 during exercise; however, the cell source of origin in the muscle is not known. Therefore, we studied the protein expression of IL-6 by immunohistochemistry in human muscle tissue from biopsies obtained at time points 0, 3, 4.5, 6, 9, and 24 h in relation to 3 h of bicycle exercise performed by healthy young males (n=12) and in resting controls (n=6). The IL-6 expression was clearly increased after exercise and remained high even by 24 h, relative to pre-exercise or resting individuals. The IL-6 immunostainings of skeletal muscle cells were homogeneous and without difference between muscle fiber types. The IL-6 mRNA peaked immediately after the exercise, and, in accordance, the IL-6 protein expression within muscle cells was most pronounced around 3 h post-exercise. However, the finding that plasma IL-6 concentration peaked in the end of exercise indicates a high turnover of muscle-derived IL-6. In conclusion, the finding of marked IL-6 protein expression exclusively within skeletal muscle fibers following exercise demonstrates that skeletal muscle fibers of all types are the dominant cell source of exercise-induced release of IL-6 from working muscle.