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keskiviikko 6. elokuuta 2008

Pari uuttaa kreatiinikatsausta

Kreatiinimonohydraatti on yksi tutkituimmista ravintolisistä tällä planeetalla. Aiheen tiimoilta ilmeistyi juuri pari katsausartikkelia Sub-Cellular Biochemistry -tiedelehdessä. Alla tiivistelmät:

Subcell Biochem. 2007;46:245-59.

Ergogenic effects of creatine in sports and rehabilitation.
Hespel P, Derave W.
Research Center for Exercise and Health, Faculty of Kinesiology and Rehabilitation Sciences, K.U. Leuven, Leuven, Belgium.

The daily oral ingestion of supplementary creatine monohydrate can substantially elevate the creatine content of human skeletal muscle. This chapter aims to summarize the current knowledge regarding the impact muscle creatine loading can have on exercise performance and rehabilitation. The major part of the elevation of muscle creatine content is already obtained after one week of supplementation, and the response can be further enhanced by a concomitant exercise or insulin stimulus. The elevated muscle creatine content moderately improves contractile performance in sports with repeated high-intensity exercise bouts. More chronic ergogenic effects of creatine are to be expected when combined with several weeks of training. A more pronounced muscle hypertrophy and a faster recovery from atrophy have been demonstrated in humans involved in resistance training. The mechanism behind this anabolic effect of creatine may relate to satellite cell proliferation, myogenic transcription factors and insulin-like growth factor-1 signalling. An additional effect of creatine supplementation, mostly when combined with training, is enhanced muscle glycogen accumulation and glucose transporter (GLUT4) expression. Thus, creatine may also be beneficial in sport competition and training characterized by daily glycogen depletion, as well as provide therapeutic value in the insulin-resistant state.

Subcell Biochem. 2007;46:183-204.

Clinical use of creatine in neuromuscular and neurometabolic disorders.
Tarnopolsky MA.
Department of Pediatrics and Medicine (Neurology and Rehabilitation), Neuromuscular and Neurometabolic Clinic, Rm 2H26, McMaster University Medical Center, 1200 Main St. W., Hamilton, Ontario, Canada, L8N 3Z5.

Many of the neuromuscular (e.g., muscular dystrophy) and neurometabolic (e.g., mitochondrial cytopathies) disorders share similar final common pathways of cellular dysfunction that may be favorably influenced by creatine monohydrate (CrM) supplementation. Studies using the mdx model of Duchenne muscular dystrophy have found evidence of enhanced mitochondrial function, reduced intra-cellular calcium and improved performance with CrM supplementation. Clinical trials in patients with Duchenne and Becker's muscular dystrophy have shown improved function, fat-free mass, and some evidence of improved bone health with CrM supplementation. In contrast, the improvements in function in myotonic dystrophy and inherited neuropathies (e.g., Charcot-Marie-Tooth) have not been significant. Some studies in patients with mitochondrial cytopathies have shown improved muscle endurance and body composition, yet other studies did not find significant improvements in patients with mitochondrial cytopathy. Lower-dose CrM supplementation in patients with McArdle's disease (myophosphorylase deficiency) improved exercise capacity, yet higher doses actually showed some indication of worsened function. Based upon known cellular pathologies, there are potential benefits from CrM supplementation in patients with steroid myopathy, inflammatory myopathy, myoadenylate deaminase deficiency, and fatty acid oxidation defects. Larger randomized control trials (RCT) using homogeneous patient groups and objective and clinically relevant outcome variables are needed to determine whether creatine supplementation will be of therapeutic benefit to patients with neuromuscular or neurometabolic disorders. Given the relatively low prevalence of some of the neuromuscular and neurometabolic disorders, it will be necessary to use surrogate markers of potential clinical efficacy including markers of oxidative stress, cellular energy charge, and gene expression patterns.

PMID: 18652078 [PubMed - in process]

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