Creatine, metabolism

Garcia-Miranda, P., Feral, M. J., and llundain, A. A. (2010). Effect of antidiuresis on renal creatine metabolism. /. Physiol. Pharmacol. 61(1), 83-88. 

Stromberger C, Bodamer OA, Stockler-Ipsiroglu S (2003) Clinical characteristics and diagnostic clues in inborn errors of creatine metabolism. J Inherit Metab Dis 26 299-308 Salomons GS, van Dooren SJ, Verhoeven NM, Marsden D, Schwartz C, Cecil KM, DeGrauw TJ, Jakobs C (2003) X-linked creatine transporter defect an overview. J Inherit Metab Dis 26 309-318... 

Item CB, Stockler-Ipsiroglu S, Stromberger C, Muhl A, Alessandri MG, Bianchi MC, et al. Arginine glycine amidinotransferase deficiency the third inborn error of creatine metabolism in humans. Am J Hum Genet 2001 69 1127-33. 

The association of muscle disease with a disturbance of creatine metabolism is a long-established contribution of biochemistry to this field, and the subject of much investigation in the past. It has been recognized for over half a century that, in contrast with normal adults, patients with nearly all types of muscle disease exhibit a creatinuria. Comprehensive... 

F2. Fitch, C. D., and Moody, L. G., Creatine metabolism in skeletal muscle. V. An intracellular abnormality of creatine trapping in dystrophic muscle. Proc. Soc. Exp. Biol. Med. 132, 219-222 (1969). 

F4. Fitch, C. D., and Sinton, D. W., A study of creatine metabolism in diseases causing muscle wasting. J. Clin. Invest. 43, 444-452 (1964). 

M. Wyss, R. Kaddurah-Daouk Creatine and creatine metabolism. Physiological Reviews 80, 1107 (2000). 

The concentration of creatinine in serum is a function of creatinine production and renal excretion. Creatinine is a product of creatine metabolism from muscle therefore its production is directly dependent on muscle mass. At steady state, the normal serum creatinine concentration is approximately 0.5 to 1.5 mg/dL for males and females. Creatinine is eliminated primarily by glomerular filtration, and as GFR declines, the serum creatinine concentration rises (Fig. 41-2). 

The serum creatinine concentration is dependent on the input function, or formation rate, and output function, or elimination rate. Its formation rate depends on the zero-order production from creatine metabolism, as well as input from other sources such as dietary intake. Creatine metabolism is directly proportional to muscle mass therefore individuals with more muscle mass have a higher serum creatinine concentration at any given degree of kidney function than those with less muscle mass. Exercise is associated with an increase of approximately 10% in the serum creatinine concentration. As the result of minimal muscle mass patients who are cachectic will have very low serum creatinine concentrations, as do those with spinal cord injuries. " Elderly patients and those with poor nutrition may also have low serum creatinine concentrations (<1 mg/dL) secondary to decreased muscle mass. Other factors that influence the serum creatinine concentration include the dietary intake of creatine. During the cooking of meat, some creatine is converted to creatinine, which is rapidly absorbed following ingestion. 

According to the creatine pathways in the body, two main categories of disorders in creatine metabolism can be expected disorders in creatine synthesis, and disorders of cellular creatine transport. 

GAMT deficiency is the first inborn error of creatine metabolism clinically characterised by mental retardation, epilepsy, and extrapyramidal... 

Stockier S, Isbrandt D, Hanefeld F, Schmidt B, Figura von K. Guanidinoacetate methyltransferase deficiency the first inborn error of creatine metabolism in man. Am J Hum Genet 1996 58 914-922... 

---