Abstract
Background: Creatine (Cr) levels are strongly dependent on diets, including animal-derived proteins. Cr is an important metabolite as it represents a source of stored energy to support physical performance and potentially sustain positive effects such as improving memory or intelligence. This study was planned to assess Cr levels in PKU children adhering to a diet low in phenylalanine (Phe) content and compared with those of children with mild hyperphenylalaninemia (MHP) on a free diet. Methods: This retrospective pilot study analyzed Cr levels from Guthrie cards in 25 PKU and 35 MHP subjects. Anthropomorphic and nutritional data of the study populations were assessed, compared and correlated. Results: Cr levels of PKU subjects were significantly lower than those of MHP subjects and correlated to the low intake of animal proteins. Although no deficiencies in PKU subjects were identified, PKU subjects were found to have a 26-fold higher risk of displaying Cr levels <25° percentile than MHP counterparts. Conclusions: This pilot study suggests that Cr levels might be concerningly low in PKU children adhering to a low-Phe diet. Confirmatory studies are needed in PKU patients of different age groups to assess Cr levels and the potential benefits on physical and intellectual performance of Cr supplementation.
Highlights
IntroductionDivided among other organs, including brain [1]
Creatine (Cr), or methylguanidinoacetic acid, is an amino acid derivative partially obtained by food and partially synthesized de novo by the liver and kidneys from arginine, glycine and methionine
Cr compensated by supplementation requirement in adults is approximately 2 g [2] and is met partly by endogenous Cr synthesis and partly through diet, where food of animal origin accounts for about the with PKUdepends need to a life-long low-Phe dietbeen to limit the intake
Summary
Divided among other organs, including brain [1]. Cr uptake occurs by active transport via the deputed Cr transporter SLC6A8 [2], called CrT1, highly expressed in organs with a high energy requirement (skeletal muscle and brain) or with absorption function (kidney and intestine). In skeletal muscles the enzyme Cr phosphokinase transforms approximately the 2/3 of Cr into phosphocreatine (PCr), used as energy source for ATP synthesis (Figure S1). Creatine (Cr) levels are strongly dependent on diets, including animal-derived proteins. This study was planned to assess Cr levels in PKU children adhering to a diet low in phenylalanine (Phe) content and compared with those of children with mild hyperphenylalaninemia (MHP) on a free diet. Results: Cr levels of PKU subjects were significantly lower than those of MHP subjects and correlated to the low intake of animal proteins. No deficiencies in PKU subjects were identified, PKU subjects were found to have a 26-fold higher risk of displaying
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