Abstract
BackgroundIntake of large neutral amino acids (LNAA) may inhibit phenylalanine (PHE) transport across the blood brain barrier and assist with blood PHE control in patients with phenylketonuria (PKU). We evaluated the interrelationship between LNAA in plasma and diet on Phe:Tyr (P:T) ratio in patients with PKU and the influence of dietary factors on plasma LNAA markers.MethodsPlasma amino acid values and 3‐day food record analysis from two studies (34 male/30 female; age 4.6‐47 years) were examined. For pediatrics (<18 years) and adults (≥18 years) the relationship between P:T ratio, plasma LNAA, and dietary intake patterns were investigated.ResultsDietary factors influencing P:T ratio included intake of total protein (g/kg), medical food (MF) protein (g/kg, % below Rx), and LNAA (g) in the full cohort (P < .05). Associations were found between plasma valine and other dietary and plasma LNAA in pediatrics (P < .05) and plasma LNAA with dietary LNAA intake in adults (P = .019). Plasma P:T ratio was inversely associated with plasma LNAA concentrations in both age groups (P < .05). Aside from histidine in pediatrics (P = .024), plasma LNAA did not differ by having plasma PHE levels within or above the therapeutic range (120‐360 μmol/L). Plasma LNAA in both age groups was similar to reported healthy control values.ConclusionP:T ratio is significantly tied to dietary LNAA, adherence to MF Rx, and plasma LNAA concentrations. Additionally, P:T ratio and valine may be effective clinical proxies for determining LNAA metabolic balance and LNAA quality of the diet in patients with PKU.
Highlights
Phenylketonuria (PKU) is an autosomal recessive genetic disorder in which the enzyme, phenylalanine hydroxylase (PAH), produced in the liver, is deficient
As long term P:T ratio has been found to associate with executive functioning, anxiety, and depression risk outcomes in PKU,[11,12] it is of clinical importance to determine the role of dietary large neutral amino acids (LNAA) from medical food and intact food sources on P:T ratio
Our research has demonstrated a clear inverse relationship between LNAA concentrations in the plasma and P:T ratio, with dietary and plasma tyrosine of greater weight than PHE
Summary
Phenylketonuria (PKU) is an autosomal recessive genetic disorder in which the enzyme, phenylalanine hydroxylase (PAH), produced in the liver, is deficient. Nutritional formula (medical food) that serves as the major dietary protein source.[1,2] The goal of the diet is to keep plasma blood PHE within the therapeutic range of 120-360 μmol/L, the level needed for normal development and cognitive function across all ages. Consumption of supraphysiologic LNAA supplements as a part of treatment in PKU may increase blood LNAA levels and reduce PHE concentrations in the blood and brain.[5,6] significance in PHE reduction only occurred in the absence of medical food. This highlights the importance of amino acid rich medical food in PHE control. P:T ratio and valine may be effective clinical proxies for determining LNAA metabolic balance and LNAA quality of the diet in patients with PKU
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
