The correlation of lipid profile and waist circumference with phenylalanine levels in adult patients with classical phenylketonuria

INTRODUCTION AND OBJECTIVES

Some studies have pointed to a relationship between Phenyketonuria (PKU) and an increased cardiovascular risk (CVR). This study aimed to evaluate the influence of metabolic control on classical CVR factors in adult patients with PKU.

MATERIAL AND METHODS

It was a cross-sectional study conducted in patients older than 18 years with a diagnosis of classical PKU and under strict dietary control. Demographic, epidemiological and laboratory variables related to CVR were collected. The variables of metabolic control were some parameters related to phenylalanine (Phe) plasma levels.

RESULTS

A total of 47 patients were included with a mean age of 36±10 years of which 30 (64%) were women. Multivariate analysis revealed that range Phe (B=-2.211, P=0.044, 95%CI: -4.354-(-0.068)) levels were within the model for triglyceride concentrations, while minimum (B=-2.803, P=0.051, 95%CI: -5.612-0.007) and range (B=-1.515, P=0.039, 95%CI: -2.945-(-0.084)) Phe levels were within the model for high-density lipoprotein cholesterol concentrations. Median Phe levels showed a stronger correlation with waist circumference (WC) (B=1.216, P=0.002, 95%CI: 0.462-1.969) than with body mass index (B=0.355, P=0.052, 95%CI: -0.004-0.714).

CONCLUSIONS

High Phe levels and wide Phe fluctuations were related to weight gain, increased WC and lipid profile abnormalities. Systematic CVR assessments and comprehensive monitoring of Phe levels may be desirable to prevent or delay cardiovascular disease in PKU patients.

Fluctuations in phenylalanine concentrations in phenylketonuria: a review of possible relationships with outcomes

Fluctuations in blood phenylalanine concentrations may be an important determinant of intellectual outcome in patients with early and continuously treated phenylketonuria (PKU). This review evaluates the studies on phenylalanine fluctuations, factors affecting fluctuations, and if stabilizing phenylalanine concentrations affects outcomes, particularly neurocognitive outcome. Electronic literature searches of Embase and PubMed were performed for English-language publications, and the bibliographies of identified publications were also searched. In patients with PKU, phenylalanine concentrations are highest in the morning. Factors that can affect phenylalanine fluctuations include age, diet, timing and dosing of protein substitute and energy intake, dietary adherence, phenylalanine hydroxylase genotype, changes in dietary phenylalanine intake and protein metabolism, illness, and growth rate. Even distribution of phenylalanine-free protein substitute intake throughout 24h may reduce blood phenylalanine fluctuations. Patients responsive to and treated with 6R-tetrahydrobiopterin seem to have less fluctuation in their blood phenylalanine concentrations than controls. An increase in blood phenylalanine concentration may result in increased brain and cerebrospinal fluid phenylalanine concentrations within hours. Although some evidence suggests that stabilization of blood phenylalanine concentrations may have benefits in patients with PKU, more studies are needed to distinguish the effects of blood phenylalanine fluctuations from those of poor metabolic control.