Changes of lipoproteins in phenylalanine hydroxylase-deficient children during the first year of life

Background: Influence of hyperphenylalaninemia on lipoproteins in early life remains unclear. Methods: We enrolled 24 phenylalanine hydroxylase (PAH)-deficient children who were classified into a phenylketonuria (PKU) group (n = 12) lacking PAH activity and a benign hyperphenylalaninemia (HPA) group (n = 12) having partial PAH activity, and their 11 non-affected siblings. We measured serum total-cholesterol, low-density lipoprotein (LDL)-cholesterol, and high-density lipoprotein (HDL)-cholesterol levels together with apolipoproteins for the first year of life, and compared them with those of 30 age-matched healthy controls. Results: The affected groups invariably had lower cholesterol levels than non-affected groups. At birth, HDL-cholesterol decrease was greatest and predominated over the LDL-cholesterol decrease: total cholesterol, 28/36% decrease to the control level in HPA/PKU; HDL-cholesterol, 33/51%; LDL-cholesterol, 20/28%. At 3. months, the opposite changes were observed: total cholesterol, 16/28%; HDL-cholesterol, 13/23%; LDL-cholesterol, 16/33%. At 12. months, LDL were still significantly lower in both groups (8/18%, p < .05 and .001), although HDL was significantly decreased only in the PKU group (15%, p < .05). Apolipoprotein A-I/A-II and B changed respectively in accordance with HDL-cholesterol and LDL-cholesterol changes. Despite similar phenylalanine levels, the PKU group invariably had lower cholesterol concentrations than the HPA group had. Conclusion: Irrespective of phenylalanine concentrations, lipoprotein synthesis in PAH-deficient children, particularly in PKU children, was suppressed in early life.