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PLoS One. 2012;7(9):e45165. doi: 10.1371/journal.pone.0045165. Epub 2012 Sep 18.

Low bone strength is a manifestation of phenylketonuria in mice and is attenuated by a glycomacropeptide diet.

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  • 1Department of Nutritional Sciences, University of Wisconsin, Madison, Wisconsin, USA.

Abstract

PURPOSE:

Phenylketonuria (PKU), caused by phenylalanine (phe) hydroxylase loss of function mutations, requires a low-phe diet plus amino acid (AA) formula to prevent cognitive impairment. Glycomacropeptide (GMP), a low-phe whey protein, provides a palatable alternative to AA formula. Skeletal fragility is a poorly understood chronic complication of PKU. We sought to characterize the impact of the PKU genotype and dietary protein source on bone biomechanics.

PROCEDURES:

Wild type (WT; Pah(+/+)) and PKU (Pah(enu2/enu2)) mice on a C57BL/6J background were fed high-phe casein, low-phe AA, and low-phe GMP diets between 3 to 23 weeks of age. Following euthanasia, femur biomechanics were assessed by 3-point bending and femoral diaphyseal structure was determined. Femoral ex vivo bone mineral density (BMD) was assessed by dual-energy x-ray absorptiometry. Whole bone parameters were used in principal component analysis. Data were analyzed by 3-way ANCOVA with genotype, sex, and diet as the main factors.

FINDINGS:

Regardless of diet and sex, PKU femora were more brittle, as manifested by lower post-yield displacement, weaker, as manifested by lower energy and yield and maximal loads, and showed reduced BMD compared with WT femora. Four principal components accounted for 87% of the variance and all differed significantly by genotype. Regardless of genotype and sex, the AA diet reduced femoral cross-sectional area and consequent maximal load compared with the GMP diet.

CONCLUSIONS:

Skeletal fragility, as reflected in brittle and weak femora, is an inherent feature of PKU. This PKU bone phenotype is attenuated by a GMP diet compared with an AA diet.

PMID:
23028819
[PubMed - indexed for MEDLINE]
PMCID:
PMC3445501
Free PMC Article
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