Muscle and Bone Health in Young Chilean Adults with Phenylketonuria and Different Degrees of Compliance with the Phenylalanine Restricted Diet

Abstract

There are concerns about muscle and bone health in patients with Phenylketonuria (PKU). Our aim was to compare muscle mass, function, and bone health among young adults with PKU who maintained or suspended dietary treatment. Methods: Three groups were considered—PKU-1: 10 patients who used a protein substitute (PS) without phenylalanine (Phe); PKU-2: 14 patients who used the PS without Phe until eighteen years old and then practiced mostly a vegan diet; and 24 matched healthy controls. A 24 h recall survey, blood parameters, body composition and bone mineral density through DEXA, rectus femoris thickness by ultrasound, hand grip strength, submaximal exercise test, and walking speed were assessed. Results: PKU-1 patients had lower hand grip strength than their matched controls, but no other differences. Compared to controls, the PKU-2 group had lower fat-free mass (p = 0.01), less spine and femoral bone mineral density (p = 0.04 and p < 0.01, respectively), and peak workload on the incremental test (p = 0.03). When comparing PKU groups, blood Phe levels were significantly lower in the PKU-1 group (p = 0.02). Conclusions: Among PKU patients, abandoning the dietary treatment and maintaining high blood Phe concentrations could be deleterious for muscles and bones. However, we cannot discard other causes of bone and muscle damage in these patients.

Vitamin Status in Patients with Phenylketonuria: A Systematic Review and Meta-Analysis

“…The included studies were published from 1994 [38] to 2023 [39], and their characteristics are detailed in Table 1. Four studies were conducted in Greece [25,27,40,41], three in Turkey [31,42,43], three in Spain [32,44,45], two in Austria [26,46], two in Chile [39,47], two in Japan [29,30], two in the United Kingdom [48,49], two in the USA [38,50], and one each in Germany [51], France [52], Poland [28], and Switzerland [53]. All studies, except for one case-control study [26], were cross-sectional and compared individuals with PKU to healthy controls.…”

“…All studies, except for one case-control study [26], were cross-sectional and compared individuals with PKU to healthy controls. The PKU groups varied from 10 [39,52] to 107 [28], while control groups ranged from 6 [38] to 1676 [49]. Five studies assessed children [25,27,28,31,40], one studied adolescents [43], children and adolescents were included in nine studies [26,32,38,41,42,45,46,50,51,53], six studies examined adults [29,30,39,48,49,52], and the remaining two studies had a mixed population [44,47].…”

“…The PKU groups varied from 10 [39,52] to 107 [28], while control groups ranged from 6 [38] to 1676 [49]. Five studies assessed children [25,27,28,31,40], one studied adolescents [43], children and adolescents were included in nine studies [26,32,38,41,42,45,46,50,51,53], six studies examined adults [29,30,39,48,49,52], and the remaining two studies had a mixed population [44,47]. Most studies included males and females [24,[26][27][28][29][30]37,38,[40][41][42]45,46,[49][50][51][52], and while it was not explicitly stated in other studies [25,27,…”

“…Folate levels were evaluated in ten studies [26,27,39,[42][43][44]46,48,49,51] (Table 3), nine of which [26,27,39,[42][43][44]46,48,49] were incorporated into the meta-analysis and one study [51] was excluded because the data were presented as the median and range. The results showed significantly higher folate concentrations in PKU patients compared to healthy controls (random-effects model, SMD: 1.378, 95% CI: 0.436, 2.320, p = 0.004, Figure 2).…”

Intake Modalities of Amino Acid Supplements: A Real-World Data Collection from Phenylketonuria Patients

“…Unfortunately, if parental supervision ensures high levels of treatment adherence during childhood, adolescents often stop following dietary restrictions [ 1 , 6 , 7 ]. Moreover, despite the risk of late-onset neurological deficits, adults also frequently discontinue diet therapy, running a further risk of suffering from a more systemic disease [ 8 , 9 , 10 , 11 ]. Accordingly, a systematic review identified age as one of the major factors associated with poor treatment adherence, highlighting a gradual decline in metabolic control from adolescence onward [ 12 ].…”