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Inadequate iron availability as a possible cause of low serum carnitine concentrations in patients with
H Böhles1, K Ullrich, W Endres
1University Children's Hospital, Frankfurt/Main, Federal Republic of Germany.
Insights
Phenylketonuria (PKU) patients on a strict diet show lower serum carnitine levels, linked to reduced iron availability and diet content. Optimizing PKU diets for iron or carnitine intake is recommended.
Area of Science:
- Biochemistry
- Nutritional Science
- Pediatric Medicine
Background:
- Decreased serum carnitine concentrations have been previously observed in phenylketonuria (PKU).
- The strict, protein-reduced diet essential for managing PKU may impact nutrient levels.
- Iron is a crucial cofactor for carnitine synthesis.
Purpose of the Study:
- To investigate the cause of decreased serum carnitine concentrations in PKU patients.
- To compare carnitine levels in PKU patients on and off diet, and with healthy controls.
- To explore the relationship between serum carnitine, iron status, and dietary factors in PKU.
Main Methods:
- Serum carnitine, hemoglobin, and ferritin levels were measured in 169 PKU patients (on diet n=107, off diet n=62) and 57 healthy controls.
- PKU patients were stratified by age and dietary adherence.
- Statistical analysis was used to compare groups and identify correlations.
Main Results:
- PKU patients on a strict diet (older than 2 years) had significantly lower serum carnitine (19.4 +/- 5.4 mumol/l) compared to those off diet (29.6 +/- 6.7 mumol/l).
- PKU patients on diet also exhibited lower hemoglobin and serum ferritin levels.
- A significant positive linear correlation was found between total serum carnitine and ferritin concentrations.
Conclusions:
- Reduced endogenous carnitine synthesis due to inadequate iron availability is a likely cause of low serum carnitine in PKU patients on diet.
- The low carnitine content of the PKU diet further contributes to decreased serum carnitine levels.
- Optimizing PKU diets to enhance iron availability or increase carnitine intake is suggested for improved patient outcomes.
Abstract:
A previous observation of decreased serum carnitine concentrations in phenylketonuria (PKU) was investigated in 169 patients either on a strict diet (n = 107; median: 8.1 years) or off diet (n = 62; median: 15.0 years). Fifty-seven metabolically healthy children (median: 8.5 years) served as controls. PKU patients on a strict diet and older than 2 years had significantly lower serum carnitine concentrations (19.4 +/- 5.4 mumol/l) than those off diet (29.6 +/- 6.7 mumol/l). PKU patients on diet also had significantly lower concentrations of haemoglobin and serum ferritin than those off diet. A linear correlation existed between total serum carnitine and ferritin concentrations up to 40 micrograms/l (r = 0.52; P less than 0.01). As iron is an essential cofactor of carnitine synthesis we conclude that reduced endogenous carnitine synthesis due to an inadequate availability of iron may be a major cause of low serum carnitine concentrations. The low carnitine content of the strict and highly protein-reduced diet additionally contributes to a decrease in the serum carnitine concentration. Our results show that a further optimization of the PKU diet increasing either iron availability or carnitine intake should be considered.