Abstract
Low-protein diets (LPDs) are the main treatment for urea cycle disorders (UCDs) and organic acidemias (OAs). In most cases, LPDs start in childhood and must be continued into adulthood. The improved life expectancy of patients with UCDs and OAs raises the question of their consequences on nutritional status in adult subjects. As this topic has so far received little attention, we conducted a review of scientific studies that investigated the nutrient intake and nutritional status in adult patients with UCDs and branched chain organic acidemias (BCOAs) on LPD. Methods: The literature search was conducted in PubMed/MEDLINE, Scopus, EMBASE and Google Scholar from 1 January 2000 to 31 May 2020, focusing on nutrient intake and nutritional status in UCD and OA adult patients. Results: Despite protein restriction is recommended as the main treatment for UCDs and OAs, in these patients, protein intake ranges widely, with many patients who do not reach safety levels. When evaluated, micronutrient intake resulted below recommended values in some patients. Lean body mass resulted in most cases lower than normal range while fat body mass (FM) was often found normal or higher than the controls or reference values. Protein intake correlated inversely with FM both in adult and pediatric UCD patients. Conclusions: The clinical management of adult patients with UCDs and BCOAs should include an accurate assessment of the nutritional status and body composition. However, as little data is still available on this topic, further studies are needed to better clarify the effects of LPDs on nutritional status in adult UCD and BCOA patients.
Highlights
Inherited metabolic diseases (IMDs) are errors of metabolism due to enzymatic defects in carbohydrates, protein, and lipid metabolism
Advances in medicine and the availability of new effective therapies have improved the survival of patients with IMDs, and the transitional care to adulthood has become a new challenge for physicians and public health systems [25]
This is the case of urea cycle disorders (UCDs) and Branched-chain organic acidemiasi (BCOAs) that require restriction of protein intake throughout life, raising concerns about growth in pediatric patients and about nutritional status and maintenance of lean body mass in adults
Summary
Inherited metabolic diseases (IMDs) are errors of metabolism due to enzymatic defects in carbohydrates, protein, and lipid metabolism. They are very different among each other, with a wide spectrum of clinical presentation and severity, with life expectancy varying from days to general population’s expectancy. Urea Cycle disorders (UCDs) are inherited diseases due to a loss of function of one of the enzymes related to urea cycle: deficiency of carbamoyl phosphate synthetase 1 (CPS1D, MIM#237300), ornithine transcarbamylase (OTCD, MIM#311250), argininosuccinatesynthetase (ASSD, MIM#215700), argininosuccinatelyase (ASLD, MIM#207900) and arginase (ARG1D, MIM#207800), the mitochondrial ornithine-citrulline antiporter (ORC1D, MIM#238970) and the CPS1-activating enzyme. The loss of function of the urea cycle causes the inability to excrete ammonium produced during protein catabolism.
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