Improved growth and nutrition status in children with methylmalonic or propionic acidemia fed an elemental medical food

BACKGROUND

Failure-to-thrive (FTT) has been described in patients with organic acidemias treated with low protein diets.

OBJECTIVE

To determine if patients with methylmalonic (MMA) or propionic acidemia (PA) can achieve normal growth and nutrition status.

METHODS

A 6-month multicenter outpatient study was conducted with infants and toddlers treated with Propimex-1 Amino Acid-Modified Medical Food With Iron (Ross Products Division, Abbott Laboratories, Columbus, OH). Main outcome measures were anthropometrics, protein status indices, plasma retinol, and alpha-tocopherol.

RESULTS

Sixteen patients completed the study. Mean baseline age was 0.54 +/- 0.02 years (range 0.03-3.00 years). By study end, mean National Center for Health Statistics (NCHS) weight centile increased from 26 to 49%; mean crown-heel length centile from 25 to 33%; and mean head circumference centile from 43 to 54%. Mean (+/- SE) protein and energy intakes by <6-month-old, 6<12-month-old, and 1<4-year-old patients were 15.3 +/- 0.9 g and 645 +/- 10 kcal; 18.3 +/- 1.1 g and 741 +/- 92 kcal; and 25.1 +/- 2.46 g and 1062 +/- 100 kcal, respectively. Plasma glycine concentrations were significantly and negatively correlated with energy intake (r=-0.77, p<0.0005). No correlation was found between dietary protein intakes and plasma ammonia concentrations. Protein status indices, retinol and alpha-tocopherol concentrations were within reference ranges at study end.

CONCLUSIONS

Propimex-1 improved growth and nutrition status in patients with MMA or PA in just 6 months when fed in sufficient amounts. Providing energy and protein for patients with FTT at intakes recommended for catch-up growth may have resulted in even better growth.

Therapeutic developments in peroxisome biogenesis disorders

Clinically, peroxisome biogenesis disorders (PBDs) are a group of lethal diseases with a continuum of severity of clinical symptoms ranging from the most severe form, Zellweger syndrome, to the milder forms, infantile Refsum disease and rhizomelic chondrodysplasia punctata. PBDs are characterised by a number of biochemical abnormalities including impaired degradation of peroxide, very long chain fatty acids, pipecolic acid, phytanic acid and xenobiotics and impaired synthesis of plasmalogens, bile acids, cholesterol and docosahexaenoic acid. Treatment of PBD patients as a group is problematic since a number of patients, especially those with Zellweger syndrome, have significant neocortical alterations in the brain at birth so that full recovery would be impossible even with postnatal therapy. To date, treatment of PBD patients has generally involved only supportive care and symptomatic therapy. However, the fact that some of the milder PBD patients live into the second decade has prompted research into possible treatments for these patients. A number of experimental therapies have been evaluated to determine whether or not correction of biochemical abnormalities through dietary supplementation and/or modification is of clinical benefit to PBD patients. Another approach has been pharmacological induction of peroxisomes in PBD patients to improve overall peroxisomal biochemical function. Well known rodent peroxisomal proliferators were found not to induce human peroxisomes. Recently, our laboratory demonstrated that sodium 4-phenylbutyrate induces peroxisome proliferation and improves biochemical function (very long chain fatty acid beta-oxidation rates and very long chain fatty acid and plasmalogens levels) in fibroblast cell lines from patients with milder PBD phenotypes. Dietary supplementation and/or modification and pharmacological induction of peroxisomes as treatment strategies for PBD patients will be the subject of this review.

Plasma and red blood cell fatty acids in peroxisomal disorders

The demonstration of abnormal levels of fatty acids or plasmalogens in plasma or red blood cells is key to the diagnosis of peroxisomal disorders. We report the levels of 62 fatty acids and plasmalogens in patients with X-linked adrenoleukodystrophy (X-ALD), Zellweger syndrome (ZS), neonatal adrenoleukodystrophy (NALD), and infantile Refsum disease (IRD), both at baseline and after dietary interventions. "Lorenzo's Oil" therapy in X-ALD normalizes the levels of saturated very long chain fatty acids in plasma, but leads to reduced levels of omega 6 and other omega 3 fatty acids, and requires monitoring and appropriate dietary supplements. Patients with ZS, NALD and IRD have reduced levels of docosahexaenoic acid (DHA) and arachidonic acid (AA) which can be normalized by the oral administration of microencapsulated DHA and AA.

Dietary docosahexaenoic acid has little effect on peroxisomes in healthy mice

NMRI mice were fed diets supplemented with 0.05, 0.2, or 2% (w/w) docosahexaenoic acid (DHA), a polyunsaturated fatty acid present in fish oil, for 3 d, 3 wk, or 3 mon. The doses of DHA were chosen to supply the mice with concentrations of DHA which approximate those that have been reported to be beneficial to patients with peroxisomal disease. Diets containing 0.05 or 0.2% DHA did not change hepatic, myocardial, and renal catalase (EC 1.11.1.6) activity except for a slight but significant increase (to 120%) in myocardial catalase activity in mice treated with the 0.05% DHA diet for 3 mon. A diet with 2% DHA induced myocardial catalase activity to 150% after both 3 d and 3 wk of administration. In the liver of mice fed this diet for 3 wk, hepatic catalase activity was increased to 140% while no induction of palmitoyl-CoA oxidase (EC 1.3.99.3), urate oxidase (EC 1.7.3.3), and L-alpha-hydroxyisovalerate oxidase (EC 1.1.3.a) was observed. With the light microscope, no changes in peroxisomal morphology were visually evaluated in catalase stained sections of liver, myocardium, and kidney of mice fed either diet. Our results show that in healthy mice a low dietary DHA dose (< 0.2%; this corresponds to a dose prescribed to peroxisomal patients) has no effect on several hepatic peroxisomal H2O2-producing enzymes, including the rate-limiting enzyme of the peroxisomal fatty acid beta-oxidation. This may indicate that such a DHA dose will not add a strong load on the often disturbed fatty acid metabolism in the liver of patients with peroxisomal disorders.