Secondary Carnitine Deficiency in Dialysis Patients: Shall We Supplement It?

Abstract

Carnitine, essential for fatty acid β-oxidation, is obtained from diet and through de novo biosynthesis. The organic cation/carnitine transporter 2 (OCTN2) facilitates carnitine cellular transport and kidney resorption. Carnitine depletion occurs in OCTN2-deficient patients, with serious clinical complications including cardiomyopathy, myopathy, and hypoketotic hypoglycaemia. Neonatal screening can detect OCTN2 deficiency. OCTN2-deficiency is also known as primary carnitine deficiency. Carnitine deficiency may result from fatty acid β-oxidation disorders, which are diagnosed via plasma acylcarnitine profiling, but also under other conditions including haemodialysis. Given the importance of the kidney in maintaining carnitine homeostasis, it is not unexpected that longterm haemodialysis treatment is associated with the development of secondary carnitine deficiency, characterised by low endogenous L-carnitine levels and accumulation of deleterious medium and long- chain acylcarnitines. These alterations in carnitine pool composition have been implicated in a number of dialysis-related disorders, including erythropoietin-resistant renal anaemia. The association between erythropoietin resistance and carnitine levels has been demonstrated, with the proportion of medium and long-chain acylcarnitines within the total plasma carnitine pool positively correlated with erythropoietin resistance. Recent research has demonstrated that carnitine supplementation results in a significant reduction in erythropoietin dose requirements in patients with erythropoietin-resistant anaemia. Few studies have been conducted assessing the treatment of carnitine deficiency and haemodialysisrelated cardiac complications, particularly in children. Thus, a study was recently conducted which showed that intravenous carnitine in children receiving haemodialysis significantly increased plasma carnitine.