Carnitine levels and mutations in the SLC22A5 gene in Faroes patients with Parkinson's disease

Abstract

Introduction: Mitochondrial dysfunction, oxidative stress and energy production have been implicated in the etiology of Parkinson's disease (PD). Several agents are under investigation for potential neuroprotective effects including acetyl-l-carnitine (ALC).

Objective: To investigate whether low carnitine levels and mutations in the SLC22A5 gene encoding the carnitine transporter are associates with PD risk in the Faroe Islands where the prevalence of both PD and carnitine transporter deficiency (CTD) is high.

Methods: We conducted a case-control study with 121 cases and 235 randomly selected controls, matched by gender and age. Blood spots were analyzed for free and total carnitine levels by QUATTRO LC triple quadrupole mass spectrometry (MS/MS) and sequencing performed for five genetic mutations in the SLC22A5 gene with ABI PRISM 3130.

Results: PD cases had significantly lower levels of free and total carnitine levels compared with controls (P < .001). However, stratifying according to mutation status, the lower levels of carnitine was only evident among the non-mutation carriers. Specifically, no difference was found in c.95A > G mutation frequency in the SLC22A5 gene among cases and controls (p = .70).

Conclusion: Low carnitine levels seem to be associated with PD, but only in individuals without the c.95A > G mutation rendering the carnitine transporter less efficient. Thus, the difference in carnitine levels is not caused by a higher frequency of c.95A > G mutation carriers in cases. The cause may be dietary or due to different gut microbiota among cases.

Keywords: Carnitine; Faroe Islands; OCTN2; Parkinson’s disease; SLC22A5 gene.