Dramatic Decrease of Carnitine Esters after Interruption of Exogenous Carnitine Supply in Hemodialysis Patients

Mass Spectrometric Analysis of L-carnitine and its Esters: Potential Biomarkers of Disturbances in Carnitine Homeostasis

PURPOSE

After a golden age of classic carnitine research three decades ago, the spread of mass spectrometry opened new perspectives and a much better understanding of the carnitine system is available nowadays. In the classic period, several human and animal studies were focused on various distinct physiological functions of this molecule and these revealed different aspects of carnitine homeostasis in normal and pathological conditions. Initially, the laboratory analyses were based on the classic or radioenzymatic assays, enabling only the determination of free and total carnitine levels and calculation of total carnitine esters' amount without any information on the composition of the acyl groups. The introduction of mass spectrometry allowed the measurement of free carnitine along with the specific and sensitive determination of different carnitine esters. Beyond basic research, mass spectrometry study of carnitine esters was introduced into the newborn screening program because of being capable to detect more than 30 metabolic disorders simultaneously. Furthermore, mass spectrometry measurements were performed to investigate different disease states affecting carnitine homeostasis, such as diabetes, chronic renal failure, celiac disease, cardiovascular diseases, autism spectrum disorder or inflammatory bowel diseases.

RESULTS

This article will review the recent advances in the field of carnitine research with respect to mass spectrometric analyses of acyl-carnitines in normal and various pathological states.

CONCLUSION

The growing number of publications using mass spectrometry as a tool to investigate normal physiological conditions or reveal potential biomarkers of primary and secondary carnitine deficiencies shows that this tool brought a new perspective to carnitine research.

Clinical significance of different carnitine levels for improving the prognosis of patients undergoing hemodialysis

OBJECTIVE

To investigate plasma-free carnitine (Fc), acylcarnitine (Ac), and total carnitine (Tc) levels in patients undergoing hemodialysis (HD), and to explore their clinical significance.

METHODS

A total of 20 subjects were in the normal control group and 133 patients undergoing HD were divided into medicated (received carnitine treatment) and non-medicated groups. The medicated group was further divided into three subgroups according to Fc level: Fc = 80-199, 200-299, and ≥ 300 μmol/L. We used non-derivative tandem mass spectrometry to determine carnitine levels, and clinical symptoms such as weakness, hypotension, and muscle cramps were recorded during dialysis.

RESULTS

Fc and Tc levels were significantly lower in the non-medicated group than in the control group, whereas Fc, Ac, and Tc levels were higher in the medicated than non-medicated group (p< .05). The medicated group had fewer symptoms during dialysis than the non-medicated group such as weakness, hypotension, and muscle cramps (p< .05). An additional comparison showed that the incidence rates of hypotension and muscle cramps in the Fc < 80-199 μmol/L group were significantly lower than those in the Fc ≥ 300 μmol/L medicated and non-medicated groups.

CONCLUSIONS

Patients undergoing HD have low carnitine levels. l-Carnitine can effectively increase Fc concentration and improve clinical symptoms; however, only the proper Fc range can reduce complications caused by dialysis. Thus, this range needs to be determined.