Incidence of carnitine transporter OCTN2 deficiency in Japanese patients with idiopathic cardiomyopathy

原发性系统性肉碱缺乏。SCD是一种罕见的新生儿代谢性疾病，以进行性心肌病、肌肉无力和雷氏样综合征为特征。SCD导致肉毒碱转运体OCTN2基因突变。据报道，心肌病是一些高加索SCD患者的唯一症状。人们认为SCD被忽视为特发性心肌病，尽管这种疾病也已知可以用左旋肉碱治疗。因此，我们对居住在秋田县的42例日本特发性心肌病患者（平均年龄：58岁，年龄范围：13 ~ 87岁）的肉碱转运蛋白缺乏发生率进行了调查。我们检查血清和尿肉毒碱水平筛选和确定值的酶循环法使用肉毒碱脱氢酶。然后，我们研究了在知情同意的受试者中显示异常肉碱值的OCTN2基因突变分析。血清中总肉碱含量为67.2±16.6μM，血清中游离肉碱含量为56.3±14.5μM，血清中酰基肉碱含量为10.9±3.7μM，尿中游离肉碱含量为90.3±150.4μmol/g肌酐，尿中酰基肉碱含量为93.2±50.3μmol/g肌酐。虽然我们发现一个受试者的肉碱水平低于正常水平，但我们没有检测到OCTN2基因突变。因此，我们在42例日本特发性心肌病患者中没有发现SCD患者。我们认为，在仅表现出心脏症状的日本患者中，肉毒碱转运蛋白缺乏的发生率相对较低。

Primary systemic carnitine deficiency. (SCD) is a rare mborn metabolic disease characterized by progressive cardiomyopathy, muscle weakness, and Reye-like syndrome. SCD is responsible for themutations of carnitine transporter OCTN2 gene. It is reported that cardiomyopathy is only symptom in some Caucasian patients with SCD. It is supposed that SCD is overlooked as idiopathic cardiomyopahty although this disease is also known to be treatable with L-carnitine administration. Thus, we investigated the incidence of carnitine transporter deficiency in unrelated 42 Japanese patients with idiopathic cardiomyopathy who live in Akita prefecture (mean age: 58 years, range of age: 13〜87). We examined serum and urinary carnitne level for screening and determined the values by an enzymatic cycling method using carnitine dehydrogenase. Then, we investigated mutational analysis of OCTN2 gene in subjects with informed consent who showed abnormal carnitine values. The value (mean±SD) of tatal carnitine in serum is 67.2±16.6μM, free carnitine in serum was 56.3±14.5μM, acylcarnitine in serum was 10.9±3.7μM, free carnitine in urine was 90.3±150.4μmol/g Creatinine, and acylcarnitine in urine was 93.2±50.3μmol/g Creatinine. Although we found a subject who showed subnormal carnitine level, we detected no mutation in OCTN2 gene. Consequently, we found no patient with SCD in 42 Japanese patients with idiopathic cardiomyopathy. We suggested that the incidence of carnitine transporter deficiency in Japanese patients who showed only cardiac symptoms is relatively low.