支链氨基酸(BCAA)亮氨酸,缬氨酸,和异亮氨酸提供单甲基支链脂肪酸(BCFA)的前体。缺乏BCFA的既定参考范围。在枫糖浆尿病(MSUD)中,一种罕见的先天性BCAA代谢错误,内产原产生受损,MSUD患者接受低蛋白(低BCAA)饮食治疗.蛋白质限制可能会影响BCFA的饮食摄入量,取决于饮食选择。根据疾病的严重程度,MSUD患者应接受或多或少的蛋白质限制饮食。蛋白质限制饮食和随后受损的内源性合成的组合可能使MSUD患者对BCFA缺乏敏感,还有未知的含义。为了调查在有利于膳食BCFA补充的MSUD中降低循环BCFA水平的可能性,我们首先建立了血浆中选定的BCFAs和饱和/不饱和脂肪酸的空腹状态参考范围.然后,通过比较空腹与非空腹队列中的分布,评估了空腹对BCFA水平的影响.为了检验BCFA缺乏可能导致MSUD病理生理学的假设,我们招募了间歇性,中间,和MSUD的经典形式,并分析了相应的BCFAz分数。没有一个BCFA物种相对于参考范围具有|z分数|>2。我们的发现不支持MSUD患者需要补充BCFA。讨论了BCFAs的起源。合成BCFA的能力受损并不表现为血浆水平降低,这表明内源性合成对于血浆水平是可有可无的。
The branched-chain amino acids (BCAA) leucine, valine, and isoleucine provide precursors for monomethyl branched-chain fatty acids (BCFA). Established reference ranges for BCFAs are lacking. In maple syrup urine disease (
MSUD), a rare inborn error of BCAA metabolism, the endogen production is impaired and
MSUD patients are treated with a low protein (low BCAA) diet. The protein restriction may affect the dietary intake of BCFA, depending on the dietary choices made. Patients with
MSUD are prescribed a more or less protein-restricted diet depending on the severity of the disease. The combination of a protein-restricted diet and subsequent impaired endogenous synthesis may render
MSUD patients sensitive to BCFA deficiency, with yet unknown implications. To investigate the possibility of lower circulatory BCFA levels in MSUD that favors dietary BCFA supplementation, we first established fasting-state reference ranges for selected BCFAs and saturated/unsaturated fatty acids in plasma. Then, the effect of fasting on BCFA levels was evaluated by comparing the distribution in a fasting versus a non-fasting cohort. To test the hypothesis that BCFA deficiency could contribute to MSUD pathophysiology, we recruited patients with intermittent, intermediate, and classical form of MSUD and analyzed the corresponding BCFA z-scores. None of the BCFA species had |z-scores| > 2 relative to the reference range. Our findings do not support the requirement of BCFA supplementation in
MSUD patients. The origin of BCFAs is discussed. Impaired capacity to synthesize BCFA do not manifest as reduced plasma levels in MSUD, suggesting that endogenous synthesis is dispensable for plasma levels.