Reduced levels of mitochondrial proteins such as NADH-ubiquinol oxidoreductase (NDUFB8) and voltage-dependent anion channel (VDAC) were observed in the affected white matter of patients with X-ALD (88), suggesting that mitochondrial content or function is impaired in X-ALD. Here, NDUFB8 is linked to X-linked adrenoleukodystrophy.