Lipid-induced endoplasmic reticulum stress in X-linked adrenoleukodystrophy

X-linked adrenoleukodystrophy (ALD) is a progressive neurodegenerative disease that is caused by mutations in the ABCD1 gene and characterized by elevated levels of very long-chain fatty acids (VLCFA) in plasma and tissues, with the most pronounced increase in the central nervous system. Virtually all male patients develop adrenal insufficiency and myelopathy (adrenomyeloneuropathy), but a subset develops a fatal cerebral demyelinating disease (known as cerebral ALD). Female patients may also develop myelopathy, but adrenal insufficiency or leukodystrophy are very rare. ALD has been associated with mitochondrial dysfunction, oxidative stress and bioenergetic failure, but the mechanism by which VLCFA accumulation triggers these effects has not been resolved thus far. In this study, we used primary human fibroblasts from normal subjects and ALD patients to investigate whether VLCFA can induce endoplasmic reticulum stress. We show that saturated VLCFA (C26:0) induce endoplasmic reticulum stress in fibroblasts from ALD patients, but not in controls. Furthermore, there is a clear correlation between the chain-length of the fatty acid and the induction of endoplasmic reticulum stress. Exposure of ALD fibroblasts to C26:0, resulted in increased expression of additional endoplasmic reticulum stress markers (EDEM1, GADD34 and CHOP) and in lipoapoptosis. This new insight into the underlying mechanism of VLCFA-induced toxicity is of great importance for the development of a disease modifying treatment for ALD aimed at the normalization of VLCFA levels in tissues.