ABCD4 and obesity due to melanocortin 4 receptor deficiency: Abcd4 is linked to vitamin B12 deficiency, which leads to a reduction in fat metabolism; the finding that Abcd4 was downregulated in the F0-HFD group (F0-HFD/F0-NC = 0.46) is consistent with the fact that it could cause or aggravate obesity [38].