A recent randomized controlled trial demonstrated that low-carbohydrate HFD could increase serum cholesterol [44] and high cholesterol and HFD could directly induce lipid accumulation in AEC2s thereby up-regulating the expression of Toll like receptor 4 (TLR4) [45] which would lead to apoptosis of AECs and lung fibrosis [46]. This evidence concerns the gene TLR4 and pulmonary fibrosis.