Low doses of LPS obtained from the gut microbiota can, under certain conditions, enter the bloodstream and cause metabolic endotoxemia, leading to low-grade chronic TLR4-dependent inflammation, which contributes to the development of metabolic diseases such as type 2 diabetes mellitus (T2DM) and obesity [146,147,148,149]. The gene discussed is TLR4; the disease is obesity due to melanocortin 4 receptor deficiency.