INS and obesity due to melanocortin 4 receptor deficiency: Decreased SCFAs, a common feature across diseases, exacerbate inflammation and impaired energy metabolism in cardiovascular diseases such as hypertension, atherosclerosis, and heart failure; inhibit insulin sensitivity in obesity, T2D, and MASLD; and lead to impaired intestinal barrier function in CD and UC, whereas elevated TMAO, by promoting thrombosis and foam cell accumulation, generally exacerbates cardiovascular disease risk.