More precisely, a high concentration of leptin in the circulating blood makes individuals susceptible to rheumatic and metabolic diseases, while a low concentration suppresses the function of immune cells, leading to frequent infections.20, 21 The general effects of leptin are attributable to leptin receptors (LEPRs) on the membranes of various types of cells, notably immune cells. The gene discussed is LEP; the disease is Other metabolic disease.