SLC22A6 and obesity due to melanocortin 4 receptor deficiency: The AVNM antibiotic cocktail has been established as an effective method of depleting the gut microbiome and — in contrast to germ-free mice, which can develop metabolic problems that can lead to obesity (43) — seemed less likely to confound the essential role of OAT1 in kidney aerobic metabolism (31, 44) and the tendency to hepatic steatosis seen in approximately 24 month old Oat1-KO mice (16).