Why Felids Are Prone to Chronic Kidney Disease: Micronutrient Cycling, Lipid Biology, and Water Conservation

The prevalence of chronic kidney disease (CKD) in aging felids is three- to four-fold higher than in other mammals, including humans. Regardless of species, serum and urinary biomarkers of CKD become effective only when little can be done to reverse progression. We propose that felids, as super water conservers and obligate hyper-carnivores, are naturally prone to form cytoplasmic lipid droplets (LDs) in their kidney cells, which predisposes felids to age-associated CKD. Furthermore, we offer a novel mechanistic basis for renal LD formation in felids. Presence of LDs in felid urine—lipuria, which is uncommon in all other mammals—could be the earliest biomarker of metabolic events in kidney cells that underpin CKD. Felids have unique anatomical, physiological, nutritional, and metabolic features, including synthesis and subsequent excretion of felinine together with branched-chain fatty acids into urine. These features offer a unique opportunity for early intervention but also are of interest in the context of comparative biology, nephrology, and renal disease.