Fatty acids of plant origin in diets fed to domestic cats accumulate in renal cytoplasmic lipid droplets and are pre-oxidative.

Background unpublished evidence: Domestic felines, even young animals, have a preponderance of cytoplasmic fatty droplets of unknown origin or cause in their kidneys. Dogs and wildcats are largely free from such ectopic deposits, as are humans, particularly in their kidneys. Such a finding in relatively young animals is highly unusual. I propose that domestic cats are inherently susceptible to such ectopic lipid because a) they are obligate carnivores and b) unused to inadvertently consuming fats of plant origin in their diets. The latter implies that such renal lipids are found to a greater extent in cats consuming commercial diet as oppose to a wild or natural diet. Preliminary evidence by the PI confirms this to be the case. Since more than half of companion animals in the UK only eat what their owners give them on a daily basis, as either wet pet foods such as tins or pouches, or pelleted dry food and brand loyalty and personal preference often means the same product is fed exclusively for long periods of time (months to years), it is incumbent upon pet food manufacturers to produce a nutritionally-balanced, 'complete' product that meets all the nutritional requirements of our dogs or cats, but for cats, without any oils of plant origin.

To date, using a combination of lipidomic techniques (thin-layer chromatography, GC-MS, ESI-MS/MS) in n=10 cats/dogs/wildcats the investigators and found that lipid droplets in domestic cats contain a high concentration of saturated fatty acids that are often found in plants such as C12:0 (lauric acid; coconut oils), C14:0 (myristic acid; palm oils) and C16:0 (palmitic acid; palm kernel oil), that were not present in dogs or wildcats. The likely source of these plant oils, therefore, is commercial diets where these cheaper oils often replace higher quality, more expensive fats such as omega-3 FA (n3 series). Hence, domestic cat likely treats these fats as toxins, to be excreted via the liver and the kidney. However, cats have long lost the capability to de-toxify many toxins, since they were never present in ancestral diet. Cats lack many desaturases and cyp450 enzymes in liver and kidney (prelim RNAseq unpublished data [n=3 cats vs n=3 dogs]). Thus, accumulation of such fats in liver and kidney is likely to be pro-oxidative, gradually initiating a condition of chronic interstitial fibrosis/necrosis (CIN) over time. CIN is the predominant non-infectious, non-cancerous cause of poor health in older domestic cats. This project will therefore investigate the following research questions:

Research questions to be addressed:
1) further characterise the lipidome of renal cytoplasmic lipid droplets in cats
2) identify the source of the predominant fatty acids e.g. types of diet
3) compare and contrast the profile with other obligate carnivores such as ferret