Feeding Healthy Beagles Medium-Chain Triglycerides, Fish Oil, and Carnitine Offsets Age-Related Changes in Serum Fatty Acids and Carnitine Metabolites

Abstract

The purpose of this study was to determine if feeding dogs medium-chain triglycerides (MCT), fish oil, and L-carnitine enriched foods offsets age-associated changes in serum fatty acids (FA) and carnitine metabolites. Forty-one healthy Beagles, mean age 9.9 years (range 3.1 to 14.8), were fed control or one of two treatment foods for 6 months. All foods were complete and balanced and met the nutrient requirements for adult dogs, and had similar concentrations of moisture, protein, and fat (approx. 7.4%, 14.0%, and 18.1%, respectively). The treatment diets both contained added L-carnitine (300 mg/kg) and 0.6% (treatment food 1) or 1.5% (treatment food 2) added fish oil. Treatment food 2 also had increased MCT from coconut oil, added corn oil, and reduced animal fat. Composition of serum FA was determined by gas chromatography of FA methyl esters. Metabolomic profiles of serum samples were determined from extracted supernatants that were split and run on GC/MS and LC/MS/MS platforms, for identification and relative quantification of small metabolites. Body composition was determined by dual energy x-ray absorptiometry. Among dog groups, there was no change in total-lean-body weight, or in serum total protein and serum albumin concentrations, based on time or dietary treatment. Serum concentrations of carnitine metabolites were decreased in geriatric (>7 years) vs. mature adult (≤7 years) dogs, and supplementation with L-carnitine attenuated the effects of aging. The ratio of PUFA to SFA was significantly greater in mature dogs at baseline (P≤0.05). Serum concentrations of eicosapentaenoic and docosahexaenoic FA increased in a dose-dependent manner. Dogs consuming treatment food 2 also had increased serum concentrations of lauric and myristic FA, and decreased concentrations of SFA, MUFA, and arachidonate (all P≤0.05) and their PUFA to SFA ratio increased. In summary, dietary MCT, fish oil, and L-carnitine counterbalanced the effects of aging on circulating concentrations of these compounds.

Letter to Editor

“…There was no effect of formula and no interaction between formula and time on test. Along with our original study,2 this new study7 supports that changes in serum phosphorus concentrations in the reference range are not the best indicator of changes in GFR, and serum phosphorus did not move in the same direction as SDMA with a change in GFR. In the current study,2 we did not speculate on the significance of the increase in serum phosphorus concentration, other than to say it was biologically insignificant as it remained within the reference interval throughout.…”

“…German, Batchelor, and Murtagh regarding our paper in JVIM on the “Relationship between lean body mass and serum renal biomarkers in healthy dogs” especially with regard to symmetric dimethylarginine (SDMA), a new serum renal biomarker for assessing glomerular filtration rate (GFR) 1. They also reviewed another paper published in PLoS One entitled “Feeding healthy Beagles medium‐chain trigylcerides, fish oil, and cartinine offsets age‐related changes in serum fatty acids and carnitine metabolites.”2 We appreciate the choice of papers to review during hospital rounds and in particular their interest in this exciting new biomarker.…”

“…The purpose of the original study2 was to determine if dogs consuming a complete and balanced adult‐food formula with added L‐carnitine, medium‐chain triglycerides (MCT), and (n‐3) FA from fish oil were able to maintain total‐lean‐body weight, total serum protein and albumin concentrations, and achieve desired alterations in serum FA profiles and carnitine metabolite concentrations. We were able to document age‐related changes in the PUFA to SFA ratio and in carnitine metabolite concentrations that could be counterbalanced by dietary enrichment with these compounds.…”

Letter to Editor

“…As a result, we enjoyed reviewing the paper, and it certainly stimulated discussion among colleagues. Since this work was a retrospective analysis of samples collected from a previous study,2 we were also prompted to read the original paper concurrently.…”

“…Therefore, we wish to make some observations on both papers, which we hope will be of value to readers of Journal of Veterinary Internal Medicine , and would very much welcome the thoughts of the authors on these matters. For the sake of clarity, we will use the term “original study” for the PLOS ONE paper,2 and “SDMA study” for the Journal of Veterinary Internal Medicine paper 1…”