Effects of a Feed Supplement Containing Fatty Acids and Chromium on Insulin Sensitivity in Old Mares: A Preliminary Study

Abstract

s / Journal of Equine Veterinary Science 31 (2011) 230-356 252 Effects of a Feed Supplement Containing Fatty Acids and Chromium on Insulin Sensitivity in Old Mares: A Preliminary Study S. Otabachian , T. Hembrooke , E.M. Carnevale , and T.M. Hess 1 1 Colorado State University, Fort Collins, CO, USA, 2 Platinum Performance Inc. , Buellton, CA, USA Introduction: Older horses are prone to developing decreased insulin sensitivity (SI) due to an increase in fat accumulation and a decrease in physical activity [1]. Studies show a relationship between obesity and inflammation with reduced SI in horses [2,3]. An increased inflammatory status in older horses is thought to be a possible cause of pituitary pars intermedia dysfunction (PPID) which predisposes horses to laminitis and insulin resistance [4]. Polyunsaturated fatty acids (PUFA) such as n-3 a-linolenic acid (ALA) are absorbed and incorporated into cell membranes. In rat and human studies PUFAs change fatty acid composition of phospholipids surrounding insulin receptors found in muscle [5,6] and reduce inflammation when incorporated into white blood cells [7]. Chromium has been found to be beneficial in diabetic experimental animals and also in conditions resulting from insulin sensitivity and defects in glucose transportation [8]. The objectives of this study were: to investigate the effects of a fatty acid supplement containing a-linoleic acid and chromium yeast in old mares (ages 16-27 years) on insulin sensitivity and inflammatory markers. Materials and Methods: Mares (n 1⁄4 14; mean 21 .6 years) were supplemented for 9 months with 190 g per day of Equine Platinum Plus Metabolic Support (EPPMS): a fatty-acid formula from Platinum Performance containing ALA with an addition of Chromium Yeast and other minerals and vitamins. Mares were fed an average 1.5 kg of a commercial concentrate (Nutrena Safe Choice ) and 7.2 kg of mixed alfalfa and grass hay divided in 2 feedings. Mares served as their own controls and were fed the same diet throughout treatment. Mares stayed at the Colorado State University Equine Reproductive Laboratory (ERL) in a nonpregnant reproductive status. In July of 2009, after 30 days of acclimation to diet and environment at the ERL, fasting blood was collected (ten hours post-feed), mares were weighed, and treatment began. At the end of the summer the horses were returned and continued treatment at the direction of the owners. Mares were maintained in a similar daily routine experienced at the ERL meaning two feedings per day, a stall with a run, and no work. In February 2010 mares returned to the ERL and in May, fasting blood samples were collected. Blood was transferred into collection tubes, centrifuged and serum maintained at -20Â C for later analysis. PAXgene Blood RNA Tubes (Â 2010 PreAnalytix GmbH) were refrigerated at 4 C for two hours post collection and then maintained in 20 C until time of RNA isolation to assess gene expression. Plasma glucose was analyzed by an enzymatic assay; insulin and cortisol analyzed by radioimmunoassay; and endogenous ACTH was analyzed using Siemens Immulite 1000 Chemiluminescence technology. Basal proxies were calculated [9] and horses were classified into two groups: metabolic (RISQUI .29). Treatments were evaluated by ANOVA, with horses nested with metabolic as a random variable and treatment and metabolic as main factors. Significant results were analyzed by the least square means analysis. Results and Discussion: Mares treated with EPPMS had lower (P < .01) plasma glucose (91.2 2.10 mg/dL) insulin (9.6 1.0 I1⁄4U/mL) concentrations, as well as lower (P < .04) beta pancreatic response (MIRG 1⁄4 4.9 .37), compared to before treatment (98.0 1.9 mg/dL glucose; 13.8 .9 I1⁄4U/mL insulin; MIRG 1⁄4 5.9 .33). Insulin sensitivity as measured by RISQUI as well as weights were higher (P < .03) after treatment (RISQUI 1⁄4 .40 .04; 498.7 10.6 kg) compared to pretreatment (.27 .03; 472.7 10.2 kg). Cortisol levels trended lower (P < .09) in treated mares (109.5 10.7 nmol/L) compared to non-treated mares (130.3 9.8 nmol/L). Inflammatory cytokines were not significantly affected by treatment. Vitamins, minerals and amino acids were present in the supplement, but effects on insulin sensitivity are inconclusive. Conclusion: Although mares treated with EPPMS showed improved insulin sensitivity in the first sample post treatment, a control group of similar breed, age, and body conditionwould be necessary to confirm results. Although body weight was evaluated, fat composition was not accessed in the initial sampling so changes are unknown.