Omega-3 Fatty Acids & Insulin Response

Obesity in horses or ponies affects up to half of the worlds population, and often this is linked to insulin dysregulation and an increased risk of developing Equine Metabolic Syndrome (EMS) or laminitis. Insulin dysregulation describes horses or ponies who metabolise insulin abnormally or in excess to ''normal'' physiological processes, such as eating.

Insulin is a hormone that plays an important role in regulating how the body utilises and stores glucose and fat. Produced by the pancreas, insulin acts as a mechanism for allowing glucose to be used as an energy source by the body and consequently lower blood glucose levels, whilst excess glucose not required for energy will be stored as fat. An increase in fat cells increases the likelihood of problems occurring, as hormones produced by these fat cells inhibit insulin from performing it's role and consequently increasing blood sugar levels. Prolonged glucose and insulin levels negatively effect the horses health, and while the mechanism is not yet clear, the risk of laminitis developing will increase.

Omega-3 Fatty Acids

Fatty acids are used as an energy source and are important functional components of cells. Essential fatty acids include omega-3 and omega-6 fatty acids, and must be consumed in a feed source as the horse cannot produce them themselves. Omega-3 fatty acids include alpha-linolenic acid (ALA), docosahexaenoic acid (DHA), and eicosapentaenoic acid (EPA). One of the most recognized benefits of Omega-3 fatty acids are their anti-inflammatory properties, as EPA inhibits activity of the enzyme cyclooxygenase, which plays a role in symptoms of inflammation and pain. However, additional research has found that omega-3 fatty acids may also play a role in reducing inflammatory cytokine production, improving glucose clearance and insulin sensitivity on horses and ponies with insulin dysregulation.

The RESEARCH

A study by Kentucky Equine Research (Pagan et al 2012) gave 4 aged, non-obese Thoroughbred geldings either oats + 60g corn oil, oats + 60g fish oil, soya oil + 60g corn oil or soya oil + 60g fish oil for 4 wk period. Plasma samples were tested for triglycerides, insulin and glucose. The research found that fish oil significantly affected glucose clearance in the high fat, soya oil+ corn oil diet but had no effect on glucose clearance in the moderate carbohydrate diet. Glucose clearance in the soya oil + fish oil diet was not significantly different to either the fish oil or corn oil diets. For aged horses on high fat diet (>500g/d of oil per day) fish oil supplementation would be advisable to assist glucose clearance.

In another study by Colorado State University (Hess et al 2013) tested marine-derived Omega-3 supplementation and linseed meal supplementation against a control in 21 mares for 90 days. Blood sample testing was performed at day 0, 30, 60 and 90. Disposition index (combined SI and β pancreatic response) increased in treatment groups, most so in the marine-derived O3 group whilst the control group saw no changes. In treated groups the insulin dysregulated mares all showed an increase in insulin sensitivity.

A review on studies in human obesity (Simpoulous 2016) revealed that the intake of Omega-6 increased and the Omega-3 decreased. This change in the composition of fatty acids parallels a significant increase in the prevalence of overweight and obesity in humans. In both humans and mammals, the increased Omega-6 to Omega-3 ratio plays an role in increasing the development of obesity via both AA eicosanoid metabolites and hyperactivity of the cannabinoid system, which can be reversed with increased intake of EPA and DHA. A balanced Omega-6: Omega-3 ratio is therefore important for health and in the prevention and management of obesity.

A systematic review and meta analysis of the link between fish oil supplementation and insulin sensitivity showed that it had a positive effect in humans with metabolic disorders (Gao et al 2017). In a pooled analysis, fish oil supplementation had no effects on insulin sensitivity compared with the placebo, but in a subgroup analysis, fish oil increased insulin sensitivity among people who were experiencing at least one symptom of metabolic disorders (p < 0.001).

Finally, In a pilot study, 10 mixed-sex and breed mixed-breed horses with EMS were fed a DHA-rich microalgae containing 16 g DHA/horse/day or served as controls for 46 days. Post-supplementation, treated horses had an increase in many circulating fatty acids, including DHA (P <.001). Treated horses also had lower serum triglycerides post-supplementation (P =.02) and a trend for reduced PBMC tumour necrosis factor (TNF). Lamintis prone ponies have higher TNF-serum levels, which activate and recruit inflammatory cells, further increasing the risk of respiratory disease, poor wound healing, skin complaints and osteoarthritis. Control horses had an increase in insulin responses to the OST (P <.01), whereas treated horses did not. These pilot data indicate that DHA supplementation alters circulating fatty acids, modulates metabolic parameters, and may reduce inflammation in horses with EMS.