Can DHA fight insulin resistance in muscles?

Muscle and exercise: can DHA fight insulin resistance?

Supplementation withomega 3 DHA (docosahexaenoic acid) helps counteract poor insulin sensitivity in skeletal muscle by blocking inflammation and lipotoxicity.

This was discovered by a team of researchers from INRA, the French National Institute of Agronomic Research, and published in The Journal of Nutritional Biochemistry.

Insulin resistance: a risk factor for type 2 diabetes 

Insulin resistance is a clinical condition characterized by the need to use higher-than-normal amounts of insulin to maintain blood glucose within normal levels because the body's cells decrease their sensitivity to the action of the hormone. If the insulin response is inadequate for the demand, a hyperglycemic state is established that can last for years and evolve into type 2 diabetes mellitus. Skeletal muscle plays an important role in controlling glucose disposal in response to insulin stimuli. Excessive intake of fatty acids triggers cellular and molecular mechanisms in muscles that lead to inflammation, mitochondrial dysfunction, impaired insulin response, decreased glucose uptake, and lipotoxicity, i.e., the damaging effects caused by the body's continuous exposure to high levels of fatty acids in the blood.

DHA reduces the effects of palmitate 

The researchers, to test the impact of DHA on inflammation, lipotoxicity, and its possible use as a preventive nutritional strategy, used both in vitro and in vivo tests. C2C12 myotubes, a mouse cell line that serves as a model to mimic muscle, were exposed to high doses of palmitic acid (a saturated fatty acid), the same thing was done on muscles of laboratory animals that had taken nutritional supplements of DHA in different doses. 

The results showed that 30 micromoles of DHA was able to prevent insulin resistance in C2C12 myotubes exposed to 50 micromoles of palmitic acid by decreasing the activity of an enzyme known as protein kinase C theta and restoring glucose uptake. In addition, DHA appeared to have protected the myotubes from the increase in signal molecules of palmitic acid-induced inflammation, including IL-6 and TNF-alpha, probably through inhibition of specific enzymes. In addition to the anti-inflammatory actions, the benefits appear to be due to the ability that DHA has on the impairment of mitochondrial fatty acid oxidation caused by palmitic acid. 

An in vivo study was also performed in mice fed a diet rich in sucrose, cholesterol, and nutritional doses of DHA. This intervention resulted in a significant reduction in plasma triglycerides and prevented the progression of atherosclerosis.

In vivo and in vitro studies confirm the protective action of DHA

According to INRA researchers, the in vitro and in vivo results suggest that DHA used at physiological doses may play a role in lipid and glucose regulation in muscle metabolism, preventing lipotoxicity and inflammation. Although further studies will need to be performed in skeletal muscle of humans undergoing supplementation, the results, as reported by the scientists, suggest that DHA supplements could be an effective strategy against metabolic disorders in muscle. To stay up to date with the latest news from Omega-3 scientific research, subscribe to our newsletter. 

Source: F. Capel, et al. "DHA at nutritional doses restores insulin sensitivity in skeletal muscle by preventing lipotoxicity and inflammation" The Journal of Nutritional Biochemistry.Published online ahead of print, doi: 10.1016/j.jnutbio.2015.04.003