The study, published in the Journal of Agricultural and Food Chemistry, reports that blood plasma glucose, insulin, and lipid concentrations are enhanced, whilst insulin sensitivity is improved in mice fed a diet rich in marine derived long-chain monounsaturated fatty acids (MUFAs).
“This study demonstrates that fish-oil-derived MUFA ingestion reduces insulin resistance, as judged by the insulin tolerance test, and attenuates metabolic syndrome by improving hyperglycemia, hyperinsulinemia, and hyperlipidemia,” wrote the study authors, led by Zhi-Hong Yang, from the Tokyo Innovation Center, Japan.
“Furthermore, intake of MUFA decreased obesity-induced inflammation by suppressing … inflammatory marker genes and arachidonic acid levels, thereby possibly, in turn, reducing insulin resistance in diet-induced obese mice,” they added.
Yang and his colleagues explained that previous research has suggested that diets rich in short chain monounsaturated fatty acids are effective in improving insulin sensitivity, leading to improvements in lipid profile, whole body inflammation, and endothelial dysfunction.
“In comparison to the well-studied shorter chain MUFA, there is little documented information on the physiological effects of long-chain MUFA,” they said.
The researchers noted that “consistently high levels of MUFA” with longer aliphatic tails (long chains of over 18 carbon) are found in some fish species, including saury, capelin, sprats, and herring. They explained that their new study determined the effects of a diet rich in fish-oil-derived long chain MUFAs on metabolic disorders and biomarkers in mice.
The researchers prepared a MUFA concentrate, found to be rich in long chain MUFAs, from saury fish oil (obtained from Nippon Suisan Kaisha, Ltd, Japan). They explained that ten male mice were then fed either a 32 per cent lard diet (control), or a 27 per cent lard plus 5 per cent saury-oil-derived MUFA concentrate diet for 6 weeks.
Fatty acid composition analysis revealed that plasma and organ omega-6 PUFA levels decreased ‘remarkably’ when mice were fed the long chain MUFA diet.
The authors speculated that this “may partly contribute to the improvement in systemic inflammation and the further alleviation of metabolic syndrome.”
MUFA intake also dramatically increased levels of long-chain MUFA C20:1 isomers and C22:1 n-11 in plasma, fat tissue, and liver.
“Intriguingly, the percentages of liver EPA and DHA were [also] significantly increased in the mice fed the MUFA diet, although the amounts of these n-3 PUFA were very low in the MUFA concentrate,” said Yang and colleagues.
The authors concluded that increased dietary intake of long chain monounsaturated fatty acids may positively correlate with improved fat tissue metabolism and decreased fat tissue inflammation, “thereby attenuating metabolic syndrome risk factors.”
Source: Journal of Agricultural and Food Chemistry
Published online ahead of print, doi: 10.1021/jf201496h
“Beneficial Effects of Dietary Fish-Oil-Derived Monounsaturated Fatty Acids on Metabolic Syndrome Risk Factors and Insulin Resistance in Mice”
Authors: Z-H Yang, H. Miyahara, T. Mori, N. Doisaki, A. Hatanaka