The researchers from the University College Cork and the Teagasc Food Research Centre in Cork, Ireland compared two groups of mice over an eight-week period, splitting them between those given a form of conjugated linoleic acid, t10c12-CLA, as part of a standard diet and those given the standard diet alone.
Metabolic markers like serum glucose, leptin, insulin and triglyceride (TAG) and liver TAG were measured, as was the microbial composition of the mice.
Conjugated linoleic acid (CLA) is a class of linoleic acid isomers occurring naturally in dairy products and some meat. T10c12-CLA has been shown to be the specific isomer responsible for the anti-obesity effect attributed to CLA. Yet these positive effects have also been shown to be accompanied by adverse effects such as hepatic steatosis - or 'fatty liver' - and hyperinsulinaemia.
The results, published in the British Journal of Nutrition, showed the supplemented mice had significantly decreased visceral (or abdominal) fat mass but body weight was not affected, when compared to the control group.
Analysis of the microbiota composition after eight weeks showed the linoleic acid group had lower proportions of Firmicutes and higher proportions of Bacteroidetes compared to the control.
The supplemented group also had altered gut microbiota composition, harbouring higher proportions of Bacteroidetes including Porphyromonadaceae, bacteria previously linked to negative effects on lipid metabolism and induction of hepatic steatosis.
They said these results suggested that the role of dietary t10c12-CLA on lipid metabolism in mice may be at least “partially mediated” by changes to gut microbiota composition and functionality.
“Dietary approaches targeting beneficial bacteria and suppressing harmful species may be a new strategy to prevent or treat hepatic steatosis and associated metabolic disorders.
“The use of fatty acid mixtures with equal proportions of conjugated linoleic acid isomers, or the use of probiotics and prebiotics to balance the potentially negative effects of t10c12-CLA on the microbiota composition may be alternatives for individuals seeking anti-obesity dietary solutions,” the researchers concluded.
They said more research on the role of CLA in non-prescription diet pills was needed since data on the effects of CLA in human subjects has so far been contradictory. The researchers said some studies however had shown that purified isomers instead of CLA mixtures had a detrimental influence.
"In most studies using mice, body fat reduction induced by t10c12-CLA supplementation is accompanied by adverse effects such as hepatic steatosis and hyperinsulinaemia," they wrote.
Source:British Journal of Nutrition
Publish online ahead of print, doi:10.1017/S000711451400350X
“Dietary trans-10, cis-12-conjugated linoleic acid alters fatty acid metabolism and microbiota composition in mice”
Authors: T. M. Marques, R. Wall, O. O'Sullivan, G. F. Fitzgerald, F. Shanahan, E. M. Quigley, P. D. Cotter, J. F. Cryan, T. G. Dinan, R. Paul Ross and C. Stanton