[Conjugated linoleic acids (CLA) and their relevance in the reduction of body fat. A critical review of the currently available data]. / Konjugierte Linolsäuren (CLA) und ihre Bedeutung für die Reduktion des Körperfetts. Eine kritische Betrachtung der momentanen Datenlage.

Various experiments on animals have shown that conjugated linoleic acids (CLA) supposedly have numerous positive effects on health including reducing body fat. Although previous studies on humans did not lead to consistent results, the popularity of CLA as a weight loss product for overweight people and as a muscle-building substance for athletes is increasing. Numerous internet providers or drugstores market CLA supplements or CLA-containing products. This article presents background information on the occurrence and biological effect of CLA and provides an up-to-date summary of studies on human subjects. Finally, whether supplementation with CLA for the reduction of body fat is useful will be evaluated.

Conjugated linoleic acids promote human fat cell apoptosis.

Conjugated linoleic acids (CLAs) are conjugated dienoic isomers of linoleic acid. Some isomers have been shown to reduce fat mass in animal and cell culture models. However, controversial results were obtained in studies of supplementation of CLAs in human subjects. In order to get more insights into the direct effects of CLAs on human fat cells, we have studied the influence of cis-9, trans-11 CLA and trans-10, cis-12 CLA on the biology of human SGBS preadipocytes and adipocytes. Both CLA isomers equally inhibited the proliferation of preadipocytes in a dose-dependent manner. Continuous treatment with 1-10 microM trans-10, cis-12 CLA, and to a weaker extent cis-9, trans-11 CLA, inhibited accumulation of lipids during adipogenic differentiation. Treatment with higher doses of CLA induced apoptosis in preadipocytes, in differentiating cells, and adipocytes. The trans-10, cis-12 isomer had a higher apoptotic potency in adipocytes than cis-9, trans-11 CLA. Taken together, the treatment of human preadipocytes and adipocytes with physiological relevant concentrations of CLAs resulted in an impairment of proliferation and differentiation and induction of apoptosis. The trans-10, cis-12 isomer was more potent than the cis-9, trans-11 isomer. Further clinical studies are needed to evaluate the effects of CLAs on human fat mass and metabolism in vivo.