Effect of CLA on the cellular lipids of Saccharomyces cerevisiae

Abstract

The yeast Saccharomyces cerevisiae was cultivated in the presence of free CLA that was either a pure trans-10,cis-12 isomer, a pure cis-9,trans-11 isomer, or a 1:1 mixture of the two, and the influence of these supplementations on the content and FA composition of the lipids in the yeast was determined. Neither the pure isomers nor their 1:1 mixture influenced the growth of the yeast, but the trans-10,cis-12 isomer reduced the amount of cellular lipids by 40%. The reduction in total cellular lipids by the trans-10,cis-12 CLA was due to a reduction in TAG. Both of the isomers were incorporated into the yeast lipids, reaching a proportion of about 33% in TAG. With the incorporation of CLA, the yeast reduced the amount and desaturation of endogenously synthesized FA. These clear and pronounced isomer-specific effects of CLA on the yeast suggest that yeast might be a useful model to obtain a more comprehensive view of the mechanisms of the action of CLA on lipid metabolism.Conjugated isomers of linoleic acid (CLA) have been reported to reduce adiposity in animals and humans (reviewed in Ref. 1), and trans-10,cis-12 CLA has been shown to be responsible for this antilipogenic effect. In particular, the amount of TAG has decreased when a diet containing trans-10,cis-12 CLA has been fed to test animals or humans. On the basis of numerous in vivo and in vitro studies, several hypotheses for this mechanism have emerged. The suggestions with the most support are modifications of the activity of enzymes essential in FA uptake and metabolism, increased energy expenditure, and decreased preadipocyte differentiation and proliferation (reviewed in Refs. 1 and 2). However, the exact mechanism of the fat or TAG reduction remains to be elucidated. Considering the effects of CLA isomers on mammalian metabolism, the results of studies carried out by different laboratories are somewhat conflicting. The effects of CLA on animal metabolism seem to be more or less isomer, dose, time, and species specific.The yeast Saccharomyces cerevisiae has been a useful model to understand the synthesis of eukaryotic TAG and its role in various cell processes (3). During growth, S. cerevisiae is able to incorporate free long-chain FA from the culture medium and accumulate them without modification in TAG and, as a result, the cellular lipid content is increased (4). Therefore, the FA composition of TAG resembles the FA composition of the growth environment of the yeast. TAG are used as an energy reserves and sources of FA for the synthesis of membrane phospholipids (5,6). All the acquired FA are not necessarily suitable for use in membrane synthesis. Thus, the third function of TAG is to serve as a storage place for such FA (7).However, less is known about how the yeast lipids are affected when the culture medium is supplemented with CLA, which is known to inhibit the development of adipose tissue in mammals. Elucidation of the effects of CLA on yeast lipids could reveal the potential of yeast as a model organism in CLA studies. Therefore, a study was...

Thetrans-10,cis-12 conjugated linoleic acid increases triacylglycerol hydrolysis in yeastSaccharomyces cerevisiae

“…Previous studies have shown that the TAG content of the yeast cells cultivated in the presence of t 10 ,c 12 CLA isomer was remarkably lower compared to the control cells, whereas the c 9, t 11 isomer raised the TAG content (Jaakola et al . , ). Such results could be caused by two scenarios, firstly by affecting TAG biosynthesis and secondly by affecting TAG degradation.…”

“…It was previously observed that the total amount of C16:1 and C18:1 and their relative proportions were reduced also in yeast when supplied with the CLA isomers, especially by the t 10, c 12 isomer (Jaakola et al . ). This gave reason to hypothesize that diminished FA desaturation by t 10 ,c 12 CLA might lead to reduced TAG accumulation.…”

“…To separate the lipid classes by thin layer chromatography as described by Jaakola et al . (), the lipid sample was dissolved in 200 μ l of dichloromethane/methanol (100 : 1). Then 10 μ l of a lipid standard mixture consisting of heptadecanoic acid (Sigma‐Aldrich, Monsanto), triheptadecanoin (Sigma‐Aldrich) and dipentadecanyl‐ l ‐ α ‐phosphatidylcholine (Larodan) containing 4 g l −1 of each standard was added to the TAG samples before applying the samples to a silica plate (Kieselgel 60; Merck, München, Germany).…”

“…The fat reducing effect of t 10 ,c 12 CLA has been found and characterized also in Saccharomyces cerevisiae (Jaakola et al . , ). A conspicuous similarity between mammalian and yeast cells has been observed, as in the yeast t 10 ,c 12 CLA also caused a dramatic decrease in the triacylglycerol (TAG) content and reduced desaturation of fatty acids (FA).…”

Esterification of conjugated linoleic acid by yeasts for increasing the value of plant materials

“…Yeasts are known to take up free long-chain fatty acids from their environment and incorporate them in cellular TAG (Dyer et al, 2002;Guo et al, 1999;Papanikolaou et al, 2001;Jaakola et al, 2005). The ability of yeasts to take up endogenous fatty acids has been studied especially with Saccharomyces cerevisiae ja Yarrowia lipolytica in the presence of multiple carbon sources or fatty acids alone.…”