Control of lipid structuring by trans- and cis-fatty acids 

Figure 1. The effect of temperature on the structure of a system consisting of monoelaidin and oleic acid in the presence of excess water. The monoelaidin/oleic acid weight ratio was fixed. (A) The contour x ray diffraction plot displays the occurrence of different interesting structures: non-viscous and viscous liquid crystals (gel-like samples), (B) the structural analysis (the unit cell parameters as a function of temperature) are presented (H 2: inverse hexagonal phase, Fd3m: cubic inverse micellar phase, and L 2: isotropic inverse micellar phase).

Figure 2. Temperature-dependence behavior of monoelaidin at different loaded amounts of oleic (A) and elaidic acids (B) in the presence of excess water. The dashed/dotted curves indicate the approximate boundaries between the different structures.

Oleic and elaidic acids are the two most abundant fatty acids in food products and vegetable oils. Synchrotron high resolution Small and Wide Angle X ray Scattering (SAXS/WAXS) investigations were performed to study their influence on a monoglyceride membrane structure. Exploring the effect of these two fatty acids on biological membrane structures is of great interest due to the implications of their daily consumption in vital biological processes related to health and disease, and their role in designing gel-like formulations for controlling the release of drugs or functional foods.

The traditional Mediterranean diet supplemented with olive oil is associated with beneficial health effects. In European countries such as Greece and Italy and in the Middle East the intake of olive oil is high and is linked in different regions to a relatively reduced blood pressure and a reduced risk of developing coronary heart disease, a reduced breast cancer, and a low level of plasma cholesterol. Various studies suggested that the consumption of olive oil, which is rich in oleic acid (monounsaturated fatty acid with the natural cis configuration), is strongly associated with positive health effects. This explains the interest in recent years in introducing to the market oleic acid-rich foods and producing synthetic oleic acid derivatives that can be used as antitumoral and antihypertensive drugs. The past decade has witnessed a tremendous interest in understanding why the consumption of oleic acid-rich diet is important to our health and wellness.

In contrast to the traditional Mediterranean diet, different industrial food products in the market are rich with trans fatty acids (unsaturated fatty acids with the non-natural trans configuration), which are produced during the well-known process of partial hydrogenation of unsaturated oils in food industry, and their dietary is associated with various negative health effects including an increased risk of coronary heart disease and cancer, and increase in body weight. This explains the growing interest in introducing to the market new food products with low and even zero trans fatty acids content. A first positive trend has been set by the food industry, e.g., in the UK, where according the latest National Diet and Nutrition Survey (2011) the trans fatty acids are now only found at low levels in foods indicating that average trans fats intake was less than 2 gr. per day for all age groups, which falls below the maximum WHO recommendations.

In this study, synchrotron SAXS was applied for studying the effect of two of the most abundant fatty acids in cis (oleic acid) and trans (elaidic acid) fat dietary intake on the structure at the nanoscale level of monoglycerides, which are unique lipids displaying a rich variety of structures at different water content and temperatures. The monoglycerides are ingredients in different food products and are interesting as they form biologically relevant intermediates during fat digestion and metabolism. Noteworthy, the difference in the molecular shape of the investigated fatty acids (elaidic acid has a rod-like molecular structure; whereas oleic acid has a more cone-like shape) has a significant impact on the lipid structuring. The experimental findings show that both fatty acids lead to a variety of diverse structures when mixed with the monoglyceride monoelaidin in the presence of excess water (monoelaidin is a lipid derived from elaidic acid). The phase transition boundaries and stability can be easily controlled by the amount of the added fatty acid and by changing the temperature. Clearly, oleic acid due to its cone-like molecular structure induces stronger interfacial membrane curvature as compared to elaidic acid, and provides the membrane with a higher flexibility. Our results are in a good agreement with previous studies suggesting that oleic acid is more efficient than elaidic acid in modifying the properties of lipid membranes. For instance, it was suggested that the reduction in the blood pressure is linked to the membrane structure that can be modified by oleic acid to regulate the biological activity.

Fig. 1 shows an example on the effect of oleic acid on controlling the nanostructure of monoelaidin in the presence of excess water. The effect of adjusting the loaded amounts of oleic and elaidic acids on the temperature-dependent structural behaviour of monoelaidin in the presence of excess water is illustrated in Fig. 2. It is fascinating to obtain these unique tuneable structures by rather simple means and to highlight the role of oleic and elaidic acids on model membrane structuring.

Retrieve article

Control of lipid structuring by trans- and cis-fatty acids;
A. Yaghmur, B. Sartori and M. Rappolt,
Langmuir 28, 10105 (2012).
doi: 10.1021/la3019716

Last Updated on Tuesday, 14 May 2019 17:05