Differential effect of butyrate on lipids of human colon cancer cells

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Abstract
Recently, we demonstrated that treatment of LS174T cells with 2 mM butyrate for one day had a significant effect on the composition of cellular fatty acids. In an attempt to further explore this phenomenon, we investigated the effect of long‐term butyrate treatment in the presence of different fatty acids in the medium on cellular phospholipids (PLs) and triacylglycerol (TG). Cells were supplemented with 100 μM sodium salts of 18:2 (n‐6), 20:4 (n‐6), 20:5 (n‐3), or 22:6 (n‐3) as a fatty acid‐free‐albumin complex. The molar ratio of the albumin and these long‐chain fatty acids (LCFAs) was 3:1. One‐half of these cultures were supplied with 2 mM butyrate, and the pH was adjusted to 7.4. The supplementation of the LCFAs and butyrate was maintained for eight days. The present study indicates that butyrate had a differential effect on the fatty acid composition of PLs and TG of LS174T cells. This includes an increase in monounsaturates and elongation of the supplemented LCFA, and this effect was more pronounced on TG than PL fatty acids. Butyrate resulted in a significant reduction in polyunsaturated fatty acid concentration only in PLs. In general, butyrate decreased the unsaturation index (UI) of the PLs but increased that of TG. The present study also confirmed our previous observation regarding the effect of LCFAs on cellular lipids. PL and TG fatty acid chain lengths reflect those of supplemented fatty acids. The UI of these two lipid fractions increased more with supplementation of n‐3 than n‐6 fatty acids. TG fatty acids are more reflective of the ability of LS174T cells to elongate, retroconvert, and incorporate the supplemented LCFAs than PLs. It is concluded that butyrate, which is produced mainly in the large intestinal tract as a result of fermentation of dietary fibers, could have a differential effect on the utilization of the LCFAs in the colon. The significance of this effect in cellular function of human tumor cells is currently being investigated.