Effect of docosahexaenoic acid on mouse mitochondrial membrane properties

Abstract

Long-chain polyunsaturated (n-3) fatty acids have been proposed to be involved in a wide variety of biological activities. In this study, mitochondrial docosahexaenoic acid (DHA) levels were increased by either dietary manipulation or by fusing the mitochondria with phospholipid vesicles made from 1-stearoyl-2-docosahexaenoyl-sn-glycero-3-phosphocholine (18:0/22:6 PC). The fused mitochondria exhibited a DHA-induced decrease in respiratory control index (RCI) and membrane potential and an increase in proton movement. The modified mitochondria also demonstrated an increase in fluidity (as detected by 1,6-diphenyl-1,3,5-hexatriene anisotropy) and changes in membrane structure detected by the fluorescence probes MC540 and pyrene decanoate. Proton movement in lipid vesicles made from mitochondrial lipid extracts was shown to be enhanced by incorporated 18:0/22:6 PC. Mitochondria were isolated from young (5-mon) and old (24-mon) mice which were maintained on either a diet rich in saturated fats (hydrogenated coconut oil) or rich in n-3 polyunsaturated fats (menhaden oil). Mitochondrial bioenergetic function was followed by RCI, state 3 respiration, ATP level, and phosphate uptake. In addition, lipid composition, phospholipid area/molecule and extent of lipid peroxidation were also determined. Decreases in RCI for the menhaden oil diet-modified mitochondria paralleled those in which DHA levels were enhanced by fusion with phospholipid vesicles. RCI reductions are attributed to DHA-induced increases in H+ movement, producing diminished mitochondrial membrane potentials. One purpose of this project was to determine if the deleterious effects of aging on mitochondrial bioenergetic function could be reversed by addition of n-3 fatty acids. The experiments reported here indicate that incorporation of long-chain polyunsaturated n-3 fatty acids into mitochondrial membranes does not appear likely to reverse the effects of age on mitochondrial function.

Docosahexaenoic acid affects cell signaling by altering lipid rafts

“…For example, Treen et al [64] were unable to see a difference in "fluidity" (fluorescence polarization of DPH and TMA-DPH) with intact Y-79 retinoblastoma cells cultured in DHA-enriched media despite observing a 4 to 5 fold increase in cellular DHA levels. Employing a different fluorescence method, several reports have indicated DHA does increase "fluidity" as assayed by probes sensing lateral mobility [60,64,65]. These observations are consistent with the hypothesis that DHA may play a major role in membrane lateral domain structure (discussed below).…”

“…In agreement, fluorescence measurements on lipid bilayers confirmed that water content in the bilayer hydrocarbon region increases with double bond content [53]. Increases in mitochondrial permeability have also been linked to DHA content [65,81]. The resultant proton leakage in turn decimates the essential trans-membrane H + gradients, an event linked to mitochondrial-linked apoptosis [82] (see below).…”

“…Ahkong et al [83] and later Meers et al [84] showed that PUFA promote the fusion of natural membranes. In a series of studies Stillwell and Jenski have fused DHA-containing phospholipid vesicles with several types of membranes and monitored the effect of fusion-augmented DHA levels on bilayer membrane [85], mitochondria [65] and T27A cell properties [3,[86][87][88][89]. DHA as either the free fatty acid or as part of a mixed chain PC (18:0-22:6PC) enhanced SUV fusion to a much larger extent than did PCs with other, less unsaturated fatty acids [85].…”

Clofibrate-Induced Relocation of Phosphatidylcholine Transfer Protein to Mitochondria in Endothelial Cells

“…It is conceivable that relocation of PC-TP to mitochondria increases the amount of 16:0/PUFA-PC species in the mitochondrial membranes. The ensuing increase of membrane fluidity is reported to generate a number of responses, such as the enhancement of membrane-associated phospholipase A 2 activity [43], proton leakage [44,45], and Ca 2ϩ efflux [46]. Furthermore, changes in phospholipid fatty acid composition can alter the activity of carnitine palmitoyltransferase I [47,48] and of the pyruvate carrier [49,50].…”

Setting the pace of life: membrane composition of flight muscle varies with metabolic rate of hovering orchid bees

“…More direct support for the hypothesis is provided by the experimental manipulation of membrane phospholipids, which shows that various mitochondrial properties, as well as the activity of Na þ -K þ -ATPase, are altered predictably through specific changes in FA composition [4,20,21]. The mechanisms responsible for activation of the membrane proteins remain unknown, but double bonds constrain rotation between carbons and cause kinks in the acyl chains.…”