Linoleic acid, α-linolenic acid and enterolactone affect lipid oxidation and expression of lipid metabolism and antioxidant-related genes in hepatic tissue of dairy cows
Fortin, É., Blouin, R., Lapointe, J., Petit, H.V., Palin, M.F. (2017). Linoleic acid, α-linolenic acid and enterolactone affect lipid oxidation and expression of lipid metabolism and antioxidant-related genes in hepatic tissue of dairy cows, 117(9), 1199-1211. http://dx.doi.org/10.1017/S0007114517000976
Plain language summary
Linoleic acid, α-linolenic acid and enterolactone affect lipid oxidation and the expression of genes related to lipid metabolism in the livers of dairy cattle:
Although many beneficial effects are attributed to the use of linseed oil (rich in polyunsaturated fatty acids [PUFAs]) in dairy cattle, a diet rich in PUFAs can also increase oxidative stress in some tissues such as the liver. In this study, dairy cow livers were cut into very thin slices, which were cultured to study the effect of different ratios of omega-6/omega-3 fatty acids (PUFAs), with or without enterolactone, a powerful antioxidant from the hull of flaxseeds. Our results show that the addition of PUFAs increases oxidative damage to lipids in the liver. Moreover, the addition of PUFAs to liver cultures results in a decrease in the expression of genes related to lipid synthesis, which could be associated with a decrease in fatty liver problems in cows at the end of gestation and early lactation. Our team also observed that the addition of enterolactone prevents lipid damage caused by the addition of PUFAs.
These results clearly demonstrate that the addition of an antioxidant, such as enterolactone, would allow the benefits associated with PUFAs (e.g., decreased fatty liver) to be provided while minimizing lipid damage. Flaxseed is rich in both PUFAs and antioxidants (e.g., enterolactone), so using the whole seed as a dietary supplement would be more beneficial than flaxseed oil for the health of dairy cow’s livers.
Although beneficial effects have been attributed to PUFA supplementation in high-yielding dairy cows, diets rich in PUFA may also increase oxidative stress in tissues such as the liver. To fully exploit the health benefits of PUFA, we believe that the addition of natural antioxidants could help in preventing oxidative damage. Using an in vitro precision-cut liver slices (PCLS) tissue culture system, we investigated the effects of different linoleic acid (LA, n-6):α-linolenic acid (ALA, n-3) ratios (LA:ALA ratio of 4, LA:ALA ratio of 15 and LA:ALA ratio of 25) in the presence or absence of the antioxidant enterolactone (ENL) on (1) the mRNA abundance of genes with key roles in hepatic lipid metabolism, oxidative stress response and inflammatory processes, (2) oxidative damages to lipids and proteins and (3) superoxide dismutase activity in early-lactating dairy cows. The addition of LA and ALA to PCLS culture media increased oxidative damage to lipids as suggested by higher concentrations of thiobarbituric acid reactive substances and increased the expression of nuclear factor erythroid 2-related factor 2 target genes. The addition of ENL was effective in preventing lipid peroxidation caused by LA and ALA. Transcript abundance of sterol regulatory element-binding transcription factor 1 and its lipogenic target genes acetyl-CoA carboxylase α, fatty acid synthase (FASN) and stearoyl-CoA desaturase (SCD) was decreased with LA and ALA, whereas ENL decreased FASN and SCD gene expression. Our results show that addition of LA and ALA to PCLS culture media lowers hepatic lipogenic gene expression and increases oxidative damages to lipids. On the other hand, addition of ENL prevents oxidative damages provoked by these PUFA.