Diets with low n-6:n-3 PUFA ratio protects rats from fructose-induced dyslipidemia and associated hepatic changes: Comparison between 18:3 n-3 and long-chain n-3 PUFA

Effect of Omega-3 Rich High-Fat Diet on Markers of Tissue Lipid Metabolism in Glucocorticoid-Treated Mice

Glucocorticoids (GCs) are some of the most widely prescribed therapies for treating numerous inflammatory diseases and multiple cancer types. With chronic use, GCs' therapeutic benefits are concurrent with deleterious metabolic side effects, which worsen when combined with a high-fat diet (HFD). One characteristic of the common Western HFD is the presence of high omega-6 polyunsaturated fatty acids (PUFAs) and a deficiency in omega-3 PUFAs. The aim of this experiment was to determine whether fat composition resulting from HFD affects glucocorticoid-induced alterations in lipid-handling by the liver and skeletal muscle. Male wild-type C57BL/6 mice were randomized into two groups: n-6 (45% fat 177.5 g lard) and n-3 (45% fat 177.5 g Menhaden oil). After 4 weeks on their diets, groups were divided to receive either daily injections of dexamethasone (3 mg/kg/day) or sterile PBS for 1 week while continuing diets. The n-3 HFD diet attenuated adipose and hepatic fatty accumulation and prevented GC-induced increases in liver lipid metabolism markers Cd36 and Fabp. N-3 HFD had little effect on markers of lipid metabolism in oxidative and glycolytic skeletal muscle and was unable to attenuate GC-induced gene expression in the muscle. The present study's result demonstrated that the change of fat composition in HFD could beneficially alter the fatty acid accumulation and associated lipid metabolism markers in mice treated with dexamethasone.

Intervention of 4% salmon phospholipid on metabolic syndrome in mice based on colonic lipidomics analysis

BACKGROUND

The incidence of metabolic syndrome (MetS) is increasing, and n-3 polyunsaturated fatty acids (PUFAs) in salmon (Oncorhynchus) phospholipids can effectively reduce the risk of MetS.

RESULTS

Under the intervention of 4% salmon phospholipid, the levels of fasting blood glucose (FBG), insulin, monocyte chemoattractant protein-1 (MCP-1), interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) were significantly reduced in the plasma of MetS mice, whereas adiponectin was significantly increased. By screening, we found that the 18 differential metabolites, consisting of seven triglycerides (TGs), six diglycerides (DGs), one phosphatidylethanolamine (PE), three sphingomyelins (SMs) and one eicosanoid, could be the key differential metabolites, and two metabolic pathways were significantly affected: glycerolipid metabolism and glycerophospholipid metabolism.

CONCLUSION

4% salmon phospholipids could affect MetS by inhibiting insulin resistance, reducing inflammatory factors and promoting the synthesis of PE, yet the mechanism required further study. Our results could help in the treatment of MetS. © 2021 Society of Chemical Industry.

Low Dietary n6/n3 Ratio Attenuates Changes in the NRF 2 Gene Expression, Lipid Peroxidation, and Inflammatory Markers Induced by Fructose Overconsumption in the Rat Abdominal Adipose Tissue

The objective of this study was to examine the benefits of different n6/n3 polyunsaturated fatty acid ratios on the lipid metabolism, insulin resistance, and oxidative stress in the adipose tissue of rats fed a high-fructose diet. Male and female rats were divided into four groups: a control group (CON) (n6/n3 ratio ~7), a high-fructose group (HF) (n6/n3 ratio ~7), an N6-HF group (n6/n3 ratio ~50), and the DHA-HF group (n6/n3 ratio ~1, with the addition of docosahexaenoic (DHA) and eicosapentaenoic (EPA) acid). The CON group received plain water and the HF group received 15% fructose in their drinking water. Fructose induced an increase in the content of serum triglycerides, serum cholesterol, and HOMA-IR index. Among the fatty acids, elevated proportions of C18:1n9 and C16:1n7, as well as an increase in total monounsaturated fatty acid (MUFA), were found in the adipose tissue of the HF group. Fructose treatment also changed oxidative parameters, including a marked increase in the serum malondialdehyde (MDA) content. Meanwhile, DHA supplementation caused a significant decrease in the serum MDA concentration in comparison with the HF group. In addition, DHA/EPA supplementation attenuated oxidative stress by increasing NRF 2 gene expression. Fructose treatment also significantly decreased the adiponectin level, while DHA supplementation ameliorated it. The changes observed in this trial, including the decrease in the content of DHA and EPA, the decreased EPA/ARA ratio, and the increase in the expression of inflammatory genes, are characteristics of the low-grade inflammation caused by fructose treatment. These changes in the rat adipose tissue could be prevented by dietary intervention consisting of DHA supplementation and a low n6/n3 ratio.

Time-of-day effects of consumption of fish oil-enriched sausages on serum lipid parameters and fatty acid composition in normolipidemic adults: A randomized, double-blind, placebo-controlled, and parallel-group pilot study

OBJECTIVES

The body clock controls diurnal rhythms of nutrient digestion, absorption, and metabolism. Fish oil (FO) contains abundant ω-3 polyunsaturated fatty acids (PUFA), including docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), that are thought to lower triglyceride (TG) levels. This randomized, placebo-controlled, double-blind, parallel-group trial aimed to confirm the effects of the time of FO intake on TG in healthy Japanese adults.

METHODS

Twenty healthy Japanese adults (age, 20-60 y) were assigned to either a group that consumed sausages enriched with FO (DHA 1010 mg; EPA 240 mg) in the morning and a placebo (DHA 40 mg; EPA 15 mg) in the evening (BF-FO) or another group that consumed FO-enriched sausages in the evening and the placebo in the morning (DN-FO). Serum lipid parameters, fatty acid (FA) composition, and messenger RNA expression of lipogenic genes in circulating blood cells were evaluated in fasting blood samples before, as well as after 4 and 8 wk of FO intake.

RESULTS

Serum concentrations of TG and total saturated FA were significantly decreased in the BF-FO group, whereas those of ω-3 PUFA were significantly and identically increased in both groups. Serum concentrations of ω-6 PUFA were significantly decreased in the BF-FO but not the DN-FO group. Messenger RNA expression of the lipogenic genes ACLY, SCD, and FASN were similarly reduced in both groups.

CONCLUSIONS

These findings suggested that the timing of FO intake affects both serum FA concentrations and TG metabolism in normolipidemic humans. The mechanisms of these effects of FO on lipid metabolism require further investigation.