Peroxisome proliferator-activated receptors (PPARs)-independent functions of fish oil on glucose and lipid metabolism in diet-induced obese mice

Abstract

BackgroundFish oil is known to improve lifestyle-related diseases. These effects occur partly via activation of PPARs by the n-3 polyunsaturated fatty acids included abundantly in fish oil. We investigated fish oil functions on glucose and lipid metabolism that are both dependent on and independent of PPARs pathway.MethodsMice were fed a diet containing 30 en% beef tallow (B diet) for twelve weeks to induce obesity. The mice were then divided into two groups which were fed either a B diet or a diet containing 30 en% fish oil (F diet). Each group was further divided into two groups which were administered PPARα and γ antagonists or vehicle once a day for three weeks.ResultsThe F diet groups showed lower triglyceride levels in plasma and liver than the B diet groups, but PPARs antagonists did not affect the triglyceride levels in either diet groups. The F diet groups also showed improvement of glucose tolerance compared with the B diet groups. However, PPARs antagonists made glucose tolerance worse in the F diet group but improved it in the B diet group. Therefore, by the administration of antagonists, glucose tolerance was inversely regulated between the B and F diets, and hypolipidemic action in the plasma and liver of the F diet group was not affected.ConclusionThese results suggest that fish oil decreases lipid levels in plasma and liver via PPARs pathway-independent mechanism, and that glucose tolerance is inversely regulated by PPARs antagonists under diets containing different oils.

Thyroid hormone contributes to the hypolipidemic effect of polyunsaturated fatty acids from fish oil: in vivo evidence for cross talking mechanisms

“…On the other hand, hypothyroidism induced a marked increase in liver expression of PPARa. Apparently, the control of serum lipids by n-3 PUFA involves different signaling pathways, a PPARadependent one for cholesterol and another, PPARa independent for triglycerides (Dallongeville et al 2001, Sugiyama et al 2008, Wakutsu et al 2010. Indeed, our finding of marked increase in PPARa protein content in the liver of hypothyroid rats may justify the normalization of serum cholesterol in hypothyroid livers and in addition supports those previous reports arguing that the hypotriglyceridemic effect of n-3 PUFA is not dependent on PPARa.…”

A high-fish-oil diet prevents adiposity and modulates white adipose tissue inflammation pathways in mice

“…This transcription factor is responsible for adipocyte differentiation and stimulates the adipogenesis of small adipocytes [49], leading to the diminished release of cytokines and an increased release of adiponectin [47]. Moreover, PPARγ is the primary transcriptional regulator of adiponectin [18].…”

Potential Adverse Effects of Omega‐3 Fatty Acids in Dogs and Cats

“…For example, omega-3 fatty acids are thought to have antitumor effects 1 and effects on blood lipid concentrations, 5,6,25 and improved receptor and ion channel functions. 26,27 Omega-6 fatty acids have a double bond between the 6th and 7th carbon from the omega-end of the fatty acid molecule. One of the omega-6 fatty acids is LA, which is considered essential in all mammals because of lack of the enzyme needed for its synthesis.…”