Interrelated effects of dihomo-γ-linolenic and arachidonic acids, and sesamin on hepatic fatty acid synthesis and oxidation in rats

An Oil Rich in γ-Linolenic Acid Differently Affects Hepatic Fatty Acid Oxidation in Mice and Rats

The effects of different dietary fats on hepatic fatty acid oxidation were compared in male ICR mice and Sprague-Dawley rats. Animals were fed diets containing 100 g/kg of either palm oil (saturated fat), safflower oil (rich in linoleic acid), an oil of evening primrose origin (γ-linolenic acid, GLA oil), perilla oil (α-linolenic acid) or fish oil (eicosapentaenoic and doxosahexaenoic acids) for 21 d. GLA, perilla and fish oils, compared with palm and safflower oils, increased the activity of fatty acid oxidation enzymes in both mice and rats, with some exceptions. In mice, GLA and fish oils greatly increased the peroxisomal palmitoyl-CoA oxidation rate, and the activity of acyl-CoA oxidase and enoyl-CoA hydratase to the same degree. The effects were much smaller with perilla oil. In rats, enhancing effects were more notable with fish oil than with GLA and perilla oils, excluding the activity of enoyl-CoA hydratase, and were comparable between GLA and perilla oils. In mice, strong enhancing effects of GLA oil, which were greater than with perilla oil and comparable to those of fish oil, were confirmed on mRNA levels of peroxisomal but not mitochondrial fatty acid oxidation enzymes. In rats, the effects of GLA and perilla oils on mRNA levels of peroxisomal and mitochondrial enzymes were indistinguishable, and lower than those observed with fish oil. Therefore, considerable diversity in the response to dietary polyunsaturated fats, especially the oil rich in γ-linolenic acid and fish oil, of hepatic fatty acid oxidation pathway exists between mice and rats.

Sesame lignans increase sympathetic nerve activity and blood flow in rat skeletal muscles

Beneficial effects of sesame lignans, especially antioxidative effects, have been widely reported; however, its potential effects on autonomic nerves have not yet been investigated. Therefore, the current study aimed to investigate the effect of sesame lignans on the autonomic nervous system. The sympathetic nerve activity in rat skeletal muscle was measured using electrophysiological approaches, with blood flow determined using the laser Doppler method. Sesame lignans were administered intragastrically at 2 and 20 mg/kg, and after 60 min, the sympathetic nerve activity was observed to increase by 45.2% and 66.1%, respectively. A significant increase in blood flow (39.6%) was also observed for the 20-mg/kg dose when measured at 55 min after administration. These sympathomimetic effects were completely prevented by subdiaphragmatic vagotomy, and the increase in blood flow was eliminated in the presence of the beta2-adrenergic receptor inhibitor butoxamine. Thus, it is proposed that sesame lignans can increase the blood flow of skeletal muscle, possibly by exciting sympathetic nerve activity through the afferent vagal nerve.

Dihomo-gamma-linolenic acid induces fat loss in C. elegans in an omega-3-independent manner by promoting peroxisomal fatty acid β-oxidation

Bioactive compounds, including some fatty acids (FAs), can induce beneficial effects on body fat-content and metabolism. In this work, we have used C. elegans as a model to examine the effects of several FAs on body fat accumulation. Both omega-3 and omega-6 fatty acids induced a reduction of fat content in C. elegans, with linoleic, gamma-linolenic and dihomo-gamma-linolenic acids being the most effective ones. These three FAs are sequential metabolites especially in omega-6 PUFA synthesis pathway and the effects seem to be primarily due to dihomo-gamma-linolenic acid, and independent of its transformation into omega-3 or arachidonic acid. Gene expression analyses suggest that peroxisomal beta oxidation is the main mechanism involved in the observed effect. These results point out the importance of further analysis of the activity of these omega-6 FAs, due to their potential application in obesity and related diseases.