Comparative effects of tuna oil and salmon oil on liver lipid metabolism and fatty acid concentrations in rats

The comparative effect of tuna oil (TO) and salmon oil (SO) on the plasma and liver lipid and fatty acid compositions in Sprague Dawley rats was investigated. The total triacylglycerol (TG) and total cholesterol (TC) concentrations in liver was significantly decreased in the TO group; TG level in liver was also significantly decreased in the SO group. The mRNA expression of HMG-CoA reductase in liver was significantly down-regulated in the TO and SO groups relative to the control group. The plasma TG and TC were decreased in TO, but not in SO; plasma low-density lipoprotein and very low-density lipoprotein levels in TO and SO were decreased compared with the control group. The total n-3 polyunsaturated fatty acid (PUFA) in plasma and liver phospholipids was significantly elevated in the TO and SO. Docosahexaenoic acid (22:6n-3) and eicosapentaenoic acid (20:5n-3) in tissues were significantly increased in the TO and SO, respectively. In this study, TO had a more beneficial effect on liver TC and plasma TG, TC, high-density lipoprotein in rats than SO. The likely mechanism for lowering liver and plasma cholesterol by n-3 PUFA is to suppress the mRNA expression of gene encoding HMG-CoA reductase responsible for cholesterol biosynthesis.

PRACTICAL APPLICATIONS

The beneficial effects of n-3 polyunsaturated fatty acids (PUFAs) from fish and fish oil on human health is derived from their role in modulating membrane lipid composition and affecting metabolic and signal-transduction pathways. In the present study, we demonstrated that n-3 PUFA, docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) from tuna and salmon oils can be effectively incorporated into tissue membranes. Tuna oil rich in DHA has more beneficial effect on liver total cholesterol (TC) and plasma triglyceride, TC and HDL in rats than salmon oil, which is rich in EPA. The present data could provide information for the potential application of fish oils as components of functional food, and selected for fortification with different fish oils.

Effects of rosiglitazone on intramyocellular lipid accumulation in Psammomys obesus

Objective: To examine the effects of rosiglitazone in intramyocellular lipid (IMCL) content in diabetic Psammomys obesus using novel electron microscopy technologies.

Background: P. obesus is an unique polygenic model of obesity and type 2 diabetes. Male diabetic P. obesus were treated daily with 5 mg/Kg Rosiglitazone by oral gavage for 14 days. Data were compared with a group of age-matched diabetic P. obesus treated with saline vehicle.

Methods: Assessment of insulin resistance and adiposity were determine before and after the treatment period by oral glucose tolerance test (oGTT) and dual energy X-ray absorptiometry (DEXA) analysis. We used a new scanning electron microscopy technology, (WETSEM) to investigate the effects of rosiglitazone administration on IMCL content, size and distribution in red gastrocnemius muscle.

Results: Rosiglitazone treatment improved glucose tolerance in P. obesus with no difference in the overall body fat content although a significant reduction in subscapular fat mass was observed. Rosiglitazone changed the distribution of lipid droplet size in skeletal muscle. Treated animals tended to have smaller lipid droplets compared with saline-treated controls.

Conclusions: Since smaller IMCL droplets are associated with improvements in insulin sensitivity, we propose that this may be an important mechanism by which rosiglitazone affects glucose tolerance.

Can dietary lipid source circadian alternation improve omega-3 deposition in rainbow trout?

With the salmonid industry currently exploiting the vast majority of globally available fish oil, there is the need to optimise fish oil utilisation by increasing its efficiency in terms of transferring the health-promoting long chain omega-3 fatty acids (n−3 LC-PUFA) into farmed fish flesh. The aim of this study was to evaluate if dietary fatty acid deposition is affected by the time of feeding, and hence identify possible innovative feeding strategies towardsmore efficient use of dietary fish oil. Over a period of 12 weeks, three diets with different lipid sources, canola oil (CO), fish oil (FO) or a 50/50 blend of the two oils (Mix), were alternated daily and fed to rainbow trout (Oncorhynchus mykiss). Six treatments were administered to fish, reference treatment (REF, continuously fed FO), control treatment (CT, continuously fed Mix), am canola oil ration (amCOR), pm canola oil ration (pmCOR), am canola oil satiation (amCOS) and pm canola oil satiation (pmCOS). Fish received either the CO diet in the am or pm feeds and received the FO diet at the opposite time. A significant increase in growth and feed consumption was noted in the pmCOS treatment. Fillet fatty acid profile was modified by associated feeding schedules and was generally reflective of dietary fatty acid profile. No significant increases in n−3 LCPUFA deposition were observed. However, both linoleic acid (18:2n−6) and α-linolenic acid (18:3n−3) contents were significantly higher in pmCOR compared to amCOR and CT. The results of the present study suggest the existence of cyclical circadian patterns in fatty acid deposition in rainbow trout.

Suppressive actions of eicosapentaenoic acid on lipid droplet formation in 3T3-L1 adipocytes

Background : Lipid droplet (LD) formation and size regulation reflects both lipid influx and efflux, and is central in the regulation of adipocyte metabolism, including adipokine secretion. The length and degree of dietary fatty acid (FA) unsaturation is implicated in LD formation and regulation in adipocytes. The aims of this study were to establish the impact of eicosapentaenoic acid (EPA; C20:5n-3) in comparison to SFA (STA; stearic acid, C18:0) and MUFA (OLA; oleic acid, C18:1n-9) on 3T3-L1 adipocyte LD formation, regulation of genes central to LD function and adipokine responsiveness. Cells were supplemented with 100 μM FA during 7-day differentiation.

Results : EPA markedly reduced LD size and total lipid accumulation, suppressing PPARγ, Cidea and D9D/SCD1 genes, distinct from other treatments. These changes were independent of alterations of lipolytic genes, as both EPA and STA similarly elevated LPL and HSL gene expressions. In response to acute lipopolysaccharide exposure, EPA-differentiated adipocytes had distinct improvement in inflammatory response shown by reduction in monocyte chemoattractant protein-1 and interleukin-6 and elevation in adiponectin and leptin gene expressions.

Conclusions : This study demonstrates that EPA differentially modulates adipogenesis and lipid accumulation to suppress LD formation and size. This may be due to suppressed gene expression of key proteins closely associated with LD function. Further analysis is required to determine if EPA exerts a similar influence on LD formation and regulation in-vivo.

Effect of a stearic acid-rich, structured triacylglycerol on plasma lipid concentrations

Background: Structured lipids are being incorporated into foods to reduce their energy value. One such lipid is rich in stearic acid.
Objective: The objective of this study was to compare the effects on plasma lipids of a stearic acid–rich triacylglycerol and a fat rich in palmitic acid in hypercholesterolemic subjects.
Design: Fifteen subjects with an average plasma cholesterol concentration of 6.13 ± 0.80 mmol/L initially ate a low-fat diet for 2 wk (run-in period), followed in random order and blinded fashion by 2 high-fat diets (for 5 wk each) containing foods derived from margarines rich either in palmitic acid or in the structured, stearic acid–rich triacylglycerol.
Results: Plasma cholesterol concentrations with the low-fat, the stearic acid–rich, and the palmitic acid–rich diets were not significantly different (5.35 ± 0.83, 5.41 ± 0.78, and 5.52 ± 0.68 mmol/L, respectively) but were significantly lower (P < 0.001) than those measured during the habitual diet period (ie, 2 wk before the study began). Neither HDL cholesterol nor plasma triacylglycerol differed significantly among the 3 study diets.
Conclusion: A similar increase in the intake of stearic and palmitic acids (differing by <5% of total energy) to ensure a high fat intake resulted in plasma total and LDL-cholesterol concentrations that did not differ significantly from concentrations measured during a period of low-fat intake.

Seasonal variations of total lipid and fatty acid contents in muscle, gonad and digestive glands of farmed jade tiger hybrid abalone in Australia

The lipid and fatty acid (FA) contents of muscle, gonad and digestive glands (DG) of Jade Tiger hybrid abalone were studied over the four seasons. Higher contents of total lipid and saturated fatty acids (SFA) were found in summer from muscle. For gonad the higher total lipid content was found in summer and spring whereas the SFA content peaked in summer only. For DG the higher contents of total lipid and SFA were recorded in all seasons except autumn. Winter samples showed significantly higher content of PUFA in all three types of tissue. High contents of eicosapentaenoic acid (EPA, 20:5 n−3), docosapentaenoic acid (DPA, 22:5 n−3) and docosahexaenoic acid (DHA, 22:6 n−3) were recorded in winter from muscle, although no marked variations were observed from gonad. For DG the high content of DHA was also observed in winter whilst EPA and DPA maintained high levels in all seasons except summer.

Developing an anion host for lipid A binding and antibacterial activity

New structural amphiphiles 2a and 2b bind the diphosphate lipid A anion and show potential as lead compounds for the development of novel antibacterial agents.

Lipid composition of Australian pork cuts 2005/2006

A study of the cholesterol content and fatty acid composition of fresh retail Australian pork was undertaken to determine whether new breeding, feeding and processing methods had resulted in any compositional changes in fresh pork in the market place since surveys undertaken in previous decades. Samples of 13 popular pork cuts were purchased from randomly selected supermarkets and butchers’ stores in urban areas across the socioeconomic scale in three States of Australia, and analysed, separable fat and separable lean, in late 2005 and early 2006. Variability was low across States for saturated and monounsaturated fatty acids, but more pronounced for polyunsaturated acids. The separable lean portions of all pork cuts contained levels of n-3 fatty acids and conjugated linoleic acid (C18:1c9t11) in measurable but not nutritionally claimable amounts, whilst total trans fatty acid levels were very low. There appeared to be some differences in fatty acid composition across States that may have resulted from feeding method. Cholesterol contents were similar to levels in the 80s and 90s for separable lean pork tissue, but presently are lower for separable fat tissue than for separable lean.

Leptin and lipid metabolism in fish

The aim of this chapter is to highlight potential links between leptin and the lipid metabolism in fish, within the context of current research interests of the fish nutrition amd aquaculture sector. In fact, it is envisaged that the whole aquacuture and fish biology sector will significantly benefit from an increased knowledge of such a powerful hormone, and it is believed this will contribute in transforming current aquaculture industry into an environmental and economical means of producing nourishing fish and seafood for the growing global population. The context is framed by a brief introduction on the current challenges in aquaculture and fish nutrition, and susequently the chapter focuses on the potential roles of leptin on voluntary food intake and lipid digestion and absorption in fish. Following this, the possible roles of leptin on lipid deposition and utilisation and the fatty acid metabolism in fish are presented and discussed. Eventually the possible interrelationships between dietary lipids and leptin are analysed underlining how knowledge gained from human nutrition could be extremely useful to tentatively address current constraints and obstacles found in the aquaculture nutrition sector. The present analysis suggests that we are likely only able to see the tip of the iceberg, and great and significant breakthrough discoveries will be likely by fathoming such fascinating area of research.

Direct measurement of the force between two lipid bilayers and observation of their fusion

The force between twophosphatidylcholine bilayers is measured as a function of their separation, showing a strong hydration repulsion at short range, as previously reported by LeNeveu et al. (LeNeveu, D.M., Rand, R.P., Parsegian, V.A. and Gingell, D. (1977) (Biophys. J. 18, 209-230). The experimental technique also allows direct observation of the molecular process by which two bilayers fuse into one.

Effects of lipoprotein lipase gene variations, a high-carbohydrate low-fat diet, and gender on serum lipid profiles in healthy Chinese Han youth

A high-carbohydrate low-fat (HC/LF) diet and lipoprotein lipase gene (LPL) Ser447Stop and Hind III polymorphisms have separately been found to be associated with triacylglycerol (TG) and high density lipoprotein cholesterol (HDL-C). This study sought to test the effects of LPL polymorphisms and an HC/LF diet on the serum lipid profile of Chinese with a lower incidence of coronary artery disease (CAD) consuming a diet with less fat and more carbohydrates. Fifty-six healthy subjects (22.89 ± 1.80 years) were given a control diet of 30.1% fat and 54.1% carbohydrates for 7 days, followed by an HC/LF diet of 13.8% fat and 70.1% carbohydrate for 6 days; there were no changes in the fatty acid composition or restrictions on total energy. Serum lipid profiles at baseline, before and after the HC/LF diet, and LPL polymorphisms were analyzed. After 6 days of the HC/LF diet, TG and the homeostasis model assessment of insulin resistance (HOMAIR) index were found to increase only in females with S447S. No decrease in HDL-C was noted. In subjects with Hind III polymorphism, increased TG was found in all females but not in males. Increased HDL-C, together with apolipoprotein (apo) AI, was found in male H- carriers but not in males with H+/H+ and females. In conclusion, LPL Ser447Stop and Hind III polymorphisms modified the effects of an HC/LF diet on the serum lipid profiles of a young Chinese population in different ways. Effective strategies for dietary interventions targeted at younger populations should take into account the interplay between genetic polymorphisms, diet, and gender.