Marine omega-3 phospholipids: metabolism and biological activities

Safety assessment of Superba™ krill powder: Subchronic toxicity study in rats

The safety of krill powder was assessed in a subchronic 13-week toxicity study where rats were fed krill powder or control diets. The krill powder inclusion in the test diet was 9.67% (w/w). There were no differences noted in body weight or food consumption in either gender. Differences in clinical chemistry values were noted in the krill powder-treated animals, but these findings were of no toxicological significance. A significant decrease in absolute heart weight, but not relative heart weight, was observed in both sexes given krill powder, although no corresponding histological changes were observed. Hepatocyte vacuolation was noted histologically in males fed krill powder. This finding was not associated with other indications of hepatic dysfunction. The no observed adverse effect level (NOAEL) for the conditions of this study was considered to be 9.67% krill powder.

Effect of fish and krill oil supplementation on glucose tolerance in rabbits with experimentally induced obesity

PURPOSE

This study was conducted to investigate the effect of fish oil (FO) and krill oil (KO) supplementation on glucose tolerance in obese New Zealand white rabbits.

METHODS

The experiments were carried out with 24 male rabbits randomly divided into four groups: KO-castrated, treated with KO; FO-castrated, treated with FO; C-castrated, non-treated; NC-non-castrated, non-treated. At the end of treatment period (2 months), an intravenous glucose tolerance test (IVGTT) was performed in all rabbits.

RESULTS

Fasting blood glucose concentrations in FO and KO animals were significantly lower than in group C. The blood glucose concentrations in FO- and KO-treated animals returned to initial values after 30 and 60 min of IVGTT, respectively. In liver, carnitine palmitoyltransferase 2 (Cpt2) and 3-hydroxy-3-methyl-glutaryl-CoA synthase 2 (Hmgcs2) genes were significantly increased in FO-fed rabbits compared with the C group. Acetyl-CoA carboxylase alpha (Acaca) expression was significantly reduced in both KO- and FO-fed rabbits. In skeletal muscle, Hmgcs2 and Cd36 were significantly higher in KO-fed rabbits compared with the C group. Acaca expression was significantly lower in KO- and FO-fed rabbits compared with the C group.

CONCLUSION

The present results indicate that FO and KO supplementation decreases fasting blood glucose and improves glucose tolerance in obese New Zealand white rabbits. This could be ascribed to the ameliorated insulin sensitivity and insulin secretion and modified gene expressions of some key enzymes involved in β-oxidation and lipogenesis in liver and skeletal muscle.

[Importance of long chain omega-3 fatty acids in prostate cancer]

The benefits of long chain polyunsaturated omega-3 fatty acids (n-3 PUFA) from fish or administered as supplements remain controversial regarding prostate cancer (PCa). Based on the currently available evidence no clear benefit of n-3 PUFA intake to generally reduce PCa incidence has been found. On the other hand n-3 PUFAs have a clear influence on the development of already existing PCa. The intake of n-3-PUFAs considerably reduces the risk of metastasis and PCa-related mortality.

Genotoxicity test and subchronic toxicity study with Superba™ krill oil in rats

The safety of krill oil was assessed in a subchronic toxicity study and in a genotoxicity test. In a 13-week study, rats were fed krill oil or control diets. There were no differences noted in body weight, food consumption or in the functional observation battery parameters in either gender. Differences in both haematology and clinical chemistry values were noted in the krill oil-treated groups. However these findings were of no toxicological significance. Significant decreases in absolute and covariant heart weight in some krill oil-treated animals were noted although no corresponding histological changes were observed. In addition, periportal microvesicular hepatocyte vacuolation was noted histologically in males fed 5% krill oil. This finding was not associated with other indications of hepatic dysfunction. Given that the effects of the 13-week toxicity study were non-toxic in nature, the no observed adverse effect level (NOAEL) for the conditions of this study was considered to be 5% krill oil. The genotoxicity experiments documented no mutagenicity of krill oil in bacteria.

Effects of Marine Phospholipids Extract on the Lipid Levels of Metastatic and Nonmetastatic Prostate Cancer Patients

High intake of omega-3 fatty acids (n-3 FAs) from fish has shown to reduce metastatic progression of prostate cancer. This clinical trial investigated the influence of high n-3 FA intake (marine phospholipids, MPL) on the FA composition of blood lipids, lysophosphatidylcholine (LPC), and on lipoproteins in prostate cancer patients and elderly men without prostate cancer. MPL supplementation resulted in a significant increase of n-3 FAs (eicosapentaenoic and docosahexaenoic acid) in blood lipids, while arachidonic acid (n-6 FA) decreased significantly. Low density lipoprotein (LDL) and high density lipoprotein (HDL) increased significantly, but the LDL increase was observed only in subjects with an inactive tumour. Similarly, LPC plasma concentration increased significantly only in patients without tumour. The missing increase of LDL and LPC after MPL supplementation in patients with actively growing (metastasizing) prostate cancer suggests that tumour cells have an elevated demand for LDL and LPC. Due to the MPL-induced increase of n-3 FAs in these blood lipids, it can be assumed that especially actively growing and metastasizing prostate cancer cells are provided with elevated amounts of these antimetastatic n-3 FAs. A hypothetic model explaining the lower incidence of metastatic progression in prostate cancer patients with high fish consumption is presented.

Omega-3 phospholipids from fish suppress hepatic steatosis by integrated inhibition of biosynthetic pathways in dietary obese mice

Non-alcoholic fatty liver disease (NAFLD) accompanies obesity and insulin resistance. Recent meta-analysis suggested omega-3 polyunsaturated fatty acids DHA and EPA to decrease liver fat in NAFLD patients. Antiinflammatory, hypolipidemic, and insulin-sensitizing effects ofDHA/EPA depend on their lipid form, with marine phospholipids showing better efficacy than fish oils. We characterized the mechanisms underlying beneficial effects of DHA/EPA phospholipids, alone or combined with an antidiabetic drug, on hepatosteatosis. C57BL/6N mice were fed for 7 weeks an obesogenic high-fat diet (cHF) or cHF-based interventions: (i) cHF supplemented with phosphatidylcholine-rich concentrate from herring (replacing 10% of dietary lipids; PC), (ii) cHF containing rosiglitazone (10 mg/kg diet; R), or (iii) PC + R. Metabolic analyses, hepatic gene expression and lipidome profiling were performed. Results showed that PC and PC + R prevented cHlF-induced weight gain and glucose intolerance, while all interventions reduced abdominal fat and plasma triacylglycerols. PC and PC + R also lowered hepatic and plasma cholesterol and reduced hepatosteatosis. Microarray analysis revealed integrated downregulation of hepatic lipogenic and cholesterol biosynthesis pathways by PC, while R-induced lipogenesis was fully counteracted in PC + R Gene expression changes in PC and PC + R were associated with preferential enrichment of hepatic phosphatidylcholine and phosphatidylethanolamine fractions by DHA/EPA. The complex downregulation of hepatic lipogenic and cholesterol biosynthesis genes and the antisteatotic effects were unique to DHA/EPA-containing phospholipids, since they were absent in mice fed soy-derived phosphatidylcholine. Thus, inhibition of lipid and cholesterol biosynthesis associated with potent antisteatotic effects in the liver in response to DHA/EPA-containing phospholipids support their use in NAFLD prevention and treatment.

Phospholipids from herring roe improve plasma lipids and glucose tolerance in healthy, young adults

BACKGROUND

Herring roe is an underutilized source of n-3 polyunsaturated fatty acids (PUFAs) for human consumption with high phospholipid (PL) content. Studies have shown that PL may improve bioavailability of n-3 PUFAs. Arctic Nutrition's herring roe product MOPL™30 is a PL: docosahexaenoic acid (DHA)-rich fish oil mixture, with a DHA:eicosapentaenoic acid (EPA) ratio of about 3:1, which is also rich in choline. In this pilot study, we determined if MOPL30 could favorably affect plasma lipid parameters and glucose tolerance in healthy young adults.

METHODS

Twenty female and one male adults, between 22 and 26 years of age, participated in the study. Participants took encapsulated MOPL30, 2.4 g/d EPA + DHA, for 14 days, and completed a three-day weighed food record before and during the capsule intake. Plasma lipids and their fatty acid (FA) composition, plasma and red blood cell (RBC) phosphatidylcholine (PC) FA composition, acylcarnitines, choline, betaine and insulin were measured before and after supplementation (n = 21), and one and four weeks after discontinuation of supplementation (n = 14). An oral glucose tolerance test was performed before and after supplementation.

RESULTS

Fasting plasma triacylglycerol and non-esterified fatty acids decreased and HDL-cholesterol increased after 14 days of MOPL30 intake (p < 0.05). The dietary records showed that PUFA intake prior to and during capsule intake was not different. Fasting plasma glucose was unchanged from before to after supplementation. However, during oral glucose tolerance testing, blood glucose at both 10 and 120 min was significantly lower after supplementation with MOPL30 compared to baseline measurements. Plasma free choline and betaine were increased, and the n-6/n-3 polyunsaturated (PUFA) ratio in plasma and RBC PC were decreased post-supplementation. Four weeks after discontinuation of MOPL30, most parameters had returned to baseline, but a delayed effect was observed on n-6 PUFAs.

CONCLUSIONS

Herring roe rich in PL improved the plasma lipid profile and glycemic control in young adults with an overall healthy lifestyle.

Fish oil and krill oil supplementations differentially regulate lipid catabolic and synthetic pathways in mice

Background

Marine derived oils are rich in long-chain polyunsaturated omega-3 fatty acids, in particular eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), which have long been associated with health promoting effects such as reduced plasma lipid levels and anti-inflammatory effects. Krill oil (KO) is a novel marine oil on the market and is also rich in EPA and DHA, but the fatty acids are incorporated mainly into phospholipids (PLs) rather than triacylglycerols (TAG). This study compares the effects of fish oil (FO) and KO on gene regulation that influences plasma and liver lipids in a high fat diet mouse model.

Methods

Male C57BL/6J mice were fed either a high-fat diet (HF) containing 24% (wt/wt) fat (21.3% lard and 2.3% soy oil), or the HF diet supplemented with FO (15.7% lard, 2.3% soy oil and 5.8% FO) or KO (15.6% lard, 2.3% soy oil and 5.7% KO) for 6 weeks. Total levels of cholesterol, TAG, PLs, and fatty acid composition were measured in plasma and liver. Gene regulation was investigated using quantitative PCR in liver and intestinal epithelium.

Results

Plasma cholesterol (esterified and unesterified), TAG and PLs were significantly decreased with FO. Analysis of the plasma lipoprotein particles indicated that the lipid lowering effect by FO is at least in part due to decreased very low density lipoprotein (VLDL) content in plasma with subsequent liver lipid accumulation. KO lowered plasma non-esterified fatty acids (NEFA) with a minor effect on fatty acid accumulation in the liver. In spite of a lower omega-3 fatty acid content in the KO supplemented diet, plasma and liver PLs omega-3 levels were similar in the two groups, indicating a higher bioavailability of omega-3 fatty acids from KO. KO more efficiently decreased arachidonic acid and its elongation/desaturation products in plasma and liver. FO mainly increased the expression of several genes involved in fatty acid metabolism, while KO specifically decreased the expression of genes involved in the early steps of isoprenoid/cholesterol and lipid synthesis.

Conclusions

The data show that both FO and KO promote lowering of plasma lipids and regulate lipid homeostasis, but with different efficiency and partially via different mechanisms.

Modulation of hepatic steatosis by dietary fatty acids

Non-alcoholic fatty liver disease (NAFLD) describes a range of conditions caused by fat deposition within liver cells. Liver fat content reflects the equilibrium between several metabolic pathways involved in triglyceride synthesis and disposal, such as lipolysis in adipose tissue and de novo lipogenesis, triglyceride esterification, fatty acid oxidation and very-low-density lipoprotein synthesis/secretion in hepatic tissue. In particular, it has been demonstrated that hepatic de novo lipogenesis plays a significant role in NAFLD pathogenesis. It is widely known that the fatty acid composition of the diet influences hepatic lipogenesis along with other metabolic pathways. Therefore, dietary fat may not only be involved in the pathogenesis of hepatic steatosis, but may also prevent and/or reverse hepatic fat accumulation. In this review, major data from the literature about the role of some dietary fats as a potential cause of hepatic fat accumulation or as a potential treatment for NAFLD are described. Moreover, biochemical mechanisms responsible for an increase or decrease in hepatic lipid content are critically analyzed. It is noteworthy that both quantitative and qualitative aspects of dietary fat influence triglyceride deposition in the liver. A high-fat diet or the dietary administration of conjugated linoleic acids induced hepatic steatosis. In contrast, supplementation of the diet with krill oil or pine nut oil helped in the prevention and/or in the treatment of steatotic liver. Quite interesting is the “case” of olive oil, since several studies have often provided different and⁄or conflicting results in animal models.

Characterization of phospholipid molecular species and peptide molecules in wheat sprout hydroalcoholic extract

The phospholipid molecular species and the main peptide molecules of wheat sprout hydroalcoholic extract have been fully characterized by normal-phase high performance liquid chromatography coupled online with positive electrospray ionization tandem mass spectrometry. The extract that resulted was rich in phospholipid molecular species formed by the combination of the two essential fatty acids (α-linoleic and α-linolenic). These species accounted for 51.7% of total phosphatidic acid, 47.3% of total phosphatidylethanolamine, 37.7% of total phosphatidylcholine, and 14.1% of total phosphatidylinositol. The last one showed the highest amounts of species containing palmitic acid, thus representing the most saturated phospholipid class. The extract was also shown to contain several peptide sequences with both potential antioxidant domains and interaction sites for phospholipids (i.e., H-Ala-Gly-Ser-Met-Met-Cys-NH2, H-Tyr-Met-Thr-Val-Val-Ala-Cys-NH2, etc.); this latter finding can have a highly positive impact on the poor peptides bioavailability. Because of the presence of essential fatty acids-rich phospholipids and bioactive peptides, wheat sprout hydroalcoholic extract can be considered a potential functional food ingredient.

Nutritional properties of dietary omega-3-enriched phospholipids

Dietary fatty acids regulate several physiological functions. However, to exert their properties, they have to be present in the diet in an optimal balance. Particular attention has been focused on tissue highly polyunsaturated fatty acids (HPUFAs) n-6/n-3 ratio, influenced by the type and the esterified form of dietary fatty acids. Dietary EPA and DHA when esterified to phospholipids (PLs) are more efficiently incorporated into tissue PLs and seem to possess peculiar properties through specific mechanism(s) of action, such as the capacity to affect endocannabinoid biosynthesis at much lower doses than EPA and DHA in triglyceride form, probably because of the above mentioned higher incorporation into tissue PLs. Downregulation of the endocannabinoid system seems to mediate the positive effects exerted by omega-3-enriched PLs on several parameters of metabolic syndrome. PLs are one of the major dietary forms of EPA and DHA we are exposed to with the everyday diet; therefore, it is not surprising that it guarantees an effective EPA and DHA nutritional activity. Future studies should address whether EPA and DHA in PL form are also more effective than other formulations in ameliorating other pathological conditions where n-3 HPUFAs seem to exert beneficial activities such as cancer and psychiatric disorders.

Enhanced cognitive function and antidepressant-like effects after krill oil supplementation in rats

Background

The purpose of the study was to evaluate the effects of krill oil (KO) on cognition and depression-like behaviour in rats.

Methods

Cognition was assessed using the Aversive Light Stimulus Avoidance Test (ALSAT). The Unavoidable Aversive Light Stimulus (UALST) and the Forced Swimming Test (FST) were used to evaluate the antidepressant-like effects of KO. Imipramine (IMIP) was used as the antidepressant reference substance.

Results

After 7 weeks of KO intake, both males and females treated with KO were significantly better in discriminating between the active and the inactive levers in the ALSAT from day 1 of training (p<0.01). Both KO and IMIP prevented resignation/depression on the third day in the UALST. Similarly, a shorter immobility time was observed for the KO and IMIP groups compared to the control in the FST (p<0.001). These data support a robust antidepressant-like potential and beneficial cognitive effect of KO. Changes in expression of synaptic plasticity-related genes in the prefrontal cortex and hippocampus were also investigated. mRNA for brain-derived neurotrophic factor (Bdnf) was specifically upregulated in the hippocampus of female rats receiving 7 weeks of KO supplementation (p=0.04) and a similar trend was observed in males (p=0.08). Males also exhibited an increase in prefrontal cortex expression of Arc mRNA, a key protein in long-term synaptic plasticity (p=0.05). IMIP induced clear effects on several plasticity related genes including Bdnf and Arc.

Conclusions

These results indicate that active components (eicosapentaenoic acid, docosahexaenoic acid and astaxanthin) in KO facilitate learning processes and provide antidepressant-like effects. Our findings also suggest that KO might work through different physiological mechanisms than IMIP.