A krill oil supplemented diet suppresses hepatic steatosis in high-fat fed rats

The Ameliorating Effects of n-3 Polyunsaturated Fatty Acids on Liver Steatosis Induced by a High-Fat Methionine Choline-Deficient Diet in Mice

The pathogenesis of non-alcoholic fatty liver disease (NAFLD) is associated with abnormalities of liver lipid metabolism. On the contrary, a diet enriched with n-3 polyunsaturated fatty acids (n-3-PUFAs) has been reported to ameliorate the progression of NAFLD. The aim of our study was to investigate the impact of dietary n-3-PUFA enrichment on the development of NAFLD and liver lipidome. Mice were fed for 6 weeks either a high-fat methionine choline-deficient diet (MCD) or standard chow with or without n-3-PUFAs. Liver histology, serum biochemistry, detailed plasma and liver lipidomic analyses, and genome-wide transcriptome analysis were performed. Mice fed an MCD developed histopathological changes characteristic of NAFLD, and these changes were ameliorated with n-3-PUFAs. Simultaneously, n-3-PUFAs decreased serum triacylglycerol and cholesterol concentrations as well as ALT and AST activities. N-3-PUFAs decreased serum concentrations of saturated and monounsaturated free fatty acids (FAs), while increasing serum concentrations of long-chain PUFAs. Furthermore, in the liver, the MCD significantly increased the hepatic triacylglycerol content, while the administration of n-3-PUFAs eliminated this effect. Administration of n-3-PUFAs led to significant beneficial differences in gene expression within biosynthetic pathways of cholesterol, FAs, and pro-inflammatory cytokines (IL-1 and TNF-α). To conclude, n-3-PUFA supplementation appears to represent a promising nutraceutical approach for the restoration of abnormalities in liver lipid metabolism and the prevention and treatment of NAFLD.

Development and evaluation of novel krill oil-based clomiphene microemulsion as a therapeutic strategy for PCOS treatment

Polycystic ovary syndrome (PCOS) is frequently diagnosed hormonal disorder with reproductive and metabolic complications. The most common symptoms include cyst in ovaries, anovulation, insulin resistance, and obesity. Clomiphene citrate, an ovulating agent, is the first-line drug used to treat PCOS. We hypothesized that clomiphene citrate, by stimulating ovarian function, with krill oil used as an oil phase to improve solubility, by addressing PCOS-associated symptoms might be effective in PCOS. Hence, our goal was to target hormonal imbalance along with PCOS-associated symptoms using a single formulation. The concentration of water (X1), oil (X2), and Smix (surfactant-cosurfactant mixture) (X3) were selected as independent variables, in a simplex lattice design, from microemulsion area derived from a pseuodoternary phase diagram while the globule size (Y1) was selected as a dependent parameter. The optimized microemulsion showed good sphericity having 41 nm globule size, 0.32 poly dispersibility index and + 31 mV zeta potential. The optimized microemulsion was further evaluated in-vivo using letrozole-induced PCOS rats. Formulation treated group reversed the effect of letrozole on body weight and estrus cycle in comparison to the disease control group (p < 0.001). The formulation was also effective in reducing insulin resistance, cholesterol and serum testosterone level (p < 0.001). The in vivo results were supported by histopathological studies where the formulation-treated group showed a marked decrease in the number of cystic follicles and a remarkable increase in the number of growing follicles at variable stages, similar to the normal control group. Thus, the results confirmed that novel krill oil-based clomiphene microemulsion may become a promising therapeutic choice for the treatment of PCOS.

The Complex of Phycobiliproteins, Fucoxanthin, and Krill Oil Ameliorates Obesity through Modulation of Lipid Metabolism and Antioxidants in Obese Rats

Phycobiliproteins, fucoxanthin, and krill oil are natural marine products with excellent activities. In the study, we prepared the complex of phycobiliproteins, fucoxanthin, and krill oil (PFK) and assessed the anti-obesity, lipid-lowering, and antioxidant activities in high-fat diet rats. The results showed that the rats significantly and safely reduced body weight gain and regulated serum biochemical parameters at 50 mg/kg phycobiliproteins, 10 mg/kg fucoxanthin, and 100 mg/kg krill oil. Furthermore, the molecular mechanism study suggested that the complex of PFK confined the enzyme activities of lipid synthesis and enhanced antioxidant activity to improve obesity indirectly. The conclusions demonstrated that the complex of PFK has potent anti-obesity and hypolipidemic effects which have potential use as a natural and healthy food and medicine for anti-obesity and lowering blood lipids in the future.

Preventive and Therapeutic Effects of Krill Oil on Obesity and Obesity-Induced Metabolic Syndromes in High-Fat Diet-Fed Mice

Obesity increases the risks of metabolic syndromes including nonalcoholic fatty liver disease (NAFLD), diabetic dyslipidemia, and chronic kidney disease. Dietary krill oil (KO) has shown antioxidant and anti-inflammatory properties, thereby being a therapeutic potential for obesity-induced metabolic syndromes. Thus, the effects of KO on lipid metabolic alteration were examined in a high-fat diet (HFD)-fed mice model. The HFD model (n = 10 per group) received an oral gavage with distilled water as a control, metformin at 250 mg/kg, and KO at 400, 200, and 100 mg/kg for 12 weeks. The HFD-induced weight gain and fat deposition were significantly reduced in the KO treatments compared with the control. Blood levels were lower in parameters for NAFLD (e.g., alanine aminotransferase, and triglyceride), type 2 diabetes (e.g., glucose and insulin), and renal dysfunction (e.g., blood urea nitrogen and creatinine) by the KO treatments. The KO inhibited lipid synthesis through the modification of gene expressions in the liver and adipose tissues and adipokine-mediated pathways. Furthermore, KO showed hepatic antioxidant activities and glucose lowering effects. Histopathological analyses revealed that the KO ameliorated the hepatic steatosis, pancreatic endocrine/exocrine alteration, adipose tissue hypertrophy, and renal steatosis. These analyses suggest that KO may be promising for inhibiting obesity and metabolic syndromes.

Partial Replacement of High-Fat Diet with Beef Tallow Attenuates Dyslipidemia and Endoplasmic Reticulum Stress in db/db Mice

High-fat diet (HFD) consumption is closely associated with an increased risk of metabolic syndromes (MetS), such as obesity, type 2 diabetes, and cardiovascular diseases (CVDs). Therefore, the consumption of alternative and functional fatty acids to replace saturated fatty acids and/or trans-fatty acids with polyunsaturated fatty acids has become an important dietary strategy for the prevention of MetS. Consumption of omega-3 fatty acids (n-3) reduces various physiological complications, including CVDs, nonalcoholic fatty liver disease, and insulin resistance, related to inflammatory responses. In this study, we investigated the partial replacement effects of HFD with beef tallow (BT) on dyslipidemia and endoplasmic reticulum (ER) stress in male db/db mice. The animals were grouped to one of four dietary intervention groups (n = 16 per group): (1) normal diet, (2) HFD, (3) HFD partially replaced with regular beef tallow (HFD+BT1), or (4) HFD partially replaced with beef tallow containing a relatively reduced omega-6 fatty acid (n-6)/n-3 ratio (HFD+BT2) than HFD+BT1. After 6 weeks of dietary intervention, 1 mg/kg of phosphate-buffered saline or tunicamycin (TM) was injected intraperitoneally. HFD+BT2 significantly suppressed the serum total cholesterol and non-high-density lipoprotein cholesterol levels more than HFD and HFD+BT1, and triglyceride levels in the epididymal adipose tissue (EAT) were remarkably decreased. Mice that received HFD+BT2 had elevated protein expressions of phospho-AMP-activated protein kinase (p-AMPK). Moreover, HFD+BT2 effectively inhibited ER stress in the liver and EAT. Consistent with our hypothesis, HFD+BT2 remarkably alleviated dyslipidemia and TM-inducible ER stress, while activating p-AMPK.

Omega-3 phospholipids and obesity-associated NAFLD: Potential mechanisms and therapeutic perspectives

Prevalence of non-alcoholic fatty liver disease (NAFLD) increases in line with obesity and type 2 diabetes, and there is no approved drug therapy. Polyunsaturated fatty acids of n-3 series (omega-3) are known for their hypolipidaemic and anti-inflammatory effects. Existing clinical trials suggest varying effectiveness of triacylglycerol- or ethyl ester-bound omega-3 in the treatment of NAFLD, without affecting advanced stages such as non-alcoholic steatohepatitis. Preclinical studies suggest that the lipid class used to supplement omega-3 may determine the extent and nature of their effects on metabolism. Phospholipids of marine origin represent an alternative source of omega-3. The aim of this review is to summarise the available evidence on the use of omega-3 phospholipids, primarily in obesity-related NAFLD, and to outline perspectives of their use in the prevention/treatment of NAFLD. A PubMed literature search was conducted in May 2021. In total, 1088 articles were identified, but based on selection criteria, 38 original papers were included in the review. Selected articles describing the potential mechanisms of action of omega-3 phospholipids have also been included. Preclinical evidence clearly indicates that omega-3 phospholipids have strong antisteatotic effects in the liver, which are stronger compared to omega-3 administered as triacylglycerols. Multiple mechanisms are likely involved in the overall antisteatotic effects, involving not only the liver but also adipose tissue and the gut. Robust preclinical evidence for strong antisteatotic effects of omega-3 phospholipids in the liver should be confirmed in clinical trials. Further research is needed on the possible effects of omega-3 phospholipids on advanced NAFLD.

Partial Replacement of Dietary Fat with Krill Oil or Coconut Oil Alleviates Dyslipidemia by Partly Modulating Lipid Metabolism in Lipopolysaccharide-Injected Rats on a High-Fat Diet

This study investigated the effects of partial replacement of dietary fat with krill oil (KO) or coconut oil (CO) on dyslipidemia and lipid metabolism in rats fed with a high-fat diet (HFD). Sprague Dawley rats were divided into three groups as follows: HFD, HFD + KO, and HFD + CO. The rats were fed each diet for 10 weeks and then intraperitoneally injected with phosphate-buffered saline (PBS) or lipopolysaccharide (LPS) (1 mg/kg). The KO- and CO-fed rats exhibited lower levels of serum lipids and aspartate aminotransferases than those of the HFD-fed rats. Rats fed with HFD + KO displayed significantly lower hepatic histological scores and hepatic triglyceride (TG) content than rats fed with HFD. The KO supplementation also downregulated the adipogenic gene expression in the liver. When treated with LPS, the HFD + KO and HFD + CO groups reduced the adipocyte size in the epididymal white adipose tissues (EAT) relative to the HFD group. These results suggest that KO and CO could improve lipid metabolism dysfunction.

Effect of pecan nuts and extra-virgin olive oil on glycemic profile and nontraditional anthropometric indexes in patients with coronary artery disease: a randomized clinical trial

BACKGROUND/OBJECTIVES

The influence of cardioprotective foods on nontraditional indexes related to dysglycemia and body fat distribution is unknown in individuals with coronary artery disease (CAD). This study aimed to evaluate the effect of a healthy diet supplemented with pecan nuts or extra-virgin olive oil on glycemic profile and adipose tissue dysfunction assessed by anthropometric indexes in patients with stable CAD.

SUBJECTS/METHODS

In a randomized, pragmatic, parallel clinical trial lasting 12 weeks, 204 individuals were allocated to three interventions: a healthy diet (control group [CG], n = 67), a healthy diet plus 30 g/day of pecan nuts (pecan nut group [PNG], n = 68), or a healthy diet plus 30 mL/day of extra-virgin olive oil (olive oil group [OOG], n = 69). Triglyceride-glucose (TyG) index (primary outcome) and other markers of glycemic profile were evaluated, and nontraditional anthropometric indexes as well. Diet quality was assessed according to the Alternate Healthy Eating Index (mAHEI).

RESULTS

After adjustment for baseline values, use of antidiabetic drugs and insulin, there were no differences in both glycemic and anthropometric profiles according to groups at the end of the study. PNG improved the quality of the diet in comparison to other groups (final mAHEI scores: CG: 19 ± 7.5; PNG: 26 ± 8; OOG: 18.9 ± 6; P < 0.001).

CONCLUSIONS

There was no difference regarding glycemic and anthropometric parameters according to interventions in patients with stable CAD. However, adding pecan nuts to a healthy diet may improve its quality. Further studies must be conducted considering dietary interventions on secondary cardiovascular prevention setting.

CLINICAL TRIALS IDENTIFIER NUMBER

NCT02202265. First Posted: July 2014; Last Update: September 2020.

Efficacy of krill oil versus fish oil on obesity-related parameters and lipid gene expression in rats: randomized controlled study

Backround

This study aimed to determine the effects of LC n-3 PUFA supplementation on the prevention and treatment of obesity and obesity-related diseases, and to compare the efficiency of different LC n-3 PUFA sources via biochemical and genetic mechanisms in rats.

Methods

Male Wistar rats were randomized into four study groups, and fed with a standard diet, High Fat Diet (HFD), HFD+%2.5 Fish Oil (FO-HFD) or HFD+%2.5 Krill Oil (KO-HFD) for eight weeks. Food consumption, weight gain, serum glucose, insulin, ghrelin and leptin concentrations, lipid profile, liver fatty acid composition, and FADS1 and FADS2 mRNA gene expression levels were measured.

Results

Weight gain in each HFD group was significantly higher than control group (p < 0.001), without any differences among them (p < 0.05). LC n-3 PUFAs modified lipid profile, but not glucose tolerance. Serum leptin levels were significantly higher in HFD groups than in the control group, however, no difference in serum ghrelin levels was observed among the groups. Liver n-3 fatty acid desaturation activity was higher (p = 0.74), and liver total lipid content was lower (p = 0.86) in KO-HFD compared to FO-HFD. FADS1 gene expression was highest in the HFD group (p < 0.001) while FADS2 gene expression was highest in the FO-HFD group (p < 0.001).

Conclusion

LC n-3 PUFAs, especially krill oil, had moderate effects on lipid profile, but limited effects on obesity related parameters, suggesting different effects of different sources on gene expression levels. Further randomized controlled trials are needed to determine the efficacy of different LC n-3 PUFA sources in the prevention and treatment of obesity in humans.

Associations between fatty acid composition in serum cholesteryl esters and liver fat, basal fat oxidation, and resting energy expenditure: a population-based study

BACKGROUND

We have repeatedly shown in short-term feeding trials that a high intake of dietary n-6 PUFAs, i.e. linoleic acid, prevents liver fat accumulation compared with saturated fat. However, population-based data is lacking and the mechanisms behind such effects are unclear.

OBJECTIVE

To investigate associations between serum cholesteryl ester (CE) fatty acids and liver fat, basal fat oxidation [respiratory quotient (RQ)], and resting energy expenditure (REE). We hypothesized that PUFA in particular is inversely associated with liver fat and that such a relation is partly explained by a PUFA-induced increase in basal fat oxidation or REE.

METHODS

Cross-sectional analyses using linear regression models in a population-based cohort with data on serum CE fatty acid composition and liver fat (n = 308).

RESULTS

Linoleic acid (18:2n-6) (β = -0.03, 95% CI: -0.06, -0.001) and Δ5 desaturase index were inversely associated, whereas, γ-linolenic acid (18:3n-6) (β = 0.59, 95% CI: 0.28, 0.90), dihomo-γ-linolenic acid (20:3n-6) (β = 1.20, 95% CI: 0.65, 1.75), arachidonic acid (20:4n-6) (β = 0.08, 95% CI: 0.002, 0.16), palmitoleic acid (16:1n-7) (β = 0.37, 95% CI: 0.04, 0.70), Δ6 desaturase, and stearoyl CoA desaturase-1 (SCD-1) index were directly associated with liver fat after adjustment for confounders. Several serum CE fatty acids were correlated with both liver fat and REE, but only the association between DHA (22:6n-3) and liver fat was clearly attenuated after adjustment for REE (from β = -0.63 95% CI: -1.24, -0.02 to β = -0.34, 95% CI: -0.95, 0.27). Palmitoleic acid and SCD-1 were weakly inversely correlated with RQ but could not explain a lower liver fat content.

CONCLUSIONS

Several serum CE fatty acids are associated with liver fat, among them linoleic acid. Although we identified novel associations between individual fatty acids and RQ and REE, our findings imply that PUFAs might prevent liver fat accumulation through mechanisms other than enhanced whole-body energy metabolism.

Advances in Technologies for Highly Active Omega-3 Fatty Acids from Krill Oil: Clinical Applications

Euphausia superba, commonly known as krill, is a small marine crustacean from the Antarctic Ocean that plays an important role in the marine ecosystem, serving as feed for most fish. It is a known source of highly bioavailable omega-3 polyunsaturated fatty acids (eicosapentaenoic acid and docosahexaenoic acid). In preclinical studies, krill oil showed metabolic, anti-inflammatory, neuroprotective and chemo preventive effects, while in clinical trials it showed significant metabolic, vascular and ergogenic actions. Solvent extraction is the most conventional method to obtain krill oil. However, different solvents must be used to extract all lipids from krill because of the diversity of the polarities of the lipid compounds in the biomass. This review aims to provide an overview of the chemical composition, bioavailability and bioaccessibility of krill oil, as well as the mechanisms of action, classic and non-conventional extraction techniques, health benefits and current applications of this marine crustacean.

Krill Oil Supplementation Reduces Exacerbated Hepatic Steatosis Induced by Thermoneutral Housing in Mice with Diet-Induced Obesity

Preclinical evidence suggests that n-3 fatty acids EPA and DHA (Omega-3) supplemented as phospholipids (PLs) may be more effective than triacylglycerols (TAGs) in reducing hepatic steatosis. To further test the ability of Omega-3 PLs to alleviate liver steatosis, we used a model of exacerbated non-alcoholic fatty liver disease based on high-fat feeding at thermoneutral temperature. Male C57BL/6N mice were fed for 24 weeks a lard-based diet given either alone (LHF) or supplemented with Omega-3 (30 mg/g diet) as PLs (krill oil; ω3PL) or TAGs (Epax 3000TG concentrate; ω3TG), which had a similar total content of EPA and DHA and their ratio. Substantial levels of TAG accumulation (~250 mg/g) but relatively low inflammation/fibrosis levels were achieved in the livers of control LHF mice. Liver steatosis was reduced by >40% in the ω3PL but not ω3TG group, and plasma ALT levels were markedly reduced (by 68%) in ω3PL mice as well. Krill oil administration also improved hepatic insulin sensitivity, and its effects were associated with high plasma adiponectin levels (150% of LHF mice) along with superior bioavailability of EPA, increased content of alkaloids stachydrine and trigonelline, suppression of lipogenic gene expression, and decreased diacylglycerol levels in the liver. This study reveals that in addition to Omega-3 PLs, other constituents of krill oil, such as alkaloids, may contribute to its strong antisteatotic effects in the liver.

Health Beneficial Food Emulsifier Produced from Fishery Byproducts

The bioavailability of DHA-bound phospholipids, especially the DHA-bound lysophospholipid (DHA-LPL) could be considered the most effective DHA chemical forms for DHA accretion in the brain. Such a DHA-LPL should also have very high emulsifying stability performance based on its analogy with conventional soy LPL. Therefore, in this study, we describe two fishery byproducts, rich in DHA-bound phospholipids, to derive DHA-LPL via sn-1 positional specific lipase partial hydrolysis of the phospholipids. Through this reaction, the DHA composition increased to 43.8 % from 29.1 % in the salmon head phospholipid-derived DHA-LPL, and to 84.0 % from 47.4 % in the squid meal phospholipid-derived DHA-LPL. In fact, these obtained DHA-LPLs exhibited far higher emulsifying stability than the conventional food emulsifiers in the market. For example, the prepared high-purity squid meal phospholipid-derived LPL sustained an emulsion form for a week even under 80°C. Thus, food emulsifiers produced from fishery byproducts are considered to exhibit very high values of both in a sense of outstandingly high health benefits and sustaining emulsions even under very high temperatures.

Offspring of obese mice display enhanced intake and sensitivity for palatable stimuli, with altered expression of taste signaling elements

Maternal body mass index and gestational weight gain predict future obesity status of the offspring. In studies of both rodents and non-human primates, maternal obesity also predicts a preference for palatable foods in the offspring. In this study, we used C57BL/6J mice to investigate whether an underlying cause for an increase in palatable food consumption in the offspring of obese mice was a change in taste function. Adult female mice were fed a normal chow (NC) or a high fat diet (HFD) for 5 weeks before mating, then also during the gestation (3 weeks) and lactation (3 weeks) periods, with offspring always maintained on a normal chow diet; thus the only experience offspring had with high fat food was via maternal exposure. Offspring exhibited similar weight, blood glucose levels and baseline water and chow intake in adulthood. Taste response was assessed after reaching maturity, using brief-access taste testing, with female offspring of obese dams showing an enhanced response to sucrose, and both sexes consuming more sucrose, sucralose and high fat diet if from obese mothers. Offspring also exhibited increased taste bud expression of mRNA for sweet receptor subunits T1R (Taste receptor type) 2 and 3, as well as other markers associated with taste signaling. Taste morphology in both groups appeared similar. Results indicate that obesity in the mother may lead to unhealthy feeding behavior in the offspring, correlating with altered expression of taste signaling elements, which likely drive increased avidity for palatable foods.

Omega-3 Phospholipids from Krill Oil Enhance Intestinal Fatty Acid Oxidation More Effectively than Omega-3 Triacylglycerols in High-Fat Diet-Fed Obese Mice

Antisteatotic effects of omega-3 fatty acids (Omega-3) in obese rodents seem to vary depending on the lipid form of their administration. Whether these effects could reflect changes in intestinal metabolism is unknown. Here, we compare Omega-3-containing phospholipids (krill oil; ω3PL-H) and triacylglycerols (ω3TG) in terms of their effects on morphology, gene expression and fatty acid (FA) oxidation in the small intestine. Male C57BL/6N mice were fed for 8 weeks with a high-fat diet (HFD) alone or supplemented with 30 mg/g diet of ω3TG or ω3PL-H. Omega-3 index, reflecting the bioavailability of Omega-3, reached 12.5% and 7.5% in the ω3PL-H and ω3TG groups, respectively. Compared to HFD mice, ω3PL-H but not ω3TG animals had lower body weight gain (−40%), mesenteric adipose tissue (−43%), and hepatic lipid content (−64%). The highest number and expression level of regulated intestinal genes was observed in ω3PL-H mice. The expression of FA ω-oxidation genes was enhanced in both Omega-3-supplemented groups, but gene expression within the FA β-oxidation pathway and functional palmitate oxidation in the proximal ileum was significantly increased only in ω3PL-H mice. In conclusion, enhanced intestinal FA oxidation could contribute to the strong antisteatotic effects of Omega-3 when administered as phospholipids to dietary obese mice.

Brief daily access to cafeteria-style diet impairs hepatic metabolism even in the absence of excessive body weight gain in rats

Numerous nutritional approaches aimed at reducing body weight have been developed as a strategy to reduce obesity. Most of these interventions rely on reducing caloric intake or limiting calories access to a few hours per day. In this work, we analyzed the effects of the extended (24 hours/day) or restricted (1 hour/day) access to a cafeteria-style (CAF) diet, on rat body weight and hepatic lipid metabolism, with respect to control rats (CTR) fed with a standard chow diet. The body weight gain of restricted-fed rats was not different from CTR, despite the slightly higher total caloric intake, but resulted significantly lower than extended-fed rats, which showed a CAF diet-induced obesity and a dramatically higher total caloric intake. However, both CAF-fed groups of rats showed, compared to CTR, unhealthy serum and hepatic parameters such as higher serum glucose level, lower HDL values, and increased hepatic triacylglycerol and cholesterol amount. The hepatic expression and activity of key enzymes of fatty acid synthesis, acetyl-CoA carboxylase (ACC), and fatty acid synthase (FAS), was similarly reduced in both CAF-fed groups of rats with respect to CTR. Anyway, while in extended-fed rats this reduction was associated to a long-term mechanism involving sterol regulatory element-binding protein-1 (SREBP-1), in restricted-fed animals a short-term mechanism based on PKA and AMPK activation occurred in the liver. Furthermore, hepatic fatty acid oxidation (FAO) and oxidative stress resulted significantly increased in extended, but not in restricted-fed rats, as compared to CTR. Overall, these results demonstrate that although limiting the total caloric intake might successfully fight obesity development, the nutritional content of the diet is the major determinant for the health status.

Increased plasma levels of palmitoleic acid may contribute to beneficial effects of Krill oil on glucose homeostasis in dietary obese mice

Omega-3 polyunsatuarted fatty acids (PUFA) are associated with hypolipidemic and anti-inflammatory effects. However, omega-3 PUFA, usually administered as triacylglycerols or ethyl esters, could also compromise glucose metabolism, especially in obese type 2 diabetics. Phospholipids represent an alternative source of omega-3 PUFA, but their impact on glucose homeostasis is poorly explored. Male C57BL/6N mice were fed for 8 weeks a corn oil-based high-fat diet (cHF) alone or cHF-based diets containing eicosapentaenoic acid and docosahexaenoic acid (~3%; wt/wt), admixed either as a concentrate of re-esterified triacylglycerols (ω3TG) or Krill oil containing mainly phospholipids (ω3PL). Lean controls were fed a low-fat diet. Insulin sensitivity (hyperinsulinemic-euglycemic clamps), parameters of glucose homeostasis, adipose tissue function, and plasma levels of N-acylethanolamines, monoacylglycerols and fatty acids were determined. Feeding cHF induced obesity and worsened (~4.3-fold) insulin sensitivity as determined by clamp. Insulin sensitivity was almost preserved in ω3PL but not ω3TG mice. Compared with cHF mice, endogenous glucose production was reduced to 47%, whereas whole-body and muscle glycogen synthesis increased ~3-fold in ω3PL mice that showed improved adipose tissue function and elevated plasma adiponectin levels. Besides eicosapentaenoic and docosapentaenoic acids, principal component analysis of plasma fatty acids identified palmitoleic acid (C16:1n-7) as the most discriminating analyte whose levels were increased in ω3PL mice and correlated negatively with the degree of cHF-induced glucose intolerance. While palmitoleic acid from Krill oil may help improve glucose homeostasis, our findings provide a general rationale for using omega-3 PUFA-containing phospholipids as nutritional supplements with potent insulin-sensitizing effects.

Fatty Acids and Effects on In Vitro and In Vivo Models of Liver Steatosis

BACKGROUND

Fatty liver, or steatosis, is a condition of excess accumulation of lipids, mainly under form of triglycerides (TG), in the liver, and it is the hallmark of non-alcoholic fatty liver disease (NAFLD). NAFLD is the most common liver disorder world-wide and it has frequently been associated with obesity, hyperlipidemia and insulin resistance. Free fatty acids (FA) are the major mediators of hepatic steatosis; patients with NAFLD have elevated levels of circulating FA that correlate with disease severity.

METHODS

Steatosis is a reversible condition that can be resolved with changed behaviors, or that can progress towards more severe liver damages such as steatohepatitis (NASH), fibrosis and cirrhosis. In NAFLD, FA of exogenous or endogenous origin accumulate in the hepatocytes and trigger liver damages. Excess TG are stored in cytosolic lipid droplets (LDs) that are dynamic organelles acting as hubs for lipid metabolism.

RESULTS

In the first part of this review, we briefly reassumed the main classes of FA and their chemical classification as a function of the presence and number of double bonds, their metabolic pathways and effects on human health. Then, we summarized the main genetic and diet-induced animal models of NAFLD, as well as the cellular models of NAFLD.

CONCLUSIONS

In recent years, both the diet-induced animal models of NAFLD as well as the cellular models of NAFLD have found ever more application to investigate the mechanisms involved in NAFLD, and we referred to their advantages and disadvantages.

Omega-3 polyunsaturated fatty acids have beneficial effects on visceral fat in diet-induced obesity model

This study evaluated the effects of omega-3 polyunsaturated fatty acids (PUFAs) on oxidative stress and energy metabolism parameters in the visceral fat of a high-fat-diet induced obesity model. Energy intake, body mass, and visceral fat mass were also evaluated. Male Swiss mice received either a control diet (control group) or a high-fat diet (obese group) for 6 weeks. After this period, the groups were divided into control + saline, control + omega-3, obese + saline, and obese + omega-3, and to these groups 400 mg·(kg body mass)-1·day-1 of fish oil (or saline) was administered orally, for 4 weeks. Energy intake and body mass were monitored throughout the experiment. In the 10th week, the animals were euthanized and the visceral fat (mesenteric) was removed. Treatment with omega-3 PUFAs did not affect energy intake or body mass, but it did reduced visceral fat mass. In visceral fat, omega-3 PUFAs reduced oxidative damage and alleviated changes to the antioxidant defense system and the Krebs cycle. The mitochondrial respiratory chain was neither altered by obesity nor by omega-3 PUFAs. In conclusion, omega-3 PUFAs have beneficial effects on the visceral fat of obese mice because they mitigate changes caused by the consumption of a high-fat diet.

Effects of different proteases enzymatic extraction on the lipid yield and quality of Antarctic krill oil

This study was investigated the effects of six proteases (papain, compound proteinase, acidic protease, neutrase, pancreatin, and alcalase) on the lipid yield and quality of krill oil. The result shown that the krill oil extracted by alcalase and compound proteinase led to comparatively higher lipid yields (5.29% and 4.90%, respectively), Content of tocopherols and vitamin A, the content of omega-3 polyunsaturated fatty acids (PUFAs) and phospholipids extracted by alcalase was relatively higher. Control and alcalase had comparatively higher concentration of astaxanthin. On the whole, compared with the extraction of solvent, enzymatic hydrolysis could improve the quality and the lipid yield of krill oil. Therefore, enzymatic hydrolysis could be used as a better method to extract krill oil.

Insect Oil as An Alternative to Palm Oil and Poultry Fat in Broiler Chicken Nutrition

Simple Summary

Recently, there has been increasing interest in the use of insects as an alternative sustainable source of protein and fat in animal feed to improve animal production and maintain ecological sustainability. Palm oil is commonly used in broiler chicken nutrition; however, due to the environmental footprint, consumers have formed negative opinions regarding its applications. Therefore, alternatives to palm oil are urgently needed. The present study was conducted to evaluate the effects of Tenebrio molitor oil as a total replacement for palm oil and poultry fat in broiler chicken diets on chicken performance, nutrient digestibility, pancreatic enzyme activity, various blood parameters and lipid fatty acid compositions of liver and breast muscle tissues. Based on the obtained results, T. molitor oil did not show any adverse impacts on performance and improved the fatty acid profiles of liver and breast muscle tissues. In conclusion, T. molitor oil may be a sustainable alternative to palm oil in broiler chicken nutrition.

Abstract

This study was conducted to evaluate the effects of Tenebrio molitor (TM) oil as a total replacement for palm oil and poultry fat in broiler chicken diets on growth performance, nutrient digestibility, pancreatic enzyme activity, selected blood parameters and the lipid fatty acid compositions of liver and breast muscle tissues. A total of 72 seven-day-old female Ross 308 broiler chickens were used. The birds were randomly distributed into three groups with 12 replicates each, using two birds per replicate for 30 days in metabolic cages. The basal diet was supplemented with 5% palm oil, poultry fat or TM oil. There was no effect (p > 0.05) caused by the dietary oil replacement on the birds’ performance and apparent nutrient digestibility. Liver size (p = 0.033), the concentration of hepatic triglycerides (p = 0.049) and total cholesterol (p = 0.048) were reduced by TM oil supplementation. Furthermore, TM oil supplementation increased n-3 and n-6 fatty acids (p = 0.006; p < 0.001, respectively) in breast muscle tissue. In conclusion, the use of TM oil in broiler chickens’ diets did not show any adverse effects on performance, nutrient digestibility and blood biochemical parameters. Moreover, TM oil supplementation improved the fatty acid profiles of liver and breast muscle tissues.

20-Week follow-up of hepatic steatosis installation and liver mitochondrial structure and activity and their interrelation in rats fed a high-fat-high-fructose diet

The incidence of obesity and its metabolic complications are rapidly increasing and become a major public health issue. This trend is associated with an increase in the prevalence of non-alcoholic fatty liver disease (NAFLD), insulin resistance and diabetes. The sequence of events leading to NAFLD progression and mitochondrial dysfunction and their interrelation remains to be elucidated. This study aimed to explore the installation and progression of NAFLD and its association with the liver mitochondrial structure and activity changes in rats fed an obesogenic diet up to 20 weeks. Male Wistar rats were fed either a standard or high-fat-high-fructose (HFHFR) diet and killed on 4, 8, 12, 16 and 20 weeks of diet intake. Rats fed the HFHFR diet developed mildly overweight, associated with increased adipose tissue weight, hepatic steatosis, hyperglycaemia and hyperinsulinaemia after 8 weeks of HFHFR diet. Hepatic steatosis and many biochemical modifications plateaued at 8-12 weeks of HFHFR diet with slight amelioration afterwards. Interestingly, several biochemical and physiological parameters of mitochondrial function, as well as its phospholipid composition, in particular cardiolipin content, were tightly related to hepatic steatosis installation. These results showed once again the interrelation between hepatic steatosis development and mitochondrial activity alterations without being able to say whether the mitochondrial alterations preceded or followed the installation/progression of hepatic steatosis. Because both hepatic steatosis and mitochondrial alterations occurred as early as 4 weeks of diet, future studies should consider these four 1st weeks to reveal the exact interconnection between these major consequences of obesogenic diet intake.

Capybara Oil Improves Hepatic Mitochondrial Dysfunction, Steatosis, and Inflammation in a Murine Model of Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) is recognized as the most common cause of liver dysfunction worldwide and is commonly associated with obesity. Evidences suggest that NAFLD might be a mitochondrial disease, which contributes to the hepatic steatosis, oxidative stress, cytokine release, and cell death. Capybara oil (CO) is a rich source of polyunsaturated fatty acids (PUFA), which is known to improve inflammation and oxidative stress. In order to determine the effects of CO on NAFLD, C57Bl/6 mice were divided into 3 groups and fed a high-fat diet (HFD) (NAFLD group and NAFLD + CO group) or a control diet (CG group) during 16 weeks. The CO (1.5 g/kg/daily) was administered by gavage during the last 4 weeks of the diet protocol. We evaluated plasma liver enzymes, hepatic steatosis, and cytokine expression in liver as well as hepatocyte ultrastructural morphology and mitochondrial function. CO treatment suppressed hepatic steatosis, attenuated inflammatory response, and decreased plasma alanine aminotransferase (ALT) in mice with NAFLD. CO was also capable of restoring mitochondrial ultrastructure and function as well as balance superoxide dismutase and catalase levels. Our findings indicate that CO treatment has positive effects on NAFLD improving mitochondrial dysfunction, steatosis, acute inflammation, and oxidative stress.

Zonation of hepatic fat accumulation: insights from mathematical modelling of nutrient gradients and fatty acid uptake

Intrinsic of non-alcoholic fatty liver diseases is an aberrant accumulation of triglycerides (steatosis), which occurs inhomogeneously within lobules. To improve our understanding of the mechanisms involved in this zonation patterning, we developed a mathematical multicompartment model of hepatic fatty acid metabolism accompanied by blood flow simulations. A model analysis determines the influence of the uptake process of fatty acids, the porto-central gradient of plasma fatty acid concentration, and the oxygen supply via blood on the zonation of triglyceride accumulation. From this theoretical perspective, the plasma oxygen gradient, but not the fatty acid gradient, leads the way to a zonated triglyceride accumulation by its decisive role in oxidative processes. In addition, the uptake mechanism of fatty acids seems to be fundamental for a pericentral dominance of steatosis. However, the mechanism of cellular fatty acid uptake from the blood is still under debate. Our theoretical approach supports the transporter-mediated uptake mechanism and reveals that the maximal velocity of fatty acid uptake affects the switching between a periportal and a pericentral triglyceride accumulation. Further research on hepatic fatty acid uptake is needed to push forward our understanding of aberrant triglyceride accumulation in diet-induced steatosis.

Marine Omega-3 Fatty Acids, Complications of Pregnancy and Maternal Risk Factors for Offspring Cardio-Metabolic Disease

Marine omega-3 polyunsaturated fatty acids (n-3 PUFA) are important nutrients during periods of rapid growth and development in utero and infancy. Maternal health and risk factors play a crucial role in birth outcomes and subsequently offspring cardio-metabolic health. Evidence from observational studies and randomized trials have suggested a potential association of maternal intake of marine n-3 PUFAs during pregnancy with pregnancy and birth outcomes. However, there is inconsistency in the literature on whether marine n-3 PUFA supplementation during pregnancy can prevent maternal complications of pregnancy. This narrative literature review summarizes recent evidence on observational and clinical trials of marine n-3 PUFA intake on maternal risk factors and effects on offspring cardio-metabolic health. The current evidence generally does not support a role of maternal n-3 PUFA supplementation in altering the incidence of gestational diabetes, pregnancy-induced hypertension, or pre-eclampsia. It may be that benefits from marine n-3 PUFA supplementation are more pronounced in high-risk populations, such as women with a history of complications of pregnancy, or women with low marine n-3 PUFA intake. Discrepancies between studies may be related to differences in study design, dosage, fatty acid interplay, and length of treatment. Further prospective double-blind studies are needed to clarify the impact of long-chain marine n-3 PUFAs on risk factors for cardio-metabolic disease in the offspring.

Activation of Macrophages in vitro by Phospholipids from Brain of Katsuwonus pelamis (Skipjack Tuna)

The biological activities of phospholipids (PLs) have attracted people's attention, especially marine phospholipids with omega-3 polyunsaturated fatty acids DHA and EPA. In this study, we investigated the immunity activation of macrophages in vitro by phospholipids from skipjack brain. The phospholipids were extracted with hexane and ethanol ultrasonication instead of the traditional method of methanol and chloroform. The content of phospholipids from Skipjack brain was 19.59 g/kg by the method (the ratio of hexane and ethanol 2:1, 40 min, 35°C, 1:9 of the ratio of material to solvent, ultrasonic power 300W, ultrasonic extraction 2 times). The RAW264.7 macrophages were stimulated by the phospholipids from the Skipjack, by which the volume, viability and phagocytosis of macrophages were increased. The concentration of NO and the activity of SOD of the cells were also enhanced. The gene expressions of IL-1β, IL-6, iNOS and TNF-α mRNA assayed by RT-PCR were up-regulated. Phospholipids from brain of Skipjack Tuna could activate macrophages immunity which displayed to induce pro-inflammatroy cytokines mRNA expression.

Effects of krill oil and lean and fatty fish on cardiovascular risk markers: a randomised controlled trial

Fish consumption and supplementation with n-3 fatty acids reduce CVD risk. Krill oil is an alternative source of marine n-3 fatty acids and few studies have investigated its health effects. Thus, we compared krill oil supplementation with the intake of fish with similar amounts of n-3 fatty acids on different cardiovascular risk markers. In an 8-week randomised parallel study, thirty-six healthy subjects aged 18–70 years with fasting serum TAG between 1·3 and 4·0 mmol/l were randomised to receive either fish, krill oil or control oil. In the fish group, subjects consumed lean and fatty fish, according to dietary guidelines. The krill and control group received eight capsules per d containing 4 g oil per d. The weekly intake of marine n-3 fatty acids from fish given in the fish group and from krill oil in the krill group were 4103 and 4654 mg, respectively. Fasting serum TAG did not change between the groups. The level of total lipids (P = 0·007), phospholipids (P = 0·015), cholesterol (P = 0·009), cholesteryl esters (P = 0·022) and non-esterified cholesterol (P = 0·002) in the smallest VLDL subclass increased significantly in response to krill oil supplementation. Blood glucose decreased significantly (P = 0·024) in the krill group and vitamin D increased significantly in the fish group (P = 0·024). Furthermore, plasma levels of marine n-3 fatty acids increased significantly in the fish and krill groups compared with the control (all P ≤ 0·0003). In conclusion, supplementation with krill oil and intake of fish result in health-beneficial effects. Although only krill oil reduced fasting glucose, fish provide health-beneficial nutrients, including vitamin D.

Omega-3 fatty acids and adipose tissue biology

This review provides evidence for the importance of white and brown adipose tissue (i.e. WAT and BAT) function for the maintenance of healthy metabolic phenotype and its preservation in response to omega-3 polyunsaturated fatty acids (omega-3 PUFA), namely in the context of diseased states linked to aberrant accumulation of body fat, systemic low-grade inflammation, dyslipidemia and insulin resistance. More specifically, the review deals with (i) the concept of immunometabolism, i.e. how adipose-resident immune cells and adipocytes affect each other and define the immune-metabolic interface; and (ii) the characteristic features of "healthy adipocytes" in WAT, which are relatively small fat cells endowed with a high capacity for mitochondrial oxidative phosphorylation, triacylglycerol/fatty acid (TAG/FA) cycling and de novo lipogenesis (DNL). The intrinsic metabolic features of WAT and their flexible regulations, reflecting the presence of "healthy adipocytes", provide beneficial local and systemic effects, including (i) protection against in situ endoplasmic reticulum stress and related inflammatory response during activation of adipocyte lipolysis; (ii) prevention of ectopic fat accumulation and dyslipidemia caused by increased hepatic VLDL synthesis, as well as prevention of lipotoxic damage of insulin signaling in extra-adipose tissues; and also (iii) increased synthesis of anti-inflammatory and insulin-sensitizing lipid mediators with pro-resolving properties, including the branched fatty acid esters of hydroxy fatty acids (FAHFAs), also depending on the activity of DNL in WAT. The "healthy adipocytes" phenotype can be induced in WAT of obese mice in response to various stimuli including dietary omega-3 PUFA, especially when combined with moderate calorie restriction, and possibly also with other life style (e.g. physical activity) or pharmacological (e.g. thiazolidinediones) interventions. While omega-3 PUFA could exert beneficial systemic effects by improving immunometabolism of WAT without a concomitant induction of BAT, it is currently not clear whether the metabolic effects of the combined intervention using omega-3 PUFA and calorie restriction or thiazolidinediones depend also on the activation of BAT function and/or the induction of brite/beige adipocytes in WAT. It remains to be established why omega-3 PUFA intervention in type 2 diabetic subjects does not improve insulin sensitivity and glucose homeostasis despite inducing various anti-inflammatory mediators in WAT, including the recently discovered docosahexaenoyl esters of hydroxy linoleic acid, the lipokines from the FAHFA family, as well as several endocannabinoid-related anti-inflammatory lipids. To answer the question whether and to which extent omega-3 PUFA supplementation could promote the formation of "healthy adipocytes" in WAT of human subjects, namely in the obese insulin-resistant patients, represents a challenging task that is of great importance for the treatment of some serious non-communicable diseases.

Effects of Antarctic krill oil on lipid and glucose metabolism in C57BL/6J mice fed with high fat diet

Background

Obesity and other metabolic diseases have become epidemic which greatly affect human health. Diets with healthy nutrition are efficient means to prevent this epidemic occurrence. Novel food resources and process technology were needed for these purpose. In this study, Antarctic krill oil (KO) extracted from a dry krill by a procedure of hot pump dehydration in combined with freezing-drying was used to investigate health effect in animals including the growth, lipid and glucose metabolism.

Methods

C57BL/6J mice were fed with a lard based high fat (HF) diet and substituted with KO for a period of 12 weeks in comparison with low fat normal control (NC) diet. Mice body weight and food consumption were recorded. Serum lipid metabolism - of C57BL/6J mice serum was measured. A glucose tolerance tests (GTTs) and pathology analysis of mice were performed at the end of the experiment.

Results

The KO fed mice had less body weight gain, less fat accumulation in tissue such as adipose and liver. Dyslipidemia induced by high fat diet was partially improved by KO feeding with significant reduction of serum low density lipoprotein-cholesterol (LDL-C) content. Furthermore, KO feeding also improved glucose metabolism in C57BL/6J mice including a glucose tolerance of about 22% vs. 32% of AUC (area under the curve) for KO vs HF diet and the fast blood glucose level of 8.5 mmol/L, 9.8 mmol/L and 9.3 mmol/L for NC, HF and KO diet groups, respectively. In addition, KO feeding also reduced oxidative damage in liver with a decrease of malondialdehyde (MDA) content and increase of superoxide dismutase (SOD) content.

Conclusion

This study provided evidence of the beneficial effects of KO on animal health from the processed technology, particularly on lipid and glucose metabolism. This study confirmed that as the Antarctic krill was extracted with a procedure of efficient energy, it might make it possible for Krill oil to be available for food industry.

Microbial diversity and composition in different gut locations of hyperlipidemic mice receiving krill oil

Low-dose (LD, 100 mg kg^-1 day^-1), moderate-dose (MD, 200 mg kg^-1 day^-1), and high-dose (HD, 600 mg kg^-1 day^-1) krill oil treatments have a stepwise, enhanced effect on alleviating hyperlipidemia, and 16S rRNA sequencing of the fecal samples demonstrates that krill oil treatment alters microbial communities. Feces may not represent all microbial communities in the gastrointestinal (GI) tract. Therefore, in this study, the stored ileal and colon samples collected from LD and HD groups were sequenced, and the location-specific modulations of microbial communities were observed after krill oil treatments. The 16S rRNA sequencing of the ileal samples showed that the LD and HD groups have similar patterns between control and high-fat diet (HFD) treatments, and six most abundant genera and 40 operational taxonomic units that respond to krill oil treatment were identified. However, the 16S rRNA sequencing of the colon samples showed that LD krill oil shifts the structure from the HFD to that of the control, whereas the HD group was distributed between the control and HFD groups. The corresponding most abundant genera and responsive OTUs totaled 4 and 45, respectively. In conclusion, different gastrointestinal tract locations contain different microbial communities. These results will help to provide a comprehensive understanding of the role of dietary krill oil in modulating the gut microbiota and alleviating hyperlipidemia.

Lipid-modifying effects of krill oil in humans: systematic review and meta-analysis of randomized controlled trials

Context

Some experimental and clinical trials have shown that krill oil, extracted from small red crustaceans, might be an effective lipid-modifying agent, but the evidence is not conclusive.

Objective

The effect of krill oil supplements on plasma lipid concentrations was assessed through a systematic review of the literature and a meta-analysis of available randomized controlled trials.

Data sources

PubMed and Scopus were searched up to March 25, 2016, to identify RCTs investigating the effect of krill oil supplements on plasma lipids.

Study selection

Randomized controlled trials that investigated the impact of at least 2 weeks of supplementation with krill oil on plasma/serum concentrations of at least one of the main lipid parameters (ie, total cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, or triglycerides) and that reported sufficient information on plasma/serum lipid levels at baseline and at the end of study in both krill oil and control groups were eligible for inclusion.

Data extraction

Two reviewers independently extracted the following data: first author's name, year of publication, study location, study design, number of participants in the krill oil and control groups, dosage of krill oil, type of control allocation, treatment duration, demographic characteristics of study participants, and baseline and follow-up plasma concentrations of lipids. Effect size was expressed as the weighted mean difference (WMD) and 95% confidence interval (95%CI).

Results

Meta-analysis of data from 7 eligible trials (14 treatment arms) with 662 participants showed a significant reduction in plasma concentrations of low-density lipoprotein cholesterol (WMD, -15.52 mg/dL; 95%CI, -28.43 to -2.61; P = 0.018) and triglycerides (WMD, -14.03 mg/dL; 95%CI, -21.38 to -6.67; P < 0.001) following supplementation with krill oil. A significant elevation in plasma concentrations of high-density lipoprotein cholesterol was also observed (WMD, 6.65 mg/dL; 95%CI, 2.30 to 10.99; P = 0.003), while a reduction in plasma concentrations of total cholesterol did not reach statistical significance (WMD, -7.50 mg/dL; 95%CI, -17.94 to 2.93; P = 0.159).

Conclusion

Krill oil supplementation can reduce low-density lipoprotein cholesterol and triglycerides. Additional clinical studies with more participants are needed to assess the impact of krill oil supplementation on other indices of cardiometabolic risk and on the risk of cardiovascular outcomes.

Antioxidant dietary approach in treatment of fatty liver: New insights and updates

Non-alcoholic fatty liver disease (NAFLD) is a common clinicopathological condition, encompassing a range of conditions caused by lipid deposition within liver cells. To date, no approved drugs are available for the treatment of NAFLD, despite the fact that it represents a serious and growing clinical problem in the Western world. Identification of the molecular mechanisms leading to NAFLD-related fat accumulation, mitochondrial dysfunction and oxidative balance impairment facilitates the development of specific interventions aimed at preventing the progression of hepatic steatosis. In this review, we focus our attention on the role of dysfunctions in mitochondrial bioenergetics in the pathogenesis of fatty liver. Major data from the literature about the mitochondrial targeting of some antioxidant molecules as a potential treatment for hepatic steatosis are described and critically analysed. There is ample evidence of the positive effects of several classes of antioxidants, such as polyphenols (i.e., resveratrol, quercetin, coumestrol, anthocyanins, epigallocatechin gallate and curcumin), carotenoids (i.e., lycopene, astaxanthin and fucoxanthin) and glucosinolates (i.e., glucoraphanin, sulforaphane, sinigrin and allyl-isothiocyanate), on the reversion of fatty liver. Although the mechanism of action is not yet fully elucidated, in some cases an indirect interaction with mitochondrial metabolism is expected. We believe that such knowledge will eventually translate into the development of novel therapeutic approaches for fatty liver.

Modulation of the Gut Microbiota by Krill Oil in Mice Fed a High-Sugar High-Fat Diet

Multiple lines of evidence suggest that the gut microbiota plays vital roles in metabolic diseases such as hyperlipidemia. Previous studies have confirmed that krill oil can alleviate hyperlipidemia, but the underlying mechanism remains unclear. To discern whether krill oil changes the structure of the gut microbiota during the hyperlipidemia treatment, 72 mice were acclimatized with a standard chow diet for 2 weeks and then randomly allocated to receive a standard chow diet (control group, n = 12) or a high-sugar-high-fat (HSHF) diet supplemented with a low (100 μg/g·d, HSHF+LD group, n = 12), moderate (200 μg/g·d, HSHF+MD group, n = 12) or high dosage of krill oil (600 μg/g·d, HSHF+HD group, n = 12), simvastatin (HSHF+S group, n = 12) or saline (HSHF group, n = 12) continuously for 12 weeks. The resulting weight gains were attenuated, the liver index and the low-density lipoprotein, total cholesterol and triglyceride concentrations showed a stepwise reduction in the treated groups compared with those of the control group. A dose-dependent modulation of the gut microbiota was observed after treatment with krill oil. Low- and moderate- doses of krill oil increased the similarity between the composition of the HSHF diet-induced gut microbiota and that of the control, whereas the mice fed the high-dose exhibited a unique gut microbiota structure that was different from that of the control and HSHF groups. Sixty-five key operational taxonomic units (OTUs) that responded to the krill oil treatment were identified using redundancy analysis, of which 26 OTUs were increased and 39 OTUs were decreased compared with those of the HSHF group. In conclusion, the results obtained in this study suggest that the structural alterations in the gut microbiota induced by krill oil treatment were dose-dependent and associated with the alleviation of hyperlipidemia. Additionally, the high-dose krill oil treatment showed combined effects on the alleviation of hyperlipidemia and obesity.

Docosahexaenoic acid attenuates LPS-stimulated inflammatory response by regulating the PPARγ/NF-κB pathways in primary bovine mammary epithelial cells

BACKGROUND

Docosahexaenoic acid (DHA) is a major dietary n-3 polyunsaturated fatty acid (n-3 PUFA) in fish oil, and has been reported to possess a number of biological properties, such as anti-inflammatory, antitumor and immune-regulatory properties. However, whether DHA exert anti-inflammatory effect on lipopolysaccharide (LPS)-induced mastitis remains unclear. In this study, we investigate the effect and underlying mechanisms of the effects of DHA on LPS-stimulated primary bovine mammary epithelial cells (bMEC).

METHODS

The experiment was divided into six groups as followed: control group, GW9662+LPS+DHA (100μM) group, LPS and LPS+DHA (25, 50 and 100μM) groups. bMEC were treated with DHA for 3h before LPS (200μg/ml) stimulation, and incubated with the PPARγ inhibitor GW9662 for 12h before DHA treatment. The mRNA levels of TNF-α, IL-6 and IL-1β were measured by quantitative real-time PCR (qRT-PCR). Western blot was employed for measuring the transcriptional activity of NF-κB and PPARγ.

RESULTS

Our results showed that DHA pretreatment significantly decreased the mRNA expression of tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6) and interleukin-1β (IL-1β) in bMEC stimulated with LPS. Besides, DHA suppressed the phosphorylation of nuclear transcription factor-kappaB (NF-κB) p65 and degradation inhibitor of NF-κBα (IκBα) in NF-κB signal pathway, and activated proliferator activated receptor gamma (PPARγ). But, all those effects were obviously abolished by addition of GW9662, a specific inhibitor of PPARγ.

CONCLUSION

In conclusion, these results indicated that DHA may attenuate LPS-stimulated inflammatory response in bMEC by suppressing NF-κB activation through a mechanism partly dependent on PPARγ activation.

Metabolites from invasive pests inhibit mitochondrial complex II: A potential strategy for the treatment of human ovarian carcinoma?

The red pigment caulerpin, a secondary metabolite from the marine invasive green algae Caulerpa cylindracea can be accumulated and transferred along the trophic chain, with detrimental consequences on biodiversity and ecosystem functioning. Despite increasing research efforts to understand how caulerpin modifies fish physiology, little is known on the effects of algal metabolites on mammalian cells. Here we report for the first time the mitochondrial targeting activity of both caulerpin, and its closely related derivative caulerpinic acid, by using as experimental model rat liver mitochondria, a system in which bioenergetics mechanisms are not altered. Mitochondrial function was tested by polarographic and spectrophotometric methods. Both compounds were found to selectively inhibit respiratory complex II activity, while complexes I, III, and IV remained functional. These results led us to hypothesize that both algal metabolites could be used as antitumor agents in cell lines with defects in mitochondrial complex I. Ovarian cancer cisplatin-resistant cells are a good example of cell lines with a defective complex I function on which these molecules seem to have a toxic effect on proliferation. This provided novel insight toward the potential use of metabolites from invasive Caulerpa species for the treatment of human ovarian carcinoma cisplatin-resistant cells.

Krill oil reduces intestinal inflammation by improving epithelial integrity and impairing adherent-invasive Escherichia coli pathogenicity

BACKGROUND

Krill oil is a marine derived oil rich in phospholipids, astaxanthin and omega-3 fatty acids. Several studies have found benefits of krill oil against oxidative and inflammatory damage.

AIMS

We aimed at assessing the ability of krill oil to reduce intestinal inflammation by improving epithelial barrier integrity, increasing cell survival and reducing pathogenicity of adherent-invasive Escherichia coli.

METHODS

CACO2 and HT29 cells were exposed to cytomix (TNFα and IFNγ) to induce inflammation and co-exposed to cytomix and krill oil. E-cadherin, ZO-1 and F-actin levels were analyzed by immunofluorescence to assess barrier integrity. Scratch test was performed to measure wound healing. Cell survival was analyzed by flow cytometry. Adherent-invasive Escherichia coli LF82 was used for adhesion/invasion assay.

RESULTS

In inflamed cells E-cadherin and ZO-1 decreased, with loss of cell-cell adhesion, and F-actin polymerization increased stress fibres; krill oil restored initial conditions and improved wound healing, reduced bacterial adhesion/invasion in epithelial cells and survival within macrophages; krill oil reduced LF82-induced mRNA expression of pro-inflammatory cytokines.

CONCLUSIONS

Krill oil improves intestinal barrier integrity and epithelial restitution during inflammation and controls bacterial adhesion and invasion to epithelial cells. Thus, krill oil may represent an innovative tool to reduce intestinal inflammation.

Krill Oil Ameliorates Mitochondrial Dysfunctions in Rats Treated with High-Fat Diet

In recent years, several studies focused their attention on the role of dietary fats in the pathogenesis of hepatic steatosis. It has been demonstrated that a high-fat diet is able to induce hyperglycemia, hyperinsulinemia, obesity, and nonalcoholic fatty liver disease. On the other hand, krill oil, a novel dietary supplement of n-3 PUFAs, has the ability to improve lipid and glucose metabolism, exerting possible protective effects against hepatic steatosis. In this study we have investigated the effects of krill oil on mitochondrial energetic metabolism in animals fed a high-fat diet. To this end, male Sprague-Dawley rats were divided into three groups and fed for 4 weeks with a standard diet (control group), a diet with 35% fat (HF group), or a high-fat diet supplemented with 2.5% krill oil (HF+KO group). The obtained results suggest that krill oil promotes the burning of fat excess introduced by the high-fat diet. This effect is obtained by stimulating mitochondrial metabolic pathways such as fatty acid oxidation, Krebs cycle, and respiratory chain complexes activity. Modulation of the expression of carrier proteins involved in mitochondrial uncoupling was also observed. Overall, krill oil counteracts the negative effects of a high-fat diet on mitochondrial energetic metabolism.

Dietary n-3 PUFA Protects Mice from Con A Induced Liver Injury by Modulating Regulatory T Cells and PPAR-γ Expression

Background

Dietary n-3 polyunsaturated fatty acids (PUFA) exert anti-inflammatory and immunoregulatory effects through down-regulating the innate and adoptive immune response. However, the effect of dietary n-3 PUFA on CD4⁺CD25⁺ regulatory T cells (Tregs) is unclear.

Aims

The current study was to examine the relationship between n-3 PUFA and Tregs as well as their immunoregulatory effect in immune-mediated liver injury.

Methods

The mice model feeding with n-3 PUFA-enriched diet was established and Tregs were analyzed. Effect of docosahexaenoic acid (DHA) on Tregs proliferation and induction was determined in vitro. The potential immunotherapeutic effect of dietary n-3 PUFA was investigated through Con A-induced hepatitis model.

Results

Long-term administration of dietary n-3 PUFA significantly increased hepatic Tregs and modulated their phenotype. n-3 PUFA or DHA directly increased natural Tregs (nTreg) proliferation but didn’t increase inducible Tregs (iTreg). In addition, the expression of peroxisome proliferator activated receptor gamma (PPAR-γ), transforming growth factor β (TGF-β) and interleukin (IL)-10 were significantly up-regulated in n-3 PUFA-enriched diet-fed mice. Finally, n-3 PUFA-enriched diet alleviated liver injury induced by Con A and down-regulated pro-inflammatory cytokines expression, accompanied by increased PPAR-γ expression.

Conclusion

Dietary n-3 PUFA enhanced Tregs generation through up-regulating PPAR-γ and TGF-β expression, and protected mice from Con A-induced liver injury. This finding provides a promising potential therapeutic method in treating inflammatory and autoimmune disease.

Krill products: an overview of animal studies

Many animal studies have been performed with krill oil (KO) and this review aims to summarize their findings and give insight into the mechanism of action of KO. Animal models that have been used in studies with KO include obesity, depression, myocardial infarction, chronic low-grade and ulcerative inflammation and are described in detail. Moreover, studies with KO in the form of krill powder (KP) and krill protein concentrate (KPC) as a mix of lipids and proteins are mentioned and compared to the effects of KO. In addition, differences in tissue uptake of the long-chain omega-3 polyunsaturated fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), when delivered in either phospholipid or triglyceride form, are addressed and the differential impact the delivery form has on gene expression profiles is explained. In our outlook, we try to highlight the potential of KO and KP supplementation in clinical settings and discuss health segments that have a high potential of showing krill product specific health benefits and warrant further clinical investigations.

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.

Lipid signaling in adipose tissue: Connecting inflammation & metabolism

Obesity-associated low-grade inflammation of white adipose tissue (WAT) contributes to development of insulin resistance and other disorders. Accumulation of immune cells, especially macrophages, and macrophage polarization from M2 to M1 state, affect intrinsic WAT signaling, namely anti-inflammatory and proinflammatory cytokines, fatty acids (FA), and lipid mediators derived from both n-6 and n-3 long-chain PUFA such as (i) arachidonic acid (AA)-derived eicosanoids and endocannabinoids, and (ii) specialized pro-resolving lipid mediators including resolvins derived from both eicosapentaenoic (EPA) and docosahexaenoic acid (DHA), lipoxins (AA metabolites), protectins and maresins (DHA metabolites). In this respect, potential differences in modulating adipocyte metabolism by various lipid mediators formed by inflammatory M1 macrophages typical of obese state, and non-inflammatory M2 macrophages typical of lean state remain to be established. Studies in mice suggest that (i) transient accumulation of M2 macrophages could be essential for the control of tissue FA levels during activation of lipolysis, (ii) currently unidentified M2 macrophage-borne signaling molecule(s) could inhibit lipolysis and re-esterification of lipolyzed FA back to triacylglycerols (TAG/FA cycle), and (iii) the egress of M2 macrophages from rebuilt WAT and removal of the negative feedback regulation could allow for a full unmasking of metabolic activities of adipocytes. Thus, M2 macrophages could support remodeling of WAT to a tissue containing metabolically flexible adipocytes endowed with a high capacity of both TAG/FA cycling and oxidative phosphorylation. This situation could be exemplified by a combined intervention using mild calorie restriction and dietary supplementation with EPA/DHA, which enhances the formation of "healthy" adipocytes. This article is part of a Special Issue entitled Oxygenated metabolism of PUFA: analysis and biological relevance."

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.