Differential Interventional Effects of Omega-6 and Omega-3 Polyunsaturated Fatty Acids on High Fat Diet-Induced Obesity and Hepatic Pathology.

Current Dietary Guidelines for Americans recommend replacing saturated fat (SFA) intake with polyunsaturated fatty acids (PUFAs) and monosaturated fatty acids (MUFAs) but do not specify the type of PUFAs, which consist of two functionally distinct classes: omega-6 (n-6) and omega-3 (n-3) PUFAs. Given that modern Western diets are already rich in n-6 PUFAs and the risk of chronic disease remains high today, we hypothesized that increased intake of n-3 PUFAs, rather than n-6 PUFAs, would be a beneficial intervention against obesity and related liver diseases caused by high-fat diets. To test this hypothesis, we fed C57BL/6J mice with a high-fat diet (HF) for 10 weeks to induce obesity, then divided the obese mice into three groups and continued feeding for another 10 weeks with one of the following three diets: HF, HF+n-6 (substituted half of SFA with n-6 PUFAs), and HF+n-3 (substituted half of SFA with n-3 PUFAs), followed by assessment of body weight, fat mass, insulin sensitivity, hepatic pathology, and lipogenesis. Interestingly, we found that the HF+n-6 group, like the HF group, had a continuous increase in body weight and fat mass, while the HF+n-3 group had a significant decrease in body weight and fat mass, although all groups had the same calorie intake. Accordingly, insulin resistance and fatty liver pathology (steatosis and fat levels) were evident in the HF+n-6 and HF groups but barely seen in the HF+n-3 group. Furthermore, the expression of lipogenesis-related genes in the liver was upregulated in the HF+n-6 group but downregulated in the HF+n-3 group. Our findings demonstrate that n-6 PUFAs and n-3 PUFAs have differential effects on obesity and fatty liver disease and highlight the importance of increasing n-3 PUFAs and reducing n-6 PUFAs (balancing the n-6/n-3 ratio) in clinical interventions and dietary guidelines for the management of obesity and related diseases.

n-3 Polyunsaturated Fatty Acids Modulate LPS-Induced ARDS and the Lung-Brain Axis of Communication in Wild-Type versus Fat-1 Mice Genetically Modified for Leukotriene B4 Receptor 1 or Chemerin Receptor 23 Knockout.

Specialized pro-resolving mediators (SPMs) and especially Resolvin E1 (RvE1) can actively terminate inflammation and promote healing during lung diseases such as acute respiratory distress syndrome (ARDS). Although ARDS primarily affects the lung, many ARDS patients also develop neurocognitive impairments. To investigate the connection between the lung and brain during ARDS and the therapeutic potential of SPMs and its derivatives, fat-1 mice were crossbred with RvE1 receptor knockout mice. ARDS was induced in these mice by intratracheal application of lipopolysaccharide (LPS, 10 µg). Mice were sacrificed at 0 h, 4 h, 24 h, 72 h, and 120 h post inflammation, and effects on the lung, liver, and brain were assessed by RT-PCR, multiplex, immunohistochemistry, Western blot, and LC-MS/MS. Protein and mRNA analyses of the lung, liver, and hypothalamus revealed LPS-induced lung inflammation increased inflammatory signaling in the hypothalamus despite low signaling in the periphery. Neutrophil recruitment in different brain structures was determined by immunohistochemical staining. Overall, we showed that immune cell trafficking to the brain contributed to immune-to-brain communication during ARDS rather than cytokines. Deficiency in RvE1 receptors and enhanced omega-3 polyunsaturated fatty acid levels (fat-1 mice) affect lung-brain interaction during ARDS by altering profiles of several inflammatory and lipid mediators and glial activity markers.

Comparing Transgenic Production to Supplementation of ω-3 PUFA Reveals Distinct But Overlapping Mechanisms Underlying Protection Against Metabolic and Hepatic Disorders.

We compared endogenous ω-3 PUFA production to supplementation for improving obesity-related metabolic dysfunction. Fat-1 transgenic mice, who endogenously convert exogenous ω-6 to ω-3 PUFA, and wild-type littermates were fed a high-fat diet and a daily dose of either ω-3 or ω-6 PUFA-rich oil for 12 wk. The endogenous ω-3 PUFA production improved glucose intolerance and insulin resistance but not hepatic steatosis. Conversely, ω-3 PUFA supplementation fully prevented hepatic steatosis but failed to improve insulin resistance. Both models increased hepatic levels of ω-3 PUFA-containing 2-monoacylglycerol and N-acylethanolamine congeners, and reduced levels of ω-6 PUFA-derived endocannabinoids with ω-3 PUFA supplementation being more efficacious. Reduced hepatic lipid accumulation associated with the endocannabinoidome metabolites EPEA and DHEA, which was causally demonstrated by lower lipid accumulation in oleic acid-treated hepatic cells treated with these metabolites. While both models induced a significant fecal enrichment of the beneficial Allobaculum genus, mice supplemented with ω-3 PUFA displayed additional changes in the gut microbiota functions with a significant reduction of fecal levels of the proinflammatory molecules lipopolysaccharide and flagellin. Multiple-factor analysis identify that the metabolic improvements induced by ω-3 PUFAs were accompanied by a reduced production of the proinflammatory cytokine TNFα, and that ω-3 PUFA supplementation had a stronger effect on improving the hepatic fatty acid profile than endogenous ω-3 PUFA. While endogenous ω-3 PUFA production preferably improves glucose tolerance and insulin resistance, ω-3 PUFA intake appears to be required to elicit selective changes in hepatic endocannabinoidome signaling that are essential to alleviate high-fat diet-induced hepatic steatosis.

Essential lipid autacoids rewire mitochondrial energy efficiency in metabolic dysfunction-associated fatty liver disease.

BACKGROUND AND AIM: Injury to hepatocyte mitochondria is common in metabolic dysfunction-associated fatty liver disease. Here, we investigated whether changes in the content of essential fatty acid-derived lipid autacoids affect hepatocyte mitochondrial bioenergetics and metabolic efficiency. APPROACH AND RESULTS: The study was performed in transgenic mice for the fat-1 gene, which allows the endogenous replacement of the membrane omega-6-polyunsaturated fatty acid (PUFA) composition by omega-3-PUFA. Transmission electron microscopy revealed that hepatocyte mitochondria of fat-1 mice had more abundant intact cristae and higher mitochondrial aspect ratio. Fat-1 mice had increased expression of oxidative phosphorylation complexes I and II and translocases of both inner (translocase of inner mitochondrial membrane 44) and outer (translocase of the outer membrane 20) mitochondrial membranes. Fat-1 mice also showed increased mitofusin-2 and reduced dynamin-like protein 1 phosphorylation, which mediate mitochondrial fusion and fission, respectively. Mitochondria of fat-1 mice exhibited enhanced oxygen consumption rate, fatty acid ß-oxidation, and energy substrate utilization as determined by high-resolution respirometry, [1- 14 C]-oleate oxidation and nicotinamide adenine dinucleotide hydride/dihydroflavine-adenine dinucleotide production, respectively. Untargeted lipidomics identified a rich hepatic omega-3-PUFA composition and a specific docosahexaenoic acid (DHA)-enriched lipid fingerprint in fat-1 mice. Targeted lipidomics uncovered a higher content of DHA-derived lipid autacoids, namely resolvin D1 and maresin 1, which rescued hepatocytes from TNFα-induced mitochondrial dysfunction, and unblocked the tricarboxylic acid cycle flux and metabolic utilization of long-chain acyl-carnitines, amino acids, and carbohydrates. Importantly, fat-1 mice were protected against mitochondrial injury induced by obesogenic and fibrogenic insults. CONCLUSION: Our data uncover the importance of a lipid membrane composition rich in DHA and its lipid autacoid derivatives to have optimal hepatic mitochondrial and metabolic efficiency.

Enzymatically-epoxidized docosahexaenoic acid, 19,20-EpDPE, suppresses hepatic crown-like structure formation and nonalcoholic steatohepatitis fibrosis through GPR120.

A hepatic crown-like structure (hCLS) formed by macrophages accumulating around lipid droplets and dead cells in the liver is a unique feature of nonalcoholic steatohepatitis (NASH) that triggers progression of liver fibrosis. As hCLS plays a key role in the progression of NASH fibrosis, hCLS formation has emerged as a potential therapeutic target. n-3 polyunsaturated fatty acids (n-3 PUFAs) have potential suppressive effects on NASH fibrosis; however, the mechanisms underlying this effect are poorly understood. Here, we report that n-3 PUFA-enriched Fat-1 transgenic mice are resistant to hCLS formation and liver fibrosis in a NASH model induced by a combination of high-fat diet, CCl4 and a Liver X receptor (LXR) agonist. Liquid chromatography-tandem mass spectrometry-based mediator lipidomics revealed that the amount of endogenous n-3 PUFA-derived metabolites, such as 17,18-dihydroxyeicosatetraenoic acid (17,18-diHETE), and 19,20-epoxy docosapentaenoic acid (19,20-EpDPE), was significantly elevated in Fat-1 mice, along with hCLS formation. In particular, DHA-derived 19,20-EpDPE produced by Cyp4f18 attenuated the hCLS formation and liver fibrosis in a G protein-coupled receptor 120 (GPR120)-dependent manner. These results indicated that 19,20-EpDPE is an endogenous active metabolite that mediates the preventive effect of n-3 PUFAs against NASH fibrosis.

Omega-3 Polyunsaturated Fatty Acids Protect against High-Fat Diet-Induced Morphological and Functional Impairments of Brown Fat in Transgenic Fat-1 Mice.

The role of omega-3 polyunsaturated fatty acids (n-3 PUFAs) in the regulation of energy homeostasis remains poorly understood. In this study, we used a transgenic fat-1 mouse model, which can produce n-3 PUFAs endogenously, to investigate how n-3 PUFAs regulate the morphology and function of brown adipose tissue (BAT). We found that high-fat diet (HFD) induced a remarkable morphological change in BAT, characterized by "whitening" due to large lipid droplet accumulation within BAT cells, associated with obesity in wild-type (WT) mice, whereas the changes in body fat mass and BAT morphology were significantly alleviated in fat-1 mice. The expression of thermogenic markers and lypolytic enzymes was significantly higher in fat-1 mice than that in WT mice fed with HFD. In addition, fat-1 mice had significantly lower levels of inflammatory markers in BAT and lipopolysaccharide (LPS) in plasma compared with WT mice. Furthermore, fat-1 mice were resistant to LPS-induced suppression of UCP1 and PGC-1 expression and lipid deposits in BAT. Our data has demonstrated that high-fat diet-induced obesity is associated with impairments of BAT morphology (whitening) and function, which can be ameliorated by elevated tissue status of n-3 PUFAs, possibly through suppressing the effects of LPS on inflammation and thermogenesis.

Lipidomic analysis revealed n-3 polyunsaturated fatty acids suppressed choroidal thinning and myopia progression in mice.

Myopia is increasing worldwide and its preventable measure should urgently be pursued. N-3 polyunsaturated fatty acids (PUFAs) have been reported to have various effects such as vasodilative and anti-inflammatory, which myopia may be involved in. This study is to investigate the inhibitory effect of PUFAs on myopia progression. A lens-induced myopia (LIM) model was prepared using C57B L6/J 3-week-old mice, which were equipped with a -30 diopter lens to the right eye. Chows containing two different ratios of n-3/n-6 PUFA were administered to the mice, and myopic shifts were confirmed in choroidal thickness, refraction, and axial length in the n-3 PUFA-enriched chow group after 5 weeks. To exclude the possibility that the other ingredients in the chow may have taken the suppressive effect, fat-1 transgenic mice, which can produce n-3 PUFAs endogenously, demonstrated significant suppression of myopia. To identify what elements in n-3 PUFAs took effects on myopia suppression, enucleated eyes were used for targeted lipidomic analysis, and eicosapentaenoic acid (EPA) were characteristically distributed. Administration of EPA to the LIM model confirmed the inhibitory effect on choroidal thinning and myopia progression. Subsequently, to identify the elements and the metabolites of fatty acids effective on myopia suppression, targeted lipidomic analysis was performed and it demonstrated that metabolites of EPA were involved in myopia suppression, whereas prostaglandin E2 and 14,15-dihydrotestosterone were associated with progression of myopia. In conclusion, EPA and its metabolites are related to myopia suppression and inhibition of choroidal thinning.

Decreased Tissue Omega-6/Omega-3 Fatty Acid Ratio Prevents Chemotherapy-Induced Gastrointestinal Toxicity Associated with Alterations of Gut Microbiome.

Gastrointestinal toxicity (GIT) is a debilitating side effect of Irinotecan (CPT-11) and limits its clinical utility. Gut dysbiosis has been shown to mediate this side effect of CPT-11 by increasing gut bacterial ß-glucuronidase (GUSB) activity and impairing the intestinal mucosal barrier (IMB). We have recently shown the opposing effects of omega-6 (n-6) and omega-3 (n-3) polyunsaturated fatty acids (PUFA) on the gut microbiome. We hypothesized that elevated levels of tissue n-3 PUFA with a decreased n-6/n-3 PUFA ratio would reduce CPT-11-induced GIT and associated changes in the gut microbiome. Using a unique transgenic mouse (FAT-1) model combined with dietary supplementation experiments, we demonstrate that an elevated tissue n-3 PUFA status with a decreased n-6/n-3 PUFA ratio significantly reduces CPT-11-induced weight loss, bloody diarrhea, gut pathological changes, and mortality. Gut microbiome analysis by 16S rRNA gene sequencing and QIIME2 revealed that improvements in GIT were associated with the reduction in the CPT-11-induced increase in both GUSB-producing bacteria (e.g., Enterobacteriaceae) and GUSB enzyme activity, decrease in IMB-maintaining bacteria (e.g., Bifidobacterium), IMB dysfunction and systemic endotoxemia. These results uncover a host-microbiome interaction approach to the management of drug-induced gut toxicity. The prevention of CPT-11-induced gut microbiome changes by decreasing the tissue n-6/n-3 PUFA ratio could be a novel strategy to prevent chemotherapy-induced GIT.

N-3 Polyunsaturated Fatty Acids Ameliorate Neurobehavioral Outcomes Post-Mild Traumatic Brain Injury in the Fat-1 Mouse Model.

Concussions and mild traumatic brain injury (m-TBI) have been identified as a consequential public health concern because of their potential to cause considerable impairments in physical, cognitive, behavioral, and social functions. Given their prominent structural and functional roles in the brain, n-3 polyunsaturated fatty acids (PUFA) have been identified as a potentially viable prophylactic agent that may ameliorate the deleterious effects of m-TBI on brain function. The purpose of the present pilot study was to investigate the effect of n-3 PUFA on neurologic function using a weight drop injury (WDI) model. Fat-1 mice, capable of synthesizing n-3 PUFA endogenously from n-6 PUFA, and their wild-type (WT) counterparts, were subjected to a mild low-impact WDI on the closed cranium, and recovery was evaluated using the neurological severity score (NSS) to assess the motor and neurobehavioral outcomes. In comparison to the WT mice, the fat-1 mice had a significantly (p ≤ 0.05) lower NSS at all time points post-WDI, and significantly greater neurological restoration measured as the time to first movement. Overall, these findings demonstrate the protective effect of n-3 PUFA against mild brain injury.

Increased lipogenesis is critical for self-renewal and growth of breast cancer stem cells: Impact of omega-3 fatty acids.

Aberrant lipid metabolism has recently been recognized as a new hallmark of malignancy, but the characteristics of fatty acid metabolism in breast cancer stem cells (BCSC) and potential interventions targeting this pathway remain to be addressed. Here, by using the in vitro BCSC models, mammosphere-derived MCF-7 cells and HMLE-Twist-ER cells, we found that the cells with stem cell-like properties exhibited a very distinct profile of fatty acid metabolism compared with that of their parental cancer cells, characterized by increased lipogenesis, especially the activity of stearoyl-CoA desaturase 1 (SCD1) responsible for the production of monounsaturated fatty acids, and augmented synthesis and utilization of the omega-6 arachidonic acid (AA). Suppression of SCD1 activity by either enzyme inhibitors or small interfering RNA (siRNA) knockdown strikingly limited self-renewal and growth of the BCSC, suggesting a key role for SCD1 in BCSC proliferation. Furthermore, elevated levels of SCD1 and other lipogenic enzymes were observed in human breast cancer tissues relative to the noncancer tissues from the same patients and correlated with the pathological grades. Interestingly, treatment of BCSC with omega-3 fatty acids, eicosapentaenoic acid and docosahexaenoic acid, effectively downregulated the expression of the lipogenic enzymes and markedly suppressed BCSC self-renewal and growth. Dietary supplementation of nude mice bearing BCSC-derived tumors with omega-3 fatty acids also significantly reduced their tumor load. These findings have demonstrated that increased lipogenesis is critical for self-renewal and growth of BCSC, and that omega-3 fatty acids are effective in targeting this pathway to exert their anticancer effect.

Beneficial effects of an endogenous enrichment in n3-PUFAs on Wnt signaling are associated with attenuation of alcohol-mediated liver disease in mice.

Alcohol-associated liver disease (ALD) is a major human health issue for which there are limited treatment options. Experimental evidence suggests that nutrition plays an important role in ALD pathogenesis, and specific dietary fatty acids, for example, n6 or n3-PUFAs, may exacerbate or attenuate ALD, respectively. The purpose of the current study was to determine whether the beneficial effects of n3-PUFA enrichment in ALD were mediated, in part, by improvement in Wnt signaling. Wild-type (WT) and fat-1 transgenic mice (that endogenously convert n6-PUFAs to n3) were fed ethanol (EtOH) for 6 weeks followed by a single LPS challenge. fat-1 mice had less severe liver damage than WT littermates as evidenced by reduced plasma alanine aminotransferase, hepatic steatosis, liver tissue neutrophil infiltration, and pro-inflammatory cytokine expression. WT mice had a greater downregulation of Axin2, a key gene in the Wnt pathway, than fat-1 mice in response to EtOH and LPS. Further, there were significant differences between WT and fat-1 EtOH+LPS-challenged mice in the expression of five additional genes linked to the Wnt signaling pathway, including Apc, Fosl1/Fra-1, Mapk8/Jnk-1, Porcn, and Nkd1. Compared to WT, primary hepatocytes isolated from fat-1 mice exhibited more effective Wnt signaling and were more resistant to EtOH-, palmitic acid-, or TNFα-induced cell death. Further, we demonstrated that the n3-PUFA-derived lipid mediators, resolvins D1 and E1, can regulate hepatocyte expression of several Wnt-related genes that were differentially expressed between WT and fat-1 mice. These data demonstrate a novel mechanism by which n3-PUFAs can ameliorate ALD.

Transgenic conversion of ω-6 to ω-3 polyunsaturated fatty acids via fat-1 reduces the severity of post-traumatic osteoarthritis.

BACKGROUND: Dietary fatty acid (FA) content has been shown to influence the development of post-traumatic osteoarthritis (PTOA) in obesity. We used the fat-1 transgenic mouse to examine the hypothesis that endogenous reduction of ω-6 to ω-3 FA ratio, under the same dietary conditions, would mitigate metabolic inflammation and the pathogenesis of PTOA in obese male and female mice. METHODS: Male and female fat-1 and wild-type littermates were fed either a control diet or an ω-6 FA-rich high-fat diet and underwent destabilization of the medial meniscus (DMM) surgery to induce PTOA. OA severity, synovitis, and osteophyte formation were determined histologically, while biomarker and lipidomic analyses were performed to evaluate levels of adipokines, insulin, pro-/anti-inflammatory cytokines, and FAs in serum and joint synovial fluid. Multivariable models were performed to elucidate the associations of dietary, metabolic, and mechanical factors with PTOA. RESULTS: We found that elevated serum levels of ω-3 FAs in fat-1 mice as compared to wild-type controls fed the same diet resulted in reduced OA and synovitis in a sex- and diet-dependent manner, despite comparable body weights. The fat-1 mice showed trends toward decreased serum pro-inflammatory cytokines and increased anti-inflammatory cytokines. Multivariable analysis for variables predicting OA severity in mice resulted in correlations with serum FA levels, but not with body weight. CONCLUSIONS: This study provides further evidence that circulating FA composition and systemic metabolic inflammation, rather than body weight, may be the major risk factor for obesity-associated OA. We also demonstrate the potential genetic use of ω-3 FA desaturase in mitigating PTOA in obese patients following injury.

Lifelong n-3 Polyunsaturated Fatty Acid Exposure Modulates Size of Mammary Epithelial Cell Populations and Expression of Caveolae Resident Proteins in Fat-1 Mice.

Omega-3 polyunsaturated fatty acids (n-3 PUFA) have been associated with reduced breast cancer risk; however, the exact mechanism remains elusive. Female wildtype (WT) and fat-1 mice were fed a 10% safflower diet until 6 weeks of age. Mammary gland epithelial cells (EC) were isolated and EC populations were determined by CD24 surface expression. Fat-1 mice expressed 65%, 20%, and 15% while WT mice expressed 65%, 26% and 9% for non-, myo- and luminal ECs, respectively. The luminal EC population was significantly greater in fat-1 mice (p ≤ 0.05), while the total number of mammary ECs were similar between groups (p = 0.79). Caveolae was isolated from ECs and Her-2/neu, ER-α and cav-1 protein expression was determined by Western blotting. Fat-1 mice had a two-fold greater ER-α (p ≤ 0.05) and a 1.5-fold greater cav-1 (p ≤ 0.05) expression than WT with a similar amount of Her-2/neu protein (p = 0.990) between groups. Overall, this study provides novel mechanistic evidence by which n-3 PUFA modifies early mammary gland development that may potentially reduce breast cancer risk later in life.

Multi-omic analysis in transgenic mice implicates omega-6/omega-3 fatty acid imbalance as a risk factor for chronic disease.

An unbalanced increase in dietary omega-6 (n-6) polyunsaturated fatty acids (PUFA) and decrease in omega-3 (n-3) PUFA in the Western diet coincides with the global rise in chronic diseases. Whether n-6 and n-3 PUFA oppositely contribute to the development of chronic disease remains controversial. By using transgenic mice capable of synthesizing PUFA to eliminate confounding factors of diet, we show here that alteration of the tissue n-6/n-3 PUFA ratio leads to correlated changes in the gut microbiome and fecal and serum metabolites. Transgenic mice able to overproduce n-6 PUFA and achieve a high tissue n-6/n-3 PUFA ratio exhibit an increased risk for metabolic diseases and cancer, whereas mice able to convert n-6 to n-3 PUFA, and that have a lower n-6/n-3 ratio, show healthy phenotypes. Our study demonstrates that n-6 PUFA may be harmful in excess and suggests the importance of a low tissue n-6/n-3 ratio in reducing the risk for chronic diseases.

The protective role of endogenous n-3 polyunsaturated fatty acids in Tau Alzheimer's disease mouse model.

OBJECTIVES: The role of n-3 polyunsaturated fatty acid (PUFA) as the main docosahexaenoic acid (DHA) in Alzheimer's disease (AD) remains controversial. Our study aimed to provide detailed information about the role of endogenous n-3 PUFAs in AD. METHODS: Here, we generated a fat-1/tau transgenic mouse AD model by crossing female tau mice with male fat-1 mice to exclude confounding variables associated with the benefit of a DHA diet in these AD mice models. PUFAs presented in these AD models were detected by gas chromatography, and the role of endogenous n-3 PUFAs was assessed by lifespan survival assay, behavioral, pathologic, and molecular biology testing as well as imaging of cerebral vasculature. RESULTS: Endogenous n-3 PUFAs were shown to improve the memory and learning ability of AD mice. One possible reason for this improvement is the reduced formation of neurotrophic factors (NFTs) and Aß amyloid plaques which usually damage hippocampal neurons. Additionally, endogenous n-3 PUFAs were demonstrated to protect cerebral vascular of AD mice, thereby increasing brain metabolism. Besides, endogenous n-3 PUFAs were observed to extend of the overall survival of tau mouse models. CONCLUSION: Endogenous n-3 PUFAs delayed the onset of Alzheimer's disease caused by tau protein dysfunction, alleviating related symptoms and significantly prolonging survival in vivo.

An omega-3 polyunsaturated fatty acid derivative, 18-HEPE, protects against CXCR4-associated melanoma metastasis.

Melanoma has a high propensity to metastasize and exhibits a poor response to classical therapies. Dysregulation of the chemokine receptor gene CXCR4 is associated with melanoma progression, and although n-3 polyunsaturated fatty acids (PUFAs) are known to be beneficial for melanoma prevention, the underlying mechanism of this effect is unclear. Here, we used the n-3 fatty acid desaturase (Fat-1) transgenic mouse model of endogenous n-3 PUFA synthesis to investigate the influence of elevated n-3 PUFA levels in a mouse model of metastatic melanoma. We found that relative to wild-type (WT) mice, Fat-1 mice exhibited fewer pulmonary metastatic colonies and improved inflammatory indices, including reduced serum tumor necrosis factor alpha (TNF-α) levels and pulmonary myeloperoxidase activity. Differential PUFA metabolites in serum were considered a key factor to alter cancer cell travelling to lung, and we found that n-6 PUFAs such as arachidonic acid induced CXCR4 protein expression although n-3 PUFAs such as eicosapentaenoic acid (EPA) decreased CXCR4 levels. In addition, serum levels of the bioactive EPA metabolite, 18-HEPE, were elevated in Fat-1 mice relative to WT mice, and 18-HEPE suppressed CXCR4 expression in B16-F0 cells. Moreover, relative to controls, numbers of pulmonary metastatic colonies were reduced in WT mice receiving intravenous injections either of 18-HEPE or 18-HEPE-pretreated melanoma cells. Our results indicate that 18-HEPE is a potential anticancer metabolite that mediates, at least in part, the preventive effect of n-3 PUFA on melanoma metastasis.

Effect of combined use of a low-carbohydrate, high-protein diet with omega-3 polyunsaturated fatty acid supplementation on glycemic control in newly diagnosed type 2 diabetes: a randomized, double-blind, parallel-controlled trial.

Background: The combined effect of a low-carbohydrate, high-protein (LCHP) diet and omega-3 (n-3) polyunsaturated fatty acid (PUFA) supplementation on patients with type 2 diabetes (T2D) is not known. Objective: The aim of this study was to evaluate the effect of an LCHP diet combined with ω-3 (LCHP+ω-3) on glycemic control in patients with T2D. Design: In this randomized, double-blind, parallel-controlled trial, 122 newly diagnosed participants with T2D were randomly assigned to receive a high-carbohydrate, low-protein diet with low ω-3 PUFAs [control (CON)], an LCHP, ω-3, or LCHP+ω-3 diet for 12 wk. The ratio of carbohydrate to protein was 42:28 in the LCHP and LCHP+ω-3 diet and 54:17 in the CON and ω-3 diet. The participants were given 6 g fish oil/d (containing 3.65 g docosahexaenoic acid, eicosapentaenoic acid, and docosapentaenoic acid/d) in the ω-3 and LCHP+ω-3 diet groups or 6 g corn oil/d (placebo) in the CON and LCHP diet groups. Results: Compared with the CON diet group, greater decreases in glycated hemoglobin (HbA1c) and fasting glucose were observed in all of the other 3 diet groups at 12 wk. Of note, HbA1c reduction in the LCHP+ω-3 diet group (-0.51%; 95% CI: -0.64%, -0.37%) was greater than that in the LCHP (P = 0.03) and ω-3 (P = 0.01) diet groups at 12 wk. In terms of fasting glucose, only the LCHP+ω-3 diet group showed a significant decrease at 4 wk (P = 0.03 compared with CON). Moreover, the reduction in fasting glucose in the LCHP+ω-3 diet group (-1.32 mmol/L; 95% CI: -1.72, -0.93 mmol/L) was greater than that in the LCHP (P = 0.04) and ω-3 (P = 0.03) diet groups at 12 wk. Conclusions: The LCHP+ω-3 diet provided greater effects on HbA1c and fasting glucose and faster effects on fasting glucose than both the LCHP and ω-3 diets, indicating the potential necessity of combining an LCHP diet with ω-3 PUFAs in T2D control. This trial was registered at chictr.org.cn/ as ChiCTR-TRC-14004704.

Suppression of Postprandial Blood Glucose Fluctuations by a Low-Carbohydrate, High-Protein, and High-Omega-3 Diet via Inhibition of Gluconeogenesis.

Hyperglycemia significantly contributes to the development and progression of metabolic diseases. Managing postprandial blood glucose fluctuations is of particular importance for patients with hyperglycemia, but safe and effective means of reducing blood glucose levels are still lacking. Five diets with varying macronutrient ratios and omega-3 fatty acid amounts were tested for their blood glucose-lowering effects in male C57BL/6J mice. The diets with potent blood glucose-lowering effects were further investigated for their underlying mechanisms and their beneficial effects on hyperglycemia models. Mice given the low-carbohydrate, high-protein, and high-omega-3 (LCHP+3) diet exhibited a rapid reduction of the blood glucose levels that remained consistently low, regardless of feeding. These effects were associated with reduced amino acid gluconeogenesis, due to the inhibition of hepatic alanine transaminase (ALT). Furthermore, the LCHP+3 intervention was effective in reducing the blood glucose levels in several disease conditions, including type 1 diabetes mellitus, hormone-induced hyperglycemia, and diet-induced metabolic syndrome. Our findings identify the LCHP+3 diet as a potent blood glucose-lowering diet that suppresses postprandial blood glucose fluctuations through the inhibition of gluconeogenesis and may have great clinical utility for the management of metabolic diseases with hyperglycemia.

Enriched Brain Omega-3 Polyunsaturated Fatty Acids Confer Neuroprotection against Microinfarction.

Cerebral microinfarcts have significant effects on the development of geriatric neurological disorders, including vascular dementia and Alzheimer's disease. However, little is known about the pathophysiological mechanisms involved in the evolution of microinfarcts and potential treatment and prevention against these microvascular ischemic lesions. In the present study, the "single cortical microinfarct model" generated via occluding a penetrating arteriole by femtosecond laser ablation and the "multiple diffuse microinfarcts model" induced by unilateral injection of cholesterol crystals through the internal carotid artery were established to investigate the pathophysiological mechanisms underlying the evolution of microinfarcts and the effects of omega-3 polyunsaturated fatty acids (ω-3 PUFAs) on alleviating microinfarct burdens and functional deficits. The occlusion of a single penetrating arteriole led to a distinct cortical microinfarct, which manifested as neuronal loss and occupation of activated glial cells in the ischemic core. Using Fat-1 transgenic mice and fish oil supplements, we demonstrated that both endogenously-generated and exogenously-delivered ω-3 PUFAs significantly inhibited the activation of receptor-interacting serine/threonine protein kinases 1 (RIPK1) and its downstream apoptosis-associated proteins, mitigated cell apoptosis, and anatomically reduced the microinfarct size. The protective effects of ω-3 PUFAs against microinfarcts were further verified in a multiple diffuse microinfarcts model, where ω-3 PUFAs significantly attenuated cell apoptosis as revealed by TUNEL staining, alleviated the diffuse microinfarct burdens and remarkably improved the functional deficits as evidenced by reduced spontaneous anxiety, increased preference for the novel object, and improved hippocampal-based learning and short-term memory. Together, these findings demonstrate that enriched brain ω-3 PUFAs are effective for reducing microinfarct burdens and improving the function deficits, which support the clinical research and application of ω-3 PUFAs in the treatment or prophylaxis in vascular dementia.

Amelioration of UVB-induced oxidative stress and inflammation in fat-1 transgenic mouse skin.

ω-3 polyunsaturated fatty acids (PUFAs), which are abundant in fish oils, are known to scavenge lipid peroxyl radicals and potentiate host immune defence. As UVB-induced oxidative stress and inflammation have been implicated in apoptotic cell death, this study was aimed to investigate the anti-inflammatory, anti-oxidative, and anti-apoptotic capacity of fat-1 transgenic mice capable of converting ω-6 to ω-3 PUFAs. Wild-type (WT) C57BL/6 mice and fat-1 mice were maintained on the AIN-93 diet supplemented with 10% safflower oil rich in ω-6 PUFAs for 5 weeks. The ω-3/ω-6 PUFA ratio was significantly higher in the dorsal skin of fat-1 mice than that in the WT mice. Upon single exposure to UVB (5.0 kJ/m2) radiation, fat-1 mice showed inflammatory as well as oxidative tissue damage and the expression of pro-inflammatory enzymes, cyclooxygenases-2 and inducible nitric oxide synthase in the skin to a much lesser extent than the WT mice. The protection of fat-1 mice from UVB-induced skin inflammation was associated with decreased phosphorylation of STAT3. Moreover, UVB-induced apoptosis was attenuated in fat-1 mouse skin. In comparison to WT animals, higher levels of Nrf2 and its target proteins, such as heme oxygenase-1, NAD(P)H:quinone oxidoreductase-1 and thioredoxin-1, were found in the skin of fat-1 mice.