Preferential deposition of dairy derived fatty acids in muscle tissue is partially due to the upregulation of CD36 in a low-birth-weight swine model.

Metabolic syndrome is a worldwide health issue. Previous research has revealed that low-birth weight (LBW) swine fed a high-fat (HF) diet were susceptible to insulin resistance (IR) and developed a preferential intestinal lipid absorption, hypertriglyceridemia, and muscle steatosis. We hypothesized that fatty acid transporters such as CD36, FATP4, and FABP2 could potentially explain the development of these conditions. In addition, dairy-derived fatty acids have been shown to be valid biomarkers to assess dairy intake, which can be utilized to investigate muscle lipid deposition in LBW swine. The overall aim of this study was to delineate molecular transport candidates responsible for intestinal lipid absorption and muscle lipid deposition in LBW swine; and secondly to determine what dietary fatty acids might accumulate preferentially in pork muscle when consuming dairy products. At 5 weeks of age, normal birth weight (NBW) and LBW piglets were randomly assigned to three experimental diets: 1-chow diet, 2-HF diet, or 3-isocaloric HF diet supplemented with full fat dairy products. At 12 weeks of age, piglets were euthanized, and carcass, fasting plasma, biceps femoris and jejunum mucosal scrapings were collected. Results showed that HF-fed LBW swine exhibited early signs of IR (fasting glucose, P < 0.05; fasting insulin, P = 0.091; HOMA-IR, P = 0.086) compared with NBW-Chow, which were attenuated with increased dairy intake. Muscle samples from HF-fed LBW swine contained significantly more triglyceride compared to Chow-fed NBW swine (P < 0.05). Increased dairy intake significantly increased myristic acid (C14:0) and DPA (C22:5n3) relative to HF feeding alone (P < 0.05). All HF-fed LBW swine (regardless of dairy intake) exhibited an upregulation of CD36 expression (but not FABP2) compared with NBW littermates in both the small intestine and muscle (P < 0.05). Interestingly, increased dairy intake significantly increased the Canadian Lean Yield percentage in LBW swine fed an HF diet (P < 0.05). Findings from this study provide evidence on the mechanistic pathway of intestinal and muscle lipid metabolism in an innovative LBW swine model. We have also revealed that increasing dairy intake can enhance the incorporation of dietary long-chain polyunsaturated fatty acids into pork, as well as increasing the predicted lean yield of the carcass.

Metabolic syndrome affects millions of people worldwide, and large animal models represent a unique opportunity for research advancement. Intensive swine production can induce low-birth weight (LBW) litters. We have developed an innovative LBW swine model to investigate insulin resistance and dyslipidemia. We present evidence to explain how LBW swine can upregulate lipid intestinal absorption as well as preferentially increase pork marbling. We have also identified a potential added value approach to increase healthy fatty acids in pork and/or increase the carcass lean yield in LBW swine.

Elucidating the role of the gut microbiota in the physiological effects of dietary fiber.

BACKGROUND: Dietary fiber is an integral part of a healthy diet, but questions remain about the mechanisms that underlie effects and the causal contributions of the gut microbiota. Here, we performed a 6-week exploratory trial in adults with excess weight (BMI: 25-35 kg/m2) to compare the effects of a high-dose (females: 25 g/day; males: 35 g/day) supplement of fermentable corn bran arabinoxylan (AX; n = 15) with that of microbiota-non-accessible microcrystalline cellulose (MCC; n = 16). Obesity-related surrogate endpoints and biomarkers of host-microbiome interactions implicated in the pathophysiology of obesity (trimethylamine N-oxide, gut hormones, cytokines, and measures of intestinal barrier integrity) were assessed. We then determined whether clinical outcomes could be predicted by fecal microbiota features or mechanistic biomarkers. RESULTS: AX enhanced satiety after a meal and decreased homeostatic model assessment of insulin resistance (HOMA-IR), while MCC reduced tumor necrosis factor-α and fecal calprotectin. Machine learning models determined that effects on satiety could be predicted by fecal bacterial taxa that utilized AX, as identified by bioorthogonal non-canonical amino acid tagging. Reductions in HOMA-IR and calprotectin were associated with shifts in fecal bile acids, but correlations were negative, suggesting that the benefits of fiber may not be mediated by their effects on bile acid pools. Biomarkers of host-microbiome interactions often linked to bacterial metabolites derived from fiber fermentation (short-chain fatty acids) were not affected by AX supplementation when compared to non-accessible MCC. CONCLUSION: This study demonstrates the efficacy of purified dietary fibers when used as supplements and suggests that satietogenic effects of AX may be linked to bacterial taxa that ferment the fiber or utilize breakdown products. Other effects are likely microbiome independent. The findings provide a basis for fiber-type specific therapeutic applications and their personalization. TRIAL REGISTRATION: Clinicaltrials.gov, NCT02322112 , registered on July 3, 2015. Video Abstract.

Dietary flaxseed reduces Myocardial Ischemic Lesions, improves cardiac function and lowers cholesterol levels despite the presence of severe obesity in JCR:LA-cp Rats.

Previous work has shown that dietary flaxseed can significantly reduce cardiac damage from a coronary artery ligation-induced myocardial infarction. However, this model uses healthy animals and the ligation creates the infarct in an artificial manner. The purpose of this study was to determine if dietary flaxseed can protect the hearts of JCR:LA-cp rats, a model of genetic obesity and metabolic syndrome, from naturally occurring myocardial ischemic lesions. Male and female obese rats were randomized into four groups (n = 8 each) to receive, for 12 weeks, either a) control diet (Con), b) control diet supplemented with 10% ground flaxseed (CFlax), c) a high-fat, high sucrose (HFHS) diet, or d) HFHS supplemented with 10% ground flaxseed (HFlax). Male and female JCR:LA-cp lean rats served as genetic controls and received similar dietary interventions. In male obese rats, serum total cholesterol and LDL-C were significantly lower in CFlax compared to Con.  Obese rats on HFHS exhibited increased myocardial ischemic lesions and diastolic dysfunction regardless of sex. HFlax significantly lowered the frequency of cardiac lesions and improved diastolic function in male and female obese rats compared to HFHS. Blood pressures were similar in obese and lean rats. No aortic atherosclerotic lesions were detectable in any group. Collectively, this study shows that a HFHS diet increased myocardial ischemic lesion frequency and abolished the protective effect of female sex on cardiac function. More importantly, the data demonstrates dietary flaxseed protected against the development of small spontaneous cardiac infarcts despite the ingestion of a HFHS diet and the presence of morbid obesity.

Hypolipidemic and cardioprotective benefits of a novel fireberry hawthorn fruit extract in the JCR:LA-cp rodent model of dyslipidemia and cardiac dysfunction.

Hawthorn is a widely used herbal alternative medicine for the treatment of various cardiovascular diseases. However, the attributed health benefits, purported to be due to the presence of phenolic compounds, may depend on both the specific species and plant part. Studies to date investigating effects of hawthorn on heart disease(s) have used well-described European and/or Asian species, while little is known regarding the bioactivity of species native to North America. Six weeks of supplementation of both fireberry hawthorn berry (native Crataegus chrysocarpa) and English hawthorn leaf (C. monogyna, naturalized in North America) in the JCR:LA-cp rat, resulted in a significant reduction in heart weight, fasting LDL-C and improved heart function (p < 0.05). Fasting triglyceride and myocardial fibrosis were also reduced, but only by the berry extract. We demonstrate that both of the Canadian-sourced hawthorn extracts (introduced leaf and native berry) have cardioprotective benefits, likely via increased availability of nitric oxide.

Beef Fat Enriched with Polyunsaturated Fatty Acid Biohydrogenation Products Improves Insulin Sensitivity Without Altering Dyslipidemia in Insulin Resistant JCR:LA-cp Rats.

The main dietary sources of trans fatty acids are partially hydrogenated vegetable oils (PHVO), and products derived from polyunsaturated fatty acid biohydrogenation (PUFA-BHP) in ruminants. Trans fatty acid intake has historically been associated with negative effects on health, generating an anti-trans fat campaign to reduce their consumption. The profiles and effects on health of PHVO and PUFA-BHP can, however, be quite different. Dairy products naturally enriched with vaccenic and rumenic acids have many purported health benefits, but the putative benefits of beef fat naturally enriched with PUFA-BHP have not been investigated. The objective of the present experiment was to determine the effects of beef peri-renal fat (PRF) with differing enrichments of PUFA-BHP on lipid and insulin metabolism in a rodent model of dyslipidemia and insulin resistance (JCR:LA-cp rat). The results showed that 6 weeks of diet supplementation with beef PRF naturally enriched due to flaxseed (FS-PRF) or sunflower-seed (SS-PRF) feeding to cattle significantly improved plasma fasting insulin levels and insulin sensitivity, postprandial insulin levels (only in the FS-PRF) without altering dyslipidemia. Moreover, FS-PRF but not SS-PRF attenuated adipose tissue accumulation. Therefore, enhancing levels of PUFA-BHP in beef PRF with FS feeding may be a useful approach to maximize the health-conferring value of beef-derived fats.

Trans-11 vaccenic acid improves insulin secretion in models of type 2 diabetes in vivo and in vitro.

SCOPE: Trans-11 vaccenic acid (VA) is a fatty acid produced by ruminants entering the human food supply through meat and dairy products, which appears not to have the health risks associated with industrially produced trans-fatty acids. In this study, we investigated the effect of VA on insulin secretion in vivo in rats and in vitro in human and rat islets after diabetogenic insult. METHODS AND RESULTS: Hyperglycemic clamp showed that VA dietary supplementation for 8 weeks significantly increased glucose turnover in rats with type 2 diabetes (T2D), accompanied by an elevated plasma C-peptide concentration, indicating improved insulin secretion. The ß-cell area and proliferation rate were higher in T2D+VA than T2D group. Isolated islets from T2D+VA rats had higher glucose-stimulated insulin secretion (GSIS) than T2D group. In vitro, VA treatment for 24 and 48 h significantly enhanced GSIS in rat and human islets after diabetogenic challenges. The mRNA expression of G-protein-coupled receptor 40 (GPR40) and regenerating islet-derived 1α (REG-1α) were consistently increased by VA in both rat and human islets. CONCLUSION: These results indicate that VA may improve insulin secretion and growth of islets in T2D, at least partly by altering GPR40 and REG-1α mRNA expression.

Vaccenic acid suppresses intestinal inflammation by increasing anandamide and related N-acylethanolamines in the JCR:LA-cp rat.

Vaccenic acid (VA), the predominant ruminant-derivedtransfat in the food chain, ameliorates hyperlipidemia, yet mechanisms remain elusive. We investigated whether VA could influence tissue endocannabinoids (ECs) by altering the availability of their biosynthetic precursor, arachidonic acid (AA), in membrane phospholipids (PLs). JCR:LA-cprats were assigned to a control diet with or without VA (1% w/w),cis-9,trans-11 conjugated linoleic acid (CLA) (1% w/w) or VA+CLA (1% + 0.5% w/w) for 8 weeks. VA reduced the EC, 2-arachidonoylglycerol (2-AG), in the liver and visceral adipose tissue (VAT) relative to control diet (P< 0.001), but did not change AA in tissue PLs. There was no additive effect of combining VA+CLA on 2-AG relative to VA alone (P> 0.05). Interestingly, VA increased jejunal concentrations of anandamide and those of the noncannabinoid signaling molecules, oleoylethanolamide and palmitoylethanolamide, relative to control diet (P< 0.05). This was consistent with a lower jejunal protein abundance (but not activity) of their degrading enzyme, fatty acid amide hydrolase, as well as the mRNA expression of TNFα and interleukin 1ß (P< 0.05). The ability of VA to reduce 2-AG in the liver and VAT provides a potential mechanistic explanation to alleviate ectopic lipid accumulation. The opposing regulation of ECs and other noncannabinoid lipid signaling molecules by VA suggests an activation of benefit via the EC system in the intestine.

Choline deficiency impairs intestinal lipid metabolism in the lactating rat.

Choline is a precursor to phosphatidylcholine (PC), a structural molecule in cellular membranes that is crucial for cell growth and function. PC is also required for the secretion of lipoprotein particles from liver and intestine. Choline requirements are increased during lactation when maternal choline is supplied to the offspring through breast milk. To investigate the effect of dietary choline on intestinal lipid metabolism during lactation, choline-supplemented (CS), phosphatidylcholine-supplemented (PCS) or choline-deficient (CD) diets were fed to dams during the suckling period. CD dams had lower plasma triacylglycerol, cholesterol and apoB in the fasted state and following a fat-challenge (P < .05). There was a higher content of neutral lipids and lower content of PC in the intestine of CD dams, compared with CS and PCS fed animals (P < .05). In addition, there was lower (P < .05) villus height in CD dams, which indicated a reduced absorptive surface area in the intestine. Choline is critical for the absorption of fat in lactating rats and choline deficiency alters intestinal morphology and impairs chylomicron secretion by limiting the supply of PC.

Accumulation of ceramide in slow-twitch muscle contributes to the development of insulin resistance in the obese JCR:LA-cp rat.

NEW FINDINGS: What is the central question of this study? The aim was to determine whether the accumulation of ceramide contributes to skeletal muscle insulin resistance in the JCR obese rat. What is the main finding and its importance? Our main new finding is that ceramides accumulate only in slow-twitch skeletal muscle in the JCR obese rat and that reducing ceramide content in this muscle type by inhibition of serine palmitoyl transferase-1 halts the progression of insulin resistance in this rat model predisposed to early development of type 2 diabetes. Our findings highlight the importance of assessing insulin signalling/sensitivity and lipid intermediate accumulation in different muscle fibre types. It has been postulated that insulin resistance results from the accumulation of cytosolic lipid metabolites (i.e. diacylglycerol/ceramide) that impede insulin signalling and impair glucose homeostasis. De novo ceramide synthesis is catalysed by serine palmitoyl transferase-1. Our aim was to determine whether de novo ceramide synthesis plays a role during development of insulin resistance in the JCR:LA-cp obese rat. Ten-week-old JCR:LA-cp obese rats were supplemented with either vehicle or the serine palmitoyl transferase-1 inhibitor l-cycloserine (360 mg l(-1) ) in their drinking water for a 2 week period, and glycaemia was assessed by meal tolerance testing. Treatment of JCR:LA-cp obese rats with l-cycloserine improved their plasma glucose and insulin levels during a meal tolerance test. Examination of muscle lipid metabolites and protein phosphorylation patterns revealed differential signatures in slow-twitch (soleus) versus fast-twitch muscle (gastrocnemius), in that ceramide levels were increased in soleus but not gastrocnemius muscles of JCR:LA-cp obese rats. Likewise, improved glycaemia in l-cycloserine-treated JCR:LA-cp obese rats was associated with enhanced Akt and pyruvate dehydrogenase signalling in soleus but not gastrocnemius muscles, probably as a result of l-cycloserine reducing elevated ceramides in this muscle type. Potential mechanisms of ceramide-mediated insulin resistance involve activation of atypical protein kinase Cζ/λ and protein phosphatase 2A; however, neither of these was altered in muscles of JCR:LA-cp obese rats. Our results suggest a key role for ceramide in the development of insulin resistance in the JCR:LA-cp obese rat, while supporting serine palmitoyl transferase-1 inhibition as a novel target for treatment of obesity-associated insulin resistance.

Interrelationship of CB1R and OBR pathways in regulation of metabolic, neuroendocrine, and behavioral responses to food restriction and voluntary wheel running.

We hypothesized the cannabinoid-1 receptor and leptin receptor (ObR) operate synergistically to modulate metabolic, neuroendocrine, and behavioral responses of animals exposed to a survival challenge (food restriction and wheel running). Obese-prone (OP) JCR:LA-cp rats, lacking functional ObR, and lean-prone (LP) JCR:LA-cp rats (intact ObR) were assigned to OP-C and LP-C (control) or CBR1-antagonized (SR141716, 10 mg/kg body wt in food) OP-A and LP-A groups. After 32 days, all rats were exposed to 1.5-h daily meals without the drug and 22.5-h voluntary wheel running, a survival challenge that normally culminates in activity-based anorexia (ABA). Rats were removed from the ABA protocol when body weight reached 75% of entry weight (starvation criterion) or after 14 days (survival criterion). LP-A rats starved faster (6.44 ± 0.24 days) than LP-C animals (8.00 ± 0.29 days); all OP rats survived the ABA challenge. LP-A rats lost weight faster than animals in all other groups (P < 0.001). Consistent with the starvation results, LP-A rats increased the rate of wheel running more rapidly than LP-C rats (P = 0.001), with no difference in hypothalamic and primary neural reward serotonin levels. In contrast, OP-A rats showed suppression of wheel running compared with the OP-C group (days 6-14 of ABA challenge, P < 0.001) and decreased hypothalamic and neural reward serotonin levels (P < 0.01). Thus there is an interrelationship between cannabinoid-1 receptor and ObR pathways in regulation of energy balance and physical activity. Effective clinical measures to prevent and treat a variety of disorders will require understanding of the mechanisms underlying these effects.

Diets enriched in trans-11 vaccenic acid alleviate ectopic lipid accumulation in a rat model of NAFLD and metabolic syndrome.

Trans11-18:1 (vaccenic acid, VA) is one of the most predominant naturally occurring trans fats in our food chain and has recently been shown to exert hypolipidemic effects in animal models. In this study, we reveal new mechanism(s) by which VA can alter body fat distribution, energy utilization and dysfunctional lipid metabolism in an animal model of obesity displaying features of the metabolic syndrome (MetS). Obese JCR:LA-cp rats were assigned to a control diet that included dairy-derived fat or the control diet supplemented with 1% VA. VA reduced total body fat (-6%), stimulated adipose tissue redistribution [reduced mesenteric fat (-17%) while increasing inguinal fat mass (29%)] and decreased adipocyte size (-44%) versus control rats. VA supplementation also increased metabolic rate (7%) concomitantly with an increased preference for whole-body glucose utilization for oxidation and increased insulin sensitivity [lower HOMA-IR (-59%)]. Further, VA decreased nonalcoholic fatty liver disease activity scores (-34%) and reduced hepatic (-27%) and intestinal (-39%) triglyceride secretion relative to control diet, while exerting differential transcriptional regulation of SREBP1 and FAS amongst other key genes in the liver and the intestine. Adding VA to dairy fat alleviates features of MetS potentially by remodeling adipose tissue and attenuating ectopic lipid accumulation in a rat model of obesity and MetS. Increasing VA content in the diet (naturally or by fortification) may be a useful approach to maximize the health value of dairy-derived fats.

Choline supplementation protects against liver damage by normalizing cholesterol metabolism in Pemt/Ldlr knockout mice fed a high-fat diet.

Dietary choline is required for proper structure and dynamics of cell membranes, lipoprotein synthesis, and methyl-group metabolism. In mammals, choline is synthesized via phosphatidylethanolamine N-methyltransferase (Pemt), which converts phosphatidylethanolamine to phosphatidylcholine. Pemt(-/-) mice have impaired VLDL secretion and developed fatty liver when fed a high-fat (HF) diet. Because of the reduction in plasma lipids, Pemt(-/-)/low-density lipoprotein receptor knockout (Ldlr(-/-)) mice are protected from atherosclerosis. The goal of this study was to investigate the importance of dietary choline in the metabolic phenotype of Pemt(-/-)/Ldlr(-/-) male mice. At 10-12 wk of age, Pemt(+/+)/Ldlr(-/-) (HF(+/+)) and half of the Pemt(-/-)/Ldlr(-/-) (HF(-/-)) mice were fed an HF diet with normal (1.3 g/kg) choline. The remaining Pemt(-/-)/Ldlr(-/-) mice were fed an HF diet supplemented (5 g/kg) with choline (HFCS(-/-) mice). The HF diet contained 60% of calories from fat and 1% cholesterol, and the mice were fed for 16 d. HF(-/-) mice lost weight and developed hepatomegaly, steatohepatitis, and liver damage. Hepatic concentrations of free cholesterol, cholesterol-esters, and triglyceride (TG) were elevated by 30%, 1.1-fold and 3.1-fold, respectively, in HF(-/-) compared with HF(+/+) mice. Choline supplementation normalized hepatic cholesterol, but not TG, and dramatically improved liver function. The expression of genes involved in cholesterol transport and esterification increased by 50% to 5.6-fold in HF(-/-) mice when compared with HF(+/+) mice. Markers of macrophages, oxidative stress, and fibrosis were elevated in the HF(-/-) mice. Choline supplementation normalized the expression of these genes. In conclusion, HF(-/-) mice develop liver failure associated with altered cholesterol metabolism when fed an HF/normal choline diet. Choline supplementation normalized cholesterol metabolism, which was sufficient to prevent nonalcoholic steatohepatitis development and improve liver function. Our data suggest that choline can promote liver health by maintaining cholesterol homeostasis.

Current issues surrounding the definition of trans-fatty acids: implications for health, industry and food labels.

The definition of trans-fatty acids (TFA) was established by the Codex Alimentarius to guide nutritional and legislative regulations to reduce TFA consumption. Currently, conjugated linoleic acid (CLA) is excluded from the TFA definition based on evidence (primarily preclinical studies) implying health benefits on weight management and cancer prevention. While the efficacy of CLA supplements remains inconsistent in randomised clinical trials, evidence has emerged to associate supplemental CLA with negative health outcomes, including increased subclinical inflammation and oxidative stress (particularly at high doses). This has resulted in concerns regarding the correctness of excluding CLA from the TFA definition. Here we review recent clinical and preclinical literature on health implications of CLA and ruminant TFA, and highlight several issues surrounding the current Codex definition of TFA and how it may influence interpretation for public health. We find that CLA derived from ruminant foods differ from commercial CLA supplements in their isomer composition/distribution, consumption level and bioactivity. We conclude that health concerns associated with the use of supplemental CLA do not repudiate the exclusion of all forms of CLA from the Codex TFA definition, particularly when using the definition for food-related purposes. Given the emerging differential bioactivity of TFA from industrial v. ruminant sources, we advocate that regional nutrition guidelines/policies should focus on eliminating industrial forms of trans-fat from processed foods as opposed to all TFA per se.

Dietary fish oil reduces glomerular injury and elevated renal hydroxyeicosatetraenoic acid levels in the JCR:LA-cp rat, a model of the metabolic syndrome.

We have previously shown nutritional intervention with fish oil (n-3 PUFA) to reduce numerous complications associated with the metabolic syndrome (MetS) in the JCR:LA-corpulent (cp) rat. In the present study, we sought to explore the potential role of fish oil to prevent glomerulosclerosis in JCR:LA-cp rats via renal eicosanoid metabolism and lipidomic analysis. Male lean and MetS JCR:LA-cp rats were fed a lipid-balanced diet supplemented with fish oil (5 or 10 % of total fat). After 16 weeks of feeding, albuminuria was significantly reduced in MetS rats supplemented with 5 or 10 % fish oil ( - 53 and - 70 %, respectively, compared with the untreated MetS rats). The 5 % fish oil diet resulted in markedly lower glomerulosclerosis ( - 43 %) in MetS rats and to a lesser extent in those supplemented with 10 % fish oil. Interestingly, untreated MetS rats had higher levels of 11- and 12-hydroxyeicosatetraenoic acids (HETE) v. lean rats. Dietary fish oil reduced these levels, as well as other (5-, 9- and 15-) HETE. Whilst genotype did not alter prostanoid levels, fish oil reduced endogenous renal levels of 6-keto PGF1α (PGI2 metabolite), thromboxane B2 (TxB2), PGF2α and PGD2 by approximately 60 % in rats fed 10 % fish oil, and TxB2 ( - 50 %) and PGF2α ( - 41 %) in rats fed 5 % fish oil. In conclusion, dietary fish oil prevented glomerular damage in MetS rats and mitigated the elevation in renal HETE levels. These results suggest a potential role for dietary fish oil to improve dysfunctional renal eicosanoid metabolism associated with kidney damage during conditions of the MetS.

Chronic dietary n-3 PUFA intervention improves dyslipidaemia and subsequent cardiovascular complications in the JCR:LA- cp rat model of the metabolic syndrome.

There is increasing interest in the potential chronic beneficial effects of dietary n-3 PUFA on the metabolic syndrome (MetS) and associated cardiovascular complications. We have recently established that increased dietary n-3 PUFA has a profound acute benefit on fasting lipids and the postprandial pro-inflammatory response in the JCR:LA-cp rat, a model of the MetS. However, it is unclear to what extent chronic dietary n-3 PUFA intervention can modulate the progression of end-stage metabolic and vascular complications. The present study aimed to determine the chronic effects of dietary n-3 PUFA supplementation on fasting and non-fasting dyslipidaemia, insulin resistance and vascular complications in the JCR:LA-cp rodent model. JCR:LA-cp rats were fed an isoenergetic lipid-balanced diet supplemented with 5 % n-3 PUFA (w/w) of the total fat (fish oil-derived EPA/DHA) for 16 weeks. Fasting and non-fasting (postprandial) plasma lipid profile was assessed. Hepatic and adipose tissue was probed for the expression of lipogenic proteins (acyl-CoA carboxylase (ACC), fatty acid synthase (FAS) and sterol regulatory element-binding protein-1 (SREBP-1)), while the activity of Jun N-terminal kinase (JNK) was assessed via Western blot to target phosphorylated JNK protein in primary enterocytes. The frequency of myocardial lesions was assessed by haematoxylin and eosin staining. Increased dietary n-3 PUFA improved both the fasting and postprandial lipid profiles (TAG, cholesterol and apoB48) in the JCR:LA-cp rat, potentially via the down-regulation of the hepatic or adipose tissue expression of lipogenic enzymes (ACC, FAS and SREBP-1). Rats fed the 5 % n-3 PUFA diet had lower (58·2 %; P < 0·01) enterocytic phosphorylated JNK protein and secreted less cholesterol (30 %; P < 0·05) into mesenteric lymph compared with the control. The chronic metabolic benefits of dietary n-3 PUFA may underlie the potential to reduce vascular complications during the MetS, including the observed reduction in the frequency (approximately 80 %) of late-stage 3 myocardial lesions.

Increased hypolipidemic benefits of cis-9, trans-11 conjugated linoleic acid in combination with trans-11 vaccenic acid in a rodent model of the metabolic syndrome, the JCR:LA-cp rat.

BACKGROUND: Conjugated linoleic acid (cis-9, trans-11 CLA) and trans-11 vaccenic acid (VA) are found naturally in ruminant-derived foods. CLA has been shown to have numerous potential health related effects and has been extensively investigated. More recently, we have shown that VA has lipid-lowering properties associated with reduced hepatic lipidogenesis and chylomicron secretion in the JCR:LA-cp rat. The aim of this study was to evaluate potential additional hypolipidemic effects of purified forms of CLA and VA in an animal model of the metabolic syndrome (the JCR:LA-cp rat). METHODS: Twenty four obese JCR:LA-cp rats were randomized and assigned to one of three nutritionally adequate iso-caloric diets containing 1% w/w cholesterol and 15% w/w fat for 16 wk: 1) control diet (CD), 2) 1.0% w/w cis-9, trans-11 CLA (CLA), 3) 1.0% w/w VA and 1% w/w cis-9, trans-11 CLA (VA+CLA). Lean rats were fed the CD to represent normolipidemic conditions. RESULTS: Fasting plasma triglyceride (TG), total cholesterol and LDL-cholesterol concentrations were reduced in obese rats fed either the CLA diet or the VA+CLA diet as compared to the obese control group (p < 0.05, p < 0.001; p < 0.001, p < 0.01; p < 0.01, p < 0.001, respectively). The VA+CLA diet reduced plasma TG and LDL-cholesterol to the level of the normolipidemic lean rats and further decreased nonesterified fatty acids compared to the CLA diet alone. Interestingly, rats fed the VA+CLA diet had a higher food intake but lower body weight than the CLA fed group (P < 0.05). Liver weight and TG content were lower in rats fed either CLA (p < 0.05) or VA+CLA diets (p < 0.001) compared to obese control, consistent with a decreased relative protein abundance of hepatic acetyl-CoA carboxylase in both treatment groups (P < 0.01). The activity of citrate synthase was increased in liver and adipose tissue of rats fed, CLA and VA+CLA diets (p < 0.001) compared to obese control, suggesting increased mitochondrial fatty acid oxidative capacity. CONCLUSION: We demonstrate that the hypolipidemic effects of chronic cis-9, trans-11 CLA supplementation on circulating dyslipidemia and hepatic steatosis are enhanced by the addition of VA in the JCR:LA-cp rat.

Impaired de novo choline synthesis explains why phosphatidylethanolamine N-methyltransferase-deficient mice are protected from diet-induced obesity.

Phosphatidylcholine (PC) is synthesized from choline via the CDP-choline pathway. Liver cells can also synthesize PC via the sequential methylation of phosphatidylethanolamine, catalyzed by phosphatidylethanolamine N-methyltransferase (PEMT). The current study investigates whether or not hepatic PC biosynthesis is linked to diet-induced obesity. Pemt(+/+) mice fed a high fat diet for 10 weeks increased in body mass by 60% and displayed insulin resistance, whereas Pemt(-/-) mice did not. Compared with Pemt(+/+) mice, Pemt(-/-) mice had increased energy expenditure and maintained normal peripheral insulin sensitivity; however, they developed hepatomegaly and steatosis. In contrast, mice with impaired biosynthesis of PC via the CDP-choline pathway in liver became obese when fed a high fat diet. We, therefore, hypothesized that insufficient choline, rather than decreased hepatic phosphatidylcholine, was responsible for the lack of weight gain in Pemt(-/-) mice despite the presence of 1.3 g of choline/kg high fat diet. Supplementation with an additional 2.7 g of choline (but not betaine)/kg of diet normalized energy metabolism, weight gain, and insulin resistance in high fat diet-fed Pemt(-/-) mice. Furthermore, Pemt(+/+) mice that were fed a choline-deficient diet had increased oxygen consumption, had improved glucose tolerance, and gained less weight. Thus, de novo synthesis of choline via PEMT has a previously unappreciated role in regulating whole body energy metabolism.

Trans-11 vaccenic acid reduces hepatic lipogenesis and chylomicron secretion in JCR:LA-cp rats.

Trans-11 vaccenic acid (VA) is the predominant trans isomer in ruminant fat and a major precursor to the endogenous synthesis of cis9,trans11-conjugated linoleic acid in humans and animals. We have previously shown that 3-wk VA supplementation has a triglyceride (TG)-lowering effect in a rat model of dyslipidemia, obesity, and metabolic syndrome (JCR:LA-cp rats). The objective of this study was to assess the chronic effect (16 wk) of VA on lipid homeostasis in both the liver and intestine in obese JCR:LA-cp rats. Plasma TG (P < 0.001), total cholesterol (P < 0.001), LDL cholesterol (P < 0.01), and nonesterified fatty acid concentrations, as well as the serum haptoglobin concentration, were all lower in obese rats fed the VA diet compared with obese controls (P < 0.05). In addition, there was a decrease in the postprandial plasma apolipoprotein (apo)B48 area under the curve (P < 0.05) for VA-treated obese rats compared with obese controls. The hepatic TG concentration and the relative abundance of fatty acid synthase and acetyl-CoA carboxylase proteins were all lower (P < 0.05) in the VA-treated group compared with obese controls. Following acute gastrointestinal infusion of a VA-triolein emulsion in obese rats that had been fed the control diet for 3 wk, the TG concentration was reduced by 40% (P < 0.05) and the number of chylomicron (CM) particles (apoB48) in nascent mesenteric lymph was reduced by 30% (P < 0.01) relative to rats infused with a triolein emulsion alone. In conclusion, chronic VA supplementation significantly improved dyslipidemia in both the food-deprived and postprandial state in JCR:LA-cp rats. The appreciable hypolipidemic benefits of VA may be attributed to a reduction in both intestinal CM and hepatic de novo lipogenesis pathways.

Feeding long-chain n-3 polyunsaturated fatty acids to obese leptin receptor-deficient JCR:LA- cp rats modifies immune function and lipid-raft fatty acid composition.

Dietary EPA and DHA modulate immunity and thereby may improve the aberrant immune function in obese states. To determine the effects of feeding fish oil (FO) containing EPA and DHA on splenocyte phospholipid (PL) and lipid-raft fatty acid composition, phenotypes and cytokine production, 14-week-old obese, leptin receptor-deficient JCR:LA-cp rats (cp/cp; n 10) were randomised to one of three nutritionally adequate diets for 3 weeks: control (Ctl, 0 % EPA+DHA); low FO (LFO, 0.8 % (w/w) EPA+DHA); high FO (HFO, 1.4 % (w/w) EPA+DHA). Lean JCR:LA-cp (+/ - or +/+) rats (n 5) were fed the Ctl diet. Obese Ctl rats had a higher proportion of n-3 PUFA in splenocyte PL than lean rats fed the same diet (P < 0.05). The lower n-6:n-3 PUFA ratio of splenocyte PL was consistent with the lower mitogen-stimulated interferon (IFN)-gamma and IL-1beta production by cells from obese rats (P < 0.05). Obese rats fed the FO diet had lower mitogen-stimulated Th1 (IFN-gamma) and Th2 (IL-4) cytokine responses, but IL-2 production (concanavalin A; ConA) did not differ (P < 0.05). The HFO diet was more effective in lowering IL-1beta and increasing IL-10 production (ConA, P < 0.05). This lower IL-1beta production was accompanied by a lower proportion of major histocompatability complex class II-positive cells and a higher incorporation of DHA into lipid rafts. This is the first study to demonstrate impaired responses to mitogen stimulation and altered fatty acid incorporation into the membrane PL of JCR:LA-cp rats. Feeding FO lowered the ex vivo inflammatory response, without altering IL-2 production from ConA-stimulated splenocytes which may occur independent of leptin signalling.

Trans-11 vaccenic acid dietary supplementation induces hypolipidemic effects in JCR:LA-cp rats.

Trans-11 vaccenic acid [VA; 18:1(n-9)] is a positional and geometric isomer of oleic acid and is the precursor to conjugated linoleic acid (CLA) in humans. Despite VA being the predominant trans monoene in ruminant-derived lipids, very little is known about its nutritional bioactivity, particularly in conditions of chronic metabolic disorders, including obesity, insulin resistance, and/or dyslipidemia. The aim of this study was to assess the potential of VA to improve dyslipidemia, insulin sensitivity, or inflammatory status in obese and insulin-resistant JCR:LA-cp rats. The obese rats and age-matched lean littermates were fed a control diet or a control diet supplemented with 1.5% (wt:wt) VA for a period of 3 wk. The incorporation of VA and subsequent conversion to CLA in triglyceride was measured in adipose tissue. Glucose and insulin metabolism were assessed via a conscious adapted meal tolerance test procedure. Plasma lipids as well as serum inflammatory cytokine concentrations were measured by commercially available assays. VA supplementation did not result in any observable adverse health effects in either lean or obese JCR:LA-cp rats. After 3 wk of feeding, body weight, food intake, and glucose/insulin metabolism did not differ between VA-supplemented and control groups. The incorporation of VA and CLA into adipose triglycerides in obese rats fed VA increased by 1.5-fold and 6.5-fold, respectively, compared with obese rats fed the control diet. The most striking effect was a 40% decrease (P < 0.05) in fasting triglyceride concentrations in VA-treated obese rats relative to obese controls. Serum Il-10 concentration was decreased by VA, regardless of genotype (P < 0.05). In conclusion, short-term dietary supplementation of 1.5% VA did not result in any detrimental metabolic effects in JCR:LA-cp rats. In contrast, dietary VA had substantial hypo-triglyceridemic effects, suggesting a new bioactivity of this fatty acid that is typically found in ruminant-derived food products.