Polyunsaturated fatty acids of marine origin induce adiponectin in mice fed a high-fat diet

Differential effect of weight loss with low-fat diet or high-fat diet restriction on inflammation in the liver and adipose tissue of mice with diet-induced obesity

OBJECTIVE

We studied the effects of weight loss induced by either a low-fat normal diet (ND) or restriction of high-fat diet (HFD) on hepatic steatosis, inflammation in the liver and adipose tissue (AT), and blood monocytes of obese mice.

METHODS

In mice with HFD-induced obesity, weight loss was achieved by switching from HFD to ND and maintaining on ND ad libitum or by restricting HFD intake to match body weight of mice with ND-induced weight loss. After diet interventions for 4 weeks, hepatic steatosis, hepatic and AT inflammation, and blood CD11c(+) monocytes were examined.

RESULTS

At 4 weeks after switching diets, body weight was reduced by 23% from baseline. To achieve the same reduced body weight required restricting calorie intake from HFD. Weight loss with either ND or HFD restriction decreased body fat mass and ameliorated liver steatosis; both effects were greater with ND-induced weight loss than HFD restriction-induced weight loss. Weight loss with ND but not HFD restriction normalized blood CD11c(+) monocytes and attenuated hepatic inflammation assessed by chemokine and CD11c expression. In contrast, weight loss with HFD restriction significantly reduced chemokine levels and CD11c(+) cells in AT compared to obese controls, and tended to reduce AT chemokines and CD11c(+) cells more than ND-induced weight loss.

CONCLUSION

In mice with diet-induced obesity, weight loss with ND was superior in alleviating hepatic inflammation and steatosis, whereas weight loss with HFD calorie restriction provided greater amelioration of AT inflammation.

Relationship between the estimates of desaturase activities and cardiometabolic phenotypes in Koreans

In the present study, we evaluated the relationships of estimated desaturase activities with cardiometabolic risk factors including abdominal obesity, atherogenic lipoprotein phenotype and inflammation in Koreans. Ninety-three healthy volunteers participated in this cross-sectional study. LDL particle size was determined using gradient gel electrophoresis and inflammatory markers including C-reactive protein, soluble intercellular adhesion molecule-1, and adiponectin were measured. Stearoyl-coA desaturase, delta-6 desaturase and delta-5 desaturase were estimated as precursor to fatty acid ratios. The results showed that stearoyl-coA desaturase was correlated with body mass index (r = 0.235, p<0.05), triglyceride (r = 0.261, p<0.001), and HDL-cholesterol (r = -0.226, p<0.05). Stearoyl-coA desaturase was associated with only triglyceride (r = 0.283, p<0.01). Delta-6 desaturase was correlated with body mass index (r = 0.236, p<0.05), waist circumference (r = 0.218, p<0.05), triglyceride (r = 0.399, p<0.001), C-reactive protein (r = 0.333, p<0.001), soluble intercellular adhesion molecule-1 (r = 0.229, p<0.05), HDL-cholesterol (r = -0.325, p<0.01), LDL particle size (r = -0.297, p<0.01) and adiponectin (r = -0.233, p<0.05). In contrast, delta-5 desaturase was correlated with body mass index (r = -0.324, p<0.01), waist circumference (r = -0.276, p<0.01), triglyceride (r = -0.329, p<0.01), C-reactive protein (r = -0.215, p<0.05), HDL-cholesterol (r = 0.262, p<0.05) and LDL particle size (r = 0.278, p<0.01). Stepwise multiple regression analysis revealed that delta-6 desaturase (p<0.01) together with waist circumference (p<0.001) were found to be independent factors for determining plasma levels of C-reactive protein (R(2) = 0.230). Estimated desaturase activities are closely associated with the features of cardiometabolic risk in Koreans.

Beneficial effects of dietary fish-oil-derived monounsaturated fatty acids on metabolic syndrome risk factors and insulin resistance in mice

The aim of this study was to elucidate the effect of fish-oil-derived monounsaturated fatty acids (MUFAs) containing large amounts of C20:1 and C22:1 isomers on metabolic disorders in mice. Male C57BL/6J mice were fed a 32% lard diet (control) or a 27% lard plus 5% saury-oil-derived MUFA diet for 6 weeks. Dietary MUFA improved insulin resistance and alleviated metabolic syndrome risk factors by reducing blood glucose and lipids. These favorable changes may be attributed to an improved adipocytokine profile. MUFA ingestion resulted in favorable changes in mRNA expression of genes involved in glucose/lipid metabolism (SCD-1, CPT1a, UCPs, and CS) as well as inflammation (MAC1, MMP3, and SAA3) and alterations in fatty acid composition. Our data suggest that marine MUFA improved glucose/lipid homeostasis and hindered the development of metabolic syndrome in obese mice.

(n-3) Fatty acids alleviate adipose tissue inflammation and insulin resistance: mechanistic insights

Obesity is associated with the metabolic syndrome, a significant risk factor for developing type 2 diabetes and cardiovascular diseases. Chronic low-grade inflammation occurring in the adipose tissue of obese individuals is causally linked to the pathogenesis of insulin resistance and the metabolic syndrome. Although the exact trigger of this inflammatory process is unknown, adipose tissue hypoxia, endoplasmic reticular stress, and saturated fatty acid-mediated activation of innate immune processes have been identified as important processes in these disorders. Furthermore, macrophages and T lymphocytes have important roles in orchestrating this immune process. Although energy restriction leading to weight loss is the primary dietary intervention to reverse these obesity-associated metabolic disorders, other interventions targeted at alleviating adipose tissue inflammation have not been explored in detail. In this regard, (n-3) PUFA of marine origin both prevent and reverse high-fat-diet-induced adipose tissue inflammation and insulin resistance in rodents. We provide an update on the pathogenesis of adipose tissue inflammation and insulin resistance in obesity and discuss potential mechanisms by which (n-3) PUFA prevent and reverse these changes and the implications in human health.

Gene-PUFA interactions and obesity risk

Although there are indications for modulatory effects of PUFA on associations between SNP and obesity risk, scientific evidence in human subjects is still scarce. The present analyses investigated interaction effects between SNP in candidate genes for obesity and PUFA in erythrocyte membranes on obesity risk. Within the second Bavarian Food Consumption Survey (cross-sectional, population-based), 568 adults provided blood samples. Fatty acid composition of erythrocyte membranes was analysed by means of GC. Genotyping was performed for twenty-one genes, including cytokines, adipokines, neurotransmitters and transcription factors. In addition, plasma IL-6 concentrations were analysed. For the statistical analysis, a logistic regression model assuming additive genetic effects was chosen. About 20 % of the study participants were classified as obese (BMI ≥ 30 kg/m(2)). Several significant gene-PUFA interactions were found, indicating regulatory effects of PUFA by gene variants of IL-2, IL-6, IL-18, TNF receptor family member 1B and 21, leptin receptor and adiponectin on obesity risk. After stratification by genotype, the strongest effects were found for rs2069779 (IL-2) and all tested PUFA as well as for rs1800795 (IL-6) and linoleic or arachidonic acid. The obesity risk of minor allele carriers significantly decreased with increasing fatty acid content. The genetic PUFA-IL-6 interaction was also reflected in plasma IL-6 concentrations. If replicated in a prospective study with sufficient statistical power, the results would indicate a beneficial effect of high PUFA supply for a substantial proportion of the population with respect to obesity risk.

Fish oil rich diet in comparison to saturated fat rich diet offered protection against lipopolysaccharide-induced inflammation and insulin resistance in mice

Background and Objective

Systemic chronic inflammation is linked to metabolic syndrome, type-2 diabetes, and heart disease. Lipopolysaccharide (LPS), a Gram negative microbial product, triggers inflammation through toll-like-receptor-4 (TLR-4) signaling. It has been reported that dietary fatty acids also modulate inflammation through TLR-4. We investigated whether fish oil (FO) rich diet in comparison to saturated fat (SF) rich diet would confer protection from pathologies induced by LPS.

Methods

Twenty C57BL/6 mice were divided into two groups. One group received FO-diet and other received SF-diet ad libitum for 60 days. Diets were isocaloric containing 45% energy from fat. After 60-days of feeding, blood was collected after overnight fast. Mice were allowed to recover for 4-days, fasted for 5-hours, challenged with 100 ng/mL of LPS intraperitonially, and bled after 2-hours. After 7-days of recuperation, mice were challenged with 500 ng/mL of LPS intraperitonially and observed for physical health.

Results

Food intake was similar in FO- and SF-fed mice. FO-fed mice compared to SF-fed mice had significantly less body weight gain (P = 0.005), epididymal fat weight (P = 0.005), fasting blood glucose (70.8 vs 83.3 ng/dL; P < 0.05), HOMA-IR (5.0 vs 13.6; P < 0.019), and serum cholesterol (167 vs 94 mg/dL; P < 0.05). When challenged with LPS, FO-fed mice had significantly lower serum IL-1β compared to SF-fed mice (2.0 vs 30.0 pg/mL; P < 0.001). After LPS-challenge, SF-fed mice had higher mortality, lost more body weight, and had greater decrease in blood glucose compared to FO-fed mice.

Conclusion

Overall, FO-diet compared to SF-diet offered protection against deleterious effects of LPS in mice.

Effects of omega-3 supplementation in combination with diet and exercise on weight loss and body composition

BACKGROUND

In addition to the metabolic and cardiovascular benefits of omega-3 (n-3) fatty acids, several studies have suggested an added weight loss-enhancing benefit to this supplement.

OBJECTIVE

The objective was to assess whether supplemental omega-3 fatty acids in conjunction with diet and exercise augment weight loss over a 6-mo period.

DESIGN

In a single-institution, placebo-controlled, randomized clinical trial, 128 individuals with a body mass index (in kg/m(2)) between 26 and 40 were assigned to receive 5 omega-3 [3.0 g eicosapentaenoic acid (EPA) plus docosahexaenoic acid (DHA) at a 5:1 ratio (EPA:DHA)] or placebo capsules daily in conjunction with lifestyle modification. The primary endpoint was weight loss; secondary endpoints included metabolic and psychometric variables. Analyses were by intention-to-treat.

RESULTS

Overweight and obese individuals were assigned to the omega-3 arm (n = 64) or to the placebo arm (n = 64). Subjects in both arms received dietary and exercise counseling. Eighty-one individuals completed the 24-wk study, and the dropout rate was 27%. Subjects in both arms lost an average of >5% of their body weight. No significant differences in weight loss were observed between the omega-3 (-5.2 kg; 95% CI: -6.0, -4.4 kg) and placebo (-5.8 kg; 95% CI: -6.7, -5.1 kg) arms. The absolute mean (±SEM) change difference was 0.61 ± 0.58 kg (P = 0.29). In addition, no significant differences in the other factors assessed were observed.

CONCLUSION

Omega-3 fatty acids were not effective as an adjunct for weight loss in this otherwise healthy, overweight population.

Fatty acid-gene interactions, adipokines and obesity

It is now recognized that the low-grade inflammation observed with obesity is associated with the development of a wide range of downstream complications. As such, there is considerable interest in elucidating the regulatory mechanisms underlying the production of inflammatory molecules to improve the prevention and treatment of obesity and its co-morbidities. White adipose tissue is no longer considered a passive reservoir for storing lipids, but rather an important organ influencing energy metabolism, insulin sensitivity and inflammation by the secretion of proteins, commonly referred to as adipokines. Dysregulation of several adipokines, such as tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6) and adiponectin, contributes to the low-grade inflammation that is a hallmark of obesity. Evidence now suggests that fatty acids represent a class of molecules that can modulate adipokine production, thereby influencing inflammatory status. Although the precise molecular mechanisms by which dietary fats regulate adipokine production remain unclear, recent findings indicate that diet-gene interactions may have an important role in the transcriptional and secretory regulation of adipokines. Single-nucleotide polymorphisms in the genes encoding TNF-α, IL-6 and adiponectin can modify circulating levels of these adipokines and, subsequently, obesity-related phenotypes. This genetic variation can also alter the influence of dietary fatty acids on adipokine production. Therefore, the current review will show that it is paramount to consider both genetic information and dietary fat intake to unravel the inter-individual variability in inflammatory response observed in intervention protocols targeting obesity.

AMPK as Target for Intervention in Childhood and Adolescent Obesity

Childhood obesity is a major worldwide health problem. Intervention programs to ameliorate the rate of obesity have been designed and implemented; yet the epidemic has no end near in sight. AMP-activated protein kinase (AMPK) has become one of the most important key elements in energy control, appetite regulation, myogenesis, adipocyte differentiation, and cellular stress management. Obesity is a multifactorial disease, which has a very strong genetic component, especially epigenetic factors. The intrauterine milieu has a determinant impact on adult life, since the measures taken for survival are kept throughout life thanks to epigenetic modification. Nutrigenomics studies the influence of certain food molecules on the metabolome profile, raising the question of an individualized obesity therapy according to metabolic (and probably) genetic features. Metformin, an insulin sensitizing agent, its known to lower insulin resistance and enhance metabolic profile, with an additional weight reduction capacity, via activation of AMPK. Exercise is coadjutant for lifestyle modifications, which also activates AMPK in several ways contributing to glucose and fat oxidation. The following review examines AMPK's role in obesity, applying its use as a tool for childhood and adolescent obesity.

The role of adipose tissue in mediating the beneficial effects of dietary fish oil

Fish oil improves several features of metabolic syndrome (MetS), such as dyslipidemia, insulin resistance and hepatic steatosis. Fish oil may mediate some of its beneficial effects by modulating the storage and/or secretory functions of adipose tissue (AT). The storage of triglycerides in AT is regulated by the availability of free fatty acids and the degree of lipolysis in AT. Fish oil has been shown to reduce lipolysis in several studies, indicating improved triglyceride storage. Importantly, AT secretes a variety of adipokines and fish oil feeding is associated with remarkable changes in the plasma levels of two key adipokines, adiponectin and leptin. Much attention has been focused on the contribution of adiponectin in fish oil-mediated improvements in MetS. However, emerging evidence also indicates a role of leptin in modulating the components of the MetS upon fish oil feeding. In addition to improving the storage and secretory functions of AT, fish oil, and the n-3 fatty acids found in fish oil, has been shown to reduce inflammation in AT. These effects may be in part a result of activation of peroxisome proliferator-activated receptor γ or inhibition of Toll-like receptor 4. Thus, there is compelling evidence that fish oil mediates its beneficial effects on MetS by improving AT storage and secretory functions and by reducing inflammation.

Docosahexaenoic acid increases cellular adiponectin mRNA and secreted adiponectin protein, as well as PPARγ mRNA, in 3T3-L1 adipocytes

Adiponectin, a protein secreted from adipose tissue, has been shown to have anti-diabetic and anti-inflammatory effects, but its regulation is not completely understood. Long-chain n-3 fatty acids eicosapentaenoic acid (20:5n-3; EPA) and docosahexaenoic acid (22:6n-3; DHA) may be involved in adiponectin regulation as they are potential ligands for peroxisome proliferator-activated receptor-γ (PPARγ), a key transcription factor for the adiponectin gene. To examine this, 3T3-L1 adipocytes were incubated with 125 µmol·L–1 EPA, DHA, palmitic, or oleic acids complexed to albumin, or with albumin alone (control) for 24 h. Adipocytes were also incubated for 24 h with EPA and DHA plus bisphenol-A-diglycidyl ether (BADGE), a PPARγ antagonist. Both EPA and DHA increased (p < 0.05) secreted adiponectin concentration compared with the control (44% and 102%, respectively), but did not affect cellular adiponectin protein content. Incubation with BADGE and DHA inhibited increases in secreted adiponectin protein, suggesting that DHA may act through a PPARγ-dependent mechanism. However, BADGE had no effect on EPA-induced increases in secreted adiponectin protein. Only DHA enhanced (p < 0.05) PPARγ and adiponectin mRNA expression compared wtih the control. Our results demonstrate that DHA increases cellular adiponectin mRNA and secreted adiponectin protein in 3T3-L1 adipocytes, possibly by a mechanism involving PPARγ. Moreover, DHA increased adiponectin concentration to a greater extent (40% more, p < 0.05) compared with EPA, emphasizing the need to consider the independent actions of EPA and DHA in adipocytes.

Adiponectin gene polymorphisms are associated with long-chain ω3-polyunsaturated fatty acids in serum phospholipids in nondiabetic Koreans

CONTEXT

Hypoadiponectinemia is caused by interactions between genetic and environmental factors, including the quality of dietary fats.

OBJECTIVE

We investigated the association of single-nucleotide polymorphisms (SNPs) in the adiponectin gene (ADIPOQ) with dietary fat intake or fatty acid (FA) composition in serum phospholipids, plasma adiponectin, and insulin resistance.

METHODS

Nondiabetic subjects (n = 1194) were genotyped for three ADIPOQ SNPs (-11377C>G; 45T>G; 276G>T) after screening of eight sites. Dietary fat intake, FA composition in serum phospholipids, adiponectin, and homeostasis model assessment of insulin resistance (HOMA-IR) were also measured.

RESULTS

The 276G carriers (n = 1082) showed lower high-density lipoprotein cholesterol (P = 0.024) and adiponectin (P < 0.001) but higher glucose (P = 0.015) and HOMA-IR (P = 0.005) than 276T/T subjects (n = 112). No associations were found in other SNPs. After adjusted for age, sex, body mass index, and the proportion of 18:2ω6 and 18:3ω3 (biomarkers of long term essential FA intake), the 276G carriers showed lower proportions of total ω3FA (P = 0.026), 20:5ω3 (P = 0.021), and 22:5ω3 (P = 0.024) in serum phospholipids. Among FAs in serum phospholipids, 18:2ω6 highly correlated with ω3-polyunsaturated FA (PUFA) intake (r = 0.260, P < 0.001) and adiponectin (r = 0.150, P < 0.001). The 276G carriers with a higher proportion of 18:2ω6 (≥12.5%) exhibited more pronounced characteristics, i.e. lower adiponectin (P < 0.001), lower high-density lipoprotein cholesterol (P = 0.004), higher HOMA-IR (P = 0.013), and lower long-chain ω3PUFAs (20:5ω3, 22:5ω3, and 22:6ω3, P < 0.001). Additionally, the effect of 276G>T on the relationship between adiponectin and HOMA-IR was modified by 18:2ω6 proportion.

CONCLUSION

ADIPOQ 276G is associated with reduced proportion of long-chain ω3PUFAs in serum phospholipids in nondiabetic Koreans.

AMP-activated protein kinase α2 subunit is required for the preservation of hepatic insulin sensitivity by n-3 polyunsaturated fatty acids

OBJECTIVE

The induction of obesity, dyslipidemia, and insulin resistance by high-fat diet in rodents can be prevented by n-3 long-chain polyunsaturated fatty acids (LC-PUFAs). We tested a hypothesis whether AMP-activated protein kinase (AMPK) has a role in the beneficial effects of n-3 LC-PUFAs.

RESEARCH DESIGN AND METHODS

Mice with a whole-body deletion of the α2 catalytic subunit of AMPK (AMPKα2(-/-)) and their wild-type littermates were fed on either a low-fat chow, or a corn oil-based high-fat diet (cHF), or a cHF diet with 15% lipids replaced by n-3 LC-PUFA concentrate (cHF+F).

RESULTS

Feeding a cHF diet induced obesity, dyslipidemia, hepatic steatosis, and whole-body insulin resistance in mice of both genotypes. Although cHF+F feeding increased hepatic AMPKα2 activity, the body weight gain, dyslipidemia, and the accumulation of hepatic triglycerides were prevented by the cHF+F diet to a similar degree in both AMPKα2(-/-) and wild-type mice in ad libitum-fed state. However, preservation of hepatic insulin sensitivity by n-3 LC-PUFAs required functional AMPKα2 and correlated with the induction of adiponectin and reduction in liver diacylglycerol content. Under hyperinsulinemic-euglycemic conditions, AMPKα2 was essential for preserving low levels of both hepatic and plasma triglycerides, as well as plasma free fatty acids, in response to the n-3 LC-PUFA treatment.

CONCLUSIONS

Our results show that n-3 LC-PUFAs prevent hepatic insulin resistance in an AMPKα2-dependent manner and support the role of adiponectin and hepatic diacylglycerols in the regulation of insulin sensitivity. AMPKα2 is also essential for hypolipidemic and antisteatotic effects of n-3 LC-PUFA under insulin-stimulated conditions.

Eicosapentaenoic acid prevents and reverses insulin resistance in high-fat diet-induced obese mice via modulation of adipose tissue inflammation

We investigated the effects of eicosapentaenoic acid (EPA) on prevention (P) and reversal (R) of high saturated-fat (HF) diet-induced obesity and glucose-insulin homeostasis. Male C57BL/6J mice were fed low-fat (LF; 10% energy from fat), HF (45% energy from fat), or a HF-EPA-P (45% energy from fat; 36 g/kg EPA) diet for 11 wk. A 4th group was initially fed HF for 6 wk followed by the HF-EPA-R diet for 5 wk. As expected, mice fed the HF diet developed obesity and glucose intolerance. In contrast, mice fed the HF-EPA-P diet maintained normal glucose tolerance despite weight gain compared with the LF group. Whereas the HF group developed hyperglycemia and hyperinsulinemia, both HF-EPA groups (P and R) exhibited normal glycemia and insulinemia. Further, plasma adiponectin concentration was lower in the HF group but was comparable in the LF and HF-EPA groups, suggesting a role of EPA in preventing and improving insulin resistance induced by HF feeding. Further analysis of adipose tissue adipokine levels and proteomic studies in cultured adipocytes indicated that dietary EPA supplementation of HF diets was associated with reduced adipose inflammation and lipogenesis and elevated markers of fatty acid oxidation. In C57BL/6J mice, EPA minimized saturated fat-induced insulin resistance and this is in part mediated by its effects on fatty acid oxidation and inflammation.

Efeito dos ácidos graxos n-3 e n-6 na expressão de genes do metabolismo de lipídeos e risco de aterosclerose

A aterosclerose, principal responsável pela patogênese do infarto miocárdico e cerebral, bem como pela gangrena e por outras doenças vasculares periféricas, permanece como principal causa de morbidade e mortalidade nas populações "ocidentalizadas". Estima-se que 17,5 milhões de pessoas morreram por doenças cardiovasculares em 2005, o que representou 30% das causas de morte nesse ano, e que, em 2015, 20 milhões de pessoas morrerão por doenças cardiovasculares no mundo. Os ácidos graxos n-3, principalmente os de cadeia longa, encontrados nos peixes, têm-se mostrado particularmente úteis na prevenção e tratamento de doenças como dislipidemias, diabetes mellitus e obesidade, apresentando importante efeito cardioprotetor. Nesse contexto, pesquisas têm evidenciado que ao menos parte dos benefícios dos ácidos graxos eicosapentaenóico e docosahexaenóico sobre o risco de doenças cardiovasculares é decorrente da modulação de genes responsivos aos receptores ativados por proliferadores de peroxissomos e envolvidos no metabolismo lipídico. Nesta revisão, pretende-se expor alguns mecanismos de ação dos ácidos graxos n-3 e n-6 sobre o metabolismo de lipídeos e de lipoproteínas. Conclui-se que muitos aspectos que contribuem para o risco de doenças cardiovasculares são afetados pela ingestão de n-3. Além da redução de triglicérides, fatores como o aumento de adiponectina, a redução da concentração de colesterol plasmático e a melhora do transporte reverso de colesterol também são responsáveis pela redução do risco de aterosclerose promovida pelos ácidos graxos n-3. No entanto, ainda são necessários estudos adicionais para definir mais claramente os mecanismos celulares e moleculares responsáveis pelo efeito cardioprotetor dos ácidos graxos n-3.

Pharmacological effects of lipid-lowering drugs on circulating adipokines

The cardioprotective effects of lipid-lowering drugs have been primarily attributed to their effects on blood lipid metabolism. However, emerging evidence indicates that lipid-lowering drugs also modulate the synthesis and secretion of adipose tissue-secreted proteins referred to as adipokines. Adipokines influence energy homeostasis and metabolism and have also been shown to modulate the vascular inflammatory cascade. The purpose of this review will be to examine the reported effects of commonly used lipid-lowering drugs (statins, fibrates, niacin and omega-3-fatty acids) on the circulating concentrations of leptin, adiponectin, tumor necrosis-factor-α (TNF-α), Retinol binding protein 4 (RBP4) and resistin. Overall, the lipid-lowering drugs reviewed have minimal effects on leptin and resistin concentrations.Conversely, circulating adiponectin concentrations are consistently increased by each lipid-lowering drug reviewed with the greatest effects produced by niacin. Studies that have examined the effects of statins, niacin and omega-3-fatty acids on TNF-α demonstrate that these agents have little effect on circulating TNF-α concentrations. Niacin and fibrates appear to lower RBP4 but not resistin concentrations. The results of the available studies suggest that a strong relationship exists between pharmacological reductions in blood lipids and adiponectin that is not obvious for other adipokines reviewed.

Plasma adiponectin concentration and insulin resistance: role of successful kidney transplantation

Adiponectin (ADPN) has been reported to be inversely correlated with insulin resistance (IR) in uremic subjects and following kidney transplantation. Kidneys have been suggested to play a part in ADPN clearance. This study sought to evaluate this hypothesis. We enrolled 67 candidates with end-stage renal disease (ESRD) along with 30 healthy unrelated donors. Plasma ADPN, IR (based on the homeostasis model assessment for IR index), and glomerular filtration rates were compared between control and patient groups. The correlations of the aforementioned variables were also compared in the patient group 1 day before and 14 days following transplantation. The changes in measured parameters were also compared with control group values. The glomerular filtration rate was significantly decreased among recipients. ADPN levels were remarkably higher in the patient group before transplantation when compared with healthy subjects (P<.001) and remained significantly higher thereafter (P<.001). Insulin resistance was higher, albeit not significantly, among ESRD patients compared with controls (P>.05) and it increased following transplantation (P=.03). There was no correlation between ADPN, IR, and glomerular filtration rate in normal individuals or ESRD patients before or after transplantation. It is our assumption that mechanisms other than kidney function are probably involved in ADPN metabolism in ESRD patients and in the immediate phase following transplantation. It does not seem that ADPN substantially affects IR either in ESRD or transplantation patients.

Combination of conjugated linoleic acid with fish oil prevents age-associated bone marrow adiposity in C57Bl/6J mice

The inverse relationship between fat in bone marrow and bone mass in the skeleton of aging subjects is well known. However, there is no precise therapy for the treatment of bone marrow adiposity. We investigated the ability of conjugated linoleic acid (CLA) and fish oil (FO), alone or in combination, to modulate bone loss using 12 months old C57Bl/6J mice fed 10% corn oil diet as control or supplemented with 0.5% CLA or 5% FO or 0.5% CLA+5% FO for 6 months. We found, CLA-fed mice exhibited reduced body weight, body fat mass (BFM) and enhanced hind leg lean mass (HLLM) and bone mineral density (BMD) in different regions measured by dual energy x-ray absorptiometry (DXA); however, associated with fatty liver and increased insulin resistance; whereas, FO fed mice exhibited enhanced BMD, improved insulin sensitivity, with no changes in BFM and HLLM. Interestingly, CLA+FO fed mice exhibited reduced body weight, BFM, peroxisome proliferator-activated receptor gamma and cathepsin K expression in bone marrow with enhanced BMD and HLLM. Moreover, CLA+FO supplementation reduced liver hypertrophy and improved insulin sensitivity with remarkable attenuation of bone marrow adiposity, inflammation and oxidative stress in aging mice. Therefore, CLA with FO combination might be a novel dietary supplement to reduce fat mass and improve BMD.

Regulation of adipokine secretion by n-3 fatty acids

Obesity leads to several chronic morbidities including type 2 diabetes, dyslipidaemia, atherosclerosis and hypertension, which are major components of the metabolic syndrome. White adipose tissue (WAT) metabolism and WAT-derived factors (fatty acids and adipokines) play an important role in the development of these metabolic disturbances. In fact, dysregulated adipokine secretion from the expanded WAT of obese individuals contributes to the development of systemic low-grade inflammation, insulin resistance and metabolic syndrome. The n-3 PUFA EPA and DHA have been widely reported to have protective effects in a range of chronic inflammatory conditions including obesity. In fact, n-3 PUFA have been shown to ameliorate low-grade inflammation in adipose tissue associated with obesity and up-regulate mitochondrial biogenesis and induce beta-oxidation in WAT in mice. Moreover, the ability of n-3 PUFA to regulate adipokine gene expression and secretion has been observed both in vitro and in vivo in rodents and human subjects. The present article reviews: (1) the physiological role of adiponectin, leptin and pre-B cell colony-enhancer factor/visfatin, three adipokines with immune-modulatory properties involved in the regulation of metabolism and insulin sensitivity and (2) the actions of n-3 PUFA on these adipokines focusing on the underlying mechanisms and the potential relationship with the beneficial effects of these fatty acids on obesity-associated metabolic disorders. It can be concluded that the ability of n-3 PUFA to improve obesity and insulin resistance conditions partially results from the modulation of WAT metabolism and the secretion of bioactive adipokines including leptin, adiponectin and visfatin.

Leptin as a potential therapeutic target for breast cancer prevention and treatment

IMPORTANCE OF THE FIELD

Obesity is considered to be an important risk factor for postmenopausal breast cancer. Elevated estrogen levels are thought to be a growth factor associated with this relationship. However, there is increasing evidence that factors produced directly in adipose tissue, adipokines, can also affect breast cancer development. Leptin is one of the adipokines that is measured in serum/plasma in increasing amounts as body weight/body fat increases.

AREAS COVERED IN THIS REVIEW

We highlight important aspects of leptin in relationship to mammary/breast tumor development. This includes findings from human, in vitro and animal studies. Information on leptin-related compounds which may have therapeutic use is presented. Additionally strategies to alter serum leptin levels by dietary and pharmacological interventions are discussed.

WHAT THE READER WILL GAIN

The reader will gain insights into the relationship of an adipose tissue protein and its potential role in breast cancer development as well as ways to intervene in leptin's actions.

TAKE HOME MESSAGE

Continued research will determine if interfering with the action of leptin has preventive or therapeutic applications in breast cancer.

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

Background

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

Results

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

Conclusions

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

Dietary DHA: time course of tissue uptake and effects on cytokine secretion in mice

Consumption of DHA has numerous beneficial effects, but little is known about these effects during the first few days of the DHA dietary intake. The main objectives of the present study were to determine the time course of DHA incorporation into phospholipids in different mouse tissues and the effects of DHA supplementation on adiponectin and leptin secretion. Mice were fed either a control diet or a DHA-rich diet, and some were killed on days 0, 4, 8, 16 and 32. Some mice were fed the DHA-rich diet for 16 d, and were then maintained on the control diet for sixteen more days (washout period). DHA supplementation increased plasma adiponectin secretion by 2·4-fold as early as 4 d after the initiation of the DHA-rich diet feeding. The adiponectin concentration remained 1·6-fold higher after the 16 d washout period. Plasma leptin levels were significantly lower after 4 d of feeding with DHA. These effects were associated with a significant increase in DHA incorporation in phosphatidylethanolamine and phosphatidylcholine of all analysed tissues (liver, heart and white adipose tissues). DHA mainly got incorporated at the expense of n-6 arachidonic acid. The present data show that DHA rapidly improved the profile of secreted adipokines, and that these protective effects were long lasting.

Plasma fatty acids and desaturase activity are associated with circulating adiponectin in healthy adolescent girls

CONTEXT

Adiponectin can be a potential predictor of future metabolic derangements and some preliminary evidence supports the role of dietary fat in influencing adiponectin levels thus, the dietary determinants of adiponectin were investigated.

OBJECTIVE

The objective of the study was to evaluate the association of adiponectin concentrations with plasma fatty acids and indices of endogenous fatty acid metabolism.

DESIGN

This was a cross-sectional descriptive analysis to investigative the determinants of adiponectin.

SETTING

All subjects were examined at a large tertiary care center located in Montréal (Québec, Canada) between 2004 and 2006.

SUBJECTS

Subjects included 180 postpubertal, adolescent daughters (age range 13.6-17.3 yr) from a 15-yr retrospective cohort of mother-daughter pairs representing gestational diabetes mellitus affected (cases) and nonaffected (controls) pregnancies between 1989 and 1991.

MAIN OUTCOME MEASURES

Plasma adiponectin concentrations, plasma fatty acids presented grouped by series name and as individual fatty acids (reported as percent of total), and calculated indices of fatty acid metabolism were measured.

RESULTS

In linear regression analyses, adjusting for both waist circumference and insulin measured 2 h after the onset of an oral glucose tolerance test, the docosahexaenoic acid sufficiency index (an indicator of docosahexaenoic acid status) and alpha-linolenic acid (C18:3 n-3) were significantly negatively associated (P <or= 0.05) with adiponectin. After accounting for dietary fat intake, these associations disappeared, indicating an effect of diet. However, the long-chain saturated fatty acid, lignoceric (C24:0), was positively associated (P <or= 0.05) and Delta 9-18 desaturase activity (estimated from the ratio of 18:1 n-9/18:0) was significantly inversely (P <or= 0.01) associated with adiponectin concentrations.

CONCLUSIONS

Adiponectin, an inverse marker of metabolic derangements, was associated with desaturase activity, indicating that possible functional alterations in fatty acid metabolism may already be present in young healthy adolescent females.

Review article: omega-3 fatty acids - a promising novel therapy for non-alcoholic fatty liver disease

BACKGROUND

Non-alcoholic fatty liver disease affects 10-35% of the adult population worldwide; there is no consensus on its treatment. Omega-3 fatty acids have proven benefits for hyperlipidaemia and cardiovascular disease, and have recently been suggested as a treatment for non-alcoholic fatty liver disease.

AIMS

To review the evidence base for omega-3 fatty acids in non-alcoholic fatty liver disease and critically appraise the literature relating to human trials.

METHODS

A Medline and PubMed search was performed to identify relevant literature using search terms 'omega-3', 'N-3 PUFA', 'eicosapentaenoic acid', 'docosahexaenoic acid', 'non-alcoholic fatty liver disease' and 'NAFLD'.

RESULTS

Omega-3 fatty acids are important regulators of hepatic gene transcription. Animal studies demonstrate that they reduce hepatic steatosis, improve insulin sensitivity and reduce markers of inflammation. Clinical trials in human subjects generally confirm these findings, but have significant design inadequacies.

CONCLUSIONS

Omega-3 fatty acids are a promising treatment for non-alcoholic fatty liver disease which require to be tested in randomized placebo-controlled trials.

Effects of three different highly purified n-3 series highly unsaturated fatty acids on lipid metabolism in C57BL/KsJ-db/db mice

Triglycerides (TG) consisting of highly purified (>97%) n-3 series highly unsaturated fatty acids, eicosapentaenoic acid (EPA), docosapentaenoic acid (DPA), and docosahexaenoic acid (DHA), were administered to C57BL/KsJ-db/db mice for 4 weeks by pair-feeding to compare their effects on lipid metabolism and to evaluate the effects of DPA on lipid metabolism. The hepatic TG level and total amount was decreased by treatment with DHA and DPA compared to the control. The efficacy of DPA was greater than that of EPA, but less than that of DHA. In contrast, EPA had the greatest serum TG reducing effect. The hepatic cytosol fraction of the DHA-treated group contained the lowest fatty acid synthase (FAS) and malic enzyme (ME) activity levels. Furthermore, the DHA-treated group contained the highest serum adiponectin concentrations. These findings indicate that the strong hepatic TG-lowering effect of DHA is due to the suppression of TG synthesis. The same tendencies were observed in DPA-treated mice, and the effect was stronger than that observed in EPA-treated mice, but equivalent to that observed in DHA-treated mice. Based on these results, DPA possesses lipid metabolism-improving effects. The beneficial effects of DPA for lipid metabolism were not superior to those of EPA and DHA, and the effect was always intermediate between those of EPA and DHA.

Adiponectin is associated with serum and adipose tissue fatty acid composition in rats

The objective of the present work is to analyse the relationships between changes in adiponectin and fatty acid composition in serum and adipose tissue in rats. Samples from serum and different adipose depots (periovarian, mesenteric and subcutaneous) were obtained from ageing rats (14- and 20-month-old) to determine fatty acid composition (gasliquid chromatography). In serum, insulin (radioimmunoassay) and adiponectin levels (enzyme-linked immunosorbent assay) were also measured, while adiponectin gene expression was analysed (real time-qPCR) in all fat depots. There were significant age-related reductions in adipose tissue saturated (SFA) and trans fatty acids and increases in monounsaturated fatty acids in parallel with diminished adiponectin expression in periovarian and mesenteric adipose tissue (p<0.05). Age-independent negative correlations were found between adiponectin gene expression in mesenteric adipose tissue and C12:0, C14:0 and C18:2 trans fatty acids (p<0.05). There was a positive association between serum adiponectin and adipose tissue oleic acid, while palmitoleic acid was negatively associated with adiponectin expression and positively correlated with insulin concentration. For the first time, positive relationships are reported between the proportion of n-6 polyunsaturated fatty acids (PUFA) in adipose tissue and adiponectin concentration and expression. In summary, adiponectin expression and serum levels are associated with fatty acid composition, with SFA, trans and palmitoleic fatty acids appearing as negative markers for adiponectin, and oleic acid and n-6 PUFA as positive ones. In addition, most associations were found in the visceral depots, highlighting the importance of visceral fat in the metabolic status.

Metabolism and secretory function of white adipose tissue: effect of dietary fat

Approximately 40% of the total energy consumed by western populations is represented by lipids, most of them being ingested as triacylglycerols and phospholipids. The focus of this review is to analyze the effect of the type of dietary fat on white adipose tissue metabolism and secretory function, particularly on haptoglobin, TNF-α, plasminogen activator inhibitor-1 and adiponectin secretion. Previous studies have demonstrated that the duration of the exposure to the high-fat feeding, amount of fatty acid present in the diet and the type of fatty acid may or may not have a significant effect on adipose tissue metabolism. However, the long-term or short-term high fat diets, especially rich in saturated fatty acids, probably by activation of toll-like receptors, stimulated the expression of proinflammatory adipokines and inhibited adiponectin expression. Further studies are needed to investigate the cellular mechanisms by which dietary fatty acids affect white adipose tissue metabolism and secretory functions.

The relationship of insulin resistance with SNP 276G>T at adiponectin gene and plasma long-chain polyunsaturated fatty acids in obese children

This study examined the association of insulin resistance with single-nucleotide polymorphism (SNP) 276G>T at adiponectin gene and the plasma long-chain polyunsaturated fatty acids (LCPUFAs) profile in obese children. One hundred thirty-one normolipidaemic obese children aged 8-13 y (53 girls and 68 boys) entered the study. The prevalence of T allele carriers at SNP276 was 48.8%. Mean [SD] values of fasting insulin and homeostasis model assessment-insulin resistance (HOMA-IR) index in noncarriers versus carriers of T allele were 12.4 [6.4] versus 20.6 [6.3] muU/mL (p = 0.039) and 2.6 [1.4] versus 4.5 [1.7] (p = 0.032). Mean [SD] values of plasma C18:3n - 3, C20:5n - 3/C20:4n - 6, and n - 6/n - 3 LCPUFA in phospholipids in noncarriers versus carriers of T allele were 0.10 [0.04] versus 0.08 [0.03] % (p = 0.013), 0.04 [0.01] versus 0.03 [0.01] % (p = 0.045), and 4.4 [0.7] versus 4.9 [0.9] % (p = 0.005), respectively. Insulin resistance was independently associated with SNP 276G>T (p = 0.002) and n - 6/n - 3 LCPUFA (p = 0.042) in plasma phospholipids, and interaction was found between SNP 276G>T and n - 6/n - 3 LCPUFA (p = 0.046). These findings suggest that obese children carriers of the SNP 276G>T may be at increased risk of metabolic complications compared with noncarriers, possibly due in part to a different plasma phospholipids profile.

n-3 PUFA: bioavailability and modulation of adipose tissue function

Adipose tissue has a key role in the development of metabolic syndrome (MS), which includes obesity, type 2 diabetes, dyslipidaemia, hypertension and other disorders. Systemic insulin resistance represents a major factor contributing to the development of MS in obesity. The resistance is precipitated by impaired adipose tissue glucose and lipid metabolism, linked to a low-grade inflammation of adipose tissue and secretion of pro-inflammatory adipokines. Development of MS could be delayed by lifestyle modifications, while both dietary and pharmacological interventions are required for the successful therapy of MS. The n-3 long-chain (LC) PUFA, EPA and DHA, which are abundant in marine fish, act as hypolipidaemic factors, reduce cardiac events and decrease the progression of atherosclerosis. Thus, n-3 LC PUFA represent healthy constituents of diets for patients with MS. In rodents n-3 LC PUFA prevent the development of obesity and impaired glucose tolerance. The effects of n-3 LC PUFA are mediated transcriptionally by AMP-activated protein kinase and by other mechanisms. n-3 LC PUFA activate a metabolic switch toward lipid catabolism and suppression of lipogenesis, i.e. in the liver, adipose tissue and small intestine. This metabolic switch improves dyslipidaemia and reduces ectopic deposition of lipids, resulting in improved insulin signalling. Despite a relatively low accumulation of n-3 LC PUFA in adipose tissue lipids, adipose tissue is specifically linked to the beneficial effects of n-3 LC PUFA, as indicated by (1) the prevention of adipose tissue hyperplasia and hypertrophy, (2) the induction of mitochondrial biogenesis in adipocytes, (3) the induction of adiponectin and (4) the amelioration of adipose tissue inflammation by n-3 LC PUFA.

Eicosapentaenoic acid stimulates AMP-activated protein kinase and increases visfatin secretion in cultured murine adipocytes

Visfatin is an adipokine highly expressed in visceral AT (adipose tissue) of humans and rodents, the production of which seems to be dysregulated in excessive fat accumulation and conditions of insulin resistance. EPA (eicosapentaenoic acid), an n-3 PUFA (polyunsaturated fatty acid), has been demonstrated to exert beneficial effects in obesity and insulin resistance conditions, which have been further linked to its reported ability to modulate adipokine production by adipocytes. TNF-alpha (tumour necrosis factor-alpha) is a pro-inflammatory cytokine whose production is increased in obesity and is involved in the development of insulin resistance. Control of adipokine production by some insulin-sensitizing compounds has been associated with the stimulation of AMPK (AMP-activated protein kinase). The aim of the present study was to examine in vitro the effects of EPA on visfatin production and the potential involvement of AMPK both in the absence or presence of TNF-alpha. Treatment with the pro-inflammatory cytokine TNF-alpha (1 ng/ml) did not modify visfatin gene expression and protein secretion in primary cultured rat adipocytes. However, treatment of these primary adipocytes with EPA (200 mumol/l) for 24 h significantly increased visfatin secretion (P<0.001) and mRNA gene expression (P<0.05). Moreover, the stimulatory effect of EPA on visfatin secretion was prevented by treatment with the AMPK inhibitor Compound C, but not with the PI3K (phosphoinositide 3-kinase) inhibitor LY294002. Similar results were observed in 3T3-L1 adipocytes. Moreover, EPA strongly stimulated AMPK phosphorylation alone or in combination with TNF-alpha in 3T3-L1 adipocytes and pre-adipocytes. The results of the present study suggest that the stimulatory action of EPA on visfatin production involves AMPK activation in adipocytes.

Effects of long chain omega-3 fatty acids on metalloproteinases and their inhibitors in combined dyslipidemia patients

We evaluate the effect of a standardized dietary supplementation with omega-3 polyunsaturated fatty acids (n-3 PUFAs) on the level of some markers of vascular remodeling in patients with combined dyslipidemia. Three hundred and thirty-three patients received placebo or n-3 PUFAs for 6 months. We evaluated body mass index, glycemic profile, blood pressure, lipid profile, lipoprotein(a), plasminogen activator inhibitor-1, homocysteine, fibrinogen, high-sensitivity C reactive protein, ADP, MMP-2 and MMP-9, and tissue inhibitors of metalloproteinase-1 and -2. A significant increase of high-density lipoprotein-cholesterol, and a significant decrease of triglycerides were present after 3 and 6 months with n-3 PUFAs intake. A significant plasminogen activator inhibitor-1, fibrinogen and high-sensitivity C reactive protein decrease was obtained after 3 and 6 months and a significant ADP increase was observed after 3 and 6 months of n-3 PUFAs. A significant MMP-2, MMP-9, tissue inhibitors of metalloproteinase-1 and tissue inhibitors of metalloproteinase-2 decrease was obtained after 6 months compared to the baseline value with n-3 PUFAs intake. n-3 PUFAs give a better lipid profile and a better improvement of coagulation, fibrinolytic and inflammatory parameters than placebo. Furthermore, lowers levels of MMP-2, MMP-9 and their tissue inhibitors are obtained with n-3 PUFAs compared to placebo.

Are all n-3 polyunsaturated fatty acids created equal?

N-3 Polyunsaturated fatty acids have been shown to have potential beneficial effects for chronic diseases including cancer, insulin resistance and cardiovascular disease. Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in particular have been studied extensively, whereas substantive evidence for a biological role for the precursor, alpha-linolenic acid (ALA), is lacking. It is not enough to assume that ALA exerts effects through conversion to EPA and DHA, as the process is highly inefficient in humans. Thus, clarification of ALA's involvement in health and disease is essential, as it is the principle n-3 polyunsaturated fatty acid consumed in the North American diet and intakes of EPA and DHA are typically very low. There is evidence suggesting that ALA, EPA and DHA have specific and potentially independent effects on chronic disease. Therefore, this review will assess our current understanding of the differential effects of ALA, EPA and DHA on cancer, insulin resistance, and cardiovascular disease. Potential mechanisms of action will also be reviewed. Overall, a better understanding of the individual role for ALA, EPA and DHA is needed in order to make appropriate dietary recommendations regarding n-3 polyunsaturated fatty acid consumption.

Plasma proteome analysis for anti-obesity and anti-diabetic potentials of chitosan oligosaccharides in ob/ob mice

Altered levels of adipokines, derived as a result of distorted adipocytes, are the major factors responsible for changing biochemical parameters in obesity that leads to the development of metabolic disorders such as insulin resistance and atherosclerosis. In our previous reports, chitosan oligosaccharides (CO) were proved to inhibit the differentiation of 3T3-L1 adipocytes. In the present study, an attempt was made to investigate the anti-obesity and anti-diabetic effect of CO on ob/ob mice, by means of differential proteomic analysis of plasma. This was followed by immunoblotting, and gene expression in adipose tissue to clarify the molecular mechanism. CO treatment showed reduced diet intake (13%), body weight gain (12%), lipid (29%) and glucose levels (35%). 2-DE results showed differential levels of five proteins namely RBP4, apoE, and apoA-IV by >2-fold down-regulation and by >2-fold of apoA-I and glutathione peroxidase (GPx) up-regulation after CO treatment. Immunoblotting studies of adiponectin and resistin showed amelioration in their levels in plasma. Furthermore, the results of gene expressions for adipose tissue specific TNF-alpha, and IL-6 secretary molecules were also down-regulated by CO treatment. Gene expressions of PPAR gamma in adipose tissue were in good agreement with the ameliorated levels of adipokines, thereby improving the pathological state. Taken together, CO might act as a potent down-regulator of obesity-related gene expression in ob/ob mice that may normalize altered plasma proteins to overcome metabolic disorders of obesity.

omega-3 polyunsaturated fatty acid supplementation for the treatment of heart failure: mechanisms and clinical potential

Heart failure (HF) is a complex clinical syndrome with multiple aetiologies. Current treatment options can slow the progression to HF, but overall the prognosis remains poor. Clinical studies suggest that high dietary intake of the omega-3 polyunsaturated fatty acids (omega-3PUFA) found in fish oils (eicosapentaenoic and docosahexaenoic acids) may lower the incidence of HF, and that supplementation with pharmacological doses prolongs event-free survival in patients with established HF. The mechanisms for these potential benefits are complex and not well defined. It is well established that fish oil supplementation lowers plasma triglyceride levels, and more recent work demonstrates anti-inflammatory effects, including reduced circulating levels of inflammatory cytokines and arachidonic acid-derived eicosanoids, and elevated plasma adiponectin. In animal studies, fish oil favourably alters cardiac mitochondrial function. All of these effects may work to prevent the development and progression of HF. The omega-3PUFA found in plant sources, alpha-linolenic acid, may also be protective in HF; however, the evidence is not as compelling as for fish oil. This review summarizes the evidence related to use of omega-3PUFA supplementation as a potential treatment for HF and discusses possible mechanisms of action. In general, there is growing evidence that supplementation with omega-3PUFA positively impacts established pathophysiological targets in HF and has potential therapeutic utility for HF patients.

Plasma n-3 Polyunsaturated Fatty Acids are negatively associated with obesity

The objective of the present study was to investigate the relationship between plasma n-3 PUFA composition and weight status. A total of 124 adults, stratified by weight status: healthy weight (n 21), overweight (n 40) and obese (n 63) were recruited. Fasting blood samples, anthropometric measures and body composition were collected. Plasma fatty acid composition was determined by GC. BMI, waist circumference and hip circumference were inversely correlated with n-3 PUFA, EPA and DHA (P < 0.05 for all) in the obese group. Obese individuals had significantly lower plasma concentrations of total n-3 PUFA, compared with healthy-weight individuals (4.53 (SD 1.11) v. 5.25 (SD 1.43) %). When subjects were pooled and stratified into quartiles of total n-3 PUFA, a significant inverse trend was found for BMI (P = 0.002), waist circumference and hip circumference (P = 0.01 and P < 0.001 respectively). Higher plasma levels of total n-3 PUFA are associated with a healthier BMI, waist circumference and hip circumference. Our findings suggest that n-3 PUFA may play an important role in weight status and abdominal adiposity.

Metabolic activity of the enteric microbiota influences the fatty acid composition of murine and porcine liver and adipose tissues

BACKGROUND

Recent reports suggest that the metabolic activity of the gut microbiota may contribute to the pathogenesis of obesity and hepatic steatosis.

OBJECTIVE

The objective was to determine whether the fat composition of host tissues might be influenced by oral administration of commensal bifidobacteria previously shown by us to produce bioactive isomers of conjugated linoleic acid (CLA).

DESIGN

Murine trials were conducted in which linoleic acid-supplemented diets were fed with or without Bifidobacterium breve NCIMB 702258 (daily dose of 10(9) microorganisms) to healthy BALB/c mice and to severe combined immunodeficient mice for 8-10 wk. To ensure that the observations were not peculiar to mice, a similar trial was conducted in weanling pigs over 21 d. Tissue fatty acid composition was assessed by gas-liquid chromatography.

RESULTS

In comparison with controls, there was an increase in cis-9, trans-11 CLA in the livers of the mice and pigs after feeding with linoleic acid in combination with B. breve NCIMB 702258 (P < 0.05). In addition, an altered profile of polyunsaturated fatty acid composition was observed, including higher concentrations of the omega-3 (n-3) fatty acids eicosapentaenoic acid and docosahexaenoic acid in adipose tissue (P < 0.05). These changes were associated with reductions in the proinflammatory cytokines tumor necrosis factor-alpha and interferon-gamma (P < 0.05).

CONCLUSIONS

These results are consistent with the concept that the metabolome is a composite of host and microbe metabolic activity and that the influence of the microbiota on host fatty acid composition can be manipulated by oral administration of CLA-producing microorganisms.

n-3 fatty acids and rosiglitazone improve insulin sensitivity through additive stimulatory effects on muscle glycogen synthesis in mice fed a high-fat diet

AIMS/HYPOTHESIS

Fatty acids of marine origin, i.e. docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) act as hypolipidaemics, but they do not improve glycaemic control in obese and diabetic patients. Thiazolidinediones like rosiglitazone are specific activators of peroxisome proliferator-activated receptor gamma, which improve whole-body insulin sensitivity. We hypothesised that a combined treatment with a DHA and EPA concentrate (DHA/EPA) and rosiglitazone would correct, by complementary additive mechanisms, impairments of lipid and glucose homeostasis in obesity.

METHODS

Male C57BL/6 mice were fed a corn oil-based high-fat diet. The effects of DHA/EPA (replacing 15% dietary lipids), rosiglitazone (10 mg/kg diet) or a combination of both on body weight, adiposity, metabolic markers and adiponectin in plasma, as well as on liver and muscle gene expression and metabolism were analysed. Euglycaemic-hyperinsulinaemic clamps were used to characterise the changes in insulin sensitivity. The effects of the treatments were also analysed in dietary obese mice with impaired glucose tolerance (IGT).

RESULTS

DHA/EPA and rosiglitazone exerted additive effects in prevention of obesity, adipocyte hypertrophy, low-grade adipose tissue inflammation, dyslipidaemia and insulin resistance, while inducing adiponectin, suppressing hepatic lipogenesis and decreasing muscle ceramide concentration. The improvement in glucose tolerance reflected a synergistic stimulatory effect of the combined treatment on muscle glycogen synthesis and its sensitivity to insulin. The combination treatment also reversed dietary obesity, dyslipidaemia and IGT.

CONCLUSIONS/INTERPRETATION

DHA/EPA and rosiglitazone can be used as complementary therapies to counteract dyslipidaemia and insulin resistance. The combination treatment may reduce dose requirements and hence the incidence of adverse side effects of thiazolidinedione therapy.

Prevention and reversal of obesity and glucose intolerance in mice by DHA derivatives

The n-3 polyunsaturated fatty acids, especially eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), exert hypolipidemic effects and prevent development of obesity and insulin resistance in animals fed high-fat diets. We sought to determine the efficacy of alpha-substituted DHA derivatives as lipid-lowering, antiobesity, and antidiabetic agents. C57BL/6 mice were given a corn oil-based high-fat (35% weight/weight) diet (cHF), or cHF with 1.5% of lipids replaced with alpha-methyl DHA ethyl ester (Substance 1), alpha-ethyl DHA ethyl ester (Substance 2), alpha,alpha-di-methyl DHA ethyl ester (Substance 3), or alpha-thioethyl DHA ethyl ester (Substance 4) for 4 months. Plasma markers of glucose and lipid metabolism, glucose tolerance, morphology, tissue lipid content, and gene regulation were characterized. The cHF induced obesity, hyperlipidemia, impairment of glucose homeostasis, and adipose tissue inflammation. Except for Substance 3, all other substances prevented weight gain and Substance 2 exerted the strongest effect (63% of cHF-controls). Glucose intolerance was significantly prevented (~67% of cHF) by both Substance 1 and Substance 2. Moreover, Substance 2 lowered fasting glycemia, plasma insulin, triacylglycerols, and nonesterified fatty acids (73, 9, 47, and 81% of cHF-controls, respectively). Substance 2 reduced accumulation of lipids in liver and skeletal muscle, as well as adipose tissue inflammation associated with obesity. Substance 2 also induced weight loss in dietary obese mice. In contrast to DHA administered either alone or as a component of the EPA/DHA concentrate (replacing 15% of dietary lipids), Substance 2 also reversed established glucose intolerance in obese mice. Thus, Substance 2 represents a novel compound with a promising potential in the treatment of obesity and associated metabolic disturbances.

Omega-3 fatty acids plus rosuvastatin improves endothelial function in South Asians with dyslipidemia

Background:

The present study was undertaken to investigate the effect of statins plus omega-3 polyunsaturated fatty acids (PUFAs) on endothelial function and lipid profile in South Asians with dyslipidemia and endothelial dysfunction, a population at high risk for premature coronary artery disease.

Methods:

Thirty subjects were randomized to rosuvastatin 10 mg and omega-3-PUFAs 4 g or rosuvastatin 10 mg. After 4 weeks, omega-3-PUFAs were removed from the first group and added to subjects in the second group. All subjects underwent baseline, 4-, and 8-week assessment of endothelial function and lipid profile.

Results:

Compared to baseline, omega-3-PUFAs plus rosuvastatin improved endothelial-dependent vasodilation (EDV: −1.42% to 11.36%, p = 0.001), and endothelial-independent vasodilation (EIV: 3.4% to 17.37%, p = 0.002). These effects were lost when omega-3-PUFAs were removed (EDV: 11.36% to 0.59%, p = 0.003). In the second group, rosuvastatin alone failed to improve both EDV and EIV compared to baseline. However, adding omega-3-PUFAs to rosuvastatin, significantly improved EDV (−0.66% to 14.73%, p = 0.001) and EIV (11.02% to 24.5%, p = 0.001). Addition of omega-3-PUFAs further improved the lipid profile (triglycerides 139 to 91 mg/dl, p = 0.006, low-density lipoprotein cholesterol 116 to 88 mg/dl, p = 0.014).

Conclusions:

Combined therapy with omega-3-PUFAs and rosuvastatin improves endothelial function in South Asian subjects with dyslipidemia and endothelial dysfunction.

Induction of lipid oxidation by polyunsaturated fatty acids of marine origin in small intestine of mice fed a high-fat diet

BACKGROUND

Dietary polyunsaturated fatty acids (PUFA), in particular the long chain marine fatty acids docosahexaenoic (DHA) and eicosapentaenoic (EPA), are linked to many health benefits in humans and in animal models. Little is known of the molecular response to DHA and EPA of the small intestine, and the potential contribution of this organ to the beneficial effects of these fatty acids. Here, we assessed gene expression changes induced by DHA and EPA in the wildtype C57BL/6J murine small intestine using whole genome microarrays and functionally characterized the most prominent biological process.

RESULTS

The main biological process affected based on gene expression analysis was lipid metabolism. Fatty acid uptake, peroxisomal and mitochondrial beta-oxidation, and omega-oxidation of fatty acids were all increased. Quantitative real time PCR, and -- in a second animal experiment -- intestinal fatty acid oxidation measurements confirmed significant gene expression differences and showed in a dose-dependent manner significant changes at biological functional level. Furthermore, no major changes in the expression of lipid metabolism genes were observed in the colon.

CONCLUSION

We show that marine n-3 fatty acids regulate small intestinal gene expression and increase fatty acid oxidation. Since this organ contributes significantly to whole organism energy use, this effect on the small intestine may well contribute to the beneficial physiological effects of marine PUFAs under conditions that will normally lead to development of obesity, insulin resistance and diabetes.

Prevention of insulin resistance by n-3 polyunsaturated fatty acids

PURPOSE OF REVIEW

Review results from recent human and animal studies regarding the effects of n-3 polyunsaturated fatty acid (PUFA) in the prevention of insulin resistance.

RECENT FINDINGS

Overall, results from animal studies indicate that fish oil and individual n-3 PUFA [alpha-linolenic acid (ALA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA)] prevented insulin resistance in animal models; results from two studies in mice showed that EPA increased insulin secretion. ALA, EPA, and DHA may act at different sites and involve different mechanisms. Fish oil or purified EPA reduced insulin resistance in some but not other human studies in normal weight and obese individuals. Discrepancies may be due to differences in health status of participants, macronutrient, fatty acid, and antioxidant nutrient composition of basal diet; amount, duration, and fatty acid composition of n-3 PUFA, and methods used to assess insulin resistance. Moderate amounts of n-3 PUFA did not improve or deteriorate glucose control in type 2 diabetics.

SUMMARY

n-3 PUFA supplementation has clinical significance in the prevention and reversal of insulin resistance. However, increased intake of n-3 PUFA should be part of an overall healthy lifestyle that includes weight control, exercise, and reduction in the intake of refined sugars, n-6, saturated, and trans fatty acids.

ADIPOQ polymorphisms, monounsaturated fatty acids, and obesity risk: the GOLDN study

Serum adiponectin levels have been positively associated with insulin sensitivity and are decreased in type 2 diabetes (T2D) and obesity. Genetic and environmental factors influence serum adiponectin and may contribute to risk of metabolic syndrome and T2D. Therefore, we investigated the effect of ADIPOQ single-nucleotide polymorphisms (SNPs), -11377C>G and -11391G>A, on metabolic-related traits, and their modulation by dietary fat in white Americans. Data were collected from 1,083 subjects participating in the Genetics of Lipid Lowering Drugs and Diet Network study. Mean serum adiponectin concentration was higher for carriers of the -11391A allele (P = 0.001) but lower for the -11377G allele carriers (P = 0.017). Moreover, we found a significant association with obesity traits for the -11391G>A SNP. Carriers of the -11391A allele had significantly lower weight (P = 0.029), BMI (P = 0.019), waist (P = 0.003), and hip circumferences (P = 0.004) compared to noncarriers. Interestingly, the associations of the -11391G>A with BMI and obesity risk were modified by monounsaturated fatty acids (MUFAs) intake (P-interaction = 0.021 and 0.034 for BMI and obesity risk, respectively). In subjects with MUFA intake above the median (> or =13% of energy intake), -11391A carriers had lower BMI (27.1 kg/m(2) for GA+AA vs. 29.1 kg/m(2) for GG, P = 0.002) and decreased obesity risk (odds ratio for -11391A = 0.52, 95% confidence interval (CI); 0.28-0.96; P = 0.031). However, we did not detect genotype-related differences for BMI or obesity in subjects with MUFA intake <13%. Our findings support a significant association between the -11391G>A SNPs and obesity-related traits and the potential to moderate such effects using dietary modification.

Cellular and molecular effects of n-3 polyunsaturated fatty acids on adipose tissue biology and metabolism

Adipose tissue and its secreted products, adipokines, have a major role in the development of obesity-associated metabolic derangements including Type 2 diabetes. Conversely, obesity and its metabolic sequelae may be counteracted by modulating metabolism and secretory functions of adipose tissue. LC-PUFAs (long-chain polyunsaturated fatty acids) of the n-3 series, namely DHA (docosahexaenoic acid; C(22:6n-3)) and EPA (eicosapentaenoic acid; C(20:5n-3)), exert numerous beneficial effects, such as improvements in lipid metabolism and prevention of obesity and diabetes, which partially result from the metabolic action of n-3 LC-PUFAs in adipose tissue. Recent studies highlight the importance of mitochondria in adipose tissue for the maintenance of systemic insulin sensitivity. For instance, both n-3 LC-PUFAs and the antidiabetic drugs TZDs (thiazolidinediones) induce mitochondrial biogenesis and beta-oxidation. The activation of this 'metabolic switch' in adipocytes leads to a decrease in adiposity. Both n-3 LC-PUFAs and TZDs ameliorate a low-grade inflammation of adipose tissue associated with obesity and induce changes in the pattern of secreted adipokines, resulting in improved systemic insulin sensitivity. In contrast with TZDs, which act as agonists of PPARgamma (peroxisome-proliferator-activated receptor-gamma) and promote differentiation of adipocytes and adipose tissue growth, n-3 LC-PUFAs affect fat cells by different mechanisms, including the transcription factors PPARalpha and PPARdelta. Some of the effects of n-3 LC-PUFAs on adipose tissue depend on their active metabolites, especially eicosanoids. Thus treatments affecting adipose tissue by multiple mechanisms, such as combining n-3 LC-PUFAs with either caloric restriction or antidiabetic/anti-obesity drugs, should be explored.

Plasma adiponectin concentrations are associated with body composition and plant-based dietary factors in female twins

Circulating adiponectin is emerging as an important link between obesity, type 2 diabetes, and cardiovascular disease (CVD). However, the spectrum of lifestyle factors that modulate the adiponectin concentration remains to be elucidated, particularly among women. We conducted a cross-sectional study of 877 female twin pairs from the TwinsUK adult twin registry. Using a co-twin design, we examined dietary and body composition influences on adiponectin by conducting matched, within-pair analyses to eliminate confounding. Following multivariable adjustment within-twin pairs, significant influences on adiponectin (log-transformed, percent change per SD of the dietary/body composition variable) were observed for nonstarch polysaccharides (3.25%; 95% CI: 0.06, 6.54; P < 0.05) and magnesium intake (3.80%; 95%CI: 0.17, 7.57; P < 0.05), with a trend toward an association for fruit and vegetable (F&V) intakes (2.55%; 95% CI: -0.26, 5.45; P = 0.08). These modest positive associations cannot be explained by confounding through other lifestyle factors shared by the twins. A significant relationship between adiponectin and 3 derived dietary patterns (F&V, dieting, traditional English), carbohydrate, protein, trans fat, and alcohol intake was also observed. Strong inverse associations with adiponectin were observed for BMI (-10.72%; 95% CI: -13.78, -7.55), total (-6.89%: 95% CI: -10.34, -3.30; P < 0.05), and central fat mass (-12.50%; 95% CI: -15.82, -9.05; P < 0.05); these relationships were significant both when twins were analyzed as individuals and when characteristics were contrasted within-twin pairs, suggesting a direct effect. We observed modest associations between dietary factors and adiponectin in female twins, independent of adiposity, and report strong inverse associations with body composition. These data reinforce the importance of weight maintenance and increasing consumption of diets rich in plant-based foods to prevent CVD and type 2 diabetes.