Resistin expression in 3T3-L1 adipocytes is reduced by arachidonic acid

A review on the relationship between Arachidonic acid 15-Lipoxygenase (ALOX15) and diabetes mellitus

Arachidonic acid 15-lipoxygenase (ALOX15), as one of the lipoxygenase family, is mainly responsible for catalyzing the oxidation of various fatty acids to produce a variety of lipid components, contributing to the pathophysiological processes of various immune and inflammatory diseases. Studies have shown that ALOX15 and its related products are widely distributed in human tissues and related to multiple diseases such as liver, cardiovascular, cerebrovascular diseases, diabetes mellitus and other diseases. Diabetes mellitus (DM), the disease studied in this article, is a metabolic disease characterized by a chronic increase in blood glucose levels, which is significantly related to inflammation, oxidative stress, ferroptosis and other mechanisms, and it has a high incidence in the population, accompanied by a variety of complications. Figuring out how ALOX15 is involved in DM is critical to understanding its role in diseases. Therefore, ALOX15 inhibitors or combination therapy containing inhibitors may deliver a novel research direction for the treatment of DM and its complications. This article aims to review the biological effect and the possible function of ALOX15 in the pathogenesis of DM.

Monoacylglycerol O-acyltransferase 1 lowers adipocyte differentiation capacity in vitro but does not affect adiposity in mice

OBJECTIVE

Monoacylglycerol O-acyltransferase 1 (Mogat1), a lipogenic enzyme that converts monoacylglycerol to diacylglycerol, is highly expressed in adipocytes and may regulate lipolysis by re-esterifying fatty acids released during times when lipolytic rates are low. However, the role of Mogat1 in regulating adipocyte fat storage during differentiation and diet-induced obesity is relatively understudied.

METHODS

Here, adipocyte-specific Mogat1 knockout mice were generated and subjected to a high-fat diet to determine the effects of Mogat1 deficiency on diet-induced obesity. Mogat1 floxed mice were also used to develop preadipocyte cell lines wherein Mogat1 could be conditionally knocked out to study adipocyte differentiation in vitro.

RESULTS

In preadipocytes, it was found that Mogat1 knockout at the onset of preadipocyte differentiation prevented the accumulation of glycerolipids and reduced the differentiation capacity of preadipocytes. However, the loss of adipocyte Mogat1 did not affect weight gain or fat mass induced by a high-fat diet in mice. Furthermore, loss of Mogat1 in adipocytes did not affect plasma lipid or glucose concentrations or insulin tolerance.

CONCLUSIONS

These data suggest Mogat1 may play a role in adipocyte differentiation in vitro but not adipose tissue expansion in response to nutrient overload in mice.

P38 MAPK pathway regulates the expression of resistin in porcine alveolar macrophages via Ets2 during Haemophilus parasuis stimulation

Haemophilus parasuis is a widespread bacterial pathogen causing acute systemic inflammation and leading to the sudden death of piglets. Resistin, a multifunctional peptide hormone previously demonstrated to influence the inflammation in porcine, was extremely increased in H. parasuis-infected tissues. However, the mechanism of resistin expression regulation in porcine, especially during pathogen infection, remains unclear. In the present study, we explored for the first time the transcription factor and signaling pathway mediating the expression of pig resistin during H. parasuis stimulation. We found that H. parasuis induced the expression of pig resistin in a time- and dose-dependent manner via the transcription factor Ets2 in porcine alveolar macrophages during H. parasuis stimulation. Moreover, the expression of Ets2 was mediated by the activation of the p38 MAPK pathway induced by H. parasuis, thus promoting resistin production. These results revealed a novel view of the molecular mechanism of pig resistin production during acute inflammation induced by pathogenic bacteria.

Ratios of serum eicosapentaenoic acid to arachidonic acid and docosahexaenoic acid to arachidonic acid were inversely associated with serum resistin levels: The Hisayama Study

AIMS/INTRODUCTION

Resistin is an adipocyte-derived polypeptide that leads to the progression of insulin resistance and subsequent atherosclerosis. Some studies have reported an association between self-reported intake of n-3 polyunsaturated fatty acids (PUFAs) and serum resistin levels. However, no studies have investigated the association between the ratio of serum levels of n-3 to serum n-6 PUFAs and the serum resistin concentration in the general population.

MATERIALS AND METHODS

We carried out a cross-sectional study of 3,200 community-dwelling Japanese individuals aged ≥40 years in 2002-2003. The ratios of serum eicosapentaenoic acid or docosahexaenoic acid to arachidonic acid (AA) were categorized into quartiles. The associations of serum eicosapentaenoic acid/AA and docosahexaenoic acid/AA with the serum resistin concentration were assessed using linear regression models with adjustment for potential confounding factors.

RESULTS

The geometric mean of serum resistin was 10.3 ng/mL. The age- and sex-adjusted geometric mean of serum resistin decreased significantly with increased levels of serum eicosapentaenoic acid/AA (quartile 1: 11.3 ng/mL; quartile 2: 10.6 ng/mL; quartile 3: 10.3 ng/mL; quartile 4: 9.3 ng/mL; P for trend <0.001). A similar association was observed for serum docosahexaenoic acid/AA (quartile 1: 11.1 ng/mL; quartile 2: 10.6 ng/mL; quartile 3: 10.1 ng/mL; quartile 4: 9.7 ng/mL; P for trend <0.001). An adjustment for potential confounding factors did not change these associations.

CONCLUSIONS

Higher ratios of serum n-3 to n-6 PUFAs were associated with lower serum resistin levels. Consumption of a large amount of n-3 PUFAs might have desirable effects on resistin-mediated diseases.

Supplementation with eicosapentaenoic and docosahexaenoic acids in late gestation in ewes changes adipose tissue gene expression in the ewe and growth and plasma concentration of ghrelin in the offspring1

Omega-3 long chain fatty acids have a positive impact on production. When consumed during late gestation, it might have fetal programming effects on the fetus, which will have lifelong impacts on development and production. The objectives of the present study were to evaluate the effect of increasing doses of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in the diet of ewes in the last third of gestation on their body weight (BW), subcutaneous adipose tissue relative mRNA abundance of genes associated with adipose tissue metabolism, and growth performance and plasma metabolites and hormones of their offspring during the finishing phase. Ewes (n = 72) were blocked by BW and allotted to pens (8 per treatment) with 3 ewes per pen. Ewes were supplemented with an EPA and DHA source (Strata G113) at concentrations of 0, 1, or 2% of dry matter intake during the last 50 d of gestation. At lambing, all ewes were penned together and offered the same diet. After weaning at 60 d of age, lambs were blocked by BW and sex and fed for 56 d. All lambs were fed the same pellet diet (61.09% ground corn, 24.08% soy hulls, 11.09% soybean meal, 1.48% Ca salt of palm oil, and 2.26% mixed mineral vitamin), and were weighed every 14 d until the end of the trial. Blood samples were collected on the weight sampling days. Dry matter intake and refusals were weighed daily. Data were analyzed as a randomized complete block design with repeated measurements (SAS 9.4). Polynomial contrast (linear-L and quadratic-Q) was used for mean separation. There were no differences in ewe body condition score, milk production, milk fat, or milk protein, but there was a trend for increased (L, P = 0.06) lactose concentration, and also differences in DGAT1 (L, P = 0.04), Δ5-desaturase (Q, P = 0.06) and Δ6-desaturase (Q, P = 0.07), PPARα (Q, P = 0.03), ELOVL2 and 5 (Q, P < 0.07), FABP4 (Q, P = 0.04), FATP1 (Q, P = 0.06), leptin (Q, P = 0.02), and resistin (L, P = 0.05). Feeding pregnant ewes an increased amount of EPA and DHA in late gestation increased final BW (L, P = 0.01), ADG (L, P = 0.04; Q, P = 0.01), DMI (Q, P ≤ 0.01), plasma glucose concentration (L, P = 0.04), and trended to decrease ghrelin concentrations (L, P = 0.07) in offspring during the finishing period. Dam supplementation did not affect G:F, nor plasma NEFA concentration (P ≥ 0.53) of lambs. Therefore, increasing supplementation of EPA and DHA in pregnant ewes has an impact on offspring performance, increasing DMI, ADG, and BW.

The Acute Effect of Oleic- or Linoleic Acid-Containing Meals on Appetite and Metabolic Markers; A Pilot Study in Overweight or Obese Individuals

Despite the abundance of plant-derived fats in our diet, their effects on appetite, and metabolic markers, remain unclear. This single-blinded 3-way cross-over pilot study aimed to investigate the ability of the two most abundant dietary plant-derived fats, oleic (OA) and linoleic (LA) acids, to modulate postprandial appetite and levels of circulating appetite and metabolic regulators in overweight/obese individuals. Meals were a high-carbohydrate control, a high-OA or a high-LA meal, and provided 30% of participants' estimated energy requirements. Meals were consumed after an overnight fast, with blood samples collected over 3¼ h. Appetite parameters were assessed via a validated visual analogue scale questionnaire. Hormones and other circulating factors were quantified using multiplex immunoassays. Eight participants (age 45.8 ± 3.6 (years), body mass index 32.0 ± 1.3 (kg/m²)) completed the study. All meals significantly increased fullness and reduced desire to eat. The control and high-OA meals significantly decreased prospective food intake. The high-LA meal increased ghrelin levels (p < 0.05), a hormone which encourages food intake. This was coupled with a significant acute increase in resistin levels, which impairs insulin signaling. Taken together, this study indicates that in overweight/obese individuals, high-LA meals may promote excess energy intake and alter glucose handling, though a larger cohort may be required to strengthen results.

An inverse association between serum resistin levels and n-3 polyunsaturated fatty acids intake was strongest in the SNP-420 G/G genotype in the Japanese cohort: The Toon Genome Study

OBJECTIVE

Resistin is secreted by monocytes/macrophages and is associated with insulin resistance, inflammation and cardiovascular diseases. In the Japanese cohort, serum resistin is tightly associated with a single-nucleotide polymorphism (SNP) at -420 (rs1862513) in the promoter region of the human resistin gene. However, interactions between SNP-420 and environmental factors remain to be elucidated. The aim of this study was to investigate the association between serum resistin levels and nutrient intake, and the effect of SNP-420 on this association.

DESIGN, PARTICIPANTS AND MEASUREMENTS

The Toon Genome Study is a cohort study of Japanese community-dwelling subjects. A total of 1981 participants were cross-sectionally analysed. Each nutrient intake was assessed using the semiquantitative food frequency questionnaire and categorized into the quartiles (Q1-Q4). Serum resistin was measured by ELISA.

RESULTS

Serum resistin tended to be inversely associated with fish intake and positively associated with meat intake after adjustment for age, sex, BMI and energy intake. Serum resistin was inversely associated with n-3 polyunsaturated fatty acids (PUFA) intake after adjustment for age, sex, BMI and energy intake (Q1 12.5, Q2 12.5, Q3 12.2, Q4 11.5 ng/mL; P for trend = .007). This inverse association was strongest in the G/G genotype of SNP-420, followed by C/G and C/C (G/G, Q1 18.9, Q2 19.5, Q3 18.4, Q4 14.5 ng/mL, P = .001; C/G, 14.4, 13.3, 13.1, 12.9, P = .015; C/C, 9.5, 9.5, 9.2, 8.8, P = .020; P for interaction = .004).

CONCLUSIONS

The inverse association between serum resistin and n-3 PUFA intake was strongest in SNP-420 G/G genotype in the Japanese cohort.

Fish oil supplementation inhibits endoplasmic reticulum stress and improves insulin resistance: involvement of AMP-activated protein kinase

The beneficial effects of fish oil consumption on glucose metabolism have been generally reported. However, the mechanism underlying the fish oil-induced protective effects against insulin resistance remains unclear. Endoplasmic reticulum (ER) stress is recognized as an important contributor to insulin resistance. The aim of this study is to evaluate whether fish oil supplementation reduces ER stress and ameliorates insulin resistance in diet-induced obese mice, and to investigate the molecular mechanism of fish oil-induced benefits on ER stress. C57BL/6J mice were fed one of the following diets for 12 weeks: the low-fat diet (LFD), the high-fat diet (HFD) or the fish oil-supplemented high-fat diet (FOD). Fish oil supplementation led to lower blood glucose, better glucose tolerance and improved insulin sensitivity in high-fat diet-induced obese mice. Importantly, fish oil administration inhibited high-fat feeding-induced ER stress and reduced adipose tissue dysfunction. The fish oil-induced improvements were accompanied by the elevation of phosphorylated AMP-activated protein kinase (AMPK) expression in white adipose tissue. Correspondingly, the results of in vitro experiments showed that docosahexaenoic acid (DHA), the main n-3 polyunsaturated fatty acid (PUFA) in the fish oil used in the study, led to a dose-dependent increase in AMPK phosphorylation and suppressed palmitic acid (PA)-triggered ER stress in differentiated 3T3-L1 adipocytes. Furthermore, AMPK inhibitor (compound C) treatment largely blocked the effects of DHA to inhibit PA-induced ER stress. Our data indicate that n-3 PUFAs suppress ER stress in adipocytes through AMPK activation, and may thereby exert protective effects against high-fat feeding-induced adipose tissue dysfunction and insulin resistance.

Beneficial Effects of n-3 Fatty Acids on Cardiometabolic and Inflammatory Markers in Type 2 Diabetes Mellitus: A Clinical Trial

OBJECTIVE

To determine the effect of supplementation with n-3 polyunsaturated fatty acids (PUFAs) on circulatory resistin and monocyte chemoattractant protein 1 (MCP-1) levels in type 2 diabetes mellitus (T2DM) patients.

SUBJECTS AND METHODS

This was a 10-week, placebo-controlled, double-blind, randomized trial of n-3 PUFAs (2,700 mg/day) versus placebo (soft gels containing 900 mg of edible paraffin). Forty-four T2DM patients were supplemented with n-3 PUFAs and another 44 patients received placebo (3 patients discontinued the trial). Serum resistin, MCP-1, and the lipid profile were measured before and after supplementation. The adiponectin-resistin index (1 + log10 [resistin] - log10 [adiponectin]) and atherogenic index (log10 triglyceride/high-density lipoprotein cholesterol) of plasma (an indicator of cardiovascular complications) were assessed. The independent Student t test was used to assess the differences between the supplement and placebo groups and the paired t test to analyze the before/after changes.

RESULTS

In this study, n-3 PUFAs reduced serum MCP-1 levels (from 260.5 to 230.5 pg/mL; p = 0.002), but they remained unchanged in the placebo group. n-3 PUFAs could not decrease serum resistin levels. The adiponectin-resistin index was significantly reduced after supplementation with n-3 PUFAs when compared to the placebo. The atherogenic index was also significantly improved after supplementation with n-3 PUFAs (from 1.459 to 1.412; p = 0.006).

CONCLUSIONS

The MCP-1 levels and lipid profile were improved after supplementation with n-3 PUFAs, but resistin serum levels were not changed. Hence, the anti-inflammatory effects of n-3 PUFAs might be mediated by targeting MCP-1.

Serum saturated fatty acid decreases plasma adiponectin and increases leptin throughout pregnancy independently of BMI

OBJECTIVE

The aim of this study was to investigate whether serum concentrations of total saturated fatty acids (SFAs), polyunsaturated fatty acids (PUFAs), and their fractions are associated with plasma adiponectin and leptin concentrations throughout pregnancy.

METHODS

A prospective cohort of 201 pregnant women was followed from gestational weeks 5 to 13, 20 to 26, and 30 to 36. Blood samples were collected at the three visits after 12 h of fasting. Fatty acid concentrations were determined using fast gas-liquid chromatography. Plasma adiponectin (μg/mL) and leptin (ng/dL) concentrations were evaluated using enzyme-linked immunosorbent assay kits. Statistical analyses included median adipokine concentrations according to the tertiles of fatty acid distribution and multiple linear mixed-effect models adjusted for body mass index, gestational age, total energy intake, alcohol consumption, and smoking.

RESULTS

Women classified in the third SFA concentration tertile had lower median values of adiponectin compared with those in the first tertile ([first trimester: first tertile = 5.36; third tertile = 5.00]; [second trimester: first tertile = 6.39; third tertile = 4.47]; [third trimester: first tertile = 6.46; third tertile = 4.60]). Similar trends were observed for the 14:0, 16:0 and 18:0 fractions. In the multiple longitudinal models, total SFA (β = -41.039; P = 0.008) and 16:0 were negatively associated with plasma adiponectin (16:0, β = -0.511; P = 0.001). Total PUFA ω-6 (β = 28.961; P = 0.002) and 18:2 ω-6 (β = 0.259, P = 0.006) were positively associated with the adiponectin. Total SFA (β = 0.110, P = 0.007), 14:0 (β = 0.072, P = 0.011), and 20:3 ω-6 (β = 0.039; P = 0.035) were positively associated with plasma leptin.

CONCLUSIONS

Total serum SFA and the 16:0 fraction were negatively associated with plasma adiponectin and positively associated with leptin concentrations. Total ω-6 PUFA was positively associated only with plasma adiponectin concentrations throughout pregnancy.

2,4,6-Trihydroxybenzaldehyde, a potential anti-obesity treatment, suppressed adipocyte differentiation in 3T3-L1 cells and fat accumulation induced by high-fat diet in C57BL/6 mice

In the present study, 2,4,6-trihydroxybenzaldehyde (THB) was evaluated for inhibitory effects on adipocyte differentiation in 3T3-L1 cells and anti-obesity effects in mice with high-fat diet (HFD)-induced obesity. Lipid accumulation measurement indicated that THB markedly inhibited adipogenesis, and this involved down-regulation of the expression of the adipogenesis-related proteins, CCAAT/enhancer-binding protein α (C/EBPα), peroxisome proliferator-activated receptor γ (PPARγ), fatty acid synthase (FAS) and sterol regulatory element-binding protein-1c (SREBP-1c), in 3T3-L1 pre-adipocyte cells. In a mouse model of HFD-induced obesity, oral administration of THB (5 and 25mg/kg for 13 weeks) reduced the HFD-induced increase in weight gain. THB administration also reduced serum levels of glucose, triglycerides, and total cholesterol. A reduction in the hypertrophy of white adipose tissue was also observed. Furthermore, THB administration inhibited HFD-induced hepatic steatosis. These results provided evidence that administration of THB alleviated HFD-induced obesity in C57BL/6 mice and revealed the potential of THB as a nutraceutical to help prevent or treat obesity and the associated metabolic disorders.

Mechanisms of enhanced insulin secretion and sensitivity with n-3 unsaturated fatty acids

The widespread acceptance that increased dietary n-3 polyunsaturated fatty acids (PUFAs), especially α-linolenic acid (ALA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), improve health is based on extensive studies in animals, isolated cells and humans. Visceral adiposity is part of the metabolic syndrome, together with insulin resistance, dyslipidemia, hypertension and inflammation. Alleviation of metabolic syndrome requires normalization of insulin release and responses. This review assesses our current knowledge of the mechanisms that allow n-3 PUFAs to improve insulin secretion and sensitivity. EPA has been more extensively studied than either ALA or DHA. The complex actions of EPA include increased G-protein-receptor-mediated release of glucagon-like peptide 1 (GLP-1) from enteroendocrine L-cells in the intestine, up-regulation of the apelin pathway and down-regulation of other control pathways to promote insulin secretion by the pancreatic β-cells, together with suppression of inflammatory responses to adipokines, inhibition of peroxisome proliferator-activated receptor α actions and prevention of decreased insulin-like growth factor-1 secretion to improve peripheral insulin responses. The receptors involved and the mechanisms of action probably differ for ALA and DHA, with antiobesity effects predominating for ALA and anti-inflammatory effects for DHA. Modifying both GLP-1 release and the actions of adipokines by n-3 PUFAs could lead to additive improvements in both insulin secretion and sensitivity.

Omega-3 polyunsaturated fatty acids increase plasma adiponectin to leptin ratio in stable coronary artery disease

BACKGROUND

Growing evidence suggests a cardioprotective role of omega-3 polyunsaturated fatty acids (PUFA). However, the exact mechanisms underlying the effects of omega-3 PUFA in humans have not yet been fully clarified.

PURPOSE

We sought to evaluate omega-3 PUFA-mediated effects on adipokines in patients with stable coronary artery disease (CAD) undergoing elective percutaneous coronary intervention (PCI).

METHODS

We conducted a prospective, double-blind, placebo-controlled, randomized study, in which adiponectin, leptin and resistin were determined at baseline, 3-5 days and 30 days during administration of omega-3 PUFA 1 g/day (n=20) or placebo (n=28).

RESULTS

As compared to controls administration of omega-3 PUFA resulted in increase of adiponectin by 13.4% (P<0.0001), reduction of leptin by 22% (P<0.0001) and increase of adiponectin to leptin (A/L) ratio by 45.5% (P<0.0001) at 30 days, but not at 3-5 days. Compared with placebo adiponectin was 12.7% higher (P=0.0042), leptin was 16.7% lower (P<0.0001) and A/L ratio was 33.3% higher (P<0.0001) in the omega-3 PUFA group at 30 days. Resistin decreased similarly in both groups after 1 month, without intergroup differences (P=0.32). The multivariate model showed that the independent predictors of changes in adiponectin at 1 month (P<0.001) were: omega-3 PUFA treatment, baseline platelet count, total cholesterol and those in leptin (P<0.0001) were: omega-3 PUFA treatment and waist circumference. Independent predictors of A/L ratio changes (P<0.0001) were: assigned treatment, current smoking and hyperlipidemia.

CONCLUSIONS

In high risk stable coronary patients after PCI omega-3 PUFA supplementation improves adipokine profile in circulating blood. This might be a novel, favourable mechanism of omega-3 PUFA action.

Effect of yellow capsicum extract on proliferation and differentiation of 3T3-L1 preadipocytes

OBJECTIVES

To evaluate the effect of effect of Yellow Capsicum extract (YCE) that is rich in capsaicin on the proliferation and differentiation of 3T3-L1 preadipocytes in vitro.

METHODS

3T3 L1 cells that were exposed to differentiation-inducing medium containing high glucose DMEM (Dulbecco's Modified Eagle's Medium) and subsequently were treated with capsaicin and YCE for their effect on adipocyte differentiation, changes in their triglyceride content, leptin secretion, expression of lipoprotein lipase, PPARγ, and CCAAT/enhancer-binding protein alpha (C/EBPα).

RESULTS

Both YCE and capsaicin inhibited proliferation and differentiation 3T3-L1 preadipocytes and suppressed accumulation of intracellular triglyceride in a dose-dependent manner. In addition, a significant decrease in the expression of lipoprotein lipase (LPL), leptin, PPARγ, and C/EBPα was noted in 3T3-L1 preadipocytes when induced to differentiate by YCE and Capsaicin.

CONCLUSIONS

The potent inhibitory action of YCE and Capsaicin on the differentiation of 3T3-L1 preadipocyte observed suggests that they (YCE and Capsaicin) have the potential to inhibit obesity that needs to be explored in future studies.

The mechanisms linking adiposopathy to type 2 diabetes

Obesity is defined as excessive accumulation of body fat in proportion to body size. When obesity occurs, the functions of adipose tissue may be deregulated, which is termed as adiposopathy. Adiposopathy is an independent risk factor for many diseases, including diabetes and cardiovascular diseases. In overweight or obese subjects with adiposopathy, hyperlipidemia exerts lipotoxicity in pancreatic islet and liver and induces pancreatic β cell dysfunction and liver insulin resistance, which are the decisive factors causing type 2 diabetes. Moreover, adipokines have been shown to play important roles in the regulation of glucose homeostasis. When adiposopathy occurs, abnormal changes in the serum adipokine profile correlate with the development and progression of pancreatic β cell dysfunction and insulin resistance in peripheral tissue. The current paper briefly discusses the latest findings regarding the effects of adiposopathy-related lipotoxicity and cytokine toxicity on the development of type 2 diabetes.

Activation of Liver X receptors in the heart leads to accumulation of intracellular lipids and attenuation of ischemia-reperfusion injury

Liver X receptor (LXR)-α and -β play a major role in lipid and glucose homeostasis. Their expression and function in the heart is not well characterized. Our aim was to describe the expression of LXRs in the murine heart, and to determine effects of cardiac LXR activation on target gene expression, lipid homeostasis and ischemia. Both LXRα and -β were expressed in heart tissues, HL-1 cells and isolated cardiomyocytes as determined by qRT-PCR. Elevated cardiac expression of LXR target genes and LXRβ was observed 24 h after in vivo permanent coronary artery ligation. The synthetic LXR agonist GW3965 induced mRNA expression of the LXR target genes in HL-1 cells and isolated cardiomyocytes. This was associated with a buildup of intracellular triglycerides and expanding lipid droplets as quantified by confocal microscopy. Mice injected with GW3965 had cardiac LXR activation as judged by increased target gene expression and lipid droplet accumulation. GW3965 in vivo and in vitro increased expression of genes inducing triglyceride synthesis, and altered expression of lipid droplet-binding protein genes. GW3965 protected HL-1 cells against hypoxia-reoxygenation induced apoptosis. LXR activation by GW3965 in vivo prior to heart isolation and perfusion with induced global ischemia and reperfusion improved left ventricular contractile function and decreased infarct size. In conclusion, LXRs are expressed in the murine heart in the basal state, and are activated by myocardial infarction. Activation of LXR by the synthetic agonist GW3965 is associated with intracardiac accumulation of lipid droplets and protection against myocardial ischemia-reperfusion injury.

Molecular nutrition research: the modern way of performing nutritional science

In spite of amazing progress in food supply and nutritional science, and a striking increase in life expectancy of approximately 2.5 months per year in many countries during the previous 150 years, modern nutritional research has a great potential of still contributing to improved health for future generations, granted that the revolutions in molecular and systems technologies are applied to nutritional questions. Descriptive and mechanistic studies using state of the art epidemiology, food intake registration, genomics with single nucleotide polymorphisms (SNPs) and epigenomics, transcriptomics, proteomics, metabolomics, advanced biostatistics, imaging, calorimetry, cell biology, challenge tests (meals, exercise, etc.), and integration of all data by systems biology, will provide insight on a much higher level than today in a field we may name molecular nutrition research. To take advantage of all the new technologies scientists should develop international collaboration and gather data in large open access databases like the suggested Nutritional Phenotype database (dbNP). This collaboration will promote standardization of procedures (SOP), and provide a possibility to use collected data in future research projects. The ultimate goals of future nutritional research are to understand the detailed mechanisms of action for how nutrients/foods interact with the body and thereby enhance health and treat diet-related diseases.

Enamel matrix derivative stimulates expression and secretion of resistin in mesenchymal cells

In this study we wanted to identify the effect of enamel matrix derivative (EMD) on adipocytokines, so-called adipokines. Primary human cells of mesenchymal origin (osteoblasts, periodontal ligament cells, mesenchymal stem cells, and pulp cells) and hematopoietic origin (monocytes) were incubated with EMD. The levels of adipokines in cell culture medium were quantified using the Lincoplex human adipocyte panel (Luminex) and by real-time PCR of mRNA isolated from cell lysates. Rats were injected with 2 mg of EMD or saline intramuscularly every third day for 14 d. Blood samples were taken before and after injections, and the level of resistin in rat plasma was measured by ELISA. We found a dramatic increase in the secretion of resistin from mesenchymal stem cells, and verified this result in all the cells of mesenchymal origin tested. However, we observed no significant changes in the amount of resistin secreted from monocytes exposed to EMD compared with the control. Injections of EMD significantly enhanced the circulating levels of resistin in rats, and EMD also significantly enhanced the activity of the resistin promoter in transfected mesenchymal stem cells, indicating a direct effect on resistin expression. Our results indicate that resistin may play a role in mediating the biological effect of EMD in mesenchymal tissues.

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.

Arachidonic acid induces acetyl-CoA carboxylase 1 expression via activation of CREB1

Acetyl-CoA carboxylase (ACC; EC 6.4.1.2) is the major enzyme of fatty acid synthesis and oxidation in response to dietary changes. In animals, there are two major isoforms of ACCs, ACC1 and ACC2, which are encoded by different genes and display distinct tissue and cellular distribution. We examined the effect of high concentration of arachidonic acid (AA) on the expression of ACC1 mRNA in HepG2 hepatoma cells cultured in the absence of insulin. After 12 h of treatment, AA was found to significantly up-regulate ACC1 mRNA level as well as that of cAMP regulatory element binding protein 1 (CREB1), implying the possible interactions between ACC1 and CREB1. In support of the hypothesis, several potential CREB1 binding sites were identified within the PII promoter of ACC1. Further experiments demonstrated that transient over-expression of CREB1 in HepG2 cells activates ACC1 PII promoter and induces the production of triacylglycerol in response to AA, indicating that the effect of AA on ACC1 is possibly regulated via CREB1.

Nutrigenomics, beta-cell function and type 2 diabetes

INTRODUCTION

The present investigation was designed to investigate the accuracy and precision of lactate measurement obtained with contemporary biosensors (Chiron Diagnostics, Nova Biomedical) and standard enzymatic photometric procedures (Sigma Diagnostics, Abbott Laboratories, Analyticon).

MATERIALS AND METHODS

Measurements were performed in vitro before and after the stepwise addition of 1 molar sodium lactate solution to samples of fresh frozen plasma to systematically achieve lactate concentrations of up to 20 mmol/l.

RESULTS

Precision of the methods investigated varied between 1% and 7%, accuracy ranged between 2% and -33% with the variability being lowest in the Sigma photometric procedure (6%) and more than 13% in both biosensor methods.

CONCLUSION

Biosensors for lactate measurement provide adequate accuracy in mean with the limitation of highly variable results. A true lactate value of 6 mmol/l was found to be presented between 4.4 and 7.6 mmol/l or even with higher difference. Biosensors and standard enzymatic photometric procedures are only limited comparable because the differences between paired determinations presented to be several mmol. The advantage of biosensors is the complete lack of preanalytical sample preparation which appeared to be the major limitation of standard photometry methods.

The role of dietary fat in adipose tissue metabolism

Energy intake and expenditure tend on average to remain adjusted to each other in order to maintain a stable body weight, which is only likely to be sustained if the fuel mix oxidised is equivalent to the nutrient content of the diet. Whereas protein and carbohydrate degradation and oxidation are closely adjusted to their intakes, fat balance regulation is less precise and that fat is more likely to be stored than oxidised. It has been demonstrated that dietary fatty acids have an influence not only on the fatty acid composition of membrane phospholipids, thus modulating several metabolic processes that take place in the adipocyte, but also on the composition and the quantity of different fatty acids in adipose tissue. Moreover, dietary fatty acids also modulate eicosanoid presence, which have hormone-like activities in lipid metabolism regulation in adipose tissue. Until recently, the adipocyte has been considered to be no more than a passive tissue for storage of excess energy. However, there is now compelling evidence that adipocytes have a role as endocrine secretory cells. Some of the adipokines produced by adipose tissue, such as leptin and adiponectin, act on adipose tissue in an autocrine/paracrine manner to regulate adipocyte metabolism. Furthermore, dietary fatty acids may influence the expression of adipokines. The nutrients are among the most influential of the environmental factors that determine the way adipose tissue genes are expressed by functioning as regulators of gene transcription. Therefore, not only dietary fat amount but also dietary fat composition influence adipose tissue metabolism.

Dietary conjugated linoleic acid decreases adipocyte size and favorably modifies adipokine status and insulin sensitivity in obese, insulin-resistant rats

Conjugated linoleic acids (CLA) have been shown to alter adiposity in some species with varying effects on insulin resistance. The objective of this 8-week study was to investigate the effects of feeding a CLA mixture (1.5%, wt/wt) on adipocyte size, insulin sensitivity, adipokine status, and adipose lipid composition in fa/fa vs lean Zucker rats. The fa/fa CLA-fed rats had smaller adipocytes and improved insulin sensitivity compared with fa/fa rats fed the control diet. Conjugated linoleic acids did not affect select markers of adipose differentiation, lipid filling, lipid uptake, or oxidation. Dietary CLA, compared with the control diet, reduced circulating leptin and elevated fasting serum adiponectin concentrations in fa/fa rats. Adipose resistin messenger RNA levels were greater in fa/fa CLA-fed rats compared with fa/fa control rats. CLA did not markedly alter adipose phospholipid fatty acid composition, and the changes in the triacylglycerol fatty acid composition reflected a lower delta-9 desaturase index of CLA-fed vs control-fed rats. In conclusion, CLA reduced adipocyte size and favorably modified adipokine status and insulin sensitivity in fa/fa Zucker rats.

Dietary combination of fucoxanthin and fish oil attenuates the weight gain of white adipose tissue and decreases blood glucose in obese/diabetic KK-Ay mice

Fucoxanthin is a marine carotenoid found in edible brown seaweeds. We previously reported that dietary fucoxanthin attenuates the weight gain of white adipose tissue (WAT) of diabetic/obese KK- A(y) mice. In this study, to evaluate the antiobesity and antidiabetic effects of fucoxanthin and fish oil, we investigated the effect on the WAT weight, blood glucose, and insulin levels of KK- A(y) mice. Furthermore, the expression level of uncoupling protein 1 (UCP1) and adipokine mRNA in WAT were measured. After 4 weeks of feeding, 0.2% fucoxanthin in the diet markedly attenuated the gain of WAT weight in KK- A(y) mice with increasing UCP1 expression compared with the control mice. The WAT weight of the mice fed 0.1% fucoxanthin and 6.9% fish oil was also significantly lower than that of the mice fed fucoxanthin alone. In addition, 0.2% fucoxanthin markedly decreased the blood glucose and plasma insulin concentrations in KK- A(y) mice. The mice fed with the combination diet of 0.1% fucoxanthin and fish oil also showed improvements similar to that of 0.2% fucoxanthin. Leptin and tumor necrosis factor (TNFalpha) mRNA expression in WAT were significantly down-regulated by 0.2% fucoxanthin. These results suggest that dietary fucoxanthin decreases the blood glucose and plasma insulin concentration of KK- A(y) along with down-regulating TNFalpha mRNA. In addition, the combination of fucoxanthin and fish oil is more effective for attenuating the weight gain of WAT than feeding with fucoxanthin alone.

The interplay between nutrients and the adipose tissue

The importance of adipose tissue in health as well as disease has been demonstrated in several studies recently, and it has become appropriate to use the term 'adipose organ' when referring to adipose tissue as a whole. The obesity epidemic, with a marked increase in the incidence of the metabolic syndrome leading to diabetes type 2 as well as cardiovascular complications, has stimulated considerable interest in adipose tissue biology. Moreover, several studies in different species have shown that limited energy intake is associated with less inflammation, improved biomarkers of health and a marked increase in longevity. In addition, there is convincing evidence that an optimal amount of adipose tissue is essential for many body functions such as immune response, reproduction and bone quality. Some nutrients and their metabolites are important as energy sources as well as ligands for many transcription factors expressed in adipose tissue, including all energy-providing nutrients both directly and indirectly as well as cholesterol, vitamin E and vitamin D. In particular, fatty acids can be effectively taken up by adipocytes and they can interact with several transcription factors crucial for growth, development and metabolic response, e.g. PPARalpha, -delta and -gamma, sterol regulatory element-binding proteins1 and 2 and liver X receptors alpha and beta). Moreover, glucose is also readily taken up and stored as fatty acids via lipogenesis in adipocytes. It is known that some metabolic signals released as proteins from adipose tissue (adipokines) are important for normal as well as pathological responses to the amount of energy stored in the adipose organ. The future challenge will be to understand the function of adipose tissue in energy homeostasis and the interplay with nutrients in order to be able to give optimal advice for the prevention and treatment of obesity.

Arachidonic Acid Can Significantly Prevent Early Insulin Resistance Induced by a High-Fat Diet

AIM

To investigate whole-body metabolic disorder and hepatic glucose output (HGO) disturbance in rats with insulin resistance induced by a short-term high-fat diet, and the effect of arachidonic acid (AA).

METHODS

Twenty-four normal male Wistar rats (230-250 g) were randomly divided into 3 groups according to their weight and fed for 12 weeks: control group, n = 8, fed with standard chow diet; high-fat (HF) group, n = 8, fed with a high-fat diet; HF+AA group, n = 8, fed with a high-fat diet and administered orally 3 mg x kg(-1) x day(-1)AA.

RESULTS

Early insulin resistance was successfully induced in HF-fed rats with hyperinsulinemia (p < 0.05), higher plasma triglyceride (TG) (p < 0.05), higher fasting liver glycogen content (p < 0.01) and higher glucose-insulin index (p < 0.01) during an oral glucose tolerance test (OGTT). The AA treatment significantly decreased the glucose-insulin index (p < 0.01), blood TG (p < 0.05) and glycogen content (p < 0.05) in liver. Both activity of phosphoenolpyruvate carboxykinase (PEPCK) (p < 0.05) and mRNA levels of PEPCK (p < 0.05) and glucose-6-phosphatase (G-6-Pase) (p < 0.01) in liver were also observed to be significantly decreased. But there were significant differences in the glucose-insulin index (p < 0.01) during OGTT, and glycogen content (p < 0.01) between the HF+AA and control groups.

CONCLUSION

AA can significantly prevent whole-body insulin resistance induced by a high-fat diet, as well as accompanied HGO disturbance in the overnight fasting state, but not thoroughly.

Usefulness of the 5′ region of the cDNA encoding acidic ribosomal phosphoprotein P0 conserved among rats, mice, and humans as a standard probe for gene expression analysis in different tissues and animal species

Housekeeping genes are often used as internal standards for gene expression analysis. When steady-state transcript levels of 4 typically used housekeeping genes, i.e., beta-actin, glyceraldehyde 3-phosphate dehydrogenase, cyclophilin, and acidic ribosomal phosphoprotein P0 (36B4), were evaluated in various rat tissues, the 36B4 gene seemed to be the most suitable as a standard to compare the expression levels of genes among different tissues. Next, for possible quantitative comparison of the expression level of this gene among different animal species, we compared the nucleotide sequence of the cDNA of 36B4 among rats, mice, and humans. As a result, highly conserved regions showing more than 97.5% identities were observed in the 5' portion of its open reading frame. When samples of synthesized mRNA encoding rat, mouse, and human 36B4 were hybridized with the entire cDNA encoding rat 36B4 as a probe, hybridization signals of mRNAs of mouse and human 36B4 were much weaker than those of mRNA encoding rat 36B4. However, when they were hybridized with an oligonucleotide probe corresponding to the highly conserved regions, they showed similar signal intensities. Thus, these highly conserved regions of the cDNA encoding 36B4 were concluded to be an effective standard for use in gene expression analysis.

Systemic Inflammation in Morbidly Obese Subjects: Response to Oral Supplementation with Alpha-Linolenic Acid

BACKGROUND

Morbidly obese patients frequently display asymptomatic chronic activation of acute phase response, with potentially adverse metabolic and cardiovascular consequences. Nutritional preparations to improve this phenomenon have rarely been administered. Aiming to investigate the supplementation of flaxseed flour, a source of omega-3 fatty acids, a prospective randomized double-blind cross-over study was designed.

METHODS

Outpatient obese subjects (n=41) were clinically and biochemically screened, and results for 24 randomized subjects are shown. Age was 40.8 +/- 11.6 years (83.3% females) and body mass index (BMI) was 47.1 +/- 7.2 kg/m2. Flaxseed flour (Farinha de Linhaca Dourada LinoLive, Cisbra, Brazil) in the amount of 30 g/day (5 g of alpha-linolenic acid - omega-3) and an equal mass of placebo (manioc flour) were administered for 2 weeks each. Variables included general biochemical investigation, white blood cell count (WBC), C-reactive protein (CRP), serum amyloid A (SAA) and fibronectin.

RESULTS

No intolerance was registered. Body weight and general biochemical indices remained stable. Initial CRP and SAA were elevated (13.7 +/- 9.9 and 17.4 +/- 8.0 ). WBC (8100 +/- 2100/mm3) and fibronectin (463.2 +/- 61.3 mg/dL) were acceptable but in the upper normal range. Corresponding findings after supplementation of flaxseed were 10.6 +/- 6.2 mg/L, 14.3 +/- 9.2 mg/L, 7300 +/- 1800/mm3 and 412.8 +/- 38.6 respectively (P<0.05). No change during the control period regarding baseline occurred when placebo was randomized to be given first; however, when it followed omega-3 supplementation, CRP and SAA recovered, whereas WBC and fibronection remained depressed during those 2 weeks (7500 +/- 2100/mm3 and 393.2 +/- 75.8 mg/dL, P<0.05).

CONCLUSIONS

1) Various inflammatory markers were elevated in the studied population, although not necessarily exceeding the normal range; 2) Significant reduction could be demonstrated; 3) Some persistent effects of flaxseed supplement 2 weeks after discontinuation were observed.

POLYUNSATURATED FATTY ACID REGULATION OF GENES OF LIPID METABOLISM

Apart from being an important macronutrient, dietary fat has recently gained much prominence for its role in regulating gene expression. Polyunsaturated fatty acids (PUFAs) affect gene expression through various mechanisms including, but not limited to, changes in membrane composition, intracellular calcium levels, and eicosanoid production. Furthermore, PUFAs and their various metabolites can act at the level of the nucleus, in conjunction with nuclear receptors and transcription factors, to affect the transcription of a variety of genes. Several of these transcription mediators have been identified and include the nuclear receptors peroxisome proliferator-activated receptor (PPAR), hepatocyte nuclear factor (HNF)-4alpha, and liver X receptor (LXR) and the transcription factors sterol-regulatory element binding protein (SREBP) and nuclear factor-kappaB (NFkappaB). Their interaction with PUFAs has been shown to be critical to the regulation of several key genes of lipid metabolism. Working out the mechanisms by which these interactions and consequent effects occur is proving to be complicated but is invaluable to our understanding of the role that dietary fat can play in disease management and prevention.

Fatty acids and expression of adipokines

Adipose tissue has been recognised as the quantitatively most important energy store of the human body for many years, in addition to its functions as mechanical and thermic insulator. In mammals, the adipose organ is localised in several depots including white as well as brown adipose tissues. The largest depots are found subcutaneously and in the abdominal region. Several secretory proteins are synthesised in adipose tissue including leptin, resistin, adiponectin, tumor necrosis factor (TNFalpha), angiotensinogen, adipsin, acylation-stimulating protein, retinol-binding protein (RBP), interleukin (IL)-1b, IL-6, IL-8, IL-10, plasminogen activator inhibitor-1 (PAI-1), fasting-induced adipose factor, fibrinogen-angiopoietin-related protein, metallothionein, tissue factor (TF), complement C3, fibronectin, haptoglobin, entactin/nidogen, collagen VI alpha 3, pigment epithelium-derived factor (PEDF), hippocampal cholinergic neurostimulating peptide (HCNP), neutrophil gelatinase-associated lipocalin (NGAL) and adiponutrin. Fatty acids may influence the expression of adipokines like leptin, resistin or adiponectin directly by interaction with transcription factors, or indirectly via unknown mechanisms possibly linked to fatty acid oxidation, synthesis or storage. Because fatty acids are the main components of adipose tissue, it is of essential interest to clarify the biological effects of different types of fatty acids on the expression of relevant adipokines.

Regulation of adipocyte differentiation and function by polyunsaturated fatty acids

A diet enriched in PUFAs, in particular of the n-3 family, decreases adipose tissue mass and suppresses development of obesity in rodents. Although several nuclear hormone receptors are identified as PUFA targets, the precise molecular mechanisms underlying the effects of PUFAs still remain to be elucidated. Here we review research aimed at elucidating molecular mechanisms governing the effects of PUFAs on the differentiation and function of white fat cells. This review focuses on dietary PUFAs as signaling molecules, with special emphasis on agonistic and antagonistic effects on transcription factors currently implicated as key players in adipocyte differentiation and function, including peroxisome proliferator activated receptors (PPARs) (alpha, beta and gamma), sterol regulatory element binding proteins (SREBPs) and liver X receptors (LXRs). We review evidence that dietary n-3 PUFAs decrease adipose tissue mass and suppress the development of obesity in rodents by targeting a set of key regulatory transcription factors involved in both adipogensis and lipid homeostasis in mature adipocytes. The same set of factors are targeted by PUFAs of the n-6 family, but the cellular/physiological responses are dependent on the experimental setting as n-6 PUFAs may exert either an anti- or a proadipogenic effect. Feeding status and hormonal background may therefore be of particular importance in determining the physiological effects of PUFAs of the n-6 family.