DHA regulates lipogenesis and lipolysis genes in mice adipose and liver

Docosahexaenoic acid (DHA) inhibits abdominal fat accumulation by promoting adipocyte apoptosis through PPARγ-LC3-BNIP3 pathway-mediated mitophagy

Obesity has always been an overwhelming health concern worldwide. Docosahexaenoic acid (DHA) reduces abdominal fat accumulation by inducing adipocyte apoptosis, but the underlying mechanism remains unclear. Mitophagy, the process of maintaining mitochondrial homeostasis, has a double-edged sword effect that positively or negatively regulates apoptosis. In this study, grass carp (Ctenopharyngodon idellus) was used as an animal model to investigate the role of mitophagy in regulating apoptosis and the potential molecular mechanisms for DHA-induced mitophagy in vivo and in vitro. Firstly, we found that DHA induced the intrinsic apoptosis in grass carp adipocytes, accompanying by activating BNIP3/NIX-mediated mitophagy. Then, suppression of mitophagy alleviated apoptosis and eliminated the inhibition of lipid accumulation induced by DHA in vivo and in vitro. Mechanistically, the DHA-induced mitophagy was caused by activating PPARγ and its DNA binding capacity to the LC3 promoter, which promoted the interaction of BNIP3 (rather than NIX) with LC3. However, the inhibition of PPARγ in vitro significantly decreased the expression of autophagy-related genes (P < 0.05), reducing the colocalization of mitochondria and lysosomes while preventing BNIP3/NIX-mediated mitophagy-mediated apoptosis and subsequently alleviating the inhibition of lipid accumulation in adipocytes induced by DHA. For the first time, we demonstrated that DHA activates mitophagy by regulating the PPARγ-LC3-BNIP3 pathway, consequently inducing apoptosis, which decreases adipocytes, inhibiting lipid accumulation in grass carp. These findings provide new insight into the mechanism of DHA-induced apoptosis mediated by mitophagy as the potential therapeutic target of inhibiting abdominal fat accumulation in vertebrates.

DHA induces adipocyte lipolysis through endoplasmic reticulum stress and the cAMP/PKA signaling pathway in grass carp (Ctenopharyngodon idella)

Docosahexaenoic acid (DHA) is a biologically active fatty acid that reduces the accumulation of lipids. However, the molecular mechanism underlying this process, particularly in fish, is not well understood. Recent studies show that endoplasmic reticulum (ER) stress triggers the activation of the unfolded protein response, which has been revealed to play an essential role in lipid metabolism. In this study, we explored the effect of DHA on ER stress and investigated the potential molecular mechanisms underlying DHA-induced adipocyte lipolysis in grass carp (Ctenopharyngodon idella) both in vivo and in vitro. We found that DHA remarkably reduced the triglyceride content, increased the secretion of glycerol, promoted lipolysis in adipocytes and evoked ER stress, whereas inhibiting ER stress using 4-phenyl butyric acid (4-PBA) inhibited the effects of DHA (P < 0.05). These results implied that ER stress potentially participates in DHA-induced adipocyte lipolysis. Additionally, STF-083010, a specific inositol-requiring enzyme 1α (IRE1α)-inhibitor, attenuated the effects of DHA on lipolysis, demonstrating that IRE1α and X-box binding protein 1 potentially participate in DHA-induced lipolysis. DHA also activated the cyclic adenosine monophosphate (cAMP)-dependent protein kinase A (PKA) pathway by increasing the level of cAMP and activating the PKA enzyme (P < 0.05). Nevertheless, H89, a PKA inhibitor, weakened DHA-induced lipolysis by inhibiting the cAMP/PKA signaling pathway. Furthermore, inhibiting ER stress using 4-PBA also inhibited lipolysis and alleviated DHA-induced activation of the cAMP/PKA signaling pathway, suggesting that ER stress may participate in DHA-induced lipolysis through the activation of the cAMP/PKA signaling pathway. Our data illustrate that DHA supplementation can be a promising nutritional strategy for ameliorating lipid accumulation in grass carp. The present study elucidated the molecular mechanism for DHA-induced lipolysis in grass carp adipocytes and emphasized the importance of ER stress and the cAMP/PKA pathway in DHA-induced lipolysis. These results deepen our understanding of ameliorating lipids deposition in freshwater fish by targeting DHA.

Differential effects of omega-3 PUFAS on tumor progression at early and advanced stages in TRAMP mice

BACKGROUND

In vitro studies evidenced antitumor effects of omega-3 polyunsaturated fatty acids ([n-3] PUFAs), but their effects on prostate cancer (PCa) remain controversial in epidemiological studies. Here we investigated whether an (n-3) PUFA-enriched diet affects tumor progression in transgenic adenocarcinoma of the mouse prostate (TRAMP), at early (12 weeks age) and advanced stages (20 weeks age).

METHODS

TRAMP mice were fed with standard rodent diet (C12, C20) or (n-3) PUFA-enriched diet containing 10% fish oil (T12, T20). A group of 8 weeks age animals fed standard diet was also used for comparison (C8). The ventral prostate was processed for histopathological and immunohistochemical analyses and serum samples submitted to biochemical assays.

RESULTS

At early stages, (n-3) PUFA increased the frequency of normal epithelium (3.8-fold) and decreased the frequency of high-grade intraepithelial neoplasia (3.3-fold) and in situ carcinoma (1.9-fold) in the gland, maintaining prostate pathological status similar to C8 group. At advanced stages, 50% of the animals developed a large primary tumor in both C20 and T20, and tumor weight did not differ (C20: 2.2 ± 2.4; T20: 2.8 ± 2.9 g). The ventral prostate of T12 and of T20 animals that did not develop primary tumors showed lower cell proliferation, tissue expressions of androgen (AR) and glucocorticoid (GR) receptors, than their respective controls. For these animals, (n-3) PUFA also avoided an increase in the number of T-lymphocytes, collagen fibers, and αSMA immunoreactivity, and preserved stromal gland microenvironment. (n-3) PUFA also lowered serum triglycerides and cholesterol, regulating the lipid metabolism of TRAMP mice.

CONCLUSIONS

(n-3) PUFAs had a protective effect at early stages of PCa, delaying tumor progression in TRAMP mice, in parallel with reductions in cell proliferation, AR, and GR and maintenance of the stromal compartment of the gland. However, (n-3) PUFAs did not prevent the development of primary tumors for the T20 group, reinforcing the need for further investigation at advanced stages of disease.

The Potential of the Marine Microalga Diacronema lutheri in the Prevention of Obesity and Metabolic Syndrome in High-Fat-Fed Wistar Rats

Long-chain polyunsaturated fatty acids n-3 series (n-3 LC-PUFAs), especially eicosapentaenoic and docosahexaenoic acids, are known to exert preventive effects on obesity and metabolic syndrome. Mainly consumed in the form of fish oil, LC-PUFAs n-3 are also found in significant quantities in other sources such as certain microalgae. The aim of this study was to evaluate the effects of Diacronema lutheri (Dia), a microalga rich in n-3 LC-PUFAs, on metabolic disorders associated with obesity. Three groups of male Wistar rats (n = 6 per group) were submitted for eight weeks to a standard diet or high-fat and high-fructose diet (HF), supplemented or not with 12% of Dia (HF-Dia). Compared to HF rats, HF-Dia rats showed a 41% decrease in plasma triacylglycerol (TAG) and an increase in plasma cholesterol (+35%) as well as in high-density lipoprotein cholesterol (+51%) without change to low-density lipoprotein cholesterol levels. Although fasting glycemia did not change, glucose and insulin tolerance tests highlighted an improvement in glucose and insulin homeostasis. Dia supplementation restored body weight and fat mass, and decreased levels of liver TAG (−75%) and cholesterol (−84%). In HF-Dia rats, leptin was decreased (−30%) below the control level corresponding to a reduction of 68% compared to HF rats. Similarly, the anti-inflammatory cytokines interleukin-4 (IL-4) and IL-10 were restored up to control levels, corresponding to a 74% and 58% increase in HF rats, respectively. In contrast, the level of IL-6 remained similar in the HF and HF-Dia groups and about twice that of the control. In conclusion, these results indicated that the D. lutheri microalga may be beneficial for the prevention of weight gain and improvement in lipid and glucose homeostasis.

Hypothalamic Overexpression of Neurosecretory Protein GL Leads to Obesity in Male C57BL/6J Mice

INTRODUCTION

The mechanisms underlying obesity are not fully understood, necessitating the creation of novel animal models for the investigation of metabolic disorders. We have previously found that neurosecretory protein GL (NPGL), a newly identified hypothalamic neuropeptide, is involved in feeding behavior and fat accumulation in rats. However, the impact of NPGL on obesity remains unclear in any animal model. The present investigation sought to elucidate whether NPGL causes obesity in the obesity-prone mouse strain C57BL/6J.

METHODS

We overexpressed the NPGL-precursor gene (Npgl) in the hypothalamus using adeno-associated virus in male C57BL/6J mice fed normal chow (NC) or a high-calorie diet (HCD). After 9 weeks of Npgl overexpression, we measured adipose tissues, muscle, and several organ masses in addition to food intake and body mass. To assess the effects of Npgl overexpression on peripheral tissues, we analyzed mRNA expression of lipid metabolism-related genes by quantitative RT-PCR. Whole body energy consumption was assessed using an O2/CO2 metabolism measurement before an apparent increase in body mass.

RESULTS

Npgl overexpression increased food intake, body mass, adipose tissues and liver masses, and food efficiency under both NC and HCD, resulting in obesity observable within 8 weeks. Furthermore, we observed fat accumulation in adipose tissues and liver. Additionally, mRNA expression of lipid metabolism-related factors was increased in white adipose tissue and the liver after Npgl overexpression. Npgl overexpression inhibited energy expenditure during a dark period.

CONCLUSION

Taken together, the present study suggests that NPGL can act as an obesogenic factor that acts within a short period of time in mice. As a result, this Npgl overexpression-induced obesity can be widely applied to study the etiology of obesity from genes to behavior.

Maternal DHA Supplementation during Pregnancy and Lactation in the Rat Protects the Offspring against High-Calorie Diet-Induced Hepatic Steatosis

Maternal supplementation during pregnancy with docosahexaenoic acid (DHA) is internationally recommended to avoid postpartum maternal depression in the mother and improve cognitive and neurological outcomes in the offspring. This study was aimed at determining whether this nutritional intervention, in the rat, protects the offspring against the development of obesity and its associated metabolic disorders. Pregnant Wistar rats received an extract of fish oil enriched in DHA or saline (SAL) as placebo by mouth from the beginning of gestation to the end of lactation. At weaning, pups were fed standard chow or a free-choice, high-fat, high-sugar (fc-HFHS) diet. Compared to animals fed standard chow, rats exposed to the fc-HFHS diet exhibited increased body weight, liver weight, body fat and leptin in serum independently of saline or DHA maternal supplementation. Nevertheless, maternal DHA supplementation prevented both the glucose intolerance and the rise in serum insulin resulting from consumption of the fc-HFHS diet. In addition, animals from the DHA-fc-HFHS diet group showed decreased hepatic triglyceride accumulation compared to SAL-fc-HFHS rats. The beneficial effects on glucose homeostasis declined with age in male rats. Yet, the preventive action against hepatic steatosis was still present in 6-month-old animals of both sexes and was associated with decreased hepatic expression of lipogenic genes. The results of the present work show that maternal DHA supplementation during pregnancy programs a healthy phenotype into the offspring that was protective against the deleterious effects of an obesogenic diet.

A New Zealand green-lipped mussel oil-enriched high-fat diet exhibits beneficial effects on body weight and metabolism in mice

To induce diet-induced obesity (DIO) in rodents, diets high in saturated fat and/or carbohydrates are commonly used. In the laboratory, standardised diets evolved over time without paying particular attention to the effect of fat composition on metabolic alterations. In the present study, customised high-fat diets (HFD) enriched with a combination of lard and different concentrations of New Zealand green-lipped mussel (Perna canaliculus) oil or MSC Hoki (Macruronus novaezelandiae, blue grenadier) liver oil, important sources of n-3 PUFA, in comparison with a solely lard-based diet, were fed to lean and DIO male C57BL/6 mice and their effects on metabolic parameters were monitored. Intriguingly, an isoenergetic HFD containing 63 % of total fat in the form of mussel oil and only 28 % in the form of lard attenuated HFD-induced body weight gain after 1 and 4 weeks, respectively. Consistently, changing a lard-enriched HFD to the mussel oil diet reduced body weight markedly even after mice had been exposed to the former diet for 10 months. The weight-reducing effect of the diet was not caused by altered energy intake or expenditure, but was associated with reduced visceral fat mass. Collectively, these data suggest a novel weight-reducing potential of green-lipped mussel oil.

The Dietary Replacement of Soybean Oil by Canola Oil Does Not Prevent Liver Fatty Acid Accumulation and Liver Inflammation in Mice

A high-carbohydrate diet (HCD) is a well-established experimental model of accelerated liver fatty acid (FA) deposition and inflammation. In this study, we evaluated whether canola oil can prevent these physiopathological changes. We evaluated hepatic FA accumulation and inflammation in mice fed with a HCD (72.1% carbohydrates) and either canola oil (C group) or soybean oil (S group) as a lipid source for 0, 7, 14, 28, or 56 days. Liver FA compositions were analyzed by gas chromatography. The mRNA expression of acetyl-CoA carboxylase 1 (ACC1) was measured as an indicator of lipogenesis. The mRNA expression of F4/80, tumor necrosis factor-α (TNF-α), interleukin (IL)-1β, IL-6, and IL-10, as mediators of liver inflammation, were also measured. The C group stored less n-6 polyunsaturated FAs (n-6 PUFAs) and had more intense lipid deposition of monounsaturated FAs (MUFAs), n-3 PUFAs, and total FAs. The C group also showed higher ACC1 expression. Moreover, on day 56, the C group showed higher expressions of the inflammatory genes F4/80, TNF-α, IL-1β, and IL-6, as well as the anti-inflammatory IL-10. In conclusion, a diet containing canola oil as a lipid source does not prevent the fatty acid accumulation and inflammation induced by a HCD.

MYCN and PRC1 cooperatively repress docosahexaenoic acid synthesis in neuroblastoma via ELOVL2

Background

The MYCN amplification is a defining hallmark of high-risk neuroblastoma. Due to irregular oncogenes orchestration, tumor cells exhibit distinct fatty acid metabolic features from non-tumor cells. However, the function of MYCN in neuroblastoma fatty acid metabolism reprogramming remains unknown.

Methods

Gas Chromatography-Mass Spectrometer (GC-MS) was used to find the potential target fatty acid metabolites of MYCN. Real-time PCR (RT-PCR) and clinical bioinformatics analysis was used to find the related target genes. The function of the identified target gene ELOVL2 on cell growth was detected through CCK-8 assay, Soft agar colony formation assay, flow Cytometry assay and mouse xenograft. Chromatin immunoprecipitation (ChIP) and Immunoprecipitation-Mass Spectrometer (IP-MS) further identified the target gene and the co-repressor of MYCN.

Results

The fatty acid profile of MYCN-depleted neuroblastoma cells identified docosahexaenoic acid (DHA), an omega-3 polyunsaturated fatty acid with anti-tumor activity, significantly increased after MYCN depletion. Compared with MYCN single-copy neuroblastoma cells, DHA level was significantly lower in MYCN-amplified neuroblastoma cells. RT-PCR and clinical bioinformatics analysis discovered that MYCN interfered DHA accumulation via ELOVL fatty acid elongase 2 (ELOVL2) which is a rate-limiting enzyme of cellular DHA synthesis. Enforced ELOVL2 expression in MYCN-amplified neuroblastoma cells led to decreased cell growth and counteracted the growth-promoting effect of MYCN overexpression both in vitro and vivo. ELOVL2 Knockdown showed the opposite effect in MYCN single-copy neuroblastoma cells. In primary neuroblastoma, high ELOVL2 transcription correlated with favorable clinical tumor biology and patient survival. The mechanism of MYCN-mediated ELOVL2 inhibition contributed to epigenetic regulation. MYCN recruited PRC1 (Polycomb repressive complex 1), catalysed H2AK119ub (histone 2A lysine 119 monoubiquitination) and inhibited subsequent ELOVL2 transcription.

Conclusions

The tumor suppressive properties of DHA and ELOVL2 are repressed by the MYCN and PRC1 jointly, which suggests a new epigenetic mechanism of MYCN-mediated fatty acid regulation and indicates PRC1 inhibition as a potential novel strategy to activate ELOVL2 suppressive functions.

n-3 PUFA Sources (Precursor/Products): A Review of Current Knowledge on Rabbit

This review compares the effects of different n-3 polyunsaturated fatty acid (PUFA) sources on biological activity, physiological/reproductive endpoints, and health implications with a special emphasis on a rabbit case study. Linoleic acid (LA) and α-linolenic acid (ALA) are members of two classes of PUFAs, namely the n-6 and n-3 series, which are required for normal human health. Both are considered precursors of a cascade of molecules (eicosanoids), which take part in many biological processes (inflammation, vasoconstriction/vasodilation, thromboregulation, etc.). However, their biological functions are opposite and are mainly related to the form (precursor or long-chain products) in which they were administered and to the enzyme-substrate preference. ALA is widely present in common vegetable oils and foods, marine algae, and natural herbs, whereas its long-chain PUFA derivatives are available mainly in fish and animal product origins. Recent studies have shown that the accumulation of n-3 PUFAs seems mostly to be tissue-dependent and acts in a tissue-selective manner. Furthermore, dietary n-3 PUFAs widely affect the lipid oxidation susceptibility of all tissues. In conclusion, sustainable sources of n-3 PUFAs are limited and exert a different effect about (1) the form in which they are administered, precursor or derivatives; (2) their antioxidant protections; and (3) the purpose to be achieved (health improvement, physiological and reproductive traits, metabolic pathways, etc.).

Trans-fatty acids aggravate anabolic steroid-induced metabolic disturbances and differential gene expression in muscle, pancreas and adipose tissue

AIMS

Although anabolic steroids (AS) and trans-fatty acids overload exerts systemic toxicity and are independent risk factors for metabolic and cardiovascular disorders, their interaction remains poorly understood. Thus, we investigated the impact of a diet rich in trans-fatty acids (HFD) combined with AS on glycemic control, lipid profile, adipose tissue, skeletal muscle and pancreas microstructure and expression of genes involved in energy metabolism.

MAIN METHODS

Forty-eight C57BL/6 mice were randomized into 6 groups treated for 12 weeks with a standard diet (SD) or a diet rich in C18:1 trans-fatty isomers (HFD), alone or combined with 10 or 20 mg/kg testosterone cypionate (AS).

KEY FINDINGS

Our results indicated that AS improved glycemic control, upregulated gene expression of Glut-4 and CPT-1 in skeletal muscle, FAS, ACC and UCP-1 in adipose tissue. AS also reduced total and LDL cholesterol in mice fed a SD. When combined with the HFD, AS was unable to induce microstructural adaptations in adipose tissue, pancreatic islets and β-cells, but potentiated GCK and Glut-2 (pancreas) and Glut-4 and CPT-1 (skeletal muscle) upregulation. HFD plus AS also downregulated FAS and ACC gene expression in adipose tissue. Combined with HFD, AS increased triacylglycerol circulating levels, improved insulin sensitivity and glycemic control in mice.

SIGNIFICANCE

Our findings indicated that HFD and AS can interact to modulates glycemic control and lipid profile by a mechanism potentially related with a reprogramming of genes expression in organs such as the pancreas, adipose tissue and skeletal muscle.

The Association of Polyunsaturated Fatty Acid δ-5-Desaturase Activity with Risk Factors for Type 2 Diabetes Is Dependent on Plasma ApoB-Lipoproteins in Overweight and Obese Adults

Background

δ-5 and δ-6 desaturases (D5D and D6D) catalyze the endogenous conversion of n-3 (ω-3) and n-6 (ω-6) polyunsaturated fatty acids (PUFAs). Their activities are negatively and positively associated with type 2 diabetes (T2D), respectively, by unclear mechanisms. Elevated plasma apoB-lipoproteins (measured as plasma apoB), which can be reduced by n-3 PUFA intake, promote T2D risk factors.

Objective

The aim of this study was to test the hypothesis that the association of D5D and D6D activities with T2D risk factors is dependent on plasma apoB.

Methods

This is a pooled analysis of 2 populations recruited for 2 different metabolic studies. It is a post hoc analysis of baseline data of these subjects [n = 98; 60% women (postmenopausal); mean ± SD body mass index (in kg/m2): 32.8 ± 4.7; mean ± SD age: 57.6 ± 6.3 y]. Glucose-induced insulin secretion (GIIS) and insulin sensitivity (IS) were measured using Botnia clamps. Plasma clearance of a high-fat meal (600 kcal/m2, 66% fat) and white adipose tissue (WAT) function (storage of 3H-triolein-labeled substrate) were assessed in a subpopulation (n = 47). Desaturase activities were estimated from plasma phospholipid fatty acids. Associations were examined using Pearson and partial correlations.

Results

While both desaturase activities were positively associated with percentage of eicosapentaenoic acid, only D5D was negatively associated with plasma apoB (r = -0.30, P = 0.003). Association of D5D activity with second-phase GIIS (r = -0.23, P = 0.029), IS (r = 0.33, P = 0.015, in women) and 6-h area-under-the-curve (AUC6h) of plasma chylomicrons (apoB48, r = -0.47, P = 0.020, in women) was independent of age and adiposity, but was eliminated after adjustment for plasma apoB. D6D activity was associated in the opposite direction with GIIS (r = 0.24, P = 0.049), IS (r = -0.36, P = 0.004) and AUC6h chylomicrons (r = 0.52, P = 0.004), independent of plasma apoB. Both desaturases were associated with plasma interleukin-1-receptor antagonist (D5D: r = -0.45, P < 0.001 in women; D6D: r = -0.33, P = 0.007) and WAT function (trend for D5D: r = 0.30, P = 0.05; D6D: r = 0.39, P = 0.027) independent of any adjustment.

Conclusions

Association of D5D activity with IS, lower GIIS, and plasma chylomicron clearance is dependent on plasma apoB in overweight and obese adults.

The composition of dietary fat alters the transcriptional profile of pathways associated with lipid metabolism in the liver and adipose tissue in the pig

The objective was to investigate the of effect chemical composition of dietary fat on transcription of genes involved in lipid metabolism in adipose tissue and the liver via transcriptional profiling in growing pigs. A total of 48 Genetiporc 6.0 × Genetiporc F25 (PIC, Inc., Hendersonville, TN) barrows (initial BW of 44.1 ± 1.2 kg) were randomly allotted to 1 of 6 dietary treatments. Each experimental diet included 95% of a corn-soybean meal basal diet and 5% cornstarch (control; CNTR), animal-vegetable blend (AV), coconut oil (COCO), corn oil (COIL), fish oil (FO), or tallow (TAL). Pigs were sacrificed on d 10 (final BW of 51.2 ± 1.7 kg) to collect tissues. Expression normalization across samples was performed by calculating a delta cycle threshold (ΔCt) value using . Delta delta cycle threshold (ΔΔCt) values were expressed relative to the CNTR treatment. In adipose tissue, adding dietary fat, regardless of the source, decreased the mRNA abundance of compared with the CNTR ( = 0.014). Pigs fed a COIL-based diet tended to have greater adipose tissue expression of ( = 0.071) than pigs fed the other dietary fat sources tested. Abundance of mRNA was greater in adipose tissue of barrows a fed COIL-based diet than barrows fed CNTR or FO-based diets ( = 0.047). In the liver, adding dietary fat, regardless of source, increased the mRNA abundance of , , , , , and ( ≤ 0.020) and tended to increase the abundance of ( = 0.071) and ( = 0.086) compared with the CNTR. Pigs fed a TAL-based diet had greater hepatic transcription of than pigs fed CNTR-, COCO-, or FO-based diets ( = 0.013). Hepatic transcription of tended to be greater in pigs fed COCO than in pigs fed other dietary fat sources ( = 0.074). Dietary omega-3 fatty acid content tended to negatively correlate with mRNA abundance of ( = 0.065) in adipose tissue and ( = 0.063) in the liver. Dietary fat SFA content was negatively correlated with in the liver ( ≤ 0.039). Dietary fat MUFA content tended to be positively correlated with , , and mRNA abundance in the liver ( ≤ 0.100). To conclude, the intake of omega-3 fatty acids suppressed the mRNA abundance of genes involved in lipolysis in both adipose tissue and the liver. Dietary SFA are greater inhibitors of lipogenesis in adipose tissue than omega-6 fatty acids. Intake of medium-chain fatty acids alters hepatic lipid metabolism differently than intake of long-chain fatty acids.

Benefits of Fish Oil Consumption over Other Sources of Lipids on Metabolic Parameters in Obese Rats

This study evaluated the effect of the consumption of different levels and sources of lipids on metabolic parameters of Wistar rats. Animals were fed with high-fat diet (HFD) containing 20% of lard for 12 weeks to cause metabolic obesity. Subsequently, the animals were divided into six groups and were fed diets with lipid concentrations of 5% or 20% of lard (LD), soybean oil (SO) or fish oil (FO), for 4 weeks. Data were submitted to analysis of variance (two-way) followed by Tukey post hoc test (p < 0.05). The groups that consumed FO showed less weight gain and lower serum levels of triacylglycerol (TAG), total cholesterol and fractions, aspartate aminotransferase (AST) activity, atherogenic index, less amount of fat in the carcass, decreased Lee index and lower total leukocyte counting (p < 0.05). These same parameters were higher in LD treatment (p < 0.05). In the concentration of 20%, carcass fat content, blood glucose levels, as well as alanine aminotransferase (ALT) and gamma glutamyl transferase (GGT) decreased in FO groups (p < 0.05). The SO group had intermediate results regarding the other two treatments (FO and LD). We concluded that fish oil intake was able to modulate positively the metabolic changes resulting from HFD.

A Diet Rich in Docosahexaenoic Acid Restores Liver Arachidonic Acid and Docosahexaenoic Acid Concentrations in Mice Homozygous for the Human Apolipoprotein E ε4 Allele

BACKGROUND

Metabolism of long-chain polyunsaturated fatty acids (LC-PUFAs) is disturbed in carriers of the apolipoprotein E (APOE) ε4 allele (APOE4). More specifically, APOE4 carriers are lower responders to ω-3 (n-3) LC-PUFA supplementation; this might be because LC-PUFA transport into cells or β-oxidation is disturbed. However, high doses of dietary docosahexaenoic acid (DHA) seem to restore DHA homeostasis in APOE4 carriers, but the contribution of hepatic fatty acid (FA) transporters is unknown.

OBJECTIVES

With the use of mice carrying human APOE isoforms, we sought to investigate whether a DHA-rich diet could restore DHA homeostasis in APOE4 mice and whether this involved hepatic FA transporters.

METHODS

Male and female mice homozygous for the APOE ε2 allele, APOE ε3 allele (APOE3), and APOE4 were fed either a diet enriched with DHA (0.7 g DHA/100 g diet) or a control diet for 8 mo and were killed at 12 mo of age. Liver and plasma FA profiles were measured by GC, and FA transporter expression was evaluated by Western immunoblotting.

RESULTS

There was a significant genotype × diet interaction for hepatic concentrations of arachidonic acid (AA) and DHA (P = 0.005 and P = 0.002, respectively) and a trend toward an interaction for liver expression of fatty acid binding protein 1 (FABP1) (P-interaction = 0.05). APOE4 mice had 60-100% higher liver AA, DHA, and FABP1 than did APOE3 mice, but only when fed the control diet. Independent of diet, APOE4 mice had 20-30% lower plasma concentrations of AA and DHA than did APOE3 mice. Overall, mice fed the DHA diet had 50% lower concentrations of liver total FAs than did mice fed the control diet.

CONCLUSIONS

These findings in transgenic mice suggest that a long-term diet rich in DHA suppresses the APOE4-specific disturbances in hepatic transport and concentration of AA and DHA and also reduces hepatic total FA concentrations, regardless of genotype.

Adiponectin prevents reduction of lipid-induced mitochondrial biogenesis via AMPK/ACC2 pathway in chicken adipocyte

Adiponectin (APN) stimulates mitochondrial biogenesis and reduces lipid content in human and animal adipocytes. However, the mechanism of adiponectin in regulating mitochondrial biogenesis in chicken adipocytes has never been reported. The objective of this study is to examine the mechanism that adiponectin plays in lipid-induced mitochondrial biogenesis and mitochondrial function in chicken adipocytes. We found that the overexpression of adiponectin reduced the membrane DAG content and elevated the membrane translocation of PKCθ. In contrast to control groups, the overexpression of adiponectin increased mitochondrial density and mitochondrial DNA contents and peroxisome proliferator-activated receptor αcoactivator 1α (PGC1-α) expression. Mitochondrial membrane potential and cytochrome C (Cyt C) content were detected by JC-1 fluorescent staining and immunofluorescence which indicated that overexpression of adiponectin enhanced mitochondrial ATP synthesis. Moreover, AMPK/ACC2 signaling pathway was activated along with the elevation of PGC1-α and TFAM by the overexpression of adiponectin, meanwhile the lipid transcription marker genes were down-regulated. This effect was alleviated by reducing adiponectin and a specific inhibitor of AMPK pathway. We concluded that adiponectin could prevent reduction of lipid-induced mitochondrial biogenesis via AMPK/ACC2 pathway in chicken adipocytes.

Omega-3 fatty acids and adipose tissue function in obesity and metabolic syndrome

The n-3 long-chain polyunsaturated fatty acids (n-3 PUFAs) such as eicosapentaenoic (EPA) and docosahexaenoic (DHA) have been reported to improve obesity-associated metabolic disorders including chronic inflammation, insulin resistance and dyslipidaemia. Growing evidence exits about adipose tissue as a target in mediating the beneficial effects of these marine n-3 PUFAs in adverse metabolic syndrome manifestations. Therefore, in this manuscript we focus in reviewing the current knowledge about effects of marine n-3 PUFAs on adipose tissue metabolism and secretory functions. This scope includes n-3 PUFAs actions on adipogenesis, lipogenesis and lipolysis as well as on fatty acid oxidation and mitochondrial biogenesis. The effects of n-3 PUFAs on adipose tissue glucose uptake and insulin signaling are also summarized. Moreover, the roles of peroxisome proliferator-activated receptor γ (PPARγ) and AMPK activation in mediating n-3 PUFAs actions on adipose tissue functions are discussed. Finally, the mechanisms underlying the ability of n-3 PUFAs to prevent and/or ameliorate adipose tissue inflammation are also revised, focusing on the role of n-3 PUFAs-derived specialized proresolving lipid mediators such as resolvins, protectins and maresins.

The autonomic nervous system and cardiovascular disease: role of n-3 PUFAs

In the last decades, a large body of experimental and clinical evidence has been accumulated showing that cardiovascular diseases are often accompanied by an imbalance in the sympathetic-vagal outflow to the heart, resulting in a chronic adrenergic activation. The arterial baroreceptor system is a key component of mechanisms contributing to the neural regulation of the cardiovascular system. Several methods have been proposed to assess autonomic activity by analyzing heart rate and blood pressure changes either spontaneously occurring or following provocations. The autonomic nervous system has been regarded as one of the putative mechanisms involved into the beneficial effects of exposure to n-3 fatty acids observed in epidemiological studies. The aim of the present review is to provide an update on the clinical evidence proposed so far linking exposure to n-3 fatty acids to autonomic nervous system modulation.

Modulation of adipocyte differentiation by omega-3 polyunsaturated fatty acids involves the ubiquitin-proteasome system

We have evaluated the effects of three different omega-3 polyunsaturated fatty acids (ω-3 PUFAs) – docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA) and docosapentaenoic acid (DPA) on fat accumulation and expression of adipogenic and inflammatory markers using both 3T3-L1 pre-adipocytes and differentiated 3T3-L1 adipocytes. Our results indicate that ω-3 PUFAs induce the degradation of fatty acid synthase through the ubiquitin-proteasome system, which is likely to have beneficial metabolic effect on adipose cells. Omega-3 PUFAs also increase overall levels of polyubiquitinated proteins, at least in part through decreasing the expression of proteasome subunits. Moreover, adipocytes are resistant to proteasome inhibition, which induces adipophilin while decreasing perilipin expression. On the other hand, ω-3 PUFAs decrease expression of SREBP1 while inducing expression of adipophilin and GLUT4. Moreover, all three ω-3 PUFAs appear to induce tumour necrosis factor-α without affecting NFκB levels. All three ω-3 PUFAs appear to have overall similar effects. Further research is needed to elucidate their mechanism of action.

Comparison of docosahexaenoic acid uptake in murine cardiomyocyte culture and tissue: significance to physiologically relevant studies

Long-chain n-3 (or omega 3) fatty acids, namely docosahexaenoic acid (DHA, 22:6n-3) and eicosapentaenoic acid (EPA, 20:5n-3) have been attributed cardioprotective properties. In this study, we evaluated the incorporation of DHA into cardiomyocytes and the shift in the omega 3/omega 6 ratio after supplementation of primary cardiomyocyte culture. Results are compared with atrial tissue concentrations attained after prolonged feeding of rats. The major difference between in vitro vs. in vivo supplementation is the paradoxical accumulation of arachidonic acid in cultured cardiomyocyte. However, this increase does not give rise to a higher PGE2 production after cellular stimulation, as compared with controls, possibly because of the associated inhibition of sPLA2 by DHA. Notably, in vitro supplementations with DHA 10 to 25μM approximate in vivo pharmacological treatments.

Adipose tissue dysregulation and metabolic consequences in childhood and adolescent obesity: potential impact of dietary fat quality

Evidence suggests that at a population level, childhood and adolescent obesity increase the long-term risk of chronic diseases such as type 2 diabetes and CVD. At an individual level, however, the metabolic consequences of obesity in youth vary immensely. Despite comparable BMI, some adolescents develop impaired glucose tolerance while others maintain normal glucose homeostasis. It has been proposed that the variation in the capacity to store lipid in the subcutaneous adipose tissue (SAT) may partially discriminate metabolically healthy from unhealthy obesity. In positive energy balance, a decreased capacity to expand SAT may drive lipid accumulation to visceral adipose tissue, liver and skeletal muscle. This state of lipotoxicity is associated with chronic low-grade inflammation, insulin resistance and dyslipidaemia. The present review examines the differential adipose tissue development and function in children and adolescents who exhibit metabolic dysregulation compared with those who are protected. Additionally, the role of manipulating dietary fat quality to potentially prevent and treat metabolic dysfunction in obesity will be discussed. The findings of the present review highlight the need for further randomised controlled trials to establish the effect of dietary n-3 PUFA on the metabolic phenotype of obese children and adolescents. Furthermore, using a personalised nutrition approach to target interventions to those at risk of, or those with established metabolic dysregulation may optimise the efficacy of modifying dietary fat quality.

Effect of diet on microRNA expression in ovine subcutaneous and visceral adipose tissues

Knowledge of the molecular mechanisms that regulate ovine adipogenesis is very limited. MicroRNAs (miRNA) have been reported as one of the regulatory mechanisms of adipogenesis. This study aimed to compare the expression of miRNA related to ovine adipogenesis in different adipose depots and to investigate whether their expression is affected by dietary fatty acid composition. We also investigated the role of miRNA in adipogenic gene regulation. Subcutaneous and visceral adipose tissue samples were collected at slaughter from 12 Canadian Arcott lambs fed a barley-based finishing diet where an algae meal (DHA-Gold; Schizochytrium spp.) replaced flax oil and barley grain at 0 or 3% DM (n = 6). Total RNA from each tissue was subjected to quantitative real time (qRT-) PCR analysis to determine the expression of 15 selected miRNA including 11 identified from bovine adipose tissues and 4 conserved between bovine and ovine species. MicroRNAs were differentially expressed according to diet in each tissue depot (miR-142-5p and miR-376d) in visceral and miR-142-5p, miR-92a, and miR-378 in subcutaneous adipose tissue; P ≤ 0.05) and in each tissue depot depending on diet (miR-101, miR-106, miR-136, miR-16b, miR-196a-1, miR-2368*, miR-2454, miR-296, miR-376d, miR-378, and miR-92a in both control and DHA-G diets and miR-478 in control; P ≤ 0.05). Six miRNA were subjected to functional analysis and 3 genes of interest (ACSL1, PPARα, and C/EBPα) were validated by qRT-PCR. Both diet and tissue depot affected expression levels of all 3 genes (P < 0.05). miR-101, miR-106, and miR-136 were negatively correlated with their respective predicted gene targets C/EBPα, PPARα, and ACSL1 in subcutaneous adipose tissue of lambs fed DHA-G. Yet miR-142-5p and miR-101 showed no correlation with ACSL1 or C/EBPα. The variability in expression patterns of miRNA across adipose depots reflects the tissue specific nature of adipogenic regulation. Although the examined miRNA appear to be conserved across ruminant species, our results indicate the presence of ovine specific regulatory mechanisms that can be influenced by diet.

Enhanced amelioration of high-fat diet-induced fatty liver by docosahexaenoic acid and lysine supplementations

Fatty liver disease is the most common pathological condition in the liver. Here, we generated high-fat diet-(HFD-) induced nonalcoholic fatty liver disease (NAFLD) in mice and tested the effects of docosahexaenoic acid (DHA) and lysine during a four-week regular chow (RC)feeding. Our results showed that 1% lysine and the combination of 1% lysine + 1% DHA reduced body weight. Moreover, serum triglyceride levels were reduced by 1% DHA and 1% lysine, whereas serum alanine transaminase activity was reduced by 1% DHA and 1% DHA + 0.5% lysine. Switching to RC reduced hepatic lipid droplet accumulation, which was further reduced by the addition of DHA or lysine. Furthermore, the mRNA expressions of hepatic proinflammatory cytokines were suppressed by DHA and combinations of DHA + lysine, whereas the mRNA for the lipogenic gene, acetyl-CoA carboxylase 1 (ACC1), was suppressed by DHA. In the gonadal adipose tissues, combinations of DHA and lysine inhibited mRNA expression of lipid metabolism-associated genes, including ACC1, fatty acid synthase, lipoprotein lipase, and perilipin. In conclusion, the present study demonstrated that, in conjunction with RC-induced benefits, supplementation with DHA or lysine further ameliorated the high-fat diet-induced NAFLD and provided an alternative strategy to treat, and potentially prevent, NAFLD.

Recombinant globular adiponectin inhibits lipid deposition by p38 MAPK/ATF-2 and TOR/p70 S6 kinase pathways in chicken adipocytes

Adiponectin plays a fundamental role in lipid and carbohydrate metabolism. However, its role in adipocyte differentiation remains controversial. To investigate the effect of gAd on lipid deposition in chicken adipocytes and its related signaling pathways, 200 μg/mL recombinant globular adiponectin, isoproterenol, SB253580, leucine, and rapamycin were used to treat chicken adipocytes. Results demonstrated that gAd increased the expression of endogenous adiponectin and AdipoR1 (P < 0.01); gAd inhibited triglyceride (TG) accumulation in chicken adipocyte and increased the release of free fatty acids (FFA) in medium; gAd decreased the expression of adipogenic marker genes CCAAT/enhancer binding protein alpha (C/EBPα) and fatty acid synthase (FAS), while activating the expression of lipolytic marker gene adipose triglyceride lipase (ATGL) (P < 0.01). Meanwhile, gAd activated the phosphorylation levels of p38 mitogen-activated protein kinase (p38 MAPK) and activating transcription factor 2 (ATF-2), and suppressed the phosphorylation levels of rapamycin (TOR) and p70 S6 Kinase (P < 0.01). In conclusion, the results demonstrate that gAd has an ability to inhibit lipids deposition in chicken adipocyte, which depends on the p38 MAPK/ATF–2 and TOR/p70 S6 Kinase pathways.

Chemoprevention of nonalcoholic fatty liver disease by dietary natural compounds

Nonalcoholic fatty liver disease (NAFLD) refers to a wide spectrum of liver disease that is not from excess alcohol consumption, but is often associated with obesity, type 2 diabetes, and metabolic syndrome. NAFLD pathogenesis is complicated and involves oxidative stress, lipotoxicity, mitochondrial damage, insulin resistance, inflammation, and excessive dietary fat intake, which increase hepatic lipid influx and de novo lipogenesis and impair insulin signaling, thus promoting hepatic triglyceride accumulation and ultimately NAFLD. Overproduction of proinflammatory adipokines from adipose tissue also affects hepatic metabolic function. Current NAFLD therapies are limited; thus, much attention has been focused on identification of potential dietary substances from fruits, vegetables, and edible plants to provide a new strategy for NAFLD treatment. Dietary natural compounds, such as carotenoids, omega-3-PUFAs, flavonoids, isothiocyanates, terpenoids, curcumin, and resveratrol, act through a variety of mechanisms to prevent and improve NAFLD. Here, we summarize and briefly discuss the currently known targets and signaling pathways as well as the role of dietary natural compounds that interfere with NAFLD pathogenesis.

Adiponectin impairs chicken preadipocytes differentiation through p38 MAPK/ATF-2 and TOR/p70 S6 kinase pathways

Adiponectin is a protein hormone secreted exclusively by adipocytes that plays an important role in the modulation of glucose and lipid metabolism. In the present study, we investigated the ability of adiponectin to stimulate chicken preadipocyte differentiation and its effect on cellular signaling pathways associated with adipocyte differentiation. Data showed that over-expression of adiponectin inhibited adipocyte differentiation and the expression of adipogenic marker gene, while activated the expression of lipolytic marker gene. Meanwhile, adiponectin led to activation of p38 mitogen-activated protein kinase (p38 MAPK)/activating transcription factor 2 (ATF-2) signaling pathway and down-regulation of target of rapamycin (TOR)/p70 S6 Kinase signaling pathway. Furthermore, the activation of p38 MAPK/ATF-2 signaling pathway was blocked by the p38 MAPK inhibitor SB253580, whereas adiponectin had a synergistic effect on the suppression of TOR/p70 S6 Kinase signaling pathway with the TOR inhibitor rapamycin. In conclusion, the results demonstrate the ability of adiponectin to inhibit chicken preadipocyte differentiation, which depends on the p38 MAPK/ATF-2 and TOR/p70 S6 Kinase pathways.

No association between the intake of marine n-3 PUFA during the second trimester of pregnancy and factors associated with cardiometabolic risk in the 20-year-old offspring

The intake of marine n-3 PUFA has been shown to decrease the risk of CVD in a number of studies. Since the development of CVD is often a lifelong process, marine n-3 PUFA intake early in life may also affect the development of later CVD. The aim of the present study was to investigate the association between maternal intake of marine n-3 PUFA during the second trimester of pregnancy and factors associated with cardiometabolic risk in the 20-year-old offspring. The study was based on the follow-up of the offspring of a Danish pregnancy cohort who participated in a study conducted from 1988 to 1989. A total of 965 pregnant women were originally included in the cohort and detailed information about the intake of marine n-3 PUFA during the second trimester was collected. In 2008–9, the offspring were invited to participate in a clinical examination including anthropometric, blood pressure (BP) and short-term heart rate variability measurements. Also, a fasting venous blood sample was drawn from them. Multiple linear regression modelling, using the lowest quintile of marine n-3 PUFA intake as the reference, was used to estimate the association with all outcomes. A total of 443 offspring participated in the clinical examination. No association between the intake of marine n-3 PUFA during the second trimester of pregnancy and offspring adiposity, glucose metabolism, BP or lipid profile was found. In conclusion, no association between the intake of marine n-3 PUFA during the second trimester of pregnancy and the factors associated with cardiometabolic risk in the 20-year-old offspring could be detected.

The effect of insulin, TNFα and DHA on the proliferation, differentiation and lipolysis of preadipocytes isolated from large yellow croaker (Pseudosciaena Crocea R.)

Fish final product can be affected by excessive lipid accumulation. Therefore, it is important to develop strategies to control obesity in cultivated fish to strengthen the sustainability of the aquaculture industry. As in mammals, the development of adiposity in fish depends on hormonal, cytokine and dietary factors. In this study, we investigated the proliferation and differentiation of preadipocytes isolated from the large yellow croaker and examined the effects of critical factors such as insulin, TNFα and DHA on the proliferation, differentiation and lipolysis of adipocytes. Preadipocytes were isolated by collagenase digestion, after which their proliferation was evaluated. The differentiation process was optimized by assaying glycerol-3-phosphate dehydrogenase (GPDH) activity. Oil red O staining and electron microscopy were performed to visualize the accumulated triacylglycerol. Gene transcript levels were measured using SYBR green quantitative real-time PCR. Insulin promoted preadipocytes proliferation, stimulated cell differentiation and decreased lipolysis of mature adipocytes. TNFα and DHA inhibited cell proliferation and differentiation. While TNFα stimulated mature adipocyte lipolysis, DHA showed no lipolytic effect on adipocytes. The expressions of adipose triglyceride lipase (ATGL), fatty acid synthase (FAS), lipoprotein lipase (LPL) and peroxisome proliferator-activated receptor α, γ (PPARα, PPARγ) were quantified during preadipocytes differentiation and adipocytes lipolysis to partly explain the regulation mechanisms. In summary, the results of this study indicated that although preadipocytes proliferation and the differentiation process in large yellow croaker are similar to these processes in mammals, the effects of critical factors such as insulin, TNFα and DHA on fish adipocytes development are not exactly the same. Our findings fill in the gaps in the basic data regarding the effects of critical factors on adiposity development in fish and will facilitate the further study of molecular mechanism by which these factors act in fish and the application of this knowledge to eventually control obesity in cultured species.

Docosahexaenoic acid ameliorates palmitate-induced lipid accumulation and inflammation through repressing NLRC4 inflammasome activation in HepG2 cells

Background

N-3 polyunsaturated fatty acids, such as docosahexaenoic acid (DHA; 22:6n-3), has clinical significance in the prevention and reversal of nonalcoholic steatohepatitis (NASH). However, the precious mechanism underlying remains unclear. The inflammasome, a multiprotein complex formed by NOD-like receptor (NLR) family members, has been recently shown to be activated in NASH and promote the cleavage of the pro-inflammatory cytokines to their maturation forms.

Methods

HepG2 cells were exposed to different dose of PA for 24 h with or without the preincubation of 50 μM DHA for another 24 h and then lipid deposition was assessed with Oil red O staining and intracellular triglyceride (TG) determination. Secretory levels of inflammatory cytokines and Caspase-1 activity were determined by ELISA assays. Gene expression and protein levels were determined by quantitative RCR and western blotting, respectively.

Results

Palmitate (PA) dose-dependently increased lipid accumulation, TG content and induced the secretion of interleukin-1β (IL-1β), IL-18, TNF-α and MCP-1 from HepG2 cells. Preincubation with DHA significantly alleviated PA-induced lipid accumulation and inflammatory agents. DHA was also found to attenuate PA-induced NOD-like receptor protein 4 (NLRC4) mRNA expression. Furthermore, PA induced caspase-1 activation in a dose-dependent manner, resulting in exacerbating of procaspase-1 and pro-IL-1β processing. Knockdown of NLRC4 partially abrogated PA-induced caspase-1 activation and IL-1β maturation and completely abolished these events in the presence of DHA.

Conclusions

Our findings indicate DHA attenuates PA-induced lipid accumulation and inflammation through suppressing NLRC4 inflammasome activation, caspase-1 activation and IL-1β cleavage.

n-3 PUFA prevent metabolic disturbances associated with obesity and improve endothelial function in golden Syrian hamsters fed with a high-fat diet

Glucose intolerance and dyslipidaemia are independent risk factors for endothelium dysfunction and CVD. The aim of the present study was to analyse the preventive effect of n-3 PUFA (EPA and DHA) on lipid and carbohydrate disturbances and endothelial dysfunction. Three groups of adult hamsters were studied for 20 weeks: (1) control diet (Control); (2) high-fat diet (HF); (3) high-fat diet enriched with n-3 PUFA (HFn-3) groups. The increase in body weight and fat mass in the HF compared to the Control group (P < 0.05) was not found in the HFn-3 group. Muscle TAG content was similar in the Control and HF groups, but significantly lower in the HFn-3 group (P = 0.008). Glucose tolerance was impaired in the HF compared to the Control group, but this impairment was prevented by n-3 PUFA in the HFn-3 group (P < 0.001). Plasma TAG and cholesterol were higher in the HF group compared to the Control group (P < 0.001), but lower in the HFn-3 group compared to the HF group (P < 0.001). HDL-cholesterol was lower in the HFn-3 group compared to the Control and HF groups (P < 0.0005). Hepatic secretion of TAG was lower in the HFn-3 group compared to the HF group (P < 0.005), but did not differ from the Control group. Hepatic gene expression of sterol regulatory element-binding protein-1c, diacylglycerol O-acyltransferase 2 and stearyl CoA desaturase 1 was lower in the HFn-3 group, whereas carnitine palmitoyl transferase 1 and scavenger receptor class B type 1 expression was higher (P < 0.05). In adipocytes and adipose macrophages, PPARγ and TNFα expression was higher in the HF and HFn-3 groups compared to the Control group. Endothelium relaxation was higher in the HFn-3 (P < 0.001) than in the HF and Control groups, and was correlated with glucose intolerance (P = 0.03) and cholesterol (P = 0.0003). In conclusion, n-3 PUFA prevent some metabolic disturbances induced by high-fat diet and improve endothelial function in hamsters.

p38 MAPK regulates calcium signal-mediated lipid accumulation through changing VDR expression in primary preadipocytes of mice

In the present study we have examined whether p38 mitogen activated protein kinase (p38 MAPK) signal pathway interacts with calcium signal on lipid accumulation in primary preadipocytes of mice. The primary preadipocytes were treated with p38 MAPK inhibitor SB203580, blockers and excitomotors of calcium channel for 24 h, respectively. Intracellular triglyceride (TG) content was measured by triglyceride kit and lipid accumulation was determined by Oil Red O staining. Meanwhile, the mRNA expressions of peroxisome proliferators-activated receptor gamma (PPARγ) gene, fatty acid synthetase (FAS) gene, lipoprotein lipase (LPL) gene, vitamin D receptor (VDR) gene and extracellular Ca(2+)-sensing receptor (CaSR) gene were analyzed with real-time PCR. The protein content and phosphorylation of VDR and p38 were tested with Western Blotting. The data showed that intracellular TG content and the mRNA expression levels of PPARγ, FAS, LPL in N group and L group as well as FAS, LPL in C group were increased significantly (P < 0.01) compared to the control. On the contrary, intracellular TG content and the mRNA expression levels of PPARγ, FAS in B group as well as intracellular TG content and PPARγ, FAS, LPL in SB group and B+SB group were decreased significantly (P < 0.01). VDR mRNA expression and protein content were decreased in B, C, and SB added groups (P < 0.01). In addition, p38 phosphorylation levels increased in N and L groups (P < 0.01) and decreased in SB added groups (P < 0.01). These findings suggest that p38 MAPK pathway through regulating VDR mRNA expression participates in mediation of calcium signal and affects calcium signal regulating lipid accumulation in mice preadipocytes through changing PPARγ, FAS and LPL mRNA expression. In addition, calcium signal have a feedback effect in phosphorylation of p38.

Calcium ameliorates obesity induced by high-fat diet and its potential correlation with p38 MAPK pathway

To investigate whether and on which pathway dietary calcium influence the obesity induced by high-fat diet, thirty male Kunming mice were fed in six groups for 4 weeks and mouse preadipocytes were divided into eight groups for different treatment. Body weight gain was measured each week. Calcium in serum and tissues, intracellular free Ca(2+) concentration ([Ca(2+)]i), blood fat and intracellular lipid content were also measured. The expression of Lipid metabolism-related genes were measured by q RT-PCR. Compared with control group, body weight gain (P < 0.05) and fat pad weight (P < 0.01) in Low calcium group decreased. Triglycerides (TG) and total Cholesterol (TC) level decreased (P < 0.01), while HDL-Cholesterol (HDL) level increased (P < 0.01). And calcium supply increased calcium content in blood serum and tissues. In tissues, adipogenesis and vitamin D receptor (VDR) genes expression decreased but lipoclasis genes expression increased. These anti-obesity effects were more obvious when supplying with 2.8% calcium, but the effects were reduced while supplying Nifedipine at the same time. The results in preadipocytes indicated that calcium-treated can reduce intracellular lipid content, along with adipogenesis and lipoclasis genes expression decrease, promoted the expression levels of p38 MAPK pathway upstream gene MKK6 (P < 0.01) and downstream gene MAPKAPK2 (P < 0.01). Treated with SB203580 could increase adipogenesis genes expression, decrease lipoclasis genes expression and ([Ca(2+)]i) (P < 0.01). These results implied that dietary calcium had remarkable effect on anti-obesity effect and p38 MAPK pathway potentially participated in calcium-mediated lipid accumulation and lipolysis in mouse preadipocytes.