Regulation of the expression of key genes involved in HDL metabolism by unsaturated fatty acids

Natural Products Targeting Liver X Receptors or Farnesoid X Receptor

Nuclear receptors (NRs) are a superfamily of transcription factors induced by ligands and also function as integrators of hormonal and nutritional signals. Among NRs, the liver X receptors (LXRs) and farnesoid X receptor (FXR) have been of significance as targets for the treatment of metabolic syndrome-related diseases. In recent years, natural products targeting LXRs and FXR have received remarkable interests as a valuable source of novel ligands encompassing diverse chemical structures and bioactive properties. This review aims to survey natural products, originating from terrestrial plants and microorganisms, marine organisms, and marine-derived microorganisms, which could influence LXRs and FXR. In the recent two decades (2000-2020), 261 natural products were discovered from natural resources such as LXRs/FXR modulators, 109 agonists and 38 antagonists targeting LXRs, and 72 agonists and 55 antagonists targeting FXR. The docking evaluation of desired natural products targeted LXRs/FXR is finally discussed. This comprehensive overview will provide a reference for future study of novel LXRs and FXR agonists and antagonists to target human diseases, and attract an increasing number of professional scholars majoring in pharmacy and biology with more in-depth discussion.

Lipid Metabolism Disorders in the Comorbid Course of Nonalcoholic Fatty Liver Disease and Chronic Obstructive Pulmonary Disease

Non-alcoholic fatty liver disease (NAFLD) is currently among the most common liver diseases. Unfavorable data on the epidemiology of metabolic syndrome and obesity have increased the attention of clinicians and researchers to the problem of NAFLD. The research results allow us to emphasize the systemicity and multifactoriality of the pathogenesis of liver parenchyma lesion. At the same time, many aspects of its classification, etiology, and pathogenesis remain controversial. Local and systemic metabolic disorders are also a part of the pathogenesis of chronic obstructive pulmonary disease and can influence its course. The present article analyzes the metabolic pathways mediating the links of impaired lipid metabolism in NAFLD and chronic obstructive pulmonary disease (COPD). Free fatty acids, cholesterol, and ceramides are involved in key metabolic and inflammatory pathways underlying the pathogenesis of both diseases. Moreover, inflammation and lipid metabolism demonstrate close links in the comorbid course of NAFLD and COPD.

ApoE and apoC-III-defined HDL subtypes: a descriptive study of their lecithin cholesterol acyl transferase and cholesteryl ester transfer protein content and activity

Background

The functionality of high-density lipoproteins (HDL) is a better cardiovascular risk predictor than HDL concentrations. One of the key elements of HDL functionality is its apolipoprotein composition. Lecithin-cholesterol acyl transferase (LCAT) and cholesterol-ester transfer protein (CETP) are enzymes involved in HDL-mediated reverse cholesterol transport. This study assessed the concentration and activity of LCAT and CETP in HDL subspecies defined by their content of apolipoproteins E (apoE) and C-III (apoC-III) in humans.

Methods

Eighteen adults (ten women and eight men, mean age 55.6, BMI 26.9 Kg/m², HbA1c 5.4%) were studied. HDL from each participant were isolated and divided into four subspecies containing respectively: No apoE and no apoC-III (E-C-), apoE but not apoC-III (E + C-), apoC-III but no apoE (E-C+) and both apoE and apoC-III (E + C+). The concentration and enzymatic activity of LCAT and CETP were measured within each HDL subspecies using immunoenzymatic and fluorometric methods. Additionally, the size distribution of HDL in each apolipoprotein-defined fraction was determined using non-denaturing electrophoresis and anti-apoA-I western blotting.

Results

HDL without apoE or apoC-III was the predominant HDL subtype. The size distribution of HDL was very similar in all the four apolipoprotein-defined subtypes. LCAT was most abundant in E-C- HDL (3.58 mg/mL, 59.6% of plasma LCAT mass), while HDL with apoE or apoC-III had much less LCAT (19.8, 12.2 and 8.37% of plasma LCAT respectively for E + C-, E-C+ and E + C+). LCAT mass was lower in E + C- HDL relative to E-C- HDL, but LCAT activity was similar in both fractions, signaling a greater activity-to-mass ratio associated with the presence of apoE. Both CETP mass and CETP activity showed only slight variations across HDL subspecies. There was an inverse correlation between plasma LCAT activity and concentrations of both E-C+ pre-beta HDL (r = − 0.55, P = 0.017) and E-C- alpha 1 HDL (r = − 0.49, P = 0.041). Conversely, there was a direct correlation between plasma CETP activity and concentrations of E-C+ alpha 1 HDL (r = 0.52, P = 0.025).

Conclusions

The presence of apoE in small HDL is correlated with increased LCAT activity and esterification of plasma cholesterol. These results favor an interpretation that LCAT and apoE interact to enhance anti-atherogenic pathways of HDL.

miR-21 promotes non-small cell lung cancer cells growth by regulating fatty acid metabolism

Background

Lung cancer is one of the most common malignant tumors worldwide. CD36 is a receptor for fatty acids and plays an important role in regulating fatty acid metabolism, which is closely related to tumorigenesis and development. The regulation of miR-21 and its role in tumorigenesis have been extensively studied in recent years. However, the relationship between miR-21 and CD36 regulated fatty acid metabolism in human non-small cell lung cancer remains unknown.

Methods

In this study, lentivirus transfection, qRT-PCR, cell migration, immunofluorescence, and western blot were used to examine the relationship between miR-21 and CD36 regulated fatty acid metabolism and the regulation role of miR-21 in human non-small cell lung cancer.

Results

This study demonstrated that up-regulation of miR-21 promoted cell migration and cell growth in human non-small cell lung cancer cells. Moreover, the intracellular contents of lipids including cellular content of phospholipids, neutral lipids content, cellular content of triglycerides were significantly increased following miR-21 mimic treatment compared with control, and the levels of key lipid metabolic enzymes FASN, ACC1 and FABP5 were obviously enhanced in human non-small cell lung cancer cells. Furthermore, down-regulation of CD36 suppressed miR-21 regulated cell growth, migration and intracellular contents of lipids in human non-small cell lung cancer cells, which suggested that miR-21 promoted cell growth and migration of human non-small cell lung cancer cells through CD36 mediated fatty acid metabolism. Inhibition of miR-21 was revealed to inhibit cell growth, migration, intracellular contents of lipids, and CD36 protein expression level in human non-small cell lung cancer cells. In addition, PPARGC1B was a direct target of miR-21, and down-regulation of PPARGC1B reversed the inhibition of CD36 expression induced by miR-21 inhibitor.

Conclusions

These results explored the mechanism of miR-21 promoted non-small cell lung cancer and might provide a novel therapeutic method in treating non-small cell lung cancer in clinic.

The impact of human breast milk components on the infant metabolism

BACKGROUND & AIMS

Breastfeeding is beneficial for mothers and infants. Underlying mechanisms and biochemical mediators thus need to be investigated to develop and support improved infant nutrition practices promoting the child health. We analysed the relation between maternal breast milk composition and infant metabolism.

METHODS

196 pairs of mothers and infants from a European research project (PreventCD) were studied. Maternal milk samples collected at month 1 and month 4 after birth were analysed for macronutrient classes, hormone, and fatty acid (FA) content. Phospholipids, acylcarnitines, and amino acids were measured in serum samples of 4-month old infants. Associations between milk components and infant metabolites were analysed with spearman correlation and linear mixed effect models (LME). P-values were corrected for multiple testing (PLME).

RESULTS

Month 1 milk protein content was strongly associated with infant serum lyso-phosphatidylcholine (LPC) 14:0 (PLME = 0.009). Month 1 milk insulin was associated to infant acetylcarnitine (PLME = 0.01). There were no associations between milk protein content and serum amino acids and milk total fat content and serum polar lipids. Middle- and odd-chain FA% in breast milk at both ages were significantly related to serum LPC and sphingomyelins (SM) species in infant serum (all PLME<0.05), while FA% 20:5n-3 and 22:6n-3 percentages were significantly associated to serum LPC 22:6 (PLME = 1.91×10-4/7.93×10-5) in milk only at month 4. Other polyunsaturated fatty acids and hormones in milk showed only weak associations with infant serum metabolites.

CONCLUSIONS

Infant serum LPC are influenced by breast milk FA composition and, intriguingly, milk protein content in early but not late lactation. LPC 14:0, previously found positively associated with obesity risk, was the serum metabolite which was the most strongly associated to milk protein content. Thus, LPC 14:0 might be a key metabolite not only reflecting milk protein intake in infants, but also relating high protein content in milk or infant formula to childhood obesity risk.

Natural products as modulators of the nuclear receptors and metabolic sensors LXR, FXR and RXR

Nuclear receptors (NRs) represent attractive targets for the treatment of metabolic syndrome-related diseases. In addition, natural products are an interesting pool of potential ligands since they have been refined under evolutionary pressure to interact with proteins or other biological targets. This review aims to briefly summarize current basic knowledge regarding the liver X (LXR) and farnesoid X receptors (FXR) that form permissive heterodimers with retinoid X receptors (RXR). Natural product-based ligands for these receptors are summarized and the potential of LXR, FXR and RXR as targets in precision medicine is discussed.

Effect of diets rich in either saturated fat or n-6 polyunsaturated fatty acids and supplemented with long-chain n-3 polyunsaturated fatty acids on plasma lipoprotein profiles

BACKGROUND/OBJECTIVES

Abnormalities in lipoprotein profiles (size, distribution and concentration) play an important role in the pathobiology of atherosclerosis and coronary artery disease. Dietary fat, among other factors, has been demonstrated to modulate lipoprotein profiles. We aimed to investigate if background dietary fat (saturated, SFA versus omega-6 polyunsaturated fatty acids, n-6PUFA) was a determinant of the effects of LCn-3PUFA supplementation on lipoprotein profiles.

SUBJECTS/METHODS

A randomized controlled clinical intervention trial in a parallel design was conducted. Healthy subjects (n=26) were supplemented with 400 mg eicosapentaenoic acid plus 2000 mg docosahexaenoic acid daily and randomized to consume diets rich in either SFA or n-6PUFA for a period of 6 weeks. Blood samples, collected at baseline and after 6 weeks of intervention, were assessed for plasma lipoprotein profiles (lipoprotein size, concentration and distribution in subclasses) determined using nuclear magnetic resonance spectroscopy.

RESULTS

Study participants receiving the SFA or the n-6PUFA enriched diets consumed similar percentage energy from fat (41 and 42% respectively, P=0.681). However, subjects on the SFA diet consumed 50% more energy as saturated fat and 77% less as linoleic acid than those consuming the n-6PUFA diet (P<0.001). The diets rich in SFA and n-6PUFA reduced the concentration of total very-low-density lipoprotein (VLDL) particles (P<0.001, both), and their subclasses and increased VLDL (P=0.042 and P=0.007, respectively) and LDL (P=0.030 and 0.027, respectively) particle size. In addition, plasma triglyceride concentration was significantly reduced by LCn-3PUFA supplementation irrespective of the dietary fat.

CONCLUSIONS

LCn-3PUFA modulated lipoprotein profiles in a similar fashion when supplemented in diets rich in either SFA or n-6PUFA.

Improvement of cardiometabolic markers after fish oil intervention in young Mexican adults and the role of PPARα L162V and PPARγ2 P12A

Polyunsaturated fatty acids (PUFA) contained in fish oil (FO) are ligands for peroxisome proliferator-activated receptors (PPAR) that may induce changes in cardiometabolic markers. Variation in PPAR genes may influence the beneficial responses linked to FO supplementation in young adults. The study aimed to analyze the effect of FO supplementation on glucose metabolism, circulating lipids and inflammation according to PPARα L162V and PPARγ2 P12A genotypes in young Mexican adults. 191 young, non-smoking subjects between 18 and 40 years were included in a one-arm study. Participants were supplemented with 2.7 g/day of EPA+DHA, during six weeks. Dietary analysis, body composition measurements and indicators for glucose metabolism, circulating lipids, and markers for inflammation were analyzed before and after intervention. An overall decrease in triglycerides (TG) and an increase in HS-ω3 index were observed in all subjects [-4.1 mg/dL, (SD:±51.7), P=.02 and 2.6%, (SD:±1.2), P<.001 respectively]. Mean fasting insulin and glycated hemoglobin (HbA1c%) were significantly decreased in all subjects [-0.547mlU/L, (SD:±10.29), P=.034 and-0.07%, (SD:±0.3), P<.001 respectively], whereas there was no change in body composition, fasting glucose, adiponectin and inflammatory markers. Subjects carrying the minor alleles of PPARα L162V and PPARγ2 P12A had higher responses in reduction of TG and fasting insulin respectively. Interestingly, doses below 2.7 g/day (1.8 g/day) were sufficient to induce a significant reduction in fasting insulin and HbA1c% from baseline (P=.019 and P<.001). The observed responses in triglycerides and fasting insulin in the Mexican population give further evidence of the importance of FO supplementation in young people as an early step towards the prevention of cardiometabolic disease.

Effects of n-3 polyunsaturated fatty acids high fat diet intervention on the synthesis of hepatic high-density lipoprotein cholesterol in obesity-insulin resistance rats

Background

n-3 polyunsaturated fatty acids (PUFA) have previously been demonstrated in association with a reduced risk of chronic diseases, including insulin resistance, cancer and cardiovascular disease. In the present study, we analyzed the effects of n-3 PUFA-rich perilla oil (PO) and fish oil (FO) high fat diet intervention against the synthesis of hepatic high-density lipoprotein cholesterol (HDL-c) in obesity-insulin resistance model rats.

Methods

In the modeling period, the male SD rats were randomly divided into 2 groups. The rats in the high fat (HF) group were given a high fat pure diet containing 20.62 % lard. In the intervention period, the model rats were intervened with purified high-fat diets rich in PO or FO, containing same energy content with high fat pure diet in HF. After the intervention, the protein and mRNA expressions status of the key genes involved in synthesis of hepatic HDL-c were measured for further analytic comparison.

Results

The obesity-insulin resistance model rats were characterized by surprisingly high levels of serum triglyceride (TG) and increased body weight (P < 0.05, each). After the intervention, there were no apparent changes in the serum HDL-c and total cholesterol (TCH). In addition, the FO could up-regulate the hepatic adenosine triphosphate (ATP) binding cassette transporter A1 (ABCA1) mRNA (P < 0.01) and protein expressions, as well as increase the level of serum apolipoprotein A-1 (apoA-1) (P < 0.0001), and elevate the hepatic apoA-1mRNA expression (P < 0.01). Different from FO, the PO specifically elevated the hepatic ABCA1mRNA expression (P < 0.01).

Conclusions

The FO high fat diets promoted the synthesis of HDL-c in the obesity-insulin resistance rats.

PRMT3 regulates hepatic lipogenesis through direct interaction with LXRα

Arginine methylation is responsible for diverse biological functions and is mediated by protein arginine methyltransferases (PRMTs). Nonalcoholic fatty liver disease (NAFLD) is accompanied by excessive hepatic lipogenesis via liver X receptor α (LXRα). Thus we examined the pathophysiological role of PRMTs in NAFLD and their relationship with LXRα. In this study, palmitic acid (PA) treatment increased PRMT3, which is correlated with the elevation of hepatic lipogenic proteins. The expression of lipogenic proteins was increased by PRMT3 overexpression, but decreased by PRMT3 silencing and use of the PRMT3 knockout (KO) mouse embryonic fibroblast cell line. PRMT3 also increased the transcriptional activity of LXRα by directly binding with LXRα in a methylation-independent manner. In addition, PA treatment translocated PRMT3 to the nucleus. In animal models, a high-fat diet increased the LXRα and PRMT3 expressions and binding, which was not observed in LXRα KO mice. Furthermore, increased PRMT3 expression and its binding with LXRα were observed in NAFLD patients. Taken together, LXRα and PRMT3 expression was increased in cellular and mouse models of NAFLD and human patients, and PRMT3 translocated into the nucleus bound with LXRα as a transcriptional cofactor, which induced lipogenesis. In conclusion, PRMT3 translocation by PA is coupled to the binding of LXRα, which is responsible for the onset of fatty liver.

Influence of genotype on the modulation of gene and protein expression by n-3 LC-PUFA in rats

It is becoming increasingly apparent that responsiveness to dietary fat composition is heterogeneous and dependent on the genetic make-up of the individual. The aim of this study was to evidence a genotype-related differential effect of n-3 long-chain polyunsaturated fatty acids (n-3 LC-PUFA) on the modulation of hepatic genes involved in cholesterol metabolism. Fourteen spontaneously hypertensive (SH) rats, which present a naturally occurring variation in the gene encoding for sterol responsive element binding protein 1 (SREBP-1), contributing to their inherited variation in lipid metabolism, and 14 Wistar-Kyoto (WK) rats were fed a control diet or an n-3 LC-PUFA enriched diet for 90 days. Plasma lipid profile, total lipid fatty acid composition in plasma and liver, and the expression of SREBP-1 and 2, 3-hydroxy-3-methyl-glutaryl-CoA reductase, low-density lipoprotein receptor, and acyl-CoA:cholesterol acyltransferase 2 encoding genes and proteins were determined. The positive effect of the enriched diet on the serum lipid profile, particularly on total cholesterol and triglyceride level, was clearly evidenced in both WK and SH rats, but n-3 LC-PUFA acted through a different modulation of gene and protein expression that appeared related to the genetic background. Our study evidences a different transcriptional effect of specific nutrients related to genetic variants.

Novel benefits of peroxisome proliferator-activated receptors on cardiovascular risk

PURPOSE OF REVIEW

This review provides an overview of newly described mechanisms by which peroxisome proliferator-activated receptors (PPARs) (α, γ, and δ) regulate several factors associated with cardiovascular risk.

RECENT FINDINGS

PPAR agonists have known effects on plasma lipoprotein levels, inflammation, and insulin resistance all of which influence the risk of cardiovascular disease. Recent studies provide more detail regarding the mechanisms behind these changes. PPAR-α activation in the enterocyte on HDL and chylomicron formation. PPAR-γ agonists reduce inflammation, in part, through direct effects on adipocytes and regulatory T cells within visceral adipose. PPAR-δ also has a relatively high expression in the macrophage. Incubation of macrophages with PPAR-δ agonists was shown to inhibit foam cell formation induced excessive levels of VLDL remnants.

SUMMARY

Treatments that activate PPAR-α, PPAR-γ, and PPAR-δ alone or in combination have the potential to reduce cardiovascular risk although multiple independent mechanisms. Treatment with PPAR agonists can reduce the burden of atherogenic postprandial lipoproteins and improve vascular function, reduce inflammation and inhibit foam cell formation. All of these would be expected to have favorable effects on cardiovascular risk. The challenge remains to develop compounds that maximize these potential cardiovascular benefits while minimizing undesirable effects of these compounds.

Regulation of lipid metabolism-related gene expression in whole blood cells of normo- and dyslipidemic men after fish oil supplementation

Background

Beneficial effects of omega-3 polyunsaturated fatty acids (n-3 PUFAs) on the lipid levels of dyslipidemic subjects are widely described in the literature. However, the underlying molecular mechanisms are largely unknown. The aim of this study was to investigate the effects of n-3 PUFAs on the expression of lipid metabolism-related genes in normo- and dyslipidemic men to unveil potential genes and pathways affecting lipid metabolism.

Methods

Ten normo- and ten dyslipidemic men were supplemented for twelve weeks with six fish oil capsules per day, providing 1.14 g docosahexaenoic acid and 1.56 g eicosapentaenoic acid. The gene expression levels were determined by whole genome microarray analysis and quantitative real-time polymerase chain reaction.

Results

Several transcription factors (peroxisome proliferator-activated receptor α (PPARα), retinoid X receptor (RXR) α, RXRγ, hepatic nuclear factor (HNF) 6, and HNF1ß) as well as other genes related to triacylglycerol (TG) synthesis or high-density lipoprotein (HDL-C) and cholesterol metabolism (phospholipids transfer protein, ATP-binding cassette sub-family G member 5, 2-acylglycerol O-acyltransferase (MOGAT) 3, MOGAT2, diacylglycerol O-acyltransferase 1, sterol O-acyltransferase 1, apolipoprotein CII, and low-density lipoprotein receptor) were regulated after n-3 PUFA supplementation, especially in dyslipidemic men.

Conclusion

Gene expression analyses revealed several possible molecular pathways by which n-3 PUFAs lower the TG level and increase the HDL-C and low-density lipoprotein level, whereupon the regulation of PPARα appear to play a central role.

Trial registration

ClinicalTrials.gov (ID: NCT01089231)

Stressing the heart of the matter: re-thinking the mechanisms underlying therapeutic effects of n-3 polyunsaturated fatty acids

Despite their clear therapeutic effects in coronary heart disease, use of n-3 polyunsaturated fatty acids (PUFAs) to treat other types of cardiovascular disease remains controversial, and serious obstacles exist in implementing them as a reliable and consistent drug therapy. The foremost of these is that a molecular mechanism and relevant dosages have not been firmly established in other forms of cardiovascular disease. In this brief review, we highlight the current state of knowledge regarding the mechanisms behind n-3 PUFA action in the cardiovascular system. We also propose the novel hypothesis that lipid peroxidation products derived from n-3 PUFAs may be driving much of their beneficial cardiovascular effects, particularly in the myocardium. We conclude by discussing evidence to support this hypothesis, and its possible clinical ramifications.

Quantitative genomics of 30 complex phenotypes in Wagyu x Angus F₁ progeny

In the present study, a total of 91 genes involved in various pathways were investigated for their associations with six carcass traits and twenty-four fatty acid composition phenotypes in a Wagyu×Angus reference population, including 43 Wagyu bulls and their potential 791 F₁ progeny. Of the 182 SNPs evaluated, 102 SNPs that were in Hardy-Weinberg equilibrium with minor allele frequencies (MAF>0.15) were selected for parentage assignment and association studies with these quantitative traits. The parentage assignment revealed that 40 of 43 Wagyu sires produced over 96.71% of the calves in the population. Linkage disequilibrium analysis identified 75 of 102 SNPs derived from 54 genes as tagged SNPs. After Bonferroni correction, single-marker analysis revealed a total of 113 significant associations between 44 genes and 29 phenotypes (adjusted P<0.05). Multiple-marker analysis confirmed single-gene associations for 10 traits, but revealed two-gene networks for 9 traits and three-gene networks for 8 traits. Particularly, we observed that TNF (tumor necrosis factor) gene is significantly associated with both beef marbling score (P=0.0016) and palmitic acid (C16:0) (P=0.0043), RCAN1 (regulator of calcineurin 1) with rib-eye area (P=0.0103), ASB3 (ankyrin repeat and SOCS box-containing 3) with backfat (P=0.0392), ABCA1 (ATP-binding cassette A1) with both palmitic acid (C16:0) (P=0.0025) and oleic acid (C18:1n9) (P=0.0114), SLC27A1(solute carrier family 27 A1) with oleic acid (C18:1n9) (P=0.0155), CRH (corticotropin releasing hormone) with both linolenic acid (OMEGA-3) (P=0.0200) and OMEGA 6:3 RATIO (P=0.0054), SLC27A2 (solute carrier family 27 A2) with both linoleic acid (OMEGA-6) (P=0.0121) and FAT (P=0.0333), GNG3 (guanine nucleotide binding protein gamma 3 with desaturase 9 (P=0.0115), and EFEMP1 (EGF containing fibulin-like extracellular matrix protein 1), PLTP (phospholipid transfer protein) and DSEL (dermatan sulfate epimerase-like) with conjugated linoleic acid (P=0.0042-0.0044), respectively, in the Wagyu x Angus F₁ population. In addition, we observed an interesting phenomenon that crossbreeding of different breeds might change gene actions to dominant and overdominant modes, thus explaining the origin of heterosis. The present study confirmed that these important families or pathway-based genes are useful targets for improving meat quality traits and healthful beef products in cattle.