Adipose modulation of high-density lipoprotein cholesterol: implications for obesity, high-density lipoprotein metabolism, and cardiovascular disease

Atherosclerosis, gut microbiome, and exercise in a meta-omics perspective: a literature review

Background

Cardiovascular diseases are the leading cause of death worldwide, significantly impacting public health. Atherosclerotic cardiovascular diseases account for the majority of these deaths, with atherosclerosis marking the initial and most critical phase of their pathophysiological progression. There is a complex relationship between atherosclerosis, the gut microbiome's composition and function, and the potential mediating role of exercise. The adaptability of the gut microbiome and the feasibility of exercise interventions present novel opportunities for therapeutic and preventative approaches.

Methodology

We conducted a comprehensive literature review using professional databases such as PubMed and Web of Science. This review focuses on the application of meta-omics techniques, particularly metagenomics and metabolomics, in studying the effects of exercise interventions on the gut microbiome and atherosclerosis.

Results

Meta-omics technologies offer unparalleled capabilities to explore the intricate connections between exercise, the microbiome, the metabolome, and cardiometabolic health. This review highlights the advancements in metagenomics and metabolomics, their applications in research, and examines how exercise influences the gut microbiome. We delve into the mechanisms connecting these elements from a metabolic perspective. Metagenomics provides insight into changes in microbial strains post-exercise, while metabolomics sheds light on the shifts in metabolites. Together, these approaches offer a comprehensive understanding of how exercise impacts atherosclerosis through specific mechanisms.

Conclusions

Exercise significantly influences atherosclerosis, with the gut microbiome serving as a critical intermediary. Meta-omics technology holds substantial promise for investigating the gut microbiome; however, its methodologies require further refinement. Additionally, there is a pressing need for more extensive cohort studies to enhance our comprehension of the connection among these element.

Modeling tissue co-regulation estimates tissue-specific contributions to disease

Integrative analyses of genome-wide association studies and gene expression data have implicated many disease-critical tissues. However, co-regulation of genetic effects on gene expression across tissues impedes distinguishing biologically causal tissues from tagging tissues. In the present study, we introduce tissue co-regulation score regression (TCSC), which disentangles causal tissues from tagging tissues by regressing gene-disease association statistics (from transcriptome-wide association studies) on tissue co-regulation scores, reflecting correlations of predicted gene expression across genes and tissues. We applied TCSC to 78 diseases/traits (average n = 302,000) and gene expression prediction models for 48 GTEx tissues. TCSC identified 21 causal tissue-trait pairs at a 5% false discovery rate (FDR), including well-established findings, biologically plausible new findings (for example, aorta artery and glaucoma) and increased specificity of known tissue-trait associations (for example, subcutaneous adipose, but not visceral adipose, and high-density lipoprotein). TCSC also identified 17 causal tissue-trait covariance pairs at 5% FDR. In conclusion, TCSC is a precise method for distinguishing causal tissues from tagging tissues.

BMI modifies HDL-C effects on coronary artery bypass grafting outcomes

BACKGROUND

Despite the recognized implications of high-density lipoprotein cholesterol (HDL-C) in cardiovascular diseases, the role of body mass index (BMI) in HDL-C association with cardiovascular outcomes remains unclear. This study investigated the possible modifying implications of BMI on the correlation between HDL-C and coronary artery bypass grafting (CABG) outcomes.

METHODS

The present cohort included isolated CABG patients (median follow-up: 76.58 [75.79-77.38] months). The participants were classified into three groups: 18.5 ≤ BMI < 25 (normal), 25 ≤ BMI < 30 (overweight), and 30 ≤ BMI < 35 (obese) kg/m². Cox proportional hazard models (CPHs) and restricted cubic splines (RCSs) were applied to evaluate the relationship between HDL-C and all-cause mortality as well as major adverse cardio-cerebrovascular events (MACCEs) in different BMI categories.

RESULTS

This study enrolled a total of 15,639 patients. Considering the final Cox analysis among the normal and overweight groups, HDL-C ≥ 60 was a significant protective factor compared to 40 < HDL-C < 60 for all-cause mortality (adjusted hazard ratio (aHR): 0.47, P: 0.027; and aHR: 0.64, P: 0.007, respectively). However, the protective effect of HDL-C ≥ 60 was no longer observed among patients with 30 ≤ BMI < 35 (aHR: 1.16, P = 0.668). RCS trend analyses recapitulated these findings; among 30 ≤ BMI < 35, no uniform inverse linear association was observed; after approximately HDL-C≈55, its increase was no longer associated with reduced mortality risk. RCS analyses on MACCE revealed a plateau effect followed by a modest rise in overweight and obese patients from HDL-C = 40 onward (nonlinear association).

CONCLUSIONS

Very high HDL-C (≥ 60 mg/dL) was not related to better outcomes among obese CABG patients. Furthermore, HDL-C was related to the post-CABG outcomes in a nonlinear manner, and the magnitude of its effects also differed across BMI subgroups.

HDL AND ITS SUBPOPULATION (HDL2 AND HDL3) PROMOTE CHOLESTEROL TRANSPORTERS EXPRESSION AND ATTENUATES INFLAMMATION IN 3T3-L1 MATURE ADIPOCYTES INDUCED BY TUMOR NECROSIS FACTOR ALPHA

Obesity activates inflammation causing dysfunction of adipocytes. Increasing high-density lipoprotein (HDL) levels in obesity may be beneficial in overcoming this effect. However, not much data is available on the effects of HDL and its subpopulations in inflamed adipocytes. The objective of this study was to investigate the effects of total HDL (tHDL) and the comparison between its subpopulations (HDL2 & HDL3) on protein and gene expression of cholesterol transporters, inflammation, and adipokines in TNF-α stimulated 3T3-L1 mature adipocytes. TNFα alone had lower adiponectin and higher protein and gene expression of IL-6 and NF-ĸβ (p65) compared to unstimulated adipocytes and these effects were attenuated by HDLs especially HDL3 (in most of the biomarkers). HDL and its subpopulation had higher cholesterol transporters expression in 3T3-L1 mature adipocytes induced by TNF-α compared to unstimulated cells. Increment of cholesterol transporters expression by HDL leads to reduce secretion of inflammatory markers [IL-6 & NF-kB (p65)] and visfatin and increases adiponectin secretion in the inflamed mature adipocytes. HDL exhibits beyond its reverse cholesterol transporter property by exhibiting anti-inflammatory effects thru the deactivation of NF-ĸβ (p65). This may contribute to reducing the progression of obesity-related complications.

Pcpe2, a Novel Extracellular Matrix Protein, Regulates Adipocyte SR-BI-Mediated High-Density Lipoprotein Uptake

Objective

To investigate the role of adipocyte Pcpe2 (procollagen C-endopeptidase enhancer 2) in SR-BI (scavenger receptor class BI)-mediated HDL-C (high-density lipoprotein cholesterol) uptake and contributions to adipose lipid storage.

Approach and Results

Pcpe2, a glycoprotein devoid of intrinsic proteolytic activity, is believed to participate in extracellular protein-protein interactions, supporting SR-BI- mediated HDL-C uptake. In published studies, Pcpe2 deficiency increased the development of atherosclerosis by reducing SR-BI-mediated HDL-C catabolism, but the biological impact of this deficiency on adipocyte SR-BI-mediated HDL-C uptake is unknown. Differentiated cells from Ldlr-/-/Pcpe2-/- (Pcpe2-/-) mouse adipose tissue showed elevated SR-BI protein levels, but significantly reduced HDL-C uptake compared to Ldlr-/- (control) adipose tissue. SR-BI-mediated HDL-C uptake was restored by preincubation of cells with exogenous Pcpe2. In diet-fed mice lacking Pcpe2, significant reductions in visceral, subcutaneous, and brown adipose tissue mass were observed, despite elevations in plasma triglyceride and cholesterol concentrations. Significant positive correlations exist between adipose mass and Pcpe2 expression in both mice and humans.

Conclusions

Overall, these findings reveal a novel and unexpected function for Pcpe2 in modulating SR-BI expression and function as it relates to adipose tissue expansion and cholesterol balance in both mice and humans.

How Clinically Relevant Is C-Reactive Protein for Blacks with Metabolic Syndrome to Predict Microalbuminuria?

Background: The metabolic syndrome (MetS) is associated with elevated urinary albumin (UA) excretion and C-reactive protein (CRP). However, potential differences in CRP levels on the association between individual components of the MetS and microalbuminuria (MA; 30-300 μg/mL) and/or UA (0-300 μg/mL) by race/ethnicity is unknown. Methods: We analyzed National Health and Nutrition Examination Surveys (NHANES) data, (1999-2010) for adults (≥20 years of age) with the MetS (N = 5700). The Sobel-Goodman mediation test examined the influence of CRP on the association between individual MetS components and both MA and UA by race/ethnicity. We applied machine learning models to predict UA. Results: CRP mediated the association between waist circumference (WC) and MA in Whites and Hispanics but not in Blacks. However, in general, the proportion of the total effect of MetS components on UA, mediated by CRP, was: 11% for high-density lipoprotein cholesterol (HDL-C) and 40% for WC (P < 0.001). In contrast to MA, the mediation effect of CRP for WC and UA was highest for Blacks (94%) compared with Whites (55%) or Hispanics (18%), P < 0.05. The prediction of an elevated UA concentration was increased in Blacks (∼51%) with the MetS when CRP was added to the random forest model. Conclusions: CRP mediates the association between UA and both HDL-C and WC in Whites and Blacks and between UA and WC in Hispanics. Moreover, the machine learning approach suggests that the incorporation of CRP may improve model prediction of UA in Blacks. These findings may favor screening for CRP in persons with the MetS, particularly in Blacks.

The role of long noncoding RNA in lipid, cholesterol, and glucose metabolism and treatment of obesity syndrome

Obesity syndromes, characterized by abnormal lipid, cholesterol, and glucose metabolism, are detrimental to human health and cause many diseases, including obesity and type II diabetes. Increasing evidence has shown that long noncoding RNA (lncRNA), transcripts longer than 200 nucleotides that are not translated into proteins, play an important role in regulating abnormal metabolism in obesity syndromes. For the first time, we systematically summarize how lncRNA is involved in complex obesity metabolic syndromes, including the regulation of lipid, cholesterol, and glucose metabolism. Moreover, we discuss lncRNA involvement in food intake that mediates obesity syndromes. Furthermore, this review might shed new light on a lncRNA-based strategy for the prevention and treatment of obesity syndromes. Recent investigations support that lncRNA is a novel molecular target of obesity syndromes and should be emphasized. Namely, lncRNA plays a crucial role in the development of obesity syndrome process. Various lncRNAs are involved in the process of lipid, cholesterol, and glucose metabolism by regulating gene transcription, signaling pathway, and epigenetic modification of metabolism-related genes, proteins, and enzymes. Food intake could also induce abnormal expression of lncRNA associated with obesity syndrome, especially high-fat diet. Notably, some nanomolecules and natural extracts may target lncRNAs, associated with obesity syndrome, as a potential treatment for obesity syndromes.

Pathophysiology of Type 2 Diabetes Mellitus

Type 2 Diabetes Mellitus (T2DM), one of the most common metabolic disorders, is caused by a combination of two primary factors: defective insulin secretion by pancreatic β-cells and the inability of insulin-sensitive tissues to respond appropriately to insulin. Because insulin release and activity are essential processes for glucose homeostasis, the molecular mechanisms involved in the synthesis and release of insulin, as well as in its detection are tightly regulated. Defects in any of the mechanisms involved in these processes can lead to a metabolic imbalance responsible for the development of the disease. This review analyzes the key aspects of T2DM, as well as the molecular mechanisms and pathways implicated in insulin metabolism leading to T2DM and insulin resistance. For that purpose, we summarize the data gathered up until now, focusing especially on insulin synthesis, insulin release, insulin sensing and on the downstream effects on individual insulin-sensitive organs. The review also covers the pathological conditions perpetuating T2DM such as nutritional factors, physical activity, gut dysbiosis and metabolic memory. Additionally, because T2DM is associated with accelerated atherosclerosis development, we review here some of the molecular mechanisms that link T2DM and insulin resistance (IR) as well as cardiovascular risk as one of the most important complications in T2DM.

Real-ambient exposure to air pollution exaggerates excessive growth of adipose tissue modulated by Nrf2 signal

Air pollution was becoming a global threat to the public health, which was primarily mediated by PM_2.5 induced cardiovascular diseases and pulmonary diseases. Recently, observational epidemiologic studies proposed the link between PM_2.5 and obesity. Consistently, the link was also supported by limited animal researches. However, the potential mechanism mediating the harmful effects of PM_2.5 was still elusive. In this study, we applied the "real-ambient exposure" system to conduct the experiments, which was closer to the status of ambient air pollution compared with the method of intratracheal instillation and concentrated air particles (CAPs) exposure system. Nuclear factor E2-related factor 2 (Nrf2) was previously reported to protect against inflammation and oxidative stress when exposed to PM_2.5. Here, we reported that Nrf2^-/- mice developed overgrowth of adipose tissue after "real-ambient exposure" to PM_2.5, compared to filtered air (FA) group. Consistently, compared to FA group, adipocytes from subcutaneous (sWAT) and gonadal (gWAT) white adipose tissue of Nrf2^-/- mice exhibited enlarged cell size in PM_2.5 exposure group. Furthermore, the levels of high-density lipoprotein (HDL) and low-density lipoprotein (LDL) in serum and liver of Nrf2^-/- mice were also altered statistically in PM_2.5 exposure group. Importantly, when the expression of lipogenic enzymes was analyzed, the levels of the related specific genes in adipose tissue and liver of Nrf2^-/- mice were altered in PM_2.5 exposure group. Interestingly, the key transcription factors modulating expression of lipogenic enzymes in liver of Nrf2^-/- mice were also found altered in PM_2.5 exposure group, such as peroxisome proliferator-activated receptor (PPARα, PPARγ). Taken together, our study mimicked the status of ambient air pollution, revealed new insights into the adverse effect of PM_2.5 exposure, provided new link between air pollution and overgrowth of adipose tissue, and supported the vital role of Nrf2 in mediating the side effects of PM_2.5.

New Perspectives on Atherogenic Dyslipidaemia and Cardiovascular Disease

Over the past few decades, atherogenic dyslipidaemia has become one of the most common phenotypic presentations of lipid abnormalities, being strongly and unequivocally associated with an increased risk of cardiovascular (CV) disease. Despite the excellent results achieved from statin and non-statin management of LDL cholesterol and CV events prevention, there still remains a significant residual risk, associated with the prevalence of non-LDL cholesterol lipid patterns characterised by elevated triglyceride levels, low HDL cholesterol, a preponderance of small and dense LDL particles, accumulation of remnant lipoproteins and postprandial hyperlipidaemia. These qualitative and quantitative lipid modifications are largely associated with insulin resistance, type 2 diabetes and obesity, the prevalence of which has grown to epidemic proportions throughout the world. In this review, we analyse the pathophysiology of this particular dyslipidaemia, its relationship with the development of atherosclerotic CV disease and, finally, briefly describe the therapeutic approaches, including changes in lifestyle and current pharmacological interventions to manage these lipid alterations aimed at preventing CV events.

Interaction between adipocytes and high-density lipoprotein:new insights into the mechanism of obesity-induced dyslipidemia and atherosclerosis

Obesity is the most common nutritional disorder worldwide and is associated with dyslipidemia and atherosclerotic cardiovascular disease. The hallmark of dyslipidemia in obesity is low high density lipoprotein (HDL) cholesterol (HDL-C) levels. Moreover, the quality of HDL is also changed in the obese setting. However, there are still some disputes on the explanations for this phenomenon. There is increasing evidence that adipose tissue, as an energy storage tissue, participates in several metabolism activities, such as hormone secretion and cholesterol efflux. It can influence overall reverse cholesterol transport and plasma HDL-C level. In obesity individuals, the changes in morphology and function of adipose tissue affect plasma HDL-C levels and HDL function, thus, adipose tissue should be the main target for the treatment of HDL metabolism in obesity. In this review, we will summarize the cross-talk between adipocytes and HDL related to cardiovascular disease and focus on the new insights of the potential mechanism underlying obesity and HDL dysfunction.

The Relation Between Metabolic Syndrome and Its Components with Breast Density in Postmenopausal Women

Background: Metabolic syndrome (MetS) could lead to an increase in fatty tissue that could be seen as a radiolucent image depicting breast density (BD) by a mammogram. We aimed to investigate the association between MetS and its separate components with BD among naturally postmenopausal women. Materials and Methods: Data of 494 postmenopausal patients who were admitted to our outpatient clinic between December 2012 and July 2015 were retrospectively reviewed. A total of 279 patients were in the without MetS group and 215 patients were in the with MetS group. Average BD percentage of the left and right breasts were measured. Basic characteristics, laboratory, and mammography results between the without MetS and the with MetS groups were compared. Results: The mean age of the patients was 53.20 ± 6.67 years in the without MetS group and 55.41 ± 6.56 years in the with MetS group. There were 219 (78.5%) patients in the without MetS group and 187 (86.9%) patients in the with MetS group with lower BD. The without MetS group had significantly higher BD scores than those patients in the with MetS group (P = 0.02). In correlation analysis, there was a negative correlation between fasting plasma glucose (FPG), systolic and diastolic blood pressures, waist circumference (WC), and BD scores. However, there was a positive correlation between high-density lipoprotein (HDL) and BD score (P = 0.046). In multivariate logistic regression analysis, it is found that lower body mass index (BMI) and parity were significantly associated with higher BD (P = 0.002 and P = 0.001; respectively). Conclusion: The lower BMI and parity may be associated with higher BD in postmenopausal women. In addition, higher HDL and lower FPG, blood pressure, triglyceride, and WC may be correlated with higher BD.

Diabetes alters the association between high-density lipoprotein subfractions and carotid intima-media thickness: The Brazilian Longitudinal Study of Adult Health (ELSA-Brasil)

INTRODUCTION

High-density lipoprotein cholesterol comprises a group of heterogeneous subfractions that might have differential effects on atherosclerosis. Moreover, prior investigations suggest that the presence of diabetes (T2D) modifies the impact of some subfractions on atherosclerosis. In this study, we aimed to evaluate the association between high-density lipoprotein cholesterol subfractions and carotid intima-media thickness in the baseline assessment of the Brazilian Longitudinal Study of Adult Health participants from the São Paulo investigation centre.

METHODS

We evaluated 3930 individuals between 35 and 74 years without previous cardiovascular disease not using lipid-lowering drugs. High-density lipoprotein cholesterol subfractions (HDL₂-C and HDL₃-C) were measured by vertical ultracentrifugation (vertical auto profile). The relationship between each high-density lipoprotein cholesterol subfraction and carotid intima-media thickness was analysed by multiple linear regression models.

RESULTS

Total high-density lipoprotein cholesterol, as well as HDL₂-C and HDL₃-C, was negatively associated with carotid intima-media thickness after adjustment for demographic data (all p < 0.001) and traditional risk factors (all p < 0.05). When stratified by T2D status, the HDL₂-C/HDL₃-C ratio showed a negative association with carotid intima-media thickness in participants with T2D ( p = 0.032), even after fully controlling for confounding variables, including total high-density lipoprotein cholesterol.

CONCLUSION

HDL₂-C, HDL₃-C and HDL₂/HDL₃-C ratio are inversely associated with carotid intima-media thickness after adjustment for traditional risk factors. Association of the HDL₂-C/HDL₃-C ratio is modified by the presence of diabetes, being more pronounced in diabetic individuals.

Antidiabetic and Antidyslipidemic Activities of the Aqueous Extract of Cochlospermum planchonii Leaves in Streptozotocin-Induced Diabetic Rats

BACKGROUND

Diabetes mellitus is considered one of the 5 principal causes of death in the world and is recognized as a global public health issue because of its multifactorial facets affecting essential biochemical processes in the body. This study investigated the antidiabetic and antidyslipidemic activities of the aqueous extract of Cochlospermum planchonii (C. planchonii) leaves in streptozotocin (STZ)-induced diabetic rats.

METHODS

Thirty adult female rats (Rattus norvegicus) weighing 153±3.41g were randomized into 6 groups of 5 animals each. STZ-induced diabetic rats were orally administered 50, 100, and 200 mg/kg body weight of the extract, respectively, once a day, and their blood glucose levels as well as variations of diabetes-associated biomarkers including alpha amylase, glucose-6-phosphate dehydrogenase (G6PDH), and lipid profile by the extract were monitored for 21 days. The results were expressed as means±SEMs and compared with repeated measures using SPSS, Data Editor, version 16.0.

RESULTS

The aqueous extract of C. planchonii leaves significantly reduced the blood glucose level in a dose-dependent manner, with the highest dose producing a 74.52% reduction after 21 days of administration, which compared significantly (P<0.01) with the control and metformin-treated groups. Similarly, STZ-induced diabetic mediated alterations in the serum lipids were significantly (P<0.01) restored by the extract. In addition, the aqueous extract of C. planchonii leaves significantly attenuated the decrease in the activity of G6PDH and the increase in the activity of α-AMY in the liver of the STZ-induced diabetic rats.

CONCLUSIONS

Overall, the aqueous extract of C. planchonii leaves could be used to manage diabetes and other related complications.

Antihyperlipidemic and hepatoprotective properties of selenium modified polysaccharide from Lachnum sp

Hyperlipidemia is one of the major health problem people suffering throughout the world, which is also a major risk factor for chronic heart disease that can lead to death. The current study was designed to investigate antihyperlipidemic and hepatoprotective effects of selenium modified exopolysaccharide of Lachnum sp. (SeLEP-1b) on high-fat induced mice model. Nitric acid-sodium selenite (HNO₃-Na₂SeO₃) method was used to selenize pure LEP-1b. FT-IR and ¹³C NMR results confirmed the modification of LEP-1b into SeLEP-1b. The main structure of SeLEP-1b was similar to the original structure of native LEP-1b and Se(O)OH group was attached to the O-6 position of C-6 in LEP-1b. Oral administration of LEP-1b and SeLEP-1b (200mg/kg) notably reduced the serum and liver lipids, atherogenic index, and enhanced the activities of antioxidant enzymes of hyperlipidemic mice, aswell improved the histopathological status of hepatic tissues. Hence, SeLEP-1b showed better effects than LEP-1b at the same doses. SeLEP-1b demonstrated promising lipid-lowering and liver protecting activities, which may be considered as a novel compound to treat hyperlipidemia and also act as a hepatoprotective agent.

Suppression of Type-II Diabetes with Dyslipidemia and Nephropathy by Peels of Musa cavendish Fruit

Musa cavendish, peels has local and traditional use to promote wound healing, hyperglycemia, ulceration etc. The present work investigated the lipid lowering; nephroprotective and glucose lowering properties of ethanolic extract of peels of Musa cavendish (EMC) in alloxan-induced diabetic rats. The EMC 250, 500 and 1000 mg/kg/day and the vehicle were administered orally to alloxan-induced diabetic rats (n = 6) for 3 weeks. Changes in plasma glucose, lipid profile along with kidney function before and after treatment with EMC were recorded. The ethanolic extract of peels of Musa cavendish reduced blood glucose, serum triglyceride, cholesterol, LDL cholesterol and creatinine levels and improvement in body weight, liver glycogen, serum HDL cholesterol, serum albumin and total protein level when compared with untreated rats. Musa cavendish has lipid lowering, nephroprotective and antidiabetic property by regulating glucose uptake in the liver and muscles by restoring the intracellular energy balance.

A fermented sorghum/millet-based beverage, Obiolor, extenuates high-fat diet-induced dyslipidaemia and redox imbalance in the livers of rats

BACKGROUND

Obiolor, a non-alcoholic beverage produced from fermented sorghum and millet malts, is widely consumed on a daily basis by the Igala tribe in Nigeria and is closely associated with good health. The effect of Obiolor on dyslipidaemia, protein oxidation, lipid peroxidation and DNA fragmentation in the liver of rats fed a high-fat diet was investigated.

RESULTS

High-fat diet-mediated alterations in liver and serum total cholesterol, triacylglycerol, high-density lipoprotein cholesterol, low-density cholesterol and very low-density lipoprotein cholesterol were significantly (P < 0.05) reversed by Obiolor. The beverage increased the activities of superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase and glucose 6-phosphate dehydrogenase in the liver of rats. These increases significantly (P < 0.05) attenuated the high-fat diet-mediated decrease in antioxidant enzymes. High-fat diet-mediated elevations in the levels of conjugated dienes, lipid hydroperoxides, malondialdehyde, protein carbonyl and DNA fragmentation in the livers of rats were lowered by the beverage.

CONCLUSION

This study showed that Obiolor extenuated high-fat diet-mediated dyslipidaemia, protein oxidation, lipid peroxidation and DNA fragmentation in rats.

Inflammation, adiposity, and atherogenic dyslipidemia in rheumatoid arthritis: is there a paradoxical relationship?

Dyslipidemia is highly prevalent in rheumatoid arthritis (RA) and appears to be present very early in the RA disease process, in some studies even before a diagnosis of clinical RA has been made. The association between lipid measures and the risk of cardiovascular disease (CVD) in RA appears to be paradoxical, whereby lower levels of total cholesterol (TC), low-density lipoprotein (LDL-C), and atherogenic ratios are associated with higher CVD risk. This may be due to the lipid-lowering effects of RA-related systemic inflammation. Therefore, standard CVD risk calculators have been shown to underperform in RA. Data also suggest that lipoprotein particle sizes and the apolipoprotein cargo of lipoproteins skew toward atherogenic dyslipidemia in RA and may contribute to the initiation and progression of atherosclerosis. Inflammatory burden in RA may also alter the anti-inflammatory and atheroprotective roles associated with high-density lipoprotein cholesterol (HDL-C). Adipose tissue is quantitatively increased in RA patients compared with matched non-RA controls and may be more inflamed and metabolically dysfunctional compared with an otherwise similar non-RA patient. In vitro, animal, and a handful of non-RA human, studies suggest that inflamed, metabolically dysfunctional adipose tissue contributes directly to lower HDL-C levels. In turn, lower HDL-C that has been altered functionally by inflammation may lead to expanded adipose mass and further adipose dysfunction and inflammation. In the last part of this review, we speculate how the RA disease state may recapitulate these processes.

Antidiabetic and antidyslipidemic activities of aqueous leaf extract of Dioscoreophyllum cumminsii (Stapf) Diels in alloxan-induced diabetic rats

ETHNOPHARMACOLOGICAL RELEVANCE

Dioscoreophyllum cumminsii (Stapf) Diels leaves are used in the management of diabetics in Nigeria. Thus, the antidiabetic activity of aqueous D. cumminsii leaf extract and its capability to halt oxidative stress and dyslipidemia in alloxan-induced diabetic rats was investigated.

METHODOLOGY

Antidiabetic was evaluated in alloxan-induced diabetes rats. Diabetic rats were treated with 50, 100 and 200mg/kg body weight of the extract.

RESULT

The aqueous extract of D. cumminsii leaves significantly reduced blood glucose level in a dose dependent manner with highest dose producing 72% reduction after 21 days administration, which was compared significantly (P<0.05) with the control group and glibenclamide treated groups. Similarly, aqueous extract of D. cumminsii significantly reversed reduction in insulin in alloxan-induced diabetic rats. Alloxan-induced diabetic mediated alterations in liver and serum cholesterol, triacylglycerides, high-density lipoprotein cholesterol (HDLc), low density lipoprotein cholesterol (LDLc) and very low-density lipoprotein cholesterol (VLDLc) were significantly (P<0.05) restored by the extract. Aqueous extract of D. cumminsii leaves significantly attenuated the decrease in the activities of superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase and glucose 6-phosphate dehydrogenase in the liver and pancreas of alloxan-induced diabetic rats. Elevation in the concentration of malondialdehyde was significantly (P<0.05) lowered by D. cumminsii leaves extract. The diabetic-mediated alteration in the architecture of liver was alleviated by the extract.

CONCLUSION

Overall, aqueous extract of D. cumminsii leaves at all doses investigated reduced blood glucose level and prevented oxidative stress and dyslipidemia in alloxan-induced diabetic rats.

Inhibition of soluble epoxide hydrolase in mice promotes reverse cholesterol transport and regression of atherosclerosis

Adipose tissue is the body largest free cholesterol reservoir and abundantly expresses ATP binding cassette transporter A1 (ABCA1), which maintains plasma high-density lipoprotein (HDL) levels. HDLs have a protective role in atherosclerosis by mediating reverse cholesterol transport (RCT). Soluble epoxide hydrolase (sEH) is a cytosolic enzyme whose inhibition has various beneficial effects on cardiovascular disease. The sEH is highly expressed in adipocytes, and it converts epoxyeicosatrienoic acids (EETs) into less bioactive dihydroxyeicosatrienoic acids. We previously showed that increasing EETs levels with a sEH inhibitor (sEHI) (t-AUCB) resulted in elevated ABCA1 expression and promoted ABCA1-mediated cholesterol efflux from 3T3-L1 adipocytes. The present study investigates the impacts of t-AUCB in mice deficient for the low density lipoprotein (LDL) receptor (Ldlr(-/-) mice) with established atherosclerotic plaques. The sEH inhibitor delivered in vivo for 4 weeks decreased the activity of sEH in adipose tissue, enhanced ABCA1 expression and cholesterol efflux from adipose depots, and consequently increased HDL levels. Furthermore, t-AUCB enhanced RCT to the plasma, liver, bile and feces. It also showed the reduction of plasma LDL-C levels. Consistently, t-AUCB-treated mice showed reductions in the size of atherosclerotic plaques. These studies establish that raising adipose ABCA1 expression, cholesterol efflux, and plasma HDL levels with t-AUCB treatment promotes RCT, decreasing LDL-C and atherosclerosis regression, suggesting that sEH inhibition may be a promising strategy to treat atherosclerotic vascular disease.

Vitamin B12 insufficiency induces cholesterol biosynthesis by limiting s-adenosylmethionine and modulating the methylation of SREBF1 and LDLR genes

Background

The dietary supply of methyl donors such as folate, vitamin B₁₂, betaine, methionine, and choline is essential for normal growth, development, and physiological functions through the life course. Both human and animal studies have shown that vitamin B₁₂ deficiency is associated with altered lipid profile and play an important role in the prediction of metabolic risk, however, as of yet, no direct mechanism has been investigated to confirm this.

Results

Three independent clinical studies of women (i) non-pregnant at child-bearing age, (ii) in early pregnancy, and (iii) at delivery showed that low vitamin B₁₂ status was associated with higher total cholesterol, LDL cholesterol, and cholesterol-to-HDL ratio. These results guided the investigation into the cellular mechanisms of induced cholesterol biosynthesis due to vitamin B₁₂ deficiency, using human adipocytes as a model system. Adipocytes cultured in low or no vitamin B₁₂ conditions had increased cholesterol and homocysteine levels compared to control. The induction of cholesterol biosynthesis was associated with reduced s-adenosylmethionine (AdoMet)-to-s-adenosylhomocysteine (AdoHcy) ratio, also known as methylation potential (MP). We therefore studied whether reduced MP could lead to hypomethylation of genes involved in the regulation of cholesterol biosynthesis. Genome-wide and targeted DNA methylation analysis identified that the promoter regions of SREBF1 and LDLR, two key regulators of cholesterol biosynthesis, were hypomethylated under vitamin B₁₂-deficient conditions, and as a result, their expressions and cholesterol biosynthesis were also significantly increased. This finding was further confirmed by the addition of the methylation inhibitor, 5-aza-2′-deoxycytidine, which resulted in increased SREBF1 and LDLR expressions and cholesterol accumulation in vitamin B₁₂-sufficient conditions. Finally, we observed that the expression of SREBF1, LDLR, and cholesterol biosynthesis genes were increased in adipose tissue of vitamin B₁₂ deficient mothers compared to control group.

Conclusions

Clinical data suggests that vitamin B₁₂ deficiency is an important metabolic risk factor. Regulation of AdoMet-to-AdoHcy levels by vitamin B₁₂ could be an important mechanism by which it can influence cholesterol biosynthesis pathway in human adipocytes.

Electronic supplementary material

The online version of this article (doi:10.1186/s13148-015-0046-8) contains supplementary material, which is available to authorized users.

Blighia sapida leaves halt elevated blood glucose, dyslipidemia and oxidative stress in alloxan-induced diabetic rats

ETHNOPHARMACOLOGICAL RELEVANCE

Blighia sapida leaves are used in the management of diabetes in Nigeria. Thus the antidiabetic activity of methanolic Blighia sapida leaf extract and its capability to halt oxidative stress and dyslipidemia in alloxan-induced diabetic rats were investigated.

METHODS

In vitro antioxidant activity of the extract (0.2-1.0mg/mL) was investigated using 2,2-diphenyl-1-1picrylhydrazyl (DPPH) radical, superoxide ion, hydrogen peroxide, and hydroxyl radical and ferric ion reducing system. Antidiabetic was evaluated in alloxan-induced diabetic rats.

RESULTS

The methanolic extract of Blighia sapida leaves at 1.0mg/mL scavenged DPPH, superoxide ion, hydrogen peroxide, and hydroxyl radical at 80.34%, 57.39%, 72.36% and 77.0% respectively, while ferric ion was significantly reduced. Single oral dose of the extract significantly reduced blood glucose level in a dose dependent manner with highest dose producing 18.6% reduction after 240min. Similar reduction was produced after 28 days of extract administration with the highest dose producing 65.65% reduction which compared significantly (P<0.05) with the control group and glibenclamide treated groups. Alloxan-induced diabetic mediated alterations in liver and serum cholesterol, triacylglycerides, high-density lipoprotein cholesterol (HDLc), low density lipoprotein (LDL) cholesterol and very low-density lipoprotein cholesterol (VLDLc) were significantly (P<0.05) restored by the extract. Methanolic extract of Blighia sapida leaves significantly attenuated the decrease in the activities of reactive oxygen species detoxifying enzymes (superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase and glucose 6-phosphate dehydrogenase) in the liver and pancreas of alloxan-induced diabetic rats. Elevation in the concentrations of malondialdehyde, conjugated dienes, lipid hydroperoxides, protein carbonyl, and fragmented DNA was significantly (P<0.05) lowered by Blighia sapida leaves extract.

CONCLUSION

Overall, methanolic extract of Blighia sapida leaves at all doses used reduced blood glucose level and prevented oxidative stress and dyslipidemia in alloxan-induced diabetic rats.

Cholesterol-induced inflammation and macrophage accumulation in adipose tissue is reduced by a low carbohydrate diet in guinea pigs

BACKGROUND/OBJECTIVES

The main objective of this study was to evaluate the effects of a high cholesterol (HC) dietary challenge on cholesterol tissue accumulation, inflammation, adipocyte differentiation, and macrophage infiltration in guinea pigs. A second objective was to assess whether macronutrient manipulation would reverse these metabolic alterations.

MATERIALS/METHODS

Male Hartley guinea pigs (10/group) were assigned to either low cholesterol (LC) (0.04g/100g) or high cholesterol (HC) (0.25g/100g) diets for six weeks. For the second experiment, 20 guinea pigs were fed the HC diet for six weeks and then assigned to either a low carbohydrate (CHO) diet (L-CHO) (10% energy from CHO) or a high CHO diet (H-CHO) (54% CHO) for an additional six weeks.

RESULTS

Higher concentrations of total (P < 0.005) and free (P < 0.05) cholesterol were observed in both adipose tissue and aortas of guinea pigs fed the HC compared to those in the LC group. In addition, higher concentrations of pro-inflammatory cytokines in the adipose tissue (P < 0.005) and lower concentrations of anti-inflammatory interleukin (IL)-10 were observed in the HC group (P < 0.05) compared to the LC group. Of particular interest, adipocytes in the HC group were smaller in size (P < 0.05) and showed increased macrophage infiltration compared to the LC group. When compared to the H-CHO group, lower concentrations of cholesterol in both adipose and aortas as well as lower concentrations of inflammatory cytokines in adipose tissue were observed in the L-CHO group (P < 0.05). In addition, guinea pigs fed the L-CHO exhibited larger adipose cells and lower macrophage infiltration compared to the H-CHO group.

CONCLUSIONS

The results of this study strongly suggest that HC induces metabolic dysregulation associated with inflammation in adipose tissue and that L-CHO is more effective than H-CHO in attenuating these detrimental effects.

Omental adipose tissue gene expression, gene variants, branched-chain amino acids, and their relationship with metabolic syndrome and insulin resistance in humans

Obesity is a complex disorder caused by several factors. Thus, the aim of the present study was to assess whether the expression of genes in the omental white adipose tissue (AT) of subjects with insulin resistance (IR) or metabolic syndrome (MetS) is associated with an elevation in serum branched-chain amino acids (BCAAs) and whether this response depends on specific genetic variants. Serum BCAA concentration, the adipocyte area, and gene variants of PPARγ, ABCA1, FTO, TCF7L2, GFOD2,BCAT2, and BCKDH were determined in 115 Mexican subjects. The gene expression in the AT and adipocytes of BCAT, BCKDH E1α, C/EBPα, PPARγ2, SREBP-1, PPARα, UCP1, leptin receptor, leptin, adiponectin, and TNFα was measured in 51 subjects. Subjects with IR showed higher values for the BMI, HOMA-IR, and adipocyte area and higher levels of serum glucose, insulin, leptin, and C-reactive protein, as well as an elevation of the AT gene expression of SREBP-1, leptin, and TNFα and a significant reduction in the expression of adiponectin, BCAT2, and BCKDH E1α, compared with non-IR subjects. The presence of MetS was associated with higher HOMA-IR as well as higher serum BCAA concentrations. Subjects with the genetic variants for BCAT2 and BCKDH E1 α showed a lower serum BCAA concentration, and those with the ABCA1 and FTO gene variant showed higher levels of insulin and HOMA-IR than non-IR subjects. AT dysfunction is the result of a combination of the presence of some genetic variants, altered AT gene expression, the presence of MetS risk factors, IR, and serum BCAA concentrations.

MicroRNAs in Lipid Metabolism and Atherosclerosis

BACKGROUND: MicroRNAs (miRNA) are mediators of post-transcriptional gene expression that likely regulate most biological pathways and networks. The study of miRNAs is a rapidly emerging field; recent findings have revealed a significant role for miRNAs in atherosclerosis and lipoprotein metabolism.CONTENT: Results from recent studies demonstrated a role for miRNAs in endothelial integrity, macrophage inflammatory response to oxidized low-density lipoprotein, vascular smooth muscle cell proliferation and cholesterol synthesis. These mechanisms are all vital to the initiation and proliferation of atherosclerosis and cardiovascular disease. The importance of miRNAs has recently been recognized in cardiovascular sciences and miRNAs will likely become an integral part of our fundamental comprehension of atherosclerosis and lipoprotein metabolism. The extensive impact of miRNA mediated gene regulation and the relative ease of in vivo applicable modifications highlight the enormous potential of miRNA-based therapeutics in cardiovascular diseases.SUMMARY: miRNA studies in the field of lipid metabolism and atherosclerosis are in their infancy, and thus there is tremendous opportunity for discovery in this understudied area. The ability to target miRNAs in vivo through delivery of miRNA-mimics to enhance miRNA function, or antimiRNAs which inhibit miRNAs, has opened new avenues for the development of therapeutics for dyslipidemias and atherosclerosis, offers a unique approach to treating disease by modulating entire biological pathways. These exciting findings support the development of miRNA antagonists as potential therapeutics for the treatment of dyslipidaemia, atherosclerosis and related metabolic diseases.KEYWORDS: atherosclerosis, lipoprotein, HDL, miRNA

MicroRNA control of high-density lipoprotein metabolism and function

Recent discoveries of microRNAs (miRNAs) that control high-density lipoprotein abundance and function have expanded our knowledge of the mechanisms regulating this important lipoprotein subclass. miRNAs have been shown to regulate gene networks that control high-density lipoprotein biogenesis and uptake, as well as discrete steps in the reverse cholesterol transport pathway. Furthermore, high-density lipoprotein itself has been shown to transport miRNAs selectively in health and disease, offering new possibilities of how this lipoprotein may alter gene expression in distal target cells and tissues. Collectively, these discoveries offer new insights into the mechanisms governing high-density lipoprotein metabolism and function and open new avenues for the development of therapeutics for the treatment of cardiovascular disease.

Hypolipidaemic effects and mechanisms of the main component of Opuntia dillenii Haw. polysaccharides in high-fat emulsion-induced hyperlipidaemic rats

The antihyperlipidaemic effects of ODP-Ia, one of the main components of Opuntia dillenii Haw. polysaccharides, were studied. Gavage administration of ODP-Ia was observed to significantly decrease serum lipid levels and to increase serum high-density lipoprotein cholesterol level in hyperlipidaemic rats. Similar suppressive patterns were also seen in hepatic total cholesterol and triglyceride levels. Moreover, the ODP-Ia administration significantly increased serum lecithin:cholesterol acyltransferase activity, increased the production of serum NO, inhibited hepatic HMG-CoA reductase activity, augmented serum and hepatic superoxide dismutase activities and decreased the serum and hepatic malondialdehyde contents in hyperlipidaemic rats. In addition, a histopathological examination revealed that ODP-Ia administration significantly suppressed inflammatory cell infiltration and the expression of VCAM-1. Together, these results indicate that ODP-Ia is a potential natural product for the treatment of hyperlipidaemia-related diseases by improving antioxidant levels, modulating the activities of enzymes involved in cholesterol metabolism, promoting the production of NO and suppressing the expression of VCAM-1, thereby suppressing lipid accumulation and inflammatory cell infiltration.