Overproduction of very low-density lipoproteins is the hallmark of the dyslipidemia in the metabolic syndrome

Triglyceride-Rich Lipoprotein Cholesterol, Small Dense LDL Cholesterol, and Incident Cardiovascular Disease

BACKGROUND

Elevated triglyceride-rich lipoprotein (TRL) and small-dense low-density lipoprotein (sdLDL) particles are hallmarks of atherogenic dyslipidemia, and their cholesterol content is hypothesized to drive atherosclerotic risk. Prospective epidemiological data pertaining to cholesterol content of TRLs and sdLDL in primary prevention populations are mostly limited to coronary heart disease.

OBJECTIVES

The purpose of this study was to prospectively evaluate whether triglyceride-rich lipoprotein cholesterol (TRL-C) and small-dense low-density lipoprotein cholesterol (sdLDL-C) concentrations associate with composite and individual incident cardiovascular disease (CVD) outcomes including myocardial infarction (MI), ischemic stroke (IS), and peripheral artery disease (PAD).

METHODS

In a prospective case-cohort study within the Women's Health Study, TRL-C and sdLDL-C (mg/dl) were directly measured in baseline blood specimens of case subjects (n = 480) and the reference subcohort (n = 496). Risk associations were evaluated for total CVD (MI, IS, PAD, and CVD death), coronary and cerebrovascular disease (MI, IS, CVD death), and individual outcomes (MI, IS, and PAD). Models were adjusted for traditional risk factors, low-density lipoprotein cholesterol, and high-sensitivity C-reactive protein.

RESULTS

The risk of both composite outcomes significantly increased across quartiles of TRL-C and sdLDL-C. TRL-C was significantly associated with MI and PAD (MI hazard ratio [HR]_Q4: 3.05 [95% confidence interval (CI): 1.46 to 6.39]; p_trend = 0.002; PAD HR_Q4: 2.58 [95% CI: 1.18 to 5.63]; p_trend = 0.019), whereas sdLDL-C was significantly associated with MI alone (HR_Q4: 3.71 [95% CI: 1.59 to 8.63]; p_trend < 0.001). Both markers weakly associated with IS. Association patterns were similar for continuous exposures and, for TRL-C, among subjects with low atherogenic particle concentrations (apolipoprotein B <100 mg/dl).

CONCLUSIONS

TRL-C strongly associates with future MI and PAD events, whereas sdLDL-C strongly associates with MI alone. These findings signal that the cholesterol content of TRLs and sdLDL influence atherogenesis independently of low-density lipoprotein cholesterol, and high sensitivity C-reactive protein, with potentially different potency across vascular beds. (Women's Health Study; NCT00000479).

Dihydroceramides in Triglyceride-Enriched VLDL Are Associated with Nonalcoholic Fatty Liver Disease Severity in Type 2 Diabetes

Plasma dihydroceramides are predictors of type 2 diabetes and related to metabolic dysfunctions, but the underlying mechanisms are not characterized. We compare the relationships between plasma dihydroceramides and biochemical and hepatic parameters in two cohorts of diabetic patients. Hepatic steatosis, steatohepatitis, and fibrosis are assessed by their plasma biomarkers. Plasma lipoprotein sphingolipids are studied in a sub-group of diabetic patients. Liver biopsies from subjects with suspected non-alcoholic fatty liver disease are analyzed for sphingolipid synthesis enzyme expression. Dihydroceramides, contained in triglyceride-rich very-low-density lipoprotein (VLDL), are associated with steatosis and steatohepatitis. Expression of sphingolipid synthesis enzymes is correlated with histological steatosis and inflammation grades. In conclusion, association of plasma dihydroceramides with nonalcoholic fatty liver might explain their predictive character for type 2 diabetes. Our results suggest a relationship between hepatic sphingolipid metabolism and steatohepatitis and an involvement of dihydroceramides in the synthesis/secretion of triglyceride-rich VLDL, a hallmark of NAFLD and type 2 diabetes dyslipidemia.

Plasma dihydroceramides are associated with NAFLD severity in type 2 diabetic patients

Plasma dihydroceramides are found in triglyceride-enriched VLDL

A role for dihydroceramide in triglyceride-rich VLDL synthesis/secretion is suggested

Expression of enzymes of hepatic sphingolipid synthesis increases with NAFLD severity

The Prevalence of Metabolic Syndrome in Ethiopian Population: A Systematic Review and Meta-analysis

Background

The metabolic syndrome is a clustering of hyperglycemia/insulin resistance, hypertension, dyslipidemia, and obesity which are risk factors for cardiovascular disease, type 2 diabetes and stroke, and all-cause mortality. The burden of metabolic syndrome is emerging alarmingly in low- and middle-income countries such as Ethiopia; however, there is lack of comprehensive estimation. This study aimed to determine the pooled prevalence of metabolic syndrome in Ethiopia.

Methods

This systematic review and meta-analysis included original articles of observational studies published in the English language. Searches were carried out in PubMed, Google Scholar, and Africa Journals from conception to August 2020. A random-effects model was used to estimate the pooled prevalence of metabolic syndrome in Ethiopia. Heterogeneity was assessed using the I 2 statistic. Subgroup analysis was also conducted based on sex/gender and study subjects. Egger's test was used to assess publication bias.

Results

Electronic and gray literature search retrieved 942 potentially relevant papers. After removing duplicates and screening with eligibility criteria, twenty-eight cross-sectional studies were included in this meta-analysis. The pooled prevalence of metabolic syndrome in Ethiopia was found to be 34.89% (95% CI: 26.77, 43.01) and 27.92% (95% CI: 21.32, 34.51) by using NCEP/ATP III and IDF criteria, respectively. The weighted pooled prevalence of metabolic syndrome was higher in females 36.74% (95% CI: 20.72, 52.75) and 34.09% (95% CI: 26.68, 41.50) compared to males 22.22% (95% CI: 14.89, 29.56) and 24.82% (95% CI: 18.34, 31.31) by using IDF and NCEP/ATP III criteria, respectively. Subgroup analysis based on the study subjects using NCEP/ATP III showed that the weighted pooled prevalence was 63.78%(95% CI: 56.17, 71.40), 44.55% (95% CI: 30.71, 52.38), 23.09% (95% CI: 19.74, 26.45), 20.83% (95% CI: 18.64, 23.01), and 18.45% (95% CI: 13.89, 23.01) among type 2 diabetes patients, hypertensive patients, psychiatric patients, HIV patients on HAART, and working adults, respectively. The most frequent metabolic syndrome components were low HDL-C 51.0% (95% CI: 42.4, 59.7) and hypertriglyceridemia 39.7% (95% CI: 32.8, 46.6).

Conclusions

The findings revealed an emerging high prevalence of metabolic syndrome in Ethiopia. Therefore, early intervention is required for the primary prevention of the occurrence of metabolic syndrome and the further reduction of the morbidity and mortality related to it.

Uncovering the role of apolipoprotein C-III in insulin resistance

Apolipoprotein C-III (apoC-III) is a small protein that is predominantly synthesized in the liver and mainly resides at the surface of triglyceride-rich lipoproteins. Its expression is upregulated by glucose and reduced by insulin, with enhanced apoC-III promoting hypertriglyceridemia and inflammation in vascular cells. The protein is also elevated in patients with diabetes, suggesting that enhanced apoC-III levels might contribute to the development of type 2 diabetes mellitus. The present review focuses on the key mechanisms by which apoC-III could promote type 2 diabetes mellitus, including exacerbation of insulin resistance in skeletal muscle, activation of β-cell apoptosis, promotion of weight gain through its effects on white adipose tissue and hypothalamus, and attenuation of the beneficial effects of high-density lipoproteins on glucose metabolism. Therapeutic strategies aimed at reducing apoC-III levels may not only reduce hypertriglyceridemia but also might improve insulin resistance, thus delaying the development of type 2 diabetes mellitus.

Plasma lipoprotein profile from nonalcoholic steatohepatitis model rats

We recently revealed that increases in particle sizes of very-low-density lipoproteins (VLDL) are highly correlated with the progression of nonalcoholic fatty liver disease (NAFLD)/nonalcoholic steatohepatitis (NASH), and VLDL particle size may be a minimally invasive indicator of these hepatic disorders. Methionine and choline-deficient (MCD) diet fed animals are usually used as a NASH model; however, the application of this minimally invasive biomarker in MCD diet fed animals remains unclear. In the present study, we measured the levels of liver disease markers and plasma lipoprotein profiles in MCD diet fed rats, and compared them with those of normal diet fed rats. Assessing lipoprotein profiles showed marked increases in VLDL particle sizes in MCD diet fed rats with pathologically and biochemically NASH-like features.

Pathogenesis and remission of type 2 diabetes: what has the twin cycle hypothesis taught us?

Type 2 diabetes has been regarded a complex multifactorial disease that lead to serious health complications including high cardiovascular risks. The twin cycle hypothesis postulated that both hepatic insulin resistance and dysfunction rather than death of beta (β) cell determine diabetes onset. Several studies were carried out to test this hypothesis, and all demonstrated that chronic excess calorie intake and ectopic fat accumulation within the liver and pancreas are fundamental to the development of this disease. However, these recent research advances cannot determine the exact cause of this disease. In this review, the major factors that contribute to the pathogenesis and remission of type 2 diabetes will be outlined. Importantly, the effect of disordered lipid metabolism, characterized by altered hepatic triglyceride export will be discussed. Additionally, the observed changes in pancreas morphology in type 2 diabetes will be highlighted and discussed in relation to β cell function.

Carbohydrate-rich Meals Have no Impact on Post-prandial Lipid Parameters in Indians with Subclinical and Overt Primary Hypothyroidism

BACKGROUND AND AIMS

The impact of altered cholesterol metabolism on post-prandial lipids in Indians with hypothyroidism is not known. This study evaluated the impact of overt primary hypothyroidism (OPH) and subclinical hypothyroidism (ScH) on post-prandial lipids after a standardised, carbohydrate-rich, mixed meal.

METHODS

Endocrinology outpatients were screened for possible inclusion into the study. Patients >18 years of age with hypothyroidism who were not taking levothyroxine and who did not present with any comorbidities underwent biochemical evaluation following a carbohydrate-rich, mixed meal. Assessments included total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein-cholesterol (HDL-C), triglycerides, lipoprotein-A (Lp-A), apolipoprotein-A1 (apo-A1), apolipoprotein-B (apo-B), insulin and fasting glucose. Assessments were carried out 1 hour, 2 hours and 4 hours after the meal. Patients were compared against healthy matched controls recruited from healthcare professionals in the hospital (asymptomatic and apparently healthy nursing staff, reception staff and ward staff).

RESULTS

Data from 194 patients (161 with ScH and 33 with OPH) and 40 euthyroid controls were analysed. Anthropometry, body mass index, glycaemia and insulin resistance were comparable among patients with OPH and ScH, and controls. LDL-C and Lp-A were significantly higher in those with OPH, compared with ScH and controls, at baseline, 1 hour, 2 hours and 4 hours after mixed meal consumption (all p<0.05). There was progressive and similar decline in post-prandial TC, LDL-C and Lp-A in all three groups. Triglycerides were similar among the OPH, ScH and control groups, both in fasting and post-prandial state, with a progressive and similar increase in post-prandial triglycerides in all three groups.

CONCLUSION

This study demonstrated that severity of hypothyroidism had no impact on post-prandial TC, LDL-C and Lp-A. In addition, hypothyroidism had no impact on post-prandial triglycerides. Therefore, we conclude that lipid profile can be reliably estimated in a non-fasting state in individuals with ScH and OPH.

The Atherogenic Index of Plasma is Independently Associated with Symptomatic Carotid Artery Stenosis

INTRODUCTION

Small, dense low-density lipoprotein (sdLDL) is strongly associated with symptomatic carotid artery stenosis, but is not routinely evaluated in ischemic stroke patients. A method using the logarithmic transformation of the ratio of the plasma concentration of triglycerides (TGY) to HDL-cholesterol (HDL-C)[(Log[TGY/HDL-C])] has been described as a surrogate marker for sdLDL termed the atherogenic index of plasma (AIP).

OBJECTIVE

To determine if the AIP is independently associated with symptomatic carotid artery stenosis.

METHODS

We conducted a single center case-controlled study using a sample of ischemic stroke patients and compared risk factors of patients with and without symptomatic carotid artery stenosis. A multivariate logistic regression model was used to determine if the AIP divided into four quartiles was independently associated with symptomatic carotid artery stenosis. This model was compared to three other lipid models. Associations between non-lipid variables and the AIP were also identified.

RESULTS

31 cases of ischemic stroke due to symptomatic carotid artery stenosis and 236 controls of ischemic stroke not due to carotid artery stenosis were identified. Of the four lipid models assessed, only the model including the AIP (model 4) was found to be significantly associated with symptomatic carotid artery stenosis. The odd's ratio (OR) for quartile 3 was 3.82 (95% CI 1.03-14.17) and the OR for quartile 4 was 4.13 (95% CI 1.09-15.54) using quartile 1 as a reference. Metabolic syndrome was the only variable associated with the AIP (OR 5.06 95% CI 2.6-9.7).

CONCLUSION

At our single center, the AIP was the only lipid parameter independently associated with symptomatic carotid artery stenosis; and metabolic syndrome was independently associated with the AIP. The AIP may serve as a useful surrogate of sdLDL in patients with symptomatic carotid artery stenosis.

The metabolic syndrome - What is it and how should it be managed?

A cluster of metabolic factors have been merged into an entity named the metabolic syndrome. Although the characteristics of this syndrome have varied over time the presently used definition was established in 2009. The presence of three abnormal findings out of five components qualifies a person for the metabolic syndrome: elevated waist circumference, elevated triglycerides, reduced high-density lipoprotein cholesterol, elevated blood pressure and elevated fasting plasma glucose. Cut points have been defined for all components apart from waist circumference, for which national or regional values are used. The metabolic syndrome predicts cardiovascular disease and type 2 diabetes. This associated risk does not exceed its components whereof elevated blood pressure is the most frequent. A successful management should, however, address all factors involved. The management is always based on healthy lifestyle choices but has not infrequently to be supported by pharmacological treatment, especially blood pressure lowering drugs. The metabolic syndrome is a useful example of the importance of multiple targets for preventive interventions. To be successful management has to be individualized not the least when it comes to pharmacological therapy. Frail elderly people should not be over-treated. Knowledge transfer of how risk factors act should be accompanied by continuous trust building and motivation. In complex situations with a mix of biological risk factors, adverse social conditions and unhealthy lifestyle, everything cannot be changed at once. It is better to aim for small steps that are lasting than large, unsustainable steps with relapses to unhealthy behaviours. A person with the metabolic syndrome will always be afflicted by its components, which is the reason that management has to be sustained over a very long time. This review summarizes the knowledge on the metabolic syndrome and its management according to present state of the art.

Dysregulated lipid metabolism links NAFLD to cardiovascular disease

Background

Non-alcoholic fatty liver disease (NAFLD) is rapidly becoming a global health problem. Cardiovascular diseases (CVD) are the most common cause of mortality in NAFLD patients. NAFLD and CVD share several common risk factors including obesity, insulin resistance, and type 2 diabetes (T2D). Atherogenic dyslipidemia, characterized by plasma hypertriglyceridemia, increased small dense low-density lipoprotein (LDL) particles, and decreased high-density lipoprotein cholesterol (HDL-C) levels, is often observed in NAFLD patients.

Scope of review

In this review, we highlight recent epidemiological studies evaluating the link between NAFLD and CVD risk. We further focus on recent mechanistic insights into the links between NAFLD and altered lipoprotein metabolism. We also discuss current therapeutic strategies for NAFLD and their potential impact on NAFLD-associated CVD risk.

Major conclusions

Alterations in hepatic lipid and lipoprotein metabolism are major contributing factors to the increased CVD risk in NAFLD patients, and many promising NASH therapies in development also improve dyslipidemia in clinical trials.

Direct assessment of very-low-density lipoprotein by mass sensitive sensor with molecularly imprinted polymers

Very-low-density lipoprotein (VLDL) contributes to the buildup of atherosclerotic plaque in the arteries and can lead to coronary heart disease. In clinical laboratory testing, the cholesterol content of VLDL (VLDL-C) cannot be assessed directly by the enzymatic colorimetric assay as it can for other lipoproteins, due to lack of a specific sample pretreatment technique. VLDL concentration relies on analyzing the endogenous triglycerides (TGs) bound in its particles and then converting to the VLDL-C estimate TGs/5. This estimation is valid for at least 12 h-fasted serum when exogenous TGs attached to chylomicrons (CMs) have been cleared from the circulation. A quartz crystal microbalance (QCM)-based sensor was generated using biomimetic sensing elements as a molecularly imprinted polymer (MIP) to directly measure actual VLDL. A novel VLDL-MIP was synthesized using methacrylic acid (MAA) and N-vinylpyrrolidone (VP) in the ratio 1:1 (v/v) as functional monomers in the presence of N, N'-(1,2-dihydroxyethylene) bis(acrylamide) (DHEBA) as a crosslinking agent. The VLDL-MIP sensor showed high sensitivity with a linear response from 2.5 mg dL^-1 to 100 mg dL^-1 of VLDL-C with a limit of detection at 1.5 mg dL^-1. Recoveries of 96-103% were achieved when the VLDL-MIP sensor was used for VLDL assessment at 38-71 mg dL^-1 concentrations. Repeatability and reproducibility of the sensor were very good with coefficients of variation at 1.63-4.74% and 4.25-9.04%, respectively. The sensor demonstrated low cross-reactivity with other lipoproteins; 6-7% of low-density lipoprotein (LDL) signals, 2-4% high-density lipoprotein (HDL), and 1% CMs compared to the signal of VLDL. Sensor results for 12 h-fasted serum and non-fasted serum correlated well with VLDL estimates TGs/5, with coefficients of determination (R²) at 0.9967 and 0.9932, respectively. This new sensor offers a new strategy for direct VLDL assessment from non-fasted serum without other sample pretreatment steps than dilution.

Non-alcoholic fatty liver disease and transient elastography

Nonalcoholic fatty liver disease (NAFLD) is a serious condition that can lead to fibrosis, cirrhosis, and hepatocellular carcinoma. NAFLD is associated with metabolic syndrome (MetS) and all of its components. According to data, around 25-30% of population has NAFLD. Giving the growing incidence of MetS, obesity and diabetes mellitus type 2, NAFLD related terminal-stage liver disease is becoming prevailing indication for liver transplantation. In order to prevent terminal stage of this disease, it is crucial to determine those that are in risk group, to modify their risk factors and monitor their potential progression. In the absence of other causes of chronic liver disease, the prime diagnosis of NAFLD in daily clinical practice includes anamnesis, laboratory results (increased levels of aminotransferases and gammaglutamil transferases) and imaging methods. The biggest challenge with NAFLD patients is to differentiate simple steatosis from nonalcoholic steatohepatitis, and detection of fibrosis, that is the main driver in NAFLD progression. The gold standard for NAFLD diagnosis still remains the liver biopsy (LB). However, in recent years many noninvasive methods were invented, such as transient elastography (TE). TE (FibroScan®, Echosens, Paris, France) is used for diagnosis of pathological differences of liver stiffness measurement (LSM) and controlled attenuation parameter (CAP). Investigations in the last years have confirmed that elastographic parameters of steatsis (CAP) and fibrosis (LSM) are reliable biomarkers to non-invasively assess liver steatosis and fibrosis respectively in NAFLD patients. A quick, straightforward and non-invasive method for NAFLD screening in patients with MetS components is TE-CAP. Once diagnosed, the next step is to determine the presence of fibrosis by LSM which should point out high risk patients. Those patients should be referred to hepatologists. LB may be avoided in a substantial number of patients if TE with CAP is used for screening.

R-α-Lipoic Acid and 4-Phenylbutyric Acid Have Distinct Hypolipidemic Mechanisms in Hepatic Cells

The constitutive activation of the mechanistic target of rapamycin complex 1 (mTORC1) leads to the overproduction of apoB-containing triacylglycerol-rich lipoproteins in HepG2 cells. R-α-lipoic acid (LA) and 4-phenylbutyric acid (PBA) have hypolipidemic function but their mechanisms of action are not well understood. Here, we reported that LA and PBA regulate hepatocellular lipid metabolism via distinct mechanisms. The use of SQ22536, an inhibitor of adenylyl cyclase, revealed cAMP’s involvement in the upregulation of CPT1A expression by LA but not by PBA. LA decreased the secretion of proprotein convertase subtilisin/kexin type 9 (PCSK9) in the culture media of hepatic cells and increased the abundance of LDL receptor (LDLR) in cellular extracts in part through transcriptional upregulation. Although PBA induced LDLR gene expression, it did not translate into more LDLR proteins. PBA regulated cellular lipid homeostasis through the induction of CPT1A and INSIG2 expression via an epigenetic mechanism involving the acetylation of histone H3, histone H4, and CBP-p300 at the CPT1A and INSIG2 promoters.

Effects of Daily Consumption of an Aqueous Dispersion of Free-Phytosterols Nanoparticles on Individuals with Metabolic Syndrome: A Randomised, Double-Blind, Placebo-Controlled Clinical Trial

Metabolic syndrome (MS) affects up to 40% of the population and is associated with heart failure, stroke and diabetes. Phytosterols (PS) could help to manage one or more MS criteria. The purpose of this study was to evaluate the therapeutic effect of daily supplementation of an aqueous dispersion of 2 g of free-phytosterols nanoparticles in individuals with MS over six months of intervention, compared with placebo. This double-blind study included 202 participants with MS randomly assigned into phytosterol (n = 102) and placebo (n = 100) groups. Participants were assessed at baseline, 4, 12 and 24 weeks. General health questions, anthropometric measurements and blood parameters were analysed. At week 24, the proportion of participants with high triglycerides (≥150 mg/dL) in the phytosterol group was 15.65% lower than in the placebo group (p-value = 0.023). Similarly, half of the participants in the phytosterol group decreased their waist circumference up to 4 cm compared with 0 cm in the placebo group (p-value = 0.0001). We reported no adverse effects (diarrhoea or vitamin D reduction); nonetheless, almost 70% of participants in the phytosterol group self-reported an improvement in bowel habits. Daily intake of free-PS nanoparticles improved some MS criteria; therefore, it might be a promising adjuvant therapy for individuals with MS (NCT02969720).

Review article: the impact of liver-directed therapies on the atherogenic risk profile in non-alcoholic steatohepatitis

BACKGROUND

Patients with non-alcoholic fatty liver disease (NAFLD), the most common cause of chronic liver disease, are at higher risk of cardiovascular disease (CVD) and associated mortality. Therefore, it is important to understand how new therapies for non-alcoholic steatohepatitis (NASH) may impact CVD risk factors in these patients.

AIMS

To summarise the effects of drug therapies on lipid and lipoprotein levels in patients with NASH and provide insight into the potential mechanisms for the observed changes.

METHODS

PubMed searches of the literature were performed and results were compiled.

RESULTS

Recent clinical trials have highlighted the safety and efficacy of drug candidates for the treatment of NASH. Several agents have shown improvements in the histological features of NASH and liver function. Pioglitazone, a drug that is currently available for type 2 diabetes and may be useful for NASH, exhibits beneficial effects on lipids. However, agents such as farnesoid X receptor agonists, which are in development for NASH, may adversely affect circulating lipids and lipoproteins.

CONCLUSIONS

NASH is a multi-system disease with a disproportionate CVD burden. Current and future drugs for NASH have had variable impact on the atherogenic risk profile. Potential co-administration of a statin may help mitigate the negative impact of some of these therapies on lipid and lipoprotein levels.

Correlations between Iron Metabolism Parameters, Inflammatory Markers and Lipid Profile Indicators in Patients with Type 1 and Type 2 Diabetes Mellitus

This study aims to establish relationships between inflammatory status, ferrokinetics and lipid metabolism in patients with diabetes mellitus. Subclinical inflammation was assessed by levels of high-sensitive C-reactive protein, tumor necrosis factor-α and erythrocyte sedimentation rate. Iron metabolism parameters included complete blood count, serum iron, transferrin and ferritin. Metabolic status assessment included lipid profile, glycated hemoglobin and microalbuminuria measurement. As a result of the study it was possible to establish both general (universal) and diabetes mellitus (DM) type-dependent relationships between the parameters of lipid profile and metabolic control in DM. High-density lipoprotein cholesterol (HDL-C) levels negatively correlated with microalbuminuria (r = −0.293; p ˂ 0.05 for type 1 diabetes and r = −0.272; p ˂ 0.05 for type 2 diabetes). Ferritin concentration positively correlated with triglyceride level (r = 0.346; p ˂ 0.05 for type 1 diabetes and r = 0.244; p ˂ 0.05 for type 2 diabetes). In type 1 diabetes, a negative correlation was discovered between estimated glomerular filtration rate (eGFR) and LDL-C (r = −0.480; p ˂ 0.05), very low-density-lipoprotein cholesterol (VLDL-C) (r = −0.490; p ˂ 0.05) and triglycerides (r = −0.553; p ˂ 0.05), and a positive one between C-reactive protein concentration and triglyceride level (r = 0.567; p ˂ 0.05). Discovered relationships between lipid profile indices, inflammatory status and microalbuminuria confirmed mutual influence of hyperlipidemia, inflammation and nephropathy in diabetes patients. Obtained results justify the strategy of early hypolipidemic therapy in patients with diabetes mellitus to prevent the development and progression of microvascular complications.

NAFLD and cardiovascular diseases: a clinical review

Non-alcoholic fatty liver DISEASE (NAFLD) is the most common chronic liver disease in Western countries and affects approximately 25% of the adult population. Since NAFLD is frequently associated with further metabolic comorbidities such as obesity, type 2 diabetes mellitus, or dyslipidemia, it is generally considered as the hepatic manifestation of the metabolic syndrome. In addition to its potential to cause liver-related morbidity and mortality, NAFLD is also associated with subclinical and clinical cardiovascular disease (CVD). Growing evidence indicates that patients with NAFLD are at substantial risk for the development of hypertension, coronary heart disease, cardiomyopathy, and cardiac arrhythmias, which clinically result in increased cardiovascular morbidity and mortality. The natural history of NAFLD is variable and the vast majority of patients will not progress from simple steatosis to fibrosis and end stage liver disease. However, patients with progressive forms of NAFLD, including non-alcoholic steatohepatitis (NASH) and/or advanced fibrosis, as well as NAFLD patients with concomitant types 2 diabetes are at highest risk for CVD. This review describes the underlying pathophysiological mechanisms linking NAFLD and CVD, discusses the role of NAFLD as a metabolic dysfunction associated cardiovascular risk factor, and focuses on common cardiovascular manifestations in NAFLD patients.

The Relationship between Protein Intake and Source on Factors Associated with Glycemic Control in Individuals with Prediabetes and Type 2 Diabetes

Type 2 diabetes (T2D) is a major contributor to morbidity and mortality largely due to increased cardiovascular disease risk. This study examined the relationships among protein consumption and sources on glycemic control and cardiovascular health in individuals with prediabetes and T2D. Sixty-two overweight or obese participants with prediabetes or T2D, aged 45–75 years were stratified into the following three groups based on protein intake: <0.8 g (gram)/kg (kilogram) body weight (bw), ≥0.8 but <1.0 g/kg bw, and ≥1.0 g/kg bw as below, meeting, and above the recommended levels of protein intake, respectively. Body mass, body mass index (BMI), hip circumference (HC), waist circumference (WC), lean mass, and fat mass (FM) were significantly higher in participants who consumed below the recommended level of protein intake as compared with other groups. Higher animal protein intake was associated with greater insulin secretion and lower triglycerides (TG). Total, low-density, and high-density cholesterol were significantly higher in participants who met the recommended protein intake as compared with the other groups. These data suggest that high protein consumption is associated with lower BMI, HC, WC, and FM, and can improve insulin resistance without affecting lipid profiles in this population. Furthermore, higher intake of animal protein can improve β-cell function and lower plasma TG.

Modifying nutritional substrates induces macrovesicular lipid droplet accumulation and metabolic alterations in a cellular model of hepatic steatosis

BACKGROUND AND AIMS

Nonalcoholic fatty liver disease (NAFLD) begins with steatosis, where a mixed macrovesicular pattern of large and small lipid droplets (LDs) develops. Since in vitro models recapitulating this are limited, the aims of this study were to develop mixed macrovesicular steatosis in immortalized hepatocytes and investigate effects on intracellular metabolism by altering nutritional substrates.

METHODS

Huh7 cells were cultured in 11 mM glucose and 2% human serum (HS) for 7 days before additional sugars and fatty acids (FAs), either with 200 µM FAs (low fat low sugar; LFLS), 5.5 mM fructose + 200 µM FAs (low fat high sugar; LFHS), or 5.5 mM fructose + 800 µM FAs (high fat high sugar; HFHS), were added for 7 days. FA metabolism, lipid droplet characteristics, and transcriptomic signatures were investigated.

RESULTS

Between the LFLS and LFHS conditions, there were few notable differences. In the HFHS condition, intracellular triacylglycerol (TAG) was increased and the LD pattern and distribution was similar to that found in primary steatotic hepatocytes. HFHS-treated cells had lower levels of de novo-derived FAs and secreted larger, TAG-rich lipoprotein particles. RNA sequencing and gene set enrichment analysis showed changes in several pathways including those involved in metabolism and cell cycle.

CONCLUSIONS

Repeated doses of HFHS treatment resulted in a cellular model of NAFLD with a mixed macrovesicular LD pattern and metabolic dysfunction. Since these nutrients have been implicated in the development of NAFLD in humans, the model provides a good physiological basis for studying NAFLD development or regression in vitro.

A lipidome-wide association study of the lipoprotein insulin resistance index

Background

The lipoprotein insulin resistance (LPIR) score was shown to predict insulin resistance (IR) and type 2 diabetes (T2D) in healthy adults. However, the molecular basis underlying the LPIR utility for classification remains unclear.

Objective

To identify small molecule lipids associated with variation in the LPIR score, a weighted index of lipoproteins measured by nuclear magnetic resonance, in the Genetics of Lipid Lowering Drugs and Diet Network (GOLDN) study (n = 980).

Methods

Linear mixed effects models were used to test the association between the LPIR score and 413 lipid species and their principal component analysis-derived groups. Significant associations were tested for replication with homeostatic model assessment-IR (HOMA-IR), a phenotype correlated with the LPIR score (r = 0.48, p <  0.001), in the Heredity and Phenotype Intervention (HAPI) Heart Study (n = 590).

Results

In GOLDN, 319 lipids were associated with the LPIR score (false discovery rate-adjusted p-values ranging from 4.59 × 10^− 161 to 49.50 × 10^− 3). Factors 1 (triglycerides and diglycerides/storage lipids) and 3 (mixed lipids) were positively (β = 0.025, p = 4.52 × 10^− 71 and β = 0.021, p = 5.84 × 10^− 41, respectively) and factor 2 (phospholipids/non-storage lipids) was inversely (β = − 0.013, p = 2.28 × 10^− 18) associated with the LPIR score. These findings were replicated for HOMA-IR in the HAPI Heart Study (β = 0.10, p = 1.21 × 10^− 02 for storage, β = − 0.13, p = 3.14 × 10^− 04 for non-storage, and β = 0.19, p = 8.40 × 10^− 07 for mixed lipids).

Conclusions

Non-storage lipidomics species show a significant inverse association with the LPIR metabolic dysfunction score and present a promising focus for future therapeutic and prevention studies.

GPR146 Deficiency Protects against Hypercholesterolemia and Atherosclerosis

Although human genetic studies have implicated many susceptible genes associated with plasma lipid levels, their physiological and molecular functions are not fully characterized. Here we demonstrate that orphan G protein-coupled receptor 146 (GPR146) promotes activity of hepatic sterol regulatory element binding protein 2 (SREBP2) through activation of the extracellular signal-regulated kinase (ERK) signaling pathway, thereby regulating hepatic very low-density lipoprotein (VLDL) secretion, and subsequently circulating low-density lipoprotein cholesterol (LDL-C) and triglycerides (TG) levels. Remarkably, GPR146 deficiency reduces plasma cholesterol levels substantially in both wild-type and LDL receptor (LDLR)-deficient mice. Finally, aortic atherosclerotic lesions are reduced by 90% and 70%, respectively, in male and female LDLR-deficient mice upon GPR146 depletion. Taken together, these findings outline a regulatory role for the GPR146/ERK axis in systemic cholesterol metabolism and suggest that GPR146 inhibition could be an effective strategy to reduce plasma cholesterol levels and atherosclerosis.

mTORC1-IRE1α pathway activation contributes to palmitate-elicited triglyceride secretion and cell death in hepatocytes

IMPACT STATEMENT

Lipotoxicity induced by saturated fatty acids (SFA) plays a pivotal role in the pathogenesis of a variety of obesity-related metabolic disorders; however, the exact mechanism(s) underlying lipotoxicity development remains elusive. The liver plays a central role in regulating intrahepatic and circulatory lipid homeostasis. In the current study, we identified that mammalian target of rapamycin complex 1 (mTORC1) activation plays an important role in regulating the detrimental effects of SFA palmitate in hepatocytes, in specific cell death, and TG overproduction. Furthermore, our data confirmed that palmitate-induced mTORC1 activation is attributable to its stimulatory effect on IRE1α, one of three canonical pathways activated during ER stress. Importantly, IRE1α inhibition prevented palmitate-triggered cell death and TG overproduction, suggesting mTORC1-IRE1α pathway is mechanistically implicated in palmitate lipotoxicity. The data obtained in the current investigation support future study to explore the therapeutic potential of targeting the mTORC1-IRE1α pathway as a novel clinical strategy for the treatment of metabolic disorders involving lipotoxicity.

High-Risk Atherosclerosis and Metabolic Phenotype: The Roles of Ectopic Adiposity, Atherogenic Dyslipidemia, and Inflammation

Current algorithms for assessing risk of atherosclerotic cardiovascular disease (ASCVD) and, in particular, the reliance on low-density lipoprotein (LDL) cholesterol in conditions where this measurement is discordant with apoB and LDL-particle concentrations fail to identify a sizeable part of the population at high risk for adverse cardiovascular events. This results in missed opportunities for ASCVD prevention, most notably in those with metabolic syndrome, prediabetes, and diabetes. There is substantial evidence that accumulation of ectopic fat and associated metabolic traits are markers for and pathogenic components of high-risk atherosclerosis. Conceptually, the subset of advanced lesions in high-risk atherosclerosis that triggers vascular complications is closely related to a set of coordinated high-risk traits clustering around a distinct metabolic phenotype. A key feature of this phenotype is accumulation of ectopic fat, which, coupled with age-related muscle loss, creates a milieu conducive for the development of ASCVD: atherogenic dyslipidemia, nonresolving inflammation, endothelial dysfunction, hyperinsulinemia, and impaired fibrinolysis. Sustained vascular inflammation, a hallmark of high-risk atherosclerosis, impairs plaque stabilization in this phenotype. This review describes how metabolic and inflammatory processes that are promoted in large measure by ectopic adiposity, as opposed to subcutaneous adipose tissue, relate to the pathogenesis of high-risk atherosclerosis. Clinical biomarkers indicative of these processes provide incremental information to standard risk factor algorithms and advanced lipid testing identifies atherogenic lipoprotein patterns that are below the discrimination level of standard lipid testing. This has the potential to enable improved identification of high-risk patients who are candidates for therapeutic interventions aimed at prevention of ASCVD.

Nonalcoholic Fatty Liver Disease 2020: The State of the Disease

Nonalcoholic fatty liver disease (NAFLD) is the most common liver disease, with a worldwide prevalence of 25%. In the United States, NAFLD and its subtype, nonalcoholic steatohepatitis, affect 30% and 5% of the population, respectively. Considering the ongoing obesity epidemic beginning in childhood, the rise in diabetes, and other factors, the prevalence of NAFLD along with the proportion of those with advanced liver disease is projected to continue to increase. This will have an important impact on public health reflected in health care costs, including impact on the need for liver transplantation, for which nonalcoholic steatohepatitis is already close to becoming the most common indication. NAFLD patients with evidence of nonalcoholic steatohepatitis and advanced fibrosis are at markedly increased risk of adverse outcomes, including overall mortality, and liver-specific morbidity and mortality, respectively. Identification of this cohort of NAFLD patients is paramount, given the associated poorer outcomes, in order to target resources to those who need it most. Various noninvasive tools have been developed in this regard. This review provides an update on the epidemiology, clinical and prognostic features, and diagnostic approach to patients with NAFLD.

VLDL and HDL attenuate endoplasmic reticulum and metabolic stress in HL-1 cardiomyocytes

Lipoproteins have a vital role in the development of metabolic and cardiovascular diseases ranging from protective to deleterious effects on target tissues. VLDL has been shown to induce lipotoxic lipid accumulation and exert a variety of negative effects on cardiomyocytes. Lipotoxicity and endoplasmic reticulum (ER) stress are proposed to be the mediators of damaging effects of metabolic diseases on cardiovascular system. We treated cardiomyocytes with lipoproteins to evaluate the adaptability of these cells to metabolic stress induced by starvation and excess of lipoproteins, and to evaluate the effect of lipoproteins and lipid accumulation on ER stress. VLDL reversed metabolic stress induced by starvation, while HDL did not. VLDL induced dose-dependent lipid accumulation in cardiomyocytes, which however did not result in reduced cell viability or induction of ER stress. Moreover, VLDL or HDL pre-treatment reduced ER stress in cardiomyocytes induced by tunicamycin and palmitic acid as measured by the expression of ER stress markers, even in conditions of increased lipid accumulation. VLDL and HDL induced activation of pro-survival ERK1/2 in cardiomyocytes; however, this activation was not involved in the protection against ER stress. Additionally, we observed that LDLR and VLDLR are regulated differently by lipoproteins and cellular stress, as lipoproteins induced VLDLR protein independently of the level of lipid accumulation. We conclude that VLDL is not a priori detrimental for cardiomyocytes and can even have beneficial effects, enabling cell survival under starvation and attenuating ER stress.

Lipotoxicity and Diabetic Nephropathy: Novel Mechanistic Insights and Therapeutic Opportunities

Lipotoxicity is characterized by the ectopic accumulation of lipids in organs different from adipose tissue. Lipotoxicity is mainly associated with dysfunctional signaling and insulin resistance response in non-adipose tissue such as myocardium, pancreas, skeletal muscle, liver, and kidney. Serum lipid abnormalities and renal ectopic lipid accumulation have been associated with the development of kidney diseases, in particular diabetic nephropathy. Chronic hyperinsulinemia, often seen in type 2 diabetes, plays a crucial role in blood and liver lipid metabolism abnormalities, thus resulting in increased non-esterified fatty acids (NEFA). Excessive lipid accumulation alters cellular homeostasis and activates lipogenic and glycogenic cell-signaling pathways. Recent evidences indicate that both quantity and quality of lipids are involved in renal damage associated to lipotoxicity by activating inflammation, oxidative stress, mitochondrial dysfunction, and cell-death. The pathological effects of lipotoxicity have been observed in renal cells, thus promoting podocyte injury, tubular damage, mesangial proliferation, endothelial activation, and formation of macrophage-derived foam cells. Therefore, this review examines the recent preclinical and clinical research about the potentially harmful effects of lipids in the kidney, metabolic markers associated with these mechanisms, major signaling pathways affected, the causes of excessive lipid accumulation, and the types of lipids involved, as well as offers a comprehensive update of therapeutic strategies targeting lipotoxicity.

Olanzapine-induced liver injury in mice: aggravation by high-fat diet and protection with sulforaphane

Olanzapine is effective to treat for schizophrenia and other mood disorders, but limited by side effects such as weight gain, dyslipidemia, and liver injury. Obesity in the US is at epidemic levels, and is a significant risk factor for drug-induced liver injury. Obesity incidence in the psychiatric population is even higher than in the US population as a whole. The purpose of this study was to test the hypothesis that obesity worsens olanzapine-induced hepatic injury, and to investigate the potential protective effects of sulforaphane. 8-week old female C57BL/6 mice were fed either a high-fat or low-fat control diet (HFD and LFD). Mice also received either olanzapine (8 mg/kg/d) or vehicle by osmotic minipump for 4 weeks. A subset of mice in the HFD + olanzapine group was administered sulforaphane, a prototypical Nrf2 inducer (90 mg/kg/d). Olanzapine alone increased body weight, without a commensurate increase in food consumption. Olanzapine also caused hepatic steatosis and injury. Combining olanzapine and HFD caused further dysregulation of glucose and lipid metabolism. Liver damage from concurrent HFD and olanzapine was worse than liver damage from high-fat diet or olanzapine alone. Sulforaphane alleviated many metabolic side effects of olanzapine and HFD. Taken together, these data show that olanzapine dysregulates glucose and lipid metabolism and exacerbates hepatic changes caused by eating a HFD. Activation of the intrinsic antioxidant defense pathway with sulforaphane can partially prevent these effects of olanzapine and may represent a useful strategy to protect against liver injury.

Mass spectrometry imaging of triglycerides in biological tissues by laser desorption ionization from silicon nanopost arrays

Mass spectrometry imaging (MSI) is used increasingly to simultaneously detect a broad range of biomolecules while mapping their spatial distributions within biological tissue sections. Matrix-assisted laser desorption ionization (MALDI) is recognized as the method-of-choice for MSI applications due in part to its broad molecular coverage. In spite of the remarkable advantages offered by MALDI, imaging of neutral lipids, such as triglycerides (TGs), from tissue has remained a significant challenge due to ion suppression of TGs by phospholipids, e.g. phosphatidylcholines (PCs). To help overcome this limitation, silicon nanopost array (NAPA) substrates were introduced to selectively ionize TGs from biological tissue sections. This matrix-free laser desorption ionization (LDI) platform was previously shown to provide enhanced ionization of certain lipid classes, such as hexosylceramides (HexCers) and phosphatidylethanolamines (PEs) from mouse brain tissue. In this work, we present NAPA as an MSI platform offering enhanced ionization efficiency for TGs from biological tissues relative to MALDI, allowing it to serve as a complement to MALDI-MSI. Analysis of a standard lipid mixture containing PC(18:1/18:1) and TG(16:0/16:0/16:0) by LDI from NAPA provided an ~49 and ~227-fold higher signal for TG(16:0/16:0/16:0) relative to MALDI, when analyzed without and with the addition of a sodium acetate, respectively. In contrast, MALDI provided an ~757 and ~295-fold higher signal for PC(18:1/18:1) compared with NAPA, without and with additional Na⁺ . Averaged signal intensities for TGs from MSI of mouse lung and human skin tissues exhibited an ~105 and ~49-fold increase, respectively, with LDI from NAPA compared with MALDI. With respect to PCs, MALDI provided an ~2 and ~19-fold increase in signal intensity for mouse lung and human skin tissues, respectively, when compared with NAPA. The complementary coverage obtained by the two platforms demonstrates the utility of using both techniques to maximize the information obtained from lipid MS or MSI experiments.

Glucose challenge metabolomics implicates the change of organic acid profiles in hyperlipidemic subjects

Hyperlipidemia (HLP) is a major risk factor of diabetes and cardiovascular disease. Here, we applied gas chromatography-mass spectrometry to study differences in postprandial organic acid profiles in healthy and HLP subjects. In fasting status, six intermediates of the tricarboxylic acid cycle showed significant differences in HLP and healthy controls (P < 0.05). The percentage changes of 17 metabolites including three intermediates of the tricarboxylic acid cycle were significantly different during the oral glucose tolerance test. Postprandial changes in ethylmalonic acid and pimelic acid were negatively associated with HOMA-IR (homeostasis model assessment of insulin resistance; all P < 0.05) in the HLP group. Postprandial metabolism of organic acid profiles revealed energy metabolism perturbations in HLP. Our findings provide new insights into the complex physiological regulation of HLP postprandial metabolism.

Dairy Foods and Dairy Fats: New Perspectives on Pathways Implicated in Cardiometabolic Health

Low-fat and nonfat dairy products have been promoted as part of a healthy dietary pattern by both US dietary guidelines and professional organizations for several decades. The basis for this recommendation stems in part from the putative negative cardiometabolic effects associated with saturated fat consumption. However, as nutrition research has shifted from a single nutrient to a whole-food/dietary pattern approach, the role of dairy foods and dairy fat in the diet-disease relationship is being reexamined. Most observational and experimental evidence does not support a detrimental relationship between full-fat dairy intake and cardiometabolic health, including risks of cardiovascular disease and type 2 diabetes. Indeed, an expanded understanding of the dairy food matrix and the bioactive properties of dairy fats and other constituents suggests a neutral or potentially beneficial role in cardiometabolic health. To consider how consuming dairy foods, including full-fat dairy, is associated with cardiometabolic health, this review provides an innovative perspective on mechanisms that link dairy consumption to 3 main biological systems at the core of metabolic health, the gastrointestinal, hepatic, and vascular systems.

Hepatic Lipoprotein Export and Remission of Human Type 2 Diabetes after Weight Loss

The role of hepatic lipoprotein metabolism in diet-induced remission of type 2 diabetes is currently unclear. Here, we determined the contributions of hepatic VLDL1-triglyceride production rate and VLDL1-palmitic acid content to changes in intra-pancreatic fat and return of first phase insulin response in a subgroup of the Diabetes Remission Clinical Trial. Liver fat, VLDL1-triglyceride production, and intra-pancreatic fat decreased after weight loss and remained normalized after 24 months of remission. First-phase insulin response remained increased only in those maintaining diabetes remission. Compared with those in remission at 24 months, individuals who relapsed after initial remission had a greater rise in the content of VLDL1-triglyceride and VLDL1-palmitic acid, re-accumulated intra-pancreatic fat, and lost first-phase response by 24 months. Thus, we observed temporal relationships between VLDL1-triglyceride production, hepatic palmitic acid flux, intra-pancreatic fat, and β-cell function. Weight-related disordered fat metabolism appears to drive development and reversal of type 2 diabetes.

Non-alcoholic fatty liver disease and cardiovascular disease: assessing the evidence for causality

Non-alcoholic fatty liver disease (NAFLD) is highly prevalent among individuals with type 2 diabetes. Although epidemiological studies have shown that NAFLD is associated with cardiovascular disease (CVD), it remains unknown whether NAFLD is an active contributor or an innocent bystander. Plasma lipids, low-grade inflammation, impaired fibrinolysis and hepatokines are potential mediators of the relationship between NAFLD and CVD. The Mendelian randomisation approach can help to make causal inferences. Studies that used common variants in PNPLA3, TM6SF2 and GCKR as instruments to investigate the relationship between NAFLD and coronary artery disease (CAD) have reported contrasting results. Variants in PNPLA3 and TM6SF2 were found to protect against CAD, whereas variants in GCKR were positively associated with CAD. Since all three genes have been associated with non-alcoholic steatohepatitis, the second stage of NAFLD, the question of whether low-grade inflammation is an important mediator of the relationship between NAFLD and CAD arises. In contrast, the differential effects of these genes on plasma lipids (i.e. lipid-lowering for PNPLA3 and TM6SF2, and lipid-raising for GCKR) strongly suggest that plasma lipids account for their differential effects on CAD risk. This concept has recently been confirmed in an extended set of 12 NAFLD susceptibility genes. From these studies it appears that plasma lipids are an important mediator between NAFLD and CVD risk. These findings have important clinical implications, particularly for the design of anti-NAFLD drugs that also affect lipid metabolism.

Dietary fructose and dyslipidemia: new mechanisms involving apolipoprotein CIII

PURPOSE OF REVIEW

Chronic consumption of fructose and fructose-containing sugars leads to dyslipidemia. Apolipoprotein (apo) CIII is strongly associated with elevated levels of triglycerides and cardiovascular disease risk. We reviewed the effects of fructose consumption on apoCIII levels and the role of apoCIII in fructose-induced dyslipidemia.

RECENT FINDINGS

Consumption of fructose increases circulating apoCIII levels compared with glucose. The more marked effects of fructose compared with glucose on apoCIII concentrations may involve the failure of fructose consumption to stimulate insulin secretion. The increase in apoCIII levels after fructose consumption correlates with increased postprandial serum triglyceride. Further, RNA interference of apoCIII prevents fructose-induced dyslipidemia in nonhuman primates. Increases in postprandial apoCIII after fructose, but not glucose consumption, are positively associated with elevated triglycerides in large triglyceride-rich lipoproteins and increased small dense LDL levels.

SUMMARY

ApoCIII might be causal in the lipid dysregulation observed after consumption of fructose and fructose-containing sugars. Decreased consumption of fructose and fructose-containing sugars could be an effective strategy for reducing circulating apoCIII and subsequently lowering triglyceride levels.

Critical Role of SREBP-1c Large-VLDL Pathway in Environment-Induced Hypertriglyceridemia of Apo AV Deficiency

Objective- APOA5 variants are strongly associated with hypertriglyceridemia, as well as increased risks of cardiovascular disease and acute pancreatitis. Hypertriglyceridemia in apo AV dysfunction often aggravates by environmental factors such as high-carbohydrate diets or aging. To date, the molecular mechanisms by which these environmental factors induce hypertriglyceridemia are poorly defined, leaving the high-risk hypertriglyceridemia condition undertreated. Previously, we reported that LXR (liver X receptor)-SREBP (sterol regulatory element-binding protein)-1c pathway regulates large-VLDL (very low-density lipoprotein) production induced by LXR agonist. However, the pathophysiological relevance of the finding remains unknown. Approach and Results- Here, we reconstitute the environment-induced hypertriglyceridemia phenotype of human APOA5 deficiency in Apoa5^-/- mice and delineate the role of SREBP-1c in vivo by generating Apoa5^-/- ;Srebp-1c^-/- mice. The Apoa5^-/- mice, which showed moderate hypertriglyceridemia on a chow diet, developed severe hypertriglyceridemia on high-carbohydrate feeding or aging as seen in patients with human apo AV deficiency. These responses were nearly completely abolished in the Apoa5^-/- ;Srebp-1c^-/- mice. Further mechanistic studies revealed that in response to these environmental factors, SREBP-1c was activated to increase triglyceride synthesis and to permit the incorporation of triglyceride into abnormally large-VLDL particles, which require apo AV for efficient clearance. Conclusions- Severe hypertriglyceridemia develops only when genetic factors (apo AV deficiency) and environmental effects (SREBP-1c activation) coexist. We demonstrate that the regulated production of large-sized VLDL particles via SREBP-1c determines plasma triglyceride levels in apo AV deficiency. Our findings explain the long-standing enigma of the late-onset hypertriglyceridemia phenotype of apo AV deficiency and suggest a new approach to treat hypertriglyceridemia by targeting genes that mediate environmental effects.

Causes and Consequences of Hypertriglyceridemia

Elevations in plasma triglyceride are the result of overproduction and impaired clearance of triglyceride-rich lipoproteins-very low-density lipoproteins (VLDL) and chylomicrons. Hypertriglyceridemia is characterized by an accumulation in the circulation of large VLDL-VLDL₁-and its lipolytic products, and throughout the VLDL-LDL delipidation cascade perturbations occur that give rise to increased concentrations of remnant lipoproteins and small, dense low-density lipoprotein (LDL). The elevated risk of atherosclerotic cardiovascular disease in hypertriglyceridemia is believed to result from the exposure of the artery wall to these aberrant lipoprotein species. Key regulators of the metabolism of triglyceride-rich lipoproteins have been identified and a number of these are targets for pharmacological intervention. However, a clear picture is yet to emerge as to how to relate triglyceride lowering to reduced risk of atherosclerosis.

Multimodal imaging of biological tissues using combined MALDI and NAPA-LDI mass spectrometry for enhanced molecular coverage

Sequential imaging of a tissue section by MALDI and NAPA-LDI mass spectrometry provides enhanced molecular coverage.

The Roles of ApoC-III on the Metabolism of Triglyceride-Rich Lipoproteins in Humans

Cardiovascular disease (CVD) is the leading cause of death globally. It is well-established based on evidence accrued during the last three decades that high plasma concentrations of cholesterol-rich atherogenic lipoproteins are causatively linked to CVD, and that lowering these reduces atherosclerotic cardiovascular events in humans (1-9). Historically, most attention has been on low-density lipoproteins (LDL) since these are the most abundant atherogenic lipoproteins in the circulation, and thus the main carrier of cholesterol into the artery wall. However, with the rise of obesity and insulin resistance in many populations, there is increasing interest in the role of triglyceride-rich lipoproteins (TRLs) and their metabolic remnants, with accumulating evidence showing they too are causatively linked to CVD. Plasma triglyceride, measured either in the fasting or non-fasting state, is a useful index of the abundance of TRLs and recent research into the biology and genetics of triglyceride heritability has provided new insight into the causal relationship of TRLs with CVD. Of the genetic factors known to influence plasma triglyceride levels variation in APOC3- the gene for apolipoprotein (apo) C-III - has emerged as being particularly important as a regulator of triglyceride transport and a novel therapeutic target to reduce dyslipidaemia and CVD risk (10).

The Association between Coffee Consumption Pattern and Prevalence of Metabolic Syndrome in Korean Adults

The inconsistent results of epidemiologic studies suggest that the health effects of coffee vary depending on coffee consumption pattern, such as the type and amount of coffee intake. This study investigated the association between coffee consumption and metabolic syndrome (MetS) in Korean adults. In total, coffee consumption patterns in 14,132 participants were assessed based on two-day, 24-h recall data. Multivariable logistic regression was used to examine the association between the type and daily servings of coffee and the prevalence of MetS. In women, the prevalence of MetS (odds ratio (OR) 0.82; 95% confidence interval (CI): 0.70, 0.96), elevated triglycerides (0.85; 0.75, 0.97), and reduced high-density lipoprotein (HDL)-cholesterol (HDL-C; 0.74; 0.66, 0.83) in 3-in-1 coffee consumers, as well as the prevalence of increased waist circumference (0.81; 0.68, 0.98) and reduced HDL-C (0.68; 0.59, 0.80) in black coffee consumers, were significantly lower compared to non-coffee consumers. Also, the inverse associations between total coffee intake, black coffee intake, and 3-in-1 coffee intake with MetS or components of MetS were more significant in individuals who consumed >1 versus ≤1 serving/day. In conclusion, coffee consumption (regardless of type) was associated with a reduced prevalence of MetS and its components in Korean women.

Gene-Based Elevated Triglycerides and Type 2 Diabetes Mellitus Risk in the Women's Genome Health Study

Objective- Higher triglyceride (TG) is a risk factor for incident type 2 diabetes mellitus (T2DM), but paradoxically, genetic susceptibility for higher TG has been associated with lower T2DM risk. There is also evidence that the genetic association may be modified by baseline TG. Whether such associations can be replicated and the interaction is selective for certain TG-rich lipoprotein particles remains to be explored. Approach and Results- Cox regression involving TG, TG-rich lipoprotein particles, and genetic determinants of TG was performed among 15 813 participants with baseline fasting status in the WGHS (Women's Genome Health Study), including 1453 T2DM incident cases during a mean 18.6 (SD=5.3) years of follow-up. A weighted, 40-single-nucleotide polymorphism TG genetic risk score was inversely associated with incident T2DM (hazard ratio [95% CI], 0.66 [0.58-0.75]/10-TG risk alleles; P<0.0001) with adjustment for baseline body mass index, HDL (high-density lipoprotein) cholesterol, and TG. TG-associated risk was higher among individuals in the low compared with the high 40-single-nucleotide polymorphism TG genetic risk score tertile (hazard ratio [95% CI], 1.98 [1.83-2.14] versus 1.68 [1.58-1.80] per mmol/L; P_interaction=0.0007). In TG-adjusted analysis, large and medium but not small TG-rich lipoprotein particles were associated with higher T2DM incidence for successively lower 40-single-nucleotide polymorphism TG genetic risk score tertiles, P_interaction=0.013, 0.012, and 0.620 across tertiles, respectively. Conclusions- Our results confirm the previous observations of the paradoxical associations of TG with T2DM while focusing attention on the larger TG-rich lipoprotein particle subfractions, suggesting their importance in clinical profiling of T2DM risk.

The regulation of hepatic fatty acid synthesis and partitioning: the effect of nutritional state

Nonalcoholic fatty liver disease (NAFLD) is an increasing global public health burden. NAFLD is strongly associated with type 2 diabetes mellitus, obesity and cardiovascular disease and begins with intrahepatic triacylglycerol accumulation. Under healthy conditions, the liver regulates lipid metabolism to meet systemic energy needs in the fed and fasted states. The processes of fatty acid uptake, fatty acid synthesis and the intracellular partitioning of fatty acids into storage, oxidation and secretion pathways are tightly regulated. When one or more of these processes becomes dysregulated, excess lipid accumulation can occur. Although genetic and environmental factors have been implicated in the development of NAFLD, it remains unclear why an imbalance in these pathways begins. The regulation of fatty acid partitioning occurs at several points, including during triacylglycerol synthesis, lipid droplet formation and lipolysis. These processes are influenced by enzyme function, intake of dietary fats and sugars and whole-body metabolism, and are further affected by the presence of obesity or insulin resistance. Insight into how the liver controls fatty acid metabolism in health and how these processes might be affected in disease would offer the potential for new therapeutic treatments for NAFLD to be developed.

Protective Effect of Ginkgolic Acid in Attenuating LDL Induced Inflammation Human Peripheral Blood Mononuclear Cells via Altering the NF-κB Signaling Pathway

Oxidized low-density lipoprotein (ox-LDL) is considered as the significant maker of inflammatory reaction. ox-LDL was reported to play a crucial role in the pathogenesis of atherosclerosis (AS). In the current study, we scrutinize the suppressive effect of ginkgolic acid against ox-LDL induced an oxidative and inflammatory response in human microvascular endothelial cells (HMEC-1) and human peripheral blood mononuclear cells (nPBMCs) and explore the mechanism of action. HMEC-1 cells are treated with ox-LDL in the presence of different concentration of ginkgolic acid. MTT 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay was performed for the estimation of cell viability effect. Reactive oxygen species (ROS), inflammatory cytokines, and NF-κB activity are also estimated. For the hPBMCs assay, the cells were isolated from the healthy volunteers and cultured. The cells were further divided into different group and received the ginkgolic acid. Additionally, ROS, inflammatory marker such as prostaglandin E2 (PGE2), lipoxygenase (LOX), nitric oxide (NO), cyclooxygenase (COX) protein expression, and mRNA expression of tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and vascular cell adhesion protein 1 (VCAM-1) were estimated in the ox-LDL treated group. The result exhibited that ginkgolic acid treatment induced the cell viability boosting in ox-LDL treatment and intracellular ROS significantly decreased by ginkgolic acid. Pro-inflammatory cytokines also downregulated via ginkgolic acid. Moreover, ginkgolic acid reduced the ox-LDL-induced NF-κB. The mRNA and protein expression of TNF-α, IL-6, and VCAM-1 considerably increased in the ox-LDL treated group and ginkgolic acid significantly reduced the mRNA and protein expression. An inflammatory marker such as PGE2, LOX, and NO were increased in the ox-LDL treated group and ginkgolic acid treated group exhibited the reduction of an inflammatory marker. Based on the result, we can conclude that ginkgolic acid significantly reduced and reversed the ox-LDL-induced modulation, suggesting its anti-inflammatory effect via the NF-κB pathway.

MiR-29 Regulates de novo Lipogenesis in the Liver and Circulating Triglyceride Levels in a Sirt1-Dependent Manner

MicroRNAs (miRNAs) are known regulators of lipid homeostasis. We recently demonstrated that miR-29 controls the levels of circulating cholesterol and triglycerides, but the mechanisms remained unknown. In the present study, we demonstrated that systemic delivery of locked nucleic acid inhibitor of miR-29 (LNA29) through subcutaneous injection effectively suppresses hepatic expression of miR-29 and dampens de novo lipogenesis (DNL) in the liver of chow-fed mice. Next, we used mice with liver-specific deletion of Sirtuin 1 (L-Sirt1 KO), a validated target of miR-29, and demonstrated that the LNA29-induced reduction of circulating triglycerides, but not cholesterol, is dependent on hepatic Sirt1. Moreover, lipidomics analysis revealed that LNA29 suppresses hepatic triglyceride levels in a liver-Sirt1 dependent manner. A comparative transcriptomic study of liver tissue from LNA29-treated wild-type/floxed and L-Sirt1 KO mice identified the top candidate lipogenic genes and hepatokines through which LNA29 may confer its effects on triglyceride levels. The transcriptomic analysis also showed that fatty acid oxidation (FAO) genes respond differently to LNA29 depending on the presence of hepatic Sirt1. Overall, this study demonstrates the beneficial effects of LNA29 on DNL and circulating lipid levels. In addition, it provides mechanistic insight that decouples the effect of LNA29 on circulating triglycerides from that of circulating cholesterol.

Plasma Levels of Retinol Binding Protein 4 Relate to Large VLDL and Small LDL Particles in Subjects with and without Type 2 Diabetes

Background: Retinol binding protein 4 (RBP4) carries retinol in plasma, but is also considered an adipokine, as it is implicated in insulin resistance in mice. Plasma RBP4 correlates with total cholesterol, low density lipoprotein (LDL)-cholesterol and triglycerides, and may confer increased cardiovascular risk. However, controversy exists about circulating RPB4 levels in type 2 diabetes mellitus (T2DM) and obesity. Here, we analyzed the relationships of RBP4 and retinol with lipoprotein subfractions in subjects with and without T2DM. Methods: Fasting plasma RBP4 (enzyme-linked immunosorbent assay) and retinol (high performance liquid chromatography) were assayed in 41 T2DM subjects and 37 non-diabetic subjects. Lipoprotein subfractions (NMR spectroscopy) were measured in 36 T2DM subjects and 27 non-diabetic subjects. Physical interaction of RBP4 with lipoproteins was assessed by fast protein liquid chromatography (FPLC). Results: Plasma RBP4 and retinol were strongly correlated (r = 0.881, p < 0.001). RBP4, retinol and the RBP4/retinol ratio were not different between T2DM and non-diabetic subjects (all p > 0.12), and were unrelated to body mass index. Notably, RBP4 and retinol were elevated in subjects with metabolic syndrome (p < 0.05), which was attributable to an association with elevated triglycerides (p = 0.013). Large VLDL, total LDL and small LDL were increased in T2DM subjects (p = 0.035 to 0.003). Taking all subjects together, RBP4 correlated with total cholesterol, non-HDL cholesterol, LDL cholesterol, triglycerides and apolipoprotein B in univariate analysis (p < 0.001 for each). Age-, sex- and diabetes status-adjusted multivariable linear regression analysis revealed that RBP4 was independently associated with large VLDL (β = 0.444, p = 0.005) and small LDL particles (β = 0.539, p < 0.001). Its relationship with large VLDL remained after further adjustment for retinol. RBP4 did not co-elute with VLDL nor LDL particles in FPLC analyses. Conclusions: Plasma RBP4 levels are related to but do not physically interact with large VLDL and small LDL particles. Elevated RBP4 may contribute to a proatherogenic plasma lipoprotein profile.

Triglycerides and endothelial function: molecular biology to clinical perspective

PURPOSE OF REVIEW

Recently, a high level of triglycerides has attracted much attention as an important residual risk factor of cardiovascular events. We will review and show the mechanisms underlying the association of endothelial dysfunction with hypertriglyceridemia and present clinical evidence for a relationship between endothelial function and triglycerides.

RECENT FINDINGS

Clinical studies have shown that hypertriglyceridemia is associated with endothelial dysfunction. It is likely that hypertriglyceridemia impairs endothelial function through direct and indirect mechanisms. Therefore, hypertriglyceridemia is recognized as a therapeutic target in the treatment of endothelial dysfunction. Although experimental and clinical studies have shown that fibrates and omega-3 fatty acids not only decrease triglycerides but also improve endothelial function, the effects of these therapies on cardiovascular events are controversial.

SUMMARY

Accumulating evidence suggests that hypertriglyceridemia is an independent risk factor for endothelial dysfunction. Triglycerides should be considered more seriously as a future target to reduce cardiovascular events. Results of ongoing studies may show the benefit of lowering triglycerides and provide new standards of care for patients with hypertriglyceridemia possibly through improvement in endothelial function.

Association of diabetes mellitus with hepatitis B and hepatitis C virus infection: evidence from an epidemiological study

Objective

To study the association between glucose metabolism disorders and hepatotropic virus infection.

Methods

A cross-sectional analysis was performed using data from the REACTION study (Risk Evaluation of Cancers in Chinese Diabetic Individuals: A Longitudinal Study). Outcomes of the analysis were test results of kidney function, liver function, lipid metabolism, and the prevalence of hepatitis B virus (HBV) infection and potential hepatitis C virus (HCV) infection (positive hepatitis C virus antibody) among individuals with and without diabetes mellitus (DM) or pre-diabetes mellitus (pre-DM).

Results

Of the 10,080 patients who participated in the study, 7665 eligible subjects were included in the analysis. There was no significant difference in the prevalence of HBV infection between DM and normal subjects, pre-DM and normal subjects, and DM or pre-DM and normal subjects (p-values of 0.9180, 0.8154, and 0.6448, respectively). There was also no significant difference in the prevalence of potential HCV infection between DM and normal subjects, pre-DM and normal subjects, and DM or pre-DM and normal subjects (p-values of 0.1190, 0.0591, and 0.5591, respectively). Lipid metabolism showed a significant difference between DM or pre-DM subjects and normal subjects (p-values were less than 0.0221 in all cases). Multiple logistic regression analysis revealed hypertension as the leading significant variable associated with DM, pre-DM, and both. Other significant factors included gender, body mass index, age, and alanine aminotransferase.

Conclusion

No significant association was detected between DM or pre-DM and HBV or potential HCV infection. Significant association was detected between lipid metabolism disorders and DM, but this association was absent in pre-DM patients when adjusting for other factors.

Visceral and ectopic fat, atherosclerosis, and cardiometabolic disease: a position statement

Findings from epidemiological studies over the past 30 years have shown that visceral adipose tissue, accurately measured by CT or MRI, is an independent risk marker of cardiovascular and metabolic morbidity and mortality. Emerging evidence also suggests that ectopic fat deposition, including hepatic and epicardial fat, might contribute to increased atherosclerosis and cardiometabolic risk. This joint position statement from the International Atherosclerosis Society and the International Chair on Cardiometabolic Risk Working Group on Visceral Obesity summarises the evidence for visceral adiposity and ectopic fat as emerging risk factors for type 2 diabetes, atherosclerosis, and cardiovascular disease, with a focus on practical recommendations for health professionals and future directions for research and clinical practice. We discuss the measurement of visceral and ectopic fat, pathophysiology and contribution to adverse health outcomes, response to treatment, and lessons from a public health programme targeting visceral and ectopic fat. We identify knowledge gaps and note the need to develop simple, clinically applicable tools to be able to monitor changes in visceral and ectopic fat over time. Finally, we recognise the need for public health messaging to focus on visceral and ectopic fat in addition to excess bodyweight to better combat the growing epidemic of obesity worldwide.