Adiponectin deficiency suppresses ABCA1 expression and ApoA-I synthesis in the liver

Sex-Related Differences in the Associations between Adiponectin and Serum Lipoproteins in Healthy Subjects and Patients with Metabolic Syndrome

The strong associations between the serum levels of adiponectin and the lipoprotein subclasses observed in healthy subjects are much weaker in patients with metabolic syndrome (MS). However, the impact of sex on these associations remained unexplored. Therefore, in the present study, we examined associations between adiponectin and the lipoprotein subclasses, analyzed by nuclear magnetic resonance spectroscopy, separately in healthy females and males, as well as in females and males with MS. We observed negative correlations between adiponectin and VLDL, IDL, and small-dense LDL in healthy males, but neither in healthy females nor in females or males with MS. Additionally, adiponectin was positively correlated with some HDL subclasses in healthy males and females with MS, but not in healthy females or males with MS. Adjusting for age and either body mass index, waist circumference, C-reactive protein, or interleukin-6 weakened the associations between adiponectin and VLDL and IDL but not small-dense LDL. The adjustment weakened the associations between adiponectin and HDL in healthy males but not in females with MS. Based on our results, we conclude that sex and the presence of MS are strong determinants of the associations between adiponectin and serum lipoproteins and that the complex regulatory network comprising adiponectin and other molecular players involved in the regulation of lipoprotein metabolism is primarily operative in healthy males and females with MS.

Serum Levels of Adiponectin Are Strongly Associated with Lipoprotein Subclasses in Healthy Volunteers but Not in Patients with Metabolic Syndrome

Metabolic syndrome (MS) is a widespread disease in developed countries, accompanied, among others, by decreased adiponectin serum levels and perturbed lipoprotein metabolism. The associations between the serum levels of adiponectin and lipoproteins have been extensively studied in the past under healthy conditions, yet it remains unexplored whether the observed associations also exist in patients with MS. Therefore, in the present study, we analyzed the serum levels of lipoprotein subclasses using nuclear magnetic resonance spectroscopy and examined their associations with the serum levels of adiponectin in patients with MS in comparison with healthy volunteers (HVs). In the HVs, the serum levels of adiponectin were significantly negatively correlated with the serum levels of large buoyant-, very-low-density lipoprotein, and intermediate-density lipoprotein, as well as small dense low-density lipoprotein (LDL) and significantly positively correlated with large buoyant high-density lipoprotein (HDL). In patients with MS, however, adiponectin was only significantly correlated with the serum levels of phospholipids in total HDL and large buoyant LDL. As revealed through logistic regression and orthogonal partial least-squares discriminant analyses, high adiponectin serum levels were associated with low levels of small dense LDL and high levels of large buoyant HDL in the HVs as well as high levels of large buoyant LDL and total HDL in patients with MS. We conclude that the presence of MS weakens or abolishes the strong associations between adiponectin and the lipoprotein parameters observed in HVs and disturbs the complex interplay between adiponectin and lipoprotein metabolism.

Reevaluating Adiponectin's impact on obesity hypertension: a Chinese case-control study

BACKGROUND

Obesity and hypertension are major risk factors for cardiovascular diseases that affect millions of people worldwide. Both conditions are associated with chronic low-grade inflammation, which is mediated by adipokines such as adiponectin. Adiponectin is the most abundant adipokine that has a beneficial impact on metabolic and vascular biology, while high serum concentrations are associated with some syndromes. This "adiponectin paradox" still needs to be clarified in obesity-associated hypertension. The aim of this study was to investigate how adiponectin affects blood pressure, inflammation, and metabolic function in obesity hypertension using a Chinese adult case-control study.

METHODS

A case-control study that had finished recruiting 153 subjects divided as four characteristic groups. Adiponectin serum levels were tested by ELISA in these subjects among these four characteristic Chinese adult physical examination groups. Waist circumference (WC), body mass index (BMI), systolic blood pressure (SB), diastolic blood pressure (DB), and other clinical laboratory data were collected. Analyzation of correlations between the research index and differences between groups was done by SPSS.

RESULTS

Serum adiponectin levels in the| normal healthy group (NH group) were significantly higher than those in the newly diagnosed untreated just-obesity group (JO group), and negatively correlated with the visceral adiposity index. With multiple linear egression analysis, it was found that, for serum adiponectin, gender, serum albumin (ALB), alanine aminotransferase (ALT) and high-density lipoprotein cholesterol (HDLC) were the significant independent correlates, and for SB, age and HDLC were the significant independent correlates, and for DB, alkaline phosphatase (ALP) was the significant independent correlate. The other variables did not reach significance in the model.

CONCLUSIONS

Our study reveals that adiponectin's role in obesity-hypertension is multifaceted and is influenced by the systemic metabolic homeostasis signaling axis. In obesity-related hypertension, compensatory effects, adiponectin resistance, and reduced adiponectin clearance from impaired kidneys and liver all contribute to the "adiponectin paradox".

Cornelian Cherry (Cornus mas L.) Fruit Extract Lowers SREBP-1c and C/EBPα in Liver and Alters Various PPAR-α, PPAR-γ, LXR-α Target Genes in Cholesterol-Rich Diet Rabbit Model

Cornelian cherry (Cornus mas L.) fruits, abundant in iridoids and anthocyanins, are natural products with proven beneficial impacts on the functions of the cardiovascular system and the liver. This study aims to assess and compare whether and to what extent two different doses of resin-purified cornelian cherry extract (10 mg/kg b.w. or 50 mg/kg b.w.) applied in a cholesterol-rich diet rabbit model affect the levels of sterol regulatory element-binding protein 1c (SREBP-1c) and CCAAT/enhancer binding protein α (C/EBPα), and various liver X receptor-α (LXR-α), peroxisome proliferator-activated receptor-α (PPAR-α), and peroxisome proliferator-activated receptor-γ (PPAR-γ) target genes. Moreover, the aim is to evaluate the resistive index (RI) of common carotid arteries (CCAs) and aortas, and histopathological changes in CCAs. For this purpose, the levels of SREBP-1c, C/EBPα, ATP-binding cassette transporter A1 (ABCA1), ATP-binding cassette transporter G1 (ABCG1), fatty acid synthase (FAS), endothelial lipase (LIPG), carnitine palmitoyltransferase 1A (CPT1A), and adiponectin receptor 2 (AdipoR2) in liver tissue were measured. Also, the levels of lipoprotein lipase (LPL), visceral adipose tissue-derived serine protease inhibitor (Vaspin), and retinol-binding protein 4 (RBP4) in visceral adipose tissue were measured. The RI of CCAs and aortas, and histopathological changes in CCAs, were indicated. The oral administration of the cornelian cherry extract decreased the SREBP-1c and C/EBPα in both doses. The dose of 10 mg/kg b.w. increased ABCA1 and decreased FAS, CPT1A, and RBP4, and the dose of 50 mg/kg b.w. enhanced ABCG1 and AdipoR2. Mitigations in atheromatous changes in rabbits' CCAs were also observed. The obtained outcomes were compared to the results of our previous works. The beneficial results confirm that cornelian cherry fruit extract may constitute a potentially effective product in the prevention and treatment of obesity-related disorders.

Obstructive Sleep Apnoea and Lipid Metabolism: The Summary of Evidence and Future Perspectives in the Pathophysiology of OSA-Associated Dyslipidaemia

Obstructive sleep apnoea (OSA) is associated with cardiovascular and metabolic comorbidities, including hypertension, dyslipidaemia, insulin resistance and atherosclerosis. Strong evidence suggests that OSA is associated with an altered lipid profile including elevated levels of triglyceride-rich lipoproteins and decreased levels of high-density lipoprotein (HDL). Intermittent hypoxia; sleep fragmentation; and consequential surges in the sympathetic activity, enhanced oxidative stress and systemic inflammation are the postulated mechanisms leading to metabolic alterations in OSA. Although the exact mechanisms of OSA-associated dyslipidaemia have not been fully elucidated, three main points have been found to be impaired: activated lipolysis in the adipose tissue, decreased lipid clearance from the circulation and accelerated de novo lipid synthesis. This is further complicated by the oxidisation of atherogenic lipoproteins, adipose tissue dysfunction, hormonal changes, and the reduced function of HDL particles in OSA. In this comprehensive review, we summarise and critically evaluate the current evidence about the possible mechanisms involved in OSA-associated dyslipidaemia.

Profiling the serum proteome during Schistosoma mansoni infection in the BALB/c mice: A focus on the altered lipid metabolism as a key modulator of host-parasite interactions

Schistosomiasis represents a condition in which every aspect of the disease, starting from skin invasion of the cercariae to egg laying by adult worms, incites a tissue response from the vertebrate host. This response, whether acute or chronic, leads to the appearance of reporter molecules of tissue injury in bodily fluids that could be surveyed as markers for disease diagnosis, status and prognosis. In this scenario, the serum proteome associated with a schistosome infection remains poorly explored; particularly by the use of high-throughput mass spectrometric instrumentation. In this study, we aimed to comparatively examine the serum proteome of control versus infected BALB/c mice, spanning the interval between the onset of egg laying and the peak of the acute phase of infection. Compositional analysis of the sera, using one dimensional reversed-phase fractionation of tryptic peptides coupled to mass spectrometry, allowed identification of 453 constituents. Among these, over 30% (143 molecules) were differentially present comparing sera from infected and non-infected mice, as revealed by quantitative label-free shotgun approach. The majority of proteins exhibiting altered levels was categorised as belonging to immune response (acute phase-related proteins) followed by those linked to lipid transport and metabolism. Inspection of the lipid profile from control and infected individuals demonstrated more pronounced and significant alterations in triglycerides, VLDL and HDL fractions (p<0,001), attesting for a disturbance in circulating lipid molecules, and suggesting a key role in host-parasite interactions. Our findings provide a global view of the serum proteome in the context of experimental schistosomiasis during the acute phase of infection. It contributes by listing key molecules that could be monitored to inform on the associated inflammatory disease status. We hope it will shed light into uncovered aspects of the Schistosoma mansoni parasitism in the vertebrate host, particularly those related to modulation of the lipid metabolism mediating immune responses.

Potential Therapeutic Agents That Target ATP Binding Cassette A1 (ABCA1) Gene Expression

The cholesterol efflux protein ATP binding cassette protein A1 (ABCA) and apolipoprotein A1 (apo A1) are key constituents in the process of reverse-cholesterol transport (RCT), whereby excess cholesterol in the periphery is transported to the liver where it can be converted primarily to bile acids for either use in digestion or excreted. Due to their essential roles in RCT, numerous studies have been conducted in cells, mice, and humans to more thoroughly understand the pathways that regulate their expression and activity with the goal of developing therapeutics that enhance RCT to reduce the risk of cardiovascular disease. Many of the drugs and natural compounds examined target several transcription factors critical for ABCA1 expression in both macrophages and the liver. Likewise, several miRNAs target not only ABCA1 but also the same transcription factors that are critical for its high expression. However, after years of research and many preclinical and clinical trials, only a few leads have proven beneficial in this regard. In this review we discuss the various transcription factors that serve as drug targets for ABCA1 and provide an update on some important leads.

Integrative metabolomics-genomics approach reveals key metabolic pathways and regulators of Alzheimer's disease

Metabolites, the biochemical products of the cellular process, can be used to measure alterations in biochemical pathways related to the pathogenesis of Alzheimer's disease (AD). However, the relationships between systemic abnormalities in metabolism and the pathogenesis of AD are poorly understood. In this study, we aim to identify AD-specific metabolomic changes and their potential upstream genetic and transcriptional regulators through an integrative systems biology framework for analyzing genetic, transcriptomic, metabolomic, and proteomic data in AD. Metabolite co-expression network analysis of the blood metabolomic data in the Alzheimer's Disease Neuroimaging Initiative (ADNI) shows short-chain acylcarnitines/amino acids and medium/long-chain acylcarnitines are most associated with AD clinical outcomes, including episodic memory scores and disease severity. Integration of the gene expression data in both the blood from the ADNI and the brain from the Accelerating Medicines Partnership Alzheimer's Disease (AMP-AD) program reveals ABCA1 and CPT1A are involved in the regulation of acylcarnitines and amino acids in AD. Gene co-expression network analysis of the AMP-AD brain RNA-seq data suggests the CPT1A- and ABCA1-centered subnetworks are associated with neuronal system and immune response, respectively. Increased ABCA1 gene expression and adiponectin protein, a regulator of ABCA1, correspond to decreased short-chain acylcarnitines and amines in AD in the ADNI. In summary, our integrated analysis of large-scale multiomics data in AD systematically identifies novel metabolites and their potential regulators in AD and the findings pave a way for not only developing sensitive and specific diagnostic biomarkers for AD but also identifying novel molecular mechanisms of AD pathogenesis.

Association between new markers of cardiovascular risk and hepatic insulin resistance in those at high risk of developing type 2 diabetes

AIM/HYPOTHESIS

Hepatic insulin resistance (HIR) is considered to be an independent predictor of metabolic disorders and plays an important role in systemic inflammation, which contributes to abnormalities in cardiovascular disease (CVD) risk factors. The aim of this study was to investigate the relationship between HIR and new markers of cardiovascular risks, including leptin/adiponectin ratio (L/A), lipoprotein(a) [Lp(a)], and tumor necrosis factor alpha (TNF-α), at comparable whole body insulin sensitivity in non-diabetic individuals with or without CVD and at high risk of developing type 2 diabetes.

METHODS

The HIR index, L/A, Lp(a), and TNF-α were measured in 50 participants with CVD and in 200 without CVD (1:4 ratio). These were also matched for the homeostatic model assessment for insulin resistance (HOMA-IR) and Matsuda-insulin sensitivity index (ISI) in an observational study design.

RESULTS

The HIR index (1.52 ± 0.14 vs. 1.45 ± 0.17, p < 0.02), L/A (3.22 ± 3.10 vs. 2.09 ± 2.27, p < 0.004), and levels of Lp(a) (66.6 ± 49.5 vs. 37.9 ± 3 6.8 mg/dL, p < 0.0001) and TNF-α (18.9 ± 21.8 vs. 5.4 ± 7.1 pg/mL, p < 0.0001) were higher in those with CVD than those without CVD. HOMA-IR and ISI were not significantly different (p = 0.88 and p = 0.35, respectively). The HIR index was directly correlated with L/A (r = 0.41, p < 0.0001), Lp(a) (r = 0.20, p < 0.002), TNF- α (r = 0.14, p < 0.03), and diastolic blood pressure (DBP) (r = 0.13, p < 0.03). The stepwise model analysis showed that L/A, Lp(a), and TNF-α explained about 20% of the variation in the HIR indices of all the participants (p < 0.02).

CONCLUSIONS/INTERPRETATIONS

Our results suggest a positive association between HIR and new markers of cardiovascular risk [L/A, Lp(a), and TNF- α] at comparable whole body insulin sensitivity in those with or without CVD and at high risk of developing type 2 diabetes.

Implementation of Christian Orthodox fasting improves plasma adiponectin concentrations compared with time-restricted eating in overweight premenopausal women

The exact mechanisms mediating the metabolic effects of Orthodox fasting remain unclear. Plasma adiponectin, biochemical and anthropometrical data were evaluated in 55 Orthodox fasters (OF) and 42 time-restricted eating controls (all women, mean age 47.8 years) at three time points: baseline, end of the dietary intervention (7 weeks) and 5 weeks after participants returned to their typical dietary habits (12 weeks from baseline). In the OF group, there was an increase in adiponectin values at 12 weeks compared with baseline (9815.99 vs 8983.52 mg/ml, p = 0.02) and a reduction in body fat mass between baseline and 12 weeks (35.44 vs 32.17%, p = 0.004) and between 7 and 12 weeks (35.33 vs 32.17%, p = 0.003). In the same group, an inverse correlation between adiponectin and waist circumference values was observed over the entire study period. Our results provide novel evidence that Orthodox fasting has favourable metabolic effects related to improved adiponectin concentrations.

Improvements in cholesterol efflux capacity of HDL and adiponectin contribute to mitigation in cardiovascular disease risk after bariatric surgery in a cohort with morbid obesity

BACKGROUND

Bariatric surgery can alleviate cardiovascular risk via effects on cardiovascular disease (CVD) risk factors such as diabetes mellitus, hypertension, and dyslipidemia. Our study aimed to assess the cholesterol efflux capacity (CEC) of HDL as a negative risk factor for CVD in individuals with obesity and identify the factors associated with improvement in CEC 3 months following bariatric surgery.

METHODS

We recruited 40 control individuals (mean BMI of 22.2 kg/m²) and 56 obese individuals (mean BMI of 45.9 kg/m²). The biochemical parameters, inflammatory status and CEC of HDL was measured for the obese individuals before bariatric surgery and at 3 months after surgery. The CEC was measured using a cell-based cholesterol efflux system of BODIPY-cholesterol-labelled THP-1 macrophages.

RESULTS

A significant reduction in BMI (- 17%, p < 0.001), resolution of insulin sensitivity (HOMA2-IR = - 23.4%, p = 0.002; Adipo IR = - 16%, p = 0.009) and inflammation [log resistin = - 6%, p = 0.07] were observed 3 months post-surgery. CEC significantly improved 3 months after surgery [Pre: 0.91 ± 0.13; Post: 1.02 ± 0.16; p = 0.001] despite a decrease in HDL-C levels. The change in CEC correlated with the change in apo A-I (r = 0.39, p = 0.02) and adiponectin levels (r = 0.35, p = 0.03).

CONCLUSION

The results suggest that improvements in CEC, through improvement in adipose tissue health in terms of adipokine secretion and insulin sensitivity could be an important pathway in modulating obesity-related CVD risk.

Obesity Affects HDL Metabolism, Composition and Subclass Distribution

Background: Obesity increases the risk of coronary heart disease, partly due to its strong association with atherogenic dyslipidemia, characterized by high triglycerides and low high-density lipoprotein (HDL) cholesterol levels. Functional impairment of HDL may contribute to the increased cardiovascular mortality, but the effect of obesity on composition, structure, and function of HDL is not well understood. Design and Methods: We determined HDL composition, HDL subclass distribution, parameters of HDL function, and activities of most important enzymes involved in lipoprotein remodeling, including lecithin–cholesterol acyltransferase (LCAT) and cholesteryl ester transfer protein (CETP) in relatively young normal weight (n = 26), overweight (n = 22), and obese (n = 20) women. Results: Obesity (body mass index (BMI) ≥ 30) was associated with noticeable changes in LCAT and CETP activities and altered HDL composition, such as decreased apolipoprotein A-I, cholesterol, and phospholipid content, while pro-inflammatory HDL serum amyloid a content was increased. We observed a marked shift towards smaller HDL subclasses in obesity linked to lower anti-oxidative capacity of serum. LCAT activity, HDL subclass distribution, and HDL-cholesterol were associated with soluble leptin receptor, adiponectin, and liver enzyme activities. Of note, most of these alterations were only seen in obese women but not in overweight women. Conclusions: Obesity markedly affects HDL metabolism, composition, and subclass distribution linked to changes in liver and adipose tissue. HDL dysfunction may contribute to increased cardiovascular risk in obesity.

Obesity-Related Changes in High-Density Lipoprotein Metabolism and Function

In obese individuals, atherogenic dyslipidemia is a very common and important factor in the increased risk of cardiovascular disease. Adiposity-associated dyslipidemia is characterized by low high-density lipoprotein cholesterol (HDL-C) levels and an increase in triglyceride-rich lipoproteins. Several factors and mechanisms are involved in lowering HDL-C levels in the obese state and HDL quantity and quality is closely related to adiponectin levels and the bioactive lipid sphingosine-1-phosphate. Recent studies have shown that obesity profoundly alters HDL metabolism, resulting in altered HDL subclass distribution, composition, and function. Importantly, weight loss through gastric bypass surgery and Mediterranean diet, especially when enriched with virgin olive oil, is associated with increased HDL-C levels and significantly improved metrics of HDL function. A thorough understanding of the underlying mechanisms is crucial for a better understanding of the impact of obesity on lipoprotein metabolism and for the development of appropriate therapeutic approaches. The objective of this review article was to summarize the newly identified changes in the metabolism, composition, and function of HDL in obesity and to discuss possible pathophysiological consequences.

Associations of HDL Subspecies Defined by ApoC3 with Non-Alcoholic Fatty Liver Disease: The Multi-Ethnic Study of Atherosclerosis

Previously, we reported that inverse associations of high-density lipoprotein (HDL) with cardiovascular disease and diabetes were only observed for HDL that lacked the pro-inflammatory protein apolipoprotein C3 (apoC3). To provide further insight into the cardiometabolic properties of HDL subspecies defined by the presence or absence of apoC3, we aimed to examine these subspecies with liver fat content and non-alcoholic fatty liver disease (NAFLD). We investigated cross-sectional associations between ELISA-measured plasma levels of apoA1 in HDL that contained or lacked apoC3 and computed tomography-determined liver fat content and NAFLD (<51 HU) at baseline (2000–2002) among 5007 participants in the Multi-Ethnic Study of Atherosclerosis (MESA) without heavy alcohol consumption (>14 drinks/week in men and >7 drinks/week in women). In multivariable-adjusted regression models, apoA1 in HDL that contained or lacked apoC3 was differentially associated with liver fat content (P_{heterogeneity} = 0.048). While apoA1 in HDL that lacked apoC3 was inversely associated with liver fat content (P_trend < 0.0001), apoA1 in HDL that contained apoC3 was not statistically significantly associated with liver fat content (P_trend = 0.57). Higher apoA1 in HDL that lacked apoC3 was related to a lower prevalence of NAFLD (OR per SD: 0.80; 95% CI: 0.72, 0.89), whereas no association was found for apoA1 in HDL that contained apoC3 (OR per SD: 0.95; 95% CI: 0.85, 1.05; P_{heterogeneity} = 0.09). Higher apoA1 in HDL that lacked apoC3 was associated with less liver fat content and a lower prevalence of NAFLD. This finding extends the inverse association of HDL lacking apoC3 from cardiovascular disease to NAFLD. Lack of biopsy-proven hepatic steatosis and fibrosis data requires the replication of our study in further studies.

Insulin deficiency, but not resistance, exaggerates cognitive deficits in transgenic mice expressing human amyloid and tau proteins. Reversal by Exendin-4 treatment

Epidemiological studies have pointed at diabetes as a risk factor for Alzheimer's disease (AD) and this has been supported by several studies in animal models of both type 1 and type 2 diabetes. However, side-by-side comparison of the two types of diabetes is limited. We investigated the role of insulin deficiency and insulin resistance in the development of memory impairments and the effect of Exendin-4 (Ex4) treatment in a mouse model of AD. Three-4-month-old female wild type (WT) mice and mice overexpressing human tau and amyloid precursor protein (TAPP) were injected with streptozotocin (STZ) or fed a high-fat diet (HFD). A second study was performed in TAPP-STZ mice treated with Ex4, a long-lasting analog of GLP-1. Plasma and brain were collected at study termination for ELISA, Western blot, and immunohistochemistry analysis. Learning and memory deficits were impaired in TAPP transgenic mice compared with WT mice at the end of the study. Deficits were exaggerated by insulin deficiency in TAPP mice but 12 weeks of insulin resistance did not affect memory performances in either WT or TAPP mice. Levels of phosphorylated tau were increased in the brain of WT-STZ and TAPP-STZ mice but not in the brain of WT or TAPP mice on HFD. In the TAPP-STZ mice, treatment with Ex4 initiated after established cognitive deficits ameliorated learning, but not memory, impairments. This was accompanied by the reduction of amyloid β and phosphorylated tau expression. Theses studies support the role of Ex4 in AD, independently from its actions on diabetes.

Links Between Adiponectin and Dementia: From Risk Factors to Pathophysiology

With the aging population, dementia is becoming one of the most serious and troublesome global public health issues. Numerous studies have been seeking for effective strategies to delay or block its progression, but with little success. In recent years, adiponectin (APN) as one of the most abundant and multifunctional adipocytokines related to anti-inflammation, regulating glycogen metabolism and inhibiting insulin resistance (IR) and anti-atherosclerosis, has attracted widespread attention. In this article, we summarize recent studies that have contributed to a better understanding of the extent to which APN influences the risks of developing dementia as well as its pathophysiological progression. In addition, some controversial results interlinked with its effects on cognitive dysfunction diseases will be critically discussed. Ultimately, we aim to gain a novel insight into the pleiotropic effects of APN levels in circulation and suggest potential therapeutic target and future research strategies.

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 role of adiponectin in cholesterol efflux and HDL biogenesis and metabolism

Cholesterol efflux is the initial step in the reverse cholesterol transport pathway by which excess cholesterol in peripheral cells is exported and subsequently packaged into high-density lipoprotein (HDL) particles. Adiponectin is the most abundantly secreted adipokine that possesses anti-inflammatory and vasculoprotective properties via interaction with transmembrane receptors, AdipoR1 and AdipoR2. Evidence suggests that low levels of adiponectin may be a useful marker for atherosclerotic disease. A proposed anti-atherogenic mechanism of adiponectin involves its ability to promote cholesterol efflux. We performed a systematic review of the role of adiponectin in cholesterol efflux and HDL biogenesis, and of the proteins and receptors believed to be implicated in this process. Nineteen eligible studies (7 clinical, 11 fundamental, 1 clinical + fundamental) were identified through Ovid Medline, Ovid Embase, and Pubmed, that support the notion that adiponectin plays a key role in promoting ABCA1-dependent cholesterol efflux and in modulating HDL biogenesis via activation of the PPAR-γ/LXR-α signalling pathways in macrophages. AdipoR1 and AdipoR2 are suggested to also be implicated in this process, however the data are conflicting/insufficient to establish any firm conclusions. Once the exact mechanisms are unravelled, adiponectin may be critical in defining future treatment strategies directed towards increasing HDL functionality and ultimately reducing atherosclerotic disease.

Beneficial Effects of Adiponectin on Glucose and Lipid Metabolism and Atherosclerotic Progression: Mechanisms and Perspectives

Circulating adiponectin concentrations are reduced in obese individuals, and this reduction has been proposed to have a crucial role in the pathogenesis of atherosclerosis and cardiovascular diseases associated with obesity and the metabolic syndrome. We focus on the effects of adiponectin on glucose and lipid metabolism and on the molecular anti-atherosclerotic properties of adiponectin and also discuss the factors that increase the circulating levels of adiponectin. Adiponectin reduces inflammatory cytokines and oxidative stress, which leads to an improvement of insulin resistance. Adiponectin-induced improvement of insulin resistance and adiponectin itself reduce hepatic glucose production and increase the utilization of glucose and fatty acids by skeletal muscles, lowering blood glucose levels. Adiponectin has also β cell protective effects and may prevent the development of diabetes. Adiponectin concentration has been found to be correlated with lipoprotein metabolism; especially, it is associated with the metabolism of high-density lipoprotein (HDL) and triglyceride (TG). Adiponectin appears to increase HDL and decrease TG. Adiponectin increases ATP-binding cassette transporter A1 and lipoprotein lipase (LPL) and decreases hepatic lipase, which may elevate HDL. Increased LPL mass/activity and very low density lipoprotein (VLDL) receptor and reduced apo-CIII may increase VLDL catabolism and result in the reduction of serum TG. Further, adiponectin has various molecular anti-atherosclerotic properties, such as reduction of scavenger receptors in macrophages and increase of cholesterol efflux. These findings suggest that high levels of circulating adiponectin can protect against atherosclerosis. Weight loss, exercise, nutritional factors, anti-diabetic drugs, lipid-lowering drugs, and anti-hypertensive drugs have been associated with an increase of serum adiponectin level.

Current and future therapies for addressing the effects of inflammation on HDL cholesterol metabolism

Cardiovascular disease (CVD) is a major cause of morbidity and mortality worldwide. Inflammatory processes arising from metabolic abnormalities are known to precipitate the development of CVD. Several metabolic and inflammatory markers have been proposed for predicting the progression of CVD, including high density lipoprotein cholesterol (HDL-C). For ~50 years, HDL-C has been considered as the atheroprotective 'good' cholesterol because of its strong inverse association with the progression of CVD. Thus, interventions to increase the concentration of HDL-C have been successfully tested in animals; however, clinical trials were unable to confirm the cardiovascular benefits of pharmaceutical interventions aimed at increasing HDL-C levels. Based on these data, the significance of HDL-C in the prevention of CVD has been called into question. Fundamental in vitro and animal studies suggest that HDL-C functionality, rather than HDL-C concentration, is important for the CVD-preventive qualities of HDL-C. Our current review of the literature positively demonstrates the negative impact of systemic and tissue (i.e. adipose tissue) inflammation in the healthy metabolism and function of HDL-C. Our survey indicates that HDL-C may be a good marker of adipose tissue health, independently of its atheroprotective associations. We summarize the current findings on the use of anti-inflammatory drugs to either prevent HDL-C clearance or improve the function and production of HDL-C particles. It is evident that the therapeutic agents currently available may not provide the optimal strategy for altering HDL-C metabolism and function, and thus, further research is required to supplement this mechanistic approach for preventing the progression of CVD.

LINKED ARTICLES

This article is part of a themed section on Targeting Inflammation to Reduce Cardiovascular Disease Risk. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v174.22/issuetoc and http://onlinelibrary.wiley.com/doi/10.1111/bcp.v82.4/issuetoc.

Weight-Loss Diets, Adiponectin, and Changes in Cardiometabolic Risk in the 2-Year POUNDS Lost Trial

CONTEXT

Compelling evidence suggests that the beneficial effects of weight-loss diet interventions on improvement of cardiometabolic risk factors may be partly through modulating secretion of adiponectin from adipose tissue.

OBJECTIVE

To investigate the effects of long-term weight-loss diets with different compositions of macronutrients on longitudinal changes in circulating adiponectin concentrations and how such changes, if they exist, affect cardiometabolic risk.

DESIGN, SETTING, AND PARTICIPANTS

In the 2-year Preventing Overweight Using Novel Dietary Strategies trial, 811 overweight or obese adults were randomly assigned to 1 of 4 diets varying in macronutrient intakes. The current analysis was restricted to participants who had baseline adiponectin measurement (n = 768). Circulating concentrations of adiponectin and cardiometabolic outcomes were repeatedly measured at baseline, 6 months, and 2 years.

MAIN OUTCOME MEASURES

Circulating concentrations of adiponectin and cardiometabolic risk factors.

RESULTS

Weight-loss diet interventions significantly increased circulating adiponectin concentrations over 2 years, similarly in 4 diet groups (P value for difference >.05). We found that the increase of adiponectin was significantly associated with reduction of waist circumference and low-density lipoprotein cholesterol, but associated with increase of high-density lipoprotein cholesterol (P < .001 for each), after adjusting for age, sex, ethnicity, follow-up time, diet group, baseline body mass index, baseline level of respective outcome trait, and concurrent weight change.

CONCLUSIONS

Our findings indicate that long-term interventions by weight-loss diets varying in macronutrients similarly increase circulating adiponectin, which may particularly improve abdominal fat distribution and lipid metabolism independently of weight change.

Lipoprotein composition in patients with type 1 diabetes mellitus: Impact of lipases and adipokines

OBJECTIVE

High cardiovascular mortality in patients with type 1 diabetes (T1DM) is widely recognized. Paradoxically, these patients have been shown to have elevated HDL-C and reduced apoB-containing lipoproteins. The purpose of this investigation was to further characterize the lipoprotein composition in T1DM and to assess the role that lipases and adipokines may play in these differences.

METHODS

T1DM patients (89) attending the Diabetes Clinic at the University of Miami and 42 healthy controls were recruited. Clinical characteristics, lipoprotein composition (by ultracentrifugation and HPLC), leptin, and adiponectin were measured in the full cohort, while a subgroup had LPL and hepatic lipase measured.

RESULTS

Subjects were predominately Caucasian and Hispanic. HgbA1c's were above goal while their mean duration of diabetes was >20 years. LPL was 2-fold elevated in diabetic women versus controls (+107%{p=0.001}) with no difference in men. Hepatic lipase was reduced 50% {p<0.001} in women but increased 50% {p=0.079} in men. Leptin was similar to controls in women but reduced in men (-60%{p<0.001}). Adiponectin was elevated in both genders (men: +55%{p=0.018}; women: +46%{p=0.007}). LDL-C was reduced in both diabetic men (-33%{p<0.001}) and women (-24%{p<0.001}) while HDL-C trended higher only in men (+13%{p=0.064}). Both total apoB (men: -31%{p<0.001}; women: -17%{p=0.016}) and triglycerides (men: -49%{p<0.001}; women: -31%{p=0.011}) were reduced in both genders while total apoA-I was increased in both (men: +31%{p<0.001}; women: +19%{p=0.008}). Both men and women had increases in LpA-I (+66%{p<0.001}; +40%{p=0.001}) which accounted for essentially the entire increase in HDL mass. VLDL lipids (men: -53→70%; women: -31→57%) were lower as was apoB (particle number) in men (-51{p<0.001}) with a similar trend in women (-35%{p=0.066}). Cholesterol esters in the particle core were depleted in both genders relative to both apoB (men: -41%; women: -37%) and triglycerides (men: -38%; women: -34%) (all{p<0.009}). There were similar differences in IDL. HDL-L lipids (except triglycerides) (men: +45→74%; women: +49→77%{p<0.006}), apoA-1 (men: +162%; women: +117%{p<0.001}), and apoA-II (men: +64%{p=0.008}; women: +55%{p=0.014}) were higher in T1DM patients. These differences produced dramatic increases in LpA-I (men: +221%; women +139%{p<0.001}) and total HDL-L mass (men: +85%; women: +78%{p<0.001}). ApoM (men: +190%; women: +149%{p<0.001}) was also dramatically increased. Conversely, HDL-D lipids were lower in both genders (-20%→50%) while apoA-I was not different in either. ApoA-II was lower only in the diabetic women (-25%{p=0.015}). LPL activity correlated primarily with IDL(-), LDL(-), HDL-L(+), and HDL-D(-) only in the women. HL correlated weakly with VLDL(+), LDL(+), HDL-L(-), and HDL-D(+) in women but had much stronger correlations with VLDL(-), IDL(-), and HDL-L(+). Adiponectin correlated with VLDL(-), IDL(-), LDL(-), HDL-L(+), and HDL-D(-) in women but only HDL-L(+) and HDL-D(-) in men. Leptin correlated with very few parameters in women but did correlate weakly with several HDL-L(-) and HDL-M(-) parameters.

CONCLUSION

Lipoprotein composition and adipokine concentrations in both genders as well as lipase activities in the women would be expected to reduce the atherosclerotic risk in these patients with T1DM. These data suggest that there are functional lipoprotein abnormalities responsible for their CV risk that are not reflected in their plasma concentrations.

The Role of Clinical Proteomics, Lipidomics, and Genomics in the Diagnosis of Alzheimer's Disease

The early diagnosis of Alzheimer’s disease (AD) has become important to the reversal and treatment of neurodegeneration, which may be relevant to premature brain aging that is associated with chronic disease progression. Clinical proteomics allows the detection of various proteins in fluids such as the urine, plasma, and cerebrospinal fluid for the diagnosis of AD. Interest in lipidomics has accelerated with plasma testing for various lipid biomarkers that may with clinical proteomics provide a more reproducible diagnosis for early brain aging that is connected to other chronic diseases. The combination of proteomics with lipidomics may decrease the biological variability between studies and provide reproducible results that detect a community’s susceptibility to AD. The diagnosis of chronic disease associated with AD that now involves genomics may provide increased sensitivity to avoid inadvertent errors related to plasma versus cerebrospinal fluid testing by proteomics and lipidomics that identify new disease biomarkers in body fluids, cells, and tissues. The diagnosis of AD by various plasma biomarkers with clinical proteomics may now require the involvement of lipidomics and genomics to provide interpretation of proteomic results from various laboratories around the world.

Pilot study on the effects of a 2-week hiking vacation at moderate versus low altitude on plasma parameters of carbohydrate and lipid metabolism in patients with metabolic syndrome

Background

Hypoxic and hypobaric conditions may augment the beneficial influence of training on cardiovascular risk factors. This pilot study aimed to explore for effects of a two-week hiking vacation at moderate versus low altitude on adipokines and parameters of carbohydrate and lipid metabolism in patients with metabolic syndrome.

Methods

Fourteen subjects (mean age: 55.8 years, range: 39 – 69) with metabolic syndrome participated in a 2-week structured training program (3 hours of guided daily hiking 4 times a week, training intensity at 55-65% of individual maximal heart rate; total training time, 24 hours). Participants were divided for residence and training into two groups, one at moderate altitude (1,900 m; n = 8), and the other at low altitude (300 m; n = 6). Anthropometric, cardiovascular and metabolic parameters were measured before and after the training period.

Results

In study participants, training overall reduced circulating levels of total cholesterol (p = 0.024), low-density lipoprotein cholesterol (p = 0.025) and adiponectin (p < 0.001). In the group training at moderate altitude (n = 8), lowering effects on circulating levels were significant not only for total cholesterol, low-density-lipoprotein cholesterol and adiponectin (all, p < 0.05) but also for triglycerides (p = 0.025) and leptin (p = 0.015), whereas in the low altitude group (n = 6), none of the lipid parameters was significantly changed (each p > 0.05). Hiking-induced relative changes of triglyceride levels were positively associated with reductions in leptin levels (p = 0.006). As compared to 300 m altitude, training at 1,900 m showed borderline significant differences in the pre-post mean reduction rates of triglyceride (p = 0.050) and leptin levels (p = 0.093).

Conclusions

Preliminary data on patients with metabolic syndrome suggest that a 2-week hiking vacation at moderate altitude may be more beneficial for adipokines and parameters of lipid metabolism than training at low altitude. In order to draw firm conclusions regarding better corrections of dyslipidemia and metabolic syndrome by physical exercise under mild hypobaric and hypoxic conditions, a sufficiently powered randomized clinical trial appears warranted.

Trial registration

ClinicalTrials.gov ID NCT02013947 (first received November 6, 2013).

Total and High Molecular Weight Adiponectin Levels and Prediction of Cardiovascular Risk in Diabetic Patients

The study aimed at assessing the potential use of lower total and HMW adiponectin levels for predicting cardiovascular risk in patients with type 2 diabetes mellitus (T2DM). Concentrations of total adiponectin or high molecular weight (HMW) adiponectin decrease in association with the development of metabolic dysfunction such as obesity, insulin resistance, or T2DM. Increased adiponectin levels are associated with a lower risk for coronary heart disease. A total of 551 individuals were assessed. The first group comprised metabolically healthy participants (143 females, and 126 males) and the second group were T2DM patients (164 females, and 118 males). Both total adiponectin and HMW adiponectin in diabetic patients were significantly lower when compared with the group of metabolically healthy individuals. There was a weak monotonic correlation between HMW adiponectin levels and triglycerides levels. Binary logistic regression analysis, gender adjusted, showed a higher cardiovascular risk in diabetic persons when both total adiponectin (OR = 1.700) and HMW adiponectin (OR = 2.785) levels were decreased. A decrease in total adiponectin levels as well as a decrease in its HMW adiponectin is associated with a higher cardiovascular risk in individuals with T2DM. This association suggests that adiponectin levels may be potentially used as an epidemiological marker for cardiovascular risk in diabetic patients.

Obesity and osteoarthritis, more than just wear and tear: pivotal roles for inflamed adipose tissue and dyslipidaemia in obesity-induced osteoarthritis

OA is a degenerative joint disease characterized by articular cartilage degradation, osteophyte formation, synovitis, and subchondral bone sclerosis. One of OAs main risk factors is obesity. To date, it is not fully understood how obesity results in OA. Historically, this link was ascribed to excessive joint loading as a result of increased body weight. However, the association between obesity and OA in non-weight-bearing joints suggests a more complex aetiology for obesity-induced OA. In the present review, the link between obesity and OA is discussed. First, the historical view of altered joint loading leading to wear and tear of the joint is addressed. Subsequently, the effects of a disturbed lipid metabolism, low-grade inflammation, and adipokines on joint tissues are discussed and linked to OA. Taken together, inflamed adipose tissue and dyslipidaemia play pivotal roles in obesity-induced OA. It becomes increasingly clear that the link between obesity and OA transcends excessive loading.

Adiponectin isoforms differentially affect gene expression and the lipidome of primary human hepatocytes

Adiponectin (APN) exerts multiple beneficial effects in obesity and protects from liver injury. Different APN isoforms circulate in serum, and here, the effect of low molecular weight (LMW) and higher molecular weight (HMW) APN on primary human hepatocytes (PHH) has been analyzed. APN is not detected in hepatocyte lysates; levels are strongly increased by HMW-APN, but not by LMW-APN, suggesting the distinct uptake/degradation of APN isoforms by PHH. Several genes with a role in fibrosis, glucose and lipid metabolism known to be regulated by HMW-APN are not affected by the LMW-isoform. Follistatin is reduced by HMW-APN and induced by LMW-APN in supernatants of PHH. Fibroblast growth factor 21 is repressed by both isoforms. Cellular triglycerides and cholesterol levels are not reduced by APN. Total phospholipids, including plasmalogens and sphingomyelins, are not changed upon APN incubation, while distinct species are either induced or repressed. Unexpectedly, total ceramide is increased by LMW-APN. Current data show that APN isoforms differentially affect hepatocyte gene expression, but do not grossly alter the hepatocyte lipidome.

Obesity and its metabolic complications: the role of adipokines and the relationship between obesity, inflammation, insulin resistance, dyslipidemia and nonalcoholic fatty liver disease

Accumulating evidence indicates that obesity is closely associated with an increased risk of metabolic diseases such as insulin resistance, type 2 diabetes, dyslipidemia and nonalcoholic fatty liver disease. Obesity results from an imbalance between food intake and energy expenditure, which leads to an excessive accumulation of adipose tissue. Adipose tissue is now recognized not only as a main site of storage of excess energy derived from food intake but also as an endocrine organ. The expansion of adipose tissue produces a number of bioactive substances, known as adipocytokines or adipokines, which trigger chronic low-grade inflammation and interact with a range of processes in many different organs. Although the precise mechanisms are still unclear, dysregulated production or secretion of these adipokines caused by excess adipose tissue and adipose tissue dysfunction can contribute to the development of obesity-related metabolic diseases. In this review, we focus on the role of several adipokines associated with obesity and the potential impact on obesity-related metabolic diseases. Multiple lines evidence provides valuable insights into the roles of adipokines in the development of obesity and its metabolic complications. Further research is still required to fully understand the mechanisms underlying the metabolic actions of a few newly identified adipokines.

Fat cell size and adipokine expression in relation to gender, depot, and metabolic risk factors in morbidly obese adolescents

OBJECTIVE

To understand the regulation of adipocyte size and adipokine expression in relation to gender, anatomic location, adiposity, and metabolic risk factors in adolescents with morbid obesity.

METHODS

Adipocyte size and adipokine expression in paired abdominal subcutaneous (SAT) and omental (VAT) surgical adipose tissues were related to gender, anatomic location, adiposity, and metabolic risk factors in a group of morbidly obese adolescents.

RESULTS

Significant depot- and/or gender-related differences in adipocyte size and adipokine expression were detected. Adjusted for body mass index, adipocyte size in both depots was larger in males than in females and was a major predictor of mRNA levels of leptin, plasminogen activator inhibitor-1, and adiponectin. Gender, but not adipocyte size, was significantly correlated with proinflammatory cytokine expression. Body mass index and waist circumference were correlated positively with VAT adipocyte size and negatively with SAT adipocyte size. VAT adiponectin and interleukin-6 expression levels were major predictors of high-density lipoprotein cholesterol concentrations, independent of gender, adiposity, and insulin sensitivity.

CONCLUSIONS

Adipose tissue morphology and function in obese adolescents are influenced by gender and anatomic location; the pattern of gender- and depot-related differences in adipocyte size and adipokine expression suggests that adolescent males, relative to the females, are at increased risk for obesity-related metabolic comorbidities.

Adiponectin expression protects against angiotensin II-mediated inflammation and accelerated atherosclerosis

Adiponectin (APN), an adipocytokine produced by adipose tissue, exerts pleiotropic actions regulating inflammation, metabolism and vascular homeostasis. APN levels are inversely correlated with obesity, type-2 diabetes, hypertension and cardiovascular disease. Although renin angiotensin system (RAS) activation in these interrelated metabolic syndrome components increases angiotensin II (AngII) levels leading to vascular damage, it is unknown whether APN under these conditions provides atheroprotection. We investigated whether increasing plasma APN provides atheroprotection in a hypertensive and accelerated atherosclerosis model. Using adenoviral gene transfer, sustained APN expression increased plasma levels of total and high-molecular weight APN, leading to a significant elevation of plasma HDL-cholesterol (HDL-C). Elevated APN levels were strongly atheroprotective, yet had no impact on blood pressure. Notably, gene expression analyses revealed that APN significantly inhibited the expression of pro-inflammatory and atherogenic genes while it increased the expression of the anti-inflammatory cytokine, IL-10 and the cholesterol efflux transporters, ABCA1 and ABCG1 in the artery wall. These findings suggest that increasing APN levels may be an effective therapeutic strategy to inhibit vascular inflammation and accelerated atherosclerosis associated with RAS activation in the metabolic syndrome.

Effect of urotensin II on apolipoprotein B100 and apolipoprotein A-I expression in HepG2 cell line

BACKGROUND

Increased apolipoprotein B100 (apo B) and decreased apolipoprotein A-I (apo A-I) production are important risk factors in atherosclerosis. Urotensin II (UII), as the most potent vasoconstrictor in human, is related with hypertension and probably atherosclerosis. Because of the relationship between the hypertension and lipoprotein metabolism in atherosclerosis, the aim of this study was to test the effect of urotensin II on apo B and apo A-I expression in hepatic (HepG2) cell line.

MATERIALS AND METHODS

HepG2 cells were treated with 10, 50, 100, and 200 nmol/L of urotensin II (n = 6). Relative apo B and apo A-I messenger RNA (mRNA) levels in conditioned media, normalized to glyceraldehyde-3-phosphate dehydrogenase, were measured with quantitative real-time polymerase chain reaction method. In addition, apo B and apo A-I levels were also estimated and compared with the controls using the western blotting method. Data were analyzed statistically by ANOVA and non-parametric tests.

RESULTS

The apo B mRNA levels were not increased significantly following the treatment with UII. However, apo B protein levels were increased significantly after the treatment with urotensin II, especially at 100 and 200 nmol/L. The apo A-I mRNA and protein levels in conditioned media also were not significantly changed. However, there was a significant decrease in apo A-I mRNA and protein levels at 200 nM UII.

CONCLUSIONS

UII might increase apo B at protein level probably through participating factors in its synthesis and/ or stability/degradation. In addition, UII may have decreasing effect at more than 200 nM concentrations on apo A-I.

Adiponectin and the cardiometabolic syndrome: an epidemiological perspective

Adiponectin is an adipocyte-derived plasma protein with cardio-vasculo-protective and anti-diabetic properties. Plasma adiponectin levels are low in patients with the cardiometabolic syndrome (a cluster of multiple risk factors based on visceral fat accumulation). Routine measurement of plasma adiponectin may be useful to encourage life-style changes.

Adiponectin as a routine clinical biomarker

Adiponectin is a protein synthesized and secreted predominantly by adipocytes into the peripheral blood. However, circulating adiponectin level is inversely related with body weight, especially visceral fat accumulation. The mechanism of this paradoxical relation remains obscure. Low circulating adiponectin concentrations (hypoadiponectinemia; <4 μg/mL) are associated with a variety of diseases, including dysmetabolism (type 2 diabetes, insulin resistance, hypertension, dyslipidemia, metabolic syndrome, hyperuricemia), atherosclerosis (coronary artery disease, stroke, peripheral artery disease), sleep apnea, non-alcoholic fatty liver disease, gastritis and gastro-esophageal reflux disease, inflammatory bowel diseases, pancreatitis, osteoporosis, and cancer (endometrial cancer, postmenopausal breast cancer, leukemia, colon cancer, gastric cancer, prostate cancer). On the other hand, hyperadiponectinemia is associated with cardiac, renal and pulmonary diseases. This review article focuses on the significance of adiponectin as a clinical biomarker of obesity-related diseases. Routine measurement of adiponectin in patients with lifestyle-related diseases is highly recommended.

Impact of dyslipidemic components of metabolic syndrome, adiponectin levels, and anti-diabetes medications on malondialdehyde-modified low-density lipoprotein levels in statin-treated diabetes patients with coronary artery disease

BACKGROUND

A residual risk of cardiovascular disease tends to persist despite standard prevention therapy with statins. This may stem partly from increased oxidized low-density lipoprotein (LDL) levels. However, how oxidized LDL can be further reduced beyond statin therapy in high-risk diabetes patients remains unclear. We aimed to clarify the clinical factors associated with oxidized LDL levels in statin-treated high-risk diabetes patients.

METHODS

This cross-sectional observational study included 210 diabetes patients with coronary artery diseases (CAD) who were treated with statins. We determined serum malondialdehyde-modified LDL (MDA-LDL), LDL cholesterol, high-density lipoprotein (HDL) cholesterol, triglyceride (TG), remnant lipoprotein cholesterol, hemoglobin (Hb) A1c, adiponectin, and C-reactive protein (CRP) levels and investigated the factors influencing the MDA-LDL level.

RESULTS

In univariate analysis, the MDA-LDL level was significantly correlated with LDL cholesterol (p < 0.0001), TG (p < 0.0001), HDL cholesterol (p = 0.017), and adiponectin (p = 0.001) levels but not with age, body mass index, waist circumference, blood pressure, or HbA1c levels. Even after adjusting for the LDL cholesterol level, the correlations between the MDA-LDL level and the TG, HDL cholesterol, and adiponectin levels were still significant. Among these significant factors, multivariate analysis revealed that the MDA-LDL level was independently associated with the LDL cholesterol, TG, and HDL cholesterol but not with adiponectin levels. The MDA-LDL level was also significantly associated with the CRP level (p = 0.014) and the remnant lipoprotein cholesterol level (p < 0.0001) independently of the LDL cholesterol level. The number of metabolic syndrome (MS) components was significantly associated with the MDA-LDL/LDL cholesterol ratio (p < 0.0001). Furthermore, the use of metformin and α-glucosidase inhibitors was inversely associated with high MDA-LDL levels (p = 0.033 and 0.018, respectively).

CONCLUSION

In statin-treated diabetes patients with CAD, the MDA-LDL level was significantly correlated with TG and HDL cholesterol levels. Adiponectin level was also significantly associated with the MDA-LDL level, but not independent of the above-mentioned factors. The management of dyslipidemic MS components, including the use of metformin or α-glucosidase inhibitors, may be important for reducing the oxidized LDL levels beyond statin therapy in high-risk diabetes patients.

Adiponectin and lipoprotein metabolism

Adiponectin is secreted by the adipose tissue and it has been shown to be down-regulated in states of insulin resistance and in cardiovascular disease. It has also been found to be correlated with various parameters of lipoprotein metabolism, and in particular, it is associated with the metabolism of high-density lipoprotein (HDL) and triglycerides; adiponectin appears to induce an increase in serum HDL, and conversely, HDL can up-regulate adiponectin levels, and in addition, adiponectin lowers serum triglycerides through enhancement of the catabolism of triglyceride-rich lipoproteins. Studies investigating whether adiponectin is causally linked with lipoprotein metabolism have yielded conflicting data, and the mechanisms underlying the interplay between adiponectin and lipoproteins remain to be elucidated. The adiponectin-HDL relationship can explain at least in part the presumed protective role of adiponectin in cardiovascular disease and the adiponectin changes observed after dieting, exercise and lipid-lowering treatment. Statins, fibrates, niacin and n-3 fatty acids may influence circulating adiponectin levels, indicating that adiponectin may mediate some of the metabolic effects of these agents. Further studies to investigate more thoroughly the role of adiponectin in lipoprotein metabolism in the human setting should be carefully planned, focusing on causality and the possible impact of adiponectin on the pathogenesis of cardiovascular disease.

Subjects with low plasma HDL cholesterol levels are characterized by an inflammatory and oxidative phenotype

BACKGROUND

Epidemiological studies have shown that low plasma levels of high-density lipoprotein (HDL) cholesterol are associated with increased risk of cardiovascular disease, but the mechanisms for the possible atheroprotective effects of HDL cholesterol have still not been fully clarified, in particular in relation to clinical studies.

OBJECTIVE

To examine the inflammatory, anti-oxidative and metabolic phenotype of subjects with low plasma HDL cholesterol levels.

METHODS AND RESULTS

Fifteen subjects with low HDL cholesterol levels (eleven males and four females) and 19 subjects with high HDL (three males and 16 females) were recruited. Low HDL cholesterol was defined as ≤10th age/sex specific percentile and high HDL-C was defined as ≥90 age/sex specific percentile. Inflammatory markers in circulation and PBMC gene expression of cholesterol efflux mediators were measured. Our main findings were: (i) subjects with low plasma HDL cholesterol levels were characterized by increased plasma levels of CRP, MMP-9, neopterin, CXCL16 and ICAM-1 as well as low plasma levels of adiponectin, suggesting an inflammatory phenotype; (ii) these individuals also had reduced paraoxonase (PON)1 activity in plasma and PON2 gene expression in peripheral blood mononuclear cells (PBMC) accompanied by increased plasma levels of oxidized LDL suggesting decreased anti-oxidative capacity; and (iii) PBMC from low HDL subjects also had decreased mRNA levels of ABCA1 and ABCG1, suggesting impaired reverse cholesterol transport.

CONCLUSION

Subjects with low plasma HDL cholesterol levels are characterized by an inflammatory and oxidative phenotype that could contribute to the increased risk of atherosclerotic disorders in these subjects with low HDL levels.

β3-Adrenoceptor activation attenuates atherosclerotic plaque formation in ApoE(-/-) mice through lowering blood lipids and glucose

AIM

To examine the effects of β3-adrenoceptor (β3-AR) activation on atherosclerotic plaque development in ApoE(-/-) mice.

METHODS

Thirty six week-old male ApoE(-/-) mice on a high-fat diet were treated with atorvastatin (10 mg·kg(-1)·d(-1), po), BRL37344 (β3-AR agonist, 1.65 or 3.30 μg/kg, ip, twice a week) or SR52390A (β3-AR antagonist, 50 μg/kg, ip, twice a week) for 12 weeks. Wild-type C57BL/6J mice receiving a normal diet were taken as healthy controls. At the end of the treatments, serum levels of triglycerides (TG), total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), non-high density lipoprotein cholesterol (nHDL-C), glucose and insulin were measured. The thoracic aortas were dissected out, the area of atherosclerotic plaques and extent of fibrosis in the plaques were examined using HE and Masson's trichome staining, respectively.

RESULTS

Compared to wild-type mice, ApoE(-/-) mice fed on a high-fat diet exhibited prominent hyperlipidemia and insulin resistance, associated with large area of atherosclerotic plaques and great extent of fibrosis in aortas. Atorvastatin significantly decreased the serum levels of TC and nHDL-C, and reduced the plaque area and collagen content in aortas. BRL37344 significantly decreased the serum levels of TG, TC, nHDL-C, glucose and insulin, and increased HDL-C and the insulin sensitivity, and dose-dependently reduced the plaque area and collagen content in aortas. SR52390A treatment did not affect any parameters studied.

CONCLUSION

The β3-AR agonist impedes the progression of atherosclerosis in ApoE(-/-) mice, through improvement of the lipid and glucose profiles.

Mild obesity reduces survival and adiponectin sensitivity in endotoxemic rats

BACKGROUND

Recent meta-analyses have reported that critically ill patients with morbid obesity (body mass index >40 kg/m(2)) have poor outcomes, but the effects and mechanisms of action of mild obesity are still unclear. The purpose of this study was to evaluate the effect of mild obesity using a lard-based, high-fat diet (HFD) on pathologic conditions and the mechanisms of adiponectin action in endotoxemic rats.

MATERIALS AND METHODS

Male Wistar rats underwent HFD feeding for 4 wk and were killed at 0, 1.5, and 6 h after lipopolysaccharide (LPS) injection. Plasma levels of adiponectin, nitric oxide, and interleukin 6; messenger RNA expression of adiponectin receptors (AdipoR1 and AdipoR2) in the liver and the skeletal muscle; blood biochemical test results; and histology of the liver were analyzed.

RESULTS

HFD-fed rats had a lower survival rate (12.8% versus 85.2%) and lower plasma adiponectin levels after LPS injection (P < 0.01). Messenger RNA expression of adiponectin receptors in the liver, but not the skeletal muscle, also decreased in HFD-fed rats (P < 0.05). Tissue injury and oxidative stress in the liver and plasma inflammatory mediator levels increased, and worsened lipid metabolism abnormalities were noted. The findings indicated that HFD decreased the sensitivity of adiponectin and was associated with an increase in oxidative stress and inflammation, which finally resulted in worsened liver injury and poor survival rate after LPS injection.

CONCLUSIONS

Short-term, HFD-induced, mild obesity is harmful to the septic host, reduces adiponectin sensitivity, and could be the cause of worsening pathologic conditions.

Hypoadiponectinemia: a useful marker of dyslipidemia in women with polycystic ovary syndrome

OBJECTIVE

Adiponectin plays a role in obesity, lipid metabolism, and anti-inflammation. Women with polycystic ovary syndrome (PCOS) are also at risk for dyslipidemia. Therefore, we investigated the association between adiponectin levels and the lipid profile including high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), and triglycerides (TGs) in women with PCOS and contemplated what role adiponectin might play in dyslipidemia with PCOS.

MATERIALS AND METHODS

We recruited 118 young Taiwanese women with PCOS. The women enrolled were not taking any medication and those with other systemic diseases of nonovarian origin, which could have affected the hypothalamic-pituitary-ovarian axis, were excluded. The serum lipid profile, metabolic and hormonal parameters, and adiponectin were measured. The lipid profile and adiponectin were analyzed and adjusted for age, body mass index (BMI), homeostasis model assessment-insulin resistance (HOMA-IR), and sex hormone-binding globulin (SHBG).

RESULTS

In a simple linear regression, adiponectin was significantly inversely related to LDL-C and TGs, but positively related to HDL-C (all p < 0.001) after logarithmic transformation. In the multiple linear regression, adiponectin was significantly related to HDL-C (p < 0.001) independent of age, BMI, HOMA-IR, and SHBG after logarithmic transformation. Using a logistic regression, the odds ratio was 0.088 between the association of increased adiponectin and abnormal HDL-C (≤ 50 mg/dL).

CONCLUSIONS

We demonstrated that adiponectin is an independent biomarker that is positively and evidently related to HDL-C and TGs in women with PCOS. Hypoadiponectinemia may be a useful marker of dyslipidemia in women with PCOS.

The Effects of Rope Training on Lymphocyte ABCA1 Expression, Plasma ApoA-I and HDL-c in Boy Adolescents

BACKGROUND

Early obesity and its transfer to the adulthood, increases likelihood incidence of coronary artery disease (CAD). ATP-binding cassette transporter (ABCA1) as a member of the ABC transporters family plays a crucial role in reverse cholesterol transport and CAD prevention.

OBJECTIVE

The current study aimed to investigate ABCA1 expression in lymphocytes, plasma apolipoprotein A-I and HDL-C in response to eight-week interval endurance rope training in overweight and obese boy adolescents.

PATIENTS AND METHODS

Thirty students (17.3 ± 1.1 yr, 85.73 ± 11.68 kg and 28.41 ± 2.36 kg / m²) volunteered and were randomly assigned into training (n= 15) and control (n = 15) groups. Exercise protocol was interval endurance rope training (8 wk, 4 d/wk and 40 min/d). Cell hemolysis and sensitive Elisa method was used for Lymphocyte ABAC1 protein expression.t-test was employed.

RESULTS

The independent-samples T-Test results showed that after 8 weeks IERT, the levels of lymphocyte ABCA1 expression (P = 0/001) and VO2max(P = 0/001) significantly increased and plasma levels of TG (P = 0.017), TC (P = 0.001), LDL-c/HDL-c (P = 0.026),TC/HDL-c (P = 0.002) and measures of BF% (P = 0/015) and BMI (P = 0.042) as anthropometric indicators significantly decreased. Changes of other variables such as increase in ApoA-I, HDL-c and decrease in LDL-c, body weight, were not significant.

CONCLUSIONS

The findings of this study proved that eight-week interval endurance rope training can have positive effects on lymphocyte ABCA1 protein expression (as gatekeeper of reverse cholesterol process) and lipid profiles among overweight and obese boy adolescents.

Serum adiponectin level is correlated with the size of HDL and LDL particles determined by high performance liquid chromatography

OBJECTIVE

Adiponectin (APN) improves insulin resistance and prevents atherosclerosis, and HDL removes cholesterol from atherosclerotic lesions. We have demonstrated that serum HDL-cholesterol (HDL-C) and APN concentrations are positively correlated and that APN accelerates reverse cholesterol transport (RCT) by increasing HDL synthesis in the liver and cholesterol efflux from macrophages. We previously reported that APN reduced apolipoprotein (apo) B secretion from the liver. It is well-known that insulin resistance influences the lipoprotein profile. In this study, we investigated the clinical significance of APN levels and insulin resistance in lipoprotein metabolism.

MATERIAL/METHOD

We investigated the correlation between serum APN concentration, HOMA-R, the lipid concentrations and lipoprotein particle size by high-performance liquid chromatography (HPLC) in 245 Japanese men during an annual health checkup.

RESULTS

Serum APN level was positively correlated with the cholesterol content in large LDL and HDL particles, but inversely correlated with the cholesterol content in large VLDL and small LDL particles. HOMA-R was negatively correlated with the cholesterol content in large LDL and HDL particles and positively correlated with the cholesterol content in large VLDL and small LDL particles. By multivariate analysis, APN was correlated with the particle size of LDL-C and HDL-C independently of age, BMI and HOMA-R.

CONCLUSIONS

APN may be associated with the formation of both HDL and LDL particles, reflecting the enhancement of RCT and the improvement in TG-rich lipoprotein metabolism and insulin resistance.

Serum adiponectin in relation to race-ethnicity and vascular risk factors in the Northern Manhattan Study

BACKGROUND

Population-based data on serum adiponectin levels, an adipocytokine secreted from adipose tissue, are lacking, particularly across race-ethnic groups. Studies have suggested an inverse association between adiponectin and vascular risk factors, but data are limited and inconsistent. We examined the cross-sectional association between adiponectin, vascular risk factors and race-ethnicity in the population-based Northern Manhattan Study (NOMAS).

METHODS

Blood samples, anthropomorphics, and vascular risk factors were collected at baseline. Multivariable linear regression analysis was conducted with log-transformed adiponectin as the dependent variable.

RESULTS

Adiponectin was measured among 2900 participants (age 69±10 years, body mass index (BMI) 28.0±5.6, 37% male, 21% white, 53% Hispanic, 24% black). The mean adiponectin was 11.4±6.2 μg/mL (median=9.8, range=2.1-53.3). After multivariable adjustment, adiponectin levels were greatest among whites, followed by Hispanics, and lowest among blacks. Lower adiponectin levels were observed in participants with the following characteristics: Male, former smoking, hypertension, diabetes, homeostasis model assessment of insulin resistance (HOMA-IR), metabolic syndrome, moderate alcohol use, elevated waist circumference, BMI, estimated glomerular filtration rate (eGFR), triglycerides, low-density lipoprotein cholesterol (LDL-C), lower high-density lipoprotein cholesterol (HDL-C), and younger age. Obesity was a stronger risk factor for decreased adiponectin among blacks than among whites or Hispanics. The associations for several vascular risk factors, including hypertension, triglycerides, and low HDL-C, with low adiponectin were stronger among individuals who were not obese than among those who were obese.

CONCLUSIONS

Adiponectin levels were lower among blacks and Hispanics and among those with various vascular risk factors, and greater with older age. The association between BMI and adiponectin varied across race-ethnic groups. Investigation of whether differences in body fat distribution may explain race-ethnic differences in adiponectin is needed.