Implications of decreased serum adiponectin for type IIb hyperlipidaemia and increased cholesterol levels of very-low-density lipoprotein in type II diabetic patients

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.

The Role of Anti-Inflammatory Adipokines in Cardiometabolic Disorders: Moving beyond Adiponectin

The global burden of obesity has multiplied owing to its rapidly growing prevalence and obesity-related morbidity and mortality. In addition to the classic role of depositing extra energy, adipose tissue actively interferes with the metabolic balance by means of secreting bioactive compounds called adipokines. While most adipokines give rise to inflammatory conditions, the others with anti-inflammatory properties have been the novel focus of attention for the amelioration of cardiometabolic complications. This review compiles the current evidence on the roles of anti-inflammatory adipokines, namely, adiponectin, vaspin, the C1q/TNF-related protein (CTRP) family, secreted frizzled-related protein 5 (SFRP5), and omentin-1 on cardiometabolic health. Further investigations on the mechanism of action and prospective human trials may pave the way to their clinical application as innovative biomarkers and therapeutic targets for cardiovascular and metabolic disorders.

Secondary dyslipidemia: its treatments and association with atherosclerosis

Dyslipidemia is classified into primary and secondary types. Primary dyslipidemia is basically inherited and caused by single or multiple gene mutations that result in either overproduction or defective clearance of triglycerides and cholesterol. Secondary dyslipidemia is caused by unhealthy lifestyle factors and acquired medical conditions, including underlying diseases and applied drugs. Secondary dyslipidemia accounts for approximately 30-40% of all dyslipidemia. Secondary dyslipidemia should be treated by finding and addressing its causative diseases or drugs. For example, treatment of secondary dyslipidemia, such as hyperlipidemia due to hypothyroidism, by using statin without controlling hypothyroidism, may lead to myopathy and serious adverse events such as rhabdomyolysis. Differential diagnosis of secondary dyslipidemia is very important for safe and effective treatment. Here, we describe an overview about diseases and drugs that interfere with lipid metabolism leading to secondary dyslipidemia. Further, we show the association of each secondary dyslipidemia with atherosclerosis and the treatments for such dyslipidemia.

Innovatively Established Analysis Method for Lipoprotein Profiles Based on High-Performance Anion-Exchange Liquid Chromatography

Separation analysis of lipoprotein classes have various methods, including ultracentrifugation, electrophoresis, and gel permeation chromatography (GPC). All major lipoprotein classes can be separated via ultracentrifugation, but performing the analysis takes a long time. Low-density lipoprotein (LDL), intermediate-density lipoprotein (IDL), and very low-density lipoprotein (VLDL) in patient samples cannot be sufficiently separated via electrophoresis or GPC. Thus, we established a new method [anion-exchange high-performance liquid chromatography (AEX-HPLC)] by using HPLC with an AEX column containing nonporous gel and an eluent containing chaotropic ions. AEX-HPLC can separate five lipoprotein fractions of high-density lipoprotein (HDL), LDL, IDL, VLDL, and others in human serum, which can be used in substitution for ultracentrifugation method. The method was also approved for clinical use in the public health-care insurance in Japan in 2014. Furthermore, we developed an additional method to measure cholesterol levels of the four leading lipoprotein fractions and two subsequent fractions (i.e., chylomicron and lipoprotein(a)). We evaluated the clinical usefulness of AEX-HPLC in patients with coronary heart disease (CHD), diabetes, and kidney disease and in healthy volunteers. Results indicate that the cholesterol levels in IDL and VLDL measured by AEX-HPLC may be useful risk markers of CHD or diabetes. Furthermore, we developed another new method for the determination of alpha-tocopherol (AT) in lipoprotein classes, and this method is composed of AEX-HPLC for the separation of lipoprotein classes and reverse-phase chromatography to separate AT in each lipoprotein class. The AT levels in LDL were significantly correlated with the lag time to copper ion-induced LDL oxidation, which is an index of oxidation resistance. The application of AEX-HPLC to measure various substances in lipoproteins will be clinically expected in the future.

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.

Age and sex differences in serum adiponectin and its association with lipoprotein fractions

Objective The correlation of adiponectin with cholesterol concentration of fractionated lipoproteins has not been well investigated. Methods This study included 174 subjects (79 men and 95 women) without diabetes. The medical record data were investigated retrospectively. The study subjects with adiponectin <8.3, > 8.3 but less 13.9, and ≥ 13.9 were classified into tertile groups: Groups A ( n = 59), B ( n = 58) and C ( n = 57), respectively. Results In women, age and HDL-C were higher in Group C than in Groups A and B, but BMI, TG, IDL-C and VLDL-C were lower in Group C than in Groups A and B. In men, BMI was lower in Group C than in Groups A and B, and HDL-C was higher in Group C than in Groups A and B. In multiple stepwise regression analysis, BMI and HDL-C were significantly correlated with adiponectin in whole, male and female subjects, but TG-rich lipoprotein cholesterol concentrations were not independently correlated. Conclusions HDL-C and BMI were independently correlated with adiponectin in non-diabetic men and women. These results suggest that high adiponectin may play a role in the increased HDL-C concentrations, implicated in the reduction of cardiovascular disease risk, in non-diabetic subjects.

Fasting remnant lipoproteins can predict postprandial hyperlipidemia

BACKGROUND

Hypertriglyceridemia and postprandial hyperlipidemia is thought to play an important role in atherosclerosis, but to select patients at high-risk for cardiovascular diseases is difficult with triglycerides (TG) alone in these patients.

METHODS

To predict postprandial hyperlipidemia without inconvenient test meal loading, we examined lipid concentrations before and after test meal loading and fasting adiponectin, and investigated which of these other than TG were significant during the fasting period in 45 healthy individuals (men: women, 26:19).

RESULTS

TG, remnant-like particle-cholesterol and -triglyceride (RemL-C, RLP-C, and RLP-TG), and TG/apolipoprotein(apo)B were significantly elevated after loading and fasting values significantly and positively correlated with incremental area under the curve (iAUC) (r=0.80, r=0.79, r=0.63, r=0.58, r=0.54; p<0.0001). Fasting adiponectin positively correlated with fasting high-density lipoprotein-cholesterol (r=0.43, p<0.005) and apoA-I (r=0.34, p<0.05), and negatively correlated with iAUC of TG, RemL-C, RLP-C, RLP-TG, and TG/apoB (r=-0.37, r=-0.41, r=-0.37, r=-0.36, r=-0.37; p<0.05). We constructed the model of multivariable linear regression analysis without fasting TG. In the sex-, BMI-, age-, and waist circumference-adjusted analysis of postprandial TG elevation 2 h after test meal loading in all participants, RemL-C, RLP-C, RLP-TG, and TG/apoB were significant factors, but adiponectin was not.

CONCLUSION

Fasting triglyceride-rich lipoprotein-related values, especially RemL-C, RLP-C, RLP-TG, and TG/apoB are useful predictors of postprandial hyperlipidemia in young healthy individuals. Although fasting adiponectin concentration correlated with the iAUCs for TG, RemL-C, RLP-C, RLP-TG, and TG/apoB, it was not a significant predictor of postprandial hyperlipidemia in multivariable linear regression analysis.

Administration of natural astaxanthin increases serum HDL-cholesterol and adiponectin in subjects with mild hyperlipidemia

BACKGROUND

Astaxanthin has been reported to improve dyslipidemia and metabolic syndrome in animals, but such effects in humans are not well known.

METHODS

Placebo-controlled astaxanthin administration at doses of 0, 6, 12, 18 mg/day for 12 weeks was randomly allocated to 61 non-obese subjects with fasting serum triglyceride of 120-200mg/dl and without diabetes and hypertension, aged 25-60 years.

RESULTS

In before and after tests, body mass index (BMI) and LDL-cholesterol were unaffected at all doses, however, triglyceride decreased, while HDL-cholesterol increased significantly. Multiple comparison tests showed that 12 and 18 mg/day doses significantly reduced triglyceride, and 6 and 12 mg doses significantly increased HDL-cholesterol. Serum adiponectin was increased by astaxanthin (12 and 18 mg/day), and changes of adiponectin correlated positively with HDL-cholesterol changes independent of age and BMI.

CONCLUSIONS

This first-ever randomized, placebo-controlled human study suggests that astaxanthin consumption ameliorates triglyceride and HDL-cholesterol in correlation with increased adiponectin in humans.

Low adiponectin state is associated with metabolic abnormalities in obese children, particularly depending on apolipoprotein E phenotype

Background

Adiponectin links obesity with insulin resistance, which causes various metabolic abnormalities including dyslipidaemia. Apolipoprotein E (apoE) phenotypes also affect lipoprotein profiles. We aimed to determine whether low adiponectin concentrations are associated with insulin resistance and downstream metabolic abnormalities in obese children.

Methods

We measured fasting concentrations of lipids, apoE, glucose, insulin and adiponectin, as well as anthropometric parameters, in 191 obese children aged 6–15 years. ApoE phenotypes were determined by isoelectric focusing. Boys ( n = 79) and girls ( n = 39) with apoE3/3 were classified into tertiles according to their adiponectin concentrations. Metabolic parameters, were compared among these three groups in boys and girls separately.

Results

The low adiponectin groups had higher median homeostasis model assessment of insulin resistance (HOMA-IR) than the middle and high adiponectin groups in both boys [5.3 (low) versus 3.1 (middle; P < 0.05) and 3.5 (high; P < 0.05)] and girls [5.0 (low) versus 4.4 (middle) and 3.0 (high; P < 0.05)]. However, only boys who were in the low adiponectin group exhibited significantly higher concentrations of blood pressure, triglycerides, LDL-cholesterol, and remnant-like particle-cholesterol, and lower concentrations of HDL-cholesterol compared with the middle or high adiponectin groups.

Conclusion

Low adiponectin concentration is associated with insulin resistance in obese children. Furthermore, decreased adiponectin with E3/3 exhibited more prominent downstream metabolic abnormalities in obese boys than in obese girls.

Characteristic comparison of triglyceride-rich remnant lipoprotein measurement between a new homogenous assay (RemL-C) and a conventional immunoseparation method (RLP-C)

BACKGROUND

Increased serum remnant lipoproteins are supposed to predict cardiovascular disease in addition to increased LDL. A new homogenous assay for remnant lipoprotein-cholesterol (RemL-C) has been developed as an alternative to remnant-like particle-cholesterol (RLP-C), an immunoseparation assay, widely used for the measurement of remnant lipoprotein cholesterol.

METHODS

We evaluated the correlations and data validation between the 2 assays in 83 subjects (49 men and 34 women) without diabetes, hypertension and medications for hyperlipidemia, diabetes, and hypertension, and investigated the characteristics of remnant lipoproteins obtained by the two methods (RLP-C and RemL-C) and their relationships with IDL-cholesterol determined by our developed HPLC method.

RESULTS

A positive correlation was significantly found between the two methods (r = 0.853, 95%CI 0.781-0.903, p < 0.0001). Bland & Altman analysis revealed that RemL-C values were likely to be significantly higher than RLP-C values, particularly in samples with high levels of remnant lipoproteins. Several data dissociations between the RemL-C and RLP-C were also observed. The HPLC chromatograms show high concentrations of chylomicron cholesterol in serum samples with RemL-C level < RLP-C level, but high concentrations of IDL-cholesterol in samples with RemL-C level > RLP-C level. RemL-C (r = 0.339, 95%CI 0.152-0.903; p = 0.0005) significantly correlated with IDL-cholesterol, but not RLP-C (r = 0.17, 95%CI -0.047-0.372; p = 0.1237) in all the samples (n = 83).

CONCLUSION

These results suggest that there is generally a significant correlation between RemL-C and RLP-C. However, RemL-C assay is likely to reflect IDL more closely than RLP-C.

Comparative study between anion-exchange HPLC and homogeneous assay methods in regard to the accuracy of high- and low-density lipoprotein cholesterol measurement

OBJECTIVES

A convenient method based on anion-exchange HPLC was recently developed to determine cholesterol levels of lipoproteins (HDL, LDL, IDL, VLDL, and chylomicron). The present study was performed to compare this HPLC method to homogenous assay in regard to measurement accuracy of HDL and LDL cholesterol.

DESIGN AND METHODS

Serum samples (n=105), including three samples from cholestasis patients, were measured by homogenous assay with Cholestest-LDL and CholestestN-HDL (Daiichi Chemicals, Tokyo) and by HPLC as reported previously (J Lipid Res 2003; 44: 1404-12).

RESULTS

The homogenous assay for HDL cholesterol correlated strongly with the HPLC method for HDL cholesterol (r=0.976). Two samples from cholestasis patients could not be measured by homogenous assay but were measured by HPLC. The homogenous assay for LDL cholesterol correlated modestly with the HPLC method for LDL cholesterol (r=0.823). Three outlier samples, from cholestasis patients with serum cholesterol levels >17 mmol/L, were observed in this correlation analysis. Homogenous assay data showed that these LDL cholesterol levels were 15.2-34.7 mmol/L. However, HPLC data showed that these LDL cholesterol levels were 3.6-8.2 mmol/L, and that the major lipoprotein fractions were VLDL and IDL. The difference in LDL cholesterol levels (homogenous assay data minus HPLC data) was positively correlated with VLDL cholesterol levels.

CONCLUSIONS

When measuring samples from cholestasis patients, homogenous assay may give inaccurate results. In contrast, the HPLC method is likely to be capable of accurately measuring HDL and LDL cholesterol levels without the involving VLDL.

Relationship of serum adiponectin and resistin to glucose intolerance and fat topography in South-Asians

OBJECTIVES

South-Asians have lower adiponectin levels compared to Caucasians. It was not clear however, if this intrinsic feature is related to aspects of glucose metabolism. This study aims to determine the relationship between body fat distribution and adipocytokine in South-Asian subjects by measuring serum adipocytokines, adiposity, insulinemia, and glucose tolerance levels.

METHODS

In this cross-sectional study, 150 South-Asians (80 males, 70 females) were included, 60 had NGT (Control group, Age 51.33 +/- 11.5, BMI 27 +/- 2.3), 60 had IGT (Age 57.7 +/- 12.5, BMI 27.2 +/- 2.7), 30 had type 2 DM (Age 49.5 +/- 10.9, BMI 28 +/- 1.7). Measures of adiposity, adipocytokines and other metabolic parameters were determined. Parameters were measured using the following: a) Plasma glucose by glucose oxidase method b) CRP by immunoturbidimetric method (Roche/Hitachi analyser) c) insulin by Medgenix INS-ELISA immunoenzymetric assay by Biosource (Belgium) d) Leptin, Adiponectin by radioimmunoassay kits by Linco Research (St. Charles MO) e) Resistin by immunoassay kits by Phoenix Pharmaceuticals INC (530 Harbor Boulevard, Belmont CA 94002, USA).

RESULTS

Adiponectin concentrations were highest in NGT, decreased in IGT and lowest in DMT2, (both p < 0.01). Leptin was significantly higher in DMT2 than IGT and NGT p = 0.02 and 0.04 respectively. There was a significant positive relationships between log adiponectin and 2-hr insulin values, p = 0.028 and history of hypertensions and a ischemic heart disease p = 0.008 with R = 0.65. There was a significant inverse correlation between log adiponectin and resistin, p < 0.01.

CONCLUSION

Resistin levels had an inverse correlation with adiponectin levels, indicating an inverse relationship between pro-inflammatory cytokines and adiponectin. Adiponectin levels were related to glucose tolerance.