Serum CETP status is independently associated with reduction rates in LDL-C in pitavastatin-treated diabetic patients and possible involvement of LXR in its association

Cholesteryl Ester Transfer Protein (CETP) Variations in Relation to Lipid Profiles and Cardiovascular Diseases: An Update

Lipid metabolism plays an essential role in the pathogenesis of cardiovascular and metabolic diseases. Cholesteryl ester transfer protein (CETP) is a crucial glycoprotein involved in lipid metabolism by transferring cholesteryl esters (CE) and triglycerides (TG) between plasma lipoproteins. CETP activity results in reduced HDL-C and increased VLDL- and LDL-C concentrations, thus increasing the risk of cardiovascular and metabolic diseases. In this review, we discuss the structure of CETP and its mechanism of action. Furthermore, we focus on recent experiments on animal CETP-expressing models, deciphering the regulation and functions of CETP in various genetic backgrounds and interaction with different external factors. Finally, we discuss recent publications revealing the association of CETP single nucleotide polymorphisms (SNPs) with the risk of cardiovascular and metabolic diseases, lifestyle factors, diet and therapeutic interventions. While CETP SNPs can be used as effective diagnostic markers, diet, lifestyle, gender and ethnic specificity should also be considered for effective treatment.

Elevated Serum Low-Density Lipoproteins-Cholesterol Levels and B1B2/B2B2 CETP Genotype Are Positively Associated with Nonalcoholic Fatty Liver Disease in Women with Gallstone Disease

Background: Nonalcoholic fatty liver disease (NAFLD) is generated by the interaction between environmental and genetic factors, and the presence of metabolic alterations. Since Taq1B cholesteryl ester transfer protein (CETP) polymorphism is associated with abnormal serum lipid values, it could be related to NAFLD. The aim of this study was to determine the role of the Taq1B CETP polymorphism with serum lipids, anthropometric variables, and the extent of steatosis in Mexican-mestizo women with gallstone disease (GD). Methods: Sixty-two women were enrolled in this cross-sectional study. Serum lipids were determined by dry chemistry. The Taq1B CETP polymorphism was determined by allelic discrimination. CETP serum levels were measured by enzyme-linked immunosorbent assay, and the extent of steatosis with a biopsy staining with Oil-Red-O. Results: Subjects with the B1B2/B2B2 genotype had higher percentage of degree of steatosis than those with B1B1 (11.95% vs. 2.19%, P = 0.008). The B1B2/B2B2 genotype (odds ratio [OR] 3.90 [confidence interval {CI} 95% 1.891-8.536], P = 0.04) and an elevated low-density lipoproteins (LDL)-cholesterol (OR 3.54 [CI 95% 1.042-2.058, P = 0.039) significantly increase the risk for NAFLD. Conclusions: This study provides evidence that the B1B2/B2B2 genotype of CETP and the elevated LDL-cholesterol serum levels increase the risk of NAFLD in women with GD.

Endocytosis of LXRs: Signaling in liver and disease

Nuclear receptors are among one of the major transcriptional factors that induces gene regulation in the nucleus. Liver X receptor (LXR) is a transcription factor which regulates essential lipid homeostasis in the body including fatty acid, cholesterol and phospholipid synthesis. Liver X receptor-retinoid X receptor (LXR-RXR) heterodimer is activated by either of the ligand binding on LXR or RXR. The promoter region of the gene which is targeted by LXR is bound to the response element of LXR. The activators bind to the heterodimer once the corepressor is dissociated. The cellular process such as endocytosis aids in intracellular trafficking and endosomal formation in transportation of molecules for essential signaling within the cell. LXR isotypes play a crucial role in maintaining lipid homeostasis by regulating the level of cholesterol. In the liver, the deficiency of LXRα can alter the normal physiological conditions depicting the symptoms of various cardiovascular and liver diseases. LXR can degrade low density lipoprotein receptors (LDLR) by the signaling of LXR-IDOL through endocytic trafficking in lipoprotein uptake. Various gene expressions associated with cholesterol level and lipid synthesis are regulated by LXR transcription factor. With its known diversified ligand binding, LXR is capable of regulating expression of various specific genes responsible for the progression of autoimmune diseases. The agonists and antagonists of LXR stand to be an important factor in transcription of the ABC family, essential for high density lipoprotein (HDL) formation. Endocytosis and signaling mechanism of the LXR family is broad and complex despite their involvement in cellular growth and proliferation. Here in this chapter, we aimed to emphasize the master regulation of LXR activation, regulators, and their implications in various metabolic activities especially in lipid homeostasis. Furthermore, we also briefed the significant role of LXR endocytosis in T cell immune regulation and a variety of human diseases including cardiovascular and neuroadaptive.

Triglyceride to High-Density Lipoprotein Cholesterol (TG/HDL-C) Ratio, a Simple but Effective Indicator in Predicting Type 2 Diabetes Mellitus in Older Adults

BACKGROUND

A simple and readily available biomarker can provide an effective approach for the surveillance of type 2 diabetes mellitus (T2DM) in the elderly. In this research, we aim to evaluate the role of triglyceride to high-density lipoprotein cholesterol (TG/HDL-C) ratio as an indicator for new-onset T2DM in an elderly Chinese population aged over 75 years.

METHODS

This longitudinal retrospective cohort study was conducted using a free database from a health check screening project in China. Participants with baseline TG and HDL measurements were enrolled, and the data of T2DM development were collected. The cumulative incident T2DM rates in different quintile groups of TG/HDL-C ratio (Q1 to Q5) were calculated and plotted. The independent effect of baseline TG/HDL-C ratio on T2DM risk during the follow-up period was tested by the Cox proportional hazard model. Subgroup analysis was also conducted to clarify the role of TG/HDL-C ratio in specific populations.

RESULTS

A total of 231 individuals developed T2DM among 2,571 subjects aged over 75 years during follow-up. Regardless of adjustment for potential confounding variables, elevated TG/HDL-C ratio independently indicated a higher risk of incident T2DM [hazard ratio (HR) = 1.29; 95% confidence interval (CI), 1.14-1.47; P < 0.01. As compared with the lowest quintile (Q1), elevated TG/HDL-C ratio quintiles (Q2 to Q5) were associated with larger HR estimates of incident T2DM [HR (95% CI), 1.35 (0.85-2.17), 1.31 (0.83-2.06), 1.85 (1.20-2.85), and 2.10 (1.38-3.20), respectively]. In addition, a non-linear correlation was found between TG/HDL-C ratio and the risk of T2DM, and the slope of the curve decreased after the cutoff point of 2.54. Subgroup analysis revealed a stronger positive correlation among male individuals and those with body mass index <24 kg/m².

CONCLUSIONS

Increased TG/HDL-C ratio indicates a greater risk of new-onset T2DM regardless of confounding variables. TG/HDL-C ratio is a simple but effective indicator in predicting T2DM in older adults. More future investigations are warranted to further promote the clinical application of TG/HDL-C ratio.

Triglyceride to high-density lipoprotein cholesterol ratio variability and incident diabetes: A 7-year prospective study in a Chinese population

AIMS/INTRODUCTION

The correlation between triglyceride to high-density lipoprotein cholesterol (TG/HDL-C) ratio variability and incident diabetes has not been fully elucidated. We aimed to characterize the relationship between TG/HDL-C ratio variability and new-onset diabetes in Chinese adults.

MATERIALS AND METHODS

A total of 45,911 patients with three TG and HDL measurements between 2006 and 2011 were enrolled. Average real variability (ARV) were used to evaluate variability, and participants were grouped according to tertiles of TG/HDL-ARV.

RESULTS

There were 3,724 cases of incident diabetes mellitus during the observation period (6.24 ± 1.2 years). The 7-year cumulative incidences of diabetes mellitus in tertiles 1, 2 and 3 were 6.13%, 8.09% and 11.77%, respectively. New-onset diabetes increased with the tertiles of TG/HDL-ARV. This association was further confirmed after adjustment for mean TG/HDL-C ratio, TG/HDL-C ratio change slope, fasting plasma glucose variability (ARV) and other traditional risk factors for diabetes, the hazard ratio value for incident diabetes was 1.38 (1.25-1.50) for the highest tertile, and risk of diabetes increases by 4% with a one standard deviation increase in TG/HDL-C ratio variability. Restricted cubic splines showed a dose-response relationship between TG/HDL-C ratio variability and incident diabetes. Similar results were obtained in various subgroup and sensitivity analyses.

CONCLUSIONS

High TG/HDL-C variability was associated with a higher risk of diabetes in Chinese adults, independent of the direction of TG/HDL-C variability.

Gender specific effect of CETP rs708272 polymorphism on lipid and atherogenic index of plasma levels but not on the risk of coronary artery disease: A case-control study

Numerous studies have shown a relationship between cholesteryl ester transfer protein (CETP) polymorphism in the synthesis of high-density lipoprotein cholesterol (HDL-C) and the coronary artery disease (CAD) susceptibility, but the results have remained inconsistent. In addition, there was no study exploring the relationship between CETP polymorphisms and atherogenic index of plasma (AIP) levels.We conducted a case-control study to evaluate the relationship between CETP rs708272 polymorphism and CAD risk and lipid levels in Chinese Han population. 556 CAD patients and 414 controls undergoing coronary angiography were consecutively enrolled in the hospital-based study. Polymerase chain reaction-ligase detection reaction (PCR-LDR) method was used to detect the different genotypes at rs708272.No significant association between CETP rs708272 polymorphism and CAD risk was observed in different genetic models. In the whole population, participants with TT genotype had higher HDL-C levels (1.17 ± 0.31 mmol/L vs 1.09 ± 0.29 mmol/L, P = .001) and lower AIP levels (0.08 ± 0.35 vs 0.16 ± 0.31, P = .004) compared to those with CC genotype, after adjusting for age, gender, smoking, essential hypertension (EH), and DM. The T allele carriers had higher HDL-C levels than the T allele non-carriers (1.13 ± 0.29 mmol/L vs 1.09 ± 0.29 mmol/L, P = .023). Furthermore, subgroup analyses based on gender were carried out. In males, the results showed that participants with TT genotype had significant higher HDL-C levels and lower AIP levels compared with CC genotype (P <.05). In addition, males with CT+TT genotypes had higher HDL-C levels and lower AIP levels than those with CC genotypes (HDL-C: CT+TT 1.11 ± 0.31vs CC 1.06 ± 0.30 mmol/L, P = .041; AIP: CT+TT 0.12 ± 0.32vs CC 0.16 ± 0.31, P = .034, respectively). However, there were no significant associations between lipid levels and CETP rs708272 polymorphism in females, after adjusting for confounders.CETP rs708272 polymorphism has a gender-specific effect on lipid and AIP levels but not on the risk of CAD.

The Association between Persistent Hypertriglyceridemia and the Risk of Diabetes Development: The Kangbuk Samsung Health Study

BACKGROUND

Hypertriglyceridemia is known to have an association with increased risks of insulin resistance and diabetes. The aim of this study was to investigate the risk of diabetes mellitus, according to changes in the concentrations of triglycerides, over time.

METHODS

A total of 15,932 non-diabetic participants (mean age 43.2 years, 68% men) who attended five consecutive annual health check-ups at Kangbuk Samsung Hospital, between January 2010 and December 2014, were recruited. Participants were classified according to their triglyceride concentrations; normal (<150 mg/dL) and abnormal (≥150 mg/dL). According to the triglyceride levels in 2010 and 2012, subjects were divided into four groups: normal-normal, normal-abnormal, abnormal-normal, and abnormal-abnormal. The risk for incident diabetes was assessed in 2014.

RESULTS

Among the total subjects, 67.5% belonged to the normal-normal group, 8.6% to the normal-abnormal group, 9.4% to the abnormal-normal group, and 14.5% to the abnormal-abnormal group. A total of 234 subjects (1.5%) were newly diagnosed with diabetes, between 2010 and 2014. Over 4 years, 1%, 1.5%, 2.1%, and 3.0% of the subjects developed diabetes in the normal-normal, normal-abnormal, abnormal-normal, and abnormal-abnormal groups, respectively. When the risk for incident diabetes was analyzed in the groups, after adjusting the confounding variables, a 1.58-fold increase in the risk of diabetes (95% confidence interval [CI], 1.10 to 2.26) was observed in the participants with persistent hypertriglyceridemia (abnormal-abnormal group). This was attenuated by further adjustments for body mass index (BMI) (hazard ratio, 1.25; 95% CI, 0.86 to 1.80).

CONCLUSION

In this large study population, persistent hypertriglyceridemia, over a period of 2 years, was significantly associated with the risk of incident diabetes, which was attenuated after adjustment for BMI.

Downregulation of cholesteryl ester transfer protein by glucocorticoids: a randomised study on HDL

BACKGROUND

High density lipoprotein (HDL) cholesterol is not decreased in hypercortisolism despite high triglycerides, which may be ascribed to effects on the cholesteryl ester transfer protein (CETP) pathway. We explored if CETP mRNA expression is modulated by glucocorticoid treatment in vitro. Effects of doubling the hydrocortisone (HCT) replacement dose on plasma CETP activity, and HDL characteristics were tested in patients with secondary adrenal insufficiency.

MATERIALS AND METHODS

Human THP-1 macrophages were incubated with corticosterone in vitro in the presence or absence of a liver X receptor (LXR) agonist, followed by determination of CETP mRNA levels by quantitative real-time PCR. In addition, a randomised double-blind cross-over study was performed in 47 patients with secondary adrenal insufficiency (university medical setting; 10 weeks exposure to a higher HCT dose (0·4-0·6 mg/kg body weight) vs. 10 weeks of a lower HCT dose (0·2-0·3 mg/kg body weight).

RESULTS

Corticosterone dose dependently decreased CETP mRNA in THP-1 macrophages. Corticosterone also decreased CETP mRNA expression after LXR pretreatment. In patients, CETP activity decreased with doubling of the HCT dose (P = 0·049), coinciding with an increase in HDL cholesterol, apolipoprotein A-I and the HDL cholesterol/apolipoprotein A-I ratio (reflecting HDL size; P < 0·01 for each). The increase in the HDL cholesterol/apolipoprotein A-I ratio was correlated with the decrease in plasma CETP activity (r = -0·442, P = 0·002).

CONCLUSION

Glucocorticoids downregulate CETP gene expression in a human macrophage cell system. In line, a higher glucocorticoid replacement dose decreases plasma CETP activity in patients, thereby contributing to higher HDL cholesterol and an increase in estimated HDL size.

Reference values assessment in a Mediterranean population for small dense low-density lipoprotein concentration isolated by an optimized precipitation method

Background

High serum concentrations of small dense low-density lipoprotein cholesterol (sd-LDL-c) particles are associated with risk of cardiovascular disease (CVD). Their clinical application has been hindered as a consequence of the laborious current method used for their quantification.

Objective

Optimize a simple and fast precipitation method to isolate sd-LDL particles and establish a reference interval in a Mediterranean population.

Materials and methods

Forty-five serum samples were collected, and sd-LDL particles were isolated using a modified heparin-Mg²⁺ precipitation method. sd-LDL-c concentration was calculated by subtracting high-density lipoprotein cholesterol (HDL-c) from the total cholesterol measured in the supernatant. This method was compared with the reference method (ultracentrifugation). Reference values were estimated according to the Clinical and Laboratory Standards Institute and The International Federation of Clinical Chemistry and Laboratory Medicine recommendations. sd-LDL-c concentration was measured in serums from 79 subjects with no lipid metabolism abnormalities.

Results

The Passing–Bablok regression equation is y = 1.52 (0.72 to 1.73) + 0.07x (−0.1 to 0.13), demonstrating no significant statistical differences between the modified precipitation method and the ultracentrifugation reference method. Similarly, no differences were detected when considering only sd-LDL-c from dyslipidemic patients, since the modifications added to the precipitation method facilitated the proper sedimentation of triglycerides and other lipoproteins. The reference interval for sd-LDL-c concentration estimated in a Mediterranean population was 0.04–0.47 mmol/L.

Conclusion

An optimization of the heparin-Mg²⁺ precipitation method for sd-LDL particle isolation was performed, and reference intervals were established in a Spanish Mediterranean population. Measured values were equivalent to those obtained with the reference method, assuring its clinical application when tested in both normolipidemic and dyslipidemic subjects.

Diabetic dyslipidaemia

PURPOSE OF REVIEW

The purpose is to discuss recent developments in the understanding of lipoprotein metabolism in diabetes, the cardiovascular risk associated with both type 1 and type 2 diabetes, recently published guidelines on the management of this risk, concerns over the use of statin treatment in diabetes, and other therapeutic options.

RECENT FINDINGS

Diabetic dyslipidaemia can be gross with massive hypertriglyceridemia, or subtle with a lipid profile which would be regarded as normal in a nondiabetic patient, but which hides underlying increases in atherogenic subfractions of LDL (e.g., small dense LDL, glycated LDL) and remnant lipoproteins. Statins can decrease these without the clinician being aware from routine biochemistry. In type 2 diabetes, HDL cholesterol levels are often reduced, whereas in type 1, insulin can raise HDL, but its antiatherogenic properties are compromised. Dyslipidaemia and hypertension predate the onset of glycaemia of diabetic proportions (metabolic syndrome). Obese people can thus die of diabetes before they develop it. Obesity should be prevented and treated. Statins decrease the risk of cardiovascular disease in diabetes or metabolic syndrome regardless of whether glycaemia worsens.

SUMMARY

One unassailable truth is that statin therapy is beneficial and should rarely, if ever, be withheld.