Increased LCAT activity and hyperglycaemia decrease the antioxidative functionality of HDL.

BACKGROUND: Type 2 diabetes mellitus increases the risk of atherosclerotic cardiovascular disease. Antioxidative properties of high density lipoprotein (HDL) are important for atheroprotection. This study investigated whether the antioxidative functionality of HDL is altered in type 2 diabetes mellitus and aimed to identify potential determinants of this parameter. MATERIALS AND METHODS: In a cross-sectional study, we investigated 74 patients with type 2 diabetes and 75 control subjects. Antioxidative properties of HDL were measured and expressed as either (i) HDL antioxidative capacity or (ii) HDL antioxidation index after multiplying HDL antioxidative capacity results with individual plasma HDL cholesterol concentrations. Lecithin:cholesterol acyltransferase (LCAT) and paraoxonase-1 (PON-1) activities were determined. RESULTS: HDL antioxidative capacity was similar in patients with diabetes and controls, while the HDL antioxidation index was decreased in patients with diabetes (P = 0.005) owing to lower plasma HDL cholesterol (P < 0.001). LCAT activity was higher and PON-1 activity lower in type 2 diabetes mellitus (each P < 0.001). In the combined subjects, HDL antioxidative capacity was inversely related to LCAT activity (P < 0.01). The HDL antioxidation index correlated negatively with blood glucose (P < 0.001), HbA1c and LCAT activity (each P < 0.01), and positively with PON-1 activity (P < 0.01). Multiple linear regression analysis demonstrated that high LCAT activity was associated with both decreased HDL antioxidation capacity (P < 0.05) and index (P < 0.001) independent of diabetes status, glycaemic control and PON-1. CONCLUSIONS: Overall, the antioxidative functionality of HDL is impaired in type 2 diabetes mellitus mostly because of lower HDL cholesterol. Hyperglycaemia, increased LCAT activity and lower PON-1 activity likely contribute to impaired antioxidative functionality of HDL.

Atorvastatin treatment lowers fasting remnant-like particle cholesterol and LDL subfraction cholesterol without affecting LDL size in type 2 diabetes mellitus: Relevance for non-HDL cholesterol and apolipoprotein B guideline targets.

The extent to which atorvastatin treatment affects LDL size, LDL subfraction levels and remnant-like particle cholesterol (RLP-C) was determined in type 2 diabetes. We also compared LDL size and RLP-C in relation to guideline cut-off values for LDL cholesterol, non-HDL cholesterol and apolipoprotein (apo) B. Changes in LDL size and RLP-C were determined in fasting plasma from type 2 diabetic patients after 30 weeks administration of atorvastatin (10 mg daily, n=65; 80 mg daily, n=62) or placebo (n=58). LDL subfraction cholesterol was measured in 74 participants. Atorvastatin lowered LDL cholesterol, non-HDL cholesterol, triglycerides, apo B and RLP-C (P<0.001 for all at each dose) and LDL mean peak particle diameter remained unchanged. Atorvastatin treatment decreased cholesterol concentrations in all LDL subfractions (P<0.001 for each dose). RLP-C at follow-up was lower in those patients achieving the non-HDL cholesterol or the apo B guideline targets (P<0.01), but the LDL cholesterol cut-off value failed to discriminate. In conclusion, atorvastatin lowers fasting RLP-C and LDL subfraction cholesterol in diabetes. The proposed guideline cut-off levels for non-HDL cholesterol and apo B may be superior to the LDL cholesterol target in discriminating between higher and lower RLP-C levels.

Common variation in cholesteryl ester transfer protein: relationship of first major adverse cardiovascular events with the apolipoprotein B/apolipoprotein A-I ratio and the total cholesterol/high-density lipoprotein cholesterol ratio.

BACKGROUND: The preference of the apolipoprotein (apo) B/apoA-I ratio over the total cholesterol/HDL cholesterol (TC/HDL-C) ratio in cardiovascular risk prediction is disputed. Cholesteryl ester transfer protein (CETP) is instrumental in lipoprotein remodelling and affects the cholesterol content in pro- and antiatherogenic lipoproteins relative to their major apolipoproteins. We tested the influence of common CETP variations on the strength of associations of a first major adverse cardiovascular event (MACE) with the apoB/apoA-I ratio compared with the TC/HDL-C ratio. METHODS: A prospective case-cohort study was performed (PREVEND cohort; no previous cardiovascular disease and no use of lipid-lowering drugs initially). Fasting serum TC/HDL-C, apoB/apoA-I, triglycerides, and common CETP variations (TaqIB [rs708272] and -629C>A [rs1800775] polymorphisms) were measured at baseline. The composite end point was incident MACE. RESULTS: A total of 532 of 6780 subjects experienced a first MACE during 10.8 years follow-up. The age- and sex-adjusted hazard ratio was 1.31 (95 % confidence interval 1.23-1.41) for the apoB/apoA-I ratio and 1.22 (95% confidence interval 1.26-1.39) for the TC/HDL-C ratio (both P < .001). These relationships were essentially similar within each TaqIB and -629C>A CETP genotype group. No interactions of the apoB/apoA-I ratio and the TC/HDL-C ratio with the TaqIB and the -629C>A CETP variations on incident MACE were observed (P > .20 for all). CONCLUSION: The relationship of first MACE with the TC/HDL-C and the apoB/apoA-I ratio is not to an important extent dependent on common CETP variations. CETP variations are unlikely to affect the strength of the relationship of first MACE with the apoB/apoA-I ratio compared with the TC/HDL-C ratio.

Lower carotid intima media thickness is predicted by higher serum bilirubin in both non-diabetic and Type 2 diabetic subjects.

BACKGROUND: Higher serum bilirubin levels may be implicated cardiovascular protection. It is unknown whether the impact of serum bilirubin on carotid artery intima media thickness (IMT), a marker of subclinical atherosclerosis, is different in diabetic subjects compared to non-diabetic subjects. We assessed relationships of IMT with serum total bilirubin in non-diabetic and Type 2 diabetic subjects without clinically manifest cardiovascular disease. METHODS: IMT, total bilirubin, transaminases, C-reactive protein (CRP) and lipid levels were measured in 40 predominantly middle-aged non-diabetic and 80 diabetic subjects. RESULTS: IMT was higher in diabetic subjects compared to non-diabetic subjects (unadjusted, p<0.001), whereas bilirubin was not different (p=0.82). In both non-diabetic and in diabetic subjects, IMT was negatively related to bilirubin (ß=-0.316, p=0.045 and ß=-0.247 p=0.014, respectively) taking account of age, sex and mean arterial pressure. In the combined subjects, IMT remained independently related to bilirubin (ß=-0.183, p=0.028) after additional adjustment for diabetes status, alcohol intake, transaminases, CRP and lipid levels. There was no interaction of bilirubin with the presence of diabetes on IMT (p=0.98). CONCLUSION: Carotid artery IMT relates negatively to bilirubin in non-diabetic and Type 2 diabetic subjects. The association of subclinical atherosclerosis with bilirubin appears to be unaltered in the diabetic state.

Plasma lipoprotein-associated phospholipase A2 is inversely correlated with proprotein convertase subtilisin-kexin type 9.

BACKGROUND AND AIMS: Lipoprotein-associated phospholipase A(2) (Lp-PLA(2)) is a pro-atherogenic phospholipase A(2), which is predominantly complexed to low-density lipoprotein (LDL) particles. Proprotein convertase subtilisin-kexin type 9 (PCSK9) provides a key step in LDL metabolism by stimulating LDL receptor degradation. We determined relationships between plasma PCSK9 and Lp-PLA(2) mass. METHODS: Lp-PLA(2) mass (turbidimetric immunoassay), PCSK9 (enzyme-linked immunosorbent assay) and (apo) lipoproteins were measured in 53 nondiabetic subjects (27 women) with body mass index <30 kg/m(2). RESULTS: Lp-PLA(2) and PCSK9 levels were both correlated positively with LDL cholesterol and non-high-density lipoprotein (HDL) cholesterol (r = 0.330 to r = 0.382, p ≤0.02). Remarkably, Lp-PLA(2) was inversely related to PCSK9 (r = -0.388, p = 0.004). The Lp-PLA(2)/apolipoprotein B ratio, as a measure of the Lp-PLA(2) content in apolipoprotein B-containing lipoproteins, was also inversely correlated with PCSK9 (r = -0.575, p <0.001). The inverse relationships of Lp-PLA(2) (p = 0.023) and the Lp-PLA(2)/apolipoprotein B ratio (p = 0.001) with PCSK9 levels remained significant after controlling for age, gender, triglycerides and HDL cholesterol. CONCLUSIONS: Despite increasing effects on LDL cholesterol, higher PCSK9 levels are unlikely to confer impaired Lp-PLA(2) metabolism. We propose to evaluate the possible influence of PCSK9 inhibiting strategies on Lp-PLA(2) regulation and vice versa to determine effects of Lp-PLA(2) inhibitors on the PCSK9 pathway.

The plasma leptin/adiponectin ratio predicts first cardiovascular event in men: a prospective nested case-control study.

OBJECTIVE: The plasma leptin/adiponectin (L/A) ratio has been proposed as a preferential marker of atherosclerosis susceptibility compared to leptin and adiponectin alone. We determined the extent to which the L/A ratio predicts incident cardiovascular disease (CVD) taking account of clinical risk factors, microalbuminuria, the total cholesterol/HDL cholesterol (TC/HDL-C ratio), triglycerides, high sensitive C-reactive protein (hs-CRP) and insulin sensitivity (homeostasis model assessment (HOMA(ir))). METHODS: A community-based prospective nested case-control study was carried out in 103 non-diabetic men who developed a first cardiovascular event (cases) and 106 male control subjects (no clinically manifest CVD and no lipid lowering drug use at baseline; median follow-up of 3.0 and 10.5 years, respectively). Plasma leptin, adiponectin, the leptin/adipnectin (L/A) ratio, as well as hs-CRP, HOMA(ir) and the TC/HDL-C ratio were determined at baseline. RESULTS: Plasma leptin levels and the L/A ratio were higher in cases vs. controls (p=0.002 for both), but the difference in adiponectin was not significant (p=0.10). Age-adjusted incident CVD was associated with plasma leptin, adiponectin and the L/A ratio (p=0.045 to p=0.001). The relationships of incident CVD with plasma leptin (p=0.19) and adiponectin (p=0.073) lost statistical significance after additional adjustment for smoking, waist circumference, hypertension, microalbuminuria, the TC/HDL-C ratio, hs-CRP and HOMA(ir). In this fully adjusted analysis, the L/A ratio remained predictive of incident CVD (hazard ratio: 1.40 (95% CI 1.05-1.87), p=0.024). CONCLUSION: This study suggests that the L/A ratio may be a preferential marker of a first cardiovascular event in men compared to plasma leptin and adiponectin levels alone.

Plasma proprotein convertase subtilisin-kexin type 9 does not change during 24h insulin infusion in healthy subjects and type 2 diabetic patients.

PURPOSE: Proprotein convertase subtilisin-kexin type 9 (PCSK9) promotes low density lipoprotein (LDL) receptor degradation, thereby providing a key pathway for LDL metabolism. PCSK9 mRNA expression may be upregulated by insulin in murine models. Here we examined effects of exogenous hyperinsulinemia on plasma PCSK9 levels in humans without and with type 2 diabetes mellitus. METHODS: A 24h moderately hyperinsulinemic glucose clamp (30 mU/kg/h) was performed in 8 healthy men and 8 male type 2 diabetic patients. Plasma PCSK9 was measured using a sandwich enzyme-linked immunosorbent assay. RESULTS: Plasma LDL cholesterol and apolipoprotein B were lowered by insulin in healthy subjects and diabetic patients (P < 0.01 for all), whereas triglycerides were also decreased in healthy subjects (P < 0.01). Plasma PCSK9 levels remained unchanged in healthy subjects (median (interquartile range) change, -23 (-63 to 25) %, P = 0.50) and in diabetic patients (change, 4 (-17 to 44) %, P = 0.20). Individual absolute and relative changes in LDL cholesterol, apolipoprotein B and triglycerides after 24h of insulin were unrelated to changes in PCSK9 (P > 0.15 for all). CONCLUSION: Plasma PCSK9 levels are not increased by exposure to moderate 24h hyperinsulinemia in healthy and type 2 diabetic individuals.

Cholesteryl ester transfer protein inhibition in cardiovascular risk management: ongoing trials will end the confusion.

As delineated in this review, cholesteryl ester transfer protein (CETP) contributes to an atherogenic lipoprotein profile by redistributing cholesteryl esters from high density lipoprotein (HDL) toward apolipoprotein B-containing lipoproteins, especially when the concentration of acceptor triglyceride-rich lipoproteins is elevated. However, this lipid transfer protein may have antiatherogenic proprerties as well. Experimental evidence is accumulating which suggests that the atheroprotective reverse cholesterol transport pathway, whereby cholesterol is removed from peripheral macrophages to the liver for metabolism and biliary excretion, is stimulated by CETP in vivo. CETP could also play a role in host defense against infection and inflammatory processes. Moreover, recently published observational studies show that higher CETP levels may confer cardiovascular protection, whereas reported associations of cardiovascular disease (CVD) with CETP gene variations are equivocal. The concept that HDL cholesterol raising through inhibition of CETP may ameliorate CVD risk has been challenged by the failure of the CETP inhibitor, torcetrapib. Adverse clinical outcome associated with the use of this CETP inhibitor has been attributed to off-target effects, which relate to stimulation of aldosterone. Other CETP inhibitors, such as dalcetrapib and anacetrapib, are unlikely to increase blood pressure. Dalcetrapib is less potent than anacetrapib, which doubles HDL cholesterol. Both inhibitors considerably lower LDL cholesterol.Serious concerns remain about the validity of the concept that HDL cholesterol raising by means of CETP inhibition is a viable strategy. Results of ongoing clinical trials with these drugs will have to be awaited before making up the balance between possible benefits and harms related to pharmacological CETP inhibition.

High plasma cholesteryl ester transfer but not CETP mass predicts incident cardiovascular disease: a nested case-control study.

OBJECTIVE: The relationship of cardiovascular disease (CVD) with plasma cholesteryl ester transfer protein (CETP) levels is controversial. We determined whether plasma cholesteryl ester transfer (CET), reflecting CETP-mediated transfer of cholesteryl esters from endogenous HDL towards apolipoprotein B-lipoproteins, predicts incident CVD. METHODS: A prospective nested case-control study was carried out in 114 men who developed CVD and 105 controls. Participants did not use lipid lowering drugs at baseline. Plasma CET was assayed using an isotope method. RESULTS: Plasma CET was 19% higher (P=0.030), whereas CETP mass was unaltered (P=0.30) in cases vs. controls. Plasma CET predicted CVD (age-adjusted hazard ratio (HR): 1.20 (95% CI 1.02-1.46, P=0.028), but incident CVD was unrelated to CETP mass (HR: 0.88 (95% CI 0.73-1.07), P=0.20). Plasma CET still predicted CVD after additional adjustment for total cholesterol/HDL cholesterol, triglycerides and non-lipid risk markers (HR: 1.22 (95% CI 1.02-1.46, P=0.031). CONCLUSION: Plasma CET rather than CETP mass may be a determinant of cardiovascular risk.

Plasma phospholipid transfer protein activity is independently determined by obesity and insulin resistance in non-diabetic subjects.

BACKGROUND: Phospholipid transfer protein (PLTP) is an emerging cardio-metabolic risk factor which is intricately involved in lipoprotein metabolism. Elevated plasma PLTP activity levels are reported in obesity and diabetes mellitus, but the relative contributions of obesity and insulin resistance to plasma PLTP activity remain unclear. We tested whether plasma PLTP activity is independently related to (central) obesity and insulin resistance in non-diabetic subjects. METHODS: The relationships of plasma PLTP activity levels (phospholipid vesicles-HDL system) with waist circumference, waist/hip ratio, body mass index (BMI) and insulin resistance (homeostasis model assessment (HOMA(ir))) were determined in 313 non-diabetic subjects (273 men). RESULTS: PLTP activity was higher in 67 subjects with enlarged waist circumference (NCEP-ATP-III criteria; 102 ± 11 AU) compared to 246 subjects with normal waist (98 ± 11 AU, P=0.027). In univariate analysis PLTP activity correlated positively with waist (r=0.188), waist/hip ratio (r=0.143), BMI (r=0.125) and HOMA(ir) (r=0.192) (P<0.05 to P<0.001). The relationship of PLTP with HOMA(ir) was confined to subjects with the highest waist circumference and waist/hip ratio. In age- and sex-adjusted multiple linear regression models, waist circumference (ß=0.158, P=0.025), but not BMI, predicted PLTP activity independently of HOMA(ir) (ß=0.126, P=0.047). Furthermore, both waist and waist/hip ratio interacted positively with HOMA(ir) on PLTP activity (ß=0.109, P=0.056 and ß=0.156, P=0.034, respectively). CONCLUSIONS: In non-diabetic subjects, both obesity and insulin resistance influence plasma PLTP activity, resulting in elevated plasma PLTP activity particularly with combined increases in obesity and insulin resistance. Higher PLTP activity could contribute to elevated cardiovascular risk in the presence of obesity and insulin resistance.

Relationship of plasma apolipoprotein M with proprotein convertase subtilisin-kexin type 9 levels in non-diabetic subjects.

PURPOSE: Apolipoprotein M (apoM) retards atherosclerosis development in murine models, and may be regulated by pathways involved in LDL metabolism. Proprotein convertase subtilisin-kexin type 9 (PCSK9) plays a key role in LDL receptor processing. We determined the extent to which plasma apoM is related to PCSK9 levels in subjects with varying degrees of obesity. METHODS: We sought correlations between plasma apoM and PCSK9, measured using recently developed ELISAs, in 79 non-diabetic subjects. RESULTS: ApoM and PCSK9 levels were both correlated positively with total cholesterol, non-HDL cholesterol, LDL cholesterol and apoB (P < 0.05 to P < 0.001). ApoM correlated positively with PCSK9 in lean individuals (n = 37, r = 0.337, P = 0.041), but not in overweight subjects (n = 32, r = 0.125, P = 0.50) and in obese subjects (n = 10, r = -0.055, P = 0.88). CONCLUSIONS: The PCSK9 pathway may contribute to plasma apoM regulation in humans. The influence of PCSK9 on circulating apoM appears to be modified by adiposity.

Carotid intima media thickness is associated with plasma adiponectin but not with the leptin:adiponectin ratio independently of metabolic syndrome.

PURPOSE: A recent report showed no benefit of the leptin:adiponectin ratio (L:A ratio) over individual adipokine levels in CHD prediction [8]. We determined associations of carotid intima media thickness (IMT) with the L:A ratio taking account of cardiovascular risk factors in a high risk population. METHODS: IMT, plasma leptin, adiponectin and the L:A ratio were determined in 161 middle-aged men and women (45% metabolic syndrome). RESULTS: IMT was associated inversely with adiponectin and positively with the L:A ratio in age- and sex-adjusted multiple linear regression analyses (P<0.001 for both). After controlling for metabolic syndrome, the independent association with adiponectin remained (P<0.001), but the relationship with the L:A ratio disappeared (P=0.126). Results were similar after additional adjustment for diabetes status or for insulin resistance. CONCLUSION: This study does not support the preferential use of the leptin:adiponectin ratio as a marker of atherosclerosis susceptibility.

Plasma apolipoprotein M responses to statin and fibrate administration in type 2 diabetes mellitus.

PURPOSE: Plasma apolipoprotein M (apoM) is potentially anti-atherogenic, and has been found to be associated positively with plasma total, LDL and HDL cholesterol in humans. ApoM may, therefore, be intricately related to cholesterol metabolism. Here, we determined whether plasma apoM is affected by statin or fibrate administration in patients with diabetes mellitus. METHODS: Fourteen type 2 diabetic patients participated in a placebo-controlled crossover study which included three 8-week treatment periods with simvastatin (40 mg daily), bezafibrate (400 mg daily), and their combination. RESULTS: ApoM was decreased by 7% in response to simvastatin (P<0.05 from baseline and placebo), and remained unchanged during bezafibrate and combined simvastatin+bezafibrate administration. Plasma apoM concentrations correlated positively with apoB-containing lipoprotein measures at baseline and during placebo (P<0.02 to P<0.001), but these relationships were lost during all lipid lowering treatment periods. CONCLUSIONS: This study suggests that, even though plasma apoM is lowered by statins, apoM metabolism is to a considerable extent independent of statin- and fibrate-affected pathways involved in cholesterol homeostasis.