Alterações simultâneas e múltiplas das funções da HDL seguem o excesso de peso / Simultaneous and multiple changes in HDL functions follow overweight

INTRODUÇÃO. A obesidade se associa a declínio na capacidade de efluxo de colesterol (CEC) mediada por HDL. Embora esse dado tenha apoiado a noção de que a disfunção do HDL contribui para a aterogênese em pacientes obesos, a perda funcional da HDL também pode envolver outros domínios funcionais e se estabelecer mesmo antes dos valores limiares para obesidade, ou seja, ainda em valores compatíveis com sobrepeso. MÉTODOS. Perfil lipídico, índice de massa corporal (IMC), medidas bioquímicas e espessura médio-intimal (cIMT) foram obtidos neste estudo transversal com 899 indivíduos assintomáticos. Funções de HDL e caracterização físico-química de HDL foram medidas em um subgrupo (n=101). RESULTADOS. Foi identificada interação do IMC sobre a associação entre HDL-C e cIMT (ß=-1,8; p<0,0001). Enquanto que, de forma geral, o HDL-C reduzido foi associado ao aumento da cIMT, os indivíduos com níveis elevados de HDL-C apresentaram associação atenuada entre o IMC e cIMT. Foi encontrada uma associação negativa entre CEC e cIMT (ß=-0,2; p<0,047) e entre atividade antioxidante de HDL e cIMT (ß=-0,2; p<0,038) mesmo após ajuste para idade, sexo, IMC, HDL-C e insulina no plasma. O IMC foi inversamente associado à inibição da agregação plaquetária mediada por HDL (r=-0,2, p<0,03) e CEC (r=-0,3, p<0,001), mas diretamente associada à atividade antioxidante (r=0,2, p<0,047). Uma variável composta de CEC e atividade antioxidante transformadas em z-score permaneceu aproximadamente constante à medida em que o tamanho de HDL se altera em função do excesso de peso. Valores crescentes dessa variável composta foram associados à cIMT (R2 polinomial=0,26, p<0,001), sugerindo que a alteração do tamanho da HDL pode representar uma adaptação biológica bem-sucedida ao excesso de peso. CONCLUSÃO. O aumento do IMC está associado à disfunção global da HDL, que contribui para aumentar a carga aterosclerótica. Nesse cenário, a alteração do tamanho da HDL não justifica o aumento do desenvolvimento da doença aterosclerótica. (AU)

Elevated CETP activity during acute phase of myocardial infarction is independently associated with endothelial dysfunction and adverse clinical outcome.

OBJECTIVE: Recent data suggests that cholesteryl ester transfer protein (CETP) activity may interact with acute stress conditions via inflammatory-oxidative response and thrombogenesis. We investigated this assumption in patients with ST-elevation myocardial infarction (STEMI). METHODS: Consecutive patients with STEMI (n = 116) were enrolled <24-h of symptoms onset and were followed for 180 days. Plasma levels of C-reactive protein (CRP), interleukin-2 (IL-2), tumor necrosis factor (TNFα), 8-isoprostane, nitric oxide (NOx) and CETP activity were measured at enrollment (D1) and at fifth day (D5). Flow-mediated dilation (FMD) was assessed by ultrasound and coronary thrombus burden (CTB) was evaluated by angiography. RESULTS: Neither baseline nor the change of CETP activity from D1 to D5 was associated with CRP, IL-2, TNFα, 8-isoprostane levels or CTB. The rise in NOx from D1 to D5 was inferior [3.5(-1; 10) vs. 5.5(-1; 12); p < 0.001] and FMD was lower [5.9(5.5) vs. 9.6(6.6); p = 0.047] in patients with baseline CETP activity above the median value than in their counterparts. Oxidized HDL was measured by thiobarbituric acid reactive substances (TBARS) in isolated HDL particles and increased from D1 to D5, and remaining elevated at D30. The change in TBARS content in HDL was associated with CETP activity (r = 0.72; p = 0.014) and FMD (r = -0.61; p = 0.046). High CETP activity at admission was associated with the incidence of sudden death and recurrent MI at 30 days (OR 12.8; 95% CI 1.25-132; p = 0.032) and 180 days (OR 3.3; 95% CI 1.03-10.7; p = 0.044). CONCLUSIONS: An enhanced CETP activity during acute phase of STEMI is independently associated with endothelial dysfunction and adverse clinical outcome.

Increased 27-hydroxycholesterol plasma level in men with low high density lipoprotein-cholesterol may circumvent their reduced cell cholesterol efflux rate.

BACKGROUND: HDL is considered the most important mechanism for the excretion of intracellular cholesterol. The liver is the only organ capable to metabolize cholesterol into bile acid. The enzymatic conversion of cholesterol to bile acid is dependent on the cytochrome P450 microsomal system which is also responsible for the generation of oxysterols. The latter's plasma concentrations may reflect the metabolic processes of specific tissues where they are generated. The objective of this study was to investigate in healthy individuals who differ according to their HDL levels the concentration of oxysterols and relate it to the HDL-dependent cell cholesterol efflux rate. METHODS: 24-Hydroxycholesterol, 25-hydroxycholesterol, 27-hydroxycholesterol were determined in plasma by GLC/mass spectrometry in 107 healthy subjects with low HDL (HDL-C<1.03mmol/l) and high HDL cholesterol (HDL-C>1.55mmol/l). HDL-dependent in vitro cell cholesterol efflux rate was measured in 29 cases. RESULTS: No differences were found in plasma oxysterol concentrations between the Low HDL and High HDL groups. There was a significant negative correlation between HDL-C and 27-hydroxycholesterol. Plasma oxysterol concentrations were significantly lower in female than in male subjects. The Low HDL male group had higher 27-hydroxycholesterol than the High HDL male group. Cell cholesterol efflux rate was lower in Low HDL than in High HDL and related inversely with 27-hydroxycholesterol. CONCLUSION: As compared to High HDL, Low HDL men have increased 27-hydroxycholesterol plasma level that may circumvent their reduced cell cholesterol efflux rate.

Metabolism of plasma cholesterol and lipoprotein parameters are related to a higher degree of insulin sensitivity in high HDL-C healthy normal weight subjects.

BACKGROUND: We have searched if plasma high density lipoprotein-cholesterol (HDL-C) concentration interferes simultaneously with whole-body cholesterol metabolism and insulin sensitivity in normal weight healthy adult subjects. METHODS: We have measured the activities of several plasma components that are critically influenced by insulin and that control lipoprotein metabolism in subjects with low and high HDL-C concentrations. These parameters included cholesteryl ester transfer protein (CETP), phospholipid transfer protein (PLTP), lecithin cholesterol acyl transferase (LCAT), post-heparin lipoprotein lipase (LPL), hepatic lipase (HL), pre-beta-1HDL, and plasma sterol markers of cholesterol synthesis and intestinal absorption. RESULTS: In the high-HDL-C group, we found lower plasma concentrations of triglycerides, alanine aminotransferase, insulin, HOMA-IR index, activities of LCAT and HL compared with the low HDL-C group; additionally, we found higher activity of LPL and pre-beta-1HDL concentration in the high-HDL-C group. There were no differences in the plasma CETP and PLTP activities. CONCLUSIONS: These findings indicate that in healthy hyperalphalipoproteinemia subjects, several parameters that control the metabolism of plasma cholesterol and lipoproteins are related to a higher degree of insulin sensitivity.

Plasma 27-hydroxycholesterol/cholesterol ratio is increased in low high density lipoprotein-cholesterol healthy subjects.

UNLABELLED: Sterol 27-hydroxylase converts cholesterol to 27-hydroxycholesterol (27-OHC) which is widely distributed among tissues and is expressed at high levels in the vascular endothelium and macrophages. There is a continuous flow of this oxysterol from the tissues into the liver, where it is converted to bile acids. OBJECTIVE: Measure plasma concentrations of 27-OHC in subjects that differ according to their plasma HDL-C concentration. METHODS: Healthy men presenting low HDL-C (<1.03 mmol/L), n=18 or high HDL-C (>1.55 mmol/L), n=18, BMI<30 kg/m² were recruited after excluding secondary causes that might interfere with their plasma lipid concentrations such as smoking, heavy drinking and diabetes. Blood samples were drawn after a 12h fasting period for the measurement of 27-OHC by the combined GC/MS analysis utilizing deuterium-label internal standards. RESULTS: The plasma ratio 27-OHC/total cholesterol (median and range nmoL/mmoL) was 50.41 (27.47-116.00) in the High HDL-C subjects and 63.34 (36.46-91.18) in the Low HDL-C subjects (p=0.0258). CONCLUSION: Our data indicate that the production of 27-OHC by extrahepatic tissues and its transport to the liver may represent an alternative pathway for a deficient reverse cholesterol transport system when plasma HDL-C is low.

Impact of seasonality on the prevalence of dyslipidemia: a large population study.

Assessment of lipid profile parameters has been considered a cornerstone in classifying individuals and populations at risk for cardiovascular disease. Recently, however, preliminary data have raised the possibility of seasonal variations in these parameters, which may cause under- or overestimation. Biological rhythms and seasonal variation of lipid profile was investigated in 227 359 consecutive individuals who underwent health checkups in primary care centers between 2008 and 2010. Plasma low-density lipoprotein cholesterol (LDL-C) >130 mg/dL was 8% more prevalent during winter than summer, with a larger difference among women and middle-aged adults (p < 0.001). High-density lipoprotein cholesterol (HDL-C) <40 mg/dL and triglycerides (TG) >150 mg/dL were respectively 9% and 5% more prevalent during the summer (p < 0.001). Variation amplitude was 3.4 ± 0.3 mg/dL for HDL-C (p = 0.005), 7 ± 2 mg/dL for LDL-C (p = 0.047), and 12 ± 9 mg/dL for TG (p = 0.058). Based on a large population sample, this study confirms the existence of biological rhythms and seasonal variation in lipid profile. This finding must be particularly accounted for in cross-sectional analyses of relative risk, prevalence, or the rate of goal achievement for lipid parameters.

Oxidized low-density lipoproteins and their antibodies: relationships with the reverse cholesterol transport and carotid atherosclerosis in adults without cardiovascular diseases.

BACKGROUND: Metabolic predictors and the atherogenicity of oxidized LDL (oxLDL) and the specific antibodies against oxLDL (oxLDL Ab) are unclear and controversial. METHODS: In 107 adults without atherosclerotic manifestations, we measured oxLDL and oxLDL Ab, and also the activities of CETP, PLTP, lipases and the carotid intima-media thickness (cIMT). Comparisons were performed for the studied parameters between the lowest and the highest tertile of oxLDL and oxLDL Ab, and the relationships between studied variables were evaluated. RESULTS: Subjects with higher oxLDL Ab present reduced hepatic lipase activity and borderline increased cIMT. In the highest oxLDL tertile, besides the higher levels of total cholesterol, LDL-C and apoB100, we found reduced CETP activity and higher cIMT. A significant correlation between oxLDL Ab and cIMT, independent of oxLDL, and a borderline correlation between oxLDL and cIMT independent of oxLDL Ab were found. In the multivariate analysis, apoAI was a significant predictor of oxLDL Ab, in contrast to regulation of oxLDL by apoB100, PLTP and inverse of CETP. CONCLUSIONS: In adults without atherosclerotic disease, the metabolic regulation and carotid atherosclerosis of oxLDL Ab and oxLDL groups, characterized a dual trait in oxLDL Ab, as a contributor to carotid atherosclerosis, much less so than oxidized LDL, and with a modest atheroprotective role.

Differences and similarities of postprandial lipemia in rodents and humans.

BACKGROUND: The rat has been a mainstay of physiological and metabolic research, and more recently mice. This study aimed at characterizing the postprandial triglyceride profile of two members of the Muridae family: the Wistar rats (Rattus norvegicus albinus) and C57BL/6 mice (Mus musculus) plus comparing them to the profile obtained in humans. METHODS: Thirty-one male and twelve female Wistar rats, ten C57BL/6 male and nine female mice received a liquid meal containing fat (17%), protein (4%) and carbohydrates (4%), providing 2 g fat/Kg. Thirty-one men and twenty-nine women received a standardized liquid meal containing fat (25%), dextromaltose (55%), protein (14%), and vitamins and minerals (6%), and providing 40 g of fat per square meter of body surface. Serial blood samples were collected at 2, 4, 6, 8 and 10 h after the ingestion in rats, at 1, 2, 3, 4, 5 and 6 h in mice and in humans at 2, 4, 6 and 8 h. Wilcoxon and Mann-Whitney tests were used. RESULTS/DISCUSSION: The triglyceride responses were evaluated after the oral fat loads. Fasting and postprandial triglyceridemia were determined sequentially in blood sample. AUC, AUIC, AR, RR and late peaks were determined. CONCLUSIONS: Rats are prone to respond in a pro-atherogenic manner. The responses in mice were closer to the ones in healthy men. This study presents striking differences in postprandial triglycerides patterns between rats and mice not correlated to baseline triglycerides, the animal baseline body weight or fat load in all animal groups.

A reduction of CETP activity, not an increase, is associated with modestly impaired postprandial lipemia and increased HDL-cholesterol in adult asymptomatic women.

BACKGROUND: The relationship between CETP and postprandial hyperlipemia is still unclear. We verified the effects of varying activities of plasma CETP on postprandial lipemia and precocious atherosclerosis in asymptomatic adult women. METHODS: Twenty-eight women, selected from a healthy population sample (n = 148) were classified according to three CETP levels, all statistically different: CETP deficiency (CETPd ≤ 4.5%, n = 8), high activity (CETPi ≥ 23.8, n = 6) and controls (CTL, CETP ≥ 4.6% and ≤ 23.7%, n = 14). After a 12 h fast they underwent an oral fat tolerance test (40 g of fat/m² of body surface area) for 8 hours. TG, TG-rich-lipoproteins (TRL), cholesterol and TRL-TG measurements (AUC, AUIC, AR, RR and late peaks) and comparisons were performed on all time points. Lipases and phospholipids transfer protein (PLTP) were determined. Correlation between carotid atherosclerosis (c-IMT) and postprandial parameters was determined. CETP TaqIB and I405V and ApoE-ε3/ε2/ε4 polymorphisms were examined. To elucidate the regulation of increased lipemia in CETPd a multiple linear regression analysis was performed. RESULTS: In the CETPi and CTL groups, CETP activity was respectively 9 and 5.3 higher compared to the CETPd group. Concentrations of all HDL fractions and ApoA-I were higher in the CETPd group and clearance was delayed, as demonstrated by modified lipemia parameters (AUC, AUIC, RR, AR and late peaks and meal response patterns). LPL or HL deficiencies were not observed. No genetic determinants of CETP deficiency or of postprandial lipemia were found. Correlations with c-IMT in the CETPd group indicated postprandial pro-atherogenic associations. In CETPd the regression multivariate analysis (model A) showed that CETP was largely and negatively predicted by VLDL-C lipemia (R² = 92%) and much less by TG, LDL-C, ApoAI, phospholipids and non-HDL-C. CETP (model B) influenced mainly the increment in ApoB-100 containing lipoproteins (R² = 85% negatively) and phospholipids (R² = 13%), at the 6(th)h point. CONCLUSION: The moderate CETP deficiency phenotype included a paradoxically high HDL-C and its sub fractions (as earlier described), positive associations with c-IMT, a postprandial VLDL-C increment predicting negatively CETP activity and CETP activity regulating inversely the increment in ApoB100-containing lipoproteins. We hypothesize that the enrichment of TG content in triglyceride-rich ApoB-containing lipoproteins and in TG rich remnants increases lipoproteins' competition to active lipolysis sites,reducing their catabolism and resulting on postprandial lipemia with atherogenic consequences.