Modulation of autoimmune arthritis severity in mice by apolipoprotein E (ApoE) and cholesterol.

Apolipoprotein E (ApoE) deficiency promoted an exacerbation of autoimmune arthritis in mice by inducing proinflammatory immune responses. In this study we analysed the contribution of hypercholesterolaemia and/or the absence of ApoE anti-inflammatory properties, unrelated to its function in the control of cholesterol metabolism, towards the acceleration of arthritis in these mutant animals. The induction and severity of collagen type II-induced arthritis (CIA) were compared for B10.RIII wild-type (WT), B10.RIII.ApoE+/- , B10.RIII.ApoE-/- and B10.RIII.low-density lipoprotein receptor (LDLR-/- ) mice with different concentrations of circulating ApoE and cholesterol. A 50-70% reduction in serum levels of ApoE was observed in heterozygous B10.RIII.ApoE+/- mice in comparison to B10.RIII.WT, although both strains of mice exhibited similar circulating lipid profiles. This ApoE reduction was associated with an increased CIA severity that remained lower than in homozygous B10.RIII.ApoE-/- mice. An important rise in circulating ApoE concentration was observed in hypercholesterolaemic B10.RIII.LDLR-/- mice fed with a normal chow diet, and both parameters increased further with an atherogenic hypercholesterolaemic diet. However, the severity of CIA in B10.RIII.LDLR-/- mice was similar to that of B10.RIII.WT controls. In conclusion, by comparing the evolution of CIA between several strains of mutant mice with different levels of serum ApoE and cholesterol, our results demonstrate that both hypercholesterolaemia and ApoE regulate the intensity of in-vivo systemic autoimmune responses.

Effect of atorvastatin on lipoprotein (a) and interleukin-10: a randomized placebo-controlled trial.

AIM: This study aimed to determine the effect of atorvastatin therapy on plasma lipoprotein (a) [Lp(a)] and biomarkers of inflammation in hypercholesterolaemic patients free of cardiovascular disease. METHODS: In this three-month randomized double-blind placebo-controlled trial, 63 hypercholesterolaemic patients were randomly treated with either placebo or atorvastatin (10 or 40 mg/day) for 12 weeks. Lp(a) and biomarkers of inflammation (C-reactive protein [CRP], interleukin [IL]-6 and -10, and tumour necrosis factor-alpha receptors [TNF-Rs]) were measured at study entry, and at four and 12 weeks of follow-up. RESULTS: At the end of the study, patients allocated to atorvastatin (10 or 40 mg/day) presented with significantly lower Lp(a) levels than those taking placebo (10 [1-41]mg/dL versus 6 [1-38]mg/dL [P = 0.02] and 21 [1-138]mg/dL versus 15 [1-103]mg/dL [P = 0.04], respectively]. In multivariate analyses, the relative changes in Lp(a) were independently related to baseline Lp(a) levels and CRP changes. No significant changes in CRP, IL-6 and TNF-Rs were observed. In contrast, IL-10 (pg/mL) increased significantly in patients taking atorvastatin (2.14 [0.49-43]pg/mL versus 4.54 [0.51-37.5]pg/mL; P = 0.01), and was even more increased with the 40-mg dose than with 10mg. CONCLUSION: Our results suggest that 12-week atorvastatin is effective in reducing Lp(a) in dyslipidaemic patients free of CVD. Furthermore, this is also the first evidence that the drug increases IL-10 in a dose-dependent manner.

¿Son todas las partículas de lipoproteínas de alta densidad iguales? / Are all high-density lipoprotein particles equal?

El análisis de las modificaciones de genes que influencian el metabolismo y la función de las lipoproteínas de alta densidad (HDL) en modelos murinos, demuestra que los cambios (aumentos o disminución) de colesterol unido a HDL no son un predictor adecuado de la susceptibilidad a la arteriosclerosis de éstos. Por tanto, los diferentes tipos de partículas de HDL generados por intervención sobre distintas potenciales dianas terapéuticas no son iguales en cuanto a su potencial antiaterogénico. El análisis del transporte reverso de colesterol específico de macrófagos, y de la capacidad de las HDL de proteger frente a la modificación oxidativa de lipoproteínas de baja densidad, aporta una mejor predicción del efecto de la modificación genética efectuada sobre la susceptibilidad a la arteriosclerosis (AU)

Analysis of the genetic modifications that influence high-density lipoprotein (HDL) metabolism and function in murine models shows that changes (whether increases or decreases) in HDL-cholesterol do not accurately predict susceptibility to arteriosclerosis in these models. Therefore, the distinct types of HDL particles generated by interventions on the various potential therapeutic targets differ in their antiatherogenic potential. Analysis of macrophage-specific reverse cholesterol transport and the ability of HDL to protect LDL against oxidative modification is better able to predict the effect of genetic modification on susceptibility to arteriosclerosis (AU)

Tratamientos vitamínicos para disminuir la concentración de homocisteína: ¿reducen el riesgo de enfermedad cerebrovascular en prevención primaria? / Vitamin treatments that lower homocysteine concentration: can they decrease cerebrovascular disease in primary prevention?

Introducción. La concentración plasmática elevada de homocisteína (Hcy) o hiperhomocisteinemia se asocia a un aumento del riesgo de enfermedad vascular en estudios de casos y controles, y, en menor grado, en estudios prospectivos. Desarrollo. Han finalizado ya diversos grandes estudios aleatorios, doble ciego y controlados con placebo, que se realizaron con el objetivo de estudiar si había una reducción del riesgo vascular al disminuir la concentración plasmática de Hcy mediante tratamientos vitamínicos específicos (folatos y/o vitaminas B12 y B6). Su objetivo era analizar si esta estrategia reducía el riesgo de enfermedad cardiovascular (estudios HOPE, NORVIT, WAFACS y WENBIT) y cerebrovascular (estudio VISP) en un contexto de prevención secundaria. Los resultados obtenidos a partir de estos estudios y un metaanálisis, que incluye otros más pequeños hasta un total de 12, mostraron que el tratamiento disminuye la concentración plasmática de Hcy, pero no el riesgo vascular. Es, sin embargo, interesante señalar que un metaanálisis reciente que analizó los efectos de estos tratamientos vitamínicos detectó un efecto protector significativo en la prevención primaria del ictus. Estos datos son consistentes con el hecho de que la hiperhomocisteinemia se relaciona más con el riesgo cerebrovascular que con el cardiovascular. Y también con la observación reciente de que la suplementación con ácido fólico en las harinas está asociada con una disminución en la mortalidad por ictus en Estados Unidos y Canadá. Conclusiones. Obviamente, estos datos requerirán de posterior confirmación, pero parece que ahora existen razones que permiten esperar un desenlace positivo de los estudios de intervención para disminuir la Hcy (AU)

Introduction. High plasma homocysteine (Hcy) concentration or hyperhomocysteinemia is associated with an increased vascular risk of disease in case-control studies and, to a lesser extent, in prospective studies. Development. Several large randomized, double-blind, placebo-controlled trials have been already conducted using specific vitamin therapies with the aim of reducing secondary cardiovascular (HOPE, NORVIT, WAFACS and WENBIT studies) and cerebrovascular (VISP study) disease risk. The results from these major secondary prevention trials and one meta-analysis, that included other smaller studies up to 12 of them, showed that treatment decreased plasma Hcy concentration but failed to reduce cardiovascular risk. It is nevertheless noteworthy that a recent meta-analysis addressing the effects of these vitamin treatments on cerebrovascular risk found a positive effect on primary stroke prevention. These data would be consistent with the fact that increased Hcy is known to be associated more strongly with stroke risk than with cardiovascular risk. Moreover, folic acid supplementation in grain food has recently been shown to be associated with a decreased stroke incidence in USA and Canada. Conclusions. Obviously, these data on primary stroke prevention will require extensive confirmation. However, there now appear to be more reasons to expect a positive outcome of Hcy intervention studies (AU)

Disodium ascorbyl phytostanol phosphate (FM-VP4), a modified phytostanol, is a highly active hypocholesterolaemic agent that affects the enterohepatic circulation of both cholesterol and bile acids in mice.

Disodium ascorbyl phytostanol phosphate (FM-VP4) is a synthetic compound derived from sitostanol and campestanol that has proved to be efficient as a cholesterol-lowering therapy in mice and human subjects. However, the mechanism of action of FM-VP4 remains unknown. The present study tests the ability of FM-VP4 to alter intestinal and liver cholesterol homeostasis in mice. Female C57BL/6J mice were fed either a control chow or a 2 % FM-VP4-enriched diet for 4 weeks. FM-VP4 reduced the in vivo net intestinal cholesterol absorption and plasma and liver cholesterol concentrations by 2.2-, 1.5- and 1.6-fold, respectively, compared with control mice. Furthermore, FM-VP4 also showed an impact on bile acid homeostasis. In FM-VP4 mice, liver and intestinal bile acid content was increased by 1.3- and 2.3-fold, respectively, whereas faecal bile acid output was 3.3-fold lower. FM-VP4 also increased the intestinal absorption of orally administered [3H]taurocholic acid to small intestine in vivo. Inhibition of intestinal cholesterol absorption by FM-VP4 was not mediated via transcriptional increases in intestine liver X receptor (LXR)-alpha, adenosine triphosphate-binding cassette transporter (ABC)-A1, ABCG5/G8 nor to decreases in intestinal Niemann-Pick C1-like 1 (NPC1L1) expression. In contrast, FM-VP4 up-regulated liver LXRalpha, ABCA1, ABCG5, scavenger receptor class BI (SR-BI) and hydroxymethylglutaryl coenzyme A reductase (HMGCoA-R) gene expression, whereas it down-regulated several farnesoid X receptor (FXR)-target genes such as cytochrome P450 family 7 subfamily A polypeptide 1 (CYP7A1) and Na+/taurocholate co-transporter polypeptide (NTCP). In conclusion, FM-VP4 reduced intestinal cholesterol absorption, plasma and liver cholesterol and affected bile acid homeostasis by inducing bile acid intestinal reabsorption and changed the liver expression of genes that play an essential role in cholesterol homeostasis. This is the first phytosterol or stanol that affects bile acid metabolism and lowers plasma cholesterol levels in normocholesterolaemic mice.

Phytosterols do not change susceptibility to obesity, insulin resistance, and diabetes induced by a high-fat diet in mice.

Most studies have focused on the cholesterol-lowering activity of phytosterols; however, other biological actions have also been attributed to these plant compounds. In this study, we investigated whether phytosterols could delay (progression phase) and/or reverse (regression phase) insulin resistance or type 2 diabetes mellitus in an experimental mouse model of diet-induced obesity, insulin resistance, and diabetes. Body mass, plasma lipid levels, insulin resistance, and hyperglycemia were determined. Phytosterol intake did not improve these metabolic parameters. Therefore, we were unable to substantiate any protective effect of phytosterol intake on diabetes development or regression in the mouse model used.

The effects of liposuction removal of subcutaneous abdominal fat on lipid metabolism are independent of insulin sensitivity in normal-overweight individuals.

BACKGROUND: Abdominal fat (both visceral and subcutaneous) accumulation is associated with an increased risk of developing insulin resistance. The latter stands as the basis upon which diabetes, hypertension, and atherogenic dyslipidemia tend to build up. Hence, abdominal liposuction (AL) could theoretically hold metabolic benefits. We undertook the present study to assess the effects of AL on carbohydrate and lipid metabolism. METHODS: This is a prospective study including 20 healthy volunteers (M2/F18) aged 39.6 +/- 7.7 years old (24-52), body mass index (BMI) = 25.3 +/- 4.7 kg/m(2) (19.8-36) who underwent AL. Before and 4 months after AL, we measured glucose and insulin concentrations, HOMA index [glucose (mM) x IRI (microUI/l)/22.5], free fatty acids (FFA), glycerol, total cholesterol and triglycerides, high-density lipoprotein (HDL)-cholesterol (HDL-c), low-density lipoprotein (LDL)-cholesterol (LDL-c), very low-density lipoprotein (VLDL)-cholesterol (VLDL-c) and apolipoproteins (apo) B, AI and AII, adiponectin (Adp), and ultra-sensitive C-reactive protein (CRP). RESULTS: Lipo-aspirate averaged 5.494 +/- 5.297 cc (600-19.000). Weight, BMI, and waist circumference decreased significantly 4 months after surgery by 4.6, 4.6 and 5.9%, respectively. There were significant decrements in FFA (-35%, p < 0.0001), glycerol (-63%, p < 0.0005), VLDL-c (-15.2%; p < 0.001), and triglycerides (-21.3%, p < 0.002), an increase in HDL-c (+10%, p < 0.03), Apo AI (+10.1%, p < 0.02), and Apo AII (+11.8%, p < 0.001). Total cholesterol, LDL-c, ApoB, and the LDL-c/ApoB ratio raised by +15% (p < 0.0005), +27.3% (p < 0.000), +15.1% (p < 0.008) and +2.76% (p < 0.008), respectively. Glucose, insulin, the HOMA index, Adp, and CRP were not significantly altered after AL. CONCLUSION: AL in healthy normal weight or slightly overweight subjects improves the major lipoprotein components of obesity-associated dyslipidemia. This improvement occurs independent of insulin sensitivity.

Role of vitamin D in the pathogenesis of type 2 diabetes mellitus.

Vitamin D deficiency has been shown to alter insulin synthesis and secretion in both humans and animal models. It has been reported that vitamin D deficiency may predispose to glucose intolerance, altered insulin secretion and type 2 diabetes mellitus. Vitamin D replenishment improves glycaemia and insulin secretion in patients with type 2 diabetes with established hypovitaminosis D, thereby suggesting a role for vitamin D in the pathogenesis of type 2 diabetes mellitus. The presence of vitamin D receptors (VDR) and vitamin D-binding proteins (DBP) in pancreatic tissue and the relationship between certain allelic variations in the VDR and DBP genes with glucose tolerance and insulin secretion have further supported this hypothesis. The mechanism of action of vitamin D in type 2 diabetes is thought to be mediated not only through regulation of plasma calcium levels, which regulate insulin synthesis and secretion, but also through a direct action on pancreatic beta-cell function. Therefore, owing to its increasing relevance, this review focuses on the role of vitamin D in the pathogenesis of type 2 diabetes mellitus.

Emerging cardiovascular risk factors in subclinical hypothyroidism: lack of change after restoration of euthyroidism.

Subclinical hypothyroidism (SH) is a frequent condition that may be associated with increased cardiovascular risk. There is current interest in determining the effect, if any, of substitutive therapy with l-thyroxine (L-T4) on cardiovascular risk factors in SH and, particularly, on those associated with emerging cardiovacular risk, such as apolipoprotein (apo) B, lipoprotein (Lp) (a), total homocysteine (t-Hcy), and C-reactive protein (CRP). Thus, the aim of this study was to assess the impact of euthyroidism restoration on these emerging risk factors in SH. Forty-two patients diagnosed with SH were consecutively recruited before treatment. These patients were treated with L-T4 for 3 to 6 months with the dose necessary to restore euthyroidism. Lp(a), fasting and postmethionine (n = 28) t-Hcy, and CRP did not change with substitutive therapy, regardless of the respective baseline values, and the decrease in apo B paralleled that of low-density lipoprotein (LDL) cholesterol. Similarly, no treatment effect was observed on homocysteine or CRP in patients with thyrotropin-stimulating hormone (TSH) >10 mIU/L. Monitoring of emerging risk factors did not offer additional arguments for treating patients with SH and, thus, is not justified in their clinical management.

Role of apoA-II in lipid metabolism and atherosclerosis: advances in the study of an enigmatic protein.

Our understanding of apolipoprotein A-II (apoA-II) physiology is much more limited than that of apoA-I. However, important and rather surprising advances have been produced, mainly through analysis of genetically modified mice. These results reveal a positive association of apoA-II with FFA and VLDL triglyceride plasma concentrations; however, whether this is due to increased VLDL synthesis or to decreased VLDL catabolism remains a matter of controversy. As apoA-II-deficient mice present a phenotype of insulin hypersensitivity, a function of apoA-II in regulating FFA metabolism seems likely. Studies of human beings have shown the apoA-II locus to be a determinant of FFA plasma levels, and several genome-wide searches of different populations with type 2 diabetes have found linkage to an apoA-II intragenic marker, making apoA-II an attractive candidate gene for this disease. The increased concentration of apoB-containing lipoproteins present in apoA-II transgenic mice explains, in part, why these animals present increased atherosclerosis susceptibility. In addition, apoA-II transgenic mice also present impairment of two major HDL antiatherogenic functions: reverse cholesterol transport and protection of LDL oxidative modification. The apoA-II locus has also been suggested as an important genetic determinant of HDL cholesterol concentration, even though there is a major species-specific difference between the effects of mouse and human apoA-II. As antagonizing apoA-I antiatherogenic actions can hardly be considered the apoA-II function in HDL, this remains a topic for future investigations. We suggest that the existence of apoA-II or apoA-I in HDL could be an important signal for specific interaction with HDL receptors such as cubilin or heat shock protein 60.

Apo(B)-dependent dyslipidemic phenotypes in type 1 diabetic patients.

BACKGROUND: The prevalence of apo(B)-dependent dyslipidemic phenotypes, which are associated with cardiovascular disease, is increased in normocholesterolemic type 2 diabetic patients. Our aim was to determine the impact of including apo(B) in the evaluation of normocholesterolemic type 1 diabetic patients. METHODS: A total of 123 type 1 diabetic patients (47% male, age 36.6+/-12.5 years) were included. The apo(B) cut-off point (1.14 g/l) was obtained from a group of 53 normolipidemic control subjects of similar age and gender distribution; for low density lipoprotein cholesterol (LDLc), triglycerides, and high density lipoprotein cholesterol (HDLc), we used the cut-off points recommended by the National Cholesterol Education Program. LDLc was determined by ultracentrifugation or Friedewald's equation, depending on triglyceride concentrations, and apo(B) by immunoturbidimetry. RESULTS: A total of 113 (92%) type 1 diabetic patients were normocholesterolemic, and 13% of these were dyslipidemic. The frequency of hyperapo(B) was similar in normocholesterolemic patients and controls (6.2 vs. 9.4%, respectively). Diabetic patients with hyperapo(B) had poorer glycemic control, higher total cholesterol, triglycerides, and LDLc, and a lower HDLc and LDLc/apo(B) ratio. CONCLUSIONS: Unlike type 2 diabetes, type 1 diabetes is not associated with an increased prevalence of hyperapo(B)-dependent dyslipidemic phenotypes. Thus, only in patients with poor glycemic control who display other components of diabetic dyslipidemia, typical for type 2 diabetes, does determining apo(B) concentrations provide additional information in type 1 diabetes.

Low-density lipoprotein particle size, triglyceride-rich lipoproteins, and glucose tolerance in non-diabetic men with essential hypertension.

The aim of the study is to investigate serum lipoproteins abnormalities including low-density lipoprotein (LDL) particle size, and their relationship with other cardiovascular risk factors in men with essential hypertension. Plasma glucose and serum insulin levels during oral glucose tolerance test (OGTT), serum lipoprotein(a), apolipoprotein (apo) A-I. apo B. cholesterol and triglycerides in serum and in lipoproteins, and LDL particle diameter were measured in thirty-eight consecutive newly-diagnosed non-diabetic untreated hypertensive men and 38 healthy male controls. Plasma glucose at baseline, 60 and 120 min during OGTT was significantly higher in patients than controls whereas serum insulin levels did not differ between patients and controls. Serum apo B and triglycerides were significantly raised in patients compared with controls (1.08 +/- 0.17 g/L [mean +/- SD] vs 0.97 +/- 0.22 g/L. p < 0.05, and 1.56 +/- 0.90 mmol/L vs 1.15 +/- 0.57 mmol/L, p < 0.05, respectively). Very-low-density lipoprotein (VLDL) triglycerides and LDL-cholesterol were increased in patients compared with controls (0.89 +/- 0.79 mmol/L and 0.54 +/- 0.35 mmol/L, p < 0.05, and 4.08 +/- 0.85 mmol/L and 3.60 +/- 0.92 mmol/L, p < 0.05, respectively) whereas high-density lipoprotein (HDL) cholesterol was lower in patients compared with controls 0.95 +/- 0.22 mmol/L and 1.07 +/- 0.20 mmol/L, p < 0.05). Adjustment for body mass index, abdominal/hip perimeter ratio and area under the glucose curve did not attenuate the relationship between hypertension and VLDL-triglycerides. Six patients and two controls had a mean LDL diameter < or = 25.5 nm and in the former serum triglycerides ranged from 1.86 mmol/L to 2.37 mmol/L. Mean LDL particle diameter in both patients and controls showed an inverse relationship with log-transformed serum triglycerides (r = - 0.51, p < 0.001 and r = - 0.47, p < 0.005, respectively). Among patients, those with serum triglycerides > or = [corrected] 1.58 mmol/L had a lesser mean LDL diameter than those with triglycerides above this threshold (25.78 +/- 0.47 nm vs 26.30 +/- 0.35 nm, p < 0.001). Higher plasma glucose, serum apo B and LDL-cholesterol as well as the decrease in serum HDL-cholesterol in patients with hypertension are consistent with high coronary heart disease risk. Not only mild hypertriglyceridemia but also high-normal serum triglycerides in themselves or as a surrogate of a predominance of small dense LDL particles in plasma convey an additional risk for cardiovascular disease in hypertensive patients even though routine plasma lipids are within or near normal range.

ApoA-II expression in CETP transgenic mice increases VLDL production and impairs VLDL clearance.

Apolipoprotein (apo)A-II is a major high density lipoprotein (HDL) protein; however, its role in lipoprotein metabolism is largely unknown. Transgenic (Tg) mice that overexpress human apoA-II present functional lecithin: cholesterol acyltransferase deficiency, HDL deficiency, hypertriglyceridemia and, when fed an atherogenic diet, increased non-HDL cholesterol and increased susceptibility to atherosclerosis. In contrast to humans, mice do not present cholesteryl ester transfer protein (CETP) activity in plasma. To study the in vivo interaction of these two proteins, we crossbred human apoA-II and CETP-Tg mice. CETP x apoA-II-Tg mice fed an atherogenic diet, compared with CETP-Tg mice presented a 2-fold decrease in HDL cholesterol and a quantitatively similar increase in total plasma cholesterol and percentage of free cholesterol, non-HDL cholesterol, and free fatty acids, together with a remarkable 112-fold increase in plasma triglycerides. Plasma triglycerides in CETP x apoA-II-Tg mice were mainly associated with very low density lipoproteins (VLDL), which were also enriched in protein content, and resulted from a combination of higher production rate compared with both of their progenitors and non-Tg control mice, and decreased catabolism compared only with CETP-Tg mice. These results show CETP x apoA-II-Tg mice to be a good model with which to study mechanisms leading to VLDL overproduction and suggest that CETP and, in particular apoA-II, may play a role in the regulation of VLDL metabolism.

Increased production of very-low-density lipoproteins in transgenic mice overexpressing human apolipoprotein A-II and fed with a high-fat diet.

We investigated the mechanisms that lead to combined hyperlipidemia in transgenic mice that overexpress human apolipoprotein (apo) A-II (line 11.1). The 11.1 transgenic mice develop pronounced hypertriglyceridemia, and a moderate increase in free fatty acid (FFA) and plasma cholesterol, especially when fed a high-fat/high-cholesterol diet. Post-heparin plasma lipoprotein lipase and hepatic lipase activities (using artificial or natural autologous substrates), the decay of plasma triglycerides with fasting, and the fractional catabolic rate of the radiolabeled VLDL-triglyceride (both fasting and postprandial) were similar in 11. 1 transgenic mice and in control mice. In contrast, a 2.5-fold increase in hepatic VLDL-triglyceride production was observed in 11. 1 transgenic mice in a period of 2 h in which blood lipolysis was inhibited. This increased synthesis of hepatic VLDL-triglyceride used preformed FFA rather than FFA of de novo hepatic synthesis. The 11.1 transgenic mice also presented reduced epididymal/parametrial white adipose tissue weight (1.5-fold), increased rate of epididymal/parametrial hormone-sensitive lipase-mediated lipolysis (1.2-fold) and an increase in cholesterol and, especially, in triglyceride liver content, suggesting an enhanced mobilization of fat as the source of preformed FFA reaching the liver. Increased plasma FFA was reverted by insulin, demonstrating that 11.1 transgenic mice are not insulin resistant. We conclude that the overexpression of human apoA-II in transgenic mice induces combined hyperlipidemia through an increase in VLDL production. These mice will be useful in the study of molecular mechanisms that regulate the overproduction of VLDL, a situation of major pathophysiological interest since it is the basic mechanism underlying familial combined hyperlipidemia.