MicroRNAs regulating oxidative stress and inflammation in relation to obesity and atherosclerosis.

A primary event in atherogenesis is the infiltration of activated inflammatory cells into the arterial wall. There they secrete reactive oxygen species and oxidize lipoproteins, inducing foam cell formation and endothelial cell apoptosis, which in turn lead to plaque growth, erosion, and rupture. In addition, there is evidence that this vicious circle between oxidative stress and inflammation occurs not only in the diseased arterial wall but also in adipose tissues in obesity. In this condition, oxidative stress and inflammation impair adipocyte maturation, resulting in defective insulin action and adipocytokine signaling. This observation raises questions regarding what molecules are probably common regulators of these pathogenic processes in adipose and vascular tissues. Candidates are small, noncoding, microRNAs (miRs) that control gene expression by inducing mRNA degradation or blocking translation. This review summarizes recent insights into the roles of miRs in regulation of oxidative stress and inflammation in vascular and adipose tissues. It emphasizes the role of miR-containing microvesicles in the interaction between inflammatory cells and endothelial cells within these tissues and in communication between these tissues, possibly explaining the similarity and the simultaneity of molecular changes and interactions in adipose and vascular tissues.

Increased PAFAH and oxidized lipids are associated with inflammation and atherosclerosis in hypercholesterolemic pigs.

OBJECTIVE: To study the association of PAF-acetyl hydrolase (PAFAH) activity with inflammation, oxidative stress, and atherosclerosis in hypercholesterolemic swine. METHODS AND RESULTS: Cholesterol-rich diet feeding of miniature pigs was associated with an increase in PAFAH activity and an increase of the PAFAH to PON1 ratio. PLA2G7 RNA (coding for PAFAH) expression was increased in blood monocytes and plaque macrophages. Increased PAFAH activity was associated with higher plasma lysophosphatidylcholine and correlated with oxidized LDL. In THP1 monocytes and macrophages and in human blood-derived macrophages, oxidized LDL induced PLA2G7 RNA expression. Atherogenic diet feeding induced the accumulation of macrophages and oxidized LDL in the arterial wall leading to atherosclerosis. PAFAH activity correlated positively with plaque size and TNFalpha expression in plaque macrophages. CONCLUSIONS: We demonstrated that an increase in PAFAH activity was associated with increased levels of lysophosphatidylcholine, oxidized LDL, and inflammation, resulting in accelerated atherosclerosis in hypercholesterolemic minipigs. The significant correlation between PLA2G7 RNA expression in plaque macrophages and plasma PAFAH activity suggests that the latter is a consequence, rather than a cause of macrophage accumulation. Our cell experiments suggest that oxidized LDL can induce PAFAH, resulting in accumulation of lysophosphatidylcholine that increases the inflammatory action of oxidized LDL.

Frequency and predictors of cholesterol target attainment in patients with stable coronary heart disease in Belgium: results from the Dyslipidemia International Study II (DYSIS II CHD).

Objectives: To document the frequency and predictors of low-density lipoprotein cholesterol (LDL-C) target value attainment among patients with coronary heart disease (CHD) in Belgium. Methods: The second Dyslipidemia International Study (DYSIS II) was an observational study of the prevalence of dyslipidemias and lipid target value attainment. Patients in this analysis were aged ≥ 18, had documented CHD, and had a full lipid profile. Use of lipid-lowering therapy (LLT), lipid profile, and LDL-C target value attainment (< 70 mg/dL) were assessed cross-sectionally at the enrollment visit. The distribution of LLTs was assessed among treated patients. Multivariate logistic regression was used to identify variables predictive of LDL-C target value attainment in treated patients. Results: We identified 409 patients with CHD in Belgium, 387 (94.6%) of whom were on LLT at the time of the lipid profile. Among treated patients, the rate of LDL-C target value attainment was 40.6%, and statin monotherapy was the most commonly used LLT (79.3%). Among users of statin monotherapy or combination therapy, simvastatin was the most commonly used treatment (41.6% of patients). Diabetes was associated with higher odds of LDL-C target value attainment (OR 2.29, 95% CI 1.33-3.93), and female gender was associated with lower odds (OR 0.48, 95% CI 0.24-0.97). Conclusion: Rates of LDL-C target value attainment are low in patients with CHD in Belgium. Intensifying statin therapy or combining it with non-statins is essential in Belgian patients for optimal LDL-C reduction.

Oxidized low-density lipoprotein correlates positively with toll-like receptor 2 and interferon regulatory factor-1 and inversely with superoxide dismutase-1 expression: studies in hypercholesterolemic swine and THP-1 cells.

BACKGROUND: Oxidized low-density lipoprotein (LDL) is associated with cardiovascular disease. Macrophages contribute to LDL oxidation, and oxidized LDL (oxLDL) affects macrophage function. We searched for the strongest gene correlates of oxLDL in macrophages in coronary plaques and studied the effect of oxLDL on their expression in THP-1 cells. METHODS AND RESULTS: Gene expression in macrophages isolated from coronary plaque macrophages from hypercholesterolemic swine was measured on Agilent Human cDNA microarrays. Compared with a universal reference, 1653 transcripts were deregulated. The expression of 11 genes correlated positively and the expression of 5 genes correlated negatively with plaque oxLDL. Interferon regulatory factor-1 (IRF1; R2 = 0.69) and toll-like receptor 2 (TLR2; R2 = 0.18) were the strongest positive correlates of oxLDL. Superoxide dismutase 1 (SOD1) was the strongest inverse correlate of oxLDL (R2 = 0.57). Immunohistochemical analysis showed colocalization of IRF1, TLR2, and SOD1 protein in macrophages and confirmed the RNA expression data. OxLDL-induced foam cell formation in THP-1 macrophages was associated with increased expression of IRF1 and TLR2 and decreased expression of SOD1. CONCLUSIONS: Our data support the hypothesis that oxLDL is a proinflammatory stimulus that induces the expression of TLR2 and IRF1, 2 important gene regulators of innate immune response, and inhibits the expression of the antioxidant SOD1.

Low Cytochrome Oxidase 1 Links Mitochondrial Dysfunction to Atherosclerosis in Mice and Pigs.

BACKGROUND: Cytochrome oxidase IV complex regulates energy production in mitochondria. Therefore, we determined the relation of COX genes with atherosclerosis in mice and pigs. METHODS AND RESULTS: First, we compared atherosclerosis in the aortic arch of age-matched (24 weeks) C57BL/6J control (n = 10), LDL-receptor deficient (n = 8), leptin-deficient ob/ob (n = 10), and double knock-out (lacking LDL-receptor and leptin) mice (n = 12). Low aortic mitochondria-encoded cytochrome oxidase 1 in obese diabetic double knock-out mice was associated with a larger plaque area and higher propensity of M1 macrophages and oxidized LDL. Caloric restriction increased mitochondria-encoded cytochrome oxidase 1 and reduced plaque area and oxidized LDL. This was associated with a reduction of titer of anti-oxidized LDL antibodies, a proxy of systemic oxidative stress. Low of mitochondria-encoded cytochrome oxidase 1 was related to low expression of peroxisome proliferative activated receptors α, δ, and γ and of peroxisome proliferative activated receptor, gamma, co-activator 1 alpha reflecting mitochondrial dysfunction. Caloric restriction increased them. To investigate if there was a diabetic/obesity requirement for mitochondria-encoded cytochrome oxidase 1 to be down-regulated, we then studied atherosclerosis in LAD of hypercholesterolemic pigs (n = 37). Pigs at the end of the study were divided in three groups based on increasing LAD plaque complexity according to Stary (Stary I: n = 12; Stary II: n = 13; Stary III: n = 12). Low mitochondria-encoded cytochrome oxidase 1 in isolated plaque macrophages was associated with more complex coronary plaques and oxidized LDL. Nucleus-encoded cytochrome oxidase 4I1 and cytochrome oxidase 10 did not correlate with plaque complexity and oxidative stress. In mice and pigs, MT-COI was inversely related to insulin resistance. CONCLUSIONS: Low MT-COI is related to mitochondrial dysfunction, oxidative stress and atherosclerosis and plaque complexity.

Weight-loss-associated induction of peroxisome proliferator-activated receptor-alpha and peroxisome proliferator-activated receptor-gamma correlate with reduced atherosclerosis and improved cardiovascular function in obese insulin-resistant mice.

BACKGROUND: Weight loss in obese insulin-resistant but not in insulin-sensitive persons reduces coronary heart disease risk. To what extent changes in gene expression are related to atherosclerosis and cardiovascular function is unknown. METHODS AND RESULTS: We studied the effect of diet restriction-induced weight loss on gene expression in the adipose tissue, the heart, and the aortic arch and on atherosclerosis and cardiovascular function in mice with combined leptin and LDL-receptor deficiency. Obesity, hypertriglyceridemia, and insulin resistance are associated with hypertension, impaired left ventricular function, and accelerated atherosclerosis in those mice. Compared with lean mice, peroxisome proliferator-activated receptors (PPAR)-alpha and PPAR-gamma expression was downregulated in obese double-knockout mice. Diet restriction caused a 45% weight loss, an upregulation of PPAR-alpha and PPAR-gamma, and a change in the expression of genes regulating glucose transport and insulin sensitivity, lipid metabolism, oxidative stress, and inflammation, most of which are under the transcriptional control of these PPARs. Changes in gene expression were associated with increased insulin sensitivity, decreased hypertriglyceridemia, reduced mean 24-hour blood pressure and heart rate, restored circadian variations of blood pressure and heart rate, increased ejection fraction, and reduced atherosclerosis. PPAR-alpha and PPAR-gamma expression was inversely related to plaque volume and to oxidized LDL content in the plaques. CONCLUSIONS: Induction of PPAR-alpha and PPAR-gamma in adipose tissue, heart, and aortic arch is a key mechanism for reducing atherosclerosis and improving cardiovascular function resulting from weight loss. Improved lipid metabolism and insulin signaling is associated with decreased tissue deposition of oxidized LDL that increases cardiovascular risk in persons with the metabolic syndrome.

Interleukin-1 receptor-associated kinase-3 is a key inhibitor of inflammation in obesity and metabolic syndrome.

BACKGROUND: Visceral obesity is associated with the rising incidence of type 2 diabetes and metabolic syndrome. Low-grade chronic inflammation and oxidative stress synergize in obesity and obesity-induced disorders. OBJECTIVE: We searched a cluster of molecules that support interactions between these stress conditions in monocytes. METHODS: RNA expressions in blood monocytes of two independent cohorts comprising 21 and 102 obese persons and 46 age-matched controls were determined by microarray and independently validated by quantitative RT-PCR analysis. The effect of three-month weight loss after bariatric surgery was determined. The effect of RNA silencing on inflammation and oxidative stress was studied in human monocytic THP-1 cells. RESULTS: Interleukin-1 receptor-associated kinase-3 (IRAK3), key inhibitor of IRAK/NFκB-mediated chronic inflammation, is downregulated in monocytes of obese persons. Low IRAK3 was associated with high superoxide dismutase-2 (SOD2), a marker of mitochondrial oxidative stress. A comparable expression profile was also detected in visceral adipose tissue of the same obese subjects. Low IRAK3 and high SOD2 was associated with a high prevalence of metabolic syndrome (odds ratio: 9.3; sensitivity: 91%; specificity: 77%). By comparison, the odds ratio of high-sensitivity C-reactive protein, a widely used marker of systemic inflammation, was 4.3 (sensitivity: 69%; specificity: 66%). Weight loss was associated with an increase in IRAK3 and a decrease in SOD2, in association with a lowering of systemic inflammation and a decreasing number of metabolic syndrome components. We identified the increase in reactive oxygen species in combination with obesity-associated low adiponectin and high glucose and interleukin-6 as cause of the decrease in IRAK3 in THP-1 cells in vitro. CONCLUSION: IRAK3 is a key inhibitor of inflammation in association with obesity and metabolic syndrome. Our data warrant further evaluation of IRAK3 as a diagnostic and prognostic marker, and as a target for intervention.

Oxidized LDL and the metabolic syndrome.

The metabolic syndrome is a common and complex disorder combining obesity, dyslipidemia, hypertension and insulin resistance. It is associated with a high cardiovascular risk that can only partially be explained by its components. There is evidence that low-grade inflammation and high oxidative stress add to this risk. Oxidized LDL, a marker of lipoprotein-associated oxidative stress, is an emerging cardiovascular risk factor. In this review, we demonstrate that the metabolic syndrome exacerbates oxidized LDL in a feedback loop. We introduce molecular mechanisms underlying this loop. Finally, we demonstrate that weight loss and statin treatment lower metabolic syndrome factors associated with a reduction of oxidized LDL. The current data warrant further investigation into the role of lifestyle and therapeutic interventions that inhibit tissue-associated oxidation of LDL in the prevention of the metabolic syndrome.

Rosuvastatin increases vascular endothelial PPARgamma expression and corrects blood pressure variability in obese dyslipidaemic mice.

AIMS: Statins improve atherosclerotic diseases through cholesterol-reducing effects. Whether the latter exclusively mediate similar benefits, e.g. on hypertension, in the metabolic syndrome is unclear. We examined the effects of rosuvastatin on the components of this syndrome, as reproduced in mice doubly deficient in LDL receptors and leptin (DKO). METHODS AND RESULTS: DKO received rosuvastatin (10 mg/kg/day or 20 mg/kg/day) or saline for 12 weeks. Saline-treated DKO mice had elevated blood pressure (BP) and nitric oxide-sensitive BP variability recorded by telemetry. Compared with saline, rosuvastatin (20 mg/kg/day) had no effect on weight gain and a minor effect on plasma cholesterol. Despite incomplete correction of insulin sensitivity, rosuvastatin fully corrected BP and its variability (P = 0.01), in conjunction with upregulation of PPARgamma (but not PPARalpha) in the aortic arch. Rosuvastatin similarly increased PPARgamma (P = 0.002) and SOD1 (P = 0.01) expression in isolated endothelial cells. Both GW9662, a PPARgamma-specific antagonist, and siRNA raised against PPARgamma abrogated rosuvastatin's effect, which was reproduced in PPARgamma- (but not PPARalpha-) dependent transactivation assays. CONCLUSION: Beyond partial improvement in insulin sensitivity, rosuvastatin normalized BP homeostasis in obese dyslipidaemic mice independently of changes in body weight or plasma cholesterol. Upregulation of PPARgamma and SOD1 in the endothelium may be involved as a unique vasculoprotective effect of statin treatment.