Aims Brown fat activation accelerates the uptake of cholesterol-enriched remnants by the liver and thereby lowers plasma cholesterol, consequently protecting against atherosclerosis development.... Show moreAims Brown fat activation accelerates the uptake of cholesterol-enriched remnants by the liver and thereby lowers plasma cholesterol, consequently protecting against atherosclerosis development. Hepatic cholesterol is then converted into bile acids (BAs) that are secreted into the intestine and largely maintained within the enterohepatic circulation. We now aimed to evaluate the effects of prolonged brown fat activation combined with inhibition of intestinal BA reabsorption on plasma cholesterol metabolism and atherosclerosis development.Methods and results APOE*3-Leiden.CETP mice with humanized lipoprotein metabolism were treated for 9 weeks with the selective beta 3-adrenergic receptor (AR) agonist CL316,243 to substantially activate brown fat. Prolonged beta 3-AR agonism reduced faecal BA excretion (-31%), while markedly increasing plasma levels of total BAs (+258%), cholic acid-derived BAs (+295%), and chenodeoxycholic acid-derived BAs (+217%), and decreasing the expression of hepatic genes involved in BA production. In subsequent experiments, mice were additionally treated with the BA sequestrant Colesevelam to inhibit BA reabsorption. Concomitant intestinal BA sequestration increased faecal BA excretion, normalized plasma BA levels, and reduced hepatic cholesterol. Moreover, concomitant BA sequestration further reduced plasma total cholesterol (-49%) and non-high-density lipoprotein cholesterol (-56%), tended to further attenuate atherosclerotic lesion area (-54%). Concomitant BA sequestration further increased the proportion of lesion-free valves (+34%) and decreased the relative macrophage area within the lesion (-26%), thereby further increasing the plaque stability index (+44%).Conclusion BA sequestration prevents the marked accumulation of plasma BAs as induced by prolonged brown fat activation, thereby further improving cholesterol metabolism and reducing atherosclerosis development. These data suggest that combining brown fat activation with BA sequestration is a promising new therapeutic strategy to reduce hyperlipidaemia and cardiovascular diseases. Show less
Thiem, K.; Hoeke, G.; Zhou, E.C.; Hijmans, A.; Houben, T.; Boels, M.G.; ... ; Diepen, J.A. van 2019
Background: C-type lectin receptors, including Dectin-2, are pattern recognition receptors on monocytes and macrophages that mainly recognize sugars and sugar-like structures present on fungi.... Show moreBackground: C-type lectin receptors, including Dectin-2, are pattern recognition receptors on monocytes and macrophages that mainly recognize sugars and sugar-like structures present on fungi. Activation of C-type lectin receptors induces downstream CARD9 signalling, leading to the production of cytokines. We hypothesized that under hyperglycaemic conditions, as is the case in diabetes mellitus, glycosylated protein (sugar-like) structures activate C-type lectin receptors, leading to immune cell activation and increased atherosclerosis development. Methods: Low-density lipoprotein receptor-deficient mice were lethally irradiated and transplanted with bone marrow from control wild-type, Dectin-2(-/-) or Card9(-/-) mice. After 6 weeks of recovery, mice received streptozotocin injections (50 mg/g BW; 5 days) to induce hyperglycaemia. After an additional 2 weeks, mice were fed a Western-type diet (0.1% cholesterol) for 10 weeks. Results and Conclusion: Deletion of haematopoietic Dectin-2 reduced the number of circulating Ly6C(hi) monocytes, increased pro-inflammatory cytokine production, but did not affect atherosclerosis development. Deletion of haematopoietic CARD9 tended to reduce macrophage and collagen content in atherosclerotic lesions, again without influencing the lesion size. Deletion of haematopoietic Dectin-2 did not influence atherosclerosis development under hyperglycaemic conditions, despite some minor effects on inflammation. Deletion of haematopoietic CARD9 induced minor alterations in plaque composition under hyperglycaemic conditions, without affecting lesion size. Show less
Thiem, K.; Hoeke, G.; Berg, S. van den; Hijmans, A.; Jacobs, C.M.; Zhou, E.; ... ; Diepen, J.A. van 2019
Inflammatory reactions activated by pattern recognition receptors (PRRs) on the membrane of innate immune cells play an important role in atherosclerosis. Whether the PRRs of the C-type lectin... Show moreInflammatory reactions activated by pattern recognition receptors (PRRs) on the membrane of innate immune cells play an important role in atherosclerosis. Whether the PRRs of the C-type lectin receptor (CLR) family including Dectin-2 may be involved in the pathogenesis of atherosclerosis remains largely unknown. Recently, the CLR-adaptor molecule caspase recruitment domain family member 9 (CARD9) has been suggested to play a role in cardiovascular pathologies as it provides the link between CLR activation and transcription of inflammatory cytokines as well as immune cell recruitment. We therefore evaluated whether hematopoietic deletion of Dectin-2 or CARD9 reduces inflammation and atherosclerosis development. Low-density lipoprotein receptor (Ldlr)- knockout mice were transplanted with bone marrow from wild-type, Dectin-2- or Card9-knockout mice and fed a Western-type diet containing 0.1% (w/w) cholesterol. After 10 weeks, lipid and inflammatory parameters were measured and atherosclerosis development was determined. Deletion of hematopoietic Dectin-2 or CARD9 did not influence plasma triglyceride and cholesterol levels. Deletion of hematopoietic Dectin-2 did not affect atherosclerotic lesion area, immune cell composition, ex vivo cytokine secretion by peritoneal cells or bone marrow derived macrophages. Unexpectedly, deletion of hematopoietic CARD9 increased atherosclerotic lesion formation and lesion severity. Deletion of hematopoietic CARD9 did also not influence circulating immune cell composition and peripheral cytokine secretion. Besides a tendency to a reduced macrophage content within these lesions, plasma MCP-1 levels decreased upon WTD feeding. Deletion of hematopoietic Dectin-2 did not influence atherosclerosis development in hyperlipidemic mice. The absence of CARD9 unexpectedly increased atherosclerotic lesion size and severity, suggesting that the presence of CARD9 may protect against initiation of atherosclerosis development. Show less
Cardiovascular diseases (CVD), which are mainly caused by the development of atherosclerosis, are the leading cause of morbidity and mortality in Western Society. Two main risk factors for the... Show moreCardiovascular diseases (CVD), which are mainly caused by the development of atherosclerosis, are the leading cause of morbidity and mortality in Western Society. Two main risk factors for the development of atherosclerosis are hyperlipidemia and inflammation, that cause accumulation of lipids and immune cells, respectively, in the arterial wall. While activation of brown adipose tissue (BAT) is a promising strategy to alleviate hyperlipidemia, reduction of inflammation is also thought to reduce atherosclerosis progression. In this thesis, we aimed to address two key objectives: 1) to identify genetic targets in mice and men that are involved in BAT activity and evaluate their effects on lipoprotein metabolism and atherosclerosis development, and 2) to identify genetic targets in mice that are involved in modulation of the immune system and evaluate their effects on atherosclerosis development. Chapter 1 serves as a general introduction in which hyperlipidemia and inflammation are introduced as the two main causes for atherosclerosis development. More specifically, firstly the physiology and role of BAT in lipoprotein metabolism and atherosclerosis development are explained. Secondly, the contribution of pro- and anti-inflammatory cytokines as well as specific receptors on immune cells in propelling immune responses are explained in the context of atherosclerosis development. Show less
Schilperoort, M.; Dam, A.D. van; Hoeke, G.; Shabalina, I.G.; Okolo, A.; Hanyaloglu, A.C.; ... ; Christian, M. 2018
Preclinical studies established BAT as an important target to combat cardiometabolic disorders and elucidated underlying mechanisms whereas clinical studies identified therapeutic handles.... Show morePreclinical studies established BAT as an important target to combat cardiometabolic disorders and elucidated underlying mechanisms whereas clinical studies identified therapeutic handles. Development of novel lipid-based PET-CT tracers and identification of translational biomarkers of BAT activity are required as alternatives to [F-18] fluorodeoxyglucose PET-CT to accelerate clinical development of BAT-activating therapeutic strategies. Show less
