Atherosclerotic cardiovascular disease (ASCVD) and metabolic dysfunction-associated steatotic liver disease (MASLD; previously known as non-alcoholic fatty liver disease) are a result of lipid... Show moreAtherosclerotic cardiovascular disease (ASCVD) and metabolic dysfunction-associated steatotic liver disease (MASLD; previously known as non-alcoholic fatty liver disease) are a result of lipid accumulation in the vascular wall and liver, respectively. In the body, lipids are transported between organs within lipoproteins, and thus disordered lipoprotein metabolism is closely associated with ASCVD and MASLD development. Active brown adipose tissue (BAT) combusts lipids to produce heat, and BAT activation is therefore considered a potential strategy to improve lipoprotein metabolism. In this thesis, I describe a new method of monitoring lipoprotein metabolism and BAT activity by PET-CT scan. To this end, a newly developed 18F-labeled lipid tracer was incorporated in optimized lipoprotein-like particles, and appeared to outperform 18F-deoxyglucose in tracing activated BAT. The results presented in this thesis also further confirm the usefulness of the APOE*3-Leiden.CETP mouse model for studying therapeutic interventions to improve lipoprotein metabolism. Using this translational model, I demonstrated that exercise at the end of the active phase and combined glucose-dependent insulinotropic polypeptide receptor and glucagon-like peptide receptor agonism, a strategy for treating diabetes and obesity in the clinic, are promising ways to combat both ASCVD and MASLD. Show less
Brown fat activation attenuates atherosclerosis development by accelerating triglyceride-rich lipoprotein turnover and/or stimulation of reverse cholesterol transport via the SRB1 (scavenger... Show moreBrown fat activation attenuates atherosclerosis development by accelerating triglyceride-rich lipoprotein turnover and/or stimulation of reverse cholesterol transport via the SRB1 (scavenger receptor class B type 1). The aim of this study was to investigate the specific role of hepatic SRB1 in the atheroprotective properties of brown fat activation.APOE*3-Leiden.CETP mice, a well-established model of human-like lipoprotein metabolism andatherosclerosis, were treated with vehicle or adenoassociated virus serotype 8-short hairpin RNA, which decreased hepatic SRB1 protein levels by 40% to 55%. After 2 weeks, mice without or with hepatic SRB1 knockdown were treated with vehicle or the β3-adrenergic receptor agonist CL316 243 to activate brown fat for 4 weeks to determine HDL (highdensity lipoprotein) catabolism and for 9 weeks to evaluate atherosclerosis. Surprisingly, hepatic SRB1 knockdown additively improved the beneficial effects of β3-adrenergic receptor agonism on atherosclerosis development. In fact, hepatic SRB1 knockdown per se not only increased HDL-cholesterol levels but also reduced plasma triglyceride and non-HDL-cholesterol levels, thus explaining the reduction in atherosclerosis development. Mechanistic studies indicated that this is due to increased lipolytic processing and hepatic uptake of VLDL (very low density lipoprotein) by facilitating VLDL-surface transfer to HDL.Hepatic SRB1 knockdown in a mouse model with an intact ApoE (apolipoprotein E)-LDLR (low density lipoprotein receptor) clearance pathway, relevant to human lipoprotein metabolism, reduced atherosclerosis and improved the beneficial effect of brown fat activation on atherosclerosis development, explained by pleiotropic effects of hepatic SRB1 knockdown on lipolytic processing and hepatic uptake of VLDL. Brown fat activation could thus be an effective strategy to treat cardiovascular disease also in subjects with impaired SRB1 function. Show less
Eenige, R. van; Ying, Z.; Tambyrajah, L; Pronk, A.C.M.; Blomberg, N.; Giera, M.; ... ; Kooijman, S. 2021
Pharmacological blockade of the cannabinoid type 1 receptor, a G protein-coupled receptor expressed in the central nervous system and various peripheral tissues, reverses diet-induced obesity and... Show morePharmacological blockade of the cannabinoid type 1 receptor, a G protein-coupled receptor expressed in the central nervous system and various peripheral tissues, reverses diet-induced obesity and dyslipidemia through the reduction of food intake and altered nutrient partitioning. This strategy is being explored for a number of therapeutic applications; however, its potency for the treatment of atherosclerotic cardiovascular disease via improvements in lipid metabolism remains unclear. Therefore, here, we aimed to investigate whether inhibition of the endocannabinoid system can attenuate atherosclerosis development through improvement of dyslipidemia. Lean, dyslipidemic female APOE∗3-Leiden.CETP transgenic mice were fed a Western-type diet supplemented with or without the cannabinoid type 1 receptor inverse agonist rimonabant (20 mg·kg body weight-1 day-1) for up to 20 weeks. Plasma lipids and bile acids were determined, and atherosclerotic lesions were scored in the aortic valve region. Rimonabant lowered plasma levels of triglyceride (TG) (-56%) and non-HDL-C (-19%) and increased HDL-C (+57%). These effects were explained by decreased VLDL-TG production (-52%) and accelerated VLDL-TG turnover accompanied by pronounced browning of white adipose tissue. In addition, rimonabant attenuated reverse cholesterol transport (-30%), increased plasma bile acid levels (+160%), and increased hepatic cholesterol accumulation (+88%). Importantly, rimonabant markedly lowered atherosclerotic lesion size (-64%), which coincided with decreased lesion severity (28% vs. 56% severe lesions) and which strongly correlated with non-HDL-C exposure (R2 = 0.60). Taken together, inhibition of the endocannabinoid system potently reverses dyslipidemia and prevents atherogenesis, even in the absence of obesity. Show less
