Our results indicate that PAR2 deficiency is associated with attenuation of atherosclerosis and may reduce lesion progression by blunting - and-induced monocyte infiltration.

Abdominal aortic aneurysm (AAA) is associated with high morbidity and mortality and is an established cause of unbalanced hemostasis. A number of hemostatic biomarkers have been associated with AAA; however, the utility of hemostatic biomarkers in AAA diagnosis and prognosis is unclear. The aim of the present study was to characterize the potential prognostic value of D-dimer and markers of altered hemostasis in a large cohort of patients with AAAs characterized by either fast or slow aneurysm growth (frequency matched for baseline diameter) and subaneurysmal dilations. We measured plasma concentrations of thrombin-antithrombin (TAT) complex, platelet factor 4 (PF4), and D-dimer in 352 patients with either fast-growing AAAs (>2 mm/y), slow-growing AAAs (<2 mm/y), subaneurysmal aortic dilations, or nonaneurysmal aortas. Plasma D-dimer and TAT were significantly elevated in both AAA and subaneurysmal dilation patients compared with controls. Individuals with D-dimer levels ≥500 ng/mL had 3.09 times the odds of subaneurysms, 6.23 times the odds of slow-growing AAAs, and 7.19 times the odds of fast-growing AAAs than individuals with D-dimer level <500 ng/mL. However, no differences in D-dimer concentration were noted between fast- and slow-growing aneurysms. Plasma D-dimer and TAT were strong independent predictors of AAA growth rate with multivariate analysis revealing a 500-ng/mL increase in D-dimer or 1-µg/mL increase in TAT led to additional 0.21-mm and 0.24-mm changes in aortic diameter per year, respectively. Rising levels of plasma TAT, in addition to D-dimer, may predict disease progression and aneurysm growth in patients with AAA or subaneurysmal dilation.

Background Hepatocellular carcinoma (HCC) is the third most common cause of cancer-related death in the world. Choline deficiency has been well studied in the context of liver disease; however, less is known about the effects of choline supplementation in HCC. Objective The objective of this study was to test whether choline supplementation could influence the progression of HCC in a high-fat-diet (HFD)–driven mouse model. Methods Four-day-old male C57BL/6J mice were treated with the chemical carcinogen, 7,12-dimethylbenz[a]anthracene, and were randomly assigned at weaning to a cohort fed an HFD (60% kcal fat) or an HFD with supplemental choline (60% kcal fat, 1.2% choline; HFD+C) for 30 wk. Blood was isolated at 15 and 30 wk to measure immune cells by flow cytometry, and glucose-tolerance tests were performed 2 wk prior to killing. Overall tumor burden was quantified, hepatic lipids were measured enzymatically, and phosphatidylcholine species were measured by targeted MS methods. Gene expression and mitochondrial DNA were quantified by quantitative PCR. Results HFD+C mice exhibited a 50–90% increase in both circulating choline and betaine concentrations in the fed state (P ≤ 0.05). Choline supplementation resulted in a 55% decrease in total tumor numbers, a 67% decrease in tumor surface area, and a 50% decrease in hepatic steatosis after 30 wk of diet (P ≤ 0.05). Choline supplementation increased the abundance of mitochondria and the relative expression of β-oxidation genes by 21% and ∼75–100%, respectively, in the liver. HFD+C attenuated circulating myeloid-derived suppressor cells at 15 wk of feeding (P ≤ 0.05). Conclusions Choline supplementation attenuated HFD-induced HCC and hepatic steatosis in male C57BL/6J mice. These results suggest a therapeutic benefit of choline supplementation in blunting HCC progression.

Background: Large-scale human and mechanistic mouse studies indicate a strong relationship between the microbiome-dependent metabolite trimethylamine N-oxide (TMAO) and several cardiometabolic diseases. This study aims to investigate the role of TMAO in the pathogenesis of abdominal aortic aneurysm (AAA) and target its parent microbes as a potential pharmacological intervention. Methods: TMAO and choline metabolites were examined in plasma samples, with associated clinical data, from 2 independent patient cohorts (N=2129 total). Mice were fed a high-choline diet and underwent 2 murine AAA models, angiotensin II infusion in low-density lipoprotein receptor–deficient ( Ldlr −/− ) mice or topical porcine pancreatic elastase in C57BL/6J mice. Gut microbial production of TMAO was inhibited through broad-spectrum antibiotics, targeted inhibition of the gut microbial choline TMA lyase (CutC/D) with fluoromethylcholine, or the use of mice genetically deficient in flavin monooxygenase 3 ( Fmo3 −/− ). Finally, RNA sequencing of in vitro human vascular smooth muscle cells and in vivo mouse aortas was used to investigate how TMAO affects AAA. Results: Elevated TMAO was associated with increased AAA incidence and growth in both patient cohorts studied. Dietary choline supplementation augmented plasma TMAO and aortic diameter in both mouse models of AAA, which was suppressed with poorly absorbed oral broad-spectrum antibiotics. Treatment with fluoromethylcholine ablated TMAO production, attenuated choline-augmented aneurysm initiation, and halted progression of an established aneurysm model. In addition, Fmo3 −/− mice had reduced plasma TMAO and aortic diameters and were protected from AAA rupture compared with wild-type mice. RNA sequencing and functional analyses revealed choline supplementation in mice or TMAO treatment of human vascular smooth muscle cells–augmented gene pathways associated with the endoplasmic reticulum stress response, specifically the endoplasmic reticulum stress kinase PERK. Conclusions: These results define a role for gut microbiota–generated TMAO in AAA formation through upregulation of endoplasmic reticulum stress–related pathways in the aortic wall. In addition, inhibition of microbiome-derived TMAO may serve as a novel therapeutic approach for AAA treatment where none currently exist.

Background: The gut microbiota is a metabolically active endocrine organ critical to the maintenance of cardiovascular health. Dietary sources of choline are metabolized by microbial enzymes to form trimethylamine (TMA). Metabolism by the host hepatic enzyme flavin-containing monooxygenase 3 (FMO3) converts TMA to the pro-inflammatory molecule trimethylamine N-oxide (TMAO). Human clinical trials have correlated high levels of circulating TMAO to an increased risk of cardiometabolic diseases. However, this meta-organismal pathway has not been evaluated in the context of abdominal aortic aneurysm (AAA). The objective of this study was to determine the effects of a high choline diet on the development of AAA. Methods: C57BL/6J male (n=20) and female (n=20) mice were fed either a standard chow control diet (n = 10 each sex) or a choline-rich diet (1%; n = 10 each sex) for 5 weeks. After 1 week of diet, basal abdominal ultrasounds were performed and angiotensin II (AngII; 1,000 ng/kg/min) was infused for 28 days via implantation of osmotic minipumps. Termination ultrasounds were performed on day 27 and mice were sacrificed on day 28. Aortas were harvested for evaluation of aneurysm progression and plasma was analyzed for the metabolites TMA, TMAO, and choline. To determine whether TMAO was elevated in human patients with AAA, plasma samples from participants with fast growing AAAs (n = 85), slow growing AAAs (n = 84), and normal (non-aneurysmal) aortas (n = 115) were analyzed for plasma TMAO levels via liquid chromatography tandem mass spectrometry (LC-MS/MS). Results: Administration of a choline-rich diet augmented the incidence (P < 0.02) and aortic diameter (P < 0.001) of AAAs in both male and female mice versus placebo-fed mice. Plasma levels of TMA, TMAO, and choline were significantly elevated in choline-fed mice versus normal chow (P < 0.05). Importantly, circulating levels of plasma TMAO were significantly elevated in a step-wise fashion with the rate of aneurysm growth versus non-aneurysmal control patients (fast growing > slow growing > normal patients; P < 0.001). Conclusions: Our results indicate increases in circulating TMAO augments the growth status of aneurysms in human patients and the incidence of AAA in a low penetrant C57BL/6J mouse model.