Streptococcal serum opacity factor promotes cholesterol ester metabolism and bile acid secretion in vitro and in vivo.

Plasma high density lipoprotein-cholesterol (HDL-C) concentrations negatively correlate with atherosclerotic cardiovascular disease. HDL is thought to have several atheroprotective functions, which are likely distinct from the epidemiological inverse relationship between HDL-C levels and risk. Specifically, strategies that reduce HDL-C while promoting reverse cholesterol transport (RCT) may have therapeutic value. The major product of the serum opacity factor (SOF) reaction versus HDL is a cholesteryl ester (CE)-rich microemulsion (CERM), which contains apo E and the CE of ~400,000 HDL particles. Huh7 hepatocytes take up CE faster when delivered as CERM than as HDL, in part via the LDL-receptor (LDLR). Here we compared the final RCT step, hepatic uptake and subsequent intracellular processing to cholesterol and bile salts for radiolabeled HDL-, CERM- and LDL-CE by Huh7 cells and in vivo in C57BL/6J mice. In Huh7 cells, uptake from LDL was greater than from CERM (2-4X) and HDL (5-10X). Halftimes for [(14)C]CE hydrolysis were 3.0±0.2, 4.4±0.6 and 5.4±0.7h respectively for HDL, CERM and LDL-CE. The fraction of sterols secreted as bile acids was ~50% by 8h for all three particles. HDL, CERM and LDL-CE metabolism in mice showed efficient plasma clearance of CERM-CE, liver uptake and metabolism, and secretion as bile acids into the gall bladder. This work supports the therapeutic potential of the SOF reaction, which diverts HDL-CE to the LDLR, thereby increasing hepatic CE uptake, and sterol disposal as bile acids.

Management of blunt cerebrovascular injury (BCVI) in the multisystem injury patient with contraindications to immediate anti-thrombotic therapy.

INTRODUCTION: Practice management guidelines for screening and treatment of patients with blunt cerebrovascular injury (BCVI) have been associated with a decreased risk of ischemic stroke. TREATMENT: of patients with BCVI and multisystem injuries that delays immediate antithrombotic therapy remains controversial. The purpose of this study was to determine the timing of BCVI treatment initiation, the incidence of stroke, and bleeding complications as a result of antithrombotic therapy in patients with isolated BCVI in comparison to those with BCVI complicated by multisystem injuries. MATERIALS AND METHODS: This study was a retrospective review of all adult blunt trauma patients admitted to a level 1 trauma center from 2009 to 2014 with a diagnosis of BCVI. RESULTS: A total of 28,305 blunt trauma patients were admitted during the study period. Of these, 323 (1.1%) had 481 BCEVIs and were separated into two groups. Isolated BCVI was reported in 111 (34.4%) patients and 212 (65.6%) patients had accompanying multisystem injuries (traumatic brain injury (TBI), solid organ injury, or spinal cord injury) that contraindicated immediate antithrombotic therapy. TREATMENT: started in patients with isolated BCVI at a median time of 30.3 (15, 52) hours after injury in contrast to 62.4 (38, 97) hours for those with multisystem injuries (p<0.001). The incidence of stroke was identical (9.9%) between groups and no bleeding complications related to antithrombotic therapy were identified. CONCLUSION: The lack of bleeding complications and equivalent stroke rates between groups suggests that the presence of TBI, solid organ injury, and spinal cord injury are not contraindications to anti-thrombotic therapy for stroke prevention in patients with BCVI.

Genetic manipulation of the ApoF/Stat2 locus supports an important role for type I interferon signaling in atherosclerosis.

Apolipoprotein F (ApoF) is a sialoglycoprotein that is a component of the HDL and LDL fractions of human serum. We sought to test the hypothesis that ApoF plays an important role in atherosclerosis in mice by modulating lipoprotein function. Atherosclerosis was assessed in male low density lipoprotein receptor knockout (Ldlr KO) and ApoF/Ldlr double knockout (DKO) mice fed a Western diet for 16 weeks. ApoF/Ldlr DKO mice showed a 39% reduction in lesional area by en face analysis of aortas (p < 0.05), despite no significant differences in plasma lipid parameters. ApoF KO mice had reduced expression of Interferon alpha (IFNα) responsive genes in liver and spleen, as well as impaired macrophage activation. Interferon alpha induced gene 27 like 2a (Ifi27l2a), Oligoadenylate synthetases 2 and 3 (Oas2 and Oas3) were significantly reduced in the ApoF KO mice relative to wild type controls. These effects were attributable to hypomorphic expression of Stat2 in the ApoF KO mice, a critical gene in the Type I IFN pathway that is situated just 425 base pairs downstream of ApoF. These studies implicate STAT2 as a potentially important player in atherosclerosis, and support the growing evidence that the Type I IFN pathway may contribute to this complex disease.

The effects of apolipoprotein F deficiency on high density lipoprotein cholesterol metabolism in mice.

Apolipoprotein F (apoF) is 29 kilodalton secreted sialoglycoprotein that resides on the HDL and LDL fractions of human plasma. Human ApoF is also known as Lipid Transfer Inhibitor protein (LTIP) based on its ability to inhibit cholesteryl ester transfer protein (CETP)-mediated transfer events between lipoproteins. In contrast to other apolipoproteins, ApoF is predicted to lack strong amphipathic alpha helices and its true physiological function remains unknown. We previously showed that overexpression of Apolipoprotein F in mice reduced HDL cholesterol levels by 20-25% by accelerating clearance from the circulation. In order to investigate the effect of physiological levels of ApoF expression on HDL cholesterol metabolism, we generated ApoF deficient mice. Unexpectedly, deletion of ApoF had no substantial impact on plasma lipid concentrations, HDL size, lipid or protein composition. Sex-specific differences were observed in hepatic cholesterol content as well as serum cholesterol efflux capacity. Female ApoF KO mice had increased liver cholesteryl ester content relative to wild type controls on a chow diet (KO: 3.4+/-0.9 mg/dl vs. WT: 1.2+/-0.3 mg/dl, p<0.05). No differences were observed in ABCG1-mediated cholesterol efflux capacity in either sex. Interestingly, ApoB-depleted serum from male KO mice was less effective at promoting ABCA1-mediated cholesterol efflux from J774 macrophages relative to WT controls.