Poststatin era in atherosclerosis management: lessons from epidemiologic and genetic studies

Lipid-Lowering Therapy and Hemorrhagic Stroke Risk: Comparative Meta-Analysis of Statins and PCSK9 Inhibitors

BACKGROUND AND PURPOSE

Statins were shown to increase hemorrhagic stroke (HS) in patients with a first cerebrovascular event in 2006 (SPARCL), likely due to off-target antithrombotic effects, but continued to sometimes be used in patients with elevated HS risk due to absence of alternative medications. Recently, the PCSK9Is (proprotein convertase subtilisin kexin 9 inhibitors) have become available as a potent lipid-lowering class with potentially less hemorrhagic propensity.

METHODS

We performed a systematic comparative meta-analysis assessing HS rates across all completed statin and PCSK9I randomized clinical trials with treatment >3 months, following PRISMA guidelines. In addition to HS rates across all trials, causal relation was probed by evaluating for dose-response relationships by medication (low versus high medication dose/potency) and by presence and type of preceding brain vascular events at inception (none versus ischemic stroke/transient ischemic attack versus HS).

RESULTS

The systematic review identified 36 statin randomized clinical trials (204 918 patients) and 5 PCSK9I randomized clinical trials (76 140 patients). Across all patient types and all medication doses/potencies, statins were associated with increased HS: relative risk 1.15, P=0.04; PCSK9Is were not (P=0.77). In the medication dose/potency analysis, higher dose/potency statins (7 trials, 62 204 patients) were associated with magnified HS risk: relative risk, 1.53; P=0.002; higher dose/potency PCSK9Is (1 trial, 27 564 patients) were not (P=0.99). In the type of index brain vascular injury analysis for statins (5 trials, 9772 patients), prior ischemic stroke/transient ischemic attack was associated with a magnified risk of HS: relative risk, 1.43; P=0.04; and index intracerebral hemorrhage was associated with an extremely high effect estimate of risk of recurrent HS: hazard ratio, 4.06. For PCSK9Is, prior ischemic stroke/transient ischemic attack (1 trial, 5337 patients) was not associated with increased HS risk (P=0.97).

CONCLUSIONS

Statins increase the risk of HS in a medication dose- and type of index brain vascular injury-dependent manner; PCSK9Is do not increase HS risk. PCSK9Is may be a preferred lipid-lowering medication class in patients with elevated HS risk, including patients with prior HS.

Metabolic Reprogramming of Macrophages in Atherosclerosis: Is It All about Cholesterol?

Hypercholesterolemia contributes to the chronic inflammatory response during the progression of atherosclerosis, in part by favoring cholesterol loading in macrophages and other immune cells. However, macrophages encounter a substantial amount of other lipids and nutrients after ingesting atherogenic lipoprotein particles or clearing apoptotic cells, increasing their metabolic load and impacting their behavior during atherosclerosis plaque progression. This review examines whether and how fatty acids and glucose shape the cellular metabolic reprogramming of macrophages in atherosclerosis to modulate the onset phase of inflammation and the later resolution stage, in which the balance is tipped toward tissue repair.

Tanshinone I inhibits vascular smooth muscle cell proliferation by targeting insulin-like growth factor-1 receptor/phosphatidylinositol-3-kinase signaling pathway

Vascular smooth muscle cell (VSMC) proliferation plays a critical role in arterial remodeling during various vascular diseases including atherosclerosis and hypertension. Tanshinone I, a major component of Salvia miltiorrhiza, exerts protective effects against cardiovascular diseases. In this study, we investigated the effects of tanshinone I on VSMC proliferation, as well as the underlying mechanisms. We found that this compound inhibited the proliferation of VSMCs in a dose-dependent manner, based on 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) and 5-ethynyl-2'-deoxyuridine (EdU) assays. Western blotting demonstrated that tanshinone I inhibited the expression of proliferation-related proteins, including cyclin-dependent kinase 4 (CDK4), cyclin D3, and cyclin D1, in a dose-dependent manner. Molecular docking showed that this compound docked to the inhibitor-binding site of the insulin-like growth factor 1 (IGF-1) receptor (IGF-1R), and the binding energy between tanshinone I and IGF-1R was -9.021 kcal/mol. Molecular dynamic simulations showed that the IGF-1R-tanshinone I binding was stable. We also found that tanshinone I dose-dependently inhibited IGF-1R activation and its downstream molecules, insulin receptor substrate (IRS)-1, phosphatidylinositol-3-Kinase (PI3K), Akt, glycogen synthase kinase-3 beta (GSK3β), mammalian target of rapamycin (mTOR), 70S6K, and ribosomal protein S6 (RPS6). Notably, activation of IGF-1R by recombinant IGF-1 rescued the activity of IGF-1R and its downstream molecules, and the proliferation of tanshinone I-treated VSMC. In addition, blocking PI3K signaling with LY294002 showed the important role of this pathway in tanshinone I-mediated suppression of VSMC proliferation. Collectively, these data demonstrated that tanshinone I might inhibit VSMC proliferation by inhibiting IGF-1R/PI3K signaling.

Inhibiting PCSK9 - biology beyond LDL control

Clinical trials have unequivocally shown that inhibition of proprotein convertase subtilisin/kexin type 9 (PCSK9) efficaciously and safely prevents cardiovascular events by lowering levels of LDL cholesterol. PCSK9 in the circulation is derived mainly from the liver, but the protein is also expressed in the pancreas, the kidney, the intestine and the central nervous system. Although PCSK9 modulates cholesterol metabolism by regulating LDL receptor expression in the liver, in vitro and in vivo studies have suggested that PCSK9 is involved in various other physiological processes. Although therapeutic PCSK9 inhibition could theoretically have undesired effects by interfering with these non-cholesterol-related processes, studies of individuals with genetically determined reduced PCSK9 function and clinical trials of PCSK9 inhibitors have not revealed clinically meaningful adverse consequences of almost completely eradicating PCSK9 from the circulation. The clinical implications of PCSK9 functions beyond lipid metabolism in terms of wanted or unwanted effects of therapeutic PCSK9 inhibition therefore appear to be limited. The objective of this Review is to describe the physiological role of PCSK9 beyond the LDL receptor to provide a rational basis for monitoring the effects of PCSK9 inhibition as these drugs gain traction in the clinic.