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Minireview Exploring the Biological Cycle of Vitamin B3 and Its Influence on Oxidative Stress: Further Molecular and Clinical Aspects.
Doroftei, B, Ilie, OD, Cojocariu, RO, Ciobica, A, Maftei, R, Grab, D, Anton, E, McKenna, J, Dhunna, N, Simionescu, G
Molecules (Basel, Switzerland). 2020;(15)
Abstract
Vitamin B3, or niacin, is one of the most important compounds of the B-vitamin complex. Recent reports have demonstrated the involvement of vitamin B3 in a number of pivotal functions which ensure that homeostasis is maintained. In addition, the intriguing nature of its synthesis and the underlying mechanism of action of vitamin B3 have encouraged further studies aimed at deepening our understanding of the close link between the exogenous supply of B3 and how it activates dependent enzymes. This crucial role can be attributed to the gut microflora and its ability to shape human behavior and development by mediating the bioavailability of metabolites. Recent studies have indicated a possible interconnection between the novel coronavirus and commensal bacteria. As such, we have attempted to explain how the gastrointestinal deficiencies displayed by SARS-CoV-2-infected patients arise. It seems that the stimulation of a proinflammatory cascade and the production of large amounts of reactive oxygen species culminates in the subsequent loss of host eubiosis. Studies of the relationhip between ROS, SARS-CoV-2, and gut flora are sparse in the current literature. As an integrated component, oxidative stress (OS) has been found to negatively influence host eubiosis, in vitro fertilization outcomes, and oocyte quality, but to act as a sentinel against infections. In conclusion, research suggests that in the future, a healthy diet may be considered a reliable tool for maintaining and optimizing our key internal parameters.
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Niacin and heart disease prevention: Engraving its tombstone is a mistake.
Superko, HR, Zhao, XQ, Hodis, HN, Guyton, JR
Journal of clinical lipidology. 2017;(6):1309-1317
Abstract
Niacin (nicotinic acid) has been used for primary and secondary coronary heart disease prevention for over 40 years. Until recently clinical trials incorporating niacin as part of an intervention strategy consistently demonstrated reduction in clinical events and lesion improvement, including ≥6% absolute mortality reduction. Two large clinical event trials in 2011 (Atherothrombosis Intervention in Metabolic Syndrome With Low HDL/High Triglycerides and Impact on Global Health Outcomes) and 2014 (Heart Protection Study 2-Treatment of HDL to Reduce the Incidence of Vascular Events) concluded that niacin added to statin therapy did not provide clinical event benefit over statin alone. This has prompted some individuals to call for an end to the use of niacin in statin-treated patients and the US Food and Drug Administration to halt marketing of statin/niacin combination tablets. There are significant differences between the earlier clinical trials that revealed cardiovascular benefit of niacin and the 2 trials that failed to demonstrate a benefit. These differences include dyslipidemia types, niacin formulation, dosing, and timing. In general, the patient population that benefits the most from incorporating niacin in their treatment regimen can be defined by elevations in low-density lipoprotein cholesterol and triglycerides, and reduced high-density lipoprotein cholesterol. The niacin formulation and dose should be capable of achieving adequate lipoprotein change. Mealtime dosing of niacin, as opposed to bedtime dosing, may avoid a counter-regulatory hormone response, including catecholamines, because of altered fuel supply potentially leading to unexpected cardiovascular outcomes.
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Niacin Therapy, HDL Cholesterol, and Cardiovascular Disease: Is the HDL Hypothesis Defunct?
Mani, P, Rohatgi, A
Current atherosclerosis reports. 2015;(8):43
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Abstract
High-density lipoprotein cholesterol (HDL-C) has been shown in epidemiologic studies to be associated with cardiovascular (CV) risk and thus significant efforts have been focused on HDL-C modulation. Multiple pharmaceutical agents have been developed with the goal of increasing HDL-C. Niacin, the most widely used medication to raise HDL-C, increases HDL-C by up to 25 % and was shown in multiple surrogate end point studies to reduce CV risk. However, two large randomized controlled trials of niacin, AIM-HIGH and HPS2-THRIVE, have shown that despite its effects on HDL-C, niacin does not decrease the incidence of CV events and may have significant adverse effects. Studies of other classes of agents such as cholesteryl ester transfer protein (CETP) inhibitors have also shown that even dramatic increases in HDL-C do not necessarily translate to reduction in clinical events. While these findings have cast doubt upon the importance of HDL-C modulation on CV risk, it is becoming increasingly clear that HDL function-related measures may be better targets for CV risk reduction. Increasing ApoA-I, the primary apolipoprotein associated with HDL, correlates with reduced risk of events, and HDL particle concentration (HDL-P) inversely associates with incident CV events adjusted for HDL-C and LDL particle measures. Cholesterol efflux, the mechanism by which macrophages in vessel walls secrete cholesterol outside cells, correlates with both surrogate end points and clinical events. The effects of niacin on these alternate measures of HDL have been conflicting. Further studies should determine if modulation of these HDL function markers translates to clinical benefits. Although the HDL cholesterol hypothesis may be defunct, the HDL function hypothesis is now poised to be rigorously tested.
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Effect on cardiovascular risk of high density lipoprotein targeted drug treatments niacin, fibrates, and CETP inhibitors: meta-analysis of randomised controlled trials including 117,411 patients.
Keene, D, Price, C, Shun-Shin, MJ, Francis, DP
BMJ (Clinical research ed.). 2014;:g4379
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Abstract
OBJECTIVE To investigate the effects on cardiovascular outcomes of drug interventions that increase high density lipoprotein levels. DESIGN Meta-analysis. STUDIES REVIEWED Therapeutic benefit of niacin, fibrates, and cholesteryl ester transfer protein (CETP) inhibitors on cardiovascular events (all cause mortality, coronary heart disease mortality, non-fatal myocardial infarction, and stroke). RESULTS 117,411 patients were randomised in a total of 39 trials. All interventions increased the levels of high density lipoprotein cholesterol. No significant effect was seen on all cause mortality for niacin (odds ratio 1.03, 95% confidence interval 0.92 to 1.15, P=0.59), fibrates (0.98, 0.89 to 1.08, P=0.66), or CETP inhibitors (1.16, 0.93 to 1.44, P=0.19); on coronary heart disease mortality for niacin (0.93, 0.76 to 1.12, P=0.44), fibrates (0.92, 0.81 to 1.04, P=0.19), or CETP inhibitors (1.00, 0.80 to 1.24, P=0.99); or on stroke outcomes for niacin (0.96, 0.75 to 1.22, P=0.72), fibrates (1.01, 0.90 to 1.13, P=0.84), or CETP inhibitors (1.14, 0.90 to 1.45, P=0.29). In studies with patients not receiving statins (before the statin era), niacin was associated with a significant reduction in non-fatal myocardial infarction (0.69, 0.56 to 0.85, P=0.0004). However, in studies where statins were already being taken, niacin showed no significant effect (0.96, 0.85 to 1.09, P=0.52). A significant difference was seen between these subgroups (P=0.007). A similar trend relating to non-fatal myocardial infarction was seen with fibrates: without statin treatment (0.78, 0.71 to 0.86, P<0.001) and with all or some patients taking statins (0.83, 0.69 to 1.01, P=0.07); P=0.58 for difference. CONCLUSIONS Neither niacin, fibrates, nor CETP inhibitors, three highly effective agents for increasing high density lipoprotein levels, reduced all cause mortality, coronary heart disease mortality, myocardial infarction, or stroke in patients treated with statins. Although observational studies might suggest a simplistic hypothesis for high density lipoprotein cholesterol, that increasing the levels pharmacologically would generally reduce cardiovascular events, in the current era of widespread use of statins in dyslipidaemia, substantial trials of these three agents do not support this concept.
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Niacin and statin combination therapy for atherosclerosis regression and prevention of cardiovascular disease events: reconciling the AIM-HIGH (Atherothrombosis Intervention in Metabolic Syndrome With Low HDL/High Triglycerides: Impact on Global Health Outcomes) trial with previous surrogate endpoint trials.
Michos, ED, Sibley, CT, Baer, JT, Blaha, MJ, Blumenthal, RS
Journal of the American College of Cardiology. 2012;(23):2058-64
Abstract
Despite substantial risk reductions targeting low-density lipoprotein cholesterol with statins, there remains significant residual risk as evidenced by incident and recurrent cardiovascular disease (CVD) events among statin-treated patients. Observational studies have shown that low levels of high-density lipoprotein cholesterol (HDL-C) are associated with increased CVD risk. It remains unclear whether strategies aimed at increasing HDL-C in addition to background statin therapy will further reduce risk. The AIM-HIGH (Atherothrombosis Intervention in Metabolic Syndrome With Low HDL/High Triglycerides: Impact on Global Health Outcomes) trial, which compared combined niacin/simvastatin with simvastatin alone, failed to demonstrate an incremental benefit of niacin among patients with atherosclerotic CVD and on-treatment low-density lipoprotein cholesterol values <70 mg/dl, but this study had some limitations. Previously, small randomized, clinical trials of niacin plus statins showed that modest regression of carotid atherosclerosis is possible in individuals with CVD, CVD risk equivalents, or atherosclerosis. This viewpoint summarizes these imaging trials studying niacin and places them in the context of the failure of AIM-HIGH to support the HDL-C-increasing hypothesis.
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Targeting high density lipoproteins in the prevention of cardiovascular disease?
Larach, DB, deGoma, EM, Rader, DJ
Current cardiology reports. 2012;(6):684-91
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Abstract
Recent studies involving HDL-raising therapeutics have greatly changed our understanding of this field. Despite effectively raising HDL-C levels, niacin remains of uncertain clinical benefit. Synthetic niacin receptor agonists are unlikely to raise HDL-C or have other beneficial effects on plasma lipids. Despite the failure in phase 3 of 2 CETP inhibitors, 2 potent CETP inhibitors that raise HDL-C levels by >100 % (and reduce LDL-C substantially) are in late stage clinical development. Infusions of recombinant HDL containing 'wild-type' apoA-I or apoA-I Milano, as well as autologous delipidated HDL, all demonstrated promising early results, and remain in clinical development. A small molecule that causes upregulation of endogenous apoA-I production is also in clinical development. Finally, upregulation of macrophage cholesterol efflux pathways through agonism of liver X receptors or antagonism of miR-33 remains of substantial interest. The field of HDL therapeutics is poised to transition from the 'HDL-cholesterol hypothesis' to the 'HDL flux hypothesis' in which the impact on flux from macrophage to feces is deemed to be of greater therapeutic benefit than the increase in steady-state concentrations of HDL cholesterol.
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Opening a new lipid "apo-thecary": incorporating apolipoproteins as potential risk factors and treatment targets to reduce cardiovascular risk.
Jacobson, TA
Mayo Clinic proceedings. 2011;(8):762-80
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Statins (3-hydroxy-3-methylglutaryl-coenzyme A reductase inhibitors) represent the cornerstone of drug therapy to reduce low-density lipoprotein (LDL) cholesterol and cardiovascular risk. However, even optimal statin management of LDL cholesterol leaves many patients with residual cardiovascular risk, in part because statins are more effective in reducing LDL cholesterol than apolipoprotein B (Apo B). Apo B may be a better marker of atherogenic risk than LDL cholesterol because Apo B measures the total number of all atherogenic particles (total atherosclerotic burden), including LDL, very low-density lipoprotein, intermediate-density lipoprotein, remnant lipoproteins, and lipoprotein(a). To determine whether Apo B is a better indicator of baseline cardiovascular risk and residual risk after lipid therapy compared with LDL cholesterol, a MEDLINE search of the literature published in English from January 1, 1975, through December 1, 2010, was conducted. On the basis of data from most population studies, elevated Apo B was more strongly associated with incident coronary heart disease than similarly elevated LDL cholesterol. Apo B was also a superior benchmark (vs LDL cholesterol) of statins' cardioprotective efficacy in both primary-prevention and secondary-prevention trials. To minimize cardiovascular risk among persons with hypercholesterolemia or dyslipidemia, the best available evidence suggests that intensive therapy with statins should be initiated to achieve the lowest possible Apo B level (with adequate drug toleration) and then other therapies (eg, niacin, bile acid resins, ezetimibe) added to potentiate these Apo B-lowering effects. In future consensus lipid-lowering treatment guidelines, Apo B should be considered as an index of residual risk, a potential parameter of treatment efficacy, and a treatment target to minimize risk of coronary heart disease.
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The resurgence of niacin: from nicotinic acid to niaspan/laropiprant.
Markel, A
The Israel Medical Association journal : IMAJ. 2011;(6):368-74
Abstract
Hypercholesterolemia is one of the main factors in the development of atherosclerotic cardiovascular disease. The advent of statins led to huge progress in the treatment of hypercholesterolemia, yet the proportion of patients with prohibitive lipid values and the high incidence of cardiovascular events despite treatment are still very high. Niacin, one of the older drugs used to treat hyperlipidemia, was shown to reduce low-density lipoprotein-cholesterol (LDL-C) and triglycerides and to markedly increase high-density lipoprotein-cholesterol (HDL-C) levels. This drug came into disuse owing to frequent side effects, mainly flushing, but in recent years a reemergence of its application has occurred, and multiple clinical trials have shown its effectiveness in the treatment of hyperlipidemia and in the reduction of cardiovascular events. New formulations such as extended-release niacin (ERN) have been developed with the purpose of reducing side effects. Lately, a new compound, laropiprant, which selectively antagonizes the prostaglandin 2 (PGD2) receptor responsible for flushing, has been developed. Laropiprant, when combined with ERN, significantly reduces the incidence of flushing. New and ongoing trials will definitively prove in the long term whether this drug combination significantly reduces the severity of flushing and the incidence of cardiovascular events.
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Effects of niacin on atherosclerosis and vascular function.
Ruparelia, N, Digby, JE, Choudhury, RP
Current opinion in cardiology. 2011;(1):66-70
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PURPOSE OF REVIEW Niacin has been used for more than 50 years in the management of atherosclerosis and is associated with improved patient outcomes. The routine use of niacin has been superseded in recent years with the advent of newer lipid-modulating interventions. Recently, however, there has been a renewed interest in its use due to the appreciation of its many beneficial effects on atherosclerosis and endothelial function, both 'lipid-targeted' and 'pleiotropic'. This review will consider the effects of niacin in the setting of clinical trials and will critically evaluate proposed mechanisms of action. RECENT FINDINGS The identification of the GPR109A receptor has promoted a greater insight into niacin's mechanism of action, with demonstrated beneficial effects on endothelial function and inflammation, in addition to its lipid modulation role. SUMMARY Whether niacin itself is used routinely in the future will depend on the outcomes of two large outcome trials (AIM-HIGH and HPS2-THRIVE). In the future, however, with even better understanding of niacin pharmacology, new drugs may be able to be engineered to capture aspects of niacin that capitalize on the benefits more specifically and also more selectively, to avoid troublesome side-effects.
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Beyond statin therapy: a review of the management of residual risk in diabetes mellitus.
Judge, EP, Phelan, D, O'Shea, D
Journal of the Royal Society of Medicine. 2010;(9):357-62
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Total cholesterol and low-density lipoprotein (LDL) cholesterol exhibit an independent, strong, continuous correlation with cardiovascular events. The effectiveness of hydroxy-3-methylglutaryl coenzyme A reductase inhibitors (statins) in the treatment and prevention of atherosclerosis is well-established. However, despite the lowering of LDL targets and the increased use of statins, patients with type 2 diabetes mellitus (DM) continue to experience a higher proportion of adverse coronary artery disease events. This is as a result of an atherogenic dyslipidaemia, characterized by low levels of high-density lipoprotein and elevated plasma triglyceride concentrations, often with high levels of cholesterol-rich remnant particles. This article will review dyslipidaemia and its role in DM, and will discuss available treatment modalities that address residual cardiovascular risk in this disease.