Niacin improves lipid profile but not endothelial function in patients with coronary artery disease on high dose statin therapy

Early Use of PCSK9 Inhibitors in the Prognosis of Patients with Acute Coronary Syndrome by Protecting Vascular Endothelial Function

INTRODUCTION

Proprotein convertase subtilisin/kexin type 9 inhibitors (PCSK9i) has a protective effect on acute coronary syndrome (ACS). However, most studies have shown that this protective effect is based on a decrease in low-density lipoprotein cholesterol, while other mechanisms remain limited. This study aimed to determine whether PCSK9i can improve the prognosis of ACS patients by protecting endothelial function.

METHODS

A total of 113 ACS patients were enrolled and randomly assigned to PCSK9i group (PCSK9i combined with statins) and control group (statins only). Blood lipids and endothelial function indicators were measured and analyzed 6 weeks before and after treatment. The effect of PCSK9i on the expression and secretion of endothelial function indicators in vascular endothelial cells were studied by cell experiments.

RESULTS

After 6 weeks of treatment, endothelial function indicators such as nitric oxide (NO), thrombomodulin, intercellular cell adhesion molecule-1, endothelin-1, and flow-mediated vasodilation were significantly improved in PCSK9i group compared with control group. Only the changes of NO and von Willebrand factor were associated with blood lipid levels, whereas the changes of other endothelial function indicators were not significantly associated with blood lipid levels. PCSK9i reduced the incidence of major adverse cardiovascular events in patients with ACS compared to those in the control group. In cell experiments, PCSK9i treatment significantly ameliorated LPS induced endothelial injury in HUVECs.

CONCLUSION

PCSK9i can protect vascular endothelial function partly independently of its lipid-lowering effect and ameliorate the prognosis of patients with ACS within 6 weeks. This mechanism may involve heat shock transcription factor 1/heat shock proteins -related signaling pathways. Early use of PCSK9i in patients with ACS should be strongly considered in clinical practice.

Changes in glucose metabolism, C-reactive protein, and liver enzymes following intake of NAD + precursor supplementation: a systematic review and meta-regression analysis

BACKGROUND

There are contradictory effects regarding the effect of NAD + precursor on glucose metabolism and liver enzymes. In order to obtain a better viewpoint from them, this study aimed to comprehensively investigate the effects of NAD + precursor supplementation on glucose metabolism, C-reactive protein (CRP), and liver enzymes.

METHODS

PubMed/MEDLINE, Web of Science, SCOPUS, and Embase databases were searched using standard keywords to identify all controlled trials investigating the glucose metabolism, CRP, and liver enzymes effects of NAD + precursor. Pooled weighted mean difference (WMD) and 95% confidence intervals (95% CI) were achieved by random-effects model analysis for the best estimation of outcomes.

RESULTS

Forty-five articles with 9256 participants' were included in this article. The pooled findings showed that NAD + precursor supplementation had a significant increase in glucose (WMD: 2.17 mg/dL, 95% CI: 0.68, 3.66, P = 0.004) and HbA1c (WMD: 0.11, 95% CI: 0.06, 0.16, P < 0.001) as well as a significant decrease in CRP (WMD: -0.93 mg/l, 95% CI -1.47 to -0.40, P < 0.001) compared with control group, and was not statistically significant with respect to insulin and homeostasis model assessment of insulin resistance (HOMA-IR). However, we found no systemic changes in aspartate transaminase (AST), alanine transaminase (ALT), or alkaline phosphatase (ALP) levels after NAD + precursor supplementation. The results of the subgroup analysis showed that the intake of NAD + precursor during the intervention of more than 12 weeks caused a greater increase in the glucose level. Furthermore, Nicotinic acid supplementation (NA) causes a greater increase in glucose and HbA1c levels than nicotinamide (NE) supplementation.

CONCLUSIONS

Overall, these findings suggest that NAD + precursor supplementation might have an increase effect on glucose metabolism as well as a decrease in CRP.

The therapeutic perspective of NAD+ precursors in age-related diseases

Nicotinamide adenine dinucleotide (NAD+) is the fundamental molecule that performs numerous biological reactions and is crucial for maintaining cellular homeostasis. Studies have found that NAD+ decreases with age in certain tissues, and age-related NAD+ depletion affects physiological functions and contributes to various aging-related diseases. Supplementation of NAD+ precursor significantly elevates NAD+ levels in murine tissues, effectively mitigates metabolic syndrome, enhances cardiovascular health, protects against neurodegeneration, and boosts muscular strength. Despite the versatile therapeutic functions of NAD+ in animal studies, the efficacy of NAD+ precursors in clinical studies have been limited compared with that in the pre-clinical study. Clinical studies have demonstrated that NAD+ precursor treatment efficiently increases NAD+ levels in various tissues, though their clinical proficiency is insufficient to ameliorate the diseases. However, the latest studies regarding NAD+ precursors and their metabolism highlight the significant role of gut microbiota. The studies found that orally administered NAD+ intermediates interact with the gut microbiome. These findings provide compelling evidence for future trials to further explore the involvement of gut microbiota in NAD+ metabolism. Also, the reduced form of NAD+ precursor shows their potential to raise NAD+, though preclinical studies have yet to discover their efficacy. This review sheds light on NAD+ therapeutic efficiency in preclinical and clinical studies and the effect of the gut microbiota on NAD+ metabolism.

NAD+ and Vascular Dysfunction: From Mechanisms to Therapeutic Opportunities

Nicotinamide adenine dinucleotide (NAD+) is an essential and pleiotropic coenzyme involved not only in cellular energy metabolism, but also in cell signaling, epigenetic regulation, and post-translational protein modifications. Vascular disease risk factors are associated with aberrant NAD+ metabolism. Conversely, the therapeutic increase of NAD+ levels through the administration of NAD+ precursors or inhibitors of NAD+-consuming enzymes reduces chronic low-grade inflammation, reactivates autophagy and mitochondrial biogenesis, and enhances oxidative metabolism in vascular cells of humans and rodents with vascular pathologies. As such, NAD+ has emerged as a potential target for combatting age-related cardiovascular and cerebrovascular disorders. This review discusses NAD+-regulated mechanisms critical for vascular health and summarizes new advances in NAD+ research directly related to vascular aging and disease, including hypertension, atherosclerosis, coronary artery disease, and aortic aneurysms. Finally, we enumerate challenges and opportunities for NAD+ repletion therapy while anticipating the future of this exciting research field, which will have a major impact on vascular medicine.

Effects of NAD+ precursor supplementation on glucose and lipid metabolism in humans: a meta-analysis

BACKGROUND

This meta-analysis was performed to investigate the effects of nicotinamide adenine dinucleotide (NAD+) precursor supplementation on glucose and lipid metabolism in human body.

METHODS

PubMed, Embase, CENTRAL, Web of Science, Scopus databases were searched to collect clinical studies related to the supplement of NAD+ precursor from inception to February 2021. Then the retrieved documents were screened, the content of the documents that met the requirements was extracted. Meta-analysis and quality evaluation was performed detection were performed using RevMan5.4 software. Stata16 software was used to detect publication bias, Egger and Begg methods were mainly used. The main research terms of NAD+ precursors were Nicotinamide Riboside (NR), Nicotinamide Mononucleotide (NMN), Nicotinic Acid (NA), Nicotinamide (NAM). The changes in the levels of triglyceride (TG), total cholesterol (TC), low-density lipoprotein (LDL), high-density lipoprotein (HDL), and fasting blood glucose were mainly concerned.

RESULTS

A total of 40 articles were included in the meta-analysis, with a sample of 14,750 cases, including 7406 cases in the drug group and 7344 cases in the control group. The results of meta-analysis showed that: NAD+ precursor can significantly reduce TG level (SMD = - 0.35, 95% CI (- 0.52, - 0.18), P < 0.0001), and TC (SMD = - 0.33, 95% CI (- 0.51, - 0.14), P = 0.0005), and LDL (SMD = - 0.38, 95% CI (- 0.50, - 0.27), P < 0.00001), increase HDL level (SMD = 0.66, 95% CI (0.56, 0.76), P < 0.00001), and plasma glucose level in the patients (SMD = 0.27, 95% CI (0.12, 0.42), P = 0.0004). Subgroup analysis showed that supplementation of NA had the most significant effect on the levels of TG, TC, LDL, HDL and plasma glucose.

CONCLUSIONS

In this study, a meta-analysis based on currently published clinical trials with NAD+ precursors showed that supplementation with NAD+ precursors improved TG, TC, LDL, and HDL levels in humans, but resulted in hyperglycemia, compared with placebo or no treatment. Among them, NA has the most significant effect on improving lipid metabolism. In addition, although NR and NAM supplementation had no significant effect on improving human lipid metabolism, the role of NR and NAM could not be directly denied due to the few relevant studies at present. Based on subgroup analysis, we found that the supplement of NAD+ precursors seems to have little effect on healthy people, but it has a significant beneficial effect on patients with cardiovascular disease and dyslipidemia. Due to the limitation of the number and quality of included studies, the above conclusions need to be verified by more high-quality studies.

NAD+ Metabolism in Cardiac Health, Aging, and Disease

Nicotinamide adenine dinucleotide (NAD⁺) is a central metabolite involved in energy and redox homeostasis as well as in DNA repair and protein deacetylation reactions. Pharmacological or genetic inhibition of NAD⁺-degrading enzymes, external supplementation of NAD⁺ precursors, and transgenic overexpression of NAD⁺-generating enzymes have wide positive effects on metabolic health and age-associated diseases. NAD⁺ pools tend to decline with normal aging, obesity, and hypertension, which are all major risk factors for cardiovascular disease, and NAD⁺ replenishment extends healthspan, avoids metabolic syndrome, and reduces blood pressure in preclinical models. In addition, experimental elevation of NAD⁺ improves atherosclerosis, ischemic, diabetic, arrhythmogenic, hypertrophic, or dilated cardiomyopathies, as well as different modalities of heart failure. Here, we critically discuss cardiomyocyte-specific circuitries of NAD⁺ metabolism, comparatively evaluate distinct NAD⁺ precursors for their preclinical efficacy, and raise outstanding questions on the optimal design of clinical trials in which NAD⁺ replenishment or supraphysiological NAD⁺ elevations are assessed for the prevention or treatment of major cardiac diseases. We surmise that patients with hitherto intractable cardiac diseases such as heart failure with preserved ejection fraction may profit from the administration of NAD⁺ precursors. The development of such NAD⁺-centered treatments will rely on technological and conceptual progress on the fine regulation of NAD⁺ metabolism.

Coronary Artery Disease and Endothelial Dysfunction: Novel Diagnostic and Therapeutic Approaches

Coronary artery disease is the leading cause of morbidity and mortality worldwide. The most common pathophysiologic substrate is atherosclerosis which is an inflammatory procedure that starts at childhood and develops throughout life. Endothelial dysfunction is associated with the initiation and progression of atherosclerosis and is characterized by the impaired production of nitric oxide. In general, endothelial dysfunction is linked to poor cardiovascular prognosis and different methods, both invasive and non-invasive, have been developed for its evaluation. Ultrasound evaluation of flow mediated dilatation of the branchial artery is the most commonly used method to assessed endothelial function while intracoronary administration of vasoactive agents may be also be used to test directly endothelial properties of the coronary vasculature. Endothelial dysfunction has also been the subject of therapeutic interventions. This review article summarizes the knowledge about evaluation of endothelial function in acute coronary syndromes and stable coronary artery disease and demonstrates the current therapeutic approaches against endothelial dysfunction.

Role of endothelial NAD+ deficiency in age-related vascular dysfunction

Age-related alterations in endothelium and the resulting vascular dysfunction critically contribute to a range of pathological conditions associated with old age. To develop therapies rationally that improve vascular health and thereby increase health span and life span in older adults, it will be essential to understand the cellular and molecular mechanisms contributing to vascular aging. Preclinical studies in model organisms demonstrate that NAD+ availability decreases with age in multiple tissues and that supplemental NAD+ precursors can ameliorate many age-related cellular impairments. Here, we provide a comprehensive overview of NAD+-dependent pathways [including the NAD+-using silent information regulator-2-like enzymes and poly(ADP-ribose) polymerase enzymes] and the potential consequences of endothelial NAD+ deficiency in vascular aging. The multifaceted vasoprotective effects of treatments that reverse the age-related decline in cellular NAD+ levels, as well as their potential limitations, are discussed. The preventive and therapeutic potential of NAD+ intermediates as effective, clinically relevant interventions in older adults at risk for ischemic heart disease, vascular cognitive impairment, and other common geriatric conditions and diseases that involve vascular pathologies (e.g., sarcopenia, frailty) are critically discussed. We propose that NAD+ precursors [e.g., nicotinamide (Nam) riboside, Nam mononucleotide, niacin] should be considered as critical components of combination therapies to slow the vascular aging process and increase cardiovascular health span.

Effect of Niacin on Carotid Atherosclerosis in Patients at Low-Density Lipoprotein-Cholesterol Goal but High Lipoprotein (a) Level: a 2-Year Follow-Up Study

Objective

To examine the effect of niacin on the progression of carotid intima-media thickness (IMT) in patients with high level of lipoprotein (Lp) (a).

Methods

Patients at low-density lipoprotein-cholesterol goal but with Lp (a) >25 mg/dL and mean carotid IMT >0.75 mm were included. Eligible patients were randomized at a 1:2 ratio into one of two groups for 24 months: control or 1,500 mg extended release niacin. The primary study outcomes were the percentage changes in mean and maximal carotid IMT. The percentage change in lipid profiles including Lp (a) was analyzed as a secondary study outcome.

Results

Among 96 randomized patients, 31 completed the study (mean age: 65 years; male: 44%). At follow-up, the percentage change in mean carotid IMT was not significantly different between the two groups (−1.4%±15.5% and −1.1%±7.3% in the control and niacin groups, respectively, p=0.95). The percentage change in maximal carotid IMT was also similar in the two groups (0.7%±16.5% and −4.4%±11.6%, respectively, p=0.35). Elevation of high-density lipoprotein-cholesterol tended to be higher in the niacin group (p=0.07), and there was a significant difference in the percentage change in hemoglobin A1c between the two groups (−1.9%±2.2% and 3.3%±6.7%, respectively, p=0.02). Reduction of Lp (a) was greater in the niacin-treated group compared to placebo, but the difference was not statistically significant.

Conclusion

Treatment with niacin for two years did not inhibit the progression of carotid intima-media thickening in patients with high Lp (a) level. However, this study may have been underpowered to evaluate the primary study outcome.

Impaired Peripheral Endothelial Function Assessed by Digital Reactive Hyperemia Peripheral Arterial Tonometry and Risk of In-Stent Restenosis

Background

Drug‐eluting stents are replacing bare‐metal stents, but in‐stent restenosis (ISR) remains a problem. Reactive hyperemia index (RHI) assessed by peripheral arterial tonometry evaluates endothelial function noninvasively. We prospectively assessed the prognostic value of RHI in predicting ISR after percutaneous coronary intervention.

Methods and Results

RHI was measured before percutaneous coronary intervention and at follow‐up (F/U) angiography (F/U RHI; 6 and 9 months post bare‐metal stents– and drug‐eluting stents– percutaneous coronary intervention, respectively) in 249 consecutive patients. At F/U, ISR (stenosis >50% of diameter) was seen in 68 patients (27.3%). F/U natural logarithm (RHI) was significantly lower in patients with ISR than in those without (0.52±0.23 versus 0.65±0.27, P<0.01); no between‐group difference in initial natural logarithm (RHI) (0.60±0.26 versus 0.62±0.25, P=0.56) was seen. By multivariate logistic regression analysis, even after adjusting for other significant parameters in univariate analysis, F/U natural logarithm (RHI) independently predicted ISR (odds ratio: 0.13; 95% CI: 0.04–0.48; P=0.002). In receiver operating‐characteristic analysis, F/U RHI was the strongest predictor of ISR (area under the curve: 0.67; 95% CI: 0.60–0.75; P<0.01; RHI <1.73 had 67.6% sensitivity, 64.1% specificity); area under the curve significantly improved from 0.62 to 0.70 when RHI was added to traditional ISR risk factors (P=0.02). Net reclassification index was significant after addition of RHI (26.5%, P=0.002).

Conclusions

Impaired RHI at F/U angiography independently correlated with ISR, adding incremental prognostic value to the ISR‐risk stratification following percutaneous coronary intervention.

Clinical Trial Registration

URL: https://www.clinicaltrials.gov/. Unique identifier: NCT02131935.

Extended-Release Niacin Versus Fenofibrate in HIV-Infected Participants With Low High-Density Lipoprotein Cholesterol: Effects on Endothelial Function, Lipoproteins, and Inflammation

BACKGROUND

Low levels of high-density lipoprotein cholesterol (HDL-C) are common in individuals with human immunodeficiency virus (HIV) infection, persist during antiretroviral therapy (ART), and are associated with increased cardiovascular disease (CVD) risk.

METHODS

Virologically controlled participants without CVD on stable ART with low HDL-C (men <40 mg/dL, women <50 mg/dL) and triglycerides >150 mg/dL were randomized to receive open-label extended-release niacin 1500 mg/day with aspirin 325 mg/day or fenofibrate 200 mg/day for 24 weeks. The primary endpoint was the week 24 within-arm change in brachial artery flow-mediated dilation (FMD) in participants with complete follow-up scans.

RESULTS

Of 99 participants, 74 had complete data (35 niacin, 39 fenofibrate). Median age was 45 years, 77% were male, median CD4(+) count was 561 cells/µL, and brachial FMD was 4.2%. Median HDL-C was 32 mg/dL for men and 38 mg/dL for women, low-density lipoprotein cholesterol was 103 mg/dL, and triglycerides were 232 mg/dL. In men, HDL-C increased a median of 3 mg/dL with niacin and 6.5 mg/dL with fenofibrate (P < .001 for both). In women, HDL-C increased a median of 16 mg/dL with niacin and 8 mg/dL with fenofibrate (P = .08 for both). After 24 weeks, there was no significant change in FMD in either arm; the median (interquartile range) change was +0.6% (-1.6 to 2.3) with niacin (P = .28) and +0.5% (-1.0 to 3.0) with fenofibrate (P = .19). Neither treatment significantly affected C-reactive protein, interleukin 6, or D-dimer levels.

CONCLUSIONS

Despite improvements in lipids, niacin or fenofibrate treatment for 24 weeks did not improve endothelial function or inflammatory markers in participants with well-controlled HIV infection and low HDL-C.

CLINICAL TRIALS REGISTRATION

NCT01426438.

Effects of established hypolipidemic drugs on HDL concentration, subclass distribution, and function

The knowledge of an inverse relationship between plasma high-density lipoprotein cholesterol (HDL-C) concentrations and rates of cardiovascular disease has led to the concept that increasing plasma HDL-C levels would be protective against cardiovascular events. Therapeutic interventions presently available to correct the plasma lipid profile have not been designed to specifically act on HDL, but have modest to moderate effects on plasma HDL-C concentrations. Statins, the first-line lipid-lowering drug therapy in primary and secondary cardiovascular prevention, have quite modest effects on plasma HDL-C concentrations (2-10%). Fibrates, primarily used to reduce plasma triglyceride levels, also moderately increase HDL-C levels (5-15%). Niacin is the most potent available drug in increasing HDL-C levels (up to 30%), but its use is limited by side effects, especially flushing.The present chapter reviews the effects of established hypolipidemic drugs (statins, fibrates, and niacin) on plasma HDL-C levels and HDL subclass distribution, and on HDL functions, including cholesterol efflux capacity, endothelial protection, and antioxidant properties.

Effect of niacin on endothelial function: a systematic review and meta-analysis of randomized controlled trials

Endothelial dysfunction is an independent predictor of incident atherosclerotic cardiovascular disease (ACVD). Niacin possesses high-density lipoprotein (HDL)-elevating, antioxidant and anti-inflammatory properties, all potentially contributing to the amelioration of endothelial function. However, controversies exist among trials reporting the effects of niacin on endothelium-dependent flow-mediated dilation (FMD) as a reliable surrogate of endothelial function. The objective of this study was to assess the effect of niacin on brachial artery FMD using a meta-analysis of available evidence. MEDLINE and Scopus databases were searched for randomized controlled trials investigating the impact of niacin therapy on brachial artery FMD. Meta-analysis of eligible studies was conducted using a random-effects model. Pooled effects were measured by weighted mean difference (WMD) and 95% confidence intervals (CIs). Quality assessment, and subgroup, meta-regression and sensitivity analyses were conducted using standard methods. Among 596 citations, 19 full-text articles were read and seven were found to be eligible for inclusion. Eligible studies involved 441 subjects comprising 228 in the niacin and 213 in the control groups. Niacin therapy significantly improved FMD (WMD: 1.98%; 95% CI: 0.91-3.05%; p = 0.0003) and this effect was robust in the sensitivity analysis. The effect size was greater in the subgroup of studies administering higher doses of niacin (≥ 2000 mg/day) as well as those studies administering niacin for primary prevention of ACVD. Meta-regression indicated no association between niacin-induced changes in FMD and changes in plasma HDL-cholesterol, low-density lipoprotein-cholesterol or triglycerides. None of the included studies could find any significant effect of niacin on nitroglycerin-mediated dilation. In conclusion, treatment with niacin improves endothelial function.

Peripheral microvascular dysfunction predicts residual risk in coronary artery disease patients on statin therapy

OBJECTIVE

Although lowering of low-density lipoprotein cholesterol (LDL-C) by statins is essential in treatment of coronary artery disease (CAD) patients, there is considerable residual risk of secondary coronary artery events (CAE). We examined whether microvascular dysfunction (MiD), measured by peripheral artery tonometry (PAT), can predict prognosis of CAD patients previously treated with statins.

METHODS

We measured log-transformed reactive hyperemia index (L_RHI) in 213 CAD patients who had already achieved LDL-C <100 by statin therapy. Patients were followed-up for secondary CAE for a median of 2.7 years. Patients were divided into two groups: L_RHI ≥ 0.54 (n = 99) and L_RHI < 0.54 (n = 114).

RESULTS

During follow-up, CAE occurred in 4 (4.0%) patients in the L_RHI ≥ 0.54 group and 18 (15.8%) patients in the L_RHI < 0.54 group (P = 0.006). Cox regression analysis indicated that L_RHI was an independent predictor for CAE even after adjustment by Framingham traditional risk factors (FRF; age, T-C/HDL-C ratio, systolic blood pressure, diabetes, current smoker, and gender) and estimated glomerular filtration rate (eGFR) for secondary CAE (HR 0.79, 95% CI: 0.66-0.95). ROC analysis for CAE prediction showed that the AUC for models including FRF only, FRF + eGFR, and FRF + eGFR + L_RHI were 0.60, 0.71, and 0.77, respectively. Moreover, adding eGFR to FRF only (0.63, P = 0.003) and adding L_RHI to the FRF + eGFR model were associated with significant improvement of net reclassification improvement (0.79, P = 0.007).

CONCLUSION

MiD measured by non-invasive PAT adds incremental predictive ability to traditional risk factors for prognosis of CAD patients successfully treated with statins.