What does the future hold for niacin as a treatment for hyperlipidaemia and cardiovascular disease?

Dietary niacin Intake and its association with all-cause and cardiovascular mortality rates in individuals with metabolic syndrome

BACKGROUND

Individuals with metabolic syndrome face elevated cardiovascular and mortality risks, and there is ongoing debate regarding the cardiovascular effects of niacin and its impact on the prognosis of metabolic syndrome.

EXPOSURE

Levels of dietary niacin intake based on 24-hour dietary recall.

METHODS

Kaplan-Meier survival curves were used to compare survival status among quartiles of dietary niacin intake. Weighted Cox proportional hazards models and restricted cubic splines were used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for the risk of all-cause and CVD mortality associated with the exposure.

RESULTS

This cohort study included 8,744 participants, and during a median follow-up period of 106 months, 1,552 (17.7%) deaths were recorded, with 511 attributed to cardiovascular disease. Kaplan-Meier curves comparing quartiles of dietary niacin intake showed significant differences in both all-cause and cardiovascular mortality rates (log-rank p < 0.001). In the fully adjusted model, the highest quartile of dietary niacin intake was associated with HRs of 0.68 (95% CI: 0.54, 0.87, P = 0.002) for all-cause mortality and 0.63 (95% CI: 0.39, 0.78, P < 0.001) for cardiovascular mortality.

CONCLUSION

The results of this cohort study suggest that higher dietary niacin intake is associated with reduced cardiovascular and all-cause mortality risks in the metabolic syndrome population. Furthermore, there appears to be a dose-response relationship between dietary niacin intake and the risks of all-cause and cardiovascular mortality.

Reuniting overnutrition and undernutrition, macronutrients, and micronutrients

Over-nutrition and its late consequences are a dominant theme in medicine today. In addition to the health hazards brought on by over-nutrition, the medical community has recently accumulated a roster of health benefits with obesity, grouped under "obesity paradox." Throughout the world and throughout history until the 20^th century, under-nutrition was a dominant evolutionary force. Under-nutrition brings with it a mix of benefits and detriments that are opposite to and continuous with those of over-nutrition. This continuum yields J-shaped or U-shaped curves relating body mass index to mortality. The overweight have an elevated risk of dying in middle age of degenerative diseases while the underweight are at increased risk of premature death from infectious conditions. Micronutrient deficiencies, major concerns of nutritional science in the 20^th century, are being neglected. This "hidden hunger" is now surprisingly prevalent in all weight groups, even among the overweight. Because micronutrient replacement is safe, inexpensive, and predictably effective, it is now an exceptionally attractive target for therapy across the spectrum of weight and age. Nutrition-related conditions worthy of special attention from caregivers include excess vitamin A, excess vitamin D, and deficiency of magnesium.

Mechanisms of aggregation inhibition by aspirin and nitrate-aspirin prodrugs in human platelets

Objectives

Aspirin is the mainstay of anti-platelet therapy in the secondary prevention of cardiovascular disease. However, problems with aspirin safety and resistance demand clinical strategies based on multiple pharmacological approaches. Prodrugs of aspirin may offer beneficial effects in terms of gastro-intestinal safety and multiple pharmacological approaches. However, the pharmacological profile of aspirin prodrugs in human platelets has not been completed yet. We aimed to compare the effects of aspirin and prodrugs of aspirin (1–5) on human platelet aggregation stimulated by ADP and collagen and associated receptor expression (GPIIb/IIIa and P-selectin) in platelet-rich plasma (PRP) and washed platelets (WP).

Methods

As aspirin is released from prodrugs following esterase hydrolysis we studied the expression and activity of butyrylcholineterase (BuChE) and carboxyesterase (CE) in plasma and platelets. The mechanism of prodrug-induced platelet aggregation inhibition was explored by studying the effects of plasma and purified human BuChE on aggregation. Finally, the relative contribution of nitric oxide (NO) bioactivity to nitrate-containing prodrugs of aspirin-induced inhibition of aggregation was determined using 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ,) a selective inhibitor of the soluble guanylyl cyclase.

Key findings

ST0702, 2, a nicotinic acid-aspirin codrug was equipotent with aspirin with respect to inhibition of collagen-induced platelet aggregation. Compound 4, a NO releasing aspirin was the most potent inhibitor of ADP-induced platelet aggregation, an effect partially reversed by ODQ. The platelet inhibitory effects of aspirin prodrugs were time-dependent as the maximal inhibitory effects against collagen-induced aggregation were achieved by aspirin at 2 min, 1 at 5 min and ST0702 at 15 min. The aspirin prodrugs were significantly less potent in WP than in PRP and the reverse was true of aspirin. In the presence of complete BuChE inhibition in PRP, there was almost complete loss of aspirin prodrug, but not aspirin anti-aggregatory activity. Interestingly, CE activity was observed in WP and platelet lysate with pNPA substrate. Accordingly, 1 and ST0702 retained 50% and 100% anti-aggregatory activity at maximal concentrations in WP, which was attenuated in the presence of esterase inhibitor phenylmethylsulphonyl fluoride.

Conclusions

The inhibitory effect of aspirin prodrugs in PRP is due to prodrug activation by BuChE. In contrast, the platelet-inhibitory effects of aspirin prodrugs in WP may be mediated through the activity of platelet CE. Compound 4, a NO-containing aspirin prodrug, may exert dual inhibitory effects in platelets. Thus, aspirin prodrugs effectively inhibit human platelet aggregation and as such may be an alternative to conventional aspirin.