The facts behind niacin

Hepatic transcript profiling in beef cattle: Effects of rumen-protected niacin supplementation

The objective of our study was to assess the effect of rumen-protected niacin supplementation on the transcriptome of liver tissue in growing Angus × Simmental steers and heifers through RNA-seq analysis. Consequently, we wanted to assess the known role of niacin in the physiological processes of vasodilation, detoxification, and immune function in beef hepatic tissue. Normal weaned calves (~8 months old) were provided either a control diet or a diet supplemented with rumen-protected niacin (6 g/hd/d) for a 30-day period, followed by a liver biopsy. We observed a significant list of changes at the transcriptome level due to rumen-protected niacin supplementation. Several metabolic pathways revealed potential positive effects to the animal's liver metabolism due to administration of rumen-protected niacin; for example, a decrease in lipolysis, apoptosis, inflammatory responses, atherosclerosis, oxidative stress, fibrosis, and vasodilation-related pathways. Therefore, results from our study showed that the liver transcriptional machinery switched several metabolic pathways to a condition that could potentially benefit the health status of animals supplemented with rumen-protected niacin. In conclusion, based on the results of our study, we can suggest the utilization of rumen-protected niacin supplementation as a nutritional strategy could improve the health status of growing beef cattle in different beef production stages, such as backgrounding operations or new arrivals to a feedlot.

Role of vitamins in the metabolic syndrome and cardiovascular disease

The prevalence of metabolic syndrome and cardiovascular disease has increased and continues to be the leading cause of mortality worldwide. The etiology of these diseases includes a complex phenotype derived from interactions between genetic, environmental, and nutritional factors. In this regard, it is common to observe vitamin deficiencies in the general population and even more in patients with cardiometabolic diseases due to different factors. Vitamins are essential micronutrients for cellular metabolism and their deficiencies result in diseases. In addition to its role in nutritional functions, increasingly, vitamins are being recognized as modulators of genetics expression and signals transduction, when consumed at pharmacological concentrations. Numerous randomized preclinical and clinical trials have evaluated the use of vitamin supplementation in the prevention and treatment of metabolic syndrome and cardiovascular disease. However, it is controversy regarding its efficacy in the treatment and prevention of these diseases. In this review, we investigated chemical basics, physiological effect and recommended daily intake, problems with deficiency and overdose, preclinical and clinical studies, and mechanisms of action of vitamin supplementation in the treatment and prevention of metabolic syndrome and cardiovascular disease.

Niacin

Nicotinic acid and nicotinamide, collectively referred to as niacin, are nutritional precursors of the bioactive molecules nicotinamide adenine dinucleotide (NAD) and nicotinamide adenine dinucleotide phosphate (NADP). NAD and NADP are important cofactors for most cellular redox reactions, and as such are essential to maintain cellular metabolism and respiration. NAD also serves as a cosubstrate for a large number of ADP-ribosylation enzymes with varied functions. Among the NAD-consuming enzymes identified to date are important genetic and epigenetic regulators, e.g., poly(ADP-ribose)polymerases and sirtuins. There is rapidly growing knowledge of the close connection between dietary niacin intake, NAD(P) availability, and the activity of NAD(P)-dependent epigenetic regulator enzymes. It points to an exciting role of dietary niacin intake as a central regulator of physiological processes, e.g., maintenance of genetic stability, and of epigenetic control mechanisms modulating metabolism and aging. Insight into the role of niacin and various NAD-related diseases ranging from cancer, aging, and metabolic diseases to cardiovascular problems has shifted our view of niacin as a vitamin to current views that explore its potential as a therapeutic.

Pleiotropic effects of niacin: Current possibilities for its clinical use

Niacin was the first hypolipidemic drug to significantly reduce both major cardiovascular events and mortality in patients with cardiovascular disease. Niacin favorably influences all lipoprotein classes, including lipoprotein[a],and belongs to the most potent hypolipidemic drugs for increasing HDL-C. Moreover, niacin causes favorable changes to the qualitative composition of lipoprotein HDL. In addition to its pronounced hypolipidemic action, niacin exerts many other, non-hypolipidemic effects (e.g., antioxidative, anti-inflammatory, antithrombotic), which favorably influence the development and progression of atherosclerosis. These effects are dependent on activation of the specific receptor HCA2. Recent results published by the two large clinical studies, AIM-HIGH and HPS2-THRIVE, have led to the impugnation of niacin's role in future clinical practice. However, due to several methodological flaws in the AIM-HIGH and HPS2-THRIVE studies, the pleiotropic effects of niacin now deserve thorough evaluation. This review summarizes the present and possible future use of niacin in clinical practice in light of its newly recognized pleiotropic effects.

Involvement of the Niacin Receptor GPR109a in the LocalControl of Glucose Uptake in Small Intestine of Type 2Diabetic Mice

Niacin is a popular nutritional supplement known to reduce the risk of cardiovascular diseases by enhancing high-density lipoprotein levels. Despite such health benefits, niacin impairs fasting blood glucose. In type 2 diabetes (T2DM), an increase in jejunal glucose transport has been well documented; however, this is intriguingly decreased during niacin deficient state. In this regard, the role of the niacin receptor GPR109a in T2DM jejunal glucose transport remains unknown. Therefore, the effects of diabetes and high-glucose conditions on GPR109a expression were studied using jejunal enterocytes of 10-week-old m+/db and db/db mice, as well as Caco-2 cells cultured in 5.6 or 25.2 mM glucose concentrations. Expression of the target genes and proteins were quantified using real-time polymerase chain reaction (RT-PCR) and Western blotting. Glucose uptake in Caco-2 cells and everted mouse jejunum was measured using liquid scintillation counting. 10-week T2DM increased mRNA and protein expression levels of GPR109a in jejunum by 195.0% and 75.9%, respectively, as compared with the respective m+/db control; high-glucose concentrations increased mRNA and protein expression of GPR109a in Caco-2 cells by 130.2% and 69.0%, respectively, which was also confirmed by immunohistochemistry. In conclusion, the enhanced GPR109a expression in jejunal enterocytes of T2DM mice and high-glucose treated Caco-2 cells suggests that GPR109a is involved in elevating intestinal glucose transport observed in diabetes.

Niacin as antidyslipidemic drug

Niacin is an important vitamin (B3) that can be used in gram doses to positively modify pathogenetically relevant lipid disorders: elevated LDL cholesterol, elevated non-HDL cholesterol, elevated triglycerides, elevated lipoprotein(a), and reduced HDL cholesterol. This review reports the latest published findings with respect to niacin's mechanisms of action on these lipids and its anti-inflammatory and anti-atherosclerotic effects. In the pre-statin era, niacin was shown to have beneficial effects on cardiovascular end-points; but in recent years, two major studies performed in patients whose LDL cholesterol levels had been optimized by a statin therapy did not demonstrate an additional significant effect on these end-points in the groups where niacin was administered. Both studies have several drawbacks that suggest that they are not representative for other patients. Thus, niacin still plays a role either as an additive to a statin or as a substitute for a statin in statin-intolerant patients. Moreover, patients with elevated triglyceride and low HDL cholesterol levels and patients with elevated lipoprotein(a) concentrations will possibly benefit from niacin, although currently the study evidence for these indications is rather poor. Niacin may be useful for compliant patients, however possible side effects (flushing, liver damage) and contraindications should be taken into consideration.

The high-fat high-fructose hamster as an animal model for niacin's biological activities in humans

OBJECTIVE

Niacin has been used for more than 50 years to treat dyslipidemia, yet the mechanisms underlying its lipid-modifying effects remain unknown, a situation stemming at least in part from a lack of validated animal models. The objective of this study was to determine if the dyslipidemic hamster could serve as such a model.

MATERIALS/METHODS

Dyslipidemia was induced in Golden Syrian hamsters by feeding them a high-fat, high-cholesterol, and high-fructose (HF/HF) diet. The effect of high-dose niacin treatment for 18 days and 28 days on plasma lipid levels and gene expression was measured.

RESULTS

Niacin treatment produced significant decreases in plasma total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), triglycerides (TG), and free fatty acids (FFA), but had no measureable effect on high-density lipoprotein cholesterol (HDL-C) in the dyslipidemic hamster. Niacin treatment also produced significant increases in hepatic adenosine ATP-Binding Cassette A1 (ABCA1) mRNA, ABCA1 protein, apolipoprotein A-I (Apo A-I) mRNA, and adipose adiponectin mRNA in these animals.

CONCLUSIONS

With the exception of HDL-C, the lipid effects of niacin treatment in the dyslipidemic hamster closely parallel those observed in humans. Moreover, the effects of niacin treatment on gene expression of hepatic proteins related to HDL metabolism are similar to those observed in human cells in culture. The HF/HF-fed hamster could therefore serve as an animal model for niacin's lowering of proatherogenic lipids and mechanisms of action relative to lipid metabolism.

The effect of pioglitazone and extended-release niacin on HDL-cholesterol in diabetes patients in a real-world setting

OBJECTIVE

This retrospective study was designed to assess the effects of the combination of pioglitazone and extended-release niacin on the lipid panel, particularly HDL-cholesterol, when used in patients with type 2 diabetes in an endocrinology specialty practice.

METHODS

The electronic medical records of 434 adult patients with type 2 diabetes receiving extended-release niacin and pioglitazone were screened for review. Patients with type 2 diabetes and hyperlipidemia were included for review if they received the combination of pioglitazone at doses ≥ 15 mg/day and extended-release niacin (Niaspan) at doses ≥ 1000 mg/day for ≥6 months. Statistical analysis used paired t-tests with p < 0.05 as statistically significant. Both ANOVA and the Tukey-Kramer test for multiple comparisons (α = 0.05) were also used.

RESULTS

A total of 47 patients, 83% were men with average age of 58, met all eligibility criteria for the study. Compared with baseline, a statistically significant increase in HDL-C (+ 25.13%, p < 0.0001) was observed at the conclusion of combination therapy. The HDL-C levels progressively increased with duration of combination treatment, and were not correlated with concomitant statin use. Significant decreases in total cholesterol and triglycerides were detected, and HbA1c decreased 0.84% during combination therapy for all therapies combined.

CONCLUSION

The combination of pioglitazone and extended-release niacin in patients with type 2 diabetes and hyperlipidemia, used in commonly prescribed doses for at least 6 months, resulted in statistically significant improvements in HDL-C, total cholesterol, and triglycerides, and did not result in deteriorations in glycemic control.

Does it make sense to combine statins with other lipid-altering agents following AIM-HIGH, SHARP and ACCORD?

Hypercholesterolemia is one of the main risk factors for the development of atherosclerotic diseases. Multiple clinical trials of lipid-lowering agents have demonstrated that lowering cholesterol effectively reduces the risk of cardiovascular events and death. Currently, treatment with 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors ("statins") is the most commonly used approach, given their superior efficacy relative to other cholesterol lowering agents. However, not all patients on statin monotherapy achieve target cholesterol levels, and even when cholesterol lowering is successful, significant residual cardiovascular risk remains. There is increasing interest in developing combination cholesterol-modifying therapies that may augment the treatment effect and minimize the side effects of statins. Although there is currently no evidence that any of the potential therapy combinations can improve clinical outcome compared to statin monotherapy alone, results of several large ongoing trials will help to clarify this important field.

Mechanisms and prospects of food protein hydrolysates and peptide-induced hypolipidaemia

Hyperlipidaemia is an important risk factor for developing cardiovascular disease, a leading global health issue. While pharmaceutical interventions have proved efficacious in acute conditions, many hypolipidaemic drugs are known to induce adverse side effects. Due to a strong positive link between functional food components and human health, emerging research has explored the application of natural food-based strategies in disease management. One of such strategies involves the use of food proteins as precursors of peptides with a wide variety of beneficial health functions. Some plant, animal and marine-derived protein hydrolysates and peptides have shown promising hypolipidaemic properties when evaluated in vitro, in cultured mammalian cells and animal models. The products exert their functions via bile acid-binding and disruption of cholesterol micelles in the gastrointestinal tract, and by altering hepatic and adipocytic enzyme activity and gene expression of lipogenic proteins, which can modulate aberrant physiological lipid profiles. The activity of the protein hydrolysates and peptides depends on their physicochemical properties including hydrophobicity of amino acid residues but there is knowledge gap on detailed structure-function relationships and efficacy in hyperlipidaemic human subjects. Based on the prospects, commercial functional food products containing hypolipidaemic peptides have been developed for enhancement of cardiovascular health.