Creatinine, total cysteine and uric acid are associated with serum retinol in patients with cardiovascular disease

Genetic influences on circulating retinol and its relationship to human health

Retinol is a fat-soluble vitamin that plays an essential role in many biological processes throughout the human lifespan. Here, we perform the largest genome-wide association study (GWAS) of retinol to date in up to 22,274 participants. We identify eight common variant loci associated with retinol, as well as a rare-variant signal. An integrative gene prioritisation pipeline supports novel retinol-associated genes outside of the main retinol transport complex (RBP4:TTR) related to lipid biology, energy homoeostasis, and endocrine signalling. Genetic proxies of circulating retinol were then used to estimate causal relationships with almost 20,000 clinical phenotypes via a phenome-wide Mendelian randomisation study (MR-pheWAS). The MR-pheWAS suggests that retinol may exert causal effects on inflammation, adiposity, ocular measures, the microbiome, and MRI-derived brain phenotypes, amongst several others. Conversely, circulating retinol may be causally influenced by factors including lipids and serum creatinine. Finally, we demonstrate how a retinol polygenic score could identify individuals more likely to fall outside of the normative range of circulating retinol for a given age. In summary, this study provides a comprehensive evaluation of the genetics of circulating retinol, as well as revealing traits which should be prioritised for further investigation with respect to retinol related therapies or nutritional intervention.

Inadequate Niacin Intake Disrupts Growth and Retinol Homeostasis Resulting in Higher Liver and Lower Serum Retinol Concentrations in Male Rats

BACKGROUND

Niacin-derived nicotinamide adenine dinucleotide is an essential cofactor for many dehydrogenase enzymes involved in vitamin A (VA) metabolism. Several countries with high prevalence of VA deficiency rely on maize, a poor source of available niacin, as a dietary staple.

OBJECTIVES

This study evaluated the interaction of dietary niacin on VA homeostasis using male Sprague-Dawley rats, aged 21 d (baseline body weight 88.3 ± 6.6 g).

METHODS

After 1 wk of acclimation, baseline samples were collected (n = 4). Remaining rats (n = 54) were split into 9 groups to receive low tryptophan, VA-deficient feed with 3 different amounts of niacin (0, 15, or 30 mg/kg) and 3 different oral VA doses (50, 350, or 3500 nmol/d) in a 3 × 3 design. After 4 wk, the study was terminated. Serum, livers, and small intestine were analyzed for retinoids using high-performance liquid chromatography. Niacin and metabolites were evaluated with nuclear magnetic resonance. Plasma pyridoxal-P (PLP) was measured with high-performance liquid chromatography.

RESULTS

Niacin intake correlated with serum retinol concentrations (r = 0.853, P < 0.001). For rats receiving the highest VA dose, liver retinol concentrations were lower in the 30-mg/kg niacin group (5.39 ± 0.27 μmol/g) than those in the 0-mg/kg and 15-mg/kg groups (9.18 ± 0.62 and 8.75 ± 0.07 μmol/g, respectively; P ≤ 0.05 for both). This phenomenon also occurred in the lower VA doses (P ≤ 0.05 for all). Growth and tissue weight at endline were associated with niacin intake (P ≤ 0.001 for all). Plasma PLP correlated with estimated niacin intake (r = 0.814, P < 0.001).

CONCLUSIONS

Optimal niacin intake is associated with lower liver VA and higher serum retinol and plasma PLP concentrations. The extent to which vitamin B intake affects VA homeostasis requires further investigation to determine if the effects are maintained in humans.

Metabolomic Profiles of Plasma Retinol-Associated Dyslipidemia in Men and Women

Background and Aims: Studies of both animals and humans show that a high intake of vitamin A is associated with a lower risk of dyslipidemia. However, an association of plasma retinol levels with dyslipidemia is unclear. Therefore, the aim of this study is to investigate an association between plasma retinol and dyslipidemia and to identify related metabolites and pathways in the general population. Methods: We included 250 participants aged 20-80 years from the Wellness Living Laboratory (WELL) China cohort. Associations between plasma retinol levels and dyslipidemia were analyzed using adjusted logistic models. Related metabolites were identified using ANCOVA, adjusted for the false discovery rate (FDR) and used for pathway analyses. Because there are sex differences in plasma retinol levels, all analyses were conducted separately by sex. Results: Plasma retinol was significantly higher in men than in women. A positive association between plasma retinol and dyslipidemia was found in both sexes. In men, the 2nd and 3rd tertiles showed significantly higher proportions of dyslipidemia than the 1st tertile (1st tertile vs. 2nd tertile: p = 0.026; 1st tertile vs. 3rd tertile: p = 0.003). In women, the 3rd tertile showed a significantly higher proportion of dyslipidemia than the 1st and 2nd tertile (3rd tertile vs. 1st tertile: p = 0.002, 3rd tertile vs. 2nd tertile: p = 0.002). Overall, 75 and 30 metabolites were significantly associated with retinol levels in men and women, respectively. According to these metabolites, lipid metabolic pathways, including glycerophospholipid, arachidonic acid, linoleic acid, alpha-linolenic acid, and glycosylphosphatidylinositol (GPI), as well as steroid hormone biosynthesis pathways were found to overlap across the sexes. These pathways showed that elevated retinol levels might be associated with hormone metabolism and inflammation status. Conclusions: We found a positive association between plasma retinol levels and dyslipidemia. Related metabolomic profiles and interrupted pathways showed that such an increase might be associated with steroid hormone synthesis and inflammation. In addition, large, population-based longitudinal studies and intervention studies are needed to confirm the role of retinol in lipid metabolism and the prevention of cardiovascular disease (CVD).

Mitochondria-targeted ratiometric fluorescent imaging of cysteine

As an indispensable biothiol, cysteine (Cys) plays a critical part in cellular redox homeostasis, and pathological and physiological processes. One of the main sources of reactive oxygen species (ROS) in human cells is the substrate end of the respiratory chain in the mitochondrial inner membrane. Therefore, it is valuable to develop probes targeting mitochondria to detect Cys. In this work, we designed a novel fluorescent probe, 2-(2-(6-(acryloyloxy) naphthalen-2-yl) vinyl)-3-ethylbenzothiazol-3-ium (ANET). The naphthyl benzothiazole is the fluorophore group and the acrylate moiety is the Cys response site to avoid the interference of homocysteine (Hcy) and glutathione (GSH). ANET combines multiple strengths for detecting Cys: targeting mitochondria, ratiometric fluorescence, high selectivity, and a large Stokes shift. After ANET reacted with Cys, the fluorescence signals changed from green (λem = 525 nm) to orange red (λem = 595 nm), and the detection limit was calculated to be 74 nM through a linear relationship between ratiometric fluorescence F595/F525 and Cys concentration. The imaging of Cys was confirmed in HepG2 cells.

β-blocker use and risk of all-cause mortality in patients with coronary heart disease: effect modification by serum vitamin A

AIMS 

Blockade of β-adrenoceptors reduces sympathetic nervous system activity and improves survival in patients with heart failure with reduced left ventricular ejection fraction (HFrEF); however, any improvement in longevity among patients with coronary heart disease (CHD) but without HFrEF remains uncertain. Vitamin A has been linked to the activation of tyrosine hydroxylase, the rate-limiting enzyme in the catecholamine synthesis pathway. We investigated if vitamin A status modified the association of β-blocker use with the risk of all-cause mortality.

METHODS AND RESULTS 

A total of 4118 patients undergoing elective coronary angiography for suspected stable angina pectoris, of whom the majority had normal left ventricular ejection fraction (LVEF) were studied. Hazard ratios (HRs) of all-cause mortality comparing treatment vs. non-treatment of β-blockers according to the tertiles of serum vitamin A were explored in Cox proportional hazards regression models. During a median follow-up of 10.3 years, 897 patients (21.8%) died. The overall LVEF was 65% and 283 (6.9%) had anamnestic HF. After multivariable adjustments for traditional risk factors, medical history, and drug therapies of cardiovascular disease, β-blocker treatment was inversely associated with the risk of all-cause mortality [HR : 0.84; 95% CI (confidence interval), 0.72-0.97]. However, the inverse association was generally stronger among patients in the upper serum vitamin A tertile (HR :0.66; 95% CI, 0.50-0.86; Pinteraction = 0.012), which remained present after excluding patients with LVEF < 40%.

CONCLUSION 

In patients with suspected CHD, β-blocker treatment was associated with improved survival primarily among patients with high serum vitamin A levels.

Metabolomics study of the effect of smoking and high-fat diet on metabolic responses and related mechanism following myocardial infarction in mice

AIMS

The present study aimed to evaluate the impact of chronic smoking and high fat diet on the post-MI metabolic features and inflammation resolution.

MAIN METHODS

Eight weeks old C57BL/6J mice were randomly divided into control(C), smoking(S), high-fat diet(H), and smoking plus high-fat diet(SH) groups for 16 weeks. MI was induced by permanent coronary ligation. Cardiac function was assessed by echocardiography at 5 days post-MI. The infarcted heart tissue was collected for the metabolic profile using metabolomics and quantification of pro-resolving mediators with immunoblotting.

KEY FINDINGS

Percentage of fractional shortening (FS%) and ejection fraction (EF%) were further reduced in SH than that in either S or H group (P < 0.05). Myocardial metabolomics analysis indicated that 3, 6, and 11 disturbed metabolic pathways were considered as the most relevant pathway (Impact > 0.1) in S, H, and SH groups, respectively. The common most relevant pathway among three groups was arachidonic acid metabolism. The levels of arachidonic acid and TXB2 were significantly higher, while the 5-LOX and HO-1 expression was significantly lower in SH group than that in either S or H group (P < 0.05).

SIGNIFICANCE

Smoking superimposed on high-fat diet could aggravate post-MI cardiac dysfunction and cause significant disturbance of metabolic pathways associated with inflammation, energy metabolism, as well as excessive oxidative stress. Smoking combined with high-fat diet could also magnify the post-MI inflammation and impair the resolution of inflammation in MI mice.

Retinol, Retinoic Acid, and Retinol-Binding Protein 4 are Differentially Associated with Cardiovascular Disease, Type 2 Diabetes, and Obesity: An Overview of Human Studies

Vitamin A is a fat-soluble essential nutrient obtained from plant- and animal-based sources that has roles in growth, vision, and metabolism. Vitamin A circulates mainly as retinol bound to retinol-binding protein 4 (RBP4), and is delivered to tissues and converted to retinoic acid, which is a ligand for several nuclear receptors. In recent years, aspects of vitamin A metabolism have been under scrutiny with regards to the development of metabolic and lifestyle diseases including cardiovascular disease (CVD), type 2 diabetes mellitus (T2DM), and overweight and obesity in humans. Studies have mainly focused on RBP4 in this context, whereas the major circulating form, retinol, and the major bioactive form, retinoic acid, have been overlooked in this regard until recently. As one of the main roles of RBP4 is to deliver retinol to tissues for biological action, the associations of retinol and retinoic acid with these diseases must also be considered. In this review, we summarize and discuss recent and available evidence from human studies with focus on retinol, retinoic acid, and RBP4 and provide an overview of these crucial components of vitamin A metabolism in CVD, T2DM, and obesity. In summary, retinol was found to be both inversely and positively associated with CVD whereas the associations with T2DM and obesity were less clear. Although only a few studies have been published on retinoic acid, it was inversely associated with CVD. In contrast, serum RBP4 was mostly found to be positively associated with CVD, T2DM, and obesity. At present, it is difficult to ascertain why the reported associations differ depending on the compound under study, but there is a clear imbalance in the literature in disfavor of retinol and retinoic acid, which needs to be considered in future human studies.