A systematic review and meta-analysis of the association between vitamin A intake, serum vitamin A, and risk of liver cancer

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.

Role of vitamins A, C, D, E in cancer prevention and therapy: therapeutic potentials and mechanisms of action

Cancer, a leading global cause of mortality, arises from intricate interactions between genetic and environmental factors, fueling uncontrolled cell growth. Amidst existing treatment limitations, vitamins have emerged as promising candidates for cancer prevention and treatment. This review focuses on Vitamins A, C, E, and D because of their protective activity against various types of cancer. They are essential as human metabolic coenzymes. Through a critical exploration of preclinical and clinical studies via PubMed and Google Scholar, the impact of these vitamins on cancer therapy was analyzed, unraveling their complicated mechanisms of action. Interestingly, vitamins impact immune function, antioxidant defense, inflammation, and epigenetic regulation, potentially enhancing outcomes by influencing cell behavior and countering stress and DNA damage. Encouraging clinical trial results have been observed; however, further well-controlled studies are imperative to validate their effectiveness, determine optimal dosages, and formulate comprehensive cancer prevention and treatment strategies. Personalized supplementation strategies, informed by medical expertise, are pivotal for optimal outcomes in both clinical and preclinical contexts. Nevertheless, conclusive evidence regarding the efficacy of vitamins in cancer prevention and treatment is still pending, urging further research and exploration in this compelling area of study.

Vitamin A - a scoping review for Nordic nutrition Recommendations 2023

Vitamin A refers to a group of fat-soluble compounds with retinol activity, including all-trans retinol and pro-vitamin A carotenoids. Bioactive compounds include retinal and all-trans retinoic acid with important functions in vision, immune function, growth, and development. The literature search that was performed for the current scoping review yielded a total of seven publications relevant to setting the recommended daily intake for vitamin A. In total, six publications assessed the relationship of serum retinol and/or dietary vitamin A intake with fracture risk (n = 2), cancer (n = 3), and deficiency after bariatric surgery (n = 1). One additional report by the European Food Safety Administration (EFSA) with updated average requirements was included. The outcomes-based systematic reviews and meta-analyses showed positive associations for vitamin A intake and serum retinol with risk of hip fracture. Weak or inconclusive associations were observed for cancer or obesity. One publication by EFSA with updated estimated average requirements and population reference intakes for dietary vitamin A intakes was published in 2015. The EFSA recommendations and estimated average requirements are based on a European reference population, with body weights derived from an assumed body mass index of 22, which might be too low and not representative of the Nordic and Baltic populations, and consequently resulting in lower estimated average requirements and recommendations. In conclusion, there were limited new outcomes-based data for vitamin A and health outcomes.

Diet-Derived Circulating Antioxidants and Risk of Digestive System Tumors: A Mendelian Randomization Study

Previous observational case-control studies have shown significant controversy over the impact of dietary intake-related circulating antioxidants on the risk of digestive system tumors. We conducted a two-sample Mendelian randomized (MR) analysis to determine whether there was a significant causal relationship between increased levels of circulating antioxidants and digestive system tumors. Our circulating antioxidants (vitamin C, carotenoids, vitamin A, and vitamin E) were derived from absolute circulating antioxidants and circulating antioxidant metabolites, and their corresponding instrumental variables were screened from published studies. The digestive system tumors we studied included colorectal, gastric, pancreatic, liver, and esophageal cancer, and the corresponding summary GAWS (genome-wide association study) data were obtained from the UK Biobank database. We first evaluated the causal relationship between each tumor and circulating antioxidants and then used meta-analysis to summarize the results of MR analysis of different tumors. No significant associations were noted for genetically predicted circulating antioxidants and higher risk of digestive system tumors in our study. The pooled ORs (odds ratio) are 0.72 (95% CI: 0.46-1.11; β-carotene), 0.93 (95% CI: 0.81-1.08; lycopene), 2.12 (95% CI: 0.31-14.66; retinol), and 0.99 (95% CI: 0.96-1.02; ascorbate) for absolute circulating antioxidants; for circulating antioxidant metabolites, the pooled ORs for digestive system tumors risk per unit increase of antioxidants were 1.29 (95% CI: 0.39-4.28; α-tocopherol), 1.72 (95% CI: 0.85-3.49; γ-tocopherol), 1.05 (95% CI: 0.96-1.14; retinol), and 1.21 (95% CI: 0.97-1.51; ascorbate), respectively. Our study suggested that increased levels of dietary-derived circulating antioxidants did not reduce the risk of digestive system tumors.

Dietary inflammatory index and incidence of and death from primary liver cancer: A prospective study of 103,902 American adults

Chronic inflammation plays an important role in primary liver cancer (PLC) etiology and can be influenced by dietary habits. No prospective study has investigated the association of dietary inflammatory index (DII) with PLC incidence and mortality. Therefore, we used prospective data from the Prostate, Lung, Colorectal and Ovarian Cancer Screening Trial to fill this gap. The DII was calculated from a validated 137-item food frequency questionnaire in a cohort of 103,902 individuals. Cox regression was used to estimate hazard ratios (HRs) for PLC incidence, and competing risk regression was used to estimate subdistribution HRs (SHRs) for PLC mortality. Restricted cubic spline regression was employed to identify the potential dose-response pattern. A total of 120 PLC cases and 102 PLC deaths were observed during follow-up. Higher DII scores from food and supplement were found to be associated with higher risks of developing PLC (HR_{Tertile 3 vs. 1} 2.05; 95% confidence interval [CI] 1.23-3.41) and death from this disease (SHR_{Tertile 3 vs. 1} 1.97; 95% CI 1.13-3.41). Similar results were obtained for DII score from food only. A nonlinear dose-response pattern was identified for the aforementioned associations (all p_nonlinearity  < 0.05). Overall, a more pro-inflammatory diet, as suggested by higher DII scores, is associated with higher risks of PLC incidence and mortality. These findings indicate that encouraging intake of more anti-inflammatory dietary components and reducing intake of pro-inflammatory components represent an attractive strategy to reduce PLC incidence and mortality.

Over-Expression of LcPDS, LcZDS, and LcCRTISO, Genes From Wolfberry for Carotenoid Biosynthesis, Enhanced Carotenoid Accumulation, and Salt Tolerance in Tobacco

It is of great importance to combine stress tolerance and plant quality for breeding research. In this study, the role of phytoene desaturase (PDS), ζ-carotene desaturase (ZDS) and carotene isomerase (CRTISO) in the carotenoid biosynthesis are correlated and compared. The three genes were derived from Lycium chinenses and involved in the desaturation of tetraterpene. Their over-expression significantly increased carotenoid accumulation and enhanced photosynthesis and salt tolerance in transgenic tobacco. Up-regulation of almost all the genes involved in the carotenoid biosynthesis pathway and only significant down-regulation of lycopene ε-cyclase (ε-LCY) gene were detected in those transgenic plants. Under salt stress, proline content, and activities of catalase (CAT), peroxidase (POD) and superoxide dismutase (SOD) were significantly increased, whereas malonaldehyde (MDA) and hydrogen peroxide (H2O2) accumulated less in the transgenic plants. The genes encoding ascorbate peroxidase (APX), CAT, POD, SOD, and pyrroline-5-carboxylate reductase (P5CR) were shown to responsive up-regulated significantly under the salt stress in the transgenic plants. This study indicated that LcPDS, LcZDS, and LcCRTISO have the potential to improve carotenoid content and salt tolerance in higher plant breeding.