Riboflavin transporter SLC52A1, a target of p53, suppresses cellular senescence by activating mitochondrial complex II

Dietary riboflavin (vitamin B2) intake and osteoporosis in U.S. female adults: unveiling of association and exploration of potential molecular mechanisms

BACKGROUND

Osteoporosis characterized by deteriorating bone loss is becoming one of the serious health problems globally. Vitamin B2, also known as riboflavin, exhibiting multiple prominent physiological traits such as antioxidant effects, reducing lipid peroxidation and regulating glutathione redox cycle, allows it to be a potential agent to improve bone loss. However, the relationship between dietary vitamin B2 intake and osteoporosis remains unelucidated. The objective of this study was to explore the association between the dietary intake of vitamin B2 and bone loss in the U.S. female adults using the National Health and Nutrition Examination Survey (NHANES) database.

METHODS

Female participants with complete information on dietary vitamin B2 intake, dual-energy X-ray absorptiometry, and other essential covariates from NHANES database were included in the current study. Multivariable logistic regression and linear regression analyses were conducted to assess the relationships of dietary vitamin B2 intake with osteoporosis and bone mineral density (BMD) levels, respectively. Subgroup analyses, interaction tests, and restricted cubic spline (RCS) regression analyses were further used to verify the stability, robustness and potential nonlinearity of the association. Mediation analysis was performed to probe the role of serum alkaline phosphatase (ALP) in the aforementioned relationship, and the network pharmacology analysis was also conducted to determine the potential pathways and key targets for vitamin B2 regulating bone health.

RESULTS

A total of 4, 241 female participants from four NHANES cycles were included in this study. After multivariate adjustment, the intake of vitamin B2 was beneficially associated with reduced risk for femur osteoporosis (ORQ4 vs. Q1=0.613; 95%CI: 0.454-0.829). A higher intake of vitamin B2 (quartile 4) was significantly correlated with decreased risk of reduced femoral BMD levels, with the β being 0.020 (95%CI: 0.007-0.033), 0.015 (95%CI: 0.002-0.027), 0.020 (95%CI: 0.009-0.031) and 0.022 (95%CI: 0.006-0.037) for the BMD of total femur, femoral neck, trochanter, and intertrochanter, respectively (all P value < 0.05). Covariate total MET was found to modify the association between vitamin B2 intake and osteoporosis (P interaction = 0.0364), with the aforementioned relationship being more pronounced in the subgroup of insufficiently active individuals. Furthermore, RCS analysis revealed that vitamin B2 intake was positively and linearly associated with reduced risk for femoral OP and increased BMD levels of total femur, trochanter and intertrochanter, while positively and nonlinearly correlated with increased BMD level of femoral neck. Additionally, the association between vitamin B2 intake, osteoporosis and BMD levels was mediated by ALP, with a mediation proportion of 12.43%, 7.58%, 12.17%, 7.64%, and 6.99% for OP, total femur, femoral neck, trochanter, and intertrochanter BMD, respectively. Finally, network pharmacology analysis indicated that vitamin B2 regulating bone health mainly through pathways like HIF-1 signaling pathway, longevity regulating pathway, p53 signaling pathway, etc. CONCLUSIONS: Higher intake of vitamin B2 is positively associated with reduced risks for femoral osteoporosis and bone loss. Vitamin B2 may represent a modifiable lifestyle factor for the prevention and management of osteoporosis.

New insights into the relationship of mitochondrial metabolism and atherosclerosis

Atherosclerotic cardiovascular and cerebrovascular diseases are the number one killer of human health. In view of the important role of mitochondria in the formation and evolution of atherosclerosis, our manuscript aims to comprehensively elaborate the relationship between mitochondria and the formation and evolution of atherosclerosis from the aspects of mitochondrial dynamics, mitochondria-organelle interaction (communication), mitochondria and cell death, mitochondria and vascular smooth muscle cell phenotypic switch, etc., which is combined with genome, transcriptome and proteome, in order to provide new ideas for the pathogenesis of atherosclerosis and the diagnosis and treatment of related diseases.

Lysine-specific demethylase 1 (LSD1) suppresses cellular senescence by riboflavin uptake-dependent demethylation activity

Cellular senescence is defined as a permanent proliferation arrest caused by various stresses, including DNA damage. We have recently identified the riboflavin transporter SLC52A1, whose expression is increased in response to senescence-inducing stimuli. Interestingly, increased expression of SLC52A1 suppresses cellular senescence through the uptake of riboflavin and an increase in intracellular flavin adenine dinucleotide (FAD), an enzyme cofactor synthesized from riboflavin. However, how FAD suppresses cellular senescence has not been fully elucidated. Therefore, in this study, we focused on lysine-specific demethylase 1 (LSD1), which uses FAD as a cofactor. First, we found that LSD1 inhibition promoted DNA damage-induced cellular senescence, whereas ectopic expression of LSD1 suppressed cellular senescence, suggesting that LSD1 suppresses senescence. In addition, the demethylation activity of LSD1 against histone H3 and p53 was increased by senescence-inducing stress in a riboflavin uptake-dependent manner. Furthermore, it was revealed that the LSD1 demethylation activity was required for suppression of pro-senescence genes Sirtuin-4 and p21 whose expression is modified by methylation status of histone H3 and possibly p53, respectively. Collectively, these results suggest that the FAD increase by senescence-inducing stress leads to LSD1-mediated demethylation of histone H3 and p53, which results in the suppression of pro-senescence genes to inhibit senescence induction.

Harnessing the fundamental roles of vitamins: the potent anti-oxidants in longevity

Aging is a complex and heterogeneous biological process characterized by telomere attrition, genomic instability, mitochondrial dysfunction, and disruption in nutrient sensing. Besides contributing to the progression of cancer, metabolic disorders, and neurodegenerative diseases, these manifestations of aging also adversely affect organ function. It is crucial to understand these mechanisms and identify interventions to modulate them to promote healthy aging and prevent age-related diseases. Vitamins have emerged as potential modulators of aging beyond their traditional roles in health maintenance. There is an increasing body of evidence that hormetic effects of vitamins are responsible for activating cellular stress responses, repair mechanisms, and homeostatic processes when mild stress is induced by certain vitamins. It is evident from this dual role that vitamins play a significant role in preventing frailty, promoting resilience, and mitigating age-related cellular damage. Moreover, addressing vitamin deficiencies in the elderly could have a significant impact on slowing aging and extending life expectancy. A review of recent advances in the role of vitamins in delaying aging processes and promoting multiorgan health is presented in this article. The purpose of this paper is to provide a comprehensive framework for using vitamins as strategic tools for fostering longevity and vitality. It offers a fresh perspective on vitamins' role in aging research by bridging biological mechanisms and clinical opportunities.

A nutrigeroscience approach: Dietary macronutrients and cellular senescence

Cellular senescence, a process in which a cell exits the cell cycle in response to stressors, is one of the hallmarks of aging. Senescence and the senescence-associated secretory phenotype (SASP)-a heterogeneous set of secreted factors that disrupt tissue homeostasis and promote the accumulation of senescent cells-reprogram metabolism and can lead to metabolic dysfunction. Dietary interventions have long been studied as methods to combat age-associated metabolic dysfunction, promote health, and increase lifespan. A growing body of literature suggests that senescence is responsive to diet, both to calories and specific dietary macronutrients, and that the metabolic benefits of dietary interventions may arise in part through reducing senescence. Here, we review what is currently known about dietary macronutrients' effect on senescence and the SASP, the nutrient-responsive molecular mechanisms that may mediate these effects, and the potential for these findings to inform the development of a nutrigeroscience approach to healthy aging.

Exploring the impact of flavin homeostasis on cancer cell metabolism

Flavins and their associated proteins have recently emerged as compelling players in the landscape of cancer biology. Flavins, encompassing flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD), serve as coenzymes in a multitude of cellular processes, such as metabolism, apoptosis, and cell proliferation. Their involvement in oxidative phosphorylation, redox homeostasis, and enzymatic reactions has long been recognized. However, recent research has unveiled an extended role for flavins in the context of cancer. In parallel, riboflavin transporters (RFVTs), FAD synthase (FADS), and riboflavin kinase (RFK) have gained prominence in cancer research. These proteins, responsible for riboflavin uptake, FAD biosynthesis, and FMN generation, are integral components of the cellular machinery that governs flavin homeostasis. Dysregulation in the expression/function of these proteins has been associated with various cancers, underscoring their potential as diagnostic markers, therapeutic targets, and key determinants of cancer cell behavior. This review embarks on a comprehensive exploration of the multifaceted role of flavins and of the flavoproteins involved in nucleus-mitochondria crosstalk in cancer. We journey through the influence of flavins on cancer cell energetics, the modulation of RFVTs in malignant transformation, the diagnostic and prognostic significance of FADS, and the implications of RFK in drug resistance and apoptosis. This review also underscores the potential of these molecules and processes as targets for novel diagnostic and therapeutic strategies, offering new avenues for the battle against this relentless disease.

Unlocking the Mitochondria for Nanomedicine-based Treatments: Overcoming Biological Barriers, Improving Designs, and Selecting Verification Techniques

Enhanced targeting approaches will support the treatment of diseases associated with dysfunctional mitochondria, which play critical roles in energy generation and cell survival. Obstacles to mitochondria-specific targeting include the presence of distinct biological barriers and the need to pass through (or avoid) various cell internalization mechanisms. A range of studies have reported the design of mitochondrially-targeted nanomedicines that navigate the complex routes required to influence mitochondrial function; nonetheless, a significant journey lies ahead before mitochondrially-targeted nanomedicines become suitable for clinical use. Moving swiftly forward will require safety studies, in vivo assays confirming effectiveness, and methodologies to validate mitochondria-targeted nanomedicines' subcellular location/activity. From a nanomedicine standpoint, we describe the biological routes involved (from administration to arrival within the mitochondria), the features influencing rational design, and the techniques used to identify/validate successful targeting. Overall, rationally-designed mitochondria-targeted-based nanomedicines hold great promise for precise subcellular therapeutic delivery.

Nutritional components as mitigators of cellular senescence in organismal aging: a comprehensive review

The process of cellular senescence is rapidly emerging as a modulator of organismal aging and disease. Targeting the development and removal of senescent cells is considered a viable approach to achieving improved organismal healthspan and lifespan. Nutrition and health are intimately linked and an appropriate dietary regimen can greatly impact organismal response to stress and diseases including during aging. With a renewed focus on cellular senescence, emerging studies demonstrate that both primary and secondary nutritional elements such as carbohydrates, proteins, fatty acids, vitamins, minerals, polyphenols, and probiotics can influence multiple aspects of cellular senescence. The present review describes the recent molecular aspects of cellular senescence-mediated understanding of aging and then studies available evidence of the cellular senescence modulatory attributes of major and minor dietary elements. Underlying pathways and future research directions are deliberated to promote a nutrition-centric approach for targeting cellular senescence and thus improving human health and longevity.