Fueling genome maintenance: On the versatile roles of NAD+ in preserving DNA integrity

A Molecular Perspective and Role of NAD+ in Ovarian Aging

The decline in female fecundity is linked to advancing chronological age. The ovarian reserve diminishes in quantity and quality as women age, impacting reproductive efficiency and the aging process in the rest of the body. NAD+ is an essential coenzyme in cellular energy production, metabolism, cell signaling, and survival. It is involved in aging and is linked to various age-related conditions. Hallmarks associated with aging, diseases, and metabolic dysfunctions can significantly affect fertility by disturbing the delicate relationship between energy metabolism and female reproduction. Enzymes such as sirtuins, PARPs, and CD38 play essential roles in NAD+ biology, which actively consume NAD+ in their enzymatic activities. In recent years, NAD+ has gained much attention for its role in aging and age-related diseases like cancer, Alzheimer's, cardiovascular diseases, and neurodegenerative disorders, highlighting its involvement in various pathophysiological processes. However, its impact on female reproduction is not well understood. This review aims to bridge this knowledge gap by comprehensively exploring the complex interplay between NAD+ biology and female reproductive aging and providing valuable information that could help develop plans to improve women's reproductive health and prevent fertility issues.

WRN loss accelerates abnormal adipocyte metabolism in Werner syndrome

BACKGROUND

Metabolic dysfunction is one of the main symptoms of Werner syndrome (WS); however, the underlying mechanisms remain unclear. Here, we report that loss of WRN accelerates adipogenesis at an early stage both in vitro (stem cells) and in vivo (zebrafish). Moreover, WRN depletion causes a transient upregulation of late-stage of adipocyte-specific genes at an early stage.

METHODS

In an in vivo study, we generated wrn-/- mutant zebrafish and performed histological stain and Oil Red O staining to assess the fat metabolism. In an in vitro study, we used RNA-seq and ATAC-seq to profile the transcriptional features and chromatin accessibility in WRN depleted adipocytes. Moreover, we performed ChIP-seq to further study the regulatory mechanisms of metabolic dysfunction in WS.

RESULTS

Our findings show that mechanistically WRN deficiency causes SMARCA5 upregulation. SMARCA5 is crucial in chromatin remodeling and gene regulation. Additionally, rescuing WRN could normalize SMARCA5 expression and adipocyte differentiation. Moreover, we find that nicotinamide riboside (NR) supplementation restores adipocyte metabolism in both stem cells and zebrafish models.

CONCLUSIONS

Our findings unravel a new mechanism for the influence of WRN in the early stage of adipogenesis and provide a possible treatment for metabolic dysfunction in WS. These data provide promising insights into potential therapeutics for ageing and ageing-related diseases.

CD38 regulates ovarian function and fecundity via NAD+ metabolism

Mammalian female reproductive lifespan is typically significantly shorter than life expectancy and is associated with a decrease in ovarian NAD+ levels. However, the mechanisms underlying this loss of ovarian NAD+ are unclear. Here, we show that CD38, an NAD+ consuming enzyme, is expressed in the ovarian extrafollicular space, primarily in immune cells, and its levels increase with reproductive age. Reproductively young mice lacking CD38 exhibit larger primordial follicle pools, elevated ovarian NAD+ levels, and increased fecundity relative to wild type controls. This larger ovarian reserve results from a prolonged window of follicle formation during early development. However, the beneficial effect of CD38 loss on reproductive function is not maintained at advanced age. Our results demonstrate a novel role of CD38 in regulating ovarian NAD+ metabolism and establishing the ovarian reserve, a critical process that dictates a female's reproductive lifespan.

Absence of mitochondrial SLC25A51 enhances PARP1-dependent DNA repair by increasing nuclear NAD+ levels

Though the effect of the recently identified mitochondrial NAD+ transporter SLC25A51 on glucose metabolism has been described, its contribution to other NAD+-dependent processes throughout the cell such as ADP-ribosylation remains elusive. Here, we report that absence of SLC25A51 leads to increased NAD+ concentration not only in the cytoplasm and but also in the nucleus. The increase is not associated with upregulation of the salvage pathway, implying an accumulation of constitutively synthesized NAD+ in the cytoplasm and nucleus. This results in an increase of PARP1-mediated nuclear ADP-ribosylation, as well as faster repair of DNA lesions induced by different single-strand DNA damaging agents. Lastly, absence of SLC25A51 reduces both MMS/Olaparib induced PARP1 chromatin retention and the sensitivity of different breast cancer cells to PARP1 inhibition. Together these results provide evidence that SLC25A51 might be a novel target to improve PARP1 inhibitor based therapies by changing subcellular NAD+ redistribution.

Highly responsive and sensitive non-enzymatic electrochemical sensor for the detection of β-NADH in food, environmental and biological samples using AuNP on polydopamine/titanium carbide composite

In this study, a polydopamine/titanium carbide adorned with gold nanoparticles (Au@PDA/TiC) composite was prepared by a simple stirring technique and it was used for the dual-technique detection of β-Nicotinamide adenine dinucleotide (NADH). The Au@PDA/TiC-modified glassy carbon electrode (GCE) oxidized NADH at a very low oxidation potential of approximately 0.60 V vs Ag/AgCl in pH = 7.0 (0.1 M PBS) via the transfer of two electrons and one proton (from NADH to NAD⁺). Based on the (i-t) amperometry mode, NADH can be quantified with a linear range of 0.018-674 μM and LOD of 0.0062 µM. In addition to the DPV mode, the electrochemical sensor had a linearity of 5-450 µM with a LOD of 3.17 µM. The developed sensor exhibited remarkable analytical performances concerning high sensitivity, electrocatalytic activity, low detection limit, wide linearity, appreciable specificity, repeatability, stability, reproducibility, and adequate recovery results in food, environmental and biological samples.

The CD73 immune checkpoint promotes tumor cell metabolic fitness

CD73 is an ectonucleotidase overexpressed on tumor cells that suppresses anti-tumor immunity. Accordingly, several CD73 inhibitors are currently being evaluated in the clinic, including in large randomized clinical trials. Yet, the tumor cell-intrinsic impact of CD73 remain largely uncharacterized. Using metabolomics, we discovered that CD73 significantly enhances tumor cell mitochondrial respiration and aspartate biosynthesis. Importantly, rescuing aspartate biosynthesis was sufficient to restore proliferation of CD73-deficient tumors in immune deficient mice. Seahorse analysis of a large panel of mouse and human tumor cells demonstrated that CD73 enhanced oxidative phosphorylation (OXPHOS) and glycolytic reserve. Targeting CD73 decreased tumor cell metabolic fitness, increased genomic instability and suppressed poly ADP ribose polymerase (PARP) activity. Our study thus uncovered an important immune-independent function for CD73 in promoting tumor cell metabolism, and provides the rationale for previously unforeseen combination therapies incorporating CD73 inhibition.

DNA Damage-Mediated Neurotoxicity in Parkinson’s Disease

Parkinson’s disease (PD) is the second most common neurodegenerative disease around the world; however, its pathogenesis remains unclear so far. Recent advances have shown that DNA damage and repair deficiency play an important role in the pathophysiology of PD. There is growing evidence suggesting that DNA damage is involved in the propagation of cellular damage in PD, leading to neuropathology under different conditions. Here, we reviewed the current work on DNA damage repair in PD. First, we outlined the evidence and causes of DNA damage in PD. Second, we described the potential pathways by which DNA damage mediates neurotoxicity in PD and discussed the precise mechanisms that drive these processes by DNA damage. In addition, we looked ahead to the potential interventions targeting DNA damage and repair. Finally, based on the current status of research, key problems that need to be addressed in future research were proposed.

Cellular rejuvenation: molecular mechanisms and potential therapeutic interventions for diseases

The ageing process is a systemic decline from cellular dysfunction to organ degeneration, with more predisposition to deteriorated disorders. Rejuvenation refers to giving aged cells or organisms more youthful characteristics through various techniques, such as cellular reprogramming and epigenetic regulation. The great leaps in cellular rejuvenation prove that ageing is not a one-way street, and many rejuvenative interventions have emerged to delay and even reverse the ageing process. Defining the mechanism by which roadblocks and signaling inputs influence complex ageing programs is essential for understanding and developing rejuvenative strategies. Here, we discuss the intrinsic and extrinsic factors that counteract cell rejuvenation, and the targeted cells and core mechanisms involved in this process. Then, we critically summarize the latest advances in state-of-art strategies of cellular rejuvenation. Various rejuvenation methods also provide insights for treating specific ageing-related diseases, including cellular reprogramming, the removal of senescence cells (SCs) and suppression of senescence-associated secretory phenotype (SASP), metabolic manipulation, stem cells-associated therapy, dietary restriction, immune rejuvenation and heterochronic transplantation, etc. The potential applications of rejuvenation therapy also extend to cancer treatment. Finally, we analyze in detail the therapeutic opportunities and challenges of rejuvenation technology. Deciphering rejuvenation interventions will provide further insights into anti-ageing and ageing-related disease treatment in clinical settings.

Molecular crosstalk between circadian clock and cancer and therapeutic implications

The circadian clock governs activity of many physiological processes, thereby playing a pivotal role in human health. Circadian disruption is closely associated with cancer development; in particular, recent discoveries have provided strong evidence supporting specific functions of different molecular clock components in either promoting or inhibiting tumorigenesis. This narrative review aims to summarize the existing data on molecular connections between the clock and cancer. These results along with future efforts pave the road to targeting the circadian clock as a novel pathway for therapeutic intervention. Given the implications of chrono-nutrition interventions such as time-restricted feeding in extending lifespan, chrono-nutrition may have preventive and therapeutic applications for individuals with and at-risk of age-related diseases including cancer.