Nicotinamide induces liver regeneration and improves liver function by activating SIRT1

Nicotinamide enhances osteoblast differentiation through activation of the mitochondrial antioxidant defense system

Although the normal physiological level of oxidative stress is beneficial for maintaining bone homeostasis, imbalance between reactive oxygen species (ROS) production and antioxidant defense can cause various bone diseases. The purpose of this study was to determine whether nicotinamide (NAM), an NAD⁺ precursor, can support the maintenance of bone homeostasis by regulating osteoblasts. Here, we found that NAM enhances osteoblast differentiation and mitochondrial metabolism. NAM increases the expression of antioxidant enzymes, which is due to increased FOXO3A transcriptional activity via SIRT3 activation. NAM has not only a preventive effect against weak and chronic oxidative stress but also a therapeutic effect against strong and acute exposure to H₂O₂ in osteoblast differentiation. Collectively, the results indicate that NAM increases mitochondrial biogenesis and antioxidant enzyme expression through activation of the SIRT3-FOXO3A axis, which consequently enhances osteoblast differentiation. These results suggest that NAM could be a potential preventive or therapeutic agent for bone diseases caused by ROS.

Cynara Scolymus (Artichoke) Improves Liver Regeneration after Partial Liver Resection in Rats

Objective: Liver regeneration is necessary to restore hepatic mass and functional capacity after partial hepatectomy (PH). Cynara scolymus (CS) is a pharmacologically important plant that contains phenolic acids and flavonoids, and experimental studies have indicated that it has antioxidant and hepatoprotective effects. The aim of this study was to investigate the role of CS in liver regeneration after PH in rats. Methods: A total of 36 Wistar albino rats weighing 280.5 ± 18.6 g were used. CS leaf extract was administered after partial hepatectomy. The rats were sacrificed at postoperative day 14, and the histological changes were assessed. The mitotic index (MI), nucleus size, hepatocyte size, and binucleation rate (BR) of hepatocytes were assessed using hematoxylin-eosin (H&E) staining. Results: The rats that received CS extract had significant differences in liver regeneration markers, including the hepatocyte size, mitotic index, and Ki-67 proliferation index (p

Morchella importuna Polysaccharides Alleviate Carbon Tetrachloride-Induced Hepatic Oxidative Injury in Mice

This study aimed to investigate the effects of Morchella importuna polysaccharides (MIPs) on carbon tetrachloride (CCl4)-induced hepatic damage in mice. A total of 144 female mice were randomly assigned to four treatment groups, namely, control, CCl4, low-dose MIP (LMIP) group, and high-dose MIP (HMIP) group. After the 10-day experiment, serum and liver were sampled for biochemical and metabolomic analyses. The HMIPs markedly decreased the liver weight under CCl4 intoxication. Furthermore, the significantly elevated concentrations of five serum biochemical parameters, including alanine aminotransferase, aspartate aminotransferase, triglyceride, total cholesterol, and total bile acid under CCl4 treatment were subverted by MIP administration in a dose-dependent manner. Moreover, MIPs relieved the increased hepatic malonaldehyde and protein carbonyl content and the decreased superoxide dismutase and catalase contents caused by CCl4 intoxication. There was also a dose-dependent decrease in the CCl4-induced inflammatory indices, such as the levels of interleukin-1, interleukin-6, tumor necrosis factor-alpha, and myeloperoxidase, with MIP administration. Subsequent ultra-high performance liquid chromatography-tandem mass spectrometry-based serum metabolomics identified nine metabolites between the control and CCl4 groups and 10 metabolites between the HMIP and CCl4 groups, including some critical metabolites involved in flavonoid biosynthesis, amino acid metabolism, energy metabolism, and toxicant degradation. These novel findings indicate that MIPs may be of therapeutic value in alleviating the oxidative stress and inflammation caused by CCl4. Liquid chromatography-mass spectrometry-based metabolomics provides a valuable opportunity for identifying potential biomarkers and elucidating the protective mechanisms of medicinal mushrooms against hepatic oxidative injury.

Soluble epoxide hydrolase deletion attenuated nicotine-induced arterial stiffness via limiting the loss of SIRT1

Arterial stiffness, a consequence of smoking, is an underlying risk factor of cardiovascular diseases. Epoxyeicosatrienoic acids (EETs), hydrolyzed by soluble epoxide hydrolase (sEH), have beneficial effects against vascular dysfunction. However, the role of sEH knockout in nicotine-induced arterial stiffness was not characterized. We hypothesized that sEH knockout could prevent nicotine-induced arterial stiffness. In the present study, Ephx2 (the gene encodes sEH enzyme) null (Ephx2^-/-) mice and wild-type (WT) littermate mice were infused with or without nicotine and administered with or without nicotinamide [NAM, sirtuin-1 (SIRT1) inhibitor] simultaneously for 4 wk. Nicotine treatment increased sEH expression and activity in the aortas of WT mice. Nicotine infusion significantly induced vascular remodeling, arterial stiffness, and SIRT1 deactivation in WT mice, which was attenuated in Ephx2 knockout mice (Ephx2^-/- mice) without NAM treatment. However, the arterial protective effects were gone in Ephx2^-/- mice with NAM treatment. In vitro, 11,12-EET treatment attenuated nicotine-induced matrix metalloproteinase 2 (MMP2) upregulation via SIRT1-mediated yes-associated protein (YAP) deacetylation. In conclusion, sEH knockout attenuated nicotine-induced arterial stiffness and vascular remodeling via SIRT1-induced YAP deacetylation.NEW & NOTEWORTHY We presently show that sEH knockout repressed nicotine-induced arterial stiffness and extracellular matrix remodeling via SIRT1-induced YAP deacetylation, which highlights that sEH is a potential therapeutic target in smoking-induced arterial stiffness and vascular remodeling.

SIRT3 is required for liver regeneration but not for the beneficial effect of nicotinamide riboside

Liver regeneration is critical to survival after traumatic injuries, exposure to hepatotoxins, or surgical interventions, yet the underlying signaling and metabolic pathways remain unclear. In this study, we show that hepatocyte-specific loss of the mitochondrial deacetylase SIRT3 drastically impairs regeneration and worsens mitochondrial function after partial hepatectomy. Sirtuins, including SIRT3, require NAD as a cosubstrate. We previously showed that the NAD precursor nicotinamide riboside (NR) promotes liver regeneration, but whether this involves sirtuins has not been tested. Here, we show that despite their NAD dependence and critical roles in regeneration, neither SIRT3 nor its nuclear counterpart SIRT1 is required for NR to enhance liver regeneration. NR improves mitochondrial respiration in regenerating WT or mutant livers and rapidly increases oxygen consumption and glucose output in cultured hepatocytes. Our data support a direct enhancement of mitochondrial redox metabolism as the mechanism mediating improved liver regeneration after NAD supplementation and exclude signaling via SIRT1 and SIRT3. Therefore, we provide the first evidence to our knowledge for an essential role for a mitochondrial sirtuin during liver regeneration and insight into the beneficial effects of NR.

[Liver regeneration: resolved and problem issues]

Liver is an exceptional organ due to unique anatomical and physiological features, as well as advanced regenerative ability. Discovery of molecular mechanisms governing liver regeneration allowed researchers to use them to enhance liver regeneration. However, significant progress in this area was achieved through the introduction of gene therapy. In this manuscript, the authors consider stem cells for cell therapy and tissue engineering, as well as an alternative to liver transplantation.

Nicotinamide Supplementation during the In Vitro Maturation of Oocytes Improves the Developmental Competence of Preimplantation Embryos: Potential Link to SIRT1/AKT Signaling

Nicotinamide (NAM), the amide form of vitamin B3, plays pivotal roles in regulating various cellular processes including energy production and maintenance of genomic stability. The current study aimed at deciphering the effect of NAM, when administered during in vitro maturation (IVM), on the developmental competence of bovine preimplantation embryos. Our results showed that low NAM concentrations reduced the oxidative stress and improved mitochondrial profile, total cleavage and 8–16 cell stage embryo development whereas the opposite profile was observed upon exposure to high NAM concentrations (10 mM onward). Remarkably, the hatching rates of day-7 and day-8 blastocysts were significantly improved under 0.1 mM NAM treatment. Using RT-qPCR and immunofluorescence, the autophagy-related (Beclin-1 (BECN1), LC3B, and ATG5) and the apoptotic (Caspases; CASP3 and 9) markers were upregulated in oocytes exposed to high NAM concentration (40 mM), whereas only CASP3 was affected, downregulated, following 0.1 mM treatment. Additionally, the number of cells per blastocyst and the levels of SIRT1, PI3K, AKT, and mTOR were higher, while the inner cell mass-specific transcription factors GATA6, SOX2, and OCT4 were more abundant, in day-8 embryos of NAM-treated group. Taken together, to our knowledge, this is the first study reporting that administration of low NAM concentrations during IVM can ameliorate the developmental competence of embryos through the potential regulation of oxidative stress, apoptosis, and SIRT1/AKT signaling.

Sirtuin 1: A Dilemma in Transplantation

Sirtuin 1, a member of sirtuin family of histone deacetylase enzymes, has been implicated in a variety of physiologic and pathologic events, including energy metabolism, cell survival, and age-related alterations. In view of the anti-inflammatory properties of sirtuin 1 along with its protective role in ischemia reperfusion injury, it might be considered as contributing to the promotion of transplantation outcome. However, the potential ability of sirtuin 1 to induce malignancies raises some concerns about its overexpression in clinic. Moreover, despite the findings of sirtuin 1 implication in thymic tolerance induction and T regulatory (Treg) cells survival, there is also evidence for its involvement in Treg suppression and in T helper 17 cells differentiation. The identification of sirtuin 1 natural and synthetic activators leads to the proposal of sirtuin 1 as an eligible target for clinical interventions in transplantation. All positive and negative consequences of sirtuin 1 overactivation/overexpression in the allograft should therefore be studied thoroughly. Herein, we summarize previous findings concerning direct and indirect influences of sirtuin 1 manipulation on transplantation.