Biomarkers of Cellular Senescence and Aging: Current State-of-the-Art, Challenges and Future Perspectives.

Population aging has increased the global prevalence of aging-related diseases, including cancer, sarcopenia, neurological disease, arthritis, and heart disease. Understanding aging, a fundamental biological process, has led to breakthroughs in several fields. Cellular senescence, evinced by flattened cell bodies, vacuole formation, and cytoplasmic granules, ubiquitously plays crucial roles in tissue remodeling, embryogenesis, and wound repair as well as in cancer therapy and aging. The lack of universal biomarkers for detecting and quantifying senescent cells, in vitro and in vivo, constitutes a major limitation. The applications and limitations of major senescence biomarkers, including senescence-associated ß-galactosidase staining, telomere shortening, cell-cycle arrest, DNA methylation, and senescence-associated secreted phenotypes are discussed. Furthermore, explore senotherapeutic approaches for aging-associated diseases and cancer. In addition to the conventional biomarkers, this review highlighted the in vitro, in vivo, and disease models used for aging studies. Further, technologies from the current decade including multi-omics and computational methods used in the fields of senescence and aging are also discussed in this review. Understanding aging-associated biological processes by using cellular senescence biomarkers can enable therapeutic innovation and interventions to improve the quality of life of older adults.

Understanding the relationship between cancer associated cachexia and hypoxia-inducible factor-1.

Cancer-associated cachexia (CAC) is a multifactorial disorder characterized by an unrestricted loss of body weight as a result of muscle and adipose tissue atrophy. Cachexia is influenced by several factors, including decreased metabolic activity and food intake, an imbalance between energy uptake and expenditure, excessive catabolism, and inflammation. Cachexia is highly associated with all types of cancers responsible for more than half of cancer-related mortalities worldwide. In healthy individuals, adipose tissue significantly regulates energy balance and glucose homeostasis. However, in metastatic cancer patients, CAC occurs mainly because of an imbalance between muscle protein synthesis and degradation which are organized by certain extracellular ligands and associated signaling pathways. Under hypoxic conditions, hypoxia-inducible factor-1 (HIF-1α) accumulated and translocated to the nucleus and activate numerous genes involved in cell survival, invasion, angiogenesis, metastasis, metabolic reprogramming, and cancer stemness. On the other hand, the ubiquitination proteasome pathway is inhibited during low O2 levels which promote muscle wasting in cancer patients. Therefore, understanding the mechanism of the HIF-1 pathway and its metabolic adaptation to biomolecules is important for developing a novel therapeutic method for cancer and cachexia therapy. Even though many HIF inhibitors are already in a clinical trial, their mechanism of action remains unknown. With this background, this review summarizes the basic concepts of cachexia, the role of inflammatory cytokines, pathways connected with cachexia with special reference to the HIF-1 pathway and its regulation, metabolic changes, and inhibitors of HIFs.

Unlocking Prognostic Genes and Multi-Targeted Therapeutic Bioactives from Herbal Medicines to Combat Cancer-Associated Cachexia: A Transcriptomics and Network Pharmacology Approach.

Cachexia is a devastating fat tissue and muscle wasting syndrome associated with every major chronic illness, including cancer, chronic obstructive pulmonary disease, kidney disease, AIDS, and heart failure. Despite two decades of intense research, cachexia remains under-recognized by oncologists. While numerous drug candidates have been proposed for cachexia treatment, none have achieved clinical success. Only a few drugs are approved by the FDA for cachexia therapy, but a very low success rate is observed among patients. Currently, the identification of drugs from herbal medicines is a frontier research area for many diseases. In this milieu, network pharmacology, transcriptomics, cheminformatics, and molecular docking approaches were used to identify potential bioactive compounds from herbal medicines for the treatment of cancer-related cachexia. The network pharmacology approach is used to select the 32 unique genes from 238 genes involved in cachexia-related pathways, which are targeted by 34 phytocompounds identified from 12 different herbal medicines used for the treatment of muscle wasting in many countries. Gene expression profiling and functional enrichment analysis are applied to decipher the role of unique genes in cancer-associated cachexia pathways. In addition, the pharmacological properties and molecular interactions of the phytocompounds were analyzed to find the target compounds for cachexia therapy. Altogether, combined omics and network pharmacology approaches were used in the current study to untangle the complex prognostic genes involved in cachexia and phytocompounds with anti-cachectic efficacy. However, further functional and experimental validations are required to confirm the efficacy of these phytocompounds as commercial drug candidates for cancer-associated cachexia.

Astragalus Complanatus Ethanol Attenuates Septic Shock by Exerting Anti-Inflammatory Effects on Macrophages.

Sepsis is a systemic inflammatory syndrome that results in multiple-organ failure caused by a dysregulated host immune response to microbial infection. Astragali complanati semen extract (ACSE) exhibits pharmacological activities, including antioxidant, anticancer, antiaging, and anti-diabetes effects. It is widely used in traditional medicine to treat liver and kidney diseases; however, the protective effect of ACSE on sepsis and its mechanisms are unknown. In the present study, we investigated the anti-inflammatory effects and potential mechanisms of the action of ACSE on sepsis. We show that ACSE improved survival rates in mouse models of acute sepsis induced by CLP (cecal ligation and puncture) and LPS stimulation. ACSE administration decreased aspartate aminotransferase (AST) and alanine aminotransferase (ALT) in sepsis-induced mice. Furthermore, ACSE reduced the levels of nitric oxide (NO), tumor necrosis factor-α (TNF-α), interleukin-1ß (IL-1ß), and interleukin-6 (IL-6) in the serum of septic mice. ACSE treatment inhibited the expression of these proinflammatory genes in LPS-stimulated J774 macrophages. Moreover, ACSE inhibited the phosphorylation of the IκB kinase (IKK) and the nuclear translocation of p65 NF-κB by LPS stimulation in macrophages. These results reveal the mechanism underlying the protective effect of ACSE against sepsis by inhibiting NF-κB activation and suggest that ACSE could be a potential therapeutic candidate to treat acute inflammatory diseases.

Clinical Outcomes Following the Early Application of Multimodal Scar Programs for Facial Incisional Wounds.

BACKGROUND: Even though scars are major issues for patients who undergo facial lacerations, programs for their prevention and early management are not well established. The purpose of this study was to evaluate the clinical outcomes of prophylactic scar assessments and early scar interventions in patients with lacerations. PATIENTS AND METHODS: A total of 116 patients underwent suture line and scar prevention treatment in the emergency room from 2014 to 2015. In the retrospective study, 46 patients who met all the criteria were included in the study. They were assigned to one of the following two scar prevention programs: the standard scar program for prevention, which included taping, silicone sheets, and ointments, and the multimodality scar program for treatment, which included triamcinolone, botulinum toxins, or CO2 fractional lasers. The patterns of early scar program were investigated for the standard scar prevention program and the multimodality scar management program, and we evaluated the scar assessment scores of the patients at 3 and 6 months. RESULTS: Scar scores for the patients who received multimodality scar management showed statistically significant improvements in Patient Scar Assessment (PSA) scales, Stony Brook Scar Evaluation Scales (SBSES), Vancouver Scar Scale (VSS) scores, and Visual Analog Scar (VAS) scales (the p values were 0.008, 0.007, 0.017, and 0.01, respectively). CONCLUSION: The multimodality scar program is more effective for scar prevention than the standard scar program. LEVEL OF EVIDENCE IV: This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Genotoxicity and subchronic general toxicity assessments of Lactobacillus curvatus WiKim 38 using Sprague-Dawley rats.

Lactobacillus curvatus WiKim 38 (LCW), isolated from kimchi, has shown novel immunomodulatory and anti-inflammatory properties. In the present study, to obtain data on the safety of LCW, we performed three genotoxicity (bacterial reverse mutation, chromosome aberration, and micronucleus) and two general toxicity (single-dosing and 13-week repeated-dosing) studies. In the genotoxicity assessment, LCW showed no increased reverse mutation for 4 strains of Salmonella typhimurium and a strain of Escherichia coli. In addition, LCW did not induce chromosome aberrations at concentrations up to 5000 µg/mL in cultured Chinese hamster lung (CHL) cells and did not induce an increased frequency of micronuclei in the bone marrow cells of rats at concentrations up to 2000 mg/kg. In the acute toxicity study using Sprague-Dawley (SD) rats, the approximate lethal dose of LCW was determined to be over 5000 mg/kg body weight (b.w.) in both sexes. Finally, in the subchronic toxicity study, no LCW-related adverse effects were observed at concentrations up to 5000 mg/kg b.w./day. Consequently, LCW is considered not to have mutagenic effects, and its no-observed-adverse-effect-level (NOAEL) is 5000 mg/kg b.w., equivalent to approximately 4.71 × 109 CFU/kg b.w., suggesting the LCW could be a potential probiotic for humans based on its safety profile.

Lysine 68 acetylation directs MnSOD as a tetrameric detoxification complex versus a monomeric tumor promoter.

Manganese superoxide dismutase (MnSOD) functions as a tumor suppressor; however, once tumorigenesis occurs, clinical data suggest MnSOD levels correlate with more aggressive human tumors, implying a potential dual function of MnSOD in the regulation of metabolism. Here we show, using in vitro transformation and xenograft growth assays that the MnSOD-K68 acetylation (Ac) mimic mutant (MnSODK68Q) functions as a tumor promoter. Interestingly, in various breast cancer and primary cell types the expression of MnSODK68Q is accompanied with a change of MnSOD's stoichiometry from a known homotetramer complex to a monomeric form. Biochemical experiments using the MnSOD-K68Q Ac-mimic, or physically K68-Ac (MnSOD-K68-Ac), suggest that these monomers function as a peroxidase, distinct from the established MnSOD superoxide dismutase activity. MnSODK68Q expressing cells exhibit resistance to tamoxifen (Tam) and cells selected for Tam resistance exhibited increased K68-Ac and monomeric MnSOD. These results suggest a MnSOD-K68-Ac metabolic pathway for Tam resistance, carcinogenesis and tumor progression.

Loss of Sirt2 increases and prolongs a caerulein-induced pancreatitis permissive phenotype and induces spontaneous oncogenic Kras mutations in mice.

Mice lacking Sirt2 spontaneously develop tumors in multiple organs, as well as when expressed in combination with oncogenic KrasG12D, leading to pancreatic tumors. Here, we report that after caerulein-induced pancreatitis, Sirt2-deficient mice exhibited an increased inflammatory phenotype and delayed pancreatic tissue recovery. Seven days post injury, the pancreas of Sirt2-/- mice display active inflammation, whereas wild-type mice had mostly recovered. In addition, the pancreas from the Sirt2-/- mice exhibited extensive tissue fibrosis, which was still present at six weeks after exposure. The mice lacking Sirt2 also demonstrated an enhanced whole body pro-inflammatory phenotype that was most obvious with increasing age. Importantly, an accumulation of a cell population with spontaneous cancerous KrasG12D mutations was observed in the Sirt2-/- mice that is enhanced in the recovering pancreas after exposure to caerulein. Finally, transcriptome analysis of the pancreas of the Sirt2-/- mice exhibited a pro-inflammatory genomic signature. These results suggest that loss of Sirt2, as well as increased age, enhanced the immune response to pancreatic injury and induced an inflammatory phenotype permissive for the accumulation of cells carrying oncogenic Kras mutations.

Acupuncture for the Treatment of Taxane-Induced Peripheral Neuropathy in Breast Cancer Patients: A Pilot Trial.

OBJECTIVES: Some chemotherapy drugs can damage the nerves and cause peripheral neuropathy which is accompanied by severe neuropathic pain or gait impairment. The purpose of this study was to assess the feasibility and the safety of acupuncture for the treatment of peripheral neuropathy following chemotherapy in Korean breast cancer patients. DESIGN: This study was a prospective single-arm observational study using before and after measurements in breast cancer patients presenting with taxane-induced peripheral neuropathy. SETTINGS/LOCATION: This study was performed at East-West Medical Center at Daegu Catholic University Hospital, Daegu, South Korea. INTERVENTIONS: Acupuncture was administered 3 times a week for 4 consecutive weeks, for 25 ± 5 minutes at each session. OUTCOME MEASURES: The primary outcome measure was severity of CIPN using the Neuropathic Pain Symptom Inventory (NPSI) assessed by a self-administered questionnaire and Nerve Conduction Study (NCS) of extremities. The secondary outcome measure was quality of life (QoL) assessed by a self-administered questionnaire using the 36-Item Short From Health Survey (SF-36). RESULTS: Acupuncture significantly reduced the severity of CIPN assessed by NPSI score. Four weeks after the last treatment, the symptoms were not aggravated. According to NCS, 42.9% of participants showed improvement of sensory neuropathy. At the end of the treatment, SF-36 scores were significantly increased for variables including physical functioning, role limitations due to physical health problems, social functioning, and general health perceptions compared to those of baseline measurement. CONCLUSIONS: Acupuncture improved symptoms of CIPN and QoL in Korean women suffering from peripheral neuropathy after chemotherapy using taxane for breast cancer. The effects of acupuncture lasted for at least 1 month after the treatment.

New economical and simple device for intraoperative expansion on small and medium sized soft tissue defects.

Intraoperative expansion has been used to cover small to large defects without disadvantages of the conventional tissue expanders. Various materials, for example, expanders and Foley catheters are being used. We introduce a new, convenient and economical device immediately available in the operating room, according to the defect size for intraoperative expansion, with latex gloves or balloons. The retrospective study was done with 20 patients who presented with skin and soft tissue defects. During the operation, expansion was done with latex gloves or balloons inflated with saline through an intravenous line and a three-way stopcock. After the inflation, the glove was removed and skin was covered with expanded tissue. A careful decision was made regarding the inflation volume and placement of the expander according to the defect size. There were no postoperative complications. The skin contracture and tension was minimal with a texture similar to the adjacent tissue. The new intraoperative expansion devices with latex gloves and balloons were cheap and made easily right in the operation room. The reconstruction of small to large sized skin defects can be done successfully, functionally and aesthetically without using expensive commercial materials.

Clinical Impact of Highly Condensed Stromal Vascular Fraction Injection in Surgical Management of Depressed and Contracted Scars.

BACKGROUND: Recent research on stromal vascular fraction (SVF) has demonstrated the presence of numerous growth factors that aid in tissue regeneration and suggest the potential for scar treatment. This study was conducted to clinically show that adding stem cells can improve the surgical outcomes of scar formation. METHODS: Between March 2014 and February 2016, 17 patients underwent injections of fat and highly condensed SVF simultaneously with scar reduction surgeries and 15 patients received scar revision with or without simultaneous application of highly condensed SVF (4.90 × 107 stem cells/ml) at our institution. Clinical photographs were taken before and after surgery, and the scars were graded using the following standard scales: the Observer Scar Assessment Scale (OSAS), Stony Brook Scar Evaluation Scale (SBSES), Vancouver Scar Scale (VSS), and Visual Analog Scale (VAS). RESULTS: All patients showed improvement, registering significant increases in scar tissue scores (P < 0.05 in all four scoring systems). Patients in the SVF group showed more improved outcomes than patients in the non-SVF group for all scar tissue scores except the SBSES (OSAS, P = 0.029; SBSES, P = 0.281; VSS, P = 0.001; VAS, P = 0.021). Subcategories of these scales reflected more favorable outcomes in terms of height and pliability; however, there was no significant change in vascularity. CONCLUSIONS: SVF injections enhance tissue regeneration by contributing stem cells and growth factors to improve outcomes in scar revisions or tissue grafts. Harvesting the SVF through liposuction also provides a cosmetic benefit. Significant SVF-related gains in the scoring of scars indicate the merit of SVF as an aspect of conventional scar management. LEVEL OF EVIDENCE IV: This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Inhibition of Sirtuin 6 Induces Neuroblastoma Differentiation.

BACKGROUND/AIM: Sirtuins (SIRTs) play crucial roles in various signaling pathways that modulate differentiation and proliferation. We sought to elucidate the role of SIRTs in differentiation and proliferation of human neuroblastoma (NB). MATERIALS AND METHODS: NB cells were treated with nicotinamide (NAM), a non-specific SIRT inhibitor, SIRT-targeted short hairpin RNAs, and retinoic acid to assess cell growth and differentiation. RESULTS: SIRTs are involved in proliferation and differentiation using NAM in BE(2)-C cells. Specifically, SIRT6 knockdown in BE(2)-C cells reduced cell proliferation, induced neurite extension, corresponding with induction of p21CIP1 expression and G1 cell-cycle arrest. These effects were rescued by forced re-overexpression of SIRT6. SIRT6 expression was reduced in differentiated human NB sections, and RA-induced differentiation in BE(2)-C cells. CONCLUSION: SIRTs have important oncogenic properties in NB beyond its established functions in aging and genome stability. SIRT6 may represent a novel target for developing future therapeutics for the treatment of aggressive NBs.

Simultaneous Use of Selective Neurectomy With Liposuction for Calf Reduction in Asians.

BACKGROUND: Calf contouring continues to be popular among Northeast Asians. Calf hypertrophy and distorted leg contours are stressful to many women. Several calf reduction techniques such as a selective neurectomy or calf muscle resection have been attempted, but have inconsistent results. OBJECTIVES: This study was designed to demonstrate improved outcomes when combining a selective neurectomy with simultaneous liposuction. METHODS: A total of 780 patients with hypertrophic calves underwent calf reduction from January 2002 to December 2010. Of these, 193 patients were treated by selective neurectomy with simultaneous liposuction. Calf hypertrophy with a circumference below 34 cm was defined as mild, calves with a circumference of 34 to 38 cm were defined as moderate, and a calf circumference above 38 cm was defined as severe. In all groups, patients whose pinch test was above 2 cm underwent a simultaneous liposuction. RESULTS: Twenty-eight cases (14.5%) were defined as mild, 72 (37.3%) were moderate, and 93 (48.2%) were severe. Over an average of 8.7 months of postoperative follow up, the reduction in calf circumference averaged 3.7 cm in the mild group (11.1%), 4.0 cm in the moderate group (10.7 %), and 4.3 cm in the severe group (10.7%). Overall, 97.5% of patients were satisfied with the results. There were no severe complications including functional problem of lower extremity reported. CONCLUSIONS: The shape, type, and fat distribution of the hypertrophic calves were considered in our patient analysis. A selective neurectomy with liposuction was performed on 193 patients. This technique allowed for a successful calf reduction and improved the patient's aesthetic satisfaction without any reported functional complications.

Liver Histological Improvement After Administration of High-Dose Vitamin C in Guinea Pig with Nonalcoholic Steatohepatitis.

Background: Vitamin C is a strong antioxidant, and the health effects of vitamin C megadoses have not been validated despite the apparent health benefits. Therefore, the present study sought to confirm the effects of vitamin C megadoses. Materials and Methods : Four groups of six guinea pigs were used. Each group was fed one of the following diets for three weeks: normal diet, methionine choline-deficient diet, methionine choline-deficient diet + vitamin C megadose (MCD + vit C 2.5 g/kg/day), and methionine-choline deficient diet + ursodeoxycholic acid (MCD + UDCA 30 mg/kg/day). The MCD diet was given to induce nonalcoholic steatohepatitis, and UDCA was used to treat nonalcoholic steatohepatitis. Three weeks after initial diet administration, the results of biochemical tests and liver biopsy were compared between the groups. Results: The cytoplasm state was similar in the MCD + vit C and MCD + UDCA groups, exhibiting clearing of the cytoplasm and ballooning degeneration. However, macrovesicular steatosis was not observed in the MCD + vit C group. Aspartate transaminase and alanine transaminase were elevated significantly following vitamin C administration. Conclusions: The present study confirmed that alone vitamin C megadoses are potential remedies for nonalcoholic steatohepatitis, based on the liver biopsy results of guinea pigs that were unable to synthesize vitamin C.

Is Robot-Assisted Surgery Really Scarless Surgery? Immediate Reconstruction with a Jejunal Free Flap for Esophageal Rupture after Robot-Assisted Thyroidectomy.

Esophageal perforation is a rare but potentially fatal complication of robot-assisted thyroidectomy (RAT). Herein, we report the long-term outcome of an esophageal reconstruction with a jejunal free flap for esophageal rupture after RAT. A 33-year-old woman developed subcutaneous emphysema and hoarseness on postoperative day1 following RAT. Esophageal rupture was diagnosed by computed tomography and endoscopy, and immediate surgical exploration confirmed esophageal rupture, as well as recurrent laryngeal nerve injury. We performed a jejunal free flap repair of the 8-cm defect in the esophagus. End-to-side microvascular anastomoses were created between the right external carotid artery and the jejunal branches of the superior mesenteric artery, and end-to-end anastomosis was performed between the external jugular vein and the jejunal vein. The right recurrent laryngeal nerve injury was repaired with a 4-cm nerve graft from the right ansa cervicalis. Esophagography at 1 year after surgery confirmed that there were no leaks or structures, endoscopy at 1 year confirmed the resolution of vocal cord paralysis, and there were no residual problems with swallowing or speech at a 5-year follow-up examination. RAT requires experienced surgeons with a thorough knowledge of anatomy, as well as adequate resources to quickly and competently address potentially severe complications such as esophageal rupture.

SIRT3-Mediated Dimerization of IDH2 Directs Cancer Cell Metabolism and Tumor Growth.

The isocitrate dehydrogenase IDH2 produces α-ketoglutarate by oxidizing isocitrate, linking glucose metabolism to oxidative phosphorylation. In this study, we report that loss of SIRT3 increases acetylation of IDH2 at lysine 413 (IDH2-K413-Ac), thereby decreasing its enzymatic activity by reducing IDH2 dimer formation. Expressing a genetic acetylation mimetic IDH2 mutant (IDH2K413Q) in cancer cells decreased IDH2 dimerization and enzymatic activity and increased cellular reactive oxygen species and glycolysis, suggesting a shift in mitochondrial metabolism. Concurrently, overexpression of IDH2K413Q promoted cell transformation and tumorigenesis in nude mice, resulting in a tumor-permissive phenotype. IHC staining showed that IDH2 acetylation was elevated in high-risk luminal B patients relative to low-risk luminal A patients. Overall, these results suggest a potential relationship between SIRT3 enzymatic activity, IDH2-K413 acetylation-determined dimerization, and a cancer-permissive phenotype. Cancer Res; 77(15); 3990-9. ©2017 AACR.

Effectiveness of Hip External Rotator Strengthening Exercise in Korean Postural Bowleg Women.

Postural bowleg is a subclinical entity with both aesthetic and functional outcomes and appears to be common in East Asian countries. Internal rotation of the hip joint is associated with varus alignment at the knee joint of the bowleg. Strengthening exercise for the hip external rotator muscles seems to be effective in improving varus alignment of bowleg, but no standardized exercise program exists. A standardized active resistance strengthening exercise for hip external rotator muscles could improve varus alignment of the lower limb in bowlegged Korean women. In this article, a case series study was conducted to observe changes following a standardized 3-month program using equipment designed for strengthening of the hip external rotator muscles. Photogrammetric and radiographic data were used to compare the gap between knees and tibiofemoral (TF) angles before and after the exercise program. As a result, on average, the knee gap decreased by 1.6 cm. The TF angle decreased by 1.5°. Regression analysis revealed a statistically significant association between changes in knee gap and TF angle. The standardized 3-month active resistance strengthening exercise program of hip external rotator muscles was effective in improving postural deviation and cosmetic outcomes in bowlegged Korean women. LEVEL OF EVIDENCE IV: This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Sirtuin 2 regulates cellular iron homeostasis via deacetylation of transcription factor NRF2.

SIRT2 is a cytoplasmic sirtuin that plays a role in various cellular processes, including tumorigenesis, metabolism, and inflammation. Since these processes require iron, we hypothesized that SIRT2 directly regulates cellular iron homeostasis. Here, we have demonstrated that SIRT2 depletion results in a decrease in cellular iron levels both in vitro and in vivo. Mechanistically, we determined that SIRT2 maintains cellular iron levels by binding to and deacetylating nuclear factor erythroid-derived 2-related factor 2 (NRF2) on lysines 506 and 508, leading to a reduction in total and nuclear NRF2 levels. The reduction in nuclear NRF2 leads to reduced ferroportin 1 (FPN1) expression, which in turn results in decreased cellular iron export. Finally, we observed that Sirt2 deletion reduced cell viability in response to iron deficiency. Moreover, livers from Sirt2-/- mice had decreased iron levels, while this effect was reversed in Sirt2-/- Nrf2-/- double-KO mice. Taken together, our results uncover a link between sirtuin proteins and direct control over cellular iron homeostasis via regulation of NRF2 deacetylation and stability.

Loss of NAD-Dependent Protein Deacetylase Sirtuin-2 Alters Mitochondrial Protein Acetylation and Dysregulates Mitophagy.

AIMS: Sirtuins connect energy generation and metabolic stress to the cellular acetylome. Currently, only the mitochondrial sirtuins (SIRT3-5) and SIRT1 have been shown to direct mitochondrial function; however, Aims: NAD-dependent protein deacetylase sirtuin-2 (SIRT2), the primary cytoplasmic sirtuin, is not yet reported to associate with mitochondria. RESULTS: This study revealed a novel physiological function of SIRT2: the regulation of mitochondrial function. First, the acetylation of several metabolic mitochondrial proteins was found to be altered in Sirt2-deficient mice, which was, subsequently, validated by immunoprecipitation experiments in which the acetylated mitochondrial proteins directly interacted with SIRT2. Moreover, immuno-gold electron microscopic images of mouse brains showed that SIRT2 associates with the inner mitochondrial membrane in central nervous system cells. The loss of Sirt2 increased oxidative stress, decreased adenosine triphosphate levels, and altered mitochondrial morphology at the cellular and tissue (i.e., brain) level. Furthermore, the autophagic/mitophagic processes were dysregulated in Sirt2-deficient neurons and mouse embryonic fibroblasts. INNOVATION: For the first time it is shown that SIRT2 directs mitochondrial metabolism. CONCLUSION: Together, these findings support that SIRT2 functions as a mitochondrial sirtuin, as well as a regulator of autophagy/mitophagy to maintain mitochondrial biology, thus facilitating cell survival. Antioxid. Redox Signal. 26, 849-863.

SIRT2 deletion enhances KRAS-induced tumorigenesis in vivo by regulating K147 acetylation status.

The observation that cellular transformation depends on breaching a crucial KRAS activity threshold, along with the finding that only a small percentage of cellsharboring KRAS mutations are transformed, support the idea that additional, not fully uncovered, regulatory mechanisms may contribute to KRAS activation. Here we report that KrasG12D mice lacking Sirt2 show an aggressive tumorigenic phenotype as compared to KrasG12D mice. This phenotype includes increased proliferation, KRAS acetylation, and activation of RAS downstream signaling markers. Mechanistically, KRAS K147 is identified as a novel SIRT2-specific deacetylation target by mass spectrometry, whereas its acetylation status directly regulates KRAS activity, ultimately exerting an impact on cellular behavior as revealed by cell proliferation, colony formation, and tumor growth. Given the significance of KRAS activity as a driver in tumorigenesis, identification of K147 acetylation as a novel post-translational modification directed by SIRT2 in vivo may provide a better understanding of the mechanistic link regarding the crosstalk between non-genetic and genetic factors in KRAS driven tumors.