Gregory R. Wagner

Lysine Glutarylation Is a Protein Posttranslational Modification Regulated by SIRT5

We report the identification and characterization of a five-carbon protein posttranslational modification (PTM) called lysine glutarylation (Kglu). This protein modification was detected by immunoblot and mass spectrometry (MS), and then comprehensively validated by chemical and biochemical methods. We demonstrated that the previously annotated deacetylase, sirtuin 5 (SIRT5), is a lysine deglutarylase. Proteome-wide analysis identified 683 Kglu sites in 191 proteins and showed that Kglu is highly enriched on metabolic enzymes and mitochondrial proteins. We validated carbamoyl phosphate synthase 1 (CPS1), the rate-limiting enzyme in urea cycle, as a glutarylated protein and demonstrated that CPS1 is targeted by SIRT5 for deglutarylation. We further showed that glutarylation suppresses CPS1 enzymatic activity in cell lines, mice, and a model of glutaric acidemia type I disease, the last of which has elevated glutaric acid and glutaryl-CoA. This study expands the landscape of lysine acyl modifications and increases our understanding of the deacylase SIRT5.

Worksite Wellness Programs for Cardiovascular Disease Prevention. A Policy Statement From the American Heart Association

With >130 million Americans employed across the United States, workplaces provide a large audience for cardiovascular disease (CVD) and stroke prevention activities. Experience has shown that workplace wellness programs are an important strategy to prevent the major shared risk factors for CVD and stroke, including cigarette smoking, obesity, hypertension, dyslipidemia, physical inactivity, and diabetes. An estimated 25% to 30% of companies’ medical costs per year are spent on employees with the major risk factors listed above.1 Employees and their families share the financial burden through higher contributions to insurance, higher copayments and deductibles, reduction or elimination of coverage, and trade-offs of insurance benefits against wage or salary increases. When programs are successful, their influence extends beyond the individual workers to immediate family members, who are often exposed to their favorable lifestyle changes. Worksite wellness programs that can reduce these risk factors can ultimately decrease the physical and economic burden of chronic diseases, including CVD, stroke, and certain cancers. The societal benefits of a healthy employed population extend well beyond the workplace. As such, comprehensive, culturally sensitive health promotion within the workplace can improve the nation’s health. The Healthy People 2010 goal is for 75% of all worksites, regardless of size, to develop comprehensive wellness programming.2 However, the development of comprehensive programs takes time and resources, especially for smaller employers. Because program development and initiation can be resource intensive, the American Heart Association (AHA) supports incremental efforts to achieve a comprehensive worksite wellness program to address CVD and stroke prevention and makes the following recommendations. 1. Components of Wellness Programs

Widespread and enzyme-independent Nε-acetylation and Nε-succinylation of proteins in the chemical conditions of the mitochondrial matrix.

Background: The mechanisms initiating protein acylation in mitochondria are unknown. Results: The pH and acyl-CoA concentrations of the mitochondrial matrix are sufficient to cause protein lysine acetylation and succinylation. Conclusion: Protein acylation in mitochondria may be a nonenzymatic event facilitated by the alkaline pH and high acyl-CoA concentrations. Significance: The mitochondrial deacylases SIRT3 and SIRT5 may have evolved to regulate nonenzymatic protein acylation. Alterations in mitochondrial protein acetylation are implicated in the pathophysiology of diabetes, the metabolic syndrome, mitochondrial disorders, and cancer. However, a viable mechanism responsible for the widespread acetylation in mitochondria remains unknown. Here, we demonstrate that the physiologic pH and acyl-CoA concentrations of the mitochondrial matrix are sufficient to cause dose- and time-dependent, but enzyme-independent acetylation and succinylation of mitochondrial and nonmitochondrial proteins in vitro. These data suggest that protein acylation in mitochondria may be a chemical event facilitated by the alkaline pH and high concentrations of reactive acyl-CoAs present in the mitochondrial matrix. Although these results do not exclude the possibility of enzyme-mediated protein acylation in mitochondria, they demonstrate that such a mechanism may not be required in its unique chemical environment. These findings may have implications for the evolutionary roles that the mitochondria-localized SIRT3 deacetylase and SIRT5 desuccinylase have in the maintenance of metabolic health.

Work, Obesity, and Occupational Safety and Health

There is increasing evidence that obesity and overweight may be related, in part, to adverse work conditions. In particular, the risk of obesity may increase in high-demand, low-control work environments, and for those who work long hours. In addition, obesity may modify the risk for vibration-induced injury and certain occupational musculoskeletal disorders. We hypothesized that obesity may also be a co-risk factor for the development of occupational asthma and cardiovascular disease that and it may modify the workers response to occupational stress, immune response to chemical exposures, and risk of disease from occupational neurotoxins. We developed 5 conceptual models of the interrelationship of work, obesity, and occupational safety and health and highlighted the ethical, legal, and social issues related to fuller consideration of obesitys role in occupational health and safety.

Asbestosis and silicosis

Interstitial fibrosis resulting from workplace exposure to asbestos and crystalline silica persists throughout the world despite knowledge of the causes and effective means for prevention. Asbestosis and silicosis occurrence is predictable among people overexposed to dusts in various industries and occupations such as mining, construction, manufacturing, and building maintenance. Asbestosis and silicosis are incurable and may be progressive even after dust exposure has ceased, therefore early recognition and supportive interventions are important. Although current disease is a result of past exposures, effective control of current workplace exposures is the only way to prevent continued occurrence of these potentially debilitating diseases. Physicians can contribute to this effort through accurate diagnosis and disease reporting.

Integration of Health Protection and Health Promotion: Rationale, Indicators, and Metrics

Objective: To offer a definition of an “integrated” approach to worker health and operationalize this definition using indicators of the extent to which integrated efforts are implemented in an organization. Methods: Guided by the question—How will we know it when we see it?—we reviewed relevant literature to identify available definitions and metrics, and used a modified Delphi process to review and refine indicators and measures of integrated approaches. Results: A definition of integrated approaches to worker health is proposed and accompanied by indicators and measures that may be used by researchers, employers, and workers. Conclusions: A shared understanding of what is meant by integrated approaches to protect and promote worker health has the potential to improve dialogue among researchers and facilitate the research-to-practice process.

Friedreich’s Ataxia reveals a mechanism for coordinate regulation of oxidative metabolism via feedback inhibition of the SIRT3 deacetylase

Friedreichs ataxia (FRDA) is the most common inherited human ataxia and is caused by a deficiency in the mitochondrial protein frataxin. Clinically, patients suffer from progressive spinocerebellar degeneration, diabetes and a fatal cardiomyopathy, associated with mitochondrial respiratory chain defects. Recent findings have shown that lysine acetylation regulates mitochondrial function and intermediary metabolism. However, little is known about lysine acetylation in the setting of pathologic energy stress and mitochondrial dysfunction. We tested the hypothesis that the respiratory chain defects in frataxin deficiency alter mitochondrial protein acetylation. Using two conditional mouse models of FRDA, we demonstrate marked hyperacetylation of numerous cardiac mitochondrial proteins. Importantly, this biochemical phenotype develops concurrently with cardiac hypertrophy and is caused by inhibition of the NAD(+)-dependent SIRT3 deacetylase. This inhibition is caused by an 85-fold decrease in mitochondrial NAD(+)/NADH and direct carbonyl group modification of SIRT3, and is reversed with excess SIRT3 and NAD(+) in vitro. We further demonstrate that protein hyperacetylation may be a common feature of mitochondrial disorders caused by respiratory chain defects, notably, cytochrome oxidase I (COI) deficiency. These findings suggest that SIRT3 inhibition and consequent protein hyperacetylation represents a negative feedback mechanism limiting mitochondrial oxidative pathways when respiratory metabolism is compromised, and thus, may contribute to the lethal cardiomyopathy in FRDA.

Managing pain in the workplace: a focus group study of challenges, strategies and what matters most to workers with low back pain

Purpose. Most working adults with low back pain (LBP) continue to work despite pain, but few studies have assessed self-management strategies in this at-work population. The purpose of this study was to identify workplace challenges and self-management strategies reported by workers remaining at work despite recurrent or persistent LBP, to be used as a framework for the development of a workplace group intervention to prevent back disability. Method. Workers with LBP (n = 38) participated in five focus groups, and audio recordings of sessions were analysed to assemble lists of common challenges and coping strategies. A separate analysis provided a general categorisation of major themes. Results. Workplace pain challenges fell within four domains: activity interference, negative self-perceptions, interpersonal challenges and inflexibility of work. Self-management strategies consisted of modifying work activities and routines, reducing pain symptoms, using cognitive strategies and communicating pain effectively. Theme extraction identified six predominant themes: knowing your work setting, talking about pain, being prepared for a bad day, thoughts and emotions, keeping moving and finding leeway. Conclusions. To retain workers with LBP, this qualitative investigation suggests future intervention efforts should focus on worker communication and cognitions related to pain, pacing of work and employer efforts to provide leeway for altered job routines.

Acute Upper and Lower Respiratory Effects in Wildland Firefighters

Objectives: To assess acute respiratory effects experienced by wildland firefighters. Methods: We studied two Interagency Hotshot Crews with questionnaires, spirometry, and measurement of albumin, eosinophilic cationic protein (ECP), and myeloperoxidase (MPO) as indicators of inflammation in sputum and nasal lavage fluid. Assessments were made preseason, postfire, and postseason. Results: Fifty-eight members of the two crews had at least two assessments. Mean upper and lower respiratory symptom scores were higher postfire compared to preseason (P < 0.001). The mean forced expiratory volume in 1 second was lower postfire compared to preseason (P < 0.001) and then recovered by postseason. Individual increases in sputum and nasal ECP and MPO from preseason to postfire were all significantly associated with postfire respiratory symptom scores. Conclusions: Wildland firefighting was associated with upper and lower respiratory symptoms and reduced forced expiratory volume in 1 second. Within individuals, symptoms were associated with increased ECP and MPO in sputum and nasal lavage fluid. The long-term respiratory health impact of wildland firefighting, especially over multiple fire seasons, remains an important concern.

SnapShot: Mammalian Sirtuins

The mammalian sirtuins have emerged as critical regulators of cellular stress resistance, energy metabolism, and tumorigenesis. In some contexts, they delay the onset of age-related diseases and promote a healthy lifespan. The seven mammalian sirtuins, SIRT1-7, share a highly conserved NAD+-binding catalytic core domain although they exhibit distinct expression patterns, catalytic activities, and biological functions. This SnapShot provides an overview of these properties, with an emphasis on their relevance to aging.