Autophagic signaling promotes systems-wide remodeling in skeletal muscle upon oncometabolic stress by D2-HG.

OBJECTIVES: Cachexia is a metabolic disorder and comorbidity with cancer and heart failure. The syndrome impacts more than thirty million people worldwide, accounting for 20% of all cancer deaths. In acute myeloid leukemia, somatic mutations of the metabolic enzyme isocitrate dehydrogenase 1 and 2 cause the production of the oncometabolite D2-hydroxyglutarate (D2-HG). Increased production of D2-HG is associated with heart and skeletal muscle atrophy, but the mechanistic links between metabolic and proteomic remodeling remain poorly understood. Therefore, we assessed how oncometabolic stress by D2-HG activates autophagy and drives skeletal muscle loss. METHODS: We quantified genomic, metabolomic, and proteomic changes in cultured skeletal muscle cells and mouse models of IDH-mutant leukemia using RNA sequencing, mass spectrometry, and computational modeling. RESULTS: D2-HG impairs NADH redox homeostasis in myotubes. Increased NAD+ levels drive activation of nuclear deacetylase Sirt1, which causes deacetylation and activation of LC3, a key regulator of autophagy. Using LC3 mutants, we confirm that deacetylation of LC3 by Sirt1 shifts its distribution from the nucleus into the cytosol, where it can undergo lipidation at pre-autophagic membranes. Sirt1 silencing or p300 overexpression attenuated autophagy activation in myotubes. In vivo, we identified increased muscle atrophy and reduced grip strength in response to D2-HG in male vs. female mice. In male mice, glycolytic intermediates accumulated, and protein expression of oxidative phosphorylation machinery was reduced. In contrast, female animals upregulated the same proteins, attenuating the phenotype in vivo. Network modeling and machine learning algorithms allowed us to identify candidate proteins essential for regulating oncometabolic adaptation in mouse skeletal muscle. CONCLUSIONS: Our multi-omics approach exposes new metabolic vulnerabilities in response to D2-HG in skeletal muscle and provides a conceptual framework for identifying therapeutic targets in cachexia.

Quality of Life Assessment in Older Adults with Dementia: A Systematic Review.

INTRODUCTION: In the absence of a cure, dementia is often managed by minimizing risk factors contributing to quality of life (QOL). Attitudes to dementia in older adults may differ from those in relatively younger adults. The aim was to conduct a systematic review of the literature to determine how QOL was assessed in adults, 65 years and older with dementia, and identify factors that influence the reported scores. METHODS: A systematic review of full-text articles addressing QOL in older adults with dementia, published in English from January 1995 to September 2020, was conducted using PubMed and PsycINFO. We included studies that assessed QOL and involved participants 65 years and older. Studies were evaluated for inclusion by 2 independent pairs of reviewers. We assessed the quality of the studies using the Joanna Briggs Institute's Critical Appraisal Checklist. Study characteristics and findings were summarized. Analysis was by narrative synthesis. We identified social and clinical factors influencing QOL scores. RESULTS: Of the 1,010 articles identified, 19 met the inclusion criteria. These 19 studies involved 6,279 persons with dementia, with sample sizes from 32 to 1,366. Mean age of participants ranged from 77.1 to 86.6 years. Five measurement tools were identified; Quality of Life in Alzheimer Disease (QOL-AD), Alzheimer Disease-Related Quality of Life (ADRQL), Quality of Life in Late-Stage Dementia (QUALID), QUALIDEM (a dementia-specific QOL tool), and DEMQOL (health-related QOL for people with dementia). Self-ratings of QOL were higher than proxy ratings. Factors commonly influencing self-ratings of QOL included depression, functional impairment, and polypharmacy. Common factors that influenced proxy ratings included functional impairment, presence of neuropsychiatric symptoms, cognitive impairment, and caregiver burden. CONCLUSION: In evaluating QOL in dementia, self- and proxy reports may complement each other to ensure that all perspectives are addressed.