Aging and obesity are the major risk factors for development of osteoarthritis (OA), the most common form of arthritis. Veterans are at high risk of developing OA, because over 12.4 millions veterans are age 65 or older, and nearly 80% of veterans are obese. For veterans and others, developing effective disease-modifying therapy for OA is a major unmet medical need. As OA progresses, failure of the synovial joint organ frequently develops, with degeneration of articular cartilage as a core disease feature. Chondrocytes, the sole cells in articular hyaline cartilage, are responsible for maintaining the homeostatic balance between extracellular matrix anabolism and catabolism. Dysfunction of chondrocytes in OA, amplified by local inflammatory processes, leads to an excess of chondrocyte catabolic activity, medicated by factors including nitric oxide (NO), matrix metalloproteinasess (MMPs) and aggrecanases. Cellular metabolism can intersect with certain epigenetic and transcription factor modifications to mediate cellular re-programming. ATP citrate lyase (ACLY) is a metabolic enzyme that converts citrate generated from mitochondria to acetyl-CoA in the cytosol and nucleus, which serves as an acetyl donor for de novo lipid synthesis and acetylation of proteins in the cytosol, and acetylation of histones and transcription factors in the nucleus, thereby modulating gene expression. Our preliminary studies reveal that human knee OA chondrocytes/cartilages have increased ACLY activity, associated with increased acetylation of histones. Pharmacologic inhibition of ACLY in OA chondrocytes increases anabolic and decreases inflammation-mediated catabolic activities through modulating acetylation of histones and transcription factors. Building on these findings in this translational project, we propose to test our central hypothesis that chondrocyte ACLY is a druggable metabolic target for OA in vivo. We will test hypotheses that (1) activation of Akt signaling by IL-1? and IGF-1, both of which are known to associate with aging and obesity and are upregulated in OA cartilage, drives increased ACLY activity in human chondrocytes; (2) Chondroprotection by limiting ACLY activity is mediated by increased chondrocyte autophagy; (3) Suppression of ACLY activity protects mice from OA development and progression in both obesity-induced OA via high-fat diet (HFD) and age-related spontaneous OA in vivo. Completion of these studies will provide new insights into how metabolic alterations modulated by ACLY influence cartilage tissue integrity, and may provide a novel approach by limiting ACLY activity to suppress or delay OA development and progression, particularly in those at increased risk due to aging and/or obesity.
Osteoarthritis (OA) is the most common form of arthritis, and an enormous and expensive public health problem. There are yet no medical therapies (disease modifying OA drugs (DMOADS)) to prevent or effectively slow the primary disease process. Age and obesity are the primary risk factors for OA development. Veterans are at high risk of developing OA, because over 12.4 millions veterans are age 65 or older, and nearly 80% of veterans are obese. Thus, the unmet medical need for new and effective therapeutics for OA is particularly urgent for the special needs of the health care of Veterans. Completion of these highly translational studies will potentially provide a novel approach to protect cartilage from degradation by targeted inhibition of ATP-citrate lyase, a metabolic enzyme that is overactive in OA, thereby suppressing OA development and progression.
|Chen, Liang-Yu; Lotz, Martin; Terkeltaub, Robert et al. (2018) Modulation of matrix metabolism by ATP-citrate lyase in articular chondrocytes. J Biol Chem 293:12259-12270|
|Serrano, Ramon L; Chen, Liang-Yu; Lotz, Martin K et al. (2018) Impaired Proteasomal Function in Human Osteoarthritic Chondrocytes Can Contribute to Decreased Levels of SOX9 and Aggrecan. Arthritis Rheumatol 70:1030-1041|
|McWherter, Charles; Choi, Yun-Jung; Serrano, Ramon L et al. (2018) Arhalofenate acid inhibits monosodium urate crystal-induced inflammatory responses through activation of AMP-activated protein kinase (AMPK) signaling. Arthritis Res Ther 20:204|
|Chen, L-Y; Wang, Y; Terkeltaub, R et al. (2018) Activation of AMPK-SIRT3 signaling is chondroprotective by preserving mitochondrial DNA integrity and function. Osteoarthritis Cartilage 26:1539-1550|
|Berenbaum, Francis; Griffin, Timothy M; Liu-Bryan, Ru (2017) Review: Metabolic Regulation of Inflammation in Osteoarthritis. Arthritis Rheumatol 69:9-21|
|June, Ronald K; Liu-Bryan, Ru; Long, Fanxing et al. (2016) Emerging role of metabolic signaling in synovial joint remodeling and osteoarthritis. J Orthop Res 34:2048-2058|
|Wang, Yun; Viollet, Benoit; Terkeltaub, Robert et al. (2016) AMP-activated protein kinase suppresses urate crystal-induced inflammation and transduces colchicine effects in macrophages. Ann Rheum Dis 75:286-94|
|Guma, Monica; Wang, Yun; Viollet, Benoit et al. (2015) AMPK Activation by A-769662 Controls IL-6 Expression in Inflammatory Arthritis. PLoS One 10:e0140452|
|Wang, Yun; Zhao, Xianling; Lotz, Martin et al. (2015) Mitochondrial biogenesis is impaired in osteoarthritis chondrocytes but reversible via peroxisome proliferator-activated receptor ? coactivator 1?. Arthritis Rheumatol 67:2141-53|
|Liu-Bryan, R (2015) Inflammation and intracellular metabolism: new targets in OA. Osteoarthritis Cartilage 23:1835-42|
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