Background/Purpose: Background: Osteoarthritis (OA) is the most frequent joint disease.The OA is a heterogeneous disorder. With acceptance of the joint as an organ, the pathogenesis of OA has been viewed as a complex process that involves all the joint structures. There are several metabolic pathways involved in cell metabolism, including glycolysis, tricarboxylic acid (TCA) cycle and fatty acid (FA) oxidation. Metabolic flexibility has been described as the ability to adapt fuel oxidation by fuel availability. During OA, it has been established a relationship between mitochondrial dysfunction and cellular damage due to impairments in mitochondrial function and metabolic flexibility. Several studies have suggested that fatty acids may play an important role in OA development and progression.

Purpose: The aim of this work was to examine the differences in glucose and fatty acid metabolism, with special focus on metabolic flexibility, in cybrids from healthy (N) or OA donors.

Methods: Methods: Cybrids were developed using 143B.TK^– Rho-0 cell line (nuclear donor) and platelets (mitochondrial donors) from healthy (N) and OA donors. Glucose and FA metabolism were measured using D-[¹⁴C(U)]glucose and [1-¹⁴C]oleic acid respectively. Metabolic flexibility was evaluated by co-culturing with glucose and oleic acid acutely by using inhibitors against glucose and FA oxidation, 20µM UK5099 and 10µM etomoxir, respectively. Incorporation of FA into lipid droplet (LD) was evaluated by thin layer chromatography and LDs were stained by LD540 and analyzed by confocal microscope and flow cytometry. Appropriate statistical analyses were performed with GraphPad Prism v6.

Results: Results: There were no changes in basal glucose metabolism between cybrids. N cybrids had higher acid-soluble metabolites, reflecting incomplete FA β-oxidation than OA cybrids (N: 127.9±9.5 nmol/mg protein, OA: 91.58±7.17 nmol/mg protein, p≤0.005). Comparing glucose and FA metabolism showed that both types of cybrids preferred to oxidize glucose. Co-culturing with glucose and Oleic acid, increased total cellular uptake and oxidation of glucose in N (oxidation: 1.28±0.09, uptake: 1.22±0.09, p≤0.05) compared to basal condition but no in OA cybrids. Inhibition of FA oxidation by etomoxir increased complete glucose oxidation of N cybrids (1.14±0.02, p≤0.0001) compared to basal condition. Combine these data indicate that N cybrids are more metabolically flexible than OA. Cybrids presented different lipid distribution patterns; N cybrids had higher incorporation into phospholipids (N: 24.36±0.93, OA: 20.64±1.02, p≤0.05) but lower into TAG (N: 64.07±1.17, OA: 70.03±0.84, p≤0.005), compared to OA cybrids. Lipid droplet (LD) formation increased in both groups incubated in presence of FA (2.07±0.09, 2.61±0.17, p≤0.0001). Furthermore, N cybrids showed less LD formation than OA (p≤0.005).

Conclusion: Conclusion: The results indicated that cybrids from OA patients had reduced metabolic flexibility compared to N cybrids. Furthermore, the results indicate that this is associated with mitochondrial impairments.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/metabolic-regulation-in-cybrids-obtained-from-healthy-and-osteoarthritic-oa-patients-impaired-metabolic-flexibility-in-oa-process/