Differential Metabolomes in Claudicating and Chronic Limb Threatening Ischemia Limb Muscles

STRUCTURED ABSTRACT Objectives The goal of this study was to compare the limb tissue metabolomic profiles from differing clinical presentations of patients with peripheral artery disease (PAD). Background PAD presents clinically as intermittent claudication (IC) and chronic limb threatening-ischemia (CLTI; pain at rest with or without tissue necrosis or gangrene). Patients with CLTI suffer high morbidity and mortality rates, which is compounded by our lack of understanding of their unique tissue biology. Methods Gastrocnemius muscle was obtained from healthy-adult volunteers (HA; n=23), IC patients (n=15), and CLTI patients (n=24) and analyzed using Ultrahigh Performance Liquid Chromatography-Tandem Mass Spectroscopy (UPLC-MS/MS). Results We identified 1114 biochemicals via global metabolomic profiling. The IC muscle metabolome largely reflected the HA profile (biochemicals p <0.05; 117 increased and 67 decreased). The CLTI metabolome differentially presented 531 metabolites ( p <0.05) v HA, defined by a majority increasing (343 v 188 decreased). IC and CLTI groups only shared 77 decreased and 127 increased metabolites, that were largely defined by alterations in lipids (including Fatty Acid, Dicarboxylate species). Altered ( p <0.05) metabolites in IC/HA and CLTI/HA comparisons reflect substantial changes in the muscle amino acid and lipid profiles, but particularly in the CLTI presentation (220 Lipid species increased or decreased). Direct comparisons of CLTI and IC revealed 159 increased ( p <0.1) and 90 decreased ( p <0.1) biochemicals, including large changes in amino acids, lipids, and nucleotides. Conclusions The limb muscle metabolome of patients with CLTI is unique and reflects novel biochemical characteristics that underlie pathophysiology. CLINICAL RELEVANCE Metabolomic profiling of the lateral gastrocnemius muscle revealed unique alterations in the metabolic pathways of patients with chronic limb threatening ischemia (CLTI) compared to intermittent claudicants (IC) and healthy adults. This points to metabolic targets that may influence disease severity and patient outcomes. The most significantly changed metabolites were related to pain and inflammation, and energy and lipid metabolism, which mirror the primary symptoms (pain, inflammation, myopathy, myosteatosis) of the CLTI patient population. These data provide critical information that aids in identifying the CLTI disease etiology and may be leveraged for development of adjuvant therapies to supplement surgical intervention.