The BIOMEPOC Project: Personalized Biomarkers and Clinical Profiles in Chronic Obstructive Pulmonary Disease

Update on metabolomic findings in COPD patients

COPD is a heterogeneous disorder that shows diverse clinical presentations (phenotypes and "treatable traits") and biological mechanisms (endotypes). This heterogeneity implies that to carry out a more personalised clinical management, it is necessary to classify each patient accurately. With this objective, and in addition to clinical features, it would be very useful to have well-defined biological markers. The search for these markers may either be done through more conventional laboratory and hypothesis-driven techniques or relatively blind high-throughput methods, with the omics approaches being suitable for the latter. Metabolomics is the science that studies biological processes through their metabolites, using various techniques such as gas and liquid chromatography, mass spectrometry and nuclear magnetic resonance. The most relevant metabolomics studies carried out in COPD highlight the importance of metabolites involved in pathways directly related to proteins (peptides and amino acids), nucleic acids (nitrogenous bases and nucleosides), and lipids and their derivatives (especially fatty acids, phospholipids, ceramides and eicosanoids). These findings indicate the relevance of inflammatory-immune processes, oxidative stress, increased catabolism and alterations in the energy production. However, some specific findings have also been reported for different COPD phenotypes, demographic characteristics of the patients, disease progression profiles, exacerbations, systemic manifestations and even diverse treatments. Unfortunately, the studies carried out to date have some limitations and shortcomings and there is still a need to define clear metabolomic profiles with clinical utility for the management of COPD and its implicit heterogeneity.

Metabolomics in COPD

The clinical presentation of chronic obstructive pulmonary disease (COPD) is highly heterogeneous. Attempts have been made to define subpopulations of patients who share clinical characteristics (phenotypes and treatable traits) and/or biological characteristics (endotypes), in order to offer more personalized care. Assigning a patient to any of these groups requires the identification of both clinical and biological markers. Ideally, biological markers should be easily obtained from blood or urine, but these may lack specificity. Biomarkers can be identified initially using conventional or more sophisticated techniques. However, the more sophisticated techniques should be simplified in the future if they are to have clinical utility. The -omics approach offers a methodology that can assist in the investigation and identification of useful markers in both targeted and blind searches. Specifically, metabolomics is the science that studies biological processes involving metabolites, which can be intermediate or final products. The metabolites associated with COPD and their specific phenotypic and endotypic features have been studied using various techniques. Several compounds of particular interest have emerged, namely, several types of lipids and derivatives (mainly phospholipids, but also ceramides, fatty acids and eicosanoids), amino acids, coagulation factors, and nucleic acid components, likely to be involved in their function, protein catabolism, energy production, oxidative stress, immune-inflammatory response and coagulation disorders. However, clear metabolomic profiles of the disease and its various manifestations that may already be applicable in clinical practice still need to be defined.

Deficient muscle regeneration potential in sarcopenic COPD patients: Role of satellite cells

Sarcopenia is a major comorbidity in chronic obstructive pulmonary (COPD). Whether deficient muscle repair mechanisms and regeneration exist in the vastus lateralis (VL) of sarcopenic COPD remains debatable. In the VL of control subjects and severe COPD patients with/without sarcopenia, satellite cells (SCs) were identified (immunofluorescence, specific antibodies, anti-Pax-7, and anti-Myf-5): activated (Pax-7+/Myf-5+), quiescent/regenerative potential (Pax-7+/Myf-5-), and total SCs, nuclear activation (terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling [TUNEL]), and muscle fiber type (morphometry and slow- and fast-twitch, and hybrid fibers), muscle damage (hematoxylin-eosin staining), muscle regeneration markers (Pax-7, Myf-5, myogenin, and MyoD), and myostatin levels were identified. Compared to controls, in VL of sarcopenic COPD patients, myostatin content, activated SCs, hybrid fiber proportions, TUNEL-positive cells, internal nuclei, and muscle damage significantly increased, while quadriceps muscle strength, numbers of Pax-7+/Myf-5- and slow- and fast-twitch, and hybrid myofiber areas decreased. In the VL of sarcopenic and nonsarcopenic patients, TUNEL-positive cells were greater, whereas muscle regeneration marker expression was lower than in controls. In VL of severe COPD patients regardless of the sarcopenia level, the muscle regeneration process is triggered as identified by SC activation and increased internal nuclei. Nonetheless, a lower regenerative potential along with significant alterations in muscle phenotype and damage, and increased myostatin were prominently seen in sarcopenic COPD.

Satellite Cells and Markers of Muscle Regeneration during Unloading and Reloading: Effects of Treatment with Resveratrol and Curcumin

We hypothesized that treatment with pharmacological agents known to increase sirtuin-1 activity (resveratrol and curcumin) may enhance muscle regeneration. In limb muscles of mice (C57BL/6J, 10 weeks) exposed to reloading for seven days following a seven-day period of hindlimb immobilization with/without curcumin or resveratrol treatment, progenitor muscle cell numbers (FACS), satellite cell subtypes (histology), early and late muscle regeneration markers, phenotype and morphometry, sirtuin-1 activity and content, and muscle function were assessed. Treatment with either resveratrol or curcumin in immobilized muscles elicited a significant improvement in numbers of progenitor, activated, quiescent, and total counts of muscle satellite cells, compared to non-treated animals. Treatment with either resveratrol or curcumin in reloaded muscles compared to non-treated mice induced a significant improvement in the CSA of both hybrid (curcumin) and fast-twitch fibers (resveratrol), sirtuin-1 activity (curcumin), sirtuin-1 content (resveratrol), and counts of progenitor muscle cells (resveratrol). Treatment with the pharmacological agents resveratrol and curcumin enhanced the numbers of satellite cells (muscle progenitor, quiescent, activated, and total satellite cells) in the unloaded limb muscles but not in the reloaded muscles. These findings have potential clinical implications as treatment with these phenolic compounds would predominantly be indicated during disuse muscle atrophy to enhance the muscle regeneration process.