Endoplasmic reticulum stress and unfolded protein response in diaphragm muscle dysfunction of patients with stable chronic obstructive pulmonary disease.

Respiratory muscle dysfunction is common in patients with chronic obstructive pulmonary disease (COPD). Chronic contractile activity induces endoplasmic reticulum (ER) stress and unfolded protein response (UPR) in animals (animals and humans). We hypothesized that the respiratory muscle dysfunction associated with COPD may upregulate ER stress and UPR expression in diaphragm of stable patients with different degrees of airway obstruction and normal body composition. In diaphragm muscle specimens of patients with mild and moderate-to-severe COPD with preserved body composition and non-COPD controls (thoracotomy because of lung localized neoplasms), expression of protein misfolding (ER stress) and UPR markers, proteolysis and apoptosis (qRT-PCR and immunoblotting), and protein aggregates (lipofuscin, histology) were quantified. All patients and non-COPD controls were also clinically evaluated: lung and muscle functions and exercise capacity. Compared with non-COPD controls, patients exhibited mild and moderate-to-severe airflow limitation and diffusion capacity and impaired exercise tolerance and diaphragm strength. Moreover, compared with the controls, in the diaphragm of the COPD patients, slow-twitch fiber proportions increased, gene expression but not protein levels of protein disulfide isomerase family A member 3 and phosphatidylinositol 3-kinase catalytic subunit type 3 were upregulated, and no significant differences were found in markers of UPR transmembrane receptor pathways (activating transcription factor-6, inositol-requiring enzyme-1α, and protein kinase-like ER kinase), lipofuscin aggregates, proteolysis, or apoptosis. In stable COPD patients with a wide range of disease severity, reduced diaphragm force of contraction, and normal body composition, ER stress and UPR signaling were not induced in the main respiratory muscle. These findings imply that ER stress and UPR are probably not involved in the documented diaphragm muscle dysfunction (reduced strength) observed in all the study patients, even in those with severe airflow limitation. Hence, in stable COPD patients with normal body composition, therapeutic strategies targeted to treat diaphragm muscle dysfunction should not include UPR modulators, even in those with a more advanced disease. NEW & NOTEWORTHY In stable chronic obstructive pulmonary disease patients with a wide range of disease severity, diaphragm muscle weakness, and normal body composition, endoplasmic reticulum stress and unfolded protein response (UPR) signaling were not induced in the main respiratory muscle. These findings imply that endoplasmic reticulum stress and UPR are not involved in the documented diaphragm muscle dysfunction observed in the study patients, even in those with severe airflow limitation. In stable chronic obstructive pulmonary disease patients with normal body composition, therapeutic strategies should not include UPR modulators.

Is iron deficiency modulating physical activity in COPD?

There is evidence that iron plays a key role in the adequate functioning of skeletal muscle. While it has been demonstrated that nonanemic iron deficiency (NAID) affects exercise tolerance and response to exercise training in patients with COPD, the impact on daily physical activities (DPAs) remains unknown. Eighteen COPD patients with NAID (ferritin <100 ng/mL or ferritin 100-299 ng/mL with a transferrin saturation <20%) and 18 COPD patients without this abnormality, matched for age, gender, and the degree of airflow limitation (control group), were enrolled to the study. The primary outcome was the level of DPA assessed by accelerometers. Patients were (mean [SD]) 66 (7) years and were mostly male (70%) and former smokers (52%). Their forced expiratory volume at 1 second was 41 (16)% predicted, carbon monoxide diffusing capacity was 47 (14)% predicted and oxygen arterial pressure reached 70 (11) mmHg. DPA and the number of steps per day were lower in NAID COPD patients compared with controls (physical activity level 1.39 vs 1.59, P<0.05; and 4,402 vs 6,975 steps/day, P<0.05, respectively). The percentage of patients with increased time spent sitting per day (>6 hours) was higher in patients with NAID compared with controls (73% vs 37%, P<0.05). In addition, the percentage of patients doing moderate to vigorous physical activity per day (>3 metabolic equivalents of task, at least 30 minutes) was lower in this group (66% vs 100%, P<0.05). The presence of iron deficiency was associated with reduced DPA in COPD patients. Further studies are needed to evaluate iron reposition and their impact on the level of physical activity in these patients.

Differences in micro-RNA expression profile between vastus lateralis samples and myotubes in COPD cachexia.

Quadriceps muscle weakness and wasting are common comorbidities in chronic obstructive pulmonary disease (COPD). Micro-RNA expression upregulation may favor muscle mass growth and differentiation. We hypothesized that the profile of muscle-enriched micro-RNAs in cultured myotubes differs between patients with COPD of a wide range of body composition and healthy controls and that expression levels of those micro-RNAs from patients with COPD and controls differ between in vivo and in vitro conditions. Twenty-nine patients with COPD [ n = 15 with muscle wasting and fat-free mass index (FFMI) 15 kg/m2 and n = 14 with normal body composition and FFMI 18 kg/m2] and 10 healthy controls (FFMI 19 kg/m2) were consecutively recruited. Biopsies from the vastus lateralis muscle were obtained in all study subjects. A fragment of each biopsy was used to obtain primary cultures, in which muscle cells were first proliferated to be then differentiated into actual myotubes. In both sets of experiments (in vivo biopsies and in vitro myotubes) the following muscle-enriched micro-RNAs from all the study subjects were analyzed using quantitative real-time PCR amplification: micro-RNA (miR)-1, miR-133a, miR-206, miR-486, miR-29b, miR-27a, and miR-181a. Whereas the expression of miR-1, miR-206, miR-486, and miR-29b was upregulated in the muscle biopsies of patients with COPD compared with those of healthy controls, levels of none of the studied micro-RNAs in the myotubes (primary cultured cells) significantly differed between patients with COPD and the controls. We conclude from these findings that environmental factors (blood flow, muscle metabolism, and inflammation) taking place in vivo (biopsies) in muscles may account for the differences observed in micro-RNA expression between patients with COPD and controls. In the myotubes, however, the expression of the same micro-RNAs did not differ between the study subjects as such environmental factors were not present. These findings suggest that therapeutic strategies should rather target environmental factors in COPD muscle wasting as the profile of micro-RNA expression in myotubes was similar in patients to that observed in the healthy controls. NEW & NOTEWORTHY Environmental factors taking place in vivo (biopsies) in the muscles may explain differences observed in micro-RNA expression between patients with chronic obstructive pulmonary disease (COPD) and controls. In the myotubes, however, the expression of the same micro-RNAs did not differ between the study subjects as such environmental factors were not present. These findings suggest that therapeutic strategies should rather target environmental factors in COPD muscle wasting and cachexia as micro-RNA expression profile in myotubes was similar between patients and controls.

Endoplasmic reticulum stress and unfolded protein response profile in quadriceps of sarcopenic patients with respiratory diseases.

Impaired muscle strength and mass (sarcopenia) are common in patients with respiratory cachexia, namely chronic obstructive pulmonary disease (COPD) and in lung cancer (LC)-cachexia. Misfolded/unfolded proteins in endoplasmic reticulum (ER) induce the compensatory unfolded protein response (UPR). Expression of ER stress and UPR markers may be differentially upregulated in vastus lateralis (VL) of patients with respiratory sarcopenia associated with either a chronic condition (COPD) or subacute (LC)-cachexia. In VL specimens from 40 COPD patients (n = 21, sarcopenic, fat-free mass index [FFMI] 16 kg/m2 and n = 19, nonsarcopenic, FFMI 18 kg/m2 ), 13 patients with LC-cachexia (FFMI 17 kg/m2 ), and 19 healthy controls (FFMI 19 kg/m 2 ), expression markers of ER stress, UPR (protein kinase-like ER kinase [PERK], activating transcription factor [ATF] 6, and inositol-requiring enzyme [IRE] 1-α), oxidative stress, autophagy, proteolysis, and apoptosis (reverse transcription polymerase chain reaction and immunoblotting), and fiber atrophy (histology) were assessed. Atrophy and muscle wasting and weakness were seen in both groups of sarcopenic patients. Compared to healthy controls, in muscles of LC-cachexia patients, expression of ER stress markers and UPR (three arms) was significantly upregulated, while in sarcopenic COPD, expression of a few ER stress markers and IRE1-α arm was upregulated. ER stress and an exaggerated UPR were observed in the VL muscle of patients with respiratory sarcopenia. The three branches of UPR were similarly upregulated in muscles of cancer cachectic patients, whereas in sarcopenic COPD patients, only IRE1 was upregulated. The differential profile of muscle UPR in chronic and subacute respiratory conditions offers a niche for the design of specific novel therapeutic approaches.

Effect of blood glucose level on standardized uptake value (SUV) in 18F- FDG PET-scan: a systematic review and meta-analysis of 20,807 individual SUV measurements.

OBJECTIVES: To evaluate the effect of pre-scan blood glucose levels (BGL) on standardized uptake value (SUV) in 18F-FDG-PET scan. METHODS: A literature review was performed in the MEDLINE, Embase, and Cochrane library databases. Multivariate regression analysis was performed on individual datum to investigate the correlation of BGL with SUVmax and SUVmean adjusting for sex, age, body mass index (BMI), diabetes mellitus diagnosis, 18F-FDG injected dose, and time interval. The ANOVA test was done to evaluate differences in SUVmax or SUVmean among five different BGL groups (< 110, 110-125, 125-150, 150-200, and > 200 mg/dl). RESULTS: Individual data for a total of 20,807 SUVmax and SUVmean measurements from 29 studies with 8380 patients was included in the analysis. Increased BGL is significantly correlated with decreased SUVmax and SUVmean in brain (p < 0.001, p < 0.001,) and muscle (p < 0.001, p < 0.001) and increased SUVmax and SUVmean in liver (p = 0.001, p = 0004) and blood pool (p = 0.008, p < 0.001). No significant correlation was found between BGL and SUVmax or SUVmean in tumors. In the ANOVA test, all hyperglycemic groups had significantly lower SUVs compared with the euglycemic group in brain and muscle, and significantly higher SUVs in liver and blood pool. However, in tumors only the hyperglycemic group with BGL of > 200 mg/dl had significantly lower SUVmax. CONCLUSION: If BGL is lower than 200 mg/dl no interventions are needed for lowering BGL, unless the liver is the organ of interest. Future studies are needed to evaluate sensitivity and specificity of FDG-PET scan in diagnosis of malignant lesions in hyperglycemia.