Pulmonary inflammation-induced alterations in key regulators of mitophagy and mitochondrial biogenesis in murine skeletal muscle

Asthma can Promote Cardiomyocyte Mitophagy in a Rat Model

Clinical observations have shown the risk of cardiovascular disease during asthmatic changes. Whether and how asthma causes heart failure is the subject of debate. Here, we aimed to investigate the possibility of cardiomyocyte mitophagy in a rat model of asthma. Twelve mature Wistar rats were randomly allocated into the Control and Asthmatic rats (n = 6). To induce asthma, ovalbumin was injected intraperitoneally on days 1 and 8 and procedure followed by nebulization from days 14 to 32. After 2 weeks, we performed the pathological examination of both lungs and heart using Hematoxylin-Eosin staining. Real-time PCR analysis was used to measure the expression of mitophagic factors, such as Optineurin, Pink1, and mitofusin 1 and 2. Typical changes like increased inter-alveolar septa thickness and interstitial pneumonia were evident in asthmatic lungs. In cardiac tissue, slight inflammatory response, and hydropic degeneration with an eosinophilic appearance were detected in the cytoplasm of cardiomyocytes. Real-time PCR analysis showed mitophagic response in pulmonary and cardiac tissues via upregulation of mitophagy-related genes like Optineurin and Pink-1 in asthmatic lungs and hearts compared to the control group (p < 0.05). Likewise, asthmatic changes increased the expression of genes associated with mitochondrial fusion in the lungs and heart. The expression of mitofusin1 and 2 was significantly increased following inflammatory response in pulmonary and cardiac tissues (p < 0.05). Our findings showed the expression of certain factors related to mitophagy during chronic asthmatic conditions. The findings open a new avenue in the understanding of cardiomyocyte injury during asthma.

Is inflammatory signaling involved in disease-related muscle wasting? Evidence from osteoarthritis, chronic obstructive pulmonary disease and type II diabetes

Muscle loss is an important feature that occurs in multiple pathologies including osteoarthritis (OA), chronic obstructive pulmonary disease (COPD) and type II diabetes (T2D). Despite differences in pathogenesis and disease-related complications, there are reasons to believe that some fundamental underlying mechanisms are inherent to the muscle wasting process, irrespective of the pathology. Recent evidence shows that inflammation, either local or systemic, contributes to the modulation of muscle mass and/or muscle strength, via an altered molecular profile in muscle tissue. However, it remains ambiguous to which extent and via which mechanisms inflammatory signaling affects muscle mass in disease. Therefore, the objective of the present review is to discuss the role of inflammation on skeletal muscle anabolism, catabolism and functionality in three pathologies that are characterized by an eventual loss in muscle mass (and muscle strength), i.e. OA, COPD and T2D. In OA and COPD, most rodent models confirmed that systemic (COPD) or muscle (OA) inflammation directly induces muscle loss or muscle dysfunctionality. However, in a patient population, the association between inflammation and muscular maladaptations are more ambiguous. For example, in T2D patients, systemic inflammation is associated with muscle loss whereas in OA patients this link has not consistently been established. T2D rodent models revealed that increased levels of advanced glycation end-products (AGEs) and a decreased mTORC1 activation play a key role in muscle atrophy, but it remains to be elucidated whether AGEs and mTORC1 are interconnected and contribute to muscle loss in T2D patients. Generally, if any, associations between inflammation and muscle are mainly based on observational and cross-sectional data. There is definitely a need for longitudinal evidence through well-powered randomized control trials that take into account confounders such as age, disease-phenotypes, comorbidities, physical (in) activity etc. This will allow to improve our understanding of the complex interaction between inflammatory signaling and muscle mass loss and hence contribute to the development of therapeutic strategies to combat muscle wasting in these diseases.