Assessing autophagy in murine skeletal muscle: current findings to modulate and quantify the autophagic flux

Reduced Liver Autophagy in High-Fat Diet Induced Liver Steatosis in New Zealand Obese Mice

Non-alcoholic fatty liver disease (NAFLD), as a consequence of overnutrition caused by high-calorie diets, results in obesity and disturbed lipid homeostasis leading to hepatic lipid droplet formation. Lipid droplets can impair hepatocellular function; therefore, it is of utmost importance to degrade these cellular structures. This requires the normal function of the autophagic-lysosomal system and the ubiquitin-proteasomal system. We demonstrated in NZO mice, a polygenic model of obesity, which were compared to C57BL/6J (B6) mice, that a high-fat diet leads to obesity and accumulation of lipid droplets in the liver. This was accompanied by a loss of autophagy efficiency whereas the activity of lysosomal proteases and the 20S proteasome remained unaffected. The disturbance of cellular protein homeostasis was further demonstrated by the accumulation of 3-nitrotyrosine and 4-hydroxynonenal modified proteins, which are normally prone to degradation. Therefore, we conclude that fat accumulation in the liver due to a high-fat diet is associated with a failure of autophagy and leads to the disturbance of proteostasis. This might further contribute to lipid droplet stabilization and accumulation.

The relationship between ANT1 and NFL with autophagy and mitophagy markers in patients with multiple sclerosis

Multiple sclerosis (MS) is the most common inflammatory neurodegenerative disease. Neurofilament light chain (NFL) is a novel adverting biomarker of axonal damage that suggested as a useful assistant in the monitoring of MS patients. It has been shown that the auto/mitophagy associated with MS pathogenesis. In this study, we aimed to study correlation between ATG5 and Parkin, as markers of autophagy and mitophagy respectively, with NFL and ANT1 in serum and cerebrospinal fluid (CSF) in MS subjects. ATG5, Parkin, NFL, and ANT1 levels were measured in a cross-sectional study of 40 MS patients compared with gender, age and BMI matching healthy volunteers. Based on our results, levels of ATG5, Parkin, and NFL significantly were elevated in both serum and CSF of MS patients comparing control individuals (p < 0.0001) but ANT1 levels significantly was decreased in both serum and CSF of MS patients comparing control individuals (p < 0.0001). The correlation indices between NFL, ANTI1, ATG5 and Parkin in both case and control groups showed a direct and moderate the correlation between ANTI1 and ATG5 in the CSF level of the control group (r = 0.554, P = 0.011). Our data support the feasibility of quantifying of NFL as a sensitive and clinically meaningful serum/CSF biomarker to follow-up nerve tissue injury in MS condition.

Cardiomyocyte Contractility and Autophagy in a Premature Senescence Model of Cardiac Aging

Globally, cardiovascular diseases are the leading cause of death in the aging population. While the clinical pathology of the aging heart is thoroughly characterized, underlying molecular mechanisms are still insufficiently clarified. The aim of the present study was to establish an in vitro model system of cardiomyocyte premature senescence, culturing heart muscle cells derived from neonatal C57Bl/6J mice for 21 days. Premature senescence of neonatal cardiac myocytes was induced by prolonged culture time in an oxygen-rich postnatal environment. Age-related changes in cellular function were determined by senescence-associated β-galactosidase activity, increasing presence of cell cycle regulators, such as p16, p53, and p21, accumulation of protein aggregates, and restricted proteolysis in terms of decreasing (macro-)autophagy. Furthermore, the culture system was functionally characterized for alterations in cell morphology and contractility. An increase in cellular size associated with induced expression of atrial natriuretic peptides demonstrated a stress-induced hypertrophic phenotype in neonatal cardiomyocytes. Using the recently developed analytical software tool Myocyter, we were able to show a spatiotemporal constraint in spontaneous contraction behavior during cultivation. Within the present study, the 21-day culture of neonatal cardiomyocytes was defined as a functional model system of premature cardiac senescence to study age-related changes in cardiomyocyte contractility and autophagy.

Oxidized protein aggregates: Formation and biological effects

The study of protein aggregates has a long history. While in the first decades until the 80ies of the 20th century only the observation of the presence of such aggregates was reported, later the biochemistry of the formation and the biological effects of theses aggregates were described. This review focusses on the complexity of the biological effects of protein aggregates and its potential role in the aging process.