No abstract

Although numerous studies have demonstrated the harmful effect of excessive fructose consumption at the systemic level, there is little information on its effects in the central nervous system. The purpose of the present work was to study the cellular alterations related to oxidative stress and protein quality control systems induced by a high-fructose diet in the brain of Syrian hamsters and their possible attenuation by exogenous melatonin. High-fructose intake induced type II diabetes together with oxidative damage, led to alterations of the unfolded protein response by activating the eIF2α branch, and impaired the macroautophagic machinery in the brain, favoring the accumulation of aggregates labeled for selective degradation and neurodegeneration markers such as β-amyloid (1-42), tau-p-S199, and tau-p-S404. Melatonin attenuated the manifestation of type II diabetes and reduced oxidative stress, deactivated eIF2α, and decreased tau-p-S404 levels in the brain of animals fed a high-fructose diet.

En el ganado vacuno, el estrés pre-sacrificio provoca la aparición de carnes conocidas como DFD (Dark, Firm, Dry), que se identifican por un descenso anómalo del pH muscular post-mortem y que muestran serios problemas de calidad, lo cual disminuye su valor comercial. El objetivo de este trabajo es conocer las diferencias en los procesos de estrés oxidativo, en los mecanismos de supervivencia/muerte celular (autofagia/apoptosis) y en biomarcadores proteómicos a las 24 h post-mortem, entre canales que mostraron un descenso normal de pH (pH = 5,4-5,8 a las 24 h post-mortem) utilizadas como CONTROL y canales con pH a las 24 h post-mortem (pH 24 ) > 6,0 clasificadas como DFD, con el fin de identificar los procesos del metabolismo muscular ligados a la aparición de carnes DFD.Se analizó el estrés oxidativo celular mediante el estudio de la actividad antioxidante total y los daños en macromoléculas (proteínas y lípidos). Las carnes DFD mostraron mayor actividad antioxidante (P < 0,05) a las 24 h post-mortem, así como mayor daño de proteínas (P < 0,05). También se analizaron biomarcadores de autofagia (Beclin-1 y LC3-II/LC3-I) y apoptosis (caspasa-3), así como los cambios producidos en el proteoma muscular. Los resultados demuestran la coexistencia de autofagia y apoptosis en el tejido muscular a las 24 h post-mortem, con diferencias de expresión significativas (P < 0,05) que permiten discriminar carnes DFD frente a carnes sin alteraciones de calidad (CONTROL).

The objective of this work was to demonstrate how the extraction method affects the reliability of biomarker detection and how this detection depends on the biomarker location within the cell compartment. Different extraction methods were used to study the sarcoplasmic and myofibrillar fractions of the Longissimus thoracis et lumborum muscle of young bulls of the Asturiana de los Valles breed in two quality grades, standard (Control) or dark, firm, and dry (DFD) meat. Protein extractability and the expression of some of the main meat quality biomarkers—oxidative status (lipoperoxidation (LPO) and catalase activity (CAT)), proteome (SDS-PAGE electrophoretic pattern), and cell stress protein (Hsp70)—were analyzed. In the sarcoplasmic fraction, buffers containing Triton X-100 showed significantly higher protein extractability, LPO, and higher intensity of high-molecular-weight protein bands, whereas the TES buffer was more sensitive to distinguishing differences in the protein pattern between the Control and DFD meat. In the myofibrillar fraction, samples extracted with the lysis buffer showed significantly higher protein extractability, whereas samples extracted with the non-denaturing buffer showed higher results for LPO, CAT, and Hsp70, and higher-intensity bands in the electrophoretic pattern. These findings highlight the need for the careful selection of the extraction method used to analyze the different biomarkers considering their cellular location to adapt the extractive process.

Leptin, as a nutritional inhibitor by repressing food intake, is critical compromised in the major common forms of obesity. Skeletal muscle is the main effector tissue for energy expenditure modifications by the effect of endocrine axes, such as leptin signaling. Our study has been carried out using skeletal muscle from leptin-deficient animal model, in order to ascertain the importance of this hormone in eating disorders. Here we report that leptindeficiency stimulates an uncontrolled oxidative phosphorylation metabolism, resulting in an excess of energy production that culminates in mitochondrial dysfunction. Thus, different nutrient sensing pathways are perturbed, loosing proteostasis and promoting lipid anabolism, that induces myofiber degeneration and drives oxidative type I fiber conversion. Melatonin treatment plays a significant role in regulating energy homeostasis and fuel utilization. This study reveals melatonin to be a decisive mitochondrial function-fate regulator, with implications for resembling physiological energy requirements and targeting glycolytic type II fibers recovery.