Skeletal muscle type-specific mitochondrial adaptation to high-fat diet relies on differential autophagy modulation.

In obesity, skeletal muscle mitochondrial activity changes to cope with increased nutrient availability. Autophagy has been proposed as an essential mechanism involved in the regulation of mitochondrial metabolism. Still, the contribution of autophagy to mitochondrial adaptations in skeletal muscle during obesity is unknown. Here, we show that in response to high-fat diet (HFD) feeding, distinct skeletal muscles in mice exhibit differentially regulated autophagy that may modulate mitochondrial activity. We observed that after 4 and 40 weeks of high-fat diet feeding, OXPHOS subunits and mitochondrial DNA content increased in the oxidative soleus muscle. However, in gastrocnemius muscle, which has a mixed fiber-type composition, the mitochondrial mass increased only after 40 weeks of HFD feeding. Interestingly, fatty acid-supported mitochondrial respiration was enhanced in gastrocnemius, but not in soleus muscle after a 4-week HFD feeding. This increased metabolic profile in gastrocnemius was paralleled by preserving autophagy flux, while autophagy flux in soleus was reduced. To determine the role of autophagy in this differential response, we used an autophagy-deficient mouse model with partial deletion of Atg7 specifically in skeletal muscle (SkM-Atg7+/- mice). We observed that Atg7 reduction resulted in diminished autophagic flux in skeletal muscle, alongside blunting the HFD-induced increase in fatty acid-supported mitochondrial respiration observed in gastrocnemius. Remarkably, SkM-Atg7+/- mice did not present increased mitochondria accumulation. Altogether, our results show that HFD triggers specific mitochondrial adaptations in skeletal muscles with different fiber type compositions, and that Atg7-mediated autophagy modulates mitochondrial respiratory capacity but not its content in response to an obesogenic diet.

Polycystin-1 regulates cardiomyocyte mitophagy.

Polycystin-1 (PC1) is a transmembrane protein found in different cell types, including cardiomyocytes. Alterations in PC1 expression have been linked to mitochondrial damage in renal tubule cells and in patients with autosomal dominant polycystic kidney disease. However, to date, the regulatory role of PC1 in cardiomyocyte mitochondria is not well understood. The analysis of mitochondrial morphology from cardiomyocytes of heterozygous PC1 mice (PDK1+/- ) using transmission electron microscopy showed that cardiomyocyte mitochondria were smaller with increased mitochondria density and circularity. These parameters were consistent with mitochondrial fission. We knocked-down PC1 in cultured rat cardiomyocytes and human-induced pluripotent stem cells (iPSC)-derived cardiomyocytes to evaluate mitochondrial function and morphology. The results showed that downregulation of PC1 expression results in reduced protein levels of sub-units of the OXPHOS complexes and less functional mitochondria (reduction of mitochondrial membrane potential, mitochondrial respiration, and ATP production). This mitochondrial dysfunction activates the elimination of defective mitochondria by mitophagy, assessed by an increase of autophagosome adapter protein LC3B and the recruitment of the Parkin protein to the mitochondria. siRNA-mediated PC1 knockdown leads to a loss of the connectivity of the mitochondrial network and a greater number of mitochondria per cell, but of smaller sizes, which characterizes mitochondrial fission. PC1 silencing also deregulates the AKT-FoxO1 signaling pathway, which is involved in the regulation of mitochondrial metabolism, mitochondrial morphology, and processes that are part of cell quality control, such as mitophagy. Together, these data provide new insights about the controls that PC1 exerts on mitochondrial morphology and function in cultured cardiomyocytes dependent on the AKT-FoxO1 signaling pathway.

Characterizing Age-related Changes in Intact Mitochondrial Proteoforms in Murine Hearts using Quantitative Top-Down Proteomics.

Cardiovascular diseases (CVDs) are the leading cause of death worldwide, and the prevalence of CVDs increases markedly with age. Due to the high energetic demand, the heart is highly sensitive to mitochondrial dysfunction. The complexity of the cardiac mitochondrial proteome hinders the development of effective strategies that target mitochondrial dysfunction in CVDs. Mammalian mitochondria are composed of over 1000 proteins, most of which can undergo post-translational protein modifications (PTMs). Top-down proteomics is a powerful technique for characterizing and quantifying all protein sequence variations and PTMs. However, there are still knowledge gaps in the study of age-related mitochondrial proteoform changes using this technique. In this study, we used top-down proteomics to identify intact mitochondrial proteoforms in young and old hearts and determined changes in protein abundance and PTMs in cardiac aging. METHODS: Intact mitochondria were isolated from the hearts of young (4-month-old) and old (24-25-month-old) mice. The mitochondria were lysed, and mitochondrial lysates were subjected to denaturation, reduction, and alkylation. For quantitative top-down analysis, there were 12 runs in total arising from 3 biological replicates in two conditions, with technical duplicates for each sample. The collected top-down datasets were deconvoluted and quantified, and then the proteoforms were identified. RESULTS: From a total of 12 LC-MS/MS runs, we identified 134 unique mitochondrial proteins in the different sub-mitochondrial compartments (OMM, IMS, IMM, matrix). 823 unique proteoforms in different mass ranges were identified. Compared to cardiac mitochondria of young mice, 7 proteoforms exhibited increased abundance and 13 proteoforms exhibited decreased abundance in cardiac mitochondria of old mice. Our analysis also detected PTMs of mitochondrial proteoforms, including N-terminal acetylation, lysine succinylation, lysine acetylation, oxidation, and phosphorylation. CONCLUSION: By combining mitochondrial protein enrichment using mitochondrial fractionation with quantitative top-down analysis using ultrahigh-pressure liquid chromatography (UPLC)-MS and label-free quantitation, we successfully identified and quantified intact proteoforms in the complex mitochondrial proteome. Using this approach, we detected age-related changes in abundance and PTMs of mitochondrial proteoforms in the heart.

Light-induced release of the cardioprotective peptide angiotensin-(1-9) from thermosensitive liposomes with gold nanoclusters.

Angiotensin-(1-9), a component of the non-canonical renin-angiotensin system, has a short half-life in blood. This peptide has shown to prevent and/or attenuate hypertension and cardiovascular remodeling. A controlled release of angiotensin-(1-9) is needed for its delivery to the heart. Our aim was to develop a drug delivery system for angiotensin-(1-9). Thermosensitive liposomes (LipoTherm) were prepared with gold nanoclusters (LipoTherm-AuNC) to increase the stability and reach a temporal and spatial control of angiotensin-(1-9) release. Encapsulation efficiencies of nearly 50% were achieved in LipoTherm, reaching a total angiotensin-(1-9) loading of around 180 µM. This angiotensin-(1-9)-loaded LipoTherm sized around 100 nm and exhibited a phase transition temperature of 43 °C. AuNC were grown on LipoTherm and the new hybrid nanosystem showed energy absorption in the near-infrared (NIR) wavelength range. By NIR laser irradiation, a controlled release of angiotensin-(1-9) was achieved from the LipoTherm-AuNC nanosystem. These nanosystems did not show any cytotoxic effect on cultured cardiomyocytes. Biological activity of angiotensin-(1-9) released from the LipoTherm-AuNC-based nanosystem was confirmed using an ex vivo Langendorff heart model.

Antihipertensivos en pacientes con COVID-19 / Anti hypertensive agents in patients with COVID-19

En 31 de diciembre del 2019 la Organización Mundial de la Salud fue informada por las autoridades sanitarias chinas de la aparición de casos de neumonía de origen desconocido en la ciudad de Wuhan en China. El 7 de Enero de 2020, científicos chinos identificaron a un nuevo coronavirus (temporalmente designado como "2019-nCoV") como el agente etiológico de la enfermedad denominada COVID-19. La secuenciación del genoma del nuevo coronavirus mostró gran similitud con el coronavirus (Covid-1 o SARS-CoV) causante del síndrome respiratorio agudo severo (SARS), ocurrido también en China entre los años 2002-2003. Por este motivo, 2019-nCoV se rebautizó como SARS-CoV-2 (Severe Acute Respiratory Syndrome Corona Virus-2) y a la fecha es responsable de la actual y grave pandemia que está ocasionando impactos sanitarios y socio-económicos a escala global. Las investigaciones con SARS-CoV establecieron que este virus ingresa a nuestras células utilizando como receptor a la enzima convertidora de angiotensina tipo 2 (ECA 2 o en inglés ACE-2: "angiotensin converting enzyme type 2"). Dado este antecedente también se confirmó que SARS-CoV-2 también utiliza esta misma enzima ya que no se habla de un mecanismo en si para ingresar a sus células blanco, especialmente a nivel de nuestro sistema respiratorio. ECA-2 es una proteasa integrante del sistema renina angiotensina "alterno o no canónico" con importantes acciones regulatorias sobre los sistemas cardiovascular, renal y pulmonar, entre otros. En este contexto, ha surgido preocupación tanto por clínicos como los propios pacientes respecto al estado de pacientes hipertensos con COVID-19 y su vulnerabilidad a infectarse con SARS-CoV-2 dado que algunos trabajos han planteado que ciertos polimorfismos en el gen ECA-2 asociados a hipertensión arterial podrían determinar una mayor expresión de ECA-2. Además, estudios preclínicos han sugerido que ciertos fármacos antihipertensivos (principalmente, inhibidores de ECA y antagonistas del receptor para angiotensina II subtipo 1) también podrían estimular una mayor expresión de ECA-2. Esta revisión tiene por objetivo presentar y discutir los antecedentes en el estado del arte respecto a esta reciente problemática. El análisis crítico de los presentes antecedentes permite concluir que no existe evidencia clínica sólida que permita afirmar que el uso de medicamentos antihipertensivos genere una mayor vulnerabilidad a la infección con SARS-CoV-2. Por lo tanto no se debe descontinuar su uso en pacientes hipertensos en riesgo de infección a SARS-CoV-2 o que padezcan COVID-19.

In December 2019, a new type of coronavirus emerged in the city of Wuhan, China. This novel virus has unleashed a pandemic that has inflicted a considerable impact on public health and the economy and has therefore become a severe concern worldwide. This new virus -named SARS-CoV-2has been rapidly investigated in order to create knowledge aimed at achieving its control. Comparative studies with SARS-CoV virus, responsible for the 2002-2003 pandemic, suggest that SARS-CoV-2 requires the same receptor to bind and infect cells: angiotensin converting enzyme 2 (ACE-2). This hypothesis has been thoroughly supported by a variety of in vitro research and is currently considered a potential therapeutic target. ACE-2 is part of the counter-regulatory renin-angiotensin system, exerting effects in pulmonary, renal and cardiovascular systems. In this context, concerns have arisen in regards to the vulnerability of hypertensive patients against COVID-19, given that there is evidence that may suggest that polymorphisms associated to hypertension may increase the expression of ACE-2. Moreover, preclinical studies have shown that antihypertensive drugs may increase the expression of this enzyme. In this review article, we present the current state of the art on this polemic topic. Our critical analysis suggest that there is no robust clinical evidence supporting the hypothesis that the use of antihypertensive drugs can increase vulnerability to infection with SARS-CoV-2. Therefore, we recommend that the use of these therapeutic agents should not be discontinued in hypertensive patients in risk to or suffering COVID-19.

Diabetes mellitus tipo 2 y cardiopatía isquémica: fisiopatología, regulación génica y futuras opciones terapéuticas / Type II diabetes and ischemic heart disease: pathophysiology, gen regulation and future therapeutic options

Resumen: En los últimos años, la diabetes mellitus tipo 2 (DM2) ha evolucionado en forma epidémica, experimentando un rápido crecimiento y afectando a millones de individuos a nivel mundial. La cardiopatía isquémica es la principal causa de mortalidad en los pacientes diabéticos, quienes poseen un mayor riesgo cardiovascular respecto a los no diabéticos. La DM2 y la cardiopatía isquémica se caracterizan por ser prevenibles, sin embargo, existen diversos factores de riesgo comunes que contribuyen a su desarrollo. Los mecanismos que explican la ateroesclerosis acelerada y el incremento de riesgo de enfermedades cardiovasculares en los pacientes diabéticos tipo 2 incluyen a la hiperglicemia, dislipidemia y la inflamación del endotelio vascular. La diabetes es resultado de una interacción compleja entre la genética y el medio ambiente. Recientemente se han descrito varios genes implicados en el desarrollo de la diabetes y cardiopatía isquémica y que podrían significar nuevas opciones terapéuticas. En este artículo se revisa la relación entre ambas patologías, los mecanismos moleculares y el descubrimiento de factores de riesgo genéticos comunes y su implicancia en el desarrollo de nuevos blancos terapéuticos.

Abstracts: In recent years, type 2 diabetes mellitus has evolved as a rapidly increasing epidemic and affects millions of people worldwide. Ischemic heart disease (IHD) is the main cause of death among diabetic patients, who have a higher cardiovascular risk than non-diabetics. Both, DM2 and IHD are characterized by being preventable, however there are several common risk factors that contribute to their development. The mechanisms that explain accelerated atherosclerosis and increased risk of cardiovascular diseases in patients with type 2 diabetes mellitus include damage by hyperglycemia, dyslipidemia and inflammation on vascular endothelium. Diabetes is the result of a complex interaction between genetics and the environment, recently, several genes have been identified that appear to be involved in diabetes and ischemic heart disease that could explain its relationship and serve as new therapeutic possibilities. In this article, we review the relationship between diabetes and ischemic heart disease, the molecular mechanisms and the discovery of genetic risk factors common to both diseases and their implication in the development of new therapeutic targets.

Autofagia en el sistema cardiovascular: pasado, presente y futuro / Cardiovascular autophagy: past, present and future

La enfermedad cardiovascular se mantiene como la principal causa de morbimortalidad a nivel mundial a pesar de los avances científicos y tecnológicos recientes, por esto existe la necesidad de búsqueda de nuevas dianas terapéuticas. La autofagia es un mecanismo de degradación de proteínas y organelos disfuncionales que ocurre en vacuolas especializadas de doble membrana denominadas autofagosomas y que requiere la participación de los lisosomas. Este proceso permite el auto abastecimiento celular de energía a través del reciclaje de diversos substratos energéticos. Se activa en respuesta a diversas formas de estrés, principalmente debido a la ausencia de nutrientes y su presencia ha sido caracterizada en todos los tipos celulares que componen el sistema cardiovascular. Existe una ventana de actividad de autofagia óptima la que se relaciona con la mantención de la homeostasis cardiovascular y su desregulación participa en la patogénesis de diversas patologías cardiovasculares. En este artículo se revisa el curso temporal que llevó el descubrimiento de la autofagia, la contribución al área del Dr. Ohsumi, reciente Premio Nobel de Medicina, los principales conceptos, mecanismos celulares y moleculares de la formación del auto-fagosoma, nodos de regulación y sintetizamos su participación en la homeostasis del corazón y en la patogénesis de las enfermedades cardiovasculares y sus perspectivas futuras.

Cardiovascular disease continues to be the leading cause of morbi-mortality worldwide despite the recent scientific and technological advances. Therefore, more research is needed to discover novel therapeutic targets. Autophagy mediates the removal of dysfunctional proteins and organelles. This process takes place in double-membrane vesicles, named autophagosomes, which later fuse with lysosomes. The mechanism allows self-renewal energy repletion through diverse energy substrate recycling. Diverse forms of cellular stress, mainly nutrient deprivation, activate this process. Autophagy has been widely characterized within the cells of the cardiovascular system. There is a window of optimal autophagy activity implicated in maintaining cardiovascular homeostasis and its dysregulation participates in the pathogenesis of different cardiovascular diseases. In this article, we review the time course of auto-phagy discovery, the Nobel Prize winner Dr. Ohsumi contribution, main concepts, mechanisms involved in autophagosome formation and its regulatory no-des. Additionally, we summarized the role of auto-phagy in cardiovascular homeostasis and pathogenesis and future perspectives.