Zinc deficiency and a high-fat diet during growth: Metabolic and adipocyte alterations in rats.

BACKGROUND AND AIMS: To evaluate the effects of a high-fat diet during post-weaning growth on intermediate metabolism and retroperitoneal adipose tissue, in adult male rats exposed to adequate or deficient zinc intake during prenatal and postnatal life. METHODS AND RESULTS: Female Wistar rats were fed low- or control-zinc diets from pregnancy to offspring weaning. Male offspring born from control mothers were fed either control or high-fat, control-zinc diets for 60 days. Male offspring born from zinc deficient mothers were fed either low-zinc or high-fat, low-zinc diets for 60 days. At 74 days of life, oral glucose tolerance test was performed. In 81-day-old offspring, blood pressure, lipid profile, plasmatic lipid peroxidation and serum adiponectin level were determined. In retroperitoneal adipose tissue, we evaluated oxidative stress, morphology and adipocytokines mRNA expression. Low-zinc diet induced adipocytes hypertrophy, increased oxidative stress, and decreased adiponectin mRNA expression in adipose tissue. Low-zinc diet increased systolic blood pressure, triglyceridemia, plasmatic lipid peroxidation and glycemia at 3 h after glucose overload. Animals fed high-fat or high-fat, low-zinc diets showed adipocytes hypertrophy, decreased adiponectin mRNA expression, and increased leptin mRNA expression and oxidative stress in adipose tissue. They also exhibited decreased serum adiponectin levels, increased triglyceridemia, plasmatic lipid peroxidation and area under the oral glucose tolerance curve. High-fat, low-zinc diet induced greater alterations in adipocyte hypertrophy, leptin mRNA expression and glucose tolerance test than high-fat diet. CONCLUSION: Zinc deficiency since early stages of intrauterine life could increase susceptibility to metabolic alterations induced by high-fat diets during postnatal life.

Adenosine A1 receptors and mitochondria: targets of remote ischemic preconditioning.

Adenosine is involved in classic preconditioning in most species and acts especially through adenosine A1 and A3 receptors. The aim of the present study was to evaluate whether remote ischemic preconditioning (rIPC) activates adenosine A1 receptors and improves mitochondrial function, thereby reducing myocardial infarct size. Isolated rat hearts were subjected to 30 min of global ischemia and 60 min of reperfusion [ischemia-reperfusion (I/R)]. In a second group, before isolation of the heart, a rIPC protocol (3 cycles of hindlimb I/R) was performed. Infarct size was measured with tetrazolium staining, and Akt/endothelial nitric oxide (NO) synthase (eNOS) expression/phosphorylation and mitochondrial function were evaluated after ischemia at 10 and 60 min of reperfusion. As expected, rIPC significantly decreased infarct size. This beneficial effect was abolished only when 8-cyclopentyl-1,3-dipropylxanthine (adenosine A1 receptor blocker) and NG-nitro-l-arginine methyl ester (NO synthesis inhibitor) were administered during the reperfusion phase. At the early reperfusion phase, rIPC induced significant Akt and eNOS phosphorylation, which was abolished by the perfusion with an adenosine A1 receptor blocker. I/R led to impaired mitochondrial function, which was attenuated by rIPC and mediated by adenosine A1 receptors. In conclusion, we demonstrated that rIPC limits myocardial infarct by activation of adenosine A1 receptors at early reperfusion in the isolated rat heart. Interestingly, rIPC appears to reduce myocardial infarct size by the Akt/eNOS pathway and improves mitochondrial function during myocardial reperfusion. NEW & NOTEWORTHY Adenosine is involved in classic preconditioning and acts especially through adenosine A1 and A3 receptors. However, its role in the mechanism of remote ischemic preconditioning is controversial. In this study, we demonstrated that remote ischemic preconditioning activates adenosine A1 receptors during early reperfusion, inducing Akt/endothelial nitric oxide synthase phosphorylation and improving mitochondrial function, thereby reducing myocardial infarct size.

Papel de los receptores A1 de adenosina en el efecto protector del precondicionamiento isquémico remoto / Role of A1 adenosine receptors on remote ischemic preconditioning

RESUMEN Introducción: Es conocido que la adenosina está involucrada en el mecanismo de precondicionamiento isquémico clásico, actuando a través de los receptores A1 y A3. Objetivo: El objetivo de nuestro estudio fue evaluar si el precondicionamiento isquémico remoto (rIPC) activa los receptores de adenosina A1 antes de la isquemia o en la reperfusión y, de ese modo, reduce el tamaño del infarto de miocardio. Corazones aislados de rata fueron sometidos a 30 minutos de isquemia y 60 minutos de reperfusión (I/R). En otro grupo de ratas, se realizó un protocolo de rIPC. El tamaño del infarto se midió con trifenil de tetrazolio. Resultados: El rIPC disminuyó significativamente el tamaño del infarto. Este efecto fue abolido cuando se administró DPCPX (bloqueante del receptor A1) o L-NAME (inhibidor de la síntesis de óxido nítrico) durante la reperfusión. Conclusión: Empleando un modelo de corazón aislado de rata demostramos que el rIPC reduce el tamaño del infarto de mio cardio mediante la activación del receptor A1 de adenosina al inicio de la reperfusión miocárdica. Este efecto protector también estaría mediado por la activación de la enzima óxido nítrico sintasa durante la reperfusión.

Loss of dystrophin is associated with increased myocardial stiffness in a model of left ventricular hypertrophy.

Transition from compensated to decompensated left ventricular hypertrophy (LVH) is accompanied by functional and structural changes. Here, the aim was to evaluate dystrophin expression in murine models and human subjects with LVH by transverse aortic constriction (TAC) and aortic stenosis (AS), respectively. We determined whether doxycycline (Doxy) prevented dystrophin expression and myocardial stiffness in mice. Additionally, ventricular function recovery was evaluated in patients 1 year after surgery. Mice were subjected to TAC and monitored for 3 weeks. A second group received Doxy treatment after TAC. Patients with AS were stratified by normal left ventricular end-diastolic wall stress (LVEDWS) and high LVEDWS, and groups were compared. In mice, LVH decreased inotropism and increased myocardial stiffness associated with a dystrophin breakdown and a decreased mitochondrial O2 uptake (MitoMVO2). These alterations were attenuated by Doxy. Patients with high LVEDWS showed similar results to those observed in mice. A correlation between dystrophin and myocardial stiffness was observed in both mice and humans. Systolic function at 1 year post-surgery was only recovered in the normal-LVEDWS group. In summary, mice and humans present diastolic dysfunction associated with dystrophin degradation. The recovery of ventricular function was observed only in patients with normal LVEDWS and without dystrophin degradation. In mice, Doxy improved MitoMVO2. Based on our results it is concluded that the LVH with high LVEDWS is associated to a degradation of dystrophin and increase of myocardial stiffness. At least in a murine model these alterations were attenuated after the administration of a matrix metalloprotease inhibitor.

Mecanismos de protección miocárdica a distancia / Remóte Mechanisms of Myocardial Protection

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