High fat diet- induced obesity decreases ErbB receptors expression in liver and adipose tissue in C57BL/6 mice

Neuregulins (NRGs) are a family of signaling proteins that bind to receptor tyrosine kinases of the ErbB family (ErbB2 to ErbB4), which can homo- or heterodimerize depending on their structural features and cell type. Many studies have proposed that decreased NRG levels are a common characteristic of obesity. In liver and adipose tissue, the increase in NRG expression has protective effects against obesity. However, it is still unknown whether ErbBs expression is altered in this pathology. We hypothesized that high fat diet-induced obesity downregulates ErbB receptors expression in obese mice compared to normal weight mice. Males C57BL/6 mice (n=6-7 for each group) were fed for 12 weeks and divided into: (i) control diet (CD; 10%-kcal fat, 20%-kcal protein, 70%-kcal carbohydrates), and (ii) high fat diet (HFD; 60%-kcal fat, 20%-kcal protein, 20%-kcal carbohydrates). General parameters and ErbBs expression (qPCR, immunohistochemistry and Western blot) were evaluated. We observed a significant increase in final body weight (47%), adipose tissue to body weight ratio (244%) and HOMA-IR (69%), among other parameters, in obese mice. In HFD group significantly decreased ErbB2 (48%) and ErbB3 (66%) mRNA levels in liver (no change in ErbB4), and ErbB2 (43%), ErbB3 (76%) and ErbB4 (35%) in adipose tissue, compared to CD. Furthermore, ErbB2 and ErbB3 protein levels decreased significantly in HFD group compared to the CD in liver. Therefore, our results suggest that HFD-induced obesity significantly decreases ErbBs expression in liver and adipose tissue in this murine model, that may be associated with alterations in the NRG pathway in obese mice.

Las neuregulinas (NRGs) son una familia de proteínas de señalización que se unen a receptores tirosina quinasas de la familia ErbB (ErbB2 a ErbB4), que pueden homo- o heterodimerizar dependiendo de sus características estructurales y del tipo celular. Estudios han propuesto que la disminución de los niveles de NRG es una característica común de la obesidad. En el hígado y el tejido adiposo (TA), el aumento de la expresión de NRG tiene efectos protectores contra la obesidad. Sin embargo, aún se desconoce si la expresión de ErbBs está alterada en esta patología. Nuestra hipótesis es que la obesidad inducida por una dieta alta en grasas (DAG) disminuye la expresión de los ErbB en ratones obesos. Ratones machos C57BL/6 (n=6-7 para c/grupo) fueron alimentados durante 12 semanas y divididos en: (i) dieta control (DC; 10%-kcal grasa, 20%-kcal proteína, 70%-kcal carbohidratos), y (ii) DAG (60%-kcal grasa, 20%-kcal proteína, 20%-kcal carbohidratos). Se evaluaron los parámetros generales y la expresión de ErbBs (qPCR, inmunohistoquímica y Western blot). Observamos un aumento significativo del peso corporal final (47%), de la relación tejido adiposo/peso corporal (244%) y del HOMA-IR (69%), entre otros parámetros, en ratones obesos. En este grupo disminuyó significativamente los niveles de ARNm de ErbB2 (48%) y ErbB3 (66%) en el hígado (sin cambios en ErbB4), y de ErbB2 (43%), ErbB3 (76%) y ErbB4 (35%) en el TA. Además, los niveles de proteína ErbB2 y ErbB3 disminuyeron significativamente, en comparación con el grupo DC en el hígado. Nuestros resultados sugieren que la obesidad inducida por DAG disminuye significativamente la expresión de ErbBs en el hígado y el TA, que puede estar asociado con alteraciones en la vía NRG en ratones obesos.

Rol de la microbiota intestinal en el desarrollo del hígado graso no alcohólico / The role of intestinal microbiota in the development of non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) encompasses a wide spectrum of hepatic pathologies ranging from simple steatosis (SS) to hepatocellular carcinoma. Intestinal microbiota (IM) is composed of trillions of microorganisms existing in the gut. It has 150 times more genes than the host. Changes in the composition and function of the IM are associated with different diseases, including NAFLD. In this condition, IM could have a pathogenic role through different mechanisms such as energy salvaging from food, an inflammatory stimulus, a modulation of the innate immune system, regulation of bile acid turnover, alteration of choline metabolism and increasing endogenous ethanol levels. This review is an update on the role of the intestinal microbiota in NAFLD and the possible mechanisms involved.

Upregulation of liver inducible nitric oxide synthase following thyroid hormone preconditioning: suppression by N-acetylcysteine

3,3-5-L-Triiodothyronine (T3) exerts significant protection against ischemia-reperfusion (IR) liver injury in rats. Considering that the underlying mechanisms are unknown, the aim of this study was to assess the involvement of inducible nitric oxide synthase (iNOS) expression and oxidative stress in T3 preconditioning (PC). Male Sprague-Dawley rats given a single dose of 0.1 mg of T3/kg were subjected to 1-hour ischemia followed by 20 hours reperfusion, in groups of animals pretreated with 0.5 g of N-acetylcysteine (NAC)/kg 0.5-hour prior to T3 or with the respective control vehicles. At the end of the reperfusion period, liver samples were taken for analysis of iNOS mRNA levels (RT-PCR), liver NOS activity, and hepatic histology. T3 protected against hepatic IR injury, with 119 percent enhancement in liver iNOS mRNA/18S rRNA ratios (p<0.05) and 12.7-fold increase (p<0.05) in NOS activity in T3-treated animals subjected to IR over values in control-sham operated rats, with a net 7.7-fold enhancement (p<0.05) in the net effect of T3 on liver iNOS expression and a net enhancement of 0.58 units in NOS activity, changes that were abolished by NAC treatment before T3. It is concluded that T3-induced liver PC is associated with upregulation of iNOS expression as a protective mechanisms against IR injury, which is achieved through development of transient and reversible oxidative stress.

The role of thyroid hormone calorigenesis in the redox regulation of gene expression

Thyroid hormone (TH; 3,3',5-triiodothyronine, T3) is required for the normal function of most tissues, with major effects on 0(2) consumption and metabolic rate. These are due to transcriptional activation of respiratory genes through the interaction of T3-liganded TH receptors with TH response elements or the activation of intermediate factors, with the consequent higher production of reactive 0(2) species (ROS) and antioxidant depletion. T3-induced oxidative stress in the liver triggers the redox upregulation of the expression of cytokines (tumor necrosis factor-alfa [TNF-alfa], interleukin-10), enzymes (inducible nitric oxide synthase, manganese superoxide dismutase), and anti-apoptotic proteins (Bcl-2), via a cascade initiated by TNF-alfa produced by Kupffer cells, involving inhibitor of kB phosphorylation and nuclear factor-kB activation. Thus, TH calorigenesis triggers an expression pattern that may represent an adaptive mechanism to re-establish redox homeostasis and promote cell survival under conditions of ROS toxicity secondary to TH-induced oxidative stress. Mechanisms of expression of respiratory and redox-sensitive genes may be functionally integrated, which could be of importance to understand the complexities of TH action and the outcome of thyroid gland dysfunction.

Correlación entre pruebas serológicas para diagnostico de micosis profundas y radiografias de tórax / Correlation between serologic tests for the diagnosis of deep mycosis and thorax radiographies

En un periodo de 9 meses, comprendido entre el 15 de enero de 1985 y el 15 de octubre de 1985, en el Departamento de Micología del Instituto Nacional de Higiene "Rafael Rangel", se investigó la presencia de micosis profundas en 276 pacientes referidos de centros asistenciales de la zona metropolitana y de otras regiones del país. Con este grupo de pacientes se realizó un estudio utilizando pruebas serológicas (doble difusión en gel) para investigar anticuerpos precipitantes contra antígenos de agentes de micosis profundas (coccidioidomicosis, paracoccidioidomicosis, histoplasmosis y aspergilosis) y pruebas de aglutinación de látex para investigar criptococosis en pacientes con antecedentes epidemiológicos sospechosos de esta enfermedad...