Advanced Glycated apoA-IV Loses Its Ability to Prevent the LPS-Induced Reduction in Cholesterol Efflux-Related Gene Expression in Macrophages.

We addressed how advanced glycation (AGE) affects the ability of apoA-IV to impair inflammation and restore the expression of genes involved in cholesterol efflux in lipopolysaccharide- (LPS-) treated macrophages. Recombinant human apoA-IV was nonenzymatically glycated by incubation with glycolaldehyde (GAD), incubated with cholesterol-loaded bone marrow-derived macrophages (BMDMs), and then stimulated with LPS prior to measurement of proinflammatory cytokines by ELISA. Genes involved in cholesterol efflux were quantified by RT-qPCR, and cholesterol efflux was measured by liquid scintillation counting. Carboxymethyllysine (CML) and pyrraline (PYR) levels, determined by Liquid Chromatography-Mass Spectrometry (LC-MS/MS), were greater in AGE-modified apoA-IV (AGE-apoA-IV) compared to unmodified-apoA-IV. AGE-apoA-IV inhibited expression of interleukin 6 (Il6), TNF-alpha (Tnf), IL-1 beta (Il1b), toll-like receptor 4 (Tlr4), tumor necrosis factor receptor-associated factor 6 (Traf6), Janus kinase 2/signal transducer and activator of transcription 3 (Jak2/Stat3), nuclear factor kappa B (Nfkb), and AGE receptor 1 (Ddost) as well as IL-6 and TNF-alpha secretion. AGE-apoA-IV alone did not change cholesterol efflux or ABCA-1 levels but was unable to restore the LPS-induced reduction in expression of Abca1 and Abcg1. AGE-apoA-IV inhibited inflammation but lost its ability to counteract the LPS-induced changes in expression of genes involved in macrophage cholesterol efflux that may contribute to atherosclerosis.

Chronic oral administration of arginine induces GH gene expression and insulin resistance.

Arginine (Arg) presents a potent growth hormone (GH) releasing activity. In vivo and in vitro studies carried out in our laboratory have demonstrated that acute treatment with Arg also increases GH gene expression. Taking into account the recognizable diabetogenic role of GH and that Arg increases insulin release, this study aimed at evaluating the effects of oral chronic administration of Arg on GH gene expression, by Northern blotting analysis, and on the insulin sensitivity, by means of the Insulin Tolerance Test (ITT), blood glucose decay rate (kitt) and insulin plasma concentration. We demonstrated that rats that consumed Arg ( approximately 35 mg/day) in drinking water, during 4 weeks, presented an increase in GH mRNA content (p < 0.01), a decreased peripheral response to insulin, as shown by the reduced blood glucose decay rate (p < 0.05), and a higher insulin plasma concentration (p < 0.01) than control group. Arg treatment did not modify the animals' food and water intake, while it decreased the heart rate and the arterial blood pressure compared to control group (p < 0.05). According to the results presented herein we conclude that chronic oral administration of arginine increases GH gene expression and induces insulin resistance. The arterial blood pressure decrease has already been pointed out in the literature, and seems to occur in response to the dilating effect of nitric oxide generated from Arg, as well as from NO generation in central and peripheral neuronal populations that express NOS and are involved in the autonomic regulation of the cardiac function.

Low ethanol consumption induces enhancement of insulin sensitivity in liver of normal rats.

Moderate amounts of alcohol intake have been reported to have a protective effect on the cardiovascular system and this may involve enhanced insulin sensitivity. We established an animal model of increased insulin sensitivity by low ethanol consumption and here we investigated metabolic parameters and molecular mechanisms potentially involved in this phenomenon. For that, Wistar rats have received drinking water either without (control) or with 3% ethanol for four weeks. The effect of ethanol intake on insulin sensitivity was analyzed by insulin resistance index (HOMA-IR), intravenous insulin tolerance test (IVITT) and lipid profile. The role of liver was investigated by the analysis of insulin signaling pathway, GLUT2 gene expression and tissue glycogen content. Rats consuming 3% ethanol showed lower values of HOMA-IR and plasma free fatty acids (FFA) levels and higher hepatic glycogen content and glucose disappearance constant during the IVITT. Neither the phosphorylation of insulin receptor (IR) and insulin receptor substrate-1 (IRS-1), nor its association with phosphatidylinositol-3-kinase (PI3-kinase), was affected by ethanol. However, ethanol consumption enhanced liver IRS-2 and protein kinase B (Akt) phosphorylation (3 times, P<0.05), which can be involved in the 2-fold increased (P<0.05) hepatic glycogen content. The GLUT2 protein content was unchanged. Our findings point out that liver plays a role in enhanced insulin sensitivity induced by low ethanol consumption.