66 research outputs found
Murine models to investigate the influence of diabetic metabolism on the development of atherosclerosis and restenosis
This is an, un-copyedited, author manuscript that has been accepted for publication in the Frontiers in BioscienceAtherosclerosis and related forms of cardiovascular disease (CVD) are associated with several genetic and environmental
risk factors, including hypercholesterolemia, diabetes mellitus (DM), hypertension, obesity and smoking. Human DM is a multisystem disorder that results from progressive failure of insulin production and insulin resistance. Most diabetic patients die from complications of atherosclerosis and CVD, and DM is also associated with increased risk of restenosis post-angioplasty. Furthermore, the incidence of DM, particularly type 2-DM, is expected to increase significantly during the next decades owing to the unhealthy effects of modern life-style habits (e.g., obesity and lack of physical exercise). Thus, it is of utmost importance to develop novel preventive and therapeutic strategies to reduce the social and health-care burden of CVD and DM. Although a
number of physiological alterations thought to promote atherosclerosis have been identified in diabetic patients, the precise
molecular mechanisms that link DM and atherosclerosis are largely unknown. Thus, the aim of this review is to discuss current
murine models of combined DM and atherosclerosis and to explore how these experimental systems are being utilized to gain mechanistic insights into diabetes-induced neointimal lesion development, as well as their potential use in evaluating the efficacy of new therapies. Our discussion includes models generated by streptozotocin treatment and those resulting from naturally occurring or targeted mutations in the mouse.Work in the laboratory of the authors is supported by grants from the Spanish Instituto de Salud Carlos III (Red Temática de Investigación Cooperativa en Enfermedades Cardiovasculares RECAVA, Red de Grupos G03/212), and from the Spanish Ministry of Education and Science and the European Regional Development Fund (SAF2004-03057, SAF2005-06058). H. G.-N. is supported by an European Union Marie Curie postdoctoral fellowship.Peer reviewe
Increased dosage of Ink4/Arf protects against glucose intolerance and insulin resistance associated with aging
Recent genome-wide association studies have linked type-2 diabetes mellitus to a genomic region in chromosome 9p21 near the Ink4/Arf locus, which encodes tumor suppressors that are up-regulated in a variety of mammalian organs during aging. However, it is unclear whether the susceptibility to type-2 diabetes is associated with altered expression of the Ink4/Arf locus. In the present study, we investigated the role of Ink4/Arf in age-dependent alterations of insulin and glucose homeostasis using Super-Ink4/Arf mice which bear an extra copy of the entire Ink4/Arf locus. We find that, in contrast to age-matched wild-type controls, Super-Ink4/Arf mice do not develop glucose intolerance with aging. Insulin tolerance tests demonstrated increased insulin sensitivity in Super-Ink4/Arf compared with wild-type mice, which was accompanied by higher activation of the insulin receptor substrate (IRS)-PI3K-AKT pathway in liver, skeletal muscle and heart. Glucose uptake studies in Super-Ink4/Arf mice showed a tendency toward increased (18)F-fluorodeoxyglucose uptake in skeletal muscle compared with wild-type mice (P = 0.079). Furthermore, a positive correlation between glucose uptake and baseline glucose levels was observed in Super-Ink4/Arf mice (P < 0.008) but not in wild-type mice. Our studies reveal a protective role of the Ink4/Arf locus against the development of age-dependent insulin resistance and glucose intolerance.Work supported by grants from the Spanish Ministry of Economy and Competiveness (MINECO) and European Regional Development Fund (SAF2007-62110, SAF2010-16044, SAF2008-0011, SAF2011-23777), and from the Instituto de Salud Carlos III (FIS: PI-CP10/00555, RECAVA: RD06/0014/0021, and EMER07-12). H.G.-N. is an investigator from ‘Miguel Servet’ programme (CP10/00555) and A.V. from MINECO. The Centro Nacional de Investigaciones Cardiovasculares (CNIC) is supported by the MINECO and the Pro-CNIC Foundation.S
Immunocytochemical evidence for growth hormone-releasing hormone in the tanycytes of the median eminence of the rat
The current study was performed to analyse the potential existence and structure
of a GHRH-transporting tuberoinfundibular system in the rat median eminence.
The immunocytochemical analysis using anti-GHRH revealed an intense
immunoreaction in the ependimary cells, tanycytes, at the level of the floor of
the infundibular recess forming part of the median eminence. The basal processes
of these cells course towards the external layer of the median eminence
and reach the growth hormone-releasing hormone (GHRH) fibres of the tuberoinfundibular
tract and this reaction was increased after intraventricular treatment
with colchicine. Thus, these observations suggest the existence of a second
or alternative cerebrospinal fluid-mediated route of GHRH transport to the
median eminence and implicate the involvement of tanycytes in the regulation
of this novel transport system
Variations in the cellular proliferation of prolactin cells from late pregnancy to lactation in rats
[EN]Lactation is a physiological process associated
with hyperactivity of hypophyseal prolactin-producing
cells. It is known that the percentage of these cells is increased
during lactation, although there are discrepancies
in the reports regarding the mechanisms responsible for
increasing the number of prolactin cells. In order to analyse
whether this increase is a result of previous proliferation,
variations in the proliferation rate of prolactinpositive
cells were determined from late pregnancy to lactation
in adult female rats by means of observation of the
immunohistochemical expression of PCNA as a marker
of cellular proliferation. During late pregnancy, a very
significant increase in the percentage of proliferating prolactin
cells was observed in comparison to non-pregnant
females in the proestrus phase (p < 0.01). Although the
percentage of prolactin-positive cells after one week of
lactation was higher than in non-lactating or in pregnant
females (p < 0.01), the proliferation rate was lower than
in the other groups studied. In sum, our results suggest
that late pregnancy constitutes a preliminary proliferative
phase preparatory to the ensuing lactation phase and that
endocrine changes in late pregnancy involve the cellular
proliferation of hypophyseal prolactin cells in order to
prepare the gland for later demands and to prevent proliferative
changes from occurring during lactation
IRS-2 Deficiency Impairs NMDA Receptor-Dependent Long-term Potentiation
The beneficial effects of insulin and insulin-like growth factor I on cognition have been documented in humans and animal models. Conversely, obesity, hyperinsulinemia, and diabetes increase the risk for neurodegenerative disorders including Alzheimer's disease (AD). However, the mechanisms by which insulin regulates synaptic plasticity are not well understood. Here, we report that complete disruption of insulin receptor substrate 2 (Irs2) in mice impairs long-term potentiation (LTP) of synaptic transmission in the hippocampus. Basal synaptic transmission and paired-pulse facilitation were similar between the 2 groups of mice. Induction of LTP by high-frequency conditioning tetanus did not activate postsynaptic N-methyl-D-aspartate (NMDA) receptors in hippocampus slices from Irs2−/− mice, although the expression of NR2A, NR2B, and PSD95 was equivalent to wild-type controls. Activation of Fyn, AKT, and MAPK in response to tetanus stimulation was defective in Irs2−/− mice. Interestingly, IRS2 was phosphorylated during induction of LTP in control mice, revealing a potential new component of the signaling machinery which modulates synaptic plasticity. Given that IRS2 expression is diminished in Type 2 diabetics as well as in AD patients, these data may reveal an explanation for the prevalence of cognitive decline in humans with metabolic disorders by providing a mechanistic link between insulin resistance and impaired synaptic transmission
Molecular mechanisms of insulin resistance in IRS-2-deficient hepatocytes
To assess the role of insulin receptor (IR) substrate (IRS)-2 in insulin action and resistance in the liver, immortalized neonatal hepatocyte cell lines have been generated from IRS-2(-/-), IRS-2(+/-), and wild-type mice. These cells maintained the expression of the differentiated liver markers albumin and carbamoyl phosphate synthetase, as well as bear a high number of IRs. The lack of IRS-2 did not result in enhanced IRS-1 tyrosine phosphorylation or IRS-1-associated phosphatidylinositol (PI) 3-kinase activity on insulin stimulation. Total insulin-induced PI 3-kinase activity was decreased by 50% in IRS-2(-/-) hepatocytes, but the translocation of PI-3,4,5-trisphosphate to the plasma membrane in these cells was almost completely abolished. Downstream PI 3-kinase, activation of Akt, glycogen synthase kinase (GSK)-3 (alpha and beta isoforms), Foxo1, and atypical protein kinase C were blunted in insulin-stimulated IRS-2(-/-) cells. Reconstitution of IRS-2(-/-) hepatocytes with adenoviral IRS-2 restored activation of these pathways, demonstrating that IRS-2 is essential for functional insulin signaling in hepatocytes. Insulin induced a marked glycogen synthase activity in wild-type and heterozygous primary hepatocytes; interestingly, this response was absent in IRS-2(-/-) cells but was rescued by infection with adenoviral IRS-2. Regarding gluconeogenesis, the induction of phosphoenolpyruvate carboxykinase and glucose 6-phosphatase by dibutyryl cAMP and dexamethasone was observed in primary hepatocytes of all genotypes. However, insulin was not able to suppress gluconeogenic gene expression in primary hepatocytes lacking IRS-2, but when IRS-2 signaling was reconstituted, these cells recovered this response to insulin. Suppression of gluconeogenic gene expression in IRS-2-deficient primary hepatocytes was also restored by infection with dominant negative Delta 256Foxo1
Molecular mechanisms of atherosclerosis in metabolic syndrome: role of reduced IRS2-dependent signaling
OBJECTIVE: The mechanisms underlying accelerated atherosclerosis in metabolic syndrome (MetS) patients remain poorly defined. In the mouse, complete disruption of insulin receptor substrate-2 (Irs2) causes insulin resistance, MetS-like manifestations, and accelerates atherosclerosis. Here, we performed human, mouse, and cell culture studies to gain insight into the contribution of defective Irs2 signaling to MetS-associated alterations.
METHODS AND RESULTS: In circulating leukocytes from insulin-resistant MetS patients, Irs2 and Akt2 mRNA levels inversely correlate with plasma insulin levels and HOMA index and are reduced compared to insulin-sensitive MetS patients. Notably, a moderate reduction in Irs2 expression in fat-fed apolipoprotein E-null mice lacking one allele of Irs2 (apoE(-/-)Irs2(+/-)) accelerates atherosclerosis compared to apoE-null controls, without affecting plaque composition. Partial Irs2 inactivation also increases CD36 and SRA scavenger receptor expression and modified LDL uptake in macrophages, diminishes Akt2 and Ras expression in aorta, and enhances expression of the proatherogenic cytokine MCP1 in aorta and primary vascular smooth muscle cells (VSMCs) and macrophages. Inhibition of AKT or ERK1/2, a downstream target of RAS, upregulates Mcp1 in VSMCs.
CONCLUSIONS: Enhanced levels of MCP1 resulting from reduced IRS2 expression and accompanying defects in AKT2 and Ras/ERK1/2 signaling pathways may contribute to accelerated atherosclerosis in MetS states
Development of a Human Extracellular Matrix for Applications Related with Stem Cells and Tissue Engineering
Murine models to investigate the influence of diabetic metabolism on the development of atherosclerosis and restenosis
This is an, un-copyedited, author manuscript that has been accepted for publication in the Frontiers in BioscienceAtherosclerosis and related forms of cardiovascular disease (CVD) are associated with several genetic and environmental
risk factors, including hypercholesterolemia, diabetes mellitus (DM), hypertension, obesity and smoking. Human DM is a multisystem disorder that results from progressive failure of insulin production and insulin resistance. Most diabetic patients die from complications of atherosclerosis and CVD, and DM is also associated with increased risk of restenosis post-angioplasty. Furthermore, the incidence of DM, particularly type 2-DM, is expected to increase significantly during the next decades owing to the unhealthy effects of modern life-style habits (e.g., obesity and lack of physical exercise). Thus, it is of utmost importance to develop novel preventive and therapeutic strategies to reduce the social and health-care burden of CVD and DM. Although a
number of physiological alterations thought to promote atherosclerosis have been identified in diabetic patients, the precise
molecular mechanisms that link DM and atherosclerosis are largely unknown. Thus, the aim of this review is to discuss current
murine models of combined DM and atherosclerosis and to explore how these experimental systems are being utilized to gain mechanistic insights into diabetes-induced neointimal lesion development, as well as their potential use in evaluating the efficacy of new therapies. Our discussion includes models generated by streptozotocin treatment and those resulting from naturally occurring or targeted mutations in the mouse.Work in the laboratory of the authors is supported by grants from the Spanish Instituto de Salud Carlos III (Red Temática de Investigación Cooperativa en Enfermedades Cardiovasculares RECAVA, Red de Grupos G03/212), and from the Spanish Ministry of Education and Science and the European Regional Development Fund (SAF2004-03057, SAF2005-06058). H. G.-N. is supported by an European Union Marie Curie postdoctoral fellowship.Peer reviewe
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