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Deregulation of mTOR complex 1 (mTORC1) signalling increases the risk for metabolic diseases, including type 2 diabetes. Here we show that β-cell-specific loss of mTORC1 causes diabetes and β-cell failure due to defects in proliferation, autophagy, apoptosis and insulin secretion by using mice with conditional (βraKO) and inducible (MIP-βraKOf/f) raptor deletion. Through genetic reconstitution of mTORC1 downstream targets, we identify mTORC1/S6K pathway as the mechanism by which mTORC1 regulates β-cell apoptosis, size and autophagy, whereas mTORC1/4E-BP2-eIF4E pathway regulates β-cell proliferation. Restoration of both pathways partially recovers β-cell mass and hyperglycaemia. This study also demonstrates a central role of mTORC1 in controlling insulin processing by regulating cap-dependent translation of carboxypeptidase E in a 4EBP2/eIF4E-dependent manner. Rapamycin treatment decreases CPE expression and insulin secretion in mice and human islets. We suggest an important role of mTORC1 in β-cells and identify downstream pathways driving β-cell mass, function and insulin processing.

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Jiménez-Palomares M, Ramos-Rodríguez JJ, López-Acosta JF, Pacheco-Herrero M, Lechuga-Sancho AM, Perdomo G, García-Alloza M, Cózar-Castellano I. Increased A␤ production prompts the onset of glucose intolerance and insulin resistance. Am J Physiol Endocrinol Metab 302: E1373-E1380, 2012. First published March 13, 2012; doi:10.1152/ajpendo.00500.2011.-Type 2 diabetes (T2D) mellitus and Alzheimer's disease (AD) are two prevalent diseases with comparable pathophysiological features and genetic predisposition. Patients with AD are more susceptible to develop T2D. However, the molecular mechanism linking AD and T2D remains elusive. In this study, we have generated a new mouse model to test the hypothesis that AD would prompt the onset of T2D in mice. To test our hypothesis, we crossed Alzheimer APPswe/PS1dE9 (APP/PS1) transgenic mice with mice partially deficient in leptin signaling (db/ϩ). Body weight, plasma glucose, and insulin levels were monitored. Phenotypic characterization of glucose metabolism was performed using glucose and insulin tolerance tests. ␤-Cell mass, islet volume, and islet number were analyzed by histomorphometry. APP/ PS1 coexpression in mice with intact leptin receptor signaling did not show any metabolic perturbations in glucose metabolism or insulin sensitivity. In contrast, APP/PS1 coexpression in db/ϩ mice resulted in nonfasting hyperglycemia, hyperinsulinemia, and hypercholesterolemia without changes in body weight. Conversely, fasting blood glucose and cholesterol levels remained unchanged. Coinciding with altered glucose metabolism, APP/PS1 coexpression in db/ϩ mice resulted in glucose intolerance, insulin resistance, and impaired insulin signaling. In addition, histomorphometric analysis of pancreata revealed augmented ␤-cell mass. Taken together, these findings provide experimental evidence to support the notion that aberrant A␤ production might be a mechanistic link underlying the pathology of insulin resistance and T2D in AD. type 2 diabetes; Alzheimer's disease; ␤-amyloid peptide; APPswe/PS1dE9 mouse; db/db mouse; ␤-cell mass ALZHEIMER'S DISEASE (AD) and type 2 diabetes (T2D) are two prevalent diseases in developed countries with comparable pathological features and genetic predisposition (3, 4, 7). Several clinical and epidemiological studies have shown a relationship between AD and T2D. Patients with T2D exhibit an increased risk for developing dementia and AD (1,11,12,14,15,19). On the other hand, patients suffering AD are more vulnerable to develop T2D (10). Patients with AD show a remarkable deposition of ␤-amyloid peptide (A␤) in brain, whereas patients with T2D present islet amyloid polypeptide deposition in pancreatic ␤-cells (6). On the other hand, patients with T2D are glucose intolerant and insulin resistant, revealing decreased insulin signaling in peripheral tissues, whereas patients with AD show signs of impaired insulin signaling in the brain (16). Taken together, these observations have spurred the hypothesis that these pathological alterations may underline the mecha...

Type 2 diabetes (T2D) is an important risk factor to suffer dementia, including Alzheimer’s disease (AD), and some neuropathological features observed in dementia could be mediated by T2D metabolic alterations. Since brain atrophy and impaired neurogenesis have been observed both T2D and AD we analyzed central nervous system (CNS) morphological alterations in the db/db mice (leptin receptor KO mice), as a model of long-term insulin resistance and T2D, and in C57Bl6 mice fed with high fat diet (HFD), as a model of diet induced insulin resistance and prediabetes. Db/db mice showed an age-dependent cortical and hippocampal atrophy, whereas in HFD mice cortex and hippocampus were preserved. We also detected increased neurogenesis and cell proliferation rates in young db/db mice when compared with control littermates. Our study shows that metabolic parameters serve as predictors of both atrophy and altered proliferation and neurogenesis in the CNS. Moreover in the cortex, atrophy, cell proliferation and neurogenesis were significantly correlated. Our data suggest that T2D may underline some of the pathological features observed in the dementia process. They also support that blood glucose control in elderly patients could help to slow down dementia evolution and maybe, improve its prognosis.

Background: Critical limb ischemia (CLI) constitutes the most aggressive form of peripheral arterial occlusive disease, characterized by the blockade of arteries supplying blood to the lower extremities, significantly diminishing oxygen and nutrient supply. CLI patients usually undergo amputation of fingers, feet, or extremities, with a high risk of mortality due to associated comorbidities. Circulating angiogenic cells (CACs), also known as early endothelial progenitor cells, constitute promising candidates for cell therapy in CLI due to their assigned vascular regenerative properties. Preclinical and clinical assays with CACs have shown promising results. A better understanding of how these cells participate in vascular regeneration would significantly help to potentiate their role in revascularization. Herein, we analyzed the initial molecular mechanisms triggered by human CACs after being administered to a murine model of CLI, in order to understand how these cells promote angiogenesis within the ischemic tissues.

Apolipoprotein D (ApoD) is an atypical apolipoprotein with an incompletely understood function in the regulation of triglyceride and glucose metabolism. We have demonstrated that elevated ApoD production in mice results in improved postprandial triglyceride clearance. This work studies the role of ApoD deficiency in the regulation of triglyceride and glucose metabolism and its dependence on aging. We used ApoD knockout (ApoD-KO) mice of 3 and 21 months of age. Body weight and food intake were measured. Hepatic histology, triglyceride content, lipoprotein lipase levels, and plasma metabolites were studied. Phenotypic characterization of glucose metabolism was performed using glucose tolerance test. β-Cell mass, islet volume, and islet number were analyzed by histomorphometry. Apolipoprotein D deficiency results in nonfasting hypertriglyceridemia in young (P = .01) and aged mice (P = .002). In young ApoD-KO mice, hypertriglyceridemia was associated with 30% to 50% increased food intake in nonfasting and fasting conditions, respectively, without changes in body weight. In addition, lipoprotein lipase levels were reduced by 35% in adipose tissue (P = .006). In aged ApoD-KO mice, hypertriglyceridemia was not associated with changes in food intake or body weight, whereas hepatic triglyceride levels were reduced by 35% (P = .02). Furthermore, nonfasting plasma insulin levels were elevated by 2-fold in young (P = .016) and aged (P = .004) ApoD-KO mice, without changes in blood glucose levels, glucose tolerance, β-cell mass, or islet number. These findings underscore the importance of ApoD in the regulation of plasma insulin levels and triglyceride metabolism, suggesting that ApoD plays an important role in the pathogenesis of dyslipidemia. © 2011 Elsevier Inc. All rights reserved. M E T A B O L I S M C L I N I C A L A N D E X P E R I M E N T A L6 0 ( 2 0 1 1 ) 1 7 6 7 -1 7 7 4Author contributions: The experiments were performed at the laboratories of DS, MDG, GP, and IC. GP, DS, and IC participated in the conception, design, analysis, and interpretation of the data. GP wrote the manuscript; and DS, IC, and MDG revised it critically for important intellectual content. MJP and MDG participated in the collection, analysis, and interpretation of the data. All authors approved the final version of the manuscript.

In atherosclerosis, circulating angiogenic cells (CAC), also known as early endothelial progenitor cells (eEPC), are thought to participate mainly in a paracrine fashion by promoting the recruitment of other cell populations such as late EPC, or endothelial colony-forming cells (ECFC), to the injured areas. There, ECFC replace the damaged endothelium, promoting neovascularization. However, despite their regenerative role, the number and function of EPC are severely affected under pathological conditions, being essential to further understand how these cells react to such environments in order to implement their use in regenerative cell therapies. Herein, we evaluated the effect of direct incubation ex vivo of healthy CAC with the secretome of atherosclerotic arteries. By using a quantitative proteomics approach, 194 altered proteins were identified in the secretome of pre-conditioned CAC, many of them related to inhibition of angiogenesis (e.g., endostatin, thrombospondin-1, fibulins) and cell migration. Functional assays corroborated that healthy CAC released factors enhanced ECFC angiogenesis, but, after atherosclerotic pre-conditioning, the secretome of pre-stimulated CAC negatively affected ECFC migration, as well as their ability to form tubules on a basement membrane matrix assay. Overall, we have shown here, for the first time, the effect of atherosclerotic factors over the paracrine role of CAC ex vivo. The increased release of angiogenic inhibitors by CAC in response to atherosclerotic factors induced an angiogenic switch, by blocking ECFC ability to form tubules in response to pre-conditioned CAC. Thus, we confirmed here that the angiogenic role of CAC is highly affected by the atherosclerotic environment.