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How is protein synthesis initiated locally in neurons? We found that mTOR (mechanistic target of rapamycin) was activated and then up-regulated in injured axons, owing to local translation of mTOR messenger RNA (mRNA). This mRNA was transported into axons by the cell size-regulating RNA-binding protein nucleolin. Furthermore, mTOR controlled local translation in injured axons. This included regulation of its own translation and that of retrograde injury signaling molecules such as importin β1 and STAT3 (signal transducer and activator of transcription 3). Deletion of the mTOR 3' untranslated region (3'UTR) in mice reduced mTOR in axons and decreased local translation after nerve injury. Both pharmacological inhibition of mTOR in axons and deletion of the mTOR 3'UTR decreased proprioceptive neuronal survival after nerve injury. Thus, mRNA localization enables spatiotemporal control of mTOR pathways regulating local translation and long-range intracellular signaling.

ObjectiveWe have previously demonstrated that zopolrestat, an inhibitor of the enzyme aldose reductase, reduces ischemic injury in hearts from diabetic and non-diabetic rats. To further explore potential cardioprotective mechanisms of zopolrestat, we measured changes in intracellular sodium, calcium, and Na+,K(+)-ATPase activity in zopolrestat treated hearts during ischemia and reperfusion.MethodsHearts from acute diabetic (Type I) and age-matched control rats were isolated and retrogradely perfused. Hearts had either control perfusion or exposure to 1 microM zopolrestat for 10 min, followed by 20 min of global ischemia and 60 min of reperfusion. Changes in intracellular sodium and calcium were measured using 23Na and 19F magnetic resonance spectroscopy, respectively, while the activity of Na+,K(+)-ATPase was measured using biochemical assays.ResultsZopolrestat blunted the rise in [Na]i during ischemia in both diabetic hearts and non-diabetic hearts. The end-ischemic [Na]i was 21.3 +/- 2.6 mM in the zopolrestat treated diabetics and 25.9 +/- 2.3 in zopolrestat treated non-diabetics, versus 31.6 +/- 2.6 mM and 32.9 +/- 2.8 mM in the untreated diabetics and untreated non-diabetics, respectively, (P = 0.002). Similarly, the rise in [Ca]i at the end of ischemia was significantly reduced in zopolrestat treated diabetic and non-diabetic hearts (P = 0.005). Zopolrestat increased the activity of Na-,K(+)-ATPase in diabetic hearts under baseline conditions (11.70 +/- 0.95 versus 7.28 +/- 0.98 mumol/h/mg protein, P = 0.005) as well as during ischemia and reperfusion. Similar changes in Na+,K(+)-ATPase activity were also observed in non-diabetic hearts.ConclusionsThe data provide additional support to the protective effects of zopolrestat and suggest that a possible mechanism of action may be associated with the attenuation of the rise in [Na]i and [Ca]i during ischemia and reperfusion.

Inflammatory cells invading islets are thought to be mediators of islet destruction in spontaneous autoimmune diabetes mellitus. Thus methods were developed to isolate and characterize in situ islet inflammatory cells from 75-95-day-old prediabetic and diabetic BB rats. Islet inflammatory cells were structurally examined using single- and double-colour flow cytometry. Functional studies consisted of cytolytic assays using normal rat islet target cells and in situ islet or spleen effector cells. Structural data reveal natural killer cells to be the major cell population (70%) of total immune cells present in inflamed islets during prediabetes. At diabetes onset, the natural killer cell population remained at a high level (47%), but an increasing population of T cells (40%) was noted also. Analyses of T-cell subsets before and after diabetes onset revealed CD4+ T cells as predominant (50-55% of total T cells) with double-negative (CD4-CD8-) T cells (25-30%) and CD8+ T cells (15-20%) also present in significant quantities. Activated T cells accounted only for a minority of T cells (< 3%). Functional studies indicate that in situ islet-derived cytolytic effector cells are more potent killers (ten-fold) of normal islet target cells than are splenic effector cells. These data suggest that in situ islet inflammatory cells (a) can be quantitatively studied both structurally and functionally; (b) express structural phenotypes differing substantially from splenic mononuclear cell populations; (c) are considerably more cytolytic than splenic effectors; and (d) should prove informative in determining the most significant autoimmune functional events prior to and during islet beta-cell destruction.

The BB rat is a model of spontaneous autoimmune diabetes. To characterize quantitatively all known immune cell subsets involved in disease pathogenesis, FACS analysis of spleen cells was performed in diabetes-prone (DP) and acutely diabetic (D) BB rats and compared with diabetes-resistant (DR) BB and normal Wistar-Furth (WF) strains. We observed increased percentages of splenic NK cells in DP and D animals compared with DR rats using an NK-specific monoclonal antibody. We found increased proportions of splenic macrophages in the T-lymphopenic DP and D rats and low macrophage contents in DR spleens compared with WF spleens. We observed that percentages of the CD4-CD8- T cell receptor alpha/beta+ (double-negative) T cell subset were strikingly increased in the lymphopenic DP and D animals, compared with DR animals. We observed increased percentages of activated splenic CD5+ T cells expressing the IL-2 receptor and MHC class II antigen in DP and D rats compared with DR animals. Our studies suggest that (a) splenic NK cells and macrophages quantitatively appear to be involved in the pathogenesis of diabetes; (b) double-negative T cells escape from the T cell depletion process; (c) a marked increase of activated splenic T cells suggests diabetes is associated with general T cell activation processes; and (d) an altered balance among the different immune cell subsets may in part explain the pathogenesis of diabetes, since marked relative changes are observed when comparing the DR strain to the DP strain in both the prediabetic and diabetic stages.

Aún persisten múltiples incógnitas acerca de los mecanismos patogénicos de una enfermedad tan prevalente hoy día como es la diabetes mellitus tipo 2 (DM2). El avance en la prevención y tratamiento de la misma dependerá en gran parte de la comprensión de estos mecanismos y para ello es imprescindible seguir utilizando modelos animales en los que realizar experimentos que serían éticamente inaceptables en humanos. La DM2 representa un heterogéneo grupo de enfermedades caracterizado por un aumento en la resistencia a la acción de la insulina en los tejidos periféricos y un deterioro en la secreción de dicha hormona por parte de la célula β pancreática, encontrándose ambas anomalías íntimamente imbricadas. La citada heterogeneidad de la DM2 se ve asi mismo reflejada en la gran diversidad de modelos animales útiles para su estudio. Se revisan los principales modelos de DM2, clasificándolos, según su mecanismo de producción, en espontáneos e inducidos. También se distinguen dos categorías en cada uno de ellos: modelos análogos, que intentan imitar a la enfermedad humana, y modelos intrínsecos, con los que se pretende contestar preguntas concretas de aspectos específicos de la misma. La decisión acerca del modelo a usar para un experimento en particular es a menudo multifactorial. De modo ideal, los experimentos deberían ser llevados a cabo en varios modelos diferentes, teniendo en cuenta que ninguno de ellos refleja por completo la complejidad de la DM2 humana y que se deben extremar las precauciones a la hora de hacer cualquier tipo de extrapolación a la clínica.There stilla are many unknown facts about the pathogenic mechanisms of such a prevalente disease nowadays as i type-2 diabetes mellitus (DM2). The advances in diabetes prevention and management will greatly depend on the understanding of these mechanisms; therefore, it will be essential to keep on using animal models on which carrying out experiments that would be urethical in humans. DM2 represents a heterogeneous group of diseases characterized by an increase in insulin resistance at periphera tissues and a deterioration in insulin secretion by pancreatic β-cells, both abnormalities being highly interweaved. The mentioned heterogeneity of DM2 is also reflected by the high diversity of useful animal models for its study. The main DM2 models are reviewed, classifying them by their mechanism of action in spontaneous or induced. Also, two categories in each one of them are distinguiseed: analogous models, which try to imitate the human disease, and intrinsic models, with which we pretend to answer specific questions about the disease. The decision about which model to case for a particular experiment usually is multifactorial. Ideally, the experiments should be carried out in several different models, taking into account that none of them completely reflects the complexity of human DM2 and that precautions should be taken when trying to extrapolate the findings to the clinical practice.

Background/Aims: Type 1 diabetes is often accompanied by gastrointestinal motility disturbances. Vagal neuropathy, hyperglycemia, and alterations in the myenteric plexus have been proposed as underlying mechanism. We therefore studied the relationship between vagal function, gastrointestinal motiliy and characteristics of the enteric nervous system in the biobreeding (BB) rat known as model for spontaneous type 1 diabetes. Methods: Gastric emptying breath test, small intestinal electromyography, relative risk-interval variability, histology and immunohistochemistry on antral and jejunal segments were performed at 1, 8 and 16 weeks after diabetes onset and on age-matched controls. Results: We observed no consistent changes in relative risk-interval variability and gastric emptying rate. There was however, a loss of phases 3 with longer duration of diabetes on small intestinal electromyography. We found a progressive decrease of nitrergic neurons in the myenteric plexus of antrum and jejunum, while numbers of cholinergic nerve were not altered. In addition, a transient inflammatory infiltrate in jejunal wall was found in spontaneous diabetic BB rats at 8 weeks of diabetes. Conclusions: In diabetic BB rats, altered small intestinal motor control associated with a loss of myenteric nitric oxide synthase expression occurs, which does not depend on hyperglycemia or vagal dysfunction, and which is preceded by transient intestinal inflammation. [ABSTRACT FROM AUTHOR]

There stilla are many unknown facts about the pathogenic mechanisms of such a prevalente disease nowadays as i type-2 diabetes mellitus (DM2). The advances in diabetes prevention and management will greatly depend on the understanding of these mechanisms; therefore, it will be essential to keep on using animal models on which carrying out experiments that would be urethical in humans. DM2 represents a heterogeneous group of diseases characterized by an increase in insulin resistance at periphera tissues and a deterioration in insulin secretion by pancreatic β-cells, both abnormalities being highly interweaved. The mentioned heterogeneity of DM2 is also reflected by the high diversity of useful animal models for its study. The main DM2 models are reviewed, classifying them by their mechanism of action in spontaneous or induced. Also, two categories in each one of them are distinguiseed: analogous models, which try to imitate the human disease, and intrinsic models, with which we pretend to answer specific questions about the disease. The decision about which model to case for a particular experiment usually is multifactorial. Ideally, the experiments should be carried out in several different models, taking into account that none of them completely reflects the complexity of human DM2 and that precautions should be taken when trying to extrapolate the findings to the clinical practice. [ABSTRACT FROM AUTHOR]