Is Lipotoxicity presents in the early stages of an experimental model of autoimmune diabetes? Further studies in the multiple low dose of streptozotocin model

An increased availability of plasma free fatty acids (FFA) seems to play a role in the early stages of experimental type 1 diabetes mellitus induced in C57BL/6J mice by multiple low doses of streptozotoxin (mld-STZ). We analyzed the temporal changes of: (1) plasma and skeletal muscle lipids and their relationship with glucose metabolism; (2) triglyceride (Tg) concentration in isolated islets; (3) intraperitoneal glucose tolerance test; and (4) insulin secretion patterns when the three mutually interactive glucose signaling pathways were activated. Animals were killed by cervical dislocation at days 4, 6, 7, 8, 9 and 12 post first injection of mld-STZ. Compared with control mice, we observed: (1) at day 6, a significant increase of plasma FFA and both muscle and islet Tg content and a significant decrease of muscle pyruvate dehydrogenase activity. These parameters further deteriorated with time. (2) plasma Tg, glucose and insulin levels and glucose tolerance test were significantly different only after day 8. (3) an increase in both phases of the glucose plus palmitate-stimulated insulin secretion was observed at day 4. This effect progressively decreased since day 7 up to day 9. Moreover, an inhibitory action of cerulenin over glucose plus palmitate-stimulated insulin secretion was observed between days 6 and 9. Taken together these results suggest that early alteration in carbohydrate and lipid metabolism could represent a "metabolic window" which would develop between days 6 and 8. Afterwards, subsequent immunological alterations, apoptosis and necrosis induced the destruction of β cells and would mask the results mentioned above.     

Short-term synaptic plasticity in the deterministic Tsodyks–Markram model leads to unpredictable network dynamics

Short-term synaptic plasticity strongly affects the neural dynamics of cortical networks. The Tsodyks and Markram (TM) model for short-term synaptic plasticity accurately accounts for a wide range of physiological responses at different types of cortical synapses. Here, we report a route to chaotic behavior via a Shilnikov homoclinic bifurcation that dynamically organizes some of the responses in the TM model. In particular, the presence of such a homoclinic bifurcation strongly affects the shape of the trajectories in the phase space and induces highly irregular transient dynamics; indeed, in the vicinity of the Shilnikov homoclinic bifurcation, the number of population spikes and their precise timing are unpredictable and highly sensitive to the initial conditions. Such an irregular deterministic dynamics has its counterpart in stochastic/network versions of the TM model: The existence of the Shilnikov homoclinic bifurcation generates complex and irregular spiking patterns and—acting as a sort of springboard—facilitates transitions between the down-state and unstable periodic orbits. The interplay between the (deterministic) homoclinic bifurcation and stochastic effects may give rise to some of the complex dynamics observed in neural systems.Short-term synaptic plasticity (STSP) is a temporal increase or decrease of synaptic strength in response to use, modulating the efficacy of synaptic transmission on timescales from a few milliseconds to several minutes (1–3). Short-term variations of the synaptic efficacy directly affect the timing and integration of presynaptic inputs to postsynaptic neurons, thereby affecting network-level dynamics and influencing brain function. Synaptic depression, an activity-regulatory mechanism that performs gain control (4), reduces cortical responses to strong stimuli (5). Recurrent cortical circuits in the presence of synaptic depression work as nonlinear adaptive filters in the visual system, with long response latencies for low-contrast stimuli and short latencies for high-contrast stimuli (6). Synaptic depression affects the responses of individual neurons and also the correlations of neural populations and the population accuracy for coding signals (7). Finally, working memory can be implemented through STSP using the dynamics of synaptic facilitation (8). Given this broad spectrum of disparate functions, it is not surprising that different cortical synapses in different cortical areas exhibit vastly different STSP dynamics (9).The Tsodyks and Markram (TM) model describes the dynamics of STSP under general conditions in an elegant and parsimonious way (1, 2). Indeed, the TM model includes several parameters that can be identified with biophysical variables (such as the time constant for refilling the readily releasable pool of vesicles) that can be regulated and account remarkably well for the highly heterogeneous dynamics in areas such as the visual and prefrontal cortices (see table 1 in ref. 10). Moreover, the TM model can explain as well the transitions between up and down cortical states (11–13).Here, we report the existence of highly irregular and chaotic-like dynamics in the TM model. Chaotic dynamics has been already suggested as a possible mechanism to explain the irregular dynamics observed in cortical activity (14), as reflected, for example, in trial-to-trial variability of neuron responses observed after multiple repetitions of the same stimulus (15, 16), and the erratic and complex transients occurring in local field potentials (17). We identified a form of chaos in the TM model, called Shilnikov chaos, which induces highly irregular transient dynamics and large sensitivity to initial conditions, even for the case of the Shilnikov chaos having an associated attractor that is unstable, rather than a stable one (18–21). The existence of Shilnikov chaos cannot, in principle, account for all of the observed complexity of cortical dynamics, but it may account for some irregularity in the overall network activity and, in particular, for facilitating transitions between large-scale brain states.     

Implications of TNF-α in the pathogenesis and management of GVHD

Clinical graft-versus-host disease (GVHD) symptoms are the result of a complex set of interactions between cellular and soluble factors. One of the key soluble factors is the proinflammatory cytokine, TNF-α, which participates in the initiating events that culminate in GVHD as well as amplifies the disease process once established. The importance of TNF-α in this process has been supported by a series of clinical experiments demonstrating strong correlation between TNF receptor-1 levels and GVHD. TNF-α has both indirect effects, through activating and proliferation pathways of T cells, the main cellular effector of GVHD, and direct effects leading to apoptosis, on GVHD target tissues. Accordingly, TNF-α has been used as a therapeutic target in experimental GVHD prevention and treatment strategies with promising clinical results. TNF-α can be pharmacologically inhibited using soluble TNF receptors or monoclonal antibodies. The optimal dosing and duration of TNF inhibition to prevent or treat GVHD remains under investigation.     

Effect of TNF-α inhibition on urinary albumin excretion in experimental diabetic rats

The objective is to assess the effect of TNF-α inhibition on urinary albumin excretion in experimental diabetic rats. Male Wistar rats, 8-week-old, were categorized into four groups, which were the control (n = 9), diabetes (n = 9), infliximab-treated diabetes (n = 10), and FR167653-treated diabetes (n = 9) groups. Diabetes was induced by intraperitoneal injection of STZ (40 mg/kg). Thereafter, infliximab was injected intraperitoneally once a month (5.5 mg/kg) and FR167653 was administered orally by mixing with the rat chow (0.08%). The effects of infliximab and FR167653 on urinary albumin excretion were observed for 12 weeks. Body weight, blood sugar, 24-h urinary TNF-α, and 24-h urinary albumin/creatinine ratio (Ualb/Ucr) levels were determined at 1, 4, 8, and 12 weeks after the STZ-injection. Treatment of rats with STZ caused a significant loss of body weight, as well as polyuria and hyperglycemia within 1 week, while the urinary excretions of albumin and TNF-α were increased. Neither infliximab nor FR167653 affected body weight or blood sugar levels, whereas both decreased urinary albumin excretion, together with a modest decrease in the urinary excretion of TNF-α. These results suggest a role of TNF-α in the pathogenesis of diabetic nephropathy and show that TNF-α inhibition is a potential therapeutic strategy.     

Disrupting the clustering of GABAA receptor α2 subunits in the frontal cortex leads to reduced γ-power and cognitive deficits

In schizophrenia, cognitive dysfunction is highly predictive of poor patient outcomes and is not responsive to current medications. Postmortem studies have suggested that cognitive deficits in schizophrenia are correlated with modifications in the number and size of inhibitory synapses. To test if these modifications lead to cognitive deficits, we have created a dominant-negative virus [adeno-associated (AAV)-DN1] that disrupts the clustering of γ-aminobutyric acid type A receptors (GABA_ARs) at postsynaptic inhibitory specializations. When injected into the frontal cortex of mice, AAV-DN1 impairs GABA_AR α2 subunit and GABA transporter 1 (GAT-1) clustering, but increases GABA_AR α1 subunit clustering on the perisomatic region, with no influence on axon-initial segment clustering. Mice expressing AAV-DN1 have prepulse inhibition deficits and impairments in working memory. Significantly, these behavioral deficits are paralleled by a reduction in electroencephalography γ-power. Collectively, our study provides functional evidence revealing that GABAergic synapses in the prefrontal cortex directly contribute to cognition and γ-power.In schizophrenia, the classical positive and negative symptoms are accompanied by striking cognitive deficits, and notably, the cognitive deficits are not ameliorated by conventional antipsychotic medications (1–3). Thus, understanding the molecular basis of these deficits is key to development of more efficacious treatments. In addition to modifications in the dopaminergic system, there is compelling evidence that modifications in signaling by γ-aminobutyric acid receptors (GABA_AR) contributes to the cognitive deficits in schizophrenia. GABA_ARs are the principle mediators of fast synaptic inhibition in the brain and are pentameric heteroligomers that are principally assembled from α1–6, β1–3, γ1–3, and δ subunits (4). Within the cortex, GABA_ARs containing α2 subunits are enriched on the axon-initial segments (AIS) and perisomatic regions of neurons, where their activation has been shown to underlie oscillatory activity and cognition (5, 6).Postmortem analysis has revealed increased levels of α2 subunit immunoreactivity on the AIS of principal cortical neurons in schizophrenia and parallel deficits in the number of GABA transporter (GAT-1) positive presynaptic elements. However, whether these modifications in inhibitory synapse structure contribute to the cognitive deficits of schizophrenia remains unknown. To address this issue we have used virally encoded dominant-negative reagents to disrupt the function of inhibitory synapses containing α2 subunits in the cortex of mice. This resulted in prepulse inhibition deficits and impairments in working memory that were paralleled by a reduction in electroencephalography γ-power. Thus, α2 subunit-containing GABA_ARs are important determinants of cognition, and selectively potentiating their activity may be beneficial in improving the outcome of patients with schizophrenia.     

Expression of TNF-α and VEGF in the esophagus of portal hypertensive rats

AIM: To investigate the expression of tumor necrosis factor-alpha (TNF-α) and vascular endothelial growth factor (VEGF) in the development of esophageal varices in portal hypertensive rats. METHODS: Thirty male Sprague-Dawley (SD) rats in the model group in which a two-stage ligation of portal vein plus ligation of the left adrenal vein was performed, were divided into three subgroups (M7, M14, and M21) in which the rats were kiued on the seventh day, the 14th d and the 21 d after the complete portal ligation. Thirty male SD rats, which underwent the sham operation in the control group, were also separated into three subgroups (C7, C14 and C21) corresponding to the models. The expression of TNF-α and VEGF in the esophagus of all the six subgroups of rats were measured with immunohistochemical SP technique. RESULTS: The portal pressure in the three model subgroups was significantly higher than that in the corresponding control subgroups (23.82±1.83 vs 11.61±0.86 cmH2O, 20.90±3.27 vs11.43±1.55 cmH2O and 20.68±2.27 vs 11.87±0.79 cmH2O respectively, vs P<0.01), as well as the number (9.3±1.6 vs 5.1?.8, 11.1±0.8 vs 5.4±1.3 and 11.7±1.5 vs 5.2?.1 respectively, P<0.01) and the total vascular area (78 972.6±3 527.8 vs 12 993.5±4 994.8 μm2, 107 207.5±4 6461.4 vs 11 862.6±5 423.2 μm2 and 110 241.4±49 262.2 vs 11 973.7±3 968.5 μm2 respectively, P<0.01) of submucosal veins in esophagus. Compared to the corresponding controls, the expression of TNP-α and VEGF in M21 was significantly higher (2.23±0.30 vs 1.13±0.28 and 1.65±0.38 vs 0.56±0.30 for TNF-α and VEGF respectively, P <0.01), whereas there was no difference in M7(1.14±0.38 vs 1.06±0.27 and 0.67±0.35 vs 0.50±0.24 for TNPa and VEGF respectively, P>0.05) and M14 (1.20±0.25 vs 1.04±0.26 and 0.65±0.18 vs 0.53±0.25 for TNF-α and VEGF respectively, P>0.05). And the expression of TNF-α and VEGF in M21 was significantly higher than that in M7 (2.23±0.30 vs1.14±0.38 and 1.65±0.38 vs 0.67±0.35 for TNF-α and VEGF respectively, P<0.01) and M14(2.23±0.30 vs 1.20±0.25 and 1.65±±0.38 vs 0.65±0.18 for TNF-a and VEGF respectively, P<0.01), but there was no difference between M7and M14(1.14±0.38 vs1.20±0.25 and 0.67±0.35 vs 0.65±0.18 for TNF-α and VEGF respectively, P>0.05). CONCLUSION: In the development of esophageal varices in portal hypertensive rats, increased TNF-α and VEGF may be not an early event, and probably play a role in weakening the esophageal wall and the rupture of esophageal varices.     

Expression of TNF-α and VEGF in the esophagus of portal hypertensive rats

AIM: To investigate the expression of tumor necrosis factor-alpha (TNF-α) and vascular endothelial growth factor (VEGF) in the development of esophageal varices in portal hypertensive rats. METHODS: Thirty male Sprague-Dawley (SD) rats in the model group in which a two-stage ligation of portal vein plus ligation of the left adrenal vein was performed, were divided into three subgroups (M7, M14, and M21) in which the rats were kiued on the seventh day, the 14^th d and the 21 d after the complete portal ligation. Thirty male SD rats, which underwent the sham operation in the control group, were also separated into three subgroups (C7, C14 and C21) corresponding to the models. The expression of TNF-α and VEGF in the esophagus of all the six subgroups of rats were measured with immunohistochemical SP technique. RESULTS: The portal pressure in the three model subgroups was significantly higher than that in the corresponding control subgroups (23.82&#177;1.83 vs 11.61&#177;0.86 cmH2O, 20.90&#177;3.27 vs 11.43&#177;1.55 cmH2O and 20.68&#177;2.27 vs 11.87&#177;0.79 cmH2O respectively, P&lt;0.01), as well as the number (9.3&#177;1.6 vs 5.1&#177;0.8, 11.1&#177;0.8 vs 5.4&#177;1.3 and 11.7&#177;1.5 vs 5.2&#177;1.1 respectively, P&lt;0.01) and the total vascular area (78 972.6&#177;3 527.8 vs 12 993.5&#177;4 994.8 um^2, 107 207.5&#177;4 6461.4 vs 11 862.6&#177;5 423.2 um^2 and 110 241.4&#177;49 262.2 vs 11 973.7&#177;3 968.5 um^2 respectively, P&lt;0.01) of submucosal veins in esophagus. Compared to the corresponding controls, the expression of TNF-α and VEGF in M21 was significantly higher (2.23&#177;0.30 vs 1.13&#177;0.28 and 1.65&#177;0.38 vs 0.56&#177;0.30 for TNF-α and VEGF respectively, P &lt;0.01), whereas there was no difference in M7 (1.14&#177;0.38 vs 1.06&#177;0.27 and 0.67&#177;0.35 vs 0.50&#177;0.24 for TNF-α and VEGF respectively, P&gt;0.05) and M14 (1.20&#177;0.25 vs 1.04&#177;0.26 and 0.65&#177;0.18 vs 0.53&#177;0.25 for TNF-α and VEGF respectively, P&gt;0.05). And the expression of TNF-α and VEGF in M21 was significantly higher than that in M7 (2.23&#177;0.30 vs 1.14&#177;0.38 and 1.65&#177;0.38 vs 0.67&#177;0.35 for TNF-α and VEGF respectively, P&lt;0.01) and M14 (2.23&#177;0.30 vs 1.20&#177;0.25 and 1.65&#177;0.38 vs 0.65&#177;0.18 for TNF-α and VEGF respectively, P&lt;0.01), but there was no difference between M7 and M14 (1.14&#177;0.38 vs 1.20&#177;0.25 and 0.67&#177;0.35 vs 0.65&#177;0.18 for TNF-α and VEGF respectively, P &gt;0.05). CONCLUSION: In the development of esophageal varices in portal hypertensive rats, increased TNF-α and VEGF may be not an early event, and probably play a role in weakening the esophageal wall and the rupture of esophageal varices.     

Absence of association between TNF-α polymorphism and cerebral large-vessel abnormalities in adults with sickle cell anemia

Stroke is a serious complication of sickle cell anemia (SCA) affecting children and adults. Recent reports suggested that tumor necrosis factor-α (TNF-α) (-308) polymorphism is an important risk factor for stroke in children with SCA. The role of TNF-α polymorphism in the frequency of brain magnetic resonance imaging (MRI) and magnetic resonance angiography (MRA) abnormalities in adults with SCA is still uncertain. Our objective was to evaluate the frequency of TNF-α polymorphism in adults with SCA and to correlate it to brain MRI and MRA findings. TNF-α (-308) polymorphism was determined in 49 adults with SCA. All subjects were evaluated with brain MRI/MRA to establish the presence of intracranial abnormalities. Thirty-three (67.3%) had abnormal brain MRA scans, 8 (16.3%) had intracranial stenosis and 29 (59.2%) showed arterial tortuosity. Forty-one (83.7%) had the GG genotype and 8 had the GA genotype. There was no correlation between homozygosity for G allele and MRA or MRI abnormalities. Although TNF-α (-308) polymorphism is a potential predictor of the genetic risk for stroke in children, we found no association between the polymorphism and large vessel abnormalities in adults with SCA.     

Does lack of Cftr gene lead to developmental abnormalities in the lung?

Lung disease is the major cause of death in cystic fibrosis (CF), but the effect of gene mutation on the morphology of the main structural compartments of the lung is poorly understood. We show here, to our knowledge for the first time, a quantitative comparison of the fine pulmonary structures of cftr mutant versus non-cf mice. Pertinent volumes and surface areas were estimated in 10 homozygous cftrm1HGU mutants and 11 non-cf littermates by unbiased stereology at the light microscopic level. Our data did not reveal any statistical differences between group means for any of the 9 parameters considered. In other words, our data do not supply any significant evidence that the lack of the Cftr gene is accompanied by any developmental abnormalities in the lung, at least as far as the parameters studied are concerned.     

Critical role of types 2 and 3 deiodinases in the negative regulation of gene expression by T₃in the mouse cerebral cortex

Thyroid hormones regulate brain development and function through the control of gene expression, mediated by binding of T(3) to nuclear receptors. Brain T(3) concentration is tightly controlled by homeostatic mechanisms regulating transport and metabolism of T(4) and T(3). We have examined the role of the inactivating enzyme type 3 deiodinase (D3) in the regulation of 43 thyroid hormone-dependent genes in the cerebral cortex of 30-d-old mice. D3 inactivation increased slightly the expression of two of 22 positively regulated genes and significantly decreased the expression of seven of 21 negatively regulated genes. Administration of high doses of T(3) led to significant changes in the expression of 12 positive genes and three negative genes in wild-type mice. The response to T(3) treatment was enhanced in D3-deficient mice, both in the number of genes and in the amplitude of the response, demonstrating the role of D3 in modulating T(3) action. Comparison of the effects on gene expression observed in D3 deficiency with those in hypothyroidism, hyperthyroidism, and type 2 deiodinase (D2) deficiency revealed that the negative genes are more sensitive to D2 and D3 deficiencies than the positive genes. This observation indicates that, in normal physiological conditions, D2 and D3 play critical roles in maintaining local T(3) concentrations within a very narrow range. It also suggests that negatively and positively regulated genes do not have the same physiological significance or that their regulation by thyroid hormone obeys different paradigms at the molecular or cellular levels.     

Lycopene supplementation reduces TNF-α via RAGE in the kidney of obese rats

Background:

The kidney is a target organ for injuries caused by advanced glycation end products (AGEs) in obesity. The receptor of AGEs (RAGE) is proinflammatory and appears to have a role in the pathogenesis of renal disease due to obesity.

Objective:

The aim was to verify the effect of obesity on renal damage and the effect of lycopene on these complications

Design and Methods:

Male Wistar rats were randomly assigned to receive a control diet (C, n=7) or a high-fat diet plus sucrose (HD+S, n=14) for 6 weeks. After this period, the HD+S animals were randomized into two groups: HD+S (n=7) and HD+S supplemented with lycopene (HD+S+L, n=7). The animals received maize oil (C and HD+S) or lycopene (HD+S+L) for a 6-week period.

Results:

The HD+S and HD+S+L animals demonstrated insulin resistance (OGTT glucose after 150 min; C: 117.6±3.9<HD+S: 138.1±5.1=HD+S+L: 137.8±5.2 mg dl⁻¹; P=0.01); however, no changes were seen in fasting glucose, plasma lipids, blood pressure or renal function. Renal concentrations of RAGE and TNF-α increased in the HD+S group and lycopene supplementation restored these to control group values (RAGE: C: 3.1±0.3=DH+S+L: 3.1±0.3<DH+S: 3.6±0.4 μg g⁻¹; P=0.014; TNF-α: C: 227.8±2.7=DH+S+L: 227.4±2.2<DH+S: 238.7±3.0 pg/ml; P=0.014).

Conclusions:

Lycopene may be beneficial in the prevention and treatment of oxidative stress and inflammation in the kidney due to obesity.     

Blockade of TNF-α rapidly inhibits pain responses in the central nervous system

There has been a consistent gap in understanding how TNF-α neutralization affects the disease state of arthritis patients so rapidly, considering that joint inflammation in rheumatoid arthritis is a chronic condition with structural changes. We thus hypothesized that neutralization of TNF-α acts through the CNS before directly affecting joint inflammation. Through use of functional MRI (fMRI), we demonstrate that within 24 h after neutralization of TNF-α, nociceptive CNS activity in the thalamus and somatosensoric cortex, but also the activation of the limbic system, is blocked. Brain areas showing blood-oxygen level-dependent signals, a validated method to assess neuronal activity elicited by pain, were significantly reduced as early as 24 h after an infusion of a monoclonal antibody to TNF-α. In contrast, clinical and laboratory markers of inflammation, such as joint swelling and acute phase reactants, were not affected by anti-TNF-α at these early time points. Moreover, arthritic mice overexpressing human TNF-α showed an altered pain behavior and a more intensive, widespread, and prolonged brain activity upon nociceptive stimuli compared with wild-type mice. Similar to humans, these changes, as well as the rewiring of CNS activity resulting in tight clustering in the thalamus, were rapidly reversed after neutralization of TNF-α. These results suggest that neutralization of TNF-α affects nociceptive brain activity in the context of arthritis, long before it achieves anti-inflammatory effects in the joints.     

J wave and ST segment elevation in the inferior leads: a latent type of variant Brugada syndrome?

In a patient referred for the evaluation of non-sustained monomorphic ventricular tachycardia on Holter recordings, ventricular fibrillation was electrically induced during electrophysiologic study. Despite the absence of structural heart diseases, his ECG revealed J wave and ST segment elevation in the inferior leads, which showed circadian variation and were augmented by the sodium channel blocker, pilsicainide. This case might lead us to notice a new concept, a 'latent' type of variant Brugada syndrome, and these ECG findings and changes might serve as its diagnostic sign.     

TLR4 mediates LPS-induced HO-1 expression in mouse liver： Role of TNF-α and IL-lβ

AIM: Heme oxygenase (HO)-I catalyzes the conversion of heme to biliverdin, iron and carbon monoxide. HO-1 is induced by many stimuli including heme, Hb, heat stress,lipopolysaccharide (LP5) and cytokines. Previous studies demonstrated that LP5 induced HO-1 gene activation and HO-1 expression in liver. However, the mechanisms of LPS-induced HO-1 expression in liver remain unknown. The effect of toll-like receptor-4 (TLR4) on LPS-induced liver HO-1 expression and the role of TNF-α and IL-1β in this condition were determined.METHODS: HO-1 expression was determined by immunofluorescent staining and immunoblotting. Double immunofluorescent staining was performed to determine the cell type of HO-1 expression in liver.RESULTS: A low dose of LPS significantly increased HO-1 expression in the liver which was localized in Kupffer cells only. Furthermore, HO-1 expression was enhanced by three doses of LPS. HO-1 expression was significantly inhibited in the liver of TLR4 mutant mice. While the liver HO-1 expression in TNF KO mice was much lower than that in C57 mice following the same LPS treatment, IL-1β KO had a slight influence on liver HO-1 expression following LPS treatment.CONCLUSION: The preserfl: results confirm that macrophages are the major source of HO-1 in the liver induced by LPS.This study demonstrates that TLR4 plays a dominant role in mediating HO-1 expression following LPS. LPS-induced HO-1 expression is mainly mediated by endogenous TNF-α, but only partially by endogenous IL-1β.