An Experimental Analysis of the Catecholamines in Hyperglycemia and Acidosis-Induced Rat Brain

The Role of Pro-Opiomelanocortin Derivatives in the Development of Type 2 Diabetes-Associated Myocardial Infarction: Possible Links with Prediabetes

Myocardial infarction is a major contributor to CVD-related mortality. T2DM is a risk factor for MI. Stress activates the HPA axis, SNS, and endogenous OPS. These POMC derivatives increase the blood glucose and cardiovascular response by inhibiting the PI3K/AkT insulin signaling pathway and increasing cardiac contraction. Opioids regulate the effect of the HPA axis and SNS and they are cardioprotective. The chronic activation of the stress response may lead to insulin resistance, cardiac dysfunction, and MI. Stress and T2DM, therefore, increase the risk of MI. T2DM is preceded by prediabetes. Studies have shown that prediabetes is associated with an increased risk of MI because of inflammation, hyperlipidemia, endothelial dysfunction, and hypertension. The HPA axis is reported to be dysregulated in prediabetes. However, the SNS and the OPS have not been explored during prediabetes. The effect of prediabetes on POMC derivatives has yet to be fully explored and understood. The impact of stress and prediabetes on the cardiovascular response needs to be investigated. This study sought to review the potential impact of prediabetes on the POMC derivatives and pathways that could lead to MI.

Brain signalling systems: A target for treating type I diabetes mellitus

From early to later stages of Type I Diabetes Mellitus (TIDM), signalling molecules including brain indolamines and protein kinases are altered significantly, and that has been implicated in the Metabolic Disorders (MD) as well as impairment of retinal, renal, neuronal and cardiovascular systems. Considerable attention has been focused to the effects of diabetes on these signalling systems. However, the exact pathophysiological mechanisms of these signals are not completely understood in TIDM, but it is likely that hyperglycemia, acidosis, and insulin resistance play significant roles. Insulin maintains normal glycemic levels and it acts by binding to its receptor, so that it activates the receptor's tyrosine kinase activity, resulting in phosphorylation of several substrates. Those substrates provide binding/interaction sites for signalling molecules, including serine/threonine kinases and indolamines. For more than two decades, our research has been focused on the mechanisms of protein kinases, CaM Kinase and Serotonin transporter mediated alterations of indolamines in TIDM. In this review, we have also discussed how discrete areas of brain respond to insulin or some of the pharmacological agents that triggers or restores these signalling molecules, and it may be useful for the treatment of specific region wise changes/disorders of diabetic brain.

Amitraz changes NE, DA and 5-HT biosynthesis and metabolism mediated by alterations in estradiol content in CNS of male rats

Amitraz is a formamidine insecticide/acaricide that alters different neurotransmitters levels, among other neurotoxic effects. Oral amitraz exposure (20, 50 and 80 mg/kg bw, 5 days) has been reported to increase serotonin (5-HT), norepinephrine (NE) and dopamine (DA) content and to decrease their metabolites and turnover rates in the male rat brain, particularly in the striatum, prefrontal cortex, and hippocampus. However, the mechanisms by which these alterations are produced are not completely understood. One possibility is that amitraz monoamine oxidase (MAO) inhibition could mediate these effects. Alternatively, it alters serum concentrations of sex steroids that regulate the enzymes responsible for these neurotransmitters synthesis and metabolism. Thus, alterations in sex steroids in the brain could also mediate the observed effects. To test these hypothesis regarding possible mechanisms, we treated male rats with 20, 50 and 80 mg/kg bw for 5 days and then isolated tissue from striatum, prefrontal cortex, and hippocampus. We then measured tissue levels of expression and/or activity of MAO, catechol-O-metyltransferase (COMT), dopamine-β-hydroxylase (DBH), tyrosine hydroxylase (TH) and tryptophan hydroxylase (TRH) as well as estradiol levels in these regions. Our results show that amitraz did not inhibit MAO activity at these doses, but altered MAO, COMT, DBH, TH and TRH gene expression, as well as TH and TRH activity and estradiol levels. The alteration of these enzymes was partially mediated by dysregulation of estradiol levels. Our present results provide new understanding of the mechanisms contributing to the harmful effects of amitraz.

The Regulation of Feeding: A Cross Talk between Peripheral and Central Signalling

Feeding and energy expenditures are modulated by the interplay of hormones and neurotransmitters in the central nervous system (CNS), where the hypothalamus plays a pivotal role in the transduction of peripheral afferents into satiety and feeding signals. Aminergic neurotransmitters such as dopamine (DA), norepinephrine (NE) and serotonin (5-hydroxytryptamine, 5-HT) are historically considered to play a key role, but a number of peptides are involved in finely tuning feeding regulation. This review summarizes the current understanding of the CNS mechanisms of orexigenic peptides, such as neuropeptide Y, orexins, and ghrelin, as well as anorectic peptides, such as leptin, neurotensin (NT), cocaine- and amphetamine regulated transcript (CART) peptide, thyrotropin-releasing hormone (TRH), corticotropin-releasing hormone (CRH), urocortin, amylin.

The Impact of a Successful Anti-Myxosporean Treatment on the Phagocyte Functions of Juvenile and Adult Sparus Aurata L

The aim of the present study was to investigate the impact of a successful anti-myxosporean medication on the innate immune system of fish intensively cultured in the Mediterranean basin. For this purpose, juvenile and adult gilthead seabream ( S. aurata L.) naturally infected with Polysporoplasma sparis in the kidney were used in a small-scale field trial. The infected fish were treated orally with the combination of salinomycin and amprolium, two drugs well known for their anti-coccidial effect in other animals. Drug efficacy and safety was evaluated in terms of changes observed in histopathology, mortality and P. sparis intensity and prevalence rate. Phagocytic functions of head-kidney leucocytes were also investigated at the end as well as one month post the medication. Salinomycin with amprolium exhibited a significant reduction in intensity and prevalence rate in both juvenile and adult fish, and no histopathological evidence for toxic side effects was observed. In addition, the successful treatment was closely correlated with a complete restoration of the diminished phagocytic ability and capacity as well as NO, and lysozyme secretion in a time dependent manner. This data suggests that salilomycin with amprolium can be an alternative treatment for myxosporean infections in warm-water fish, possibly exhibiting their action through the enhancement of host innate functions.

Excessively High Magnetic Resonance Signal in Preterm Infants and Neuropsychobehavioural Follow-up at 2 Years

The diffuse excessive high-signal intensity (DEHSI) findings in the T2 weighted scans of white matter (WM), besides the corresponding low signal in the T1 weighted images, are usually more evident around the periventricular regions. It is not clear whether the DEHSI should be considered as a diffuse WM injury rather than a sign of delayed maturation of the WM. Eighty nine preterm infants at the full-term equivalent age (FEA) were studied using conventional Magnetic Resonance (MR) imaging of the brain. Based on the MR findings, the infants studied were divided into three groups: the control group presenting normal WM, the DEHSI group and the group with other WM lesions. Ten newborns were not included in the statistical analysis because they presented evidence of precedent germinal matrix hemorrhage (GMH-IVH) which cannot be considered as WM lesions. Seventy nine infants were enrolled in a program of neuropsychobehavioural study follow-up until 24 months of age. Each infant was evaluated for those variables which mostly affect the occurrence of neuropsychomotor disability. In the DEHSI infant group, significantly lower mean pH and mean base excess (BE) values were found in comparison to controls, while the mean birth weight (BW) was significantly higher. No significant difference was observed between the mean 1st minute Apgar Score, mean birth gestational age (GA) and assisted ventilation mean duration of controls and DEHSI groups. Finally, no significant difference between the parameters studied was found by comparing the WM lesion infants group to the DEHSI infants one. Our observations, together with follow-up studies, even up to school age, confirm that DEHSI has a clinical significance and cannot be considered as a simple indicator of delayed WM maturation.

Cannabinoid Receptors and Their Relationships with Neuropsychiatric Disorders

Cannabinoids are the costituents of the marijuana plants. The central effects of exogenous cannabinoids are implicated in enhancing mood, altering emotional states, and interfering in the formation of short-term memory. Cannabinoid receptors are G protein-coupled receptors with seven transmembrane domains that are expressed on the cell surface with their binding domain exposed to the extracellular space. To date, two cannabinoid receptors have been cloned, CB1 and CB2. Recent evidence suggests that a third ‘CB3’ receptor may be cloned in the near future. The endocannabinoids may represent the first members of a new classes of neuromodulators, that are not stored in cell vesicles, but rather synthesised by the cell on demand. The endogenous cannabinoid system could play a central role in several neuropsychiatric disorders and is also involved in other conditions such as pain, spasticity and neuroprotection. Implication of cannabinoid system in the pathogenesis and development of schizophrenia is also discussed.

Regulation of protein kinases and coregulatory interplay of S-100beta and serotonin transporter on serotonin levels in diabetic rat brain

Protein kinases are critical component in the regulation of signal transduction pathways, including neurotransmitters. Our previous studies have shown that serotonin (5-HT) altered under diabetic condition was accompanied by alterations of protein kinase C-alpha (PKC-alpha) and CaMKII, and those alterations were reversed after insulin administration. The current study showed that alloxan-induced diabetic animals revealed hyperglycemia and was associated with an increase in the content of 5-HT, PKC-alpha expression and PKC activity (P < 0.05) simultaneously in striatum (ST), midbrain (MB), pons medulla (PM), cerebellum (CB), and cerebral cortex (CCX) from 7 days to 60 days. Although the 5-HT levels in hippocampus (HC) and hypothalamus (HT) were not altered, the PKC-alpha expression and PKC activity showed increases (P < 0.05) in level in HC. Insulin administration reversed all these changes to a normal level. In contrast, the in vitro study has shown that the 5-HT levels correlated with PKC-alpha expressions as well as PKC activity (P < 0.05) only in ST, MB, and CB either after induction with phorbol 12-myristate 13-acetate (PMA) or blocking with chelerythrine, whereas PM and CCX remained elevated (P < 0.05), implying a regulatory role for PKC-alpha only in ST, MB, and CB. However, our consecutive studies have shown that the 5-HT level in PM was regulated by p38-mitogen-activated protein kinase (p38-MAPK) both in vivo and in vitro, whereas the 5-HT level in CCX was coregulated by S-100beta by protein-protein interaction with serotonin transporter (SERT) via 8-bromoadenosine 3',5'-cyclic monophosphate sodium salt (8-Br-cAMP)-induced cAMP/PKAII pathway(s).

Glycemia management in neurocritical care patients: a review

Intensive research investigating the relation between the management of glycemia and outcome in patients receiving neurocritical care has underlined the possible benefits and adverse events related to glucose control. Here, we review experimental and clinical studies investigating the effects of hypoglycemia and hyperglycemia on the brain that advance current knowledge on managing glycemia in patients receiving neurocritical care.

Altered basal and stimulated accumbens dopamine release in obese OLETF rats as a function of age and diabetic status

The Otsuka Long-Evans Tokushima Fatty (OLETF) rat lacking the CCK-1 receptor is hyperphagic, prefers palatable and high-calorie meals, and gradually develops obesity and type 2 diabetes. To determine dopamine levels in this strain, we used in vivo quantitative (no net flux) microdialysis at three different ages representing nondiabetic (8 wk), prediabetic (18 wk), and diabetic (56 wk) stages in OLETF and age-matched lean Long-Evans Tokushima Otsuka (LETO) controls. Results showed significantly elevated basal dopamine levels in the caudomedial nucleus accumbens of OLETF rats compared with LETO at younger ages (8 wk: 20.10 +/- 5.61 nM vs. 15.85 +/- 5.63 nM; 18 wk: 7.37 +/- 3.71 nM vs. 4.75 +/- 1.25 nM, means +/- SD). In contrast, at 56 wk of age, a profound decline in extracellular dopamine concentrations was seen in both strains with a tendency for a greater effect in OLETF rats (1.78 +/- 0.40 nM vs. 2.39 +/- 0.42 nM). Further, extracellular fraction, an index for reuptake, was higher in 56-wk-old OLETF compared with LETO (0.648 +/- 0.049 vs. 0.526 +/- 0.057). Potassium-stimulated dopamine efflux revealed an increased capacity of vesicular pool in OLETF rats compared with LETO across all age groups with an accentuated strain difference at 56 wk. These findings demonstrate altered striatal dopamine functions (i.e., increased stimulated release and uptake) in obese OLETF rat. This could be due to the lack of functional CCK-1 receptors, or metabolic and hormonal factors associated with the development of obesity and insulin resistance, or both.

Combined insulin and bicarbonate therapy elicits cerebral edema in a juvenile mouse model of diabetic ketoacidosis

Cerebral edema in diabetic ketoacidosis (DKA-CE) occurs primarily in children and can develop during DKA therapy. The treatment factors contributing to DKA-CE remain elusive. Our objectives were to characterize an age-appropriate DKA mouse model and to determine which DKA therapies contribute to DKA-CE. Juvenile mice were briefly fed a high-fat diet and injected with two pancreatic beta-cell toxins: streptozocin and alloxan. Severe insulin and leptin deficiencies associated with hyperosmolar ketoacidosis rapidly developed, indicating DKA. DKA mice were treated with re-hydration +/- insulin and brain water content (BWC) measured as an indicator of DKA-CE. As expected, glucose and beta-OH-butyrate corrected in DKA mice that received rehydration and insulin. BWC significantly increased above control levels only in DKA mice that received combined insulin and bicarbonate therapy, indicating the development of DKA-CE. Microscopically, DKA-CE brains had perineuronal and perivascular edema, with microvacuolation in the white matter tracts. These results indicate that insulin-deficient juvenile mice develop biochemical changes that are similar to those of DKA in children. Increased BWC was observed only in DKA mice that received combined insulin and bicarbonate therapy, suggesting that rapid systemic alkalinization in the presence of insulin may contribute to DKA-CE.

An acute hyperglycemia or acidosis-induced changes of indolamines level correlates with PKC-alpha expression in rat brain

Hyperglycemia and ketoacidosis are the two most serious factors in acute metabolic complications of both type 1 and type 2 diabetes. Dysfunction of the central nervous system is a well-documented complication of diabetes. We and others have previously reported that acute or chronic diabetes in animal's results in altered brain neurotransmitter levels. In this study, we investigated the effects of acute (7 days) glucose-induced hyperglycemia and sodium acetoacetate (NaAcAc) or ammonium chloride (NH4Cl) induced acidosis on the level of indolamines (5-hydroxytryptamine (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA)) as well as PKC-alpha expression/activity in discrete areas of rat brain. Glucose-induced (500 mg/kg, bw) hyperglycemic ( approximately 249 mg%) rats showed significant (p<0.05) increase in 5-HT levels in mid brain (MB), pons medulla (PM) and cerebellum (CB), respectively. 5-HIAA level increased in hippocampus (HC) (p<0.05) as compared to control. The rats treated with sodium acetoacetate (NaAcAc) for 7 days (60 mg/kg, bw) showed significant decrease (p<0.05) of 5-HT level in hypothalamus (HT). Whereas, the 5-HIAA level increased in MB (p<0.05). Similarly, the PKC-alpha expression as well as the enzyme activity showed significant increase in HC, MB, PM and CB under glucose-induced hyperglycemia and that changes correlated the changes of indolamines, suggesting that the hyperglycemia may be the major metabolic disorder in diabetic complications.

A short-term diabetes induced changes of catecholamines and p38-MAPK in discrete areas of rat brain

Chronic diabetes is associated with the alteration of second messengers and CNS disorders. We have recently identified that protein kinases (CaMKII and PKC-alpha) and brain neurotransmitters are altered during diabetes as well as in hyperglycemic and acidotic conditions. In this study, we investigated the effects of acute diabetes on the levels of dopamine (DA), norepinephrine (NE), epinephrine (E) and p38-Mitogen-Activated Protein Kinase (p38-MAPK) in striatum (ST), hippocampus (HC), hypothalamus (HT), midbrain (MB), pons medulla (PM), cerebellum (CB) and cerebral cortex (CCX). Alloxan (45 mg/kg) diabetic untreated rats that showed hyperglycemia (>260 mg%), revealed significant increases of DA level in ST (1.5 fold), HC (2.2 fold) and PM (2.0 fold) and the E level also found to be increased significantly in HT (2.4 fold), whereas the NE level was decreased in CB (0.5 fold), after 7 days of diabetes. Immunoblotting study of p38-MAPK expression under identical conditions showed significant alterations in ST, HC, HT and PM (p<0.05) correlated with the changes of catecholamines (DA and E). On the other hand, the above changes were reversed in insulin-treated diabetic rats maintained under normal glucose level (80 -110 mg %). These results suggest that p38-MAPK may regulate the rate of either the synthesis or release of DA and E in corresponding brain areas, but not NE, under these conditions.

Involvement of Ca2+/calmodulin-dependent protein kinase II in the modulation of indolamines in diabetic and hyperglycemic rats

Hyperglycemia and acidosis are the key factors in diabetic complications. It has been shown that acute or chronic diabetes alters serotonin levels in brain. However, the mechanism of hyperglycemia- or acidosis-induced changes in serotonin levels remains poorly understood. Because Ca2+-dependent protein kinases play a major role in the regulation of serotonin synthesis and release, we investigated the effect of diabetes, hyperglycemia, and acidosis on the level of indolamines [5-hydroxytryptamine (5-HT) and/or 5-hydroxyindoleacetic acid (5-HIAA)] and Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) enzyme activity or protein expression in different brain regions. Alloxan-induced (45 mg/kg bw) diabetic rats (30 days) showed increased level of 5-HT in striatum (ST; 183%), midbrain (MB; 199%), pons medulla (PM; 151%), cerebellum (CB; 214%), and cerebral cortex (CCX; 162%) compared with control (P < 0.05), and these changes were reversed after insulin administration. Rats treated with glucose (500 mg/kg bw) for 30 days showed a 146%, 183%, 208%, and 177% (P < 0.05) increase in 5-HT levels in ST, PM, CB, and CCX, respectively. 5-HIAA level increased in hippocampus (HC; 172%) and in MB (145%; P < 0.05). In addition, rats treated with sodium acetoacetate (NaAcAc) for 30 days (60 mg/kg bw) showed significant increases (P < 0.05) of 5-HT level in ST (152%) and MB (174%). However, the levels of 5-HIAA increased only in MB (151%, P < 0.05). Rats treated with NH4Cl, which induced acidosis (150 mg/kg bw), showed an increased level of 5-HT only in HC (165%, P < 0.05). The increased activity and protein expression of CaMKII in ST, MB, PM, CB, and CCX under diabetic conditions were correlated with the levels of indolamines changes during diabetic, hyperglycemic, or acidotic conditions. These results suggest that CaMKII may be involved in the regulation of indolamines in diabetic animals.

PKC-alpha mediated alterations of indoleamine contents in diabetic rat brain

We previously have reported that acute or chronic diabetes in animals resulted in altered neurotransmitter levels. In this study, we investigated the concentrations of 5-hydroxytryptamine (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) in discrete areas of brain viz. striatum (ST), hippocampus (HC), hypothalamus (HT), midbrain (MB), pons medulla (PM), cerebellum (CB) and cerebral cortex (CCX) of control, untreated diabetic and insulin treated diabetic rats after 30 days. Alloxan (45 mg/kg) diabetic untreated rats, which showed hyperglycemia (>250 mg%), revealed significant increases of 5-HT level in ST, MB, PM, CB and CCX and the 5-HIAA level found to be increased significantly in ST, HC and MB. Whereas the insulin treated rats, which was maintained under normal glucose level (80-110 mg%), showed no significant changes in any of the areas studied. The expressions of PKC-alpha studied by immunoblotting also showed significant changes in ST, HC, MB, PM, CB and CCX that is identical to the changes of both 5-HT and 5-HIAA under similar condition, suggesting that the PKC-alpha may regulate the synthesis and release of indoleamines in diabetic animals.