Clonazepam increases in vivo striatal extracellular glucose in diabetic rats after glucose overload

Bimodal Release Two-In-One Clonazepam Matrix Lozenge Tablets for Managing Anxiety-Related Disorders: Formulation, Optimization and In Vivo Evaluation

Clonazepam (CLZ), an antipsychotic drug reported for its efficiency in managing anxiety-related disorders, is being marketed only as conventional tablets. Some patients have abstention to swallow the conventional tablets; therefore, the proposed study was aimed at developing a buccal lozenge tablet by direct compression of two types of optimized granules. Conazepam’s water solubility was first enhanced by a solid dispersion technique for a fast and better dissolution of type 1 granules, while the impact of gelling polymers was investigated on controlled-release type 2 granules. The optimized formulae met the acceptable pharmacopeial limits for tablets’ evaluation. A differential scanning calorimetry study revealed the compatibility between the drug and used excipients. All formulae gave a burst release of CLZ in the first hour of investigation, followed by a sustained release over 24 h. The formula that showed the highest prolonged in vitro release (99.0 + 0.1%), following the Higuchi diffusion model (R2 = 0.99), was then selected for further study. The formula succeeded in controlling the induced stress in a rat model with a significant impact on the behavioral tests throughout the experiment. The results were further confirmed by a pharmacokinetic study that showed a significant increase in Cmax, Tmax, and AUC (1.5, 2, and 3.9 folds), respectively, compared to oral suspension. The newly proposed delivery system has proven a better efficacy with a reduced dosing frequency.

Diabetes, a Contemporary Risk for Parkinson's Disease: Epidemiological and Cellular Evidences

Diabetes mellitus (DM), a group of diseases characterized by defective glucose metabolism, is the most widespread metabolic disorder affecting over 400 million adults worldwide. This pathological condition has been implicated in the pathogenesis of a number of central encephalopathies and peripheral neuropathies. In further support of this notion, recent epidemiological evidence suggests a link between DM and Parkinson’s disease (PD), with hyperglycemia emerging as one of the culprits in neurodegeneration involving the nigrostriatal pathway, the neuroanatomical substrate of the motor symptoms affecting parkinsonian patients. Indeed, dopaminergic neurons located in the mesencephalic substantia nigra appear to be particularly vulnerable to oxidative stress and degeneration, likely because of their intrinsic susceptibility to mitochondrial dysfunction, which may represent a direct consequence of hyperglycemia and hyperglycemia-induced oxidative stress. Other pathological pathways induced by increased intracellular glucose levels, including the polyol and the hexosamine pathway as well as the formation of advanced glycation end-products, may all play a pivotal role in mediating the detrimental effects of hyperglycemia on nigral dopaminergic neurons. In this review article, we will examine the epidemiological as well as the molecular and cellular clues supporting the potential susceptibility of nigrostriatal dopaminergic neurons to hyperglycemia.

Simultaneous recording of brain extracellular glucose, spike and local field potential in real time using an implantable microelectrode array with nano-materials

Glucose is the main substrate for neurons in the central nervous system. In order to efficiently characterize the brain glucose mechanism, it is desirable to determine the extracellular glucose dynamics as well as the corresponding neuroelectrical activity in vivo. In the present study, we fabricated an implantable microelectrode array (MEA) probe composed of platinum electrochemical and electrophysiology microelectrodes by standard micro electromechanical system (MEMS) processes. The MEA probe was modified with nano-materials and implanted in a urethane-anesthetized rat for simultaneous recording of striatal extracellular glucose, local field potential (LFP) and spike on the same spatiotemporal scale when the rat was in normoglycemia, hypoglycemia and hyperglycemia. During these dual-mode recordings, we observed that increase of extracellular glucose enhanced the LFP power and spike firing rate, while decrease of glucose had an opposite effect. This dual mode MEA probe is capable of examining specific spatiotemporal relationships between electrical and chemical signaling in the brain, which will contribute significantly to improve our understanding of the neuron physiology.

Diet-induced obesity impairs hypothalamic glucose sensing but not glucose hypothalamic extracellular levels, as measured by microdialysis

BACKGROUND/OBJECTIVES

Glucose from the diet may signal metabolic status to hypothalamic sites controlling energy homeostasis. Disruption of this mechanism may contribute to obesity but its relevance has not been established. The present experiments aimed at evaluating whether obesity induced by chronic high-fat intake affects the ability of hypothalamic glucose to control feeding. We hypothesized that glucose transport to the hypothalamus as well as glucose sensing and signaling could be impaired by high-fat feeding.

SUBJECTS/METHODS

Female Wistar rats were studied after 8 weeks on either control or high-lard diet. Daily food intake was measured after intracerebroventricular (i.c.v.) glucose. Glycemia and glucose content of medial hypothalamus microdialysates were measured in response to interperitoneal (i.p.) glucose or meal intake after an overnight fast. The effect of refeeding on whole hypothalamus levels of glucose transporter proteins (GLUT) 1, 2 and 4, AMPK and phosphorylated AMPK levels was determined by immunoblotting.

RESULTS

High-fat rats had higher body weight and fat content and serum leptin than control rats, but normal insulin levels and glucose tolerance. I.c.v. glucose inhibited food intake in control but failed to do so in high-fat rats. Either i.p. glucose or refeeding significantly increased glucose hypothalamic microdialysate levels in the control rats. These levels showed exacerbated increases in the high-fat rats. GLUT1 and 4 levels were not affected by refeeding. GLUT2 levels decreased and phosphor-AMPK levels increased in the high-fat rats but not in the controls.

CONCLUSIONS

The findings suggest that, in the high-fat rats, a defective glucose sensing by decreased GLUT2 levels contributed to an inappropriate activation of AMPK after refeeding, despite increased extracellular glucose levels. These derangements were probably involved in the abolition of hypophagia in response to i.c.v. glucose. It is proposed that 'glucose resistance' in central sites of feeding control may be relevant in the disturbances of energy homeostasis induced by high-fat feeding.

Effect of fish oil intake on glucose levels in rat prefrontal cortex, as measured by microdialysis

Background

Brain glucose sensing may contribute to energy homeostasis control. The prefrontal cortex (PFC) participates in the hedonic component of feeding control. As high-fat diets may disrupt energy homeostasis, we evaluated in male Wistar rats whether intake of high-fat fish-oil diet modified cortical glucose extracellular levels and the feeding induced by intracerebroventricular glucose or PFC glucoprivation.

Methods

Glucose levels in PFC microdialysates were measured before and after a 30-min meal. Food intake was measured in animals receiving intracerebroventricular glucose followed, 30-min. later, by 2-deoxy-D-glucose injected into the PFC.

Results

The fish-oil group showed normal body weight and serum insulin while fat pads weight and glucose levels were increased. Baseline PFC glucose and 30-min. carbohydrates intake were similar between the groups. Feeding-induced PFC glucose levels increased earlier and more pronouncedly in fish-oil than in control rats. Intracerebroventricular glucose inhibited feeding consistently in the control but not in the fish-oil group. Local PFC glucoprivation with 2-DG attenuated glucose-induced hypophagia.

Conclusions

The present experiments have shown that, following food intake, more glucose reached the prefrontal cortex of the rats fed the high-fat fish-oil diet than of the rats fed the control diet. However, when administered directly into the lateral cerebral ventricle, glucose was able to consistently inhibit feeding only in the control rats. The findings indicate that, an impairment of glucose transport into the brain does not contribute to the disturbances induced by the high-fat fish-oil feeding.

Resveratrol and red wine function as antioxidants in the nervous system without cellular proliferative effects during experimental diabetes

Chronic hyperglycemia increases oxidative stress status and has been associated with neurological complications in diabetic individuals. This study compared the antioxidant properties of red wine or resveratrol in different brain areas of diabetic and non-diabetic rats, and investigated the effect of them on hippocampal cell proliferation in hippocampal dentate gyrus of diabetic rats. Streptozotocin-induced diabetic and control rats were treated with red wine (4 mL/kg), resveratrol (20 mg/kg), or saline, by oral gavage, for 21 days. Lipid peroxidation (TBARS), catalase and superoxide dismutase were measured to evaluate the oxidative stress and the BrdU-positive cells were assessed to measure changes in cellular proliferation. In diabetic animals, resveratrol showed antioxidant property in the hippocampus and in the striatum, while red wine had an antioxidant effect only in the hippocampus. Neither red wine nor resveratrol reversed the lower hippocampal cell proliferation in diabetic rats. Daily doses of red wine or resveratrol have an antioxidant effect in rats depending on the brain area and the glycemic status.