The effects of abnormalities of glucose homeostasis on the expression and binding of muscarinic receptors in cerebral cortex of rats

The distribution pattern of M2 and Adrenergicα2 receptors on inferior colliculi in male newborns of diabetic rats

AIMS

Despite the high prevalence of diabetes in the world, its possible effects throughut pregnancy on neonatal auditory nervous system development are still unknown. In the present research, maternal diabetes' impact on the M2 and Adrenergic_α2 receptors expression in the inferior colliculus (IC) of male newborn rats was investigated. Main methods Female rats were grouped into three: sham, insulin-treated diabetic, and diabetic. Diabetes was induced through streptozotocin (STZ) injection as one dose intraperitoneally (65 mg/kg). After mating and delivery, male rats were euthanized on P0, P7, and P14. Immunohistochemistry (IHC) was used to study the distribution pattern of receptors. Key findings The present study indicated that the expression of M2 receptors in the diabetic group was significantly increased in pairwise comparisons in the sham and diabetic treated with insulin groups (P<0.001, each). The highest M2 expression was for the diabetic group on P14 and the lowest one was for the sham group on P0. The Adrenergic_α2a receptors expression in the diabetic group was significantly reduced in pairwise comparisons in the sham and diabetic treated with insulin groups (P <0.001, each). The highest Adrenergic_α2a expression was for the sham group on P14 and the lowest one was for the diabetic group on P0. There was no significant difference between the sham and insulin groups regarding all receptors expression.

SIGNIFICANCE

This study demonstrated a time-dependent significant decrease in Adrenergic_α2a but a time-dependent significant increase in M2 receptors expression.

Glucose transporter 3 in neuronal glucose metabolism: Health and diseases

Neurons obtain glucose from extracellular environment for energy production mainly depending on glucose transporter 3 (GLUT3). GLUT3 uptakes glucose with high affinity and great transport capacity, and is important for neuronal energy metabolism. This review summarized the role of neuronal GLUT3 in brain metabolism, function and development under both physiological conditions and in diseases, aiming to provide insights into neuronal glucose metabolism and its effect on brain. GLUT3 stabilizes neuronal glucose uptake and utilization, influences brain development and function, and ameliorates aging-related manifestations. Neuronal GLUT3 is regulated by synaptic activity, hormones, nutrition, insulin and insulin-like growth factor 1 in physiological conditions, and is also upregulated by hypoxia-ischemia. GLUT3-related neuronal glucose and energy metabolism is possibly involved in the pathogenesis, pathophysiological mechanism, progression or prognosis of brain diseases, including Alzheimer's disease, Huntington's disease, attention-deficit/hyperactivity disorder and epilepsy. GLUT3 may be a promising therapeutic target of these diseases. This review also briefly discussed the role of other glucose transporters in neuronal glucose metabolism, which work together with GLUT3 to sustain and stabilize glucose and energy supply for neurons. Deficiency in these glucose transporters may also participate in brain diseases, especially GLUT1 and GLUT4.

Real-time effects of insulin-induced hypoglycaemia on hippocampal glucose and oxygen

The hippocampus plays a vital role in learning and memory and is susceptible to damage following hypoglycaemic shock. The effect of an acute administration of insulin on hippocampal function has been described in terms of behavioural deficits but its effect on hippocampal oxygen and glucose is unclear. Glucose oxidase biosensors (detecting glucose) and carbon paste electrodes (detecting oxygen) were implanted into the hippocampus of Sprague Dawley rats. Animals were allowed to recover and real-time recordings were made in order to determine the effects of fasting, insulin administration (15 U/kg; i.p.) and reintroduction of food on hippocampal oxygen and glucose. Fasting caused a significant decrease in hippocampal glucose over the course of 24h. Insulin administration produced a significant decrease in hippocampal glucose along with a significant increase in hippocampal oxygen. Finally, the reintroduction of food resulted in glucose levels significantly increasing along with a transient but significant increase in oxygen levels. The findings presented here suggest that even a single acute period of hypoglycaemia may substantially disrupt hippocampal oxygen and glucose and therefore affect hippocampal function.

Kampo formulations, chotosan, and yokukansan, for dementia therapy: existing clinical and preclinical evidence

Cognitive deficits and behavioral and psychological symptoms of dementia (BPSD) are typical features of patients with dementia such as Alzheimer's disease (AD), vascular dementia (VD), and other forms of senile dementia. Clinical evidence has demonstrated the potential usefulness of chotosan (CTS) and yokukansan (YKS), traditional herbal formulations called Kampo medicines, in the treatment of cognitive disturbance and BPSD in dementia patients, although the indications targeted by CTS and YKS in Kampo medicine differ. The availability of CTS and YKS for treating dementia patients is supported by preclinical studies using animal models of dementia that include cognitive/emotional deficits caused by aging and diabetes, dementia risk factors. These studies have led not only to the concept of a neuronal basis for the CTS- and YKS-induced amelioration of cognitive function and emotional/psychiatric symptom-related behavior in animal models, but also to a proposal that ingredient(s) of Uncariae Uncis cum Ramulus, a medicinal herb included in CTS and YKS, may play an important role in the actions of these formulae in dementia patients. Further studies are needed to clarify the active ingredients of these formulae and their target endogenous molecules implicated in the anti-dementia drug-like actions.

Cholinergic receptor alterations in the brain stem of spinal cord injured rats

Cholinergic receptors in upper motor neurons of brain stem control locomotion and coordination. Present study unravels cholinergic alterations in brain stem during spinal cord injury to understand signalling pathway changes which may be associated with spinal cord injury mediated motor deficits. We evaluated cholinergic function in brain stem by studying the expression of choline acetyl transferase and acetylcholine esterase. We quantified metabotropic muscarinic cholinergic receptors by receptor assays for total muscarinic, muscarinic M1 and M3 receptor subunits, gene expression studies using Real Time PCR and confocal imaging using FITC tagged secondary antibodies. The gene expression of ionotropic nicotinic cholinergic receptors and confocal imaging were also studied. The results from our study showed metabolic disturbance in cholinergic pathway as choline acetyl transferase is down regulated and acetylcholine esterase is up regulated in spinal cord injury group. The significant decrease in muscarinic receptors showed by decreased receptor number along with down regulated gene expression and confocal imaging accounts for dysfunction of metabotropic acetylcholine receptors in spinal cord injury group. Ionotropic acetylcholine receptor alterations were evident from the decreased gene expression of alpha 7 nicotinic acetylcholine receptors and confocal imaging. The motor coordination was analysed by Grid walk test which showed an increased foot slips in spinal cord injured rats. The significant reduction in brain stem cholinergic function might have intensified the motor dysfunction and locomotor disabilities.