Modulation of Monoaminergic Neural Circuits

Role of ketone bodies in diabetes-induced dementia: sirtuins, insulin resistance, synaptic plasticity, mitochondrial dysfunction, and neurotransmitter

Patients with type 2 diabetes can have several neuropathologies, such as memory deficits. Recent studies have focused on the association between metabolic imbalance and neuropathological problems, and the associated molecular pathology. Diabetes triggers neuroinflammation, impaired synaptic plasticity, mitochondrial dysfunction, and insulin resistance in the brain. Glucose is a main energy substrate for neurons, but under certain conditions, such as fasting and starvation, ketone bodies can be used as an energy fuel for these cells. Recent evidence has shed new light on the role of ketone bodies in regulating several anti-inflammation cellular pathways and improving glucose metabolism, insulin action, and synaptic plasticity, thereby being neuroprotective. However, very high amount of ketone bodies can be toxic for the brain, such as in ketoacidosis, a dangerous complication that may occur in type 1 diabetes mellitus or alcoholism. Recent findings regarding the relationship between ketone bodies and neuropathogenesis in dementia are reviewed in this article. They suggest that the adequately low amount of ketone bodies can be a potential energy source for the treatment of diabetes-induced dementia neuropathology, considering the multifaceted effects of the ketone bodies in the central nervous system. This review can provide useful information for establishing the therapeutic guidelines of a ketogenic diet for diabetes-induced dementia.

High Fructose Corn Syrup-Moderate Fat Diet Potentiates Anxio-Depressive Behavior and Alters Ventral Striatal Neuronal Signaling

The neurobiological mechanisms that mediate psychiatric comorbidities associated with metabolic disorders such as obesity, metabolic syndrome and diabetes remain obscure. High fructose corn syrup (HFCS) is widely used in beverages and is often included in food products with moderate or high fat content that have been linked to many serious health issues including diabetes and obesity. However, the impact of such foods on the brain has not been fully characterized. Here, we evaluated the effects of long-term consumption of a HFCS-Moderate Fat diet (HFCS-MFD) on behavior, neuronal signal transduction, gut microbiota, and serum metabolomic profile in mice to better understand how its consumption and resulting obesity and metabolic alterations relate to behavioral dysfunction. Mice fed HFCS-MFD for 16 weeks displayed enhanced anxiogenesis, increased behavioral despair, and impaired social interactions. Furthermore, the HFCS-MFD induced gut microbiota dysbiosis and lowered serum levels of serotonin and its tryptophan-based precursors. Importantly, the HFCS-MFD altered neuronal signaling in the ventral striatum including reduced inhibitory phosphorylation of glycogen synthase kinase 3β (GSK3β), increased expression of ΔFosB, increased Cdk5-dependent phosphorylation of DARPP-32, and reduced PKA-dependent phosphorylation of the GluR1 subunit of the AMPA receptor. These findings suggest that HFCS-MFD-induced changes in the gut microbiota and neuroactive metabolites may contribute to maladaptive alterations in ventral striatal function that underlie neurobehavioral impairment. While future studies are essential to further evaluate the interplay between these factors in obesity and metabolic syndrome-associated behavioral comorbidities, these data underscore the important role of peripheral-CNS interactions in diet-induced behavioral and brain function. This study also highlights the clinical need to address neurobehavioral comorbidities associated with obesity and metabolic syndrome.

Evaluation of the neuro-protective effect of Artemisia judaica extract in a murine diabetic model

Chronic hyperglycemia is associated with several negative outcomes including neuronal injury. Medicinal plants supplementation has been widely applied to treat or decrease diabetic complications. Here, the possible neuroprotective effect of Artemisia judaica extract (AjE. 300 mg kg^-1  day^-1 ) against neuronal deficits in diabetes model induced by high-fat diet (HFD) administration and streptozotocin (STZ, 30 mg/Kg) injection in rats was investigated. Diabetic rats showed a disturbance in the neuronal redox homeostasis as confirmed by the elevated lipoperoxidation and nitric oxide formation along with the decreased antioxidant molecules. In addition, a state of neuroinflammation and apoptosis were recorded in the brain tissue in diabetic rats. Furthermore, HFD/STZ provoked neurochemical alterations. However, AjE administration was found to abrogate significantly the neuronal impairments associated with diabetes. This neuroprotective effect comes from its strong antioxidant, anti-inflammatory, antiapoptotic, and neuromodulatory activity; suggesting that AjE may be applied to alleviate neurological impairments in diabetic patients. PRACTICAL APPLICATIONS: Diabetes mellitus (DM) is a metabolic disorder characterized by high blood glucose level comes from the dysregulation of insulin production and/or its action. The persisted hyperglycemia is correlated with the progression of several physical complications including renal, hepatic, vascular, retinal, and neuronal dysfunction. Artemisia is used in the nutritional and medicinal proposes due to the enriched bioactive molecules such as essential oil, flavonoids, phenolics, sesquiterpenoids, triterpenoids, and artemisinin. And we found that Artemisia judaica extract (AjE) administration was able to abrogate significantly the neuronal impairments associated with diabetes. This neuroprotective effect comes from its strong antioxidant, anti-inflammatory, anti-apoptotic and neuromodulatory activity; suggesting that AjE may be applied to alleviate neurological impairments in diabetic patients.

Naproxen, a Nonsteroidal Anti-Inflammatory Drug, Can Affect Daily Hypobaric Hypoxia-Induced Alterations of Monoamine Levels in Different Areas of the Brain in Male Rats

Goswami, Ananda Raj, Goutam Dutta, and Tusharkanti Ghosh. Naproxen, a nonsteroidal anti-inflammatory drug can affect daily hypobaric hypoxia-induced alterations of monoamine levels in different areas of the brain in male rats. High Alt Med Biol. 17:133-140, 2016.-The oxidative stress (OS)-induced prostaglandin (PG) release, in hypobaric hypoxic (HHc) condition, may be linked with the changes of brain monoamines. The present study intends to explore the changes of monoamines in hypothalamus (H), cerebral cortex (CC), and cerebellum (CB) along with the motor activity in rats after exposing them to simulated hypobaric condition and the role of PGs on the daily hypobaric hypoxia (DHH)-induced alteration of brain monoamines by administering, an inhibitor of PG synthesis, naproxen. The rats were exposed to a decompression chamber at 18,000 ft for 8 hours per day for 6 days after administration of vehicle or naproxen (18 mg/kg body wt.). The monoamine levels (epinephrine, E; norepinephrine, NE; dopamine, DA; and 5-hydroxytryptamine, 5-HT) in CC, CB, and H were assayed by high-performance liquid chromatography (HPLC) with electrochemical detection, and the locomotor behavior was measured by open field test. The NE and DA levels were decreased in CC, CB, and H of the rat brain in HHc condition. The E and 5-HT levels were decreased in CC, but in H and CB, they remained unaltered in HHc condition. These DHH-induced changes of monoamines in brain areas were prevented after administration of naproxen in HHc condition. The locomotor behavior remained unaltered in HHc condition and after administration of naproxen in HHc condition. The DHH-induced changes of monoamines in the brain in HHc condition are probably linked with PGs that may be induced by OS.

Brain signaling systems in the Type 2 diabetes and metabolic syndrome: promising target to treat and prevent these diseases

The changes in the brain signaling systems play an important role in etiology and pathogenesis of Type 2 diabetes mellitus (T2DM) and metabolic syndrome (MS), being a possible cause of these diseases. Therefore, their restoration at the early stages of T2DM and MS can be regarded as a promising way to treat and prevent these diseases and their complications. The data on the functional state of the brain signaling systems regulated by insulin, IGF-1, leptin, dopamine, serotonin, melanocortins and glucagon-like peptide-1, in T2DM and MS, are analyzed. The pharmacological approaches to restoration of these systems and improvement of insulin sensitivity, energy expenditure, lipid metabolism, and to prevent diabetic complications are discussed.

Insulin reverses anxiety-like behavior evoked by streptozotocin-induced diabetes in mice

Clinical and preclinical data suggest that diabetes is often associated with anxiety. Insulin, a peptide hormone has been reported to have key functions in the brain and in alleviating several psychological impairments, occur as a consequence of diabetes. However, its effects in diabetes-induced anxiety are scanty. The present study examined whether; insulin can reverse the anxiety-like behavior in streptozotocin (STZ)-induced diabetes in mice. After 8-weeks of diabetes induced by STZ (200 mg/kg, intraperitoneally (i.p.)), mice were given insulin (1-2 IU/kg/day, i.p.)/ diazepam (1 mg/kg/day, i.p.)/ vehicle for 14 days and evaluated for behavioral effects in three validated models of anxiety viz. elevated plus maze (EPM), light-dark (L/D) and hole board (HB) tests. STZ-induced diabetic mice elicited significant behavioral effects which include, decreased percentage open arm entries and time in EPM, reduced latency and time spent in light chamber in L/D, decreased number of head dips, squares crossed and rearings in HB tests respectively. Insulin treatment attenuated the behavioral effects evoked by STZ-induced diabetes in mice as indicated by increased open arms activity in EPM, decreased aversion in light chamber during L/D test and increased exploratory behavior in HB test. In conclusion, this study revealed that insulin can reverse anxiety-like behavior in STZ-induced diabetes in mice.

The functional state of hormone-sensitive adenylyl cyclase signaling system in diabetes mellitus

Diabetes mellitus (DM) induces a large number of diseases of the nervous, cardiovascular, and some other systems of the organism. One of the main causes of the diseases is the changes in the functional activity of hormonal signaling systems which lead to the alterations and abnormalities of the cellular processes and contribute to triggering and developing many DM complications. The key role in the control of physiological and biochemical processes belongs to the adenylyl cyclase (AC) signaling system, sensitive to biogenic amines and polypeptide hormones. The review is devoted to the changes in the GPCR-G protein-AC system in the brain, heart, skeletal muscles, liver, and the adipose tissue in experimental and human DM of the types 1 and 2 and also to the role of the changes in AC signaling in the pathogenesis and etiology of DM and its complications. It is shown that the changes of the functional state of hormone-sensitive AC system are dependent to a large extent on the type and duration of DM and in experimental DM on the model of the disease. The degree of alterations and abnormalities of AC signaling pathways correlates very well with the severity of DM and its complications.

Effect of Bacopa monniera on stress induced changes in plasma corticosterone and brain monoamines in rats

Bacopa monniera (BM) is well known for its neuropharmacological effects. Our previous studies indicated the adaptogenic effect of standardized extract of BM in various stress models. In the present study, effect of BM was evaluated on acute stress (AS) and chronic unpredictable stress (CUS) induced changes in plasma corticosterone and monoamines-noradrenaline (NA), dopamine (DA) and serotonin (5-HT) in cortex and hippocampus regions of brain in rats. Panax root powder (Panax quinquefolium) was taken as standard. Subjecting animals to AS (immobilization for 150 min once only) and CUS (different stressors for 7 days) resulted in significant elevation in plasma corticosterone levels, which was significantly countered by treatment with BM at a dose of 40 and 80 mg/kg p.o. similar to the effects of Panax quinquefolium (PQ) at 100 mg/kg p.o. AS exposure significantly increased the levels of 5-HT and decreased NA content in both the brain regions while DA content was significantly increased in cortex and decreased in hippocampus regions. In CUS regimen, levels of NA, DA and 5-HT were significantly depleted in cortex and hippocampus regions of brain. Treatment with BM (40 and 80 mg/kg) attenuated the stress induced changes in levels of 5-HT and DA in cortex and hippocampus regions but was ineffective in normalizing the NA levels in AS model, whereas PQ treatment significantly reverted back the effects of stress. In CUS model, pretreatment with BM and PQ significantly elevated the levels of NA, DA and 5-HT levels in cortex and levels of NA and 5-HT in hippocampus regions. Hence, our study indicates that the adaptogenic activity of BM might be due to the normalization of stress induced alteration in plasma corticosterone and levels of monoamines like NA, 5-HT and DA in cortex and hippocampus regions of the brain, which are more vulnerable to stressful conditions analogous to the effects of PQ.

Chronic treatment with bromocriptine modifies metabolic adjustments in response to restraint stress in rats

1. We investigated the influence of bromocriptine (BR) chronic treatment in the autonomic adjustments to energetic metabolism during restraint stress (RS). To achieve this, Wistar male rats were chronically treated with BR before the application of RS. The rats were divided into two groups: those treated with BR and control rats, treated with saline. 2. Chronic treatment with BR did not affect rat growth and induced a 20% higher basal plasma glucose concentration. During RS, BR rats presented higher plasma glucose concentrations than the control animals. Despite this, the 30-min analysis of the areas under the glucose curve showed that the control rats presented a hyperglycemic response to RS two-fold greater than the BR rats. 3. RS induced an increase in plasma lactate concentration in both groups of rats; however, the 30-min analyses under the lactate curves showed that BR rats presented a lactate response to RS three times higher than control rats. 4. RS induced an increase in plasma free fatty acids (FFA) concentration in both groups; however, plasma FFA concentration of BR rats returned to the basal values at the end of RS. In contrast, in the control group, this concentration continued to rise until the end of RS. 5. The results showed that BR chronic treatment shifts the balance of substrate utilization in response to RS, suggesting that the essential role of lactate in the metabolism homeostasis may be altered by chronic BR treatment.

Cardiovascular and renal actions of melanocyte-stimulating hormone peptides

PURPOSE OF REVIEW

Melanocyte stimulating hormones (MSHs, melanocortins) have important roles in feeding and energy metabolism and in inflammation. Recent observations have uncovered major functions for these peptides, particularly gamma-MSH, in cardiovascular regulation and sodium metabolism.

RECENT FINDINGS

Both alpha- and gamma-MSH acutely elevate blood pressure and heart rate through central stimulation of sympathetic nervous outflow. This action of alpha-MSH is mediated by the melanocortin 4 receptor (MC4R), whereas sympathetic nervous stimulation by gamma-MSH does not involve its receptor MC3R but rather is likely due to activation of a sodium channel in the central nervous system. In contrast, gamma-MSH deficiency in rodents, or disruption of MC3R, leads to marked salt-sensitive hypertension, again through a central mechanism: a small dose of exogenous peptide delivered into the cerebroventricular system of mice with gamma-MSH deficiency restores blood pressure to normal. This salt-sensitive hypertension is accompanied by the development of insulin resistance; the mechanism linking these two consequences of a high-salt diet is not yet known but may involve activation of the sympathetic nervous system.

SUMMARY

The study of MSH peptides in blood pressure regulation offers a new opportunity to gain insight into the mechanisms underlying salt sensitivity and its link to insulin resistance, and to new therapies.