Effects of chronic stress on hypothalamic lnterleukin-1beta, interleukin-2, and gonadotrophin-releasing hormone gene expression in ovariectomized rats

[Ketamine and suicidal behavior: Contribution of animal models of aggression-impulsivity to understanding its mechanism of action]

More than two-thirds of suicides occur during a major depressive episode. Acting out prevention measures and therapeutic options to manage the suicidal crisis are limited. The impulsive-aggressive dimensions are vulnerability factors associated with suicide in patients suffering from a characterized depressive episode: this can be a dimension involved in animals. Impulsive and aggressive rodent models can help analyze, at least in part, the neurobiology of suicide and the beneficial effects of treatments. Ketamine, a glutamatergic antagonist, by rapidly improving the symptoms of depressive episodes, would help reduce suicidal thoughts in the short term. Animal models share with humans impulsive and aggressive endophenotypes modulated by the serotonergic system (5-HTB receptor, MAO-A enzyme), neuroinflammation or the hypothalamic-pituitary-adrenal axis and stress. Significant effects of ketamine on these endophenotypes remain to be demonstrated.

Pharmacological Mechanism of Ketamine in Suicidal Behavior Based on Animal Models of Aggressiveness and Impulsivity: A Narrative Review

Around 700,000 people die from suicide each year in the world. Approximately 90% of suicides have a history of mental illness, and more than two-thirds occur during a major depressive episode. Specific therapeutic options to manage the suicidal crisis are limited and measures to prevent acting out also remain limited. Drugs shown to reduce the risk of suicide (antidepressants, lithium, or clozapine) necessitate a long delay of onset. To date, no treatment is indicated for the treatment of suicidality. Ketamine, a glutamate NMDA receptor antagonist, is a fast-acting antidepressant with significant effects on suicidal ideation in the short term, while its effects on suicidal acts still need to be demonstrated. In the present article, we reviewed the literature on preclinical studies in order to identify the potential anti-suicidal pharmacological targets of ketamine. Impulsive-aggressive traits are one of the vulnerability factors common to suicide in patients with unipolar and bipolar depression. Preclinical studies in rodent models with impulsivity, aggressiveness, and anhedonia may help to analyze, at least in part, suicide neurobiology, as well as the beneficial effects of ketamine/esketamine on reducing suicidal ideations and preventing suicidal acts. The present review focuses on disruptions in the serotonergic system (5-HT_B receptor, MAO-A enzyme), neuroinflammation, and/or the HPA axis in rodent models with an impulsive/aggressive phenotype, because these traits are critical risk factors for suicide in humans. Ketamine can modulate these endophenotypes of suicide in human as well as in animal models. The main pharmacological properties of ketamine are then summarized. Finally, numerous questions arose regarding the mechanisms by which ketamine may prevent an impulsive-aggressive phenotype in rodents and suicidal ideations in humans. Animal models of anxiety/depression are important tools to better understand the pathophysiology of depressed patients, and in helping develop novel and fast antidepressant drugs with anti-suicidal properties and clinical utility.

The rat cumulative allostatic load measure (rCALM): a new translational assessment of the burden of stress

Determinants of lifetime health are complex and emphasize the need for robust predictors of disease risk. Allostatic load (AL) has become a clinical framework to estimate the cumulative biological burden associated with chronic stress. To assist knowledge translation in the developmental origins of health and disease field, clinically valid methods for reliable AL assessment in experimental models are urgently needed. Here, we introduce the rat cumulative allostatic load measure (rCALM), as a new preclinical knowledge translation tool to assess the burden of chronic stress. First, we identified an array of stress-associated physiological markers that are particularly sensitive to hypothalamic-pituitary-adrenal axis dysregulation by ancestral prenatal stress. Second, we determined which of these markers are susceptible to an intervention by environmental enrichment (EE) to mitigate AL. The markers most responsive to stress and EE therapy were assembled to become operationalized in the rCALM. Third, the new rCALM was validated for the ability to indicate future disease risks. The results show that the rCALM estimates the burden of chronic stress and serves as a proxy to estimate stress resilience and vulnerability to disease. Using the rCALM we showed that enrichment therapy can offset the adverse health outcomes linked to a high AL. Thus, the rCALM provides a model for the development of new test strategies that facilitate knowledge translation in preclinical animal models.

Effect of short-term and prolonged stress on the biosynthesis of gonadotropin-releasing hormone (GnRH) and GnRH receptor (GnRHR) in the hypothalamus and GnRHR in the pituitary of ewes during various physiological states

Using an ELISA assay, the levels of GnRH and GnRHR were analysed in the preoptic area (POA), anterior (AH) and ventromedial hypothalamus (VM), stalk/median eminence (SME); and GnRHR in the anterior pituitary gland (AP) of non-breeding and breeding sheep subjected to short-term or prolonged stress. The ELISA study was supplemented with an analysis of plasma LH concentration. Short-term footshock stimulation significantly increased GnRH levels in hypothalamus in both seasons. Prolonged stress elevated or decreased GnRH concentrations in the POA and the VM, respectively during anoestrus, and lowered GnRH amount in the POA-hypothalamus of follicular-phase sheep. An up-regulation of GnRHR levels was noted in both, anoestrous and follicular-phase animals. In the non-breeding period, a prolonged stress procedure increased GnRHR biosynthesis in the VM and decreased it in the SME and AP, while in the breeding time the quantities of GnRHR were significantly lower in the whole hypothalamus. In follicular-phase ewes the fluctuations of GnRH and GnRHR levels under short-term and prolonged stress were reflected in the changes of LH secretion, suggesting the existence of a direct relationship between GnRH and GnRH-R biosynthesis and GnRH/LH release in this period. The study showed that stress was capable of modulating the biosynthesis of GnRH and GnRHR; the pattern of changes was dependent upon the animal's physiological state and on the time course of stressor application. The obtained results indicate that the disturbances of gonadotropin secretion under stress conditions in sheep may be due to a dysfunction of GnRH and GnRHR biosynthetic pathways.

GABAergic regulation of the HPA and HPG axes and the impact of stress on reproductive function

The hypothalamic-pituitary-adrenal (HPA) and hypothalamic-pituitary-gonadal (HPG) axes are regulated by GABAergic signaling at the level of corticotropin-releasing hormone (CRH) and gonadotropin-releasing hormone (GnRH) neurons, respectively. Under basal conditions, activity of CRH and GnRH neurons are controlled in part by both phasic and tonic GABAergic inhibition, mediated by synaptic and extrasynaptic GABAA receptors (GABAARs), respectively. For CRH neurons, this tonic GABAergic inhibition is mediated by extrasynaptic, δ subunit-containing GABAARs. Similarly, a THIP-sensitive tonic GABAergic current has been shown to regulate GnRH neurons, suggesting a role for δ subunit-containing GABAARs; however, this remains to be explicitly demonstrated. GABAARs incorporating the δ subunit confer neurosteroid sensitivity, suggesting a potential role for neurosteroid modulation in the regulation of the HPA and HPG axes. Thus, stress-derived neurosteroids may contribute to the impact of stress on reproductive function. Interestingly, excitatory actions of GABA have been demonstrated in both CRH neurons at the apex of control of the HPA axis and in GnRH neurons which mediate the HPG axis, adding to the complexity for the role of GABAergic signaling in the regulation of these systems. Here we review the effects that stress has on GnRH neurons and HPG axis function alongside evidence supporting GABAARs as a major interface between the stress and reproductive axes.

Changes in proinflammatory cytokines and white matter in chronically stressed rats

Although the pathogenesis of depression, an incapacitating psychiatric ailment, remains largely unknown, previous human and animal studies have suggested that both proinflammatory cytokines and altered oligodendrocytes play important roles in the condition. This study examined these two factors in the brains of rats following unpredictable chronic mild stress for 4 weeks, with the hypothesis that chronic stress may affect oligodendrocytes and elevate proinflammatory cytokines in the brain. After suffering unpredictable stressors for 4 weeks, the rats showed depression-like behaviors, including decreased locomotion in the open field, increased immobility time in the forced swim test, and decreased sucrose consumption and less sucrose preference when compared with controls. Immunohistochemical staining of brain sections showed higher immunoreactivity of proinflammatory cytokines in certain brain regions of stressed rats compared with controls; lower immunoreactivity of myelin basic protein and fewer mature oligodendrocytes were seen in the prefrontal cortex, but no demyelination was detected. These results are interpreted and discussed in the context of recent findings from human and animal studies.

Dynamic microglial alterations underlie stress-induced depressive-like behavior and suppressed neurogenesis

The limited success in understanding the pathophysiology of major depression may result from excessive focus on the dysfunctioning of neurons, as compared with other types of brain cells. Therefore, we examined the role of dynamic alterations in microglia activation status in the development of chronic unpredictable stress (CUS)-induced depressive-like condition in rodents. We report that following an initial period (2-3 days) of stress-induced microglial proliferation and activation, some microglia underwent apoptosis, leading to reductions in their numbers within the hippocampus, but not in other brain regions, following 5 weeks of CUS exposure. At that time, microglia displayed reduced expression of activation markers as well as dystrophic morphology. Blockade of the initial stress-induced microglial activation by minocycline or by transgenic interleukin-1 receptor antagonist overexpression rescued the subsequent microglial apoptosis and decline, as well as the CUS-induced depressive-like behavior and suppressed neurogenesis. Similarly, the antidepressant drug imipramine blocked the initial stress-induced microglial activation as well as the CUS-induced microglial decline and depressive-like behavior. Treatment of CUS-exposed mice with either endotoxin, macrophage colony-stimulating factor or granulocyte-macrophage colony-stimulating factor, all of which stimulated hippocampal microglial proliferation, partially or completely reversed the depressive-like behavior and dramatically increased hippocampal neurogenesis, whereas treatment with imipramine or minocycline had minimal or no anti-depressive effects, respectively, in these mice. These findings provide direct causal evidence that disturbances in microglial functioning has an etiological role in chronic stress-induced depression, suggesting that microglia stimulators could serve as fast-acting anti-depressants in some forms of depressive and stress-related conditions.

Metabolic syndrome: a brain disease

Recent research indicates an association between brain dysfunction and the pathogenesis of metabolic syndrome. To investigate this, we created a Medline search (up to December 2011) of articles in PubMed. The results indicated that refined carbohydrates, saturated and total fat, high levels of ω-6 fatty acids, and low levels of ω-3 fatty acids and other long chain polyunsaturated fatty acids (PUFA), all in conjunction with sedentary behaviour and mental stress can predispose to inflammation. Increased sympathetic activity, with increased secretion of catecholamine, cortisol, and serotonin can cause oxidative stress, which may damage the arcuate nucleus as well as the hypothalamus and macrophages, and the liver may release pro-inflammatory cytokines. These, in conjunction with an underlying deficiency in long chain PUFA, may damage the arcuate nucleus as well as neuropeptide-Y and pro-opiomelanocortin neurons and insulin receptors in the brain, especially during fetal life, infancy, and childhood, resulting in their dysfunction. Of the fatty acids in the brain, 30%-50% are long chain PUFA, which are incorporated in the cell membrane phospholipids. Hence, ω-3 fatty acids, which are also known to enhance parasympathetic activity and increase the secretion of anti-inflammatory cytokines interleukin (IL)-4 and IL-10 as well as acetylcholine in the hippocampus, may be protective. Therefore, treatment with ω-3 fatty acids may be applied for the prevention of metabolic syndrome.

Acceleration of irregular estrous cycle in forced running by midbrain raphe lesions in female rats

It is known that over-exercise or forced running interrupts the regular ovulatory (estrous) cycle in female mammals, including women. The serotonin content of the brain changes under stress conditions. In this experiment, radiofrequency lesions were made in the dorsal (DRL) or median (MRL) raphe nuclei of the midbrain, in which serotonergic neurons are abundant, and changes in the estrous cycle with forced running using an electric-motor running wheel were examined in female rats. Through the tests, the estrous cycle was checked by taking vaginal smears. Female rats with a regular 4-day estrous cycle were forced to run in the wheel for 30 min daily over 15 days. As a result, 27.3% of the control and 30.0% of the sham-operated rats showed an irregular estrous cycle. In contrast, 100% of the DRL and 87.5% of the MRL rats showed an irregular cycle (P<0.05 vs. control and sham). Statistical analysis revealed that the median onset day of an irregular cycle was in excess of 15 days in both the control and sham groups. In the DRL and MRL groups, the median onset days of the irregular cycle were day 5 and 3, respectively, being shorter than those in control and sham groups (P<0.01). These results indicate that the dorsal and median raphe nuclei play an important role in preventing the effect of stress conditions in the ovulatory system in female rats.

Neuroendocrine regulation of GnRH release and expression of GnRH and GnRH receptor genes in the hypothalamus-pituitary unit in different physiological states

This review is focused on the relationship between neuroendocrine regulation of GnRH/LH secretion and the expression of GnRH and GnRH receptor (GnRHR) genes in the hypothalamic-pituitary unit during different physiological states of animals and under stress. Moreover, the involvement of hypothalamic GABA-ergic, Beta-endorphinergic, CRH-ergic, noradrenergic, dopaminergic and GnRH-ergic systems in the regulation of expression of the GnRH and GnRHR genes as well as secretion of GnRH/LH is analyzed. It appears that the neural mechanisms controlling GnRH gene expression in different physiological states may be distinct from those regulating GnRH/LH release. The hypothalamic GnRHR gene is probably located in different neural systems and may act in a specific way on GnRH gene expression and GnRH release.

Acute stress rapidly decreases plasma testosterone in a free-ranging male songbird: potential site of action and mechanism

We used a free-ranging, seasonally breeding adult male songbird, the rufous-winged sparrow, Aimophila carpalis, to investigate the effects of acute stress-induced by capture followed by restraint, on the hypothalamo-pituitary-testicular axis. Intra- and interindividual comparisons revealed that males decreased their plasma testosterone (T) by 37-52% in response to acute stress. The decrease occurred within 15 min of capture and persisted for at least another 15 min. Within 15 min, the decrease in plasma T was not associated with a reduction in plasma luteinizing hormone (LH). Thirty minutes after capture and restraint, the decrease in plasma T either was likewise not associated with decreased plasma LH (intraindividual comparison) or concurred with a reduction in plasma LH (interindividual comparison). These observations indicate that effects of stress may have been mediated at the pituitary gland and also directly at the testicular levels. To address this question, we measured the hormonal response to an injection of the glutamate receptor agonist N-methyl-d,l-aspartate (NMA) to stimulate to stimulate the release of gonadotropin-releasing hormone (GnRH) or of GnRH to stimulate the release of LH. Treatment with NMA did not change plasma LH, presumably because the birds were in breeding condition and already secreting GnRH at a maximum rate. Administration of GnRH increased plasma LH equally in birds that were or were not stressed before the treatment. An injection of purified ovine LH (oLH) increased plasma T equally in birds that were or were not acutely stressed before the hormone injection. Thus, the observed acute stress-induced decrease in plasma T was apparently not mediated by decreased responsiveness of the pituitary gland to GnRH or of the testes to LH. Decreased plasma T following stress may involve a direct impairment of the testicular endocrine function.

Stress and IL-1beta contribute to the development of depressive-like behavior following peripheral nerve injury

The physiological link between neuropathic pain and depression remains unknown despite a high comorbidity between these two disorders. A mouse model of spared nerve injury (SNI) was used to test the hypothesis that nerve injury precipitates depression through the induction of inflammation in the brain, and that prior exposure to stress exacerbates the behavioral and neuroinflammatory consequences of nerve injury. As compared with sham surgery, SNI induced mechanical allodynia, and significantly increased depressive-like behavior. Moreover, SNI animals displayed increased interleukin-1beta (IL-1beta) gene expression within the frontal cortex and concurrent increases in the expression of glial fibrillary acidic protein (GFAP) within the periaqueductal grey (PAG). Additionally, exposure to chronic restraint stress for 2 weeks before SNI exacerbated mechanical allodynia and depressive-like behavior, and resulted in an increase in IL-1beta gene expression in the frontal cortex and brain-derived neurotrophic factor (BDNF) gene expression in PAG. Treatment with metyrapone (MET), a corticosteroid synthesis inhibitor, before stress eliminated deleterious effects of chronic stress on SNI. Finally, this study showed that interference with IL-1beta signaling, through administration of IL-1 receptor antagonist (IL-1ra), ameliorated the effects of neuropathic pain on depressive-like behavior. Taken together, these data suggest that peripheral nerve injury leads to increased cytokine expression in the brain, which in turn, contributes to the development of depressive-like behavior. Furthermore, stress can facilitate the development of depressive-like behavior after nerve injury by promoting IL-1beta expression.

Nova-1 mediates glucocorticoid-induced inhibition of pre-mRNA splicing of gonadotropin-releasing hormone transcripts

Glucocorticoid (GC) is known to affect the reproductive system by suppressing the gonadotropin-releasing hormone (GnRH) gene expression in the hypothalamus. However, the mechanism of this effect is poorly understood. We show here that the GC-induced reduction of GnRH mRNA is due to attenuation of a post-transcriptional process i.e. splicing of intron A. Treatment of dexamethasone (DEX), a synthetic GC, lowered GnRH mRNA transcripts and was accompanied by reduced excision of the first intron (intron A) from the GnRH pre-mRNA both in vitro and in vivo. While seeking to identify the splicing factors involved in GC-inhibited GnRH pre-mRNA splicing, we found that DEX down-regulated neuro-oncological ventral antigen-1 (Nova-1) mRNA and protein and that knockdown of Nova-1 reduced intron A excision from GnRH pre-mRNA. Nova-1 overexpression reversed the DEX-induced reduction of intron A excision. Nova-1 appears to promote intron A excision by binding to the distal region of exon 1 of the GnRH pre-mRNA. Taken together, our findings indicate that the intron A excision by Nova-1 is a target of GC for down-regulation of GnRH gene expression, and more importantly, we characterized Nova-1, a brain-enriched splicing regulator responsible for GnRH pre-mRNA splicing.

Interleukin-1 (IL-1): a central regulator of stress responses

Ample evidence demonstrates that the pro-inflammatory cytokine interleukin-1 (IL-1), produced following exposure to immunological and psychological challenges, plays an important role in the neuroendocrine and behavioral stress responses. Specifically, production of brain IL-1 is an important link in stress-induced activation of the hypothalamus-pituitary-adrenal axis and secretion of glucocorticoids, which mediate the effects of stress on memory functioning and neural plasticity, exerting beneficial effects at low levels and detrimental effects at high levels. Furthermore, IL-1 signaling and the resultant glucocorticoid secretion mediate the development of depressive symptoms associated with exposure to acute and chronic stressors, at least partly via suppression of hippocampal neurogenesis. These findings indicate that whereas under some physiological conditions low levels of IL-1 promote the adaptive stress responses necessary for efficient coping, under severe and chronic stress conditions blockade of IL-1 signaling can be used as a preventive and therapeutic procedure for alleviating stress-associated neuropathology and psychopathology.

Neuroimmunology of the circadian clock

Circadian timekeeping is a ubiquitous feature of all eukaryotes which allows for the imposition of a biologically appropriate temporal architecture on an animal's physiology, behavior and metabolism. There is growing evidence that in mammals the processes of circadian timing are under the influence of the immune system. Such a role for the neuroimmune regulation of the circadian clock has inferences for phenomena such as sickness behavior. Conversely, there is also accumulating evidence for a circadian influence on immune function, raising the likelihood that there is a bidirectional communication between the circadian and immune systems. In this review, we examine the evidence for these interactions, including circadian rhythmicity in models of disease and immune challenge, distribution of cytokines and their receptors in the suprachiasmatic nucleus of the hypothalamus, the site of the master circadian pacemaker, and the evidence for endogenous circadian timekeeping in immune cells.

Brain interleukin-1 mediates chronic stress-induced depression in mice via adrenocortical activation and hippocampal neurogenesis suppression

Several lines of evidence implicate the pro-inflammatory cytokine interleukin-1 (IL-1) in the etiology and pathophysiology of major depression. To explore the role of IL-1 in chronic stress-induced depression and some of its underlying biological mechanisms, we used the chronic mild stress (CMS) model of depression. Mice subjected to CMS for 5 weeks exhibited depressive-like symptoms, including decreased sucrose preference, reduced social exploration and adrenocortical activation, concomitantly with increased IL-1 beta levels in the hippocampus. In contrast, mice with deletion of the IL-1 receptor type I (IL-1rKO) or mice with transgenic, brain-restricted overexpression of IL-1 receptor antagonist did not display CMS-induced behavioral or neuroendocrine changes. Similarly, whereas in wild-type (WT) mice CMS significantly reduced hippocampal neurogenesis, measured by incorporation of bromodeoxyuridine (BrdU) and by doublecortin immunohistochemistry, no such decrease was observed IL-1rKO mice. The blunting of the adrenocortical activation in IL-1rKO mice may play a causal role in their resistance to depression, because removal of endogenous glucocorticoids by adrenalectomy also abolished the depressive-like effects of CMS, whereas chronic administration of corticosterone for 4 weeks produced depressive symptoms and reduced neurogenesis in both WT and IL-1rKO mice. The effects of CMS on both behavioral depression and neurogenesis could be mimicked by exogenous subcutaneous administration of IL-1 beta via osmotic minipumps for 4 weeks. These findings indicate that elevation in brain IL-1 levels, which characterizes many medical conditions, is both necessary and sufficient for producing the high incidence of depression found in these conditions. Thus, procedures aimed at reducing brain IL-1 levels may have potent antidepressive actions.

Effects of prenatal maternal stress by repeated cold environment on behavioral and emotional development in the rat offspring

It has been reported that many types of stresses, which caused physiological and psychological alterations in dams as prenatal maternal stress, affected behavioral and emotional traits of their offspring. However, effects of environmental temperature changes, which induce various stress responses in both animals and humans, have not been assessed as prenatal maternal stress. Repeated cold stress (RCS) is a type of chronic cold stress in which environmental temperature changes rapidly and frequently several times within a day. In the present study, to investigate effects of chronic maternal stress by the RCS on behavioral and emotional development of the rat offspring (prenatal RCS rats), the RCS stress was loaded to pregnant rats between day 9 and 19 after fertilization. The prenatal RCS rats showed similar locomotor activity in an open field to control rats that were borne by non-stressed pregnant rats. On the other hand, the prenatal RCS rats showed significantly higher startle responses than the control rats in a light enhanced startle paradigm. However, treatment of diazepam decreased the startle responses in the prenatal RCS rats to the same degree as those in the control rats. The results indicated that prenatal RCS affected emotional development of the rat offspring, but not locomotor activity. Comparison of the present results with the previous studies suggests that there might be unknown common mechanisms among different prenatal maternal stresses that induce similar behavioral developmental alteration.

Increased concentrations of lipoprotein(a), circadian rhythms and metabolic reactions evoked by acute myocardial infarction, associated with acute reactions in relation to large breakfasts

Of 54 patients with acute coronary artery disease (CAD) that were included in this study, 41 patients had acute myocardial infarction (AMI), five patients possible MI, four patients unstable angina and the remaining four angina pectoris. The control subjects (n = 85) were randomly selected from the general population of the city of Moradabad of similar age range after exclusion for CAD (n = 9), diabetes (n = 6) and excess intake of trans fatty acids (n = 20). The incidence of lipoprotein(a) excess (> 30 mg/dl; 42.6 vs 24.7%; P < 0.05) and mean concentration of lipoprotein(a) (Lp[a], 6.4 mg/dl, 95% confidence interval: 2.8-10.5; P < 0.05) was significantly greater in the acute CAD group compared with control subjects. Mean total cholesterol and triglycerides were significantly higher and mean nitrite level lower in the study group as compared with the control group.There was a significant greater incidence of cardiac events in the second quarter of the day compared with the fourth quarter. Lp(a), triglycerides, blood glucose, plasma insulin, malondialdehyde, diene conjugates, TBARS and TNF-alpha and IL-6 levels, which were significantly greater during the acute phase, showed a significant decline and serum nitrite and coenzyme Q demonstrated an increase at 4 weeks of follow-up when the acute reactions evoked by MI had been controlled. Large breakfasts were a predisposing factor for cardiac events in the second quarter of the day and it was significantly associated with metabolic reactions. The findings indicate that acute reactions as a result or as circadian rhythms appear to be important in the pathogenesis of AMI-associated complications and that a large breakfast in association with nitrite deficiency may further trigger the circadian rhythms. However, more studies in a larger number of subjects would be necessary in order to confirm our findings.

Can brain dysfunction be a predisposing factor for metabolic syndrome?

The various mechanisms that may explain the association between brain dysfunction and the pathogenesis of metabolic syndrome (MS) leading to cardiovascular disease and type 2 diabetes have been reviewed. A Medline search was conducted until September 2003, and articles published in various national and international journals were reviewed. Experts working in the field were also consulted. Compelling evidence was found that saturated and total fat and low dietary n-3 fatty acids and other long-chain polyunsaturated fatty acids (PUFAs) in conjunction with sedentary behavior and mental stress combined with various personality traits can enhance sympathetic activity and increase the secretion of catecholamine, cortisol and serotonin, all of which appear to be underlying mechanisms involved in MS. Excess secretion of these neurotransmitters in conjunction with underlying long-chain PUFA deficiency may damage the neurons in the ventromedial hypothalamus and insulin receptors in the brain, in particular during fetal life, infancy and childhood, and lead to their dysfunction. Since 30-50% of the fatty acids in the brain are long-chain PUFAs, especially omega-3 fatty acids which are incorporated in the cell membrane phospholipids, it is possible that their supplementation may have a protective effect. Omega-3 fatty acids are also known to enhance parasympathetic activity and to increase the secretion of anti-inflammatory cytokines as well as acetylecholine in the hippocampus. It is possible that a marginal deficiency of long-chain PUFAs, especially n-3 fatty acids, due to poor dietary intake during the critical period of brain growth and development in the fetus, and later in the infant and also possibly in the child, adolescent and adult may enhance the release of tumor necrosis factor-alpha (TNF-alpha) interleukin (IL)-1, 2 and 6 and cause neuronal dysfunction. Experimental studies indicate that ventromedial hypothalamic lesions in rats induce hyperphagia, resulting in glucose intolerance and insulin resistance. Treatment with neuropeptide Y abolished hyperphagia and ob mRNA (leptin mRNA) in this animal model. Long-term infusion of norepinephrine and serotonin into the ventromedial hypothalamus impaired pancreatic islet function inasmuch as ventromedial hypothalamic norepinephrine and serotonin levels were elevated in hyperinsulinemic and insulin-resistant animals. Treatment with insulin was associated with restoration of hypothalamic neurotransmitter abnormalities, indicating that ventromedial hypothalamus dysfunction can impair pancreatic beta cells resulting in metabolic abnormalities consistent with MS. Treatment with omega-3 fatty acids, beta blockers, ACE inhibitors, estrogen, and meditation may have a beneficial effect on insulin receptors and ventromedial hypothalamic dysfunction. However, no definite or precise insight into the pathophysiological link between MS, brain function and nutrition is available. Despite this, epidemiological studies and intervention trials indicate that treatment with n-3 fatty acids may be adopted in clinical practice and used to direct therapy for prevention of type 2 diabetes, hypertension, coronary artery disease (CAD), and atherosclerosis, thereby indicating that MS may also respond to this treatment.

Can perinatal supplementation of long-chain polyunsaturated fatty acids prevent diabetes mellitus?

It is suggested that the negative correlation between breast-feeding and insulin resistance and diabetes mellitus can be related to the presence of significant amounts of long-chain polyunsaturated fatty acids in the human breast milk. Based on this, it is proposed that provision of adequate amounts of long chain polyunsaturated fatty acids during the critical periods of brain growth and development can prevent or postpone the development diabetes mellitus.

Effects of interleukin-1 beta on the steroid-induced luteinizing hormone surge: role of norepinephrine in the medial preoptic area

Interleukin-1beta (IL-1beta), a cytokine, is known to inhibit the preovulatory surge of luteinizing hormone (LH); however, the mechanism by which it does so is unclear. This study was done to see if this effect is mediated through hypothalamic catecholamines. Adult female Sprague-Dawley rats were ovariectomized and implanted with a push-pull cannula in the medial preoptic area (MPA) of the hypothalamus. They were injected subcutaneously with 30 microg of Estradiol on the day 8 after surgery and with 2mg of Progesterone on day 10 at 1000 h. On the day of perfusion (day 10), the rats were injected with IL-1beta or its vehicle at 1300 h. Perfusate samples from the MPA and blood samples from a jugular catheter were collected from 1300 to 1800 h. Catecholamine concentrations in the perfusate were measured using high performance liquid chromatography (HPLC)-EC and LH levels in the serum using RIA. Norepinephrine release in the MPA of control rats increased significantly at 1530, 1600, and 1630 h paralelling an increase in LH at 1600 h. In contrast, IL-1beta treatment blocked the LH surge and the rise in norepinephrine release in the MPA. No changes were observed in dopamine release, both in control and IL-treated animals. These results demonstrate for the first time that IL-induced suppression of the LH surge is probably mediated through inhibition of norepinephrine release in the MPA.

Is type 2 diabetes mellitus a disorder of the brain?

I propose that type 2 diabetes mellitus is due to damage to neurons in the ventromedial hypothalamus or to a defect in the action or properties of insulin or insulin receptors in the brain. These neuronal abnormalities are probably secondary to a marginal deficiency of long-chain polyunsaturated fatty acids during the critical periods of brain growth and development. Hence, supplementation of adequate amounts of long-chain polyunsaturated fatty acids during the third trimester of pregnancy to 2 y postterm can prevent or postpone the development of diabetes mellitus.

Is obesity an inflammatory condition?

Obesity may be a low-grade systemic inflammatory disease. Overweight and obese children and adults have elevated serum levels of C-reactive protein, interleukin-6, tumor necrosis factor-alpha, and leptin, which are known markers of inflammation and closely associated with cardiovascular risk factors and cardiovascular and non-cardiovascular causes of death. This may explain the increased risk of diabetes, heart disease, and many other chronic diseases in the obese. The complex interaction between several neurotransmitters such as dopamine, serotonin, neuropeptide Y, leptin, acetylcholine, melanin-concentrating hormone, ghrelin, nitric oxide, and cytokines and insulin and insulin receptors in the brain ultimately determines and regulates food intake. Breast-feeding of more than 12 mo is associated with decreased incidence of obesity. Breast milk is a rich source of long-chain polyunsaturated fatty acids (LCPUFAs) and brain is especially rich in these fatty acids. LCPUFAs inhibit the production of proinflammatory cytokines and enhance the number of insulin receptors in various tissues and the actions of insulin and several neurotransmitters. LCPUFAs may enhance the production of bone morphogenetic proteins, which participate in neurogenesis, so these fatty acids might play an important role in brain development and function. It is proposed that obesity is a result of inadequate breast feeding, which results in marginal deficiency of LCPUFAs during the critical stages of brain development. This results in an imbalance in the structure, function, and feedback loops among various neurotransmitters and their receptors, which ultimately leads to a decrease in the number of dopamine and insulin receptors in the brain. Hence, promoting prolonged breast feeding may decrease the prevalence of obesity. Exercise enhances parasympathetic tone, promotes antiinflammation, and augments brain acetylcholine and dopamine levels, events that suppress appetite. Acetylcholine and insulin inhibit the production of proinflammatory cytokines and provide a negative feedback loop for postprandial inhibition of food intake, in part, by regulating leptin action. Statins, peroxisome proliferator-activated receptor-gamma binding agents, non-steroidal antiinflammatory drugs, and infant formulas supplemented with LCPUFAs, and LCPUFAs themselves, which suppress inflammation, may be beneficial in obesity.