José Cipolla-Neto

Hypothalamic involvement in chronic migraine

OBJECTIVES Chronic migraine (CM), previously called transformed migraine, is a frequent headache disorder that affects 2%-3% of the general population. Analgesic overuse, insomnia, depression, and anxiety are disorders that are often comorbid with CM. Hypothalamic dysfunction has been implicated in its pathogenesis, but it has never been studied in patients with CM. The aim was to analyze hypothalamic involvement in CM by measurement of melatonin, prolactin, growth hormone, and cortisol nocturnal secretion. METHODS A total of 338 blood samples (13/patient) from 17 patients with CM and nine age and sex matched healthy volunteers were taken. Melatonin, prolactin, growth hormone, and cortisol concentrations were determined every hour for 12 hours. The presence of comorbid disorders was also evaluated. RESULTS An abnormal pattern of hypothalamic hormonal secretion was found in CM. This included: (1) a decreased nocturnal prolactin peak, (2) increased cortisol concentrations, (3) a delayed nocturnal melatonin peak in patients with CM, and (4) lower melatonin concentrations in patients with CM with insomnia. Growth hormone secretion did not differ from controls. CONCLUSION These results support hypothalamic involvement in CM, shown by a chronobiologic dysregulation, and a possible hyperdopaminergic state in patients with CM. Insomnia might be an important variable in the study findings.

Melatonin, energy metabolism, and obesity: a review

Melatonin is an old and ubiquitous molecule in nature showing multiple mechanisms of action and functions in practically every living organism. In mammals, pineal melatonin functions as a hormone and a chronobiotic, playing a major role in the regulation of the circadian temporal internal order. The anti‐obesogen and the weight‐reducing effects of melatonin depend on several mechanisms and actions. Experimental evidence demonstrates that melatonin is necessary for the proper synthesis, secretion, and action of insulin. Melatonin acts by regulating GLUT4 expression and/or triggering, via its G‐protein‐coupled membrane receptors, the phosphorylation of the insulin receptor and its intracellular substrates mobilizing the insulin‐signaling pathway. Melatonin is a powerful chronobiotic being responsible, in part, by the daily distribution of metabolic processes so that the activity/feeding phase of the day is associated with high insulin sensitivity, and the rest/fasting is synchronized to the insulin‐resistant metabolic phase of the day. Furthermore, melatonin is responsible for the establishment of an adequate energy balance mainly by regulating energy flow to and from the stores and directly regulating the energy expenditure through the activation of brown adipose tissue and participating in the browning process of white adipose tissue. The reduction in melatonin production, as during aging, shift‐work or illuminated environments during the night, induces insulin resistance, glucose intolerance, sleep disturbance, and metabolic circadian disorganization characterizing a state of chronodisruption leading to obesity. The available evidence supports the suggestion that melatonin replacement therapy might contribute to restore a more healthy state of the organism.

Hemispheric asymmetry and imprinting: The effect of sequential lesions to the hyperstriatum ventrale

SummaryThe respective roles in the imprinting process of parts (IMHV) of the left and right hyperstriatum ventrale of the chick brain were examined by destroying first one and then the other IMHV in a two-stage operation. One hundred and eight chicks were dark-reared to ≃ 19 h post-hatch and exposed to a training stimulus for 2 h. Chicks were anaesthetised ≃ 3 h after the end of training. Lesions were placed in either (i) right IMHV (N = 18 birds), (ii) left IMHV (N = 18) or (iii) left or right hyperstriatum accessorium (HA; N = 18). Fifty-four chicks served as sham-operated controls. Chicks were returned to the dark incubator, and, 15–20 h after the operation, the chicks’ approach towards the training stimulus and to a second novel stimulus was measured (Test 1). After this test the chicks were again anaesthetised and a second lesion was made, this lesion being placed in the corresponding structure (IMHV or HA) of the hemisphere contralateral to that with the first lesion. The chicks’ preferences were measured 15–20 h later (Test 2). In Test 1, all birds strongly preferred the training stimulus. In Test 2, sham-operated controls and HA chicks continued to prefer the training stimulus as did chicks with the initial lesion in the left IMHV. However, chicks with the initial lesion in the right IMHV failed to show a preference for the training stimulus. Thus, if the right IMHV is destroyed first the presence of the left IMHV is crucial for retention. In contrast, if the left IMHV is destroyed first the presence of the right IMHV is not crucial for retention: chicks continue to prefer the training stimulus after the right IMHV has been lesioned. In these circumstances, therefore, some region outside IMHV takes on a memory function. The results imply that at least two memory systems are formed during imprinting. One of these involves the left IMHV, the other does not. The putative second system is fully able to sustain recall in the normal chicks by ≃ 26 h after training: if bilateral lesions to IMHV (N = 28 chicks) are made at this time, retention, measured 15–20 h later, is not significantly different from that of sham-operated control chicks (N = 25).

Amnesic effects of bilateral lesions placed in the hyperstriatum ventrale of the chick after imprinting

SummaryThe purpose of this study was to investigate whether bilateral lesions to a part of the hyperstriatum ventrale (IMHV) impair retention if they are placed after chicks have been imprinted. Domestic chicks were hatched and reared in darkness and exposed to an imprinting (training) stimulus for 2 h commencing ≃ 22 h post hatch. The chicks were then anaesthetised and bilateral lesions placed in IMHV (N = 16) birds, hyperstriatum accessorium (HA; N = 16) or the lateral part of the cerebral hemispheres (LCA; N = 16). Forty-eight sham-operated chicks served as controls. Chicks were returned to the dark incubator, and, 15–20 h after the operation, their approach towards the training stimulus and to a second novel stimulus was measured. The controls and the chicks with lesions in HA and LCA showed a strong preference for the training stimulus and hence a high level of retention. The preferences of these three experimental groups did not differ significantly from one another. The mean preference of chicks with lesions in IMHV was significantly less than that of the sham-operated controls (P<0.01) and of chicks lesioned in HA (P<0.05). Bilateral lesions to IMHV therefore selectively impair retention of a preference acquired through imprinting. This impairment is unlikely to be a non-specific consequence of defective sensory processing or motor performance because the four groups did not differ from each other in (i) the time taken accurately to peck a rocking bead, (ii) the accuracy of pecking millet seeds and (iii) the performance of a simultaneous visual discrimination task involving heat reinforcement.

In vivo activation of insulin receptor tyrosine kinase by melatonin in the rat hypothalamus

Melatonin is the pineal hormone that acts via a pertussis toxin‐sensitive G‐protein to inhibit adenylate cyclase. However, the intracellular signalling effects of melatonin are not completely understood. Melatonin receptors are mainly present in the suprachiasmatic nucleus (SCN) and pars tuberalis of both humans and rats. The SCN directly controls, amongst other mechanisms, the circadian rhythm of plasma glucose concentration. In this study, using immunoprecipitation and immunoblotting, we show that melatonin induces rapid tyrosine phosphorylation and activation of the insulin receptor β‐subunit tyrosine kinase (IR) in the rat hypothalamic suprachiasmatic region. Upon IR activation, tyrosine phosphorylation of IRS‐1 was detected. In addition, melatonin induced IRS‐1/PI(3)‐kinase and IRS‐1/SHP‐2 associations and downstream AKT serine phosphorylation and MAPK (mitogen‐activated protein kinase) phosphorylation, respectively. These results not only indicate a new signal transduction pathway for melatonin, but also a potential cross‐talk between melatonin and insulin.

Melatonin inhibits insulin secretion and decreases PKA levels without interfering with glucose metabolism in rat pancreatic islets

Abstract: The effect of melatonin (0.1 μM) on freshly isolated islets from adult rats was investigated. Melatonin caused a marked decrease of insulin secretion by islets in response to glucose. The mechanism involved was then examined. Melatonin did not interfere with glucose metabolism as indicated by the measurement of glucose oxidation. However, the content of the protein kinase A (PKA) catalytic α‐subunit was significantly decreased in islets exposed to melatonin for 1 hr in the presence of 8.3 mM glucose, whereas that of the protein kinase C (PKC) α‐subunit remained unchanged. Melatonin also inhibited forskolin‐induced insulin secretion, a well known activator of adenylate cyclase (AC) activity. This may explain the low content of insulin found in islets incubated in the presence of melatonin for 3 hr. In fact, 3′,5′ ‐cyclic adenosine monophosphate (cAMP), a product of AC activity, stimulates insulin synthesis. These findings led us to postulate that a down‐regulation of the PKA signaling pathway may be the mechanism involved in the melatonin inhibition of the process of glucose‐induced insulin secretion.

Melatonin, 3 mg, is effective for migraine prevention.

There is increasing evidence that melatonin secretion and pineal function are related to headache disorders. Altered melatonin levels have been found in cluster headache, migraine with and without aura,1 menstrual migraine,2 and chronic migraine.3 A great variety of melatonin mechanisms may be linked to headache pathophysiology.3 Melatonin may have anti-inflammatory effect, it scavenges toxic free radicals, reduces the up-regulation of proinflammatory cytokines, and inhibits nitric oxide synthase activity and dopamine release. It also interferes with membrane stabilization, γ-aminobutyric acid and opioid analgesia potentiation, protection from glutamate neurotoxicity, neurovascular regulation, and serotonin modulation. Melatonin and indomethacin share similar chemical structure.4 Melatonin is then a possible candidate for migraine prevention. We tested the hypothesis of the potential effectiveness of melatonin for migraine prophylaxis. We performed an open-label trial of melatonin, 3 mg, for migraine prevention. Forty patients with episodic migraine with or without aura according to the International …

Daily rhythm of glucose‐induced insulin secretion by isolated islets from intact and pinealectomized rat

Abstract: It is well known that pinealectomy induces in rats a diminished glucose tolerance, insulin resistance, a reduction in GLUT4 content in adipose and muscular tissues, a decrease in hepatic and muscular glycogenesis, impairment of glucagon action and an increase in blood pyruvate concentration. In addition, it has been shown that melatonin suppresses insulin secretion in several experimental conditions. The objective of the present study was to investigate the daily rhythm of glucose‐induced insulin secretion and glucose oxidation by isolated pancreatic islets and to investigate the effect of chronic absence of melatonin (30 days of pinealectomy) on this rhythmic process. The data obtained confirmed the presence of a strong 24‐hr rhythm of insulin secretion by isolated pancreatic islets. In addition, it was demonstrated that the glucose‐metabolizing ability of the B‐cell follows a daily rhythm phase locked to insulin secretion rhythm. Most interesting, however, was the demonstration that the daily rhythmic processes of insulin secretion and B‐cell –[U‐14C]‐glucose oxidation by isolated pancreatic islets is completely modified by the chronic absence of the pineal gland. Thus, pinealectomy induced in all groups an increase in 24‐hr mean glucose‐stimulated insulin secretion and [U‐14C]‐glucose oxidation, in addition to some alterations in the rhythmic amplitude and a remarkable phase‐advancing of the daily curves for 8.3 mm glucose (a condition similar to that observed in fed animals and where the B‐cells are supposedly more active). These observations strongly suggest that the presence of the pineal gland may be necessary for the proper synchronization of these metabolic rhythms with other circadian rhythms like activity–rest and feeding.

Activation of insulin and IGF-1 signaling pathways by melatonin through MT1 receptor in isolated rat pancreatic islets

Abstract:  Melatonin diminishes insulin release through the activation of MT1 receptors and a reduction in cAMP production in isolated pancreatic islets of neonate and adult rats and in INS‐1 cells (an insulin‐secreting cell line). The pancreas of pinealectomized rats exhibits degenerative pathological changes with low islet density, indicating that melatonin plays a role to ensure the functioning of pancreatic beta cells. By using immunoprecipitation and immunoblotting analysis we demonstrated, in isolated rat pancreatic islets, that melatonin induces insulin growth factor receptor (IGF‐R) and insulin receptor (IR) tyrosine phosphorylation and mediates the activities of the PI3K/AKT and MEK/ERKs pathways, which are involved in cell survival and growth, respectively. Thus, the effects of melatonin on pancreatic islets do not involve a reduction in cAMP levels only. This indoleamine may regulate growth and differentiation of pancreatic islets by activating IGF‐I and insulin receptor signaling pathways.

Melatonin and the circadian entrainment of metabolic and hormonal activities in primary isolated adipocytes.

Abstract:  The aim of this work was to investigate the effect of the in vitro circadian‐like exposure to melatonin [in the presence or absence of insulin (Ins)] on the metabolism and clock gene expression in adipocytes. To simulate the cyclic characteristics of the daily melatonin profile, isolated rat adipocytes were exposed in a circadian‐like pattern to melatonin added to the incubating medium for 12 hr (mimicking the night), followed by an equal period without melatonin (mimicking the day) combined or not with Ins. This intermittent incubation was interrupted when four and a half 24‐hr cycles were fulfilled. At the end, either during the induced night (melatonin present) or the induced day (melatonin absent), the rates of lipolysis and D‐[U‐14C]‐glucose incorporation into lipids were estimated, in addition to the determination of lipogenic [glucose‐6‐phosphate dehydrogenase and fatty acid synthase (FAS)] and lipolytic (hormone sensitive lipase) enzymes and clock gene (Bmal‐1b, Clock, Per‐1 and Cry‐1) mRNA expression. The leptin release was also measured. During the induced night, the following effects were observed: an increase in the mRNA expression of Clock, Per‐1 and FAS; a rise in lipogenic response and leptin secretion; and a decrease in the lipolytic activity. The intermittent exposure of adipocytes to melatonin temporally and rhythmically synchronized their metabolic and hormonal function in a circadian fashion, mimicking what is observed in vivo in animals during the daily light–dark cycle. Therefore, this work helps to clarify the physiological relevance of the circadian pattern of melatonin secretion and its interactions with Ins, contributing to a better understanding of the adipocyte biology.