Epilepsy and hormones: a critical review

The effect of levetiracetam and oxcarbazepine monotherapy on thyroid hormones and bone metabolism in children with epilepsy: A prospective study

BACKGROUND

Long-term treatment with certain antiepileptic drugs may lead to thyroid function disturbances or alterations in bone metabolism; the data on the effects of new antiepileptic drugs on this are limited and conflicting, especially in children with epilepsy. Therefore, the aim of this study was to investigate the effects of levetiracetam and oxcarbazepine on thyroid hormone levels and bone metabolism in children with epilepsy.

METHODS

A total of 51 children with new-onset partial epilepsy were selected. They were randomly treated with either levetiracetam (n = 25), or oxcarbazepine (n = 26) monotherapy. Eight of the 51 patients were excluded for failing to take the drug continuously or failing to undergo a regular review. Thus, 43 patients were finally included (levetiracetam: 23 patients, oxcarbazepine: 20 patients). A control group consisting of age- and sex-matched healthy subjects (n = 20) was included for comparison. Serum triiodothyronine, tetraiodothyronine, free triiodothyronine, free thyroxine, thyroid-stimulating hormone, calcium, phosphorus, alkaline phosphatase, osteocalcin, parathyroid hormone, and 25-hydroxyvitamin D levels and bone mineral density values were measured before and at 6 and 12 months after therapy in all groups.

RESULTS

At baseline, thyroid hormone levels, bone metabolism index, and bone mineral density values did not differ between the control group and the drug-treated groups. Levetiracetam-treated patients showed no significant changes in thyroid hormone levels, bone metabolism, and bone mineral density during the 12-month follow-up period compared with baseline values. In the oxcarbazepine group, compared to baseline values, serum free thyroxine levels decreased after 12 months of treatment (Z = -3.115, p = 0.002), and after 6 and 12 months of treatment, calcium levels decreased (Z = -3.705, p < 0.001 and Z = -3.884, p < 0.001, respectively) and parathyroid hormone levels increased (Z = -3.698, p < 0.001 and Z = -3.921, p < 0.001, respectively); however, all other parameters did not differ from baseline values.

CONCLUSION

Our data show that levetiracetam treatment has no significant effect on thyroid function and bone metabolism in children with epilepsy. Long-term use of oxcarbazepine may reduce serum free thyroxine levels, resulting in impaired thyroid function, and may reduce serum calcium and increase parathyroid hormone levels, leading to bone metabolism disorders.

Anti-apoptotic Actions of Allopregnanolone and Ganaxolone Mediated Through Membrane Progesterone Receptors (PAQRs) in Neuronal Cells

The neurosteroids progesterone and allopregnanolone regulate numerous neuroprotective functions in neural tissues including inhibition of epileptic seizures and cell death. Many of progesterone's actions are mediated through the nuclear progesterone receptor (PR), while allopregnanolone is widely considered to be devoid of hormonal activity and instead acts through modulation of GABA-_A receptor activity. However, allopregnanolone can also exert hormonal actions in neuronal cells through binding and activating membrane progesterone receptors (mPRs) belonging to the progestin and adipoQ receptor (PAQR) family. The distribution and functions of the five mPR subtypes (α, β, γ, δ, ε) in neural tissues are briefly reviewed. mPRδ has the highest binding affinity for allopregnanolone and is highly expressed throughout the human brain. Low concentrations (20 nM) of allopregnanolone act through mPRδ to stimulate G protein (G_s)-dependent signaling pathways resulting in reduced cell death and apoptosis in mPRδ-transfected cells. The 3-methylated synthetic analog of allopregnanolone, ganaxolone, is currently undergoing clinical trials as a promising GABA-_A receptor-selective antiepileptic drug (AED). New data show that low concentrations (20 nM) of ganaxolone also activate mPRδ signaling and exert anti-apoptotic actions through this receptor. Preliminary evidence suggests that ganaxolone can also exert neuroprotective effects by activating inhibitory G protein (G_i)-dependent signaling through mPRα and/or mPRβ in neuronal cells. The results indicate that mPRs are likely intermediaries in multiple actions of natural and synthetic neurosteroids in the brain. Potential off-target effects of ganaxolone through activation of mPRs in patients receiving long-term treatment for epilepsy and other disorders should be considered and warrant further investigation.

Urinary volatile metabolites of amygdala-kindled mice reveal novel biomarkers associated with temporal lobe epilepsy

Epilepsy is a chronic neurological disorder affecting mammals, including humans. Uncontrolled epilepsy is associated with poor quality of life, accidents, and sudden death. In particular, temporal lobe epilepsy (TLE) is the most common type of pharmacoresistant epilepsy, which easily gets out of control in human adults. The aim of this study was to profile urinary volatile organic compounds (VOCs) in a mouse model of TLE using solid-phase microextraction (SPME) gas chromatography mass spectrometry (GC-MS). Thirteen urinary VOCs exhibited differential abundance between epileptic and control mice, and the corresponding areas under the receiver operating characteristic (ROC) curve were greater than 0.8. Principal component analysis (PCA) based on these 13 VOCs separated epileptic from sham operated-mice, suggesting that all these 13 VOCs are epilepsy biomarkers. Promax rotation and dendrogram analysis concordantly separated the 13 VOCs into three groups. Stepwise linear discriminant analysis extracted methanethiol; disulfide, dimethyl; and 2-butanone as predictors. Based on known metabolic systems, the results suggest that TLE induced by amygdala stimulation could affect both endogenous metabolites and the gut flora. Future work will elucidate the physiological meaning of the VOCs as end-products of metabolic networks and assess the impact of the metabolic background involved in development of TLE.

Cortisol levels and seizures in adults with epilepsy: A systematic review

Stress has been suggested as a trigger factor for seizures in epilepsy patients, but little is known about cortisol levels, as indicators of stress, in adults with epilepsy. This systematic review summarizes the evidence on this topic. Following PRISMA guidelines, 38 articles were selected: 14 analyzing basal cortisol levels, eight examining antiepileptic drugs (AEDs) effects, 13 focused on seizure effects, and three examining stress. Higher basal cortisol levels were found in patients than in healthy people in studies with the most homogeneous samples (45% of 38 total studies). Despite heterogeneous results associated with AEDs, seizures were related to increases in cortisol levels in 77% of 38 total studies. The only study with acute stress administration found higher cortisol reactivity in epilepsy than in healthy controls. In studies using self-reported stress, high seizure frequency was related to increased cortisol levels and lower functional brain connectivity. Findings suggest that epilepsy could be considered a chronic stress model. The potential sensitizing role of accumulative seizures and issues for future research are discussed.

Preclinical evidence of ghrelin as a therapeutic target in epilepsy

Ghrelin, an orexigenic peptide synthesized by endocrine cells of the gastric mucosa, plays a major role in inhibiting seizures. However, the underlying mechanism of ghrelin's anticonvulsant action is still unclear. Nowadays, there are considerable evidences showing that ghrelin is implicated in various neurophysiological processes, including learning and memory, neuroprotection, neurogenesis, and inflammatory effects. In this review, we will summarize the effects of ghrelin on epilepsy. It may provide a comprehensive picture of the role of ghrelin in epilepsy.

Impact of rapamycin on status epilepticus induced hippocampal pathology and weight gain

Growing evidence implicates the dentate gyrus in temporal lobe epilepsy (TLE). Dentate granule cells limit the amount of excitatory signaling through the hippocampus and exhibit striking neuroplastic changes that may impair this function during epileptogenesis. Furthermore, aberrant integration of newly-generated granule cells underlies the majority of dentate restructuring. Recently, attention has focused on the mammalian target of rapamycin (mTOR) signaling pathway as a potential mediator of epileptogenic change. Systemic administration of the mTOR inhibitor rapamycin has promising therapeutic potential, as it has been shown to reduce seizure frequency and seizure severity in rodent models. Here, we tested whether mTOR signaling facilitates abnormal development of granule cells during epileptogenesis. We also examined dentate inflammation and mossy cell death in the dentate hilus. To determine if mTOR activation is necessary for abnormal granule cell development, transgenic mice that harbored fluorescently-labeled adult-born granule cells were treated with rapamycin following pilocarpine-induced status epilepticus. Systemic rapamycin effectively blocked phosphorylation of S6 protein (a readout of mTOR activity) and reduced granule cell mossy fiber axon sprouting. However, the accumulation of ectopic granule cells and granule cells with aberrant basal dendrites was not significantly reduced. Mossy cell death and reactive astrocytosis were also unaffected. These data suggest that anti-epileptogenic effects of mTOR inhibition may be mediated by mechanisms other than inhibition of these common dentate pathologies. Consistent with this conclusion, rapamycin prevented pathological weight gain in epileptic mice, suggesting that rapamycin might act on central circuits or even peripheral tissues controlling weight gain in epilepsy.

Use of dietary therapies amongst patients with GLUT1 deficiency syndrome

PURPOSE

GLUT-1 deficiency syndrome (GLUT1DS) is a neurologic disorder manifesting as epilepsy, abnormal movements, and cognitive delay. The currently accepted treatment of choice is the classic 4:1 ratio ketogenic diet.

METHODS

A 2-page survey was distributed to all attendees of a family-centered conference for GLUT1DS in July 2015. The surveys were completed by parents, collected anonymously, and information analyzed in a database.

RESULTS

Surveys were received from 92 families, of which 90 (98%) had been treated with dietary therapies. Diets used were extremely varied: 59 were treated with the classic ketogenic diet (KD), 29 with the Modified Atkins Diet (MAD), 4 with the Medium-chain Triglyceride (MCT) Diet and 2 with the low glycemic index treatment. The mean diet duration was 5.5 years (range: 1 month-20 years). Of those with seizures, 95% of the children had >50% seizure reduction and 80% had >90% seizure reduction. Children who were seizure-free were currently younger on average (8.2 vs. 11.6 years, p=0.01) and slightly younger at GLUT1DS diagnosis (3.8 vs. 5.3 years, p=0.05). There was an equal percentage of children seizure-free receiving the KD/MCT Diets compared to the MAD/Low Glycemic Index Treatment (74% vs. 63%, p=0.30). The majority (64%) were not receiving anticonvulsants.

CONCLUSION

This represents the largest series of KD experience in children with GLUT1DS. Nearly all patients surveyed were on dietary therapies for long durations with reported excellent seizure control, often without anticonvulsant drugs. Several different ketogenic diets were utilized with similar efficacy. Early diagnosis and treatment were correlated with success.

[Algorithms of mono- and polytherapy in clinical epileptology]

The large number of antiepileptic drugs (AEDs) at the physician's disposal provides not only a broad therapeutic potential in the treatment of epilepsy (EP), but creates difficulties in the adequate choice of AED. The sufficient experience in the management of patients with epilepsy has been gained so far in the world, based on which the International League Against Epilepsy (ILAE), updated classification, adopted the basic definition of efficiency, remission, resistance, evidence of research on the effectiveness of AED therapy, and introduced the concept of "resolved" epilepsy. In this article, a group of Russian experts suggest recommendations on the main steps in the choice of therapy in epilepsy. Possible drug interactions between different AEDs and other drugs as well as main characteristics of mono- and polytherapy of epilepsy are described. Some features of the use of AEDs in the elderly, characteristics of the "female" epilepsy related to the reproductive function and basic requirements for the therapy of epilepsy in children are presented.

Second generation anti-epileptic drugs adversely affect reproductive functions in young non-epileptic female rats

Reproductive endocrine disturbances are a major health concern in women with epilepsy due to their long term use of antiepileptic drugs (AEDs). Second generation AEDs such as topiramate (TPM) and gabapentin are frequently used for the treatment of epilepsy as well as migraine, bipolar disorder etc. Despite the widespread clinical complications, however the definitive mechanism(s) mediating the side effects of TPM and gabapentin remain obscure. The present study was aimed to evaluate the long term effects of TPM and gabapentin on reproductive functions in young female Wistar rats. Estrous cyclicity, ovarian histology as well as estradiol, LH, leptin and insulin hormones level were studied to elucidate the long-term effect of these AEDs monotherapy on reproductive functions in non-epileptic animals. Further to explore the effects on gonadotropin releasing hormone (GnRH) neuroendocrine plasticity, the expression of GnRH, gamma-amino butyric acid (GABA), glutamic acid decarboxylase (GAD), glial fibrilliary acidic protein (GFAP) and polysialylated form of neural cell adhesion molecule (PSA-NCAM) was studied in median eminence (ME) region of these animals by immunohistochemistry, Western blot hybridization and RT-PCR. Our results demonstrate that TPM and gabapentin treatment for 8 weeks cause reproductive dysfunction as ascertained by disturbed hormonal levels and estrous cyclicity as well as alterations in GABAergic system and GnRH neuronal-glial plasticity. Our findings suggest that treatment with TPM and gabapentin disrupts the complete hypothalamo-hypophyseal-gonadal axis (HPG) through GnRH pulse generator in hypothalamus.

GABAB Receptor Blockade Prevents Antiepileptic Action of Ghrelin in the Rat Hippocampus

PURPOSE

Ghrelin has been shown to have antiepileptic function. However, the underlying mechanisms by which, ghrelin exerts its antiepileptic effects are still unclear. In the present study; we investigated antiepileptic mechanism of ghrelin through GABAB receptors using CGP35348 (selective GABAB receptor antagonist).

METHODS

Male Wistar rats' hippocampi were bilaterally microinjected with the single dose or 10-day ghrelin (0.3 nmol/µl/side). CGP35348, GABAB receptor antagonist, (12.5 µg/µl/side) or saline injected into the dorsal hippocampus 20 minutes before ghrelin administration. Thirty min after ghrelin microinjection, a single convulsive dose of pentylenetetrazole (PTZ) (50 mg/kg) was injected intraperitoneally (i.p). Afterwards, seizure duration and total seizure score (TSS) were assessed for 30 minutes in all animals.

RESULTS

Our results demonstrated that acute and chronic intrahippocampal (i.h.) injection of ghrelin could significantly (p<0.001) attenuate the severity of seizures. Ghrelin 0.3 nmol/µl/side decreased duration of seizure significantly both in acute (p<0.001) and chronic (p<0.01) injections. The ghrelin antiepileptic effect was completely antagonized by GABAB blockade. The suppression of both duration and TSS induced by ghrelin in hippocampus was significantly (p<0.001) blocked by CGP35348 in PTZ-induced seizures.

CONCLUSION

In summary, our findings suggest that GABAB receptors may mediate the antiepileptic action of ghrelin in the hippocampus. Therefore, it is possible to speculate that ghrelin acts in the hippocampus to modulate seizures via GABA.

The novel insulin resistance parameters RBP4 and GLP-1 in patients treated with valproic acid: just a sidestep?

Valproic acid (VPA), as one of the most widely prescribed antiepileptic drugs (AED) for many types of epilepsy in adults and children, is associated with weight gain, alteration of adipocytokine homeostasis, insulin resistance and Non-Alcoholic Fatty Liver Disease (NAFLD). Retinol-binding protein 4 (RBP4) and Glucagon-like peptide-1 (GLP-1) are considered as important new targets in modern type 2 diabetes mellitus therapy linked to insulin resistance, NAFLD and visceral obesity acting via peripheral or central mechanisms. We herein demonstrate the lack of an influence of VPA treatment on RBP4 and GLP-1 in otherwise healthy patients. In summary, the absence of any relationship with RBP4 and GLP-1 concentrations does not suggest a role of these novel insulin resistance parameters as potential regulators of glucose and fat metabolism during VPA-therapy.

Polycystic ovary syndrome in patients with epilepsy: a study in 102 Chinese women

PURPOSE

The incidence of polycystic ovary syndrome (PCOS) increases in women with epilepsy (WWE), which appears to vary with ethnicity. This study was conducted to determine the incidence and risk factors of PCOS in Chinese WWE.

METHODS

The study was carried out in 102 of 139 Chinese WWE at reproductive ages, with 32 receiving valproic acid (VPA), 40 receiving other antiepileptic drugs (AEDs), and 30 without AEDs therapy. PCOS was defined as having 2 or more of the following components: polycystic ovaries, hyperandrogenism, and amenorrhoea or oligomenorrhoea (a/oligomenorrhoea).

RESULTS

One or more isolated components of PCOS were found in 56 (54.9%) patients, with 29 (28.4%) having polycystic ovaries, 20 (19.6%) with a/oligomenorrhea, 7 (6.9%) with hyperandrogenism, and 13 (12.7%) with defined PCOS. Their average age at the start of seizure was 13.8±6.5 years, younger than that of patients without these disorders (16.9±8.6 years, p<0.05). VPA therapy increased the incidence of PCOS (11/32, 34.4%), in addition to increased blood levels of testosterone and luteinizing hormone (LH) as well as LH to FSH (follicle-stimulating hormone) ratio. No significant relationship was found between the incidence of PCOS and the type, duration, or frequency of seizures in these WWE.

CONCLUSION

There is an increased incidence of PCOS in Chinese WWE at reproductive ages, by more than 2 times of that in the general population. Risk factors include seizures starting at a young age and VPA therapy.

The antiepileptic effect of sodium valproate during different phases of the estrous cycle in PTZ-induced seizures in rats

Catamenial epilepsy is a form of epilepsy which is related to the menstrual cycle. Cyclic variation in the levels of ovarian hormones plays a pivotal role in its pathogenesis. Sodium valproate (VPA) is one of the oldest antiepileptic drugs (AEDs) which inhibits hepatic metabolizing enzymes. The aim of this study was to evaluate the antiepileptic effects of VPA during different phases of the estrous cycle in rats. 72 adult female Wistar rats in three groups (control, 75 and 100 mg/kg VPA), each with four subgroups (proestrous, estrous, metestrous and diestrous) were used (n = 6). Initially, puberty was assessed using vaginal smears and rats with two regular cycles were selected. VPA with doses 75 and 100 mg/kg was administered intraperitoneally (i.p) in the treatment groups followed by i.p. injection of 80 mg/kg pentylentetrazol (PTZ) in the treatment and control groups. After induction of seizure by PTZ, initiation time of myoclonic seizures (ITMS), initiation time of tonic-clonic seizures (ITTS), seizures duration (SD) and mortality rate (MR) were recorded for 30 min. Data were presented as mean±SD, one-way ANOVA followed by Tukey-Kramer multiple comparison post hoc test were used for analysis of data (P < 0.05). The results of this study showed that VPA significantly improved antiepileptic parameters including ITMS, ITTS, SD, and MR, in which they were significantly more prominent during the luteal phase than the follicular phase (P < 0.05). In addition, there was no significant difference neither between proestrous and estrous nor between metestrous and diestrous in each separately group of rats (P > 0.05).

Weight gain following treatment with valproic acid: pathogenetic mechanisms and clinical implications

In the last years, a growing body of literature indicates an association between valproic acid therapy and weight gain. Weight gain during valproate treatment can be observed within the first 3 months of therapy and women seem to be more susceptible than men. The mechanism through which valproic acid may induce a weight gain is still controversial. The scope of this paper is to investigate the possible causal link between treatment and weight gain in epileptic patients. Systematic review of published epidemiological studies has been done in order to evaluate the real extent of this side effect of valproic acid and its clinical implications, such as an increased risk of insulin resistance and other secondary metabolic abnormalities. The knowledge of the potential of valproic acid to cause significant changes in body weight will help in appropriate selection and modification of antiepileptic therapy to minimize the risk for weight abnormalities. Measurements of body weight before initiation of valproic acid therapy should be done as part of the monitoring of patients with epilepsy to detect changes before there are serious adverse consequences; an increase of 2 kg of body weight after 1 month of treatment should imply considerations to change antiepileptic drug therapy.

Antiepileptic drugs, sex hormones, and PCOS

Reproductive endocrine dysfunction in women with epilepsy is an important issue, and in recent years there is growing evidence to support the effect on sex hormones of both epilepsy per se and various antiepileptic drugs (AEDs). Focal epileptic discharges from the temporal lobe may have a direct influence on the function of the hypothalamic-pituitary axis, thereby altering the release of sex steroid hormones. The role of laterality and severity of epilepsy is still conflicting. The use of the liver enzyme-inducing AEDs--such as phenobarbital, phenytoin, and carbamazepine--can increase serum sex hormone-binding globulin concentrations, leading to diminished bioactivity of testosterone (T) and estradiol. Valproic acid, an enzyme inhibitor, has been associated with the occurrence of reproductive endocrine disorders characterized by high serum T, free androgen index, androstenedione, dehydroepiandrosterone sulfate concentrations, and with polycystic changes in ovaries and menstrual disorders. A better understanding of the effects of AEDs on sex hormones is key to selecting the appropriate AEDs and is crucial for reproductive health in female patients.

Hormonal alterations following seizures

Postictal increases in prolactin (PRL), luteinizing hormone, and follicle-stimulating hormone have been recorded in patients with both generalized tonic-clonic and partial seizures. Elevations of PRL and luteinizing hormone were seen immediately and at 20 minutes after generalized tonic-clonic seizures in male and female patients. Usually, PRL blood levels return to normal values within 1 hour. Previous studies have evaluated the utility of the transient increases in PRL, neuron-specific enolase, and S-100 protein as markers of epileptic seizures in children and adults. The conclusion was that measurement of serum PRL is a reliable confirmatory test in the presence of a seizure, but only modestly effective as a screening test for suspected seizures. Temporal lobe epilepsy is associated with abnormalities of reproductive physiology, but the mechanisms of hormonal dysregulation are not clear. A direct influence of epilepsy on the reproductive endocrine system is suggested by acute changes in PRL and gonadotropin levels following generalized and partial seizures, pointing to a possible relationship between temporolimbic epileptiform discharges and particular reproductive endocrine disorders. Chronic effects of the epileptic state and the acute impact of seizures could alter hypothalamic function, as indicated by downstream pulsatile secretion of luteinizing hormone. The brain controls reproductive function primarily through hypothalamic regulation of pituitary secretion regions of the hypothalamus. These are areas that are involved in the regulation, production, and secretion of gonadotropin-releasing hormone and receive extensive direct connections from the cerebral hemispheres, especially from temporolimbic structures, most notably from the amygdala, that are commonly involved in temporal lobe epilepsy. Significant relationships have been uncovered through which ictal and postictal effects of seizures and epilepsy may influence the function of this complex neuroendocrine system.

Subclinical hyperthyroidism and sudden unexpected death in epilepsy

Epilepsy is the most common serious neurological condition and sudden unexpected death in epilepsy (SUDEP) is the most important direct epilepsy-related cause of death. Information concerning risk factors for SUDEP is conflicting, but high seizure frequency is a potential risk factor. Additionally, potential pathomechanisms for SUDEP are unknown, but it is very probable that cardiac arrhythmias during and between seizures or transmission of epileptic activity to the heart via the autonomic nervous system potentially play a role. In parallel, several studies have shown a link between hormones and epilepsy. However, exact knowledge regarding the association of thyroid hormones and epilepsy is lacking. As subclinical hyperthyroidism has been linked with increased risk of cardiovascular disease, we propose in this paper that SUDEP, at least in some cases, could be related with subclinical thyroid dysfunction.

Xenobiotics in the limbic system--affecting brain's network function

Xenobiotic compounds enter the brain through nutrition, environmentals, and drugs. In order to maintain intrinsic homeostasis, the brain has to adapt to xenobiotic influx. Among others, steroid hormones appear as crucial mediators in this process. However, especially in the therapy of neurological diseases or brain tumors, long-term application of neuroactive drugs is advised. Several clinically important malignancies based on hormonal dysbalance rise up after treatment with neuroactive drugs, for example, sexual and mental disorders or severe cognitive changes. A drug-hormone cross talk proceeding over drug-mediated cytochrome P450 induction predominantly in the limbic system and the blood-brain barrier, consequently altered steroid hormone metabolism, and P450-mediated change of steroid hormone receptor expression and signaling may serve as an explanation for such disorders. Especially, the interplay between the expression of AR and P450 at the blood-brain barrier and in structures of the limbic system is of considerable interest in understanding brain's reaction on xenobiotic treatment. This chapter summarizes present models and concepts on brain's reaction after xenobiotics crossing the blood-brain barrier and invading the limbic system.