Chronic administration of sodium valproic acid slows pubertal maturation in inbred DBA/2J mice: skeletal, histological, and endocrinological evidence

Impairments of social interaction in a valproic acid model in mice

Background

A rodent autism spectrum disorder (ASD) model based on prenatal exposure to valproic acid (VPA) is widely recognized as a prominent model. Social behavior in rodent ASD models has primarily been evaluated through a three-chamber approach test. However, in this study, we focused on social attention in the VPA model of ASD.

Methods

In male C57BL/6 J mice, attentional behaviors toward conspecifics were examined through reaching tasks around 9-11 weeks of age. On embryonic day 12.5, pregnant mice underwent a subcutaneous injection of 600 mg/kg VPA sodium salt dissolved in 0.9% saline solution (VPA group) or saline solution alone (Sal group) into their neck fat. Thirty-six mice-nine each in the VPA and saline groups, and 18 partners-underwent training in reaching behavior. Subsequently, we examined whether the VPA or Sal group demonstrated focused attention toward their partners during reaching tasks. A two-way analysis of variance (ANOVA) (condition [VPA/Sal] × situation [face-to-face (attention)/not paying attention (not attention)]) was conducted on the average success rate of the situation. Additionally, we measured the duration of sniffing behavior between pairs of mice in an open field twice in total at 4 and 8 weeks of age before reaching task. The pairs were constructed by pairing a VPA or Sal group mouse with its partner, with the objective of facilitating initial encounters between the mice. A one-way ANOVA was conducted on the average duration of sniffing behavior data from 4 weeks and a second one-way ANOVA on data from 8 weeks.

Results

The analysis revealed a significant interaction between condition and situation in the reaching task [F (1, 28) = 6.75, p = 0.015, ηp 2 = 0.19]. The simple main effect test exhibited that the "not paying attention" rate was significantly higher than that of the "face-to-face" in the VPA group (p < 0.01). The results revealed a not significant difference in the average duration of sniffing behavior at 4 weeks [F (3, 32) = 2.71, p = 0.06, n.s., ηp 2 = 0.20], but significant difference at 8 weeks [F (3, 32) = 4.12, p < 0.05, ηp 2 = 0.28]. Multiple comparisons using the Bonferroni method revealed significant differences in the sniffing duration at 8 weeks between from the partner toward the VPA mouse and from the partner toward the Sal mouse (p < 0.05).

Conclusion

The VPA rodent model of ASD exhibited differences in social attention compared to the saline group. By focusing on social attention and exploring various ASD models, insights can be gained from the neural mechanisms underlying gaze abnormalities during social interaction in individuals with ASD.

Thyroid hormones, Sertoli cell proliferation and differentiation in progenies from carbamazepine-treated rat dams during pregnancy and lactation

Carbamazepine (CBZ) is used in the control of seizure and affective disorders, causing hypothyroidism. Thyroid hormones regulate the Sertoli cell proliferation and differentiation. Clinical aspects must be considered since epileptic fertile women need to continuously use CBZ during pregnancy and lactation. This study aimed to evaluate the effects of CBZ on testis development of rat offspring from dams treated during pregnancy/lactation. Rat dams received CBZ (20 mg kg^-1  day^-1 ) or vehicle by intra-peritoneal route during gestation and lactation. Progenies were euthanised at 4, 14, 41, 63 and 93-days post-partum (dpp) for the evaluation of T3, T4 and TSH plasma total levels. Testicular cross sections were submitted to anti-Ki67, anti-PCNA, anti-p27^kip1 and anti-transferrin immunolabelling for the evaluation of Sertoli cells. There was a significant reduction in p27^kip1 -positive Sertoli cell numerical densities and an increase in TSH level at 14 dpp. CBZ exposure affected the volume density of transferrin-positive immunolabelling at 63 dpp. These results suggest that CBZ may cause a dysregulation of the controller system of thyroid hormones homeostasis leading to an increase in the proliferation rate at the neonatal phase and a differentiation delay of the Sertoli cell, culminating in an altered function at late puberty. The occurrence of hypothyroidism cannot be completely discarded.

The model beetle Tribolium castaneum can be used as an early warning system for transgenerational epigenetic side effects caused by pharmaceuticals

Pharmaceuticals are not currently tested for transgenerational and epigenetic side effects. The use of vertebrates as preclinical research models is limited by their long generation times, low numbers of progeny and ethical concerns. In contrast, invertebrates such as insects breed rapidly, produce many offspring and are more ethically acceptable, allowing them to be used for high-throughput screening. Here, we established Tribolium castaneum as a model to screen for the effect of drugs on complex fitness parameters and the expression of epigenetic regulatory genes. We tested diets supplemented with the psychoactive drug valproic acid (VPA), which is a histone deacetylase inhibitor, or the antioxidant curcumin, which is a histone acetyltransferase inhibitor. We found that VPA delayed development, reduced longevity, and increased female body weight compared to a control diet. Fertility and fecundity declined and the expression of epigenetic regulatory genes was induced in the untreated F1 generation. In contrast, curcumin did not affect development or body weight, but it increased longevity, caused a significant reduction in fertility, and induced the expression of epigenetic regulatory genes mostly in the treated F0 generation. VPA and curcumin administered to vertebrate models have similar effects to those we observed in T. castaneum, confirming that this beetle is potentially useful as an alternative model to screen for the epigenetic effect of drugs. T. castaneum also provides a valuable early warning system for transgenerational epigenetic risk factors that are difficult to detect in mammals.

Effects of valproic acid on longitudinal bone growth

Valproic acid is widely used in the treatment of children with epilepsy. Evidence indicates that valproic acid has teratogenic effects on the skeletal system. In addition, the use of valproic acid in children has been associated with short stature. Thus, we hypothesized that valproic acid could also affect bone growth after skeletal morphogenesis is completed. To test this hypothesis, we cultured fetal rat metatarsal bones in the presence of valproic acid. Valproic acid markedly suppressed metatarsal longitudinal growth. To determine the underlying mechanisms, we studied cell proliferation and hypertrophy in the growth plate, the site where bone growth takes place. At the end of the culture period, valproic acid-treated bones exhibited narrow growth plate proliferative and hypertrophic zones and an expanded ossification center. In addition, valproic acid suppressed chondrocyte proliferation in the metatarsal rudiments. Our results suggest that valproic acid suppresses longitudinal bone growth by inhibiting cartilage formation and accelerating ossification of the growth plate. These findings warrant a prospective study on the effects of valproic acid on growth in children treated with valproic acid.

Effects of chronic valproate treatment on reproductive endocrine hormones in female and male Wistar rats

Valproate (VPA) has been claimed to induce endocrine disorders in both sexes in humans. There is sparse information regarding the mechanisms behind these disturbances. By using an animal model, we wanted to study the effect of valproate on hormonal function in non-epileptic rats. Female rats were given 0 (vehicle control, n=15), 200mg/kg (n=15), or 300 mg/kg (n=20) valproate twice daily by gavage for 90 days, resulting in mean valproate concentrations within the therapeutic range 4-6h after the last dose given. Serum testosterone concentrations remained unchanged, while estradiol levels were significantly reduced in both treatment groups, leading to significantly increased testosterone/estradiol ratios. Follicle stimulating hormone (FSH) levels remained unaltered in valproate treated rats, whereas the luteinizing hormone (LH) concentrations were reduced at the lowest valproate dose. Male rats received 0 (vehicle control, n=15), 200mg/kg (n=15), or 400mg/kg (n=20) valproate twice daily by gavage for 90 days, resulting in mean valproate concentrations within the therapeutic range 4-6h after the last dose. Serum testosterone levels were not significantly changed, but there was a highly significant increase in FSH and LH concentrations at the high dose. In conclusion, the study demonstrates a drug-induced effect of valproate on endocrine function in both male and female rats. The results indicate that the drug exerts its effect primarily at the gonadal level, although a centrally mediated effect cannot be ruled out.

Morphological changes in the testis after long-term valproate treatment in male Wistar rats

Uncertainty exists about the effect of antiepileptic drugs on gonadal function. In females, long-term valproate treatment has been shown to induce endocrine disturbances and an increased number of ovarian cysts. The aim of the present study was to investigate whether valproate can also induce morphological changes in the testis of male animals. In addition, possible morphological changes in the liver, heart, lungs, lymphatic nodes, pancreas, kidney or brain were studied. The carcinogenic implications were evaluated by the measurement of p53. Male Wistar rats were fed perorally with valproate mixture 200 mg kg(-1)(n= 15) or 400 mg kg(-1)(n= 20), or control solution (n= 15) twice daily for 90 days. Serum concentrations measured 4-6 hours after the last dose were 105 and 404 micromol l(-1)in low- and high-dose valproate treated animals respectively. There was a highly significant, 51% decrease (P< 0.001) in testicular weight in the high-dose treated valproate rats with no changes in the other groups. There was widespread testicular atrophy with histologically verified spermatogenic arrest in 15/20 of the high-dose valproate treated animals. No changes in the testis were seen in the low-dose valproate treated rats, nor in the control rats. There were no morphological changes in the other investigated organs. None of the groups showed over-expression of p53. In conclusion, a dose-dependent effect of chronic valproate treatment was found on testicular morphology in rats. Caution must be taken before these results can be applied to humans.

Neurobiological mechanisms of the onset of puberty in primates

An increase in pulsatile release of LHRH is essential for the onset of puberty. However, the mechanism controlling the pubertal increase in LHRH release is still unclear. In primates the LHRH neurosecretory system is already active during the neonatal period but subsequently enters a dormant state in the juvenile/prepubertal period. Neither gonadal steroid hormones nor the absence of facilitatory neuronal inputs to LHRH neurons is responsible for the low levels of LHRH release before the onset of puberty in primates. Recent studies suggest that during the prepubertal period an inhibitory neuronal system suppresses LHRH release and that during the subsequent maturation of the hypothalamus this prepubertal inhibition is removed, allowing the adult pattern of pulsatile LHRH release. In fact, y-aminobutyric acid (GABA) appears to be an inhibitory neurotransmitter responsible for restricting LHRH release before the onset of puberty in female rhesus monkeys. In addition, it appears that the reduction in tonic GABA inhibition allows an increase in the release of glutamate as well as other neurotransmitters, which contributes to the increase in pubertal LHRH release. In this review, developmental changes in several neurotransmitter systems controlling pulsatile LHRH release are extensively reviewed.

Sodium valproate alters GnRH-GABA interactions during development in seizure-prone mice

During reproductive maturation, characteristic changes occur in the morphology of the gonadotropin releasing hormone (GnRH) cell population within the hypothalamus. In the early stages of development, GnRH neurons are bipolar cells; however, just before pubertal onset, the majority of these neurons transform into unipolar cells. Our laboratory has reported that valproic acid (VPA), an antiepileptic medication that has previously been shown to slow the velocity of pubertal development in both humans and seizure-prone mice, is capable of delaying the normal process of GnRH morphological differentiation. As VPA is primarily believed to act via a GABAergic mechanism, the present study investigated potential influences of VPA on GnRH-GABA interactions within the medial preoptic area (mPOA) across pubertal development (experiment 1), as well as in adult animals (experiment 2). The results from experiment 1 revealed the expected drug effects on GnRH cell morphology. For VPA animals, there was a greater percentage of bipolar neurons at every time period except for the 24-day sample. Additionally, VPA animals had greater numbers of bipolar and unipolar GnRH neurons with GABA associations across all ages. However, experiment 2 showed a lack of drug effects on GnRH-GABA interactions in adulthood. These results suggest that VPA may delay GnRH cell morphological maturation by altering the density of GABAergic inputs to GnRH neurons. These inputs may normally play a role in timing the activation of the GnRH pulse generator. However, any neuroendocrine effects of VPA in adulthood are most likely due to the actions of VPA at another level of the hypothalamic-pituitary-gonadal axis.

GABA levels within the medial preoptic area: effects of chronic administration of sodium valproic acid

Sodium valproic acid (VPA) is a widely prescribed anticonvulsant medication that has been shown to interfere with pubertal maturation of the reproductive system, and induce endocrine abnormalities in adults, within a subset of the clinical population. While VPA's mechanism of action is still poorly understood, it may exert its anti-reproductive effects by enhancing GABAergic inhibition of the GnRH neuronal population within the medial preoptic area (mPOA). The purpose of this study was to determine if chronic administration of VPA alters GABA levels within the mPOA region. In Experiment 1, the mPOA, caudate, and arcuate nucleus regions were harvested from VPA-treated and control mice. Analysis of whole tissue content of GABA revealed that levels were lower in the caudate and arcuate nucleus regions of VPA-treated animals, whereas there were no group differences for the mPOA region. Collapsing across drug group, there was also a trend for males having overall higher levels of GABA as compared to females. In Experiments 2 and 3, mice were implanted with microdialysis probes within the mPOA region and sampled for extracellular GABA levels. Females (Exp. 3) were sampled either on diestrous, proestrous, or estrous. Results from males (Exp. 2) revealed that VPA enhanced extracellular GABA levels in the mPOA region compared with controls. However, GABA levels for both groups remained stable across the sampling period. Conversely, in Exp. 3, females showed cyclical release of GABA across the sampling period. For control females, GABA levels increased during the afternoon on all cycle days, but the rise on proestrus was smaller than on other cycle days. VPA-treated animals showed an overall reduction in GABA levels compared with controls. Furthermore, while GABA increased over sampling time on estrus and diestrus days of the cycle, there was not a significant rise in GABA on proestrus. These data indicate: (1) regional specificity in VPA effects upon GABA levels, (2) a sex difference in the effects of VPA on GABA levels within the mPOA, and (3) GABA levels increase on the afternoon of all days of the estrous cycle with VPA attenuating the rise seen on the afternoon of proestrus. These results provide evidence that VPA effects upon the reproductive axis may involve changes in GABA release, and that males and females show different patterns of neurochemical response to the drug.

Risk of excessive weight gain in epileptic children treated with valproate

We sought to identify factors associated with excessive weight gain in children treated with valproate, excluding patients fed by gastrostomy or treated with medications known to affect appetite (eg, stimulants). Weight and height were recorded before treatment and at the time of follow-up; a measure of adiposity, body mass index, was computed and expressed in kg/m2, and weight and height for age were converted to Z-score. Putative risk factors included sex, age at start of treatment, monotherapy at start of treatment, duration of follow-up, mental retardation, seizure type (generalized or partial), etiology (idiopathic or cryptogenic versus remote symptomatic), and dose of valproate. Fifty-five children (30 girls, 25 boys), ranging in age at the start of therapy from 1.8 to 16.9 years were followed for 8.6 to 33.8 months. Forty-three patients had primarily generalized seizures, 34 had idiopathic or cryptogenic epilepsy (including 30 with generalized idiopathic epilepsy), and 18 had mental retardation. Valproate was the first antiepileptic drug for 21 patients, and 43 were on monotherapy at the time of follow-up. Height Z-score decreased significantly in girls but was stable in boys. There was a significant increase in body mass index and in weight Z-score. Body mass index was greater than the 90th percentile for age in 14 patients at the start of treatment and in 20 patients at follow-up. Decrease in height Z-score was significantly correlated with female sex and duration of follow-up. Changes in weight Z-score and body mass index were significantly correlated with initial weight Z-score and initial body mass index, respectively, but not with age at start of therapy, duration of follow-up, sex, seizure type, etiology, dose of valproate, or monotherapy.

Lithium for prepubertal depressed children with family history predictors of future bipolarity: a double-blind, placebo-controlled study

BACKGROUND

Because of negative studies of TCAs for prepubertal major depressive disorder (PMDD) and because of the potentially high switch rate of PMDD to prepubertal bipolarity (BP), it was hypothesized that lithium would be efficacious treatment for PMDD in children who also had family history (FH) predictors of future BP.

METHODS

A double-blind, placebo-controlled, and pharmacokinetically dosed study of lithium for PMDD with FH predictors of future BP was performed. Random assignment was stratified by FH of BP-I or mania versus loaded/multigenerational (L/M) FH of MDD without BP-I or mania. Comprehensive assessments were done during a six week outpatient protocol that included weekly serum lithium levels.

RESULTS

Mean age was 10.7+/-1.2 years; 17 subjects were randomized to active and 13 to placebo; 80% had FH of BP-I or mania (40% of parents had BP-I or mania); and 20% had FH of L/M MDD. Using both intent to treat with last observation carried forward (n = 30) and completer (n = 24) analyses, there were no significant differences on continuous or categorical measures between active and placebo groups. Mean serum lithium level was 0.99+/-0.16 mEq/l. There were no significant differences between mean total daily dose or mean serum lithium levels between responders and non-responders.

LIMITATIONS

Four subjects on active drug were discontinued because of dose-limiting side effects (three were cognitive impairment). Future studies of treatment for PMDD should consider alternative drugs.

CLINICAL RELEVANCE

Lithium was not significantly more efficacious than placebo for PMDD with FH predictors of future BP.