Regulation of the expression of serotonin N-acetyltransferase gene in Japanese quail (Coturnix japonica): II. Effect of vitamin A deficiency

Mitochondria and immunity in chronic fatigue syndrome

It is widely accepted that the pathophysiology and treatment of myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) could be considerably improved. The heterogeneity of ME/CFS and the confusion over its classification have undoubtedly contributed to this, although this would seem a consequence of the complexity of the array of ME/CFS presentations and high levels of diverse comorbidities. This article reviews the biological underpinnings of ME/CFS presentations, including the interacting roles of the gut microbiome/permeability, endogenous opioidergic system, immune cell mitochondria, autonomic nervous system, microRNA-155, viral infection/re-awakening and leptin as well as melatonin and the circadian rhythm. This details not only relevant pathophysiological processes and treatment options, but also highlights future research directions. Due to the complexity of interacting systems in ME/CFS pathophysiology, clarification as to its biological underpinnings is likely to considerably contribute to the understanding and treatment of other complex and poorly managed conditions, including fibromyalgia, depression, migraine, and dementia. The gut and immune cell mitochondria are proposed to be two important hubs that interact with the circadian rhythm in driving ME/CFS pathophysiology.

Integrating Autism Spectrum Disorder Pathophysiology: Mitochondria, Vitamin A, CD38, Oxytocin, Serotonin and Melatonergic Alterations in the Placenta and Gut

BACKGROUND

A diverse array of data has been associated with autism spectrum disorder (ASD), reflecting the complexity of its pathophysiology as well as its heterogeneity. Two important hubs have emerged, the placenta/prenatal period and the postnatal gut, with alterations in mitochondria functioning crucial in both.

METHODS

Factors acting to regulate mitochondria functioning in ASD across development are reviewed in this article.

RESULTS

Decreased vitamin A, and its retinoic acid metabolites, lead to a decrease in CD38 and associated changes that underpin a wide array of data on the biological underpinnings of ASD, including decreased oxytocin, with relevance both prenatally and in the gut. Decreased sirtuins, poly-ADP ribose polymerase-driven decreases in nicotinamide adenine dinucleotide (NAD+), hyperserotonemia, decreased monoamine oxidase, alterations in 14-3-3 proteins, microRNA alterations, dysregulated aryl hydrocarbon receptor activity, suboptimal mitochondria functioning, and decreases in the melatonergic pathways are intimately linked to this. Many of the above processes may be modulating, or mediated by, alterations in mitochondria functioning. Other bodies of data associated with ASD may also be incorporated within these basic processes, including how ASD risk factors such as maternal obesity and preeclampsia, as well as more general prenatal stressors, modulate the likelihood of offspring ASD.

CONCLUSION

Such a mitochondria-focussed integrated model of the pathophysiology of ASD has important preventative and treatment implications.

The rhythm of retinoids in the brain

The retinoids are a family of compounds that in nature are derived from vitamin A or pro-vitamin A carotenoids. An essential part of the diet for mammals, vitamin A has long been known to be essential for many organ systems in the adult. More recently, however, they have been shown to be necessary for function of the brain and new discoveries point to a central role in processes ranging from neuroplasticity to neurogenesis. Acting in several regions of the central nervous system including the eye, hippocampus and hypothalamus, one common factor in its action is control of biological rhythms. This review summarizes the role of vitamin A in the brain; its action through the metabolite retinoic acid via specific nuclear receptors, and the regulation of its concentration through controlled synthesis and catabolism. The action of retinoic acid to regulate several rhythms in the brain and body, from circadian to seasonal, is then discussed to finish with the importance of retinoic acid in the regular pattern of sleep. We review the role of vitamin A and retinoic acid (RA) as mediators of rhythm in the brain. In the suprachiasmatic nucleus and hippocampus they control expression of circadian clock genes while in the cortex retinoic acid is required for delta oscillations of sleep. Retinoic acid is also central to a second rhythm that keeps pace with the seasons, regulating function in the hypothalamus and pineal gland.

Daily rhythms of catalase and glutathione peroxidase expression and activity are endogenously driven in the hippocampus and are modified by a vitamin A-free diet

OBJECTIVES

Alterations in enzymatic antioxidant defense systems lead to a deficit of cognitive functions and altered hippocampal synaptic plasticity. The objectives of this study were to investigate endogenous rhythms of catalase (CAT) and glutathione peroxidase (GPx) expression and activity, as well as CREB1 mRNA, in the rat hippocampus, and to evaluate to which extent the vitamin A deficiency could affect those temporal patterns.

METHODS

Rats from control and vitamin A-deficient (VAD) groups received a diet containing 4000 IU of vitamin A/kg diet, or the same diet devoid of vitamin A, respectively, during 3 months. Rats were maintained under 12-hour-dark conditions, during 10 days before the sacrifice. Circadian rhythms of CAT, GPx, RXRγ, and CREB1 mRNA levels were determined by reverse transcriptrase polymerase chain reaction in hippocampus samples isolated every 4 hours during a 24-hour period. CAT and GPx enzymatic activities were also determined by kinetic assays. Regulatory regions of clock and antioxidant enzymes genes were scanned for E-box, RXRE, and CRE sites.

RESULTS

E-box, RXRE, and CRE sites were found on regulatory regions of GPx and CAT genes, which display a circadian expression in the rat hippocampus. VAD phase shifted CAT, GPx, and RXRγ endogenous rhythms without affecting circadian expression of CREB1.

DISCUSSION

CAT and GPx expression and enzymatic activity are circadian in the rat hippocampus. The VAD affected the temporal patterns antioxidant genes expression, probably by altering circadian rhythms of its RXR receptors and clock factors; thus, it would impair the temporal orchestration of hippocampal daily cognitive performance.

Enhanced effect of daytime restricted feeding on the circadian rhythm of streptozotocin-induced type 2 diabetic rats

There is increasing awareness of the link between impaired circadian clocks and multiple metabolic diseases. However, the impairment of the circadian clock by type 2 diabetes has not been fully elucidated. To understand whether and how the function of circadian clock is impaired under the diabetic condition, we examined not only the expression of circadian genes in the heart and pineal gland but also the behavioral rhythm of type 2 diabetic and control rats in both the nighttime restricted feeding (NRF) and daytime restricted feeding (DRF) conditions. In the NRF condition, the circadian expression of clock genes in the heart and pineal gland was conserved in the diabetic rats, being similar to that in the control rats. DRF shifted the circadian phases of peripheral clock genes more efficiently in the diabetic rats than those in the control rats. Moreover, the activity rhythm of rats in the diabetic group was completely shifted from the dark phase to the light phase after 5 days of DRF treatment, whereas the activity rhythm of rats in the control group was still under the control of the suprachiasmatic nucleus (SCN) after the same DRF treatment. Furthermore, the serum glucose rhythm of type 2 diabetic rats was also shifted and controlled by the external feeding schedule, ignoring the SCN rhythm. Therefore, DRF shows stronger effect on the reentrainment of circadian rhythm in the type 2 diabetic rats, suggesting that the circadian system in diabetes is unstable and more easily shifted by feeding stimuli.

Melatonin and its synthesizing enzymes (arylalkylamine N-acetyltransferase-like and hydroxyindole-O-methyltransferase) in avian eggs and early embryos

The presence of melatonin and the enzymes (transcripts and activities) involved in its synthesis, i.e. arylalkylamine N-acetyltransferase (AA-NAT) and hydroxyindole-O-methyltransferase (HIOMT), was investigated in the eggs and early embryos of Japanese quail at Hamburger-Hamilton stages 1-10. Melatonin was present in the egg yolk (approximately 70 pg/g) and albumen (approximately 20 pg/g). The average content of melatonin was approximately 416 pg/egg. AA-NAT and HIOMT transcripts were present in the oocytes, blastoderms, and ovarian follicles. AA-NAT-like and HIOMT activities were detected in quail egg yolk. The activity of AA-NAT in yolk was comparable with that found in the pineal gland when calculated per milligram of yolk or pineal gland, but was significantly lower when re-calculated per milligram of protein in the yolk or pineal gland. AA-NAT-like activity was also identified in the ovarian follicles. Low HIOMT activity was detected in yolk, but not in the ovarian follicle. Both enzymes were essentially absent from early embryos although some residual activities, probably of yolk origin, were present in the stage 1 embryo. Melatonin and all the constituents needed for its synthesis (serotonin, AA-NAT and HIOMT activities) are contained within the avian yolk and could be used by the embryo from the very beginning of its development. The role of extrapineal melatonin in early avian development may be in protecting the embryo from the action of free radicals formed during intensive embryonic metabolism and/or it may participate (together with serotonin) in a 'diffuse neuroendocrine system' acting at early developmental stages, before differentiation of the nervous system.

Transition from embryonic to adult transcription pattern of serotonin N-acetyltransferase gene in avian pineal gland

The study reports the change of transcription pattern of serotonin N-acetyltransferase gene and melatonin receptor genes during ontogenesis of the avian pineal gland. The RT-PCR technique was used to investigate the expression of the arylalkylamine N-acetyltransferase (AA-NAT) and melatonin receptor genes during development of the pineal glands isolated from Japanese quail (Coturnix coturnix japonica) embryos incubated from 3 days on until hatching (17 days), and in some organs (pineal, brain hemisphere, eye, leg, heart) of the 3-day-old quail embryo. It was shown that two phases of AA-NAT expression are observed during pineal gland development. The first, embryonic-type phase, lasts from the beginning until 7-10 days of incubation, and is marked by the presence of two RT-PCR products for AA-NAT: the shorter mature form without intron (238 bp), and the longer form (323 bp) containing an unprocessed intron of 85 bp. The second, adult-type phase is characterized by the presence of a single mature transcript, containing no intron; it starts from 7 to 10 days of incubation and lasts until hatching and in the adult pineal. The duration of this transition time from the embryonic to the adult transcription pattern in the quail pineal gland from 7 to 10 days of incubation we attribute to asynchronic embryo development, because quail chicks usually hatch between the 16th and 19th day of incubation. Analysis of the AA-NAT protein sequences for chick and quail (GeneBank accession no. U 46 502 and AF 007 068, respectively) revealed their perfect homology with the part of protein read from the sequence present in the adult-type phase of the pineal gland (the RT-PCR product of 238 bp). The presence of the intron (in the 323 bp RT-PCR product, accession no. AY 197 460) in the embryonic-phase of the pineal gland changes the reading frame of the mRNA sequence and the hypothetical resulting protein loses its homology with the chick and quail AA-NAT enzyme starting with 105th amino acid of the complete chick AA-NAT protein comprising 205 amino acids (accession no. U 46 502). In the whole embryos at stages 1-8 (according to the Hamburger-Hamilton classification) both RT-PCR products with and without intron were consistently found, and individual tissues from 3-day-old embryos also produced two AA-NAT products, i.e., the expression was of the embryonic-type. At the time of transition from the embryonic to the adult AA-NAT transcription pattern, in 7-11-day-old embryos, all three melatonin receptor transcripts (mel-1a, mel-1b, and mel-1c) were observed in the pineals, without consistent modifications of the band intensity. In the adult pineal, a single mature AA-NAT transcript was present as well as all three melatonin receptor transcripts, usually with preferential expression of the mel-1a band. The transition time from the embryonic to adult AA-NAT expression pattern coincides well with the acquisition of functional activity and the appearance of melatonin synthesis in the embryonic pineal reported for chicken, as related to quail. We suggest that the change in transcription pattern of the AA-NAT gene may reflect another, still unknown mechanism of regulating AA-NAT activity during ontogenesis, at the level of mRNA processing, whose specificity (or not) for embryonic development we wish to establish in the future.

Presence and developmental regulation of serotonin N-acetyltransferase transcripts in oocytes and early quail embryos (Coturnix coturnix japonica)

By RT-PCR two transcripts for arylalkylamine N-acetyltransferase (AA-NAT; serotonin N-acetyltransferase; EC 2.3.1.87), the key enzyme in melatonin synthesis, were found, for the first time, in the oocytes and blastoderms from freshly laid eggs (323- and 238-bp RT-PCR products), and one (238-bp product) in the pineal gland of Japanese quail (Coturnix coturnix japonica). The two products differed by an intron of 85-bp present in the 323-bp band and absent from the 238-bp band. The identity of the products was confirmed by restriction analysis and sequencing. The ratio of the 323:238-bp bands changed during oogenesis from approximately 17:1 in small 3-mm oocytes to approximately 4:1 in immature vitellogenic oocytes and approximately 1:1 in mature, preovulatory oocytes; it was reversed to approximately 0.2:1 in blastoderms from fertile freshly laid eggs, corresponding to embryo of approximately 40,000 cells. It is proposed that the longer 323-bp product, containing an intron, represents a translationally inactive form of the transcript, stored in maternal RNA. The shorter 238-bp product lacking an intron may represent the mature active AA-NAT mRNA found in the pineal gland and in early embryos, and-to a lower proportion-in older oocytes. These data constitute the first direct proof of an intron sequence in maternal RNA of avian oocyte. It is possible that differential processing of the immature mRNA is part of a transcriptional regulation mechanism of AA-NAT activity. A possible role of extrapineal melatonin in early avian development is discussed.

Molecular cloning and circadian regulation of cryptochrome genes in Japanese quail (Coturnix coturnix japonica)

The circadian system is thought to have three components: input, pacemaker (internal clock), and output. Cryptochromes (Cry) are important clock genes, and recent findings indicate that these genes not only act as circadian photoreceptors but are also essential components in the negative feedback of the circadian system. As a first step toward understanding the avian circadian system, the authors tried to clone Japanese quail homologs of mammalian Crys and analyze their expression patterns in different circumstances. Partial cDNAs of qCry1 and qCry2, which are homologs of mammalian Cry1 and Cry2, respectively, were obtained and their gene expressions were analyzed. Both qCry1 and qCry2 mRNAs were present in all the tissues examined. The oscillation patterns of the qCry1 transcripts were tissue specific and generally showed robust changes between daytime and nighttime; except for lung and testis tissues (which showed no detectable changes between daytime and nighttime), daytime levels were higher in all of the tissues examined. This rapid oscillation in qCry1 persisted through constant darkness or constant illumination, indicating that an endogenous clock controls these changes. In contrast, the expression of qCry2 did not oscillate in any tissue examined. In addition, in tissues of the pineal gland and eye, unexpected light exposure in the dark period was able to block the decrease in qCry1 transcripts or induce its expression. These findings, in conjunction with the established roles of CRYs in other species, led the authors to propose that in the circadian system, qCRYs may play important roles similar to the known roles of CRYs of other species, such as acting as circadian photoreceptors and as components of the circadian system.

Regulation of hydroxyindole-O-methyltransferase gene expression in Japanese quail (Coturnix coturnix japonica)

Hydroxyindole-O-methyltrasferase (HIOMT) plays an important role as the final enzyme in the synthesis of melatonin. In this study, the expression of the HIOMT gene in Japanese quail was investigated with respect to tissue distribution and the effects of light and vitamin A deficiency. HIOMT mRNA in the pineal gland and eye had a clear daily rhythm with peak values in daytime. The testis also contained a detectable amount of HIOMT mRNA, which did not display a rhythmic change over a 24-h period. When birds were rendered vitamin A deficient through feeding with a vitamin A-free diet, the daily rhythm of the HIOMT gene almost disappeared in both the pineal gland and eye due to increases in the nighttime values. Our previous observations and these results suggest that vitamin A and a photo-signal are required to maintain the rhythmic expression of the HIOMT gene as well as the arylalkylamine N-acetyltransferase gene.

Differential regulation of IGFBP-2 and IGFBP-5 gene expression by vitamin A status in Japanese quail

To investigate the involvement of the insulin-like growth factor (IGF) system in vitamin A (VA)-supported growth, we examined the effects of VA status on IGF binding protein (IGFBP)-2 and -5 gene expression in Japanese quail. VA deficiency caused a reduction in IGFBP-2 mRNA only in lung, without effect in other tissues. However, the expression of IGFBP-5 mRNA was more sensitive to the change of VA status. IGFBP-5 mRNA levels were significantly reduced by VA depletion in a tissue-specific manner, which preceded the decrease in body weight. A single injection of retinoic acid or retinol to VA-deficient quail did not affect the levels of IGFBP-2 mRNA, but it rapidly induced the expression of IGFBP-5 mRNAs in some tissues. These results are the first to show that gene expression of some IGFBPs in vivo are under the control of VA status and suggest a possible involvement of the IGF system in mediating the physiological actions of VA in the growth of Japanese quail.

Vitamin A deficiency reduces insulin-like growth factor (IGF)-I gene expression and increases IGF-I receptor and insulin receptor gene expression in tissues of Japanese quail (Coturnix coturnix japonica)

The insulin-like growth factor (IGF) system is regulated by various stimuli, including hormones, growth factors and nutritional status. We examined the effects of vitamin A on components of the IGF system in Japanese quail. Male quail (1 d old) fed a vitamin A-deficient diet for 14 or 21 d developed vitamin A deficiency, as confirmed by a depletion of serum retinol and hepatic retinyl palmitate. Consuming the vitamin A-deficient diet for 14 d did not affect growth rate, but decreased the serum IGF-I concentrations by 22% compared with the control group. The decreased serum IGF-I levels were accompanied by 21-52% lower levels of IGF-I mRNA in the testis, lung, liver and heart, whereas IGF-I receptor (IGF-IR) and insulin receptor (IR) gene expressions were unaffected in these tissues. Continuous feeding of the vitamin A-deficient diet for 21 d retarded growth and further decreased the levels of serum IGF-I and tissue IGF-I mRNA. Serum IGF-I levels were reduced by approximately 50%; IGF-I mRNA levels were > 90% lower in the liver and lung and approximately 60% lower in the heart and testis. In contrast, levels of the IGF-IR and IR mRNAs were approximately 100% greater in some tissues examined. When vitamin A-deficient quail received a single injection of retinol or retinoic acid (0.1 mg/bird), tissue IGF-I, IGF-IR and IR gene expressions did not change after 4 h. These results suggest a possible physiologic role of the IGF system in mediating vitamin A-supported growth of Japanese quail.

Developmental changes in the mRNA levels of IGF-I and its related genes in the reproductive organs of Japanese quail (Coturnix coturnix japonica)

Summary Insulin-like growth factor-I (IGF-I) is involved in the regulation of growth and differentiation of a variety of vertebrate tissues. The biological actions of IGF-I are mediated mainly by the IGF-I receptor (IGF-IR) and partly by the insulin receptor (IR) and modulated by IGF binding proteins (IGFBP). We conducted studies designed to clarify the possible roles of IGF system in the development of the avian reproductive organs. We cloned cDNAs of IGF-I, IGF-IR, IR and IGFBP-2 of Japanese quail and simultaneously measured the expression of these genes in the quail liver, testis and oviduct at different ages using a lysate RNase protection assay. Hepatic IGF-I mRNA levels increased rapidly and remained elevated during the rapid-growing period, which coincided with the period of rapid increase in testicular weight. IGF-I mRNA was detected at each stage of developing testis examined. Its level was high at the early stage and decreased with age. IGFBP-2 mRNA in testis exhibited a similar expression pattern to that of IGF-I, whereas a divergence in IGF-I and IGF-IR gene expression was observed. Both IGF-IR and IR mRNAs increased when the testis grew rapidly and decreased when sexual maturation was almost completed. These results suggest that IGF-I may serve as an autocrine/paracrine regulator as well as an endocrine regulator in the testicular development and function of Japanese quail. In the oviduct, IGF-I, IGF-IR, IR and IGFBP-2 mRNAs were also developmentally regulated. A rapid growth of the oviduct was accompanied by a significant increase in the level of IGF-I mRNA. The expression of genes encoding IGF-IR, IR and IGFBP-2 in the oviduct exhibited a similar developmental change to that of IGF-I. These results suggest that IGF-I mainly works in an autocrine and/or paracrine manner in the oviduct during the development of this organ. The findings of the present study provide further evidence of an important role for IGF system in the development and function of the avian reproductive system.

Cloning of complementary deoxyribonucleic acids encoding quail (Coturnix coturnix japonica) retinoic acid receptor ss isoforms and changes in their gene expression during gonadotropic growth

Retinoids have important effects on the development of the reproductive system, where they act via their specific nuclear receptors: retinoic acid receptors (RARalpha, ss, gamma) and retinoid X receptors (RXRalpha, ss, gamma). The research reported here was conducted in an effort to clone quail RARbeta+ cDNA (qRARbeta) and to evaluate the expression of qRARbeta+ mRNAs in different tissues and during the development of gonadotropic organs. Two complete cDNAs of qRARbeta1 and qRARbeta2 were isolated by a combination of reverse transcription-polymerase chain reaction and 5'- and 3'-rapid amplification of cDNA ends techniques. An RNase protection assay revealed the widespread expression of qRARbeta1 and beta2 with large tissue-specific variations. The qRARbeta1 isoform was predominant in the testis, whereas qRARbeta2 was dominant in the other tissues examined with the exception of the brain, where both isoforms were almost equally expressed. In the developing testes, the qRARbeta1 mRNA level was high between 30 and 40 days of age, the period during which the testes grew rapidly. The level declined thereafter to its initial level. In contrast, qRARbeta2 mRNA did not exhibit obvious changes. In the developing oviducts, both qRARbeta1 and beta2 mRNAs reached their peak levels by 30 days of age, just before the rapid development of the oviduct occurred, and then decreased to almost undetectable levels when the oviduct developed to the laying stage (over 2.88 g in weight). Similar expression patterns of qRARbeta1 and beta2 were also observed in the developing follicles from the prehierarchical (<2-mm diameter) to the largest preovulatory follicle. In contrast, neither qRARbeta1 nor beta2 mRNA exhibited developmental changes in the brain. These results suggest that RARbeta+ may play an important role in the development of the reproductive systems of birds.

Retinoic acid accelerates the development of reproductive organs and egg production in Japanese quail (Coturnix coturnix japonica)

The effects of retinoic acid on the development of reproductive organs and egg production in female Japanese quail (Coturnix coturnix japonica) were investigated. Female quail were fed a diet containing retinoic acid at 4 mg/kg (RA) or two diets containing retinyl acetate at 5000 IU/kg (VA1) or 14 000 IU/kg (VA2) after being fed a vitamin A-free diet for 2 wk (experiment 1). The oviduct and ovary grew more rapidly (P < 0.05) in RA-treated quail than in VA-treated quail at 5 wk of age. In addition, the body weight of RA-fed quail was also greater (P: < 0.05) than that of VA-fed quail at 5 wk. The RA-treated quail laid their first eggs approximately 5 days earlier (P < 0.05) than the VA-treated quail. Furthermore, these RA-fed quail laid more eggs (P < 0.05) than those VA-fed quail during the experimental period. To confirm the results of experiment 1, a similar experiment was conducted to record the first egg and total eggs laid by quail fed VA2 or RA (experiment 2). The early onset of oviposition was again observed in the RA-treated group (P < 0.01). These results suggest that retinoic acid has a stimulating effect on the reproductive system of female Japanese quail, as has been previously shown in the reproductive system of male Japanese quail.