Molecular cloning and tissue expression of chicken AdipoR1 and AdipoR2 complementary deoxyribonucleic acids

The role of AdipoQ on proliferation, apoptosis, and hormone Secretion in chicken primary adenohypophysis cells

Adiponectin (AdipoQ), an adipokine secreted by adipocytes, has been reported to exist widely in various cell types and tissues, including the adenohypophysis of chickens. However, the molecular mechanism by which AdipoQ regulates the function of chicken adenohypophysis remains elusive. In this study, we investigated the effects of AdipoQ on proliferation, apoptosis, secretion of related hormones (FSH, LH, TSH, GH, PRL and ACTH) and expression of related genes (FSHβ, LHβ, GnRHR, TSHβ, GH, PRL and ACTH) in primary adenohypophysis cells of chickens by using real-time fluorescent quantitative PCR (RT-qPCR), cell counting kit-8 (CCK-8), flow cytometry, enzyme-linked immunosorbent assay (ELISA) and Western blot (WB) assays. Our results showed that AdipoQ promoted the proliferation of chicken primary adenohypophysis cells, up-regulated the mRNA expression of proliferation-related genes CDK1, PCNA, CCND1 and P21 (P < 0.05), as well as the increased protein expression of CDK1 and PCNA (P < 0.05). Furthermore, AdipoQ inhibited apoptosis of chicken primary adenohypophysis cells, resulting in down-regulation of pro-apoptotic genes Caspase3, Fas, and FasL mRNA expression, and decreased Caspase3 protein expression (P < 0.05). Moreover, there was an up-regulation of anti-apoptotic gene Bcl2 mRNA and protein expression (P < 0.05). Additionally, AdipoQ suppressed the secretion of FSH, LH, TSH, GH, PRL, and ACTH (P < 0.05), as well as the mRNA expression levels of related genes (P < 0.05). Treatment with AdipoRon (a synthetic substitute for AdipoQ) and co-treatment with RNA interference targeting AdipoQ receptors 1/2 (AdipoR1/2) had no effect on the secretion of FSH, LH, TSH, GH, PRL, and ACTH, as well as the mRNA expression levels of the related genes. This suggests that AdipoQ's regulation of hormone secretion and related gene expression is mediated by the AdipoR1/2 signaling axis. Importantly, we further demonstrated that the mechanism of AdipoQ on FSH, LH, TSH and GH secretion is realized through AMPK signaling pathway. In conclusion, we have revealed, for the first time the molecular mechanism by which AdipoQ regulates hormone secretion in chicken primary adenohypophysis cells.

The Role of Adipokines in the Control of Pituitary Functions

The pituitary gland is a key endocrine gland in all classes of vertebrates, including mammals. The pituitary gland is an important component of hypothalamus-pituitary-target organ hormonal regulatory axes and forms a functional link between the nervous system and the endocrine system. In response to hypothalamic stimuli, the pituitary gland secretes a number of hormones involved in the regulation of metabolism, stress reactions and environmental adaptation, growth and development, as well as reproductive processes and lactation. In turn, hormones secreted by target organs at the lowest levels of the hormonal regulatory axes regulate the functions of the pituitary gland in the process of hormonal feedback. The pituitary also responds to other peripheral signals, including adipose-tissue-derived factors. These substances are a broad group of peptides known as adipocytokines or adipokines that act as endocrine hormones mainly involved in energy homeostasis. Adipokines, including adiponectin, resistin, apelin, chemerin, visfatin, and irisin, are also expressed in the pituitary gland, and they influence the secretory functions of this gland. This review is an overview of the existing knowledge of the relationship between chosen adipose-derived factors and endocrine functions of the pituitary gland, with an emphasis on the pituitary control of reproductive processes.

Hormonal regulation of visfatin and adiponectin system in quail muscle cells

Visfatin and adiponectin are two adipokines known to regulate energy homeostasis and stress response within different peripheral tissues. Their role and regulation in highly metabolically active tissue such as the muscle is of particular interest. As modern poultry exhibit insulin resistance, obesity, and hyperglycemia along with a lack of insight into the regulation of these avian adipokines, we undertook the present work to determine the regulation of visfatin and adiponectin system by cytokines and obesity-related hormones in a relevant in vitro model of avian muscle, quail muscle (QM7) cells. Cells were treated with pro-inflammatory cytokine IL-6 (5 and 10 ng/mL) and TNFα (5 and 10 ng/mL), as well as leptin (10 and 100 ng/mL) and both orexin-A and orexin-B (ORX-A/B) (5 and 10 ng/mL). Results showed significant increases in visfatin mRNA abundance under both cytokines (IL-6 and TNFα), and down regulation with ORX-B treatment. Adiponectin expression was also upregulated by pro-inflammatory cytokines (IL-6 and TNFα), but down regulated by leptin, ORX-A, and ORXB. High doses of IL-6 and TNFα up regulated the expression of adiponectin receptors AdipoR1 and AdipoR2, respectively. Leptin and orexin treatments also down regulated both AdipoR1 and AdipoR2 expression. Taken together, this is the first report showing a direct response of visfatin and the adiponectin system to pro-inflammatory and obesity-related hormones in avian muscle cells.

Presence, Tissue Localization, and Gene Expression of the Adiponectin Receptor 1 in Testis and Accessory Glands of Male Rams during the Non-Breeding Season

Adiponectin (ADIPOQ) is a member adipocytokines, and its actions are supported by two receptors, ADIPOQ receptor 1 and -2, respectively (ADIPOR1 and -R2). Our study was performed to evaluate the ADIPOR1 presence and location and its gene expression in reproductive tissues of the male ram, during its non-breading season. The different portions of the male ram reproductive system (testis, epididymis, seminal vesicle, ampoule vas deferens, bulb-urethral gland) were collected in a slaughterhouse. Immunohistochemistry showed ADIPOR1 positive signals in the cytoplasm of all the glandular epithelial cells, with a location near the nucleus; in the testes, the positive reaction was evidenced in the cytoplasm in the basal portion of the germinal epithelial cells. The immune reaction intensity was highest (p < 0.001) in the prostate and seminal vesicles glands than that of other parts of the ram reproductive tract. RT-qPCR detected the ADIPOR1 transcript in the testes, epididymis, vas deferens, bulbourethral glands, seminal vesicles, and prostate; the expression levels were high (p < 0.01) in the prostate and low (p < 0.01) in the testis, epididymis, and bulbourethral glands. The present results evidenced the possible ADIPOQ/ADIPOR1 system's role in regulating the testicular activity of male rams during the non-breading season.

Appropriate cold stimulation changes energy distribution to improve stress resistance in broilers

Appropriate cold stimulation can improve stress resistance in broilers and alleviate the adverse impacts of a cold environment. To investigate the effects of intermittent mild cold stimulation (IMCS) on energy distribution in the livers of broilers, 96 healthy 1-d-old Ross-308 male broilers were randomly divided into the control group (CC) and the cold stimulation group (H5). The CC group was raised at a normal thermal temperature, i.e., 35 °C until 3 d, after which the temperature was dropped gradually by 0.5 °C/d until 20 °C at 33 d. This temperature was maintained until 49 d. The H5 group was raised at the same temperature as the CC group until 14 d (35 to 29.5 °C) and at 3 °C below the temperature of the CC group starting at 0930 hours for 5 h every other day from 15 to 35 d (26 to 17°C). The temperature was returned to 20 °C at 36 d and maintained until 49 d. At 50 d, all broilers were subjected to acute cold stress (ACS) at 10 °C for 6 and 12 h. We found that IMCS had positive effects on production performance. Using transcriptome sequencing of the broiler livers, 327 differentially expressed genes (DEG) were identified, and highly enriched in fatty acid biosynthesis, fatty acid degradation, and the pyruvate metabolism pathway. When compared to the CC group, the mRNA levels of ACAA1, ACAT2, ACSL1, CPT1A, LDHB, and PCK1 in the H5 group were increased at 22 d (P < 0.05). The LDHB mRNA level was upregulated in the H5 group at 29 d compared to the CC group (P < 0.05). After 21 d of IMCS (at 36 d), the mRNA expression levels of ACAT2 and PCK1 were found to be significantly increased in the H5 group compared to the CC group (P < 0.05). Seven days after the IMCS had ended (at 43 d), the mRNA levels of ACAA1, ACAT2, and LDHB in the H5 group were higher than in the CC group (P < 0.05). The mRNA levels of heat shock protein (HSP) 70, HSP90, and HSP110 in the H5 group were higher than in the CC group after 6 h of ACS (P < 0.05). The protein levels of HSP70 and HSP90 in the H5 group were downregulated after 12 h of ACS, compared to the CC group (P < 0.05). These results indicated that IMCS at 3 °C lower than the normal temperature could improve energy metabolism and stress resistance in the livers of broilers, alleviate the damage of short-term ACS on broilers, help broilers adapt to the low temperature, and maintain stable of energy metabolism in the body.

Seasonal and sexual variation in mRNA expression of selected adipokine genes affecting fat deposition and metabolism of the emu (Dromaius novaehollandiae)

Emus are farmed for fat production. Oil rendered from their back and abdominal fat pads has good anti-oxidant and anti-inflammatory properties and has ingredients that promote cell growth. Our objective is to examine the mRNA expression of 7 emu adipokine genes (eFABP4, eSCD1, eAdipoQ, eAdipoR1, eAdipoR2, eLEP and eLepR) to identify gene markers that may help improve emu fat production. Back and abdominal fat tissues from 11 adult emus were biopsied at four time points (April, June, August and November). Total RNA was isolated and cDNA was synthesized. Gene specific primers were designed for partial cloning fragments to amplify the open reading frame of the 7 genes. eLEP was not expressed in emu fat tissue. Nucleotides and amino acids sequences of the 6 expressed gene were compared with homologs from other species and phylogenetic relationships established. Seasonal mRNA expression of each gene was assessed by quantitative RT-PCR and differential expression analysed by the 2-ΔΔCT method. The 6 expressed genes showed seasonal variation in expression and showed association of expression level with back fat adiposity. More whole-genome scanning studies are needed to develop novel molecular markers that can be applied to improve fat production in emus.

Adiponectin/adiponectin receptors mRNA expression profiles in chickens and their response to feed restriction

Adiponectin (ADPN) is related to fatty acid synthesis and oxidation in mammals. In chickens, the lipid metabolism, structure and sequence of ADPN are different from that in mammals. The aim of this study was to determine the role of ADPN in broilers lipid metabolism by investigating the temporal and spatial expression profiles of ADPN and its receptors, as well as their response to feed restriction. The results showed that the abdominal fat has the highest expression level, followed by the duodenum, glandular stomach, heart, hypothalamus, liver, and skeletal muscle. Broilers have high energy mobilization during their early stage of growth, in which the fat demand in the liver and muscles is high, thus the expression of ADPN and its receptor are also increased. To study the effects of feed restriction on ADPN and lipid metabolism, broilers were fasted for 12 h and refeed for 2 h. The results showed that fasting decreased the concentration of triglyceride (TG) (P < 0.05) and total cholesterol (TCHO) (P < 0.05) in plasma. The mRNA expression of ADPN in the liver (P < 0.05), breast (P < 0.05) and thigh (P < 0.05), and the mRNA expression of ADPNR1 in the liver (P < 0.05) and duodenum (P < 0.05) were significantly increased in the Fasted group. All above phenomena were recovered after refeeding, suggesting that feed restriction may promote the utilization of fatty acids in active metabolism tissues through ADPN, to guarantee the energy homeostasis of the body. However, the AMP-activated protein kinase (AMPK) signaling pathway and hepatic lipid metabolism were not necessary to cause the above changes under this experimental condition.

Sex- and season-dependent differences in the expression of adiponectin and adiponectin receptors (AdipoR1 and AdipoR2) in the hypothalamic-pituitary-adrenal axis of the Eurasian beaver (Castor fiber L.)

Adiponectin, a product of the Adipoq gene, is an adipocyte-derived protein hormone of the cytokine family and the most abundantly expressed adipokine. Adiponectin and its receptors AdipoR1 and AdipoR2 (collectively referred to as the adiponectin system) are widely expressed in the central nervous system and other tissues, which suggests that this hormone has pleiotropic effects. Adiponectin could also play a role in the modulation of the hypothalamic-pituitaryadrenal (HPA) hormonal regulatory axis. There is a general scarcity of data on the adiponectin system in wild animals where annual changes in reproductive activity are linked with fluctuations in the activity of the HPA axis. The Eurasian beaver (Castor fiber L.) could be an interesting and suitable model for investigating the above processes. We hypothesized that the expression of the adiponectin system in the tissues of the beaver HPA axis is sex- and season-dependent. The study was performed on adult animals harvested during three different stages of reproductive activity: April ('breeding'), July ('post-breeding') and November ('pre-breeding'). The expression of the adiponectin system was confirmed in all branches (mediobasal hypothalamus, pituitary, adrenal cortex) of the HPA axis in both sexes and during all periods of reproductive activity. The expression of Adipoq, AdipoR1 and AdipoR2 was generally dependent on sex and the period of the reproductive season. The expression of adiponectin system genes was particularly pronounced in the adrenal cortex. These findings suggest that the adiponectin system in the Eurasian beaver could link reproductive processes with stress responses and energy metabolism.

Should I Lay or Should I Grow: Photoperiodic Versus Metabolic Cues in Chickens

While photoperiod has been generally accepted as the primary if not the exclusive cue to stimulate reproduction in photoperiodic breeders such as the laying hen, current knowledge suggests that metabolism, and/or body composition can also play an influential role to control the hypothalamic-pituitary gonadal (HPG)-axis. This review thus intends to first describe how photoperiodic and metabolic cues can impact the HPG axis, then explore and propose potential common pathways and mechanisms through which both cues could be integrated. Photostimulation refers to a perceived increase in day-length resulting in the stimulation of the HPG. While photoreceptors are present in the retina of the eye and the pineal gland, it is the deep brain photoreceptors (DBPs) located in the hypothalamus that have been identified as the potential mediators of photostimulation, including melanopsin (OPN4), neuropsin (OPN5), and vertebrate-ancient opsin (VA-Opsin). Here, we present the current state of knowledge surrounding these DBPs, along with their individual and relative importance and, their possible downstream mechanisms of action to initiate the activation of the HPG axis. On the metabolic side, specific attention is placed on the hypothalamic integration of appetite control with the stimulatory (Gonadotropin Releasing Hormone; GnRH) and inhibitory (Gonadotropin Inhibitory Hormone; GnIH) neuropeptides involved in the control of the HPG axis. Specifically, the impact of orexigenic peptides agouti-related peptide (AgRP), and neuropeptide Y (NPY), as well as the anorexigenic peptides pro-opiomelanocortin (POMC), and cocaine-and amphetamine regulated transcript (CART) is reviewed. Furthermore, beyond hypothalamic control, several metabolic factors involved in the control of body weight and composition are also presented as possible modulators of reproduction at all three levels of the HPG axis. These include peroxisome proliferator-activated receptor gamma (PPAR-γ) for its impact in liver metabolism during the switch from growth to reproduction, adiponectin as a potential modulator of ovarian development and follicular maturation, as well as growth hormone (GH), and leptin (LEP).

Adiponectin and its receptor genes' expression in response to Marek's disease virus infection of White Leghorns

Marek’s disease virus (MDV) causes T-cell lymphoma in susceptible chicken and is also related to an imbalance of the lipid metabolism. Adiponectin is a circulatory cytokine secreted from adipose tissue and exerts critical metabolic functions. Although the associations between adiponectin and diseases, including lipid disorder and noncardiac vascular diseases, have been reported, little is known about the relationship between MDV infection and adiponectin. Here, we challenged white Leghorns from Marek’s disease (MD)-susceptible and MD-resistant lines with MDV at 7 D of age and then explored the body weight and plasma lipoprotein levels at 21 D after MDV infection. Meanwhile, adiponectin and the expression of its receptors were detected using quantitative real-time PCR and Western blot. The results showed that MDV infection induced body weight loss in all the experimental birds. Meanwhile, the concentrations of total cholesterol and high-density lipoprotein were lower after the infection, although there was no significant difference (P > 0.05). However, the infection did not affect adiponectin circulating levels in plasma. MD-susceptible birds had much lower plasma adiponectin than MD-resistant birds (P < 0.01). In abdominal fat, there was no significant difference in adiponectin mRNA level. Still, we observed a significant decrease in adiponectin protein concentration, as well as adipoR1 and adipoR2, at both mRNA and protein levels in the infected compared with the noninfected MD-susceptible chickens. In the spleen, MDV infection significantly reduced the adiponectin mRNA expression but increased the protein in MD-susceptible chickens, which decreased both adipoR1 mRNA expression and protein levels. Also interestingly, the adipoR1 mRNA expression level was significantly increased in MD-susceptible chickens in the liver after MDV infection. All findings in the present study provided interesting insights into adiponectin metabolism in chickens after MDV infection, which helps to advance the understanding of lipid metabolism in response to herpesvirus infection.

Phytogenic feed- and water-additives improve feed efficiency in broilers via modulation of (an)orexigenic hypothalamic neuropeptide expression

Fueled by consumer preference for natural and antibiotic-free products, phytogenics have become the fastest growing segment of the animal feed additives. Yet, their modes of action are not fully understood. This study was undertaken to determine the effect of 5 phytogenics (3 feed- and 2 water-supplements) on the growth performance of commercial broilers, and their potential underlying molecular mechanisms. Day-old male Cobb 500 chicks (n = 576) were randomly assigned into 48 pens consisting of 6 treatments (Control; AVHGP; SCP; BHGP; AVSSL; SG) in a complete randomized design (12 birds/pen, 8 pens/treatment, 96 birds/treatment). Chicks had ad libitum access to feed and water. Individual body weight (BW) was recorded weekly and feed intake was measured daily. Core body temperatures were continuously recorded using thermo-loggers. At d 35, hypothalamic tissues were excised from the thermo-logger-equipped chickens (n = 8 birds/treatment) to determine the expression of feeding-related neuropeptides. Both feed (AVHGP, SCP, BHGP) and water-supplemented (AVSSL, SG) phytogenics significantly improved feed efficiency (FE) compared to the control birds. This higher FE was achieved via a reduction in core body temperature and improvement of market BW, without changes in feed intake in broilers supplemented with phytogenic water additives as compared to the control group. Broilers fed dietary phytogenics, however, attained higher feed efficiency via a reduction in feed intake while maintaining similar BW as the control group. At the molecular levels, the effects of the phytogenic water additives seemed to be mediated by the activation of the hypothalamic AgRP-ORX-mTOR-S6k1 and inhibition of CRH pathways. The effect of the phytogenic feed additives appeared to be exerted through the activation of AdipoQ, STAT3, AMPK, and MC1R pathways. This is the first report describing the likely central mechanisms through which phytogenic additives improve the growth performance and feed efficiency in broilers.

Adipokines Expression and Effects in Oocyte Maturation, Fertilization and Early Embryo Development: Lessons from Mammals and Birds

Some evidence shows that body mass index in humans and extreme weights in animal models, including avian species, are associated with low in vitro fertilization, bad oocyte quality, and embryo development failures. Adipokines are hormones mainly produced and released by white adipose tissue. They play a key role in the regulation of energy metabolism. However, they are also involved in many other physiological processes including reproductive functions. Indeed, leptin and adiponectin, the most studied adipokines, but also novel adipokines including visfatin and chemerin, are expressed within the reproductive tract and modulate female fertility. Much of the literature has focused on the physiological and pathological roles of these adipokines in ovary, placenta, and uterine functions. The purpose of this review is to summarize the current knowledge regarding the involvement of leptin, adiponectin, visfatin, and chemerin in the oocyte maturation, fertilization, and embryo development in both mammals and birds.

The effect of dietary coenzyme Q10 on plasma metabolites and hepatic gene expression in broiler breeder hens

1. This study was performed to evaluate the effects of dietary supplementation of coenzyme Q10 (CoQ10) on laying rate, body weight, plasma metabolites and some liver gene expression in broiler breeder hens. 2. A total of 128 broiler breeder hens (Arbor Acres Plus, 47 weeks of age) were randomly distributed to four dietary groups supplemented with different levels of CoQ10 (0, 300, 600 or 900 mg/kg diet) with four replicates of eight hens each. During 47-54 weeks of age, laying rate, egg mass and body weight were recorded weekly. To assay plasma biochemical indicators, blood samples were collected at 54 weeks of age. At the end of the experiment, for evaluating the abdominal fat weight, liver weight and expression of the adiponectin and proliferator-activated receptor-α (PPAR-α) genes in the liver, eight hens per treatment were selected, weighed and humanely killed by decapitation. 3. Dietary supplementation of CoQ10 linearly decreased abdominal fat weight, alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities by increased levels of CoQ10. The plasma levels of glucose, cholesterol and alkaline phosphatase (ALP) activity were quadratically decreased by increased levels of CoQ10. The best plasma levels of glucose, cholesterol and ALP activity were estimated at 562.5, 633.3 and 517.8 mg CoQ10/kg diet, respectively. Adiponectin and PPARα gene expression exhibited a linear increased by increased levels of CoQ10. 4. In conclusion, addition of CoQ10 to the diet influenced lipid metabolism and expression of the adiponectin and PPAR-α genes, which might be partially due to the improvement in mitochondrial metabolism and energy production. However, further studies are necessary to determine the effects of CoQ10 on these indicators in broiler breeder hens during ageing.

Molecular Mechanisms in Skeletal Muscle Underlying Insulin Resistance in Women Who Are Lean With Polycystic Ovary Syndrome

CONTEXT

Skeletal muscle molecular mechanisms underlying insulin resistance in women with polycystic ovary syndrome (PCOS) are poorly understood.

OBJECTIVE

To provide insight into mechanisms regulating skeletal muscle insulin resistance in women who are lean with PCOS.

PARTICIPANTS AND METHODS

A hyperinsulinemic-euglycemic clamp with skeletal muscle biopsies was performed. Thirteen women who are lean who have hyperandrogenism and PCOS and seven age- and body mass index-matched healthy control subjects were enrolled. Skeletal muscle protein expression and phosphorylation were analyzed by Western blotting and intramuscular lipid content was measured by thin-layer chromatography.

RESULTS

Women with PCOS had 25% lower whole-body insulin sensitivity and 40% lower plasma adiponectin concentration than in control subjects. Intramuscular triacylglycerol, sn-1.3 diacylglycerol, and ceramide contents in skeletal muscle were higher (40%, 50%, and 300%, respectively) in women with PCOS than in control subjects. Activation of insulin signaling did not differ between groups. In women with PCOS, the insulin-stimulated glucose oxidation was reduced and insulin-stimulated dephosphorylation of pyruvate dehydrogenase (PDH) Ser293 was absent. AMP-activated protein kinase (AMPK) α2 protein expression and basal Thr172 phosphorylation were 45% and 50% lower in women with PCOS than in control subjects, respectively.

CONCLUSIONS

Whole-body insulin resistance in women who are lean who have hyperandrogenism and PCOS was not related to changes in the proximal part of the insulin signaling cascade in skeletal muscle despite lipid accumulation. Rather, reduced insulin sensitivity was potentially related to plasma adiponectin levels playing a modulating role in human skeletal muscle via AMPK. Furthermore, abnormal PDH regulation may contribute to reduced whole-body metabolic flexibility and thereby insulin resistance.

Mechanisms of Adiponectin Action in Fertility: An Overview from Gametogenesis to Gestation in Humans and Animal Models in Normal and Pathological Conditions

Adiponectin is the most abundant plasma adipokine. It mainly derives from white adipose tissue and plays a key role in the control of energy metabolism thanks to its insulin-sensitising, anti-inflammatory, and antiatherogenic properties. In vitro and in vivo evidence shows that adiponectin could also be one of the hormones controlling the interaction between energy balance and fertility in several species, including humans. Indeed, its two receptors—AdipoR1 and AdipoR2—are expressed in hypothalamic–pituitary–gonadal axis and their activation regulates Kiss, GnRH and gonadotropin expression and/or secretion. In male gonads, adiponectin modulates several functions of both somatic and germ cells, such as steroidogenesis, proliferation, apoptosis, and oxidative stress. In females, it controls steroidogenesis of ovarian granulosa and theca cells, oocyte maturation, and embryo development. Adiponectin receptors were also found in placental and endometrial cells, suggesting that this adipokine might play a crucial role in embryo implantation, trophoblast invasion and foetal growth. The aim of this review is to characterise adiponectin expression and its mechanism of action in male and female reproductive tract. Further, since features of metabolic syndrome are associated with some reproductive diseases, such as polycystic ovary syndrome, gestational diabetes mellitus, preeclampsia, endometriosis, foetal growth restriction and ovarian and endometrial cancers, evidence regarding the emerging role of adiponectin in these disorders is also discussed.

Ctrp9 and adiponectin receptors in Nile tilapia (Oreochromis niloticus): Molecular cloning, tissue distribution and effects on reproductive genes

As the close paralog of adiponectin, C1q/TNF-Related Protein 9 (CTRP9) has been reported to be involved in the regulation of glucose and fat metabolism, immunization and endothelial cell functions. However, information regarding the actions of Ctrp9 on reproduction is extremely limited in fish. As a first step, Ctrp9, adiponectin receptor 1 (Adipor1) and Adipor2 were identified from Nile tilapia. The open reading frame (ORF) of ctrp9 was 1020 bp which encoded a 339 amino acids. Moreover, the ORFs of adipor1 and adipor2 were 1131 bp and 1134 bp encoding 376 and 377 amino acids, respectively. Tissue distribution showed that ctrp9 mRNA levels were highest in the kidney in both sexes. And, the expression of adipor1 and adipor2 were widely distributed in all tissues examined, exhibiting high levels in the brain, gonad, gut and stomach. In addition, intraperitoneal (i.p.) injection of gCtrp9 (globular Ctrp9) suppressed the hypothalamic expression of gnrh2 (gonadotropin-releasing hormone 2) and gnrh3, as well as gthα (gonadotropic hormone α), fshβ (follicle-stimulating hormone β), lhβ (luteinizing hormone β), lhr (LH receptor) and fshr (FSH receptor) mRNA levels in the pituitary. The mRNA levels of adipor1, but not adipor2, in the gonads were also inhibited after injection. Moreover, the levels of serum E2 (estrogen) in female and T (testosterone) in male were significantly decreased after injection of gCtrp9. Overall, our data provides novel data indicating, for the first time, a regulatory effect of CTRP9 on teleost reproduction.

Identification, characterization, and expression analysis of adiponectin receptors in black carp Mylopharyngodon piceus in response to dietary carbohydrate

In the present study, three cDNAs of AdipoRs (MpAdipoR1a, MpAdipoR1b, and MpAdipoR2) were identified from juvenile black carp Mylopharyngodon piceus. There were 375, 378, and 356 amino acids in the MpAdipoR1a, MpAdipoR1b, and MpAdipoR2, respectively. BLAST analysis reveals that MpAdipoRs share high identities with other known AdipoRs from zebrafish, rainbow trout, human, etc. And there were all seven transmembrane regions in the amino acid sequences of MpAdipoR1s and MpAdipoR2, respectively. The relative expression levels of MpAdipoR1s were higher in the liver, blood, brain, and eyes in black carp (p < 0.05). Relatively higher expression of MpAdipoR2 was detected in the liver (p < 0.05) and then in the adipose tissues and blood by real-time PCR assays. The relative expression levels of AdipoR mRNA in the liver, muscle, brain, blood, and adipose tissues were detected by real-time PCR in black carp fed with four levels of dietary carbohydrate (CHO) (10.65, 19.43, 28.84, and 37.91%) for 9 weeks, respectively. The expression levels of MpAdipoR1s in the liver, muscle, brain, and blood were induced and reached to the maximum at optimal dietary CHO (19.43 or 28.84%) and then were decreased at 37.91% dietary CHO, although there were no significant differences on the expression levels of MpAdipoR1a in the liver between 19.43, 28.84, and 37.91% dietary CHO. Similarly, MpAdipoR2 were also induced to the maximal levels in the liver, muscle, brain, and blood at optimal dietary CHO (19.43 or 28.84%) compared with that at 10.65% dietary CHO, although no significant differences were observed on the expression levels of MpAdipoR2 in the liver and muscle between groups fed 19.43 and 37.91% dietary CHO (p > 0.05). However, the expression levels of MpAdipoRs in the adipose tissues were significantly downregulated at excessive dietary CHO (37.91%) compared with other groups (p < 0.05). These results indicated that MpAdipoRs were inducible proteins and might enhance the understanding of their vital roles in the regulation of glucose metabolic homeostasis in black carp.

Molecular and functional characterization of the adiponectin (AdipoQ) gene in goat skeletal muscle satellite cells

Objective

It is commonly accepted that adiponectin binds to its two receptors to regulate fatty acid metabolism in adipocytes. To better understand their functions in the regulation of intramuscular adipogenesis in goats, we cloned the three genes (adiponectin [AdipoQ], adiponectin receptor 1 [AdipoR1], and AdipoR2) encoding these proteins and detected their mRNA distribution in different tissues. We also determined the role of AdipoQ in the adipogenic differentiation of goat skeletal muscle satellite cells (SMSCs).

Methods

SMSCs were isolated using 1 mg/mL Pronase E from the longissimus dorsi muscles of 3-day-old female Nanjiang brown goats. Adipogenic differentiation was induced in satellite cells by transferring the cells to Dulbecco’s modified Eagle’s medium supplemented with an isobutylmethylxanthine, dexamethasone and insulin cocktail. The pEGFP-N1-AD plasmid was transfected into SMSCs using Lipofectamine 2000. Expression of adiponectin in tissues and SMSCs was detected by quantitative polymerase chain reaction and immunocytochemical staining.

Results

The three genes were predominantly expressed in adipose and skeletal muscle tissues. According to fluorescence and immunocytochemical analyses, adiponectin protein expression was only observed in the cytoplasm, suggesting that adiponectin is localized to the cytoplasm of goat SMSCs. In SMSCs overexpressing the AdipoQ gene, adiponectin promoted SMSC differentiation into adipocytes and significantly (p<0.05) up-regulated expression of AdipoR2, acetyl-CoA carboxylase, fatty-acid synthase, and sterol regulatory element-binding protein-1, though expression of CCAAT/enhancer-binding protein-α, peroxisome proliferator-activated receptor γ, and AdipoR1 did not change significantly.

Conclusion

Adiponectin induced SMSC differentiation into adipocytes, indicating that adiponectin may promote intramuscular adipogenesis in goat SMSC.

Adiponectin: A New Regulator of Female Reproductive System

Adiponectin is the hormone that belongs to the group of adipokines, chemical agents mainly derived from the white adipose tissue. The hormone plays pleiotropic roles in the organism, but the most important function of adiponectin is the control of energy metabolism. The presence of adiponectin and its receptors in the structures responsible for the regulation of female reproductive functions, such as hypothalamic-pituitary-gonadal (HPG) axis, indicates that adiponectin may be involved in the female fertility regulation. The growing body of evidence suggests also that adiponectin action is dependent on the actual and hormonal status of the animal. Present study presents the current knowledge about the presence and role of adiponectin system (adiponectin and its receptors: AdipoR1 and AdipoR2) in the ovaries, oviduct, and uterus, as well as in the hypothalamus and pituitary, the higher branches of HPG axis, involved in the female fertility regulation.

Chicken Is a Useful Model to Investigate the Role of Adipokines in Metabolic and Reproductive Diseases

Reproduction is a complex and essential physiological process required by all species to produce a new generation. This process involves strict hormonal regulation, depending on a connection between the hypothalamus-pituitary-gonadal axis and peripheral organs. Metabolic homeostasis influences the reproductive functions, and its alteration leads to disturbances in the reproductive functions of humans as well as animals. For a long time, adipose tissue has been recognised as an endocrine organ but its ability to secrete and release hormones called adipokines is now emerging. Adipokines have been found to play a major role in the regulation of metabolic and reproductive processes at both central and peripheral levels. Leptin was initially the first adipokine that has been described to be the most involved in the metabolism/reproduction interrelation in mammals. In avian species, the role of leptin is still under debate. Recently, three novel adipokines have been discovered: adiponectin (ADIPOQ, ACRP30), visfatin (NAMPT, PBEF), and chemerin (RARRES2, TIG2). However, their mode of action between mammalian and nonmammalian species is different due to the different reproductive and metabolic systems. Herein, we will provide an overview of the structure and function related to metabolic and reproductive mechanisms of the latter three adipokines with emphasis on avian species.

Increased high molecular weight adiponectin, but decreased total adiponectin and kisspeptin, in central precocious puberty compared with aged-matched prepubertal girls

The aim of the present study was to compare serum leptin, kisspeptin, total adiponectin, high molecular weight (HMW) adiponectin and neuropeptide Y (NPY) levels between girls with central precocious puberty (CPP; n = 26, 7–9.5 years old) and age-matched controls (n = 29) including or excluding obese girls. Leptin and NPY levels were comparable between CPP and control girls. Kisspeptin levels were lower in the CPP than control group, and were positively correlated with oestrogen in the control group and with systolic and diastolic blood pressure in the CPP group. Kisspeptin levels were negatively correlated with FSH and LH in the CPP group. Total adiponectin levels were lower in CPP than control girls, and were negatively correlated with Tanner stage and body mass index, but positively correlated with the quantitative insulin sensitivity check index in the control group. HMW adiponectin was higher in the CPP than control group, and was positively correlated with Tanner stage and LH in all girls. Total adiponectin had a strong positive correlation with HMW adiponectin in the CPP group (r = 0.915) compared with the control group (r = 0.371). In conclusion, kisspeptin may be associated with increased oestrogen in prepubertal girls, but with increased blood pressure in girls with CPP. In girls entering puberty, HMW adiponectin was increased and associated with reproductive parameters. Based on these observations, HMW adiponectin probably plays an essential role in the initiation of puberty and is a candidate marker for the prediction of CPP.

Impact of Food Restriction on the Expression of the Adiponectin System and Genes in the Hypothalamic-Pituitary-Ovarian Axis of Pre-Pubertal Ewes

Adiponectin, a cytokine secreted typically by adipocytes, has been implicated as a molecular switch between female reproduction and energy balance. The present study was undertaken to investigate the expression of adiponectin system and patterns of genes in the hypothalamic-pituitary-ovary (HPO) axis of food-restricted pre-pubertal ewes. Eighteen 2-month-old female ewes were assigned to 3 groups after a pre-feeding ad libitum for 10 days (six in each group): the control group (C), the low-food-restricted group (LR) and the high-food-restricted group (HR), which were fed with 100%, 70% and 50% of ad libitum food intake, respectively. The hypothalamus, pituitary, ovary and serum were collected after food restriction for 2 months. Results by ELISA showed that food restriction increased serum adiponectin concentrations. Quantitative real-time PCR showed that the gene transcriptions for adiponectin receptor 1 (AdipoR1) and 2 (AdipoR2) were enhanced in the hypothalamic-pituitary-ovarian (HPO) axis, while KISS-1/GPR-54 and gonadotropin-releasing hormone (GnRH) in the hypothalamus and luteinizing hormone β-subunit (LHβ) and follicle-stimulating hormone β-subunit (FSHβ) in the pituitary were reduced after food restriction. Immunohistochemistry results demonstrated that AdipoR1 localized in the oocytes of follicles in the ovary. These results suggest that the alterations in the expression of adiponectin and its receptors in response to food restriction might negatively influence the HPO axis.

Adiponectin and colorectal cancer

Colorectal cancer is an obesity-related malignancy. Adiponectin is an adipokine produced exclusively by adipose tissue, and its concentration in the serum is reduced in obesity. A low serum level of adiponectin is associated with an increased risk of various types of malignancies including colorectal cancer. These facts suggest that the epidemiological link between obesity and cancer may have a significant association with adiponectin. Although numerous studies of colorectal cancer have been reported, the results are conflicting about the anti-cancer effect of adiponectin, and how adiponectin affects carcinogenesis or cancer development remains controversial. Because adiponectin has multiple systemic effects and exists as a high serum concentration protein, the main role of adiponectin should be regulation of homeostasis, and it would not likely act as an anti-cancerous hormone. However, as epidemiological evidence shows, a low adiponectin level may be a basic risk factor for colorectal cancer. We speculate that when the colonic epithelium is stimulated or damaged by another carcinogen under the condition of a low adiponectin level, carcinogenesis is promoted and cancer development is facilitated. In this report, we summarize recent findings of the correlation between adiponectin and colorectal cancer and investigate the effect of adiponectin on colorectal cancer.

Identification of protective components that prevent the exacerbation of goose fatty liver: Characterization, expression and regulation of adiponectin receptors

Fat accumulation in the liver is a natural process in goose, which prepares goose for long-distance migration. In contrast to mammalian fatty liver that usually progresses into an irreversible status, steatohepatitis, goose fatty liver can return to normal without obvious pathological damage, suggesting a protective system exists in goose liver. This study was to identify the components of this system. We first focused on goose adiponectin receptor 1 and 2 (Adipor1/2) as they have ceramidase activity, and can cleave ceramide, a group of proinflammatory signaling lipid species. Quantitative analysis indicated that tumor necrosis factor alpha (Tnfα), a key proinflammatory cytokine, was down-regulated in goose fatty liver by overfeeding. This inhibition of Tnfα was accompanied with reduced adiponectin and increased Adipor1/2 in the adipose tissues and in the livers of the overfed geese, respectively. To investigate the regulation of goose Adipor2 in the context of fatty liver, we treated goose primary hepatocytes with fatty liver associated factors. Data indicated that Adipor2 was upregulated by glucose and oleate but not palmitate. Its expression was even suppressed by high level of insulin. The regulation of Adipor1 by these factors was quite similar to that of Adipor2 except that glucose did not induce Adipor1. Together, these findings suggest the upregulation of Adipor1/2 may, at least partially, contribute to the inhibition of inflammation in goose fatty liver, and the expression of Adipor1/2 can be regulated by fatty liver-associated factors.

Adiponectin expression in the porcine pituitary during the estrous cycle and its effect on LH and FSH secretion

Female reproductive success is closely associated with nutritional status and energy balance. In this context, adiponectin appears to be a key hormone connecting reproductive system function and metabolism regulation. It is hypothesized that adiponectin expression in the pituitary depends on the phase of the estrous cycle. The effect of adiponectin on luteinizing hormone (LH) and follicle-stimulating hormone (FSH) secretion is also postulated. Changes in the adiponectin gene and protein expression in the porcine anterior (AP) and posterior (NP) pituitaries as well as the effect of in vitro administration of adiponectin on basal and gonadotropin-releasing hormone (GnRH)- and/or insulin-stimulated LH and FSH secretion were investigated on days 2-3, 10-12, 14-16, and 17-19 of the estrous cycle. Adiponectin gene was more pronounced on days 2-3 in AP but on days 10-12 in NP. Protein concentration in AP was the highest on days 10-12 and in NP on days 10-12 and 17-19 of the cycle. In vitro, adiponectin did not affect basal LH secretion but increased FSH release by AP cells. Adiponectin administration affected GnRH- and/or insulin-induced LH and FSH output in a manner dependent on the phase of the estrous cycle. In this study we indicated for the first time adiponectin expression in the porcine AP and NP that was dependent on the phase of the estrous cycle. In vitro studies indicated that adiponectin may affect gonadotropin secretion. The above suggests that the studied adipokine may influence female reproductive functions via its effect on LH and FSH secretion by gonadotrophs, but the cellular mechanism of its action remains unknown.

Modulation of ovarian steroidogenesis by adiponectin during delayed embryonic development of Cynopterus sphinx

The aim of present study was to evaluate role of adiponectin in ovarian steroidogenesis during delayed embryonic development of Cynopterus sphinx. This study showed significantly low circulating adiponectin level and a decline in expression of adiponectin receptor 1 (AdipoR1) in the ovary during the period of delayed embryonic development as compared with the normal development. The adiponectin treatment in vivo during the period of delayed development caused significantly increased in circulating progesterone and estradiol levels together with increased expression of AdipoR1 in the ovary. The in vitro study confirmed the stimulatory effect of adiponectin on progesterone synthesis. Both in vivo and in vitro studies showed that the effects of adiponectin on ovarian steroidogenesis were mediated through increased expression of luteinizing hormone-receptor, steroidogenic acute regulatory protein and 3β-hydroxyl steroid dehydrogenase enzyme. The adiponectin treatment may also promote progesterone synthesis by modulating ovarian angiogenesis, cell survival and rate of apoptosis.

Expression profile of hypothalamic neuropeptides in chicken lines selected for high or low residual feed intake

The R(+) and R(-) chicken lines have been divergently selected for high (R(+)) or low (R(-)) residual feed intake. For the same body weight and egg production, the R(+) chickens consume 40% more food than their counterparts R(-) lines. In the present study we sought to determine the hypothalamic expression profile of feeding-related neuropeptides in these lines maintained under fed or food-deprived conditions. In the fed condition, the suppressor of cytokine signaling 3 (SOCS3) was 17-fold lower (P<0.05) and the ghrelin receptor was 7-fold higher (P<0.05) in R(+) compared to R(-) chicken lines. The hypothalamic expression of the other studied genes remained unchanged between the two lines. In the fasted state, orexigenic neuropeptide Y and agouti-related peptide were more responsive, with higher significant levels in the R(+) compared to R(-) chickens, while no significant differences were seen for the anorexigenic neuropeptides pro-opiomelanocortin and corticotropin releasing hormone. Interestingly, C-reactive protein, adiponectin receptor 1 and ghrelin receptor gene expression were significantly higher (12-, 2- and 3-folds, respectively), however ghrelin and melanocortin 5 receptor mRNA levels were lower (4- and 2-folds, P=0.05 and P=0.03, respectively) in R(+) compared to R(-) animals. We identified several key feeding-related genes that are differently expressed in the hypothalamus of R(+) and R(-) chickens and that might explain the difference in feed intake observed between the two lines.

Implications of adiponectin in linking metabolism to testicular function

Obesity is a major health problem, contributing to the development of various diseases with aging. In humans, obesity has been associated with reduced testosterone production and subfertility. Adipose tissue is an important source of hormones having influences on both metabolism and reproduction. Among them, the production and secretion of adiponectin is inversely correlated to the severity of obesity. The purpose of this review of literature is to present the current state of knowledge on adiponectin research to determine whether this hormone affects reproduction in men. Surprisingly, evidences show negative influences of adiponectin on GnRH secretion from the hypothalamus, LH and FSH secretion from the pituitary and testosterone at the testicular level. Thus far, the involvement of adiponectin in the influence of metabolism on reproduction in men is limited. However, adiponectin and its receptors are expressed by different cell types of the male gonad, including Leydig cells, spermatozoa, and epididymis. In addition, actions of adiponectin at the testicular level have been shown to promote spermatogenesis and sperm maturation. Therefore, autocrine/paracrine actions of adiponectin in the testis may contribute to support male reproductive function.

Orange-spotted grouper (Epinephelus coioides) adiponectin receptors: molecular characterization, mRNA expression, and subcellular location

Adiponectin is an abundantly secreted adipokine from adipose tissue in mammals, which plays important roles in the regulation of glucose and lipid metabolism. The biological function of adiponectin is mediated by at least two receptors (AdipoR1 and AdipoR2). Although both of them were identified in mammals, there are few researches about adiponectin and its receptors in teleosts. In this study, two types of adiponectin receptors have been isolated and characterized in the orange-spotted grouper (Epinephelus coioides). The cDNAs of grouper AdipoR1 and AdipoR2 are 1444 and 2034 bp in length, encoding proteins of 376 amino acids and 375 amino acids, respectively. Multiple alignment results showed that there was a variable region at the N-terminal of AdipoR1/R2, which has never been reported. Both AdipoR1 and AdipoR2 were found to be widely expressed in various tissues of grouper. Compared to AdipoR2, AdipoR1 expressed at higher levels in the nervous system and pituitary gland, but at lower levels in some peripheral tissues, including heart, liver, adipose tissue, stomach, intestine and especially gonad. Fasting and refeeding experiments showed that the mRNA expressions of AdipoR1/R2 were up-regulated by fasting in the muscle and adipose tissue of grouper, and restored rapidly to normal levels after refeeding. However, the mRNA expressions of AdipoR1/R2 in the hypothalamus and liver of grouper were insensitive to fasting. By indirect immunofluorescence, we demonstrated that grouper AdipoR1/R2 were integral membrane proteins; the C-terminals were extracellular, while the N-terminals were intracellular.

Expression of adiponectin and its receptors in avian species

Adipose tissue is a dynamic endocrine organ secreting a variety of hormones that affect physiological functions within the central nervous system, cardiovascular system, reproductive, and immune systems. The endocrine role of avian adipose tissue remains enigmatic as many of the classical hormones found in mammalian adipose tissue have not been found in avians. This mini-review summarizes our current knowledge on avian adiponectin, one of the most abundant adipose tissue hormones, and its receptors. We cloned the genes encoding chicken adiponectin and its receptors, AdipoR1 and AdipoR2. Using anti-chicken adiponectin antibody, we found that chicken adipose tissue and plasma predominantly contain a unique polymer of adiponectin with a mass greater than 669kDa, unlike mammalian adiponectin which is found as three distinct oligomers. Mass spectrometric analyses of chicken adiponectin revealed certain post-translational modifications that are likely to favor the unique multimerization of adiponectin in chickens. Unlike adiponectin, the nucleotide sequences of chicken AdipoR1- and AdipoR2 cDNA are highly similar to that of mammalian adiponectin receptors. Both adiponectin and adiponectin receptors are widely expressed in several tissues in the chicken. Herein, we review the unique biochemistry of adiponectin as well as expression of adiponectin and its receptors in the chicken. Future studies should focus on elucidating the role of adiponectin, AdipoR1, and AdipoR2 on metabolism, steroidogenesis, and adipose tissue remodeling during growth and reproduction in birds.

Expression of adiponectin receptors 1 (AdipoR1) and 2 (AdipoR2) in the porcine pituitary during the oestrous cycle

BACKGROUND

Adiponectin, protein secreted mainly by white adipose tissue, is an important factor linking the regulation of metabolic homeostasis and reproductive processes. The biological activity of the hormone is mediated via two distinct receptors, termed adiponectin receptor 1(AdipoR1) and adiponectin receptor 2 (AdipoR2). The present study analyzed mRNA and protein expression of AdipoR1 and AdipoR2 in the anterior (AP) and posterior (NP) pituitary of cyclic pigs.

METHODS

The total of 20 animals was assigned to one of four experimental groups (n=5 per group) as follows: days 2-3 (early-luteal phase), 10-12 (mid-luteal phase), 14-16 (late-luteal phase), 17-19 (follicular phase) of the oestrous cycle. mRNA and protein expression were analyzed using real-time PCR and Western Blot methods, respectively.

RESULTS

The lowest AdipoR1 gene expression was detected in AP on days 10-12 relative to days 2-3 and 14-16 (p<0.05). In NP, AdipoR1 mRNA levels were elevated on days 10-12 and 14-16 (p<0.05). AdipoR2 gene expression in AP was the lowest on days 10-12, and an expression peak occurred on days 2-3 (p<0.05). In NP, the lowest (p<0.05) expression of AdipoR2 mRNA was noted on days 17-19. The AdipoR1 protein content in AP was the lowest on days 17-19 (p<0.05), while in NP the variations in protein expression levels during the oestrous cycle were negligible. AdipoR2 protein in AP was most abundant on days 10-12, and it reached the lowest level on days 2-3 and 17-19 of the cycle (p<0.05). The presence of AdipoR2 protein in NP was more pronounced on days 10-12 (p<0.05).

CONCLUSIONS

Our study was the first experiment to demonstrate that AdipoR1 and AdipoR2 mRNAs and proteins are present in the porcine pituitary and that adiponectin receptors expression is dependent on endocrine status of the animals.

Adiponectin deficit during the precarious glucose economy of early lactation in dairy cows

In rodents and primates, insulin resistance develops during pregnancy and fades after parturition. In contrast, dairy cows and other ruminants maintain insulin resistance in early lactation (EL). This adaptation favors mammary glucose uptake, an insulin-independent process, at a time when the glucose supply is scarce. Reduction in circulating levels of the insulin-sensitizing hormone adiponectin promotes insulin resistance in other species, but whether it contributes to insulin resistance in EL dairy cows is unknown. To address this question, plasma adiponectin was measured in high-yielding dairy cows during the transition from late pregnancy (LP) to EL. Plasma adiponectin varied in quadratic fashion with the highest levels in LP, a maximal reduction of 45% on the day after parturition and a progressive return to LP values over the next 8 wk. Adiponectin circulated nearly exclusively in high molecular weight complexes in LP, and this distribution remained unaffected in EL. The reduction of plasma adiponectin in EL occurred without changes in adiponectin mRNA in adipose tissue but was associated with repression of the expression of proteins associated with the endoplasmic reticulum and involved in assembly of adiponectin oligomers. Finally, EL increased the expression of the adiponectin receptor 1 in muscle and adiponectin receptor 2 in liver but had no effect on the expression of these receptors in adipose tissue and in the mammary gland. These data suggest that reduced plasma adiponectin belongs to the subset of hormonal adaptations in EL dairy cows facilitating mammary glucose uptake via promotion of insulin resistance.

Potencial envolvimento da adiponectina e seus receptores na modulação da esteroidogênese em corpo lúteo de cadelas ao longo do diestro

No ciclo estral de cadelas a fase luteínica, denominada diestro, compreende um período que varia de 60 a 100 dias em animais não-prenhes, caracterizado pela elevação plasmática de progesterona nos primeiros 20 dias pós ovulação (p.o). A adiponectina é a mais abundante proteína secretada pelo tecido adiposo, porém sua concentração plasmática diminui significativamente em alterações metabólicas como resistência insulínica e Diabetes mellitus tipo2, alterações descritas como relacionadas em algumas cadelas com o período de diestro. O objetivo do estudo foi determinar a expressão e imunolocalização do sistema adiponectina (adiponectina e seus receptores, adipoR1 e adipoR2) no corpo lúteo de cadelas ao longo do diestro, correlacionando-o ao perfil hormonal de 17β-estradiol e progesterona, assim como à expressão de um dos genes alvo do sistema, o PPAR-γ. Para realização do estudo foram coletados corpos lúteos de 28 cadelas durante ovariosalpingohisterectomia de eleição nos dias 10, 20, 30, 40, 50, 60 e 70 pós ovulação (o dia zero da ovulação foi considerado aquele no qual a concentração plasmática de progesterona atingiu 5ng/mL). Os corpos lúteos foram avaliados por imunohistoquímica para adiponectina e seus receptores e a expressão do RNAm do PPAR-γ por PCR em tempo real. A análise estatística da avaliação gênica foi realizada com o teste ANOVA, seguido por comparação múltipla Newman-Keuls. O sinal da adiponectina apresentou-se mais intenso até os primeiros 20 dias p.o, momento de regência da progesterona; houve queda gradativa após este período, coincidindo com a ascensão do 17β-estradiol, cujo pico foi notado próximo do dia 40 p.o. A queda marcante da adiponectina ocorreu após 50 dias p.o. O sinal do adipoR1 mostrou-se bem evidente até os 40 dias p.o e o do adipoR2 até os 50 dias p. o, decaindo posteriormente. Foi observada maior expressão do gene PPAR-γ aos 10, 30 e 70 dias p.o. Estes resultados mostram que a expressão protéica da adiponectina e de seus receptores se altera ao longo do diestro e que estas alterações podem estar relacionados às alterações hormonais e expressão do PPAR- γ, participando do mecanismo fisiológico de desenvolvimento, manutenção, atividade e regressão luteínica em cadelas.

Effects of adiponectin on ovarian folliculogenesis and steroidogenesis in the vespertilionid bat, Scotophilus heathi

The bat Scotophilus heathi undergo anovulation, known as delayed ovulation, coinciding with the period of seasonal adiposity due to fat accumulation. Because adiponectin is a well known fat cell product, it might be responsible for adiposity related anovulation in S. heathi. The aim of this study was thus to evaluate the effects of adiponectin treatment on ovarian activity in S. heathi. The bat during the period of delayed ovulation was treated with adiponectin (25 μg/day) for 12 days. Changes taken place in the ovarian activity of the treated bat was compared with the control bat and results obtained are presented here. Adiponectin treatment significantly decreased body mass by depleting adipose tissue. It acts directly upon the ovary and promotes antral follicular development by stimulating cell proliferation and modulating ovarian steroidogenesis. The bat treated with adiponectin showed significant decrease in circulating androstenedione (A4) and estradiol (E2) levels, but increase in circulating progesterone (P4) level. The inhibitory effect of adiponectin on androgen synthesis may be due to decreased thecal-interstitial cells differentiation in stroma by suppressing adiponectin receptor type 1 (AdipoR1), luteinizing hormone (LH) and insulin receptors in the ovary of S. heathi. The study provides evidences suggesting that the adiponectin treatment suppresses adiposity and restores normal ovarian activity.

Localization of adiponectin and its receptor and its possible roles in the ovary of a vespertilionid bat, Scotophilus heathi

The aim of this study was to evaluate the seasonal variation in serum adiponectin levels and ovarian expression of adiponectin and its receptor in the Scotophilus heathi bat and their relationship to the changes in the body fat mass, serum insulin and luteinizing hormone (LH) levels, and ovarian activity. A very high level of circulating adiponectin was found during recrudescence, whereas a very low level of circulating adiponectin was observed during pre-ovulatory period. The increased circulating adiponectin level coincided with fat deposition, insulin resistance and hyperinsulinemia (HI) in S. heathi. Immunocytochemical study in the ovary of bat showed localization of adiponectin mainly in thecal-interstitial cells (TICs), and adiponectin receptor 1 (AdipoR1) in the granulosa cells of growing follicles, but showed no staining in atretic follicle. Seasonal changes in ovarian adiponectin and AdipoR1 levels showed two peaks (during recrudescence and ovulatory phases) coinciding with two periods of follicular development. Adiponectin in the absence of LH, as occur during recrudescence, stimulates androstenedione (A4) synthesis in vitro by up-regulating the insulin receptor (IR). Adiponectin in presence of LH, as occur during pre-ovulatory phase, inhibits A4 synthesis in vitro by down-regulating androgen receptor (AR). Further, the in vitro study showed that adiponectin, in presence of LH, also promotes luteinizing hormone receptor (LH-R) and steroidogenic acute regulatory protein (StAR) level in the ovary, which might help in development of ovulatory follicles. In brief, adiponectin in the absence of LH induces increased A4 synthesis and consequently the condition of delayed ovulation, whereas in the presence LH suppresses both synthesis and action of A4 and thus induces preovulatory condition in the ovary of S. heathi.

Cloning and characterization of chicken fat mass and obesity associated (Fto) gene: fasting affects Fto expression

Fat mass and obesity associated gene (Fto), also known as Fatso, is a member of the Fe-II and 2-oxoglutarate-dependent dioxygenase superfamily. Recent studies in humans and rodents suggest that Fto is involved in food intake regulation and lipid metabolism, whereas single nucleotide mutations in the Fto gene are associated with obesity and type 2 diabetes. The Fto gene is highly conserved from green algae to humans, but little is known about the avian Fto gene or protein. The objectives of the current study were to clone full-length chicken Fto cDNA and to determine the effect of age or feeding status on Fto expression. With the use of rapid amplification of cDNA ends, the full-length chicken Fto cDNA was cloned and found to share 63% to 66% homology with the mammalian Fto nucleotide sequence. Several regions of the chicken Fto protein, including the substrate (2-oxoglutarate) binding domains, were found to be identical to mammalian Fto protein. Western blotting with anti-human Fto antibody and reverse transcription PCR studies showed that Fto protein and gene were ubiquitously expressed in various tissues of the chicken. With the use of quantitative PCR, Fto mRNA levels were found to be higher in liver and skeletal muscle of 8-wk-old chickens than in 4-wk-old chickens. In addition, alterations in feeding status resulted in significant changes in Fto mRNA and Fto protein expression in the liver but not in skeletal muscle and adipose tissue of broiler chickens. Taken together, our data suggest that Fto probably plays a significant role in liver function and energy metabolism in the chicken.

Evaluation of adiponectin gene expression in the abdominal adipose tissue of broiler chickens: feed restriction, dietary energy, and protein influences adiponectin messenger ribonucleic acid expression

We studied the effects of feed restriction and different energy and protein contents of the diet on BW, abdominal adipose tissue percentage, and adiponectin gene expression in abdominal adipose tissue in broiler chickens. Two experiments were conducted to determine whether feed restriction and dietary energy and protein levels alter adiponectin mRNA abundance in broiler chicks. Body weight and abdominal adipose tissue percentage were recorded and abdominal adipose tissue samples were collected at sampling days. Adiponectin mRNA expression in abdominal adipose tissue was quantitated using real-time quantitative PCR. We found that BW, abdominal adipose tissue percentage, and adiponectin gene expression were decreased in restricted chicks compared with those fed ad libitum at 32 d of age, but feed restriction had no effect on abdominal adipose tissue percentage and adiponectin gene expression at 49 d of age (experiment 1). Body weight was increased significantly in broilers fed on low-energy diets compared with those fed high-energy diets in experiment 1. Also, increasing levels of dietary protein increased BW in broiler chicks in experiment 2. A positive response in adiponectin gene expression and abdominal adipose tissue percentage was achieved by decreasing protein level in the diet of chicks at 32 d of age, but dietary protein had no effect on adiponectin gene expression at 49 d of age (experiment 1). Also, in experiment 2, abdominal adipose tissue percentage increased as dietary protein with fixed level of energy decreased in broiler chickens at 42 and 56 d of age. In experiment 1, increasing dietary energy levels increased adiponectin gene expression and abdominal adipose tissue percentage in chicks at 32 d of age. Also, we showed that dietary energy had an effect on abdominal adipose tissue percentage at 49 d of age. In experiment 2, a high-energy diet with a fixed level of protein increased abdominal adipose tissue percentage in chicks at 42 and 56 d of age. Dietary energy and protein levels had no significant effect on adiponectin gene expression in abdominal adipose tissue in broilers.

Adiponectin receptors are downregulated in human gastric cancer

BACKGROUND

Adiponectin has been shown to have suppressive effects on tumor development, but the expression of adiponectin receptors in tumor tissue has not been fully elucidated. The purpose of this study was to quantitatively evaluate the expression of two adiponectin receptors, AdipoR1 and AdipoR2, in gastric cancer tissue.

METHODS

The mRNA levels of AdipoR1 and AdipoR2 were evaluated by quantitative reverse transcription polymerase chain reaction (RT-PCR) and immunohistochemical staining in 67 gastric cancer tissues and their normal counterparts. In addition, the effects of cytokines on AdipoR1 and AdipoR2 expression in cultured gastric cancer cells were examined.

RESULTS

As compared to findings in the normal counterparts, AdipoR1 mRNA expression, standardized by β-actin mRNA, tended to be lower (cancer 0.488 ± 0.039, normal 0.955 ± 0.281, p = 0.0726) and AdipoR2 expression was significantly lower (0.818 ± 0.081, 1.500 ± 0.222, p = 0.0035) in gastric cancer tissue. Immunohistochemical examination showed the same tendency for AdipoR1 and AdipoR2 expression in epithelial cells. Moreover, AdipoR2 was strongly expressed in interstitial cells. However, the expression levels of these receptors did not show a strong correlation with various pathological factors. An in vitro experiment using two gastric cancer cell lines, MKN-74 and NUGC-3, showed that the expression levels of AdipoR1 and AdipoR2 were significantly decreased by transforming growth factor (TGF)-β in a dose-dependent manner.

CONCLUSIONS

Two major adiponectin receptors were decreased in gastric cancer as compared to findings in normal gastric epithelium. TGF-β may be involved in this receptor downregulation. This downregulation may be an ideal strategy for cancer cells to escape the antiproliferative effects of adiponectin in the initial phase of tumor development.

Effect of adiponectin on bovine granulosa cell steroidogenesis, oocyte maturation and embryo development

BACKGROUND

Adiponectin is an adipokine, mainly produced by adipose tissue. It regulates several reproductive processes. The protein expression of the adiponectin system (adiponectin, its receptors, AdipoR1 and AdipoR2 and the APPL1 adaptor) in bovine ovary and its role on ovarian cells and embryo, remain however to be determined.

METHODS

Here, we identified the adiponectin system in bovine ovarian cells and embryo using RT-PCR, immunoblotting and immunohistochemistry. Furthermore, we investigated in vitro the effects of recombinant human adiponectin (10 micro g/mL) on proliferation of granulosa cells (GC) measured by [3H] thymidine incorporation, progesterone and estradiol secretions measured by radioimmunoassay in the culture medium of GC, nuclear oocyte maturation and early embryo development.

RESULTS

We show that the mRNAs and proteins for the adiponectin system are present in bovine ovary (small and large follicles and corpus luteum) and embryo. Adiponectin, AdipoR1 and AdipoR2 were more precisely localized in oocyte, GC and theca cells. Adiponectin increased IGF-1 10(-8) M-induced GC proliferation (P < 0.01) but not basal or insulin 10(-8) M-induced proliferation. Additionally, adiponectin decreased insulin 10(-8) M-induced, but not basal or IGF-1 10(-8) M-induced secretions of progesterone (P < 0.01) and estradiol (P < 0.05) by GC. This decrease in insulin-induced steroidogenesis was associated with a decrease in ERK1/2 MAPK phosphorylation in GC pre-treated with adiponectin. Finally, addition of adiponectin during in vitro maturation affected neither the percentage of oocyte in metaphase-II nor 48-h cleavage and blastocyst day 8 rates.

CONCLUSIONS

In bovine species, adiponectin decreased insulin-induced steroidogenesis and increased IGF-1-induced proliferation of cultured GC through a potential involvement of ERK1/2 MAPK pathway, whereas it did not modify oocyte maturation and embryo development in vitro.

Adiponectin action from head to toe

Adiponectin, the most abundant protein secreted by white adipose tissue, is known for its involvement in obesity-related disorders such as insulin resistance, type 2 diabetes mellitus and atherosclerosis. Moreover, modulation of the circulating adiponectin concentration is observed in pathologies that are more or less obesity-related, such as cancer and rheumatoid arthritis. The wide distribution of adiponectin receptors in various organs and tissues suggests that adiponectin has pleiotropic effects on numerous physiological processes. Besides its well-known insulin-sensitizing, anti-inflammatory and antiatherosclerotic properties, accumulating evidence suggests that adiponectin may also have anticancer properties and be cardioprotective. A beneficial effect of adiponectin on female reproductive function was also suggested. Since adiponectin has numerous beneficial biological functions, its use as a therapeutic agent has been suggested. However, the use of adiponectin or its receptors as therapeutic targets is complicated by the presence of different adiponectin oligomeric isoforms and production sites, by multiple receptors with differing affinities for adiponectin isoforms, and by cell-type-specific effects in different tissues. In this review, we discuss the known and potential roles of adiponectin in various tissues and pathologies. The therapeutic promise of administration of adiponectin and the use of its circulating levels as a diagnostic biomarker are further discussed based on the latest experimental studies.