Restricted feeding modulates peripheral clocks and nutrient sensing pathways in rats.

OBJECTIVE: Feeding restriction in rats alters the oscillators in suprachiasmatic, paraventricular, and arcuate nuclei, hypothalamic areas involved in food intake. In the present study, using the same animals and experimental protocol, we aimed to analyze if food restriction could reset clock genes (Clock, Bmal1) and genes involved in lipid metabolism (Pgc1a, Pparg, Ucp2) through nutrient-sensing pathways (Sirt1, Ampk, Nampt) in peripheral tissues. METHODS: Rats were grouped according to food access: Control group (CG, food ad libitum), Restricted night-fed (RF-n, food access during 2 h at night), Restricted day-fed (RF-d, food access during 2 h in the daytime), and Day-fed (DF, food access during 12 h in the daytime). After 21 days, rats were decapitated at ZT3 (0900-1000 h), ZT11 (1700-1800 h), or ZT17 (2300-2400 h). Blood, liver, brown (BAT) and peri-epididymal (PAT) adipose tissues were collected. Plasma corticosterone and gene expression were evaluated by radioimmunoassay and qPCR, respectively. RESULTS: In the liver, the expression pattern of Clock and Bmal1 shifted when food access was dissociated from rat nocturnal activity; this phenomenon was attenuated in adipose tissues. Daytime feeding also inverted the profile of energy-sensing and lipid metabolism-related genes in the liver, whereas calorie restriction induced a pre-feeding increased expression of these genes. In adipose tissues, Sirt1 expression was modified by daytime feeding and calorie restriction, with concomitant expression of Pgc1a, Pparg, and Ucp2 but not Ampk and Nampt. CONCLUSION: Feeding restriction reset clock genes and genes involved in lipid metabolism through nutrient-sensing-related genes in rat liver, brown, and peri-epididymal adipose tissues.

Restricted feeding modulates peripheral clocks and nutrient sensing pathways in rats

ABSTRACT Objective: Feeding restriction in rats alters the oscillators in suprachiasmatic, paraventricular, and arcuate nuclei, hypothalamic areas involved in food intake. In the present study, using the same animals and experimental protocol, we aimed to analyze if food restriction could reset clock genes ( Clock, Bmal1 ) and genes involved in lipid metabolism ( Pgc1a, Pparg, Ucp2 ) through nutrient-sensing pathways ( Sirt1, Ampk, Nampt ) in peripheral tissues. Materials and methods: Rats were grouped according to food access: Control group (CG, food ad libitum ), Restricted night-fed (RF-n, food access during 2 h at night), Restricted day-fed (RF-d, food access during 2 h in the daytime), and Day-fed (DF, food access during 12 h in the daytime). After 21 days, rats were decapitated at ZT3 (0900-1000 h), ZT11 (1700-1800 h), or ZT17 (2300-2400 h). Blood, liver, brown (BAT) and peri-epididymal (PAT) adipose tissues were collected. Plasma corticosterone and gene expression were evaluated by radioimmunoassay and qPCR, respectively. Results: In the liver, the expression pattern of Clock and Bmal1 shifted when food access was dissociated from rat nocturnal activity; this phenomenon was attenuated in adipose tissues. Daytime feeding also inverted the profile of energy-sensing and lipid metabolism-related genes in the liver, whereas calorie restriction induced a pre-feeding increased expression of these genes. In adipose tissues, Sirt1 expression was modified by daytime feeding and calorie restriction, with concomitant expression of Pgc1a , Pparg , and Ucp2 but not Ampk and Nampt . Conclusion: Feeding restriction reset clock genes and genes involved in lipid metabolism through nutrient-sensing-related genes in rat liver, brown, and peri-epididymal adipose tissues.

Oxytocin participates on the effects of vasoactive intestinal peptide on food intake and plasma parameters.

Vasoactive intestinal peptide (VIP) is a neurotransmitter with anorectic effect that acts in the hypothalamus to regulate food intake. Oxytocin is a neuropeptide produced in the hypothalamus that controls energy homeostasis and has an inhibitory role on food intake. Thus, the present study aims at verifying the role of oxytocin as a mediator of VIP on energy homeostasis. For this purpose, intracerebroventricular microinjection of oxytocin receptor antagonist (vasotocin, OVT) or vehicle (NaCl 0.9%) was carried out in male rats, and after 15 min, VIP or saline was microinjected. After 15 min of the second microinjection, food intake was evaluated or euthanasia was undertaken for blood collection. There was a reduction on food intake after VIP microinjection and the pretreatment with OVT partially reversed this effect. Hyperglycemia was observed after VIP microinjection, and pretreatment with OVT partially blocked this effect. Plasma corticosterone concentration was significantly increased after VIP or OVT. Plasma levels of free fatty acids were decreased by VIP, but not when VIP was microinjected after OVT. Thus, OVT partially reversed VIP-induced hypophagia and changes on plasma metabolic parameters, suggesting a role for oxytocin as a mediator of VIP effects on energy homeostasis.

Restricted Feeding Schedules Modulate in a Different Manner the Expression of Clock Genes in Rat Hypothalamic Nuclei.

Food access restriction is associated to changes in gene expression of the circadian clock system. However, there are only a few studies investigating the effects of non-photic synchronizers, such as food entrainment, on the expression of clock genes in the central oscillators. We hypothesized that different feeding restriction patterns could modulate the expression of clock genes in the suprachiasmatic nucleus (SCN) "master" clock and in extra-SCN oscillators such as the paraventricular (PVN) and arcuate (ARC) hypothalamic nuclei. Wistar rats were divided into four groups: Control group (CG; food available ad libitum), Restricted night-fed (RF-n; food access during 2 h at night), Restricted day-fed (RF-d; food access during 2 h at daytime), Day-fed (DF; food access during 12 h at daytime). After 21 days, rats were decapitated between ZT2-ZT3 (0800-0900 h); ZT11-ZT12 (1700-1800 h), or ZT17-18 (2300-2400 h). Plasma corticosterone was measured by radioimmunoassay (RIA). The expression of Clock, Bmal1, Per1, Per2, Per3, Cry1, Cry2, Rev-erbα, and Rorα were assessed in SCN, PVN, and ARC hypothalamic nuclei by RT-PCR and calculated by the 2[-DeltaDeltaCT(Cyclethreshold)](2-ΔΔCT) method. Restricted food availability during few h led to decreased body weight in RF-n and RF-d groups compared to controls and DF group. We also observed an anticipatory corticosterone peak before food availability in RF-n and RF-d groups. Furthermore, the pattern of clock gene expression in response to RF-n, RF-d, and DF schedules was affected differently in the SCN, PVN, and ARC hypothalamic nuclei. In conclusion, the master oscillator in SCN as well as the oscillator in PVN and ARC, all brain areas involved in food intake, responds in a tissue-specific manner to feeding restriction.

Progesterone-induced amplification and advancement of GnRH/LH surges are associated with changes in kisspeptin system in preoptic area of estradiol-primed female rats.

The time course effects of ovarian steroids on kisspeptin and GnRH/LH systems is not totally clarified. We investigated the temporal relationship among kisspeptin and GnRH mRNA and kisspeptin content in the preoptic area (POA), GnRH content and release in the medial basal hypothalamus (MBH) and plasma LH levels under different steroid treatments. Ovariectomized rats treated with oil (OVOO), oil plus single dose of estradiol (OVOE), oil plus single dose of progesterone (OVOP), estradiol for 3 days plus oil (OVEO) or estradiol for 3 days plus progesterone (OVEP) were hourly decapitated from 10:00 to 17:00 or had the MBH microdialyzed from 09:00 to 19:00. Estradiol and progesterone acutely increased POA kisspeptin content without altering POA kisspeptin mRNA levels. Short-term exposure to both hormones stimulated MBH GnRH content, although no GnRH/LH surges had occurred. Chronic estradiol-treatment increased both kisspeptin mRNA levels and content in the POA, demonstrating that long exposure to estradiol is required to activate the whole kisspeptin synthesis machinery. This was followed by the peak in the GnRH/LH release. In estradiol-primed rats, progesterone further increased POA kisspeptin content, amplified and advanced GnRH/LH surges, with no additional change on POA kisspeptin mRNA. The data show an estradiol-induced temporal association between kisspeptin increase in the POA and GnRH/LH surges. Interestingly, the classic action of progesterone in amplifying and accelerating the GnRH/LH surges seems to occur by a mechanism which involves POA kisspeptin system.

The Increase in Signaling by Kisspeptin Neurons in the Preoptic Area and Associated Changes in Clock Gene Expression That Trigger the LH Surge in Female Rats Are Dependent on the Facilitatory Action of a Noradrenaline Input.

In rodents, kisspeptin neurons in the rostral periventricular area of the third ventricle (RP3V) of the preoptic area are considered to provide a major stimulatory input to the GnRH neuronal network that is responsible for triggering the preovulatory LH surge. Noradrenaline (NA) is one of the main modulators of GnRH release, and NA fibers are found in close apposition to kisspeptin neurons in the RP3V. Our objective was to interrogate the role of NA signaling in the kisspeptin control of GnRH secretion during the estradiol induced LH surge in ovariectomized rats, using prazosin, an α1-adrenergic receptor antagonist. In control rats, the estradiol-induced LH surge at 17 hours was associated with a significant increase in GnRH and kisspeptin content in the median eminence with the increase in kisspeptin preceding that of GnRH and LH. Prazosin, administered 5 and 3 hours prior to the predicted time of the LH surge truncated the LH surge and abolished the rise in GnRH and kisspeptin in the median eminence. In the preoptic area, prazosin blocked the increases in Kiss1 gene expression and kisspeptin content in association with a disruption in the expression of the clock genes, Per1 and Bmal1. Together these findings demonstrate for the first time that NA modulates kisspeptin synthesis in the RP3V through the activation of α1-adrenergic receptors prior to the initiation of the LH surge and indicate a potential role of α1-adrenergic signaling in the circadian-controlled pathway timing of the preovulatory LH surge.

Type 1 cannabinoid receptor modulates water deprivation-induced homeostatic responses.

The present study investigated the type 1 cannabinoid receptor (CB1R) as a potential candidate to mediate the homeostatic responses triggered by 24 h of water deprivation, which constitutes primarily a hydroelectrolytic challenge and also significantly impacts energy homeostasis. The present results demonstrated for the first time that CB1R mRNA expression is increased in the hypothalamus of water-deprived (WD) rats. Furthermore, the administration of ACEA, a CB1R selective agonist, potentiated WD-induced dipsogenic effect, whereas AM251, a CB1R antagonist, attenuated not only water but also salt intake in response to WD. In parallel with the modulation of thirst and salt appetite, we confirmed that CB1Rs are essential for the development of appropriated neuroendocrine responses. Although the administration of ACEA or AM251 did not produce any effects on WD-induced arginine vasopressin (AVP) secretion, oxytocin (OXT) plasma concentrations were significantly decreased in WD rats treated with ACEA. At the genomic level, ACEA significantly decreased AVP and OXT mRNA expression in the hypothalamus of WD rats, whereas AM251 potentiated both basal and WD-induced stimulatory effects on the transcription of AVP and OXT genes. In addition, we showed that water deprivation alone upregulated proopiomelanocortin, Agouti-related peptide, melanin-concentrating hormone, and orexin A mRNA levels in the hypothalamus, and that CB1Rs regulate main central peptidergic pathways controlling food intake, being that most of these effects were also significantly influenced by the hydration status. In conclusion, the present study demonstrated that CB1Rs participate in the homeostatic responses regulating fluid balance and energy homeostasis during water deprivation.

Cardiovascular alterations at different stages of hypertension development during ethanol consumption: time-course of vascular and autonomic changes.

The aim of the present work was to establish a time-course correlation between vascular and autonomic changes that contribute to the development of hypertension during ethanol ingestion in rats. For this, male Wistar rats were subjected to the intake of increasing ethanol concentrations in their drinking water during four weeks. Ethanol effects were investigated at the end of each week. Mild hypertension was already observed at the first week of treatment, and a progressive blood pressure increase was observed along the evaluation period. Increased pressor response to phenylephrine was observed from first to fourth week. α1-Adrenoceptor protein in the mesenteric bed was enhanced at the first week, whereas ß2-adrenoceptor protein in the aorta was reduced after the second week. In the third week, ethanol intake facilitated the depressor response to sodium nitroprusside, whereas in the fourth week it reduced nitrate content in aorta and increased it plasma. The bradycardic component of the baroreflex was impaired, whereas baroreflex tachycardia was enhanced at the third and fourth weeks. AT1A receptor and C-type natriuretic peptide (CNP) mRNAs in the nucleus tractus solitarius were increased at the fourth week. These findings suggest that increased vascular responsiveness to vasoconstrictor agents is possibly a link factor in the development and maintenance of the progressive hypertension induced by ethanol consumption. Additionally, baroreflex changes are possibly mediated by alterations in angiotensinergic mechanisms and CNP content within the brainstem, which contribute to maintaining the hypertensive state in later phases of ethanol ingestion. Facilitated vascular responsiveness to nitric oxide seems to counteract ethanol-induced hypertension.

Anandamide modulates the neuroendocrine responses induced by extracellular volume expansion.

(1) The aim of the present study was to evaluate the effects of intracerebroventricular administration of anandamide (AEA), an inhibitor of fatty acid amide hydrolase activity (URB597) and a CB1 receptor (CB1 R) antagonist (AM251) on the homeostatic responses elicited by extracellular volume expansion (EVE) in male adult rats. (2) Pretreatment with AEA (100 ng/4 µL) significantly reduced the effect of hypertonic (H-) EVE on plasma concentrations of prolactin (PRL), oxytocin (OT) and corticosterone, but not vasopressin (AVP). Administration of URB597 (20 µg/5 µL) alone significantly reduced PRL, OT, AVP and corticosterone in the H-EVE group. Conversely, URB597 and AEA had no significant effect on basal hormone concentrations. Pretreatment with AM251 (200 ng/2 µL) potentiated OT but did not change AVP plasma levels in the H-EVE group. (3) Hypertonic EVE significantly increased AVP and OT mRNA expression in the supraoptic nucleus (SON), an effect that was blunted in AEA-pretreated rats. Pretreatment with AEA did not change the percentage of vasopressinergic or oxytocinergic neurons colocalizing c-Fos in the SON, but increased nitrate concentrations in the median eminence of animals subjected to H-EVE. (4) The present data suggest that: (i) vasopressinergic and oxytocinergic neurons may be differentially affected by AEA; (ii) activation of CB1 R may restrain the response of the neurohypophyseal system (NHS) to EVE; (iii) the hypothalamic-pituitary-adrenal axis, PRL and the NHS may still be sensitive to AEA after EVE, with these effects probably not dependent on AEA metabolism; and (iv) AEA and nitric oxide could interact in vivo as modulators to directly control stress-induced responses.