Role of oxytocin signaling in the regulation of body weight

Delivery by cesarean section leads to heavier adult bodyweight in prairie voles (Microtus ochrogaster)

Delivery by cesarean section now makes up 32.1 % of all births in the United States. Meta-analyses have estimated that delivery by cesarean section is associated with a > 50 % increased risk for childhood obesity by 5 years of age. While this association is independent of maternal obesity, breastfeeding, and heritable factors, studies in humans have been unable to test for a causal role of cesarean delivery in this regard. Here, we set out to use an animal model to experimentally test whether delivery by cesarean section would increase offspring weight in adulthood. Delivery by cesarean section may exert neurodevelopmental consequences by impacting hormones that are important at birth as well as during metabolic regulation in later life, such as oxytocin and vasopressin. The prairie vole (Microtus ochrogaster) has long been studied to investigate the roles of oxytocin and vasopressin in brain development and social behavior. Here, we establish that prairie voles tolerate a range of ambient temperatures, including conventional 22° housing, which makes them translationally appropriate for studies of diet-induced obesity. We also studied vole offspring for their growth, sucrose preference, home cage locomotor activity, and food consumption after birth by either cesarean section or vaginal delivery. At sacrifice, we collected measures of weight, length, and adipose tissue to analyze body composition in adulthood. Voles delivered by cesarean section had consistently greater bodyweights than those born vaginally, despite having lower food consumption and greater locomotive activity. Cesarean-delivered animals were also longer, though this did not explain their greater body weights. While cesarean delivery had no effect on vasopressin, it resulted in less oxytocin immunoreactivity within the hypothalamus in adulthood. These results support the case that cesarean section delivery plays a causal role in increasing offspring body weight, potentially by affecting the oxytocin system.

Neuroimaging and neuroendocrine insights into food cravings and appetite interventions in obesity

This article reviews the previous studies on the distinction between food cravings and appetite, and how they are regulated by hormones and reflected in brain activity. Based on existing research, food cravings are defined as individual preferences influenced by hormones and psychological factors, which differ from appetite, as they are not necessarily related to hunger or nutritional needs. The article also evaluates the neuroimaging findings about food cravings, and interventions to reduce food cravings, such as mindfulness training, alternative sweeteners, non-invasive brain stimulation techniques, cognitive-behavioral therapy, and imaginal retraining, and points out their advantages, disadvantages, and limitations. Furthermore, the article delves into the potential future directions in the field, emphasizing the need for a neuroendocrine perspective, considerations for associated psychiatric disorders, innovative clinical interventions, and emerging therapeutic frontiers in obesity management. The article outlines the neuro-endocrine basis of food cravings, including ghrelin, leptin, melanocortin, oxytocin, glucagon-like peptide-1, baclofen, and other hormones and their brain regions of action. The article argues that food cravings are an important target for obesity, and more research is needed to explore their complex characteristics and mechanisms, and how to effectively interact with their neuro-endocrine pathways. The article provides a new perspective and approach to the prevention and treatment of obesity.

Serum Oxytocin Levels Decrease 12 Months Following Sleeve Gastrectomy and Are Associated with Decreases in Lean Mass

Oxytocin (OXT), an anorexigenic hormone, is also bone anabolic. Further, OXT administration results in increases in lean mass (LM) in adults with sarcopenic obesity. We examine, for the first time, associations of OXT with body composition and bone endpoints in 25 youth 13-25 years old with severe obesity who underwent sleeve gastrectomy (SG) and 27 non-surgical controls (NS). Forty participants were female. Subjects underwent fasting blood tests for serum OXT and DXA for areal bone mineral density (aBMD) and body composition. At baseline, SG vs. NS had higher median body mass index (BMI) but did not differ for age or OXT levels. Over 12 months, SG vs. NS had greater reductions in BMI, LM, and fat mass (FM). OXT decreased in SG vs. NS 12 months post-SG. While baseline OXT predicted a 12-month BMI change in SG, decreases in OXT levels 12 months post-SG were not associated with decreases in weight or BMI. In SG, decreases in OXT were positively associated with decreases in LM but not with decreases in FM or aBMD. Loss of LM, a strong predictor of BMD, after bariatric surgery may reduce functional and muscular capacity. OXT pathways may be targeted to prevent LM loss following SG.

Peripherally restricted oxytocin is sufficient to reduce food intake and motivation, while CNS entry is required for locomotor and taste avoidance effects

OBJECTIVES

Oxytocin (OT) has a well-established role in reproductive behaviours; however, it recently emerged as an important regulator of energy homeostasis. In addition to central nervous system (CNS), OT is found in the plasma and OT receptors (OT-R) are found in peripheral tissues relevant to energy balance regulation. Here, we aim to determine whether peripheral OT-R activation is sufficient to alter energy intake and expenditure.

METHODS AND RESULTS

We first show that systemic OT potently reduced food intake and food-motivated behaviour for a high-fat reward in male and female rats. As it is plausible that peripherally, intraperitoneally (IP) injected OT crosses the blood-brain barrier (BBB) to produce some of the metabolic effects within the CNS, we screened, with a novel fluorescently labelled-OT (fAF546-OT, Roxy), for the presence of IP-injected Roxy in CNS tissue relevant to feeding control and compared such with BBB-impermeable fluorescent OT-B₁₂ (fCy5-OT-B_12; BRoxy). While Roxy did penetrate the CNS, BRoxy did not. To evaluate the behavioural and thermoregulatory impact of exclusive activation of peripheral OT-R, we generated a novel BBB-impermeable OT (OT-B₁₂ ), with equipotent binding at OT-R in vitro. In vivo, IP-injected OT and OT-B₁₂ were equipotent at food intake suppression in rats of both sexes, suggesting that peripheral OT acts on peripheral OT-R to reduce feeding behaviour. Importantly, OT induced a potent conditioned taste avoidance, indistinguishable from that induced by LiCl, when applied peripherally. Remarkably, and in contrast to OT, OT-B₁₂ did not induce any conditioned taste avoidance. Limiting the CNS entry of OT also resulted in a dose-dependent reduction of emesis in male shrews. While both OT and OT-B₁₂ proved to have similar effects on body temperature, only OT resulted in home-cage locomotor depression.

CONCLUSIONS

Together our data indicate that limiting systemic OT CNS penetrance preserves the anorexic effects of the peptide and reduces the clinically undesired side effects of OT: emesis, taste avoidance and locomotor depression. Thus, therapeutic targeting of peripheral OT-R may be a viable strategy to achieve appetite suppression with better patient outcomes.

Analysis of the femoral neck from rats in the periestropause treated with oxytocin and submitted to strength training

Among the interventions used to prevent osteoporosis in female organisms, strength training (ST) and oxytocin (OT) stand out, as a promising hormone with anabolic action on bone. This study aimed to verify whether the combined action of OT and ST, compared to isolated interventions, potentiates the bone remodeling process of the femoral neck of Wistar rats during periestropause. Forty Wistar rats (18 months) with irregular estrous cycle were randomly distributed into groups: 1-Vehicle (Veh; NaCl 0.15 mol/L ip); 2-Oxytocin (Ot; 134 μg/kg/ip); 3-Strength training (St); 4-Ot + St. The animals of the 1, 2 and 4 groups received two intraperitoneal injections with an interval of 12 h every 30 days, totaling 8 injections at the end of the experimental period (18 to 21 months). The animals in the St and Ot + St groups performed ST on a ladder 3 times a week, maximal voluntary carrying capacity (MVCC) test monthly. After 120 days, the animals were euthanized; the femur was collected for analysis of biomechanical testing, densitometry, bone microtomography, Raman spectroscopy, tissue PCR, and blood for analysis of bone biomarkers, liver damage, and oxidative stress. The main effects in the Ot group were observed in the maximum load and energy in the compression testing (femoral head), and stiffness and energy in the three-points bending testing (femur diaphysis). In addition, the main effects occurred on the bone mineral density (BMD), cortical thickness (Ct.Th), number of pores (Po.N), polar moment of inertia (J), trabecular thickness (Tb.Th), and connectivity density (Conn.Dn), Bone alkaline phosphatase (Alp), Tumor necrosis factor receptor superfamily member 11b (Opg), Tumor necrosis factor ligand superfamily member 11 (Rankl) and Cathepsin K (Ctsk) expression. There was an effect in the tartrate-resistant acid phosphatase (TRAP) and alkaline phosphatase (ALP). In the St group, the main effect was observed on the energy (compression and the three-points bending), stiffness, aBMD, BMD, cortical bone area (Ct.Ar), Po.N, trabecular bone volume (BV/TV), Tb.Th and in the mineralization ratio (ѵ₁PO₄/proline), Runt-related transcription factor 2 (Runx2), Bone morphogenetic protein 2 (Bmp2), Alp, Osteopontin/secreted phosphoprotein 1 (Opn/Spp1), Opg, Tumor necrosis factor receptor superfamily member 11ª (Rank), Rankl, Ctsk expression. There was an effect in the TRAP and ALP. The interaction in the combination of therapies in the Ot + St group was verified in energy to maximum load (compression and three-points bending testing), stiffness, BMD, Ct.Th, J, Tb.Th and ѵ₁PO₄/proline. In the gene analysis there was interaction in the Runx2, Osterix/Sp7 transcription factor (Osx/Sp7), Bmp2, Alp, Osteocalcin/Bone gamma-carboxyglutamate protein (Ocn/Bglap), Opg, Rankl and Acid phosphatase 5, tartrate resistant (Trap/Acp5) expression. In addition, the combination of OT and ST resulted in a higher maximum load compared to the Veh group, with higher BV/TV than the Ot group, higher Rankl and Ctsk expression than Veh and Ot groups, and lower Po.N and lower activity of TRAP than the other groups. In oxidative stress, total antioxidant capacity (TAC) was lower. These results showed that the combination of interventions is a promising anabolic strategy for the prevention of osteoporosis in the period of periestropause, standing out from the effects of isolated interventions.

Oxytocin as a potential pharmacological tool to combat obesity

The neuropeptide oxytocin (OT) has emerged as an important anorexigen in the regulation of food intake and energy balance. It has been shown that the release of OT and activation of hypothalamic OT neurons coincide with food ingestion. Its effects on feeding have largely been attributed to limiting meal size through interactions in key regulatory brain regions governing the homeostatic control of food intake such as the hypothalamus and hindbrain in addition to key feeding reward areas such as the nucleus accumbens and ventral tegmental area. Furthermore, the magnitude of an anorexigenic response to OT and feeding-related activation of the brain OT circuit are modified by the composition and flavor of a diet, as well as by a social context in which a meal is consumed. OT is particularly effective in reducing consumption of carbohydrates and sweet tastants. Pharmacologic, genetic, and pair-feeding studies indicate that OT-elicited weight loss cannot be fully explained by reductions of food intake and that the overall impact of OT on energy balance is also partly a result of OT-elicited changes in lipolysis, energy expenditure, and glucose regulation. Peripheral administration of OT mimics many of its effects when it is given into the central nervous system, raising the questions of whether and to what extent circulating OT acts through peripheral OT receptors to regulate energy balance. Although OT has been found to elicit weight loss in female mice, recent studies have indicated that sex and estrous cycle may impact oxytocinergic modulation of food intake. Despite the overall promising basic research data, attempts to use OT in the clinical setting to combat obesity and overeating have generated somewhat mixed results. The focus of this mini-review is to briefly summarize the role of OT in feeding and metabolism, address gaps and inconsistencies in our knowledge, and discuss some of the limitations to the potential use of chronic OT that should help guide future research on OT as a tailor-made anti-obesity therapeutic.

The adaptation of maternal energy metabolism to lactation and its underlying mechanisms

Maternal energy metabolism undergoes a singular adaptation during lactation that allows for the caloric enrichment of milk. Changes in the mammary gland, changes in the white adipose tissue, brown adipose tissue, liver, skeletal muscles and endocrine pancreas are pivotal for this adaptation. The present review details the landmark studies describing the enzymatic modulation and the endocrine signals behind these metabolic changes. We will also update this perspective with data from recent studies showing transcriptional and post-transcriptional mechanisms that mediate the adaptation of the maternal metabolism to lactation. The present text will also bring experimental and observational data that describe the long-term consequences that short periods of lactation impose to maternal metabolism.

Distinct promoter regions of the oxytocin receptor gene are hypomethylated in Prader-Willi syndrome and in Prader-Willi syndrome associated psychosis

Prader-Willi syndrome (PWS) is a rare neurodevelopmental disorder caused by a loss of usually paternally expressed, maternally imprinted genes located on chromosome 15q11-q13. Individuals with PWS display a specific behavioral phenotype and have a higher susceptibility than the general population for certain psychiatric conditions, especially psychosis. An impairment of the oxytocin system has been described in Prader-Willi syndrome, but has not yet been investigated in detail on the epigenetic level. Recent studies have pointed out altered methylation patterns of the oxytocin receptor gene (OXTR) in various psychiatric disorders, including psychosis. In this study, we investigated methylation rates of CpG dinucleotides in the promoter region of the oxytocin receptor gene via bisulfite-sequencing using DNA extracted from peripheral blood samples of 31 individuals with PWS and 14 controls matched for age, sex, and BMI. Individuals with PWS show significantly lower methylation in the intron 1 region of the OXTR than neurotypical controls (p = 0.012). Furthermore, male PWS subjects with psychosis show significantly lower methylation of the OXTR exon 1 region than those without psychosis (p = 0.002). Transcription factor binding site analysis revealed E2F1 as a transcription factor potentially binding to the exon 1 region. E2F1 is physiologically regulated by Necdin, an anti-apoptotic protein whose corresponding gene is located within the PWS locus. This study provides evidence of a disruption of the Oxytocin system on an epigenetic level in PWS in general and in individuals with PWS and psychosis.

The physiological control of eating: signals, neurons, and networks

During the past 30 yr, investigating the physiology of eating behaviors has generated a truly vast literature. This is fueled in part by a dramatic increase in obesity and its comorbidities that has coincided with an ever increasing sophistication of genetically based manipulations. These techniques have produced results with a remarkable degree of cell specificity, particularly at the cell signaling level, and have played a lead role in advancing the field. However, putting these findings into a brain-wide context that connects physiological signals and neurons to behavior and somatic physiology requires a thorough consideration of neuronal connections: a field that has also seen an extraordinary technological revolution. Our goal is to present a comprehensive and balanced assessment of how physiological signals associated with energy homeostasis interact at many brain levels to control eating behaviors. A major theme is that these signals engage sets of interacting neural networks throughout the brain that are defined by specific neural connections. We begin by discussing some fundamental concepts, including ones that still engender vigorous debate, that provide the necessary frameworks for understanding how the brain controls meal initiation and termination. These include key word definitions, ATP availability as the pivotal regulated variable in energy homeostasis, neuropeptide signaling, homeostatic and hedonic eating, and meal structure. Within this context, we discuss network models of how key regions in the endbrain (or telencephalon), hypothalamus, hindbrain, medulla, vagus nerve, and spinal cord work together with the gastrointestinal tract to enable the complex motor events that permit animals to eat in diverse situations.

Peptides in the regulation of glucagon secretion

Glucose homeostasis is maintained by the glucoregulatory hormones, glucagon, insulin and somatostatin, secreted from the islets of Langerhans. Glucagon is the body's most important anti-hypoglycemic hormone, mobilizing glucose from glycogen stores in the liver in response to fasting, thus maintaining plasma glucose levels within healthy limits. Glucagon secretion is regulated by both circulating nutrients, hormones and neuronal inputs. Hormones that may regulate glucagon secretion include locally produced insulin and somatostatin, but also urocortin-3, amylin and pancreatic polypeptide, and from outside the pancreas glucagon-like peptide-1 and 2, peptide tyrosine tyrosine and oxyntomodulin, glucose-dependent insulinotropic polypeptide, neurotensin and ghrelin, as well as the hypothalamic hormones arginine-vasopressin and oxytocin, and calcitonin from the thyroid. Each of these hormones have distinct effects, ranging from regulating blood glucose, to regulating appetite, stomach emptying rate and intestinal motility, which makes them interesting targets for treating metabolic diseases. Awareness regarding the potential effects of the hormones on glucagon secretion is important since secretory abnormalities could manifest as hyperglycemia or even lethal hypoglycemia. Here, we review the effects of each individual hormone on glucagon secretion, their interplay, and how treatments aimed at modulating the plasma levels of these hormones may also influence glucagon secretion and glycemic control.

Intranasal oxytocin reduces attentional bias to food stimuli

Attentional biases to food-related stimuli have been demonstrated in response to hunger as well as during restrained eating. Such biases are often associated with obesity, but healthy-weight individuals who do not self-report hunger have also demonstrated attentional biases to stimuli signalling food using laboratory-based cognitive tasks. Levels of the anorectic neuropeptide oxytocin are elevated by food intake and, when administered intranasally, oxytocin inhibits food intake in the laboratory. To investigate whether oxytocin can affect appetite via an action on attentional processes, 40 adults (29 women; mean age 24.0 years old) self-administered 24 IU of oxytocin or placebo intranasally. Forty minutes after administration, participants ate a small snack to maintain alertness and ameliorate deprivation-induced hunger before starting a computerized dot-probe attentional bias task that presented 180 trials of paired visual stimuli comprising neutral, food, social and/or romantic images (500 ms presentation time). Reaction times to probe stimuli that appeared after the offset of the visual images indicated a significant attentional bias to food pictures after placebo; this effect was significantly attenuated by oxytocin, p < .001. The effect of oxytocin on attentional bias to the food pictures was not altered by the type of stimulus paired with the food image, and was independent of BMI, age, sex, self-rated eating behaviour, and self-reported parental bonding; however, the effect was modulated by self-reported food cravings and trait stress. The findings support and extend previous work which has suggested that oxytocin can counteract attentional biases to food-related stimuli in a sample with anorexia by demonstrating the same effect for the first time in a cohort who do not have an eating disorder.

Oxytocin as an Anti-obesity Treatment

Obesity is a growing health concern, as it increases risk for heart disease, hypertension, type 2 diabetes, cancer, COVID-19 related hospitalizations and mortality. However, current weight loss therapies are often associated with psychiatric or cardiovascular side effects or poor tolerability that limit their long-term use. The hypothalamic neuropeptide, oxytocin (OT), mediates a wide range of physiologic actions, which include reproductive behavior, formation of prosocial behaviors and control of body weight. We and others have shown that OT circumvents leptin resistance and elicits weight loss in diet-induced obese rodents and non-human primates by reducing both food intake and increasing energy expenditure (EE). Chronic intranasal OT also elicits promising effects on weight loss in obese humans. This review evaluates the potential use of OT as a therapeutic strategy to treat obesity in rodents, non-human primates, and humans, and identifies potential mechanisms that mediate this effect.

Intranasal Oxytocin Improves Lean Muscle Mass and Lowers LDL Cholesterol in Older Adults with Sarcopenic Obesity: A Pilot Randomized Controlled Trial

OBJECTIVES

Obesity is associated with sarcopenia in older adults, and weight loss can lead to further muscle mass loss. Oxytocin decreases with age, and animal studies suggest that oxytocin administration has trophic effects on skeletal muscle cells and reduces adiposity. We conducted a clinical trial to examine the safety and preliminary efficacy of intranasal oxytocin for older adults with sarcopenic obesity.

DESIGN

A double-blind, placebo-controlled randomized controlled trial of intranasal oxytocin (24 IU 4 times per day) for 8 weeks.

SETTING AND PARTICIPANTS

Twenty-one older (67.5 ± 5.4 years), obese (30-43 kg/m2), sedentary (<2 strenuous exercise per week) adults with slow gait speed (<1 m/s, proxy measure of sarcopenia) were recruited.

MEASURES

Generalized estimating equations were used to evaluate the effect of oxytocin on safety/tolerability of oxytocin administration and whole body muscle and fat mass.

RESULTS

At baseline, body mass index (BMI) was 36.8 ± 3.6 kg/m2, fat mass 46.09 ± 6.99 kg, lean mass 50.98 ± 11.77 kg, fasting plasma glucose (FPG) 92.0 ± 8.9 mg/dL, hemoglobin A1c (HbA1c) 5.7% ± 0.4%, low density lipoprotein (LDL) 111.3 ± 41.5 mg/dL, high-density lipoprotein (HDL) 47.85 ± 10.96 mg/dL, and triglycerides 140.55 ± 83.50 mg/dL. Oxytocin administration was well tolerated without any significant adverse events. Oxytocin led to a significant increase of 2.25 kg in whole body lean mass compared with placebo (P < .01) with a trend toward decreasing fat mass, and a significantly reduced plasma LDL cholesterol by -19.3 mg/dL (P = .023) compared against placebo. There were no significant changes in BMI, appetite scores, glycemia, plasma HDL, triglycerides, or depressive symptoms.

CONCLUSIONS AND IMPLICATIONS

This proof-of-concept study indicates that oxytocin may be useful for the treatment of sarcopenic obesity in older adults. Oxytocin administration may also provide additional cardiovascular benefits.

The Effects of Oxytocin on Appetite Regulation, Food Intake and Metabolism in Humans

The hypothalamic peptide oxytocin and its receptor are involved in a range of physiological processes, including parturition, lactation, cell growth, wound healing, and social behavior. More recently, increasing evidence has established the effects of oxytocin on food intake, energy expenditure, and peripheral metabolism. In this review, we provide a comprehensive description of the central oxytocinergic system in which oxytocin acts to shape eating behavior and metabolism. Next, we discuss the peripheral beneficial effects oxytocin exerts on key metabolic organs, including suppression of visceral adipose tissue inflammation, skeletal muscle regeneration, and bone tissue mineralization. A brief summary of oxytocin actions learned from animal models is presented, showing that weight loss induced by chronic oxytocin treatment is related not only to its anorexigenic effects, but also to the resulting increase in energy expenditure and lipolysis. Following an in-depth discussion on the technical challenges related to endogenous oxytocin measurements in humans, we synthesize data related to the association between endogenous oxytocin levels, weight status, metabolic syndrome, and bone health. We then review clinical trials showing that in humans, acute oxytocin administration reduces food intake, attenuates fMRI activation of food motivation brain areas, and increases activation of self-control brain regions. Further strengthening the role of oxytocin in appetite regulation, we review conditions of hypothalamic insult and certain genetic pathologies associated with oxytocin depletion that present with hyperphagia, extreme weight gain, and poor metabolic profile. Intranasal oxytocin is currently being evaluated in human clinical trials to learn whether oxytocin-based therapeutics can be used to treat obesity and its associated sequela. At the end of this review, we address the fundamental challenges that remain in translating this line of research to clinical care.

Serotonin, food intake, and obesity

The role of serotonin in food intake has been studied for decades. Food intake is mainly regulated by two brain circuitries: (i) the homeostatic circuitry, which matches energy intake to energy expenditure, and (ii) the hedonic circuitry, which is involved in rewarding and motivational aspects of energy consumption. In the homeostatic circuitry, serotonergic signaling contributes to the integration of metabolic signals that convey the body's energy status and facilitates the ability to suppress food intake when homeostatic needs have been met. In the hedonic circuitry, serotonergic signaling may reduce reward-related, motivational food consumption. In contrast, peripherally acting serotonin promotes energy absorption and storage. Disturbed serotonergic signaling is associated with obesity, emphasizing the importance to understand the role of serotonergic signaling in food intake. However, unraveling the serotonin-mediated regulation of food intake is complex, as the effects of serotonergic signaling in different brain regions depend on the regional expression of serotonin receptor subtypes and downstream effects via connections to other brain regions. We therefore provide an overview of the effects of serotonergic signaling in brain regions of the homeostatic and hedonic regulatory systems on food intake. Furthermore, we discuss the disturbances in serotonergic signaling in obesity and its potential therapeutic implications.

Intestinal Electrical Stimulation Alters Hypothalamic Expression of Oxytocin and Orexin and Ameliorates Diet-Induced Obesity in Rats

BACKGROUND

Intestinal electrical stimulation (IES) has been proposed as a potential treatment for obesity. The aim of this study was to explore the central mechanism underlying the reduction of food intake and body weight by IES by studying the expression of anorexigenic- and orexigenic-peptide-containing neurons in the hypothalamus.

MATERIALS AND METHODS

Diet-induced obese (DIO) rats were divided into three groups to receive sham, IES, and pair-feeding for 4 weeks. Food intake was measured automatically and presented as daily and body weight measured weekly. The expressions of oxytocin, an anorexigenic neuropeptide, in the paraventricular nucleus of the hypothalamus (PVN) and the supraoptic nuclei of the hypothalamus (SON) and orexin-A, an orexigenic neuropeptide, in the lateral hypothalamic area (LHA) were studied using immunohistochemistry.

RESULTS

Compared with sham, IES reduced daily food intake by 28.3% at week 1, 35.6% at week 2, 15.6% at week 3, and 27.1% at week 4. Consistently, IES reduced body weight by 6.3%, compared with a weight gain of 7.2% in sham, and a slight weight loss of 0.5% in pair-feeding. Compared with sham, IES increased the expression of oxytocin-immunoreactive neurons in PVN and SON. Compared with sham, IES decreased the expression of orexin-immunoreactive neurons in LHA. Rats with pair-feeding also showed a relative decease in weight without any changes in the central hormones.

CONCLUSION

IES reduces food intake and body weight and improves glucose tolerance and insulin sensitivity in DIO rats. Its central mechanisms involve enhancement of anorexigenic peptides and suppression of orexigenic peptides in the hypothalamus.

Effects of peripheral oxytocin administration on body weight, food intake, adipocytes, and biochemical parameters in peri- and postmenopausal female rats

Recent studies have revealed that the administration of oxytocin has beneficial effects on the regulation of body weight, food intake, and metabolic functions, especially in obese individuals. Obesity is common in women after the menopause and drives many components of metabolic syndrome. Weight gain in menopausal women has been frequently reported. Although obesity and associated metabolic disorders are frequently observed in peri- and postmenopausal women, there are few medical interventions for these conditions. In this study, we evaluated the effects of chronic oxytocin administration on appetite, body weight, and fat mass in peri- and postmenopausal female rats. Sixteen naturally premenopausal or menopausal rats were intraperitoneally injected with oxytocin (1,000 μg/day) for 12 days. The daily changes in their body weight and food intake were measured at the same time as the oxytocin and vehicle injections. Intraperitoneally administering oxytocin for 12 days significantly reduced food intake, body weight, and visceral adipocyte size. In addition, oxytocin administration caused reductions in serum triglyceride and low-density lipoprotein-cholesterol levels, while it did not disturb hepatic or renal functions or locomotor activity. This is the first study to show the effects of oxytocin on the metabolic and feeding functions of peri- and postmenopausal female rats. Oxytocin might be a useful treatment for metabolic disorders caused by the menopause or aging.

Positive selection signatures in Anqing six-end-white pig population based on reduced-representation genome sequencing data

Anqing six-end-white (AQ) pig performs well on resistance to coarse fodder and disease, reproduction and meat quality, offering high potential for exploitation. Environmental conditions and strict selections from local farmers have cultivated the AQ pig to be an outstanding and unique local pig breed. Thus we aim to detect genetic positive selection signatures within the AQ pig population to explore underlying genetic mechanisms. A relative extended haplotype homozygosity (REHH) test was performed in the population of 79 AQ pigs to seek evidence demonstrating that selective actions have left an imprint on the whole genome. In total, 430 500 REHH tests were performed on 53 067 core regions with average REHH tests of 8.11, average lengths of 11.50 kb and an overall length of 610.38 Mb which accounted for 26.94% of the whole genome. Finally, a total of 1819 core haplotypes (P < 0.01) and 586 candidate genes were obtained. These genes were mainly related to meat quality (MYOG, SNX19), resistance to disease (CRISPLD2, CD14) and reproduction traits (ERBB2, NRP2). A panel of genes within the 30 top significant REHH tests was mainly categorized to traits of meat quality and disease resistance. Among 13 KEGG pathways, MAPK, GnRH and Oxytocin signaling pathways, associated with the biological processes of crucial economic traits, were noteworthy. The excellent characteristics of the AQ pig benefited from the combination of natural and human factors. We provide a sketch map that shows the distribution of selection footprints on the whole genome of AQ pig and found potential genes for future studies.

Oxytocin, eating behavior, and metabolism in humans

The hypothalamic peptide oxytocin has been increasingly recognized as a hormone and neurotransmitter with important effects on energy intake, metabolism, and body weight and is under investigation as a potential novel therapeutic agent for obesity. The main neurons producing oxytocin and expressing the oxytocin receptor are strategically located in brain areas known to be critically involved in homeostatic energy balance as well as hedonic and motivational aspects of eating behavior. In this chapter, we will review the central and peripheral physiology of oxytocin and the interaction of oxytocin with key hormones and neural circuitries that affect food intake and metabolism. Next, we will synthesize the available data on endogenous oxytocin levels related to caloric intake, body weight, and metabolic status. We will then review the effects of exogenous oxytocin administration on eating behavior, body weight, and metabolism in humans, including in healthy individuals as well as specific populations with suspected perturbations involving oxytocin pathways. Finally, we will address the promise and fundamental challenges of translating this line of research to clinical care.

Central oxytocin signaling inhibits food reward-motivated behaviors and VTA dopamine responses to food-predictive cues in male rats

Oxytocin potently reduces food intake and is a potential target system for obesity treatment. A better understanding of the behavioral and neurobiological mechanisms mediating oxytocin's anorexigenic effects may guide more effective obesity pharmacotherapy development. The present study examined the effects of central (lateral intracerebroventricular [ICV]) administration of oxytocin in rats on motivated responding for palatable food. Various conditioning procedures were employed to measure distinct appetitive behavioral domains, including food seeking in the absence of consumption (conditioned place preference expression), impulsive responding for food (differential reinforcement of low rates of responding), effort-based appetitive decision making (high-effort palatable vs. low-effort bland food), and sucrose reward value encoding following a motivational shift (incentive learning). Results reveal that ICV oxytocin potently reduces food-seeking behavior, impulsivity, and effort-based palatable food choice, yet does not influence encoding of sucrose reward value in the incentive learning task. To investigate a potential neurobiological mechanism mediating these behavioral outcomes, we utilized in vivo fiber photometry in ventral tegmental area (VTA) dopamine neurons to examine oxytocin's effect on phasic dopamine neuron responses to sucrose-predictive Pavlovian cues. Results reveal that ICV oxytocin significantly reduced food cue-evoked dopamine neuron activity. Collectively, these data reveal that central oxytocin signaling inhibits various obesity-relevant conditioned appetitive behaviors, potentially via reductions in food cue-driven phasic dopamine neural responses in the VTA.

Potential shortcomings in current studies on the effect of intranasal oxytocin in Anorexia Nervosa and healthy controls - A systematic review and meta-analysis

RATIONALE

The psychopathology of anorexia nervosa (AN) includes altered social cognition and information processing of fear and anxiety. Oxytocin, a neuromodulating hormone, may influence these functions and could be valuable for the treatment of AN.

OBJECTIVE

The current study aimed at reviewing the effect of intranasal oxytocin (IN-OT) on attentional bias (AB) and emotion recognition (ER) in AN.

METHODS

A systematic literature review was done for free-text and the MeSH-terms: anorexia nervosa, feeding and eating disorders, and oxytocin. Six publications, reporting from 4 unique clinical trials, were included in this review. A meta-analysis was conducted to examine the effects of IN-OT on AB towards food images and ER on healthy controls (HC) and patients with AN.

RESULTS

Overall, IN-OT did not influence AB towards food images (effect size = 0.20 [- 0.16, 0.57], p = 0.28) and had no effect on ER (effect size = - 0.01 [- 0.27, 0.26], p = 0.97) in patients with AN and healthy control (HC) subjects collectively. Assessing HC and AN separately in subgroup analyses did not show any significant effect on AB and ER in neither of the subgroups. All tests were done between 15 and 55 min post-administration of IN-OT, while peak concentration in the cerebrospinal fluid has been determined to be at 75 min.

CONCLUSION

The current level of evidence is moderate showing no effect of IN-OT on AB or ER in AN. However, brain exposure may not have been sufficient which future studies with IN-OT need to ensure by considering dose and dose-to-task interval.

The New Frontier in Oxytocin Physiology: The Oxytonic Contraction

Oxytocin (Oxt) is a nine amino acid peptide important in energy regulation and is essential to stress-related disorders. Specifically, low Oxt levels are associated with obesity in human subjects and diet-induced or genetically modified animal models. The striking evidence that Oxt is linked to energy regulation is that Oxt- and oxytocin receptor (Oxtr)-deficient mice show a phenotype characterized by late onset obesity. Oxt-/- or Oxtr-/- develop weight gain without increasing food intake, suggesting that a lack of Oxt reduce metabolic rate. Oxt is differentially expressed in skeletal muscle exerting a protective effect toward the slow-twitch muscle after cold stress challenge in mice. We hypothesized that Oxt potentiates the slow-twitch muscle as it does with the uterus, triggering "the oxytonic contractions". Physiologically, this is important to augment muscle strength in fight/flight response and is consistent with the augmented energetic need at time of labor and for the protection of the offspring when Oxt secretion spikes. The normophagic obesity of Oxt-/- or Oxtr-/- mice could have been caused by decreased skeletal muscle tonicity which drove the metabolic phenotype. In this review, we summarized our findings together with the recent literature on this fascinating subjects in a "new oxytonic perspective" over the physicology of Oxt.

Mitochondrial Dynamics and Microglia as New Targets in Metabolism Regulation

Energy homeostasis regulation is essential for the maintenance of life. Neuronal hypothalamic populations are involved in the regulation of energy balance. In order play this role, they require energy: mitochondria, indeed, have a key role in ensuring a constant energy supply to neurons. Mitochondria are cellular organelles that are involved in dynamic processes; their dysfunction has been associated with many diseases, such as obesity and type 2 diabetes, indicating their importance in cellular metabolism and bioenergetics. Food intake excess can induce mitochondrial dysfunction with consequent production of reactive oxygen species (ROS) and oxidative stress. Several studies have shown the involvement of mitochondrial dynamics in the modulation of releasing agouti-related protein (AgRP) and proopiomelanocortin (POMC) neuronal activity, although the mechanisms are still unclear. However, recent studies have shown that changes in mitochondrial metabolism, such as in inflammation, can contribute also to the activation of the microglial system in several diseases, especially degenerative diseases. This review is aimed to summarize the link between mitochondrial dynamics and hypothalamic neurons in the regulation of glucose and energy homeostasis. Furthermore, we focus on the importance of microglia activation in the pathogenesis of many diseases, such as obesity, and on the relationship with mitochondrial dynamics, although this process is still largely unknown.

Oxytocin Ameliorates Impaired Behaviors of High Fat Diet-Induced Obese Mice

Excessive intake of fat is a major risk factor for lifestyle-related diseases such as heart disease and also affects brain function such as object recognition memory, social recognition, anxiety behavior, and depression-like behavior. Although oxytocin (OXT) has been reported to improve object recognition, social recognition, anxiety behavior, and depression-like behavior in specific conditions, previous studies did not explore the impact of OXT in high-fat diet (HFD)-fed mice. Furthermore, it remains unclear whether intake of HFD affects OXT/oxytocin receptor (OXTR) in the brain. Here, we demonstrated that peripheral OXT administration improves not only social recognition but also object recognition and depressive-like behavior in HFD-fed mice. In contrast, peripheral OXT administration to HFD-fed male mice increased fear and anxiety-related behavior. In addition, we observed that intake of HFD decreased OXTR and c-fos mRNA expression in the hippocampus, specifically. Furthermore, peripheral OXT administration increased OXT mRNA expression in the hypothalamus. Altogether, these findings suggest that OXT has the potential to improve various recognition memory processes via peripheral administration but also has side effects that increase fear-related behavior in males.

Neural Regulation of Feeding Behavior

Food intake and energy homeostasis determine survival of the organism and species. Information on total energy levels and metabolic state are sensed in the periphery and transmitted to the brain, where it is integrated and triggers the animal to forage, prey, and consume food. Investigating circuitry and cellular mechanisms coordinating energy balance and feeding behaviors has drawn on many state-of-the-art techniques, including gene manipulation, optogenetics, virus tracing, and single-cell sequencing. These new findings provide novel insights into how the central nervous system regulates food intake, and shed the light on potential therapeutic interventions for eating-related disorders such as obesity and anorexia.

Circulating Oxytocin Is Genetically Determined and Associated With Obesity and Impaired Glucose Tolerance

CONTEXT

Despite the emerging evidence on the role of oxytocin (OXT) in metabolic diseases, there is a lack of well-powered studies addressing the relationship of circulating OXT with obesity and diabetes.

OBJECTIVES AND DESIGN

Here, we measured OXT in a study cohort (n = 721; 396 women, 325 men; mean age ± SD, 47.7 ± 15.2 years) with subphenotypes related to obesity, including anthropometric traits such as body mass index [BMI (mean ± SD), 26.8 ± 4.6 kg/m2], waist-to-hip ratio (WHR; 0.88 ± 0.09), blood parameters (glucose, 5.32 ± 0.50 mmol/L; insulin, 5.3 ± 3.3 µU/mL), and oral glucose tolerance test to clarify the association with OXT. We also tested in a genome-wide association study (GWAS) whether the interindividual variation in OXT serum levels might be explained by genetic variation.

RESULTS

The OXT concentration was increased in subjects with elevated BMI and positively correlated with WHR, waist circumference, and triglyceride levels. The OXT concentration in subjects with BMI <25 kg/m2 was significantly lower (n = 256; 78.6 pg/mL) than in subjects with a BMI between 25 and 30 kg/m2 (n = 314; 98.5 pg/mL, P = 6 × 10-6) and with BMI >30 kg/m2 (n = 137; 106.4 pg/mL, P = 8 × 10-6). OXT levels were also positively correlated with plasma glucose and insulin and were elevated in subjects with impaired glucose tolerance (P = 4.6 × 10-3). Heritability of OXT was estimated at 12.8%. In a GWAS, two hits in linkage disequilibrium close (19 kb) to the OXT reached genome-wide significant association (top-hit rs12625893, P = 3.1 × 10-8, explained variance 3%).

CONCLUSIONS

Our data show that OXT is genetically affected by a variant near OXT and is associated with obesity and impaired glucose tolerance.

Role of Body Mass Index and gestational weight gain on preterm birth and adverse perinatal outcomes

The association of body mass index (BMI) and gestational weight gain (GWG) with preterm birth (PTB) remains controversial in the literature. To evaluate different maternal BMI and GWG categories, according to the initial BMI, in relation to different PTB subtypes and perinatal outcomes, we conducted a secondary analysis of a multicentre cross-sectional study, along with a nested case-control study including PTB from 20 centers in Brazil. Pre-pregnancy underweight was associated with a lower risk of provider-initiated PTB, while overweight and obesity were associated with a higher risk of provider-initiated PTB and a lower risk of spontaneous preterm birth. Insufficient gestational weight gain was associated with a higher prevalence of spontaneous PTB and preterm premature rupture of membranes. Excessive GWG correlated with a higher prevalence of provider-initiated PTB or preterm premature rupture of membranes. Irrespective of the initial BMI, the greater the rate of GWG, the higher the predicted probability of all PTB subtypes, except for spontaneous PTB in underweight women and those with normal BMI. On multivariate analysis, the initial BMI was shown to be the only factor associated with pi-PTB. Briefly, further studies evaluating the risk for PTB should consider that GWG may have a different role depending on the initial BMI and PTB subtype.

Eating behaviour and oxytocin in patients with childhood-onset craniopharyngioma and different grades of hypothalamic involvement

BACKGROUND

Patients with childhood-onset craniopharyngioma (CP) often suffer from tumour or treatment-related hypothalamic lesions (HL). These lesions may alter production of oxytocin, which plays a major role in the regulation of eating behaviour and body composition.

OBJECTIVE

In CP with different degrees of HL, we investigated associations between HL, eating behaviour/eating attitudes, and oxytocin saliva concentrations (OSC).

METHODS

In a cross-sectional case-control study on 34 CP and 73 healthy controls, OSC were measured before, and 60 minutes after breakfast by immunoassay. Eating behaviour, attitudes, and habits were assessed by standardized questionnaires.

RESULTS

CP with anterior + posterior HL presented with more adverse eating behaviours/symptoms of eating disorders than CP without HL, CP with anterior HL, and controls. Eating behaviour in CP with anterior HL was similar to controls, except for their tendency towards high dietary restraints. Decreases in postprandial compared with fasting OSC were associated with adverse eating behaviour in CP and controls and with higher BMI in CP.

CONCLUSIONS

CP with anterior HL and CP with anterior + posterior HL present with distinct patterns of eating behaviour. Reduced postprandial compared with fasting OSC is associated with weight problems in CP and with adverse eating behaviour and symptoms of eating disorders in both CP and controls.

Oxytocin and Vasopressin Systems in Obesity and Metabolic Health: Mechanisms and Perspectives

PURPOSE OF REVIEW

The neurohypophysial endocrine system is identified here as a potential target for therapeutic interventions toward improving obesity-related metabolic dysfunction, given its coinciding pleiotropic effects on psychological, neurological and metabolic systems that are disrupted in obesity.

RECENT FINDINGS

Copeptin, the C-terminal portion of the precursor of arginine-vasopressin, is positively associated with body mass index and risk of type 2 diabetes. Plasma oxytocin is decreased in obesity and several other conditions of abnormal glucose homeostasis. Recent data also show non-classical tissues, such as myocytes, hepatocytes and β-cells, exhibit responses to oxytocin and vasopressin receptor binding that may contribute to alterations in metabolic function. The modulation of anorexigenic and orexigenic pathways appears to be the dominant mechanism underlying the effects of oxytocin and vasopressin on body weight regulation; however, there are apparent limitations associated with their use in direct pharmacological applications. A clearer picture of their wider physiological effects is needed before either system can be considered for therapeutic use.

A pilot study of metabolic fitness effects of weight-supported walking in women with obesity

Background

This is an exploratory pilot study of novel technology enabling people with mobility disability to walk with minimal effort, in the “sedentary range”. The study’s premise is that impairment of the leading physical activity of daily living, walking, is a major contributor to a dysmetabolic state driving many prevalent “civilization diseases” associated with insulin resistance.

Methods

We explore within-subject changes in standard oral glucose tolerance (OGT) tests including metabotropic molecules after 22 twice-weekly, 30-minute bouts of weight-supported light-moderate physical activity in 16 non-diabetic obese, otherwise healthy, reproductive-age, volunteer women walking on an “anti-gravity” lower-body positive pressure (LBPP) treadmill.

Results

Subjects had reference base-line fasting plasma glucose and triglycerides (TG) but 2-hr OGT insulin levels of 467 ± 276 pmol • liter^-1 (mean± S.D.) indicating nascent insulin resistance, compared to post-study 308 ± 179 (p = 0.002). Fasting TG decreased from 0.80 ± 0.30 mmol • liter^-1 to 0.71 ± 0.25 (p = 0.03). Concomitantly plasma total ghrelin decreased from 69.6 ± 41.6 pmol • liter^-1 to 56.0 ± 41.3 (p = 0.008). There were no statistically significant changes in body weight or any correlations between weight change and cardiometabolic markers. However, there were robust positive correlations between changes among different classes of peptides including C-reactive protein–Interleukin 6, leptin–adiponectin, β-endorphin–oxytocin and orexin A (r ² = 0.48–0.88).

Conclusion

We conclude that brief, low-dose physical activity, walking on an anti-gravity LBPP treadmill may improve cardiometabolic risk, exhibiting favorable changes in neuro-regulatory peptides without weight loss in people with problems walking.

Oxytocin in metabolic homeostasis: implications for obesity and diabetes management

Oxytocin was once understood solely as a neuropeptide with a central role in social bonding, reproduction, parturition, lactation and appetite regulation. Recent evidence indicates that oxytocin enhances glucose uptake and lipid utilization in adipose tissue and skeletal muscle, suggesting that dysfunction of the oxytocin system could underlie the pathogenesis of insulin resistance and dyslipidaemia. Murine studies revealed that deficiencies in oxytocin signalling and oxytocin receptor expression lead to obesity despite normal food intake, motor activity and increased leptin levels. In addition, plasma oxytocin concentration is notably lower in obese individuals with diabetes, which may suggest an involvement of the oxytocin system in the pathogenesis of cardiometabolic disease. More recently, small scale studies demonstrated that intranasal administration of oxytocin was associated with significant weight loss as well as improvements in insulin sensitivity and pancreatic β-cell responsivity in human subjects. The multi-pronged effects of oxytocin signalling on improving peripheral insulin sensitivity, pancreatic function and lipid homeostasis strongly suggest a role for this system as a therapeutic target in obesity and diabetes management. The complexity of obesity aetiology and the pathogenesis of obesity-related metabolic complications underscore the need for a systems approach to better understand the role of oxytocin in metabolic function.

The relationship between oxytocin, dietary intake and feeding: A systematic review and meta-analysis of studies in mice and rats

The neuropeptide oxytocin has been associated with food intake and feeding behaviour. This systematic review aimed to investigate the impact of oxytocin on dietary intake and feeding behaviour in rodent studies. Six electronic databases were searched to identify published studies to April 2018. Preclinical studies in mice and rats were included if they reported: (1) a dietary measure (i.e. food or nutrient and/or behaviour (2) an oxytocin measure, and (3) relationship between the two measures. A total of 75 articles (n = 246 experiments) were included, and study quality appraised. The majority of studies were carried out in males (87%). The top three oxytocin outcomes assessed were: exogenous oxytocin administration (n = 126), oxytocin-receptor antagonist administration (n = 46) and oxytocin gene deletion (n = 29). Meta-analysis of exogenous studies in mice (3 studies, n = 43 comparisons) and rats (n = 8 studies, n = 82 comparisons) showed an overall decrease in food intake with maximum effect shown at 2 h post-administration.

Oxytocin Administration Alleviates Acute but Not Chronic Leptin Resistance of Diet-Induced Obese Mice

Whereas leptin administration only has a negligible effect on the treatment of obesity, it has been demonstrated that its action can be improved by co-administration of leptin and one of its sensitizers. Considering that oxytocin treatment decreases body weight in obese animals and humans, we investigated the effects of oxytocin and leptin cotreatment. First, lean and diet-induced obese (DIO) mice were treated with oxytocin for 2 weeks and we measured the acute leptin response. Second, DIO mice were treated for 2 weeks with saline, oxytocin (50 μg/day), leptin (20 or 40 µg/day) or oxytocin plus leptin. Oxytocin pre-treatment restored a normal acute leptin response, decreasing food intake and body weight gain. Chronic continuous administration of oxytocin or leptin at 40 µg/day decreased body weight in the presence (leptin) or in the absence (oxytocin) of cumulative differences in food intake. Saline or leptin treatment at 20 µg/day had no impact on body weight. Oxytocin and leptin cotreatments had no additional effects compared with single treatments. These results point to the fact that chronic oxytocin treatment improves the acute, but not the chronic leptin response, suggesting that this treatment could be used to improve the short-term satiety effect of leptin.

Oxytocin and Prader-Willi Syndrome

In the chapter, we explore the relationship between the peptide hormone, oxytocin (OT), and behavioral and metabolic disturbances observed in the genetic disorder Prader-Willi Syndrome (PWS). Phenotypic and genotypic characteristics of PWS are described, as are the potential implications of an abnormal OT system with respect to neural development including the possible effects of OT dysfunction on interactions with other regulatory mediators, including neurotransmitters, neuromodulators, and hormones. The major behavioral characteristics are explored in the context of OT dysfunction, including hyperphagia, impulsivity, anxiety and emotion dysregulation, sensory processing and interoception, repetitive and restrictive behaviors, and dysfunctional social cognition. Behavioral overlaps with autistic spectrum disorders are discussed. The implications of OT dysfunction on the mechanisms of reward and satiety and their possible role in informing behavioral characteristics are also discussed. Treatment implications and future directions for investigation are considered.

Oxytocin and the warm outer glow: Thermoregulatory deficits cause huddling abnormalities in oxytocin-deficient mouse pups

Oxytocin is a social and reproductive hormone that also plays critical roles in a range of homeostatic processes, including thermoregulation. Here, we examine the role of oxytocin (OT) as a mediator of brown adipose tissue (BAT) thermogenesis, cold-induced huddling, and thermotaxis in eight-day-old (PD8) OT 'knock out' (OTKO) mouse pups. We tested OTKO and wildtype (WT) pups in single- and mixed-genotype groups of six, exposing these to a period of ambient warmth (~35°C) followed by a period of cold (~21.5°C). Whether huddling exclusively with other OTKO or alongside WT pups, OTKO pups showed reduced BAT thermogenesis and were significantly cooler when cold-challenged. Huddles of OTKO pups were also significantly less cohesive than WT huddles during cooling, suggesting that thermoregulatory deficits contribute to contact abnormalities in OTKO pups. To further explore this issue, we examined thermotaxis in individuals and groups of four OTKO or WT pups placed on the cool end of a thermocline and permitted to freely locomote for 2h. When tested individually, male OTKO pups displayed abnormal thermotaxis, taking significantly longer to move up the thermocline and settling upon significantly lower temperatures than WT pups during the 2h test. OTKO mouse pups thus appear to have deficits in both thermogenesis and thermotaxis-the latter deficit being specific to males. Our results add to a growing body of work indicating that OT plays critical roles in thermoregulation and also highlight the entanglement of social and thermoregulatory processes in small mammals such as mice.

Hypothalamic Alterations in Neurodegenerative Diseases and Their Relation to Abnormal Energy Metabolism

Neurodegenerative diseases (NDDs) are disorders characterized by progressive deterioration of brain structure and function. Selective neuronal populations are affected leading to symptoms which are prominently motor in amyotrophic lateral sclerosis (ALS) or Huntington’s disease (HD), or cognitive in Alzheimer’s disease (AD) and fronto-temporal dementia (FTD). Besides the common existence of neuronal loss, NDDs are also associated with metabolic changes such as weight gain, weight loss, loss of fat mass, as well as with altered feeding behavior. Importantly, preclinical research as well as clinical studies have demonstrated that altered energy homeostasis influences disease progression in ALS, AD and HD, suggesting that identification of the pathways leading to perturbed energy balance might provide valuable therapeutic targets Signals from both the periphery and central inputs are integrated in the hypothalamus, a major hub for the control of energy balance. Recent research identified major hypothalamic changes in multiple NDDs. Here, we review these hypothalamic alterations and seek to identify commonalities and differences in hypothalamic involvement between the different NDDs. These hypothalamic defects could be key in the development of perturbations in energy homeostasis in NDDs and further understanding of the underlying mechanisms might open up new avenues to not only treat weight loss but also to ameliorate overall neurological symptoms.

Thermoregulatory disorders in Huntington disease

Huntington disease (HD) is a paradigmatic autosomal-dominant adult-onset neurodegenerative disease. Since the identification of an abnormal expansion of a trinucleotide repeat tract in the huntingtin gene as the underlying genetic defect, a broad range of transgenic animal models of the disease has become available and these have helped to unravel the relevant molecular pathways in unprecedented detail. Of note, some of the most informative of these models develop thermoregulatory defects such as hypothermia, problems with adaptive thermogenesis, and an altered circadian temperature rhythm. Both central, e.g., in the hypothalamus and peripheral, i.e., the brown adipose tissue and skeletal muscle, problems contribute to the phenotype. Importantly, these structures and pathways are also affected in human HD. Yet, currently the evidence for bona fide thermodysregulation in human HD patients remains anecdotal. This may be due to a lack of reliable tools for monitoring body temperature in an outpatient setting. Regardless, study of the temperature phenotype has contributed to the identification of unexpected molecular targets, such as the PGC-1α pathway.

Molecular and Neuroendocrine Approaches to Understanding Trade-offs: Food, Sex, Aggression, Stress, and Longevity-An Introduction to the Symposium

Life history strategies are composed of multiple fitness components, each of which incurs costs and benefits. Consequently, organisms cannot maximize all fitness components simultaneously. This situation results in a dynamic array of trade-offs in which some fitness traits prevail at the expense of others, often depending on context. The identification of specific constraints and trade-offs has helped elucidate physiological mechanisms that underlie variation in behavioral and physiological life history strategies. There is general recognition that trade-offs are made at the individual and population level, but much remains to be learned concerning the molecular neuroendocrine mechanisms that underlie trade-offs. For example, we still do not know whether the mechanisms that underlie trade-offs at the individual level relate to trade-offs at the population level. To advance our understanding of trade-offs, we organized a group of speakers who study neuroendocrine mechanisms at the interface of traits that are not maximized simultaneously. Speakers were invited to represent research from a wide range of taxa including invertebrates (e.g., worms and insects), fish, nonavian reptiles, birds, and mammals. Three general themes emerged. First, the study of trade-offs requires that we investigate traditional endocrine mechanisms that include hormones, neuropeptides, and their receptors, and in addition, other chemical messengers not traditionally included in endocrinology. The latter group includes growth factors, metabolic intermediates, and molecules of the immune system. Second, the nomenclature and theory of neuroscience that has dominated the study of behavior is being re-evaluated in the face of evidence for the peripheral actions of so-called neuropeptides and neurotransmitters and the behavioral repercussions of these actions. Finally, environmental and ecological contexts continue to be critical in unmasking molecular mechanisms that are hidden when study animals are housed in enclosed spaces, with unlimited food, without competitors or conspecifics, and in constant ambient conditions.

Revisiting the wandering womb: Oxytocin in endometriosis and bipolar disorder

Hippocrates attributed women's high emotionality - hysteria - to a 'wandering womb'. Although hysteria diagnoses were abandoned along with the notion that displaced wombs cause emotional disturbance, recent research suggests that elevated levels of oxytocin occur in both bipolar disorder and endometriosis, a gynecological condition involving migration of endometrial tissue beyond the uterus. We propose and evaluate the hypothesis that elevated oxytocinergic system activity jointly contributes to bipolar disorder and endometriosis. First, we provide relevant background on endometriosis and bipolar disorder, and then we examine evidence for comorbidity between these conditions. We next: (1) review oxytocin's associations with personality traits, especially extraversion and openness, and how they overlap with bipolar spectrum traits; (2) describe evidence for higher oxytocinergic activity in both endometriosis and bipolar disorder; (3) examine altered hypothalamic-pituitary-gonadal axis functioning in both conditions; (4) describe data showing that medications that treat one condition can improve symptoms of the other; (5) discuss fitness-related impacts of endometriosis and bipolar disorder; and (6) review a pair of conditions, polycystic ovary syndrome and autism, that show evidence of involving reduced oxytocinergic activity, in direct contrast to endometriosis and bipolar disorder. Considered together, the bipolar spectrum and endometriosis appear to involve dysregulated high extremes of normally adaptive pleiotropy in the female oxytocin system, whereby elevated levels of oxytocinergic activity coordinate outgoing sociality with heightened fertility, apparently characterizing, overall, a faster life history. These findings should prompt a re-examination of how mind-body interactions, and the pleiotropic endocrine systems that underlie them, contribute to health and disease.

Hormonal factors in the control of the browning of white adipose tissue

Adipose tissue has been historically classified into anabolic white adipose tissue (WAT) and catabolic brown adipose tissue (BAT). Recent studies have revealed the plasticity of WAT, where white adipocytes can be induced into 'brown-like' heat-producing adipocytes (BRITE or beige adipocytes). Recruiting and activating BRITE adipocytes in WAT (so-called 'browning') is believed to provide new avenues for the treatment of obesity-related diseases. A number of hormonal factors have been found to regulate BRITE adipose development and activity through autocrine, paracrine and systemic mechanisms. In this mini-review we will discuss the impact of these factors on the browning process, especially those hormonal factors identified with direct effects on white adipocytes.

Involvement of central nesfatin-1 neurons on oxytocin-induced feeding suppression in rats

Peripheral anorectic hormones, such as peptide YY (PYY) and oxytocin (OXT), suppress food intake. A newly identified anorectic neuropeptide, nesfatin-1, is synthesized in both peripheral tissue and the central nervous system, particularly by various nuclei in the hypothalamus and brainstem. Here, we examined the effects of intraperitoneal (ip) administration of PYY_3-36, OXT, and OXT analog, on nesfatin-1-immunoreactive (ir) neurons in the rat hypothalamus and brainstem, using Fos double fluorescence-immunohistochemistry. The ip administration of OXT and OXT analog significantly increased the number of nesfatin-1-ir neurons expressing Fos-ir in the paraventricular nucleus, the arcuate nucleus, and the nucleus tractus solitarius, but not in the supraoptic nucleus, the lateral hypothalamic area, and the area postrema. No differences in the percentage of nesfatin-1-ir neurons expressing Fos in the nuclei of the hypothalamus and brainstem were observed, between rats treated with vehicle or those treated with PYY_3-36. The decreased food intake, induced by OXT and OXT analog, was attenuated significantly by pretreatment with intracerebroventricular administration of antisense nesfatin-1. These results suggested that nesfatin-1-expressing neurons in the hypothalamus and brainstem may play a role in sensing the peripheral level of OXT and its suppression of feeding in rats.

Appetite Regulation: Hormones, Peptides, and Neurotransmitters and Their Role in Obesity

Understanding body weight regulation will aid in the development of new strategies to combat obesity. This review examines energy homeostasis and food intake behaviors, specifically with regards to hormones, peptides, and neurotransmitters in the periphery and central nervous system, and their potential role in obesity. Dysfunction in feeding signals by the brain is a factor in obesity. The hypothalamic (arcuate nucleus) and brainstem (nucleus tractus solitaris) areas integrate behavioral, endocrine, and autonomic responses via afferent and efferent pathways from and to the brainstem and peripheral organs. Neurons present in the arcuate nucleus express pro-opiomelanocortin, Neuropeptide Y, and Agouti Related Peptide, with the former involved in lowering food intake, and the latter two acutely increasing feeding behaviors. Action of peripheral hormones from the gut, pancreas, adipose, and liver are also involved in energy homeostasis. Vagal afferent neurons are also important in regulating energy homeostasis. Peripheral signals respond to the level of stored and currently available fuel. By studying their actions, new agents maybe developed that disable orexigenic responses and enhance anorexigenic signals. Although there are relatively few medications currently available for obesity treatment, a number of agents are in development that work through these pathways.

Serum Irisin and Oxytocin Levels as Predictors of Metabolic Parameters in Obese Children

OBJECTIVE

Irisin and oxytocin can affect energy homeostasis and it has been suggested that they may play an important role in reducing obesity and diabetes. In this study, we aimed to determine the relationship between metabolic parameters (including irisin and oxytocin levels) and anthropometric parameters in obese children.

METHODS

Ninety obese children (mean age, 13.85±1.63 years) and 30 healthy controls (mean age, 14.32±1.58 years) were enrolled in this study. Anthropometric and laboratory parameters (glucose, insulin, lipid, oxytocin, and irisin levels) were analyzed. The serum irisin and oxytocin levels were measured by enzyme-linked immunosorbent assay. Bioelectrical impedance was used to determine body composition.

RESULTS

Irisin level was higher in the patients than in the controls (p=0.018), and this higher irisin level was correlated with increased systolic blood pressure, body mass index, waist/hip ratio, fat percentage, fat mass, glucose level, insulin level, and homeostasis model assessment of insulin resistance. Serum oxytocin level was significantly decreased in obese children compared to the controls (p=0.049). Also, among the 60 obese patients, oxytocin level was significantly lower in patients with than in those without metabolic syndrome (8.65±2.69 vs. 10.87±5.93 ng/L, respectively), while irisin levels were comparable (p=0.049 and p=0.104, respectively). There were no statistically significant relationships between oxytocin or irisin levels and lipid levels (p>0.05).

CONCLUSION

Obese children had significantly higher irisin levels than the healthy controls. Additionally, this study shows for the first time that oxytocin level is significantly lower in obese compared with non-obese children and also lower in obese children with metabolic syndrome compared to those without.

First experiences with neuropsychological effects of oxytocin administration in childhood-onset craniopharyngioma

PURPOSE

The hypothalamic hormone oxytocin plays a major role in regulation of behavior and body composition. Quality of survival is frequently impaired in childhood craniopharyngioma patients due to sequelae such as behavioral deficits and severe obesity caused by tumor or treatment-related hypothalamic lesions.

METHODS

In our pilot cross-sectional study, we analyzed emotion recognition abilities and oxytocin concentrations in saliva and urine before and after single nasal administration of 24 IU oxytocin in 10 craniopharyngioma patients. Four craniopharyngioma presented with grade I lesions (limited to anterior hypothalamic areas) and 6 craniopharyngioma with grade II lesions (involving mammillary bodies and posterior hypothalamic areas). Emotional tasks were assessed before and after administration of oxytocin using the Geneva multimodal emotion portrayals corpus and the Multidimensional Mood Questionnaire.

RESULTS

All patients presented with detectable levels of oxytocin before administration. Nasal administration of oxytocin was well-tolerated and resulted in increased oxytocin concentrations in saliva and urine. After oxytocin administration, craniopharyngioma patients with postsurgical lesions limited to the anterior hypothalamus area showed improvements in emotional identifications compared to craniopharyngioma patients with lesions of anterior and posterior hypothalamic areas. Focusing on correct assignments to positive and negative emotion categories, craniopharyngioma patients improved assignment to negative emotions.

CONCLUSIONS

Oxytocin might have positive effects on emotion perception in craniopharyngioma patients with specific lesions of the anterior hypothalamic area. Further studies on larger cohorts are warranted.

Deficiency in prohormone convertase PC1 impairs prohormone processing in Prader-Willi syndrome

Prader-Willi syndrome (PWS) is caused by a loss of paternally expressed genes in an imprinted region of chromosome 15q. Among the canonical PWS phenotypes are hyperphagic obesity, central hypogonadism, and low growth hormone (GH). Rare microdeletions in PWS patients define a 91-kb minimum critical deletion region encompassing 3 genes, including the noncoding RNA gene SNORD116. Here, we found that protein and transcript levels of nescient helix loop helix 2 (NHLH2) and the prohormone convertase PC1 (encoded by PCSK1) were reduced in PWS patient induced pluripotent stem cell-derived (iPSC-derived) neurons. Moreover, Nhlh2 and Pcsk1 expression were reduced in hypothalami of fasted Snord116 paternal knockout (Snord116p-/m+) mice. Hypothalamic Agrp and Npy remained elevated following refeeding in association with relative hyperphagia in Snord116p-/m+ mice. Nhlh2-deficient mice display growth deficiencies as adolescents and hypogonadism, hyperphagia, and obesity as adults. Nhlh2 has also been shown to promote Pcsk1 expression. Humans and mice deficient in PC1 display hyperphagic obesity, hypogonadism, decreased GH, and hypoinsulinemic diabetes due to impaired prohormone processing. Here, we found that Snord116p-/m+ mice displayed in vivo functional defects in prohormone processing of proinsulin, pro-GH-releasing hormone, and proghrelin in association with reductions in islet, hypothalamic, and stomach PC1 content. Our findings suggest that the major neuroendocrine features of PWS are due to PC1 deficiency.