Sex- and Gender-Based Pharmacological Response to Drugs.

In humans, the combination of all sex-specific genetic, epigenetic, and hormonal influences of biologic sex produces different in vivo environments for male and female cells. We dissect how these influences of sex modify the pharmacokinetics and pharmacodynamics of multiple drugs and provide examples for common drugs acting on specific organ systems. We also discuss how gender of physicians and patients may influence the therapeutic response to drugs. We aim to highlight sex as a genetic modifier of the pharmacological response to drugs, which should be considered as a necessary step toward precision medicine that will benefit men and women. SIGNIFICANCE STATEMENT: This study discusses the influences of biologic sex on the pharmacokinetics and pharmacodynamics of drugs and provides examples for common drugs acting on specific organ systems. This study also discusses how gender of physicians and patients influence the therapeutic response to drugs.

Ghrelin, Ghrelin O-Acyltransferase, and Carbohydrate Metabolism During Pregnancy in Calorie-Restricted Mice.

Acylation of ghrelin is mediated by ghrelin O-acyltansferase (GOAT). Exogenous acylated ghrelin (AG) stimulates growth hormone (GH) and food intake. In non-pregnant (NP) animals, the GOAT-ghrelin-GH axis prevents hypoglycemia caused by caloric restriction (CR). In humans, maternal malnutrition challenges glucose metabolism, which is a key determinant of fetal health. To clarify the role of AG and GH, we compared effects of CR on the GOAT-ghrelin-GH axis in pregnant (P) and NP mice. C57BL/6 wild type (WT) and GOAT knock-out (KO) P and NP mice were freely fed (FF) or subjected to 50% CR for one week. CR was started in P mice on Day 10.5 after conception. We measured body composition, blood glucose, plasma ghrelin and GH, stomach, hypothalamus and pituitary GOAT and ghrelin expression, and liver glycogen content and Pck1 expression. GOAT and AG were undetectable in KO. In NP mice, CR did not affect blood glucose (-1.3 mmol/l, p>0.05) in WT but was lowered (-1.8 mmol/l, p<0.0001) in KO. GH and Pck1 mRNA expression increased in WT but not in KO. In P mice, CR markedly lowered glucose (-2.7 mmol/l; p<0.0001) in WT and caused fatal hypoglycemia in KO, despite similarly elevated GH in WT and KO mice. KO animals are more prone to hypoglycemia than WT. GH, which is high in P animals, does not prevent hypoglycemia caused by CR during pregnancy. Our data suggest a specific role of AG in the regulation of gluconeogenesis to maintain euglycemia during pregnancy when energy availability is limited.

Safety and Tolerability of Whole Soybean Products: A Dose-Escalating Clinical Trial in Older Adults with Obesity.

Soybean products have nutrients, dietary fiber, and phytoalexins beneficial for cardiovascular and overall health. Despite their high consumption in Asian populations, their safety in Western diets is debated. We conducted a dose-escalating clinical trial of the safety and tolerability of soybean products in eight older adults (70-85 years) with obesity. Whole green soybean pods grown under controlled conditions were processed to flour (WGS) at the United States Department of Agriculture using common cooking techniques such as slicing and heat treatment. WGS incorporated into food products was consumed at 10 g, 20 g, and 30 g/day for one week at each dose. The gastrointestinal outcomes, clinical biomarkers, and adverse events were evaluated. We explored the stimulation of phytoalexin (glyceollin) production in live viable soybean seeds (LSS-G). We compared the compositions of WGS and LSS-G with commercial soybean flour and its fermented and enzymatically hydrolyzed forms. We found that although 30 g WSG was well-tolerated, and it made participants feel full. Our processing produced glyceollins (267 µg/g) in LSS-G. Processing soybean flour decreased the iron content, but reduced the oligosaccharides, which could attenuate flatulence. Providing soybean flour at <30 g/day may be prudent for overall health and to prevent the exclusion of other food groups and nutrients in older adults with obesity.

Results of a phase Ib study of SB-121, an investigational probiotic formulation, a randomized controlled trial in participants with autism spectrum disorder.

Autism Spectrum Disorder (ASD) is a neurodevelopmental disorder characterized by core impairments in social communication as well as restricted, repetitive patterns of behavior and/or interests. Individuals with ASD, which includes about 2% of the US population, have challenges with activities of daily living and suffer from comorbid medical and mental health concerns. There are no drugs indicated for the core impairments of ASD. As such, there is a significant need for the development of new medication strategies for individuals with ASD. This first-in-human placebo-controlled, double-blind, crossover study investigated the safety (primary objective) and efficacy of oral SB-121, a combination of L. reuteri, Sephadex® (dextran microparticles), and maltose administered once daily for 28 days in 15 autistic participants. SB-121 was safe and well tolerated. SB-121-associated directional improvements in adaptive behavior measured by Vineland-3 and social preference as measured with eye tracking were noted. These results provide support for further clinical evaluation of SB-121 as a treatment in autistic patients. To evaluate the safety and tolerability of multiple doses of SB-121 in subjects with autism spectrum disorder. Single-center, randomized, placebo-controlled, double-blind, crossover trial. 15 patients with autism spectrum disorder were randomized and analyzed. Daily dosing of SB-121 or placebo for 28 days, followed by approximately a 14 day washout, then 28 days of dosing with other treatment. Incidence and severity of adverse events, presence of Limosilactobacillus reuteri and Sephadex® in stool, and incidence of bacteremia with positive L. reuteri identification. Additional outcomes include changes from baseline on cognitive and behavior tests as well as biomarker levels. Adverse event rates were similar between SB-121 and placebo, with most reported as mild. There were no severe or serious adverse events. No participants had features of suspected bacteremia or notable changes in vital signs, safety laboratory, or ECG parameters from baseline. There was a statistically significant increase from baseline in the Vineland-3 Adaptive Behavior Composite score (p = 0.03) during SB-121 treatment. There was a trend for increased social/geometric viewing ratio following SB-121 treatment compared to placebo. SB-121 was safe and well tolerated. SB-121-associated directional improvements in adaptive behavior measured by Vineland-3 and social preference as measured with eye tracking were noted.Trial registration: clinicaltrials.gov Identifier: NCT04944901.

Rice Flour and Bran Enriched with Blueberry Polyphenols Increases Storage Stability and Decreases Arsenic Content in Bran.

A low-cost method utilizing rice co-products to concentrate and stabilize blueberry polyphenols was developed that decreased the arsenic (As) content in rice bran. After concentration at 10 g/L, brown rice flour displayed a higher total anthocyanin content in both blueberry juice (2.7 mg/g) and pomace extract (2.6 mg/g) when compared to white rice flour. Defatted rice bran enriched with blueberry juice (10 g/L) had the highest concentration of polyphenols (16.0 mg/g), and defatted bran enriched with pomace extract had the highest concentration of anthocyanins (5.32 mg/g). Enriched rice flour and bran contained higher levels of anthocyanins when using pomace extracts. Polyphenols and anthocyanins were found to be highly stable at 37 °C in rice flour and bran samples combined with pomace extract. Polyphenol enrichment also produced lower total and inorganic arsenic (i-As) levels in defatted rice bran. Inorganic arsenic (i-As) concentrations in defatted rice bran enriched with blueberry juice and pomace extracts were reduced by 20.5% and 51.6%, respectively. Overall, rice flour and bran that are enriched with polyphenols and anthocyanins from blueberry pomace extracts are shelf and color stable, had low sugar content, and represent unique health-promoting food ingredients.

The distribution and mechanism of action of ghrelin in the CNS demonstrates a novel hypothalamic circuit regulating energy homeostasis.

The gastrointestinal peptide hormone ghrelin stimulates appetite in rodents and humans via hypothalamic actions. We discovered expression of ghrelin in a previously uncharacterized group of neurons adjacent to the third ventricle between the dorsal, ventral, paraventricular, and arcuate hypothalamic nuclei. These neurons send efferents onto key hypothalamic circuits, including those producing neuropeptide Y (NPY), Agouti-related protein (AGRP), proopiomelanocortin (POMC) products, and corticotropin-releasing hormone (CRH). Within the hypothalamus, ghrelin bound mostly on presynaptic terminals of NPY neurons. Using electrophysiological recordings, we found that ghrelin stimulated the activity of arcuate NPY neurons and mimicked the effect of NPY in the paraventricular nucleus of the hypothalamus (PVH). We propose that at these sites, release of ghrelin may stimulate the release of orexigenic peptides and neurotransmitters, thus representing a novel regulatory circuit controlling energy homeostasis.

Biological, physiological, pathophysiological, and pharmacological aspects of ghrelin.

Ghrelin is a peptide predominantly produced by the stomach. Ghrelin displays strong GH-releasing activity. This activity is mediated by the activation of the so-called GH secretagogue receptor type 1a. This receptor had been shown to be specific for a family of synthetic, peptidyl and nonpeptidyl GH secretagogues. Apart from a potent GH-releasing action, ghrelin has other activities including stimulation of lactotroph and corticotroph function, influence on the pituitary gonadal axis, stimulation of appetite, control of energy balance, influence on sleep and behavior, control of gastric motility and acid secretion, and influence on pancreatic exocrine and endocrine function as well as on glucose metabolism. Cardiovascular actions and modulation of proliferation of neoplastic cells, as well as of the immune system, are other actions of ghrelin. Therefore, we consider ghrelin a gastrointestinal peptide contributing to the regulation of diverse functions of the gut-brain axis. So, there is indeed a possibility that ghrelin analogs, acting as either agonists or antagonists, might have clinical impact.

Animal models of obesity and diabetes mellitus.

More than one-third of the worldwide population is overweight or obese and therefore at risk of developing type 2 diabetes mellitus. In order to mitigate this pandemic, safer and more potent therapeutics are urgently required. This necessitates the continued use of animal models to discover, validate and optimize novel therapeutics for their safe use in humans. In order to improve the transition from bench to bedside, researchers must not only carefully select the appropriate model but also draw the right conclusions. In this Review, we consolidate the key information on the currently available animal models of obesity and diabetes and highlight the advantages, limitations and important caveats of each of these models.

A healthy gastrointestinal microbiome is dependent on dietary diversity.

BACKGROUND: Like all healthy ecosystems, richness of microbiota species characterizes the GI microbiome in healthy individuals. Conversely, a loss in species diversity is a common finding in several disease states. This biome is flooded with energy in the form of undigested and partially digested foods, and in some cases drugs and dietary supplements. Each microbiotic species in the biome transforms that energy into new molecules, which may signal messages to physiological systems of the host. SCOPE OF REVIEW: Dietary choices select substrates for species, providing a competitive advantage over other GI microbiota. The more diverse the diet, the more diverse the microbiome and the more adaptable it will be to perturbations. Unfortunately, dietary diversity has been lost during the past 50 years and dietary choices that exclude food products from animals or plants will narrow the GI microbiome further. MAJOR CONCLUSION: Additional research into expanding gut microbial richness by dietary diversity is likely to expand concepts in healthy nutrition, stimulate discovery of new diagnostics, and open up novel therapeutic possibilities.

Antidiabetic Potential of Purple and Red Rice (Oryza sativa L.) Bran Extracts.

Pigmented rice contains anthocyanins and proanthocyanidins that are concentrated in the bran layer. In this study, we determined the phenolic, flavonoid, anthocyanin, and proanthocyanidin content of five rice bran (1 brown, 2 red, and 2 purple) extracts. Each bran extract was evaluated for inhibitory effects on α-amylase and α-glucosidase activity, two key glucosidases required for starch digestion in humans. All purple and red bran extracts inhibited α-glucosidase activity, however only the red rice bran extracts inhibited α-amylase activity. Additionally, each bran extract was examined for their ability to stimulate glucose uptake in 3T3-L1 adipocytes, a key function in glucose homeostasis. Basal glucose uptake was increased between 2.3- and 2.7-fold by exposure to the red bran extracts, and between 1.9- and 3.1-fold by exposure to the purple bran extracts. In red rice bran, the highest enzyme inhibition and glucose uptake was observed with a proanthocyanidin-enriched fraction. Both IITA red bran and IAC purple bran increased expression of GLUT1 and GLUT4 mRNA, and genes encoding insulin-signaling pathway proteins.

A novel gastrointestinal microbiome modulator from soy pods reduces absorption of dietary fat in mice.

OBJECTIVE: Simplification of diets, low in variety but high in energy, contributes to the loss in diversity observed in the obese gastrointestinal (GI) microbiome. A novel GI microbiome modulator (GIMM) as a dietary intervention was developed. METHODS: Mice were fed either an obesogenic diet (ObD) or an ObD containing 15% activated soy pod fiber (ObD-ASPF) for 30 days. The diets were isocaloric and balanced for macronutrient content. ASPF is a novel fiber preparation from whole soy pods that is activated to produce glyceollins. RESULTS: Mice fed ObD-ASPF did not gain body fat. This was associated with decreased absorption of calories (P < 0.05) and increased fecal excretion of triglycerides, which may be attributed to decreased bile acid secretion (P < 0.05). A shift (P < 0.05) in abundances of microbiota in 10 genera was observed. Mice fed ObD-ASPF had elevated plasma concentrations of the anti-inflammatory IL-10 (P < 0.05) and decreased (P < 0.05) plasma concentrations of the neutrophil chemoattractant CXCL1. CONCLUSIONS: A novel dietary intervention derived from soy pods that acts to hinder absorption of dietary fat and glucose in mice was developed. More studies with this GIMM in animal models of diet-induced nonalcoholic fatty liver diseases, type 2 diabetes, and autism are needed.

A novel and selective beta-melanocyte-stimulating hormone-derived peptide agonist for melanocortin 4 receptor potently decreased food intake and body weight gain in diet-induced obese rats.

alphaMSH has generally been accepted as the endogenous ligand for melanocortin 4 receptor (MC4R), which plays a major role in energy homeostasis. Targeting MC4R to develop antiobesity agents, many investigators have performed a structure-activity relationship (SAR) studies based on alphaMSH structure. In this report, we performed a SAR study using human betaMSH (5 - 22) (DEGPYRMEHFRWGSPPKD, peptide 1) as a lead sequence to develop potent and selective agonists for MC4R and MC3R. The SAR study was begun with a truncation of N terminus of betaMSH (5 - 22) together with acetylation of the N terminus and amidation of the C terminus of the peptide. Introduction of a cyclic disulfide constrain and replacement of L-Phe with D-Phe afforded a super potent agonist (peptide 5). Furthermore truncation at the C terminus generated a small and potent MC4R and MC3R agonist (Ac-YRcyclo[CEHdFRWC]amide, peptide 6), which exhibited no MC5R and greatly reduced MC1R activity. Molecular modeling of Ac-YRcyclo[CEHdFRWC]amide (peptide 6) revealed that Arg2 in the peptide formed a salt bridge with Glu4. Subcutaneous or intracerebroventricular administration of peptide 6 in rats showed potent in vivo efficacy as evidenced by its effects in reducing energy balance, increasing fat use, and decreasing weight gain in both acute and chronic rat metabolic studies. Furthermore, the antiobesity effect by peptide 6 was manifested only in wild-type but not MC4R-deficient mice, indicating that antiobesity effects of the peptide were attributed largely through MC4R but not MC3R agonist activity of the peptide.

Discovery of a beta-MSH-derived MC-4R selective agonist.

A series of novel, disulfide-constrained human beta-melanocyte stimulating hormone (beta-MSH)-derived peptides were optimized for in vitro melanocortin-4 receptor (MC-4R) binding affinity, agonist efficacy, and selectivity. The most promising of these, analogue 18, was further studied in vivo using chronic rat food intake and body weight models.

Potent peptide agonists for human melanocortin 3 and 4 receptors derived from enzymatic cleavages of human beta-MSH(5-22) by dipeptidyl peptidase I and dipeptidyl peptidase IV.

Human beta-MSH(1-22) was first isolated from human pituitary as a 22-amino acid (aa) peptide derived from a precursor protein, pro-opiomelanocortin (POMC). However, Bertagna et al. demonstrated that a shorter human beta-MSH(5-22), (DEGPYRMEHFRWGSPPKD), is a true endogenous peptide produced in human hypothalamus. In this report, we demonstrated that in vitro enzymatic cleavage of native human beta-MSH(5-22) with two ubiquitous dipeptidyl peptidases (DPP), DPP-I and DPP-IV, generated two potent MC3/4R peptide analogues, beta-MSH(7-22) (GPYRMEHFRWGSPPKD) and beta-MSH(9-22) (YRMEHFRWGSPPKD). In fact, the MC4R binding affinity and functional potency of beta-MSH(7-22) (Ki=4.6 nM, EC50=0.6 nM) and beta-MSH(9-22) (Ki=5.7 nM, EC50=0.6 nM) are almost an order of magnitude greater than those of their parent peptide, beta-MSH(5-22) (MC4R, Ki=23 nM, EC50= 3nM). Furthermore, the DPP-I/DPP-IV cleaved peptide, beta-MSH(9-22), when administered intracerebroventricularly (ICV) at a dose of 3 nmol/rat, potently induced an acute negative energy balance in a diet-induced obese rat model, while its parent molecule, beta-MSH(5-22), administered at the same dose did not have any effect. These data suggest that DPP-I and DPP-IV may play a role in converting the endogenous beta-MSH(5-22) to more potent peptides that regulate energy homeostasis in the hypothalamus.

Gastrointestinal microbiome modulator improves glucose tolerance in overweight and obese subjects: A randomized controlled pilot trial.

OBJECTIVE: The objective of this study was to examine the effects of a gastrointestinal microbiome modulator (GIMM) containing inulin, ß-glucan, blueberry anthocyanins, and blueberry polyphenols on metabolic parameters, fecal markers of gut microbiota, and satiety. DESIGN AND METHODS: Thirty overweight or obese individuals aged 18 to 70years, were enrolled in a randomized controlled trial. Participants consumed the test product or placebo daily for four weeks. Stool samples were collected and blood was drawn at baseline and week four for assessments of gut microbiota, satiety hormones, glucose control, and lipid measures. Subjective satiety was assessed weekly. Linear models were used to compare differences from baseline to week four. RESULTS: GIMM consumption improved blood glucose tolerance (p=0.008), and increased satiety (p=0.03). There were no statistically significant differences in insulin sensitivity, fecal markers of gut microbiota, plasma satiety hormones, or serum lipid concentrations between the groups. However, plasma satiety hormones and fecal short chain fatty acid concentrations increased in the test group compared to the placebo. CONCLUSIONS: GIMM consumption for four weeks, increases satiety, and improves glucose tolerance possibly through insulin-independent pathways.

Addition of a Gastrointestinal Microbiome Modulator to Metformin Improves Metformin Tolerance and Fasting Glucose Levels.

BACKGROUND: Adverse effects of metformin are primarily related to gastrointestinal (GI) intolerance that could limit titration to an efficacious dose or cause discontinuation of the medication. Because some metformin side effects may be attributable to shifts in the GI microbiome, we tested whether a GI microbiome modulator (GIMM) used in combination with metformin would ameliorate the GI symptoms. METHODS: A 2-period crossover study design was used with 2 treatment sequences, either placebo in period 1 followed by GIMM in period 2 or vice versa. Study periods lasted for 2 weeks, with a 2-week washout period between. During the first week, type 2 diabetes patients (T2D) who experienced metformin GI intolerance took 500 mg metformin along with their assigned NM504 (GIMM) or placebo treatment with breakfast and with dinner. In the second week, the 10 subjects took 500 mg metformin (t.i.d.), with GIMM or placebo consumed with the first and third daily metformin doses. Subjects were permitted to discontinue metformin dosing if it became intolerable. RESULTS: The combination of metformin and GIMM treatment produced a significantly better tolerance score to metformin than the placebo combination (6.78 ± 0.65 [mean ± SEM] versus 4.45 ± 0.69, P = .0006). Mean fasting glucose levels were significantly (P < .02) lower with the metformin-GIMM combination (121.3 ± 7.8 mg/dl) than with metformin-placebo (151.9 ± 7.8 mg/dl). CONCLUSION: Combining a GI microbiome modulator with metformin might allow the greater use of metformin in T2D patients and improve treatment of the disease.

Acylated ghrelin is not required for the surge in pituitary growth hormone observed in pregnant mice.

OBJECTIVE: Ghrelin is produced by the stomach, hypothalamus and pituitary. It circulates as acylated ghrelin (AG, which stimulates growth hormone (GH) secretion) and unacylated ghrelin (UAG). Acylation is mediated by the enzyme ghrelin O-acyltransferase (GOAT). In mice, pregnancy is associated with a marked increase in circulating pituitary GH. We investigated the role of AG and UAG in the surge of plasma GH concentrations in pregnant mice at the end of pregnancy. DESIGN: Using a mouse model generated on a C57BL/6 background (wild type, WT) in which the GOAT gene has been deleted (KO), we measured plasma AG, UAG and GH concentrations and tissue (stomach, pituitary and hypothalamus) preproghrelin and GOAT mRNA in non-pregnant (NP) and pregnant (P), WT and KO mice. RESULTS: GOAT deletion was associated with undetectable concentrations of AG. UAG concentrations were similar in all groups. In both WT and KO animals, mean GH concentrations increased 30 to 50 times during pregnancy. There was a tendency toward lower median GH concentrations in KO (301 ng/mL) compared to WT (428 ng/mL) mice (p=0.059). Preproghrelin expression was not affected by GOAT deletion or by pregnancy in the stomach. In contrast, pituitary and hypothalamic ghrelin gene expression were lower in KO-NP and KO-P mice compared to their WT counterparts. CONCLUSION: The complete absence of ghrelin acylation, which is associated with undetectable AG concentrations, does not prevent the marked increase in pituitary GH concentrations observed in pregnant mice, suggesting that AG is not the major mediator of GH secretion during pregnancy.

The level of circulating octanoate does not predict ghrelin O-acyl transferase (GOAT)-mediated acylation of ghrelin during fasting.

BACKGROUND: Acyl-ghrelin is a 28-amino acid peptide released from the stomach. Ghrelin O-acyl transferase (GOAT) attaches an 8-carbon medium-chain fatty acid (MCFA) (octanoate) to serine 3 of ghrelin. This acylation is necessary for the activity of ghrelin. Animal data suggest that MCFAs provide substrate for GOAT and an increase in nutritional octanoate increases acyl-ghrelin. OBJECTIVES: To address the question of the source of substrate for acylation, we studied whether the decline in ghrelin acylation during fasting is associated with a decline in circulating MCFAs. METHODS: Eight healthy young men (aged 18-28 years, body mass index range, 20.6-26.2 kg/m(2)) had blood drawn every 10 minutes for acyl- and desacyl-ghrelin and every hour for free fatty acids (FFAs) during the last 24 hours of a 61.5-hour fast and during a fed day. FFAs were measured by a highly sensitive liquid chromatography-mass spectroscopy method. Acyl- and desacyl-ghrelin were measured in an in-house assay; the results were published previously. Ghrelin acylation was assessed by the ratio of acyl-ghrelin to total ghrelin. RESULTS: With the exception of MCFAs C8 and C10, all other FFAs, the MCFAs (C6 and C12), and the long-chain fatty acids (C14-C18) significantly increased with fasting (P < .05). There was no significant association between the fold change in ghrelin acylation and circulating FFAs. CONCLUSIONS: These results suggest that changes in circulating MCFAs are not linked to the decline in ghrelin acylation during fasting and support the hypothesis that acylation of ghrelin depends at least partially on the availability of gastroluminal MCFAs or the regulation of GOAT activity.

GH-releasing peptide-2 increases fat mass in mice lacking NPY: indication for a crucial mediating role of hypothalamic agouti-related protein.

Ghrelin, an endogenous GH secretagogue, is capable of stimulating adiposity in rodents. Because such adiposity was thought to be mediated by hypothalamic NPY neurons, we investigated by which mechanism a synthetic ghrelin receptor agonist, GHRP-2, would generate a positive energy balance in NPY-deficient [Npy(-/-) mice] and wild-type controls. A dose-dependent increase in body weight and food intake was observed during daily sc injections with GHRP-2. Pre- and posttreatment analysis of body composition indicated increased fat mass and bone mass but not lean mass. Respiratory quotient was increased in GHRP-2-treated mice, indicating preservation of fat. Hypothalamic mRNA levels of agouti- related protein (AGRP), an orexigenic melanocortin receptor antagonist, increased after GHRP-2 treatment. Competitive blockade of AGRP action by melanocortin-receptor agonist MT-II prevented GHRP-induced weight gain in Npy(-/-) mice. In conclusion, chronic peripheral treatment with a ghrelin receptor agonist induced a positive energy balance leading to fat gain in the absence of NPY. These effects could be mediated in part by AGRP. To date, there are few therapeutics that can produce a positive energy balance. Ghrelin receptor agonists offer a treatment option for syndromes like anorexia nervosa, cancer cachexia, or AIDS wasting.

Vasoactive intestinal polypeptide/pituitary adenylate cyclase-activating peptide receptor 2 deficiency in mice results in growth retardation and increased basal metabolic rate.

Vasoactive intestinal polypeptide (VIP) and pituitary adenylate cyclase-activating peptide (PACAP) are two closely related peptides that bind two homologous G protein-coupled receptors, VIP/PACAP receptor 1 (VPAC1R) and VIP/PACAP receptor II (VPAC2R), with equally high affinity. Recent reports suggest that VPAC2R plays a role in circadian rhythm and T cell functions. To further elucidate the functional activities of VPAC2R, we generated VPAC2R-deficient mice by deleting exons VIII-X of the VPAC2R gene. The VPAC2R-deficient mice showed retarded growth and had reduced serum IGF-I levels compared with gender-matched, wild-type siblings. The mutant mice appeared healthy and fertile at a young adult age. However, older male mutant mice exhibited diffuse seminiferous tubular degeneration with hypospermia and reduced fertility rate. The mutant mice appeared to have an increase in insulin sensitivity. VPAC2R-deficient mice had increased lean mass and decreased fat mass with reduced serum leptin levels. Indirect calorimetry experiments showed that the respiratory quotient values immediately following the transition into the dark cycle were significantly higher in male knockout mice for about 4 h. Additionally, male and female VPAC2R-deficient mice presented an increased basal metabolic rate (23% and 10%, respectively) compared with their wild-type siblings. Our results suggest that VPAC2R plays an important role in growth, basal energy expenditure, and male reproductive functions.