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.

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.

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 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.

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.

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.

Ghrelin

BACKGROUND

The gastrointestinal peptide hormone ghrelin was discovered in 1999 as the endogenous ligand of the growth hormone secretagogue receptor. Increasing evidence supports more complicated and nuanced roles for the hormone, which go beyond the regulation of systemic energy metabolism.

SCOPE OF REVIEW

In this review, we discuss the diverse biological functions of ghrelin, the regulation of its secretion, and address questions that still remain 15 years after its discovery.

MAJOR CONCLUSIONS

In recent years, ghrelin has been found to have a plethora of central and peripheral actions in distinct areas including learning and memory, gut motility and gastric acid secretion, sleep/wake rhythm, reward seeking behavior, taste sensation and glucose metabolism.

Ghrelin in obesity

Ghrelin was discovered for its ability to bind the growth hormone secretagogue receptor (GHSR1a) and stimulate growth hormone release. However, much research conducted with this novel stomach hormone is focused on proposed roles for it to participate in regulating energy balance. Exogenous administration of ghrelin stimulates food consumption in experimental animals and humans, presenting the hormone as the first to stimulate appetite after peripheral administration and implicates it for an etiology of obesity. The hormone also presents other exceptional characteristics that solicit need for future study. The peptide is modified by acylation with a mediumchain fatty acid on its third residue, and it is that ghrelin peptide that binds GHS-R1a. Enzymes or transfer proteins responsible for such acylation and de-acylation remain unknown. Specific assays for both acyl- and des-acyl ghrelin are not available nor are methods to prevent de-acylation in blood samples. Such knowledge is important because des-acyl ghrelin is reported to bestow biology distinct from that of ghrelin and that signal may actually oppose those prescribed for its acylated parent. This review of ghrelin data relating to obesity recognizes the complexity of ghrelin endocrinology and attempts to be cautious when discussing studies that measured ghrelin during different physiological states. Although much more exploration is needed, we placed more emphasis on reviewing studies during different physiological states when conclusions are less dependent on measurement of ghrelin. Despite these shortcomings, we conclude that there is ample evidence indicating ghrelin participates in regulating energy balance.

Glyceollins, soy isoflavone phytoalexins, improve oral glucose disposal by stimulating glucose uptake

Soy glyceollins, induced during stress, have been shown to inhibit cancer cell growth in vitro and in vivo. In the present study, we used prediabetic rats to examine the glyceollins effect on blood glucose. During an oral glucose tolerance test (OGTT), the blood glucose excursion was significantly decreased in the rats treated with oral administration of either 30 or 90 mg/kg glyceollins. Plasma analysis demonstrated that glyceollins are absorbed after oral administration, and duration of exposure extends from 20 min to at least 4 h postadministration. Exposure of 3T3-L1 adipocytes to glyceollins significantly increased both insulin-stimulated and basal glucose uptake. Basal glucose uptake was increased 1.5-fold by exposure to 5 μM glyceollin in a dose-response manner. Coincubation with insulin significantly stimulated maximal glucose uptake above basal uptake levels and tended to increase glucose uptake beyond the levels of either stimulus alone. On a molecular level, polymerase chain reaction showed significantly increased levels of glucose transporter GLUT4 mRNA in 3T3-L1 adipocytes, especially when the cells were exposed to 5 μM glyceollins for 3 h in vitro. It correlated with elevated protein levels of GLUT4 detected in the 5 μM glyceollin-treated cells. Thus, the simulative effect of the glyceollins on adipocyte glucose uptake was attributed to up-regulation of glucose transporters. These findings indicate potential benefits of the glyceollins as an intervention in prediabetic conditions as well as a treatment for type 1 and type 2 diabetes by increasing both the insulin-mediated and the basal, insulin-independent, glucose uptake by adipocytes.

Combination of a Beta adrenoceptor modulator and a norepinephrine-serotonin uptake inhibitor for the treatment of obesity

We report the novel combination of a selective beta adrenoceptor modulator and a norepinephrine-serotonin uptake inhibitor (sibutramine) with potential for the treatment of obesity. The synthesis and characterization of 6-[4-[2-[[(2S)-3-(9H-carbazol-4-yloxy)-2-hydroxypropyl]amino]-2-methylpropyl]phenoxy]pyridine-3-carboxamide (LY377604), a human β3-adrenergic receptor agonist and β1- and β2-adrenergic receptor antagonist with no sympathomimetic activity at the β1- and β2-adrenergic receptors, is reported. Some in vivo data in both rats and humans is presented.

Fat and water 1H MRI to investigate effects of leptin in obese mice

Leptin is known to be associated with regulation of body weight and fat content. The effects of exogenous leptin on abdominal visceral (VS) and subcutaneous (SC) fat volume and hepatic fat-to-water ratio in leptin-deficient obese mice were investigated by (1)H magnetic resonance imaging (MRI). Chemical shift-selected fat and water (1)H MRI of control and leptin-treated mice were obtained 1 day before treatment and after 7 days of treatment (0.3 mg/kg/day). Hepatic fat-to-water ratio and VS fat volume decreased significantly with treatment, whereas SC fat volume did not change. Noninvasive measurement of fat and water content in different body regions using MRI should prove useful for evaluating new drugs for the treatment of obesity and other metabolic disorders.

GOAT links dietary lipids with the endocrine control of energy balance

CNS nutrient sensing and afferent endocrine signalling are established as parallel systems communicating metabolic status and energy availability in vertebrates. The only afferent endocrine signal known to require modification with a fatty acid side chain is the orexigenic hormone ghrelin. We find that the ghrelin O-acyl transferase (GOAT) which is essential for ghrelin acylation, is regulated by nutrient availability, depends on specific dietary lipids as acylation substrates and modulates body fat mass in mice.

Overview of rodent models for obesity research

Animal obesity models differ widely in type and extent of obesity. They are either based on environmental factors (e.g., high-fat diet-induced obesity), spontaneous mutants (i.e., ob/ob mice), genetically engineered animals (e.g., mice with melanocortin receptor subtype-4 gene disruption (knock-out), or mechanical intervention (e.g., chemical lesion of the ventromedial hypothalamus). This unit reviews available rodent models to study obesity and attempts to highlight the greatest utility for each model.

Potent oxindole based human β3 adrenergic receptor agonists

The synthesis and biological evaluation of a series of oxindole beta(3) adrenergic receptor agonists is described. A modulation of rat atrial tachycardia was observed with substitution at the 3-position of the oxindole moiety.

Preproghrelin-derived peptide, obestatin, fails to influence food intake in lean or obese rodents

OBJECTIVES

Obestatin has been initially characterized as a new peptide derived from the ghrelin precursor, which suppresses food intake and inhibits the orexigenic and prokinetic actions of ghrelin when injected peripherally or centrally in lean mice. However, reproducing these data remains controversial. Reasons for the disparity may be the use of different doses, routes, and animal models. We aimed to investigate the effects of peripheral and intracisternal (IC) injection of obestatin on feeding, gastric motility, and blood glucose in rats as well as in diet-induced obese (DIO) mice.

RESEARCH METHODS AND PROCEDURES

Food intake and gastric emptying of a semi-liquid caloric meal were measured after intraperitoneal (IP) injection of obestatin in rats and DIO mice. Gastric phasic motility and blood glucose were monitored in urethane-anesthetized rats after IC or intravenous (IV) injection of obestatin.

RESULTS

Obestatin injected intraperitoneally at doses ranging from 0.1 to 3 mg/kg influenced neither acute food intake nor gastric emptying in rats. Obestatin injected intravenously at 0.3 or 3 mg/kg and IC at 7.5 or 30 microg/rat modified neither fasted gastric phasic motility nor blood glucose levels, while ghrelin (30 microg/kg, IV) increased and vagotomy suppressed gastric motility, and an oligosomatostatin analog (3 microg/rat, IC) decreased blood glucose. Obestatin, injected intraperitoneally (0.3 mg/kg) in DIO mice, did not alter feeding response to a fast, while urocortin 1 (10 microg/kg, IP) induced a 73.3% inhibition at 2 hours.

DISCUSSION

Our data demonstrate that peripheral administration of obestatin did not modify food intake in rats or obese mice or gastric motor function in rats.

Structure-Activity Relationships of β -MSH Derived Melanocortin-4 Receptor Peptide Agonists

The recent emergence of obesity as a major health threat in the industrialized world has intensified the search for novel and effective pharmacologic treatment. The proopiomelanocortin (POMC)-melanocortin 4 receptor (MC4R) axis has been shown to regulate food intake and energy homeostasis and is considered among the most promising antiobesity targets. Our initial efforts in this area have focused on affinity and selectivity directed optimization of the native beta-MSH(5-22) sequence and resulted in the discovery of a potent MC4R agonist: Ac-Tyr-Arg-[Cys-Glu-His-D-Phe-Arg-Trp-Cys]-NH(2) (10). Subcutaneous administration of this peptide produced an excellent in vivo efficacy in reducing food intake and increasing fat metabolism. Additionally, suppression of food intake was observed in wild type but not in MC4R deficient mice, suggesting that the effects observed in the wild type mice were mediated through MC4R signaling. Subsequent optimization efforts led to the identification of a novel series of disulfide constrained hexapeptides as exemplified by Ac-[hCys-His-D-Phe-Arg-Trp-Cys]-NH(2) (100). These cyclic hexapeptides showed a further improved potency in binding MC4R and an enhanced selectivity over MC1R. At a dose of 0.07 mg/kg analog 102 reduced food intake by 38% and increased fat utilization by 58% in rats. These cyclic peptides provide novel and enhanced reagents for the elucidation of melanocortin receptors biology and may find applications in the treatment of obesity and related metabolic disorders.

Potent benzimidazolone based human β3-adrenergic receptor agonists

The synthesis and biological evaluation of a series of benzimidazolone beta(3) adrenergic receptor agonists are described. A trend toward the reduction of rat atrial tachycardia upon increasing steric bulk at the 3-position of the benzimidazolone moiety was observed.

Potent and selective MC-4 receptor agonists based on a novel disulfide scaffold

Extensive structure-activity relationship studies utilizing a beta-MSH-derived cyclic nonapeptide, Ac-Tyr-Arg-[Cys-Glu-His-D-Phe-Arg-Trp-Cys]-NH(2) (3), led to identification of a series of novel MC-4R selective disulfide-constrained hexapeptide analogs including Ac-[hCys-His-D-Phe-Arg-Trp-Cys]-NH(2) (12). The structural modifications associated with profound influence on MC-4R potency and selectivity were ring size, ring conformation, and the aromatic substitution of the D-Phe7. These cyclic peptide analogs provide novel and enhanced reagents for use in the elucidation of melanocortin-4 receptor-related physiology, and may additionally find application in the treatment of obesity and related metabolic disorders.

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.

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.

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.

Synthesis and biological evaluation of an orally active ghrelin agonist that stimulates food consumption and adiposity in rats

2-(2-Amino-2-methyl-propionylamino)-5-phenyl-pentanoic acid [1-[1-(4-methoxy-phenyl)-1-methyl-2-oxo-2-pyrrolidin-1-yl-ethyl]-1H-imidazol-4-yl]-amide (LY444711, 6) is an orally active ghrelin agonist that binds with high affinity to and is a potent activator of the growth hormone secretagogue receptor 1a (GHS-R1a) receptor. In rat models of feeding behavior and pharmacology, 6 creates a positive energy balance and induces adiposity by stimulating food consumption and sparing fat utilization. As an orally active ghrelin agonist, 6 represents a new pharmacological tool to investigate the orexigenic role of ghrelin in regulating energy homeostasis.

Physiology: does gut hormone PYY3-36 decrease food intake in rodents?

Batterham et al. report that the gut peptide hormone PYY3-36 decreases food intake and body-weight gain in rodents, a discovery that has been heralded as potentially offering a new therapy for obesity. However, we have been unable to replicate their results. Although the reasons for this discrepancy remain undetermined, an effective anti-obesity drug ultimately must produce its effects across a range of situations. The fact that the findings of Batterham et al. cannot easily be replicated calls into question the potential value of an anti-obesity approach that is based on administration of PYY3-36.

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.

Evaluation of a quantitative magnetic resonance method for mouse whole body composition analysis

OBJECTIVE

To evaluate applicability, precision, and accuracy of a new quantitative magnetic resonance (QMR) analysis for whole body composition of conscious live mice.

RESEARCH METHODS AND PROCEDURES

Repeated measures of body composition were made by QMR, DXA, and classic chemical analysis of carcass using live and dead mice with different body compositions. Caloric lean and dense diets were used to produce changes in body composition. In addition, different strains of mice representing widely diverse populations were analyzed.

RESULTS

Precision was found to be better for QMR than for DXA. The coefficient of variation for fat ranged from 0.34% to 0.71% compared with 3.06% to 12.60% for DXA. Changes in body composition in response to dietary manipulation were easily detected using QMR. An increase in fat mass of 0.6 gram after 1 week (p < 0.01) was demonstrated in the absence of hyperphagia or a change in mean body weight.

DISCUSSION

QMR and DXA detected similar fat content, but the improved precision afforded by QMR compared with DXA and chemical analysis allowed detection of a significant difference in body fat after 7 days of consuming a diet rich in fat even though average body weight did not significantly change. QMR provides a very precise, accurate, fast, and easy-to-use method for determining fat and lean tissue of mice without the need for anesthesia. Its ability to detect differences with great precision should be of value when characterizing phenotype and studying regulation of body composition brought about by pharmacological and dietary interventions in energy homeostasis.

Quantitative magnetic resonance (QMR) method for bone and whole-body-composition analysis

OBJECTIVE

to evaluate the applicability, precision, and accuracy of the new EchoMRI quantitative magnetic resonance (QMR) method for in-vitro bovine bone analysis and in-vivo whole-body-composition analysis of conscious live mice.

RESEARCH METHODS AND PROCEDURES

bovine tibia bone samples were measured by QMR and dual-energy X-ray adsorptiometry (DEXA). Repeated measures of whole-body composition were made using live and dead mice with different levels of fat by QMR and DEXA and by classic chemical analysis of the mouse carcass.

RESULTS

bone-mineral density (BMD) and bone-mineral content (BMC) measured in bovine tibia by QMR and DEXA were highly correlated. Precision of fat and lean measurement in mice was found to be better for QMR than for DEXA. The coefficient of variation ( CV) for fat was 0.34-0.71% for QMR compared with 3.06-12.60% for DEXA.

DISCUSSION

QMR offers more specific parameters of bone structure than does DEXA. QMR and DEXA did not differ in the total amount of fat detected in live mice but QMR had improved precision. QMR was superior to DEXA in measuring fat in very small mice.

CONCLUSIONS

in bone tissue there is a strong correlation between hydrogen NMR signal and bone-mineral density as measured by X-ray. QMR provides a very precise, accurate, fast, and easy to use method for determining fat and lean mass of mice without the need for anesthesia. Its ability to detect differences and monitor changes in body composition in mice with great precision should be of great value in characterizing phenotypes and studying drugs affecting obesity.

Peptides that regulate food intake: antagonism of opioid receptors reduces body fat in obese rats by decreasing food intake and stimulating lipid utilization

Agonists to opioid receptors induce a positive energy balance, whereas antagonists at these receptors reduce food intake and body weight in rodent models of obesity. An analog of 3,4-dimethyl-4-(3-hydroxyphenyl)piperidine, LY255582, is a potent non-morphinan antagonist for mu-, kappa-, and delta-receptors (K(i) of 0.4, 2.0, and 5.2 nM, respectively). In the present study, we examined the effects of oral LY255582 treatment on caloric intake, calorie expenditure, and body composition in dietary-induced obese rats. Acute oral treatment of LY255582 produced a dose-dependent decrease in energy intake and respiratory quotient (RQ), which correlated with the occupancy of central opioid receptors. Animals receiving chronic oral treatment with LY255582 for 14 days maintained a negative energy balance that was sustained by increased lipid use. Analysis of body composition revealed a reduction in fat mass accretion, with no change in lean body mass, in animals treated with LY255582. Therefore, chronic treatment with LY255582 reduces adipose tissue mass by reducing energy intake and stimulating lipid use.

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.

Body composition of prolactin-, growth hormone, and thyrotropin-deficient Ames dwarf mice

Ames dwarf mice have primary deficiency of prolactin (PRL), growth hormone (GH), and thyroid-stimulating hormone (TSH), and live considerably longer than normal animals from the same line. In view of the documented effects of GH, PRL, and thyroid hormones on lean and fat body mass and skeletal growth, and the suspected relationship of body size and composition to life expectancy, it was of interest to examine age-related changes in body composition of Ames dwarf mice. Lean mass, fat mass, bone area, and bone mineral content (BMC) were determined in dwarf and normal mice at the ages of 2, 4.5 6, and 18 mo using dual X-ray absorptiometry. In addition to the expected significant declines in lean mass, bone area, and BMC, dwarf mice exhibited attenuation of the age-related increase in bone mineral density and delayed or attenuated increase in percentage of body fat. Percentage of body fat was lower in adult dwarfs than in the corresponding normal controls. Patterns of age-related changes in body composition in Ames dwarf mice are consistent with the recent report of age-related changes in body composition in PRL receptor knockout mice. We suspect that reduction in relative adiposity may contribute to the previously reported increase in insulin sensitivity of Ames dwarf mice and thus may be a factor in delayed aging and increased longevity of these animals.

High circulating ghrelin: a potential cause for hyperphagia and obesity in prader-willi syndrome

Prader-Willi syndrome (PWS) is a genetic disorder occurring in 1 of 10,000-16,000 live births and is characterized by excessive appetite with progressive massive obesity as well as short stature and mental retardation. Most patients have GH deficiency and hypogonadotropic hypogonadism. The causes of the hyperphagia and abnormal GH secretion are unknown. To determine whether ghrelin, a novel GH secretagogue with orexigenic properties, is elevated in PWS, we measured fasting plasma ghrelin concentration; body composition (dual-energy x-ray absorptiometry); and subjective ratings of hunger (visual analog scale) in seven subjects (6 males and 1 female; age, 26 +/- 7 yr; body fat, 39 +/- 11%, mean +/- SD) with PWS (diagnosis confirmed by genetic test) and 30 healthy subjects (reference population, 15 males and 15 females; age, 32 +/- 7 yr; body fat, 36 +/- 11%) fasted overnight. All subjects were weight stable for at least 6 months before admission to the study. The mean plasma ghrelin concentration was higher in PWS than in the reference population (307 +/- 164 vs. 109 +/- 24 fmol/ml; P < 0.001), and this difference remained significant after adjustment for percentage body fat (P < 0.001). Plasma ghrelin was also higher (P = 0.0004) in PWS than in five healthy subjects fasted for 36 h. A positive correlation was found between plasma ghrelin and subjective ratings of hunger (r = 0.71; P = 0.008). Furthermore, in subjects with PWS, the concentration of the hormone was not different before and after ingestion of 2 ml and a satiating amount of the same liquid meal (ghrelin concentrations: 307 +/- 164 vs. 306 +/- 205 vs. 260 +/- 134 fmol/ml, respectively; ANOVA for repeated measures, P = 0.56). This is the first evidence that ghrelin, a novel orexigenic hormone, is elevated in subjects with PWS. Our finding suggests that ghrelin may be responsible, at least in part, for the hyperphagia observed in PWS.

Plasma ghrelin, obesity, and the polycystic ovary syndrome: correlation with insulin resistance and androgen levels

In addition to its orexigenic properties, ghrelin has been shown to modulate the secretory pattern of pituitary hormones, and it may exert direct effects on peripheral organs such as the gonads and endocrine pancreas. To study possible interactions among ghrelin, glucose homeostasis, and the reproductive system, we investigated 10 obese women with polycystic ovary syndrome (OB-PCOS) in comparison with 10 age- and body mass index-matched obese subjects (OB). Plasma levels of insulin, glucose, androgens, and ghrelin were measured at baseline condition and after 7 months of therapy (hypocaloric diet + metformin or placebo). Plasma ghrelin levels were lower in OB-PCOS than in OB (P < 0.05). A strong negative correlation between ghrelin and androstenedione levels was found in both populations at baseline (OB-PCOS: P < 0.01; OB: P < 0.001) and after therapy (OB-PCOS: P < 0.01; OB: P < 0.05), whereas no correlation was found between ghrelin and other androgens. In both groups, the markers of insulin resistance in fasting and stimulated conditions (glucose/insulin ratio, homeostasis model insulin resistance index, homeostasis model applied to the oral glucose tolerance test) demonstrated decreased insulin sensitivity. However, a negative correlation between plasma ghrelin and all these markers was observed only in the OB-PCOS group (P < 0.05). Accordingly, a negative correlation between ghrelin variation and treatment-induced changes of the glucose/insulin ratio, HOMA-R, and HOMA(OGTT) was observed only in the OB-PCOS group (P < 0.05). In conclusion, OB-PCOS women have lower ghrelin levels than those expected based on the presence of obesity. Only in OB-PCOS, ghrelin negatively correlates with insulin sensitivity. In addition, regardless of the presence of PCOS, a marked negative correlation exists between ghrelin and androstenedione levels, suggestive of an interaction between ghrelin and steroid synthesis or action.

Hypophysectomy prevents ghrelin-induced adiposity and increases gastric ghrelin secretion in rats

OBJECTIVE

The novel gastric hormone ghrelin has recently been identified as an important modulator of energy homeostasis. Leptin-responsive hypothalamic neuropeptide Y/Agouti-related protein neurons are believed to mediate afferent ghrelin signals. Little is known, however, about ghrelin-induced efferent signals. We therefore investigated if hypothalamic-pituitary axes have a role in transferring ghrelin-induced changes of energy balance to the periphery.

RESEARCH METHODS AND PROCEDURES

We subcutaneously injected hypophysectomized, as well as adrenalectomized, thyroidectomized, and sham-operated control rats with GH secretagogues [ghrelin, growth hormone (GH)-releasing peptide] for 1 week. Body weight, food intake, and body composition (chemical carcass analysis) were analyzed and compared with vehicle-treated controls. In addition, we quantified circulating levels of endogenous ghrelin in hypophysectomized and GH-treated normal rats.

RESULTS

GH-secretagogue treatment of sham-operated control rats dose-proportionally increased food intake, body weight, and fat mass compared with vehicle-injected controls (p < 0.01). These effects, however, were not observed in ghrelin-treated hypophysectomized, thyroidectomized, or adrenalectomized rats, indicating an essential role for the pituitary axis in ghrelin-induced adiposity. Circulating levels of endogenous ghrelin were reduced by administration of GH in normal rats and were about 3-fold higher in hypophysectomized rats (n = 20, p = 0.001), suggesting a regulatory feedback loop involving the stomach and the pituitary to regulate gastric ghrelin secretion.

DISCUSSION

According to these results, the endocrine pituitary is mediating ghrelin-induced changes toward a positive energy balance and is involved in the regulation of ghrelin secretion through a gastro-hypophyseal feedback loop.

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.

Extent and direction of ghrelin transport across the blood-brain barrier is determined by its unique primary structure

The novel hormone ghrelin is a potent orexigen that may counterbalance leptin. Ghrelin is the only secreted molecule requiring post-translational acylation with octanoic acid to ensure bioactivity. Ghrelin, predominantly derived from the stomach, may target neuroendocrine networks within the central nervous system (CNS) to regulate energy homeostasis. This would require ghrelin to cross the blood-brain barrier (BBB). In mice, we examined whether ghrelin crosses the BBB and whether its lipophilic side chain is involved in this process. We found that saturable systems transported human ghrelin from brain-to-blood and from blood-to-brain. Mouse ghrelin, differing from human ghrelin by two amino acids, was a substrate for the brain-to-blood but not for the blood-to-brain transporter and so entered the brain to a far lesser degree. des-Octanoyl ghrelin entered the brain by nonsaturable transmembrane diffusion and was sequestered once within the CNS. In summary, we show that ghrelin transport across the BBB is a complex, highly regulated bidirectional process. The direction and extent of passage are determined by the primary structure of ghrelin, defining a new role for the unique post-translational octanoylation.

Role of ghrelin polymorphisms in obesity based on three different studies

OBJECTIVE

Associations between preproghrelin DNA variants and obesity-related phenotypes were studied in 3004 subjects from the Québec Family Study (QFS), the HERITAGE Family Study (HERITAGE), and the Swedish Obese Subjects (SOS) Study.

RESEARCH METHODS AND PROCEDURES

Body mass index (BMI), fat mass (FM) from underwater weighing, and abdominal fat from computerized tomography were measured. The ghrelin polymorphisms were identified by polymerase chain reaction.

RESULTS

Arg51Gln QFS subjects (n = 6) had lower ghrelin concentrations (p = 0.007) than Arg51Arg subjects (n = 14). White preproghrelin Met72Met subjects in HERITAGE had the lowest BMI (p = 0.020), and those in the QFS cohort had the lowest FM (p < 0.001). Met72 carrier status (Met72+) was associated with lower FM (p = 0.026) and higher insulin-like growth factor-1 levels (p = 0.019) among blacks. Met72Met QFS subjects had less visceral fat (p = 0.002) and a lower fasting respiratory quotient (p = 0.037). HERITAGE Met72+ white subjects also showed lower exercise respiratory quotient (p = 0.030) and higher maximal oxygen uptake (p = 0.023). Furthermore, the prevalence of Met72+ was higher (19.2%; p < 0.05) in SOS subjects whose BMI was < or =25 kg/m(2) than in those with BMI >25 kg/m(2) (14.8%). SOS Met72+ obese women had a lower (11.4%; p = 0.032) prevalence of hypertension than noncarriers (23.9%).

DISCUSSION

Arg51Gln mutation was associated with lower plasma ghrelin levels but not with obesity. The preproghrelin Met72 carrier status seems to be protective against fat accumulation and associated metabolic comorbidities.

Targeted disruption of the melanin-concentrating hormone receptor-1 results in hyperphagia and resistance to diet-induced obesity

The hypothalamic neuropeptide melanin-concentrating hormone (MCH) has been implicated in a variety of physiological functions including the regulation of feeding and energy homeostasis. Two MCH receptors (MCHR1 and MCHR2) have been identified so far. To decipher the functional role of the MCH receptors, we have generated and phenotypically characterized mice rendered deficient in MCHR1 expression by homologous recombination. Inactivation of MCHR1 results in mice (MCHR1-/-) that are resistant to diet-induced obesity. With a high-fat diet, body fat mass is significantly lower in both male (4.7 +/- 0.6 g vs. 9.6 +/- 1.2 g) and female (3.9 +/- 0.2 vs. 5.8 +/- 0.5 g) MCHR1-/- mice than that of the wild-type control (P < 0.01), but the lean mass remains constant. When normalized to body weight, female mice are hyperphagic, and male mice are hyperphagic and hypermetabolic, compared with wild-type mice. Consistent with the lower fat mass, both leptin and insulin levels are significantly lower in male MCHR1-/- mice than in the wild-type controls. Our data firmly establish MCHR1 as a mediator of MCH effects on energy homeostasis and suggest that inactivation of MCHR1 alone is capable to counterbalance obesity induced by a high-fat diet.

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.

Chronic central infusion of cocaine- and amphetamine-regulated transcript (CART 55-102): effects on body weight homeostasis in lean and high-fat-fed obese rats

BACKGROUND

Cocaine- and amphetamine-regulated transcript (CART) is expressed within hypothalamic nuclei implicated in the regulation of feeding behaviour. It is up-regulated by leptin, and CART-derived peptides acutely inhibit food intake.

OBJECTIVE

The present study was designed to assess the long-term effects of central CART administration on food intake, body weight, plasma levels of glucose, insulin, leptin, free fatty acids and triglycerides, and on fuel utilisation in normal and high-fat-fed obese rats.

DESIGN

Normal and high-fat-fed obese rats were cannulated intracerebroventricularly (i.c.v.) and infused for 6 days with CART (55-102) or its vehicle. At day 4, animals were placed in an indirect calorimeter for a 24 h period during which the respiratory quotient and the energy expenditure were determined hourly.

RESULTS

In both normal and obese animals, the chronic i.c.v. infusion of CART (55-102) had marked, sustained inhibitory effects on food intake and body weight gain that were accompanied by decreases in plasma insulin and leptin levels. Using indirect calorimetry, it was observed that CART infusion promoted an increase in lipid oxidation in normal and in obese animals, although this increase reached statistical significance only in the obese group. The hypothalamic CART mRNA expression was found to be higher in obese rats (displaying hyperleptinaemia) than in normal animals.

CONCLUSION

The data together show that chronic i.c.v. CART infusion is effective in inhibiting food intake, favouring lipid oxidation and limiting fat storage, both in normal and high-fat-diet-induced obese rats. The CART pathway thus seems to be an important determinant of body weight homeostasis in normal animals as well as in a model of nutritionally induced obesity.

Rodent obesity models: an overview

Animal obesity models differ widely in type and extent of obesity. They are either based on environmental factors (eg. high fat diet induced obesity), spontaneous mutants (i.e. ob/ob mice), genetically engineered animals (eg. mice with melanocortin receptor subtype-4 gene disruption (knock-out)) or mechanical intervention (eg. chemical lesion of the ventromedial hypothalamus). This article reviews available rodent models to study obesity and attempts to highlight the greatest utility for each model.

Weight gain decreases elevated plasma ghrelin concentrations of patients with anorexia nervosa

OBJECTIVE

Ghrelin is a new gastric hormone that has been identified as an endogenous ligand for the growth hormone (GH) secretagogue receptor subtype 1a (GHS-R1a). Ghrelin administration however not only stimulates GH secretion but also induces adiposity in rodents by increasing food intake and decreasing fat utilization. We hypothesized that impaired ghrelin secretion in anorexia nervosa may be involved in the pathogenesis of this eating disorder. To examine this hypothesis and to further investigate the role for ghrelin in regulating energy homeostasis, we analyzed circulating ghrelin levels in patients with anorexia nervosa and examined possible correlations with clinical parameters before and after weight gain.

METHODS

Plasma ghrelin levels were measured in overnight fasting plasma samples from 36 female patients with anorexia nervosa (age: 25.0+/-1.2 years, BMI: 15.2+/-0.2 kg/m(2)) before and after weight gain following psychotherapeutic treatment intervention in a psychosomatic institution. Plasma ghrelin levels were also measured in fasting plasma samples from 24 age-matched female controls (31+/-1.4 years, BMI: 22.9+/-0.45 kg/m(2)). For quantification of ghrelin levels a commercially available radioimmunoassay (Phoenix Pharmaceuticals, USA) was used.

RESULTS

Fasting plasma ghrelin levels in anorectic patients were significantly higher (1057+/-95 pg/ml) than in normal age-matched female controls (514+/-63 pg/ml n=24, P=0.02). Therapeutic intervention in a psychosomatic institution caused an BMI increase of 14% (P<0.001) leading to a significant decrease in circulating ghrelin levels of 25%, (P=0.001). A significant negative correlation between Deltaghrelin and DeltaBMI was observed (correlation coefficient: -0.47, P=0.005, n=36).

CONCLUSION

We show for the first time that fasting plasma levels of the novel appetite-modulating hormone ghrelin are elevated in anorexia nervosa and return to normal levels after partial weight recovery. These observations suggest the possible existence of ghrelin resistance in cachectic states such as caused by eating disorders. Future studies are necessary to investigate putative mechanisms of ghrelin resistance such as a possible impairment of intracellular ghrelin receptor signaling in pathophysiological states presenting with cachexia.

Absence of cocaine- and amphetamine-regulated transcript results in obesity in mice fed a high caloric diet

Cart (cocaine- and amphetamine-regulated transcript) was first identified to be a major brain mRNA up-regulated by cocaine and amphetamine. The CART protein has been established as a satiety factor closely associated with the action of leptin. To assess CART's role as an anorexigenic signal, we have generated CART-deficient mice by gene targeting. On a high fat diet, CART-deficient and female heterozygous mice, but not male heterozygous mice, showed statistically significant increases in weekly food consumption, body weight, and fat mass compared with their wild-type littermates. Furthermore, CART-deficient and female heterozygous mice were significantly heavier when fed a high fat diet than on a regular chow diet at 17 wk of age and at the 14th wk of the feeding studies. However, wild-type or male heterozygous mice showed no weight variations attributable to caloric contents of the diet at that age. Contrary to the obese phenotypes shown in MC4R-, proopiomelanocortin-, or leptin-deficient mice, our results showed that CART deficiency predisposed mice to become obese on a calorically dense diet. The results also show that CART may not be a major anorectic signal compared with proopiomelanocortin or leptin in the regulation of energy homeostasis.

Plasma ghrelin concentration and energy balance: overfeeding and negative energy balance studies in twins

Central (intracerebral ventral) and peripheral (subcutaneous and intraperitoneal) administration of ghrelin causes obesity in rodents by increasing food intake and decreasing fat oxidation. Recent studies in humans have shown that plasma ghrelin concentration was inversely related to body fat and was lower in Pima Indians, a population susceptible to obesity. Whether ghrelin plays a role in the etiology of obesity in humans is unknown. We, therefore, measured plasma ghrelin concentration before and after two interventions in monozygotic twins previously studied at Laval University, Quebec City. Twelve pairs of monozygotic twins were overfed by 84,000 kcal over a 100-day period, whereas another seven pairs of monozygotic twins were submitted to a 53,000 kcal negative energy balance induced by exercise over a 93-day period. At baseline, for all the subjects, plasma ghrelin concentration was negatively correlated with body mass and body fatness (r varying from 0.36 to 0.45). The intraclass coefficient for the twin resemblance (r(I) = 0.75; p = 0.006) indicated that plasma ghrelin concentration is a familial trait. In response to the 100-day intervention, plasma ghrelin exhibited a non-significant decrease of 61 +/- 30 fmol/l (p = 0.18) with overfeeding and a non-significant increase of 58 +/- 34 fmol/l (p = 0.17) with negative energy balance. However, there was no relationship between baseline plasma ghrelin concentration and the magnitude of body weight change in both interventions. These first experimental data under "clamped energy balance conditions" do not provide evidence that plasma ghrelin is involved in the etiology of human obesity. However, studies in free-living individuals are needed to clarify this question.

Circulating ghrelin levels are decreased in human obesity

Ghrelin is a novel endogenous natural ligand for the growth hormone (GH) secretagogue receptor that has recently been isolated from the rat stomach. Ghrelin administration stimulates GH secretion but also causes weight gain by increasing food intake and reducing fat utilization in rodents. To investigate the possible involvement of ghrelin in the pathogenesis of human obesity, we measured body composition (by dual X-ray absorption) as well as fasting plasma ghrelin concentrations (radioimmunoassay) in 15 Caucasians (8 men and 7 women, 31+/-9 years of age, 92+/-24 kg body wt, and 29+/-10% body fat, mean +/- SD) and 15 Pima Indians (8 men and 7 women, 33+/-5 years of age, 97+/-29 kg body wt, and 30+/-8% body fat). Fasting plasma ghrelin was negatively correlated with percent body fat (r = -0.45; P = 0.01), fasting insulin (r = -0.45; P = 0.01) and leptin (r = -0.38; P = 0.03) concentrations. Plasma ghrelin concentration was decreased in obese Caucasians as compared with lean Caucasians (P < 0.01). Also, fasting plasma ghrelin was lower in Pima Indians, a population with a very high prevalence of obesity, compared with Caucasians (87+/-28 vs. 129+/-34 fmol/ml; P < 0.01). This result did not change after adjustment for fasting plasma insulin concentration. There was no correlation between fasting plasma ghrelin and height. Prospective clinical studies are now needed to establish the role of ghrelin in the pathogenesis of human obesity.

Harnessing the power of the group for latency-aged sexual abuse victims

For children who have been sexually abused, group therapy is often a preferred treatment modality. Although much consideration has been given to what structured activities, goals, and objectives should be included in groups for sexually abused children, limited attention has been paid to the dynamics and processes inherent in the group. This article follows the dynamic unfolding of a short-term structured group for latency-aged, female sexual abuse victims. Special emphasis is placed on listening to the messages underlying children's actions and responding to the message rather than suppressing or limiting the behavior. It is argued that by attending to group dynamics and processes in a theme-focused group, structured activities become more effective and the power of the group can be harnessed to foster opportunities for healing that otherwise might go unrecognized.

Increased weight gain after ovariectomy is not a consequence of leptin resistance

The positive correlation between leptin and body fat mass has caused some investigators to speculate that leptin resistance contributes to obesity. Loss of ovarian function in human and rat is associated with increased fat mass gain and increased circulating leptin levels. To study whether ovariectomy produces leptin resistance, Sprague-Dawley female rats were ovariectomized or sham operated and injected with leptin for 35 days. Ovariectomy (OVX) produced hyperphagia and increased gain in both lean and fat mass. Daily leptin injections initially decreased food intake significantly, but feeding gradually increased to a stable level by day 16 and remained at that level for the duration of study. Body composition analysis indicated that chronic injection of leptin to OVX rats dramatically decreased (P < 0.05) fat mass [30 +/- 2 (SE) g, vehicle, to 3 +/- 1 g, leptin]. Using indirect calorimetry, we observed that OVX did not change energy expenditure or total level of fuel utilization. Leptin administration increased fat utilization and prevented reduction in calorie expenditure that is typically associated with food restriction. Leptin treatment to OVX rats decreased plasma triglyceride, free fatty acid, and insulin concentrations, whereas glucose concentration was normal. Withdrawal of leptin triggered hyperphagia, indicating that leptin biology remained throughout the duration of the chronic treatment. The same dose of leptin produced qualitatively similar data in sham-operated rats. Thus we concluded that the loss of ovarian function in rats is not associated with a change in leptin sensitivity.

Ghrelin induces adiposity in rodents

The discovery of the peptide hormone ghrelin, an endogenous ligand for the growth hormone secretagogue (GHS) receptor, yielded the surprising result that the principal site of ghrelin synthesis is the stomach and not the hypothalamus. Although ghrelin is likely to regulate pituitary growth hormone (GH) secretion along with GH-releasing hormone and somatostatin, GHS receptors have also been identified on hypothalamic neurons and in the brainstem. Apart from potential paracrine effects, ghrelin may thus offer an endocrine link between stomach, hypothalamus and pituitary, suggesting an involvement in regulation of energy balance. Here we show that peripheral daily administration of ghrelin caused weight gain by reducing fat utilization in mice and rats. Intracerebroventricular administration of ghrelin generated a dose-dependent increase in food intake and body weight. Rat serum ghrelin concentrations were increased by fasting and were reduced by re-feeding or oral glucose administration, but not by water ingestion. We propose that ghrelin, in addition to its role in regulating GH secretion, signals the hypothalamus when an increase in metabolic efficiency is necessary.

Chronic leptin administration promotes lipid utilization until fat mass is greatly reduced and preserves lean mass of normal female rats

Leptin is a hormone synthesized and secreted from adipose tissue. To study the physiologic effects of chronic leptin treatment, normal adult female Sprague-Dawley rats were injected subcutaneously for 35 days. Twice daily injections (250 microgram/day, b.i.d.) resulted in a significant (P<0.05) decrease in food intake that was maintained for 10 days before gradually returning to control level by day 21. Leptin decreased body weight by a maximum of 12% of the initial body weight on day 22 and remained reduced for the duration of the treatment. After 35 days of treatment, visible peritoneal adipose tissue was not detected. Body composition analysis showed that chronic injection of leptin resulted in a dramatic decrease in fat content (28+/-2 to 4+/-2 g, P<0.05; mean+/-SEM) while the lean content remained unchanged. Rats pair-fed to the leptin-treated group but treated with vehicle had the same body composition (23+/-3 g fat mass) as that measured for the ad libitum fed controls. Using indirect calorimetry we observed that leptin decreased respiratory quotient and thus increased fat oxidation. Leptin also prevented energy expenditure reduction typically associated with food restriction. Leptin treatment for 35 days decreased plasma triglyceride (0.75+/-0.07 to 0.30+/-0.03 mM, P<0.05), free fatty acid (0.56+/-0.06 to 0.32+/-0.04 mM) and insulin (3.2+/-0.5 to 1. 4+/-0.4 ng/ml, P<0.05) concentrations despite the fact that food intake was normalized by day 35. Withdrawal of leptin triggered hyperphagia indicating that leptin biology remained throughout the duration of the chronic treatment. These data suggest that leptin reduces fat mass by initially decreasing appetite and by maintaining enhanced fat utilization even when food intake has returned to that of vehicle-treated control.

Pharmacological characterization of (125)I-1229U91 binding to Y1 and Y4 neuropeptide Y/Peptide YY receptors

1229U91 (GW1229 or GR231118) [lle,Glu,Pro,Dpr,Tyr, Arg,Leu,Arg, Tyr-NH(2))2 cyclic (2,4'),(2'4)-diamide] has been reported by several research groups to be a potent antagonist at the Y1 neuropeptide Y (NPY) receptor subtype. However, 1229U91 also displaces (125)I-peptide YY (PYY) with high affinity from the Y4 subtype. Previously, we reported that 1229U91 had full agonist properties for the Y4 receptor. To characterize the pharmacological properties of 1229U91 directly, we had it radioiodinated with the chloromine-T method. (125)I-1229U91 bound to cell lines expressing the human Y1 and Y4 receptors with high affinity. The K(d) and B(max) for (125)I-1229U91 binding to Y1 were 14.9 pM and 1458 fmol/mg protein, respectively. The Y4 receptor bound (125)I-1229U91 with a K(d) of 12.5 pM and a B(max) of 1442 fmol/mg protein. When competing (125)I-1229U91 binding from Y1 and Y4 receptors, a similar rank order of potency was observed: 1229U91 > [Leu(31),Pro(34)]-NPY >/= [Leu(31),Pro(34)]-PYY > PYY >/= NPY > NPY(2-36) > PYY(3-36). Pancreatic polypeptide (PP) potently displaced (125)I-1229U91 from the Y4 receptor, but displayed little affinity for Y1. In autoradiographic studies with rat brain sections, (125)I-1229U91 bound with a distribution similar to that reported for the Y1 receptor when localized with (125)I-[Leu(31),Pro(34)]-PYY. Brain regions exhibiting binding sites for (125)I-PP were not detected with this radioligand. Those include the interpeduncular nucleus and the periventricular nucleus of the hypothalamus. Furthermore, (125)I-labeled rat PP was not displaced from these areas with 10 nM 1229U91. Thus, (125)I-1229U91 is a high affinity Y1 and Y4 radioligand and binds with a distribution in the rat brain consistent with the localization of the Y1 receptor.