Glucose-dependent insulinotropic polypeptide monoclonal antibodies prevent and treat obesity in wild-type and hyperphagic mice.

OBJECTIVE: This study aimed to investigate whether a glucose-dependent insulinotropic polypeptide (GIP) monoclonal antibody (mAb) will promote weight loss in wild-type mice and to determine effects of this mAb in preventing weight gain in ob/ob mice. METHODS: Phosphate-buffered saline (PBS) or GIP mAb was injected intraperitoneally to wild-type mice fed a 60% high-fat diet (HFD). After 12 weeks, mice that received PBS were divided into two groups and were fed a 37% HFD for 5 weeks; one group received PBS, and one group received GIP mAb. In a separate study, PBS or GIP mAb was injected intraperitoneally to ob/ob mice fed normal mouse chow for 8 weeks. RESULTS: PBS-treated mice gained significantly more than those treated with GIP mAb, with no difference in food consumption detected. Obese mice fed a 37% HFD and PBS continued to gain weight (+2.1% ± 0.9%), whereas mice administered GIP mAb lost 4.1% ± 1.4% body weight (p < 0.01). Leptin-deficient mice consumed similar amounts of chow, and, after 8 weeks, the PBS- and GIP mAb-treated mice gained 250.4% ± 9.1% and 192.4% ± 7.3%, respectively (p < 0.01). CONCLUSIONS: These studies support the hypothesis that a reduction in GIP signaling appears to affect body weight without suppressing food intake and might provide a novel, useful method for the treatment and prevention of obesity.

SiGe quantum wells with oscillating Ge concentrations for quantum dot qubits.

Large-scale arrays of quantum-dot spin qubits in Si/SiGe quantum wells require large or tunable energy splittings of the valley states associated with degenerate conduction band minima. Existing proposals to deterministically enhance the valley splitting rely on sharp interfaces or modifications in the quantum well barriers that can be difficult to grow. Here, we propose and demonstrate a new heterostructure, the "Wiggle Well", whose key feature is Ge concentration oscillations inside the quantum well. Experimentally, we show that placing Ge in the quantum well does not significantly impact our ability to form and manipulate single-electron quantum dots. We further observe large and widely tunable valley splittings, from 54 to 239 µeV. Tight-binding calculations, and the tunability of the valley splitting, indicate that these results can mainly be attributed to random concentration fluctuations that are amplified by the presence of Ge alloy in the heterostructure, as opposed to a deterministic enhancement due to the concentration oscillations. Quantitative predictions for several other heterostructures point to the Wiggle Well as a robust method for reliably enhancing the valley splitting in future qubit devices.

Perioperative outcomes in dogs and cats undergoing pancreatic surgery: 81 cases (2008-2019).

OBJECTIVES: To identify and describe the type and frequency of perioperative factors in dogs and cats undergoing pancreatic surgery under referral care. METHODS: Medical records from a small animal surgical referral practice were retrospectively reviewed to identify dogs and cats that underwent pancreatic surgery between 2008 and 2019. Inclusion criteria included complete medical record, histopathology results and follow-up of at least 14 days postoperatively or until death. Variables collected included signalment, history, presenting complaint, preoperative diagnostic results, intraoperative complications, surgical findings/procedures, postoperative complications and histopathology results. Cases were excluded if pertinent information or a histopathology report was missing from the medical record. The frequency of these variables was reported. RESULTS: There were 81 client-owned animals identified that met the inclusion criteria (57 dogs and 24 cats). The most common pancreatic procedure performed in dogs was partial pancreatectomy 63.2% (36/57) and in cats was pancreatic biopsy 62.5% (15/24). The most common histologic diagnosis in dogs was pancreatic islet cell carcinoma 50.9% (29/57) and in cats was pancreatitis 41.7% (10/24). The overall mortality rate was 13.6% (11/81), with a 10.5% (6/57) mortality rate in dogs and a 20.8% (5/24) mortality rate in cats. CLINICAL SIGNIFICANCE: In this series of dogs and cats, pancreatic surgery under referral care carried a low to moderate mortality rate.

Effects of gastric inhibitory polypeptide (GIP) immunoneutralization on mouse motor coordination and memory.

Gastric inhibitory polypeptide (GIP) is a regulatory peptide expressed in the mammalian upper small intestine, and both GIP and its receptor (GIPR) are expressed in the cortex and hippocampus regions of the brain as well. While learning and memory deficits have been observed in GIPR-/- mice, the effects of peripheral GIP immunoneutralization on motor-coordination, learning, and memory have not been examined. In the present study, adult GIPR-/- mice (KO) and age-matched wild-type C57BL/6 J mice (WT) received weekly vehicle PBS injections for 12 weeks, while a third group of wild-type mice were injected weekly for 12 weeks with 30 mg/kg body weight humanized GIP-mAb (AB) to assess the possibility of long-term effects of peripheral GIP antagonism on rodent memory and behavior. All mice groups then underwent a battery of tests that evaluated motor behavior, body coordination, and memory. Performance deficits in several memory studies after 12 weeks of treatment were demonstrated in KO, but not in AB or WT mice. Body coordination performance showed no significant differences among the 3 groups. A similar short-term study (3 injections over 9 days) was also conducted and the results were similar to those from the long-term study. Thus, short-term and long-term peripheral GIP antagonism by GIP-mAb did not appear to affect learning and memory in mice, consistent with the notion that the GIP-mAb does not cross the blood brain barrier. Furthermore, our studies indicate that GIP signaling in the brain appears to involve local neurocrine pathways.

Optimal Omeprazole Dosing and Symptom Control: A Randomized Controlled Trial (OSCAR Trial).

BACKGROUND: Proton pump inhibitors (PPIs) are potent inhibitors of acid secretion and are the mainstay of therapy for gastroesophageal reflux disease (GERD). Initially designed to be taken 30 min before the first daily meal, these agents are commonly used suboptimally, which adversely affects symptom relief. No study to date has assessed whether correcting dosing regimens would improve symptom control. The objective of this study was to determine whether patients with persistent GERD symptoms on suboptimal omeprazole dosing experience symptomatic improvement when randomized to commonly recommended dosing regimen and to evaluate the economic impact of suboptimal PPI dosing in GERD patients. METHODS: Patients with persistent heartburn symptoms ≥ 3 times per week treated with omeprazole 20 mg daily were enrolled and randomized to commonly recommended dosing or continued suboptimal dosing of omeprazole. The primary outcomes were changes in symptom, frequency, and severity, as determined using the Gastroesophageal Reflux Disease Symptom Assessment Scale (GSAS) 4 weeks after the intervention was administered. In secondary analysis, an alternative measure of symptom load was used to infer potential costs. RESULTS: Sixty-four patients were enrolled. GSAS symptom, frequency, and severity scores were significantly better when dosing was optimized for overall and heartburn-specific symptoms (P < 0.01 for all parameters). Cost savings resulting from reduced medical care and workplace absenteeism were estimated to be $159.60 per treated patient, with cost savings potentially exceeding $4 billion annually in the USA. DISCUSSION: Low-cost efforts to promote commonly recommended PPI dosing can dramatically reduce GERD symptoms and related economic costs. ClinicalTrials.gov, number: NCT02623816.

Enzymatic Assays for Studying Intramembrane Proteolysis.

Proteolysis within the membrane is catalyzed by a diverse family of proteases immersed within the hydrophobic environment of cellular membranes. These ubiquitous intramembrane-cleaving proteases (I-CLiPs) hydrolyze the transmembrane domains of a large variety of membrane-embedded proteins to facilitate signaling events essential to normal biological functions found in all forms of life. The importance of this unique class of enzyme is highlighted by its central involvement in a variety of human pathologies, including Alzheimer's disease (AD), Parkinson's disease, cancer, and the virulence of a number of viral, bacterial, and fungal pathogens. I-CLiPs therefore represent promising targets for the therapeutic treatment of numerous diseases. The key to understanding the normal biological function of I-CLiPs and capitalizing on their therapeutic potential is through a thorough understanding of the complex catalytic mechanisms that govern this unusual class of enzyme. This is an intrinsically difficult endeavor, given that these enzymes and their substrates reside within lipid membranes, making any in vitro assay technically challenging to design and execute. Here, we describe several in vitro enzymatic assays for the study of the AD-associated γ-secretase protease, which have aided the development of potent γ-secretase-targeting compounds as candidate therapeutics. These assays have also been applied in various forms for the study of other I-CLiPs, providing valuable mechanistic insights into some of the functional similarities and differences between several members of this fascinating family of proteases.

Paediatric primary cutaneous marginal zone B-cell lymphoma: does it differ from its adult counterpart?

BACKGROUND: Primary cutaneous marginal zone B-cell lymphoma (PCMZL) has rarely been reported in patients younger than 20 years. OBJECTIVES: To report our experience with PCMZL in the paediatric/adolescent age group. METHODS: Medical records of patients diagnosed with PCMZL before age 20 years and managed at two cutaneous lymphoma clinics in the U.S.A. and Israel from 1992 to 2015 were reviewed. RESULTS: The study group included 11 patients (six girls; median age 16 years, range 6-19·5); 10 had generalized/multifocal (T3) and one had regional/localized (T2) disease. Lesions were located on the limbs in all patients and the trunk in six; two had facial lesions. Staging in all but one was based on whole-body computed tomography or positron emission tomography. Initial management in most patients included nonradiation modalities: one patient with localized disease received intralesional steroids; six patients with multifocal disease received the following: topical/intralesional steroids (n = 3); excision (n = 2); 'watch and wait' (n = 1). No extracutaneous progression was noted during a median follow-up of 5·5 years (mean 7·5, range 0·5-14). At present, five patients are in complete remission. CONCLUSIONS: Based on our data (largest series in the literature with the longest follow-up), the clinicopathological presentation and course of PCMZL in the paediatric/adolescent age group are similar to those in adults. Given the indolent course and the long life expectancy of these young patients, the cumulative risk of imaging studies and the age-related potential toxicity of treatment, especially radiation, should be taken into consideration.

Effect of HIV diagnosis disclosure on psychosocial outcomes in Thai children with perinatal HIV infection.

A provider-assisted, counselling-based, paediatric HIV disclosure model was developed and implemented at two tertiary-care hospitals in Bangkok, Thailand. All undisclosed perinatally acquired HIV-infected children, aged 7-18 years, and their caretakers were offered the four-step disclosure service, including: screening, readiness assessments and preparation, disclosure sessions, and follow-up evaluations. To assess psychosocial outcomes of disclosure, we compared the scores of the Children Depression Inventory and the PedsQL 4.0™ at baseline and at two-month and six-month follow-up visits, and compared the scores of the Child Behavioral Checklist at baseline and at six-month follow-up. Disclosure was made to 186 children, 160 of whom completed post-disclosure assessments. The median Children's Depression Inventory score in 135 children decreased significantly from 11 at baseline to 8 at two-month and six-month follow-up (p < 0.01). The median PedsQL 4.0™ scores in 126 children increased significantly from 78 at baseline to 80 at two-month and 84 at six-month follow-up (p = 0.04). The median Child Behavioral Checklist scores were not significantly changed. In conclusion, paediatric HIV diagnosis disclosure using this model was found to have positive effect on the children's mood and quality of life, and no negative effect on children's behaviours. This disclosure programme should be expanded to improve the psychosocial health of HIV-infected children.

Gastric inhibitory polypeptide immunoneutralization attenuates development of obesity in mice.

Previous reports have suggested that the abrogation of gastric inhibitory polypeptide (GIP) signaling could be exploited to prevent and treat obesity and obesity-related disorders in humans. This study was designed to determine whether immunoneutralization of GIP, using a newly developed specific monoclonal antibody (mAb), would prevent the development of obesity. Specific mAb directed against the carboxy terminus of mouse GIP was identified, and its effects on the insulin response to oral and to intraperitoneal (ip) glucose and on weight gain were evaluated. Administration of mAb (30 mg/kg body wt, BW) to mice attenuated the insulin response to oral glucose by 70% and completely eliminated the response to ip glucose coadministered with human GIP. Nine-week-old C57BL/6 mice injected with GIP mAbs (60 mg·kg BW(-1)·wk(-1)) for 17 wk gained 46.5% less weight than control mice fed an identical high-fat diet (P < 0.001). No significant differences in the quantity of food consumed were detected between the two treatment groups. Furthermore, magnetic resonance imaging demonstrated that subcutaneous, omental, and hepatic fat were 1.97-, 3.46-, and 2.15-fold, respectively, lower in mAb-treated animals than in controls. Moreover, serum insulin, leptin, total cholesterol (TC), low-density lipoprotein (LDL), and triglycerides were significantly reduced, whereas the high-density lipoprotein (HDL)/TC ratio was 1.25-fold higher in treated animals than in controls. These studies support the hypothesis that a reduction in GIP signaling using a GIP-neutralizing mAb might provide a useful method for the treatment and prevention of obesity and related disorders.

Consumer use of over-the-counter proton pump inhibitors in patients with gastroesophageal reflux disease.

OBJECTIVES: Optimal administration of proton pump inhibitor (PPI) for the treatment of gastroesophageal reflux disease (GERD) requires consideration of meal timing. Since becoming available over the counter (OTC), no studies have assessed treatment patterns and symptom control in OTC consumers. The objective of this study was to survey dosing patterns and symptom control in OTC and prescription PPI users. METHODS: Patients at five clinics were surveyed regarding diagnosis of GERD, use of OTC or prescription PPIs, information on time of day dosing, demographics, and Gastroesophageal Reflux Disease Symptom Assessment Scale (GSAS; 2001, Johnson & Johnson). RESULTS: Of the 1,959 patients surveyed, 610 (31%) used PPIs for GERD. Of these, 190 (31%) and 223 (37%) received prescriptions from gastroenterologists (GIs) and primary care physicians (PCPs), respectively; 197 (32%) purchased OTC PPIs. Of the patients prescribed PPIs by GIs, 71% were optimal users, whereas 47% of patients receiving prescriptions from PCPs and 39% of consumers used PPIs optimally (P<0.001 compared with GIs). GSAS symptom, frequency, and severity scores were significantly better in patients prescribed PPIs by GIs (all P<0.001, GI compared with PCP and consumer). GSAS symptom, frequency, and severity scores were also significantly better in patients using PPIs optimally (P<0.001 for all parameters) compared with those taking PPIs suboptimally or excessively. CONCLUSIONS: Patients receiving prescription PPI from a GI are more likely to be optimal users with better symptom control. Conversely, consumers are more likely to be suboptimal users with inadequate symptom control.

Obesity and the gastrointestinal tract: you are what you eat.

Obesity represents a complex multifactorial syndrome that develops from interactions among genetic and environmental factors and is a leading cause of illness and death. The prevalence of obesity in the United States has increased dramatically since 1975. Although often ignored, the gastrointestinal tract, and the gastrointestinal regulatory peptides in particular, constitutes an ideal starting point for defining and investigating obesity as it represents the route by which all nutrients are ingested, processed, and absorbed. Another important factor to consider when evaluating the etiology of obesity is the capacity for all animals to store nutrients. Insulin is the most potent anabolic hormone, and it appears to have evolved from the need to maximize energy efficiency, obviating the requirement to continuously forage for food. Organisms expressing this important peptide possessed a distinct survival advantage and flourished. During the course of evolution, insulin biosynthesis translocated from the intestine to pancreatic islets, which necessitated a messenger from the intestine to complete the "enteroinsular axis." The eventual development of glucose-dependent insulinotropic polypeptide (GIP) and other incretins fulfilled this requirement. GIP appears to offer an additional survival benefit by not only stimulating intestinal glucose transport and maximally releasing insulin to facilitate nutrient storage but also by its insulin-mimetic properties, including enhanced uptake of glucose by adipocytes. This physiological redundancy offered by insulin and GIP ensured the survival of organisms during times when food was scarce. As food is no longer scarce, at least in the West, this survival advantage appears to have contributed to the current obesity epidemic.

First-trimester hyperglycosylated human chorionic gonadotropin and development of hypertension.

OBJECTIVE: This study aimed to determine whether urine levels of hyperglycosylated human chorionic gonadotropin (HhCG) in the first trimester are predictive of subsequent development of hypertension during pregnancy METHOD: This prospective cohort study consisted of women seeking care before 12 weeks gestation. A clean catch urine was obtained at the first prenatal visit and tested for HhCG and creatinine levels. The median HhCG levels and multiples of the median (MoM) by gestational age were compared between the groups that either developed hypertension or did not. RESULTS: Urine HhCG were determined for 204 women between 4 weeks 4 days to 11 weeks 6 days. The median HhCG of those who developed gestational hypertension (n = 7) or preeclampsia (n = 15) did not differ from the group that did not (median: 284 ng/mg creatinine vs 365 ng/mg; p = 0.55). If the MoM of HhCG for the no hypertension group was 1.00, the MoM of HhCG for the hypertension group was 0.93 (p = 0.93). A possible association was observed after 10 weeks between low HhCG levels and the development of late-onset hypertension (≥34 weeks). CONCLUSIONS: Prenatal screening for subsequent hypertension is unreliable with a single measurement of maternal urine HhCG at 10 weeks or less.

Epizootic neoplasia of the lateral line system of lake trout (Salvelinus namaycush) in New York's Finger Lakes.

This article documents an epizootic of inflammation and neoplasia selectively affecting the lateral line system of lake trout (Salvelinus namaycush) in 4 Finger Lakes in New York from 1985 to 1994. We studied more than 100 cases of this disease. Tumors occurred in 8% (5/64) of mature and 21% (3/14) of immature lake trout in the most severely affected lake. Lesions consisted of 1 or more neoplasm(s) in association with lymphocytic inflammation, multifocal erosions, and ulcerations of the epidermis along the lateral line. Lesions progressed from inflammatory to neoplastic, with 2-year-old lake trout showing locally extensive, intense lymphocytic infiltrates; 2- to 3-year-old fish having multiple, variably sized white masses up to 3 mm in diameter; and fish over 5 years old exhibiting 1 or more white, cerebriform masses greater than 1 cm in diameter. Histologic diagnoses of the tumors were predominantly spindle cell sarcomas or benign or malignant peripheral nerve sheath neoplasms, with fewer epitheliomas and carcinomas. Prevalence estimates did not vary significantly between sexes or season. The cause of this epizootic remains unclear. Tumor transmission trials, virus isolation procedures, and ultrastructural study of lesions failed to reveal evidence of a viral etiology. The Finger Lakes in which the disease occurred did not receive substantially more chemical pollution than unaffected lakes in the same chain during the epizootic, making an environmental carcinogen an unlikely primary cause of the epizootic. A hereditary component, however, may have contributed to this syndrome since only fish of the Seneca Lake strain were affected.

Detection and quantification of tricyclic antidepressants and other psychoactive drugs in urine by HPLC/MS/MS for pain management compliance testing.

A sensitive, specific, and rapid high-pressure liquid chromatography/mass spectrometry/mass spectrometry method was developed for the quantitation of 11 tricyclic antidepressants and/or their metabolites; fluoxetine and norfluoxetine; cyclobenzaprine; and trazodone in urine. Samples were alkalinized with 0.2 N NaOH and extracted into 2 ml of hexane: ethyl acetate (1:1), evaporated to dryness, and reconstituted with 100 µl of 20 mM ammonium formate: methanol (20:80). The chromatographic separation was performed using an Allure Biphenyl 100 × 3.2 mm, 5-µ column with a mobile phase consisting of 20 mM ammonium formate: methanol (20:80 v/v) at a flow rate of 0.5 ml/min. The detection was accomplished by multiple-reaction monitoring via electrospray ionization source operating in the positive ionization mode. The calibration curve was linear over the investigated concentration range, 25-2,000 ng/ml, for each analyte using 1.0 ml of urine. The lower limit of quantitation for each analyte was 25 ng/ml. The intra- and inter-day precisions had coefficient of variation less than 15% and the accuracy was within the range from 88% to 109%. The method proved adequate for the tricyclic antidepressants analysis of urine for emergency clinical toxicology and pain management compliance testing.

Evolutionary expression of glucose-dependent-insulinotropic polypeptide (GIP).

Glucose-dependent insulinotropic polypeptide (GIP) is a mammalian incretin hormone released into the circulation following nutrient ingestion. We examined the functional evolution of GIP and its relationship with insulin to delineate their respective roles in promoting nutrient efficiency. Expression patterns were examined in the sea lamprey (Petromyzon marinus), a basal vertebrate lacking a distinct pancreas, and in the zebrafish, Xenopus laevis, chicken, and mouse, organisms possessing extraintestinal pancreata. Although sea lamprey genomic analysis predicted a potential GIP-like gene, transcripts were not detected, and insulin expression was confined to the caudal pancreatic bud. GIP was detected in both the intestine and pancreas of the zebrafish and X. laevis. In contrast, GIP and insulin expression were limited to the intestine and pancreas, respectively, in chicken and mouse. Phylogenetic analysis of the glucagon-like ligands suggested proglucagon as the common ancestor, supporting the theory that GIP arose as a gene duplication of proglucagon. Insulin-secreting cells in the sea lamprey intestine may have obviated the need for an enteroinsular axis, and zebrafish may represent an evolutionary transition where GIP does not yet function as an incretin hormone. These observations are consistent with the hypothesis that GIP and insulin influence survival advantage by enhancing the efficiency of nutrient absorption and energy storage.

Evolutionary conservation of glucose-dependent insulinotropic polypeptide (GIP) gene regulation and the enteroinsular axis.

Glucose-dependent insulinotropic polypeptide (GIP), an important component of the enteroinsular axis, is a potent stimulator of insulin secretion, functioning to maintain nutrient efficiency. Although well-characterized in mammals, little is known regarding GIP transcriptional regulation in Danio rerio (Dr). We previously demonstrated that DrGIP is expressed in the intestine and the pancreas, and we therefore cloned the Dr promoter to compare GIP transcriptional regulation in Dr and mammals. Although no significant homology was indentified between the highly conserved mammalian promoter and the DrGIP promoter, 1072-bp of the DrGIP promoter conferred tissue-specific expression in mammalian cell lines. Deletional analysis of the DrGIP promoter identified two regions that, when deleted, reduced transcription by 75% and 95%, respectively. Mutational analysis of the upstream region suggested involvement of an Nkx binding site, although we were unable to identify the factor binding to this site. The cis element in the downstream region was found to be a GATA binding site. Lastly, overexpression and shRNA experiments identified PAX4 as a potential repressor of DrGIP expression. These findings provide evidence that despite the identification of species-specific transcriptional regulators and differences in GIP expression patterns between D. rerio and mammals, a moderate degree of regulatory conservation appears to exist.

Glucose-dependent insulinotropic polypeptide stimulates the proliferation of colorectal cancer cells.

Although numerous epidemiological studies have provided convincing evidence for an increase in the prevalence of colorectal cancer (CRC) in obese individuals, the precise mechanisms involved have not been elucidated. Glucose-dependent insulinotropic polypeptide (GIP) is a gastrointestinal regulatory peptide whose primary physiologic role is to stimulate postprandial pancreatic insulin secretion. Like insulin, GIP has been linked to enhanced nutrient efficiency, which occurred during the course of evolution. Its expression is increased in obesity, and we thus initiated studies to examine whether GIP might contribute to the pathogenesis of obesity-related CRC. RT-PCR and Western analysis demonstrated the presence of the GIP receptor (GIPR) in several human CRC cell lines. GIP stimulated the proliferation of MC-26 cells, a mouse CRC cell line, in a concentration-dependent manner. Western analysis showed that GIP induced the activity of several downstream signaling molecules known to be involved in cellular proliferation in a concentration- and time-dependent manner. These studies indicate that the presence of GIP receptors in CRC may enable ligand binding and, in so doing, stimulate CRC cell proliferation. The overexpression of GIP, which occurs in obesity, might thereby be contributing to the enhanced rate of carcinogenesis observed in obesity.

Discovery of notch-sparing gamma-secretase inhibitors.

Overwhelming evidence supports a central role for the amyloid beta-peptide (Abeta) in the pathogenesis of Alzheimer's disease (AD), and the proteases that produce Abeta from its precursor protein APP are top targets for therapeutic intervention. Considerable effort has focused on targeting gamma-secretase, which generates the C-terminus of Abeta; however, gamma-secretase inhibitors cause serious toxicities due to interference with the Notch signaling pathway. We have been working toward compounds that directly alter gamma-secretase activity to reduce Abeta production without affecting the proteolysis of Notch. Using purified enzyme and substrate, we have shown that gamma-secretase can be selectively inhibited in this way by naphthyl-substituted gamma-aminoketones and gamma-aminoalcohols. These early hits, however, suffered from chemical instability and/or poor potency. Iterative design, synthesis and evaluation have led to the discovery of Notch-sparing gamma-secretase inhibitors with substantially increased potencies in biochemical and cellular assays. These compounds are of low molecular weight and are under evaluation for drug-like properties. The discovery and development of these compounds will be discussed.

Expression of glucose-dependent insulinotropic polypeptide in the zebrafish.

In mammals, glucose-dependent insulinotropic polypeptide (GIP) is synthesized predominately in the small intestine and functions in conjunction with insulin to promote nutrient deposition. However, little is known regarding GIP expression and function in early vertebrates like the zebrafish, a model organism representing an early stage in the evolutionary development of the compound vertebrate pancreas. Analysis of GIP and insulin (insa) expression in zebrafish larvae by RT-PCR demonstrated that although insa was detected as early as 24 h postfertilization (hpf), GIP expression was not demonstrated until 72 hpf, shortly after the completion of endocrine pancreatic development but prior to the commencement of independent feeding. Furthermore, whole mount in situ hybridization of zebrafish larvae showed expression of GIP and insa in the same tissues, and in adult zebrafish, RT-PCR and immunohistochemistry demonstrated GIP expression in both the intestine and the pancreas. Receptor activation studies showed that zebrafish GIP was capable of activating the rat GIP receptor. Although previous studies have identified four receptors with glucagon receptor-like sequences in the zebrafish, one of which possesses the capacity to bind GIP, a functional analysis of these receptors has not been performed. This study demonstrates interactions between the latter receptor and zebrafish GIP, identifying it as a potential in vivo target for the ligand. Finally, food deprivation studies in larvae demonstrated an increase in GIP and proglucagon II mRNA levels in response to fasting. In conclusion, the results of these studies suggest that although the zebrafish appears to be a model of an early stage of evolutionary development of GIP expression, the peptide may not possess incretin properties in this species.