Yuko Ishida

Identification of ghrelin in the house musk shrew (Suncus murinus): cDNA cloning, peptide purification and tissue distribution

Ghrelin is the endogenous ligand for the growth hormone (GH) secretagogue receptor, and the sequence of ghrelin has been determined in many species from fish to mammals. In the present study, to reveal the production of ghrelin in the house musk shrew (Suncus murinus, order: Insectivora, suncus is used as a laboratory name), we determined the cDNA sequence and structure of suncus ghrelin and also demonstrated the ghrelin-producing cells in the gastrointestinal tract. Results of cDNA cloning and mass spectrometry analysis revealed that suncus ghrelin is composed of 18 or 26 amino acid residues and that the 3rd Ser was acylated mainly by n-octanoic acid. The 10 amino acids of the N-terminal region of suncus mature ghrelin were consistent with those of other mammals. Quantitative RT-PCR revealed that suncus ghrelin mRNA is highly expressed in the gastric corpus and pyloric antrum, and low expression levels were found in various tissues, including the intestinal tract. Ghrelin cells were found only in the corpus and antrum by immunohistochemistry and in situ hybridization, and most of the ghrelin cells were closed-type cells with relatively rich cytoplasm and scattered in the glandular body and base of the gastric mucosa. The density of ghrelin cells in the corpus was significantly greater than that in the antrum. The results of this study together with our recent results regarding motilin production in the suncus indicate that the suncus will be a useful model animal for study of physiological function of the motilin/ghrelin family.

Molecular identification of GHS-R and GPR38 in Suncus murinus

We previously identified ghrelin and motilin genes in Suncus murinus (suncus), and also revealed that motilin induces phase III-like strong contractions in the suncus stomach in vivo, as observed in humans and dogs. Moreover, repeated migrating motor complexes were found in the gastrointestinal tract of suncus at regular 120-min intervals. We therefore proposed suncus as a small laboratory animal model for the study of gastrointestinal motility. In the present study, we identified growth hormone secretagogue receptor (GHS-R) and motilin receptor (GPR38) genes in the suncus. We also examined their tissue distribution throughout the body. The amino acids of suncus GHS-R and GPR38 showed high homology with those of other mammals and shared 42% amino acid identity. RT-PCR showed that both the receptors were expressed in the hypothalamus, medulla oblongata, pituitary gland and the nodose ganglion in the central nervous system. In addition, GHS-R mRNA expressions were detected throughout the stomach and intestine, whereas GPR38 was expressed in the gastric muscle layer, lower intestine, lungs, heart, and pituitary gland. These results suggest that ghrelin and motilin affect gut motility and energy metabolism via specific receptors expressed in the gastrointestinal tract and/or in the central nervous system of suncus.

Absorption of bovine angiogenin into peripheral blood of rats orally administered milk basic protein

Bovine angiogenin is a major component of the bone resorption inhibitory activity of milk basic protein (MBP). The intestinal absorption of bovine angiogenin was investigated in a rat model, where it was detected in an intact form in the peripheral blood after the oral administration of MBP. This finding demonstrates that orally administered bovine angiogenin is absorbed without being degraded.

Milk Basic Protein Facilitates Increased Bone Mass in Growing Mice

Milk basic protein (MBP) comprises a group of basic whey proteins and is effective in preventing bone loss by promoting bone deposition (bone formation) and suppressing withdrawn (bone resorption). We previously revealed the bone protective effects of MBP during life phases involving excessive bone resorption, such as in adults and postmenopausal women, and in animal models (ovariectomized rats and mice). However, it was unclear whether MBP increases bone mass during the growth stage, when there is more bone formation than resorption. We therefore investigated the effect of MBP supplementation on bone mass in 6-wk-old mice provided water supplemented with MBP [0.01%, 0.1%, 1.0% (w/w)] or deionized water (control) ad libitum for 10 wk. Analysis by micro-computerized tomography showed that MBP significantly increased tibia cortical bone mineral density and femur trabecular bone volume to tissue volume compared with mice provided deionized water. Next, the function of MBP in bone remodeling (bone formation and resorption) was evaluated using an in vitro system and the results demonstrated that MBP directly promoted osteoblast proliferation and inhibited osteoclastogenesis. Moreover, the plasma level of insulin-like growth factor-1 was increased by MBP supplementation, suggesting that MBP indirectly promoted osteoblast proliferation/differentiation. These effects enhance bone formation and/or inhibit bone resorption, resulting in increased bone mass in growing mice.

M2024 Ghrelin Stimulates Gastric Contraction in a Specific Physiological Condition In Vivo and In Vitro in the House Musk Shrew (Suncus Murinus), a Ghrelin-And Motilin-Producing Laboratory Animal

Background: While gastroparesis usually presents with nausea or vomiting, abdominal pain also may be part of the presenting illness. The importance of pain in gastroparesis and its associated factors are largely unexplored. Aims: Define abdominal pain prevalence in gastroparesis and relate to demography, etiology, severity, quality of life, gastric retention, and analgesic vs. prokinetic/antiemetic drug use. Methods: 339 gastroparesis patients were enrolled from 6 centers of the NIDDK Gastroparesis Clinical Research Consortium from 1/ 07-11/09. Survey, exam, and gastric emptying data were compared in those with pain vs. no pain and pain as the predominant symptom vs. predominant nausea or vomiting. Results: 243 patients (72%) noted abdominal pain; pain was the predominant symptom in 65 (19%) vs. nausea or vomiting in 194 (57%). On Patient Assessment of GI Symptoms surveys, upper abdominal pain scores were higher in those with pain (3.5±1.4) vs. no pain (1.9±1.8, P<0.0001). Lower abdominal pain scores also were higher with (2.3±1.7) vs. no pain (1.4±1.5, P<0.0001). Higher percentages of those with pain were women (86 vs. 76%, P= 0.04) and had idiopathic etiology (70 vs. 54%, P=0.007). Infection-like prodromes were similar with (17%) vs. no pain (19%, P=0.75). Investigator-rated gastroparesis severity was similar with vs. no pain (P=0.25). Patient Assessment of GI Quality of Life (PAGI-QOL) scores were lower with pain (2.3±1.1 vs. 2.8±1.1, P<0.0007). SF-36 physical function (P<0.0001), energy/fatigue (P=0.004), emotional wellbeing (P=0.02), social function (P= 0.0004), pain (P<0.0001), and general health (P=0.02) scores were lower with pain. 4 hr gastric retention (normal <10%) was similar with (32±24%) vs. no pain (33±22%, P=0.91). Opiate use was higher with pain (P<0.0001), while antidepressant (P=0.22), neuropathic pain modulator (P=0.10), prokinetic (P=0.40), and antiemetic (P=0.13) use did not significantly differ. Compared to those with predominant nausea or vomiting, patients with predominant pain had higher upper abdominal pain scores (P<0.0001), but similar severity (P= 0.91), lower abdominal pain scores (P=0.21), 4 hr gastric retention (P=0.96), PAGI-QOL and SF-36 scores (P=NS). Conclusions: Abdominal pain is prevalent in gastroparesis and is predominant in 1 in 5 patients. Pain, like nausea and vomiting, impairs quality of life. Pain is associated with female gender and idiopathic etiology but not gastric retention. Increased opiate use reflects its health care impact and underscores a need to investigate new treatment options for pain. Our findings provide insight into this important symptom and emphasize its negative influence in gastroparesis.