Steady-state energy balance in animal models of obesity and weight loss.

OBJECTIVE: We wanted to exam the steady-state energy balance by using high-fat diet-induced obese (DIO) rats and mice as models for positive energy balance, and gastric bypassed (GB) rats and gene knockout of muscarinic acetylcholine M3 receptor (M3KO) mice as models for negative energy balance. METHODS: One hundred and thirty-two rats and mice were used. Energy balance was measured by a comprehensive laboratory animal monitoring system. Gene expression was analysed by in situ hybridisation in M3KO mice. RESULTS: DIO rats reached the plateau of body weight 28 weeks after starting high-fat diet (25% heavier than controls), whereas DIO mice reached the plateau after 6 weeks (23% heavier than controls). At the plateau, DIO rats had higher calorie intake during the light phase but not during the dark phase, while mice had the same calorie intake per day as controls. DIO rats and mice had lower energy expenditure (EE) and respiratory exchange ratio (RER) than controls. GB-rats reached the plateau (15% weight loss) 2 weeks after surgery and had the same calorie intake as sham-operated controls. EE, but not RER, was higher in GB rats than controls during the dark phase. The lean M3KO mice (25% lighter than wild-type (WT) mice at the plateau between 6 and 15 months of age) had the same calorie intake but higher EE, RER and hypothalamic mRNA expression of NPY, AgRP and leptin receptor than WT mice. CONCLUSION: When body weight gain or loss reached a plateau, the steady-state energy balance was mainly maintained by EE and/or RER rather than calorie intake.

Topical application of acetic acid in cytoreduction of gastric cancer. A technical report using mouse model.

BACKGROUND AND AIM: Application of acetic acid topically to the mucosal or serosal side of the stomach has been well used to create a chronic gastric ulcer model. The aim of the present study was to apply it as a new cytoreductive approach in a mouse model of gastric cancer. METHODS: A total of 43 genetically engineered mice, the so-called (INS-GAS) mice that develop spontaneously gastric cancer at 10-14 months of age, were included. Acetic acid-induced ulcer method was applied to mice under isofluran anesthesia. The ulcer at the cancer side was made by exposing either the anterior serosal or posterior mucosal side of gastric wall to 0.1 mL of 60% or 100% acetic acid for 30 or 60 s with a cylindrical metal mold (4 mm ID). Route to the serosal side was intra-abdominal and one to the mucosal side was through a small hole made in the forestomach. The opposite side of gastric wall (no treatment with acetic acid) was used as the corresponding control. After the mice were sacrificed, the stomachs were collected 1, 3, 6 h or 1, 3 and 7 days, postoperatively, and evaluated by visual inspection and histology. RESULTS: Gastric cancer was found in both the anterior and posterior walls of the corpus in all 43 mice. Intraluminal pH value was between 11 and 13. Severe necrosis in the cancer was observed in the side exposing to acetic acid, but not in the control side, shortly after the treatment (i.e. within 30 or 60 min). The muscularis mucosa and muscle layers were less damaged, regardless of the side of the treatment. Ulcer formation in the cancer took place 1, 3 or 7 days later. The ulcer depth was sometimes at the muscularis mucosa and muscle layers. At 3 and 7 days, regeneration of epithelial cells was clearly observed in the ulcer margin in the stomach of mice. CONCLUSIONS: Topical application of acetic acid either from mucosal or serosal surface promptly caused the necrosis of tumor, suggesting the potential approach of this simple and reliable method as a cytoreductive treatment of gastric cancer in patients through endoscopy or laparoscopy.

Characterization and Fitness Cost of Tn7100, a Novel Integrative and Conjugative Element Conferring Multidrug Resistance in Haemophilus influenzae.

A multidrug-resistant (MDR) strain of Haemophilus influenzae, Hi-228, with phenotypic resistance toward ampicillin, cefotaxime, chloramphenicol, gentamicin, and azithromycin, was isolated in Oslo, Norway. The strain was part of a clonal outbreak (2016-2017) comprising five ST143 strains with identical resistotypes. Hi-228 carries a novel integrative and conjugative element (ICE), Tn7100, contributing to this remarkable and previously unreported MDR profile. Tn7100 contains the following resistance genes: bla TEM-1B, catA2, aac(6')-Im, aph(2″)-Ib, mef (E), and mel. The latter four are previously unreported or rarely reported in H. influenzae. In this study, we investigated the genetic environment, mechanisms of transfer, impact on phenotypic susceptibility, and fitness cost of this ICE. We found that Tn7100 has an overall structure similar to the previously described ICE Tn6686, with bla TEM-1B and catA2 carried by Tn3 and Tn10, respectively. The major difference between Tn7100 and Tn6686 is that Tn7100 lacks tet(B) but carries the resistance gene pairs aac(6')-Im and aph(2″)-Ib and mef (E) and mel. The gene pairs are located on the novel transposable elements Tn7470 and Tn7471, which have high sequence identities to a plasmid in Enterobacterales and an ICE in streptococcal species, respectively. Tn7100 does circularize and is transferable, however, at a low frequency. Head-to-head competition experiments showed that uptake of Tn7100 reduces bacterial fitness. Our study shows that MDR strains are capable of clonal spread and that the H. influenzae supragenome comprises an increasingly wide range of transferable resistance genes, with evidence of transfer from unrelated genera. The findings offer a glimpse into the genome dynamics of H. influenzae, highlighting the importance of rational antibiotic usage to contain antimicrobial resistance and the emergence of MDR strains in this important pathogen.

New Approaches for Weight Loss: Experiments Using Animal Models.

The number of people who are overweight and obese are continuously increasing both in the adult and adolescent populations. Coinciding with this is the increased prevalence of health problems such as type 2 diabetes (T2D). Bariatric surgery is the only proven long-term treatment of obesity and may induce remission of T2D, although the underlying mechanisms are unknown. The translational studies presented here might provide insight on the mechanism of steady-state energy balance of the obese phenotype using a special time-restricted feeding regimen for weight loss during the steady-state energy balance; mechanism by vagal blocking therapy (vBLoc® therapy) as a new treatment for obesity; and possible mechanism behind the remission of T2D following gastric bypass surgery.

Vagal Blocking for Obesity Control: a Possible Mechanism-Of-Action.

BACKGROUND: Recently, the US FDA has approved "vagal blocking therapy or vBLoc® therapy" as a new treatment for obesity. The aim of the present study was to study the mechanism-of-action of "VBLOC" in rat models. METHODS: Rats were implanted with VBLOC, an intra-abdominal electrical device with leads placed around gastric vagal trunks through an abdominal incision and controlled by wireless device. Body weight, food intake, hunger/satiety, and metabolic parameters were monitored by a comprehensive laboratory animal monitoring system. Brain-gut responses were analyzed physiologically. RESULTS: VBLOC reduced body weight and food intake, which was associated with increased satiety but not with decreased hunger. Brain activities in response to VBLOC included increased gene expression of leptin and CCKb receptors, interleukin-1ß, tumor necrosis factor, and transforming growth factor ß1 in the brainstem; increased CCK, somatostatin, and tyrosine hydroxylase in the hippocampus; increased NPY, AgRP, and Foxa2 in the hypothalamus; and reduced CCKb receptor, melanocortin 4 receptor, and insulin receptor in the hypothalamus. Plasma concentrations of CCK, gastrin, glucagon, GLP-1, and PYY and gastric acid secretion were unchanged in response to VBLOC. CONCLUSIONS: Based on the present study, we may suggest that VBLOC induces satiety through vagal signaling, leading to reduced food intake and loss of body weight.

PYY-Dependent Restoration of Impaired Insulin and Glucagon Secretion in Type 2 Diabetes following Roux-En-Y Gastric Bypass Surgery.

Roux-en-Y gastric bypass (RYGB) is a weight-reduction procedure resulting in rapid resolution of type 2 diabetes (T2D). The role of pancreatic islet function in this restoration of normoglycemia has not been fully elucidated. Using the diabetic Goto-Kakizaki (GK) rat model, we demonstrate that RYGB restores normal glucose regulation of glucagon and insulin secretion and normalizes islet morphology. Culture of isolated islets with serum from RYGB animals mimicked these effects, implicating a humoral factor. These latter effects were reversed following neutralization of the gut hormone peptide tyrosine tyrosine (PYY) but persisted in the presence of a glucagon-like peptide-1 (GLP-1) receptor antagonist. The effects of RYGB on secretion were replicated by chronic exposure of diabetic rat islets to PYY in vitro. These findings indicate that the mechanism underlying T2D remission may be mediated by PYY and suggest that drugs promoting PYY release or action may restore pancreatic islet function in T2D.

Denervation suppresses gastric tumorigenesis.

The nervous system plays an important role in the regulation of epithelial homeostasis and has also been postulated to play a role in tumorigenesis. We provide evidence that proper innervation is critical at all stages of gastric tumorigenesis. In three separate mouse models of gastric cancer, surgical or pharmacological denervation of the stomach (bilateral or unilateral truncal vagotomy, or local injection of botulinum toxin type A) markedly reduced tumor incidence and progression, but only in the denervated portion of the stomach. Vagotomy or botulinum toxin type A treatment also enhanced the therapeutic effects of systemic chemotherapy and prolonged survival. Denervation-induced suppression of tumorigenesis was associated with inhibition of Wnt signaling and suppression of stem cell expansion. In gastric organoid cultures, neurons stimulated growth in a Wnt-mediated fashion through cholinergic signaling. Furthermore, pharmacological inhibition or genetic knockout of the muscarinic acetylcholine M3 receptor suppressed gastric tumorigenesis. In gastric cancer patients, tumor stage correlated with neural density and activated Wnt signaling, whereas vagotomy reduced the risk of gastric cancer. Together, our findings suggest that vagal innervation contributes to gastric tumorigenesis via M3 receptor-mediated Wnt signaling in the stem cells, and that denervation might represent a feasible strategy for the control of gastric cancer.

Eating behavior and glucagon-like peptide-1-producing cells in interposed ileum and pancreatic islets in rats subjected to ileal interposition associated with sleeve gastrectomy.

BACKGROUND: Ileal interposition-sleeve gastrectomy (II-SG) has been developed as a metabolic surgery based on the hindgut hypothesis. The aim of the present study was to test this hypothesis by studying the eating behavior, metabolic changes, and glucagon-like peptide-1 (GLP-1)-producing cells in rat models. METHODS: Male Sprague-Dawley rats were subjected to laparotomy, II, SG, or II-SG. Eating behavior and metabolic parameters were monitored by an open-circuit indirect calorimeter designed for a comprehensive laboratory animal monitoring system. GLP-1-producing cells were examined by quantitative immunohistochemistry. RESULTS: After II alone, satiety ratio, i.e., intermeal interval/meal size, was reduced, while calorie intake was increased at 2 and 6 weeks postoperatively. Respiratory exchange ratio, VCO(2)/VO(2), was increased to above 1.0 (i.e., carbohydrate metabolism) during both daytime and nighttime at 2 weeks postoperatively. After SG alone, GLP-1-producing cells were increased in the pancreatic islets (in terms of volume density), but not in the ileum (number/mm). After II-SG, the rate of eating was reduced, while meal duration (min) was increased during both daytime and nighttime at 2 weeks postoperatively. GLP-1-producing cells were increased by about 2.5-fold in the interposed ileum and also increased to the same extent in the pancreatic islets as seen after SG alone. The increased GLP-1-producing cells in the pancreatic islets after SG or II-SG were located around the insulin-producing ß cells. CONCLUSIONS: The present study provides evidence supporting the hindgut hypothesis. II-SG increased GLP-1 production both in the interposed ileum and in the pancreatic islets, leading to metabolic beneficial effects and altered eating behavior.

Mechanistic comparison between gastric bypass vs. duodenal switch with sleeve gastrectomy in rat models.

BACKGROUND: Both gastric bypass (GB) and duodenal switch with sleeve gastrectomy (DS) have been widely used as bariatric surgeries, and DS appears to be superior to GB. The aim of this study was to better understand the mechanisms leading to body weight loss by comparing these two procedures in experimental models of rats. METHODS: Animals were subjected to GB, DS or laparotomy (controls), and monitored by an open-circuit indirect calorimeter composed of comprehensive laboratory animal monitoring system and adiabatic bomb calorimeter. RESULTS: Body weight loss was greater after DS than GB. Food intake was reduced after DS but not GB. Energy expenditure was increased after either GB or DS. Fecal energy content was increased after DS but not GB. CONCLUSION: GB induced body weight loss by increasing energy expenditure, whereas DS induced greater body weight loss by reducing food intake, increasing energy expenditure and causing malabsorption in rat models.