title: Bariatric surgery and T2DM improvement mechanisms: a mathematical model.
abstract: BACKGROUND
  Consensus exists that several bariatric surgery procedures produce a rapid improvement of glucose homeostasis in obese diabetic patients, improvement apparently uncorrelated with the degree of eventual weight loss after surgery. Several hypotheses have been suggested to account for these results: among these, the anti-incretin, the ghrelin and the lower-intestinal dumping hypotheses have been discussed in the literature. Since no clear-cut experimental results are so far available to confirm or disprove any of these hypotheses, in the present work a mathematical model of the glucose-insulin-incretin system has been built, capable of expressing these three postulated mechanisms. The model has been populated with critically evaluated parameter values from the literature, and simulations under the three scenarios have been compared.
  
  
  RESULTS
  The modeling results seem to indicate that the suppression of ghrelin release is unlikely to determine major changes in short-term glucose control. The possible existence of an anti-incretin hormone would be supported if an experimental increase of GIP concentrations were evident post-surgery. Given that, on the contrary, collected evidence suggests that GIP concentrations decrease post-surgery, the lower-intestinal dumping hypothesis would seem to describe the mechanism most likely to produce the observed normalization of Type 2 Diabetes Mellitus (T2DM) after bariatric surgery.
  
  
  CONCLUSIONS
  The proposed model can help discriminate among competing hypotheses in a context where definitive data are not available and mechanisms are still not clear.
authors.affiliation: Department of Mathematics, Faculty of Science, Kasetsart University, Bangkok, Thailand.
authors.forename: Puntip
authors.initials: P
authors.lastname: Toghaw
authors.forename: Alice
authors.initials: A
authors.lastname: Matone
authors.forename: Yongwimon
authors.initials: Y
authors.lastname: Lenbury
authors.forename: Andrea
authors.initials: A
authors.lastname: De Gaetano
mesh_terms: D050110:Bariatric Surgery; D003924:Diabetes Mellitus, Type 2 / Q000150:complications* / Q000503:physiopathology / Q000601:surgery*; D018819:Dipeptidyl Peptidase 4 / Q000502:physiology; D005749:Gastric Inhibitory Polypeptide / Q000502:physiology; D054439:Ghrelin / Q000378:metabolism; D052216:Glucagon-Like Peptide 1 / Q000502:physiology; D005947:Glucose / Q000378:metabolism; D006801:Humans; D054795:Incretins / Q000037:antagonists & inhibitors / Q000502:physiology; D007328:Insulin / Q000502:physiology; D007422:Intestines / Q000503:physiopathology; D055641:Mathematical Concepts; D008954:Models, Biological; D009765:Obesity / Q000150:complications* / Q000503:physiopathology / Q000601:surgery*; D016896:Treatment Outcome
chemical_list: D054439:Ghrelin; D054795:Incretins; D007328:Insulin; D005749:Gastric Inhibitory Polypeptide; D052216:Glucagon-Like Peptide 1; C042807:DPP4 protein, human; D018819:Dipeptidyl Peptidase 4; D005947:Glucose