Influence of gastric inhibitory polypeptide on pentagastrinstimulated gastric acid secretion in patients with type 2 diabetes and healthy controls

AIM： Gastric inhibitory polypeptide is secreted from intestinal K-cells in response to nutrient ingestion and acts as an incretin hormone in human physiology. While animal experiments suggested a role for GIP as an inhibitor of gastric secretion, the GIP effects on gastric acid output in humans are still controversial. METHODS： Pentagastrin was administered at an infusion rate of 1 μg . kg^-1 . h^-1 over 300 min in 8 patients with type 2 diabetes （2 female, 6 male, 54± 10 years, BMI 30.5 ± 2.2 kg/m^2; no history of autonomic neuropathy） and 8 healthy subjects （2/6, 46 ± 6 years., 28.9 ± 5.3 kg/ m^2）. A hyperglycaemic clamp （140 mg/dl） was performed over 240 min. Placebo, GIP at a physiological dose （1 pmol . kg^-1 . min^-1）, and GIP at a pharmacological dose （4 mol . kg^-1 . min^-1） were administered over 60 min each. Boluses of placebo, 20 pmol GIP/kg, and 80 pmol GIP/kg were injected intravenously at the beginning of each infusion period, respectively. Gastric volume, acid and chloride output were analysed in 15-min intervals. Capillary and venous blood samples were drawn for the determination of glucose and total GIP. Statistics were carried out by repeated-measures ANOVA and one-way ANOVA. RESULTS： Plasma glucose concentrations during the hyperglycaemic clamp experiments were not different between patients with type 2 diabetes and controls. Steady-state GIP plasma levels were 61 ±8 and 79 ± 12 pmol/I during the low-dose and 327±35 and 327± 17 pmol/I during the high-dose infusion of GIP, in healthy control subjects and in patients with type 2 diabetes, respectively （P= 0.23 and p 0.99）. Pentagastrin markedly increased gastric acid and chloride secretion （P〈 0.001）. There were no significant differences in the rates of gastric acid or chloride output between the experimental periods with placebo or any dose of GIP. The temporal patterns of gastric acid and chloride secretion were similar in patients with type 2 diabetes and healthy controls （P= 0.86 and P= 0.61, respectively）. CONCLUSION： Pentagastrin-stimulated gastric acid secretion is similar in patients with type 2 diabetes and healthy controls. GIP administration does not influence gastric acid secretion at physiological or pharmacological plasma levels. Therefore, GIP appears to act as an incretin rather than as an enterogastrone in human physiology.

Rikkunshito increases peripheral incretin-hormone levels in humans and rats

BACKGROUND It was reported that rikkunshito(TJ-43)improved the cisplatin-induced decreases in the active form of ghrelin in plasma;however,other effects on gastrointestinal hormones have not been investigated.AIM To investigate the effects of TJ-43 on peripheral levels of incretin hormones,including gastric inhibitory polypeptide(GIP)and glucagon-like polypeptide-1(GLP-1),in humans and rats.METHODS Patients were divided into two groups,namely patients who received TJ-43 immediately following surgery[TJ-43(+)group]and those who received TJ-43 on postoperative day 21[TJ-43(-)group],and the plasma levels of active GIP and active GLP-1 were assessed.In animal experiments,rats were treated with TJ-43[rat(r)TJ-43(+)group]or without[rTJ-43(−)group]by gavage for 4 wk,and the plasma active GIP and active GLP-1 levels were measured.The expression of incretin hormones in the gastrointestinal tract and insulin in the pancreas were investigated by immunohistochemistry.Furthermore,the cyclic adenosine monophosphate activities were assessed in pancreatic tissues from rats treated with or without TJ-43 in vivo,and the blood glucose levels and plasma insulin levels were measured in rats treated with or without TJ-43 in oral glucose tolerance tests.RESULTS In humans,the active incretin hormone levels increased,and values were significantly greater in the TJ-43(+)group compared those in the TJ-43(-)group.In rats,the plasma active incretin levels significantly increased in the rTJ-43(+)group compared with those in the rTJ-43(-)group.GIP and GLP-1 expressions were enhanced by TJ-43 treatment.Moreover,plasma insulin levels increased and blood glucose levels were blunted in the rTJ-43(+)group.CONCLUSION The results show that TJ-43 may be beneficial for patients who undergo pancreatic surgery.

Cystic fibrosis-related diabetes:The unmet need

Cystic fibrosis(CF)is a common autosomal recessive disease.Life expectancy of patients with CF continues to improve mainly driven by the evolving therapies for CF-related organ dysfunction.The prevalence of CF-related diabetes(CFRD)increases exponentially as patients’age.Clinical care guidelines for CFRD from 2010,recommend insulin as the mainstay of treatment.Many patients with CFRD may not require exogenous insulin due to the heterogeneity of this clinical entity.Maintenance of euglycemia by enhancing endogenous insulin production,secretion and degradation with novel pharmacological therapies like glucagonlike peptide-1 agonist is an option that remains to be fully explored.As such,the scope of this article will focus on our perspective of glucagon-like peptide-1 receptor agonist in the context of CFRD.Other potential options such as sodiumglucose cotransporter-2 and dipeptidyl peptidase 4 inhibitors and their impact on this patient population is limited and further studies are required.