Long-term consumption of fermented soybean-derived Chungkookjang enhances insulinotropic action unlike soybeans in 90% pancreatectomized diabetic rats

Eur J Nutr. 2007 Feb;46(1):44-52. doi: 10.1007/s00394-006-0630-y. Epub 2007 Jan 2.

Abstract

Background: We previously reported that Chungkookjang (CKJ), fermented unsalted soybeans, exhibited better anti-diabetic action than cooked soybeans (CSB) in vitro, but its effectiveness and mechanism have not been studied in vivo.

Aim of the study: We investigated whether CKJ modulated insulin resistance, insulin secretion, and pancreatic beta-cell growth and survival in 90% pancreatectomized (Px) diabetic rats.

Methods: The Px rats weighing 201 +/- 12 g were divided into four groups and fed for 8 weeks with a CSB diet, a CKJ diet, a casein diet, or a casein diet plus rosiglitazone (20 mg/kg body weight/day). With the exception of protein sources and contents of isoflavonoid aglycones and glycosides, the composition of the diets was made identical by adding soybean oil and cellulose to a casein diet. At the end of the experimental periods, hyperglycemic clamp was performed in conscious, unstressed and overnight fasted Px rats to measure insulin secretion capacity. Insulin/IGF-1 signaling was measured by immunoblotting in isolated islets from the treated rats, and beta-cell mass, proliferation and apoptosis were also determined by immunohistochemistry.

Results: After 8-week administration, CSB did not modulate glucose-stimulated insulin secretion, but surprisingly, CKJ enhanced insulin secretion. In addition, CKJ potentiated insulin/IGF-1 signaling in islets via the induction of insulin receptor substrate-2 expression, leading to increasing pancreatic duodenal homeobox-1, insulin promoter transcription factor. In parallel with the enhancement of the signaling, CKJ elevated pancreatic beta-cell hyperplasia by increasing its proliferation and decreasing apoptosis, whereas CSB did not.

Conclusion: Based on these results, the fermentation of soybeans predominantly with Bacillus subtilis generated isoflavonoid aglycones and small peptides, which improved insulinotropic action in islets of type 2 diabetic rats. Overall, the anti-diabetic action of CKJ was superior to CSB in type 2 diabetic rats.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Apoptosis / drug effects
  • Area Under Curve
  • Blood Glucose / metabolism
  • Cell Division / drug effects*
  • Cell Survival
  • Dexamethasone / pharmacology
  • Diabetes Mellitus / therapy*
  • Fermentation
  • Glucose Clamp Technique
  • Glycine max / chemistry*
  • Humans
  • Hypoglycemic Agents / administration & dosage
  • Hypoglycemic Agents / pharmacology*
  • Immunohistochemistry
  • Insulin / metabolism*
  • Insulin Resistance
  • Insulin Secretion
  • Insulin-Secreting Cells / drug effects*
  • Insulin-Secreting Cells / metabolism
  • Male
  • Pancreatectomy
  • Random Allocation
  • Rats
  • Rats, Sprague-Dawley
  • Soy Foods

Substances

  • Blood Glucose
  • Hypoglycemic Agents
  • Insulin
  • Dexamethasone