Beneficial effects of combination therapy of phloretin and metformin in streptozotocin-induced diabetic rats and improved insulin sensitivity in vitro

Food Funct. 2020 Jan 29;11(1):392-403. doi: 10.1039/c9fo01326a.

Abstract

The GLUT4 and PI3K/AKT signaling pathways are the key sensors of energy status and they regulate glucose and lipid metabolism. Phloretin activates the PI3K/AKT pathway by promoting GLUT4 translocation and expression, thereby improving glucose consumption and tolerance. As metformin can regulate glucose metabolism, we hypothesized that phloretin can amplify its gluco-regulatory effects. Male Sprague Dawley rats were fed with a high-fat and high-sugar diet for 8 weeks and injected with a low dose of streptozotocin to induce type 2 diabetes. The diabetic rats were randomized to receive phloretin (100 mg kg-1 d-1), metformin (250 mg kg-1 d-1), or phloretin + metformin via oral gavage for another 4 weeks. Random blood glucose, serum insulin, free fatty acid, total cholesterol, triglyceride, and low-density lipoprotein levels were detected in type 2 diabetic rats. Hematoxylin-eosin and Oil Red O staining were used to observe the pathological changes in the liver, pancreas, and adipose tissues of type 2 diabetic rats. The expression levels of IRS-1, PI3K, P-AKT, and GLUT4 in skeletal muscle were detected using western blotting. Phloretin plus metformin improved fasting blood glucose levels, glucose tolerance, and insulin sensitivity in type 2 diabetic rats. In addition, this combination reduced lipid accumulation, improved the pathological changes in the liver, pancreas, and adipose tissue, and increased IRS-1, PI3K, P-AKT, and GLUT4 expression in skeletal muscle and the liver of type 2 diabetic rats. Thus, phloretin can be used in a potential combination therapy with metformin for the prevention and rescue of type 2 diabetes.

MeSH terms

  • Adipose Tissue / pathology
  • Animals
  • Diabetes Mellitus, Experimental / drug therapy*
  • Glucose Transporter Type 4 / metabolism
  • Insulin Receptor Substrate Proteins / metabolism
  • Insulin Resistance*
  • Liver / pathology
  • Male
  • Metformin / therapeutic use*
  • Pancreas / pathology
  • Phloretin / therapeutic use*
  • Phosphatidylinositol 3-Kinases / metabolism
  • Proto-Oncogene Proteins c-akt / metabolism
  • Random Allocation
  • Rats
  • Rats, Sprague-Dawley
  • Signal Transduction / drug effects*

Substances

  • Glucose Transporter Type 4
  • Insulin Receptor Substrate Proteins
  • Slc2a4 protein, mouse
  • Metformin
  • Proto-Oncogene Proteins c-akt
  • Phloretin