Elevated Resting and Postprandial Digestive Proteolytic Activity in Peripheral Blood of Individuals With Type-2 Diabetes Mellitus, With Uncontrolled Cleavage of Insulin Receptors

J Am Coll Nutr. 2019 Aug;38(6):485-492. doi: 10.1080/07315724.2018.1545611. Epub 2019 Apr 9.


Objective: To examine resting and postprandial peripheral protease activity in healthy controls and individuals with type 2 diabetes mellitus (T2DM) and pre-T2DM. Methods: Individuals with T2DM or pre-T2DM and healthy controls (mean age 55.8 years) were studied before and for a span of 300 minutes following a single high-calorie McDonald's breakfast. Metalloproteases-2/-9 (MMP-2/-9), elastase, and trypsin activities were assessed in whole blood before and following the meal using a novel high-precision electrophoretic platform. Also assessed were circulating levels of inflammatory biomarkers and insulin receptor density on peripheral blood mononuclear cells (PBMCs) in relationship to protease activity. Results: Premeal MMP-2/-9 and elastase activity levels in T2DM and in pre-T2DM participants were significantly elevated as compared to controls. The T2DM group showed a significant increase in elastase activity 15 minutes after the meal; elastase activity continued to increase to the 30-minute time point (p < 0.01). In control participants, MMP-2/-9, elastase, and trypsin were significantly increased at 15 minutes after the meal (p < 0.05) and returned to premeal values within a period of approximately 30 to 60 minutes post meal. PBMCs incubated for 1 hour with plasma from T2DM and pre-T2DM participants had significantly lower levels of insulin receptor density compared to those incubated with plasma from control participants (p < 0.001). Conclusions: The results of this study suggest that individuals with T2DM and pre-T2DM have higher resting systemic protease activity than nonsymptomatic controls. A single high-calorie/high-carbohydrate meal results in further elevations of protease activity in the systemic circulation of T2DM and pre-T2DM, as well as in healthy controls. The protease activity in turn can lead to a downregulation of insulin receptor density, potentially supporting a state of insulin resistance.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Diabetes Mellitus, Type 2* / blood
  • Diabetes Mellitus, Type 2* / epidemiology
  • Diabetes Mellitus, Type 2* / physiopathology
  • Female
  • Humans
  • Male
  • Middle Aged
  • Peptide Hydrolases / blood*
  • Postprandial Period / physiology*
  • Receptor, Insulin* / blood
  • Receptor, Insulin* / metabolism
  • Rest / physiology


  • Receptor, Insulin
  • Peptide Hydrolases