Inhibiting adipose tissue M1 cytokine expression decreases DPP4 activity and insulin resistance in a type 2 diabetes mellitus mouse model

PLoS One. 2021 May 27;16(5):e0252153. doi: 10.1371/journal.pone.0252153. eCollection 2021.

Abstract

Adipose tissue inflammation is a major cause of the pathogenesis of obesity and comorbidities. To study the involvement of M1/M2 cytokine expression of adipose tissue in the regulatory mechanisms of dipeptidyl peptidase 4 (DPP4) and insulin resistance in diabetes, stromal vascular fractions (SVFs) were purified from inguinal adipose tissue of diabetic (Leprdb/db) and non-diabetic (Lepr+/+) mice followed by analysis of M1/M2 cytokine expression. SVFs of Leprdb/db mice exhibited increased TNF-α, IL-6, IL-1β, CCL2, and DPP4 mRNA expression but decreased IL-10 mRNA expression. Plasma from Leprdb/db mice induced TNF-α, IL-6, IL-1β, CCL2, and DPP4 mRNA expression and plasma from Lepr+/+ mice induced IL-10 mRNA expression in SVFs from Leprdb/db mice. Injection of Lepr+/+ plasma into the adipose tissue of Leprdb/db mice decreased mRNA expression of TNF-α, IL-6, IL-1β, CCL2, and DPP4 and protein expression of pJNK and DPP4 in SVFs, reduced mRNA expression of ICAM, FMO3, IL-1β, iNOS, TNF-α, IL-6, and DPP4 and protein expression of ICAM, FMO3, and DPP4 in liver, and suppressed mRNA expression of TNF-α, IL-6, IL-1β, and DPP4 in Kupffer cells. Plasma from Leprdb/db mice did not induce M1 cytokine expression in SVFs from Leprdb/db-Jnk1-/- mice. Altogether, we demonstrate that diabetes induces M1 but decreases M2 cytokine expression in adipose tissue. Diabetic plasma-induced M1 expression is potentially through pJNK signaling pathways. Non-diabetic plasma reverses M1/M2 cytokine expression, plasma CCL2 levels, DPP4 activity, and Kupffer cell activation in diabetes. Our results suggest M1/M2 cytokine expression in adipose tissue is critical in diabetes-induced DPP4 activity, liver inflammation, and insulin resistance.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cytokines / metabolism
  • Diabetes Mellitus, Experimental / metabolism*
  • Dipeptidyl Peptidase 4 / metabolism*
  • Female
  • Insulin Resistance*
  • Male
  • Mice
  • Mice, Inbred C57BL
  • Mice, Knockout

Substances

  • Cytokines
  • Dipeptidyl Peptidase 4
  • Dpp4 protein, mouse

Grants and funding

LW Chen: National Science Council (MOST 107-2314-B-010-043-MY3) www.most.gov.tw LW Chen: Kaohsiung Veterans General Hospital (VGHKS109-097) www.vghks.gov.tw The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.