Upregulated NLRP3 Inflammasome Activation in Patients With Type 2 Diabetes

TLDR

Despite recent focus on the NLRP3 inflammasome’s role in type 2 diabetes, little is known about its ex‑vivo activation profile in diabetic patients. The study aimed to investigate patterns of NLRP3 inflammasome activation in monocyte‑derived macrophages from drug‑naïve newly diagnosed type 2 diabetes patients. Monocyte‑derived macrophages were isolated from these patients and stimulated ex‑vivo to assess inflammasome activation. MDMs from type 2 diabetic patients exhibited increased NLRP3, ASC, and proinflammatory cytokine expression, heightened IL‑1β maturation, IL‑18 secretion, and caspase‑1 cleavage upon danger‑signal stimulation, with mitochondrial ROS and NLRP3 required for IL‑1β synthesis, and metformin therapy reduced IL‑1β maturation via AMPK activation.

Abstract

Despite the recent attention focused on the roles of the nucleotide binding and oligomerization domain-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome in the pathogenesis of type 2 diabetes, little is known about the ex vivo profile of inflammasome activation in type 2 diabetic patients. In this study, we investigated patterns of NLRP3 inflammasome activation in monocyte-derived macrophages (MDMs) from drug-naïve patients with newly diagnosed type 2 diabetes. Type 2 diabetic subjects had significantly increased mRNA and protein expression of NLRP3, apoptosis-associated speck-like protein containing a CARD (ASC), and proinflammatory cytokines in MDMs cultured with autologous sera compared with healthy controls. Upregulated interleukin (IL)-1β maturation, IL-18 secretion, and caspase-1 cleavage were observed in MDMs from type 2 diabetic patients after stimulation with various danger molecules (ATP, high-mobility group protein B1, free fatty acids, islet amyloid polypeptide, and monosodium uric acid crystals). Mitochondrial reactive oxygen species and NLRP3 were required for IL-1β synthesis in MDMs. Finally, 2 months of therapy with the antidiabetic drug metformin significantly inhibited the maturation of IL-1β in MDMs from patients with type 2 diabetes through AMP-activated protein kinase (AMPK) activation. Taken together, these data suggest that NLRP3 inflammasome activation is elevated in myeloid cells from type 2 diabetic patients and that antidiabetic treatment with metformin contributes to modulation of inflammasome activation in type 2 diabetes.