Increased Circulating IL-32 Is Associated With Placenta Macrophage-derived IL-32 and Gestational Diabetes Mellitus

Placenta-derived inflammation plays a vital role in the pathophysiology of gestational diabetes mellitus (GDM). IL-32 is a novel pro-inflammatory cytokine and metabolic regulator involved in the development of metabolic disease. We investigated the effect of IL-32 in GDM.

First-trimester C-reactive protein (CRP) level was monitored in a case-control study of 186 women with GDM and 186 women without. Placental tissue was lysed and analyzed by high-resolution liquid chromatography-tandem mass spectrometry. Circulating level of inflammatory cytokines IL-32, IL-6, and TNF-α were measured by ELISA kits. The expression of placenta-derived macrophages, inflammatory cytokines, and related pathway proteins were assessed by reverse transcriptase-quantitative PCR, western blot, immunohistochemistry, or immunofluorescence.

First-trimester CRP level in peripheral blood was closely associated with glucose and insulin resistance index and was an independent correlation with the development of GDM. High-resolution liquid chromatography-tandem mass spectrometry revealed that placenta-derived CRP expression was dramatically elevated in women with GDM. Interestingly, the expression of placenta-derived IL-32 was also increased and located in the macrophages of placental tissue. Meanwhile, the expression of IL-6, TNF-α, and p-p38 were up-regulated in the placental tissues with GDM. Either IL-6 or TNF-α was colocated with IL-32 in the placental tissue. Importantly, circulating IL-32 throughout pregnancy was increased in GDM and was related to placental-derived IL-32 expression, circulating IL-6, and TNF-α, glucose and insulin resistance index.

Increased circulating IL-32 throughout pregnancy was closely associated with placenta macrophage-derived IL-32 expression and GDM. First trimester IL-32 level in peripheral blood may serve to predict the development of GDM.