Hyposialylated IgG activates endothelial IgG receptor FcγRIIB to promote obesity-induced insulin resistance
Keiji Tanigaki, … , Philip W. Shaul, Chieko Mineo
Keiji Tanigaki, … , Philip W. Shaul, Chieko Mineo
Published November 27, 2017
Citation Information: J Clin Invest. 2018;128(1):309-322. https://doi.org/10.1172/JCI89333.
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Hyposialylated IgG activates endothelial IgG receptor FcγRIIB to promote obesity-induced insulin resistance

Abstract

Type 2 diabetes mellitus (T2DM) is a common complication of obesity. Here, we have shown that activation of the IgG receptor FcγRIIB in endothelium by hyposialylated IgG plays an important role in obesity-induced insulin resistance. Despite becoming obese on a high-fat diet (HFD), mice lacking FcγRIIB globally or selectively in endothelium were protected from insulin resistance as a result of the preservation of insulin delivery to skeletal muscle and resulting maintenance of muscle glucose disposal. IgG transfer in IgG-deficient mice implicated IgG as the pathogenetic ligand for endothelial FcγRIIB in obesity-induced insulin resistance. Moreover, IgG transferred from patients with T2DM but not from metabolically healthy subjects caused insulin resistance in IgG-deficient mice via FcγRIIB, indicating that similar processes may be operative in T2DM in humans. Mechanistically, the activation of FcγRIIB by IgG from obese mice impaired endothelial cell insulin transcytosis in culture and in vivo. These effects were attributed to hyposialylation of the Fc glycan, and IgG from T2DM patients was also hyposialylated. In HFD-fed mice, supplementation with the sialic acid precursor N-acetyl-D-mannosamine restored IgG sialylation and preserved insulin sensitivity without affecting weight gain. Thus, IgG sialylation and endothelial FcγRIIB may represent promising therapeutic targets to sever the link between obesity and T2DM.

Authors

Keiji Tanigaki, Anastasia Sacharidou, Jun Peng, Ken L. Chambliss, Ivan S. Yuhanna, Debabrata Ghosh, Mohamed Ahmed, Alexander J. Szalai, Wanpen Vongpatanasin, Robert F. Mattrey, Qiushi Chen, Parastoo Azadi, Ildiko Lingvay, Marina Botto, William L. Holland, Jennifer J. Kohler, Shashank R. Sirsi, Kenneth Hoyt, Philip W. Shaul, Chieko Mineo

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Figure 5

IgG from HFD-fed mice attenuates insulin-induced eNOS activation and transendothelial transport of insulin via FcγRIIB and eNOS antagonism, and IgG from T2DM subjects blunts insulin action in human endothelium via FcγRIIB.

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IgG from HFD-fed mice attenuates insulin-induced eNOS activation and tra...
(A) BAECs were preincubated for 30 minutes with IgG isolated from control diet–fed (Con-IgG) or HFD-fed (HFD-IgG, 10 μg/ml) mice, and eNOS activity stimulated by insulin (100 nM) was measured. n = 6. (B and C) BAECs were transfected with or without control RNAi or RNAi targeting FcγRIIB. Downregulation of FcγRIIB was assessed by immunoblotting (B) using anti-FcγRIIB or anti-eNOS antibody to evaluate protein loading. (C) Forty-eight hours after transfection, cells were pretreated with CRP (25 μg/ml), Con-IgG, or HFD-IgG (10 μg/ml) for thirty minutes, and eNOS activity stimulated by insulin was measured. n = 16. (D) HAECs were preincubated with Con-IgG or HFD-IgG (10 μg/ml), and eNOS activity under basal conditions or with insulin treatment was measured. n = 3. (E) Confluent HAEC monolayers on Transwells were preincubated for 30 minutes with CRP, Con-IgG, or HFD-IgG in the absence or presence of the NOS inhibitor L-NAME (2 mM) or the NO donor SNAP (100 nM). FITC-conjugated insulin (50 nM) was added to the upper chamber, and the amount of insulin transcytosed to the lower chamber was evaluated after 2 hours. n = 7. (F) Using the study design and methods described for E, endothelial cell insulin transcytosis was evaluated without versus with CRP, Con-IgG, or HFD-IgG treatment, in the presence of subtype-matched control antibody (C, 10 μg/ml) or the FcγRIIB-blocking antibody AT10 (BL, 10 μg/ml). n = 6. (G) Insulin-induced eNOS activation was evaluated in HAECs with or without treatment with IgG from nondiabetic individuals (Con) or T2DM patients. n = 6. (H) Additional NOS activity assays were performed in the presence of the subtype-matched control antibody (C) or the FcγRIIB-blocking antibody (BL). n = 3. Values represent the mean ± SEM. *P < 0.05, ***P < 0.005, and ****P < 0.001, by 1-way ANOVA with Tukey’s post-hoc test.