Depletion of Regulatory T Cells in Visceral Adipose Tissues Contributes to Insulin Resistance in Hashimoto's Thyroiditis

Abstract

Hashimoto's Thyroiditis (HT) is a common organ-specific autoimmune disorder associated with a high incidence, and insulin resistance is highly related to autoimmune. Here, we examined the insulin sensitivity in HT patients and found decreased insulin sensitivity occurred in HT patients. To explore the relationship between impaired insulin sensitivity and immune status, we established HT model mice which showed similar pathological features and immune features to HT patients. In HT model mice, reinfusion of regulatory T cells (Tregs) from peripheral blood of normal mice could improve insulin sensitivity and decrease the inflammation. Anti-CD25 antibodies blocked beneficial effects from reinfusion of Tregs, but delayed administration of anti-CD25 antibodies could not abolished the effect from Tregs. Delayed administration of anti-CD25 antibodies abolished exogenous Tregs in peripheral blood, but there were increased exogenous Tregs located to visceral adipose tissues (VATs) which modulated the expression of cytokines in VATs. These findings suggest that insulin resistance exists in HT patients and it associates with the decreased Tregs and increased inflammation in the VATs.

Keywords: Hashimoto's Thyroiditis; cytokines; insulin resistance; regulatory T cells; visceral adipose tissues.

Figure 1

Abnormal insulin sensitivity and peripheral immune status are associated with HT patients. (A) Autoantibodies to thyroid peroxidase and thyroid globulin increased in HT patients (^*p < 0.05; ^**p < 0.01 compared with normal control). (B) Insulin sensitivity decreased in HT patients compared with normal control (^*p < 0.05; ^**p < 0.01 compared with normal control). (C) Lipid metabolism was not changed between HT patients and normal control. (D) Expression pattern of cytokines was changed between HT patients and normal control (^**p < 0.01 compared with normal control).

Figure 2

T cell subsets in peripheral blood were different between HT patients and normal control. (A) Increased CD4⁺ T cell and deceased CD8⁺ T cells were found in peripheral blood from HT patients (^*p < 0.05 compared with normal control). (B–E) Increased Th1 and Th17 cells were found in HT patients, but Tregs were decreased in HT patients (^*p < 0.05; ^**p < 0.01 compared with normal control).

Figure 3

Establishment of HT model mice and the insulin sensitivity of HT model mice was changed. (A) The progress of experiment design. (B) Bodies weight did not change between groups. (C,F,G) Thyroid weight was increased in HT model mice, and the reinfusion of Tregs improved the pathological changes (^*p < 0.05; ^**p < 0.01 compared with EAT group). (D,E) Insulin sensitivity of HT model mice was impaired compared with control mice.

Figure 4

Pathological changes were observed in HT model mice and the reinfusion of Tregs showed beneficial effects to HT model mice.

Figure 5

T cell subsets were changed in peripheral blood from HT model mice. (A) CD3⁺ cells were not changed in each groups. (B) Higher ratio of CD4⁺/CD8⁺ was found in HT model mice and the reinfusion of Tregs rescued imbalance of CD4⁺/CD8⁺ (^**p < 0.01 compared with EAT group). This beneficial effect was blocked by anti-CD25 antibodies. (C) CD25⁺Foxp3⁺ Tregs decreased in peripheral blood from HT model mice and they were rescued by the reinfusion of Tregs, but it was abolished by anti-CD25 antibodies (^**p < 0.01 compared with EAT group).

Figure 6

T cell subsets were changed in visceral adipose tissues from HT model mice. (A) CD3⁺ cells were not changed in each groups. (B) Higher ratio of CD4⁺/CD8⁺ was found in HT model mice and the reinfusion of Tregs rescued imbalance of CD4⁺/CD8⁺ (^**p < 0.01 compared with EAT group). This beneficial effect was blocked by anti-CD25 antibodies. (C) CD25⁺Foxp3⁺ Tregs decreased in visceral adipose tissues from HT model mice and they were rescued by the reinfusion of Tregs, and it was partly abolished by anti-CD25 antibodies (^**p < 0.01 compared with EAT group; ^*p < 0.01 compared with EAT group).

Figure 7

Administration of anti-CD25 antibodies after the reinfusion did not abolished the beneficial effects from exogenous Tregs. (A) Design of the experiment. (B) Insulin sensitivity was rescued even combined with anti-CD25 antibodies (^*p < 0.05; ^**p < 0.01 compared with EAT group). (C) We analyzed T cell subsets which were CD4⁺CD25⁺Foxp3⁺ Tregs, and delayed administration of anti-CD25 antibodies decreased exogenous Tregs in peripheral blood but not in visceral adipose tissues.

Figure 8

Reinfusion of Tregs changed the pattern of cytokines in both of peripheral blood and visceral adipose tissues. (A) Exogenous Tregs normalized the pattern of cytokines in peripheral blood of HT model mice, but it could be blocked by anti-CD25 antibodies (^*p < 0.05 compared with EAT group). (B) Exogenous Tregs normalized the pattern of cytokines in visceral adipose tissues of HT model mice, but it could be blocked by anti-CD25 antibodies (^*p < 0.05 compared with EAT group). (C) Exogenous Tregs normalized the pattern of cytokines in visceral adipose tissues of HT model mice, and it could not be blocked by delayed administration of anti-CD25 antibodies (^*p < 0.05 compared with EAT group).