Impact of GAD65 and IA2 autoantibodies on islet allograft survival

Introduction

Islet transplantation (ITx) shows promise in treating T1D, but the role of islet autoantibodies on graft survival has not been clearly elucidated. We aimed to analyze the effect of GAD65 and IA2 autoantibody status on graft survival and attainment of insulin independence in subjects with T1D who underwent ITx.

Method

We conducted a retrospective cohort study on 47 ITx recipients from 2000 to 2018. Islet infusion was performed via intrahepatic portal (n=44) or onto the omentum via laparoscopic approach (n=3). Immunosuppression involved anti-IL2 receptor antibody, anti-TNF, and dual combinations of sirolimus, tacrolimus, or mycophenolate mofetil (Edmonton-like) in 38 subjects (80.9%). T-cell depletion induction with Edmonton-like maintenance was used in 9 subjects (19%). GAD65 and IA2 autoantibodies were assessed pre-transplant and post-transplant (monthly) until graft failure, and categorized as persistently negative, persistently positive, or seroconverters. Graft survival was analyzed using U-Mann-Whitney test, and Quade's nonparametric ANCOVA adjusted for confounders. Kaplan-Meier and Log-Rank tests were employed to analyze attainment of insulin independence. P value <0.05 indicated statistical significance.

Results

ITx recipients with persistent autoantibody negativity (n = 21) showed longer graft function (98 [61 - 182] months) than those with persistent autoantibody positivity (n = 18; 38 [13 - 163] months), even after adjusting for immunosuppressive induction protocol (P = 0.027). Seroconverters (n=8) had a median graft survival time of 73 (7.7 - 167) months, which did not significantly differ from the other 2 groups. Subjects with persistently single antibody positivity to GAD65 (n = 8) had shorter graft survival compared to negative islet autoantibody (GAD65/IA2) subjects (n = 21; P = 0.016). Time of graft survival did not differ in subjects with single antibody positivity to IA2. The proportion of insulin independence attainment was similar irrespective of autoantibody status.

Conclusion

The persistence of islet autoantibodies, as markers of islet autoimmunity, may represent an underappreciated contributing factor to the failure of transplanted β cells. Whether induction with T-cell depletion may lead to improved graft survival, independent of islet autoantibody status, could not be evaluated in our cohort. Larger prospective studies are needed to further address the role of islet autoantibody status on islet graft survival.

Relationship of vaspin and apelin levels with insulin resistance and atherosclerosis in metabolic syndrome

AIMS

We aimed to investigate, circulating vaspin, apelin-12 and apelin-36 levels in subjects with metabolic syndrome (MetS) and also to search for the association of vaspin and apelin levels with insulin resistance (IR), high sensitivity C-reactive protein (HsCRP), Carotid Artery Intima-Media Thickness (CIMT) and cardiovascular risk factors.

METHODS

In this observational case-control study, a total of forty one patients with MetS (30 women and 11 men mean age, 41.3±9.4 years) and thirty nine healthy comparison subjects (27 women and 12 men; mean age, 38.4±6.1 years) were enrolled. Serum HsCRP, lipid profile, insulin levels and the homeostasis model assessment of insulin resistance (HOMA-IR) were evaluated. Apelin-12, apelin-36 and vaspin serum levels were measured via ELISA. High-resolution B-mode ultrasonography was performed.

RESULTS

The two study groups did not differ as to age, sex, blood pressure, smoking history. Vaspin, apelin-12 and apelin-36 levels were significantly elevated in patients with MetS when compared with that of control subjects (P<0.001). Serum vaspin levels showed a statistically significant association with CIMT (r=0.365, P<0.001) and HsCRP (r=0.316, P<0.01) levels, whereas both serum apelin-12 and 36 levels were positively correlated with HOMA-IR (r=0.344/0.462 P<0.01).

CONCLUSION

Based on the findings of this study, Serum vaspin and apelin levels were found significantly higher in patients with MetS than age-matched control subjects and significantly associated with coronary atherosclerosis. These adipocytokines might play a part in the pathogenesis of MetS. Also serum Apelin levels can be used as specific markers for insulin sensitivity in patients with MetS.