Study populations
Among 7426 patients with T2DM, a total of 2496 (33.61%) patients were using insulin therapy. Among these patients, two pregnant patients, two patients using systemic glucocorticoid, another 22 patients with changes in their lowering glucose drugs treatment in the last 3 months, and 134 patients with infection were excluded. Moreover, a hundred patients with positive glutamate decarboxylase antibody (GAD-Ab) were excluded. A total of 1863 patients completed IA measurement and were finally enrolled for analysis. There were 902 (48.4%) patients with IA > 5% (Fig. 1), and the mean IA level was 11.06 (10.39, 11.72) %.
Clinical characteristics of the patients with positive IAs.
Compared with patients with negative IA (IA ≤ 5%), patients with positive IAs (IA > 5%) was associated with higher age, diabetic duration, total cholesterol, low density lipoprotein-cholesterol (LDL-c), high density lipoprotein-cholesterol (HDL-c), fasting blood glucose (FBG), insulin levels, GAD-Ab levels, and the proportion of cancer. Alanine transferase (ALT), triglyceride and the proportion of smoking was lower in patients with IA > 5% than in the others (Table 1). To increase the specificity of IA, and reduce the ratio of false positive and false negative, we also analyzed the characteristics of patients with IA > 10% and IA < 1%. The further analysis showed that the differences of age, ALT, total cholesterol, triglyceride, LDL-c, FBG, insulin levels, GAD-Ab, and the proportion of smoking and the complication of cancer between patients with IA > 10% and ≤ 1% were enlarged. Moreover, HOMA2-IR was higher in patients with IA > 10% than in patients with IA ≤ 1%. HbA1c seemed also higher (but not statistically significant) in patients with IA > 10%. The prevalence of diabetic complications between the patients with positive and negative IA were all similar (Table 1).
Table 1
| IA ≤ 5% (n = 961) | IA > 5% (n = 902) | p value | IA ≤ 1% (n = 278) | IA > 10% (n = 581) | p value |
Age (year) | 63.1(62.3,63.9) | 64.5(63.7,65.2) | 0.029 | 62.6(61.1,64.2) | 65.4(64.5,66.4) | 0.004 |
Gender (male %) | 532(55.4) | 472(52.3) | 0.193 | 155(55.8) | 293(50.4) | 0.175 |
Smoking (%) | 176(18.3) | 120(13.3) | 0.003 | 69(24.8) | 68(11.7) | < 0.001 |
Family history (%) | 219(22.8) | 187(20.7) | 0.287 | 71(25.5) | 121(20.8) | 0.145 |
BMI (kg/m2) | 24.8(24.6,25) | 24.8(24.6,25) | 0.998 | 24.6(24.2,25.1) | 24.7(24.4,25.0) | 0.854 |
Diabetic duration (year) | 12.6(12.1,13) | 13.4(12.9,13.8) | 0.012 | 13.3(12.5,14.2) | 13.6(13.0,14.1) | 0.687 |
ALT (g/L) | 26.7(24.5,28.9) | 23.5(21.9,25.1) | 0.049 | 30.4(26.0,34.7) | 23.8(21.6,25.9) | < 0.001 |
AST (g/L) | 20.7(19.3,22.2) | 18.9(18,19.7) | 0.691 | 21.7(19.0,24.4) | 19.1(18.1,20.2) | 0.513 |
Creatinine (µmol/L) | 77.3(74.7,80) | 80.1(76.9,83.3) | 0.475 | 79.3(73.7,84.8) | 78.9(75.4,82.3) | 0.820 |
Uric Acid (µmol/L) | 308.5(302.2,314.8) | 307.6(300.1,315) | 0.361 | 310.8(299.4,322.2) | 302.3(293.1,311.5) | 0.083 |
Total cholesterol (mmol/L) | 4.7(4.4,5.1) | 4.8(4.4,5.1) | 0.032 | 4.3(4.1,4.4) | 4.6(4.4,4.8) | 0.004 |
Triglyceride (mmol/L) | 2(1.9,2.2) | 1.8(1.7,1.9) | 0.058 | 2.3(1.8,2.7) | 1.7(1.5,1.8) | 0.015 |
LDL-c (mmol/L) | 2(2,2.1) | 2.1(2.1,2.2) | 0.003 | 1.8(1.7,1.9) | 2.2(2.1,2.2) | < 0.001 |
HDL-c (mmol/L) | 1.2(1.2,1.2) | 1.2(1.2,1.3) | 0.053 | 1.2(1.2,1.3) | 1.3(1.2,1.3) | 0.675 |
White blood cell (×109) | 6(5.9,6.1) | 6(5.9,6.1) | 0.984 | 5.9(5.8,6.1) | 6.0(5.9,6.1) | 0.922 |
Neutrophil ratio (%) | 59.4(58.6,60.1) | 59.6(58.9,60.4) | 0.829 | 58.7(57.3,60.1) | 59.6(58.7,60.6) | 0.339 |
Hemoglobin (g/L) | 130.5(129,132) | 129.2(127.9,130.5) | 0.315 | 129.7(127.6,131.8) | 128(126.5,129.5) | 0.248 |
FBG (mmol/L) | 8.4(8.2,8.7) | 9.1(8.8,9.4) | < 0.001 | 7.9(7.5,8.3) | 9.0(8.7,9.4) | < 0.001 |
Fasting Insulin (mU/L) | 22.2(18.9,25.6) | 41.4(34.2,48.6) | < 0.001 | 27.4(21.5,33.2) | 54.0(43.8,64.3) | < 0.001 |
Insulin-120min (mU/L) | 54.4(49,59.7) | 93(79,107) | < 0.001 | 60.7(52.7,68.7) | 115.6(96.2,134.9) | < 0.001 |
Fasting CP (ng/ml) | 1.5(1.3,1.6) | 1.4(1.3,1.5) | 0.451 | 1.4(1,1.8) | 1.4(1.3,1.5) | 0.049 |
CP-120min (ng/ml) | 3.1(3,3.3) | 3(2.9,3.2) | 0.361 | 3.0(2.7,3.3) | 3.0(2.8,3.1) | 0.569 |
HOMA2-IR | 1.5(1.4,1.6) | 1.7(1.5,2) | 0.191 | 1.3(1.2,1.4) | 1.7(1.5,2) | 0.025 |
HOMA2-β (%) | 49.1(46.3,51.8) | 46.6(43.6,49.6) | 0.082 | 48.6(43.9,53.2) | 46.5(42.7,50.3) | 0.107 |
HbA1c (%) | 9(8.8,9.1) | 8.8(8.7,9) | 0.177 | 8.6(8.4,8.8) | 8.8(8.7,9.0) | 0.102 |
GAD-Ab (IU/ml) | 4.5(4.2,4.9) | 5.6(5.2,6) | < 0.001 | 3.3(2.7,3.9) | 5.5(5.0,6.0) | < 0.001 |
IA (%) | 2.2(2.1,2.3) | 20.4(19.3,21.5) | < 0.001 | 0.3(0.3,0.3) | 27.8(26.7,29.3) | < 0.001 |
Hypertension (%) | 566(58.9) | 547(60.6) | 0.450 | 176(63.3) | 346(59.6) | 0.297 |
Fatty liver (%) | 291(30.3) | 246(27.3) | 0.167 | 86(30.9) | 152(26.2) | 0.166 |
Cancer (%) | 36(3.7) | 63(7) | 0.002 | 5(1.8) | 44(7.6) | < 0.001 |
DKD (%) | 191(19.9) | 207(22.9) | 0.113 | 55(19.8) | 124(21.3) | 0.654 |
Neuropathy (%) | 257(26.7) | 273(30.3) | 0.100 | 72(25.9) | 168(28.9) | 0.372 |
Retinopathy (%) | 263(27.4) | 258(28.6) | 0.570 | 79(28.4) | 178(30.6) | 0.525 |
Atherosclerosis (%) | 662(68.9) | 638(70.7) | 0.391 | 188(67.6) | 416(71.6) | 0.233 |
Data are mean (95%CI) or number (percentage). IA, insulin antibody; BMI, body mass index; ALT, Alanine transferase; AST, Aspartate transferase; LDL-c, low density lipoprotein cholesterol; HDL-c, high density lipoprotein cholesterol; FBG, fasting blood glucose; CP, C peptide; HOMA2-IR, homeostasis model assessment 2 of insulin resistance; HOMA2-β, homeostasis model assessment 2 of β cell function. HbA1c, hemoglobin; GAD-Ab, glutamic acid decarboxylase antibody. |
Logistics regression analysis for risk factors of IA
To identify the factors that influenced IA levels, we performed a Logistics regression analysis, including factors which were different between IA positive and negative groups, such as age, diabetic duration, ALT, total cholesterol, triglyceride, LDL-c, FGB, GAD-Ab, HOMA2-IR, accompanied by cancer or smoking, and the kinds of oral hypoglycemic agents (OHAs) as independent variables. As a result, diabetic duration, ALT, triglyceride, FGB, GAD-Ab, kinds of OHAs, and cancer remained in the regression model and were significantly associated with IA levels (p all < 0.05, Table 2).
Table 2
Logistics regression analysis for risk factors of insulin antibodies.
| OR | 95% Confidence interval | p value |
Diabetes duration | 1.019 | 1.001 ~ 1.037 | 0.042 |
Kinds of OHAs | 0.875 | 0.771 ~ 0.991 | 0.036 |
ALT | 0.996 | 0.992 ~ 1.000 | 0.053 |
Triglyceride | 0.920 | 0.867 ~ 0.976 | 0.005 |
FBG | 1.069 | 1.029 ~ 1.111 | 0.001 |
GAD-Ab | 1.025 | 1.004 ~ 1.047 | 0.021 |
With cancer | 0.533 | 0.310 ~ 0.917 | 0.023 |
OR, odds ratio; OHAs, oral hypoglycemic agents; ALT, Alanine transferase; FBG, fasting blood glucose; LDL-c, low density lipoprotein cholesterol; GAD-Ab, glutamic acid decarboxylase antibody. |
Distribution and IA levels of patients treated with different insulin regimens
The proportion of different insulin therapy among the patients with T2DM using insulin therapy were shown in Fig. 2A. Among the insulin therapy regimens with the population more than 1%, glargine with OHAs was the most used (28.8%), and the patients using biphasic insulin aspart 30/50 constituted the largest proportion of patients with positive IAs (13.7%). The proportion of positive IAs was lowest in patients using glargine only (31.9%) and highest in patients using human insulin only (70.3%), p < 0.001 (Fig. 2A). After adjusted diabetic duration, ALT, triglyceride, FGB, kinds of OHAs, and cancer, which were risk factors in the logistics regression, the ANCOVA test showed that among the different insulin therapy regimens, glargine induced lowest IA levels (6.7[5.8,7.5], and insulin aspart caused highest IA levels (17.7[13.6,21.8] %), p < 0.001, Fig. 2B.
Effects of OHAs on IA levels.
Among the OHAs, α-glucosidase was the most used drug combined with insulin therapy (33.0%), and the proportion of positive IAs was highest in patients using thiazolidinediones (TZDs) (51.4%, p = 0.121, Fig. 3A). The IA levels in patients using sulfonylureas/glinides, metformin, and Dipeptidyl peptidase-4 (DPP-4) inhibitors were all significantly lower than in patients without these drugs (the controls were the patients using all the other OHAs and patients without any OHAs or glucagon-like peptide 1 receptor agonists (GLP-1RAs)) (p all < 0.01, Fig. 3B), and patients using DPP-4 inhibitors had lowest IA level (8.2[6.5,10.0] %, Fig. 3B). After adjust diabetic duration, ALT, triglyceride, FGB, and cancer, ANCOVA test showed that the differences between the patients with or without these drugs remained significant (DPP-4 inhibitors, p = 0.026; metformin, p = 0.002; sulfonylureas/glinides, p < 0.001). The proportion of patients treated with OHAs was 83.0% in patients taking insulin glargine, which was only 51.4% in patients using mixed insulin (biphasic aspart, biphasic lispro and biphasic human insulin) in the present study (p < 0.001). On the other hand, the proportion of patients who were using glargine and deremir were similar in patients with different OHAs (42.0-55.1%) except sulfonylureas/glinides (75.0%) (p < 0.001, Supplementary table 1).