The goal of this study is to investigate the association between oxidative stress and telomere length shortening in the comorbid depression and diabetes. Therefore, 71 patients with newly diagnosed type 2 diabetes (T2D) and 52 subjects with normal glycemic level (control, Ctrl) were enrolled. Depressive status was identified with the Depression Subscale of Hospital Anxiety and Depression Scale (HADS-D). Leukocyte telomere length ratio (T/S ratio) was determined with quantitative PCR. Oxidative stress status was evaluated with 8-hydroxy-desoxyguanosine (8-OHdG) assay kit. Some other biochemical blood testing was also performed. The data showed that T2D patients had higher proportion of depression evaluated by the HADS-D (
Telomeres are tandem repeats of DNA sequence, TTAGGG at the end of eukaryotic chromosomes [
Recently increasing evidence showed the association between the shortening of leucocyte telomere length and several age-related diseases, including type 2 diabetes [
The association of psychological stress and illness with telomere length change has also been reported lately [
Although the telomere length decrease is identified in diabetic or depressive patients, respectively, there is no research work reported in the population of cooccurring depression and diabetes till now. Therefore, the aim of our study was to investigate the association between oxidative stress and telomere length shortening in the comorbid depression and diabetes.
A total of 71 patients with newly diagnosed type 2 diabetes (T2D) (male 40/female 31) were recruited from the Division of Endocrinology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China, between January 2011 and June 2012. The subjects were questioned about their medical history and family history. The enrolled subjects were diagnosed with T2D no more than 1 month and had not received any antidiabetic agents yet. The diagnosis of diabetes was in accordance with World Health Organization criteria (fasting plasma glucose ≥ 7 mmol/L or 2-hour plasma glucose ≥ 11.1 mmol/L) [
All subjects took physical examination by a physician. Blood pressure was measured in the sitting position after resting for 10 min. Waist circumference was measured midway between the lowest rib and the iliac crest in the upright standing position. Hip circumference was measured at the greater trochanter.
For screening of depression, we used the Depression Subscale of Hospital Anxiety and Depression Scale (HADS-D), which consists of 7 questions [
Participants were fasted overnight for 10 hours and had blood samples drawn from an antecubital vein, then immediately aliquoted into cryotubes as plasma, buffy coat, and red blood cells. Fasting plasma glucose (FPG) was measured using glucose oxidase method (AVE 2852 half auto biochemical analyzer), fasting insulin (FIN) was measured using electrochemiluminescence assay (Elecsys 2010, Roche Instrument Center AG), and HbA1c was measured using high pressure liquid chromatography (variant II, Bio-Rad). Peripheral insulin resistance was estimated by homeostasis model assessment (HOMA-IR = FIN
All buffy-coat cryotubes were stored in freezers at −80°C. Genomic DNA was extracted from peripheral white blood cells using the QG-Mini80 workflow with DB-S kit (Fujifilm Corporation, Tokyo, Japan) as instructed.
Telomere length ratio (T/S ration) was measured using a quantitative PCR-based technique [
The primers are as follows. Telomere-F 5′-CGGTTTGTTTGGGTTTGGGTTTGGGTTTGGGTTTGGGTT-3′. Telomere-R 5′-GGCTTGCCTTACCCTTACCCTTACCCTTACCCTTACCCT-3′.
Cycling conditions of telomere were as follows: 95°C incubation for 10 minutes followed by 35 cycles of 95°C for 15 seconds and 56°C for 1 min. As for the cycling conditions of
8-OHdG in leucocyte DNA was quantified with OxiSelect oxidative DNA damage ELISA kit (Cell Biolab, Inc, San Diego, USA), which can be used to evaluate the degree of antioxidant stress [
Analyses were performed with the SPSS 11.5 (SPSS) statistical package. Significance was defined as the
Subjects with and without T2D did not differ significantly in terms of the proportion of smokers, drinkers, and the use of aspirin, statin, and antihypertension drugs. The subjects in T2D group were significantly older than in the control group. The sex ratio was similar in the two groups.
The values of BMI, waist circumference, WHR, the values of systolic blood pressure, diastolic blood pressure, HbA1c, FPG, HOMA-IR, TC, TG, and 8-OHdG were higher in the patients with T2D, while the HDL level was lower in the T2D group. The T/S ratio in the T2D group was significantly shorter than in the control group (Table
Demographic, clinical, and biochemical parameters of the study subjects of T2D and Ctrl.
T2D |
Ctrl |
| |
---|---|---|---|
Age (yrs) |
|
|
0.028 |
Male [( |
40 (56.34) | 30 (57.69) | 0.881 |
Current smokers [( |
21 (29.58) | 14 (26.92) | 0.784 |
Current drinkers [( |
13 (18.31) | 8 (15.38) | 0.670 |
Use of aspirin [( |
8 (11.27) | 4 (7.69) | 0.509 |
Use of statin [( |
7 (9.86) | 4 (7.69) | 0.677 |
Use of antihypertensive drugs[( |
6 (8.45) | 5 (9.62) | 0.823 |
HADS-D score (point)* | 8 (6, 9) | 8 (6, 9) | 0.200 |
HADS-D ≥ 10 [( |
17 (23.9) | 5 (9.6) | 0.041 |
BMI (kg/m2) |
|
|
0.000 |
Waist circumstance (cm) | 87.5 (81.8, 94.0) | 82.0 (78.0, 86.0) | 0.000 |
WHR | 0.84 (0.77, 0.89) | 0.80 (0.74, 0.84) | 0.000 |
Systolic blood pressure (mmHg) | 132 (120, 141) | 127 (123, 130) | 0.040 |
Diastolic blood pressure (mmHg) | 81 (75, 88) | 74 (68, 80) | 0.000 |
HbA1c (%) | 8.29 (7.58, 8.90) | 5.10 (4.80, 5.40) | 0.000 |
FPG (mmol/L) |
|
|
0.000 |
FIN (mIU/L) | 11.44 (6.99, 13.29) | 12.22 (7.8, 14.32) | 0.520 |
HOMA-IR | 4.51 (2.73, 5.54) | 2.93 (2.00, 3.29) | 0.000 |
Total cholesterol (mmol/L) |
|
|
0.000 |
Triglyceride (mmol/L) | 1.86 (1.12, 2.31) | 1.20 (0.86, 1.32) | 0.000 |
HDL-cholesterol (mmol/L) |
|
|
0.020 |
LDL-cholesterol (mmol/L) |
|
|
0.050 |
8-OHdG (ng/mL) |
|
|
0.000 |
T/S ratio |
|
|
0.000 |
Data are means ± SD,
T2D: type 2 diabetic group, Ctrl: control group, HADS-D: Depression Subscale of Hospital Anxiety and Depression Scale, BMI: body mass index, WHR: waist-to-hip ratio, FPG: fasting plasma glucose, FIN: fasting insulin, HOMA-IR: homeostasis model assessment-insulin resistance
*The total score of HADS-D is 21 and depression was identified as the score ≥10.
T2D group was further divided into two subgroups as with depression [T2D(D+)] and without depression (T2D(D−)); similarly, Ctrl groups also were subclassified as Ctrl(D+) and Ctrl(D−). Among the four subgroups, no significant difference was found in the indexes of age, proportion of male, smokers, drinkers, drugs used, SBP, FIN, HDL, and LDL. Comparing with the T2D(D−) patients, the T2D(D+) ones had higher HADS-D scores and T/S ratio with similar level of BMI, WHR, SBP, DBP, HbA1c, FPG, HOMA-IR, lipids, and 8-OHdG. Comparing with Ctrl(D+) patients, the T2D(D+) ones had higher proportion of hypotensive drugs and higher level of HbA1c, FPG, and TC. No remarkable difference was found in T/S, HOMA-IR, and 8-OHdG. Comparing with the Ctrl(D−) subjects, the Ctrl(D+) ones had higher BMI besides HADS-D scores. The Ctrl(D−) also showed lower level of telomere length (Table
Demographic, clinical, and biochemical parameters of the study subjects of subgroups with/without depression in T2Da and Ctrlb groups.
T2D | Ctrl |
|
| |||
---|---|---|---|---|---|---|
D+ | D− | D+ | D− | |||
|
|
|
|
|||
Age (yrs) |
|
|
|
|
1.823 | 0.147 |
Male [( |
10 (58.82) | 24 (44.44) | 3 (50.00) | 19 (41.30) | — | 0.656 |
Current smokers [( |
5 (29.41) | 16 (29.63) | 2 (33.33) | 12 (26.09) | — | 0.971 |
Current drinkers [( |
2 (11.76) | 11 (20.37) | 1 (16.67) | 7 (15.22) | — | 0.834 |
Use of aspirin [( |
1 (5.88) | 7 (12.96) | 0 (0.00) | 4 (8.70) | — | 0.653 |
Use of statin [( |
3 (17.65) | 4 (7.41) | 1 (16.67) | 3 (6.52) | — | 0.474 |
Use of antihypertensive drugs [( |
3 (17.64)# | 3 (5.56)# | 0 (0.00) | 5 (10.87) | — | 0.00 |
HADS-D (point) | 12 (10, 12)*⊙ | 7 (6, 8)# | 12 (10, 12)* | 7 (6, 8) | — | 0.000 |
BMI (kg/m2) |
|
|
|
|
5.033 | 0.003 |
Waist circumstance (cm) | 87 (80, 91)* | 88 (82, 94)* | 81 (77, 87) | 82 (78, 86) | — | 0.000 |
WHR | 0.82 |
0.85 |
0.82 |
0.80 |
— | 0.006 |
Systolic blood pressure (mmHg) | 134 (120, 141) | 131 (120, 141) | 128 (123, 130) | 126 (123, 130) | — | 0.171 |
Diastolic blood pressure (mmHg) | 79 (70, 84) | 82 (75, 89)* | 78 (72, 85) | 74 (68, 131) | — | 0.004 |
HbA1c (%) | 8.4 (8, 9.1)*# | 8.2 (7.5, 8.7)*# | 5.3 (5.2, 5.5) | 5.1 (4.7, 5.4) | — | 0.000 |
FPG (mmol/L) |
|
|
|
|
101.427 | 0.000 |
FIN (mIU/L) | 12.55 |
11.09 |
12.95 |
12.00 |
— | 0.617 |
HOMA-IR | 5.54 |
4.19 |
3.09 |
2.91 |
— | 0.000 |
Total cholesterol (mmol/L) |
|
|
|
|
6.821 | 0.000 |
Triglyceride (mmol/L) |
1.89 |
1.91 |
1.74 |
1.23 |
— | 0.001 |
|
|
|
|
1.841 | 0.143 | |
LDL-cholesterol (mmol/L) |
|
|
|
|
1.458 | 0.229 |
8-OHdG (ng/mL) |
|
|
|
|
15.722 | 0.000 |
T/S ratio | 1.70 |
2.11 |
2.01 |
2.32 |
— | 0.000 |
Data are means ± SD,
T2D: type 2 diabetic group, Ctrl: control group, HADS-D: Depression Subscale of Hospital Anxiety and Depression Scale, BMI: body mass index, WHR: waist-to-hip ratio, FPG: fasting plasma glucose, FIN: fasting insulin, HOMA-IR: homeostasis model assessment-insulin resistance
asubgroup with/without depression in T2D is shown as T2D(D+)/T2D(D−), respectively,
bsubgroup with/without depression in Ctrl group is shown as Ctrl(D+)/Ctrl(D−), respectively.
The chi-square test showed that the T2D patients had higher proportion of depression than control subjects, evaluated by the HADS-D (
The correlation between T/S ratio and other factors was analyzed in the whole population of the two groups (
Correlation between T/S ratio and 8-OHdG(a), HADS-D (b), and age (c) in the whole population studied.
It was shown that HbA1c (
It was shown that HbA1c (
Stepwise multiple linear regression in T2D subjects was applied to evaluate independent predictors of T/S ratio. The results showed that both HADS-D and 8-OHdG were the major independent predictors of T/S ratio (
Predictors of leukocyte telomere length in type 2 diabetic patients.
Univariate analysis | Multiple linear regression | |||
---|---|---|---|---|
Unstandardized |
|
Unstandardized |
| |
Age | −0.027 | 0.000 | −0.012 |
0.002 |
BMI | 0.011 | 0.683 | ||
Waist circumference | −0.006 | 0.390 | ||
WHR | 0.074 | 0.920 | ||
SBP | −0.005 | 0.138 | −0.006 |
0.001 |
DBP | −0.002 | 0.748 | ||
FPG | −0.204 | 0.000 | −0.062 |
0.023 |
HbA1c | −0.287 | 0.000 | −0.157 |
0.000 |
FIN | −0.003 | 0.744 | ||
HOMA-IR | −0.026 | 0.135 | 0.016 |
0.097 |
Total cholesterol | −0.014 | 0.823 | ||
Triglyceride | −0.041 | 0.473 | ||
HDL | 0.28 | 0.242 | ||
LDL | −0.071 | 0.326 | ||
HADS-D | −0.115 | 0.000 | −0.057 |
0.000 |
8-OHdG | −0.599 | 0.000 | −0.238 |
0.001 |
The result showed that oxidative stress could play an important role in the mechanism of telomere length shortening. Reactive oxygen species may induce deoxyguanosine conversion to 8-OHdG in the cellular nucleus, which is then released into blood [
Interestingly, in diabetic group, the depressive ones had shorter telomere than those without depression, while their glycemia and 8-OHdG were in similar levels. That may be explained with the bias due to the small sample size in our study. Otherwise, there is the possibility that the depressive status might be more prone to induce telomere shortening throughout another mechanism rather than oxidative stress. Therefore, more studies must be made to answer this confusing question.
Insulin resistance is reported to be in relation to telomere length as the HOMA-IR and BMI are the important indexes for insulin resistance [
The development of depression may be related to many factors. Aged females are reported with higher risk of depression [
In this study, the status of depression was evaluated with the HADS-D. This scale was initially designed to identify depression in clinical psychiatric hospitals, yet it has also been adopted to screen depression in nonhospitalized population and considered to be accurate and convenient [
There are still some limitations in this study. Firstly, this is a cross-sectional study and the sample size was small. So we should draw the conclusion very carefully and prospective studies with large sample size are needed to verify the findings. Secondly, although only the newly diagnosed patients were enrolled in this study, the hyperglycemic status without obvious diabetic symptoms might exist earlier before the diabetes was diagnosed [
In summary, this study indicated that oxidative stress contributes to both telomere length shortening and depression development in newly diagnosed type 2 diabetic patients. What is more, in depression status some other mechanisms besides oxidative stress may also affect the telomere length. To fully elucidate the complicated interactions of diabetes and depression with oxidative stress and cell senility, more research work is needed in the future.
Type 2 diabetes
Control group
Telomere length ratio
Human 8-hydroxy-desoxyguanosine
The Depression Subscale of Hospital Anxiety and Depression Scale
Homeostasis model assessment-insulin resistance
Reactive oxygen species
Fasting plasma glucose
Fasting insulin
Total cholesterol
Triacylglycerols
High-density lipoprotein cholesterol
Low-density lipoprotein cholesterol
Body mass index
Waist-to-hip ratio.
The authors declare that they have no conflict of interests.
The authors thank all their colleagues working in the Department of Internal Medicine, Tongji Medical College, Huazhong University of Science and Technology. This work was supported in part by Grants from National Nature Science Foundation of China (no. 81070190), Nature Science Foundation of Hubei province (no. 2009CDB049 and no. 2011CDB207), and the Fundamental Research Funds for the Central Universities (HUST 2012QN190).