Basic characteristics of the study population and sex differences:
In total, 260 women and 260 men younger than 65 years with T1D were included. Complete data for the purpose of this study were obtained from 227 men and 235 women (mean age 43.6 ± 13.6 years; mean duration of diabetes 22.1 ± 11.3 years). As shown in Table 1, women and men did not differ in the mean age and mean duration of the diabetes but women had higher HbA1c than men while men had higher HOMA-IR than women. Men reported more often smoking and history of hypertension than women. Women and men reported similar frequency of dyslipidemia and cardiovascular and microvascular disease. No differences between women and men were found for prevalence of polymorphism of the gene for cx37. Body mass index and waist circumference were higher in men, whereas total body fat content was higher in women. Women and men did not differ in pulse pressure and lipid parameters with the exception of AIP which was higher (i.e. less favorable) in men. Men had higher values of vitamin D and GGT than women and no differences were detected for hsCRP and FIB-4.
Regarding vascular parameters, women had lower ABI, TBI and higher ORI (less favorable value) than men, while men had higher CIMT, BSCar, BSFem, uACR and lower cystatin C clearance than women.
Table 1: Demographics and history data (all data are means ± SD, if not stated differently)
|
Women
(n=227)
|
Men
(n=235)
|
p
|
Age (years)
|
43.8 ± 12.7
|
43.3 ± 14.4
|
0.693
|
Duration of diabetes (years)
|
21.7 ± 10.2
|
22.5 ± 12.3
|
0.448
|
Prevalence of smoking (%)
|
31.9 %
|
43 %
|
0.011
|
Prevalence of hypertension (%)
|
37.9 %
|
49.8 %
|
< 0.001
|
Prevalence of dyslipidemia (%)
|
30.1 %
|
34.9 %
|
0.275
|
Gene for connexin 37 n (%) TT/CT/CC genotype
|
21/104/102 (9.3/45.8/44.9)
|
24/101/110
(10.2/43.0/46.8)
|
0.816
|
Prevalence of known ASCVD n (%)
|
21 (9.2)
|
30 (12.7)
|
0.239
|
Prevalence of retinopathy/treatment
n (%)
|
111/47 (48.8/20.8)
|
115/54 (48.9/23.1)
|
1.000/0.575
|
Prevalence of nephropathy n (%)
|
65 (28.6)
|
73 (30.6)
|
0.612
|
Prevalence of diabetic foot n (%)
|
17 (7.4)
|
27 (11.5)
|
0.156
|
Body mass index (kg.m-2)
|
25.4 ± 4.5
|
26.9 ± 4.2
|
< 0.001
|
Waist circumference (cm)
|
80.2 ± 10.7
|
92.4 ± 12.0
|
< 0.001
|
Total body fat (%)
|
27.9 ± 7.3
|
19.29 ± 7.6
|
< 0.001
|
Pulse pressure (mm Hg)
|
53.2 ± 13.4
|
55.7 ± 14.4
|
0.054
|
Non- HDL cholesterol (mmol/l)
|
3.18 ± 0.85
|
3.33 ± 0.91
|
0.068
|
Atherogenic index of plasma
|
-0.27 ± 0.26
|
-0.09 ± 0.27
|
< 0.001
|
Remnant cholesterol (mmol/l)
|
0.56 ± 0.37
|
0.60 ± 0.43
|
0.285
|
Lipoprotein (a) (mg/l)
|
254.1 ± 369.6
|
251.2 ± 332.1
|
0.929
|
hsCRP (mg/l)
|
2.21 ± 2.25
|
2.19 ± 3.29
|
0.939
|
HbA1c (mmol/mol)
|
68.1 ± 14.8
|
62.7 ± 14.6
|
< 0.001
|
HOMA-IR
|
0.99 ± 3.75
|
1.29 ± 2.88
|
< 0.001
|
Plasma vitamin D (nmol/l)
|
53.39 ± 27.17
|
58.12 ± 22.1
|
0.05
|
Gama-glutamyl transferase (ukat/l)
|
0.38 ± 0.35
|
0.63 ± 0.84
|
< 0.001
|
FIB-4
|
0.87 ± 0.49
|
0.98 ± 0.73
|
0.059
|
Ankle brachial index
|
1.04 ± 0.11
|
1.11 ± 0.18
|
< 0.001
|
Toe brachial index
|
0.8 ± 0.12
|
0.86 ± 0.14
|
< 0.001
|
CIMT (mm)
|
0.69 ± 0.16
|
0.76 ± 0.18
|
< 0.001
|
Belcaro score carotid I/II/III/IV n (%)
|
141/79/6/1 (61.7/35.2/2.6/0.004)
|
103/103/27/2
(43.8/43.8/11.5/0.008)
|
< 0.001
|
Belcaro score femoral I/II/III/IV n (%)
|
166/37/24/0
(72.7/16.3/10.6/0)
|
136/67/31/1
(57.9/28.5/13.2/0.004)
|
< 0.001
|
Oliva Roztocil index
|
0.27 ± 0.04
|
0.26 ± 0.04
|
< 0.001
|
Urine Albumine/Creatinine (mg/mol creatinine)
|
7.82 ± 37.37
|
17.3 ± 62.26
|
0.049
|
Cystatin C clearance (ml/s/1,73m2)
|
1.80 ± 0.65
|
1.49 ± 0.42
|
< 0.001
|
Abbreviations: ASCVD: cardiovascular disease of atherosclerotic origin, CIMT: intima-media thickness of common carotid artery, FIB-4: fibrosis 4 liver index, HOMA-IR: Homeostatic Model Assessment for Insulin Resistance, hsCRP -C-reactive protein measured by high sensitivity method
All patients were treated by intensified insulin therapy, 49% of women and 43% of men used the insulin pump therapy. In addition, 25% of women and 31% of men used continuous glucose sensors or flash glucose monitoring during last year regularly. In addition, 8% of women and 6% of men needed additional metformin therapy to improve their insulin sensitivity. Men were treated by higher mean insulin dose (0.66 ± 0.19 vs. 0.62 ± 0.22 IU/kg/day, p< 0.01) and more frequently treated by ACE/ARB1 inhibitors than women (46% vs. 35%, p< 0.01) while no difference was observed for hypolipidemic treatment (24% and 29%). In addition, 30% women reported menopausal status.
Determinants of directly measured vascular and renovascular parameters:
ABI (Figure 1a) was positively and strongly associated with age, moderately with waist circumference, with Lp(a) lower than 600 mg/l, and with GGT (p<0.001, p=0.029, p=0.025, and p=0.026 for GGT equal or more than 0.65 ukat/l, respectively) and it was inversely and strongly associated with female sex, pulse pressure, and inversely and moderately with RLPC (p=0.003, p<0.001, and p=0.022, respectively). No modifying effect of sex was observed. Regarding modifying effect of cx37 gene polymorphism, in CC homozygotes ABI was positively and moderately associated with RLPC (p=0.03) and it was inversely and moderately associated with GGT (p=0.032 for GGT equal or more than 0.65 ukat/l, respectively) and inversely and moderately with Lp(a) (p=0.027).
TBI (Figure 1b) was inversely and strongly associated with age, female sex, pulse pressure, and Lp(a) (p<0.001, p=0.01, p<0.001, and p=0.01, respectively) and it was inversely and moderately associated with hsCRP (p=0.035, with individual coefficients p=0.005-0.49 with the highest predicted values for hsCRP 0.5, followed by 1.5-2.5 and 0.5-1.5, respectively). Regarding modifying effect of sex, in females it was positively and moderately associated with higher body fat and with higher AIP, and inversely and strongly with history of smoking (p=0.029 and p=0.04, and p=0.01, respectively). Regarding modifying effect of cx37 gene, in CC homozygotes TBI was inversely and strongly associated with reported dyslipidemia (p=0.007) and positively and moderately with female sex (p=0.04).
Figure 1:
Determinants of Ankle brachial index (a) and Toe brachial index (b) in type 1 diabetes (x axis - logarithmic transformation of p-value/ p values depicted as inverse logarithm: longer bars correspond to lower p-value; black bars indicate significant association and/or modification by sex or connexin37 gene polymorphism; gray bars: no association and no interaction; minus/plus signs at the basis of the bars means positive or inverse association). Abbreviations: FIB-4- Fibrosis-4 Liver Index; GGT – gama-glutamyl transferase; HbA1c - glycated hemoglobin, HOMA-IR - Homeostatic Model Assessment for Insulin Resistance; Connexin37 gene CC - CC homozygotes
BSCar (Figure 2a) was strongly and positively associated with age, CC homozygosity, HbA1c, history of smoking, pulse pressure, and waist circumference (p<0.001, p=0.006, p=0.01, p<0.001, p<0.001, and p=0.002, respectively). No modifying effect of sex was observed. Regarding modifying effect of cx37 gene polymorphism, in CC homozygotes BSCar was inversely and strongly associated with RLPC and positively and moderately with AIP (p=0.01 and p=0.04, respectively).
BSFem (Figure 2b) was positively and strongly associated with age, HbA1c, smoking and waist circumference and moderately with female sex and pulse pressure (p<0.001, p=0.002, p=0.002, and p<0.001, and p=0.03 and p=0.03, respectively) and it was inversely and strongly associated with body fat (p<0.001). Regarding modifying effect of sex, in females BSFem was inversely and strongly associated with non-HDL cholesterol and positively and strongly with diabetes duration (p=0.007 and p=0.002, respectively). Regarding modifying effect of cx37 gene polymorphism, in CC homozygotes BSFem was positively and moderately associated with non-HDL cholesterol (p=0.02)
Figure 2: Determinants of Belcaro score of carotid (a) and femoral (b) arteries in type 1 diabetes
(x axis: p values depicted as inverse logarithm: longer bars correspond to lower p-value; black bars indicate significant association and/or modification by sex or connexin37 gene polymorphism; gray bars: no association and no interaction; minus/plus signs at the basis of the bars means positive or inverse association). Abbreviations: FIB-4- Fibrosis-4 Liver Index ; GGT – gama-glutamyl transferase; HbA1c - glycated hemoglobin, HOMA-IR - Homeostatic Model Assessment for Insulin Resistance, Connexin37 gene CC - CC homozygotes
CIMT was positively and strongly associated with age and non-HDL cholesterol, and moderately with diabetes duration and HbA1c (p<0.001 and p=0.007, and p=0.02 and p=0.02, respectively) and it was inversely and strongly associated with plasma vitamin D (p=0.009). Regarding modifying effect of sex, in females it was positively and moderately associated with Lp(a) (p=0.03) and inversely and moderately with non-HDL cholesterol (p=0.05). No modifying effect of cx37 gene polymorphism was detected.
uACR (Figure 3a) was positively and strongly associated with female sex, duration of diabetes, HbA1c, history of hypertension, pulse pressure, AIP and FIB-4, and moderately with RLPC, Lp(a) and CC homozygosity (p=0.003, p=0.01, p<0.001, p<0.001, p=0.004 p<0.001 and p=0.01, and p=0.02, p=0.02 and p=0.02, respectively) and it was inversely and strongly associated with body fat (p<0.001). Regarding modifying effect of sex, in females uACR was inversely and strongly associated with duration of diabetes (p=0.01). Regarding modifying effect of cx37 gene polymorphism, in CC homozygotes uACR was inversely and strongly associated with HbA1c (p=0.01).
ORI (Figure 3b) was positively and strongly associated with age, diabetes duration, smoking, and pulse pressure (p=0.002, p<0.001, p=0.004, and p<0.001, respectively) and it was inversely and moderately associated with female sex and strongly with plasma vitamin D (p=0.02 and p<0.001. respectively). Regarding modifying effect of sex, in females ORI was positively and strongly associated with plasma vitamin D (p=0.003). Regarding modifying effect of cx37 gene, in CC homozygotes ORI was positively and moderately associated with history of hypertension and RLPC (p=0.02 and p=0.02, respectively) and inversely and moderately with female sex (p=0.05).
Figure 3: Determinants of urine albumin/ creatinine ratio (a) and Oliva Roztocil index (b) in type 1 diabetes (x axis - logarithmic transformation of p-value/ p values depicted as inverse logarithm: longer bars correspond to lower p-value; black bars indicate significant association and/or modification by sex or connexin37 gene polymorphism; gray bars: no association and no interaction; minus/plus signs at the basis of the bars means positive or inverse association) Abbreviations: FIB-4- Fibrosis-4 Liver Index, GGT – gama-glutamyl transferase; HbA1c - glycated hemoglobin, HOMA-IR - Homeostatic Model Assessment for Insulin Resistance, ORI – Oliva Roztocil Index, Connexin37 gene CC - CC homozygotes
Cystatin C clearance was inversely and strongly associated with AIP, Lp(a), hypertension, and moderately with pulse pressure and smoking (p<0.001, p=0.01, p=0.01, and p=0.02 and p=0.02, respectively) and it was positively and moderately associated with age (p=0.05). Regarding modifying effect of sex, in females, cystatin C clearance was positively and moderately associated with age (p=0.02). Regarding modifying effect of cx37 gene, in CC homozygotes cystatin C clearance was associated positively and strongly with AIP (p=0.01).
Finally, regarding intercorrelations between continuous vascular parameters (ABI, TBI, uACR, ORI), inverse strong linear correlation was found only between TBI and ORI (r= -0.46).