Utility of Insulin Resistance in Estimating Cardiovascular Risk in Subjects with Type 1 Diabetes According to the Scores of the Steno Type 1 Risk Engine

BACKGROUND

We sought to assess the potential of insulin resistance (IR) for estimating cardiovascular disease (CVD) risk in adults with type 1 diabetes (T1DM) according to the scores of the Steno Type 1 Risk Engine (ST1RE).

METHODS

A total of 179 adults with T1DM (50.8% men, age 41.2 ± 13.1 years, duration of T1DM 16 (12-23) years) without established CVD were evaluated. IR was assessed by the estimation of insulin sensitivity (eIS) using two validated prediction equations: the estimated insulin sensitivity developed from the Pittsburgh Epidemiology of Diabetes Complications Study (eIS-EDC) and the estimated insulin sensitivity developed from Coronary Artery Calcification in T1DM Study (eIS-CACTI) ST1RE was used to estimate 10-year CVD risk and to classify subjects into three groups according to their risk: low (<10%; n = 105), moderate (10-20%; n = 53), and high (≥20%; n = 21).

RESULTS

Both eIS-EDC and eIS-CACTI correlated negatively with ST1RE scores (eIS-EDC: r = -0.636, p < 0.001; eIS-CACTI: r = -0.291, p < 0.001). The C-statistic for predicting moderate/high risk and high risk was 0.816 (95% confidence interval (CI): 0.754-0.878) and 0.843 (95% CI: 0.772-0.913), respectively, for the eIS-EDC equation, and was 0.686 (95% CI: 0.609-0.763) and 0.646 (95% CI: 0.513-0.778), respectively, for the eIS-CACTI equation. The eIS-EDC equation had a significantly higher C-statistic both for moderate-/high-risk (p = 0.001) and high-risk (p = 0.007) subjects. Two cut-off points of eIS-EDC were identified for detecting moderate/high risk (8.52 mg·kg^-1·min^-1; sensitivity 74% and specificity 76%) and high risk (8.08 mg·kg^-1·min^-1; sensitivity 65% and specificity 95%) with potential applicability in clinical practice.

CONCLUSIONS

eIS negatively correlates with the score of CVD risk in the ST1RE. Two cut-off points of eIS are reported with potential utility in clinical practice for detecting adults with T1DM with the highest CVD risk.

Arterial stiffness is highly correlated with the scores obtained from the Steno Type 1 Risk Engine in subjects with T1DM

Objectives

Currently used risk scores for type 2 diabetes mellitus (T2DM) clearly underestimate cardiovascular risk in type 1 diabetes (T1DM). Hence, there is a need to develop novel and specific risk-estimation tools for this population. We aimed to assess the relationship between the Steno Type 1 Risk Engine (ST1RE) and arterial stiffness (AS), and to identify potential cut-off points of interest in clinical practice.

Design and methods

A total of 179 patients with T1DM (50.8% men, mean age 41.2±13.1 years), without established cardiovascular disease, were evaluated for clinical and anthropometric data (including classical cardiovascular risk factors), and AS measured by aortic pulse-wave velocity (aPWV). The ST1RE was used to estimate 10-year cardiovascular risk and patients were classified into 3 groups: low- (<10%; n = 105), moderate- (10–20%; n = 53) and high-risk (≥20%; n = 21).

Results

When compared with the low- and moderate-risk groups, patients in the high-risk group were older, had higher prevalence of hypertension, dyslipidemia and insulin-resistance, and had higher body-mass index and HbA_1c. aPWV increased in parallel with estimated cardiovascular risk (6.4±1.0, 8.4±1.3 and 10.3±2.6m/s; p<0.001). As an evaluation of model performance, the C-statistic of aPWV was 0.914 (95% confidence interval [CI]:0.873–0.950) for predicting moderate/high-risk and 0.879 (95%CI:0.809–0.948) for high-risk, according to the ST1RE. The best cut-off points of aPWV were 7.3m/s (sensitivity:86%, specificity:83%) and 8.7m/s (sensitivity:76%, specificity:86%) for moderate/high- and high-risk, respectively.

Conclusions

AS is highly correlated with the scores obtained from the ST1RE. We have identified two cut-off points of AS that can clearly discriminate moderate/high- and high-risk T1DM patients, which could be of great value in clinical practice.

FGF-23/Vitamin D Axis in Type 1 Diabetes: The Potential Role of Mineral Metabolism in Arterial Stiffness

Objective

To investigate the usefulness of Fibroblast Growth Factor 23 (FGF-23) and vitamin D as possible biomarkers of pre-clinical atherosclerosis, assessed as arterial stiffness (AS), in a group of subjects with type 1 diabetes (T1DM) and no previous cardiovascular events.

Research Design and Methods

68 T1DM patients and 68 age- and sex-matched controls were evaluated for 1) age, sex, diabetes duration, physical activity, smoking, alcohol intake, BMI, blood pressure, fasting plasma glucose, HbA_1c, estimated glomerular filtration rate (eGFR) and lipid profile; 2) microvascular complications; 3) blood concentrations of FGF-23 and mineral metabolism parameters (calcium, phosphate, parathyroid hormone (PTH) and 25-hydroxy-vitamin D (25(OH)D)); 4) AS, assessed as aortic pulse wave velocity (aPWV); and 5) low-grade inflammation (hsCRP, IL-6, sTNFαR1, sTNFαR2) and endothelial dysfunction (ED) markers (ICAM-1, VCAM-1, E-Selectin).

Results

Patients with T1DM had higher aPWV compared with controls (p<0.001), but they did not present differences in 25(OH)D (70.3(50.4–86.2)nmol/L vs. 70.7(59.7–83.0)nmol/L; p = 0.462) and in FGF-23 plasma concentrations (70.1(38.4–151.9)RU/mL vs. 77.6(51.8–113.9)RU/mL; p = 0.329). In T1DM patients, higher concentrations of FGF-23 were positively associated with aPWV after adjusting for eGFR and classical cardiovascular risk factors (model 1: ß = 0.202, p = 0.026), other mineral metabolism parameters (model 2: ß = 0.214, p = 0.015), microvascular complications, low-grade inflammation and ED markers (model 3: ß = 0.170, p = 0.045). Lower 25(OH)D concentrations were also associated with higher aPWV after adjusting for all the above-mentioned factors (model 3: ß = -0.241, p = 0.015).

Conclusions

We conclude that both FGF-23 plasma concentrations (positively) and 25(OH)D serum concentrations (negatively) are associated with AS in patients with T1DM and no previous cardiovascular events.

The effect of age and sex on metabolism and urinary excretion of antipyrine

BACKGROUND

Drug-metabolizing capacity is generally reduced in the elderly. The purpose of this investigation was to study antipyrine clearance and metabolite excretion in old subjects of both sexes.

METHODS

Saliva clearance of antipyrine and the production clearances of antipyrine metabolites were studied in young and elderly volunteers of both sexes. Seventy-six elderly subjects (mean age 81 years) were compared with a group of 24 young subjects (mean age 29 years).

RESULTS

After oral administration, salivary antipyrine clearance declined with age in both males and females, whether or not this variable was corrected for weight, and antipyrine half-life was significantly prolonged in elderly groups of either sex. The percentage urinary excretion of the antipyrine metabolites (hydroxymethylantipyrine, HMA; norantipyrine, NORA; and 4-hydroxyantipyrine, OHA) was reduced at 48 h in the elderly compared to young subjects by 23%, 31%, and 10%, respectively, in males, and by 41%, 41%, and 24%, respectively, in females. The formation clearance of HMA was reduced by 47% in males and by 52% in females. NORA clearance declined by 42 and 56%, respectively, in males and females. A decrease of 30% in males and 44% in females was observed in OHA clearance.

CONCLUSIONS

The findings suggest that aging leads to altered disposition of antipyrine in both males and females and that the main metabolic pathways of the compound are not different in the elderly.

Accuracy of the one-sample method for determination of antipyrine clearance in elderly subjects

The purpose of this study was to evaluate the validity of the one-sample abbreviated method for determination of the pharmacokinetic parameters of antipyrine in the elderly. Antipyrine pharmacokinetics were studied in 15 elderly women (mean age 86 years). Antipyrine (1 g) was administered orally and pharmacokinetic parameters were determined by the one-sample (24 h) and multiple-sample (3, 6, 9, 12 and 24 h) methods. Mean antipyrine clearance for the one-sample study (19.72 +/- 1.51) was almost identical to that obtained with the multiple-sample approach (20.73 +/- 1.57), and the two methods were very well correlated (r = 0.989). Relative standard deviations between individual clearances values for multiple-sample vs. one-sample studies averaged 1.6%. Values of elimination half-life were likewise very similar for the abbreviated (17.41 +/- 1.21) and complete (17.99 +/- 1.09) methods, with a significant correlation (r = 0.857). Although values were underestimated by 10% in the one-sample approach, no difference in the volume of distribution with the multiple-sample study was observed. When the unbiased volume of distribution value was determined from the total elimination curve against time, the influence of biased volume of distribution resulted in a 5.1% deviation in antipyrine clearance in the one sample method. The findings indicate that antipyrine pharmacokinetic parameters can be estimated with reasonable precision and accuracy in the elderly using a simplified one-sample procedure.

Effects of aging on antipyrine clearance: predictive factors of metabolizing capacity

The purpose of this study was to identify variables that can account for the decline of antipyrine clearance (CLAP) in elderly adults and that may help predict a reduction in metabolizing capacity. For comparison, ClAP was determined in 177 elderly (mean age 82 years) and 25 young (mean age 29 years) volunteers. Antipyrine (1 g) was administered orally and ClAP was determined by the one-sample saliva method. Mean ClAP was reduced by 38% and antipyrine half-life increased by 64% in old subjects. Multiple regression analysis of ClAP revealed an independent value for age, serum aspartate transaminase (AST), and height in the elderly. The independent variables collectively accounted for 27% of the variance explained. Age, high serum AST, use of diuretics, and no consumption of drugs known to stimulate oxidative metabolism were selected by multivariate analysis (logistic model) as independent predictors of a low metabolizing capacity. The findings indicate that factors other than age may contribute to impaired hepatic oxidative metabolism in the elderly.

Assessment of antipyrine kinetics from saliva or plasma: influence of age

The purpose of this study was to investigate whether antipyrine estimation in saliva provides valid information on plasma antipyrine clearance (APCl) and can be useful as an index of changes in drug metabolism with age. Antipyrine kinetics was studied in 93 elderly (mean age 82 years) and 23 young (mean age 29 years) volunteers. Plasma antipyrine half-life (APt1/2) increased and plasma APCl declined with age. No significant difference between plasma- and saliva-derived parameters was found in either young or old subjects. However, the saliva/plasma ACCl ratio tended to increase with age. A highly significant correlation between saliva and plasma APCl or APt1/2 was found in young subjects. Values were less closely related in the elderly and the slope of the saliva/plasma APCl relationship was significantly different in both groups of subjects. Residual variance was higher in the regressions corresponding to the elderly. The findings in the study indicate that the relationship between saliva and plasma kinetics in young subjects becomes less reproducible with age.