Recent Advances of Intervention to Inhibit Progression of Carotid Intima-Media Thickness in Patients With Type 2 Diabetes Mellitus

Carotid intima-media thickness as a surrogate marker of cardiovascular disease in diabetes

BACKGROUND

Diabetes mellitus is associated with a high risk of cardiovascular disease. Carotid intima-media thickness (CIMT) is increasingly used as a surrogate marker for atherosclerosis. Its use relies on its ability to predict future clinical cardiovascular end points.

METHODS

This review examines the evidence linking CIMT as a surrogate marker of vascular complications in people with type 1 and type 2 diabetes. We have also reviewed the various treatment strategies which have been shown to influence CIMT.

CONCLUSIONS

CIMT measurement is an effective, noninvasive tool which can assist in identifying people with diabetes who are at higher risk of developing microvascular and macrovascular complications. It may also help to evaluate the effectiveness of various treatment strategies used to treat people with diabetes.

Ultrasound protocols to measure carotid intima-media thickness in trials; comparison of reproducibility, rate of progression, and effect of intervention in subjects with familial hypercholesterolemia and subjects with mixed dyslipidemia

BACKGROUND

Current ultrasound protocols to measure carotid intima-media thickness (CIMT) in trials rather differ. The ideal protocol combines high reproducibility with a high precision in the measurement of the rate of change in CIMT over time and with a precise estimate of a treatment effect. To study these aspects, a post-hoc analysis was performed using data from two randomized double-blind, placebo-controlled trials: one among 872 subjects with familial hypercholesterolemia (FH) and the other among 752 subjects with mixed dyslipidemia (MD), respectively. Participants were randomized to torcetrapib or placebo on top of optimal atorvastatin therapy.

METHODS

CIMT information was collected from the left and right carotid artery from two walls (the near and far wall) of three segments (common carotid, bifurcation, and internal carotid artery) at four different angles (right: 90, 120, 150, and 180 degrees on Meijer's carotid arc; left: 270, 240, 210, and 180 degrees, respectively). Based on combinations of these measurements, 60 different protocols were constructed to estimate a CIMT measure per participant (20 protocols for mean common CIMT, 40 protocols for mean maximum CIMT). For each protocol we assessed reproducibility (intra-class correlation coefficient (ICC), mean difference of duplicate base-line scans); 2-year progression rate in the atorvastatin group with its standard error (SE); and treatment effect (difference in rate of change in CIMT between torcetrapib and placebo) with its SE.

RESULTS

Reproducibility: ICC ranged from 0.77 to 0.91 among FH patients and from 0.68 to 0.86 among MD patients. CIMT progression rates ranged from -0.0030 to 0.0020 mm/year in the FH trial and from 0.00084 to 0.01057 mm/year in the MD trial, with SE ranging from 0.00054 to 0.00162 and from 0.00083 to 0.00229, respectively. The difference in CIMT progression rate between treatment arms ranged from -0.00133 to 0.00400 mm/year in the FH trial and from -0.00231 to 0.00486 mm/year in the MD trial. The protocol with the highest reproducibility, highest CIMT progression/precision ratio, and the highest treatment effect/precision ratio were those measuring mean common CIMT with measurements of the near and far wall at multiple angles. When the interest is in the mean maximum CIMT, protocols using multiple segments and angles performed the best.

CONCLUSION

Our findings support the position that the number and specific combination of segments, angles, and walls interrogated are associated with differences in reproducibility, magnitude, and precision of progression of CIMT over time, and treatment effect. The best protocols were mean common CIMT protocols in which both the near and far walls are measured at multiple angles.

Carotid intima-media thickness in individuals with and without type 2 diabetes: a reproducibility study

Background

The use of carotid intima-media thickness (carotid IMT) as a surrogate marker of cardiovascular disease is increasing and the method has now also been applied in several trials investigating patients with type 2 diabetes (T2D). Even though knowledge about methodology is of highest importance in order to make accurate power calculations and analyses of results, no reproducibility studies have been performed in this group of patients. The aim of this study was to quantify the variability of the measurement of carotid IMT in individuals with and without T2D.

Methods

We used B-mode ultrasound and a computerized software programme (MIA vascular tools) for analysis of carotid IMT. Measurement of carotid IMT in the far wall of the common carotid artery (CCA) was done for 30 patients with T2D and 30 persons without T2D. The examinations were done by two different sonographers and two different readers on two separate days in order to quantify sonographer-, reader-, and day-to-day variability.

Results

Comparisons of measurement of carotid IMT in CCA between sonographers (sonographer variability) resulted in limits of agreement (LoA) from -0.18 to 0.13 mm for patients with T2D and -0.12 to 0.10 mm for persons without T2D. This means, that a second scanning of the same person with 95% probability would be within this interval of the first scanning. Comparisons between readers assessing the same scanning (reader variability) resulted in LoA from -0.05 to 0.07 mm and -0.04 to 0.05 mm respectively. LoA of the day-to-day variability was -0.13 to 0.18 mm and -0.09 to 0.18 mm respectively. This corresponds to coefficients of variations (CV) of the sonographer- and day-to-day variability of 10% in patients with T2D and 8% in persons without T2D. The CV of the reader variability was 4% and 3% respectively.

Conclusion

Measurement of carotid IMT in the CCA can be determined with good and comparable reproducibility in both patients with T2D and persons without T2D. These findings support the use of carotid IMT in clinical trials with T2D patients and suggest that the numbers of patients needed to detect a given difference will be the same whether the patients have T2D or not.

Long-term effects of pioglitazone on carotid atherosclerosis in Japanese patients with type 2 diabetes without a recent history of macrovascular morbidity

AIM

No previous studies have evaluated the long-term anti-atherosclerotic effects of pioglitazone in Asian patients with type 2 diabetes. Therefore, the present study investigated the protective effects of pioglitazone on the progression of carotid intima-media thickness (IMT), an established surrogate marker of cardiovascular events in Japanese type 2 diabetic patients without a recent history of cardiovascular morbidity.

METHODS

This 2.5-4-year, randomized, open-label, blinded endpoint study was conducted in 6 centers across Japan. Patients received pioglitazone with or without other oral glucose-lowering drugs (excluding another thiazolidinedione) (n=89) or oral glucose-lowering drugs, excluding thiazolidinediones (n=97). Treatment was adjusted to achieve HbA(1c) <6.5%. The primary endpoints of the study were the absolute changes from the baseline to final visit in max- and mean-IMT in the average of bilateral common carotid arteries.

RESULTS

Pioglitazone induced carotid IMT regression compared to baseline measurements (from 1.060 ± 0.2368 to 0.992 ± 0.1921 mm; p=0.0042 in max-IMT and from 0.839 ± 0.1873 to 0.780 ± 0.1571 mm; p=0.0019 in mean-IMT). Although the between-group difference did not reach statistical significance, the regression of carotid IMT values was greater in the pioglitazone-treatment group than in the non-pioglitazone group, (max-IMT: -0.069 ± 0.2199 mm vs -0.031 ± 0.2327 mm, respectively; p=NS, mean-IMT: -0.058 ± 0.1718 mm vs -0.043 ± 0.1644 mm, respectively; p=NS).

CONCLUSIONS

Pioglitazone induced and maintained the long-term regression of carotid IMT in Japanese type 2 diabetic patients. This suggests that pioglitazone may inhibit the progression of atherosclerosis in this patient group. Further studies are required to verify these findings.

Is A1C Variability an Independent Predictor for the Progression of Atherosclerosis in Type 2 Diabetic Patients?

Background

Little is known about the relative contribution of long-term glycemic variability to the risk of macrovascular complications in type 2 diabetes. This study was conducted to evaluate the effect of A1C variability on the progression of carotid artery intima-media thickness (IMT) in type 2 diabetic patients.

Methods

Among type 2 diabetic patients who visited Hallym University Sacred Heart Hospital from March 2007 to September 2009, 120 patients who had carotid artery IMT measured annually and A1C checked every three months for at least one year were analyzed. Individual A1C variability was defined as the standard deviation (SD) of five A1C levels taken every three months for approximately one year. Change in IMT was defined as an increase in IMT on follow-up measurement. The association between the SD of A1C and changes in IMT was evaluated.

Results

With greater A1C variability, there was a greater increase in the mean IMT (r = 0.350, P < 0.001) of the carotid artery. After adjusting for confounding factors that may influence IMT, A1C variability was significantly associated with the progression of IMT (r = 0.222, P = 0.034). However, the SD of A1C was not a significant independent risk factor for the progression of IMT in multiple regression analysis (β = 0.158, P = 0.093).

Conclusion

Higher A1C variability is associated with IMT progression in type 2 diabetic patients; however, it is not an independent predictor of IMT progression. Overall glycemic control is the most important factor in the progression of IMT.

Imaging of atherosclerosis: carotid intima-media thickness

Carotid ultrasound provides quantitative measurements of carotid intima-media thickness (CIMT) that can be used to assess cardiovascular disease (CVD) risk in individuals and monitor ongoing disease progression and regression in clinical trials. It is non-invasive, rapid, reproducible, and carries no risk. Numerous epidemiological studies have established that CIMT is a marker of subclinical atherosclerosis and is associated with established CVD risk factors and with both prevalent and incident CVD. The use of CIMT in outcome trials as a surrogate or predictor of CVD outcomes is widespread. Carotid ultrasound is being employed to test the efficacy of CVD treatment in order to identify potential useful drugs earlier and to possibly speed regulatory approval. Successive trials have generated lessons learned and applied, with slow but steady improvement in CIMT measurement reproducibility.

Findings of clinical trials that evaluate the impact of medical therapies on progression of atherosclerosis

BACKGROUND

Arterial wall imaging has been increasingly employed in clinical trials to evaluate the impact of medical therapies on progression of atherosclerosis.

SCOPE

A selective overview of major findings from clinical trials that assessed the impact of medical therapies on atherosclerosis progression.

FINDINGS

Targeting established risk factors including LDL cholesterol, HDL cholesterol and blood pressure has a beneficial impact on disease progression.

CONCLUSION

As a result, vascular imaging has been employed in the early evaluation of experimental therapies.

Genetic risk factors and the anti-atherosclerotic effect of pioglitazone on carotid atherosclerosis of subjects with type 2 diabetes--a retrospective study

AIM

Pioglitazone, an agonist of peroxisome proliferator-activated receptor gamma, showed various anti-atherosclerotic effects on type 2 diabetic patients. This retrospective study was done to ascertain which risk factor(s) associate with anti-atherosclerotic effects of pioglitazone.

METHODS

We enrolled 160 diabetic patients treated through diet only and 62 treated with pioglitazone and annually evaluated carotid maximum (MaxIMT) and averaged intima-media thickness (AveIMT) for 2 years. We analyzed the relation of 99 single-nucleotide polymorphisms (SNP) as well as conventional risk factors with the progression or regression of carotid atherosclerosis.

RESULTS

The D allele of the angiotensin-converting enzyme (ACE) gene and 677 allele of the methylene-tetrahydrofolate reductase (MTHFR) gene showed a significant association with increases in MaxIMT among the diabetic subjects treated through diet only. The pioglitazone-treated carriers of the D allele showed an attenuation of MaxIMT as compared with the diet-treated carriers. The pioglitazone-treated carriers of the 677T allele carriers showed a significant attenuation of MaxIMT compared with the diet-treated carriers.

CONCLUSIONS

Pioglitazone may exert anti-atherosclerotic effects on type 2 diabetics carrying the ACE gene's D allele and/or MTHFR gene's 677T allele, who showed a progression of carotid atherosclerosis without the drug.

Role of reactive oxygen species in the progression of type 2 diabetes and atherosclerosis

Type 2 diabetes is the most prevalent and serious metabolic disease all over the world, and its hallmarks are pancreatic beta-cell dysfunction and insulin resistance. Under diabetic conditions, chronic hyperglycemia and subsequent augmentation of reactive oxygen species (ROS) deteriorate beta-cell function and increase insulin resistance which leads to the aggravation of type 2 diabetes. In addition, chronic hyperglycemia and ROS are also involved in the development of atherosclerosis which is often observed under diabetic conditions. Taken together, it is likely that ROS play an important role in the development of type 2 diabetes and atherosclerosis.

Association of arterial stiffness with HbA1c in 1,000 type 2 diabetic patients with or without hypertension

The objective is to evaluate the association of arterial stiffness [brachial-ankle pulse wave velocity (ba-PWV)] with glycemic control and duration of type 2 diabetes in diabetic subjects with or without hypertension. One thousand Chinese diabetic patients (562 with hypertension, 438 without hypertension) were included in this study. All patients underwent ba-PWV and biochemical measurements. Ba-PWV was significantly higher in diabetic subjects with hypertension than those without hypertension (1779 +/- 341 vs. 1691 +/- 342 cm/s, P < 0.0001), and these subjects were under similar glycemic control (6.9 +/- 1.5 vs. 6.9 +/- 1.3, P = 0.86). In diabetic and hypertensive subjects, ba-PWV was positively associated with HbA1c (1715 +/- 314 vs. 1851 +/- 335 cm/s, in subjects with HbA1c < 6.5% and with HbA1c > 7.0%, respectively, P < 0.0001), as well as duration of diabetes (1671 +/- 342 vs. 1791 +/- 313 vs. 1861 +/- 338 cm/s, in subjects with duration of diabetes <5 years, 5-10 years, and >10 years, respectively, P all < 0.05). In diabetic subjects without hypertension, ba-PWV was not associated with HbA1c (P = 0.47), but associated with duration of diabetes (1503 +/- 272 vs. 1692 +/- 354 cm/s, in subjects with duration of diabetes <5 years and >10 years, respectively, P = 0.0013). Ba-PWV was higher in diabetic subjects with hypertension than in diabetic subjects without hypertension, suggesting the independent effect of hypertension on arterial stiffness in diabetic subjects. Ba-PWV positively correlated with HbA1c and duration of diabetes in subjects with diabetes and hypertension, suggesting the importance of early glycemic control in the prevention of arterial stiffness and vascular complications.

Study rationale and design of the CIMT trial: the Copenhagen Insulin and Metformin Therapy trial

BACKGROUND

Patients with type 2 diabetes (T2DM) have an increased mortality rate primarily because of macrovascular disease. Where T2DM patients cannot be managed sufficiently through diet, exercise and peroral antidiabetic drugs, that is when haemoglobin A1c (HbA1c) is above 7.0%, it is yet unknown whether a combination of metformin and insulin analogues is superior to insulin analogues alone. Nor is it known which insulin analogue regimen is the optimal.

OBJECTIVE

The primary objective of this trial is to evaluate the effect of an 18-month treatment with metformin vs. placebo in combination with one of three insulin analogue regimens, the primary outcome measure being carotid intima-media thickness (CIMT) in T2DM patients.

DESIGN

A randomized, stratified, multicentre trial having a 2 x 3 factorial design. The metformin part is double masked and placebo controlled. The insulin treatment is open. The intervention period is 18 months.

PATIENT POPULATION

Nine hundred and fifty patients with T2DM and HbA1c > or = 7.5% on treatment with oral hypoglycaemic agents or on insulin treatment and deemed able, by the investigator, to manage once-daily insulin therapy with a long-acting insulin analogue.

RANDOMIZATION

Central randomization stratified for age (above 65 years), previous insulin treatment and treatment centre.

INTERVENTIONS

Metformin 1 g x two times daily vs. placebo (approximately 475 patients vs. 475 patients) in combination with insulin detemir before bedtime (approximately 315 patients) or biphasic insulin aspart 30 before dinner with the possibility to increase to two or three injections daily (approximately 315 patients) or insulin aspart before the main meals (three times daily) and insulin detemir before bedtime (approximately 315 patients). Intervention follows a treat-to-target principle in all six arms aiming for an HbA1c < or = 7.0%.

OUTCOME MEASURES

Primary outcome measure is the change in CIMT from baseline to 18 months. Secondary outcome measures comprises the composite outcome of death, acute myocardial infarction, stroke or amputation assessed by an adjudication committee blinded to intervention, other cardiovascular clinical outcomes, average postprandial glucose increment from 0 to 18 months, hypoglycaemia and any inadvertent medical episodes. In addition, change in plaque formation in the carotids, HbA1c, cardiovascular biomarkers, body composition, progression of microvascular complications and quality of life will be assessed as tertiary outcome measures. TIME SCHEDULE: Patient enrolment started May 2008. Follow-up is expected to finish in March 2011.

CONCLUSION

CIMT is designed to provide evidence as to whether metformin is advantageous even during insulin treatment and to provide evidence regarding which insulin analogue regimen is most advantageous with regard to cardiovascular disease.

Review: Stroke in type 2 diabetes

Stroke is the second most frequent cause of death worldwide and the most frequent cause of permanent disability. Patients with diabetes are at 1.5 to three times the risk of stroke compared with the general population. Cerebrovascular disease causes 20% of deaths in diabetic patients. Interestingly, there are some striking differences of stroke patterns between diabetic and non-diabetic subjects suffering a stroke. Even more important is the fact that diabetes dramatically increases the risk of stroke in younger subjects as well as women. These data highlight the need for detection and treatment of diabetes particularly in these patient groups. This review summarises several aspects of stroke in type 2 diabetes, focusing on differences from non-diabetic stroke.

Diabetic neuropathy is closely associated with arterial stiffening and thickness in Type 2 diabetes

AIMS

Interaction of vascular and metabolic factors appears to contribute to the pathogenesis of diabetic neuropathy. The aim of the study was to assess the impact of arterial stiffening and thickness on diabetic neuropathy in Type 2 diabetes.

METHODS

In 294 patients with Type 2 diabetes, neuropathy was assessed by four components: the presence of neuropathic symptoms, the absence of ankle tendon reflexes, perception of vibration scores and heart rate variation. We measured intima-media thickness (IMT) of carotid arteries to assess arterial thickening, and brachial-ankle pulse-wave velocity (PWV) and brachial pulse pressure (PP) which reflect arterial stiffening.

RESULTS

Diabetic neuropathy, defined as > or = two of the four components, was significantly associated with age, duration, glycated haemoglobin (HbA(1c)), systolic blood pressure, diastolic blood pressure, PP, hypertension, retinopathy, urinary albumin excretion rate, nephropathy stages, PWV and IMT. PWV and PP were significantly associated with neuropathy independent of conventional cardiovascular risk factors. Multiple logistic regression analysis revealed that PWV, retinopathy, age, and HbA(1c), were significant independent determinants of neuropathy.

CONCLUSIONS

The present cross-sectional study indicates that markers for vascular wall properties such as PWV, IMT and PP are significantly associated with diabetic neuropathy. PWV and PP are significant determinants of neuropathy independent of conventional cardiovascular risk factors. Multifactorial intervention to inhibit progression of the atherosclerotic process may slow progression of neuropathy.

Alterações das propriedades funcionais e estruturais de grandes artérias no diabetes mellitus

Alterações funcionais e estruturais das grandes artérias exercem um importante papel na patogênese das doenças cardiovasculares. O diabetes mellitus, ao lado da hipertensão arterial e do envelhecimento, pode induzir essas alterações em diferentes territórios arteriais, e assim levar ao desenvolvimento de aterosclerose e suas conseqüências cardiovasculares. A principal alteração da função das grandes artérias é o aumento da rigidez, enquanto que a principal alteração estrutural é o maior espessamento da camada intima-media da artéria carótida, encontradas em ambos os tipos 1 e 2 de diabetes. Os mecanismos destas alterações estruturais e funcionais arteriais no diabetes incluem a resistência à insulina, o acúmulo de colágeno devido à glicação enzimática inadequada, disfunção endotelial e do sistema nervoso autônomo. O aumento de rigidez arterial é um marcador de risco cardiovascular em pacientes diabéticos, e o tratamento tanto do diabetes per se quanto de dislipidemia e hipertensão arterial associadas pode modificar beneficamente essas alterações arteriais.