Microangiopathy is independently associated with presence, severity and composition of carotid atherosclerosis in type 2 diabetes

Nutrition, Metabolism & Cardiovascular Diseases (2011) 21, 286e293 available at www.sciencedirect.com

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Microangiopathy is independently associated with presence, severity and composition of carotid atherosclerosis in type 2 diabetes S. Vigili de Kreutzenberg a,*, A. Coracina a, A. Volpi b, G.P. Fadini a, A.C. Frigo c, G. Guarneri a, A. Tiengo a, A. Avogaro a a

Department of Clinical and Experimental Medicine, University of Padova, Via Giustiniani, 2, 35128 Padova, Italy Diabetologic Unit, Montebelluna Hospital, Treviso, Italy c Department of Environmental Medicine and Public Health, University of Padova, Italy b

Received 14 July 2009; received in revised form 7 October 2009; accepted 9 October 2009

KEYWORDS Type 2 diabetes mellitus; Microangiopathy; Carotid atherosclerosis

Abstract Background and aims: Common mechanisms for the development of micro- and macroangiopathic diabetic complications have been suggested. We aimed to cross-sectionally investigate strength and characteristics of the association between carotid atherosclerosis and microangiopathy in type 2 diabetic patients. Methods and results: Common carotid artery intimaemedia thickness (cIMT), carotid plaque (CP) type and degree of stenosis were evaluated by ultrasound, along with the determination of anthropometric parameters, HbA1c, lipid profile, assessment of diabetic retinopathy and nephropathy, in 662 consecutive patients with type 2 diabetes mellitus (T2DM). Patients were divided according to high/low cIMT, presence/absence of CP and of retinopathy and nephropathy. Patients with CP were older, more prevalently males, past smokers, had longer diabetes duration, significantly lower HDL cholesterol and more prevalent ischemic heart disease (all p < 0.05) as compared to those with cIMT < 1 mm. Microangiopathies were more prevalent in patients with CP than in those without. At multivariate logistic regression, factors independently associated with the presence of CP were age, past smoke, HDL cholesterol, retinopathy and retinopathy plus nephropathy. A significant independent correlation of CP stenosis with stage of retinopathy and nephropathy was found. Finally, echolucent CPs were associated with a lower prevalence of proliferative retinopathy than CP containing calcium deposits. Conclusion: In T2DM, retinopathy, alone or in combination with nephropathy, is independently associated to CP, and severity of microangiopathy correlates with severity of carotid

* Corresponding author. Tel.: þ39 49 8212183; fax: þ39 49 8754179. E-mail address: [email protected] (S. Vigili de Kreutzenberg). 0939-4753/$ - see front matter ª 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.numecd.2009.10.003

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atherosclerosis. These observations, together with the different prevalence of proliferative retinopathy according to CP types, point to possible common pathogenic mechanisms in microand macrovascular complications. ª 2009 Elsevier B.V. All rights reserved.

Introduction A ‘‘common soil’’ for the development of micro- and macroangiopathic diabetic complications has been proposed [1,2]. Cardiovascular risk factors may contribute differently to vascular disease according to artery size and district, but common pathogenic pathways may underlie both microvascular and atherosclerosis remodelling. For instance, an increasing interest is being devoted to the study of microangiopathy and angiogenesis within the atherosclerotic plaque [3]. This might be of particular value in diabetes, which is the major cause of microangiopathy and a strong risk factor for atherosclerosis. As for macroangiopathy, carotid intimaemedia thickness (cIMT) is considered a parameter of subclinical atherosclerosis, and previous studies have documented a significant role of cIMT in macroangiopathy prediction in both non-diabetic and diabetic populations [4e7]. Accordingly, assessment of carotid atherosclerosis by means of cIMT ultrasound measurement and plaque detection is rapidly becoming an accepted way to detect generalized atherosclerosis. Indeed, carotid artery plaque burden has been positively correlated with angiographic evidence of coronary atherosclerosis [8]. In addition, multiple studies have shown that cIMT is independently associated with coronary heart disease (CHD) and stroke, even after adjustment for traditional risk factors [9e12]. The Hoorn Study showed that individuals with prediabetes or type 2 diabetes had significantly increased carotid artery stiffness as well as increased cIMT as compared to normal subjects [13]. Similarly, Wei et al. found increased cIMT in Mexican and MexicanAmerican cohorts with type 2 diabetes [14]; this association remained significant even after adjustment for traditional risk factors. Comparable findings were offered by the ARIC study [15]. Similarly to carotid atherosclerosis, diabetic retinopathy was shown to be an independent predictor of cardiovascular events and death [16,17]. Likewise, an abnormal urinary albumin excretion was also shown to be a powerful predictor of cardiovascular disease in both nondiabetic and diabetic populations [18]. Cheung and colleagues have recently demonstrated that the presence of retinopathy entails an increased CHD risk, independently of known risk factors [17]. Additional data have shown that retinal abnormalities relate to risk of CHD, supporting a prominent role for microangiopathy in the development of CHD [19]. Interestingly, Malecki and colleagues described diabetic retinopathy as independently associated with cIMT and endothelial dysfunction, measured by flow-mediated dilatation [20]. On the other hand, Spijkerman and colleagues found that markers of early vascular disease were not associated with progression of retinopathy, that retinal microvascular disease is of

limited value in risk stratification for future cardiovascular events, and it did not correlate with endothelial dysfunction [21]. Further, among young subjects with type 1 diabetes, the mean cIMT was shown to be significantly higher in those with retinopathy or microalbuminuria [22]. Thus, it is still unclear whether or not microvascular complications are markers of cardiovascular disease, or whether they can be used as an indicator of precocious vascular dysfunction. Moreover, the literature provides little data on the correlation between severity of micro- and overt macroangiopathy, as well as on the association of microangiopathy with CP composition. In light of these premises, we sought to determine, in a large cohort of type 2 diabetic outpatients, strength and type of the association between diabetic microvascular complications (retinopathy and nephropathy) and extracranial atherosclerosis, defined by the presence of CP.

Methods Patients’ recruitment and characterization The study was approved by local Institution and Ethic committee. Subjects suitable to be included in the study were all consecutive type 2 diabetic patients who underwent a diagnostic carotid artery high-resolution B-mode ultrasonography at the outpatient Diabetes Clinics of Padova University and of Montebelluna Hospital (Treviso) between January 2006 and June 2007. Consecutive type 2 diabetic patients aged more than 45 and periodically followed-up in the two Diabetology Clinics were screened by supra-aortic vessel ultrasonography, independently of metabolic control, presence of other micro- or macrovascular complications, carotid bruits and carotid stenosis suspicion. Inclusion criteria were (i) a diagnosis of type 2 diabetes mellitus, ascertained by ADA criteria and/or ongoing pharmacological anti-hyperglycemic therapy and (ii) an informed consent. Exclusion criterion was the presence of type 1 diabetes (defined at time of diagnosis by clinical characteristics, C-peptide below the detectable threshold and/or presence of anti-islet antibodies). On the basis of these criteria, the study sample included a total of 662 type 2 diabetic patients, who were representative of general adult diabetic population. Clinical history and pharmacological treatment were recorded for all patients. Glycated hemoglobin, total cholesterol, HDL cholesterol, triglyceride, and urinary albumin were determined in the 3 months preceding or immediately following vascular examination. Arterial hypertension was defined as a systolic blood pressure 140 mmHg and/or a diastolic blood pressure 90 mmHg or use of anti-hypertensive drugs. Patients underwent an

288 assessment of macrovascular complications as follows. Carotid artery ultrasound was used to identify and characterise carotid atherosclerosis (see bottom). Coronary heart disease was defined as one of the following: (1) a history of hospital admission for acute myocardial infarction (AMI) or an episode of angina confirmed by coronary angiography; (2) a 12-lead ECG positive for prior AMI or angina by Minnesota coding system (criteria I: 1e3, IV: 1e3, V: 1e2, and VII: 1); (3) a history of coronary artery by-pass graft (CABG) or percutaneous transluminal coronary angioplasty. All patients had had at least one ECG in the 3 months preceding enrolment. Microvascular complications were defined as follows. A dilated fundus examination was performed during the same interval period by computerized microperimetry (MP-1 Microperimeter, Nidek Technologies, Japan) and then interpreted by an experienced ophthalmologist. Diabetic retinopathy (DR) was diagnosed and staged according to the EDTRS classification [23]. Urinary albumin was calculated as albuminuria/creatininuria ratio (ACR) or as albumin excretion rate (AER in mg/min). Patients were then divided into those with normoalbuminuria (ACR < 30 mg/g or AER < 20 mg/min) and those with diabetic nephropathy (DN), defined as micro(ACR: 30e300 mg/g or AER: 20e200 mg/min) or macroalbuminuria (ACR > 300 mg/g or AER > 200 mg/min). We considered the mean of three consecutive determinations, accomplished in the 6 months preceding the study, in the absence of urinary tract infections, uncontrolled hyperglycemia or hypertension.

Ultrasound examination All subjects were studied lying in supine position, with the operator seated at the head bed, using a Philips HDI 5000 ultrasound system equipped with a 7.5 MHz probe. During supra-aortic vessels ultrasonographic exam, the common carotid intimaemedia thickness (cIMT) and the presence and type of CP were recorded. Carotid IMT scanning and reading was performed as suggested by the Mannheim Carotid IntimaeMedia Thickness Consensus (2004e2006) [24]. Briefly, IMT was measured from the mediaeadventitia interface to the intimaelumen interface, on the far wall of right and left common carotid artery (CCA), in a minimum 10 mm arterial segment, 1 cm distally from the bifurcation of internal carotid artery or from the bulb. The segment of interest was assessed in a longitudinal view, strictly perpendicular to the ultrasound beam, at an appropriate depth of focus. The mean of at least 4 determinations for each site was calculated, and the higher value was considered for statistical analysis. Carotid plaques (CP) were defined as a thickness >1.5 mm as measured from the mediaeadventitia interface to the intimaelumen interface. In case of presence of a plaque in the site of interest, cIMT was measured in the nearest plaque-free segment. On the basis of echogenicity, CP were divided into: echogenic (higher content of fibrous tissue and calcification), echolucent (lipid rich), heterogeneous (mixed echolucent and echogenic), as previously described [25,26]. The same operator performed the echocolordoppler exams in both Vascular Laboratories. The cIMT value of 1 mm was chosen as the cut-off measure for cIMT, as suggested in literature [27].

S. Vigili de Kreutzenberg et al.

Statistical analysis Patients were divided into three groups according to IMT (cIMT < 1 mm; cIMT 1 mm) and the presence/absence of CP. Mean and standard deviation were provided for continuous variables. Comparison of two or more groups was conducted with Student’s t-test or ANOVA (with LSD post hoc test), respectively, for continuous variables. Percentage of patients was reported for categorical variables and the group comparison was done with the chisquare or the Fisher exact test. Variables that resulted statistically significant at p  0.10 in the univariate analysis, were introduced in a multivariate logistic regression model adjusting for study center, sex, age, and diabetes duration and a backward selection method was used with a significance level of 0.05. The strength of the association between independent CP determinants and the presence of CP was also assessed using ROC curves, based on the calculation of true-positive and false-positive rates at consecutive cut points. Linear correlations between stage of retinopathy or nephropathy and carotid stenosis were assessed using the non-parametric Spearman’s correlation. Data were analyzed using the SAS software version 9.1 or SPSS ver 13.0, both for Windows.

Results Study population Table 1 summarises the main demographic and clinical characteristics of the study population. Upon ultrasound examination, 148 patients had a cIMT < 1 mm without carotid plaque (CP), 28 patients had cIMT  1 mm without CP, and 486 had CP (73.4% of total). CP appeared heterogeneous in 57% of these patients; echogenic in 29% and echolucent in 14%. As compared to the reference group (cIMT < 1 mm), patients with CP, independently of plaque composition, were older, more often males, had lower HDL cholesterol levels, were more often past smokers, were more likely to have CHD and hypertension. Patients with a cIMT  1 mm without CP were older and had lower HDL cholesterol. In Table 1 the distribution of microangiopathies is stratified according to carotid atherosclerosis: patients with CP were more likely to have retinopathy, nephropathy or both than those without CP.

Association between microangiopathies and carotid plaques To examine whether microangiopathies are associated with CP, we performed a multiple regression analysis. Due to the very small number of subjects with cIMT  1 mm but without CP, comparisons were performed only between cIMT < 1 mm and CP patients. The model included age, sex, BMI, lipids, HbA1c, history of smoke, CHD, hypertension, and prevalent therapies as explanatory variables (Table 2). As a result, variables independently associated with CP were: age (O.R.: 1.618; 95% confidence interval (C.I.): 1.413e1.866; p Z 0.0001), smoke (past O.R.: 2.321; 95% C.I.: 1.394e3.970; present O.R.: 1.314; 95% C.I.: 0.713e

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Table 1 Clinical characteristics of study subjects. Patients were divided into 3 groups according to their cIMT (using a cut-off of 1 mm) and the presence of carotid plaques. No Plaque

Plaque (n Z 486)

p

65  7 46/54 11  11 30.6  5.5 1.07  0.09 183  39 108  32 55  14 127  62 7.8  1.3 64/21/14 93/7 25/75 22/78

67  8c 59/41c 13  9c 29.3  4.4 e 191  36 109  30 55  14c 139  88 7.8  1.5 50/38/12c 81/19c 16/84c 17/83

<0.0001a 0.0187b 0.0087a 0.2719a <0.0001a 0.0545a 0.1369a 0.0176a 0.5916a 0.6630a 0.0015b 0.0078b 0.0007b 0.0546b

62/22/16 68 27 36

79/14/7 71 19 62

57/31/12 80 53 52

0.0681b 0.0055b <0.0001b 0.0024b

72/14/8/6

78/11/11/0

52/18/17/13c

<0.0001d

cIMT < 1 mm (n Z 148)

cIMT  1 mm (n Z 28)

Age (years) Sex (M/F) (%) Duration of diabetes (years) Body mass index (kg/m2) IMT (mm) Total cholesterol (mg/dl) LDL cholesterol (mg/dl) HDL cholesterol (mg/dl) Triglycerides (mg/dl) HbA1c (%) Smoke (%) never/past/now CHD no/yes (%) Hypertension (%) (no/yes) Dyslipidemia (%) (no/yes)

61  9 47/53 10  9 29.7  5.7 0.75  0.10 198  37 115  32 58  16 132  69 7.6  1.4 64/20/16 90/10 30/70 25/75

Treatment (%) OHA/insulin  OHA/diet HBP AP Lipid therapy Microangiopathy burden (%) None/nephropathy/ retinopathy/both

OHA Z oral hypoglycemic agent; HBP Z high blood pressure treatment; and AP Z anti-platelet agents. a Student’s t-test or ANOVA. b Chi-square. c Significantly different from the cIMT < 1 mm group in post hoc test. d Fisher’s exact test.

2.487; p Z 0.0067), HDL cholesterol continuous for 5 mg/ml of increment (O.R.: 0.926; 95% C.I.: 0.862e0.996; p Z 0.0372), retinopathy and/or nephropathy (nephropathy O.R.: 1.162; 95% C.I.: 0.661e2.100; retinopathy O.R.: 3.437; 95% C.I.: 1.712e7.568; retinopathy plus nephropathy O.R.: 3.256; 95% C.I.: 1.433e8.532; p < 0.0011).

The association of age, HDL cholesterol, smoking, and retinopathy plus nephropathy with CP was also assessed by constructing and plotting together receiver operating characteristic (ROC) curves (Fig. 1) We found that the simultaneous presence of independent CP determinants increases the area under ROC curve, but that diabetic

Table 2 Multivariate logistic regression analysis. The dependent variable was the presence of CP. Variables that were significant at a p < 0.10 in the univariate analysis of Table 1 (comparison between CP group and cIMT < 1 mm group), were entered in the model as independent variables, adjusting for study center, sex, age, and diabetes duration. A backward selection method was used with a significance level of 0.05.

Age (continuous for 5 years of increment)

Odds ratio

95% Confidence interval

p

1.618

1.413 O 1.866

<0.0001

Smoke

Never Current Past

1 1.314 2.321

e 0.713 O 2.487 1.394 O 3.970

0.0067

Retinopathy and/or nephropathy

None Nephropathy Retinopathy Both

1 1.162 3.437 3.256

e 0.661 O 2.100 1.712 O 7.568 1.433 O 8.532

0.0011

0.926

0.862 O 0.996

0.0372

HDL cholesterol (continuous for 5 mg/ml of increment)

290

S. Vigili de Kreutzenberg et al. rho Z 0.19; p < 0.001; Fig. 2B), which remained significant after correction for the above-mentioned confounders (r Z 0.12; p Z 0.004).

Association between microangiopathies and plaque echogenicity

Figure 1 Receiver Operating Characteristic (ROC) curves. ROC curve were plotted to assess the incremental diagnostic accuracy of adding microangiopathies to other independent CP predictors in the diagnosis of CP. Black line: age; violet line: age þ smoke; blue line: age þ smoke þ HDL; cyan line: age þ smoke þ HDL þ microangiopathy. (For interpretation of the references to colour in this figure legend, the reader is refered to the web version of this article.)

Patients with CP were divided into 3 groups according to plaque echographic aspect. Then, the prevalence of proliferative retinopathy was assessed according to plaque echographic composition. We found that proliferative retinopathy was 5.7 times more prevalent in patients having CP containing calcium deposits (echogenic plaques or heterogeneous plaques) than in patients with echolucent plaques (Fig. 2C). This remained significant after correction for age, sex, body mass index, duration of diabetes, HbA1c, smoke, and presence of hypertension, dyslipidemia or coronary artery disease in a logistic categorical multivariable analysis. Similarly, the prevalence of macroalbuminuria was 2.4 times higher in patients with mixed or calcific plaques than in patients with fibrous plaques (Fig. 2D). However, after correction for the above-mentioned confounders, macroalbuminuria was not associated with CP type.

Discussion microangiopathy (retinopathy plus nephropathy), along with age, smoking habit and HDL cholesterol is not significantly superior (Fig. 1 and Table 3) to either age, or age plus smoking habit, or age plus smoking habit plus HDL cholesterol, in predicting CP.

Strength of the association between microangiopathies and carotid stenosis After showing an independent association between microangiopathies and carotid atherosclerosis, we wondered whether more severe forms of microangiopathy are associated with higher burden of carotid atherosclerosis. We found a significant direct correlation between retinopathy stage and carotid stenosis, (ANOVA < 0.001; Spearman’s rho Z 0.21; p < 0.001; Fig. 2A), which remained significant after correction for age, sex, duration of diabetes, HbA1c, BMI, presence of dyslipidemia, hypertension, smoking and CHD (r Z 0.19; p < 0.001). We also found a significant association between stage of nephropathy (none, microalbuminuria, macroalbuminuria) and carotid stenosis (ANOVA < 0.001; Spearman’s

The major findings of this study are that (i) in type 2 diabetic patients, retinopathy alone or in combination with nephropathy significantly and independently associates with carotid artery plaques; (ii) a direct correlation exists between severity of diabetic microangiopathies and extent of carotid atherosclerotic burden; (iii) among different plaque composition, calcific CPs are more likely to be associated with diabetic microangiopathy. Carotid atherosclerosis is highly prevalent in the aging population. Ebrahim and colleagues reported a prevalence of CP(s) of 65% and 75% in men and women aged >70 years, respectively [28]. In another study, the prevalence of carotid disease at ultrasound was 66.5% in a population aged 65e94 years [29]. Herein, we confirm a high prevalence of CP(s) (73%) in type 2 diabetic patients with a mean age of about 66 years. Due to this high prevalence, detection of CP is likely to override the information provided by cIMT measurement in our cohort [30]. However, when we repeated statistical analyses considering cIMT as the independent variable, predictors of cIMT were the same as of CP, along with anti-hypertensive and anti-platelet medications (not shown). These results strengthen the

Table 3 ROC curve data. Receiver Operating Characteristic (ROC) curves were built and analyzed to explore the incremental effect of independent predictors of carotid atherosclerosis. Between brackets, 95% confidence interval for AUC. Model

Akaike’s information criterion

p

AUC

Intercept only Age Age þ smoke Age þ smoke þ HDL Age þ smoke þ HDL þ nephropathy/retinophathy

649.132 599.993 589.464 586.813 575.799

<0.0001 <0.0001 <0.0001 <0.0001 <0.0001

e 0.688 0.723 0.720 0.743

(0.637e0.7343) (0.677e0.766) (0.674e0.768) (0.698e0.787)

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Figure 2 A, B) Correlation between the stage of microangiopathy and carotid artery stenosis. When patients were divided according to stage of retinopathy (A) or nephropathy (B), we found a significant correlation as assessed by ANOVA and post hoc LSD tests or Spearman’s non-parametric correlation (see text). *Statistically significant versus no retinopathy or no nephropathy. Max carotid stenosis is the percent of maximal carotid occlusion. (C, D) Association between carotid plaque composition and prevalence of advanced retinopathy (C) or nephropathy (D). When patients were divided according to ultrasound characteristics of carotid plaques (echolucent: lipid rich; echogenic: calcific; heterogeneous: mixed), we found a significantly lower prevalence of proliferative retinopathy and macroalbuminuria (black bars) and a higher prevalence of non-proliferative retinopathy and normo-/ microalbuminutia (white bars) in patients with lipid-rich plaques as compared to patients with calcium-rich plaques. *Statistically significant versus echolucent plaques.

association between micro- and macroangiopathy, both overt and subclinical. We found that age, smoking and HDL cholesterol were independently associated with CP in type 2 diabetes. Age is clearly a major determinant of plaque formation and composition: extracranial atherosclerosis increases linearly with age [31], and plaques become progressively more atheromatous and devoid of smooth muscle cells with advancing age, potentially translating into vulnerable plaques [32]. There is also evidence from different population of subjects that progression of extracranial atherosclerosis is determined by HDL cholesterol levels [33e35]. The association between smoking and CP(s) was not unexpected, as cigarette smoking has been previously shown to be associated with intimaemedia thickness, extracranial atherosclerosis progression [33], and occurrence of stroke in young subjects [36e38]. The coexistence of carotid atherosclerosis with retinal ischemia has been observed since two decades [39]. Klein et al. have suggested that evaluation of retinal arterial changes may allow assessment of the independent contribution of arteriolar disease to various ischemic syndromes in

the heart, brain and other organs [40]. Additionally, retinopathy has been found to be associated with prevalent coronary heart disease, stroke, and carotid artery thickening and endothelial dysfunction [20,41]. Several studies have evaluated the association between cIMT and diabetic microangiopathic complications. In the Atherosclerosis Risk in Communities Study [42] and in the Chennai Urban Rural Epidemiology Study [43] the link between diabetic retinopathy and cIMT was independent of age, diabetes duration and glucose control. On the other hand, no association was demonstrated between cIMT and diabetic retinopathy in the Cardiovascular Health Study (CHS) [44], and in the Hoorn Study [45]. A significant association has been extensively demonstrated between cIMT and microalbuminuria in type 2 diabetic subjects [46e49]. Furthermore, in a subgroup of the Fenofibrate Intervention and Event Lowering in Diabetes (FIELD) study, this association was demonstrated even for albumin excretion rate in the normal range [50]. In this study, we found that retinopathy (alone or in combination with nephropathy) is more prevalent in diabetic patients with CP(s) than in those without, after correction for potential confounders.

292 At variance, we could not find an independent association between CP and diabetic nephropathy alone, defined as micro- or macroalbuminuria. Available data are scant in the literature: previous studies have shown significantly higher incidence of carotid atherosclerosis in diabetic patients with early nephropathy although this association was not independent [51]. In this study, we show for the first time a linear correlation between severity of microangiopathies and degree of carotid atherosclerotic stenosis. Thus, patients with more advanced stages of retinopathy or with macroalbuminuria had more stenotic CP(s) than patients with early retinopathy or normo-/microalbuminuria, independently of confounding factors, including age, disease duration and HbA1c. This notion strengthens the association between micro- and macrovascular diabetic complications. This association was also assessed using the area under ROC curves, which provides the possibility of comparing different diagnostic combination of independent predictors. We show that the combined presence of age, history of past smoking and HDL cholesterol have a fair accuracy in predicting the presence of CP. However, by adding the presence of microangiopathies there is no significant improvement in diagnostic prediction, suggesting that these data do not have direct implications in clinical practice. Moreover, due to the cross-sectional nature of this study, a definite causeeeffect relationship between micro- and macroangiopathy cannot be demonstrated. Nonetheless, we believe that results of the present study may help shedding light over the pathophysiological connections between development and progression of micro- and macrovascular diseases in diabetes. This is exquisitely intuitive from the observation of a strikingly differential prevalence of proliferative retinopathy and macroalbuminuria according to plaque echogenicity. Many studies have shown that plaque echogenicity correlates with plaque histology, with the echolucent plaques being more rich in lipids and blood vessels, while echogenic plaques being more rich in calcium deposits [25]. We found an independently lower prevalence of proliferative retinopathy in patients with echolucent (lipid rich) plaques than in patients with calcium-rich plaques. This result is totally new and not trivial, suggesting that patients with echolucent plaques, that are characterized by high intraplaque angiogenesis, would be much less prone to retinal angiogenesis, than patients with calcium-rich plaques, that typically contain less blood vessels. This manichean dichotomy strongly recalls the concept of ‘‘diabetic paradox’’, according to which angiogenesis is enhanced in the retina and inhibited in diabetic peripheral tissues, and vice versa [52,53]. Unfortunately, the mechanisms that drive this clinical picture are still not understood. The strength of the present study relies on the high number of patients studied by a single operator. On the other hand, main limitation of this study is its cross-sectional design, that does not allow further insight into the natural history of chronic complication development, with respect to possible interplay between micro- and macroangiopathy. In conclusion, we show for the first time in type 2 diabetic outpatients that microangiopathy is independently associated with presence, severity and composition of carotid atherosclerosis. This comprehensive relationship

S. Vigili de Kreutzenberg et al. emphasizes the possible common or interacting pathogenetic mechanisms in the onset/progression of microvascular and macrovascular complications.

Acknowledgements None.

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