Relation of serum sialic acid to blood coagulation activity in type 2 diabetes

The connections of sialic acids and diabetes mellitus: therapeutic or diagnostic value?

Modulation of sialic acids is one of the important pathological consequences of both type 1 and type 2 diabetes mellitus with or without the micro- and macrovascular complications. However, the mechanistic, therapeutic and/or diagnostic implications of these observations are uncoordinated and possibly conflicting. This review critically analyses the scientific investigations connecting sialic acids with diabetes mellitus. Generally, variations in the levels and patterns of sialylation, fucosylation and galactosylation were predominant across various tissues and body systems of diabetic patients, but the immune system seemed to be most affected. These might be explored as a basis for differential diagnosis of various diabetic complications. Sialic acids are predominantly elevated in nearly all forms of diabetic conditions, particularly nephropathy and retinopathy, which suggests some diagnostic value but the mechanistic details were not unequivocal from the available data. The plausible mechanistic explanations for the elevated sialic acids are increased desialylation by sialidases, stimulation of hexosamine pathway and synthesis of acute phase proteins as well as oxidative stress. Additionally, sialic acids are also profoundly associated with glucose transport and insulin resistance in human-based studies while animal-based studies revealed that the increased desialylation of insulin receptors by sialidases, especially NEU1, might be the causal link. Interestingly, inhibition of the diabetes-associated NEU1 desialylation was beneficial in diabetes management and might be considered as a therapeutic target. It is hoped that the article will provide an informed basis for future research activities on the exploitation of sialic acids and glycobiology for therapeutic and/or diagnostic purposes against diabetes mellitus.

Sialic acids Neu5Ac and KDN in adipose tissue samples from individuals following habitual vegetarian or non-vegetarian dietary patterns

Sialic acids (Sias) are a class of sugar molecules with a parent nine-carbon neuraminic acid, generally present at the ends of carbohydrate chains, either attached to cellular surfaces or as secreted glycoconjugates. Given their position and structural diversity, Sias modulate a wide variety of biological processes. However, little is known about the role of Sias in human adipose tissue, or their implications for health and disease, particularly among individuals following different dietary patterns. The goal of this study was to measure N-Acetylneuraminic acid (Neu5Ac), N-Glycolylneuraminic acid (Neu5Gc), and 2-keto-3-deoxy-D-glycero-D-galacto-nononic acid (KDN) concentrations in adipose tissue samples from participants in the Adventist Health Study-2 (AHS-2) and to compare the abundance of these Sias in individuals following habitual, long-term vegetarian or non-vegetarian dietary patterns. A method was successfully developed for the extraction and detection of Sias in adipose tissue. Sias levels were quantified in 52 vegans, 56 lacto-vegetarians, and 48 non-vegetarians using LC-MS/MS with Neu5Ac-D-1,2,3-13C3 as an internal standard. Dietary groups were compared using linear regression. Vegans and lacto-ovo-vegetarians had significantly higher concentrations of Neu5Ac relative to non-vegetarians. While KDN levels tended to be higher in vegans and lacto-ovo-vegetarians, these differences were not statistically significant. However, KDN levels were significantly inversely associated with body mass index. In contrast, Neu5Gc was not detected in human adipose samples. It is plausible that different Neu5Ac concentrations in adipose tissues of vegetarians, compared to those of non-vegetarians, reflect a difference in the baseline inflammatory status between the two groups. Epidemiologic studies examining levels of Sias in human adipose tissue and other biospecimens will help to further explore their roles in development and progression of inflammatory conditions and chronic diseases.

Association of D-dimer with microalbuminuria in patients with type 2 diabetes mellitus

BACKGROUND

Microalbuminuria has been reported to be related to incidence of cardiovascular complications in diabetes. No consistent findings have been obtained on the relationships of microalbuminuria with blood coagulation and fibrinolysis. The purpose of this study was to determine whether microalbuminuria is associated with blood markers reflecting coagulation and fibrinolysis activities in patients with type 2 diabetes.

METHODS

The relationships of albumin excretion rate (AER) with atherosclerosis-related variables, including blood coagulation and fibrinolysis markers, were investigated in patients with type 2 diabetes who showed normoalbuminuria (AER: less than 20 microg/min) and microalbuminuria (AER: 20 microg/min or higher and less than 200 microg/min).

RESULTS

AER was significantly correlated with body mass index (BMI), maximum intima-media thickness of common carotid arteries, blood HDL cholesterol, uric acid, creatinine and D-dimer. On the other hand, AER showed no significant correlation with blood platelets, fibrinogen, thrombin-antithrombin III complex, plasmin-alpha2 plasmin inhibitor complex and plasminogen activator inhibitor-1. In multiple regression analysis, using age, sex, BMI, pulse pressure, hemoglobin A1c, HDL cholesterol, uric acid, creatinine, D-dimer and history of anti-thrombotic therapy as explanatory variables, only D-dimer showed a significant correlation with AER. The mean level of log-converted D-dimer after adjustment for age and sex was significantly higher in subjects with microalbuminuria than in those with normoalbuminuria.

CONCLUSIONS

D-dimer is associated with microalbuminuria in patients with diabetes and this suggests that glomerular dysfunction is in part mediated by hypercoagulability.

Serum level of sialic acid (SA) and carbohydrate-deficient transferrin (CDT) in type 2 diabetes mellitus with microvascular complications

Sialic acid (SA) is responsible for the composition of different isoforms of transferrin and is reported to be a marker of microvascular complications in type 2 diabetes mellitus. Therefore, we explored the serum concentration of SA, and the less sialylated isoforms of transferrin, termed carbohydrate-deficient transferrin (CDT), in relation to the presence of microvascular complications in type 2 diabetes mellitus. We studied 21 patients with type 2 diabetes with microangiopathy and 22 patients without complications who were hospitalized at a diabetic clinic. The prevalence of microvascular complications was based on clinical history, fundoscopy, and laboratory tests. Blood samples were taken for measurements of SA, CDT, total transferrin, glucose, HbA1c, fibrinogen, C-reactive protein (CRP), and indicators of renal dysfunction (i.e., creatinine, urea, albumin excretion rate (AER), and glomerular filtration rate (GFR)). A rise in serum SA and a decrease in CDT concentrations were observed in both diabetic groups with and without complications, and there were no differences between the two groups of patients. There was a statistically significant correlation between serum SA and CDT in diabetic subjects with microvascular complications, but not in patients without such complications. This proves that the serum changes in CDT and SA levels in the course of type 2 diabetes mellitus are associated with each other in the presence of microangiopathy.

Sialic acid is an inflammation marker associated with a history of deep vein thrombosis

INTRODUCTION

Deep vein thrombosis (DVT) induces a systemic chronic inflammation and it has been associated with atherosclerosis. Increased levels of total sialic acid (TSA) have been shown to correlate with inflammation and atherosclerotic processes. The aim of this study was to investigate whether or not increased levels of TSA are associated with a history of DVT and with inflammation and coagulation markers, as well as with the lipid profile.

MATERIALS AND METHODS

TSA, fibrinogen, C-reactive protein (CRP), fibrin D-dimer (D-dimer), prothrombin fragment 1+2 (F1+2), endogenous thrombin generation, cholesterol and triglycerides were measured in 68 patients who had suffered, in the previous 6-12 months, a first episode of idiopathic DVT, and in 68 age- and sex-matched healthy subjects.

RESULTS

Levels of TSA, fibrinogen, CRP and D-dimer observed in patients were significantly higher than those detected in healthy subjects. TSA positively correlated with fibrinogen (R=0.47, p<0.01), cholesterol (R=0.46, p<0.01), triglycerides (R=0.38, p<0.01) and CRP (R=0.28, p<0.05). The logistic regression analysis confirmed that both high fibrinogen (> or =340 mg/dl) and cholesterol (> or =267 mg/dl) levels significantly and independently influence the TSA concentration. TSA levels above the 95th percentile of controls (>72 mg/dl) were detected in 33% of patients (OR=8.9; p<0.0001; 95% CI 2.4 to 31.7).

CONCLUSIONS

Patients with a history of DVT had associated high levels of TSA. In these patients, TSA correlated to markers of inflammation activity and lipid profile. Thus, TSA appears to be a useful vascular inflammatory marker in idiopathic DVT.

Association of pulse pressure with fibrinolysis in patients with type 2 diabetes

INTRODUCTION

Pulse pressure is a potent risk factor for atherosclerotic disease. The purpose of this cross-sectional study was to determine whether pulse pressure is associated with blood coagulation and fibrinolysis in patients with diabetes.

MATERIALS AND METHODS

The relationships between pulse pressure and atherosclerotic risk factors, including blood coagulation and fibrinolysis markers, were investigated in subjects with type 2 diabetes.

RESULTS

Pulse pressure was found to be significantly correlated with blood fibrinolysis markers, such as plasmin-alpha2-antiplasmin complex (PAP) and D-dimer, but not with platelets and blood coagulation markers, such as fibrinogen and thrombin-antithrombin III complex (TAT). The mean pulse pressure levels in the highest tertiles of PAP and D-dimer were significantly higher than those in the lowest tertiles, while the differences in the mean pulse pressure levels among tertile groups of platelets, fibrinogen and TAT were not significant. These relationships of pulse pressure with PAP and D-dimer were not altered by adjustment for age, sex and history of therapy with antihypertensive and/or antithrombotic drugs. On the other hand, neither systolic nor diastolic blood pressure showed significant correlations with PAP, D-dimer, platelets, fibrinogen and TAT. Pulse pressure was also significantly correlated with age, aortic pulse wave velocity, intima-media thickness of the common carotid arteries and serum sialic acid.

CONCLUSIONS

Pulse pressure is associated with blood fibrinolysis as well as atherosclerotic progression in patients with type 2 diabetes. The results of this study suggest that pulse pressure affects atherosclerotic progression through altering hemostatic functions in patients with diabetes.

Sialic acid: a novel marker of cardiovascular disease?

The global burden posed by cardiovascular disease (CVD), due to a rising incidence of known risk factors, underlines an urgent need to identify other potential risk factors. Sialic acid (SA), an abundant terminal monosaccharide of glycoconjugates, is a possible risk factor for CVD. Although large-scale epidemiological surveys have shown that serum total sialic acid (TSA) is positively associated with mortality from coronary artery disease (CAD) and stroke, studies investigating the correlation between serum TSA and the severity of atherosclerosis are conflicting. Clinical and epidemiological studies indicate that serum TSA is a marker of a sustained inflammatory response in CVD, rather than causal in nature. Data also indicates ethnic variation in baseline TSA. This article reviews current methods for determining serum TSA and evidence supporting serum TSA as a risk factor for CVD. Potential mechanisms for this role are examined. The use of serum TSA as a marker of atherosclerotic disease is evaluated.

Sialic acid in cardiovascular diseases

Sialic acid, the acylated derivatives of 9-carbon sugar neuraminic acid, present as terminal component of oligosaccharide chains of many glycoproteins and glycolipids, has been recognized to be involved in the regulation of a great variety of biological phenomena. Studies have shown that serum sialic acid predicts both coronary heart disease and stroke mortality and reflects the existence or activity of an atherosclerotic process. Most of the studies have shown an elevation in serum sialic acid concentration in coronary heart disease and a positive correlation between the raised serum sialic acid and the severity of the coronary lesions is observed. However, a few contradictory reports are also available. Racial differences in serum sialic acid have also been reported and correlated with international differences in the prevalence of atherosclerosis. Reduced sialic acid content of platelets, erythrocytes and lipoproteins may play important role in the pathogenesis of atherosclerosis. Elucidation of the mechanism of alternation in sialic acid concentration may throw more light on its potential clinical utility. Hence more studies are needed to designates sialic acid as a cardiovascular risk factor/marker.

Age-dependent relation of serum sialic acid concentration to aortic pulse wave velocity in type 2 diabetes

OBJECTIVE

The purpose of this study was to determine whether age affects the significance of serum sialic acid concentration as a marker of atherosclerosis in patients with diabetes.

METHODS

In this cross-sectional study, we investigated the relationship of serum sialic acid concentration to aortic pulse wave velocity (a-PWV) and the effects of age on this relationship in patients with type 2 diabetes.

RESULTS

In the elderly (70 years or over) diabetic patients, a-PWV showed a significant positive correlation with serum sialic acid. This relationship was also significant after adjustment for age, duration of diabetes, body mass index, systolic blood pressure, LDL cholesterol, HDL cholesterol and fibrinogen levels. In elderly diabetic patients, a-PWV also showed a significant positive correlation with age and duration of diabetes and a significant negative correlation with serum HDL cholesterol level. On the other hand, in the younger (31-60 years) diabetic patients, there was no significant correlation between serum sialic acid level and a-PWV, while a-PWV showed significant positive correlations with age, duration of diabetes and plasma fibrinogen level.

CONCLUSIONS

Serum sialic acid level reflects atherosclerosis in elderly diabetic patients but not in younger diabetic patients. This may explain recent controversial findings regarding the relationship between serum sialic acid level and incidence of coronary heart disease in diabetes.