Relation of angiographically defined coronary artery disease and plasma concentrations of insulin, lipid, and apolipoprotein in normolipidemic subjects with varying degrees of glucose tolerance

Nontraditional atherosclerotic risk factors and extent of coronary atherosclerosis in patients with combined impaired fasting glucose and impaired glucose tolerance

Partially inconsistent data exist on mutual relations between nontraditional atherosclerotic risk factors, including the magnitude of insulin resistance (IR), as well as on their relevance for atherogenesis in the metabolic syndrome. Subjects exhibiting combined impaired fasting glucose and impaired glucose tolerance (IFG/IGT) are exposed to an exceptionally high risk for atherogenesis and development of type 2 diabetes mellitus. Because of islet Beta-cell dysfunction, the usefulness of commonly used indices of IR is limited in IFG/IGT. Our aim was to assess the relationship between extent of angiographic coronary artery disease (CAD) and nontraditional atherosclerotic risk factors (including IR by a clamp-based golden standard method) in IFG/IGT. Fifty-three subjects (32 men, 21 women; mean age, 55 +/- 11 years) with stable angina, preserved left ventricular systolic function, and IFG/IGT were divided into 3 groups: group A (no coronary stenoses >50%, n = 22), group B (1-vessel CAD, n = 15), and group C (2/3-vessel CAD, n = 16). Insulin sensitivity was quantified by a hyperinsulinemic euglycemic clamp technique and expressed as M. M value, plasma homocysteine (Hcy) level, and asymmetric dimethyl-L-arginine (ADMA)/L-arginine ratio were independent determinants of CAD extent as shown by forward stepwise discriminant function analysis. Compared with group A (M = 32.7 +/- 9.3 micromol/kg fat-free mass [FFM] per minute; Hcy, 8.1 +/- 1.4 micromol/L), lower M and higher Hcy levels were found in group B (M = 16.9 +/- 8.2 micromol/kg FFM per minute, P < .001; Hcy, 11.2 +/- 2.9 micromol/L, P = .003) and C (M = 16.4 +/- 7.8 micromol/kg FFM per minute, P < .001; Hcy, 12.8 +/- 3.9 micromol/L, P < .001). The ADMA/L-arginine ratio was increased in group C (0.0078 +/- 0.0011) compared with group A (0.0063 +/- 0.0013, P = .03) and B (0.0058 +/- 0.0012, P = .01). Multivariate correlates (P < .05) of plasma Hcy concentrations were M (beta = -.34 +/- .12, P = .008), creatinine clearance (beta = -.23 +/- .10, P = .03) and fasting insulin (beta = .25 +/- .12, P = .04). This indicates an additive contribution of IR, plasma Hcy, and elevated ADMA/L-arginine ratio to the extent of angiographic CAD in combined IFG/IGT.

Abnormal glucose tolerance--a common risk factor in patients with acute myocardial infarction in comparison with population-based controls

BACKGROUND

A high prevalence of newly detected diabetes and impaired glucose tolerance (abnormal glucose tolerance) was recently reported in patients with acute myocardial infarction. It is important to verify whether this finding is specific for the patients or attributable to the population, from which they were recruited.

OBJECTIVE

To verify whether abnormal glucose tolerance is more prevalent in patients than in controls chosen from the same population and to compare metabolic characteristics between the two groups.

DESIGN AND SUBJECTS

The metabolic state was assessed in patients (n = 181) admitted with acute myocardial infarction and no history of diabetes before discharge and after 3 months. Sex- and age-matched controls (n = 185) without previously known diabetes or cardiovascular disease except hypertension were recruited from the general population.

MAIN OUTCOME MEASURES

Oral glucose tolerance test, glucosylated haemoglobin A1c (HbA1c), insulin, proinsulin, lipid profile, fibrinolytic function and inflammatory markers.

RESULTS

Abnormal glucose tolerance was more common (number/all classified) in patients at discharge 113/168 (67%) and after 3 months 95/145 (66%) than in controls 65/185 (35%) (P < 0.001). Dyslipidaemia (70% vs. 29%; P < 0.001) and previously treated hypertension (32% vs. 18%; P = 0.028) were more frequent amongst patients whilst obesity (18% vs. 24%) did not differ significantly. Blood glucose, HbA1c, proinsulin, proinsulin/insulin ratio, triglycerides, insulin resistance (by HOMA) and fibrinogen were consistently higher in patients than controls (P < 0.01).

CONCLUSIONS

Abnormal glucose tolerance was almost twice as common amongst patients with acute myocardial infarction as in matched controls. Impaired glycaemic control accompanied by insulin resistance, dyslipidaemia, hypertension, together with increased plasma fibrinogen and proinsulin levels were main features characterizing patients.

High fasting glucose levels as a predictor of worse clinical outcome in patients with coronary artery disease: results from the Bezafibrate Infarction Prevention (BIP) study

BACKGROUND

A high fasting glucose level may be a marker not only for microvascular complications, but also for macrovascular complications. We evaluated the clinical significance of a high fasting glucose level (> or =110 mg/dL), detected either at baseline or during follow-up, in the Bezafibrate Infarction Prevention (BIP) study.

METHODS

The BIP study was a secondary prevention prospective double-blind study comparing bezafibrate to placebo. A total of 3122 patients with documented coronary artery heart disease who were aged 45 to 74 years and had a total cholesterol level between 180 and 250 mg/dL, low-density lipoprotein cholesterol level < or =180 mg/dL, a high-density lipoprotein cholesterol level < or =45 mg/dL, a triglyceride level < or =300 mg/dL, and a fasting glucose < or =160 mg/dL were randomized to receive 400 mg of bezafibrate daily or placebo.

RESULTS

The primary end point of the BIP study was fatal myocardial infarction, non-fatal myocardial infarction, or sudden death. Secondary end points included hospitalization for unstable angina, percutaneous transluminal coronary angioplasty, and coronary artery bypass grafting. At baseline, 330 patients (11%) had diabetes mellitus, and 293 patients (9%) had an impaired fasting blood glucose level (IFG). During 6.2 years of follow-up, diabetes mellitus developed in 186 patients (6%), IFG developed in 366 patients (12%), and 62% of patients remained with normal fasting glucose levels (NFG). Patients with diabetes mellitus and IFG both at baseline or developing during follow-up had a significantly higher rate of secondary end points than paients with NFG (P <.0001). Bezafibrate treatment reduced secondary end points only in patients with NFG (P =.04).

CONCLUSION

Diabetes mellitus and IFG were common in the BIP study and were predictive of a worse clinical outcome that was not attenuated with bezafibrate treatment.

Inflammation and immune system response against unstable angina and its relationship with coronary angiographic findings

The aim of this study was to assess the relations between inflammation, immune response, and coronary angiographic findings in patients with unstable angina pectoris (UAP). Recent studies suggest a role for inflammation in the pathophysiology of UAP. Although activation of neutrophils, monocytes and lymphocytes has been shown in UAP, no studies have correlated the activation findings with clinical and angiographic features of patients with UAP. Seventy-three patients undergoing coronary angiography were classified according to their ischaemic syndrome, stable angina pectoris (SAP) (n = 25) and UAP (n = 48). Patients with UAP were classified using the Braunwald classification; UAP class I (n = 15), UAP class II (n = 15), and UAP class III (n = 18). Patients with UAP were also classified into a progression to myocardial infarction (MI (+)) group (n = 15) and a non-progression to myocardial infarction (MI(-)) group (n = 33). Venous blood samples were taken from all patients. Cell surface receptors (CD4, CD8, CD3, CD14, CD45, CD56+16, and HLA-DR) were detected by flow cytometry using monoclonal antibodies tagged with fluorescent markers and serum levels of C-reactive protein (CRP) were measured. The serum levels of CRP and the percentages of HLA-DR, CD14, and CD16+56 were higher in UAP than SAP. The serum levels of CRP and percentages of HLA-DR, CD14, and CD16+56 were higher in UAP class II than UAP class I. The serum levels of CRP and percentages of HLA-DR, CD14, and CD16+56 were higher in UAP class III than UAP class II and UAP class I. The serum levels of CRP and percentages of CD16+56 were higher in the MI(+) group than the MI(-) group. The CRP levels in serum and the percentages of cell surface antigens had no correlation with extent of coronary artery disease (no differences among one, two or three vessels) but Type C lesion had significantly higher percentages of HLA-DR, CD14, CD16+56 and the serum levels of CRP than Type A and Type B lesions. This investigation shows that inflammatory and immunologial components may be detectable in UAP and were correlated with the clinical severity, progression to myocardial infarction, and lesion morphology, but were not correlated with the extent of coronary artery disease.

HMG-CoA reductase inhibitors: Is the endothelium the main target?

Endothelial dysfunction is an early event in atherosclerosis and could be considered a response to the injury induced by major risk factors. There is evidence that endothelial dysfunction is intimately involved in the onset and the progression of cardiovascular disease through abnormalities in the production, release or degradation of endothelium-derived factors, mainly nitric oxide and endothelin 1. Several reports have shown that drugs of the statin class could have multiple beneficial effects related to endothelium-mediated vasoactive, antithrombotic, antiproliferative and anti-inflammatory actions. Thus, the question arises of whether endothelial cells are the main target of statin therapy, in the setting of both hypercholesterolemia and normocholesterolemia. Experimental and clinical studies are reported that could support this hypothesis.

Disturbances of glucose metabolism in men referred for coronary arteriography. Postload glycemia as predictor for coronary atherosclerosis

OBJECTIVE

In some studies, fasting and postload glycemia are a strong predictor of coronary events and cardiac death. Therefore, we investigated the relationship between fasting and postload glucose concentrations and coronary status in 363 men referred for coronary arteriography without a previous history of diabetes.

RESEARCH DESIGN AND METHODS

A total of 363 men (mean age 53.0 +/- 9.1 years, mean BMI 27.9 +/- 3.7 kg/m2) with positive results of exercise testing were included in the study. A standard oral glucose tolerance test (OGTT) with glucose and insulin estimations was performed on all subjects. The concentrations of total cholesterol, HDL cholesterol, triglycerides, and HbA1c were also measured. All patients were divided into four groups, according to coronary status: no changes in coronary arteries (group 0, n = 61), one-vessel disease (group 1, n = 113), two-vessel disease (group II, n = 116), and three-vessel disease (group III, n = 73).

RESULTS

The highest postload glucose concentrations were observed in group III. Also, insulin concentrations and HbA1c increased with the progression of atherosclerotic lesions in the coronary arteries. Based on results of the OGTT, 16% of the patients (n = 59) fulfilled the World Health Organization criteria for type 2 diabetes and 36% of the patients (n = 131) met criteria for impaired glucose tolerance. Significant correlations were observed between the number of involved vessels and postload glycemia, HbA1c, fasting insulin, and postload insulin. The multiple stepwise regression analysis showed that age, total cholesterol, and HDL cholesterol independently correlated with the number of involved vessels.

CONCLUSIONS

We conclude that patients with advanced changes in the coronary arteries experience more pronounced metabolic disturbances. Postload glycemia could be an important predictor of nondiagnosed disturbances of glucose metabolism.

Relation between lipoprotein (a) and in vitro oxidation of apolipoprotein B-containing lipoproteins

OBJECTIVES

To assess the relationship between lipoprotein (a) [Lp (a)] and lipoprotein oxidation in patients with coronary artery disease (CAD).

DESIGN AND METHODS

Oxidation of apolipoprotein (apo)B-containing lipoproteins, vitamin E, carotenoids, lipid-lipoprotein levels were determined in 171 CAD and 70 non-CAD subjects.

RESULTS

In CAD patients with Lp (a) concentrations >/= 30 mg/dL; total cholesterol (TC), low density lipoprotein cholesterol (LDL-C), malondialdehyde (MDA), and apo B levels were significantly higher and lag-time and age were significantly lower than those of CAD patients with Lp (a) concentrations < 30 mg/dL. In non-CAD subjects with Lp (a) concentrations >/= 30 mg/dL; TC, LDL-C, and vitamin E levels were significantly higher and lag-time was significantly lower than those of non-CAD subjects with Lp (a) concentrations < 30 mg/dL. In CAD patients, Lp (a) correlated negatively with lag-time and positively with MDA levels. Lp (a) correlated negatively with lag-time and vitamin E levels in non-CAD subjects.

CONCLUSIONS

We have shown that plasma apo B-containing lipoproteins of both CAD and non-CAD subjects with Lp (a) levels >/= 30 mg/dL are more susceptible to in vitro oxidative modification than those of subjects with Lp (a) levels < 30 mg/dL. The relationship between Lp (a) and enhanced susceptibility of apo B-containing lipoproteins to oxidation, appears to support routine investigation of Lp (a).

Salubrious effect of vitamin C and vitamin E on tamoxifen-treated women in breast cancer with reference to plasma lipid and lipoprotein levels

Tamoxifen, a non-steroidal antiestrogen, has been used in the hormonal treatment for breast cancer. The hepatic estrogenic effect of tamoxifen causes severe triglyceridemia. The combined effect of tamoxifen, vitamin C and vitamin E on plasma lipid and lipoprotein is important, since, vitamin C and vitamin E encumbered the lipid abnormalities instigated by tamoxifen. Therefore supplementation of vitamin C (Celin 500 mg) and vitamin E (Evion 400 mg) for 90 days along with tamoxifen (10 mg twice a day) to postmenopausal breast cancer patients was ventured. In tamoxifen-treated patients, total cholesterol (TC), free cholesterol (FC), phospholipids (PL), free fatty acids (FFA), low density lipoprotein cholesterol (LDL) levels were decreased and the triglycerides (TG), ester cholesterol (EC), high density lipoprotein cholesterol (HDL) and very low density lipoprotein cholesterol (VLDL) levels were increased. Combination therapy reduce all the cholesterol level and VLDL, LDL. TG levels were significantly decreased and HDL, EC levels were significantly increased. These results suggested that tamoxifen treatment is the most effective during co-administration of vitamin C and vitamin E in that they reduce the tamoxifen-induced hypertriglyceridemia.

[Autonomic neuropathy in patients with impaired glucose tolerance]

Impaired glucose tolerance (IGT) is a clinical situation characterized by mild hyperglycemia, which is estimated to afflict 7.8% of the Brazilian population. Diabetic neuropathy is the most common complication in diabetes mellitus and it is related to morbidity and lethality in this disease. The association between IGT and peripheral neuropathy is still a matter of great concern.

PURPOSE AND METHOD

In order to determine if IGT is associated with autonomic neuropathy a cross-sectional study in 44 patients with impaired glucose tolerance test (Group 1) was performed. The patients were compared to 43 control individuals (Group 2). Every patient in each group underwent anamnesis and standardized autonomic tests which consisted of heart frequency test, Valsalva maneuver, postural test and sinus arrhythmia. Routine hematologic exams as well as GTT were also made.

RESULTS

Patients in group 1 had more systemic arterial hypertension, centripetal obesity, fasting and post-feeding hyperglycemia and dyslipidemia when compared with group 2. When we analysed the autonomic tests, the sinus arrhythmia test was abnormal in 54.5% of the patients in group 1 and in 32.5% in group 2 (p = 0.0039) and the Valsalva maneuver was abnormal in 34.1% of group 1 and in 7% of group 2 (p = 0.004). The postural test was not different in both groups (p = 0.334).

CONCLUSION

Our results show that the involvement of the autonomic nervous system was more frequent in patients with IGT when compared to controls. These findings can explain the increased lethality due to vasculopathies observed in this group of patients and also alert physicians to care for patients with impaired glucose tolerance test.

Glucose tolerance status and severity of coronary artery disease in men referred to coronary arteriography

Increasing attention is being paid to disturbances in glucose metabolism as key explanatory factors for the development of coronary artery disease. We studied the prevalence of impaired glucose tolerance and non-insulin-dependent diabetes and the levels of plasma insulin after an oral glucose tolerance test in 99 men with heart disease but without a history of diabetes referred to coronary arteriography; we also compared the outcome with a matched control group (n = 116). The severity of atherosclerosis in coronary angiograms was evaluated according to glucose tolerance status. Among the 99 patients with coronary artery disease, 37.4% had an abnormal oral glucose tolerance test result, whereas only 18.1% of the control group had an abnormal result (p < 0.01). Moreover, patients with heart disease and normal glucose tolerance were hyperinsulinemic compared with the control group (p < 0.01). By analysis of variance no statistically significant difference in severity of coronary atherosclerosis on coronary angiograms was found. In conclusion, we demonstrated frequent disturbances in glucose metabolism indicating insulin resistance in patients with ischemic heart disease without a history of diabetes, but we could not demonstrate a relation between these disturbances and degree of coronary atherosclerosis.

Effect of glucose, insulin, and insulin-like growth factor-I on glucose transport activity in cultured rat vascular smooth muscle cells

Glucose transport activity in cultured rat vascular smooth muscle cells (VSMCs) was examined under various concentrations of D-glucose, insulin, and insulin-like growth factor-I (IGF-I). Confluent cultures of VSMCs were incubated with serum-free medium containing 0-25 mmol/l of D-glucose for 24-49 h. The basal rate of 2-deoxyglucose uptake was reduced in association with increasing concentrations of D-glucose. Uptake of 2-deoxyglucose into the cells was linear between 0 and 15 min of incubation regardless of the glucose concentration. The uptake was inhibited by the addition of 10 mumol/l cytochalasin B or 100 mmol/l D-glucose indicating that the effects were mediated by specific integral glucose carriers. The effect of D-glucose was time-dependent and reversible. Insulin increased the uptake of 2-deoxyglucose in a dose-dependent manner, and its effect was dependent on the preincubation dose of D-glucose. Insulin-stimulated uptake was lower in the cells pre-exposed to 25 mmol/l D-glucose than in the cells pre-exposed to concentrations of D-glucose below 5.5 mmol/l. After a long-term incubation with insulin, the insulin-stimulated glucose transport was inhibited. Recovery of glucose transport activity was assessed by incubating cells with D-glucose for 24-48 h to induce desensitization. After a 24 h glucose conditioning, the uptake of 2-deoxyglucose was lower in the cells preincubated with 25 mmol/l glucose than in the cells preincubated with 5.5 mmol/l glucose. The effect of the glucose conditioning was reversible and dependent on the preincubation dose of D-glucose. IGF-I was a more potent stimulator of glucose transport than insulin. Wortmannin, an inhibitor of phosphatidylinositol 3-kinase (PI3-kinase), inhibited the uptake of glucose stimulated by insulin or IGF-I in a dose-dependent manner. Our results suggest that D-glucose regulates its own uptake independently of insulin and modulates the ability of insulin to induce insulin resistance in the cultured rat VSMCs. Glucose attenuated the effect of insulin, and led to a progressive decrease in the activity of the glucose transport effector system. Activation of wortmannin-sensitive PI3-kinase may be involved in the signaling pathways of the insulin- and IGF-I-stimulated glucose uptake in VSMCs. This mechanism of insulin resistance may be relevant to the formation of cellular defects in the vascular wall in patients with diabetes mellitus.

HDL subparticles and coronary artery disease in NIDDM

Decreased HDL cholesterol levels are associated with an increased risk of coronary artery disease (CAD) in non insulin dependent diabetes mellitus (NIDDM). The aim of this study was to compare HDL subparticles with apo A-I (LpAI) and those with apo A-I and apo A-II (LpAI/AII) in subjects with and without NIDDM and to study the relationship between HDL subparticles and CAD in NIDDM. Lipids, apo A-I and HDL subparticles were measured in 240 subjects with NIDDM and in 248 age and gender matched controls. Subjects with NIDDM had higher triglyceride levels (2.5 +/- 1.8 vs. 1.4 +/- 0.8 mmol/1, P < 0.001), lower HDL cholesterol (0.9 +/- 0.3 vs. 1.2 +/- 0.3 mmol/l, P < 0.001), apo A-I (124.7 +/- 22.4 vs. 139.8 +/- 24.1 mg/dl, P < 0.001) and LpAI/AII (82.4 +/- 18.2 vs. 94.9 +/- 16.7 mg/dl, P < 0.001) in comparison to controls. LpAI levels were similar in both groups. Diabetic subjects with CAD (n = 109) had higher triglycerides (2.7 +/- 1.9 vs. 2.3 +/- 1.8 mmol/l, P = 0.02) and lower HDL cholesterol (0.8 +/- 0.2 vs. 1.0 +/- 0.3 mmol/l, P <0.001), apo A-I (115.5 +/- 20.1 vs. 132.3 +/- 21.4 mg/dl, P < 0.001), LpAI (40.2 +/- 9.1 vs. 44.4 +/- 12.4 mg/dl, P = 0.06), and LpAI/AII levels (75.4 +/- 18.0 vs. 88.3 +/- 16.2 mg/dl, P < 0.001) in comparison to diabetic subjects without CAD (n = 131). In a multivariate analysis, apo A-I was found to be the best predictor of CAD in subjects with NIDDM. In conclusion, reduced HDL cholesterol levels found in NIDDM are, principally, due to reduced concentrations of apo A-I and apo A-II-containing particles (LpAI/AII). While LpAI and LpAI/AII levels were lower in NIDDM subjects with CAD, plasma apo A-I is the best predictor of CAD in NIDDM.