Late adulthood mortality among African-American and white American people with Type 1 diabetes according to age at diabetes diagnosis.

AIMS: To estimate the overall and cause-specific mortality in a population of African-Americans and white Americans with a low socio-economic status who had young-onset insulin-treated diabetes and had survived beyond the age of 40 years, and to examine whether any excess risk varied according to age at diabetes onset. METHODS: Using the Southern Community Cohort Study, we conducted a mortality follow-up of a cohort of mostly low-income participants aged 40-79 years (mean 50 years) at cohort entry with insulin-treated diabetes diagnosed before age 30 years (n=475) and without diabetes (n=62 266). Childhood onset was defined as diabetes diagnosed before age 20 years (n=162), while young-adulthood onset was defined as diabetes diagnosed between ages 20 and 29 years (n=313). Cause-specific mortality was based on both underlying and contributing causes of death, obtained from death certificates. Multivariable Cox analysis was performed. RESULTS: During follow-up (mean 9.5 years), 38.7% of those with and 12.9% of those without diabetes died. Compared with those without diabetes, increases in mortality rate were generally similar among those with childhood- and young-adulthood-onset diabetes for deaths from: all causes (childhood: hazard ratio 4.3, CI 3.3-5.5; young adulthood: hazard ratio 4.9, CI 4.0-5.8); ischaemic heart disease (childhood: hazard ratio 5.7, CI 3.5-9.4; young adulthood: hazard ratio 7.9, CI 5.6-11.0); heart failure (childhood: hazard ratio 7.3, CI 4.2-12.7; young adulthood: hazard ratio 5.4, CI 3.3-8.9); sepsis (childhood: hazard ratio 10.3, CI 6.1-17.3; young adulthood: hazard ratio 8.8, CI 5.7-13.5); renal failure (childhood: hazard ratio 15.1, CI 8.6-26.5; young adulthood: hazard ratio 18.2, CI 12.3-27.1); respiratory disorders (childhood: hazard ratio 3.9, CI 2.3-6.7; young adulthood: hazard ratio 5.3, CI 3.7-7.7); suicide/homicide/accidents (childhood: hazard ratio 2.3, CI 0.72-7.0; young adulthood: hazard ratio 5.8, CI 3.4-10.2); and cancer (childhood: hazard ratio 2.1, CI 0.98-4.4; young adulthood: hazard ratio 1.2, CI 0.55-2.5). CONCLUSIONS: We observed high excess long-term mortality for all-cause, renal failure, ischemic heart disease and heart failure mortality in African-American and white American people with early-onset insulin-treated diabetes.

CD36 is upregulated in mice with periodontitis and metabolic syndrome and involved in macrophage gene upregulation by palmitate.

BACKGROUND: We reported that high-fat diet (HFD)-induced metabolic syndrome (MetS) exacerbates lipopolysaccharide (LPS)-stimulated periodontitis and palmitate, the major saturated fatty acid in the HFD, amplified LPS-stimulated gene expression in vitro. As CD36 is a major receptor for fatty acids, we investigated periodontal CD36 expression in mice with periodontitis and MetS, and the role of CD36 in inflammatory gene expression in macrophages stimulated by palmitate. METHODS: MetS and periodontitis were induced in mice by HFD and periodontal injection of LPS, respectively. The periodontal CD36 expression and its relationship with alveolar bone loss were studied using immunohistochemistry, real-time PCR, and correlation analysis. The role of CD36 in upregulation of inflammatory mediators by LPS and palmitate in macrophages was assessed using pharmacological inhibitor and small interfering RNA. RESULTS: Periodontal CD36 expression was higher in mice with both MetS and periodontitis than that in mice with periodontitis or MetS alone and was correlated with osteoclastogenesis and alveolar bone loss. In vitro studies showed that CD36 expression in macrophages was upregulated by LPS and palmitate, and targeting CD36 attenuated palmitate-enhanced gene expression. CONCLUSION: CD36 expression is upregulated in mice with periodontitis and MetS and involved in gene expression in macrophages stimulated by palmitate and LPS.

Simvastatin inhibits lipopolysaccharide-induced osteoclastogenesis and reduces alveolar bone loss in experimental periodontal disease.

BACKGROUND AND OBJECTIVE: Statins are inhibitors of 3-hydroxy-3-methylglutaryl coenzyme A reductase and have anti-inflammatory effects independent of cholesterol lowering. Recent clinical studies have indicated that statin intake has a beneficial effect on periodontal disease. However, the underlying mechanisms have not been well understood. In the current study, we employed a rat model with lipopolysaccharide (LPS)-induced periodontal disease and determined the effect of simvastatin, a commonly prescribed statin, on osteoclastogenesis, gingival inflammation and alveolar bone loss. MATERIAL AND METHODS: Sprague-Dawley rats were injected with Aggregatibacter actinomycetemcomitans LPS in periodontal tissue three times per week for 8 wk and part of the rats with LPS injection were also given simvastatin via gavage. After the treatments, the rat maxillae were scanned by microcomputed tomography and the images were analyzed to determine alveolar bone loss. To explore the underlying mechanisms, the effect of simvastatin on osteoclastogenesis and gingival expression of proinflammatory cytokines were also determined by tartrate-resistant acid phosphatase staining and real-time polymerase chain reaction assays, respectively. RESULTS: Results showed that LPS treatment markedly increased bone loss, but administration of simvastatin significantly alleviated the bone loss. Results also showed that LPS treatment stimulated osteoclastogenesis and the expression of inflammatory cytokines, but simvastatin significantly modulates the stimulatory effect of LPS on osteoclastogenesis and cytokine expression. CONCLUSION: This study demonstrated that simvastatin treatment inhibits LPS-induced osteoclastogenesis and gingival inflammation and reduces alveolar bone loss, indicating that the intake of simvastatin may hinder the progression of periodontal disease.

Low density lipoprotein metabolism by human macrophages activated with low density lipoprotein immune complexes. A possible mechanism of foam cell formation.

Human macrophages play a key role in atherogenesis and are believed to be the progenitors of the cholesteryl ester (CE)-laden foam cells present in early atherosclerotic lesions. Several mechanisms by which macrophages accumulate CE have been recently described. One involves a perturbation in LDL metabolism subsequent to macrophage activation. Thus, we decided to study the effect of macrophage activation by immune complexes on N-LDL metabolism. Initially, LDL-containing immune complexes (LDL-IC) were chosen, since increased plasma levels of these IC have been reported in patients with coronary heart disease. Human macrophages stimulated for 22 h with LDL-IC (250 micrograms/ml) and incubated afterwards for 20 h with 10 micrograms/ml 125I-N-LDL showed a six- and fourfold increase in the accumulation and degradation, respectively, of 125I-N-LDL over the values observed in nonstimulated cells. Scatchard analysis of 125I-N-LDL-specific binding suggests an increase (20-fold) in the number of LDL receptors in macrophages stimulated with LDL-IC. We studied other immune complexes varying in size and antigen composition. Some of the IC were able to stimulate, although to a lesser degree, the uptake of N-LDL by macrophages. Lipoprotein IC are more efficient and have the greatest capacity to increase N-LDL uptake and CE accumulation. We conclude that human macrophage activation by LDL-IC leads to an increase in LDL receptor activity and promotes in vitro foam cell formation.

A trend of increase in periodontal interleukin-6 expression across patients with neither diabetes nor periodontal disease, patients with periodontal disease alone, and patients with both diseases.

BACKGROUND AND OBJECTIVE: Epidemiological studies have established that patients with diabetes have increased prevalence and severity of periodontal disease. However, the periodontal expression of inflammatory cytokines and matrix metalloproteinases (MMPs) in diabetic patients has not been well characterized. The objective of this study was to determine the difference in the periodontal expression of MMP-1, MMP-8, interleukin-6, tumor necrosis factor-alpha and interleukin-1beta between diabetic and nondiabetic patients. MATERIAL AND METHODS: Periodontal tissue specimens were collected from nine nondiabetic patients without periodontal disease (group 1), from 11 nondiabetic patients with periodontal disease (group 2) and from seven diabetic patients with periodontal disease (group 3). The expression of MMP-1, MMP-8, interleukin-6, tumor necrosis factor-alpha and interleukin-1beta was quantified using real-time polymerase chain reaction. RESULTS: The nonparametric Kruskal-Wallis test showed that the difference in interleukin-6 expression among the groups was statistically significant (p = 0.04). Furthermore, the generalized Kruskal-Wallis nonparametric linear-by-linear association test showed a statistically significant trend of increase in the expression of interleukin-6 from group 1 to group 2 to group 3 (p = 0.02) and a suggestion of such a trend for MMP-1 (p = 0.05). No increase in MMP-8 expression was observed in patients in group 3 compared to patients in groups 1 and 2. Although the average expression levels of MMP-1, interleukin-1beta and tumor necrosis factor-alpha were increased from group 1 to group 3, the differences were not statistically significant. CONCLUSION: A trend of increased interleukin-6 expression in periodontal tissues was observed across patients with neither diabetes nor periodontal disease, patients with periodontal disease alone, and patients with both diseases.

Platelet lipoproteins. A comparative study with serum lipoproteins.

The nature of human platelet lipoproteins was studied in two series of experiments. In the first series, whole platelets were utilized for extraction of lipoproteins by three different methods: chloroform/methanol/phenol; saline; or sucrose-gradient ultracentrifugation of platelet homogenates. By polyacrylamide gel electrophoresis we were able to demonstrate the existence of lipoprotein in the extracts obtained by the last two methods. These lipoproteins were found not to share antigenic determinants with alpha and beta serum lipoproteins. The second series of experiments utilized platelets solubilized either in sodium deoxycholate or sodium dodecyl sulfate. The solubilized product was characterized by double immunodiffusion and polyacrylamide gel electrophoresis. The nonidentity between plasma and platelet lipoproteins previously demonstrated in the first series of experiments was confirmed. This nonidentity was also supported by a comparison between the apoproteins of purified serum lipoproteins and platelet proteins released after solubilization with sodium dodecyl sulfate. No identical protein fractions were found. Our results suggest that, unlike erythrocyte membrane lipoproteins, the platelet lipoproteins are structurally different from plasma lipoproteins.

Immune mechanisms of atherosclerosis in diabetes mellitus.

It was recently proposed that the increased levels of modified lipoproteins in diabetic patients may be responsible for the accelerated development of macrovascular complications associated with the disease. Modified lipoproteins are believed to induce the transformation of macrophages into foam cells and, in some cases, to induce endothelial cell damage. In addition, modified lipoproteins trigger an immune response leading to the formation of antibodies and then to the formation of LDL-containing immune complexes. In this review, we summarize the evidence linking LDL glycation and oxidation with intracellular accumulation of cholesterol esters and foam-cell formation, and we discuss their potential for inducing an autoimmune response and the formation of lipoprotein-containing immune complexes. The formation of LDL-ICs seems particularly significant, because these ICs are avidly taken up by macrophages through their Fc receptors and induce not only massive intracellular accumulation of CE but also a paradoxical increase in LDL-receptor expression. Our experimental data suggest that the uptake of LDL-IC is facilitated by RBC adsorption, in agreement with the role of RBC in the adsorption of circulating IC and their delivery to phagocytic cells. In addition, macrophages are activated when ingesting LDL-IC and release IL-1 beta and TNF-alpha, which can contribute to the initiation and progression of an atheromatous lesion by several mechanisms. Although it is difficult to envisage how LDL-IC could initiate an endothelial lesion, it is easy to speculate about their role as cofactors in the initiation and progression of the atherosclerotic process.

Lipoprotein-immune complexes and diabetic vascular complications.

In earlier studies, we showed that incubation of HMM with LDL IC led to cellular CE accumulation and to the transformation of macrophages into foam cells. This study demonstrates that the stimulation of macrophages with RBC-LDL-IC also increases the uptake of native LDL, most likely because of an increased LDL receptor number, as shown by Scatchard plot analysis (x-axis intercept 1267 vs. 352 ng LDL/mg protein in control cells). To determine whether the increase in LDL-receptor activity was secondary to a decrease in the macrophage free (nonassociated) cholesterol content, we measured the T-UC and the UC associated with intracellular intact LDL and demonstrated that 50% of the T-UC is associated with intact LDL. UC not associated with LDL (free cholesterol) was lower in LDL-IC-stimulated cells than in control cells. These results suggest that UC associated with nondegraded intracellular LDL is nonregulatory, a conclusion that was also supported by finding increased sterol synthesis (192.8 +/- 22.9 pmol/mg protein vs. 94.8 +/- 11.8) in RBC-LDL-IC-stimulated macrophages. In conclusion, the uptake of RBC-LDL-IC by macrophages led to increased intracellular accumulation of CE and UC, to a decrease in the cell regulatory pool of free cholesterol, and to an increase in LDL-receptor activity.

Cytokines, modified lipoproteins, and arteriosclerosis in diabetes.

Modified lipoproteins, particularly different forms of oxidized LDL (ox-LDL), have been reported to elicit humoral immune responses both in experimental animals and humans. In diabetes, glycation and oxidation processes coexist and lead to the formation of glycoxidation products. Ox-LDL has been demonstrated in atheromatous lesions, anti-ox-LDL antibodies have been detected in circulation and in atheromatous plaques, and immune complexes (ICs) formed with LDL and anti-LDL (LDL-IC) have been isolated from the serum of patients with manifestations of atherosclerosis. In addition, in vitro formed LDL-ICs and ICs isolated from patients have been demonstrated to cause intracellular accumulation of cholesteryl esters (CEs) in human macrophages and fibroblasts. The accumulation of CEs in macrophages exposed to LDL-ICs is unique to this type of IC and is associated with paradoxical overexpression of LDL receptor and with increased synthesis and release of interleukin 1 beta and tumor necrosis factor (TNF) alpha. The overexpression of LDL receptors is higher in LDL-IC-stimulated macrophages that release markedly high amounts of TNF-alpha than in macrophages that release low amounts of TNF-alpha into the medium. The release of cytokines in the subendothelial space may have a significant role in promoting the interaction of endothelial cells with mononuclear cells, causing endothelial cell damage directly or indirectly, and also in inducing smooth muscle cell proliferation. Thus, in view of the above data, it can be concluded that humoral autoimmunity may play a significant role in the pathogenesis of atherosclerosis in diabetes.

Influence of glycemic control on interaction of very-low- and low-density lipoproteins isolated from type I diabetic patients with human monocyte-derived macrophages.

The VLDL and LDL fractions were isolated from 29 patients with type 1 diabetes at the time of admission to the hospital to restore glycemic control and again at discharge. These lipoprotein fractions were incubated with human monocyte-derived macrophages, and the rates of macrophage CE synthesis were determined. The rates of CE synthesis in human macrophages were significantly greater (P less than 0.005) when incubated with VLDL isolated from type I diabetic patients before compared with after glycemic control was attained and averaged 1.84 +/- 0.52 and 1.09 +/- 0.27 nmol (1.20 +/- 0.34 and 0.71 +/- 0.18 micrograms) [14C]cholesteryl oleate synthesized.mg cell protein-1 x 20 h-1, respectively. In contrast, when LDL isolated from the same patient during the same period was incubated with human macrophages, the rates of cellular cholesteryl ester synthesis did not differ significantly and averaged 4.23 +/- 1.26 and 3.91 +/- 0.96 nmol (2.75 +/- 0.82 and 2.55 +/- 0.63 micrograms) [14C]cholesteryl oleate synthesized.mg-1 cell protein.20 h-1, respectively. There was a significant increase in the total cholesterol content of VLDL isolated before glycemic control compared with that isolated after glycemic control was attained (P less than 0.05) resulting from a significant increase in the FC and CE (P less than 0.05) contents of these VLDL particles. There was a significant decrease in the ratio of FC to PL in VLDL, but not LDL, isolated after glycemic control (P less than 0.05). The percentage of apoE in VLDL was significantly decreased (P less than 0.05) after glycemic control was attained.(ABSTRACT TRUNCATED AT 250 WORDS)

Isolation, characterization, and metabolism of the glycated and nonglycated subfractions of low-density lipoproteins isolated from type I diabetic patients and nondiabetic subjects.

The total low-density lipoprotein (LDL) fraction was isolated from 21 patients with type I diabetes and 7 nondiabetic normolipemic subjects. The LDL was separated into two subfractions, one glycated (G-LDL) and one nonglycated (N-LDL), using affinity chromatography. G-LDL comprised 21.1 +/- 3.6 and 5.2 +/- 0.6% of the total LDL in diabetic patients and normal subjects, respectively. G-LDL isolated from both diabetic patients and normal subjects was significantly more glycated than N-LDL isolated from the same subject. G-LDL isolated from both diabetic patients and normal subjects was enriched in triglycerides. The metabolism of N-LDL and G-LDL was investigated in human fibroblasts, which express only the classical LDL receptor, and in human monocyte-derived macrophages, which also express a receptor for G-LDL. In fibroblasts, the rates of receptor-mediated accumulation of N-LDL isolated from normal subjects and diabetic patients were significantly greater (P < 0.01) than those of G-LDL. In contrast, when the same LDL subfractions were incubated with human monocyte-derived macrophages, the rates of receptor-mediated accumulation of G-LDL isolated from both groups were significantly greater (P < 0.01) than those of N-LDL. Rates of degradation of G-LDL by human macrophages were not significantly different from those of N-LDL during short-term incubations but reached statistical significance (P < 0.05) when LDL subfractions were incubated with cells for 24 h.(ABSTRACT TRUNCATED AT 250 WORDS)

Anti-modified LDL antibodies, LDL-containing immune complexes, and susceptibility of LDL to in vitro oxidation in patients with type 2 diabetes.

We investigated the hypothesis that modified lipoproteins trigger an immune response leading to the production of autoantibodies and subsequently to the formation of atherogenic immune complexes (IC). We recruited 20 type 2 diabetic patients with macrovascular disease, 14 nondiabetic patients with coronary artery disease (CAD), and 34 healthy control subjects matched for age, sex, and race. Serum antibodies to oxidized and glycated LDL did not differ significantly among the 3 groups. Serum IC contained variable, but not statistically different, amounts of IgG, IgM, and IgA. In contrast, the content of cholesterol in IC isolated from diabetic patients was significantly higher than that in IC isolated from control subjects, and the content of apolipoprotein (apo)-B was significantly higher than that in IC isolated from control subjects and patients with CAD. Cholesteryl ester accumulation in human monocyte-derived macrophages incubated with IC, a measure of the atherogenic potential of IC, was significantly higher in macrophages incubated with red blood cell-adsorbed IC isolated from diabetic patients compared with IC isolated from control subjects (P < 0.03) or from patients with CAD (P < 0.04) and was strongly correlated with the content of apoB (r = 0.68, P < 0.001) and cholesterol (r = 0.61, P < 0.001) in IC. LDL from diabetic patients was more susceptible to oxidation in vitro, was significantly smaller, and contained significantly less alpha-tocopherol than LDL isolated from subjects in the other groups. In addition, the n-3 polyunsaturated fatty acid content of phospholipids and cholesteryl esters in LDL isolated from diabetic patients was significantly increased (P < 0.05) compared with that from patients with CAD or from control subjects. We postulate that LDL size, susceptibility to oxidation, and lipid fatty acid composition may play a critical role in the production of antibodies to oxidized LDL and consequently in the formation of LDL-containing IC in patients with type 2 diabetes.

Glycosylation of low-density lipoprotein enhances cholesteryl ester synthesis in human monocyte-derived macrophages.

Glucose can react with the lysine residues of low-density lipoproteins (LDLs) and convert the lipoprotein to a form with a receptor-mediated uptake by cultured cells that is impaired. However, in contrast to other modified lipoproteins taken up by both murine and human macrophages via the scavenger-receptor pathway that may induce the formation of foam cells, glycosylated LDL is not recognized by murine macrophages, and thus far, it has not been shown to lead to marked intracellular accumulation of cholesterol in human macrophages. This study illustrates that glycosylated LDL incubated with human monocyte-derived macrophages, at a concentration of 100 micrograms LDL/ml medium, stimulates significantly more cholesteryl ester (CE) synthesis than does control LDL (10.65 +/- 1.5 vs. 4.8 +/- 0.13 nmol.mg-1 cell protein.20 h-1; P less than .05). At LDL concentrations similar to those of plasma, the rate of CE synthesis in macrophages incubated with glycosylated LDL is more markedly enhanced than that observed in cells incubated with control LDL (3-fold increase). The marked stimulation of CE synthesis in human macrophages exposed to glycosylated LDL is paralleled by a significant increase in CE accumulation in these cells (P less than .001). The increase in CE synthesis and accumulation seem to be mediated by an increase in the degradation of glycosylated LDL by human macrophages. Glycosylated LDL enters the macrophages and is degraded by the classic LDL-receptor pathway in slightly smaller amounts than control LDL, but its degradation by pathways other than the classic LDL receptor or scavenger receptor is markedly enhanced.(ABSTRACT TRUNCATED AT 250 WORDS)

Enhancement of platelet aggregation by low-density lipoproteins from IDDM patients.

Low-density lipoprotein (LDL) is known to enhance platelet sensitivity to some aggregating agents. In this study, we observed that LDL isolated from patients with insulin-dependent diabetes mellitus (IDDM) enhanced thrombin-induced platelet aggregation to a greater extent than LDL isolated from matched controls (P less than .01). Thromboxane B2 production during aggregation was also significantly more enhanced by LDL isolated from IDDM than by control LDL (P less than .01). There was no difference in the lipid composition (free and esterified cholesterol, total phospholipids, and triglycerides) of LDL isolated from diabetic and control subjects. In contrast, the extent of glycosylation of LDL isolated from diabetic patients was significantly greater than that observed in LDL from normal subjects (P less than .01), and a positive correlation (r = .605, P less than .01) between the degree of LDL glycosylation and the rate of platelet aggregation was observed. LDL glycosylated in vitro enhanced thrombin-, collagen-, and adenosine 5'-diphosphate-induced platelet aggregation to a greater extent than control LDL (P less than .01). Although LDL glycosylated in vitro was taken up by platelets to a greater extent than control LDL (P less than .05), the lipid composition (free cholesterol and phospholipid) of platelets was not significantly changed. We postulate that an increased degree of glycosylation of LDL may enhance its uptake by platelets and lead to increased platelet reactivity to aggregating agents, probably by altering the structure of the platelet membrane. The enhancement of platelet aggregation by LDL may contribute to the accelerated development of atherosclerosis in diabetes mellitus.

LDL from patients with well-controlled IDDM is not more susceptible to in vitro oxidation.

Increased susceptibility of LDL to oxidation has been shown to be associated with the presence of coronary heart disease and may account for the accelerated vascular disease seen in diabetes. The response of LDL to in vitro oxidative stress has been proposed as a measure of the predisposition of LDL to the in vivo subendothelial oxidative stress. Increased susceptibility to oxidation has been demonstrated recently in diabetic patients with poorly controlled IDDM. Thus, we conducted studies to determine whether the increased susceptibility of LDL to oxidation was secondary to diabetes per se or to the level of glycemic control. Fifteen IDDM patients with good glycemic control and with no evidence of macrovascular disease or proteinuria were compared with healthy age-, sex-, race-, and BMI-matched nondiabetic subjects. Fasting blood glucose levels averaged 12.1 +/- 1.1 (mean +/- SE) vs. 4.9 +/- 0.1 mmol/l in the diabetic versus the control groups, respectively. HbA1c levels averaged 7.7 +/- 0.5 vs. 4.4 +/- 0.2%, reflecting well-controlled diabetes (P < 0.0001). Total, LDL, VLDL, and HDL cholesterol, triglyceride, and lipoprotein(a) levels did not differ between the groups. The particle size, lipid composition, fatty acid content, antioxidant content, and glycation were similar for LDL isolated from both groups. A rapid LDL preparation technique was used to compare LDL susceptibility to oxidation under the following conditions: final LDL cholesterol concentration of 100 microg/ml, 5 micromol/l of CuCl2 at 25 degrees C. There was no difference in the susceptibility to in vitro oxidation of LDL isolated from IDDM patients compared with control subjects. There was no correlation of glycemic control with any of the parameters of the in vitro oxidation of LDL. LDL from patients with well-controlled IDDM does not differ in composition or in susceptibility to in vitro oxidative stress compared with LDL from nondiabetic subjects.

Platelet function during continuous insulin infusion treatment in insulin-dependent diabetic patients.

Patients with diabetes mellitus manifest increased in vitro platelet aggregation and increased synthesis of the proaggregant and vasoconstrictor, thromboxane A2 (TXA2). We studied the effects of continuous insulin infusion treatment on platelet aggregation and arachidonic acid (AA)-stimulated platelet TXA2 synthesis (15 and 30 s post-AA, 1 mM) in 16 type I diabetic patients. Strict glycemic control was induced with the Biostator for 2 days and maintained for 12-14 days with continuous subcutaneous insulin infusion (CSII). The average premeal plasma glucose level (4/day) fell from 184 +/- 15, before treatment, to 107 +/- 6 mg/dl on the final day (P less than 0.001). After control, platelet synthesis of TXA2, measured by radioimmunoassay of its stable metabolite, immunoreactive TXB2 (iTXB2), decreased in all patients (30 s: 276 +/- 31 versus 199 +/- 28 ng iTXB2/ml/5 X 10(5) platelets; P less than 0.05). The reduction in platelet iTXB2 synthesis (15 and 30 s) was greater in poorly controlled patients (HbA1c greater than 12%; N = 8), and for all patients the decrease in iTXB2 (15 and 30 s) was correlated with the prestudy HbA1c level (15 s: r = 0.6; P less than 0.01). In contrast, platelet aggregation responses did not improve during intensive insulin treatment. The ED50 for AA (dose producing 50% maximum aggregation at 1 min) was unchanged after 2 wk of treatment and the ED50 for aggregation induced by ADP fell significantly in patients with HbA1c greater than 12% (2.8 +/- 1.3 versus 1.2 +/- 0.6 microM; P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Antibodies to oxidized LDL predict coronary artery disease in type 1 diabetes: a nested case-control study from the Pittsburgh Epidemiology of Diabetes Complications Study.

The pathogenesis of excess cardiovascular risk in type 1 diabetes is unclear. LDL cholesterol is only weakly predictive, and its concentration is often normal in type 1 diabetes. We therefore examined whether markers of LDL oxidation such as antibodies to oxidized LDL (Ab-OxLDL) and LDL-containing immune complexes, rather than LDL concentration, were predictive of coronary artery disease (CAD) in type 1 diabetes. This nested case-control study from an epidemiologic cohort study included 49 incident cases of myocardial infarction (MI), angina, or CAD death and 49 age-, sex-, and duration-matched control subjects. Ab-OxLDL was measured by enzyme immunoassay and the apolipoprotein B (ApoB) content of immune complexes (ApoB-IC) precipitated by polyethylene glycol by immunoelectrophoresis in baseline stored samples. Ab-OxLDL was inversely, and ApoB-IC directly, related to subsequent CAD. In multivariate analyses, Ab-OxLDL remained a significant independent predictor along with previously recognized predictors, hypertension and Beck depression score. In conclusion, oxidation of LDL and the immune response it elicits may play a role in predicting the development of CAD in type 1 diabetes and explain at least some of the enhanced CAD risk in type I diabetes.

Fc-gamma receptor cross-linking by immune complexes induces matrix metalloproteinase-1 in U937 cells via mitogen-activated protein kinase.

Matrix metalloproteinase-1 (MMP-1) secreted by macrophages potentially contributes to plaque rupture. Because large quantities of immunoglobulin G and ICs (ICs), including low density lipoprotein-containing ICs (LDL-ICs), are present in atherosclerotic lesions, we examined the effect of LDL-ICs on macrophage MMP-1 expression. With the use of ICs prepared with human LDL and rabbit anti-LDL antiserum, our enzyme-linked immunosorbent assays and Northern blots showed that MMP-1 secretion and expression by U937 histiocytes were induced by LDL-ICs. Furthermore, our results showed that blocking of Fc-gamma receptor I and II (FcgammaRI and FcgammaRII) inhibited 70% and 55%, respectively, of the LDL-IC-induced secretion of MMP-1. Finally, our data showed that both PD98059, an inhibitor of the mitogen-activated protein kinase pathway, and Ro-31-2880, an inhibitor of protein kinase C, inhibited LDL-IC-stimulated MMP-1 secretion in a dose-dependent manner, with 96% and 95% inhibition, respectively, at the respective doses of 50 micromol/L and 80 nmol/L. In conclusion, this study demonstrated for the first time that LDL-ICs induce macrophage MMP-1 secretion by cocross-linking FcgammaRI and FcgammaRII and triggering a protein kinase C-dependent mitogen-activated protein kinase pathway. These results suggest that LDL-ICs and other ICs localized in atherosclerotic plaques may be potent stimulators for macrophage MMP-1 expression and may contribute to plaque rupture and acute coronary events.

Pathogenesis of atherosclerosis in diabetes mellitus.

Numerous studies have shown that patients with diabetes mellitus have accelerated atherosclerotic vascular disease, and major advances in understanding it pathogenesis have been made. Current suggestions are that endothelial injury may be the initial event in the genesis of atherosclerosis, followed by platelet adhesion and aggregation at the site of injury. In diabetes, evidence of endothelial dysfunction is present. Smooth muscle cell proliferation is an important pathologic finding in atherosclerosis. This process is stimulated by a platelet mitogen, which has been partially characterized. The mitogen has not been studied in diabetes. Lipid accumulation in the area of the atherosclerotic lesion is primarily in the form of intracellular and extracellular esterified cholesterol. In uncontrolled diabetes, elevated plasma low density lipoprotein levels and decreased plasma high density lipoprotein levels favor lipid deposition in large vessels. There is evidence of a thrombotic state in certain diabetic patients. Collectively, these abnormalities of endothelial, platelet, smooth muscle, lipoprotein, and coagulation behavior may be viewed as contributing to the problem of accelerated atherosclerosis in diabetes. A thorough understanding of the pathogenesis of this process aids in designing appropriate preventive therapeutic approaches.

Release of platelet plasminogen activator inhibitor 1 in whole blood is increased in patients with type II diabetes.

OBJECTIVE: To compare platelet plasminogen activator inhibitor 1 (PAI-1) release in type II diabetic patients and healthy control subjects. RESEARCH DESIGN AND METHODS: We studied a group of 27 diabetic patients and a group of 16 nondiabetic control subjects. Whole-blood platelet aggregation, defined as a decrease in platelet count during shaking (180 rpm) of blood samples at 37 degrees C, and plasma PAI-1 antigen concentrations were measured in parallel at time 0, 7.5, 15, 30, 60, 120, and 180 min. RESULTS: Platelet aggregation did not differ significantly between the two groups at any time period. However, the increase in plasma PAI-1 antigen concentration over basal levels at time 0 was higher for the group of diabetic patients when compared with their matched control subjects. The increment of PAI-1 antigen was 61.8 +/- 29.4 vs. 35.9 +/- 13.4 ng/ml (P < 0.005, means +/- SD) after 180 min for the diabetic and control subjects, respectively. Platelet PAI-1 release was correlated to very-low-density lipoprotein cholesterol and triglyceride plasma levels, but not to HbA1c levels. CONCLUSIONS: Platelets of patients with type II diabetes release significantly more PAI-1 than platelets of healthy subjects at the same level of platelet aggregation. This may contribute to enhanced thrombosis in diabetes.