In combination with other factors, hyperglycemia may cause the accelerated progression of atherosclerosis in people with diabetes. Arterial smooth muscle cell (SMC) proliferation and accumulation contribute to formation of advanced atherosclerotic lesions. Therefore, we investigated the effects of hyperglycemia on SMC proliferation and accumulation in vivo and in isolated arteries and SMCs by taking advantage of a new porcine model of diabetes-accelerated atherosclerosis, in which diabetic animals are hyperglycemic without receiving exogenous insulin. We show that diabetic animals fed a cholesterol-rich diet, like humans, develop severe lesions of atherosclerosis characterized by SMC accumulation and proliferation, whereas lesions in nondiabetic animals contain fewer SMCs after 20 weeks. However, high glucose (25 mmol/l) does not directly stimulate the proliferation of SMCs in isolated arterial tissue from diabetic or nondiabetic animals, or of cultured SMCs from these animals or from humans. Furthermore, the mitogenic actions of platelet-derived growth factor, IGF-I, or serum are not enhanced by high glucose. High glucose increases SMC glucose metabolism through the citric acid cycle and the pentose phosphate pathway by 240 and 90%, respectively, but <10% of consumed glucose is metabolized through these pathways. Instead, most of the consumed glucose is converted into lactate and secreted by the SMCs. Thus, diabetes markedly accelerates SMC proliferation and accumulation in atherosclerotic lesions. The stimulatory effect of diabetes on SMCs is likely to be mediated by effects secondary to the hyperglycemic state. Diabetes 50:851-860, 2001 I t is estimated that 75-80% of adults with diabetes die from complications of atherosclerosis. The progression of atherosclerotic lesions is accelerated by diabetes (1). Thus, stroke, coronary heart disease, and peripheral arterial disease are more common and occur at an earlier age in diabetic people than in the general population (1-2).The cellular mechanisms underlying the accelerated progression of atherosclerotic lesions in diabetic arteries are still largely unknown. Hyperinsulinemia, lipid abnormalities, and hyperglycemia have each been suggested to cause this response. Because smooth muscle cell (SMC) proliferation and accumulation are key events in the development of advanced lesions, a number of studies have investigated the regulation of SMC proliferation. Studies on the effects of hyperinsulinemia show that direct mitogenic effects of insulin on SMCs are weak and that the principal mitogenic response elicited by insulin is mediated through a cross-reaction at high unphysiological insulin concentrations with the IGF-I receptor (3-6). Thus, a direct mitogenic action of hyperinsulinemia on SMCs in vivo is unlikely.It is becoming increasingly clear that many of the complications of diabetes arise from hyperglycemia that cannot be completely prevented using the methods of blood glucose control available today. This is particularly apparent for retinopathy, nephropathy,...

Arterial smooth muscle cell (SMC) proliferation contributes to a number of vascular pathologies. Prostaglandin E 2 (PGE 2 ), produced by the endothelium and by SMCs themselves, acts as a potent SMC growth inhibitor. The growth-inhibitory effects of PGE 2 are mediated through activation of G-protein-coupled membrane receptors, activation of adenylyl cyclases (ACs), formation of cAMP, and subsequent inhibition of mitogenic signal transduction pathways in SMCs. Of the 10 different mammalian AC isoforms known today, seven isoforms (AC2-7 and AC9) are expressed in SMCs from various species. We show that, despite the presence of several different AC isoforms, the principal AC isoform activated by PGE 2 in human arterial SMCs is a calmodulin kinase II-inhibited AC with characteristics similar to those of AC3. AC3 is expressed in isolated human arterial SMCs and in intact aorta. We further show that arterial SMCs isolated from AC3-deficient mice are resistant to PGE 2 -induced growth inhibition. In summary, AC3 is the principal AC isoform activated by PGE 2 in arterial SMCs, and AC3 mediates the growth-inhibitory effects of PGE 2 . Because AC3 activity is inhibited by intracellular calcium through calmodulin kinase II, AC3 may serve as an important integrator of growth-inhibitory signals that stimulate cAMP formation and growth factors that increase intracellular calcium.

The VH26 germline gene occupies two different loci, due to gene duplication, and is one of the most frequently expressed human immunoglobulin VH genes. This report identifies the alleles of each VH26 locus and describes distinct patterns of VH26 polymorphism in three ethnic groups. Oligonucleotide probes targeting VH26 were used in sequence-specific RFLP analysis of DNA from 72 Caucasians, 52 Asians, 35 American Blacks, and members of six families. The A locus, on a 7.0-kb TaqI band, was detected in 89% of Caucasians, 75% of Asians, and 26% of Blacks (x2 = 46, P < 0.0005). The B locus, detected on a 5.0-kb band in nearly all subjects, was found to have additional alleles occurring at 6.8 kb in 10% of Asians and 3% of Blacks (X2 = 7.8, P < 0.02) and at 3.7 kb in 1.4% of Caucasians, 21% of Asians, and 9% of Blacks (x2 = 13.8, P < 0.001). In Asians only, the 3.7-kb hybridization band represented a multiple-duplication unit containing three or four gene copies. Duplications of other VH26 alleles, and null alleles of the B locus, were also seen. An exact VH26 sequence was cloned from the 5.0-kb allele and likely exists in the 7.0-and 6.8-kb alleles. A novel sequence cloned from the 3.7-kb allele differed from VH26 by nine nucleotides and appears to have evolved by gene conversion in CDR2. The total diploid gene dose of the A and B loci ranged from one to as many as six copies of VH26-containing genes, and from zero to as many as six to eight copies of the 3.7-kb allele. We conclude that ethnic differences in polymorphism exist at both VH26 loci. These differences could influence VH26 expression because they involve variations in gene copy number and coding region sequence. (J. Clin. Invest. 1995. 96:1591-1600

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Aims/hypothesis. Diabetes accelerates cardiovascular disease caused by atherosclerosis. Accordingly, diabetes accelerates atherosclerotic lesion progression and increases arterial smooth muscle cell proliferation. We hypothesized that diabetes can exert growth-promoting effects on smooth muscle cells via increased advanced glycation end-products or by dyslipidaemia. Methods. Primary human arterial smooth muscle cells were stimulated with advanced glycation end-products, other ligands of the receptor for advanced glycation end-products or fatty acids common in triglycerides. Cell proliferation was measured as DNA synthesis, cell cycle distribution and cell number. Effects of oleate on cellular phospholipids, diacylglycerol, triglycerides and cholesterol esters were analyzed by thin-layer chromatography, and oleate accumulation into diacylglycerol was confirmed by gas chromatography. Results. Human arterial smooth muscle cells express the receptor for advanced glycation end-products, but its ligands N ε -(carboxymethyl)lysine-modified proteins, methylglyoxal-modified proteins, S100B polypeptide and amyloid-β (1-40) peptide, exert no mitogenic action. Instead, oleate, one of the most common fatty acids in triglycerides, enhances platelet-derived growth factor-BB-mediated proliferation and oleate-containing 1,2-diacylglycerol formation in smooth muscle cells. This mitogenic effect of oleate depends on phospholipase D activity and is associated with an increased formation of oleate-enriched 1,2-diacylglycerol. Conclusion/interpretation. Oleate, not ligands of the receptor for advanced glycation end-products, acts as an enhancer of human smooth muscle cell proliferation. Thus, lipid abnormalities, rather than hyperglycaemia, could be a major factor promoting proliferation of smooth muscle cells in atherosclerotic lesions. [Diabetologia (2003[Diabetologia ( ) 46:1676[Diabetologia ( -1687 Keywords Atherosclerosis, diabetes, diacylglycerol, fatty acids, platelet-derived growth factor, phospholipase D, triglycerides. Atherosclerosis is accelerated by both Type I and Type 2 diabetes [1] by mechanisms that are poorly understood. Proliferation of arterial smooth muscle cells (SMCs) in lesions of atherosclerosis plays an important role in progression of early fatty streaks to fibroatheromas. We have recently reported that increased SMC proliferation in fibroatheromas occurs concomitantly with hyperglycaemia and an increased plasma triglyceride concentration in a porcine model of diabetes-accelerated atherosclerosis [2]. However, increased plasma glucose concentrations do not directly stimulate proliferation of SMCs isolated from these animals or from human subjects [2]. In this study, we investigated advanced glycation end-products (AGEs)