Endothelial vasodilator function is related to low-density lipoprotein particle size and low-density lipoprotein vitamin E content in type 1 diabetes

Advanced cardiovascular physiology in an individual with type 1 diabetes after 10-year ketogenic diet

Adults with type 1 diabetes (T1D) have an elevated risk for cardiovascular disease (CVD) compared with the general population. HbA1c is the primary modifiable risk factor for CVD in T1D. Fewer than 1% of patients achieve euglycemia (<5.7% HbA1c). Ketogenic diets (KD; ≤50 g carbohydrate/day) may improve glycemia and downstream vascular dysfunction in T1D by reducing HbA1c and insulin load. However, there are concerns regarding the long-term CVD risk from a KD. Therefore, we compared data collected in a 60-day window in an adult with T1D on exogenous insulin who consumed a KD for 10 years versus normative values in those with T1D (T1D norms). The participant achieved euglycemia with an HbA1c of 5.5%, mean glucose of 98 [5] mg/dL (median [interquartile range]), 90 [11]% time-in-range 70-180 mg/dL (T1D norms: 1st percentile for all), and low insulin requirements of 0.38 ± 0.03 IU/kg/day (T1D norms: 8th percentile). Seated systolic blood pressure (SBP) was 113 mmHg (T1D norms: 18th percentile), while ambulatory awake SBP was 132 ± 15 mmHg (T1D target: <130 mmHg), blood triglycerides were 69 mg/dL (T1D norms: 34th percentile), low-density lipoprotein was 129 mg/dL (T1D norms: 60th percentile), heart rate was 56 beats/min (T1D norms: >1SD below the mean), carotid-femoral pulse wave velocity was 7.17 m/s (T1D norms: lowest quartile of risk), flow-mediated dilation was 12.8% (T1D norms: >1SD above mean), and cardiac vagal baroreflex gain was 23.5 ms/mmHg (T1D norms: >1SD above mean). Finally, there was no indication of left ventricular diastolic dysfunction from echocardiography. Overall, these data demonstrate below-average CVD risk relative to T1D norms despite concerns regarding the long-term impact of a KD on CVD risk.NEW & NOTEWORTHY Adults with type 1 diabetes (T1D) have a 10-fold higher risk for cardiovascular disease (CVD) compared with the general population. We assessed cardiovascular health metrics in an adult with T1D who presented with a euglycemic HbA1c after following a ketogenic diet for the past 10 years. Despite concerns about the ketogenic diet increasing CVD risk, the participant exhibited below-average CVD risk relative to others with T1D when considering all outcomes together.

Nutraceuticals against Oxidative Stress in Autoimmune Disorders

Antioxidant mechanisms are constituted of enzymes, endogenous, and non-enzymatic, exogenous, which have the role of counterbalancing oxidative stress. Intake of these compounds occurs in the diet. Vegetables, plants, and fruits contain a wide range of alkaloids, polyphenols, and terpenoids which are called “phytochemicals”. Most of these substances are responsible for the positive properties of fruits and vegetables, which are an essential part of a healthy life with roles in ameliorating chronic illnesses and favoring longevity. Nutraceuticals are substances contained in a food or fragment of it influencing health with positive effects on health helping in precenting or treating disorders. We conducted a review illustrating the principal applications of nutraceuticals in autoimmune disorders. Literature reported several studies about exogenous dietary antioxidant supplementation in diverse autoimmune diseases such as rheumatoid arthritis, lupus, diabetes, and multiple sclerosis. In these pathologies, promising results were obtained in some cases. Positive outcomes were generally associated with a reduction of oxidative stress parameters and a boost to antioxidant systems, and sometimes with anti-inflammatory effects. The administration of exogenous substances through food derivates or dietary supplements following scientific standardization was demonstrated to be effective. Further bias-free and extended studies should be conducted that include ever-increasing oxidative stress biomarkers.

Endothelial function improvement in patients with familial hypercholesterolemia receiving PCSK-9 inhibitors on top of maximally tolerated lipid lowering therapy

BACKGROUND

Treatment with protein convertase subtilisin kexin type 9 inhibitors (PCSK-9i) reduced cholesterol levels and cardiovascular events in patients with hypercholesterolemia. We assessed changes in lipid profile, oxidation markers and endothelial function in patients with familial hypercholesterolemia (FH) after a 12-week treatment with a PCSK-9i.

METHODS

Patients with FH starting a treatment with PCSK-9i were included. Total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), lipoprotein(a) (Lp(a)), small dense LDL (assessed by LDL score), 11-dehydro-thromboxane (11-TXB2), 8-isoprostaglandin-2alpha (8-iso-PGF2α), flow-mediated dilation (FMD) and reactive hyperaemia index (RHI) were evaluated before starting PCSK-9i treatment and after a 12-week treatment.

RESULTS

Twenty-five subjects were enrolled (52% males, mean age 51.5 years). At the 12-week assessment, we observed a 38% median reduction in TC, 52% in LDL-C, 7% in Lp(a) and 46% in LDL score. In parallel, 11-TXB2 and 8-iso-PGF2α showed a reduction of 18% and 17%, respectively. FMD changed from 4.78% ± 2.27 at baseline to 10.6% ± 5.89 at 12 weeks (p < 0.001), with RHI changing from 2.37 ± 1.23 to 3.76 ± 1.36 (p < 0.001). A multivariate analysis showed that, after adjusting for potential confounders, change in LDL score was an independent predictor of changes in FMD (β = -0.846, p = 0.015) and in 8-iso-PGF2α (β = 0.778, p = 0.012).

CONCLUSIONS

Small dense LDL reduction (assessed by LDL score) is related to changes in oxidation markers and endothelial function in patients with FH treated with PCSK-9i.

The Novel Small-molecule Annexin-A1 Mimetic, Compound 17b, Elicits Vasoprotective Actions in Streptozotocin-induced Diabetic Mice

The formyl peptide receptor (FPR) family are a group of G-protein coupled receptors that play an important role in the regulation of inflammatory processes. It is well-established that activation of FPRs can have cardioprotective properties. Recently, more stable small-molecule FPR1/2 agonists have been described, including both Compound 17b (Cmpd17b) and Compound 43 (Cmpd43). Both agonists activate a range of signals downstream of FPR1/2 activation in human-engineered FPR-expressing cells, including ERK1/2 and Akt. Importantly, Cmpd17b (but not Cmpd43) favours bias away from intracellular Ca²⁺ mobilisation in this context, which has been associated with greater cardioprotection in response to Cmpd17b over Cmpd43. However, it is unknown whether these FPR agonists impact vascular physiology and/or elicit vasoprotective effects in the context of diabetes. First, we localized FPR1 and FPR2 receptors predominantly in vascular smooth muscle cells in the aortae of male C57BL/6 mice. We then analysed the vascular effects of Cmpd17b and Cmpd43 on the aorta using wire-myography. Cmpd17b but not Cmpd43 evoked a concentration-dependent relaxation of the mouse aorta. Removal of the endothelium or blockade of endothelium-derived relaxing factors using pharmacological inhibitors had no effect on Cmpd17b-evoked relaxation, demonstrating that its direct vasodilator actions were endothelium-independent. In aortae primed with elevated K⁺ concentration, increasing concentrations of CaCl₂ evoked concentration-dependent contraction that is abolished by Cmpd17b, suggesting the involvement of the inhibition of Ca²⁺ mobilisation via voltage-gated calcium channels. Treatment with Cmpd17b for eight weeks reversed endothelial dysfunction in STZ-induced diabetic aorta through the upregulation of vasodilator prostanoids. Our data indicate that Cmpd17b is a direct endothelium-independent vasodilator, and a vasoprotective molecule in the context of diabetes.

Relationship between Impairment of the Vascular Endothelial Function and the CHA2DS2-VASc Score in Patients with Sinus Rhythm and Non-valvular Atrial Fibrillation

Objective and methods There is little information concerning the influence of the heart rhythm on the vascular endothelial function in patients with non-valvular atrial fibrillation (AF) compared with studies concerning sinus rhythm (SR). The present study included paroxysmal (n=184) or chronic (n=53) AF patients without heart failure and control subjects with SR (n=79) matched for age, gender and the CHA₂DS₂-VASc score. Paroxysmal AF was defined as episodes that terminated spontaneously within 7 days, while chronic AF was defined as longstanding AF that was refractory to cardioversion for 12 months or longer. There were no significant differences in the numbers of patients receiving renin-angiotension-aldosterone system inhibitors or statins among the three groups. Results Among the 237 AF patients (155 men, mean age 64±9 years, mean CHA₂DS₂-VASc score 1.8±1.4), the flow-mediated dilatation (FMD) was 5.4%±2.6% in the paroxysmal AF group, 4.3%±2.1% in the chronic AF group and 6.5%±3.5% in the SR group. There were significant differences among the 3 groups (all, p<0.05). Nitroglycerin-induced dilatation (NMD) was noted in 14.6%±6.5% of the paroxysmal AF group, 16.5%±9.1% of the chronic AF group and 12.7%±5.9% of the SR group, with no significant differences among the 3 groups. There was a significant negative correlation between the CHA₂DS₂-VASc scores and the FMDs value in all 3 groups (paroxysmal AF group:r=-0.322, p<0.01; chronic AF group:r=-0.291, p<0.05; SR group:r=-0.326, p<0.01). Conclusion In comparison with SR, the frequency and duration of AF episodes appear to cause deterioration of the vascular endothelial function.

Exercise as medicine - evidence for prescribing exercise as therapy in 26 different chronic diseases

This review provides the reader with the up-to-date evidence-based basis for prescribing exercise as medicine in the treatment of 26 different diseases: psychiatric diseases (depression, anxiety, stress, schizophrenia); neurological diseases (dementia, Parkinson's disease, multiple sclerosis); metabolic diseases (obesity, hyperlipidemia, metabolic syndrome, polycystic ovarian syndrome, type 2 diabetes, type 1 diabetes); cardiovascular diseases (hypertension, coronary heart disease, heart failure, cerebral apoplexy, and claudication intermittent); pulmonary diseases (chronic obstructive pulmonary disease, asthma, cystic fibrosis); musculo-skeletal disorders (osteoarthritis, osteoporosis, back pain, rheumatoid arthritis); and cancer. The effect of exercise therapy on disease pathogenesis and symptoms are given and the possible mechanisms of action are discussed. We have interpreted the scientific literature and for each disease, we provide the reader with our best advice regarding the optimal type and dose for prescription of exercise.

GPER inhibits diabetes-mediated RhoA activation to prevent vascular endothelial dysfunction

The effect of estrogen receptors on diabetes-induced vascular dysfunction is critical, but ambiguous. Individuals with diabetic vascular disease may require estrogen receptor-specific targeted therapy in the future. The G protein-coupled estrogen receptor (GPER) has beneficial effects on vascular function. However, its fundamental mechanisms are unclear. The RhoA/Rho-kinase pathway contributes to diabetic vascular complications, whereas estrogen can suppress Rho-kinase function. Thus, we assumed that GPER inhibits diabetes-mediated RhoA activation to prevent vascular dysfunction. We further investigated the underlying mechanisms involved in this process. Vascular endothelial cells and ex vivo cultured ovariectomized (OVX) C57BL/6 mouse aortae were treated with high glucose (HG) alone or in combination with GPER agonist (G1). G1 treatment was also administered to OVX db/db mice for 8 weeks. An ex-vivo isovolumic myograph was used to analyze the endothelium-dependent vasodilation and endothelium-independent contraction of mouse aortae. Apoptosis, oxidative stress, and inflammation were attenuated in G1-pretreated vascular endothelial cells. G1 significantly decreased the phosphorylation of inhibitory endothelial nitric oxide (NO) synthase residue threonine 495 (eNOS Thr495), inhibited RhoA expression, and increased NO production. Additionally, G1 rescued the impaired endothelium-dependent relaxation and inhibited RhoA activation in the thoracic aorta of OVX db/db mice and ex-vivo cultured OVX C57BL/6 mouse aortae treated with HG. Estrogens acting via GPER could protect vascular endothelium, and GPER activation might elicit ERα-independent effect to inhibit RhoA/Rho-kinase pathway. Additionally, GPER activation might reduce vascular smooth muscle contraction by inhibiting RhoA activation. Thus, the results of the present study suggest a new therapeutic paradigm for end-stage vascular dysfunction by inhibiting RhoA/Rho-kinase pathway via GPER activation.

Impact of diabetes on cardiovascular disease: an update

Cardiovascular diseases are the most prevalent cause of morbidity and mortality among patients with type 1 or type 2 diabetes. The proposed mechanisms that can link accelerated atherosclerosis and increased cardiovascular risk in this population are poorly understood. It has been suggested that an association between hyperglycemia and intracellular metabolic changes can result in oxidative stress, low-grade inflammation, and endothelial dysfunction. Recently, epigenetic factors by different types of reactions are known to be responsible for the interaction between genes and environment and for this reason can also account for the association between diabetes and cardiovascular disease. The impact of clinical factors that may coexist with diabetes such as obesity, dyslipidemia, and hypertension are also discussed. Furthermore, evidence that justify screening for subclinical atherosclerosis in asymptomatic patients is controversial and is also matter of this review. The purpose of this paper is to describe the association between poor glycemic control, oxidative stress, markers of insulin resistance, and of low-grade inflammation that have been suggested as putative factors linking diabetes and cardiovascular disease.

Chronic supplementation of paeonol combined with danshensu for the improvement of vascular reactivity in the cerebral basilar artery of diabetic rats

One of the leading causes of death in the world is cerebrovascular disease. Numerous Chinese traditional medicines, such as Cortex Moutan (root bark of Paeonia suffruticosa Andrew) and Radix Salviae miltiorrhizae (root and rhizome of Salvia miltiorrhiza Bunge), protect against cerebrovascular diseases and exhibit anti-atherosclerotic effects. Traditional medicines have been routinely used for a long time in China. In addition, these two herbs are prescribed together in clinical practice. Therefore, the pharmacodynamic interactions between the active constituents of these two herbs, which are paeonol (Pae) and danshensu (DSS), should be particularly studied. The study of Pae and DSS can provide substantial foundations in understanding their mechanisms and empirical evidence to support clinical practice. This study investigated the effects and possible mechanisms of the pharmacodynamic interaction between Pae and DSS on cerebrovascular malfunctioning in diabetes. Experimental diabetes was induced in rats, which was then treated with Pae, DSS, and Pae + DSS for eight weeks. Afterward, cerebral arteries from all groups were isolated and equilibrated in an organ bath with Krebs buffer and ring tension. Effects of Pae, DSS, and Pae + DSS were observed on vessel relaxation with or without endothelium as well as on the basal tonus of vessels from normal and diabetic rats. Indexes about oxidative stress were also determined. We report that the cerebral arteries from diabetic rats show decreased vascular reactivity to acetylcholine (ACh) which was corrected in Pae, DSS, and Pae + DSS treated groups. Furthermore, phenylephrine (PE)-induced contraction response decreased in the treated groups. Phenylephrine and CaCl(2)-induced vasoconstrictions are partially inhibited in the three treated groups under Ca2+-free medium. Pre-incubated with tetraethylammonium, a non-selective K+ channel blocker, the antagonized relaxation responses increased in DSS and Pae + DSS treated diabetic groups compared with those in diabetic and Pae-treated diabetic groups. In addition, superoxide dismutase activity and thiobarbituric acid reactive substances content significantly changed in the presence of Pae + DSS. We therefore conclude that both Pae and DSS treatments prevent diabetes-induced vascular damage. Furthermore, Pae + DSS prove to be the most efficient treatment regimen. The combination of Pae and DSS produce significant protective effects through the reduction of oxidative stress and through intracellular Ca2+ regulatory mechanisms.

Improvement of vascular function by acute and chronic treatment with the GPR30 agonist G1 in experimental diabetes mellitus

The G-protein coupled estrogen receptor 30 (GPR30) is a seven-transmembrane domain receptor that mediates rapid estrogen responses in a wide variety of cell types. This receptor is highly expressed in the cardiovascular system, and exerts vasodilatory effects. The objective of the present study was to investigate the effects of GPR30 on vascular responsiveness in diabetic ovariectomized (OVX) rats and elucidate the possible mechanism involved. The roles of GPR30 were evaluated in the thoracic aorta and cultured endothelial cells. The GPR30 agonist G1 induced a dose-dependent vasodilation in the thoracic aorta of the diabetic OVX rats, which was partially attenuated by the nitric oxide synthase (NOS) inhibitor, nitro-L-arginine methylester (L-NAME) and the GPR30-selective antagonist G15. Dose-dependent vasoconstrictive responses to phenylephrine were attenuated significantly in the rings of the thoracic aorta following the acute G1 administration in the diabetic OVX rats. This effect of G1 was abolished partially by L-NAME and G15. The acute administration of G1 increased significantly the eNOS activity and the concentration of NO in the endothelial cells exposed to high glucose. G1 treatment induced an enhanced endothelium-dependent relaxation to acetylcholine (Ach) in the diabetic OVX rats. Further examination revealed that G1 induced vasodilation in the diabetic OVX rats by increasing the phosphorylation of eNOS. These findings provide preliminary evidence that GPR30 activation leads to eNOS activation, as well as vasodilation, to a certain degree and has beneficial effects on vascular function in diabetic OVX rats.

Clinical applications of advanced lipoprotein testing in diabetes mellitus

Traditional lipid profiles often fail to fully explain the elevated cardiovascular risk of individuals with diabetes mellitus. Advanced lipoprotein testing offers a novel means to evaluate dyslipidemia and refine risk estimation. Numerous observational studies have demonstrated a characteristic pattern of elevated levels of small, dense LDL particles, out of proportion to traditional lipid levels, in patients with both diabetes mellitus and the metabolic syndrome. Commonly used glucose and lipid-lowering agents have varied effects in patients with diabetes on both LDL and HDL subfractions. The exact role of advanced lipoprotein testing in patients with diabetes mellitus and the metabolic syndrome remains unclear but may offer improved assessment of cardiovascular risk compared with traditional lipid measurements.

Gender differences in vascular reactivity of aortas from streptozotocin-induced diabetic mice

The aim of the present study was to assess gender differences in diabetes-related vascular reactivity in murine aortas. Diabetes is a risk factor for ischemic heart disease, cerebral ischemia, and atherosclerosis, conditions in which endothelial dysfunction plays a pathogenetic role. We examined vascular responses in aortas isolated from streptozotocin (STZ)-induced type 1 diabetic mice and age-matched control mice, and looked for gender differences in the diabetes-induced changes in these responses. For each gender, the plasma adiponectin levels were lower in diabetic mice than in the controls, and they were significantly higher in females than in males. The acetylcholine (ACh)-induced endothelium-dependent relaxation of aortic rings was impaired (vs. that in the age-matched controls) in diabetic male mice, but not in diabetic female mice. The sodium nitroprusside-induced endothelium-independent aortic relaxation was not altered by diabetes in either male or female mice. The norepinephrine-induced aortic contraction was enhanced (vs. that in the control group) in diabetic female mice, but not in diabetic male mice, whereas in the presence of N(G)-nitro-L-arginine neither gender exhibited a significant diabetes-induced change in this contraction. The clonidine-induced and insulin-induced endothelium-dependent aortic relaxations were impaired only in the diabetic female group (vs. the age-matched controls). These results suggest that: a) in male diabetic mice, which exhibited low adiponectin levels, these were impairments of both the aortic relaxation and nitric oxide (NO) production induced by ACh, whereas b) in female diabetic mice, there were impairments of the aortic relaxations induced by both insulin and clonidine.

Competing-risk analysis of ESRD and death among patients with type 1 diabetes and macroalbuminuria

Patients with both type 1 diabetes and CKD have an increased risk of adverse outcomes. The competing risks of death and ESRD may confound the estimates of risk for each outcome. Here, we sought to determine the major predictors of the cumulative incidence of ESRD and pre-ESRD mortality in patients with type 1 diabetes and macroalbuminuria while incorporating the competing risk for the alternate outcome into a Fine-Gray competing-risks analysis. We followed 592 patients with macroalbuminuria for a median of 9.9 years. During this time, 56 (9.5%) patients died and 210 (35.5%) patients developed ESRD. Predictors of incident ESRD, taking baseline renal function and the competing risk for death into account, included an elevated HbA(1c), elevated LDL cholesterol, male sex, weight-adjusted insulin dose, and a shorter duration of diabetes. By contrast, predictors of pre-ESRD death, taking baseline renal function and the competing risk for ESRD into account, included only age, the presence of established macrovascular disease, and elevated cholesterol levels. This competing-risks approach has potential to highlight the appropriate targets and strategies for preventing premature mortality in patients with type 1 diabetes.

Short-term type 1 diabetes alters the mechanism of endothelium-dependent relaxation in the rat carotid artery

The aim of the present study was to examine the effect of an early stage of streptozotocin-induced diabetes on the mechanism(s) of endothelium-dependent relaxation. Diabetes was induced by a single injection of streptozotocin (48 mg/kg iv), and the ACh-induced relaxation of rat carotid arteries was examined 6 wk later. A diabetes-induced increase in superoxide levels, determined by L-012-induced chemiluminescence, from carotid arteries was associated with endothelial nitric oxide (NO) synthase (eNOS) uncoupling and increased catalytic subunit of NADPH oxidase expression. The sensitivity and maximum response to ACh were similar in normal and diabetic rats despite a decrease in NO release detected by 4-amino-5-methylamino-2′,7′-difluorofluorescein. In normal rats, N-nitro-l-arginine (100 μM) plus 1 H-[1,2,4]oxadiazolo-[4,3-a]quinoxalin-1-one (10 μM), to inhibit NOS and soluble guanylate cyclase (sGC), respectively, abolished ACh-induced relaxation, whereas in diabetic rats, the maximum relaxation to ACh was attenuated (maximum relaxation: 25 ± 5%), but not abolished, by that treatment. The remaining ACh-induced relaxation was abolished by NO scavengers, cupric chloride (to degrade nitrosothiols), or blockers of endothelial K+ channels. Western blot analysis of the carotid arteries indicated that diabetes significantly increased the expression of eNOS but decreased the proportion of eNOS expressed as the dimer. These findings demonstrate that in early diabetes, ACh-induced relaxation is maintained but is resistant to NOS inhibition. In early diabetes, nitrosothiol-mediated opening of K+ channels may act in conjunction with NO stimulation of sGC to maintain endothelium-dependent relaxation despite the increase in vascular superoxide levels.

Hereditary deficiency of gp91(phox) is associated with enhanced arterial dilatation: results of a multicenter study

BACKGROUND

NADPH oxidase is believed to modulate arterial tone, but its role in humans is still unclear. The objective of this study was to evaluate whether NADPH oxidase is involved in flow-mediated arterial dilation (FMD).

METHODS AND RESULTS

Twenty-five patients with hereditary deficiency of gp91(phox), the catalytic core of NADPH oxidase, (X-CGD), 25 healthy subjects, and 25 obese patients matched for sex and age were recruited. FMD, platelet gp91(phox), serum levels of nitrite and nitrate as markers of nitric oxide generation, oxidized low-density lipoprotein, and urinary excretion of isoprostanes as markers of oxidative stress were determined. Platelet gp91(phox) expression was downregulated in X-CGD patients (1.0+/-0.8 mean fluorescence; P<0.001) and upregulated in obese patients (4.1+/-2.2 mean fluorescence; P=0.01) compared with healthy subjects (2.9+/-1.7 mean fluorescence). Urinary excretion of isoprostanes was reduced in X-CGD patients (41.7+/-33.3 pg/mg creatinine; P=0.04) and increased in obese patients (154.4+/-91 pg/mg creatinine; P<0.001) compared with healthy subjects (69.5+/-52.4 pg/mg creatinine). Obese patients had higher serum oxidized low-density lipoprotein than healthy subjects (35.3+/-6.7 versus 24.8+/-9.8 U/L; P<0.001) and X-CGD patients (28.5+/-7.2 U/L; P<0.001). X-CGD patients had significantly higher FMD (14.7+/-5.9%) compared with healthy subjects (7.9+/-2.5%; P<0.001); obese patients had lower FMD (5.3+/-3.0%; P=0.028) compared with healthy subjects. Serum nitrite and nitrate levels were significantly higher in patients with X-CGD (36.0+/-10.8 micromol/L; P=0.016) and lower in obese patients (9.3+/-11.0 micromol/L; P=0.001) compared with healthy subjects (27.1+/-19.1 micromol/L). Serum nitrite and nitrate levels significantly correlated with FMD (R(s)=0.403, P<0.001) and platelet gp91(phox) (R(s)=-0.515, P<0.001). FMD inversely correlated with platelet gp91(phox) (R(s)=-0.502, P<0.001) and isoprostanes (R(s)=-0.513, P<0.001).

CONCLUSIONS

This study provides the first evidence that, in humans, gp91(phox) is implicated in the modulation of arterial tone.

Lipid disorders in type 1 diabetes

Patients with type 1 diabetes (T1D) also present with lipid disorders. Quantitative abnormalities of lipoproteins are observed in T1D patients with poor glycaemic control (increased plasma triglycerides and low-density lipoprotein [LDL] cholesterol) or nephropathy (increased triglycerides and LDL cholesterol, low level of high density lipoprotein [HDL] cholesterol). In cases of T1D with optimal glycaemic control, plasma triglycerides and LDL cholesterol are normal or slightly decreased, while HDL cholesterol is normal or slightly increased. Several qualitative abnormalities of lipoproteins, which are potentially atherogenic, are observed in patients with T1D, even in those with good metabolic control. These abnormalities include increased cholesterol-to-triglyceride ratios within very low-density lipoprotein (VLDLs), increased triglycerides in LDLs and HDLs, compositional changes in the peripheral layer of lipoproteins, glycation of apolipoproteins, increased oxidation of LDLs and an increase in small, dense LDL particles. These qualitative changes in lipoproteins are likely to impair their function. In vitro, VLDLs and LDLs from patients with T1D induced abnormal responses in the cellular cholesterol metabolism of human macrophages. HDLs from patients with T1D are thought to be less effective in promoting cholesterol efflux from cells, and have been shown to have reduced antioxidative and vasorelaxant properties. These qualitative abnormalities are not fully explained by hyperglycaemia and may be partly due to peripheral hyperinsulinaemia associated with subcutaneous insulin administration. However, the precise consequences of these qualitative lipid changes on the development of cardiovascular disease in T1D are, as yet, unknown.

Gender differences in endothelial function in aortas from type 2 diabetic model mice

Type 2 diabetes mellitus is associated with high mortality and morbidity, mainly due to coronary artery disease and atherosclerosis, although female gender is a protective factor in the development of, for example, atherosclerosis and hypertension. Our main aim was to investigate gender differences in endothelial function in aortas from type 2 diabetic model mice. The nonfasting plasma glucose level was significantly elevated in diabetic mice (both males and females). The plasma insulin level was not different between controls and diabetics (either gender). The plasma adiponectin level was decreased by diabetes, and was lower in males. In control aortas (from males or females), the clonidine-induced relaxation was abolished by Akt-inhibitor treatment. In diabetic males (versus both control males and diabetic females): a) the clonidine- and insulin-induced endothelium-dependent aortic relaxations were impaired, but the acetylcholine (ACh)-induced and sodium nitroprusside (SNP)-induced aortic relaxations were not, b) the norepinephrine (NE)-induced aortic contractile response was enhanced, c) systemic blood pressure was elevated, and d) the clonidine-stimulated Ser-473 phosphorylation of Akt in the aorta was decreased. These results suggest that endothelial functions dependent on the Akt pathway are abrogated by type 2 diabetes only in male mice.

Plasma tetrahydrobiopterin/dihydrobiopterin ratio: a possible marker of endothelial dysfunction

BACKGROUND

Although endothelium-dependent vasodilatation has been used as a marker of endothelial dysfunction (ED), there have been no reliable plasma markers for ED. Oxidative stress, which is a major determinant of ED, oxidizes tetrahydrobiopterin (BH4), an essential cofactor of endothelial type nitric oxide synthase (eNOS), and resulted in the relative deficiency of BH4.

METHODS AND RESULTS

In 163 patients with cardiovascular disorders, the plasma levels of BH4 and 7, 8-dihydrobiopterin (BH2) by high performance liquid chromatography were measured and compared with the flow-mediated (FMD) vasodilatory response of the brachial artery, which was measured by ultrasonography. The effects of atorvastatin on plasma pteridine levels and FMD were examined in patients with multiple coronary risk factors. There was a positive relationship between FMD and plasma BH4 levels and a negative relationship between FMD and plasma BH2 levels. Subsequently, a strong positive relationship between FMD and the BH4/BH2 ratio (r=0.585, P<0.0001) was found. Although we did not find any significant relationship between pteridine levels and individual traditional risk factors, the BH4/BH2 ratio in patients with more than 2 risk factors showed significant reductions compared with that in those without risk factors. Statin treatment improved FMD in association with an increase in the plasma BH4/BH2 ratio.

CONCLUSIONS

Plasma pteridine levels were associated with endothelial dysfunction in cardiovascular disorders.

Flow-mediated vasodilatation: variation and interrelationships with plasma lipids and lipoproteins

OBJECTIVE

Endothelial dysfunction is a critical, prerequisite step in atherosclerosis, and may be evaluated by flow-mediated vasodilatation (FMD). The objective of this study was to examine interrelationships between FMD and plasma lipids and lipoproteins, and to determine the between-operator and within-subject variability associated with this technique.

MATERIAL AND METHODS

FMD, plasma lipids and lipoproteins, including small dense LDL (sdLDL), were measured twice in 40 healthy volunteers, 4 weeks apart. Interrelationships between mean FMD responses and plasma lipids and lipoproteins were examined by correlation analysis. FMD measurements were taken by two independent operators, allowing determination of between-operator variability. Within-subject variability was determined by obtaining two measurements, 4 weeks apart, in every subject, and carried out by the same operator.

RESULTS

FMD was inversely related to plasma triglycerides (r = -0.47, p = 0.002), total cholesterol/HDL cholesterol (r = -0.35, p = 0.03) and apolipoprotein B (r = -0.36, p = 0.02), but not to other plasma lipids and lipoproteins. When measuring variation in FMD, the following results were found: Between operators (SD = 4.0 FMD%) and within subjects (SD = 2.9 FMD%).

CONCLUSIONS

The associations between FMD, plasma triglycerides and apoB provide evidence supporting a role for triglyceride-rich lipoproteins in endothelial dysfunction.

[Dyslipidemias in type 1 diabetes: a current approach]

With the intensive glycemic control in the therapy of type 1 diabetes mellitus (T1DM) patients, cardiovascular disease has been the main cause of mortality. Identification of risk factors, such as dyslipidemia is considered of great importance in terms of avoiding chronic micro and macro vascular complications. The statements for prevention of coronary artery disease in diabetes are generally are related do type 2 diabetes mellitus and little attention is paid to T1DM. Defining therapeutical targets and indications for treatment are more controversial in these patients due to their young ages. The present study aims to emphasize the importance of establishing the diagnosis of dyslipidemia in this group of patients as well as indicate the appropriate and early treatment, in order to reach the targets of treatment and reduce the atherogenic lipid profile.

Endothelial dysfunction in diabetes mellitus

Diabetes mellitus is associated with an increased risk of cardiovascular disease, even in the presence of intensive glycemic control. Substantial clinical and experimental evidence suggest that both diabetes and insulin resistance cause a combination of endothelial dysfunctions, which may diminish the anti-atherogenic role of the vascular endothelium. Both insulin resistance and endothelial dysfunction appear to precede the development of overt hyperglycemia in patients with type 2 diabetes. Therefore, in patients with diabetes or insulin resistance, endothelial dysfunction may be a critical early target for preventing atherosclerosis and cardiovascular disease. Microalbuminuria is now considered to be an atherosclerotic risk factor and predicts future cardiovascular disease risk in diabetic patients, in elderly patients, as well as in the general population. It has been implicated as an independent risk factor for cardiovascular disease and premature cardiovascular mortality for patients with type 1 and type 2 diabetes mellitus, as well as for patients with essential hypertension. A complete biochemical understanding of the mechanisms by which hyperglycemia causes vascular functional and structural changes associated with the diabetic milieu still eludes us. In recent years, the numerous biochemical and metabolic pathways postulated to have a causal role in the pathogenesis of diabetic vascular disease have been distilled into several unifying hypotheses. The role of chronic hyperglycemia in the development of diabetic microvascular complications and in neuropathy has been clearly established. However, the biochemical or cellular links between elevated blood glucose levels, and the vascular lesions remain incompletely understood. A number of trials have demonstrated that statins therapy as well as angiotensin converting enzyme inhibitors is associated with improvements in endothelial function in diabetes. Although antioxidants provide short-term improvement of endothelial function in humans, all studies of the effectiveness of preventive antioxidant therapy have been disappointing. Control of hyperglycemia thus remains the best way to improve endothelial function and to prevent atherosclerosis and other cardiovascular complications of diabetes. In the present review we provide the up to date details on this subject.

Impairment of endothelium-dependent ACh-induced relaxation in aorta of diabetic db/db mice--possible dysfunction of receptor and/or receptor-G protein coupling

Diabetes is a risk factor of ischemic heart disease, cerebral ischemia, and atherosclerosis, in which endothelial dysfunction plays a role in the pathogenesis. We examined vascular responses in the aorta of pre-diabetic db/db mice with normoglycemia, hyperlipidemia, and hyperinsulinemia (6 weeks old), and diabetic db/db mice with hyperglycemia, hyperlipidemia, and hyperinsulinemia (11 weeks old) in comparison with age-matched non-diabetic db/+ mice. Prostaglandin F2alpha (PGF2alpha)-induced contraction was significantly enhanced in the aorta of diabetic but not pre-diabetic db/db mice compared to age-matched non-diabetic db/+ mice. Acetylcholine (ACh), adenosine-5'-diphosphate (ADP), NaF, a G protein activator and A-23187, a Ca-ionophore, caused endothelium-dependent and nitric oxide (NO)-mediated relaxation, and sodium nitroprusside (SNP), an NO donor, caused endothelium-independent relaxation in the pre-contracted aorta of db/db mice. Maximal endothelium-dependent ACh-induced relaxation was reduced in diabetic but not pre-diabetic db/db mice compared to age-matched db/+ mice, while maximal SNP-induced relaxation was not different between diabetic and non-diabetic mice. ACh-induced relaxation in diabetic db/db mice was not affected by ozagrel, a thromboxane A2 (TXA2) synthetase inhibitor, or acetylsalicylic acid (aspirin), a cyclooxygenase inhibitor, suggesting no involvement of endogenous TXA2 or prostanoids in the reduction of relaxation. Maximal endothelium-dependent ADP-, A-23187-, and NaF-induced relaxation was not reduced in diabetic db/db mice. EC50 values for ACh- and SNP-induced relaxation were increased in diabetic but not pre-diabetic db/db mice, suggesting decreases in sensitivity to NO in diabetic mice. Two-week treatment with KV-5070, a PPARgamma agonist, lowered plasma glucose, triglyceride (TG), and insulin but not cholesterol, and reversed the reduced ACh-induced relaxation. In conclusion, ACh-induced endothelium-dependent relaxation is impaired in diabetic db/db mice, probably due to the dysfunction of ACh receptors and/or receptor-G protein coupling. Endothelial dysfunction was not genetic and was considered to be initiated primarily by hyperglycemia, and was improved by anti-diabetic treatment with a PPARgamma agonist.

Evidence for prescribing exercise as therapy in chronic disease

Considerable knowledge has accumulated in recent decades concerning the significance of physical activity in the treatment of a number of diseases, including diseases that do not primarily manifest as disorders of the locomotive apparatus. In this review we present the evidence for prescribing exercise therapy in the treatment of metabolic syndrome-related disorders (insulin resistance, type 2 diabetes, dyslipidemia, hypertension, obesity), heart and pulmonary diseases (chronic obstructive pulmonary disease, coronary heart disease, chronic heart failure, intermittent claudication), muscle, bone and joint diseases (osteoarthritis, rheumatoid arthritis, osteoporosis, fibromyalgia, chronic fatigue syndrome) and cancer, depression, asthma and type 1 diabetes. For each disease, we review the effect of exercise therapy on disease pathogenesis, on symptoms specific to the diagnosis, on physical fitness or strength and on quality of life. The possible mechanisms of action are briefly examined and the principles for prescribing exercise therapy are discussed, focusing on the type and amount of exercise and possible contraindications.

Serum lipids and the progression of nephropathy in type 1 diabetes

OBJECTIVE

Dyslipidemia contributes to the progression of microvascular disease in diabetes. However, different lipid variables may be important at different stages of nephropathy. This study examines the pattern of dyslipidemia associated with the progression of nephropathy in patients with type 1 diabetes.

RESEARCH DESIGN AND METHODS

A total of 152 patients with type 1 diabetes were recruited in order to represent various phases of nephropathy. Patients were followed for 8-9 years, during which time they received standard care. Renal progression was defined a priori as a doubling in albumin excretion (in patients with normo- or microalbuminuria) or a decline in creatinine clearance (in those with macroalbuminuria). A panel of lipid variables was determined and correlated with indexes of progression.

RESULTS

In patients with normoalbuminuria (n = 66), progression was associated with male sex (P < 0.05), borderline albuminuria (P = 0.02), and LDL-free cholesterol (P = 0.02). In patients with microalbuminuria (n = 51), progression was independently associated with triglyceride content of VLDL and intermediate-density lipoprotein (both P < 0.05). In patients with macroalbuminuria (n = 36), a significant decline in the renal function (>3 ml x min(-1) x year(-1)) was independently associated with poor glycemic control, hypertension, and LDL size (P < 0.05). When all patients with progressive nephropathy were analyzed together, only LDL cholesterol was predictive on multivariate analysis (P < 0.05), which masked the importance of triglyceride enrichment in microalbuminuria.

CONCLUSIONS

Lipid variables are associated with progression of diabetic kidney disease, but the relationship is not the same at all stages. This finding has implications for the design of renoprotective strategies and the interpretation of clinical trials in type 1 diabetes.

Effect of chronic oral supplementation with vitamins on the endothelial function in chronic smokers

Cigarette smoking has been associated with endothelial dysfunction including impaired endothelium-dependent flow-mediated dilation (FMD). In cigarette smokers, increased oxygen-derived free radicals have been suspected of being one of the major causes of endothelial dysfunction, owing possibly to the inactivation of nitric oxide by free radicals. Vitamins C and E are widely used antioxidant vitamins, which have also been reported to effectively improve the endothelial function in several conditions. To test the effect of moderate-term oral antioxidant vitamin supplementation on the endothelial function in smokers, the authors evaluated the combined effect of vitamins C and E, administered in normal dosages, on FMD in young male smokers. A prospective interventional study was performed. In 15 healthy male subjects (mean age, 24.4 +/-2.5 years old). They studied FMD in the brachial artery by using high-resolution ultrasound. The vascular effects of moderate-term oral supplementation with vitamin C (1.0 g/day) and vitamin E (500 mg/day) were determined during reactive hyperemia, which causes endothelium-dependent FMD. They performed a vascular function study 3 times including before vitamin supplement, after 25 days of vitamin supplement, and 4 weeks after the cessation of the vitamin supplement. The flow-mediated dilator response measurements were repeated twice a day before vitamin supplements, and the repeatability obtained from these measurements was found acceptable (variability of FMD <2%). The oral antioxidant vitamin supplement significantly restored FMD (3.8 +/-2.2% vs 5.9 +/-2.5%; p<0.05), however, this effect disappeared 4 weeks after the vitamin supplementations ended. The combined usual dosage of vitamins C and E supplements was found to improve the endothelial function in chronic smokers.

Assessment of flow-mediated vasodilatation (FMD) of the brachial artery: effects of technical aspects of the FMD measurement on the FMD response

AIMS

The ability to assess endothelial function non-invasively with B-mode ultrasound has lead to its widespread application in a variety of studies. However, the absolute values obtained using this approach vary considerably across studies. We studied whether technical aspects of the methodology can explain the wide variety in absolute values across studies.

METHODS AND RESULTS

A literature search was performed to identify published reports on flow-mediated vasodilatation (FMD) of the brachial artery published between 1992 and 2001. Information on type of equipment (wall track/B-mode), location of the measurement (antecubital fossa/upper arm), occlusion site (lower/upper arm), occlusion duration (min), and occlusion pressure was extracted. Patient characteristics were also extracted. For the healthy populations, mean FMD varied from 0.20 to 19.2%; for the coronary heart disease (CHD) patients FMD varied from -1.3 to 14%; for subjects with diabetes mellitus FMD varied from 0.75 to 12%. Compared with occlusion at the upper arm, lower arm occlusion was related to decreased FMD (mean difference in FMD -2.47%; 95% CI 0.55-4.39). An occlusion duration of > or =4.5 min was related to an increased FMD compared with an occlusion time of < or =4 min (mean difference 1.30%; 95% CI 0.35-2.46). These findings were adjusted for other technical aspects of the methodology and for differences in risk factors between populations.

CONCLUSION

Mean FMD differs widely between studies. There is a great overlap between populations (healthy, CHD, diabetics). Our findings suggest that the technical aspects of the measurements, the location, and the duration of the occlusion may explain some of these differences, whereas type of equipment, location of the measurement, and occlusion pressure do not.

Increased breath biomarkers of oxidative stress in diabetes mellitus

BACKGROUND

Oxidative stress has been implicated in the major complications of diabetes mellitus, including retinopathy, nephropathy, neuropathy and accelerated coronary artery disease. There is a clinical need for a marker of oxidative stress which could potentially identify diabetic patients at increased risk for these complications. We measured oxidative age, a new breath marker of oxidative stress, in diabetic patients.

METHODS

Three groups were studied: type 1 diabetes mellitus (n=9), type 2 diabetes mellitus (n=53) and non-diabetic normals (n=39). Volatile organic compounds (VOCs) in breath were assayed by gas chromatography and mass spectroscopy to construct the breath methylated alkane contour (BMAC), a three-dimensional display of oxidative stress markers, C4-C20 alkanes and monomethylated alkanes. The collective abundance of these VOCs was reduced to a single value, the oxidative age, comprising the volume under the curve of the BMAC corrected for chronological age.

RESULTS

Oxidative age was significantly increased in type 1 diabetes (mean=0.103, S.E.M.=0.119, p<0.01) and type 2 diabetes (mean=0.103, S.E.M.=0.047, p<0.05) compared to age-matched normals (mean=-0.248, S.E.M.=0.079). No significant correlation between oxidative age and blood glucose or hemoglobin A1C was observed in either group.

CONCLUSIONS

Oxidative age, a marker of oxidative stress, was significantly increased in both type 1 and type 2 diabetes mellitus. Oxidative age merits further study as a candidate marker of risk for the complications of diabetes mellitus.

Insulin resistance and endothelial dysfunction

Insulin has multiple metabolic actions, including effects on blood vessels. Insulin normally increases blood flow by a mechanism which involves generation of nitric oxide (NO) via the arginine-NO pathway. Although insulin itself is a weak and physiologically unimportant vasodilatator, it appears to markedly potentiate endothelium-dependent vasodilatation. Therefore, anything that impairs insulin action in endothelial cells can be expected to be associated with endothelial dysfunction, i.e. loss of NO bioactivity in the vessel wall. Consistent with the idea that insulin resistance and endothelial dysfunction frequently coexist, all insulin-resistant conditions examined to date have been associated with endothelial dysfunction. However, the latter can also be caused by factors other than insulin resistance-such as a high concentration of low-density lipoprotein (LDL) cholesterol. Therapies which reverse insulin resistance-such as exercise, insulin and inhibitors of the renin-angiotensin-aldosterone (RAA) axis-also reverse endothelial dysfunction, which may thus be an inherent feature of insulin resistance.

Low-density lipoprotein subfractions and cardiovascular risk in hypertension: relationship to endothelial dysfunction and effects of treatment

Although hypertensive patients are at particular risk of vascular complications, the possible contribution of an atherogenic lipoprotein profile and endothelial dysfunction to this risk is unclear. We investigated this by measuring LDL subfractions and flow-mediated dilation (FMD) (reflecting endothelial dysfunction) in a cohort of high-risk hypertensive patients. We studied 84 hypertensive patients (74 men; mean age, 64 years; SD 8). Chylomicron-free LDL subfractions were analyzed by disc polyacrylamide gel electrophoresis, producing an LDL score, with higher scores being equivalent to a greater proportion of the more atherogenic LDL subfractions. High-resolution ultrasound was used to assess endothelium-dependent brachial artery FMD after reactive hyperemia after vessel occlusion. Baseline levels were compared with 61 age- and gender-matched healthy normotensive control subjects. Mean LDL score was higher and FMD impaired in hypertensive subjects compared with control subjects. These indexes were significantly improved after 6 months of cardiovascular risk factor management. LDL score correlated significantly with the 10-year Framingham coronary heart disease risk score, with a negative correlation with FMD (both P<0.001). Abnormal atherogenesis and endothelial dysfunction are both present in hypertension and appear to be related to each other, potentially leading to vascular complications. The abnormal LDL scores also correlate with the 10-year cardiovascular risk and can be positively influenced by cardiovascular risk management.

Significance of small dense low-density lipoproteins and other risk factors in patients with various types of coronary heart disease

BACKGROUND

It remains unclear how closely the small dense low-density lipoprotein (LDL) (diameter < or =25.5 nm) is associated with various types of coronary heart disease (CHD) in Japanese patients, an ethnic group with lower serum cholesterol levels and less massive obesity compared with Western populations.

METHODS AND RESULTS

We measured mean LDL particle diameter by gradient gel electrophoresis in 571 patients with CHD and in 263 healthy subjects who served as control patients. Patients with CHD were classified into acute coronary syndrome (ACS), stable CHD and vasospastic angina. High-density lipoprotein cholesterol and apolipoprotein-A1 and -B were significantly different between patients with CHD and controls. LDL size in patients with CHD was markedly smaller than that in controls in both men and women (25.5 +/- 0.7 vs 25.9 +/- 0.4 and 25.7 +/- 0.7 vs 26.0 +/- 0.5 nm, respectively). LDL cholesterol was significantly higher in patients with ACS than in other groups. Plasma levels of high-density lipoprotein cholesterol decreased as the number of diseased vessels or angiographic coronary severity evaluated by Gensini score increased, but the LDL size was comparable irrespective of the type of CHD and the extent and severity of the lesions. Multiple logistic regression analysis revealed that small dense LDL was independently associated with the incidence of CHD in both sexes (odds ratio [OR] 3.5, 95% CI 2.1-5.7, and OR 2.9, 95% CI 1.5-5.6, P <.005).

CONCLUSION

Our study suggests that the small dense LDL is strongly associated with various types of CHD, independent of traditional and nontraditional coronary risk factors, but is not related to the severity and extent of the coronary lesions.

Vascular reactivity in diabetes mellitus

Cardiovascular disease is responsible for 70% of the deaths in diabetes mellitus. Endothelial dysfunction occurs early in atherosclerosis and can now be assessed accurately and reproducibly by noninvasive means. Hyperglycemia, insulin resistance, microvascular complications, and coexistent conditions have been shown to impair endothelial function in diabetes. Resistance to insulin's vasodilatory effect and increased free radical generation are probable mechanisms responsible for the endothelial dysfunction in this state. Improvement in glycemic control, insulin and insulin sensitizers, cholesterol lowering, hypolipidemic agents, angiotensin-converting enzyme inhibitors, and angiotensin II receptor blockers have improved clinical cardiovascular outcomes and have also been shown to improve endothelial function. Strategies designed to assess and improve endothelial function may be further beneficial in terms of cardiovascular outcomes in diabetes mellitus, and need to be tested in a clinical setting.

Small-sized low-density lipoproteins of subclass B from patients with end-stage renal disease effectively augment tumor necrosis factor-alpha-induced adhesive properties in human endothelial cells

Increased prevalence of small-sized low-density lipoprotein (LDL) subclass B (diameter < 25.5 nm) possibly is involved in the multifactorial process of cardiovascular disease in patients with end-stage renal disease. Given these epidemiological observations, mechanisms underlying the combined effect of a proinflammatory insult and LDL of different subclasses (subclass A, diameter > 25.5 nm, and subclass B) in a cellular model were investigated. For this, human umbilical vein endothelial cells were preexposed to LDL, then stimulated with tumor necrosis factor-alpha (TNF-alpha). Modulatory effects of LDL phenotypes on the activation of adhesion molecules, monocyte adherence, and transcriptional activity of nuclear factor-kappaB (NF-kappaB) and activator protein-1 (AP-1) were investigated. Our data show that subclass B LDLs were metabolized through nonspecific scavenger receptors and specific LDL-receptor pathways in endothelial cells. Furthermore, LDL subclass B in comparison to subclass A more effectively enhanced monocyte recruitment and adhesive properties of endothelial cells in response to TNF-alpha. These effects appeared not to be mediated by oxidative stress-responsive NF-kappaB because modulation of this transcription factor by LDL was moderate and similar for both LDL phenotypes. Conversely, effects of LDL subclass B were considered to be caused by augmented AP-1 binding activity. In conclusion, the present model provides new clues in atherogenic mechanisms of small-sized LDLs, which sensitize vascular cells to inflammatory signals more effectively than normal-sized LDLs.

Endothelial dysfunction in human diabetes

In nondiabetic individuals, a poor response to an endothelium-dependent vasodilator in coronary vessels has been shown to increase the likelihood of a future cardiovascular event. Such prospective data are not as yet available in patients with type 1 or type 2 diabetes. However, consistent with the greatly increased cardiovascular risk in these patients, endothelial dysfunction has been almost universally found to characterize patients with type 2 diabetes particularly. Endothelial dysfunction frequently coexists with features of insulin resistance, such as the presence of small dense low-density lipoprotein (LDL) particles even in nondiabetic individuals. This association is independent of obesity and other causes of endothelial dysfunction, such as LDL cholesterol, hypertension, and smoking. In patients with type 1 diabetes, endothelial dysfunction has been found in approximately half of the studies. In some but not all studies, endothelial dysfunction has been especially severe in patients with poor glycemic control. Reversal or amelioration of endothelial dysfunction has been documented by many commonly used therapeutic agents such as successful insulin therapy, fibrates, and angiotensin-converting enzyme inhibitors, but also with some but not all agents that act as antioxidants. Long-term studies addressing the prognostic significance of endothelial dysfunction and its reversal are urgently needed to determine whether measurement of endothelial function could be used to identify individuals at risk better than can be done at present using classic risk factor assessment among patients with type 2 diabetes especially.

Cardiovascular risk factors as determinants of endothelium-dependent and endothelium-independent vascular reactivity in the general population

OBJECTIVES

We examined to what extent the variation in risk factors for coronary heart disease (CHD) and the Framingham risk score (FRS) explain the variation in vascular reactivity in adults aged 30 to 53 years.

BACKGROUND

The role of risk factors in determining vascular reactivity in the general population has not been quantified.

METHODS

Risk factors for CHD were measured, and the FRS was calculated in 69 healthy volunteers. Lipoprotein particle size was measured using proton-nuclear magnetic resonance spectroscopy. Forearm plethysmography was used to assess blood flow responses to acetylcholine (ACh), bradykinin (BK), glyceryl trinitrate (GTN), noradrenaline and N(G)-monomethyl-L-arginine (L-NMMA).

RESULTS

Lower ACh and BK responses were associated with a higher body mass index (BMI), a higher total cholesterol to high-density lipoprotein (HDL) cholesterol ratio, lower HDL cholesterol and a cigarette smoking habit (all p < 0.05). Higher low-density lipoprotein (LDL) cholesterol was also associated with a lower BK response (p = 0.001). A decreased GTN response was associated with a higher BMI and total cholesterol to HDL cholesterol ratio (both p < 0.05). A decreased L-NMMA response was associated with a smoking habit (p < 0.001). Lipoprotein particle sizes did not independently predict any vascular response. A high FRS was associated with a reduced response to ACh (p = 0.07), BK (p = 0.003) and L-NMMA (p = 0.003), and the relationship was stronger in women than in men. Altogether, risk factors explained 13%, 9%, 8% and 15% of the response to ACh, BK, GTN and L-NMMA, respectively.

CONCLUSIONS

Lipids, BMI and smoking are important determinants of vascular reactivity. The FRS is predictive of agonist-stimulated, endothelium-dependent vasodilation and basal NO release. However, much of the variation in the vascular responses to these drugs, at this age, remains unexplained.

Soluble adhesion molecules, endothelial function and vitamin E in type 1 diabetes

BACKGROUND

Elevated levels of soluble adhesion molecules are found in subjects with vascular disease and inconsistently in subjects with conditions predisposing them to atherosclerosis, such as hypercholesterolaemia and diabetes. Oxidized low-density lipoprotein (LDL), protein kinase C and lower than normal levels of NO appear to be important for expression of adhesion molecules, raising the possibility that vitamin E is useful for downregulating levels. We have recently shown that administration of 1000 IU vitamin E for 3 months will improve endothelial vasodilator function (EVF) in uncomplicated type-1 diabetes.

OBJECTIVE

To determine whether levels of soluble adhesion molecules in young subjects with uncomplicated diabetes are elevated, whether there is a relationship between levels of soluble adhesion molecule and EVF as well as parameters of diabetes and lipid levels and whether an improvement in EVF related to vitamin E therapy is also associated with a decrease in levels of soluble adhesion molecules.

DESIGN

A randomized, placebo-controlled, study.

RESULTS

There was no difference between levels of soluble vascular cell adhesion molecule-1 (VCAM-1; 621 +/- 17 versus 635 +/- 37 ng/ml) and P-selectin (59 +/- 2 versus 57 +/- 6 ng/ml) for the diabetic and control groups. For the diabetic cohort, levels of soluble VCAM-1 were inversely related to flow-mediated vasodilatation of the brachial artery (r = -0.41, P < 0.005) and directly related to levels of total cholesterol (r = 0.44, P < 0.005) and LDL cholesterol (r = 0.42, P < 0.01) and duration of diabetes (r = 0.55, P < 0.0005) but there was no relationship with susceptibility of LDL to oxidation or vitamin-E content of LDL. Levels of soluble P-selectin were directly related to duration of diabetes (r = 0.43, P < 0.05) and inversely related to size of LDL particles (r = 0.32, P < 0.05) but were not related to EVF. Vitamin E produced no change in levels of soluble P-selectin and VCAM-1.

CONCLUSIONS

Levels of soluble VCAM-1 and P-selectin in young subjects with type-1 diabetes and no evidence of overt vascular disease do not appear to be elevated and are not influenced by vitamin-E supplementation.

Flow-mediated vasoactivity and circulating adhesion molecules in hypertriglyceridemia: association with small, dense LDL cholesterol particles

BACKGROUND

Endothelial dysfunction is considered one of the earliest events in the process of atherosclerosis, and an impaired vasodilatory response has been reported in patients with dyslipidemias. However, the independent association between hypertriglyceridemia and endothelial dysfunction is controversial, and the relation between endothelium-dependent vasodilation and circulating cell adhesion molecules as markers of endothelial dysfunction has not been fully determined.

METHODS

Brachial artery flow mediated vasodilation (FMV) and the soluble forms of vascular cell adhesion molecule-1 (sVCAM-1) and intercellular adhesion molecule-1 (sICAM-1) were determined after overnight fasting in 16 men with hypertriglyceridemia (age 33 +/- 6 years) and in 16 age-matched healthy men with normal triglycerides and cholesterol. Subjects who smoked and those with known cardiovascular disease, diabetes, hypertension, recent or active infections, or any other disease that could affect leukocyte activation were excluded from the study.

RESULTS

Compared with normal subjects, subjects with hypertriglyceridemia showed a higher level of sVCAM-1 and sICAM-1 (both P <.001), a reduced FMV (P <.01), and a smaller LDL particle size (P <.05). FMV had a significant inverse correlation with sVCAM-1 (r = -0.61, P <.001) and sICAM-1 (r = -0.38, P <.03). LDL particle size had a strong, direct association with FMV (r = 0.75, P <.001) and an inverse association with adhesion molecules. By multiple regression analysis, triglycerides (P <.001) and small LDL particle size (P <.002) predicted a reduced FMV.

CONCLUSIONS

Serum level of cell adhesion molecules is increased and FMV is impaired in young healthy men with hypertriglyceridemia compared with age-matched men with normal lipid levels. Small, dense LDL particles may play a role in determining endothelial dysfunction in these subjects.

Vitamin E supplementation improves endothelial function in type I diabetes mellitus: a randomized, placebo-controlled study

OBJECTIVES

We sought to determine, in a double-blind, placebo-controlled, randomized study, whether vitamin E supplementation (1,000 IU for three months) would improve impaired conduit and resistance vessel endothelial vasodilator function (EVF) and systemic arterial compliance (SAC) in type I diabetes mellitus (DM).

BACKGROUND

Oxidative stress is thought to be important in the pathogenesis of impaired EVF. Consistent with this hypothesis, we have recently shown that impaired EVF is related to low density lipoprotein (LDL) vitamin E content (VEC) in young subjects with type 1 DM.

METHODS

We assessed EVF in the brachial artery (using noninvasive ultrasound, flow-mediated vasodilation [FMD]; n = 41) and in the forearm resistance vessels (by flow responses to intrabrachial acetylcholine [ACh]; n = 21) and measured SAC (simultaneous aortic blood flow and carotid pressure measurements; n = 41) before and after active or placebo therapy.

RESULTS

The LDL VEC was increased by 127% after supplementation, resulting in a significant reduction in the oxidative susceptibility of LDL. There was no time-dependent change in FMD or in the response to ACh or SAC in the placebo group. A significant improvement in FMD (2.6 +/- 0.6% to 7.0 +/- 0.7%, p < 0.005) and the dose response to ACh (p < 0.05) were observed in those randomized to vitamin E therapy. Systemic arterial compliance was not affected by vitamin E (0.41 +/- 0.03 vs. 0.49 +/- 0.06 arbitrary compliance units, p = NS). The change in FMD was related to the change in LDL VEC (r = 0.42, p < 0.05) and the change in the oxidative susceptibility of LDL (r = 0.64, p < 0.0001).

CONCLUSIONS

Short-term daily oral supplementation with vitamin E improves EVF in both the conduit and resistance vessels of young subjects with type I DM.

Treating ambulatory ischemia in coronary disease by manipulating the cell biology of atherosclerosis

Obstructive coronary artery disease is the most common cause of morbidity and mortality in the developed world. Our understanding of the pathobiology of coronary atherosclerosis provides us with new opportunities to reduce myocardial ischemia by interventions that address these mechanisms directly. These interventions include lipid-lowering therapies that improve local coronary vasomotion, inflammation, and the procoagulant state. These interventions have also been shown to result in important reductions in clinical events, including angina pectoris, myocardial ischemia and infarction, and death. Ambulatory electrocardiography provides a versatile and quantifiable measure of regional myocardial ischemia. Reductions in ischemia, as quantified by this diagnostic modality, are associated with improved clinical outcomes that may reflect improvements in the cellular pathophysiology of coronary atherosclerosis. This review discusses new information regarding the interactions between low-density lipoprotein cholesterol, the cell biology of atherosclerosis, and the activity of ischemia in patients with coronary artery disease.