Increased plasma endothelin-1 and intraplatelet cyclic guanosine monophosphate in men with disturbed glucose metabolism

Plasma endothelin-1, the nitric oxide (NO) mediator intraplatelet cyclic guanosine monophosphate (cGMP), the prostacyclin mediator cyclic adenosine monophosphate (cAMP) and the macrophage derived inflammatory mediator plasma neopterin were measured in men with Type 2 diabetes mellitus (n=91), impaired glucose tolerance (IGT; n=51), previously abnormal glucose tolerance (PAGT; n=20), and 34 healthy control men. Plasma endothelin-1was higher in men with Type 2 diabetes mellitus than in controls [4.1 (1.0-14.3) vs. 2.1 (0.2-8. 7) ng/l; P<0.001). Intraplatelet cGMP was higher in men with PAGT [0. 84 (0.57-2.76) pmol/10(9) platelets; P<0.05], IGT [0.85 (0.48-3.53); P<0.001] and Type 2 diabetes mellitus [0.90 (0.47-3.86); P<0.001] than in controls [0.70 (0.42-1.70]. No differences existed between groups concerning intraplatelet cAMP or plasma neopterin. Plasma endothelin-1 correlated with fasting plasma glucose (r=0.33; P<0.001) and HbA1(c) (r=0.29; P<0.001). In conclusion, elevated plasma endothelin-1 in Type 2 diabetes mellitus and its relationship to glucose and HbA1(c) suggest a putative role for endothelin-1 in diabetic endothelial cell damage. Increased cGMP indicating enhanced production/activity of NO suggests that factors other than reduced NO activity contribute to enhanced platelet aggregation in diabetes.

Homocysteine is related to neopterin and endothelin-1 in plasma of subjects with disturbed glucose metabolism and reference subjects

Hyperhomocysteinemia is an independent risk factor for vascular disease. In order to evaluate relations between hyperhomocysteinemia and endothelial and leukocyte function, the investigators related homocysteine to indices of endothelial function (plasma endothelin-1 [p-ET-1] and intraplatelet levels of the nitric oxide [NO] and prostacyclin mediators 3'-5' guanosine monophosphate [cGMP] and cyclic 3'-5' adenosine monophosphate [cAMP]) and the monocyte-derived inflammatory mediator neopterin in 168 men (mean age 69, range 49-72 years) with disturbed glucose metabolism and a reference group of 52 male subjects (mean age 70, range 61-79 years). Among the 168 patients with disturbed glucose metabolism plasma (p)-homocysteine correlated significantly with age (r=0.20; p<0.01), glycosylated hemoglobin (HbA1c) (r=0.17; p<0.05), triglycerides (r=0.20; p<0.05), intraplatelet GMP (r=0.16; p<0.05), p-ET-1 (r=0.21; p<0.05), and p-neopterin (r=0.31; p<0.001). The correlation between p-homocysteine and p-ET-1 persisted (p<0.01) in multiple regression analysis. Among the 52 reference subjects p-homocysteine correlated significantly with p-ET-1 (r=0.32; p<0.05) and p-neopterin (r=0.37; p<0.01). The correlation between p-homocysteine and p-neopterin persisted (p<0.05) in multiple regression analysis. In conclusion, homocysteine is related to neopterin and endothelin-1 in plasma of subjects with disturbed glucose metabolism and in reference subjects, suggesting that homocysteine exerts its deleterious effects on vascular function through interference with endothelial and leukocyte function.

Hormone replacement therapy in healthy postmenopausal women. Effects on intraplatelet cyclic guanosine monophosphate, plasma endothelin-1 and neopterin

OBJECTIVES

To evaluate beneficial effects of postmenopausal hormone replacement therapy (HRT) on endothelial function, measured as intraplatelet cyclic guanosine monophosphate (cGMP, mediator of nitric oxide), cyclic adenosine monophosphate (cAMP, mediator of prostacyclin) and plasma endothelin-1 (ET-1), and on monocyte activation, measured as plasma neopterin.

DESIGN

Part 1: double-blind randomized trial for 3 months; part 2: open study for 9 months.

SETTING

The study was performed at the Department of Endocrinology, University Hospital, Malmö, Sweden.

SUBJECTS

Fifty-one postmenopausal women participated in part 1 and 46 in part 2. Inclusion criteria included a history of amenorrhoea for at least 6 months before the study and body mass index >/= 24 kg m-2.

INTERVENTION

Randomization for either placebo (n = 24) or HRT (n = 27). HRT was given as 2 mg oestradiol valerate for the first 3 months with the addition of 10 mg medroxyprogesterone for 10 days every third month thereafter.

MEASUREMENTS

Performed at baseline and after 3 and 12 months of the study.

RESULTS

In the HRT group, intraplatelet cGMP increased from 0.56 (0.35-0.94) to 0.61 (0.42-3. 40) and 0.65 (0.43-1.08) pmol (109 platelets)-1 after 3 and 12 months, respectively (P = 0.01), whereas plasma ET-1 decreased from 3.2 (1.1-6.8) to 2.0 (0.8-5.1) and 1.8 (0.4-15.4) pg mL-1 (P < 0. 001). Intraplatelet cAMP and plasma neopterin were unchanged. When smokers (n = 15) and non-smokers (n = 12) in the HRT group were analysed separately, significant effects were seen only amongst smokers. The control group showed unchanged levels of cGMP, cAMP, ET-1 and neopterin.

CONCLUSIONS

These data suggest beneficial effects of HRT on endothelial function which may account for anti-atherogenic effects of HRT in postmenopausal women, especially in smokers. No effects of HRT were seen upon monocyte activation.

Increasing neopterin and decreasing endothelin-1 in plasma during insulin infusion in women

Leukocyte-derived inflammatory mediators and endothelial production of vasoconstrictive factors, such as endothelin-1, and vasodilatory and platelet anti-aggregatory factors, such as nitric oxide (NO) and prostacyclin (PGI2), may have a role in the pathogenesis of atherosclerosis. In this study we evaluated whether insulin affects the monocyte-derived inflammatory mediator neopterin and endothelin- in plasma (p), and NO and PGI2 mediators cyclic 3'-5' guanosine monophosphate (cGMP) and cyclic 3'-5' adenosine monophosphate (cAMP) in platelets. P-neopterin was measured by enzyme linked immunosorbent assay (ELISA), and p-endothelin-1, intraplatelet cAMP and cGMP were measured by radioimmunoassay (RIA) before and after euglycaemic hyperinsulinaemic clamping in 51 healthy postmenopausal women aged 53-54 years. "Placebo clamping" with NaCl infusion was performed in a subgroup of 5/51 women. During euglycaemic hyperinsulinaemic clamping, p-endothelin-1 decreased (from 3.3+/-0.2 pg/ml to 2.4+/-0.2 pg/ml; p<0.01), whereas p-neopterin (from 5.0+/-1.1 nmol/l to 6.2+/-1.4 nmol/l; p<0.001) and both intraplatelet cGMP (from 0.61+/-0.03 to 0.68+/-0.03 pmol/10(9) platelets; p<0.05) and cAMP (from 4.00+/-0.14 to 4.76+/-0.20 pmol/10(9) platelets; p<0.001) increased. Increases in cGMP (from 0.79+/-0.05 to 1.07+/-0.15 pmol/10(9) platelets; p = 0.14) and cAMP (from 4.76+/-0.15 to 5.52+/-0.36 pmol/10(9) platelets; p = 0.08) also occurred during NaCl infusion, whereas neopterin and endothelin-1 values were unchanged. In conclusion, insulin administration was associated with decreasing p-endothelin-1 levels and increasing levels of p-neopterin and intraplatelet cyclic nucleotides in accordance with vasodilatation and monocyte activation.

Increasing plasma fibrinogen, but unchanged levels of intraplatelet cyclic nucleotides, plasma endothelin-1, factor VII, and neopterin during cholesterol lowering with fluvastatin

Lipid-lowering statin treatment reduces cardiovascular morbidity and mortality and improves endothelial function in patients with hypercholesterolemia. The aim of the present study was to evaluate plasma levels of fibrinogen, factor VII, and the macrophage-derived inflammatory mediator neopterin during lipid lowering. In addition, the endothelial production of platelet antiaggregatory and vasodilatory factors such as nitric oxide and prostacyclin, and vasoconstrictive factors such as endothelin-1, was assessed. Plasma fibrinogen, factor VII, endothelin-1, and the neopterin and intraplatelet nitric oxide and prostacyclin mediators cyclic 3'-5'guanosine monophosphate (cGMP) and cyclic 3'-5'adenosine monophosphate (cAMP) were measured before and 6 months after the institution of treatment with fluvastatin in 17 patients (eight men and nine women, median age 60 years) with vascular disease and previously untreated hypercholesterolemia. After 6 months, a decrease of 1.62 mmol/l [1.26-2.18 (19%); P < 0.01] was noted in levels of total cholesterol, and a decrease of 1.70 mmol/l [1.52-2.30 (28%); P < 0.01] in levels of low-density lipoprotein cholesterol. Plasma levels of fibrinogen had increased [from 4.81 g/l (4.26-5.27) to 5.17 g/l (4.81-5.67); P < 0.05], whereas no significant changes had occurred in intraplatelet levels of cGMP [decrease by 0.05 pmol/10(9) platelets (-0.17 to 0.24); NS], cAMP [decrease by 0.13 pmol/10(9) platelets (-0.37 to 0.86); NS], plasma endothelin-1 [decrease by 0.05 pg/ml (-0.60 to 0.70); NS], plasma factor VII [from 1.14 IE/ml (0.58-1.38) to 1.22 IE/ml (0.96-1.46); NS], or plasma neopterin [from 8.6 nmol/l (7.1-11.5) to 8.7 nmol/l (7.9-11.3); NS]. In conclusion, during cholesterol-lowering treatment with fluvastatin, plasma levels of fibrinogen increased whereas intraplatelet cyclic nucleotide levels and plasma endothelin-1, factor VII and neopterin levels were unchanged.

Increasing plasma neopterin and persistent plasma endothelin during follow-up after acute cerebral ischemia

Release of inflammatory mediators from leukocytes and endothelial release of vasoactive factors are both important in the pathogenesis of atherosclerosis. To evaluate the concentrations of a specific marker for macrophage activation, neopterin, and the potent endothelial derived vasoconstrictive peptide endothelin-1 (ET-1), during the acute and chronic stages of cerebral ischemia, plasma concentrations of neopterin and ET-1 were measured in 59 patients with acute cerebral infarction or transient ischemic attack (median age 73 years, range 43-93, 27 men) and after a 1-year follow-up in 57/59 (97%) of patients. Plasma neopterin was higher at follow-up (6.3 nmol/L [3.7-21.6] vs 5.6 nmol/L [3.5-17.2]; p < 0.05) than at the acute stage, whereas the plasma ET-1 concentration was unchanged. Plasma concentrations of both neopterin and ET-1 correlated directly with age both in the acute stage (r = 0.42 and r = 0.35, respectively; p < 0.01) and after follow-up (r = 0.34; p < 0.05 and r = 0.27; p = 0.05, respectively). In conclusion, plasma neopterin increased after acute cerebral ischemia, indicating chronic inflammatory activity and continuous macrophage activation in ischemic cerebrovascular diseases.

Endothelial derived vasoactive factors and leukocyte derived inflammatory mediators in subjects with asymptomatic atherosclerosis

To clarify relationships between the (endothelial vasodilatory and vasoconstrictive function) and leukocyte inflammatory mediators in subjects with asymptomatic atherosclerosis, we measured (intraplatelet cyclic 3',5'-guanosine monophosphate [cGMP] and cyclic 3',5'-adenosine monophosphate [cAMP]), plasma endothelin (ET-1), and plasma neopterin in 197 subjects with asymptomatic atherosclerosis (median age 63 years, range 49-69 years). We measured neutrophil protease 4 (NP4), tumor necrosis factor (TNFmu), soluble tumor necrosis factor receptor-1 (sTNFR-1), and neutrophil gelatinase associated lipocalin (NGAL) in 152 of the 197 subjects. Intraplatelet cGMP correlated inversely with plasma ET-1 (r=-0.22; p=0.01), which confirms earlier in vitro data of the inhibitory effect of ET-1 on NO production and/or the cGMP mediated inhibitory effect of NO on ET-1 production. Plasma neopterin as well as NP4 correlated directly with intraplatelet cGMP (r=0.24; p<0.01 and r=0.33; p<0.001, respectively). Intraplatelet cAMP correlated directly with plasma TNFmu (r=0.17; p<0.05) and sTNFR-1 (r=0.20; p<0.05). The relationship between leukocyte derived inflammatory mediators and intraplatelet cyclic nucleotides suggest an antiaggregating effect of leukocytes upon platelets, which may constitute a negative feedback mechanism that inhibits platelet activation during the atherosclerotic inflammatory process.

Increasing levels of leukocyte-derived inflammatory mediators in plasma and cAMP in platelets during follow-up after acute cerebral ischemia

Inflammatory mediators secreted by activated leukocytes play a role in the pathogenesis of atherosclerosis. They may also affect the production of vasodilatory and platelet antiaggregatory factors such as nitric oxide (NO) and prostacyclin (PGI2) from the vascular endothelium. Production of NO and PGI2, the effecs of which are mediated by cyclic 3',5'-guanosine monophosphate (cGMP) and cyclic 3',5'-adenosine monophosphate (cAMP), respectively, is disturbed in atherosclerosis, whereas increased NO levels have been found in acute cerebral ischemia. To investigate leukocyte activation and its possible influence upon endothelial function in cerebral ischemia we measured plasma neutrophil gelatinase-associated lipocalin (NGAL) and soluble tumor necrosis factor receptor protein-1 (sTNFR-1) by ELISA, and intraplatelet cAMP and cGMP by radioimmunoassay in 59 patients with acute ischemic stroke or transient ischemic attack (mean age 71 years, 27 males) and after a 1-year follow-up in 57/59 (97%) patients. NGAL (152 +/- 58 vs. 126 +/- 48 microgram/l), sTNFR-1 (3.50 +/- 2.2 vs. 2.59 +/- 1.31 microgram/l), and cAMP (5.12 +/- 1.71 vs. 4.06 +/- 0.92 pmol/10(9) platelets) were higher (p < 0.001) after follow-up than in acute cerebral ischemia. At follow-up sTNFR-1 and cGMP partially correlated (r = 0.31; p < 0.05), controlling for age and platelet count. In conclusion, plasma NGAL and sTNFR-1 and intraplatelet AMP increase after acute cerebral ischemia, indicating chronic inflammatory activity and endothelial activation. Plasma sTNFR-1 levels are related to intraplatelet cGMP levels.

Intraplatelet cyclic 3'-5' guanosine monophosphate is related to serum cholesterol

Nitric oxide (NO) exerts its vasodilator and antiaggregatory effects through activation of soluble guanylate cyclase and the consequent increase in the concentration of cGMP in target cells. We conducted this study in order to evaluate relationships between intraplatelet cGMP levels and risk factors for atherosclerosis in middle aged subjects. Intraplatelet cGMP was determined by radioimmunoassay and related to age, BMI, blood pressure, antihypertensive treatment, total, LDL and HDL cholesterol, triglycerides, blood glucose, HbA1c, smoking habit and intimal thickness of the common carotid artery in 265 subjects participating in a health survey (age 59 +/- 6 years, range 48-68 years, 121 females, 144 males). Intraplatelet cGMP concentration was inversely correlated with total serum cholesterol (r = -0.18; p < 0.01) and HDL cholesterol (r = -0.14, p < 0.05) as well as with platelet count (r = -0.29; p < 0.001). When platelet count was adjusted for, only the correlation between total serum cholesterol and cGMP remained significant. No significant correlations could be demonstrated between intraplatelet cGMP levels and measurable parameters of atherosclerosis. Lower levels of the vasodilating and antiaggregating mediator cGMP in platelets are related to higher levels of serum total cholesterol. These results favour the hypothesis of a relationship between lipid levels and NO associated vasodilator and antiaggregating function in atherosclerosis.