Endothelin-1 and big endothelin-1 in NIDDM patients with and without microangiopathy

Metabolic interactions between hyperhomocysteinemia and endothelin-1 among Tunisian patients with acute coronary diseases

BACKGROUND

Acute coronary syndromes (ACS) are complex and polygenic diseases which are a real problem of public health. These syndromes require multidisciplinary studies to understand the pathogenesis mechanisms and metabolic interactions between different risk factors.This study aimed to explore the variation of two coronary risk parameters not mentioned by Framingham cohorts, hyperhomocysteinemia and endothelin-1 (ET-1) in Tunisian coronary and the study of the variation of these parameters based on various cardiac risk factors and metabolic relationship between them.To 157 coronary and 142 healthy subjects, the concentration of homocysteine was quantified by fluorescence polarization immunoassay; the concentration of ET-1 was measured by an analytical technique, the High Performance Liquid Chromatography (HPLC) coupled with mass spectrometry.

RESULTS

Our study showed that homocysteine and ET-1 were significantly higher in patients compared to healthy subjects (24.40 ± 12.5 μmol/L vs 7.44 ± 2.5 μmol/L p <0.00001) for homocysteine and (15.2 ± 5.3 nmol/L vs 7.1 ± 2.7 nmol/L, p <0.00001) for ET-1. On the other hand, homocysteine varies according to tobacco and diabetes while ET-1 depends on the sex, hypertension, smoking, obesity and dyslipidemia and a statistically negative correlation was shown between homocysteine and ET-1 in coronary patients (r = -0.66 p <0.00001).

CONCLUSION

The study of the variation of these two parameters in coronary patients and metabolic exploration of the relationship between homocysteine and ET-1 according to various risk factors and the interactions between themselves facilitates the decision of therapeutic treatment.

Structural alterations of the glomerular wall and vessels in early stages of diabetes mellitus: (light and transmission electron microscopic study)

OBJECTIVE

The capillary changes at the initial stage of diabetes may show an angioarchitecture clearly different from those of later stages and/or very severe glomerular change. However, the onset of alterations in the early phases is unclear. This study attempts to determine the structural alterations of the glomerular wall and vessels in the early stage of diabetes.

MATERIAL AND METHODS

Twenty-five adult rats were used in this study. They were divided into two groups: the first group of five was used as a control. The second group of 20 (the experimental group) was injected intraperitoneally by a single dose of streptozotocin to induce hyperglycemia. Rats were sacrificed after ten days, two months, and four months. Five rats at two months of age with hyperglycemia were treated with insulin for eight weeks. Renal tissues were prepared by routine technique for light and transmission electron microscopic evaluation.

RESULTS

By light microscopy after ten days of induced hyperglycemia, there were no structural modifications detected either in renal glomerular fine vessels or in the glomerular basement membrane of the glomerular capillaries. After two months, there was a moderate glomerular enlargement and dilatation of glomerular capillaries, afferent, and efferent arterioles. After four months, glomerular basement membrane thickening was the only structural alteration observed. Recovery of the glomerular alterations was observed after two months of treatment with insulin.

CONCLUSION

In early stages of diabetes mellitus in rats, there was an increase in the diameter of glomerular vessels. In later stages of the disease, the reverse was seen, but insulin treatment had a positive role in reversing these changes in the study subjects.

Association between endothelin-1 and collagen deposition in db/db diabetic mouse kidneys

Endothelin-1 has been implicated in diabetic kidney injury, but there are few firm data establishing the temporal and spatial expression of kidney endothelin-1 in diabetes. We performed an immunohistochemical and histopathological analysis to determine endothelin-1 peptide expression in the kidneys of diabetic db/db mice and non-diabetic db/m controls. Diabetic mice were studied at 8 weeks, before histological damage is evident, and again at 16 weeks, when significant glomerular injury has occurred. Urinary endothelin-1 was 6.2- and 3.6-fold higher in 8- and 16-week diabetic mice compared to age-matched controls (P<0.01 db/db vs. db/m). Compared to non-diabetic kidneys, immunoreactive endothelin-1 was first elevated 2.5-fold (P=0.02) in the tubulointerstitial compartment at 8-week and remained high (3.8-fold, P<0.01) at 16 weeks. In contrast, glomerular endothelin-1 was elevated 3.2-fold (P=0.03) only in 16-week diabetic mice. Glomerular and tubulointerstitial endothelin-1 were unchanged in 8- and 16-week non-diabetic mice. Elevated endothelin-1 in diabetic mice associated temporally and spatially with collagen deposition, especially in the tubulointerstitial compartment. The localization of kidney endothelin-1 is consistent with a role for this peptide in renal fibrogenesis. These results also highlight the potential role of ET-1 in the pathogenesis of early tubulointerstitial changes in diabetes.

Obstructive sleep apnea: Plasma endothelin-1 precursor but not endothelin-1 levels are elevated and decline with nasal continuous positive airway pressure

Assessment of plasma endothelin-1 (ET-1) reveals conflicting results in cerebral and noncerebral conditions. Obstructive sleep apnea (OSA) syndrome has been used as a definite challenge for the investigation of endothelin measurements. Despite marked sleep-related breathing disturbances in untreated patients peripherally measurable ET-1 concentrations remained within the normal range and did not change after an appropriate therapy with continuous positive airway pressure (CPAP). In contrast, its precursor, big ET-1, was considerably elevated in untreated patients and dropped to normal values after long-term CPAP depending on compliance. Relatively stable big ET-1 elevations in untreated patients, during sleep and wakefulness, suggest that a general endothelial alteration beyond that explained by a direct impact of nocturnal breathing disturbances on the vascular system occurs. CPAP-therapy effectively lowered plasma big ET-1 in compliant patients and thus possibly their related risk for vascular diseases. Big ET-1 has been demonstrated to be a more appropriate marker of endothelial alteration than ET-1 because of its longer half-life. Simultaneous measurements are to be recommended.

Plasma endothelin and big endothelin concentrations and serum endothelin-converting enzyme activity following aneurysmal subarachnoid hemorrhage

OBJECT

Pathogenesis of delayed ischemia after aneurysmal subarachnoid hemorrhage (SAH) seems to be complex. An important mediator of chronic vasospasm may be endothelin (ET)-1 with its powerful and long-lasting vasoconstricting activity. In this prospective study the author investigated the correlations between serial plasma concentrations of ET-1 and big ET-1 as well as the ET-1/big ET-1 molar concentration ratio and serum endothelin-converting enzyme (ECE)-1 activity, and ischemic complications after SAH.

METHODS

To measure plasma ET-1 (51 patients), big ET-1 immunoreactivity (22 patients), and serum ECE-1 activity (13 patients), blood samples were obtained on admission, in the morning after aneurysm surgery, and during the 2nd week after hemorrhage in 51 consecutive patients (28 men and 23 women, with a mean age of 50.8 years) with aneurysmal SAH. Mean plasma concentrations of ET-1 in patients with SAH (mean +/- standard deviation: on admission, 4.2 +/- 2 pg/ml; after surgery, 4.3 +/- 2.2 pg/ml; and during the 2nd week after SAH, 3.7 +/- 1.9 pg/ml) differed from those in healthy volunteers (2.9 +/- 1.2 pg/ml; p < 0.01). Plasma concentrations of ET-1 and big ET-1 as well as the ET-1/big ET-1 ratio did not change significantly with elapsed time following SAH; however, serum ECE-1 activity during the 2nd week after SAH was higher in patients with SAH than that in controls (162 +/- 43 compared with 121 +/- 56 pg/ml, respectively; p = 0.028). Plasma ET-1 concentrations (p < 0.05) and the ET-1/big ET-1 ratios (p = 0.063) were higher but plasma big ET-1 concentrations were lower (p < 0.05) in patients who experienced symptomatic delayed cerebral ischemia, compared with other patients with SAH. In addition, in cases in which follow-up computerized tomography scans or magnetic resonance images demonstrated permanent ischemic lesions attributable to vasospasm, patients had higher ET-1 concentrations than did other patients with SAH.

CONCLUSIONS

The plasma ET-1 concentration correlates with delayed cerebral ischemia after SAH, suggesting that an increased ET conversion rate in the endothelium predicts ischemic symptoms. Increased serum ECE-1 activity during the 2nd week may reflect the severity of endothelial injury to cerebral arteries.

The relation between plasma endothelin-1 levels and metabolic control, risk factors, treatment modalities, and diabetic microangiopathy in patients with Type 2 diabetes mellitus

We evaluated the possible relation between plasma endothelin-1 (ET-1) levels and metabolic control, risk factors, treatment modalities, and diabetic microangiopathy, including nephropathy, neuropathy, and retinopathy in patients with Type 2 diabetes and healthy control group. Sixty-eight (39 females and 29 males) patients with Type 2 diabetes and 14 (6 females and 8 males) healthy subjects were included in the study. Plasma ET-1 levels were found to be 10.46+/-1.24 pmol/l in the diabetic group, whereas 7.97+/-0.41 pmol/l in the control group, which was statistically significant (P<.01). We also found elevated plasma ET-1 levels in patients with the least one microvascular complication when compared with the uncomplicated diabetes group (P=.02). Moreover, plasma ET-1 levels of the uncomplicated group was higher than the control group (P<.05). Plasma ET-1 levels were significantly elevated in hypertensive diabetics than normotensive diabetics (t=2.58, P=.012). It was also found to be elevated in diabetic patients with diabetes duration of more than 10 years when compared with patients less than 10 years (P=.02). These findings can be interpreted as the increased damage of microvascular complications in the disease process that may lead to elevated ET-1 levels. Mean plasma ET-1 levels in diabetic patients with a family history of diabetes was found to be higher than patients with no family history of diabetes. Genetical and environmental factors may have an effect on ET-1 level. We also studied the correlations of plasma ET-1 levels on age, sex, fasting blood glucose levels, treatment modalities HbA1c, hyperlipidemia, C-peptide, Body Mass Index, and smoking, but did not find any statistically significant difference. In conclusion, plasma ET-1 levels are well correlated with microangiopathy, hypertension, increased disease duration, and family history of diabetes, but poorly correlated with metabolic control, treatment modalities, age, sex, hyperlipidemia, obesity, and smoking.

Effect of insulin and heparin on glucose-induced vascular damage in cell culture

BACKGROUND

Clinical trials have shown that tight glycemic control reduces the risk of diabetic microvascular complications, namely retinopathy, nephropathy, and neuropathy. The mechanism of these microvascular complications is not yet fully elucidated. The present study describes the effect of different concentrations of glucose on vascular endothelial cells (ECs) and vascular smooth muscle cells (VSMCs) in cell culture. Our objective was to shed some light through this biological study on the mechanism and prevention of diabetic microvascular complications.

METHODS

ECs and VSMCs were treated with 5 mmol/L (90 mg/dL) or 30 mmol/L (540 mg/dL) D-glucose or D-glucose plus insulin or D-glucose plus insulin and heparin in culture. ECs were studied with light microscopy (LM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) for surface changes. The cultured ECs were treated with vimentin antibodies and VSMCs with actin antibodies for immunoflourescence microscopy (IFM) study. Endothelin-1 (ET-1) assay was done on ECs culture medium using enzyme-linked immunosorbent assay (ELISA).

RESULTS

LM, SEM, and TEM of ECs treated with a physiological concentration (90 mg/dL) of D-glucose appeared the same as control. However, LM and SEM of ECs treated with a high concentration of D-glucose (540 mg/dL) showed pronounced intercellular gaps. This finding was further confirmed by TEM study. These gaps were minimally or not at all discernible when insulin, heparin, or a combination of both was added to the culture medium. IFM showed increased vimentin expression with a high concentration of D-glucose. Vimentin expression was attenuated with the addition of insulin or heparin in the medium and more markedly with combined insulin and heparin. Significant correlations were obtained between glucose levels, vimentin expression, and ET-1 levels. The higher the glucose level, the higher is the ET-1 production and the greater vimentin expression in ECs. Cultured VSMCs treated with a high concentration of D-glucose showed enhanced actin expression. Actin expression was blunted with the addition of insulin or heparin in the culture medium.

CONCLUSIONS

These biological findings indicate the salutary effect of insulin or insulin and heparin in the mitigation of vascular disorganization caused by a high concentration of D-glucose.