Hormone replacement therapy: relation to homocysteine and prooxidant-antioxidant status in healthy postmenopausal women

OBJECTIVES

Studies have consistently shown a lower cardiovascular risk in women who received postmenopausal hormone replacement therapy (HRT).

DESIGN AND METHODS

In this study, the effects of HRT were investigated on plasma total homocysteine (tHcy) and the oxidant-antioxidant status in postmenopausal women. 35 of postmenopausal receiving (2 mg estrodiol valerate + 1 mg cyproterone acetate) HRT group, the remaining 25 received orally placebo (NHRT group).

RESULTS

There was no significant change in plasma tHcy levels between HRT and NHRT groups. Malondialdehyde (MDA) and total thiol (t-SH) correlated significantly with tHcy (0.388 and 0.478, respectively) content, and there was a significant negative correlation between E2 level and glutathione transferase (GST) activity (-0.425) in HRT group. Superoxide dismutase (SOD) and HDL-C correlated significantly with t-SH level (0.339 and 0.336, respectively) in plasma after HRT.

CONCLUSION

Our results show that HRT is beneficial in the protection against oxidative damage, and prevents atherosclerotic complications.

The evaluation of lipid peroxidation and acute effect of octreotide on lipid peroxidation in patients with active acromegaly

BACKGROUND

Although lipid peroxidation has been suggested to play a role in the etiology of many diseases, there is no report about its role in acromegaly in the literature. In the present study, we analyzed the basal levels of lipid peroxides (LPO) in newly diagnosed acromegalic patients, and to evaluate whether octreotide (OCT) has any effect on lipid peroxidation in these patients.

METHODS

Plasma lipid peroxide levels before and after acute OCT administration were measured in 12 newly diagnosed acromegalic patients. Blood samples were drawn at basal and 4, 8, and 24 h after octreotide injection (100 microg s.c.). Plasma concentrations of lipid peroxides were estimated from measurement of thiobarbituric acid reactive substance (TBARS), using 1,1,3,3-tetra-ethoxypropane as a standard.

RESULTS

This study shows that acromegalic patients have significantly higher basal plasma lipid peroxides levels compared to hours after OCT injection (p<0.001). Although a significant decrease was observed after 8 and 24 h in comparison to basal level (p<0.001), the lipid peroxide levels tended to increase at 24 h though still low when compared to basal level.

CONCLUSION

Acromegalic patients have high basal lipid peroxide levels, which was significantly decreased after OCT administration.

Plasma antioxidants and type 2 diabetes mellitus

Reports indicate that some complications of diabetes mellitus are associated with increased activity of free radicals and accumulation of lipid peroxidation products. The organism's susceptibility to free radical stress and peroxidative damage is related to the balance between the free radical load and the adequacy of antioxidant defenses. In the present study, the relationship between plasma oxidants and antioxidants in diabetes mellitus was investigated. Thirty patients with type-2 diabetes mellitus were examined as well as twenty healthy controls (matched for age and sex against the diabetic patients). The plasma insulin and C-peptide levels in the diabetic group were significantly lower (p < 0.001) than that of the control group. The mean plasma fructosamine, lipid peroxide, lipids and low-density lipoprotein cholesterol (LDL-C) levels were significantly high (p < 0.001) in the diabetic group compared to the control group. There were not any significant differences in the plasma high-density lipoprotein cholesterol (HDL-C) levels between the patients and the control group (p < 0.001). The type-2 diabetes mellitus patients exhibited higher activities of plasma superoxide dismutase (SOD) than control values, whereas plasma glutathione peroxidase (GPx) activities were significantly lower. Our results suggest that there seems to be an imbalance between plasma oxidant and antioxidant systems in patients with type-2 diabetes mellitus. The estimation of plasma antioxidant levels and their replenishment by exogenous agents when necessary may be useful in the prevention of the diabetic complications.

Changes of oxidative stress in various tissues by long-term administration of vitamin E in hypercholesterolemic rats

BACKGROUND

Free radical-mediated oxidative stress has been implicated in the genesis and progression of atherosclerosis.

METHODS

The lipid peroxides and antioxidant status of various tissues were investigated in hypercholesterolemic rats and the effect of vitamin E supplementation on defense systems.

RESULTS

Cholesterol-feeding caused a significant increase in the lipid peroxide concentrations of plasma, erythrocytes, liver and brain. In addition, a significant decrease in glutathione (GSH) content, glutathione peroxidase (GSH-Px) and glutathione transferase (GSH-ST) activities were found in erythrocytes and liver but superoxide dismutase (SOD) activity remained unchanged in these tissues in comparison to the control group. Vitamin E supplementation to hypercholesterolemic rats induced a significantly decrease in lipid peroxide concentrations and a significant increase in the GSH content, GSH-Px and GSH-ST activities in erythrocytes and liver.

CONCLUSIONS

Long-term administration of vitamin E may play an important role in suppressing oxidative stress, and thus, may be useful for the prevention and/or early treatment of hypercholesterolemia.

Protective effects of vitamins A and E pretreatment in venous ischemia/reperfusion injury

It has been suggested that venous ischemia is more injurious to tissue viability than is arterial ischemia of equivalent duration. The precise mechanism of tissue damage due to venous ischemia is still not well-determined. Current research has shown that it is multifactorial, and that lipid peroxides, prostanoid metabolism, and a free radical mechanism are the major contributors. Vitamins A and E are lipid-soluble vitamins that have been suggested to be successful in the treatment of arterial ischemia/reperfusion injury due to their antioxidant properties. In the present study, the authors examined the protective effects of vitamins A and E pretreatment on reperfusion injury induced by venous occlusion of rat epigastric island flaps based on an epigastric artery and vein pedicle. In the first part of the study, to determine critical ischemia time, epigastric island skin flaps (3 x 6 cm) were elevated on their vascular pedicles in 40 male Sprague Dawley rats. Total venous occlusion of the skin flap was produced by ligating all draining veins and clamping the epigastric vein. Arterial inflow was left intact. Rats were randomly assigned to five groups (n=8) for 2, 5, 7, 9, and 10 hr of venous ischemia. Despite the occurrence of widespread reperfusion injury, reflow was established (p<0.005) at 9 hr. In the second part of the study, 20 rats were randomly divided into four groups (n=5). The effects of vitamins A and E following 9 hr ischemia/reperfusion injury were examined. Rats were pretreated with vitamin E, vitamin A and vitamins A+E for 5 days. At the end of the fifth day, each rat had undergone an epigastric island skin flap and venous occlusion, as described above. Mean surviving flap area (percent) and plasma lipid peroxides (TBARs), total thiol content (t-SH), glutathione peroxidase (Gpx), and superoxide dismutase (SOD) were determined for each rat. Results suggest that, in the prevention of venous ischemia/reperfusion injury, vitamin A and vitamin E are not effective when used as single agents; however, when used in combination, they significantly increase surviving flap area by a synergistic effect.

Thymosin alpha-1: evidence for an antiatherogenic effect

In the present study, the effects of thymosin alpha1 on lipid peroxidation were studied in an in vivo model of experimental hypercholesterolemia. In groups II-IV, rabbits were fed a high-cholesterol diet 2% (w/w) for 10 weeks. Thereafter, rabbits in group III were fed a normal diet for another 14 days and those in group IV were given a normal diet plus 25 microg/kg thymosin alpha1 intraperitoneally every other day for the same period. At the end of this period, plasma and erythrocyte lipid levels and susceptibility of erythrocytes to lipid peroxidation were determined in all groups. Hypercholesterolemic rabbits had high plasma and erythrocyte lipid peroxide (TBARS) levels compared to control animals fed a normal diet. Plasma and erythrocyte TBARS levels significantly decreased in the thymosin-alpha1-injected rabbits. In thymosin-alpha1-treated animals (group IV), most of the lipid plaques were replaced by fibrous tissue. These findings suggest that thymosin alpha1 may have some beneficial effects on the treatment of atherosclerosis by normalizing blood lipid levels and by substantially protecting endothelial cells against free radical injury.

Vitamin E and ATPases: protection of ATPase activities by vitamin E supplementation in various tissues of hypercholesterolemic rats

It has been shown that the lipid composition of plasma membrane can be modified in vivo by dietary fat. It has also been observed that an increase in the cholesterol content of plasma membranes results in decreased activities of ATPases. In the present study, we evaluated the changes in the activities of ATPases from erythrocytes, hepatocytes, and kidney cortex caused by cholesterol-rich diet in rats and subsequently examined the role of vitamin E administration on the cholesterol-induced effects in these tissues. Administration of hypercholesterolemic diet to the rats for 4.5 months, significantly decreased membrane Na(+)-K(+)-ATPase and Ca+2-ATPase activities in comparison to the controls in all tissues studied. Vitamin E supplementation to the hypercholesterolemic rats led to a recovery in membrane ATPase activities. In conclusion, vitamin E supplementation to the rats provided protection against hypercholesterolemic diet-induced impairment of membrane-bound ATPases.

The effect of methimazole on the oxidant and antioxidant system in patients with hyperthyroidism

The present study was designed to evaluate the changes in the plasma lipid peroxidation and antioxidant system in 15 adult volunteer patients in hyperthyroid and euthyroid states. In these patients, plasma concentrations of lipid peroxides were decreased and, ascorbic acid and vitamin E levels were significantly increased in euthyroid status in comparison to hyperthyroid status. A significant increase in the plasma GPx activity (P < 0.01) and a decrease in GST (P < 0.001) was observed after euthyroidism was sustained with methimazole therapy. In conclusion, hyperthyroidism tends to enhance lipid peroxide content and an increase in GST and decreases in GPx, vitamin E and ascorbic acid levels accompany to this change in the plasma. The achievement of euthyroidism led an improvement in these parameters.

Effects of thymosin alpha-1 on erythrocyte lipid levels and erythrocyte membrane (Na(+)-K+)-ATPase activity in experimental hypercholesterolemia

Thymosin alpha-1 is an active polypeptide isolated from thymus. This polypeptide is widely used in the diagnosis and treatment of many diseases, especially immune diseases. In this present study, we examined the effects of thymosin alpha-1 on plasma and erythrocyte lipid levels and the changes in erythrocyte membrane (Na+, K+)ATPase activity in hypercholesterolemic rabbits. The erythrocyte lipid levels decreased, whereas the erythrocyte membrane (Na+, K+)ATPase activity increased significantly in these rabbits after thymosin alpha-1 injection. These findings suggest that thymosin alpha-1 is effective on both the lipid level and erythrocyte membrane (Na+, K+)ATPase activity.

The role of thymosin F5 on anemia in hypercholesterolemic rabbits

New Zealand White rabbits were made hypercholesterolemic by feeding a high cholesterol diet (20 g/kg diet) for 3 months. Plasma cholesterol concentrations were monitored as a function of time. At the end of 3 months, the plasma lipid levels, the whole blood, erythrocyte and haemoglobin-bound 2,3-DPG levels and leucocyte counts increased, whereas erythrocyte counts, hematocrit and haemoglobin levels decreased significantly in hypercholesterolemic rabbits. At the end of 3 months, the rabbits in the experimental group were divided into two groups. The first group was fed a standard diet for 21 days. The second group received 0.5 mg/kg thymosin F5 injection i.p. every other day for 21 days. After this period, the plasma lipid levels, the whole blood, erythrocyte and haemoglobin-bound 2,3-DPG levels, erythrocyte and leucocyte counts, hematocrit and haemoglobin levels were measured. Rabbits fed diets supplemented with thymosin F5 had markedly lower plasma lipid levels, erythrocyte counts, hematocrit and haemoglobin levels and enhanced leucocyte counts, but did not have significantly less whole blood, erythrocyte and haemoglobin-bound 2,3-DPG levels. We conclude that thymosin F5 has lipid-lowering effects in hypercholesterolemic rabbits. The data further suggest that effects of thymosin F5 on haematological parameters are due to the cholesterol decrease and not to the direct regulatory mechanism.