Insulin resistance syndrome in postmenopausal women with cardiological syndrome X

Type 2 diabetes mellitus and other cardiovascular risk factors are no more common during menopause: longitudinal study

OBJECTIVE

The aim of this study was to undertake a prospective study of the changes in certain risk factors for cardiovascular disease occurring during menopause.

METHODS

A longitudinal cohort study of 475 women was followed up for 6 years (Pizarra Study). The final menstrual period was defined after at least 6 months of amenorrhea. The women were classified into three groups: group 1, no menopause at either the first or second study; group 2, no menopause at the first study but menopause at the second study (6 y later); and group 3, menopause at the first study (and also at the second). The following are the main outcome measures used: age; body mass index; waist circumference; waist-to-hip ratio; skinfold thickness; arm circumference; intake of macronutrients (quantitative questionnaire); systolic and diastolic blood pressures; cholesterol, triglycerides; high-density lipoprotein cholesterol; uric acid; homeostasis model assessment of insulin resistance; and the prevalence of obesity, hypertension, type 2 diabetes mellitus, impaired glucose tolerance, and impaired fasting glucose.

RESULTS

None of the cardiovascular risk factors studied changed during the passage from premenopause to postmenopause, independently of age or physical activity.

CONCLUSIONS

Menopause is a biological condition of the human species, for which has recently received attempts at medicalization that were not always justified. If menopause is not accompanied by any other cardiovascular risk factor independently of age, the stigma of menopause being considered a risk factor should cease. Although the results have the strength of a prospective study, the sample size forced us to consider these findings as preliminary.

Thrombin activatable fibrinolysis inhibitor and other hemostatic parameters in patients with polycystic ovary syndrome

OBJECTIVES

To investigate the plasma levels of thrombin-activatable fibrinolysis inhibitor (TAFI) in women with polycystic ovary syndrome (PCOS) and its correlation with various metabolic, hormonal and hemostatic parameters.

METHODS

Forty-eight women with PCOS and 43 age- and BMI-matched ovulatory controls were recruited during a 20-month study period. Blood samples were drawn for all tests, which included plasma lipids and lipoproteins, reproductive hormones, glucose, insulin, TAFI antigen concentration, plasminogen activator inhibitor-1 (PAI-1) activity, fibrinogen concentration, thrombomodulin, thrombin-antithrombin (TAT) complexes, D-dimer, Protein C Antigen, Protein S Antigen, Antithrombin III (AT III) and activated protein C (APC) resistance.

RESULTS

Plasma TAFI levels of PCOS patients were found to be significantly higher than in healthy controls (93.8%+/-30.6%vs. 79.8% +/- 22.4%, p < 0.05). Plasma levels of D-dimer, AT III, PAI-1 and thrombomodulin were also significantly higher in women with PCOS compared with healthy controls. All the other hemostatic parameters (including TAT complexes; Protein C; APC; and Protein S) were comparable between the two study groups.

CONCLUSION

This study showed that plasma levels of TAFI, PAI-1, D-dimer, AT III and thrombomodulin were significantly increased in women with PCOS compared with age- and BMI-matched controls.

Effects of Metformin on Microvascular Function and Exercise Tolerance in Women With Angina and Normal Coronary Arteries

OBJECTIVES

This study sought to determine whether metformin improves vascular function or myocardial ischemia in nondiabetic subjects.

BACKGROUND

Metformin prevents diabetes and may reduce coronary events in patients with diabetes, but effects on microvascular function and angina are not clear.

METHODS

We conducted an 8-week double-blind, randomized, placebo-controlled study of metformin 500 mg twice a day in 33 nondiabetic women with a prior history of normal coronary angiography but two consecutive positive (ST-segment depression > or =1 mm) exercise tolerance tests. All parameters were measured at baseline and at 8 weeks, together with an in vivo assessment of forearm (skin) microvascular function using laser Doppler imaging combined with iontophoresis.

RESULTS

In comparison with placebo (n = 17), metformin recipients (n = 16) showed significant reductions in weight and in homeostatic model assessment for insulin resistance (p < 0.05, intention to treat). Endothelium-dependent microvascular responses improved significantly with metformin (2-way repeated analysis of variance, p = 0.0003), but responses with placebo were unchanged (p = 0.50). A comparison of change in acetylcholine responses between metformin and placebo recipients was significant, whether analyzed by a 2-way analysis of variance (p < 0.0001) or change in area under curves (mean change +392 perfusion units, 95% confidence interval [CI] 20 to 764). Endothelium-independent responses were not altered. Maximal ST-segment depression (-0.84 mm, 95% CI -1.49 to -0.20, p = 0.013), Duke score (6.1 U, 95% CI 1.8 to 10.5, p = 0.008), and chest pain incidence (-0.11 episodes/day, 95% CI -0.22 to 0.00, p = 0.056) improved in metformin relative to placebo recipients.

CONCLUSIONS

Metformin may improve vascular function and decrease myocardial ischemia in nondiabetic women with chest pain and angiographically normal coronary arteries. Larger controlled trials of longer duration are warranted.

Assessment of insulin sensitivity from measurements in the fasting state and during an oral glucose tolerance test in polycystic ovary syndrome and menopausal patients

BACKGROUND

Polycystic ovary syndrome (PCOS) and menopausal subjects are characterized by an increased cardiovascular and type 2 diabetes mellitus risk, at least partially related to insulin disturbances. The evaluation of insulin resistance in these patients could be useful as primary prevention. The aim of the study was to verify the validity of several indexes of insulin sensitivity in PCOS and menopausal subjects by comparing the data obtained by these indexes to those of euglycemic-hyperinsulinemic clamp studies.

METHODS

One hundred PCOS and 110 menopausal subjects were analyzed; all subjects underwent an oral glucose tolerance test (75 g) and euglycemic-hyperinsulinemic clamp study. Seven PCOS patients and 13 menopausal subjects had impaired glucose tolerance or type 2 diabetes mellitus and were excluded from the study. After analysis of correlation coefficients between the evaluated indexes and the clamp studies, the sensitivity and specificity of different cut-off values for each parameter were analyzed by receiver operating characteristic (ROC) curves.

RESULTS

The best correlation coefficients with clamp studies were obtained with the Avignon insulin sensitivity index (SiM) (R(s) = 0.7812) in PCOS patients and the Matsuda and De Fronzo index (R(s) = 0.6178) in menopausal patients. The best predictive index of insulin resistance in PCOS was a Avignon insulin sensitivity basal index (SibB) value of 62 or less (78% sensitivity, 95% specificity) and an insulin area under the curve (AUC) of 7,000 microIU/ml or more (>/=50,225 pmol/liter) x 120 min (83% sensitivity, 90% specificity). In the menopausal population, the best predictive performance was obtained by an insulin AUC of 10,000 microIU/ml or more (>/=71,750 pmol/liter) x 240 min (70% sensitivity, 88% specificity).

CONCLUSIONS

The presence of high correlation coefficients does not necessarily mean that the indexes of insulin resistance have an optimal predictive performance; this is probably due to the presence of many borderline values. The simple evaluation of insulin AUC seems to effectively replace the euglycemic-hyperinsulinemic clamp in routine clinical practice, allowing results superimposable to those obtained by minimal model analysis.

Insulin resistance as a contributor to myocardial ischaemia independent of obstructive coronary atheroma: a role for insulin sensitisation?

There is good evidence to suggest that insulin resistance and its surrogate markers are at least modest independent cardiovascular risk factors. However, as well as long term effects on atheromatous coronary disease, there is a well described correlation between markers of insulin resistance and endothelial dysfunction. In this review, the evidence for a relation between endothelial dysfunction and myocardial ischaemia is summarised. The evidence for a correlation between insulin resistance and endothelial dysfunction and the proposed cellular mechanisms are also examined. Finally, the potential role for insulin sensitising strategies is looked at and recent data examining their effects on both endothelial function and clinical symptoms is examined. In conclusion, it was found that insulin sensitising modalities have a potential role in the amelioration of angina and that randomised controlled studies are therefore warranted.

Use of naltrexone in postmenopausal women with exaggerated insulin secretion: a pilot study

OBJECTIVE

To determine the effect of naltrexone (an opiate receptor blocker) on insulin metabolism in postmenopausal women with different insulinemic patterns.

DESIGN

Randomized placebo-controlled study.

SETTING

Academic research environment.

PATIENT(S)

Forty-one healthy normoinsulinemic or hyperinsulinemic postmenopausal women.

INTERVENTION(S)

Oral glucose tolerance test (OGTT) before and after 5 weeks of the opioid antagonist (naltrexone, 50 mg/d orally) or the placebo administration; euglycemic-hyperinsulinemic glucose clamp.

MAIN OUTCOME MEASURE(S)

Glucose, insulin, and C-peptide plasma levels assessed in fasting condition and during the OGTT. Insulin sensitivity was calculated as total body glucose utilization.

RESULT(S)

Naltrexone reduced fasting and stimulated insulin response to the glucose load while inducing a significant improvement of the hepatic extraction, only in the hyperinsulinemic patients. No differences were found in the C-peptide pancreatic secretion and in the peripheral insulin sensitivity. No net change in the glycoinsulinemic metabolism was observed in normoinsulinemic patients or in placebo-controlled normoinsulinemic and hyperinsulinemic subjects.

CONCLUSION(S)

Similar to that reported in premenopausal women, endogenous opioid peptides are involved in the modulation of glycoinsulinemic metabolism in postmenopause. Through a prevalent action on liver insulin metabolism, without any clear improvement of insulin resistance and pancreatic beta-cell function, the chronic administration of naltrexone appears to reduce the hyperinsulinemia in those women with an exaggerated insulin response to the OGTT.

A shift in myocardial substrate, improved endothelial function, and diminished sympathetic activity may contribute to the anti-anginal impact of very-low-fat diets

A new category of anti-anginal drug - exemplified by ranolazine - is believed to work by partially inhibiting cardiac oxidation of fatty acids; oxidation of glucose requires less oxygen per mol of ATP generated, and thus is preferable to fat oxidation when oxygen availability is limiting in underperfused cardiac tissue. Unfortunately, there is no reason to believe that these drugs inhibit fat oxidation selectively in the heart; thus, chronic use of these drugs can be expected to increase body fat stores until the original rate of fat oxidation is restored by mass action - presumably negating the therapeutic benefit in angina, while exacerbating the manifold adverse effects of insulin resistance syndrome. The rational way to decrease cardiac metabolic reliance on fatty acids is to consume a very-low-fat quasi-vegan diet (i.e., 10% fat calories). Indeed, such diets are known to have a rapid and substantial therapeutic impact on anginal symptoms, while concurrently benefiting insulin sensitivity, markedly improving serum lipid profile, promoting leanness, and lessening coronary risk. A reduction in diurnal insulin secretion might also be achieved, which would be expected to decrease sympathetic activity. While reduced myocardial demand for oxygen doubtless contributes to the beneficial impact of such diets on angina, it is likely that improved cardiac perfusion consequent to improved endothelium-dependent vasodilation also plays a role in this regard. Supplemental carnitine, also beneficial in angina, appears to improve utilization of glucose in the ischemic myocardium by lowering elevated acetyl-coA levels and thereby disinhibiting pyruvate dehydrogenase. Certain other nutraceuticals may aid control of angina by improving endothelial function. In the longer term, these measures have the potential to slow or reverse the progression of stenotic lesions that underlie most cases of angina. These safe and relatively inexpensive nutritional strategies for coping with angina deserve far more attention than orthodox medical practice has thus far accorded them.

Different long-term course between chest pain and exercise-induced ST depression in syndrome X

The aim of the present study was to assess the long-term clinical course of patients with syndrome X, focusing on different courses between exercise-induced ST depression and chest pain. Forty-three patients with syndrome X were followed up for 6.4 +/- 3.8 years. They were divided into the 3 groups according to chest pain: disappeared (n = 24), improved (n = 14), or unchanged (n = 5). No patients had cardiac events and all had a favorable long-term prognosis. In patients showing disappearance of chest pain, exercise-induced ST depression and rate-pressure product (RPP) at peak exercise did not change during follow-up. However, ST depression and RPP decreased significantly in those with improved chest pain. These observations suggest that abnormal pain perception plays an important role in the development of chest pain.

The role played by neural crest cells in the development of syndrome X: a hypothesis

This study evaluated the components and the related hormone releasing organs, the mechanism of action of these hormones, and the origins of the cells and organs in a disorder known as metabolic syndrome X, the prevalence of which is rapidly increasing particularly among the adult population of industrial societies. Metabolic syndrome X, involving carbohydrate and lipid metabolism disorders and cardiovascular disorders caused by the release of primary hormones, alpha and beta cells of the islets of Langerhans of pancreas, adrenal gland medulla's chromaffin cells, sympathetic nervous system neurons and ganglia, adenohypophysis, neurohypophysis and hypothalamus, were evaluated for being neuroectodermal and mainly having neural crest origin. Generally the cells, tissues and organs involved are neuroectodermal and especially have neural crest origins; and to conclude, in prevention, diagnosis and treatment of this disorder the priority is the analysis and understanding of the migration, differentiation and adaptation at the target of neural crest cells.

Naloxone decreases insulin secretion in hyperinsulinemic postmenopausal women and may positively affect hormone replacement therapy

OBJECTIVE

To evaluate the influence of the opioid system on glyco-regulation in postmenopausal women before and after hormone replacement therapy (HRT).

DESIGN

Prospective nonrandomized clinical study.

SETTING

Academic research environment.

PATIENT(S)

Twenty-one healthy normo- or hyperinsulinemic postmenopausal women.

INTERVENTION(S)

Oral glucose tolerance test (OGTT) (saline study), OGTT with IV injection of naloxone (naloxone study), and hyperinsulinemic euglycemic clamp performed before treatment, after 12 weeks of estrogen replacement therapy (ERT), and after 12 additional weeks of estro-progestin combined therapy (i.e., HRT).

MAIN OUTCOME MEASURE(S)

Glucose, insulin, and c-peptide plasma levels assessed in fasting condition and during the two OGTTs (area under the curve [AUC]). Evaluation of fractional hepatic insulin extraction (FHIE) and peripheral sensitivity to insulin.

RESULT(S)

At baseline, there is a greater increase of the FHIE and a more significant reduction of the insulin AUC in the hyperinsulinemic patients during the naloxone study compared with the saline study. In these women, ERT enhanced the c-peptide AUC and improved the FHIE; naloxone infusion mainly increased these two parameters. HRT did not induce any further change.

CONCLUSION(S)

Endogenous opioid peptides are involved in the modulation of carbohydrate metabolism in menopause in hyperinsulinemic patients more than in other patients. The favorable changes of the glyco-insulinemic metabolism induced by HRT may be partially due to the induction of the opioidergic activity.

Occlusive vascular diseases in oral contraceptive users. Epidemiology, pathology and mechanisms

Despite being an unprecedented departure from normal physiology, the combined oral contraceptive is not only highly effective, but it also has a remarkably good safety record. Concerns over safety persist, though, particularly with regard to venous thromboembolism (VTE), stroke and myocardial infarction (MI). Epidemiological studies consistently show an increase in risk of VTE, but the results are more contentious with regard to arterial diseases. Despite 40 years of research, the mechanisms behind these adverse effects are not understood. In this review, we integrate information from published studies of the epidemiology and pathology of the occlusive vascular diseases and their risk factors to identify likely explanations for pathogenesis in oral contraceptive users. Oral contraceptives induce both prothrombotic and fibrinolytic changes in haemostatic factors and an imbalance in haemostasis is likely to be important in oral contraceptive-induced VTE. The complexity of the changes involved and the difficulty of ascribing clinical significance has meant that uncertainty persists. A seriously under-researched area concerns vascular changes in oral contraceptive users. Histologically, endothelial and intimal proliferation have been identified in women exposed to high plasma estrogen concentrations and these lesions are associated with thrombotic occlusion. Other structural changes may result in increased vascular permeability, loss of vascular tone and venous stasis. With regard to arterial disease risk, epidemiological information relating to dose effects and joint effects with other risk factors, and studies of pathology and changes in risk factors, suggests that oral contraceptive use per se does not cause arterial disease. It can, nevertheless, synergise very powerfully with subclinical endothelial damage to promote arterial occlusion. Accordingly, the prothrombotic effects of the oral contraceptive estrogen intervene in a cycle of endothelial damage and repair which would otherwise remain clinically silent or would ultimately progress - in, for example, the presence of cigarette smoking or hypertension - to atherosclerosis. Future work in this area should focus on modification of the effects of established risk factors by oral contraceptive use rather than modification of the supposed risk of oral contraceptive use by established risk factors. Attempts to understand vascular occlusion in oral contraceptive users in terms of the general features of VTE or with reference to atherosclerosis may be limiting, and future work needs to acknowledge that such occlusions may have unique features. Unequivocal identification of the mechanisms involved would contribute considerably to the alleviation of fears over vascular disease and to the development of even safer formulations.

Menopausal status and risk factors for cardiovascular disease

OBJECTIVES

Changes in cardiovascular risk factors with menopausal status are difficult to study, owing to the high correlation of menopausal status with age. Therefore we examined cardiovascular risk factors in a meticulously selected population in which the contrast in oestrogen status between pre- and postmenopausal women of the same age was maximized.

DESIGN

Risk factors were compared in 93 premenopausal and 93 postmenopausal women who were matched on age (range 43-55 years).

SETTING

The women were selected from respondents to a mailed questionnaire about the menopause, which was sent to all women aged 40-60 years in the Dutch town of Zoetermeer (n = 12 675; response 54%).

SUBJECTS

Postmenopausal women who were at least 3 years after menopause or whose menses had stopped naturally before age 48 were age-matched with premenopausal women with regular menses and without menopausal complaints.

RESULTS

Compared to premenopausal women, postmenopausal women had significantly increased levels of total cholesterol (10.0%, 95% confidence interval 5.1-14.0), low density lipoprotein (LDL) cholesterol (14.0%, 6.9-19.9), and apolipoprotein B (8.2%, 0.6-15.5). The difference was present within 3 years after onset of menopause and did not show a trend towards an increase with the number of postmenopausal years. No differences were found in high density lipoprotein (HDL) cholesterol, triglycerides, apolipoprotein A1, blood glucose, insulin, body mass index, waist-to-hip ratio, and systolic and diastolic blood pressure.

CONCLUSIONS

The results of this study add to the evidence that total cholesterol, LDL cholesterol and apolipoprotein B are the primary cardiovascular risk factors affected by menopause.

Endothelial and metabolic characteristics of patients with angina and angiographically normal coronary arteries: comparison with subjects with insulin resistance syndrome and normal controls

OBJECTIVES

This study was performed to characterize the endothelial and metabolic alterations of patients with angina and angiographically normal coronary arteries ("cardiac" syndrome X [CSX]) compared with subjects with insulin resistance syndrome ("metabolic" syndrome X [MSX]) and normal controls.

BACKGROUND

Previous studies have found high endothelin-1 levels, impaired endothelium-dependent vasodilation and insulin resistance in patients with angina pectoris and angiographically normal coronary arteries. On the other hand, subjects with insulin resistance syndrome have shown high endothelin-1 levels.

METHODS

Thirty-five subjects were studied: 13 patients with angina pectoris and angiographically normal coronary arteries (CSX group); 9 subjects with insulin resistance syndrome (MSX group) and 13 normal controls. All subjects received an acute intravenous bolus of insulin (0.1 U/kg) combined with a euglycemic clamp and forearm indirect calorimetry. Endothelin-1 levels, nitrite/nitrate (NOx) levels, end products of nitric oxide metabolism, glucose infusion rates (index of insulin sensitivity) and their incremental areas (deltaAUCs [area under curves]) were measured during this period.

RESULTS

Basal endothelin-1 levels were higher in CSX and MSX groups than in normal controls (8.19 +/- 0.46 and 6.97 +/- 0.88 vs. 3.67 +/- 0.99 pg/ml; p < 0.01), while basal NOx levels were significantly higher in MSX group than in CSX and normal controls (36.5 +/- 4.0 vs. 24.2 +/- 3.3 and 26.8 +/- 3.2 mol/liter, p < 0.05). After insulin administration, the deltaAUCs of NOx (p < 0.05) were lower in CSX group than in MSX and normal controls, and the deltaAUCs of endothelin-1 were lower in group CSX than in normal controls. Glucose infusion rate was significantly lower in CSX and MSx groups than in normal controls (p < 0.01), suggesting that in both CSX and MSX groups insulin resistance is present. A positive correlation was found between the deltaAUCs of nitric oxide and the AUCs of glucose infusion rate.

CONCLUSIONS

Blunted nitric oxide and endothelin responsiveness to intravenously infused insulin is a typical feature of patients with angina pectoris and angiographically normal coronary arteries and may contribute to the microvascular dysfunction observed in these subjects.

Reduced responsiveness to endothelin-1 in peripheral resistance vessels of patients with syndrome X

OBJECTIVES

This study sought to assess the contribution and action of nitric oxide and endothelin-1 in peripheral resistance vessels of patients with syndrome X.

BACKGROUND

Patients with syndrome X may have a generalized disorder of vascular and endothelial function, promoting vasospasm.

METHODS

Changes in blood flow responses to intrabrachial infusion of the endothelium-dependent vasodilators substance P and acetylcholine, the endothelium-independent nitric oxide donor sodium nitroprusside and the endothelin type A (ET(A)) receptor antagonist BQ-123 were assessed using venous occlusion plethysmography in 10 patients with syndrome X and 10 matched control subjects. Vasoconstrictor responses to the nitric oxide synthase inhibitor L-N(G)-monomethyl arginine (L-NMMA) and endothelin-1 were also determined.

RESULTS

There were no significant differences in the responses to acetylcholine, substance P, sodium nitroprusside or BQ-123 between patients and control subjects. However, despite similar degrees of vasoconstriction in response to L-NMMA in both groups, endothelin-1 caused a reduction in forearm blood flow of only 20 +/- 2% in patients with syndrome X compared with 35 +/- 3% in matched control subjects at 90 min (p < 0.001). Although plasma endothelin-1 concentrations were not significantly higher in patients with syndrome X (4.8 vs. 4.0 pg/ml, p = 0.17), the vasoconstriction caused by endothelin-1 infusion correlated inversely with plasma endothelin-1 concentrations (r = -0.51, p = 0.04).

CONCLUSIONS

Patients with syndrome X had normal basal and stimulated nitric oxide activity and basal endogenous ET(A) receptor-mediated vascular tone. However, despite otherwise normal vascular function, there was reduced responsiveness to exogenous endothelin-1, possibly reflecting overactivity of this system and ET(A) receptor downregulation.

Is there a menopausal metabolic syndrome?

Estradiol-17 beta has beneficial effects on a range of metabolic risk factors for coronary heart disease and the decline in estrogen concentrations at the menopause would be expected to have adverse effects. Review of the literature on effects of the menopause and of estradiol-17 beta provides evidence for the following changes occurring at or after the menopause: increased total cholesterol and triglycerides; decreased high density lipoprotein (HDL) and HDL subfraction 2; increased low density lipoprotein, particularly in the small, dense subfraction; increased lipoprotein (a); increased insulin resistance; decreased insulin secretion; decreased insulin elimination; increased android fat distribution; impaired vascular function; increased factor VII and fibrinogen, and reduced sex-hormone binding globulin. Many of these changes will themselves have adverse effects on other metabolic risk factors. This complex of inter-correlated adverse changes in metabolic risk factors justifies identification of a distinct menopausal metabolic syndrome which originates in estrogen deficiency and which could contribute to the increased risk of coronary heart disease seen in postmenopausal women. Estrogen replacement can diminish the expression of this syndrome.

Insulin resistance in cardiac syndrome X and variant angina: influence of physical capacity and circulating lipids

Insulin resistance has been demonstrated in patients with angina pectoris irrespective of detectable atherosclerosis at coronary angiograms. We compared insulin sensitivity, lipid profiles, and exercise capacity in 20 patients with syndrome X, 15 patients with variant angina, and 20 healthy controls to investigate whether the presentation of the insulin resistance syndrome differs between the two patient groups with disparate vascular abnormalities. All patients had angiographically normal coronary arteries. Maximal oxygen uptake (VO2 max) was determined at bicycle exercise testing. Insulin sensitivity (SI) was assessed by the minimal model analysis of the intravenous glucose tolerance test. Patients with variant angina had significantly lower VO2 max than controls (mean +/- SE, 25.6 +/- 1.5 vs 30.6 +/- 1.4 ml x kg-1 x min-1, p < 0.05), whereas VO2 max in patients with syndrome X was intermediate (27.1 +/- 1.3 ml x kg-1 x min-1). Compared with controls, patients with syndrome X and variant angina had reduced insulin sensitivity (controls, 1.47 +/- 0.16 10(-4) x min-1/per pmol/L vs syndrome X, 0.86 +/- 0.11 10(-4) x min-1 per pmol/L and variant angina, 0.96 +/- 0.15 x 10(-4) x min-1 per pmol/L; analysis of variance, p < 0.05). Only patients with syndrome X exhibited fasting hyperinsulinemia. Patients with syndrome X also had higher fasting concentrations of triglycerides and total cholesterol and lower concentrations of high-density lipoprotein cholesterol than controls. When adjusting SI for variances of VO2 max, differences in SI vanished between controls and patients with variant angina but not between controls and patients with syndrome X. Thus syndrome X and variant angina are both associated with insulin resistance, but lipid abnormalities are only prominent in patients with syndrome X. A variable expression in terms of concomitant disturbances of lipid profiles and disparate influences of physical capacity suggests different underlying mechanisms.

Metabolic effects of the menopause and oestrogen replacement

There is little doubt that the metabolic disturbances seen following the loss of ovarian function are most important in the development of cardiovascular disease in women. The loss of hormones at the menopause appears to reduce both insulin secretion and elimination, but increasing insulin resistance thereafter brings about an increase in circulating insulin concentrations. Changes in lipids and lipoproteins are in an adverse direction, as are changes in body fat distribution, and changes in haemostatic factors would tend to favour coagulation rather than fibrinolysis. HRT with oestrogen appears to improve most of the metabolic abnormalities related to the menopause, but this is in part dependent on the type of oestrogen used and the route of administration. The addition of progestogen may influence the metabolic changes induced by oestrogens, and this will vary according to the type of the progestogen. Overall, the metabolic effects of any of the current HRT regimens would seem likely to be beneficial for CHD. Nevertheless, future HRT regimens should ideally be tailored to produce the most favourable changes in CHD metabolic risk factors, particularly in the case of the regimens which attempt to avoid cyclical bleeding.