Insulin resistance, cardiovascular risk factors and ultrasonically measured early arterial disease in normotensive Type 2 diabetic subjects

BACKGROUND

The objective of the study was to examine the relationship between serum fasting insulin, insulin sensitivity S(i), cardiovascular risk factors, and asymptomatic early atherosclerosis in normotensive Type 2 diabetic subjects.

METHODS

Specific insulin was measured using an enzyme-linked immunosorbent assay (ELISA) and insulin sensitivity was assessed with an insulin-modified frequently sampled intravenous glucose tolerance test (FSIVGTT). Early atherosclerotic change was assessed using carotid intima media thickness (IMT) and an arterial ultrasound score (AUS) measured by high-resolution B-mode ultrasound.

RESULTS

On bivariate analysis, there was a positive correlation between S(i) and high density lipoprotein (HDL) cholesterol (r(s)=0.27, p<0.05), and a negative correlation between S(i) and body mass index (BMI) (r(s)=-0.42, p<0.001), HbA(1c) (r(s)=-0.29, p<0.05) and serum triglyceride (r(s)=-0.30, p<0.05). There was a positive correlation between carotid IMT and age (r(s)=0.41, p<0.0005), and a positive association with male sex (p<0.0001) as well as with smoking (p<0.0001). However, we found no correlation between carotid IMT and fasting specific insulin (r(s)=-0.04) or S(i) (r(s)=-0.08). On multiple regression analyses, only age and serum triglycerides appeared to be significant independent variables with respect to carotid IMT whereas age, male sex and smoking emerged jointly significant with respect to AUS. There were no independent associations between carotid IMT or AUS with other variables including using either fasting specific insulin or S(i) as markers on insulin resistance separately.

CONCLUSION

Carotid IMT and AUS in Type 2 diabetes are closely associated with age, male sex and smoking. The relationships between serum insulin and insulin resistance with ultrasonically measured early arterial disease in Type 2 diabetes remain unclear.

Myocardial injury in major aortic surgery

PURPOSE

The purpose of this study was to examine the effects of major aortic surgery and its associated oxidative stress and injury on the myocardium.

METHODS

Plasma from 27 patients who underwent thoracoabdominal aortic aneurysm (TAAA) repair and 17 patients who underwent infrarenal aortic aneurysm (AAA) repair was collected at incision, aortic crossclamping, and reperfusion and 1, 8, and 24 hours thereafter. Samples were assayed for the myocardial specific protein troponin-T, total antioxidant status, and lipid hydroperoxides.

RESULTS

Ten patients experienced cardiac dysfunction in the first 24 hours after surgery (eight patients in the TAAA group and two patients in the AAA group). Immediately after reperfusion, total antioxidant status levels dropped in all patients with TAAA and with AAA; this was more marked in patients with TAAA, leading to a significant difference between the two groups at this time point and for up to 1 hour thereafter (P <.01). Patients with TAAA showed a sharp rise in lipid hydroperoxide levels immediately after reperfusion, and levels were significantly higher than in patients with AAA (P =.0007). In patients with AAA, no significant change in troponin-T was observed throughout the study period; whereas in patients with TAAA, levels were significantly elevated at 8 and 24 hours after reperfusion (P <.01). Troponin-T levels significantly correlated with total antioxidant status (r = -0.5) and lipid hydroperoxides (r = 0.78) but not with systolic blood pressure.

CONCLUSION

Supracoeliac aortic crossclamping is associated with a significant release of the myocardial injury marker troponin-T. This seems to correlate with the severity of oxidative rather than hemodynamic stresses. Ameliorating oxidative injury during TAAA surgery may therefore have a cardioprotective effect.

Plasma antioxidants: evidence for a protective role against reactive oxygen species following cardiac surgery

Total plasma antioxidant status (TPAS), lipid peroxide concentration (LPX) and cardiac troponin T (cTnT) were measured in 24 patients undergoing coronary artery bypass grafting (CABG) with cardiopulmonary bypass (CPB). Samples were obtained preoperatively and at 1.5 h, 6 h, 24 h and 72 h after CPB. The absolute TPAS values were significantly lower at 1.5 h, 6 h, 24 h and 72 h after CPB than were preoperative values (P < 0.05). The LPX concentration was significantly elevated at 1.5 h after CPB (P < 0.05). Cardiac troponin T concentrations were significantly elevated at all time points postoperatively (P < 0.05). Preoperative TPAS values were significantly correlated with the magnitude of fall in TPAS at 1.5 h (P < 0.05). The greater the fall in TPAS between 0 and 1.5 h, the less LPX was formed between 0 and 1.5 h. The LPX at 1.5 h displayed a significant correlation with cTnT release from myocardial myocytes (P < 0.05). These data provide evidence for the first time that the consumption of antioxidants during CABG surgery with CPB protects against the production of reactive oxygen species and subsequent myocyte necrosis. Furthermore, the availability of protective antioxidants is dependent upon preoperative TPAS.

Effects of four years' treatment with biosynthetic human growth hormone (GH) on glucose homeostasis, insulin secretion and lipid metabolism in GH-deficient adults

OBJECTIVE

To study the effects of long-term growth hormone (GH) treatment on lipid metabolism and carbohydrate tolerance in GH-deficient adults.

DESIGN

Open trial of GH treatment for 4 years. GH dose was (median, range) 0.025 (0.010-0.050) IU/kg daily.

PATIENTS

Thirteen GH-deficient hypopituitary adults (seven men, six women), aged (median, range) 47 (24-65) years were followed for 4 years.

MEASUREMENTS

Fasting lipids, lipoproteins, apolipoproteins, glucose and insulin concentrations were measured at yearly intervals during GH therapy. A 75-g oral glucose tolerance test (OGTT) was also performed yearly, during which circulating glucose and insulin were measured at 30-minute intervals for 3 h.

RESULTS

Fasting total and low density lipoprotein (LDL) cholesterol concentrations decreased on GH therapy, but no change was observed in fasting triglyceride or high density lipoprotein (HDL) concentrations. Compared to pretreatment values, total and LDL cholesterol levels were significantly lower at 1 year (mean +/- SEM) (6.39 +/- 0.46 vs. 5.71 +/- 0.38 mmol/l, P < 0.05; 4.46 +/- 0.36 vs. 3.24 +/- 0.20 mmol/l, P < 0.01, respectively) and the reductions were maintained for the 4 years. Apolipoproteins A-1 and B did not differ significantly from the pretreatment levels. Fasting plasma glucose increased significantly at the first year (4.9 +/- 0.1 vs. 5.3 +/- 0.1 mmol/l, P < 0.05) but it returned to the pretreatment value in the following years. Fasting plasma insulin increased significantly at 1 year (4.3 (1.0-13.6) vs. 11.9 (1.2-26.9) mU/l, P < 0.05) and showed a progressive downward trend but remained significantly raised throughout the subsequent years. The 3-h area under the glucose curve (AUC) during the OGTT tended to be increased at the first year (P = 0.07) and it returned to the pretreatment level in the following years. The AUC of plasma insulin was significantly raised at 1 year (P = 0.024) and it returned to the pretreatment level in the following years.

CONCLUSIONS

Four years of GH therapy in GH-deficient adults resulted in a sustained improvement in total and LDL cholesterol concentrations. Mild fasting hyperinsulinaemia persisted, although an initial deterioration in glucose tolerance, associated with post-glucose hyperinsulinaemia, was not sustained.

Investigation into voltage breakdown in glyceryl trinitrate patches

There are clinical reports of explosions occurring in glyceryl trinitrate (GTN) patches left on patients who are defibrillated and it is widely recommended that such patches are removed before attempting defibrillation. We devised an experimental set up that simulated the electrical conditions under which human defibrillation is conducted, thus making possible accurate measurements of defibrillator wave form. No problems occurred with GTN patches that incorporated a plastic backing. However, with GTN patches that incorporated a metal mesh backing, an explosive effect was consistently observed when current from the defibrillator electrode flowed through the metallic backing. The GTN paste in the patches was unaffected and therefore, we conclude that the apparent explosions reported are solely due to voltage breakdown as the paddle voltage is close to 3 kV resulting from the 360 J of energy. Our results emphasise the need for good technique during defibrillation to avoid current flow through such patches. In addition, our results have implications for the design of patches used for the transcutaneous delivery of drugs.

Cardiovascular outcomes in type 2 diabetes. A double-blind placebo-controlled study of bezafibrate: the St. Mary's, Ealing, Northwick Park Diabetes Cardiovascular Disease Prevention (SENDCAP) Study

OBJECTIVE

To determine whether serum lipid intervention, in addition to conventional diabetes treatment, could alter cardiovascular outcomes in type 2 diabetes.

RESEARCH DESIGN AND METHODS

There were 164 type 2 diabetic subjects (117 men, 47 women) without a history of clinical cardiovascular disease randomized to receive either bezafibrate or placebo daily on a double-blind basis in addition to routine diabetes treatment and followed prospectively for a minimum of 3 years. Serial biochemical and noninvasive vascular assessments, carotid and femoral artery B-mode ultrasound measurements, and those pertaining to coronary heart disease (CHD)--clinical history, the World Health Organization (WHO) cardiovascular questionnaire, and resting and exercise electrocardiogram (ECG)--were recorded.

RESULTS

Bezafibrate treatment was associated with significantly greater reductions over 3 years in median serum triglyceride (-32 vs. 4%, P = 0.001), total cholesterol (-7 vs. -0.3%, P = 0.004), and total-to-HDL cholesterol ratio (-12 vs. -0.0%, P = 0.001), and an increase in HDL cholesterol (6 vs. -2%, P = 0.02) as compared with placebo. There was a trend toward a greater reduction of fibrinogen (-18 vs. -6%, P = 0.08) at 3 years. No significant differences between the two groups were found in the progress of ultrasonically measured arterial disease. In those treated with bezafibrate, there was a significant reduction (P = 0.01, log-rank test) in the combined incidence of Minnesota-coded probable ischemic change on the resting ECG and of documented myocardial infarction.

CONCLUSIONS

Improving dyslipidemia in type 2 diabetic subjects had no effect on the progress of ultrasonically measured arterial disease, although the lower rate of "definite CHD events" in the treated group suggests that this might result in a reduction in the incidence of coronary heart disease.

ACP Broad Sheet no 151: September 1997. Investigation of dyslipidaemias

Images

Lipid peroxidation, antioxidant status and troponin-T following cardiopulmonary bypass. A comparison between intermittent crossclamp with fibrillation and crystalloid cardioplegia

OBJECTIVE

Intermittent crossclamp with fibrillation affords equivalent myocardial protection to cold crystalloid cardioplegia in patients undergoing elective coronary artery surgery. This study is a direct comparison between the two techniques with regards to free radical activity.

METHODS

The study design was part of a prospective randomised trial. We studied 24 consecutive patients with ejection fraction of 30% or greater undergoing elective coronary artery surgery. Patients were randomised into two groups. In group 1 (n = 13) the myocardium was protected by intermittent aortic cross clamping with fibrillation and group 2 (n = 11) by antegrade cold crystalloid cardioplegia. The determinants of free radical activity were serial peripheral venous samples for lipid peroxidation and plasma antioxidant status (before and at 1, 6, 24 and 72 h after the end of cardiopulmonary bypass). The determinant of the efficacy of myocardial protection was serial peripheral venous samples of cardiac troponin-T taken at the same time intervals.

RESULTS

The groups were similar with respect to age, sex distribution, preoperative ventricular function, left main stem disease, number of grafts and bypass times. Lipid peroxidation measurements at the 1 h time point were higher than preoperative values (7.24 +/- 1.19 vs. 4.48 +/- 0.69 and 9.36 +/- 1.46 vs. 4.98 +/- 1.02 (mean +/- S.E) in groups 1 and 2, respectively (units in mmol/l) thereafter values decreased to near preoperative values by 72 h. There was no significant difference between the groups (P = 0.42). Total plasma antioxidant status values at the 1 h time point were lower than the preoperative values for all patients (1.33 +/- 0.07 vs. 1.63 +/- 0.06 and 1.42 +/- 0.07 vs. 1.63 +/- 0.05 (mean +/- standard error) in groups 1 and 2, respectively, (units in mmol/l) and thereafter at the subsequent time points increased but never attained their preoperative value. There was no statistically significant difference between the two groups (P = 0.59). Troponin-T measurements showed no significant difference between the two groups at all time points (P = 0.2217).

CONCLUSIONS

This study shows that lipid peroxidation is initially elevated and the defence mechanisms against oxygen free radicals-antioxidant status'-are depressed following cardiopulmonary bypass. The degree of oxygen free radical activity produced during ischaemia and reperfusion was similar in both types of myocardial protection employed in this study.

Fasting and postprandial lipid abnormalities in hypopituitary women receiving conventional replacement therapy

Hypopituitary patients, particularly women, have excess mortality, mostly due to vascular disease. We have studied circulating lipid and lipoprotein concentrations, fasting and over 24 h, in hypopituitary women and men and in matched controls. Firstly, 67 hypopituitary patients (36 women) and 87 normal controls (54 women) were studied after an overnight fast. Secondly, 12 patients (6 women) and 14 matched controls (7 women) were studied over 24 h of normal meals and activity. The patients were all GH deficient and were replaced with cortisol, T4, and sex hormones where appropriate, but not with GH. In the first study, circulating triglycerides, total cholesterol, high density lipoprotein (HDL) cholesterol, and low density lipoprotein (LDL) cholesterol were measured after an overnight fast. In the second study, fasting levels of apolipoprotein B, apolipoprotein A1, and lipoprotein(a) were also measured, and then circulating triglyceride and total cholesterol concentrations were measured over 24 h. Fasting concentrations of triglyceride (mean +/- SEM, 1.73 +/- 0.22 vs. 1.11 +/- 0.09 mmol/L; P = 0.0025), total cholesterol (6.45 +/- 0.25 vs. 5.59 +/- 0.21 mmol/L; P = 0.002), LDL cholesterol (4.58 +/- 0.24 vs. 3.80 +/- 0.19 mmol/L; P = 0.007), and apolipoprotein B (135 +/- 10 vs. 111 +/- 9 mg/dL; P = 0.048) were elevated in hypopituitary compared to control women. The lipid alterations were observed in older and younger women and occurred independently of sex hormone or glucocorticoid replacement. Fasting values were not significantly different in hypopituitary and control men. Patients and controls (women and men) had similar fasting HDL cholesterol, apolipoprotein A1, and lipoprotein(a) concentrations. Although the differences that existed in fasting lipid values were most marked in women, the men were also abnormal in this respect, in that a higher proportion of hypopituitary than control men had total and LDL cholesterol above recommended values (> or = 6.2 and > or = 4.1 mmol/L, respectively). In the postprandial period (0730-2030 h), the areas under the curve (AUC) for circulating triglyceride and total cholesterol were significantly higher in hypopituitary than control women (P = 0.0089 and P = 0.0016, respectively). The AUC for triglyceride and total cholesterol over 24 h were also significantly increased (P = 0.009 and P = 0.0004, respectively). No significant differences were observed for postprandial and 24-h AUC for triglyceride and total cholesterol concentrations in men. We conclude that hypopituitarism with conventional replacement therapy is associated with unfavorable fasting and postprandial lipid and lipoprotein concentrations, particularly in women. The changes may contribute to the observed increased vascular morbidity and mortality.

Elevated leptin concentrations in growth hormone-deficient hypopituitary adults

BACKGROUND

Hypopituitarism with growth hormone (GH) deficiency is associated with obesity characterized by central (abdominal) distribution of fat. Recent work has demonstrated that leptin, a product of obese gene, is raised in obesity.

OBJECTIVE

To study circulating leptin levels in GH-deficient hypopituitary adults and to investigate its anthropometric, gender and metabolic relations.

METHODS

After an overnight fast of 10-12 hours, anthropometric parameters and body composition were measured and blood was collected for the measurement of circulating leptin, glucose, intact insulin, proinsulin, IGF-I, total cholesterol, triglycerides, high density lipoprotein (HDL) cholesterol and low density lipoprotein (LDL) cholesterol.

SUBJECTS

Fifteen (7 men) GH-deficient hypopituitary adults (maximum stimulated serum GH to provocative testing < 6 mU/l) and 21 (10 men) normal control subjects matched for age, gender and body mass index (BMI).

RESULTS

Fasting serum leptin was significantly higher in hypopituitary patients than controls (12.0 +/- 1.8 vs 8.0 +/- 1.5 micrograms/l, P = 0.04). The increase was more marked in obese (BMI > 26.0 kg/m2) patients compared with obese controls (15.3 +/- 2.0 vs 8.8 +/- 2.3 micrograms/l, P = 0.03) than in lean patients and controls. Obese control women and men had higher leptin levels than non-obese (women, 16.6 +/- 2.7 vs 8.6 +/- 0.6 micrograms/l, P = 0.03; men, 4.9 +/- 0.5 vs 2.9 +/- 0.6 micrograms/l, P = 0.035). Similar changes were observed for obese versus non-obese patients, although the changes did not reach statistical significance. Women in each group had significantly higher leptin concentrations than men (patients: 15.5 +/- 2.3 vs 7.3 +/- 1.4 micrograms/l, P = 0.009; controls: 12.6 +/- 2.4 vs 4.3 +/- 0.5 micrograms/l, P = 0.0001). These gender differences remained significant even when expressed in relation to BMI (patients: 0.57 +/- 0.09 vs 0.26 +/- 0.05 ng.m2/ml.kg, P = 0.009; controls: 0.43 +/- 0.05 vs 0.16 +/- 0.02 ng.m2/ml.kg, P = 0.0001). Serum leptin was positively associated with body mass index (P = 0.003), percentage body fat mass (P = 0.0001) and inversely related with age (P = 0.043). It demonstrated no relation with body weight, waist circumference, waist to hip ratio, fasting IGF-I, glucose, insulin, proinsulin, total cholesterol, triglycerides, HDL and LDL cholesterol in patients nor controls; 85% of variance in leptin was explained by a model including body mass index, gender, age and hypopituitarism.

CONCLUSIONS

Leptin concentrations are raised in GH-deficient hypopituitary adults to a greater extent than would be expected from the degree of obesity.

Dyslipidaemia is associated with insulin resistance in women with polycystic ovaries

OBJECTIVE

Polycystic ovary syndrome (PCOS) is characterized by hyperinsulinaemia and insulin resistance. Previous reports of lipid abnormalities in the syndrome have produced conflicting results which may, in part, be related to the lack of appropriate controls for the obese women with PCOS. Only one study has related lipid levels to insulin sensitivity. The objective of this study was to assess lipids and lipoproteins in women with PCOS, to compare the results with weight matched controls, and to relate the findings to indices of insulin secretion and action, and to menstrual history.

DESIGN

A cross-sectional study of insulin sensitivity and lipids in a cohort of PCO subjects compared to weight and ethnic group matched controls.

PATIENTS AND METHODS

We have therefore investigated glucose tolerance, plasma lipids and lipoproteins in 19 lean (LP) and 55 obese (OP) patients with PCO and compared the results with those in 22 lean (LC) and 15 obese (OC) control women. Insulin sensitivity was measured in the same subjects with a short insulin (0.05 U/kg i.v. insulin) tolerance test (LP, n = 18; OP, n = 20; LC, n = 19; OC, n = 11).

RESULTS

Results are expressed as mean +/- SEM or median (interquartile range). Fasting plasma glucose levels were similar in the four groups but the plasma glucose area was higher after oral glucose (75 g) in both the lean and obese PCOS groups than in their controls (LC 32.4 +/- 0.7 vs LP 35.2 +/- 1.2, P < 0.01; OC 34.7 +/- 1.8 vs OP 37.8 +/- 1.5 mmol/l/3 h, P < 0.01). Insulin sensitivity was significantly reduced in obese PCOS women (LC 196 +/- 9 vs LP 179 +/- 9, NS; OC 168 +/- 12 vs OP 133 +/- 9 mmol/l/min, P < 0.01). Total serum cholesterol levels were similar in the four groups but HDL2-cholesterol was reduced in both obese and lean PCOS (LC 0.42 (0.38-0.62), LP 0.31 (0.26-0.44), P < 0.05; OC 0.34 (0.21-0.47), OP 0.21 (0.12-0.32) mmol/l, P < 0.01). Total HDL-cholesterol was decreased significantly only in the obese PCOS group. Body mass index correlated significantly and negatively with total HDL-cholesterol and with HDL2-cholesterol levels both within the PCOS group and the control women. Using multiple regression insulin insensitivity contributes significantly beyond BMI to the low HDL-cholesterol in women with polycystic ovaries.

CONCLUSION

Polycystic ovary syndrome is associated with biochemical risk factors for premature vascular disease, which cannot be explained by obesity alone.

Relative fasting hypoinsulinaemia and ultrasonically measured early arterial disease in type 2 diabetes. The SENDCAP Study Group, St. Mary's, Ealing, Northwick Park Diabetes Cardiovascular Disease Prevention Study

Macrovasular disease is the most important cause of morbidity and mortality in Type 2 (non-insulin-dependent) diabetes. Dyslipidaemia and hyperinsulinaemia have been proposed as aetiological factors. This paper describes the interrelationships between fasting serum insulin, serum lipids, and the extent of ultrasonically measured early arterial disease in Type 2 diabetic subjects screened for entry into a prospective study set up to ascertain whether improving serum lipids can alter the progress of arterial disease in Type 2 diabetes. Measurements were made of the initima media thickness (IMT) in the carotid artery, and an arterial ultrasound score (AUS) based on appearances of both carotid and femoral arteries was calculated for 192 established Type 2 diabetic subjects, males and females, mean age 51 (range 35-66) years, median duration of diabetes 3.5 years, with no known cardiovascular disease. Multiple regression analysis showed that carotid IMT increased with age and was inversely related to serum insulin (variance accounted for, R2, = 8.8%, p = 0.0002). AUS increased with age and was related inversely to serum insulin, or to C-peptide when this was substituted in the model. In addition to age and serum insulin, AUS was positively associated with non-HDL cholesterol and negatively with HDL 3 cholesterol (R2 = 26%, p = 0.0001). Early thickening and damage to the arterial wall in Type 2 diabetes may be related to relative fasting hypoinsulinaemia.