Epidemiologic and clinical aspects of insulin resistance and hyperinsulinemia

The effectiveness comparisons of eugenosedin-A, glibenclamide and pioglitazone on diabetes mellitus induced by STZ/NA and high-fat diet in SHR

OBJECTIVES

Eugenosedin-A (Eu-A), an adrenergic and serotonergic antagonist, is known to have anti-metabolic syndrome effects. In this study, we evaluated its protective effects against diabetes mellitus (DM) in spontaneous hypertensive rats (SHR) and compared it with two anti-diabetes medications, glibenclamide (Gli) and pioglitazone (Pio).

METHODS

We divided 10-week-old SHRs into five groups: a control group fed a normal diet; an untreated DM group induced by injecting the SHRs with STZ/NA and feeding them a high-fat diet (HFD); and three treated groups (after giving STZ/NA and HFD) gavage given with Eu-A, Gli or Pio (5 mg/kg per day) for 4 weeks.

KEY FINDINGS

The untreated DM group weighed less and had hyperglycaemia, hypoinsulinemia and hyperlipidemia. They were also found to have aberrant glucose-dependent insulin pathways, glucose metabolism and lipid synthesis proteins, while the controls did not. Eu-A, Gli and Pio ameliorated the above biochemical parameters in the treatment groups. Eu-A and Pio, but not Gli, improved hypertension and tachycardia.

CONCLUSIONS

Taken together, Eu-A ameliorated DM, hypertension and tachycardia by improving glucose, lipid homeostasis and anti-adrenergic, serotonergic activities. We concluded that Eu-A could be used in the development of an effective agent for controlling DM and its complications.

The effect of ginger powder supplementation on insulin resistance and glycemic indices in patients with type 2 diabetes: a randomized, double-blind, placebo-controlled trial

OBJECTIVE

To identify the effect of some herbal products on insulin resistance. Regarding the scientific evidences existing about ginger, this research was therefore carried out to identify the effect of ginger supplementation on insulin resistance and glycemic indices in diabetes mellitus.

METHODS

This is a randomized, double-blind, placebo-controlled trial in which 88 participants affected by diabetes were randomly assigned into ginger (GG) and placebo (PG) groups. The GG received 3 one-gram capsules containing ginger powder whereas the PG received 3 one-gram microcrystalline-containing capsules daily for 8 weeks. HbA1c, fructosamine, fasting blood sugar (FBS), fasting insulin, homeostasis model assessment insulin resistance index (HOMA-IR), β-cell function (β%), insulin sensitivity (S%) and the quantitative insulin sensitivity check index (QUICKI) were assessed before and after the intervention.

RESULTS

FBS mean showed a decrease of 10.5% (p=0.003) in the GG whereas the mean had an increase of 21% in the PG (p=0.01). Variation in HbA1c mean was in line with that of FBS. Statistical difference was found in the two groups before and after the intervention in terms of median of fasting insulin level, S% and HOMA-IR (P<0.005). Moreover QUICKI mean increased significantly in the two groups, the mean difference, however, was significantly higher in the GG.

CONCLUSIONS

The study demonstrated that daily consumption of 3 one-gram capsules of ginger powder for 8 weeks is useful for patients with type 2 diabetes due to FBS and HbA1c reduction and improvement of insulin resistance indices such as QUICKI index.

Relationship between Plasma Adiponectin Levels and Metabolic Risk Profiles in Taiwanese Children

OBJECTIVE

Adiponectin, a novel adipokine with antiinflammatory and insulin-sensitizing properties, has an important role in glucose metabolism and is negatively correlated with body fat amount in adults. The purpose of this study was to evaluate the association of plasma adiponectin level with metabolic risk profiles and insulin resistance status among Taiwanese children.

RESEARCH METHODS AND PROCEDURES

We enrolled 1,248 children (608 boys and 640 girls) to ascertain their demographic, anthropometric, and cardiovascular risk factors distribution in Taipei. We measured plasma insulin, adiponectin, and leptin levels by radioimmunoassay (Linco Research Inc, St. Charles, MO). We calculated an insulin resistance index (IRI) using the Homeostasis Model Assessment model and also calculated an insulin resistance syndrome (IRS) summary score for each individual by adding the quartile ranks from the distribution of systolic blood pressure, serum triglyceride, high-density lipoprotein-cholesterol (HDL-C) (inverse), and insulin levels.

RESULTS

In general, the boys had larger BMI, higher systolic blood pressure, serum total cholesterol, and triglyceride, and lower plasma leptin and adiponectin levels than girls. Plasma adiponectin levels were correlated negatively with BMI, leptin, insulin, IRI, and IRS summary score but positively correlated with HDL-C in both boys and girls. In multivariate regression analyses, adiponectin was negatively associated with insulin (girls only), IRI (girls only), and IRS score, and positively associated with HDL-C in both genders even after adjusting for age, BMI, plasma leptin level, and other potential confounders.

DISCUSSION

These data suggest that plasma adiponectin levels were negatively associated with metabolic risk profiles that may have played a protective role in the development of insulin resistance among Taiwanese school children.

Prevalence and risk factors for type 2 diabetes mellitus in the Chinese adult population: the InterASIA Study

AIMS

To estimate the prevalence of impaired fasting glucose and type 2 diabetes mellitus (T2DM) and identify the potential risk factors of T2DM in Chinese adults.

METHODS

A nationally representative sample of 15,236 Chinese adults aged 35-74 years was selected by 4-stage random stratified sampling in 2000-2001 for present study.

RESULTS

The prevalence of T2DM in Chinese adults aged 35-74 years was 5.49% (it was 2.51% in China, 1994). The odds ratios (ORs) (95% confidence interval [CI]) for developing T2DM were 2.14 (1.08-4.22) for family history of diabetes, 3.90 (1.39-10.94) for waist-to-hip ratio (WHR) (0.83-0.91 vs. <0.83), 4.82 (1.43-16.28) for WHR (>or=0.92 vs. <0.83), and 3.14 (1.42-6.92) for triglycerides (TG) level (>or=200mg/dl vs. <150 mg/dl) among men but 2.74 (1.14-6.62) for family history of diabetes, 1.92 (1.04-3.56) for hypertension, 3.37 (1.67-6.77) for TG level (150-199 mg/dl vs. <150 mg/dl), and 3.79 (1.62-8.91) for TG level (>or=200mg/dl vs. <150mg/dl) among women.

CONCLUSIONS

The prevalence of T2DM in Chinese adults has increased as compared with previous data for China. An effective intervention program regarding T2DM should focus on lifestyle modification and weight reduction.

Beneficial effect of low ethanol intake on the cardiovascular system: possible biochemical mechanisms

Low ethanol intake is known to have a beneficial effect on cardiovascular disease. In cardiovascular disease, insulin resistance leads to altered glucose and lipid metabolism resulting in an increased production of aldehydes, including methylglyoxal. Aldehydes react non-enzymatically with sulfhydryl and amino groups of proteins forming advanced glycation end products (AGEs), altering protein structure and function. These alterations cause endothelial dysfunction with increased cytosolic free calcium, peripheral vascular resistance, and blood pressure. AGEs produce atherogenic effects including oxidative stress, platelet adhesion, inflammation, smooth muscle cell proliferation and modification of lipoproteins. Low ethanol intake attenuates hypertension and atherosclerosis but the mechanism of this effect is not clear. Ethanol at low concentrations is metabolized by low K_m alcohol dehydrogenase and aldehyde dehydrogenase, both reactions resulting in the production of reduced nicotinamide adenine dinucleotide (NADH). This creates a reductive environment, decreasing oxidative stress and secondary production of aldehydes through lipid peroxidation. NADH may also increase the tissue levels of the antioxidants cysteine and glutathione, which bind aldehydes and stimulate methylglyoxal catabolism. Low ethanol improves insulin resistance, increases high-density lipoprotein and stimulates activity of the antioxidant enzyme, paraoxonase. In conclusion, we suggest that chronic low ethanol intake confers its beneficial effect mainly through its ability to increase antioxidant capacity and lower AGEs.

The effects of antihypertensive agents on endometrial thickness in asymptomatic, hypertensive, postmenopausal women

OBJECTIVE

The aim of this study was to investigate, by using transvaginal ultrasonography, the possible effects on endometrial thickness of antihypertensive agents in asymptomatic postmenopausal women.

DESIGN

A prospective study in an outpatient menopause clinic of a university hospital. We included 288 postmenopausal women in this study, and we compared three groups of postmenopausal women as follows: (1) normotensive postmenopausal women, (2) hypertensive women treated with an antihypertensive drug (beta-blocker, non-beta-blocker, or beta-blocker plus non-beta-blocker), and (3) untreated hypertensive women who had had hypertension for at least 1 year. Hypertensive women treated with a drug had been receiving treatment for 1 year. All women were interviewed and examined. Measurements of endometrial thickness were carried out by vaginal ultrasonography.

RESULTS

Sixty-two women (22%) were normotensive, and 226 (78%) of 288 women were hypertensive. Of the 226 women, 122 (54%) were receiving an antihypertensive drug. The mean (+/- SD) endometrial thicknesses in groups A, B, and C were 4.5 (+/- 1.3), 5.4 (+/- 1.5), and 6.4 (+/- 1.7) mm, respectively. Significant difference was obtained among the groups (P = 0.004).

CONCLUSIONS

Our data indicate that the mean endometrial thickness is significantly greater in asymptomatic, hypertensive women receiving antihypertensive drugs than among untreated hypertensive and normotensive women.

Plasma leptin, fatty acids, and tumor necrosis factor-receptor and insulin resistance in children

OBJECTIVE

To evaluate the effect of plasma leptin, nonsterified fatty acids (NEFAs), and tumor necrosis factor-receptor 1 (TNFR1) on plasma insulin and insulin-resistance status in children.

RESEARCH METHODS AND PROCEDURES

One thousand thirty-two children (521 boys and 511 girls) were included in this study. We measured plasma insulin and leptin levels by radioimmunoassay, plasma NEFA levels by enzymatic acyl-coenzyme A synthase-acyl-coenzyme A oxidase spectrophotometric methods, and TNFR1 levels by enzyme-linked immunosorbent assay. We calculated insulin resistance index (IRI) using homeostasis model assessment and calculated insulin-resistance syndrome summary score (IRS) by adding the quartile ranks from the distribution of systolic blood pressure (BP), serum triglyceride, high-density lipoprotein-cholesterol (inverse), and insulin levels.

RESULTS

Overweight children had higher BP, plasma leptin, and insulin levels and higher IRI and IRS than normal-weight children. Plasma leptin and TNFR1 were positively correlated with insulin levels, IRI, and IRS. The correlation coefficients of leptin and TNFR1 in IRI were 0.53 and 0.12, respectively, for boys and 0.25 and 0.18, respectively, for girls. In multivariate regression analyses, TNFR1 was positively associated with insulin level and IRI in girls; NEFA was positively associated only with IRS. Plasma leptin levels were significantly positively associated with insulin levels, IRI, and IRS, even after adjusting for BMI and other potential confounders.

DISCUSSION

Overweight children had higher BP, plasma insulin, and leptin levels and adverse insulin-resistance status than normal-weight children. Plasma leptin levels, rather than NEFA and TNFR1, may play a significant role in the development of hyperinsulinemia and insulin resistance in children.

Alcohol reduces insulin-hypertension relationship in a general population: the Hisayama study

Insulin resistance may be a factor in the etiology of hypertension, and habitual alcohol intake may modify this relationship. We prospectively examined this hypothesis in 1,133 nonhypertensive, nondiabetic Japanese subjects, aged 40-79 years. Alcohol drinkers were more frequent among men than women at baseline (57.7 vs. 8.2%). The age-adjusted incidence of hypertension significantly increased with the elevating baseline insulin levels in women (P =.003 for trend), but not in men. The age- and sex-adjusted insulin levels and insulin resistance index decreased with elevating alcohol intake, while fasting glucose levels remained unchanged, suggesting that alcohol improves insulin sensitivity. Among nondrinkers, the age-adjusted incidence of hypertension significantly increased with elevating insulin tertiles in both sexes (P =.048 and.002 for trend in men and women, respectively), but not among drinkers. Our findings suggest a close association between insulin resistance and the incidence of hypertension in Japanese. However, alcohol modified and reduced this relationship.

Links between body mass index, total body fat, cholesterol, high-density lipoprotein, and insulin sensitivity in patients with obesity related to depression, anger, and anxiety

OBJECTIVE

Define links between psychosocial parameters and metabolic variables in obese females before and after a low-calorie diet.

METHOD

Nine female obese patients (age 36.1 +/- 7.1 years, body mass index [BMI] > 30 kg/m2) were investigated before and after a 6-week low-calorie diet accompanied by behavior therapy. Blood lipids, insulin sensitivity (Bergman protocol), fat distribution (by dual-energy X-ray absorptiometry [DEXA]), as well as psychological parameters such as depression, anger, anxiety, symptom load, and well-being, were assessed before and after the dieting period.

RESULTS

The females lost 9.6 +/- 2.8 kg (p < .0001) of body weight, their BMI was reduced by 3.5 +/- 0.3 kg/m2 (p < .0001), and insulin sensitivity increased from 3.0 +/- 1.8 to 4.3 +/- 1.5 mg/kg (p = .05). Their abdominal fat content decreased from 22.3 +/- 5.5 to 18.9 +/- 4.5 kg (p < .0001). In parallel, psychological parameters such as irritability (p < .05) and cognitive control (p < .0001) increased, whereas feelings of hunger (p < .05), externality (p < .05), interpersonal sensitivity (p < .01), paranoid ideation (p < .05), psychoticism (p < .01), and global severity index (p < .01) decreased. Prospectively, differences in body fat (percent) were correlated to nervousness (p < .05). Waist-to-hip ratio (WHR) differences were significantly correlated to sociability (p < .05) and inversely to emotional instability (p < .05), whereas emotional instability was inversely correlated to differences in insulin sensitivity (p < .01).

DISCUSSION

Weight reduction may lead to better somatic risk factor control. Women with more nervousness and better sociability at the beginning of a diet period may lose more weight than others.

Insulin improves fasting and postprandial lipemia in type 2 diabetes

BACKGROUND: The purpose of the investigation presented here was to study the effects of insulin therapy in type 2 diabetes mellitus (type 2 DM) not only on glycemic control but also on other components of the metabolic syndrome, including lipid metabolism, blood pressure, and body weight. METHODS: Twelve patients with type 2 DM were studied before and after replacement of sulphonylurea treatment with insulin for 4 months. RESULTS: Insulin therapy resulted in a significant decrease in fasting glucose levels by 26%; glycated hemoglobin decreased by 17% and fructosamine values by 19%. With insulin treatment, fasting plasma triglyceride levels decreased by 28% and total HDL cholesterol and HDL(3) cholesterol increased by 17 and 11%, respectively. Low-density lipoprotein (LDL) cholesterol showed no significant change. The magnitude of postprandial lipemia after ingestion of a standard fatty meal decreased by 38%. Insulin treatment was also accompanied by a 21% increase in lipoprotein lipase (LPL) activity in postheparin plasma and by a 20% increase in cholesteryl ester transfer protein (CETP) activity. Hepatic lipase activity was not changed significantly with insulin. Mean BMI decreased from 28.5+/-4.2 to 28.0+/-3.1 kg/m(2) (P=0.02), which is in keeping with the finding that peripheral insulin levels did not increase and which can be explained by the fact that the insulin regimen was combined with dietary counseling. Accordingly, blood pressure showed no significant change. CONCLUSION: Our study demonstrates that judicious replacement of sulfonylurea treatment with insulin therapy, together with dietary counseling, can result in a simultaneous improvement in the major stigmata of the metabolic syndrome, i.e. a significant improvement in glycemic control and lipid metabolism without unfavorable effects on body weight and blood pressure.

Salt intake, hypertension and diabetes mellitus

Diabetes mellitus affects approximately 135 million people in the world. Diabetes and hypertension are both relatively common diseases in westernised countries. Both entities increase with age. Essential hypertension accounts for the majority of hypertension in people with type 2 diabetes, who constitute more than 90% of those with a dual diagnosis of diabetes and hypertension. The benefit conferred per mm Hg blood pressure reduction appears to be greater in persons with type 2 diabetes than in those with hypertension and non-coexistent diabetes mellitus. Similar to a subset of patients with essential hypertension, type 2 diabetic patients manifest dietary NaCl-induced exacerbation of hypertension. Recent guidelines have emphasised that the target blood pressure levels for patients with diabetes should be lower than in other hypertensive groups. An increased total body sodium and enhanced vascular reactivity are found in people with diabetes and most type 2 diabetic patients are salt sensitive. Type 2 diabetes with hypertension is associated with reduced renal plasma flow when dietary salt intake is high. Experimental, observational and interventional evidence support the benefits of sodium restriction in hypertensives. However, the full effects of sodium restriction are usually not obvious for at least 5 weeks. Other favourable effects of moderate reduction in sodium intake are a regress left ventricular hypertrophy, decrease in diuretic-induced potassium wastage, reduction in proteinuria, protection against stroke and from osteoporosis and renal stones, and enhancement of the antihypertensive effect of the antihypertensive agents.

The long term health consequences of polycystic ovary syndrome

Women with polycystic ovary syndrome have both insulin resistance and beta cell dysfunction. Consequently, they are at increased risk of developing diabetes and cardiovascular disease. Women with polycystic ovary syndrome present to clinicians at a young age and as such offer a unique opportunity to identify insulin resistant patients at an early stage. This enables the modification of risk factors and diagnosis of diabetes before the onset of macro- and micro-vascular symptoms. Increased emphasis should thus be placed on long term risk management and diabetic screening with advice on smoking, exercise and, if appropriate, weight loss. Where possible drugs that exacerbate insulin resistance should be avoided and consideration should be given to the use of insulin sensitising agents, particularly in the obese.

Effects of a low-energy diet and an insulin-sensitizing agent on ambulatory blood pressure in overweight hypertensive patients

OBJECTIVE

To clarify the role of insulin resistance and hyperinsulinaemia in the pathogenesis of obesity-related hypertension.

DESIGN

An open study comparing the effects of weight reduction by low-energy diet and treatment with troglitazone, an insulin-sensitizing agent.

SETTING

A tertiary teaching hospital.

PATIENTS

Thirty overweight hypertensive patients (15 men and 15 women, mean age 61 years, mean body mass index 29.1 kg/m2).

INTERVENTIONS

Fifteen patients were assigned to a weight-reduction programme by low-energy diet (3360 kJ/day) for 3 weeks; the remaining 15 patients were treated with troglitazone (400 mg/day) for 8 weeks.

MAIN OUTCOME MEASURES

Casual and ambulatory blood pressures, glucose and lipid metabolism, and insulin sensitivity.

RESULTS

The baseline values of body mass index, fasting and post-glucose plasma insulin, and casual and ambulatory blood pressures were comparable between the two groups. Weight reduction (4.1 +/- 0.3 kg, mean +/- SEM) was associated with significant decreases in plasma insulin, blood glucose, homeostasis model assessment (HOMA) insulin resistance index, serum triglyceride, casual blood pressure (7.7 +/- 2.3/ 3.9 +/- 1.4 mmHg) and 24 h blood pressure (8.3 +/- 1.9/ 4.3 +/- 1.1 mmHg). Treatment with troglitazone caused comparable decreases in the metabolic parameters and HOMA index, but did not change casual or 24 h blood pressure (0.8 +/- 3.4/0.8 +/- 2.1 and 1.5 +/- 2.4/ 1.0 +/- 1.9 mmHg, respectively).

CONCLUSIONS

Insulin resistance/hyperinsulinaemia may not have an important role in the pathogenesis of obesity-related hypertension. The antihypertensive effect of weight reduction seems to be mediated mainly by other mechanisms.

Hypomagnesemia is linked to low serum HDL-cholesterol irrespective of serum glucose values

Hypomagnesemia is common in diabetic subjects, and is especially common in poorly controlled diabetes, suggesting that diabetes low serum magnesium status is osmotic diuresis-dependent. To assess the relationship between serum magnesium and HDL-cholesterol concentration adjusted by serum glucose values. We assessed the serum magnesium levels of 50 controlled (HbA(1c)</=7.5% and FPG<126 mg/dl), 110 non-controlled (HbA(1c)>7.5% and FPG>/=126 mg/dl) type II diabetic patients, 40 subjects with impaired fasting glucose (IFG) (FPG>/=110 mg/dl and <126 mg/dl) and 190 healthy volunteers (FPG<110 mg/dl). Healthy volunteers were required to have normal blood pressure and normal laboratory tests. Subjects in the groups included were matched by age and body mass index (BMI). The average of diabetes duration was of 11.4+/-6.6, and 10.9+/-6.2 years, P=NS, for the controlled and non-controlled diabetic patients, respectively. Thirty (60.0%) controlled diabetic subjects, 58 (52. 7%) non-controlled diabetic patients, 21 (52.5%) subjects with IFG, and 39 (20.5%) healthy volunteers had serum magnesium levels </=1.7 mg/l. Serum HDL-cholesterol value showed significant graded increase with serum magnesium levels irrespective of glucose values. Results of this study suggest that hypomagnesemia by an etiopathogenic pathway glycemia independent seems to be involved to decrease HDL-cholesterol.

Association of insulin resistance with salt sensitivity and nocturnal fall of blood pressure

Insulin resistance was demonstrated in hypertensive patients and in salt-sensitive subjects. It was recently reported that the salt-sensitive state was related to a reduced fall in blood pressure during the night in essential hypertension. In the present study, the relationship among insulin sensitivity, blood pressure response to salt intake, and nocturnal fall in blood pressure was examined in 20 subjects with nondiabetic and nonobese essential hypertension during a low-salt and a high-salt diet. The subjects were maintained on a low-salt diet (50 mmol/d) and a high-salt diet (255 mmol/d) for 1 week each, in random order. On the sixth day of each diet, blood pressure was measured every hour for 24 hours with an automatic device. Insulin sensitivity was measured according to the steady-state plasma glucose (SSPG) method on the seventh day of each diet. Salt-induced increase in blood pressure, which we defined as the change in 24-hour mean arterial pressure between the low and the high dietary salt intakes, was significantly correlated with SSPG (r=0.60, P<0.01) during the high-salt period. There was a significant negative correlation (r=-0.61, P<0.01) between SSPG and a nocturnal fall in mean arterial pressure during the high-salt period. Salt-induced increase in blood pressure was inversely correlated with a nocturnal fall in mean arterial pressure (r=-0.52, P<0.02) with the high-salt diet. These results suggest that insulin resistance, salt sensitivity, and failed nocturnal fall in blood pressure are associated with each other in subjects with essential hypertension.

Improvement of insulin resistance in essential hypertension by long-acting Ca antagonist benidipine

To investigate whether the long-acting Ca channel blocker, benidipine improves insulin resistance in patients with essential hypertension, insulin sensitivity was measured using the steady state plasma glucose (SSPG) method in 11 or 14 nonobese and nondiabetic hypertensive subjects before and after treatment with benidipine or placebo, respectively, and 11 healthy control subjects. SSPG level was significantly higher in two hypertensive groups, indicating reduced insulin sensitivity than in controls. SSPG level significantly decreased after benidipine treatment, with a decrease of blood pressure. SSPG level and blood pressure did not change in the placebo group. As for oral glucose tolerance test, the area under the curve of insulin diminished significantly after benidipine treatment. SSPG level significantly correlated with intra-platelet Ca2+ concentrations in 9 hypertensive subjects. The long-acting Ca channel blocker benidipine has partially improved insulin resistance in essential hypertension, contributing to the prevention of atherosclerosis associated with insulin resistance.

Obesity, hypertension, and vascular disease

Obesity, hypertension, and related metabolic and hemodynamic abnormalities contribute significantly to cardiovascular disease in westernized societies such as the United States. Both obesity and hypertension are more prevalent among minorities such as black and Hispanic populations. Obesity substantially increases the likelihood of hypertension, and weight reduction has been shown to be an effective hygienic measure in reducing blood pressure. There is accumulating evidence that central obesity, particularly obesity that is distributed in the paraomental (visceral) region, especially predisposes one to hypertension and related metabolic abnormalities that contribute cerebrovascular disease.

Alpha 1-blockers in hypertension

Hypertension is a heterogeneous disease and this is reflected in the marked variability in response to monotherapy. Co-administering antihypertensive therapies has several theoretical benefits, namely enhanced efficacy, improved tolerability, increased compliance and, in some cases, potentially beneficial changes in biochemical variables associated with increased cardiovascular risk, such as improvements in lipid profiles. alpha 1-Blockers, such as doxazosin, have several favourable properties which should be advantageous when used with other agents. Their mechanism of action is complementary to that of each of the other four main groups of antihypertensive drugs and, in each case, enhanced efficacy has been observed when alpha 1-blockade has been added to monotherapy with other drug classes. Synergistic effects have been seen when an alpha 1-blocker is administered together with either a calcium channel blocker or angiotensin-converting enzyme inhibitor. While alpha 1-blockers induce regression of left ventricular hypertrophy, the possibility of enhanced effects during multiple therapy has not been explored. alpha 1-Blockers exert positive effects on lipids (limited data suggest that they are able to reverse the deleterious lipid effects of diuretics and beta-blockers) and exert neutral or positive effects on glucose homeostasis. Further studies are needed to determine whether alpha 1-blockers can alleviate the adverse effects of beta-blockers or diuretics on glucose homeostasis. alpha 1-Blockers, when given concomitantly with other antihypertensive drugs, are well tolerated, conferring advantages with respect to patient compliance. The current data favour the use of alpha 1-blockers as an additional component of antihypertensive therapy, but further studies are needed to address the metabolic and end-organ effects of such treatment regimens.

Enhanced insulin response to oral glucose load in patients with angina pectoris associated with ST segment elevation in the absence of epicardial coronary arterial obstruction

The authors treated 10 patients with microvascular angina (MVA) manifesting angina pectoris, ST segment elevation suggestive of transmural myocardial ischemia, and no epicardial arterial obstruction. Since such patients frequently showed abnormal responses to oral glucose loading, the authors investigated the glucose and insulin responses to glucose loading in 10 MVA patients, 25 patients with vasospastic angina (VAP), 25 patients with effort angina (EAP), and 25 control subjects. Insulinogenic index, peripheral insulin activity [= 10(4)/(peak glucose x insulin at glucose peak)], glucose area, and insulin area were calculated. The MVA group included two patients with impaired glucose tolerance and two newly diagnosed diabetic patients. These proportions were similar to those in the VAP and EAP groups. Glucose levels at 30 to 180 min and insulin levels at 90 to 120 min in the MVA group were higher than in the control group. Peak glucose, glucose area, peak insulin, and insulin area were higher in the MVA group than in the control group (p<0.01). Those in the VAP and EAP groups were also higher. Insulin/glucose ratio at 120 min was higher, peripheral insulin activity, lower, in the disease groups than in the control group (p<0.05). The MVA patients showed a hyperglycemic and hyperinsulinemic response to oral glucose loading, as did the patients with EAP and VAP. Enhanced insulin response to oral glucose loading may also contribute to the pathogenesis of MVA.

Intracellular starvation in the insulin resistance syndrome and type II diabetes mellitus

Statistical associations of insulin resistance, type II diabetes, hypertension and hyperlipidemia have been well documented, but the pathophysiology of the 'insulin resistance syndrome' is unknown. This article explores the hypothesis that intracellular starvation plays a central role in the development of type II diabetes, hypertension and hyperlipidemia. According to this hypothesis, insulin resistance leads to inadequate intracellular glucose, which in turn leads to insufficient amounts of adenosine triphosphate needed for ion transfer, and to drive energy-requiring reactions. Indirect evidence supporting this hypothesis is presented. Intracellular starvation is also discussed as an alternative to the 'glucose hypothesis' to explain certain complications of diabetes.

Insulin receptor exon 11+/- isoform mRNA in spontaneously hypertensive and adrenocorticotropin-hypertensive rats

OBJECTIVE

To test the hypothesis that insulin resistance of the spontaneously hypertensive rat (SHR) and adrenocorticotropin-hypertensive rat is related to a difference in the proportion of the functionally different, alternatively spliced exon 11 isoforms of the insulin receptor.

DESIGN

We determined the proportions of mRNA for the exon 11+ and exon 11- isoforms in various tissues of SHR and Wistar-Kyoto rats aged 3, 6, 9 and 12 weeks, which span the pre-hypertensive phase through to established hypertension, as well as in Sprague-Dawley rats with adrenocorticotropin-induced hypertension and Sprague-Dawley controls.

METHODS

Detection of mRNA involved a reverse-transcriptase polymerase chain reaction technique specific for each isoform and quantification was by slot and dot blot hybridization.

RESULTS

Mean proportions of exon 11+ mRNA in SHR, Wistar-Kyoto rats, adrenocorticotropin-hypertensive rats and Sprague-Dawley control rats at each age were 95% for liver, 82% for adipose tissue, 77% for kidney, 66% for adrenal, 53% for heart, 26% for cerebral cortex, 23% for hypothalamus, and 3% for skeletal muscle. There was also no difference in concentration of total insulin receptor mRNA.

CONCLUSIONS

The absence of any difference in proportions of insulin receptor mRNA isoforms argues against the hypothesis that an alteration of differential splicing plays a role in the models of hypertension studied.

Role of aldehydes in fructose induced hypertension

Aldehydes are formed in tissues of humans and animals as intermediates of glucose and fructose metabolism and due to lipid peroxidation. N-acetyl cysteine (NAC), an analogue of the dietary amino acid cysteine, binds aldehydes thus preventing their damaging effect on physiological proteins. We measured systolic blood pressure (SBP), platelet cytosolic free calcium [Ca2+]i and tissue aldehyde conjugates in fructose induced hypertensive Wistar-Kyoto (WKY) rats and examined the effect of NAC in the diet on these parameters. Animals age 7 weeks were divided into three groups of 6 animals each and were treated as follows: WKY-control (chow diet and normal drinking water); WKY-Fructose (chow diet and 4% fructose in drinking water); WKY-Fructose+NAC (1.5% NAC in chow diet and 4% fructose in drinking water). After 11 weeks, systolic blood pressure, platelet [Ca2+]i and kidney aldehyde conjugates were all significantly higher in fructose treated rats. NAC treatment prevented these changes. These results suggest that aldehydes may be the cause of fructose induced hypertension and elevated cytosolic free calcium.

Effects of glucose/insulin perturbations on aging and chronic disorders of aging: the evidence

Among changes associated with aging is a decline in glucose tolerance. The reported causes are increased insulin resistance from receptor and/or post receptor disturbances and diminished pancreatic islet B-cell sensitivity to glucose. Many recent reports indicate that insulin resistance with hyperinsulinemia and/or hyperglycemia contribute to or even causes many chronic disorders associated with aging, i.e., chronic metabolic perturbations including noninsulin-dependent diabetes mellitus, obesity, hypertension, lipid abnormalities, and atherosclerosis. How could such disturbances in glucose/insulin metabolism lead to many chronic disorders associated with aging? In aging, similar to diabetes, the elevation in circulating glucose and other reducing sugars secondary to age-induced insulin resistance can react nonenzymatically with proteins and nucleic acids to form products that affect function and diminish tissue elasticity. Also, perturbations in glucose/insulin metabolism are associated with enhanced lipid peroxidation secondary to greater free radical formation. Free radicals of oxygen are important known causes of tissue damage and have been associated with many aspects of aging including inflammatory diseases, cataracts, diabetes, and cardiovascular diseases. Augmented free radical formation and lipid peroxidation are not uncommon in diabetes mellitus, commonly associated with "premature aging". Ingestion of sugars, fats, and sodium have been linked to decreased insulin sensitivity, while caloric restriction, exercise, ingestion of chromium, vanadium, soluble fibers, magnesium, and certain antioxidants are associated with greater insulin sensitivity. Thus, manipulation of diet by influencing the glucose/insulin system may favorably affect lifespan and reduce the incidence of chronic disorders associated with aging.

Insulin receptor gene in hypertension

The first molecular genetic association with human essential hypertension (HT) involved the insulin receptor gene (INSR). This highly significant result in Caucasians was for an insertion/deletion polymorphism in intron 9. A polymorphism in exon 8 showed a weak association, but a microsatellite in intron 2 proved negative for HT, although has shown an association with plasma insulin in Japanese. A similar spectrum of genetic associations for variants spanning INSR has been noted for insulin-dependent diabetic patients with rapidly-progressing renal disease, a subgroup having a strong family history of essential HT. Association with HT has also been found for an INSR variant in CHinese. Insulin resistance secondary to an INSR 'defect', or other causes, would increase insulin, which has cardiovascular effects, and insulin can raise angiotensinogen. Also, insulin is co-secreted with amylin, which can increase renin secretion. In the spontaneously HT rat there is evidence for reduced down-regulation of INSR expression in response to NaCl-loading, consistent with a promoter effect. When combined with observations of insulin resistance in essential HT patients and their pre-HT offspring, the possibility of dys-regulation of INSR merits attention in disease etiology in a proportion of essential HT patients.

Calcium channel blockers and hypertension: evolving perspective--1996

In recent years, calcium channel blockers (CCBs) have been used extensively in the United States and elsewhere as antihypertensive agents, and their availability has been an important advance in the management of hypertension. As antihypertensive agents, the CCBs thus appear considerably more versatile than most previous vasodilators. The available studies indicate that CCBs are metabolically neutral and do not exacerbate dyslipidemia or impair glucose tolerance. In contrast to diuretics and beta-blockers, CCBs do not appear to alter insulin sensitivity. The CCBs also differ from previous vasodilators because of their favorable accompanying effects on the heart and kidney. Despite the attributes of CCBs enumerated earlier, a number of recent retrospective analyses by Psaty et al. (JAMA 1995;274:620-625) have suggested that CCBs may be detrimental and may promote adverse cardiovascular events. I have recently reviewed the results of Psaty's meta-analysis and report (Arch Intern Med 1995;155: 2150-2156). I have emphasized that it is the rate of drug delivery into the systemic circulation that produces profound effects on the hemodynamic and neurohumoral responses to a dihydropyridine CCB drug. During chronic treatment with dihydropyridines, major fluctuations in blood pressure (rapid onset and offset of antihypertensive effects) during the dosing interval may persist for drugs and formulations that are short acting. In contrast, slow-release formulations of otherwise rapidly absorbed dihydropyridines achieve a more gradual and sustained antihypertensive effect. It is probable that newer CCB formulations that do not provoke intermittent sympathetic activation and do not evoke a cardioacceleratory response would not be expected to promote adverse cardiovascular events.

Metabolic manifestations of low-dose diuretics

Hypertension has been defined and treated as a disease of abnormal systolic and diastolic blood pressure. Recent data have, however, demonstrated that effective blood-pressure control has not resulted in the expected decrease in coronary artery disease. These findings are probably a result of hypertension being a complex inherited syndrome of cardiovascular risk factors, all of which are genetically linked and all of which contribute to the development of cardiovascular disease in these patients. Included in the hypertension syndrome are abnormalities of lipid profile, insulin resistance, changes in renal function, left ventricular hypertrophy and reduced arterial compliance. In many patients, high blood pressure is a late manifestation of this disease process. Since all cardiovascular risk factors contribute to heart disease in these patients, they should all be considered in the management of this disease process. Diuretics and beta blockers, when used at high doses, negatively impact lipid metabolism and insulin sensitivity, while angiotensin converting enzyme (ACE) inhibitors and calcium antagonists tend to have a neutral effect on these metabolic risk factors. These findings have resulted in decreased use of diuretics and beta blockers in favor of newer agents such as ACE inhibitors and calcium antagonists. However, recent data have demonstrated that when used at low doses (6.25 or 12.5 mg of hydrochlorothiazide), diuretics lack significant metabolic side effects while bringing about significant reductions in blood pressure. Thus, at these doses, hydrochlorothiazide is a useful drug in the treatment of hypertension, both as monotherapy and in combination therapy.

No difference in the proportion of insulin receptor exon 11 +/- isoform mRNA in the liver of rats after development of hypertension

1. There are two functionally different isoforms of the insulin receptor in humans and rats. We hypothesized that a change in their relative proportion could be of relevance to insulin resistance in hypertension. 2. A reverse-transcriptase polymerase chain reaction technique was established for the detection of mRNA for the exon 11+ and exon 11- isoforms and the proportion of each was determined in 3, 6, 9 and 12 week old spontaneously hypertensive rats and Wistar-Kyoto rats, as well as adrenocorticotrophin (ACTH)-induced hypertensive rats and controls. 3. The proportion of the exon 11+ form (approximately 95%) and exon 11- form (approximately 5%) was similar in the liver of all rats studied. 4. We conclude that there is no change in insulin receptor isoform expression in the liver in the models of hypertension studied.

Sympathoadrenergic overactivity and lipid metabolism

Epidemiological studies have identified high heart rates as a risk factor for coronary heart disease mortality, and heart rate was found to correlate with the severity of coronary atherosclerosis. Heart rate was positively correlated with serum concentrations of total cholesterol, triglycerides, and non-HDL cholesterol. Since heart rate responds sensitively to sympathoadrenergic activity, it was hypothesized that catecholamines play a crucial role in the unfavorable lipid alterations. In addition to influences on circulating lipids, the question arose whether catecholamines have more specific effects on molecular species of structural lipids. Of particular importance is the question of the involvement of catecholamines in the recently suggested correlation between arachidonic acid and stroke mortality. It is therefore attempted to delineate the possible effects of catecholamines on the fatty acid composition of the phospholipids of heart muscle and vasculature. This was achieved in rats by either catecholamine injection or by swimming, a condition known to be associated with marked sympatho-adrenergic stimulation. In swimming rats, linoleic acid was decreased by up to 40% in heart phospholipids, whereas stearic acid and arachidonic acid were increased. Similarly, chronic norepinephrine treatment in rats resulted in a net decrease in linoleic acid and an increase in arachidonic acid and docosahexaenoic acid, which was particularly pronounced when rats were fed an n-3 polyunsaturated fatty acid (PUFA)-rich oil diet. Thus, catecholamines do affect the PUFA composition of heart membranes, mainly through an increase in arachidonic acid content. To further define the action of catecholamines on structural lipids, isolated rat ventricular myocytes in culture were subjected four times to 30 minutes of isoproterenol (10(-6) M) stimulation over 48 hours. No changes in membrane lipid parameters were observed, although the beating rate was increased by 30% during the stimulation. When the cell membranes were enriched in n-3 PUFAs (in association with a decrease in arachidonic acid), the positive chronotropic effect elicited by isoproterenol was raised to + 50%, indicating the modulation of adrenergic function by membrane PUFAs. However, isoproterenol treatment again had no effect on the phospholipid fatty acid composition. Thus, the effect of catecholamines on membrane lipids observed in intact organism appears to be indirect and to involve most probably organs such as the liver and adipose tissue. Catecholamines are expected to induce a lipolysis-linked quantitative and qualitative alteration in circulating fatty acids, which in turn alter the heart membrane composition, similar to the composition changes elicited by diet lipid alterations. Since there is increasing evidence that such fatty acid changes affect the activity of membrane proteins, the possibility emerges that this mechanism may contribute to the catecholamine-linked cardiovascular mortality.

Excess catecholamines and the metabolic syndrome: should central imidazoline receptors be a therapeutic target?

A sympathetic overactivity plays a major role in the pathogenesis of cardiovascular diseases in Westernized affluent societies. Of importance is an increased caloric intake and psychosocial stress which are associated with a raised central sympathetic outflow and unfavourable changes in metabolic parameters. Normalization of central sympathetic outflow could thus be a major therapeutic target. The newly developed antihypertensive drugs moxonidine and rilmenidine reduce the excitatory activity of neurons of the rostral ventrolateral medulla (RVLM) via binding to imidazoline receptors. Using radio telemetry, it is shown that, in contrast to the first generation centrally acting drug clonidine, moxonidine did not result in rebound of blood pressure after drug withdrawal in rats with spontaneous hypertension. In accordance, moxonidine is characterized by a low affinity for alpha-adrenoceptors and exhibits few side-effects. It is proposed that normalization of central sympathetic outflow represents a causal approach for improving crucial features of the metabolic syndrome.

Doxazosin. An update of its clinical pharmacology and therapeutic applications in hypertension and benign prostatic hyperplasia

Doxazosin is a long-acting alpha 1-adrenoceptor antagonist structurally related to prazosin and terazosin. Its antihypertensive effect is produced by a reduction in the smooth muscle tone of peripheral vascular beds resulting in a decrease in total peripheral resistance without significant effect on cardiac output or heart rate. In benign prostatic hyperplasia, doxazosin's effect of relieving bladder outflow obstruction is produced through a reduction in prostatic tone mediated via alpha 1-adrenoceptor blockade. In most comparative trials doxazosin has proven to be equally effective as the comparator drug in the treatment of mild to moderate hypertension. It has been used in a variety of patient populations including the elderly, Blacks, smokers, and patients with concomitant disease states such as renal dysfunction, hypercholesterolaemia, non-insulin dependent diabetes mellitus (NIDDM) and respiratory disease. Doxazosin has also been used successfully in combination with beta-adrenoceptor antagonists, diuretics, calcium channel antagonists, and angiotensin-converting enzyme inhibitors in patients with hypertension that is uncontrolled with monotherapy. Doxazosin has a beneficial effect on some of the risk factors associated with coronary heart disease including elevated serum lipid levels, impaired glucose metabolism, insulin resistance and left ventricular hypertrophy. Modest decreases in total cholesterol, low density lipoprotein cholesterol and triglycerides are seen with doxazosin therapy while small increases in high density lipoprotein cholesterol and the high density lipoprotein cholesterol/total cholesterol ratio are consistently reported. Some studies have reported an improvement in glucose tolerance although this effect has been more consistently seen in nondiabetic patients than in patients with NIDDM. Additionally, doxazosin produces a similar reduction in left ventricular hypertrophy to other antihypertensive agents. Modelling-based calculations suggest that doxazosin significantly reduces the risk of developing coronary heart disease in patients with mild to moderate hypertension, although this remains to be confirmed in long term prospective studies. Doxazosin appears to be a promising agent in the treatment of urinary symptoms associated with benign prostatic hyperplasia. Similar to other alpha 1-adrenoceptor antagonists, doxazosin treatment produces increases in peak and mean urinary flow rates and improves other objective and symptomatic measures.(ABSTRACT TRUNCATED AT 400 WORDS)

Association of hyperinsulinemia and serum free fatty acids with serum high density lipoprotein-cholesterol

A total of 155 Japanese subjects (79 men and 76 women) who were classified as having normal or borderline glucose tolerance, according to the criteria for the 50-g oral glucose tolerance test (GTT) of the Japanese Diabetes Society, were analyzed for factors related to serum high density lipoprotein (HDL)-cholesterol concentration, especially the responses of insulin and free fatty acid (FFA) after a glucose challenge. In men, significant negative univariate correlations were observed with body mass index (P < 0.01), the summed values of triceps and subscapular skin-folds (P < 0.01), serum insulin concentration at all time intervals, and serum FFA at 30 and 60 min of GTT. Serum insulin at 60, 120, and 180 min, sum insulin, and FFA at 30 and 60 min of GTT were significantly related to serum HDL-cholesterol after adjustment for body mass index and triglyceride concentration. Multiple linear regression analysis with the step-forward method showed that sum insulin (P < 0.01), FFA at 60 min of GTT (P < 0.001), and alcohol consumption (P < 0.01) were independently related to serum HDL-cholesterol concentration. Only the triglyceride concentration was inversely correlated (P < 0.05) with HDL-cholesterol concentration in women. These data indicate that both insulin and FFA concentration, as markers of insulin resistance, apparently influence on HDL kinetics in men, but not in women. The lack of this association in women was appeared to related to the degree of obesity.

Obese patients with type 2 diabetes poorly controlled by insulin and metformin: effects of adjunctive dexfenfluramine therapy on glycaemic control

Dexfenfluramine is well known for its weight reducing action and has been reported to improve glycaemic control in obese Type 2 diabetic patients not adequately controlled on conventional oral hypoglycaemic therapy. In this double-blind placebo-controlled study, 20 obese Type 2 diabetic patients with mean HbA1c of 8.8 +/- 0.5% (normal range 3.5-6.0%), and mean body mass index (BMI) of 34.4 +/- 1.0 kg m-2, who were poorly controlled on insulin (mean dosage 58.0 +/- 6.1 units day-1) were randomized to receive either additional dexfenfluramine or placebo for 12 weeks. Seventeen of these patients were already taking maximum tolerated metformin therapy (mean dosage 1.6 +/- 0.2 g day-1) and the other three were unable to tolerate any at all. At baseline, the dexfenfluramine and placebo groups were similar in all parameters studied. After the 12-week treatment period, median HbA1c had fallen in dexfenfluramine treated patients from 8.5 (interquartile range (IR): 7.5-10.3) to 7.1% (IR: 6.7-7.5; p < 0.02). The fall in HbA1c in individual patients after treatment with dexfenfluramine was strongly associated with weight loss (r = 0.69; p < 0.04), although as a group the changes in weight and BMI were not statistically significant. Placebo was without effect. These results show that in the obese patient with Type 2 diabetes who is poorly controlled despite large daily doses of insulin and metformin, adjunctive dexfenfluramine can improve glycaemic control without exacerbating weight gain.

Quantitative characterization of insulin-glucose response in Watanabe heritable hyperlipidemic and cholesterol-fed rabbits and the effect of cilazapril

A great deal of evidence suggests that insulin resistance, via hyperinsulinemia, contributes to hyperlipoproteinemia and coronary atherosclerosis. When Watanabe heritable hyperlipidemic (WHHL) rabbits, an animal model of familial hypercholesterolemia (FH), are compared with normolipidemic Japanese White (JW) rabbits, an elevated fasting plasma insulin level and a heightened plasma insulin response to an intravenous (i.v.) glucose challenge are found. To elucidate the mechanism behind this phenomenon, a two-compartment model of the glucose/insulin system was fitted to empirical time courses of glucose and insulin concentrations during an i.v. glucose tolerance test (IVGTT) by nonlinear least-square regression, and the model parameters such as the glucose utilization rate constant, insulin degradation rate constant, and pancreas sensitivity were determined. WHHL rabbits showed decreased values of glucose utilization and insulin degradation rate constants and slightly higher values of pancreas sensitivity. This suggests that insulin resistance occurs in extrapancreatic tissues, and that this may be attributable to insulin receptor and/or post-insulin receptor abnormalities. Cholesterol feeding did not significantly change glucose tolerance or insulin action in JW rabbits. The effects of an angiotensin-converting enzyme (ACE) inhibitor, cilazapril, on insulin resistance were also examined in WHHL and JW rabbits. A decreased insulin response to an i.v. glucose challenge and increased glucose utilization and insulin degradation rate constants were observed in WHHL rabbits that had been treated with cilazapril, indicating that cilazapril improved insulin resistance in WHHL rabbits, possibly by increasing the number of insulin receptors. No significant differences were found in glucose tolerance and insulin action in JW rabbits before and after cilazapril administration.(ABSTRACT TRUNCATED AT 250 WORDS)

High serum insulin, insulin resistance and their associations with cardiovascular risk factors. The northern Sweden MONICA population study

OBJECTIVES

To estimate the prevalence of insulin resistance and high serum insulin levels and to investigate their relationship to other cardiovascular risk factors.

DESIGN

Cross-sectional cardiovascular risk factor survey.

SETTING

Northern Sweden.

SUBJECTS

A subsample of the population-based Northern Sweden MONICA Study. This subsample underwent an oral glucose tolerance test after an overnight fast, and consisted of 354 men and 404 women in the 25-64-year age range.

MAIN OUTCOME MEASURES

Delineation of low insulin sensitivity and high serum insulin by the diagnostic test technique, prevalence of these variables and their associations with cardiovascular risk factors.

RESULTS

The participants were classified into four subgroups by an insulin sensitivity index and fasting serum insulin. The combination of low insulin sensitivity and high serum insulin was present in 17% of the male and in 18% of the female 25-64-year-old population. In both sexes this combination was closely associated (P < 0.001) with body mass index, waist-hip ratio, blood pressure and serum triglycerides, and correlated inversely with serum HDL cholesterol (P < 0.001). When high serum insulin was present as an isolated entity it was as closely associated with other cardiovascular risk factors such as isolated low insulin sensitivity, except that impaired glucose tolerance occurred exclusively in the group with isolated low insulin sensitivity.

CONCLUSIONS

The combination of insulin resistance and high insulin levels is associated with a marked clustering of cardiovascular risk factors and is present in one-sixth of the middle-aged population in the north of Sweden.

Interrelation between angiographic severity of coronary artery disease and plasma levels of insulin, C-peptide and plasminogen activator inhibitor-1

Plasma insulin, C-peptide and plasminogen activator inhibitor-1 (PAI-1) levels were measured in 64 men with coronary artery disease (CAD) documented by angiography. Coronary arteriograms were analyzed, and the severity and diffusion of coronary lesions were quantified by score systems. C-peptide and PAI-1 levels in patients with CAD were significantly higher than in 30 control subjects. Insulin, C-peptide and PAI-1 showed a highly significant correlation with the severity scores for coronary lesions (C-peptide more than insulin), but only a weak correlation with diffusion scores. Highly significant correlations were found between insulin and PAI-1, and even greater ones between C-peptide and PAI-1. It has been proposed that hyperinsulinemia may be involved in the etiology of atherosclerotic cardiovascular disease by dysregulating lipoprotein metabolism and blood pressure. These findings support that hypothesis and suggest that insulin secretion may be an index of the severity of CAD. Because a direct effect of insulin on the cells that synthesize PAI-1 has been shown, the present data further indicate that the effect of insulin on fibrinolysis may be another way by which hyperinsulinemia accelerates atherogenesis.

A review of the effects of resistance training for individuals with diabetes mellitus

Although the effectiveness of exercise as a treatment modality for the management of diabetes mellitus has long been recognized, a vital component of the exercise prescription has been overlooked. In addition to endurance training, resistance training may provide physiologic benefits to the individual with diabetes that, in some cases, may equal or exceed those gained through aerobic training. These benefits may include improved blood lipid profiles, increased absolute left ventricular wall contractility, decreased resting blood pressure, improved insulin sensitivity and glucose tolerance, improved glycemic control, improved muscular strength and endurance, and increased bone and connective tissue strength. By utilizing a combination of aerobic and resistance training, the individual with diabetes experiences a more comprehensive exercise program that can improve most areas of health and physical fitness. In addition, having a greater number of exercise modality options may enhance exercise compliance.

Vascular insulin abnormalities, hypertension, and accelerated atherosclerosis

There is accumulating evidence that insulin resistance, glucose intolerance, and hyperinsulinemia exist in people with high blood pressure, and it has been suggested that insulin resistance and hyperinsulinemia may be of great importance in the origin of hypertension and its ultimate clinical course. Of importance are the recent observations that persons with normal glucose tolerance, selected on the basis of hyperinsulinemia, had higher blood pressure than matched individuals with normoinsulinemia. Hypertension in in insulin-resistant states generally has been attributed to hyperinsulinemia, with resulting increases in sympathetic nervous system activity. However, recent data from our laboratory suggest that cellular insulin resistance rather than hyperinsulinemia per se may lead to hypertension. The basic tenet proposed in this article is that a deficiency of insulin at the cellular level represents a common mechanism that is involved in the development of hypertension in both type I and type II diabetes mellitus. Insulin has an important role in the modulation of cellular calcium metabolism. Decreased insulin action on vascular smooth muscle cells may contribute both to hypertension and to accelerated atherosclerosis. Recent observations suggest that an impaired cellular response to insulin predisposes to increased vascular smooth muscle tone (the hallmark of hypertension in the diabetic state). For example, recently reported studies from our laboratory demonstrate that insulin attenuates the vascular contractile response to phenylephrine, serotonin, and potassium chloride. Thus, it appears that insulin normally modulates (attenuates) vascular smooth muscle contractile responses to vasoactive factors, and insulin resistance should accordingly be associated with enhanced vascular reactivity.

Effects of a high-fat, sucrose diet on serum insulin and related atherosclerotic risk factors in rats

Hyperinsulinemia, hypertension, hypertriglyceridemia and obesity are all risk factors for atherosclerosis. The clustering of these risk factors in the same individual greatly increases the risk for atherosclerosis and has been termed 'Syndrome X' or 'The Deadly Quartet' The purpose of the present study was to investigate the effects of diet on these risk factors in inbred, female Fischer 344 rats. Animals were raised on ad lib diets consisting of high-fat, sucrose (HFS) or low-fat, complex-carbohydrate (LFCC). After 2 years, the HFS rats were obese (38% +/- 1% vs. 15% +/- 1% body fat), hypertensive (140 +/- 3 vs. 123 +/- 3 mmHg), hyperinsulinemic (439 +/- 118 vs. 98 +/- 10 pmol/l), and hypertriglyceridemic (1.1 +/- 0.2 vs. 0.4 +/- 0.07 mmol/l). The HFS rats also exhibited enhanced clotting and impaired fibrinolytic response to streptokinase. All these differences between the two groups were statistically significant (P < 0.05). Insulin was significantly correlated with body weight (r = 0.71), triglycerides (r = 0.48), and systolic blood pressure (r = 0.70). Total cholesterol was slightly, but not significantly higher, in the HFS group (2.8 +/- 0.3 vs 2.2 +/- 0.1 mmol/l) while HDL-cholesterol was unchanged. These results show that many risk factors for atherosclerosis can be induced in inbred rats by feeding a HFS diet. Aggregation of risk factors was found in the HFS group but not in the LFCC group. In fact, most of the rats on the LFCC diet developed no risk factors after 2 years, indicating that the development of risk factors is not an aging phenomenon.