Glucose, insulin, and somatostatin infusion for the determination of insulin sensitivity in vivo

Chemerin in Participants with or without Insulin Resistance and Diabetes

Chemerin is a chemokine/adipokine, regulating inflammation, adipogenesis and energy metabolism whose activity depends on successive proteolytic cleavages at its C-terminus. Chemerin levels and processing are correlated with insulin resistance. We hypothesized that chemerin processing would be higher in individuals with type 2 diabetes (T2D) and in those who are insulin resistant (IR). This hypothesis was tested by characterizing different chemerin forms by specific ELISA in the plasma of 18 participants with T2D and 116 without T2D who also had their insulin resistance measured by steady-state plasma glucose (SSPG) concentration during an insulin suppression test. This approach enabled us to analyze the association of chemerin levels with a direct measure of insulin resistance (SSPG concentration). Participants were divided into groups based on their degree of insulin resistance using SSPG concentration tertiles: insulin sensitive (IS, SSPG ≤ 91 mg/dL), intermediate IR (IM, SSPG 92-199 mg/dL), and IR (SSPG ≥ 200 mg/dL). Levels of different chemerin forms were highest in patients with T2D, second highest in individuals without T2D who were IR, and lowest in persons without T2D who were IM or IS. In the whole group, chemerin levels positively correlated with both degree of insulin resistance (SSPG concentration) and adiposity (BMI). Participants with T2D and those without T2D who were IR had the most proteolytic processing of chemerin, resulting in higher levels of both cleaved and degraded chemerin. This suggests that increased inflammation in individuals who have T2D or are IR causes more chemerin processing.

Assessment of Insulin Secretion and Insulin Resistance in Human

The impaired insulin secretion and increased insulin resistance (or decreased insulin sensitivity) play a major role in the pathogenesis of all types of diabetes mellitus (DM). It is very important to assess the pancreatic β-cell function and insulin resistance/ sensitivity to determine the type of DM and to plan an optimal management and prevention strategy for DM. So far, various methods and indices have been developed to assess the β-cell function and insulin resistance/sensitivity based on static, dynamic test and calculation of their results. In fact, since the metabolism of glucose and insulin is made through a complex process related with various stimuli in several tissues, it is difficult to fully reflect the real physiology. In order to solve the theoretical and practical difficulties, research on new index is still in progress. Also, it is important to select the appropriate method and index for the purpose of use and clinical situation. This review summarized a variety of traditional methods and indices to evaluate pancreatic β-cell function and insulin resistance/sensitivity and introduced novel indices.

Optimized fasting and OGTT-based simple surrogate methods for assessing insulin sensitivity

AIMS

Simple surrogate indices of insulin sensitivity have been conceived to deal with costly and complicated approaches, such as the hyperinsulinemic-euglycemic clamp; however, their use has not been widespread given their variabilities in different populations. In this paper, we present two simple surrogate indices, one that uses fasting glucose and insulin values and the other based on the values from the oral glucose tolerance test.

MATERIALS AND METHODS

The proposed methods integrate easy-to-obtain anthropometric measures. Evolutionary algorithms were used to optimize the proposed methods by maximizing its correlation with the Stumvoll MCR method.

RESULTS AND CONCLUSION

When the proposed indices were applied to three study groups (control subjects, metabolic syndrome, marathon runners), a reduction in the intergroup variability of the insulin sensitivity was obtained. Moreover, the proposed index based on the oral glucose tolerance test (OGTT), which considers the glucose metabolism process and the hepatic and peripheral insulin sensitivity, showed stronger correlations with the Stumvoll method and lower intergroup variability than the fasting one.

Impact of race/ethnicity on insulin resistance and hypertriglyceridaemia

OBJECTIVE

Insulin sensitivity affects plasma triglyceride concentration and both differ by race/ethnicity. The purpose of this study was to provide a comprehensive assessment of the variation in insulin sensitivity and its relationship to hypertriglyceridaemia between five race/ethnic groups.

RESEARCH DESIGN AND METHODS

In this cross-sectional study, clinical data for 1025 healthy non-Hispanic White, Hispanic White, East Asian, South Asian and African American individuals were analysed. Insulin-mediated glucose disposal (a direct measure of peripheral insulin sensitivity) was measured using the modified insulin suppression test. Statistical analysis was performed using analysis of co-variance.

RESULTS

Of the study participants, 63% were non-Hispanic White, 9% were Hispanic White, 11% were East Asian, 11% were South Asian and 6% were African American. Overall, non-Hispanic Whites and African Americans displayed greater insulin sensitivity than East Asians and South Asians. Triglyceride concentration was positively associated with insulin resistance in all groups, including African Americans. Nevertheless, for any given level of insulin sensitivity, African Americans had the lowest triglyceride concentrations.

CONCLUSION

Insulin sensitivity, as assessed by a direct measure of insulin-mediated glucose disposal, and its relationship to triglyceride concentration vary across five race/ethnic groups. Understanding these relationships is crucial for accurate cardiovascular risk stratification and prevention.

Long-Term Testosterone Administration on Insulin Sensitivity in Older Men With Low or Low-Normal Testosterone Levels

Background

Serum testosterone levels and insulin sensitivity both decrease with age. Severe testosterone deficiency is associated with the development of insulin resistance. However, the effects of long-term testosterone administration on insulin sensitivity in older men with low or low-normal testosterone levels remain unknown.

Methods

The Testosterone Effects on Atherosclerosis in Aging Men Trial was a placebo-controlled, randomized, double-blind trial. The participants were 308 community-dwelling men, ≥60 years old, with total testosterone 100 to 400 ng/dL or free testosterone <50 pg/mL. A subset of 134 nondiabetic men (mean age, 66.7 ± 5.1 years) underwent an octreotide insulin suppression test at baseline and at 3 and 36 months after randomization to measure insulin sensitivity. Insulin sensitivity was estimated as the steady-state plasma glucose (SSPG) concentration at equilibrium during octreotide and insulin administration. Secondary outcomes included total lean mass (TLM) and total fat mass (TFM) by dual energy x-ray absorptiometry.

Results

There was a significant (P = 0.003) increase in SSPG in the placebo group, whereas no change was seen in testosterone-treated subjects from baseline to 36 months; however, the between-group differences in change in SSPG over 3 years were not statistically significant (+15.3 ± 6.9 mg/dL in the placebo group vs +6.2 ± 6.4 mg/dL in the testosterone group; mixed-model effect, P = 0.17). Changes in SSPG with testosterone treatment were not associated with changes in serum total or free testosterone concentrations. Changes in TFM but not TLM were associated with increases in SSPG. Stratification by age or baseline total testosterone level did not show significant intervention effects.

Conclusion

Testosterone administration for 36 months in older men with low or low-normal testosterone levels did not improve insulin sensitivity.

Accurate method to estimate insulin resistance from multiple regression models using data of metabolic syndrome and oral glucose tolerance test

Aims/Introduction

How to measure insulin resistance (IR) accurately and conveniently is a critical issue for both clinical practice and research. In the present study, we tried to modify the β‐cell function, insulin sensitivity, and glucose tolerance test (BIGTT) in patients with normal glucose tolerance (NGT) and abnormal glucose tolerance (AGT) by oral glucose tolerance test (OGTT) and metabolic syndrome (MetS) components.

Materials and Methods

There were 327 participants enrolled and divided into NGT or AGT. Data from 75% of the participants were used to build the models, and the remaining 25% were used for external validation. Steady‐state plasma glucose (SSPG) concentration derived from the insulin suppression test was regarded as the standard measurement for IR. Five models were built from multiple regression: model 1 (MetS model with sex, age and MetS components); model 2 (simple OGTT model with sex, age, plasma glucose, and insulin concentrations at 0 and 120 min during OGTT); model 3 (full OGTT model with sex, age, and plasma glucose and insulin concentrations at 0, 30, 60, 90, 120, and 180 min during OGTT); model 4 (simple combined model): model 1 and model 2; and model 5 (full model): model 1 and 3.

Results

In general, our models had higher r² compared with surrogates derived from OGTT, such as homeostasis model assessment‐insulin resistance and quantitative insulin sensitivity check index. Among them, model 5 had the highest r² (0.505 in NGT, 0.556 in AGT, respectively).

Conclusions

Our modified BIGTT models proved to be accurate and easy methods for estimating IR, and can be used in clinical practice and research.

Acute hyperglycemia reduces myocardial blood flow reserve and the magnitude of reduction is associated with insulin resistance: a study in nondiabetic humans using contrast echocardiography

The effect of acute hyperglycemia per se on coronary perfusion in humans is undefined. We evaluated the effects of short-term hyperglycemia on myocardial blood flow reserve (MBFR) in healthy nondiabetic volunteers. Twenty-one nondiabetic volunteers (76 % females, mean ± SD, age 48 ± 5 years) had noninvasive MBFR assessment while exposed to pancreatic clamp with somatostatin and replacement glucagon and growth hormone infusions, with frequent interval plasma glucose (PG) monitoring. Insulin was infused at 0.75 mU/kg/min to mimic postprandial plasma insulin concentrations, and glucose was infused to maintain euglycemia (PG 93.9 ± 7.3 mg/dl) followed by hyperglycemia (PG 231.5 ± 18.1 mg/dl). Myocardial contrast echocardiography (MCE) was performed during each glycemic steady state using continuous infusion of Definity at rest and during regadenoson (Lexiscan 5 ml (400 μg) intravenous bolus) infusion to quantify myocardial blood flow (MBF) and determine MBFR. Insulin resistance (IR) was assessed by glucose infusion rate (GIR; mg/kg/min) at euglycemia. Median stress MBF, MBFR, and β reserve were significantly reduced during acute hyperglycemia versus euglycemia (stress MBF 3.9 vs 5.4, P = 0.02; MBFR 2.0 vs 2.7, P < 0.0001; β reserve 1.45 vs 2.4, P = 0.007). Using a median threshold GIR of 5 mg/kg/min, there was a correlation between GIR and hyperglycemic MBFR (r = 0.506, P = 0.019). MBFR, as determined noninvasively by MCE, is significantly decreased during acute hyperglycemia in nondiabetic volunteers, and the magnitude of this reduction is modulated by IR.

Effects of bariatric surgery on glucose homeostasis and type 2 diabetes

Obesity is an important risk factor for type 2 diabetes mellitus (T2DM). Weight loss improves the major factors involved in the pathogenesis of T2DM, namely insulin action and beta cell function, and is considered a primary therapy for obese patients who have T2DM. Unfortunately, most patients with T2DM fail to achieve successful weight loss and adequate glycemic control from medical therapy. In contrast, bariatric surgery causes marked weight loss and complete remission of T2DM in most patients. Moreover, bariatric surgical procedures that divert nutrients away from the upper gastrointestinal tract are more successful in producing weight loss and remission of T2DM than those that simply restrict stomach capacity. Although upper gastrointestinal tract bypass procedures alter the metabolic response to meal ingestion, by increasing early postprandial plasma concentrations of glucagon-like peptide 1 and insulin, it is not clear whether these effects make an important contribution to long-term control of glycemia and T2DM once substantial surgery-induced weight loss has occurred. Nonetheless, the effects of surgery on body weight and metabolic function indicate that bariatric surgery should be part of the standard therapy for T2DM. More research is needed to advance our understanding of the physiological effects of different bariatric surgical procedures and possible weight loss-independent factors that improve metabolic function and contribute to the resolution of T2DM.

Vinegar lacks antiglycemic action on enteral carbohydrate absorption in human subjects

The antiglycemic effects of vinegar have been known for more than a century and have been demonstrated in animal as well as human studies. Although the exact mechanism of vinegar action is not known, several possibilities have been proposed including suppression of disaccharidase activity, delayed gastric emptying, enhanced glucose uptake in the periphery and conversion to glycogen, and increased satiety. We hypothesized that by suppressing endogenous insulin secretion, we could estimate the glucose absorption rate from an oral carbohydrate load and determine the effects of vinegar ingestion on this rate. To do so, 5 subjects had 4 studies at 1-week intervals, randomly receiving placebo twice (60 mL water) and vinegar twice (20 mL apple cider vinegar, 40 mL water), followed 2 minutes later by a meal of mashed potatoes (0.75 g carbohydrate per kilogram body weight) that was consumed over 20 minutes. At the beginning of the meal, an oral octreotide/insulin suppression test (25-microg bolus octreotide; 180 minute infusion 5 mU/m(2) body surface area per minute regular human insulin, and 0.5 microg/min octreotide) was begun. Blood samples for insulin and glucose were drawn at 20-minute intervals. The oral octreotide/insulin suppression test suppressed endogenous insulin secretion for the first 100 minutes of the study. During this time, the rate of rise of glucose was modestly but significantly (P = .01) greater after vinegar ingestion compared to placebo, suggesting that vinegar does not act to decrease glycemia by interference with enteral carbohydrate absorption.

Current approaches for assessing insulin sensitivity and resistance in vivo: advantages, limitations, and appropriate usage

Insulin resistance contributes to the pathophysiology of diabetes and is a hallmark of obesity, metabolic syndrome, and many cardiovascular diseases. Therefore, quantifying insulin sensitivity/resistance in humans and animal models is of great importance for epidemiological studies, clinical and basic science investigations, and eventual use in clinical practice. Direct and indirect methods of varying complexity are currently employed for these purposes. Some methods rely on steady-state analysis of glucose and insulin, whereas others rely on dynamic testing. Each of these methods has distinct advantages and limitations. Thus, optimal choice and employment of a specific method depends on the nature of the studies being performed. Established direct methods for measuring insulin sensitivity in vivo are relatively complex. The hyperinsulinemic euglycemic glucose clamp and the insulin suppression test directly assess insulin-mediated glucose utilization under steady-state conditions that are both labor and time intensive. A slightly less complex indirect method relies on minimal model analysis of a frequently sampled intravenous glucose tolerance test. Finally, simple surrogate indexes for insulin sensitivity/resistance are available (e.g., QUICKI, HOMA, 1/insulin, Matusda index) that are derived from blood insulin and glucose concentrations under fasting conditions (steady state) or after an oral glucose load (dynamic). In particular, the quantitative insulin sensitivity check index (QUICKI) has been validated extensively against the reference standard glucose clamp method. QUICKI is a simple, robust, accurate, reproducible method that appropriately predicts changes in insulin sensitivity after therapeutic interventions as well as the onset of diabetes. In this Frontiers article, we highlight merits, limitations, and appropriate use of current in vivo measures of insulin sensitivity/resistance.

Improvement of insulin resistance by troglitazone ameliorates cardiac sympathetic nervous dysfunction in patients with essential hypertension

BACKGROUND

It was recently suggested that insulin resistance is significantly correlated with activation of the cardiac sympathetic nervous system in patients with essential hypertension.

OBJECTIVES

To examine the effects of troglitazone, an agent used to treat insulin resistance, on cardiac sympathetic nervous dysfunction and insulin resistance in patients with essential hypertension.

METHODS

The study participants included 34 patients (14 men, 20 women) with mild essential hypertension and 17 normal controls (group C, seven men). The patients were randomly divided into two groups, one treated with 400 mg troglitazone and antihypertensive drugs (group T, n = 17) and the other treated with antihypertensive drugs only (group N, n = 17). We evaluated insulin resistance and cardiac sympathetic nervous function before and after 6 months of treatment. Insulin resistance was evaluated using steady-state plasma glucose (SSPG; mg/dl) concentrations and cardiac sympathetic nervous function was evaluated using the heart-to-mediastinum ratio (H : M) and mean washout rate measured by 123I-meta-iodobenzylguanidine (MIBG) cardiac imaging.

RESULTS

There were significant differences in SSPG (P < 0.01), early (P < 0.05) and delayed (P < 0.05) phases of H : M and washout rate (P < 0.05) between the hypertensive patients and group C. The SSPG concentration was significantly improved after treatment only in group T, from 153.3 to 123.7 mg/dl (P < 0.01). The early and delayed phases of H : M and washout rate also were significantly improved (P < 0.05) (from 2.59 to 2.63, from 2.12 to 2.27 and from 18.1 to 13.7%, respectively) in only group T.The change in SSPG was significantly correlated with the changes in H : M and washout rate (r = -0.639 and 0.577, respectively).

CONCLUSION

Troglitazone had a beneficial effect on cardiac sympathetic nervous function through a decrease in insulin resistance in patients with essential hypertension.

Improvement of endothelial function and insulin sensitivity with vitamin C in patients with coronary spastic angina: possible role of reactive oxygen species

OBJECTIVES

This study was designed to examine the effect of antioxidant supplementation on the endothelial function and insulin sensitivity in patients with coronary spastic angina (CSA).

BACKGROUND

Insulin resistance may play a key role in coronary heart disease, and there is a possible link between acetylcholine-induced coronary vasoconstriction and hyperinsulinemia in patients with CSA. Endothelial dysfunction is present in the systemic arteries in CSA patients, and reactive oxygen species may cause inactivation of nitric oxide in these patients.

METHODS

We measured flow-mediated dilation of the brachial artery using ultrasound technique in 22 patients with CSA and 20 control subjects. We also evaluated glucose tolerance using a 75-g oral glucose tolerance test and insulin sensitivity using steady-state plasma glucose (SSPG) methods in the same patients.

RESULTS

The incidence of impaired glucose tolerance was higher in the CSA group than in the control group. Vitamin C infusion augmented flow-mediated dilation and decreased SSPG levels in the CSA group (from 3.27 +/- 0.77% to 7.00 +/- 0.59% [p < 0.001 by analysis of variance (ANOVA)] and from 177.3 +/- 13.3 to 143.1 +/- 14.9 mg/dl [p = 0.047 by ANOVA], respectively) but not in the control group (from 6.47 +/- 0.66% to 6.80 +/- 0.60% and from 119.8 +/- 11.7 mg/dl to 118.1 +/- 11.3 mg/dl, respectively). The steady-state plasma insulin levels were not affected by vitamin C infusion in either group.

CONCLUSIONS

Vitamin C improves both endothelial function and insulin sensitivity in patients with CSA. Thus, reactive oxygen species and/or decreased nitric oxide bioactivity may play an important role in the genesis of both endothelial dysfunction and insulin resistance in patients with CSA.

Effect of salt on insulin sensitivity differs according to gender and degree of salt sensitivity

The aim of the present study was to investigate the effect of salt intake on insulin sensitivity and the relation between salt sensitivity and insulin sensitivity in genetically hypertension-prone individuals. Twenty-eight healthy subjects (13 men and 15 women) with a family history of hypertension were examined at baseline, after 1 week of salt restriction (10 mmol/d), and after 1 week of salt loading (240 mmol/d). Insulin sensitivity was measured with the hyperinsulinemic euglycemic clamp after the low- and high-salt diets. Salt sensitivity was defined as the difference in mean arterial blood pressure between the high-salt and the low-salt diets. There was no significant relationship between insulin sensitivity and salt sensitivity after either of the 2 diets. In the men, salt sensitivity was inversely related to plasma renin activity (r=-0.61, P=0.03) and plasma aldosterone (r=-0.74, P=0.004), whereas salt sensitivity in women was directly correlated with the salt-induced increase in body weight (r=0.68, P=0.005). In men, the high-salt diet induced a change in glucose disposal that was strongly correlated with the degree of salt sensitivity (r=0.83, P=0. 0004), plasma renin activity (r=-0.82, P=0.0006), and plasma aldosterone concentrations (r=-0.87, P=0.00009) (eg, the greater the salt sensitivity and the lower the activity of the renin-angiotensin-aldosterone system, the greater improvement in insulin sensitivity). No such relationships were observed in women. In conclusion, increased salt sensitivity and decreased activity of the renin-angiotensin-aldosterone system predict improved insulin sensitivity with high-salt intake compared with low-salt intake in men, suggesting an interaction among salt intake, salt sensitivity, the renin-angiotensin-aldosterone system, and insulin action.

Relationship between insulin resistance and cardiac sympathetic nervous function in essential hypertension

BACKGROUND

It has been suggested that hyperinsulinemia and insulin resistance participate in the pathogenesis of hypertension, in part by activating sympathetic activity.

OBJECTIVE

We aimed to examine the relationship between insulin resistance and cardiac sympathetic nervous function in patients with essential hypertension using 123I-metaiodobenzylguanidine (MIBG) cardiac scintigraphy.

METHODS AND RESULTS

Twenty-eight patients (18 men) with essential hypertension and 11 (seven men) control individuals with a mean age of 55.8+/-3.3 years were recruited. Patients with diabetes mellitus, congestive heart failure or coronary artery disease were excluded from this study. To evaluate insulin resistance, we used steady-state plasma glucose (SSPG; mg/dl) levels measured by the SSPG method. To evaluate cardiac sympathetic nervous function, we calculated the heart-to-mediastinum ratio from the delayed MIBG image (H:M-D) and the mean washout rate (WOR, %). There were significant differences (P<0.01) in SSPG, H:M-D and WOR between the essential hypertension and control individual groups (125 versus 103 mg/dl, 2.2 versus 2.4, and 32 versus 23%, respectively). Stepwise regression analysis showed that SSPG and plasma norepinephrine level are independent predictors for the cardiac sympathetic nervous function obtained from MIBG scintigraphy.

CONCLUSIONS

These findings indicate that insulin resistance is significantly related to activation of the cardiac sympathetic nervous function associated with left ventricular hypertrophy in patients with essential hypertension.

Effect of insulin resistance on left ventricular hypertrophy and dysfunction in essential hypertension

BACKGROUND

In hypertensive patients, the relationships between glucose tolerance and left ventricular hypertrophy (LVH) and left ventricular diastolic function (LVDF) have been described in several reports.

OBJECTIVE

In this study, we examined the relationships between insulin resistance and LVH and LVDF in hypertensive patients from the therapeutic perspective.

METHODS AND RESULTS

The study participants were essential hypertensive patients with impaired glucose tolerance (IGT-HT, n = 26), hypertensive patients with normal glucose tolerance (NGT-HT, n = 39), and normotensive control individuals (n = 18). Insulin resistance was evaluated by the insulin suppression test by use of the steady-state plasma glucose (SSPG) level. Left ventricular mass index (LVMI) and LVDF, which was determined by the E:A ratio, were estimated by echocardiography. Temocapril, an angiotensin-converting enzyme inhibitor, was administered in an open, non-randomized manner with a mean dose of 2.8+/-0.2 mg/ day, and the mean administration period was 18 weeks. The systolic and diastolic blood pressure, the LVMI, and the SSPG level were significantly higher in the hypertensive patients than in the control individuals. The mean systolic and diastolic blood pressures were significantly decreased by treatment with Temocapril. Before treatment, stepwise regression analysis showed that SSPG is an independent predictor for LVMI and LVDF. After treatment, the changes in LVMI (D-LVMI; %) (-15.1+/-1.5), the changes in LVDF (D-E:A; %) (-38.2+/-4.1), and the changes in insulin resistance (D-SSPG; %) (-13.7+/-1.7) were significantly higher in the IGT-HT group than in the NGT-HT group (-11.4+/-1.1, -18.1+/-1.7, -9.4+/-1.4, respectively), and the D-SSPG was an independent predictor for D-LVMI and D-E :A.

CONCLUSIONS

The results of this study indicate that insulin resistance is an important factor affecting LVH and LVDF.

Insulin resistance as an independent risk factor for carotid artery wall intima media thickening in vasospastic angina

Studies have shown the presence of insulin resistance together with compensatory hyperinsulinemia in vasospastic angina as well as obstructive coronary artery disease. There is growing evidence that the development of coronary atherosclerosis may be closely related to systemic atherosclerosis as well as coronary spasm. However, no information is available about the possible relationship between insulin resistance and the existence of carotid atherosclerosis in vasospastic angina without segmental stenosis or luminal irregularities in coronary angiograms. To evaluate the independent effect of insulin resistance on carotid intima media thickening, we performed insulin sensitivity tests (steady-state plasma glucose method) on 40 patients with vasospastic angina and 24 control subjects with angiographically intact coronary arteries. Both oral glucose tolerance tests and lipid analyses were performed. Using B-mode ultrasonography, we assessed intima media thickness and plaque formation of common carotid arteries in these subjects. The steady-state plasma glucose level in the vasospastic angina group was about twofold higher than that of the control group, confirming the presence of insulin resistance in patients with vasospastic angina. The patients with vasospastic angina showed a significant increase in the average intima media thickness of the carotid wall and frequency of plaque formation, although they were comparable to the control subjects in risk factors other than insulin resistance. The intima media thickness was correlated with age (r = .62, P < .001), 2-hour insulin area (r = .45, P < .01), and steady-state plasma glucose level (r = .68, P < .0001) in patients with vasospastic angina. Similar correlations were observed in the control subjects. Multiple regression analyses of data indicated that 67% of the variation in the intima media thickness could be accounted for by age, steady-state plasma glucose level, and cigarette-years in vasospastic angina. In addition, differences in IMT were independently related to vasospastic angina. These results suggest that insulin resistance in association with compensatory hyperinsulinemia may be an important pathogenic factor for the development of coronary artery spasms and systemic early atherosclerosis.

Alterations in the glucose-stimulated insulin secretory dose-response curve and in insulin clearance in nondiabetic insulin-resistant individuals

Plasma glucose and insulin responses to a graded i.v. infusion of glucose were compared in two groups of glucose-tolerant women divided on the basis of their insulin sensitivity. Resistance to insulin-mediated glucose disposal was measured using the insulin suppression test, and the women studied were chosen to represent the highest and lowest quartiles of insulin resistance seen in the normal population. The sensitivity of the pancreatic beta-cell to glucose was assessed by measuring the glucose, insulin, and C peptide concentrations in response to continuous graded i.v. infusions of glucose at rates of 1, 2, 3, 4, 6, and 8 mg/kg x min for 40 min each. In addition, insulin secretion rates in response to the graded glucose infusion, calculated over each sampling period, were derived from deconvolution of peripheral plasma C peptide concentrations, using a two-compartment model of C peptide kinetics and standard parameters for C peptide clearance. Although plasma glucose concentrations were only slightly higher throughout the glucose infusion, the insulin concentrations were approximately doubled in the insulin-resistant subjects. When expressed as a function of the molar increments in plasma glucose achieved during the glucose infusion studies, the insulin-resistant women had a 90% higher (684 +/- 55 vs. 360 +/- 36 pmol/L x mmol/L; P < 0.001) total integrated plasma insulin response as the glucose concentration was increased from 5 to 9 mmol/L. However, the total integrated insulin secretory rate was only increased by 37% (1494 +/- 133 vs. 1093 +/- 125 pmol/mmol/L x min; P < 0.05) in the insulin-resistant group. This discrepancy suggested that insulin clearance was lower in the insulin-resistant subjects, and the calculation of this value, as the ratio of the total secretion of insulin to the area under the plasma insulin curve, was significantly lower in the insulin-resistant group (1.25 +/- 0.05 vs. 1.87 +/- 0.16 L/min x m2; P < 0.005). These results show that the hyperinsulinemia of insulin resistance results from an increase in insulin secretion secondary to a shift to the left of the glucose-stimulated insulin response curve as well as a decrease in insulin clearance.

High prevalence of small LDL particles in non-insulin-dependent diabetic patients with nephropathy

To determine whether small-sized low density lipoprotein (LDL) is associated with a high incidence of coronary heart disease in diabetic nephropathy, we measured the LDL particle size in non-insulin-dependent diabetes mellitus (NIDDM) patients with various degrees of albuminuria (n = 95) and age-, weight-matched non-diabetic control subjects (n = 31). The diabetic subjects were divided into three groups, normoalbuminuric, microalbuminuric and macroalbuminuric NIDDM, based on the amount of albuminuria. The average diameter of LDL particles was determined by non-denaturing polyacrylamide gradient (2-16%) gel electrophoresis. The plasma lipid and lipoprotein concentrations were comparable between the non-diabetic controls and normoalbuminuric NIDDM, whereas the plasma triglyceride, very-low-density lipoprotein (VLDL) or LDL concentration was significantly increased in diabetic nephropathy. The mean LDL particle size was significantly smaller in microalbuminuric NIDDM compared with the controls or normoalbuminuric NIDDM, and the LDL size was further decreased in macroalbuminuric NIDDM. The incidence of small LDL (diameter < 255 A) was remarkably increased in microalbuminuric (58%) and macroalbuminuric NIDDM (67%) compared to the control (13%) and normoalbuminuric NIDDM (27%). Corresponding to the decreased LDL size, the cholesterol content of the LDL was significantly depleted in NIDDM with nephropathy. The high prevalence of small LDL in diabetic nephropathy was also observed even when hypertriglyceridemic or hypertensive subjects were excluded from each group. The increment in triglyceride-rich lipoprotein (d < 1.006) after oral fat-loading was increased, and postheparin lipoprotein lipase activity was decreased significantly in diabetic nephropathy. These abnormalities were significantly associated with LDL particle size. Multivariate regression analysis revealed that the amount of albuminuria was closely associated with the average LDL particle size, and this association was independent of the plasma triglyceride level. Neither insulin resistance nor glycemic control was directly associated with LDL particle diameter. The present study indicates that LDL particles become smaller in diabetic nephropathy, and this may be associated primarily with abnormal triglyceride metabolism. However, in addition to hypertriglyceridemia, other metabolic abnormalities caused by diabetic nephropathy may also be involved in the pathogenesis of small LDL particles.

Improvement of insulin sensitivity and dyslipidemia with a new alpha-glucosidase inhibitor, voglibose, in nondiabetic hyperinsulinemic subjects

This study was undertaken to investigate the effect of voglibose, a new alpha-glucosidase inhibitor, on glucose and lipid metabolism in nondiabetic hyperinsulinemic subjects. Sixteen nondiabetic subjects with hyperinsulinemia participated in the study. They were divided into two groups of eight subjects with normal (NGT) and impaired (IGT) glucose tolerance. A meal tolerance test and a 75-g oral glucose tolerance test (OGTT) were performed at the beginning (baseline phase) and end (treatment phase) of the 12-week treatment. Serum lipid levels were measured every 4 weeks throughout the treatment phase and follow-up phase (8 weeks). All patients received 1 0.2-mg tablet of voglibose before each test meal (3 tablets per day). We also measured insulin sensitivity using a steady-state plasma glucose (SSPG) method in eight normotensive hyperinsulinemic subjects and in eight age- and body mass index (BMI)-matched control subjects before and after the drug treatment. Voglibose significantly decreased the responses of plasma glucose and insulin on the meal tolerance test. The area under the curve for 2-hour insulin during the 75-g OGTT decreased after treatment, whereas that for 2-hour glucose did not change before and after treatment. SSPG was reduced after treatment, indicating improvement of insulin sensitivity. Moreover, treatment with voglibose resulted in a significant decline of triglyceride level and an elevation of high-density lipoprotein (HDL) cholesterol and apolipoprotein A-1. These values returned to near-baseline levels after the drug was discontinued. Consequently, we conclude that this agent not only has a direct hypoglycemic effect through decreased absorption of carbohydrate, but also a hypoinsulinemic and hypolipidemic effect via improved insulin sensitivity.

Role of insulin resistance associated with compensatory hyperinsulinemia in ischemic stroke

BACKGROUND AND PURPOSE

Although insulin resistance and hyperinsulinemia play a crucial role in the pathogenesis of atherosclerosis, little is known about their roles in ischemic stroke. The purpose of this study was to clarify whether insulin resistance and hyperinsulinemia are causative factors in the pathogenesis of ischemic stroke.

METHODS

Thirty-four consecutive patients with ischemic stroke, who were normotensive, nondiabetic, and not obese, were classified into three groups--atherothrombotic infarction (n = 16), lacunar infarction (n = 10), and cardioembolic infarction (n = 8)--based on clinical findings, brain imaging, and cerebral angiography. Both oral glucose tolerance tests and lipid analyses were performed. Insulin sensitivity was determined by the steady state plasma glucose method with the use of octreotide acetate. Data were compared with those of healthy control subjects (n = 15).

RESULTS

Steady state plasma glucose levels were significantly higher in the atherothrombotic infarction group compared with control subjects and the other two stroke groups, indicating the presence of insulin resistance in patients with atherothrombotic infarction. In the atherothrombotic infarction group, the 2-hour insulin area (area under the plasma insulin concentration curve) during a 75-g oral glucose tolerance test was significantly increased and dyslipidemic changes (increased triglyceride and apolipoprotein B, decreased high-density lipoprotein) were observed, whereas these changes were not found in the lacunar infarction and cardioembolic stroke groups.

CONCLUSIONS

Insulin resistance in association with compensatory hyperinsulinemia and dyslipidemia may be an important pathogenetic factor underlying the development of atherothrombotic infarction.

Normalization of insulin resistance in non-obese essential hypertension by cilazapril treatment

To determine whether ACE inhibitor other than captopril improves insulin sensitivity in patients with essential hypertension, we measured insulin sensitivity to glucose utilization using SSPG method in 10 lean hypertensive subjects before and after chronic cilazapril treatment (1.5 +/- 0.2 mg/day, 15.6 +/- 2.1 weeks). The results were compared with those obtained in 10 healthy control subjects. SSPG obtained by insulin sensitivity test was significantly higher in hypertensive subjects, indicating a lower insulin sensitivity than in controls. After cilazapril treatment, SSPG reduced significantly to the level which was statistically not different from control subjects. Hyperinsulinemia diminished after treatment, while no significant change of blood glucose was observed during oral glucose tolerance test in hypertensive subjects. Plasma HDL cholesterol increased by cilazapril treatment. Cilazapril treatment has beneficial effect in the reversal of insulin resistance in patients with essential hypertension.

Insulin resistance associated with compensatory hyperinsulinemia as an independent risk factor for vasospastic angina

BACKGROUND

It is generally believed that coronary artery spasm plays an important role in the progression of obstructive coronary artery disease. Since insulin resistance together with hyperinsulinemia plays an important role in the pathogenesis of coronary atherosclerosis, we investigated the association of hyperinsulinemia and insulin resistance with vasospastic angina (VAP).

METHODS AND RESULTS

The study population consisted of 60 patients with VAP and 42 control subjects (62 subjects with normal glucose tolerance and 40 with impaired glucose tolerance). Insulin sensitivity was determined by the steady-state plasma glucose (SSPG) method for nondiabetic, normotensive, nonobese subjects (16 control subjects, 16 obstructive coronary artery disease patients, and 16 VAP patients). Compared with the control group, the 2-hour insulin area (area under the plasma insulin concentration-time curve) during a 75-g oral glucose tolerance test was significantly higher in both VAP groups with normal and impaired glucose tolerance. A high frequency of vasospastic angina was observed in subjects with clustered risk factors for insulin resistance syndrome, suggesting a close association of VAP with this syndrome. In stepwise discriminant analysis, the 2-hour insulin area was significantly associated with VAP independent of other risk factors. SSPG level in VAP was about twofold over control, indicating the presence of insulin resistance in patients with VAP. However, no differences were found between patients with VAP and obstructive coronary artery disease with respect to mean SSPG level.

CONCLUSIONS

SSPG level was significantly elevated in patients with VAP and obstructive coronary artery disease compared with control subjects. This indicates that hyperinsulinemia is secondary to insulin resistance, both of which are thought to play important roles as risk factors for VAP in the early atheromatous lesion and in the future development of occlusive lesions when chronically present.

Insulin resistance rather than hyperinsulinemia more closely associated with essential hypertension

In order to clarify which of the two, insulin resistance or hyperinsulinemia, are more contributable to non obese and non diabetic hypertension, insulin sensitivity test was performed. By multiple regression analysis, mean, systolic, and diastolic blood pressure were inversely correlated with glucose clearance. During insulin sensitivity test, plasma catecholamines levels and FENa were not changed by insulin infusion. In the present study, it is demonstrated that insulin has no hypertensive effect under the mild hyperinsulinemia (45-55 microU/ml). We conclude that insulin resistance rather than hyperinsulinemia may be more closely associated with non obese and non diabetic hypertension.

Day-to-day variation of insulin sensitivity in patients with type 1 diabetes: role of gender and menstrual cycle

The aim of the present study was to compare the day-to-day variations of the insulin sensitivity in male and female Type 1 diabetic patients and to assess the insulin sensitivity in the follicular and luteal phases of the menstrual cycle. Ten male and 20 female Type 1 diabetic patients participated in the study. The insulin sensitivity was assessed by the insulin (0.4 mU kg-1 min-1)-glucose/(4.5 mg kg-1 min-1)-infusion test (IGIT). In 5 of the female patients, a simultaneous i.v. influsion of somatostatin (100 micrograms h-1) was given (SIGIT). Each patient was studied twice, with 2 weeks separating the two tests. The day-to-day variations of the insulin sensitivity were almost identical in the male and female patients, the coefficients of variation being 13% in both groups. In 15 of the female patients, ovulation occurred. In these women, the mean blood-glucose levels between 120 and 240 min after the onset of the IGIT/SIGIT were 9.8 +/- 1.1 mmol l-1 in the follicular phase and 10.3 +/- 1.0 mmol l-1 in the luteal phase, n.s. (95% confidence interval for the difference (luteal-follicular) -0.8-1.9 mmol l-1). Although the present study cannot exclude minor changes of insulin sensitivity during the menstrual cycle, our results suggest that the changes of the metabolic control during the menstrual cycle, experienced by many women with Type 1 diabetes, are largely attributable to mechanisms other than variations of insulin sensitivity.

Insulin resistance in young salt-sensitive normotensive subjects

Insulin resistance has been demonstrated in patients with essential hypertension, and insulin-mediated sodium retention is believed to contribute to hypertension in these individuals. Recently, a hyperinsulinemic response to an oral glucose load has been found in salt-sensitive normotensive subjects, suggesting that insulin resistance may be present in these hypertension-prone individuals before the development of hypertension. In the present study, we examined the relation between insulin sensitivity and blood pressure response to salt intake in young, lean normotensive subjects on a high and a low salt diet. Insulin sensitivity was estimated by the "insulin suppression test," i.e., by measuring the plasma glucose and insulin concentrations achieved during a 180-minute infusion of somatostatin, insulin, and glucose in 18 healthy male volunteers (age, 21-28 years) given a standardized low salt diet (20 mmol/day) for 2 weeks, supplemented by either 220 mmol of NaCl per day or placebo in a single-blind randomized order for 1 week each. We defined salt sensitivity as a significant decrease in mean arterial blood pressure (> 3 mm Hg [p < 0.05]) measured for 60 minutes at 1-minute intervals on the low salt diet. By this definition, seven of the 18 subjects were salt sensitive. Although insulin infusion resulted in similar plasma insulin levels (approximately 50 milliunits/L) in both groups, concomitant glucose infusion resulted in plasma glucose levels that were more than 50% higher in the salt-sensitive than in the salt-resistant group (p < 0.005 by two-way analysis of variance).(ABSTRACT TRUNCATED AT 250 WORDS)

The short insulin tolerance test for determination of insulin sensitivity: a comparison with the euglycaemic clamp

The glucose clamp technique is currently regarded as the standard test for measuring insulin sensitivity against which other methods are compared but is unsuitable for routine screening of patients outside a hospital base. There is thus a need for a simpler test to measure insulin sensitivity. We have therefore compared the glucose disappearance rate KITT in the first 15 min of the insulin tolerance test (ITT) with the M and M/I values derived from the standard euglycaemic clamp in nine normal subjects and eight subjects with Type 2 (non-insulin dependent) diabetes mellitus and coexisting obesity. All subjects underwent the ITT and euglycaemic clamp in random order. Nine subjects later had a repeat ITT to determine the reproducibility of the test. In the ITT, 0.1 U kg-1 body weight, human Actrapid insulin was given as an IV bolus and simultaneous arterialized and venous blood samples were obtained every minute for 15 min. The first order rate constant for the disappearance of glucose KITT over the period 3-15 min was taken as a measure of insulin sensitivity. The euglycaemic clamp was performed with an insulin infusion of 50 mU kg-1 h-1 for 120 min and a variable rate glucose infusion to maintain blood glucose concentration at 0.5 mmol l-1 below fasting level to minimize the effect of endogenous insulin secretion. The ratio of the mean rate of glucose infused (M, mumol kg-1 min-1) to the plasma insulin over the last 30 min of the clamp was taken as a measure of tissue sensitivity to insulin (M/I) assuming endogenous glucose output was suppressed.(ABSTRACT TRUNCATED AT 250 WORDS)

Simultaneous evaluation of insulin secretion and action using a model

For the simultaneous evaluation of insulin secretion and insulin sensitivity, a glucose regulation model has been developed. In order to estimate the parameters of the model, an intravenous glucose infusion test (GIT, 100 mg/kg.min x 2 min and 10 mg/kg.min x 118 min) was carried out on 15 healthy subjects (N), 12 subjects with impaired glucose tolerance (IGT), 20 non-insulin-dependent diabetics (NIDDM) and 13 patients with chronic pancreatitis (CP). The coefficient (microU/mg) for insulin secretion depending on blood glucose concentration in IGT, NIDDM and CP were lower (35.9 +/- 2.7, 24.5 +/- 3.3, 43.1 +/- 3.1) than in N (77.5 +/- 7.9). The coefficients (microU.min/mg) for insulin secretion depending on rate of change in blood glucose concentration in IGT and NIDDM were significantly lower (6.5 +/- 2.1, 3.8 +/- 1.2) than in N (52.8 +/- 8.8). The insulin sensitivity index (ISI; 10(-2) mg/(microU/ml).kg.min) in NIDDM was lower (4.98 +/- 0.75) than in N (11.37 +/- 1.08). Administration of exogenous insulin did not significantly affect the value of ISI in N and NIDDM. ISI showed a tendency to increase (15.09 +/- 1.92) in CP. It was demonstrated that the proposed model which estimates both insulin secretory ability and insulin sensitivity simultaneously is quite useful for analyzing the mechanism of impaired glucose tolerance.

Possible role for the glucose-fatty acid cycle in dexamethasone-induced insulin antagonism in rats

This study was undertaken to elucidate the mechanism(s) involved in glucocorticoid-induced insulin antagonism. Male Sprague-Dawley rats (200 to 210 g) were injected with 1 mg/kg dexamethasone-phosphate (Dex) or the vehicle every other day for 10 days. Two days after the last injection, fasted anesthetized animals were infused (per kg body weight per min) with 8 mg glucose, 5 mU porcine insulin and 1.4 micrograms somatostatin with blood sampling before, and at 10 min intervals between 90 and 130 min after the pancreatic suppression test was begun. At the end of the test, abdominal muscle was quickly freeze-clamped and the substrate and products of the rate-determining reactions of glycolysis and glycogenesis were measured. Dex-treated rats had higher basal (0 min) and steady-state levels (90-130 min) of both glucose and insulin signifying insulin antagonism. The pattern of muscle tissue metabolites revealed no free intracellular glucose in either group and concentrations of all other metabolites in the Dex-treated rats were less than those in the control animals (except for a small increase in glycogen). These results suggest a site of insulin antagonism between (and including) insulin binding and glucose transport. Further studies in the Dex-treated rats revealed normal: a) insulin binding to freshly isolated hepatocytes; b) basal and insulin-stimulated xylose transport in soleus muscle; c) basal and insulin-stimulated glucose uptake in hemidiaphragms. These normal in-vitro results suggested that a circulating factor may be responsible. Repeat pancreatic suppression tests in the Dex-treated rats revealed blunted suppression of serum FFA concentrations.(ABSTRACT TRUNCATED AT 250 WORDS)

Insulin action in cirrhosis

In vivo insulin sensitivity and adipocyte insulin binding and action were assessed in 16 patients with histologically proven hepatic cirrhosis and 11 age-, weight- and sex-matched normal control subjects. The cirrhotic group displayed impaired oral glucose tolerance, despite an exaggerated serum immunoreactive insulin response, and in vivo insulin resistance as assessed both by the euglycemic hyperinsulinemic clamp and the glucose-insulin infusion techniques. Adipocytes of the cirrhotic patients bound significantly less insulin than those of the control subjects (2.21 +/- 0.12% vs. 2.64 +/- 0.13%; p less than 0.05). Although the adipocytes from the cirrhotic patients were less sensitive to insulin stimulation in vitro (half-maximal stimulation at 60.0 +/- 8.0 vs. 21.8 +/- 3.3 pM; p less than 0.001), they exhibited higher maximum rates of lipogenesis. Comparison of the responses of the alcoholic, primary biliary cirrhosis and cryptogenic subgroups suggested pronounced differences in the maximum rates of lipogenesis. There were significant negative correlations between specific binding to adipocytes and both fasting serum immunoreactive insulin and in vivo insulin resistance as assessed by glucose-insulin infusion. Monocyte insulin binding was normal in the cirrhotic group and did not correlate with in vivo insulin resistance. It is concluded that both binding and postbinding defects in insulin target organ cells contribute to the marked in vivo insulin resistance of hepatic cirrhosis.

Impaired insulin action in newly diagnosed type 1 (insulin-dependent) diabetes mellitus

Hepatic and peripheral insulin sensitivity were investigated in five newly diagnosed Type 1 (insulin-dependent) diabetic subjects before and after 1 week of twice daily insulin therapy. Eight weight-matched control subjects were also studied. Hepatic glucose production and glucose utilization were measured basally and during two sequential 2-h insulin (25 and 40 mU X kg-1 X h-1)/ glucose infusion periods. In the untreated hyperglycaemic diabetic patients hepatic glucose production was 16.3 +/- 2.6, 8.1 +/- 1.1 and 3.6 +/- 2.8 mumol X kg-1 X min-1 respectively for each of the three periods (mean +/- SEM), and fell with treatment to 12.5 +/- 1.4, 0.5 +/- 0.5 and 0.5 +/- 0.5 mumol X kg-1 X min-1. Hepatic glucose production for normal subjects was 13.4 +/- 0.7, 2.3 +/- 0.8 and less than 0.1 mumol X kg-1 X min-1. Glucose utilization was 12.7 +/- 1.4, 18.2 +/- 0.7 and 22.1 +/- 3.4 mumol X kg-1 X min-1 before treatment in the diabetic subjects, and 11.8 +/- 1.7, 20.9 +/- 3.3 and 30.1 +/- 3.6 after treatment. These values compare with those in the euglycaemic control subjects (13.4 +/- 0.7, 18.7 +/- 1.6 and 36.3 +/- 2.7 mumol X kg-1 X min-1). The pre-treatment metabolic clearance rate of glucose in all diabetic studies with insulin levels greater than 30 mU/l was 2.6 +/- 0.4 and rose to 3.9 +/- 0.5 ml X kg-1 X min-1 following insulin therapy.(ABSTRACT TRUNCATED AT 250 WORDS)

In vitro insulin resistance of human adipocytes isolated from subjects with noninsulin-dependent diabetes mellitus

To assess possible cellular mechanisms of in vitro resistance in noninsulin-dependent diabetes mellitus (NIDDM), maximum insulin-stimulated glucose transport and utilization and insulin binding were measured in adipocytes isolated from weight-matched normal glycemic subjects and patients with NIDDM. Glucose transport rate was determined by measuring the amount of [U-14C]-D-glucose taken up by incubating adipocytes at trace concentrations of glucose (300 nM), and glucose metabolism by estimating the amount of lactate, CO2, triglyceride, and total glucose carbons retained in the cells following incubating at 5.5 mM glucose. Insulin binding was measured at 50, 100, and 200 pM [mono125I-tyrosinyl A14]insulin. Both maximum insulin-stimulated glucose transport and utilization in adipocytes from diabetic subjects were 40% (P less than 0.01) and 32% (P less than 0.05) lower, respectively, than values obtained for subjects with normal glucose tolerance. In addition, the maximum capacity of glucose transport was correlated with the maximum capacity of glucose utilization (r = 0.81, P less than 0.001). Furthermore, fasting plasma glucose concentrations of diabetic subjects were negatively correlated with both maximum insulin-stimulated glucose transport (r = -0.56, P less than 0.05) and glucose utilization (r = -0.67, P less than 0.05). Since basal glucose transport in adipocytes from diabetic subjects was also 33% lower than in adipocytes from normal subjects, there was no change in the relative ability of insulin to stimulate glucose transport. However, there was a 64% decrease in the sensitivity of the glucose transport system to insulin (P less than 0.05), unrelated to concomitant changes in insulin binding. These results demonstrate that both maximal insulin-stimulated glucose transport and utilization, and the sensitivity of the glucose transport system to insulin, was decreased in adipocytes isolated from subjects with NIDDM. These in vitro defects were associated with impaired glucose metabolism in vivo, consistent with the view that the metabolic alterations observed at the cellular level may contribute to the in vivo insulin resistance of NIDDM.

Insulin production rate, hepatic insulin retention and splanchnic carbohydrate metabolism after oral glucose ingestion in hyperinsulinaemic Type 2 (non-insulin-dependent) diabetes mellitus

To differentiate peripheral and hepatic insulin resistance in hyperinsulinaemic overweight Type 2 (non-insulin-dependent) diabetic patients (n = 17; 143 +/- 4% ideal body weight; mean +/- SEM) arterial concentrations and splanchnic exchange of glucose, pyruvate, lactate, non-esterified fatty acids, beta-hydroxybutyrate and acetoacetate, as well as the insulin production rate, were determined before and during oral glucose loads of 25 g or 100 g. Insulin production rate, hepatic insulin retention and splanchnic exchange of glucose and metabolites were estimated by means of the hepatic venous catheter technique. In the basal state insulin production rate was greater in overweight Type 2 diabetic patients (2.57 +/- 0.28 pmol.kg-1. min-1) than in healthy control subjects (1.68 +/- 0.17 pmol.kg-1.min-1; p less than 0.01). After ingestion of 25 g glucose, the cumulative insulin production rate exceeded normal values (p less than 0.05), but was below normal with 100 g glucose (p less than 0.01). Relative insulin trapping by the splanchnic bed in the diabetic patients was 54 +/- 3%, not different from normal. Following a 100 g glucose load, splanchnic insulin retention fell by 20% in the patients, and less consistently so in healthy controls. Splanchnic glucose output was normal in the diabetic patients both in the basal state and after glucose ingestion although the induced arterial blood glucose levels were greater in the diabetic patients than in control subjects (p less than 0.005). Splanchnic output of pyruvate (p less than 0.025), lactate (p less than 0.01), and beta-hydroxybutyrate (p less than 0.005) were greater in the basal state in the diabetic patients than in healthy subjects. However, no difference in splanchnic exchange was seen between the two groups in their metabolites' respective response to glucose ingestion. These data suggest that obese hyperinsulinaemic Type 2 diabetic patients may represent a subgroup of diabetic patients with predominantly peripheral, but compensated hepatic, insulin resistance being associated with an increased basal insulin production rate which only exhausts after ingestion of a large glucose load.

Relationship between insulin resistance, insulin secretion, very low density lipoprotein kinetics, and plasma triglyceride levels in normotriglyceridemic man

We have previously postulated that resistance to insulin-mediated glucose uptake was the basic metabolic abnormality in patients with endogenous hypertriglyceridemia. In this situation, glucose tolerance would tend to deteriorate, and could only be maintained by the increased secretion of insulin. Although the ensuing hyperinsulinemia might prevent the development of glucose intolerance, we suggested that it would also lead to increased hepatic very low density (VLDL) triglyceride (TG) synthesis and secretion. In the current study we have quantified these four metabolic variables in 16 nonobese human subjects with plasma TG concentrations less than 175 mg/dl. The results demonstrate the following degree of correlation: insulin resistance (Formula: see text) insulin response to food (Formula: see text) VLDL-TG secretion rate (Formula: see text) plasma TG concentration. These data indicate that nonobese subjects with normal TG levels have the same relationship between degree of insulin sensitivity, insulin response to food, VLDL-TG secretion, and TG concentration previously described in patients with endogenous hypertriglyceridemia.