间歇低氧大鼠肝细胞GLUT-2、GCK表达与胰岛素抵抗的相关性研究

目的 检测葡萄糖转运蛋白-2(GLUT-2)、葡萄糖激酶(GCK)在间歇低氧大鼠模型肝细胞中表达的变化,探讨间歇低氧引起胰岛素抵抗的相关机制.方法 24只6周龄健康雄性SpragueDawley(SD)大鼠按照随机数字表法分为对照组、间歇低氧4周组(IH4组)和间歇低氧8周组(IH8组),每组8只.间歇低氧组按预设通气模式每天给予间歇低氧暴露8h,对照组给予间歇压缩空气,暴露时间同IH4组.实验结束后测定各组大鼠空腹血糖、空腹胰岛素,计算稳态模型评估-胰岛素抵抗指数(HOMA-IR)及胰岛素敏感性指数(ISI).免疫组织化学染色观察肝细胞GLUT-2、GCK蛋白表达变化,并利用平均灰度值对蛋白进行定量分析.结果 与对照组相比,IH4组及IH8组空腹血糖、空腹胰岛素、HOMA-IR均升高,ISI均降低,且IH8组更明显(F=161.92、51.46、126.99、83.87,P均＜0.05).与对照组相比,IH4组及I-H8组肝细胞GLUT-2、GCK蛋白表达均降低,且IH8组更显著(F=184.91、240.85,P均＜0.05).Pearson相关分析显示,GLUT-2、GCK平均灰度值与ISI呈负相关(r=-0.886、-0.906,P均＜0.05),与HOMA-tR呈正相关(r=0.894、0.869,P均＜0.05).结论 间歇低氧暴露使大鼠肝细胞GLUT-2、GCK蛋白表达下调,可能参与间歇低氧条件下胰岛素抵抗的发生.     

Comparison among different insulin sensitivity indices in obese patients.

AIMS: Recently, several indices have been proposed for the measurement of insulin sensitivity (IS). We set out to make a comparison between fasting insulin, and different IS indices in obese subjects. PATIENTS AND METHODS: Fasting and post load (75 g) glucose and insulin were measured in a consecutive series of 767 (626 F, 141 M) obese (body mass index > 30 kg/m(2)) out-patients, with no known history of diabetes (DM). Mean (+/- sd) age was 46.7 +/- 13.8 years in females and 45.6 +/- 14.3 years in males. Indices of IS based on fasting homeostasis assessment model (HOMA) and post-load (ISI) glucose and insulin and either parameter (1A, and 1B scores) were determined. RESULTS: DM was diagnosed in 21.4% of females, and 20.6% of males, and impaired glucose tolerance in 24% females and 21.3% males. Fasting and post-load glucose, triglyceride and HDL-cholesterol were correlated with all indices in both sexes (P < 0.05). The relative risk of different conditions in the upper quartile of ISI was similar to that observed in the upper quartile of HOMA. The HOMA index was similarly associated with low HDL-cholesterol and hypertriglyceridaemia as fasting insulin, while it showed a greater association with diabetes; ISI was similarly associated with all three conditions as the HOMA index. CONCLUSIONS: Indices of IS based on fasting glucose and insulin show a greater association with diabetes, but not with other abnormalities related to insulin resistance, when compared with fasting insulin levels. Indices based on post-load glucose and insulin do not offer any advantage over those based on fasting values.     

Impaired beta-cell function and insulin sensitivity in Japanese subjects with normal glucose tolerance

The development of type 2 diabetes mellitus is characterized by both impaired beta-cell function and increasing insulin resistance. To clarify the roles of them in developing type 2 diabetes, we evaluated insulin resistance by HOMA-IR and insulin secretion by HOMA beta-cell in 453 Japanese subjects whose fasting plasma glucose (FPG) and HbA(1c) levels were within normal range. HOMA beta-cell was found to decrease in the over 30 years groups, while HOMA-IR increased with body mass index (BMI). To analyze the reserve capacity of insulin secretion and insulin sensitivity, the 67 of them, who underwent a standard oral glucose tolerance test and were diagnosed with normal glucose tolerance (NGT), were divided into four degrees of BMI age-adjusted to 50 years. They were compared for insulinogenic index and ISI composite proposed by Matsuda and DeFronzo across the range of BMI. ISI composite was significantly less in the highest BMI group, while insulin secretion did not increase in the higher BMI groups. The subjects with higher BMI had remarkably lower insulinogenic indices than those with lower BMI. These data suggest that insulin secretory reserve is insufficient to compensate for increased insulin resistance in Japanese people with NGT at about 50 years of age.     

Detection of insulin resistance in Turkish adults: a hospital-based study

Aim: The aim of the present study was to investigate the usefulness of insulin sensitivity check indices in our hospital population.
Methods: Both HOMA (insulin X glucose in mmol/l/22.5) and QUICKI (1/log insulin in μu/ml + log glucose in mg/dl) indices were calculated from fasting values in 1774 subjects from the medical records of Baskent University Adana Hospital.
Results: Subjects with diabetes, hyperlipidaemia and central obesity were characterized by significantly higher HOMA and lower QUICKI indices than those of healthy subjects. A fall in the QUICKI index (0.3469 ± 0.028 in healthy subjects and 0.3247 ± 0.025 in non-obese diabetics) as well as an increase in HOMA index (2.24 ± 1.26 in healthy subjects and 3.59 ± 2.08 in non-obese diabetics) corresponded to metabolic and clinical manifestations of insulin resistance in various groups of subjects. Age, low HDL cholesterol, male sex, type 2 DM and hypertension were independent risk factors for CAD. Age, male sex, waist circumference and CAD were found to be risk factors for hypertension. Fasting insulin and glucose levels contain sufficient information to assess insulin sensitivity over a wide range in a diverse population. The following can be accepted as mean values to assess insulin resistance in our hospital population: 0.3469 ± 0.028 for the QUICKI index and 2.24 ± 1.26 for the HOMA index
Conclusions: HOMA and QUICKI indices are simple and reproducible methods for determining insulin sensitivity in humans.     

Association between Circulating Tumor Necrosis Factor-Alpha, Interleukin-6, and Insulin Resistance in Normal-Weight Women with Polycystic Ovary Syndrome

Background: Insulin resistance is a common finding in both obese and lean women with polycystic ovary syndrome (PCOS). Factors contributing to insulin resistance are still controversial. The purpose of the study was to compare the tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) concentrations in normal weight women with PCOS and a weightmatched healthy control group, and also to evaluate the role of these cytokines in the pathogenesis of insulin resistance. Methods: Thirty-two women with PCOS and 25 age- and weight-matched healthy controls participated in this study. Patients were evaluated clinically and by pelvic ultrasound. Fasting insulin, glucose, lipid profile, follicle-stimulating hormone (FSH), leutinizing hormone (LH), prolactin, testosterone, sex hormone binding globulin (SHBG), 17-hydroxyprogesterone, IL-6, TNF-alpha concentrations, and insulin sensitiviy indices homeostasis model assessment (HOMA) and quantitative insulin sensitivity check index (QUICKI) were measured. Results: TNF-alpha and IL-6 concentrations were significantly higher in women with PCOS than in the control group. Significant correlations were found between TNF-alpha serum concentrations and Body Mass Index (BMI), waist circumference, triglyceride concentrations, fasting insulin, and insulin resisitance indices (p < 0.001). IL-6 concentrations were correlated with fasting glucose and insulin resistance (p < 0.05). Conclusions: The study demonstrated that TNF-alpha and IL-6 concentrations were elevated in normal weight women with PCOS. The findings may contribute to evidence of insulin resistance in lean women with PCOS.     

The plasminogen activator system in young and lean women with polycystic ovary syndrome

The purpose of the study was to evaluate the plasminogen activator inhibitor-1 (PAI-1) levels and PAI-1 activity in young and lean women with PCOS and to compare with controls matched for age and weight. Thirty two women with PCOS and 25 weight and age-matched healthy controls participated in this study. Patients were evaluated clinically and by pelvic ultrasound and fasting blood samples were taken for hematological and biochemical tests. Fasting insulin, glucose, lipid profile, FSH, LH, PRL, testosterone, SHBG, 17-hydroxyprogesterone, androstenedione, PAI-1 antigen; PAI-1 activity, insulin sensitivity indices (HOMA and QUICKI) were measured. PAI-1 Ag and activity were significantly higher in PCOS women than healthy control group. PAI-1 levels were directly correlated with BMI, insulin levels and insulin sensitivity indices. PAI-1 activity was also correlated with insulin levels and insulin resistance. As a conclusion PAI-1 Ag levels and activity were increased in lean PCOS women and these were directly correlated with insulin resistance. The finding may contribute to evidence of increase risk of cardiovascular disease and anovulatory infertility in PCOS women.     

Reduced insulin secretion in normoglycaemic patients with beta-thalassaemia major.

AIMS: To assess insulin sensitivity and secretion in the fasting state in regularly transfused patients with beta-thalassaemia major with normal glucose response during an oral glucose tolerance test and to estimate its possible relation to iron overload. METHODS: We measured fasting glucose, insulin and C-peptide levels in 24 patients with beta-thalassaemia major and 18 control subjects matched for age and body mass index. Insulin sensitivity and insulin release index were calculated according to the homeostasis model assessment (HOMA). Correlations with age, body mass index and serum ferritin were also calculated. RESULTS: Fasting glucose levels in patients were increased compared with control subjects (5.5 +/- 0.12 vs. 4.7 +/- 0.13 mmol/l, mean +/- SEM, P < 0.001). Pancreatic B-cell insulin secretion in the fasting state (estimated by SC(HOMA)) was lower in thalassaemic patients (SC(HOMA) 88.5 +/- 11.11 vs. 184.3 +/- 23.72 in control subjects, P < 0.001). Patients were then divided into those with impaired (IFG) and normal (NFG) fasting glucose. SC(HOMA) was higher in the patients with NFG compared with those with IFG patients (110.6 +/- 17.63 vs. 66.3 +/- 10.88, respectively, P < 0.05) but estimated insulin sensitivity (ISI(HOMA)) was similar. Plasma values of C-peptide correlated positively with ferritin (r = 0.42, P = 0.04) and SC(HOMA) (r = 0.45, P = 0.02) and negatively with ISI(HOMA) (r = -0.43, P = 0.03). CONCLUSIONS: These results support the concept that impaired B-cell function, as reflected by a reduction in the insulin secretion index, is present in beta-thalassaemic patients with normoglycaemia before changes in oral glucose tolerance tests are apparent.     

Abnormal Glucose Tolerance in β-Thalassemia: Assessment of Risk Factors

In β-thalassemia (β-thal) major, the pathogenetic mechanisms leading from siderosis to diabetes are poorly understood. We assessed the glycometabolic status in transfusion-dependent Egyptian β-thal patients and evaluated their possible risk factors for abnormal glucose tolerance (AGT). An oral glucose tolerance test (OGTT) was done on 54 multi-transfused patients and 28 age-matched normal controls, measuring their serum insulin levels at 0 and 120 min. Insulin sensitivity and insulin release indices were calculated. Indicators of iron overload and liver status were recorded. Thirteen patients (24.1%) had AGT. Cases with AGT had significantly higher mean postprandial insulin, fasting insulin resistance index (FIRI) and homeostasis model assessment (HOMA) insulin resistance (IR), p?=?0.0001 for all, and significantly lower mean HOMA β cell, p?=?0.007, when compared with normal glucose tolerance (NGT) cases. Abnormal glucose tolerance is common in multi-transfused β-thal major patients and could be attributed to early impaired β-cell function with increasing IR.     

Sagittal abdominal diameter is associated with insulin sensitivity in Chinese hypertensive patients and their siblings

The purpose of the study is to observe the relation between anthropometric measurements, focusing on sagittal abdominal diameter (SAD), and insulin sensitivity indices in Chinese hypertensive patients and their siblings. In total, 907 participants, 537 hypertensive and 370 nonhypertensive, from 311 Taiwanese families were drawn from the Stanford Asia and Pacific Program for Hypertension and Insulin Resistance for the study. The participants received anthropometric measurements and 75-g oral glucose tolerance tests after an overnight fast. Fasting insulin, homeostasis model assessment for insulin resistance (HOMA-IR), and the insulin sensitivity index ISI(0,120) were chosen as surrogate measures of insulin sensitivity. In addition to Pearson and partial correlations, we used generalized estimating equations (GEEs) to examine the association between anthropometric measurements and insulin sensitivity indices. A small deviance in the GEEs indicates the goodness of model fit, irrespective of the independence among variables. The hypertensive patients were older in age, wider in waist circumference (WC), larger in body mass index (BMI) and SAD, and more insulin resistant than the nonhypertensive counterparts. The logarithmic transformation of fasting insulin, HOMA-IR, and ISI(0,120) significantly correlated with SAD, WC, and BMI before and after adjustments for age and sex. The deviances of SAD in the GEEs were similar to those of WC in all subjects, while BMI had smaller deviances than SAD and WC in the hypertensive patients. Our results suggest that the performance of SAD in predicting insulin sensitivity is comparable with WC in Chinese hypertensive patients and their siblings. BMI, however, seems to have better association with insulin sensitivity than SAD and WC in the patients with hypertension.     

Revised QUICKI provides a strong surrogate estimate of insulin sensitivity when compared with the minimal model

OBJECTIVE: To compare insulin sensitivity (Si) from a frequently sampled intravenous glucose tolerance test (FSIGT) and subsequent minimal model analyses with surrogate measures of insulin sensitivity and resistance and to compare features of the metabolic syndrome between Caucasians and Indian Asians living in the UK. SUBJECTS: In all, 27 healthy male volunteers (14 UK Caucasians and 13 UK Indian Asians), with a mean age of 51.2+/-1.5 y, BMI of 25.8+/-0.6 kg/m(2) and Si of 2.85+/-0.37. MEASUREMENTS: Si was determined from an FSIGT with subsequent minimal model analysis. The concentrations of insulin, glucose and nonesterified fatty acids (NEFA) were analysed in fasting plasma and used to calculate surrogate measure of insulin sensitivity (quantitative insulin sensitivity check index (QUICKI), revised QUICKI) and resistance (homeostasis for insulin resistance (HOMA IR), fasting insulin resistance index (FIRI), Bennetts index, fasting insulin, insulin-to-glucose ratio). Plasma concentrations of triacylglycerol (TAG), total cholesterol, high density cholesterol, (HDL-C) and low density cholesterol, (LDL-C) were also measured in the fasted state. Anthropometric measurements were conducted to determine body-fat distribution. RESULTS: Correlation analysis identified the strongest relationship between Si and the revised QUICKI (r=0.67; P=0.000). Significant associations were also observed between Si and QUICKI (r=0.51; P=0.007), HOMA IR (r=-0.50; P=0.009), FIRI and fasting insulin. The Indian Asian group had lower HDL-C (P=0.001), a higher waist-hip ratio (P=0.01) and were significantly less insulin sensitive (Si) than the Caucasian group (P=0.02). CONCLUSION: The revised QUICKI demonstrated a statistically strong relationship with the minimal model. However, it was unable to differentiate between insulin-sensitive and -resistant groups in this study. Future larger studies in population groups with varying degrees of insulin sensitivity are recommended to investigate the general applicability of the revised QUICKI surrogate technique.     

Failure of mathematical indices to accurately assess insulin resistance in lean, overweight, or obese women with polycystic ovary syndrome

Insulin resistance is a common metabolic feature of polycystic ovary syndrome (PCOS). In this study, we examined the validity of the mathematical indices [the quantitative insulin sensitivity check index (QUICKI) and the homeostasis model of assessment (HOMA)] that calculate insulin sensitivity and their correlation to glucose utilization with the insulin infusion rate in 40 mU/m(2).min by the euglycemic clamp (M) in women with PCOS. We studied 59 women with PCOS (20 lean, 16 overweight, and 23 obese subjects). Euglycemic clamp testing was performed, and QUICKI, HOMA, total testosterone, fasting insulin, fasting glucose, and glucose-to-insulin ratio were estimated. No difference was found in testosterone and glucose levels among the three groups. Lean or overweight women compared with obese women differed in insulin levels, glucose-to-insulin ratio, QUICKI, and HOMA (P < 0.01). No statistical difference was found between lean and overweight women in the above parameters. M differed when lean women were compared with overweight (P < 0.002) or obese women (P < 0.0001); however, no statistical difference was observed between overweight and obese women. No significant correlation was found between M and QUICKI or HOMA. We conclude that mathematical indices should be applied with caution in different insulin-resistant populations and should not be considered a priori equivalent to the euglycemic clamp technique.     

Fluvastatin improves insulin resistance in nondiabetic dyslipidemic patients

Statins have multiple actions, independent of their classical effects on lipoproteins. The data about the effects of statins on insulin resistance is controversial. This study was designed to search the statin effects on nondiabetic dyslipidemic patients. Thirty-five (17 male, 18 female) consecutive dyslipidemic patients 54.25 +/- 8.81 yr were enrolled in the study. After a standard follow-up period of lifestyle modification, the patients were given fluvastatin 40 mg/d for 8 wk. Serum analyses were done both before and after treatment. Insulin resistance was assessed by homeostasis assessment model (HOMA). Fasting plasma triglyceride, total and LDL cholesterol, fasting insulin, and HOMA index were significantly reduced and HDL cholesterol was improved after fluvastatin treatment. HOMA-IR was not correlated with triglycerides, LDL, HDL, or total cholesterol levels. The same situation was present for both fasting plasma insulin and fasting plasma glucose levels. Also age was not associated with HOMA-IR and fasting plasma insulin levels. As a conclusion, the present study indicates that fluvastatin treatment improves insulin resistance in dyslipidemic patients who do not have diabetes or impaired fasting glucose. Also, the effect of fluvastatin on insulin resistance is not associated with the lowering of triglycerides. The latter finding indicates that the effect of statins on insulin sensitivity may not be related with the lowering of triglycerides in dyslipidemic patients.     

Clinical significance of the insulin resistance index as assessed by homeostasis model assessment

To examine the clinical significance of the insulin resistance index as determined by homeostasis model assessment (HOMA-IR), we investigated the relationship between HOMA-IR and the insulin resistance estimated by the euglycemic-hyperinsulinemic clamp method in various subgroups and compared the significance of HOMA-IR with that of fasting plasma insulin levels (FIRI). HOMA-IR was significantly correlated to the inverse of the glucose infusion rate (1/GIR) in both diabetic and non-diabetic subjects (r=0.747, P<0.0001 and r=0.419, P<0.002, respectively). In the diabetic patients, treatment with sulfonylureas did not weaken this correlation (r=0.833, P<0.0001). HOMA-IR was found to be closely related to FIRI (r=0.932, P<0.0001), but HOMA-IR was more closely associated with 1/GIR than FIRI was. HOMA-IR as well as 1/GIR was correlated with the visceral fat area (VFA) more closely than with the subcutaneous fat area (SFA), while FIRI was correlated almost equally with both of them. In conclusion, HOMA-IR is a convenient and beneficial method for evaluating insulin resistance, especially in subjects with visceral fat accumulation, and reflects insulin resistance obtained by euglycemic clamp more accurately than FIRI alone.     

The investigation of insulin resistance in patients with idiopathic hirsutism

Hirsutism, which is characterized by excessive growth of terminal hair in a male pattern, is a common clinical condition in women. It may result from various causes including polycystic ovary syndrome, nonclassic adrenal hyperplasia, adrenal or ovarian tumors, or it may be idiopathic. Idiopathic hirsutism (IH) is considered to be one of the most common forms of hirsutism. Although not universal, insulin resistance and hyperinsulinemia have been demonstrated in women with polycystic ovary syndrome. Because there are not enough data showing whether patients with IH also have insulin resistance, we intended to investigate the presence/absence of insulin resistance in women with IH. Thirty-two women with IH [mean age, 24.8 +/- 1.2 yr; body mass index (BMI), 24.6 +/- 0.8 kg/m2] and 17 healthy women (mean age, 25.8 +/- 0.6 yr; BMI, 22.5 +/- 0.6 kg/m2) were included in the study. Eight of 32 patients with IH had BMI higher than 30 kg/m2. The presence of insulin resistance was investigated by using basal insulin levels, the oral glucose tolerance test, the i.v. insulin tolerance test, and the homeostasis model assessment (HOMA) score in both groups. Six (18.7%) patients had impaired glucose tolerance (IGT). Overall, patients with IH had significantly (P < 0.05) higher basal insulin levels (10.5 +/- 1.1 mU/liter vs. 5.7 +/- 0.9 mU/liter) and HOMA scores (2.0 +/- 0.2 vs. 1.1 +/- 0.2) and lower plasma glucose disappearance rate values (5.2 +/- 0.2 vs. 6.0 +/- 0.3) than control subjects. However, patients with IGT were notably more obese than the patients with a normal glucose tolerance test. Analyses after omitting the patients with IGT showed that there was still a significant (P < 0.05) difference in terms of basal insulin levels and HOMA scores. Six of eight (75%) obese patients with IH showed IGT. These data suggest that IH is associated with insulin resistance and an increased prevalence of IGT in obese patients.     

2型糖尿病患者血清乳酸脱氢酶与胰岛素抵抗的相关性

目的探讨2型糖尿病(T2DM)患者血清乳酸脱氢酶(LDH)与胰岛素抵抗的相关性。方法选取2016年10月至2017年12月安徽省马鞍山市人民医院内分泌科住院的T2DM患者138例。患者入院后行口服葡萄糖耐量试验(OGTT),即清晨空腹状态下口服75 g葡萄糖,分别抽取口服葡萄糖前,口服葡萄糖后30、60、120 min静脉血,检测血糖及胰岛素水平。根据稳态模型胰岛素抵抗(HOMA-IR)指数标准将患者分为HOMA-IR<2.5组(50例)和HOMA-IR≥2.5组(88例)。收集并比较2组患者一般资料、相关生化指标、LDH及Matsuda胰岛素敏感指数(Matsuda ISI)等数据。根据LDH三分位数水平将患者分为<172 IU/L、172~197 IU/L和>197 IU/L 3个亚组,比较3个亚组胰岛β细胞功能相关指标HOMA-IR和Matsuda ISI及其他相关指标。采用SPSS 24.0统计软件进行分析。根据数据类型,组间比较采用独立样本t检验、Mann-Whitney U检验、χ2检验、单因素方差分析或Kruskal-Wallis H检验。指标相关性采用Spearman非参数相关分析。多因素logistic回归用于评估发生胰岛素抵抗的危险因素。结果与HOMA-IR<2.5组比较,HOMA-IR≥2.5组患者LDH、空腹血糖、各时间点胰岛素等显著升高,Matsuda ISI显著降低,差异有统计学意义(P<0.05)。<172 IU/L、172~197 IU/L和>197 IU/L 3个亚组中HOMA-IR≥2.5人数分别占50.00%(23/46)、52.17%(24/46)和89.13%(41/46)。随着LDH水平升高,HOMA-IR显著升高,Matsuda ISI显著降低,同时3亚组OGTT各时间点胰岛素不同,差异有统计学意义(P<0.05)。相关分析显示,LDH与HOMA-IR呈正相关(r=0.289,P<0.05),与Matsuda ISI呈负相关(r=-0.314,P<0.001)。校正年龄等相关因素后,多因素logistic回归分析显示,LDH为发生胰岛素抵抗的独立预测因素之一(OR=2.99,95%CI 1.83~4.67;P<0.001)。结论LDH与胰岛β细胞功能指标HOMA-IR及Matsuda ISI存在显著相关性,可以作为简单易行的指标来初步评估T2DM患者胰岛素抵抗的严重程度,协助调整治疗方案。     

Measuring insulin sensitivity in postmenopausal women covering a range of glucose tolerance: comparison of indices derived from the oral glucose tolerance test with the euglycemic-hyperinsulinemic clamp

This study compares indices of insulin sensitivity derived from fasting and oral glucose tolerance test (OGTT) glucose and insulin measurements, with respect to the reference measure (M/I), obtained from the euglycemic-hyperinsulinemic clamp, in postmenopausal women with varying glucose tolerance status. Fasting plasma insulin index, homeostasis model assessment index, and OGTT-derived indices (insulin 120-minute, Matsuda, metabolic clearance rate [MCR] of glucose, insulin sensitivity [ISI], and Cederholm indices) were calculated and compared with the M/I value in 112 postmenopausal women. All indices examined were significantly correlated with M/I (0.28 < or = r(2) < or = 0.56). Association studies revealed that on average, 48% of women were grouped in the same tertile of insulin sensitivity when using M/I and fasting plasma insulin index, and 54% when using M/I and insulin 120-minute index. However, concordance with M/I tertiles were 57%, 58%, 64%, 64%, and 68% for homeostasis model assessment, Matsuda, MCR, ISI, and Cederholm indices, respectively. Finally, correlation coefficients between M/I and insulin sensitivity indices were generally lower in women with normal glucose tolerance compared with women with impaired glucose tolerance or type 2 diabetes mellitus. These results suggest that in postmenopausal women, surrogate indices of insulin sensitivity obtained from OGTT data and incorporating a measurement of body weight or body mass index) (Cederholm, ISI, and MCR indices) appear to be superior to those without OGTT data or body weight-body mass index measurements and, therefore, could offer a better estimate of insulin sensitivity, allowing an improved clinical evaluation of this population at higher risk of cardiovascular disease and type 2 diabetes mellitus.     

Validation of the insulin sensitivity index (ISI(0,120)): comparison with other measures

The purpose of this study was to explore possible calculations using oral glucose tolerance test (OGTT) values in order to develop a simple measure of insulin sensitivity. We devised a formula for an insulin sensitivity index, ISI(0,120), that uses the fasting (0 min) and 120 min post-oral glucose (OGTT) insulin and glucose concentrations. It appears to be generalizable across a spectrum of glucose tolerance and obesity. Most importantly, our data show that ISI(0,120) correlates well, when applied prospectively in comparative studies, with the insulin sensitivity index obtained from the euglycemic hyperinsulinemic clamp (r = 0.63, P < 0.001). This correlation was demonstrably superior to other indices of insulin sensitivity such as the HOMA formula presented by Matthews, and performed comparably to the computerized HOMA index. Measurement of insulin sensitivity has traditionally been possible only in research settings because of the invasiveness and expense of the methods used. Clinical investigators have therefore sought more practical methods to obtain an index of insulin sensitivity. Such an index should approximate insulin sensitivity as measured by the euglycemic hyperinsulinemic clamp (M). We present ISI(0,120), a simple yet sensitive measure of insulin sensitivity which is adaptable for use in clinical settings as well as large epidemiologic studies.     

Comparison between beta-cell function and insulin resistance indexes in prepubertal and pubertal obese children

Several methods have been developed to assess insulin resistance (IR), insulin secretion, and sensitivity: some of them, such as the homeostasis model assessment (HOMA) for IR (HOMA IR) and for insulin secretion (HOMA beta cell) and the quantitative insulin sensitivity check index (QUICKI) are based on fasting levels of glucose (fasting G) and insulin (fasting I); others, such as the pancreatic insulin response to glucose (IRG) and the insulin sensitivity index (ISI) are derived from the glycemic and insulinemic responses to the oral glucose tolerance test (OGTT). The aim of the study was to compare these indexes in a large group of prepubertal and pubertal obese subjects and verify whether the data from fasting samples were enough for evaluating IR and insulin secretion or if OGTT was mandatory. A total of 405 obese subjects (221 boys and 184 girls) was studied. Ninty-three were prepubertal (Tanner stage I), 98 early pubertal (stage II to III) and 214 late pubertal (stage IV to V). In each subject, a 120-minute OGTT was performed, and the glycemic (mean blood glucose [MBG]) and insulinemic (mean serum insulin [MSI]) responses, expressed as AUC/120, as well as IRG and ISI were calculated. The fasting I/fasting G ratio (FIGR), HOMA IR, HOMA beta cell, and QUICKI were then measured. FIGR and HOMA IR increased in both sexes during puberty, but in girls, the increase was already evident from stage I to stage II to III, while in boys, it was evident only from stage II to III to stage IV to V. QUICKI decreased in girls at the onset of puberty and was lower than in boys in stage II to III; on the other hand, HOMA beta cell did not show any variation. IRG increased throughout puberty, although it was higher in boys than in girls in stages II to III and IV to V, while ISI decreased at the onset of puberty in boys; HOMA IR correlated with MSI and IRG, and HOMA beta cell with MSI in pubertal subjects only. In conclusion, the indexes deriving from fasting samples, such as FIGR and HOMA IR, proved to be enough for evaluating IR in prepubertal and pubertal obese subjects, as did QUICKI for insulin sensitivity, However, OGTT is still useful for assessing insulin secretion, because IRG is more sensitive in depicting the pubertal variations of IR than HOMA beta cell.     

Elevated total and central adiposity and low physical activity are associated with insulin resistance in children

The aim of this study was 2-fold: (1) to examine insulin resistance, blood lipid levels, and inflammatory markers in 9- to 11.5-year-old obese and lean children and (2) to identify factors that influence insulin resistance in this cohort of youths. Body mass index, skinfold thickness, waist circumference, physical activity (4-day triaxial accelerometer), cardiorespiratory fitness (submaximal bicycle ergometer test), and dietary intake (3-day food records) were evaluated in 27 obese and 27 lean boys and girls. Fasting blood samples were analyzed for insulin, glucose, lipids and lipoproteins, C-reactive protein (CRP), interleukin 6, soluble intercellular adhesion molecule, and soluble vascular cell adhesion molecule. Homeostasis model assessment (HOMA) was used to evaluate insulin resistance (HOMA-IR). Obese children presented higher HOMA-IR, CRP, and blood lipid levels (all P < .01) compared with lean children. Total body fat and waist circumference were positively associated with fasting insulin (r > or = 0.51), HOMA-IR (r > or = 0.56), CRP (r > or = 0.51), and blood triacylglycerol (r > or = 0.38), and were inversely correlated with high-density lipoprotein cholesterol (r > or = -0.39; all P < .01). Cardiorespiratory fitness was inversely associated with HOMA-IR (r = -0.24; P < .05), but this association disappeared when adjusted for age, sex, and fat mass. Waist circumference and total daily physical activity explained 49% of the variance in HOMA-IR in these children. In conclusion, these findings suggest that total and central adiposity are positively associated and physical activity is negatively associated with insulin resistance in children. Interventions to improve glucose metabolism in youth should target at reducing total body and abdominal fat and increasing physical activity. The lack of association between inflammatory markers and HOMA-IR suggests that obesity may precede the elevation of these markers in the evolution of insulin resistance in youth.     

Insulin resistance in hypertensives: effect of salt sensitivity, renin status and sodium intake

OBJECTIVE: Homeostasis Model Assessment (HOMA index) is predictive of insulin sensitivity in normal and diabetic patients. This study was designed to see if insulin resistance in hypertensives, measured using the HOMA index, differs, based on salt sensitivity, renin status and sodium intake. METHODS: Fasting insulin and glucose were determined in subsets of 426 essential hypertensives, and normotensives. HOMA was calculated as fasting glucose (mmol) x fasting insulin (muU/ml)/22.5. RESULTS: Four hundred and twenty-six essential hypertensives and normotensives from four HERMES centers form the basis of this report. There was no difference in the HOMA index between hypertensives and normotensives (P= 0.291) or between hypertensives grouped according to blood pressure salt sensitivity (P = 0.153). However, when essential hypertensives were subgrouped by renin status, the low-renin group had significantly lower (P< 0.01) HOMA index than the normal/high-renin group. When normal/high-renin group was divided into modulators and non-modulators, the nonmodulators had significantly higher HOMA index (P< 0.001) than other hypertensive subsets. The effect of sodium intake on the HOMA index was significant only for non-modulators (P< 0.002), with salt restriction increasing insulin resistance. CONCLUSION: Insulin sensitivity differs among subsets of essential hypertension, non-modulators being most insulin resistant and the low-renin subset insulin sensitive. Salt restriction might have an adverse effect on insulin sensitivity in non-modulators. The reduction in cardiovascular risk seen in low-renin hypertensives may be related to their increased insulin sensitivity; in contrast, the clustering of cardiovascular risk factors seen in nonmodulators may be due to increased insulin resistance.