Limitation of the homeostasis model assessment to predict insulin resistance and beta-cell dysfunction in older people

CONTEXT: Studies in older people have shown inconsistent agreement between homeostasis model assessment of insulin resistance (HOMA-IR) and dynamic measures of insulin action and have not evaluated HOMA beta-cell. OBJECTIVE: We compared measures of insulin sensitivity and beta-cell function from the frequently sampled iv glucose tolerance test (FSIGT) to HOMA models. DESIGN/PATIENTS/SETTING/INTERVENTION: Two hundred fourteen young and old with normal glucose tolerance (NGT) and old with impaired glucose tolerance (IGT) participated in a retrospective analysis of FSIGT data in a university medical setting. MAIN OUTCOME MEASURE: Sensitivity to insulin (S(I)) and acute insulin response to glucose (AIRg) from FSIGT were compared with HOMA models. RESULTS: S(I) and HOMA-IR measures identified similar patterns of increasing insulin resistance in the two older groups, compared with younger people with NGT, with the greatest degree of insulin resistance in older people with IGT (P < 0.05 vs. young and old NGT for both S(I) and HOMA-IR). Agreement between HOMA-IR and S(I) was moderate (weighted kappa = 0.51). AIRg was similar in young and old NGT but was markedly decreased in old IGT (P < 0.05 vs. young and old NGT). HOMA-beta-cell was similar in the three groups. Agreement between HOMA beta-cell and AIRg was weak (weighted kappa = 0.35). CONCLUSIONS: HOMA-IR may detect age-related insulin resistance when comparing large populations of older people. However, dynamic testing appears to be necessary to quantitate diminished insulin secretion in older people.     

Short-term exercise improves beta-cell function and insulin resistance in older people with impaired glucose tolerance

BACKGROUND: There is a high prevalence of diabetes and impaired glucose tolerance (IGT) in the older population. Normal aging is associated with insulin resistance and impaired insulin secretion, with greater defects in people with IGT. Short-term exercise has been found to increase insulin sensitivity, but little is known about acute exercise effects on beta-cell function in older people with IGT. METHODS: We assessed the effects of 7 consecutive days of supervised aerobic exercise (1 h/d at 60-70% heart rate reserve) in 12 sedentary older people with IGT. Screening included oral glucose tolerance test, stress/maximal O(2) uptake test, and dual-energy x-ray absorptiometry scan. Participants had a frequently sampled iv glucose tolerance test at baseline and 15-20 h after the seventh exercise session. Insulin sensitivity (S(I)), glucose disappearance constant (Kg, a measure of iv glucose tolerance), acute insulin response to glucose (AIRg), and disposition index (AIRg x S(I)), a measure of beta-cell function in relation to insulin resistance, were calculated. RESULTS: Exercise was well tolerated. Body weight, fasting glucose, fasting insulin, and iv glucose tolerance were unchanged with exercise. S(I) increased by 59%, AIRg decreased by 12%, and disposition index increased by 31%. There was no significant change in fasting lipid, catecholamine, leptin, or adiponectin levels. CONCLUSIONS: Short-term exercise not only improved insulin resistance but also significantly enhanced beta-cell function in older people with IGT. These effects of short-term exercise on beta-cell function cannot be explained by changes in body weight or circulating levels of lipids, leptin, adiponectin, or catecholamines.     

Differences in insulin resistance and pancreatic B‐cell function in obese subjects with isolated impaired glucose tolerance and isolated impaired fasting glucose

Aims To investigate changes in insulin action and insulin secretion in obese subjects with different categories of impaired glucose regulation (IGR): impaired glucose tolerance (IGT), impaired fasting glucose (IFG), and combined IFG/IGT (CGI). Methods A total of 222 subjects underwent an oral glucose tolerance test and a frequently sampled intravenous glucose tolerance test (FSIGTT); 100 had normal glucose tolerance (subdivided into 32 lean NGT, 68 obese NGT), and 122 were obese with IGR (82 IGT, 14 IFG and 26 CGI). The insulin sensitivity index (S_I) was assessed by Bergman's minimal model method with FSIGTT; insulin secretion was determined by acute insulin response to glucose (AIRg). The disposition index (DI), the product of AIRg and S_I, was used to determine whether AIRg was adequate to compensate for insulin resistance. Results S_I was similar in NGT and IGR obese subgroups. AIRg was significantly increased in obese NGT as compared with lean NGT, significantly reduced in IGT, and further reduced in IFG and CGI subjects as compared with obese NGT subgroups. DI was reduced in NGT obese individuals. Within the obese IGR subgroups, IFG and CGI subjects had even lower DI value than IGT subjects. Conclusions Obese Chinese subjects with IGR have a similar degree of insulin resistance but differ in insulin secretion. Subjects with IFG and CGI have a more prominent deficiency in insulin secretion than subjects with IGT.     

Insulin sensitivity and first-phase insulin secretion in obese Chinese with hyperglycemia in 30 and/or 60 min during glucose tolerance tests

The purpose of this study was to investigate insulin sensitivity and first-phase insulin secretion in obesity with hyperglycemia in 30 and/or 60 min during oral glucose tolerance (OGTT, glucose > or = 11.1 mmol/l, post-loading hyperglycemia, PLH) in Chinese population. A total of 196 nondiabetic subjects were included in the present study, among them 99 had normal glucose tolerance (NGT, subdivided into 32 lean NGT and 67 obese NGT), 74 had obesity with impaired glucose tolerance (IGT) and 23 had obesity with PLH. A standard 75-g oral glucose tolerance test was performed after fasting and at 30 min, 1, 2 and 3 h. Insulin sensitivity index (S(I)) was assessed by the Bergman's minimal model method with frequently sampled intravenous glucose tolerance test (FSIGTT), insulin secretion was determined by acute insulin response to glucose (AIRg). The disposition index (DI), the product of AIRg and S(I) was used to determine whether AIRg was adequate to compensate for insulin resistance. S(I) was significantly equally lower in three obese subgroups. AIRg was significantly increased in obese NGT as compared with lean NGT controls, and reduced to the same extent in IGT and PLH subjects. There was no significant difference among lean NGT, IGT and PLH subjects. DI value was reduced from obese NGT individuals, IGT and PLH subjects had a similar lower level of DI. In conclusion, our present results demonstrated that the pathophysiological basis of obese subjects with PLH were clearly insulin resistance and defective in first-phase insulin secretion as that in IGT subjects in Chinese population.     

Different contributions of insulin resistance and beta-cell dysfunction in overweight Israeli Arabs with IFG and IGT

BACKGROUND: Impaired glucose tolerance (IGT) and impaired fasting glucose (IFG) are both intermediate stages that exist between normal glucose tolerance and overt type 2 diabetes. Epidemiological studies demonstrated that the two categories define distinct populations. In this study, we examined the contributions of insulin resistance and beta-cell dysfunction to both states in overweight subjects of Arab origin. METHODS: Twelve subjects with isolated IFG, 10 with isolated IGT, and 20 with IFG and IGT (combined glucose in tolerance-CGT) were compared with 30 subjects with normal glucose tolerance (NGT) subjects; all were of Arab origin and were overweight or obese. Different indices for insulin resistance and beta-cell function were calculated from oral glucose tolerance (OGTT) values. RESULTS: Subjects with isolated IFG and CGT were more obese and had significantly higher values of insulin resistance than subjects with isolated IGT and NFG. There was no significant difference between the insulin resistance in subjects with isolated IGT and that in subjects with NGT. Indices of beta cell function were severely reduced among subjects with isolated IGT and CGT when compared with those with both isolated IFG and NGT, while subjects with isolated IFG had similar beta-cell indices to subjects with NGT. CONCLUSION: These data demonstrate that beta-cell dysfunction and insulin resistance contribute differently to the pathogenesis of IFG and IGT among overweight Arab subjects.     

The Impact of a Family History of Type 2 Diabetes on Insulin Secretion and Insulin Sensitivity in Individuals With Varying Glucose Tolerance

IntroductionThis study was performed to investigate the impact of a family history of type 2 diabetes (T2DM) on insulin resistance and beta-cell dysfunction in populations with varying glucose tolerance.MethodsAmong the total of 142 participants, 73 subjects with no family history of T2DM (FH?) included 42 with normal glucose tolerance (NGT/FH?) and 31 with impaired glucose tolerance (IGT/FH?); and 69 first-degree relatives of patients with T2DM (FH+) included 36 with NGT (NGT/FH+) and 33 with IGT (IGT/FH+). Insulin resistance was evaluated by Insulin Sensitivity Index (ISI) based on the euglycemic hyperinsulinemic clamp. Islet beta-cell function was assessed by disposition index (DI) for the acute insulin response to glucose (AIRg) using intravenous glucose tolerance test. Metabolic data were compared between groups after adjustment for age, sex, body mass index and waist-to-hip ratio.ResultsThe NGT/FH+ group showed lower level of ISI (P = 0.023) than the NGT/FH? group, whereas no difference was found in AIRg or DI between these 2 subgroups. In the FH? individuals, both ISI and DI of the IGT/FH? group decreased compared with the NGT/FH? group (both P < 0.05). In the FH+ individuals, no difference was found in ISI between the IGT/FH+ and NGT/FH+ groups, whereas the IGT/FH+ group had a lower level of AIRg and DI than the NGT/FH+ group (both P < 0.0001).ConclusionsThis study showed that the pathophysiological changes were different between individuals with and without a family history of T2DM during the glucose tolerance aggravation.     

beta-Cell function in subjects spanning the range from normal glucose tolerance to overt diabetes: a new analysis

The nature of the progressive beta-cell failure occurring as normal glucose tolerant (NGT) individuals progress to type 2 diabetes (T2DM) is incompletely understood. We measured insulin sensitivity (by a euglycemic insulin clamp) and insulin secretion rate (by deconvolution of plasma C-peptide levels during an oral glucose tolerance test) in 188 subjects [19 lean NGT (body mass index [BMI] 相似文献   

Insulin secretion and insulin sensitivity at different stages of glucose tolerance: a cross-sectional study of Japanese type 2 diabetes

To evaluate the factors causing glucose intolerance in type 2 diabetes in Japan, insulin secretion and insulin sensitivity were compared across the range of glucose tolerance. Subjects were divided into 3 groups: normal glucose tolerance (NGT), impaired glucose tolerance (IGT), and type 2 diabetes (DM) according to the criteria of the World Health Organization (WHO). We examined insulin secretion and insulin sensitivity using fasting blood glucose and insulin levels and 75 g oral glucose tolerance test (OGTT). We used homeostasis model assessment (HOMA) beta-cell and insulinogenic index (30 minutes) to estimate insulin secretion and HOMA-insulin resistance (IR) and insulin sensitivity index (ISI) composite for insulin sensitivity. Although insulin resistance plays an important role in the development of diabetes in many ethnic populations, the differences in insulin sensitivity between NGT and IGT and between IGT and DM are small in Japanese patients. On the other hand, as glucose intolerance increases, insulin secretion decreases most remarkably both between NGT and IGT and between IGT and DM in Japanese patients. Decreasing insulin secretion and decreasing insulin sensitivity both occur in developing type 2 diabetes in Japanese patients, but decreased basal and early-phase insulin secretion had more pronounced contribution to glucose tolerance than the indices of insulin sensitivity. Japanese type 2 diabetic patients are characterized by a larger decrease in insulin secretion and show less attribution of insulin resistance.     

1193例住院高血压病患者胰岛素分泌和敏感性情况

目的用口服葡萄糖耐量试验中各点血糖和胰岛素的值来计算反映胰岛素敏感性及β细胞功能的参数,回顾性研究住院高血压病人糖代谢情况。方法根据WHO和美国糖尿病协会标准计算血糖分布情况,去除新诊断的糖尿病病人后,分成正常血糖(NGT)、单纯性空腹血糖升高(IFG)、单纯性餐后血糖升高(IGT)和空腹、餐后血糖均升高(IFG,／IGT)组进行比较。再分别以口服75g葡萄糖后30min或60min血糖正常值为标准对NGT组和IGT组进行分组。用HOMA-IR和Composite胰岛素敏感性指数(ISI)计算胰岛素敏感性,HOMA-B和△I／AG计算β细胞功能。结果1193例住院的原发性高血压病人中,新诊断的糖尿病病人为11．1％,其中57．9％仅有餐后血糖升高。IGT、和IFG／ICT组的HOMA-IR高于NGT组,Composite ISI和AI／AG低于NGT组。无论是否30min或60min血糖升高,IGT组的Composite ISI均低于30min和60min血糖正常的NGT组。30min和(或)60min血糖升高的NGT组△I／AG低于30min和60min血糖正常的NGT组。结论IGT或IFG／IGT的高血压患者同时存在空腹和总体胰岛素敏感性的下降和糖负荷后早期β细胞分泌功能的受损。30min和(或)60min血糖升高的NGT高血压病人存在糖负荷后早期β细胞分泌功能的受损。     

Pancreatic beta-cell function and insulin sensitivity in japanese subjects with impaired glucose tolerance and newly diagnosed type 2 diabetes mellitus

To clarify whether pancreatic beta-cell function and/or insulin resistance contributes to development of glucose intolerance in Japanese subjects, we investigated 551 subjects who underwent a 75-g oral glucose tolerance test (OGTT). Subjects were divided into 3 groups: normal glucose tolerance (NGT, n = 238), impaired glucose tolerance (IGT, n = 211), and newly diagnosed type 2 diabetes mellitus (n = 102). The diabetics were subdivided into 3 subgroups as follows: diabetes with normal fasting glucose (fasting plasma glucose [FPG] < 110 mg/dL), diabetes with impaired fasting glucose (FPG 110 to 125 mg/dL), and diabetes with diabetic fasting glucose (FPG >or= 126 mg/dL). Insulinogenic index as early-phase insulin secretion, homeostasis model assessment (HOMA-beta and HOMA-resistance), and 4 different formulas of insulin sensitivity index were assessed by plasma glucose and insulin concentrations obtained at fasting or during a 75-g OGTT. Both early-phase insulin secretion and insulin sensitivity were low even in the IGT stage compared with NGT. The transition from IGT to diabetes was accompanied by a progressive deterioration of insulin reserve as well as insulin resistance. During the further progression in diabetes, insulinogenic index decreased additionally, whereas declines in insulin sensitivity were relatively small. In conclusion, both impaired insulin secretion and insulin resistance may contribute to the underlying mechanisms of glucose intolerance in Japanese subjects.     

Impaired beta-cell function in the presence of reduced insulin sensitivity determines glucose tolerance status in acromegalic patients

OBJECTIVE: Abnormal glucose tolerance is often demonstrated in acromegalic patients. Although insulin resistance is a common feature of acromegaly, it remains unclear whether the extent of insulin resistance per se determines the abnormal glucose tolerance. In order to elucidate this issue, we investigated insulin sensitivity and beta-cell function in acromegalic patients. DESIGN: Twenty-four acromegalic patients were studied in comparison with 24 healthy control subjects. To estimate insulin sensitivity and beta-cell function, we used correct homeostasis model assessment (HOMA) model, a computer-solved model. We also investigated the effects of surgical success on both parameters. RESULTS: HOMA insulin sensitivity (HOMA-%S) in the acromegalic patients was 74 +/- 51 (SD)%, significantly lower than that in 24 healthy controls (144 +/- 49%). HOMA-%S in 12 normal glucose tolerance (NGT) patients was 54 +/- 31%, not significantly different from that in impaired glucose tolerance (IGT; n = 11) or diabetes mellitus (DM; n = 1) patients (93 +/- 60%). By contrast, HOMA beta-cell function (HOMA-%beta) in the NGT acromegalic patients was 163 +/- 67%, significantly higher than the IGT/DM acromegalic patients (89 +/- 34%) and the healthy controls (72 +/- 19%). In 11 patients who achieved complete normalization of GH excess after surgery, HOMA-%S significantly increased to control ranges (from 76 +/- 26 to 159 +/- 61%) within 2 weeks after the surgical success. CONCLUSIONS: We conclude that insulin sensitivity is reduced to a similar extent in acromegalic patients with normal glucose tolerance and those with impaired glucose tolerance or diabetes. Compensatory hyperfunction of beta-cells appears to counterbalance the reduced insulin sensitivity in the acromegalic patients with normal glucose tolerance but not in those with impaired glucose tolerance or diabetes.     

Impaired early- but not late-phase insulin secretion in subjects with impaired fasting glucose

Subjects with impaired fasting glucose (IFG) are at increased risk for type 2 diabetes. We recently demonstrated that IFG subjects have increased hepatic insulin resistance with normal insulin sensitivity in skeletal muscle. In this study, we quantitated the insulin secretion rate from deconvolution analysis of the plasma C-peptide concentration during an oral glucose tolerance test (OGTT) and compared the results in IFG subjects with those in subjects with impaired glucose tolerance (IGT) and normal glucose tolerance (NGT). One hundred and one NGT subjects, 64 subjects with isolated IGT, 24 subjects with isolated IFG, and 48 subjects with combined (IFG + IGT) glucose intolerance (CGI) received an OGTT. Plasma glucose, insulin, and C-peptide concentrations were measured before and every 15 min after glucose ingestion. Insulin secretion rate (ISR) was determined by deconvolution of plasma C-peptide concentration. Inverse of the Matsuda index of whole body insulin sensitivity was used as a measure of insulin resistance; 56 subjects also received a euglycemic hyperinsulinemic clamp. The insulin secretion/insulin resistance (disposition) index was calculated as the ratio between incremental area under the ISR curve (∆ISR[AUC]) to incremental area under the glucose curve (∆G[AUC]) factored by the severity of insulin resistance (measured by Matsuda index during OGTT or glucose disposal during insulin clamp). Compared to NGT, the insulin secretion/insulin resistance index during first 30 min of OGTT was reduced by 47, 49, and 74% in IFG, IGT, and CGI, respectively (all < 0.0001). The insulin secretion/insulin resistance index during the second hour (60–120 min) of the OGTT in subjects with IFG was similar to that in NGT (0.79 ± 0.6 vs. 0.72 ± 0.5, respectively, P = NS), but was profoundly reduced in subjects with IGT and CGI (0.31 ± 0.2 and 0.19 ± 0.11, respectively; P < 0.0001 vs. both NGT and IFG). Early-phase insulin secretion is impaired in both IFG and IGT, while the late-phase insulin secretion is impaired only in subjects with IGT.     

Metabolic abnormalities underlying the different prediabetic phenotypes in obese adolescents

OBJECTIVE: The aim of this study was to define the metabolic abnormalities underlying the prediabetic status of isolated impaired fasting glucose (IFG), isolated impaired glucose tolerance (IGT), and combined IFG/IGT in obese youth. RESEARCH DESIGN AND METHODS: We used state-of-the-art techniques (hyperinsulinemic-euglycemic and hyperglycemic clamps), applying a model of glucose-stimulated insulin secretion to the glucose and C-peptide concentration, in 40 normal glucose tolerance (NGT), 17 IFG, 23 IGT, and 11 IFG/IGT obese adolescents. Percent fat (by dual-energy x-ray absorptiometry), age, gender and ethnicity were comparable among groups. RESULTS: Peripheral insulin sensitivity was similar between the IFG and NGT groups. In contrast, the IGT and IFG/IGT groups showed marked reductions in peripheral insulin sensitivity (P < 0.002). Basal hepatic insulin resistance index (basal hepatic glucose production x fasting plasma insulin) was significantly increased in IFG, IGT, and IFG/IGT (P < 0.009) compared with NGT. Glucose sensitivity of first-phase insulin secretion was progressively lower in IFG, IGT, and IFG/IGT compared with NGT. Glucose sensitivity of second-phase secretion showed a statistically significant defect only in the IFG/IGT group. In a multivariate regression analysis, glucose sensitivity of first-phase secretion and basal insulin secretion rate were significant independent predictors of FPG (total r(2) = 25.9%). CONCLUSIONS: IFG, in obese adolescents, is linked primarily to alterations in glucose sensitivity of first-phase insulin secretion and liver insulin sensitivity. The IGT group is affected by a more severe degree of peripheral insulin resistance and reduction in first-phase secretion. IFG/IGT is hallmarked by a profound insulin resistance and by a new additional defect in second-phase insulin secretion.     

Relative conributions of beta-cell function and tissue insulin sensitivity to fasting and postglucose-load glycemia

We performed hyperglycemic clamps in 283 nondiabetic Caucasians and, with multiple linear regression, determined the contribution of beta-cell function and tissue insulin sensitivity to variations in glycemia and insulinemia during oral glucose tolerance tests (OGTTs). Impaired glucose tolerance (IGT) subjects had reduced insulin sensitivity (P < .02) and beta-cell function (P < .0001). Normal glucose tolerance (NGT) subjects with first-degree type 2 diabetic relatives had reduced first and second phase insulin secretion (both, P < .05), but normal insulin sensitivity (P = .37). Beta-Cell function and insulin sensitivity accounted for one fourth of the variability in glucose tolerance. Fasting plasma glucose in subjects with NGT (n = 185) was a function of both phases of insulin secretion and of insulin sensitivity (all, P < .05), whereas, in IGT subjects (n = 98), it was a function of first phase insulin secretion and insulin sensitivity (P < .01). Two-hour glycemia was a function of second phase secretion and insulin sensitivity (P < .01). Fasting and 2-hour plasma insulin levels were determined by insulin sensitivity (and glycemia) in NGT subjects (P < .001), but by second phase secretion in IGT (P < .001). We conclude that beta-cell function is reduced in subjects with IGT; glycemia and insulinemia are not regulated by the same mechanisms in IGT and NGT; insulin sensitivity does not contribute to insulinemia in IGT; family history of diabetes influences beta-cell function, but not insulin sensitivity in Caucasians.     

不同糖耐量水平人群血清真胰岛素和胰岛素原水平的临床意义

目的 探讨不同糖耐量者血清真胰岛素（ＴＩ）及胰岛素原（ＰＩ）水平的变化及临床意义。方法 用特异的单克隆抗体夹心放大酶联免疫分析法（ＢＡ－ＥＬＩＳＡ）检测１３５例正常糖耐量（ＮＧＴ）、８６例糖耐量低减（ＩＧＴ）及１０１例Ⅱ型糖尿病（ＤＭ）者口服葡萄糖耐量试验（ＯＧＴＴ）各点血清ＴＩ及ＰＩ水平。结果 ３组血清空腹ＴＩ差异无显著性（Ｐ〉０．０５）,免疫反应胰岛素（ＩＲＩ）Ⅱ型ＤＭ组明显升高（Ｐ〈０．０１     

In middle-aged siblings of patients with type 2 diabetes mellitus normal glucose tolerance is associated with insulin resistance and with increased insulin secretion. The SPIDER study

OBJECTIVES: To evaluate the frequency of impaired glucose tolerance (IGT) and of Type 2 diabetes mellitus (Type 2 DM) in siblings of patients with Type 2 DM, and to assess insulin release and insulin sensitivity in siblings with normal glucose tolerance (NGT), compared with NGT spouses of probands without family history of Type 2 DM. DESIGN AND METHODS: We evaluated 87 families including 103 Type 2 DM patients (87 probands), and we carried out an oral glucose tolerance test (OGTT) in 130 siblings and in 60 spouses. Among NGT subjects, 12 siblings and 16 spouses underwent a low-dose insulin-glucose infusion test (LDIGIT) to evaluate C-peptide release and insulin sensitivity. RESULTS: After the OGTT, 24 siblings were classified as having Type 2 DM, 31 as IGT, and only 14 spouses as IGT (P=0.0012 vs siblings). NGT siblings (n=75) showed higher insulin levels at 120 min than NGT spouses (n=46) at OGTT, in spite of identical blood glucose levels; at LDIGIT, NGT siblings secreted more C-peptide and showed a lower insulin sensitivity than NGT spouses. CONCLUSIONS: These data indicate that middle-aged siblings of probands with Type 2 DM have a high frequency of IGT and Type 2 DM, and that NGT siblings have increased insulin resistance and increased insulin secretion when compared with adequate controls.     

Failure to adequately adapt reduced insulin sensitivity with increased insulin secretion in women with impaired glucose tolerance

Summary To study the islet adaptation to reduced insulin sensitivity in normal and glucose intolerant post-menopausal women, we performed a euglycaemic, hyperinsulinaemic clamp in 108 randomly selected women, aged 58–59 years. Of the 20 women with the lowest insulin sensitivity, 11 had impaired glucose tolerance (IGT) whereas 9 had normal glucose tolerance (NGT). These women together with 15 women with medium insulin sensitivity and 16 women with high insulin sensitivity and NGT were further examined with arginine stimulation at three glucose levels (fasting, 14 and >25 mmol/l). In NGT, the acute insulin response (AIR) to 5 g i. v. arginine at all three glucose levels and the slope_AIR, i. e. the glucose potentiation of insulin secretion, were markedly increased in the women with the lowest insulin sensitivity and NGT compared to those with medium or high insulin sensitivity. In contrast, in low insulin sensitivity, AIR was significantly lower in IGT than in NGT (at glucose 14 mmol/l p=0.015, and at >25 mmol/l p=0.048). The potentiation of AIR induced by low insulin sensitivity in women with NGT was reduced by 74% (AIR at 14 mmol/l glucose) and 57% (AIR at >25 mmol/l glucose), respectively, in women with IGT. Also the slope_AIR was lower in IGT than in NGT (p=0.025); the increase in slope_AIR due to low insulin sensitivity was abolished in IGT. In contrast, glucagon secretion was not different between women with IGT as opposed to NGT. We conclude that as long as there is an adequate beta-cell adaptation to low insulin sensitivity with increased insulin secretory capacity and glucose potentiation of insulin secretion, NGT persists.Abbreviations NIDDM Non-insulin-dependent diabetes mellitus - AIR acute insulin response - AGR acute glucagon response     

Insulin resistance and impaired glucose tolerance in obese children and adolescents referred to a tertiary-care center in Israel

OBJECTIVE: To establish the prevalence of insulin resistance and impaired glucose tolerance (IGT) and their determinants in a cohort of obese children and adolescents. METHODS: A retrospective design was used. The study group included 234 patients with a body mass index (BMI) greater than the 95th percentile for age and gender and 22 patients with a BMI between the 85th and 95th percentile for age and gender referred for evaluation to a major tertiary-care center in Israel. Ages ranged from 5 to 22 y. Estimates of insulin resistance (homeostatic model assessment (HOMA-IR)); insulin sensitivity (ratio of fasting glucose (GF) to fasting insulin (IF) (GF/IF), the quantitative insulin sensitivity check index (QUICKI)), and pancreatic beta-cell function (HOMA-derived beta-cell function (HOMA %B)) were derived from fasting measurements. An oral glucose tolerance test (OGTT) was performed in 192 patients to determine the presence of IGT. RESULTS: Insulin resistance was detected in 81.2% of the patients, IGT in 13.5%, and silent diabetes in one adolescent girl. Only two patients with IGT also had impaired fasting glucose (IFG). The prevalence of IGT was higher in adolescents than prepubertal children (14.7 vs 8.6%). GF/IF and QUICKI decreased significantly during puberty (P<0.005), whereas HOMA-IR and HOMA %B did not. Insulin resistance and insulin sensitivity indexes were not associated with ethnicity, presence of acanthosis nigricans or family history of type 2 diabetes. Patients with obesity complications had lower insulin sensitivity indexes than those without (P=0.05). Compared with subjects with normal glucose tolerance (NGT), patients with IGT had significantly higher fasting blood glucose (85.9+/-6.5 vs 89.2+/-10.6 mg/dl, P<0.05), higher 2-h post-OGGT insulin levels (101.2+/-74.0 vs 207.6+/-129.7 microU/ml, P<0.001), a lower QUICKI (0.323+/-0.031 vs 0.309+/-0.022, P<0.05), and higher fasting triglyceride levels (117.4+/-53.1 vs 156.9+/-68.9, P=0.002). However, several of the fasting indexes except QUICKI failed to predict IGT. There was no difference between the group with IGT and the group with NGT in fasting insulin, HOMA-IR, HOMA %B or the male-to-female ratio, age, BMI-SDS, presence of acanthosis nigricans, ethnicity, and family history of type 2 diabetes.CONCLUSIONS:Insulin resistance is highly prevalent in obese children and adolescents. The onset of IGT is associated with the development of severe hyperinsulinemia as there are no predictive cutpoint values of insulin resistance or insulin sensitivity indexes for IGT, and neither fasting blood glucose nor insulin levels nor HOMA-IR or HOMA %B are effective screening tools; an OGTT is required in all subjects at high risk. Longitudinal studies are needed to identify the metabolic precursors and the natural history of the development of type 2 diabetes in these patients.     

Insulin secretion and incretin hormones after oral glucose in non-obese subjects with impaired glucose tolerance

Subjects with impaired glucose tolerance (IGT) are usually overweight and exhibit insulin resistance with a defective compensation of insulin secretion. In this study, we sought to establish the interrelation between insulin secretion and insulin sensitivity after oral glucose in non-obese subjects with IGT and we also examined this interrelation in relation to the 2 main incretins, glucagon-like peptide (GLP-1) and gastric inhibitory polypeptide (GIP). To that end, 13 women with IGT and 17 women with normal glucose tolerance (NGT) underwent an oral glucose tolerance test (OGTT) with measurements of glucose, insulin, C-peptide, GLP-1, and GIP. Insulin secretion (TIS) and insulin sensitivity (OGIS) were assessed using models describing the relationship between glucose, insulin and C-peptide data. These models allowed estimation also of the hepatic extraction of insulin. The age (54.2 +/- 9.7 [mean +/- SD] years) and body mass index (BMI; 26.0 +/- 4.0 kg/m(2)) did not differ between the groups. Subjects with IGT displayed lower TIS during the initial 30 minutes after oral glucose (0.97 +/- 0.17 [mean +/- SEM] v 1.75 +/- 0.23 nmol/L in NGT; P =.018) and lower OGIS (397 +/- 21 v 463 +/- 12 mL/min/m(2); P =.005). The incremental 30-minute TIS times OGIS (reflecting insulin secretion in relation to insulin sensitivity) was significantly reduced in IGT (359 +/- 51 v 774 +/- 91 nmol/min/m(2), P =.001). This measure correlated inversely to the 2-hour glucose level (r = -0.71; P <.001). In contrast, TIS over the whole 180-minute period was higher in IGT (26.2 +/- 2.4 v 20.0 +/- 2.0 nmol/L; P =.035). Hepatic insulin extraction correlated linearly with OGIS (r = 0.71; P <.001), but was not significantly different between the groups although there was a trend with lower extraction in IGT (P =.055). Plasma levels of GLP-1 and GIP increased after oral glucose. Total secretion of these incretin hormones during the 3-hour test did not differ between the 2 groups. However, the 30-minute increase in GLP-1 concentrations was lower in IGT than in NGT (P =.036). We conclude that also in non-obese subjects with IGT, when adiposity is controlled for in relation to NGT, defective early insulin secretion after oral glucose is a key factor. This defective beta-cell function is associated with, and may be caused by, a reduced early GLP-1 response.     

不同糖耐量者血清超敏C-反应蛋白表达及与胰岛素抵抗的相关性研究

目的探讨不同糖耐量者血清超敏C-反应蛋白(hs-CRP)的表达及与胰岛素抵抗的相关性。方法对2004年10月至2005年4月中国医科大学附属第一医院体检中心90名体检者(男53名,女37名),根据标准75g口服葡萄糖耐量试验(OGTT)分为正常糖耐量(NGT)组、单纯空腹血糖受损(IFG)组、单纯糖耐量异常(IGT)组、同时合并IFG/IGT组及2型糖尿病(T2DM)组,采用酶联免疫吸附(ELISA)法分别检测各组血清hs-CRP,并与稳态模型胰岛素抵抗指数(HOMA-IR)作相关分析。结果IFG组、IFG/IGT组及T2DM组hs-CRP均明显高于NGT组,并与糖代谢指标及HOMA-IR呈正相关。结论T2DM患者早在IFG阶段就已经存在炎症状态,炎症可能参与了T2DM的发生与发展。