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.     

阿托伐他汀对大鼠胰岛功能影响的量效和时效关系

目的 观察阿托伐他汀对Wistar大鼠胰岛功能及糖耐量的影响,研究其效应与剂量、时间的相关性.方法 将60只8周龄正常Wistar大鼠采用随机数字表法分为正常对照组(生理盐水2 ml/d,n=10)、低剂量阿托伐他汀组(阿托伐他汀5 mg· kg-1·d-1,n=1O)、中剂量阿托伐他汀组(阿托伐他汀25 mg·kg-1·d-1,n=10)和高剂量阿托伐他汀组(阿托伐他汀50 mg·kg-1·d-1,n=30).于干预第0、4、8周分别行口服葡萄糖耐量试验(OGTr),测定血糖、血清胰岛素,计算稳态模型评估-β细胞功能指数(HOMA-β)、第一时相胰岛素分泌指数(△I30/△G30)、稳态模型评估-胰岛素抵抗指数(HOMA-IR)、胰岛素曲线下面积(AUCi)、葡萄糖曲线下面积(AUCg)和处置指数.然后将高剂量阿托伐他汀组部分大鼠采用随机数字表法分为两组,继续给药组仍给予高剂量阿托伐他汀灌胃,洗脱组改为生理盐水灌胃,4周后再次行OGTT检测.并取血行甘油三酯、总胆固醇检测.结果 干预8周后高剂量阿托伐他汀组OGTT 0、15、30、60、120 min的胰岛素水平及HOMA-β、△I30/△G30、AUCi、AUCg、HOMA-IR均低于正常对照组(F=4.168 ～ 306.493,P均＜0.05);干预4周时各组及干预8周时中、低剂量阿托伐他汀组均未见相似效应(P均＞0.05).经4周药物洗脱期后,洗脱组的OGTT0、15、30、60、120 min胰岛素水平(F=4.64 ～ 15.58,P均＜0.05)及上述指标均高于继续给药组(t=29.044、4.433、4.429、2.964,P均＜0.05).但各剂量阿托伐他汀组间血糖和处置指数均未见明显影响(P均＞0.05).HOMA-β、△I30/△G30、AUCi随阿托伐他汀剂量的增加和时间的延长,均逐渐降低,具有剂量及时间依赖关系(F=213.970、63.839、18.222,P均＜0.01).HOMA-IR、AUCg随阿托伐他汀剂量的增加逐渐降低,随着时间的延长逐渐升高,也呈剂量及时间依赖关系(F=214.437,P ＜O.01;F=9.33,P ＜O.05).结论 阿托伐他汀可抑制大鼠胰岛β细胞胰岛素分泌,改善胰岛素敏感性,并与给药剂量和时间有关,但对血糖影响不明显.     

增龄对大鼠胰岛β细胞功能的影响

目的观察不同月龄大鼠的糖代谢指标变化,了解在基础和糖刺激下增龄对大鼠胰岛β细胞功能的影响。方法以4月龄（青年组,n=15）、14月龄（中年组,n=15）和24月龄（老年组,n=15）健康雄性Wistar大鼠为研究对象,进行口服葡萄糖耐量试验（OGTT）和胰岛素释放试验（IRT）,比较三组间基础血糖和胰岛素水平的差异,计算糖负荷后胰岛素增值与血糖增值的比值（ΔI10/ΔG10）,120min葡萄糖、胰岛素曲线下面积（AUCg,AUCi）,葡萄糖与胰岛素曲线下面积比值（AUCi/g）,胰岛素抵抗指数（HOMA-IR）,胰岛β细胞功能指数（HOMA-β）等,以分析各组间胰岛功能的差异。结果随着月龄的增长,空腹血糖有升高的趋势,但未达到统计学差异。OGTT后老年组大鼠表现为血糖达峰时间延长,血糖峰值增加,OGTT2h血糖及AUCg增加,即老年组大鼠出现糖耐量异常状态,主要表现为餐后高血糖。青年组、中年组和老年组大鼠空腹胰岛素水平分别为（0.59±0.14）、（1.60±0.15）、（2.37±0.04）μg/L（两两相比均P〈0.01）;IRT中,老年组大鼠胰岛素达峰时间延迟,ΔI10/ΔG10降低,AUCi增加（P〈0.05）。使用稳态模型评估,HOMA-β在青年、中年和老年组中呈递增趋势,但未达到统计学差异;而HOMA-IR在青年、中年和老年组分别为3.09±0.80、8.34±0.72、13.14±1.59（两两相比均P〈0.01）。结论正常老龄大鼠存在一定的胰岛素抵抗和代偿性胰岛素分泌增加,但由于胰岛素分泌的早期时相受损,仍然出现糖负荷后血糖增高状态。     

Decreased Beta cell function and insulin sensitivity contributed to coronary artery disease in patients with normal glucose tolerance

Aim: To investigate the association among insulin sensitivity, insulin secretion, beta cell function and coronary artery disease (CAD) in patients with normal glucose tolerance.Methods: One hundred eighty-nine patients with normal glucose tolerance (NGT) participated in this study and underwent coronary angiography. We estimated the severity of CAD by counting the number of diseased vessels and Gensini score using coronary angiography. The HOMA-IR index and Matsuda index were used to estimate insulin sensitivity. Insulin secretion was assessed using the HOMA-β index, insulinogenic index and AUC-insulin/glucose. Beta cell function was assessed using the basal disposition index, early-phase disposition index and total disposition index. We finally determined the relationship between CAD and these indices.Results: There were statistically significant differences in the HOMA-IR, Matsuda index, basal disposition index, early-phase disposition index and total disposition index both in the single- and multiple-diseased vessel groups when compared to the 0-diseased vessel group; however, there was no significant difference between the single- and multiple- diseased vessel groups. Moreover, HOMA-β, the insulinogenic index and AUC-ins/glu showed no significant difference among the three groups. Multivariate logistic regression analysis suggested that the HOMA-IR, Matsuda index, early-phase disposition index and total disposition index were independent risk factors for the presence of CAD.Conclusion: Insulin resistance and beta cell function were closely related to the incidence of CAD in patients with normal glucose tolerance.     

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.     

Timing of prenatal androgen excess determines differential impairment in insulin secretion and action in adult female rhesus monkeys

This study determined whether timing of prenatal androgen excess resulted in differential impairment of insulin-glucose homeostasis in adult female rhesus monkeys. Ten female rhesus monkeys exposed to testosterone propionate starting on gestational day 40 (early treated), 9 females exposed to testosterone propionate starting between gestational days 100-115 (late treated), and 15 control females were studied. The modified minimal model was used to examine various measures derived from an i.v. glucose tolerance test, with regression analysis performed between these variables and body mass index. In addition, the disposition index (DI) and the hyperbolic relationship between insulin sensitivity (S(I)) and acute insulin response to glucose were examined. Early treated females demonstrated impaired pancreatic beta-cell function, as shown by diminished DI and decreased percentile ranking for the hyperbolic relationship between S(I) and acute insulin response to glucose. In contrast, late treated females exhibited both an increase in DI and a negative relationship between body mass index and S(I). These results suggest that prenatal androgen excess in female rhesus monkeys, regardless of gestational timing, perturbs insulin-glucose homeodynamics, with androgen excess in early and late gestation impairing pancreatic beta-cell function and altering insulin sensitivity, respectively.     

糖化血红蛋白与胰岛β细胞功能关系的研究

目的 探讨不同糖代谢状态糖化血红蛋白（HbA1c）与胰岛β细胞功能的关系.方法 选取2010年6月至2013年2月为评价糖耐量水平而来南京大学医学院鼓楼医院内分泌科就诊者913例,所有受试者均行75 g口服葡萄糖耐量试验（OGTT）及胰岛素释放试验,测定HbA1c,根据HbA1c水平将受试者分为HbA1c ＜5.7％（277例）、5.7％≤HbA1c≤6.4％（391例）及HbA1c＞6.4％组（245例）;根据OGTT结果分为正常糖耐量组（NGT,205例）,糖调节受损组（IGR,328例）及2型糖尿病组（T2DM,380例）.以1/稳态模型胰岛素抵抗指数（1/HOMA-IR）、Matsuda胰岛素敏感指数（ISIM）评价胰岛素敏感性,以处置指数DI（早时相DI30、总时相DI120）评估校正胰岛素敏感性之后的胰岛β细胞功能.多组计量资料间比较采用方差分析,分类计数资料采用卡方检验,胰岛功能相关指数在校正性别、年龄、BMI之后采用一般线性模型进行比较.结果 与HbA1c ＜5.7％组相比,5.7％≤HbA1c≤6.4％组的DI30、DI120、ISIM、1/HOMA-IR分别下降了39％、33％、13％、14％;HbA1c＞6.4％组的DI30、DI120、ISIM、1/HOMA-IR分别下降了68％、66％、21％、32％（F=12.765 ～ 317.316,均P＜0.05）.在正常糖耐量阶段的人群中,5.7％≤HbA1c≤6.4％组的DI30、DI120明显低于HbA1c＜5.7％组（F=4.516、4.215,P＜0.05）;在HbA1c＜ 5.7％的人群中,DI30及DI120按照NGT→ IGR→T2DM的方向下降（F =87.604、108.369,P＜0.05）.结论 胰岛β细胞功能的进行性衰退及胰岛素抵抗共同促进了HbA1 c的升高;HbA1c与血糖结合能够更好地反映个体胰岛功能情况.     

Impact of Traits of Metabolic Syndrome on β-Cell Function and Insulin Resistance in Normal Fasting, Normal Glucose Tolerant Subjects

Abstract Objective: Metabolic syndrome, impaired fasting glucose (IFG), and impaired glucose tolerance (IGT) predict risk for type 2 diabetes mellitus (T2DM). To determine if increased risk preceded development of these abnormalities, β-cell function and insulin resistance were assessed in euglycemic subjects with and without traits of metabolic syndrome. Methods: A total of 562 apparently healthy Latin-American subjects were screened for metabolic syndrome [National Education Cholesterol Program Adult Treatment Panel III (NECP ATP III)]. Early pancreatic insulin response ΔInsulin(0-30)/ΔGlucose(0-30), Matsuda index, disposition index (DI), and homeostasis model assessment of insulin resistance (HOMA-IR) ratio were obtained from oral glucose tolerance testing (0-180?min). Results: ΔI(0-30)/ΔG(0-30), Matsuda index, DI, and HOMA-IR deteriorated in direct proportion with number of traits of metabolic syndrome, and with increases in glucose levels within the euglycemic range. DI was the most sensitive index. In subjects with 1, 2, 3, and 4-5 traits, DI was 21.4%, 40%, 57%, and 76% lower, respectively, than in subjects with no traits. As a single trait, abdominal obesity was associated with insulin resistance, whereas, low high-density lipoprotein cholesterol (HDL-C), alone or combined with high triglycerides, was not associated with insulin resistance or β-cell dysfunction. Combined impairments in β-cell function and insulin sensitivity were responsible for the increases in fasting and 2-h plasma glucose concentrations within the euglycemic range. Conclusions: Impaired β-cell function and increased insulin resistance are present much before development of metabolic syndrome, IFG, or IGT. β-Cell function and insulin sensitivity worsen in direct proportion with number of traits of metabolic syndrome and increases in glucose levels. Compared to abdominal obesity, low HDL-C±high triglycerides may bear a lesser weight in predicting risk of T2DM.     

Impaired glucose tolerance and reduced beta-cell function in overweight Latino children with a positive family history for type 2 diabetes

The objective of this study was to examine relationships between impaired glucose tolerance (IGT) and body composition and insulin-related phenotypes in 150 overweight Latino children with a family history of type 2 diabetes. Glucose tolerance was assessed by an oral glucose challenge. Body composition was assessed by dual energy x-ray absorptiometry and magnetic resonance imaging. Insulin sensitivity, the acute insulin response, and the disposition index (DI), as an index of beta-cell function, were determined by an iv glucose tolerance test and compared between normal glucose-tolerant and IGT children. IGT was present in 28% of children, and was similar across obesity groups, but higher in children exposed to gestational diabetes mellitus (41% IGT). There were no significant differences in body composition, fat distribution, insulin sensitivity, or acute insulin response, but DI was significantly lower in IGT children by 16% (P < 0.02), and DI was inversely related to age. In conclusion, IGT is present in 28% of overweight Latino children with a family history of type 2 diabetes, is not influenced by obesity, is more prevalent in children exposed to gestational diabetes mellitus, and is related to poor beta-cell function, which shows signs of deterioration with age in this population.     

Evaluation of proposed oral disposition index measures in relation to the actual disposition index

Aims While the disposition index provides a useful measure of B‐cell function, its calculation requires the performance of a frequently sampled intravenous glucose tolerance test (FSIVGTT). Recently, the demonstration of a hyperbolic relationship between indices of insulin secretion and insulin sensitivity derived from the oral glucose tolerance test (OGTT) has led to the introduction of two novel OGTT‐based measures of B‐cell function analogous to the disposition index: (i) the insulin secretion‐sensitivity index‐2 (ISSI‐2) (defined as the ratio of the area‐under‐the‐insulin‐curve to the area‐under‐the‐glucose curve, multiplied by the Matsuda index) and (ii) insulinogenic index (IGI)/fasting insulin. However, neither of these two measures has been directly compared with the disposition index. Methods Two hundred and thirteen non‐diabetic children (122 boys, 91 girls) underwent both OGTT and FSIVGTT, allowing for the calculation of ISSI‐2, IGI/fasting insulin and the disposition index. Results ISS1‐2 and IGI/fasting insulin were strongly correlated with each other (r = 0.82, P < 0.0001). Both measures correlated with the disposition index, with ISSI‐2 showing a modestly stronger association (ISSI‐2: r = 0.24, P = 0.0003; IGI/fasting insulin: r = 0.21, P = 0.0022). Standardized linear regression analyses confirmed that the relationship between log ISSI‐2 and the disposition index (standardized regression coefficient = 0.224, P = 0.001) was stronger than that between log IGI/fasting insulin and the disposition index (standardized regression coefficient = 0.166, P = 0.015). Conclusions The OGTT‐derived measures ISSI‐2 and IGI/fasting insulin exhibit modest correlations with the disposition index. These relationships require further assessment in other patient populations.     

单纯空腹血糖受损和单纯空腹高血糖型糖尿病的代谢特征

目的评估初发的单纯空腹血糖受损（iIFG）和单纯空腹高血糖型糖尿病（IFH）患者的胰岛素分泌及胰岛素敏感性特征,进一步探讨进展为IFH的相关因素。方法2004—2005年瑞金医院内分泌科门诊初诊病人,隔夜空腹10h后行口服葡萄糖耐量试验,其中同时行胰岛素释放试验1852例。其中糖耐量正常（NGT）557例;iIFG221例;IFH81例。比较各组的代谢指标及胰岛素分泌和胰岛素敏感性指数。结果对1852例接受者操作特征曲线（ROC）分析确定的糖耐量异常（除外糖尿病）发生的最佳空腹血糖切点为5．590mmol／L,2型糖尿病发生的最佳空腹血糖切点为6．695mmol／L。从NGT→iIFD→IFH,早期相胰岛素分泌和胰岛素敏感性指数均逐渐降低。结论初发的iIFG和IFH均有显著的早期相胰岛素分泌缺陷和胰岛素敏感性降低。B细胞胰岛素分泌缺陷和胰岛素抵抗均是从NGT向iIFG向IFH的进展过程中的重要因素。     

老年2型糖尿病和糖耐量受损患者血清铁蛋白与胰岛素抵抗和胰岛β细胞功能相关

目的 探讨60岁以上老年2型糖尿病和糖耐量受损(IGT)患者血清铁蛋白(SF)水平与胰岛素抵抗、胰岛β细胞功能之间的相关性.方法 入选2型糖尿病组患者1 143例,IGT组448例和正常糖耐量组(NGT)2 950名.测定身高、体重、血压、总胆固醇、甘油三酯(TG)、空腹血糖(FPG)、餐后2 h血糖(2hPG)、空腹胰岛素(FINS)和SF水平.采用稳态模型、QUICK来评估胰岛素抵抗,采用稳态模型和处置指数(DI)来评估胰岛β细胞功能.结果 2型糖尿病组SF水平高于NGT组(P<0.01);NGT、IGT和2型糖尿病组稳态模型评估的胰岛素抵抗指数(HOMA-IR)呈增高趋势(P<0.05),稳态模型评估的胰岛素β细胞功能指数(HOMA-β)、QUICK、DI呈递减趋势(均P<0.05).Spearman相关分析和偏相关分析显示,校正年龄和性别后,SF与FPG、2hPG、TG、FINS、HOMA-IR呈正相关,与HOMA-β、QUICK、DI呈负相关.多元逐步回归分析显示,QUICK、体重指数、TG是影响SF的独立危险因素.结论 老年2型糖尿病患者体内铁超负荷;随着SF的升高,胰岛素抵抗逐渐增加,而胰岛β细胞功能呈下降趋势.

Abstract：

Objective To investigate the relationship between serum ferritin and p-cell function,insulin resistance in elderly patients(age>60 years)with type 2 diabetes and impaired glucose tolerance.Methods Total 1143 patients with type 2 diabetes,448 patients with impaired glucose tolerance(IGT),and 2 950 subjects with normal glucose tolerance(NGT)were recruited for the measurments of height,weight,serum triglyceride(TG),total cholesterol,fasting plasma glucose(FPG),fasting insulin(FINS),postprandial 2 h plasma glucose(2hPG),and serum ferritin.Homeostasis model assessment of insulin resistance(HOMA-IR)and QUICK index were used to estimate insulin resistance,and homeostasis model assessment of β cell function(HOMA-p)and disposition index(DI)to evaluate p-cell function.Results The results showed that the level of serum ferritin was significantly higher in type2 diabetes mellitus group than NGT group(P<0.01).HOMA-IR was gradually increased,and HOMA-β,QUICK,and DI decreased from NGT to IGT,type 2 diabetes mellitus groups(all P < 0.05).Spearman and partial correlation analysis showed that partial adjustment for age and sex,serum ferritin was positively associated with FPG,2hPG,TG,FINS,and HOMA-IR,and negatively associated with HOMA-β,QUICK,and DI.Stepwise regression showed that serum ferritin was associated with QUICK,BMI,and TG.Conclusion The results suggest that iron overload exists in elderly patients with type 2 diabetes.With increasing serum ferritin level,insulin resistance increases and p-cell function decreases in the elderly patients with abnormal glucose metabolism.     

新疆汉、维民族糖调节受损人群胰岛素分泌功能和胰岛素作用功能的研究

目的 评估新疆汉、维民族在IFG,IGT及IGR阶段的胰岛素分泌功能和胰岛素作用功能。 方法 采用多中心研究进行横断面调查,行OGTT试验。用胰岛素抵抗指数（HOMA-IR）评估IR,胰岛β细胞功能指数（HOMA-β）评估基础胰岛素分泌;ΔI30/ΔG30评价胰岛素早相分泌,ΔI30/ΔG30/HOMA-IR评估葡萄糖处置指数（DI）。 结果 WC、BMI、血脂、FIns、2 hIns在汉、维民族不同糖代谢组差异有统计学意义。IFG组与NGT、IGT组比较,汉、维族人群的HOMA-IR差异有统计学意义。在汉族中NGT组与IGT、IGR组比较,HOMA-β差异有统计学意义（P=0.030、0.044）,而在维族只有IFG组与NGT组比较差异有统计学意义（P=0.001）。ΔI30/ΔG30、DI在两民族不同糖代谢组差异均无统计学意义。 结论 汉族人群IR在IFG阶段,胰岛素分泌功能在IGT阶段起主要作用。IR和胰岛素分泌功能在维族人群IFG阶段起重要作用。胰岛素早相分泌及葡萄糖处置功能在糖调节受损阶段作用不显著。     

Ethnic differences in insulin sensitivity and beta-cell function among Asian men

Background and objectives:

Lean Asian Indians are less insulin sensitive compared with Chinese and Malays, but the pancreatic beta-cell function among these ethnic groups has yet to be studied in depth. We aimed to study beta-cell function in relation to insulin sensitivity among individuals of Chinese, Malay and Asian-Indian ethnicity living in Singapore.

Subjects and methods:

This is a sub-group analysis of 59 normoglycemic lean (body mass index (BMI) <23 kg m⁻²) adult males (14 Chinese, 21 Malays and 24 Asian Indians) from the Singapore Adults Metabolism Study. Insulin sensitivity was determined using fasting state indices (homeostatic model assessment—insulin resistance), the euglycemic-hyperinsulinemic clamp (ISI-clamp) and a liquid mixed-meal tolerance test (LMMTT) (Matsuda insulin sensitivity index (ISI-Mat)). Beta-cell function was assessed using fasting state indices (homeostatic model assessment—beta-cell function) and from the LMMTT (insulinogenic index and insulin secretion index). The oral disposition index (DI), a measure of beta-cell function relative to insulin sensitivity during the LMMTT, was calculated as a product of ISI-Mat and insulin secretion index.

Results:

Asian Indians had higher waist circumference and percent body fat than Chinese and Malays despite similar BMI. Overall, Asian Indians were the least insulin sensitive whereas the Chinese were most insulin sensitive. Asian Indians had higher beta-cell function compared with Chinese or Malays but these were not statistically different. Malays had the highest incremental area under the curve for glucose during LMMTT compared with Asian Indians and Chinese. However, there were no significant ethnic differences in the incremental insulin area under the curve. The oral DI was the lowest in Malays, followed by Asian Indians and Chinese.

Conclusion:

Among lean Asians, Chinese are the most insulin sensitive whereas Asian Indians are the least insulin sensitive. However, Malays demonstrate higher postprandial glucose excursion with lower beta-cell response compare with Chinese or Asian Indians. The paths leading to type 2 diabetes mellitus might differ between these Asian ethnic groups.     

Assessing 1-h plasma glucose and shape of the glucose curve during oral glucose tolerance test

OBJECTIVE: To assess the cutoff values at different time points for impaired glucose regulation (IGR) and diabetes, the glucose curve and isolated 1-h hyperglycemia were monitored during an oral glucose tolerance test (OGTT). METHODS: Two thousand eight hundred and eighty-six subjects (1300 men and 1586 women) were recruited to have an OGTT. Plasma was collected at 0, 30, 60, 120, and 180 min to analyze glucose and insulin. The diagnosis of impaired fasting glucose, impaired glucose tolerance, and diabetes was based on World Health Organization and American Diabetes Association's criteria. Those with fasting plasma glucose (FPG) < 5.6 and 2-h plasma glucose (PG) < 7.8, but 1-h PG > or = 7.8 and < 11.1 mmol/l were defined as 1h-High7.8, and those with FPG < 7.0 and 2-h PG < 11.1, but 1-h PG > or =11.1 mmol/l as 1h-High11.1. The cutoff values were calculated by receiver operating characteristic (ROC) curve. The correlation between beta-cell function and the area under the curve of glucose (AUCg) and the shape index was analyzed with linear regression. RESULTS: The cutoff values for IGR were 5.6, 9.7, 10.1, 7.8 and 6.1 mmol/l for blood glucose at 0, 30, 60, 120 and 180 min, 24 for AUCg and 1.3 mmol/l for the shape index. The cutoff values for diabetes were 6.8, 11.2, 13, 11.1 and 7 mmol/l for 0, 30, 60, 120 and 180 min, 30.9 for AUCg and 2 mmol/l for the shape index. Both AUCg and the shape index were inversely related to beta-cell function. The profiles of glucose and insulin in the subgroup with isolated 1-h hyperglycemia were very different from those seen in subjects with normal glucose tolerance or IGR. CONCLUSIONS: The present study provides new information on measures other than the fasting and 2-h PG to evaluate glucose metabolism in vivo and stimulates further research aimed at assessing the value of the OGTT 1-h PG concentration prospectively.     

Insulin sensitivity, insulin secretion and beta-cell function during puberty in overweight Hispanic children with a family history of type 2 diabetes

OBJECTIVE: To examine cross-sectional differences in insulin sensitivity, insulin secretion and beta-cell function during puberty in overweight Hispanic boys and girls with a family history of type 2 diabetes. STUDY DESIGN AND PARTICIPANTS: This cross-sectional, observational study included 214 8-13-y-old Hispanic children with a BMI percentile > or = 85th percentile and family history of type 2 diabetes. METHODS AND ANALYSES: Participants underwent a physical examination, body composition measures, oral glucose tolerance test (OGTT), and frequently-sampled intravenous glucose tolerance test. Unadjusted and adjusted general linear models (GLM) tested whether insulin/glucose dynamics differed by Tanner stage and gender. RESULTS: Unadjusted group comparisons showed that fasting insulin increased whereas insulin sensitivity (SI) and the disposition index (DI) (a measure of pancreatic beta-cell function) decreased across Tanner stage groups (all P < 0.05). No differences in the acute insulin response to glucose (AIRg), fasting glucose or 2-h glucose were found. After adjusting for covariates, there was no independent effect of Tanner stage on SI (P = 0.9) or AIRg (P = 0.2), but DI was slightly lower in later Tanner stages suggesting decreased beta-cell function in the more mature groups (P = 0.10). CONCLUSIONS: Overweight Hispanic children with a family history of type 2 diabetes may represent a unique population given that pubertal insulin resistance was not evident once analyses controlled for body composition. Longitudinal analyses are required to determine whether the slightly diminished beta-cell function in later Tanner stages plays a role in the development of type 2 diabetes.     

Time to the Peak,Shape of the Curve and Combination of These Glucose Response Characteristics During Oral Glucose Tolerance Test as Indicators of Early Beta-cell Dysfunction in Obese Adolescents

Objective:Characteristics of the glucose response during oral glucose tolerance test (OGTT) may reflect differences in insulin secretion and action. The aim was to examine whether timing of the glucose peak, shape of the glucose curve and their combination could be indicators of beta-cell dysfunction in obese/severely obese adolescents with normal glucose tolerance (NGT).Methods:Data from 246 obese/severely obese adolescents who completed OGTT were reviewed. Out of 184 adolescents with NGT, 174 could be further classified into groups based on timing of the glucose peak (early/30 minutes vs late/≥60 minutes) and shape of the glucose curve (monophasic vs biphasic). Groups were compared with respect to insulin sensitivity (whole body insulin sensitivity index - WBISI), early-phase insulin secretion (insulinogenic index - IGI) and beta-cell function relative to insulin sensitivity (oral disposition index - oDI).Results:Late glucose peak (p=0.004) and monophasic glucose curve (p=0.001) were both associated with lower oDI after adjustment for age, sex, puberty stage and body mass index z-score. Among obese/severely obese adolescents with NGT, those with coexistent late glucose peak and monophasic glucose curve had lower oDI than those with early glucose peak and biphasic glucose curve (p=0.002). Moreover, a combination of late glucose peak and monophasic glucose curve was the most powerful predictor of the lowest oDI quartile [odds ratio (OR): 11.68, 95% confidence interval: 3.048-44.755, p<0.001].Conclusion:Late timing of the glucose peak, monophasic shape of the glucose curve and, in particular, a combination of those characteristics during OGTT may indicate early beta-cell dysfunction in obese/severely obese adolescents with NGT.     

Persistence of impaired pancreatic beta-cell function in children treated for acute lymphoblastic leukaemia

Treatment for acute lymphoblastic leukaemia can induce alterations of glucose metabolism, but long-term follow-up data on this topic are still absent. We aimed to study glucose metabolism by intravenous and oral glucose tolerance testing in 32 children affected by acute lymphoblastic leukaemia and who were off-therapy for at least 1 year. 22 (69%) children presented with impaired first-phase insulin response, which in nine children was associated with impaired glucose tolerance and in one child with overt diabetes. Fasting insulin (4.65 mU/L, 95% CI 1.1-8.1; p=0.008), insulinogenic index (0.46; 0.02-0.98; p=0.03), and homoeostatic model assessment beta-cell function (80.1, 7.2-153; p=0.02) were reduced in the children with impaired insulin response. Chemotherapy for acute lymphoblastic leukaemia is associated with beta-cell function damage, which persists even after therapy has been stopped.     

Low glycaemic index diet and disposition index in type 2 diabetes (the Canadian trial of Carbohydrates in Diabetes): a randomised controlled trial

AIMS/HYPOTHESIS: We recently found that oral glucose tolerance over 1 year in type 2 diabetic patients declined to a significantly lesser degree on a low-glycaemic-index than on a reduced-carbohydrate diet. Here, we examined whether that finding was associated with an improvement in disposition index, an index of beta cell function defined as the product of insulin sensitivity and insulin secretion. Since this is a report of secondary analysis on a previously published trial, the results should be considered as hypothesis-generating. METHODS: Type 2 diabetic patients treated by diet alone (n = 162) were randomised by computer to high-carbohydrate/high-glycaemic index (High-GI, n = 52), high-carbohydrate/low-glycaemic index (Low-GI, n = 56) or low-carbohydrate/high-monounsaturated-fat (Low-CHO, n = 54) diets for 1 year in a multi-centre, parallel-design clinical trial conducted at University teaching hospitals. At baseline and at 3, 6 and 12 months participants underwent 75 g OGTTs; 27 participants dropped out or were excluded. Indices of insulin sensitivity, insulin secretion and disposition index, derived from the OGTT, were compared among diets. Those assessing the outcomes were blinded to group assignment. RESULTS: Neither muscle insulin sensitivity index nor insulinogenic index differed significantly among diets. However, a significant time x diet interaction existed for disposition index (muscle insulin sensitivity index x insulinogenic index) (p = 0.036). After 3 months, disposition index tended to be higher on Low-CHO than on Low-GI diets, namely by 0.07 h(-1) (95% CI -0.04, 0.18). However, by 12 months this reversed and disposition index became higher on Low-GI than on Low-CHO, namely by 0.12 h(-1) (0.01, 0.23; p < 0.05, baseline disposition index 0.23 h(-1)). There were no important adverse effects associated with the treatments. CONCLUSIONS/INTERPRETATION: These results suggest that, in patients with type 2 diabetes on diet alone, a Low-GI diet for 1 year increases disposition index, an index of beta cell function, compared with a Low-CHO diet.