应用高葡萄糖钳夹技术评价糖耐量异常的Graves病患者胰岛β细胞功能及胰岛素抵抗

目的应用高葡萄糖钳夹技术评价糖耐量异常（IGT）的Graves病（GD）患者胰岛B细胞功能及胰岛素抵抗。方法筛选合并IGT的GD患者6例（均为初诊未治）,应用高葡萄糖钳夹技术检测胰岛素分泌及胰岛素敏感性,并与正常对照组10例进行比较,所有研究对象均检测谷氨酸脱羧酶（GAD）抗体。结果合并IGT的GD组与正常对照组比较,第一时相胰岛素分泌[（636．31±105．54）mIU／L比（233．56±21．33）mIU／L]、第二时相胰岛素分泌[（146．68±25．0）mIU／L比（67．06±6．23）mIU／L]、最大胰岛素分泌量[（195．05±32．94）mIU／L比（87．64±9．78）mIU／L],胰岛素敏感性指数（11．52±1．90比21．72±3．25）,差异均有统计学意义（P值均〈0．05）。所有研究对象GAD抗体检测均为阴性。结论GAD抗体阴性的GD合并IGT患者胰岛素分泌呈亢进状态,胰岛素敏感性显著低于正常对照组。     

Distinct role of adiposity and insulin resistance in glucose intolerance: studies in ventromedial hypothalamic-lesioned obese rats

It remains unclear whether adiposity plays an important role in glucose intolerance independently of insulin resistance. We investigated whether adiposity and insulin resistance had distinct roles in glucose intolerance in rats. We examined glucose tolerance and insulin resistance using ventromedial hypothalamic (VMH)-lesioned rats in the dynamic and the static phases of obesity (2 and 14 weeks after lesioning, respectively). Rats were fed either normal chow or a fructose-enriched diet (60% of total calories). The intravenous glucose tolerance test (IVGTT) was performed by bolus injection of glucose solution (1 g/kg) and blood sampling after 0, 5 10, 30, and 60 minutes. Insulin resistance was evaluated from the steady-state plasma glucose (SSPG) value during continuous infusion of glucose, insulin, and somatostatin. SSPG was not increased in VMH-lesioned rats in the dynamic phase of obesity, but increased markedly in the static phase. The area under the glucose curve (glucose AUC) during IVGTT was increased in VMH-lesioned rats in the static phase, but not in the dynamic phase, when compared with their sham-operated counterparts. A fructose-enriched diet for 2 or 14 weeks increased SSPG values to a similar extent in both sham-operated and VMH-lesioned rats without inducing excess adiposity, but glucose intolerance was only developed in the obese rats. The plasma leptin level, an excellent indicator of adiposity, was significantly related to the glucose AUC independently of the insulin level. Insulin resistance or increased adiposity alone is not sufficient to impair glucose tolerance, but increased adiposity plays an important role in the development of glucose intolerance in an insulin-resistant state.     

Metabolic adaptations to chronic glucose infusion in rats

Aims/hypothesis Several studies have employed the chronic glucose infusion protocol to quantify the metabolic adaptations associated with a prolonged glucose challenge. However, the limited number of indices and time points reported by these studies has generated an incomplete picture of this process. In this study we aimed to generate an integrative and dynamic picture of the physiological adaptations that occur during chronic glucose infusion.Methods Sprague–Dawley rats were infused with either 50% dextrose or saline (2 ml/h) for a period of between 0 and 6 days. Glucose, insulin and NEFA dynamics were determined from daily blood samples. Subsets of animals were killed daily for histological determination of beta cell mass, size and replication rates. The mathematical model of coupled beta cell mass, insulin and glucose (the IG model) was used to estimate insulin sensitivity, beta cell function and net neogenesis from this data.Results Glucose-infused rats displayed transient hyperglycaemia, persistent hyperinsulinaemia and unchanged NEFA levels. Insulin sensitivity decreased by approximately 80% during the first day of glucose infusion, but had returned to pre-infusion levels by Day 3. Beta cell function was four to six times higher than in control rats throughout the experiment. Beta cell mass doubled over the 6 days of glucose infusion due to three phases of adaptation: (i) neogenesis; (ii) hypertrophy and hyperplasia; and (iii) continued hyperplasia coupled to a second wave of neogenesis.Conclusions/interpretation Contrary to the results reported for perfused pancreas and in vitro experiments, we found that chronic glucose infusion elevated beta cell function. The prediction of a second wave of beta cell neogenesis, coupled with our previous report of focal areas on Day 3, suggests the existence of delayed acinar-to-islet transdifferentiation.     

老年糖尿病前期患者胰岛素抵抗和胰岛β细胞分泌功能

目的:研究老年空腹血糖异常(IFG)和糖耐量低减(IGT)患者的胰岛素抵抗(IR)和胰岛β细胞分泌功能。方法:将84例老年患者分为正常血糖组(NGT)、IGT组、IFG组和IGT与IFG重叠组(IFG/IGT),测定患者的空腹及餐后2h血糖和胰岛素,计算胰岛素敏感性指数(ISI)、胰岛β细胞分泌指数(HBCI)并进行对比性分析。结果:与NGT组比较IFG、IGT及IFG/IGT组的餐后2h血糖(2hPG)、空腹及餐后2h胰岛素(2hINS)水平均显著升高(P<0.01),但ISI均显著下降(P<0.01),IGT与IFG/IGT组HBCI明显降低(P<0.05);与IFG组比较IGT与IFG/IGT组FPG、2hPG、2hINS水平显著升高,HBCI明显下降(P<0.05~<0.01)。结论:IFG、IGT及IFG/IGT患者均存在明显IR,而胰岛β细胞分泌功能下降在IGT及IFG/IGT组患者明显。     

Beta-cell hypersensitivity for glucose precedes loss of glucose-induced insulin secretion in 90% pancreatectomized rats

Summary Glucose-induced insulin secretion is impaired in the presence of chronic hyperglycaemia. Insulin secretion was studied in a diabetic rat model prior to the beta cells becoming non-responsive to glucose in order to map out the sequence of changes that accompany chronic hyperglycaemia. In vitro pancreas perfusions were carried out 1 and 2 weeks after a 90% pancreatectomy; controls underwent a sham pancreatectomy. One week post 90% pancreatectomy: (i) non-fasting plasma glucose values were 2–3 mmol/l above normal, (ii) the in vitro insulin response to 16.7 mmol/l glucose was 20 ± 4% of shams, a response that was appropriate for the surgical reduction in beta-cell mass, (iii) the beta-cell sensitivity for glucose was increased as reflected by left-shifted dose-response curves for glucose-induced insulin secretion (half maximal insulin output 5.7 mmol/l glucose vs 16.5 mmol/l glucose in shams) and glucose potentiation of arginine-induced insulin secretion (half maximal insulin output 3.5 mmol/l glucose vs 14.8 mmol/l glucose in shams). This heightened beta-cell sensitivity for glucose was not a result of the hyperglycaemia, because similarly reduced half-maximal insulin responses were found after a 60% pancreatectomy, a surgical procedure in which plasma glucose values remained normal. In summary, a rise in beta-cell sensitivity for glucose precedes the loss of glucose-induced insulin secretion in diabetic rats.     

他汀类调脂药对大鼠胰岛胰岛素分泌的影响及机制研究

目的 观察不同他汀类药物对大鼠胰岛葡萄糖刺激的胰岛素分泌(GSIS)的抑制作用及机制.方法 新鲜分离或经24 h培养的胰岛均匀分为对照组、阿托伐他汀组、氟伐他汀组和普伐他汀组,对照组给予Kreb-Ringer碳酸氢盐缓冲液,他汀类药物组分别给予100μmol/L阿托伐他汀、氟伐他汀和普伐他汀,水浴30 min或过夜培养24 h.各组经2.8、5.5、11.1、16.7、25.0 mmol/L葡萄糖刺激后,37℃水浴法测定胰岛GSIS变化,生物化学发光法测定三磷酸腺苷(ATP)含量.结果 100μmol/L阿托伐他汀水浴30 min后,在16.7 mmol/L葡萄糖刺激下,与相应对照组比较,ATP含量[(9.54±1.64)pmol/胰岛比(12.33±1.89)pmol/胰岛]及胰岛素分泌(1.60±0.21比2.39±0.30)均下降(P＜0.05);100 μmol/L氟伐他汀过夜培养24 h后,在16.7 mmol/L葡萄糖刺激下,与相应对照组比较,ATP含量[(10.24±2.01)pmol/胰岛比(12.31±2.16)pmol/胰岛]及胰岛素分泌(3.12±0.32比4.17±0.37)也均下降(P＜0.05).结论 阿托伐他汀、氟伐他汀通过抑制胰岛ATP的生成而抑制GSIS,抑制程度与其脂溶性强弱有关.

Abstract：

Objective To evaluate the inhibitory effect of statins on glucose-stimulated insulin secretion (GSIS) of pancreatic islet in rat and to explore its mechanisms. Methods According to the average volume, freshly isolated or 24-hour cultured pancreatic islets were randomly divided into control group( incubated with Kreb-Ringer bicarbonate buffer), the atorvastatin group( incubated with 100 μ mol/L atorvastatin), the fluvastatin group (incubated with 100 μ mol/L fluvastatin)and the pravastatin group (incubated with 100 μ mol/L pravastatin). Stimulated by 2. 8,5. 5,11.1,16. 7 mmol/L and 25.0 mmol/L glucose respectively, the effect of 100 μ mol/L statins on ATP content and GSIS was compared in the four groups. GSIS was performed by the 37℃ bath incubation method and ATP content was measured by chemiluminescence method. Results Incubated with 100 μ mol/L atorvastatin for 30 minutes, in the presence of 16. 7 mmol/L glucose, the ATP content [(9. 54 ± 1. 64) pmol/islet vs ( 12. 33 ± 1.89) pmol/islet] and GSIS (1.60 ± 0. 21 vs 2. 39 ± 0. 30) were significantly reduced in comparison with the control group (P＜0. 05). Cultured with 100 μmol/L fluvastatin for 24 hours, the ATP content [( 10. 24 ±2.01 )pmol/islet vs (12. 31 ±2. 16) pmol/islet] and GSIS (3. 12 ± 0. 32 vs 4. 17 ±0. 37 ) were all significantly decreased at the higher glucose concentration of 16. 7 mmol/L ( P ＜ 0. 05). Conclusion Atorvastatin and fluvastatin may inhibit GSIS by decreasing ATP content in pancreatic islet and the inhibitory effect is related to the strength of its lipophilicity.     

多次取样的静脉糖耐量试验中胰岛素分泌率的测定和计算

目的 在体内C－肽动力学二室模型及标准参数法基础上,计算多次取样的静脉糖耐量试验（FSIVGTT）中胰岛素分泌率（ISR）。方法 15例糖耐量正常者及11例2型糖尿病者均行口服糖耐量试验（OGTT）及FSIVGTT。所有标本用己糖激酶法测定葡萄糖,用放免法测定胰岛素（INS）、C－肽,根据自编计算机程序,计算各时点ISR。结果 FSIVGTT中,对照组INS、C－肽浓度高峰出现于4min时,无明显第二分泌峰;2型糖尿病组只有5例0－4min时有小的分泌峰,曲线高峰于60－80min。对照组ISR曲线第一分泌峰于2min,较INS及C－肽曲线提前（P＝0.000),22min时出现第二个明显的分泌峰;11例2型糖尿病者的ISR曲线均在2－4min（中位数2min）出现了小的分泌峰。结论 在用血INS及C－肽浓度作为评价β肽浓度作为评价β细胞功能的指标时,应考虑其体内分布、清除过程的影响;对2型糖尿病组,ISR曲线能较好地反映其第一时相INS分泌,在对照组,则对反映第二时相分泌较为敏感。     

Effect of 2-deoxyglucose on islet cell morphology and insulin secretion

Summary The effect of 2-deoxyglucose (2-DG) on islet cell morphology and portal vein insulin levels was studied. The B-cells did not show any alteration in their fine structure, except for an increase in dense bodies. Six hrs after 2-DG administration degranulation was observed in some of these cells. Insulin levels were low 45 min after 2-DG administration, in spite of the marked hyperglycemia, and slightly higher than normal after 6 hrs. The A-cells remained well granulated at all times after 2-DG injection. The D-cells showed signs of functional activity, such as microvilli formation, increased lamellar ergastoplasm and free ribosomes. The significance of these findings is discussed. Traduzione a cura di G.U.     

Kinetics of insulin secretion following glucose infusion in patients with atherosclerotic peripheral vascular disease

Summary Kinetics of insulin secretion following an i.v. glucose infusion, according to the protocol described by Cerasi and Luft, were studied in 19 patients with angiographically documented atherosclerotic peripheral vascular disease and in a group of appropriate controls without clinical signs of disease. No significant differences were noted between patients and controls in plasma cholesterol levels and in the K value following a standard i.v. glucose tolerance test. Blood glucose levels were significantly lower in the patients, whereas mean plasma insulin and triglyceride levels were significantly higher. Analysis of the glucose and insulin responses to the glucose infusion test indicated that 31.6% of the patients had a delayed and sluggish insulin response to the glucose load, fitting the criteria suggested for the diagnosis of prediabetes, versus 10% of the appropriate controls. In particular, simulation of the plasma insulin responses by a square-wave glucose stimulus, confirmed that in a significantly higher number of patients the early insulin peak was below normal limits. The results of this study suggest that increased insulin secretion is not present in patients with atherosclerotic vascular disease, in contrast to reports by other authors, and that inefficient insulin secretory mechanisms may be observed in these patients, thus possibly contributing to the development of the atherosclerotic disease.     

Melatonin inhibits insulin secretion and decreases PKA levels without interfering with glucose metabolism in rat pancreatic islets

The effect of melatonin (0.1 microM) on freshly isolated islets from adult rats was investigated. Melatonin caused a marked decrease of insulin secretion by islets in response to glucose. The mechanism involved was then examined. Melatonin did not interfere with glucose metabolism as indicated by the measurement of glucose oxidation. However, the content of the protein kinase A (PKA) catalytic alpha-subunit was significantly decreased in islets exposed to melatonin for 1 hr in the presence of 8.3 mM glucose, whereas that of the protein kinase C (PKC) alpha-subunit remained unchanged. Melatonin also inhibited forskolin-induced insulin secretion, a well known activator of adenylate cyclase (AC) activity. This may explain the low content of insulin found in islets incubated in the presence of melatonin for 3 hr. In fact, 3',5' -cyclic adenosine monophosphate (cAMP), a product of AC activity, stimulates insulin synthesis. These findings led us to postulate that a down-regulation of the PKA signaling pathway may be the mechanism involved in the melatonin inhibition of the process of glucose-induced insulin secretion.     

口服葡萄糖耐量试验中30分钟和(或)60分钟高血糖者胰岛素敏感性及1相胰岛素分泌功能的研究

目的研究肥胖的口服葡萄糖耐量试验(OGTT)中30min和(或)60min高血糖者(PLH)胰岛素抵抗和胰岛素分泌功能。方法共有165位受试者包括正常对照(NC)、单纯性肥胖(NGT)、肥胖PLH和肥胖糖耐量低减(IGT)接受了OGTT和静脉葡萄糖耐量试验。用HOMA-IR和SI评估胰岛素抵抗,△I30/△G30和AIRg评价β细胞功能,处理指数(DI=AIRg×SI)评价AIRg对胰岛素抵抗的代偿度。结果与NC组相比,NGT、PLH、IGT组的HOMA-IR升高,SI降低,后三组间差异无统计学意义。与NC、PLH和IGT组比较,NGT组AIRg升高,前三组间无统计学差异;与NC、PLH和IGT组比较,NGT组△I30/△G30升高,PLH组△I30/△G30高于NC组,而PLH和IGT组间以及NC和IGT组间△I30/△G30无统计学差异。与NC组相比,NGT、PLH、IGT组DI指数降低;NGT组DI指数高于PLH和IGT组,后二组间差异无统计学意义。结论上海地区肥胖的PLH人群与肥胖的IGT患者存在着程度近似的胰岛素抵抗和β细胞功能缺陷。     

Changes in insulin, somatostatin, and glucagon secretion during the development of obesity in ventromedial hypothalamic-lesioned rats

Changes in insulin, somatostatin, and glucagon secretion during the development of obesity in rats after ventromedial hypothalamic (VMH) lesions were evaluated by measuring fasting hormone levels and their secretion from the isolated perfused pancreas. Fasting peripheral insulin levels were not altered 1 week after the VMH lesions but became progressively elevated at 3-4, 8-9, and 11-12 weeks compared to the values in sham-operated and age-matched control rats. In the portal vein, insulin levels also progressively increased in VMH-lesioned rats, but the portal-peripheral gradient of insulin in the later phase of VMH obesity was significantly lower than in the early phase after VMH lesions. On the contrary, the arginine-induced insulin release from the perfused pancreas was highest at 1 week and gradually decreased thereafter, although it continued to remain higher than that of controls. The perfusate somatostatin response to arginine also was exaggerated in the VMH-lesioned rats. However, both the peripheral glucagon level and the glucagon secretion from the perfused pancreas of the VMH-lesioned rats were not significantly different from the controls. These results show that VMH lesions result in an increased insulin and somatostatin secretion. Using the cyclically perfused liver in situ, we have found that the hepatic extraction rate of insulin is indeed reduced in rats 8-9 weeks after VMH lesioning, and so have at least partly accounted for the decreased portal-peripheral gradient of insulin in the later VMH postoperative phase.     

Effect of ageing on insulin and insulin-glucose sensitivity tests in rats

Summary Insulin tolerance tests have shown old rats to respond to injection of the hormone by a sharp and lasting drop in blood sugar. The difference between these animals and young and adult ones lies in their inability to restore a normal blood glucose level. Glucose tolerance and insulin-glucose tolerance tests show that glucose uptake under the influence of the hormone is significantly reduced with age in absolute terms. However, the difference in glucose assimilation coefficient in the absence or presence of insulin (ΔK) is comparable in all age groups; thus senile rats were found to be as sensitive even to small doses of hormone as the adult ones, if basal levels are taken into account.     

脂联素受体在胰岛细胞表达,脂联素促进胰岛素的分泌

目的　检测脂联素受体(AR)在大鼠胰岛细胞的表达和脂联素对体外胰岛细胞分泌胰岛素的影响。方法　RT PCR和免疫细胞化学方法检测AR1、AR2的mRNA和蛋白表达;并在体外用脂联素(100μg/L)和不同浓度葡萄糖(3. 3, 5. 6, 16. 7mmol/L)处理胰岛细胞,放免法测定上清液的胰岛素浓度。结果　RT PCR扩增出胰岛AR1和AR2基因,并经直接和亚克隆测序证实;胰岛免疫细胞化学荧光染色AR1和AR2呈阳性;经脂联素处理后的胰岛细胞,在高糖(16. 7mmol/)培养 6~24h,其胰岛素分泌持续增加(均P<0. 05)。结论　胰岛细胞上存在AR1和AR2,以前者为主。在高糖情况下,一定浓度的脂联素可在体外促进胰岛细胞的胰岛素分泌和释放。     

Diminished inhibitory effect of noradrenaline on insulin release from mouse islets transplanted to kidney

Insulin release is inhibited by adrenergic alpha-2 agonism in normal beta-cells. To test whether the inhibitory response to noradrenaline is modified by transplantation, we studied insulin release from freshly isolated islets and from syngeneic islets transplanted under the kidney capsule of non-diabetic C57BL/6 mice. When perifused in vitro, fresh islets, as well as grafts harvested 1 or 3 weeks after transplantation, reacted to 2.5 mol/l noradrenaline with a complete inhibition of insulin release induced by 16.7 mmol/ld-glucose. In contrast, islet grafts harvested after 6, 12, or 21 weeks exhibited a conspicuous insulin secretory response to 16.7 mmol/l glucose in the presence of 2.5 mol/l noradrenaline. Also a concentration of 0.25 mol/l, noradrenaline inhibited the glucose-induced insulin release from fresh islets but not from 6-week-old islet grafts. It is concluded that transplantation under the kidney capsule induces a decreased inhibitory responsiveness to noradrenaline in islet grafts.     

Effect of prolonged in vivo glucose infusion on insulin secretion in rats with previous glucose intolerance.

This work was designed to investigate the effect of an additional hyperglycemia on the subsequent in vivo insulin secretion in rats with various degrees of glucose intolerance. Four groups of rats received a unique injection of a low concentration of streptozotocin (STZ): 20, 27, 30, or 35 mg/kg corresponding, respectively, to STZ 20, STZ 27, STZ 30, or STZ 35 rats. Control rats were injected with citrate buffer. In all STZ groups, impaired glucose tolerance and insulin secretion were observed. These defects were roughly proportional to STZ concentration. Three weeks after STZ administration, hyperglycemia (17 mM) was produced by a 48-h glucose infusion via an indwelling catheter. Insulin secretion in response to glucose was investigated 3 h after stopping glucose infusion, by performing iv glucose tolerance tests. Insulin secretion in response to glucose doubled in control rats previously submitted to glucose infusion, and still more in rats with mild glucose intolerance (three and four times higher in STZ 20 and STZ 27 rats, respectively). By contrast, glucose infusion increased insulin secretion only slightly in STZ 30 rats and it was unchanged in STZ 35 rats. These data show that prolonged hyperglycemia has an improving effect on insulin secretion in rats with mild glucose intolerance, whereas the potentiating effect of previous hyperglycemia is lost in rats with more severe glucose intolerance.     

瘦素对离体大鼠胰岛分泌胰岛素的双向影响

目的 了解不同浓度的瘦素，在不同条件下对离体大鼠胰岛分泌胰岛素的影响。方法 利用细胞培养技术，在不同的葡萄糖浓度（5.6mmol/L或16.7mmol/L）和不同作用时间（10min或2h)下，以0,1,5,10,15,50ak 100μg/L瘦素作用大鼠胰岛，观察其对胰岛素分泌的影响；用放免法检测培养物上清液胰岛素浓度。结果 培养液葡萄糖浓度为5.6mmol/L，培养10min，1μg/L、5μg/L瘦素促进被孵育的胰岛的胰岛素分泌；培养2h,5μg/L瘦素促进基础胰岛素分泌，≥50μg/L瘦素抑制胰岛素分泌。葡萄糖浓度为16.7mmol/L，培养10min，≥50μg/L瘦素抑制胰岛素分泌；培养2h，≥5μg/L瘦素抑制胰岛素分泌。结论 重组瘦素对离体大鼠胰岛分泌胰岛素具有双向作用，并受瘦素浓度、作用时间和环境葡萄糖浓度等因素变化的影响。     

Triglycerides and glucose index as an insulin resistance marker in a sample of healthy adults

AimTo assess the association between elevated triglycerides/glucose index (TGI) and insulin resistance (IR) or hyperinsulinemia after oral glucose tolerance test (OGTT) in a sample of healthy adults.MethodsWe conducted an analytical cross-sectional study in euthyroid non-diabetic adults, who attended the outpatient service of a private clinic in Lima-Peru during the 2012–2016 period. Participants were categorized in two groups according to the presence or absence of elevated TGI, IR or hyperinsulinemia after OGTT. A TGI value ≥ 8.65 was considered as elevated. We defined IR as a Homeostasis Model Assessment (HOMA-IR) value ≥ 2.28 and hyperinsulinemia after OGTT as a serum insulin value ≥ 80μU/mL after 120 min of 75-g glucose intake. We elaborated crude and adjusted Poisson regression models to assess the association between elevated TGI and IR or hyperinsulinemia after OGTT. The reported association measure was the prevalence ratio (PR) with their respective 95% confidence intervals (95%CI).ResultsWe analyzed 118 individuals, the average age was 37.5 ± 11.3 years, 21 (17.8%) were males and the median BMI was 22.7 ± 1.6 kg/m². The prevalence of elevated TGI was 25.4% (n=30) while the prevalence of IR and hyperinsulinemia after OGTT was 24.6% (n=29) and 17.0% (n=20) respectively. In the adjusted model, elevated TGI was associated with both IR (aPR=6.36; 95%CI: 3.41–11.86) and hyperinsulinemia after OGTT (aPR=4.19; 95%CI: 1.81–9.70).ConclusionsWe found that elevated TGI was associated with both IR markers in a sample of euthyroid adults without T2DM and with a normal BMI. The simplicity of the TGI calculation makes it the first-choice alternative when the hyperinsulinemic-euglycemic clamp or HOMA-IR are not available.     

Effects of glucose and meal ingestion on incretin secretion in Japanese subjects with normal glucose tolerance

Aims/Introduction: Gastric inhibitory polypeptide (GIP) and glucagon‐like peptide‐1 (GLP‐1) are the major incretins; their secretion after various nutrient loads are well‐evaluated in Caucasians. However, little is known of the relationship between incretin secretion and differing nutritional loading in Japanese subjects. In the present study, we evaluated GIP and GLP‐1 secretion in Japanese subjects with normal glucose tolerance (NGT) after glucose loading (75 g glucose and 17 g glucose) and meal ingestion. Materials and Methods: A total of 10 Japanese NGT subjects participated in 75 g oral glucose tolerance test (OGTT), 17 g OGTT and meal tolerance test (MTT). Plasma glucose (PG), serum insulin (IRI), serum C‐peptide (CPR), plasma total GIP, and plasma total GLP‐1 levels during OGTT and MTT were determined. Results: Area under the curve (AUC)‐GIP was increased in proportion to the amount of glucose, and was highest in MTT, showing that GIP secretion is also stimulated by nutrients other than glucose, such as lipid. In contrast, although the larger glucose load tended to induce a larger GLP‐1 release, AUC‐GLP‐1 was not significantly different among the three loading tests (75 g OGTT, 17 g OGTT, MTT) irrespective of the kind or amount of nutrition load. Conclusions: Our results suggest that nutritional composition might have a greater effect on GIP secretion than that on GLP‐1 secretion in Japanese NGT subjects . (J Diabetes Invest, doi: 10.1111/j.2040‐1124.2011.00143.x, 2012)     

Glucose tolerance and plasma insulin response to intravenous glucose infusion and test meal in rats with microencapsulated islet allografts

Summary Albino Oxford rats made diabetic with 75 mg/kg streptozotocin were intraperitoneally transplanted with 2500–2900 alginate-polylysine microencapsulated Lewis islets (n=9, total islet tissue volume 8.0–11.0 l), or a similar volume of non-encapsulated Lewis islets (n=5). All rats with microencapsulated islets became normoglycaemic, and remained normoglycaemic for 5–16 weeks. In rats with non-encapsulated islet grafts, only a temporary decrease in blood glucose was observed, and all were again severely hyperglycaemic at 1 week after implantation. At 5–6 weeks after transplantation, glucose tolerance in rats with microencapsulated islets was tested by intravenous glucose infusion (10 mg/min over 20 min) and test meal administration (n=4). During glucose infusion, maximum glucose levels were 13.0±0.4 mmol/l in rats with microcapsules and 8.9±0.4 mmol/l in healthy control rats (p<0.01). Concomitant maximum plasma insulin levels were 215±17 pmol/l in rats with microcapsules and 715±85 pmol/l in controls (p<0.001). After the test meal, maximum blood glucose was 10.6±0.9 mmol/l in rats with microcapsules and 6.2±0.1 mmol/l in controls (p<0.001), with concomitant maximum plasma insulin levels of 247±11 pmol/l and 586±59 pmol/l, respectively (p<0.001). In conclusion, although the glucose tolerance is impaired and plasma insulin responses to intravenous glucose-load and test-meal are reduced, the alginate-polylysine membrane does provide adequate immunoisolation for the prolongation of allograft survival, resulting in prolonged normoglycaemia in streptozotocin diabetic rats.