Effects of early excision and grafting on cytokines and insulin resistance in burned rats

Burn wound excision and grafting is a common clinical practice that decreases patient morbidity and mortality. It is not known, however, if the salutary effects of this procedure are related to effects on interleukin 6 (IL-6) and tumor necrosis factor (TNF-) α, and to reducing insulin resistance after burn. Sprague–Dawley rats were randomly divided into three groups: control, burn, burn ± excision groups. Rats in burn group were given a third-degree scald burn covering 30% total body surface area (TBSA) and no wound excision. Rats in burn ± excision group were subjected to a 30% third-degree burn followed by complete excision and allografting of the injury site within 15 min after burn. The rats in control group were treated in the same manner as the burn group, except that they were immersed in a room-temperature water. Glucose tolerance tests (GTT) were observed at 3 days after burn, euglycemic–hyperinsulinemic glucose clamps were performed at 4 days after burn and interleukin 6 (IL-6) and tumor necrosis factor (TNF-) α were determined after euglycemic–hyperinsulinemic glucose clamps. The levels of IL-6 and TNF-α increased after burn. Significant differences in GTT were observed between control and burn groups, and the rate of glucose infused measured in burned rats was significantly decreased compared with that in control at 4 days after burn. Early excision and grafting significantly decreased levels of IL-6 and TNF-α, and further reduced insulin resistance following thermal injury compared with burn group. Conclusion: Early excision and grafting appeared to have an effect on inflammatory mediators and further reduced insulin resistance induced by major burns.     

胰岛素强化治疗对烫伤大鼠心肌保护作用的研究

目的 了解胰岛素强化治疗对重度烫伤大鼠心肌的保护作用，并探讨其作用机制。方法 将18只SD大鼠分为3组，每组6只。强化组及烫伤组大鼠背部脱毛造成30％TBSA的Ⅲ度烫伤。强化组伤后即输注胰岛素等渗盐水（含胰岛素0．12U／m1）及100g／L葡萄糖，使大鼠血糖水平控制在4．0～6．6 mmol／L之间，补液总量为2ml·kg^-1。·％TBSA^-1·8h^-1；烫伤组伤后仅给予等渗盐水，总量同前。假伤组模拟烫伤，伤后补充生理量的液体。于伤前及伤后1、2、3、4、5、6 h 抽取大鼠静脉血测定其血糖值。各组大鼠伤后均经右颈动脉插管人左心室并连接生理记录仪，观察左心室收缩压（LVSP）及左心室舒张末期压（LVEDP）。伤后6h，处死各组大鼠，留取左心室组织标本用于心肌细胞肌钙蛋白T的检测。结果 烫伤组大鼠伤后1～6h的血糖值为（7．6±1．7）～（8．4±4．7）mmol／L，均高于强化组[（4．5±0．9）～（5．2±1．3）mmol／L，P〈0．01]。伤后1h，烫伤组LVSP[（60±11）mmHg（1mmHg=0．133kPa）]降低、LVEDP[（21．3±11．3）mmHg]升高，与强化组[（72±8）、（11．7±5．2）mmHg]比较，差异有统计学意义（P〈0．05）。烫伤后各组大鼠肌钙蛋白T在心肌细胞内大量缺失，而强化组缺失程度明显低于烫伤组（P〈0．05）。结论 胰岛素强化治疗对重度烫伤大鼠左心室功能具有明显的保护作用，此作用可能与抑制心肌细胞蛋白的缺失有关。     

胰岛素干预对严重烧伤后早期大鼠血管内皮细胞的保护效应

目的了解胰岛素对严重烧伤后早期大鼠血管内皮细胞的保护效应，并分析相关机制。方法将sD大鼠分成假伤组（7只）、烧伤组（7只）和处理组（7只）。后2组制成30％TBSAⅢ度烧伤（用94℃水浴烫伤）模型，假伤组37℃水浴模拟致伤过程。伤后即刻，各组经腹腔注射等渗盐水（40ml／kg）抗休克，同时处理组皮下注射胰岛素3U／kg、另2组同法注射等体积等渗盐水。伤后24h透射电镜下观察各组大鼠主动脉内皮细胞形态及结构，检测其血糖、血清一氧化氮（NO）及各型一氧化氮合酶（NOS）水平。结果镜下可见，处理组较烧伤组主动脉内皮细胞受损程度明显减轻。伤后24h，假伤组、烧伤组、处理组大鼠血糖分别为（4．9±0.8）、（8．2±1.0）、（7．1±0.．7）mmol/L，后2组均显著高于假伤组（P〈0．01），但处理组明显低于烧伤组（P〈0．05）。处理组血清NO、总NOS和结构型NOS（cNOS）水平均明显高于烧伤组（P〈0．01），但2组血清诱导型NOS水平比较，差异无统计学意义（P〉0、05）。结论胰岛素干预可保护严重烧伤后早期大鼠的血管内皮细胞，其机制可能与促cNOS水平升高从而使生理态NO合成增加有关。     

mTOR partly mediates insulin resistance by phosphorylation of insulin receptor substrate-1 on serine residues after burn

Mammalian target of rapamycin (mTOR) is an important mediator for cross talk between nutritional signals and metabolic signals of insulin by downregulating insulin receptor substrate proteins. Therefore, mTOR inhibition could become a therapeutic strategy in insulin-resistant states, including insulin resistance induced by burn. We tested this hypothesis in the rat model of 30% TBSA full thickness burn, using the mTOR inhibitor rapamycin. Rapamycin (0.4 mg/kg, i.p.) was injected 2 h before euglycemic-hyperinsulinemic glucose clamps at 4 days after burn. IRS-1, phospho-serine³⁰⁷, phospho-tyrosine of IRS-1 and phospho-mTOR in muscle tissue were determined by immunoprecipitation and Western blot analysis or immunohistochemistry. Plasma TNF-α, insulin and C-peptide were determined before and after euglycemic-hyperinsulinemic glucose clamps. Our data showed that TNF-α, insulin and C-peptide significantly increased in the early stage after burn (P < 0.01). The infused rates of total 10% glucose (GIR, mg/kg min) significantly decreased at 4 days after burn. The level of IRS-1 serine³⁰⁷ phosphorylation in muscle in vivo significantly increased after burn (P < 0.01), while insulin-induced tyrosine phosphorylation of IRS-1 significantly decreased (P < 0.01). Inhibition of mTOR by rapamycin inhibited the phosphorylation of mTOR, reduced serine³⁰⁷ phosphorylation, elevated tyrosine phosphorylation and partly prevented the decrease of GIR after burn. However, TNF-α, insulin and C-peptide were not decreased by rapamycin treatment postburn. Taken together, these results indicate that the mTOR pathway is an important modulator of the signals involved in the acute regulation of insulin-stimulated glucose metabolism, and at least, partly contributes to burn-induced insulin resistance. mTOR inhibition may become a therapeutic strategy in insulin-resistant states after burn.     

Effect of surgically removing subcutaneous fat by abdominoplasty on leptin concentrations and insulin sensitivity

The aim of this study was to identify the effect of surgically removing subcutaneous fat by abdominoplasty on leptin concentrations and insulin sensitivity. An open clinical trial with a noninterventional parallel group was carried out in 12 obese women. After randomization, 6 volunteers were selected for abdominoplasty, and the other 6 women were considered as the noninterventional group. A metabolic profile, including leptin concentrations, and insulin tolerance test to assess insulin sensitivity were performed on all volunteers before intervention or nonintervention and 40-50 days afterward. A significant reduction in body mass index (30.7 +/- 0.9 versus 29.6 +/- 0.7 kg/m; P = 0.02) and in leptin concentrations (41.3 +/- 10.6 versus 32.0 +/- 10.2 ng/mL; P = 0.02) was observed after abdominoplasty. Insulin sensitivity did not change after intervention. In conclusion, surgically removing subcutaneous fat by abdominoplasty decreased leptin concentrations, with no change in insulin sensitivity.     

局部应用胰岛素对烫伤大鼠创面愈合的影响

目的观察局部应用小剂量胰岛素对烫伤大鼠创面愈合的影响,探讨其可能的作用机制.方法制作深Ⅱ度烫伤大鼠模型.部分大鼠创面下浸润注射0.1、1.0 U胰岛素,分别设为B、C组;以创面下浸润注射等渗盐水(A组)和腹部皮下注射0.1 U胰岛素(D组)的烫伤大鼠作为对照.记录各组创面愈合时间,伤后3 d起隔日计算A、B、C组的创面愈合百分率.观察各组创面愈合后的组织形态学改变,采用流式细胞仪对各组创面表皮细胞进行细胞周期分析,并测定血糖浓度的变化. 结果A、B、C、D组创面愈合时间分别为(24.57±5.19)、(18.36±4.12)、(21.46±2.97)、(24.50±1.05)d,B组较其他3组明显缩短(P<0.01).伤后5、9、11、13、15、17、19 d B组创面愈合率均明显高于A组,且伤后17 d时明显高于C组(P<0.05～0.01).组织形态学观察可见A组表皮层薄,钉脚数量少,真皮层内多见纤维细胞;B、C组表皮层增厚,钉脚数量多,真皮层内多见成纤维细胞.B组伤后4 d S期细胞比例明显高于A组(P<0.01);B组伤后4、5 d G2-M期细胞比例均明显高于A、C组(P<0.05～0.01).烫伤后24 h A组血糖波动在3.42～4.62 mmol/L;B组血糖变化规律与A组相似;C、D组注射后1 h血糖明显降低(P<0.01),注射后4 h逐渐恢复正常.结论局部应用小剂量胰岛素能明显地促进烫伤大鼠创面愈合,胰岛素可加速修复细胞的增殖分裂可能是其作用机制之一.     

NN414, a SUR1/Kir6.2-selective potassium channel opener, reduces blood glucose and improves glucose tolerance in the VDF Zucker rat

A novel potassium channel opener compound, NN414, selective for the SUR1/Kir6.2 subtype of the ATP-sensitive potassium channel, was used to examine the effect of reducing beta-cell workload in the male Vancouver diabetic fatty (VDF) Zucker rat model of mild type 2 diabetes. Two chronic dosing protocols of NN414 of 3 weeks' duration were compared with appropriate vehicle-treated controls. In the first group, rats received NN414 (continued group; 1.5 mg/kg p.o. twice daily), during which an oral glucose tolerance test (OGTT) (on day 19 of dosing) was performed and insulin secretion from an in situ perfused pancreas preparation (on day 21) was measured. The second group received NN414 (discontinued group; same dose), but active treatment was replaced by vehicle treatment 2 days before the OGTT and for a further 2 days before the perfused pancreas study. Basal glucose was significantly reduced by NN414, with the fall averaging 0.64 mmol/l after 3 weeks of treatment (P < 0.0001). The glucose excursion and hyperinsulinemia during the OGTT were significantly different between the continued, discontinued, and vehicle groups (glucose area under the curve [AUC]: 640 +/- 29, 740 +/- 27, and 954 +/- 82 mmol. l(-1). min(-1), respectively, P < 0.0001; insulin AUC: 38.9 +/- 4.2, 44.2 +/- 4.2, and 55.1 +/- 2.6 nmol.l(-1).min(-1), respectively, P < 0.0001). Hyperinsulinemia during the pancreas perfusion with 4.4 mmol/l glucose was significantly reduced in both treatment groups versus vehicle (P < 0.0005). Insulin secretory responsiveness to a step increase in glucose from 4.4 to 16.6 mmol/l, calculated relative to basal, was significantly improved in the continued group versus vehicle (P < 0.01). In conclusion, administration of NN414 for 3 weeks in VDF rats reduces basal hyperglycemia, improves glucose tolerance, and reduces hyperinsulinemia during an OGTT and improves insulin secretory responsiveness ex vivo. NN414 may therefore represent a novel approach to the prevention and treatment of impaired glucose tolerance and type 2 diabetes.     

The use of a bioactive skin substitute decreases length of stay for pediatric burn patients

BACKGROUND: To optimize burn care for children, the authors introduced a protocol incorporating the use of a bioactive skin substitute, TransCyte (Advanced Tissue Sciences, La Jolla, CA). This study was designed to determine whether this management plan was safe, efficacious, and decreased hospital inpatient length of stay (LOS) compared with conventional burn management in children. METHODS: All pediatric burns greater than 7% total body surface area (TBSA) that occurred after October 1999 underwent wound closure with TransCyte (n = 20). These cases were compared with the previous 20 consecutive burn cases greater than 7% TBSA that received standard therapy. Standard therapy consisted of application of antimicrobial ointments and hydrodebridement. The following information was obtained: burn mechanism, age, size of burn, requirement of autograft, and LOS. Data were analyzed using the student's t test. RESULTS: Data for age, percent TBSA burn and LOS are reported as means +/- SEM. The children who received standard therapy were 2.99 +/- 0.7 years compared with those receiving TransCyte were 3.1 +/- 0.8 years. There was no difference between the treatment groups with regard to percent TBSA burn: standard therapy, 14.3 +/- 1.4% TBSA versus TransCyte, 12.7 +/- 1.3% TBSA. There was no difference in the type of burns in each group, the majority were liquid scald type, 70% in the standard therapy group versus 90% in the TransCyte group. Only 1 child in the TransCyte group required autografting (5%) compared with 7 children in the standard therapy group (35%). Children treated with TransCyte had a statistically 6 significant decreaed LOS compared with those receiving standard therapy, 5.9 +/- 0.9 days versus 13.8 +/- 2.2 days, respectively (P =.002). CONCLUSIONS: This is the first study using TransCyte in children. The authors found that this protocol of burn care was safe, effective, and significantly reduced the LOS. This new approach to pediatric burn care is effective and improves the quality of care for children with burns.     

胰岛素强化治疗对严重烫伤大鼠血清凋亡配体的作用

目的 了解大鼠严重烫伤后血清凋亡相关配体的变化及胰岛素强化治疗的作用.方法 将150只Wistar大鼠随机分为假伤组、烫伤组和治疗组.烫伤组和治疗组烫伤后立即腹腔注射等渗盐水40 mL/kg复苏;治疗组伤后24 h皮下注射胰岛素0.25 U/100 g,以后每12小时注射1次,共注射5 d.第1～5天的剂量分别为0.25、0.50、0.75、1.00、1.25 U/100 g,将大鼠血糖控制在3～6 mmol/L.假伤组浸入37℃温水假伤后不进行液体复苏.于伤后1、4、7、10、14 d抽取各组大鼠腹主动脉血,采用酶联免疫吸附测定法检测血清TNF-α、可溶性Fas配体(sFasL)、可溶性Fas受体(sFas);放射免疫法检测血清胰岛素水平.结果 烫伤组大鼠伤后1 d血清TNF-α水平[(30.9±8.7)ng/L]即达高峰,与假伤组[(12.7±2.8)ng/L]和治疗组[(16.8±4.7)ng/L]比较,差异有统计学意义(P<0.01),以后逐渐下降;治疗组大鼠伤后血清TNF-α水平虽然有所上升,但在伤后7 d内明显低于烫伤组(P<0.01).烫伤组、治疗组大鼠血清sFasL分别在伤后7～14 d和4～10 d高于假伤组(P<0.05),此后逐渐恢复至正常水平.伤后4～10 d治疗组sFas水平明显高于烫伤组及假伤组(P<0.05).伤后7、10 d烫伤组大鼠血清sFasL与sFas比值高于假伤组,而治疗组则在伤后7 d低于烫伤组(P<0.05),伤后14 d 2组均接近正常水平.烫伤组大鼠血清胰岛素水平在伤后4～10d低于假伤组(P<0.05).治疗组从伤后第1天起血清胰岛素水平即显著升高,伤后4 d[(327±15)μU/mL]达高峰,并显著高于假伤组[(42±15)μU/mL,P<0.01]和烫伤组[(28±10)μU/mL,P<0.01],随着治疗的进行,该指标逐渐恢复到正常水平.结论 胰岛素可能通过调节凋亡配体的分泌而抑制烧伤后细胞凋亡.     

Insulin resistance, secretion and breakdown are increased 9 months following severe burn injury

Insulin resistance in the acute burn period has been well described, however, it is unknown if alterations in glucose metabolism persist beyond discharge from the acute injury. To measure the duration of insulin resistance following recovery from the acute burn injury, we performed a prospective cross-sectional study with a standard 2-h oral glucose tolerance test in 46 severely burned children at 6, 9 or 12 months following initial injury. Glucose uptake and insulin secretion were assessed following the glucose load. Results were compared to those previously published in healthy children. At 6 months after burn, the 2-h glucose concentration was significantly (P<0.001) greater than controls, and the area under the curve (AUC) of glucose was significantly higher compared to 12 months and to healthy children (P=0.027 and P<0.001, respectively). The 9-month AUC glucose was higher than controls (P<0.01). The 6-month 2-h insulin was significantly higher than controls, as was the AUC of insulin in all time points post-burn. The AUC of C-peptide was significantly greater at 6 months after injury compared to 9 and 12 months (P<0.01 for both). Increased 2h and AUC glucose and insulin indicate that glucose metabolism is still affected at 6 and 9 months after injury, and coincides with previously documented defects in bone and muscle metabolism at these time points. Insulin breakdown is also still increased in this population. Further study of this population is warranted to determine if specific treatment is needed.     

The site of insulin resistance in acute uremia

In order to define the mechanism of glucose intolerance in acutely uremic rats, various studies were carried out 24 hours after bilateral nephrectomy. Glucose removal following intravenous glucose was significantly (p is less than 0.001) decreased in uremic rats compared with sham-operated rats (k = 2.1 +/- 0.03 per cent vs. 5.1 +/- 0.2 per cent). This deterioration in glucose tolerance was associated with higher insulin levels in uremic rats from one to 40 minutes after glucose administration, suggesting that insulin resistance accounted for the decrease in glucose removal by uremic rats. To identify the site of the insulin resistance, we compared the ability of insulin to enhance net glucose uptake by isolated perfused liver and muscle (hindlimb) preparations obtained from uremic and sham-operated rats. Insulin suppressed glucose outflow from perfused livers of uremic rats at least as well as it did from livers of sham-operated rats, and suppression occurred at both maximal ( greater than 600 micromicron./ml.) and threshold (75 micromicron./ml.) perfusate insulin levels. In contrast, there was a significant decrease in the ability of insulin (mean perfusate level = 225 micromicron./ml.) to enhance glucose uptake of perfused hindlimbs of uremic as compared with sham-operated rats. These results suggest that the insulin resistance of acute uremia may be due primarily to decreased insulin-mediated uptake of glucose by skeletal muscle without any decrease in sensitivity of the liver to insulin.     

Tolbutamide and burn hypermetabolism

Comparatively low level of serum insulin and tissue insulin resistance are characteristic of the stage of burn hypermetabolism. In order to evaluate the effect of tolbutamide in reducing burn hypermetabolism rate, 18 adult male rabbits weighing 1.8-2.5 Kg were subjected to 30% TBSA full thickness burns and randomized into treated and control groups. In the treated group, tolbutamide (90mg/Kg/day) was introduced into the stomach from 4 hours to 10 days postburn. Animals of both group were fed with specified food (protein 15%, glucose 80%) after burn. The values of serum glucose, insulin, glucagon, oxygen expenditure and other nutritional indices were measured before burn and 1, 3, 6, 10 days postburn. Their changes were as follows: (1) Serum glucose levels of the treated group were obviously lower than those of the control group (P less than 0.01). (2) Serum insulin levels and the ratio of I/G (insulin/glucagon) of the treated group were significantly higher than those of the control group (P less than 0.01). (3) The indices of cumulative N balance, oxygen expenditure, serum albumin in the treated group were better than that in the control (P less than 0.05-0.001). It is concluded that tolbutamide can reduce burn hypermetabolism probably through the following ways: 1. stimulation of the secretion of insulin and enhancement of the effect of insulin; 2. inhibition of the secretion of glucagon; 3. improvement in tissue insulin resistance and promotion of glucose utilization of skeletal muscles.     

几种深Ⅱ度烧伤创面处理方法的回顾及改善创面微循环的初步实验研究

目的回顾性分析几种深Ⅱ度烧伤创面的修复方法,探讨改善创面微循环对创面愈合的意义. 方法 (1)对于笔者单位烧伤患者的深Ⅱ度创面,应用削痂疗法治疗614例、磨痂疗法治疗32例、清创后异体皮覆盖86例、外用磺胺嘧啶银后创面暴露1 836例、外用中药京万红烫伤膏包扎治疗408例.统计、分析各种疗法的治疗效果.(2)制作大鼠深Ⅱ度烫伤模型.伤后5 min内分别由其尾静脉注入等渗盐水(对照组,10只)、巴曲酶(治疗组,10只),创面均外用磺胺嘧啶银.测定两组大鼠伤前及伤后0.5-72.0 h的创面皮肤血流灌注单位,计算其伤后14、18 d的创面愈合率、收缩率及创面愈合时间.用组织学方法观察两组大鼠创面愈合后的皮肤毛囊数. 结果 (1)削痂疗法术后2-3周创面愈合,其中烧伤总面积50%～79%TBSA的患者治愈率94.8%,总面积80%～98%TBSA者治愈率93.4%.磨痂疗法磨痂+异体皮覆盖术后(13.8±2.1)d创面愈合,无瘢痕形成.清创后异体皮覆盖其中82例患者术后(18.0±2.3)d创面愈合.外用磺胺嘧啶银后暴露其中1 658例患者用药后(26.0±3.2)d痂下愈合.外用京万红烫伤膏后包扎患者多有细菌感染,其中下肢创面愈合时间为(26.0±2.8)d.(2)治疗组大鼠伤后2.0-72.0 h创面局部血流灌注单位均明显高于对照组(P<0.01).伤后14、18 d,治疗组创面愈合率明显高于对照组(P<0.01),但两组创面收缩率接近(P>0.05).治疗组创面愈合时间短于对照组(P<0.01).伤后30 d,对照组大鼠真皮层中残存少量毛囊,数量明显少于治疗组(P<0.01). 结论深Ⅱ度烧伤后早期采用削痂、磨痂或清创后覆盖异体皮的方法处理创面,可减轻感染、缩短疗程、提高治愈率和愈合质量.使用巴曲酶可改善深Ⅱ度烧伤创面微循环,加快愈合速度.     

The dynamics of glucose metabolism under calcineurin inhibitors in the first year after renal transplantation in nonobese patients

BACKGROUND: The incidence of glucose metabolism disturbances after transplantation often is based on the use of hypoglycemic agents and not on the results of glucose tolerance tests (GTTs), which may camouflage the real incidence. A lack of information also exists regarding the profile of glucose metabolism during the first year after transplant. METHODS: Oral GTT along with insulin measurements and drugs pharmacokinetics were prospectively performed at days 30, 60, 180, and 360 after transplant to diagnose disturbances of glucose metabolism after renal transplantation, in nonobese patients receiving either tacrolimus (n=55) or cyclosporine (n=29), along with mycophenolate mofetil and steroids. RESULTS: The incidence of impaired glucose tolerance or diabetes mellitus reached a peak at 60 days and decreased at 1 year. It could not be adequately diagnosed using fasting plasma glucose in a decreased abnormal (>99 ng/mL) range. In both groups, insulin secretion, evaluated by the Homeostasis Model Assesment (HoMA-beta), decreased (P<0.005) from the condition of normal GTT (101+/-56%) to impaired glucose tolerance (72+/-35%) and diabetes mellitus (54+/-25%). In the cyclosporine group, insulin secretion was normal and stable throughout the study period, but in the tacrolimus group, insulin secretion recovered over time and was inversely correlated with tacrolimus exposure. Insulin resistance (HoMA-IR) did not change. CONCLUSIONS: This study shows the need to perform an oral GTT at 60 days and at the end of the first year of renal transplantation to adequately diagnose impaired glucose metabolism.     

Insulin tolerance during endotoxic shock in 10-day-old rats

PURPOSE: The purpose was to investigate insulin tolerance during endotoxic shock in 10-day-old rats. MATERIALS AND METHODS: [(14)C]Deoxy-glucose (2DG) with or without insulin (1 unit/kg) was injected to 10-day-old and 6-week-old rats 3 h after an injection of endotoxin (lipopolysaccharide: LPS). Plasma concentrations of glucose and 2DG were serially measured for 45 min. Gluconeogenesis was measured in hepatocytes isolated from control and endotoxic 10-day-old rats to evaluate effects of insulin on gluconeogenesis. RESULTS: In endotoxic 10-day-old rats, plasma glucose concentration at 45 min was 48 +/- 3% (P < 0.05) of value at 0 min, and when insulin was injected with 2DG, it was 29 +/- 4% (P < 0.05) after insulin injection. Plasma 2DG disappearance was enhanced by insulin injection in the control (t(1/2) = 17.9 vs 20.5 min, P < 0.05), but not in the endotoxic rats (t(1/2) = 17.9 vs 18.4 min), indicating the presence of insulin tolerance in septic rats. Insulin decreased gluconeogenesis (P < 0.05) in hepatocytes from both control and endotoxic 10-day-old rats. In endotoxic 6-week-old rats, plasma glucose concentration was decreased to 46 +/- 10% at 45 min and further decreased to 38 +/- 4% (P < 0.05) by insulin injection. Plasma 2DG disappearance was enhanced by insulin injection in the control (t(1/2) = 11.8 vs 17.4 min, P < 0.05) and in the septic rats (t(1/2) = 14.8 vs 12.2 min). However, the enhancement of plasma 2DG disappearance by insulin was less (P < 0.05) in the septic rats than in the control, confirming reports of other investigators which showed insulin tolerance in septic shock. CONCLUSION: Although hepatocytes from endotoxic rats retained insulin sensitivity, insulin tolerance which was evaluated by 2DG disappearance occurred during septic shock in newborn rats.     

Effects of insulin treatment in type 2 diabetic patients on intracellular lipid content in liver and skeletal muscle

Insulin resistance is frequently associated with increased lipid content in muscle and liver. Insulin excess stimulates tissue lipid accumulation. To examine the effects of insulin and improved glycemia on insulin sensitivity and intracellular lipids, we performed stepped (1, 2, and 4 mU x min(-1) x kg(-1)) hyperinsulinemic-euglycemic clamps in eight type 2 diabetic and six nondiabetic control subjects at baseline and after 12 and 67 h of insulin-mediated near-normoglycemia (118 +/- 7 mg/dl). Intrahepatocellular lipids (IHCLs) and intramyocellular lipids (IMCLs) of soleus (IMCL-S) and tibialis anterior muscle (IMCL-TA) were measured with (1)H nuclear magnetic resonance spectroscopy. At baseline, nondiabetic subjects had an approximate twofold higher insulin sensitivity (P < 0.02) and lower IHCLs than diabetic patients (5.8 +/- 1.2 vs. 18.3 +/- 4.2%, P < 0.03), in whom IMCL-TA negatively correlated with insulin sensitivity (r = -0.969, P < 0.001). After a 67-h insulin infusion in diabetic patients, IMCL-S and IHCLs were increased (P < 0.05) by approximately 36 and approximately 18%, respectively, and correlated positively with insulin sensitivity (IMCL-S: r = 0.982, P < 0.0005; IHCL: r = 0.865, P < 0.03), whereas fasting glucose production, measured with D-[6,6-(2)H(2)]glucose, decreased by approximately 10% (P < 0.04). In conclusion, these results indicate that IMCLs relate to insulin resistance in type 2 diabetic patients at baseline and that insulin-mediated near-normoglycemia for approximately 3 days reduces fasting glucose production but stimulates lipid accumulation in liver and muscle without affecting insulin sensitivity.     

Early differential defects of insulin secretion and action in 19-year-old caucasian men who had low birth weight

Several studies have linked low birth weight (LBW) and type 2 diabetes. We investigated hepatic and peripheral insulin action including intracellular glucose metabolism in 40 19-year-old men (20 LBW, 20 matched control subjects), using the hyperinsulinemic-euglycemic clamp technique at two physiological insulin levels (10 and 40 mU/m(2) per min), indirect calorimetry, and [3-(3)H]glucose. Insulin secretion was examined during an oral and intravenous glucose tolerance test. Fasting p-glucose was higher in the LBW group (5.6 +/- 0.1 vs. 5.4 +/- 0.1; P < 0.05). Basal plasma glycerol concentrations were significantly lower in the LBW group. Insulin-stimulated glycolytic flux was significantly reduced, and suppression of endogenous glucose production was enhanced in the LBW group. Nevertheless, basal and insulin-stimulated rates of whole-body peripheral glucose disposal, glucose oxidation, lipid oxidation, exogenous glucose storage, and nonoxidative glucose metabolism were similar in the two groups. Insulin secretion was reduced by 30% in the LBW group, when expressed relative to insulin sensitivity (disposition index = insulin secretion x insulin action). We propose that reduced insulin-stimulated glycolysis precedes overt insulin resistance in LBW men. A lower insulin secretion may contribute to impaired glucose tolerance and ultimately lead to diabetes.     

A comparison of troglitazone and metformin on insulin requirements in euglycemic intensively insulin-treated type 2 diabetic patients

Troglitazone and metformin lower glucose levels in diabetic patients without increasing plasma insulin levels. We compared the insulin sparing actions of these two agents and their effects on insulin sensitivity and insulin secretion in 20 type 2 diabetic patients. To avoid the confounding effect of improved glycemic control on insulin action and secretion, patients were first rendered euglycemic with 4 weeks of continuous subcutaneous insulin infusion (CSII) before randomization to CSII plus troglitazone (n = 10) or CSII plus metformin (n = 10); euglycemia was maintained for another 6-7 weeks. Insulin sensitivity was assessed by a hyperinsulinemic-euglycemic clamp 1) at baseline, 2) after 4 weeks of CSII, and 3) after CSII plus either troglitazone or metformin. The 24-h glucose, insulin, and C-peptide profiles were performed on the day before the second and third glucose clamps. Good glycemic control was achieved with CSII alone and was maintained with CSII plus an oral agent (mean 24-h glucose: troglitazone, 6.2+/-0.6 mmol/l; metformin, 6.2 +/-0.3 mmol/l). Insulin requirements decreased 53% with troglitazone compared with CSII alone (48+/-4 vs. 102+/-13 U/day, P < 0.001), but only 31% with metformin (76+/-13 vs. 110+/-18 U/day, P < 0.005). The 24-h C-peptide profiles were similar. Normal fasting hepatic glucose output was maintained with both agents despite lower insulin levels than on CSII alone. Insulin sensitivity did not change significantly with CSII alone or with CSII plus metformin, but improved 29% with CSII plus troglitazone (P < 0.005 vs. CSII alone) and was then 45% higher than in the CSII plus metformin patients (P < 0.005). In conclusion, metformin has no effect on insulin-stimulated glucose disposal independent of glycemic control in type 2 diabetes. Troglitazone (600 mg/day) has greater insulin-sparing effects than metformin (1,700 mg/day) in CSII-treated euglycemic patients. This is probably explained by the peripheral tissue insulin-sensitizing effects of troglitazone.     

Insulin sensitivity and exogenous insulin clearance in Graves' disease. Measurement by the glucose clamp technique and continuous indirect calorimetry

Insulin sensitivity was measured in a group of seven thyrotoxic patients and in a group of seven normal subjects by means of the glucose clamp technique. Infusion of insulin at a rate of 0.80 +/- 0.05 mU/kg X min in the hyperthyroid patients and of 0.55 +/- 0.04 mU/kg X min in the control group was performed to obtain a steady-state plasma insulin concentration of approximately 50 microU/ml. Substrate oxidation rates were measured in the postabsorptive state and during the 2 h of the clamp by means of continuous indirect calorimetry. In the postabsorptive state, hyperthyroid patients presented a preferential oxidation of lipids. During the period 60-120 min of the clamp, mean plasma glucose (92 +/- 2 versus 93 +/- 2 mg/dl), insulin (50 +/- 5 versus 58 +/- 3 microU/ml), and total glucose metabolism (5.8 +/- 0.7 versus 6.1 +/- 0.3 mg/kg X min) were similar in the hyperthyroid patients and the control subjects. The rate of glucose oxidation was higher in hyperthyroid patients than in control subjects (4.3 +/- 0.5 versus 2.2 +/- 0.2 mg/kg X min, P less than 0.001), while that of lipid oxidation was similar in both groups (0.6 +/- 0.2 versus control 0.7 +/- 0.1 mg/kg X min). The calculated metabolic clearance rate of insulin was markedly higher in the hyperthyroid patients (1144 +/- 132 ml/min) than in the normal subjects (812 +/- 56 ml/min, P less than 0.025). It is concluded that insulin sensitivity is not altered in the thyrotoxic state. The major route of insulin-stimulated glucose disposal in the hyperthyroid patients appears to be glucose oxidation.     

Restoration of euglycemia and normal acute insulin response to glucose in obese subjects with type 2 diabetes following bariatric surgery

Insulin resistance and loss of glucose-stimulated acute insulin response (AIR) are the two major and earliest defects in the course of type 2 diabetes. We investigated whether weight loss after bariatric surgery in patients with morbid obesity and type 2 diabetes could restore euglycemia and normal AIR to an intravenous glucose tolerance test (IVGTT). We studied 25 morbidly obese patients-12 with type 2 diabetes, 5 with impaired glucose tolerance, and 8 with normal glucose tolerance (NGT)-before and after a biliopancreatic diversion (BPD) with Roux-en-Y gastric bypass (RYGBP). Twelve individuals with normal BMI served as control subjects. Twelve months after surgery, in the diabetes group, BMI decreased from 53.2 +/- 2.0 to 29.2 +/- 1.7 kg/m(2), fasting glucose decreased from 9.5 +/- 0.83 to 4.5 +/- 0.13 mmol/l, and fasting insulin decreased from 168.4 +/- 25.9 to 37.7 +/- 4.4 pmol/l (mean +/- SE; P < 0.001). AIR, the mean of insulin concentration at 2, 3, and 5 min over basal in the IVGTT, increased by 770 and 935% at 3 and 12 months after surgery, respectively (from 24.0 +/- 22.7 to 209 +/- 43.4 and 248 +/- 33.1 pmol/l, respectively; P < 0,001). Conversely, in the NGT group, the AIR decreased by 40.5% (from 660 +/- 60 to 393 +/- 93 pmol/l; P = 0.027) 12 months after surgery. BPD with RYGBP performed in morbidly obese patients with type 2 diabetes leads to significant weight loss, euglycemia, and normal insulin sensitivity; but most importantly, it restores a normal beta-cell AIR to glucose and a normal relationship of AIR to insulin sensitivity. This is the first study to demonstrate that the lost glucose-induced AIR in patients with type 2 diabetes of mild or moderate severity is a reversible abnormality.