The effects of rosiglitazone on insulin sensitivity, lipolysis, and hepatic and skeletal muscle triglyceride content in patients with type 2 diabetes

We examined the effect of three months of rosiglitazone treatment (4 mg b.i.d.) on whole-body insulin sensitivity and in vivo peripheral adipocyte insulin sensitivity as assessed by glycerol release in microdialysis from subcutaneous fat during a two-step (20 and 120 mU.m(-2).min(-1)) hyperinsulinemic-euglycemic clamp in nine type 2 diabetic subjects. In addition, the effects of rosiglitazone on liver and muscle triglyceride content were assessed by (1)H-nuclear magnetic resonance spectroscopy. Rosiglitazone treatment resulted in a 68% (P < 0.002) and a 20% (P < 0.016) improvement in insulin-stimulated glucose metabolism during the low- and high- dosage-insulin clamps, respectively, which was associated with approximately 40% reductions in plasma fatty acid concentration (P < 0.05) and hepatic triglyceride content (P < 0.05). These changes were associated with a 39% increase in extramyocellular lipid content (P < 0.05) and a 52% increase in the sensitivity of peripheral adipocytes to the inhibitory effects of insulin on lipolysis (P = 0.04). In conclusion, these results support the hypothesis that thiazolidinediones enhance insulin sensitivity in patients with type 2 diabetes by promoting increased insulin sensitivity in peripheral adipocytes, which results in lower plasma fatty acid concentrations and a redistribution of intracellular lipid from insulin responsive organs into peripheral adipocytes.     

Differential effects of rosiglitazone and metformin on adipose tissue distribution and glucose uptake in type 2 diabetic subjects

We evaluated the effects of rosiglitazone (4 mg b.i.d.) and metformin (1 g b.i.d.) monotherapy for 26 weeks on adipose tissue insulin-stimulated glucose uptake in patients (n = 41) with type 2 diabetes. Before and after the treatment, glucose uptake was measured using 2-[(18)F]fluoro-2-deoxyglucose and positron emission tomography and adipose tissue masses were quantified using magnetic resonance imaging. Rosiglitazone improved insulin-stimulated whole-body glucose uptake by 44% (P < 0.01 vs. placebo). Mean body weight was unchanged in the rosiglitazone group, while it decreased by 2.0 kg in the metformin group (P < 0.05 vs. placebo). In visceral adipose tissue, glucose uptake increased by 29% (from 17.8 +/- 2.0 to 23.0 +/- 2.6 micro mol x kg(-1) x min(-1), P < 0.05 vs. placebo) in the rosiglitazone group but to a lesser extent (17%) in the metformin group (from 16.2 +/- 1.5 to 18.9 +/- 1.7 micro mol x kg(-1) x min(-1), P < 0.05 vs. baseline). Because the visceral adipose tissue mass simultaneously decreased with both treatments (P < 0.05), no change was observed in total visceral glucose uptake per depot. Rosiglitazone significantly enhanced glucose uptake in the femoral subcutaneous area, either when expressed per tissue mass (from 10.8 +/- 1.2 to 17.1 +/- 1.7 micro mol x kg(-1) x min(-1), P < 0.01 vs. placebo) or per whole-fat depot (P < 0.05 vs. placebo). In conclusion, metformin treatment resulted in improvement of glycemic control without enhancement of peripheral insulin sensitivity. The improved insulin sensitivity of the nonabdominal subcutaneous adipose tissue during treatment with rosiglitazone partly explains the enhanced whole-body insulin sensitivity and underlies the central role of adipose tissue for action of peroxisome proliferator-activated receptor gamma agonist in vivo.     

Effects of metformin and rosiglitazone treatment on insulin signaling and glucose uptake in patients with newly diagnosed type 2 diabetes: a randomized controlled study

The effect of metformin or rosiglitazone monotherapy versus placebo on insulin signaling and gene expression in skeletal muscle of patients with newly diagnosed type 2 diabetes was determined. A euglycemic-hyperinsulinemic clamp, combined with skeletal muscle biopsies and glucose uptake measurements over rested and exercised muscle, was performed before and after 26 weeks of metformin (n = 9), rosiglitazone (n = 10), or placebo (n = 11) treatment. Insulin-mediated whole-body and leg muscle glucose uptake was enhanced 36 and 32%, respectively, after rosiglitazone (P < 0.01) but not after metformin or placebo treatment. Insulin increased insulin receptor substrate 1 (IRS-1) tyrosine phosphorylation, IRS-1-associated phosphatidylinositol (PI) 3-kinase activity, and phosphorylation of Akt Ser473 and AS160, a newly described Akt substrate that plays a role in GLUT4 exocytosis, approximately 2.3 fold before treatment. These insulin signaling parameters were unaltered after metformin, rosiglitazone, or placebo treatment. Expression of selected genes involved in glucose and fatty acid metabolism in skeletal muscle was unchanged between the treatment groups. Low-intensity acute exercise increased insulin-mediated glucose uptake but was without effect on insulin signaling. In conclusion, the insulin-sensitizing effects of rosiglitazone are independent of enhanced signaling of IRS-1/PI 3-kinase/Akt/AS160 in patients with newly diagnosed type 2 diabetes.     

Pioglitazone reduces hepatic fat content and augments splanchnic glucose uptake in patients with type 2 diabetes

The effect of pioglitazone on splanchnic glucose uptake (SGU), endogenous glucose production (EGP), and hepatic fat content was studied in 14 type 2 diabetic patients (age 50 +/- 2 years, BMI 29.4 +/- 1.1 kg/m(2), HbA(1c) 7.8 +/- 0.4%). Hepatic fat content (magnetic resonance spectroscopy) and SGU (oral glucose load- insulin clamp technique) were quantitated before and after pioglitazone (45 mg/day) therapy for 16 weeks. Subjects received a 7-h euglycemic insulin (100 mU. m(-2). min(-1)) clamp, and a 75-g oral glucose load was ingested 3 h after starting the insulin clamp. Following glucose ingestion, the steady-state glucose infusion rate during the insulin clamp was decreased appropriately to maintain euglycemia. SGU was calculated by subtracting the integrated decrease in glucose infusion rate during the 4 h after glucose ingestion from the ingested glucose load. 3-[(3)H]glucose was infused during the initial 3 h of the insulin clamp to determine rates of EGP and glucose disappearance (R(d)). Pioglitazone reduced fasting plasma glucose (10.0 +/- 0.7 to 7.5 +/- 0.6 mmol/l, P < 0.001) and HbA(1c) (7.8 +/- 0.4 to 6.7 +/- 0.3%, P < 0.001) despite increased body weight (83 +/- 3 to 86 +/- 3 kg, P < 0.001). During the 3-h insulin clamp period before glucose ingestion, pioglitazone improved R(d) (6.9 +/- 0.5 vs. 5.2 +/- 0.5 mg. kg(-1). min(- 1), P < 0.001) and insulin-mediated suppression of EGP (0.21 +/- 0.04 to 0.06 +/- 0.02 mg. kg(-1). min(-1), P < 0.01). Following pioglitazone treatment, hepatic fat content decreased from 19.6 +/- 3.6 to 10.4 +/- 2.1%, (P < 0.005), and SGU increased from 33.0 +/- 2.8 to 46.2 +/- 5.1% (P < 0.005). Pioglitazone treatment in type 2 diabetes 1) decreases hepatic fat content and improves insulin-mediated suppression of EGP and 2) augments splanchnic and peripheral tissue glucose uptake. Improved splanchnic/peripheral glucose uptake and enhanced suppression of EGP contribute to the improvement in glycemic control in patients with type 2 diabetes.     

Reversal of nonalcoholic hepatic steatosis, hepatic insulin resistance, and hyperglycemia by moderate weight reduction in patients with type 2 diabetes

To examine the mechanism by which moderate weight reduction improves basal and insulin-stimulated rates of glucose metabolism in patients with type 2 diabetes, we used (1)H magnetic resonance spectroscopy to assess intrahepatic lipid (IHL) and intramyocellular lipid (IMCL) content in conjunction with hyperinsulinemic-euglycemic clamps using [6,6-(2)H(2)]glucose to assess rates of glucose production and insulin-stimulated peripheral glucose uptake. Eight obese patients with type 2 diabetes were studied before and after weight stabilization on a moderately hypocaloric very-low-fat diet (3%). The diabetic patients were markedly insulin resistant in both liver and muscle compared with the lean control subjects. These changes were associated with marked increases in IHL (12.2 +/- 3.4 vs. 0.6 +/- 0.1%; P = 0.02) and IMCL (2.0 +/- 0.3 vs. 1.2 +/- 0.1%; P = 0.02) compared with the control subjects. A weight loss of only approximately 8 kg resulted in normalization of fasting plasma glucose concentrations (8.8 +/- 0.5 vs. 6.4 +/- 0.3 mmol/l; P < 0.0005), rates of basal glucose production (193 +/- 7 vs. 153 +/- 10 mg/min; P < 0.0005), and the percentage suppression of hepatic glucose production during the clamp (29 +/- 22 vs. 99 +/- 3%; P = 0.003). These improvements in basal and insulin-stimulated hepatic glucose metabolism were associated with an 81 +/- 4% reduction in IHL (P = 0.0009) but no significant change in insulin-stimulated peripheral glucose uptake or IMCL (2.0 +/- 0.3 vs. 1.9 +/- 0.3%; P = 0.21). In conclusion, these data support the hypothesis that moderate weight loss normalizes fasting hyperglycemia in patients with poorly controlled type 2 diabetes by mobilizing a relatively small pool of IHL, which reverses hepatic insulin resistance and normalizes rates of basal glucose production, independent of any changes in insulin-stimulated peripheral glucose metabolism.     

罗格列酮联合二甲双胍治疗2型糖尿病临床疗效分析

目的观察罗格列酮联合二甲双胍治疗2型糖尿病的临床效果。方法将65例符合2型糖尿病诊断标准的门诊患者随机分组,试验组35例,予以口服罗格列酮及二甲双胍联合治疗;对照组30例,仅予以口服罗格列酮治疗。观察两组患者治疗前及治疗12周后FBG、FINS、DBP、SBP和IRI变化情况,并监测患者肝肾功能和血常规。结果治疗后两组患者血糖、血压及胰岛素均较治疗前有显著下降（P〈0.05）;试验组FBG、FINS、DBP、SBP及IRI等指标下降幅度均大于对照组,差异有统计学意义（P〈0.05）;两组患者均无肝、肾功能损害。结论罗格列酮联合二甲双胍治疗2型糖尿病,具有改善患者胰岛素抵抗和降低血压的作用,且临床疗效确切,优于单独使用罗格列酮。     

西格列汀联合二甲双胍对2型糖尿病伴骨质疏松症患者骨代谢的影响

目的探讨西格列汀联合二甲双胍对2型糖尿病伴骨质疏松患者骨转换标志物和骨密度的影响。方法选取2015年1月至2016年1月在本院明确诊断的2型糖尿病合并骨质疏松患者95例,随机分为3组,二甲双胍(metformin,M)+阿卡波糖组(acarbose,A)(M+A组)32例、西格列汀(sitagliptin,S)+阿卡波糖组(S+A组)31例、西格列汀+二甲双胍+阿卡波糖组(S+M+A组)32例,治疗随访48周。治疗前及治疗48周后测定体质量指数(body mass index,BMI)、血清空腹血糖(fasting plasma glucose,FPG)、餐后2小时血糖(2-hour postprandial plasma glucose,2h PG)、糖化血红蛋白(glycated hemoglobin A1c,Hb A1c)、25-羟基维生素D[25-hydroxyvitamin D,25(OH)D]、骨钙素(osteocalcin,OC)、I型胶原羧基端肽β特殊系列(β-cterminal cross-linked telpeptide,β-CTX)、骨特异碱性磷酸酶(bone specific alkaline phosphatase,b-ALP)。采用双能X线吸收测定法(dual energy X-ray absorptiometry,DXA)测定患者腰椎2~4及股骨颈的骨密度(bone mineral density,BMD)。比较各组治疗前后BMI、生化指标、骨转换指标和BMD的变化。结果 5例患者因药物不耐受而脱落,90例患者完成治疗随访,3组各30例。M+A组、S+A组、S+M+A组患者治疗前BMI[(25.1±1.5、25.2±1.6、25.1±1.7)kg/m2]、FPG[(8.45±0.81、8.43±0.83、8.46±0.91)mmol/L]、2h PG[(11.54±1.58、11.68±1.61、11.72±1.70)mmol/L]、Hb A1c[(7.92±0.71、7.95±0.73、7.94±0.75)%]比较差异无统计学意义(均P0.05);治疗后BMI[(24.2±1.6、24.1±1.5、23.5±1.4)kg/m2]、FPG[(6.51±0.69、6.49±0.67、6.15±0.71)mmol/L]、2h PG[(9.10±0.72、9.18±0.89、8.11±0.51)mmol/L]、Hb A1c[(6.71±0.51、6.74±0.53、6.18±0.58)%]均较治疗前显著下降,差异有统计学意义(均P0.05);治疗后S+M+A组与M+A组和S+A组BMI、FPG、2h PG、Hb A1c比较下降更显著,差异有统计学意义(均P0.05);M+A组与S+A组BMI、FPG、2h PG、Hb A1c比较差异无统计学意义(均P0.05)。M+A组、S+A组、S+M+A组患者治疗前b-ALP[(12.5±1.9、12.6±2.1、12.4±2.4)U/L]、OC[(14.2±1.8、14.3±1.7、14.1±1.9)μg/L]、β-CTX[(413.5±65.3、420.4±70.5、428.1±69.6)ng/L]和腰椎2~4的BMD[(0.417±0.091、0.415±0.086、0.419±0.095)g/cm2]及股骨颈的BMD[(0.483±0.086、0.492±0.092、0.487±0.094)g/cm2]比较差异无统计学意义(均P0.05);治疗后b-ALP[(15.8±2.4、16.1±2.5、20.4±2.9)U/L]、OC[(16.9±2.2、17.2±2.4、20.5±2.6)μg/L]明显升高,β-CTX[(351.7±45.8、352.9±47.9、319.5±50.9)ng/L]明显下降,腰椎2~4的BMD[(0.552±0.087、0.572±0.079、0.632±0.084)g/cm2]及股骨颈BMD[(0.617±0.073、0.621±0.073、0.715±0.083)g/cm2]增加,与治疗前比较差异有统计学意义(均P0.05);治疗后S+M+A组与M+A组和S+A比较,b-ALP、OC、BMD升高更显著,β-CTX下降更显著,差异有统计学意义(均P0.05);M+A组与S+A组b-ALP、OC、β-CTX、BMD比较差异无统计学意义(均P0.05)。3组患者治疗前、后25(OH)D变化无统计学意义(均P0.05)。结论西格列汀和二甲双胍除了具有降低血糖的作用外,还能够促进骨形成、抑制骨吸收,增加糖尿病合并骨质疏松患者骨密度,且两药联合应用有叠加增强作用。     

Agouti expression in human adipose tissue: functional consequences and increased expression in type 2 diabetes

It is well recognized that the agouti/melanocortin system is an important regulator of body weight homeostasis. Given that agouti is expressed in human adipose tissue and that the ectopic expression of agouti in adipose tissue results in moderately obese mice, the link between agouti expression in human adipose tissue and obesity/type 2 diabetes was investigated. Although there was no apparent relationship between agouti mRNA levels and BMI, agouti mRNA levels were significantly elevated in subjects with type 2 diabetes. The regulation of agouti in cultured human adipocytes revealed that insulin did not regulate agouti mRNA, whereas dexamethasone treatment potently increased the levels of agouti mRNA. Experiments with cultured human preadipocytes and with cells obtained from transgenic mice that overexpress agouti demonstrated that melanocortin receptor (MCR) signaling in adipose tissue can regulate both preadipocyte proliferation and differentiation. Taken together, these results reveal that agouti can regulate adipogenesis at several levels and suggest that there are functional consequences of elevated agouti levels in human adipose tissue. The influence of MCR signaling on adipogenesis combined with the well-established role of MCR signaling in the hypothalamus suggest that adipogenesis is coordinately regulated with food intake and energy expenditure.     

Role of selenium in type 2 diabetes,insulin resistance and insulin secretion

Selenium is a trace mineral essential for life that acts physiologically through selenoproteins. Among other actions, the endogenous antioxidant selenoprotein glutathione peroxidase and the selenium transporter in blood, selenoprotein P,seem to play an important role in type 2 diabetes mellitus and insulin resistance by weakening the insulin signaling cascade through different mechanisms. Recent findings also suggest that selenoproteins also affect insulin biosynthesis and insulin secretion. Thi...     

声辐射力脉冲成像评估2型糖尿病胰岛素抵抗患者肝脏功能

目的应用声辐射力脉冲成像(ARFI)中的声触诊组织量化(VTQ)技术评估2型糖尿病(T2DM)胰岛素抵抗(IR)患者肝脏弹性的改变。方法收集62例T2DM患者,分为IR组(n=32)和非IR组(n=30);检测空腹血糖、空腹胰岛素、低密度脂蛋白胆固醇(LDL-C)、高密度脂蛋白胆固醇(HDL-C)、总胆固醇(TC)、甘油三酯(TG),并计算稳态模型IR指数;应用VTQ技术测定肝脏剪切波速度(SWV),分析其与IR及脂代谢相关血液指标的相关性。结果 IR组平均肝脏SWV值为(1.33±0.18)m/s,非IR组平均肝脏SWV值为(1.04±0.10)m/s,差异有统计学意义(P0.05)。随着肝脏SWV值升高,TC、TG、LDL-C升高而HDL-C降低。结论 T2DM患者肝脏SWV值与IR情况及血脂水平有密切关系;ARFI技术可用于评估T2DM IR患者的肝脏弹性及脂代谢情况。     

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.     

CCNG2 and CDK4 is associated with insulin resistance in adipose tissue

BackgroundThe involvement of cyclin G2 (CCNG2) and cyclin-dependent kinase-4 (CDK4), cell cycle regulatory proteins, in adipose tissue metabolism and insulin resistance is still unknown. The objective of this study was to analyze CCNG2 and CDK4 levels in visceral (VAT) and subcutaneous adipose tissue (SAT) from nonobese and morbidly obese patients and their relationship with insulin resistance.MethodsWe studied the mRNA and protein levels of CCNG2 and CDK4 in VAT and SAT from 12 nonobese and 23 morbidly obese patients (11 with low [MO-L-IR] and 12 with high insulin resistance [MO-H-IR]).ResultsThe nonobese patients had a significantly greater CCNG2 expression in VAT (P = .004) and SAT (P<.001) than the MO-L-IR and MO-H-IR patients. The MO-H-IR patients had a significantly lower CDK4 expression in VAT than the MO-L-IR (P = .026), but similar to the nonobese patients. CDK4 and CCNG2 expression correlated significantly in VAT (r = 0.511, P<.001) and SAT (r = .535, P = .001). In different multiple regression analysis models, CCNG2 and CDK4 expression in VAT was mainly predicted by glucose (P = .047 and P = .008, respectively), and CCNG2 expression in SAT was mainly predicted by body mass index (P = .041). No significant associations were found with CDK4 expression in SAT. Moreover, VAT CCNG2 expression was the main determinant of the improvement in the homeostasis model assessment of insulin resistance index at 3 months after bariatric surgery (B = -271.7, P = .026).ConclusionOur data show for the first time that the human CCNG2 and CDK4 expression of VAT are inversely associated with glucose and insulin resistance.     

Angiotensin receptor blockers improve insulin resistance in type 2 diabetic rats by modulating adipose tissue

Adipose tissue is recognized as a pivotal organ in the development of insulin resistance. This study seeks to determine the effect of angiotensin receptor blockade (ARB) on insulin resistance of adipocytes in culture and in a rat model of type 2 diabetes. Treatment of Otsuka Long-Evans Tokushima Fatty rats with the ARB L158809 for six months significantly lowered fasting plasma glucose, cholesterol and triglyceride levels but led to higher plasma adiponectin levels. Insulin resistance, measured by an intraperitoneal glucose tolerance test, of the treated rats was significantly improved along with an increase in the number of small differentiated adipocytes; however, epididymal fat mass decreased. Treatment significantly lowered lipid peroxidation and MCP-1 expression while increasing adiponectin production by the adipose tissue. ARB treatment significantly improved insulin sensitivity and markedly suppressed AT2-induced oxidative stress, PAI-1 and MCP-1 levels and NF-kappaB activation of adipocytes in culture. Treatment increased adiponectin and PPARgamma expression along with intracellular triglyceride levels reflecting differentiation of the cultured adipocytes. Our study suggests that ARB treatment improves insulin resistance by modification of adipose tissue thereby blunting the development of diabetes.     

初诊2型糖尿病心理性胰岛素抵抗患者的健康教育

目的 提高初诊2型糖尿病心理性胰岛素抵抗患者的健康教育效果.方法 将126例住院初诊2型糖尿病心理性胰岛素抵抗患者按住院时间段分为对照组60例和观察组66例,对照组给予常规糖尿病健康教育,观察组在此基础上针对心理性胰岛素抵抗原因给予强化教育.结果 入院后2周观察组胰岛素知识与注射技能考试成绩显著优于对照组(均P＜0.01),空腹血糖及餐后2h血糖水平显著低于对照组(均P＜0.05).结论 强化心理性胰岛素抵抗相关内容教育有利于初诊2型糖尿病心理性胰岛素抵抗患者掌握胰岛素相关知识,从而有效控制血糖.     

Regulation of glucose transport and insulin signaling by troglitazone or metformin in adipose tissue of type 2 diabetic subjects.

Type 2 diabetic subjects failing glyburide therapy were randomized to receive additional therapy with either metformin (2,550 mg/day) or troglitazone (600 mg/day) for 3-4 months. Biopsies of subcutaneous abdominal adipose tissue were obtained before and after therapy. Glycemic control was similar with both treatments. Metformin treatment increased insulin-stimulated whole-body glucose disposal rates by 20% (P < 0.05); the response to troglitazone was greater (44% increase, P < 0.01 vs. baseline, P < 0.05 vs. metformin). Troglitazone-treated subjects displayed a tendency toward weight gain (5 +/- 2 kg, P < 0.05), increased adipocyte size, and increased serum leptin levels. Metformin-treated subjects were weight-stable, with unchanged leptin levels and reduced adipocyte size (to 84 +/- 4% of control, P < 0.005). Glucose transport in isolated adipocytes from metformin-treated subjects was unaltered from pretreatment. Glucose transport in both the absence (321 +/- 134% of pre-Rx, P < 0.05) and presence of insulin (418 +/- 161%, P < 0.05) was elevated after troglitazone treatment. Metformin treatment had no effect on adipocyte content of GLUT1 or GLUT4 proteins. After troglitazone treatment, GLUT4 protein expression was increased twofold (202 +/- 42%, P < 0.05). Insulin-stimulated serine phosphorylation of Akt was augmented after troglitazone (170 +/- 34% of pre-Rx response, P < 0.05) treatment and unchanged by metformin. We conclude that the ability of troglitazone to upregulate adipocyte glucose transport, GLUT4 expression, and insulin signaling can contribute to its greater effect on whole-body glucose disposal.     

Insulin-receptor gene and its expression in patients with insulin resistance

We studied the structure of the insulin-receptor gene in normal individuals and in four unrelated patients with leprechaunism (Minn-1, Ark-1, Ark-2, Can-1) and four unrelated patients with the type A syndrome of insulin resistance, both disorders associated with genetic alterations in affinity, binding capacity, and kinase activity of the insulin receptor. Genomic cloning and Southern blot analysis indicate that the normal human insulin-receptor gene is greater than or equal to 150 kilobases long and consists of a minimum of 17 exons, 6 in the genomic region of the alpha-subunit and 11 in the region of the beta-subunit. Three of the patients, one with leprechaunism and two with type A syndrome, have decreases in insulin-receptor mRNA but on genomic blot analysis have no obvious abnormalities in the insulin-receptor gene. No distinctive pattern of restriction-fragment-length polymorphisms or evidence for major insertion or deletion mutations of the insulin-receptor gene was found in any of the patients. These data indicate that the insulin-receptor gene is greater than 35 times larger than coding regions and has a complex structure. Although leprechaunism and type A syndrome are most likely due to defects in the structure and expression of the insulin-receptor gene, they are likely to be associated with specific point mutations rather than major changes in gene structure.     

Decreased expression of heat shock protein 72 in skeletal muscle of patients with type 2 diabetes correlates with insulin resistance

Oxidative stress has been ascribed a role in the pathogenesis of diabetes and its complications, and stress proteins have been shown to protect organisms in vitro and in vivo against oxidative stress. To study the putative role of one of the most abundant cytoprotective stress proteins, inducible cytoplasmic 72-kDa-mass heat shock protein (Hsp-72), in the pathogenesis of diabetes, we measured its mRNA concentration in muscle biopsies from six type 2 diabetic patients and six healthy control subjects (protocol 1) as well as in 12 twin pairs discordant for type 2 diabetes and 12 control subjects undergoing a euglycemic-hyperinsulinemic clamp in combination with indirect calorimetry (protocol 2). The amount of Hsp-72 mRNA in muscle was significantly lower in type 2 diabetic patients than in healthy control subjects (in protocol 1: 5.2 +/- 2.2 vs. 53 +/- 32 million copies of Hsp-72 mRNA/microg total RNA, n = 6, P = 0.0039; in protocol 2: 3.2 +/- 3.3 vs. 43 +/- 31 million copies of Hsp-72 mRNA/microg total RNA, n = 12, P = 0.0001). Hsp-72 mRNA levels were also markedly reduced in the nondiabetic co-twins compared with healthy control subjects (5.8 +/- 5.0 vs. 43 +/- 31, n = 12, P = 0.0001), but they were also statistically significantly different from their diabetic co-twins when the difference between the pairs was compared (P = 0.0280). Heat shock protein mRNA content in muscle of examined patients correlated with the rate of glucose uptake and other measures of insulin-stimulated carbohydrate and lipid metabolism. In conclusion, the finding of decreased levels of Hsp-72 mRNA in skeletal muscle of patients with type 2 diabetes and its relationship with insulin resistance raises the question of whether heat shock proteins are involved in the pathogenesis of skeletal muscle insulin resistance in type 2 diabetes.