钙调磷酸酶抑制剂胰岛毒性作用的机制及临床意义

本文就钙调磷酸酶抑制剂引起胰岛毒性作用的机制予以综述,并着重探讨了钙调磷酸酶 抑制剂在肾移植、胰岛移植中的应用及前景。

视神经萎缩蛋白1与糖尿病心肌病相关性的研究进展

糖尿病心肌病(DCM)是指单纯由高血糖引起的心肌细胞或心脏微血管损伤及代谢障碍。有研究表明,DCM与线粒体融合异常密切相关。视神经萎缩蛋白1(Opa1)是线粒体融合的主要蛋白之一。在高血糖环境下,Opa1表达减少,造成线粒体融合障碍,进而引起心肌细胞能量代谢障碍、氧化应激、胰岛素抵抗与脂毒性增加、细胞凋亡等,最终导致DCM。上调Opa1的表达则能使DCM的症状得到改善。该文就Opa1与DCM的相关性的研究进展做一综述,为DCM的研究提供新思路。

瘦素对游离脂肪酸致大鼠胰岛β细胞脂毒性的保护作用

目的 探讨瘦素对于游离脂肪酸(FFA)导致的大鼠胰岛β细胞脂毒性的保护作用。方法体外分离Wistar大鼠胰岛进行培养,根据培养液中加入不同物质而分为4组:(1)对照组,(2)瘦素组,(3)FFA组,(4)FFA+瘦素组。培养72h后测定胰岛内甘油三酯(TG)含量,基础状态及葡萄糖刺激下胰岛素分泌情况,并用RT-PCR方法检测胰岛β细胞内脂肪酸氧化酶-肉毒碱软脂酰转移酶Ⅰ(CPT-Ⅰ)、脂肪酸合成酶-乙酰辅酶A羧化酶(ACC)以及过氧化质体增殖物激活受体α(PPARα)和PPARγ的mRNA表达情况 结果 (1)FFA使胰岛内TG含量增加(P<0.01),瘦素使胰岛内TG含量减少(P<0.01)。(2)瘦素抑制基础状态及高糖负荷后胰岛素分泌(均P<0.01);FFA使基础胰岛素分泌增加而高糖负荷后胰岛素分泌的增高幅度明显低于对照组(均P<0.01)。(3)瘦素使CPT-Ⅰ和PPARα表达增加(分别P<0.01和P<0.05),ACC和PPARγ表达减少(均P<0.01);FFA使CPT-Ⅰ和ACC表达增加,PPARα和PPARγ表达减少(均P<0.01)。结论 FFA使胰岛内TC聚集增加,基础状态胰岛素分泌增加而高糖负荷后胰岛素分泌减少,形成高胰岛素血症。而瘦素可以通过PPARα和PPARγ途径使胰岛内脂肪酸氧化酶表达增加,脂肪酸合成酶表达减少,胰岛内TG聚集减少,同时抑制胰岛素分泌,减轻高胰岛素血症。

Association of chronic viral hepatitis B with insulin resistance

AIM:To investigate the relationship between chronic viral hepatitis B(CVHB) and insulin resistance(IR) in Korean adults.METHODS:A total of 7880 adults(3851 men,4029 women) who underwent a comprehensive medical examination were enrolled in this study.Subjects diagnosed with either diabetes mellitus,or any other disorder that could influence their insulin sensitivity,were rejected.Anthropometry,metabolic risk factors,hepatitis B surface antigen,hepatitis B surface antibody,hepatitis B core antibody,fasting plasma glucose and insulin were measured for all subjects.Homeostasis model assessment(HOMA),quantitative insulin check index(QUICKI),and Mf fm index were used for determining insulin sensitivity.Each participant was categorized into a negative,recovery,or CVHB group.To compare variables between groups,a t-test and/or one-way analysis of variance were used.Partial correlation coefficients were computed to present the association between insulin resistance and other variables.Multiple logistic regression analysis was used to assess the independent association between CVHB and IR.RESULTS:The mean age of men and women were 48.9 and 48.6 years,respectively.Subjects in the CVHB group had significantly higher waist circumference [(86.0 ± 7.7 cm vs 87.3 ± 7.8 cm,P = 0.004 in men),(78.3 ± 8.6 cm vs 80.5 ± 8.5 cm,P < 0.001 in women)],cystatin C [(0.96 ± 0.15 mg/dL vs 1.02 ± 0.22 mg/dL,P < 0.001 in men),(0.84 ± 0.15 mg/dL vs 0.90 ± 0.16 mg/dL,P < 0.001 in women)],fasting insulin [(5.47 ± 3.38 U/mL vs 6.12 ± 4.62 U/mL,P < 0.001 in men),(4.57 ± 2.82 U/mL vs 5.06 ± 3.10 U/mL,P < 0.001 in women)] and HOMA index [(1.24 ± 0.86 vs 1.43 ± 1.24,P < 0.001 in men),(1.02 ± 0.76 vs 1.13 ± 0.87,P = 0.033 in women)] compared to control group.The HOMA index revealed a positive correlation with body mass index(BMI)(r = 0.378,P < 0.001),waist circumference(r =0.356,P < 0.001),percent body fat(r = 0.296,P < 0.001),systolic blood pressure(r = 0.202,P < 0.001),total cholesterol(r = 0.134,P < 0.001),triglycerides(r = 0.292,P < 0.001),cystatin C(r = 0.069,P < 0.001) and uric acid(r = 0.142,P < 0.001).The QUICKI index revealed a negative correlation with BMI(r =-0.254,P < 0.001),waist circumference(r = 0-0.243,P < 0.001),percent body fat(r =-0.217,P < 0.001),systolic blood pressure(r =-0.132,P < 0.001),total cholesterol(r =-0.106,P < 0.001),triglycerides(r =-0.205,P < 0.001),cystatin C(r =-0.044,P < 0.001) and uric acid(r =-0.096,P < 0.001).For subjects identified with IR,the odds ratio of an accompanying diagnosis of chronic hepatitis B was 1.534(95% CI:1.158-2.031,HOMA index criteria) or 1.566(95% CI:1.124-2.182,QUICKI criteria) after adjustment for age,gender,BMI,and amount of alcohol consumption.CONCLUSION:Our study demonstrates that CVHB is associated with IR.CVHB may need to be monitored for occurrence of IR and diabetes mellitus.

Insulin resistance and hepatitis C

Insulin resistance is the major feature of the metabolic syndrome and depends on insulin secretion and insulin sensitivity. In chronic hepatitis C, insulin resistance and type 2 diabetes mellitus are more often seen than in healthy controls or chronic hepatitis B patients. Hepatitis C virus （HCV） infection promotes insulin resistance, mainly by increased TNF production together with enhancement of suppressor of cytokine （SOC-3）; both events block PI3K and Akt phosphorylation. Two types of insulin resistance could be found in chronic hepatitis C patients＇. ＂viral＂ and ＂metabolic＂ insulin resistance. Insulin resistance in chronic hepatitis C is relevant because it promotes steatosis and fibrosis. The mechanisms by which insulin resistance promotes fibrosis progression include： （1） steatosis, （2） hyperleptinemia, （3） increased TNF production, （4） impaired expression of PPARy receptors. Lastly, insulin resistance has been found as a common denominator in patients difficult-to-treat like cirrhotics, overweight, HIV coinfected and Afro-American. Insulin resistance together with fibrosis and genotype has been found to be independently associated with impaired response rate to peginterferon plus ribavirin. Indeed, in genotype 1, the sustained response rate was twice （60%） in patients with HOMA ≤ 2 than patients with HOMA 〉 2. In experiments carried out on Huh-7 cells transfected by full length HCVRNA, interferon alpha blocks HCV replication. However, when insulin （at doses of 128 μU/mL, similar that seen in the hyperinsulinemic state） was added to interferon, the ability to block HCV replication disappeared, and the PKR synthesis was abolished. In summary, hepatitis C promotes insulin resistance and insulin resistance induces interferon resistance, steatosis and fibrosis progression.

Pathophysiology of insulin resistance and steatosis in patients with chronic viral hepatitis

Chronic hepatitis due to any cause leads to cirrhosis and end-stage liver disease.A growing body of literature has also shown that fatty liver due to overweight or obesity is a leading cause of cirrhosis.Due to the obesity epidemic,fatty liver is now a significant problem in clinical practice.Steatosis has an impact on the acceleration of liver damage in patients with chronic hepatitis due to other causes.An association between hepatitis C virus (HCV) infection,steatosis and the onset of insulin resistance has been reported.Insulin resistance is one of the leading factors for severe fibrosis in chronic HCV infections.Moreover,hyperinsulinemia has a deleterious effect on the management of chronic HCV.Response to therapy is increased by decreasing insulin resistance by weight loss or the use of thiazolidenediones or metformin.The underlying mechanisms of this complex interaction are not fully understood.A direct cytopathic effect of HCV has been suggested.The genomic structure of HCV (suggesting that some viral sequences are involved in the intracellular accumulation of triglycerides),lipid metabolism,the molecular links between the HCV core protein and lipid droplets (the core protein of HCV and its transcriptional regulatory function which induce a triglyceride accumulation in hepatocytes) and increased neolipogenesis and inhibited fatty acid degradation in mitochondria have been investigated.

Angiotensin-receptor blockers as therapy for mild-to-moderate hypertension-associated non-alcoholic steatohepatitis

AIM： TO evaluate insulin resistance, cytolysis and nonalcoholic steatohepatitis （NASH） score （NAS） using the Kleiner and Brunt criteria in 54 patients with NASH and mild-to-moderate hypertension, treated with telmisartan vs valsartan for 20 mo. METHODS： All patients met the NCEP-ATP Ⅲ criteria for metabolic syndrome. Histology confirmed steatohepatitis, defined as a NAS greater than five up to 3 wk prior inclusion, using the current criteria. Patients with viral hepatitis, chronic alcohol intake, drug abuse or other significant immune or metabolic hepatic pathology were excluded. Subjects were randomly assigned either to the valsartan （V） group （standard dose 80 mg o.d., n = 26）, or to the telmisartan （T） group （standard dose 20 mg o.d., n = 28）. Treatment had to be taken daily at the same hour with no concomitant medication or alcohol consumption allowed. Neither the patient nor the medical staff was aware of treatment group allocation. Paired liver biopsies obtained at inclusion （visit 1） and end of treatment （EOT） were assessed by a single blinded pathologist, not aware of patient or treatment group. Blood pressure, BMI, ALT, AST, HOMA-IR, plasma triglycerides （TG） and total cholesterol （TC） were evaluated at inclusion and every 4 mo until EOT （visit 6）. RESULTS： At EOT we noticed a significant decrease in ALT levels vs inclusion in all patients and this decrease did not differ significantly in group T vs group V. HOMA-IR significantly decreased at EOT vs inclusion in all patients but in group T, the mean HOMA-IR decrease per month was higher than in group V. NAS significantly diminished at EOT in all patients with a higher decrease in group T vs group V. CONCLUSION： Angiotensin receptor blockers seem to be efficient in hypertension-associated NASH. Telmisartan showed a higher efficacy regarding insulin resistance and histology, perhaps because of its specific PPAR-gamma ligand effect.

Molecular mechanisms of insulin resistance in chronic hepatitis C

It is now widely recognized that chronic hepatitis C (CHC)is associated with insulin resistance(IR)and type 2 diabetes,so can be considered a metabolic disease.IR is most strongly associated with hepatitis C virus(HCV)genotype 1,in contrast to hepatic steatosis, which is associated with genotype 3 infection.Apart from the well-described complications of diabetes,IR in CHC predicts faster progression to fibrosis and cirrhosis that may culminate in liver failure and hepatocellular carcinoma.More recently,it has been recognized that IR in CHC predicts a poor response to antiviral therapy. The molecular mechanisms for the association between IR and HCV infection are not well defined.This review will elaborate on the clinical associations between CHC and IR and summarize current knowledge regarding the molecular mechanisms that potentially mediate HCV-associated IR.

Identification of an allosteric hotspot for additive activation of PPARγ in antidiabetic effects

Thiazolidinediones(TZDs),such as rosiglitazone(RSG),which activates peroxisome proliferator activated receptor-y(PPARy),are a potent class of oral antidiabetic agents with good durability.However,the clinical use of TZDs is challenging because of their side effects,including weight gain and hepatotoxicity.Here,we found that bavachinin(BVC),a lead natural product,additively activates PPARγ with lowdose RSG to preserve the maximum antidiabetic effects while reducing weight gain and hepatotoxicity in db/db mice caused by RSG monotherapy.Structural and biochemical assays demonstrated that an unexplored hotspot around Met329 and Ser332 in helix 5 is triggered by BVC cobinding to RSG-bound PPARy,thereby allosterically stabilizing the active state of the activation-function 2 motif responsible for additive activation with RSG.Based on this hotspot,we discovered a series of new classes of allosteric agonists inducing the activity of TZDs in the same manner as BVC.Together,our data illustrate that the hotspot of PPARγ is druggable for the discovery of new allosteric synergists,and the combination thera py of allosteric synergists and TZD drugs may provide a potential alternative approach to the treatment of type 2 diabetes mellitus.

本刊2010年第6期部分文题介绍

1．低氧诱导因子-1与糖尿病并发症 2．巨噬细胞与糖尿病大血管病变 3．PPAR7激动剂对胰岛β细胞脂毒性的干预作用 4．单核细胞趋化蛋白-1与糖尿病肾病 5．拮抗TSAb单链抗体的制备及鉴定 6．不同剂量木糖醇对糖尿病大鼠肾小球Ⅳ型胶原表达的影响 7．IRE1信号通路与2型糖尿病 8．糖化血清白蛋白检测在糖尿病血糖检测中的优势 9．内质网应激与2型糖尿病发病机制的研究进展.