Volume 07 · Issue 06 · 2015

Patients with type 2 diabetes mellitus (T2DM) are often accompanied by cardiovascular disease, which becomes the main cause of disability and death. Vascular endothelial dysfunction is an early predictor of vascular disease in diabetic patients, and can independently predict the risk of cardiovascular disease in patients with T2DM^[1]。 The pathological mechanism of endothelial dysfunction in patients with T2DM is very complex. The main pathophysiological factors causing diabetic endothelial dysfunction include insulin resistance, oxidative stress, inflammatory response, protein kinase C activation and epigenetics. Therefore, this paper mainly discusses the molecular mechanism of vascular endothelial dysfunction in T2DM.

Type 2 diabetes mellitus (T2DM), often associated with hepatic microvascular disease and hepatic inflammation, is an independent risk factor for non-alcoholic fatty liver disease (NAFLD)^[1]。 In recent years, the prevalence of NAFLD in T2DM patients has increased year by year. According to the latest research report, the prevalence of NAFLD in T2DM patients is 42.6% ~76.0%, and about 33% of NAFLD patients have diabetes^[2]。 Microcirculation disorder is one of the important reasons for the formation of NAFLD, and hepatic sinusoidal endothelial cell (LSEC) dysfunction is the initiation and key link of hepatic microcirculation disorder^[3]。 LSEC is the main component of hepatic sinus wall, which has the physiological functions of providing multi-pore barrier, scavenging, maintaining the resting state of hepatic stellate cells (HSC) and mediating the self-repair of liver injury^[4]。 The fenestral structure of LSEC is a unique marker distinguishing it from vascular endothelial cells, and it plays an important role in regulating the substance exchange between sinusoidal blood flow and surrounding tissues. LSEC dysfunction can cause abnormal sinusoidal blood flow, lipid metabolism disorder, sinusoidal capillarization and hepatocyte metabolism disorder, etc., resulting in abnormal liver structure and function. The persistent high glucose and lipotoxicity in the diabetic state exacerbates the impairment of LSEC function, therefore, the role of LSEC dysfunction in the formation of NAFLD cannot be ignored. This paper focuses on analyzing the mechanism of LSEC function in the occurrence and development of hepatic microcirculation disorder and NAFLD in diabetic patients.

Uric acid is the end product of purine metabolism, and human blood uric acid levels gradually increase in the process of evolution. The reasons are, on the one hand, genetic factors. The uricase gene and promoter of human beings have undergone genetic variation, so the uricase level is lower than that of other mammals; On the other hand, environmental factors, the westernization of modern human lifestyle and the large intake of high fructose diet are important reasons for the increase of blood uric acid. At present, hyperuricemia (HUA) is defined as: blood uric acid concentration>7 mg/dl in men and postmenopausal women (the conversion factor from old unit mg/dl to new unit μ mol/L is 59.5, the same below), and blood uric acid concentration>5.8 mg/dl in premenopausal women^[1]。

To evaluate the vascular endothelial function and explore the related influencing factors in patients with abnormal glucose metabolism by use of ultrasound technology.

A total of 109 participants selected from endocrinology outpatients of Beijing Hospital from October 2011 to June 2013 were enrolled in this study. Oral glucose tolerance test(OGTT) was carried out, including fasting plasma glucose(FPG) and postprandial glucose(PPG), fasting and 2 hours after glucose load testing insulin, C-peptide, glycated hemoglobin A_1c(HbA_1c), glycated albumin(GA), lipids, liver and kidney function, blood uric acid,flow-mediated endothelium-dependent vasodilation (FMEDD), serum nitric oxide (NO), endothelin-1(ET-1), serum malondialdehyde(MDA) and superoxide dismutase(SOD).With the receiver operating characteristic (ROC)curve, the best critical points of fasting and glucose loading vascular endothelial function were obtained.

(1)The critical points of FMEDD in the state of abnormal glucose metabolism: fasting FMEDD was 13.37%, Youden index was 0.467, and the area under the curve was 0.786 (95%CI:0.697-0.876); FMEDD of OGTT 2 h was 10.67%,Youden index was 0.458, and the area under the curve was 0.774(95%CI:0.687- 0.861). (2)Body mass index(BMI), FPG, HbA_1c, GA, triglyceride (TG), MDA in the patients withabnormal fasting FMEDD were significantly higher than those in the normalgroup(t=- 3.013,- 4.567,- 3.487,- 4.611,- 2.309,- 2.909, all P<0.05); and the homeostasis model assessment-β(HOMA-β), NO, SOD were significantly lower than those in the normal group(t=2.765,2.472, 5.937, all P<0.05). PPG, HbA_1c, GA in the patients with abnormal FMEDD after glucose load were significantly higher than those in the normal group(t=-4.907,-4.236,-3.896, all P<0.05); and the HOMA-β, NO, SOD were all significantly lower than those in the normal group(t=2.704,4.675,4.633, all P<0.05).(3) FPG,HbA_1c,GA were negatively correlated with fasting FMEDD(r=- 0.460,- 0.390,- 0.391, all P<0.05), whereas fasting NO, SOD, HOMA - β were positively correlated with fasting FMEDD(r=0.301,0.321, 0.310, all P<0.05). PPG, HbA_1c, GA were negatively correlated with FMEDD after glucose load (r=- 0.460,- 0.450,- 0.389, all P<0.05), whereas NO, SOD, HOMA- β were positively correlated with FMEDD after glucose load(r=0.196,0.360,0.257, all P<0.05).

Blood sugar levels, islet β-cell function index, vasodilators, and the indicators of antioxidative stress can affect vascular endothelial functions in different state of glucose metabolism.

To explore the effects of irisin on endothelial cells cultured with high glucose and the possible mechanism-involved.

Human umbilical vein endothelial cells (HUVECs) were pre-incubated with inhibitors against phosphatidylinositol- 3-kinase (PI3K) (LY294002) or endothelial nitric oxide synthase(eNOS) (L-NAME) for 30 min before irisin was added, then divided into 6 groups: normal glucose (NG) group, high glucose (HG) group, high glucose + irisin (Irisin) group, high glucose + LY294002 + irisin (LY) group, high glucose +L -NAME + irisin(L - NAME) group, high glucose + LY294002+L-NAME+irisin (LY+L-NAME) group, cultured for 48 h. Terminal deoxynucleotidyl transferase biotin- dUTP nick end labeling (TUNEL) staining was applied to identify the apoptotic endothelial cells. Reactive oxygen species assay kit and reverse transcription polymerase chain reaction(RT-PCR) was used to determine the oxidative stress in HUVECs. The expression levels of protein kinase B(Akt), phospheralyted Akt(P-Akt), eNOS and phospheralyted eNOS(P-eNOS) were measured by Western blotting. Moreover, HUVECs were transfected with eNOS-siRNA, and cultured in high glucose and then divided into 4 groups: NG+Scr-siRNA group, HG+Scr-siRNA group, HG+Scr-siRNA+irisin group and HG+eNOS-siRNA+irisin group, cultured for 48 h. After treatment, the cells were double-stained with fluorescein isothiocyanate/propidium iodide (Annexin V-FITC/PI) and analyzed by flow cytometry. Data were compared using one-way analysis of variance (ANOVA).

The apoptotic rate of HUVECs in HG group were significantly higher than that in NG group (25.6% ± 3.2% vs 6.0% ± 1.5%,t=- 13.55,P<0.01), while it significantly decreased in Irisin group than that in HG group (19.8% ± 2.3% vs 25.6% ±3.2%,t=- 3.55,P<0.01). The apoptotic rate of HUVECs in LY, L-NAME and LY+L-NAME group were all significantly higher than that in Irisin group (t=- 3.85,- 5.19,- 7.11, all P<0.01). After eNOS gene silencing in HUVECs, the cellular apoptotic rate significantly increased in HG+Scr-siRNA group when compared with that in NG+Scr-siRNA group (58.0%±7.8% vs 12.4%±2.8%,t=-13.48,P<0.01). The cellular apoptotic rate significantly decreased in HG+Scr-siRNA+irisin group when compared with that in HG+Scr-siRNA group (27.8%±5.3% vs 58.0%± 7.8%,t=-7.84,P<0.01), while it significantly increased in HG+eNOS-siRNA+irisin group than that in HG+ Scr-siRNA+irisin group (48.1%±5.5% vs 27.8%±5.3%,t=-6.48,P<0.01). The relative P-Akt/Akt, P-eNOS/eNOS levels in HG group were significantly lower than those in NG group (allP<0.01). The relative P-Akt/Akt, P-eNOS/eNOS levels in irisin group were significantly higher than those in HG group (allP<0.01). The relative P-Akt/Akt, P-eNOS/eNOS levels in LY, L-NAME and LY+L-NAME group were significantly lower than those in Irisin group (allP<0.01).

Irisin prevents high glucose- induced endothelial oxidative stress and apoptosis. The protective effect of irisin on HUVECs apoptosis is mediated through the PI3K- Akt- eNOS signaling pathway. Irisin could be a potential therapeutic approach for diabetic vascular complications.

To investigate the effect of oxidized low-density lipoprotein(oxLDL) on the relaxation function and fenestrae regulation in human liver sinusoidal endothelial cells(HLSECs).

Cells were treated with 100 mg/L oxLDL(oxLDL group). Meanwhile, the normal group was established and untreated. After incubation of HLSECs for 24 h, real time quantitative reverse transcription- polymerase chain reaction (qRT - PCR) and Western blotting were used to detect the mRNA and protein expression of endothelial nitric oxide synthase(eNOS), endothelin-1(ET-1) and caveolin-1(Cav-1) in HLSECs. The fenestra morphology, number and distribution in the cells were visualized by using scanning electron microscopy. Data were analyzed with t test.

Compared with the those in control, the mRNA expression of ET-1 and Cav-1 overexpressed by 2.62- and 2.49-folds(2.62±0.32 vs 1.00±0.00 and 2.49±0.27 vs 1.00±0.00), and the protein expression of ET-1 and Cav-1 overexpressed by 2.31- and 2.96-folds(1.34±0.10 vs 0.58±0.03 and 0.71 ±0.03 vs 0.24±0.02) in oxLDL group, respectively; the mRNA and protein expression of eNOS significantly decreased by 45% and 54% (0.55 ±0.12 vs 1.00± 0.00 and 0.34±0.02 vs 0.74± 0.04) in response to oxLDL versus control(t=32.54, 26.62, 6.29, 16.71, 22.09, 15.20, all P<0.05). The fenestra morphology of HLSECs has changed obviously in oxLDL group, oxLDL caused a significant decrease in the porosity, diameter and number of fenestrae compared with those in the control group, even the fenestrae were disappeared in some regions.

oxLDL can upregulate the expression of ET-1 and Cav-1, downregulate the expression of eNOS. These effects promote the process of relaxation dysfunction and defenstration of HLSECs.

To investigate the association between dawn phenomenon and islet α-cell and β-cell function in patients with type 2 diabetes.

Two hundred and eighteen patients with type 2 diabetes who performed continuous glucose monitoring from January 2012 to January 2014 were divided into two groups: patients without dawn phenomenon and patients with dawn phenomenon. Biochemical indicators were detected in two groups. Oral glucose tolerance test, insulin releasing test and glucagon releasing test were performed to investigate the differences of α-cell and β-cell function between groups after fasting and glucose-load. The correlation and regression analysis were performed between dawn phenomenon and other indicators.

The level of HbA_1c,the increment of fasting glucose and nocturnal nadir glucose(BG₁),the glucose increment before and after breakfast(BG₂),24 hours mean blood glucose(24 hMG) and HOMA- IR were significantly higher in patients with dawn phenomenon compared to those in patients without dawn phenomenon((8.3%±2.2%) vs (7.7%±1.9%), (1.41±0.33) vs (0.96±0.26)mmol/L, (2.40±0.48) vs (1.90±0.42)mmol/L,(10.69±2.25) vs (9.36±1.82)mmol/L,(4.3±0.9) vs (3.4±0.8),t=2.1282, 10.9955, all P<0.05). Insulin sensitivity index(ISI) was lower in patients with dawn phenomenon than those in patients without dawn phenomenon(t=2.1328,P<0.05).The level of glucagon, glucagon/insulin ratio, glucagon/glucose ratio and area under curve of glucagon were significantly higher in patients with dawn phenomenon than those in patients without(t=2.000-10.2190, P<0.05). Logistic regression analysis showed that dawn phenomenon was positively related to HOMA-IR, glucagon/insulin ratio, BG₂ and BG₁(all P<0.05), and negatively related to ISI (P<0.05).

Dawn phenomenon is associated with the dysfunction of islet α-cell and β-cell.Improving islet function may help to improve the dawn phenomenon and optimize glycemic control.

To detect the expression and significance of peroxisome proliferator-activated receptor β in rectus abdominis and abdominal subcutaneous adipose tissue of patients with gestational diabetes mellitus(GDM).

Totally 40 women with GDM, who delivered through cesarean section at the Affiliated Hospital of Qingdao University from September 2012 to May 2013, were selected as the GDM group, and another 40 normal pregnant women were chosen as control. The serum levels of fasting plasma glucose(FPG), fasting insulin(FIN), total cholesterol(TC), triglyceride(TG), high density lipoprotein cholesterol(HDL-C) and low density lipoprotein cholesterol(LDL-C) were determined in the women of both groups. Natural logarithm of insulin resistance index[ln(HOMA-IR)] was calculated. The expression of PPAR- β mRNA and protein in rectus abdominis and abdominal subcutaneous adipose tissue were investigated. The statistical data was analyzed with independent - samplest test and Pearson correlation analysis.

The levels of FPG, FIN,ln(HOMA-IR), TG and LDL-C in GDM group were all significantly higher than those in control group(t=4.447,20.435,12.076,1.482,3.041, all P<0.05), while the level of HDL-C in GDM group was significantly lower than that in control group(t=-4.058,P<0.05). No significant difference was found in the level of TC between the two groups(t=2.171,P>0.05). The expression of PPAR-β mRNA and protein in rectus abdominis and abdominal subcutaneous adipose tissue were both significantly lower than those in control group(0.48±0.13 vs 0.80±0.09, 0.46±0.14 vs 0.80±0.08, 0.48±0.11 vs 0.83±0.07, 0.46±0.12 vs 0.86± 0.11, respectively,t=- 12.483,- 13.185,- 16.931,- 15.560, all P<0.05). In GDM group, the expression of PPAR- β mRNA in rectus abdominis and abdominal subcutaneous adipose tissue was nagtively correlated with the levels of ln(HOMA- IR), TG and LDL- C(r=- 0.696 to- 0.498,P<0.01), while it was positively correlated with the level of HDL-C(r=0.551,0.551,P<0.01).The expression of PPAR-β protein in rectus abdominis and abdominal subcutaneous adipose tissue was nagtively correlated with the levels of ln(HOMA- IR), TG and LDL-C(r=-0.916 to -0.717,P<0.01), while it was positively correlated with the level of HDL-C (r=0.716,0.863,P<0.01).

The pregnant women with GDM have obvious dyslipidaemia. The decrease of the expressions of PPAR-β is prabablely involved in the insulin resistance of GDM, moreover, it is closely related to dyslipidaemia in GDM patients.

To observe the effects of intermedin(IMD) on oxidative stress induced by myocardial ischemia reperfusion injury in diabetic rats, investigate the mechanism of IMD on myocardial oxidative stress in diabetic status.

By using random number table method, 74 healthy male Sprague-Dawley (SD) rats were divided into five groups: sham group (NS,n=12), ischemia-reperfusion (NIR,n=12), diabetes sham group (DS,n=14), diabetes, ischemia-reperfusion group (DIR,n=18), IMD-treated group (IMD group,n=18). Diabetes was induced by streptozotocin in SD rats. Animals were subjected to myocardial ischemia via left circumflex artery ligation for 30 minutes followed by 2 hours of reperfusion. IMD was administered formally 10 minutes before reperfusion in IMD group. Rat blood glucose, body weight and other state changes were measured. Serum activity of lactate dehydrogenase(LDH) and creatine kinaseisoenzyme (CK-MB)was measured by chemistry method. At the end of experiment, the activity of malondialdehyde(MDA), superoxide dismutase (SOD, colorimetry method) and the content of nitric oxide synthase (NOS), nitric oxide (NO) in myocardium during the reperfusion period were measured. mRNA expression of p22,p67 and gp91 in myocardial tissue was detected by fluorescence quantitative polymerase chain reaction(PCR). Mean data between groups was analyzed by one-way ANOVA method.

After pretreatment with IMD, the activity of serum CK-MB, LDH and MDA content in myocardial tissue decreased obviously in IMD group compared with those of DIR group((1832±257) vs (3916±269)U/L, (4321±196) vs (4923±321)U/L, (20.9±1.3) vs (26.3±0.7)nmol/mg prot,F=83.315,76.549,32.961,all P<0.05).The activity of SOD, the content of NOS, NO in myocardial were significantly elevated in IMD group when compared with those in DIR group (F=43.025, 3.879, 2.511, P<0.05).Compared with those in DIR group, p22,p67 and gp91 mRNA expression levels in myocardial tissue of IMD group decreased significantly (F=3.461,2.115, 7.091,P<0.05) .

Diabetes could aggravate myocardial ischemia reperfusion injury.By inhibitingoxidative stress, IMD may represent a promising novel therapeutic target mitigating diabetic ischemic heart injury.

To investigate the role for erythropoietin(EPO) on insulin signaling of palmitate (PA) induced HepG2 cells.

HepG2 cells were intervened with palmitic acid (250 nmol/L), EPO (10 U) and resveratrol (Rsv, 10 nmol/L), activator of nicotinamide adenine dinucleotide - dependent deacetylase sirtuin- 1 (SIRT1), respectively. Cells were randomly assigned into: control, insulin (Ins, 100 pmol/L), palmitic acid (PA), PA+ EPO (10 U) and PA+ resveratrol (10 nmol/L), respectively. Then HepG2 cells under both normal and palmitic acid were transfected with SIRT1 RNAi mixed with lipofacfectamine 2000 and were divided into following four groups: control, EPO, EPO + Scramble, EPO + siSIRT1. The expression of insulin receptor substrate 2 (IRS- 2), phosphatidylinositol 3 kinase/ protein kinase B(PI3K/AKT) and SIRT1 were detected by Western blotting. The expression of SIRT1 mRNA level was determined by quantitative reverse transcription polymerase chain reaction(qRT-PCR). Independent samples t-test was used for data analysis.

Compared with control group (1.00 ± 0.03), levels of pIRS-2(Ser731) increased and pAKT(Ser473) ,SIRT1 decreased significantly in palmitate induced HepG2 cells (1.25±0.06, 0.77±0.02, 0.74±0.03,t=6.048,-13.686, -10.649, respectively, all P<0.05). After EPO treatment, levels of pAKT(Ser473) and SIRT1 under insulin resistance conditions were significantly enhanced while pIRS- 2 (Ser731) were significantly decreased (1.60±0.14 vs 1.00±0.08, 1.39±0.03 vs 1.00±0.03, 0.70±0.03 vs 1.00± 0.11,t=6.330, 25.868,- 4.853, all P<0.05). However, when SIRT1 expression was inhibited by small interfering RNA (SiRNA), neither PI3Kp85 nor pAKT(Ser473) levels were altered in response to EPO under both normal and insulin resistant conditions.

EPO positively regulates impaired PI3K/AKT signaling caused by PA through SIRT1 in HepG2 cells.

neonatal diabetes mellitus (NDM) refers to a type of monogenic diabetes in which patients develop within 6 months after birth and need to receive insulin therapy for at least 2 weeks^[1]。 There are two types of NDM: transient neonatal diabetes mellitus (TNDM) and permanent NDM (permanent neonatal diabetes mellitus (PNDM). TNDM Most of them achieve complete remission within 18 months of onset, but about half of them develop T2DM in childhood or later and persist for life. According to the known genetic pathogenesis, TNDM can be roughly divided into three types: TNDM1, TNDM2 and TNDM3. TNDM1, namely 6q24 TNDM, accounts for the majority of TNDM, and is related to the abnormality of the 6q24 region of chromosome.

With the development of economy, the lifestyle of our residents has changed tremendously, and the prevalence of diabetes is rising rapidly. More and more evidence shows that diabetes can cause damage to the central nervous system, damage to the integrity and function of brain tissue, and cognitive dysfunction, so it is also called diabetic encephalopathy (DE). In recent years, it has been suggested that diabetes mellitus may be a chronic inflammatory response mediated by cytokines, and inflammation plays an important role in the pathogenesis of diabetes mellitus^[1]。 High mobility group protein B1 (HMGB1) is a pro-inflammatory factor that acts on advanced glycosylation end products (AGEs) and Toll-like receptors (TLRs), activating nuclear factor-κ B (NF-κ B), leading to a series of cascade metabolic reactions. High mobility group protein B1-AGEs/TLR-NF-κ B (HMGB1-RAGE/TLR-NF-κ B) signaling pathway may play an important role in the development and development of diabetic inflammation^[2]In this paper, the research progress of this pathway and DE in recent years is briefly summarized.

Diabetes is one of the major health problems that endanger the development of society. Although the etiology is complex, the central role of pancreatic islets in the regulation of blood glucose homeostasis is unquestionable. Restoring the function and number of pancreatic islet beta cells has been the key to clinical treatment of diabetes. Cell cycle analysis showed that islet β cells proliferated very slowly, and the vast majority (97% ~99%) were in G0/1 phase^[1,2,3]。 The molecular mechanisms that prevent beta cells from switching through the G1/S phase cycle are unknown. Retinoblastoma protein (Rb) is an important molecule that regulates cell cycle transition in G1/S phase. It has similar pocket-shaped DNA binding regions with retinoblastoma-like protein 1 (p107) and retinoblastoma-like protein 2 (p130), and belongs to the pocket protein family^[3,4,5]。 Research on the family of pocket proteins has mainly focused on the field of oncology. Recent studies have shown that the expression of islet Rb gene in patients with type 2 diabetes mellitus is significantly reduced^[6]Its role in the expansion of pancreatic islet cells is receiving increasing attention. This paper reviews the research progress of pocket protein family in the regulation of islet development and homeostasis.

In recent years, with the change of diet and lifestyle, the incidence of diabetes in the population has shown an increasing trend. According to the latest report of the International Diabetes Federation (IDF), the total number of diabetic patients worldwide was about 381.8 million in 2013, and this number will reach 591.9 million in 2035^[1]。 With the progression of the disease, stepped treatment regimens are often recommended by domestic and foreign guidelines for blood glucose management in patients with type 2 diabetes mellitus (T2DM). In 2012, the American Diabetes Society (ADA) and the European Society for Diabetes Research (EASD) issued a position statement entitled "Hyperglycemic Management in Type 2 Diabetes: A Patient-Centered Pathway", recommending that basal insulin therapy should be initiated when single or combined oral hypoglycemic drugs fail to satisfactorily control blood glucose^[2]。

Ninety years ago, the discovery of insulin brought a great turn in the fate of diabetics. With the development of insulin and its preparations, safe and effective control of blood sugar is no longer out of reach. Because type 2 diabetes mellitus (T2DM) is characterized by insulin resistance and impaired insulin secretion at diagnosis, and progressive decline in islet beta cell function as the disease progresses. Therefore, in addition to the timely initiation of insulin therapy to maintain glycemic control to prevent and reduce complications, the adjustment process of insulin dose is also of interest in the treatment protocol.