Circulating Serum Myonectin Levels in Obesity and Type 2 Diabetes Mellitus.

OBJECTIVE: Myonectin is one of the myokines and has gained interest as a potential new strategy to combat obesity and its associated disorders, such as type 2 diabetes mellitus (T2DM).The objective of this study was to investigate circulating serum myonectin levels in nondiabetes and T2DM and elucidate possible relationships between serum myonectin levels and metabolic parameters in patients with T2DM. DESIGN: A total of 362 Chinese patients with T2DM and 100 age- and sex-matched healthy controls were recruited in this study. Clinical characteristics, blood biochemistry, and circulating myonectin levels were measured by enzyme-linked immunosorbent assay. RESULTS: Circulating myonectin levels were significantly decreased in T2DM compared with controls. Obese nondiabetic controls had significantly lower serum myonectin levels compared with lean nondiabetic controls. In diabetic patients, serum myonectin concentrations were significantly negatively correlated with body mass index (BMI), total cholesterol (TC), triglyceride (TG), low-density lipoprotein cholesterol (LDL-C), C-reactive protein (CRP), hemoglobin A1c (HbA1c), fasting insulin (Fins), the homeostatic model assessment of insulin resistance (HOMA-IR), visceral fat area, and subcutaneous fat area. After adjusting for covariates, multivariate stepwise regression analysis demonstrated that BMI, LDL-C, TG, HOMA-IR, and visceral fat were the main independent predictors of low serum myonectin concentrations. CONCLUSIONS: Circulating myonectin levels were decreased in T2DM patients and in obese subjects. Moreover, serum myonectin levels were correlated with metabolic markers of T2DM. These data suggest that myonectin may be a useful marker in predicting the development of obesity and T2DM.

miRNA­342 suppresses renal interstitial fibrosis in diabetic nephropathy by targeting SOX6.

Diabetic kidney disease (DKD) is one of the major microvascular complications in patients with type 1 and/or type 2 diabetes, the first cause of end­stage renal disease (ESRD) in several countries and regions. However, the pathogenesis of DKD and the mechanisms through which it leads to ESRD remain unknown. Thus, in this study, we aimed to elucidate some of these mechanisms. The expression of microRNA (miRNA or miR)­342­3p and SRY­box 6 (SOX6) in the renal tissues of mice with DKD and mouse renal mesangial cells (MCs) was determined by RT­qPCR and western blot analysis. The diabetic kidney environment was established using high­glucose medium. SOX6 was verified as a target gene of miR­342­3p by dual­luciferase activity assay. In addition, western blot analysis was employed to determine the changes in the levels of several biomarkers of fibrosis [transforming growth factor (TGF)­ß1, fibronectin (FN), collagen IV (referred to as C­IV) and phosphatase and tensin homolog (PTEN)]. Compared with THE control mice, the expression of miR­342­3p in the kidney tissues of mice with DKD was downregulated, whereas that of SOX6 was upregulated. The same phenomenon was observed in the MCs cultured in high­glucose medium. Subsequently, miR­342­3p inhibited SOX6 expression, promoted cell proliferation and inhibited the apoptosis of MCs. Moreover, the overexpression of miR­342­3p suppressed high glucose­induced renal interstitial fibrosis. In addition, it was found that miR­342­3p inhibited SOX6 expression by binding to the 3'­UTR of SOX6. On the whole, the findings of this study demonstrate that miR­342­3p suppresses the progression of DKD by inducing the degradation of SOX6. Thus, the miR­342­3p/SOX6 axis may serve as a novel therapeutic target in the treatment of DKD.

Apigenin prevents metabolic syndrome in high-fructose diet-fed mice by Keap1-Nrf2 pathway.

Chronic dietary high fructose leads to various kinds of undesirable metabolic effects. Apigenin, a naturally occurring plant flavone, is plentiful in fruits and vegetables. The aim of this study was to identify the protective effects of apigenin on metabolic syndrome and elucidate potential underlying mechanisms. The animal model was established by 4-weeks high fructose feeding. Insulin resistance was estimated by oral glucose tolerance test and homeostasis model assessment-insulin resistance index. Liver function was evaluated by serum AST and ALT, hepatic histopathological alternation, and lipid accumulation in the liver. The alterations of lipid profile was evaluated by TG, TC, LDL-C and HDL-C levels in serum. Administration of apigenin exerted beneficial effects through improving insulin resistance, alleviating liver injury, and inhibiting the alterations of lipid profile in high fructose-fed mice. In addition, apigenin potently facilitated the accumulation of Nrf2 nuclear translocation and accompanied by increasing HO-1 and NQO1 protein expressions, which are responsible for attenuating oxidative stress. Molecular docking results demonstrated that potential interaction of apigenin with the Nrf2-binding site in the Keap1 protein. In summary, we demonstrated that apigenin prevented high fructose-induced metabolic syndrome probably by inhibiting binding of Keap1 to Nrf2, and thus Nrf2 nuclear translocation, subsequently resulting in increased the expressions of anti-oxidative genes including HO-1 and NQO1.

Honokiol protects pancreatic ß cell against high glucose and intermittent hypoxia-induced injury by activating Nrf2/ARE pathway in vitro and in vivo.

Obstructive sleep apnea hypopnea syndrome (OSAHS) is associated with glucose intolerance, insulin resistance and type 2 diabetes mellitus (T2DM). Although several studies have revealed that intermittent hypoxia (IH) in OSAHS may further aggravate pancreatic ß cell damage and promote the evolution of type 2 diabetes (T2DM) by increasing oxidative stress, the underlying mechanisms are unclear. Honokiol, a potent radical scavenger, has been demonstrated to ameliorate oxidative stress in many cases. The present study aimed to explore the potential mechanism of IH and diabetes synergistically damage and destruct the pancreatic ß cell, examine the effects of honokiol on ameliorating pancreatic ß cell injury in this context and explore the mechanism of such effects. High glucose (HG) cultured INS-1 cells were exposed to 50 µM of honokiol for 24, 48 and 72 h with or without IH intervention. T2DM rats were treated with honokiol and exposed to 80 s of IH followed by 160 s of normoxia for 8 weeks. The cell proliferation, apoptosis and oxidative stress were measured. Blood glucose, insulin, glucagon and HOMA-IR (Homeostasis model assessment -insulin resistence) were also detected, and the expression of nuclear factor erythroid 2-related factor 2 (Nrf2) and heme oxygenase-1 (HO-1) were detected by immunofluorescence staining and western blotting. Honokiol can reduce oxidative stress, cytotoxicity and apoptosis in the INS-1 cells of rats receiving HG treatment or both HG and IH treatment. IH can further aggravate pancreas dysfunction, cause a marked elevation in fasting blood glucose, glucagon, HOMA-IR and oxidative stress levels in DM rats. In addition, honokiol can effectively activate the Nrf2/ARE pathway and reverse this pancreatic dysfunction in vivo and in vitro. These findings indicate that honokiol acts as a potent ROS scavenger via Nrf2/ARE pathway and effectively attenuates oxidative stress and improves pancreatic ß cell function of DM rats under IH treatment.

The relationship between circulating irisin levels and tissues AGE accumulation in type 2 diabetes patients.

Advanced glycation end-products (AGEs), measured by skin autofluorescence (AF), are a factor in the development or worsening of many degenerative diseases, such as diabetes and atherosclerosis. Irisin levels have been associated with diabetes, endothelial dysfunction and atherosclerosis. The objective of the present study was to investigate whether circulating irisin levels are correlated with skin AF values in type 2 diabetes patients. A total of 362 Chinese type 2 diabetic patients and 100 age- and sex-matched healthy controls were recruited in the present study. Clinical characteristics, blood biochemistry and circulating irisin levels were measured. Skin AF was measured using an AGE reader. Circulating irisin levels were significantly lower, while skin AF values were increased in type 2 diabetes compared with controls (P<0.05 respectively). By dividing the distribution of skin AF values into tertiles, serum irisin levels gradually lowered with increasing skin AF values (P<0.05). After adjusting for covariates, multivariate stepwise regression analysis demonstrated that serum lower irisin levels were independently associated with skin AF (P=0.009). Circulating irisin levels were lower in type 2 diabetes patients compared with healthy controls. Lower levels of irisin are independently associated with elevated skin AF values, indicating that circulating irisin levels could be associated with AGEs accumulation, which is one of the reasons causing vascular complications in diabetic patients.

Association of diabetic vascular complications with poor sleep complaints.

BACKGROUND: Literatures reported that poor sleep complaints were associated with a great deal of health outcomes. However, there are few studies on the association of poor sleep complaints with diabetic vascular complications. METHODS: Aiming on the association, a cross-sectional survey was conducted among 1220 diabetic patients in this study. Poor sleep complaints were composed of difficulty falling asleep, early final awakening, short sleep and long sleep. The diabetic vascular complications involved in the study were diagnosed according to the Standards of Medical Care in Diabetes (ADA 2016). RESULTS: Our findings indicated that short sleep remained independently associated with diabetic kidney disease (DKD) (OR > 1, P < 0.05) after the adjustments; long sleep independently associated with diabetic retinopathy (DR) (OR > 1, P < 0.05); early final awakening and short sleep independently associated with cardiovascular disease (OR > 1, P < 0.05); short sleep independently associated with peripheral arterial disease (OR > 1, P < 0.05); there was no association between poor sleep complaints and neuropathy (P > 0.05). CONCLUSIONS: The study suggests that the poor sleep complaints were distinguishably associated with diabetic vascular complications. Clinicians should take poor sleep complaints into account in diabetes treatment.

Efficacy and safety of vildagliptin, sitagliptin, and linagliptin as add-on therapy in Chinese patients with T2DM inadequately controlled with dual combination of insulin and traditional oral hypoglycemic agent.

OBJECTIVE: We aimed to evaluate the efficacy and safety of the three dipeptidyl peptidase 4 (DPP-4) inhibitors (vildagliptin, sitagliptin, and linagliptin) as add-on therapy in Chinese patients with type 2 diabetes mellitus (T2DM)inadequately controlled on dual combination of insulin and metformin or acarbose. METHODS: A total of 535 T2DM patients who failed to achieve glycemic control with insulin and a traditional oral hypoglycemic agent were randomized to receive vildagliptin, sitagliptin, or linagliptin. Body mass index, glycosylated hemoglobin (HbA1c), fasting and postprandial plasma glucose (FPG and PPG), insulin dose, and adverse events were evaluated during the study. RESULTS: The baseline HbA1c was 9.59 ± 1.84 % (vildagliptin group), 9.22 ± 1.60 % (sitagliptin group), and 9.58 ± 1.80 % (linagliptin group). At week 12 it was 8.16 ± 1.29 % (vildagliptin), 8.56 ± 1.96 % (linagliptin), and 8.26 ± 1.10 % (sitagliptin). The changes in HbA1c from baseline were -1.33 ± 0.11 % (vildagliptin), -0.84 ± 0.08 % (sitagliptin) and -0.81 ± 0.08 % (linagliptin), the vildagliptin group had the greatest reduction in HbA1c (P < 0.05). The proportions of patients that reached target HbA1c were 66.27 % (vildagliptin), 52.73 % (sitagliptin), and 55.49 % (linagliptin), the vildagliptin group had the highest one (P < 0.05). The baseline FPG and PPG values in the three groups were at the same level. At week 12, mean FPG levels in the vildagliptin (7.31 ± 1.50 mmol/L) and linagliptin (6.90 ± 1.55 mmol/L) groups were significantly lower than in the sitagliptin group (8.02 ± 4.48 mmol/L; P < 0.05); the linagliptin group had the lowest mean PPG followed by the vildagliptin group which was also significant lower (P = 0.000) than the sitagliptin group. Additionally, the required insulin dosage in the vildagliptin group was the lowest among the groups at weeks 6 and 12. Only mild AEs were reported during the study. CONCLUSION: The three DPP-4 inhibitors appear to be effective and safe as add-on therapy for T2DM patients on dual combination of insulin and a traditional OHA. Vildagliptin was more effective in decreasing insulin requirement and achieving glycemic control when compared to the other two.

Impact of inflammatory markers on the relationship between sleep quality and incident cardiovascular events in type 2 diabetes.

AIMS: To analyze relevance of sleep quality with CVD in T2D patients and determine whether inflammation prompted by poor sleep has impact on the CVD. METHODS: 332 T2D patients were recruited and their sleep qualities were evaluated by PSQI. The patients with PSQI score >7 were in the poor sleep group, and the others were in the good sleep group. Plasma samples of the patients were obtained to measure inflammatory markers. Correlation analyses and regression analyses were performed to examine the cross-sectional relationships among the poor sleep, inflammatory markers and CVD. RESULTS: The morbidity of CVD was significantly higher in the poor sleep patients compared to the good sleep patients (P=0.000). PSQI score ORs were both >1 for CVD in model 1 and model 2 (P<0.05). PSQI score were positively related to IL-6 and ICAM-1(P<0.05), negatively to FBI (P<0.05), but not related to CRP in linear regression models. Multiple logistic regression analysis showed IL-6 and ICAM-1, but not FBI and CRP, were related to CVD (P<0.05). CONCLUSIONS: Poor sleep is regarded as a plausible risk factor for CVD in T2D patients, and may be mediated by certain inflammatory markers.

C-reactive protein/oxidised low-density lipoprotein/ß2-glycoprotein I complex promotes atherosclerosis in diabetic BALB/c mice via p38mitogen-activated protein kinase signal pathway.

BACKGROUND: The aim of this study was to investigate the effect of C-reactive protein/oxidised low-density lipoprotein/ß2-glycoprotein I (CRP/oxLDL/ß2GPI) complex on atherosclerosis (AS) in diabetic BALB/c mice. METHODS: BALB/c mice were fed high-fat and normal diet. Eight weeks later, the mice fed with high-fat diet were injected with streptozotocin (STZ) to induce diabetes. The diabetic mice were respectively injected twice monthly with 20 µg oxLDL, 20 µg ß2GPI, 40 µg oxLDL/ß2GPI complex, 44 µg CRP/oxLDL/ß2GPI complex, and PBS. Aortas were stained with Sudan IV to investigate lipid plaque formation. The infiltration condition of smooth muscle cells (SMCs), macrophages, and T cells in the aortas were determined by immunohistochemistry (IH). The mRNA expressions of receptors associated with lipid metabolism were quantified by real-time PCR. The phosphorylation of p38 mitogen-activated protein kinase (p38MAPK) and MKK3/6 in aorta tissues were assessed by Western blot. The expression of inflammation cytokines was evaluated by protein chip. RESULTS: The lipid plaques were more extensive, the lumen area was obviously narrower, the ratio of intima and media thickness were increased, and the normal internal elastic lamia structure and endothelial cell disappeared (P < 0.05) in the oxLDL and CRP/oxLDL/ß2GPI groups (P < 0.05). CRP/oxLDL/ß2GPI complex dramatically promoted infiltration of SMCs, macrophages, and T cells, improved the mRNA expression of ABCA1 and ABCG1, but reduced the mRNA expression of SR-BI and CD36 and increased the phosphorylation of p38MAPK and MKK3/6 (all P < 0.05). The highest expression levels of IL-1, IL-9, PF-4, bFGF, and IGF-II were detected in the CRP/oxLDL/ß2GPI group (P < 0.05). CONCLUSIONS: CRP/oxLDL/ß2GPI complex aggravated AS in diabetic BALB/c mice by increasing lipid uptake, the mechanism of which may be mediated by the p38MAPK signal pathway.

P-glycoprotein regulating biphasic insulin secretion in rat pancreatic beta cells.

BACKGROUND: A 65-kD mdr1 (multi-drug resistance protein 1, P-glycoprotein)-like protein has been suggested to be the regulatory protein to the chloride channel protein 3 (ClC-3) mediating insulin granules acidification and release in mouse pancreatic beta cells. But the protein has not been deeply investigated. In this study, we identified existence of the 65-kda protein in rat islets and preliminarily explored its biological functions. METHODS: Total RNAs of rat kidneys served as positive controls, and pancreas, islets and INS-1 cells were extracted for reverse-transcript PCR (RT-PCR), respectively. The cDNAs were run with specific primers selected from the mRNA of abcb1b encoding P-glycoprotein. All PCR products were visualized in agarose gel electrophoresis and sequenced. Homogenates of rat islets and INS-1 cells were applied to SDS-PAGE. P-glycoprotein was detected by a specific monoclonal antibody, C219. Biphasic insulin release was measured in static incubations of rat islets with radioimmunology assay. RESULTS: Compared with positive control, expression of the P-glycoprotein mRNA segments were detected in the islets, INS-1 cells and pancreas. Sequence analysis confirmed that the PCR products were matched with mRNA of P-glycoprotein. A 65-kda protein was recognized by the antibody in the islets homogenate but not in that of INS-1 cells in Western-blotting. Instead, the homogenate of INS-1 cells contained a 160-kda protein recognized by the antibody. Insulin secretion of rat islets were stimulated by high glucose (16.7 mmol/L), and showed biphasic curve during 60-minute incubation. After co-incubation with cyclosporine A (CsA), specific inhibitor to P-glycoprotein, the second phase of insulin secretion was reduced significantly while the first phase was not influenced. CONCLUSIONS: The 65-kda protein expressed in rat islets is most likely a mini-P-glycoprotein. It may play a key role regulating biphasic insulin release.

[High D-glucose alters PI3K and Akt signaling and leads to endothelial cell migration, proliferation and angiogenesis dysfunction].

OBJECTIVE: To investigate the effects of high D-glucose on migration, proliferation, and angiogenesis of endothelial cells and to make sure whether PI3K and Akt signaling pathway plays an important role in the pathogenesis of diabetic vascular complications. METHODS: Human umbilical vein endothelial cells (HUVECs) were cultured. D-glucose of the concentrations of 5 mmol/L, 15 mmol/L, and 30 mmol/L and mannitol of the concentrations of 5 mmol/L, 15 mmol/L, and 30 mmol/L were added in to the medium, the migration rate of the cells was measured by wound healing test and the cell proliferation was examined with CellTiter 96 AQ(ueous) One Solution cell proliferation assay. Matrigel was spread on 96-well plate, and culture of HUVECs with D-glucose and mannitol of different concentrations were added. Microscopic photography was used to calculate the total area of vascular bed, average vessel length, vessel number, branch points, so as to observe the angiogenesis. Immuno-precipitation was used to detect the expression of p85/PI3K. Western blotting was used to detect the protein expression of p85/PI3K, p-PI3K, GSK3beta (downstream kinase of Akt), p-Akt (Threonine308) and p-GSK3beta. LY294002, a PI3K inhibitor, of the concentrations of 0.1 micromol/L, 1 micromol/L, and 10 micromol/L was added into the culture fluid with 5 mmol/L D-glucose, then the endothelial cell migration, proliferation number, total area of blood bed, etc were observed. RESULTS: The migration rate of the 5 mmol/L D-glucose group was 100 +/- 23/microm2, and D-glucose dose-dependently decreased the migration rate, e.g. the migration rates of the 15 mmol/L and 30 mmol/L D-glucose groups were 77 +/- 18/microm2 and 46 +/- 18/microm2 respectively, both significantly lower than that of the 5 mmol/L D-glucose group (both P < 0.01). LY294002 of the concentrations of 0.1 micromol/L, 1 micromol/L, and 10 micromol/L dose-dependently decrease the endothelial cells migration rates to 68 +/- 16/microm2, 36 +/- 12/microm2, and 13 +/- 3/microm2 respectively (all P < 0.01) The cell proliferation rate of the 5 mmol/L, 15 mmol/L) and 30 mmol/L D-glucose groups were 59,128 +/- 7415/well, 33,144 +/- 9082/well, and 11,625 +/- 4196/well respectively, showing that D-glucose dose-dependently decreased the cell proliferation (all P < 0.01). LY294002 of the concentrations of 0.1 micromol/L, 1 micromol/L, and 10 micromol/L dose-dependently decrease the endothelial cell proliferation to 42,560 +/- 4213/well, 17,688 +/- 7198/well, and 5704 +/- 558/well respectively (all P < 0.01). 15 mmol/L and 30 mmol/L D-glucose decreased the numbers of total area of vascular bed, average tubule length, number of capillaries, and number of vessel branch pint formed on the Matrigel. LY294002 dose-dependently inhibited the angiogenesis (P < 0.05 or P < 0.01) 15 mmol/L and 30 mmol/L D-glucose dose-dependently inhibited the phosphorylation of p85/P13K and Akt (P < 0.05 and P < 0.01). However, D-glucose did not influence the protein expression of p85/PI3K and Akt. Mannitol did not influence the cell proliferation, angiogenesis, and the expression of p85/PI3K, phosphorylated p85/PI3K, Akt, phosphorylated Akt (Thr308), and phosphorylated GSK3beta. CONCLUSION: Hyperglycemia-impaired PI3K-Akt signaling may lead to migration, proliferation and angiogenesis dysfunction of endothelial cells in diabetes patients, which is likely to contribute to the pathogenesis of diabetic vascular complications.