Chronic ghrelin administration suppresses IKK/NF-κB/BACE1 mediated Aß production in primary neurons and improves cognitive function via upregulation of PP1 in STZ-diabetic rats.

Diabetic rats display cognition impairments accompanied by activation of NF-κB signalling and increased Aß expression. Ghrelin has been suggested to improve cognition in diabetic rats. In this study, we investigated the role of ghrelin on cognition and NF-κB mediated Aß production in diabetic rats. A diabetic rat model was established with streptozotocin (STZ) injection, and diabetic rats were intracerebroventricularly administered with ghrelin or (D-lys3)-GHRP-6 (DG). Our results showed that diabetic rats had cognition impairment in the Morris water maze test, accompanied by the higher expression of Aß in the hippocampus. Western blot analysis showed that diabetic rats exhibited significantly decreased levels of GHSR-1a and protein phosphatase 1 (PP1) in the hippocampus and increased activation of the IKK/NF-κB/BACE1 pathway. Chronic ghrelin administration upregulated hippocampal PP1 expression, suppressed IKK/NF-κB/BACE1 mediated Aß production, and improved cognition in STZ-induced diabetic rats. These effects were reversed by DG. Then, primary rat hippocampal neurons were isolated and treated with high glucose, followed by Ghrelin and DG, PP1 or IKK. Similar to the in vivo results, high glucose suppressed the expression levels of GHSR-1a and PP1, activated the IKK/NF-κB/BACE1 pathway, increased Aß production. Ghrelin suppressed IKK/NF-κB/BACE1 induced Aß production. This improvement was reversed by DG and a PP1 antagonist and was enhanced by the IKK antagonist. Our findings indicated that chronic ghrelin administration can suppress IKK/NF-κB/BACE1 mediated Aß production in primary neurons with high glucose treatment and improve the cognition via PP1 upregulation in diabetic rats.

[Characteristics of newly diagnosed diabetes patients with young onset in the West China Hospital of Sichuan University].

OBJECTIVE: To investigate the clinical characteristics, metabolic status, insulin resistance and insulin secretory function of diabetic patients with early onset. METHODS: The study was undertaken in the West China Hospital of Sichuan University. Characteristics of 342 admitted diabetic patients with early onset (EOD group, diagnosed at age 15-45 years old) were reviewed and compared with 296 admitted patients with late onset (LOD group, diagnosed at age >45 years old). All of the participants had negative islet autoantibodies. Homeostasis model assessment 2 of insulin resistant (HOMA2-IR) and HOMA2 of insulin sencitivity (HOMA2-% S) were measured to estimate insulin resistance and insulin sensitivity. HOMA2 of beta-cell function (HOMA2-% beta) index was used to estimate beta-cell secretory function. We also compared clinical characteristics and metabolic status between the two groups. RESULTS: EOD patients were more likely to have ketosis, ketoacidosis, insulin therapy and positive diabetic family history than LOD patients (P < 0.05). Levels of systolic blood pressure (SBP), diastolic blood pressure (DBP), body mass index (BMI), waist-to-hip ratio (WHR), fasting and postprandial insulin (Fins, PIns), fasting and postprandial plasma C-peptide (FCP, PCP) were significantly lower, and glycosylated hemoglobin A1c (HbA1), triglycerides (TG), fasting and postprandial blood glucose (FPG, PPG) were significantly higher in EOD patients than in LOD patients (P < 0.05). EOD patients had lower prevalence of hypertension, central obesity, hyperuricemia, metabolic syndrome (MS) and co-exist of three or more metabolic disorders than LOD patients (P < 0.05). EOD patients had decreased levels of HOMA2-% beta, deltaI30/deltaG30 and HOMA2-IR, increased HOMA2-%S, and increased proportions with FCP < 0.2 nmol/L and FIns < 2.9 microU/mL compared with LOD patient (P < 0.05). Linear regression analyses showed that HOMA2-%beta, deltaI30/deltaG30, positive diabetic family history were independent risk factors predicting early onset of diabetes. CONCLUSION: Early onset diabetic patients are characterized with low prevalence of metabolic disorders, insulin resistance and severe insulin secretion dysfunction. Loss of beta-cell function may play a major role in the development of early onset diabetes in this population.

[The changes of gastrointestinal hormones GLP-1, PYY and ghrelin in patients with newly diagnosed type 2 diabetes mellitus].

OBJECTIVE: To study the changes of plasma glucagon-like peptide-1 (GLP-1), serum peptide-YY (PYY) and Ghrelin and their secretion functions in patients with newly diagnosed type 2 diabetes mellitus (T2DM). METHOD: A total of 102 subjects were enrolled, including 32 normal-glucose-tolerance controls (NGT) and 70 patients with newly diagnosed T2DM. Height, body mass, waist circumference (WC) and hip circumference were measured. The plasma lipids and 0 h, 1/2 h, 2 h plasma glucose, insulin (INS), GLP-1, serum PYY and Ghrelin in a standard meal test in each subject were detected, and body mass index (BMI), homeostasis model assessment of insulin resistance (HOMA-IR), insulin sensitivity index (ISI), homeostasis model assessment of beta cell function (HOMA-B) and early insulin secretion function index (DeltaI30/DeltaG30) were calculated. All these variables were compared between the two groups. RESULTS: Compared with those in NGT group, the WC, fasting plasma glucose (FPG), postprandial plasma glucose (2 h-PG), triglyceride (TG), HOMA-IR were significantly higher (P 0.05), while INS(30), HOMA-B, ISI, DeltaI30/DeltaG30 were significantly lower in T2DM group (P<0. 05). In addition, in T2DM group, 0 h, 1/2 h, 2 h plasma GLP-1 and serum PYY and the area under the curve (AUC) of GLP-1 (GLP-lAuc ) and PYY (PYYAc) in standard meal test were significantly lower (P<0. 05), but the serum Ghrelin and GhrelinA, were significantly higher (P<0. 05). Meanwhile, the secretory peak of GLP-1 and PYY after standard meal in T2DM patients all disappeared. In T2DM group, PYYAUC and TG were negatively correlated (P<0.05), the fasting serum Ghrelin level was negatively associated with total cholesterol (TC), and GhrelinAuc was positively associated with HOMA-B, but negatively with the low-density lipoprotein cholesterol (LDL-C) and FPG (P(<0. 05). CONCLUSION: Patients with newly diagnosed T2DM have decreased fasting and postprandial GLP-1 and PYY levels, along with changes of their secretion mode and increased levels of Ghrelin.

Diabetes influences the fusion of autophagosomes with lysosomes in SH-SY5Y cells and induces Aß deposition and cognitive dysfunction in STZ-induced diabetic rats.

Diabetes has been regarded as an independent risk factor for Alzheimer's disease (AD). Our previous study found that diabetes activated autophagy, but lysosome function was impaired. Autophagy-lysosome dysfunction may be involved in Aß deposition in diabetic cognitive impairment. In the present study, we used STZ-induced diabetic rats and SH-SY5Y cells to investigate whether diabetes inhibits autophagosome fusion with lysosomes. We found that in the in vivo study, STZ-induced diabetic rats exhibited cognitive dysfunction, and the lysosome function-related factors CTSL, CTSD, and Rab7 were decreased (P < 0.05). In an in vitro study, the mRFP-GFP-LC3 assay showed that the fusion of autophagosomes with lysosomes was partly blocked in SH-SY5Y cells. High glucose treatment downregulated the number of autophagolysosomes, downregulated CTSD, CTSL, and Rab7 expression (P < 0.05), and then influenced the function of ACP2 to partly block the fusion of autophagosomes and lysosomes to inhibit Aß clearance. These findings indicate that high glucose treatment affected lysosome function, interfered with the fusion of autophagosomes with lysosomes, and partly blocked autophagic flux to influence Aß clearance.

[Molecular scanning of mtDNA gene in two early-onset diabetic pedigrees].

OBJECTIVE: To search for new potential diabetogenic mtDNA defects by scanning mtDNA genome in mitochondrial DNA diabetes (MDM) pedigrees. METHODS: Blood samples were collected from the family members in two suspected MDM pedigrees, which were both maternal transmitted and early-onset diabetes. The whole mtDNA genome except D-loop was detected by direct sequencing in probands of these two diabetic pedigrees. Novel mutations displayed by direct sequencing were then screened in 200 normal glucose tolerant controls and 100 early-onset diabetic patients. RESULTS: We found a novel nt14319T --> C mutation in No. 2 pedigree, but no pathogenic mutation was found in No. 1 pedigree. The mutation of nt14319T --> C, which not being reported previously, locate in the region of ND6 subunit, causing amino acid change (asparagine --> aspartic acid). The frequencies of 14319T/C substitution in 100 early-onset diabetic patients and 200 control subjects were 6% and 5%(P > 0.05). CONCLUSION: A novel mutation 14319T --> C was identified in No. 2 pedigree. All three diabetic family members in this pedigree haboured 14319T --> C mutation, indicating that it may be the major pathogenic mutation for this family.

The Research on the Relationship of RAGE, LRP-1, and Aß Accumulation in the Hippocampus, Prefrontal Lobe, and Amygdala of STZ-Induced Diabetic Rats.

Diabetes mellitus (DM) has been regarded as an important risk factor for Alzheimer's disease (AD), and diabetic patients and animals have shown cognitive dysfunction. More research has shown that the amyloid-ß (Aß), which is a hallmark of AD, was found deposited in the hippocampus of diabetic rats. This Aß accumulation is regulated by the receptor for advanced glycation end products (RAGE) and low-density lipoprotein receptor-related protein (LRP-1). However, the expression of RAGE and LRP-1 in diabetic rats is not very clear. In the present study, we used streptozotocin (STZ)-induced diabetic rats to investigate whether the expression of RAGE and LRP-1 is related to Aß1-42 deposition at the hippocampus, prefrontal lobe, and amygdala in DM. We found that diabetic rats had longer escape latency and less frequency of entrance into the target zone than that of the control group (P < 0.05) in the Morris water maze (MWM) test. The Aß1-42 expression in the hippocampus and prefrontal lobe significantly increased in the DM group compared to the control group (P < 0.05). RAGE increased (P < 0.05), while LRP-1 decreased (P < 0.05) in the hippocampus tissue and prefrontal lobe tissue of DM rats. The Aß1-42 deposition was correlated with RAGE positively (P < 0.05), but with LRP-1 negatively (P < 0.05). Further, the expression levels of Aß1-42, RAGE, and LRP-1 were not changed in the amygdala between the diabetic rats and the control group. These findings indicated that upregulating RAGE and/or downregulating LRP-1 at the hippocampus and the prefrontal lobe contributed to the Aß1-42 accumulation and then further promoted the cognitive impairment of diabetic rats.

Elevation of serum apelin-13 associated with proliferative diabetic retinopathy in type 2 diabetic patients.

AIM: To compare apelin-13, a ligand of G-protein-coupled receptor which has been shown to be involved in retinal angiogenesis, and vascular endothelial growth factor (VEGF) serum levels in type 2 diabetes mellitus (T2DM) with or without retinopathy, and to investigate the relationship between the serum concentration of apelin-13 and diabetes retinopathy. METHODS: Sixty-nine patients with T2DM were enrolled. Of the 69 patients, 16 had proliferative diabetic retinopathy (PDR group), 23 had non-PDR (NPDR group) and 30 had no retinopathy (T2DM group). Subjects' information, including demographics, medical history, and use of medications were recorded. Their serum samples were collected for measuring the levels of C-reactive protein (CRP), serum lipid and glycosylated hemoglobin. Apelin-13 and VEGF serum levels were measured by enzyme-linked immunosorbent assay. Kruskal-Wallis test and one-way ANOVA were used to compare the differences among these groups. Chi-square test was used to assess categorical variables. Correlations between variables were investigated by Spearman rho correlation test and stepwise regression analysis. All statistical analyses were performed through SPSS 17.0 software. RESULTS: Sex, age, body mass index (BMI), blood pressure, CRP, hemoglobin A1c (HbA1c) have no significantly difference in the three groups. Serum level of apelin-13 was significantly elevated in PDR group as compared with T2DM group (P=0.041). Differences of VEGF serum concentration in the three groups were statistically significant (P=0.007, P=0.007 and P<0.001, respectively). Spearman rho correlation test showed that serum apelin-13 was positively correlated with BMI, serum triglycerides, VEGF, but not with age, duration of diabetes, blood pressure, CRP, HbA1c and total-cholesterol. Stepwise regression analysis showed that BMI also significantly associated with serum apelin-13 (P=0.002), while VEGF and serum triglycerides were irrelevant. CONCLUSION: This study elucidated a positive association of apelin-13 serum level with PDR, but not with VEGF. Apelin-13 may influence the promotion of PDR but unrelated with VEGF.