Differential Glucose-Regulation of MicroRNAs in Pancreatic Islets of Non-Obese Type 2 Diabetes Model Goto-Kakizaki Rat

The Goto-Kakizaki (GK) rat is a well-studied non-obese spontaneous type 2 diabetes (T2D) animal model characterized by impaired glucose-stimulated insulin secretion (GSIS) in the pancreatic beta cells. MicroRNAs (miRNAs) are short regulatory RNAs involved in many fundamental biological processes. We aim to identify miRNAs that are differentially-expressed in the pancreatic islets of the GK rats and investigate both their short- and long term glucose-dependence during glucose-stimulatory conditions

Serum aspirin esterase is strongly associated with glucose and lipids in healthy subjects: different association patterns in subjects with type 2 diabetes mellitus

<p>Abstract</p> <p>Background</p> <p>Aspirin esterase (AE) activity can account for part of aspirin pharmacokinetics in the circulation, possibly being associated with the impairment of aspirin effectiveness as an inhibitor of platelet aggregation.</p> <p>Aims</p> <p>The study was aimed at investigating the correlations of serum AE activity with cholinesterase (ChE) and metabolic variables in healthy subjects in comparison to subjects with type 2 diabetes mellitus (T2DM).</p> <p>Methods</p> <p>In cardiovascular disease-free T2DM subjects and healthy controls, the AE activity levels and/or the correlation patterns between AE and the other variables were analyzed.</p> <p>Results</p> <p>Neither AE nor ChE activities were higher in the subjects with T2DM. Serum AE activity strongly correlated with ChE as well as glucose/lipids variables such as total cholesterol and triglyceride in healthy subjects, while the correlations between AE and glucose/lipids variables were not present in T2DM subjects.</p> <p>Conclusions</p> <p>These data may reflect the pathophysiological changes between healthy and T2DM subjects. Our data may thus provide the basis for future studies to unravel the mechanisms.</p

Shikonin Increases Glucose Uptake in Skeletal Muscle Cells and Improves Plasma Glucose Levels in Diabetic Goto-Kakizaki Rats

Glucose is the most common substrate for energy metabolism. Despite the varying demands for glucose, the body needs to regulate its internal environment and maintain a constant and stable condition. Glucose homeostasis requires harmonized interaction between several tissues, achieving equilibrium between glucose output and uptake. In this thesis we aimed to investigate factors modulating glucose homeostasis in a rat model of type 2 diabetes, the Goto-Kakizaki (GK) rat. In addition, we investigated sex differences in hepatic carbohydrate and lipid metabolism in healthy rats. In Paper I, three-week but not three-day treatment with a Southeast Asian herb, Gynostemma pentaphyllum (GP), significantly reduced plasma glucose (PG) levels in GK rats. An intra-peritoneal glucose tolerance test (IPGTT) was significantly improved in GP-treated compared to placebo-treated group. In the GP treated rats, the glucose response in an intra-peritoneal pyruvate tolerance test was significantly lower, indicating decreased gluconeogenesis, and hepatic glucose output (HGO) was reduced. GP-treatment significantly reduced hepatic glycogen content, but not glycogen synthase activity. The study provides evidence that the GP extract exerted anti-diabetic effect in GK rats, reducing PG levels and HGO, suggesting that GP improves the hepatic insulin sensitivity by suppressing gluconeogenesis. In Paper II, shikonin, a naphthoquinone derived from the Chinese plant Lithospermum erythrorhizon, increased glucose uptake in L6 myotubes, but did not phosphorylate Akt. Furthermore we found no evidence for the involvement of AMP activated protein kinase (AMPK) in shikonin induced glucose uptake. Shikonin increased the intracellular levels of calcium in these cells and stimulated the translocation of GLUT4 from intracellular vesicles to the cell surface in L6 myotubes. In GK rats treated with shikonin once daily for 4 days, PG levels were significantly decreased. In an insulin sensitivity test, the absolute PG levels were significantly lower in the shikonin-treated rats. These findings suggest that shikonin increases glucose uptake in muscle cells via an insulin-independent pathway dependent on calcium. In Paper III, GK and control Wistar rats were injected daily for up to 4 weeks with either a non-hematopoietic erythropoietin analog ARA290 or with placebo. PG levels in GK but not Wistar rats were significantly lower in ARA290-treated compared to placebo. After 2 and 4 weeks, the IPGTT was significantly improved in ARA290 treated GK rats. In insulin and pyruvate tolerance tests, glucose responses were similar in ARA290 and placebo groups. In isolated GK rat islets, glucose-stimulated insulin release was two-fold higher and islet intracellular calcium concentrations in response to several secretagogues were significantly higher in ARA290-treated than in placebo-treated GK rats. These findings indicate that treatment with ARA290 significantly improved glucose tolerance in diabetic GK rats, most likely due to improvement of insulin release. In Paper IV, sex differences in hepatic carbohydrate and lipid metabolism were characterized in healthy rats. No sex-differences were observed regarding hepatic triglyceride content, fatty acid oxidation rates or insulin sensitivity. Male rats had higher ratios of insulin to glucagon levels, increased hepatic glycogen content, a lower degree of AMPK phosphorylation, a higher rate of glucose production and higher expression levels of gluconeogenic genes, as compared to female rats. A sex-dependent response to mild starvation was observed with males being more sensitive. In conclusion, sex-differences reflect a higher capacity of the healthy male rat liver to respond to increased energy demands. Key words: glucose homeostasis, type 2 diabetes, GK rats, L6 myotubes, hepatic glucose output, insulin sensitivity, sex differences

Balance perturbation system to improve balance compensatory responses during walking in old persons

Ageing commonly disrupts the balance control and compensatory postural responses that contribute to maintaining balance and preventing falls during perturbation of posture. This can lead to increased risk of falling in old adults (65 years old and over). Therefore, improving compensatory postural responses during walking is one of the goals in fall prevention programs. Training is often used to achieve this goal. Most fall prevention programs are usually directed towards improving voluntary postural control. Since compensatory postural responses triggered by a slip or a trip are not under direct volitional control these exercises are less expected to improve compensatory postural responses due to lack of training specificity. Thus, there is a need to investigate the use balance perturbations during walking to train more effectively compensatory postural reactions during walking

Transcriptomic alterations in the heart of non-obese type 2 diabetic Goto-Kakizaki rats

BACKGROUND: There is a spectacular rise in the global prevalence of type 2 diabetes mellitus (T2DM) due to the worldwide obesity epidemic. However, a significant proportion of T2DM patients are non-obese and they also have an increased risk of cardiovascular diseases. As the Goto-Kakizaki (GK) rat is a well-known model of non-obese T2DM, the goal of this study was to investigate the effect of non-obese T2DM on cardiac alterations of the transcriptome in GK rats. METHODS: Fasting blood glucose, serum insulin and cholesterol levels were measured at 7, 11, and 15 weeks of age in male GK and control rats. Oral glucose tolerance test and pancreatic insulin level measurements were performed at 11 weeks of age. At week 15, total RNA was isolated from the myocardium and assayed by rat oligonucleotide microarray for 41,012 genes, and then expression of selected genes was confirmed by qRT-PCR. Gene ontology and protein-protein network analyses were performed to demonstrate potentially characteristic gene alterations and key genes in non-obese T2DM. RESULTS: Fasting blood glucose, serum insulin and cholesterol levels were significantly increased, glucose tolerance and insulin sensitivity were significantly impaired in GK rats as compared to controls. In hearts of GK rats, 204 genes showed significant up-regulation and 303 genes showed down-regulation as compared to controls according to microarray analysis. Genes with significantly altered expression in the heart due to non-obese T2DM includes functional clusters of metabolism (e.g. Cyp2e1, Akr1b10), signal transduction (e.g. Dpp4, Stat3), receptors and ion channels (e.g. Sln, Chrng), membrane and structural proteins (e.g. Tnni1, Mylk2, Col8a1, Adam33), cell growth and differentiation (e.g. Gpc3, Jund), immune response (e.g. C3, C4a), and others (e.g. Lrp8, Msln, Klkc1, Epn3). Gene ontology analysis revealed several significantly enriched functional inter-relationships between genes influenced by non-obese T2DM. Protein-protein interaction analysis demonstrated that Stat is a potential key gene influenced by non-obese T2DM. CONCLUSIONS: Non-obese T2DM alters cardiac gene expression profile. The altered genes may be involved in the development of cardiac pathologies and could be potential therapeutic targets in non-obese T2DM

Excessive Islet NO Generation in Type 2 Diabetic GK Rats Coincides with Abnormal Hormone Secretion and Is Counteracted by GLP-1

BACKGROUND: A distinctive feature of type 2 diabetes is inability of insulin-secreting beta-cells to properly respond to elevated glucose eventually leading to beta-cell failure. We have hypothesized that an abnormally increased NO production in the pancreatic islets might be an important factor in the pathogenesis of beta-cell dysfunction. PRINCIPAL FINDINGS: We show now that islets of type 2 spontaneous diabetes in GK rats display excessive NO generation associated with abnormal iNOS expression in insulin and glucagon cells, increased ncNOS activity, impaired glucose-stimulated insulin release, glucagon hypersecretion, and impaired glucose-induced glucagon suppression. Pharmacological blockade of islet NO production by the NOS inhibitor N(G)-nitro-L-arginine methyl ester (L-NAME) greatly improved hormone secretion from GK islets suggesting islet NOS activity being an important target to inactivate for amelioration of islet cell function. The incretin hormone GLP-1, which is used in clinical practice suppressed iNOS and ncNOS expression and activity with almost full restoration of insulin release and partial restoration of glucagon release. GLP-1 suppression of iNOS expression was reversed by PKA inhibition but unaffected by the proteasome inhibitor MG132. Injection of glucose plus GLP-1 in the diabetic rats showed that GLP-1 amplified the insulin response but induced a transient increase and then a poor depression of glucagon. CONCLUSION: The results suggest that abnormally increased NO production within islet cells is a significant player in the pathogenesis of type 2 diabetes being counteracted by GLP-1 through PKA-dependent, nonproteasomal mechanisms

Pathogenesis of peroxisomal deficiency disorders (Zellweger syndrome) may be mediated by misregulation of the GABAergic system via the diazepam binding inhibitor

BACKGROUND: Zellweger syndrome (ZS) is a fatal inherited disease caused by peroxisome biogenesis deficiency. Patients are characterized by multiple disturbances of lipid metabolism, profound hypotonia and neonatal seizures, and distinct craniofacial malformations. Median live expectancy of ZS patients is less than one year. While the molecular basis of peroxisome biogenesis and metabolism is known in considerable detail, it is unclear how peroxisome deficiency leads to the most severe neurological symptoms. Recent analysis of ZS mouse models has all but invalidated previous hypotheses. HYPOTHESIS: We suggest that a regulatory rather than a metabolic defect is responsible for the drastic impairment of brain function in ZS patients. TESTING THE HYPOTHESIS: Using microarray analysis we identify diazepam binding inhibitor/acyl-CoA binding protein (DBI) as a candidate protein that might be involved in the pathogenic mechanism of ZS. DBI has a dual role as a neuropeptide antagonist of GABA(A) receptor signaling in the brain and as a regulator of lipid metabolism. Repression of DBI in ZS patients could result in an overactivation of GABAergic signaling, thus eventually leading to the characteristic hypotonia and seizures. The most important argument for a misregulation of GABA(A) in ZS is, however, provided by the striking similarity between ZS and "benzodiazepine embryofetopathy", a malformation syndrome observed after the abuse of GABA(A) agonists during pregnancy. IMPLICATIONS OF THE HYPOTHESIS: We present a tentative mechanistic model of the effect of DBI misregulation on neuronal function that could explain some of the aspects of the pathology of Zellweger syndrome

A water-based training program that include perturbation exercises to improve stepping responses in older adults: study protocol for a randomized controlled cross-over trial

<p>Abstract</p> <p>Background</p> <p>Gait and balance impairments may increase the risk of falls, the leading cause of accidental death in the elderly population. Fall-related injuries constitute a serious public health problem associated with high costs for society as well as human suffering. A rapid step is the most important protective postural strategy, acting to recover equilibrium and prevent a fall from initiating. It can arise from large perturbations, but also frequently as a consequence of volitional movements. We propose to use a novel water-based training program which includes specific perturbation exercises that will target the stepping responses that could potentially have a profound effect in reducing risk of falling. We describe the water-based balance training program and a study protocol to evaluate its efficacy (Trial registration number #NCT00708136).</p> <p>Methods/Design</p> <p>The proposed water-based training program involves use of unpredictable, multi-directional perturbations in a group setting to evoke compensatory and volitional stepping responses. Perturbations are made by pushing slightly the subjects and by water turbulence, in 24 training sessions conducted over 12 weeks. Concurrent cognitive tasks during movement tasks are included. Principles of physical training and exercise including awareness, continuity, motivation, overload, periodicity, progression and specificity were used in the development of this novel program. Specific goals are to increase the speed of stepping responses and improve the postural control mechanism and physical functioning. A prospective, randomized, cross-over trial with concealed allocation, assessor blinding and intention-to-treat analysis will be performed to evaluate the efficacy of the water-based training program. A total of 36 community-dwelling adults (age 65–88) with no recent history of instability or falling will be assigned to either the perturbation-based training or a control group (no training). Voluntary step reaction times and postural stability using stabiliogram diffusion analysis will be tested before and after the 12 weeks of training.</p> <p>Discussion</p> <p>This study will determine whether a water-based balance training program that includes perturbation exercises, in a group setting, can improve speed of voluntary stepping responses and improve balance control. Results will help guide the development of more cost-effective interventions that can prevent the occurrence of falls in the elderly.</p

Gene Expression Profiles of Beta-Cell Enriched Tissue Obtained by Laser Capture Microdissection from Subjects with Type 2 Diabetes

Background: Changes in gene expression in pancreatic beta-cells from type 2 diabetes (T2D) should provide insights into their abnormal insulin secretion and turnover. Methodology/Principal Findings: Frozen sections were obtained from cadaver pancreases of 10 control and 10 T2D human subjects. Beta-cell enriched samples were obtained by laser capture microdissection (LCM). RNA was extracted, amplified and subjected to microarray analysis. Further analysis was performed with DNA-Chip Analyzer (dChip) and Gene Set Enrichment Analysis (GSEA) software. There were changes in expression of genes linked to glucotoxicity. Evidence of oxidative stress was provided by upregulation of several metallothionein genes. There were few changes in the major genes associated with cell cycle, apoptosis or endoplasmic reticulum stress. There was differential expression of genes associated with pancreatic regeneration, most notably upregulation of members of the regenerating islet gene (REG) family and metalloproteinase 7 (MMP7). Some of the genes found in GWAS studies to be related to T2D were also found to be differentially expressed. IGF2BP2, TSPAN8, and HNF1B (TCF2) were upregulated while JAZF1 and SLC30A8 were downregulated. Conclusions/Significance: This study made possible by LCM has identified many novel changes in gene expression tha