In the well-fed state a relatively high activity of the pyruvate dehydrogenase complex (PDC) reduces blood glucose levels by directing the carbon of pyruvate into the citric acid cycle. In the fasted state a relatively low activity of the PDC helps maintain blood glucose levels by conserving pyruvate and other three carbon compounds for gluconeogenesis. The relative activities of the pyruvate dehydrogenase kinases (PDKs) and the opposing pyruvate dehydrogenase phosphatases determine the activity of PDC in the fed and fasted states. Up regulation of PDK4 is largely responsible for inactivation of PDC in the fasted state. PDK4 knockout mice have lower fasting blood glucose levels than wild type mice, proving that up regulation of PDK4 is important for normal glucose homeostasis. In type 2 diabetes, up regulation of PDK4 also inactivates PDC, which promotes gluconeogenesis and thereby contributes to the hyperglycemia characteristic of this disease. When fed a high fat diet, wild type mice develop fasting hyperglycemia but PDK4 knockout mice remain euglycemic, proving that up regulation of PDK4 contributes to hyperglycemia in diabetes. These finding suggest PDK4 inhibitors might prove useful in the treatment of type 2 diabetes.
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New diabetes management systems based on interactive communication have been introduced recently, accompanying rapid advances in information technology; these systems are referred to as "ubiquitous diabetes management systems." In such ubiquitous systems, patients and medical teams can communicate via Internet or telecommunications, with patients uploading their glucose data and personal information, and medical teams sending optimal feedback. Clinical evidence from both long-term and short-term trials has been reported by some researchers. Such systems appear to be effective not only in reducing the levels of HbA1c but also in stabilizing glucose control. However, most notably, evidence for the cost-effectiveness of such a system should be demonstrated before it can be propagated out to the general population in actual clinical practice. To establish a cost-effective model, various types of clinical decision supporting software designed to reduce the labor time of physicians must first be developed. A number of sensors and devices for monitoring patients' data are expected to be available in the near future; thus, methods for automatic interconnections between devices and web charts were also developed. Further investigations to demonstrate the clinical outcomes of such a system should be conducted, hopefully leading to a new paradigm of diabetes management.
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O-Linked β-
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Mitochondria play key roles in energy production and intracellular reactive oxygen species (ROS) generation. Lines of evidence have shown that mitochondrial dysfunction contributes to the development of metabolic syndrome. The causes of mitochondrial dysfunction are complex, but overnutrition and sedentary living are among the best known causes of mitochondrial dysfunction. ATP synthesized in the mitochondria is exchanged for cytosolic ADP by adenine nucleotide translocator (ANT) to provide a continuous supply of ADP to mitochondria. We recently found that ANT function is essential for peroxisome proliferator-activated receptor-γ coactivator 1-α (PGC-1α)'s action on endothelial cells. PGC-1α is a transcriptional coactivator of nuclear receptors, playing an important role in fatty acid oxidation and mitochondrial biogenesis. Recent studies have shown that PGC-1α decreases intracellular ROS generation by increasing the expression of antioxidant genes. In our study, PGC-1α reduced cell apoptosis and ROS generation in endothelial cells by increasing ATP/ADP translocase activity of ANT and ANT1 expression. Here we review the role of ANT in maintaining proper mitochondrial function, and possible role of ANT dysfunction in the pathogenesis of metabolic syndrome.
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Years before insulin was discovered, anti-inflammatory sodium salicylate was used to treat diabetes in 1901. Intriguingly for many years that followed, diabetes was viewed as a disorder of glucose metabolism, and then it was described as a disease of dysregulated lipid metabolism. The diabetes research focused on the causal relationship between obesity and insulin resistance, a major characteristic of type 2 diabetes. It is only within the past 20 years when the notion of inflammation as a cause of insulin resistance began to surface. In obesity, inflammation develops when macrophages infiltrate adipose tissue and stimulate adipocyte secretion of inflammatory cytokines, that in turn affect energy balance, glucose and lipid metabolism, leading to insulin resistance. This report reviews recent discoveries of stress kinase signaling involving molecular scaffolds and endoplasmic reticulum chaperones that regulate energy balance and glucose homeostasis. As we advance from a conceptual understanding to molecular discoveries, a century-old story of inflammation and insulin resistance is re-born with new ideas.
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Reduction of beta cell function and a beta cell mass is observed in both type 1 and type 2 diabetes. Therefore, restoration of this deficiency might be a therapeutic option for treatment of diabetes. Islet transplantation has benefits, such as reduced incidence of hypoglycemia and achievement of insulin independence. However, the major drawback is an insufficient supply of islet donors. Transplantation of cells differentiated
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The metabolic syndrome refers to a well defined group of risk factors, including central obesity and inflammation, for the development of diabetes and cardiovascular disease. Interestingly, many studies have recently led to the emergence of somewhat unexpected relationships between several infectious diseases and various aspects of the metabolic syndrome. Our understanding of the mechanisms underlying these interactions is also rapidly developing and some of these are summarized in this article. We will focus first on bacterial infection, and most notably the role of gut microbiota in regulaton of both obesity and inflammation. In particular, we focus on the role of inflammasomes and propose that understanding the role of Toll-like receptors and Nod-like receptors in the pathogenesis of inflammatory disorders with or without infection may provide novel targets for prevention and/or treatment of associated diseases. Secondly, chronic bacterial or viral infection and emerging links with metabolism will be reviewed. Finally, consideratons of biomarkers for metabolic syndrome, in particular lipocalin-2, and their link with infection will be discussed.
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Type 2 diabetes mellitus (T2DM) is increasing in prevalence worldwide. The complications associated with T2DM result in increased mortality and financial cost for those affected. T2DM has long been known to be associated with insulin resistance in peripheral tissues and a relative degree of insulin deficiency. However, the concept that insulin secretion and insulin sensitivity are not linked through a hyperbolic relationship in T2DM has continuously been demonstrated in many clinical trials. Thus, in order to prevent and treat T2DM, it is necessary to identify the substance(s) that will improve the function and survival of the pancreatic β-cells in both normal and pathologic conditions, so that production and secretion of insulin can be enhanced. Incretin hormones, such as glucagon-like peptide (GLP)-1 and glucose-dependent insulinotropic polypeptide (GIP), have been shown to lower the postprandial and fasting glucose and the glycated hemoglobin levels, suppress the elevated glucagon level, and stimulate glucose-dependent insulin synthesis and secretion. In this report, we will review the biological actions and mechanisms associated with the actions of incretin hormones, GLP-1 and GIP, on β-cell health and compare the differences between GLP-1 and GIP.
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To determine the factors responsible for the dramatic increase in the prevalence of diabetes in Korea. A computerized literature survey was conducted to evaluate the risk factors for Type 2 diabetes mellitus (T2DM) in Korea, including genome-wide association studies. National Statistics gross national income data was integrated with the reported prevalence of diabetes to evaluate the relationship between diabetes and the economic growth. The strength of the association was evaluated using measures of effect size, such as odds ratio and relative risks. The putative risk factors identified in Korean studies are very similar to the risk factors identified from the other countries, including genetic background. Genome-wide association studies reported relative risks of 1.5 or less, indicating that no single gene is associated with the risk of T2DM. The scientific evidence suggests that the dramatic increase in the incidence and prevalence of T2DM in Korea is related to the economic development of Korea, which has a direct influence on health policy, as well as an individual's health behaviors. We expect to observe the current diabetes incidence rates until the key risk factors are present for long enough in our society, at which point we would expect to start observing a more gradual increase in both the incidence and prevalence of T2DM in Korea.
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