Myricetin Protects Against High Glucose-Induced β-Cell Apoptosis by Attenuating Endoplasmic Reticulum Stress via Inactivation of Cyclin-Dependent Kinase 5

BACKGROUND: Chronic hyperglycemia has deleterious effects on pancreatic β-cell function and turnover. Recent studies support the view that cyclin-dependent kinase 5 (CDK5) plays a role in β-cell failure under hyperglycemic conditions. However, little is known about how CDK5 impair β-cell function. Myricetin, a natural flavonoid, has therapeutic potential for the treatment of type 2 diabetes mellitus. In this study, we examined the effect of myricetin on high glucose (HG)-induced β-cell apoptosis and explored the relationship between myricetin and CDK5. METHODS: To address this question, we subjected INS-1 cells and isolated rat islets to HG conditions (30 mM) in the presence or absence of myricetin. Docking studies were conducted to validate the interaction between myricetin and CDK5. Gene expression and protein levels of endoplasmic reticulum (ER) stress markers were measured by real-time reverse transcription polymerase chain reaction and Western blot analysis. RESULTS: Activation of CDK5 in response to HG coupled with the induction of ER stress via the down regulation of sarcoendoplasmic reticulum calcium ATPase 2b (SERCA2b) gene expression and reduced the nuclear accumulation of pancreatic duodenal homeobox 1 (PDX1) leads to β-cell apoptosis. Docking study predicts that myricetin inhibit CDK5 activation by direct binding in the ATP-binding pocket. Myricetin counteracted the decrease in the levels of PDX1 and SERCA2b by HG. Moreover, myricetin attenuated HG-induced apoptosis in INS-1 cells and rat islets and reduce the mitochondrial dysfunction by decreasing reactive oxygen species production and mitochondrial membrane potential (Δψm) loss. CONCLUSION: Myricetin protects the β-cells against HG-induced apoptosis by inhibiting ER stress, possibly through inactivation of CDK5 and consequent upregulation of PDX1 and SERCA2b.

Mechanisms of Vascular Calcification: The Pivotal Role of Pyruvate Dehydrogenase Kinase 4

Vascular calcification, abnormal mineralization of the vessel wall, is frequently associated with aging, atherosclerosis, diabetes mellitus, and chronic kidney disease. Vascular calcification is a key risk factor for many adverse clinical outcomes, including ischemic cardiac events and subsequent cardiovascular mortality. Vascular calcification was long considered to be a passive degenerative process, but it is now recognized as an active and highly regulated process similar to bone formation. However, despite numerous studies on the pathogenesis of vascular calcification, the mechanisms driving this process remain poorly understood. Pyruvate dehydrogenase kinases (PDKs) play an important role in the regulation of cellular metabolism and mitochondrial function. Recent studies show that PDK4 is an attractive therapeutic target for the treatment of various metabolic diseases. In this review, we summarize our current knowledge regarding the mechanisms of vascular calcification and describe the role of PDK4 in the osteogenic differentiation of vascular smooth muscle cells and development of vascular calcification. Further studies aimed at understanding the molecular mechanisms of vascular calcification will be critical for the development of novel therapeutic strategies.

Serum Total Bilirubin Levels Provide Additive Risk Information over the Framingham Risk Score for Identifying Asymptomatic Diabetic Patients at Higher Risk for Coronary Artery Stenosis

BACKGROUND: The diagnosis of coronary artery disease (CAD) is often delayed in patients with type 2 diabetes. Serum total bilirubin levels are inversely associated with CAD. However, no studies have examined whether this can be used as a biochemical marker for identifying asymptomatic diabetic patients at higher risk for having obstructive CAD. METHODS: We performed a cross-sectional study of 460 consecutive asymptomatic patients with type 2 diabetes. All patients underwent coronary computed tomographic angiography, and their serum total bilirubin levels were measured. Obstructive CAD was defined as > or =50% diameter stenosis in at least one coronary artery. RESULTS: Serum total bilirubin tertiles showed an inverse association with the prevalence of obstructive CAD. In multivariate logistic regression analysis, the odds ratio for the highest versus the lowest tertile of total bilirubin was 0.227 (95% confidence interval [CI], 0.130 to 0.398), and an increment of 1 micromol/L in serum total bilirubin level was associated with a 14.6% decrease in obstructive CAD after adjustment for confounding variables. Receiver operating characteristic curve analysis showed that the area under the curve for the Framingham Risk Score (FRS) plus serum total bilirubin level was 0.712 (95% CI, 0.668 to 0.753), which is significantly greater than that of the FRS alone (P=0.0028). CONCLUSION: Serum total bilirubin level is inversely associated with obstructive CAD and provides additive risk information over the FRS. Serum total bilirubin may be helpful for identifying asymptomatic patients with type 2 diabetes who are at higher risk for obstructive CAD.

Clinical Features and Causes of Endogenous Hyperinsulinemic Hypoglycemia in Korea

BACKGROUND: Endogenous hyperinsulinemic hypoglycemia (EHH) is characterized by an inappropriately high plasma insulin level, despite a low plasma glucose level. Most of the EHH cases are caused by insulinoma, whereas nesidioblastosis and insulin autoimmune syndrome (IAS) are relatively rare. METHODS: To evaluate the relative frequencies of various causes of EHH in Korea, we retrospectively analyzed 84 patients who were diagnosed with EHH from 1998 to 2012 in a university hospital. RESULTS: Among the 84 EHH patients, 74 patients (88%), five (6%), and five (6%) were diagnosed with insulinoma, nesidioblastosis or IAS, respectively. The most common clinical manifestation of EHH was neuroglycopenic symptoms. Symptom duration before diagnosis was 14.5 months (range, 1 to 120 months) for insulinoma, 1.0 months (range, 6 days to 7 months) for nesidioblastosis, and 2.0 months (range, 1 to 12 months) for IAS. One patient, who was diagnosed with nesidioblastosis in 2006, underwent distal pancreatectomy but was later determined to be positive for insulin autoantibodies. Except for one patient who was diagnosed in 2007, the remaining three patients with nesidioblastosis demonstrated severe hyperinsulinemia (157 to 2,719 microIU/mL), which suggests that these patients might have had IAS, rather than nesidioblastosis. CONCLUSION: The results of this study suggest that the prevalence of IAS may be higher in Korea than previously thought. Therefore, measurement of insulin autoantibody levels is warranted for EHH patients, especially in patients with very high plasma insulin levels.

Serum Ceruloplasmin Level as a Predictor for the Progression of Diabetic Nephropathy in Korean Men with Type 2 Diabetes Mellitus

BACKGROUND: Oxidative stress is known to be associated with progression of diabetic kidney disease. Ceruloplasmin acts as a pro-oxidant under conditions of severe oxidative stress. Thus, we conducted a longitudinal observational study to evaluate whether the serum ceruloplasmin level is a predictive biomarker for progression of diabetic nephropathy. METHODS: A total of 643 Korean men with type 2 diabetes mellitus were enrolled. Serum ceruloplasmin was measured using a nephelometric method. Progression of diabetic nephropathy was defined as transition in albuminuria class (i.e., normoalbuminuria to microalbuminuria, microalbuminuria to macroalbuminuria, or normoalbuminuria to macroalbuminuria) and/or a greater than 2-fold increase of serum creatinine at follow-up compared with the baseline value. RESULTS: During the follow-up period (median, 2.7 years; range, 0.3 to 4.4 years), 49 of 643 patients (7.6%) showed the progression of diabetic nephropathy and three patients (0.5%) developed end-stage renal disease. Baseline ceruloplasmin levels were higher in the progressors than in the nonprogressors (262.6+/-40.9 mg/L vs. 233.3+/-37.8 mg/L, P<0.001). Kaplan-Meier analysis showed a significantly higher incidence of nephropathy progression according to ceruloplasmin tertile (log-rank test, P<0.001). The hazard ratio (HR) for progression of diabetic nephropathy was significantly higher in the highest ceruloplasmin tertile category compared with the lowest ceruloplasmin tertile category, even after adjusting for confounding variables (HR, 3.32; 95% confidence interval, 1.28 to 8.61; P=0.003). CONCLUSION: Baseline serum ceruloplasmin is an independent predictive factor for the progression of diabetic nephropathy in patients with type 2 diabetes mellitus.

Management of Non-alcoholic Fatty Liver Disease / 임상당뇨병

Non-alcoholic fatty liver disease (NAFLD) is a common condition that may progress to end-stage liver disease. Recently, it has been recognized as a hepatic manifestation of metabolic syndrome and an independent risk factor for cardiovascular disease. Therefore, managing this common disorder is becoming an important public health issue. The management of NAFLD is based on gradual weight loss through lifestyle modification. Reducing total calorie intake and carbohydrates in the diet is beneficial for NAFLD patients. Regular exercise reduces hepatic fat content independent of weight loss. However, such life style changes are known to be difficult to maintain in the long term for most patients. Despite the growing need for pharmacologic therapy, there is currently no effective agent for the treatment of NAFLD. Several large clinical trials have shown promising but inconsistent effects of pioglitazone and vitamin E in improving NAFLD. Trials with ursodeoxycholic acid or metformin have been disappointing.Recently, promising evidence has shown that incretin-based therapies may improve NAFLD. Larger clinical trials are required before a definite conclusion can be made.

Mitochondrial dysfunction and activation of iNOS are responsible for the palmitate-induced decrease in adiponectin synthesis in 3T3L1 adipocytes

Mitochondrial dysfunction and endoplasmic reticulum (ER) stress are considered the key determinants of insulin resistance. Impaired mitochondrial function in obese animals was shown to induce the ER stress response, resulting in reduced adiponectin synthesis in adipocytes. The expression of inducible nitric oxide synthase (iNOS) is increased in adipose tissues in genetic and dietary models of obesity. In this study, we examined whether activation of iNOS is responsible for palmitate-induced mitochondrial dysfunction, ER stress, and decreased adiponectin synthesis in 3T3L1 adipocytes. As expected, palmitate increased the expression levels of iNOS and ER stress response markers, and decreased mitochondrial contents. Treatment with iNOS inhibitor increased adiponectin synthesis and reversed the palmitate-induced ER stress response. However, the iNOS inhibitor did not affect the palmitate-induced decrease in mitochondrial contents. Chemicals that inhibit mitochondrial function increased iNOS expression and the ER stress response, whereas measures that increase mitochondrial biogenesis (rosiglitazone and adenoviral overexpression of nuclear respiratory factor-1) reversed them. Inhibition of mitochondrial biogenesis prevented the rosiglitazone-induced decrease in iNOS expression and increase in adiponectin synthesis. These results suggest that palmitate-induced mitochondrial dysfunction is the primary event that leads to iNOS induction, ER stress, and decreased adiponectin synthesis in cultured adipocytes.

Disseminated Mycobacterium intracellulare Infection in an Immunocompetent Host / 결핵및호흡기질환

Disseminated Mycobacterium avium complex (MAC) infection can occur in immunocompromised patients, and rarely in immunocompetent subjects. Due to the extensive distribution of the disease, clinical presentation of disseminated MAC may mimic malignancies, and thorough examinations are required in order to make accurate diagnosis. We report a case of disseminated Mycobacterium intracellulare disease in an immunocompetent patient, which involved the lung, lymph nodes, spleen, and multiple bones. F-18 fluorodeoxyglucose positron-emission tomography imaging showed multiple hypermetabolic lesions, which are suggestive of typical hematogenous metastasis. However, there was no evidence of malignancy in serial biopsies, and M. intracellulare was repeatedly cultured from respiratory specimens and bones. Herein, we should know that disseminated infection can occur in the immunocompetent subjects, and it can mimic malignancies.

A Case of Nonketotic Hyperglycemia as a Manifestation of Generalized Convulsive Status Epilepticus / 대한내과학회지

Seizure is one of the manifestations of nonketotic hyperglycemia (NKH). Partial motor seizures are observed in most cases and, occasionally, with epilepsia partialis continua. Generalized convulsive status epilepticus caused by NKH is rare. In this report, we present a case of a 68-year-old man who developed generalized convulsive status epilepticus as an initial manifestation of NKH.

Fatal Rhabdomyolysis in a Patient with Liver Cirrhosis after Switching from Simvastatin to Fluvastatin

HMG-CoA reductase inhibitors (statins) are widely used to treat hypercholesterolemia. Among the adverse effects associated with these drugs are statin-associated myopathies, ranging from asymptomatic elevation of serum creatine kinase to fatal rhabdomyolysis. Fluvastatin-induced fatal rhabdomyolysis has not been previously reported. We describe here a patient with liver cirrhosis who experienced fluvastatin-induced fatal rhabdomyolysis. This patient had been treated with simvastatin (20 mg/day) for coronary artery disease and was switched to fluvastatin (20 mg/day) 10 days before admission. He was also taking aspirin, betaxolol, candesartan, lactulose, and entecavir. Rhabdomyolysis was complicated and continued to progress. He was treated with massive hydration, urine alkalization, intravenous furosemide, and continuous renal replacement therapy for acute renal failure, but eventually died due to rhabdomyolysis complicated by hepatic failure. In conclusion, fluvastatin should be used with caution in patients with liver cirrhosis, especially with other medications metabolized with CYP2C9.