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Apoptosis of pancreatic beta cells is a feature of type 2 diabetes and its prevention may have therapeutic benefit. High glucose concentrations induce apoptosis of islet cells, and this requires the proapoptotic Bcl-2 homology domain 3 (BH3)-only proteins Bim and Puma. We studied the stress pathways induced by glucotoxicity in beta cells that result in apoptosis. High concentrations of glucose or ribose increased expression of the transcription factor CHOP (C/EBP homologous protein) but not endoplasmic reticulum (ER) chaperones, indicating activation of proapoptotic ER stress signaling. Inhibition of ER stress prevented ribose-induced upregulation of Chop and Puma mRNA, and partially protected islets from glucotoxicity. Loss of Bim or Puma partially protected islets from the canonical ER stressor thapsigargin. The antioxidant N -acetyl-cysteine also partially protected islets from glucotoxicity. Islets deficient in both Bim and Puma, but not Bim or Puma alone, were significantly protected from killing induced by the mitochondrial reactive oxygen species donor rotenone. Our data demonstrate that high concentrations of glucose induce ER and oxidative stress, which causes cell death mediated by Bim and Puma. We observed significantly higher Bim and Puma mRNA in islets of human donors with type 2 diabetes. This indicates that inhibition of Bim and Puma, or their inducers, may prevent beta-cell destruction in type 2 diabetes.

Aims/hypothesis We determined whether hepatic fat content and plasma adiponectin concentration regulate VLDL₁ production. Methods A multicompartment model was used to simultaneously determine the kinetic parameters of triglycerides (TGs) and apolipoprotein B (ApoB) in VLDL₁ and VLDL₂ after a bolus of [²H₃]leucine and [²H₅]glycerol in ten men with type 2 diabetes and in 18 non-diabetic men. Liver fat content was determined by proton spectroscopy and intra-abdominal fat content by MRI. Results Univariate regression analysis showed that liver fat content, intra-abdominal fat volume, plasma glucose, insulin and HOMA-IR (homeostasis model assessment of insulin resistance) correlated with VLDL₁ TG and ApoB production. However, only liver fat and plasma glucose were significant in multiple regression models, emphasising the critical role of substrate fluxes and lipid availability in the liver as the driving force for overproduction of VLDL₁ in subjects with type 2 diabetes. Despite negative correlations with fasting TG levels, liver fat content, and VLDL₁ TG and ApoB pool sizes, adiponectin was not linked to VLDL₁ TG or ApoB production and thus was not a predictor of VLDL₁ production. However, adiponectin correlated negatively with the removal rates of VLDL₁ TG and ApoB. Conclusions/interpretation We propose that the metabolic effect of insulin resistance, partly mediated by depressed plasma adiponectin levels, increases fatty acid flux from adipose tissue to the liver and induces the accumulation of fat in the liver. Elevated plasma glucose can further increase hepatic fat content through multiple pathways, resulting in overproduction of VLDL₁ particles and leading to the characteristic dyslipidaemia associated with type 2 diabetes.

Type 2 diabetes mellitus (DM) is a progressive disease and the rate of progression from non-diabetes to DM varies considerably between individuals, ranging from a few months to many years. It is important to understand the mechanisms underlying the progression of diabetes. In the present study, a high-resolution metabolomics (HRM) analysis was performed to detect potential biomarkers and pathways regulating the mode of onset by comparing subjects who developed and did not develop type 2 DM at the second year in a 3-year prospective cohort study. Metabolic profiles correlated with progression to DM were examined. The subjects (n=98) were classified into four groups: Control (did not develop DM for 3 years), DM (diagnosed with DM at the start of the study), DM onset at the third year and DM onset at the second year. The focus was on the comparison of serum samples of the DM groups with onset at the second and third year from the first year, where these two groups had not developed DM, yet. Analyses involved sample examination using liquid chromatography-mass spectrometry-based HRM and multivariate statistical analysis of the data. Metabolic differences were identified across all analyses with the affected pathways involved in metabolism associated with steroid biosynthesis and bile acid biosynthesis. In the first year, higher levels of cholesterol {mass-to charge ratio (m/z) 369.35, (M+H-H2O)+}, 25-hydroxycholesterol [m/z 403.36, (M+H)+], 3α,7α-dihydroxy-5β-cholestane [m/z 443.33, (M+K)+], 4α-methylzymosterol-4-carboxylate [m/z 425.34, (M+H-H2O)+], and lower levels of 24,25-dihydrolanosterol [m/z 429.40, (M+H)+] were evident in the group with DM onset at the second year compared with those in the group with DM onset at the third year. These results, with a focus on the cholesterol biosynthesis pathway, point to important aspects in the development of DM and may aid in the development of more effective means of treatment and prevention.

Danon disease is a rare X-linked dominant lysosomal disease due to the primary deficiency of lysosome-associated membrane protein 2 (LAMP2) gene. Cardiomyopathy, skeletal myopathy and mental retardation are the typical triad of Danon disease. More than 60 LAMP2 mutations have been reported. The molecular mechanism is defects in LAMP2 protein (due to LAMP2 mutation) which causes insidious glycogen accumulation in cardiac muscle cells and resulting in cardiac hypertrophy and electrophysiological abnormalities. However, there are significant differences between the male and female Danon disease patients with regard to clinical features and cardiac manifestations. The clinical symptoms are variable, from asymptomatic to sudden cardiac death. Wolff-Parkinson-White syndrome is more common in male than female patients. Hypertrophic cardiomyopathy is predominant in male patients, whereas the similar prevalence of hypertrophic and dilated cardiomyopathy in female patients. Male patients are diagnosed usually at teenage, whereas the diagnosis and events occurred approximately 15 years later in female than male patients. Heart transplantation is the reliable treatment once the occurrence of heart failure and should be considered as early as possible due to its rapid progression.