Screening for Active Small Molecules in Mitochondrial Complex I Deficient Patient's Fibroblasts, Reveals AICAR as the Most Beneficial Compound

Congenital deficiency of the mitochondrial respiratory chain complex I (CI) is a common defect of oxidative phosphorylation (OXPHOS). Despite major advances in the biochemical and molecular diagnostics and the deciphering of CI structure, function assembly and pathomechanism, there is currently no satisfactory cure for patients with mitochondrial complex I defects. Small molecules provide one feasible therapeutic option, however their use has not been systematically evaluated using a standardized experimental system. In order to evaluate potentially therapeutic compounds, we set up a relatively simple system measuring different parameters using only a small amount of patient's fibroblasts, in glucose free medium, where growth is highly OXPOS dependent. Ten different compounds were screened using fibroblasts derived from seven CI patients, harboring different mutations

Metformin reduces liver glucose production by inhibition of fructose-1-6-bisphosphatase.

Metformin is a first-line drug for the treatment of individuals with type 2 diabetes, yet its precise mechanism of action remains unclear. Metformin exerts its antihyperglycemic action primarily through lowering hepatic glucose production (HGP). This suppression is thought to be mediated through inhibition of mitochondrial respiratory complex I, and thus elevation of 5'-adenosine monophosphate (AMP) levels and the activation of AMP-activated protein kinase (AMPK), though this proposition has been challenged given results in mice lacking hepatic AMPK. Here we report that the AMP-inhibited enzyme fructose-1,6-bisphosphatase-1 (FBP1), a rate-controlling enzyme in gluconeogenesis, functions as a major contributor to the therapeutic action of metformin. We identified a point mutation in FBP1 that renders it insensitive to AMP while sparing regulation by fructose-2,6-bisphosphate (F-2,6-P2), and knock-in (KI) of this mutant in mice significantly reduces their response to metformin treatment. We observe this during a metformin tolerance test and in a metformin-euglycemic clamp that we have developed. The antihyperglycemic effect of metformin in high-fat diet-fed diabetic FBP1-KI mice was also significantly blunted compared to wild-type controls. Collectively, we show a new mechanism of action for metformin and provide further evidence that molecular targeting of FBP1 can have antihyperglycemic effects

Intravenous AICAR administration reduces hepatic glucose output and inhibits whole body lipolysis in type 2 diabetic patients

Aims/hypothesis: The 5&prime;-AMP-activated protein kinase (AMPK) pathway is intact in type 2 diabetic patients and is seen as a target for diabetes treatment. In this study, we aimed to assess the impact of the AMPK activator 5-aminoimidazole-4-carboxamide riboside (AICAR) on both glucose and fatty acid metabolism in vivo in type 2 diabetic patients.Methods: Stable isotope methodology and blood and muscle biopsy sampling were applied to assess blood glucose and fatty acid kinetics following continuous i.v. infusion of AICAR (0.75 mg kg&minus;1 min&minus;1) and/or NaCl (0.9%) in ten male type 2 diabetic patients (age 64&thinsp;&plusmn;&thinsp;2 years; BMI 28&thinsp;&plusmn;&thinsp;1 kg/m2).Results Plasma glucose rate of appearance (R a) was reduced following AICAR administration, while plasma glucose rate of disappearance (R d) was similar in the AICAR and control test. Consequently, blood glucose disposal (R d expressed as a percentage of R a) was increased following AICAR infusion (p&thinsp;&lt;&thinsp;0.001). Accordingly, a greater decline in plasma glucose concentration was observed following AICAR infusion (p&thinsp;&lt;&thinsp;0.001). Plasma NEFA R a and R d were both significantly reduced in response to AICAR infusion, and were accompanied by a significant decline in plasma NEFA concentration. Although AMPK phosphorylation in skeletal muscle was not increased, we observed a significant increase in acetyl-CoA carboxylase phosphorylation (p&thinsp;&lt;&thinsp;0.001).Conclusions/interpretation: The i.v. administration of AICAR reduces hepatic glucose output, thereby lowering blood glucose concentrations in vivo in type 2 diabetic patients. Furthermore, AICAR administration stimulates hepatic fatty acid oxidation and/or inhibits whole body lipolysis, thereby reducing plasma NEFA concentration. <br /

Decentralisation. New modes of governance and administrative responsibility

Shifts in governance can be conceived of as a response to policy capacities being shared-in a material sense-between centralized and decentralized levels of government. A comparative case study is conducted of three conceptually different shifts in governance. Unclear responsibility relations lead to "paradoxes of decentralization," in which the applied mode of governance blocks the intended improvements. Three case studies are presented to illustrate these mechanisms. There is no "best" way of decentralizing responsibilities; requirements of governance modes are ambiguous. The sharing of policy capacities between central and decentralized levels of governance requires internally inconsistent governance arrangements. © 2012 SAGE Publications