Obesity is a major public health problem, predisposing subjects to metabolic syndrome, type 2 diabetes, and cardiovascular diseases. Specific prolyl 4-hydroxylases (P4Hs) regulate the stability of the hypoxia-inducible factor (HIF), a potent governor of metabolism, with isoenzyme 2 being the main regulator. We investigated whether HIF-P4H-2 inhibition could be used to treat obesity and its consequences. Hif-p4h-2–deficient mice, whether fed normal chow or a high-fat diet, had less adipose tissue, smaller adipocytes, and less adipose tissue inflammation than their littermates. They also had improved glucose tolerance and insulin sensitivity. Furthermore, the mRNA levels of the HIF-1 targets glucose transporters, glycolytic enzymes, and pyruvate dehydrogenase kinase-1 were increased in their tissues, whereas acetyl-CoA concentration was decreased. The hepatic mRNA level of the HIF-2 target insulin receptor substrate-2 was higher, whereas that of two key enzymes of fatty acid synthesis was lower. Serum cholesterol levels and de novo lipid synthesis were decreased, and the mice were protected against hepatic steatosis. Oral administration of an HIF-P4H inhibitor, FG-4497, to wild-type mice with metabolic dysfunction phenocopied these beneficial effects. HIF-P4H-2 inhibition may be a novel therapy that not only protects against the development of obesity and its consequences but also reverses these conditions.

e Small-molecule inhibition of hypoxia-inducible factor prolyl 4-hydroxylases (HIF-P4Hs) is being explored for the treatment of anemia. Previous studies have suggested that HIF-P4H-2 inhibition may also protect the heart from an ischemic insult. Hif-p4h-2 gt/gt mice, which have 76 to 93% knockdown of Hif-p4h-2 mRNA in endothelial cells, fibroblasts, and cardiomyocytes and normoxic stabilization of Hif-␣, were subjected to ligation of the left anterior descending coronary artery (LAD). Hif-p4h-2 deficiency resulted in increased survival, better-preserved left ventricle (LV) systolic function, and a smaller infarct size. Surprisingly, a significantly larger area of the LV remained perfused during LAD ligation in Hif-p4h-2 gt/gt hearts than in wildtype hearts. However, no difference was observed in collateral vessels, while the size of capillaries, but not their number, was significantly greater in Hif-p4h-2 gt/gt hearts than in wild-type hearts. Hif-p4h-2 gt/gt mice showed increased cardiac expression of endothelial Hif target genes for Tie-2, apelin, APJ, and endothelial nitric oxide (NO) synthase (eNOS) and increased serum NO concentrations. Remarkably, blockage of Tie-2 signaling was sufficient to normalize cardiac apelin and APJ expression and resulted in reversal of the enlarged-capillary phenotype and ischemic cardioprotection in Hif-p4h-2 gt/gt hearts. Activation of the hypoxia response by HIF-P4H-2 inhibition in endothelial cells appears to be a major determinant of ischemic cardioprotection and justifies the exploration of systemic small-molecule HIF-P4H-2 inhibitors for ischemic heart disease.H ypoxia-inducible factor (HIF) prolyl 4-hydroxylase 2 (HIF-P4H-2, also known as PHD2 and EglN1) is the main regulator of the oxygen-dependent proteasomal degradation of the HIF-␣ subunit (1-3). Inhibition of HIF-P4H-2 stabilizes HIF-␣, which initiates the cellular hypoxia response involving the upregulation of several hundred genes, such as those for erythropoietin and vascular endothelial growth factor (1-3). Hif-p4h-2/ EglN1 deletion is embryonic lethal, and universal conditional inactivation of Hif-p4h-2/EglN1 leads to severe erythrocytosis, hyperactive angiogenesis, and congestive heart failure (CHF) (4, 5). CHF does not appear to be a major consequence of Hif-p4h-2/ EglN1 inactivation in the heart but rather a cause of the severe polycythemia observed in these mice (6). Mice with cardiomyocyte-specific Hif-p4h-2/EglN1 deletion develop mild cardiac dysfunction after 8 months of age (6, 7) but show a reduced infarct size and improved mechanical recovery following ligation of the left anterior descending coronary artery (LAD) (7).By using the gene trap (gt) strategy, we have generated a mouse line with tissue-specific Hif-p4h-2/EglN1 inactivation (Hif-p4h-2 gt/gt ) (8). These mice have a 92% reduction of cardiac Hif-p4h-2 mRNA levels and normoxic stabilization of Hif-1␣ and Hif-2␣ in the heart (8). Hif-p4h-2 gt/gt mice show 85 to 15% reductions in Hif-p4h-2 mRNA levels in other tissues, but unlike mice with broad...

We show here that mice hypomorphic for hypoxia-inducible factor prolyl 4-hydroxylase-2 (HIF-P4H-2) (Hif-p4h-2 (gt/gt)), the main regulator of the stability of the HIFα subunits, have normoxic stabilization of HIF-1α and HIF-2α in their skeletal muscles. The size of the capillaries, but not their number, was increased in the skeletal muscles of the Hif-p4h-2 (gt/gt) mice, whereas the amount of glycogen was reduced. The expression levels of genes for glycolytic enzymes, glycogen branching enzyme 1 and monocarboxylate transporter 4, were increased in the Hif-p4h-2 (gt/gt) skeletal muscles, whereas no significant increases were detected in the levels of any vasculature-influencing factor studied. Serum lactate levels of the Hif-p4h-2 (gt/gt) mice recovered faster than those of the wild type following exercise. The Hif-p4h-2 (gt/gt) mice had elevated hepatic phosphoenolpyruvate carboxykinase activity, which may have contributed to the faster clearance of lactate. The Hif-p4h-2 (gt/gt) mice had smaller infarct size following limb ischemia-reperfusion injury. The increased capillary size correlated with the reduced infarct size. Following ischemia-reperfusion, glycogen content and ATP/ADP and CrP/Cr levels of the skeletal muscle of the Hif-p4h-2 (gt/gt) mice were higher than in the wild type. The higher glycogen content correlated with increased expression of phosphofructokinase messenger RNA (mRNA) and the increased ATP/ADP and CrP/Cr levels with reduced apoptosis, suggesting that HIF-P4H-2 deficiency supported energy metabolism during ischemia-reperfusion and protection against injury. Key messages: HIF-P4H-2 deficiency protects skeletal muscle from ischemia-reperfusion injury. The mechanisms involved are mediated via normoxic HIF-1α and HIF-2α stabilization. HIF-P4H-2 deficiency increases capillary size but not number. HIF-P4H-2 deficiency maintains energy metabolism during ischemia-reperfusion.

Aims: βcell stress and dysfunction may contribute to islet autoimmunity and progression to clinical type 1 diabetes. We present a protocol of three randomised controlled trials assessing the effects of glucagon-like peptide 1 (GLP − 1) analogue liraglutide in three early stages of type 1 diabetes. Methods:We will test 10-to 30-year-old people with multiple islet autoantibodies for their glucose metabolism and randomise participants with stage 1 (multiple islet autoantibodies and normoglycaemia), stage 2 (multiple islet autoantibodies and dysglycaemia) and early stage 3 (clinical diagnosis) type 1 diabetes, 10−14 persons in each, to a 6-month intervention with liraglutide or placebo with 6-month follow-up in the stage 2 and stage 3 trials and 18-month follow-up in the stage 1 trial. Primary efficacy outcome in the stage 1 and stage 2 trials is a first-phase insulin response in an intravenous glucose tolerance test and C-peptide area under the curve in a 2-h mixed-meal tolerance test in the stage 3 trial. In addition, safety and tolerability of liraglutide treatment will be assessed. Conclusions:Most prevention trials of type 1 diabetes have targeted the immune system. Treatment with GLP-1 analogue liraglutide supports the pancreatic βcells, which should likewise attenuate islet autoimmunity. Our innovative study design allows simultaneous investigation of an intervention in three groups of people who represent various early stages of type 1 diabetes and maximises the eligibility to participate.