Type 2 diabetes mellitus affects 9.6% of the adults in the United States and more than 200 million people worldwide. Diabetes can be a devastating disease, but it can now be treated with nine classes of approved drugs (insulins, sulfonylureas, glinides, biguanides, α-glucosidase inhibitors, thiazolidinediones, glucagon-like peptide 1 mimetics, amylin mimetics, and dipeptidyl peptidase 4 inhibitors), in addition to diet and exercise regimens. Choosing which drug to give a patient is based on efficacy and also availability, cost, safety, tolerability, and convenience. Personalized medicine promises a path for individually optimized treatment choices, but realizing this promise will require a more comprehensive characterization of disease and drug response. In this issue of the JCI, Shu et al. make significant progress by integrating diverse data supporting the hypothesis that genetic variation in organic cation transporter 1 (OCT1) affects the response to the widely used biguanide metformin (see the related article beginning on page 1422). We discuss metformin, OCT1, pharmacogenetics, and how the integrative genomics revolution is likely to change our understanding and treatment of diabetes.
Marc L. Reitman, Eric E. Schadt
Diabetic foot ulcers (DFUs), a leading cause of amputations, affect 15% of people with diabetes. A series of multiple mechanisms, including decreased cell and growth factor response, lead to diminished peripheral blood flow and decreased local angiogenesis, all of which can contribute to lack of healing in persons with DFUs. In this issue of the JCI, Gallagher and colleagues demonstrate that in diabetic mice, hyperoxia enhances the mobilization of circulating endothelial progenitor cells (EPCs) from the bone marrow to the peripheral circulation (see the related article beginning on page 1249). Local injection of the chemokine stromal cell–derived factor–1α then recruits these EPCs to the cutaneous wound site, resulting in accelerated wound healing. Thus, Gallagher et al. have identified novel potential targets for therapeutic intervention in diabetic wound healing.
Harold Brem, Marjana Tomic-Canic
In the 40 years since Harvard medical student Gilbert Omenn first described a rare, inherited disorder producing a paradoxical combination of immunodeficiency and immune dysregulation, the pathogenesis of Omenn syndrome (OS) has remained mysterious. In separate studies reported in this issue of the JCI, two mouse models bearing mutations in the V(D)J recombinase analogous to those causing human OS have been shown to recapitulate the disease and provide insight into the genesis of immunodeficiency combined with autoimmunity and atopy in OS and other disease settings (see the related articles beginning on pages 1260 and 1270).
Serre-Yu Wong, David B. Roth
Hypoglycemia commonly causes brain fuel deprivation, resulting in functional brain failure, which can be corrected by raising plasma glucose concentrations. Rarely, profound hypoglycemia causes brain death that is not the result of fuel deprivation per se. In this issue of the JCI, Suh and colleagues use cell culture and in vivo rodent studies of glucose deprivation and marked hypoglycemia and provide evidence that hypoglycemic brain neuronal death is in fact increased by neuronal NADPH oxidase activation during glucose reperfusion (see the related article beginning on page 910). This finding suggests that, at least in the setting of profound hypoglycemia, therapeutic hyperglycemia should be avoided.
Philip E. Cryer
Diabetes results from the absolute or relative deficiency of insulin-producing β cells. The prospect that non-β pancreatic cells could be harnessed to become β cells has led to interest in understanding the plasticity of pancreatic cells. Recent studies, however, have shown that adult β cells are largely derived from preexisting β cells. In this issue of the JCI, Desai et al. show that acinar cells, the major cell type in the pancreas, do not contribute to new β cells formed during pancreatic regeneration (see the related article beginning on page 971). These studies suggest that the fate of adult pancreatic cell lineages is immutable. However, also in this issue of the JCI, Collombat et al. demonstrate that inducing a single transcription factor named Arx in adult β cells causes these cells to undergo massive transdifferentiation into α and pancreatic polypeptide endocrine cells (see the related article beginning on page 961). This finding points to an unexpected plasticity of postnatal pancreatic endocrine cells.
Jorge Ferrer, Mercè Martín, Joan Marc Servitja
Erythropoietin (EPO) is the hormonal regulator of red cell production and provided the paradigm for oxygen-regulated gene expression that led to the discovery of hypoxia-inducible factor (HIF). In this issue of the JCI, Rankin and colleagues show, using targeted gene inactivation, that induction of Epo expression in murine liver is dependent on the integrity of HIF-2α, and not HIF-1α (see the related article beginning on page 1068). These results demonstrate distinct functions for different HIF-α isoforms that could potentially be exploited in therapeutic approaches to anemia.
Peter J. Ratcliffe
Components of the renin-angiotensin system (RAS) are expressed in a number of areas in the brain involved in cardiovascular control. However, it has been difficult to link RAS actions in circumscribed brain regions to specific physiological functions. In a study appearing in this issue of the JCI, Sakai and associates use a combination of sophisticated transgenic techniques and stereotaxic microinjection of recombinant viral vectors to demonstrate a pivotal role in the regulation of thirst and salt appetite of angiotensin II generated in the subfornical organ in the brain (see the related article beginning on page 1088).
Kelly K. Parsons, Thomas M. Coffman
IFN-γ has long been recognized as a signature proinflammatory cytokine that plays a central role in inflammation and autoimmune disease. There is now emerging evidence indicating that IFN-γ possesses unexpected properties as a master regulator of immune responses and inflammation. In this issue of the JCI, Guillonneau et al. show that indefinite allograft survival induced by CD40Ig treatment is mediated by CD8+CD45RClow T cells through the production of IFN-γ (see the related article beginning on page 1096), supporting the emerging view that IFN-γ is critical in the self-regulation of inflammation. These contradictory roles of IFN-γ, perhaps best understood by the principle of yin and yang, represent one of nature’s paradoxes, whereby the same cytokine functions as an inducer as well as a regulator for inflammation. Understanding this complex process of IFN-γ signaling is essential, as it has therapeutic implications.
The deregulation of homeobox (HOX) genes in acute myeloid leukemia (AML) and the potential for these master regulators to perturb normal hematopoiesis is well established. To date, overexpression of HOX genes in AML has been attributed to specific chromosomal aberrations and abnormalities involving mixed-lineage leukemia (MLL), an upstream regulator of HOX genes. The finding reported in this issue of the JCI by Scholl et al. that caudal-type homeobox transcription factor 2 (CDX2), which is capable of affecting HOX gene expression during embryogenesis, is overexpressed in 90% of patients with AML and induces a transplantable AML in murine models provides an alternative mechanism for HOX-induced leukemogenesis and yields important insights into the hierarchy of HOX gene regulation in AML (see the related article beginning on page 1037).
Kim L. Rice, Jonathan D. Licht
Although it was first described in 1989, our understanding of coenzyme Q10 (CoQ10) deficiency is only now coming of age with the recent first description of the underlying molecular defects. The diverse clinical presentations, classifiable into four major syndromes, raise the question as to whether the deficiencies are primary or secondary. Recent studies, including the one by Mollet, Rötig, and colleagues reported in this issue of the JCI, document molecular defects in three of the nine genes required for CoQ10 biosynthesis, all of which are associated with early and severe clinical presentations (see the related article beginning on page 765). It is anticipated that defects in the other six genes will cause similar early-onset encephalomyopathies. Awareness of CoQ10 deficiency is important because individuals with primary or secondary variants may benefit from oral CoQ10 supplementation.
Salvatore DiMauro, Catarina M. Quinzii, Michio Hirano
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