Although genomic technologies have advanced the characterization of gene regulatory networks downstream of transcription factors, the identification of pathways upstream of these transcription factors has been more challenging. In this study we present a gene signature-based approach for connecting signaling pathways to transcription factors, as exemplified by p73. We generated a p73 gene signature by integrating whole-genome chromatin immunoprecipitation and expression profiling. The p73 signature was linked to corresponding signatures produced by drug candidates, using the in silico Connectivity Map resource, to identify drugs that would induce p73 activity. Of the pharmaceutical agents identified, there was enrichment for direct or indirect inhibitors of mammalian Target of Rapamycin (mTOR) signaling. Treatment of both primary cells and cancer cell lines with rapamycin, metformin, and pyrvinium resulted in an increase in p73 levels, as did RNA interference-mediated knockdown of mTOR. Further, a subset of genes associated with insulin response or autophagy exhibited mTOR-mediated, p73-dependent expression. Thus, downstream gene signatures can be used to identify upstream regulators of transcription factor activity, and in doing so, we identified a new link between mTOR, p73, and p73-regulated genes associated with autophagy and metabolic pathways.

Little is known about the biological function of histone deacetylase 11 (HDAC11), which is the lone class IV HDAC. Here, we demonstrate that deletion of HDAC11 in mice stimulates brown adipose tissue (BAT) formation and beiging of white adipose tissue (WAT). Consequently, HDAC11-deficient mice exhibit enhanced thermogenic potential and, in response to high-fat feeding, attenuated obesity, improved insulin sensitivity, and reduced hepatic steatosis. Ex vivo and cell-based assays revealed that HDAC11 catalytic activity suppresses the BAT transcriptional program, in both the basal state and in response to β-adrenergic receptor signaling, through a mechanism that is dependent on physical association with BRD2, a bromodomain and extraterminal (BET) acetyl-histone-binding protein. These findings define an epigenetic pathway for the regulation of energy homeostasis and suggest the potential for HDAC11-selective inhibitors for the treatment of obesity and diabetes.

Results indicate that an active lifestyle is characterized by elevated mitochondrial content and oxidative, not thermogenic, markers of WAT.

To better understand how glucokinase (GK) missense mutations associated with human glycemic diseases perturb glucose homeostasis, we generated and characterized mice with either an activating (A456V) or inactivating (K414E) mutation in the gk gene. Animals with these mutations exhibited alterations in their blood glucose concentration that were inversely related to the relative activity index of GK. Moreover, the threshold for glucose-stimulated insulin secretion from islets with either the activating or inactivating mutation were left-or right-shifted, respectively. However, we were surprised to find that mice with the activating mutation had markedly reduced amounts of hepatic GK activity. Further studies of bacterially expressed mutant enzymes revealed that GK A456V is as stable as the wild type enzyme, whereas GK K414E is thermolabile. However, the ability of GK regulatory protein to inhibit GK A456V was found to be less than that of the wild type enzyme, a finding consistent with impaired hepatic nuclear localization. Taken together, this study indicates that it is necessary to have knowledge of both thermolability and the interactions of mutant GK enzymes with GK regulatory protein when attempting to predict in vivo glycemic phenotypes based on the measurement of enzyme kinetics.Studies over the past 2 decades have firmly established that glucokinase (GK) 3 plays a key role in determining the blood glucose concentration in mammals. In humans, there is a reciprocal but nonlinear relationship between GK activity and the blood glucose concentration. First, heterozygous gene mutations that diminish enzyme expression or otherwise lower catalytic flux cause maturity onset diabetes of the young type (MODY)-GK (1-4), a disease characterized by mild hyperglycemia. Second, inactivating mutations in both alleles of the human GK gene lead to persistent neonatal diabetes-GK, a severe but rare form of hereditary hyperglycemia that, if untreated, is fatal (5). Third, heterozygous gene mutations that increase the activity of GK cause persistent hyperinsulinemic hypoglycemia of infancy (PHHI)-GK, a disease that is characterized by clinically significant hypoglycemia (6 -8).The analysis of genetically engineered rodent models has unequivocally established that GK gene expression in both pancreatic ␤-cells and hepatocytes independently contributes to the maintenance of blood glucose homeostasis (9 -14). Increased GK in either cell type leads to more glucose uptake and glucose phosphorylation, whereas diminished GK expression has the opposite effect. In the ␤ cell, these changes impact insulin secretion by altering the threshold for glucose-stimulated insulin secretion. Indeed, in mice with a ␤ cell-specific knock-out of GK, glucose-stimulated insulin secretion is so markedly impaired that death occurs shortly after birth due to severe hyperglycemia. In the liver, alterations in GK activity directly affect rates of glucose uptake and glycogen synthesis. However, the total absence of GK in hepatocytes, unlike ␤ cells, result...