Atf4 regulates obesity, glucose homeostasis, and energy expenditure.
OBJECTIVE
We evaluate a potential role of activating transcription factor 4 (Atf4) in invertebrate and mammalian metabolism.


METHODS
With two parallel approaches-a fat body-specific green fluorescent protein enhancer trap screen in D. melanogaster and expression profiling of developing murine fat tissues-we identified Atf4 as expressed in invertebrate and vertebrate metabolic tissues. We assessed the functional relevance of the evolutionarily conserved expression by analyzing Atf4 mutant flies and Atf4 mutant mice for possible metabolic phenotypes.


RESULTS
Flies with insertions at the Atf4 locus have reduced fat content, increased starvation sensitivity, and lower levels of circulating carbohydrate. Atf4 null mice are also lean, and they resist age-related and diet-induced obesity. Atf4 null mice have increased energy expenditure potentially accounting for the lean phenotype. Atf4 null mice are hypoglycemic, even before substantial changes in fat content, indicating that Atf4 regulates mammalian carbohydrate metabolism. In addition, the Atf4 mutation blunts diet-induced diabetes as well as hyperlipidemia and hepatosteatosis. Several aspects of the Atf4 mutant phenotype resemble mice with mutations in components of the target of rapamycin (TOR) pathway. Consistent with the phenotypic similarities, Atf4 null mice have reduced expression of genes that regulate intracellular amino acid concentrations and lower intracellular concentration of amino acids, a key TOR input. Further, Atf4 mutants have reduced S6K activity in liver and adipose tissues.


CONCLUSIONS
Atf4 regulates age-related and diet-induced obesity as well as glucose homeostasis in mammals and has conserved metabolic functions in flies.
Seo
Jin
J
Department of Developmental Biology, University of Texas Southwestern Medical Center, Dallas, Texas, USA.
Fortuno
Edgardo S
ES
Suh
Jae Myoung
JM
Stenesen
Drew
D
Tang
Wei
W
Parks
Elizabeth J
EJ
Adams
Christopher M
CM
Townes
Tim
T
Graff
Jonathan M
JM
D051701:Activating Transcription Factor 4 / Q000235:genetics* / Q000502:physiology; D000596:Amino Acids / Q000097:blood; D000818:Animals; D017124:Conserved Sequence; D000242:Cyclic AMP / Q000378:metabolism; D003920:Diabetes Mellitus / Q000235:genetics / Q000517:prevention & control; D004331:Drosophila melanogaster / Q000235:genetics / Q000502:physiology; D004734:Energy Metabolism; D005227:Fatty Acids / Q000032:analysis; D020869:Gene Expression Profiling; D017930:Genes, Reporter; D005947:Glucose / Q000378:metabolism*; D049452:Green Fluorescent Proteins / Q000235:genetics; D006706:Homeostasis; D007003:Hypoglycemia / Q000235:genetics; D007814:Larva / Q000502:physiology; D051379:Mice; D018345:Mice, Knockout; D008817:Mice, Mutant Strains / Q000235:genetics; D008822:Mice, Transgenic; D009154:Mutation; D009765:Obesity / Q000235:genetics / Q000503:physiopathology* / Q000517:prevention & control; D010641:Phenotype
D000596:Amino Acids; C081452:Atf4 protein, mouse; D005227:Fatty Acids; D051701:Activating Transcription Factor 4; D049452:Green Fluorescent Proteins; D000242:Cyclic AMP; D005947:Glucose
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