FOXN3 Regulates Hepatic Glucose Utilization.
A SNP (rs8004664) in the first intron of the FOXN3 gene is associated with human fasting blood glucose. We find that carriers of the risk allele have higher hepatic expression of the transcriptional repressor FOXN3. Rat Foxn3 protein and zebrafish foxn3 transcripts are downregulated during fasting, a process recapitulated in human HepG2 hepatoma cells. Transgenic overexpression of zebrafish foxn3 or human FOXN3 increases zebrafish hepatic gluconeogenic gene expression, whole-larval free glucose, and adult fasting blood glucose and also decreases expression of glycolytic genes. Hepatic FOXN3 overexpression suppresses expression of mycb, whose ortholog MYC is known to directly stimulate expression of glucose-utilization enzymes. Carriers of the rs8004664 risk allele have decreased MYC transcript abundance. Human FOXN3 binds DNA sequences in the human MYC and zebrafish mycb loci. We conclude that the rs8004664 risk allele drives excessive expression of FOXN3 during fasting and that FOXN3 regulates fasting blood glucose.
University of Utah Molecular Medicine Program, University of Utah School of Medicine, Salt Lake City, UT 84112, USA; Division of Endocrinology, Metabolism and Diabetes, Department of Internal Medicine, University of Utah School of Medicine, Salt Lake City, UT 84112, USA.
Santhosh
S
Karanth
Department of Pediatrics, University of Utah School of Medicine, Salt Lake City, UT 84108, USA.
Erin K
EK
Zinkhan
University of Utah Molecular Medicine Program, University of Utah School of Medicine, Salt Lake City, UT 84112, USA; Department of Neurobiology and Anatomy, University of Utah School of Medicine, Salt Lake City, UT 84132, USA.
Jonathon T
JT
Hill
University of Utah Molecular Medicine Program, University of Utah School of Medicine, Salt Lake City, UT 84112, USA; Department of Pediatrics, University of Utah School of Medicine, Salt Lake City, UT 84108, USA; Department of Neurobiology and Anatomy, University of Utah School of Medicine, Salt Lake City, UT 84132, USA.
H Joseph
HJ
Yost
University of Utah Molecular Medicine Program, University of Utah School of Medicine, Salt Lake City, UT 84112, USA; Division of Endocrinology, Metabolism and Diabetes, Department of Internal Medicine, University of Utah School of Medicine, Salt Lake City, UT 84112, USA; Department of Biochemistry, University of Utah School of Medicine, Salt Lake City, UT 84112, USA. Electronic address: amnons@u2m2.utah.edu.
Amnon
A
Schlegel
D000483:Alleles; D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D015536:Down-Regulation / Q000235:genetics; D005215:Fasting / Q000097:blood; D005947:Glucose / Q000378:metabolism*; D006019:Glycolysis / Q000235:genetics; D056945:Hep G2 Cells; D006801:Humans; D008099:Liver / Q000378:metabolism*; D008297:Male; D008954:Models, Biological; D020641:Polymorphism, Single Nucleotide / Q000235:genetics; D016271:Proto-Oncogene Proteins c-myc / Q000378:metabolism; D051381:Rats; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D012307:Risk Factors; D015027:Zebrafish
D001786:Blood Glucose; D016271:Proto-Oncogene Proteins c-myc; D012097:Repressor Proteins; D005947:Glucose