Dual Roles for Glucokinase in Glucose Homeostasis as Determined by Liver and Pancreatic β Cell-specific Gene Knock-outs Using Cre Recombinase

• Published in: The Journal of biological chemistry Vol. 274; no. 1; pp. 305 - 315
• Main Authors: Postic, Catherine, Shiota, Masakazu, Niswender, Kevin D., Jetton, Thomas L., Chen, Yeujin, Moates, J. Michael, Shelton, Kathy D., Lindner, Jill, Cherrington, Alan D., Magnuson, Mark A.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.01.1999
• Subjects: Albumins - genetics; Alleles; Animals; Base Sequence; DNA Primers; Gene Deletion; Glucokinase - genetics; Glucokinase - metabolism; Glucose - metabolism; Homeostasis; Insulin - genetics; Integrases - genetics; Islets of Langerhans - enzymology; Islets of Langerhans - metabolism; Liver - enzymology; Liver - metabolism; Mice; Mice, Knockout; Transgenes; Viral Proteins
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.274.1.305

Glucokinase (GK) gene mutations cause diabetes mellitus in both humans and mouse models, but the pathophysiological basis is only partially defined. We have used cre-loxPtechnology in combination with gene targeting to perform global, β cell-, and hepatocyte-specific gene knock-outs of this enzyme in mice. Gene targeting was used to create a triple-loxed gk allele, which was converted by partial or total Cre-mediated recombination to a conditional allele lacking neomycin resistance, or to a null allele, respectively. β cell- and hepatocyte-specific expression of Cre was achieved using transgenes that contain either insulin or albumin promoter/enhancer sequences. By intercrossing the transgenic mice that express Cre in a cell-specific manner with mice containing a conditional gk allele, we obtained animals with either a β cell or hepatocyte-specific knock-out of GK. Animals either globally deficient in GK, or lacking GK just in β cells, die within a few days of birth from severe diabetes. Mice that are heterozygous null for GK, either globally or just in the β cell, survive but are moderately hyperglycemic. Mice that lack GK only in the liver are only mildly hyperglycemic but display pronounced defects in both glycogen synthesis and glucose turnover rates during a hyperglycemic clamp. Interestingly, hepatic GK knock-out mice also have impaired insulin secretion in response to glucose. These studies indicate that deficiencies in both β cell and hepatic GK contribute to the hyperglycemia of MODY-2.