Enhanced insulin secretion and cholesterol metabolism in congenic strains of the spontaneously diabetic (Type 2) Goto Kakizaki rat are controlled by independent genetic loci in rat chromosome 8.
OBJECTIVE
Genetic investigations in the spontaneously diabetic (Type 2) Goto Kakizaki (GK) rat have identified quantitative trait loci (QTL) for diabetes-related phenotypes. The aims of this study were to refine the chromosomal mapping of a QTL ( Nidd/gk5) identified in chromosome 8 of the GK rat and to define a pathophysiological profile of GK gene variants underlying the QTL effects in congenics.


METHODS
Genetic linkage analysis was carried out with chromosome 8 markers genotyped in a GKxBN F2 intercross previously used to map diabetes QTL. Two congenic strains were designed to contain GK haplotypes in the region of Nidd/gk5 transferred onto a Brown Norway (BN) genetic background, and a broad spectrum of diabetes phenotypes were characterised in the animals.


RESULTS
Results from QTL mapping suggest that variations in glucose-stimulated insulin secretion in vivo, and in body weight are controlled by different chromosome 8 loci (LOD3.53; p=0.0004 and LOD4.19; p=0.00007, respectively). Extensive physiological screening in male and female congenics at 12 and 24 weeks revealed the existence of GK variants at the locus Nidd/gk5, independently responsible for significantly enhanced insulin secretion and increased levels of plasma triglycerides, phospholipids and HDL, LDL and total cholesterol. Sequence polymorphisms detected between the BN and GK strains in genes encoding ApoAI, AIV, CIII and Lipc do not account for these effects.


CONCLUSIONS
We refined the localisation of the QTL Nidd/gk5 and its pathophysiological characteristics in congenic strains derived for the locus. These congenic strains provide novel models for testing the contribution of a subset of GK alleles on diabetes phenotypes and for identifying diabetes susceptibility genes.
Wallis
R H
RH
The Wellcome Trust Centre for Human Genetics, University of Oxford, Roosevelt Drive, Headington, Oxford OX3 7BN, UK.
Wallace
K J
KJ
Collins
S C
SC
McAteer
M
M
Argoud
K
K
Bihoreau
M T
MT
Kaisaki
P J
PJ
Gauguier
D
D
D000818:Animals; D020296:Animals, Congenic / Q000235:genetics / Q000378:metabolism*; D001786:Blood Glucose / Q000032:analysis; D001835:Body Weight; D002784:Cholesterol / Q000378:metabolism*; D002874:Chromosome Mapping / Q000379:methods; D033481:Chromosomes, Mammalian / Q000235:genetics*; D003924:Diabetes Mellitus, Type 2 / Q000235:genetics / Q000378:metabolism*; D004195:Disease Models, Animal; D005260:Female; D008040:Genetic Linkage / Q000235:genetics; D020022:Genetic Predisposition to Disease / Q000235:genetics; D016678:Genome; D005838:Genotype; D007328:Insulin / Q000097:blood / Q000378:metabolism*; D000078790:Insulin Secretion; D008055:Lipids / Q000097:blood; D008297:Male; D008969:Molecular Sequence Data; D010641:Phenotype; D040641:Quantitative Trait Loci / Q000235:genetics; D051381:Rats; D011914:Rats, Inbred BN / Q000235:genetics / Q000378:metabolism; D006113:United Kingdom
D001786:Blood Glucose; D007328:Insulin; D008055:Lipids; D002784:Cholesterol