Chromosomal mapping of genetic loci associated with non-insulin dependent diabetes in the GK rat.

Goto-Kakizaki (GK) rats are a well characterized model for non-insulin dependent diabetes mellitus (NIDDM). We have used a combination of physiological and genetic studies to identify quantitative trait loci (QTLs) responsible for the control of glucose homeostasis and insulin secretion in a F2 cohort bred from spontaneously diabetic GK rats. The genetic dissection of NIDDM allowed us to map up to six independently segregating loci predisposing to hyperglycaemia, glucose intolerance or altered insulin secretion, and a seventh locus implicated in body weight. QTLs implicated in glucose tolerance and adiposity map to the same region of rat chromosome 1, and may indicate the influence of a single locus. Our study demonstrates that distinct combinations of genetic loci are responsible for different physiological characteristics associated with the diabetic phenotype in the GK rat, and it constitutes an important step for directing the search for the genetic factors involved in human NIDDM.

Sensitivity to cerebral ischaemic insult in a rat model of stroke is determined by a single genetic locus.

Ischaemic stroke is a complex disorder caused by a combination of genetic and environmental factors. Clinical and epidemiological studies have provided strong evidence for genetic influences in the development of human stroke and several mendelian traits featuring stroke have been described. The genetic analysis of the non-mendelian, common ischaemic stroke in humans is hindered by the late onset of the disease and the mode of inheritance, which is complex, polygenic and multifactorial. An important approach to the study of such polygenic diseases is the use of appropriate animal models in which individual contributing factors can be recognized and analysed. The spontaneously hypertensive stroke-prone rat (SHRSP) is an experimental model of stroke characterized by a high frequency of spontaneous strokes as well as an increased sensitivity to experimentally induced focal cerebral ischaemia. Rubattu et al. performed a genomewide screen in an F2 cross obtained by mating SHRSP and SHR, in which latency to stroke on Japanese rat diet was used as a phenotype. This study identified three major quantitative trait loci (QTLs), STR-1-3. Of these, STR-2 and 3 conferred a protective effect against stroke in the presence of SHRSP alleles and STR-2 co-localized with the genes encoding for atrial natriuretic and brain natriuretic factors. Our investigation was designed to identify the genetic component responsible for large infarct volumes in the SHRSP in response to a focal ischaemic insult by performance of a genome scan in an F2 cross derived from the SHRSP and the normotensive reference strain, WKY rat. We identified a highly significant QTL on rat chromosome 5 with a lod score of 16.6 which accounts for 67% of the total variance, co-localizes with the genes encoding atrial and brain natriuretic factor and is blood pressure independent.

A major quantitative trait locus influences hyperactivity in the WKHA rat.

The syndrome of hyperactivity describes behavioural disorders existing mainly in children and characterized by increased levels of motor activity, inattention and impulsivity. Overall the aetiology is poorly understood due to the heterogeneity of the pathology although psychological, biological and social factors acting singly or in concert are generally thought to be involved. In animal studies the observed hyperactivity phenotype results from relative participation of exploration, emotionality and general activity. Studies using brain lesions, neuropharmacology and gene knock-out strategies have shown that specific elements of the brain dopaminergic system can subserve hyperactivity. Evidence of a genetic contribution comes from family and twin studies but also from the ability to select divergent animal lines on the basis of their differential activity. The Wistar-Kyoto (WKY) and Wistar-Kyoto hyperactive (WKHA) rats are such strains--distinct for their low and high activity scores in a novel environment, respectively. Here, we report the detection of a major hyperactivity-related QTL on chromosome 8, explaining 29% of the variance of an intercross between these strains. This study represents the first behavioural QTL analysis in rat and provides a new starting point for biologically categorizing different forms of hyper-activity.

Global microRNA expression profiles in insulin target tissues in a spontaneous rat model of type 2 diabetes.

AIMS/HYPOTHESIS: MicroRNAs regulate a broad range of biological mechanisms. To investigate the relationship between microRNA expression and type 2 diabetes, we compared global microRNA expression in insulin target tissues from three inbred rat strains that differ in diabetes susceptibility. METHODS: Using microarrays, we measured the expression of 283 microRNAs in adipose, liver and muscle tissue from hyperglycaemic (Goto-Kakizaki), intermediate glycaemic (Wistar Kyoto) and normoglycaemic (Brown Norway) rats (n = 5 for each strain). Expression was compared across strains and validated using quantitative RT-PCR. Furthermore, microRNA expression variation in adipose tissue was investigated in 3T3-L1 adipocytes exposed to hyperglycaemic conditions. RESULTS: We found 29 significantly differentiated microRNAs (p(adjusted) < 0.05): nine in adipose tissue, 18 in liver and two in muscle. Of these, five microRNAs had expression patterns that correlated with the strain-specific glycaemic phenotype. MiR-222 (p(adjusted) = 0.0005) and miR-27a (p(adjusted) = 0.006) were upregulated in adipose tissue; miR-195 (p(adjusted) = 0.006) and miR-103 (p(adjusted) = 0.04) were upregulated in liver; and miR-10b (p(adjusted) = 0.004) was downregulated in muscle. Exposure of 3T3-L1 adipocytes to increased glucose concentration upregulated the expression of miR-222 (p = 0.008), miR-27a (p = 0.02) and the previously reported miR-29a (p = 0.02). Predicted target genes of these differentially expressed microRNAs are involved in pathways relevant to type 2 diabetes. CONCLUSION: The expression patterns of miR-222, miR-27a, miR-195, miR-103 and miR-10b varied with hyperglycaemia, suggesting a role for these microRNAs in the pathophysiology of type 2 diabetes, as modelled by the Gyoto-Kakizaki rat. We observed similar patterns of expression of miR-222, miR-27a and miR-29a in adipocytes as a response to increased glucose levels, which supports our hypothesis that altered expression of microRNAs accompanies primary events related to the pathogenesis of type 2 diabetes.

Genetic influences on the end-stage effector phase of arthritis.

K/BxN T cell receptor transgenic mice are a model of inflammatory arthritis, most similar to rheumatoid arthritis, that is critically dependent on both T and B lymphocytes. Transfer of serum, or just immunoglobulins, from arthritic K/BxN animals into healthy recipients provokes arthritis efficiently, rapidly, and with high penetrance. We have explored the genetic heterogeneity in the response to serum transfer, thereby focussing on the end-stage effector phase of arthritis, leap-frogging the initiating events. Inbred mouse strains showed clear variability in their responses. A few were entirely refractory to disease induction, and those which did develop disease exhibited a range of severities. F1 analyses suggested that in most cases susceptibility was controlled in a polygenic additive fashion. One responder/nonresponder pair (C57Bl/6 x NOD) was studied in detail via a genome scan of F2 mice; supplementary information was provided by the examination of knock-out and congenic strains. Two genomic regions that are major, additive determinants of the rapidity and severity of K/BxN serum-transferred arthritis were highlighted. Concerning the first region, on proximal chromosome (chr)2, candidate assignment to the complement gene C5 was confirmed by both strain segregation analysis and functional data. Concerning the second, on distal chr1, coinciding with the Sle1 locus implicated in susceptibility to lupus-like autoimmune disease, a contribution by the fcgr2 candidate gene was excluded. Two other regions, on chr12 and chr18 may also contribute to susceptibility to serum-transferred arthritis, albeit to a more limited degree. The contributions of these loci are additive, but gene dosage effects at the C5 locus are such that it largely dominates. The clarity of these results argues that our focus on the terminal effector phase of arthritis in the K/BxN model will bear fruit.

A pharmacogenetic approach to blood pressure in Lyon hypertensive rats. A chromosome 2 locus influences the response to a calcium antagonist.

In a backcross population (n = 281) derived from a cross of the Lyon hypertensive rat with Lyon normotensive rat, we investigated whether genetic factors influence the acute cardiovascular responses to pharmacological modulation of the renin-angiotensin system, the sympathetic nervous system, and the voltage-sensitive L-type calcium channels. Using microsatellite markers, a quantitative trait locus was identified and mapped on rat chromosome 2 that specifically influences the systolic (peak LOD score 4.4) and diastolic (peak LOD score 4.1) blood pressure responses to administration of a dihydropyridine calcium antagonist, PY108-068. The locus accounted for 10.3 and 10.4% of the total variances in the systolic and diastolic responses to PY108-068, respectively. In marked contrast, the locus had no effect on either basal blood pressure or on the responses to acute administration of a ganglionic blocking agent, trimetaphan, or of an angiotensin II subtype 1 receptor antagonist, losartan. These findings provide strong direct support for the paradigm that genetic factors may influence the response to antihypertensive drugs and suggest that the heterogeneity seen in the responses to different antihypertensive agents in human essential hypertension may have a significant genetic determination.

Mapping of quantitative trait loci for blood pressure and cardiac mass in the rat by genome scanning of recombinant inbred strains.

In the HXB and BXH recombinant inbred strains derived from the spontaneously hypertensive rat and the normotensive Brown Norway rat, we determined the strain distribution patterns of 500 genetic markers to scan the rodent genome for quantitative trait loci regulating cardiac mass and blood pressure. The markers spanned approximately 1,139 cM of the genome and were tested for correlations with left ventricular mass adjusted for body weight, and with systolic, diastolic, and mean arterial pressures. The marker for the dopamine 1A receptor (Drd1a) on chromosome 17 showed the strongest correlation with left ventricular heart weight (P = .00038, r = -0.59) and the relationship to heart weight was independent of blood pressure. The markers showing the strongest correlations with systolic, diastolic, and mean arterial pressure were D19Mit7 on chromosome 19 (P = .0012, r = .55), D2N35 on chromosome 2 (P = .0008, r = .56), and Il6 on chromosome 4 (P = .0018, r = .53), respectively. These studies demonstrate that the HXB and BXH strains can be effectively used for genome scanning studies of complex traits and have revealed several chromosome regions that may be involved in the genetic control of blood pressure and cardiac mass in the rat.

Insulin secretion in adult rats after intrauterine exposure to mild hyperglycemia during late gestation.

We investigated the effects of intrauterine mild hyperglycemia during late fetal life on glucose regulation and insulin secretion in adult rats. Unrestrained pregnant rats were continuously infused with glucose during the last week of pregnancy to induce mild hyperglycemia (6.5-8 mM). Control rats were infused with a glucose-free solution. The offspring were studied, as adults, from 1 to 20 mo by performing glucose tolerance and insulin secretion tests. Young-adult rats from hyperglycemic dams showed mild glucose intolerance and impairment of glucose-induced insulin secretion. This situation gradually evolved to basal hyperglycemia and severe impairment of glucose tolerance and insulin secretion. Insulin secretion was also studied in vitro in 20-mo-old rats with the isolated perfused-pancreas technique. Insulin release in response to glucose stimulation from pancreases of hyperglycemic dams was similar to that of controls, and the response to arginine was increased but not significantly. The possible involvement of enhanced sympathetic nervous system activity in the impairment of insulin secretion in adult rats from hyperglycemic mothers was then investigated by performing glucose tolerance and insulin secretion tests in the presence of the alpha 2-blocker idazoxan in 8-mo-old rats. Under these conditions, rats from hyperglycemic dams recovered almost normal glucose tolerance, and glucose-induced insulin secretion was greatly improved. These data show that mild hyperglycemia induced in the fetus during late pregnancy leads to persistent impairment of glucose regulation and insulin secretion. They suggest that the impairment of insulin secretion in vivo results from a perturbation of the neuroregulation of insulin secretion rather than an intrinsic pancreatic beta-cell defect.

Inheritance of diabetes mellitus as consequence of gestational hyperglycemia in rats.

Our study investigated whether a deterioration of glucose homeostasis and insulin secretion in adult female rats from hyperglycemic dams could be transmitted to the next generation independent of genetic interferences. Dams (F0) were rendered hyperglycemic by continuous glucose infusion during the last week of pregnancy. Females born of these rats (F1) exhibited glucose intolerance and impaired insulin secretion in vivo at adulthood. When they were 3 mo old, they were matched with males born of control dams. During pregnancy, their glucose tolerance remained impaired compared with that of controls. Consequently, F2 newborns of F1 hyperglycemic dams showed the main features of newborns from diabetic mothers: they were hyperglycemic, hyperinsulinemic, and macrosomic. As adults, they displayed basal hyperglycemia and defective glucose tolerance and insulin secretion. This indicates that the long-range deteriorating effects on glucose homeostasis of gestational hyperglycemia in the F1 generation are transmitted to the F2 generation and suggests that a perturbed fetal metabolic environment contributes to the inheritance of diabetes mellitus.

Higher maternal than paternal inheritance of diabetes in GK rats.

Results from crosses between Goto-Kakizaki (GK) rats, which exhibit spontaneous non-insulin-dependent diabetes mellitus (NIDDM), and outbred nondiabetic Wistar rats have demonstrated an effect of maternal inheritance on diabetes in offspring of the first generation (F1). At 6 weeks of age, F1 offspring of sex-directed crosses exhibited plasma glucose values intermediate between GK and Wistar parents. Hyperglycemia in F1 rats born of female GK rats (F1GK) was more marked than in those born of female Wistar (F1W) rats. At 3 months of age, F1 rats showed a marked impairment of both glucose tolerance and insulin secretion, which was intermediate between GK and Wistar rats. Glucose intolerance was more pronounced in F1GK rats than in F1W. By contrast, insulin secretion in F1W rats was more deteriorated than in F1GK rats. No deletion in mitochondrial DNA was observed in the GK rats, which decreased the possibility of a mitochondrial inheritance effect as an explanation of our findings. These data support a polygenic model in diabetes inheritance of NIDDM and suggest that, in addition to genetic factors, a perturbed maternal metabolism can contribute to its inheritance.

The cardiovascular effects of salidroside in the Goto-Kakizaki diabetic rat model.

Many factors, including hyperglycemia, hypertension, obesity, dyslipidemia, and a sedentary lifestyle, contribute to a high prevalence of cardiovascular disease. Specific vascular impairment treatments in the context of diabetes and vascular risk need to be improved. Salidroside is the primary active component of Rhodiola rosea and has documented antioxidative, cardioprotective, and vasculoprotective properties. The aim of this study was to test the hypothesis that salidroside has protective effects against hyperglycemia, hypertension, and vasodilation impairment in the Goto-Kakizaki (GK) rat model of diabetes. We evaluated cardiovascular parameters (e.g., daytime/nighttime systolic and diastolic blood pressure, heart rate, and activity), metabolic parameters (e.g., body weight, food and water consumption, serum fructosamine level, glucose tolerance), eNOS / phospho-eNOS expression level and in vitro vascular reactivity of aorta and second-order mesenteric arteries in Wistar-Kyoto (control) and GK (diabetic) rats treated with salidroside (40 mg/kg) or placebo (water) for 5 weeks. GK rats showed hypertension, marked glucose intolerance, and impaired endothelium-dependent and endothelium-independent vasodilation capacity. Salidroside showed beneficial effects on endothelial and non-endothelial vasodilation and likely acts on the endothelium and smooth muscle cells through the soluble guanylyl cyclase pathway. Despite its vascular effects, salidroside had no effect on blood pressure and heart rate in GK and control rats, it did not improve glucose metabolism or limit hypertension in the GK model of type 2 diabetes.

Applicability of a "speed" congenic strategy to dissect blood pressure quantitative trait loci on rat chromosome 2.

The identification of any quantitative trait locus (QTL) via a genome scan is only the first step toward the ultimate goal of gene identification. The next step is the production of congenic strains by which the existence of a QTL may be verified and the implicated chromosomal region be reduced to a size applicable to positional cloning of the causal gene. We used a speed congenic breeding protocol previously verified in mice for 2 blood pressure QTLs on rat chromosome 2. Four congenic strains were produced through introgression of various segments of chromosome 2 from Wistar-Kyoto rats from Glasgow colonies [WKY((Gla)) rats] into the recipient stroke-prone spontaneously hypertensive rats from Glasgow colonies [SHRSP((Gla))], and vice versa. The number of backcross generations required for each strain to achieve complete homozygosity at 83 background genetic markers in a "best" male varied between 3 and 4. Transfer of the region of rat chromosome 2 containing both QTLs from WKY((Gla)) into an SHRSP((Gla)) genetic background lowered both baseline and salt-loaded systolic blood pressure by approximately 20 and approximately 40 mm Hg in male congenic rats compared with the SHRSP parental strain (F=53.4, P<0.005; F=28.0, P< 0.0005, respectively). In contrast, control animals for stowaway heterozygosity presented no deviation from the blood pressure values recorded for the SHRSP((Gla)), indicating that if such heterozygosity exists, its effect on blood pressure is negligible. A reciprocal strategy in which 1 or both QTLs on rat chromosome 2 were transferred from SHRSP((Gla)) into a WKY((Gla)) genetic background resulted in statistically significant but smaller blood pressure increases for 1 of these QTLs. These results confirm the existence of blood pressure QTLs on rat chromosome 2 and demonstrate the applicability of a speed congenic strategy in the rat and emphasize the important role of the genetic background.

Successful isolation of a rat chromosome 1 blood pressure quantitative trait locus in reciprocal congenic strains.

Linkage analyses in experimental crosses of hypertensive and normotensive rats have strongly suggested the presence of a quantitative trait locus (QTL) influencing blood pressure on rat chromosome 1, at or near the Sa gene. To confirm the presence of such a locus and move toward identification of the causative gene, we have developed, through targeted breeding over 10 generations using an Sa gene polymorphism to select breeders at each generation, 2 congenic strains, 1 containing a segment of spontaneously hypertensive rat (SHR) chromosome 1 in a Wistar-Kyoto rat (WKY) genetic background (WKY.SHR-Sa), and the other a segment of WKY chromosome 1 in an SHR background (SHR.WKY-Sa). WKY.SHR-Sa contains at least approximately 26 cM of SHR chromosome 1, between markers mD7mit206 and D1Mit2 (and including the SHR allele of the Sa gene), and SHR.WKY-Sa carries at least approximately 15 cM of WKY chromosome 1, between mD7mit206 and D1Wox34 (and including the WKY allele of the Sa gene). Blood pressure of WKY.SHR-Sa rats measured at 16, 20, and 25 weeks of age was significantly higher than that of WKY, whereas blood pressure of SHR.WKY-Sa rats was significantly lower than that of SHR. At 25 weeks, the mean differences in systolic and diastolic blood pressure between WKY.SHR-Sa and WKY were +11.5 mm Hg (P=0.001) and +11.6 mm Hg mm Hg (P<0.001), respectively. The corresponding differences between SHR.WKy-Sa and SHR were -11.3 mm Hg (P=0.002) and -9.1 mm Hg (P=0.005), respectively. The differences represent about one fifth of the blood pressure difference between SHR and WKY. Renal Sa mRNA levels in the congenic strains reflected their Sa allele with a high level in WKY. SHR-Sa and a low level in SHR.WKY-Sa, consistent with previous data suggesting that the level of Sa expression is primarily determined by cis-acting elements in or near the Sa gene. Our results show that we have successfully isolated a major rat chromosome 1 blood pressure QTL located in the vicinity of the Sa gene in reciprocal congenic strains derived from SHR and WKY. The strains can now be used to further define the region containing the QTL and also to characterize intermediary mechanisms through which the QTL influences blood pressure. In addition, comparison of the regions introgressed in our congenic strains with the location of the peak LOD score for chromosome 1 blood pressure QTL in second filial generation progeny derived from our SHRxWKY cross suggests that there may be at least 1 further QTL influencing blood pressure on this rat chromosome.

Analysis of quantitative trait loci for blood pressure on rat chromosomes 2 and 13. Age-related differences in effect.

Previous studies have suggested the presence of quantitative trait loci (QTLs) influencing blood pressure on rat chromosomes 2 and 13. In this study, we mapped the QTLs in F2 rats derived from a cross of the spontaneously hypertensive rat and the Wistar-Kyoto rat and analyzed the effect of the QTLs on blood pressures measured longitudinally between 12 and 25 weeks of age. We analyzed 16 polymorphic markers spanning 147.3 cM on chromosome 2 and 13 markers spanning 91.6 cM on chromosome 13. Both chromosomes contained QTLs with highly significant effects on blood pressure (peak logarithm of the odds [LOD] scores, 5.64 and 5.75, respectively). On chromosome 2, the peak was localized to a position at anonymous marker D2Wox7, 2.9 cM away from the gene for the sodium-potassium ATPase alpha 1-subunit. On chromosome 13, the major peak coincided with the marker D13Mit2, 21.7 cM away from the renin gene, but there was a suggestion of multiple peaks. The effect of the QTL on chromosome 2 was seen throughout from 12 to 25 weeks of age, whereas interestingly, the effect for the QTL on chromosome 13 was maximal at 20 weeks of age but disappeared at 25 weeks of age, presumably because of the effect of either epistatic factors or environmental influences. The findings provide important information on QTLs influencing blood pressure on rat chromosomes 2 and 13 that will be useful in localizing and identifying the causative genes and emphasize the importance of age being taken into account when the effects of individual QTLs on a trait that shows significant age-related changes are being analyzed.

Detection, cloning, and distribution of minisatellites in some mammalian genomes.

The chromosomal distribution of minisatellites (cloned and/or detected using natural or synthetic tandem repeats) is strikingly different in man and mouse. In man, the vast majority is clustered in the terminal band of a subset of chromosome arms. Interestingly, the class of shorter tandem repeats called microsatellites is widespread along the chromosomes, suggesting that minisatellites can be created or maintained only in certain regions. In order to gain a better knowledge of these areas, we have studied a sub-telomeric cosmid from the pseudoautosomal region. Sixty kilobases of human genomic DNA starting approximately 20 kilobases from the human sex chromosomes telomere have previously been independently isolated in two cosmid clones (locus DXYS14) (Cooke et al., 1985); Rouyer et al., 1986). We have studied in more detail one of the two cosmids from this locus and found that it contains four different minisatellite structures representing 20 kilobases of the cosmid. These structures are unrelated to each other or to the minisatellite family described by Jeffreys et al. (1985). They display different degrees of polymorphism correlated with varying amounts of inner homogeneity. Combined with the previous description of an additional minisatellite (Cooke et al., 1985; Inglehearn and Cooke, 1990) in the contiguous cosmid, our observation shows that these structures may represent an important proportion of the DNA in sub-telomeric regions.

Are animal models of diabetes relevant to the study of the genetics of non-insulin-dependent diabetes in humans?

Although it is well-recognized that non-insulin-dependent diabetes-mellitus (NIDDM) shown a strong genetic component the search for candidate genes has been very difficult since NIDDM is a complex, heterogeneous, multifactorial syndrome resulting from both genetic susceptibility and environmental risk factors. Therefore, the use of inbred animal models is an essential component of genetic investigations in this field. As these lines are genetically homogeneous, it is possible to direct mating for optimal genetic crosses and control environmental factors. Strains with spontaneous NIDDM may be constituted from animals with one or several genetic mutation(s) transmitted generation to generation or selected from non-diabetic outbred animals by repeated breeding. The ob/ob and db/db mice, which are rodent models of NIDDM and obesity, belong to the first category. Recent studies using the positional cloning approach allowed the mapping of ob gene and identification of its product, leptin, which is a protein secreted by white adipose tissue and involved in the control of food intake. The db gene encodes the leptin receptor. The search for genetic linkage was undertaken in polygenic models, especially the Goto-Kakisaki (GK) rat which was obtained by selective breeding of individuals with glucose intolerance from a non-diabetic Wistar rat colony. Though precise definition of sub-phenotypes of glucose tolerance and insulin secretion, the mapping of microsatellite markers and QTL analysis, it has proved possible to identify many independent loci containing genes regulating glucose homeostasis and insulin secretion. In another polygenic model, the OLETF rat, a locus present on chromosome X was identified. Many complementary approaches in different strains may lead to the identification of candidate genes for NIDDM and help direct the search for candidate genes in humans who show synteny relationships with rodents.

Subtle metabolic and liver gene transcriptional changes underlie diet-induced fatty liver susceptibility in insulin-resistant mice.

AIMS/HYPOTHESIS: Complex changes in gene expression are associated with insulin resistance and non-alcoholic fatty liver disease (NAFLD) promoted by feeding a high-fat diet (HFD). We used functional genomic technologies to document molecular mechanisms associated with diet-induced NAFLD. MATERIALS AND METHODS: Male 129S6 mice were fed a diet containing 40% fat (high-fat diet, HFD) for 15 weeks. Glucose tolerance, in vivo insulin secretion, plasma lipid profile and adiposity were determined. Plasma metabonomics and liver transcriptomics were used to identify changes in gene expression associated with HFD-induced NAFLD. RESULTS: In HFD-fed mice, NAFLD and impaired glucose and lipid homeostasis were associated with increased hepatic transcription of genes involved in fatty acid uptake, intracellular transport, modification and elongation, whilst genes involved in beta-oxidation and lipoprotein secretion were, paradoxically, also upregulated. NAFLD developed despite strong and sustained downregulation of transcription of the gene encoding stearoyl-coenzyme A desaturase 1 (Scd1) and uncoordinated regulation of transcription of Scd1 and the gene encoding sterol regulatory element binding factor 1c (Srebf1c) transcription. Inflammatory mechanisms appeared to be stimulated by HFD. CONCLUSIONS/INTERPRETATION: Our results provide an accurate representation of subtle changes in metabolic and gene expression regulation underlying disease-promoting and compensatory mechanisms, collectively contributing to diet-induced insulin resistance and NAFLD. They suggest that proposed models of NAFLD pathogenesis can be enriched with novel diet-reactive genes and disease mechanisms.

Genetic control of plasma lipid levels in a cross derived from normoglycaemic Brown Norway and spontaneously diabetic Goto-Kakizaki rats.

AIMS/HYPOTHESIS: Dyslipidaemia is a main component of the insulin resistance syndrome. The inbred Goto-Kakizaki (GK) rat is a model of spontaneous type 2 diabetes and insulin resistance, which has been used to identify diabetes-related susceptibility loci in genetic crosses. The objective of our study was to test the genetic control of lipid metabolism in the GK rat and investigate a possible relationship with known genetic loci regulating glucose homeostasis in this strain. MATERIALS AND METHODS: Plasma concentration of triglycerides, phospholipids, total cholesterol, HDL, LDL and VLDL cholesterol were determined in a cohort of 151 hybrids of an F2 cross derived from GK and non-diabetic Brown Norway (BN) rats. Data from the genome-wide scan of the F2 hybrids were used to test for evidence of genetic linkage to the lipid quantitative traits. RESULTS: We identified statistically significant quantitative trait loci (QTLs) that control the level of plasma phospholipids and triglycerides (chromosome 1), LDL cholesterol (chromosome 3) and total and HDL cholesterol (chromosomes 1 and 5). These QTLs do not coincide with previously identified diabetes susceptibility loci in a similar cross. The significance of lipid QTLs mapped to chromosomes 1 and 5 is strongly influenced by sex. CONCLUSION/INTERPRETATION: We established that several genetic loci control the quantitative variations of plasma lipid variables in a GKxBN cross. They appear to be distinct from known GK diabetes QTLs, indicating that lipid metabolism and traits directly relevant to glucose and insulin regulation are controlled by different gene variants in this strain combination.