Nob3 is a major obesity quantitative trait locus (QTL) identified in an intercross of New Zealand Obese (NZO) mice with C57BL/6J (B6), and by introgression of its 38 Mbp peak region into B6 ...(B6.NZO-Nob3.38). B6.NZO-Nob3.38 mice carrying the NZO allele exhibited markedly increased body weight, fat mass, lean mass and a lower energy expenditure, than the corresponding B6 allele carriers. For positional cloning of the responsible obesity gene, five additional congenic lines (RCS) were generated and characterized, allowing to define a critical genomic interval comprising 43 genes. mRNA profiling and western blotting indicated that Ifi202b, a member of the Ifi200 family of interferon inducible transcriptional modulators, was expressed in NZO-allele carriers but was undetectable in tissues of homozygous B6-allele carriers due to a microdeletion, including the first exon and the 5'-flanking region of Ifi202b in B6. Transcriptome analysis of adipose tissue of RCS revealed a marked induction of 11β-hydroxysteroid dehydrogenase type 1 (11β-Hsd1) expression in mice expressing Ifi202b. Furthermore, siRNA-mediated Ifi202b suppression in 3T3-L1 adipocytes resulted in a significant inhibition of 11β-Hsd1 expression, whereas an adenoviral-mediated overexpression of Ifi202b increased 11β-Hsd1 mRNA levels. Expression of human IFI orthologues was significantly increased in visceral adipose tissue of obese subjects. We suggest that the disruption of Ifi202b in B6 is responsible for the effects of the obesity QTL Nob3, and that Ifi202b modulates fat accumulation through expression of adipogenic genes such as 11β-Hsd1.
Dysregulation of fatty acid oxidation plays a pivotal role in the pathophysiology of obesity and insulin resistance. Medium- and short-chain-3-hydroxyacyl-coenzyme A (CoA) dehydrogenase (SCHAD) (gene ...name, hadh) catalyze the third reaction of the mitochondrial β-oxidation cascade, the oxidation of 3-hydroxyacyl-CoA to 3-ketoacyl-CoA, for medium- and short-chain fatty acids. We identified hadh as a putative obesity gene by comparison of two genome-wide scans, a quantitative trait locus analysis previously performed in the polygenic obese New Zealand obese mouse and an earlier described small interfering RNA-mediated mutagenesis in Caenorhabditis elegans. In the present study, we show that mice lacking SCHAD (hadh−/−) displayed a lower body weight and a reduced fat mass in comparison with hadh+/+ mice under high-fat diet conditions, presumably due to an impaired fuel efficiency, the loss of acylcarnitines via the urine, and increased body temperature. Food intake, total energy expenditure, and locomotor activity were not altered in knockout mice. Hadh−/− mice exhibited normal fat tolerance at 20 C. However, during cold exposure, knockout mice were unable to clear triglycerides from the plasma and to maintain their normal body temperature, indicating that SCHAD plays an important role in adaptive thermogenesis. Blood glucose concentrations in the fasted and postprandial state were significantly lower in hadh−/− mice, whereas insulin levels were elevated. Accordingly, insulin secretion in response to glucose and glucose plus palmitate was elevated in isolated islets of knockout mice. Therefore, our data indicate that SCHAD is involved in thermogenesis, in the maintenance of body weight, and in the regulation of nutrient-stimulated insulin secretion.
Induction of skeletal muscle (SM) mitochondrial stress by expression of uncoupling protein 1 (UCP1) in mice results in a healthy metabolic phenotype associated with increased secretion of FGF21 from ...SM. Here, we investigated whether SM mitochondrial uncoupling can compensate obesity and insulin resistance in the NZO mouse, a polygenic diabesity model. Male NZO mice were crossed with heterozygous UCP1 transgenic (tg) mice (mixed C57BL/6/CBA background) and further backcrossed to obtain F1 and N2 offspring with 50 and 75 % NZO background, respectively. Male F1 and N2 progeny were fed a high-fat diet ad libitum for 20 weeks from weaning. Blood glucose was reduced, and diabetes (severe hyperglycemia >300 mg/dl) was fully prevented in both F1- and N2-tg progeny compared to a diabetes prevalence of 15 % in F1 and 42 % in N2 wild type. In contrast, relative body fat content and plasma insulin were decreased, and glucose tolerance was improved, in F1-tg only. Both F1 and N2-tg showed decreased lean body mass. Accordingly, induction of SM stress response including FGF21 expression and secretion was similar in both F1 and N2-tg mice. In white adipose tissue, expression of FGF21 target genes was enhanced in F1 and N2-tg mice, whereas lipid metabolism genes were induced in F1-tg only. There was no evidence for induction of browning in either UCP1 backcross. We conclude that SM mitochondrial uncoupling induces FGF21 expression and prevents diabetes in mice with a 50–75 % NZO background independent of its effects on adipose tissue.
Abstract only
Intestinal lipid metabolism is comprised of multi‐steps of vesicle trafficking. ADP‐ribosylation factor‐related protein 1 (ARFRP1) regulates protein trafficking between intracellular ...organelles. To study the role of ARFRP1 in intestinal lipid metabolism,
Arfrp1
was deleted in mouse intestine (
Arfrp1
vil−/−
), or depleted by siRNA transfection in Caco‐2 cells. Lipid absorption and lipoprotein production were examined. Decreased lipid absorption was detected in oral fat tolerance test in
Arfrp1
vil−/−
mice. However, the apolipoprotein (Apo) B48 and ApoA4 in the plasma were higher, whereas the level of ApoA1 was markedly lower. Fractionation of the plasma showed that the chylomicron fractions of
Arfrp1
vil−/−
mice contain lower triglyceride level, indicating that the
Arfrp1
vil−/−
enterocytes produce a large number of chylomicron particles that are smaller in size containing less fat. Caco‐2 cells demonstrated that the defect in
Arfrp1
expression caused decreased lipid release, but normal lipid uptake. In conclusion, ARFRP1 plays important roles in chylomicron lipidation in the Golgi and the secretion of ApoA1 in the intestine.
Grant Funding Source
: Deutsche Forschungsgemeinschaft (Schu 750/5‐2; Schu 750/5‐3; GRK 1459; SFB958), Alexander von Humboldt Foundation
GLUT8 is a class 3 sugar transport facilitator which is predominantly expressed in testis and also detected in brain, heart, skeletal muscle, adipose tissue, adrenal gland, and liver. Since its ...physiological function in these tissues is unknown, we generated a Slc2a8 null mouse and characterized its phenotype. Slc2a8 knockout mice appeared healthy and exhibited normal growth, body weight development and glycemic control, indicating that GLUT8 does not play a significant role for maintenance of whole body glucose homeostasis. However, analysis of the offspring distribution of heterozygous mating indicated a lower number of Slc2a8 knockout offspring (30.5:47.3:22.1%, Slc2a8+/+, Slc2a8+/−, and Slc2a8−/− mice, respectively) resulting in a deviation (p=0.0024) from the expected Mendelian distribution. This difference was associated with lower ATP levels, a reduced mitochondrial membrane potential and a significant reduction of sperm motility of the Slc2a8 knockout in comparison to wild-type spermatozoa. In contrast, number and survival rate of spermatozoa were not altered. These data indicate that GLUT8 plays an important role in the energy metabolism of sperm cells.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
1 Department of Pharmacology, German Institute of Human Nutrition Potsdam-Rehbruecke, Nuthetal; 2 Research Group Neurogenetics, Leibniz-Institute for Neurobiology, Magdeburg; 3 Department of ...Pharmacology and Toxicology, Pharmaceutical Institute of the University of Tübingen; 4 Department of Internal Medicine, Division of Endocrinology, Nephrology, Vascular Disease and Clinical Chemistry, University of Tübingen, Tubingen; 5 Max Planck Institute for Molecular Genetics, Berlin-Dahlem, Germany; and 6 Centre for Genomic Regulation, Barcelona, Spain
Submitted 5 June 2008
; accepted in final form 2 September 2008
Homozygous deletion of the gene of the neuronal glucose transporter GLUT3 ( Slc2a3 ) in mice results in embryonic lethality, whereas heterozygotes ( Slc2a3 +/– ) are viable. Here, we describe the characterization of heterozygous mice with regard to neuronal function, glucose homeostasis, and, since GLUT3 might be a component of the neuronal glucose-sensing mechanism, food intake and energy balance. Levels of GLUT3 mRNA and protein in brain were reduced by 50% in Slc2a3 +/– mice. Electrographic features examined by electroencephalographic recordings give evidence for slightly but significantly enhanced cerebrocortical activity in Slc2a3 +/– mice. In addition, Slc2a3 +/– mice were slightly more sensitive to an acoustic startle stimulus (elevated startle amplitude and reduced prepulse inhibition). However, systemic behavioral testing revealed no other functional abnormalities, e.g., in coordination, reflexes, motor abilities, anxiety, learning, and memory. Furthermore, no differences in body weight, blood glucose, and insulin levels were detected between wild-type and Slc2a3 +/– littermates. Food intake as monitored randomly or after intracerebroventricular administration of 2-deoxyglucose or D -glucose, or food choice for carbohydrates/fat was not affected in Slc2a3 +/– mice. Taken together, our data indicate that, in contrast to Slc2a1 , a single allele of Slc2a3 is sufficient for maintenance of neuronal energy supply, motor abilities, learning and memory, and feeding behavior.
glucose transporter 3; knockout; glucose sensing; food in take; neurons and astrocytes
Address for reprint requests and other correspondence: A. Schürmann, Dept. of Pharmacology, German Institute of Human Nutrition, Potsdam-Rehbruecke, Arthur-Scheunert-Allee 114-116, D-14558 Nuthetal, Germany (e-mail: schuermann{at}dife.de )
Aims: New Zealand obese (NZO) mice exhibit a polygenic syndrome of obesity, insulin resistance, and hypercholesterolemia that resembles the human metabolic syndrome. This study was performed in order ...to locate genes responsible for elevated serum cholesterol and to compare their effects under a standard and high fat diet.
Methods: A backcross population of NZO with SJL mice (NZO×F1(SJL×NZO)) was generated. Mice were raised on a normal or high fat diet and were monitored for 22 weeks (body weight, serum cholesterol, and blood glucose). A genome-wide scan was performed by genotyping of approximately 200 polymorphic microsatellite markers by PCR and linkage analysis was performed with the MAPMAKER program.
Results: In the genome-wide scan, a single susceptibility locus for hypercholesterolemia (
Chol1/NZO, maximum LOD score 14.5 in a combined population of 523 backcross mice) was identified on chromosome 5. Cholesterol levels were significantly elevated in both male and female homozygous carriers of the
Chol1/NZO allele. The locus maps 40
cM distal of the previously described obesity locus
Nob1 in the vicinity of the marker D5Mit244 and in the vicinity of hypercholesterolemia QTL previously identified in the NZB, CAST, and C57BL/6J strains.
Chol1/NZO was not associated with elevated body weight, serum insulin, or hyperglycemia. The high fat diet significantly increased serum cholesterol levels, but the fat content of the diet did not alter the absolute effect of Chol1/NZO.
Conclusions: Chol1/NZO is a major susceptibility locus on the distal mouse chromosome 5, which produces gender-independent hypercholesterolemia in NZO mice. The effect of
Chol1/NZO was independent of the dietary fat content and was not associated with the other traits of the metabolic syndrome. Thus, it is suggested that the responsible gene might be involved in cholesterol metabolism.
Inactivation of the transcription factor AP-2β in a genetically mixed C57BL/6/129S1 mouse strain resulted in perinatal lethality as a consequence of massively enhanced apoptotic death of renal ...epithelial cells (Genes Dev 1997;11:1938–1948). Recently, we observed that the phenotype is modulated by genetic background because AP-2β mutant mice, backcrossed onto 129P2 background, survive approximately 2 weeks after birth, allowing for a detailed analysis of kidney function. Here we show that kidneys reveal varying amounts of cysts derived from all tubular structures (proximal and distal tubuli, collecting ducts). However, all mice died irrespective of the degree of cyst formation. Serum analysis of AP-2β mutant animals revealed defective tubular secretory function and ion homeostasis including severe hypocalcemia, hyperphosphatemia, and hyperuremia. Because hormonal calcium regulation was not impaired, the mice developed secondary renal hyperparathyroidism as typically observed in patients with terminal renal failure. We further demonstrate that molecular defects in the collecting duct system lead to insufficient water retention and urinary concentration. In summary, our studies reveal essential, nonredundant roles of AP-2β in renal tubular functions.
Polygenic type 2 diabetes in mouse models is associated with obesity and results from a combination of adipogenic and diabetogenic alleles. Here we report the identification of a candidate gene for ...the diabetogenic effect of a QTL (Nidd/SJL, Nidd1) contributed by the SJL, NON, and NZB strains in outcross populations with New Zealand Obese (NZO) mice. A critical interval of distal chromosome 4 (2.1 Mbp) conferring the diabetic phenotype was identified by interval-specific congenic introgression of SJL into diabetes-resistant C57BL/6J, and subsequent reporter cross with NZO. Analysis of the 10 genes in the critical interval by sequencing, qRT-PCR, and RACE-PCR revealed a striking allelic variance of Zfp69 encoding zinc finger domain transcription factor 69. In NZO and C57BL/6J, a retrotransposon (IAPLTR1a) in intron 3 disrupted the gene by formation of a truncated mRNA that lacked the coding sequence for the KRAB (Krüppel-associated box) and Znf-C2H2 domains of Zfp69, whereas the diabetogenic SJL, NON, and NZB alleles generated a normal mRNA. When combined with the B6.V-Lepob background, the diabetogenic Zfp69SJL allele produced hyperglycaemia, reduced gonadal fat, and increased plasma and liver triglycerides. mRNA levels of the human orthologue of Zfp69, ZNF642, were significantly increased in adipose tissue from patients with type 2 diabetes. We conclude that Zfp69 is the most likely candidate for the diabetogenic effect of Nidd/SJL, and that retrotransposon IAPLTR1a contributes substantially to the genetic heterogeneity of mouse strains. Expression of the transcription factor in adipose tissue may play a role in the pathogenesis of type 2 diabetes.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Type 2 diabetes-like hyperglycemia in a backcross model of NZO and SJL mice: characterization of a susceptibility locus on
chromosome 4 and its relation with obesity.
L Plum ,
R Kluge ,
K Giesen ,
J ...Altmüller ,
J R Ortlepp and
H G Joost
Institute of Pharmacology and Toxicology, Medical Faculty of the Technical University Aachen, Germany.
Abstract
A backcross model of New Zealand obese mice (NZO) with the lean, atherosclerosis-resistant SJL strain was established to locate
genes responsible for obesity, insulin resistance, and type 2 diabetes-like hyperglycemia. In male NZO x F1 backcross mice,
a major susceptibility locus for the development of hyperglycemia and hypoinsulinemia (Nidd/SJL) was identified on chromosome
4 between the markers D4Mit278 and D4Mit232, 10-28 cM distal of the previously described Nidd1 locus. The diabetogenic allele
has presumably been contributed by the SJL genome, and it appeared to be responsible for approximately 60% of the total prevalence
of hyperglycemia. The presence of Nidd/SJL did not alter body weight or weight gain by week 12. Thereafter, it was associated
with reduced weight gain or weight loss, presumably as a consequence of decompensated hyperglycemia. In all male backcross
mice, the prevalence of hyperglycemia at week 22 increased with the body weight at week 12, suggesting that the development
of hyperglycemia was dependent on the degree of obesity. In the absence of Nidd/SJL, mice weighing <50 g at week 12 did not
develop hyperglycemia by week 22. In contrast, in animals carrying the diabetogenic allele, the prevalence of hyperglycemia
was 20 and 64% when the 12-week weight was <45 and 45-50 g, respectively. These data are consistent with the conclusion that
Nidd/SJL represents a diabetes gene that lowers the obesity threshold for the development of hyperglycemia and hypoinsulinemia.
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