Project description:The goals and objectives: To study Type 2 diabetes progression and the development of insulin resistance in two animal models with and without a high fat diet superimposed on these models. Background: Diabetes is a systemic metabolic imbalance involving multiple tissues/organs, and an early hallmark feature of this disease state is insulin resistance. Multifactorial interactions of genetics, prenatal environmental factors (fetal programming) and postnatal environmental factors (nutrition and activity) likely contribute to the diabetic phenotype.Animal models can serve as a valuable tool for studying diabetes disease progression and for identifying useful biomarkers of type 2 diabetes. Several inbred rodent models are available for diabetes related studies. The GK rat is an obvious choice among available inbred models as the genetic basis for this inheritable form of diabetes is polygenic (5), unlike most other inbred rodent models that exhibit single gene defects. Many of the characteristics of the GK rat mirror human diabetes (hyperglycemia, glucose intolerance, insulin resistance), although hyperlipidemia does not appear to be prominent in the GK rat. Due to its polygenic mode of inheritance and 100% penetrance, the GK rat may be a useful model for human diabetes. Induced animal models can also be useful in diabetes studies. One such model is metabolic syndrome resulting from experimentally induced fetal programming (produced by maternal malnutrition or by exposure to corticosteroids in the third trimester). Both in humans and animals, accumulating evidence suggests that alterations in the human fetal environment can result in permanent physiologic changes that manifest as increased incidence of adult onset pathology. Numerous epidemiological studies have forged a strong link between low birth weight and the development of metabolic syndrome in adulthood. From such observations has arisen the concept of “fetal programming” whereby exposure to some factor(s) during crucial stages in development can permanently alter or “reset” physiologic/metabolic functions. In the rat, exposure to corticosteroids during a “window” in third trimester gestation (CS programming) results in fetal growth retardation and insulin resistance in adult offspring. Genetic factors play a primarily role in the etiology of diabetes in the GK rat, whereas fetal environmental factors are causative in CS programming. (It should be noted that although altered fetal environmental effects, most likely stemming from maternal hyperglycemia, have been implicated to play some role in the decreased pancreatic B cell mass in GK rats, these effects occur earlier in gestation and therefore differ from programming by CS in late gestation.) A comparison of the development of insulin resistance in the GK rat with development in the CS programmed rat will provide insight into genetic and fetal environmental factors in disease development. Superimposing dietary alterations (i.e., high fat feeding) (11) on both animal models may aid in the dissection of multiple interacting factors (genetic, fetal environmental factors, postnatal environmental factors) on the development and progression of insulin resistance and type 2 diabetes. Such studies may also aid in the identification of useful biomarkers for insulin resistance and type 2 diabetes in humans. Proposed research: Experiments are designed to study disease progression and the development of insulin resistance in two animal models: the GK rat and the CS programmed rat, with and without a high fat diet superimposed on these models. Animals will be maintained in our facility from weaning (GK rats) or birth (CS programmed - WKY), and body weights taken weekly. Appropriate diets (normal or high fat) will be introduced at weaning. Groups of animals (N=6) will be sacrificed at 5 different ages: 4, 8, 12, 16, and 20 weeks. Plasma samples will be analyzed for markers of hyperglycemia, hyperinsulinemia, dyslipidimia, and for selected other hormonal factors which may contribute to disease etiology (adiponectin, leptin, corticosterone). At sacrifice, muscle is harvested, flash-frozen in liquid nitrogen, and warehoused in our tissue collection maintained at - 80 degrees C for this and possible future work. Study will initially focus on examination of selected molecular markers of insulin resistance at the mRNA level in rat gastrocnemius muscles (IRS-1, PDK4). Keywords: Type 2 diabetes, biomarker, rat, muscle, time series Overall design: The study contains: 50 gastrocnemius muscle samples from GK (GotoKakizake) rats and 51 gastrocnemius muscle samples from WKY (WistarKyoto) rats feeded with normal diet (ND) and high fat diet (HFD) and sacrificed at 5 different ages: 4, 8, 12, 16, and 20 weeks. So, each time point contains 5 GK muscle samples with ND, 5 GK muscle samples with HFD, 5 WKY muscle samples with ND and 5 WKY muscle samples with HFD.
Project description:BACKGROUND:Murine kobuviruses (MuKV) are newly recognized picornaviruses first detected in murine rodents in the USA in 2011. Little information on MuKV epidemiology in murine rodents is available. Therefore, we conducted a survey of the prevalence and genomic characteristics of rat kobuvirus in Guangdong, China. RESULTS:Fecal samples from 223 rats (Rattus norvegicus) were collected from Guangdong and kobuviruses were detected in 12.6% (28) of samples. Phylogenetic analysis based on partial 3D and complete VP1 sequence regions showed that rat kobuvirus obtained in this study were genetically closely related to those of rat/mouse kobuvirus reported in other geographical areas. Two near full-length rat kobuvirus genomes (MM33, GZ85) were acquired and phylogenetic analysis of these revealed that they shared very high nucleotide/amino acids identity with one another (95.4%/99.4%) and a sewage-derived sequence (86.9%/93.5% and 87.5%/93.7%, respectively). Comparison with original Aichivirus A strains, such human kobuvirus, revealed amino acid identity values of approximately 80%. CONCLUSION:Our findings indicate that rat kobuvirus have distinctive genetic characteristics from other Aichivirus A viruses. Additionally, rat kobuvirus may spread via sewage.
Project description:Muscle atrophy is a widespread ill condition occurring in many diseases, which can reduce quality of life and increase morbidity and mortality. We developed a new method using non-invasive ultrasonography to measure soleus and gastrocnemius lateralis muscle atrophy in the hindlimb-unloaded rat, a well-accepted model of muscle disuse. Soleus and gastrocnemius volumes were calculated using the conventional truncated-cone method and a newly-designed sinusoidal method. For Soleus muscle, the ultrasonographic volume determined in vivo with either method was linearly correlated to the volume determined ex-vivo from excised muscles as muscle weight-to-density ratio. For both soleus and gastrocnemius muscles, a strong linear correlation was obtained between the ultrasonographic volume and the muscle fiber cross-sectional area determined ex-vivo on muscle cryosections. Thus ultrasonography allowed the longitudinal in vivo evaluation of muscle atrophy progression during hindlimb unloading. This study validates ultrasonography as a powerful method for the evaluation of rodent muscle atrophy in vivo, which would prove useful in disease models and therapeutic trials.
Project description:Oxidative decarboxylation of L-[1-14C]glutamine was studied in isolated chick and rat skeletal muscles incubated in the presence of glucose, insulin and plasma concentrations of amino acids. (1) The rate of oxidative decarboxylation of L-[1-14C]glutamine was high, and exceeded that of L-[1-14C]leucine in all muscles. (2) The rate of oxidative decarboxylation of L-[1-14C]glutamine increased with increasing intracellular concentrations of glutamine. (3) The activities of glutamine aminotransferases K and L were more than 10-fold greater in rat than in chick skeletal muscles. (4) Mitochondrial phosphate-activated glutaminase activity was approx. 10-fold greater in chick than in rat skeletal muscles and increased with increasing glutamine concentrations. (5) An inhibitor of glutaminase, 6-diazo-5-oxo-L-norleucine, inhibited the rate of glutamine decarboxylation in chick, but not in rat, skeletal muscle. These findings suggest that glutamine degradation in skeletal muscle may be substantial and may make an important contribution to the regulation of intramuscular glutamine concentrations. A species difference in the pathways and the subcellular location for the conversion of glutamine into 2-oxoglutarate in rat and chick skeletal muscles is implied by the relative activities of glutamine-degrading enzymes.
Project description:Systemic infection with Escherichia coli significantly decreased feed intake, slowed growth of the whole body and skeletal muscles, and severely inhibited muscle protein accumulation in both chicks and rats. Treatment with naproxen (6-methoxy-alpha-methyl-2-naphthaleneacetic acid), an inhibitor of prostaglandin production, decreased weight losses of body and muscle, and significantly inhibited muscle protein wasting in infected chicks and rats. E. coli infection increased net protein degradation by 44.8% (P less than 0.05) and prostaglandin E2 production by 148% (P less than 0.05) in isolated extensor digitorum communis muscle from chicks on day 2 after infection. Naproxen treatment significantly decreased net protein degradation and prostaglandin E2 production in infected chicks to values seen in muscles of healthy controls. Quantitatively and qualitatively similar results were seen in isolated rat epitrochlearis muscle.
Project description:Gene copy number variation plays a large role in the evolution of genomes. In Rattus norvegicus and other rodent species, the Y-chromosome has accumulated multiple copies of Sry loci. These copy number variations have been previously linked with changes in phenotype of animal models such as the spontaneously hypertensive rat (SHR). This study characterizes the Y-chromosome in the Sry region of Rattus norvegicus, while addressing functional variations seen in the Sry protein products.Eleven Sry loci have been identified in the SHR with one (nonHMG Sry) containing a frame shift mutation. The nonHMGSry is found and conserved in the related WKY and SD rat strains. Three new, previously unidentified, Sry loci were identified in this study (Sry3BII, Sry4 and Sry4A) in both SHR and WKY. Repetitive element analysis revealed numerous LINE-L1 elements at regions where conservation is lost among the Sry copies. In addition we have identified a retrotransposed copy of Med14 originating from spliced mRNA, two autosomal genes (Ccdc110 and HMGB1) and a normal mammalian Y-chromosome gene (Zfy) in the Sry region of the rat Y-chromosome. Translation of the sequences of each Sry gene reveals eight proteins with amino acid differences leading to changes in nuclear localization and promoter activation of a Sry-responsive gene. Sry-? (coded by the Sry2 locus) has an increased cytoplasmic fraction due to alterations at amino acid 21. Sry-? has altered gene regulation of the Sry1 promoter due to changes at amino acid 76.The duplication of Sry on the Rattus norvegicus Y-chromosome has led to proteins with altered functional ability that may have been selected for functions in addition to testis determination. Additionally, several other genes not normally found on the Y-chromosome have duplicated new copies into the region around the Sry genes. These suggest a role of active transposable elements in the evolution of the mammalian Y-chromosome in species such as Rattus norvegicus.
Project description:Native to China and Mongolia, the brown rat (Rattus norvegicus) now enjoys a worldwide distribution. While black rats and the house mouse tracked the regional development of human agricultural settlements, brown rats did not appear in Europe until the 1500s, suggesting their range expansion was a response to relatively recent increases in global trade. We inferred the global phylogeography of brown rats using 32 k SNPs, and detected 13 evolutionary clusters within five expansion routes. One cluster arose following a southward expansion into Southeast Asia. Three additional clusters arose from two independent eastward expansions: one expansion from Russia to the Aleutian Archipelago, and a second to western North America. Westward expansion resulted in the colonization of Europe from which subsequent rapid colonization of Africa, the Americas and Australasia occurred, and multiple evolutionary clusters were detected. An astonishing degree of fine-grained clustering between and within sampling sites underscored the extent to which urban heterogeneity shaped genetic structure of commensal rodents. Surprisingly, few individuals were recent migrants, suggesting that recruitment into established populations is limited. Understanding the global population structure of R. norvegicus offers novel perspectives on the forces driving the spread of zoonotic disease, and aids in development of rat eradication programmes.