TALLYHO/JngJ Mice Research Articles

Differential miRNA Expression Patterns between TallyHo/JngJ Mice and Non-Diabetic SWR/J Mice

Abstract Type 2 diabetes mellitus (T2DM) increases the susceptibility of bone fragility. The underlying mechanisms have, however, remained largely unknown. MicroRNAs (miRNAs) are short single-stranded non-coding RNA molecules with utility as biomarkers due to their easy accessibility and stability in bodily fluids. Here, we aimed to use an unbiased approach to identify miRNAs dysregulated in a polygenic mouse model of T2DM. Genome-wide analysis of miRNAs in serum, bone marrow and bone from the polygenic TallyHo/JngJ (TH) mice, which recapitulate T2DM in humans, was performed. This analysis was compared to the recommended control SWR/J and a strain-matched non-diabetic control (TH-ND). When comparing TH mice with TH-ND using an adjusted P-value (FDR) cut-off of 0.2 to identify differentially expressed miRNAs, mmu-miR-466i-5p and mmu-miR-1195 were found to be up-regulated in both serum and in bone marrow. Dysregulated miRNAs were not found in bone tissue. When comparing TH-ND mice with SWR/J using the same FDR cut-off, mmu-miR-351-5p and mmu-miR-322-3p were upregulated in both bone marrow and serum, while mmu-miR-449a-5p and mmu-miR-6240 were downregulated in bone marrow and serum. Dysregulated miRNAs in bone marrow or cortical bone compared to serum between TH-ND mice and SWR/J were investigated for their cell-type enrichment to identify putative donor cells and their gene target networks. Gene target network analysis revealed genes involved in diabetes-related signaling pathways as well as in diabetic bone disease. Cell-type enrichment analysis identified hsa-miR-449a enriched in immune cells, hsa-miR-592 in hepatocytes and endothelial cells, while hsa-miR-424-3p, hsa-miR-1-3p and hsa-miR-196b-5p were enriched in mesenchymal stem cells and their derived tissues. In conclusion, our comparative miRNA profiling sheds light on differential expression patterns between SWR/J and both subgroups of TH. No differences were observed between TH and TH-ND suggesting the genetical background of SWR/J may be responsible for the change of dysregulated miRNA.

Utility and Limitations of TALLYHO/JngJ as a Model for Type 2 Diabetes-Induced Bone Disease.

Type 2 diabetes mellitus (T2DM) increases risk of fractures due to bone microstructural and material deficits, though the mechanisms remain unclear. Preclinical models mimicking diabetic bone disease are required to further understand its pathogenesis. The TALLYHO/JngJ (TH) mouse is a polygenic model recapitulating adolescent-onset T2DM in humans. Due to incomplete penetrance of the phenotype ~25% of male TH mice never develop hyperglycemia, providing a strain-matched nondiabetic control. We performed a comprehensive characterization of the metabolic and skeletal phenotype of diabetic TH mice and compared them to either their nondiabetic TH controls or the recommended SWR/J controls to evaluate their suitability to study diabetic bone disease in humans. Compared to both controls, male TH mice with T2DM exhibited higher blood glucose levels, weight along with impaired glucose tolerance and insulin sensitivity. TH mice with/without T2DM displayed higher cortical bone parameters and lower trabecular bone parameters in the femurs and vertebrae compared to SWR/J. The mechanical properties remained unchanged for all three groups except for a low-energy failure in TH mice with T2DM only compared to SWR/J. Histomorphometry analyses only revealed higher number of osteoclasts and osteocytes for SWR/J compared to both groups of TH. Bone turnover markers procollagen type 1 N-terminal propeptide (P1NP) and tartrate-resistant acid phosphatase (TRAP) were low for both groups of TH mice compared to SWR/J. Silver nitrate staining of the femurs revealed low number of osteocyte lacunar and dendrites in TH mice with T2DM. Three-dimensional assessment showed reduced lacunar parameters in trabecular and cortical bone. Notably, osteocyte morphology changed in TH mice with T2DM compared to SWR/J. In summary, our study highlights the utility of the TH mouse to study T2DM, but not necessarily T2DM-induced bone disease, as there were no differences in bone strength and bone cell parameters between diabetic and non-diabetic TH mice. © 2023 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Protective effects of a mitochondria-targeted small peptide SS31 against hyperglycemia-induced mitochondrial abnormalities in the liver tissues of diabetic mice, Tallyho/JngJ mice

Type 2 Diabetes mellitus (T2DM) has become a major public health issue associated with a high risk of late-onset Alzheimer’s disease (LOAD). Mitochondrial dysfunction is one of the molecular events that occur in the LOAD pathophysiology. The present study was planned to investigate the molecular alterations induced by hyperglycemia in the mitochondria of diabetic mice and further explore the possible ameliorative role of the mitochondria-targeted small peptide, SS31 in diabetic mice. For this purpose, we used a polygenic mouse model of type 2 diabetes, TALLYHO/JngJ (TH), and nondiabetic, SWR/J mice strains. The diabetic status in TH mice was confirmed at 8 weeks of age. The 24 weeks old experimental animals were segregated into three groups: Non-diabetic controls (SWR/J mice), diabetic (TH mice) and, SS31 treated diabetic TH mice. The mRNA and protein expression levels of mitochondrial proteins were investigated in all the study groups in the liver tissues using qPCR and immunoblot analysis. Also, the mitochondrial functions including H2O2 production, ATP generation, and lipid peroxidation were assessed in all the groups. Mitochondrial dysfunction was observed in TH mice as evident by significantly elevated H2O2 production, lipid peroxidation, and reduced ATP production. The mRNA expression and Western blot analysis of mitochondrial dynamics (Drp1 and Fis1 – fission; Mfn1, Mfn2, and Opa1 -fusion), and biogenesis (PGC-1α, Nrf1, Nrf2, and TFAM) genes were significantly altered in diabetic TH mice. Furthermore, SS31 treatment significantly reduced the mitochondrial abnormalities and restore mitochondrial functions in diabetic TH mice.

Mitochondrial Dysfunctioning Induced by Hyperglycemia in the Liver Tissues of Diabetic Mice, TALLYHO/JngJ Strain and Ameliorative Action of a Small Peptide, SS31

Type 2 Diabetes mellitus (T2DM) has become a major public health issue associated with high risk of late onset of Alzheimer’s disease (LOAD). Mitochondrial dysfunction is one of the molecular events that occurs in the LOAD pathophysiology. The present study was planned to investigate the molecular alterations induced by hyperglycemia in the mitochondria of diabetic mice and further explore the possible ameliorative role of mitochondria-targeted small peptide, SS31 in diabetic mice. For this purpose, we used a polygenic mouse model of type 2 diabetes, TALLYHO/JngJ (TH), and nondiabetic, SWR/J mice strains. The diabetic status in TH mice was confirmed by carrying out at 8 weeks of age. The 24 weeks old experimental animals were segregated into three groups: Nondiabetic controls (SWR/J mice), diabetic (TH mice) and, SS31 treated diabetic TH mice. mRNA and protein expression levels of mitochondrial proteins were investigated in all the study groups in the liver tissues using qPCR and immunoblot analysis. Also, the mitochondrial functions including H2O2 production, ATP generation and lipid peroxidation were assessed in all the groups. Mitochondrial dysfunction was observed in TH mice as evident by significantly elevated H2O2 production, lipid peroxidation and reduced ATP production. The mRNA expression and Western blot analysis of mitochondrial dynamics (Drp1 and Fis1 – fission; Mfn1, Mfn2 and Opa1 -fusion), and biogenesis (PGC-1α, Nrf1, Nrf2 and TFAM) genes were significantly altered in diabetic TH mice. Furthermore, SS31 treatment helps in a significant reduction the mitochondrial abnormalities and restore mitochondrial functions in diabetic TH mice.

Mitochondria-Targeted Small Peptide, SS31 Ameliorates Diabetes Induced Mitochondrial Dynamics in Male TallyHO/JngJ Mice.

The escalating burden of type 2 diabetes (T2D) and its related complications has become a major public health challenge worldwide. Substantial evidence indicates that T2D is one of the culprits for the high prevalence of Alzheimer's disease (AD) in diabetic subjects. This study aimed to investigate the possible mitochondrial alterations in the pancreas induced by hyperglycemia in diabetes. We used a diabetic TallyHO/JngJ (TH) and non-diabetic, SWR/J mice strains. The diabetic and non-diabetic status in animals was assessed by performing intraperitoneal glucose tolerance test at four time points, i.e., 4, 8, 16, and 24weeks of age. We divided 24-week-old TH and SWR/J mice into 3 groups: controls, diabetic TH mice, and diabetic TH mice treated with SS31 peptide. After the treatment of male TH mice with SS31, intraperitoneally, for 4weeks, we studied mitochondrial dynamics, biogenesis, and function. The mRNA and protein expression levels of mitochondrial proteins were evaluated using qPCR and immunoblot analysis. The diabetic mice after 24weeks of age showed overt pancreatic injury as demonstrated by disintegration and atrophy of β cells with vacuolization and reduced islet size. Mitochondrial dysfunction was observed in TH mice, as evidenced by significantly elevated H2O2 production, lipid peroxidation, and reduced ATP production. Furthermore, mRNA expression and immunoblot analysis of mitochondrial dynamics genes were significantly affected in diabetic mice, compared with controls. However, treatment of animals with SS31 reduced mitochondrial dysfunction and restored most of the mitochondrial functions and mitochondrial dynamics processes to near normal in TH mice. In conclusion, mitochondrial dysfunction is established as one of the molecular events that occur in the pathophysiology of T2D. Further, SS31 treatment may confer protection against the mitochondrial alterations induced by hyperglycemia in diabetic TallyHO/JngJ mice.

Converging evidence points towards a role of insulin signaling in regulating compulsive behavior

Obsessive–compulsive disorder (OCD) is a neuropsychiatric disorder with childhood onset, and is characterized by intrusive thoughts and fears (obsessions) that lead to repetitive behaviors (compulsions). Previously, we identified insulin signaling being associated with OCD and here, we aim to further investigate this link in vivo. We studied TALLYHO/JngJ (TH) mice, a model of type 2 diabetes mellitus, to (1) assess compulsive and anxious behaviors, (2) determine neuro-metabolite levels by 1 H magnetic resonance spectroscopy (MRS) and brain structural connectivity by diffusion tensor imaging (DTI), and (3) investigate plasma and brain protein levels for molecules previously associated with OCD (insulin, Igf1, Kcnq1, and Bdnf) in these subjects. TH mice showed increased compulsivity-like behavior (reduced spontaneous alternation in the Y-maze) and more anxiety (less time spent in the open arms of the elevated plus maze). In parallel, their brains differed in the white matter microstructure measures fractional anisotropy (FA) and mean diffusivity (MD) in the midline corpus callosum (increased FA and decreased MD), in myelinated fibers of the dorsomedial striatum (decreased FA and MD), and superior cerebellar peduncles (decreased FA and MD). MRS revealed increased glucose levels in the dorsomedial striatum and increased glutathione levels in the anterior cingulate cortex in the TH mice relative to their controls. Igf1 expression was reduced in the cerebellum of TH mice but increased in the plasma. In conclusion, our data indicates a role of (abnormal) insulin signaling in compulsivity-like behavior.

Metabolic Syndrome and Salt-Sensitive Hypertension in Polygenic Obese TALLYHO/JngJ Mice: Role of Na/K-ATPase Signaling.

We have demonstrated that Na/K-ATPase acts as a receptor for reactive oxygen species (ROS), regulating renal Na+ handling and blood pressure. TALLYHO/JngJ (TH) mice are believed to mimic the state of obesity in humans with a polygenic background of type 2 diabetes. This present work is to investigate the role of Na/K-ATPase signaling in TH mice, focusing on susceptibility to hypertension due to chronic excess salt ingestion. Age-matched male TH and the control C57BL/6J (B6) mice were fed either normal diet or high salt diet (HS: 2, 4, and 8% NaCl) to construct the renal function curve. Na/K-ATPase signaling including c-Src and ERK1/2 phosphorylation, as well as protein carbonylation (a commonly used marker for enhanced ROS production), were assessed in the kidney cortex tissues by Western blot. Urinary and plasma Na+ levels were measured by flame photometry. When compared to B6 mice, TH mice developed salt-sensitive hypertension and responded to a high salt diet with a significant rise in systolic blood pressure indicative of a blunted pressure-natriuresis relationship. These findings were evidenced by a decrease in total and fractional Na+ excretion and a right-shifted renal function curve with a reduced slope. This salt-sensitive hypertension correlated with changes in the Na/K-ATPase signaling. Specifically, Na/K-ATPase signaling was not able to be stimulated by HS due to the activated baseline protein carbonylation, phosphorylation of c-Src and ERK1/2. These findings support the emerging view that Na/K-ATPase signaling contributes to metabolic disease and suggest that malfunction of the Na/K-ATPase signaling may promote the development of salt-sensitive hypertension in obesity. The increased basal level of renal Na/K-ATPase-dependent redox signaling may be responsible for the development of salt-sensitive hypertension in polygenic obese TH mice.

Light at night exacerbates metabolic dysfunction in a polygenic mouse model of type 2 diabetes mellitus

AimsElectric lighting is beneficial to modern society; however, it is becoming apparent that light at night (LAN) is not without biological consequences. Several studies have reported negative effects of LAN on health and behavior in humans and nonhuman animals. Exposure of non-diabetic mice to dim LAN impairs glucose tolerance, whereas a return to dark nights (LD) reverses this impairment. We predicted that exposure to LAN would exacerbate the metabolic abnormalities in TALLYHO/JngJ (TH) mice, a polygenic model of type 2 diabetes mellitus (T2DM). Materials and methodsWe exposed 7-week old male TH mice to either LD or LAN for 8–10 weeks in two separate experiments. After 8 weeks of light treatment, we conducted intraperitoneal glucose tolerance testing (ipGTT) followed by intraperitoneal insulin tolerance testing (ipITT). In Experiment 1, all mice were returned to LD for 4 weeks, and ipITT was repeated. Key findingsThe major results of this study are i) LAN exposure for 8 weeks exacerbates glucose intolerance and insulin resistance ii) the effects of LAN on insulin resistance are reversed upon return to LD, iii) LAN exposure results in a greater increase in body weight compared to LD exposure, iv) LAN increases the incidence of mice developing overt T2DM, and v) LAN exposure decreases survival of mice with T2DM. SignificanceIn conclusion, LAN exacerbated metabolic abnormalities in a polygenic mouse model of T2DM, and these effects were reversed upon return to dark nights. The applicability of these findings to humans with T2DM needs to be determined.

Ucp1 and metabolism-related gene expression response to high fat diets in brown adipose tissue of TALLYHO/JngJ vs. C57BL/6J mice

In the midst of the ongoing obesity epidemic, brown adipose tissue (BAT) has emerged as a potential therapeutic target. BAT is a thermogenic organ in mammals that is characterized by adipocytes with numerous mitochondria. BAT uses cellular free fatty acids derived from the lipolysis of triglyceride droplets to generate heat via the action of uncoupling protein 1 (Ucp1), located in the inner mitochondrial membrane. In this study, we analyzed mRNA and protein levels of Ucp1 and genes related to inflammation, mitochondrial biogenesis, and lipolysis in BAT of the TALLYHO/JngJ (TH) mouse, a polygenic model of obesity and type 2 diabetes. At four weeks of age, TH and C57BL/6J (B6) mice were weaned onto chow or high fat (HF) diets. At twenty weeks of age, mice were killed, and interscapular BAT was collected. BAT of TH mice appeared discolored and larger than that of B6. mRNA and protein levels in BAT were measured using qPCR and western blot analysis, respectively. There were no significant differences in Ucp1 mRNA levels between TH and B6 mice on either diet. Inflammatory marker interleukin 6 (IL6) mRNA levels were significantly increased in TH mice on HF diets compared to other groups. Interestingly, HF diets increased adipose triglyceride lipase (ATGL) mRNA levels in B6 mice, but not in TH. In summary, we observed genotype-dependent responses to HF diets for IL6 and ATGL expressions in BAT of TH and B6 mice. These results may signify increased inflammation and reduced lipolysis in BAT during the development of obesity.

Model-based pharmacokinetic and pharmacodynamic analysis for acute effects of a small molecule inhibitor of diacylglycerol acyltransferase-1 in the TallyHo/JngJ polygenic mouse

The purpose of this study was to evaluate the acute effect of a small molecule inhibitor of DGAT-1 on triglycerides (TG) and cholesterol in polygenic type 2 diabetic TallyHo/JngJ (TH) mice. PF-04620110, a potent and selective DGAT-1 inhibitor, was used as a model compound in this study and which was administered to TH and ICR mice.The concentration of the model compound that produced 50% of maximum lowering of TG level (IC50) in TH mice was not significantly different from that in ICR mice, when estimated using the model-based pharmacokinetic and pharmacodynamic assay, a two-compartmental model and an indirect response model.The clearance of the inhibitor in TH mice was fivefold higher than that in ICR mice, suggesting significantly altered pharmacokinetics. Moreover, the in vitro metabolic elimination kinetic parameters (ke,met), determined using liver microsomes from TH and ICR mice were 1.24 ± 0.14 and 0.174 ± 0.116 min−1, respectively.Thus, we report that the differences in the acute effects of the small molecule DAGT-1 inhibitor between TH mice and ICR mice can be attributed to altered pharmacokinetics caused by an altered metabolic rate for the compound in TH mice.

Canagliflozin Improves Glycemic Control and Beta-Cell Mass in the TallyHo Polygenic Model of Type 2 Diabetes

SGLT2 inhibitors reduce insulin resistance and may improve beta-cell function in humans with T2D. We studied the effects of Canagliflozin (Cana) on glucose homeostasis, islet architecture and endocrine cell fate in male TallyHO/JngJ (TH) mice, a new model of T2D, which mimics many aspects of polygenic T2D in humans. By 8 weeks of age, all TH mice developed moderate obesity and hyperglycemia compared to control SWR/J mice; ∼60% of TH mice converted quickly to overt diabetes, characterized by elevated BG values (>400mg/dL) (HG mice), while the remaining cohort maintained lower BG values (250-400mg/dL) until the end of the study (LG mice). Mice from both groups (HG, LG) were then randomized to receive Chow or Chow-containing Cana (100ppm) diet for 10 weeks, prior to sacrifice. Cana treatment significantly decreased the fasting BG levels only in the HG mice (HG/Cana) compared with untreated HG/Chow mice (207.7±34.6 vs. 452.2±163.4mg/dL, p<0.0001), improved glucose and insulin excursion curves during an ipGTT (p<0.0001 for AUC values) and decreased HbA1c values (4.3±0.7 vs. 6.2±0.93%, p<0.0001). Non-fasting plasma insulin and C-peptide levels, pancreatic insulin content and HOMA-B index were all significantly higher in HG/Cana than in HG/Chow mice, suggesting improved beta-cell function by Cana. Immunofluorescence staining for islet hormones showed that, compared to untreated animals, Cana reestablished the islet area and the beta-cell number/islet in HG mice (possibly due to reduced apoptosis of beta-cells), in addition to decreased number of alpha- and delta-cells/islet. In HG/Cana mice, the majority of Ins+ cells expressed the glucose transporter Glut2, while its expression was undetectable in Ins+ cells of the HG/Chow mice, further suggesting an improvement in glucose sensing capability of beta-cells with Cana treatment. Our study shows that Cana has beneficial effects on preserving beta-cell mass, identity and function in a model of early onset T2D. Disclosure I. Popescu: None. G.M. Mussman: None. C.B. Hughes: None. T.J. Janes: None. P. Ray: None. R. Bunn: None. J. Fowlkes: None. K.M. Thrailkill: None.

Intermittent Hypoxia Exacerbates Pancreatic β-Cell Dysfunction in A Mouse Model of Diabetes Mellitus

The effects of intermittent hypoxia (IH) on pancreatic function in the presence of diabetes and the underlying mechanisms are unclear. We hypothesized that IH would exacerbate pancreatic β-cell dysfunction and alter the fatty acids in the male Tallyho/JngJ (TH) mouse, a rodent model of type 2 diabetes. TH mice were exposed for 14 d to either 8 h of IH or intermittent air (IA), followed by an intraperitoneal glucose tolerance test (IPGTT) and tissue harvest. The effect of IH on insulin release was determined by using a β3-adrenergic receptor (AR) agonist. During IH, pancreatic tissue pO2 decreased from 20.4 ± 0.9 to 5.7 ± 2.6 mm Hg, as determined by electron paramagnetic resonance oximetry. TH mice exposed to IH exhibited higher plasma glucose levels during the IPGTT (P < 0.001) while the insulin levels tended to be lower (P = 0.06). Pancreatic islets of the IH group showed an enhancement of the caspase-3 staining (P = 0.002). IH impaired the β-AR agonist-mediated insulin release (P < 0.001). IH increased the levels of the total free fatty acids and saturated fatty acids (palmitic and stearic acids), and decreased levels of the monounsaturated fatty acids in the pancreas and plasma. Ex vivo exposure of pancreatic islets to palmitic acid suppressed insulin secretion and decreased islet cell viability. Intermittent hypoxia increases pancreatic apoptosis and exacerbates dysfunction in a polygenic rodent model of diabetes. An increase in free fatty acids and a shift in composition towards long chain saturated fatty acid species appear to mediate these effects.

Reduced aldehyde dehydrogenase activity and arginine vasopressin receptor 2 expression in the kidneys of male TALLYHO/JngJ mice of prediabetic age

The TALLYHO/JngJ (TH) mouse is a novel polygenic model of type 2 diabetes and exhibits obesity, hyperglycemia (males), hyperinsulinemia, hyperlipidemia, and enlarged pancreatic islets. Since the kidney is damaged by hyperglycemia in other animal models, the present study aimed to determine the kidney phenotype of TH mice using immunoblot and histological analyses of the kidneys of 6-week-old (prediabetic) and 16-week-old TH mice. Interestingly, even 6-week-old male TH mice showed significant increases in kidney weight, compared to C57BL/B6 (B6) mice. Cuboidal parietal epithelium was observed in the Bowman's capsule in male TH mice at the prediabetic age. Water accumulated inside the kidneys of male TH mice in an age-dependent manner, but not in B6 mice. Since Swr/J mice are reported to develop diabetes insipidus and share 86.8% genotype homology with TH mice, the expression level of arginine vasopressin receptor 2 (AVPR2), a candidate protein for diabetes insipidus, was examined and determined to be significantly reduced in the kidneys of prediabetic male TH mice, compared to B6 mice. Aldehyde dehydrogenase (ALDH) activity in the kidneys of prediabetic male TH mice was significantly lower than that in age-matched male B6 mice, while there were no differences between female TH and B6 mice. These results suggest that the kidney phenotype of prediabetic TH mice occurs only in males, accompanied by a reduction in ALDH activity and AVPR2 expression. The kidney phenotype of male TH mice at a prediabetic age becomes evident before the onset of diabetes.

Prominent Bone Loss Mediated by RANKL and IL-17 Produced by CD4+ T Cells in TallyHo/JngJ Mice

Increasing evidence that decreased bone density and increased rates of bone fracture are associated with abnormal metabolic states such as hyperglycemia and insulin resistance indicates that diabetes is a risk factor for osteoporosis. In this study, we observed that TallyHo/JngJ (TH) mice, a polygenic model of type II diabetes, spontaneously developed bone deformities with osteoporotic features. Female and male TH mice significantly gained more body weight than control C57BL/6 mice upon aging. Interestingly, bone density was considerably decreased in male TH mice, which displayed hyperglycemia. The osteoblast-specific bone forming markers osteocalcin and osteoprotegerin were decreased in TH mice, whereas osteoclast-driven bone resorption markers such as IL-6 and RANKL were significantly elevated in the bone marrow and blood of TH mice. In addition, RANKL expression was prominently increased in CD4+ T cells of TH mice upon T cell receptor stimulation, which was in accordance with enhanced IL-17 production. IL-17 production in CD4+ T cells was directly promoted by treatment with leptin while IFN-γ production was not. Moreover, blockade of IFN-γ further increased RANKL expression and IL-17 production in TH-CD4+ T cells. In addition, the osteoporotic phenotype of TH mice was improved by treatment with alendronate. These results strongly indicate that increased leptin in TH mice may act in conjunction with IL-6 to preferentially stimulate IL-17 production in CD4+ T cells and induce RANKL-mediated osteoclastogenesis. Accordingly, we propose that TH mice could constitute a beneficial model for osteoporosis.

Genetic and genomic analysis of hyperlipidemia, obesity and diabetes using (C57BL/6J × TALLYHO/JngJ) F2 mice.

BackgroundType 2 diabetes (T2D) is the most common form of diabetes in humans and is closely associated with dyslipidemia and obesity that magnifies the mortality and morbidity related to T2D. The genetic contribution to human T2D and related metabolic disorders is evident, and mostly follows polygenic inheritance. The TALLYHO/JngJ (TH) mice are a polygenic model for T2D characterized by obesity, hyperinsulinemia, impaired glucose uptake and tolerance, hyperlipidemia, and hyperglycemia.ResultsIn order to determine the genetic factors that contribute to these T2D related characteristics in TH mice, we interbred TH mice with C57BL/6J (B6) mice. The parental, F1, and F2 mice were phenotyped at 8, 12, 16, 20, and 24 weeks of age for 4-hour fasting plasma triglyceride, cholesterol, insulin, and glucose levels and body, fat pad and carcass weights. The F2 mice were genotyped genome-wide and used for quantitative trait locus (QTL) mapping. We also applied a genetical genomic approach using a subset of the F2 mice to seek candidate genes underlying the QTLs. Major QTLs were detected on chromosomes (Chrs) 1, 11, 4, and 8 for hypertriglyceridemia, 1 and 3 for hypercholesterolemia, 4 for hyperglycemia, 11 and 1 for body weight, 1 for fat pad weight, and 11 and 14 for carcass weight. Most alleles, except for Chr 3 and 14 QTLs, increased phenotypic values when contributed by the TH strain. Fourteen pairs of interacting loci were detected, none of which overlapped the major QTLs. The QTL interval linked to hypercholesterolemia and hypertriglyceridemia on distal Chr 1 contains Apoa2 gene. Sequencing analysis revealed polymorphisms of Apoa2 in TH mice, suggesting Apoa2 as the candidate gene for the hyperlipidemia QTL. Gene expression analysis added novel information and aided in selection of candidates underlying the QTLs.ConclusionsWe identified several genetic loci that affect the quantitative variations of plasma lipid and glucose levels and obesity traits in a TH × B6 intercross. Polymorphisms in Apoa2 gene are suggested to be responsible for the Chr 1 QTL linked to hypercholesterolemia and hypertriglyceridemia. Further, genetical genomic analysis led to potential candidate genes for the QTLs.

Proteomic analysis of pancreas in a polygenic mouse model of type 2 diabetes

TALLYHO/JngJ (TH) mice are a polygenic model for type 2 diabetes. We conducted a proteomic analysis in pancreas using 2D‐DIGE and mass spectrometry to identify molecules pathologically relevant to the diabetes in TH mice. Total protein was extracted from pancreas of TH and C57BL/6J mice and labeled with CyDye. Isoelectric focusing in the first dimension was conducted at pH 3‐10 to separate proteins based on pI, and in the second dimension in 8‐14% gradient SDS‐PAGE to separate proteins based on size. Differentially expressed protein spots were excised, digested with trypsin and subjected to MALDI‐TOF mass spectrometry. We observed changes in protein amounts or evidence of modifications in antioxidant defense proteins and heat shock proteins in TH mice. Proteins involved in growth and survival of pancreatic beta‐cells were also identified. In summary, the proteins identified in this study may provide links of molecular processes to the development of diabetes in TH mice, and their respective genes may serve as candidates for susceptibility genes in this polygenic model. Supported in part by NIH/NIDDK‐1R01DK077202‐01A2, AHA‐0855300E, &amp; pilot and feasibility grant from the UT Obesity Research Center.

Effects of Food Restriction on Phenotypes of TALLYHO/JngJ Mouse

Background: Food restriction has been reported to ameliorate diabetes and obesity. In this study, we examined the effects of the food restriction on phenotypes of TALLYHO/JngJ (TH) mouse, a recently developed diabetic model animal. Methods: 3 week-old TH mice were divided into 2 groups (n = 20 each for food-restricted (THR) and free-fed (THF)) and THR mice were fed the same amount of food as normal control mice (C57BL/6, n = 20). Body weight was weekly monitored till 14 weeks of age. The half of animals were sacrificed at 8 weeks of age, and liver, kidney, and fat weight were measured. The histopathology of liver and brown fat tissues and mRNA expression of leptin in adipose tissue were analyzed. The oral glucose tolerance test and insulin resistance test was done at 14 weeks of age. The plasma concentrations of glucose, free fatty acid, triglyceride, cholesterol and leptin were analyzed. Results: The THR mice had lower body weights than the THF mice, similar to C57BL/6 mice, with reduced fat deposition in liver and brown fat tissue. The plasma levels of glucose, triglyceride and free fatty acid were decreased in the THR group. The THR mice, however, carried more fat than normal mice, with increased plasma leptin concentration and leptin mRNA expression in fats and no alteration in plasma cholesterol levels. Furthermore, the THR mice revealed glucose intolerance with impaired after-meal insulin secretion and slight insulin resistance Conclusion: The food restriction apparently ameliorated the obesity and di abetic phenotypes of TH mice. However, plasma concentration of cholesterol were not improved in THR mice with increased adiposity index and glucose intolerance, suggesting the genetically prone tendency of obesity and diabetes development in TH mice possibly with an impairment in cholesterol metabolism. (KOREAN DIABETES J 32:304-316, 2008)

Phenotypic characterization of polygenic type 2 diabetes in TALLYHO/JngJ mice

The TALLYHO/JngJ (TH) strain is a newly established, polygenic mouse model for type 2 diabetes (T2D) and obesity, and we have previously reported some key physiological features of this model after the overt onset of diabetes. In the present work, we conducted a comprehensive phenotypic characterization of TH in order to completely characterize this new and relevant model for human T2D and obesity. We monitored the development of obesity and diabetes starting at 4 weeks of age by measuring body weight, glucose tolerance, and plasma levels of insulin, glucose, and triglyceride. Additionally, histological alterations in the pancreas and glucose uptake and glucose transporter 4 (GLUT4) content in soleus muscle were also examined. Compared with age- and sex-matched C57BL/6J (B6) mice, both male and female TH mice were significantly heavier, hyperleptinemic, and hyperinsulinemic at 4 weeks of age, without glucose intolerance or hyperglycemia. TH mice maintained higher body weights throughout the study period of 16 weeks. The hyperinsulinemia in TH mice worsened with age, but to a lesser degree in females than in males. Both the male and the female TH mice had enlarged pancreatic islets. Male TH mice showed impaired glucose tolerance at 8 weeks that became more prominent at 16 weeks. Plasma glucose levels continuously increased with age in male TH mice resulting in frank diabetes, while female TH mice remained normoglycemic throughout the study. Impaired glucose tolerance and hyperglycemia in male TH mice were accompanied by impaired 2-deoxyglucose uptake in the soleus muscle at basal and insulin-stimulated states, but without any reduction in GLUT4 content. Interestingly, male TH mice exhibited a drastic elevation in plasma triglyceride levels in the pre-diabetic stage that was maintained throughout the study. These findings suggest that obesity and insulin resistance are an inherent part of the TH phenotype and glucose intolerance is evident preceding progression to overt diabetes in male TH mice.