Laboratory animals exhibiting obesity and diabetes syndromes

Restoration of the ER stress response protein TDAG51 in hepatocytes mitigates NAFLD in mice

Endoplasmic reticulum stress is associated with insulin resistance and the development of nonalcoholic fatty liver disease. Deficiency of the endoplasmic reticulum stress response T-cell death-associated gene 51 (TDAG51) (TDAG51-/-) in mice promotes the development of high-fat diet (HFD)-induced obesity, fatty liver, and hepatic insulin resistance. However, whether this effect is due specifically to hepatic TDAG51 deficiency is unknown. Here, we report that hepatic TDAG51 protein levels are consistently reduced in multiple mouse models of liver steatosis and injury as well as in liver biopsies from patients with liver disease compared to normal controls. Delivery of a liver-specific adeno-associated virus (AAV) increased hepatic expression of a TDAG51-GFP fusion protein in WT, TDAG51-/-, and leptin-deficient (ob/ob) mice. Restoration of hepatic TDAG51 protein was sufficient to increase insulin sensitivity while reducing body weight and fatty liver in HFD fed TDAG51-/- mice and in ob/ob mice. TDAG51-/- mice expressing ectopic TDAG51 display improved Akt (Ser473) phosphorylation, post-insulin stimulation. HFD-fed TDAG51-/- mice treated with AAV-TDAG51-GFP displayed reduced lipogenic gene expression, increased beta-oxidation and lowered hepatic and serum triglycerides, findings consistent with reduced liver weight. Further, AAV-TDAG51-GFP-treated TDAG51-/- mice exhibited reduced hepatic precursor and cleaved sterol regulatory-element binding proteins (SREBP-1 and SREBP-2). In vitro studies confirmed the lipid-lowering effect of TDAG51 overexpression in oleic acid-treated Huh7 cells. These studies suggest that maintaining hepatic TDAG51 protein levels represents a viable therapeutic approach for the treatment of obesity and insulin resistance associated with nonalcoholic fatty liver disease.

Contribution of animal models to diabetes research: Its history, significance, and translation to humans

Diabetes mellitus is still expanding globally and is epidemic in developing countries. The combat of this plague has caused enormous economic and social burdens related to a lowered quality of life in people with diabetes. Despite recent significant improvements of life expectancy in patients with diabetes, there is still a need for efforts to elucidate the complexities and mechanisms of the disease processes to overcome this difficult disorder. To this end, the use of appropriate animal models in diabetes studies is invaluable for translation to humans and for the development of effective treatment. In this review, a variety of animal models of diabetes with spontaneous onset in particular will be introduced and discussed for their implication in diabetes research.

Feeding Soy Protein Concentrates with Low and High Isoflavones Alters 9 and 18 Weeks Serum Isoflavones and Inflammatory Protein Levels in Lean and Obese Zucker Rats

Soy's anti-inflammatory properties contribute to the health benefits of soy foods. This study was designed to investigate the bioavailability of soy isoflavones and whether the isoflavone content of soy protein concentrate diet would affect serum inflammatory proteins in an obese (fa/fa) Zucker rat model. Six-week-old male lean (L) and obese (O) Zucker rats were fed a casein control diet (C), soy protein concentrate with low isoflavones (SPC-LIF), or soy protein concentrate with high isoflavones (SPC-HIF) (7 rats/dietary group) before being killed at 9 and 18 weeks. Serum samples were analyzed for isoflavones and inflammatory proteins. At both time points, serum total (aglycone + conjugates) genistein, daidzein, and equol concentrations were significantly higher in L-SPC-HIF and O-SPC-HIF groups compared with L-SPC-LIF and O-SPC-LIF groups, respectively, and were not detectable in either L-C or O-C groups. At week 9, serum C-reactive protein (CRP) concentration was significantly lower in O-SPC-HIF group compared with O-C and O-SPC-LIF group, whereas proteins tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) levels did not differ between any groups. At week 18, serum CRP levels in both O-SPC-HIF and O-SPC-LIF groups were significantly lower compared with the O-C group. TNF-α level was higher in the O-SPC-LIF group compared with both O-C and O-SPC-HIF groups, whereas IL-6 levels were not different between any groups. Taken together, feeding Zucker rats SPC-LIF and SPC-HIF diets led to different serum isoflavone concentrations in both L and O Zucker rats and altered CRP and TNF-α levels in obese Zucker rats compared with controls.

Comparative genomic analyses of multiple backcross mouse populations suggest SGCG as a novel potential obesity-modifier gene

To nominate novel disease genes for obesity and type 2 diabetes (T2D), we recently generated two mouse backcross populations of the T2D-susceptible New Zealand Obese (NZO/HI) mouse strain and two genetically different, lean and T2D-resistant strains, 129P2/OlaHsd and C3HeB/FeJ. Comparative linkage analysis of our two female backcross populations identified seven novel body fat-associated quantitative trait loci (QTL). Only the locus Nbw14 (NZO body weight on chromosome 14) showed linkage to obesity-related traits in both backcross populations, indicating that the causal gene variant is likely specific for the NZO strain as NZO allele carriers in both crosses displayed elevated body weight and fat mass. To identify candidate genes for Nbw14, we used a combined approach of gene expression and haplotype analysis to filter for NZO-specific gene variants in gonadal white adipose tissue (gWAT), defined as the main QTL-target tissue. Only two genes, Arl11 and Sgcg, fulfilled our candidate criteria. In addition, expression QTL analysis revealed cis-signals for both genes within the Nbw14 locus. Moreover, retroviral overexpression of Sgcg in 3 T3-L1 adipocytes resulted in increased insulin-stimulated glucose uptake. In humans, mRNA levels of SGCG correlated with BMI and body fat mass exclusively in diabetic subjects, suggesting that SGCG may present a novel marker for metabolically unhealthy obesity. In conclusion, our comparative-cross analysis could substantially improve the mapping resolution of the obesity locus Nbw14. Future studies will shine light on the mechanism by which Sgcg may protect from the development of obesity.

The transcription factors CREBH, PPARa, and FOXO1 as critical hepatic mediators of diet-induced metabolic dysregulation

The liver is a critical mediator of lipid and/or glucose homeostasis and is a primary organ involved in dynamic changes during feeding and fasting. Additionally, hepatic-centric pathways are prone to dysregulation during pathophysiological states including metabolic syndrome (MetS) and non-alcoholic fatty liver disease. Omics platforms and GWAS have elucidated genes related to increased risk of developing MetS and related disorders, but mutations in these metabolism-related genes are rare and cannot fully explain the increasing prevalence of MetS-related pathologies worldwide. Complex interactions between diet, lifestyle, environmental factors, and genetic predisposition jointly determine inter-individual variability of disease risk. Given the complexity of these interactions, researchers have focused on master regulators of metabolic responses incorporating and mediating the impact of multiple environmental cues. Transcription factors are DNA binding, terminal executors of signaling pathways that modulate the cellular responses to complex metabolic stimuli and are related to the control of hepatic lipid and glucose homeostasis. Among numerous hepatic transcription factors involved in regulating metabolism, three emerge as key players in transducing nutrient sensing, which are dysregulated in MetS-related perturbations in both clinical and preclinical studies: cAMP Responsive Element Binding Protein 3 Like 3 (CREB3L3), Peroxisome Proliferator Activated Receptor Alpha (PPAR), and Forkhead Box O1 (FOXO1). Additionally, these three transcription factors appear to be amenable to dietary and/or nutrient-based therapies, being potential targets of nutritional therapy. In this review we aim to describe the activation, regulation, and impact of these transcription factors in the context of metabolic homeostasis. We also summarize their perspectives in MetS and nutritional therapies.

The Inflammatory Profile of Obesity and the Role on Pulmonary Bacterial and Viral Infections

Obesity is a globally increasing health problem, entailing diverse comorbidities such as infectious diseases. An obese weight status has marked effects on lung function that can be attributed to mechanical dysfunctions. Moreover, the alterations of adipocyte-derived signal mediators strongly influence the regulation of inflammation, resulting in chronic low-grade inflammation. Our review summarizes the known effects regarding pulmonary bacterial and viral infections. For this, we discuss model systems that allow mechanistic investigation of the interplay between obesity and lung infections. Overall, obesity gives rise to a higher susceptibility to infectious pathogens, but the pathogenetic process is not clearly defined. Whereas, viral infections often show a more severe course in obese patients, the same patients seem to have a survival benefit during bacterial infections. In particular, we summarize the main mechanical impairments in the pulmonary tract caused by obesity. Moreover, we outline the main secretory changes within the expanded adipose tissue mass, resulting in chronic low-grade inflammation. Finally, we connect these altered host factors to the influence of obesity on the development of lung infection by summarizing observations from clinical and experimental data.

Strain-based and sex-biased differences in adrenal and pancreatic gene expression between KK/HlJ and C57BL/6 J mice

Background

The ever-increasing prevalence of diabetes and associated comorbidities serves to highlight the necessity of biologically relevant small-animal models to investigate its etiology, pathology and treatment. Although the C57BL/6 J model is amongst the most widely used mouse model due to its susceptibility to diet-induced obesity (DIO), there are a number of limitations namely [1] that unambiguous fasting hyperglycemia can only be achieved via dietary manipulation and/or chemical ablation of the pancreatic beta cells. [2] Heterogeneity in the obesogenic effects of hypercaloric feeding has been noted, together with sex-dependent differences, with males being more responsive. The KK mouse strain has been used to study aspects of the metabolic syndrome and prediabetes. We recently conducted a study which characterized the differences in male and female glucocentric parameters between the KK/HlJ and C57BL/6 J strains as well as diabetes-related behavioral differences (Inglis et al. 2019). In the present study, we further characterize these models by examining strain- and sex-dependent differences in pancreatic and adrenal gene expression using Affymetrix microarray together with endocrine-associated serum analysis.

Results

In addition to strain-associated differences in insulin tolerance, we found significant elevations in KK/HlJ mouse serum leptin, insulin and aldosterone. Additionally, glucagon and corticosterone were elevated in female mice of both strains. Using 2-factor ANOVA and a significance level set at 0.05, we identified 10,269 pancreatic and 10,338 adrenal genes with an intensity cut-off of ≥2.0 for all 4 experimental groups. In the pancreas, gene expression upregulated in the KK/HlJ strain related to increased insulin secretory granule biofunction and pancreatic hyperplasia, whereas ontology of upregulated adrenal differentially expressed genes (DEGs) related to cell signaling and neurotransmission. We established a network of functionally related DEGs commonly upregulated in both endocrine tissues of KK/HlJ mice which included the genes coding for endocrine secretory vesicle biogenesis and regulation: PCSK2, PCSK1N, SCG5, PTPRN, CHGB and APLP1. We also identified genes with sex-biased expression common to both strains and tissues including the paternally expressed imprint gene neuronatin.

Conclusion

Our novel results have further characterized the commonalities and diversities of pancreatic and adrenal gene expression between the KK/HlJ and C57BL/6 J strains as well as differences in serum markers of endocrine physiology.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-021-07495-4.

Growth Performance After Agouti-Signaling Protein 1 (Asip1) Overexpression in Transgenic Zebrafish

The melanocortin system is a key structure in the regulation of energy balance. Overexpression of inverse agonists, agouti-signaling protein (ASIP), and agouti-related protein (AGRP) results in increased food intake, linear growth, and body weight. ASIP regulates dorsal-ventral pigment polarity through melanocortin 1 receptor (MC1R) and overexpression induces obesity in mice by binding to central MC4R. Asip1 overexpression in transgenic zebrafish (asip1-Tg) enhances growth, yet experiments show fish overexpressing Asip1 do not develop obesity even under severe feeding regimes. Asip1-Tg fish do not need to eat more to grow larger and faster; thus, increased food efficiency can be observed. In addition, asip1-Tg fish reared at high density are able to grow far more than wild-type (WT) fish reared at low density, although asip1-Tg fish seem to be more sensitive to crowding stress than WT fish, thus making the melanocortin system a target for sustainable aquaculture, especially as the U.S. Food and Drug Association has recently approved transgenic fish trading.

Eurocristatine, a plant alkaloid from Eurotium cristatum, alleviates insulin resistance in db/db diabetic mice via activation of PI3K/AKT signaling pathway

Eurocristatine (ECT) is an alkaloid isolated from Eurotium cristatum, and it has been used in multiple applications. However, its use as a treatment for type 2 diabetes mellitus (T2DM) has not yet been reported. In this study, we investigated the anti-T2DM effect of ECT and explored its potential molecular mechanism. In vivo, after treatment with ECT (20, 40 mg/kg) for 6 weeks, fasting blood glucose (FBG) was remarkably reduced in db/db mice. Moreover, glucose tolerance, insulin sensitivity and hyperinsulinemia were ameliorated treatment with ECT. The values of aspartate aminotransferase (AST) and alanine aminotransferase (ALT) also showed that ECT could alleviate liver toxicity caused by diabetes in db/db mice. In vitro, ECT (15 and 30 μM) alleviated insulin resistance by increasing glucose consumption, glucose uptake and glycogen content in high glucose-induced HepG2 cells. The Western blotting (WB) results showed that ECT could upregulate the expression of phosphatidylinositol 3-kinase (PI3K), increase the phosphorylation of insulin receptor substrate 1 (IRS1) and protein kinase B (AKT) in vivo and in vitro. Besides, ECT improved the glycogen content by inhibiting the expression of glycogen synthase kinase3β (GSK3β) and promoting that of glycogen synthase (GS). Furthermore, administration of the PI3K/AKT signaling pathway inhibitor LY294002 abolished the beneficial effects of ECT. These findings are the first to verify that ECT has the potential to improve glucose metabolism and alleviate insulin resistance by activating the PI3K/AKT signaling pathway in db/db mice.

Thirty Mouse Strain Survey of Voluntary Physical Activity and Energy Expenditure: Influence of Strain, Sex and Day-Night Variation

We measured indirect calorimetry and activity parameters, VO₂ and VCO₂ to extract respiratory exchange ratio (RER) and energy expenditure in both sexes of 30 inbred mouse strains of 6 genetic families at 9–13 weeks during one photophase and the subsequent scotophase. We observed a continuous distribution of all traits. While males had higher body weights than females, we observed no sex difference for food and water intake. All strains drank and fed more during the night even if they displayed no day–night difference in activity traits. Several strains showed absent or weak day–night variation in one or more activity traits and these included FVB and 129X1, males of 129S1, SWR, NZW, and SM, and females of SJL. In general females showed higher rearing and ambulatory activity with 6 and 9 strains, respectively, showing a sex difference. Fine motor movements, like grooming, showed less sex differences. RER underlied a strong day–night difference and no sex effect. Only FVB females and males of the RIIIS and SM strain had no day–night variation. Energy expenditure underlies a large day–night variation which was absent in SWR and in FVB females and RIIIS males. In general, female bodies had a tendency to higher energy expenditure values, which became a significant difference in C3H, MAMy, SM, DBA1, and BUB. Our data illustrate the diversity of these traits in male and female inbred mice and provide a resource in the selection of strains for future studies.

In Vivo and In Vitro Models of Diabetes: A Focus on Pregnancy

Diabetes in pregnancy is associated with an increased risk of poor outcomes, both for the mother and her offspring. Although clinical and epidemiological studies are invaluable to assess these outcomes and the effectiveness of potential treatments, there are certain ethical and practical limitations to what can be assessed in human studies.Thus, both in vivo and in vitro models can aid us in the understanding of the mechanisms behind these complications and, in the long run, towards their prevention and treatment. This review summarizes the existing animal and cell models used to mimic diabetes, with a specific focus on the intrauterine environment. Summary of this review.

Over-expression of miR-34c leads to early-life visceral fat accumulation and insulin resistance

Overweight children and adolescents are at high risk for adult and late life obesity. This report investigates some underlying mechanisms contributing to obesity during early life in an animal model. We generated a strain of transgenic mice, cU2, overexpressing human microRNA 34c, a microRNA functionally implicated in adipogenesis. Male and female cU2 mice exhibit significant weight gain, accompanied by marked increase in abdominal fat mass and metabolic abnormalities, including reduction of both glucose clearance rate and insulin sensitivity, as early as two months of age. Adipogenesis derailment at this early age is suggested by decreased expression of adiponectin, the fat mass and obesity-associated gene, and the adiponectin receptor R1, coupled with a reduction of the brown fat biomarker PAT2 and the adipogenesis inhibitor SIRT1. Notably, adiponectin is an important adipokine and an essential regulator of glucose and fatty acid homeostasis. cU2 mice may provide a crucial animal model for investigating the role of miR-34c in early onset insulin resistance and visceral fat mass increase, contributing to accelerated body weight gain and metabolic disorders. Intervention in this dysregulation may open a new preventive strategy to control early-life weight gain and abnormal insulin resistance, and thus prevalent adult and late life obesity.

Strain and sex-based glucocentric & behavioral differences between KK/HlJ and C57BL/6J mice

INTRODUCTION

Small-animal models are the most widely used preclinical model for studying the etiology, pathology and treatment of diabetes, prediabetes and diabetic comorbidities. Diabetic patients are burdened with higher rates of depression, anxiety and cognitive decline due to inadequate control of blood glucose levels, vascular damage and aberrant CNS insulin signaling. The C57BL/6J model is amongst the most widely used mouse model due to its susceptibility to diet-induced obesity (DIO). This strain has also been well-characterized in behavioral research studies. However the C57BL/6J model has a number of limitations: [1] overt fasting hyperglycemia can only be induced by dietary manipulation and/or chemical ablation of the pancreatic beta cells. [2] There is heterogeneity in the obesogenic response to hypercaloric feeding as well as sex-dependent differences, with males being more responsive. The KK inbred strain has been used to study aspects of the metabolic syndrome and prediabetes due to inherent glucose intolerance, hyperinsulinemia and insulin resistance. However KK/HlJ mice are less well-characterized and there have been fewer behavioral studies reported. The aim of this study was to examine differences in male and female glucocentric parameters between KK/HlJ and C57BL/6J mice, and to compare their performance in a variety of standard behavioral tests relating to general, anxiogenic and cognitive paradigms.

METHODS

Strain differences in male and female KK/HlJ and C57BL/6J mouse adiposity, glucose and insulin parameters were studied together with group differences in standard Open Field, Object Recognition, Elevated Plus Maze, Light-Dark Transition, Porsolt test, Marble Burying, Social Recognition and Morris Water Maze tests. Correlations between behavioral variables were analyzed.

RESULTS AND CONCLUSION

In addition to being uniformly larger, hyperinsulinemic and more insulin intolerant than C57BL/6J mice, we observed marked strain and sex-differences in KK/HlJ behavior. KK/HlJ mice exhibited less locomotor and vertical exploratory behavior in comparison to C57BL/6J, whereas object exploration and novel object discrimination were superior in KK/HlJ mice. Female KK/HlJ mice were faster swimmers, whereas the males exhibited greater spatial cognition and place-learning during the MWM test.

In vitro models to study insulin and glucocorticoids modulation of trimethyltin (TMT)-induced neuroinflammation and neurodegeneration, and in vivo validation in db/db mice

Brain susceptibility to a neurotoxic insult may be increased in a compromised health status, such as metabolic syndrome. Both metabolic syndrome and exposure to trimethyltin (TMT) are known to promote neurodegeneration. In combination the two factors may elicit additive or compensatory/regulatory mechanisms. Combined effects of TMT exposure (0.5-1 μM) and mimicked metabolic syndrome-through modulation of insulin and glucocorticoid (GC) levels-were investigated in three models: tridimensional rat brain cell cultures for neuron-glia effects; murine microglial cell line BV-2 for a mechanistic analysis of microglial reactivity; and db/db mice as an in vivo model of metabolic syndrome. In 3D cultures, low insulin condition significantly exacerbated TMT's effect on GABAergic neurons and promoted TMT-induced neuroinflammation, with increased expression of cytokines and of the regulator of intracellular GC activity, 11β-hydroxysteroid dehydrogenase 1 (11β-Hsd1). Microglial reactivity increased upon TMT exposure in medium combining low insulin and high GC. These results were corroborated in BV-2 microglial cells where lack of insulin exacerbated the TMT-induced increase in 11β-Hsd1 expression. Furthermore, TMT-induced microglial reactivity seems to depend on mineralocorticoid receptor activation. In diabetic BKS db mice, a discrete exacerbation of TMT neurotoxic effects on GABAergic neurons was observed, together with an increase of interleukin-6 (IL-6) and of basal 11β-Hsd1 expression as compared to controls. These results suggest only minor additive effects of the two brain insults, neurotoxicant TMT exposure and metabolic syndrome conditions, where 11β-Hsd1 appears to play a key role in the regulation of neuroinflammation and of its protective or neurodegenerative consequences.

A collective diabetes cross in combination with a computational framework to dissect the genetics of human obesity and Type 2 diabetes

To explore the genetic determinants of obesity and Type 2 diabetes (T2D), the German Center for Diabetes Research (DZD) conducted crossbreedings of the obese and diabetes-prone New Zealand Obese mouse strain with four different lean strains (B6, DBA, C3H, 129P2) that vary in their susceptibility to develop T2D. Genome-wide linkage analyses localized more than 290 quantitative trait loci (QTL) for obesity, 190 QTL for diabetes-related traits and 100 QTL for plasma metabolites in the outcross populations. A computational framework was developed that allowed to refine critical regions and to nominate a small number of candidate genes by integrating reciprocal haplotype mapping and transcriptome data. The efficiency of the complex procedure was demonstrated for one obesity QTL. The genomic interval of 35 Mb with 502 annotated candidate genes was narrowed down to six candidates. Accordingly, congenic mice retained the obesity phenotype owing to an interval that contains three of the six candidate genes. Among these the phospholipase PLA2G4A exhibited an elevated expression in adipose tissue of obese human subjects and is therefore a critical regulator of the obesity locus. Together, our broad and complex approach demonstrates that combined- and comparative-cross analysis exhibits improved mapping resolution and represents a valid tool for the identification of disease genes.

Identification of novel LEPR mutations in Pakistani families with morbid childhood obesity

Background

Mutations in the genes encoding leptin (LEP), the leptin receptor (LEPR), and the melanocortin 4 receptor (MC4R) are known to cause severe early-onset childhood obesity. The aim of the current study was to examine the prevalence of damaging LEP, LEPR, and MC4R mutations in Pakistani families having a recessive heritance of early-onset obesity.

Methods

Using targeted resequencing, the presence of rare mutations in LEP, LEPR, and MC4R, was investigated in individuals from 25 families suspected of having autosomal recessive early-onset obesity. Segregation patterns of variants were assessed based on chip-based genotyping.

Results

Homozygous LEPR variants were identified in two probands. One carried a deletion (c.3260AG) resulting in the frameshift mutation p.Ser1090Trpfs*6, and the second carried a substitution (c.2675C > G) resulting in the missense mutation p.Pro892Arg. Both mutations were located within regions of homozygosity shared only among affected individuals. Both probands displayed early-onset obesity, hyperphagia and diabetes. No mutations were found in LEP and MC4R.

Conclusions

The current study highlights the implication of LEPR mutations in cases of severe early-onset obesity in consanguineous Pakistani families. Through targeted resequencing, we identified novel damaging mutations, and our approach may therefore be utilized in clinical testing or diagnosis of known forms of monogenic obesity with the aim of optimizing obesity treatment.

Electronic supplementary material

The online version of this article (10.1186/s12881-018-0710-x) contains supplementary material, which is available to authorized users.

Two Novel Candidate Genes for Insulin Secretion Identified by Comparative Genomics of Multiple Backcross Mouse Populations

To identify novel disease genes for type 2 diabetes (T2D) we generated two backcross populations of obese and diabetes-susceptible New Zealand Obese (NZO/HI) mice with the two lean mouse strains 129P2/OlaHsd and C3HeB/FeJ. Subsequent whole-genome linkage scans revealed 30 novel quantitative trait loci (QTL) for T2D-associated traits. The strongest association with blood glucose [12 cM, logarithm of the odds (LOD) 13.3] and plasma insulin (17 cM, LOD 4.8) was detected on proximal chromosome 7 (designated Nbg7p, NZO blood glucose on proximal chromosome 7) exclusively in the NZOxC3H crossbreeding, suggesting that the causal gene is contributed by the C3H genome. Introgression of the critical C3H fragment into the genetic NZO background by generating recombinant congenic strains and metabolic phenotyping validated the phenotype. For the detection of candidate genes in the critical region (30-46 Mb), we used a combined approach of haplotype and gene expression analysis to search for C3H-specific gene variants in the pancreatic islets, which appeared to be the most likely target tissue for the QTL. Two genes, Atp4a and Pop4, fulfilled the criteria from our candidate gene approaches. The knockdown of both genes in MIN6 cells led to decreased glucose-stimulated insulin secretion, indicating a regulatory role of both genes in insulin secretion, thereby possibly contributing to the phenotype linked to Nbg7p In conclusion, our combined- and comparative-cross analysis approach has successfully led to the identification of two novel diabetes susceptibility candidate genes, and thus has been proven to be a valuable tool for the discovery of novel disease genes.

A Novel Diabetic Mouse Model for Real-Time Monitoring of Clock Gene Oscillation and Blood Pressure Circadian Rhythm

Diabetic patients have an increased prevalence of blood pressure (BP) circadian rhythm disruption, which is associated with an increased risk of target organ damage and detrimental cardiovascular events. Limited information is available regarding the role of clock genes in the disruption of BP circadian rhythm in diabetes due to the lack of a diabetic animal model that allows real-time monitoring of clock gene oscillation. Here, we generated a novel diabetic db/db-mPer2^Luc mouse model by crossing type 2 diabetic db/db mice with mPer2^Luc knock-in mice. The daily rhythms of BP, heart rate, locomotor activity, and food and water intake were acquired by radiotelemetry or using metabolic chambers. The daily oscillation of mPer2 bioluminescence was recorded by LumiCycle in real-time in tissue explants and using the IVIS system in vivo. Our results show that db/db-mPer2^Luc mice are obese, diabetic, and glucose intolerant. The db/db-mPer2^Luc mice displayed a compromised BP daily rhythm, which was associated with disrupted daily rhythms in baroreflex sensitivity, locomotor activity, and metabolism, but not heart rate or food and water intake. The phase of the mPer2 daily oscillation was advanced to different extents in the explanted peripheral tissues from db/db-mPer2^Luc mice relative to control mice. In contrast, no phase shift was detected in mPer2 daily oscillations in the explanted SCN. Moreover, advanced phase shift of the mPer2 daily oscillation was detected in the liver, kidney and submandibular gland in vivo of db/db-mPer2^Luc mice. In conclusion, the diabetic db/db-mPer2^Luc mouse is a novel animal model that allows real-time monitoring of mPer2 circadian rhythms ex vivo and in vivo. The results from db/db-mPer2^Luc mice suggest that the desynchrony of mPer2 daily oscillation in peripheral tissues contributes to the loss of BP daily oscillation in diabetes.

Lipidomic analysis reveals significant lipogenesis and accumulation of lipotoxic components in ob/ob mouse organs

To further understand the role of lipogenesis and lipotoxicity in the development of obesity and diabetes, lipidomes of various organs from ob/ob mice and their wild type controls were analyzed by shotgun lipidomics at 10, 12, and 16 weeks of age. We observed that the amounts of fatty acyl (FA) chains corresponding to those from de novo synthesis (e.g., 16:0, 16:1, and 18:1 FA) were substantially elevated in ob/ob mice, consistent with increased expression of genes and proteins involved in biosynthesis. Polyunsaturated fatty acid species were moderately increased in the examined tissues of ob/ob mice, since they can only be absorbed from diets or elongated from the ingested n-3 or n-6 FA. Different profiles of FA chains between ob/ob mouse liver and skeletal muscle reflect diverging lipogenesis pathways in these organs. Amounts of vaccenic acids (i.e., 18:1(n-7) FA) in 12- and 16-week ob/ob mouse liver were significantly increased compared to their controls, indicating enhanced de novo synthesis of this acid through 16:1(n-7) FA in the liver starting at 12 weeks of age. Coincidentally, synthesis of triacylglycerol from monoacylglycerol in the liver was also increased in ob/ob mice starting at 12 weeks of age, as revealed by simulation of triacylglycerol synthesis. Moreover, levels of lipotoxic lipid classes were significantly higher in ob/ob mice than their age-matched controls, supporting the notion that elevated lipotoxic components are tightly associated with insulin resistance in ob/ob mice. Taken together, the current study revealed that lipogenesis and lipotoxicity in ob/ob mice likely contribute to insulin resistance and provides great insights into the underlying mechanisms of diabetes and obesity.

Cell-Specific "Competition for Calories" Drives Asymmetric Nutrient-Energy Partitioning, Obesity, and Metabolic Diseases in Human and Non-human Animals

The mammalian body is a complex physiologic “ecosystem” in which cells compete for calories (i.e., nutrient-energy). Axiomatically, cell-types with competitive advantages acquire a greater number of consumed calories, and when possible, increase in size and/or number. Thus, it is logical and parsimonious to posit that obesity is the competitive advantages of fat-cells (adipocytes) driving a disproportionate acquisition and storage of nutrient-energy. Accordingly, we introduce two conceptual frameworks. Asymmetric Nutrient-Energy Partitioning describes the context-dependent, cell-specific competition for calories that determines the partitioning of nutrient-energy to oxidation, anabolism, and/or storage; and Effective Caloric Intake which describes the number of calories available to constrain energy-intake via the inhibition of the sensorimotor appetitive cells in the liver and brain that govern ingestive behaviors. Inherent in these frameworks is the independence and dissociation of the energetic demands of metabolism and the neuro-muscular pathways that initiate ingestive behaviors and energy intake. As we demonstrate, if the sensorimotor cells suffer relative caloric deprivation via asymmetric competition from other cell-types (e.g., skeletal muscle- or fat-cells), energy-intake is increased to compensate for both real and merely apparent deficits in energy-homeostasis (i.e., true and false signals, respectively). Thus, we posit that the chronic positive energy balance (i.e., over-nutrition) that leads to obesity and metabolic diseases is engendered by apparent deficits (i.e., false signals) driven by the asymmetric inter-cellular competition for calories and concomitant differential partitioning of nutrient-energy to storage. These frameworks, in concert with our previous theoretic work, the Maternal Resources Hypothesis, provide a parsimonious and rigorous explanation for the rapid rise in the global prevalence of increased body and fat mass, and associated metabolic dysfunctions in humans and other mammals inclusive of companion, domesticated, laboratory, and feral animals.

Bushen Huoxue Attenuates Diabetes-Induced Cognitive Impairment by Improvement of Cerebral Microcirculation: Involvement of RhoA/ROCK/moesin and Src Signaling Pathways

Type 2 Diabetes mellitus (T2DM) is closely correlated with cognitive impairment and neurodegenerative disease. Bushen Huoxue (BSHX) is a compound Chinese medicine used clinically to treat diabetes-induced cognitive impairment. However, its underlying mechanisms remain unclear. In the present study, KKAy mice, a genetic model of type 2 diabetes with obesity and insulin resistant hyperglycemia, received a daily administration of BSHX for 12 weeks. Blood glucose was measured every 4 weeks. After 12 weeks, BSHX treatment significantly ameliorated the T2DM related insults, including the increased blood glucose, the impaired spatial memory, decreased cerebral blood flow (CBF), occurrence of albumin leakage, leukocyte adhesion and opening capillary rarefaction. Meanwhile, the downregulation of the tight junction proteins (TJ) claudin-5, occludin, zonula occluden-1 (ZO-1) and JAM-1 between endothelial cells, amyloid-β (Aβ) accumulation in hippocampus, increased AGEs and RAGE, and expression of RhoA/ROCK/moesin signaling pathway and phosphorylation of Src kinase in KKAy mice were significantly protected by BSHX treatment. These results indicate that the protective effect of BSHX on T2DM-induced cognitive impairment involves regulation of RhoA/ROCK1/moesin signaling pathway and phosphorylation of Src kinase.

Development of an enteric nanoparticle of marine sulfated polysaccharide propylene glycol alginate sodium sulfate for oral administration: formulation design, pharmacokinetics and efficacy

OBJECTIVES

Propylene glycol alginate sodium sulfate (PSS) is poorly absorbed by oral administration due to its large molecular weight and slightly degradability in stomach acidic environment. Here, a novel enteric-coated nano formulation of PSS (enteric PSS-NP) was prepared to improve its bioavailability and efficacy.

METHODS

The enteric PSS-NP was prepared by double (W₁ /O/W₂ ) emulsion and solvent evaporation method. The drug release characteristics in vitro were studied in artificial gastrointestinal fluid. And the pharmacokinetics and efficacy of enteric PSS-NP were separately investigated in normal rats and type 2 diabetic db/db mice.

KEY FINDINGS

The enteric PSS-NP were in spherical shape and exhibited negative zeta potential. The releasing characteristics of enteric PSS-NP in vitro showed that it possessed a strong pH-sensitive release character. Single-dose (50 mg/kg) oral pharmacokinetic study in rat plasma showed that enteric PSS-NP could improve the relative bioavailability significantly compared with PSS solution. Furthermore, the efficacy of enteric PSS-NP in vivo was better than that of PSS solution at equivalent doses.

CONCLUSIONS

The study showed that enteric-coated formulation of PSS had the intestinal-targeted absorption and improved pharmacodynamics, which indicated that enteric PSS-NP could be developed into a new formulation product in the future.

Animal models of obesity and diabetes mellitus

More than one-third of the worldwide population is overweight or obese and therefore at risk of developing type 2 diabetes mellitus. In order to mitigate this pandemic, safer and more potent therapeutics are urgently required. This necessitates the continued use of animal models to discover, validate and optimize novel therapeutics for their safe use in humans. In order to improve the transition from bench to bedside, researchers must not only carefully select the appropriate model but also draw the right conclusions. In this Review, we consolidate the key information on the currently available animal models of obesity and diabetes and highlight the advantages, limitations and important caveats of each of these models.

Alteration of Liver Peroxisomal and Mitochondrial Functionality in the NZO Mouse Model of Metabolic Syndrome

PURPOSE

Metabolic syndrome (MetS) consists of five risk factors: elevated blood pressure and fasting glucose, visceral obesity, dyslipidemia, and hypercholesterinemia. The physiological impact of lipid metabolism indicated as visceral obesity and hepatic lipid accumulation on MetS is still under debate. One major cause of disturbed lipid metabolism might be dysfunction of cellular organelles controlling energy homeostasis, i.e., mitochondria and peroxisomes.

EXPERIMENTAL DESIGN

The New Zealand Obese (NZO) mouse model exhibits a polygenic syndrome of obesity, insulin resistance, triglyceridemia, and hypercholesterolemia that resembles human metabolic syndrome. We applied a multi-omics approach combining lipidomics with liver transcriptomics and top-down MS based organelle proteomics (2D-DIGE) of highly enriched mitochondria and peroxisomes in male mice, to investigate molecular mechanisms related to the impact of lipid metabolism in the pathophysiology of the metabolic syndrome.

CONCLUSIONS AND CLINICAL RELEVANCE

Proteome analyses of liver organelles indicate differences in fatty acid and cholesterol metabolism, mainly influenced by PG-C1α/PPARα and other nuclear receptor mediated pathways. These results are in accordance with altered serum lipid profiles and elevated organelle functionality. These data emphasize that metabolic syndrome is accompanied with increased mitochondria and peroxisomal activity to cope with dyslipidemia and hypercholesterinemia driven hepatic lipid overflow in developing a fatty liver.

Anti-Diabetic Effect of Organo-Chalcogen (Sulfur and Selenium) Zinc Complexes with Hydroxy-Pyrone Derivatives on Leptin-Deficient Type 2 Diabetes Model ob/ob Mice

Since the discovery of the anti-diabetic effects of zinc (Zn) complex, we synthesized several Zn complexes and evaluated their effects using the KKA^y type 2 diabetes mouse model. Recently, we demonstrated that organo-chalcogen (sulfur and selenium) Zn complexes elicit strong anti-diabetic effects. In this study, we treated leptin-deficient ob/ob mice with organo-chalcogen Zn complexes, and evaluated the resulting anti-diabetic effects in a mouse model of diabetes arising from pathogenic mechanisms different from those in KKA^y mice. C57BL/6J ob/ob mice orally received either bis(3-hydroxy-2-methyl-4(H)-pyran-4-thiono)Zn, [Zn(hmpt)₂] or bis(3-hydroxy-2-methyl-4(H)-pyran-4-seleno)Zn, [Zn(hmps)₂], daily for 28 days. Both Zn complexes elicited potent blood glucose-lowering effects and improved HbA1c values. Moreover, glucose intolerance improved as evidenced by the oral glucose tolerance test, and fasting plasma insulin levels decreased in both types of Zn complex-treated mice. Zn concentrations in the liver and pancreas of [Zn(hmpt)₂]-treated mice and in the pancreas of [Zn(hmps)₂]-treated mice were increased, respectively. The results suggest that the present Zn complexes mainly exerted an anti-diabetic effect in the liver or pancreas. This study is the first to demonstrate that potent Zn complexes elicit anti-diabetic effects in not only KKA^y but also ob/ob mice via a normalizing effect on insulin secretion and fasting blood glucose levels.

Effect of berberine on the renal tubular epithelial-to-mesenchymal transition by inhibition of the Notch/snail pathway in diabetic nephropathy model KKAy mice

Renal tubular epithelial-to-mesenchymal transition (EMT) and renal tubular interstitial fibrosis are the main pathological changes of diabetic nephropathy (DN), which is a common cause of end-stage renal disease. Previous studies have suggested that berberine (BBR) has antifibrotic effects in the kidney and can reduce apoptosis and inhibit the EMT of podocytes in DN. However, the effect of BBR on the renal tubular EMT in DN and its mechanisms of action are unknown. This study was performed to explore the effects of BBR on the renal tubular EMT and the molecular mechanisms of BBR in DN model KKAy mice and on the high glucose (HG)-induced EMT in mouse renal tubular epithelial cells. Our results showed that, relative to the model mice, the mice in the treatment group had an improved general state and reduced blood glucose and 24-h urinary protein levels. Degradation of renal function was ameliorated by BBR. We also observed the protective effects of BBR on renal structural changes, including normalization of an index of renal interstitial fibrosis and kidney weight/body weight. Moreover, BBR suppressed the activation of the Notch/snail pathway and upregulated the α-SMA and E-cadherin levels in DN model KKAy mice. BBR was further found to prevent HG-induced EMT events and to inhibit the HG-induced expression of Notch pathway members and snail1 in mouse renal tubular epithelial cells. Our findings indicate that BBR has a therapeutic effect on DN, including its inhibition of the renal tubular EMT and renal interstitial fibrosis. Furthermore, the BBR-mediated EMT inhibition occurs through Notch/snail pathway regulation.

Adeno-associated virus-mediated expression of myostatin propeptide improves the growth of skeletal muscle and attenuates hyperglycemia in db/db mice

Inhibition of myostatin, a negative growth modulator for muscle, can functionally enhance muscle mass and improve glucose and fat metabolism in myostatin propeptide (MPRO) transgenic mice. This study was to investigate whether myostatin inhibition by adeno-associated virus (AAV)-mediated gene delivery of MPRO could improve muscle mass and achieve therapeutic effects on glucose regulation and lipid metabolism in the db/db mice and the mechanisms involved in that process. Eight-week-old male db/db mice were administered saline, AAV-GFP and AAV-MPRO/Fc vectors and monitored random blood glucose levels and body weight for 36 weeks. Body weight gain was not different during follow-up among the groups, but AAV-MPRO/Fc vectors resulted high level of MPRO in the blood companied by an increase in skeletal muscle mass and muscle hypertrophy. In addition, AAV-MPRO/Fc-treated db/db mice showed significantly lower blood glucose and insulin levels and significantly increased glucose tolerance and insulin sensitivity compared with the control groups (P<0.05). Moreover, these mice exhibited lower triglyceride (TG) and free fatty acid (FFA) content in the skeletal muscle, although no difference was observed in fat pad weights and serum TG and FFA levels. Finally, AAV-MPRO/Fc-treated mice had enhanced insulin signaling in the skeletal muscle. These data suggest that AAV-mediated MPRO therapy may provide an important clue for potential clinical applications to prevent type II diabetes, and these studies confirm that MPRO is a therapeutic target for type II diabetes.

Anti-Hyperglycemic Activity of Zinc Plus Cyclo (His-Pro) in Genetically Diabetic Goto-Kakizaki and Aged Rats

We previously reported that treatment of streptozotocin-induced diabetic rats with zinc plus cyclo (his-pro) (CHP) decreased fed blood glucose levels and water intake. The present study was conducted to examine the dose-dependent, acute, and chronic treatment effects of CHP on oral glucose tolerance (OGT), fed blood glucose levels, water intake, and plasma insulin levels in young and aged Sprague-Dawley (S-D) rats, nondiabetic Wistar rats, and genetically diabetic Goto-Kakizaki (G-K) rats. Acute gastric gavage of 10 mg zinc plus 1.0 mg CHP/kg body weight significantly improved OGT in 4- and 13-month-old nondiabetic S-D rats and in 2-month-old diabetic G-K rats. Young S-D and G-K rats returned to pretreatment OGT values 1 week after acute gavage of zinc plus CHP (ZC), but improved OGT values persisted for at least 1 week after gavage in aged S-D rats. OGT values and fed blood glucose decreased to the greatest extent among other treatments when G-K rats were given free access to drinking water containing 1.0 to 1.5 mg CHP/L plus 10 mg zinc/L for 2 weeks. Although food and water intake showed a tendency to decrease, no statistically significant differences were observed in young G-K rats. Plasma insulin levels and blood glucose levels in both normal and diabetic G-K rats decreased with 2-week treatment with ZC. To test the direct effects of ZC on muscle tissue, we observed the effect of various doses of ZC on normal and G-K rat muscle slices. The optimal level of CHP alone for maximal muscle glucose uptake in muscle slices from normal rats was 10 microg/mL and 5.0 microg/mL in G-K rats, and ZC stimulated glucose uptake. However, no statistically significant difference was demonstrated between normal and G-K rat tissues in this study. These results indicate that oral intake of an optimal dose of ZC stimulates blood glucose metabolism, probably by stimulating muscle glucose utilization.

The Cancer Drug Dasatinib Increases PGC-1α in Adipose Tissue but Has Adverse Effects on Glucose Tolerance in Obese Mice

Dasatinib (Sprycel) is a tyrosine kinase inhibitor approved for treatment of chronic myeloid leukemia. In this study, we identify dasatinib as a potent inducer of Peroxisome proliferator-activated receptor gamma coactivator (PGC)-1α mRNA. Dasatinib increased PGC-1α mRNA expression up to 6-fold in 3T3-F442A adipocytes, primary adipocytes, and epididymal white adipose tissue from lean and diet-induced obese mice. Importantly, gene expression translated into increased PGC-1α protein content analyzed in melanoma cells and isolated mitochondria from adipocytes. However, dasatinib treatment had adverse effect on glucose tolerance in diet-induced obese and Ob/Ob mice. This correlated with increased hepatic PGC-1α expression and the gluconeogenesis genes phosphoenolpyruvate carboxykinase and glucose-6-phosphatase. In conclusion, we show that dasatinib is a potent inducer of PGC-1α mRNA and protein in adipose tissue. However, despite beneficial effects of increased PGC-1α content in adipose tissue, dasatinib significantly impaired glucose tolerance in obese but not lean mice. As far as we are aware, this is the first study to show that dasatinib regulates PGC-1α and causes glucose intolerance in obese mice. This should be considered in the treatment of chronic myeloid leukemia.

Five stages of progressive β-cell dysfunction in the laboratory Nile rat model of type 2 diabetes

We compared the evolution of insulin resistance, hyperglycemia, and pancreatic β-cell dysfunction in the Nile rat (Arvicanthis niloticus), a diurnal rodent model of spontaneous type 2 diabetes (T2D), when maintained on regular laboratory chow versus a high-fiber diet. Chow-fed Nile rats already displayed symptoms characteristic of insulin resistance at 2 months (increased fat/lean mass ratio and hyperinsulinemia). Hyperglycemia was first detected at 6 months, with increased incidence at 12 months. By this age, pancreatic islet structure was disrupted (increased α-cell area), insulin secretion was impaired (reduced insulin secretion and content) in isolated islets, insulin processing was compromised (accumulation of proinsulin and C-peptide inside islets), and endoplasmic reticulum (ER) chaperone protein ERp44 was upregulated in insulin-producing β-cells. By contrast, high-fiber-fed Nile rats had normoglycemia with compensatory increase in β-cell mass resulting in maintained pancreatic function. Fasting glucose levels were predicted by the α/β-cell ratios. Our results show that Nile rats fed chow recapitulate the five stages of progression of T2D as occurs in human disease, including insulin-resistant hyperglycemia and pancreatic islet β-cell dysfunction associated with ER stress. Modification of diet alone permits long-term β-cell compensation and prevents T2D.

Repeated ozone exposure exacerbates insulin resistance and activates innate immune response in genetically susceptible mice

BACKGROUND

Inhaled ozone (O3) has been demonstrated as a harmful pollutant and associated with chronic inflammatory diseases such as diabetes and vascular disorders. However, the underlying mechanisms by which O3 mediates harmful effects are poorly understood.

OBJECTIVES

To investigate the effect of O3 exposure on glucose intolerance, immune activation and underlying mechanisms in a genetically susceptible mouse model.

METHODS

Diabetes-prone KK mice were exposed to filtered air (FA), or O3 (0.5 ppm) for 13 consecutive weekdays (4 h/day). Insulin tolerance test (ITT) was performed following the last exposure. Plasma insulin, adiponectin, and leptin were measured by ELISA. Pathologic changes were examined by H&E and Oil-Red-O staining. Inflammatory responses were detected using flow cytometry and real-time PCR.

RESULTS

KK mice exposed to O3 displayed an impaired insulin response. Plasma insulin and leptin levels were reduced in O3-exposed mice. Three-week exposure to O3 induced lung inflammation and increased monocytes/macrophages in both blood and visceral adipose tissue. Inflammatory monocytes/macrophages increased both systemically and locally. CD4 + T cell activation was also enhanced by the exposure of O3 although the relative percentage of CD4 + T cell decreased in blood and adipose tissue. Multiple inflammatory genes including CXCL-11, IFN-γ, TNFα, IL-12, and iNOS were up-regulated in visceral adipose tissue. Furthermore, the expression of oxidative stress-related genes such as Cox4, Cox5a, Scd1, Nrf1, and Nrf2, increased in visceral adipose tissue of O3-exposed mice.

CONCLUSIONS

Repeated O3 inhalation induces oxidative stress, adipose inflammation and insulin resistance.

Beneficial Effects of Supplementation of the Rare Sugar "D-allulose" Against Hepatic Steatosis and Severe Obesity in Lep(ob)/Lep(ob) Mice

A rare sugar, D-allulose (also called D-psicose), has recently been applied as a food supplement in view of controlling diabetes and obesity in Japan. D-allulose has been proven to have unique effects against hyperglycemia and hyperlipidemia in a number of studies using several species of rats and mice. However, the antiobesity effects of D-allulose have not yet been assessed in Lep(ob)/Lep(ob) (ob/ob) mice. Therefore, this study explored the dietary supplemental effects of this sugar in leptin-deficient ob/ob mice. Consequently, the subchronic ingestion of D-allulose in ob/ob mice for 15 wk significantly decreased the body and liver weights, and the loss of body weight was involved in the reduction of the total fat mass, including abdominal visceral fat, and not fat-free body mass, including muscle. Furthermore, D-allulose improved hepatic steatosis, as evaluated using hepatic histological studies and MRI. In the normal mice, none of these parameters were influenced by the single or long-term ingestion of D-allulose. These results indicate that dietary supplementation of D-allulose especially influences postprandial hyperglycemia and obesity-related hepatic steatosis, without exercise therapy or dietary restriction. Therefore, D-allulose may be useful as a supplement for preventing and improving obesity and obesity-related disorders.

Obesity genetics in mouse and human: back and forth, and back again

Obesity is a major public health concern. This condition results from a constant and complex interplay between predisposing genes and environmental stimuli. Current attempts to manage obesity have been moderately effective and a better understanding of the etiology of obesity is required for the development of more successful and personalized prevention and treatment options. To that effect, mouse models have been an essential tool in expanding our understanding of obesity, due to the availability of their complete genome sequence, genetically identified and defined strains, various tools for genetic manipulation and the accessibility of target tissues for obesity that are not easily attainable from humans. Our knowledge of monogenic obesity in humans greatly benefited from the mouse obesity genetics field. Genes underlying highly penetrant forms of monogenic obesity are part of the leptin-melanocortin pathway in the hypothalamus. Recently, hypothesis-generating genome-wide association studies for polygenic obesity traits in humans have led to the identification of 119 common gene variants with modest effect, most of them having an unknown function. These discoveries have led to novel animal models and have illuminated new biologic pathways. Integrated mouse-human genetic approaches have firmly established new obesity candidate genes. Innovative strategies recently developed by scientists are described in this review to accelerate the identification of causal genes and deepen our understanding of obesity etiology. An exhaustive dissection of the molecular roots of obesity may ultimately help to tackle the growing obesity epidemic worldwide.

The green algal carotenoid siphonaxanthin inhibits adipogenesis in 3T3-L1 preadipocytes and the accumulation of lipids in white adipose tissue of KK-Ay mice

BACKGROUND

Siphonaxanthin, a xanthophyll present in green algae, has been shown to possess antiangiogenic and apoptosis-inducing activities.

OBJECTIVE

We evaluated the antiobesity effects of siphonaxanthin by using a 3T3-L1 cell culture system and in diabetic KK-Ay mice.

METHODS

3T3-L1 cells were differentiated with or without 5 μmol/L siphonaxanthin, and lipid accumulation and critical gene expressions for adipogenesis were examined. In vivo, 4-wk-old male KK-Ay mice were administered daily oral treatment of 1.3 mg siphonaxanthin for 6 wk and body weight, visceral fat weight, serum variables, and gene expressions involved in lipid metabolism were evaluated.

RESULTS

Compared with the other carotenoids evaluated, siphonaxanthin potently inhibited adipocyte differentiation. Siphonaxanthin significantly suppressed lipid accumulation at noncytotoxic concentrations of 2.5 and 5 μmol/L by 29% and 43%, respectively. The effects of siphonaxanthin were largely limited to the early stages of adipogenesis. Siphonaxanthin significantly inhibited protein kinase B phosphorylation by 48% and 72% at 90 and 120 min, respectively. The expressions of key adipogenesis genes, including CCAAT/enhancer binding protein α (Cebpa), peroxisome proliferator activated receptor γ (Pparg), fatty acid binding protein 4 (Fabp4), and stearoyl coenzyme A desaturase 1 (Scd1), were elevated by 1.6- to 166-fold during adipogenesis. After 8 d of adipocyte differentiation, siphonaxanthin significantly lowered gene expression of Cebpa, Pparg, Fabp4, and Scd1 by 94%, 83%, 95%, and 90%, respectively. Moreover, oral administration of siphonaxanthin to KK-Ay mice significantly reduced the total weight of white adipose tissue (WAT) by 13%, especially the mesenteric WAT by 28%. Furthermore, siphonaxanthin administration reduced lipogenesis and enhanced fatty acid oxidation in adipose tissue. Siphonaxanthin was observed to highly accumulate in mesenteric WAT, and the accumulation in the mesenteric WAT was almost 2- and 3-fold that in epididymal (P = 0.14) and perirenal (P < 0.05) WAT, respectively.

CONCLUSION

These results provide evidence that siphonaxanthin may effectively regulate adipogenesis in 3T3-L1 cells and diabetic KK-Ay mice.

Histopathological analyses of diabetic nephropathy in sucrose-fed Otsuka Long-Evans Tokushima fatty rats

BACKGROUND

Otsuka Long-Evans Tokushima fatty (OLETF) rats are an established model of diabetic nephropathy. However, diabetes and diabetic nephropathy (DN) in OLETF rats develop later than in other animal type 2 diabetes models.

OBJECTIVES

This study was conducted to investigate the serial changes in the histopathological characteristics of DN in sucrose-fed OLETF rats by biochemical and morphometric analyses.

METHODS

We conducted sucrose feeding to examine the progression of DN. One group of OLETF rats was given water containing 30% sucrose ad libitum (SO) and the other group was given water without 30% sucrose (TO). Consecutive observations were made at 4-week intervals from 16 to 50 weeks of age in TO rats, and from 16 to 42 weeks of age in SO rats. Examination parameters included body weight, serum glucose level, urine albumin-to-creatinine ratio (UACR), light microscopy (LM) and electron microscopy (EM).

RESULTS

The UACR was over 300 mg/g in 32-week-old SO rats (after 16 weeks of sucrose feeding) and in 38-week-old TO rats. LM indicated that glomerular hypertrophy and mesangial matrix expansion in SO rats increased compared to that of age-matched TO rats especially at 42 weeks of age (p < 0.05). EM also showed that glomerular basement membrane thickness and podocyte foot process width of SO rats were significantly greater than those of age-matched TO rats (p < 0.05).

CONCLUSION

Our results suggested that dietary manipulation by sucrose feeding may cause deterioration of DN and could hasten the onset of diabetes and DN in OLETF rats.

Antidiabetic effects of the Cimicifuga racemosa extract Ze 450 in vitro and in vivo in ob/ob mice

INTRODUCTION

It was the aim of the present experiments to examine potential antidiabetic effects of the Cimicifuga racemosa extract Ze 450.

METHODS

Ze 450 and some of its components (23-epi-26-deoxyactein, protopine and cimiracemoside C) were investigated in vitro for their effects on AMP-activated protein kinase (AMPK) compared to metformin in HepaRG cells. Ze 450 (given orally (PO) and intraperitonally (IP)), metformin (PO) and controls were given over 7 days to 68 male ob/ob mice. Glucose and insulin concentrations were measured at baseline and during an oral glucose tolerance test (OGTT).

RESULTS

Ze 450 and its components activated AMPK to the same extent as metformin. In mice, Ze 450 (PO/IP) decreased significantly average daily and cumulative weight gain, average daily food and water intake, while metformin had no effect. In contrast to metformin, PO Ze 450 virtually did not change maximum glucose levels during OGTT, however, prolonged elimination. Ze 450 administered PO and IP decreased significantly post-stimulated insulin, whereas metformin did not. HOMA-IR index of insulin resistance improved significantly after IP and PO Ze 450 and slightly after metformin. In summary, the results demonstrate that Ze 450 reduced significantly body weight, plasma glucose, improved glucose metabolism and insulin sensitivity in diabetic ob/ob mice. In vitro experiments suggest that part of the effects may be related to AMPK activation.

CONCLUSIONS

Ze 450 may have utility in the treatment of type 2 diabetes. However, longer term studies in additional animal models or patients with disturbed glucose tolerance or diabetes may be of use to investigate this further.

Sudachitin, a polymethoxylated flavone, improves glucose and lipid metabolism by increasing mitochondrial biogenesis in skeletal muscle

Background

Obesity is a major risk factor for insulin resistance, type 2 diabetes, and stroke. Flavonoids are effective antioxidants that protect against these chronic diseases. In this study, we evaluated the effects of sudachitin, a polymethoxylated flavonoid found in the skin of the Citrus sudachi fruit, on glucose, lipid, and energy metabolism in mice with high-fat diet-induced obesity and db/db diabetic mice. In our current study, we show that sudachitin improves metabolism and stimulates mitochondrial biogenesis, thereby increasing energy expenditure and reducing weight gain.

Methods

C57BL/6 J mice fed a high-fat diet (40% fat) and db/db mice fed a normal diet were treated orally with 5 mg/kg sudachitin or vehicle for 12 weeks. Following treatment, oxygen expenditure was assessed using indirect calorimetry, while glucose tolerance, insulin sensitivity, and indices of dyslipidemia were assessed by serum biochemistry. Quantitative polymerase chain reaction was used to determine the effect of sudachitin on the transcription of key metabolism-regulating genes in the skeletal muscle, liver, and white and brown adipose tissues. Primary myocytes were also prepared to examine the signaling mechanisms targeted by sudachitin in vitro.

Results

Sudachitin improved dyslipidemia, as evidenced by reduction in triglyceride and free fatty acid levels, and improved glucose tolerance and insulin resistance. It also enhanced energy expenditure and fatty acid β-oxidation by increasing mitochondrial biogenesis and function. The in vitro assay results suggest that sudachitin increased Sirt1 and PGC-1α expression in the skeletal muscle.

Conclusions

Sudachitin may improve dyslipidemia and metabolic syndrome by improving energy metabolism. Furthermore, it also induces mitochondrial biogenesis to protect against metabolic disorders.

Early pregnancy urinary biomarkers of fatty acid and carbohydrate metabolism in pregnancies complicated by gestational diabetes

AIMS

Alterations in organic acid biomarkers from fatty acid and carbohydrate metabolism have been documented in type 2 diabetes patients. However, their association with gestational diabetes mellitus (GDM) is largely unknown.

METHODS

Participants were 25 GDM cases and 25 non-GDM controls. Biomarkers of fatty acid (adipate, suberate and ethylmalonate) and carbohydrate (pyruvate, l-lactate and β-hydroxybutyrate) metabolism were measured in maternal urine samples collected in early pregnancy (17 weeks) using liquid chromatography-mass spectrometry methods. Logistic regression were used to calculate odds ratios (OR) and 95% confidence intervals (CI).

RESULTS

GDM cases and controls differed in median urinary concentrations of ethylmalonate (3.0 vs. 2.3μg/mg creatinine), pyruvate (7.4 vs. 2.1μg/mg creatinine), and adipate (4.6 vs. 7.3μg/mg creatinine) (all p-values <0.05). Women in the highest tertile for ethylmalonate or pyruvate concentrations had 11.4-fold (95%CI 1.10-117.48) and 3.27-fold (95%CI 0.72-14.79) increased risk of GDM compared with women in the lowest tertile for ethylmalonate and pyruvate concentrations, respectively. Women in the highest tertile for adipate concentrations, compared with women in the lowest tertile, had an 86% reduction in GDM risk (95%CI 0.02-0.97).

CONCLUSIONS

These preliminary findings underscore the importance of altered fatty acid and carbohydrate metabolism in the pathogenesis of GDM.

The genetic basis of obesity-associated type 2 diabetes (diabesity) in polygenic mouse models

Obesity-associated diabetes (“diabesity”) in mouse strains is characterized by severe insulin resistance, hyperglycaemia and progressive failure, and loss of beta cells. This condition is observed in inbred obese mouse strains such as the New Zealand Obese (NZO/HlLt and NZO/HlBomDife) or the TALLYHO/JngJ mouse. In lean strains such as C57BLKS/J, BTBR T+tf/J or DBA/2 J carrying diabetes susceptibility genes (“diabetes susceptible” background), it can be induced by introgression of the obesity-causing mutations Lep<ob> (ob) or Lepr<db> (db). Outcross populations of these models have been employed in the genome-wide search for mouse diabetes genes, and have led to positional cloning of the strong candidates Pctp, Tbc1d1, Zfp69, and Ifi202b (NZO-derived obesity) and Sorcs1,Lisch-like, Tomosyn-2, App, Tsc2, and Ube2l6 (obesity caused by the ob or db mutation). Some of these genes have been shown to play a role in the regulation of the human glucose or lipid metabolism. Thus, dissection of the genetic basis of obesity and diabetes in mouse models can identify regulatory mechanisms that are relevant for the human disease.

Macrophage contact dependent and independent TLR4 mechanisms induce β-cell dysfunction and apoptosis in a mouse model of type 2 diabetes

Type 2 diabetes (T2D) is evolving into a global disease and patients have a systemic low-grade inflammation, yet the role of this inflammation is still not established. One plausible mechanism is enhanced expression and activity of the innate immune system. Therefore, we evaluated the expression and the function of the toll-like receptor 4 (TLR4) on pancreatic β-cells in primary mouse islets and on the murine β-cell line MIN6 in the presence or absence of macrophages. Diabetic islets have 40% fewer TLR4 positive β-cells, but twice the number of TLR4 positive macrophages as compared to healthy islets. Healthy and diabetic islets respond to a TLR4 challenge with enhanced production of cytokines (5–10-fold), while the TLR4 negative β-cell line MIN6 fails to produce cytokines. TLR4 stimulation induces β-cell dysfunction in mouse islets, measured as reduced glucose stimulated insulin secretion. Diabetic macrophages from 4-months old mice have acquired a transient enhanced capacity to produce cytokines when stimulated with LPS. Interestingly, this is lost in 6-months old diabetic mice. TLR4 activation alone does not induce apoptosis in islets or MIN-6 cells. In contrast, macrophages mediate TLR4-dependent cell-contact dependent (3-fold) as well as cell-contact independent (2-fold) apoptosis of both islets and MIN-6 cells. Importantly, diabetic macrophages have a significantly enhanced capacity to induce β-cell apoptosis compared to healthy macrophages. Taken together, the TLR4 responsiveness is elevated in the diabetic islets and mainly mediated by newly recruited macrophages. The TLR4 positive macrophages, in both a cell-contact dependent and independent manner, induce apoptosis of β-cells in a TLR4 dependent fashion and TLR4 activation directly induces β-cell dysfunction. Thus, targeting either the TLR4 pathway or the macrophages provides a novel attractive treatment regime for T2D.

Adipocytes from New Zealand obese mice exhibit aberrant proinflammatory reactivity to the stress signal heat shock protein 60

Adipocytes release immune mediators that contribute to diabetes-associated inflammatory processes. As the stress protein heat shock protein 60 (Hsp60) induces proinflammatory adipocyte activities, we hypothesized that adipocytes of diabetes-predisposed mice exhibit an increased proinflammatory reactivity to Hsp60. Preadipocytes and mature adipocytes from nonobese diabetic (NOD), New Zealand obese (NZO), and C57BL/6J mice were analyzed for Hsp60 binding, Hsp60-activated signaling pathways, and Hsp60-induced release of the chemokine CXCL-1 (KC), interleukin 6 (IL-6), and macrophage chemoattractant protein-1 (MCP-1). Hsp60 showed specific binding to (pre-)adipocytes of NOD, NZO, and C57BL/6J mice. Hsp60 binding involved conserved binding structure(s) and Hsp60 epitopes and was strongest to NZO mouse-derived mature adipocytes. Hsp60 exposure induced KC, IL-6, and MCP-1 release from (pre-)adipocytes of all mouse strains with a pronounced increase of IL-6 release from NZO mouse-derived adipocytes. Compared to NOD and C57BL/6J mouse derived cells, Hsp60-induced formation of IL-6, KC, and MCP-1 from NZO mouse-derived (pre-)adipocytes strongly depended on NF κ B-activation. Increased Hsp60 binding and Hsp60-induced IL-6 release by mature adipocytes of NZO mice suggest that enhanced adipocyte reactivity to the stress signal Hsp60 contributes to inflammatory processes underlying diabetes associated with obesity and insulin resistance.

Modulation of hyperglycemia and TNFα-mediated inflammation by helichrysum and grapefruit extracts in diabetic db/db mice

Type-2 diabetes is associated with a chronic low-grade systemic inflammation accompanied by an increased production of adipokines/cytokines in the obese adipose tissue, which may be overcome by flavonoid-rich extracts.

Lifelong obesity in a polygenic mouse model prevents age- and diet-induced glucose intolerance- obesity is no road to late-onset diabetes in mice

Aims/Hypothesis

Visceral obesity holds a central position in the concept of the metabolic syndrome characterized by glucose intolerance in humans. However, until now it is unclear if obesity by itself is responsible for the development of glucose intolerance.

Methods

We have used a novel polygenic mouse model characterized by genetically fixed obesity (DU6) and addressed age- and high fat diet-dependent glucose tolerance.

Results

Phenotype selection over 146 generations increased body weight by about 2.7-fold in male 12-week DU6 mice (P<0.0001) if compared to unselected controls (Fzt:DU). Absolute epididymal fat mass was particularly responsive to weight selection and increased by more than 5-fold (P<0.0001) in male DU6 mice. At an age of 6 weeks DU6 mice consumed about twice as much food if compared to unselected controls (P<0.001). Absolute food consumption was higher at all time points measured in DU6 mice than in Fzt:DU mice. Between 6 and 12 weeks of age, absolute food intake was reduced by 15% in DU6 mice (P<0.001) but not in Fzt:DU mice. In both mouse lines feeding of the high fat diet elevated body mass if compared to the control diet (P<0.05). In contrast to controls, DU6 mice did not display high fat diet-induced increases of epididymal and renal fat. Control mice progressively developed glucose intolerance with advancing age and even more in response to the high fat diet. In contrast, obese DU6 mice did neither develop a glucose intolerant phenotype with progressive age nor when challenged with a high fat diet.

Conclusions/Interpretation

Our results from a polygenic mouse model demonstrate that genetically pre-determined and life-long obesity is no precondition of glucose intolerance later in life.

Genetic and epigenetic control of metabolic health

Obesity is characterized as an excess accumulation of body fat resulting from a positive energy balance. It is the major risk factor for type 2 diabetes (T2D). The evidence for familial aggregation of obesity and its associated metabolic diseases is substantial. To date, about 150 genetic loci identified in genome-wide association studies (GWAS) are linked with obesity and T2D, each accounting for only a small proportion of the predicted heritability. However, the percentage of overall trait variance explained by these associated loci is modest (~5-10% for T2D, ~2% for BMI). The lack of powerful genetic associations suggests that heritability is not entirely attributable to gene variations. Some of the familial aggregation as well as many of the effects of environmental exposures, may reflect epigenetic processes. This review summarizes our current knowledge on the genetic basis to individual risk of obesity and T2D, and explores the potential role of epigenetic contribution.

Phenotypic characterization of the KK/HlJ inbred mouse strain

Detailed histopathological diagnoses of inbred mouse strains are important for interpreting research results and defining novel models of human diseases. The aim of this study was to histologically detect lesions affecting the KK/HlJ inbred strain. Mice were examined at 6, 12, and 20 months of age and near natural death (ie, moribund mice). Histopathological lesions were quantified by percentage of affected mice per age group and sex. Predominant lesions were mineralization, hyperplasia, and fibro-osseous lesions. Mineralization was most frequently found in the connective tissue dermal sheath of vibrissae, the heart, and the lung. Mineralization was also found in many other organs but to a lesser degree. Hyperplasia was found most commonly in the pancreatic islets, and fibro-osseous lesions were observed in several bones. The percentage of lesions increased with age until 20 months. This study shows that KK/HlJ mice demonstrate systemic aberrant mineralization, with greatest frequency in aged mice. The detailed information about histopathological lesions in the inbred strain KK/HlJ can help investigators to choose the right model and correctly interpret the experimental results.