The metabolic response to a high-fat diet reveals obesity-prone and -resistant phenotypes in mice with distinct mRNA-seq transcriptome profiles.

OBJECTIVES: The aim of this study was to explore the phenotypic differences underpinning obesity susceptibility or resistance based on the metabolic and transcriptional profiling of C57BL/6J mice fed a high-fat diet (HFD). METHODS: The mice were fed either a normal diet or HFD for 12 weeks. After 6 weeks, the mice on HFD were classified as either obesity-prone (OP) or obesity-resistant (OR) depending on the body weight gain. RESULTS: Lipid profiles from plasma and liver significantly improved in OR mice relative to the OP group. Energy expenditure was greater in OR mice than in OP mice, with a simultaneous decrease in body fat mass. Epididymal white adipose tissue (eWAT) and liver were enlarged in OP mice (with visible immune-cell infiltration), but these effects were attenuated in OR mice compared with OP mice. Overall glucose metabolism was enhanced in OR mice compared with OP mice, including homeostasis model assessment for insulin resistance, plasma glucose and insulin concentrations, glucokinase activity and hepatic glycogen. Plasma adipokines and proinflammatory cytokines were upregulated in OP mice, and these changes were attenuated in OR mice. Transcriptomic profiles of eWAT and liver revealed common and divergent patterns of transcriptional changes in OP and OR mice, and pointed to differential metabolic phenotypes of OP and OR mice. There were substantial differences between OP and OR mice in molecular pathways, including atherosclerosis signaling, sperm motility, cAMP-mediated signaling in eWAT; and fibrosis, agranulocyte adhesion and diapedesis, and atherosclerosis signaling in liver. CONCLUSIONS: Taken altogether, the results provide robust evidence of major divergence in the transcriptomes, phenotypes and metabolic processes between obesity susceptibility and obesity resistance in the HFD-fed C57BL/6J mice.

Integrative systems analysis of diet-induced obesity identified a critical transition in the transcriptomes of the murine liver and epididymal white adipose tissue.

BACKGROUND: It is well known that high-fat diet (HFD) can cause immune system-related pathological alterations after a significant body weight gain. The mechanisms of the delayed pathological alterations during the development of diet-induced obesity (DIO) are not fully understood. METHODS: To elucidate the mechanisms underlying DIO development, we analyzed time-course microarray data obtained from a previous study. First, differentially expressed genes (DEGs) were identified at each time point by comparing the hepatic transcriptome of mice fed HFD with that of mice fed normal diet. Next, we clustered the union of DEGs and identified annotations related to each cluster. Finally, we constructed an 'integrated obesity-associated gene regulatory network (GRN) in murine liver'. We analyzed the epididymal white adipose tissue (eWAT) transcriptome usig the same procedure. RESULTS: Based on time-course microarray data, we found that the genes associated with immune responses were upregulated with an oscillating expression pattern between weeks 2 and 8, relatively downregulated between weeks 12 and 16, and eventually upregulated after week 20 in the liver of the mice fed HFD. The genes associated with immune responses were also upregulated at late stage, in the eWAT of the mice fed HFD. These results suggested that a critical transition occurred in the immune system-related transcriptomes of the liver and eWAT around week 16 of the DIO development, and this may be associated with the delayed pathological alterations. The GRN analysis suggested that Maff may be a key transcription factor for the immune system-related critical transition thatoccurred at week 16. We found that transcription factors associated with immune responses were centrally located in the integrated obesity-associated GRN in the liver. CONCLUSIONS: In this study, systems analysis identified regulatory network modules underlying the delayed immune system-related pathological changes during the development of DIO and could suggest possible therapeutic targets.

Pep19 drives epitope spreading in periodontitis and periodontitis-associated autoimmune diseases.

BACKGROUND AND OBJECTIVE: Epitope spreading is one of valid mechanisms operating in immunopathological processes of infection-induced autoimmune diseases. We hypothesized that the peptide 19 from Porphyromonas gingivalis heat shock protein (HSP) 60 (Pep19) may be the dominant epitope from which epitope-specific immune response to subdominant epitopes may diversify sequentially into autoimmune responses directed at human neoepitopes in P. gingivalis-induced periodontitis and autoimmune diseases. However, the exact feature and mechanism on how Pep19 may drive epitope spreading into human autoantigens in chronic periodontitis or P. gingivalis-induced experimental periodontitis has not been clarified. The present study was performed with the following specific aims: (i) to delineate retrospectively the features of epitope spreading by human cross-sectional analysis; (ii) to demonstrate prospectively the epitope spreading into new antigenic determinants in an ordered, predictable and sequential manner in experimental periodontitis; and (iii) to clarify the mechanism on how immunization with Pep19 may mobilize helper T cells or elicit B-cell responses to human autoantigens and neoantigen. MATERIAL AND METHODS: The study was devised for two independent investigations - a cross-sectional analysis on clinical subjects and a prospective analysis on experimental periodontitis - each being subdivided further into two additional independent observations. Cross-sectional dot immunoblot pattern against a panel of peptides of P. gingivalis HSP60 and human HSP60 was performed among age-dependent healthy subjects and between healthy subjects, patients with chronic periodontitis and patients with autoimmune disease, to identify epitope spreading. A peptide-specific T-cell line was established for phenotype analysis and for proliferation assay to an array of identical peptides. An identical prospective analysis was performed in P. gingivalis-induced experimental periodontitis or in Pep19-immunized mice. Cross-reactivity of anti-Pep19 monoclonal antibody was also investigated. RESULTS: A dominant immune response exclusively to Pep19 prevailed in healthy human subjects (before the age of 40) and mice that persisted in chronic periodontitis and autoimmune diseases without being replaced further by subsequent subdominant epitopes. A sequential epitope spreading provoked by Pep19 to subdominant autoantigen peptide 19 from human HSP60 (Hu19) in most healthy human subjects and mice, and to autoantigen peptide 9 from human HSP60 (Hu9) and neoantigen oxidized low-density lipoprotein (ox-LDL) in P. gingivalis-induced chronic periodontitis and autoimmune diseases could be demonstrated in a reproducible and predictable manner. T-cell proliferative activity to multiple autoantigens Hu19, Hu9 and ox-LDL, and cross-reactivity of anti-Pep19 monoclonal antibody to these epitopes may be proposed as cellular and molecular mechanisms responsible for the phenomenon. Moreover, the predictive value of Pep19 for Hu9 increased remarkably in the disease group when compared with that of the healthy group. CONCLUSION: Taken together, epitope spreading to Hu19, Hu9 and ox-LDL provoked by Pep19 could be proposed as a solid phenomenon observed in P. gingivalis-induced chronic periodontitis and infection-induced autoimmune diseases in a reproducible and predictable manner. T-cell proliferative activity to these peptides and cross-reactivity of anti-Pep19 antibodies to multiple human autoantigens could be proposed as cellular and molecular mechanisms responsible for this phenomenon.

Time-course microarrays reveal modulation of developmental, lipid metabolism and immune gene networks in intrascapular brown adipose tissue during the development of diet-induced obesity.

OBJECTIVE: The aim of this study was to establish the time-course of molecular events in intrascapular brown adipose tissue (iBAT) during the development of diet-induced obesity using microarrays and molecular network analysis. DESIGN: C57BL/6J male inbred mice were fed a high-fat diet (HFD) or normal diet (ND) and killed at multiple time-points over 24 weeks. METHODS: Global transcriptional changes in iBAT were determined by time-course microarrays of pooled RNA (n=6, pools per time-point) at 2, 4, 8, 20 and 24 weeks using Illumina MouseWG-6 v2.0 Beadchips. Molecular networks were constructed using the Ingenuity knowledgebase based on differentially expressed genes at each time-point. RESULTS: Body weight and subcutaneous adipose were progressively increased over 24 weeks, whereas iBAT was significantly increased between 6 and 12 weeks in HFD-fed C57BL/6J mice compared with controls. Blood glucose and insulin levels were increased between 16 and 24 weeks. Time-course microarrays, revealed 155 differentially expressed genes at one or more time-points over 24 weeks in the iBAT of HFD-fed mice compared with controls. Time-course network analysis revealed a network of skeletal muscle development genes that was activated between 2 and 4 weeks, subsequently a network of immune trafficking genes was activated at 8 weeks. After 20 and 24 weeks, multiple lipid metabolism and immune response networks were activated. Several target genes identified by time-course microarrays were independently validated using RT-qPCR. Tnnc1 was upregulated early between 2 and 4 weeks, later Cd68 and Col1a1 were upregulated between 20 and 24 weeks, whereas 11ß-hydroxysteroid dehydrogenase (Hsd11b1) was consistently downregulated during the development of diet-induced obesity. CONCLUSION: Molecular networks in iBAT are modulated in a time-dependent manner in response to a HFD. A broad range of gene targets exists to alter molecular changes within iBAT during the development of diet-induced obesity.

Anti-atherogenic property of ferulic acid in apolipoprotein E-deficient mice fed Western diet: comparison with clofibrate.

Anti-atherogenic effect of ferulic acid (0.02%, w/w) was investigated in comparison with the clofibrate (0.02%, w/w) in apolipoprotein E-deficient (apo E(-/-)) mice fed Western diet. Concentrations of total cholesterol (total-C), apolipoprotein B (apo B) in the plasma and epididymal adipose tissue weight were significantly lower in the ferulic acid and clofibrate supplemented groups compared to the control group. The ratio of apo B to apo A-I was also significantly lower in those groups than in the control group. Activities of hepatic ACAT and HMG-CoA reductase were only significantly lower in the ferulic acid and clofibrate groups, respectively than in the control group. The numbers of mice that exhibited aortic fatty plaque were 8/10 in control groups vs. 0/10 in the ferulic acid or clofibrate group. The activities of anti-oxidant enzymes (superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase and paraoxonase) in the hepatocyte and erythrocyte were significantly higher in the ferulic acid group than in the control group. In contrast, hepatic TBARS level was only markedly lower in the ferulic acid group. These results provide a new insight into the anti-atherogenic property of ferulic acid in the apo E(-/-) mice fed a Western diet.