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.

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.

microRNAs in the regulation of adipogenesis and obesity.

Worldwide obesity is a growing health problem, associated with increased risk of chronic disease. Understanding the molecular basis of adipogenesis and fat cell development in obesity is essential to identify new biomarkers and therapeutic targets for the development of anti-obesity drugs. microRNAs (miRNAs) appear to play regulatory roles in many biological processes associated with obesity, including adipocyte differentiation, insulin action and fat metabolism. Recent studies show miRNAs are dysregulated in obese adipose tissue. During adipogenesis miRNAs can accelerate or inhibit adipocyte differentiation and hence regulate fat cell development. In addition miRNAs may regulate adipogenic lineage commitment in multipotent stem cells and hence govern fat cell numbers. Recent findings suggest miR-519d may be associated with human obesity, but larger case-control studies are needed. Few miRNA targets have been experimentally validated in adipocytes but interestingly both miR-27 and miR-519d target PPAR family members, which are well established regulators of fat cell development. In this review recent advances in our understanding of the role of miRNAs in fat cell development and obesity are discussed. The potential of miRNA based therapeutics targeting obesity is highlighted as well as recommendations for future research which could lead to a breakthrough in the treatment of obesity.

Identification of a novel multifunctional structural domain in the herpes simplex virus type 1 genome: implications for virus latency.

A domain, previously termed RE1, exists within the herpes simplex virus type 1 genome potentially influencing expression of immediate early genes and the latency associated transcripts. This domain consists of 10 tandem copies of a CT-rich sequence. We demonstrate that this domain binds multiple host-cell factors that may allow RE1 to act either as a transcriptional regulator and/or to affect nucleosomal and DNA structure in the latent genome.

A beta-subclass phosphatidylinositol-specific phospholipase C from squid (Loligo forbesi) photoreceptors exhibiting a truncated C-terminus.

A PCR-based strategy has been used to isolate a full length cDNA encoding a phosphatidylinositol-specific phospholipase C from a sized cDNA squid (Loligo forbesi) retinal library. The predicted protein sequence contains 875 amino acids, with calculated M(r) 98,181, and has marked similarity with PLC beta-isoforms, including conservation of the 'X' and 'Y' regions. It is unique in having a major C-terminal truncation. A major protein of apparent M(r) 120,000 estimated by SDS-PAGE has been isolated from squid photoreceptors and identified by partial protein sequence analysis to correspond to the protein sequence predicted from the cDNA clone. This protein has been shown to hydrolyse phosphatidylinositol 4,5-bisphosphate. It is not yet clear whether this represents the major light-activated PLC in squid vision.