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Winter mortality is a major factor regulating population size of the mountain pine beetle, Dendroctonus ponderosae Hopkins (Coleoptera: Curculionidae). Glycerol is the major cryoprotectant in this freeze intolerant insect. We report findings from a gene expression study on an overwintering mountain pine beetle population over the course of 35 weeks. mRNA transcript levels suggest glycerol production in the mountain pine beetle occurs through glycogenolytic, gluconeogenic and potentially glyceroneogenic pathways, but not from metabolism of lipids. A two-week lag period between fall glycogen phosphorylase transcript and phosphoenolpyruvate carboxykinase transcript up-regulation suggests that gluconeogenesis serves as a secondary glycerol-production process, subsequent to exhaustion of the primary glycogenolytic source. These results provide a first look at the details of seasonal gene expression related to the production of glycerol in the mountain pine beetle.

The contribution of peroxisomal proliferator-activated receptor (PPAR)-γ agonism in pancreatic β-cells to the antidiabetic actions of thiazolidinediones has not been clearly elucidated. Genetic models of pancreatic β-cell PPARγ ablation have revealed a potential role for PPARγ in β-cell expansion in obesity but a limited role in normal β-cell physiology. Here we overexpressed PPARγ1 or PPARγ2 specifically in pancreatic β-cells of mice subjected to high-fat feeding using an associated adenovirus (β-PPARγ1-HFD and β-PPARγ2-HFD mice). We show β-cell-specific PPARγ1 or PPARγ2 overexpression in diet-induced obese mice exacerbated obesity-induced glucose intolerance with decreased β-cell mass, increased islet cell apoptosis, and decreased plasma insulin compared with obese control mice (β-eGFP-HFD mice). Analysis of islet lipid composition in β-PPARγ2-HFD mice revealed no significant changes in islet triglyceride content and an increase in only one of eight ceramide species measured. Interestingly β-PPARγ2-HFD islets had significantly lower levels of lysophosphatidylcholines, lipid species shown to enhance insulin secretion in β-cells. Gene expression profiling revealed increased expression of uncoupling protein 2 and genes involved in fatty acid transport and β-oxidation. In summary, transgenic overexpression of PPARγ in β-cells in diet-induced obesity negatively impacts whole-animal carbohydrate metabolism associated with altered islet lipid content, increased expression of β-oxidative genes, and reduced β-cell mass., Funding agencies:Canadian Diabetes Association University of Northern British Columbia Research Project Awards

Cold-induced mortality has historically been a key aspect of mountain pine beetle,Dendroctonus ponderosaeHopkins (Coleoptera: Curculionidae), population control, but little is known about the molecular basis for cold tolerance in this insect. We used RNA-seq analysis to monitor gene expression patterns of mountain pine beetle larvae at four time points during their overwintering period—early-autumn, late-autumn, early-spring, and late-spring. Changing transcript profiles over the winter indicates a multipronged physiological response from larvae that is broadly characterized by gene transcripts involved in insect immune responses and detoxification during the autumn. In the spring, although transcripts associated with developmental process are present, there was no particular biological process dominating the transcriptome.

BackgroundMountain pine beetles, Dendroctonus ponderosae Hopkins (Coleoptera: Curculionidae), are native to western North America, but have recently begun to expand their range across the Canadian Rocky Mountains. The requirement for larvae to withstand extremely cold winter temperatures and potentially toxic host secondary metabolites in the midst of their ongoing development makes this a critical period of their lives.ResultsWe have uncovered global protein profiles for overwintering mountain pine beetle larvae. We have also quantitatively compared the proteomes for overwintering larvae sampled during autumn cooling and spring warming using iTRAQ methods. We identified 1507 unique proteins across all samples. In total, 33 proteins exhibited differential expression (FDR

s / Can J Diabetes 36 (2012) S24eS76 S62 glucolipotoxicity and chronic ER stress. Interestingly, double BaxBak knockout resulted in an acute and transient up-regulation of the islet ER stress response. Together, these data suggest that Bax and Bak, both separately and in combination, are important for beta-cell loss in diabetes and have novel roles in the regulation of beta-cell organelle stress upstream of apoptosis execution.