Forced swim test induces divergent global transcriptomic alterations in the hippocampus of high versus low novelty-seeker rats

BACKGROUND: Many neuropsychiatric disorders, including stress-related mood disorders, are complex multi-parametric syndromes. Susceptibility to stress and depression is individually different. The best animal model of individual differences that can be used to study the neurobiology of affect regards spontaneous reactions to novelty. Experimentally, when naive rats are exposed to the stress of a novel environment, they display a highly variable exploratory activity and are classified as high or low responders (HR or LR, respectively). Importantly, HR and LR rats do not seem to exhibit a substantial differentiation in relation to their ‘depressive-like’ status in the forced swim test (FST), a widely used animal model of ‘behavioral despair’. In the present study, we investigated whether FST exposure would be accompanied by phenotype-dependent differences in hippocampal gene expression in HR and LR rats. RESULTS: HR and LR rats present a distinct behavioral pattern in the pre-test session but develop comparable depressive-like status in the second FST session. At 24 h following the second FST session, HR and LR rats (stressed and unstressed controls) were sacrificed and hippocampal samples were independently analyzed on whole rat genome Illumina arrays. Functional analysis into pathways and networks was performed using Ingenuity Pathway Analysis (IPA) software. Notably, hippocampal gene expression signatures between HR and LR rats were markedly divergent, despite their comparable depressive-like status in the FST. These molecular differences are reflected in both the extent of transcriptional remodeling (number of significantly changed genes) and the types of molecular pathways affected following FST exposure. A markedly higher number of genes (i.e., 2.28-fold) were statistically significantly changed following FST in LR rats, as compared to their HR counterparts. Notably, genes associated with neurogenesis and synaptic plasticity were induced in the hippocampus of LR rats in response to FST, whereas in HR rats, FST induced pathways directly or indirectly associated with induction of apoptotic mechanisms. CONCLUSIONS: The markedly divergent gene expression signatures exposed herein support the notion that the hippocampus of HR and LR rats undergoes distinct transcriptional remodeling in response to the same stress regimen, thus yielding a different FST-related ‘endophenotype’, despite the seemingly similar depressive-like phenotype

Significant changes in hepatic transcriptome and circulating miRNAs are associated with diet-induced metabolic syndrome in apoE3L.CETP mice

Long-term exposure to excess dietary fat leads to obesity and the metabolic syndrome (MetS). The purpose of the present study was to identify global changes in liver gene expression and circulating miRNAs in a humanized mouse model of diet-induced MetS. Male apoE3L.CETP mice received a high-fat diet (HFD) or a low-fat diet (LFD) for different time periods and the progression of MetS pathology was monitored. A separate group of mice was divided into responders (R) or nonresponders (NR) and received HFD for 16 weeks. We found that mice receiving the HFD developed manifestations of MetS and displayed an increasing number of differentially expressed transcripts at 4, 8, and 12 weeks compared with mice receiving the LFD. Significantly changed genes were functionally annotated to metabolic diseases and pathway analysis revealed the downregulation of genes in cholesterol and fatty acid biosynthesis and upregulation of genes related to lipid droplet formation, which was in line with the development of hepatic steatosis. In the serum of the apoE3L.CETP mice we identified three miRNAs that were upregulated specifically in the HFD group. We found that responder mice have a distinct gene signature that differentiates them from nonresponders. Comparison of the two diet intervention studies revealed a limited number of common differentially expressed genes but the expression of these common genes was affected in a similar way in both studies. In conclusion, the characteristic hepatic gene signatures and serum miRNAs identified in the present study provide novel insights to MetS pathology and could be exploited for diagnostic or therapeutic purposes

Body weight-dependent and independent improvement in lipid metabolism after Roux-en-Y gastric bypass in ApoE*3Leiden.CETP mice

BACKGROUND/OBJECTIVES: The incidence of obesity and metabolic syndrome (MetS) has rapidly increased worldwide. Roux-en-Y gastric bypass (RYGB) achieves long-term weight loss and improves MetS-associated comorbidities. Using a mouse model with a humanized lipoprotein metabolism, we elucidated whether improvements in lipid and glucose metabolism after RYGB surgery are body weight loss-dependent or not. SUBJECTS/METHODS: Male ApoE*3Leiden.CETP (ApoE3L.CETP) mice fed Western type diet for 6 weeks underwent RYGB or Sham surgery. Sham groups were either fed ad libitum or were body weight-matched (BWm) to the RYGB mice to discriminate surgical effects from body weight loss-associated effects. Before and after surgery, plasma was collected to assess the metabolic profile, and glucose tolerance and insulin sensitivity were tested. Twenty days after surgery, mice were sacrificed, and liver was collected to assess metabolic, histological and global gene expression changes after surgery. RESULTS: RYGB induced a marked reduction in body weight, which was also achieved by severe food restriction in BWm mice, and total fat mass compared to Sham ad libitum mice (Sham AL). Total cholesterol, non-high-density lipoprotein cholesterol (non-HDL-C) and ceramide were strongly reduced 20 days after surgery in RYGB compared to BWm mice. Glucose tolerance and insulin sensitivity improved 13 days after surgery similarly in RYGB and BWm mice. Liver histology confirmed lipid reduction in RYGB and BWm mice while the transcriptomics data indicated altered genes expression in lipid metabolism. CONCLUSIONS: RYGB surgery improves glucose metabolism and greatly ameliorates lipid metabolism in part in a body weight-dependent manner. Given that ApoE3L.CETP mice were extensively studied to describe the MetS, and given that RYGB improved ceramide after surgery, our data confirmed the usefulness of ApoE3L.CETP mice after RYGB in deciphering the metabolic improvements to treat the MetS

Circulating microRNAs -192 and -194 are associated with the presence and incidence of diabetes mellitus

Abstract We sought to identify circulating microRNAs as biomarkers of prevalent or incident diabetes. In a pilot study of 18 sex- and age-matched patients with metabolic syndrome, nine of whom developed diabetes during 6 years of follow-up, an array of 372 microRNAs discovered significantly elevated serum levels of microRNAs -122, -192, -194, and -215 in patients who developed diabetes mellitus type 2 (T2DM). In two cross-sectional validation studies, one encompassing sex- and age-matched groups of patients with T2DM, impaired fasting glucose (IFG) and euglycemic controls (n = 43 each) and the other 53 patients with type 1 diabetes and 54 age- and BMI-matched euglycemic controls, serum levels of miR-192, miR-194, and mi215 were significantly higher in diabetic subjects than in probands with euglycemia or IFG. In a longitudinal study of 213 initially diabetes-free patients of whom 35 developed diabetes during 6 years of follow-up, elevated serum levels of microRNAs 192 and 194 were associated with incident T2DM, independently of fasting glucose, HbA1c and other risk factors. Serum levels of miR-192 and miR-194 were also elevated in diabetic Akt2 knockout mice compared to wild type mice. In conclusion, circulating microRNAs -192 and -194 are potential biomarkers for risk of diabetes