BackgroundObesity is frequently complicated by comorbid conditions, yet how excess adipose contributes is poorly understood. Although adipocytes in obese individuals induce systemic inflammation via secreted cytokines, another potential mediator has recently been identified (i.e. adipocyte-derived exosomes). We hypothesized that adipocyte-derived exosomes contain mediators capable of activating end-organ inflammatory and fibrotic signaling pathways.MethodsWe developed techniques to quantify and characterize exosomes shed by adipocytes from 7 obese (age: 12–17.5 years, BMI: 33–50 kg/m2) and 5 lean (age: 11–19 years, BMI: 22–25 kg/m2) subjects.ResultsAbundant exosomal miRNAs, but no mRNAs, were detected. Comparison of obese vs. lean visceral adipose donors detected 55 differentially-expressed miRNAs (p<0.05; fold change≥|1.2|). qRT-PCR confirmed downregulation of miR-148b (ratio = 0.2 [95% confidence interval = 0.1, 0.6]) and miR-4269 (0.3 [0.1, 0.8]), and upregulation of miR-23b (6.2 [2.2, 17.8]) and miR-4429 (3.8 [1.1 to 13.4]). Pathways analysis identified TGF-β signaling and Wnt/ β-catenin signaling among the top canonical pathways expected to be altered with visceral adiposity based on projected mRNA targets for the 55 differentially expressed miRNAs. A select mRNA target was validated in vitro.ConclusionThese data show that visceral adipocytes shed exosomal-mediators predicted to regulate key end-organ inflammatory and fibrotic signaling pathways.

Objective Exosomes from obese adipose contain dysregulated microRNAs linked to insulin signaling, as compared to lean controls, providing a direct connection between adiposity and insulin resistance. The current study tested the hypotheses that gastric bypass surgery and its subsequent weight loss would normalize adipocyte-derived-exosomal microRNAs associated with insulin signaling and the associated metabolome related to glucose homeostasis. Methods African-American female subjects with obesity (N=6; age: 38.5±6.8 years; BMI: 51.2±8.8 kg/m2) were tested before and one year after surgery. Insulin resistance (HOMA), serum metabolomics and global microRNA profiles of circulating adipocyte-derived exosomes were evaluated via ANCOVA and correlational analyses. Results One-year post-surgery, patients showed decreased BMI (−18.6±5.1 kg/m2; p<0.001), ameliorated insulin resistance (HOMA: 1.94±0.6 pre-surgery, 0.49±0.1 post-surgery; p<0.001), and altered metabolites including branched chain amino acids. Biological pathways analysis of predicted mRNA targets of 168 surgery-responsive microRNAs (p<0.05) identified the insulin signaling pathway (p=1.27E-10; 52/138 elements), among others, in our dataset. The insulin signaling pathway was also a target of 10 microRNAs correlated to changes in HOMA (p<0.05; r>0.4), and 48 microRNAs correlated to changes in BCAA levels. Conclusions These data indicate that circulating adipocyte-derived exosomes are modified following gastric bypass surgery and correlate to improved post-surgery insulin resistance.

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Hippocampal function varies along its septotemporal axis, with the septal (dorsal) pole more frequently involved in spatial learning and memory and the temporal (ventral) pole playing a greater role in emotional behaviors. One feature that varies across these subregions is adult neurogenesis. New neurons are more numerous in the septal hippocampus but are more active in the temporal hippocampus during water maze training. However, many other aspects of adult neurogenesis remain unexplored in the context of septal versus temporal subregions. In addition, the dentate gyrus contains another functionally important anatomical division along the transverse axis, with the suprapyramidal blade showing greater experience-related activity than the infrapyramidal blade. Here we ask whether new neurons differ in their rates of survival and maturation along the septotemporal and transverse axes. We found that neurogenesis is initially higher in the infrapyramidal than suprapyramidal blade, but these cells are less likely to survive, resulting in similar densities of neurons in the two blades by four weeks. Across the septotemporal axis, neurogenesis was higher in septal than temporal pole, while the survival rate of new neurons did not differ. Maturation was assessed by immunostaining for the neuronal marker, NeuN, which increases in expression level with maturation, and for the immediate-early gene, Arc, which suggests a neuron is capable of undergoing activity-dependent synaptic plasticity. Maturation occurred approximately 1–2 weeks earlier in the septal pole than in the temporal pole. This suggests that septal neurons may contribute to function sooner; however, the prolonged maturation of new temporal neurons may endow them with a longer window of plasticity during which their functions could be distinct from those of the mature granule cell population. These data point to subregional differences in new neuron maturation and suggest that changes in neurogenesis could alter different hippocampus-dependent behaviors with different time courses.