Distinct transcriptional responses across tissue-resident macrophages to short-term and long-term metabolic challenge

The innate immune system safeguards the organism from both pathogenic and environmental stressors. Even physiological levels of nutrients affect organismal and intra-cellular metabolism and challenge the immune system. In the long term, over-nutrition leads to low-grade systemic inflammation. Here, we investigate tissue-resident components of the innate immune-system –macrophages and their response to short-term and long-term nutritional challenges. We analyze the transcriptomes of seven tissue-resident macrophage populations upon metabolic challenge and identify adipose tissue macrophages and the IL-1 pathway as early sensors of metabolic changes. Furthermore, by comparing functional responses between macrophage subtypes, we propose a regulatory, anti-inflammatory role of heat shock proteins of the HSP70 family in response to a metabolic challenge. Our data provides a resource for assessing the impact of nutrition and over-nutrition on the spectrum of macrophages across tissues with a potential for identification of systemic responses. Overall design: To investigate the short-term and long-term metabolic challenges mice were subjected to two nutritional protocols: 12h fasting, followed by 2h refeeding (FARE) and high fat diet (HFD) for 8 weeks. In the HFD experiment mice were additionally treated with Streptozotocin (STZ) at week 4 which resulted with islet ablation and hyperglycemia. Macrophages were isolated and purified using fluorescence-activated cell sorting (FACS). Six tissue resident macrophages populations (adipose tissue macrophages, microglia, pancreatic islet macrophages, Kupffer cells, colonic macrophages, peritoneal macrophages) and monocytes were isolated from fasted and refed mice (six up to ten replicates per condition). Three tissue macrophage populations (microglia, pancreatic islet macrophages, peritoneal macrophages) were isolated from mice fed by normal diet, by HFD and by HFD treated with STZ (three up to five replicates per condition). PolyA RNA fraction was extracted from purified macrophage populations and subjected to RNA-Seq.