Myriam Aouadi group
Since the discovery of macrophages in adipose tissue, many laboratories have focused their effort on understanding the contribution of these immune cells to metabolic diseases. Despite great progress in characterizing obesity as a state of low-grade inflammation, very little is known about the multiple phenotypes and functions of macrophages in metabolic tissues. The lack of methods to carefully investigate cell-to-cell variability in macrophage phenotype and to manipulate gene expression in a cell-specific manner has delayed answering these crucial questions. Our lab takes advantage of sophisticated methods to investigate macrophage subpopulations and their function in obesity-associated metabolic complications.
Study the mechanism whereby factors produced by liver macrophages regulate insulin sensitivity.
We have recently discovered that mice fed a high fat diet (HFD) become rapidly obese and insulin resistant independently of liver inflammation, which was thought to be an important driver in obesity-induced insulin resistance. On the other hand, depletion studies have shown that removing liver macrophages (LMs) prevents insulin resistance induced by obesity, suggesting an important role of LMs in the regulation of insulin sensitivity. Using RNAseq, we identified genes specifically expressed by liver macrophages, whose expression significantly increases with obesity and insulin resistance. We then took advantage of a powerful and unique tool, called glucan encapsulated RNAi particles (GeRP), that deliver siRNA and silence genes specifically in macrophages in vivo.
This technology is based on small interfering RNA (siRNA) encapsulated within glucan particles derived from baker’s yeast. By using intraperitoneal injections, we showed that GeRPs delivered siRNA and silenced genes specifically in macrophages in the adipose tissue of obese mice. However, by using intravenous administration, we showed that GeRPs delivered siRNA and silenced genes in LMs but not in hepatocytes or macrophages within other tissues.
Using this unique method, we found that silencing genes of interest specifically in LMs improves insulin sensitivity in obese mice. This project has so far confirmed that liver macrophages can play a role in the regulation of insulin sensitivity independantly of inflammation. This opened a new avenue towards the discovery of the multiple roles of immune cells other than only the inflammatory response.
Identify distinct phenotypes and functions of macrophages in liver and adipose tissue.
Macrophages are able to modulate their properties upon contact with different cell types as well as extracellular matrix. Their intrinsic heterogeneity during differentiation is compounded by reciprocal interactions with neighbouring cells, including other macrophages. In many different tissues, macrophages can occupy different anatomical niches and perform specialized functions even within the same organ. Emerging data suggest that macrophages acquire specialized functions, which are tailored for assisting local homeostasis, within each particular organ.
We use scRNAseq, metabolomics, flow cytometry, CytOF and in situ transcriptomic to study the heterogeneity of resident macrophage in liver and adipose tissue in health and metabolic disease.
Decoding the phenotype of macrophages through the study of non-coding RNA
We aim at identifying dysregulated genes but also non-coding RNAs such as microRNAs, enhancer RNAs, and long non-coding RNAs which have recently emerged as important regulators of gene expression, and which expression have been associated with several diseases.
Using the Global Run-On sequencing (GRO-seq) to directly measure rates of nascent transcription genome-wide, we propose to identify all transcript, genes and non-coding RNAs dysregulated in LMs in obesity that could be involved in the development of insulin resistance.
We are especially interested in enhancers, which are regions of DNA important for the regulation of genes transcription, and can be transcribed as non-coding RNAs called enhancer-derived RNAs (eRNAs).
The eRNAs can regulate the expression of the nearby gene, and have also been shown to be superior markers for active enhancers because of their small size and high dynamic ranges.
The mining of the GRO-seq data for eRNAs transcription to map functional enhancers, combined with genome-wide de novo motif analysis performed at sites of eRNAs dysregulation in LMs from obese and insulin resistant mice compared to lean mice, will allow us to identify the transcription factor(s) that could be involved in gene dysregulation in LMs in obesity.
- Integrated Cardio Metabolic Center/Astrazeneca start-up fund (2015-2020).
- Swedish Research Council (2016-2020).
- Roft Luft foundation through the SRP Diabetes at Karolinska Institutet (2016-2017).
- Novonordisk Foundation through the Tripartite Immuno-metabolism Consortium (2016-2020).
- Diabetes Wellness Foundation (2017)
Myriam Aouadi, PhD, Group leader
I received my PhD in December 2005 from the University of Nice Sophia-Antipolis, France, in the laboratory of Yannick Le Marchand-Brustel. My worked focussed on the role of MAPK pathways in the commitment of embryonic stem cells in different lineages. I found that p38MAPK is an important player in the early steps of neurogenesis and myogenesis, while it is required for the late stages of adipogenesis. In 2006, I joined the laboratory of Michael Czech at the University of Massachusetts to work on the emerging field of immunometabolism, that investigates the interactions between immune and metabolic cells. During my postdoctoral studies, I developed a method to deliver siRNA specifically to macrophages in vivo. This unique technology allows the study of particular factors expressed by macrophages specifically. In 2009, I became assistant professor at the University of Massachusetts and used this novel technology to show that while macrophages in the adipose tissue could be detrimental to insulin sensitivity they could be beneficial as well.
I started my laboratory at the Integrated Cardio-Metabolic Center at the Karolinska institute in November 2014. My lab investigates the multiple roles and heterogeneity of liver and adipose tissue macrophages in metabolic diseases.
Team work, curiosity, passion and enthusiasm are the important qualities that I am looking for and found in my lab members.
Emelie Barreby, PhD student
I received my Master’s degree in Biomedicine from Karolinska Institutet in 2013. I am studying macrophage heterogeneity in the liver during health and metabolic disease, in order to understand the role of liver macrophages in the development of insulin resistance and type 2 diabetes.
Cecilia Morgantini, MD, PhD, Postdoctoral fellow
I trained as a physician in Internal Medicine and Metabolism at the University of Pisa (Italy) under the supervision of Prof. Ele Ferrannini. As a clinical fellow I interacted with patients with diabetes, and during this time I developed the desire to bring the bench to the bedside by working on the physiology of metabolic diseases. I therefore spent two years of my residency program in the Atherosclerosis Research Unit of UCLA, working on high-density-lipoprotein (HDL) functions and ApoA-I mimetic peptides in a mouse model of diabetes. In 2014 I obtained my phD from Scuola Superiore Sant’Anna in Pisa, where I carried on my studies on HDL functions and compositions in the pathogenesis of cardiovascular disease in type 2 diabetes focusing only on human. As part of my PhD program I also joined Lewis’ Lab at the Banting and Best Diabetes Center in Toronto, conducting integrative physiology studies attempting to determine the regulation of intestinal lipoprotein particle production. At the beginning of 2015 I joined, as a postdoc, the laboratory of Dr. Myriam Aouadi where I currently focus on molecular and cellular mechanisms involved in the development of insulin resistance and type 2 diabetes.
Laura Levi, Lab manager, PhD
I took my masters in industrial biotechnology at the University Federico II of Naples. For two years, I worked as a technician at the research center of Novartis Vaccines & Diagnostics in Siena. Next step was to perform my PhD at Karolinska Institutet by focusing on the connection between chronic infection and cancer development in in vitro and in vivo models. I have been part of Dr. Aouadi’s lab since early 2016. As a research assistant, I provide technical support in the different projects.
André Sulen, Postdo, PhD
I graduated as a PhD from the University of Bergen (Norway) in 2016, my project evaluated signal transduction in blood leukocytes as biomarkers for environmental stress exerted on the healthy population. Interesting results from a cross-sectional study led us to describe how hydrogen sulfide can cause sustained activation of MAPK p38 in monocytes. It is well known that environmental cues regulate inflammation by modulating monocyte and macrophage transcriptional programs, and in February 2017 I started as a postdoc in Dr. Aouadi´s group, where I will use single-cell methods to better characterize the role of immune cells in adipose tissue during development of insulin resistance and type 2 diabetes.
Connie Xu (M.Sc. in Medical Science), Laboratory technician
I am a recent graduate from the Master’s program in Biomedicine at Karolinska Institutet. Through my studies, I have gained experience in flow cytometry, single-cell RNA sequencing and most recently, Padlock in situ sequencing. I was first exposed to research in the field of Immunology during my Bachelor’s degree project, where I was introduced to the basic research of NK cells. Since then, all research projects that I have participated in have been related to immune cells. With Type 2 Diabetes (T2D) running in my family, I became interested in the role of the immune system in T2D and insulin resistance. As of June 2017, I have joined the Aouadi group as a Lab technician and will be working on projects involving single-cell RNA sequencing and in situ sequencing.
Marcela Aparicio-Vergara, PhD, former postdoctoral fellow, now research manager of Nutrition & Health at NutriLeads, Netherlands.
Francisco Verdeguer, PhD, former postdoctoral fellow, now group leader at the University of Zurich.
Jennifer Jager, Principal Investigator at University of Nice, France.
Macrophage heterogeneity and energy metabolism.
Exp. Cell Res. 2017 11;360(1):35-40
Liver innate immune cells and insulin resistance: the multiple facets of Kupffer cells.
J. Intern. Med. 2016 Aug;280(2):209-20
Lipid storage by adipose tissue macrophages regulates systemic glucose tolerance.
Am. J. Physiol. Endocrinol. Metab. 2014 Aug;307(4):E374-83
Local proliferation of macrophages contributes to obesity-associated adipose tissue inflammation.
Cell Metab. 2014 Jan;19(1):162-171
Activation of the Nlrp3 inflammasome in infiltrating macrophages by endocannabinoids mediates beta cell loss in type 2 diabetes.
Nat. Med. 2013 Sep;19(9):1132-40
Gene silencing in adipose tissue macrophages regulates whole-body metabolism in obese mice.
Proc. Natl. Acad. Sci. U.S.A. 2013 May;110(20):8278-83
Insulin signalling mechanisms for triacylglycerol storage.
Diabetologia 2013 May;56(5):949-64
Glucan particles for selective delivery of siRNA to phagocytic cells in mice.
Biochem. J. 2011 Jun;436(2):351-62
Coronin 2A mediates actin-dependent de-repression of inflammatory response genes.
Nature 2011 Feb;470(7334):414-8
RNAi-based therapeutic strategies for metabolic disease.
Nat Rev Endocrinol 2011 Apr;7(8):473-84
Orally delivered siRNA targeting macrophage Map4k4 suppresses systemic inflammation.
Nature 2009 Apr;458(7242):1180-4