Research

A major focus of the O'Rourke Lab centers on understanding the mechanisms involved in insulin resistance and how adipocytes process glucose. Adipocytes in diabetic individuals are especially impaired in this respect. Our laboratory's unique adipose tissue resource, including well-annotated human subcutaneous and visceral adipose tissue, enables our group to correlate our discoveries at the bench with patient physiology, histology and outcomes related to gastric surgery, weight loss and disease remission. The two- and three-dimensional human and adipocyte cell culture models our lab has created allow detailed interrogation of these tissues.

We also use murine models to study adipose tissue in lean and obese mice, and we use adipose tissue transplants to investigate the regulatory effects on metabolism and insulin resistance. A key objective of our work is to create a therapeutic vehicle using engineered adipose tissue transplants to treat adipose tissue dysfunction seen in type 2 diabetes. We use advanced technologies, such as transcriptomics, RNA sequencing and single-cell sequencing, flow cytometry, and a range of cellular metabolic assays to help us answer questions about adipocyte dysfunction and how it impacts systemic metabolism.

The O'Rourke Laboratory uses several strategies to deepen our understanding of adipose tissue biology and dysfunction in obesity, metabolic disease and cancer, including:

Clarifying the Role of the Extracellular Matrix (ECM)

The ECM is comprised of molecules that surround adipocytes and adipose tissue and regulate adipocyte cell metabolism. In diabetic individuals, our lab has demonstrated that adipose tissue is altered, and that the ECM contributes to adipocyte dysfunction with respect to glucose metabolism. Our work continues to better understand the mechanisms by which those impairments occur and to develop methods to manipulate the ECM to improve adipocyte, and systemic, metabolism. 

Bioengineering Artificial Matrices as a Therapeutic Vehicle in Diabetes

In collaboration with bioengineers, we are developing artificial matrices, also called bioscaffolds, in which we can grow adipocytes. By manipulating the matrices, we can engineer healthier adipocytes that can be transplanted into mice with diabetes and obesity in effort to cure these diseases.

Defining Preadipocyte Subpopulations Within Human Adipose Tissue

In addition to studying matrix–adipocyte interactions, we also investigate the ways in which the ECM interacts with stem cells that give rise to adipocytes within adipose tissue. Currently, we use single cell RNA sequencing to define preadipocyte and macrophage subpopulations within human adipose tissue in diabetes. Our objective is to understand which types may confer a metabolic benefit or be detrimental.

We are developing novel methods to isolate, extract and manipulate these cells in vitro to understand how they function–and how we can make them healthier. Our objective with this work, too, is to develop tissue that can be used as a therapeutic vehicle to improve metabolic dysfunction. 

Investigating Additional Cell–Cell and Cell–Matrix Interactions

Our laboratory conducts research into other cell types, including macrophages, several types of immune cells and endothelial cells. The aim of this work is to better understand how these cell types communicate with adipocytes and the extracellular matrix so that we can identify the regulating mechanisms and engineer healthier adipose tissue.

Studying Adipocyte—Cancer Crosstalk

Our lab, and others, have hypothesized that dysfunctional adipocytes and adipose tissue may contribute to the development and growth of pancreatic cancer. We are studying the crosstalk between pancreatic cancer cells and adipocytes in in vitro murine pancreatic cancer models.

The O'Rourke Laboratory has advanced the understanding of adipose tissue biology and dysfunction and its role in metabolic disease and, more recently, cancer in many ways. Some our findings include:

• Implication of the ECM in adipose tissue dysfunction in the context of diabetes. Our work found that in tissue in 2D culture from patients without diabetes, the ECM prevents metabolic dysfunction with respect to glucose metabolism in adipocytes, while the ECM in tissue from patients with the disease negatively impacts glucose metabolism. Our findings tell us that the ECM is a promising means to influence adipose tissue metabolism. 
• Further work investigating ECM–cellular interactions in our 3D culture systems has implicated advanced glycation end products and Rho signaling as key players in regulating ECM–adipocyte metabolic crosstalk and may alter how adipocytes metabolize glucose. In our work on understanding fat metabolism in adipocytes, we've implicated beta-adrenergic signaling pathways.
• Our research on the role of inflammation and fibrosis in adipose tissue, likely a chronic state in obesity, has homed in on cell stress and hypoxia as a trigger of inflammatory processes within adipose tissue. More specifically, we have pinpointed p38 mitogen-activated protein kinase as an important regulator in hypoxia in adipose tissue.
• Our group was the first to report and define the role of the human adipose tissue natural killer (NK) cell phenotype, with upregulated NKG2D, in the context of diabetes and obesity in a mouse model as well as in human tissue. We also were the first to demonstrate, in a mouse model, that ablating the NK cells improved systemic insulin resistance, suggesting that NK cells might serve as a potential therapeutic target.
• In recent, collaborative work on pancreatic cancer cell–adipocyte crosstalk, we have found that adipocytes support the growth and spread of cancer cells. Additionally, we have identified glutamine as a potentially important mediator in these processes.

Our findings have the potential to advance how we treat obesity, diabetes and cancer, leading us toward truly personalized approaches. In the area of diagnostics, we are working toward use of histological, cellular and a host of other correlates as predictors of disease and of outcomes after bariatric surgery or other weight loss intervention, so that we can better target therapy to the patients most likely to benefit. Our overarching goal is to generate new methods for cell-based therapies using patients' own adipocyte stem cells as the vehicle.

We work closely with many basic scientists, surgeon-scientists and bioengineers. Some current collaborations include investigations with:

• Carey Lumeng, MD, PhD, of Internal Medicine, on adipose tissue biology.
• Tim Frankel, MD, a surgical oncologist in the Section of General Surgery, on adipocyte–pancreatic cancer crosstalk. 
• Lonnie Shea, PhD, of Biomedical Engineering, on extracellular matrix–adipocyte crosstalk
• Andy Putnam, PhD, of Biomedical Engineering and Cardiovascular Medicine, on matrix–adipocyte crosstalk with an emphasis on characterizing the mechanical properties of tissue.

We continue to explore the interactions between adipocytes and other cell types within adipose tissue and their role in regulating cellular function. In particular, we are interested in endothelial cells that give rise to blood vessel growth in adipose tissue. Evidence suggests these processes are also impaired in diabetes.

We are expanding our bioengineered matrices work to gain a greater understanding of the role of mechanical factors in addition to molecular interactions. Our observations to date suggest that mechanical properties of these matrices may have detrimental effects on adipocyte metabolism.