Dr. Graf's laboratory's research focus is on the relationships between obesity and changes in
lipid and lipoprotein metabolism that link obesity to cardiovascular diseases and diabetes.
We have two main areas of research. The first of these projects focuses on the active elimination of
cholesterol from the body in a process termed “Reverse Cholesterol Transport”. Currently available therapies
target cholesterol synthesis and absorption to reduce plasma cholesterol and lower the risk cardiovascular disease.
However, an emerging body of work suggests that the flux of cholesterol through lipoproteins (LDL and HDL) is more
relevant to cardiovascular disease than their absolute levels in plasma. In addition, research from our lab and
others suggests that cholesterol in the liver may play an active role in the development of non-alcoholic fatty
liver disease, a common complication of obesity.
A transport protein complex called ABCG5 ABCG8, or G5G8 for short, is expressed in both the liver and intestine
and represents the major route for cholesterol elimination from the body. We have recently shown that the loss of
this transporter worsens the development of fatty liver disease and that acutely increasing its levels can restore
some aspects of liver function in a mouse model of obesity and fatty liver disease. However, little is known about
what regulates the activity of this cholesterol “pump”. The goal of this project is to determine how this pump is
regulated such that therapeutics can be developed to accelerate cholesterol elimination in the treatment of both
cardiovascular and liver disease.
The second project focuses on the role that fat, or adipose tissue, plays in the development of obesity-related
metabolic disorders. Adipose tissue was once thought to simply be a storage organ, but work over the last decade
has demonstrated that it plays a pivotal role in the development of insulin resistance, systemic inflammation and
increased risk of cardiovascular disease and Type 2 diabetes. Using a unique model of rapid-onset obesity and insulin
resistance, we conducted experiments to evaluate changes in gene expression in adipose tissue. The two major pathways
disrupted in this model are involved in the regulation of biological rhythms and in lung development. These results
suggest that the adipose tissue of obese mice is asynchronous with the rest of the body and that fat cells may undergo
genetic reprogramming during the development of adipose dysfunction. Experiments are ongoing to determine if these
pathways are casual bystanders during the development of adipose dysfunction or play a causative role. If the latter
is true, these pathways will be explored further to determine if therapeutics that target these pathways would be useful
in the treatment of obesity-related metabolic diseases.