Jimin Ren, Ph.D.
Jimin Ren, Ph.D., is using magnetic resonance spectroscopic (MRS) methods to analyze how muscle metabolizes carbohydrates and fat. His objective is to understand not only how normal muscle functions, but also the pathologies of such diseases as diabetes, metabolic syndrome, and mitochondrial myopathies. Metabolic syndrome is a set of obesity-related abnormalities including high blood pressure, insulin resistance, and abnormally high lipid levels that increase risk of cardiovascular disease and diabetes. Mitochondrial myopathies are metabolic disorders of the cell's power plants, mitochondria.
In one effort, Dr. Ren and colleagues Dean Sherry, Ph.D., and Craig Malloy, M.D., have developed an MRS analytical technique to measure the amount of lipid within the muscle cells of people with such diseases. Distinguishing this intramyocellular lipid from lipid contained in fat cells outside muscle cells has been extremely difficult. However, such measurement is critical if researchers are to understand the roles of the two lipid repositories in both normal muscle and that of people with such disorders as metabolic syndrome, insulin resistance, and diabetes. For example, although elevated levels of intramyocellular lipid has been associated with insulin resistance, such high levels are also found in athletes, who are presumably healthy.
MRS is the only analytical tool capable of distinguishing and quantifying the two forms of lipid. Dr. Ren and his colleagues have developed a long echo time MRS technique that enables them to obtain an MRS spectrum that resolves the two lipid forms in patients and to determine their concentrations in muscle tissue. A key to the new analytical technique is the AIRC's 7 Tesla MRI machine, whose higher resolution and detection sensitivity enables the researchers to pinpoint smaller regions of muscle and measure their lipid composition.
The current method for making such measurements is to take a biopsy tissue sample surgically and to isolate and analyze it for the relevant molecules. However, MRS analysis has the advantages that it is noninvasive, takes only minutes, and enables researchers to zero in repeatedly on the same target area of tissue, measuring fat metabolism in muscle over time.
Ren and his colleagues are also applying new MRS analytical techniques to quantify molecules important in metabolizing lipids in muscle cells. Important among these is acetyl carnitine, which is a key molecular link in the pathway by which lipids are broken down in mitochondria and fed into the tricarboxylic acid cycle (TCA) to generate energy. By tracing levels of acetyl carnitine in the muscle cells of people with such disorders as mitochondrial myopathies and metabolic syndrome, Ren and his colleagues seek to understand the pathologic mechanism of the diseases.
For publication information please view Dr. Ren's faculty profile.