By Cindy Abole
Public Relations

For centuries, Greeks and people from other Mediterranean cultures have prized olive oil for its use in cooking, fuel, and culinary and medicinal medicine. Olive oil makes a positive impact on health and offers other benefits such as lowering the risk of heart disease and cancer as well as preventive effects for people diagnosed with diabetes and other illnesses.

Dr. Ashley Cowart

These findings are of special interest to biochemist L. Ashley Cowart, Ph.D., and her colleagues. Cowart, assistant professor in the Department of Biochemistry and Molecular Biology, has focused her research on characterizing how saturated fat affects sphingolipid metabolism in diabetes and the metabolic syndrome since 2005. Sphingolipids are a class of lipid molecules that have been shown to regulate signaling pathways that mediate cell growth, cell death and cell aging. Specifically, the sphingolipid ceramide has been shown to cause insulin resistance in muscle cells.
In 2009, Cowart and Wei Hu, Ph.D., broadened the scope of her research to investigate not only how saturated fats drive ceramide synthesis, but how unsaturated fats, specifically oleate, can prevent ceramide synthesis. Her findings were published in the Journal of Biological Chemistry and in an editorial comment on the Nature Publishing Group's Lipodomics Gateway April 27.

For this project, Cowart's team aimed to determine how fats regulate ceramide synthesis and insulin resistance and the role this process might play in Type 2 diabetes. She found that while saturated fat increased ceramides and caused insulin resistance, oleate could completely block ceramide generation that resulted from saturated fat, and this prevented saturated fat-induced insulin resistance.

"While monounsaturated fats such as oleate benefit human health in multiple ways, this work demonstrated that perhaps one of the most important benefits could be the prevention of insulin resistance that would result from a diet high in saturated fat," said Cowart.

According to Cowart, the prevention of ceramide production may serve as a key mechanism by which dietary oleate benefits human health. She and her team are currently evaluating mice-fed diets that reflect different fatty acid compositions to determine ceramide production levels and obesity-induced insulin resistance. Based on these models, a diet high in saturated fats (including palmitate, which occurs at high levels in dairy) produces high insulin resistance compared to a diet high in monounsaturated fats, including oleate. According to Cowart, the body can make fatty acid, but dietary fat serves important roles in health and disease.

Olive oil is composed of up to 80 percent monounsaturated fatty acids and other natural antioxidants that resist oxidation better than polyunsaturates. Other beneficial effects of monounsaturated fatty acids include helping to keep the body's high-density lipid protein (HDL) or good cholesterol levels up and low-density lipid protein (LDL) or bad cholesterol down.

Cowart's research will promote further study in the mouse-diet induced obesity model aimed at understanding the impact of dietary fat on tissues including the liver, heart and adipose. Her work is funded through the Department of Veterans affairs and also supported by a Center for Biomedical Research Excellence grant, which allowed her to collaborate with others including specialists at MUSC's Lipidomics Core Facility. This facility allowed her team to conduct lipid measurements using cutting-edge high-throughput mass spectrometry methodology.