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.
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
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.