Monthly Archives: May 2014

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Newswise BALTIMORE May 21, 2014. Researchers at the University of Maryland School of Medicine have identified a mutation in a fat-storage gene that appears to increase the risk for type 2 diabetes and other metabolic disorders, according to a study published online today in the New England Journal of Medicine.

The researchers discovered the mutation in the hormone-sensitive lipase (HSL) gene by studying the DNA of more than 2,700 people in the Old Order Amish community in Lancaster County, Pa. HSL is a key enzyme involved in breaking down stored fat (triglycerides) into fatty acids, thereby releasing energy for use by other cells.

We found that Amish people with this mutation have defects in fat storage, increased fat in the liver, high triglycerides, low "good" (HDL) cholesterol, insulin resistance and increased risk of developing type 2 diabetes, says the studys senior author, Coleen M. Damcott, Ph.D., an assistant professor of medicine in the Division of Endocrinology, Diabetes and Nutrition and member of the Program for Personalized and Genomic Medicine at the University of Maryland School of Medicine.

In this study, 5.1 percent of the Old Order Amish study participants had at least one copy of the mutation. Four people had two copies of the mutation and consequently produced no HSL enzyme, Dr. Damcott says. The mutation is less common in non-Amish Caucasians of European descent (0.2%), thus the higher prevalence of the mutation in the Amish makes it possible to characterize its full range of effects.

Future studies of this gene will allow us to look more closely at the effects of its deficiency on human metabolism to better understand the function of the HSL protein and its impact on fat and glucose metabolism, Dr. Damcott says. These studies will also examine the potential of using HSL as a drug target for treating type 2 diabetes and related complications.

She notes that type 2 diabetes is a complex disease whose susceptibility is often determined by interactions between genetics and lifestyle factors, such as overeating and physical inactivity. Susceptibility genes for diabetes may be involved in several different metabolic pathways in the body, including storage and release of fat for energy.

Discovery of this mutation adds to the growing list of insights gained from genomic studies that can be used to develop new treatments and customize existing treatments for type 2 diabetes and related metabolic disorders, Dr. Damcott says.

E. Albert Reece, M.D., Ph.D., M.B.A., vice president for medical affairs at the University of Maryland and the John Z. and Akiko K. Bowers Distinguished Professor and dean of the University of Maryland School of Medicine, says, This discovery offers intriguing new evidence of how genetics may play a role in how people develop type 2 diabetes and provides a possible target for medical intervention. Through our Program for Personalized and Genomic Medicine, we are always striving to devise effective therapies to fit an individuals genetic make-up.

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University of Maryland Researchers Identify Mutation in Fat-Storage Gene That Appears to Increase Type 2 Diabetes Risk

PUBLIC RELEASE DATE:

22-May-2014

Contact: Karin Eskenazi ket2116@cumc.columbia.edu 212-342-0508 Columbia University Medical Center

NEW YORK, NY (May 22, 2014) Researchers have discovered how a gene commonly linked to obesityFTOcontributes to weight gain. The study shows that variations in FTO indirectly affect the function of the primary cilium, a little-understood hair-like appendage on brain and other cells. Specific abnormalities of cilium molecules, in turn, increase body weight, in some instances, by affecting the function of receptors for leptin, a hormone that suppresses appetite. The findings, made in mice, suggest that it might be possible to modify obesity through interventions that alter the function of the cilium, according to scientists at Columbia University Medical Center (CUMC).

"If our findings are confirmed, they could explain how common genetic variants in the gene FTO affect human body weight and lead to obesity," said study leader Rudolph L. Leibel, MD, the Christopher J. Murphy Memorial Professor of Diabetes Research, professor of pediatrics and medicine, and co-director of the Naomi Berrie Diabetes Center at CUMC. "The better we can understand the molecular machinery of obesity, the better we will be able to manipulate these mechanisms and help people lose weight."

The study was published on May 6 in the online edition of Cell Metabolism.

Since 2007, researchers have known that common variants in the fat mass and obesity-associated protein gene, also known as FTO, are strongly associated with increased body weight in adults. But it was not understood how alterations in FTO might contribute to obesity. "Studies have shown that knocking out FTO in mice doesn't necessarily lead to obesity, and not all humans with FTO variants are obese," said Dr. Leibel. "Something else is going on at this location that we were missing."

In experiments with mice, the CUMC team observed that as FTO expression increased or decreased, so did the expression of a nearby gene, RPGRIP1L. RPGRIP1L is known to play a role in regulating the primary cilium. "Aberrations in the cilium have been implicated in rare forms of obesity," said Dr. Leibel. "But it wasn't clear how this structure might be involved in garden-variety obesity."

Dr. Leibel and his colleague, George Stratigopoulos, PhD, associate research scientist, hypothesized that common FTO variations in noncoding regions of the gene do not change its primary function, which is to produce an enzyme that modifies DNA and RNA. Instead, they suspected that FTO variations indirectly affect the expression of RPGRIP1L. "When Dr. Stratigopoulos analyzed the sequence of FTO's intronits noncoding, or nonprotein-producing, portionwe found that it serves as a binding site for a protein called CUX1," said Dr. Leibel. "CUX1 is a transcription factor that modifies the expression of RPGRIP1L."

Next, Dr. Stratigopoulos set out to determine whether RPGRIP1L plays a role in obesity. He created mice lacking one of their two RPGRIP1L genes, in effect, reducing but not eliminating the gene's function. (Mice that lack both copies of the gene have several serious defects that would obscure the effects on food intake.) Mice with one copy of RPGRIP1L had a higher food intake, gained significantly more weight, and had a higher percentage of body fat than controls.

Originally posted here:
Study shows how common obesity gene contributes to weight gain