Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Fat in the liver -- not the belly -- is a better marker for disease risk

26.08.2009
New findings from nutrition researchers at Washington University School of Medicine in St. Louis suggest that it's not whether body fat is stored in the belly that affects metabolic risk factors for diabetes, high blood triglycerides and cardiovascular disease, but whether it collects in the liver.

Having too much liver fat is known as nonalcoholic fatty liver disease. The researchers report online in the journal PNAS Early Edition that when fat collects in the liver, people experience serious metabolic problems such as insulin resistance, which affects the body's ability to metabolize sugar.

They also have increases in production of fat particles in the liver that are secreted into the bloodstream and increase the level of triglycerides.

For years, scientists have noted that where individuals carried body fat influences their metabolic and cardiovascular risk. Increased fat inside the belly, known as visceral fat, is associated with an increased risk of diabetes and heart disease.

"Data from a large number of studies shows that visceral fat is associated with metabolic risk, which has led to the belief that visceral fat might even cause metabolic dysfunction," says senior investigator Samuel Klein, M.D. "However, visceral fat tracks closely with liver fat. We have found that excess fat in the liver, not visceral fat, is a key marker of metabolic dysfunction. Visceral fat might simply be an innocent bystander that is associated with liver fat."

Klein, the Danforth Professor of Medicine and Nutritional Science, directs the Division of Geriatrics and Nutritional Science and the Center for Applied Research Studies, as well as Washington University's Center for Human Nutrition. He says most of our body fat, called subcutaneous fat, is located under our skin, but about 10 percent is present inside the belly, while much smaller amounts are found inside organs such as the liver and muscle.

This study compared obese people with elevated and normal amounts of liver fat. All subjects were matched by age, sex, body mass index, percent body fat and degree of obesity. Through careful evaluations of obese people with different amounts of visceral fat or liver fat, Klein's team determined that excess fat inside the liver identifies those individuals who are at risk for metabolic problems.

"We don't know exactly why some fats, particularly triglycerides, will accumulate inside the liver and muscle in some people but not in others," says first author Elisa Fabbrini, M.D., Ph.D., assistant professor of medicine. "But our data suggest that a protein called CD36, which controls the transport of fatty acids from the bloodstream into different tissues, is involved."

Fatty acids are the building blocks for making fats, known as triglycerides. Klein, Fabbrini and their colleagues found that CD36 levels were lower in fat tissue and higher in muscle tissue among people with elevated liver fat.

Fabbrini and Klein say changes in CD36 activity could be responsible for diverting circulating fatty acids away from fat tissue and into liver and muscle tissue, where they are converted to triglyceride. Increased tissue uptake of fatty acids could be responsible for metabolic dysfunction.

Klein says those who are obese but don't have high levels of fat in the liver should be encouraged to lose weight, but those with elevated liver fat are at particularly high risk for heart disease and diabetes. He says they need to be treated aggressively to help them lose weight because dropping pounds can make a big difference.

"Fatty liver disease is completely reversible," he says. "If you lose a small amount of weight, you can markedly reduce the fat content in your liver. In fact, even two days of calorie restriction can cause a large reduction in liver fat and improvement in liver insulin sensitivity."

Fabbrini E, Magkos F, Mohammed S, Pietka T, Abumrad NA, Patterson BW, Okunade A, Klein S. Intrahepatic fat, not visceral fat, is linked with metabolic complications of obesity. PNAS Early Edition (2009), published online Aug. 24, 2009. www.pnas.org/cgi/doi/10.1073/pnas.0904944106

(related papers)

Deivanayagam S, Mohammed BS, Vitola BE, Naguib GH, Keshen TH, Kirk EP, Klein S. Nonalcoholic fatty liver disease is associated with hepatic and skeletal muscle insulin resistance in overweight adolescents. American Journal of Clinical Nutrition, 88(2) pp. 257-262, Aug. 2008.

Korenblat K, Fabbrini E, Mohammed BS, Klein S. Liver, muscle and adipose tissue insulin resistance is directly related to intrahepatic triglyceride content in obese subjects. Gastroenterology 134: 1369-1375, 2008.

Kirk E, Reeds DN, Finck BN, Mayurranjan MS, Klein S. Effects of acute and chronic calorie restriction on insulin action in obese men and women. Gastroenterology 136: 1552-1560, 2009.

This research was supported by grants from the National Institute of Diabetes and Digestive and Kidney Diseases and the National Center for Research Resources of the National Institutes of Health.

Washington University School of Medicine's 2,100 employed and volunteer faculty physicians also are the medical staff of Barnes-Jewish and St. Louis Children's hospitals. The School of Medicine is one of the leading medical research, teaching and patient care institutions in the nation, currently ranked third in the nation by U.S. News & World Report. Through its affiliations with Barnes-Jewish and St. Louis Children's hospitals, the School of Medicine is linked to BJC HealthCare.

Jim Dryden | EurekAlert!
Further information:
http://www.wustl.edu

More articles from Health and Medicine:

nachricht Investigators may unlock mystery of how staph cells dodge the body's immune system
22.09.2017 | Cedars-Sinai Medical Center

nachricht Monitoring the heart's mitochondria to predict cardiac arrest?
21.09.2017 | Boston Children's Hospital

All articles from Health and Medicine >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: The pyrenoid is a carbon-fixing liquid droplet

Plants and algae use the enzyme Rubisco to fix carbon dioxide, removing it from the atmosphere and converting it into biomass. Algae have figured out a way to increase the efficiency of carbon fixation. They gather most of their Rubisco into a ball-shaped microcompartment called the pyrenoid, which they flood with a high local concentration of carbon dioxide. A team of scientists at Princeton University, the Carnegie Institution for Science, Stanford University and the Max Plank Institute of Biochemistry have unravelled the mysteries of how the pyrenoid is assembled. These insights can help to engineer crops that remove more carbon dioxide from the atmosphere while producing more food.

A warming planet

Im Focus: Highly precise wiring in the Cerebral Cortex

Our brains house extremely complex neuronal circuits, whose detailed structures are still largely unknown. This is especially true for the so-called cerebral cortex of mammals, where among other things vision, thoughts or spatial orientation are being computed. Here the rules by which nerve cells are connected to each other are only partly understood. A team of scientists around Moritz Helmstaedter at the Frankfiurt Max Planck Institute for Brain Research and Helene Schmidt (Humboldt University in Berlin) have now discovered a surprisingly precise nerve cell connectivity pattern in the part of the cerebral cortex that is responsible for orienting the individual animal or human in space.

The researchers report online in Nature (Schmidt et al., 2017. Axonal synapse sorting in medial entorhinal cortex, DOI: 10.1038/nature24005) that synapses in...

Im Focus: Tiny lasers from a gallery of whispers

New technique promises tunable laser devices

Whispering gallery mode (WGM) resonators are used to make tiny micro-lasers, sensors, switches, routers and other devices. These tiny structures rely on a...

Im Focus: Ultrafast snapshots of relaxing electrons in solids

Using ultrafast flashes of laser and x-ray radiation, scientists at the Max Planck Institute of Quantum Optics (Garching, Germany) took snapshots of the briefest electron motion inside a solid material to date. The electron motion lasted only 750 billionths of the billionth of a second before it fainted, setting a new record of human capability to capture ultrafast processes inside solids!

When x-rays shine onto solid materials or large molecules, an electron is pushed away from its original place near the nucleus of the atom, leaving a hole...

Im Focus: Quantum Sensors Decipher Magnetic Ordering in a New Semiconducting Material

For the first time, physicists have successfully imaged spiral magnetic ordering in a multiferroic material. These materials are considered highly promising candidates for future data storage media. The researchers were able to prove their findings using unique quantum sensors that were developed at Basel University and that can analyze electromagnetic fields on the nanometer scale. The results – obtained by scientists from the University of Basel’s Department of Physics, the Swiss Nanoscience Institute, the University of Montpellier and several laboratories from University Paris-Saclay – were recently published in the journal Nature.

Multiferroics are materials that simultaneously react to electric and magnetic fields. These two properties are rarely found together, and their combined...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

“Lasers in Composites Symposium” in Aachen – from Science to Application

19.09.2017 | Event News

I-ESA 2018 – Call for Papers

12.09.2017 | Event News

EMBO at Basel Life, a new conference on current and emerging life science research

06.09.2017 | Event News

 
Latest News

Rainbow colors reveal cell history: Uncovering β-cell heterogeneity

22.09.2017 | Life Sciences

Penn first in world to treat patient with new radiation technology

22.09.2017 | Medical Engineering

Calculating quietness

22.09.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>