Nutrition is not the only factor driving obesity, which has grown to epidemic proportions in the Western world. New Tel Aviv University research has shown that fat mass in cells expands with disuse, and that the mechanics of "cellular expansion" plays a primary role in fat production. The research was published in The Biophysical Journal.
To understand how obesity develops, Prof. Amit Gefen, Dr. Natan Shaked and Naama Shoham of TAU's department of biomedical engineering, together with Prof. Dafna Benayahu of the department of cell and developmental biology, used stateof- the-art technology to analyze the accumulation of fat in the body at the cellular level. By exposing the mechanics of fat production at a cellular level, the researchers offer insight into the development of obesity.
With a better understanding of the process, the researchers are now creating a platform to develop new therapies and technologies to prevent or even reverse fat gain.
Two years ago, the researchers were awarded a grant from the Israel Science Foundation to investigate how mechanical forces increase the fat content within fat cells. "We wanted to find out why a sedentary lifestyle results in obesity, other than making time to eat more hamburgers," said Gefen. "We found that fat cells exposed to sustained, chronic pressure – such as what happens to the buttocks when you're sitting down – experienced accelerated growth of lipid (fat) droplets.
"Contrary to muscle and bone tissue, which get mechanically weaker with disuse, fat deposits in fat cells expanded when they experienced sustained loading, by as much as 50 percent. This was a substantial discovery."
The researchers discovered that, once it accumulated lipid droplets, the structure of a cell and its mechanics changed dramatically.
Using a cutting-edge atomic force microscope and other microscopy technologies, they were able to observe the material composition of the transforming fat cell, which became stiffer as it expanded. This stiffness alters the environment of surrounding cells by physically deforming them, pushing them to change their own shape and composition.
"When they gain mass and change their composition, expanding cells deform neighboring cells, forcing them to differentiate and expand," said Gefen.
"This proves that you're not just what you eat. You're also what you feel – and what you're feeling is the pressure of increased weight and the sustained loading in the tissues of the buttocks of the couch potato."
"If we understand the etiology of getting fatter, of how cells in fat tissues synthesize nutritional components under a given mechanical loading environment, we can think about different practical solutions to obesity," Gefen said. "If you can learn to control the mechanical environment of cells, you can then determine how to modulate the fat cells to produce less fat."
VITAMIN D HELPS BREAST CANCER PATIENTS
Breast cancer patients with high levels of vitamin D in their blood are twice as likely to survive the disease as women with low levels of the vitamin, University of California, San Diego School of Medicine researchers reported in a recent issue of Anticancer Research.
In previous studies, family medicine specialist Prof.
Cedric Garland showed that low vitamin D levels were linked to a high risk of premenopausal breast cancer.
That finding, he said, prompted him to question the relationship between 25-hydroxyvitamin D – a metabolite produced by the body from the ingestion of vitamin D – and breast cancer survival rates.
Garland and colleagues performed a statistical analysis of five studies, including nearly 4,500 breast cancer patients, of 25-hydroxyvitamin D obtained at the time of patient diagnosis and their follow-up for an average of nine years.
"Vitamin D metabolites increase communication between cells by switching on a protein that blocks aggressive cell division," said Garland. "As long as vitamin D receptors are present, tumor growth is prevented and kept from expanding its blood supply. The vitamin receptors are not lost until a tumor is very advanced. This is the reason for better survival in patients whose vitamin D blood levels are high."
"The study has implications for including vitamin D as an adjuvant to conventional breast cancer therapy," said co-author and colleague Prof. Heather Hofflich.
Garland recommended randomized controlled clinical trials to confirm the findings but suggested physicians consider adding vitamin D into a breast cancer patient's standard care now and then closely monitoring the patient.
"There is no compelling reason to wait for further studies to incorporate vitamin D supplements into standard care regimens, since a safe dose of vitamin D needed to achieve high serum levels, above 30 nanograms per milliliter, has already been established," said Garland.
According to the US National Institutes of Health, the current recommended daily allowance for vitamin D is 600 International Units for most adults and 800 IU for those over 70 years old. Although only highly excessive levels of vitamin D may be harmful, Garland urged patients to go to a doctor and check their vitamin D levels before substantially increasing vitamin D intake.
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