Issue 01 - May 14, 2008

• Exploring Omega-3s for Prostate Cancer Treatment
• Fat Cells: A Constant Number
• Hormone Triggers an Urge to Eat

Exploring Omega-3s for Prostate Cancer Treatment

Prostate cancer is one of the most common cancers in America, affecting an estimated one in six men. Now, with an AICR grant, molecular biologist Linda A. deGraffenried is turning up some promising findings on how fish oils may play a role in treating an advanced form of this cancer.

Androgen deprivation therapy is a common treatment because androgen stimulates prostate cancer growth. Androgen is a class of hormones. Testosterone, which promotes male characteristics, is one of the most familiar androgens. Starving cells of androgen is successful at first, but typically within two to three years, some of the cancer cells begin to thrive again.

The result: renewed prostate cancer growth that is often fatal.

The Omega-3 Link

Dr. deGraffenried’s research focuses on the role omega-3 fatty acids may play in preventing androgen-deprived prostate cancer cells from starting to grow again. Omega-3 fatty acids are essential fats – the body cannot make them – found in fish, such as salmon, tuna, and mackerel.

Dr. deGraffenried is an Assistant Professor in the Division of Medical Oncology at the University of Texas Health Science Center at San Antonio. Her laboratory studies have shown that when androgen-deprived cells were exposed to omega-3s, cell growth stopped. Omega-6 is another essential fatty acid; it is found in seeds, nuts, and vegetable oils. When androgen-deprived cells were exposed to omega-6s, cells continued to grow.

The How’s and Why’s

In the AICR-funded study, Dr. deGraffenried is taking her research one step further by examining how omega-3s may stop cell growth. Her work is focusing on the androgen receptor, which plays a key role in regulating androgen. Scientists have found that if the androgen receptor is blocked, prostate cancer cell growth stops.

In one part of the study, Dr. deGraffenried exposed androgen-deprived cells to either omega-3 or omega-6 fatty acid for several hours. Genetic analysis showed that omega-3 fatty acids stopped the androgen-receptor gene from functioning, while the omega-6 fatty acids did not.

Simultaneous to the AICR study, Dr. deGraffenried and her colleagues are testing the effectiveness of different omega-3 to omega-6 ratios. The goal is to ensure that patients will consume the amount of omega-3 that is effective and able to be incorporated into a healthful diet.

--

For information on treatment and resources for prostate cancer, AICR offers CancerResource: A Resource Guide for Those Living with Cancer.  The brochure Nutrition and the Cancer Survivor examines how diet and lifestyle can play a role in reducing recurrence and/or secondary tumors.

News Roundup

Fat Cells: A Constant Number

Fat cells may shrink or enlarge, but a new study has found that the number of fat cells adults have stays about the same throughout adulthood. How many fat cells (called adipocytes) we have appears to be determined during childhood and adolescence. After adolescence, the number of fat cells level off and remain constant, the authors found.

In the paper, published in May’s Nature, the Swedish researchers first compared the number of adipocytes between 595 adults with previously reported data on children and adolescents. The adults were both lean and obese. Analysis showed that lean individuals had fewer adipocytes than obese individuals, and that the total number for each weight category stayed constant in adults over 20 years old. Even after weight loss surgery, when calorie intake and BMI decreased, the numbers of adipocytes remained stable.

The researchers then wanted to know if adipoctyes are replaced during adulthood. To do this, they used a novel technique made possible by nuclear testing during the Cold War. The bombs released a form of carbon in the atmosphere, which was taken up by plants and then by humans. Scientists have long used the amount of C14 in an organism as a way of “dating” the organism. Cells that contain this substance, C14, are also essentially “dated.”

Researchers collected adipocytes from 35 lean and obese adults. Some of the adults were born before the nuclear testing and some afterwards. Assuming the number of fat cells would be the same, the researchers calculated the number of new cells by measuring how many adipocytes had the nuclear remnant. The conclusion: about 10 percent of adipocytes die and re-grow every year for adults of all body sizes.

The study shows that the number of fat cells is a major determinant in body fat, and that this number is set by young adulthood. Given that high body fat is convincingly linked to many different cancers, as well as a host of other diseases, this study highlights the importance of maintaining a healthy weight for people of all ages.

Hormone Triggers an Urge to Eat

Next time you go to the grocery store hungry and return with a lot of unplanned goodies, you may have an explanation. A new study has shown that ghrelin, a gut hormone known to stimulate the appetite, also activates the pleasure regions in the brain. Researchers have long theorized there are two triggers that drive us to eat: one controlled by the metabolism when our bodies need energy, the other sparked by stimuli unrelated to energy needs.

The study, published in the May issue of Cell Metabolism, showed that these two drives may be related. In the study, researchers looked at the brain activity in 20 non-obese and not hungry participants who were shown pictures of food and scenery. Then, some of the participants were given ghrelin and participants were shown the same pictures. In the ghrelin group, regions of the brain associated with motivation, vision, and pleasure were activated. Compared to the ghrelin-free participants, the ghrelin group also reported a significant increase in hunger.