Route to obesity passes through tongue
November 26, 2008Obesity gradually numbs the taste sensation of rats to sweet foods and drives them to consume larger and ever-sweeter meals, according to neuroscientists. Findings from the Penn State study could uncover a critical link between taste and body weight, and reveal how flab hooks the brain on sugary food.
"When you have a reduced sensitivity to palatable foods, you tend to consume it in higher amounts," said Andras Hajnal, associate professor of neural and behavioral sciences at Penn State College of Medicine. "It is a vicious circle."
Previous studies have suggested that obese persons are less sensitive to sweet taste and crave sweet foods more than lean people. However, little is known about the specific differences between obese and lean individuals in their sense of taste and the pleasure they derive from sweet foods.
Hajnal and his Penn State colleague Peter Kovacs, a post-doctoral fellow, investigated these differences by studying the taste responses of two strains -- OLETF and LETO rats.
Compared to the lean and healthy LETO rats, the taste responses in OLETF rats mirror those in obese humans. These rats have normal body weight at first, but they tend to chronically overeat due to a missing satiety signal, become obese and develop diabetes. The obese rats also show an increased preference for sweet foods and also are willing to work harder to obtain sweet solutions as a reward for their learning.
"When you have excess body weight, the brain is supposed to tell you not to eat more, or not choose high caloric meals" said Hajnal. "But this control apparently fails and thus the obesity epidemic is rising, and we want to find out how the sense of taste drives up food intake."
The researchers implanted electrodes in the rodents' brains to record the firing of nerve cells when the rats' tongues were exposed to various tastes -- salt, citric acid, plain water and six different concentrations of sucrose.
Hajnal and Kovacs specifically looked at differences in processing taste in the pontine parabrachial nucleus (PBN), a part of the brain that uses nerve cells to relay information from the surface of the tongue to the brain.
"We found that compared to the LETO rats, the OLETF rats had about 50 percent fewer neurons firing when their tongues were exposed to sucrose, suggesting that obese rats are overall less sensitive to sucrose," explained Hajnal, whose findings appeared in a recent issue of the Journal of Neurophysiology. The response to salt was the same for both strains.
However, when the obese rats were fed a stronger concentration of sucrose, their nerve cells fired more vigorously than in the lean rats. In other words, obese rats have a weaker response to weak concentrations and a stronger response to strong concentrations.
"These findings tell us that there is a difference in activation of neurons between lean and obese rats when they are exposed varying concentrations of sucrose," noted Hajnal. "If you sense sweetness less, you may be inclined to eat sweeter foods."
The Penn State researchers believe that the increased consumption of sweet foods over time could be influencing the brain's reward center by relaying progressively weaker nerve signals, which affects the perception of taste of the meals through the PBN.
In obese humans, an increase in the weight-height ratio is usually accompanied by a decrease in dopamine, which is a neurotransmitter associated with the brain's pleasure system.
"In these obese rats, like in humans, the dopamine system is suppressed and it is very possible that the obese rats are seeking a hedonistic experience or reward by eating larger meals and when they have a chance they also eat more sweets," Hajnal added.
The findings linking taste responses and obesity could hold an important message for a condition that affects more than 60 percent of adult Americans.
For instance, Hajnal points to an ever-increasing amount of fat and sugar in processed foods. The enhanced taste of these foods, he says, stimulates our taste and food reward neurons on a chronic basis, making them less sensitive over time. And what do we do when this happens?
"Instead of eating less, we seek out higher palatability," Hajnal explained. "We simply start putting an extra spoonful of sugar in our coffee."
Source: Penn State
-
Receptor for tasting fat identified in humans (w/ Audio)
Jan 12, 2012 |
not rated yet |
1
-
Gastric bypass surgery changes food preferences
Jul 27, 2011 |
4 / 5 (1) |
0
-
The Medical Minute: How sweet it was...
Nov 29, 2010 |
not rated yet |
0
-
Penn State researchers take on the epidemic of diabetes and obesity
Nov 03, 2010 |
not rated yet |
1
-
Gastric bypass alters sweet taste function
Nov 02, 2010 |
not rated yet |
0
-
Engineers build first sub-10-nm carbon nanotube transistor
Feb 01, 2012 |
4.9 / 5 (32) |
30
-
Something old, something new: Evolution and the structural divergence of duplicate genes
Jan 31, 2012 |
4.6 / 5 (7) |
1
-
The hidden nanoworld of ice crystals: Revealing the dynamic behavior of quasi-liquid layers
Jan 30, 2012 |
5 / 5 (4) |
1
-
Stock market network reveals investor clustering
Jan 27, 2012 |
3.9 / 5 (23) |
8
-
Of microchemistry and molecules: Electronic microfluidic device synthesizes biocompatible probes
Jan 26, 2012 |
5 / 5 (2) |
0
-
Is Everyday Technology Killing Us?
Feb 08, 2012
-
Exercise and weight loss
Feb 08, 2012
-
Why do we have head aches? Our brains can't feel anything.
Feb 07, 2012
-
"The end of diseases" by David Agus, interview from Daily Show with Jon Stewart
Feb 04, 2012
-
Oncolytic adenovirus
Feb 04, 2012
-
Nutrition label stuffs and diets
Feb 02, 2012
- More from Physics Forums - Medical Sciences
More news stories
Starve a virus, feed a cure? Findings show how some cells protect themselves against HIV
A protein that protects some of our immune cells from the most common and virulent form of HIV works by starving the virus of the molecular building blocks that it needs to replicate, according to research published online ...
46 minutes ago |
5 / 5 (1) |
0
|
Injured boomers beware: Know when to see doctor
(AP) -- It happened to nurse Jane Byron years after an in-line skating fall, business owner Haralee Weintraub while doing "men's" push-ups, and avid cyclist Gene Wilberg while lifting a heavy box.
2 hours ago |
5 / 5 (1) |
0
FDA-approved drug rapidly clears amyloid from the brain, reverses Alzheimer's symptoms in mice
Neuroscientists at Case Western Reserve University School of Medicine have made a dramatic breakthrough in their efforts to find a cure for Alzheimer's disease. The researchers' findings, published in the journal Science, show t ...
Medicine & Health / Neuroscience
Feb 09, 2012 |
4.9 / 5 (54) |
21
|
Green tea found to reduce disability in the elderly
(Medical Xpress) -- A lot of research has been done over the past several years looking into the health benefits of green tea. As a result, scientists have found that regular consumption of the beverage leads ...
Teen school drop-outs three times as likely to be on benefits in later life
Teen school drop-outs are almost three times as likely to be on benefits in later life as their peers who complete their schooling, indicates research published online in the Journal of Epidemiology and Community Health.
Feb 06, 2012 |
not rated yet |
13
Scientists discover molecular secrets of 2,000-year-old Chinese herbal remedy
For roughly two thousand years, Chinese herbalists have treated Malaria using a root extract, commonly known as Chang Shan, from a type of hydrangea that grows in Tibet and Nepal. More recent studies suggest that halofuginone, ...
New method to examine batteries -- MRI from the inside
There is an ever-increasing need for advanced batteries for portable electronics, such as phones, cameras, and music players, but also to power electric vehicles and to facilitate the distribution and storage of energy derived ...
A mitosis mystery solved: How chromosomes align perfectly in a dividing cell
Although the process of mitotic cell division has been studied intensely for more than 50 years, Whitehead Institute researchers have only now solved the mystery of how cells correctly align their chromosomes during symmetric ...
Researchers find extensive RNA editing in human transcriptome
In a new study published online in Nature Biotechnology, researchers from BGI, the world's largest genomics organization, reported the evidence of extensive RNA editing in a human cell line by analysis of RNA-seq data, demons ...
The proteins ensuring genome protection
Researchers from the University of Geneva (UNIGE), Switzerland, have discovered the crucial role of two proteins in developing a cell 'anti-enzyme shield'. This protection system, which operates at the level of molecular ...
Lab study raises questions over nano-particle impact
Tests involving chickens have raised questions about the impact on health from engineered nano-particles, the ultra-fine grains commonly used in drugs and processed foods, scientists said on Sunday.