Bear-ly Understanding Diabetes

May 30, 2014 by

May 30, 2014

By Medical Discovery News

What can studying grizzly bears reveal about human diabetes?

While they are some of the largest bears on earth, Grizzly bears aren’t usually accused of being fat. Regardless, these animals are helping scientists discover new and better treatments for human obesity and diabetes.

Grizzlies spend the late summers consuming more than 50,000 calories per day. As a comparison, a moderately active 50-year-old human female is recommended 2,300. Grizzlies then hibernate for up to seven months, relying on the pounds of stored fat they accumulated before winter. While hibernating, bears do not eat, urinate, or defecate. 

Scientists wondered if all the weight and fat bears gain results in diabetes like it does in humans. Overweight people face an increased risk of type 2 diabetes, in which the body does not make enough of the hormone insulin or cells do not respond to it. Insulin helps move a type of sugar called glucose from the blood into cells, where it is used for energy and as a precursor for other molecules the body needs. If sugar levels in the blood remain elevated and the body doesn’t have enough insulin, cells are starved for energy, leading to damaged eyes, kidneys, nerves, and hearts. 

Interestingly, Grizzly bears can actually control their insulin responsiveness. When they are the fattest, they are most sensitive to insulin, thereby keeping their blood sugar levels healthy. Soon after going into hibernation, they switch to complete insulin resistance, meaning they develop type 2 diabetes. But unlike humans, their blood sugar levels remain normal. When they awaken in the spring, their insulin responsiveness is restored. Bears do this not so much to regulate their blood sugar levels as to regulate their storage and utilization of fat. So how do bears control their insulin responsiveness? And could it lead to new treatments for type 2 diabetes in humans?

PTEN is a protein that regulates cells’ sensitivity to insulin. Scientists know exactly when Grizzlies increase or decrease PTEN activity, they just don’t know how. People with a PTEN mutation have a metabolism similar to Grizzlies’.  These people have an increased risk of obesity and cancer but a decreased risk of developing type 2 diabetes because they are more sensitive to insulin.

Grizzlies have also evolved to the ability to accumulate large amounts of fat only in their adipose tissue, just below the skin so it doesn’t interfere with the rest of their bodies. In humans, on the other hand, fat can accumulate in many places like the liver, in muscles, and around other internal organs, which are all highly unhealthy places to keep fat. Bears can also have elevated levels of cholesterol without the serious consequences of cardiovascular disease.

During hibernation, the Grizzly bears’ kidneys shut down. But despite the high levels of toxins that accumulate in the blood without working kidneys, they don’t die or even suffer from it like a human would. When they wake up, their kidney function is restored with no permanent damage.

After millions of years of evolution, Grizzly bears and other animals have developed solutions for biological challenges humans still face. Studying them is a new approach that has the potential to create treatments for many human conditions.

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How Much Sugar Is Safe?

January 31, 2014 by

Jan. 31, 2014

By Medical Discovery News

Sugar

Former Mayor Michael Bloomberg of New York City caused a controversy when he tried to ban the sale of sugary drinks more than 16 ounces. Thus the “Big Gulp” rebellion was born and the ban was later overturned by the courts. Yet the rates of diabetes, heart disease, and obesity remain out of control in the U.S.

In the U.S., 24 million people over age 20 have diabetes. Another 78 million have pre-diabetes with blood glucose levels higher than they should be – the start of glucose intolerance.  And down the road, this may lead to life-threatening heart disease (the No. 1 killer of adults), which is also linked to obesity affecting more than 80 million Americans.

Much of the obesity epidemic has been blamed on unhealthy eating and poor nutrition. Refined sugar has been identified as a source of excess calories. According to the U.S. Departments of Agriculture and Health and Human Services, almost 50 percent of sugar in the diets of Americans comes from sugary drinks and sweetened fruit drinks. The debate over just how much sugar is too much in terms of our health was addressed by a recent study and the results are sending shock waves through the medical community. 

In the experiment, one group of mice ate a normal diet and another group ate a diet where one quarter of the calories came from sugar similar to that in high fructose corn syrup. This level of sugar is pretty equal to that consumed naturally by 15 to 25 percent of the U.S. population. This is equivalent to a person consuming three cans of a sugary beverage a day in an otherwise sugar-free diet. Current nutrition guidelines consider this to be at the top of the safe level of sugar for people.

After 26 weeks of a monitored diet, all the mice were released into an experimental natural environment. Over the next 32 weeks, twice as many sugar-fed female mice died compared to the control group. The sugar-fed male mice produced 25 percent fewer offspring and held 26 percent less territory than mice from the control group. Overall, dietary sugar was linked to a shorter life span, limited reproduction, and lowered competitive success. 

Metabolic measurements on the sugar-fed mice showed changes in glucose clearance and increases in cholesterol levels, but these were considered minor. Nevertheless, life outcomes called Organismal Performance Assays were significantly affected. This may represent a new way to gauge important changes in overall life parameters without corresponding physiological changes.

This certainly raises the question of how much sugar is too much, and the debate over the appropriate level of refined sugar for good human nutrition will continue. It will be interesting to watch in the coming months and years to see if these results are substantiated and if they lead to new nutritional guidelines. Who knows – maybe Mayor Bloomberg was right after all!

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The Trouble with Sugar Substitutes

December 20, 2013 by

Dec. 20, 2013

By Medical Discovery News

Those reaching for a packet of artificial sweetener to satisfy a sweet tooth without adding calories may want to think again – the long-time diet staple may actually lead to serious unintended side effects.

Artificial sweeteners include the recently launched Stevia products like Truvia and the compounds  aspartame (found in Equal), saccharin (Sweet N’ Low), and sucralose (Splenda). These were developed because they add no caloric content to the foods they are added to, but they stimulate the sweet receptors on the tongue. Non-caloric sweeteners are popular with those working to control their weight because of the allure of no calories without sacrificing sweetness.

Consider one product – yogurt. There can be 200 calories or more in those sweetened with sugar while the artificially sweetened varieties come in under 100 calories. The shine of artificial sweeteners may be wearing off though, as some recent studies suggest their use may actually lead to weight gain.

The first sign that artificial sweeteners weren’t as harmless as they seem was a study in the 1970s that linked saccharin to bladder cancer, although those results aren’t substantiated, and approved artificial sweeteners are now considered generally safe for human consumption.

In a new study at Washington University in St. Louis, scientists looked at people with a body mass index (BMI) of over 42 (30 and over is considered obese), who don’t have diabetes and don’t regularly use sweeteners. Individuals were divided into two groups and given the artificial sweetener sucralose or water before ingesting a solution of glucose, the same amount given during a glucose tolerance test. On a separate day, the groups were reversed so researchers could compare the effects in each person.  

The results were surprising. When individuals drank sucralose before ingesting glucose, their insulin levels peaked at a higher level and increased by about 20 percent more than those drinking water alone. This means that sucralose was affecting insulin and blood glucose levels. Previously, scientists thought that these sweeteners did not have an effect on sugar metabolism. 

It turns out that there are sweet responsive receptors in the gut and pancreas that are similar to those found on the human tongue. When they are stimulated, they can cause an increase in the release of hormones including insulin. This in turn causes more sugar to be absorbed in the gut and subsequently higher levels in the blood. For unknown reasons, it happens only in the obese. An elevation in insulin levels can contribute to insulin resistance and type 2 diabetes. 

One thing is for sure – further research will help scientists understand the effects of artificial sweeteners on human metabolism.

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