UF scientists find sugar may have a sour side

December 06, 2005

Suddenly sugar isn't looking so sweet.

University of Florida researchers have identified one possible reason for rising obesity rates, and it all starts with fructose, found in fruit, honey, table sugar and other sweeteners, and in many processed foods.

Fructose may trick you into thinking you are hungrier than you should be, say the scientists, whose studies in animals have revealed its role in a biochemical chain reaction that triggers weight gain and other features of metabolic syndrome - the main precursor to type 2 diabetes. In related research, they also prevented rats from packing on the pounds by interrupting the way their bodies processed this simple sugar, even when the animals continued to consume it.

The findings, reported in the December issue of Nature Clinical Practice Nephrology and in this month's online edition of the American Journal of Physiology-Renal Physiology, add to growing evidence implicating fructose in the obesity epidemic and could influence future dietary guidelines. UF researchers are now studying whether the same mechanism is involved in people.

"There may be more than just the common concept that the reason a person gets fat is because they eat too many calories and they don't do enough exercise," said Richard J. Johnson, M.D., the J. Robert Cade professor of nephrology and chief of nephrology, hypertension and transplantation at UF's College of Medicine. "And although genetic predispositions are obviously important, there's some major environmental force driving this process. Our data suggest certain foods and, in particular, fructose, may actually speed the process for a person to become obese."

Physical inactivity, increased caloric intake and consumption of high-fat foods undoubtedly account for part of the problem, Johnson said. But Americans are feasting on more fructose than ever. It's in soft drinks, jellies, pastries, ketchup and table sugar, among other foods, and is the key component in high fructose corn syrup, a sugar substitute introduced in the early 1970s.

Since then, fructose intake has soared more than 30 percent, and the number of people with metabolic syndrome has more than doubled worldwide, to more than 55 million in the United States alone, Johnson said. The condition, characterized by insulin resistance, obesity and elevated triglyceride levels in the blood, is linked to the development of type 2 diabetes and hypertension.

"If you feed fructose to animals they rapidly become obese, with all features of the metabolic syndrome, so there is this strong causal link," Johnson said, "And a high-fructose intake has been shown to induce certain features of the metabolic syndrome pretty rapidly in people."

Now UF research implicates a rise in uric acid in the bloodstream that occurs after fructose is consumed, Johnson said. That temporary spike blocks the action of insulin, which typically regulates how body cells use and store sugar and other food nutrients for energy. If uric acid levels are frequently elevated, over time features of metabolic syndrome may develop, including high blood pressure, obesity and elevated blood cholesterol levels.

Researchers from UF and the Baylor College of Medicine studied rats fed a high-fructose diet for 10 weeks. Compared with rats fed a control diet, those on the high-fructose diet experienced a rise in uric acid in the bloodstream and developed insulin resistance.

"When we blocked or lowered uric acid, we were able to largely prevent or reverse features of the metabolic syndrome," Johnson said. "We were able to significantly reduce weight gain, we were able to significantly reduce the rise in the triglycerides in the blood, the insulin resistance was less and the blood pressure fell."

UF researchers are now studying the uric acid pathway in cell cultures in the laboratory, in animals and in people, and are also eyeing it as a possible factor in the development of cardiovascular and kidney diseases because of its effects on blood vessel responses. They are conducting a National Institutes of Health-funded trial to determine if lowering uric acid in blacks with hypertension improves blood pressure control and are collaborating with scientists at Baylor to determine if lowering uric acid will reduce blood pressure in adolescents with hypertension.

"We cannot definitively state that fructose is driving the obesity epidemic," said Johnson. "But we can say that there is evidence supporting the possibility that it could have a contributory role - if not a major role. I think in the next few years we'll have a better feel for whether or not these pathways that can be shown in animals may be relevant to the human condition."

Findings to date suggest certain sugar carbohydrates are actually better than others, he added, because some do not activate the uric acid pathway.

"It may well be we don't need to cut out carbohydrates but just certain types of carbohydrates," Johnson said. "So this may be an alternative to the Atkins type of approach, which cuts out carbohydrates indiscriminately."

As scientists learn more about the pathway, Johnson said, and as studies are completed in people, the findings may influence how to make wise choices about the foods we eat.

"With the caveat that people are different from rodents in many ways, the link between urate levels, blood pressure elevation and insulin resistance demonstrated in rats fed fructose is extremely provocative," said Brian F. Mandell, M.D., Ph.D., vice chairman of medicine for education and a professor of medicine at the Cleveland Clinic Lerner College of Medicine of Case Western Reserve University. "Whether the fructose supplementation to the diet in the United States is partially responsible for the 'epidemic' of obesity remains to be proven - but this is an association which can be tested, and the work of Dr. Johnson and his collaborators makes the evaluation of the fructose-metabolic link in people an academic and public health imperative."
-end-


University of Florida

Related Diabetes Articles from Brightsurf:

New diabetes medication reduced heart event risk in those with diabetes and kidney disease
Sotagliflozin - a type of medication known as an SGLT2 inhibitor primarily prescribed for Type 2 diabetes - reduces the risk of adverse cardiovascular events for patients with diabetes and kidney disease.

Diabetes drug boosts survival in patients with type 2 diabetes and COVID-19 pneumonia
Sitagliptin, a drug to lower blood sugar in type 2 diabetes, also improves survival in diabetic patients hospitalized with COVID-19, suggests a multicenter observational study in Italy.

Making sense of diabetes
Throughout her 38-year nursing career, Laurel Despins has progressed from a bedside nurse to a clinical nurse specialist and has worked in medical, surgical and cardiac intensive care units.

Helping teens with type 1 diabetes improve diabetes control with MyDiaText
Adolescence is a difficult period of development, made more complex for those with Type 1 diabetes mellitus (T1DM).

Diabetes-in-a-dish model uncovers new insights into the cause of type 2 diabetes
Researchers have developed a novel 'disease-in-a-dish' model to study the basic molecular factors that lead to the development of type 2 diabetes, uncovering the potential existence of major signaling defects both inside and outside of the classical insulin signaling cascade, and providing new perspectives on the mechanisms behind insulin resistance in type 2 diabetes and possibly opportunities for the development of novel therapeutics for the disease.

Tele-diabetes to manage new-onset diabetes during COVID-19 pandemic
Two new case studies highlight the use of tele-diabetes to manage new-onset type 1 diabetes in an adult and an infant during the COVID-19 pandemic.

Genetic profile may predict type 2 diabetes risk among women with gestational diabetes
Women who go on to develop type 2 diabetes after having gestational, or pregnancy-related, diabetes are more likely to have particular genetic profiles, suggests an analysis by researchers at the National Institutes of Health and other institutions.

Maternal gestational diabetes linked to diabetes in children
Children and youth of mothers who had gestational diabetes during pregnancy are at increased risk of diabetes themselves, according to new research published in CMAJ (Canadian Medical Association Journal).

Two diabetes medications don't slow progression of type 2 diabetes in youth
In youth with impaired glucose tolerance or recent-onset type 2 diabetes, neither initial treatment with long-acting insulin followed by the drug metformin, nor metformin alone preserved the body's ability to make insulin, according to results published online June 25 in Diabetes Care.

People with diabetes visit the dentist less frequently despite link between diabetes, oral health
Adults with diabetes are less likely to visit the dentist than people with prediabetes or without diabetes, finds a new study led by researchers at NYU Rory Meyers College of Nursing and East Carolina University's Brody School of Medicine.

Read More: Diabetes News and Diabetes Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.