Apple peel compound boosts brown fat, reduces obesity in mice

ScienceDaily (June 20, 2012) — Obesity and its associated problems such as diabetes and fatty liver disease are increasingly common global health concerns. A new study by University of Iowa researchers shows that a natural substance found in apple peel can partially protect mice from obesity and some of its harmful effects.

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The findings suggest that the substance known as ursolic acid reduces obesity and its associated health problems by increasing the amount of muscle and brown fat, two tissues recognized for their calorie-burning properties.

The study, which was published June 20 in the journal PLoS ONE, was led by Christopher Adams, M.D., Ph.D., UI associate professor of internal medicine and a Faculty Scholar at the Fraternal Order of Eagles Diabetes Research Center at the UI.

"From previous work, we knew that ursolic acid increases muscle mass and strength in healthy mice, which is important because it might suggest a potential therapy for muscle wasting," Adams says. "In this study, we tested ursolic acid in mice on a high-fat diet -- a mouse model of obesity and metabolic syndrome. Once again, ursolic acid increased skeletal muscle. Interestingly, it also reduced obesity, pre-diabetes and fatty liver disease.

"Since muscle is very good at burning calories, the increased muscle in ursolic acid-treated mice may be sufficient to explain how ursolic acid reduces obesity. However, we were surprised to find that ursolic acid also increased brown fat, a fantastic calorie burner. This increase in brown fat may also help protect against obesity."

Until quite recently, researchers believed that only infants had brown fat, which then disappeared during childhood. However, improved imaging techniques have shown that adults do retain a very small amount of the substance mostly in the neck and between the shoulder blades. Some studies have linked increased levels of brown fat with lower levels of obesity and healthier levels of blood sugar and blood lipid, leading to the suggestion that brown fat may be helpful in preventing obesity and diabetes.

The UI team, which also included Steven Kunkel, Christopher Elmore, Kale Bongers, Scott Ebert, Daniel Fox, Michael Dyle, and Steven Bullard, studied mice on a high-fat diet over a period of several weeks. Half of the animals also received ursolic acid in their high-fat food. Interestingly, mice whose diet included ursolic acid actually ate more food than mice not getting the supplement, and there was no difference in activity between the two groups. Despite this, the ursolic acid-treated mice gained less weight and their blood sugar level remained near normal. Ursolic acid-treated mice also failed to develop obesity-related fatty liver disease, a common and currently untreatable condition that affects about one in five American adults.

Further study showed that ursolic acid consumption increased skeletal muscle, increasing the animals' strength and endurance, and also boosted the amount of brown fat. Because both muscle and brown fat burn calories, the researchers investigated energy expenditure in the mice and showed that ursolic acid-fed mice burned more calories than mice that didn't get the supplement.

"Our study suggests that ursolic acid increases skeletal muscle and brown fat leading to increased calorie burning, which in turn protects against diet-induced obesity, pre-diabetes and fatty liver disease," Adams says. "Brown fat is beneficial and people are trying to figure out ways to increase it. At this point, we don't know how ursolic acid increases brown fat, or if it increases brown fat in healthy mice. And, most importantly, we don't know if ursolic acid will benefit people. Our next step is to determine if ursolic acid can help patients."

The research was supported by funding from the Fraternal Order of Eagles Diabetes Research Center at the University of Iowa, the National Institute of Arthritis and Musculoskeletal and Skin Diseases of the National Institutes of Health (grant 5R01AR059115-03), the Department of Veterans Affairs, and the University of Iowa Research Foundation.

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Compound in soy products may help lower blood pressure

ScienceDaily (Mar. 26, 2012) — Soy-based food products have taken grocery store shelves by storm, and the benefits of soy are steadily beginning to emerge. Eating foods that contain isoflavones -- a key compound in soy milk, tofu, green tea and even peanuts -- every day may help young adults lower their blood pressure. Moreover, and for the first time, there appears to be a particular benefit for African Americans, who have hypertension prevalence rates near 42 percent, according to research presented March 25 at the American College of Cardiology's 61st Annual Scientific Session.

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"What's unique about this study is that the results are very applicable to the general population. Our results strongly suggest a blood pressure benefit for moderate amounts of dietary isoflavone intake in young black and white adults," said Safiya Richardson, a graduating medical student at Columbia University's College of Physicians and Surgeons and the study's lead investigator. "Our study is the first to show a benefit in African Americans, who have a higher incidence of high blood pressure, with an earlier onset and more severe end-organ damage."

Compared to those consuming less than 0.33 mg of isoflavones per day, those reporting the most isoflavone intake (more than 2.5 mg per day) had a significantly lower systolic blood pressure (-5.5 mmHg lower on average). To help put this into context, an 8 ounce glass of soy milk has about 22 mg of isoflavones, and 100 g of roasted soybeans have as much as 130 mg.

"This could mean that consuming soy protein, for example, in combination with a DASH diet -- one that is high in fruits and vegetables, low-fat dairy and whole grains -- could lead to as much as a 10 mmHg drop in systolic blood pressure for pre-hypertensives, greatly improving their chances of not progressing to hypertension," said Richardson. "Any dietary or lifestyle modification people can easily make that doesn't require a daily medication is exciting, especially considering recent figures estimating that only about one third of American hypertensives have their blood pressure under control."

Isoflavones are thought to work by increasing the production of enzymes that create nitric oxide (NO), a substance that helps to dilate or widen blood vessels, thereby reducing the pressure created by blood against the vessel walls. Richardson said this mechanism may partially explain why the study was able to find an association with smaller amounts of isoflavone intake than examined previously. The relatively pronounced results in the overall biracial cohort may be driven by a more intense effect of isoflavones in African Americans, Richardson said. This is because endothelial dysfunction, a condition in which the blood vessels have a hard time either producing or using NO, plays a bigger role in hypertension in African Americans than it does in whites.

"It's possible that these foods may help compensate for this," she said. "Based on our results and those of previous studies, we would encourage the average adult to consider including moderate amounts of soy products in a healthy, well-balanced diet to reduce the chances of developing high blood pressure. For people with hypertension, it's important that they talk with their doctor about isoflavones as a possible addition to a low sodium DASH diet that could reduce the need for medication."

Richardson added that different soy products have different concentrations of isoflavones, so it is important for consumers to do their homework.

Researchers analyzed data from year-20 of the Coronary Artery Risk Development in Young Adults (CARDIA) study, which is an NIH-funded study created to examine the development and determinants of cardiovascular disease. This study began in 1985 with 5,115 African American and white Americans aged 18-30 years old who have been followed and reexamined at various intervals. Year-20 was the first year that participants completed an extensive dietary survey. Multivariable linear regression models evaluated the relation between daily isoflavone intake and systolic BP (SBP) after dividing patients across quartiles according to self-reported isoflavone intake. Even after controlling for age, sex, BMI, smoking, alcohol, physical activity and total caloric intake, the relationship between daily isoflavones and lower systolic blood pressure remained.

Richardson says this study helps lay the groundwork for randomized controlled trials to help better understand the association between isoflavones and blood pressure.

Richardson presented the study "Dietary Isoflavone Intake is Associated with Lower Systolic Blood Pressure: the Coronary Artery Risk Development in Young Adults (CARDIA) Study" on March 25, 2012 in McCormick Place South, Hall A.

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