Use your bean (and grain)

Substituting legumes and whole grains for rice
can decrease activity of enzyme promoting atherosclerosis

A new study in the August issue of the Journal of Lipid Research suggests substituting whole grains and legumes in place of processed, refined rice can reduce the activity of an enzyme implicated in atherosclerosis while also improving control over blood-sugar levels.
 
In a study conducted at Yonsei University in Seoul, South Korea, researchers randomly split into two groups of patients with impaired fasting glucose or who had been diagnosed recently with type 2 diabetes. Participants in one group were allowed to consume their usual diet dominated by refined rice, while participants in the other group were instructed to replace rice in their diet with a mixture of black soybeans, barley and brown rice for three meals a day for 12 weeks.

Legume

Researchers observed significant decreases in fasting glucose, insulin and other diabetic markers in the modified diet group compared to the control group, indicating that those participants had improved control over blood-sugar levels. Lower levels of plasma malondialdehyde, a marker for oxidative stress, also were found in the modified diet group; it has been suggested that increases in oxidative stress and damage caused by free radicals not kept in check may be linked to diabetes.
 
Also, while no differences were observed between the two groups when it came to general measures, such as body mass index and the energy levels that the participants reported, levels of the proinflammatory cytokine interleukin-6 were significantly lower in the modified diet group.
 
Probably the most important result of this study? The activity of lipoprotein-associated phospholipase A2, called Lp-PLA2 for short, was decreased in the modified diet group. This would explain the increase in IL-6 in the control group: Increased levels of this enzyme are associated with increasing levels of several inflammatory cytokines. Lp-PLA2 is an enzyme produced by inflammatory cells that breaks down oxidized phospholipids in low-density lipoprotein. Lp-PLA2 also is used as a marker in diagnosing cardiac disease.
 
It is still unclear how Lp-PLA2 activity and substantial improvement in glucose and insulin metabolism are linked to diet. However, the paper’s authors point to two possibilities. They suggest decreased Lp-PLA2 activity could be linked to the increased protein in the modified diet. Also, because whole grains and legumes contain many antioxidants, the rate of oxidation of molecules that might ordinarily get broken down in the presence of a normal diet might be slowed.
 
The authors conclude that “grains should be consumed in a minimally refined form, and frequent consumption of vegetables and legumes should be recommended to reduce cardiovascular risk factors.”

Mary L. ChangMary L. Chang (mchang@asbmb.org) is publications manager for ASBMB.