2012 Annual Report
1a.Objectives (from AD-416):
1. Identify bioactive food components and food patterns that inhibit
atherosclerosis and angiogenesis using cell culture, animal models and human subjects under the following sub-objectives:
a) Determine bioavailability of avenanthramides from oats and characterize their
potency and molecular mechanism of inhibition of vascular smooth muscle cell
proliferation using cell culture systems and the femoral artery injury mouse model.
b) Elucidate the molecular mechanism of catechins and curcumin and other dietary
bioactive compounds on the inhibition of angiogenesis associated with adipose tissue growth and obesity.
c) Determine the comparative bioavailability and biopotency of tocopherols versus
tocopheryl phosphate on the inhibition of femoral artery injury model of vascular
atherosclerosis and restenosis.
2. Determine the anti-inflammatory and anti-proliferative effects of avenanthramides of oats and derivatives on several colonic cancer cells lines and mouse models of inflammatory bowel disease and colon cancer.
1b.Approach (from AD-416):
The main objective of this project plan is to determine bioavailability, potency and mechanism of action of several bioactive food components, including avenanthramides(Avns) of oats, curcumin of turmeric, catechins of green tea and isomers of tocopherol in the prevention of atherosclerosis and angiogenesis as they relate to CVD, obesity and cancer. Specifically, we will determine bioavailability of Avns from oats and characterize their potency and mechanism of inhibition of vascular smooth muscle cell proliferation using cell culture and the femoral artery injury mouse model. Further, we will investigate the anti-inflammatory and antiproliferative effects of Avns of oats and derivatives on several cancer cells lines and mouse models of inflammatory bowel disease and colon cancer. We will also elucidate the molecular mechanism of catechins and curcumin and other dietary bioactive compounds on the inhibition of angiogenesis associated with adiposity and obesity. We also plan to investigate the comparative biopotency of' alpha-tocopherol (alpha-T) versus alpha-tocopheryl phosphate (alpha-TP) on the inhibition inflammatory cytokines and monocyte adhesion in cell culture systems and on comparative bioavailability and efficacy of alpha-T vs. alpha-TP on femoral artery injury model of atherosclerosis.
We have continued assessing the metabolic changes induced by high fat diet and curcumin (bioactive component of turmeric spice) supplementation in LDLr-/- mice. We selected this animal model over other mice models because it is more relevant to human atherosclerosis, a condition in which blood vessel walls thicken due to build up of fatty material like cholesterol. First, we found that when curcumin was added into cell culture in vitro, it increased expression of FOXO3a, a factor found in immune cells called macrophages. The increased expression of FOXO3a in turn induced expression of FOXO3a-target genes, such as CD36 and aP2, which are involved in lipid accumulation in cells and resistance of macrophages to oxidative stress. However, in vivo, we found that curcumin had the opposite effect on the expression of these genes in LDLr-/- mice. We proposed that this may contribute to the lipid lowering effect of curcumin in plasma by increasing lipid uptake into tissues, and thus exposing macrophages to lower levels of circulating lipids and related oxidative stress. Supplementing the high fat diet of LDLr-/- mice with curcumin for 16 weeks reduced their body weight gain, fat tissues and development of atheroma lesions in the heart or vascular system. Atheromas are fatty lesions that can rupture and block arteries causing heart attack. We learned that this effect of curcumin was not due to curcumin’s suppression of appetite, food intake, or absorption of fat from the intestine. In addition, curcumin reduced free fatty acid and insulin levels in blood significantly and tended to decrease glucose and triglycerides in this animal model. Curcumin also suppressed high fat diet-induced fat accumulation in liver. To gain deeper insight into the molecular mechanisms of this lipid lowering effect of curcumin, we investigated the molecular targets by which curcumin reduces plasma lipid levels. We found that curcumin activates several molecules involved in lipid metabolism, energy expenditure, and thermogenesis (heat production) by increasing the break-down of lipids into their basic constituents (fatty acids) and their oxidation to generate energy and heat. These phenomena along with curcumin’s suppression of insulin, blood lipids, and angiogenesis in fat tissues leads to less expansion of body fat, less body weight gain, better levels of blood lipids, and reduced risk of atherosclerosis. Moving forward, we plan to assess the activity of several of the above mentioned molecular components in tissues of animals treated with a high fat diet in combination with several doses of curcumin. These experiments will provide a platform to translate these findings to human.
Observational studies have suggested an association of whole grain diet with reduced risk of developing obesity, diabetes, heart disease, and certain cancers. In collaboration with Nutritional Immunology and Energy Metabolism Laboratories, we have designed and are conducting a study in human (45-65 yrs) comparing consumption of diets rich in whole grains (n=40) vs. diets rich in refined grains (n=40) on several markers of cardiovascular health, immune and digestive system. The study is underway and currently, 7 subjects have started the study and 12 are about to begin participating. Results have the potential to identify whole grains as a dietary intervention to improve physiological functions in multiple bodily systems.
Epidemiological data have indicated association of adiposity (having excess body fat) with prostate cancer. We have established a collaborative study with the University of Illinois to determine the relationship of diet, adiposity and outcome of clinically localized prostate cancer. We have analyzed several samples for fatty acid profiles and levels of leukotrienes and prostaglandins (compounds involved in inflammation) in plasma and prostate tissue to correlate them with the dietary component.
Daily dosing of male IL-10 deficient mice (mouse model of inflammatory bowel disease) with avenanthramides, a bioactive component of oats, for 10 wks showed no positive or negative effects on inflammatory markers in intestines.
Through internal collaborative efforts under HNRCA-initiated Cardiovascular and Cognitive (CVC) clusters, we have designed and are conducting a study to measure the interaction of whole grain vs. refined grain with statin drugs consumed by the participating subjects in the previously mentioned whole grain study. We are investigating whether a diet high in fiber such as whole grains interacts with the absorption and metabolism of cholesterol-lowering drugs, statins.
In addition we have collaborated in the design of animal model of colon cancer under the HNRCA-initiated “Cancer” Cluster, which is underway. Also, we are participating in the design of the “Network of Inflammation and Diet,” an Inflammation Cluster project.
We have continued evaluating whether the natural vitamin E analogue, alpha-tocopheryl phosphate (alpha-TP) is capable of modulating cellular reactions and the molecular events involved in inflammation and atherosclerosis. We have found, using an in vitro system, that alpha-TP is formed from alpha-tocopherol (alpha-T) in primary vascular smooth muscle cells in a reaction that is stimulated by the tocopherol associated protein (TAP), and may support the formation of new blood vessels in the vascular system. In a similar reaction, gamma-TP is also formed from gamma-T, an important component of the U.S. diet. Alpha-TP was more active than alpha-T, and gamma-TP was more active than alpha-TP in inhibiting proliferation of monocytes and CD36 scavenger receptor expression, a receptor important for angiogenesis (growth of new blood vessels from existing ones), adhesion, lipid transport, atherosclerosis and inflammation. Gene expression upon T cell stimulation was differently affected after supplementation of old mice with gamma-T or alpha-T, possibly as a result of the formation of gamma-TP or alpha-TP, respectively. In cultured differentiated adipocytes, alpha-TP inhibited a set of genes important for lipid uptake and metabolism, which may facilitate lipid uptake in these cells and prevent systemic lipotoxicity. Proper function of fat cells with respect to fatty acid uptake and release is a vital aspect of converting fat into energy; dysfunction of these reactions can result in obesity, atherosclerosis and type 2 diabetes mellitus. In addition, it has been proposed that fat cells play a major role in preventing toxic effects of fat by removing excess fatty acids from the circulation and thus reducing the exposure of other cells to their potentially harmful effects.
Curcumin reduces fatty liver. The accumulation of fat deposits in the liver caused by a high fat diet is associated with chronic inflammation, which provides an environment for the potential development of liver dysfunction and cancer. ARS-funded researchers at JMUSDA-HNRCA at Tufts University, Boston, Massachusetts have found that supplementing Western style high fat diet in laboratory mice with increasing doses of curcumin of turmeric spice reduced the formation of fatty liver. This finding suggests that consumption of turmeric may reduce the risk of liver cancer.
Newly discovered form of vitamin E (aTP) alters genes. One of the natural forms of vitamin E (alpha-TP), has recently been shown to be a biologically active form of vitamin E. ARS-funded researchers at JMUSDA-HNRCA at Tufts University, Boston, Massachusetts, compared the alpha-TP form with regular vitamin E. They have found that alpha-TP may be more effective than regular vitamin E to activate certain genes that are important for blood vessel formation. This indicates that alpha-TP may help wounds to heal more quickly.
Consumption of curcumin, a bioactive component of turmeric spice, may reduce heart disease. Eating a diet high in fat induces obesity and increases risk of heart disease, which can be prevented to some extent by consuming foods that contain certain natural substances. ARS-funded researchers at JMUSDA-HNRCA at Tufts University, Boston, Massachusetts investigated the effect of consuming curcumin, a compound present in turmeric and curry spices, on body weight gain, obesity and heart disease in animal model of heart disease. They found that curcumin suppressed body fat and body weight gain and reduced several risk factors for heart disease and diabetes. These observations in animal models provide a platform to translate their findings to humans.