Jennifer M. K. Cheong

Bio: Jennifer M. K. Cheong is an academic researcher from Purdue University. The author has contributed to research in topics: Bone resorption & Bone remodeling. The author has an hindex of 7, co-authored 8 publications receiving 189 citations.

Soy Isoflavones and Bone Health: The Relationship Is Still Unclear

Abstract: Evidence of the effect of purified soy isoflavones and soy protein isolates containing isoflavones on bone health in rats and in humans is inconsistent. Differences may be because of synergies or antagonisms among the isoflavones, threshold or biphasic dose effects, life stage of animals or human subjects, estrogen status, and environment-genetic interactions, including the ability to produce metabolites upon ingestion of isoflavones. At this time, the benefits of soy protein and isoflavones on bone health are inconclusive. This overview will summarize these discrepancies and will suggest future studies to clarify the conditions under which these dietary substances can be helpful for bones.

Soy Isoflavones Do Not Affect Bone Resorption in Postmenopausal Women: A Dose-Response Study Using a Novel Approach with 41Ca

Abstract: Introduction: The purpose of this 3-way crossover study was to identify the effective dose of soy protein isolate enriched with isoflavones for suppressing bone resorption in postmenopausal women using a novel, rapid assessment of antibone resorbing treatments. Methods: Thirteen postmenopausal women (≥6 yr since menopause) were predosed with 41Ca iv. After a 200-d baseline period, subjects were given 43 g soy protein/d that contained 0, 97.5, or 135.5 mg total isoflavones in randomized order. The soy protein isolate powder was incorporated into baked products and beverages. Each 50-d intervention phase was preceded by a 50-d pretreatment phase for comparison. Serum isoflavone levels and biochemical markers were measured at the end of each phase. Twenty-four-hour urine samples were collected approximately every 10 d during each phase for 41Ca/Ca analysis by accelerator mass spectrometry. Results: Serum isoflavone levels reflected the amount of isoflavones consumed in a dose-dependent manner. None of the is...

Bone Seeking Labels as Markers for Bone Turnover: Effect of Dosing Schedule on Labeling Various Bone Sites in Rats

Abstract: Urinary excretion of bone labels can be used to monitor bone resorption. Here we investigate the effects of dosing frequency on label incorporation of various sites when bone turnover was perturbed by ovariectomy. We compared tritiated tetracycline (3H-TC) and 45Ca in two studies. Nine-month-old rats were given single or multiple injections of 3H-TC and 45Ca and sacrificed after 7 or 14 days. Six-month-old OVX rats were given 3H-TC and 41Ca tracers 1 or 3 months following ovariectomy (OVX + 1 mo or OVX + 3 mo, when bone turnover was higher or lower, respectively) and sacrificed 1 week, 1 month, 3 months, or 6 months postdose. Twenty-four-hour urine pools over 2–4 consecutive days as well as the proximal tibia, femur midshaft, lumbar vertebrae (L1–L4), and remaining skeleton were analyzed for 3H, 45Ca, and calcium content. Bone turnover as assessed by urinary 3H-TC was greater in OVX + 1 mo compared to OVX + 3 mo rats up to 6 months postdose. 45Ca labeling efficiency (% dose/g Ca) was significantly higher than for 3H and labeling was higher in trabecular-rich than cortical-rich bone. This study affirms that a single administration of either 3H-TC or 45Ca is a useful approach to measuring bone turnover directly. The amount of label incorporation into bone was greater in bone sites that were more metabolically active and in all sites when closer vs farther from OVX.

Bone-seeking labels as markers for bone turnover: validation of urinary excretion in rats

Abstract: Urinary excretion of tritiated tetracycline (3H-TC) and 41Ca tracers was validated as reflecting skeletal disappearance of these bone-seeking tracers as a direct measure of bone turnover following ovariectomy in rats Tritiated tetracycline (3H-TC) and Ca tracers have been used to measure bone resorption in animal models, but urinary excretion of these labels has not been directly compared to skeletal turnover We aimed to evaluate the use of bone-seeking labels by comparing label release into urine with label in the skeleton when bone turnover was perturbed following ovariectomy Sixty-four 6-month-old ovariectomized (OVX) rats were randomized to one of eight groups in a 2 × 4 design that differed in time of 3H-TC and 41Ca administration following ovariectomy (1 month, when bone turnover would be accelerated following estrogen depletion or 3 months when bone loss due to OVX had slowed down) and time of euthanasia (1 week, 1 month, 3 months, and 6 months post-dose) Twenty-four-hour urine pools over two to four consecutive days and total skeleton were collected and recovered for the assessment of 3H-TC and 41Ca Urinary 3H-TC levels reflected skeletal 3H-TC levels (r = 093; p < 00001) over a wide range of bone turnover rates in response to an intervention Urinary 41Ca and 3H-TC excretion were highly correlated (r = 095, p < 00001) This study confirms that bone-seeking label excretion into the urine directly measures bone turnover

3H-tetracycline as a proxy for 41Ca for measuring dietary perturbations of bone resorption

Abstract: Our group is interested in evaluating early effects of dietary interventions on bone loss. Postmenopausal women lose bone following reduction in estrogen which leads to increased risk of fracture. Traditional means of monitoring bone loss and effectiveness of treatments include changes in bone density, which takes 6 months to years to observe effects, and changes in biochemical markers of bone turnover, which are highly variable and lack specificity. Prelabeling bone with 41Ca and measuring urinary 41Ca excretion with accelerator mass spectrometry provides a sensitive, specific, and rapid approach to evaluating effectiveness of treatment. To better understand 41Ca technology as a tool for measuring effective treatments on reducing bone resorption, we perturbed bone resorption by manipulating dietary calcium in rats. We used 3H-tetracycline (3H-TC) as a proxy for 41Ca and found that a single dose is feasible to study bone resorption. Suppression of bone resorption, as measured by urinary 3H-TC, by dietary calcium was observed in rats stabilized after ovariectomy, but not in recently ovariectomized rats.

Health Effects of Soy Protein and Isoflavones in Humans

Abstract: Epidemiological investigations suggest that soy consumption may be associated with a lower incidence of certain chronic diseases. Clinical studies also show that ingestion of soy proteins reduces the risk factors for cardiovascular disease. This led to the approval of the food-labeling health claim for soy proteins in the prevention of coronary heart disease by the U.S. FDA in 1999. Similar health petitions for soy proteins have also been approved thereafter in the United Kingdom, Brazil, South Africa, the Philippines, Indonesia, Korea, and Malaysia. However, the purported health benefits are quite variable in different studies. The Nutrition Committee of the American Heart Association has assessed 22 randomized trials conducted since 1999 and found that isolated soy protein with isoflavones (ISF) slightly decreased LDL cholesterol but had no effect on HDL cholesterol, triglycerides, lipoprotein(a), or blood pressure. The other effects of soy consumption were not evident. Although the contributing factors to these discrepancies are not fully understood, the source of soybeans and processing procedures of the protein or ISF are believed to be important because of their effects on the content and intactness of certain bioactive protein subunits. Some studies have documented potential safety concerns on increased consumption of soy products. Impacts of soy products on thyroid and reproductive functions as well as on certain types of carcinogenesis require further study in this context. Overall, existing data are inconsistent or inadequate in supporting most of the suggested health benefits of consuming soy protein or ISF.

Current Knowledge in Soybean Composition

Abstract: The soybean [Glycine max (L.) Merr.] is grown worldwide for its high protein and oil contents. Characterization of soybean seed components lends itself to understanding how soybean production can meet the needs of a growing world population. For this article, literature was reviewed and condensed to create a well-rounded picture of the current understanding of structural, functional, and nutritional properties of soybean components. Natural variation in soybean protein, lipid, and carbohydrate components, as well as the minor constituents phytic acid and isoflavones, are mentioned. Environment- or genetic-induced shifts in natural variation are described with respect to nutrition and functional improvements in soybean.

Selective estrogen receptor modulators and phytoestrogens.

Abstract: Scientific achievements in the last two decades have revolutionized the treatment and prevention of breast cancer. This is mainly because of targeted therapies and a better understanding of the relationship between estrogen, its receptor, and breast cancer. One of these discoveries is the use of synthetic selective estrogen modulators (SERMs) such as tamoxifen in the treatment strategy for estrogen receptor (ER)-positive breast cancer. Hundreds of thousands of lives have been saved because of this advance. Not only is tamoxifen used in the treatment strategy for patients who have breast cancer, but also for prevention in high-risk premenopausal women. Another synthetic SERM, raloxifene, which was initially used to prevent osteoporosis, is also as effective as tamoxifen for prevention in high-risk postmenopausal women. In certain regions of the world, particularly in Asia, a low incidence of breast cancer has been observed. These women have diets that are high in soy and low in fat, unlike the Western diet. Interest in the protective effects of soy derivatives has led to the research of phytoestrogens and metabolites of soy that are described by some as natural SERMs. As a result, many clinical questions have been raised as to whether phytoestrogens, which are also found in other natural foods, can protect against breast cancer. This article reviews the development and role of the more common SERMs, tamoxifen and raloxifene. In addition, this paper will also highlight the emerging studies on phytoestrogens and their similarity and dissimilarity to SERMs.