Biomedical subjects

Susan E Appt

Publications and source records attributed to Susan E Appt.

12 recordsLinked to original sources

PubMed2006

Destruction of primordial ovarian follicles in adult cynomolgus macaques after exposure to 4-vinylcyclohexene diepoxide: a nonhuman primate model of the menopausal transition.

OBJECTIVE: To determine whether the 4-vinylcyclohexene diepoxide (VCD)-treated mouse menopause model, which involves accelerated atresia of primordial follicles and induces gradual ovarian failure (while sparing the ovarian stroma), can be adapted to nonhuman primates. DESIGN: Controlled periclinical trial (nonhuman primates). SETTING: Comparative Medicine Clinical Research Center. ANIMAL(S): Four adult female cynomolgus monkeys. INTERVENTION(S): Once-daily i.m. injections for 15 days as follows: vehicle or VCD doses of 80 mg/kg, 160 mg/kg, 250 mg/kg. Ovaries were removed 27 days after treatment, and pathological determinations were made at necropsy. MAIN OUTCOME MEASURE(S): Baseline and interim hematologic and biochemical measures, physical exams, and body weights. Follicle counts and organ evaluation at necropsy. RESULT(S): A nearly complete elimination of primordial, intermediate, primary and secondary follicles was achieved with 250 mg/kg VCD. A 50% reduction in primordial and primary follicles was observed with 160 mg/kg VCD. No effect of 80 mg/kg VCD per day was observed. Clinical health measures remained within normal range except for transient, mild increases in liver enzymes and an inflammatory response at the injection site with 250 mg/kg. Postmortem evaluations (9 months) revealed no gross or histological lesions in the organs studied. CONCLUSION(S): These results demonstrate that the monkey ovary is susceptible to VCD and that as in rodents, primordial and primary follicles are targeted selectively.

Animals↗

PubMed2006

Effects of high-dose soy isoflavones and equol on reproductive tissues in female cynomolgus monkeys.

Soy isoflavonoids have well-established estrogenic properties in cell culture and rodent models, raising concerns that high isoflavonoid intake may promote development of uterine and breast cancers. To address this concern we evaluated the effects of high-dose isoflavonoid supplements on reproductive tissues in a postmenopausal primate model. Thirty adult female ovariectomized monkeys (Macaca fascicularis) were randomized to receive a control diet 1) alone, 2) with 509 mg/day of the soy isoflavones genistein and daidzein (IF), or 3) with 1020 mg/day of racemic equol (EQ), an isoflavan, for approximately 1 mo. Doses are expressed in aglycone units as calorically scaled human equivalents. Total serum isoflavonoid levels 4 h postfeeding were <20 nmol/L, 2570.7 nmol/L, and 6944.8 nmol/L for control, IF, and EQ groups, respectively. Equol was the predominant serum isoflavonoid in both IF (72.5%) and EQ (99.7%) groups. Aglycones represented 0.9% (IF) and 0.5% (EQ) of total serum isoflavonoids. Histologically, uteri and mammary glands were diffusely atrophic in all groups. Uterine weight, endometrial thickness, glandular area, and epithelial proliferation in the uterus were not significantly different among treatment groups (ANOVA P > 0.1 for all). Endometrial progesterone receptor gene expression was significantly increased in the IF group (P = 0.02), while protein expression was not altered (ANOVA P > 0.1). Within the mammary gland, proliferation and indicators of estrogen exposure did not differ among treatment groups (ANOVA P > 0.1 for all). These findings indicate that high doses of dietary soy isoflavonoids have minimal uterotrophic or mammotrophic effects in an established primate model.

Animals↗

PubMed2006

Low dose estrogens inhibit coronary artery atherosclerosis in postmenopausal monkeys.

OBJECTIVES: To determine if low dose conjugated equine estrogens (CEE) result in a reduction of coronary artery atherosclerosis progression, and to relate these findings to previous studies using the traditional dose. METHODS: Adult female monkeys (Macaca fascicularis) were fed an atherogenic diet for 10 months, to induce fatty streaks and small plaques comparable to those present in early postmenopausal women, and then ovariectomized and treated orally with: CEE (0.30 mg/day women's equivalent dose, n=28) or placebo (n=25) daily for 24 months. Body weight and estradiol were measured at 3, 6, 12 and 18 months and plasma lipids were measured at baseline and every 6 months. RESULTS: Despite the lack of effect on plasma lipid profiles, monkeys treated with low dose CEE had marked reductions in coronary artery atherosclerosis plaque extent (intimal area) in all three main coronary arteries: left anterior descending artery (52% less, 0.044 mm(2) versus 0.091 mm(2), p=0.04); left circumflex artery (62% less, 0.045 mm(2) versus 0.119 mm(2), p=0.006) and right circumflex artery (42% less, 0.018 mm(2) versus 0.031 mm(2), p=0.20). The overall mean coronary atherosclerosis extent was 52% lower in CEE treated animals (0.042 mm(2) versus 0.088 mm(2), p=0.02). CONCLUSION: Low dose CEE (0.30 mg/woman/day equivalent) was effective in reducing coronary atherosclerosis and the magnitude of the protection was comparable to previously reported studies using doses equivalent to 0.625 mg/woman/day. This study provides an experimental basis for the assumption that low dose CEE may be as effective as the traditional dose in inhibiting coronary atherosclerosis progression in early postmenopausal subjects.

Animals↗

PubMed2006

Effects of soybean glyceollins and estradiol in postmenopausal female monkeys.

Glyceollins are a novel class of soybean phytoalexins with potential cancer-protective antiestrogenic effects. The purpose of this study was to evaluate the estrogen-antagonist effects of glyceollin-enriched soy protein on biomarkers for breast cancer risk. Thirty female postmenopausal cynomolgus macaques were randomized to one of three dietary treatments for 3 wk: 1) estradiol (E2, 1 mg/day) + casein/lactalbumin (control); 2) E2 + soy protein isolate (SPI) containing 194 mg/day isoflavonoids; and 3) E2 + glyceollin-enriched soy protein (GLY) containing 189 mg/day isoflavonoids + 134 mg/day glyceollins. Doses are expressed in calorically scaled human equivalents. Mean serum glyceollin concentrations at 4 h postfeeding were 134.2 +/- 34.6 nmol/L in the GLY group and negligible in the SPI group (P = 0.0007). Breast proliferation was significantly increased in the control group (+237%, P = 0.01) but not in the SPI group (+198%, P = 0.08) or GLY group (+36%, P = 0.18). Gene expression of trefoil factor 1 and progesterone receptor, two markers of estrogen receptor activity in breast epithelium, were also significantly higher in the control (P < 0.05 for both) but not in the GLY group. These preliminary findings suggest that soybean glyceollins are natural compounds with potential estrogen-modulating properties in the breast.

Animals↗

PubMed2006

Concentrations of isoflavones in macaques consuming standard laboratory monkey diet.

The soy isoflavones genistein and daidzein, as well as the daidzein metabolite equol, have structural similarities to mammalian estrogens and bind with varying affinity to both known subtypes of the estrogen receptor. Consequently, prospective studies in both humans and animals have begun to evaluate the potential effects of isoflavones on estrogen receptor-mediated phenomena. However, many diets of laboratory-housed animals derive their protein from soy and thus likely contain substantial quantities of isoflavones. Exposing experimental subjects to these isoflavones via such diets could confound studies, particularly those evaluating the effects of estrogen or estrogen-like ligands. The aim of this study was to compare the levels of circulating concentrations of isoflavones and their metabolites in monkeys fed either a soy-free diet, a soy-based diet providing 130 mg of isoflavone (daidzein, genistein, and glycitein aglycon equivalents) daily, or a commercially available 'chow' diet containing an unspecified amount of soybean meal. Animals consuming the commercial diet had serum concentrations of daidzein, genistein, and glycitein that were significantly higher than those of animals fed a soy-free diet but similar to those of monkeys fed a soybased diet formulated to be high in isoflavones. Notably, animals fed the commercial diet also had serum equol concentrations that were similar to or, in some cases, in excess of serum concentrations in the animals fed the soy diet. These data argue for the use of soy-free diets in studies investigating estrogenic effects on physiologic or behavioral endpoints.

Animal Nutritional Physiological Phenomena↗

PubMed2005

Determination of plasma genistein fatty acid esters following administration of genistein or genistein 4'7-O-dioleate in monkeys.

Soy-derived isoflavone phytoestrogens, such as genistein (4',5,7-trihydroxyisoflavone), have been shown to protect low-density lipoprotein from oxidation. In addition, human plasma was previously shown to be capable of converting genistein into lipophilic fatty acid esters that accumulate in lipoproteins in vitro. We developed a method for the quantitation of genistein fatty acid esters in plasma. Furthermore, the method was utilized to measure genistein ester concentrations in monkey plasma following administration of genistein or genistein 4',7-O-dioleate. After extraction from plasma, genistein fatty acid esters were separated from unesterified genistein by Sephadex LH-20 column chromatography. The genistein ester fraction was hydrolyzed by saponification and purified by a second chromatography on Sephadex LH-20. The hydrolyzed genistein esters were measured by time-resolved fluoroimmunoassay. Adult female rhesus monkeys (n=10) received a subcutaneous injection of genistein (24 mg, n=2) or genistein 4',7-O-dioleate (71 mg, n=3) or an oral dose of genistein (24 mg, n=2) or genistein 4',7-O-dioleate (71 mg, n=3). Plasma was collected at 4, 8, and 24 h post-dosing. Following subcutaneous administration of genistein 4',7-O-dioleate, the plasma concentrations of genistein esters became elevated in two out of three monkeys with 8-h values exceeding 7.5 nmol/L and 24-h values above 12 nmol/L. Other treatments resulted in lower plasma values ranging between 2.7 and 6.1 nmol/L. The lower limit of detection for the method was 1.44 nmol/L. Subcutaneously administered genistein 4',7-O-dioleate was also converted to water-soluble conjugates, but oral administration did not elevate plasma genistein fatty acid ester levels. The results suggest that it may be possible to introduce intact genistein ester molecules into plasma by parenteral but not oral administration.

Administration, Oral↗

PubMed2005

Controversies about HRT--lessons from monkey models.

Lessons from monkey models contribute significantly to a better understanding of the controversies in reconciling the differences in postmenopausal hormone treatment outcomes between observational and randomized trial data. Monkey studies brought attention to premenopausal estrogen deficiency with resulting premature coronary artery atherosclerosis. Recently, those monkey studies were confirmed for premenopausal women in the NHLBI-sponsored Women's Ischemia Syndrome Evaluation (WISE) Study. Monkey studies have provided convincing evidence for the primary prevention of coronary artery atherosclerosis when estrogens are administered soon after the development of estrogen deficiency. Equally convincing are the data from monkey studies indicating the total loss of these estrogens beneficial effects if treatment is delayed for a period equal to six postmenopausal years for women. An attempt has been made using the monkey model to identify the hormone treatment regimen most effective in preventing the progression of coronary artery atherosclerosis. By a substantial margin, the most effective approach is that of using estrogen containing oral contraceptive during the perimenopausal transition, followed directly by hormone replacement therapy postmenopausally. Because of similarities between human and nonhuman breast, monkeys have had a major role in clarifying controversies surrounding the breast cancer risk of estrogen only versus estrogen plus progestin therapies. The results of monkey studies suggest little or no effects of estrogen only treatment; whereas, estrogen+progestin clearly increases breast cancer risk.

Animals↗

PubMed2004

Practical measurement of total and bioavailable estradiol in female macaques.

BACKGROUND: Commercially available, direct assay kits provide a simple and rapid means for measuring estradiol. Similarly, ammonium sulfate precipitation of SHBG-bound steroids is a reliable alternative to equilibrium dialysis or ultrafiltration for assessing bioavailability. However, while these techniques are useful for humans, they have yet to be evaluated systematically for macaques-species which are frequently used to model estrogen effects on women's health. METHODS: A reference assay (which included chromatography) and two modified versions of a human kit (one in which monkey serum was assayed directly, and another in which an extraction step was added) were used to measure estradiol in matching samples. Ammonium sulfate precipitation and an established ultrafiltration technique were used to assess bioavailability. RESULTS: Values from both kit modifications correlated significantly with those from the reference assay. Although both modifications underestimated values, the addition of the extraction step resulted in far more useful estimates due to the consistency of underestimation across the standard curve. Measures of bioavailability from ammonium sulfate precipitation and ultrafiltration were strongly correlated and consistent across all concentrations. CONCLUSIONS: Simplified techniques developed for humans can be used in macaques, although the addition of an extraction step markedly improves the performance of direct assay kits.

Animals↗

PubMed2004

Usefulness of the monkey model to investigate the role soy in postmenopausal women's health.

Some of the important health issues for postmenopausal women include cardiovascular disease, osteoporosis, breast cancer, and relief of menopausal symptoms. Ovariectomized cynomolgus monkeys (Macaca fascicularis) have many strengths as models for research in this area including a close phylogenetic relationship to humans, similarities in lipid/lipoprotein metabolism and coronary artery anatomy, similar skeletal anatomical and morphological characteristics, mammary glands with similar pathophysiological characteristics, and a 28-day menstrual cycle with similar hormonal fluctuations. Monkeys (macaques) also experience declining ovarian function and irregular menstrual cycles (natural menopause) when they approach 24 to 29 yr of age. However, because of their very short life span after natural menopause, ovariectomized macaques are used to model postmenopausal women. The cynomolgus monkey model has been useful in defining the potential cardiovascular benefits of soy foods and soy supplements; however, it remains unclear whether the observations are generalizable to all women or only to those who, like cynomolgus monkeys, convert the soy isoflavone daidzein to the metabolite equol. Particularly important has been the use of the cynomolgus monkey model to understand the effects of soy on breast health. There is evidence from a cynomolgus monkey trial to suggest that soy/soy phytoestrogens have no estrogen agonist effects for breast. Finally, soy/soy phytoestrogens do not appear to be an adequate alternative to postmenopausal hormone therapy. Nevertheless, important attributes of soy have been identified, and it may have potential as a complementary component to hormone therapy.

Animals↗

PubMed2003

MPA and postmenopausal coronary artery atherosclerosis revisited.

Whether progestins, particularly medroxyprogesterone acetate (MPA), attenuate the cardiovascular benefits of postmenopausal estrogen replacement therapy (ERT) has been controversial for over a decade. Concerns related first to findings that MPA attenuated increases of high density lipoprotein cholesterol (HDLC) concentrations of postmenopausal women compared to conjugated equine estrogen (CEE) alone. That observation was followed by early cynomolgus monkey studies that suggested MPA decreased estrogen's cardiovascular benefits (vascular reactivity and coronary artery atherosclerosis inhibition). In a more recent and larger trial with cynomolgus monkeys, no differences were seen in the coronary artery atherosclerosis protective effect of CEE when MPA was co-administered (HRT). The lack of attenuation of ERTs benefits by progestins has also been seen in at least three studies of carotid artery intima-media thickness (IMT) of postmenopausal women. Additionally, the majority of studies of vascular reactivity of postmenopausal women have not found differences when CEE is given alone or with MPA. Seven observational studies of cardiovascular outcomes of postmenopausal women permit separate consideration of ERT versus HRT use; there is no evidence of attenuation of ERTs benefits by progestin use. In conclusion, it is evident that the current experimental, clinical, and observational data do not provide evidence that progestins attenuate estrogen's cardiovascular benefits.

Animals↗

PubMed2003

Treatment with antibiotics reduces plasma equol concentration in cynomolgus monkeys (Macaca fascicularis).

To explore the importance of equol on health outcomes in future studies, it was necessary to develop a method to reduce equol production. Female monkeys (n = 22) fed a soy diet were treated twice daily with vehicle (control; n = 4), doxycycline (2.5 mg/kg; n = 4), metronidazole (125 mg/d; n = 3), kanamycin (1000 mg/d; n = 4), vancomycin (100 mg/d; n = 3) or kanamycin+vancomycin (n = 4). Plasma samples were collected 4 h postfeeding at baseline, after 4 wk of treatment and 8 wk after the end of treatment and analyzed for isoflavonoid concentrations. Fecal swabs were collected at baseline and at the end of antibiotic treatment for analysis of Gram(+) and Gram(-) bacterial growth. Equol concentrations were reduced (P < 0.05) compared with baseline by 80, 93, 98 and 99% after treatment with metronidazole (955 +/- 164 vs. 193 +/- 53 nmol/L), kanamycin (545 +/- 211 vs. 37.1 +/- 17.6 nmol/L), vancomycin (607 +/- 163 vs. 8.9 +/- 8.2 nmol/L) and kanamycin+vancomycin (721 +/- 169 vs. 17.4 +/- 17.3 nmol/L), respectively. Daidzein concentrations were increased (P < 0.05) compared with baseline by treatment with doxycycline (336 +/- 87 vs. 576 +/- 76 nmol/L), kanamycin (168 +/- 67 vs. 374 +/- 15 nmol/L), and kanamycin+vancomycin (166 +/- 35 vs. 384 +/- 78 nmol/L). Similar increases (P < 0.05) in dihydrodaidzein were observed after treatment with kanamycin (31.2 +/- 6.2 vs. 479 +/- 188 nmol/L) and metronidazole (56.0 +/- 27.9 vs. 414 +/- 212 nmol/L). Isoflavonoid concentrations returned to baseline values after antibiotic treatment was terminated. Gram(+) bacterial growth was reduced by all treatments, including Control, compared with baseline. In conclusion, treatment with antibiotics resulted in a marked reduction in plasma equol concentrations and altered plasma isoflavonoid patterns in cynomolgus monkeys.

Administration, Oral↗

PubMed2002

Dietary soy and soy isoflavones have gender-specific effects on plasma lipids and isoflavones in golden Syrian f(1)b hybrid hamsters.

The specific components of soy responsible for its beneficial effects on plasma lipids are unknown. Golden Syrian F(1)B Hybrid hamsters (75 male, 74 female) were evaluated for the effect of dietary soy and soy isoflavones on plasma lipids. They were fed the following diets for 16 wk: casein/lactalbumin (C/L), soy protein with isoflavones [Soy(+)], soy protein with isoflavones removed [Soy(-)], Soy(-) plus isoflavone extract (IF), and C/L + IF. At necropsy, plasma total cholesterol, HDL cholesterol (HDLC), LDL + VLDL cholesterol (LDL + VLDLC), isoflavones, and uterine and accessory gland weights were measured. Male hamsters fed the three soy-containing diets had lower LDL + VLDLC concentrations than those fed the two C/L diets (P < 0.01), and those fed Soy(-) + IF did not differ from those fed Soy(+). In females, diet did not affect plasma LDL + VLDLC concentration. Females fed Soy(+) or Soy(-) had higher HDLC (P < 0.05) than those fed C/L. HDLC was not affected by diet in males. Due to higher equol production (P < 0.01), males had greater plasma isoflavone concentrations (P < 0.01) than females. There was a positive association between plasma total isoflavones and LDL + VLDLC (r = 0.65, P < 0.05) in females. These data suggest gender differences in plasma lipid and isoflavone responses to soy- based diets in Syrian F(1)B Hybrid hamsters, which offer an opportunity to explore effects of sex hormones on isoflavone metabolism and the effects of isoflavones on lipid metabolism.

Animals↗