Long-Term Feeding Soy Protein Concentrates Protect Against Hepatic Steatosis Independent of Isoflavone Levels.

The health benefits of soy foods are attributed to the high-quality protein and the bioactive compounds such as isoflavones. We previously reported that feeding obese (fa/fa) Zucker rats soy protein concentrates (SPCs) with low isoflavone (LIF) and high isoflavone (HIF) for 9 weeks significantly reduced liver steatosis compared to a casein control (C) diet. The current study extended the dietary treatments to 18 weeks to investigate the long-term effect of LIF and HIF SPC diets. 6-week-old male lean (L, n = 21) and obese (O, n = 21) Zucker rats were fed a casein C diet, LIF and HIF SPC diets for 18 weeks and body weight (BW) was recorded twice weekly. Rats were killed after 18 weeks to measure liver steatosis and serum aspartate aminotransferase and alanine aminotransferase. Obese rats had significantly greater final BW, liver weight, liver weight as the percentage of BW, and steatosis score compared to lean rats in all three dietary groups. The obese high-isoflavones (OHIF) group had significantly higher BW compared to obese control (OC) group (P < .0001) and obese low-isoflavones (OLIF) group (P = .01). OC group had significantly greater liver weight, liver weight as the percentage of BW, and liver steatosis score compared to OLIF (P = .0077, P < .0001 and P < .0001, respectively) and OHIF (P = .0094, P < .0001, and P < .0001, respectively) groups. Taken together, long-term feeding of SPC diets protected against liver steatosis regardless of isoflavone levels.

Feeding Soy Protein Concentrates with Low and High Isoflavones Alters 9 and 18 Weeks Serum Isoflavones and Inflammatory Protein Levels in Lean and Obese Zucker Rats.

Soy's anti-inflammatory properties contribute to the health benefits of soy foods. This study was designed to investigate the bioavailability of soy isoflavones and whether the isoflavone content of soy protein concentrate diet would affect serum inflammatory proteins in an obese (fa/fa) Zucker rat model. Six-week-old male lean (L) and obese (O) Zucker rats were fed a casein control diet (C), soy protein concentrate with low isoflavones (SPC-LIF), or soy protein concentrate with high isoflavones (SPC-HIF) (7 rats/dietary group) before being killed at 9 and 18 weeks. Serum samples were analyzed for isoflavones and inflammatory proteins. At both time points, serum total (aglycone + conjugates) genistein, daidzein, and equol concentrations were significantly higher in L-SPC-HIF and O-SPC-HIF groups compared with L-SPC-LIF and O-SPC-LIF groups, respectively, and were not detectable in either L-C or O-C groups. At week 9, serum C-reactive protein (CRP) concentration was significantly lower in O-SPC-HIF group compared with O-C and O-SPC-LIF group, whereas proteins tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) levels did not differ between any groups. At week 18, serum CRP levels in both O-SPC-HIF and O-SPC-LIF groups were significantly lower compared with the O-C group. TNF-α level was higher in the O-SPC-LIF group compared with both O-C and O-SPC-HIF groups, whereas IL-6 levels were not different between any groups. Taken together, feeding Zucker rats SPC-LIF and SPC-HIF diets led to different serum isoflavone concentrations in both L and O Zucker rats and altered CRP and TNF-α levels in obese Zucker rats compared with controls.

Hepatic Proteomics Analysis of Nonalcoholic Fatty Liver Disease Obese Rat Model After Short- and Long-Term Soy Protein Isolate Feeding.

To identify possible mechanisms involved in the development and progression of nonalcoholic fatty liver disease (NAFLD), we conducted shotgun proteomics analysis on liver of obese Zucker rats fed either casein (CAS) or soy protein isolate (SPI) for 8 and 16 weeks. Rats (7 weeks old, n = 8-9/group) were randomly assigned to either a CAS-based or an SPI-based diet. Rats were killed after 8 or 16 weeks of feeding and livers were stored at -80°C. Ingenuity Pathway Analysis (IPA) software was used to facilitate interpretation of proteomics data. Predictions of activation or inhibition of molecules in the data were made based on activation z-score and P value of overlap (P < .05). Activation z-scores ≥2.0 indicate that a molecule is predicted to be activated, whereas activation z-scores of less than or equal to -2.0 indicate that a target molecule is predicted to be inhibited. Upstream regulator analysis with IPA revealed Neuregulin 1 (NRG1) to be the top activated protein in (z-score = 2.48, P < .05), and MKNK1 as the top inhibited protein (z-score = -2.83, P < .05) in SPI diet compared with CAS diet after both 8 and 16 weeks of SPI feeding. Regulator effects analysis also predicted that some proteins would be participating, directly or indirectly, in the inhibition of immune response functions (such as leukocyte migration) and lipid metabolism (such as synthesis of lipids) in SPI-fed rats relative to CAS-fed rats. Our results suggest that SPI diet modifies the expression of proteins that could be involved in the reduction of NAFLD.

A Comparison of Short- and Long-Term Soy Protein Isolate Intake and Its Ability to Reduce Liver Steatosis in Obese Zucker Rats Through Modifications of Genes Involved in Inflammation and Lipid Transport.

Obesity can lead to several health disorders including nonalcoholic fatty liver disease (NAFLD), the aggregation of lipids within hepatocytes, and consequent inflammation of the liver tissue. Previously, we reported that feeding obese Zucker rats with soy protein isolate (SPI) can reduce liver steatosis. To understand how SPI reduced liver steatosis, we conducted global gene expression analysis on liver samples obtained from these rats after short- (8 weeks) and long-term SPI feeding (16 weeks). We compared and contrasted these data using Ingenuity Pathway Analysis (IPA) software. This study focused mainly on target molecules that could be participating in inflammation processes and lipid metabolism that are well-known components of NAFLD. Inflammatory response was predicted to be inhibited in animals fed the SPI diet at both 8 and 16 weeks of experiment. This general prediction was based on negative activation z scores obtained through IPA (z score < -2.0, P < .00001) for eight aspects of immune function/inflammatory response. Lipid metabolism was predicted to be strongly enhanced in rats fed the SPI diet for 16 weeks than for 8 weeks. This prediction was based on positive activation z scores (z scores >2.0, P < .00001) of eight functions involved in lipid transport and metabolism. We observed that the longer the rats were fed the SPI diet, the more beneficial it resulted against NAFLD. Based on our findings, the predicted reductions in inflammatory mechanisms while enhancing lipid transport out of the liver could be the reasons behind the reduction of liver steatosis.

A diet containing high- versus low-daidzein does not affect bone density and osteogenic gene expression in the obese Zucker rat model.

Phytoestrogens are nonsteroidal plant compounds with similar chemical structures to mammalian estrogen capable of mimicking the effect of estrogen in selective tissues. A diet rich in phytoestrogens is associated with a variety of health benefits including decreased risks for heart disease, breast cancer, and osteoporosis. Obesity has long thought to be associated with improved bone density due to increased mechanical loading, but recent literature suggests obesity may actually decrease bone health. Daidzein, a soy-derived phytoestrogen, has been shown to improve parameters of bone health in lean animal models of osteoporosis but has not been tested in obese animals. Following a one-week acclimation to a standard AIN-93G diet, 19 five-week-old female obese Zucker rats (OZR) were randomly assigned to a modified AIN-93G diet containing either high daidzein (HD, 0.121 g kg-1 feed) or low daidzein (LD, 0.01 g kg-1 feed). After 8 weeks, tibias and femurs were removed to assess true density (Archimedes principal), mechanical strength (three-point bending test), and femoral osteogenic gene expression. Serum was collected to assess osteocalcin and deoxypyridinoline. Our results indicated that there were no significant differences between the measures for tibial or femoral true density or mechanical strength for the rats in the HD and LD diet groups. Similarly, there were no significant differences in gene expressions related to osteogenic pathways, or serum biomarkers of bone formation and resorption. Overall, an increased dose of daidzein from soy protein supplementation does not elicit an improvement in markers of bone health in obese Zucker rats.

Dehydroepiandrosterone (DHEA) Feeding Protects Liver Steatosis in Obese Breast Cancer Rat Model.

Obesity is a major health problem in the US and globally. Obesity is associated with the risk of cardiovascular disease, type 2 diabetes, cancers, hyperlipidemia, and liver steatosis development. Dehydroepiandrosterone (DHEA) is a dietary supplement used as an anti-obesity supplement. Previously, we reported that DHEA feeding protects 7,12-dimethylbenz(a)anthracene (DMBA)-induced mammary tumors. The objectives of this study were to investigate the effects of obesity and DHEA feeding on liver steatosis, body weight gain, and serum DHEA, DHEA sulfate (DHEA-S), insulin-like growth factor-1 (IGF-1), and insulin-like growth factor binding protein-3 (IGFBP-3) levels. Female Zucker rats were randomly assigned to either a control diet or a control diet with DHEA supplementation for 155 days. Livers were collected for histological examination. Serum was collected to measure DHEA, DHEA-S, IGF-1, and IGFBP-3. Our results show that DHEA-fed rats had significantly less liver steatosis (p < 0.001) than control-fed rats and gained less weight (p < 0.001). DHEA feeding caused significant decreases (p < 0.001) in the serum levels of IGF-1 and IGFBP-3 and significantly increased (p < 0.001) serum levels of DHEA and DHEA-S. Our results suggest that DHEA feeding can protect against liver steatosis by reducing body weight gain and modulating serum IGF-1 and IGFBP-3 levels in an obese breast cancer rat model.

A diet containing a high- versus low-daidzein level does not protect against liver steatosis in the obese Zucker rat model.

The prevalence of obesity is increasing worldwide. Obesity increases the risk for non-alcoholic fatty liver disease through adipokine dysregulation and inflammation. Previously, we have reported that a high-isoflavone soy protein isolate (HISPI) diet is associated with significantly heavier body weights and reduced liver steatosis in obese Zucker rats (OZR) compared to a casein diet. The objective of this study was to investigate whether daidzein, a soy isoflavone in HISPI, is responsible for increased body weight gain or reduced liver steatosis. We hypothesized that a casein diet containing high daidzein (HD) compared to low daidzein (LD) would mitigate hepatic steatosis in female OZR. We used 19 five-week-old female OZR (fa/fa). Rats were randomly assigned to a modified AIN-93G diet containing HD (0.121 g kg-1 feed) or LD (0.01 g kg-1 feed). Rats were weighed twice weekly. Feed intake was measured once weekly, and kcal per kg of body weight was calculated. After 8 weeks, rats were sacrificed. Serum and livers were collected. Sections of the liver lobe were fixed in 10% buffered formalin and stained with hematoxylin and eosin. Steatosis was semiquantitated as a score of 1 to 4 based upon the relative degree of steatosis within hepatocytes: (1) <25%, (2) 25%-50%, (3) 50%-75%, and (4) >75%. Serum leptin and adiponectin were measured by ELISA. Our results did not show significant differences in mean liver steatosis scores, body weights, energy intake, and serum leptin and adiponectin levels between diet groups. In conclusion, daidzein may not be the main component of HISPI responsible for increasing body weight or reducing liver steatosis in OZR.

Short- and Long-Term Soy Diet Versus Casein Protects Liver Steatosis Independent of the Arginine Content.

Nonalcoholic fatty liver disease, a major cause of abnormal liver function, is often associated with obesity. Arginine (ARG) plays a role in modulating body weight/fat, but limited data exist as to the role of ARG in soy protein's ability to protect from liver steatosis. We investigated the role of native ARG in the soy protein isolate (SPI) in reducing liver steatosis in male obese Zucker rats. Rats (N=48; 6 weeks old) were randomly assigned to one of three diets for 8 or 16 weeks: the casein (CAS) diet as control (0.6% ARG), CAS diet supplemented to contain 1.3% ARG, or an SPI diet containing isoflavones (1.3% ARG). SPI and ARG rats gained significantly more weight (P<.05) than CAS rats after 16 weeks only. The SPI rats had lower liver steatosis scores after 8 and 16 weeks (P<.05 and P<.001, respectively) compared to CAS and ARG rats. SPI rats had lower serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels (P<.05) compared to CAS after 16 weeks, and AST was lower (P<.05) compared to ARG rats. After 16 weeks, the SPI rats had lower (P<.05) serum ALT and AST levels than at 8 weeks. Our results suggest that a longer period of SPI feeding results in lower liver steatosis and serum ALT and AST levels, while the ARG diet had no effect on steatosis or ALT and AST levels. We found that the SPI diet reduced (P<.001) serum tumor necrosis factor-α (TNF-α) compared to CAS and ARG diets after 8 and 16 weeks. The SPI diet significantly reduced (P<.001) interleukin-6 (IL-6) when compared to the CAS diet at 8 weeks, but there was no significant difference at 16 weeks. Based on the findings of our study, the protective effect of SPI in reducing liver steatosis is not modulated by its native arginine content.

Dehydroepiandrosterone intake protects against 7,12-dimethylbenz(a)anthracene-induced mammary tumor development in the obese Zucker rat model.

Obesity has been epidemic in the US for over two decades; almost 65% of adults in the US are overweight. Obesity has been linked with the risk of development of various cancers, including breast cancer. Dehydroepiandrosterone (DHEA) is an over-the-counter dietary supplement used as an immunomodulating, anti-depressant, anti-aging, anti-cardiovascular disease, and anti-cancer agent and anti-obesity supplement. The objectives of this study were to investigate the long-term effects of obesity and DHEA treatment on body weight gain and on 7,12-dimethylbenz(a)anthracene (DMBA)-induced mammary tumor development. Forty-three six-week-old obese female Zucker rats were used. Rats were randomly assigned and had ad libitum access to water and a diet of either chow (2016) as a control diet or chow with the addition of DHEA at a concentration of 6 g/kg of chow as a DHEA diet. All rats were orally gavaged at age 50 days with 65 mg DMBA/kg body weight. Rats were weighed and palpated twice weekly for detection of mammary tumors and sacrificed 155 days post-DMBA treatment. Obese rats fed the DHEA diet gained significantly less weight than obese control diet rats (P<0.001). At the end of the experiment, 55% of the control diet group developed mammary tumors, while no tumors were detected in the DHEA diet group (P<0.001). Our results suggest that DHEA treatment can reduce body weight gain and protects against DMBA-induced mammary tumor development in the obese Zucker rat model.

Dietary soy intake and breast cancer risk.

PURPOSE/OBJECTIVES: To conduct a metasynthesis of the literature on human studies of the relationship between dietary soy intake and breast cancer risk. DATA SOURCES: Publications in English reporting human studies were searched with the terms soy and breast cancer, using Ovid, PubMed, and EBSCO databases. Only human studies investigating the relationship of soy intake to breast cancer development in women published from January 1997 through June 2008 were included in the review. DATA SYNTHESIS: A total of 364 publications were located; 18 of the studies met the inclusion criteria and 18 additional studies were located through other publications identified in the search. Because four articles reported on the same two studies, a total of 34 studies were included in the review. CONCLUSIONS: The naturally occurring dietary intake of soy food or its components appears safe for women without breast cancer; however, the safety of high supplements of soy or its components is less certain. IMPLICATIONS FOR NURSING: Nurses should become more knowledgeable about soy foods and supplements and include soy intake in dietary assessments. Nurses caring for women at high risk for or with a history of breast cancer should confer with dietitians on current practice recommendations. Women with health issues should avoid initiating high intake of soy dietary supplements until the possible effects are better understood.

Dietary saturated fat reduces alcoholic hepatotoxicity in rats by altering fatty acid metabolism and membrane composition.

Rats fed a saturated fat diet are protected from experimentally induced alcoholic liver disease, but the molecular mechanisms underlying this phenomenon remain in dispute. We fed male Sprague-Dawley rats intragastrically by total enteral nutrition using diets with or without ethanol. In 1 control and 1 ethanol group, the dietary fat was corn oil at a level of 45% of total energy. In other groups, saturated fat [18:82 ratio of beef tallow:medium-chain triglyceride (MCT) oil] was substituted for corn oil at levels of 10, 20, and 30% of total energy, while keeping the total energy from fat at 45%. After 70 d, liver pathology, serum alanine aminotransferase (ALT), biochemical markers of oxidative stress, liver fatty acid composition, cytochrome P450 2E1 (CYP2E1) expression and activity and cytochrome P450 4A (CYP4A) expression were assessed. In rats fed the corn oil plus ethanol diet, hepatotoxicity was accompanied by oxidative stress. As dietary saturated fat content increased, all measures of hepatic pathology and oxidative stress were progressively reduced, including steatosis (P < 0.05). Thus, saturated fat protected rats from alcoholic liver disease in a dose-responsive fashion. Changes in dietary fat composition did not alter ethanol metabolism or CYP2E1 induction, but hepatic CYP4A levels increased markedly in rats fed the saturated fat diet. Dietary saturated fat also decreased liver triglyceride, PUFA, and total FFA concentrations (P < 0.05). Increases in dietary saturated fat increased liver membrane resistance to oxidative stress. In addition, reduced alcoholic steatosis was associated with reduced fatty acid synthesis in combination with increased CYP4A-catalyzed fatty acid oxidation and effects on lipid export. These findings may be important in the nutritional management and treatment of alcoholic liver disease.