Journal of Nutrition Biochemical, Molecular, and Genetic Mechanisms

Genistein and a Soy Extract Differentially Affect Three-Dimensional Bone Parameters and Bone-Specific Gene Expression in Ovariectomized Mice [Biochemical, Molecular, and Genetic Mechanisms]

Zhang, Y., Li, Q., Wan, H.-Y., Helferich, W. G., Wong, M.-S. — Fri, 20 Nov 2009 10:01:58 PST

Soy isoflavone preparations, such as purified genistein and a soy extract (Novasoy), were reported previously to exert beneficial effects on bones. Our purpose in this study was to compare the effects of genistein and Novasoy on 3-dimensional trabecular bone parameters and the expression of bone-specific genes in ovariectomized (OVX) mice. The sham-operated mice were fed the control diet and OVX mice were fed diets containing genistein or Novasoy or the control diet, with or without 17β-estradiol treatment, for 5 wk. Trabecular bone parameters of tibias were measured by microcomputed tomography and gene expression was assayed by real-time PCR. Consumption of diets containing genistein or Novasoy partially prevented the ovariectomy-induced increase in body weight but did not alter the uterus weight of the OVX mice. Novasoy, but not purified genistein, significantly preserved trabecular bone mass, bone volume, and trabecular bone separation in the proximal tibial metaphysis. Purified genistein decreased mRNA expression of receptor activator of nuclear factor-B ligand (RANKL), carbonic anhydrase II, and cathepsin K and enhanced the ratio of osteoprotegrin:RANKL mRNA expression in the tibial head of the OVX mice. In contrast, the diet containing Novasoy suppressed the OVX-induced increase in serum alkaline phosphatase but did not alter bone-specific gene expression of tibia. Our study demonstrated that a soy extract containing a similar level of genistein in the form of Novasoy is more effective than purified genistein in improving tibial trabecular bone quality in OVX mice, but the mechanism of action might be distinct from that of genistein.

Dietary Soy Protein Reduces Cardiac Lipid Accumulation and the Ceramide Concentration in High-Fat Diet-Fed Rats and ob/ob Mice [Biochemical, Molecular, and Genetic Mechanisms]

Fri, 20 Nov 2009 10:01:58 PST

Obesity is an epidemic condition strongly associated with cardiovascular morbidity and mortality. Heart disease secondary to obesity is associated with myocardial steatosis, leading to ceramide synthesis and cell dysfunction in a process known as lipotoxicity. Soy protein has been demonstrated to reduce lipotoxicity in the liver and pancreas in different rodent models of obesity. Thus, our purpose in the present work was to assess the effect of dietary soy protein on cardiac lipid accumulation and ceramide formation during obesity and to evaluate its effect in the following 2 rodent models of obesity: 1) a diet-induced obesity model in Sprague-Dawley rats was produced by feeding rats a control or a high-fat casein or soy protein diet for 180 d; and 2) wild-type and ob/ob mice were fed a casein or soy protein diet for 90 d. Soy protein intake led to lower cholesterol and triglyceride concentrations in the hearts of rats and ob/ob mice in association with a greater PPAR mRNA concentration and a lower level of sterol regulatory element binding protein-1 mRNA than those fed casein. The ceramide concentration was also lower in hearts of rats and ob/ob mice that were fed soy protein in association with lower serine palmitoyl transferase (SPT)-1 and tumor necrosis factor- mRNA concentrations. These results indicate that dietary soy protein can reduce the heart ceramide concentration by reducing the expression of SPT-1, a key enzyme in the formation of this sphingolipid in the heart of obese rodents, and by reducing lipid accumulation. Thus, soy protein consumption may be considered as a dietary therapeutic approach for lipotoxic cardiomyopathy prevention.

Conjugated Linoleic Acid Activates AMP-Activated Protein Kinase and Reduces Adiposity More Effectively When Used with Metformin in Mice [Biochemical, Molecular, and Genetic Mechanisms]

Jiang, S., Wang, Z., Riethoven, J.-J., Xia, Y., Miner, J., Fromm, M. — Fri, 20 Nov 2009 10:01:58 PST

Trans-10, cis-12 (t10c12) conjugated linoleic acid (CLA) reduces lipid levels in adipocytes, but the mechanisms involved are still emerging. The hypotheses of this study were that t10c12 CLA treatment activated AMP-activated protein kinase (AMPK) and that the effectiveness of a low dose of t10c12 CLA would be increased when combined with an AMPK activator. We demonstrated t10c12 CLA, directly or indirectly, activated AMPK and increased the amount of phosphorylated acetyl-CoA carboxylase (ACC) in 3T3-L1 adipocytes. Compound C, a potent inhibitor of AMPK, attenuated the phosphorylation of ACC, integrated stress response (ISR), inflammatory response, reduction in key lipogenic transcription factors, and triglyceride (TG) reduction that otherwise occurred in t10c12 CLA-treated adipocytes. Treatment of adipocytes or mice with a low dose of t10c12 CLA in conjunction with the AMPK activator metformin resulted in more TG loss than treatment with the individual chemicals. Additionally, although an inflammatory response was required for robust TG reduction, the combination of t10c12 CLA with AMPK activators had a similar TG loss with a reduced inflammatory response. A microarray analysis of the transcriptional response to either t10c12 CLA, metformin, or the combination, indicated the responses were very similar, with a correlation coefficient of 0.91 or better for genes in the ISR or lipid-related pathways. Altogether, these results support our hypotheses that t10c12 CLA activates AMPK, directly or indirectly, and that metformin increases the effectiveness of t10c12 CLA in reducing TG amounts in adipocytes.

Diallyl Trisulfide Protects Rats from Carbon Tetrachloride-Induced Liver Injury [Biochemical, Molecular, and Genetic Mechanisms]

Hosono-Fukao, T., Hosono, T., Seki, T., Ariga, T. — Fri, 20 Nov 2009 10:01:59 PST

Alk(en)yl sulfides have been found to be responsible for the anticancer, antithrombotic, and antioxidant effects of garlic. We sought to identify the most potent structure of sulfides that exhibits a hepatoprotective effect against carbon tetrachloride (CCl₄)-induced acute liver injury in rats. Rats were pretreated with diallyl trisulfide (DATS) i.g. at a dose of 500 µmol/kg body weight for 5 d. On d 6, CCl₄ was administered i.g. at a dose of 2.5 mL/kg body weight. Twenty-four hours after CCl₄ administration, rats were killed and plasma and liver samples collected. DATS pretreatment significantly suppressed the CCl₄-induced elevation of plasma aspartate aminotransferase and alanine aminotransferase activities (P < 0.05). Histological observations supported the hepatoprotective effects. Western blot and spectrophotometric analyses indicated that DATS suppressed cytochrome P450 2E1 activity and its protein level and elevated those of glutathione S-transferase. Dipropyl trisulfide (DPTS), which is a saturated alkyl chain analogue of DATS, did not affect CCl₄-induced liver toxicity or drug-metabolizing enzymes. These results suggest that hepatoprotective activity of trisulfides is due to their regulation of drug-metabolizing enzymes. Furthermore, the effects of 6 kinds of alk(en)yl trisulfides, including DATS and DPTS, on phase II enzyme activity were examined in rats. Alk(en)yl trisulfides were administered i.g. (500 µmol/kg body weight) to rats for 5 d. Only the allyl group-containing DATS and allyl methyl trisulfide enhanced these activities.

Dietary Saturated Fat Modulates the Association between STAT3 Polymorphisms and Abdominal Obesity in Adults [Biochemical, Molecular, and Genetic Mechanisms]

Tue, 20 Oct 2009 10:01:50 PDT

Signal transducer and activator of transcription 3 (STAT3) plays a key role in body weight regulation and glucose homeostasis, 2 important determinants of metabolic syndrome (MetS). Dietary fat is a key environmental factor that may interact with genotype to affect MetS risk. In this study, we investigated the relationship between STAT3 polymorphisms and MetS phenotypes and determined potential interactions with dietary fatty acids. STAT3 polymorphisms (rs8069645, rs744166, rs2306580, rs2293152, and rs10530050), biochemical measurements, and dietary fat composition were determined in the LIPGENE-SU.VI.MAX study of MetS cases and matched controls (n = 1754). STAT3 polymorphisms were not associated with MetS risk. However, minor G allele carriers for rs8069645, rs744166, and rs1053005 and major GG homozygotes for rs2293152 had increased risk of abdominal obesity compared with noncarriers [odds ratio (OR) = 2.22, P = 0.0005; OR = 2.08, P = 0.0017; OR = 2.00, P = 0.0033; and OR = 1.95, P = 0.028, respectively]. The number of risk alleles additively increased obesity risk (P = 0.0003). Dietary SFA intake exacerbated these effects; among all participants with the highest SFA intake (≥15.5% of energy), individuals carrying >2 risk alleles had further increased risk of obesity (OR = 3.30; 95% CI = 1.50–7.28; P = 0.0079) compared with those carrying ≤1 risk allele. Interaction analysis confirmed this gene-nutrient interaction whereby increasing SFA intake was predictive of increased waist circumference (P = 0.038). In conclusion, STAT3 gene polymorphisms influenced the risk of abdominal obesity, which is modulated by dietary SFA intake, suggesting novel gene-nutrient interactions.

Supplemental Dietary Inulin Influences Expression of Iron and Inflammation Related Genes in Young Pigs [Biochemical, Molecular, and Genetic Mechanisms]

Tue, 20 Oct 2009 10:01:50 PDT

We have previously shown improved hemoglobin (Hb) repletion efficiency by supplementing a 50:50 mixture of short (P95) and long-chain (HP) inulin (Synergy 1, BENEO-Orafti) into a corn-soybean meal-basal diet (BD) for young pigs. In this study, weanling pigs (5 or 6 wk old) were fed the BD or the BD + 4% of P95, HP, or Synergy 1 (50:50 mixtures of HP and P95) for 5–7 wk. Blood Hb concentrations of pigs were measured weekly and digesta samples were collected at the end of the trial. In a replicate experiment, total RNA was isolated from the liver and mucosa of duodenum, ileum, cecum, and colon of all pigs at the end of the trial. Relative mRNA expression of 27 genes, including iron and inflammation-related genes, was quantified using real-time quantitative-PCR. Although all 3 types of inulin resulted in similar improvements (P < 0.05) in blood Hb concentration and liver ferritin protein amount, neither type of inulin was detectable in the digesta of cecum or colon. Supplemental inulin enhanced the expression of iron-storing protein genes but decreased that of inflammation-related genes. Such effects were more pronounced (P < 0.05) in the mucosa of the lower than the upper gut and were seen on 7 genes in liver. In conclusion, all 3 types of inulin shared similar efficacy and possibly similar modes of action in improving dietary iron utilization by young pigs. Suppressing inflammation-induced genes that can negatively influence iron metabolism might help explain the benefit of inulin.

Trigonelline Is a Novel Phytoestrogen in Coffee Beans [Biochemical, Molecular, and Genetic Mechanisms]

Allred, K. F., Yackley, K. M., Vanamala, J., Allred, C. D. — Fri, 18 Sep 2009 10:01:30 PDT

Drinking coffee has been associated with the development of several endocrine-related cancers. The interpretation of these data has often been limited to the role that caffeine plays. Trigonelline (Trig), a niacin-related compound, is a natural constituent of coffee accounting for ~1% dry matter in roasted beans. Studies exploring the effects of this bioactive compound on mammalian cells are limited. The initial purpose of our studies was to determine whether Trig alters the actions of estradiol (E₂), using proliferation of estrogen-dependent human breast cancer (MCF-7) cells as a model system. When cells were cotreated with suboptimal doses of E₂ (10 pmol/L) and Trig (100 pmol/L), an additive enhancement of MCF-7 growth was observed. In the absence of E₂, Trig stimulated MCF-7 cell proliferation in a dose-responsive manner and significantly enhanced cell growth at concentrations as low as 100 pmol/L. Cotreatment of MCF-7 cells with Trig and ICI 182,780, an estrogen receptor (ER) antagonist, inhibited Trig-induced cell proliferation. Trig treatment also induced activation of estrogen response element reporter assays in MCF-7 cells and increased expression of ER target genes (pS2, progesterone receptor, and cyclin D1) similar to E₂. While our data demonstrate that Trig activates the ER, competitive binding assays showed that Trig does not compete E₂ off of the ER at any concentration. This suggests that Trig is activating the ER through a separate mechanism. Collectively, these data demonstrate that Trig even at low concentrations stimulates MCF-7 cell growth and that this effect is mediated through ER, clearly identifying Trig as a novel phytoestrogen.

Infant Formula Promotes Bone Growth in Neonatal Piglets by Enhancing Osteoblastogenesis through Bone Morphogenic Protein Signaling [Biochemical, Molecular, and Genetic Mechanisms]

Fri, 18 Sep 2009 10:01:30 PDT

Relatively few studies have examined the effects of formula feeding relative to breast-feeding on bone in the neonate. Using peripheral quantitative CT scan and histomorphometric analysis, we demonstrated that neonatal piglets fed with soy-based formula (SF) and cow milk-based formula (MF) for 21 or 35 d had greater bone mineral density and content than breast-fed piglets (BF) (P < 0.05). Osteoblast numbers and bone formation rate at postnatal d 35 were greater in SF compared with other groups (P < 0.05), whereas osteoclast numbers were lower in both MF and SF groups than in the BF group (P < 0.05). Osteoblastogenesis was greater in ex vivo bone marrow cell cultures from SF than in MF or BF piglets (P < 0.05). Bone formation markers in serum were greater, whereas bone resorption markers were lower in the MF- and SF-fed groups than in the BF group (P < 0.05). Bone morphogenic protein (BMP) 2 and alkaline phosphatase mRNAs were upregulated in the MF and SF groups compared with the BF group (P < 0.05), whereas receptor activator of NF-B ligand was downregulated (P < 0.05). Extracellular signal-regulated kinase, p38, Smad1/5/8 phosphorylation, and runt-related transcription factor 2 expression were greater in bone from the MF and SF groups compared with the BF group (P < 0.05). In vitro studies showed that 2.5% serum from SF- or MF-fed piglets was able to stimulate osteoblast differentiation but not in the presence of the BMP blocker noggin. Therefore, formula feeding promoted bone growth compared with BF. SF piglets had the highest bone volume over tissue volume. This suggests that SF-fed piglets may have the best quality bone. The anabolic effects of SF on bone appear to be mediated through enhanced BMP signaling.

Methylselenol, a Selenium Metabolite, Induces Cell Cycle Arrest in G1 Phase and Apoptosis via the Extracellular-Regulated Kinase 1/2 Pathway and Other Cancer Signaling Genes [Biochemical, Molecular, and Genetic Mechanisms]

Zeng, H., Wu, M., Botnen, J. H. — Thu, 20 Aug 2009 10:02:29 PDT

Methylselenol has been hypothesized to be a critical selenium (Se) metabolite for anticancer activity in vivo, and our previous study demonstrated that submicromolar methylselenol generated by incubating methionase with seleno-l-methionine inhibits the migration and invasive potential of HT1080 tumor cells. However, little is known about the association between cancer signal pathways and methylselenol's inhibition of tumor cell invasion. In this study, we demonstrated that methylselenol exposure inhibited cell growth and we used a cancer signal pathway-specific array containing 15 different signal transduction pathways involved in oncogenesis to study the effect of methylselenol on cellular signaling. Using real-time RT-PCR, we confirmed that cellular mRNA levels of cyclin-dependent kinase inhibitor 1C (CDKN1C), heme oxygenase 1, platelet/endothelial cell adhesion molecule, and PPAR genes were upregulated to 2.8- to 5.7-fold of the control. BCL2-related protein A1, hedgehog interacting protein, and p53 target zinc finger protein genes were downregulated to 26–52% of the control, because of methylselenol exposure. These genes are directly related to the regulation of cell cycle and apoptosis. Methylselenol increased apoptotic cells up to 3.4-fold of the control and inhibited the extracellular-regulated kinase 1/2 (ERK1/2) signaling and cellular myelocytomatosis oncogene (c-Myc) expression. Taken together, our studies identify 7 novel methylselenol responsive genes and demonstrate that methylselenol inhibits ERK1/2 pathway activation and c-Myc expression. The regulation of these genes is likely to play a key role in G1 cell cycle arrest and apoptosis, which may contribute to the inhibition of tumor cell invasion.

Butyrate Enhances the Intestinal Barrier by Facilitating Tight Junction Assembly via Activation of AMP-Activated Protein Kinase in Caco-2 Cell Monolayers [Biochemical, Molecular, and Genetic Mechanisms]

Peng, L., Li, Z.-R., Green, R. S., Holzman, I. R., Lin, J. — Thu, 20 Aug 2009 10:02:30 PDT

Butyrate, one of the SCFA, promotes the development of the intestinal barrier. However, the molecular mechanisms underlying the butyrate regulation of the intestinal barrier are unknown. To test the hypothesis that the effect of butyrate on the intestinal barrier is mediated by the regulation of the assembly of tight junctions involving the activation of the AMP-activated protein kinase (AMPK), we determined the effect of butyrate on the intestinal barrier by measuring the transepithelial electrical resistance (TER) and inulin permeability in a Caco-2 cell monolayer model. We further used a calcium switch assay to study the assembly of epithelial tight junctions and determined the effect of butyrate on the assembly of epithelial tight junctions and AMPK activity. We demonstrated that the butyrate treatment increased AMPK activity and accelerated the assembly of tight junctions as shown by the reorganization of tight junction proteins, as well as the development of TER. AMPK activity was also upregulated by butyrate during calcium switch-induced tight junction assembly. Compound C, a specific AMPK inhibitor, inhibited the butyrate-induced activation of AMPK. The facilitating effect of butyrate on the increases in TER in standard culture media, as well as after calcium switch, was abolished by compound C. We conclude that butyrate enhances the intestinal barrier by regulating the assembly of tight junctions. This dynamic process is mediated by the activation of AMPK. These results suggest an intriguing link between SCFA and the intracellular energy sensor for the development of the intestinal barrier.

Zinc Deficiency Affects DNA Damage, Oxidative Stress, Antioxidant Defenses, and DNA Repair in Rats [Biochemical, Molecular, and Genetic Mechanisms]

Song, Y., Leonard, S. W., Traber, M. G., Ho, E. — Thu, 20 Aug 2009 10:02:30 PDT

Approximately 12% of Americans do not consume the Estimated Average Requirement for zinc and could be at risk for marginal zinc deficiency. Zinc is an essential component of numerous proteins involved in the defense against oxidative stress and DNA damage repair. Studies in vitro have shown that zinc depletion causes DNA damage. We hypothesized that zinc deficiency in vivo causes DNA damage through increases in oxidative stress and impairments in DNA repair. Sprague-Dawley rats were fed zinc-adequate (ZA; 30 mg Zn/kg) or severely zinc-deficient (ZD; <1 mg Zn/kg) diets or were pair-fed zinc-adequate diet to match the mean feed intake of ZD rats for 3 wk. After zinc depletion, rats were repleted with a ZA diet for 10 d. In addition, zinc-adequate (MZA 30 mg Zn/kg) or marginally zinc-deficient (MZD; 6 mg Zn/kg) diets were given to different groups of rats for 6 wk. Severe zinc depletion caused more DNA damage in peripheral blood cells than in the ZA group and this was normalized by zinc repletion. We also detected impairments in DNA repair, such as compromised p53 DNA binding and differential activation of the base excision repair proteins 8-oxoguanine glycosylase and poly ADP ribose polymerase. Importantly, MZD rats also had more DNA damage and higher plasma F₂-isoprostane concentrations than MZA rats and had impairments in DNA repair functions. However, plasma antioxidant concentrations and erythrocyte superoxide dismutase activity were not affected by zinc depletion. These results suggest interactions among zinc deficiency, DNA integrity, oxidative stress, and DNA repair and suggested a role for zinc in maintaining DNA integrity.

Docosahexaenoic Acid Modifies the Clustering and Size of Lipid Rafts and the Lateral Organization and Surface Expression of MHC Class I of EL4 Cells [Biochemical, Molecular, and Genetic Mechanisms]

Shaikh, S. R., Rockett, B. D., Salameh, M., Carraway, K. — Thu, 20 Aug 2009 10:02:30 PDT

An emerging molecular mechanism by which docosahexaenoic acid (DHA) exerts its effects is modification of lipid raft organization. The biophysical model, based on studies with liposomes, shows that DHA avoids lipid rafts because of steric incompatibility between DHA and cholesterol. The model predicts that DHA does not directly modify rafts; rather, it incorporates into nonrafts to modify the lateral organization and/or conformation of membrane proteins, such as the major histocompatibility complex (MHC) class I. Here, we tested predictions of the model at a cellular level by incorporating oleic acid, eicosapentaenoic acid (EPA), and DHA, compared with a bovine serum albumin (BSA) control, into the membranes of EL4 cells. Quantitative microscopy showed that DHA, but not EPA, treatment, relative to the BSA control diminished lipid raft clustering and increased their size. Approximately 30% of DHA was incorporated directly into rafts without changing the distribution of cholesterol between rafts and nonrafts. Quantification of fluorescence colocalization images showed that DHA selectively altered MHC class I lateral organization by increasing the fraction of the nonraft protein into rafts compared with BSA. Both DHA and EPA treatments increased antibody binding to MHC class I compared with BSA. Antibody titration showed that DHA and EPA did not change MHC I conformation but increased total surface levels relative to BSA. Taken together, our findings are not in agreement with the biophysical model. Therefore, we propose a model that reconciles contradictory viewpoints from biophysical and cellular studies to explain how DHA modifies lipid rafts on several length scales. Our study supports the notion that rafts are an important target of DHA's mode of action.