H. Lu

Dietary Fat Content and Fiber Type Modulate Hind Gut Microbial Community and Metabolic Markers in the Pig

Obesity leads to changes in the gut microbial community which contribute to the metabolic dysregulation in obesity. Dietary fat and fiber affect the caloric density of foods. The impact of dietary fat content and fiber type on the microbial community in the hind gut is unknown. Effect of dietary fat level and fiber type on hindgut microbiota and volatile fatty acid (VFA) profiles was investigated. Expression of metabolic marker genes in the gut, adipose tissue and liver was determined. A 2×2 experiment was conducted in pigs fed at two dietary fat levels (5% or 17.5% swine grease) and two fiber types (4% inulin, fermentable fructo-oligosaccharide or 4% solka floc, non-fermentable cellulose). High fat diets (HFD) resulted in a higher (P<0.05) total body weight gain, feed efficiency and back fat accumulation than the low fat diet. Feeding of inulin, but not solka floc, attenuated (P<0.05) the HFD-induced higher body weight gain and fat mass accumulation. Inulin feeding tended to lead to higher total VFA production in the cecum and resulted in a higher (P<0.05) expression of acyl coA oxidase (ACO), a marker of peroxisomal β-oxidation. Inulin feeding also resulted in lower expression of sterol regulatory element binding protein 1c (SREBP-1c), a marker of lipid anabolism. Bacteria community structure characterized by DGGE analysis of PCR amplified 16S rRNA gene fragments showed that inulin feeding resulted in greater bacterial population richness than solka floc feeding. Cluster analysis of pairwise Dice similarity comparisons of the DGGE profiles showed grouping by fiber type but not the level of dietary fat. Canonical correspondence analysis (CCA) of PCR- DGGE profiles showed that inulin feeding negatively correlated with back fat thickness. This study suggests a strong interplay between dietary fat level and fiber type in determining susceptibility to obesity.

Butyrate supplementation to gestating sows and piglets induces muscle and adipose tissue oxidative genes and improves growth performance

Weaned pigs often experience growth reduction immediately after weaning due to multiple stress factors associated with weaning. We tested the effect of prenatal and postnatal butyrate supplementation on growth performance of piglets. In study 1, piglets were orally gavaged with 0.3% butyrate from day 4 after birth to weaning (day 21). Butyrate increased ADG by 13% compared to saline treated control. Expression of peroxisome proliferator activated receptor gamma coactivator 1 alpha (PGC-1α) was higher in muscle, adipose tissue, and ileum of butyrate-supplemented animals. Also, peroxisome proliferator activated receptor alpha (PPARα) was induced (P < 0.05) in the subcutaneous adipose tissue (SCAT) and muscle (longissimus dorsi [LD]) of butyrate-supplemented piglets. In vitro, butyrate increased (P < 0.05) fatty acid oxidation in primary adipocytes and suppressed basal lipolysis by 62% compared to untreated cells. Butyrate suppressed (P < 0.05) lipogenesis ((14)C-glucose incorporation into lipids) in adipocytes. This was accompanied by an approximately 30% reduction in the mRNA expression of fatty acid synthase (P < 0.05) in butyrate-treated cells vs. controls. Piglets born to sows that were supplemented with 0.3% butyrate during the last trimester of gestation had a 15% higher (P < 0.05) body weight at 12 wk than controls. In summary, butyrate supplementation to gestating sows and piglets enhanced postweaning growth performance, which may be mediated by increased substrate oxidation in butyrate treated animals.

Interactive effects of dietary protein source and exogenous protease on growth performance, immune competence and jejunal health of broiler chickens

A total of 672 male 7-day-old broiler chicks were used in a 14-day cage study to evaluate the interactive effects of dietary protein source and exogenous protease on nutrient digestibility and intestinal physiology. Birds were fed a common starter diet from Days 0 to 7 and switched to experimental diets from Days 7 to 21. Four corn-based dietary treatments were arranged in a 2 × 2 factorial arrangement with factors being two major sources of protein [soybean meal (SBM) or canola meal] and diets offered with or without exogenous protease. Bodyweight gain and gain:feed were higher (P < 0.001) in the diets based on SBM than in the diets based on canola meal and protease was more effective (P < 0.05) in enhancing performance in SBM-based diets. Ileal nitrogen digestibility was increased (P < 0.01) by protease use in diets based on both major protein sources. However, ileal digestible energy was increased (P < 0.05) by protease only in the SBM-based diet resulting in an interaction between diet protein source and exogenous protease. Jejunal villus height tended to be higher (P = 0.07) in birds fed diets based on SBM and protease use increased (P < 0.05) crypt depth only in the SBM-free diets resulting in a significant interaction between protein source and protease use. Patterns of gene expression in jejunal tissue suggested that both dietary protein source and exogenous protease influence the expression of genes responsible for mucin secretion, amino acid transport and immune functionality in an age-dependent manner. It can be concluded that SBM may be a more suitable protein source for young broiler chickens than canola meal and that use of canola meal as a major source of dietary protein may have negative implications for performance, nitrogen digestibility and gut health. However, exogenous protease appears to be more compatible with substrates presented by SBM than is the case for canola meal based on advantages conferred in nutrient digestibility and performance. The beneficial effects of exogenous protease may be linked both to enhanced protein and energy digestibility and improved gut morphological characteristics, secretory and absorptive dynamics and immune resilience.

Regulation of adipocyte differentiation and gene expression-crosstalk between TGFβ and wnt signaling pathways

Obesity results in reduced differentiation potential of adipocytes leading to adipose tissue insulin resistance. Elevated proinflammatory cytokines from adipose tissue in obesity, such as TNFα have been implicated in the reduced adipocyte differentiation. Other mediators of reduced adipocyte differentiation include TGFβ and wnt proteins. Although some overlap exists in the signaling cascades of the wnt and TGFβ pathways it is unknown if TGFβ or wnt proteins reciprocally induce the expression of each other to maximize their biological effects in adipocytes. Therefore, we investigated the possible involvement of TGFβ signaling in wnt induced gene expression and vice versa in 3T3-L1 adipocyte. Effect of TGFβ and Wnt pathways on differentiation was studied in preadipocytes induced to differentiate in the presence of Wnt3a or TGFβ1 and their inhibitors (FZ8-CRD and SB431542, respectively). Regulation of intracellular signaling and gene expression was also studied in mature adipocytes. Our results show that both TGFβ1 and Wnt3a lead to increased accumulation of β-catenin, phosphorylation of AKT and p44/42 MAPK. However, differences were found in the pattern of gene expression induced by the two proteins suggesting that distinct, but complex, signaling pathways are activated by TGFβ and wnt proteins to independently regulate adipocyte function.

Microbial Ecology along the Gastrointestinal Tract

The ecosystem of the human gastrointestinal (GI) tract traverses a number of environmental, chemical, and physical conditions because it runs from the oral cavity to the anus. These differences in conditions along with food or other ingested substrates affect the composition and density of the microbiota as well as their functional roles by selecting those that are the most suitable for that environment. Previous studies have mostly focused on Bacteria, with the number of studies conducted on Archaea, Eukarya, and Viruses being limited despite their important roles in this ecosystem. Furthermore, due to the challenges associated with collecting samples directly from the inside of humans, many studies are still exploratory, with a primary focus on the composition of microbiomes. Thus, mechanistic studies to investigate functions are conducted using animal models. However, differences in physiology and microbiomes need to be clarified in order to aid in the translation of animal model findings into the context of humans. This review will highlight Bacteria, Archaea, Fungi, and Viruses, discuss differences along the GI tract of healthy humans, and perform comparisons with three common animal models: rats, mice, and pigs.

Heat stress in pigs is accompanied by adipose tissue–specific responses that favor increased triglyceride storage

Heat stress (HS) negatively affects all aspects of performance in pigs. Although certain tissue-specific responses in the liver, skeletal muscle, and intestine are known, there is paucity of information on responses within the adipose tissue. Therefore, the objective of this study was to delineate adipose tissue responses during HS in pigs. Thirty crossbred (Ossabaw × Duroc × Landrace) pigs were assigned to 3 treatments for 7 d. Treatments were 1) control and libitum fed (CON) with room temperature set at 20°C ± 1°C, 2) pair fed (PF) with room temperature as the CON treatment but pair fed to HS pigs, and 3) HS with room temperature 35°C ± 1°C and ad libitum access to feed. Compared with CON pigs, HS pigs had decreased feed intake and elevated skin temperature and respiration rate ( < 0.01). Blood urea nitrogen was higher ( = 0.01) in HS pigs compared with CON pigs only in males. In both subcutaneous and mesenteric adipose tissue, mRNA abundance of phosphoenolpyruvate carboxykinase (PCK1) was more elevated ( < 0.01) in HS groups compared with the CON and PF groups. Heat stress also caused increased heat shock protein 70 (HSP70; = 0.067) and CCAT/enhancer-binding homologous protein (CHOP) content ( < 0.05) in the mesenteric fat compared with the CON treatment. In conclusion, induction of PCK1 expression in adipose tissue by HS suggests elevated glyceroneogenesis might be involved in the increased fat storage in pigs under HS.

Time-series responses of swine plasma metabolites to ingestion of diets containing myo-inositol or phytase

The effect of the ingestion of diets containing either myo-inositol or exogenous phytase on plasma metabolites was examined using 29 kg barrows. The diets were: control (maize, soya, rapeseed, rice bran), control plus 2 g/kg myo-inositol, control plus 1000 phytase units (FYT)/kg or 3000 FYT/kg exogenous phytase. Pigs were housed in a PigTurn device and blood was collected, from jugular catheters, via an automated system at -30, (30 min before feeding), 0, 15, 30, 45, 60, 90, 120, 150, 180, 240, 300 and 360 min post-feeding. The addition of 2 g/kg myo-inositol to the basal diet resulted in an increase in plasma myo-inositol concentration that was evident 45-60 min after diet introduction and persisted to 360 min post-feeding. Similarly, supplementation of the basal diet with either 1000 or 3000 FYT/kg exogenous phytase resulted in an increase in plasma myo-inositol concentration that was still rising 360 min post-feeding. Plasma P concentration was increased over time by the addition of 1000 and 3000 FYT/kg phytase, but not by the addition of myo-inositol. Other plasma metabolites examined were not affected by dietary treatment. It can be concluded that oral delivery of myo-inositol results in rapid increase in plasma myo-inositol concentrations that peak approximately 45-60 min after feeding. Use of supplemental phytase achieves similar increases in myo-inositol concentration in plasma but the appearance is more gradual. Furthermore, supplementation of pig diets with exogenous phytase results in rapid appearance of P in plasma that may be sustained over time relative to diets with no added phytase.