Overfeeding increases very low density lipoprotein diameter and causes the appearance of a unique lipoprotein particle in association with failed yolk deposition

Dietary silymarin improves performance by altering hepatic lipid metabolism and cecal microbiota function and its metabolites in late laying hens

BACKGROUND

Liver lipid dysregulation is one of the major factors in the decline of production performance in late-stage laying hens. Silymarin (SIL), a natural flavonolignan extracted from milk thistle, is known for its hepatoprotective and lipid-lowering properties in humans. This study evaluates whether SIL can provide similar benefits to late-stage laying hens. A total of 480 68-week-old Lohmann Pink laying hens were randomly assigned into 5 groups, each group consisting of 6 replicates with 16 hens each. The birds received a basal diet either without silymarin (control) or supplemented with silymarin at concentrations of 250, 500, 750, or 1,000 mg/kg (SIL250, SIL500, SIL750, SIL1000) over a 12-week period.

RESULTS

The CON group exhibited a significant decline in laying rates from weeks 9 to 12 compared to the initial 4 weeks (P = 0.042), while SIL supplementation maintained consistent laying rates throughout the study (P > 0.05). Notably, the SIL500 and SIL750 groups showed higher average egg weight than the CON group during weeks 5 to 8 (P = 0.049). The SIL750 group had a significantly higher average daily feed intake across the study period (P < 0.05), and the SIL500 group saw a marked decrease in the feed-to-egg ratio from weeks 5 to 8 (P = 0.003). Furthermore, the SIL500 group demonstrated significant reductions in serum ALT and AST levels (P < 0.05) and a significant decrease in serum triglycerides and total cholesterol at week 12 with increasing doses of SIL (P < 0.05). SIL also positively influenced liver enzyme expression (FASN, ACC, Apo-VLDL II, FXR, and CYP7A1; P < 0.05) and altered the cecal microbiota composition, enhancing species linked to secondary bile acid synthesis. Targeted metabolomics identified 9 metabolites predominantly involved in thiamin metabolism that were significantly different in the SIL groups (P < 0.05).

CONCLUSIONS

Our study demonstrated that dietary SIL supplementation could ameliorate egg production rate in late stage laying hens, mechanistically, this effect was via improving hepatic lipid metabolism and cecal microbiota function to achieve. Revealed the potentially of SIL as a feed supplementation to regulate hepatic lipid metabolism dysregulation. Overall, dietary 500 mg/kg SIL had the best effects.

Effects of DHAV-3 infection on innate immunity, antioxidant capacity, and lipid metabolism in ducks with different DHAV-3 susceptibilities

The aim of the experiment was to evaluate the status of innate immunity, oxidative status and lipid accumulation in ducklings exhibiting varying susceptibilities to DHAV-3 infection. In the experiment, ducklings with different DHAV-3 susceptibilities were used. Samples were collected at 6, 12, 15, and 24 h post infection (hpi), with 5 samples per time point. Plasma biochemistry, antioxidant enzyme activities, lipid content of liver and kidney were detected in the experiment. Elevated plasma level of total bilirubin, direct bilirubin, and creatinine indicated the injury of liver and kidney in susceptible ducklings (P < 0.05). The histopathological sections showed the injury in kidney. During the infection time, there was an increase in the concentrations of reactive oxygen species and oxidative damage markers (malondialdehyde and nitric oxide) in plasma of susceptible ducklings, particularly at 24 hpi (P < 0.05). Compared with the resistant ducklings, DHAV-3 infection resulted in a significant increase in the plasma total triglyceride (TG) level and a decrease in glucose level in susceptible ducklings. Gene expression of the innate immune response was both investigated in liver and kidney. In resistant ducklings, the expressions levels of pattern recognition receptors RIG-I, MDA5 remained constant. In contrast, the gene expressions peaked at 24 hpi in the susceptible ducklings. DHAV-3 infection promoted the expression of IFN, IL6, IL12β, caspase-8 or caspase-9 in both liver and kidney of susceptible ducklings. In conclusion, DHAV-3 infection led to the mobilization of antioxidant defenses, alterations in lipid metabolism, and oxidative stress in susceptible ducklings during DHAV-3 infection.

Dietary yolk supplements and rate of yolk deposition do not influence sex ratios in Japanese Quail

Birds appear to have the ability to bias offspring sex ratios in response to environmental and social conditions. The mechanisms responsible remain unknown, however one previous study indicated a link between rates of ovarian follicle growth and the sexes of resulting eggs. This could indicate that either follicles destined to retain male or female follicles grow at different rates, or the rate of ovarian follicle growth determines the sex chromosome that will be retained to influence the sex of the resulting offspring. We tested for evidence of both possibilities by staining yolk rings that are indicative of daily growth. First, we tested for a correlation between the number of yolk rings and the sexes of the resulting germinal discs collected from each egg, and second, we tested whether experimentally decreasing follicle growth rates with a dietary yolk supplement impacts the sexes of the resulting germinal discs. There was no significant correlation between the number of yolk rings and the sexes of the resulting embryos, and decreasing follicle growth rates did not impact sexes of resulting germinal discs. These results indicate that offspring sex is not related to the rate of ovarian follicle growth in quail.

Comparative Analysis of Different Proteins and Metabolites in the Liver and Ovary of Local Breeds of Chicken and Commercial Chickens in the Later Laying Period

The liver and ovary perform a vital role in egg production in hens. In the later laying period, the egg-laying capacity of female hens, particularly that of local breeds, declines significantly. Hence, it is essential to study the features and conditions of the ovary and liver during this period. In this research, we characterized the proteins and metabolites in the liver and ovary of 55-week-old Guangyuan gray chickens (Group G) and Hy-Line gray chickens (Group H) by using liquid chromatography chip/electrospray ionization quadruple time-of-flight/mass spectroscopy (LC-MS/MS). In total, 139 differentially expressed proteins (DEPs) and 186 differential metabolites (DMs) were identified in the liver, and 139 DEPs and 36 DMs were identified in the ovary. The upregulated DEPs and DMs in both the liver and ovary of Group G were primarily enriched in pathways involved in amino acid and carbohydrate metabolism. This suggests that energy metabolism was highly active in the Guangyuan gray chickens. In contrast, the upregulated DEPs and DMs in Group H were mainly enriched in pathways associated with lipid metabolism, which may explain the higher egg production and the higher fatty liver rate in Hy-Line gray hens in the later laying period. Additionally, it was found that the unique protein s-(hydroxymethyl) glutathione dehydrogenase (ADH4) in Group G was implicated in functions such as fatty acid degradation, glycolysis, and pyruvate metabolism, whereas the unique proteins, steroid sulfatase (STS), glucosylceramidase (LOC107050229), and phospholipase A2 Group XV (PLA2G15), in Group H were involved in the metabolism of steroid hormones and glycerol phosphate. In conclusion, variations in how carbohydrates, lipids, and amino acids are processed in the liver and ovary of local breeds of chicken and commercial hens towards the end of their laying period could explain the disparities in their egg production abilities.

Dietary yolk supplementation decreases rates of yolk deposition in Japanese quail

Generation of egg yolk by birds requires the synthesis and deposition of large amounts of protein and lipid, and is often accompanied by the incorporation of additional physiological mediators. While there has been much work examining the relative quantities of yolk components, as well as potential adaptive patterns of their allocation, we still do not have a full understanding of what controls yolk formation and composition. Once ovarian follicles are recruited into the preovulatory hierarchy, the yolk is deposited in concentric rings, with one ring deposited per day. Previous studies have shown that there is substantial interspecific and intraspecific variation in the number of rings in yolks, and thus the number of days it took those yolks to grow. We hypothesized that the ability to grow follicles to maturity quickly is limited by the availability of materials to make yolk precursors in the female, either in body reserves or in dietary access. To test this, we supplemented the diets of Japanese quail with hard-boiled chicken yolk and examined the influences of treatment and female body condition on follicle growth rates. Contrary to predictions, females with higher body condition indices produced yolks that grew more slowly, and yolks from supplemented birds grew more slowly than controls. These results indicate that females can modulate the rate of yolk incorporation into developing follicles, and that an energy balance that is too high may not be optimal for the fast growth of developing ovarian follicles.

The Diverse Roles of 17β-Estradiol in Non-Gonadal Tissues and Its Consequential Impact on Reproduction in Laying and Broiler Breeder Hens

Estradiol-17β (E2) has long been studied as the primary estrogen involved in sexual maturation of hens. Due to the oviparous nature of avian species, ovarian production of E2 has been indicated as the key steroid responsible for activating the formation of the eggshell and internal egg components in hens. This involves the integration and coordination between ovarian follicular development, liver metabolism and bone physiology to produce the follicle, yolk and albumen, and shell, respectively. However, the ability of E2 to be synthesized by non-gonadal tissues such as the skin, heart, muscle, liver, brain, adipose tissue, pancreas, and adrenal glands demonstrates the capability of this hormone to influence a variety of physiological processes. Thus, in this review, we intend to re-establish the role of E2 within these tissues and identify direct and indirect integration between the control of reproduction, metabolism, and bone physiology. Specifically, the sources of E2 and its activity in these tissues via the estrogen receptors (ERα, ERβ, GPR30) is described. This is followed by an update on the role of E2 during sexual differentiation of the embryo and maturation of the hen. We then also consider the implications of the recent discovery of additional E2 elevations during an extended laying cycle. Next, the specific roles of E2 in yolk formation and skeletal development are outlined. Finally, the consequences of altered E2 production in mature hens and the associated disorders are discussed. While these areas of study have been previously independently considered, this comprehensive review intends to highlight the critical roles played by E2 to alter and coordinate physiological processes in preparation for the laying cycle.

Hepatic glycerolipid metabolism is critical to the egg laying rate of Guangxi Ma chickens

Yolk formation in liver is an important process for egg production in hens. The correlations between egg laying rate decline and liver function changes in Guangxi Ma chickens remain unclear. In this study, a total of 21,750 genes and 76,288 transcripts were identified in the RNA expression profiles isolated from liver tissues of 5 groups of Guangxi Ma chickens divided according to the age and egg laying rate. Numerous differential genes (DEGs) were identified after pairwise comparison among samples, and time series analysis categorization (age-related factors) revealed that down-regulated DEGs with aging were predominantly involved in lipid transportation and metabolic processes in the low egg laying rate groups. Notably, functional enrichment analysis confirmed that DGAT2, LIPG, PNPLA2, LPL, CEL, LIPC, DGKD, AGPAT2, AGPAT1 and AGPAT3 were highlighted as hub genes in glycerolipid metabolism pathway, which may be an essential non-age related factors of egg laying rate by regulating the synthesis of triacylglycerol (TAG) in liver. Finally, we categorized DEGs in Guangxi Ma chickens with different egg laying rate caused by age-related factors and found that DEGs with different expression patterns performing different biological functions. The analysis of DEGs with lower egg laying rate caused by non-age related factors and showed that the transportation of TAG was suppressed. Furthermore, critical genes and pathways involved in the synthesis of TAG in livers were identified, which dynamically regulated the formation of yolk precursors. Our results expanded the knowledge of the molecular mechanisms of the yolk precursor synthesis in chicken livers. The results will be helpful to explore the factors that affect egg laying rate from the perspective of yolk synthesis and provide a theoretical basis for improving the egg production of Guangxi Ma chickens.

Feeding level is associated with altered liver transcriptome and follicle selection in the hen

Genetic selection for particular traits in domestic animals may have altered the optimal feedback regulation among systems regulating appetite, growth, and reproduction. Broiler breeder chickens have been selected for fast and efficient growth and, unless feed restricted, consume excessively resulting in poor reproductive efficiency. We examined the effect of dietary treatment in full fed (FF) and restricted fed (RF) broiler breeder hens on ovarian responses and on liver morphology and transcriptome associated with reproductive function. Although FF broiler breeder hens had lower egg production (p < 0.01), the total number of ovarian follicles >8 mm (p < 0.01), 6-8 mm (p < 0.03), and 3-5 mm (p < 0.04) were greater in FF hens compared to RF hens. There was a large amount of lipid accumulation in the liver of FF hens and differential gene analysis yielded 120 genes that were differentially expressed >2-fold in response to feeding level (p < 0.01; FDR < 0.05). Elevated T3 may indicate that general metabolism was affected by diet and GHR (p < 0.01) and IGF1 (p < 0.04) mRNA expression were both greater in the liver of FF hens as compared to RF hens. It is likely that selection for increased growth, associated with enhanced activity of the IGF1 system, has altered nutritional coupling of feed intake to follicle development.

Sexual Maturity Promotes Yolk Precursor Synthesis and Follicle Development in Hens via Liver-Blood-Ovary Signal Axis

Several reproductive hormones were reported to be involved in regulating egg yolk precursor synthesis in chickens; however, the mechanism that shows how the liver-blood-ovary signal axis works in relation to age changes has not been reported yet. Therefore, in this study, we observe the morphology and histology of the liver and ovary and determine the serum biochemical parameters and the expression abundance of the critical genes from d90 to 153. Results show that the body weight and liver weight were significantly increased from d132, while the ovary weight increased from d139. Aside from the increase in weight, other distinct changes such as the liver color and an increased deposition of large amounts of yolk precursors into the ovarian follicles were observed. On d139, we observed small fatty vacuoles in the hepatocytes. The results of serum biochemical parameters showed a significant increase in the estradiol (E₂) level, first on d125, and then it reached its peak on d132. Meanwhile, the levels of follicle-stimulating hormone (FSH) increased initially and then remained at a high level from d146 to d153, while the levels of luteinizing hormone (LH) increased significantly on d132 and reached the top level on d153. Moreover, the levels of lecithin (LEC), vitellogenin (VTG), very low density lipoprotein y (VLDLy), triglyceride (TG), and total cholesterol (TC) were significantly increased at d125 and were close from d146 to d153. The mRNA and protein expression of estrogen receptor-alpha (ER-α) and E₂ levels in the liver and serum, respectively, showed similar changes. Moreover, with reference to an increase in serum E₂ level, the mRNA expression of genes related to yolk precursor synthesis (very low density apolipoprotein-II, ApoVLDL-II) and vitellogenin-II (VTG-II), lipogenesis (fatty acid synthase, FAS), and lipid transport (microsomal triglyceride transport protein, MTTP) in the liver showed up-regulation. These results suggest that the correlation between liver-blood-ovary alliances regulate the transport and exchange of synthetic substances to ensure synchronous development and functional coordination between the liver and ovary. We also found that E₂ is an activator that is regulated by FSH, which induces histological and functional changes in the hepatocytes through the ER-α pathway.

Integrative analysis of transcriptomic data related to the liver of laying hens: from physiological basics to newly identified functions

BACKGROUND

At sexual maturity, the liver of laying hens undergoes many metabolic changes to support vitellogenesis. In published transcriptomic approaches, hundreds of genes were reported to be overexpressed in laying hens and functional gene annotation using gene ontology tools have essentially revealed an enrichment in lipid and protein metabolisms. We reanalyzed some data from a previously published article comparing 38-week old versus 10-week old hens to give a more integrative view of the functions stimulated in the liver at sexual maturity and to move beyond current physiological knowledge. Functions were defined based on information available in Uniprot database and published literature.

RESULTS

Of the 516 genes previously shown to be overexpressed in the liver of laying hens, 475 were intracellular (1.23-50.72 fold changes), while only 36 were predicted to be secreted (1.35-66.93 fold changes) and 5 had no related information on their cellular location. Besides lipogenesis and protein metabolism, we demonstrated that the liver of laying hens overexpresses several clock genes (which supports the circadian control of liver metabolic functions) and was likely to be involved in a liver/brain/liver circuit (neurotransmitter transport), in thyroid and steroid hormones metabolisms. Many genes were associated with anatomical structure development, organ homeostasis but also regulation of blood pressure. As expected, several secreted proteins are incorporated in yolky follicles but we also evidenced that some proteins are likely participating in fertilization (ZP1, MFGE8, LINC00954, OVOCH1) and in thyroid hormone maturation (CPQ). We also proposed that secreted proteins (PHOSPHO1, FGF23, BMP7 but also vitamin-binding proteins) may contribute to the development of peripheral organs including the formation of medullar bones to provide labile calcium for eggshell formation. Thirteen genes are uniquely found in chicken/bird but not in human species, which strengthens that some of these genes may be specifically related to avian reproduction.

CONCLUSIONS

This study gives additional hypotheses on some molecular actors and mechanisms that are involved in basic physiological function of the liver at sexual maturity of hen. It also revealed some additional functions that accompany reproductive capacities of laying hens, and that are usually underestimated when using classical gene ontology approaches.

Identification of key genes and molecular mechanisms associated with low egg production of broiler breeder hens in ad libitum

Background

Overfeeding reduces laying performance in broiler breeder hens, which is associated with obesity, hepatic steatosis and systemic inflammation. To unravel the underlying mechanisms governing the effect of feeding regimes on energy metabolism and egg production, a transcriptomics approach was carried out for screening differentially expressed genes (DEGs) in ovary, liver and adipose tissues of broiler chickens under ad libitum and restricted feeding.

Results

It showed that 289, 388 and 204 DEGs were identified in the adipose, liver and ovary, respectively. These DEGs were significantly enriched in phagosome pathway, lipid transport, activity and nutrient reservoir activity in ovary; steroid hormone biosynthesis and metabolism of xenobiotics by cytochrome P450 pathways in adipose tissue; and the metabolic pathways, peroxisome proliferator-activated receptor (PPAR) and Jak-STAT signaling pathway in liver. Estrogen receptor 1, identified as one of important hubs by constructing PPI network, was up-regulated in ad libitum group, which would make more apolipoproteins be transferred to ovary.

Conclusions

High expression of VTGs, APOB, CYBB and CTSS in ovary would induce excess lipid deposit, oxidative stress and potential damage to ovulation. Our results contribute to understanding effects of feeding regimes on metabolic regulation during egg production of broiler breeder hens and also provide new evidence of metabolic regulation from integrated multi-tissue processes.

Electronic supplementary material

The online version of this article (10.1186/s12864-019-5801-3) contains supplementary material, which is available to authorized users.

Different susceptibility to fatty liver-haemorrhagic syndrome in young and older layers and the interaction on blood LDL-C levels between oestradiols and high energy-low protein diets

1. The objective of the study was to investigate the susceptibility of young and older laying hens to fatty liver-haemorrhagic syndrome (FLHS) and to evaluate the reliability of different blood lipid fractions for predicting or diagnosing FLHS. 2. Forty young hens and 40 older hens were caged individually. Each group of hens was randomly allotted to four treatments for 21 days: either a control, an oestradiol group, a high energy-low protein diet (HELPD) group or a HELPD + oestradiol group. Blood levels of oestradiol, triglyceride (TG), cholesterol (CHOL), high density lipoprotein-cholesterol (HDL-C) and low-density lipoprotein-cholesterol (LDL-C), liver total lipids, hepatic haemorrhagic scores and productive performance were assessed. 3. In older hens, β-oestradiol increased (P < 0.05) liver total lipids, hepatic haemorrhagic scores and the incidence of FLHS but reduced (P < 0.05) productive performance; however, such changes were not observed in young hens. 4. In two groups of hens, serum TG, CHOL and HDL-C levels were increased (P < 0.001) by β-oestradiol. Hens with FLHS had higher serum TG, CHOL and HDL-C (P < 0.001) than non-FLHS birds in the older layer group of hens. 5. An interaction (β-oestradiol × HELPD) (P < 0.05) for LDL-C levels was observed in both groups of hens. In young hens, β-oestradiol induced a decrease (P = 0.004) in serum LDL-C levels but the effect was attenuated by HELPD. In older hens, HELPD caused an increase (P = 0.02) in serum LDL-C although the effect depended on the presence of β-oestradiol. 6. In conclusion, older layers were more susceptible to FLHS than young layers after oestradiol treatment. Blood TG, CHOL and HDL-C rather than LDL-C levels can be used as a prediction tool for the overall susceptibility to FLHS in older rather than young layers. There were interactions between oestradiol and HELPD on blood LDL-C levels in laying hens.

Avian Liver: The Forgotten Organ

Simple Summary

The liver is a multi-purpose organ, with involvement in bile secretion, and lipid, carbohydrate and protein metabolism, as well as a number of other metabolic functions. This organ can adapt easily to changes in feed and the environment. Being at the centre of a number of digestive, metabolic and productive activities, it is essential to have a better understanding of this organ and the factors affecting liver functionality.

Abstract

Despite having huge responsibilities in avian species, published reports on the influence of dietary factors and other possible constraints on the size, development and function of liver are limited. Consideration of the factors that could influence and alter liver function is therefore of critical relevance. In the current review, aspects of liver structure and function, and the influence of feed restriction, anti-nutritional factors, structural components and feed additives on liver are discussed. Effects of feed technology techniques such as thermal treatment and pelleting, feed particle size and whole grain feeding on the liver are also reviewed. A discussion of lipogenesis and lipid storage in poultry is presented to provide a better understanding and to differentiate the normal pathways of lipid metabolism from abnormal (i.e., disordered) pathways. The liver is the main site of fat synthesis in poultry, but under certain conditions, excessive fat can accumulate in the liver and cause problems. Factors contributing to the fatty liver syndrome are also examined.

Accumulation of α-hexabromocyclododecane (α-HBCDD) in tissues of fast- and slow-growing broilers (Gallus domesticus)

The aim of the current study was to describe the fate of ingested α-hexabromocyclododecane (α-HBCDD) in fast-growing (FG) and slow-growing (SG) broilers, through an exposure to a dietary concentration of 50 ng α-HBCDD g^-1 feed during 42 and 84 days, respectively. Depuration parameters were assessed in SG broilers successively exposed during 42 days and depurated during 42 days. At market age, SG broilers had ingested 42% more feed than FG broilers, while their body weight gain per g of feed ingested was 34% lower. No isomerization of α- to β- or γ-HBCDD forms occurred, while OH-HBCDD was identified as a product of α-HBCDD metabolism. Irrespective of the strain, abdominal fat displayed the highest α-HBCDD concentration on a lipid weight basis, followed leg muscles and then breast muscle, liver and plasma. The accumulation ratios of α-HBCDD were slightly higher in SG (6.7, 2.1, 2.6 and 9.9 in leg muscles, breast muscle, liver and abdominal fat, respectively) than in FG broilers (5.2, 2.2, 1.1 and 8.4, respectively). The elimination half-lives in SG broilers were 20, 12 and 19 d in leg muscles, breast muscle and abdominal fat, respectively, to which dilution through growth contributed for around 50%. The overall assimilation efficiency of α-HBCDD was estimated at 58 and 50% in FG and SG broilers, respectively, while 22 and 17% of α-HBCDD ingested were estimated to be eliminated in excreta as metabolites.

The physiology of lipid storage and use in reptiles

Lipid metabolism is central to understanding whole-animal energetics. Reptiles store most excess energy in lipid form, mobilise those lipids when needed to meet energetic demands, and invest lipids in eggs to provide the primary source of energy to developing embryos. Here, I review the mechanisms by which non-avian reptiles store, transport, and use lipids. Many aspects of lipid absorption, transport, and storage appear to be similar to birds, including the hepatic synthesis of lipids from glucose substrates, the transport of triglycerides in lipoproteins, and the storage of lipids in adipose tissue, although adipose tissue in non-avian reptiles is usually concentrated in abdominal fat bodies or the tail. Seasonal changes in fat stores suggest that lipid storage is primarily for reproduction in most species, rather than for maintenance during aphagic periods. The effects of fasting on plasma lipid metabolites can differ from mammals and birds due to the ability of non-avian reptiles to reduce their metabolism drastically during extended fasts. The effect of fasting on levels of plasma ketones is species specific: β-hydroxybutyrate concentration may rise or fall during fasting. I also describe the process by which the bulk of lipids are deposited into oocytes during vitellogenesis. Although this process is sometimes ascribed to vitellogenin-based transport in reptiles, the majority of lipid deposition occurs via triglycerides packaged in very-low-density lipoproteins (VLDLs), based on physiological, histological, biochemical, comparative, and genomic evidence. I also discuss the evidence for non-avian reptiles using 'yolk-targeted' VLDLs during vitellogenesis. The major physiological states - feeding, fasting, and vitellogenesis - have different effects on plasma lipid metabolites, and I discuss the possibilities and potential problems of using plasma metabolites to diagnose feeding condition in non-avian reptiles.

Phospholipids and terpenes modulate Caco-2 transport of açaí anthocyanins

Anthocyanins (ANC) are common polyphenolics in plants, but are poorly absorbed into the bloodstream upon consumption. Phospholipids (PL) and terpenes (TP) may serve as enhancing agents in absorption. This study evaluated their role in transepithelial transport within a Caco-2 cell monolayer-model system and impact on ANC stability. Açaí fruit ANC were isolated and found to transport, at a low rate (1.22%), in the absence of soy lecithin phospholipids and Valencia orange terpenes, yet their addition significantly increased the transport of both cyanidin-3-glucoside and cyanidin-3-rutinoside. The best transport results (5.21%) were observed when combinations of PL (5000 mg/l) and TP (50mg/l) were used. The presence of PL and TP had no influence on ANC degradation over a 40 day storage period. Results demonstrated the potential of PL and TP to increase intestinal transport of ANC, and present advancement towards the formulation of functional foods that support improved ANC absorption.

Feed restriction ameliorates metabolic dysregulation and improves reproductive performance of meat-type country chickens

Restricted feed intake improves egg production in Cornish×Plymouth Rock (broiler) hens. Red-feather (RF) and Black-feather (BF) chickens are 2 local strains of non-broiler meat-type chickens whose egg production has declined with continued selection for meat yield, and which are unstudied regarding restricted feeding and egg-laying improvement. Sixteen week old RF and BF pullets were either fed ad libitum (AL) or restricted to 85% AL intake (R). At 35wk and 50wk R-hens showed improved egg production and less abnormal ovarian morphology than AL-hens. Obesity, hepatic steatosis, lipotoxic change to plasma lipids, and systemic inflammation induced by AL feeding in RF and BF hens were similar to those observed previously in AL-broiler hens. Egg production was negatively correlated to body weight, fractional abdominal fat weight and plasma NEFA concentrations in AL hens (P<0.05). AL-hen hierarchical follicles accumulated ceramide and increased interleukin-1β production (P<0.05) in conjunction with increased granulosa cell apoptosis, follicle atresia, ovarian regression, and reduced plasma 17β-estradiol concentrations (P<0.05). The present outcomes from non-broiler but nevertheless meat-type country chicken strains indicate that selection for rapid growth and increased meat yield fundamentally changes energy metabolism in a way that renders hens highly susceptible to reproductive impairment from lipid dysregulation and pro-inflammatory signaling rather than impaired resource allocation per se.

Obesity-induced dysfunctions in female reproduction: lessons from birds and mammals

Follicle wall rupture and ovum release, i.e., ovulation, has been described as a controlled inflammatory event. The process involves tissue remodeling achieved through leukocyte-mediated proteolysis. In birds, ovulation is the first step in the energy-intensive process of egg formation, yet hens that consume energy in excess of productive requirements experience impaired egg-laying ability. Broiler chickens, selected for rapid lean muscle gain, and coincidentally hyperphagia, develop adult obesity when given free access to feed. Obese broiler hens experience elevated circulating concentrations of insulin and leptin, changes in lipid and lipoprotein metabolism similar to those of human metabolic syndrome, as well as increased systemic inflammation. Overall, the manifestations in poultry are similar to those of women with polycystic ovary syndrome. It was shown recently that, in hens, as in mammals, changes in lipid synthesis and metabolism cause granulosa cell apoptosis and altered immune function and hormone production, further compromising ovarian function. To date, there is insufficient information on the means used by the ovary to direct leukocyte function toward successful ovulation. More information is needed regarding the control of proteolytic actions by leukocytes with regards to the roles of specific enzymes in both ovulation and atresia. The broiler hen has provided unique insight into the interrelations of energy intake, obesity, leukocyte function, and reproduction. Additional work with this model can serve the dual purposes of improving avian reproduction and providing novel insights into polycystic ovary syndrome in women.

Corticosterone regulation of ovarian follicular development is dependent on the energy status of laying hens

Glucocorticoids participate in the arousal of stress responses and trigger physiological adjustments that shift energy away from reproduction toward survival. Ovarian follicular development in avians is accompanied by the supply of yolk precursors, which are mainly synthesized in the liver. Therefore, we hypothesized energy status and hepatic lipogenesis are involved in the induction of reproductive disorders by glucocorticoids in laying hens. The results show that corticosterone decreased the laying performance by suppressing follicular development in energy-deficit state, rather than in energy-sufficient state. In corticosterone-treated hens, the suppressed follicular development was associated with the reduced availability of yolk precursor, indicated by the plasma concentration of VLDL and vitellogenin and the decreased proportion of yolk-targeted VLDL (VLDLy). Corticosterone decreased the expression of apolipoprotein B and apolipoprotein VLDL-II in the liver. A drop in VLDL receptor content and an increase in the expression of tight junction proteins occludin and claudin1 were also observed in hierarchical follicles. The results suggest corticosterone-suppressed follicular development is energy dependent. The decreased apolipoprotein synthesis and VLDLy secretion by liver are responsible for the decreased availability of circulating yolk precursor, and the upregulation of occludin and claudin expression further prevents yolk deposition into oocytes.

Mobilization of ectopic yolk in Gallus domesticus: a novel reverse lipid transport process

In many oviparous animals, bursting type atresia of ovarian follicles occurs during the reproductive cycle resulting in the escape of yolk into the extracellular compartment. In birds, this ectopic yolk is rapidly cleared by an unknown process that involves the appearance of yolk-engorged macrophage-like cells. To study this unique type of lipid transport, we injected young male chickens intra-abdominally with egg yolk. Absorption of egg yolk from the body cavity markedly increased the triacylglyceride-rich fraction (TRL) of plasma lipoproteins and was coincident with increased levels of plasma triacylglycerides (TAG) but not non-esterified fatty acids (NEFA). Thus, the transport of yolk lipids from the abdominal cavity appears to occur in lipoproteins and be more similar to the transport of hepatic TAG to the periphery via lipoproteins than to transport of adipose TAG to the periphery via NEFA released by the action of lipases. When macrophages were exposed to yolk in vitro, they quickly phagocytized yolk; however, it is unclear if this level of phagocytosis contributes significantly to total yolk clearance. Instead, the chicken macrophage may function more as a facilitator of yolk clearance through modification of yolk lipoproteins and the regulation of the local and systemic immune response to ectopic yolk. Yolk appears to be anti-inflammatory in nature. Yolk did not increase inflammatory cytokines IL-1, IL-6 and IFNγ either in vivo or in vitro; in fact, yolk dampened many inflammatory changes caused by lipopolysaccharide (LPS). Conversely, LPS-induced inflammation retarded yolk clearance from the abdominal cavity and plasma TAG levels.

Palmitic acid in chicken granulosa cell death-lipotoxic mechanisms mediate reproductive inefficacy of broiler breeder hens

In vivo and in vitro approaches were used to elucidate mechanisms of palmitate-induced cytotoxicity of follicle granulosa cells in fuel-overloaded broiler hens. In contrast to their energy-restricted counterparts, broiler breeder hens fed ad libitum for 2 wk had dyslipidemia, atresia within hierarchical ovarian follicles, and a 34% reduction in egg production (P < 0.05). Based on vital staining of freshly isolated granulosa cells with annexin V/propidium iodide, there were increases in apoptosis consistent with suppressed Akt activation (P < 0.05). Supplementing primary granulosa cell cultures with 0.5 mM palmitate for 48 or 96 h increased apoptosis (P < 0.05). Palmitate-induced cell death was accompanied by increased acyl-CoA oxidase, carnitine palmitoyl transferase-1, serine palmitoyl transferase, and sphingomyelinase transcripts and increased concentrations of proinflammatory interleukin-1β (P < 0.05). Triacsin-C inhibition of fatty acyl-CoA synthesis blunted interleukin-1β production and rescued granulosa cultures from palmitate-induced cell death. That there was partial to complete prevention of cell death with addition of the free radical scavenger pyrrolidine dithiocarbamate, the sphingomyelinase inhibitor imipramine, or the de novo ceramide synthesis inhibitor fumonisin B1, supported the notion that palmitate-induced granulosa cell cytotoxicity operated through a palmitate-derived metabolite. Palmitoyl-CoA may be channeled into β-oxidation and/or into bioactive metabolites that increase free radical generation, an inflammatory response, and ceramide production. In conclusion, palmitate-derived metabolites activated apoptotic machinery in avian granulosa cells, which caused ovarian follicular atresia and reduced egg production in fuel-overloaded broiler breeder hens.

Ceramide accumulation and up-regulation of proinflammatory interleukin-1β exemplify lipotoxicity to mediate declines of reproductive efficacy of broiler hens

The study was conducted to delineate fundamental mechanisms that initiate the deleterious effect of fuel overloading on reproductive efficacy of broiler breeder hens. Sixty hens at age 26 wk were fed recommended amounts of feed (160 g/d per hen) or allowed voluntary feeding (approximately 30% more than restriction). At age 35 and 50 wk, hens were sampled for further analyzes. Voluntary feeding resulted in poor egg production, high rate of mortality, and abnormal ovarian structure (mainly overt hierarchical follicle atresia at age 35 wk and ovarian involution at age 50 wk). In contrast to feed-restricted hens, voluntary feeding also induced metabolic dysregulations that comprised enhanced adiposity; hepatic triacylglycerol accumulation; and elevated concentrations of plasma glucose, NEFAs, very low density lipoprotein, triacylglycerol, phospholipids, and sphingomyelin (P < 0.05). Furthermore, hepatic and circulating ceramide and sphingomyelin accumulation, and up-regulation of proinflammatory IL-1β expression in liver and adipose tissues (P < 0.05) systemically manifested the development of lipotoxicity in feed-satiated hens. Lipotoxicity leading to impaired ovarian dysfunctions, including follicle atresia, ovarian regression, and a decline of circulating estradiol levels (P < 0.05) in feed-satiated hens, was further exemplified by ceramide accumulation and up-regulation of IL-1β, serine palmitoyltransferase, and sphingomyelinase transcript abundance, but suppressed protein kinase Akt activation (P < 0.1 to 0.05) within the hierarchical follicles. This study provides the first in vivo evidence of the actions of ceramide and IL-1β in mediating overfeeding-induced follicle atresia and progression of ovarian involution in broiler hens.

Consumption of high-oleic acid ground beef increases HDL-cholesterol concentration but both high- and low-oleic acid ground beef decrease HDL particle diameter in normocholesterolemic men

On the basis of previous results from this laboratory, this study tested the hypothesis that ground beef high in MUFA and low in SFA would increase the HDL-cholesterol (HDL-C) concentration and LDL particle diameter. In a crossover dietary intervention, 27 free-living normocholesterolemic men completed treatments in which five 114-g ground beef patties/wk were consumed for 5 wk with an intervening 4-wk washout period. Patties contained 24% total fat with a MUFA:SFA ratio of either 0.71 (low MUFA, from pasture-fed cattle) or 1.10 (high MUFA, from grain-fed cattle). High-MUFA ground beef provided 3.21 g more 18:1(n-9), 1.26 g less 18:0, 0.89 g less 16:0, and 0.36 g less 18:1(trans) fatty acids per patty than did the low-MUFA ground beef. Both ground beef interventions decreased plasma insulin and HDL(2) and HDL(3) particle diameters and increased plasma 18:0 and 20:4(n-6) (all P ≤ 0.05) relative to baseline values. Only the high-MUFA ground beef intervention increased the HDL-C concentration from baseline (P = 0.02). The plasma TG concentration was positively correlated with the plasma insulin concentration (r = 0.40; P < 0.001) and negatively correlated with HDL-C (r = -0.47; P < 0.001) and plasma 18:0 (r = -0.24; P < 0.01). Plasma insulin and HDL diameters were not correlated (r = 0.01; P > 0.50), indicating that reductions in these measures were not coordinately regulated. The data indicate that dietary beef interventions have effects on risk factors for cardiovascular disease that are independent (insulin, HDL diameters) and dependent (HDL-C) on beef fatty acid composition.

The role of feeding regimens in regulating metabolism of sexually mature broiler breeders

A trial was conducted to determine the effects of different rearing feed regimens on plasma hormone and metabolite levels and hepatic lipid metabolism and gene expression on sexually mature broiler breeders. Cobb 500 birds were divided into 2 groups at 4 wk and fed either an everyday (ED) or skip-a-day (SKP) regimen. At 24 wk of age, all birds were switched over to an ED regimen. At 26.4 wk, breeder hens were randomly selected and killed at intervals after feeding. Livers were sampled from 4 hens at 4-h intervals for 24 h for a total of 28 samples per treatment. Blood was sampled from 4 hens per sampling time; sampling times were 0, 30, and 60 min and 2 and 4 h after feeding and then every 4 h up to 24 h for a total of 36 samples per treatment. Main feeding regimen, time, and interaction effects were analyzed. Significant interaction effects were found between time and feeding regimen for acetyl-coenzyme A carboxylase and malic enzyme mRNA expression. The peak for acetyl-coenzyme A carboxylase expression was higher in ED-reared birds, whereas the peak for malic enzyme expression was higher in SKP-reared birds. Overall, plasma levels of insulin-like growth factor-II were higher in SKP-reared birds. Overall, plasma corticosterone levels were also higher in SKP-reared birds and significant interaction effects between time and feeding regimen were seen. The expression of apolipoprotein A1 was significantly higher in ED-reared birds: significant interaction effects were also noted. Other researchers also found some of the differences observed in the present study in 16-wk-old pullets. In summary, different feeding regimens alter metabolic responses, some of which carry over into sexual maturity.

Hamburger high in total, saturated and trans-fatty acids decreases HDL cholesterol and LDL particle diameter, and increases TAG, in mildly hypercholesterolaemic men

The consumption of high-fat hamburger enriched with SFA and trans-fatty acids may increase risk factors for coronary vascular disease, whereas hamburger enriched with MUFA may have the opposite effect. Ten mildly hypercholesterolaemic men consumed five, 114 g hamburger patties per week for two consecutive phases. Participants consumed high-SFA hamburger (MUFA:SFA = 0·95; produced from pasture-fed cattle) for 5 weeks, consumed their habitual diets for 3 weeks and then consumed high-MUFA hamburger (MUFA:SFA = 1·31; produced from grain-fed cattle) for 5 weeks. These MUFA:SFA ratios were typical of ranges observed for retail ground beef. Relative to habitual levels and levels during the high-MUFA phase, the high-SFA hamburger: increased plasma palmitic acid, palmitoleic acid and TAG (P < 0·01); decreased HDL cholesterol (HDL-C) and LDL particle diameter percentile distributions (P < 0·05); and had no effect on LDL cholesterol or plasma glucose (P>0·10). Plasma palmitoleic acid was positively correlated with TAG (r 0·90), VLDL cholesterol (r 0·73) and the LDL:HDL ratio (r 0·45), and was negatively correlated with plasma HDL-C (r − 0·58), whereas plasma palmitic, stearic and oleic acids were negatively correlated with LDL particle diameter (all P ≤ 0·05). Because plasma palmitoleic acid was derived from Δ9 desaturation of palmitic acid in liver, we conclude that alterations in hepatic stearoyl-CoA desaturase activity may have been responsible the variation in HDL-C and TAG caused by the high-SFA and high-MUFA hamburgers.

Plasma yolk precursor dynamics during egg production by female greater scaup (Aythya marila): Characterization and indices of reproductive state

We characterized dynamics of the plasma yolk precursors vitellogenin (VTG), very-low-density lipoprotein (total VLDL-TG), and VLDL particle size distribution during egg production by female greater scaup (order: Anseriformes, Aythya marila). We also evaluated VTG and total VLDL-TG as physiological indices of reproductive state. Mean (+/-1 SE) plasma concentrations of VTG and total VLDL-TG for females with nondeveloped ovaries were 0.58 +/- 0.05 microg Zn mL(-1) and 3.75 +/- 0.29 mmol TG L(-1), respectively. Yolk precursor concentrations increased rapidly to maximum levels in association with small increases in ovary mass during rapid follicle growth. Mean concentrations of VTG and total VLDL-TG for females with a full ovarian follicle hierarchy were 3.38 +/- 0.40 microg Zn mL(-1) and 7.31 +/- 2.56 mmol TG L(-1), respectively. Concentrations of VTG and total VLDL remained elevated throughout the laying cycle and decreased markedly by 3 d into incubation. Individual reproductive state (non-egg producing vs. egg producing) was more accurately identified by plasma profiles of VTG (90%) than by those of total VLDL-TG (74%). Greater scaup VLDL particle sizes during egg production were within the range for predicted yolk-targeted VLDL size (25-44 nm). We conclude that plasma profiles of VTG and total VLDL-TG can be used as nonlethal, physiological indices of reproductive state in greater scaup and should be of great utility to a variety of evolutionary, ecological, and applied conservation studies of reproduction in waterfowl.

Immunological cell and serum metabolite response of 60-week-old commercial laying hens to an alfalfa meal molt diet

The practice of induced molting involves the restriction of light, feed removal and optionally water for 5-14 days. However, there is growing concern regarding feed removal and animal welfare issues. With this in mind, alternative diets have been developed to produce similar molting effects as that of feed deprivation. Alfalfa, which largely consists of insoluble fiber, can be used as a molting diet. In this study, heterophil and lymphocyte counts, serum chemistry, and organ weight parameters were evaluated in hens that were deprived of feed or fed alfalfa during a nine day induced molt. Full-fed hens were used as the control. Blood serum parameters assessed included calcium, magnesium, glucose, total protein, ketone bodies, uric acid, and cholesterol. White blood cells were counted and categorized by cell type. On the ninth day of the trial, the hens were euthanized and the liver, spleen, heart, intestine, pancreas, ovary, oviduct, and kidney were collected and weighed. On day 8 birds molted with alfalfa or by feed deprivation had significantly higher (P<0.05) levels of ketone bodies and cholesterol and lower levels of calcium, and magnesium compared to the full-fed hens while birds molted by feed deprivation exhibited significantly lower levels of uric acid. Birds molted by both methods exhibited significant reductions in ovary, oviduct, liver and pancreas weights and increased spleen weights when compared to the non-molted hens. On days 0, 2, and 6 there were no significant differences (P>0.05) in either heterophil or lymphocyte percentages. However, heterophil percentages were higher in feed withdrawal birds than full-fed birds on day 4 but lymphocyte percentages were higher in full-fed birds compared to feed withdrawal birds. On day 8 of the induced molt lymphocyte percentages were higher from full-fed birds when compared to feed withdrawal birds but no significant differences were detectable for heterophil percentages. Based on reproductive organ weight loss and changes in serum and immunological responses of birds during molt, it appears that alfalfa meal can be an effective molt induction alternative.

Molting in Salmonella enteritidis-challenged laying hens fed alfalfa crumbles. III. Blood plasma metabolite response

The objective of this study was to examine an alfalfa crumble diet as an alternative molt diet and compare the physiological response of hens to the responses of feed-deprived molted hens. Hens >50 wk old were placed into 6 treatment groups (12 hens per group in trial 1 and 10 hens per group in trial 2): nonmolted Salmonella enterica serovar Enteritidis positive (FF+), nonmolted Salmonella Enteritidis negative (FF-), feed withdrawal Salmonella Enteritidis positive (FW+), FW Salmonella Enteritidis negative (FW), alfalfa Salmonella Enteritidis positive (ALC+), and ALC Salmonella Enteritidis negative (ALC-). Each hen in the Salmonella Enteritidis-positive groups was challenged on the fourth day of the study with 1 mL of 10(6)-cfu Salmonella Enteritidis. Blood was collected on d 2, 5, 9, and 12 of the trial. Blood plasma was collected and metabolite concentrations were analyzed for glucose, calcium, cholesterol, uric acid, total protein, and triglycerides. The feed intakes of the FF hens were 4- to 6-fold greater (P <or= 0.05) than those of the ALC birds in both trials. Over the 12 d of molt, the FW+ hens lost more (P <or= 0.05) BW than all other groups except the FW- hens, whereas the FW-, ALC-, and ALC+ hens lost more BW than the FF hen groups. Uric acid concentrations were generally lower in molted hens compared with the FF hen groups during the initial stages of molt. On d 9 of both trials, concentrations of calcium and total protein were higher (P <or= 0.05) in the FF hens than in the other groups. The FF hen groups exhibited higher (P <or= 0.05) concentrations of triglycerides than the FW and ALC groups in both trials on d 5, 9, and 12. Based on the results from these studies, ALC diets can limit some of the potential physiological stress indicators that accompany feed deprivation during an induced molt.

What comes first, the zebra finch or the egg: temperature-dependent reproductive, physiological and behavioural plasticity in egg-laying zebra finches

Avian reproduction is generally timed to synchronize chick-rearing with periods of increased food abundance. Consequently, the energetically demanding period of egg production may coincide with periods of lower food availability, fluctuating temperature and more unstable weather. Little is known about the physiological mechanisms underlying temperature-induced variation in egg production. We therefore examined the influence of low ambient temperature (7 degrees C vs 21 degrees C) on reproductive output (e.g. egg mass, clutch size, laying interval, laying rate), daily food consumption and lipid variables in zebra finches Taeniopygia guttata. When faced with egg production at 7 degrees C, laying zebra finches increased energy intake by 12.67 kJ day(-1), and were thus able to maintain body condition (e.g. body mass, fat and muscle score) and circulating triacylglyceride at levels comparable to those at 21 degrees C. However, when producing eggs at 7 degrees C, females took longer to initiate egg laying (6.5 vs 6.1 days at 21 degrees C), and ultimately laid fewer eggs (5.5 vs 6.0 eggs) at a slower rate (0.90 eggs day(-1) vs 0.95 eggs day(-1)). These temperature-related declines in reproductive output were accompanied by decreases in modal (from 36.6 at 21 degrees C to 24.3 nm at 7 degrees C) and median very low density lipoprotein (VLDL) particle diameter (from 29.6 to 26.4 nm) and in the proportion of VLDL particles that were capable of passing through the pores in the ovary to access the developing ovarian follicles (i.e. particles with diameters between 25 and 44 nm; from 45.90% to 32.55%). However, variation in reproductive output was not related to any static concentration or structural measure of VLDL. Therefore, other temperature-dependent mechanisms must be involved in the physiological processes that regulate reproductive output of passerine birds at low ambient temperatures.

High Transcript Level of Fatty Acid-Binding Protein 11 but Not of Very Low-Density Lipoprotein Receptor Is Correlated to Ovarian Follicle Atresia in a Teleost Fish (Solea senegalensis)1

Transcripts encoding a fatty acid-binding protein (FABP), Fabp11, and two isoforms of very low-density lipoprotein receptor (Vldlr; vitellogenin receptor) were characterized from the ovary of Senegalese sole (Solea senegalensis). Phylogenetic analyses of vertebrate FABPs demonstrated that Senegalese sole Fabp11, as zebrafish (Danio rerio) homologous sequences, is part of a newly defined teleost fish FABP subfamily that is a sister clade of tetrapod FABP4/FABP5/FABP8/FABP9. RT-PCR revealed high levels of vldlr transcript splicing variants in the ovaries and, to a lesser extent, in somatic tissues, whereas fabp11 was highly expressed in the ovaries, liver, and adipose tissue. In situ hybridization analysis showed vldlr and fabp11 mRNAs in previtellogenic oocytes, whereas no hybridization signals were detected in the larger vitellogenic oocytes. Transcript expression of fabp11 was strongly upregulated in somatic cells surrounding atretic follicles. Real-time quantitative RT-PCR demonstrated that ovarian transcript levels of vldlr and fabp11 had a significant positive correlation with the percentage of follicles in previtellogenesis and atresia, respectively. These results suggest that the expression level of vldlr transcripts may be used as a precocious functional marker to quantify the number of oocytes recruited for vitellogenesis and that fabp11 mRNA may be a very useful molecular marker for determining cellular events and environmental factors that regulate follicular atresia in fish.

Glycosylphosphatidylinositol-anchored high-density lipoprotein-binding protein 1 plays a critical role in the lipolytic processing of chylomicrons

The triglycerides in chylomicrons are hydrolyzed by lipoprotein lipase (LpL) along the luminal surface of the capillaries. However, the endothelial cell molecule that facilitates chylomicron processing by LpL has not yet been defined. Here, we show that glycosylphosphatidylinositol-anchored high-density lipoprotein-binding protein 1 (GPIHBP1) plays a critical role in the lipolytic processing of chylomicrons. Gpihbp1-deficient mice exhibit a striking accumulation of chylomicrons in the plasma, even on a low-fat diet, resulting in milky plasma and plasma triglyceride levels as high as 5000 mg/dl. Normally, Gpihbp1 is expressed highly in heart and adipose tissue, the same tissues that express high levels of LpL. In these tissues, GPIHBP1 is located on the luminal face of the capillary endothelium. Expression of GPIHBP1 in cultured cells confers the ability to bind both LpL and chylomicrons. These studies strongly suggest that GPIHBP1 is an important platform for the LpL-mediated processing of chylomicrons in capillaries.

Characterization of very-low density lipoprotein particle diameter dynamics in relation to egg production in a passerine bird

During avian egg production, oestrogen mediates marked increases in hepatic lipid production and changes in the diameter of assembled very-low density lipoprotein (VLDL). A nearly complete shift from generic VLDL (∼70 nm in diameter), which transports lipids to peripheral tissues, to yolk-targeted VLDL (VLDLy) (∼30 nm), which supplies the yolk with energy-rich lipid, has been observed in the plasma of laying domestic fowl. We validated an established dynamic laser scattering technique for a passerine songbird Taeniopygia guttata, the zebra finch, to characterize the dynamics of VLDL particle diameter distribution in relation to egg production. We predicted that non-gallinaceous avian species that have not been selected for maximum egg production would exhibit less dramatic shifts in lipid metabolism during egg production. As predicted, there was considerable overlap between the VLDL particle diameter distributions of laying and non-laying zebra finches. But unexpectedly, non-laying zebra finches had VLDL diameter distributions that peaked at small particles and had relatively few large VLDL particles. As a result, laying zebra finches, in comparison, had diameter distributions that were shifted towards larger VLDL particles. Nevertheless,laying zebra finches, like laying chickens, had larger proportions of particles within proposed VLDLy particle diameter ranges than non-laying zebra finches (e.g. sVLDLy: 50% vs 37%). Furthermore, zebra finches and chickens had similar modal (29.7 nm in both species) and median (32.7 nm vs 29.6 nm) VLDL particle diameters during egg production. Therefore,although zebra finches and chickens exhibited opposing directional shifts in VLDL particle diameter distribution during egg production, the modifications to VLDL particle structure in both species resulted in the realization of a common goal, i.e. to produce and maintain a large proportion of small VLDL particles of specific diameters that are capable of being incorporated into newly forming egg yolks.)

Enzymatic O-methylation of flavanols changes lag time, propagation rate, and total oxidation during in vitro model triacylglycerol-rich lipoprotein oxidation

3'-O-Methyl derivatives of flavan-3-ols, (+)-catechin (C), (-)-epicatechin (EC), and (-)-catechin gallate (CG) were prepared enzymatically. Hexanal (EC and CG family, 5 mmol/L) and conjugated diene (C and EC family, 0.25-10 mmol/L) formation following CuSO4-mediated triacylglycerol-rich lipoprotein oxidation was measured. All EC and CG compounds significantly reduced hexanal formation (p < 0.02). O-Methylation improved the ability of CG (more polar) while reducing the ability of EC (less polar) to limit hexanal formation. 3'-O-methyl EC was 18% (p < 0.001) and 4'-O-methyl 65% (p < 0.001) less able than EC to suppress hexanal formation. At >1 micromol/L all EC and C compounds significantly increased lag time. Parent compounds were more effective (> 4-fold increase) than metabolites (1.5-fold increase). Parent compounds did not influence propagation rate (DeltaOD/min). At >1 mmol/L O-methylated EC and C reduced propagation by 20-40% (p < 0.01). Notably, at 0.25 mmol/L O-methylated EC and C increased propagation rates 22% (p < 0.01) despite prolonging lag time.

Overfeeding-induced ovarian dysfunction in broiler breeder hens is associated with lipotoxicity

In mammals, triacylglycerol (TAG) accumulation in nonadipose tissue, termed lipotoxicity, develops with obesity and can provoke insulin resistance, overt diabetes, and ovarian dysfunction. Leptin, an adipose tissue hormone, may mediate these effects. Feed-satiated broiler breeder hens manifest lipotoxicity-like symptoms. Changes in body and organ weights, hepatic and plasma TAG, nonesterified fatty acids (NEFA), ovarian morphology, and egg production in response to acute voluntary increases of feed intake were measured in 2 studies with Cobb 500 broiler breeder hens provided with either 145 or > or = 290 g of feed/d per hen for 10 d. In both studies, no hen fed 145 g of feed/d exhibited ovarian abnormalities, whereas approximately 50% of feed-satiated hens did. Egg production in feed-satiated hens was reduced from 73.3 to 55.8% (P = 0.001). Morphology indicated that apoptosis-induced atresia occurred in the hierarchical follicles. Fractional weight of yolk increased from 29.3 to 30.6% (P = 0.016) and no longer correlated to egg weight. Body, liver, and abdominal adipose weights were significantly greater (P < 0.05) in feed-satiated hens, as were plasma concentrations of glucose, NEFA, TAG, insulin, and leptin (P < 0.05). Feed-satiated hens with abnormal ovaries had significantly more liver and abdominal fat, greater plasma leptin and TAG concentrations, and more saturated fatty acids in plasma NEFA than did feed-satiated hens with normal ovaries. Differences in severity of lipotoxic metabolic and hormonal responses among feed-satiated hens were closely linked to the incidence of ovarian abnormalities and granulosa cell susceptibility to apoptosis and necrosis.

Lipoprotein profiles and components in Tsaiya ducks under ad libitum feeding and fasting

This study investigated lipoprotein compositions and distribution in Tsaiya ducks under ad libitum feeding and fasting. The study was conducted on each of thirty Tsaiya ducks over two 4-week periods. Each of the 30 Tsaiya ducks was randomly allocated into an ad libitum feeding group or a 3-day fasting group during the growing period (8-12 weeks old) and during the initial laying period (26-30 weeks old; 10-14 weeks after the onset of laying), respectively. Experimental results indicated that HDL (high-density lipoprotein) is the primary lipoprotein species in growing ducks but that in laying ducks the major population of lipoprotein is VLDL (very low density lipoprotein). Protein and cholesteryl ester were identified as the major components of HDL during both periods; triacylglycerol (TG) was the largest proportion of VLDL in both periods. In laying ducks VLDL contains more TG than in growing ducks; VLDL particle sizes in laying ducks were larger than in growing ducks. Fasting significantly decreased VLDL levels during both periods. The TG content in most lipoproteins was also decreased by fasting during both test periods. In contrast, the cholesteryl ester and free cholesterol in most lipoproteins were increased by fasting. The particle size of HDL and VLDL also decreased during fasting. This study indicated that lipoprotein profiles and components in Tsaiya ducks during the laying period were different from during the growing period and were affected by fasting.

Integral apolipoproteins increase surface-located triacylglycerol in intact native apoB-100-containing lipoproteins

High-resolution NMR was used to measure the presence and quantity of triacylglycerol (TAG) in the surface of intact native apolipoprotein B-100-containing lipoprotein particles that are made by chickens in response to estrogen treatment and that in hens are deposited in yolk follicles (VLDLy). Integration of 13C NMR resonances shows that intact VLDLy particles contain more surface TAG (5.1 +/- 0.6 mol%, 6.7 +/- 0.8 weight %) than predicted by apolipoprotein-free models using similarly acyl-heterogenous TAG. Change in downfield chemical shift values of surface to core TAG in VLDLy was 0.8 ppm compared with 1.3 ppm in vesicles prepared with purified egg phosphatidylcholine and TAG isolated from the VLDLy, indicating that reduced surface TAG hydration may contribute to the resistance to lipase hydrolysis characteristic of this lipoprotein species. Apolipoprotein-mediated changes in surface lipid composition and lipid hydration provide possible general mechanisms for selectivity in lipoprotein substrate characteristics.

Caponization and testosterone implantation effects on blood lipid and lipoprotein profile in male chickens

To understand the role of lipid metabolism in increasing body fat accumulation after caponization of male chickens, trials were conducted to determine the effects of levels of testosterone implantation on lipoprotein composition. Male chickens were caponized at 12 wk and selected at 16 wk for a 10-wk feeding experiment. Fifteen male and 15 caponized (capon) chickens were used in trial 1. Ten sham operated chickens (sham) and 40 capons were randomly divided among 4 treatments in trial 2; the treatments were as follows: implantation of cholesterol (1.62 mm i.d. x 3.16 mm o.d., 9.24+/-0.36 mg) or implantation of testosterone at low (1 mm i.d. x 3 mm, o.d., 5.88+/-0.23 mg), medium (1.62 mm i.d. x 3.16 mm, o.d., 9.81+/-0.17 mg), or high (2 mm i.d. x 4 mm, o.d., 16.7+/-0.24 mg) dose. The results of trial 1 showed that caponization decreased (P < 0.05) blood testosterone concentrations and increased (P < 0.05) abdominal fat weight and relative abdominal fat weight in capons. Caponization also increased low density lipoprotein (LDL), high density lipoprotein (HDL), LDL protein, and HDL protein and decreased LDL-free cholesterol (LDL-FC), HDL-FC, and HDL-phospholipid (HDL-PL) percentages (P < 0.05). In trial 2 capons implanted with increasing testosterone levels exhibited proportional increases in blood testosterone concentration, although blood testosterone concentration in implanted capons were not fully restored to those of the sham group. High dose testosterone implantation inhibited abdominal fat accumulation and increased glucose and glycerol concentrations compared with the cholesterol implantation. Caponization of male chickens decreased the androgen level and increased the blood triacylglyceride content. Caponization also changed the lipoprotein profiles, which resulted in increased lipid storage capacity. The testosterone concentration, therefore, must achieve threshold concentrations to inhibit lipid accumulation in the testosterone implanted capon.

Effects of fasting on serum lipids and lipoprotein profiles in the egg-laying hen (Gallus domesticus)

The effects of a 24-h fast on serum lipids and lipoprotein profiles in commercial laying hens were investigated. Blood was analyzed at 34 and 46 weeks of age from Single Comb White Leghorn hens that had been either fed ad libitum or had been fasted for 24 h prior to collection. At 12 weeks, birds were divided into 16 biological isolation units, with 8 replicate units assigned to each treatment group. Four birds out of 10 in each unit were tagged for bleeding. Parameters evaluated included total serum cholesterol and triglycerides, mean diameters of very low density lipoproteins (VLDLs) for the 10th, 50th, and 90th percentiles of serum total VLDL, mean total population VLDL particle diameter (MPD), and percentage serum cholesterol recovered in VLDL, low density lipoprotein (LDL), and high density lipoprotein (HDL) fractions. Fasting led to decreases in total serum cholesterol and triglycerides, and a decrease in mean serum VLDL particle diameter in the 90th population percentile. At Week 34, percentage serum cholesterol recovered from LDL was increased, whereas percentage serum cholesterol recovered from HDL was decreased due to fasting. At Week 46, MPD and percentage serum cholesterol recovered from VLDL were decreased, whereas percentage serum cholesterol recovered from HDL was increased due to fasting. It was concluded that a 24-h fast decreased serum lipids (cholesterol and triglycerides) and the size of VLDL particles in the 90th population percentile in commercial laying hens. Furthermore, bird age influenced the effects of a 24-h fast on MPD and the redistribution of serum cholesterol among VLDL, LDL, and HDL particles.

The metabolic cost of avian egg formation: possible impact of yolk precursor production?

Little is known about the energy costs of egg production in birds. We showed in previous papers that, during egg production, European starlings (Sturnus vulgaris) undergo a 22% increase in resting metabolic rate (RMR) and that the maintenance and activity costs of the oviduct are responsible for 18% of the variation in elevated laying RMR. Therefore, other energy-consuming physiological mechanisms must be responsible for the remaining unexplained variation in elevated laying RMR. Yolk precursor [vitellogenin (VTG) and very-low-density lipoprotein (VLDL)] production is likely to be costly because it signifies a marked increase in the biosynthetic activity of the liver. We documented the pattern of yolk precursor production in response to daily injections of 17beta-estradiol (E2) in zebra finches (Taeniopygia guttata). Based on this pattern we carried out an experiment in order to evaluate the metabolic costs of producing VTG and VLDL. Our E2 treatment resulted in a significant increase in plasma VTG and VLDL levels within the natural breeding range for the species. Although RMR was measured during the period of active hepatic yolk precursor production, it did not differ significantly within individuals in response to the treatment or when comparing E2-treated birds with sham-injected birds. This could mean that yolk precursor production represents low energy investment. However, we discuss these results in light of possible adjustments between organs that could result in energy compensation.

Molecular Mechanism for Changes in Proteoglycan Binding on Compositional Changes of the Core and the Surface of Low-Density Lipoprotein–Containing Human Apolipoprotein B100

OBJECTIVE

The aim of this study was to investigate the molecular mechanism for changes in proteoglycan binding and LDL receptor affinity on two compositional changes in LDL that have been associated with atherosclerosis: cholesterol enrichment of the core and modification by secretory group IIA phospholipase A2 (sPLA2) of the surface.

METHODS AND RESULTS

Transgenic mice expressing recombinant apolipoprotein (apo) B and sPLA2 were generated. Recombinant LDL were isolated and tested for their proteoglycan and LDL receptor-binding activity. The results show site A (residues 3148-3158) in apoB100 becomes functional in sPLA2-modified LDL and that site A acts cooperatively with site B (residues 3359-3369), the primary proteoglycan-binding site in native LDL, in the binding of sPLA2-modified LDL to proteoglycans. Our results also show that cholesterol enrichment of LDL is associated with increased affinity for proteoglycans and for the LDL receptor. This mechanism is likely mediated by a conformational change of site B and is independent of site A in apoB100.

CONCLUSIONS

Site A in apoB100 becomes functional in sPLA2-modified LDL and acts cooperatively with site B resulting in increased proteoglycan-binding activity. The increased binding for proteoglycans of cholesterol-enriched LDL is solely dependent on site B.

Effects of F-strain Mycoplasma gallisepticum inoculation on serum very low density lipoprotein diameter and fractionation of cholesterol among lipoproteins in commercial egg-laying hens

Experimental inoculation with the F-strain of Mycoplasma gallisepticum (FMG) at 12 wk of age has been shown to affect the performance, liver, reproductive organs, and yolk lipid characteristics of commercial layers. Therefore, this study was conducted to determine the serum lipoprotein characteristics of commercial egg-laying hens at 16 wk of age and throughout lay after inoculation with FMG at 12 wk of age. Mean diameters of very low density lipoproteins (VLDL) were determined for the 10th, 50th, and 90th percentiles of serum total VLDL of each hen. Percentages of total serum cholesterol recovered in VLDL and low and high density lipoprotein particle classes were also determined. Inoculation of birds with FMG at 12 wk did not change the physical properties or relative concentrations of their circulating lipoproteins. However, the age of the bird had significant differential effects on all the parameters examined. These data demonstrate that FMG-inoculation at 12 wk of age does not affect the lipoproteins of laying hens, but because these birds were housed in biological isolation units, these results do not preclude the possibility that these yolk precursors may be affected in FMG-infected birds that are housed in facilities in which there are increased levels of environmental stress. These data further suggest that alterations in liver, reproductive organs, and yolk lipid characteristics in response to FMG, as noted in previous reports on commercial layers, are not mediated through changes in circulating VLDL diameters.

Characterization of lipoproteins from the turtle, Trachemys scripta elegans, in fasted and fed states

The lipid and apolipoprotein composition of VLDL, IDL, LDL, HDL(2) and HDL(3) were examined in the turtle, Trachemys scripta elegans, in fasted and fed states. The lipid composition of turtle lipoproteins was very similar to their human counterparts. The major apolipoprotein found in LDL, IDL and VLDL, which has a molecular weight of approximately 550 kD, is a homologue of apoB100. The major apolipoprotein found in both HDL(2) and HDL(3), has a molecular weight of 28-kD and is homologous to human apoA-I. HDL(3) also contains a 6.5 kD protein that is homologous to apoA-II, while HDL(2) has two low molecular weight proteins of 6 kD and 7 kD which are also found on the triglyceride rich lipoproteins (TRL). The 7 kD protein is homologous to apoC-III, while the 6 kD protein has a similar size and distribution as apoC-II or apoC-I. In addition, HDL(2) also possesses a protein of 15.8 kD that has no obvious mammalian homologue. In both size and apolipoprotein composition, turtle HDL(2) resembles human HDL(2b) while turtle HDL(3) resembles human HDL(3). In the fasted state, turtles contained very little TRL. When fed a high fat diet, the amount of IDL and LDL sized particles increased significantly.

Validation of a modified PCR-based method for identifying mutant restricted ovulator chickens: substantiation of genotypic classification by phenotypic traits

Upon photostimulation, restricted ovulator (RO) female chickens exhibit endogenous hyperlipidemia, develop atherosclerotic lesions, and generally fail to lay eggs. This phenotype results from a point mutation in the gene specifying the very low density lipoprotein receptor (VLDLR), whose protein product normally mediates the massive oocytic uptake of egg yolk precursors from the circulation. Taking advantage of the single base change in the mutant VLDLR allele, a PCR-based method for the rapid identification of RO chickens was developed at the Biocenter and University of Vienna, Austria. However, this procedure was incompletely validated because phenotypic data were not obtained and conventional progeny testing of sons and grandsons was not performed. Here, the assay validation was completed by providing plasma lipid concentrations, plasma very low density lipoprotein particle sizes, or egg production records of PCR-genotyped females and their brothers and sires to demonstrate that each bird's phenotypic traits substantiated their genotypic classification. Moreover, several methodological modifications resulted in improved chemical safety, speed, and cost of preparing and analyzing genomic DNA from chicken erythrocytes. Because the ovaries of mutant RO females generally contain numerous vitellogenic follicles in the absence of a functional oocyte plasma membrane VLDLR, the existence of an alternate system for the oocytic uptake of plasma very low density lipoprotein and vitellogenin is suggested, whereas a physiological explanation as to why some, but not all, mutant RO hens are able to ovulate and lay eggs is lacking.

Feed restriction significantly alters lipogenic gene expression in broiler breeder chickens

Broiler breeder pullets were divided into two groups at 21 wk of age. One group was given free access to feed (ad libitum) and the other fed a limited amount of feed (restricted). At 22 wk, all birds were photostimulated and maintained throughout an egg-laying cycle ending at 36 wk. Samples of liver and abdominal fat pad were collected just before photostimulation (prelight), after photostimulation at first egg and at peak egg production (plateau). Hepatic expression of sterol regulatory element binding protein-1, ATP-citrate lyase, fatty acid synthase, malic enzyme, acetyl-CoA carboxylase and stearoyl-CoA (Delta9) desaturase 1 genes in ad libitum birds declined from their highest levels just before photostimulation as the birds came into and maintained egg production. In contrast, the restricted birds had significant (P < 0.05) increases in the expression of these genes after photostimulation at first egg with a subsequent decline as they reached peak egg production. Hepatic expression of fatty acid binding protein, VLDL apolipoprotein (apoVLDL-II) and apoB genes increased significantly (P < 0.05) in both ad libitum and restricted breeders after photostimulation, whereas apoA1 gene expression declined during this time. Abdominal fat pad weights were significantly (P < 0.05) higher in the ad libitum compared with restricted birds after photostimulation. Lipoprotein lipase in this tissue showed a pattern of expression similar to that observed for the hepatic lipogenic enzyme genes. In conclusion, feed restriction during the pullet-to-breeder transition period significantly (P < 0.05) altered hepatic lipogenic gene expression in broiler breeders.

Apolipoprotein A-I is necessary for the in vivo formation of high density lipoprotein competent for scavenger receptor BI-mediated cholesteryl ester-selective uptake

The severe depletion of cholesteryl ester (CE) in steroidogenic cells of apoA-I(-/-) mice suggests that apolipoprotein (apo) A-I plays a specific role in the high density lipoprotein (HDL) CE-selective uptake process mediated by scavenger receptor BI (SR-BI) in vivo. The nature of this role, however, is unclear because a variety of apolipoproteins bind to SR-BI expressed in transfected cells. In this study the role of apoA-I in SR-BI-mediated HDL CE-selective uptake was tested via analyses of the biochemical properties of apoA-I(-/-) HDL and its interaction with SR-BI on adrenocortical cells, hepatoma cells, and cells expressing a transfected SR-BI. apoA-I(-/-) HDL are large heterogeneous particles with a core consisting predominantly of CE and a surface enriched in phospholipid, free cholesterol, apoA-II, and apoE. Functional analysis showed apoA-I(-/-) HDL to bind to SR-BI with the same or higher affinity as compared with apoA-I(+/+) HDL, but apoA-I(-/-) HDL showed a 2-3-fold decrease in the V(max) for CE transfer from the HDL particle to adrenal cells. These results indicate that the absence of apoA-I results in HDL particles with a reduced capacity for SR-BI-mediated CE-selective uptake. The reduced V(max) illustrates that HDL properties necessary for binding to SR-BI are distinct from those properties necessary for the transfer of HDL CE from the core of the HDL particle to the plasma membrane. The reduced V(max) for HDL CE-selective uptake likely contributes to the severe reduction in CE accumulation in steroidogenic cells of apoA-I(-/-) mice.

Quantitative analysis of surface-located triacylglycerol in intact emulsion particles

The amount of triacylglycerol (TG) in the surface monolayer of intact phospholipid-stabilized emulsions was determined using (13)C nuclear magnetic resonance ((13)C NMR). (13)C NMR spectra of emulsions composed of bulk long-chain or medium-chain TG were prepared with [(13)C(3)]-carbonyl-enriched triolein, tripalmitin, or trioctanoin, and were analyzed and compared with NMR spectra of phosphatidylcholine vesicles with and without added TG. Identification of carbonyl peaks intermediate between those of phosphatidylcholine carbonyls and bulk TG confirmed the presence of surface TG in each emulsion. The surface of emulsions contained 2.2 mol % tripalmitin and 1.4 mol % triolein, but significantly more medium-chain TG, 9.1 mol % trioctanoin, as predicted by measurements of TG in phospholipid vesicles. Thus, medium-chain TGs are more accessible than long-chain TGs to enzymes or pro-oxidants in the continuous phase of phospholipid-stabilized emulsion systems. The quantitative determination of surface-located TG in intact particles will advance the understanding of emulsion colloidal properties, physicochemical stability, and metabolic behavior.

Effects of photostimulatory light intensity on ovarian morphology and carcass traits at sexual maturity in modern and antique egg-type pullets

The effects of light intensity during sexual maturation on ovarian and carcass morphology at first oviposition [sexual maturity (SM)] were examined in two Single Comb White Leghorn (SCWL) strains. A modern commercial layer strain (COMM; Shaver Starcross 288) and an antique randombred control strain (ANT) were used to compare the effects of changes in laying stock on their response to varying light intensities from photostimulation (PS) until SM. Two hundred pullets from each strain were reared following COMM breeder guidelines. At 18 wk of age, 32 COMM and 32 ANT pullets were individually caged in individually lit cages and photostimulated with light intensities of 1, 5, 50, and 500 lx. Each bird was processed when it reached SM, and carcass and ovarian morphology were assessed. The ANT birds came into production 9.1 d later than the COMM birds, on average. The ANT pullets consumed 7.0% more feed per day than COMM pullets but gained at a slower rate (ANT = 12.9 g/d; COMM = 15.0 g/d). The ANT birds reached SM at a greater weight and with a smaller ovary than did COMM birds. Although the number of large yellow follicles (LYF) was similar between strains (mean = 6.72), both LYF weight and first egg weight were lower in ANT birds than in COMM birds. The COMM layer strain was more growth efficient and had a greater emphasis on ovary maintenance. Light intensity had no effect on the timing of SM or on BW at SM, indicating that all intensities used were effectively able to stimulate the sexual maturation process. However, ovary weight and number of LYF exhibited an increasing dose response to light intensity, particularly in the COMM birds. Overall, the birds photostimulated with 1 lx of light had reduced ovary development and were heavier than their counterparts exposed to 50 and 500 lx. Within the ANT strain, LYF numbers were not significantly affected by light intensities, whereas, within the COMM strain, LYF numbers were 4.88, 6.63, 7.88, and 8.13 for the 1-, 5-, 50-, and 500-lx intensity groups, respectively. Although light intensity did not affect the rate of sexual maturation, it altered ovarian morphology and carcass lipid stores. A light intensity of 1 lx was limiting to ovarian follicle formation and caused increased carcass weight compared with birds on higher light intensity treatments. The COMM birds were more negatively affected by low light intensity than were the ANT birds, indicating that light intensity may be a more critical environmental factor with modern, highly efficient SCWL strains than has previously been thought. Light intensity can affect the reproductive development and likely the associated egg production potential of modern layer stocks.