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

Arginine, soy isoflavone and hydroxypropylmethylcellulose have protective effects against obesity in broiler breeder hens fed on high-energy diets

1. The present study was undertaken to determine the effects of arginine, soy isoflavone (ISF) and hydroxypropylmethylcellulose (HPMC) on obesity in broiler breeder hens. 2. A total of 320 Cobb 500 hens, 45 weeks of age, were assigned to 64 floor pens. The experiment was conducted as a completely randomised design in a factorial arrangement (2 × 2 × 2 × 2) with 4 replicates of 5 hens in each pen. Factors included two concentrations of HPMC (0 and 1%), two concentrations of arginine (8.4 and 12 g/kg), two concentrations of ISF (zero and three times more than that present in basal diets) and two contents of energy (11.7 and 14.6 MJ/kg). Performance criteria and blood characteristics of hens were measured during the experimental period. Expression of genes involved in lipid metabolism was determined in the liver at 55 weeks of age. 3. Hens given high-energy diets showed increased BW (body weight), ovary weight and abdominal fat pad and enhanced plasma glucose, triglyceride (TG), cholesterol, haemoglobin, haematocrit and low lymphocyte percentages. The expression of malic enzyme, peroxisome proliferator-activated receptor-α (PPARα), peroxisome proliferator-activated receptor-γ (PPARγ) and inducible nitric oxide (iNOS) increased and sterol regulatory element binding protein-1c (SREBP1c) decreased with increasing energy content of diets. Arginine addition decreased TG, cholesterol and A1-c haemoglobin concentration and increased PPARα, PPARγ and iNOS expression. Inclusion of ISF and HPMC decreased BW, egg weight, plasma TG, cholesterol and increased egg production and also enhanced PPARγ and iNOS expression. Significant interactions were observed between energy concentration and ISF and HPMC on BW. 4. The results of the current study revealed that ISF, HPMC and arginine have beneficial effects on controlling the metabolism of obese broiler breeder hens and using a mix of these products minimises the harmful effects of obesity.

The epigenetic lorax: gene-environment interactions in human health

Over the last decade, we have witnessed an explosion of information on genetic factors underlying common human diseases and disorders. This 'human genomics' information revolution has occurred as a backdrop to a rapid increase in the rates of many human disorders and diseases. For example, obesity, Type 2 diabetes, asthma, autism spectrum disorder and attention deficit hyperactivity disorder have increased at rates that cannot be due to changes in the genetic structure of the population, and are difficult to ascribe to changes in diagnostic criteria or ascertainment. A likely cause of the increased incidence of these disorders is increased exposure to environmental factors that modify gene function. Many environmental factors that have epidemiological association with common human disorders are likely to exert their effects through epigenetic alterations. This general mechanism of gene-environment interaction poses special challenges for individuals, educators, scientists and public policy makers in defining, monitoring and mitigating exposures.

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.

A twice-a-day feeding regimen optimizes performance in broiler breeder hens

To evaluate the effects of different methods of feed allocation on performance, plasma hormone concentration, and ovarian morphology, an experiment was conducted using 32 Cobb 500 broiler breeder hens. The experiment was started at 27 wk and lasted to 39 wk of age. Feeding regimens included: i) hens with an ad libitum feeding program, ii) hens that received their restricted feed once a day, iii) hens that received their restricted feed twice a day, and iv) hens that received their restricted feed 3 times a day. Each hen was assumed as an experimental unit and treatments were replicated 8 times. Daily egg production, BW, and egg and yolk weights were measured. Two blood samples were taken 3 and 6 h after the first feed allocation every 2 wk. Plasma samples were assayed for glucose, triacylglycerol (TAG), cholesterol, as well as leptin-like concentration, glucagon, triiodothyronine, thyroxine, progesterone, estradiol, and testosterone. Liver, abdominal fat pad, and ovary were collected at necropsy. Ovaries were weighed and follicles were characterized as large yellow follicles, small yellow follicles, and large white follicles. Results showed inferior egg production in ad libitum-fed birds along with high levels of plasma glucose, TAG, cholesterol, leptin-like concentration, and testosterone. Twice-a-day-fed birds produced more egg in the entire production period than once-a-day-fed birds. Better performance of twice-a-day-fed hens was associated with lower plasma glucose, TAG, and leptin-like concentration, whereas their estradiol and glucagon were higher than once-a-day-fed hens. Results obtained in our study suggest that allocation of restricted feed 2 times a day may alleviate or delay lipotoxicity development and improve reproductive performance in broiler breeder hens.

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.

Early energy and protein reduction: effects on growth, blood profiles and expression of genes related to protein and fat metabolism in broilers

1. A total of 320-d-old Ross broilers were used in a 6-week study to investigate the effects of feeding lower energy and protein diets from d 8 to 14 on growth performance, blood profiles, and gene expression of leptin and myostatin. 2. Broilers were randomly allotted to 4 treatments, each treatment applied to 4 pens with 20 birds in each. During first week, all the birds were fed on a common starter diet (13.4 MJ ME/kg, 230 g/kg CP and 11.0 g/kg lysine). The birds were then subjected to their respective treatment diets from d 8 to 14. Treatment diets comprised two ME levels, 13.4 and 12.0 MJ/kg, each with two levels of CP, 230 and 184 g/kg. This was followed by feeding common starter and finisher diets for the last 4 weeks. 3. Dietary protein reduction resulted in poor performance and feed efficiency while energy reduction resulted in poor feed efficiency between d 8 and 14. From d 14 to 42 birds previously fed diets lower in energy and protein showed similar body weight gain and feed intake to well-fed birds. Moreover from d 8 to 14, birds fed on energy and protein-reduced diets had lower nutrient metabolisability coefficients. 4. The blood urea nitrogen (BUN) and relative weights of heart and breast muscle were lower in birds fed protein-reduced diets while energy reduction resulted in lower plasma glucose, abdominal fat and intestinal weight at d 14. At d 42, birds fed on the protein-reduced diets had lower BUN, breast muscle weight and small intestine length, while feeding on the energy-reduced diets resulted in lower abdominal fat. 5. Upregulated myostatin mRNA expression in breast muscle and downregulation of leptin mRNA expression in abdominal fat were observed in birds fed on protein and energy-reduced diets, respectively. 6. In conclusion, early nutrient reduction affected growth performance and produced lesser abdominal fat in broilers. Moreover, early energy and/or protein reduction could change muscle and fat metabolism by regulating the expressions of myostatin and leptin.

Palmitate modulates intracellular signaling, induces endoplasmic reticulum stress, and causes apoptosis in mouse 3T3-L1 and rat primary preadipocytes

Although fatty acids enhance preadipocyte differentiation in the presence of adequate hormone cocktails, little is known regarding their effects in the absence of these hormones. We have now shown that palmitate, a common long-chain saturated fatty acid, induced apoptosis in both mouse 3T3-L1 and rat primary preadipocytes grown in a normal serum-containing medium. Treatment of preadipocytes with palmitate induced multiple endoplasmic reticulum (ER) stress responses, evidenced by increased protein content of CHOP and GRP78 and splicing of XBP-1 mRNA, as well as altered phosphorylation of eIF2alpha and increased phosphorylation of JNK and Erk1/2. Intriguingly, palmitate induced an early activation of Akt but diminished both Akt activation and its protein mass after prolonged incubation (>6 h). In association with these changes, palmitate reduced expression of beta-catenin and its downstream target, c-Myc and cyclin D1, two key prosurvival proteins. Overexpression of constitutively active Akt did not block the apoptotic effect of palmitate. Cotreatment with unsaturated fatty acids (oleate, linoleate) or with LiCl (a glycogen synthase kinase-3beta inhibitor) attenuated the palmitate-induced apoptosis. Subsequent analysis suggested that the unsaturated fatty acids probably counteracted palmitate by reducing, not eliminating, ER stress, whereas LiCl probably improved viability by activating the Wnt signaling pathway. Cotreatment of palmitate with a standard adipogenic hormone cocktail also abolished the apoptotic effect and promoted adipocyte differentiation. Collectively, our results suggest that palmitate causes multiple cellular stresses that may lead to apoptosis in preadipocytes in the absence of adipogenic stimuli, highlighting the importance of exogenous hormones in directing cell fate in response to increased fatty acid influx.

Functional Annotation of Genomic Data with Metabolic Inference

Metabolomics is an appealing new approach in systems biology aimed at enabling an improved understanding of the dynamic biochemical composition of living systems. Biological systems are remarkably complex. Importantly, metabolites are the end products of cellular regulatory processes, and their concentrations reflect the ultimate response of a biological system to genetic or environmental changes. In this article, we describe the components of lipid metabolomics and then use them to investigate the metabolic basis for increased abdominal adiposity in 2 strains of divergently selected chickens. Lipid metabolomics were chosen due to the availability of well-developed analytical platforms and the pervasive physiological importance of lipids in metabolism. The analysis suggests that metabolic shifts that result in increased abdominal adiposity are not universal and vary with genetic background. Metabolomics can be used to reverse engineer selection programs through superior metabolic descriptions that can then be associated with specific gene networks and transcriptional profiles.