Broiler chicken adipose tissue dynamics during the first two weeks post-hatch

Recent Research on Mechanisms of Feeding Regulation in Chicks

Food intake affects poultry productivity. A complete understanding of these regulatory mechanisms provides new strategies to improve productivity. Food intake is regulated by complex mechanisms involving many factors, including the central nervous system, gastrointestinal tract, hormones, and nutrients. Although several studies have been conducted to elucidate regulatory mechanisms in chickens, the mechanisms remain unclear. To update the current knowledge on feeding regulation in chickens, this review focuses on recent findings that have not been summarized in previous reviews, including spexins, adipokines, neurosecretory proteins GL and GM, and central intracellular signaling factors.

Age-Related Changes in Hepatic Lipid Metabolism and Abdominal Adipose Deposition in Yellow-Feathered Broilers Aged from 1 to 56 Days

The objective of this study was to evaluate the age-related changes in hepatic lipid metabolism, adipocyte hyperplasia, hypertrophy, and lipid metabolism in the abdominal adipose tissue of yellow-feathered broilers. Blood, liver, and abdominal adipose samples were collected on days 1, 7, 14, 21, 28, 35, 42, 49, and 56. Body, liver, and abdominal weight increased (p < 0.05) with age-related changes. The triacylglycerol content peaked on day 14, and total cholesterol content peaked on day 56. The adipocyte diameter and area peaked on day 56, and total DNA content peaked on day 7. The age-related changes in hepatic lipogenesis-related gene (ChREBP, SREBP-1c, ACC, FAS, SCD1) expression mainly occurred during days 1 to 21, hepatic lipolysis-related gene (CPT1, LPL, ApoB) expression mainly occurred during days 1 to 14, and abdominal adipose-deposition-related gene (PPARα, CPT1, LPL, PPARγ, C/EBPβ) expression occurred during days 1 to 14. These results demonstrated a dynamic pattern of hepatic lipid metabolism and abdominal adipose deposition in yellow-feathered broilers, which provides practical strategies to regulate hepatic lipid metabolism and reduce abdominal adipose deposition in yellow-feathered broilers.

Age-associated changes in the growth development of abdominal fat and their correlations with cecal gut microbiota in broiler chickens

Excess abdominal fat is a common phenomenon in broiler chickens. Gut microbiota could regulate lipid metabolism through their effects on short-chain fatty acids (SCFAs) production. This study was conducted to investigate the potential relationship between abdominal fat development and cecal microorganism populations. Abdominal fat and cecum contents were collected at 3, 7, 14, 21, 28, 35, and 42 d of age. The results showed that abdominal fat weight increased with age. The abdominal fat percentage was higher between 7 and 21 d of age than at 3 d (P < 0.05), and it increased again at 28 to 42 d (P < 0.05). Morphological analysis showed that adipocyte diameter and cross-sectional area (CSA) increased significantly after 14 d of age (P < 0.05). Moreover, gut microbiota analysis indicated that the Chao1 and Shannon indices were higher between 14 and 28 d than at 3 d of age (P < 0.05). Furthermore, LEfse analysis revealed that Faecalibacterium, Anaerotruncus, Anaeroplasma, Subdoligranulum, and Clostridium emerged to become dominant at 14 d. A greater abundance of Bacteroides, Ruminococcus, Dehalobacterium, and Lactobacillus were determined at 28 d when compared with 14 d of age. Parabacteroides, Ochrobactrum, Lactobacillus, Blautia, Alistipes, Dehalobacterium, Odoribacter, and Suuterella were found to be predominant at 42 d. PICRUSt analysis revealed that amino acid metabolism, lipid metabolism, and terpenoids and polyketides metabolism were elevated at 14 d; the immune and digestive systems were significantly developed at 28 d. In addition, cecum propionic acid and butyric acid contents gradually increased (P < 0.05), while the isobutyric acid contents gradually decreased with advancing age (P < 0.05). Correlation analysis among SCFAs, differential genera and abdominal fat suggested that Coprobacillus, Shigella, and Butyricicoccus had negative correlations with propionic acid, butyric acid, and abdominal fat weight, but positive correlations with isobutyric acid. Isobutyric acid was identified as being negatively associated with abdominal fat weight, while the reverse was found for propionic acid and butyric acid. In conclusion, abdominal fat development is correlated with the emergence of specific microbes and d 14 may be a pivotal age for establishing this relationship.

Stage-specific nutritional management and developmental programming to optimize meat production

Over the past few decades, genetic selection and refined nutritional management have extensively been used to increase the growth rate and lean meat production of livestock. However, the rapid growth rates of modern breeds are often accompanied by a reduction in intramuscular fat deposition and increased occurrences of muscle abnormalities, impairing meat quality and processing functionality. Early stages of animal development set the long-term growth trajectory of offspring. However, due to the seasonal reproductive cycles of ruminant livestock, gestational nutrient deficiencies caused by seasonal variations, frequent droughts, and unfavorable geological locations negatively affect fetal development and their subsequent production efficiency and meat quality. Therefore, enrolling livestock in nutritional intervention strategies during gestation is effective for improving the body composition and meat quality of the offspring at harvest. These crucial early developmental stages include embryonic, fetal, and postnatal stages, which have stage-specific effects on subsequent offspring development, body composition, and meat quality. This review summarizes contemporary research in the embryonic, fetal, and neonatal development, and the impacts of maternal nutrition on the early development and programming effects on the long-term growth performance of livestock. Understanding the developmental and metabolic characteristics of skeletal muscle, adipose, and fibrotic tissues will facilitate the development of stage-specific nutritional management strategies to optimize production efficiency and meat quality.

Low-protein diets supplemented with isoleucine alleviate lipid deposition in broilers through activating 5' adenosine monophosphate-activated protein kinase and janus kinase 2/signal transducer and activator of transcription 3 signaling pathways

This study aimed to evaluate the effect of isoleucine (Ile) on growth performance, meat quality and lipid metabolism of broilers fed a low-protein diet (LPD). The 396 one-day-old male Cobb broilers were allocated to 4 treatment groups as follows: control diet (CON), LPD, LPD + 0.13% Ile (LPD-LI) and LPD + 0.26% Ile (LPD-HI), with nine replicates of 11 broilers each for 42 d. The Ile increased average daily gain, average daily feed intake, fiber density and the mRNA level of myosin heavy chain (MyHC)-I in breast muscle, and decreased feed to gain ratio, shear force, fiber diameter and the mRNA level of MyHC-IIb in breast muscle, which were impaired by the LPD. Compared to the LPD group, broilers in LPD-LI and LPD-HI groups had lower serum lipid levels, liver fat content, abdominal adipose percentage and mRNA levels of peroxisome proliferator-activated receptor-γ, CCAAT/enhancer binding protein-α, ki-67, topoisomerase II alpha (TOP2A) and thioredoxin-dependent peroxidase 2 in abdominal adipose and liver X receptors-α, sterol regulatory element binding protein 1 (SREBP1), acetyl-CoA carboxylase (ACC) and fatty acid synthase (FAS) in liver, and higher mRNA levels of peroxisome proliferator activated receptor-α, carnitine palmitoyl-transferase 1 (CPT-1), and acyl-CoA oxidase 1 (ACOX1) in liver, which were equal to the CON levels. A LPD supplemented with Ile decreased enzyme activities of ACC and FAS in liver and glycerol-3-phosphate dehydrogenase and TOP2A in abdominal adipose, and increased enzyme activities of CPT-1 and ACOX1 in liver. Furthermore, Ile supplementation enhanced the mRNA level of leptin receptor and protein levels of phospho-5' adenosine monophosphate-activated protein kinase (AMPK), mechanistic target of rapamycin, ribosomal protein 70 S6 kinase, janus kinase 2 (JAK2), and signal transducer and activator of transcription 3 (STAT3), and decreased the protein level of SREBP1 in the liver of broilers in LPD group. In conclusion, dietary supplementation with Ile to 0.83% could improve growth performance and meat quality and alleviate lipid deposition of broilers fed a LPD through activating AMPK and JAK2/STAT3 signaling pathways.

Fermented grape seed meal promotes broiler growth and reduces abdominal fat deposition through intestinal microorganisms

The fermentation of grape seed meal, a non-conventional feed resource, improves its conventional nutritional composition, promotes the growth and development of livestock and fat metabolism by influencing the structure and diversity of intestinal bacteria. In this study, the nutritional components of Fermented grape seed meal (FGSM) and their effects on the growth performance, carcass quality, serum biochemistry, and intestinal bacteria of yellow feather broilers were investigated. A total of 240 male 14-day-old yellow-feathered broilers were randomly selected and divided into four groups, with three replicates of 20 chickens each. Animals were fed diets containing 0% (Group I), 2% (Group II), 4% (Group III), or 6% (Group IV) FGSM until they were 56 days old. The results showed that Acid soluble protein (ASP) and Crude protein (CP) contents increased, Acid detergent fiber (ADF) and Neutral detergent fiber (NDF) contents decreased, and free amino acid content increased in the FGSM group. The non-targeted metabolome identified 29 differential metabolites in FGSM, including organic acids, polyunsaturated fatty acids, and monosaccharides. During the entire trial period, Average daily gain (ADG) increased and Feed conversion ratio (FCR) decreased in response to dietary FGSM supplementation (p < 0.05). TP content in the serum increased and BUN content decreased in groups III and IV (p < 0.05). Simultaneously, the serum TG content in group III and the abdominal fat rate in group IV were significantly reduced (p < 0.05). The results of gut microbiota analysis showed that FGSM could significantly increase the Shannon and Simpson indices of broilers (35 days). Reducing the relative abundance of Bacteroidetes significantly altered cecal microbiota composition by increasing the relative abundance of Firmicutes (p < 0.05). By day 56, butyric acid content increased in the cecal samples from Group III (p < 0.05). In addition, Spearman's correlation analysis revealed a strong correlation between broiler growth performance, abdominal fat percentage, SCFAs, and gut microbes. In summary, the addition of appropriate levels of FGSM to rations improved broiler growth performance and reduced fat deposition by regulating gut microbes through differential metabolites and affecting the microbiota structure and SCFA content of the gut.

RNA-seq Based Transcriptome Analysis Reveals The Cross-Talk of Macrophage and Adipocyte of Chicken Subcutaneous Adipose Tissue during The Embryonic and Post-Hatch Period

With high fecundity and short production cycle, poultry is one of the important sources of meat. During the embryonic and post-hatch period, the higher death rate caused huge economic losses in poultry production. Our previous study showed that chick subcutaneous adipose tissue is an important energy supply tissue besides yolk. Therefore, the metabolic mechanism of subcutaneous adipose tissue in chicks could provide a new perspective of brooding. The objectives of the current study were to evaluate the differences between chick subcutaneous adipose tissue and abdominal adipose tissue before and after hatching and reveal the cross-talk of different cells within the chick subcutaneous adipose tissue. The results of RNA-seq and weighted gene co-expression network analysis (WGCNA) of chick subcutaneous and abdominal adipose tissues showed that the function of chick subcutaneous tissue was related to immunoreaction, and macrophage could be the major immune infiltration cell type in chicken subcutaneous adipose tissue, which were also verified by qPCR, HE stain, and IHC. The results of free fatty acids (FFAs)-induced the cross-talk between macrophages and adipocytes showed that FFAs-Ccl2 (chicken CCL26) axis could have an important role in lipid transportation in adipose tissue. The results of Oil Red O and Nile red stain demonstrated that macrophages have the ability to absorb FFAs quickly. Interestingly, according to the genomic organization of CCL family with representative vertebrate species, we found that chicken CCL26 could be the major chemokine in chicken adipocyte as the status of CCL2 in mammal adipocyte. In conclusion, we demonstrate that FFA-induced Ccl2 (chicken CCL26) secretion is crucial in determining fat depot-selective adipose tissue macrophage (ATM) infiltration, which could be an important medium of lipid transportation in chicken subcutaneous adipose tissue. These findings may have multiple important implications for understanding macrophage biology with chick subcutaneous adipose tissue and provide theoretical basis for lipid metabolism in poultry brooding.

Long-Lasting Effects of Incubation Temperature During Fetal Development on Subcutaneous Adipose Tissue of Broilers

Increasing evidence indicates that fetal programming may cause permanent effects on offspring adipose tissue and body composition. Previous study showed reduction in newly-hatched broiler chick adiposity by manipulating incubation temperature during fetal development. The present study examined whether incubation temperature during fetal development has long-term effects on post-hatching fat deposition in broilers. Broiler breeder eggs (Cobb-500^®) were incubated under constant low (36°C, LT), control (37.5°C, CT) or high (39°C, HT) temperature from day 13 onward, giving to eggshell temperature of 37.3 ± 0.08°C, 37.8 ± 0.2°C, and 38.8 ± 0.3°C, respectively. Male chicks were reared under recommended temperatures until 42 days old. LT 21 days old broilers exhibited higher blood cholesterol than CT broilers, and higher triglycerids, VLDL, and LDL, and lower HDL than CT and HT broilers. LT broilers presented higher liver cholesterol than CT broilers and lower ether extract percentage than CT broilers. Adipocyte count was lower in the abdomen than in the thigh. Until day 21 of age, feed intake was higher in LT than in HT broilers. At day 42 of age, blood cholesterol and LDL were higher in HT broilers than in CT and LT broilers. Liver cholesterol was higher in LT than in HT broilers. LT treatment reduced neck and increased thigh adipocyte size compared to CT treatment, while the HT treatment reduced abdomen and neck adipocyte size compared to other two treatments and in the thigh compared to LT treatment. In CT broilers, thigh adipocytes were smaller than abdomen and neck adipocytes. HT treatment increased adipocyte number per area in the neck compared to LT and CT treatment, and LT and HT treatments reduced adipocyte count in the thigh compared to CT treatment. CT broilers presented higher adipocyte count in the thigh than the abdomen and neck, while HT broilers presented higher adipocyte count in the neck than the abdomen and thigh. Cell proliferation was lower in the abdomen than in the thigh. The results show incubation temperature manipulation during fetal development has long-term and distinct effects on regional adiposity, and can be used to modulate broiler fat deposition.

Avian Neuropeptide Y: Beyond Feed Intake Regulation

Neuropeptide Y (NPY) is one of the most abundant and ubiquitously expressed neuropeptides in both the central and peripheral nervous systems, and its regulatory effects on feed intake and appetite- have been extensively studied in a wide variety of animals, including mammalian and non-mammalian species. Indeed, NPY has been shown to be involved in the regulation of feed intake and energy homeostasis by exerting stimulatory effects on appetite and feeding behavior in several species including chickens, rabbits, rats and mouse. More recent studies have shown that this neuropeptide and its receptors are expressed in various peripheral tissues, including the thyroid, heart, spleen, adrenal glands, white adipose tissue, muscle and bone. Although well researched centrally, studies investigating the distribution and function of peripherally expressed NPY in avian (non-mammalian vertebrates) species are very limited. Thus, peripherally expressed NPY merits more consideration and further in-depth exploration to fully elucidate its functions, especially in non-mammalian species. The aim of the current review is to provide an integrated synopsis of both centrally and peripherally expressed NPY, with a special focus on the distribution and function of the latter.

Oxidative Stability, Carcass Traits, and Muscle Fatty Acid and Amino Acid Profiles in Heat-Stressed Broiler Chickens

The objective was to elucidate the effects of chronic heat stress on carcass traits, muscle oxidative stability, muscle fatty acids and amino acid profiles in broiler chickens. A total of 100-day-old male Ross broiler chicks were divided into two equal groups of five replicates. The control group (TN) was maintained on a thermoneutral condition, while the experimental group (HS) was subjected to 8 h of heat stress (34 °C). The HS group showed lower dressing percentage and breast yield compared with the TN group (p = 0.040 and 0.042, respectively). Meanwhile, heat stress significantly increased the percentage of abdominal fat in broiler chickens (p = 0.001). The HS group showed significantly lower levels of PUFA (linoleic, docosahexaenoic and eicosapentaenoic) in the breast (p = 0.003, 0.002 and 0.001, respectively) and thigh (p = 0.001, 0.009 and 0.003, respectively) muscles than did the TN group. The levels of α-lenolinec acid in the breast and thigh muscles did not differ between both experimental groups (p = 0.818 and 0.060, respectively). With exception of threonine, tyrosine and phenylalanine, the levels of essential AA in the breast muscles were significantly (p ˂ 0.05) reduced in the HS group. The HS group showed significantly higher concentration of malondialdehyde (MDA) in the breast muscles (p = 0.032). Meanwhile, the concentration of MDA in the thigh muscles did not differ between both experimental groups (p = 0.149). Furthermore, the HS group showed significantly lower superoxide dismutase and catalase in heart tissues (p = 0.005 and 0.001, respectively). In conclusion, chronic thermal stress deteriorates carcass yield and the oxidative stability of breast muscles, as well as the levels of PUFA and essential AA in broiler chickens. However, the oxidative stability of thigh muscles was not affected.

Fighting Fat With Fat: n-3 Polyunsaturated Fatty Acids and Adipose Deposition in Broiler Chickens

Modern broiler chickens are incredibly efficient, but they accumulate more adipose tissue than is physiologically necessary due to inadvertent consequences of selection for rapid growth. Accumulation of excess adipose tissue wastes feed in birds raised for market, and it compromises well-being in broiler-breeders. Studies driven by the obesity epidemic in humans demonstrate that the fatty acid profile of the diet influences adipose tissue growth and metabolism in ways that can be manipulated to reduce fat accretion. Omega-3 polyunsaturated fatty acids (n-3 PUFA) can inhibit adipocyte differentiation, induce fatty acid oxidation, and enhance energy expenditure, all of which can counteract the accretion of excess adipose tissue. This mini-review summarizes efforts to counteract the tendency for fat accretion in broilers by enriching the diet in n-3 PUFA.

Dietary Curcumin Improves Energy Metabolism, Brain Monoamines, Carcass Traits, Muscle Oxidative Stability and Fatty Acid Profile in Heat-Stressed Broiler Chickens

The aim of the present study was to elucidate the impacts of dietary curcumin supplementation on energy metabolism, brain monoamines and muscle oxidative stability in heat-stressed broilers. In total, 120 day-old chicks were allocated into three equal groups of four replicates. The first group (T₁) was maintained on a thermoneutral condition, while the second group (T₂) was subjected to 8 h of thermal stress (34 °C), and both groups fed the basal diet with no supplement. The third group (T₃) was exposed to the same thermal stress conditions and fed the basal diet supplemented with curcumin (100 mg kg^-1 diet). The dietary curcumin supplementation significantly increased the breast yield (p = 0.004), but reduced the percentage of abdominal fat (p = 0.017) compared with the T₂ group. The addition of curcumin to broiler diets significantly improved the levels of monounsaturated fatty acids (MUFAs) and polyunsaturated fatty acids (PUFAs) in breast and thigh muscles compared with the T₂ group (p < 0.05). The curcumin-supplemented group showed significantly lower levels of malondialdehyde in the breast and thigh muscles than that of the T₂ group (p = 0.001 and 0.015, respectively). The dietary curcumin supplementation significantly improved the levels of ATP and CoQ10 in liver tissues (p = 0.012 and 0.001, respectively) and brain serotonin (p = 0.006) as compared to the T2 group. Meanwhile, the heat-stressed group showed significantly higher levels of ADP and Na,K-ATPase in the liver tissues than that of the other experimental groups (p = 0.011 and 0.027, respectively). It could be concluded that dietary curcumin supplementation may improve carcass yield, energy biomarkers, brain serotonin and muscle oxidative stability of heat-stressed broiler chickens.

Transcriptional Insights into Key Genes and Pathways Underlying Muscovy Duck Subcutaneous Fat Deposition at Different Developmental Stages

Simple Summary

Subcutaneous fat is an important factor affecting the meat quality and feed conversion rate of waterfowl. The current study compared the transcriptome data of Muscovy duck subcutaneous fat among three developmental stages, aiming at exploring the key regulatory genes for subcutaneous fat deposition. The results generated abundant candidate genes and pathways involving in subcutaneous fat deposition in Muscovy duck. This study provides an important reference for revealing the developmental mechanisms of subcutaneous fat in duck.

Abstract

Subcutaneous fat is a crucial trait for waterfowl, largely associated with meat quality and feed conversion rate. In this study, RNA-seq was used to identify differentially expressed genes of subcutaneous adipose tissue among three developmental stages (12, 35, and 66 weeks) in Muscovy duck. A total of 138 and 129 differentially expressed genes (DEGs) were identified between 35 and 12 weeks (wk), and 66 and 35 wk, respectively. Compared with 12 wk, subcutaneous fat tissue at 35 wk upregulated several genes related to cholesterol biosynthesis and fatty acid biosynthesis, including HSD17B7 and MSMO1, while it downregulated fatty acid beta-oxidation related genes, including ACOX1 and ACSL1. Notably, most of the DEGs (92.2%) were downregulated in 66 wk compared with 35 wk, consistent with the slower metabolism of aging duck. Protein network interaction and function analyses revealed GC, AHSG, FGG, and FGA were the key genes for duck subcutaneous fat from adult to old age. Additionally, the PPAR signaling pathway, commonly enriched between the two comparisons, might be the key pathway contributing to subcutaneous fat metabolism among differential developmental stages in Muscovy duck. These results provide several candidate genes and pathways potentially involved in duck subcutaneous fat deposition, expanding our understanding of the molecular mechanisms underlying subcutaneous fat deposition during development.

Difference in developmental dynamics between subcutaneous and abdominal adipose tissues in goose (Anser Cygnoides)

Goose (Anas cygnoides), as a typical species domesticated from a migratory bird, has maintained the capability of depositing excess lipid and preferentially accumulating fat within the abdomen and subcutaneous, which not only leads to decrease in yield of meat product, but also affects the feed conversion rate. Here, an experiment was conducted to examine the difference in developmental dynamics between subcutaneous (SAT) and abdominal adipose tissues (AAT) in goose. The results showed that SAT could be clearly observed at embryonic days (E) 15, whereas AAT were clearer until E20. Although the weights of SAT and AAT showed a significant rising with advancing age (P < 0.05), their gains were not completely uniform, and more adipose deposited preferentially toward AAT after birth (P < 0.05). Additionally, a clear expansion in adipocyte size was observed in AAT and SAT during embryonic stages (P < 0.05). The average adipocyte area in AAT continued to increase after birth (P < 0.05), while the cell areas in SAT were relatively invariable (P > 0.05). Furthermore, the expression levels of FABP4/aP2, ACSL1 and PPARγ were much higher in SAT than in AAT, whereas relative higher expression level of IL-6 was observed in the AAT during embryonic stages. After birth, the more expression of LPL and PPARα were detected in AAT than did in SAT (P < 0.05), whereas greater ATGL expression was in SAT (P < 0.05). Taken together, these findings suggest that AAT may display greater fat storage capacity than SAT accompanied by changes in cell area and lipogenic capacity. Considering that there is disparity in the individual adipose tissues, we suggested that careful consideration for the precise interventions used to control SAT or AAT deposition in meat-producing animals to improve feed efficiency.

Effects of miR-125b-5p on Preadipocyte Proliferation and Differentiation in Chicken

Our previous studies have shown that miR-125b-5p was highly expressed and significantly upregulated during abdominal fat deposition in chickens. However, the role of miR-125b in the regulation of adipogenesis is not clear in chickens. Therefore, we evaluated the effects of miR-125b-5p on preadipocyte proliferation and differentiation and the interaction between miR-125b-5p and the acyl-CoA synthetase bubblegum family member 2 (ACSBG2) gene in adipogenesis in chicken abdominal adipose tissue. Here, transfection tests of miR-125b-5p mimic/inhibitor were performed in preadipocytes, and the effects of miR-125b-5p on preadipocytes proliferation and differentiation were analyzed. The target site of miR-125b-5p in the 3'UTR (untranslated region) of ACSBG2 were verified by a luciferase reporter assay. Our results showed that miR-125b-5p overexpression inhibited proliferation and reduced the number of cells in S phase and G2/M phase in preadipocytes; conversely, miR-125b-5p inhibition promoted the proliferation and increased the number of cells in S phase and G2/M phase. In adipocytes after induction, miR-125b-5p overexpression led to a notable increase in the accumulation of lipid droplets as well as in the concentration of triglycerides, while miR-125b-5p inhibition had the opposite effect. Furthermore, miR-125b-5p could directly bind to the 3'UTR of ACSBG2, and its overexpression could significantly repress the mRNA and protein expression of ACSBG2. These results indicate that miR-125b-5p can inhibit preadipocyte proliferation and can promote preadipocyte differentiation to affect adipogenesis in chicken abdominal adipose tissues, at least partially by downregulating ACSBG2.

Role of Corticosterone in Lipid Metabolism in Broiler Chick White Adipose Tissue

Excessive accumulation of body fat in broiler chickens has become a serious problem in the poultry industry. However, the molecular mechanism of triglyceride accumulation in chicken white adipose tissue (WAT) has not been elucidated. In the present study, we investigated the physiological importance of the catabolic hormone corticosterone, the major glucocorticoid in chickens, in the regulation of chicken WAT lipid metabolism. We first examined the effects of fasting on the mRNA levels of lipid metabolism-related genes associated with WAT, plasma corticosterone, and non-esterified fatty acid (NEFA). We then examined the effects of corticosterone on the expression of these genes in vivo and in vitro. In 10-day-old chicks, 3 h of fasting significantly decreased mRNA levels of lipoprotein lipase (LPL) in WAT and significantly elevated plasma concentrations of NEFA. Six hours of fasting significantly increased mRNA levels of adipose triglyceride lipase (ATGL) in WAT and significantly elevated plasma concentrations of corticosterone. On the other hand, fasting significantly reduced mRNA levels of LPL in WAT and elevated plasma concentrations of NEFA in 29-day-old chicks without affecting mRNA levels of ATGL in WAT or plasma corticosterone concentrations. Oral administration of corticosterone significantly reduced mRNA levels of LPL and significantly increased the mRNA levels of ATGL in WAT in 29-day-old chicks without affecting plasma NEFA concentrations. The addition of corticosterone to primary chicken adipocytes significantly increased mRNA levels of ATGL, whereas mRNA levels of LPL tended to decrease. NEFA concentrations in the culture medium were not influenced by corticosterone levels. These results suggest that plasma corticosterone partly regulates the gene expression of lipid metabolism-related genes in chicken WAT and this regulation is different from the acute elevation of plasma NEFA due to short-term fasting.

Effect of Vitamin E Supplementation on Deposition and Gene Expression Profiling of Abdominal Fat in Broiler Chickens

The aim of this study was to study the regulation of abdominal fat deposition by DL-α-tocopherol acetate (vitamin E) in broilers. Diets supplemented with 50 IU vitamin E significantly diminished abdominal fat deposition in broilers at day 35. Transcriptome sequencing results for abdominal fat tissues of the control (FC) and 50 IU vitamin E-supplemented (FT) groups identified 602 differentially expressed genes (DEGs), which were enriched in cellular process, cell and cell part, and binding Gene Ontology terms. Pathway functional analysis revealed that the DEGs were enriched in 42 metabolic pathways. Notably, the most enriched pathway, fatty acid biosynthesis, was found to play a key role in lipid metabolism. Further, the key regulators of lipid metabolism, including fatty acid synthase, acetyl-CoA carboxylase alpha, and acyl-CoA synthetase long-chain family member 1, demonstrated decreased expression following vitamin E supplementation. Herein, we have identified pathways and genes regulated by vitamin E, thereby providing novel insights into the nutrients regulating abdominal fat deposition in broilers.

Effect of Soybean Meal Substitution by Raw Chickpea Seeds on Thermal Properties and Fatty Acid Composition of Subcutaneous Fat Tissue of Broiler Chickens

Simple Summary

A soybean meal, commonly used as a primary source of protein in animal diets, is often obtained from processing genetically modified soybean varieties. The tendency to reduce the use of feeds containing transgenic constituents increases the need for alternative sources of dietary protein. In this study, we fed broiler chickens diets containing either soybean meal or raw chickpea seeds. We examined the effect of such a substitution on broilers’ subcutaneous fat tissue, which has numerous important physiological functions in chickens.

Abstract

In this study, the effect of soybean meal substitution by raw chickpea seeds on the thermal properties and fatty acid profile of subcutaneous fat tissue of broiler chickens was examined. The experiment, performed on Ross 308 chickens, lasted for 42 days. Tight subcutaneous fat tissue was analyzed using differential scanning calorimetry (DSC) measurements while the fatty acid composition of subcutaneous adipose tissue was determined chromatographically. There was no effect of soybean meal substitution on fat crystallization temperature or crystallization enthalpy. However, the total calorimetric enthalpy of the melting of low-melting monounsaturated and saturated triacylglycerols differed between groups. Fatty acid proportions in the subcutaneous fat tissue of broiler chickens were also altered. Among others, chickpea seed inclusion decreased the content of main saturated acid (palmitic acid) and increased the content of main monounsaturated (oleic) and tri-unsaturated (linolenic) acids. The results show that the soybean meal substitution by raw chickpea seeds in the feed can affect the structural properties of adipose tissue in broiler chickens, including the thermal transformation of unsaturated fatty acids. Due to the numerous physiological functions of subcutaneous fat tissue, understanding these mechanisms can promote the use of alternative protein both in poultry and human nutrition.

Dietary supplement of essential oil from oregano affects growth performance, nutrient utilization, intestinal morphology and antioxidant ability in Pekin ducks

A study was conducted to investigate the effects of oregano essential oil (EO) on growth performance, nutrients utilization, intestinal morphology, intestinal barrier-related gene expression and antioxidant capability in meat ducks. A total of 360 1-day-old ducks were divided into three groups (12 replicates pens per diet of 10 ducks in each pen): negative control (no essential oil or antibiotic), positive control (antibiotic: 500 mg/kg aureomycin of diet) and oregano EO (100 mg/kg of diet). The experiment was carried out for 35 days. Ducks were given feed and water ad libitum. Ducks fed EO supplement showed similar body weight and feed to gain ratio to antibiotic fed ducks. EO supplementation significantly increased (p < .05) feed intake (day 1-35), jejunal villus height (VH) to crypt depth (CD) ratio, serum superoxide dismutase activities (SOD) and jejunal total antioxidant capacity (T-AOC) of ducks compared to controls. Ducks fed diets supplemented with oregano EO also had decreased (p < .05) jejunal CD, serum and hepatic malondialdehyde (MDA) concentration, and the mRNA expression of jejunal zonula occludens-3 (ZO-3) and secretory immunoglobulin A (sIgA) genes in comparison to the control group. Compared to the antibiotic supplementation group, the mRNA expression of claudin1 (CLND1) and CLND2 significantly increased (p < .05), but the mRNA expression of ZO-3 and mucin 2 markedly decreased (p < .05) in the jejunum of ducks in oregano EO supplementation group. These results suggest that oregano EO improves the antioxidant capacity and intestinal defence and structural measures and may aide in helping to maintain enteric health in production without growth-promoting antibiotics.

MicroRNAs and their regulatory networks in Chinese Gushi chicken abdominal adipose tissue during postnatal late development

Background

Abdominal fat is the major adipose tissue in chickens. The growth status of abdominal fat during postnatal late development ultimately affects meat yield and quality in chickens. MicroRNAs (miRNAs) are endogenous small noncoding RNAs that regulate gene expression at the post-transcriptional level. Studies have shown that miRNAs play an important role in the biological processes involved in adipose tissue development. However, few studies have investigated miRNA expression profiles and their interaction networks associated with the postnatal late development of abdominal adipose tissue in chickens.

Results

We constructed four small RNA libraries from abdominal adipose tissue obtained from Chinese domestic Gushi chickens at 6, 14, 22, and 30 weeks. A total of 507 known miRNAs and 53 novel miRNAs were identified based on the four small RNA libraries. Fifty-one significant differentially expressed (SDE) miRNAs were identified from six combinations by comparative analysis, and the expression patterns of these SDE miRNAs were divided into six subclusters by cluster analysis. Gene ontology enrichment analysis showed that the SDE miRNAs were primarily involved in the regulation of fat cell differentiation, regulation of lipid metabolism, regulation of fatty acid metabolism, and unsaturated fatty acid metabolism in the lipid metabolism- or deposition-related biological process categories. In addition, we constructed differentially expressed miRNA–mRNA interaction networks related to abdominal adipose development. The results showed that miRNA families, such as mir-30, mir-34, mir-199, mir-8, and mir-146, may have key roles in lipid metabolism, adipocyte proliferation and differentiation, and cell junctions during abdominal adipose tissue development in chickens.

Conclusions

This study determined the dynamic miRNA transcriptome and characterized the miRNA–mRNA interaction networks in Gushi chicken abdominal adipose tissue for the first time. The results expanded the number of known miRNAs in abdominal adipose tissue and provide novel insights and a valuable resource to elucidate post-transcriptional regulation mechanisms during postnatal late development of abdominal adipose tissue in chicken.

Changes in adipose tissue physiology during the first two weeks posthatch in chicks from lines selected for low or high body weight

Chickens from lines selected for low (LWS) or high (HWS) body weight (BW) differ in appetite and adiposity. Mechanisms associated with the predisposition to becoming obese are unclear. The objective of the experiment was to evaluate developmental changes in depot-specific adipose tissue during the first 2 wk posthatch. Subcutaneous (SQ), clavicular (CL), and abdominal (AB) depots were collected at hatch (DOH) and days 4 (D4) and 14 (D14) posthatch for histological and mRNA measurements. LWS chicks had decreased SQ fat mass on a BW basis with reduced adipocyte size from DOH to D4 and increased BW and fat mass with unchanged adipocyte size from D4 to D14. HWS chicks increased in BW from DOH to D14 and increased in fat mass in all three depots with enlarged adipocytes in the AB depot from D4 to D14. Meanwhile, CCAAT/enhancer-binding protein-α, neuropeptide Y, peroxisome proliferator-activated receptor-γ, and acyl-CoA dehydrogenase mRNAs differed among depots between lines at different ages. Plasma nonesterified fatty acids were greater in LWS than HWS at D4 and D14. From DOH to D4, LWS chicks mobilized SQ fat and replenished the reservoir through hyperplasia, whereas HWS chicks were dependent on hyperplasia and hypertrophy to maintain adipocyte size and depot mass. From D4 to D14, adipose tissue catabolism and adipogenesis slowed. Whereas LWS fat depots and adipocyte sizes remained stable, HWS chicks rapidly accumulated fat in CL and AB depots. Chicks predisposed to be anorexic or obese have different fat development patterns during the first 2 wk posthatch.

Responses to peripheral neuropeptide Y in avian adipose tissue are diet, depot, and time specific

The goal of this research was to determine the effect of dietary macronutrient composition on peripheral neuropeptide Y (NPY)-induced changes in adipose tissue dynamics in chicks. Chicks were fed one of three isocaloric diets from the day of hatch: high carbohydrate (HC), high fat (HF), or high protein (HP). On day 4 post-hatch, 0 (vehicle), 60, or 120 µg/kg BW of NPY was injected intraperitoneally, and subcutaneous, clavicular and abdominal adipose tissue samples were collected at 1 and 3 h post-injection. The effect of NPY was most pronounced in chicks fed the HF or HP diet. In the subcutaneous fat at 1 h post-injection, 60 µg/kg BW of NPY was associated with an increase in NPY receptor 2 (NPYR2) mRNA in chicks fed the HP diet and a decrease in 1-acylglycerol-3-phosphate O-acyltransferase 2 (AGPAT2) mRNA in chicks fed the HC diet. In response to 120 µg/kg BW of NPY, there was greater AGPAT2 mRNA in the clavicular fat of chicks that consumed the HP diet and less CCAAT/enhancer-binding protein alpha in the abdominal fat of chicks that were provided the HF diet. There were no gene expression changes in the abdominal fat at 3 h post-injection, whereas there were decreases in AGPAT2, adipose triglyceride lipase, fatty acid binding protein 4 and NPY mRNA in the clavicular fat of chicks fed the HP diet. Results demonstrate that diet affects exogenous NPY-dependent physiological effects in a time- and depot-dependent manner in chick adipose tissue.

Peripheral neuropeptide Y differentially influences adipogenesis and lipolysis in chicks from lines selected for low or high body weight

Neuropeptide Y (NPY) stimulates appetite and promotes lipid deposition. We demonstrated a differential sensitivity in the food intake response to central NPY in chicks from lines selected for low (LWS) or high (HWS) body weight, but have not reported whether such differences exist in the periphery. At 5days, LWS and HWS chicks were intraperitoneally injected with 0 (vehicle), 60, or 120μg/kg BW NPY and subcutaneous adipose tissue and plasma were collected at 1, 3, 6, 12, and 24h (n=12). NPY injection increased glycerol-3-phosphate dehydrogenase (G3PDH) activity at 1 and 3h and reduced plasma non-esterified fatty acids (NEFAs) at 1 and 12h. G3PDH activity was greater in HWS than LWS while NEFAs were greater in LWS. At 1h, peroxisome proliferator-activated receptor gamma (PPARγ), CCAAT/enhancer binding protein (C/EBP)α, and microsomal triglyceride transfer protein (MTTP) mRNAs were reduced in NPY-injected chicks whereas NPY receptor 1 (NPYR1) was increased. Expression of stearoyl-CoA desaturase (SCD1) was increased by NPY at 1h in HWS but not LWS. PPARγ (3 and 6h), C/EBPβ (3h), C/EBPα (6h) and NPYR1 and 2 (24h) mRNAs were greater in NPY- than vehicle-injected chicks. At several times, adipose triglyceride lipase, MTTP, perilipin 1, NPYR1, and NPYR2 mRNAs were greater in LWS than HWS, while expression of SCD1, glycerol-3-phosphate acyltransferase 3 and lipoprotein lipase was greater in HWS than LWS. Thus, NPY promotes fat deposition and inhibits lipolysis in chicks, with line differences indicative of greater rates of lipolysis in LWS and adipogenesis in HWS.

The effects of dietary macronutrient composition on lipid metabolism-associated factor gene expression in the adipose tissue of chickens are influenced by fasting and refeeding

Background

Broiler chickens are compulsive feeders that become obese as juveniles and are thus a unique model for metabolic disorders in humans. However, little is known about the relationship between dietary composition, fasting and refeeding and adipose tissue physiology in chicks. Our objective was to determine how dietary macronutrient composition and fasting and refeeding affect chick adipose physiology during the early post-hatch period.

Methods

Chicks were fed one of three isocaloric diets after hatch: high-carbohydrate (HC; control), high-fat (HF; 30% of ME from soybean oil) or high-protein (HP; 25% vs. 22% crude protein). At 4 days post-hatch, chicks were fed (continuous ad libitum access to food), fasted (3 h food withdrawal), or refed (fasted for 3 h and refed for 1 h). Subcutaneous, clavicular, and abdominal adipose tissue was collected for histological analysis and to measure gene expression, and plasma to measure non-esterified fatty acid (NEFA) concentrations (n = 6–10 per group).

Results

Adipose tissue weights were reduced in chicks that were fed the HP diet and adipocyte diameter was greater in the adipose tissue of chicks that ate the HF diet. Consumption of diets differing in protein and fat content also affected gene expression; mRNAs encoding fatty acid binding protein 4 and a lipolytic enzyme, monoglyceride lipase, were greater in chicks fed the HC and HF than HP diet in all three adipose tissue depots. Fasting influenced gene expression in a depot-dependent manner, where most fasting and refeeding-induced changes were observed in the clavicular fat of chicks that consumed the HC diet. Fasting increased plasma NEFA concentrations in chicks fed the HC and HP diets.

Conclusions

The decreased adipose tissue deposition in chicks fed the HP diet is likely explained by decreased rates of adipogenesis. Consumption of the HF diet was associated with greater adipose tissue deposition and larger adipocytes, likely as a result of greater rates of adipocyte hypertrophy. The depot-dependent effects of diet and fasting on gene expression may help explain mechanisms underlying metabolic distinctions among subcutaneous and visceral fat depots in humans.

Dietary overload lithium decreases the adipogenesis in abdominal adipose tissue of broiler chickens

To investigate the toxic effects of dietary overload lithium on the adipogenesis in adipose tissue of chicken and the role of hypothalamic neuropeptide Y (NPY) in this process, one-day-old male chicks were fed with the basal diet added with 0 (control) or 100mg lithium/kg diet from lithium chloride (overload lithium) for 35days. Abdominal adipose tissue and hypothalamus were collected at day 6, 14, and 35. As a percentage of body weight, abdominal fat decreased (p<0.001) at day 6, 14, and 35, and feed intake and body weight gain decreased during day 7-14, and day 15-35 in overload lithium treated broilers as compared to control. Adipocyte diameter and DNA content in abdominal adipose tissue were significantly lower in overload-lithium treatment than control at day 35, although no significant differences were observed at day 6 and 14. Dietary overload lithium decreased (p<0.01) transcriptional expression of preadipocyte proliferation makers ki-67 (KI67), microtubule-associated protein homolog (TPX2), and topoisomerase 2-alpha (TOP2A), and preadipocyte differentiation transcriptional factors peroxisome proliferator-activated receptor-γ (PPARγ), and CCAAT/enhancer binding protein (C/EBP) α mRNA abundance in abdominal adipose tissue. In hypothalamus, dietary overload lithium influenced (p<0.001) NPY, and NPY receptor (NPYR) 6 mRNA abundance at day 6 and 14, but not at day 35. In conclusion, dietary overload lithium decreased the adipogenesis in abdominal adipose tissue of chicken, which was accompanied by depressing transcriptional expression of adipogenesis-associated factors. Hypothalamic NPY had a potential role in the adipogenesis in abdominal adipose tissue of broilers with a short-term overload lithium treatment.

Recent advances in the understanding of how neuropeptide Y and -melanocyte stimulating hormone function in adipose physiology

Communication between the brain and the adipose tissue has been the focus of many studies in recent years, with the "brain-fat axis" identified as a system that orchestrates the assimilation and usage of energy to maintain body mass and adequate fat stores. It is now well-known that appetite-regulating peptides that were studied as neurotransmitters in the central nervous system can act both on the hypothalamus to regulate feeding behavior and also on the adipose tissue to modulate the storage of energy. Energy balance is thus partly controlled by factors that can alter both energy intake and storage/expenditure. Two such factors involved in these processes are neuropeptide Y (NPY) and α-melanocyte stimulating hormone (α-MSH). NPY, an orexigenic factor, is associated with promoting adipogenesis in both mammals and chickens, while α-MSH, an anorexigenic factor, stimulates lipolysis in rodents. There is also evidence of interaction between the 2 peptides. This review aims to summarize recent advances in the study of NPY and α-MSH regarding their role in adipose tissue physiology, with an emphasis on the cellular and molecular mechanisms. A greater understanding of the brain-fat axis and regulation of adiposity by bioactive peptides may provide insights on strategies to prevent or treat obesity and also enhance nutrient utilization efficiency in agriculturally-important species.