Biology of leptin in the pig

Metabolic Profile of Growing Immune- and Surgically Castrated Iberian Pigs Fed Diets of Different Amino Acid Concentration

The purpose of the current study was to further characterize the performance and nitrogen retention differences previously observed between immunocastrated (IC) and surgically castrated (SC) pure Iberian pigs. Fifty-four pigs were used (three sexes: IC males, IC females and SC males), fed three isoenergetic diets (160, 140 and 120 g CP/kg DM; six pigs/treatment combination) from 40 kg BW until slaughter (105 kg BW). Plasmatic post-absorptive metabolites and hormones, and backfat tissue composition were determined. The IC males showed a trend towards higher plasmatic creatinine (p = 0.06) and IGF-1 concentrations than SC males and IC females (p < 0.001). SC males showed a higher predisposition to carcass fatness and insulin resistance compared to IC males. Plasmatic isoleucine concentration was higher in IC and SC males compared to IC females (p < 0.01), and valine was greater in IC males compared to the rest of the pigs (p < 0.001). Total branched-chain amino acids (AA) were greater in IC males than in IC females (p < 0.01). Total plasmatic essential AA concentrations tended to be greater in IC males (p = 0.09). The present results support the increased performance and nitrogen retention capacity previously observed in IC male Iberian pigs compared to SC males and IC females, which can be attributed to increased anabolic capacity related with lean growth in Iberian IC males.

Exploring and Identifying Candidate Genes and Genomic Regions Related to Economically Important Traits in Hanwoo Cattle

The purpose of the current review was to explore and summarize different studies concerning the detection and characterization of candidate genes and genomic regions associated with economically important traits in Hanwoo beef cattle. Hanwoo cattle, the indigenous premium beef cattle of Korea, were introduced for their marbled fat, tenderness, characteristic flavor, and juiciness. To date, there has been a strong emphasis on the genetic improvement of meat quality and yields, such as backfat thickness (BFT), marbling score (MS), carcass weight (CW), eye muscle area (EMA), and yearling weight (YW), as major selection criteria in Hanwoo breeding programs. Hence, an understanding of the genetics controlling these traits along with precise knowledge of the biological mechanisms underlying the traits would increase the ability of the industry to improve cattle to better meet consumer demands. With the development of high-throughput genotyping, genomewide association studies (GWAS) have allowed the detection of chromosomal regions and candidate genes linked to phenotypes of interest. This is an effective and useful tool for accelerating the efficiency of animal breeding and selection. The GWAS results obtained from the literature review showed that most positional genes associated with carcass and growth traits in Hanwoo are located on chromosomes 6 and 14, among which LCORL, NCAPG, PPARGC1A, ABCG2, FAM110B, FABP4, DGAT1, PLAG1, and TOX are well known. In conclusion, this review study attempted to provide comprehensive information on the identified candidate genes associated with the studied traits and genes enriched in the functional terms and pathways that could serve as a valuable resource for future research in Hanwoo breeding programs.

Leptin receptor-expressing cells in the ventromedial nucleus of the hypothalamus contribute to enhanced CCK-induced satiety following central leptin injection

Others have shown that leptin and cholecystokinin (CCK) act synergistically to suppress food intake. Experiments described here tested whether leptin in the ventromedial hypothalamus (VMH) contributes to the synergy with peripheral CCK in male Sprague Dawley rats. A subthreshold injection of 50-ng leptin into the VMH 1 h before a peripheral injection of 1 µg/kg CCK did not change the response to CCK in rats offered chow or low-fat purified diet, but did exaggerate the reduction in intake of high-fat diet 30 min and 1 h after injection in rats that had been food deprived for 8 h. By contrast, deletion of leptin receptor-expressing cells in the VMH using leptin-conjugated saporin (Lep-Sap) abolished the response to peripheral CCK in chow-fed rats. Lateral ventricle injection of 2-µg leptin combined with peripheral CCK exaggerated the inhibition of chow intake for up to 6 h in control rats treated with Blank-saporin, but not in Lep-Sap rats. Blank-Saporin rats offered low- or high-fat purified diet also demonstrated a dose-response inhibition of intake that reached significance with 1 µg/kg of CCK for both diets. CCK did not inhibit intake of Lep-Sap rats in either low- or high-fat-fed rats. Thus, although basal activation of VMH leptin receptors makes a significant contribution to the synergy with CCK, increased leptin activity in the VMH does not exaggerate the response to CCK in intact rats offered low-fat diets, but does enhance the response in those offered high-fat diet.NEW & NOTEWORTHY Leptin is a feedback signal in the control of energy balance, whereas cholecystokinin (CCK) is a short-term satiety signal that inhibits meal size. The two hormones synergize to promote satiety. We tested whether leptin receptors in the ventromedial nucleus of the hypothalamus (VMH) contribute to the synergy. The results suggest that there is a requirement for a baseline level of activation of leptin receptors in the VMH in order for CCK to promote satiety.

SINE Insertion May Act as a Repressor to Affect the Expression of Pig LEPROT and Growth Traits

Retrotransposon is an important component of the mammalian genome. Previous studies have shown that the expression of protein-coding genes was affected by the insertion of retrotransposon into the proximal genes, and the phenotype variations would be related to the retrotransposon insertion polymorphisms (RIPs). In this study, leptin (LEP), leptin receptor (LEPR), and leptin receptor overlapping transcript (LEPROT), which play important roles in the regulation of fat synthesis and body weight, were screened to search for the RIPs and their effect on phenotype and gene expression, as well as to further study the function of the insertion. The results showed that three RIPs located in intron 1 of LEPROT and intron 2 and 21 of LEPR were identified, and they were all SINEA1, which was one type of retrotransposon. The SINE insertion at the LEPROT was the dominant allele in native pig breeds. The age of 100 kg body weight of SINE+/+ Large White individuals was significantly higher than those of SINE+/− and SINE−/− individuals (p < 0.05). The LEPROT gene expression in the liver and suet of 30-day-old SINE−/− Sujiang piglets were significantly higher than those of SINE+/+ and SINE+/− piglets (p < 0.01). The dual-luciferase reporter gene assay showed that SINE insertion in PK15 and 3T3-L1 cells significantly reduced the promoter activity of the LEPROT gene (p < 0.01). Therefore, SINE insertion can be a repressor to reduce the expression of LEPROT and could be a useful molecular marker for assisted selection of growth traits in pig breeding.

Rules of thumb to obtain, isolate, and preserve porcine peripheral blood mononuclear cells

One of the most used biospecimens in immunology are peripheral blood mononuclear cells (PBMC). PBMC are particularly useful when evaluating immunity through responses of circulating B- and T-cells, during an infection, or after a vaccination. While several reviews and research papers have been published aiming to point out critical steps when sampling, isolating, and cryopreserving human PBMC -or even analyzing any parameter before sampling that could impair the immune assays' outcomes-, there are almost no publications in swine research dealing with these topics. As it has been demonstrated, several factors, such as stress, circadian rhythmicity, or the anticoagulant used have serious negative impact, not only on the separation performance of PBMC, but also on the ulterior immune assays. The present review aims to discuss studies carried out in humans that could shed some light for swine research. When possible, publications in pigs are also discussed. The main goal of the review is to encourage swine researchers to standardize protocols to obtain, manage and preserve porcine PBMC, as well as to minimize, or at least to consider, the bias that some parameters might induce in their studies before, during and after isolating PBMC.

Supplementation with Fermented Feedstuff Enhances Orexin Expression and Secretion Associated with Increased Feed Intake and Weight Gain in Weaned Pigs

The health status of weaned pigs is crucial for their subsequent growth performance. Supplementation with fermented feedstuff is able to improve the feed intake and growth of weaned pigs; however, the exact mechanism behind this is not clear. Hence, in the present study a total of 320 Duroc × Landrace × Yorkshire weaned pigs were selected and allocated to the following two groups: unfermented diet group (UFD) and fermented diet group (FD). The experimental period lasted 21 days. At the end of the experiment, feces, blood, and gastrointestinal tissue samples (including the stomach, jejunum, and ileum) were collected and used for further analysis. The results of growth performance suggested that the FD group had significantly increased (p < 0.05) average daily feed intake (ADFI) and average daily gain (ADG) during the first week, during the last two weeks, and over the entire three-week period compared with the UFD group. The results of the apparent nutrient digestibility of pigs showed that, compared with the UFD group, the FD group showed increased phosphorus (p < 0.05) and CP (p < 0.1) digestibility. There were no significant differences in the serum biochemical parameters between the UFD and FD groups. Moreover, our results showed that the FD group showed significantly increased gene expression of SGLT1 and PepT1 in the jejunum (p < 0.05). Compared with the UFD group, the FD group showed an increased (p < 0.05) serum orexin level and prepro-orexin (PPOX) expression in the gastric fundus, jejunum, and ileum mucosa and increased IGF-1 and IGFR expression in the jejunum. Collectively, these results indicated that supplementation with fermented feedstuff in the diet effectively enhanced the feed intake and growth of weaned pigs and that this may have been caused by the increased orexin, IGF-1, and IGFR serum levels.

Leptin gene contributes to beef marbling standard, meat brightness, meat firmness, and beef fat standard of the Kumamoto sub-breed of Japanese Brown cattle

The Kumamoto sub-breed of Japanese Brown cattle has unique characteristics, such as great growth rate, and their contribution as future breeding materials is expected. To develop a DNA marker for their breeding, we investigated the effects of Leptin gene, controlling energy homeostasis, on carcass traits of the Kumamoto sub-breed. Sequence comparison identified five single nucleotide polymorphisms (SNPs): four linked synonymous mutations and one nonsynonymous mutation. Statistical analysis revealed that c.239C > T (p.A80V) had significant effects on the traits related with quality grade: beef marbling standard (p = 0.0132), meat brightness (p = 0.0383), and meat firmness (p = 0.0115). The C allele showed favorable effects; these scores of the C/C cattle were significantly higher than those of the C/T cattle. On the other hand, the effect of c.399T > C was observed on meat firmness (p = 0.0172) and beef fat standards (BFS) (p = 0.0129). The C/C cattle showed higher values of these traits than the T/T cattle. Our data suggested that these SNPs in Leptin gene could be used as a DNA marker for breeding of the Kumamoto sub-breed.

Impacts of Betaine Addition in Sow and Piglet's Diets on Growth Performance, Plasma Hormone, and Lipid Metabolism of Bama Mini-Pigs

The present study evaluated the effects of betaine addition in sow and piglet's diets on growth performance, plasma hormone, and lipid metabolism of Bama mini-pigs. A total of 26 pregnant Bama mini-pigs and 104 weaned piglets were selected and divided into different dietary treatment groups (details in “Materials and Methods”). Blood and muscle samples were collected at 65-, 95-, and 125-day-old, respectively. The results showed that betaine addition in sow-offspring diets increased (P < 0.05) the body weight at 125-day-old, average daily gain from 35- to 65-day-old, and average daily feed intake at 35–65 and 35–95 days old of pigs compared with the control group. Betaine addition in sow-offspring diets increased (P < 0.05) the plasma gastrin level at 95-day-old, while betaine addition in sow diets decreased (P < 0.05) the plasma peptide YY and leptin levels at 65-day-old pigs. In the longissimus dorsi muscle of pigs, betaine addition in sow and sow-offspring diets increased (P < 0.05) the C12:0 content at 65-day-old while decreased at 95-day-old. Moreover, betaine addition in sow-offspring diets increased the C24:0 content and decreased the C18:1n9t content at 125-day-old (P < 0.05). In the biceps femoris muscle, the contents of C12:0 at 65-day-old and C20:4n6 at 125-day-old were decreased (P < 0.05) after the betaine addition in both sow and piglet's diets. In addition, betaine addition in sow diets decreased (P < 0.05) the C20:0 content at 125-day-old, while betaine addition in sow-offspring diets increased the C18:3n6 and decreased C24:0 contents at 65-day-old pigs (P < 0.05). In the psoas major muscle, betaine addition in sow and sow-offspring diets decreased (P < 0.05) the contents of C18:1n9t at 65-day-old and C20:1 at 95-day-old, while betaine addition in sow diets decreased (P < 0.05) the intramuscular fat content at 125-day-old. Moreover, betaine addition in sow-offspring diets was also associated with muscle lipid deposition and metabolisms by regulating the gene expressions related to fatty acid metabolism. These findings suggested that betaine addition in sow-offspring diets could improve the growth performance, whereas betaine addition in both sow and sow-offspring diets could enhance lipid quality by altering plasma hormone level and fatty acid composition and regulating the gene expressions related to fatty acid metabolism.

Regulation of Swine Growth by Backfat Tissue during Growing and Finishing Stages

Simple Summary

Swine have a large influence on livestock animals. In particular, Korean native pigs (KNPs) have unique traits in their body composition including lipids and proteins. In this study, we performed RNA-sequencing analysis to identify porcine transcriptomic changes during growing and finishing stages in the backfat tissue of KNP and Yorkshire pig crossbreeds. Enrichment analysis revealed that differentially expressed genes (DEGs) were significantly influenced by lipid metabolism and hormonal changes. Network analysis showed that the LEP and ACTC1 genes were connected with significant terminologies which resulted from up- and down-regulated DEGs. The results of our analysis indicate that backfat tissue could regulate swine biology during stages of growth. Consequently, our analysis provided comprehensive understanding for transcriptomic changes during growth periods.

Abstract

Recently, interest in the function of pig backfat (BF) has increased in the field of livestock animals, and many transcriptome-based studies using commercial pig breeds have been conducted. However, there is a lack of comprehensive studies regarding the biological mechanisms of Korean native pigs (KNPs) and Yorkshire pig crossbreeds. In this study, therefore, BF samples of F1 crossbreeds of KNPs and Yorkshire pigs were investigated to identify differentially expressed genes (DEGs) and their related terms using RNA-sequencing analysis. DEG analysis identified 611 DEGs, of which 182 were up-regulated and 429 were down-regulated. Lipid metabolism was identified in the up-regulated genes, whereas growth and maturation-related terminologies were identified in the down-regulated genes. LEP and ACTC1 were identified as highly connected core genes during functional gene network analysis. Fat tissue was observed to affect lipid metabolism and organ development due to hormonal changes driven by transcriptional alteration. This study provides a comprehensive understanding of BF contribution to crossbreeds of KNPs and Yorkshire pigs during growth periods.

DNA polymorphisms of FGFBP1, leptin, κ-casein, and αs1-casein genes and their association with reproductive performance in dromedary she-camels

In livestock, selection programs on reproductive traits are time consuming due to long generation interval and low heritability; however understanding the genetic factors that influence reproductive performance facilitates an accurate selection and genetic improvement of these quantitative traits. Therefore, the aim of this study was to identify the effect of lactation order and polymorphisms of FGFBP1, leptin, κ-casein, and αs1-casein genes on reproductive performance in dromedary she-camels. Blood samples were collected from one hundred she-camels using vacutainer tube containing EDTA as an anticoagulant for DNA extraction. PCR-DNA sequencing approach was performed to investigate the polymorphisms in fragments for coding sequence (CDS) parts of FGFBP1 (539-bp) and leptin (359-bp), 5'-flanking region of κ-casein (488-bp) and intervening non-coding fragment spanning from exon 4 to exon 6 (924-bp) of αs1-casein genes. Results revealed that there were single nucleotide polymorphisms (SNPs) in the investigated genes between enrolled she-camels except for leptin gene that elicited a monomorphic pattern. The identified SNPs allocated camels into different groups according to which animal harbored the explored SNPs. Multiple linear regression analysis (MLR) reveled that identified SNPs and parity order had significant effects on age at first calving (AFC), days open (DO), calving interval (CI), number of services/conception (NS/C) and milk yield traits. Determination coefficients (R²) value indicated also that variability in the phenotypic measurements of studied traits might be correlated with the identified SNPs in the reproduction related genes. This study highlights that parity order has a remarkable effect on reproductive performance. Single nucleotide polymorphisms in the investigated genes could be also used as proxy predictors and genetic markers that permit a marker assisted selection for reproductive performance traits in dromedary she-camels.

Transcriptomic Profiling of Skeletal Muscle Reveals Candidate Genes Influencing Muscle Growth and Associated Lipid Composition in Portuguese Local Pig Breeds

Simple Summary

Screening and interpretation of differentially expressed genes and associated biological pathways was conducted among experimental groups with divergent phenotypes providing valuable information about the metabolic events occurring and identification of candidate genes with major regulation roles. This comparative transcriptomic analysis includes the first RNA-seq analysis of the Longissimus lumborum muscle tissue from two Portuguese autochthonous pig breeds with different genetic backgrounds, Alentejano and Bísaro. Moreover, a complementary candidate gene approach was employed to analyse, by real time qPCR, the expression profile of relevant genes involved in lipid metabolism, and therefore with potential impacts on meat composition. This study contributes to explaining the biological basis of phenotypical differences occurring between breeds, particularly the ones related to meat quality traits that affect consumer interest.

Abstract

Gene expression is one of the main factors to influence meat quality by modulating fatty acid metabolism, composition, and deposition rates in muscle tissue. This study aimed to explore the transcriptomics of the Longissimus lumborum muscle in two local pig breeds with distinct genetic background using next-generation sequencing technology and Real-Time qPCR. RNA-seq yielded 49 differentially expressed genes between breeds, 34 overexpressed in the Alentejano (AL) and 15 in the Bísaro (BI) breed. Specific slow type myosin heavy chain components were associated with AL (MYH7) and BI (MYH3) pigs, while an overexpression of MAP3K14 in AL may be associated with their lower loin proportion, induced insulin resistance, and increased inflammatory response via NFkB activation. Overexpression of RUFY1 in AL pigs may explain the higher intramuscular (IMF) content via higher GLUT4 recruitment and consequently higher glucose uptake that can be stored as fat. Several candidate genes for lipid metabolism, excluded in the RNA-seq analysis due to low counts, such as ACLY, ADIPOQ, ELOVL6, LEP and ME1 were identified by qPCR as main gene factors defining the processes that influence meat composition and quality. These results agree with the fatter profile of the AL pig breed and adiponectin resistance can be postulated as responsible for the overexpression of MAP3K14′s coding product NIK, failing to restore insulin sensitivity.

Effects of Opuntia ficus-indica in the diet of primiparous sows on the metabolic profile during late gestation and lactation and feed intake during lactation

The goal of this study was to evaluate the effects of dietary Opuntia ficus-indica L. (OFI) on the metabolic profile of primiparous sows during late gestation and lactation, and its impact on voluntary feed intake (VFI) during lactation. From day 85 of gestation to weaning, 32 sows were divided into four feeding schemes (n = 8 sows/scheme): Basal diet (BD) without OFI supplementation; Test scheme I, BD during gestation and BD + OFI during lactation; Test scheme II, BD + OFI during both gestation and lactation, and Test scheme III, BD + OFI during gestation and BD during lactation. Blood samples were obtained during gestation (day 85 and 100) and lactation (day 0, 3, 7, 14 and 21) to determine plasma glucose, insulin, triglycerides, leptin, osteocalcin, ghrelin and agouti-related protein (AgRP). VFI was higher (20% higher than that of controls) in sows that received dietary OFI during lactation (p < .05). The concentration of plasma glucose was lower in sows that consumed OFI than sows fed the conventional diet (p < .05). Plasma insulin concentrations were higher in sows that consumed OFI, than in sows that did not (p < .05). Triglyceride concentrations during gestation, farrowing and lactation were also lower in sows that consumed OFI (p < .05). OFI intake caused lower plasma concentrations of leptin during lactation (p < .05). Osteocalcin was higher in sows that consumed OFI versus controls (p < .05): 8.6% and 13.4% during gestation and lactation respectively. From day 3 of lactation, sows that consumed OFI had higher concentrations of ghrelin (p < .05). The concentration of plasma AgRP was higher (p < .05) in sows that consumed OFI versus controls: 3.1% and 14.2% in gestation and lactation respectively. We concluded that OFI intake by primiparous sows during late gestation and lactation favourably modulated the factors that caused insulin resistance and increased sow performance.

Detection of polymorphisms in the bovine leptin receptor gene affects fat deposition in two Chinese beef cattle breeds

Leptin receptor (LEPR) gene play a pivotal role in the regulation of fat deposition and energy homeostasis. This study investigated the presence and frequency of polymorphisms of bovine LEPR gene and determine whether the polymorphisms are associated with the fat deposition in two Chinese beef cattle breeds. Quantitative real-time polymerase chain reactions identified that the expression of LEPR gene was highest in the liver and subcutaneous fat. Four single nucleotide polymorphisms (SNPs) were identified including g.24169C > T, g.24256T > A, g.24267 G > C and g.24413T > A. A greater backfat thickness was associated with the AA genotype of g.24256T > A compared to the TT genotype. A greater intramuscular fat content was associated with the GG genotype of g.24267 G > C compared to the CC genotype. Both g.24169C > T and g.24413T > A were not correlated with fat deposition. These results indicated that the SNP g.24256T > A and g.24267 G > C of LEPR gene may be useful markers for genetic improvement of fat deposition in Chinese beef cattle breeds.

Lipid Deposition and Metabolism in Local and Modern Pig Breeds: A Review

Modern pig breeds, which have been genetically improved to achieve fast growth and a lean meat deposition, differ from local pig breeds with respect to fat deposition, fat specific metabolic characteristics and various other properties. The present review aimed to elucidate the mechanisms underlying the differences between fatty local and modern lean pig breeds in adipose tissue deposition and lipid metabolism, taking into consideration morphological, cellular, biochemical, transcriptomic and proteomic perspectives. Compared to modern breeds, local pig breeds accumulate larger amounts of fat, which generally contains more monounsaturated and saturated fatty acids; they exhibit a higher adipocyte size and higher activity of lipogenic enzymes. Studies using transcriptomic and proteomic approaches highlighted several processes like immune response, fatty-acid turn-over, oxidoreductase activity, mitochondrial function, etc. which differ between local and modern pig breeds.

Impact of genotype, body weight and sex on the prenatal muscle transcriptome of Iberian pigs

Growth is dependent on genotype and diet, even at early developmental stages. In this study, we investigated the effects of genotype, sex, and body weight on the fetal muscle transcriptome of purebred Iberian and crossbred Iberian x Large White pigs sharing the same uterine environment. RNA sequencing was performed on 16 purebred and crossbred fetuses with high body weight (340±14g and 415±14g, respectively) and 16 with low body weight (246±14g and 311±14g, respectively), on gestational day 77. Genotype had the greatest effect on gene expression, with 645 genes identified as differentially expressed (DE) between purebred and crossbred animals. Functional analysis showed differential regulation of pathways involved in energy and lipid metabolism, muscle development, and tissue disorders. In purebred animals, fetal body weight was associated with 35 DE genes involved in development, lipid metabolism and adipogenesis. In crossbred animals, fetal body weight was associated with 60 DE genes involved in muscle development, viability, and immunity. Interestingly, the results suggested an interaction genotype*weight for some DE genes. Fetal sex had only a modest effect on gene expression. This study allowed the identification of genes, metabolic pathways, biological functions and regulators related to fetal genotype, weight and sex, in animals sharing the same uterine environment. Our findings contribute to a better understanding of the molecular events that influence prenatal muscle development and highlight the complex interactions affecting transcriptional regulation during development.

Comparing the mRNA expression profile and the genetic determinism of intramuscular fat traits in the porcine gluteus medius and longissimus dorsi muscles

BACKGROUND

Intramuscular fat (IMF) content and composition have a strong impact on the nutritional and organoleptic properties of porcine meat. The goal of the current work was to compare the patterns of gene expression and the genetic determinism of IMF traits in the porcine gluteus medius (GM) and longissimus dorsi (LD) muscles.

RESULTS

A comparative analysis of the mRNA expression profiles of the pig GM and LD muscles in 16 Duroc pigs with available microarray mRNA expression measurements revealed the existence of 106 differentially expressed probes (fold-change > 1.5 and q-value < 0.05). Amongst the genes displaying the most significant differential expression, several loci belonging to the Hox transcription factor family were either upregulated (HOXA9, HOXA10, HOXB6, HOXB7 and TBX1) or downregulated (ARX) in the GM muscle. Differences in the expression of genes with key roles in carbohydrate and lipid metabolism (e.g. FABP3, ORMDL1 and SLC37A1) were also detected. By performing a GWAS for IMF content and composition traits recorded in the LD and GM muscles of 350 Duroc pigs, we identified the existence of one region on SSC14 (110-114 Mb) displaying significant associations with C18:0, C18:1(n-7), saturated and unsaturated fatty acid contents in both GM and LD muscles. Moreover, we detected several genome-wide significant associations that were not consistently found in both muscles. Further studies should be performed to confirm whether these associations are muscle-specific. Finally, the performance of an eQTL scan for 74 genes, located within GM QTL regions and with available microarray measurements of gene expression, made possible to identify 14 cis-eQTL regulating the expression of 14 loci, and six of them were confirmed by RNA-Seq.

CONCLUSIONS

We have detected significant differences in the mRNA expression patterns of the porcine LD and GM muscles, evidencing that the transcriptomic profile of the skeletal muscle tissue is affected by anatomical, metabolic and functional factors. A highly significant association with IMF composition on SSC14 was replicated in both muscles, highlighting the existence of a common genetic determinism, but we also observed the existence of a few associations whose magnitude and significance varied between LD and GM muscles.

Physiological and metabolic control of diet selection

The fact that most farm animals have no dietary choice under commercial practices translates the dietary decisions to the carers. Thus, a lack of understanding of the principles of dietary choices is likely to result in a high toll for the feed industry. In healthy animals, diet selection and, ultimately, feed intake is the result of factoring together the preference for the feed available with the motivation to eat. Both are dynamic states and integrate transient stimulus derived from the nutritional status, environmental and social determinants of the animal with hard-wired genetic mechanisms. Peripheral senses are the primary inputs that determine feed preferences. Some of the sensory aspects of feed, such as taste, are innate and genetically driven, keeping the hedonic value of feed strictly associated with a nutritional frame. Sweet, umami and fat tastes are all highly appetitive. They stimulate reward responses from the brain and reinforce dietary choices related to essential nutrients. In contrast, aroma (smell) recognition is a plastic trait and preferences are driven mostly by learned experience. Maternal transfer through perinatal conditioning and the individual’s own innate behaviour to try or to avoid novel feed (often termed as neophobia) are known mechanisms where the learning process strongly affects preferences. In addtition, the motivation to eat responds to episodic events fluctuating in harmony with the eating patterns. These signals are driven mainly by gastrointestinal hormones (such as cholecystokinin [CCK] and glucagon-like peptide 1 [GLP-1]) and load. In addition, long-term events generate mechanisms for a sustainable nutritional homeostasis managed by tonic signals from tissue stores (i.e. leptin and insulin). Insulin and leptin are known to affect appetite by modulating peripheral sensory inputs. The study of chemosensory mechanisms related to the nutritional status of the animal offers novel tools to understand the dynamic states of feed choices so as to meet nutritional and hedonic needs. Finally, a significant body of literature exists regarding appetite driven by energy and amino acids in farm animals. However, it is surprising that there is scarcity of knowledge regarding what and how specific dietary nutrients may affect satiety. Thus, a better understanding on how bitter compounds and excess dietary nutrients (i.e. amino acids) play a role in no-choice animal feeding is an urgent topic to be addressed so that right choices can be made on the animal’s behalf.

Changes in faecal bacteria during fattening in finishing swine

Body fat accumulation in mice and human is linked to the percentage of Firmicutes and Bacteroidetes, two bacterial phyla dominant in the large intestine. However, little is known about the relationship between the composition of the gut microbiota and fattening in pig. This study aimed to investigate the abundance of Firmicutes, Bacteroidetes, and Bacteroides, which is the major genus within Bacteroidetes, in porcine faeces during fattening. Ten 4-month-old crossbred pigs were given free access to commercial feed for fattening and water for 14 weeks. Daily feed intake and body weight were measured every 2 weeks. Faecal samples were collected at 0, 4, 8, and 14 weeks, and plasma samples were collected every 2 weeks. Daily feed intake increased until 8 weeks, and then decreased. Body weight increased with fattening during the experimental period. Feed efficiency showed high values at 0-4 and 6-8 weeks. The level of Firmicutes increased (P < 0.05), whereas those of Bacteroides and Bacteroidetes decreased (P < 0.05) with fattening. The total short chain fatty acid content in the faeces increased (P < 0.05) with fattening until 8 weeks and then decreased (P < 0.05) at 14 weeks. There were no significant relationships between the level of Firmicutes and feed intake or plasma leptin concentration. The levels of Bacteroidetes and Bacteroides correlated with feed intake, body weight, and plasma leptin or plasma urea nitrogen (PUN) concentration. Our results suggested that the level of Firmicutes increased and those of Bacteroidetes and Bacteroides decreased with increase in feed intake and body weight, similar to previous results obtained for mice and human. However, energy extraction from feed was not influenced by compositional alteration of gut flora, because daily gain and feed efficiency did not show high values towards the end of the fattening period. Manipulating the gut microbiota might help improve fattening performance, although further studies are necessary to understand the relationships between the composition of gut microbiota and energy absorption.

Development and validation of an assay for measurement of leptin in pig saliva

Background

Leptin has been measured in human in saliva samples. However, the low leptin concentration found in this biological fluid makes necessary the use of high sensitive methods. To the authors’ knowledge, leptin has not been measured in porcine saliva. This study aimed to develop and validate a time-resolved immunofluorometric assay (TR-IFMA) for salivary leptin measurements in pigs, using a species-specific antibody, and to evaluate how salivary leptin changes with body weight, food ingestion, and in experimental models of stress and inflammation. Polyclonal antibodies were produced in rabbits immunized with recombinant porcine leptin and used to develop a sandwich TR-IFMA.

Results

The method had intra-assay and inter-assay coefficients of variation lower than 10 and 16 %, respectively. The assay was accurate and the low limit of detection allowed detection of leptin in all analyzed samples. Salivary leptin concentration was positively correlated to body weight (r = 0.58, P = 0.01) and increased after food ingestion (P < 0.001) and after 24 h of applying a model of experimental inflammation by turpentine injection (P < 0.05). However, it did not significantly change after a model of acute stress consisting of a nose snare restraining.

Conclusion

These results indicate that the developed assay can measure leptin in porcine saliva in a reliable way and that leptin in saliva is influenced by body weight, food ingestion and inflammation.

Regulation of Leptin mRNA and Protein Expression in Pituitary Somatotropes

Leptin, the ob protein, regulates food intake and satiety and can be found in the anterior pituitary. Leptin antigens and mRNA were studied in the anterior pituitary (AP) cells of male and female rats to learn more about its regulation. Leptin antigens were found in over 40% of cells in diestrous or proestrous female rats and in male rats. Lower percentages of AP cells were seen in the estrous population (21 ± 7%). During peak expression of antigens, co-expression of leptin and growth hormone (GH) was found in 27 ± 4% of AP cells. Affinity cytochemistry studies detected 24 ± 3% of AP cells with leptin proteins and growth hormone releasing hormone (GHRH) receptors. These data suggested that somatotropes were a significant source of leptin. To test regulatory factors, estrous and diestrous AP populations were treated with estrogen (100 pM) and/or GHRH (2 nM) to learn if either would increase leptin expression in GH cells. To rule out the possibility that the immunoreactive leptin was bound to receptors in somatotropes, leptin mRNA was also detected by non-radioactive in situ hybridization in this group of cells. In estrous female rats, 39 ± 0.9% of AP cells expressed leptin mRNA, indicating that the potential for leptin production was greater than predicted from the immunolabeling. Estrogen and GHRH together (but not alone) increased percentages of cells with leptin protein (41 ± 9%) or mRNA (57 ± 5%). Estrogen and GHRH also increased the percentages of AP cells that co-express leptin mRNA and GH antigens from 20 ± 2% of AP cells to 37 ± 5%. Although the significance of leptin in GH cells is not understood, it is clearly increased after stimulation with GHRH and estrogen. Because GH cells also have leptin receptors, this AP leptin may be an autocrine or paracrine regulator of pituitary cell function.

Differential expression of six genes in fat-type Hungarian Mangalica and other pigs

Abstract. In order to identify potential variances in gene expression of phenotypically different pig breeds, six fat-metabolism-related genes were analyzed in backfat and muscle tissues of fat-type Mangalica (MAN), Mangalica × Duroc (MD), and lean-type Hungarian Large White (HLW) and Pietrain × Duroc (PD) pigs by means of quantitative reverse transcription PCR (qRT-PCR). Higher (P < 0.05) adipocyte fatty-acid-binding protein (A-FABP) expression was observed in backfat and muscle tissues of purebred and crossbred MAN than in those of HLW and PD. In all breeds and crosses, adiponectin (ADIPOQ) was predominantly expressed in backfat at a similar level (P > 0.05), whereas muscle ADIPOQ expression was highest (P < 0.05) in MAN and MD. Levels of fatty acid synthase (FASN) mRNA were greatest in MAN, moderate in MD, and lowest in HLW and PD backfat and muscle. The fat mass and obesity-associated gene (FTO) was more abundant in MAN and MD backfat, whereas muscle expressions did not differ (P > 0.05) between breeds. Regarding leptin (LEP) expression, MAN produced the greatest levels in backfat, while HLW produced the lowest. In muscle, highest LEP was detected in MAN and MD. Between groups, perilipin 2 (PLIN2) was expressed similarly in backfat; however, PLIN2 was more abundant in muscle of MAN and MD than in that of HLW and PD. Differences in gene expression can contribute to the development of the characteristic fatty phenotype in MAN pigs. The identification of differentially expressed genes facilitates targeted sequencing and genotyping efforts for further studies.

The effect of SCD and LEPR genetic polymorphisms on fat content and composition is maintained throughout fattening in Duroc pigs

The effects of the stearoyl-CoA desaturase (SCD; AY487830:g.2228T>C) and leptin receptor (LEPR; NM_001024587:g.1987C>T) polymorphisms on fat content and fatty acid (FA) composition were investigated throughout fattening. Samples of Longissimus thoracis (LT) and subcutaneous fat (SF) from 214 Duroc barrows were collected from 160days to slaughter age (220days) using a longitudinal design. Results indicated that the positive effect of the T allele at the SCD gene on monounsaturated FA and of the T allele at the LEPR gene on saturated FA are maintained throughout the growing-finishing period, both in LT and SF. In LEPR, however, compositional changes, particularly in SF, are a result of increased fatness. There is very limited evidence of genotype by age interaction, and thus it is concluded that the combined selection for the SCD T and LEPR C alleles is a good strategy to increase the MUFA/SFA ratio regardless of the age at slaughter.

Effects of Dietary Crude Protein Levels and Cysteamine Supplementation on Protein Synthetic and Degradative Signaling in Skeletal Muscle of Finishing Pigs

Dietary protein levels and cysteamine (CS) supplementation can affect growth performance and protein metabolism of pigs. However, the influence of dietary protein intake on the growth response of CS-treated pigs is unclear, and the mechanisms involved in protein metabolism remain unknown. Hence, we investigated the interactions between dietary protein levels and CS supplementation and the effects of dietary crude protein levels and CS supplementation on protein synthetic and degradative signaling in skeletal muscle of finishing pigs. One hundred twenty barrows (65.84 ± 0.61 kg) were allocated to a 2 × 2 factorial arrangement with five replicates of six pigs each. The primary variations were dietary crude protein (CP) levels (14% or 10%) and CS supplemental levels (0 or 700 mg/kg). The low-protein (LP) diets (10% CP) were supplemented with enough essential amino acids (EAA) to meet the NRC AA requirements of pigs and maintain the balanced supply of eight EAA including lysine, methionine, threonine, tryptophan, valine, phenylalanine, isoleucine, and leucine. After 41 days, 10 pigs per treatment were slaughtered. We found that LP diets supplemented with EAA resulted in decreased concentrations of plasma somatostatin (SS) (P<0.01) and plasma urea nitrogen (PUN) (P<0.001), while dietary protein levels did not affect other traits. However, CS supplementation increased the average daily gain (P<0.001) and lean percentage (P<0.05), and decreased the feed conversion ratio (P<0.05) and back fat (P<0.05). CS supplementation also increased the concentrations of plasma insulin-like growth factor 1 (IGF-1) (P<0.001), and reduced the concentrations of leptin, SS, and PUN (P<0.001). Increased mRNA abundance of Akt1 and IGF-1 signaling (P<0.001) and decreased mRNA abundance of Forkhead Box O (FOXO) 4 (P<0.01) and muscle atrophy F-box (P<0.001) were observed in pigs receiving CS. Additionally, CS supplementation increased the protein levels for the phosphorylated mammalian target of rapamycin (mTOR), eIF-4E binding protein 1, and ribosomal protein S6 kinase 1 (P<0.001). There were no interactions between dietary protein levels and CS supplementation for all traits. In conclusion, dietary protein levels and CS supplementation influenced growth and protein metabolism through independent mechanisms in pigs. In addition, LP diets supplemented with EAA did not affect growth performance and other traits except the concentrations of SS and PUN probably through maintenance of protein synthesis and degradation signaling. Moreover, CS supplementation improved growth performance by increasing plasma IGF-1 concentrations possibly through alterations of mTOR and Akt/FOXO signaling pathways in skeletal muscle of finishing pigs.

Adipose depots differ in cellularity, adipokines produced, gene expression, and cell systems

The race to manage the health concerns related to excess fat deposition has spawned a proliferation of clinical and basic research efforts to understand variables including dietary uptake, metabolism, and lipid deposition by adipocytes. A full appreciation of these variables must also include a depot-specific understanding of content and location in order to elucidate mechanisms governing cellular development and regulation of fat deposition. Because adipose tissue depots contain various cell types, differences in the cellularity among and within adipose depots are presently being documented to ascertain functional differences. This has led to the possibility of there being, within any one adipose depot, cellular distinctions that essentially result in adipose depots within depots. The papers comprising this issue will underscore numerous differences in cellularity (development, histogenesis, growth, metabolic function, regulation) of different adipose depots. Such information is useful in deciphering adipose depot involvement both in normal physiology and in pathology. Obesity, diabetes, metabolic syndrome, carcass composition of meat animals, performance of elite athletes, physiology/pathophysiology of aging, and numerous other diseases might be altered with a greater understanding of adipose depots and the cells that comprise them-including stem cells-during initial development and subsequent periods of normal/abnormal growth into senescence. Once thought to be dormant and innocuous, the adipocyte is emerging as a dynamic and influential cell and research will continue to identify complex physiologic regulation of processes involved in adipose depot physiology.

Expression of leptin and its long form receptor at the porcine maternal-fetal interface: contrasting healthy and arresting conceptus attachment sites during early and mid-pregnancy

BACKGROUND

It is well established that spontaneous conceptus loss in swine is associated with an imbalance of both angiogenic and immunological factors. Leptin (LEP), a metabolic hormone, has also been implicated in the promotion of angiogenesis. In this study, LEP and its long form receptor (OB-Rb) were evaluated during porcine pregnancy to assess their basal level of expression and their potential role in conceptus development.

METHODS

Expression and secretion of LEP and OB-Rb were quantified in the endometrium of non-pregnant (n = 5), and in the endometrium and chorioallantoic membrane (CAM) of pregnant sows (parity 2 to 5) at gestational days (gd) 20 (n = 8) and 50 (n = 8). Data were analyzed by a 3-way ANOVA testing the effects of conceptus health, tissue type and gestational day.

RESULTS

Leptin and OB-Rb transcripts were significantly higher (P < 0.05) in pregnant than in non-pregnant sows. Significantly greater LEP (P < 0.001) was detected in the endometrial tissue at gd20 compared with gd50. At the protein level, the lowest LEP expression (P < 0.01) was detected in the CAM at gd50, while OB-Rb protein was significantly lower (P < 0.01) at gd50 in the CAM than in the endometrium collected from gd20 and gd50 conceptus attachment sites. Immunofluorescence staining confirmed the expression of these proteins at both gestational days and in both tissue types.

CONCLUSIONS

Changes in the expression patterns of LEP and OB-Rb between gd20 and gd50 suggest a role for the LEP/OB-R complex at the early stages of porcine pregnancy, possibly affecting the attachment process. Further mechanistic studies are warranted to understand the specific role of leptin in porcine pregnancy.

Genome-wide association and pathway analysis of feed efficiency in pigs reveal candidate genes and pathways for residual feed intake

Residual feed intake (RFI) is a complex trait that is economically important for livestock production; however, the genetic and biological mechanisms regulating RFI are largely unknown in pigs. Therefore, the study aimed to identify single nucleotide polymorphisms (SNPs), candidate genes and biological pathways involved in regulating RFI using Genome-wide association (GWA) and pathway analyses. A total of 596 Yorkshire boars with phenotypes for two different measures of RFI (RFI1 and 2) and 60k genotypic data was used. GWA analysis was performed using a univariate mixed model and 12 and 7 SNPs were found to be significantly associated with RFI1 and RFI2, respectively. Several genes such as xin actin-binding repeat-containing protein 2 (XIRP2),tetratricopeptide repeat domain 29 (TTC29),suppressor of glucose, autophagy associated 1 (SOGA1),MAS1,G-protein-coupled receptor (GPCR) kinase 5 (GRK5),prospero-homeobox protein 1 (PROX1),GPCR 155 (GPR155), and FYVE domain containing the 26 (ZFYVE26) were identified as putative candidates for RFI based on their genomic location in the vicinity of these SNPs. Genes located within 50 kbp of SNPs significantly associated with RFI and RFI2 (q-value ≤ 0.2) were subsequently used for pathway analyses. These analyses were performed by assigning genes to biological pathways and then testing the association of individual pathways with RFI using a Fisher's exact test. Metabolic pathway was significantly associated with both RFIs. Other biological pathways regulating phagosome, tight junctions, olfactory transduction, and insulin secretion were significantly associated with both RFI traits when relaxed threshold for cut-off p-value was used (p ≤ 0.05). These results implied porcine RFI is regulated by multiple biological mechanisms, although the metabolic processes might be the most important. Olfactory transduction pathway controlling the perception of feed via smell, insulin pathway controlling food intake might be important pathways for RFI. Furthermore, our study revealed key genes and genetic variants that control feed efficiency that could potentially be useful for genetic selection of more feed efficient pigs.

Effect of peripartal feeding strategy on colostrum yield and composition in sows

Research showed a positive association between back fat (BF) change the week before farrowing and colostrum yield (CY). This study tested the causality of this association, hence to optimize CY by altering the sows' peripartal feeding strategy. Sows were randomly divided into 2 treatment groups at d 108 of gestation. The first group (L, n = 28) received 1.5 kg feed·d(-1), the second group (H, n = 22) received 3 times 1.5 kg feed·d(-1) until farrowing. Daily feed intake and CY were measured. Colostrum was analyzed for nutrient composition, AA and fatty acids, IgG and IgA. Sow serum was obtained at d 108 of gestation and d 1 of lactation after overnight fasting and analyzed for NEFA, (iso)butyrylcarnitine (C4), creatinine, urea, 3-OH-butyrylcarnitine (3-OH-C4), IgG, and IgA. Based on BF at d 108, sows were divided into body condition (BC) groups: skinny (<17 mm, n = 15), moderate (17 to 23 mm, n = 21), fat (>23 mm, n = 14). We performed ANOVA with treatment and BC as fixed factors and Scheffé post-hoc test. The week before farrowing, the L group had the lowest daily feed intake (DFI; 1.5 kg), and within the H group, fat sows (3.8 kg) had a lower DFI than skinny sows (4.3 kg; p = 0.006). The H group tended to have a greater total CY (P = 0.074) and had a greater CY/kg liveborn piglet (P = 0.018) than the L group. Compared with sows in moderate BC, fat sows had a lower total CY (P = 0.044) and a lower CY/kg liveborn piglet (P = 0.005). The H group had a greater concentration of lactose (p = 0.009) and n-3 PUFA (p < 0.001) but a lower concentration of protein (p = 0.040) in colostrum than the L group. The concentration of IgG and IgA did not differ between treatment and BC groups. Serum parameters at d 108 were similar between the treatment groups and BC groups. At d 1, the H group mobilized less body fat (NEFA: p = 0.002) and protein (creatinine: p < 0.001, C4: p = 0.016) reserves but had a greater ratio urea:NEFA (p < 0.001) and less ketone bodies (3-OH-C4: p < 0.001) compared with the L group. This indicates a more balanced entry of metabolites in the citric acid cycle and thus a better support of the maternal peripartal metabolism in the H group. Serum parameters did not differ between BC groups. Both CY and composition can be influenced by the peripartal feeding strategy and BC. The highest CY and most beneficial colostrum composition were obtained when sows entered the farrowing unit in a moderate BC and were provided a high peripartal feeding strategy.

Changes in back fat thickness during late gestation predict colostrum yield in sows

Directing protein and energy sources towards lactation is crucial to optimise milk production in sows but how this influences colostrum yield (CY) remains unknown. The aim of this study was to identify associations between CY and the sow's use of nutrient resources. We included 37 sows in the study that were all housed, fed and managed similarly. Parity, back fat change (ΔBF), CY and performance parameters were measured. We obtained sow serum samples 3 to 4 days before farrowing and at D1 of lactation following overnight fasting. These were analysed for non-esterified fatty acids (NEFA), urea, creatinine, (iso)butyrylcarnitine (C4) and immunoglobulins G (IgG) and A (IgA). The colostrum samples collected 3, 6 and 24 h after the birth of the first piglet were analysed for their nutrient and immunoglobulins content. The technical parameters associated with CY were parity group (a; parities 1 to 3=value 0 v. parities 4 to 7=value 1) and ΔBF D85-D109 of gestation (mm) (b): CY (g)=4290-842a-113b. (R 2=0.41, P<0.001). The gestation length (P<0.001) and the ΔBF between D109 and D1 of lactation (P=0.050) were identified as possible underlying factors of the parity group. The metabolic parameters associated with CY were C4 at 3 to 4 days before farrowing (a), and 10logC4 (b) and 10logNEFA (c) at D1 of lactation: CY (g)=3582-1604a+1007b-922c (R 2=0.39, P=0.001). The colostrum composition was independent of CY. The negative association between CY and ΔBF D85-D109 of gestation could not be further explained based on our data. Sows that were catabolic 1 week prior to farrowing seemed unable to produce colostrum to their full potential. This was especially the case for sows with parities 4 to 7, although they had a similar feed intake, litter birth weight and colostrum composition compared with parities 1 to 3 sows. In conclusion, this study showed that parity and the use of body fat and protein reserves during late gestation were associated with CY, indicating that proper management of the sow's body condition during late gestation could optimise the intrinsic capacity of the sow's CY.

Effects of nesfatin-1 on food intake and LH secretion in prepubertal gilts and genomic association of the porcine NUCB2 gene with growth traits

Nesfatin-1, a product of the nucleobindin 2 (NUCB2) gene, purportedly plays important roles in whole-body energy homeostasis. Experiments were conducted to determine how NUCB2 expression in fat depots may be controlled in the pig and to test the hypothesis that nesfatin-1 regulates appetite and LH secretion in the gilt. Prepubertal gilts were used to study expression of NUCB2 in fat and the effects of intracerebroventricular (i.c.v.) injection of nesfatin-1 on food intake and pituitary hormone secretion. Growing pigs (gilts and barrows at 22 wk of age, n = 1,145) or sexually mature gilts (n = 439) were used to test association of SNP in the NUCB2 gene with growth traits. The expression of NUCB2 was similar for subcutaneous fat compared with perirenal fat. An i.c.v. injection of the melanocortin-4 receptor agonist [Nle⁴, d-Phe⁷]-α-melanocyte-stimulating hormone did not alter expression of NUCB2 mRNA in the hypothalamus but reduced (P = 0.056) NUCB2 mRNA expression in subcutaneous fat. Short-term (7 d) submaintenance feeding reduced (P < 0.05) BW and did not alter expression of mRNA for NUCB2, visfatin, or leptin but increased (P < 0.05) expression of adiponectin mRNA in fat. Central injection of nesfatin-1 suppressed (P < 0.001) feed intake. Secretion of LH was greater (P < 0.01) after i.c.v. injection of nesfatin-1 than after saline. Single nucleotide polymorphisms in the porcine NUCB2 gene were not associated with adiposity of growing pigs or age at puberty in gilts but were associated (P < 0.05) with BW at puberty. These data indicate that NUCB2 is expressed in fat depots of the pig and that the level of expression is sensitive to stimulation of appetite-regulating pathways in the hypothalamus. It is confirmed herein that nesfatin-1 can regulate appetite in the pig and affect the gonadotropic axis of the prepubertal pig. Association of SNP in the porcine NUCB2 gene with BW at puberty suggests that regulation of appetite by nesfatin-1 in the pig affects growth, which may have important consequences for adult phenotypes.

Peripartum changes in orexigenic and anorexigenic hormones in relation to back fat thickness and feeding strategy of sows

Highly prolific sows often experience peripartum hypophagia, resulting in decreased production rate. Leptin, ghrelin, and resistin are known as feed intake-regulating hormones in many species, but it is yet unknown how feeding strategy and body condition will affect these hormones around parturition in sows. In the present study, a total of 63 sows, parity 2 to 7 were divided over 2 treatment groups which were fed either restricted (RESTRICT) or ad libitum (ADLIB) during the peripartum period (day 106 of gestation until day 7 of lactation). Within each treatment group, sows were assigned to 1 of 3 body condition groups based on back fat thickness at day 106 of gestation: <18 mm (LEAN), between 18 and 22 mm (MODERATE), and >22 mm (FAT). Postprandial blood samples were taken on days 107, 109, and 112 of gestation and on days 1, 3, and 5 of lactation. With RIA, leptin, ghrelin, and resistin of each sample were analyzed. For both leptin and resistin, the hormonal profile gradually increased throughout the peripartum period (P < 0.001), whereas ghrelin peaked on day 109 of gestation compared with day 107 of gestation and day 1 of lactation. Other time points were intermediate between those two (P < 0.001). The peripartum profile of leptin was significantly higher for FAT sows than for the 2 other condition groups. No effect of body condition on ghrelin and resistin concentrations was observed. None of the 3 measured hormones were affected by feeding strategy. In conclusion, during the peripartum period feed intake of sows did not affect leptin, ghrelin, or resistin profiles. Leptin was the only hormone investigated that reflected body condition. Although body condition and late gestation feed intake have been previously described as risk factors for peripartum hypophagia, they did not induce hypophagia in any of the sows or affect the profile of the observed feed intake-regulating hormones during the peripartum period.

Transcriptional Characterization of Porcine Leptin and Leptin Receptor Genes

The leptin (LEP) and its receptor (LEPR) regulate food intake and energy balance through hypothalamic signaling. However, the LEP-LEPR axis seems to be more complex and its expression regulation has not been well described. In pigs, LEP and LEPR genes have been widely studied due to their relevance. Previous studies reported significant effects of SNPs located in both genes on growth and fatness traits. The aim of this study was to determine the expression profiles of LEP and LEPR across hypothalamic, adipose, hepatic and muscle tissues in Iberian x Landrace backcrossed pigs and to analyze the effects of gene variants on transcript abundance. To our knowledge, non porcine LEPR isoforms have been described rather than LEPRb. A short porcine LEPR isoform (LEPRa), that encodes a protein lacking the intracellular residues responsible of signal transduction, has been identified for the first time. The LEPRb isoform was only quantifiable in hypothalamus while LEPRa appeared widely expressed across tissues, but at higher levels in liver, suggesting that both isoforms would develop different roles. The unique LEP transcript showed expression in backfat and muscle. The effects of gene variants on transcript expression revealed interesting results. The LEPRc.1987C>T polymorphism showed opposite effects on LEPRb and LEPRa hypothalamic expression. In addition, one out of the 16 polymorphisms identified in the LEPR promoter region revealed high differential expression in hepatic LEPRa. These results suggest a LEPR isoform-specific regulation at tissue level. Conversely, non-differential expression of LEP conditional on the analyzed polymorphisms could be detected, indicating that its regulation is likely affected by other mechanisms rather than gene sequence variants. The present study has allowed a transcriptional characterization of LEP and LEPR isoforms on a range of tissues. Their expression patterns seem to indicate that both molecules develop peripheral roles apart from their known hypothalamic signal transduction function.

A gene variation (rs12691) in the CCAT/enhancer binding protein α modulates glucose metabolism in metabolic syndrome

BACKGROUND AND AIMS

CCAAT/enhancer-binding protein alpha (CEBPA) is a transcription factor involved in adipogenesis and energy homeostasis. Caloric restriction reduces CEBPA protein expression in patients with metabolic syndrome (MetS). A previous report linked rs12691 SNP in CEBPA to altered concentration of fasting triglycerides. Our objective was to assess the effects of rs12691 in glucose metabolism in Metabolic Syndrome (MetS) patients.

METHODS AND RESULTS

Glucose metabolism was assessed by static (glucose, insulin, adiponectin, leptin and resistin plasma concentrations) and dynamic (disposition index, insulin sensitivity index, HOMA-IR and acute insulin response to glucose) indices, performed at baseline and after 12 weeks of 4 dietary interventions (high saturated fatty acid (SFA), high monounsaturated fatty acid (MUFA), low-fat and low-fat-high-n3 polyunsaturated fatty acid (PUFA)) in 486 subjects with MetS. Carriers of the minor A allele of rs12691 had altered disposition index (p = 0.0003), lower acute insulin response (p = 0.005) and a lower insulin sensitivity index (p = 0.025) indicating a lower insulin sensitivity and a lower insulin secretion, at baseline and at the end of the diets. Furthermore, A allele carriers displayed lower HDL concentration.

CONCLUSION

The presence of the A allele of rs12691 influences glucose metabolism of MetS patients.

An overview of molecular and cellular mechanisms associated with porcine pregnancy success or failure

Prenatal mortality remains one of the major constraints for the commercial pig industry in North America. Twenty to thirty per cent of the conceptuses are lost early in gestation and an additional 10-15% is lost by mid-to-late gestation. Research over the last two decades has provided critical insights into how uterine capacity, placental efficiency, genetics, environment, nutrition and immune mechanisms impact successful conceptus growth; however, the exact cause and effect relationship in the context of foetal loss has yet to be determined. Similar to other mammalian species such as the human, mouse, rat, and primates, immune cell enrichment occurs at the porcine maternal-foetal interface during the window of conceptus attachment. However, unlike other species, immune cells are solely recruited by conceptus-derived signals. As pigs have epitheliochorial placentae where maternal and foetal tissue layers are separate, it provides an ideal model to study immune cell interactions with foetal trophoblasts. Our research is focused on the immune-angiogenesis axis during porcine pregnancy. It is well established that immune cells are recruited to the maternal-foetal interface, but their pregnancy specific functions and how the local milieu affects angiogenesis and inflammation at the site of foetal arrest remain unknown. Through a better understanding of how immune cells modulate crosstalk between the conceptus and the mother, it might be possible to therapeutically target immune cells and/or their products to reduce foetal loss. In this review, we provide evidence from the literature and from our own work into the immunological factors associated with porcine foetal loss.

Effect of N,N-dimethylglycine supplementation in parturition feed for sows on metabolism, nutrient digestibility and reproductive performance

The current pilot study assessed the influence of N,N-dimethylglycine (DMG) on insulin sensitivity, glucose and fat metabolism, nutrient digestibility and reproductive performance of sows in the peripartal period. At day 105 of gestation, 25 sows were randomly assigned to the control (n = 13) or the DMG group (n = 12). Sows from the DMG group were supplemented with 1 g DMG/kg feed until day 3 of lactation. After an overnight fast 1 day after farrowing, a blood sample of each sow was drawn. The plasma was analyzed for insulin, glucose, fructosamine, leptin, thiobarbituric acid reactive substances (TBARS), ferric reducing ability of plasma (FRAP), non-esterified fatty acids (NEFA) and triglycerides (TG) and an oral glucose tolerance test was performed. A rectal feces sample was collected and the apparent fecal digestibility (AFD) of crude fat (CFAT), crude protein (CP) and nitrogen-free extract (NFE) was calculated after proximate analyses. Finally, a colostrum sample was collected from each sow and analyzed for the presence of DMG. Reproductive performance parameters were recorded. The results showed an improvement in the AFD of CFAT, CP and NFE when DMG was supplemented. This beneficial effect confirms the hypothesis that DMG acts as an emulsifying agent. The improvement in digestibility in the DMG group was accompanied by a numerical increase in plasma TG (P = 0.067). Plasma NEFA concentrations were not different between treatment groups. DMG supplementation neither affected glucose clearance nor influenced plasma insulin, glucose, fructosamine or leptin levels. TBARS and FRAP also remained unaffected, despite previously reported anti-oxidative properties of DMG. Furthermore, no significant impact on reproductive performance could be recorded. In conclusion, DMG supplementation significantly improved nutrient digestibility. Possible beneficial effects on energy metabolism and reproductive performance of sows should be tested when DMG is supplemented for a longer period of time or at a higher dose.

Effect of feed restriction on hormones, performance, carcass traits, and meat quality in immunocastrated pigs

The aim of this study was to assess the effect of feed restriction applied to immunocastrated pigs in the period after the second vaccination (V2) against GnRH on hormonal status, performance, carcass traits, and meat quality. Immunocastrated pigs (IC) were compared with entire males (EM) and surgical castrates fed ad libitum. Pigs (Large White × Landrace) × Pietrain were either left entire or surgically castrated within 1 wk after birth (SC, n = 22). At 83 d of age, the entire males were further allotted to treatment groups (individual housing) of ad libitum fed EM (n = 24), ad libitum fed IC (IC-L, n = 21), or restrictively fed IC (IC-R, n = 21). At that time, the first vaccination (V1) was applied to IC-L and IC-R pigs. One week after V2 (age 130 d), feed restriction (≈ 80% of the ad libitum feed intake of SC pigs) was applied to IC-R pigs. The experiment ended 5 wk after V2, when pigs were 165 d old. Immunocastration successfully reduced boar taint compounds and size of reproductive organs. At 130 d, serum leptin concentrations were similar in all groups, whereas IGF-I concentration was less in SC (P ≤ 0.002) than in the other groups. Three weeks after V2, leptin concentrations of both IC groups were in between EM (least) and SC (greatest). The reverse was observed for IGF-I. Feed restriction had no effect on leptin or IGF-I concentrations in IC pigs. In the period V1 to V2, performance differed mainly between EM and SC, whereas both IC groups had feed intake and feed conversion ratio similar to EM and intermediate daily BW gain, not differing from either EM or SC. After V2, IC-L pigs increased their feed intake to the concentrations of SC, with faster growth compared with the other 3 groups (P < 0.05) and fatter carcasses compared with EM pigs (P = 0.007). Similar performance and carcass leanness were observed for IC-R and EM pigs. During preslaughter handling more carcass lesions were noted in EM and IC-R than in IC-L or SC pigs (P < 0.002). Neither immunocastration nor feed restriction had any effect on meat quality, but EM had greater drip loss, less intramuscular fat, and decreased tenderness than SC pigs. In conclusion, restricting feed intake can increase production efficiency but also aggressiveness of IC pigs.

Leptin in farm animals: where are we and where can we go?

Fat affects meat quality, value and production efficiency as well as providing energy reserves for pregnancy and lactation in farm livestock. Leptin, the adipocyte product of the obese (ob) gene, was quickly seen as a predictor of body fat content in animals approaching slaughter and an aid to assessing reproductive readiness in females. Its participation in inflammation and immune responses that help animals survive infection and trauma has clear additional relevance to meat and milk production. Furthermore, almost a decade of discoveries of nucleotide polymorphisms in the leptin and leptin receptor genes has suggested useful applications relating to feed intake regulation, the efficiency of feed use, the composition of growth, the timing of puberty, mammogenesis and mammary gland function and fertility in cattle, pigs and poultry. The current review attempts to summarise where research has taken us in each of these aspects and speculates on where future research might lead.

Mapping QTL for fat area ratios and serum leptin concentrations in a Duroc purebred population

The reduction of extra subcutaneous, intermuscular and abdominal fat is important to increase the carcass lean percentage of pigs. Image analyses of fat area ratios were effective for estimation of separated fat in pig carcasses. Serum concentrations of leptin are useful as physiological predictors of fat accumulation in pigs. The objectives of the present study were to perform a quantitative trait locus (QTL) analysis for fat area ratios and serum leptin concentrations in a Duroc purebred population. Pigs (n = 226 to 538) were measured for fat area ratios of carcass cross-sections at the fifth to sixth thoracic vertebrae, half body length and last thoracic vertebra using an image analysis system, and serum leptin concentration. In total, animals were genotyped for 129 markers and used for QTL analysis. For fat area ratios, four significant and 12 suggestive QTLs were detected on chromosomes 1, 6, 7, 8, 9, 12 and 13. Significant QTLs were detected on the same region of chromosome 6, which was located near a leptin receptor gene. For serum leptin concentrations, two significant and two suggestive QTLs were detected on chromosomes 6, 9, and 16, and the QTLs on chromosome 6 were also in the same region for fat area ratios.

Joint effects of porcine leptin and leptin receptor polymorphisms on productivity and quality traits

Leptin signalling plays a fundamental role in growth, fatness and body composition. The aim of this study was to investigate the porcine LEP gene sequence in an Iberian × Landrace experimental cross to identify polymorphisms associated with productivity and quality traits. Because of the documented effects on these traits of the LEPR c.1987C>T polymorphism, the LEP and LEPR c.1987C>T polymorphisms and their interactions have been jointly investigated. The LEP gene sequencing has allowed the identification of 39 polymorphisms, eight of which are novel. Three intronic SNPs, LEP g.1382C>T, LEP g.1387C>T and LEP g.1723A>G, have been genotyped, and association analyses have been carried out. Analyses of LEP g.1387C>T, fully linked to LEP g.1382C>T, have revealed additive effects on live and carcass weights and dominant effects on several backfat thickness measurements. Novel effects of both LEP and LEPR polymorphisms on fatty acid composition in subcutaneous fat have been detected, probably mediated through the effects on fatness. The results reported here suggest that the T alleles of both LEP g.1387C>T and LEPR c.1987C>T, which are fixed in the Iberian pigs, would lead to an increase in growth, fatness and saturated fatty acid content in fat, which could be explained by an increased feed intake.

Leptin and reproductive function

Adipose tissue plays a dynamic role in whole-body energy homeostasis by acting as an endocrine organ. Collective evidence indicates a strong link between neural influences and adipocyte expression and secretion of leptin. Developmental changes in these relationships are considered important for pubertal transition in reproductive function. Leptin augments secretion of gonadotropin hormones, which are essential for initiation and maintenance of normal reproductive function, by acting centrally at the hypothalamus to regulate gonadotropin-releasing hormone (GnRH) neuronal activity and secretion. The effects of leptin on GnRH are mediated through interneuronal pathways involving neuropeptide-Y, proopiomelanocortin and kisspeptin. Increased infertility associated with diet induced obesity or central leptin resistance are likely mediated through the kisspeptin-GnRH pathway. Furthermore, Leptin regulates reproductive function by altering the sensitivity of the pituitary gland to GnRH and acting at the ovary to regulate follicular and luteal steroidogenesis. Thus leptin serves as a putative signal that links metabolic status with the reproductive axis. The intent of this review is to examine the biological role of leptin with energy metabolism, and reproduction.