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In the current study we have performed two experiments to evaluate the effects of adipogenic induction media on dedifferentiated fat (DFAT) cells redifferentiation into mature adipocytes. In experiment 1, we aimed to evaluate whether it is necessary to use insulin in the induction media to allow DFAT cells differentiation into mature adipocytes by establishing two experimental treatments where insulin was either withdrawn from the culture medium, after 72 h of a normal induction period (Treatment 1: Insulin - ) or kept in culture media (Treatment 2: Insulin + ) for 16 d. In experiment 2, we aimed to evaluate if the lack of 3-isobutyl-1-methylxanthine (IBMX) in the induction medium would affect the differentiation of DFAT cells into mature adipocytes. For that, DFAT cells were induced to differentiate into lipid assimilating adipocytes using an induction medium containing IBMX (Treatment 1: IBMX + ) or without IBMX (Treatment 2: IBMX - ) during the first 72 h of induction. In both experiments we have evaluated the mRNA expression of lipid metabolism markers and cell morphology through Oil-Red staining as indicators of differentiation of DFAT cells into lipid-assimilating cells. The results of Experiment 1 revealed no differences in mRNA expression for any of the lipid metabolism markers with exception of GLUT4 ( P =0.02), which was greater in Insulin - compared to Insulin + treatment. Similarly, no differences were observed for mRNA expression of adipogenic markers between IBMX + and IBMX - treatments with exception of FABP4 ( P =0.01), which was greater for the IBMX - compared to IBMX + treatment. In both experiments we did not observed any differences in cell morphology among treatments. Our results suggest that neither insulin nor IBMX are required to accelerate redifferentiation process of pig-derived DFAT cells.

An increasing body of evidences has demonstrated the ability of the mature adipocyte to dedifferentiate into a population of proliferative-competent cells known as dedifferentiated fat (DFAT) cells. As early as the 1970s, in vitro studies showed that DFAT cells may be obtained by ceiling culture, which takes advantage of the buoyancy property of lipid-filled cells. It was documented that DFAT cells may acquire a phenotype similar to mesenchymal stem cells and yet may differentiate into multiple cell lineages, such as skeletal and smooth muscle cells, cardiomyocytes, osteoblasts, and adipocytes. Additionally, recent studies showed the ability of isolated mature adipocytes to dedifferentiate in vivo and the capacity of the progeny cells to redifferentiate into mature adipocytes, contributing to the increase of body fatness. These findings shed light on the potential for use of DFAT cells, not only for clinical purposes but also within the animal science field, because increasing intramuscular fat without excessive increase in other fat depots is a challenge in livestock production. Knowledge of the mechanisms underlying the dedifferentiation and redifferentiation of DFAT cells will allow the development of strategies for their use for clinical and animal science purposes. In this review, we highlight several aspects of DFAT cells, their potential for clinical purposes, and their contribution to adipose tissue mass in livestock.

This study assessed the effect of myostatin on adipogenesis by porcine intramuscular preadipocytes. Intramuscular preadipocytes were isolated from the longissimus dorsi muscle of newborn pigs. Myostatin inhibited intramuscular preadipocyte differentiation in a dose-dependent manner. Myostatin treatment during preadipocyte differentiation significantly (P < 0.05) inhibited the expression of the adipogenic marker genes CCAAT/enhancer-binding protein β, CCAAT/enhancer-binding protein α, peroxisome proliferator-activated receptor γ, sterol regulatory element-binding protein-1c, fatty acid-binding protein, and adiponectin. Myostatin also significantly (P < 0.05) reduced the release of glycerol and decreased both adipose triglyceride lipase and hormone-sensitive lipase expression in intramuscular adipocytes. Our study suggests that myostatin acts as an extrinsic regulatory factor in regulating intramuscular adipogenesis.

Among several potential animal models that can be used for adipogenic studies, Wagyu cattle is the one that presents unique molecular mechanisms underlying the deposit of substantial amounts of intramuscular fat. As such, this review is focused on current knowledge of such mechanisms related to adipose tissue deposition using Wagyu cattle as model. So abundant is the lipid accumulation in the skeletal muscles of these animals that in many cases, the muscle cross-sectional area appears more white (adipose tissue) than red (muscle fibers). This enhanced marbling accumulation is morphologically similar to that seen in numerous skeletal muscle dysfunctions, disease states and myopathies; this might indicate cross-similar mechanisms between such dysfunctions and fat deposition in Wagyu breed. Animal models can be used not only for a better understanding of fat deposition in livestock, but also as models to an increased comprehension on molecular mechanisms behind human conditions. This revision underlies some of the complex molecular processes of fat deposition in animals.

The abundance and cross-linking of intramuscular connective tissue contributes to the background toughness of meat, and is thus undesirable. Connective tissue is mainly synthesized by intramuscular fibroblasts. Myocytes, adipocytes and fibroblasts are derived from a common pool of progenitor cells during the early embryonic development. It appears that multipotent mesenchymal stem cells first diverge into either myogenic or non-myogenic lineages; non-myogenic mesenchymal progenitors then develop into the stromal-vascular fraction of skeletal muscle wherein adipocytes, fibroblasts and derived mesenchymal progenitors reside. Because non-myogenic mesenchymal progenitors mainly undergo adipogenic or fibrogenic differentiation during muscle development, strengthening progenitor proliferation enhances the potential for both intramuscular adipogenesis and fibrogenesis, leading to the elevation of both marbling and connective tissue content in the resulting meat product. Furthermore, given the bipotent developmental potential of progenitor cells, enhancing their conversion to adipogenesis reduces fibrogenesis, which likely results in the overall improvement of marbling (more intramuscular adipocytes) and tenderness (less connective tissue) of meat. Fibrogenesis is mainly regulated by the transforming growth factor (TGF) β signaling pathway and its regulatory cascade. In addition, extracellular matrix, a part of the intramuscular connective tissue, provides a niche environment for regulating myogenic differentiation of satellite cells and muscle growth. Despite rapid progress, many questions remain in the role of extracellular matrix on muscle development, and factors determining the early differentiation of myogenic, adipogenic and fibrogenic cells, which warrant further studies.

If one were to compare today's animal growth research to research from a mere 50 yr ago, one would see programs with few similarities. The evolution of this research from whole-animal through cell-based and finally molecular and genomic studies has been enhanced by the identification, isolation, and in vitro evaluation of adipose- and muscle-derived stem cells. This paper will highlight the struggles and the milestones that make this evolving area of research what it is today. The contribution of adipose and muscle stem cell research to development and growth, tissue regeneration, and final carcass composition are reviewed.

Twenty-four pregnant Nellore cows were randomly assigned into 2 feeding level groups (control [CTL]; fed 1.0 times the maintenance requirement; n = 12; and overnourished [ON]; fed at 1.5 times the maintenance requirement; n = 12) to evaluate effects of maternal overnutrition on fetal skeletal muscle development. Cows were slaughtered at 135, 190, and 240 d of gestation and samples of fetal LM were collected for analysis of mRNA expression analysis and for histological evaluation of collagen content and number of muscle cells. There was no interaction between gestational period and maternal nutrition for the variables evaluated (P > 0.05). The mRNA expression of Cadherin-associated protein, β 1 (β-catenin) tended to be greater in fetuses from ON cows (P = 0.08), while myogenic differentiation 1 (MyoD; P = 0.56), myogenin (MyoG; P = 0.70), and the number of muscle cells (P = 0.90) were not affected by maternal overnutrition. Gestational period did not affect the mRNA expression of β-catenin (P = 0.60) and MyoG (P = 0.21). The mRNA expression of MyoD tended to increase with days of gestation (P = 0.06). The mRNA expression of zinc finger protein 423 (Zfp423; P < 0.0001), C/EBPα (P = 0.01), and PPARγ (P < 0.0001) were enhanced in ON fetuses. No effects of days of gestation were observed for mRNA expression of Zfp423 (P = 0.75) and C/EBPα (P = 0.48). The mRNA expression of PPARγ in fetuses at 190 d of gestation tended to be greater than those at 135 and 240 d of gestation (P = 0.06). The mRNA expression of transforming growth factor β (TGF-β; P < 0.0001), collagen type III, α I (COL3A1; P < 0.0001), and collagen content (P = 0.01) were increased in ON fetuses. Gestational period did not affect the mRNA expression of collagen type I, α I (COL1A1; P = 0.65). The mRNA expression of COL3A1 (P = 0.09) in fetuses at 190 d of gestation tended to be greater than fetuses at 135 and 240 d of gestation. The mRNA expression of TGF-β in fetuses at 190 d of gestation was greater than in fetuses at 135 d of gestation (P = 0.03), and the values observed in fetuses at 240 d of gestation did not differ from the other gestational time points. The least value of collagen content (P = 0.01) was observed in fetuses at 135 d of gestation, and no differences were observed among the other gestational time points. These data shows that maternal overnutrition enhances fibrogenesis and likely adipogenesis without compromising myogenesis in fetal skeletal muscle of cattle.

Adipose tissue is derived from numerous sources, and in recent years this tissue has been shown to provide numerous cells from what seemingly was a population of homogeneous adipocytes. Considering the types of cells that adipose tissue-derived cells may form, these cells may be useful in a variety of clinical and scientific applications. The focus of this paper is to reflect on this area of research and to provide a list of potential (future) research areas.

The link between AMP-activated protein kinase (AMPK) and myogenesis remains poorly defined. AMPK has two catalytic α subunits, α1 and α2. We postulated that AMPK promotes myogenesis in an isoform-specific manner. Primary myoblasts were prepared from AMPK knockout (KO) mice and AMPK conditional KO mice, and knockout of the α1 but not the α2 subunit resulted in downregulation of myogenin and reduced myogenesis. Myogenin expression and myogenesis were nearly abolished in the absence of both AMPKα1 and AMPKα2, while enhanced AMPK activity promoted myogenesis and myotube formation. The AMPKα1-specific effect on myogenesis was likely due to the dominant expression of α1 in myoblasts. These results were confirmed in C2C12 cells. To further evaluate the necessity of the AMPKα1 subunit for myogenesis in vivo, we prepared both DsRed AMPKα1 knockout myoblasts and enhanced green fluorescent protein (EGFP) wild-type myoblasts, which were cotransplanted into tibialis anterior muscle. A number of green fluorescent muscle fibers were observed, showing the fusion of engrafted wild-type myoblasts with muscle fibers; on the other hand, very few or no red muscle fibers were observed, indicating the absence of myogenic capacity of AMPKα1 knockout myoblasts. In summary, these results indicate that AMPK activity promotes myogenesis through a mechanism mediated by AMPKα1.

This study was developed aiming to evaluate the effects of maternal feed-restriction ond evelopment of gastrointestinal tract (GIT) of bovine fetus at different gestational stages. Feed-restricted cows were fed 1.2 times the maintenance level while the control group was fed ad libitum. Pregnant cows were slaughtered at 136, 189, 239, and 269 days of gestation and gastrointestinal tracts of the fetuses were evaluated. No effects of maternal nutrition on body weight (P 1⁄4 0.17) and body length (P 1⁄40.13) of the fetuses were observed. No major effects of feed restriction on GIT mass of the fetuses were observed (P 1⁄4 0.51). However, the weight of small intestine per unit of body weight was 11.24% greater (P 1⁄40.04) in fetuses from restricted dams. Additionally, the length of small intestine and its villi were 12.93% and 16.44% respectively greater (P o .001) in fetuses from restricted dams compared to those from non-restricted dams. These data indicates that maternal feed-restriction does not affect the development of most of fetal gastrointestinal parts besides small intestine which in turn increases its surface area as a response of maternal feed restriction.

Beef cattle are raised for their lean tissue, and excessive fat accumulation accounts for large amounts of waste. On the other hand, intramuscular fat or marbling is essential for the palatability of beef. In addition, tender beef is demanded by consumers, and connective tissue contributes to the background toughness of beef. Recent studies show that myocytes, adipocytes, and fibroblasts are all derived from a common pool of progenitor cells during embryonic development. It appears that during early embryogenesis, multipotent mesenchymal stem cells first diverge into either myogenic or adipogenic-fibrogenic lineages; myogenic progenitor cells further develop into muscle fibers and satellite cells whereas adipogenic-fibrogenic lineage cells develop into the stromal-vascular fraction of skeletal muscle where reside adipocytes, fibroblasts, and resident fibro-adipogenic progenitor cells (the counterpart of satellite cells). Strengthening myogenesis (i.e., formation of muscle cells) enhances lean growth, promoting intramuscular adipogenesis (i.e., formation of fat cells) increases marbling, and reducing intramuscular fibrogenesis (i.e., formation of fibroblasts and synthesis of connective tissue) improves overall tenderness of beef. Because the abundance of progenitor cells declines as animals age, it is more effective to manipulate progenitor cell differentiation at an early developmental stage. Nutritional, environmental, and genetic factors shape progenitor cell differentiation; however, up to now, our knowledge regarding mechanisms governing progenitor cell differentiation remains rudimentary. In summary, altering mesenchymal progenitor cell differentiation through nutritional management of cows, or fetal programming, is a promising method to improve cattle performance and carcass value.

Clenbuterol was intended as a treatment for respiratory diseases in horses, but has been used in multiple species, including humans, for its repartitioning of fat to lean effects (free fatty acids are released from adipose tissue to be used by tissues of higher priority). In the horse industry clenbuterol application is restricted to the treatment of chronic obstructive pulmonary disease and reactive airway disease (heaves). Negative effects of clenbuterol exposure include a decrease in maximum oxygen intake and increased muscle fatigue upon exercise. As a result of these and other negative effects, clenbuterol remains strictly controlled by the US Food and Drug Administration.

Fatty acid binding protein 4 (FABP4) is an important adipocyte gene, with roles in fatty acid transport and fat deposition in animals as well as human metabolic syndrome. However, little is known about the functional regulation of FABP4 at the cellular level in bovine. We designed and selected an effective shRNA (small hairpin RNA) against bovine FABP4, constructed a corresponding adenovirus (AD-FABP4), and then detected its influence on mRNA expression of four differentiation-related genes (PPAR(y), CEBPA, CEBPB, and SREBF1) and three lipid metabolism-related genes (ADIPOQ, LEP and LEPR) of adipocytes. The FABP4 mRNA content, derived from bovine adipocytes, decreased by 41% (P < 0.01) after 24 h and 66% (P < 0.01) after 72 h of AD-FABP4 infection. However, lower mRNA content of FABP4 did not significantly alter levels of differentiation-related gene expression at 24 h following AD-FABP4 treatment of bovine-derived preadipocytes (P = 0.54, 0.78, 0.89, and 0.94, respectively). Meanwhile, knocking down (partially silencing) FABP4 significantly decreased ADIPOQ (P < 0.05) and LEP (P < 0.01) gene expression after 24 h of AD-FABP4 treatment, decreased ADIPOQ (P < 0.01) and LEP (P < 0.01) gene expression, but increased LEPR mRNA expression (P < 0.01) after a 72-h treatment of bovine preadipocytes. We conclude that FABP4 plays a role in fat deposition and metabolic syndrome by regulating lipid metabolism-related genes (such as ADIPOQ, LEP and LEPR), without affecting the ability of preadipocytes to differentiate into adipocytes.

The dynamics of human and animal adipogenesis has been defined using several traditional cell systems including stromal vascular cells and adipocyte-related cell lines. But a relatively new cell system using progeny cells stemming from the dedifferentiation of purified cultures of mature adipocytes may be used for studying the development and biology of adipocytes. In this research, we show that isolated (and purified) mature adipocytes derived from Wagyu cattle dedifferentiate into progeny cells, and that these spindle-shaped, proliferative-competent daughter cells possess ability to proliferate. We outline the optimum cell culture system and offer precautionary thoughts for effective mature adipocyte culture. Collectively, this represents a novel cell model which may provide new insights into cell development, physiology and use as a model for animal production/composition, tissue engineering and disease treatment.

A 2×3 factorial experiment was conducted with 72 weanling, crossbred steers (with Hereford, Angus and Charolais genetics and initial BW of 280.5±5.8 kg) with the objective of determining the effect of dietary and feed withdrawal (FW) treatments on plasma concentrations of glucose, insulin, growth hormone (GH) and leptin and on intramuscular and subcutaneous (SQ) adipose cellularity. Supplementation was a 50/50 mixture of flax and sunflower oil at 5% of diet (OIL) versus a control (CON; without oil) diet, which were the dietary treatments and were applied to steers experiencing three feed withdrawal (FW) treatments. The FW treatments were no FW, a single 48 h FW (FW×1) before initiation of fattening at one year of age or 48 h FW at 8 week intervals from weaning to initiation of fattening (FW×4). Plasma was harvested from jugular blood collected from all steers after each FW and samples of pars costalis diaphgramatis (PCD) muscle and SQ from the brisket were collected from the steers at slaughter for adipocyte enumeration. Cell number was determined by computerized image enumeration and electronically by a particle counter. Plasma concentrations of glucose and hormones responded to age of steers at the time of sample procurement ( P =0.001–0.053), and a diet×FW interaction ( P =0.015) was observed for insulin, because steers fed the OIL diet in the FW×4 treatment had lower insulin concentrations than of those in the other FW treatments. Concentrations of growth hormone (GH) decreased ( P =0.028) due to FW from 7.17±1.02 ng/mL in steers in the no FW treatment to 5.04±0.78 and 5.46±1.22 ng/mL for steers in FW×1 and FW×4 treatments, respectively. Leptin concentrations were unaffected by diet or FW treatment. The relationship for cells enumerated by the particle counter versus the Motic computer program was significant ( P =0.01) for both PCD and SQ fat with r 2 values of 0.55 and 0.24, respectively, for total cells of diameters from 30 to 300 μm. Number of adipocytes with diameters from 80 to 140 μm in the PCD were greater ( P =0.038 and 0.028) in OIL than in CON fed steers. The percent of total number of cells in the 30–60 μm diameter range in the PCD were greater in steers in FW×1 and FW×4 than in no FW treatments when counted by either method. Provision of dietary oil and FW treatments had no effect on plasma metabolites and may be the reason for the absence of a response in total adipocyte numbers due to FW.

A 2 × 3 factorial experiment was conducted with 72 weanling (about 180 d old), crossbred steers (with Hereford, Angus and Charolais genetics and initial body weight of 280.5 ± 5.8 kg) to determine the effect of dietary supplementation with a 50/50 mixture of flax and sunflower oils at 5% of diet, to steers in three feed withdrawal (FW) treatments on production factors, carcass characteristics, adipocyte marker; peroxisome proliferator activated receptor γ (PPARγ) RNA expression and fatty acid composition of muscle ( Pars costalis diaphragmatis ; PCD) and subcutaneous fat (SQ from brisket). The FW treatments were no FW, a single 48 h FW (FW × 1) before start of fattening or 48 h FW at 8 week intervals from weaning to start of fattening (FW × 4). Individually penned steers were fed mixed hay and rolled barley diets containing no oil (Control; CON) or 5% oil (OIL) through growing, transition and fattening phases. Interaction of dietary oil and FW treatments did not affect any of the production factors. Decreased ( P = 0.008) dry matter intake (DMI) of the OIL diet was noted through the growing period; thus decreasing ( P = 0.019) total DMI by 112 kg/hd for the experiment and improved gain per unit feed ( P = 0.019) for the growing period. The FW × 1 treatment reduced ( P = 0.004) average daily gain (ADG) through the transition period, but ADG tended to improve ( P = 0.081) during fattening and steers in FW treatments gained 1.38 ± 0.07 versus 1.25 ± 0.06 kg/d for those in the no FW treatment. Differences due to dietary oil or the FW treatments were not observed for any of the carcass characteristics. A diet × FW interaction ( P = 0.001) was observed for PPARγ expression in the PCD and SQ. Adipocyte marker expression was greater in PCD of steers in the FW × 4 treatment with values for OIL fed steers being greater than of CON fed steers. Feeding the OIL diet increased ( P = 0.001) the weight percent of C18:1t10, C18:1t11, conjugated linoleic acid and n3 fatty acids by 178, 152, 66 and 32%, respectively. The n6:n3 ratio in PCD was decreased in OIL fed steers. Results indicate that repeated FW can enhance adipocyte marker expression in muscle thus improving the potential to increase marbling fat in steers, while oil, comprised of n3 and n6 fatty acids, increased biologically active fatty acids and decreased n6:n3 fatty acid ratios of tissues, without affecting productivity or carcass characteristics of the steers.

Obesity and metabolic syndromes are examples whereby excess energy consumption and energy flux disruptions are causative agents of increased fatness. Because other, as yet elucidated, cellular factors may be involved and because potential treatments of these metabolic problems involve systemic agents that are not adipose depot-specific in their actions, should we be thinking of adipose depot-specific (cellular) treatments for these problems? For sure, whether treating obesity or metabolic syndrome, the characteristics of all adipose depot-specific adipocytes and stromal vascular cells should be considered. The focus of this paper is to begin to align metabolic dysfunctions with specific characteristics of adipocytes.

We evaluated the effects of betaine supplementation on liver weight, liver/body weight, serum parameters and morphological changes. Compared with the control and overfed groups, the geese that were fed the betaine diet showed increased liver weight and decreased abdominal adipose tissue weight compared with the overfeeding groups. Betaine treatment also significantly increased ChE, HDL, LDH and ALT levels (P

The existence of myogenic satellite cells was reported some 47 years ago, and, since that time, satellite cell research has flourished. So much new information is generated (daily) on these cells that it can be difficult for individuals to keep abreast of important issues related to their activation and proliferation, the modulation of the activity of other cell types, the differentiation of the cells to facilitate normal skeletal muscle growth and development, or to the repair of damaged myofibers. The intent of this review is to summarize new information about the extrinsic regulation of myogenic satellite cells and to provide specific mechanisms involved in altering satellite cell physiology. Where possible, examples from agriculturally important animals are used for illustrative purposes.

The quality and value of the carcass in domestic meat animals are reflected in its protein and fat content. Preadipocytes and adipocytes are im- portant in establishing the overall fatness of a carcass, as well as being the main contributors to the marbling component needed for consumer preference of meat products. Although some fat accumulation is essential, any excess fat that is deposited into adipose depots other than the marbling fraction is energetically un- favorable and reduces efficiency of production. Hence, this review is focused on current knowledge about the biology and regulation of the important cells of adipose tissue: preadipocytes and adipocytes.

The effect of feed withdrawal for 48 h, prior to initiation of the finishing (fattening) period (75 d) on carcass marbling fat was studied in 120 European × British cross-bred heifers with an average weight of 585 ± 39 kg. Heifers were randomized in a 2 × 2 factorial design experiment with two dietary management treatments, where half the heifers were provided the feed components of steam rolled barley and barley silage either free choice or as a total mixed ration (TMR) containing 87% steam rolled barley and 13% barley silage with ad libitum vitamins and minerals via salt blocks for all animals. Within each dietary management treatment, 30 heifers were denied feed (water was available) for 48 h prior to the two week adaptation to the high grain diet preceding the 75 d finishing period. At the end of the 48 h feed denial blood samples were collected from the jugular vein prior to feeding for determination of glucose and insulin concentrations, which indicated that 48 h feed withdrawal consistently decreased ( P = 0.0001) plasma concentrations of both glucose and insulin but the ratios of the concentrations of glucose to insulin were not affected. At slaughter samples of subcutaneous fat from the brisket (BF) and skirt muscle ( pars costalis diaphragmatis ; PCD) were procured for determination of chemical fat content, fat dissected from the muscle and for enumeration of adipocytes, less than 35 μm in diameter and to determine the average cell size in the dissected fat and from the BF by flow-cytometry of adipocytes fixed in osmium tetroxide. The carcass characteristics were also obtained. Although no differences due feed withdrawal for 48 h were evident for carcass weight, percent lean (saleable) meat yield, rib eye area, average fat cover, fat content of PCD or BF, the US marbling score was increased ( P = 0.048) and the amount of dissected fat from the muscle tended to be higher ( P = 0.107), thus 81% of the carcasses graded “US Choice” or “Canada AAA,” or displayed at least a “small” amount of intramuscular fat as compared ( P = 0.0807) to 68% of the heifers not denied feed. Based on more than three years of weekly prices of carcasses that graded “Canada AAA” and “Canada AA,” these experimental results suggested that the expected price of a finished heifer could increase by $4.61 Canadian if a 48 h feed withdrawal was imposed prior to initiation of the finishing phase. Although significant differences in adipocyte numbers due to a single time 48 h feed withdrawal prior to initiation of the finishing phase were not detected, the carcass quality factors were affected leading to an odds ratio of 1.84 times in favour of cattle carcasses to grade “Canada AAA” than if fed continuously.

In this document, we have integrated knowledge about two major cellular markers found in cells of the adipocyte lineage (an adipogenic marker and a metabolic marker). This review provides information as to how differentiation of a cell (such as an adipofibroblast, fibroblast or preadipocyte) to become a viable (and new) adipocyte is under different regulation than that experienced by an immature adipocyte that is just beginning to accumulate lipid. The differentiation, prior to lipid-filling, involves PPARγ. Subsequently, lipid-filling of the adipocyte relies on a late subset of genes and, depending on depot specificity, involves GLUT-4 or any number of other metabolic markers.

Satellite cells are the major myogenic stem cells residing inside skeletal muscle and are indispensable for muscle regeneration. Satellite cells remain largely quiescent but are rapidly activated in response to muscle injury, and the derived myogenic cells then fuse to repair damaged muscle fibers or form new muscle fibers. However, mechanisms eliciting metabolic activation, an inseparable step for satellite cell activation following muscle injury, have not been defined. We found that a noncanonical Sonic Hedgehog (Shh) pathway is rapidly activated in response to muscle injury, which activates AMPK and induces a Warburg-like glycolysis in satellite cells. AMPKα1 is the dominant AMPKα isoform expressed in satellite cells, and AMPKα1 deficiency in satellite cells impairs their activation and myogenic differentiation during muscle regeneration. Drugs activating noncanonical Shh promote proliferation of satellite cells, which is abolished because of satellite cell-specific AMPKα1 knock-out. Taken together, AMPKα1 is a critical mediator linking noncanonical Shh pathway to Warburg-like glycolysis in satellite cells, which is required for satellite activation and muscle regeneration.

Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPq Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES Fundação de Apoio a Pesquisa e à Inovação Tecnológica do Estado de Sergipe - FAPITEC/SE Thirteen reference genes were investigated to determine their stability to be used as a housekeeping in gene expression studies in skeletal muscle of chickens. Five different algorithms were used for ranking of reference genes and results suggested that individual rankings of the genes differed among them. The stability of the expression of reference genes were validated using samples obtained from the Pectoralis major muscle in chicken. Samples were obtained from chickens in different development periods post hatch and under different nutritional diets. For gene expression calculation the ΔΔCt approach was applied to compare relative expression of pairs of genes within each of 52 samples when normalized to mitochondrially encoded cytochrome c oxidase II (MT-CO2) target gene. Our findings showed that hydroxymethylbilane synthase (HMBS) and hypoxanthine phosphoribosyl transferase 1 (HPRT1) are the most stable reference genes while transferrin receptor (TFRC) and beta-2-microglobulin (B2M) ranked as the least stable genes in the Pectoralis major muscle of chickens. Moreover, our results revealed that HMBS and HPRT1 gene expression did not change due to dietary variations and thus it is recommended for accurate normalization of RT-qPCR data in chicken Pectoralis major muscle.

Obesity is presently being combated by fitness regimens, drugs and diet. Increasing our understanding of the physiology of adipocytes, by deducing the regulatory pathways involved in lipid metabolism and all aspects of adipogenesis, will provide alternative strategies to reduce adverse problems of obesity. Research has suggested that mature fat cells may dedifferentiate to form proliferative-competent fat cell precursors. Knowledge of the dedifferentiation process will allow us to gain a solid grip on adipogenesis.

The effect of breed and diet on insulin response to glucose challenge and its relation to intramuscular fat deposition was determined in 36 steers with 12 each of greater than 87% Wagyu (referred to as Wagyu), Wagyu x Limousin, and Limousin breeds. Weaned steers were blocked by weight into heavy, medium, and light calves and placed in six pens with two pens per weight type and with two steers of each breed per pen. Three pens with steers from each weightclass were fed backgrounding and finishing diets for 259 d, while the other three pens were fed the same diets where 6% of the barley grain was replaced with sunflower oil. Prior to initiation of the finishing phase of the study the intravenous glucose tolerance test (VGTIT) was conducted in all steers. Once steers were judged as carrying adequate 12th-rib fat, based on weight and days on feed, they were harvested and graded and samples of the longissimus muscle were procured for determination of fat content and fatty acid composition. Dietary oil improved (P = 0.011; 0.06) ADG and feed conversion efficiency of steers during the latter part of backgrounding and only ADG during early part ofthe finishing period. Generally percent kidney, pelvic, and heart fat was the only adiposity assessment increased (P = 0.003) by dietary oil. The IVGTT results indicated that insulin response to intravenous glucose was lower in Limousin steers than in Wagyu steers. Dietary oil decreased (P = 0.052) fasting plasma insulin concentration in Wagyu steers compared with Limousin steers. The correlation coefficients among the IVGTT measures and intramuscular fat content or marbling score were less than 0.4, and only a negative trend existed between fasting insulin and USDA marbling scores. However, the carcasses of the Wagyu steers graded US Choice, and 66% of the Wagyu carcasses graded US Prime, which were substantially better than the quality grades obtained for the carcasses from the other breed types. Dietary oil did not affect muscle fat content but increased (P = 0.01) conjugated linoleic acid (CLA) concentrations by 339%. Results indicated that IVGTT measures were not appropriate indices of marbling potential in cattle and that dietary oil can enhance CLA content of beef.

A preliminary study was conducted to quantify the lipid produced by differentiated 3T3-L1 cells after incubation in Dulbecco’s Modified Eagle Medium (DMEM) containing 10% foetal bovine serum (FBS), supplemented with or without dimethyl-sulphoxide (DMSO; 9•6 g/l) and acetone (1•2 g/l). The two media treatments were applied to 3T3-L1 cells, plated at either 15K or 30K cells per well in 24-well plates. Cells were grown to confluence (96 h) and then treated with dexamethasone, methyl-isobutylxanthine and insulin for 48 h and later maintained in their respective media treatments for another 144 h. Cells from each treatment were recovered after two, 5-min incubations with trypsin, washed and resuspended in DMEM and counted on a haemocytometer. The lipid in the cells was extracted with hexane derivatized with tetramethyl-guanidine and analysed by gas chromatography. Final mean cell density was 6•8 (s.e. 0•18)✕105and 4•6 (s.e. 0•19)✕105when initially plated at 30K and 15K cells per well, respectively. Inclusion of DMSO and acetone in the medium did not affect final cell numbers. Plating density did not affect concentration of lipid (0•55 (s.e. 0•08) mg per 1✕105cells) but inclusion of DMSO and acetone led to overall decreases in total lipid concentration. Results indicate that initial plating density influenced final cell number in treatment cultures, but that DMSO and acetone treatments only had an effect on final lipid concentration. Collectively, these data suggest that the application of treatments to cell cultures may be influenced by the carrier vehicle that the treatment is contained in and this should be considered when developing an in vitro system to evaluate growth and development of adipocytes.

Adipose tissue contains a large portion of stem cells. These cells appear morphologically like fibroblasts and are primarily derived from the stromal cell fraction. Mature (lipid-filled) adipocytes possess the ability to become proliferative cells and have been shown to produce progeny cells that possess the same morphological (fibroblast-like) appearance as the stem cells from the stromal fraction. A closer examination of mature adipocyte-derived progeny cells may prove to be an emerging area of growth/metabolic physiology that may modify present thinking about adipose tissue renewal capabilities. Knowledge of these cells may also prove beneficial in cell-based therapies for tissue repair, regeneration, or engineering.

The utility of co-culture systems in defining the interactions between two different cell types has been well documented in the literature but is a relatively new tool for use in the study of cells derived from normal muscle tissue from meat animals. The majority of myonuclei in postnatal skeletal muscle cells (myofibers) result from satellite cell proliferation, differentiation and fusion with existing myofibers. As such, satellite cell culture systems that mimic postnatal myofibers have great potential for delineating the process of growth and repair of muscle mass. Other ways to simulate the environment of postnatal myofibers might include the development of co-culture systems using satellite cells, or satellite cell-derived myotubes, and other mesodermal cells commonly found associated with muscle tissue in vivo. This brief review describes our initial efforts to develop a defined satellite cell and preadipocyte co-culture system. We provide useful information about defined media requirements and requirements for proper cell orientation and growth on two different growth planes. We present summary data to suggest that differences were found between members of the insulin-like growth factor (IGF) and IGF-binding protein (IGFBP) families of polypeptides, when conditioned media samples were analyzed from co-cultures composed of 3T3-L1 preadipocytes and satellite cells (with different propensities to undergo morphological fusion to form multinucleated myotubes). We also provide information about potential problems to avoid when initiating and conducting co-culture experiments. Such a co-culture system has application in the study of human obesity and also in the regulation of fat deposition in meat animals.

Insulin-like growth factors (IGFs) and their binding proteins play an essential role in regulating animal growth and metabolism. The initial portion of the current review focuses on the physiological effects of the IGFs and delineates their role as regulators of animal growth and metabolism. The role of IGFs as mediators of growth hormone effects, as insulin-like metabolic regulators and as foetal growth regulators is discussed. The remainder of the review is devoted to the IGF binding proteins, their modulation of IGF action and their role in foetal and postnatal regulation of growth.

This study was performed to assess the relationship between serum growth hormone (GH) and insulin-like growth factor 1 (IGF-1) levels, slaughter weight, and myogenic satellite cell growth kinetics of Targhee rams. Serum was collected from 19 rams at 15-min intervals over a period of 4h. Radioimmunoassays of serum samples for GH revealed considerable variation (within individual rams) over the sampling period, with mean values ranging from 0·63 to 4·88 μg/l (mean overall 2·3 (s.e. 0·33) μg/l; no. = 19). There was no significant correlation between GH levels and slaughter weight (r = −0·11; P > 0·05) at 155 (s.e. 1·08) days. Serum IGF-1 levels of (individual) rams were invariant over the sampling period, with individual means ranging from 62 to 233 μg/l (mean overall of 117 (s.e. 45·6) ugll; no. = 19). IGF-1 was not strongly correlated with slaughter weight (r = +0·35; P > 0·05). Satellite cells were isolated from the left m. semimembranosus of all rams at slaughter and grown in culture to evaluate proliferation amount and differentiation extent. The correlations between serum GH levels and satellite cell proliferation and differentiation in vitro were r = −0·53 (P < 0·05) and r = −0·52 (P < 0·05), respectively. Serum IGF-1 showed no significant correlations to proliferation (r = +0·07; P > 0·05) or to differentiation (r = −0·07; P > 0·05) of the satellite cells. These data suggest that serum GH levels in Targhee rams may not reflect muscle growth potential if correlated to body weight of 155 days. Furthermore, as IGF-1 was not correlated significantly with slaughter weight or to variables of satellite cell proliferation and differentiation, another mode of satellite cell regulation (possibly paracrine controllers) is more likely at play to coordinate the satellite cell involvement in muscle growth in Targhee rams at 155 days.

Carcass and meat quality traits of 16 pregnant and 5 non-pregnant cows fed at 1.2 times maintenance and 16 pregnant and 6 non-pregnant fed ad libitum were evaluated. Pregnancy did not affect final body weight (FBW; P = 0.0923), cold carcass yield (CCY; P = 0.0513), longissimus muscle area (LMA; P = 0.8260), rib fat thickness (RFT; P = 0.1873) and shear force (WBSF; P = 0.9707). A lower FBW ( P = 0.0028), LMA ( P = 0.0048) and RFT ( P = 0.0001) were observed in feed restricted cows. However, no differences were found for CCY ( P = 0.7243) and WBSF ( P = 0.0759) among feeding level groups. These data suggests that carcass and meat quality traits are not affected by pregnancy status in Nellore cows. Moreover, although cows experiencing feed restriction did have reduced deposition of subcutaneous fat and lean tissue, there were no major impacts on meat quality traits.

This study was designed to determine the effects of dietary oil and feed withdrawal treatments on fatty acid composition of phospholipids of triacylglycerol in pars costalis diaphragmatis muscle and subcutaneous fat from the brisket. A 2 × 3 factorial experiment was conducted with crossbred steers with an initial body weight of 280.5 ± 5.8 kg. Steers were fed either a control or an oil containing diet where 5% of the control diet was replaced with an equal mixture sunflower and flax oil while undergoing one of three feed withdrawal treatments: no withdrawal, a single 48 h withdrawal before initiation of fattening at one year of age, or 48 h withdrawal at 8 wk intervals from weaning to initiation of fattening. At time of processing samples of muscle and fat were obtained and analyzed to determine fatty acid composition. Disproportionate distribution of the fatty acids was observed by diet, feed withdrawal regimen and whether the sample was from muscle or fat. Differences are discussed in detail, and our data suggests a special function for the fatty acids that accumulate in specific positions of the triacylglycerol due to treatment.

Methods are described to obtain adipose tissue for cell isolation, under adverse isolation conditions whereby no scientific controls were in place. Such methods could be used by laboratories of institutions where controlled environments (surgery rooms, abattoirs) are not available. While not ideal, we show that a variety of adipocytes and adipocyte-like cells may be isolated from such methods. These types of procedures may facilitate a greater number of persons entering into the research arena with adipocytes, and are easily adaptable to other animal models.

As research funding becomes more competitive, it will be imperative for researchers to break the mentality of a single laboratory/single research focus and develop an interdisciplinary research team aimed at addressing real world challenges. Members of this team may be at the same institution, may be found regionally, or may be international. However, all must share the same passion for a topic that is bigger than any individual's research focus. Moreover, special consideration should be given to the professional development issues of junior faculty participating in interdisciplinary research teams. While participation may be "humbling" at times, the sheer volume of research progress that may be achieved through interdisciplinary collaboration, even in light of a short supply of grant dollars, is remarkable.

Citation analysis numbers are being used as measures of faculty productivity and/or impact. However, after establishing initial citation numbers how does one conduct maintenance on their citation record? During this time of budgetary uncertainty it is more vital than ever to incorporate citation analysis into annual review packages or any departmental report that relies on such faculty data. The focus of this paper is to describe the next step in this process.

In an era in which academic institutions are held more accountable, a problem, which does not seem to have an immediate resolution, exists: how does one demonstrate the quality of one's work? Specifically, how does one show that his or her research is making an impact and is thought to be important? A variety of measures of scientific journal article importance, reflected mostly by citation analyses, have been focused on as being potential gold standards. However, although several measures have been reported, keeping a record of citation of individual research papers, primarily due to the effort involved in finding accurate information, is not for wimps.

The ability of ovine-derived satellite cells to attach, proliferate and differentiate in response to seven horse serum-supplemented media and eleven substrata was evaluated in vitro. Satellite cells attached equally well when exposed to CRCM-30, Medium-199 and high glucose Dulbecco's modified Eagles medium (DMEM, P less than 0.05). Proliferation of satellite cells was greatest using McCoy's 5A, supplemented with 15% horse serum (P less than 0.05), and differentiation was most efficient with low glucose DMEM, supplemented with 1% horse serum (P less than 0.05). Pig-skin gelatin facilitated the greatest ovine satellite cell proliferative and differentiative responses when compared to the performance of ten other substrata (P less than 0.05). Further, 0.5 mg/16 mm2-well pig-skin gelatin appeared to be the optimum concentration of substratum for expression of satellite cell growth characteristics. Thus, consideration must be given to the processes of attachment and proliferation in experiments attempting to maximize satellite cell differentiation in vitro.

Cell cultures were established from the skeletal muscle tissue of 6-13 months old rainbow trout and 12-14 months old yellow perch. Approximately 27,000 +/- 5,000 cells/g (trout; N = 5) and 5,000 +/- 1,200 cells/g of tissue (perch; N = 4) were obtained. Isolation and propagation were qualitatively greater for both species when the cells (younger fish producer more cells than older fish) were exposed to DMEM + 15% FBS, rather than L-15 + 15% FBS, at 20 degrees C (trout) and at 24 degrees C (yellow perch). Two morphologically distinct cell types were observed in cultures of both species, some of which eventually formed very small myotubes, which displayed immunocytological reactivity for myogenin, myosin heavy chain, and alpha-actinin; the second population of cells remained unstained. Successful cryopreservation was achieved using a 5% DMSO and 95% serum mixture, but post-thawing viabilities were low 5-27% (trout) and 14-30% (perch). Further research is needed in order to determine cell type specificity of isolated cells.

Japanese Wagyu cattle are well known for their extremely high marbling and lower subcutaneous adipose tissue compared with Angus cattle. However, mechanisms for differences in adipose deposition are unknown. The objective of this paper was to evaluate breed differences in the structure of subcutaneous adipose tissue, adipogenesis, and mitogenesis of stromal vascular (SV) cells between Wagyu and Angus cattle. Subcutaneous biopsy samples were obtained from 5 Wagyu (BW = 302 ± 9 kg) and 5 Angus (BW = 398 ± 12 kg) heifers at 12 mo of age, and samples were divided into 3 pieces for histological examination, biochemical analysis, and harvest of SV cells. Adipogenesis of SV cells was assessed by the expression of adipogenic markers and Oil Red-O staining, while mitogenesis was evaluated by an MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium dromide) test, phosphorylation of extracellular signal-regulated kinase (ERK) and protein kinase B (PKB; AKT). Based on histological analysis, Wagyu had larger adipocytes compared with Angus. At the tissue level, protein expression of peroxisome proliferator-activated receptor γ (PPARG) in Wagyu was much lower compared with that of Angus. Similarly, a lower mRNA expression of PPARG was found in Wagyu SV cells. No significant difference was observed for the zinc finger protein 423 (ZNF423) expression between Wagyu and Angus. As assessed by Oil Red-O staining, Wagyu SV cells possessed a notable trend of lower adipogenic capability. Interestingly, higher mitogenic ability was discovered in Wagyu SV cells, which was associated with an elevated phosphorylation of ERK1/2. There was no difference in AKT phosphorylation of SV cells between Wagyu and Angus. Moreover, exogenous fibroblast growth factor 2 (FGF2) enhanced mitogenesis and ERK1/2 phosphorylation of SV cells to a greater degree in Angus compared with that in Wagyu. Expression of transforming growth factor β 3 (TGFB3) and bone morphogenetic protein 2 (BMP2) in Wagyu SV cells was lower than that of Angus, providing potential clues for breed differences on proliferation of SV cells in these two cattle breeds. The results of this study suggest that subcutaneous adipose-derived SV cells of Wagyu possess a lower trend of adipogenesis but higher mitogenesis compared with those of Angus.

In the present manuscript, the methods required to generate purified cultures of mature adipocytes, as well as stromal vascular cells, from the same isolation are detailed. Also, we describe the in vitro conditions for the dedifferentiation of the isolated mature adipocytes. These two types of cells may be used to reevaluate differences between presently available cellular models for lipogenesis/lipolysis and might provide a new cellular physiological system for studies utilizing the proliferative progeny from mature adipocyte dedifferentiation. Alternative possibilities to the dedifferentiation phenomenon are proposed, as this new area of research is novel.

Grazing animals cause major alterations to vegetation structure and botanical composition through their selective grazing, trampling and excretal deposition (Hester et al., 2005). Through these effects they modify habitats and thus the populations of invertebrates and other organisms at higher trophic levels. Herbivores are thus key drivers of ecosystem function and nutrient dynamics within grazed plant communities. Changes in grazing intensity and the species mix of grazing livestock can therefore have important implications for resulting biodiversity. Ongoing reform of the European Union Common Agricultural Policy (CAP) will lead to a shift in the way financial support for livestock is distributed and hence to changes in grazing management practices. Farmers will increasingly receive financial support subject to cross-compliance with various environmental conditions and for delivery of specific environmental and social objectives. In some areas, livestock are likely to be increasingly viewed as tools for habitat management rather than solely as producers of food and other commodities. Against this backdrop of policy change the British Society of Animal Science and the British Ecological Society organized a joint symposium at the BSAS Annual Meeting in April 2005 on the links between farm animals and biodiversity. Four papers from this symposium are presented as mini-reviews in the current issue of Animal Science. David Oglethorpe set the policy context in his review of the environmental implications of CAP reform (Oglethorpe, 2005). His paper highlighted the likely changes in the livestock sector that will ensue including a polarization of agriculture into intensive producers versus environmental managers, increasing extensification in the uplands and some substitution of beef with sheep. Jerry Tallowin then presented a review of the impact of grazing management on grassland biodiversity (Tallowin et al., 2005). His paper showed that lenient grazing pressure by cattle in species-rich grassland was sufficient to maintain botanical diversity but did not enhance it over a 5-year period. For species-poor grassland, grazing management could alter sward structure but, in the absence of seed sources, botanical diversity was resistant to change. There is obviously much research still be done in this area to support the development of suitable agri-environment measures under Pillar 2 support mechanisms. David Buckingham went on to consider the extent to which grassland management might influence habitat quality for farmland birds (Buckingham and Peach, 2005). His paper showed that the exacting requirements of declining granivorous birds pose the greatest challenges while the needs of soil invertebrate feeding species are more easily met under agri-environmental schemes. In the final paper by Bruno Martin, the influence of pasture diversity on cheese quality was the theme (Martin et al., 2005). This paper reviewed recent work, primarily from France, which has examined the links between the diet of grazing animals and the sensory characteristics of various Protected Designation of Origin cheeses. The review highlighted the sometimes subtle, but none the less important influence of the grazing environment on food quality. The purpose of the symposium was to draw together animal scientists, conservation biologists, ecologists and socio-economists to consider the changing role of farm livestock within the new ‘decoupled’ economic environment. Judging by the popularity of the symposium and the vibrant nature of the discussion that followed each paper, there are plenty of issues still to consider and the hope is that some of the contacts made at the meeting will yield fruitful collaborations in the future.

Adipose and muscle tissues undergo regulated growth and differentiation processes that are modulated by a wide range of factors. The interactions between myogenic cells and adipocytes play a significant role in growth and development, including the rate and extent of myogenesis, muscle growth, adipogenesis, lipogenesis/lipolysis, and in the utilization of energy substrates. Important hormones and growth factors involved in the regulation of these processes include glucocorticoids, insulin-like growth factors, various cytokines, insulin, and leptin. Interactions among these axes have important implications in their influence on relative fat and lean deposition and the efficiency of energy utilization in growth and development. As research progresses to better clarify the interactions among adipose tissue depots and muscle of different fiber types, pathways will become better understood, ultimately leading to the optimized management of fat and lean growth in domestic livestock species. This review will focus on elements of intercellular signaling, using data from cell culture studies to illustrate specific examples of signaling pathways between cells.

Ability to assess how solidly one is participating in their research arena is a metric that is of interest to many persons in academia. Such assessment is not easily defined, and differences exist in terms of which metric is the most accurate. In reality, no single production metric exists that is easy to determine and acceptable by the entire scientific community. Here we propose the SP-index to quantify the scientific production of researchers, representing the product of the annual citation number by the accumulated impact factors of the journals whereby the papers appeared, divided by the annual number of published papers. This article discusses such a productivity measure and lends support for the development of unified citation metrics for use by all participating in science research or teaching.

The purpose of this study was to determine if tenderness of callipyge (CLPG) longissimus dorsi muscle (LM) could be improved by: (1) extending the aging period to 48 days postmortem or (2) preventing rigor shortening by clamping. In CLPG and normal (NML) chops respectively, initial Warner-Bratzler shear values (WBS) were lower (P0.05) in clamped (CL) (5.5 and 3.6 kg) compared to unclamped (UCL) (7.4 and 4.9 kg) LM. In CLPG, an acceptable WBS (3.6 kg) was reached at 48 days PM, whereas, NML lambs reached an acceptable level (3.8 kg) by 3 days PM. Sarcomere lengths (SL) of CL (1.68 μm) were longer (P0.05) than for UCL (1.44 μm) and were negatively correlated with WBS (r=-0.55; P0.1). The appearance of Troponin-T (TNT) degradation product coincided with tender WBS values; 3 days postmortem in NML UCL and 48 days postmortem in CLPG. In conclusion, clamping reduced WBS possibly by reducing rigor shortening. Extended aging resulted in CLPG LM with acceptable WBS values, concurrent with the appearance of TNT degradation products.

Molecular mechanisms of peroxisome proliferator activated receptors (PPARs) are being defined rapidly, as illustrated by the volume of papers published. Much of the research is directed towards a clinical end-point/application; however, the non-homogeneous nature of adipose depots in laboratory animals is spurring similar research in domestic meat animals (such as beef cattle). Moreover, the size of adipose depots in meat animals remains an attractive feature for using them to obtain cells for PPAR research. Examination of meat-animal depot-specific PPAR moieties may provide novel information about adipocyte regulation that might be extrapolated to all animals.