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Physiol. Genomics 21: 343-350, 2005. First published March 22, 2005; doi:10.1152/physiolgenomics.00184.2004
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Received 12 August 2004; accepted in final form 15 March 2005.
Physiological Genomics 21:343-350 (2005)
1094-8341/05 $8.00 © 2005 American Physiological Society

Identification of genes expressed differentially in subcutaneous and visceral fat of cattle, pig, and mouse

Daisuke Hishikawa1,*, Yeon-Hee Hong1,*, Sang-gun Roh1, Hisae Miyahara1, Yukihiko Nishimura1, Ai Tomimatsu1, Hiroaki Tsuzuki1, Chizu Gotoh1, Masaaki Kuno1, Ki-Choon Choi1, Hong-gu Lee2, Kwang-keun Cho3, Hisashi Hidari4 and Shinichi Sasaki1

1 Department of Food Production Science, Faculty of Agriculture, Shinshu University, Nagano-ken, Japan
2 School of Agricultural Biotechnology, College of Agriculture and Life Science, Seoul National University, Seoul, Republic of Korea
3 Department of Animal Resources Technology, Jinju National University, Jinju, Republic of Korea
4 Field Center of Animal Science and Agriculture, Obihiro University of Agriculture and Veterinary Medicine, Obihiro, Japan


   ABSTRACT
TOP
 ABSTRACT
INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 GRANTS
 REFERENCES
 
The factors that control fat deposition in adipose tissues are poorly understood. It is known that visceral adipose tissues display a range of biochemical properties that distinguish them from adipose tissues of subcutaneous origin. However, we have little information on gene expression, either in relation to fat deposition or on interspecies variation in fat deposition. The first step in this study was to identify genes expressed in fat depot of cattle using the differential display RT-PCR method. Among the transcripts identified as having differential expression in the two adipose tissues were cell division cycle 42 homolog (CDC42), prefoldin-5, decorin, phosphate carrier, 12S ribosomal RNA gene, and kelch repeat and BTB domain containing 2 (Kbtbd2). In subsequent experiments, we determined the expression levels of these latter genes in the pig and in mice fed either a control or high-fat diet to compare the regulation of fat accumulation in other animal species. The levels of CDC42 and decorin mRNA were found to be higher in visceral adipose tissue than in subcutaneous adipose tissue in cattle, pig, and mice. However, the other genes studied did not show consistent expression patterns between the two tissues in cattle, pigs, and mice. Interestingly, all genes were upregulated in subcutaneous and/or visceral adipose tissues of mice fed the high-fat diet compared with the control diet. The data presented here extend our understanding of gene expression in fat depots and provide further proof that the mechanisms of fat accumulation differ significantly between animal species.

differential display and reverse transcriptase-polymerase chain reaction; fat depot


   INTRODUCTION
TOP
 ABSTRACT
 INTRODUCTION
MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 GRANTS
 REFERENCES
 
THERE ARE TWO TYPES OF ADIPOSE TISSUE, subcutaneous and visceral. Recent studies indicate that adipocytes in these two fat depots show differences in basal metabolic properties, for example, in regulating volume, lipid composition, and so on (22, 24). There is considerable current interest in visceral adipose tissue because of its relationship with various diseases such as cardiovascular disease, type 2 diabetes mellitus, hyperlipidemia, and syndrome X. There are a number of potential reasons why visceral adipose tissue may contribute to abnormalities in metabolism; among these are its anatomical site and pattern of venous drainage, and the presence of intrinsic and unique features of visceral adipocytes. The venous drainage of visceral adipose tissue is via the portal system, directly providing free fatty acid as a substrate for hepatic lipoprotein metabolism and glucose production (16, 22, 24). Additionally, in vitro studies using labeled tracers have demonstrated that visceral adipocytes have higher rates of lipid turnover than subcutaneous adipose tissue (19, 20).

Fat depot metabolism is also of importance in the commercial rearing of livestock such as cattle and pigs. One of the most important themes in the animal industry is the production of high quality meat at low cost. A better understanding of the specific accumulation mechanisms of fat depots should contribute to improved production efficiency in the animal industry.

Recently, gene expression profiles in normal and abnormal tissues have been produced using DNA chips, PCR subtractions, and mRNA differential display (5, 8, 9, 13, 28). Gene expression profiling has been used to search for factors that determine normal or abnormal differentiation mechanisms in adipocytes from ob/ob and db/db mice, and in 3T3-L1 preadipocytes (15, 17, 23). Despite the importance of understanding physiological differences between normal and abnormal fat depots, limited data are available to date. To help improve this situation, we have examined gene expression profiles in subcutaneous and visceral fat depots of cattle using differential display and reverse transcriptase-polymerase chain reaction (DDRT-PCR) analysis. This study identified a number of genes that showed different expression patterns in the two types of adipose tissue. The expression levels of some of these genes were subsequently investigated in adipose tissues of pigs and in control and high-fat-diet mice to investigate interspecies differences in fat depot metabolism.


   MATERIALS AND METHODS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
RESULTS
 DISCUSSION
 GRANTS
 REFERENCES
 
Animals.
Bovine and porcine abdominal subcutaneous and visceral adipose tissues were sampled from 10 female Japanese Black cattle (18–24 mo of age) and 10 crossbred castrated male swine (body mass ~100 kg) at a local abattoir. Cattle were weaned at ~6 mo of age, placed on a standard "growing" diet until 9–10 mo of age, and then given free access to water and "concentrate" diet during a fattening period until they were 18–24 mo of age. The concentrate used in the fattening period contained 71% total digestible nutrients (TDN), 14% crude protein, 10% crude fiber, 10% crude ash, 2% crude fat, 0.3% phosphorus, and 0.3% calcium. Pigs were weaned at ~2.5 mo of age, placed on a standard growing diet until 4 mo of age, and thereafter given free access to water and fed a "finishing" diet during a fattening period until their body weight reached 100 kg. The finishing diet contained 77% TDN, 12% crude protein, 5% crude fiber, 7% crude ash, 2% crude fat, 0.3% phosphorus, and 0.45% calcium. White adipose tissues were rapidly separated from subcutaneous and visceral (abdomen and ovaries) fat sites, immediately frozen in liquid nitrogen, and stored at –80°C until RNA extraction. Three-week-old male C57BL/6J mice were obtained from Charles River Japan. They were housed individually in cages with wire-mesh bottoms at a temperature of 20–22°C and a humidity of 50 to 60% under a 12:12-h light-dark cycle. The animals had free access to water and chow (Oriental Yeast, Chiba, Japan) containing 8.5% (wt/wt) fat, 43.7% carbohydrate, and 29.7% protein, with an energy content of 3.69 kcal/g, for an acclimatization period of 1 wk. The mice were then weighed and divided into two groups of six with approximately equal mean body weights. One group was fed the standard diet and the other received a high-fat diet for 6 wk (4–10 wk of age). The high-fat diet was obtained from Research Diet and contained 41% fat, 36% carbohydrate, and 23% protein, with an energy content of 4.33 kcal/g; its fat source was the same as that of the standard diet and it contained the same absolute amounts of protein and fiber as did the standard diet. The animals were weighed every week. At the end of the experimental period, the mice were killed by decapitation. White adipose tissues were rapidly separated from subcutaneous and visceral (epididymal) fat sites, immediately frozen in liquid nitrogen, and stored at –80°C until RNA extraction. All experiments were conducted in accordance with the Shinshu University Guide for the Care and Use of Experimental Animals and approved by an Institutional Review Board.

Total RNA extraction and DDRT-PCR.
Total RNA was extracted from pooled adipose tissues of Japanese Black cattle by the acid guanidium thiocyanate-phenol-chloroform method (11) and was treated with DNase I to eliminate possible contamination with genomic DNA. DDRT-PCR was performed between subcutaneous and visceral adipose tissues using a Differential Display Kit (Takara, Tokyo, Japan). We used 9 forward primers and 24 reverse primers for DDRT-PCR amplification. In total, we used 216 forward and reverse primer combinations to screen for genes differentially expressed in subcutaneous and visceral adipose tissues of cattle. Total RNA (250 ng) was subjected to reverse transcription in a 10-µl reaction mixture containing 1x first-strand synthesis buffer, 1 mM each dNTP, 0.1 µM anchored oligo(dT) primer, and 20 U of avian myeloblastosis virus-RT. The reaction mixture was incubated for 3 min at 70°C, followed by 1 h at 42°C after the addition of RT, and the reaction was terminated by incubation for 10 min at 75°C. PCR amplification was performed in a 20-µl reaction mixture composed of 1x PCR reaction buffer, 15 mM MgCl2, 20 µM each dNTP, 1 U of Taq DNA polymerase, 1 µM of 1 of 24 anchor primers, and 1 µM of 1 of 9 arbitrary primers. The PCR protocol consisted of an initial denaturation at 95°C for 3 min; 40 cycles of denaturation at 94°C for 30 s, annealing at 40°C for 2 min, and extension at 72°C for 30 s; and a final extension at 72°C for 5 min. All reactions were performed in duplicate.

Gel electrophoresis and elution of DNA fragments.
The amplified PCR products (10 µl) were separated on an 8% polyacrylamide gel under nondenaturing conditions in Tris-borate-EDTA buffer for ~3.5 h at 40 W. Gels were stained with ethidium bromide and exposed to UV light, and then scanned for comparison of changes in gene expression between visceral and subcutaneous adipose tissues of cattle. Differentially displayed PCR bands were excised from the gel, washed twice with 100 µl of RNase-free water, and boiled for 5 min in a water bath. The DNA fragments were then either subjected to reamplification or immediately frozen at –20°C.

Cloning and sequencing of amplified products.
Extracted DNA fragments were subjected to reamplification in a 40-µl reaction mixture under the same conditions as the initial PCR. The resulting products were separated by electrophoresis on a 1.2% agarose gel, and their sizes were compared with those of the initial fragments present on the original DDRT-PCR gels. They were then cloned into the pGEM-T vector (Promega, Madison, WI). Recombinant plasmids containing cDNA inserts were purified, and the nucleotide sequences of the inserts were determined with an automated sequencer (ABI 310) and a Dye Terminator reaction kit (Perkin Elmer, Norwalk, CT). DNA homology searches were performed, using the BLAST protocol provided by the National Center for Biotechnology Information, of nucleotide sequences in the GeneBank database.

Semiquantitative RT-PCR.
Primers, targeted to identified clones, were designed to contain 18–23 bases and have a melting temperature of 56–60°C. RT-PCR was performed on subcutaneous and visceral adipose tissues of seven Japanese Black cattle, six control and six high-fat diet-fed C57BL/6J mice, and six crossbred pigs as described above. The primers used for semiquantitative RT-PCR amplification in this experiment were designed from well-conserved sequences to amplify genes in all three species. PCR products were separated on a 1.2% agarose gel. Preliminary experiments showed that the linear amplification phase occurred from 28 to 33 cycles; all subsequent amplifications were therefore performed under these conditions. The housekeeping gene ß-actin was used as an internal control. PCR products were resolved on a 1.2% agarose gel; the DNA was visualized by ethidium bromide staining and analyzed with NIH image software, where band intensity is expressed in pixels. Relative gene expression was calculated as the ratio of band intensity of the cloned gene to that of the ß-actin. The amplified cDNAs were subcloned into pGEM-T easy vector, and the sequences were confirmed using an automated DNA sequencer.

Statistical analysis.
Data are presented as means ± SE of six or seven animals. Comparisons were tested by ANOVA, followed by Fisher’s protected least significant difference as a post hoc analysis. Significance was set at P < 0.05.


   RESULTS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
DISCUSSION
 GRANTS
 REFERENCES
 
Differential display and isolation of fat depot-related cDNA fragments.
We used a DDRT-PCR method to isolate genes differentially expressed in subcutaneous and visceral adipose tissues of Japanese Black cattle. Under standard differential display (DD) conditions, and after analysis of the agarose gels, we isolated 16 and 13 cDNA fragments highly expressed in subcutaneous and visceral adipose tissues, respectively. We selected and isolated bands that showed at least a twofold difference in level of expression between subcutaneous or visceral adipose tissues. Details of the 29 genes are given in Table 1; we categorized the genes into eight functional groups to aid interpretation of gene expression in these fat depots.


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  		Table 1. cDNA fragments isolated by DDRT-PCR

 
Confirmation of DDRT-PCR by RT-PCR in cattle.
To confirm the differential expression of the genes, semiquantitative RT-PCR, using specific primers, was performed. The primer sequences, their target genes, and their product sizes are shown in Table 2. These analyses were carried out in animals different from those used for the DD experiment to ensure that the observed differential expression was not due to a particular genetic background or response of a single animal. RNA from four to six cattle was used for this purpose. Of 29 initial candidates, we confirmed differential expression between subcutaneous and visceral fat, in agreement with the expression patterns of DDRT-PCR, for cell division cycle 42 homolog (CDC42), prefoldin-5, decorin, phosphate carrier, 12S ribosomal RNA gene, and kelch repeat and BTB domain containing 2 (Kbtbd2) (Figs. 2 and 3). Of the 29 genes initially identified as showing apparent differential expression between the two adipose tissues, 23 proved to be false positives. Semiquantitative RT-PCR analysis of the 29 candidate genes showed that there were no significant differences in expression of 23 of the genes between the two adipose tissues of cattle, pigs, and mice (data not shown).


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  		Table 2. Primers used for semiquantitative RT-PCR

 
Comparison of gene expression pattern in cattle, mouse, and pig.
The expression patterns of the six differentially expressed genes described above were examined in subcutaneous and visceral adipose tissues of pigs and mice fed either the control or high-fat diet. The primers of the six genes used in our experiment were designed from conserved sequences of cattle, mouse, and pig genes. Mice fed a high-fat diet from age 4–10 wk showed a greater increase in body weight than those fed a control diet (Fig. 1). In addition, the amounts of subcutaneous and visceral fat in the animals fed the high-fat diet were ~1.5 and 2.5 times greater, respectively, than in mice fed the standard diet.



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  		Fig. 1. Growth curves of mice fed either a control or a high-fat diet. Data are means ± SE of values from 6 mice.

 
The levels of CDC42 mRNA were higher in visceral adipose tissue than in subcutaneous adipose tissue in cattle, pigs, and mice fed the control diet (Fig. 2). CDC42 mRNA levels were elevated significantly in both subcutaneous and visceral adipose tissues of mice fed the high-fat diet compared with those fed the standard diet (Fig. 2).



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  		Fig. 2. Levels of CDC42, prefoldin-5, and decorin mRNA in subcutaneous and visceral adipose tissues of 7 cattle, 6 mice fed control and high-fat diets, and 6 pigs. The RT-PCR results shown are representative of 6–7 independent experiments with the same protocol. ß-actin was used as an internal control for RT-PCR analysis. M, 100-bp molecular size marker; S, subcutaneous adipose tissue; V, visceral adipose tissue; HF, mice fed the high-fat diet; C, mice fed the control diet. Each column represents the mean ± SE of 6–7 animals. *Significant difference between subcutaneous and visceral fat of each animal (P < 0.05). **Significant difference between same tissue of mice fed control and high-fat diets (P < 0.05).

 
The levels of prefoldin-5 mRNA were significantly higher in subcutaneous adipose tissue than in visceral adipose tissue in cattle and mice fed the standard diet (Fig. 2). In mice fed the high-fat diet, prefoldin-5 mRNA levels were increased in both tissues (Fig. 2). The pattern of prefoldin-5 expression was different in pigs than in cattle and mice; in the pig, mRNA levels were higher in visceral adipose tissue than in subcutaneous adipose tissue (Fig. 2).

Decorin mRNA levels were higher in visceral adipose tissue than in subcutaneous adipose tissue in cattle, pigs, and mice fed the control diet (Fig. 2). Mice fed the high-fat diet showed a significant elevation of decorin mRNA in visceral adipose tissues (Fig. 2).

The expression of the phosphate carrier gene was significantly higher in subcutaneous adipose tissue than in visceral adipose tissue in cattle (Fig. 3). In contrast, in pigs and in mice fed the control diet, expression was significantly higher in visceral adipose tissue. Mice fed a high-fat diet had significantly increased levels of phosphate carrier gene mRNA levels in both adipose tissues (Fig. 3).



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  		Fig. 3. Levels of phosphate carrier, 12S rRNA, and Kbtdb2 mRNA in subcutaneous and visceral adipose tissues of 7 cattle, 6 mice fed control and high-fat diets, and 6 pigs. The RT-PCR results shown are representative of 6–7 independent experiments with the same protocol. ß-actin was used as an internal control for RT-PCR analysis. For definitions, see legend to Fig. 2. Each column represents the mean ± SE of 6–7 animals. *Significant difference between subcutaneous and visceral fat of each animal (P < 0.05). **Significant difference between same tissue of mice fed control and high-fat diets (P < 0.05).

 
The expression pattern of 12S rRNA differed in the three species examined: in cattle, mRNA levels were significantly higher in subcutaneous adipose tissue; in pigs, the two adipose tissues showed similar levels of expression; in mice fed the control diet, mRNA levels were significantly higher in visceral adipose tissue (Fig. 3). Both adipose tissues showed significant upregulation of 12S rRNA in mice fed the high-fat diet (Fig. 3).

The level of Kbtbd2 mRNA was higher in subcutaneous adipose tissue than in visceral adipose tissue in cattle (Fig. 3). In contrast, in both pigs and in mice fed the control diet, Kbtbd2 expression was higher in visceral adipose tissue than in subcutaneous adipose tissue. The levels of Kbtdb2 were elevated significantly in subcutaneous adipose tissue in mice fed the high-fat diet (Fig. 3).


   DISCUSSION
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
GRANTS
 REFERENCES
 
We have identified six genes that are differentially expressed in subcutaneous and visceral adipose tissues of cattle and furthermore shown that these genes also show differential expression patterns in pigs and mice. Comparison of the patterns of expression of genes belonging to different functional groups suggests that many factors control where fat is deposited. Our data can be interpreted in two ways. First, the regulation of fat accumulation in individual depots is clearly different for genes involved in different metabolic processes, for example in the cell matrix, mitochondria, and signal transduction. Second, gene expression patterns vary between different species, suggesting that control of the metabolic processes of fat depot development is likely to be species specific. Various factors have been implicated in fat depot development: location of fat depot (e.g., visceral vs. subcutaneous), regulation of the regenerative capacity of individual depots, and regulation of metabolic status by paracrine and autocrine signals generated by different cell types present in a particular depot. Although visceral obesity appears to be associated with increased morbidity, the basis of this association is not clear. In cattle, visceral adipose tissues dramatically increase after 10 mo of age despite the absence of any physiological abnormality. In pigs, subcutaneous fat rapidly accumulates after 3 mo of age. This comparison suggests that, not only are there differences in the accumulation of fat over the whole body in cattle, pigs, and mice, but fat accumulation in each adipose tissue is controlled by species-specific regulatory mechanisms.

CDC42 is a member of the Rho GTPase family. Rho proteins containing CDC42 act as molecular switches to control cellular processes by cycling between the active GTP-bound and inactive GTP-bound states. CDC42 mRNA level does not change during differentiation of 3T3-L1 preadipocytes to adipocytes (25). Moreover, a recent study has demonstrated an important role for CDC42 as a novel signaling molecule in the insulin action pathway leading to glucose transporter-4 translocation and stimulation of glucose transport. In addition, it was found that CDC42 is downstream of G{alpha}q/11 in that signaling system and lies upstream of phosphatidylinositol 3-kinase and PKC{lambda} (30). The high expression level of CDC42 in visceral fat of cattle, pig, and mice and in high-fat diet induction of mice may indicate a difference of insulin action in fat depots and in high-fat diet induction. The importance of CDC42 action in specific fat depots remains to be explored, but the data suggest complex effects dependent on the interplay of circulating insulin signaling and CDC42 expression. In addition, the pattern of expression of CDC42 is similar in cattle, pigs, and mice in showing higher expression levels in visceral adipose tissue than in subcutaneous adipose tissue; this consistency of expression pattern may indicate that CDC42 is more involved with the development of visceral than subcutaneous fat.

Prefoldin is a recently discovered chaperone protein that functions by directing unfolded target proteins to cytosolic chaperonin. Prefoldin binds to nascent actin during its biosynthesis and may thereby block the irreversible agglutination of actin (31). The relative expression of prefoldin-5 was different in subcutaneous and visceral adipose tissues of pigs compared with cattle and mice. It may indicate that, during fat accumulation, the cytoskeleton differs in the two fat depots in animal species and is further changed by high-fat diet induction. Because the extracellular matrix is linked to the nucleus by cytoskeletal fibers that facilitate hormonal signal transduction (4), during adipose tissue enlargement, structural changes take place that may affect cytoskeleton and extracellular matrix protein expression. With regard to this, our previous results showed that cytoskeletal nonmuscle-type cofilin is differentially expressed in visceral fat and may play a role in lipid accumulation (10). Although the function of prefoldin-5 is still unclear, the differential expression of prefoldin-5 in fat depots may indicate that the cytoskeleton can affect cell morphology and may also be a factor in the etiology of interspecies differences.

We also found that decorin expression is higher in visceral adipose tissue than in subcutaneous adipose tissue of cattle, pigs, and mice. Decorin is a proteoglycan and is present in the extracellular matrix. Proteoglycans have been suggested to play important roles in the morphogenesis of many organs. A recent study suggested that alteration in the expression level of extracellular matrix proteins may contribute to the development of obesity-associated adipose tissue growth (7). The relatively high level of expression of decorin in visceral adipose tissue and after induction by a high-fat diet may contribute to the proliferation and development of adipose tissue. It may suggest that the extracellular matrix is changed in individual fat depots, with fat accumulation being different depending on the environment of each fat depot in the whole body.

Both the phosphate carrier and 12S ribosomal RNA genes are mitochondrial genes. Mitochondria generate most of the ATP used by cells to drive reactions that require an input of free energy. The phosphate carrier gene catalyzes the transport of inorganic phosphate across the inner mitochondrial membrane into the matrix compartment for the oxidative phosphorylation of ADP to ATP (14). The 12S ribosomal RNA gene codes an essential part of the decoding site of the ribosome and a subunit association crucial for either RNA-protein or RNA-RNA interactions (18, 34). The differential expression of these mitochondrial genes in subcutaneous and visceral fat depots, between animal species, and after high-fat diet are indicative of differences in mitochondrial function presumably linked to differences in energy requirements.

The kelch motif is an ancient and evolutionarily widespread sequence motif of 44–56 amino acids in length (27). In general, kelch-repeat ß-propellers are involved in protein-protein interactions; however, the modest sequence identity between kelch motifs, the diversity of domain architectures, and the partial information on this protein family in any single species all present difficulties for developing a coherent view of the kelch-repeat domain and kelch-repeat protein families (1, 27, 33). Kbtdb2 also has a BTB/POZ domain characteristic of a protein-protein interaction interface (3). The BTB domain is known to have various functions: repression of transcriptional activity, punctate localization of the protein in the nucleus, and interaction with components of the histone deacetylase complex (2). The biological function of Kbtdb2 in adipose tissue remains to be determined, although there is the intriguing possibility of changes in protein-protein interactions in the development of fat depots.

Interestingly, the six differentially expressed genes isolated from cattle in our study are upregulated in subcutaneous and/or visceral adipose tissues of mice fed a high-fat diet. With the exception of prefoldin-5, the genes were highly expressed in the visceral adipose tissues of mice fed a control diet. This observation shows that many genes with different biochemical functions can influence the development of adipose tissue fat depots. However, these six genes were not changed during adipocyte differentiation of 3T3-L1 cells and of bovine and porcine primary preadipocytes (data not shown). We suggest that the process of fat accumulation in individual depots is not related to adipocyte differentiation from preadipocytes, even though such differentiation is still occurring during fat accumulation. Therefore, the upregulation of the expression of these six genes by the high-fat diet indicates that they may be involved both with the development of adipose tissues and with fat accumulation. Furthermore, these six genes differentially expressed in regional fat depots may contribute to the regional differences in the development of the each adipose tissue. There is a need to obtain a more detailed picture of how the many cell types present in different fat depots of each animal (e.g., adult adipocytes, preadipocytes, stem/progenitor cells, tissue macrophages, neurons, and endothelial cells) interact with each other and sense and respond to the metabolic and inflammatory status of the entire organism.

It is well known that nutritional state is one of the important factors on gene expression profiles (12, 29, 32). Recent studies have demonstrated that expression of genes related to adipocyte differentiation and lipid metabolism is regulated by nutritional status; the pattern of development of adipose tissue can be altered by variations in nutrition (6, 21, 26, 32). Livestock such as cattle and pigs are commonly fed according to a feeding program in which the diet varies at different stages of the animals’ development. Although expression of the six genes identified here can be altered by changes in the nutritional conditions, such as diets either high or low in energy and protein, the patterns of differential gene expression in regional fat depots were consistent in cattle and pigs raised using a standard feeding program. The main objective of the present study was to determine which genes typically show differential expression in different fat depots of cattle and pigs that had been raised under the standard conditions used in the livestock industry. Clearly, the next stage of this investigation will be to characterize how changes in nutritional status influence the growth performances of cattle and pigs.

In this study, we found 29 genes (from 8 functional groups) that appeared to show differential expression in fat depots of Japanese Black cattle. Six of these genes were confirmed as being differentially expressed and were studied in detail in cattle, pigs, and mice fed either a standard or a high-fat diet. Subcutaneous and visceral fat tissues are thought to display marked differences in both basal and stimulated lipolysis or lipogenesis after differentiation of preadipocytes to adipocytes. Further studies have to be performed examining the metabolic properties of each type of fat tissue to determine whether there are differences between subcutaneous and visceral adipose tissues. The question arises whether regional, not completely specified, regulatory mechanisms account for these different findings. As mentioned above, characteristic patterns of maturation and proliferation of adipocytes can be found at every adipose tissue depot. However, specific biomarkers of changes in cellular physiology and metabolism brought on by accumulation of fat in an individual depot that are truly associated with the development of adipose tissues of animal species are clearly needed. Our gene expression profiles indicate that adipose tissues can show characteristic biochemical differences and that these differences may vary between species. Such information contributes to our understanding of the metabolic processes involved in the formation of fat depots.


   GRANTS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 GRANTS
REFERENCES
 
This work was partly supported by Grant-in-Aid No. 15780178 to S.-G. Roh and No. 15580246 to S. Sasaki for Scientific Research from the Ministry of Education, Science, Sports and Culture of Japan.


   FOOTNOTES
 
Article published online before print. See web site for date of publication (http://physiolgenomics.physiology.org).

* D. Hishikawa and Y.-H. Hong contributed equally to this work. Back

Address for reprint requests and other correspondence: S.-G. Roh, Dept. of Food Production Science, Faculty of Agriculture, Shinshu Univ., Nagano-ken 399-4598, Japan (e-mail: sangroh{at}gipmc.shinshu-u.ac.jp).

doi:10.1152/physiolgenomics.00184.2004.


   REFERENCES
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 GRANTS
 REFERENCES
 

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