J. Anim. Sci. 2004. 82:3493-3499
© 2004 American Society of Animal Science
ANIMAL GROWTH, PHYSIOLOGY, AND REPRODUCTION |
Effect of heat exposure on uncoupling protein-3 mRNA abundance in porcine skeletal muscle
M. Katsumata1,
M. Matsumoto,
S. Kawakami2 and
Y. Kaji
Department of Animal and Grassland Research, National Agriculture Research Center for Kyushu Okinawa Region, Kumamoto 861-1192, Japan
 |
Abstract
|
|---|
Exposure to cold increases abundance of mRNA for uncoupling protein-3 (UCP3) in skeletal muscle, whereas the influence of exposure to heat is unknown. Thus, we conducted a study to investigate the influence of heat exposure on UCP3 mRNA abundance in porcine skeletal muscle. Three pigs aged 110 to 120 d, with an average BW of 75 kg, from each of eight litters were used. Each littermate was assigned to one of three treatment groups; one group was reared at 32°C and fed ad libitum (32AL) for 4 wk, whereas the other two groups were maintained at 23°C for the same period, and either pair-fed the intake of their 32AL littermates (23PF), or fed ad libitum (23AL). The RNase protection assay revealed that UCP3 mRNA abundance in longissimus dorsi and rhomboideus muscles was higher (P < 0.05) in the 32AL group than the 23PF group. The 23AL group also had significantly higher UCP3 mRNA abundance than the 23PF group in these muscles. Plasma total 3,5,3'-triiodothyronine concentration of the 32AL group was lower (P < 0.05) than that of the 23PF group, whereas mRNA abundance of thyroid hormone receptor (TR) isoforms, TR
1 and TR2, in these muscles was not affected, suggesting that the 32AL group was in a relatively hypo-thyroid state. Because thyroid hormone up-regulates UCP3 expression, these results indicate that factors other than thyroid hormone may play a role in regulating UCP3 mRNA abundance in skeletal muscle of heat-exposed pigs.
Key Words: Uncoupling Protein-3 • 3,5,3'-Triiodothyronine • Thyroid Hormone Receptor • Heat Exposure • Skeletal Muscle • Pig
|
Introduction
|
|---|
Uncoupling protein-3 (UCP3) is a member of the mitochondrial anion carrier family primarily expressed in skeletal muscle and brown adipose tissue (Boss et al., 1997
; Matsuda et al., 1997). Due to its high homology to UCP1, which plays an important role in adaptive thermogenesis, a primary function of UCP3 was thought to be control of thermogenesis. Thyroid hormone increases abundance of mRNA for UCP3 in skeletal muscle and brown adipose tissue, whereas the hypothyroid state is associated with lower abundance of UCP3 mRNA in skeletal muscle (Gong et al., 1997; Larkin et al., 1997; Lanni et al., 1999). Because thyroid hormone is a key regulator of thermogenesis in mammals, these findings suggest that UCP3 plays a role in controlling thermogenesis. Although UCP3 mRNA abundance in rat skeletal muscle is upregulated by cold exposure (Lin et al., 1998), the influence of heat exposure on UCP3 mRNA abundance is unknown. Uncoupling protein-3 mRNA abundance is possibly affected by heat exposure because heat exposure may cause downregulation of thermogenesis (Collin et al., 2001a,b). In addition, heat exposure causes hypothyroidism in animals (Sano et al., 1982; Collin et al., 2002), suggesting that UCP3 mRNA abundance may be downregulated by heat exposure. However, upregulation of UCP3 mRNA in muscle induced by fasting refutes a role for UCP3 in controlling thermogenesis because fasting is generally associated with a decrease in thermogenesis (Bezaire et al., 2001). Further, evidence suggests a role for UCP3 in eliminating reactive oxygen species generated in mitochondria (Brand et al., 2002).
On the basis of these earlier investigations, this study was conducted to elucidate the influence of heat exposure on UCP3 mRNA abundance in porcine skeletal muscle, especially in relation to thyroid status. Our aim is to investigate underlying mechanisms of hindered performances of pigs during hot seasons. Thus, long-term rather than acute effects of heat exposure were evaluated in the current study.
|
Materials and Methods
|
|---|
Animals and Experimental Design
Eight litters of Duroc x (Large White x Landrace) pigs, 110 to 120 d of age, were used. Three barrows of similar BW were selected and were transferred to air-conditioned rooms 1 wk before the experimental period. Pigs were kept individually throughout the 1 wk of adaptation period and 4 wk of the experimental period. Average initial BW of the pigs was 75 kg. Pigs of this BW are markedly influenced by a high ambient temperature (Katsumata et al., 1996). Littermates were assigned randomly to one of the three treatment groups: one group was reared at 32°C and fed ad libitum (32AL), whereas the other two groups were maintained at 23°C and either pair-fed on the basis of the diet consumption of their 32AL littermates (23PF) or fed ad libitum (23AL). The diet provided to the pigs included 140 g of CP and 3.39 Mcal of digestible energy/kg of diet (as-fed basis). The diet for the 23PF group was provided as three meals at equal size at 0900, 1300, and 1600 to avoid the large postprandial heat increment caused by one large meal. Drinking water was always available.
Following the regular management and care for pigs of National Agricultural Research Center for Kyushu Okinawa Region (KONARC), the pigs were slaughtered at 0900 at the abattoir of KONARC by electrical stunning followed by exsanguination. As noted previously, the specific aim of this study was to determine the long-term effects of ambient temperature and/or nutritional status rather than the acute effects of feeding. Therefore, the diet was removed 18 h before the sampling. Nonetheless, a criticism may arise that this food deprivation affected gene expression of UCP3 and thyroid hormone receptor (TR) isoforms. Thus, we tested whether 18-h food deprivation affected mRNA abundance of UCP3 and TR isoforms in muscle from pigs kept at 26°C; five barrows aged 9 wk were subjected to 18-h food deprivation before tissue samplings, whereas another five barrows aged 9 wk were allowed free access to diet until tissue sampling.
Muscles selected for analysis of UCP3 and TR mRNA isoforms were longissimus dorsi (LD; a predominant fast-twitch oxidative-glycolytic muscle) and rhomboideus (a mixed slow- and fast-twitch oxidative-glycolytic muscle). We selected these functionally and metabolically distinct muscles because muscle-type dependency in the regulation of UCP3 gene expression had been already reported (Samec et al., 1998a,b). Muscles were taken rapidly, divided into 5-g portions, frozen in liquid N, and stored at –80°C. Care was taken to ensure that muscles were sampled at the same relative point in relation to depth and distance from origin. In particular, samples of LD were taken from the midback region. There was a concern that it might be technically difficult to get appropriate blood samples when animals are slaughtered at the abattoir. Further, we wanted to avoid stress due to blood sampling with puncture shortly before the tissue samplings. Thus, blood samples were collected via jugular vein venipuncture 19 h before the tissue sampling. Plasma was stored at –20°C until analysis for plasma total 3,5,3'-triiodothyronine (T3) concentration by RIA carried out by SRL, Inc. (Tokyo, Japan). Plasma NEFA concentration was determined by using a commercially available kit (NEFA C-Test Wako, Wako Pure Chemicals, Osaka, Japan). All experimental procedures were carried out in accordance with the Regulation of Animal Experiments of KO-NARC and approved by their Animal Experiments Committee.
Total RNA Extraction and RNase Protection Assay
Total RNA was extracted from 0.5-g portions of frozen muscle samples by the guanidinium thiocyanate method (Chomczynski and Sacchi, 1987) and quantified by absorbance at 260 nm. The integrity of total RNA was routinely checked by agarose gel electrophoresis and ethidium bromide staining of the two ribosomal RNA bands. Messenger RNA of porcine LD muscle was purified from 100 µg of its total RNA by using a commercial kit (OligotexTM-dT30 <Super>, Takara, Kyoto, Japan), and the aliquot was used to generate first-strand cDNA using a commercial kit (first Strand cDNA Synthesis Kit for RT-PCR [AMV], Roche Diagnostics, Tokyo, Japan). Polymerase chain reaction was carried out on this cDNA to generate an UCP3 DNA fragment, using oligonucleotide primers based on the published porcine UCP3 cDNA sequence (Werner et al., 1999). The 5' primer (5'-CG[GAATTC]CGCATCACGAGGAA TGCCATC-3') representing nucleotides 799 to 817 of the UCP3 sequence contained an EcoRI recognition site (in parentheses). The 3' primer (5'-CCC[AAGCTT]GG TCCGAAGGCAGAGACAAAG-3') was the complement of nucleotides 904 to 922 and contained HindIII recognition site (in parentheses). The resulting PCR product was digested with EcoRI and HindIII to give a 130-bp DNA fragment, cloned into Bluescript KS (Stratagene, La Jolla, CA), and the DNA sequence was verified by fluorescent double-stranded DNA sequencing. The plasmid DNA was linearized by EcoRI digestion and used as a template to generate an antisense riboprobe in an in vitro transcription system using T3 RNA polymerase in the presence of [-32P]UTP. This UCP3 riboprobe had a full length of 200 nucleotides, of which 130 were protected.
The riboprobes used for TR isoforms were constructed to detect mRNA of TR1 and TR2 isoforms in porcine muscle (White and Dauncey, 1999). The total RNA used was extracted from two different muscles, LD and rhomboideus. The RNase protection assay for UCP3 mRNA with the novel riboprobe was carried out in duplicate using 25-µg samples of total RNA and the assay for TR isoforms was carried out as single assay using 50-µg samples of total RNA. The method of RNase protection assay has been described previously (Katsumata et al., 1999). Samples were hybridized with a small molar excess of the radiolabeled antisense UCP3 and TR isoforms to ensure linearity of the assay with respect to RNA. After 16 h of hybridization at 45°C, excess nonprotected RNA was digested with RNase A (50 mg/L; approximately 1 U/sample) and RNase T1 (30 x 104/L; approximately 80 U/sample). The protected hybridization products were purified by extraction in phenol/chloroform/isoamyl alcohol (25:24:1) and separated on 6% polyacrylamide sequencing gels. The dried gels were exposed to x-ray film at –80°C, and relative intensities of the protected bands were quantified by densitometry (Densitograph, Atto, Osaka, Japan).
Real-Time Reverse Transcription PCR Analysis
We confirmed previously that RNase protection assay and real-time reverse-transcription (RT) PCR analysis gave the same results in different studies; a low-lysine diet up-regulates GLUT4 mRNA abundance in porcine muscle (Katsumata et al., 2001, 2003; our unpublished observation). Based on these experiences, real-time RT-PCR analysis was conducted to test whether 18-h food deprivation affected mRNA abundance of UCP3, TR1 and TR2. ß-Actin was used as an internal standard. One microgram of each total RNA sample was subjected to RT to obtain first-strand cDNA using a commercial kit (SuperScript First-Strand Synthesis System for RT-PCR; Invitrogen Corp., Carlsbad, CA). Quantification of mRNA was performed with the Roche Diagnostics apparatus using a Light Cycler-Fast Start DNA Master SYBR Green I kit (Roche Diagnostics K. K., Tokyo, Japan). Linearity of each assay was always checked with a standard curve at 10-fold serial dilution of a standard sample from 0.1 to 0.0001, as recommended by the manufacturer. Further, all the tested samples were subjected to 0.01 dilutions as all the amplification plots stayed within the range of each standard curve. Forward and reverse primers were as follows, respectively; UCP3, 5'-CAACATCACGAGGAATGCCATC-3' and 5'-AAGGCAGAGACAAAGTGGCAGG-3'; TR1,5'-TCCGACGCCATCTTTGAACTG-3' and 5'-GATCATGCGGAGGTCAGTCAC-3'; TR2, 5'-GGACGACACG GAAGTGGCTC-3' and 5'-TGCGGACCCTGAACAACA TGC-3'; ß-actin, 5'-TCCTGTGGCATCCATGAAACT-3' and 5'-GAAGCATTTGCGGTGCACGAT-3' (Nudel et al., 1983).
Statistical Analyses
The statistical analysis was carried out by using the GLM procedure of SAS (SAS Inst., Inc., Cary, NC). The data obtained from pigs of the 32AL, 23AL, and 23PF groups were subjected to ANOVA for a randomized block design, where litters were blocks, and treatments were the main effects, whereas the data obtained from pigs aged 9 wk were subjected to one-way ANOVA. Comparisons between means were made by the LSMEANS statement of the GLM procedure, computing the least significant differences. Differences were considered significant when P < 0.05. Results were expressed as means and pooled standard errors.
|
Results
|
|---|
Growth performance and concentrations of plasma total T3 and NEFA are shown in Table 1. As expected, food intake and growth rate were less (P < 0.01) in the 32AL group than in the 23AL group. Interestingly, despite the same food intake, the growth rate of the 32AL group was less (P < 0.01) than that of the 23PF group. As a result, feed efficiency was less (P < 0.05) in the 32AL group compared with the 23PF group. Plasma total T3 concentration of the 23PF group was greater (P < 0.05) than those of the 32AL and 23AL groups, whereas no difference was observed between the 32AL and the 23AL groups (P = 0.680). Concentration of plasma NEFA was not affected by the treatments (P = 0.811).
View this table:
[in this window]
[in a new window]
|
Table 1. Growth performance and concentrations of plasma total 3,5,3'-triiodothyronine (T3) and nonesterified fatty acida
|
|
As shown in Table 2, the effects of food deprivation for 18 h on abundance of mRNA for UCP3, TR1, and TR2 in LD and rhomboideus of pigs at 9 wk of age were not detected. Neither ambient temperature nor food intake affected mRNA abundance of TR isoforms (Figure 1). An autoradiograph obtained using the newly constructed riboprobe, showing protected bands of 130 bp for UCP3 and results from the RNase protection analysis of UCP3 mRNA, are given in Figure 2. Although we had expected that UCP3 mRNA abundance would be downregulated at a high ambient temperature, the abundance in LD and rhomboideus of the 32AL group was 10- and 6-fold higher than that of the 23PF group, respectively (P < 0.01; Figure 3). Further, UCP3 mRNA abundance in these two muscles of the 23AL groups was also higher than that of the 23PF group (P < 0.01; Figure 3). No differences were observed in UCP3 mRNA abundance between the 32AL and the 23AL groups (Figure 3).
View this table:
[in this window]
[in a new window]
|
Table 2. Effect of 18-h food deprivation on uncoupling protein-3 (UCP3), thyroid hormone receptor 1 (TR1), and thyroid hormone receptor 2 (TR2) mRNA abundance in longissimus dorsi and rhomboideus from pigs at 9 wk of agea
|
|
View larger version (23K):
[in this window]
[in a new window]
|
Figure 1. Abundance of mRNA for thyroid hormone receptor (TR) isoforms in longissimus dorsi (LD) and rhomboideus from pigs reared at 32°C (32AL) or maintained at 23°C and either pair-fed the intake of their 32AL littermates (23PF), or fed ad libitum (23AL). Mean value of TR1 from each muscle of the 32 AL group is expressed as 1. Values represent means and pooled SE, n = 8.
|
|
View larger version (52K):
[in this window]
[in a new window]
|
Figure 2. Autoradiograph from RNase protection assay illustrating uncoupling protein-3 (UCP3) mRNA abundance in rhomboideus muscle in two littermate groups of pigs reared at 32°C (32AL) or maintained at 23°C and either pair-fed the intake of their 32AL littermates (23PF) or fed ad libitum (23AL). Duplicate measurements were made. The gel had been exposed to x-ray film for 48 h.
|
|
View larger version (20K):
[in this window]
[in a new window]
|
Figure 3. Abundance of mRNA for uncoupling protein-3 (UCP3) in longissimus dorsi and rhomboideus from pigs reared at 32°C (32AL) or maintained at 23°C and either pair-fed the intake of their 32AL littermates (23PF), or fed ad libitum (23AL). Mean values of the 32AL group are expressed as 1. Values are the means and pooled SE, n = 8. Values with different letters differ, P < 0.05.
|
|
|
Discussion
|
|---|
Real-time RT-PCR analysis did not detect effects of food deprivation for 18 h on mRNA abundance of UCP3, TR1, and TR2 in LD and rhomboideus. Indeed, as indicated by the large variation particularly observed in TR2 mRNA abundance in rhomboideus, one of the reasons that the assay did not detect the effects of the food deprivation might have been the size of the experiment. However, no definite tendency was observed. Therefore, food deprivation for 18 h may not be long enough to affect mRNA abundance of these genes at least in porcine skeletal muscle. Thus, we believe that the observed change in mRNA abundance of UCP3 and TR isoforms from the 32AL, 23AL, and 23PF groups are the results of long-term effects of thermal environment and/or nutritional status. On the other hand, as it is generally accepted that food deprivation upregulates UCP3 mRNA expression in the muscle of other species, a time study to elucidate the effects of feed intake on UCP3 mRNA abundance in porcine muscle may be necessary. The most important finding is that UCP3 mRNA abundance in LD and rhomboideus was significantly greater in the 32AL and the 23AL groups than in the 23PF group. Two opposite interpretations of this finding may be possible; UCP3 mRNA abundance was increased in the 32AL and 23AL groups, or it was down-regulated in the 23PF group. According to our latest study with rats fed ad libitum, UCP3 mRNA abundance in LD of rats was increased after 4 d exposure to 32°C, whereas it was not different from that of rats fed kept at 23°C when the exposure was elongated to 14 d (unpublished observations). The data showed that UCP3 mRNA expression was upregulated shortly after the application of heat exposure and then down-regulated toward to the level of the 23°C group over the next 10 d. As rats were fed ad libitum, feed intake was approximately 40% lower in rats kept at 32°C compared with rats kept at 23°C. Relatively severe food restriction by 50 to 60%, resulting in decreased BW, downregulates or does not affect UCP3 mRNA abundance in rodent muscle (Cusin et al., 1998; Cha et al., 2004). Therefore, the upregulation of UCP3 mRNA in rat muscle shortly after the application of heat exposure is probably due to heat exposure per se. Thus, upregulation of UCP3 mRNA abundance in the 32AL group, rather than downregulation in the 23PF group, might have occurred in the current study. This latest study also shows that the critical window for detecting temperature-related differences in UCP3 mRNA abundance in rat muscle is following heat exposure is applied, not 14 d later. This suggests that the magnitude of upregulation of UCP3 mRNA abundance in the 32AL group might have been possibly greater than that of the 23AL group shortly after heat exposure was applied. Conceivably, a possible explanation for the higher UCP3 mRNA abundance in the 23AL group compared with the 23PF group may be body fat content. Bao et al. (1998) reported that the short form of human UCP3 mRNA abundance is positively correlated with body fat content, and its long form tends to increase as a function of obesity. Further, overweight is associated with higher UCP3 mRNA abundance in rats (Rodriguez et al., 2003). Body fat content of pigs in the 23AL group might have been higher than that of pigs in the 23PF group.
As predicted, pigs kept at a high ambient temperature had significantly lower plasma total T3 concentrations when the comparison was made at the same level of food intake (32AL vs. 23PF). This finding agrees with the results of earlier studies showing that heat exposure induces hypothyroidism in animals (Sano et al., 1982; Collins et al., 2002). Further, no clear effects of the treatments were observed on TR isoforms mRNA abundance. Thus, in view of a function of thyroid hormone in promoting expression of UCP3 mRNA in skeletal muscle, higher UCP3 mRNA abundance of the 32AL group compared with the 23PF group could not be explained by thyroid status. Therefore, an alternative explanation of the mechanisms causing higher UCP3mRNA abundance in the 32AL group compared with that in the 23PF group is required.
It has been observed that UCP3 expression is high in situations where plasma fatty acid concentration is elevated. This suggests that UCP3 plays a significant role in the metabolism of fatty acids (Millet et al. 1997; Samec et al. 1998a,b; Weigle et al. 1998; Schrauwen et al., 2001, 2002). Chronic malnutrition followed by food deprivation for 46 or 24 h in rats markedly upregulated UCP3 mRNA abundance in gastrochemius and tibialis anterior muscles (Samec et al. 1998a,b). Although UCP3 mRNA expression in soleus muscle was also upregulated by the food deprivation in these studies, the magnitude of response was much lower compared than that in the other two muscles. Gastrochemius and tibialis anterior are fast-twitch, glycolytic/oxidative-glycolytic type muscles with high capacity to shift between glucose and fatty acids as fuel substrates, whereas soleus is a slow-twitch, oxidative type muscle with higher dependency on fatty acids. The higher magnitude of upregulation of UCP3 mRNA in gastrochemius and tibialis anterior can be attributed to the higher capacity of these muscles to shift between glucose and fatty acids as fuel substrates. We observed that proportions of oxidative and slow-twitch fibers in rhomboideus in the pig were 1.6- and 5-fold higher compared with LD, respectively (Katsumata et al., 2000). Thus, if fatty acids play a dominant role in regulating UCP3 mRNA abundance in the current study, UCP3 mRNA expression in LD and rhomboideus could differentially respond to the treatments. Schrauwen et al. (2002) has shown that the circulating level of plasma fatty acid at rest does not necessarily reflect UCP3 expression in muscle. As shown in Table 1
, plasma NEFA concentration was not affected by the treatments. Further, in our previous studies, high ambient temperature did not affect plasma NEFA concentration in finishing pigs (our unpublished observations). Thus, after at least 4 wk of exposure to a high ambient temperature, factors other than fatty acids might have played a role in regulating UCP3 mRNA abundance in porcine skeletal muscle. Another possible explanation for higher UCP3 mRNA abundance in the 32AL group may be oxidative stress. It has been suggested that heat stress induces oxidative stress in cells and animals (Bernabucci et al., 2002; Lakritz et al., 2002; Ozawa et al., 2002). Evidence indicates a biochemical role for UCP3 in eliminating reactive oxygen species generated in mitochondria (Vidal-Puig et al., 2000; Brand et al., 2002; Echtay et al. 2002). This suggests that UCP3 mRNA abundance in skeletal muscle is upregulated in heat-exposed pigs to eliminate excess reactive oxygen species in mitochondria. Indeed, Petzke et al. (2003) reported recently that abundance of UCP2 and UCP3 mRNA in rat muscle correlated to levels of oxidative stress induced by different dietary protein levels. However, to our knowledge, no one has yet proved that oxidative stress per se upregulates expression of UCP3. Thus, further studies are required to conclude that oxidative stress plays a role in regulation of UCP3 mRNA expression in skeletal muscle.
The present findings suggest that UCP3 mRNA expression in porcine muscle is upregulated by heat exposure. Although thyroid hormones and fatty acids play a significant role in regulating gene expression of UCP3 in muscle, different factors might have been involved in this upregulation. In view of a postulated function of UCP3 in eliminating reactive oxygen species from mitochondria, one possible candidate explaining this upregulation may be oxidative stress caused by heat exposure. However, further studies are necessary in this respect because there is currently no direct evidence supporting a role of oxidative stress in regulation of UCP3 expression.
|
Implications
|
|---|
Heat stress hinders productivity of pig production in regions where pigs are exposed to high ambient temperature during the summer season. Although the exact physiological function of uncoupling protein-3 is still a controversial issue, upregulation of uncoupling protein-3 expression may promote uncoupling of oxidative phosphorylation from adenosine triphosphate synthesis in mitochondria. The present findings suggest that upregulation of uncoupling protein-3 due to heat exposure may contribute to hindered performance by pigs at high ambient temperature. Because our knowledge on physiological significance of uncoupling protein-3 in performance of farm animals is limited, this may be an extremely important future research subject of farm animal physiology.
|
Footnotes
|
|---|
2 Current address: Dept. of Anim. Products Res., Natl. Inst. of Livestock and Grassland Sci., Tochigi, 329-2793, Japan. 
1 Correspondence: Dept. of Anim. Physiol. and Nutr., Natl. Inst. of Livestock and Grassland Sci., Ibaraki, 305-0901, Japan (e-mail: masaya{at}affrc.go.jp).
Received for publication May 27, 2004.
Accepted for publication August 10, 2004.
|
Literature Cited
|
|---|
Bao, S., A. Kennedy, B. Wojciechowski, P. Wallace, E. Ganaway, and W. T. Garvey. 1998. Expression of mRNAs encoding uncoupling proteins in human skeletal muscle. Effects of obesity and diabetes. Diabetes 47:1935–1940.[Abstract]
Bernabucci, U., B. Ronchi, N. Lacetera, and A. Nardone. 2002. Markers of oxidative status in plasma and erythrocytes of transition dairy cows during hot season. J. Dairy Sci. 85:2173–2179.[Abstract/Free Full Text]
Bezaire, V., W. Hofmann, J. K. Kramer, L. P. Kozak, and M. E. Harper. 2001. Effects of fasting on muscle mitochondrial energetics and fatty acid metabolism in Ucp3(–/–) and wild-type mice. Am. J. Physiol. Endocrinol. Metab. 281:E975–E982.[Abstract/Free Full Text]
Boss, O., P. Samec, A. Paoloni-Giacobino, C. Rossier, A. Dullo, J. Seydoux, P. Muzzin, and J.-P. Giacobino. 1997. Uncoupling protein-3: A new member of the mitochondrial carrier family with tissue-specific expression. FEBS Lett. 408:39–42.[Medline]
Brand, M. D., R. Pamplona, M. Portero-Otin, J. R. Requena, S. J. Roebuck, J. A. Buckingham, J. C. Clapham, and S. Cadenas. 2002. Oxidative damage and phospholipids fatty acyl composition in skeletal muscle mitochondria from mice underexpression or overexpressing uncoupling protein 3. Biochem. J. 368:597–603.[Medline]
Cha, S. H., Z. Hu, and M. D. Lane. 2004. Long-term effects of a fatty acid synthase inhibitor on obese mice: Food intake, hypothalamic neuropeptides, and UCP3. Biochem. Biophys. Res. Com. 317:301–308.[Medline]
Chomczynski, P., and N. Sacchi. 1987. Single-step method of RNA isolation by acid guanidinium thiocyanate-phenol-chloroform extraction. Anal. Biochem. 162:156–159.[Medline]
Collin, A., Y. Lebreton, M. Fillaut, A. Vincent, F. Thomas, and P. Herpin. 2001a. Effects of exposure to high temperature and feeding level on regional blood flow and oxidative capacity of tissues in piglets. Exp. Physiol. 86:83–91.[Abstract]
Collin, A., V. Maria-Joao, and J. Le Dividich. 2002. Effect of high temperature on body temperature and hormonal adjustment in piglets. Reprod. Nutr. Dev. 42:45–53.
Collin, A., J. van Milgen, S. Dubois, and J. Noblet. 2001b. Effect of high temperature and feeding level on energy utilization in piglets. J. Anim. Sci. 79:1849–1857.[Abstract/Free Full Text]
Cusin, I., K. E. Zakrzewska, O. Boss, P. Muzzin, J.-P. Giacobino, D. Ricquier, B. Jeanrenaud, and F. Rohner-Jeanrenaud. 1998. Chronic central leptin infusion enhances insulin-stimulated glucose metabolism and favors the expression of uncoupling proteins. Diabetes 47:1014–1019.[Abstract]
Echtay, K. S., D. Roussel, J. St-Pierre, M. B. Jekabsons, S. Cadenas, J. A. Stuart, J. A. Harper, S. J. Roebuck, A. Morrison, S. Pickering, J. C. Clapham, and M. D. Brand. 2002. Superoxide activates mitochondrial uncoupling proteins. Nature 415:96–99.[Medline]
Gong, D.-W., Y. He, M. Karas, and M. Reitman. 1997. Uncoupling protein-3 is a mediator of thermogenesis regulated by thyroid hormone, ß3-adrenergic agonists, and leptin. J. Biol. Chem. 272:24129–24132.[Abstract/Free Full Text]
Katsumata, M., Y. Kaji, and M. Saitoh. 1996. Growth and carcass fatness responses of finishing pigs to dietary fat supplementation at a high ambient temperature. Anim. Sci. 62:591–598.
Katsumata, M., K. A. Burton, J. Li, and M. J. Dauncey. 1999. Suboptimal energy balance selectively up-regulates muscle GLUT gene expression but reduces insulin-dependent uptake during postnatal development. FASEB J. 13:1405–1413.[Abstract/Free Full Text]
Katsumata, M., D. Cattaneo, P. White, K. A. Burton, and M. J. Dauncey. 2000. Growth hormone receptor gene expression in porcine skeletal and cardiac muscle is selectively regulated by postnatal undernutrition. J. Nutr. 130:2482–2488.[Abstract/Free Full Text]
Katsumata, M., S. Kawakami, Y. Kaji, R. Takada, and M. J. Dauncey. 2001. Low lysine diet selectively up-regulates muscle GLUT4 gene and protein expression during postnatal development. Pages 237–239 in Energy Metabolism in Animals. EAAP Publ. No. 103. Wageningen Pers, Wageningen, The Netherlands.
Katsumata, M., M. Matsumoto, and Y. Kaji. 2003. Effects of a low lysine diet on glucose metabolism in skeletal muscle of growing pigs. Pages 187–190 in Progress in research on energy and protein metabolism. EAAP Publ. No. 109. Wageningen Academic Publishers, Wageningen, The Netherlands.
Lakritz, J., M. J. Leonard, P. A. Eichen, G. E. Rottinghaus, G. C. Johnson, and D. E. Spiers. 2002. Whole-blood concentrations of glutathione in cattle exposed to heat stress or a combination of heat stress and endophyte-infected tall fescue toxins in controlled environmental conditions. Am. J. Vet. Res. 63:799–803.[Medline]
Lanni, A., L. Beneduce, A. Lombardi, M. Moreno, O. Boss, P. Muzzin, J. P. Giacobino, and F. Goglia. 1999. Expression of uncoupling protein-3 and mitochondrial activity in the transition from hypothyroid to hyperthyroid state in rat skeletal muscle. FEBS Lett. 444:250–254.[Medline]
Larkin, S., E. Mull, W. Miao, R. Pittner, K. Albrandt, C. Moore, A. Young, M. Denaro, and K. Beaumont. 1997. Regulation of the third member of the uncoupling protein family, UCP3, by cold and thyroid hormone. Biochem. Biophys. Res. Commun. 240:222–227.[Medline]
Lin, B., S. Coughlin, and P. F. Pilgh. 1998. Bidirectional regulation of uncoupling protein-3 and GLUT-4 mRNA in skeletal muscle by cold. Am. J. Physiol. Endocrinol. Metab. 275:E386–E391.[Abstract/Free Full Text]
Matsuda, J., K. Hosoda, H. Itoh, C. Son, K. Doi, T. Tanaka, Y. Fukunaga, G. Inoue, H. Nishimura, Y. Yoshimasa, Y. Yamori, and K. Nakao. 1997. Cloning of rat uncoupling protein-3 and uncoupling protein-2 cDNAs: Their gene expression in rats fed high-fat diet. FEBS Lett. 418:200–204.[Medline]
Millet, L., H. Vidal, F. Andreelli, D. Larrouy, J.-P. Riou, D. Ricquier, M. Laville, and D. Langin. 1997. Increased uncoupling protein-2 and -3 mRNA expression during fasting in obese and lean humans. J. Clin. Invest. 100:2665–2670.[Medline]
Nudel, U., R. Zakut, M. Shani, S. Neumans, Z. Levy, and D. Yaffe. 1983. The nucleotide sequence of the rat cytoplasmic beta-actin gene. Nucleic Acids Res. 11:1759–1771.[Abstract/Free Full Text]
Ozawa, M., M. Hirabayashi, and Y. Kanai. 2002. Developmental competence and oxidative state of mouse zygotes heat-stressed maternally or in vitro. Reproduction 124:683–689.[Abstract]
Petzke, K. J., M. Friedrich, C. C. Metges, and S. Klaus. 2003. Long-term dietary protein intake affects uncoupling protein mRNA gene expression in liver and muscle of rats. Pages 65–68 in Progress in research on energy and protein metabolism. EAAP Publ. No. 109. Wageningen Academic Publishers, Wageningen, The Netherlands.
Rodriguez, A. M., P. Roca, M. L. Bonet, C. Pico, P. Oliver, and A. Palou. 2003. Positive correlation of skeletal muscle UCP3 mRNA levels with overweight in male, but not in female, rats. Am. J. Physiol. 285:R880–R888.
Samec, S., J. Seydoux, and A. G. Dulloo. 1998a. Interorgan signaling between adipose tissue metabolism and skeletal muscle uncoupling protein homologs: Is there a role for circulating free fatty acids? Diabetes 47:1693–1698.[Abstract]
Samec, S., J. Seydoux, and A. G. Dulloo. 1998b. Role of UCP homologues in skeletal muscles and brown adipose tissue: Mediators of thermogenesis or regulators of lipids as fuel substrate? FASEB J. 12:715–724.[Abstract/Free Full Text]
Sano, H., K. Takahashi, K. Ambo, and T. Tsuda. 1982. Turnover and oxidation rates of blood glucose and heat production in sheep exposed to heat. J. Dairy Sci. 66:856–861.
Schrauwen, P., W. H. M. Saris, and M. K. C. Hesselink. 2001. An alternative function for human uncoupling protein 3: Protection of mitochondria against accumulation of nonesterified fatty acids inside the mitochondrial matrix. FASEB J. 15:2497–2502.[Abstract/Free Full Text]
Schrauwen, P., V. Hinderling, M. K. C. Hesselink, G. Schaart, E. Kornips, W. H. M. Saris, M. Westerterp-Plantenga, and W. Langhans. 2002. Etomoxir-induced increase in UCP3 supports a role of uncoupling protein 3 as a mitochondrial fatty acid anion exporter. FASEB J. Available: http://www.fasebj.org/cgi/doi/10.1096/fj.02-0275fje. Accessed Aug. 19, 2002.
Vidal-Puig, A. J., D. Grujic, C.-Y. Zhang, T. Hagen, O. Boss, Y. Ido, A. Szczepanik, J. Wade, V. Mootha, R. Cortright, D. M. Muoio, and B. B. Lowell. 2000. Energy metabolism in uncoupling protein 3 gene knockout mice. J. Biol. Chem. 275:16258–16266.[Abstract/Free Full Text]
Weigle, D. S., L. E. Selfridge, M. W. Schwartz, R. J. Seeley, D. E. Cummings, P. J. Havel, J. L. Kuijper, and H. BeltrandelRio. 1998. Elevated fatty acids induce uncoupling protein 3 expression in muscle: A potential explanation for the effect of fasting. Diabetes 47:298–302.[Abstract]
Werner, P., S. Neuenschwander, and G. Stranzinger. 1999. Characterization of the porcine uncoupling proteins 2 and 3 (UCP2 & UCP3) and their localization to chromosome 9 p by somatic cell hybrids. Anim. Genet. 30:221–224.[Medline]
White, P., and M. J. Dauncey. 1999. Differential expression of thyroid hormone receptor isoforms is strikingly related to cardiac and skeletal muscle phenotype during postnatal development. J. Mol. Endocrinol. 23:241–254.[Abstract]
Top
Abstract
Introduction
