Studies examining gene expression with RT-PCR typically normalize their mRNA data to a constitutively expressed housekeeping gene. The validity of a particular housekeeping gene must be determined for each experimental intervention. We examined the expression of various housekeeping genes following an acute bout of endurance (END) or resistance (RES) exercise. Twenty-four healthy subjects performed either a interval-type cycle ergometry workout to exhaustion ( approximately 75 min; END) or 300 single-leg eccentric contractions (RES). Muscle biopsies were taken before exercise and 3 h and 48 h following exercise. Real-time RT-PCR was performed on beta-actin, cyclophilin (CYC), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), and beta2-microglobulin (beta2M). In a second study, 10 healthy subjects performed 90 min of cycle ergometry at approximately 65% of Vo(2 max), and we examined a fifth housekeeping gene, 28S rRNA, and reexamined beta2M, from muscle biopsy samples taken immediately postexercise. We showed that CYC increased 48 h following both END and RES exercise (3- and 5-fold, respectively; P < 0.01), and 28S rRNA increased immediately following END exercise (2-fold; P = 0.02). beta-Actin trended toward an increase following END exercise (1.85-fold collapsed across time; P = 0.13), and GAPDH trended toward a small yet robust increase at 3 h following RES exercise (1.4-fold; P = 0.067). In contrast, beta2M was not altered at any time point postexercise. We conclude that beta2M and beta-actin are the most stably expressed housekeeping genes in skeletal muscle following RES exercise, whereas beta2M and GAPDH are the most stably expressed following END exercise.

Women oxidize more fat as compared to men during endurance exercise and several groups have shown that the mRNA content of selected genes related to fat oxidation are higher in women (e.g. hormone sensitive lipase, β-hydroxyacyl-CoA dehydrogenase, CD36). One of the possible mechanisms is that women tend to have a higher area percentage of type I skeletal muscle fibers as compared with men. Consequently, we hypothesized that sex would influence the basal mRNA and protein content for genes involved in metabolism and the determination of muscle fiber type. Muscle biopsies from the vastus lateralis were collected from healthy men and women. We examined mRNA content globally using Affymetrix GeneChips, and selected genes were examined and/or confirmed by RT-PCR. Furthermore, we examined protein content by Western blot analysis. Stringent gene array analysis revealed 66 differentially expressed genes representing metabolism, mitochondrial function, transport, protein biosynthesis, cell proliferation, signal transduction pathways, transcription and translation. Stringent gene array analysis and RT-PCR confirmed that mRNA for; acyl-coenzyme A acyltransferase 2 (ACAA2), trifunctional protein β (HADHB), catalase, lipoprotein lipase (LPL), and uncoupling protein-2 (UCP-2) were higher in women. Targeted gene analysis revealed that myosin heavy chain I (MHCI), peroxisome proliferator-activated receptor (PPAR)δ were higher in women compared with men. Surprisingly, there were no significant sex based differences in protein content for HADHB, ACAA2, catalase, PPARδ, and MHC1. In conclusion, the differences in the basal mRNA content in resting skeletal muscle suggest that men and women are transcriptionally “primed” for known physiological differences in metabolism however the mechanism behind sex differences in fiber type remains to be determined.

We used cDNA microarrays to screen for differentially expressed genes during recovery from exercise-induced muscle damage in humans. Male subjects (n = 4) performed 300 maximal eccentric contractions, and skeletal muscle biopsy samples were analyzed at 3 h and 48 h after exercise. In total, 113 genes increased 3 h postexercise, and 34 decreased. At 48 h postexercise, 59 genes increased and 29 decreased. On the basis of these data, we chose 19 gene changes and conducted secondary analyses using real-time RT-PCR from muscle biopsy samples taken from 11 additional subjects who performed an identical bout of exercise. Real-time RT-PCR analyses confirmed that exercise-induced muscle damage led to a rapid (3 h) increase in sterol response element binding protein 2 (SREBP-2), followed by a delayed (48 h) increase in the SREBP-2 gene targets Acyl CoA:cholesterol acyltransferase (ACAT)-2 and insulin-induced gene 1 (insig-1). The expression of the IL-1 receptor, a known regulator of SREBP-2, was also elevated after exercise. Taken together, these expression changes suggest a transcriptional program for increasing cholesterol and lipid synthesis and/or modification. Additionally, damaging exercise induced the expression of protein kinase H11, capping protein Z alpha (capZalpha), and modulatory calcineurin-interacting protein 1 (MCIP1), as well as cardiac ankryin repeat protein 1 (CARP1), DNAJB2, c-myc, and junD, each of which are likely involved in skeletal muscle growth, remodeling, and stress management. In summary, using DNA microarrays and RT-PCR, we have identified novel genes that respond to skeletal muscle damage, which, given the known biological functions, are likely involved in recovery from and/or adaptation to damaging exercise.

Higher fat and lower carbohydrate and amino acid oxidation are observed in women compared with men during endurance exercise. We hypothesized that the observed sex difference is due to estrogen and that menstrual cycle phase or supplementation of men with 17beta-estradiol (E(2)) would coordinately influence the mRNA content of genes involved in lipid and/or carbohydrate metabolism in skeletal muscle. Twelve men and twelve women had muscle biopsies taken before and immediately after 90 min of cycling at 65% peak oxygen consumption (Vo(2peak)). Women were studied in the midfollicular (Fol) and midluteal (Lut) phases, and men were studied after 8 days of E(2) or placebo supplementation. Targeted RT-PCR was used to compare mRNA content for genes involved in transcriptional regulation and lipid, carbohydrate, and amino acid metabolism. Sex was the greatest predictor of substrate metabolism gene content. Sex affected the mRNA content of FATm, FABPc, SREBP-1c, mtGPAT, PPARdelta, PPARalpha, CPTI, TFP-alpha, GLUT4, HKII, PFK, and BCOADK (P < 0.05). E(2) administration significantly (P < 0.05) affected the mRNA content of PGC-1alpha, PPARalpha, PPARdelta, TFP-alpha, CPTI, SREBP-1c, mtGPAT, GLUT4, GS-1, and AST. Acute exercise increased the mRNA abundance for PGC-1alpha, HSL, FABPc, CPTI, GLUT4, HKII, and AST (P < 0.05). Menstrual cycle had a small effect on PPARdelta, GP, and glycogenin mRNA content. Overall, women have greater mRNA content for several genes involved in lipid metabolism, which is partially due to an effect of E(2).

Fu MH, Tupling AR. Protective effects of Hsp70 on the structure and function of SERCA2a expressed in HEK-293 cells during heat stress. Am J Physiol Heart Circ Physiol 296: H1175-H1183, 2009. First published February 27, 2009 doi:10.1152/ajpheart.01276.2008.-Heat shock protein 70 (Hsp70) can physically interact with and prevent thermal inactivation of sarco(endo)plasmic reticulum Ca 2ϩ -ATPase (SERCA) 1a, the SERCA isoform expressed in adult fasttwitch skeletal muscle. This study examined whether Hsp70 could physically interact with and prevent thermal inactivation of SERCA2a, the SERCA isoform expressed in heart. HEK-293 cells were cotransfected with cDNAs encoding human Hsp70 and rabbit SERCA2a (S2a/Hsp70). Cells cotransfected with SERCA2a cDNA and pMT2 (S2a/pMT2) were used as control. One-half of the cells was heat shocked at 40°C for 1 h (HS), and one-half was maintained at 37°C before harvesting the cells and isolating microsomes. Western blot analysis showed that Hsp70 and SERCA2a were colocalized in the microsomal fraction. The levels of Hsp70 were approximately fivefold higher (P Ͻ 0.05) in S2a/Hsp70 compared with S2a/pMT2 and approximately twofold higher (P Ͻ 0.05) following HS in all cells. Coimmunoprecipitation demonstrated that Hsp70 directly binds to SERCA2a. Following HS, maximal SERCA2a activity was reduced (ϳ52%, P Ͻ 0.05) in S2a/pMT2 but was increased (ϳ33%, P Ͻ 0.05) in S2a/Hsp70. Thermal inactivation of SERCA2a in S2a/pMT2 was associated with decreased (ϳ49%, P Ͻ 0.05) binding capacity for fluorescein isothiocyanate (FITC) and increased carbonyl (ϳ42%, P Ͻ 0.05) and nitrotyrosine (ϳ40%, P Ͻ 0.05) levels in SERCA2a. By contrast, the HS-induced increase in maximal SERCA2a activity observed in S2a/Hsp70 corresponded with no change (P Ͼ 0.05) in FITC-binding capacity and reductions in carbonyl (ϳ40%, P Ͻ 0.05) and nitrotyrosine (ϳ23%, P Ͻ 0.05) levels in SERCA2a compared with S2a/pMT2. These results show that Hsp70 forms a protective interaction with SERCA2a during HS actually reducing oxidation and nitrosylation of SERCA2a thus increasing its maximal activity. coimmunoprecipitatoin; carbonyl; nitrotyrosine; nucleotide binding site SARCO(ENDO)PLASMIC reticulum Ca 2ϩ -ATPases (SERCAs) are typical of the class of P-type ATPases that bind specific ions to be transported, hydrolyze ATP to form a phosphoprotein intermediate, and undergo conformational changes resulting in ion translocation (29). SERCA pumps are 110-kDa integral membrane proteins that consist of 10 transmembrane helexes (M1-M10), three cytoplasmic domains (A, actuator; N, nucleotide-binding; P, phosphorylation), and small luminal loops (48). In humans, 3 genes (ATP2A1-3) generate multiple isoforms (SERCAla,b, SERCA2a-c, SECA3a-f) by developmental or tissue-specific alternative splicing (14). Two SERCA isoforms predominate in adult striated muscle, namely SERCA1a and SERCA2a. The SERCA1a isoform consists of 994 amino acids and accounts for Ͼ99% of the SERCA isoforms expressed in adult fast-twitch skeletal muscle, whereas SERCA2a consists...