Immunochemical identification and study of an interspecific thymus antigen (AgT-1)

A new interspecific human and animal thymic antigen (AgT-1) was identified immunochemically. It was shown that AgT-1 is a protein with a molecular mass about 40000 dalton, electrophoretic mobility of alpha 1-globulins and isoelectric points 4.0 and 4.5. Heating of the protein to 80 degrees C led to the loss of its immunochemical activity. Antisera to AgT-1 were obtained by immunization of rabbits by conjugated extract of bovine thymus in complete Freund's adjuvant. AgT-1 was identified immunochemically in bovine embryonal thymus, spleen and liver. In addition to these organs, AgT-1 was discovered in lung extracts of adult animals. Identical antigen was identified in the embryonal thymus and extracts of human small intestine. AgT-1 antibodies inhibited the biological activity of the active thymic fraction (AFT-6) in recovering the sensitivity of spleen fRFC from thymectomized mice to the inhibitory action of azathioprin. The data indicate that the biological activity of AFT-6 is partly due to the molecules having antigenic determinants of AgT-1.     

Expression profiles of Toll-like receptors 1, 2 and 5 in selected organs of commercial and indigenous chickens

Toll-like receptors (TLRs) are members of the cellular receptors that constitute a major component of the evolutionary conserved pattern recognition system (PRR). TLRs are expressed in a wide variety of tissues and cell types. In this study we compared the expression profiles of the chicken TLR1, TLR2 and TLR5 genes in a range of organs (lung, ovary, liver, thymus, duodenum, spleen and large intestine) in commercial Hy-Line (HL) and indigenous Green-legged Partridgelike (GP) chickens. The level of mRNA was determined with RT-qPCR using the TaqMan probes for target and reference (ACTB) genes. We determined that the tissue profiles differed with respect to each TLR and they were ranked as follows: spleen, lungs, large intestine (TLR1), large intestine, lungs, thymus/ovary (TLR2) and lungs, thymus, liver (TLR5). A differential expression between HL and GP chickens was determined for TLR1 and TLR5 genes in large intestine and thymus of HL (P?<?0.05) and GP (P?<?0.05) chickens. We conclude that the commercial chickens expressed higher levels of TLR1 mRNA in large intestine and TLR5 mRNA in thymus than indigenous chickens.     

Hymenolepis microstoma: Correlation of histopathological host response and organ hypertrophy

The histological host response of female CF-1 mice to Hymenolepis microstoma involves dramatic changes in the host's bile duct and liver. These changes are similar to those described by previous investigators using different strains of mice. The histological changes which occur in bile duct and liver tissues of female CF-1 mice are accompanied by a significant hypertrophy of these organs; the wet weights of the bile duct and liver increase almost 2000 and 50%, respectively, in infected mice. No significant histopathological changes are found in the spleen or small intestine tissues of infected mice, yet the wet weight of both of these organs increases almost 100%. The magnitude of the histopathological changes which occur in the bile duct could possibly account for the increase in wet weight, i.e., there is significant fibrosis, but the histological changes in the liver, spleen, and small intestine do not appear to be of sufficient magnitude to account for the increases in wet weight.     

Different DNA repair strategies to combat the threat from 8-oxoguanine

Oxidative DNA damage is one of the most common threats to genome stability and DNA repair enzymes provide protection from the effects of oxidized DNA bases. In mammalian cells, base excision repair (BER) mediated by the OGG1 and MYH DNA glycosylases prevents the accumulation of 8-oxoguanine (8-oxoG) in DNA. When steady-state levels of DNA 8-oxoG were measured in myh(-/-) and myh(-/-)/ogg1(-/-) mice, an age-dependent accumulation of the oxidized purine was found in lung and small intestine of doubly defective myh(-/-)/ogg1(-/-) mice. Since there is an increased incidence of lung and small intestinal cancer in myh(-/-)/ogg1(-/-) mice, these findings are consistent with a causal role for unrepaired oxidized DNA bases in cancer development. We previously presented in vitro evidence that mismatch repair (MMR) participates in the repair of oxidative DNA damage and msh2(-/-) mouse embryo fibroblasts also have increased steady state levels of DNA 8-oxoG. To investigate whether DNA 8-oxoG also accumulates in vivo, basal levels were measured in several organs of 4-month-old msh2(-/-) mice and their wild-type counterparts. Msh2(-/-) mice had significantly increased levels of DNA 8-oxoG in spleen, heart, liver, lung, kidney and possibly small intestine but not in bone marrow, thymus or brain. The tissue-specificity of DNA 8-oxoG accumulation in msh2(-/-) and other DNA repair defective mice suggests that DNA protection of different organs is mediated by different combinations of repair pathways.     

MICROASSAY OF ADENOSINE-3′,5′-MONOPHOSPHATE (CYCLIC AMP) IN BRAIN AND OTHER TISSUES BY THE LUCIFERIN-LUCIFERASE SYSTEM1

Abstract— A simple, sensitive and specific method for assaying cyclic AMP in various tissues is reported. Cyclic AMP was isolated from contaminating nucleotides and was converted to ATP with a phosphodiesterase-myokinase-pyruvate kinase system. The ATP was determined enzymically in a liquid scintillation counter by the firefly luciferin-luciferase technique. This procedure was capable of detecting as little as 5 × 10^?14 mol of cyclic AMP and could therefore be used for analyses on less than 1 mg of brain. The assay was reproducible and linear over a wide range of tissue concentrations. In the rat, the highest levels of cyclic AMP (2.7–4.2 pmol/mg wet wt. of tissue) were present in the pineal, heart, pituitary, thyroid, cerebellar cortex, kidney, adrenal, liver and pyloric region of the stomach; intermediate levels (1.5–2.7 pmol/mg wet wt. of tissue) were found in testis, skin, aorta, intestine, submaxillary gland, spleen, muscle and cerebral cortex, moderately low levels (1.0–1.5 pmol/mg wet wt. of tissue) were found in lung, trachea and greater curvature of the stomach; whereas low levels (0.15–0.60 pmol/mg wet wt. of tissue) were found in adipose tissue.     

COMPARISON OF DNA RENEWAL IN GERM-FREE AND CONVENTIONAL MICE USING [125I]IODODEOXYURIDINE AND [3H]THYMIDINE

Germ-free (GF) and conventional (CV) C3H mice received a single injection of 1 μCi [³H]thymidine and 3 μCi [¹²⁵I]iododeoxyuridine to provide simultaneous labeling of DNA with the two precursors. Thymus, spleen, mesenteric lymph nodes, bone marrow (femora), small intestine, colon and skin were examined for total organ activity and rate of DNA renewal 1–8 days after injection. Precursor incorporation, assayed on day 1, was lower in the thymus, mesenteric lymph nodes and femora (and, to a lesser extent, in the spleen and colon) of GF mice as compared to CV animals. The opposite was observed in the small intestine and skin, i.e. total organ activity was higher in GF animals. Differences in precursor incorporation were partly due to differences in organ weights between the two groups of mice. In comparison to CV animals, DNA renewal rates were diminished in the mesenteric lymph nodes, bone marrow, colon (following a 3-day plateau) and spleen of GF mice. Little, if any, difference was observed between the two groups with respect to the rate of DNA turnover in the thymus and skin. Radioactivity of the small intestine remained constant for 2 days. Thereafter intestinal activity in GF mice declined at an initial slow rate between days 2 and 5 followed by a rapid decrease between days 5 and 8. In CV mice the first phase of activity loss was short with the rapid decline in intestinal activity beginning on day 3. From the slopes of the regression lines, the percentage thymidine reutilization was estimated. Reutilization varied from 0 to 63% in the various organs examined, with the greatest difference between GF and CV mice occurring in the mesenteric lymph nodes.     

Gene expression profiles in genetically different mice infected with Toxoplasma gondii: ALDH1A2, BEX2, EGR2, CCL3 and PLAU

Toxoplasma gondii can modulate host cell gene expression; however, determining gene expression levels in intermediate hosts after T. gondii infection is not known much. We selected 5 genes (ALDH1A2, BEX2, CCL3, EGR2 and PLAU) and compared the mRNA expression levels in the spleen, liver, lung and small intestine of genetically different mice infected with T. gondii. ALDH1A2 mRNA expressions of both mouse strains were markedly increased at day 1-4 postinfection (PI) and then decreased, and its expressions in the spleen and lung were significantly higher in C57BL/6 mice than those of BALB/c mice. BEX2 and CCR3 mRNA expressions of both mouse strains were significantly increased from day 7 PI and peaked at day 15-30 PI (P<0.05), especially high in the spleen liver or small intestine of C57BL/6 mice. EGR2 and PLAU mRNA expressions of both mouse strains were significantly increased after infection, especially high in the spleen and liver. However, their expression patterns were varied depending on the tissue and mouse strain. Taken together, T. gondii-susceptible C57BL/6 mice expressed higher levels of these 5 genes than did T. gondii-resistant BALB/c mice, particularly in the spleen and liver. And ALDH1A2 and PLAU expressions were increased acutely, whereas BEX2, CCL3 and EGR2 expressions were increased lately. Thus, these demonstrate that host genetic factors exert a strong impact on the expression of these 5 genes and their expression patterns were varied depending on the gene or tissue.     

Ganglioside expression in tissues of mice lacking the tumor necrosis factor receptor 1

This study presents a comparative analysis of gangliosides from lymphoid (spleen and thymus) and other tissues (brain, liver, lung, muscle) of C57BL/6 mice homozygous (-/-) and heterozygous (+/-) for the tumor necrosis factor receptor 1 (TNFRp55). Quantitative and qualitative differences in the expression of the lipid-bound N-acetylneuraminic (Neu5Ac) and N-glycolylneuraminic acid (Neu5Gc) and of various ganglioside biosynthesis pathways were detected between the tissues of the TNFRp55 -/- and the control TNFRp55 +/- mice. Sialic acid profiles showed a strong decrease in the absolute amount of sialic acids (Neu5Ac + Neu5Gc) in the lungs and thymus of homozygous (1.41 and 0.3 ng/mg wet weight, respectively) compared with control heterozygous animals (7.18 and 2.05 ng/mg wet weight, respectively). Considerable differences of Neu5Ac/Neu5Gc ratios in the lungs, muscle, spleen, and thymus were also detected. The gangliosides GM3(Neu5Ac) and GM3(Neu5Gc) were the dominant gangliosides in the lungs of the control animals, whereas the knockout mice almost completely lacked these structures in this organ. Reduced expression of GM1b-type gangliosides (GM1b and GalNAc-GM1b) was also found in the lungs, spleen, and thymus of the TNFRp55 knockout mice. On the other hand, neolacto-series gangliosides were more abundant in the lungs, brain, and muscle of the knockout mice, whereas their expression in the liver, spleen, and thymus was similar in both groups of animals. This study provides in vivo evidence that TNF signaling via the TNFRp55 is involved in the acquisition of a distinct ganglioside assembly in different mouse organs. TNFRp55 signaling seems to be especially important for the activation of the GM1b-type ganglioside biosynthetic pathway that is a unique characteristic of the mouse lymphoid tissues.     

Cardiomyocyte-specific Loss of Diacylglycerol Acyltransferase 1 (DGAT1) Reproduces the Abnormalities in Lipids Found in Severe Heart Failure

Diacylglycerol acyltransferase 1 (DGAT1) catalyzes the final step in triglyceride synthesis, the conversion of diacylglycerol (DAG) to triglyceride. Dgat1^−/− mice exhibit a number of beneficial metabolic effects including reduced obesity and improved insulin sensitivity and no known cardiac dysfunction. In contrast, failing human hearts have severely reduced DGAT1 expression associated with accumulation of DAGs and ceramides. To test whether DGAT1 loss alone affects heart function, we created cardiomyocyte-specific DGAT1 knock-out (hDgat1^−/−) mice. hDgat1^−/− mouse hearts had 95% increased DAG and 85% increased ceramides compared with floxed controls. 50% of these mice died by 9 months of age. The heart failure marker brain natriuretic peptide increased 5-fold in hDgat1^−/− hearts, and fractional shortening (FS) was reduced. This was associated with increased expression of peroxisome proliferator-activated receptor α and cluster of differentiation 36. We crossed hDgat1^−/− mice with previously described enterocyte-specific Dgat1 knock-out mice (hiDgat1^−/−). This corrected the early mortality, improved FS, and reduced cardiac ceramide and DAG content. Treatment of hDgat1^−/− mice with the glucagon-like peptide 1 receptor agonist exenatide also improved FS and reduced heart DAG and ceramide content. Increased fatty acid uptake into hDgat1^−/− hearts was normalized by exenatide. Reduced activation of protein kinase Cα (PKCα), which is increased by DAG and ceramides, paralleled the reductions in these lipids. Our mouse studies show that loss of DGAT1 reproduces the lipid abnormalities seen in severe human heart failure.     

Increased thymidylate synthase (EC 2.1.1.45) activity in normal and neoplastic proliferation

Thymidylate (dTMP) synthase (EC 2.1.1.45) activity was measured in 100,000 x g supernatant fluid with a sensitive, rapid radio assay. The activity in normal rat liver was low (0.098-0.204 nmol/hr/mg protein). dTMP synthase specific activities in rat thymus, spleen, bone marrow, testis, lung, heart, brain, kidney, and small intestine were 6297, 1842, 1500, 788, 215, 76, 61, 39 and 24%, respectively, of that of the liver. The activity in 5-day-old rat liver was 16-fold higher than in adult. dTMP synthase activity increased in rat hepatomas to 7- to 125-fold of that of normal rat liver. There was a significant correlation between the increase in synthase activity and the proliferation rates of the hepatomas. In 8 human colon carcinomas, dTMP synthase activity increased to 2.9- to 8-fold of that of normal human colon mucosa. In leukemic leukocytes from 3 leukemia patients, activity was 8- to 10-fold higher than in normal leukocytes.     

A survey of polar and non-polar lipids of mouse organs

Total lipid was extracted from mouse (Mus musculus) heart, kidney, lung, liver, intestine, brain, stomach, dermis and epidermis and analyzed by quantitative thin-layer chromatography. All of the tissues contained phospholipids, triglycerides, sterols and free fatty acids. All tissues except brain contained small amounts of steryl esters, and all except stomach contained some glycosylceramides. Wax diesters were found in both the dermis and epidermis. Only epidermis contained a high proportion of ceramides. Acylglucosylceramides were uniquely present in epidermis.     

Organ-specific sulfation patterns of heparan sulfate generated by extracellular sulfatases Sulf1 and Sulf2 in mice

Heparan sulfate endosulfatases Sulf1 and Sulf2 hydrolyze 6-O-sulfate in heparan sulfate, thereby regulating cellular signaling. Previous studies have revealed that Sulfs act predominantly on UA2S-GlcNS6S disaccharides and weakly on UA-GlcNS6S disaccharides. However, the specificity of Sulfs and their role in sulfation patterning of heparan sulfate in vivo remained unknown. Here, we performed disaccharide analysis of heparan sulfate in Sulf1 and Sulf2 knock-out mice. Significant increases in ΔUA2S-GlcNS6S were observed in the brain, small intestine, lung, spleen, testis, and skeletal muscle of adult Sulf1(-/-) mice and in the brain, liver, kidney, spleen, and testis of adult Sulf2(-/-) mice. In addition, increases in ΔUA-GlcNS6S were seen in the Sulf1(-/-) lung and small intestine. In contrast, the disaccharide compositions of chondroitin sulfate were not primarily altered, indicating specificity of Sulfs for heparan sulfate. For Sulf1, but not for Sulf2, mRNA expression levels in eight organs of wild-type mice were highly correlated with increases in ΔUA2S-GlcNS6S in the corresponding organs of knock-out mice. Moreover, overall changes in heparan sulfate compositions were greater in Sulf1(-/-) mice than in Sulf2(-/-) mice despite lower levels of Sulf1 mRNA expression, suggesting predominant roles of Sulf1 in heparan sulfate desulfation and distinct regulation of Sulf activities in vivo. Sulf1 and Sulf2 mRNAs were differentially expressed in restricted types of cells in organs, and consequently, the sulfation patterns of heparan sulfate were locally and distinctly altered in Sulf1 and Sulf2 knock-out mice. These findings indicate that Sulf1 and Sulf2 differentially contribute to the generation of organ-specific sulfation patterns of heparan sulfate.     

Analyses of the genomic methylation status of the human cyclin A1 promoter by a novel real-time PCR-based methodology

The role of CpG methylation in the regulation of tissue-specific gene expression is highly controversial. Cyclin A1 is a tissue-specifically expressed gene that is strongly methylated in non-expressing tumor cell lines. We have established a novel real-time PCR method to quantitate genomic CpG methylation of the cyclin A1 promoter. Genomic DNA samples from different human organs were treated with bisulfite and amplified with methylation-specific primers and with primers amplifying methylated as well as non-methylated DNA. PCR product quantitation was obtained by using a fluorogenic probe labeled with FAM and TAMRA. These analyses demonstrated that the human cyclin A1 promoter was methylated in kidney, colon, spleen, testis, and small intestine, but not in brain, liver, pancreas, or heart. Expression of cyclin A1 was predominantly found in testis. Low level expression of cyclin A1 was present in spleen, prostate, leukocytes, colon, and thymus. Taken together, our data provide evidence that CpG methylation patterns of the human cyclin A1 promoter in human organs do not generally correlate with cyclin A1 gene expression in vivo.     

The activity and distribution of gamma-glutamyl transpeptidase (y-GT) in human foetal organs.

The activity and distribution of y-GT was investigated in a number of organs from human foetuses aged from 14 to 24 weeks post menstruationem. Over this period, enzyme activity increased in the kidney, pancreas and thymus, but decreased in the small intestine. No trend could be established for the liver, although activity was high. In the lung, spleen, brain and adrenals, y-GT was either detectable at very low levels or could not be demonstrated. The possible relationship between y-GT activity in some human tumours and the enzyme level in the corresponding foetal organs is discussed.     

Tissue specific expression and developmental regulation of two genes coding for rat fatty acid binding proteins

We have examined the tissue distribution and developmental regulation of two low molecular weight cytosolic fatty acid binding proteins. Based on their initial site of isolation, they have been referred to as liver and intestinal fatty acid binding proteins (FABP). Cloned cDNAs were used to probe blots of RNAs extracted from a wide variety of adult rat tissues as well as small intestine and liver RNA obtained from fetal, suckling, and weaning animals. The highest concentrations of "liver" FABP mRNA were found in small intestine and liver. "Intestinal" FABP mRNA is most abundant in small bowel RNA while only trace amounts were encountered in liver. Both mRNAs were detectable in stomach, colon, pancreas, spleen, lung, heart, testes, adrenal, and brain RNA at 1-8% the concentrations observed in small intestine. Accumulation of both mRNAs in the small intestinal epithelium increases during development. The mRNAs are first detectable between the 19th and 21st day of gestation. They undergo a coordinated 3-4-fold increase in concentration within the first 24 h after birth. Thereafter, gut levels of intestinal FABP mRNA remain constant during the suckling period while liver FABP mRNA increases an additional 2-fold. Liver FABP mRNA levels are also induced in hepatocytes during the first postnatal day but subsequently do not change during the suckling and weaning phase, despite marked alterations in hepatic fatty acid metabolism. These observations support the concept that the major role of these proteins is to facilitate the entry of lipids into cells and/or their subsequent intracellular transport and compartmentalization. The data also raise questions about the identity of extragastrointestinal FABPs.     

beta-Glucocerebrosidase activity in murine epidermis: characterization and localization in relation to differentiation.

The intercellular lipids of the stratum corneum, which are highly enriched in ceramides, are critical for the mammalian epidermal permeability barrier. During the terminal stages of epidermal differentiation, the glucosylceramide content is dramatically reduced, while the content of free ceramides increases. To investigate whether beta-glucocerebrosidase (beta-GlcCer'ase) could be responsible for this change in lipid content, we characterized its activity in murine epidermis, compared enzyme activity to other murine tissues, and localized beta-GlcCer'ase activity within the epidermis. Epidermal extracts demonstrated linear 4-methylumbelliferyl-beta-D-glucose hydrolysis (to 3 h) with protein concentrations between 1 and 250 micrograms/ml. Whole epidermis contained comparable beta-glucosidase activity (9.1 +/- 0.4 nmol/min per mg DNA) to murine brain and liver, and 5-fold higher activity than spleen. Epidermal beta-glucosidase activity was stimulated greater than 15-fold by sodium taurocholate at pH 5.6, and inhibited at acidic pH (3.5-4.0). Bromoconduritol B epoxide (greater than or equal to 1.0 microM), inhibited epidermal enzyme activity by greater than 75%, while activity in brain, liver, and spleen was only inhibited by 6, 17, and 14%, respectively. Moreover, beta-GlcCer'ase mRNA expression in murine epidermis exceeded levels in liver, brain, and spleen. Finally, beta-GlcCer'ase activity was highest in the outer, more differentiated epidermal cell layers including the stratum corneum. In summary, mammalian epidermis contains an usually high percentage (approximately 75%) of beta-glucocerebrosidase activity, and the concentration of activity in the more differentiated cell layers may account for the replacement of glucosylceramide by ceramides in the outer epidermis.     

Radioresistance of Intermediate TCR Cells and Their Localization in the Body of Mice Revealed by Irradiation

Extrathymic generation of T cells in the liver and in the intestine was recently demonstrated. We investigated herein whether such T cells, especially those in the liver, are present in other organs of mice. This investigation is possible employing our recently introduced method with which even a minor proportion of extrathymic, intermediate TCR cells in organs other than the liver can be identified. Intermediate TCR cells expressed higher levels of IL-2Rβ and LFA-1 than bright TCR cells (i.e., T cells of thymic origin) as revealed by two-color staining. Although intermediate TCR cells were present at a small proportion in the spleen and thymus, they predominated in these organs after irradiation (9 Gy) and bone marrow reconstitution, or after low dose irradiation (6 Gy). This was due to that intermediate TCR cells were relatively radioresistant, whereas bright TCR cells were radiosensitive. Microscopic observation and immunochemical staining showed that intermediate TCR cells in the spleen localized in the red pulp and those in the thymus localized in the medulla. These intermediate TCR cells displayed a large light scatter, similar to such cells in the liver. The present results suggest that intermediate TCR cells may proliferate at multiple sites in the body.     

Modulation of the chemokines KC and MCP-1 by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in mice

Activation of the aryl hydrocarbon receptor (AhR) by TCDD may lead to the induction of proinflammatory cytokines in various cell types and organs such as liver leading to active chronic inflammation. Here we studied the expression of the chemokines keratinocyte chemoattractant (KC) and monocyte chemoattractant protein 1 (MCP-1) in different organs of mice after exposure to TCDD. TCDD exposure led to an early and clear induction of KC in liver and spleen on day 1 which was sustained over a period of 10 days. The level of MCP-1 mRNA was induced by TCDD on day 1 in spleen, lung, kidney, and liver, which was further increased at day 7. Increase of KC and MCP-1 at day 7 in liver, thymus, kidney, adipose, and heart was associated with elevated levels of the macrophage marker F4/80, indicating the infiltration of macrophages in these organs. Induction of KC requires a functional AhR since mice with a mutation in the AhR nuclear localization domain (AhR(nls)) were found to be resistant to TCDD-induced expression of KC. These results are the first showing the induction of the chemokines KC and MCP-1 in multiple organs of mice associated with an increase of the macrophage marker F4/80 indicating the involvement in TCDD's inflammatory response like infiltration of macrophages.     

DGAT1 deficiency decreases PPAR expression and does not lead to lipotoxicity in cardiac and skeletal muscle

Diacylglycerol (DAG) acyl transferase 1 (Dgat1) knockout ((-/-)) mice are resistant to high-fat-induced obesity and insulin resistance, but the reasons are unclear. Dgat1(-/-) mice had reduced mRNA levels of all three Ppar genes and genes involved in fatty acid oxidation in the myocardium of Dgat1(-/-) mice. Although DGAT1 converts DAG to triglyceride (TG), tissue levels of DAG were not increased in Dgat1(-/-) mice. Hearts of chow-diet Dgat1(-/-) mice were larger than those of wild-type (WT) mice, but cardiac function was normal. Skeletal muscles from Dgat1(-/-) mice were also larger. Muscle hypertrophy factors phospho-AKT and phospho-mTOR were increased in Dgat1(-/-) cardiac and skeletal muscle. In contrast to muscle, liver from Dgat1(-/-) mice had no reduction in mRNA levels of genes mediating fatty acid oxidation. Glucose uptake was increased in cardiac and skeletal muscle in Dgat1(-/-) mice. Treatment with an inhibitor specific for DGAT1 led to similarly striking reductions in mRNA levels of genes mediating fatty acid oxidation in cardiac and skeletal muscle. These changes were reproduced in cultured myocytes with the DGAT1 inhibitor, which also blocked the increase in mRNA levels of Ppar genes and their targets induced by palmitic acid. Thus, loss of DGAT1 activity in muscles decreases mRNA levels of genes involved in lipid uptake and oxidation.