摘要:

The role of energy intake in regulating growth hormone receptor (GHR) gene expression has been assessed in young growing pigs living at thermal neutrality (26°C) for a 4‐wk period. To determine the importance of altering metabolic demand while maintaining food intake constant, littermates were also studied in a cold environment (10°C). Results were tissue‐specific: the level of GHR mRNA per unit total RNA in liver was greater on high than low (high = 2 × low) food intake (P<0.001), whereas in muscle it was elevated on the low compared with the high intake diet (P<0.02) and also at 10°C compared with 26°C (P<0.04). When results for GHR mRNA were expressed per unit weight of tissue, only the effects of diet on liver and temperature on muscle remained significant. The changes in hepatic GHR mRNA may have been driven in part by nutritionally induced changes in thyroid status, because both plasma 3,5,3‘‐triiodothyronine concentration and liver 5‘‐deiodinase activity were greater on the high than the low intake diet (P<0.001). Levels of liver GHR mRNA probably had a direct influence on growth of the animals, as they were positively correlated with plasma IGF‐I and growth rate (P<0.001), whereas muscle GHR mRNA may have had a metabolic role when energy supplies were limited.— Dauncey, M. J., Burton, K. A., White, P., Harrison, A. P., Gilmour, R. S., Duchamp, C., Cattaneo, D. Nutritional regulation of growth hormone receptor gene expression.FASEB J.8: 81‐88; 1994.

ISSN:0892-6638    

DOI:10.1096/fasebj.8.1.7507871

出版商:Wiley    

年代:1994

数据来源: WILEY

摘要:

Hepatocyte‐like mhAT3F cells have been derived from the hepatoma of a transgenic mouse expressing the SV40 large T antigen under the control of the antithrombin III gene regulatory region (Antoine, B., Levrat, F., Vallet, V., Berbar, T., Cartier, N., Dubois, N., Briand, P., and Kahn, A. (1992) Gene expression in hepatocyte‐like lines established by targeted carcinogenesis in transgenic mice.Exp. Cell. Res.200, 175–185; F. Levrat et al., unpublished results). In these cells, thel‐PK gene is transcriptionally activated by glucose, as it is in vivo and in cultured hepatocytes. However, in contrast to thel‐PK gene regulation in the liver and isolated hepatocytes, the glucose responsiveness does not require insulin and is not blocked by cyclic AMP. In mhAT3F cells, the insensitivity to insulin might be due to the replacement of insulin‐dependent glucokinase by insulin‐independent hexokinases able to phosphorylate glucose in the absence of the hormone. The glucose‐dependent activation of thel‐PK gene is delayed, requires ongoing protein synthesis, and is mediated by the same glucose response element as in vivo and in isolated hepatocytes. These results suggest that the glucose‐dependent signaling pathway responsible for the transcriptional activation of glycolytic and lipogenic genes requires glucose phosphorylation, a phenomenon that is insulin‐dependent in the liver but insulin‐independent in cultured hepatoma cells. Nevertheless, the action of glucose 6‐phosphate is most likely indirect.— Lefrançois‐Martinez, A.‐M., Diaz‐Guerra, M.‐J. M., Vallet, V., Kahn, A., Antoine, B. Glucose‐dependent regulation of the L‐pyruvate kinase gene in a hepatoma cell line is independent of insulin and cyclic AMP.FASEB J.8: 89‐96; 1994.

ISSN:0892-6638    

DOI:10.1096/fasebj.8.1.8299894

出版商:Wiley    

年代:1994

数据来源: WILEY

摘要:

Dietary copper deficiency impairs cardiovascular function by depression of catecholamine metabolism, and alteration of the structure and function of cardiac mitochondria. Heat shock proteins (HSPs) are a group of cellular homeostatic proteins that are induced in vascular tissue by catecholaminergic transmission after exposure to stress. We investigated the effects of dietary copper deficiency on the induction and accumulation of HSPs in several cardiovascular tissues. Stress‐induced levels of aortic HSP70 mRNA were reduced in copper‐deficient (CuD) rats when compared with copper‐adequate (CuA) controls. Cocaine‐induced HSP70 mRNA accumulation was not different between CuA and CuD rats, suggesting that reduced HSP70 levels in restrained CuD animals may result from altered catecholaminergic neurotransmission. The level of HSP60 mRNA was specifically reduced in the atria of CuD rats, which may be associated with altered mitochondrial structure and function. These results describe a novel relationship between dietary copper deficiency and the expression of highly conserved cellular stress response proteins. Loss of these essential homeostatic proteins in vascular tissue may contribute to the impairment of cardiovascular function known to accompany copper deficiency.— Matz, J. M., Blake, M. J., Saari, J. T., Bode, A. M. Dietary copper deficiency reduces heat shock protein expression in cardiovascular tissues.FASEB J.8: 97‐102; 1994.

ISSN:0892-6638    

DOI:10.1096/fasebj.8.1.8299895

出版商:Wiley    

年代:1994

数据来源: WILEY

摘要:

Hyperglycemia is postulated to cause chronic changes in the vasculature of diabetic patients, suggesting structural or genetic alterations. We have characterized the glucose induced alterations of gene expression in cultured bovine aortic smooth muscle cells using the recently developed mRNA differential display method. After five days of incubation with either 5.5 or 22 mM glucose, RNA preparations were isolated from confluent cells and probed with 10 candidate clones identified after screening up to 3000 mRNA species. Among these, three clones (2A, 2C, 3) showed significant changes in expression by Northern blot analysis. Elevated glucose levels decreased the mRNA expression of clones 2A and 3 to 51 ± 7% (P<.01) and 59 ± 10% (P<.05)(mean% of control ± SEM), respectively. Expression of clone 2C was increased in 22 mM glucose condition to 221 ± 23% (P<.05). Nucleotide sequence analysis showed that clone 3 had 77% homology to the 3'‐noncoding region of human elongation factor 2, a member of the GTPase family which is essential for polypeptide synthesis. Clones 2A and 2C do show no homology to known nucleotide sequences. These results indicate that physiologically attainable high glucose conditions can significantly effect gene expression in aortic smooth muscle cells. Furthermore, mRNA differential display can be used in metabolic studies to identify new genes regulated by nutrients such as glucose.— Y., Nishio, L. P. Aiello, G. L. King. Glucose induced genes in bovine aortic smooth muscle cells identified by mRNA differential display.FASEB J.8: 103‐106; 1994.

ISSN:0892-6638    

DOI:10.1096/fasebj.8.1.8299882

出版商:Wiley    

年代:1994

数据来源: WILEY

摘要:

Hereditary fructose intolerance (HFI) is a potentially fatal autosomal recessive disease of carbohydrate metabolism. HFI patients are deficient in aldolase B, the isozyme expressed in fructose‐metabolizing tissues. The eight protein coding exons, including splicing signals, of the aldolase B gene from one American HFI patient were amplified by the polymerase chain reaction (PCR). Single‐strand conformational polymorphism (SSCP) analysis and direct sequence determination were applied to the amplified fragments. The mutations in the patient's alleles were identified as a nonsense mutation (R59op) in exon 3 and a missense mutation (C134R) in exon 5. These mutations were confirmed by sequence determination of cloned PCR‐amplified exons 3 and 5 from the patient. Allele specific oligonucleotide (ASO) hybridizations of amplified exons 3 and 5 showed the Mendelian inheritance of both mutations. Site‐directed mutagenesis was used to generate an expression plasmid for the C134R mutation, and the mutant enzyme was expressed in bacteria. Assays of partially purified enzyme preparations showed that this missense mutation results in an apparently unstable enzyme that retains partial activity. This is the first evidence for a partially active aldolase B from an HFI individual with an identified mutation, and supports the hypothesis that adequate gluconeogenesis/glycolysis is maintained in HFI patients by the presence of partially active enzymes.— Brooks, C. C., Tolan, D. R. A partially active mutant aldolase B from a patient with hereditary fructose intolerance.FASEB J.8: 107‐113; 1994.

ISSN:0892-6638    

DOI:10.1096/fasebj.8.1.8299883

出版商:Wiley    

年代:1994

数据来源: WILEY

摘要:

The response of the murine genes encoding the subunits of branched‐chainα‐ketoacid dehydrogenase complex (BCKAD) to changes in dietary protein was determined. Steady‐state RNA levels for two of the subunits, E1βand E2, decreased by two‐ to fourfold in the livers of mice fed 0% protein isocaloric diets compared to the levels observed in mice fed standard (23%) or high (50%) protein isocaloric diets. In contrast, the levels of RNA encoding the E1αsubunit did not change significantly in response to these dietary protein changes. The hepatic decreases in E1βand E2 RNA associated with 0% protein isocaloric diets were reversible, with prompt return to baseline levels following 48 hours of 50% protein isocaloric diets ad libitum. In kidney, no significant changes in the RNAs encoding any of the three BCKAD subunits were observed in response to changes in dietary protein. Studies of RNA variations associated with growth and development in several murine tissues, including liver and kidney, demonstrated coordinated changes between all subunits. Similar coordinated changes were observed during 3T3‐L1 adipocyte differentiation. These studies suggest that the responses of the BCKAD subunit genes to alterations in dietary protein are noncoordinated and tissue‐specific, in contrast to the coordinated changes observed during growth and/or differentiation. The differences in BCKAD subunit RNA levels observed under varying nutritional and developmental conditions suggest that multiple regulatory mechanisms modulate BCKAD subunit expression.— Chinsky, J. M., Bohlen, L. M., Costeas, P. A. Noncoordinated responses of branched‐chainα‐ketoacid dehydrogenase subunit genes to dietary protein.FASEB J.8: 114‐120; 1994.

ISSN:0892-6638    

DOI:10.1096/fasebj.8.1.7507870

出版商:Wiley    

年代:1994

数据来源: WILEY

摘要:

Low‐density lipoprotein (LDL) subclass pattern B is a common genetically influenced lipoprotein profile characterized by a predominance of small, dense LDL particles, and associated with increased levels of triglyceride‐rich lipoproteins, reductions in high‐density lipoprotein cholesterol (HDL‐C), and increased risk of coronary artery disease compared to individuals with a predominance of larger LDL (pattern A). We sought to determine whether LDL subclass patterns are associated with response of plasma lipoprotein levels to changes in dietary fat and carbohydrate content. In a randomized cross‐over study, 105 men consumed, for six weeks each, high‐fat (46%) and low‐fat (24%) solid food diets, with replacement of fat by carbohydrate. Diet‐induced changes in subjects who exhibited pattern B (n= 18) following the high‐fat diet differed significantly from those in subjects with pattern A (n= 87): in pattern B subjects LDL cholesterol (LDL‐C) reductions were two‐fold greater and plasma apolipoprotein (apo) B levels decreased significantly. These differences remained significant after adjustment for levels of plasma LDL‐C, apo B, HDL‐C, and body mass index. Thus, LDL subclass pattern is a factor that contributes significantly to interindividual variation of plasma lipoprotein response to a low‐fat, high‐carbohydrate diet.— Dreon, D. M., Fernstrom, H. A., Miller, B., Krauss, R. M. Low‐density lipoprotein subclass patterns and lipoprotein response to a reduced‐fat diet in men.FASEB J.8: 121‐126; 1994.

ISSN:0892-6638    

DOI:10.1096/fasebj.8.1.8299884

出版商:Wiley    

年代:1994

数据来源: WILEY

摘要:

Glutamine produced and stored in skeletal muscle is an important source of nitrogen and energy for the whole body in health and disease and, unsurprisingly, glutamine turnover in muscle is subject to substantial metabolic control.l‐Glutamate, a necessary substrate for glutamine synthetase, is transported into muscle cells by Na+‐dependent and ‐independent transport systems. In primary cultures of rat skeletal muscle myotubes (a useful model system for studies of muscle metabolism and membrane transport), Na+‐dependent glutamate transport (Km≈ 0.7 mM glutamate) shows adaptive up‐regulation (65% increase in transport Vmaxfrom 2.7 to 4.4 nmol · min–1· mg protein–1) in cells within 24 h of glutamine depletion (t1/2for increase of ≈ 4 h), whereas Na+‐ndependent glutamate uptake remains unaltered. Up‐regulation of transport is suppressed by inhibitors of gene transcription (actinomycin‐D) and translation (cycloheximide) and is reversed by glutamine supplementation. Increased glutamate transport capacity should provide extra substrate for glutamine synthesis in muscle cells. Thus, in concert with previously discovered increases in cell glutamine transport capacity and glutamine synthetase activity, it may represent part of a coordinated response to decreased glutamine availability (e.g., under circumstances of increased glutamine utilization by other tissues in vivo).— Low, S. Y., Rennie, M. J., Taylor, P. M. Sodium‐dependent glutamate transport in cultured rat myotubes increases after glutamine deprivation.FASEB J.8: 127‐131; 1994.

ISSN:0892-6638    

DOI:10.1096/fasebj.8.1.7905447

出版商:Wiley    

年代:1994

数据来源: WILEY

ISSN:0892-6638    

DOI:10.1096/fasebj.8.1.8299886

出版商:Wiley    

年代:1994

数据来源: WILEY