Low back pain is a common disabling musculoskeletal disorder, whose prevention and treatment are problematic. The main reason is that current imaging techniques do not identify the source of pain in the vast majority of cases. The diagnosis of low back disorder is, therefore, often based on non-specific signs, such as deep tissue pain and altered motor patterns. Unfortunately, there is little agreement on how these patterns change with pain. While most authors agree that force generated by the muscles is usually diminished (the mechanism is unknown), electromyographic (EMG) recordings are equivocal -both hyper-and hypoactivity have been reported (Ahern et al. 1988). The contradictory results may reflect two major disadvantages connected with clinical studies. First, as a direct consequence of the difficulty of localizing the primary tissue damage, the clinical studies may involve heterogeneous populations of patients with different primary afflictions (affecting intervertebral disks, ligaments, facet joints, muscles, etc.). Second, in clinical studies there is no healthy 'norm' to which the patients could be compared. Data from the individual's pain-free history are rarely available and there is a certain inter-individual variability in motion patterns even within the healthy population. Uncontrolled factors such as these are responsible for the current poor understanding of the

Inclusion of the PPARalpha (peroxisome-proliferator-activated receptor alpha) activator WY 14,643 in the diet of normal mice stimulated the hepatic expression of not only genes of the fatty acid oxidation pathway, but also those of the de novo lipid synthetic pathways. Induction of fatty acid synthase mRNA by WY 14,643 was greater during the light phase of the diurnal cycle, when food intake was low and PPARalpha expression was high. Hepatic fatty acid pathway flux in vivo showed a similar pattern of increases. The abundance of mRNAs for genes involved in hepatic cholesterol synthesis was also increased by WY 14,643, but was associated with a decrease in cholesterogenic carbon flux. None of these changes were apparent in PPARalpha-null mice. Mice of both genotypes showed the expected decreases in 3-hydroxy-3-methylglutaryl-CoA reductase mRNA levels and cholesterol synthesis in response to an increase in dietary cholesterol. The increase in fatty acid synthesis due to WY 14,643 was not mediated by increased expression of SREBP-1c (sterol regulatory element binding protein-1c) mRNA, but by an increase in cleavage of the protein to the active form. An accompanying rise in stearoyl-CoA desaturase mRNA expression suggested that the increase in lipogenesis could have resulted from an alteration in membrane fatty acid composition that influenced SREBP activation.

The aim of the present study was to determine whether peroxisome-proliferator-activated receptor-alpha (PPARalpha) deficiency disrupts the normal regulation of triacylglycerol (TAG) accumulation, hepatic lipogenesis and glycogenesis by fatty acids and insulin using PPARalpha-null mice. In wild-type mice, hepatic TAG concentrations increased (P<0.01) with fasting (24 h), with substantial reversal after refeeding (6 h). Hepatic TAG levels in fed PPARalpha-null mice were 2.4-fold higher than in the wild-type (P<0.05), increased with fasting, but remained elevated after refeeding. PPARalpha deficiency also impaired hepatic glycogen repletion (P<0.001), despite normal insulin and glucose levels after refeeding. Higher levels of plasma insulin were required to support similar levels of hepatic lipogenesis de novo ((3)H(2)O incorporation) in the PPARalpha-null mice compared with the wild-type. This difference was reflected by corresponding changes in the relationship between plasma insulin and the mRNA expression of the lipogenic transcription factor sterol-regulatory-element-binding protein-1c, and that of one of its known targets, fatty acid synthase. In wild-type mice, hepatic pyruvate dehydrogenase kinase (PDK) 4 protein expression (a downstream marker of altered fatty acid catabolism) increased (P<0.01) in response to fasting, with suppression (P<0.001) by refeeding. Although PDK4 up-regulation after fasting was halved by PPARalpha deficiency, PDK4 suppression after refeeding was attenuated. In summary, PPARalpha deficiency leads to accumulation of hepatic TAG and elicits dysregulation of hepatic lipid and carbohydrate metabolism, emphasizing the importance of precise control of lipid oxidation for hepatic fuel homoeostasis.

A cDNA has been isolated from human heart that is homologous to a member of the low density lipoprotein (LDL) receptor gene family recently identified in rabbit. It was named the very low density lipoprotein (VLDL) receptor, although its physiological function is not yet known. The predicted human protein shows 97.4% sequence homology to the rabbit protein, much more than the approximately 75% observed between their LDL receptor proteins. The sequence is also highly conserved in the hamster and the African green monkey. The mRNA was identified as a 3.9 kb transcript by Northern blotting in Hep G2 cells, cultured arterial smooth muscle cells and human skin fibroblasts, where its level was unaffected by sterols. The mRNA was not detected in EBV-lymphoblasts or in monocyte-macrophages by Northern blotting or by RT-PCR. In human tissues in vivo, the mRNA was expressed predominantly in heart and skeletal muscle, and also in ovary and kidney, but not in the liver. Although the 3.9 kb mRNA was the major transcript, a larger variant of 5.2 kb was also detectable and was predominant in skeletal muscle. Amplification of the mRNA from cultured human cells also revealed a potential splice variant that lacked 84 bp coding for a region equivalent to the O-linked sugars domain of the LDL receptor. It was a minor component in most cell types, but was predominant in Hep G2 cells.

Familial hypercholesterolemia (FH), caused by many different mutations in the low-density lipoprotein (LDL)-receptor gene, invariably leads to severe premature coronary heart disease (CHD) in homozygous individuals. Heterozygous FH patients are less severely affected but are still at increased risk of CHD in most populations. Although FH homozygotes in China are affected similarly to those elsewhere, heterozygotes are not detected in the general population and obligate heterozygotes are often not hypercholesterolemic by Western standards. Mutations in the LDLreceptor genes of 10 homozygous FH patients from the Jiang-su province of China and their heterozygous parents were analyzed. These include one large and two minor deletions and eight point mutations: four are predicted to introduce a premature stop codon, five to result in a single amino acid substitution or deletion, and one to produce a protein with an abnormal cytoplasmic tail. Expression of the mutant LDL-receptor cDNAs in vitro confirmed that these mutations impaired LDL-receptor function and that several would cause a receptor-negative phenotype. Thus, the lack of clinical expression in obligate FH heterozygotes is not due to unusually "mild" mutations in the LDL-receptor gene, and other genetic or environmental factors must therefore be important in determining phenotypic expression. (Arierioseler Thromb. 1994;14:85-94.)

Plasma lipoprotein(a) (Lp(a)) concentrations vary considerably between individuals. To examine the variation for products of the same and different apolipoprotein(a) (apo(a)) alleles, conditions were established whereby phenotyping immunoblots could be used to estimate the concentration of Lp(a) associated with the constituent apo(a) isoforms. In these studies 28 distinct isoforms were identified, each differing by a single kringle IV unit. Tracking the isoforms through 10 families showed that there could be up to 200-fold difference in the Lp(a) concentration associated with the same-sized isoform produced from different alleles. In contrast there was typically < 2.5-fold variation in the Lp(a) concentration associated with the same allele. However, there were four occasions where the concentration associated with a particular allele was reduced below the typical range from one generation to the next. A nonlinear, inverse trend with isoform size was apparently superimposed upon the other factors that determine Lp(a) concentration. Inheritance of familial hypercholesterolemia or familial-defective apoB1j0 had little consistent effect upon Lp(a) concentration. In both the families and in other unrelated individuals the distribution of isoforms and their associated concentrations provided evidence for the presence ofat least two and possibly more subpopulations of apo(a) alleles with different sizes and expression.

Methapyrilene (MP) exposure of animals can result in an array of adverse pathological responses including hepatotoxicity. This study investigates gene expression and histopathological alterations in response to MP treatment in order to 1) utilize computational approaches to classify samples derived from livers of MP treated rats based on severity of toxicity incurred in the corresponding tissue, 2) to phenotypically anchor gene expression patterns, and 3) to gain insight into mechanism(s) of methapyrilene hepatotoxicity. Large-scale differential gene expression levels associated with the exposure of male Sprague-Dawley rats to the rodent hepatic carcinogen MP for 1, 3, or 7 days after daily dosage with 10 or 100 mg/kg/day were monitored. Hierarchical clustering and principal component analysis were successful in classifying samples in agreement with microscopic observations and revealed low-dose effects that were not observed histopathologically. Data from cDNA microarray analysis corroborated observed histopathological alterations such as hepatocellular necrosis, bile duct hyperplasia, microvesicular vacuolization, and portal inflammation observed in the livers of MP exposed rats and provided insight into the role of specific genes in the studied toxicological processes.Keywords. Toxicogenomics; gene expression; methapyrilene; toxicity classification; rat liver; histopathology; phenotypic anchorage; hepatotoxicity.INTRODUCTION Methapyrilene (MP) is an antihistaminic compound once used as a popular over-the-counter sleep-aid component and also used in cold and allergy medications. It was found to induce hepatocellular carcinomas and cholangiocarcinomas in rats (20, 31, 33) and was subsequently withdrawn from the market. However, its carcinogenicity appears to be species-specific because no evidence has been found of MPassociated carcinogenesis in mice (3), guinea pigs, hamsters (32), or humans (36).MP was negative in the DNA adduct formation assay (8, 9, 34) and has not been found to be mutagenic with the Ames assay or other mutation assays (7, 38). Furthermore, MP did not induce unscheduled DNA synthesis (4) and did not cause sister-chromatid exchange (24). These data are consistent with the hypothesis that MP is carcinogenic in rats via nonmutagenic mechanisms (36,54). MP is extensively metabolized by the liver (29, 53), and phase I metabolism plays a major role in its toxicity because cytochrome P450 inhibitors afford protection from the toxicity of MP (43). The oxidative potential of methapyrilene and/or metabolites and increased cellular proliferation have been proposed to play a central role in the observed toxicity (9,45,49). Bile duct cannulation of MP treated rats affords protection from MP hepatic toxicity suggesting that enterohepatic recirculation of glucuronidated metabolites plays a role in MP toxicity (45). In humans, methapyrilene has a very short half-life, a relatively high apparent volume of distribution, and total

In the current study, we have determined the cDNA and the genomic sequences of the arylacetamide deacetylase (AADA) gene in mice and rats. The AADA genes in the rat and mouse consist of five exons and have 2.4 kilobases of homologous promoter sequence upstream of the initiating ATG codon. AADA mRNA is expressed in hepatocytes, intestinal mucosal cells (probably enterocytes), the pancreas and also the adrenal gland. In mice, there is a diurnal rhythm in hepatic AADA mRNA concentration, with a maximum 10 h into the light (post-absorptive) phase. This diurnal regulation is attenuated in peroxisome proliferator-activated receptor ␣ knockout mice. Intestinal but not hepatic AADA mRNA was increased following oral administration of the fibrate, Wy-14,643. The homology of AADA with hormone-sensitive lipase and the tissue distribution of AADA are consistent with the view that AADA plays a role in promoting the mobilization of lipids from intracellular stores and in the liver for assembling VLDL. This hypothesis is supported by parallel changes in AADA gene expression in animals with insulin-deficient diabetes and following treatment with orotic acid.