APOE Promoter Research Articles

GH002: A Novel and Potent Agents for Elevating HDL-Cholesterol

The aim of this study was to evaluate whether the positive effect of GH002 on high-density lipoprotein (HDL) cholesterolin vitroandin vivo. In vitro assay, effects of GH002 on apolipoprotein (apo) A-I was studied using stable-transfected HepG2 cells with recombinant vector including apoA-I promoter; Effects of GH002 on apoA-I, apoA-II and apoC-III production were determined using HepG2 cells.In vivoassay, Effects of GH002 on lipid profile were investigated in hyperlipidemic rats. The results showed that GH002 can effectively activate apoA-I promoter, enhance apoA-I and apoA-II secretionin vitro, whereas reduce apoC-III production significantly. Furthermore, afterin vivostudy that the hyperlipidemic rats were treated with GH002, HDL-cholesterol levels were increased significantly (P<0.01) at 2 weeks (100 mg/kg, 28.8%) and 3 weeks (30mg/kg, 19.8% and 100mg/kg, 36.4%, respectively) compared with control group. Triglyceride levels were reduced significantly at 2 and 3 weeks (19.5%,P<0.05 and 28.1%,P<0.01 respectively). Total cholesterol levels also were reduced at 3 weeks (19.1%,P<0.05) after 100mg/kg GH002 administration, but GH002 didn’t increase the ratio of liver/body weight compared with the control group at the end of the experiments. It is therefore reasonable to assume that GH002 is an effectively HDL-cholesterol enhancer by regulating apoA-I gene expression, consequently enhancing apoA-I, apoA-II secretion and reducing apoC-III production.

Compensatory increase in lipogenic gene expression in adipose tissue of transgenic mice expressing constitutively active AMP-activated protein kinase-alpha1 in liver

We previously described a line of transgenic mice selectively expressing constitutively active AMPK-α1 under the control of liver-specific human apoE promoter with the hepatic control region sequence. In the short-term activation, the CA-AMPK-α1 transgenic mice at age 10–12weeks exhibited normal hepatic triglyceride content as compared to wild-type mice due to compensatory increase in mRNA expression of genes in the cholesterol and fatty acid synthesis pathways. But it was not known whether the lipogenic gene expression in white adipose tissue also changed. Here we characterized mRNA expression profile of main lipogenic genes in the cholesterol and fatty acid biosynthesis pathway in white adipose tissue. The data show that short-term chronic activation of AMPK in liver caused marked compensatory increase in lipogenic gene expression both in liver due to induction of Srebp-2 and in white adipose tissue due to upregulation of Srebp-1c. These results support the notion that in addition to its well-recognized function for fat storage adipose tissue can play an adaptive role in fatty acid synthesis when fatty acid synthesis is severely reduced in liver, the main lipogenic organ in mammals.

Age-Related Binding of Proximal Region of ApoE Promoter to Nuclear Proteins of Mouse Cerebral Cortex

Mouse ApolipoproteinE (ApoE) gene has maximum promoter activity in the proximal region (-212 to +54) which includes different regulatory elements. These elements bind to specific protein factors and influence the expression of genes which are involved in key brain functions that decline with age. As there is no information on the binding of apoE promoter to nuclear proteins as a function of age, we have analyzed the binding of USF, AP1 and one negative element sequence present in ApoE proximal promoter to nuclear proteins of the cerebral cortex of mice of different ages. The findings show the formation of one complex with USF and two complexes with AP1 and negative element. The intensity of these complexes varies with age, indicating differential binding of protein factors to specific elements of apoE promoter, which reflect age-related regulation of apoE -mediated brain functions.

Studies in mice, hamsters, and rats demonstrate that repression of hepatic apoA-I expression by taurocholic acid in mice is not mediated by the farnesoid-X-receptor

It is claimed that apoA-I expression is repressed in mice by cholic acid (CA) and its taurine conjugate, taurocholic acid (TCA) via farnesoid X receptor (FXR) activation. We measured apoA-I expression in mice, hamsters, and rats treated with highly potent and selective synthetic FXR agonists or with TCA. All of the synthetic agonists bound to FXR with high affinity in a scintillation proximity assay. However, TCA did not compete with the radioligand up to the highest concentration used (100 μM). The C-site regulatory region of apoA-I, through which FXR has been reported to regulate its expression, is completely conserved across the species investigated. In both male and female human apoA-I-transgenic mice, we reproduced the previously reported strong inhibition of human apoA-I expression upon treatment with the typical supraphysiological dose of TCA used in such studies. However, in contrast to some previous reports, TCA did not repress murine apoA-I expression in the same mice. Also, more-potent and -selective FXR agonists did not affect human or murine apoA-I expression in this model. In LDL receptor-deficient mice and Golden Syrian hamsters, selective FXR agonists did not affect apoA-I expression, whereas in Wistar rats, some even increased apoA-I expression. In conclusion, selective FXR agonists do not repress apoA-I expression in rodents. Repression of human apoA-I expression by TCA in transgenic mice is probably mediated through FXR-independent mechanisms.

SiRNA-induced liver ApoB knockdown lowers serum LDL-cholesterol in a mouse model with human-like serum lipids

Increased serum apolipoprotein (apo)B and associated LDL levels are well-correlated with an increased risk of coronary disease. ApoE⁻/⁻ and low density lipoprotein receptor (LDLr)⁻/⁻ mice have been extensively used for studies of coronary atherosclerosis. These animals show atherosclerotic lesions similar to those in humans, but their serum lipids are low in apoB-containing LDL particles. We describe the development of a new mouse model with a human-like lipid profile. Ldlr CETP⁺/⁻ hemizygous mice carry a single copy of the human CETP transgene and a single copy of a LDL receptor mutation. To evaluate the apoB pathways in this mouse model, we used novel short-interfering RNAs (siRNA) formulated in lipid nanoparticles (LNP). ApoB siRNAs induced up to 95% reduction of liver ApoB mRNA and serum apoB protein, and a significant lowering of serum LDL in Ldlr CETP⁺/⁻ mice. ApoB targeting is specific and dose-dependent, and it shows lipid-lowering effects for over three weeks. Although specific triglycerides (TG) were affected by ApoB mRNA knockdown (KD) and the total plasma lipid levels were decreased by 70%, the overall lipid distribution did not change. Results presented here demonstrate a new mouse model for investigating additional targets within the ApoB pathways using the siRNA modality.

An APOE Haplotype Associated with Decreased ε4 Expression Increases the Risk of Late Onset Alzheimer's Disease

This paper addresses a tenet of the literature on APOE, i.e., the relationship between the effects of the ε4, one of the established genetic risk factor for Alzheimer's disease (AD), and its expression levels as determined by APOE promoter polymorphisms. Five polymorphisms (-491 rs449647, -427 rs769446, -219 rs405509, and ε rs429358-rs7412) were studied in 1308 AD patients and 1082 control individuals from the Central-Northern Italy. Major findings of the present study are the following: 1) the variants -219T and ε4 increase the risk for late onset AD (LOAD) when they are both present in cis on the same chromosome (in phase); 2) the correlation between the haplotype (-219T/ε4) and AD risk persists when the data are stratified by age; 3) this haplotype likely anticipates the age of onset of the disease. These data, while confirming the association between -219T and AD, highlight the importance of the phase of the alleles for the observed effects on AD risk, suggesting that this information has to be taken into account when assessing the AD genetic risk. Moreover, the data help to clarify the apparent discrepancy that emerges from the genetic analysis where an SNP characterizing the haplotype responsible for an increased risk for LOAD is coherently associated with a reduced expression of ApoE levels. Our data are compatible with the hypothesis of a complex role of ApoE in the AD pathogenesis, with positive and negative effects occurring concomitantly according to its expression levels and its protein-protein interactions largely unclarified.

Macrophage-specific Up-regulation of Apolipoprotein E Gene Expression by STAT1 Is Achieved via Long Range Genomic Interactions

In atherogenesis, macrophage-derived apolipoprotein E (apoE) has an athero-protective role by a mechanism that is not fully understood. We investigated the regulatory mechanisms involved in the modulation of apoE expression in macrophages. The experiments showed that the promoters of all genes of the apoE/apoCI/apoCIV/apoCII gene cluster are enhanced by multienhancer 2 (ME.2), a regulatory region that is located 15.9 kb downstream of the apoE gene. ME.2 interacts with the apoE promoter in a macrophage-specific manner. Transient transfections in RAW 264.7 macrophages showed that the activity of ME.2 was strongly decreased by deletion of either 87 bp from the 5' end or 131 bp from the 3' end. We determined that the minimal fragment of this promoter that can be activated by ME.2 is the proximal -100/+73 region. The analysis of the deletion mutants of ME.2 revealed the importance of the 5' end of ME.2 in apoE promoter transactivation. Chromatin conformational capture assays demonstrated that both ME.2 and ME.1 physically interacted with the apoE promoter in macrophages. Our data showed that phorbol 12-myristate 13-acetate-induced differentiation of macrophages is accompanied by a robust induction of apoE and STAT1 expression. In macrophages (but not in hepatocytes), STAT1 up-regulated apoE gene expression via ME.2. The STAT1 binding site was located in the 174-182 region of ME.2. In conclusion, the specificity of the interactions between the two multienhancers (ME.1 and ME.2) and the apoE promoter indicates that these distal regulatory elements play an important role in the modulation of apoE gene expression in a cell-specific manner.

Regulator of G Protein Signaling (RGS16) Inhibits Hepatic Fatty Acid Oxidation in a Carbohydrate Response Element-binding Protein (ChREBP)-dependent Manner

G protein-coupled receptor (GPCR) pathways control glucose and fatty acid metabolism and the onset of obesity and diabetes. Regulators of G protein signaling (RGS) are GTPase-activating proteins (GAPs) for G(i) and G(q) α-subunits that control the intensity and duration of GPCR signaling. Herein we determined the role of Rgs16 in GPCR regulation of liver metabolism. Rgs16 is expressed during the last few hours of the daily fast in periportal hepatocytes, the oxygen-rich zone of the liver where lipolysis and gluconeogenesis predominate. Rgs16 knock-out mice had elevated expression of fatty acid oxidation genes in liver, higher rates of fatty acid oxidation in liver extracts, and higher plasma β-ketone levels compared with wild type mice. By contrast, transgenic mice that overexpressed RGS16 protein specifically in liver exhibited reciprocal phenotypes as well as low blood glucose levels compared with wild type littermates and fatty liver after overnight fasting. The transcription factor carbohydrate response element-binding protein (ChREBP), which induces fatty acid synthesis genes in response to high carbohydrate feeding, was unexpectedly required during fasting for maximal Rgs16 transcription in liver and in cultured primary hepatocytes during gluconeogenesis. Thus, RGS16 provides a signaling mechanism for glucose production to inhibit GPCR-stimulated fatty acid oxidation in hepatocytes.

Alcohol Induces RNA Polymerase III-dependent Transcription through c-Jun by Co-regulating TATA-binding Protein (TBP) and Brf1 Expression

Chronic alcohol consumption is associated with steatohepatitis and cirrhosis, enhancing the risk for hepatocellular carcinoma. RNA polymerase (pol) III transcribes a variety of small, untranslated RNAs, including tRNAs and 5S rRNAs, which determine the biosynthetic capacity of cells. Increased RNA pol III-dependent transcription, observed in transformed cells and human tumors, is required for oncogenic transformation. Given that alcohol consumption increases risk for liver cancer, we examined whether alcohol regulates this class of genes. Ethanol induces RNA pol III-dependent transcription in both HepG2 cells and primary mouse hepatocytes in a manner that requires ethanol metabolism and the activation of JNK1. This regulatory event is mediated, at least in part, through the ability of ethanol to induce expression of the TFIIIB components, Brf1, and the TATA-binding protein (TBP). Induction of TBP, Brf1, and RNA pol III-dependent gene expression is driven by enhanced c-Jun expression. Ethanol promotes a marked increase in the direct recruitment of c-Jun to TBP, Brf1, and tRNA gene promoters. Chronic alcohol administration in mice leads to enhanced expression of TBP, Brf1, tRNA, and 5S rRNA gene transcription in the liver. These alcohol-dependent increases are more pronounced in transgenic animals that express the HCV NS5A protein that display increased incidence of liver tumors. Together, these results identify a new class of genes that are regulated by alcohol through the co-regulation of TFIIIB components and define a central role for c-Jun in this process.

Association of promoter polymorphism of apolipoprotein E gene with cerebral vasospasm after spontaneous SAH

Cerebral vasospasm (CV) is the main complication of spontaneous subarachnoid hemorrhage (SAH), affecting clinical outcome of patients with SAH. Accumulating evidence indicates that apolipoprotein E (apoE protein, APOE gene) gene polymorphism is associated with prognosis of patients with SAH. The current study aimed to investigate the association of promoter polymorphism of APOE with CV in patients with SAH. One hundred and one patients with spontaneous SAH were involved in this study. Venous blood samples were collected to identify the promoter genotype of APOE by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). CV was judged by transcranial Doppler sonography (TCD) combined with patients' condition. Associations of APOE promoter polymorphism with CV after SAH were analyzed by χ(2) test, uni- and multivariate logistic regression analyses. In 101 patients, 42 of 87 patients (48.3%) with promoter -219T allele showed CV, which was significantly different from those with -219G allele (23/61, 37.7%, P=0.04). Uni- and multivariate logistic regression analyses also showed that promoter -219T was a risk factor to predispose CV after SAH. However, there was no significant association between promoter -491A/T (rs#449647) or -427C/T (rs#769446) polymorphisms and SAH induced CV (P>0.05). Our finding suggests that patients with APOE -219T promoter are apt to CV after spontaneous SAH.

Pioglitazone increases apolipoprotein A-I production by directly enhancing PPRE-dependent transcription in HepG2 cells

Pioglitazone, a hypoglycemic agent, has been shown to increase plasma HDL cholesterol, but the mechanism is incompletely understood. We further investigated effects of pioglitazone on transcriptional regulation of apolipoprotein (apo)A-I gene and functional properties of pioglitazone-induced apoA-I-containing particles. Pioglitazone dose-dependently stimulated apoA-I promoter activities in HepG2 cells. A peroxisome proliferator-activated receptor (PPAR)-response element located in site A (-214 to -192 bp, upstream of the transcription start site) of the promoter is required for pioglitazone-induced apoA-I gene transcription. Deletion of site A (-214 to -192 bp), B (-169 to -146 bp), or C (-134 to -119 bp), which clusters a number of cis-acting elements for binding of different transcription factors, reduced the basal apoA-I promoter activities, and no additional pioglitazone-sensitive elements were found within this region. Overexpression or knock-down of liver receptor homolog-1, a newly identified nuclear factor with strong stimulatory effect on apoA-I transcription, did not alter pioglitazone-induced apoA-I transcription. Pioglitazone-induced apoA-I transcription is mainly mediated through PPARalpha but not PPARgamma in hepatocytes. Pioglitazone induced production of HDL enriched in its subfraction containing apoA-I without apoA-II, which inhibited monocyte adhesion to endothelial cells in vitro. In conclusion, pioglitazone increases apoA-I production by directly enhancing PPAR-response element-dependent transcription, resulting in generation of apoA-I-containing HDL particles with increased anti-inflammatory property.

Effect of TNFα on activities of different promoters of human apolipoprotein A-I gene

Human apolipoprotein A-I (ApoA-I) is a major structural and functional protein component of high-density lipoproteins. The expression of the apolipoprotein A-I gene (apoA-I) in hepatocytes is repressed by pro-inflammatory cytokines such as IL-1β and TNFα. Recently, two novel additional (alternative) promoters for human apoA-I gene have been identified. Nothing is known about the role of alternative promoters in TNFα-mediated downregulation of apoA-I gene. In this article we report for the first time about the different effects of TNFα on two alternative promoters of human apoA-I gene. Stimulation of HepG2 cells by TNFα leads to activation of the distal alternative apoA-I promoter and downregulation of the proximal alternative and the canonical apoA-I promoters. This effect is mediated by weakening of the promoter competition within human apoA-I 5′-regulatory region (apoA-I promoter switching) in the cells treated by TNFα. The MEK1/2-ERK1/2 cascade and nuclear receptors PPARα and LXRs are important for TNFα-mediated apoA-I promoter switching.

Apolipoprotein E isoform-dependent effects on anxiety and cognition in female TR mice

Compared with apoE3, apoE4 is associated with increased risk to develop age-related cognitive decline, particularly in women. In this study, young, middle-aged, and old female mice expressing human apoE under control of the mouse apoE promoter were behaviorally analyzed. Cognitive performance in the water maze decreased with age in all mice. Compared with apoE2 and apoE3 mice, apoE4 mice showed better cognitive performance and higher measures of anxiety than apoE2 and apoE3 mice. Measures of anxiety correlated with cognitive performance in the water maze and passive avoidance tests and might have contributed to the enhanced cognitive performance of the apoE4 mice. ApoE4 mice showed better water maze learning and higher cortical apoE levels than mice expressing apoE4 in astrocytes under control of the GFAP promoter. This was not seen in apoE3 mice. There were no line differences in either genotype in spatial memory retention in the probe trial following the last day of hidden platform training. Thus, the promoter used to express apoE4 critically modulates its effects on brain function.

The APOE-491 A/T promoter polymorphism effect on cognitive profile of Alzheimer's patients

Alzheimer's Disease (AD) is a neurodegenerative disorder with a complex aetiology displayed by multiple pathogenic factors. The APOE ɛ4 allele represents the only established genetic risk factor for sporadic AD; in addition, previous findings on three single nucleotide polymorphisms (SNPs) located on the APOE promoter region, have led to a growing interest in their potential role in AD pathogenesis. The −491 A/T promoter polymorphism has been the one most frequently shown to be associated with AD, as it influences the APOE coding region transcription. The aim of this study was to evaluate the possible effect of the −491 A/T polymorphism on the cognitive profile of sporadic AD patients with a disease severity ranging from mild to moderate. Our results showed that patients carrying the −491 AA genotype had poorer cognitive performances than the −491 AT ones, statistically significant in demanding tests of visual attention, especially for the late-onset AD (LOAD). No further differences on cognitive profile were observed when stratifying AA and AT patients according to their APOE genotype. These results suggest a possible functional effect of the −491 A/T promoter on the neuropsychological performances of AD. This role seems to be independent of APOE genotype. In fact the effect of −491 A/T occurs predominantly on attention while the APOE ɛ4 allele mainly affects memory performances. According to the biological effect exerted on APOE transcription, the −491 A/T polymorphism could be considered a disease modifier more than a risk factor for sporadic AD.

Prediction Models That Include Genetic Data

Can alternative modeling approaches that integrate genetic data help to improve the prediction of risk for common diseases? In this issue of Circulation: Cardiovascular Genetics , Stengard et al1 set out to answer this question with regard to several genetic variations of the APOE gene and risk for ischemic heart disease (IHD). In their study, they included 3686 women and 2772 men with no medical history of IHD from the Copenhagen City Heart Study and sought to correlate IHD events to risk factors such as abnormal lipid levels, hypertension, diabetes, smoking history, and various APOE genotype data during a mean of 6.5 years of follow-up. Article see p 22 The traditional statistical approach to this analysis would be to use Cox proportional hazard modeling to map the hazard of developing IHD to a linear combination of significant risk factors. Stengard et al adopted an interesting alternative procedure that is consistent with the intuition that risk factors may have different effects in subjects with different unmeasured exposures (for example different genetic backgrounds and/or other unknown variables). Therefore, rather than looking for the risk factors that have a homogeneous effect on the hazard for IHD, the authors used the rule induction algorithm PRIM to discover subgroups of subjects with varying combinations of phenotypic risk factors for IHD and APOE alleles e2, e3, and e4. They then used the PRIM again to further segregate these subgroups according to additional genotypes in …

Orphan nuclear receptor Nur77 participates in human apolipoprotein A5 gene expression

The orphan nuclear receptor Nur77 (NR4A1) has been reported to play a crucial role in the modulation of diverse metabolic processes in liver. Here, we reported the identification of human apolipoprotein A5 (ApoA5), which implicated in lowering plasma triglyceride levels, as a novel target gene of Nur77. Nur77 induced the human ApoA5 promoter activity. Using 5′-deletion and mutagenesis of human ApoA5 promoter analysis and chromatin immunoprecipitation assays, it was shown that Nur77 directly regulated human ApoA5 gene expression by binding to a Nur77 response element (AAAGGTCA) located in the proximal human ApoA5 promoter region. In addition, we demonstrated that blocking of Nur77 transcriptional activity via overexpression of dominant negative Nur77 suppressed human ApoA5 promoter activity and mRNA expression in human hepatoma cells, HepG2. Taken together, our results demonstrated that Nur77 is a novel regulator of human ApoA5 gene expression and provide a new insight into the role of this orphan nuclear receptor in lipoprotein metabolism and triglyceride homeostasis.

Apolipoprotein E/C1 Locus Variants Modify Renal Cell Carcinoma Risk

Lipid peroxidation is considered a unifying mechanistic pathway through which known risk factors induce renal cell carcinoma (RCC). We hypothesized that genes selected a priori for their role in lipid peroxidation would modify cancer risk. We genotyped 635 single nucleotide polymorphisms (SNP) in 38candidate genes in 777 Caucasian RCC cases and 1,035 controls enrolled in a large European case-control study. Top candidate SNPs were confirmed among 718 Caucasian cases and 615 controls in a second study in the United States. Two of the three SNPs (rs8106822 and rs405509) that replicated in the U.S. study were within a regulatory region of the APOE promoter. The OR for rs8106822 A>G variant was 1.22(AG) and 1.41(GG) (P(trend) = 0.01) in the European study, 1.05(AG) and 1.51(GG) (P(trend) = 0.03) in the U.S. study, and 1.15(AG) and 1.44(GG) (P(trend) = 0.001) among 1,485 cases and 1,639 controls combined. The rs405509 G>T variant was associated with risk in the European (OR, 0.87(TG); OR, 0.71(TT); P(trend) = 0.02), the U.S. (OR, 0.68(TG); OR, 0.71(TT); P(trend) = 0.02), and both studies combined (OR(TG), 0.79; OR(TT), 0.71; P(trend) = 0.001), as was the G-G haplotype (r(2) = 0.64; P= 4.7 x 10(-4)). This association is biologically plausible as SNP rs405509 was shown to modify protein binding and transcriptional activity of the APOE protein in vitro and is in linkage disequilibrium with key known variants defining the e2, e3, and e4 alleles that modify risk of atherosclerosis, Alzheimer's disease risk, and progression to AIDS. In two large case-control studies, our findings further define a functional region of interest at the APOE locus that increases RCC susceptibility.

Activation of testicular orphan receptor 4 by fatty acids

Nuclear receptors can be activated by chemicals, metabolites, hormones or environmental compounds to regulate gene expression. Bioassay-guided screening of mouse tissue extracts found that natural fatty acids of a certain carbon length and level of unsaturation could activate the mouse orphan nuclear receptor, testicular orphan receptor 4 (TR4). Subsequent experiments focused on γ-linoleic acid, a compound identified during screening of mouse tissues that exerts regulatory activity in TR4 transactivation assays. γ-linoleic acid positively modulates TR4 activity to promote the expression of downstream genes such as apolipoprotein E (ApoE) and phosphoenolpyruvate carboxykinase, and to activate a reporter carrying direct repeat 1 from the ApoE promoter. It also induced the interaction of TR4 with transcription coregulators such as RIP140 and PCAF. Comparisons of transactivation by TR4 and the metabolism-related peroxisome proliferator-activated nuclear receptors indicate that γ-linoleic acid regulation is specific to TR4. The data suggest that TR4 might exert its physiological function by sensing certain lipids. Identifying these compounds could be useful for examining the physiological pathways in which TR4 and its target genes are involved.

Apolipoprotein genotype does not influence MS severity, cognition, or brain atrophy

The influence of APOE allelic heterogeneity on multiple sclerosis (MS) disease severity has been reported in multiple datasets with conflicting results. Several studies have reported an unfavorable association of APOE epsilon4 with more severe clinical disease course while, in contrast, APOE epsilon2 has been associated with a more benign disease course. In this study, we examine the influence of heterogeneity of the APOE gene on disease severity in a large, Australian, population-based MS cohort. Associations between APOE allele status, 2 promoter region single nucleotide polymorphisms (-219 G/T and +113 C/G), and 4 measures of disease severity were tested in 1,006 patients with relapsing-remitting MS and secondary progressive MS: 1) Multiple Sclerosis Severity Score; 2) Progression Index (Expanded Disability Status Scale/disease duration); 3) age at first symptom; and 4) interval between the first and second attack. The Symbol Digit Modalities Test was used as a single cognitive marker in 889 patients. Brain atrophy was measured in 792 patients using the intercaudate ratio. APOE epsilon4 and epsilon3 carriers were stratified by -219 G/T or +113 C/G to investigate haplotypic heterogeneity in the APOE gene region. In this MS study, neither APOE allele status nor promoter region heterogeneity at positions -219 G/T or +113 C/G influenced the clinical disease severity, cognition, or cerebral atrophy. Allelic and haplotypic heterogeneity of the APOE gene region does not influence multiple sclerosis disease course in this well-defined Australian multiple sclerosis cohort.

084 MICE OVER-EXPRESSING SALMON CALCITONIN HAVE STRONGLY ATTENUATED BONE AND CARTILAGE CHANGES AFTER DESTABILIZATION OF THE MEDIAL MENISCUS

Purpose: The pathogenesis of osteoarthritis (OA) involves both bone and cartilage changes. The peptide hormone calcitonin is produced by the thyroidal C-cells and is well-known for its inhibitory actions on bone resorbing osteoclasts. We investigated the effect on the articular cartilage and subchondral bone, after destabilization of the medial meniscus (DMM) in mice over-expressing salmon calcitonin (sCT) compared to control littermates. Methods: Mice over-expressing salmon calcitonin behind the liver ApoE promoter and wild-type littermate control were used for the experiments. Phenotype determination was performed by evaluating circulating serum levels of salmon calcitonin by specific ELISA. Northern Blot expression analysis was carried out to investigate the liver-specific expression of the transgene. Noncalcified plastic embedded vertebrae from mice of 6 and 12 month of age were used for histomophometric investigations. Serum samples were collected for osteocalcin measurements and urine for Dpd/creatinine measurements. In a preliminary experiment 10 week old mice were subjected to microsurgery to introduce DMM or sham operated, after which bone and cartilage degradation was monitored. After 7 weeks the study was terminated and the knee joints isolated for histological analysis by safranin’O staining. Results: Characterization of the transgenic mice was carried out by Northern Blot expression analysis and serum levels of sCT were about 8-times higher than endogenous CT levels in transgenic mice. Transgenic mice had >1000 pg/mL serum sCT and wild-type mice had no detectable levels. Von Kossa staining revealed an increase in trabecular bone volume (BV/TV) 100% after 6 month and 150% after 12 month in sCT mice when compared to controls (P<0.05). Trabecular number and thickness increased significantly (P<0.05) in transgenic mice at 6 and 12 months of age, and trabecular separation decreased in transgenic mice (P<0.05). Additionally, the osteoblasts number and bone formation rate were quantified by histomorphometry and together with the measurements of osteocalcin revealed that bone formation was not affected in transgenic mice. Mice having their medial meniscus transected for 7 weeks had major damage to cartilage and subchondral bone, which were visualized by histology. Sham operated animals, wild-type and transgenic mice, had maximum 8% erosion of the articular cartilage surface of both femur and tibia combined. DMM-operated wild-type mice had collapse of the trabecular structure and thickening of the subchondral bone and complete loss of articular cartilage in the medial tibial plateau of the joint compartment. These degenerative changes in the entire joint were however hampered in transgenic mice. The cartilage degradation comprised only 38% of the tibial plateau and 10% of the femoral chondyle and the subchondral bone and trabecular structure of the underlying bone were comparable to sham operated animals. Conclusions: Salmon calcitonin over-expressing mice had higher bone volume compared to wild-type. Mice over-expressing salmon calcitonin were protected against cartilage erosion, collapse of the subchondral compartment and bone thickening compared to wildtype litter mate controls. This data suggest that salmon calcitonin may have positive effects on the pathogenesis of OA however more studies are necessary to confirm these preliminary results.