Living with the BRCA1 and BRCA2 genetic mutation: learning how to adapt to a virtual chronic illness.

The objective of this study was to understand how women living with the BRCA1 and BRCA2 genetic mutation adapt to this life transition and to identify the main adaptive tasks. A qualitative inquiry inspired by grounded theory revealed that participants cognitively appraised their test result in the same manner as women who have been diagnosed with breast cancer. Consequently, participants had to adapt to a condition that they perceived as a chronic illness. The following three main tasks were identified: Physical Task: Attempting to Limit the Impact of the Test Result, Psychological Task: Living with Uncertainty, and Social Task: Finding Effective Support. In conclusion, although these women live with the possibility of developing breast cancer, their experiences mirror those of individuals living with a chronic illness, and they must therefore adapt accordingly in a physical, psychological, and social manner.

Restoring ADL function after wrist surgery in children with cerebral palsy: a novel Bilateral robot system design.

Cerebral palsy is a leading cause of disability in children and reducing its effects on arm function will improve quality of life. Our goal is to train children with CP after wrist tendon transfer surgery using a robotic therapy system consisting of two robot arms and wrist robots. The therapeutic goal is to determine if the robot training combined with surgery intervention improved functional outcomes significantly more than surgery alone. To accomplish this long-term goal we have developed a Bilateral ADL Exercise Robot, BiADLER aimed at training children with CP in reach to grasp coordination on ADLs. Specifically, the robot will provide active training using an assist-as-needed. This paper presents the design concepts.

Living with the BRCA genetic mutation: an uncertain conclusion to an unending process.

Women carrying a BRCA1 or BRCA2 genetic mutation have an up to 80% lifetime risk of developing breast cancer. It is especially important to understand the experiences of these women, as their lives are permeated with the threat of cancer. This qualitative study examined the experiences of six young women of reproductive age (age < 45 years) who were identified as carriers. The analysis of the semi-structured interviews inspired by grounded theory methodology, showed that participants experienced the same type of uncertainty demonstrated by women who have already been diagnosed with breast cancer.

Human trophoblast invasion and spiral artery transformation: the role of PECAM-1 in normal pregnancy, preeclampsia, and fetal growth restriction.

During early human pregnancy extravillous cytotrophoblasts invade the uterus and spiral arteries transforming them into large vessels of low resistance. Failure of trophoblast invasion and spiral artery transformation occurs in preeclampsia and fetal growth restriction (FGR); these processes are not well understood. Recent studies have suggested that cytotrophoblasts that invade spiral arteries mimic the endothelial cells they replace and express PECAM-1. It was also reported that in preeclampsia, cytotrophoblasts fail to express PECAM-1 and that failure to express endothelial cell adhesion molecules may account for failed trophoblast invasion. Despite the possible importance of adhesion molecules in trophoblast invasion, no study has systematically investigated the expression of PECAM-1 in the placental bed throughout the period of invasion, particularly in the myometrial segments where the key failure occurs. There are no studies on PECAM-1 expression in the placental bed in FGR. We have examined the expression of PECAM-1 in placental bed biopsies and placentas from 8 to 19 weeks of gestation and in the placenta and placental bed in the third trimester in cases of preeclampsia, FGR, and control pregnancies. PECAM-1 was expressed on endothelium of vessels in the placenta and placental bed but not by villous or extravillous trophoblasts in normal or pathological samples. These findings do not support a role for PECAM-1 in normal invasion or in the pathophysiology of preeclampsia or FGR.

Determinants of mammographic densities among women of Asian, Native Hawaiian, and Caucasian ancestry.

This cross-sectional study explored the relation between mammographic densities (a predictor of breast cancer risk), ethnicity, and dietary factors among women in Hawaii. Thirty-nine postmenopausal women with Japanese, Chinese, Caucasian, and Native Hawaiian ancestry who had received a screening mammogram completed a medical, reproductive, and dietary history. Using a computerized method, we determined the total and the dense area of the breast and calculated the ratio between the two. Blood lipids were measured using standard methods. For statistical analysis, we applied analysis of variance and multiple linear regression. Whereas the mean dense area of the breast was one third smaller in Asian than in Caucasian and Native Hawaiian women, the percent of the breast occupied by dense tissue in the Asian women was slightly higher than in the Caucasian/Hawaiian group, possibly a result of the Asian women's smaller breast size. The exploratory analysis indicated inverse relations of body mass index, high-density lipoprotein cholesterol (HDLC), age at menarche, and soy intake with mammographic densities, as well as direct relations of estrogen use and family history with mammographic densities. The results of this study suggest that variations in these factors may be responsible for ethnic differences in mammographic densities and in breast cancer risk.

Clinical evaluation of a new non-isotopic leptin immunoassay.

OBJECTIVE: Evaluate the new Active human leptin ELISA available through Diagnostic Systems Laboratories Inc for use in clinical research laboratories. DESIGN: Fasting plasma samples for this study were obtained randomly from human subjects. Precision, linearity, recovery, and interference studies were performed, in addition to method comparison with the conventional leptin RIA method and comparison between laboratories. SETTING: University of Hawaii at Manoa, Division of Medical Technology and the Native Hawaiian Health Research-RCMI laboratory. PARTICIPANTS: Native Hawaiians were selected for this study since this population has consistently demonstrated a higher incidence rate of obesity and Type 2 diabetes and thus, potentially have high leptin levels. RESULTS: At leptin concentrations of 2.3, 16.6, and 45.6 ng/ mL, within-run imprecision (n = 5) ranged from 3.1%, 1.6%, and 4.2%, and the between-run imprecision (n = 10) ranged from 6.8%, 4.1%, and 2.7%. The comparison-of-method gave a linear regression equation of y = 0.92x + 1.6 mg/dL (r = 0.96, n = 74, S(y/x) 2.0) when compared to the Linco human leptin RIA method. The dilution curve showed acceptable linearity within the reportable range of the assay, and the recovery was 88.5% to 112%. No interference was detected with hemoglobin up to 1 g/dL, and with triglyceride, up to 1.8 g/dL. However, bilirubin, 10 mg/dL, did show significant interference. CONCLUSION: Overall, we feel that the new Active Human Leptin assay offers a safe and rapid alternative method appropriate for clinical research laboratories and epidemiological studies.

Alcohol and other risk factors for drowning among male active duty U.S. army soldiers.

BACKGROUND: Risk factors for drowning are largely undocumented among military populations. HYPOTHESIS: Accident report narratives will provide important information about the role of alcohol use and other behaviors in drownings among active duty male U.S. Army soldiers. METHODS: Using a case series design, we describe drowning deaths reported to the U.S. Army Safety Center (1980-1997), documenting associated demographic factors, alcohol use, and other risk-taking behaviors. RESULTS: Drowning victims (n = 352) were disproportionately young, black, and single, with less time-in-service, and no college experience. Most drownings occurred off-duty (89%). Alcohol use was involved in at least 31% of the cases overall. Alcohol use was also associated with a 10-fold increase in reckless behavior (OR 9.6, 95% Cl 4.5-20.7) and was most common among drownings in Europe (OR = 4.3, 95% Cl 1.5-13.4). Most drownings occurred where no lifeguard was present (68%), but almost two-thirds occurred in the presence of others, with CPR initiated in less than one-third of these cases. Drownings involving minority victims were less likely to involve alcohol, but more likely to occur in unauthorized swimming areas. While most drownings did not involve violations of safety rules, over one-third of the cases involved some form of reckless behavior, particularly for those under age 21. CONCLUSIONS: Intervention programs should be tailored to meet the needs of the demographic subgroups at highest risk since behavioral risk factors vary by race and age. CPR training and skills maintenance can improve survival rates. Narrative data are important for developing hypotheses and understanding risk factors for injuries.

Modulation of hepatic lipoprotein synthesis and secretion by taxifolin, a plant flavonoid.

In the present study, the effects of taxifolin, a plant flavonoid, on lipid, apolipoprotein B (apoB), and apolipoprotein A-I (apoA-I) synthesis and secretion were determined in HepG2 cells. Pretreatment of cells with (+/-)-taxifolin led to an inhibition of cholesterol synthesis in a dose- and time-dependent manner, with an 86 +/- 3% inhibition at 200 microM observed within 24 h. As to the mechanism underlying this inhibitory effect, taxifolin was shown to inhibit the activity of HMG-CoA reductase by 47 +/- 7%. In addition, cellular cholesterol esterification, and triacylglycerol and phospholipid syntheses, were also significantly suppressed in the presence of taxifolin. ApoA-I and apoB synthesis and secretion were then studied by pulse-chase experiments. ApoA-I secretion was found to increase by 36 +/- 10%. In contrast, an average reduction of 61 +/- 8% in labeled apoB in the medium was apparent with taxifolin. This effect on secretion appeared not to be exerted at the transcriptional level. Rather, the effect on apoB secretion was found to be exerted in the early stages of apoB degradation and to be sensitive to dithiothreitol (DTT) and insensitive to N-acetyl-leucyl-leucyl-norleucinal, suggesting a proteolytic pathway involving a DTT-sensitive protease. Fractionation of secreted apoB revealed a slight shift in the distribution of secreted apoB-containing lipoproteins. Cholesteryl ester, rather than triacylglycerol, was shown to be the lipid that primarily regulated apoB secretion. In summary, our data suggest that taxifolin decreases hepatic lipid synthesis with a concomitant decrease and increase in apoB and apoA-I secretion, respectively.

Tocotrienol: a review of its therapeutic potential.

OBJECTIVES: To summarize new knowledge surrounding the physiological activity of tocotrienol, a natural analogue of tocopherol. RESULTS: The biological activity of vitamin E has generally been associated with its well-defined antioxidant property, specifically against lipid peroxidation in biological membranes. In the vitamin E group, alpha-tocopherol is considered to be the most active form. However, recent research has suggested tocotrienol to be a better antioxidant. Moreover, tocotrienol has been shown to possess novel hypocholesterolemic effects together with an ability to reduce the atherogenic apolipoprotein B and lipoprotein(a) plasma levels. In addition, tocotrienol has been suggested to have an anti-thrombotic and anti-tumor effect indicating that tocotrienol may serve as an effective agent in the prevention and/or treatment of cardiovascular disease and cancer. CONCLUSION: The physiological activities of tocotrienol suggest it to be superior than alpha-tocopherol in many situations. Hence, the role of tocotrienol in the prevention of cardiovascular disease and cancer may have significant clinical implications. Additional studies on its mechanism of action, as well as, long-term intervention studies, are needed to clarify its function. From the pharmacological point-of-view, the current formulation of vitamin E supplements, which is comprised mainly of alpha-tocopherol, may be questionable.

The prognostic impact of BCL2 protein expression in acute myelogenous leukemia varies with cytogenetics.

BCL2 protein exerts an antiapoptotic effect on cells and decreases chemosensitivity. To determine whether BCL2 expression is prognostic of patient outcome in acute myelogenous leukemia (AML), we measured its level in 198 newly diagnosed, untreated AML patients by Western blotting using whole-cell lysates from low-density peripheral blood cells. BCL2 expression was not associated with the percentage of blasts (R2 = 0.10), French-American-British classification type, or cytogenetic abnormality. Smoothed martingale residual plots indicated that high BCL2 protein level was an adverse prognostic factor for patients with either favorable or intermediate prognosis cytogenetics [FIPC; inv(16), t(8:21), t(15:17), or diploid or insufficient metaphases] but was a favorable prognostic factor for patients with unfavorable prognosis cytogenetics (UC; -5, -7, +8, 11q23, Ph1, or miscellaneous changes). Patients with FIPC and high BCL2 (highest quartile) had a significantly shorter median survival (78 weeks versus not reached; P = 0.009) than did those with lower (lower three quartiles) levels of BCL2. Among those with UC, as BCL2 level decreased from the fourth quartile to the third or the combined first and second quartiles, the median survival decreased (from 94 to 45 or 17 weeks, respectively; P = 0.003). Lower expression of BCL2 in UC was associated with shorter remission duration (P = 0.05). In multivariate analyses performed using either overall or event-free survival as the end point, for either all patients or within either cytogenetic subgroup, BCL2 level was an independent prognostic factor. Similar analysis revealed that BCL2 level was an independent predictor of remission duration for UC patients as well. These data suggest that BCL2 is involved differently in different types (favorable versus unfavorable) of AML and that therapeutic strategies aimed at modulating BCL2 function may be more likely to work in patients with favorable cytogenetic abnormalities.

Detection of t(12;21) in childhood acute lymphoblastic leukemia by fluorescence in situ hybridization.

Metaphase preparations from 36 patients with acute lymphoblastic leukemia (ALL) have been retrospectively screened by fluorescence in situ hybridization (FISH) to determine the incidence of translocation (12;21) and the potential usefulness of FISH as an adjunct to conventional cytogenetic analysis. With the use of specific chromosome paints, 4 of 31 patients with B-lineage childhood ALL (13%) demonstrated rearrangements of chromosomes 12 and 21, and therefore, were considered to harbor the translocation, which had not previously been detected by conventional karyotyping. However, none of these positive cases revealed the standard reciprocal t(12;21)(p12;q22) as the sole abnormality involving chromosomes 12 and 21. The study confirms the feasibility and advantages of introducing FISH screening for t(12;21) in pediatric ALL cases and demonstrates the usefulness of FISH screening as a backup to concurrent cytogenetic analysis to resolve variant translocations and aberrant results. The presence of t(12;21) has also been correlated to clinical data to assess the prognostic significance of this translocation on its own or in association with other prognostic features.

Effects of gamma-tocotrienol on ApoB synthesis, degradation, and secretion in HepG2 cells.

gamma-Tocotrienol (gamma-T3), a naturally occurring analog of tocopherol (vitamin E), has been shown to have a hypocholesterolemic effect in animals and humans. Unlike tocopherol, it has also been shown to reduce plasma apoB levels in hypercholesterolemic subjects. The aim of this study was to define the mechanism of action of gamma-T3 on hepatic modulation of apoB production using cultured HepG2 cells as the model system. HepG2 cells preincubated with gamma-T3 were initially shown to inhibit the rate of incorporation of [14C]acetate into cholesterol in a concentration- and time-dependent manner, with a maximum 86+/-3% inhibition at 50 micromol/L observed within 6 hours. gamma-T3, on the other hand, had no significant effect on the uptake of [14C]glycerol into pools of cellular triacylglycerol and phospholipid relative to untreated control. The rate of apoB synthesis and secretion was then studied by an [35S]methionine pulse-labeling experiment and quantified by immunoprecipitating apoB on chasing up to 3 hours. An average reduction of 24+/-3% in labeled apoB in the media was apparent with gamma-T3 despite a 60+/-2% increase in apoB synthesis. Fractionation of secreted apoB revealed a relatively denser lipoprotein particle, suggesting a less stable particle. Using a digitonin-permeabilized HepG2 cell system, the effects of gamma-T3 on apoB translocation and degradation in the endoplasmic reticulum were further investigated. The generation of a specific N-terminal 70-kDa proteolytic fragment proved to be a sensitive measure of the rate of apoB translocation and degradation. The abundance of this fragment increased significantly in gamma-T3-treated cells relative to untreated control cells (50+/-21%) after 2 hours of chase. In addition, the presence of gamma-T3 resulted in an average decrease of 64+/-8% in intact apoB. Taken together, the data suggest that gamma-T3 stimulates apoB degradation possibly as the result of decreased apoB translocation into the endoplasmic reticulum lumen. It is speculated that the lack of cholesterol availability reduces the number of secreted apoB-containing lipoprotein particles by limiting translocation of apoB into the endoplasmic reticulum lumen.

Low and maximally phosphorylated levels of the retinoblastoma protein confer poor prognosis in newly diagnosed acute myelogenous leukemia: a prospective study.

A prior retrospective study suggested that the level of retinoblastoma protein (RB) expression was prognostic for survival in acute myelogenous leukemia (AML). Individuals with no/low RB protein expression were considered to have loss of RB function, and those with maximally phosphorylated (maxphos) RB were also felt to have nonfunctional RB. To confirm this, we prospectively investigated whether the level of RB expression was prognostic in AML in a larger cohort of patients. RB level was measured by Western blot and immunohistochemical analysis on peripheral blood samples from 210 newly diagnosed AML patients. Patients were divided into three groups based on the level of RB protein expression (i.e., no or low, elevated, and maxphos) or into two groups on the basis of presumed RB function, altered function (AF-RB, low and maxphos RB), versus normal function (NF-RB, elevated RB). By combined results of Western blot and immunohistochemical analysis, 20%, 65%, and 15% of patients had low, elevated, and maxphos RB, respectively. Most patients with acute promyelocytic leukemia (APL) with a French-American-British classification of M3 were in the low RB group, likely reflecting a lower proliferative rate of promyelocytes. Analysis was performed with and without these APL patients. The median survival was significantly shorter for both patients with low RB expression (48 weeks, P = 0.05, including APL patients; 34 weeks, corrected P = 0.008, with APL patients excluded) and maxphos RB expression (51 weeks, P = 0.007) compared to those with elevated RB expression (122 weeks including and 98 weeks excluding APL patients). Differences were greatest among patients with nonfavorable prognosis cytogenetics (median survival, 34 weeks versus 85 weeks; corrected P = 0.001 for AF-RB versus NF-RB). Remission duration was also significantly shorter for non-APL patients with AF-RB versus NF-RB (median survival, 36 weeks versus not reached; corrected P = 0.02). In multivariate analyses, including cytogenetics, performance status, age, antecedent hematological disorder, and RB status, with and without APL patients included, no/low and maxphos-RB protein expression were independent predictors for poorer survival. This prospective study confirms that the level of expression of RB is a strong prognostic factor in AML, with an inferior survival experience being associated with no/low RB and maxphos RB expression. Therefore, therapeutic decisions based on the level of RB expression may be indicated, and protocols to incorporate this are currently under development.

Effects of tocotrienol on the intracellular translocation and degradation of apolipoprotein B: possible involvement of a proteasome independent pathway.

gamma-Tocotrienol (gamma-T3), a HMG CoA reductase inhibitor, was previously shown to stimulate the intracellular degradation of apolipoprotein B (apoB) in HepG2 cells. The aim of this study was to explore the effects of gamma-T3 on the proteasome dependent co-translational degradation and the proteasome independent post-translational degradation of apoB. Previous studies have shown that apoB translocation across the endoplasmic reticulum (ER) membrane governs the co-translational degradative pathway of apoB. Therefore, we first examined the effects of gamma-T3 on this pathway using a specific translocation assay derived from HepG2 cells. Our results indicated that gamma-T3 reduced the efficiency of apoB translocation across the ER membrane, suggesting that co-translational degradation may be partially involved. Evidence of an ER associated post-translational degradation was also provided upon pre-treating digitonin-permeabilized HepG2 cells with a proteasome inhibitor, lactacystin. When chased for 2h, ER degradation of apoB was observed and was further enhanced in the presence of gamma-T3 versus untreated control, in spite of proteasome inhibition. Combined with the ability of ALLN, a proteasome and cysteine protease inhibitor, to block the post-translational degradation of apoB, the data suggest that gamma-T3 diverted more apoB to a cytosolic proteasomal dependent and possibly an ER-associated proteasomal independent degradation pathways.

Herpetic geometric glossitis in a pediatric patient with acute myelogenous leukemia.

Herpetic geometric glossitis, a recently described form of lingual herpes simplex virus type 1 (HSV-1) infection, has been reported in 6 human immunodeficiency virus (HIV) patients and 1 cardiac transplant patient who was receiving immunosuppressant therapy. An HIV-seronegative immunocompromised pediatric patient with acute myelogenous leukemia who developed herpetic geometric glossitis is described. Herpetic geometric glossitis can present in both adult and pediatric immunocompromised patients. The symptoms, morphology, laboratory findings and treatment of this infection are summarized. The possible consequences of untreated herpetic glossitis include superinfection and undernourishment. Although previously described patients responded to 1000 mg per day (divided in 5 doses) or oral acyclovir, with complete resolution of fissures, this patient developed herpetic geometric glossitis while receiving acyclovir and required higher doses of oral antiviral therapy (acyclovir, 3000 mg/day divided in 5 doses) to treat his HSV-1 lingual infection. Empiric treatment of an immunocompromised patient who has newly acquired painful tongue fissures or furrows with systemic acyclovir should be considered.

Epidermolytic acanthomas: clinical characteristics and immunohistochemical features.

Epidermolytic hyperkeratosis in bullous congenital ichthyosiform erythroderma results from mutations in the K1 and K10 genes. Epidermolytic acanthomas are solitary or multiple lesions with microscopic features that are identical to those in bullous congenital ichthyosiform erythroderma. In this study, the clinical and epidemiologic characteristics of epidermolytic acanthomas were summarized, and the expression of keratins (using antibodies to K1, K6, K10, K14, K16, and K19) in five solitary epidermolytic acanthomas was determined using immunohistochemistry techniques. The intensity of staining for K1 and K10 was (a) less in the altered granular layer, as compared to the adjacent nonaltered granular layer of the lesional skin, and (b) less in the lesional skin as compared to the perilesional, histologically normal-appearing skin. Expression of K6 and K16 was noted not only in the basal layer and suprabasal layers of the lesions, but also in the corresponding layers of the adjacent normal skin. Staining for K14 was also observed in the basal layers and suprabasal layers of the lesional and adjacent normal epidermis; within the lesional and perilesional normal skin, the intensity of positive staining for K14 was greater in the basal layers than in the suprabasal layers of the epidermis. The specimens did not stain for K19. In conclusion, using immunohistochemistry techniques on solitary epidermolytic acanthomas, we were able to demonstrate (1) an abnormality in K1 and K10 expression in the lesional skin as compared to the adjacent, histologically normal-appearing skin and (b) the expression of hyperproliferative keratins not only with the lesional skin, but also in the perilesional normal skin. We hypothesize that the pathogenesis of epidermolytic hyperkeratosis in lesions of solitary epidermolytic acanthomas results from mutations in the K1 and K10 genes.

In vitro translation and translocation of apolipoprotein B in a cell-free system from HepG2 cells.

An mRNA-dependent cell-free system has been developed from HepG2 cells by hydrolysis of endogenous mRNA with micrococcal nuclease. When supplied with RNA extracted from HepG2 cells, the system synthesized liver specific proteins such as albumin and apolipoprotein B100. Significant amounts of microsomes were also detected in the lysate by measuring NADH-cytochrome c reductase activity and ultracentrifugation. Protease protection assays showed the capability of the HepG2 lysate to translocate newly-synthesized proteins such as apolipoprotein Al, albumin, and apoB into the microsomes as they were protected from digestion with exogenously added protease K, but not protected in the presence of protease K and Triton X-100. The system also proved to be very active toward translation of exogenous mRNAs as evidenced by efficient translation of brome mosaic virus RNA. The HepG2 translation-translocation system appears to provide a unique homologous system for studies on the biogenesis of liver specific proteins, particulary apoB100.

Expression of cathepsin B and aryl hydrocarbon hydroxylase activities, and of apolipoprotein B in human hepatoma cells maintained long-term in a serum-free medium.

We have established the human hepatoma cell line, HepG2, in a defined, serum-free medium. These cells were maintained and studied over a 100-generation period (i.e. 10 serial transfers). Cells maintained in serum-free medium exhibited growth parameters (i.e. saturation density, efficiency of plating, and population doubling time) similar to those obtained with HepG2 cells maintained in serum-supplemented medium. Serum-free cells were also similar to their serum-supplemented counterparts with respect to the expression of cathepsin B activity and the induction of aryl hydrocarbon hydroxylase by 2,3,7,8-tetrachlorodibenzo-p-dioxin. Significantly, HepG2 cells maintained in serum-free conditions also retained the ability to synthesize and secrete proteins, including the liver plasma protein, apo-lipoprotein B. These results indicate that the serum-free medium used in this study supports the long-term growth and maintenance of human hepatoma, HepG2, cells in culture. Inasmuch as these cells retain phenotypes, including differentiated markers previously reported for their serum-supplemented counterparts, they may provide a more reliable, standardized culture system to study the expression, secretion, and regulation of proteins during biological and pathologic processes.

Hormonal regulation of human apolipoprotein E gene expression in HepG2 cells.

1. Hormonal regulation of apolipoprotein E (apoE) gene expression by insulin and thyroid hormone was studied in a human hepatoma cell line, HepG2. 2. Changes at the mRNA level, mRNA translation, in vivo synthesis and secretion were monitored. 3. Both insulin and triiodothyronine were found to have no significant effect on apoE mRNA levels. 4. Insulin treatment caused an inhibition of: (a) the in vitro translation of endogenous apoE mRNA in a HepG2 cell-free system (25%), and (b) the incorporation of radioactivity into newly-synthesized apoE in an in vivo pulse-chase labeling experiment (32%). 5. Interestingly, apoE secretion rate was found to be significantly reduced with insulin (84%) suggesting that a major portion of newly-synthesized apoE may be shunted into a degradative pathway. 6. Using a similar experimental approach, triiodothyronine showed no significant effect on the rate of apoE synthesis or translation (6-15% decrease), however a slight reduction (20%) in secretion rate was shown. 7. Overall, apoE gene expression does not appear to be influenced by triiodothyronine significantly but is modulated by insulin at the translational and post-translational level.

Insulin modulation of human apolipoprotein B mRNA translation: studies in an in vitro cell-free system from HepG2 cells.

Insulin modulation of apolipoprotein B gene expression was studied at the translational level by the use of a cell-free translation system from a hepatoma cell-line, HepG2. Extracts of HepG2 cells lysed with lysolecithin were found to have high in vitro protein synthesizing activity utilizing endogenous mRNA. The level of peptide chain initiation was high, as suggested by a significant inhibition of translation by edeine. The translation products of endogenous mRNA in HepG2 cell-free lysate were probed with anti-apolipoprotein B antibodies to investigate its synthesis. A 550 kilodalton (kDa) polypeptide was selected by a polyclonal antibody, as well as a monoclonal antibody, against the C-terminal end of apolipoprotein B molecule. This in vitro synthesized polypeptide was also found to compare well in size with the in vivo product. The HepG2 lysate was also shown to efficiently synthesize in vitro a number of other proteins including albumin, apolipoprotein E, apolipoprotein A1, and actin. The in vitro synthesis of polypeptides as large as 500 kDa was unexpected and has not previously been demonstrated in a cell-free system. The HepG2 translation system was used to investigate the effect of insulin on the in vitro translation of apolipoprotein B. Lysates prepared from HepG2 cells treated with insulin were found to have lower translational activity (by an average of 52.3%) for apolipoprotein B compared with lysates from control untreated cells. In vitro synthesis of actin and apolipoprotein E were unaffected under these conditions. The insulin-stimulated decline in in vitro apolipoprotein B synthesis was not due to a change in apolipoprotein B mRNA levels as determined by slot- and Northern-blot analyses, suggesting that the inhibitory effect of insulin may be exerted partly at the level of apolipoprotein B mRNA translation.