Ketolytic and glycolytic enzymatic expression profiles in malignant gliomas: implication for ketogenic diet therapy

BACKGROUND

Recent studies in animal models, based on the hypothesis that malignant glioma cells are more dependent on glycolysis for energy generation, have shown promising results using ketogenic diet (KD) therapy as an alternative treatment strategy for malignant glioma, effectively starving glioma cells while providing ketone bodies as an energy source for normal neurons and glial cells. In order to test this treatment strategy in humans, we investigated the relative expression of several key enzymes involved in ketolytic and glycolytic metabolism in human anaplastic glioma (WHO grade III) and glioblastoma (GBM, WHO grade IV).

METHODS

Immunohistochemistry was performed on formalin fixed paraffin embedded sections from 22 brain biopsies (17 GBM, 3 anaplastic astrocytoma and 2 anaplastic oligoastrocytoma) using antibodies raised against glycolytic and ketolytic enzymes. The glycolytic enzymes included hexokinase-II (HK2) and pyruvate kinase M2 isoform (PKM2). The ketone body metabolic enzymes included: succinyl CoA: 3-oxoacid CoA transferase (OXCT1), 3-hydroxybutyrate dehydrogenase 1 and 2 (BDH1 and BDH2), and acetyl-CoA acetyltransferase 1 (ACAT1). The immunoreactivities were graded using a semi-quantitative scale based on the percentage of positive cells: POS (>20%), LOW (5-20%), and very low (VLOW) (<5%). Focal non-neoplastic "normal" brain tissue within the biopsy specimens served as internal controls.

RESULTS

The rate limiting mitochondrial ketolytic enzymes (OXCT1 and BDH1) were either LOW or VLOW, concordantly in 14 of the 17 GBMs and in 1 of 5 anaplastic gliomas, whereas at least one of the glycolytic enzymes was POS in 13 of these 17 GBMs and all 5 anaplastic gliomas. Cytosolic BDH2 and mitochondrial ACTAT1 were, surprisingly, POS in most of these tumors.

CONCLUSION

Our results showing that malignant gliomas have differential expression of ketolytic and glycolytic enzymes are consistent with previous studies that have shown that these are genetically heterogeneous tumors. It seems reasonable to hypothesize that patients with low or very low expression of key ketolytic enzymes in their malignant gliomas may respond better to the KD therapy than those patients with positive expression of these enzymes. Further studies in animal models and/or a large-scale clinical trial would be needed to test this hypothesis.

Treatment of advanced glioma with an energy restricted ketogenic diet: Case report and literature summary

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Background: We initiated a pilot study to evaluate an energy restricted ketogenic diet (ERKD) as treatment for patients with glioblastoma multiforme (GBM) whose brain tumor had progressed with standard therapy. Methods: This reports documents our experience using an ERKD with an IRB approved, clinical trials #NCTO1535911 registered treatment protocol and briefly summarizes the 5 published case reports that document favorable responses with ERKD. Results: Our patient, a 55-year-old white male, presented with a left sided visual field cut, decreased analytical mental skills, a slow methodical wide based gait and a right posterior brain mass with a histological diagnosis of GBM. After documented progression following surgery, radiation therapy and TMZ the patient was treated with ERKD. He was hospitalized to induce a decrease in glucose and an increase in ketones using Ketocal 20-25 Cal/Kg. Adherence and efficacy to the diet was monitored using AM and PM measurements of blood glucose and ketones. Initial treatment with Ketocal decreased his blood glucose so that his PM glucose was <80mg/dl and increased his PM ketones to >3mm(our protocol’s target concentrations). However, his AM glucose was still >80mg/dl and his AM ketones decreased to >2mM. Because of the low palatability of the Ketocal, the patient was switched to a ketogenic regular food diet with a 3:1 ratio of fat to proteins and carbohydrates. Out of the hospital and on this diet his PM ketones remained > 3mM and his AM > 2mM, but his AM and PM blood glucose increased to > 80mg/dl. After 4 weeks of treatment with the ERKD, the patient’s disease advanced; his vision, mobility and cognition decreased and MRI demonstrated tumor growth and he withdrew from the study. Five patients with advanced brain tumors and favorable responses to ERKD have been reported. The best response was a C.R. 5 years after diagnosis. In 4 of the 5 patients ERKD was combined with one of the standard modalities of treatment. At last report 3 of the 5 patients were C.R. and 2 had documented disease progression after stopping the ERKD. Conclusions: Investigation of ERKD in patients with malignant brain tumors using an approved, registered protocol under the guidance of a dietician is feasible.

Metabolic profiles of ketolysis and glycolysis in malignant gliomas: Possible predictors of response to ketogenic diet therapy

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Background: The enzymatic differences in energy metabolism between normal brain tissues and malignant gliomas formed the basis for animal model studies that showed increased survival in mice with orthotopically transplanted glioblastoma multiforme (GBM) treated with energy restricted ketogenic diet (ERKD). To test the hypothesis that human brain tumors may also be sensitive to ERKD, we used immunohistochemistry reactions on formalin fixed paraffin embedded tumor samples to evaluate for the presence of enzymes important for the metabolism of ketones and glucose. Methods: Immunoreactivities were graded using a semi-quantitative scale based on the percentage of positive cells: low positive<5% (LOW); intermediate (INT) 5-20%; and highly positive (HIGH) >20%. Focal non-neoplastic “normal” brain tissue present within the specimens served as positive internal controls. Results: Succinyl CoA: 3-oxoacid CoA transferase (OXCT1) and 3-hydroxybutyrate dehydrogenase 1 (BDH1) are mitochondrial enzymes important for metabolizing beta hydroxy butyrate, the main ketone in blood. Both of these enzymes were either decreased or absent (INT or LOW) concordantly in 14 of the 17 (82%) GBMs, and in 1 of 6 (17%) anaplastic astrocytomas (AA). Two of the enzymes in the glycolytic pathway hexokinase-2 and pyruvate kinase M2 were concordantly LOW or INT in only 3 of the 17 GBMs that also were LOW or INT for both OXCT1 and BDH1. The remaining brain tumors were positive for at least one of these glycolytic enzymes. Mitochondrial enzymes were not globally deficient. The mitochondrial enzyme acetyl CoA transferase (ACAT1) was present in 9 of the 14 GBM specimens that were LOW or INT for the mitochondrial enzymes OXCT1 and BDH1. Conclusions: Our data showing that many, but not all, malignant gliomas lack ketolytic enzymes, support the rationale of ERKD as investigational treatment for patients with malignant gliomas. Moreover, we hypothesize that it is important to test individual tumor samples for the expression of these enzymes prior to ERKD, as patients with malignant gliomas that have diminished capacity to metabolize ketones likely may derive the most benefit from ERKD.

Impaired expression of ketone metabolizing enzymes in malignant gliomas: Implication for ketogenic diet therapy

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Background: Malignant glial cells may have altered expression of mitochondrial enzymes that are key for deriving energy from ketones. The novel strategy of treating malignant gliomas with a ketogenic diet has been tested in animal models with promising results. To evaluate the applicability of these findings to human patients we tested the hypothesis that high grade human gliomas may lack or have decreased expression of mitochondrial enzymes that are important for metabolizing ketones. Methods: We evaluated the expression of 2 key mitochondrial enzymes involved in ketone metabolism in 22 patients (17 males and 5 females, mean age 55,range 30-85) with either glioblastoma (GBM, WHO grade IV) or anaplastic glioma (WHO grade III) (Table). Immunohistochemistry reactions were performed on formalin-fixed paraffin-embedded sections from brain biopsies, using antibodies raised against succinyl CoA: 3-oxoacid CoA transferase (OXCT1) and 3-hydroxybutyrate dehydrogenase 1 (BDH1). Immunoreactivities were graded using a semi-quantitative scale based on the percentage of positive cells: negative (NEG) ≤ 5%; intermediate (INT) 5-20%; and positive (POS) more than 20%. Focal non-neoplastic “normal” brain tissue present within the specimens expressed both enzymes and served as an internal positive control. Results: Either absent or marked decreased expression of OXCT1 and BDH1 were observed in most GBM and anaplastic glioma. Concordance for absent or marked decrease expression of both OXCT1 and BDH1 was observed in 14 of the 17 (82%) GBM’s, and 1 of 5 (20%) anaplastic gliomas. Conclusions: These data support the rationale for a pilot clinical study investigating the therapeutic utility of a ketogenic diet in selected glioma patients. Malignant gliomas with diminished expression of key enzymes (e.g., OXCT1, BDH1) may benefit from the ketogenic diet therapy, whereas those with positive expression of these enzymes likely will not. [Table: see text]

Regulation of glucose- and mitochondrial fuel-induced insulin secretion by a cytosolic protein histidine phosphatase in pancreatic beta-cells

We report localization of a cytosolic protein histidine phosphatase (PHP; approximately 16 kDa) in INS 832/13 cells, normal rat islets, and human islets. siRNA-mediated knockdown of PHP markedly reduced glucose- or mitochondrial fuel-induced but not KCl-induced insulin secretion. siRNA-mediated knockdown of PHP also attenuated mastoparan-induced insulin secretion, suggesting its participation in G protein-sensitive signaling steps, leading to insulin secretion. Functional assays revealed that the beta-cell PHP catalyzes the dephosphorylation of ATP-citrate lyase (ACL). Silencing of PHP expression markedly reduced ACL activity, suggesting functional regulation of ACL by PHP in beta-cells. Coimmunoprecipitation studies revealed modest effects of glucose on the interaction between PHP and ACL. Confocal microscopic evidence indicated that glucose promotes association between ACL and nm23-H1, a known kinase histidine kinase, but not between PHP and ACL. Furthermore, metabolic viability of INS 832/13 cells was resistant to siRNA-PHP, suggesting no regulatory roles of PHP in cell viability. Finally, long-term exposure (24 h) of INS 832/13 cells or rat islets to high glucose (30 mM) increased the expression of PHP. Such increases in PHP expression were also seen in islets derived from the Zucker diabetic fatty rat compared with islets from the lean control animals. Together, these data implicate regulatory roles for PHP in a G protein-sensitive step involved in nutrient-induced insulin secretion. In light of the current debate on putative regulatory roles of ACL in insulin secretion, additional studies are needed to precisely identify the phosphoprotein substrate(s) for PHP in the cascade of events leading to nutrient-induced insulin secretion.

Regulatory roles for Tiam1, a guanine nucleotide exchange factor for Rac1, in glucose-stimulated insulin secretion in pancreatic beta-cells

Using various biochemical, pharmacological and molecular biological approaches, we have recently reported regulatory roles for Rac1, a small G-protein, in glucose-stimulated insulin secretion (GSIS). However, little is understood with respect to localization of, and regulation by, specific regulatory factors of Rac1 in GSIS. Herein, we investigated regulatory roles for Tiam1, a specific nucleotide exchange factor (GEF) for Rac1, in GSIS in pancreatic beta-cells. Western blot analysis indicated that Tiam1 is predominantly cytosolic in distribution. NSC23766, a specific inhibitor of Tiam1-mediated activation of Rac1, markedly attenuated glucose-induced, but not KCl-induced insulin secretion in INS 832/13 cells and normal rat islets. Further, NSC23766 significantly reduced glucose-induced activation (i.e. GTP-bound form) and membrane association of Rac1 in INS 832/13 cells and rat islets. Moreover, siRNA-mediated knock-down of Tiam1 markedly inhibited glucose-induced membrane trafficking and activation of Rac1 in INS 832/13 cells. Interestingly, however, in contrast to the inhibitory effects of NSC23766, Tiam1 gene depletion potentiated GSIS in these cells; such a potentiation of GSIS was sensitive to extracellular calcium. Together, our studies present the first evidence for a regulatory role for Tiam1/Rac1-sensitive signaling step in GSIS. They also provide evidence for the existence of a potential Rac1/Tiam1-independent, but calcium-sensitive component for GSIS in these cells.

Cigarette smoke components inhibited intercellular communication and differentiation in human pancreatic ductal epithelial cells

Smoking is a well-documented risk factor for the development of pancreatic adenocarcinoma. Although the most abundant polycyclic aromatic hydrocarbons (PAHs) in cigarette smoke are methylated anthracenes and phenanthrenes, the epigenetic toxicity of these compounds has not been extensively studied. We previously showed that methylanthracenes, which possess a bay-like structure, affect epigenetic events such as an induced release of arachidonic acid, inhibition of gap junctional intercellular communication (GJIC) and induction of mitogen-activated protein kinases in a pluripotent rat liver epithelial stem cell line. Anthracenes with no bay-like structures were inactive. These biological effects are all molecular events associated with the promotional phase of cancer. A human immortalized, nontumorigenic pancreatic ductal epithelial cell line, H6c7, was examined to study the epigenetic toxicity of PAHs related to pancreatic cancer by using scrape-loading dye transfer, immunostaining, RT-PCR and telomerase assay methods. H6c7 cells were GJIC-incompetent and exhibited high telomerase activity when grown in growth factor and hormone-supplemented medium. In the presence of the cAMP elevating drugs (forskolin and IBMX) the cells became GJIC competent and expressed connexins. Telomerase activity was also decreased by cAMP elevating drug treatment. After induction of cAMP, 1-methylanthracene with bay-like structures inhibited GJIC, whereas the 2-methylanthracene lacking a bay-like structure had no effect on GJIC. Telomerase activity remained high in 1-methylanthracene treatment but not with 2-methylanthracene. These results indicate that a prominent component of cigarette smoke, namely methylanthracenes with distinct structural configurations, could be a potential etiological agent contributing to the epigenetic events of pancreatic cancer.

Recruiting older women to research studies: the san diego cooperative mammography project

BACKGROUND

Despite the growing number of older people in the population, this age group continues to be under represented in clinical trials. As a result, physicians must base treatment decisions for older patients on data from studies involving primarily younger, and presumably healthier, adults. Little experience is available to guide the development of study methodologies that will enhance the recruitment of older patients to clinical studies.

METHODS

This pilot study compared two methods of recruiting women 75 years and older to a clinical research study related to their most recent screening mammogram. The effectiveness of a single, "in-person" invitation to participate made during the screening mammogram appointment was compared with the effectiveness of a single invitation to participate sent "by-mail" following a screening mammogram.

RESULTS

Both methods succeeded in recruiting a sizable sample (N=2,394). The "in-person" invitation to participate was more labor-intense and less likely to be inclusive of all eligible women, but secured a significantly greater proportion of the women to participate. However, once recruited, women in the "by-mail" method were significantly more likely to comply with the optional elements of the study and to express a willingness to continue with follow-up studies than those recruited by the "in-person" method.

CONCLUSIONS

Lack of participation of older women in clinical research may be more a reflection of not being asked, rather than their lack of willingness to participate, thus reinforcing the key role health care providers can play in recruiting older women to clinical studies.

Glucose and insulin regulate glycosylphosphatidylinositol-specific phospholipase D expression in islet beta cells

Insulin resistance is associated with a compensatory islet hyperactivity to sustain adequate insulin biosynthesis and secretion to maintain near euglycemia. Both glucose and insulin are involved in regulating proteins required for insulin synthesis and secretion within the islet and islet hypertrophy. We have determined that glycosylphosphatidylinositol-specific phospholipase D (GPI-PLD) is present within the secretory granules of islet beta cells. To determine if GPI-PLD is regulated in islet beta cells, we examined the effect of glucose and insulin on GPI-PLD expression in rat islets and murine insulinoma cell lines. Glucose (16.7 mmol/L) increased cellular GPI-PLD activity and mRNA levels 2- to 7-fold in isolated rat islets and betaTC3 and betaTC6-F7 cells. Insulin (10(-7) mol/L) also increased GPI-PLD mRNA levels in rat islets and betaTC6-F7 cells 2- to 4-fold commensurate with an increase in GPI-PLD biosynthesis. To determine if islet GPI-PLD expression is increased in vivo under conditions of islet hyperactivity, we compared GPI-PLD mRNA levels in islets and liver from ob/ob mice and their lean littermates. Islet GPI-PLD mRNA was increased 5-fold while liver mRNA and serum GPI-PLD levels were reduced 30% in ob/ob mice compared with lean littermate controls. These results suggest that glucose and insulin regulate GPI-PLD mRNA levels in isolated islets and beta-cell lines. These regulators may also account for the increased expression of GPI-PLD mRNA in islets from ob/ob mice, a model of insulin resistance and islet hyperactivity.

Cell-type specificity of short-range transcriptional repressors

Transcriptional repressors can be classified as short- or long-range, according to their range of activity. Functional analysis of identified short-range repressors has been carried out largely in transgenic Drosophila, but it is not known whether general properties of short-range repressors are evident in other types of assays. To study short-range transcriptional repressors in cultured cells, we created chimeric tetracycline repressors based on Drosophila transcriptional repressors Giant, Drosophila C-terminal-binding protein (dCtBP), and Knirps. We find that Giant and dCtBP are efficient repressors in Drosophila and mammalian cells, whereas Knirps is active only in insect cells. The restricted activity of Knirps, in contrast to that of Giant, suggests that not all short-range repressors possess identical activities, consistent with recent findings showing that short-range repressors act through multiple pathways. The mammalian repressor Kid is more effective than either Giant or dCtBP in mammalian cells but is inactive in Drosophila cells. These results indicate that species-specific factors are important for the function of the Knirps and Kid repressors. Giant and dCtBP repress reporter genes in a variety of contexts, including genes that were introduced by transient transfection, carried on episomal elements, or stably integrated. This broad activity indicates that the context of the target gene is not critical for the ability of short-range repressors to block transcription, in contrast to other repressors that act only on stably integrated genes.

Increased expression of GPI-specific phospholipase D in mouse models of type 1 diabetes

Glycosylphosphatidylinositol-specific phospholipase D (GPI-PLD) is a high-density lipoprotein-associated protein. However, the tissue source(s) for circulating GPI-PLD and whether serum levels are regulated are unknown. Because the diabetic state alters lipoprotein metabolism, and liver and pancreatic islets are possible sources of GPI-PLD, we hypothesized that GPI-PLD levels would be altered in diabetes. GPI-PLD serum activity and liver mRNA were examined in two mouse models of type 1 diabetes, a nonobese diabetic (NOD) mouse model and low-dose streptozotocin-induced diabetes in CD-1 mice. With the onset of hyperglycemia (2- to 5-fold increase over nondiabetic levels), GPI-PLD serum activity and liver mRNA increased 2- to 4-fold in both models. Conversely, islet expression of GPI-PLD was absent as determined by immunofluorescence. Insulin may regulate GPI-PLD expression, because insulin treatment of diabetic NOD mice corrected the hyperglycemia along with reducing serum GPI-PLD activity and liver mRNA. Our data demonstrate that serum GPI-PLD levels are altered in the diabetic state and are consistent with liver as a contributor to circulating GPI-PLD.

Polyhydroxybenzoates inhibit ascorbic acid activation of mitochondrial glycerol-3-phosphate dehydrogenase: implications for glucose metabolism and insulin secretion

Glycerol-3-phosphate dehydrogenase from pig brain mitochondria was stimulated 2.2-fold by the addition of 50 microm l-ascorbic acid. Enzyme activity, dependent upon the presence of l-ascorbic acid, was inhibited by lauryl gallate, propyl gallate, protocatechuic acid ethyl ester, and salicylhydroxamic acid. Homogeneous pig brain mitochondrial glycerol-3-phosphate dehydrogenase was activated by either 150 microm L-ascorbic acid (56%) or 300 microm iron (Fe(2+) or Fe(3+) (62%)) and 2.6-fold by the addition of both L-ascorbic acid and iron. The addition of L-ascorbic acid and iron resulted in a significant increase of k(cat) from 21.1 to 64.1 s(-1), without significantly increasing the K(m) of L-glycerol-3-phosphate (10.0-14.5 mm). The activation of pure glycerol-3-phosphate dehydrogenase by either L-ascorbic acid or iron or its combination could be totally inhibited by 200 microm propyl gallate. The metabolism of [5-(3)H]glucose and the glucose-stimulated insulin secretion from rat insulinoma cells, INS-1, were effectively inhibited by 500 microm or 1 mm propyl gallate and to a lesser extent by 5 mm aminooxyacetate, a potent malate-aspartate shuttle inhibitor. The combined data support the conclusion that l-ascorbic acid is a physiological activator of mitochondrial glycerol-3-phosphate dehydrogenase, that the enzyme is potently inhibited by agents that specifically inhibit certain classes of di-iron metalloenzymes, and that the enzyme is chiefly responsible for the proximal signal events in INS-1 cell glucose-stimulated insulin release.

An indirect role for upstream stimulatory factor in glucose-mediated induction of pyruvate kinase and S14 gene expression

Transcription of the L-type pyruvate kinase (L-PK) and S14 genes is induced in hepatocytes in response to increased glucose metabolism. The regulatory sequences of these genes responsible for induction by glucose have been mapped to related E-box containing motifs in the promoters. Similarly, L-PK promoter activity is stimulated in a differentiated pancreatic beta-cell line, INS-1, in response to elevated glucose. By mutational analysis, we demonstrate that the sequence requirements for glucose induction in the INS-1 cell are identical to those observed in the hepatocyte, suggesting that the same transcriptional factor(s) is responsible for regulation of L-PK expression in the two cell types. One nuclear factor that binds to the glucose regulatory sequences of both of these genes is the Upstream Stimulatory Factor (USF), a ubiquitous E-box binding protein. Mice deleted for the USF2 gene display a severely delayed response to carbohydrate feeding (Vallet et al. [26]). This observation, however, does not differentiate between a direct and an indirect role for USF in the process. To gain further insight into the possible involvement of USF in glucose signaling, we have used a recombinant adenoviral construct that expresses a dominant negative form of USF. This dominant negative can dimerize with endogenous USF and is shown to inhibit DNA binding of USF in hepatocytes and INS-1 cells. However, expression of the dominant negative USF did not block the ability of glucose to stimulate L-PK or S14 gene expression in hepatocytes or L-PK promoter activity in INS-1 cells. We conclude that USF does not act by binding to the glucose regulatory sequences of the S14 or L-PK genes and the role of USF in the process of glucose induction is indirect.

Natural electrophoresis of norepinephrine and ascorbic acid

The electric field produced by cell membranes, extending only a few nanometers, is 1000 times stronger than the electric fields required to produce dissociation of molecular complexes. Using the complex formed by norepinephrine (NE) and ascorbic acid (AA), we have demonstrated the quantitative binding of AA to NE, the use of capillary electrophoresis to measure quantitative binding of nonelectrolyte complexes, the determination of a dissociation constant (Kd) from electric field-dissociation constants (Ke), and a model for natural dissociation of the NE-AA complex due to the electric field generated by a cell membrane. NE-AA dissociation constants show little effect of NE concentration or pH changes. NE-related compounds also bind AA: epinephrine > norepinephrine > tyrosine > histamine > phenylalanine. Serotonin does not bind AA. Phosphorylated AA and glucose also bind NE at 0.05 and 0.08 of the AA binding, respectively. Natural electrophoresis of molecular complexes allows compounds to travel through the body in a protected state and still be available for physiological activity upon reaching a membrane.

Upstream stimulatory factor regulates Pdx-1 gene expression in differentiated pancreatic beta-cells

The homeobox gene Pdx-1 plays a key role in the development of the pancreas. In the adult, however, expression of the Pdx-1 gene is restricted to pancreatic beta-cells and endocrine cells of duodenal epithelium. Recently, the transcription factor, upstream stimulatory factor (USF), has been shown to bind in vitro to a mutationally sensitive E-box motif within the 5'-flanking region of the Pdx-1 gene [Sharma, Leonard, Lee, Chapman, Leiter and Montminy (1996) J. Biol. Chem. 271, 2294-2299]. In the present study, we show that USF not only binds to the Pdx-1 gene promoter but also functionally regulates the expression of the Pdx-1 gene in differentiated pancreatic beta-cells. Adenovirus-mediated overexpression of a dominant negative form of USF2 decreased binding of endogenous USF to the E-box element by approximately 90%. This reduction in endogenous USF binding led to a greater than 50% decrease in Pdx-1 gene promoter activity, which, in turn, resulted in marked reductions in Pdx-1 mRNA and protein levels. Importantly, the lower Pdx-1 protein levels led to a greater than 50% reduction in Pdx-1 binding activity to the A3 element on the insulin gene promoter, and a significant reduction in insulin mRNA levels. Overall, our results show that USF functionally regulates Pdx-1 gene expression in differentiated pancreatic beta-cells and provide the first functional data for a role of USF in the regulation of a normal cellular gene.

Effects of estrogen and estrogen-progestin on mammographic parenchymal density. Postmenopausal Estrogen/Progestin Interventions (PEPI) Investigators

BACKGROUND

In longitudinal studies, greater mammographic density is associated with an increased risk for breast cancer.

OBJECTIVE

To assess differences between placebo, estrogen, and three estrogen-progestin regimens on change in mammographic density.

DESIGN

Subset analysis of a 3-year, multicenter, double-blind, randomized, placebo-controlled trial.

SETTING

Seven ambulatory study centers.

PARTICIPANTS

307 of the 875 women in the Postmenopausal Estrogen/Progestin Interventions Trial. Participants had a baseline mammogram and at least one follow-up mammogram available, adhered to treatment, had not taken estrogen for at least 5 years before baseline, and did not have breast implants.

INTERVENTION

Treatments were placebo, conjugated equine estrogens (CEE), CEE plus cyclic medroxyprogesterone acetate (MPA), CEE plus daily MPA, and CEE plus cyclic micronized progesterone (MP).

MEASUREMENTS

Change in radiographic density (according to American College of Radiology Breast Imaging Reporting and Data System grades) on mammography.

RESULTS

Almost all increases in mammographic density occurred within the first year. At 12 months, the percentage of women with density grade increases was 0% (95% CI, 0.0% to 4.6%) in the placebo group, 3.5% (CI, 1.0% to 12.0%) in the CEE group, 23.5% (CI, 11.9% to 35.1%) in the CEE plus cyclic MPA group, 19.4% (CI, 9.9% to 28.9%) in the CEE plus daily MPA group, and 16.4% (CI, 6.6% to 26.2%) in the CEE plus cyclic MP group. At 12 months, the odds of an increase in mammographic density were 13.1 (95% CI, 2.4 to 73.3) with CEE plus cyclic MPA, 9.0 (CI, 1.6 to 50.1) with CEE plus daily MPA, and 7.2 (CI, 1.3 to 40.0) with CEE plus cyclic micronized progesterone compared with CEE alone.

CONCLUSIONS

Further study of the magnitude and meaning of increased mammographic density due to use of estrogen and estrogen-progestins is warranted because mammographic density may be a marker for risk for breast cancer.

Mouse glycosylphosphatidylinositol-specific phospholipase D (Gpld1) characterization

Glycosylphosphatidylinositol-specific phospholipase D (GPI-PLD) is an 110-kDa monomeric protein found in the circulation that is capable of degrading the GPI anchor utilized by dozens of cell-surface proteins in the presence of detergent. This protein is relatively abundant (5-10 microgram/ml in human serum), yet its sites of synthesis, gene structure, and overall function are unclear. It is our purpose to use the mouse system to determine its putative roles in lipid transport, pathogen control, and diabetes. We have isolated murine full-length cDNA for GPI-PLD from a pancreatic alpha cell library. The deduced amino acid sequence shows 74% homology to bovine and human GPI-PLD. There is a single structural gene (Gpld1) mapping to mouse Chromosome (Chr) 13, and among nine tissues, liver showed the greatest abundance of GPI-PLD mRNA. Genetic differences in serum GPI-PLD activity were seen among four mouse strains, and no correlation was seen between GPI-PLD activity and circulating levels of high density lipoproteins in these mice. This is the first report of map position and genetic regulation for Gpld1. This information will enable us to further study the expression and function of GPI-PLD in normal and pathological conditions.

Reconstitution of glucotoxic HIT-T15 cells with somatostatin transcription factor-1 partially restores insulin promoter activity

We have reported that chronic culture of HIT-T15 cells in medium containing supraphysiologic glucose concentrations (11.1 mmol/l) causes a decrease in insulin mRNA levels, insulin content, and insulin release. Furthermore, decreases in insulin gene transcription and binding activity of two essential beta-cell transcription factors, somatostatin transcription factor-1 (STF-1; also known as GSTF, IDX-1, IPF-1, PDX-1, and GSF) and RIPE-3b1 activator, are associated with this glucotoxic effect. In this study, we observed that the loss of RIPE-3b1 occurs much earlier (79% decrease at passage [p]81) than the loss of STF-1 (65% decrease at p104), with abolishment of both factors by p122. Since the STF-1, but not the RIPE-3b1 activator, gene has been cloned, we examined its restorative effects on insulin gene promoter activity after reconstitution with STF-1 cDNA. Basal insulin promoter activities normalized to early (p71-74) passage cells (1.000 +/- 0.069) were 0.4066 +/- 0.093 and 0.142 +/- 0.034 for intermediate (p102-106) and late (p118-122) passage cells, respectively. Early, intermediate, and late passage cells, all chronically cultured in medium containing 11.1 mmol/l glucose, were transfected with STF-1 alone or cotransfected with E2-5, an E-box factor known to be synergistically associated with STF-1. Compared with basal levels, we observed a trend toward an increase in insulin promoter activity in intermediate passage cells with STF-1 transfection (1.43-fold) that became a significant increase when E2-5 was cotransfected (1.78-fold). In late passage cells, transfection of STF-1 alone significantly stimulated a 2.2-fold increase in the insulin promoter activity. Cotransfection of STF-1 and E2-5 in late passage cells stimulated insulin promoter activity 2.8-fold, which was 40% of the activity observed in early passage cells. Control studies in glucotoxic betaTC-6 cells deficient in RIPE-3b1 activator but not STF-1 did not demonstrate an increase in insulin promoter activity after STF-1 transfection. We conclude that loss of RIPE-3b1 activity precedes loss of STF-1 activity in glucotoxic HIT-T15 cells and that defective promoter activity can be partially restored by STF-1 transfection and predict that eventual cloning of the RIPE-3b1 gene will allow cotransfection studies with both factors that will allow full reconstitution of insulin promoter activity.

Glucose rapidly and reversibly decreases INS-1 cell insulin gene transcription via decrements in STF-1 and C1 activator transcription factor activity

We have reported that chronic exposure of HIT-T15 cells to supraphysiological concentrations of glucose over many months leads to decreased insulin gene transcription and decreased binding activities of two beta-cell-specific transcription factors, STF-1 and C1 activators, and have postulated that these events may provide a mechanism for glucose toxicity on beta-cell function. We now report that culturing the highly differentiated rat insulinoma cell line, INS-1, in glucose concentrations above 8.0 mM caused a marked decrease in insulin mRNA levels within 24 h. The decrease in insulin mRNA levels was reversed by further incubation of the cells in 4.0 mM glucose. Transient transfection of a chloramphenicol acetyltransferase reporter gene regulated by the 5'-regulatory sequences of the human insulin gene showed that elevated glucose concentrations caused a large decrease in insulin gene promoter activity. The decrease in insulin gene promoter activity was associated with reductions in the binding activities of both STF-1 and C1 activator, and these were partially reversed by lowering the glucose concentration. The decrease in STF-1 binding activity was associated with decreased STF-1 mRNA and occurred independently of changes in STF-1 promoter activity, suggesting a posttranscriptional regulatory mechanism. Furthermore, the decrease in insulin gene expression was found to occur independently of changes in cell proliferation. We conclude that physiologically relevent elevations in glucose can reversibly diminish insulin gene transcription by reducing the expression and/or binding activity of two critical beta-cell transcription factors.

Differentiation of glucose toxicity from beta cell exhaustion during the evolution of defective insulin gene expression in the pancreatic islet cell line, HIT-T15

Chronic exposure of HIT-T15 cells to supraphysiologic glucose concentration diminishes insulin gene expression and decreased binding of two critical insulin gene transcription factors, STF-1 and RIPE-3b1 activator. To distinguish whether these changes are caused by glucose toxicity or beta cell exhaustion, HIT-T15 cells grown from passage 75 through 99 in media containing 11.1 mM glucose were switched to 0.8 mM glucose at passage 100. They regained binding of STF-1 and RIPE-3b1 activator and had a partial but minimal return of insulin mRNA expression. In a second study, inclusion of somatostatin in the media-containing 11.1 mM glucose inhibited insulin secretion; however, despite this protection against beta cell exhaustion, dramatic decreases in insulin gene expression, STF-1 and RIPE-3b1 binding, and insulin gene promoter activity still occurred. These data indicate that the glucotoxic effects caused by chronic exposure to supraphysiologic concentration of glucose are only minimally reversible and that they are not due simply to beta cell exhaustion. These observations carry with them the clinical implication that Type II diabetic patients who remain hyperglycemic for prolonged periods may have secondary glucose toxic effects on the beta cell that could lead to defective insulin gene expression and worsening of hyperglycemia.

Effects of tacrolimus (FK506) on human insulin gene expression, insulin mRNA levels, and insulin secretion in HIT-T15 cells

FK506 (tacrolimus) is an immunosuppressive drug which interrupts Ca2+-calmodulin-calcineurin signaling pathways in T lymphocytes, thereby blocking antigen activation of T cell early activation genes. Regulation of insulin gene expression in the beta cell may also involve Ca2+-signaling pathways and FK506 has been associated with insulin-requiring diabetes mellitus during clinical use. The purpose of this study was to characterize the effects of FK506 on human insulin gene transcription, insulin mRNA levels, and insulin secretion using as a model the HIT-T15 beta cell line. FK506 had no acute effect on insulin secretion in the HIT cell, but caused a reversible time- and dose-dependent (10(-9)-10(-6) M) decrease in HIT cell insulin secretion. Decreased insulin secretion in the presence of FK506 was also accompanied by a dose-dependent decrease in HIT cell insulin content, insulin mRNA levels, and expression of a human insulin promoter-chloramphenicol acetyl transferase (CAT) reporter gene. FK506 decreased HIT cell expression of the human insulin promoter-CAT reporter gene by 40% in the presence of both low (0.4 mM) at high (20 mM) glucose concentrations. Western blot analysis of HIT cell proteins gave evidence for the presence of calcineurin in the HIT cell. These findings suggest that FK506 may have direct effects to reversibly inhibit insulin gene transcription, leading to a decline in insulin mRNA levels, insulin synthesis, and ultimately insulin secretion.

Parenchymal scarring is associated with restrictive spirometric defects in patients with chronic thromboembolic pulmonary hypertension

The finding of a restrictive pulmonary defect may divert clinicians from considering the diagnosis of chronic thromboembolic pulmonary hypertension because lung volumes are usually normal in this disorder. We have, however, encountered a significant number of these patients with reduced lung volumes. Furthermore, we have observed many patients who have developed parenchymal scars and/or pleural thickening. To determine whether such findings are associated with lung volume restriction, we analyzed patients evaluated at our institution for chronic thromboembolic pulmonary hypertension over a 20-month period in whom thoracic high-resolution CT scans and pulmonary function testing had been performed. Patients with obstructive or restrictive lung disease from another cause were excluded. We compared the presence of lung restriction (total lung capacity below 80% of predicted) with the extent of parenchymal scarring, pleural thickening, and pulmonary artery diameter on CT scans. Of 191 patients evaluated, 51 met criteria for entry. Eleven patients (22%) had lung restriction. Parenchymal scarring was highly associated with lung restriction (p = 0.01). Neither pleural thickening (p = 0.08) nor pulmonary artery diameter (p = 0.80) was associated with lung restriction.

CONCLUSIONS

A significant number of patients with chronic thromboembolic pulmonary hypertension may have restrictive lung defects. The restriction may be due to parenchymal scarring.

Suppression of adenylate kinase catalyzed phosphotransfer precedes and is associated with glucose-induced insulin secretion in intact HIT-T15 cells

Adenine nucleotide metabolism was characterized in intact insulin secreting HIT-T15 cells during the transition from non-stimulated (i. e. 0.2 mM glucose) to the glucose-stimulated secretory state. Metabolic dynamics were monitored by assessing rates of appearance of 18O-labeled phosphoryls of endogenous nucleotides in cells incubated in medium enriched in [18O]water. Most prominent of the metabolic alterations associated with stimulated insulin secretion was the suppression in the rate of adenylate kinase (AK)-catalyzed phosphorylation of AMP by ATP. This was manifest as a graded decrease of up to 50% in the rate of appearance of beta-18O-labeled species of ADP and ATP and corresponded to the magnitude of the secretory response elicited over a range of stimulatory glucose concentrations. The only nucleotide exhibiting a significant concentration change associated with suppression of AK activity was AMP, which decreased by about 50%, irrespective of the glucose concentration. Leucine-stimulated secretion also decreased the rate of AK-catalyzed phosphotransfer. This secretory stimulus-related suppression of AK-catalyzed phosphotransfer occurs within 45 s of glucose addition, precedes insulin secretion, depends on the internalization and metabolism of glucose, and is independent of membrane depolarization and the influx of extracellular calcium. The secretory stimulus-induced decrease in AK-catalyzed phosphotransfer, therefore occurs prior to or at the time of KATP+ channel closure but it is not associated with or a consequence of events occurring subsequent to KATP+ channel closure. These results indicate that AK-catalyzed phosphotransfer may be a determinant of ATP to ADP conversion rates in the KATP+ channel microenvironment; secretory stimuli-linked decreased rates of AK-catalyzed ADP generation from ATP (and AMP) would translate into an increased probability of ATP-liganded and, therefore, closed state of the channel.

Chronic exposure of betaTC-6 cells to supraphysiologic concentrations of glucose decreases binding of the RIPE3b1 insulin gene transcription activator

We have shown previously that chronic exposure of HIT-T15 cells to supraphysiologic glucose concentrations causes decreased insulin gene transcription and decreased binding activities of two beta-cell specific transcription factors, STF-1 and the RIPE3b1 activator, and have suggested that these events may provide a mechanism for glucose toxicity on beta-cell function. However, this contention can be criticized because it is not clear whether these observations are unique to the HIT-T15 cell or generalizable to other beta-cell lines and the islet. Therefore, we cultured betaTC-6 cells for up to 41 wk in either 11.1 or 0.8 mM glucose. We observed a passage-dependent decrease in insulin content and insulin mRNA levels in betaTC-6 cells chronically cultured in 11.1 mM glucose. Cells chronically cultured in 0.8 mM glucose had higher insulin mRNA levels than cells chronically cultured in 11.1 mM glucose. The relative activity of a chloramphenicol acetyl transferase (CAT) reporter gene controlled by the 5' regulatory region of the human insulin gene was decreased in late passage betaTC-6 cells chronically cultured in 11.1 mM glucose, but was preserved in late passages of cells chronically cultured in 0.8 mM glucose. Electromobility shift assays demonstrated that binding of a specific nuclear protein that recognizes the RIPE3b1 binding site of the insulin gene was markedly diminished in late passage cells chronically exposed to 11.1 mM glucose, whereas binding activities of STF-1 and ICE activators were unchanged. RIPE3b1 binding activity was preserved in late passage cells chronically exposed to 0.8 mM glucose. Mutation of the RIPE3b1 binding site almost completely abolished insulin gene transcription as well as binding activity. We conclude that chronic exposure of betaTC-6 cells to high glucose concentrations paradoxically decreases insulin gene transcription, in part, by decreasing activity of the trans-activating factor which binds to the RIPE3b1 sequence. This study uniquely demonstrates that altered binding to the RIPE3b1 sequence mediates glucose toxicity in betaTC-6 cells, thus reinforcing the importance of this cis-acting element in the regulation of insulin gene transcription. We conclude that the phenomenon of glucose toxicity decreasing binding of transcription factors and thereby reducing insulin gene expression is not a feature solely of HIT-T15 cells and may be demonstrable generally in beta-cell lines.

Insulin-secreting cell lines: classification, characteristics and potential applications

The use of primary beta-cells in biochemical and molecular research is limited by the availability of pancreatic endocrine tissue. Numerous investigators have attempted to establish an insulin-secreting cell line that retains normal regulation of insulin secretion. Different approaches have been used, including induction of pancreatic tumors by irradiation or viral infection, immortalization of beta-cells in vitro, and development of transgenic mice with targeted expression of a recombinant oncogene in the beta-cell. Few of these attempts have proven successful, because cell differentiation and proliferation capacities are mutually exclusive. The most widely used insulin-secreting cell lines are RIN, HIT, beta TC, MIN6 and INS-1 cells. These cells contain mainly insulin and small amounts of glucagon and somatostatin. RIN cells, except for the subclone RIN-38, are not glucose-responsive. HIT cells and beta TC cells secrete insulin in response to glucose, but their dose-response curve is markedly shifted to the left MIN6, INS-1 and a newly available subclone of beta TC cells (beta TC-6 F7) are reported to retain normal regulation of glucose-induced insulin secretion. Although the behaviour of none of these cell lines perfectly mimics primary beta-cell physiology, they are extremely valuable tools for the study of molecular events underlying beta-cell function and dysfunction. In addition, insulin-secreting cell lines represent a potential source of transplantable tissue to overcome the limited availability of primary islets for this procedure.

Somatostatin coordinately regulates glucagon gene expression and exocytosis in HIT-T15 cells

Somatostatin (SRIF) regulates secretion from several endocrine cell types. SRIF inhibits both insulin and glucagon secretion and reduces insulin gene expression. However, whether SRIF inhibition of glucagon secretion from the pancreatic alpha cell is mediated via pertussis toxin-sensitive G-proteins is not presently known, nor has it been determined whether SRIF can regulate glucagon gene expression. Consequently, we performed studies in the transformed islet cell line HIT-T15 to determine whether the inhibitory effect of SRIF on glucagon exocytosis is preserved in this cell line, whether this effect is mediated through a pertussis toxin-sensitive mechanism, and whether SRIF has an inhibitory effect on glucagon gene expression. Confocal microscopy with immunostaining revealed that 15-25% of HIT-T15 cells contained glucagon. In static incubations forskolin (FSK, 1 microM) increased glucagon secretion 3.6 +/- 0.9-fold (P < 0.01) and mixed amino acids (15 mM) increased glucagon secretion 2.8 +/- 0.4-fold (P < 0.01). Addition of SRIF significantly inhibited both forskolin- and amino acid-stimulated secretion. Maximal inhibition of both FSK- and amino acid-stimulated secretion occurred at SRIF concentrations > or = 10(-8) M and these inhibitory effects were completely prevented by pertussis toxin pretreatment. In addition to inhibiting glucagon secretion, SRIF significantly reduced both basal and FSK-stimulated glucagon mRNA levels and this reduction in glucagon mRNA was completely prevented by the addition of cyclic AMP analogue. Glucagon gene promoter activity, as assessed by transient transfection experiments, was stimulated 2.1 +/- 0.25-fold by forskolin (P < 0.01). This effect was significantly inhibited by SRIF (71 +/- 4% reduction from FSK alone, P < 0.04) suggesting that SRIF inhibition of the glucagon promoter may, at least in part, account for the observed decrease in glucagon mRNA levels. These studies uniquely demonstrate that glucagon secretion from the HIT-T15 cell line is inhibited by SRIF through a pertussis toxin-sensitive mechanism and that SRIF also inhibits glucagon gene expression in part by reducing glucagon promoter activity. These findings indicate that SRIF can coordinately regulate glucagon delivery by the alpha cell both at the level of gene expression and hormone exocytosis.

Chromium speciation by anion-exchange high-performance liquid chromatography with both inductively coupled plasma atomic emission spectroscopic and inductively coupled plasma mass spectrometric detection

Development of a new method for the determination of Cr(III) and Cr(VI) is described. Anion-exchange high-performance liquid chromatography (HPLC) was used to separate Cr(III) and Cr(VI) with on-line detection by inductively coupled plasma atomic emission spectroscopy (ICP-AES) at 2766 A in preliminary studies, and inductively coupled plasma mass spectrometry (ICP-MS) with single-ion monitoring at m/z 52 and m/z 53 for final work. A mobile phase consisting of ammonium sulfate and ammonium hydroxide was used, and a simple chelation procedure with EDTA was followed to stabilize the Cr(III) species in standard solutions. ICP-MS results indicated the feasibility of using chromium isotope m/z 53 instead of the more abundant m/z 52 isotope due to a high mobile-phase background most significantly from the SO+ polyatomic interference. The absolute detection limits based on peak-height calculations were 40 pg for Cr(III) and 100 pg for Cr(VI) in aqueous media by HPLC-ICP-MS. The linear dynamic range extended from 5 ppb (ng/ml) to 1 ppm (micrograms/ml) for both species. By HPLC-ICP-AES, detection limits were 100 ng for Cr(III) and 200 ng for Cr(VI). Cr(III) was detected in NIST-SRM 1643c (National Institute of Standards and Technology-Standard Reference Material, Trace Elements in Water) by HPLC-ICP-MS at the 20 ppb level.

AIDS-related spontaneous pneumothorax. Risk factors and treatment

OBJECTIVE

To define risk factors and optimum therapy for AIDS-related spontaneous pneumothorax (PTX).

DESIGN

Case-control study.

SETTING

Tertiary care center.

PATIENTS

Thirty-five patients with AIDS who developed spontaneous PTX between January 1, 1988 and December 31, 1991, of whom 27 (77.1%) did so in the setting of Pneumocystis carinii pneumonia (PCP). Forty-one patients who were diagnosed as having PCP and did not develop PTX served as the control group.

RESULTS

Using logistic regression, a history of cigarette smoking, aerosolized pentamidine treatment, and the observation of pneumatoceles by chest radiography were associated with an increased risk of PTX. Although not associated with an increased risk of occurrence of PTX, the use of systemic corticosteroids for PCP treatment was associated with a longer requirement for chest tube drainage. Although chest tube drainage alone was often successful, chemical and surgical pleurodesis was often effective in treating prolonged air leaks and was associated with a lower incidence of recurrent PTX, although this difference did not achieve statistical significance (p = 0.07).

CONCLUSIONS

Patients at high risk of developing AIDS-related spontaneous PTX can be identified. Systemic corticosteroids may increase the risk of morbidity from AIDS-related PTX. Chemical and surgical pleurodesis may be of value in short-term treatment and in reducing the risk of recurrence.

Reduction of insulin gene transcription in HIT-T15 beta cells chronically exposed to a supraphysiologic glucose concentration is associated with loss of STF-1 transcription factor expression

Chronic exposure of HIT-T15 beta cells to elevated glucose concentrations leads to decreased insulin gene transcription. The reduction in expression is accompanied by diminished binding of a glucose-sensitive transcription factor (termed GSTF) that interacts with two (A+T)-rich elements within the 5' flanking control region of the insulin gene. In this study we examined whether GSTF corresponds to the recently cloned insulin gene transcription factor STF-1, a homeodomain protein whose expression is restricted to the nucleus of endodermal cells of the duodenum and pancreas. We found that an affinity-purified antibody recognizing STF-1 supershifted the GSTF activator complex formed from HIT-T15 extracts. In addition, we demonstrated a reduction in STF-1 mRNA and protein levels that closely correlated with the change in GSTF binding in HIT-T15 cells chronically cultured under supraphysiologic glucose concentrations. The reduction in STF-1 expression in these cells could be accounted for by a change in the rate of STF-1 gene transcription, suggesting a posttranscriptional control mechanism. In support of this hypothesis, no STF-1 mRNA accumulated in HIT-T15 cells passaged in 11.1 mM glucose. The only RNA species detected was a 6.4-kb STF-1 RNA species that hybridized with 5' and 3' STF-1-specific cDNA probes. We suggest that the 6.4-kb RNA represents an STF-1 mRNA precursor and that splicing of this RNA is defective in these cells. Overall, this study suggests that reduced expression of a key transcriptional regulatory factor, STF-1, contributes to the decrease in insulin gene transcription in HIT-T15 cells chronically cultured in supraphysiologic glucose concentration.

The reduction of insulin gene transcription in HIT-T15 beta cells chronically exposed to high glucose concentration is associated with the loss of RIPE3b1 and STF-1 transcription factor expression

The most important regulator of insulin gene expression in pancreatic beta- cells is glucose, which affects gene transcription, mRNA translation, and secretion. Insulin gene transcription is both positively and negatively regulated by glucose. Recently, we have shown that the inhibition of insulin gene transcription caused by passaging HIT T-15 beta-cells, in the presence of high glucose, was due, in part, to reduced expression of a key regulator of insulin enhancer-mediated expression, somatostatin transcription factor-1 (STF-1). In this study, we have examined whether the activity of the other essential transcription regulators of insulin gene expression, the RIPE3b1 and insulin control element (ICE) activators, were also influenced in these HIT T-15 cells. The results show that the binding and trans-activation functions of the RIPE3b1 activator are reduced in parallel with the loss in STF-1 and insulin gene expression. In contrast, the regulatory properties of the ICE activator are unaffected. Our studies indicate that insulin gene transcription is inhibited by glucose through a mechanism involving reduced expression of both the RIPE3b1 and STF-1 activators in HIT T-15 cells but is independent of the ICE activator.

Differentiating glucose toxicity from glucose desensitization: a new message from the insulin gene

Our perspective is that the concepts of glucose toxicity and glucose desensitization should be differentiated because they carry very different connotations. The term glucose desensitization most properly refers to a pharmacological event involving a temporary, readily induced, physiological and reversible state of cellular refractoriness because of repeated or prolonged exposure to high concentrations of glucose. The term glucose toxicity should be reserved for nonphysiological, irreversible alterations in cellular function caused by chronic exposure to high glucose concentrations. With regard to the pancreatic islet beta-cell, the mechanism of action for glucose desensitization seems most likely to be expressed at the level of the insulin exocytotic apparatus or insulin stores within the beta-cell, whereas the mechanism of action for glucose toxicity may be at the level of insulin gene transcription. This differentiation raises the possibility that exposure of patients to chronic hyperglycemia may cause glucose toxic effects on the process of insulin gene transcription and/or expression that are irreversible. If so, this may contribute to so-called secondary drug failure and, in any event, reemphasizes the need to intensify therapeutic efforts to better regulate glycemia in type II diabetes.

Chronic pulmonary thromboembolism: detection of regional hypoperfusion with CT

PURPOSE

To study the relationship of regional hypoperfusion and areas of decreased lung attenuation on computed tomographic (CT) scans of patients with chronic pulmonary thromboembolism.

MATERIALS AND METHODS

Preoperative CT scans of five patients (four men and one woman, aged 29-72 years) with chronic pulmonary thromboembolism were reviewed and compared with axial single photon emission CT (SPECT) perfusion scans obtained at similar levels. Regions of varying attenuation and perfusion were scored on a three-point scale.

RESULTS

In the five patients, 198 regions were identified. Of 176 abnormal regions at SPECT, 133 were abnormal at CT (sensitivity, 75.6%). Eleven of 22 regions interpreted as normal at SPECT were judged to have normal attenuation at CT (specificity, 50%). The overall accuracy of CT for detecting areas of hypoperfusion was 72.7% (P = .011).

CONCLUSION

A mosaic pattern of lung attenuation at CT is a sign of variable regional perfusion and may suggest chronic pulmonary thromboembolism as a cause for pulmonary hypertension.

Women and social security: a progressive approach

This article explores some major assumptions underlying the Social Security system and alternative approaches to rendering the system more economically viable, meeting the income needs of the elderly and/or providing greater equity under its benefit and taxation provisions. It attempts to show that the current structure of Social Security not only reinforces but also exacerbates the underlying economic inequalities in our nation's political economy under the guise of a social insurance program. In addressing selected benefit and taxation issues, the article focuses on how working and older women are faring in the 1990s under the Social Security system. It argues that although the program theoretically is gender neutral, its impact is not. Women, particularly those who are single, are poorly served. The article concludes that a progressive restructuring of the Social Security system itself is imperative if we are to meet the needs of a large percentage of workers, older people, and the economic and social demands of the 1990s and beyond. It also offers some suggestions for such change.

The roentgenographic findings associated with air embolism in sport scuba divers

Records on all patients with arterial gas embolism (AGE) presenting to UCSD from 1982-1989 and for whom chest radiographs were available were reviewed. Of the 31 patients, 13 roentgenograms (42%) showed evidence of pulmonary barotrauma demonstrated by pneumomediastinum (N = 8), subcutaneous emphysema (N = 3), pneumocardium (N = 2), pneumoperitoneum (N = 1), or pneumothorax (N = 1). Pneumopericardium was not seen. Sixteen (52%) of the 31 patients had pulmonary infiltrates. Radiographic evidence of barotrauma was on occasion subtle, and in four cases was overlooked. Evidence of barotrauma (i.e., extra-alveolar air) was often identified along the left cardiac border, aortic arch, descending aorta, and hilar vessels. Subtle findings of ectopic air can confirm the clinical diagnosis of AGE; however, radiographic evidence of concomitant near drowning occurs more frequently.

Chronic exposure of HIT cells to high glucose concentrations paradoxically decreases insulin gene transcription and alters binding of insulin gene regulatory protein

Chronically culturing HIT-T15 cells in media containing high glucose concentrations leads to decreased insulin mRNA levels, insulin content, and insulin secretion. These changes can be prevented by culturing the cells in media containing lower glucose levels (Robertson, R. P., H.-J. Zhang, K. L. Pyzdrowski, and T. F. Walseth. 1992. J. Clin. Invest. 90:320-325). The mechanism of this seemingly paradoxical phenomenon was examined by transiently transfecting HIT cells with a chloramphenicol acetyl transferase (CAT) reporter gene controlled by the 5'-regulatory domain of the human insulin gene (INSCAT). Early passages of HIT cells readily expressed INSCAT, whereas late passages of cells chronically cultured in 11.1 mM glucose expressed only 28.7 +/- 2.3% (mean +/- SEM) of the CAT activity expressed in early passages. In contrast, late passages of HIT cells chronically cultured in 0.8 mM glucose retained the ability to express the INSCAT reporter gene to 69.6 +/- 10.0% of the CAT activity observed in early passages. The decrease in INSCAT expression in late passages of cells serially cultured in 11.1 mM glucose was associated with the inability to form a specific nuclear protein-DNA complex with the CT motifs of the human insulin promoter. Formation of this specific protein-DNA complex was preserved in late passages of HIT cells when serially cultured in 0.8 mM glucose. Mutations of the CT motifs caused markedly diminished CAT activity in all passages examined. These data indicate that chronic exposure of the beta cell to high glucose concentrations can paradoxically decrease insulin gene transcription, in part, by altering the ability of a regulatory protein (GSTF) to interact with the insulin gene promoter. This provides a potential mechanism for glucotoxic effects on the beta cell at the level of the insulin gene.

Interpreting the mammogram report

The standardization of imaging techniques, interpretation and reporting has become an important issue as the use of mammographic screening has increased. Each mammogram report should indicate whether the breast is fatty or consists of dense glandular tissue. A brief description of abnormalities should be followed by the conclusion and recommendations. Well-circumscribed lesions have a 98 percent benign rate; these lesions generally do not require biopsy but can be followed at six-month intervals for a period of time. The overall rate of malignancy for biopsies prompted by mammography is 20 to 35 percent. Lesions interpreted as highly suspicious are malignant in 75 to 90 percent of cases. Mammographically detected tumors are generally smaller than palpable tumors at the time of diagnosis. In addition, patients who have mammographically detected lesions are more often node-negative and therefore have a better prognosis than patients with palpable lesions.

Increase in Gs and cyclic AMP generation in HIT cells. Evidence that the 45-kDa alpha-subunit of Gs has greater functional activity than the 52-kDa alpha-subunit

Cyclic AMP accumulation in response to forskolin, cholera toxin, or isoproterenol is dramatically increased in HIT T-15 cells, a clonal cell line of Syrian hamster pancreatic islet beta cells, as a function of passage number. Forskolin and cholera toxin elevate cyclic AMP levels 5- to 10-fold higher in later passages (87-100) than in earlier passages (70-80). A similar phenomenon is observed with isoproterenol (10 microM) which increases cyclic AMP levels 56-fold in older HIT cells (passage 94), whereas only marginally stimulating cyclic AMP production in younger cells (passage 70-82). To determine whether a change in the stimulatory or inhibitory guanine nucleotide regulatory proteins, Gs or Gi, was responsible for these observations, ADP-ribosylation of HIT cell membranes with cholera toxin and pertussis toxin was examined. All passages contained two cholera toxin substrates at 52 and 45 kDa. The amount of 52 kDa did not appear to change with passage number, but the amount of 45 kDa increased in the later passages (89 and 94). The ratio of 45 to 52 kDa cholera toxin substrate, as determined by densitometric analysis, increased from 0.1 in passages 70, 75, and 82 to 0.45 at passage 89. No passage related changes in a 40-kDa pertussis toxin substrate were observed. An increase in the amount of the 45-kDa alpha-subunit of Gs was confirmed on immunoblots using antisera specific for the alpha-subunits of Gs. The amount of functional Gs present in various HIT cell passages was examined by determining the extent to which extracts from HIT cell membranes reconstituted guanine nucleotide-sensitive adenylyl cyclase in S49 cyc- membranes. Extracts derived from passage 94 reconstituted three to four times more adenylyl cyclase activity in cyc- membranes than extracts from passages 70, 75, and 82. These data indicate that an increase in functional Gs in later passages may be the underlying cause for the increased responsiveness to isoproterenol and forskolin in later passages. These data also suggest that functional differences exist between the Gs alpha-subunits, with the smaller 45-kDa subunit being more efficacious in coupling to cyclic AMP synthesis than the larger 52-kDa subunit. This is a departure from the commonly held view that the two subunits have similar efficacies in stimulating adenylyl cyclase.

Endobronchial metastases due to colorectal carcinoma

Metastatic disease from colorectal carcinoma to the tracheobronchial tree has previously been reported in only 15 cases. Various modalities of treatment have been attempted but have met with limited success. We describe an additional nine cases, as documented by fiberoptic bronchoscopy, treated by Nd-Yag laser therapy debulking. Improvement in bronchial patency was evidenced visually in each case, and relief of symptoms occurred in eight cases. Survival periods of up to 21 months occurred. This type of metastatic disease may be more common than previously reported and combination therapy to include Nd-Yag laser debulking offers a safe and effective alternative in the palliative management of pulmonary symptoms and increased survival in select patients.

Computed tomography of the chest in the trauma patient

Thirty-six (1.5%) of 2340 patients admitted to the Trauma Unit at UCSD Medical Center over a 26-month period had 46 chest CT scans. A retrospective review of these cases showed that CT was useful in the diagnosis and management of suspected post-traumatic infective complications, assessment of suspected sternoclavicular joint dislocation, and localisation of bullet fragments. Other unsuspected abnormalities (pneumothoraces, misplaced endotracheal tube, intraperitoneal air, and axillary vein disruption) were also well demonstrated. However, CT failed to demonstrate some skeletal injuries, in particular, manubriosternal joint dislocation and vertebral fracture. Our experience supports a role for chest CT in certain limited clinical situations following trauma.

Chronic thromboembolic occlusion in the adult can mimic pulmonary artery agenesis

In the first 100 patients operated on for C T-E PH, three were referred with the diagnosis of UPAA having been made elsewhere. We found that many features of these two conditions are so similar that differential diagnosis is very difficult. Shared features may include findings on chest x-ray film, pulmonary angiography, CT scan and MRI studies. Since the two conditions vary substantially with respect to the methods of potential surgical correction, recognition of this possible differential diagnostic dilemma is important.

Computed tomography in the diagnosis of traumatic rupture of the thoracic aorta

Over a 26-month period, 25 patients admitted to the Trauma Unit at UCSD Medical Center following blunt trauma were investigated for suspected traumatic rupture of the thoracic aorta by computed tomography (CT) of the chest. A retrospective review of these patients was performed. Twenty-one (84%) also had CT of other body areas, most commonly the head or abdomen. Nine of the 25 patients subsequently had aortography; in 15 patients the CT findings were felt at the time to exclude rupture, and one patient was not investigated further because of severe head injuries. In general, if CT failed to show a mediastinal haematoma, aortography was not performed. However, five patients with CT evidence of a haematoma, including two with vertebral fractures, were not investigated by aortography. Two of the 25 patients (8%) had angiographically proven aortic ruptures; in both CT had shown not only a haematoma but also an abnormal outline of the aorta on contrast-enhanced scans. The haematoma was large in one patient and small in the other. Although 10 of the 25 patients had unenhanced scans, no case of aortic rupture is known to have been missed. During the same study period, 47 patients were investigated for suspected aortic rupture solely by aortography. Four patients (8% of this group) had aortic rupture, and two had subclavian or innominate artery ruptures. Only a minority (approximately one-quarter) also had CT of the head or abdomen. The role of CT in the diagnosis of traumatic rupture of the aorta is critically assessed in the light of our experience and a review of the literature.

Real-time breast sonography: application in 300 consecutive patients

Sonography, disappointing as a primary screening method, has emerged as the single most helpful adjunct to mammography in evaluation of the clinically and/or mammographically abnormal breast. Sonography can reliably diagnose simple cysts presenting as palpable masses or as indeterminate, nonpalpable lesions on mammography. However, differentiation of benign from malignant solid masses cannot be reliably accomplished by sonography. The expense of an automated breast sonographic scanner has deterred many radiologists from the purchase of such a unit. The authors have used both an automated breast scanner and a real-time 10-MHz hand-held unit. This paper describes their experience with the real-time unit, demonstrating both normal and pathologic anatomy. Special emphasis has been placed on the sonographic diagnosis of a simple cyst because this lesion was the cause of one-quarter of all palpable masses and nonpalpable, mammographically dominant masses. Cysts are sharply marginated and anechoic. Posterior enhancement visible in 78 of 80 cysts was not demonstrable on all images in 25% of cysts.

Abdominal wall CT: a pictorial essay

Abdominal CT demonstrates clearly the anatomy of the abdominal wall. This radiographic technique may provide valuable information when pathology is suspected in this region or in the adjacent peritoneum. The muscles, subcutaneous tissues and vascular structures of the abdominal wall should be examined thoroughly when reading routine abdominal CT films. This paper reviews abnormalities identified involving the abdominal wall including hernias, masses, vessels, hematomas, abscesses, ascites, neuromuscular diseases and miscellaneous entities.

Furosemide during sustained left atrial hypertension in functionally anephric dogs: intravascular and extravascular pulmonary fluid volumes. V

The response of intravascular (PBV) and extravascular (EVLW) pulmonary fluid volume was examined using double-indicator techniques (thermal-green dye) in 11 open-chest anesthetized dogs during the production of sustained left atrial (LA) hypertension by a LA balloon over a period of 195 min. In 6 of these animals data were also acquired after the intravenous administration of furosemide (1 mg/kg). The renal effects of the diuretic were blocked by tying off the ureters and the vascular supply of both kidneys. Left atrial pressure (N = 11) was abruptly increased from 2.2 +/- 2.1 mm Hg to 30.2 +/- 4.0 mm Hg (P less than 0.01) and maintained at that level for 120 min. Data were obtained prior to pressure elevation, immediately upon pressure elevation, and then every 60 min for a total of 120 min. At that point EVLW had increased (8.1 +/- 0.8 cc/kg at control to 21.7 +/- 2.0 cc/kg at 120 min, P less than 0.001), as had PBV (6.2 +/- 2.1 cc/kg to 9.1 +/- 3.1 cc/kg P less than 0.01). After furosemide injection (N = 6), LA pressure declined (mean peak reduction of approximately 6 mm Hg at 60-75 min, P less than 0.01), aortic and pulmonary arterial pressure both declined (P less than 0.01). However, EVLW remained unchanged, though PBV decreased significantly (peak decrease at 75 min after furosemide administration of 2.0 +/- 0.4 cc/kg, P less than 0.01). In the untreated dogs, EVLW continued to climb (P less than 0.05 vs treated dogs at 75 min postfurosemide).(ABSTRACT TRUNCATED AT 250 WORDS)

Extravascular lung water in patients with mitral stenosis: relationship to pulmonary capillary wedge pressure and Kerley B lines

To evaluate the relationship between extravascular lung water, pulmonary capillary wedge pressure, and chest radiographic findings, extravascular lung water (EVLW) was assessed using double indicator-dilution techniques in 34 adult patients with mitral stenosis. Seven patients were studied 6 to 12 months after successful mitral valve replacement. In the 27 preoperative patients, septal lines were found to be indicative of elevated EVLW only in the presence of intravascular congestion. An excellent correlation between EVLW and pulmonary capillary wedge pressure was observed in these patients (r = .81, p less than .001), whereas only a rough correlation between scored radiographic findings and EVLW was observed. Postoperatively, septal lines were invariably associated with normal filling pressures and EVLW. Thus in both preoperative and postoperative mitral stenosis patients, interstitial Kerley B lines are insensitive markers of elevated extravascular lung water in the absence of pulmonary vascular engorgement. This emphasizes the importance of interpreting radiographic findings of extravascular fluid in conjunction with evaluation of the vascular bed in patients with chronic postcapillary hypertension.