Relation of ascorbic acid to bone mineral density and self-reported fractures among US adults

Ascorbic acid is an essential nutrient involved in collagen formation, and its deficiency is associated with abnormal bone development. To examine the relation of ascorbic acid to bone mineral density and the prevalence of self-reported fractures, the authors analyzed data collected from 13,080 adults enrolled in the Third National Health and Nutrition Examination Survey (NHANES III) during 1988-1994. Because they identified three-way interactions among smoking, history of estrogen use, and dietary and serum ascorbic acid in postmenopausal women, they analyzed these relations stratified by smoking and estrogen use. Dietary ascorbic acid intake was independently associated with bone mineral density among premenopausal women (p = 0.002). Among men, serum ascorbic acid was associated in a nonlinear fashion with bone mineral density (p < 0.05), and dietary ascorbic acid intake was associated in a nonlinear fashion with self-reported fracture (p = 0.05). Among postmenopausal women without a history of smoking or estrogen use, serum ascorbic acid was unexpectedly associated with lower bone mineral density (p = 0.01). However, among postmenopausal women with a history of smoking and estrogen use, a standard deviation increase in serum ascorbic acid was associated with a 49% decrease in fracture prevalence (p = 0.001). Dietary and serum ascorbic acid measures were associated inconsistently with bone mineral density and self-reported fracture among adult participants in NHANES III.

Unscheduled bleeding during initiation of continuous combined hormone replacement therapy: a direct comparison of two combinations of norethindrone acetate and ethinyl estradiol to medroxyprogesterone acetate and conjugated equine estrogens

OBJECTIVE

To determine whether there are differences between continuous combined hormone replacement therapies on bleeding control.

DESIGN

Nine hundred and forty-five postmenopausal women were randomized to one of seven double-blind treatment groups (placebo, 0.25 mg norethindrone acetate (NA)/5 microg ethinyl estradiol (EE), 1 mg NA/5 microg EE, 0.5 mg NA/10 microg EE, 1 mg NA/10 microg EE, 5 microg EE, and 10 micro EE) or unmasked 0.625 mg conjugated equine estrogens (CEE)/2.5 mg medroxyprogesterone acetate (MPA). Treatment was for 12 months; subjects kept daily diaries recording whether they had bleeding and/or spotting.

RESULTS

The results focused on currently commercially available hormone replacement therapy products (femhrt [1 mg NA/5 microg EE] and Prempro [0.625 mg CEE/2.5 mg MPA]) as well as a high-dose NA/EE dose combination (1/10) over the first 6 months of use, the most critical period in establishing treatment adherence. At the end of month 6 there was a greater incidence of amenorrhea with both NA/EE dose combinations compared with CEE/MPA (p = 0.009 for 1 mg NA/5 microg EE and p = 0.006 for 1 mg NA/10 microg EE). Statistically significantly more women were amenorrheic at every month based on cumulative amenorrhea for 1 mg NA/5 microg (p < 0.05) compared with CEE/MPA; at months 3 and 6 more women were amenorrheic on 1 mg NA/10 microg EE compared with CEE/MPA using the cumulative amenorrhea parameter.

CONCLUSIONS

The results indicate that statistically significantly more women attained amenorrhea based on various parameters when administered continuous combined NA/EE compared with CEE/MPA. The potential for long-term treatment compliance based on better bleeding control may optimize the opportunity to prevent osteoporosis as well as other associated health benefits.

Interactions of Exo1p with components of MutLalpha in Saccharomyces cerevisiae

Previously, we reported evidence suggesting that Saccharomyces cerevisiae MutLalpha, composed of Mlh1p and Pms1p, was a functional member of the gyrase b/Hsp90/MutL (GHL) dimeric ATPase superfamily characterized by highly conserved ATPase domains. Similar to other GHL ATPases, these putative ATPase domains of MutLalpha may be important for the recruitment and/or activation of downstream effectors. One downstream effector candidate is Exo1p, a 5'-3' double stranded DNA exonuclease that has previously been implicated in DNA mismatch repair (MMR). Here we report yeast two-hybrid results suggesting that Exo1p can interact physically with MutLalpha through the Mlh1p subunit. We also report epistasis analysis involving MutLalpha ATPase mutations combined with exo1Delta. One interpretation of our genetic results is that MutLalpha ATPase domains function to direct Exo1p and other functionally redundant exonucleases during MMR. Finally, our results show that much of the increase in spontaneous mutation observed in an exo1Delta strain is REV3-dependent, in turn suggesting that Exo1p is also involved in one or more MMR-independent mutation avoidance pathways.

Relation of serum ascorbic acid to mortality among US adults

PURPOSE

To examine the relation between serum ascorbic acid (SAA), a marker of dietary intake (including supplements), and cause-specific mortality.

SUBJECTS AND METHODS

We analyzed data from a probability sample of 8,453 Americans age > or = 30 years at baseline enrolled in the Second National Health and Nutrition Examination Survey (NHANES II), who were followed for mortality endpoints. We calculated relative hazard ratios as measures of disease association comparing the mortality rates in three biologically relevant SAA categories.

RESULTS

Participants with normal to high SAA levels had a marginally significant 21% to 25% decreased risk of fatal cardiovascular disease (CVD) (p for trend = 0.09) and a 25% to 29% decreased risk of all-cause mortality (p for trend <0.001) compared to participants with low levels. Because we determined that gender modified the association between SAA levels and cancer death, we analyzed these associations stratified by gender. Among men, normal to high SAA levels were associated with an approximately 30% decreased risk of cancer deaths, whereas such SAA levels were associated with an approximately two-fold increased risk of cancer deaths among women. This association among women persisted even after adjustment for baseline prevalent cancer and exclusion for early cancer death or exclusion for prevalent cancer.

CONCLUSIONS

Low SAA levels were marginally associated with an increased risk of fatal CVD and significantly associated with an increased risk for all-cause mortality. Low SAA levels were also a risk factor for cancer death in men, but unexpectedly were associated with a decreased risk of cancer death in women. If the association between low SAA levels and all-cause mortality is causal, increasing the consumption of ascorbic acid, and thereby SAA levels, could decrease the risk of death among Americans with low ascorbic acid intakes.

The predicted beta12-beta13 loop is important for inhibition of PP2Acalpha by the antitumor drug fostriecin

The potential anticancer agent fostriecin (FOS) is a potent inhibitor of the protein Ser/Thr phosphatases PP2A and PP4 and a weaker inhibitor of PP1. Random mutagenesis and automated screening in yeast identified residues in human PP2Acalpha important for inhibitory FOS binding. A C269S substitution in the predicted beta12-beta13 loop decreased the FOS sensitivity of intact cells and increased the IC(50) of PP2Acalpha by 10-fold in vitro. Changing PP2Acalpha Cys-269 to phenylalanine, the equivalent residue in PP1, and the Y267G and G270D substitutions caused a similar effect. The results provide information relevant to the design of novel protein Ser/Thr phosphatase inhibitory drugs.

Long-range repression by multiple polycomb group (PcG) proteins targeted by fusion to a defined DNA-binding domain in Drosophila

A tethering assay was developed to study the effects of Polycomb group (PcG) proteins on gene expression in vivo. This system employed the Su(Hw) DNA-binding domain (ZnF) to direct PcG proteins to transposons that carried the white and yellow reporter genes. These reporters constituted naive sensors of PcG effects, as bona fide PcG response elements (PREs) were absent from the constructs. To assess the effects of different genomic environments, reporter transposons integrated at nearly 40 chromosomal sites were analyzed. Three PcG fusion proteins, ZnF-PC, ZnF-SCM, and ZnF-ESC, were studied, since biochemical analyses place these PcG proteins in distinct complexes. Tethered ZnF-PcG proteins repressed white and yellow expression at the majority of sites tested, with each fusion protein displaying a characteristic degree of silencing. Repression by ZnF-PC was stronger than ZnF-SCM, which was stronger than ZnF-ESC, as judged by the percentage of insertion lines affected and the magnitude of the conferred repression. ZnF-PcG repression was more effective at centric and telomeric reporter insertion sites, as compared to euchromatic sites. ZnF-PcG proteins tethered as far as 3.0 kb away from the target promoter produced silencing, indicating that these effects were long range. Repression by ZnF-SCM required a protein interaction domain, the SPM domain, which suggests that this domain is not primarily used to direct SCM to chromosomal loci. This targeting system is useful for studying protein domains and mechanisms involved in PcG repression in vivo.

Thymidine Incorporation Is Highly Predictive of Colony Formation and Can Be Used for High-Throughput Screening

The primary goal of anticancer chemotherapy is to kill cancer cells. Therefore, it is of critical importance that any assay that is used to determine the toxicity of a potential anticancer drug accurately measures viability. While colony formation is widely regarded as the most accurate measure of viability following drug treatment, it is laborious, time consuming, and difficult to carry out with non-adherent cells. For these reasons, it is not suitable for moderate- to high-throughput screening applications. We sought to identify a convenient and reliable assay that would accurately reproduce colony formation results and be amenable to high-throughput applications. Here, we describe a modification of the 3H-thymidine incorporation assay that meets these criteria. The assay can be carried out in 96-well plates with minimal handling of reagents and media. It can be performed with non-adherent and adherent cell lines. Most importantly, LC50 values obtained with this assay show excellent agreement with colony formation results. Taken together, these advantages make the modified 3H-thymidine incorporation assay well suited for high-throughput viability assays in anticancer drug discovery and development.

Androgen effects on the central nervous system in the postmenopausal woman

Interest in the effects of androgens on the central nervous system (CNS) in postmenopausal women dates back to at least fifty years. The mechanisms of action of androgens on the CNS are extremely complex and multi-faceted. Much data has been accumulated in recent years that suggest a beneficial role of androgens in several aspects of CNS function. These include positive effects on mood, cognition, memory, and libido. The information continues to be preliminary in nature and requires further investigations. There is evidence of altered androgen metabolism triggered by exogenous postmenopausal estrogen therapy. While promising, the current body of evidence does not yet support the routine addition of androgens to postmenopausal hormone therapy.

Fixation of periprosthetic femoral shaft fractures: a biomechanical comparison of two techniques

OBJECTIVE

To determine which of two currently used techniques for the treatment of periprosthetic femoral shaft fractures provides the greater fixation rigidity and strength.

DESIGN

A laboratory study using six matched pairs of femurs.

METHODS

Embalmed femur prosthesis constructs had a simulated periprosthetic fracture created and were fixed with a plate with proximal cables and distal bicortical screws (Ogden concept) or two allograft struts and cables. Fixation stability was compared in various loading modalities before and after cycling. They were then tested to failure.

OUTCOME MEASUREMENTS

Fixation rigidity was defined as the ratio of applied load to the amount of displacement at the fracture.

RESULTS

In all loading modalities, the Ogden construct was more rigid than the allograft strut fixation. The Ogden construct required 1,295 newtons for failure and the allograft strut fixation required 950 newtons (p < 0.05).

CONCLUSION

The Ogden construct provided a more rigid and stronger initial fixation of a periprosthetic fracture than did the allograft construct.

Safety of estrogen/androgen regimens

A persistent view of testosterone as the "male hormone" deprives many clinically androgen deficient women of effective treatment, although data from the 1960s to the present have indicted the importance of androgens to libido and feelings of well-being in women, providing relief from vasomotor symptoms that are unresponsive to estrogen alone. The safety of androgen replacement therapy is reviewed in this article. The risk of androgen toxicity is influenced by dosage and route of administration. Most products developed for use in men produce androgen levels that are too high for safety in women. Low-dose androgen replacement therapy as used in women, 1.25 mg esterified estrogen (EE) + 2.5 mg methyltestosterone (MT), or a half-strength preparation, 0.625 mg EE plus 1.25 mg MT, is unlikely to produce commonly described side effects: liver dysfunction, adverse lipid effects or virilization, as reviewed in this article. The potential for adverse endometrial effects if used by women with uteri unless a progestogen is used is also discussed. Low-dose estrogen/androgen therapy offers beneficial cardiovascular effects, primarily regarding lipids, atherogenesis and vasodilation. Androgens may act independently on the cardiovascular system and may be mediated by estrogen metabolites (aromatization products) or by secondary effects of androgens on estrogen bioavailability and metabolism (sex hormone binding globulin [SHBG] effects). They may improve vasomotor stability and reduce triglyceride (TG) levels. The marked reduction in TG in the estrogen/androgen (E/A) regimen is of note because women who experience oophorectomy have significantly increased levels of TG as compared with women who are naturally menopausal. Androgens offer positive effects on bone. Various types of studies--including cell culture, preclinical and observational--have attempted to document potential associations between androgens and breast cancer. Androgen administration has been shown to induce down-regulation of mammary epithelial proliferation and estrogen receptor expression, suggesting that E/A therapy might reduce the risk of breast cancer associated with ERT. However, studies of the relation of breast cancer to elevated circulating androgen levels have yielded inconsistent results. Testosterone may have an indirect effect on breast cancer risk because of its association with estrogen levels. Testosterone's effect on estrogen bioavailability may be of importance since an increase in serum testosterone levels could lead to a decrease in the percent of estradiol bound to SHBG. For the surgically menopausal woman faced with significant symptoms and health risks associated with estrogen withdrawal, E/A supplementation offers a reasonable course of treatment.

Perimenopausal women in estrogen vasomotor trials: contribution to placebo effect and efficacy outcome

OBJECTIVE

To determine the difference, if any, in the placebo response when both perimenopausal and postmenopausal women are enrolled, compared with postmenopausal women alone, in a study assessing the efficacy of synthetic conjugated estrogen tablets on moderate-to-severe vasomotor symptoms (MSVS).

METHODS

A total of 120 healthy women (72 active; 48 placebo) complaining of moderate-to-severe vasomotor symptoms were enrolled in a randomized, placebo-controlled, double-blind, multicenter clinical trial. In all, 109 patients completed treatment to week 12. Women were enrolled using minimal inclusion and exclusion criteria, and included perimenopausal women (n = 34; 0 to 6 months since last menses) as well as menopausal women (n = 79; > 12 months since last menses).

RESULTS

Changes in MSVS in the intent-to-treat (ITT) population showed differences between the active and placebo treatments at weeks 4 (p < 0.022), 8 (p < 0.010) and 12 (p < 0.010). At week 12, the mean percentage reduction in MSVS was 81% for the active treatment group and 58% in the placebo treatment group. To examine the placebo response, the ITT population was broken down into groups defined by the time since their last menses. The perimenopausal group (0 to 6 months since last menses) demonstrated a consistently higher placebo response than that of the postmenopausal groups (> 12 months since last menses).

CONCLUSIONS

Perimenopausal women contributed to a higher placebo response, compared with the rate of response previously reported in clinical studies of estrogen replacement in postmenopausal women. Including perimenopausal women in future vasomotor symptom trials will require study populations of sufficient size to maintain the statistical power to demonstrate a difference between therapeutic response to active or placebo treatment.

Postmenopausal hormone therapy and risk of stroke: The Heart and Estrogen-progestin Replacement Study (HERS)

BACKGROUND

Observational studies have shown that postmenopausal hormone therapy may increase, decrease, or have no effect on the risk of stroke. To date, no clinical trial has examined this question. To investigate the relation between estrogen plus progestin therapy and risk of stroke among postmenopausal women, we analyzed data collected from the Heart & Estrogen-progestin Replacement Study (HERS), a secondary coronary heart disease prevention trial.

METHODS AND RESULTS

Postmenopausal women (n=2763) were randomly assigned to take conjugated estrogen plus progestin or placebo. Primary outcomes for these analyses were stroke incidence and stroke death during a mean follow-up of 4.1 years. The number of women with strokes was compared with the number of women without strokes. A total of 149 women (5%) had 1 or more strokes, 85% of which were ischemic, resulting in 26 deaths. Hormone therapy was not significantly associated with risk of nonfatal stroke (relative hazard [RH] 1.18; 95% CI 0.83 to 1.66), fatal stroke (RH 1.61; 95% CI 0.73 to 3.55), or transient ischemic attack (RH 0.90; 95% CI 0.57 to 1.42). Independent predictors of stroke events included increasing age, hypertension, diabetes, current cigarette smoking, and atrial fibrillation. Black women were at increased risk compared with white women, and unexpectedly, body mass index was inversely associated with stroke risk.

CONCLUSIONS

Hormone therapy with conjugated equine estrogen and progestin had no significant effect on the risk for stroke among postmenopausal women with coronary disease.

Surgically induced endometriosis attenuates accrual of bone mineral density in growing rats

OBJECTIVE

A possible association of endometriosis with decreased bone mineral density in women has been proposed. It has been reported that cortical and trabecular bone mass of the distal portion of the radius is decreased in patients with endometriosis. The objective of this study was to investigate the relationship between endometriosis and bone mineral density with the use of a rat model.

STUDY DESIGN

Cycling female Sprague-Dawley rats (180 days old) were randomly assigned to 1 of 2 groups. The treatment group (n = 16) underwent surgical induction of endometriosis. Female rats (n = 17) with surgically transplanted abdominal muscle served as control animals. Dual-energy x-ray absorptiometry measurements were obtained before surgery and after 90 days with a Lunar DPX-MD+ (GE Lunar, GE Medical Systems, Milwaukee, Wis) bone densitometer, with software standardized for small animal research.

RESULTS

Experimental animals had grossly visible endometriotic disease at necropsy (90 days). The mean net change in total bone mineral density from baseline to 90 days in the control group was +0.019 +/- 0.002 g/cm2, whereas the mean net change in total bone mineral density for the experimental group was +0.013 +/- 0.002 g/cm2. The experimental group gained less bone than the control group (P = .02).

CONCLUSION

The age-appropriate increase in bone mineral density known to occur in this animal model is attenuated by surgically induced endometriosis. This finding supports the idea that endometriosis might be associated with decreased bone mineral density.

Peripheral arterial disease in randomized trial of estrogen with progestin in women with coronary heart disease: the Heart and Estrogen/Progestin Replacement Study

BACKGROUND

Postmenopausal estrogen use has been associated with reduced carotid atherosclerosis in observational studies, but this relationship has not been confirmed in a clinical trial. The impact of estrogen on atherosclerotic disease in other peripheral arteries is unknown.

METHODS AND RESULTS

Postmenopausal women with coronary heart disease (CHD) and an intact uterus (n=2763) were randomly assigned to conjugated equine estrogens (0.625 mg) combined with medroxyprogesterone acetate (2.5 mg) daily or to placebo in a secondary CHD prevention trial. This analysis focuses on incident peripheral arterial procedures and deaths in the 2 treatment groups; peripheral vascular disease was a predefined secondary outcome. During a mean of 4.1 years of follow-up, 311 peripheral arterial events were reported in 213 women, an annual incidence of 2.9%. The number of women who had peripheral arterial events was 99 among those assigned to active estrogen/progestin and 114 among those assigned to placebo, a nonsignificant difference (relative hazard 0. 87, 95% CI 0.66 to 1.14). In the placebo group, hypertension and diabetes mellitus were independently associated with higher rates of peripheral arterial events, and plasma HDL cholesterol and body mass index were associated with lower rates of peripheral arterial events. In the estrogen/progestin group, current smoking and diabetes were independent predictors of peripheral arterial events. Incident peripheral arterial disease was not a significant predictor of coronary, cardiovascular, or total mortality.

CONCLUSIONS

Treatment with oral conjugated estrogen plus medroxyprogesterone acetate was not associated with a significant reduction in incident peripheral arterial events in postmenopausal women with preexisting CHD.

Transdermal testosterone treatment in women with impaired sexual function after oophorectomy

BACKGROUND

The ovaries provide approximately half the circulating testosterone in premenopausal women. After bilateral oophorectomy, many women report impaired sexual functioning despite estrogen replacement. We evaluated the effects of transdermal testosterone in women who had impaired sexual function after surgically induced menopause.

METHODS

Seventy-five women, 31 to 56 years old, who had undergone oophorectomy and hysterectomy received conjugated equine estrogens (at least 0.625 mg per day orally) and, in random order, placebo, 150 microg of testosterone, and 300 microg of testosterone per day transdermally for 12 weeks each. Outcome measures included scores on the Brief Index of Sexual Functioning for Women, the Psychological General Well-Being Index, and a sexual-function diary completed over the telephone.

RESULTS

The mean (+/-SD) serum free testosterone concentration increased from 1.2+/-0.8 pg per milliliter (4.2+/-2.8 pmol per liter) during placebo treatment to 3.9+/-2.4 pg per milliliter (13.5+/-8.3 pmol per liter) and 5.9+/-4.8 pg per milliliter (20.5+/-16.6 pmol per liter) during treatment with 150 and 300 microg of testosterone per day, respectively (normal range, 1.3 to 6.8 pg per milliliter [4.5 to 23.6 pmol per liter]). Despite an appreciable placebo response, the higher testosterone dose resulted in further increases in scores for frequency of sexual activity and pleasure-orgasm in the Brief index of Sexual Functioning for Women (P=0.03 for both comparisons with placebo). At the higher dose the percentages of women who had sexual fantasies, masturbated, or engaged in sexual intercourse at least once a week increased two to three times from base line. The positive-well-being, depressed-mood, and composite scores of the Psychological General Well-Being Index also improved at the higher dose (P=0.04, P=0.03, and P=0.04, respectively, for the comparison with placebo), but the scores on the telephone-based diary did not increase significantly.

CONCLUSIONS

In women who have undergone oophorectomy and hysterectomy, transdermal testosterone improves sexual function and psychological well-being.

A biomechanical comparison of Schuhli nuts or cement augmented screws for plating of humeral fractures

Schuhli locking nuts can be used in poor quality cortical bone to enhance fixation stability as an alternative to cement augmented screws. This study compared the fixation strength and stability of plate constructs using Schuhli locking nuts with standard screws and cement augmented screws for fixation of simulated humeral shaft fractures in a test model with osteoporosis. The constructs were tested in axial compression, 4-point bending, and torsion to determine fixation stability. The humeri were cycled in torsion (4.5 Nm) for 1000 cycles to simulate upper extremity use during the early postoperative period and retested for stability. The Schuhli locking nuts and cement augmented screws had significantly greater fixation stability than the standard screws before (range, 6-14 times greater) and after cycling in torsional loading (range, 3-3.6 times greater). Although cement augmented screws and Schuhli augmentation showed increased fixation stability compared with the standard screws in axial and 4-point bending before cycling (range, 1.3-1.4 times greater), this was not significant. Compared with Schuhli fixation, cement augmented screws showed no significant difference in fixation stability in all loading modes before and after cycling. Schuhli locking nuts offer the stability of cement augmentation while avoiding its potential adverse effects on fracture healing with extravasation and thermal necrosis.

Fixation of periprosthetic femoral shaft fractures occurring at the tip of the stem: a biomechanical study of 5 techniques

This study evaluated 5 currently used periprosthetic femoral shaft fracture fixation techniques to determine which technique provided the greatest fixation stability. Periprosthetic fractures in 30 synthetic femurs were fixed with a plate with cables, plate with proximal cables and distal bicortical screws (Ogden concept), plate with proximal unicortical screws and distal bicortical screws, plate with proximal unicortical screws and cables and distal bicortical screws, or 2 allograft cortical strut grafts with cables. These specimens were then tested in 3 physiologic loading modes. The plate constructs with proximal unicortical screws and distal bicortical screws or with proximal unicortical screws, proximal cables, and distal bicortical screws were significantly more stable in axial compression, lateral bending, and torsional loading than the other fixation constructs studied.

A Drosophila ESC-E(Z) protein complex is distinct from other polycomb group complexes and contains covalently modified ESC

The extra sex combs (ESC) and Enhancer of zeste [E(Z)] proteins, members of the Polycomb group (PcG) of transcriptional repressors, interact directly and are coassociated in fly embryos. We report that these two proteins are components of a 600-kDa complex in embryos. Using gel filtration and affinity chromatography, we show that this complex is biochemically distinct from previously described complexes containing the PcG proteins Polyhomeotic, Polycomb, and Sex comb on midleg. In addition, we present evidence that ESC is phosphorylated in vivo and that this modified ESC is preferentially associated in the complex with E(Z). Modified ESC accumulates between 2 and 6 h of embryogenesis, which is the developmental time when esc function is first required. We find that mutations in E(z) reduce the ratio of modified to unmodified ESC in vivo. We have also generated germ line transformants that express ESC proteins bearing site-directed mutations that disrupt ESC-E(Z) binding in vitro. These mutant ESC proteins fail to provide esc function, show reduced levels of modification in vivo, and are still assembled into complexes. Taken together, these results suggest that ESC phosphorylation normally occurs after assembly into ESC-E(Z) complexes and that it contributes to the function or regulation of these complexes. We discuss how biochemically separable ESC-E(Z) and PC-PH complexes might work together to provide PcG repression.

Estrogen and progestin, lipoprotein(a), and the risk of recurrent coronary heart disease events after menopause

CONTEXT

Lipoprotein(a) [Lp(a)] has been identified as an independent risk factor for coronary heart disease (CHD) events. However, few data exist on the clinical importance of Lp(a) lowering for CHD prevention. Hormone therapy with estrogen has been found to lower Lp(a) levels in women.

OBJECTIVE

To determine the relationships among treatment with estrogen and progestin, serum Lp(a) levels, and subsequent CHD events in postmenopausal women.

DESIGN AND SETTING

The Heart and Estrogen/progestin Replacement Study (HERS), a randomized, blinded, placebo-controlled secondary prevention trial conducted from January 1993 through July 1998 with a mean follow-up of 4.1 years at 20 centers.

PARTICIPANTS

A total of 2763 postmenopausal women younger than 80 years with coronary artery disease and an intact uterus. Mean age was 66.7 years.

INTERVENTION

Participants were randomly assigned to receive either conjugated equine estrogens, 0.625 mg, plus medroxyprogesterone acetate, 2.5 mg, in 1 tablet daily (n = 1380), or identical placebo (n = 1383).

MAIN OUTCOME MEASURES

Lipoprotein(a) levels and CHD events (nonfatal myocardial infarction and CHD death).

RESULTS

Increased baseline Lp(a) levels were associated with subsequent CHD events among women in the placebo arm. After multivariate adjustment, women in the second, third, and fourth quartiles of baseline Lp(a) level had relative hazards (RHs) (compared with the first quartile) of 1.01 (95% confidence interval [CI], 0.64-1.59), 1.31 (95% CI, 0.85-2.04), and 1.54 (95% CI, 0.99-2.39), respectively, compared with women in the lowest quartile (P for trend = .03). Treatment with estrogen and progestin reduced mean (SD) Lp(a) levels significantly (-5.8 [15] mg/dL) (-0.20 [0.53] micromol/L) compared with placebo (0.3 [17] mg/dL) (0.01 [0.60] micromol/L) (P<.001). In a randomized subgroup comparison, women with low baseline Lp(a) levels had less benefit from estrogen and progestin than women with high Lp(a) levels; the RH for women assigned to estrogen and progestin compared with placebo were 1.49 (95% CI, 0.97-2.26) in the lowest quartile and 1.05 (95% CI, 0.67-1.65), 0.78 (0.52-1.18), and 0.85 (0.58-1.25) in the second, third, and fourth quartiles, respectively (P for interaction trend = .03).

CONCLUSIONS

Our data suggest that Lp(a) is an independent risk factor for recurrent CHD in postmenopausal women and that treatment with estrogen and progestin lowers Lp(a) levels. Estrogen and progestin therapy appears to have a more favorable effect (relative to placebo) in women with high initial Lp(a) levels than in women with low levels. This apparent interaction needs confirmation in other trials.

Serum ascorbic acid and gallbladder disease prevalence among US adults: the Third National Health and Nutrition Examination Survey (NHANES III)

BACKGROUND

Ascorbic acid-deficient guinea pigs frequently develop gallstones, and ascorbic acid status may also affect the risk of gallbladder disease in humans. To examine the relationship of ascorbic acid, an antioxidant nutrient involved in cholesterol catabolism, to gallbladder disease, we analyzed data collected from a probability sample of US adults.

METHODS

Analyses of data from 7042 women and 6088 men enrolled in the Third National Health and Nutrition Examination Survey, 1988-1994, were performed. Multiple logistic regression models stratified by sex were examined, controlling for the effects of age, race, diet, body mass index, and other potential confounders.

RESULTS

A total of 761 women (11%) and 235 men (4%) reported a history of clinical gallbladder disease (symptomatic gallstones or cholecystectomy). Of the 9650 participants without a history of clinical gallbladder disease or abdominal pain consistent with gallbladder disease, and with valid abdominal ultrasonography, 408 (8%) of 4863 women and 274 (6%) of 4787 men had asymptomatic gallstones. Serum ascorbic acid level was inversely related to prevalence of clinical and asymptomatic gallbladder disease among women, but not among men. Among women, each SD (27 micromol/L) increase in serum ascorbic acid level was independently associated with a 13% lower prevalence of clinical gallbladder disease (P = .006) and asymptomatic gallstones (P = .048).

CONCLUSION

Ascorbic acid, which affects the catabolism of cholesterol to bile acids and, in turn, the development of gallbladder disease in experimental animals, may affect the risk of gallbladder disease among women.

Correlates of high HDL cholesterol among women with coronary heart disease

BACKGROUND

The National Cholesterol Education Program (NCEP) has designated high-density lipoprotein cholesterol (HDL-C) > or =60 mg/dL a "negative" coronary heart disease (CHD) risk factor, but a substantial proportion of coronary events occur among women despite high HDL-C levels.

METHODS AND RESULTS

The objective of this study was to characterize postmenopausal women with prevalent CHD despite HDL-C > or =60 mg/dL and to identify factors that may attenuate the protective effect of high HDL-C. We analyzed baseline data from a randomized, double-blind study of estrogen/progestin replacement therapy in 2763 postmenopausal women <80 years old with CHD. Demographics, CHD risk factors, medications, anthropometrics, and lipid levels were compared among women with low, normal, and high HDL-C by NCEP criteria with and without stratification by use of lipid-lowering medications. Independent correlates of high HDL-C were determined by logistic regression analysis. HDL-C > or =60 mg/dL was present in 20% of participants. Women with high HDL-C were older, better educated, had fewer CHD risk factors, lower triglyceride levels and total cholesterol/HDL-C ratio, and were more likely to report past estrogen and current calcium antagonist, niacin, and statin use. beta-Blocker, diuretic, and fibrate use was less common. Older age, alcohol consumption, niacin, and calcium antagonist use and prior estrogen use were independently associated with high HDL-C, whereas waist-to-hip ratio, smoking, triglyceride level, and beta-blocker and fibrate use were inversely associated (all P <.05).

CONCLUSIONS

High HDL-C, as defined by the NCEP, occurred in 20% of women with CHD in this cohort without a concomitantly higher prevalence of other CHD risk factors. Redefinition of "high" HDL-C levels for women may be warranted.

Functional analysis of repressor binding sites in the iab-2 regulatory region of the abdominal-A homeotic gene

Spatial boundaries of homeotic gene expression are initiated and maintained by two sets of transcriptional repressors: the gap gene products and the Polycomb group proteins. Previously, the Hunchback (HB) protein has been implicated in setting the anterior expression limit of the UBX homeotic protein in parasegment 6. Here we investigate DNA elements and trans-acting repressors that control spatial expression of the Abdominal-A (ABD-A) homeotic protein. Analysis of a 1.7-kb enhancer element [iab-2(1.7)] from the iab-2 regulatory region shows that in contrast to Ubx enhancer elements, both HB and Krüppel (KR) are required to set the ABD-A anterior boundary in parasegment 7. DNase I footprinting and site-directed mutagenesis show that HB and KR are direct regulators of this iab-2 enhancer. The single KR site can be moved to a new location 100 bp away and still maintain repressive activity, whereas relocation by 300 bp abolishes activity. These results suggest that KR repression occurs through a local quenching mechanism. We also show that the gap repressor Giant (GT) initially establishes a posterior expression limit at PS9, which shifts posteriorly after the blastoderm stage. Finally, we show that this iab-2 enhancer contains multiple binding sites for the Polycomb group protein Pleiohomeotic (PHO). These iab-2 PHO sites are required in vivo for chromosome pairing-dependent repression of a mini-white reporter. However, the PHO sites are not sufficient to maintain repression of a homeotic reporter gene anterior to PS7. Full maintenance at late embryonic stages requires additional sequences adjacent to the iab-2(1.7) enhancer.

Differential toxicities of anticancer agents among DNA repair and checkpoint mutants of Saccharomyces cerevisiae

Most cytotoxic anticancer agents damage DNA directly, interfere with DNA metabolism or chromosome segregation, and are particularly toxic in dividing cells. Although a considerable amount of information on the mechanisms of action of these agents is available, the molecular bases for selective tumor cell killing by chemotherapy are largely unknown. Many genetic alterations found in sporadic and hereditary cancers affect functions in DNA repair and cell cycle control and result in sensitivity to DNA damaging agents. We have therefore set out to determine the effects of these cancer mutations on sensitivity or resistance to various chemotherapeutic agents. Because most of the affected genes are well conserved among eukaryotes, we have carried out a comprehensive analysis of a panel of isogenic yeast strains, each defective in a particular DNA repair or cell cycle checkpoint function, for sensitivity to the Food and Drug Administration-approved cytotoxic anticancer agents. Widely different toxicity profiles were observed for 23 agents and X-rays, indicating that the type of DNA repair and cell cycle checkpoint mutations in individual tumors could strongly influence the outcome of a particular chemotherapeutic regimen.

New technique for treatment of unstable distal femur fractures by locked double-plating: case report and biomechanical evaluation

BACKGROUND

A comminuted, intra-articular distal femur fracture was surgically treated by the authors with a locked, double-plating technique because fixation stability could not be initially achieved by using a standard double-plating technique. The purpose of this study was to determine biomechanically whether a locked double-plate construct would enhance fixation stability compared with a nonlocked double-plate construct.

METHODS

Six matched pairs of mildly osteopenic femurs were selected and all had a reproducible intra-articular fracture pattern created. Each pair underwent fixation with either a double-plating construct or a locked, double-plating construct that was randomly assigned. The instrumented femurs were then mechanically tested in several loading modes to determine fixation stability. After initial testing, specimens were cyclically loaded and retested for stability.

RESULTS

The locked, double-plating construct provided significantly greater fixation stability than the standard double-plating construct in precycling and postcycling biomechanical testing.

CONCLUSION

The technique described is particularly applicable for severely comminuted fractures of the distal femur and fractures in osteopenic bone with poor screw purchase. It offers a simple alternative for enhancing fixation stability, which avoids the potential complications of methylmethacrylate-enhanced screw fixation.