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Idris Mohamed and James K Yeh

Long-term aromatase inhibitor use causes bone loss and increases fracture risk secondary to induced estrogen deficiency. We postulated that alfacalcidol (A; vitamin D3 analog) could help prevent the Letrozole (L)-induced mineral bone loss. Fifty intact 1-month-old female rats were randomly divided into basal group; age-matched control group (AMC); L group: oral administration of 2 mg/kg per day; A group: oral administration of 0.1 μg/kg per day; and group L+A for a period of 8 weeks. Eight-week administration of L resulted in a significant increase in body weight, bone length, bone area, bone formation, and bone resorption activities when compared with the AMC group. However, the bone mass and bone mineral density (BMD) were significantly lower than the AMC group. Serum levels of testosterone, LH, FSH, and IGF-1 were significantly higher and serum estrone and estradiol were lower along with a decrease in ovary+uterus horn weight, when compared with the AMC groups. None of those parameters were affected by A treatment, except suppression of bone resorption activities and increased trabecular bone mass and femoral BMD, when compared with the AMC group. Results of L+A combined intervention showed that bone length, bone area, and bone formation activities were higher than the AMC group, and the bone resorption activities were lower and BMD was significantly higher than that of the L group. This study demonstrates that the combined intervention of L and A not only enhances bone growth, but also increases bone density, and the effects of L and A are independent and additive.

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SW Lockley, DJ Skene, K James, K Thapan, J Wright, and J Arendt

Although melatonin treatment has been shown to phase shift human circadian rhythms, it still remains ambiguous as to whether exogenous melatonin can entrain a free-running circadian system. We have studied seven blind male subjects with no light perception who exhibited free-running urinary 6-sulphatoxymelatonin (aMT6s) and cortisol rhythms. In a single-blind design, five subjects received placebo or 5 mg melatonin p.o. daily at 2100 h for a full circadian cycle (35-71 days). The remaining two subjects also received melatonin (35-62 days) but not placebo. Urinary aMT6s and cortisol (n=7) and core body temperature (n=1) were used as phase markers to assess the effects of melatonin on the During melatonin treatment, four of the seven free-running subjects exhibited a shortening of their cortisol circadian period (tau). Three of these had taus which were statistically indistinguishable from entrainment. In contrast, the remaining three subjects continued to free-run during the melatonin treatment at a similar tau as prior to and following treatment. The efficacy of melatonin to entrain the free-running cortisol rhythms appeared to be dependent on the circadian phase at which the melatonin treatment commenced. These results show for the first time that daily melatonin administration can entrain free-running circadian rhythms in some blind subjects assessed using reliable physiological markers of the circadian system.

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James K Yeh, Jodi F Evans, Qing-Tian Niu, and John F Aloia

Clinical and in vitro data suggest a link between the elevation of the melanocortin peptide, ACTH, and longitudinal growth. Overproduction of ACTH in familial glucocorticoid deficiency (FGD) is associated with increased growth and ACTH increases the differentiation of chondrocytes along the endochondral pathway in vitro. Using the leptin-deficient obese (ob/ob) mouse along with lean control littermates (n = 9–10), we investigated the effects of adrenalectomy (ADX)-induced elevated ACTH with and without peripheral administration of the MC3-R-specific agonist, γ2-melanocyte stimulating hormone (γ2-MSH), on longitudinal growth. Naso-anal and tibial growth were measured together with growth plate parameters; both total and zonal heights together with the proliferative index. Data were analyzed using two-way ANOVA with post hoc comparisons made using the Bonferroni correction. ADX significantly increased naso-anal length in lean mice and ADX plus γ2-MSH administration significantly increased naso-anal length above ADX alone in ob/ob mice. γ2-MSH administration to ADX lean and ob/ob mice significantly increased tibial length. In ob/ob mice, these changes occurred in the context of reduced food intake. Analysis of total and zonal growth plate heights suggest an increase in hypertrophic differentiation and an overall increase in growth plate turnover in ADX lean and ob/ob mice. These in vivo data show that ADX enhances linear growth and the results of γ2-MSH treatment suggest that the melanocortin system plays a role in linear growth.

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S Y James, A G Mackay, L Binderup, and K W Colston

Abstract

The anti-proliferative effects of the novel vitamin D analogue, EB1089, were assessed in the hormone-dependent breast cancer cell line, MCF-7, in vitro. In the present study, EB1089 was shown to be at least an order of magnitude more potent at inhibiting MCF-7 cell proliferation than the native hormone, lα,25-dihydroxyvitamin D3 (1,25(OH)2D3). Treatment of MCF-7 cell cultures with combinations of oestradiol and EB1089 ranging from 5 × 10−11 m to 5 × 10−9 m revealed the ability of EB1089 to suppress the mitogenic effects of oestradiol in these cells dose-dependently, as determined by [3H]thymidine incorporation and cell counts. EB1089 also exhibited a significant time- and dose-dependent decrease in MCF-7 oestrogen receptor (ER) concentration, as assessed by ligand binding assay. A fourfold reduction of ER levels by 5 × 10−9 m EB1089 relative to control ER levels was observed, whilst 5 × 10−9 m 1,25(OH)2D3 produced a significant but less dramatic decrease in ER levels. In addition, reduction of ER protein in EB1089-treated cell cultures was also demonstrated using an oestrogen receptor enzyme immunoassay.

The interaction of EB1089 and anti-oestrogens on the oestradiol-stimulated growth of MCF-7 cells was investigated. The treatment of cell cultures with 5 × 10−10 m EB1089 in combination with the pure anti-oestrogen, ICI 182,780 (5 × 10−8 m), and in the presence of between 5 × 10−10 m and 5 × 10−9 m oestradiol, produced an augmented inhibition of MCF-7 cell proliferation compared with the actions of either compound alone.

This study demonstrates that EB1089 is a potent anti-proliferative agent of breast cancer cells in vitro, and that part of its mechanism to inhibit cell growth may involve the modulation of ER expression, such that the responsiveness of cells to the growth-stimulatory effects of oestradiol is diminished. This new vitamin D analogue has potential in the treatment of breast cancer.

Journal of Endocrinology (1994) 141, 555–563

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K. FOTHERBY, FRANCES JAMES, SORAYA KAMYAB, A. I. KLOPPER, and G. R. WILSON

SUMMARY

The excretion of pregnanediol, pregnanetriol and the 6-oxygenated metabolites of progesterone by fifteen women has been measured throughout pregnancy. During the first trimester the level of excretion of the 6-oxygenated metabolites varied from 0·4 to 2·2 mg./day and at the end of pregnancy the range was from 3·5 to 11·6 mg./day. During the last 6 weeks of pregnancy, pregnanediol excretion was relatively constant, whereas in seven of the patients the excretion of the 6-oxygenated metabolites continued to increase. Except at the end of pregnancy there was a close correlation between the 6-oxygenated metabolites and pregnanediol excretion. The results suggest that the 6-oxygenated metabolites and pregnanediol have the same precursor and that little, if any, of a 6-oxygenated progesterone is secreted during pregnancy.

There appears to be little increase in pregnanetriol excretion during pregnancy; six of the subjects showed a significantly higher excretion in the third trimester compared with the first trimester of pregnancy, but the values were not outside the normal range for non-pregnant subjects. The specificity of the method of Fotherby & Love (1960) for the estimation of pregnanetriol was examined when applied to pregnancy urine.

Between 1·1 and 2·4 % of administered progesterone was excreted as the 6-oxygenated metabolites. In only one of five subjects was pregnanetriol excretion increased after progesterone administration.

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Marleen B Dommerholt, Derek A Dionne, Daria F Hutchinson, Janine K Kruit, and James D Johnson

Caloric restriction (CR) is the only environmental intervention with robust evidence that it extends lifespan and delays the symptoms of aging, but its mechanisms are incompletely understood. Based on the prolonged longevity of knockout models, it was hypothesized that the insulin-IGF pathway could be a target for developing a CR mimic. This study aimed to test whether CR has additive effects on glucose homeostasis and beta-cell function in mice with reduced insulin gene dosage. To study models with a range of basal insulin levels, wild-type C57BL/6J and mice on an Ins2 / background, were put on 8 weeks of 40% CR at various ages. Both male and female mice rapidly lost weight due to a reduced WAT mass. Glucose tolerance was improved and fasting glucose levels were reduced by CR in both wild type and 45- and 70-week-old Ins2 / mice. The effects of CR and reduced insulin on glucose tolerance were non-additive in 20-week-old mice. Interestingly, mice on CR generally exhibited an inability to further depress blood glucose after insulin injection, pointing to possible alterations in insulin sensitivity. In conclusion, our results demonstrate that CR can cause weight loss in the context of reduced insulin production, but that CR-improved glucose homeostasis does not occur near the ‘insulin floor’ in young mice. Collectively, these data shed further light on the relationships between CR, insulin and glucose homeostasis.

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Melissa F Jackson, Dung Luong, Dor Dor Vang, Dilip K Garikipati, James B Stanton, O Lynne Nelson, and Buel D Rodgers

The natural aging process results in the physiological decline of multiple tissues and organ systems. Changes commonly occur with middle age and include decreased skeletal muscle mass, bone mineral density, cardiac output, and insulin sensitivity, and increased adiposity, all of which can contribute to the onset of sarcopenia, osteoporosis, heart failure, or type 2 diabetes. Recent studies suggest that myostatin may influence many of these systems. We therefore sought to determine whether they are affected by aging, especially in ‘middle-aged’ Mstn −/− mice (12–20 months old (m.o.)). Although body weights were similar in wild-type (WT) and Mstn −/− mice, lean fat-free mass and skeletal muscles composed of predominantly type I, II, and mixed fibers were significantly heavier in Mstn −/− mice. These differences were accompanied by lower total adiposity, especially in female mice, white and brown fat pad weights, and adipocyte size. Hearts were heavier in Mstn −/− mice across a large age range (3–24 m.o.) and exhibited signs of dilated cardiomyopathy at rest, which include lower strain measurements compared with WT myocardium. However, Mstn −/− mice responded better to isoproterenol stress tests with greater increases in fractional shortening and ejection fraction—differences that were again more apparent in females and which are consistent with physiological cardiac hypertrophy. Spleens and kidneys were also smaller, although histologically normal, in Mstn −/− mice. These data together suggest that attenuating myostatin could potentially prevent or possibly treat pathological conditions that develop with age. Additional studies are nevertheless needed to definitively assess potential risks to cardiac function.

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David R Broom, Masashi Miyashita, Lucy K Wasse, Richard Pulsford, James A King, Alice E Thackray, and David J Stensel

Acute exercise transiently suppresses the orexigenic gut hormone acylated ghrelin, but the extent to which exercise intensity and duration determine this response is not fully understood. The effects of manipulating exercise intensity and duration on acylated ghrelin concentrations and hunger were examined in two experiments. In experiment one, nine healthy males completed three, 4-h conditions (control, moderate-intensity running (MOD) and vigorous-intensity running (VIG)), with an energy expenditure of ~2.5 MJ induced in both MOD (55-min running at 52% peak oxygen uptake (V.O2peak)) and VIG (36-min running at 75% V.O2peak). In experiment two, nine healthy males completed three, 9-h conditions (control, 45-min running (EX45) and 90-min running (EX90)). Exercise was performed at 70% V.O2peak. In both experiments, participants consumed standardised meals, and acylated ghrelin concentrations and hunger were quantified at predetermined intervals. In experiment one, delta acylated ghrelin concentrations were lower than control in MOD (ES = 0.44, P = 0.01) and VIG (ES = 0.98, P < 0.001); VIG was lower than MOD (ES = 0.54, P = 0.003). Hunger ratings were similar across the conditions (P = 0.35). In experiment two, delta acylated ghrelin concentrations were lower than control in EX45 (ES = 0.77, P < 0.001) and EX90 (ES = 0.68, P < 0.001); EX45 and EX90 were similar (ES = 0.09, P = 0.55). Hunger ratings were lower than control in EX45 (ES = 0.20, P = 0.01) and EX90 (ES = 0.27, P = 0.001); EX45 and EX90 were similar (ES = 0.07, P = 0.34). Hunger and delta acylated ghrelin concentrations remained suppressed at 1.5 h in EX90 but not EX45. In conclusion, exercise intensity, and to a lesser extent duration, are determinants of the acylated ghrelin response to acute exercise.

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Elizabeth K Fletcher, Monica Kanki, James Morgan, David W Ray, Lea M Delbridge, Peter J Fuller, Colin D Clyne, and Morag J Young

We previously identified a critical pathogenic role for mineralocorticoid receptor (MR) activation in cardiomyocytes that included a potential interaction between the MR and the molecular circadian clock. While glucocorticoid regulation of the circadian clock is undisputed, studies on MR interactions with circadian clock signalling are limited. We hypothesised that the MR influences cardiac circadian clock signalling, and vice versa. Aldosterone or corticosterone (10 nM) regulated Cry1, Per1, Per2 and ReverbA (Nr1d1) gene expression patterns in H9c2 cells over 24 h. MR-dependent regulation of circadian gene promoters containing GREs and E-box sequences was established for CLOCK, Bmal, CRY1 and CRY2, PER1 and PER2 and transcriptional activators CLOCK and Bmal modulated MR-dependent transcription of a subset of these promoters. We also demonstrated differential regulation of MR target gene expression in hearts of mice 4 h after administration of aldosterone at 08:00 h vs 20:00 h. Our data support MR regulation of a subset of circadian genes, with endogenous circadian transcription factors CLOCK and BMAL modulating the response. This unsuspected relationship links MR in the heart to circadian rhythmicity at the molecular level and has important implications for the biology of MR signalling in response to aldosterone as well as cortisol. These data are consistent with MR signalling in the brain where, like the heart, it preferentially responds to cortisol. Given the undisputed requirement for diurnal cortisol release in the entrainment of peripheral clocks, the present study highlights the MR as an important mechanism for transducing the circadian actions of cortisol in addition to glucocorticoid receptor (GR) in the heart.

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Vincent Ricchiuti, Christine G Lian, Eveline M Oestreicher, Loc Tran, James R Stone, Tham Yao, Ellen W Seely, Gordon H Williams, and Gail K Adler

We tested the hypothesis that 17β-estradiol (E2) has dual effects on the heart, increasing levels of proteins thought to have beneficial cardiovascular effects (e.g. endothelial nitric oxide (NO) synthase (eNOS)) as well as those thought to have detrimental cardiovascular effects (e.g. type 1 angiotensin II (AngII) receptor (AT1R)). Ovariectomized Wistar rats consuming a high-sodium diet received one of four treatments (n=7 per group): group 1, placebo pellets; group 2, E2 (0.5 mg/pellet, 21-day release); group 3, NOS inhibitor, N ω-nitro-l-arginine-methyl-ester (l-NAME; 40 mg/kg per day for 14 days) plus Ang II (0.225 mg/kg per day on days 11–14); group 4, E2 plus l-NAME/Ang II. E2 increased cardiac levels of estrogen receptors ESR1 and ESR2, an ESR-associated membrane protein caveolin-3, eNOS, and phosphorylated (p)eNOS, thus, exerting potentially beneficial cardiovascular effects on NO. However, E2 also increased cardiac levels of proteins associated with cardiovascular injury and inflammation including, AT1R, protein kinase C delta (PRKCD), phosphorylated PRKC, and phosphorylated extracellular signal regulated kinase (pMAPK)3/1, plasminogen activator inhibitor-1 (PAI-1), osteopontin and ED-1, a monocyte/macrophage-specific protein. E2 treatment led to similar protein changes in the hearts of l-NAME/Ang II-treated rats except that the increase in peNOS was prevented, and l-NAME/Ang II and E2 had additive effects in increasing cardiac PRKCD and PAI-1. Thus, the highest levels of cardiac PAI-1 and PRKCD occurred in l-NAME/Ang II-treated rats receiving E2. In summary, E2 treatment increased cardiac expression of AT1R as well as the expression of pro-inflammatory and prothrombotic factors.