Enzyme-triggered CO-releasing molecules (ET-CORMs): evaluation of biological activity in relation to their structure.

Acyloxydiene-Fe(CO)3 complexes act as enzyme-triggered CO-releasing molecules (ET-CORMs) and can deliver CO intracellularly via esterase-mediated hydrolysis. The protective properties of structurally different ET-CORMs on hypothermic preservation damage and their ability to inhibit VCAM-1 expression were tested on cultured human umbilical vein endothelial cells (HUVEC) and renal proximal tubular epithelial cells (PTEC) using a structure-activity approach. Cytotoxicity of ET-CORMs, protection against hypothermic preservation damage, and inhibition of VCAM-1 expression were assessed. Cytotoxicity of 2-cyclohexenone and 1,3-cyclohexanedione-derived ET-CORMs was more pronounced in HUVEC compared to PTEC and was dependent on the position and type of the ester (acyloxy) substituent(s) (acetate>pivalate>palmitate). Protection against hypothermic preservation injury was only observed for 2-cyclohexenone-derived ET-CORMs and was not mediated by the ET-CORM decomposition product 2-cyclohexenone itself. Structural requirements for protection by these ET-CORMs were different for HUVEC and PTEC. Protection was affected by the nature of the ester functionality in both cell lines. VCAM-1 expression was inhibited by both 2-cyclohexenone- and 1,3-cyclohexanedione-derived ET-CORMs. 2-Cyclohexenone, but not 1,3-cyclohexanedione, also inhibited VCAM-1 expression. We demonstrate that structural alterations of ET-CORMs significantly affect their biological activity. Our data also indicate that different ET-CORMs behave differently in various cell types (epithelial vs endothelial). These findings warrant further studies not only to elucidate the structure-activity relation of ET-CORMs in mechanistic terms but also to assess if structural optimization will yield ET-CORMs with restricted cell specificity.

Body composition and resting energy expenditure in humans: role of fat, fat-free mass and extracellular fluid.

OBJECTIVE: The objective of this study was to determine whether there are independent effects of extracellular fluid volume (ECF) and fat mass (FM) on resting energy expenditure (REE) relative to fat-free mass (FFM) in adult men and women. METHODS: Multiple linear regression analysis was used to relate REE, as determined by indirect calorimetry, to FFM and FM (measured using dual energy X-ray absorptiometry) and ECF (measured using bromide space and/or the radiosulfate washout space) in 153 women and 100 men with varying amounts of body fat. RESULTS: REE correlated significantly with FFM and FM in women (r=0.65 and r=0.63, both P<0.001) and men (r=0.62 and r=0.48, both P<0.001, FFM and FM, respectively). In a multiple linear regression analysis FFM, FM and age significantly contributed to the ability to predict REE in both genders. The models that were derived were not significantly different between women and men. In women the contribution to REE from FM was easier to detect when FM was greater. Adjustment of FFM for ECF did not improve the relationship between FFM and REE. CONCLUSIONS: FFM, FM and age are significant, independent predictors of REE in both men and women. Adjustment of FFM for ECF does not improve the ability of FFM to predict REE, which suggests that ECF is a highly integrated component of FFM in healthy adults. Expressing REE relative to FFM alone will introduce errors when lean and obese populations are compared.

Meal fatty acid uptake in human adipose tissue: technical and experimental design issues.

The adipose tissue uptake of dietary fat has been studied using fatty acid radiotracers incorporated into a meal, followed by adipose tissue biopsies. A number of experimental design issues, including the use of isotopic tracers to measure meal fatty acid oxidation and plasma appearance of tracer, as well as the heterogeneity of adipose tissue fatty acid uptake, have been addressed. We examined these questions in a study of 24 volunteers (12 men and 12 women) who consumed a meal containing [(3)H]triolein and [(14)C]triolein. Slight differences in the purity of [(3)H]triolein vs. [(14)C]triolein were found, which could affect the apparent adipose tissue uptake of meal fatty acids. The adipose tissue triglyceride specific activity from bilateral biopsy sites agreed well, implying that a unilateral biopsy is satisfactory for measuring tracer uptake. Meal fatty acid oxidation measured using [(3)H]triolein and [(14)C]triolein was well correlated (r = 0.79, P < 0.0001). The peak tracer appearance in plasma chylomicrons occurred 1 h after the ingestion of a second, unlabeled meal. Our findings have implications for the experimental design of future meal fatty acid tracer/adipose tissue biopsy studies.

Meal fatty acid uptake in adipose tissue: gender effects in nonobese humans.

We tested for gender differences in dietary fatty acid metabolism in 12 nonobese men and 12 nonobese women using the meal fatty acid tracer/adipose tissue biopsy study design. In addition to determining body composition, measurements of regional adipose tissue lipoprotein lipase activity, blood flow, and fat cell size were performed to place the meal fatty acid kinetic studies in perspective. Twenty-four hours after ingesting the test meal, the concentration of meal fatty acids was greater (P < 0.05) in abdominal subcutaneous than in thigh adipose tissue in both men (0. 61 +/- 0.12 vs. 0.45 +/- 0.09 mg/g) and women (0.59 +/- 0.10 vs. 0. 43 +/- 0.05) but was not different between men and women. A greater percentage of dietary fat was stored in subcutaneous adipose tissue in women than in men (38 +/- 3 vs. 24 +/- 3%, respectively, P < 0. 05), and a greater portion of meal fatty acid disposal was unaccounted for in men. Significant gender differences in regional adipose tissue blood flow after meal ingestion were noted; the differences were in the direction that could support greater nutrient storage in lower body fat in women.

Metabolic acidosis and thiamine deficiency.

We describe a 19-year-old patient who was receiving home parenteral nutrition in whom lactic acidosis developed. A review of her home parenteral nutrition formula revealed the absence of multivitamins, most significantly thiamine. After thiamine administration, the acidosis resolved, and the patient experienced pronounced clinical improvement. Clinicians must be aware that thiamine is essential for normal glucose metabolism and that thiamine deficiency can lead to lactic acidosis. Thiamine deficiency should be included in the differential diagnosis of lactic acidosis. The recent shortage of intravenous multivitamin preparations has led to documented cases of lactic acidosis as a result of thiamine deficiency, and a previous shortage led to several deaths due to lactic acidosis as a consequence of thiamine deficiency. All patients receiving parenteral nutrition must also receive adequate vitamin supplementation.

Evaluation and management of amenorrhea.

All women who enter menopause experience amenorrhea unless they receive hormone replacement therapy. In younger women, amenorrhea unrelated to pregnancy and lactation can be a distressing symptom. In addition to its psychologic morbidity, amenorrhea may be the manifesting feature of a wide array of anatomic and endocrine abnormalities. Amenorrhea results in impaired fertility. When estrogen levels are low, changes in mineral, glucose, and fat metabolism accompany amenorrhea. These metabolic changes affect bone and cardiovascular health, increasing the risk of osteoporosis and coronary heart disease in later life. Amenorrhea with hyperandrogenism, most commonly caused by the polycystic ovarian syndrome, may cause endometrial hyperplasia and increases the risk of endometrial adenocarcinoma. Because of the broad differential diagnosis of amenorrhea, establishing an accurate diagnosis can prove challenging. In this article, we outline one approach to the assessment of patients with amenorrhea and to the management of its common causes and consequences.

Nifedipine, but not verapamil, acutely elevates parathyroid hormone levels in premenopausal women.

BACKGROUND: Calcium channel antagonist therapy in humans has been associated with changes in anterior pituitary, thyroid and adrenal hormone secretion. Human studies assessing effects of calcium channel antagonists on calciotropic hormones have been few and typically involved small numbers of subjects studied for short periods of time. Few of these previously published studies have included women. The endocrine effects of calcium channel antagonists in women have become increasingly important as more women are taking these agents for diseases such as hypertension, angina, Raynaud's phenomenon and migraine. OBJECTIVE: To assess both acute and chronic effects of calcium channel antagonists on calciotropic hormones in women. DESIGN: A four-week prospective, randomized trial. SUBJECTS: Twenty-nine premenopausal women, randomly assigned to receive either 240 mg of sustained release verapamil or 30 mg of sustained release nifedipine daily. LABORATORY END-POINTS: Total and ionized serum calcium, phosphate, creatinine, parathyroid hormone (PTH), parathyroid hormone-related protein (PTHrP) and calcitonin, measured at baseline, after 24 hours, and 28 days of treatment. RESULTS: Total and ionized calcium, phosphate, creatinine, PTHrP and calcitonin levels were not altered significantly after 24 hours or 28 days in any of the subjects, when compared to baseline. There were no significant differences in PTH levels after 24 hours or 28 days of verapamil treatment. There was a significant increase in serum PTH levels after 24 hours of nifedipine therapy; however, these differences were not evident after 28 days of therapy. CONCLUSIONS: The short-term administration of nifedipine results in increased release of parathyroid hormone; however, long-term administration has no significant effect on the concentrations of calciotropic hormones.

Detection of subtle aluminum-related renal osteodystrophy.

We compared the sensitivity of aurin tricarboxylic acid (ATA) or acid solochrome azurine (ASA) for detecting bone aluminum histochemically in 87 biopsy specimens obtained between 1983 and 1987 from 84 patients receiving dialysis therapy. Two consecutive biopsy sections were stained, one with ATA and the other with ASA, and then interpreted independently by two experienced observers. Three groups were established: group 1 (N = 61) had positive results of both ATA and ASA staining, group 2 (N = 25) had negative ATA but positive ASA sections, and group 3 (N = 1) had negative results of both ATA and ASA. No significant differences existed between groups 1 and 2 for age of the patients or serum calcium or immunoreactive parathyroid hormone levels. Patients in group 1 had significantly higher bone aluminium content (110 versus 61 micrograms/g dry ash weight), higher serum aluminum levels (151 versus 26 ng/ml), and longer duration of dialysis (85 versus 30 months) than did patients in group 2. Bone biopsy diagnoses (group 1 versus group 2) included low-turnover bone disease, 8 versus 7; osteomalacia, 26 versus 0; mixed uremic bone disease, 10 versus 1; hyperparathyroidism, 12 versus 14; and mild uremic bone disease, 5 versus 4. On the basis of ATA staining, 7 of 15 patients with low-turnover and 1 of 11 patients with mixed uremic bone disease may have been incorrectly diagnosed as having non-aluminum-related bone disorders. The levels of bone and serum aluminum were lower in group 2 than in group 1 but still much higher than normal.(ABSTRACT TRUNCATED AT 250 WORDS)