Effects of a low-calorie diet associated with weight loss on lipoprotein-associated phospholipase A2 (Lp-PLA2) activity in healthy obese women.

INTRODUCTION: Platelet-activating factor acetylhydrolase (PAF-AH or Lp-PLA(2)) is a Ca(2+)-independent phospholipase A(2) primarily associated in plasma with low density lipoproteins (LDL), especially with small dense LDL (sdLDL) particles. Increased plasma Lp-PLA(2) levels have been associated with increased cardiovascular risk in large clinical trials. AIM: To assess the effects of weight loss on Lp-PLA(2) activity and to examine the association of Lp-PLA(2) activity changes with the alterations of sdLDL, the primary carrier of Lp-PLA(2) in plasma. METHODS: Twenty-eight obese, non-diabetic women participated in a weight reduction program. Anthropometric parameters were assessed and parameters of glucose metabolism, lipid profile, Lp-PLA(2) activity, and LDL phenotype (using a 3% polyacrylamide gel-tube electrophoresis method), were determined at baseline and after 4months of weight loss. RESULTS: A 10% diet-induced weight loss resulted in significant improvement in most parameters of lipid and glucose metabolism. Moreover, Lp-PLA(2) activity was significantly reduced (-10.2%, p<0.01). Mean LDL particle diameter did not change after the weight loss program. The cholesterol levels of very low-density lipoprotein (VLDL) and large-buoyant LDL particles were significantly reduced, but neither the cholesterol levels of sdLDL particles nor the % proportion of the sdLDL-cholesterol over the total LDL-cholesterol were changed after the intervention program. Interestingly, the changes in Lp-PLA(2) activity were correlated with the changes of VLDL-cholesterol (r=0.39, p<0.05), but not with the changes of anthropometric or other lipid variables. CONCLUSIONS: A low-calorie diet associated with weight loss in obese women resulted in the significant reduction of the plasma levels of Lp-PLA(2), the potentially new predictor for incident atherosclerotic disease.

Short-term human chorionic gonadotropin-induced testosterone rise does not modify leptin levels in eugonadal men.

The aim of this study was to monitor serum leptin concentrations after altering the levels of testosterone, by intramuscular administration of human chorionic gonadotropin (hCG), in eugonadal men. A 7-day monitoring of hCG, testosterone and leptin levels was performed after intramuscular administration of a dose of 5000 IU hCG in these men. Thirty fertile men aged 23-38 years were studied. In addition, 30 women aged 18-34 years with normal ovulatory cycles were studied, to verify reports of sexual dimorphism in serum leptin levels. These 60 individuals were divided into four groups, according to their sex and body mass index (BMI) values. In men, blood samples were collected at 09.00, after an overnight fast, for the determination of hCG, testosterone and leptin levels, and, immediately thereafter, a dose of 5000 IU hCG was administered intramuscularly. Further blood samples were collected at 24-h intervals for a period of 7 days for determination of the same hormones. In women, blood samples were collected only once, at 09.00, after an overnight fast between the 3rd and the 6th day of the menstrual cycle, for determination of serum estradiol and leptin levels. Our results showed that the mean value of leptin in thin men and women was significantly lower than that in obese men and women, respectively. The mean value of leptin in thin women was significantly higher than that in obese men. Serum leptin concentrations decreased significantly, 168 h after short-term hCG administration. There was a significant positive correlation between BMI values and serum leptin concentrations, in both men and women. Our results support the view that hCG administration in eugonadal men does not influence serum leptin levels. Moreover, a short-term increase of serum testosterone levels, after one dose of hCG, is not sufficient to affect and modify leptin secretion mechanisms in vivo.

Increased growth factor activity in the aqueous humour of patients with exfoliation syndrome.

BACKGROUND: To investigate the growth factor activity in the aqueous humour of patients with exfoliation syndrome (XFS). METHODS: We collected 154 aqueous humour samples (69 from patients with XFS and 85 from age-matched controls) prior to routine extracapsular cataract surgery. Growth factor activity was investigated using a [3H]thymidine incorporation assay on McCoy cells that assesses DNA synthesis. Albumin concentration was measured by a radio-immunoassay as an index of blood aqueous barrier integrity. N-Acetylglucosaminidase (NAG) activity, a marker of cellular breakdown, was ascertained by a fluorometric method. RESULTS: XFS aqueous samples exhibited significantly higher growth factor activity than to the control samples (P<0.001). Albumin concentration was also higher in the XFS group. NAG activity was similar in the two groups. No relationship between growth factor activity and the other parameters investigated was found. CONCLUSIONS: Increased growth factor activity was detected in the aqueous humour of patients with XFS. This finding may be related to the pathogenesis of XFS.

The significance of PSA/IGF-1 ratio in differentiating benign prostate hyperplasia from prostate cancer.

The importance of insulin-like growth factor 1 (IGF-1) in human serum for the early diagnosis of prostate cancer is controversial. The IGF-1/PSA ratio may improve the performance of prostate specific antigen (PSA) as a prostate cancer marker. IGF-1, along with PSA and free PSA concentration, was measured in the serum of 34 patients with prostate cancer and in 131 patients with benign prostatic hyperplasia (BPH). Although IGF-1 concentration did not significantly differ between the groups, PSA/IGF-1 ratio could clearly distinguish the two groups. In patients with cancer but not in patients with BPH, IGF-1 concentration correlated with PSA and free PSA. The values of PSA and free PSA correlated with each other for both groups. Receivers Operating Curve (ROC) analysis indicated a better sensitivity to specificity ratio for PSA/IGF-1 than for PSA or Free/Total (F/T) PSA.

Leptin levels in maternal and cord serum: relationship with fetal development and placental weight.

OBJECTIVE: To test the hypothesis that the circulating levels of leptin in the maternal and cord serum correlate with the birthweight of the newborns and with the weight of the placenta. METHODS: In a population of 85 women from northern Greece who gave birth to an equal number of full-term infants, we calculated the concentration of leptin in the maternal serum as well as in the cord serum, right after delivery, by using an immunoradiometric assay. The correlation between these values, the maternal BMI before pregnancy and at the time of delivery, the neonatal BMI, Ponderal Index, and the placental weight was studied. RESULTS: Mean maternal leptin showed a statistically significant difference from mean cord serum leptin (14.7 and 7.07 ng/ml, respectively) and was positively correlated to the maternal BMI at the time of delivery (r = 0.3, P = 0.016), but not to neonatal BMI. A positive correlation between the mean cord serum leptin and the BMI of the neonates (r = 0.26, P = 0.031 ) was found. There was no correlation between the maternal BMI at the time of delivery and the neonatal BMI. Similarly, no correlation could be established between the placental weight and the levels of leptin in the maternal or in the cord serum but a positive correlation between placental weight, neonatal BMI and weight, and mothers' BMI was observed. Finally, although a noteworthy difference between the mean leptin levels of neonates of two different sexes was observed (male 5.9 ng/ml, female 7.8 ng/ml), that difference never reached a statistically significant level. CONCLUSIONS: The maternal leptin level could not be used as a reliable marker of fetal growth but a positive correlation between cord serum leptin and fetus growth is suggested.

Leptin concentrations during oral glucose tolerance test (OGTT) in obese and normal weight women.

OBJECTIVE: To examine possible changes of leptin concentrations after the acute administration of glucose orally (OGTT). DESIGN: Seventy-five grams of glucose were administered per os in one group of obese and normal weight individuals and concentrations of glucose, insulin and leptin were measured at 0, 30, 60, 90 and 120 min. In an age matched control group of individuals with similar BMI water was given and leptin concentrations were measured before and after 30, 60, 90 and 120 min. SUBJECTS: Twenty-seven obese women aged 34+/-1.57 y with BMI 37.1+/-0.8 kg/m2 and 16 normal weight women, aged 32+/-1.13 y with BMI 23.6+/-0.3 kg/m2 formed the experimental group, while 10 obese and 10 normal weight females with similar age and BMI were used as controls. MEASUREMENTS: Weight, height, BMI, body fat, glucose, insulin and leptin at baseline and during OGTT. Variations of the above parameters were calculated from the area under the curve (AUC). RESULTS: Fasting leptin concentrations and AUC were higher in obese than in normal weight women. In obese women, leptin increased significantly in comparison to its basal concentrations 30 and 60 min after the glucose loading. Insulin was also increased, as expected. No correlation was found between insulin and leptin concentrations after glucose loading. Basal concentrations of leptin did not correlate with those of glucose and insulin. No changes in leptin concentrations were found in normal weight women after OGTT. However, a significant positive correlation was found between insulin and basal leptin. Finally, leptin concentrations did not change in obese and normal weight controls after water administration. CONCLUSION: A significant increase in leptin concentrations was found 30 and 60 min after glucose loading in obese individuals. No such increase was found in normal-weight women.

Possible role of transferrin in exfoliation syndrome.

Protein concentration was measured in 30 exfoliation syndrome samples and 22 age matched controls. Exfoliation samples contained significantly more protein than controls. We also analyzed by SDS gel electrophoresis 32 aqueous samples, 12 with exfoliation syndrome and 20 age matched controls. A novel finding in all samples was a double band with 77 kDa and 78 kDa. These bands probably represent transferrin isoforms, with different carbohydrate side chains. Exfoliation samples contained a lower amount of the 77 kDa band in comparison to the amount of the 78 kDa band. The lower relative concentration of this transferrin isoform in the exfoliation syndrome samples may be indicative of its possible involvement in the disorder. A different oligosaccharide side chain in combination with a relatively high protein concentration may lead to sedimentation of this molecule. On the other hand, laminin, a glycoprotein detected previously in exfoliation material, contains similar oligosaccharide side chains with transferrin. Thus the oligosaccharide side chains of both proteins may be influenced by the same factors.

In vivo binding of the radioiodinated peptide YIGSR on B16 melanoma cells.

It has been reported that metastatic melanoma cell lines selectively bind in vitro with the synthetic laminin pentapeptide tyrosyl-isoleucyl-glycyl-seryl-arginine (YIGSR). The aim of this study was to investigate whether the same peptide can bind on melanoma cells in vivo as well. Iodine-125-labeled YIGSR was administered to B16 melanoma-bearing animals. Microscopic autoradiography of tumor and organ sections taken 24 h after peptide administration showed that the peptide did accumulate on the surface of certain tumor cells. The peptide binding cells were frequent in metastatic sites and tumors grown for 24 days and rare in tumors grown for 10 days. A similarly radiolabeled control pentapeptide (peptide DRLKY) did not bind to any tumor cell. It is suggested that the YIGSR binding tumor cells may represent a distinct melanoma cell population with a high metastatic potential.

Detection of a high molecular weight heparin binding acidic growth factor in human placenta.

A heparin binding fibroblast growth factor with a molecular weight of approximately 45 kDa has been detected in human placenta. The protein was extracted from placenta and purified by a combination of ammonium sulfate precipitation, DE-52 anion exchange chromatography, G100 gel exclusion and heparin sepharose affinity chromatography. The molecule was shown to be monomeric after treatment with beta-mercaptoethanol, and had an acidic isoelectric point. The properties of the polypeptide described in this paper (45 kDa, Pi 4-5, monomeric, heparin binding fibroblast growth factor), suggest that it may represent an as yet undescribed growth factor.

Effects of sodium carbonate on milk yield, milk composition, and blood components of dairy cows in early lactation.

Eighteen multiparous Friesian cows were paired according to lactation number and expected calving date and assigned randomly to one of two diets in a crossover design experiment to study effects of sodium carbonate on milk yield, milk composition, blood metabolites plus Na, and K in early lactation. Diets were concentrate containing either 0 or 1.2% sodium carbonate (as fed) for ad libitum intake plus 7.0 kg of wet brewers grains and 5.5 kg of long-stemmed alfalfa hay per cow daily. Dry matter intake, milk yield, milk protein percentage and yield, and percentages of milk lactose and milk SNF were not significantly affected. Compared with the control diet, the sodium carbonate treatment increased milk fat percentage (3.98 vs. 3.53%) and yield (1.23 vs. 1.07 kg/d), 4% FCM yield (30.9 vs. 28.2 kg/d) and milk total solids (12.47 vs. 12.04%). No significant differences were observed in blood plasma concentrations of glucose, CP, urea, acetate, beta-hydroxybutyrate, triglycerides, FFA, Na, or K when sodium carbonate was added to diets for early lactation cows.

Cellular and tissue distribution of a single-strand-specific nuclease.

1. Specific antibodies which were raised against a single-strand-specific nuclease isolated from rat liver microsomes were used for characterizing this enzyme and determining its cellular and tissue distribution. 2. The single-strand-specific nuclease does not show any homology with other known nucleolytic enzymes. 3. It is mainly localized in microsomes and cytosol; traces of it are also found in nuclei, but it could not be detected in mitochondria. 4. Using the same specific antibodies we attempted to detect this nuclease in some other tissues which exhibit high metabolic rates, namely kidneys, heart and spleen. 5. Thus, with the aid of immunological techniques we were able to determine that at least part of the total poly(U) nucleolytic activity observed in kidney and heart is due to a nuclease immunologically identical to the enzyme under study. Kidneys were the best source for this enzyme.

Single-strand-specific nuclease from rat liver endoplasmic reticulum: characterization and mode of action.

1. The characteristics and mode of action of a single-strand-specific nuclease isolated from rat liver endoplasmic reticulum are investigated with respect to its DNA and RNA substrates. 2. The RNase activity of the enzyme is slightly influenced by the presence of divalent cations but the DNase activity is enhanced by divalent cations particularly Mn2+. 3. Activity is partially inhibited by the presence of EGTA; this effect is reversed most efficiently by the addition of Mn2+. 4. The enzyme exhibits small pH dependence between pH 6-9 and maximum activity is observed at pH 7-7.5 for both DNase and RNase activities. 5. Sulfhydryl group reagents do not affect its action but histidyl group reagents exert a small but definite effect. 6. The enzyme degrades DNA and RNA endonucleolytically producing fragments which possess 3'-OH and 5'-phosphate termini. 7. Monomers are not produced even after prolonged degradation. 8. The end product of poly(U)degradation ranges between two and four building blocks but the DNA product is longer probably due to considerable percentage of secondary structure.

The DNase activity of an endoplasmic reticulum nuclease and its effect on DNA synthesis in vitro.

An endoplasmic reticulum nuclease which was isolated previously in this laboratory from rat liver ( Kouidou et al. (1981) Eur.J. Bioch . 120, 9-14) was found to degrade linear and circular single stranded DNA but not double stranded DNA. The DNA fragments resulting from this cleavage were longer than 20 nucleotides. In addition the nuclease was found to improve the efficiency of DNA template used by DNA polymerase I in DNA synthesis in vitro. The results were the same whether incubation of the template with the nuclease was prior to addition of DNA polymerase I or simultaneously with polymerization. When nuclease was added after the completion of polymerization by DNA polymerase I it was ineffective unless the product was denatured. These data further corroborate the observation that double stranded DNA is not cleaved by this enzyme.

Endoplasmic reticulum nuclease. Purification and specificity.

An endonuclease, which was originally identified for its RNA polymerase inhibitory activity, was isolated from rat liver endoplasmic reticulum. The enzyme yields on gel chromatography four active fractions of different molecular weights (Mr 5.3 X 10(4), 9 X 10(4), 1.55 X 10(5) and Sephacryl S-200 fraction at V0). Each fraction contains polypeptide chains which give a single band on sodium dodecylsulphate electrophoresis (Mr 5.4 X 10(4). This indicates that the enzyme is an oligomeric protein and each of its subunits exhibits the same or very similar molecular weights. Deoxyribonucleoside and ribonucleoside triphosphates can bind to the endoplasmic reticulum nuclease. Binding is enhanced in the presence of divalent cations particularly Mg2+. The enzyme exhibits mainly RNase activity but can also degrade denatured DNA and DNA . RNA hybrids which contain breaks in one of the two strands. Poly(A) and mainly poly(U) are most susceptible to its nucleolytic activity whereas poly(C) is completely resistant.