Transformation of amyloid-like fibers, formed from an elastin-based biopolymer, into a hydrogel: an X-ray photoelectron spectroscopy and atomic force microscopy study.

Previous studies have revealed the propensity of elastin-based biopolymers to form amyloid-like fibers when dissolved in water. These are of interest when considered as "ancestral units" of elastin in which they represent the simplest sequences in the hydrophobic regions of the general type XxxGlyGlyZzzGly (Xxx, Zzz = Val, Leu). We normally refer to these biopolymers based on elastin or related to elastin units as "elastin-like polypeptides". The requirement of water for the formation of amyloids seems quite interesting and deserves investigation, the water representing the natural transport medium in human cells. As a matter of fact, the "natural" supramolecular organization of elastin is in the form of beaded-string-like filaments and not in the form of amyloids whose "in vivo" deposition is associated with some important human diseases. Our work is directed, therefore, to understanding the mechanism by which such hydrophobic sequences form amyloids and any conditions by which they might regress to a non-amyloid filament. The elastin-like sequence here under investigation is the ValGlyGlyValGly pentapeptide that has been previously analyzed both in its monomer and polymer form. In particular, we have focused our investigation on the apparent stability of amyloids formed from poly(ValGlyGlyValGly), and we have observed these fibers evolving to a hydrogel after prolonged aging in water. We will show how atomic force microscopy can be combined with X-ray photoelectron spectroscopy to gain an insight into the spontaneous organization of an elastin-like polypeptide driven by interfacial interactions. The results are discussed also in light of fractal-like assembly and their implications from a biomedical point of view.

AFM study of the elastin-like biopolymer poly(ValGlyGlyValGly).

In this paper, we report an AFM study on the supramolecular structures adopted by the synthetic polypentapeptide poly(ValGlyGlyValGly), whose monomeric sequence is an abundant, simple building block of elastin. The polypeptide was analyzed by deposition from both methanolic and aqueous suspensions, showing different behaviors. In methanol, the polypeptide is able to evolve, in a time-dependent way, from layers to ribbons to beaded filaments. When the equilibrium is reached, the formation of well-defined dendritic structures is also observed. This restructuring of the polypentapeptide seems to be reminiscent of a sort of Rayleigh instability. When deposited from aqueous suspensions, the polypeptide self-assembles either in fibrillar networks or in amyloid-like patterns, both of them being found in elastin or elastin-related polypeptides. As a general finding, poly(ValGlyGlyValGly) seems to constitute an excellent mimetic of the supramolecular properties of native elastin.

Zinc supplementation improves glucose disposal in patients with cirrhosis.

Zinc deficiency is common in cirrhosis, and was proved to affect nitrogen metabolism. In experimental animals, zinc status may also affect glucose disposal, and acute zinc supplementation improves glucose tolerance in healthy subjects. This study was aimed at measuring the effects of long-term oral zinc supplements on glucose tolerance in cirrhosis. The time courses of glucose, insulin, and C-peptide in response to an intravenous (i.v.) glucose load were analyzed by the minimal-model technique before and after long-term oral zinc supplements (200 mg three times per day for 60 days) in 10 subjects with advanced cirrhosis and impaired glucose tolerance or diabetes. The test was performed using a simplified procedure, based on 20 blood samples collected within 4 hours from the glucose load. Normal values were obtained in 25 age-matched healthy subjects. Zinc levels were low to normal or reduced before treatment, and were normalized by oral zinc. Glucose disappearance improved by greater than 30% in response to treatment. There were no changes in pancreatic insulin secretion and systemic delivery, or in the hepatic extraction of insulin. Insulin sensitivity (SI), which was reduced by 80% before treatment, did not change. Glucose effectiveness (SG) was nearly halved in cirrhosis before treatment (0.013 [SD 0.007] min(-1) v. 0.028 [SD 0.009] in controls; P < .001), and increased to 0.017 (SD 0.009) after zinc (P < .05 v. baseline). The return to normal of plasma zinc levels after long-term zinc treatment in advanced cirrhosis improves glucose tolerance via an increase of the effects of glucose per se on glucose metabolism. Poor zinc status may contribute to the impaired glucose tolerance and diabetes of cirrhosis.

Achievement of near-normal body weight as the prerequisite to normalize sex hormone-binding globulin concentrations in massively obese men.

OBJECTIVE: To investigate the effects of weight loss on sex hormone-binding globulin (SHBG) in massively obese males and whether normal SHBG concentrations could be obtained regardless or not of the achievement of normal body weight values. DESIGN AND SUBJECTS: Sera were collected for SHBG determination from 63 massively obese men, partly before they underwent biliopancreatic diversion (pre-op group = 11) and partly during the post-surgical follow up (post-op group = 52), and twenty normal weight healthy control men. MEASUREMENTS: Serum SHBG was measured using a noncompetitive liquid-phase immunoradiometric assay. RESULTS: Baseline general characteristics were similar in both obese groups. Obese patients in the post-op group had lost 46.4 +/- 2.9 kg since they had undergone operation, namely during a mean period of 14.9 +/- 13.8 (range 1-58) months follow up. Obese groups had significantly lower SHBG than normal weight controls (66.2 +/- 18.6 nmol/l). However, pre-op obese (19.9 +/- 5.5 nmol/l) had significantly lower values than post-op obese subjects (45.5 +/- 24.8 nmol/l; P < 0.001). There were a highly significant correlation between SHBG and individual BMI values (r = -0.629; P < 0.001). Moreover, the post-op obese with BMI values lower or equal to 28 had significantly higher SHBG concentrations than those with BMI greater than 28 (62.8 +/- 22.2 nmol/l vs 32.1 +/- 19.6 nmol/l; P < 0.001), but not significantly different with respect to normal weight controls. CONCLUSIONS: Massively obese men weight loss can completely reverse SHBG abnormalities, which can be restored to the normal range when near-normal body weight is achieved. Since reduced SHBG concentrations can be an independent risk factor for the development of diabetes and cardiovascular disease, this represents an additional benefit of weight loss program in massively obese individuals.

Effects of beta-blockade on hepatic conversion of amino acid nitrogen and on urea synthesis in cirrhosis.

beta-Blockers are widely used to prevent gastrointestinal hemorrhage in cirrhosis. The metabolic effects of treatment are scarcely studied: hepatic function reportedly does not change significantly, but beta-adrenoceptors have been reported to regulate protein and amino acid metabolism. We studied hepatic nitrogen metabolism in response to constant alanine infusion in seven patients with cirrhosis before and 7 to 10 days after treatment with oral propranolol (60 to 100 mg/d). Beta-blockade was effective: it decreased heart rate by 25%, abolished orthostatic tachycardia, and reduced portal blood flow by 20%. Alanine-stimulated urea nitrogen synthesis rate (UNSR) was higher in patients with propranolol treatment, without any difference in aminonitrogen concentration. The kinetics of hepatic conversion of amino acid nitrogen into urea--ie, functional hepatic nitrogen clearance (FHNC)--increased by 30%, from (mean +/- SD) 17.0 +/- 4.1 to 22.0 +/- 6.6 L/h (P < .01). Increased urea production during alanine infusion resulted in negative nitrogen exchange even at the peak of alpha-aminonitrogen concentration. Basal insulin level was only slightly reduced during propranolol treatment, whereas the insulin response to alanine was significantly blunted. No differences in glucagon and cortisol were demonstrated. Epinephrine and norepinephrine levels were high-normal and did not vary after treatment. Increased urea production and stimulation of hepatic nitrogen clearance during beta-blockade may be mediated by relative hypoinsulinemia or by direct involvement of beta-adrenoceptors in the control of nitrogen metabolism, possibly by regulation of amino acid uptake and release in peripheral tissues.

Insulin regulates testosterone and sex hormone-binding globulin concentrations in adult normal weight and obese men.

There are no studies in vivo on the effects of insulin on androgens and sex hormone-binding globulin (SHBG) in men. We, therefore, investigated the effects of insulin suppression on testosterone and SHBG in two groups of eight nondiabetic adult obese men and six healthy normal weight men who underwent diazoxide treatment (100 mg, three times daily) for 7 days. Blood samples for hormone determination were obtained before the subjects had been selected for the study, immediately before diazoxide administration, and on the last day of treatment. A 24-h oral glucose tolerance test was also performed for glucose, insulin, and C-peptide determinations before and on the last day of treatment. Only one subject experienced significant side-effects, and no significant changes in mean body weight were found during the treatment. Diazoxide administration worsened glucose tolerance in several subjects and reduced fasting and glucose-stimulated insulin levels by approximately 50% in both control and obese subjects. No significant difference was present between historical and pretreatment hormone values in either group. Moreover, there were no differences in pretreatment gonadotropin and SHBG concentrations between the two groups, whereas testosterone (free and total) levels were lower in the obese than in the control subjects. After diazoxide administration, testosterone (free and total) decreased slightly, but significantly, whereas LH and SHBG significantly increased in both groups. Diazoxide treatment increased estradiol levels in controls, but not in obese men. In conclusion, these results indicate that in vivo, insulin is capable of stimulating testosterone production and, simultaneously, of inhibiting SHBG concentrations in both normal weight and obese men.

Body weight, fat distribution and the menopausal status in women. The VMH Collaborative Group.

Since sex hormones are involved in the regulation of body composition and adipose tissue metabolism, in this study we investigated whether menopause may alter body weight and fat distribution in women. Data were obtained from the Virgilio-Menopause-Health Study, which is a longitudinal epidemiological project aimed at investigating the relationship between menopause and related plasma hormonal concentrations, body weight, fat distribution and health. Only data from the first cross-sectional examination are presented. Out of the 952 women living in the town of Virgilio, Mantua (Italy) and born between January 1st, 1932 and December 31st, 1946, 596 (62.6%) participated in the study. Since incomplete data were present in 19 women, 577 was the final sample size available for statistical analysis. The protocol included a collection of blood for hormones and biochemistry, a full clinical history with socioeconomic and personal information, drug use, smoking, dietary and physical activity habits, and several anthropometric measurements. According to the clinical and hormonal status, 160 women were classified as pre-menopausal, 124 as peri-menopausal and 293 as post-menopausal. After adjusting for age, we found that body mass index (BMI) was significantly higher in peri-menopausal than in pre-menopausal women and remained slightly, but again significantly, higher in post-menopausal women. Although waist-to-hip and waist-to-thigh ratios increased significantly and progressively from pre- to post-menopause, any difference was not significant after adjusting for age. Diet, physical activity and smoking habits did not explain the difference in BMI values. No difference was found in the use of estro-progestagen compounds between the groups.(ABSTRACT TRUNCATED AT 250 WORDS)

The hypothalamic-pituitary-adrenal axis in obese women with different patterns of body fat distribution.

To investigate whether obese subjects with abdominal obesity may be characterized by hyperactivity of the hypothalamic-pituitary-adrenal axis, we examined two groups of obese women with a waist to hip ratio (WHR) lower than 0.80 (n = 13), therefore having peripheral body fat distribution (P-BFD), or a WHR higher than 0.85 (n = 12), thus having abdominal body fat distribution (A-BFD). A group of seven normal weight healthy women served as controls. All subjects underwent the following protocol study that included 1) measurement of daily urinary free cortisol excretion rate; 2) a CRF test (human CRF, 1 microgram/kg BW, as iv bolus), with blood samples taken at regular intervals for ACTH and cortisol determination; and 3) an ACTH test, performed by administering two boli of ACTH (Synacthen, 0.2 microgram/kg BW, iv), at 90-min intervals, with blood samples taken for cortisol determination. Each woman also had a control saline study. Basal levels of both ACTH and cortisol rose significantly after CRF administration in all groups, but this increase was significantly higher in A-BFD than in P-BFD and control women. A significant correlation was found between the incremental area of cortisol and that of ACTH during the CRF test (r = 0.502), but not between these parameters and WHR values. Although the cortisol increase after the ACTH test was higher in A-BFD than in the other groups, these differences were only significant at 60 min during the test and when the analysis for repeated measures was applied. On the contrary, the incremental cortisol area after the ACTH test was not significantly different in the three groups. Moreover, it was not significantly correlated with the incremental cortisol area after CRF test or WHR values. Daily urinary free cortisol excretion rates (per g creatinine), however, were significantly higher in A-BFD than in P-BFD and control women. These results, therefore, suggest that obese women with A-BFD may have hyperactivity of the hypothalamic-pituitary-adrenal axis. This abnormality could be central in origin, due to hypersecretion of CRF or ACTH; alternatively, it could represent an adaptive phenomenon secondary to a state of functional cortisol resistance.

Dosage analysis at the CSF1 and CSF1R loci in a new case of partial trisomy 5q.

We report on a new case of trisomy for the distal portion of chromosome 5q, arising from a maternal balanced translocation, t(5;22)(q33;q13). The patient presented with mental retardation and peculiar craniofacial anomalies, similar to those already described in trisomy 5q3. Overall, the phenotype bore some resemblance to that of the Brachmann-De Lange syndrome. The extent of the duplicated region was investigated through a combined molecular-cytogenetic approach, using 5q probes for gene dosage analysis by Southern blot, which allowed confirmation of breakpoint assignment to band 5q33. Since most manifestations of trisomy 5q3 are observed in patients with duplications spanning 5q34-qter, it seems that the critical sequences involved in phenotype determination lie within this very distal segment.

The relative contribution of androgens and insulin in determining abdominal body fat distribution in premenopausal women.

To investigate the relative contribution of insulin and sex hormones in determining the abdominal pattern of fat distribution in premenopausal women, five groups of age-matched subjects were examined: Group 1 consisted of 14 normal weight eumenorrheic women (NO); Group 2 of 9 obese eumenorrheic women (OB); Group 3 of 14 normal weight hyperandrogenic women with polycystic ovary syndrome (NO-HA); Group 4 of 10 obese hyperandrogenic women with polycystic ovary syndrome (OB-HA) and, finally, Group 5 of 10 obese hyperandrogenic women with polycystic ovary syndrome and acanthosis nigricans (OB-HA-AN). Both the two normal weight groups and the three obese groups were matched for body mass index values. Sex hormone pattern showed significantly higher LH and testosterone levels in hyperandrogenic women with respect to NO and OB women but obese hyperandrogenic groups (OB-HA and OB-HA-AN) presented significantly lower LH concentrations than NO-HA. Fasting and glucose-stimulated insulin levels were significantly higher in OB than NO, in OB-HA and OB-HA-AN than in OB and NO-HA, and in OB-HA-AN than in OB-HA, without any significant difference between OB and NO-HA. Body fat distribution, expressed by the waist to hip ratio (WHR), showed progressively higher values (p less than 0.01) from NO to OB, NO-HA, OB-HA and, particularly, OB-HA-AN women. Determination coefficients r2 obtained from simple regression analysis showed that the sum of insulin values during the glucose tolerance test and testosterone levels had a more significant power in determining WHR variability.(ABSTRACT TRUNCATED AT 250 WORDS)