Plasma homocysteine after insulin infusion in type II diabetic patients with and without methionine intolerance.

BACKGROUND: A high prevalence of hyperhomocysteinemia has been reported in type II diabetic patients with documented vascular disease; hence the hypothesis that hyperhomocysteinemia may contribute to overall mortality in diabetic patients. The link between insulin and homocysteine metabolism has not been completely clarified yet; in particular, only few data are available on the effects of insulin in vivo on homocysteine metabolism in the presence of abnormalities of sulphur amino acid metabolism (methionine intolerance). MATERIALS AND METHODS: To establish whether methionine intolerance and which of its determinants could influence total plasma homocysteine in response to insulin infusion in vivo in type II diabetic patients, we submitted 18 patients (Group A) with normal and 18 patients with abnormal (hyperhomocysteinemia) (Group B) response to oral methionine load to a glucose/clamp study. At time 0, and 30, 60 and 120 minutes after hyperinsulinemia, homocysteine and methionine plasma levels were assessed. In order to evaluate the cause of methionine intolerance, all patients were assayed for fasting homocysteine-cysteine ratio (as a marker of suspected heterozygosis for cystathionine-beta-synthase deficit), MTHFR C (677)T status and homocysteine-related vitamin status (serum vitamin B (6) [PLP], vitamin B (12) and folate). RESULTS: After hyperinsulinemia, plasma methionine was reduced (by about - 30 % at 120 minutes vs. basal values) within both groups, whereas tHcy tend to decrease in group A following insulin administration (up to - 6.6 +/- 3.6 % vs. basal values at 120 minutes) with a significantly higher variability, while in patients with "methionine intolerance" (group B) tHcy tended to increase (up to + 29.05 +/- 8.3 % vs. basal values at 120 min from the clamp). Serum folic acid (7.45 +/- 2.8 vs. 4.82 +/- 2.5 nmol/L, p < 0.05), Vit. B (12) (348 +/- 78 vs. 242 +/- 65 pmol/L, p < 0.05) and PLP (84.1 +/- 23.6 vs. 50.6 +/- 32.4 nmol/L; p < 0.01) were significantly higher in group A than in group B; PLP levels significantly correlated with homocysteine after 4 h methionine load (n = 36; r = - 0.327, p < 0.05); group A showed also a significantly lower prevalence of suspected heterozygosis for cystathionine-beta-synthase deficit (1/18 [11.1 %] vs. 5/18 [33.3 %], p < 0.05) and MTHFR T allele presence (4/18 [22.2 %] vs. 11/18 [61.1 %], p < 0.01). A stepwise regression analysis with tHcy plasma level variations (event A = reduction; event B = increase) as the dependent variable showed that low serum folate and PLP levels and presence of MTHFR T allele were the variables associated with insulin-induced tHcy increase. CONCLUSIONS: Methionine intolerance may influence the effect of insulin administration on plasma homocysteine in patients affected by type 2 diabetes. To prevent a possible acute (and repeated) hyperhomocysteinemia due to insulin administration in cases of methionine intolerance, it may be useful to assess the presence of methionine intolerance (tHcy after oral methionine loading) and Hcy-related vitamin status in all patients due to be subjected to insulin therapy.

Relevance of different apolipoprotein content in binding of homocysteine to plasma lipoproteins.

BACKGROUND AND AIMS: In plasma the atherogenic thiol homocysteine (Hcy) circulates either free or bound to proteins (Pb-Hcy). The present study sets out to evaluate the lipoprotein-Hcy (LP-Hcy) binding in vivo and the possible influence of different apolipoprotein content in this binding, being lipoprotein oxidation a possible mechanism of Hcy-induced damage. METHODS AND RESULTS: In 34 healthy subjects we assayed fasting plasma lipoprotein and correspondent apolipoprotein (apo A-I, apo A-II, apo C-II, apo C-III, apo B, apo(a) and apo E content, and Hcy bound to different plasma protein fractions; moreover ten subjects underwent an oral methionine load in order to evaluate possible "dynamic" modifications of Pb-Hcy and LP-Hcy after induction of hyperhomocysteinemia. Pb-Hcy (mean values 9.22 +/- 1.7 mumol/L) represented about 78% of total plasma Hcy (mean values 11.8 +/- 1.8 mumol/L). Pb-Hcy distribution between the different fractions was as follows (mumol/L): VLDL = 0.25 +/- 0.08 (2.7%); LDL = 0.88 +/- 0.22 (9.5%); HDL = 1.40 +/- 0.36 (15.2%); fractions with density greater than 1.21 g/mL (Lipoprotein-Free Protein Fraction, LPDS) = 6.7 +/- 1.2 (72.6%). Hcy/protein ratios (nmol/mg of protein) in each protein fraction were: VLDL = 0.32 +/- 0.19, LDL = 0.43 +/- 0.37, HDL = 0.26 +/- 0.18, LPDS < 0.1, thus suggesting a higher binding capacity for Hcy by VLDL and LDL. These data were confirmed by the higher increase in Hcy content in LDL and VLDL (76 and 90%, respectively vs 36% and 3.1% for HDL and LPDS fractions) after hyperhomocysteinemia. Lp-Hcy binding significantly correlated with the apo B content of VLDL and LDL and Apo A-I content of HDL. CONCLUSIONS: An important fraction of plasma Hcy circulates bound to LP (about 27% of Pb-Hcy); VLDL and LDL show the highest binding capacity for Hcy, probably due to their content in Apo B, a possible high capacity binding site for Hcy.

Hyperhomocysteinemia and related factors in 600 hospitalized elderly subjects.

Hyperhomocysteinemia (HHcy) is a metabolic disorder frequently occurring in the elderly population. Recently several reports have suggested abnormalities in homocysteine (tHcy) metabolism implicating HHcy as a metabolic link in the multifactorial processes characterizing many geriatric illnesses-with special emphasis on atherosclerotic vascular diseases and cognitive impairment. The present study was undertaken in a large sample of elderly hospitalized subjects to determine (1) the prevalence of HHcy, (2) the association of HHcy with vascular and cognitive disorders, and (3) the factors independently predicting Hhcy. Six hundred elderly subjects (264 men and 336 women; mean age, 79 +/- 9 years) were randomly chosen from those admitted as inpatients over a period of 3 years. In all patients, body mass index (BMI), mid-upper arm muscle area (MUAMA), plasma cholesterol, triglycerides, total proteins, albumin, lymphocyte count, creatinine, homocysteine (fasting and 4 hours after methionine oral load), serum vitamin B(6), vitamin B(12), and folate concentrations were measured. The presence of disease or use of medications known to affect homocysteine plasma levels were also recorded. The mean fasting tHcy level was 16.8 +/- 12 micromol/L in the whole sample, 18.18 +/- 13.25 micromol/L in men, and 15.86 +/- 12.14 micromol/L in women (P =.005 men v women). The mean Hcy level 4 hours after methionine load was 37.95 +/- 20.9 in the whole sample. Prevalence of hyperhomocysteinemia (fasting Hcy > or = 15 micromol/L or 4 hours after methionine load > or = 35 micromol/L) was 61% (365/600) (67% in men and 56% in women, P <.05). HHcy was rarely (8%) an isolated disorder; in addition to diabetes (20%), renal failure (48.2%), and malnutrition (20.2%), it was often associated with heart failure (30%), malignancies (20.5%), and the use of diuretics (56%) and anticonvulsant drugs (13%). Plasma homocysteine progressively increases across subjects from those with no diabetes, malnutrition, renal failure, obesity, inflammatory bowel disease, heart failure to those with 1, 2, or more concurrent diseases. Multiple stepwise regression analysis showed that 72% of plasma total fasting tHcy variability was explained by age, serum folate, plasma albumin, use of diuretics, and renal function (measured as plasma creatinine clearance). In conclusion, the present study documents that hyperhomocysteinemia, in elderly hospitalized patients is (1) a common finding, (2) frequently associated with vascular and cognitive disorders, and (3) probably a secondary phenomenon in most cases. The major predictor of high plasma homocysteine levels were age, serum folate, plasma albumin, plasma creatinine clearance, and use of diuretic drugs. These variables explain a large proportion of plasma Hcy variability.

Continuous combined hormone replacement therapy with oral 17beta-estradiol and norethisterone acetate improves homocysteine metabolism in postmenopausal women.

OBJECTIVE: To evaluate the effect of a continuous combined oral hormone replacement therapy (HRT) on basal and post-methionine load homocysteine levels in postmenopausal women. DESIGN: Twenty-two postmenopausal women (PMW) were randomly allocated to receive either continuous combined oral HRT (2 mg of estradiol plus 1 mg of norethisterone acetate; n = 11) or no treatment (controls, n = 11) for 6 months. A methionine oral load (0.1 g/kg body weight) was performed in each subject at time 0 and after 6 months. Serum homocysteine levels were measured by high-performance liquid chromatography in samples collected at time 0 and at 4, 8, and 24 h after the methionine load, while levels of vitamin B6 (by high-performance liquid chromatography) and B12 and folate (both by ELISA) were assayed in samples collected at time 0. RESULTS: Serum levels of glucose and body mass index increased in treated PMW, whereas folate decreased in controls. In treated PMW, basal homocysteine tended to decrease (10.6 +/- 3.3 micromol/L vs. 9.62 +/- 2.8 micromol/L, p = 0.062), whereas in controls it significantly increased (10.7 +/- 2.65 micromol/L vs. 12.17 +/- 3.89 micromol/L, p < 0.05). This increase was not significant after correction for vitamin status (p = 0.072). Homocysteine values 4 h (31.9 +/- 13.53 micromol/L vs. 39.83 +/- 22.53 micromol/L, p < 0.05) and 8 h (35.1 +/- 13.13 vs. 43.34 +/- 22.15 micromol/L) after methionine, and integrated homocysteine response to methionine (392.5 +/- 133.8 micromol/24 h vs. 458.8 +/- 104.8 micromol/24 h; p < 0.05), were significantly reduced in HRT-treated, but not in untreated, PMW. CONCLUSIONS: Continuous combined oral HRT with17beta-estradiol plus norethisterone acetate reduces homocysteine levels, mainly after a methionine load. This effect seems to be independent of vitamin status and may have positive implications for the prevention of cardiovascular diseases in PMW.

Ursodeoxycholic acid complexation with 2-hydroxypropyl-beta-cyclodextrin increases ursodeoxycholic acid biliary excretion after single oral administration in rats.

Complexation of ursodeoxycholic acid (UDCA) with 2-hydroxypropyl-beta-cyclodextrin (HPbetaCD) improves the water solubility and the dissolution rate of UDCA and may therefore increase its bioavailability. We compared the amount and the rate of biliary excretion of UDCA and biliary lipid secretion after a single oral administration of UDCA in 3 different pharmaceutical formulations [UDCA-HPbetaCD ('urso-beta-cyclodextrin'), UDCA suspension and UDCA capsule] at 3 different dosages each, in 11 groups (2 control groups) of bile fistula rats. UDCA excretion increased with an increase in dose, biliary UDCA recovery and peak secretion were significantly higher after administration of UDCA-HPbetaCD than after UDCA in suspension or capsule. This enhancement of biliary excretion may achieve greater UDCA enrichment in the bile acid pool than conventional pharmaceutical UDCA formulations, this giving to UDCA-HPbetaCD a considerable therapeutical potential.

Peroxidation indices and total antioxidant capacity in plasma during hyperhomocysteinemia induced by methionine oral loading.

Hyperhomocysteinemia is a risk factor for vascular disease, although its mechanism of action is not fully clear. Different experimental studies have suggested that homocysteine (Hcy) exerts a pro-oxidant effect in the presence of metal ions (Fe and Cu). To test for a similar effect in vivo, we studied plasma markers of lipid and protein oxidation during hyperhomocysteinemia induced by an oral methionine load. Twenty-nine subjects (aged 61 +/- 25 years; 17 women), 25 of whom underwent oral methionine (100 mg/kg) loading, were studied; in every case, we measured total plasma Hcy, malondialdehyde (MDA), conjugated dienes (DIE), and oxidized protein ([PTOX] carbonylic groups) in basal conditions and 4, 6, 8, and 24 hours after methionine loading. Four participants acted as controls. In every case, we also measured total plasma antioxidant capacity (ANTOX) in basal conditions and 8 hours after methionine loading. Eight hours after methionine loading, plasma Hcy increased from 17.6 +/- 11.4 to 54.3 +/- 31.6 nmol/mL, PTOX from 0.33 +/- 0.18 to 0.71 +/- 0.33 nmol/mg protein, DIE from 493 +/- 163 to 590 +/-202 optical density units, and MDA from 1.66 +/- 0.81 to 2.1 +/- 0.93 nmol/mL. There was a significant correlation (Spearman's r) between Hcy and both PTOX (r = .86, P = .01) and MDA (r = .47, P < .05) 8 hours after methionine loading. No significant modifications of the plasma parameters were found during the observation period in controls. ANTOX at 8 hours was significantly (paired ttest) reduced in probands (from 1.74 +/- 0.59 to 1.14 +/- 0.55 mmol/mL, P = .014); no significant difference was observed for plasma ANTOX in controls. Hyperhomocysteinemia due to oral methionine loading induced an increase in plasma oxidation markers. In the absence of hyperhomocysteinemia, no significant modifications were observed. These findings, together with the decrease in ANTOX and the corresponding increase in total plasma Hcy, are consistent with a pro-oxidant effect of acute hyperhomocysteinemia in vivo.

N -Acetyl-cysteine reduces homocysteine plasma levels after single intravenous administration by increasing thiols urinary excretion.

A decrease of plasma homocysteine (Hcy) may represent a therapeutic promise for reducing the impact of atherosclerosis. N -Acetyl-cysteine (NAC) is a thiol-containing compound interfering with endogenous thiols, cysteine (Cys) and Hcy, by forming with them mixed disulphides with a possibly more efficient renal clearance. The aim of this work was to assess the effect of NAC intravenous infusion on plasma levels of different forms of Hcy and particularly to verify the effect on Hcy renal excretion. We collected basal blood samples at 0.5, 1, 2, 5, 8 and 24 h after the beginning of NAC infusion (50 mg kg(-1)body wt.) and also 24-h urine samples of the day of NAC infusion and of the day before and of the day after the infusion in ten healthy subjects (mean age 73+/-15). Urinary and plasma thiols (Hcy, Cys and NAC) were assayed by HPLC. Both total plasma Hcy (approx. 69%vs basal values) and Cys (approx. 40%vs basal values) fell progressively, reaching a minimum 5 h after infusion start; total free (i.e. not bound to proteins) Hcy (2.2+/-1.8 down from 4.4+/-4.2 nmol ml(-1)) and Cys (70.4+/-39.8 down from 113. 3+/-61.2 nmol ml(-1)) decreased as well. Reduced (thiolic-free form) Hcy and Cys decreased during infusion, though not as pronounced as for the other forms. Percentagewise, out of the total plasma levels, Hcy and Cys total free form and reduced form tended to increase over infusion as well as their difference (i.e. the plasma mixed disulphide moiety), thus supporting the idea that excess NAC displaces thiols from their plasma binding sites forming mixed disulphides. Urinary total Cys and Hcy excretion significantly increased at the end of the day of NAC infusion (tenfold for Cys and fivefold for Hcy) and reduced appreciably on the following day. Also urinary excretion of the free form of Cys and Hcy increased at the end of the day of NAC infusion, although in a lower amount with respect of total amounts, meaning a reduction of percentage Cys and Hcy excreted as the free form; for none of the patients had proteinuria, the 'free' form of urine thiols has to be identified in the 'reduced' form, the difference between the total and free form reflecting the 'mixed disulphide' moiety. NAC intravenous administration induces an efficient and rapid reduction of plasma thiols, particularly of Hcy; our data support the hypothesis that NAC displaces thiols from their binding protein sites and forms, in excess of plasma NAC, mixed disulphides (NAC-Hcy) with an high renal clearance. This effect may represent the start of an alternative approach in the treatment of hyperhomocysteinaemic conditions.

The influence of 2-hydroxypropyl-beta-cyclodextrin on the haemolysis induced by bile acids.

Cyclodextrins improve the water-solubility of drugs and can mask their haemolytic effect in parenteral use. Because the mechanism by which bile acids induce haemolysis is poorly understood, it has been investigated in the presence of 2-hydroxypropyl-beta-cyclodextrin (HP-beta-CyD). The haemolytic effect of 1.8 mM solutions of cholic acid, chenodeoxycholic acid (CDCA), deoxycholic acid and ursodeoxycholic acid (UDCA) in isotonic buffer at pH 7.4 was investigated at 37 degrees C in the presence of HP-beta-CyD at concentrations from 0.18 to 32 mM. No haemolytic effect was evident for cholic acid and UDCA. The haemolytic effect of the other bile acids was reduced by addition of HP-beta-CyD and was prevented at a molar ratio of 1:1 owing to complex formation. An HP-beta-CyD:bile acid molar ratio greater than 5:1 had a different effect on the erythrocyte membrane, irrespective of the identity of the bile acid; the effect was in accordance with the complexion affinities. In the absence of HP-beta-CyD, the haemolytic effect of CDCA and deoxycholic acid appeared related to their capacity to form a surface monolayer and to solubilize the components of the erythrocyte membrane. The haemolytic effect observed after complexation of the bile acids appeared to be solely the effect of HP-beta-CyD, which was able to form a reversible inclusion complex with lipophilic components of the erythrocyte membranes at concentrations higher than 12 mM.

Chronic administration of ursodeoxycholic and tauroursodeoxycholic acid changes microsomal membrane lipid content and fatty acid compositions in rats.

We studied the effect of oral supplementation with ursodeoxycholate (UDCA) or tauroursodeoxycholate (TUDCA) on the lipid content and fatty acid composition of rat hepatic microsomes. UDCA and TUDCA significantly increased the total amount of lipids with the exception of cholesteryl-esters. UDCA significantly increased the triglycerides and phosphatidylethanolamine (PE) microsomal content, and decreased the cholesterol/phospholipids and the phosphatidylcholine (PC)/PE ratio. Both treatments increased the percentage oleic acid and of polyunsaturated fatty acids (PUFA) in each class of lipids. UDCA and TUDCA had a different action on PUFA microsomal molar percentage of phospholipids: UDCA increased the relative percentage of PUFA in the PE fraction, while TUDCA increased the relative percentage of PUFA in the PC fraction. These changes in the hepatic lipid content and composition might in part explain both cytoprotective action of these hydrophillic bile acids and their effect on membrane fluidity.

Improvement of ursodeoxycholic acid bioavailability by 2-hydroxypropyl-beta-cyclodextrin complexation in healthy volunteers.

Tablets containing the inclusion complex of ursodeoxycholic acid (UDCA) with 2-hydroxypropyl-beta-cyclodextrin were prepared by direct compression. Plasma concentrations of UDCA were determined in six healthy volunteers after oral administration of tablets containing the inclusion complex or UDCA alone (Ursacol). Following the administration of the complex tablets, the mean area under the plasma concentration curve (AUC) and the maximum UDCA plasma concentration (Cmax) were significantly higher than those obtained after the administration of the commercial ones. Moreover, the time of maximum plasma concentration (tmax) appeared at a shorter time. These results may be explained by the increase of the UDCA dissolution rate via complex formation.

Different resistance of mammalian red blood cells to hemolysis by bile salts.

To evaluate why hemolysis of red blood cells (RBC) by bile acids varies in different mammalian species, we determined the mean corpuscular volume (MCV), lipid content and the concentrations of the conjugates of deoxycholate and of NaCl inducing 50% hemolysis of RBC from healthy humans, pigs, horses, cows, sheep and jaundiced humans. A volume of 0.05 mL of washed RBC at 1% hematocrit, which has the same lipid content but different phospholipid composition and number of erythrocytes (owing to the variable MCV), was incubated in taurodeoxycholate (TDC) solution (0-5 mM) to determine the TDC concentration inducing 50% hemolysis (TDC50). The TDC50 was highest in RBC of sheep and decreased within the series sheep > pig > cow > horse > healthy human > jaundiced human, which have generally increasing MCV. The osmotic resistance followed an inverse order, with jaundiced human > healthy human > horse > cow > pig > sheep. Although we found no correlation between the TDC50 and phospholipid composition of the erythrocytes tested, the extent of bile salt-induced hemolysis seemed to depend on both the MCV and the number of erythrocytes in the incubation medium.

Composition of ascitic fluid in liver cirrhosis: bile acid and lipid content.

The concentrations of lipids, bile acids and proteins were evaluated in the ascitic fluid and plasma of 23 cirrhotics. Ascitic fluid density was highly correlated with its protein content, represented mostly by low molecular weight proteins. The ratio of plasma to ascitic fluid concentrations of nine examined proteins increased with molecular weight, indicating a selective ultrafiltration of the peritoneal transudate. Low density lipoproteins in ascitic fluid had modified electrophoretic mobility. Total cholesterol had a higher plasma to ascitic fluid ratio than high density lipoprotein cholesterol, whereas bile acids and proteins had similar plasma to ascitic fluid ratios. Indeed, bile acids strongly bind to circulating albumin: consequently ascitic fluid contains more cholic acid (less hydrophobic) than other bile acids. Analysis of both plasma and ascitic fluid composition in cirrhotics provides useful information on processes regulating passage of blood components into the peritoneal cavity.

[Ultrasonographic study in breast immersion]. / L'esame ultrasonografico in immersione della mammella.

100 breast symptomatic patients have been examined with ultrasound, using an automated water-path scanner (Senomatic 3D CGR), and commercial B-mode or real-time scanners. All the patients were also examined with xeromammography. Normal breast patterns, as well as benign and malignant breast lesions, are presented.