Impaired glucose tolerance is not associated with lipid intolerance

Post-prandial (pp) hypertriglyceridaemia (HTG) has an important role in the development of atherosclerosis in Type 2 diabetes. Impaired glucose tolerance (IGT) is associated with an increased risk of atherosclerosis and increased level of fasting triglycerides (TG). The aim of this study was to analyse pp HTG and the composition of TG-rich lipoproteins in carefully selected subjects with IGT in comparison to controls with normal glucose tolerance (NGT). Fifteen men with IGT and 27 men with NGT, aged 44 to 70 yr, were examined. All study participants were non-smokers and had fasting TG <4.6 mmol/l. The subjects underwent an oral glucose tolerance test (75 g glucose) and a lipid-glucose tolerance test (LGTT; 92 g fat, 126 g carbohydrate), that allowed the assessment of lipid and glucose tolerance in one test. HbA1C, plasma glucose and lipids were measured by routine methods. Lipoprotein subfraction analysis of VLDL (VLDL1: Sf60-400 and VLDL2: Sf20-60) was conducted in a fasting state, as well as 4 hr after the LGTT using a density gradient ultracentrifugation with a subsequent compositional analysis. No significant difference was found either for fasting or pp TG, or for area under curve (AUC) -TG (12.21 +/- 4.27 mmol/l x 6 hr vs 13.95 +/- 6.74 mmol/l x 6 hr; p>0.05) between the IGT and NGT. A highly significant correlation was found between the fasting TG and the AUC-TG (r=0.925; p<0.01). To avoid bias by differences in fasting plasma TG known to affect lipid tolerance we investigated 11 matched pairs for fasting TG. Also, the matched-pairs evaluation pp TG course did not differ significantly from the IGT and NGT. No significant difference for fasting or pp levels of VLDL1 and VLDL2, or for the TG content of chylomicron, VLDL1 and VLDL2 and for the percentage of TG in VLDL1 and VLDL2 was found between the IGT and NGT group. In conclusion, IGT subjects with a similar level of fasting TG do not exhibit lipid intolerance. Our data suggest that glucose intolerance should precede lipid intolerance.

Postchallenge plasma glucose and glycemic spikes are more strongly associated with atherosclerosis than fasting glucose or HbA1c level

OBJECTIVE

To observe the relationship of fasting plasma glucose (FPG), postchallenge plasma glucose (PG) (30, 60, 90, and 120 min during an oral glucose tolerance test [OGTT], as well as maximal PG during an OGTT, postchallenge glucose spikes [PGS], and glucose under the OGTT curve), and HbA1c to intima-media thickness (IMT) as a marker of atherosclerosis.

RESEARCH DESIGN AND METHODS

OGTT, ultrasound measurement of carotid IMT, and various atherosclerosis risk factors, such as family history of diabetes, obesity, and/or hyperlipoproteinemia, but without known diabetes, were analyzed in 582 individuals aged 40-70 years and at risk for type 2 diabetes.

RESULTS

In univariate analysis, all examined glycemic parameters were significantly correlated to IMT. The 2-h postchallenge plasma glucose showed the strongest odds ratio (OR) of 1.88 (1.34-2.63) in relation to abnormal IMT. All PG variables, except for 30-min glucose in OGTT, showed a significant OR, whereas the OR for HbA1c and FPG was not significant. In logistic regression analysis, 2-h PG was identified as the strongest determinant of IMT from all glycemic parameters. The 2-h PG and PGS, but not FPG, were associated with a significant rise of IMT in tertiles of HbA1c. Glycemic parameters were strongly related to each other and to many atherosclerosis risk factors. In multivariate analysis including a variety of atherosclerosis risk factors, 2-h PG was a significant independent determinant of IMT.

CONCLUSIONS

PG and PGS are more strongly associated with carotid IMT than FPG and HbA1c level and modify substantially the risk for atherosclerosis, estimated by HbA1c alone, in a cohort at risk for diabetes and in the early diabetes stage.

Partial sequence identification of grapevine-leafroll-associated virus-1 and development of a highly sensitive IC-RT-PCR detection method

Using immunocapture reverse transcription PCR (IC-RT-PCR) a specific PCR product from GLRaV-1 infected vine samples was amplified with the help of degenerate primers deduced from the conserved HSP70 region of closteroviruses. 511 basepairs of the 5'end of GLRaV-1 HSP70 gene were identified. Within this region, putative GLRaV-1 specific primers were designed and an IC-RT-PCR detection procedure was developed which is about 125 times more sensitive than the established ELISA method. No PCR product was amplified in GLRaV-2,-3 and -4 infected plants which indicates the specificity of the primers. This procedure may serve as an alternative method for GLRaV-1 detection where the sensitivity of ELISA is insufficient.

Urate attenuates oxidation of native low-density lipoprotein by hypochlorite and the subsequent lipoprotein-induced respiratory burst activities of polymorphonuclear leukocytes

Oxidation converts native low-density lipoprotein (LDL) into a signal molecule promoting inflammatory processes during atherogenesis. The exact contribution of different antioxidants in prevention of LDL oxidation is not known. Uric acid efficiently scavenges oxidants including hypochlorite. We investigated the effect of different urate concentrations (25-500 micromol/l) on the oxidation of isolated native LDL by sodium hypochlorite (1000 micromol/l). While relative electrophoretic mobility declined continuously with increasing urate concentrations in the oxidation medium, lipid peroxidation as measured by TBARS was blunted only at high molar urate/NaOCl ratios. By decreasing oxidative modifications, urate dose-dependently (beginning with a urate/NaOCl ratio of 1:40) diminished stimulatory effects of oxidized LDL on the respiratory burst of resting polymorphonuclear leukocytes (PMNL). Protecting effects of urate against the proinflammatory action of oxidized LDL on activated cells were evident only at a molar urate/NaOCl ratio of 1:2 suggesting different sensitivities of PMNL to LDL oxidation state in dependence on their activity state.

Physicochemical binding properties of the proteoglycan receptor for serum lipoproteins

Proteoheparan sulfate can be adsorbed to a methylated silica surface in a monomolecular layer via its transmembrane hydrophobic protein core domain. Due to electrostatic repulsion, its anionic polysugar side chains are stretched out into the blood substitute solution representing a co-receptor for specific lipoprotein binding through basic amino acid-rich residues within their apolipoproteins. The binding process was studied by ellipsometric techniques showing that oxLDL had a deleterious effect on heparan sulfate proteoglycan binding and conformation. Ca2+ binding to and storage on the proteoheparan sulfate/LDL compound formed a 'heterotrimeric' HS-PG/LDL/Ca2+ complex of high stability, aggregability and deposit coating. On the other hand, HDL bound to heparan sulfate proteoglycan protected against LDL docking and completely suppressed calcification of the proteoglycan/lipoprotein complex.

Diminished susceptibility to in vitro oxidation of low-density lipoproteins in hypercholesterolemia: key role of alpha-tocopherol content

Oxidizability of low-density lipoproteins (LDL) in hypercholesterolemia is of clinical relevance, but previous studies revealed diverging results. Therefore, we studied ex vivo oxidation of LDL in plasma samples of 57 hypercholesterolemic and 20 normocholesterolemic volunteers. LDL were isolated by ultracentrifugation and analyzed for lipids and alpha-tocopherol. The formation of conjugated dienes, lipoperoxides and malondialdehyde was measured at 0.1 micromol/l LDL, 3.2 micromol/l CuSO4. We found prolongation of the lagtime (53.6/65.8/71.4 min) with tertiles (< or = 3.17/3.89/14.2 mmol/l) of LDL-cholesterol (LDL-C). Regression analysis revealed that the lagtime increased with the apparent concentrations of cholesterol (P = 0.003) and alpha-tocopherol (P = 0.001) in the oxidation assay. A multiple regression model with the apparent concentrations of alpha-tocopherol, triglycerides and cholesterol explained 40% of the variation in lagtime. The close relationship between plasma concentrations of LDL-C and LDL-alpha-tocopherol (P = 0.002) indicated that LDL contained more of this antioxidant in hypercholesterolemia. This might provide an explanation for the positive relationship between lagtime and LDL-C. The latter was independent of whether LDL-C or LDL-protein was chosen for standardization of the oxidation assay. The formation of conjugated dienes (P = 0.000), lipoperoxides (P = 0.038) and malondialdehyde (P = 0.001) increased with the cholesterol level in the assay. This may be due to the increased load of LDL with cholesterol esters as a substrate for oxidation in hypercholesterolemia. Our data do not support the opinion that hypercholesterolemia is characterized by increased susceptibility of LDL to oxidation.

Relation of free and specifically bound leptin to insulin secretion in patients with impaired glucose tolerance (IGT)

Impaired glucose tolerance (IGT) is frequently associated with an increased fat mass and an altered fat distribution. The adipocyte derived hormone, leptin has been shown to interact with insulin at various levels and may be intimately involved in this process. However, only limited data concerning the interaction of insulin, glucose tolerance and leptin are available and no data exist on the potential influence of bound vs. free circulating leptin. We therefore studied free and bound leptin in 136 patients (77 males, 59 females) with IGT, in relation to plasma glucose, insulin, proinsulin and C-peptide levels as well as serum free and bound leptin concentrations during an oral glucose tolerance test (oGTT). The expected positive relation of free serum leptin levels with body mass index (BMI) was found. Free leptin concentrations were higher in women than in men. Analysis in tertiles revealed a significant relation between free leptin (16-58, 60-160, and 169-932 pmol/l) and mean fasting insulin levels (65, 93, and 100 pmol/l). This relationship remained significant in a multiple regression analysis with BMI and gender as covariates. Similar independent relationships to leptin serum levels were observed for HbA1c and plasma C peptide levels and the proinsulin/insulin ratio but not for plasma glucose and proinsulin levels. These data suggest a fine tuning of leptin by small changes in circulating insulin levels observed in impaired glucose tolerance.

Increased intimal-medial thickness in newly detected type 2 diabetes: risk factors

OBJECTIVE

To examine carotid intimal-medial thickness (IMT) and its determinants in newly detected type 2 diabetic subjects, classified according to the new criteria of the American Diabetes Association, in comparison with age- and sex-matched control subjects with normal glucose tolerance.

RESEARCH DESIGN AND METHODS

This study was case-controlled, with matched pairs for 71 newly diagnosed type 2 diabetic individuals. Subjects aged 40-70 years were recruited from a risk population for diabetes seen in the Risk Factors in IGT for Atherosclerosis and Diabetes (RIAD) Study. Standard risk factors, 75-g oral glucose tolerance test with real insulin, proinsulin, and C-peptide, and ultrasound measurement of the IMT of the common carotid artery were performed.

RESULTS

The diabetic subjects, both men and women, displayed carotid intimal-medial thickening, even in the subgroup with fasting plasma glucose between 7.0 and 7.8 mmol/l. HbA1c was significantly increased in the diabetic patients (6.33 vs. 5.48%). Insulin, proinsulin, and C-peptide were also significantly higher. Among the coronary risk factors, triglycerides and plasminogen activator inhibitor were significantly increased. After age and sex adjustment. IMT in the diabetic group was correlated to triglycerides and the total-to-HDL cholesterol ratio. In the total group, IMT was significantly correlated to blood pressure, 2-h glucose in oral glucose tolerance testing, triglycerides, albuminuria, and the total-to-HDL cholesterol ratio, and inversely correlated to HDL cholesterol. No independent determinant of IMT was found in the diabetic group by multivariate analysis.

CONCLUSIONS

Newly detected type 2 diabetic patients exhibit a higher degree of early atherosclerosis than normal glucose-tolerant subjects matched for age and sex. Our data suggest that hyperglycemia, together with a clustering of risk factors, and in particular dyslipidemia, may cause intimal-medial thickening in the early phases of diabetes.

Antioxidative action of the novel calcium channel antagonist mibefradil on low-density lipoproteins

OBJECTIVE

Mibefradil is a novel calcium channel antagonist that selectively blocks T-channels. It acts to reduce hypertension, is cardioprotective and reduces ischemic episodes. Oxidative modification of low-density lipoproteins (LDL) is well known to contribute to coronary atherosclerosis and we therefore investigated to see whether mibefradil had antioxidative action on LDL.

METHODS

Human LDL were isolated by ultracentrifugation. In vitro oxidation of LDL (0.1 micromol x l(-1) protein) in the presence of various concentrations of mibefradil was initiated by 3.2 micromol x l(-1) copper ions. The kinetics of formation of conjugated dienes was followed photometrically. Malondialdehyde and lipoperoxides were determined at maximum oxidation. LDL (0.3 micromol x l(-1)) were also pre-incubated with mibefradil (120 micromol x l(-1)). Excessive mibefradil was separated by column technique. The resultant LDL were oxidized using copper ions or (AAPH) 2,2'-azobis(2-amidinopropane) hydrochloride.

RESULTS

The presence of mibefradil in the concentration range from 10 to 200 micromol x l(-1) had dose-dependent effects. These were protection of LDL against oxidation measured as prolongation of the lagtime up to 250%, and reduction in the formation of malondialdehyde down to 65% and of lipoperoxides to 20%. Pre-incubation of LDL with mibefradil prolonged the lagtime of Cu-mediated oxidation up to 132% and of AAPH-mediated oxidation up to 138%.

CONCLUSION

In addition to the T-channel blocking and antiproliferative effects, our results provide arguments for a protective role of mibefradil (10-200 micromol x l(-1)) on LDL against in vitro oxidation. This was shown with three independent parameters (lagtime, malondialdehyde and lipoperoxides) and in different oxidation models.

Prevalence of diabetes-specific autoantibodies in patients at risk for adult onset diabetes mellitus

To evaluate the potential of autoimmune markers in identifying patients with slowly progressive IDDM in the prediabetic state, we screened a population of 151 patients aged 37-70 years with impaired glucose tolerance (IGT) for the presence of islet cell antibodies (ICA), insulin autoantibodies (IAA), antibodies to glutamic acid decarboxylase (GADA), and antibodies to tyrosine phosphatase IA-2 (IA-2A). Autoantibodies were found in 5 (3.3%) patients with IGT suggesting the presence of an autoimmune-mediated beta cell destruction. All of them were positive for high level ICA (> 20 JDF-U) and 1 ICA positive subject had additional GADA (100 GADA-U). In contrast, none of the subjects had IA-2A or IAA. We here demonstrate a low prevalence of autoimmune diabetes among middle-aged subjects with IGT. ICA and GADA but not IA-2A or IAA may represent autoimmune markers for slowly progressive IDDM before the manifestation of the disease.

Hypochlorite-modified low-density lipoprotein stimulates human polymorphonuclear leukocytes for enhanced production of reactive oxygen metabolites, enzyme secretion, and adhesion to endothelial cells

Hypochlorite-oxidized low-density lipoprotein ((-)OCl-LDL) has been shown to stimulate various functions of human polymorphonuclear leukocytes (PMNLs). Incubation of PMNLs with (-)OCl-LDL (produced by incubation of 0.4 mM LDL cholesterol with 1 mM NaOCl for 40 min at 37 degrees C) but not native or copper-oxidized LDL induced a substantial generation of reactive oxygen species (ROS) as measured by means of chemiluminescence with one peak at 10-12 min. Upon stimulation with (-)OCl-LDL about 70% of ROS (hydrogen peroxide and superoxide anion) were released from the cells into the extracellular environment. The (-)OCl-LDL-induced increase of the respiratory burst was dependent upon the dose, exposure time, and extent of LDL oxidation. Cytochalasin B, an inhibitor of phagocytosis, markedly diminished the LDL-induced ROS generation to nearly 40% of control values. (-)OCl-LDL enhanced the adhesion of PMNLs to human umbilical venous endothelial cells 2.5-fold as compared to native LDL and promoted the secretion of the active granule enzymes lysozyme and beta-glucuronidase. Together, the results suggest a potential role of LDL-activated PMNLs in initiating and/or maintaining the inflammatory process during the early phase of atherosclerotic lesion development. Alternatively, PMNLs may also play a protective role by phagocytosing oxidized LDL and, thus, preventing further detrimental atherogenic effects of oxidized LDL.

Effects of fluvastatin therapy on lipids, antioxidants, oxidation of low density lipoproteins and trace metals

OBJECTIVE

Oxidation of low density lipoproteins (LDL) is thought to be an important step in the development of atherosclerosis. Trace metals are involved in oxidative processes. It was of interest to determine whether lipid-lowering therapy with fluvastatin, a potent HMGCoA reductase inhibitor, affected LDL oxidation and trace metal levels.

METHODS

Twenty hypercholesterolemic patients were treated with fluvastatin (40 mg twice daily) or placebo for 8 weeks in a double-blind, randomized study. LDL composition, antioxidants and oxidizability as well as plasma zinc, copper, selenium and manganese concentrations were investigated.

RESULTS

After fluvastatin treatment, total cholesterol was reduced by 24%, triglycerides fell by 26% and plasma Zn fell by 8%. Cu, Se and Mn changed insignificantly. LDL were separated by ultracentrifugation. LDL were reduced by 18%, LDL-C by 29% and LDL-TG by 19%. The concentrations of alpha-tocopherol and retinol in LDL changed insignificantly. LDL preparations were incubated with copper ions (204 mumol.1(-1) LDL-C/3.2 mumol.1(-1) Cu) and formation of conjugated dienes was monitored at 234 nm for 5 h. Treatment with fluvastatin caused a reduction of diene production by 16% and of diene production rate by 14%, effects being significantly different from placebo (P = 0.02). The change of the lagtime did not reach significance; however, it was positively correlated with the change in LDL alpha-tocopherol. In the placebo group, no significant effects were observed.

CONCLUSION

Fluvastatin therapy had lipid-lowering and antioxidative effects.

Glibenclamide, but not acarbose, increases leptin concentrations parallel to changes in insulin in subjects with NIDDM

OBJECTIVE

To hypothesize if glibenclamide, which increases insulin levels, also increases leptin concentrations.

RESEARCH DESIGN AND METHODS

Leptin is a hormone that regulates weight in mice. In obese humans, leptin concentrations are increased, suggesting resistance to the effects of this hormone. Although short-term infusion of insulin during the hyperinsulinemiceuglycemic clamp does not increase leptin concentration, the effect of oral antidiabetic agents on leptin concentration is unknown. Differing effects can be expected, since glibenclamide acts via stimulation of insulin secretion, whereas acarbose inhibits alpha-glucosidases of the small intestine and has no direct effect on insulin levels. We examined the effect of acarbose (n = 4), glibenclamide (n = 6), and placebo (n = 6) on insulin and leptin levels during 24-h periods before and after 16 weeks of therapy.

RESULTS

We observed a significant diurnal variation in leptin concentrations. This was inversely related to insulin levels during the 24-h follow-up with usual diet. Neither the placebo nor acarbose altered leptin concentrations. However, glibenclamide increased leptin concentrations parallel to insulin levels. There were only minor changes in body weight during the l6-week follow-up: decrease in the placebo group (change -0.5 kg/m2, P = 0.07) and acarbose (change -0.7 kg/m2, P = 0.046) and increase in the glibenclamide group (change 0.8 kg/m2, P = 0.27). However, individual subjects who gained weight had increases in their leptin concentrations. The diurnal variation in leptin concentrations was preserved after glibenclamide.

CONCLUSIONS

Glibenclamide increases circadian leptin and insulin concentrations, whereas acarbose does not. This observation may help to explain weight gain in subjects treated with glibenclamide and stable weight in those treated with acarbose in the long run.

Impact of concentrations of glycated hemoglobin, alpha-tocopherol, copper, and manganese on oxidation of low-density lipoproteins in patients with type I diabetes, type II diabetes and control subjects

The late organ complications in diabetic patients are associated with enhanced oxidation of low-density lipoproteins (LDL). The role of vitamin and trace metal concentrations in this process is not clear. Therefore, we compared the oxidative susceptibility and alpha-tocopherol concentration of LDL with the levels of glycated hemoglobin (HbA1c), copper and manganese. Sixty-three diabetic patients (23 female and 40 male; 53 of type II, 10 of type I) and 35 control subjects (17 female and 18 male) were investigated. The in vitro-formation of conjugated dienes in purified LDL preparations in the presence of copper was followed as absorbance at 234 nm. LDL exhibited a shorter lagtime (44.5 +/- 10.1 vs. 67.8 +/- 16.0 and 50.1 +/- 14.3 vs. 68.8 +/- 14.6 min) for type I and type II diabetic patients vs. sex and age-matched controls, P < 0.001. For all subjects together the lagtime was inversely correlated to HbA1c (r = -0.230, P = 0.023) and positively correlated to LDL alpha-tocopherol/LDL (mol/mol). This ratio was lower in diabetic patients (P < 0.01 for type II) than in control subjects. The copper and manganese plasma levels were not different between diabetic and nondiabetic groups. However, parameters of LDL oxidizability (amount and rate of oxidation) were positively correlated with both copper and manganese concentrations. We conclude that in diabetes the resistance of LDL against oxidation is diminished in relation to the quality of glucose control.

Increased clearance of low density lipoprotein precursors in patients with heterozygous familial defective apolipoprotein B-100: a stable isotope approach

In familial defective apolipoprotein B-100 (FDB) the presence of a mutant apolipoprotein (apo) B-100 (FDB3500Q/W) in LDL markedly reduces their affinity for the LDL receptor, leading to elevated LDL cholesterol levels. However, the hypercholesterolemia in most FDB patients is relatively mild when compared with, e.g., familial hypercholesterolemia (FH). In order to study mechanisms that may partly alleviate the clinical consequences of FDB, we investigated the in vivo kinetics of apoB-100-containing lipoproteins in five FDB heterozygotes (total cholesterol: 7.84 +/- 1.37 mmol/I; total apoB: 1.68 +/- 0.37 g/l; mean +/- SD) and six normolipidemic controls (4.61 +/- 0.62 mmol/l; 0.98 +/- 0.12 g/l) using a stable isotope approach. During and after a 10-12 h primed, constant infusion of either [13C6]phenylalanine or [2H3]leucine, tracer enrichment was determined in apoB-100 from ultracentrifugally isolated VLDL1 (Sf 60-400), VLDL2 (Sf 20-60), IDL (Sf 12-20), LDL1 (Sf 7-12), and LDL2 (Sf 0-7). The rates of apoB-100 production, catabolism, and transfer were estimated by model-based compartmental analysis. The overall fractional catabolic rate (FCR) of IDL apoB-100 in FDB was substantially increased (2.99 +/- 0.68 pools/day vs. 1.70 +/- 0.23 pools/day in controls, P < 0.01). The fractional rate of apoB-100 transfer from IDL to LDL in FDB was decreased (0.97 +/- 0.13 pools/day vs. 1.24 +/- 0.10 pools/day, P < 0.05). The FCR of LDL apoB-100 in FDB was decreased (0.18 +/- 0.07 pools/day vs. 0.56 +/- 0.05 pools/, P < 0.01). Finally, the input rate of LDL apoB-100 in FDB was markedly decreased (9.45 +/- 2.96 mg/kg day1 vs. 15.54 +/- 1.70 mg/kg day1, P < 0.05). Our data suggest that the relatively small increase of LDL concentrations in FDB is due to an increased clearance of LDL precursor particles via the LDL-receptor and apoE-receptors as well as a decreased conversion of IDL to LDL - two mechanisms that distinguish FDB from FH.

Very fast ultracentrifugation of serum lipoproteins: influence on lipoprotein separation and composition

A very short run time and small sample volumes in the separation of lipoproteins by preparative ultracentrifugation are needed for several investigations. Recently, a very fast sequential separation method was described that needs only 100 min for one run in a centrifugal field of 625,000 x g. We studied the influence of centrifugal fields of this dimension on lipoprotein separation and lipoprotein particle integrity using a Beckman Optima TLX ultracentrifuge with a TLA-120.2 rotor. Rotor speed (120/90/60/30.10(3) rev./min) and run time (100 min/3 h/6.7 h/27 h) were selected in such a way that the product of centrifugal field and run time remained constant. The first conditions correspond to the very fast ultracentrifugation (VFU) procedure with a centrifugal field of 625,000 x g. Thirty different plasma samples covering a wide range of lipid and protein concentrations were separated in the course of two centrifugal runs at densities of 1.006 and 1.063 kg/l which yielded very-low-density lipoproteins (VLDL), low-density lipoproteins (LDL), and the subnatant of low-density lipoproteins, including high-density lipoproteins (HDL) and concomitant sedimented plasma proteins. The major lipid components of the lipoproteins, triacylglycerols, free and esterified cholesterol, phospholipids and the apolipoproteins B and A-I, were estimated considering the masses of the tube contents after a slicing procedure. Measurements of lipids and proteins showed a very good recovery of better than 94% and 91%, respectively, and precision-within-series (coefficient of variation) of better than 4.2% and 6.5%, respectively. The effects of the rotor speed on the lipoprotein structure appeared to be weak. With increasing rotor speed, VLDL and LDL lipid constituents principally tended to decrease, whereas they increased in the subnatant of the LDL-run. The mean lipoprotein mass composition, considering the mass percentage of each measured particle constituent, did not show significant alterations. Total protein decreased in VLDL and in LDL and increased in the subnatant of the LDL-run. As checked by an enzyme-linked immunosorbent assay (ELISA) and sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE), the protein effects were due to nearly complete disappearance of contaminating plasma proteins, especially albumin as the major contamination of VLDL and LDL. The apolipoproteins (apo) B-100, A-I, E and C-I to C-III remained nearly unaffected. The main advantages of VFU were the very short run time (cumulative flotation time is 3.4 h) and the elemination of albumin without repeated runs. The procedure was suitable for the assessment of lipid and protein constituents in lipoproteins from very small plasma samples (500 microliters).

Recovery of cholesterol and triacylglycerol in very-fast ultracentrifugation of human lipoproteins in a large range of concentrations

Very-fast ultracentrifugation using a benchtop ultracentrifuge was applied to the analysis of lipoproteins in 0.5 ml of human plasma. VLDL, IDL and LDL were flotated at densities of 1.006, 1.019 and 1.063 kg/l in runs lasting 30, 100 and 100 minutes. Chylomicrons, if present, were flotated in a separate run. HDL were isolated by precipitation of the apolipoprotein B-containing lipoproteins from total plasma using polyethylene glycol. Three series of separations were routinely performed: 1. VLDL run alone (632 samples), 2. VLDL run + LDL run (122 samples), and 3. Chylomicron separation + VLDL run + IDL run (92 samples). The concentrations of cholesterol and triacylglycerol were obtained for plasma, chylomicrons, VLDL, IDL, LDL and HDL. Plasma values ranged from 1.8 to 37.1 mmol/l cholesterol and 0.26 to 50.2 mmol/l triacylglycerol. The plasma triacylglycerol concentrations were corrected for free glycerol by 3% (for triacylglycerols < 2.5 mmol/l) and by 2% (for triacylglycerols > or = 2.5 mmol/l). The recovery rate of lipids after ultracentrifugation was determined by comparing the concentrations in lipoproteins and in plasma. It was near to 100% and decreased for samples with extremely high lipid concentrations.

Efficacy of alpha-glucosidase inhibitors on lipids in NIDDM subjects with moderate hyperlipidaemia

This paper summarizes literature data concerning the action of acarbose, an alpha-glucosidase inhibitor, on the concentrations of plasma lipids. Clinical trials in which acarbose has been used in the treatment of non-insulin-dependent diabetics have sometimes shown that it reduces serum triglycerides while it has little or no effect on serum cholesterol levels. The results of a randomized double-blind placebo-controlled study lasting 24 weeks are discussed in more detail. Under the controlled conditions, the effects of acarbose treatment on fasting concentrations of cholesterol, HDL-cholesterol, and triglycerides did not reach statistical significance for the entire patient group. However, in the highest tertile of initial cholesterol concentrations acarbose treatment led to significant lowering of the cholesterol concentration and of the total-to-HDL-cholesterol ratio. The most important benefits of acarbose were observed after a test meal given on day 0 and on week 24 of treatment. The triglyceride increment 1 h postprandial was significantly lowered. This was associated by a significant decrease of the insulin increment. Reduction of hyperinsulinaemia appears to be the mechanism by which acarbose treatment can improve plasma lipid concentrations.

Impact of hormone replacement therapy on postprandial lipoproteins and lipoprotein(a) in normolipidemic postmenopausal women

In 43 normolipidemic postmenopausal women we studied fasting and postprandial (oral fat load with 50 g fat per square meter; blood sampling for 5 h) lipoprotein components and lipoprotein(a) levels before and with the administration of conjugated equine estrogens opposed by medrogestone (on days 11-21). Data was compared intraindividually; the second testing was performed during the last 5 days of the combined estrogen/progestogen phase of the third cycle. Fasting low-density lipoprotein (LDL) and total cholesterol concentrations decreased significantly; high-density lipoprotein (HDL) cholesterol, including subfractions HDL2 and HDL3, was not changed. Fasting triglyceride concentrations increased. All lipoprotein fractions measured showed a postprandial elevation with the exception of chylomicron cholesterol concentrations. There was a significant effect of hormone replacement therapy on the postprandial course of total cholesterol (decrease; P < 0.001), VLDL cholesterol (increase; P = 0.025), and the triglyceride proportion in the LDL plus HDL fraction (increase; P < 0.001). With hormone replacement therapy the postprandial curve of total triglycerides was increased only 1 h after the fat load while chylomicron triglyceride concentrations were lowered after 5 h. VLDL triglycerides were not influenced. In all patients with lipoprotein(a) levels above 10 mg/dl, this parameter decreased (about 25%). Although increasing fasting triglyceride concentrations, hormone replacement therapy does not bring about an exaggerated postprandial increase in triglycerides. Postprandial chylomicron clearance is evidently promoted. Hormone replacement therapy leads to a small increase in triglycerides in the LDL plus HDL fraction by inhibiting hepatic lipase activity. Moreover, the decrease in lipoprotein(a) levels may contribute to the antiatherosclerotic effect.

Very-fast ultracentrifugation of human plasma lipoproteins: influence of the centrifugal field on lipoprotein composition

A short run-time in separation of lipoproteins by preparative ultracentrifugation is desirable for several reasons. Recently, a method was described that needs only 100 min for one run in a centrifugal field of 625,000 x g. It is assumed that lipoprotein separation depends on the rotor speed but this has not been systematically studied in centrifugal fields of this order. We performed such a study. Rotor speeds of 120, 90, 60 and 30 x 10(3) rev./min and run-times of 100 min, 3 h, 6.7 h and 27 h were selected in such a way that the product of centrifugal field and run-time remained constant. The first conditions correspond to the 'very fast ultracentrifugation' (VFU) procedure with a centrifugal field of 625,000 x g. The Optima tabletop ultracentrifuge, the rotor TLA-120.2 and thick wall open tubes for 1 ml were used. Thirteen different plasma samples covering a wide range of cholesterol and triglyceride concentrations were separated into VLDL, LDL and HDL in the course of two centrifugal runs at densities of 1.006 and 1.063. The constituents of the lipoproteins were calculated considering the mass of the tube contents after slicing. Recoveries of cholesterol, triglycerides and protein were 97%, 98% and 90%, respectively. The influence of the rotor speed on the apparent composition of the lipoproteins was small. With increasing rotor speed, VLDL-cholesterol became higher (by 14%, P < 0.001), VLDL-triglyceride became lower (by 6%, P < 0.012), LDL-cholesterol became lower (by 9%, P < 0.000). The effects on LDL-triglyceride and on HDL-cholesterol and HDL-triglyceride, did not reach statistical significance. Protein in VLDL and in LDL decreased and increased in 'HDL' (the subnatant of the LDL run). As checked by SDS-PAGE the protein effects were due to complete disappearance of albumin from VLDL and LDL while the apolipoproteins B-100, E and C-I to C-III remained unaffected. It is concluded that the main advantages of VFU are the short run-time and the disappearance of albumin from VLDL and LDL. The other compositional changes need to be further investigated.

Beneficial effects on serum lipids in noninsulin dependent diabetics by acarbose treatment

Acarbose (Bay g 5421, Glucobay; CAS 56180-94-0) inhibits alpha-glucosidases of the small intestine and thus delays glucose release from complex carbohydrates. It is therefore efficient as a first-line drug in the treatment of noninsulin-dependent diabetics (NIDDM) insufficiently treated with diet alone. Information is scarce whether under acarbose treatment the lipid metabolism can also be improved. Therefore the changes of triglycerides, cholesterol and HDL-cholesterol were analyzed in a randomized double-blind placebo-controlled trial. In brief, 94 NIDDM aged 43 to 70, after a pretreatment period of at least 3 months, were treated with 100 mg acarbose t.i.d. or placebo for 24 weeks. The patients were recruited after a 4-week screening phase with reinforcement of diet. The most impressive results of acarbose treatment were lowering of blood glucose and insulin, especially in the postprandial state, and of HbA1 (glycosylated hemoglobin). Results on lipids: The initial serum cholesterol levels showed a broad spectrum. Low concentrations remained unchanged under acarbose, while high concentrations (the upper tercile) decreased from 273 to 251 mg/dl. This effect was statistically significant compared to placebo. HDL-cholesterol levels increased continuously under acarbose and placebo as well thus indicating some study effect. Similarly, fasting triglycerides leveled down under acarbose and placebo. However, drastic differences appeared in postprandial triglycerides which were checked 1 and 5 h after a test meal given at entry and at finish of the study. The lowering by acarbose compared to placebo was highly significant for the 1 h postprandial concentrations. It is concluded that acarbose treatment can reduce elevated cholesterol concentrations and postprandial triglyceride concentrations.(ABSTRACT TRUNCATED AT 250 WORDS)

Efficacy of a combined bezafibrate retard-colestyramine treatment in patients with hypercholesterolemia

In a placebo-controlled randomized study the effect of combined bezafibrate-colestyramine therapy in comparison with monotherapy with both drugs was investigated. 47 patients with primary hypercholesterolemia received 400 mg bezafibrate (Cedur) retard/d, subsequently bezafibrate retard plus colestyramine (24 g/d) or colestyramine plus placebo in a double-blind fashion. The combination therapy was most effective (LDL decrease 36%, HDL-C increase 31%, apoprotein B decrease 28%), bezafibrate and colestyramine were equally effective with regard to LDL-C and apoprotein B, but only bezafibrate decreased triglycerides (-37%) and increased HDL-C (+24%). Bezafibrate was well-tolerated, but gastro-intestinal side-effects were frequent during therapy with colestyramine, and 16 patients tolerated only a reduced dosage of this drug. From the results presented it can be concluded that combined therapy with bezafibrate retard plus colestyramine is highly effective in the treatment of severe hypercholesterolemia.

Effects of a bezafibrate sustained release formulation on plasma lipoproteins in patients with hypercholesterolemia. Importance of timing of tablet intake for efficacy

The therapeutic effect of a single sustained release tablet of bezafibrate (Cedur retard, 400 mg) in primary hypercholesterolemia type IIa and type IIb was investigated in a placebo-controlled randomised study comparing the efficacy of morning vs. evening intake. The decrease in total cholesterol with the morning intake was 18.5% vs. 16.5% for the evening intake (n.s.). HDL-cholesterol increased more in patients taking bezafibrate retard at morning (29.6% vs. 22.4%, p less than 0.05). Bezafibrate was well tolerated. Animal experiments and precursor studies of cholesterol synthesis in man indicate peak activity of HMG-CoA reductase between 1 a.m. and 3 a.m. The data suggest that with normal eating habits during day time other modes of action of bezafibrate besides HMG-CoA reductase inhibition such as reduction of VLDL-synthesis in the liver and an increased fractional catabolic rate, could contribute to the therapeutic effect.

[Intraindividual comparison of the elimination kinetics of Lipofundin S and Intralipid in consecutive lipid tolerance tests]

Two intravenous fat tolerance tests (IVFTT) were performed in 16 healthy volunteers and 8 patients suffering from hypertriglyceridemia (HTG). We compared Lipofundin S (Braun, Melsungen) with Intralipid (Kabi Vitrum, Stockholm), using both 10- and 20% concentrations. Time intervals between the tests were 1 h for the volunteers and 2 h for the patients with HTG, respectively. Fractional elimination rates were obtained from light scattering intensity of serum samples. They were significantly higher for Lipofundin S (9.61%/min for healthy men and 12.48%/min for healthy women) compared to Intralipid (7.09%/min for healthy men and 9.41%/min for healthy women). This difference occurred independently of (1) serum triglyceride concentrations and sex of the volunteers, (2) concentrations of lipid emulsions (10 vs. 20%), and (3) the test sequence (Lipofundin S or Intralipid first). This means that the elimination kinetics during an IVFTT are not influenced by a foregoing test. Similar features of both emulsion types were: (1) Faster elimination in women compared to men, and in healthy volunteers compared to HTG patients; (2) inverse correlation between fractional elimination rates and serum triglyceride concentrations. Fractional elimination rates of Lipofundin S and Intralipid were closely interrelated. Obviously there exists an intra-individually characteristic elimination capacity for exogenous triglycerides.

Elimination and metabolism of a fat emulsion containing medium chain triglycerides (lipofundin MCT 10%)

Medium chain triglycerides (MCT) are supposed to be advantageous on account of rapid energy supply in parental nutrition. However, data on the elimination rate of MCT-containing emulsions during an intravenous fat-tolerance test (IVFTT) are scarce. We performed this test (0.1 g lipid/kg body weight) in 18 young healthy volunteers (nine females and nine males) using Lipofundin MCT 10% (50% MCT; egg phospholipids as emulsifier). Our results indicate that both elimination and metabolization of the emulsion are fast: a prompt decrease of light-scattering index and of triglyceride concentrations in serum, an immediate appearance of post-load fatty acids and of beta-hydroxybutyrate were observed. This was in good agreement with the findings obtained during 6-hr infusions in the same probands. Fractional elimination rates k2 obtained from light-scattering indices are 7.29 +/- 2.73%/min in males and 11.59 +/- 3.38%/min in females, indicating a higher removal capacity in women. In the same subjects, the corresponding k2 values for Lipofundin S 10% (containing only long chain triglycerides) were higher, reflecting an elimination rate that is faster due to the use of soya bean phospholipids as emulsifier. In comparison, k2 values based on the course of the triglyceride concentrations are generally lower.

Intraindividueller Vergleich der Eliminationskinetik von Lipofundin^®S und Intralipid^® in aufeinanderfolgenden Fettoleranztests

Wir führten je zwei intravenöse Fettoleranztests (IVFTT) bei 16 gesunden Personen und 8 Patienten mit Hypertriglyceridämie (HTG) aus. Dabei verglichen wir Lipofundin^® S (Braun, Melsungen) mit Intralipid^® (Kabivitrum, Stockholm), beide in 10- und 20%igen Konzentrationen. Der Zeitabstand betrug 1 h bei Gesunden und 2 h bei Probanden mit HTG. Die fraktionellen Eliminationsraten K2 wurden aus der Streulichtintensität des Serums ermittelt. Sie waren signifikant höher für Lipofundin S (9,61%/min für gesunde Manner und 12,48%/ min für gesunde Frauen) im Vergleich zu Intralipid (7,09%/min für gesunde Manner und 9,41%/min für gesunde Frauen). Diese Differenz trat auf unabhängig von: 1. Der Serumtriglyceridkonzentration und dem Geschlecht der Probanden, 2. den Konzentrationen der Lipidemulsionen (10 oder 20%) und 3. der Testfolge (Lipofundin S oder Intralipid zuerst). Dies bedeutet, daß die Eliminationskinetik im IVFTT von dem vorausgegangenen Test beeinflußt war. Gemeinsamkeiten zwischen beiden Emulsionstypen waren: 1. Schnellere Elimination bei Frauen im Vergleich zu Männern und bei Gesunden im Vergleich zu HTG-Patienten und 2. negative Korrelation der fraktionellen Eliminationsraten zur Serumtriglyceridkonzentration. Die fraktionellen Eliminationsraten von Lipofundin S und Intralipid waren eng korreliert. Offenbar gibt es eine intraindividuell charakteristische Elimínationskapazität für exogene Triglyceride.

Loss of fat, water, and protein during very low calorie diets and complete starvation

The magnitude and composition of weight loss obtained in obese women on two forms of very low calorie protein-supplemented diets (Cambridge diet, Dresden drink) as well as by complete starvation has been investigated. With the VLCD, nitrogen equilibrium was reached on the 10th day of fasting, the cumulative nitrogen balance also being compensated. Nearly half of the body weight loss is due to loss of fat. In order to assess the benefit of fasting regimes, we propose to measure at least two parameters which are independent of each other, e.g., nitrogen balance and total body water. Both types of VLCD were equally effective, safe, and acceptable in achieving rapid body weight reduction.

[Metabolism kinetic characterization of hypertriglyceridemias in drug therapy variations]

In 26 male patients with primary hypertriglyceridemia (HTG) the radioglycerol labelling technique was used to assess triglyceride production rates and fractional catabolic rates pertaining to the rapidly turning-over compartment of endogenously produced triglycerides (TG). On the basis of these data the patients were allotted to 3 groups: group I with predominating TG overproduction, group II with predominating disturbances of TG removal from the bloodstream, and group III with a combination of both dysfunctions. All patients were examined prior to and after 4 weeks of drug intake at the metabolic ward. Each group got a medical treatment aiming at removing the pathogenetic cause of the HTG. Biguanides used in group I decreased TG production rates without affecting fractional catabolic rates. In group II an anabolic steroid (chlormethyltestosterone) proved to be able to improve TG removal, but this improvement was accompanied by a significant lowering of HDL cholesterol and an increase in LDL cholesterol. In contrast, clofibric acid influenced both overproduction and removal impairment in group III. Our results give an insight into mechanisms of action of certain lipid-lowering drugs providing a basis for future improvements in the elimination of the risk factor HTG.

Testicular cysts: US findings

Testicular cysts have been considered rare. However, of 307 men who underwent high-resolution ultrasonography (10 MHz) of the scrotum, 30 (9.8%) had testicular cysts. Thirty-three testes were involved, 23 with single cysts, eight with clusters of multiple tiny cysts, and two with more than one focus of cyst. One cyst was aspirated intraoperatively, and one cyst of the tunica albuginea was proved at surgery. Eighty cadaveric testes were scanned also, and cysts were found in one. In two cases, the pathologic report, reviewed retrospectively, failed to mention the cyst, but these cysts could have been overlooked. Further work is needed to determine when or if these testicular lesions need follow-up and what significance they have, if any.

Elimination kinetics of Lipofundin MCT: bolus injection and infusion compared

Fifteen healthy young probands (nine males, six females) underwent an intravenous fat tolerance test (IVFTT) and, on the following day, a fat infusion lasting 6 hr. The emulsion tested was Lipofundin MCT 10%. One half of its triglyceride mass contains medium chain fatty acids. The IVFTT was started by injection of 0.1 g lipid per kg body weight into the fasting proband. Lipid elimination was estimated by measurement of light-scattering intensity of serum samples collected during a 60-min period. Individual fraction elimination rate constants covered a considerable range (K2 = 8.84 +/- 3.45%/min). The infusion test was performed at a rate of 0.1 g lipid per kg body weight and hr and lasted 6 hr. Serum triglyceride concentrations were determined enzymatically. They increased from 0.941 +/- 0.285 mmol/liter at the fasting state to a plateau level of 1.753 +/- 0.306 mmol/liter during infusion, and returned to initial levels 1 to 2 hr after the infusion was terminated. Individual triglyceride increments during infusion were significantly correlated with half-life periods of lipid elimination during IVFTT (r = 0.792, p less than 0.001). This relationship was derived using a model of the stationary state during infusion. We conclude that elimination kinetics of exogenous fat given either as bolus or infusion are ruled by the same fractional elimination rate constant K2. The IVFTT provides an estimate of the stationary triglyceride increment during a lipid infusion lasting several hr.

Predictive value of the index of desirable body weight for total body fat mass as measured by dilution of tritiated water--problems and limitations

The index of desirable body weight is currently used for classification of patients' weights. We examined how it is related to the degree of adiposity, and whether it can serve in the prediction of body fat to the same degree as Quetelet's index. Sixty-five women and 142 men comprising a wide range of weight indices were studied. Body fat (F) was measured by the tritium dilution technique with a precision of +/- 1.26 kg. Regressions of F/W0 on the index of desirable weight W/W0 gave a correlation coefficient of 0.969 for women and 0.939 for men. Regressions of F/H2 on Quetelet's index W/H2 had correlation coefficients of the same order, i.e. 0.971 for women and 0.936 for men. Hence both indices are equally powerful for calculation of body fat within the study population. Further progress was achieved by multiple regression of F on W and W0 which yielded correlation coefficients of 0.976 for women and 0.953 for men. The residual standard deviation reflecting the mean difference between calculated and estimated fat was 3.4 kg for women and 3.8 kg for men. Despite this self-consistency, prediction of body fat for persons outside the study population is only possible within wide limits. These are given by about twice the residual standard deviation. Therefore, prediction of body fat from weight indices can only be used for detection of larger abnormalities in body composition.

Effects of high doses of oestrogens and androgens on lipoproteins: observations in the treatment of excessive growth with sexual hormones

In a prospective study we investigated the changes of lipoprotein metabolism under therapy with high doses of oestrogens or androgens, applied to stop the excessive growth of very tall girls or boys. Therapy with 2 mg ethinyl oestradiol sulfonate per week for one year in 11 girls resulted in an increase in serum triglycerides, which was reversible after cessation, and a minimal rise of total cholesterol and HDL-cholesterol in the phase of adaptation to this treatment. Therapy with 1000 mg testosterone oenanthate per month for one year lead to a fall of triglycerides and HDL-cholesterol. These changes are considered as a regulative phenomenon, without consequences for the application of the high dosage therapy with these steroid hormones in the treatment of excessive growth.