Telomere length increase after weight loss induced by bariatric surgery: results from a 10 year prospective study.

BACKGROUND/OBJECTIVES: Obesity contributes to telomere attrition. Studies focusing on short-term effects of weight loss have been unable to identify protection of telomere length. This study investigates long-term effects of pronounced weight loss induced by bariatric surgery on telomere length. SUBJECTS/METHODS: One hundred forty-two patients were recruited in a prospective, controlled intervention study, follow-up investigations were done after 10.46±1.48 years. A control group of normal weight participants was recruited and followed from 1995 to 2005 in the Bruneck Study. A total of 110 participants from each study was matched by age and sex to compare changes in telomere length. Quantitative PCR was used to determine telomere length. RESULTS: Telomere length increased significantly by 0.024±0.14 (P=0.047) in 142 bariatric patients within 10 years after surgery. The increase was different from telomere attrition in an age- and sex-matched cohort population of the Bruneck Study (-0.057±0.18; ß=0.08; P=0.003). Significant changes in telomere length disappeared after adjusting for baseline body mass index (BMI) because of general differences in BMI and telomere length between the two study populations (ß=0.07; P=0.06). Age was proportional to telomere length in matched bariatric patients (r=0.188; P=0.049) but inversely correlated with telomere length in participants of the Bruneck Study (r=-0.197; P=0.039). There was no association between percent BMI/excess weight loss and telomere attrition in bariatric patients. Baseline telomere length in bariatric patients was inversely associated with baseline plasma cholesterol and triglyceride concentrations. Telomere shortening was associated with lower high-density lipoprotein cholesterol and higher fasting glucose concentration at baseline in bariatric patients. CONCLUSIONS: Increases in relative telomere length were found after bariatric surgery in the long term, presumably due to amelioration of metabolic traits. This may overrule the influence of age and baseline telomere length and facilitate telomere protection in patients experiencing pronounced weight loss.

Acute effects of concentric and eccentric exercise on glucose metabolism and interleukin-6 concentration in healthy males.

Acute muscle-damaging eccentric exercise (EE) negatively affects glucose metabolism. On the other hand, long-term eccentric endurance exercise seems to result in equal or superior positive effects on glucose metabolism compared to concentric endurance exercise. However, it is not known if acute non-muscle-damaging EE will have the same positive effects on glucose metabolism as acute concentric exercise (CE). Interleukin-6 (IL-6) released from the exercising muscles may be involved in the acute adaptations of glucose metabolism after CE and non-muscle-damaging EE. The aim of this study was to assess acute effects of uphill walking (CE) and non-muscle-damaging downhill walking (EE) on glucose metabolism and IL-6 secretion. Seven sedentary non-smoking, healthy males participated in a crossover trial consisting of a 1 h uphill (CE) and a 1 h downhill (EE) walking block on a treadmill. Venous blood samples were drawn before (pre), directly after (acute) and 24 h after (post) exercise. An oral glucose tolerance test (OGTT) was performed before and 24 h after exercise. Glucose tolerance after 1 and 2 hours significantly improved 24 hours after CE (-10.12±3.22%: P=0.039; -13.40±8.24%: P=0.028). After EE only the 1-hour value was improved (-5.03±5.48%: P=0.043). Acute IL-6 concentration rose significantly after CE but not after EE. We conclude that both a single bout of CE and a single bout of non-muscle-damaging EE elicit positive changes in glucose tolerance even in young, healthy subjects. Our experiment indicates that the overall metabolic cost is a major trigger for acute adaptations of glucose tolerance after exercise, but only the IL-6 production during EE was closely related to changes in glycaemic control.

A common polymorphism in the promoter of UCP2 is associated with decreased risk of obesity in middle-aged humans.

Obesity is the most common nutritional disorder in Western society. Uncoupling protein-2 (UCP2) is a recently identified member of the mitochondrial transporter superfamily that is expressed in many tissues, including adipose tissue. Like its close relatives UCP1 and UCP3, UCP2 uncouples proton entry in the mitochondrial matrix from ATP synthesis and is therefore a candidate gene for obesity. We show here that a common G/A polymorphism in the UCP2 promoter region is associated with enhanced adipose tissue mRNA expression in vivo and results in increased transcription of a reporter gene in the human adipocyte cell line PAZ-6. In analyzing 340 obese and 256 never-obese middle-aged subjects, we found a modest but significant reduction in obesity prevalence associated with the less-common allele. We confirmed this association in a population-based sample of 791 middle-aged subjects from the same geographic area. Despite its modest effect, but because of its high frequency (approximately 63%), the more-common risk allele conferred a relatively large population-attributable risk accounting for 15% of the obesity in the population studied.

Plasminogen activator inhibitor 1 and visceral obesity during pronounced weight loss after bariatric surgery.

BACKGROUND AND AIMS: Elevated plasminogen activator inhibitor 1 (PAI-1) concentrations are a hallmark of obesity and are considered to contribute to the development of cardiovascular disease. As adipose tissue constitutes a major source for PAI-1 in obesity, we investigated the individual contribution of subcutaneous and intra-abdominal fat on PAI-1 concentrations during pronounced weight loss after bariatric surgery. METHODS AND RESULTS: Thirty-seven obese adults were examined before and 18 months after surgery. Abdominal fat distribution was determined by ultrasound, metabolic parameters and plasma PAI-1 levels by standard methods. BMI was reduced by 9.2 ± 4.9 kg/m(2), while total fat mass and visceral fat diameter (VFD) decreased by 20.7 ± 11.9 kg and 4.2 ± 2.3 cm, respectively. Concomitantly, PAI-1 levels diminished by 3.2 ± 5.6 ng/ml (all p ≤ 0.015). Change in PAI-1 levels was correlated with change in VFD (r = 0.441, p = 0.008), but not with subcutaneous fat diameter. In stepwise multiple regression analysis change in VFD was an independent predictor of change in PAI-1 concentrations. When adjusted for age and sex or total fat mass associations between PAI-1 and VFD remained significant. CONCLUSION: We demonstrate that VFD is a major determinant for PAI-1 concentrations during pronounced weight loss after bariatric surgery. Thus, significant reduction of visceral fat mass may contribute to the reduced cardiovascular morbidity and mortality after bariatric surgery by a concomitant decrease in PAI-1 concentrations.

The role of apolipoprotein A5 in non-alcoholic fatty liver disease.

BACKGROUND: Apolipoprotein A5 (apoA5) is a recently described liver-specific protein that has been shown to influence triglyceride (TG) metabolism. ApoA5 transgenic mice display dramatically reduced TG levels, while in contrast apoA5 deficiency in humans was reported to result in marked hypertriglyceridemia. ApoA5 exerts its extracellular effects by increasing lipolysis of TG-rich lipoproteins, while in vitro data suggest additional intrahepatic effects. METHODS: In this study the authors set out to investigate a possible role of apoA5 in non-alcoholic fatty liver disease (NAFLD). We thus determined hepatic apoA5 expression in 15 obese subjects with histologically proven NAFLD undergoing bariatric surgery. In addition, the authors established a hepatic cell culture model of apoA5 knockdown by transfecting human hepatoma cells (HepG2) with apoA5 small interfering (si) RNA, and determined intracellular TG content and expression levels of key enzymes and transcription factors of intrahepatic lipid metabolism in these cells. RESULTS: Pronounced weight loss and associated histologically verified improvement of hepatic steatosis were accompanied by significant reductions of hepatic apoA5 mRNA expression levels. Significant apoA5 knockdown in HepG2 cells resulted in a marked decrease of intracellular TG content. When HepG2 cells were co-transfected with apoA5 and peroxisome proliferator-activated receptor gamma (PPARγ), reductions in hepatic TG accumulation were significantly less pronounced when compared to apoA5 siRNA transfected HepG2 cells. CONCLUSIONS: In obese subjects, hepatic apoA5 mRNA expression decreases after weight loss and improvements in hepatic steatosis. The authors' in vitro data demonstrate that apoA5 influences intrahepatic TG metabolism and that these intracellular effects of apoA5 are accompanied by changes in PPARγ mRNA expression. In summary, the data suggest that as well as several other factors, apoA5 might be involved in the pathogenesis of hepatic steatosis.

Evinacumab to treat hypercholesterolemia.

Cardiovascular disease is the most common cause of death worldwide and is mainly due to atherosclerosis. Elevated levels of low-density lipoprotein cholesterol (LDL-C) are the main risk factor for atherosclerosis. Treatment with existing therapies for dyslipidemia and life-style changes are often sufficient to reach the lipid targets and decrease the cardiovascular risk of patients. However, there are patients who cannot reach their targets. Especially patients with genetically caused dyslipidemias, such as familial hypercholesterolemia, often are not able to reach the targets, leading to an increased cardiovascular risk and higher mortality. Evinacumab is a human monoclonal antibody which binds and inhibits angiopoietin-like protein 3 (ANGPTL3). The inhibition of ANGPTL3 leads to increased activity of the lipoprotein lipase (LPL) and the endothelial lipase (EL). LPL is the main enzyme for hydrolyzation of triglyceride-rich lipoproteins. EL is a phospholipase which preferentially hydrolyzes high-density lipoprotein (HDL) but also decreases circulating LDL-C. The increased LPL and EL activity reduces circulating levels of very-low-density lipoprotein cholesterol, triglycerides, LDL-C and HDL-cholesterol. Evinacumab leads to a significant decrease in circulating lipids and attainment of lipid targets in these patients. Further studies with evinacumab to assess its lipid-decreasing potential and to evaluate its impact on cardiovascular risk and mortality are eagerly awaited.

Human immunodeficiency virus type 1 activates the classical pathway of complement by direct C1 binding through specific sites in the transmembrane glycoprotein gp41.

Human immunodeficiency virus type 1 (HIV-1), in contrast to animal retroviruses such as murine leukemia virus, is not lysed by human complement. Nevertheless, HIV-1 activates complement via the classical pathway independent of antibody, and C3b deposition facilitates infection of complement receptor-bearing cells. Using gel exclusion chromatography on Sephacryl S-1000, purified virions were found to bind 125I-labeled C1q, but not 125I-labeled dimeric proenzyme C1s. Virions activated the C1 complex, reconstituted from C1q, proenzyme C1r, and 125I-labeled proenzyme C1s, to an extent comparable with that obtained with immunoglobulin G-ovalbumin immune complexes. To determine the activating viral component, recombinant viral proteins were used: in the solid phase, soluble gp41 (sgp41) (the outer membrane part of gp41, residues 539-684 of gp160) bound C1q, but not dimeric proenzyme C1s, while gp120 was ineffective. In the fluid phase, sgp41 activated the C1 complex in a dose- and time-dependent manner, more efficiently than aggregated Ig, but less efficiently than immune complexes. To localize the C1 activating site(s) in gp41, synthetic peptides (15-residue oligomers spanning amino acids 531-695 of gp160) were used. Peptides covering positions 591-605 and 601-620 and, to a lesser extent, positions 561-575, had both the ability to bind C1q and to induce C3 deposition. These data provide the first experimental evidence of a direct interaction between the C1 complex and HIV-1, and indicate that C1 binding and activation are mediated by specific sites in gp41.

Effect of bariatric surgery on circulating chemerin levels.

BACKGROUND: Subclinical inflammation in obesity is critical for development of several obesity-associated disorders. We set out to investigate the effect of pronounced weight loss on circulating chemerin levels, a chemoattractant protein that also influences adipose cell function by paracrine and autocrine mechanisms. MATERIAL AND METHODS: Thirty-two obese patients undergoing bariatric surgery were tested before and on an average of 18 months after gastric banding or gastric bypass surgery. RESULTS: Pronounced weight loss after bariatric surgery was accompanied by improvements in parameters of lipid and glucose metabolism and increased adiponectin levels. Chemoattractant chemerin significantly decreased from 175.91 +/- 24.50 to 145.53 +/- 26.44 ng mL(-1) after bariatric surgery (P < or = 0.01). Concomitantly, hs-CRP as a marker of subclinical inflammation was significantly reduced after weight reduction (P < or = 0.01). CONCLUSIONS: We hypothesize that weight-loss induced reduction in circulating chemerin might in conjunction with other factors be associated with diminished recruitment of macrophages in adipose tissue and reduction of subclinical inflammation, which again could partly explain beneficial long-term effects of weight reduction in obese subjects.

Effect of postprandial lipemia on plasma concentrations of A-FABP, RBP-4 and visfatin.

BACKGROUND AND AIMS: Several studies indicate that changes in the plasma concentrations of adipocyte-fatty acid binding protein (A-FABP), retinol binding protein-4 (RBP-4) and visfatin are associated with chronic states of insulin resistance. Recent studies have shown that postprandial lipemia induces an acute state of insulin resistance. The aim of this study was to investigate the effect of postprandial lipemia on the plasma concentrations of A-FABP, RBP-4 and visfatin. METHODS AND RESULTS: In a within-subject crossover study, we administered a standardized high-fat meal to 24 healthy subjects (12 males and 12 females). Plasma concentrations of adipocytokines were measured in the morning after an overnight fast and during postprandial lipemia, i.e. 2, 4 and 6 hours after meal ingestion (postprandial experiment). To exclude potential confounding factors affecting the adipocytokine plasma concentrations, a control experiment without meal ingestion was performed over the same time period (postabsorptive control experiment). Comparing plasma concentrations of A-FABP, RBP-4 and visfatin between the postprandial and the postabsorptive control experiments, we found no significant differences. Within either of the two experiments, a decrease of A-FABP was noted reaching, however, statistical significance only in the postprandial experiment, i.e. 2 and 4 hours after meal ingestion. CONCLUSION: Postprandial lipemia has no significant effect on the plasma concentrations of visfatin, A-FABP or RBP-4 in relation to their postabsorptive plasma profiles. We conclude that prolonged states of insulin resistance are required to affect plasma concentrations of these adipocytokines.

Pharmacological and non-pharmacological treatment of non-alcoholic fatty liver disease.

Non-alcoholic fatty liver disease (NAFLD) comprises a disease spectrum ranging from simple steatosis and steatohepatitis to cirrhosis. Based on its strongest risk factors namely visceral obesity and insulin resistance, NAFLD is thought to be the hepatic manifestation of the metabolic syndrome and is considered to be the most common liver disorder in Western countries. Pathophysiological mechanisms include an enlarged pool of fatty acids, subclinical inflammation, oxidative stress and imbalances of various adipocytokines such as adiponectin. Accordingly, targets for therapeutic interventions are miscellaneous: amelioration of obesity by pharmacological, surgical or lifestyle intervention has been evaluated with success in numerous, but not all studies. Some efficacy was reported for metformin and short-term glitazone treatment. In a large recently reported trial, vitamin E supplementation improved biochemical and histological markers in subjects with non-alcoholic steatohepatitis. Blockade of the endocannabinoid system has been proposed to be a promising target in NAFLD; however, very recently the cannabinoid receptor blocker rimonabant has been withdrawn because of central nervous system toxicity. Cytoprotective therapies and statins have been mainly ineffective in NAFLD. New but so far insufficiently studied therapeutic approaches include inhibitors of the renin-angiotensin system as well as incretin mimetics respectively.

Effect of pronounced weight loss on visceral fat, liver steatosis and adiponectin isoforms.

BACKGROUND: Weight loss induced by bariatric surgery is an effective method to reverse obesity and comorbidities. The aim of this prospective weight loss study was to investigate changes of body fat distribution in relation to adiponectin and its isoforms and further to investigate the influence of both body fat distribution and adiponectin on the degree of liver steatosis. DESIGN: Fifteen severely obese female patients (body mass index 43.1 +/- 4.1, mean age 34.5 +/- 8.6 years) were examined before and after surgical treatment. Grading of fatty liver disease and the subcutaneous and visceral fat diameters were determined by abdominal ultrasonography. Metabolic parameters were determined using standard methods; serum total adiponectin and its isoforms were detected by enzyme immuno assay (EIA). RESULTS: Mean weight loss was 28.3 kg, which was mostly due to a loss in fat mass, accompanied by an increase in total adiponectin and the high molecular weight (HMW) adiponectin isoform. Visceral adipose tissue (VAT) diameter was highly correlated with liver steatosis, even more strongly than the parameters of liver function. In addition, liver steatosis correlated negatively with HMW adiponectin and binary logistic regression revealed that changes in fat mass, HMW adiponectin and alanine aminotransferase (ALT) were the best predictors for changes in the degree of hepatic steatosis. CONCLUSIONS: Our results suggest that circulating HMW adiponectin is associated with both VAT and liver steatosis. In summary, the major findings were that the VAT diameter is highly correlated with liver steatosis, even stronger than the parameters of liver function and the association of HMW adiponectin with liver steatosis was better than with total adiponectin.

Effect of obesity and insulin sensitivity on adiponectin isoform distribution.

BACKGROUND: Adiponectin is an insulin-sensitizing, antiatherogenic and anti-inflammatory adipocytokine that circulates in three isoforms: a trimer [low-molecular weight (LMW)], a hexamer (trimer-dimer) of medium molecular weight (MMW) and a multimeric high molecular weight (HMW) isoform. Evidence is accumulating that HMW adiponectin is the active isoform of the adipocytokine. We investigated the impact of adipose tissue and insulin sensitivity on adiponectin isoform distribution. MATERIALS AND METHODS: One hundred and eighty-seven normolipidaemic, non-diabetic lean or obese subjects with or without insulin resistance participating in the Salzburg Atherosclerosis Prevention program in subjects at High Individual Risk (SAPHIR) were included in the study. Insulin sensitivity was determined by the short insulin tolerance test and the homeostasis model assessment (HOMA) index. Serum adiponectin isoform distribution was determined by an enzyme immunoassay. RESULTS: Total adiponectin as well as HMW/total adiponectin ratio was significantly increased in female subjects. Circulating total adiponectin levels were lowest in obese patients due to reduced concentrations of HMW adiponectin. As determined by stepwise regression analysis, besides age and high density lipoprotein (HDL) cholesterol, visceral fat area and waist-to-hip ratio predicted concentrations of HMW adiponectin, while insulin sensitivity had no influence on either total adiponectin or its isoforms. CONCLUSIONS: Our results underline that determination of adiponectin isoforms are more useful than measurement of total adiponectin in clinical settings. Our data suggest that adiponectin concentrations are strongly associated with visceral fat area but not with insulin sensitivity. Thus, we hypothesize that insulin resistance is a consequence rather than the cause of hypoadiponectinaemia in obese subjects.

Effect of valproic acid treatment on body composition, leptin and the soluble leptin receptor in epileptic children.

PURPOSE: The aim of the study was to determine the influence of valproic acid (VPA) treatment on leptin, the soluble leptin receptor (sOB-R), the sOB-R/leptin ratio, body composition and insulin resistance in epileptic children. METHODS: A cross-sectional cohort study was conducted at the Medical University Innsbruck, Austria. Children >6 years with idiopathic epilepsy and antiepileptic drug therapy since at least six months were eligible. Leptin concentration, the sOB-R, the sOB-R/leptin ratio, body composition and glucose homeostasis were determined. RESULTS: 87 children (median [range] age 12.8 years [6.0-18.6]) were on treatment with VPA, 55 (12.3 years [6.4-18.3]) on other AEDs, comprising the non-VPA group. VPA-treated children had higher leptin concentrations, body-mass-index standard-deviation score (SDS), body fat (each p<0.001), serum insulin concentrations (p=0.014) and homeostasis model assessment (HOMA) index (p=0.009), as well as a lower sOB-R/leptin ratio (p<0.001) when compared to the non-VPA group. Overweight VPA-treated children showed lower sOB-R concentrations and a lower sOB-R/leptin ratio (each p<0.001) as well as higher body fat and leptin levels (each p<0.001) compared to lean VPA-treated children. CONCLUSION: VPA monotherapy was associated with higher body weight, body fat and serum leptin concentrations as well as impaired glucose homeostasis. Low sOB-R concentrations and a low sOB-R/leptin ratio in overweight VPA-treated patients might contribute to disturbances in glucose homeostasis and to the development of the metabolic syndrome in these children later in life.

Effect of intradialytic parenteral nutrition in patients with malnutrition-inflammation complex syndrome on body weight, inflammation, serum lipids and adipocytokines: results from a pilot study.

OBJECTIVE: Evaluation of the influence of intradialytic parenteral nutrition (IDPN) in patients suffering from Malnutrition-Inflammation Complex Syndrome (MICS) on nutritional status, inflammation, adipocytokines and serum lipids. SUBJECTS: Six patients with MICS were assigned to IDPN, whereas six patients matched for age, sex, body mass index (BMI) and co-morbidity without malnutrition served as controls. Patients were recruited from Outpatient Dialysis Unit, Medical University Innsbruck and from Dialysis Unit, Hospital Feldkirch. RESULTS: In all patients with IDPN, dry body weight increased during the interventional period whereas body weight remained stable in patients without IDPN. Tumor necrosis factor (TNF)-alpha levels were higher in patients with MICS compared with controls at all time points. Total cholesterol, LDL- and HDL-levels significantly increased during dialysis at all time points in controls but not in patients with MICS. Albumin, C-reactive protein, interleukin-6 (IL-6), soluble interleukin-2 receptor (sIL-2R) and adipocytokines did not differ between patients and controls during the study period. CONCLUSIONS: IDPN in patients with MICS increases body weight despite not influencing inflammatory status. Furthermore, IDPN does not induce a pro-atherogenic lipid composition enhancing the risk for atherosclerosis. Thus, IDPN is a safe and effective treatment of malnutrition in patients with MICS.

Relationship between cholesteryl ester transfer protein and atherogenic lipoprotein profile in morbidly obese women.

OBJECTIVE: Obesity is associated with increased morbidity and mortality from atherosclerotic disease. Lipid abnormalities contribute to the increased relative risk in obese subjects. Cholesteryl ester transfer protein (CETP) mass is increased in these patients and might mediate the atherogenic lipoprotein pattern observed in obesity. METHODS AND RESULTS: Twenty-one morbidly obese, middle-aged, female subjects participated in this prospective study. Subjects were examined before and 1 year after surgical treatment. Fat mass was determined by body impedance analysis; CETP mass, by ELISA; CETP activity, by exogenous substrate assay; and LDL particle diameter, by gradient gel electrophoresis. Mean weight loss after 1 year was 28.7 kg; mean fat mass loss was 22.6 kg. Mean CETP mass decreased from 1.81 to 1.32 microg/mL (P=0.008); mean CETP activity decreased from 244 to 184 nmol x mL(-1) x h(-1) (P=0.004); and in parallel, the mean diameter of LDL particles increased (256.8 to 258.4 A, P=0.04). CONCLUSIONS: We conclude that weight loss is associated with a pronounced decrease in CETP mass and activity and a consistent increase in LDL particle diameter. After 1 year of this prospective study in morbidly obese subjects undergoing weight loss by surgical treatment, it has been determined that some features of the atherogenic lipoprotein profile can be reversed.

HIV-1 rsgp41 depends on calcium for binding of human c1q but not for binding of gp120.

Human immunodeficiency virus type 1 activates the complement cascade via the classical pathway by direct binding of C1q through specific sites in the TM surface protein, gp41. In this paper we investigated the divalent cation dependence of the interaction between HIV-1 gp41 and C1q or gp120. A solid phase radioimmunoassay was used to investigate the interaction between a recombinant soluble form of HIV-1 gp41 (rsgp41) and C1q and an enzyme linked immunoassay was used to investigate the interaction between rsgp41 and gp120. The interaction between C1q and rsgp41, but not between C1q and immune complexes, was dependent upon the presence of calcium. Calcium could not be replaced by larger cations such as strontium, barium, lead or smaller ions such as magnesium and manganese. Zinc increased binding to 22% of binding achieved with calcium. The interaction between rsgp41 and gp120 was not dependent upon the presence of divalent ions. Thus, calcium is required for the interaction between rsgp41 and C1q, whereas the interaction between rsgp41 and gp120 is independent of divalent cations.

Sera from HIV-1 infected individuals in all stages of disease preferentially recognize the V3 loop of the prototypic macrophage-tropic glycoprotein gp120 ADA.

The outer membrane glycoprotein gp120 and the transmembrane glycoprotein gp41 are predominant targets of the humoral immune response to infection by human immunodeficiency virus type 1. The third hypervariable region (V3 loop) is the principal neutralizing domain and is the primary target of neutralizing antibodies directed against the envelope proteins of HIV-1. The V3 loop is also the major determinant for HIV-1 cell-specific tropism. To further characterize the humoral immune response directed against the gp120 envelope proteins, we expressed two prototypic gp120 envelope proteins (LAI/HXB2 and ADA) and chimeric gp120 envelope proteins in stable transfected Drosophila melanogaster Schneider 2 cells. Sera from four infected adults over the course of infection [McNearney et al. (1992) Proc. natn. Acad. Sci. U.S.A. 89, p. 10,242] were assayed for reactivity with the respective envelope proteins. Sera obtained at early stages preferentially recognized the gp120 envelope protein ADA, whereas in later stages of infection the sera showed diminished reactivity with both gp120 LAI/HXB2 and gp120 ADA. Chimeric envelope proteins revealed that the humoral response was directed primarily against the V3 loop of gp120 ADA. Furthermore, 22 sera from HIV-1 infected individuals in different stages of the disease were tested. Reactivity of sera with the gp120 envelope protein ADA was seven-fold higher than with the gp120 envelope protein LAI/HXB2. Our results suggest that the humoral immune response is preferentially elicited against the V3 loop of the prototypic macrophage-tropic gp120 envelope protein ADA.

Pronounced postprandial lipemia impairs endothelium-dependent dilation of the brachial artery in men.

OBJECTIVE: Pronounced postprandial lipemia has been established as a risk factor for cardiovascular disease, but reports regarding its effect on endothelial function have been controversial. In the present study the influence of a standardized fatty meal with its ensuing postprandial lipemia of highly varying magnitude on endothelium-dependent dilation (EDD) was investigated. METHODS: In 17 healthy, normolipidemic men EDD of the brachial artery was quantified in two series of three measurements each. In both series initial measurements were performed at 08:00 h after an overnight fast followed by measurements at 12:00 and 16:00 h, in the first series with continued fasting and in the second following the ingestion of a standardized fatty test meal 4 and 8 h postprandially. RESULTS: Measurements of EDD in the fasting state revealed the recently appreciated diurnal variation with higher values in noon and afternoon hours compared with morning values (2.5+/-1.6% at 08:00, 7.5+/-2.7% at 12:00, and 7.0+/-2.1% at 16:00 h, P<0.001 by analysis of variance). Postprandial EDD values measured at 12:00 h were, at the average, lower than fasting EDD values measured at 12:00 h and correlated inversely with the magnitude of postprandial triglyceridemia (r=-0.81, P<0.001). In multivariate analysis, higher postprandial lipemia was associated with impaired postprandial EDD (P<0.001) independent of fasting triglycerides, low density lipoprotein (LDL) and high density lipoprotein (HDL) cholesterol, insulin, age and body mass index. CONCLUSION: We conclude that pronounced postprandial lipemia is associated with transient impairment of endothelial function. Our findings support the notion that impaired triglyceride metabolic capacity plays an important role in atherogenesis.

Interaction of several complement proteins with gp120 and gp41, the two envelope glycoproteins of HIV-1.

OBJECTIVE: To study the binding of human complement proteins to gp41 and gp120 of HIV-1. METHODS: The interaction of complement proteins with gp41 and gp120 and their effect on the gp41-gp120 complex in enzyme-linked immunosorbent assays (ELISA) and on stably transfected Schneider-2 cells expressing a gp41-gp120 complex was investigated. The molecular basis of these interactions was analysed by computer-supported sequence analysis. RESULT: gp41 strongly binds human complement regulatory proteins factors H and properdin, and weakly binds factors I and B. The binding occurs with recombinant soluble (rs) gp41 fixed on ELISA plates as well as gp41-gp120 complex expressed on Schneider-2 cells. The basis for this binding potential might be an amino-acid (aa) sequence of gp41 displaying homologies to sites in human C3. rgp120 also binds C3(H2O), a C3b-like form of C3, and C4b. These binding features of gp120 can be explained by homology of constant region (CR) 4 in gp120 to sites in C4b binding protein. Additionally, CR1 in gp120 exhibits a weak similarity to human properdin. Preincubation of rsgp41 with either factor H or properdin, and of rgp120 with C3b or C4b affected the interaction between rsgp41 and rgp120. Incubation of Schneider-2 cells, expressing a functional gp41-gp120 complex, with factor H reduced the detectable amount of gp120. This effect was similar to that induced by soluble CD4. CONCLUSION: These results strongly suggest that HIV-1 envelope proteins interact with human complement proteins. Additionally, C3b-like features of gp41 and the C3b/C4b binding structures in gp120 may affect the non-covalent association between gp41 and gp120.

Structure-function relationships of the HIV-1 envelope V3 loop tropism determinant: evidence for two distinct conformations.

OBJECTIVE: The V3 loop of the HIV-1 envelope glycoprotein gp120 is an important determinant of HIV-1-specific cell tropism. Nine different purified envelope proteins were prepared in order to examine the association between the structure of the gp120 proteins and functional properties of HIV-1 virions differing in their tropism for T-cell lines and macrophages. RESULTS: Six monoclonal antibodies to the V3 loop reacted preferentially with T-cell line-tropic gp120 envelope proteins, and one monoclonal antibody reacted preferentially with macrophage-tropic gp120 envelope proteins. T-cell line-tropic gp120 envelope proteins were at least 10-fold more susceptible to V3 loop proteolytic cleavage by human thrombin, and 1000-fold more susceptible to V3 loop proteolytic cleavage by human mast cell tryptase than macrophage-tropic gp120 envelope proteins. CONCLUSIONS: These findings suggest that there are two distinct conformations for the V3 loop of T-cell line-tropic and macrophage-tropic gp120 envelope proteins.