Effect of chronic kidney disease on macrophage cholesterol efflux.

AIMS: Patients with chronic kidney disease (CKD) have a high risk to develop atherosclerosis. The capacity of high-density lipoproteins (HDL) or serum to accept cholesterol from macrophages and the capacity of macrophages to export excess cholesterol are critical for the atheroprotective role of reverse cholesterol transport. HDL cholesterol acceptor capacity was reported to be decreased in middle aged hemodialysis patients, but the role of confounding factors remains unclear. MAIN METHODS: We measured the cholesterol acceptor capacity (CAC) of HDL or serum in 12 pediatric and 17 young adult patients with CKD stages 3-5, 14 young adult hemodialysis patients and 15 adult renal transplant recipients without associated diseases and matched controls using THP-1 macrophages. Moreover we studied the cholesterol export capacity (CEC) of patients' monocyte-derived macrophages (HMDMs) to control serum or HDL. KEY FINDINGS: In adults with CKD stages 3-5 serum CAC was slightly increased, whereas CEC of HMDMs was unaltered in both, adult and pediatric patients. In hemodialysis patients, however, serum CAC was markedly reduced to 85±11% of control (p<0.001), presumably due to low serum apolipoprotein A-I. Interestingly, CEC of HMDMs from dialysis patients was increased. In transplant patients no alterations were found. SIGNIFICANCE: CKD without hemodialysis does not reduce cholesterol export from macrophages. Hemodialysis patients might benefit from therapies aiming to restore serum CAC by increasing apolipoprotein A-I. The enhanced export of cholesterol by HMDMs from dialysis patients may represent an adaptive response.

Profound Changes in Sex Hormone Levels during Cross-Sex Hormone Therapy of Transsexuals do not Alter Serum Cholesterol Acceptor Capacity.

INTRODUCTION: Men and postmenopausal women exhibit a higher risk for atherosclerosis than premenopausal women. These differences were often attributed to sex steroids, but the role of estrogen and testosterone in atherosclerosis are more complex than anticipated. Cross-sex hormone therapy of transsexuals is an interesting model, which has been used to study hormonal effects on serum lipid profile, insulin resistance, and body composition. However, studies on macrophage cholesterol efflux, the first step in reverse cholesterol transport, are not available. AIM: The aim of this study was to evaluate the effect of cross-sex hormone therapy in transsexuals on the capacity of serum to accept cholesterol from macrophages. METHODS: Cholesterol acceptor capacity (CAC) of serum from transsexuals before and after at least 6 months of hormone treatment was measured using macrophage tissue culture models. MAIN OUTCOME MEASURES: CAC of serum using the human acute monocytic leukemia cell line (THP-1 cells). RESULTS: Unexpectedly, the CAC of serum from male to female (MtF) transsexuals was not increased, but decreased after hormone therapy. Serum from female to male (FtM) transsexuals showed no changes in CAC. CONCLUSIONS: Despite drastic changes in hormone status, no increase in CAC was detected in MtF patients, and no alteration in CAC was seen in FtM patients. These data further challenge the traditional view that estrogen and testosterone exert beneficial and detrimental effects, respectively, on lipoprotein metabolism and ultimately atherosclerosis.

Metabolic features of Protochlamydia amoebophila elementary bodies--a link between activity and infectivity in Chlamydiae.

The Chlamydiae are a highly successful group of obligate intracellular bacteria, whose members are remarkably diverse, ranging from major pathogens of humans and animals to symbionts of ubiquitous protozoa. While their infective developmental stage, the elementary body (EB), has long been accepted to be completely metabolically inert, it has recently been shown to sustain some activities, including uptake of amino acids and protein biosynthesis. In the current study, we performed an in-depth characterization of the metabolic capabilities of EBs of the amoeba symbiont Protochlamydia amoebophila. A combined metabolomics approach, including fluorescence microscopy-based assays, isotope-ratio mass spectrometry (IRMS), ion cyclotron resonance Fourier transform mass spectrometry (ICR/FT-MS), and ultra-performance liquid chromatography mass spectrometry (UPLC-MS) was conducted, with a particular focus on the central carbon metabolism. In addition, the effect of nutrient deprivation on chlamydial infectivity was analyzed. Our investigations revealed that host-free P. amoebophila EBs maintain respiratory activity and metabolize D-glucose, including substrate uptake as well as host-free synthesis of labeled metabolites and release of labeled CO2 from (13)C-labeled D-glucose. The pentose phosphate pathway was identified as major route of D-glucose catabolism and host-independent activity of the tricarboxylic acid (TCA) cycle was observed. Our data strongly suggest anabolic reactions in P. amoebophila EBs and demonstrate that under the applied conditions D-glucose availability is essential to sustain metabolic activity. Replacement of this substrate by L-glucose, a non-metabolizable sugar, led to a rapid decline in the number of infectious particles. Likewise, infectivity of Chlamydia trachomatis, a major human pathogen, also declined more rapidly in the absence of nutrients. Collectively, these findings demonstrate that D-glucose is utilized by P. amoebophila EBs and provide evidence that metabolic activity in the extracellular stage of chlamydiae is of major biological relevance as it is a critical factor affecting maintenance of infectivity.