Differences in faecal microbiome composition between adult patients with UCD and PKU and healthy control subjects

Urea cycle disorders (UCDs) are a group of rare inherited metabolic diseases causing hyperammonemic encephalopathy. Despite intensive dietary and pharmacological therapy, outcome is poor in a subset of UCD patients. Reducing ammonia production by changing faecal microbiome in UCD is an attractive treatment approach. We compared faecal microbiome composition of 10 UCD patients, 10 healthy control subjects and 10 phenylketonuria (PKU) patients. PKU patients on a low protein diet were included to differentiate between the effect of a low protein diet and the UCD itself on microbial composition. Participants were asked to collect a faecal sample and to fill out a 24 h dietary journal. DNA was extracted from faecal material, taxonomy was assigned and microbiome data was analyzed, with a focus on microbiota involved in ammonia metabolism.In this study we show an altered faecal microbiome in UCD patients, different from both PKU and healthy controls. UCD patients on dietary and pharmacological treatment had a less diverse faecal microbiome, and the faecal microbiome of PKU patients on a protein restricted diet with amino acid supplementation showed reduced richness compared to healthy adults without a specific diet. The differences in the microbiome composition of UCD patients compared to healthy controls were in part related to lactulose use. Other genomic process encodings involved in ammonia metabolism, did not seem to differ. Since manipulation of the microbiome is possible, this could be a potential treatment modality. We propose as a first next step, to study the impact of these faecal microbiome alterations on metabolic stability.

TAKE HOME MESSAGE

The faecal microbiome of UCD patients was less diverse compared to PKU patients and even more compared to healthy controls.

Improvement of lipid profile is accompanied by atheroprotective alterations in high-density lipoprotein composition upon tumor necrosis factor blockade: a prospective cohort study in ankylosing spondylitis

OBJECTIVE

Cardiovascular mortality is increased in ankylosing spondylitis (AS), and inflammation plays an important role. Inflammation deteriorates the lipid profile and alters high-density lipoprotein cholesterol (HDL-c) composition, reflected by increased concentrations of serum amyloid A (SAA) within the particle. Anti-tumor necrosis factor (anti-TNF) treatment may improve these parameters. We therefore undertook the present study to investigate the effects of etanercept on lipid profile and HDL composition in AS.

METHODS

In 92 AS patients, lipid levels and their association with the inflammation markers C-reactive protein (CRP), erythrocyte sedimentation rate, and SAA were evaluated serially during 3 months of etanercept treatment. HDL composition and its relationship to inflammation markers was determined in a subgroup of patients, using surface-enhanced laser desorption/ionization time-of-flight analysis.

RESULTS

With anti-TNF treatment, levels of all parameters of inflammation decreased significantly, whereas total cholesterol, HDL-c, and apolipoprotein A-I (Apo A-I) levels increased significantly. This resulted in a better total cholesterol:HDL-c ratio (from 3.9 to 3.7) (although the difference was not statistically significant), and an improved Apo B:Apo A-I ratio, which decreased by 7.5% over time (P=0.008). In general, increases in levels of all lipid parameters were associated with reductions in inflammatory activity. In addition, SAA was present at high levels within HDL particles from AS patients with increased CRP levels and disappeared during treatment, in parallel with declining plasma levels of SAA.

CONCLUSION

Our results show for the first time that during anti-TNF therapy for AS, along with favorable changes in the lipid profile, HDL composition is actually altered whereby SAA disappears from the HDL particle, increasing its atheroprotective ability. These findings demonstrate the importance of understanding the role of functional characteristics of HDL-c in cardiovascular diseases related to chronic inflammatory conditions.

ApoAI-phosphatidylcholine infusion neutralizes the atherothrombotic effects of C-reactive protein in humans

BACKGROUND

High-density lipoprotein (HDL) exerts a variety of anti-atherothrombotic functions, including a potent anti-inflammatory impact. In line, the direct pro-inflammatory effects of C-reactive protein (CRP) can be attenuated by HDL in vitro.

OBJECTIVE

To evaluate whether this also holds true in humans, we assessed the ability of reconstituted HDL to neutralize CRP-mediated activation of coagulation and inflammation.

METHODS

Fifteen healthy male volunteers received an infusion of recombinant human (rh)CRP (1.25 mg kg(-1) body weight). In eight of these volunteers, an infusion of human apoAI reconstituted with phosphatidylcholine (apoAI-PC; 80 mg kg(-1) body weight) preceded rhCRP infusion.

RESULTS

Infusion of rhCRP alone elicited an inflammatory response and thrombin generation. In individuals who received apoAI-PC prior to rhCRP, these effects were abolished. Parallel tests in primary human endothelial cells showed that apoAI-PC preincubation with rhCRP abolished the CRP-mediated activation of inflammation as assessed by IL-6 release. Although we were able to show that rhCRP co-eluted with HDL after size-exclusion chromatography, plasmon surface resonance indicated the absence of a direct interaction between HDL and CRP.

CONCLUSION

Infusion of apoAI-PC prior to rhCRP in humans completely prevents the direct atherothrombotic effects of rhCRP. These findings imply that administration of apoAI-PC may offer benefit in patients with increased CRP.

Perioperative hyperinsulinaemic normoglycaemic clamp causes hypolipidaemia after coronary artery surgery

BACKGROUND

Glucose-insulin-potassium (GIK) administration is advocated on the premise of preventing hyperglycaemia and hyperlipidaemia during reperfusion after cardiac interventions. Current research has focused on hyperglycaemia, largely ignoring lipids, or other substrates. The present study examines lipids and other substrates during and after on-pump coronary artery bypass grafting and how they are affected by a hyperinsulinaemic normoglycaemic clamp.

METHODS

Forty-four patients were randomized to a control group (n=21) or to a GIK group (n=23) receiving a hyperinsulinaemic normoglycaemic clamp during 26 h. Plasma levels of free fatty acid (FFA), total and lipoprotein (VLDL, HDL, and LDL)-triglycerides (TG), ketone bodies, and lactate were determined.

RESULTS

In the control group, mean FFA peaked at 0.76 (sem 0.05) mmol litre(-1) at early reperfusion and decreased to 0.3-0.5 mmol litre(-1) during the remaining part of the study. GIK decreased FFA levels to 0.38 (0.05) mmol litre(-1) at early reperfusion, and to low concentrations of 0.10 (0.01) mmol litre(-1) during the hyperinsulinaemic clamp. GIK reduced the area under the curve (AUC) for FFA by 75% and for TG by 53%. The reduction in total TG was reflected by a reduction in the VLDL (-54% AUC) and HDL (-42% AUC) fraction, but not in the LDL fraction. GIK prevented the increase in ketone bodies after reperfusion (-44 to -47% AUC), but was without effect on lactate levels.

CONCLUSIONS

Mild hyperlipidaemia was only observed during early reperfusion (before heparin reversal) and the hyperinsulinaemic normoglycaemic clamp actually resulted in hypolipidaemia during the largest part of reperfusion after cardiac surgery.

Lipopolysaccharide is transferred from high-density to low-density lipoproteins by lipopolysaccharide-binding protein and phospholipid transfer protein

Lipopolysaccharide (LPS), the major outer membrane component of gram-negative bacteria, is a potent endotoxin that triggers cytokine-mediated systemic inflammatory responses in the host. Plasma lipoproteins are capable of LPS sequestration, thereby attenuating the host response to infection, but ensuing dyslipidemia severely compromises this host defense mechanism. We have recently reported that Escherichia coli J5 and Re595 LPS chemotypes that contain relatively short O-antigen polysaccharide side chains are efficiently redistributed from high-density lipoproteins (HDL) to other lipoprotein subclasses in normal human whole blood (ex vivo). In this study, we examined the role of the acute-phase proteins LPS-binding protein (LBP) and phospholipid transfer protein (PLTP) in this process. By the use of isolated HDL containing fluorescent J5 LPS, the redistribution of endotoxin among the major lipoprotein subclasses in a model system was determined by gel permeation chromatography. The kinetics of LPS and lipid particle interactions were determined by using Biacore analysis. LBP and PLTP were found to transfer LPS from HDL predominantly to low-density lipoproteins (LDL), in a time- and dose-dependent manner, to induce remodeling of HDL into two subpopulations as a consequence of the LPS transfer and to enhance the steady-state association of LDL with HDL in a dose-dependent fashion. The presence of LPS on HDL further enhanced LBP-dependent interactions of LDL with HDL and increased the stability of the HDL-LDL complexes. We postulate that HDL remodeling induced by LBP- and PLTP-mediated LPS transfer may contribute to the plasma lipoprotein dyslipidemia characteristic of the acute-phase response to infection.