Changes in apolipoprotein E-containing high-density lipoprotein (HDL) have little impact on HDL-cholesterol measurements using homogeneous assays in normolipidemic and dyslipidemic subjects

Sichuan dark tea improves lipid metabolism and prevents aortic lipid deposition in diet-induced atherosclerosis model rats

Background and aims

Sichuan dark tea (ST), Zangcha, is a traditional fermented Chinese tea found in Sichuan and Tibet and claimed for beneficial effects against lifestyle-related metabolic disorders. We examined the effects of ST on lipid metabolism and atherosclerosis.

Methods and results

Sichuan dark tea was given to fat-rich diet-induced atherosclerosis model rats in comparison with dark-fermented Chinese Pu-erh tea (PT) and Japanese green tea (GT). After 8 weeks of feeding, ST and PT induced an increase in high-density lipoprotein (HDL)-cholesterol and a decrease in glucose, and ST decreased triglyceride in plasma. ST also induced low pH in the cecum. There was no significant change in their body weight among the fat-feeding groups but a decrease was found in the visceral fat and liver weight in the ST group. Accordingly, ST reduced lipid deposition in the aorta in comparison with PT and GT. ST increased mRNA of LXRα, PPARα, PPARγ, and ABCA1 in the rat liver. The extract of ST stimulated the AMPK pathway to increase the expression of ABCA1 in J774 cells and increased expression of lipoprotein lipase and hormone-sensitive lipase in 3T3L1 cells, consistent with its anti-atherogenic effects in rats. High-performance liquid chromatography analysis showed unique spectra of original specific compounds of caffeine and catechins in each tea extract, but none of them was likely responsible for these effects.

Conclusion

Sichuan dark tea increases plasma HDL and reduces plasma triglyceride to decrease atherosclerosis through AMPK activation. Further study is required to identify specific components for the effects of this tea preparation.

Soluble LR11 competes with amyloid β in binding to cerebrospinal fluid-high-density lipoprotein

BACKGROUND

LR11 is a member of the low-density lipoprotein (LDL) receptor family with high expression in neurons. Some cell surface LR11 is cleaved and secreted into the cerebrospinal fluid (CSF) as soluble LR11 (sLR11). Patients with Alzheimer's disease (AD), particularly apolipoprotein E4 carriers, have high CSF-sLR11 and low CSF-amyloid β (Aβ) concentrations. Therefore, we assessed whether sLR11 is bound to CSF-high-density lipoprotein (HDL) and whether sLR11 competes with Aβ in binding to apoE in CSF-HDL.

METHODS

We measured CSF-sLR11 concentrations (50 controls and 16 patients with AD) using enzyme immunoassay. sLR11 and apoE distribution in the CSF was evaluated using non-denaturing two-dimensional gel electrophoresis (N-2DGE). ApoE bound to sLR11 or Aβ was identified using co-immunoprecipitation assay.

RESULTS

CSF-sLR11 concentrations were higher in patients with AD than controls (adjusted for sLR11 using phospholipid). N-2DGE analysis showed that sLR11 and Aβ comigrated with a large apoE-containing CSF-HDL. Moreover, fewer apoE was bound to Aβ when a higher amount of apoE was bound to sLR11 in patients with AD who presented with ε4/4.

CONCLUSION

sLR11 binds to CSF-HDL and competes with Aβ in binding to apoE in CSF-HDL, indicating that sLR11 affects Aβ clearance via CSF-HDL.

Low-density lipoprotein (LDL)-dependent uptake of Gram-positive lipoteichoic acid and Gram-negative lipopolysaccharide occurs through LDL receptor

Lipoteichoic acid (LTA) and lipopolysaccharide (LPS) are bacterial lipids that stimulate pro-inflammatory cytokine production, thereby exacerbating sepsis pathophysiology. Proprotein convertase subtilisin/kexin type 9 (PCSK9) negatively regulates uptake of cholesterol by downregulating hepatic lipoprotein receptors, including low-density lipoprotein (LDL) receptor (LDLR) and possibly LDLR-related protein-1 (LRP1). PCSK9 also negatively regulates Gram-negative LPS uptake by hepatocytes, however this mechanism is not completely characterized and mechanisms of Gram-positive LTA uptake are unknown. Therefore, our objective was to elucidate the mechanisms through which PCSK9 regulates uptake of LTA and LPS by investigating the roles of lipoproteins and lipoprotein receptors. Here we show that plasma PCSK9 concentrations increase transiently over time in septic and non-septic critically ill patients, with highly similar profiles over 14 days. Using flow cytometry, we demonstrate that PCSK9 negatively regulates LDLR-mediated uptake of LTA and LPS by HepG2 hepatocytes through an LDL-dependent mechanism, whereas LRP1 and high-density lipoprotein do not contribute to this uptake pathway. Bacterial lipid uptake by hepatocytes was not associated with cytokine production or hepatocellular injury. In conclusion, our study characterizes an LDL-dependent and LDLR-mediated bacterial lipid uptake pathway regulated by PCSK9, and provides evidence in support of PCSK9 inhibition as a potential therapeutic strategy for sepsis.

Immune-mediated acquired lecithin-cholesterol acyltransferase deficiency: A case report and literature review

BACKGROUND

Recessive inherited disorder lecithin-cholesterol acyltransferase (LCAT) deficiency causes severe hypocholesterolemia and nephrotic syndrome. Characteristic lipoprotein subfractions have been observed in familial LCAT deficiency (FLD) with renal damage.

OBJECTIVE

We described a case of acquired LCAT deficiencies with literature review.

METHODS

The lipoprotein profiles examined by gel permeation-high-performance liquid chromatography (GP-HPLC) and native 2-dimensional electrophoresis before and after prednisolone (PSL) treatment.

RESULTS

Here we describe the case of a 67-year-old man with severely low levels of cholesterol. The serum LCAT activity was undetectable, and autoantibodies against it were detected. The patient developed nephrotic syndrome at the age of 70 years. Renal biopsy revealed not only membranous glomerulonephritis but also lesions similar to those seen in FLD. We initiated PSL treatment, which resulted in remission of the nephrotic syndrome. In GP-HPLC analysis, lipoprotein profile was similar to that of FLD although lipoprotein X level was low. Acquired LCAT deficiencies are extremely rare with only 7 known cases including ours. Patients with undetectable LCAT activity levels develop nephrotic syndrome that requires PSL treatment; cases whose LCAT activity levels can be determined may also develop nephrotic syndrome, but spontaneously recover.

CONCLUSION

Lipoprotein X may play a role in the development of renal impairment in individuals with FLD. However, the effect might be less significant in individuals with acquired LCAT deficiency.