Application of partition coefficient methods to predict tissue:plasma affinities in common farm animals: Influence of ionisation state

Tissue affinities are conventionally determined from in vivo steady-state tissue and plasma or plasma-water chemical concentration data. In silico approaches were initially developed for preclinical species but standardly applied and tested in human physiologically-based kinetic (PBK) models. Recently, generic PBK models for farm animals have been made available and require partition coefficients as input parameters. In the current investigation, data for species-specific tissue compositions have been collected, and prediction of chemical distribution in various tissues of livestock species for cattle, chicken, sheep and swine have been performed. Overall, tissue composition was very similar across the four farm animal species. However, small differences were observed in moisture, fat and protein content in the various organs within each species. Such differences could be attributed to factors such as variations in age, breed, and weight of the animals and general conditions of the animal itself. With regards to the predictions of tissue:plasma partition coefficients, 80 %, 71 %, 77 % of the model predictions were within a factor 10 using the methods of Berezhkovskiy (2004), Rodgers and Rowland (2006) and Schmitt (2008). The method of Berezhkovskiy (2004) was often providing the most reliable predictions except for swine, where the method of Schmitt (2008) performed best. In addition, investigation of the impact of chemical classes on prediction performance, all methods had very similar reliability. Notwithstanding, no clear pattern regarding specific chemicals or tissues could be detected for the values predicted outside a 10-fold change in certain chemicals or specific tissues. This manuscript concludes with the need for future research, particularly focusing on lipophilicity and species differences in protein binding.

The expanding organelle lipidomes: current knowledge and challenges

Lipids in cell membranes and subcellular compartments play essential roles in numerous cellular processes, such as energy production, cell signaling and inflammation. A specific organelle lipidome is characterized by lipid synthesis and metabolism, intracellular trafficking, and lipid homeostasis in the organelle. Over the years, considerable effort has been directed to the identification of the lipid fingerprints of cellular organelles. However, these fingerprints are not fully characterized due to the large variety and structural complexity of lipids and the great variability in the abundance of different lipid species. The process becomes even more challenging when considering that the lipidome differs in health and disease contexts. This review summarizes the information available on the lipid composition of mammalian cell organelles, particularly the lipidome of the nucleus, mitochondrion, endoplasmic reticulum, Golgi apparatus, plasma membrane and organelles in the endocytic pathway. The lipid compositions of extracellular vesicles and lamellar bodies are also described. In addition, several examples of subcellular lipidome dynamics under physiological and pathological conditions are presented. Finally, challenges in mapping organelle lipidomes are discussed.

Young and undamaged recombinant albumin alleviates T2DM by improving hepatic glycolysis through EGFR and protecting islet β cells in mice

BACKGROUND

Albumin is the most abundant protein in serum and serves as a transporter of free fatty acids (FFA) in blood vessels. In type 2 diabetes mellitus (T2DM) patients, the reduced serum albumin level is a risk factor for T2DM development and progression, although this conclusion is controversial. Moreover, there is no study on the effects and mechanisms of albumin administration to relieve T2DM. We examined whether the administration of young and undamaged recombinant albumin can alleviate T2DM in mice.

METHODS

The serum albumin levels and metabolic phenotypes including fasting blood glucose, glucose tolerance tests, and glucose-stimulated insulin secretion were studied in db/db mice or diet-induced obesity mice treated with saline or young, undamaged, and ultrapure rMSA. Apoptosis assays were performed at tissue and cell levels to determine the function of rMSA on islet β cell protection. Metabolic flux and glucose uptake assays were employed to investigate metabolic changes in saline-treated or rMSA-treated mouse hepatocytes and compared their sensitivity to insulin treatments.

RESULTS

In this study, treatment of T2DM mice with young, undamaged, and ultrapure recombinant mouse serum albumin (rMSA) increased their serum albumin levels, which resulted in a reversal of the disease including reduced fasting blood glucose levels, improved glucose tolerance, increased glucose-stimulated insulin secretion, and alleviated islet atrophy. At the cellular level, rMSA improved glucose uptake and glycolysis in hepatocytes. Mechanistically, rMSA reduced the binding between CAV1 and EGFR to increase EGFR activation leading to PI3K-AKT activation. Furthermore, rMSA extracellularly reduced the rate of fatty acid uptake by islet β-cells, which relieved the accumulation of intracellular ceramide, endoplasmic reticulum stress, and apoptosis. This study provided the first clear demonstration that injections of rMSA can alleviate T2DM in mice.

CONCLUSION

Our study demonstrates that increasing serum albumin levels can promote glucose homeostasis and protect islet β cells, which alleviates T2DM.

Structural Characterization and Quantitation of Ether-Linked Glycerophospholipids in Peroxisome Biogenesis Disorder Tissue by Ultraviolet Photodissociation Mass Spectrometry

The biological impact of ether glycerophospholipids (GP) in peroxisomal disorders and other diseases makes them significant targets as biomarkers for diagnostic assays or deciphering pathology of the disorders. Ether lipids include both plasmanyl and plasmenyl lipids, which each contain an ether or a vinyl ether bond at the sn-1 linkage position, respectively. This linkage, in contrast to traditional diacyl GPs, precludes their detailed characterization by mass spectrometry via traditional collisional-based MS/MS techniques. Additionally, the isomeric nature of plasmanyl and plasmenyl pairs of ether lipids introduces a further level of complexity that impedes analysis of these species. Here, we utilize 213 nm ultraviolet photodissociation mass spectrometry (UVPD-MS) for detailed characterization of phosphatidylethanolamine (PE) and phosphatidylcholine (PC) plasmenyl and plasmanyl lipids in mouse brain tissue. 213 nm UVPD-MS enables the successful differentiation of these four ether lipid subtypes for the first time. We couple this UVPD-MS methodology to reversed-phase liquid chromatography (RPLC) for characterization and relative quantitation of ether lipids from normal and diseased (Pex7 deficiency modeling the peroxisome biogenesis disorder, RCDP) mouse brain tissue, highlighting the ability to pinpoint specific structural features of ether lipids that are important for monitoring aberrant lipid metabolism in peroxisomal disorders.