Analysis of the bone metabolism by quantitative computer tomography and clinical chemistry in a primate model (Callithrix jacchus)

Background Common marmosets are widely used as experimental primates; however, little is still known about their bone physiology. Therefore, the aim of our study was to analyse body weight, age and bone‐specific blood parameters in relation to morphological bone parameters. Methods Fifty‐eight common marmosets were analysed for blood calcium (Ca), inorganic phosphor (P_i), alkaline phosphatase (AP) and 17‐β‐estradiol (E2). The examination of bone parameters was undertaken in the lumbar spine by computer tomography. Results There was a correlation between bone mineral density (BMD) and body weight, trabecular area ratio and polar moment as well as between BMD and AP or Ca (only males), whereas there were no correlations between BMD and age, P_i or E2 in all analysed genders. Conclusions Our data support the assumption that the common marmoset is a reliable primate model to study changes in bone metabolism because of the similarity of our results to humans.     

Mutations of the ER to plastid lipid transporters TGD1, 2, 3 and 4 and the ER oleate desaturase FAD2 suppress the low temperature‐induced phenotype of Arabidopsis tocopherol‐deficient mutant vte2

Previous studies with the tocopherol‐deficient Arabidopsis thaliana vte2 mutant demonstrated an important role for tocopherols in the development of transfer cell walls and maintenance of photoassimilate export capacity during low‐temperature (LT) adaptation. To further understand the processes linking tocopherol deficiency and the vte2 LT phenotypes, a genetic screen was performed for sve mutations (suppressor of the vte2 low temperature‐induced phenotype). The three strongest sve loci had differing impacts on LT‐induced sugar accumulation, photoassimilate export reduction and vascular‐specific callose deposition in vte2. sve1 completely suppressed all vte2 LT phenotypes and is a new allele of fad2, the endoplasmic reticulum‐localized oleate desaturase. sve2 showed partial suppression, and is a new allele of trigalactosyldiacylglycerol1 (tgd1), a component of the ER‐to‐plastid lipid ATP‐binding cassette (ABC) transporter. Introduction of tgd2, tgd3 and tgd4 mutations into the vte2 background similarly suppressed the vte2 LT phenotypes, indicating a key role for ER‐to‐plastid lipid transport in the vte2 LT phenotype. sve7 partially suppressed all vte2 LT phenotypes by affecting fatty acid and lipid metabolism at low temperatures only. Detailed analyses of acyl lipid composition indicated that all suppressors alleviated the increase in the level of linoleic acid esterified to phosphatidylcholine (PC‐18:2) in LT‐treated vte2, and this alleviation significantly correlated with their extent of suppression of photoassimilate export. Identification and characterization of the sve loci showed that the PC‐18:2 change is an early and key component in vte2 LT‐induced responses, and highlighted the interaction of tocopherols with non‐plastid lipid metabolism.     

Beneath the minerals, a layer of round lipid particles was identified to mediate collagen calcification in compact bone formation

Astronauts lose 1-2% of their bone minerals per month during space flights. A systematic search for a countermeasure relies on a good understanding of the mechanism of bone formation at the molecular level. How collagen fibers, the dominant matrix protein in bones, are mineralized remains mysterious. Atomic force microscopy was carried out, in combination with immunostaining and Western blotting, on bovine tibia to identify unrecognized building blocks involved in bone formation and for an elucidation of the process of collagen calcification in bone formation. Before demineralization, tiles of hydroxyapatite crystals were found stacked along bundles of collagen fibers. These tiles were homogeneous in size and shape with dimensions 0.69 x 0.77 x 0.2 micro m(3). Demineralization dissolved these tiles and revealed small spheres with an apparent diameter around 145 nm. These spheres appeared to be lipid particles since organic solvents dissolved them. The parallel collagen bundles had widths mostly <2 micro m. Composition analysis of compact bones indicated a high content of apolar lipids, including triglycerides and cholesterol esters. Apolar lipids are known to form lipid droplets or lipoproteins, and these spheres are unlikely to be matrix vesicles as reported for collagen calcification in epiphyseal cartilages. Results from this study suggest that the layer of round lipid particles on collagen fibers mediates the mineral deposition onto the fibers. The homogeneous size of these lipid particles and the presence of apolipoprotein in demineralized bone tissue suggest the possibility that these particles might be of lipoprotein origin. More studies are needed to verify the last claim and to exclude the possibility that they are secreted lipid droplets.     

Linker chains of the gigantic hemoglobin of the earthworm Lumbricus terrestris: primary structures of linkers L2, L3, and L4 and analysis of the connectivity of the disulfide bonds in linker L1

The extracellular hemoglobin (Hb) of the earthworm, Lumbricus terrestris, has four major kinds of globin chains: a, b, c, and d, present in equimolar proportions, and additional non-heme, non-globin scaffolding chains called linkers that are required for the calcium-dependent assembly of the full-sized molecule. The amino acid sequences of all four of the globin chains and one of the linkers (L1) have previously been determined. The amino acid sequences via cDNA of each of the three remaining linkers, L2, L3, and L4, have been determined so that the sequences of all constituent polypeptides of the hemoglobin are now known. Each linker has a highly conserved cysteine-rich segment of approximately 40 residues that is homologous with the seven ligand-binding repeats of the human low-density lipoprotein receptor (LDLR). Analysis of linker L1 shows that the connectivity of the three disulfide bonds is exactly the same as in the LDLR ligand-binding repeats. The presence of a calcium-binding site comprising one glutamyl and three aspartyl residues in both the LDLR repeats and in the linkers supports the suggestion that calcium is required for the folding and disulfide connectivity of the linkers as in the LDLR repeats. Linker L2 is markedly heterogeneous and contains unusual glycine-rich sequences near the NH2-terminus and a polar zipper-like sequence with imperfect repeats of Asp-Asp-His at the carboxyl terminus. Similar Asp-Asp-His repeats have been found in a protein homologous to superoxide dismutase in the hemolymph of certain mussels. These repeats may function as metal-binding sites.     

The G0/G1 switch gene 2 (G0S2): Regulating metabolism and beyond

The G0/G1 switch gene 2 (G0S2) was originally identified in blood mononuclear cells following induced cell cycle progression. Translation of G0S2 results in a small basic protein of 103 amino acids in size. It was initially believed that G0S2 mediates re-entry of cells from the G0 to G1 phase of the cell cycle. Recent studies have begun to reveal the functional aspects of G0S2 and its protein product in various cellular settings. To date the best-known function of G0S2 is its direct inhibitory capacity on the rate-limiting lipolytic enzyme adipose triglyceride lipase (ATGL). Other studies have illustrated key features of G0S2 including sub-cellular localization, expression profiles and regulation, and possible functions in cellular proliferation and differentiation. In this review we present the current knowledge base regarding all facets of G0S2, and pose a variety of questions and hypotheses pertaining to future research directions.     

Association of three polymorphisms of scavenger receptor class BI gene (exon8, exon1, intron5) with coronary stenosis in a coronary Tunisian population

Background

The potential role of scavenger receptor class BI (gene name SCARB1) in the regulation of lipoproteins metabolism and atherosclerosis has attracted considerable interest. We tested the relationship of SCARB1 polymorphisms with significant coronary stenosis (SCS) and lipid profile in a coronary Tunisian population.

Methods

Three SCARB1 polymorphisms (exon8 (C/T), exon1 (G/A), intron5 (C/T)) were studied in 316 Tunisian patients undergoing coronary angiography. SCS was defined as a luminal narrowing of ≥ 50% in at least one major coronary artery. Lipid profile was measured. Genotyping was performed using PCR–RFLP.

Results

Individuals with TT genotypes of exon8 were associated with higher concentrations of plasma HDL-C and ApoAI in the group without SCS. Carriers of T allele of exon8 were associated with 41% lower risk of SCS. This protective effect seemed to be particularly significant in women, nondiabetics and nonsmokers. Subjects homozygous for the variant allele of intron5 were significantly associated with an increased risk of SCS, particularly in smokers. AA genotype of exon1 was associated with an increased risk of SCS in diabetics and in patients with metabolic syndrome. The (CAT) haplotype was associated with increase in the risk of SCS compared to the wild haplotype and had a 4-fold greater risk of SCS than patients with haplotype (TGC) which seems to be the most protective against SCS.

Conclusion

Carriers of T allele of exon8 in SCARB1 seemed to increase HDL-C and ApoAI concentrations and reduce the risk of SCS. The intron5, exon1 and (CAT) haplotype seemed to have an atherogenic effect.     

5-(4-Hydroxyphenyl)-3H-1,2-dithiole-3-thione-based fibrates as potential hypolipidemic and hepatoprotective agents

Hypolipidemic effects of the newly synthesized 5-(4-hydroxyphenyl)-3H-1,2-dithiole-3-thione-based fibrates were evaluated in Triton WR-1339 and high-fat diet (HFD)-induced hyperlipidemic mice. Preliminary screening of all the synthesized compounds was done by using an acute model (Triton WR-1339 model), in which compound 6 shown more significant antidyslipidemic activity than fenofibrate (FF). The compound 6 was also found to reduce serum triglyceride (TG), total cholesterol (TC) and low density lipoprotein cholesterin (LDL) in HFD-induced hyperlipidemic mice. Moreover, compound 6 displayed hepatoprotective effect, a significant amelioration in hepatic indices (AST and ALT) toxicity was observed and the histological examination showed that compound 6 inhibited the development of hepatic lipid accumulation and ameliorated the damage in hepatic tissue compared to model mice. Additional effects such as the potent antioxidant and anti-inflammatory action confirmed and reinforced the efficacy of compound 6 as a new agent of dual-effect hypolipidemic and hepatoprotective activities.     

Characterization of 1-(2-[18F] fluoro-3-pyridyl)-4-(2-isopropyl-1-oxo- isoindoline-5-yl)-5-methyl-1H-1,2,3-triazole, a PET ligand for imaging the metabotropic glutamate receptor type 1 in rat and monkey brains

Neurovascular degeneration contributes to the pathogenesis of Alzheimer's disease (AD). Because erythropoietin (EPO) promotes endothelial regeneration, we investigated the therapeutic effects of EPO in animal models of AD. In aged Tg2576 mice, EPO receptors (EPORs) were expressed in the cortex and hippocampus. Tg2576 mice were treated with daily injection of EPO (5000 IU/kg/day) for 5 days. At 14 days, EPO improved contextual memory as measured by fear-conditioning test. EPO enhanced endothelial proliferation and the level of synaptophysin expression in the brain. EPO also increased capillary density, and decreased the level of the receptor for advanced glycation endproducts (RAGE) in the brain, while decreasing in the amount of amyloid plaque and amyloid-β (Aβ). In cultured human endothelial cells, EPO enhanced angiogenesis and suppressed the expression of the RAGE. These results show that EPO improves memory and ameliorates endothelial degeneration induced by Aβ in AD models. This pre-clinical evidence suggests that EPO may be useful for the treatment of AD.     

Ablating both Fabp1 and Scp2/Scpx (TKO) induces hepatic phospholipid and cholesterol accumulation in high fat-fed mice

Although singly ablating Fabp1 or Scp2/Scpx genes may exacerbate the impact of high fat diet (HFD) on whole body phenotype and non-alcoholic fatty liver disease (NAFLD), concomitant upregulation of the non-ablated gene, preference for ad libitum fed HFD, and sex differences complicate interpretation. Therefore, these issues were addressed in male and female mice ablated in both genes (Fabp1/Scp2/Scpx null or TKO) and pair-fed HFD. Wild-type (WT) males gained more body weight as fat tissue mass (FTM) and exhibited higher hepatic lipid accumulation than WT females. The greater hepatic lipid accumulation in WT males was associated with higher hepatic expression of enzymes in glyceride synthesis, higher hepatic bile acids, and upregulation of transporters involved in hepatic reuptake of serum bile acids. While TKO had little effect on whole body phenotype and hepatic bile acid accumulation in either sex, TKO increased hepatic accumulation of lipids in both, specifically phospholipid and cholesteryl esters in males and females and free cholesterol in females. TKO-induced increases in glycerides were attributed not only to complete loss of FABP1, SCP2 and SCPx, but also in part to sex-dependent upregulation of hepatic lipogenic enzymes. These data with WT and TKO mice pair-fed HFD indicate that: i) Sex significantly impacted the ability of HFD to increase body weight, induce hepatic lipid accumulation and increase hepatic bile acids; and ii) TKO exacerbated the HFD ability to induce hepatic lipid accumulation, regardless of sex, but did not significantly alter whole body phenotype in either sex.     

Natural products as modulators of the nuclear receptors and metabolic sensors LXR,FXR and RXR

Nuclear receptors (NRs) represent attractive targets for the treatment of metabolic syndrome-related diseases. In addition, natural products are an interesting pool of potential ligands since they have been refined under evolutionary pressure to interact with proteins or other biological targets.This review aims to briefly summarize current basic knowledge regarding the liver X (LXR) and farnesoid X receptors (FXR) that form permissive heterodimers with retinoid X receptors (RXR). Natural product-based ligands for these receptors are summarized and the potential of LXR, FXR and RXR as targets in precision medicine is discussed.