Clinical characteristics and plasma lipids in subjects with familial combined hypolipidemia: a pooled analysis

Angiopoietin-like 3 (ANGPTL3) regulates lipoprotein metabolism by modulating extracellular lipases. Loss-of function mutations in ANGPTL3 gene cause familial combined hypolipidemia (FHBL2). The mode of inheritance and hepatic and vascular consequences of FHBL2 have not been fully elucidated. To get further insights on these aspects, we reevaluated the clinical and the biochemical characteristics of all reported cases of FHBL2. One hundred fifteen FHBL2 individuals carrying 13 different mutations in the ANGPTL3 gene (14 homozygotes, 8 compound heterozygotes, and 93 heterozygotes) and 402 controls were considered. Carriers of two mutant alleles had undetectable plasma levels of ANGPTL3 protein, whereas heterozygotes showed a reduction ranging from 34% to 88%, according to genotype. Compared with controls, homozygotes as well as heterozygotes showed a significant reduction of all plasma lipoproteins, while no difference in lipoprotein(a) [Lp(a)] levels was detected between groups. The prevalence of fatty liver was not different in FHBL2 subjects compared with controls. Notably, diabetes mellitus and cardiovascular disease were absent among homozygotes. FHBL2 trait is inherited in a codominant manner, and the lipid-lowering effect of two ANGPTL3 mutant alleles was more than four times larger than that of one mutant allele. No changes in Lp(a) were detected in FHBL2. Furthermore, our analysis confirmed that FHBL2 is not associated with adverse clinical sequelae. The possibility that FHBL2 confers lower risk of diabetes and cardiovascular disease warrants more detailed investigation.     

Mutations in PDGFRB Cause Autosomal-Dominant Infantile Myofibromatosis

Infantile myofibromatosis (IM) is a disorder of mesenchymal proliferation characterized by the development of nonmetastasizing tumors in the skin, muscle, bone, and viscera. Occurrence within families across multiple generations is suggestive of an autosomal-dominant (AD) inheritance pattern, but autosomal-recessive (AR) modes of inheritance have also been proposed. We performed whole-exome sequencing (WES) in members of nine unrelated families clinically diagnosed with AD IM to identify the genetic origin of the disorder. In eight of the families, we identified one of two disease-causing mutations, c.1978C>A (p.Pro660Thr) and c.1681C>T (p.Arg561Cys), in PDGFRB. Intriguingly, one family did not have either of these PDGFRB mutations but all affected individuals had a c.4556T>C (p.Leu1519Pro) mutation in NOTCH3. Our studies suggest that mutations in PDGFRB are a cause of IM and highlight NOTCH3 as a candidate gene. Further studies of the crosstalk between PDGFRB and NOTCH pathways may offer new opportunities to identify mutations in other genes that result in IM and is a necessary first step toward understanding the mechanisms of both tumor growth and regression and its targeted treatment.     

Accumulation of altered aspartyl residues in erythrocyte membrane proteins from patients with sporadic amyotrophic lateral sclerosis

Spontaneous protein deamidation of labile asparagines (Asn), generating abnormal l-isoaspartyl residues (IsoAsp), is associated with cell aging and enhanced by an oxidative microenvironment. The presence of isopeptide bonds impairs protein structure/function. To minimize the damage, IsoAsp can be “repaired” by the protein l-isoaspartyl/d-aspartyl O-methyltransferase (PIMT) and S-adenosylmethionine (AdoMet) is the methyl donor of this reaction. PIMT is a repair enzyme that initiates the conversion of l-isoAsp (or d-Asp) residues to l-Asp residues. Amyotrophic lateral sclerosis (ALS) is a severe neurodegenerative disease principally affecting motor neurons. The condition of oxidative stress reported in familial and sporadic forms of ALS prompted us to investigate Asn deamidation in ALS tissue. Erythrocytes (RBCs) were selected as a model system since they are unable to replace damaged proteins and protein methylesterification is virtually the only AdoMet-consuming reaction operating in these cells. Our data show that, in vitro assay, abnormal IsoAsp residues were significantly higher in ALS patients erythrocyte membrane proteins with an increased methyl accepting capability relative to controls (p < 0.05). Moreover, we observed a reduction in AdoMet levels, while AdoHcy concentration was comparable to that detected in the control, resulting in a lower [AdoMet]/[AdoHcy] ratio. Then, the accumulation of altered aspartyl residues in ALS patients is probably related to a reduced efficiency of the S-adenosylmethionine (AdoMet)-dependent repair system causing increased protein instability at Asn sites. The increase of abnormal residues represents a new protein alteration that may be present not only in red blood cells but also in other cell types of patients suffering from ALS.     

Novel mutations in SAR1B and MTTP genes in Tunisian children with chylomicron retention disease and abetalipoproteinemia

Monogenic hypobetalipoproteinemias include three disorders: abetalipoproteinemia (ABL) and chylomicron retention disease (CMRD) with recessive transmission and familial hypobetalipoproteinemia (FHBL) with dominant transmission. We investigated three unrelated Tunisian children born from consanguineous marriages, presenting hypobetalipoproteinemia associated with chronic diarrhea and retarded growth. Proband HBL-108 had a moderate hypobetalipoproteinemia, apparently transmitted as dominant trait, suggesting the diagnosis of FHBL. However, she had no mutations in FHBL candidate genes (APOB, PCSK9 and ANGPTL3). The analysis of MTTP gene was also negative, whereas SAR1B gene resequencing showed that the patient was homozygous for a novel mutation (c.184G>A), resulting in an amino acid substitution (p.Glu62Lys), located in a conserved region of Sar1b protein. In the HBL-103 and HBL-148 probands, the severity of hypobetalipoproteinemia and its recessive transmission suggested the diagnosis of ABL. The MTTP gene resequencing showed that probands HBL-103 and HBL-148 were homozygous for a nucleotide substitution in the donor splice site of intron 9 (c.1236+2T>G) and intron 16 (c.2342+1G>A) respectively. Both mutations were predicted in silico to abolish the function of the splice site. In vitro functional assay with splicing mutation reporter MTTP minigenes showed that the intron 9 mutation caused the skipping of exon 9, while the intron 16 mutation caused a partial retention of this intron in the mature mRNA. The predicted translation products of these mRNAs are non-functional truncated proteins.     

Crystallographic,Spectroscopic, and Theoretical Investigation of the Efficiently Separated 21R and 21S‐Diastereoisomers of Argatroban

Argatroban ( I ), a potent noncovalent reversible thrombin inhibitor, is used as an anticoagulant for the parenteral treatment of heparin‐induced thrombocytopenia (HIT) patients. By virtue of its pharmacological properties and the well‐balanced risks and benefits, argatroban is now emerging as a clinically relevant antithrombotic agent. The availability of this drug as a mixture of 21R and 21S‐diastereoisomers, in a ratio of roughly 64:36, prompted us to design an efficient separation setup of the two epimers. We pursued our efforts on their detailed structural analysis with the aim of understanding their different activity and aqueous solubility. These investigations were accompanied by a modeling study of the two diastereoisomers, with particular attention on the easy interconverting half‐chair of the tetrahydroquinoline system and its preferred conformation, which is determined by the configuration at C21. These results, together with the analysis of their physicochemical profiles, provide new useful information for the development of the individual diastereoisomers. Chirality 25:871–882, 2013. © 2013 Wiley Periodicals, Inc.     

Identification of a novel arylpiperazine scaffold for fatty acid amide hydrolase inhibition with improved drug disposition properties

We herein describe the systematic approach used to develop new analogues of compound 2, recently identified as a potent and selective fatty acid amide hydrolase (FAAH) inhibitor. Aiming at identifying new scaffolds endowed with improved drug disposition properties with respect to the phenylpyrrole-based lead, we subjected it to two different structural modification strategies. This process allowed the identification of derivatives 4b and 5c as potent, reversible and non-competitive FAAH inhibitors.     

Geographical markers for <Emphasis Type="Italic">Saccharomyces cerevisiae</Emphasis> strains with similar technological origins domesticated for rice-based ethnic fermented beverages production in North East India

Autochthonous strains of Saccharomyces cerevisiae from traditional starters used for the production of rice-based ethnic fermented beverage in North East India were examined for their genetic polymorphism using mitochondrial DNA-RFLP and electrophoretic karyotyping. Mitochondrial DNA-RFLP analysis of S. cerevisiae strains with similar technological origins from hamei starter of Manipur and marcha starter of Sikkim revealed widely separated clusters based on their geographical origin. Electrophoretic karyotyping showed high polymorphism amongst the hamei strains within similar mitochondrial DNA-RFLP cluster and one unique karyotype of marcha strain was widely distributed in the Sikkim-Himalayan region. We conceptualized the possibility of separate domestication events for hamei strains in Manipur (located in the Indo-Burma biodiversity hotspot) and marcha strains in Sikkim (located in Himalayan biodiversity hotspot), as a consequence of less homogeneity in the genomic structure between these two groups, their clear separation being based on geographical origin, but not on technological origin and low strain level diversity within each group. The molecular markers developed based on HinfI-mtDNA-RFLP profile and the chromosomal doublets in chromosome VIII position of Sikkim-Himalayan strains could be effectively used as geographical markers for authenticating the above starter strains and differentiating them from other commercial strains.