Decreased serum apolipoprotein AII/AI ratio in systemic amyloidosis

Discovery and Identification of Serum Succinyl-Proteome for Postmenopausal Women with Osteoporosis and Osteopenia

OBJECTIVE

For the purpose of providing evidence for the treatment of osteoporosis and osteopenia, this study retrospectively identified succinylation-modified sites and proteins in postmenopausal women, and bioinformatics analysis were performed.

METHODS

From January 2016 to June 2018, a total of 30 postmenopausal women aged from 55 to 70 years old were assigned to three groups: 10 cases with osteoporosis; 10 cases with osteopenia; and 10 cases with normal bone mass. Subsequently, the serum samples were collected from all cases for succinyl-proteome. Measures comprised label-free quantitative analysis, succinylation enrichment techniques, the liquid chromatograph-mass spectrometer/mass spectrometer (LC-MS/MS) methods, and bioinformatics.

RESULTS

A total of 113 succinylation sites on 35 proteins were identified based on quantitative information. The variation of the different multiple folds were more than 1.2 times as a significant increase for up-regulated and less than 1/1.2 times as a significant decrease for down-regulated. Among the quantified succinylation sites, 66 were up-regulated and 11 down-regulated in the Osteopenia/Normal comparison group, 24 were up-regulated and 44 down-regulated in the Osteoporosis/Osteopenia comparison group, 45 were up-regulated and 32 down-regulated in the Osteoporosis/Normal comparison group. Among the quantified succinylation proteins, 24 were up-regulated and 7 down-regulated in the Osteopenia/Normal comparison group, 15 were up-regulated and 20 down-regulated in the Osteoporosis/Osteopenia comparison group, 20 were up-regulated and 17 down-regulated in the Osteoporosis/Normal comparison group. The percentage of proteins differed in immune response, signaling pathway, proteolysis, lymphocyte, leukocyte, and cell activation. Four differentially expressed proteins (apolipoprotein A-I, apolipoprotein A-II, hemoglobin subunit alpha, and haptoglobin) contained quantitative information; they were mediated with receptors, factors, mechanisms, that related to bone metabolism. Hemoglobin subunit alpha was screened for diagnosis of osteopenia.

CONCLUSIONS

The succinyl-proteome experimental data indicated that apolipoprotein A-I, apolipoprotein A-II, hemoglobin subunit alpha, and haptoglobin were valuable for diagnosis and treatment in postmenopausal women with osteoporosis and osteopenia.

The relationship between high density lipoprotein subclass profile and apolipoprotein concentrations

The HDL fraction in human plasma is heterogeneous in terms of size, shape, composition, and surface charge. The HDL subclasses contents were quantified by 2-dimensional non-denaturing gel electrophoresis, immunoblotting, and image analysis. This research review systematically analyzed the relationship between the contents of HDL subclasses and the concentrations and ratios of the 5 major plasma apolipoproteins (apo). As the concentration of apoA-I increases, the contents of all HDL subclasses increase significantly. The most significant association was observed between large-sized HDL2b contents and apoA-I. ApoA-II played a dual function in the contents of HDL subclasses, and both small-sized HDL3b and HDL3a and large-sized HDL2b tended to increase with apoA-II concentration. An increase in the concentrations of apoC-II, C-III, and B-100 resulted in higher levels of small-sized HDL particles and lower levels of large-sized HDL particles. Plasma apoB- 100, apoC-II, and apoC-III appear to play a coordinated role in assembly of HDL particles and the determination of their contents. Higher concentrations of apoA-I could inhibit the reduction in content of large-sized HDL2b effected by apoB-100, C-II, and C-III. The preβ1-HDL contents increased significantly and those of HDL2b declined progressively with an increased apoB-100/apoA-I or a decreased apoC-III/apoC-II ratio. In summary, each apo has distinct but interrelated roles in HDL particle generation and metabolism. ApoA-I and apoC-II concentrations are independent determinants of HDL subtypes in circulation and apoA-I levels might be a more powerful factor to influence HDL subclasses distribution. Moreover, apoB- 100/apoA-I ratio could reliably and sensitively reflect the HDL subclass profile.

Apolipoprotein A-II, genetic variation on chromosome 1q21-q24, and disease susceptibility

PURPOSE OF REVIEW

Apolipoprotein (apo) A-II is the second most abundant HDL apolipoprotein; however its function remains largely unknown. Owing to the lack of consequences of apoA-II deficiency in humans, it has long been considered an apolipoprotein of minor importance. Overexpression of apoA-II in transgenic mice, however, causes combined hyperlipidemia and, in some cases, insulin resistance. This, and the location of the apoA-II gene in chromosome 1q23, a hot region in the search for genes associated with familial combined hyperlipidemia, insulin resistance and type 2 diabetes mellitus, has greatly increased interest in this protein.

RECENT FINDINGS

ApoA-II is biochemically and genetically linked to familial combined hyperlipidemia. Given that the chromosome 1q21-q24 region is associated with insulin resistance or type 2 diabetes, this region is a now a focus of interest in the study of these complex, often overlapping diseases. However, no polymorphisms that increase apoA-II levels have been identified to date in humans. Other nonstructural loci may regulate apoA-II plasma concentration. Further, plasma apoA-II concentration is increased by saturated fat intake. Several reports have added to our understanding of the relationship between apoA-II mutations and amyloidosis both in humans and mice.

SUMMARY

An increased plasma concentration of apoA-II might contribute to familial combined hyperlipidemia or type 2 diabetes mellitus expression, which emphasizes the need to understand its function and metabolism. Genetic studies in well characterized patients and genomic and proteomic approaches in cell and mouse models may help to achieve this understanding.

Low serum apolipoprotein AI levels in amyloidosis related to familial Mediterranean fever

Amyloidosis (A) related to familial Mediterranean fever (FMF) causes serious morbidity and mortality in children. Our study evaluates serum levels of apolipoprotein (Apo) AI, AII, B, and E and Apo AII/AI ratios as a non-invasive diagnostic tool for amyloidosis in children with FMF and FMF-A. Results were compared with those of patients with childhood nephrotic syndrome (NS) and healthy children (controls). Significantly lower serum levels of Apo AI (90.20+/-28.30 mg/dl) were documented in patients with FMF-A than in all other groups (FMF 126.89+/-51.07 mg/dl, NS 140.38+/-33.73 mg/dl, and controls 134.67+/-12.73 mg/dl) ( P<0.01). Diagnostic sensitivity, specificity, and predictive value for this test were 85%, 80%, and 85%, respectively. Apo AII/AI ratio results were essentially equal in all groups ( P>0.05). It is concluded that a decreased Apo AI serum level, but not Apo AII/AI ratio, is a useful, non-invasive test for the early diagnosis of FMF-A in children.

Changes in plasma apolipoprotein AI and AII concentrations in murine reactive amyloidosis

Based on the recent findings that patients with systemic amyloidosis have reduced plasma apolipoprotein AII (apoAII) concentrations, this study assessed the behaviour of apolipoprotein AI (apoAI) and apoAII in a murine model of reactive amyloidosis. ICR mice were subjected to a single inflammatory stimulus and then sacrificed at the end of week 1 (group I), week 2 (group II) or week 8 (group III). Amyloid deposits were found in approximately one-half of the animals. Plasma apoAI and apoAII concentrations were reduced in all stimulated animals compared with control animals. In groups II and III, apoAII and apoAII/apoAI ratios were lower in the amyloidotic animals than in nonamyloidotic animals, similar to findings in the human amyloidosis patients. Both apoAI and apoAII mRNA in the liver were reduced in group I, but not in group II or III. Both apoAI and apoAII were detected immunohistochemically in the amyloid deposits in groups I and II, but not in group III. Thus, the reduction of plasma apoAs in the amyloid-forming phase may be due, in part, to the involvement of high-density lipoproteins in the deposits. However, that in the chronic phase may be affected by other mechanisms.