Plasma concentrations of apolipoproteins A-I, B, and M in patients with critical limb ischemia

Plasma apolipoprotein M predicts overall survival in metastatic breast cancer patients

PURPOSE

Apolipoprotein M (APOM) is a plasma apolipoprotein closely involved with lipid metabolism and inflammation. In vitro studies suggest that APOM may also have a tumor-suppressive role in breast cancer. In the present study, we aimed to evaluate the impact of plasma APOM levels on the prognosis of breast cancer patients.

METHODS

We measured APOM levels using an enzyme-linked immunosorbent assay in 75 patients with ER-positive/HER2-negative metastatic breast cancer. The endpoint was overall survival (OS) at 24 months.

RESULTS

During the 24-month follow-up period, 34.7% of the patients died. Baseline APOM levels were significantly reduced in patients who deceased during follow-up compared to survivors (42.7 ± 14.5 µg/mL versus 52.2 ± 13.8 µg/mL; P = 0.003). Cox regression analysis showed a hazard ratio of 0.30 [95% confidence interval 0.15-0.61]; P < 0.001 per doubling of APOM levels. Correction for age, C-reactive protein, menopausal state, histology of the primary tumor, metastatic site, number of metastases, endocrine resistance, scheduled therapy line, and kind of scheduled therapy indicated that circulating APOM predicted OS independently of these parameters (HRper doubling = 0.23 [0.09-0.56; P = 0.001).

CONCLUSIONS

Our study suggests that circulating APOM is significantly linked with reduced mortality in metastatic breast cancer patients.

ApoA-I Nanotherapy Rescues Postischemic Vascular Maladaptation by Modulating Endothelial Cell and Macrophage Phenotypes in Type 2 Diabetic Mice

BACKGROUND

Diabetes is a major risk factor for peripheral arterial disease. Clinical and preclinical studies suggest an impaired collateral remodeling and angiogenesis in response to atherosclerotic arterial occlusion in diabetic conditions, although the underlying mechanisms are poorly understood.

OBJECTIVE

To clarify the cellular and molecular mechanisms underlying impaired postischemic adaptive vascular responses and to evaluate rHDL (reconstituted HDL)-ApoA-I nanotherapy to rescue the defect in type 2 diabetic mouse model of hindlimb ischemia.

METHODS AND RESULTS

Hindlimb ischemia was induced by unilateral femoral artery ligation. Collateral and capillary parameters together with blood flow recovery were analyzed from normoxic adductor and ischemic gastrocnemius muscles, respectively, at day 3 and 7 post-ligation. In response to femoral artery ligation, collateral lumen area was significantly reduced in normoxic adductor muscles. Distally, ischemic gastrocnemius muscles displayed impaired perfusion recovery and angiogenesis paralleled with persistent inflammation. Muscle-specific mRNA sequencing revealed differential expression of genes critical for smooth muscle proliferation and sprouting angiogenesis in normoxic adductor and ischemic gastrocnemius, respectively, at day 7 post-ligation. Genes typical for macrophage (Mϕ) subsets were differentially expressed across both muscle types. Cell-specific gene expression, flow cytometry, and immunohistochemistry revealed persistent IFN-I response gene upregulation in arterial endothelial cells, ECs and Mϕs from T2DM mice associated with impaired collateral remodeling, angiogenesis and perfusion recovery. Furthermore, rHDL nanotherapy rescued impaired collateral remodeling and angiogenesis through dampening EC and Mϕ inflammation in T2DM mice.

CONCLUSIONS

Our results suggest that an impaired collateral remodeling and sprouting angiogenesis in T2DM mice is associated with persistent IFN-I response in ECs and Mϕs. Dampening persistent inflammation and skewing ECs and Mϕ phenotype toward less inflammatory ones using rHDL nanotherapy may serve as a potential therapeutic target for T2DM peripheral arterial disease.

Serum apolipoprotein A-I concentration differs in coronary and peripheral artery disease

Coronary artery and peripheral artery diseases represent different clinical outcomes of atherosclerosis and despite sharing common risk factors the ultimate reasons determining disease presentation are still unclear. The present study sought to define and compare the serum lipid and apolipoprotein profiles of patients undergoing coronary artery bypass grafting and those treated invasively for symptomatic lower extremity peripheral artery disease. Altogether 218 coronary and 280 peripheral artery disease patients treated between 2013 and 2014 in the Tampere University Hospital, Tampere, Finland, with available lipid measurements within two years prior to the intervention were retrospectively analysed. The Extended Friedewald formula neural network model was used to obtain apolipoprotein and lipoprotein subfraction values. Patients undergoing coronary artery bypass surgery had a clear male predominance (82% versus 53%, p < 0.001), lower median age (69 versus 74 years, p < 0.001) and a lower prevalence of smoking (18% versus 32%, p = 0.001) and pulmonary disease (12% versus 20%, p = 0.023) compared to peripheral artery disease patients. There were some differences in the serum lipid profiles between the study groups in the univariable analyses. When controlling for the statistically significant differences in age, sex, urgency of treatment and comorbidities between the groups in a multivariable logistic regression model, higher serum concentrations of apolipoprotein A-I were significantly and independently associated with coronary artery disease (OR 1.11 for 0.01 g/L increase, p = 0.044). In conclusion, patients undergoing coronary artery bypass grafting appear to have higher apolipoprotein A-I levels when compared to patients treated for peripheral artery disease.

Plasma apoM and S1P levels are inversely associated with mortality in African Americans with type 2 diabetes mellitus

apoM is a minor HDL apolipoprotein and carrier for sphingosine-1-phosphate (S1P). HDL apoM and S1P concentrations are inversely associated with atherosclerosis progression in rodents. We evaluated associations between plasma concentrations of S1P, plasma concentrations of apoM, and HDL apoM levels with prevalent subclinical atherosclerosis and mortality in the African American-Diabetes Heart Study participants (N = 545). Associations between plasma S1P, plasma apoM, and HDL apoM with subclinical atherosclerosis and mortality were assessed using multivariate parametric, nonparametric, and Cox proportional hazards models. At baseline, participants' median (25th percentile, 75th percentile) age was 55 (49, 62) years old and their coronary artery calcium (CAC) mass score was 26.5 (0.0, 346.5). Plasma S1P, plasma apoM, and HDL apoM were not associated with CAC. After 64 (57.6, 70.3) months of follow-up, 81 deaths were recorded. Higher concentrations of plasma S1P [odds ratio (OR) = 0.14, P = 0.01] and plasma apoM (OR = 0.10, P = 0.02), but not HDL apoM (P = 0.89), were associated with lower mortality after adjusting for age, sex, statin use, CAC, kidney function, and albuminuria. We conclude that plasma S1P and apoM concentrations are inversely and independently associated with mortality, but not CAC, in African Americans with type 2 diabetes after accounting for conventional risk factors.

Evaluation of Expression Level of Apolipoprotein M as a Diagnostic Marker for Primary Venous Thromboembolism

Recently, decreased levels of apolipoprotein M (ApoM) were shown to be associated with higher risk of recurrent venous thromboembolism (VTE) in male patients. However, the role of ApoM in primary VTE is unknown. We aimed in our study to analyze the plasma levels of ApoM in patients with VTE in order to evaluate the diagnostic importance of ApoM in primary VTE. A total of 357 patients with suspected first episode of VTE were recruited prospectively in the SCORE study. Plasma samples from 307 patients were available for quantifying the plasma levels of ApoM in patients with VTE using sandwich enzyme-linked immunosorbent assay method. Among the whole population, plasma levels (mean [standard deviation]) of ApoM were not significantly different between patients with VTE (0.72 [0.20]) and non-VTE patients (0.72 [0.16]), P = .99. Similarly, in regression analyses, no significant association of ApoM plasma levels with the risk of VTE was found on univariate (odds ratio [OR] =1.0, 95% confidence interval [CI] 0.21-4.84, P = .99) and multivariate analysis (OR = 1.25, 95% CI = 0.19-8.34, P = .819) after adjusting for age, body mass index, and smoking. Moreover, results did not differ significantly after stratification of data according to sex ( P > .05). In this study, our results do not suggest a diagnostic role for ApoM plasma levels in patients with primary VTE. Moreover, the current study suggests that role of ApoM as a risk factor may differ for primary VTE and recurrent VTE in male patients.

The association between apolipoprotein M and insulin resistance varies with country of birth

BACKGROUND AND AIMS

Risk of type 2 diabetes mellitus (T2DM) differs according to ethnicity. Levels of apolipoprotein M (ApoM) have been shown to be decreased in T2DM. However, its role in different ethnicities is not known. We examined the differences in plasma ApoM levels in Swedish residents born in Iraq (Iraqis) and Sweden (Swedes) in relation to T2DM and insulin resistance (IR).

METHODS AND RESULTS

Iraqis and Swedes, aged 45-65 years residing in Rosengård area of Malmö were randomly selected from census records and underwent an oral glucose tolerance test. Plasma levels of ApoM were quantified in 162 participants (Iraqis, n = 91; Swedes, n = 71) by a sandwich ELISA method. Age-, sex-, and body mass index (BMI) adjusted plasma ApoM levels differed by country of birth, with Swedes having 18% higher levels compared to Iraqis (p = 0.001). ApoM levels (mean ± SD) were significantly decreased in Swedes with T2DM (0.73 ± 0.18) compared to those with normal glucose tolerance (NGT) (0.89 ± 0.24; p = 0.03). By contrast, no significant difference in ApoM levels was found between Iraqis with T2DM (0.70 ± 0.17) and those with NGT (0.73 ± 0.13; p = 0.41). In multivariate linear regression analysis with an interaction term between IR and country of birth, low ApoM levels remained significantly associated with IR in Swedes (p = 0.008), independently of age, sex, BMI, family history of diabetes, HDL, LDL, and triglycerides, but not in Iraqis (p = 0.35).

CONCLUSION

Our results show that ApoM levels differ according to country of birth and are associated with IR and T2DM only in Swedes.

Enchanced levels of apolipoprotein M during HBV infection feedback suppresses HBV replication

Background

Chronic liver diseases can interfere with hepatic metabolism of lipoproteins, apolipoproteins. Hepatitis B virus (HBV) is a major etiological agent causing acute and chronic liver diseases. Apolipoprotein M (ApoM) is a high-density lipoprotein (HDL) apolipoprotein and exclusively expressed in the liver parenchyma cells and in the tubular cells of the kidney. This study was to determine the correlation between HBV infection and ApoM expression.

Materials and methods

Serum ApoM levels in patients with HBV infection and in healthy individuals were measured by ELISA, ApoM mRNA expression were determined by RT-PCR, and the expression of S and E proteins of HBV, as well as the synthesis of viral DNA were measured by ELISA and real-time PCR.

Results

The levels of serum ApoM was significantly elevated in patients as compared to healthy individuals (P < 0.001), ApoM promoter activity, mRNA and protein expression were all stimulated in cells transfected with infectious HBV clone. In addition, ApoM decreases the expression of S and E proteins of HBV and the synthesis of viral DNA.

Conclusion

Raised ApoM levels in HBV infection may in turn suppress HBV replication, one of the protective mechanisms of nature.

Plasma apolipoprotein M responses to statin and fibrate administration in type 2 diabetes mellitus

PURPOSE

Plasma apolipoprotein M (apoM) is potentially anti-atherogenic, and has been found to be associated positively with plasma total, LDL and HDL cholesterol in humans. ApoM may, therefore, be intricately related to cholesterol metabolism. Here, we determined whether plasma apoM is affected by statin or fibrate administration in patients with diabetes mellitus.

METHODS

Fourteen type 2 diabetic patients participated in a placebo-controlled crossover study which included three 8-week treatment periods with simvastatin (40 mg daily), bezafibrate (400 mg daily), and their combination.

RESULTS

ApoM was decreased by 7% in response to simvastatin (P<0.05 from baseline and placebo), and remained unchanged during bezafibrate and combined simvastatin+bezafibrate administration. Plasma apoM concentrations correlated positively with apoB-containing lipoprotein measures at baseline and during placebo (P<0.02 to P<0.001), but these relationships were lost during all lipid lowering treatment periods.

CONCLUSIONS

This study suggests that, even though plasma apoM is lowered by statins, apoM metabolism is to a considerable extent independent of statin- and fibrate-affected pathways involved in cholesterol homeostasis.