Insulin resistance and pre-eclampsia: a role for tumor necrosis factor-alpha?

Is Afamin a novel biomarker for gestational diabetes mellitus? A pilot study

BACKGROUND

In search of potential early biomarkers for timely prediction of gestational diabetes mellitus (GDM), we focused on afamin, a vitamin E-binding protein in human plasma.. Afamin plays a role in anti-apoptotic cellular processes related to oxidative stress and is associated with insulin resistance and other features of metabolic syndrome. During uncomplicated pregnancy its serum concentrations increase linearly. The aim of this study was to investigate the suitability of afamin as early marker for predicting GDM.

METHODS

In a first-trimester cohort from a prospective observational study of adverse pregnancy outcomes we secondarily analyzed afamin concentrations in 59 patients diagnosed with GDM and 51 controls. Additionally, afamin concentrations were cross-sectionally examined in a mid-trimester cohort of 105 women and compared with results from a simultaneously performed oral glucose tolerance test (OGTT). Subgroup analysis comparing patients treated with either insulin (iGDM) or dietary intervention (dGDM) was performed in both cohorts. Patients were recruited at the University Hospital Essen, Germany, between 2003 and 2016.

RESULTS

Results were adjusted for body-mass-index (BMI) and gestational age. First and mid-trimester cohorts yielded significantly elevated afamin concentrations in patients with pathological OGTT compared to patients without GDM (first trimester cohort: mean, 113.4 mg/l; 95% CI, 106.4-120.5 mg/l and 87.2 mg/l; 95% CI, 79.7-94.7 mg/l; mid-trimester cohort: mean, 182.9 mg/l; 95% CI, 169.6-196.2 mg/l and 157.3 mg/l; 95% CI, 149.1-165.4 mg/l, respectively). In the first-trimester cohort, patients developing iGDM later in pregnancy presented with significantly higher afamin concentrations compared to patients developing dGDM and compared to patients without GDM. In the mid-trimester cohort, mean concentrations of afamin differed significantly between patients with dGDM compared to controls and between patients with iGDM and controls. Patients with iGDM showed only slightly higher afamin levels compared to patients with dGDM.

CONCLUSION

Afamin may serve as a new early biomarker for pathological glucose metabolism during pregnancy. Further research is needed to determine afamin's concentrations during pregnancy, its predictive value for early detection of pregnancies at high risk to develop GDM and its diagnostic role during the second trimester.

Cytokines, angiogenic, and antiangiogenic factors and bioactive lipids in preeclampsia

Preeclampsia is a low-grade systemic inflammatory condition in which oxidative stress and endothelial dysfunction occurs. Plasma levels of soluble receptor for vascular endothelial growth factor (VEGFR)-1, also known as sFlt1 (soluble fms-like tyrosine kinase 1), an antiangiogenic factor have been reported to be elevated in preeclampsia. It was reported that pregnant mice deficient in catechol-O-methyltransferase (COMT) activity show a preeclampsia-like phenotype due to a deficiency or absence of 2-methoxyoestradiol (2-ME), a natural metabolite of estradiol that is elevated during the third trimester of normal human pregnancy. Additionally, autoantibodies (AT1-AAs) that bind and activate the angiotensin II receptor type 1 a (AT1 receptor) also have a role in preeclampsia. None of these abnormalities are consistently seen in all the patients with preeclampsia and some of them are not specific to pregnancy. Preeclampsia could occur due to an imbalance between pro- and antiangiogenic factors. VEGF, an angiogenic factor, is necessary for the transport of polyunsaturated fatty acids (PUFAs) to endothelial cells. Hence reduced VEGF levels decrease the availability of PUFAs to endothelial cells. This leads to a decrease in the formation of anti-inflammatory and angiogenic factors: lipoxins, resolvins, protectins, and maresins from PUFAs. Lipoxins, resolvins, protectins, maresins, and PUFAs suppress insulin resistance; activation of leukocytes, platelets, and macrophages; production of interleukin-6 and tumor necrosis factor-α; and oxidative stress and endothelial dysfunction; and enhance production of prostacyclin and nitric oxide (NO). Estrogen enhances the formation of lipoxin A4 and NO. PUFAs also augment the production of NO and inhibit the activity of angiotensin-converting enzyme and antagonize the actions of angiotensin II. Thus, PUFAs can prevent activation of angiotensin II receptor type 1 a (AT1 receptor). Patients with preeclampsia have decreased plasma phospholipid concentrations of arachidonic acid (AA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA), the precursors of lipoxins (from AA), resolvins (from EPA and DHA), and protectins (from DHA) and prostaglandin E1 (PGE1 from DGLA: dihomo-γ-linolenic acid) and prostacyclin (PGI2 derived from AA). Based on these evidences, it is proposed that preeclampsia may occur due to deficiency of PUFAs and their anti-inflammatory products: lipoxins, resolvins, protectins, and maresins.

Are insulin resistance index, IGF-1 and metabolic syndrome components correlates with severe preeclampsia?

OBJECTIVE

Analyse the relation between insulin resistance and severe preeclampsia (SPE).

METHODS

Case control study paired by body mass index and gestational age; including 16 patients with severe SPE and 16 normotensive controls. Insulin resistance was assessed through the HOMA-IR and QUICKI-IS indexes.

RESULTS

There was no significant difference between the groups regarding the HOMA-IR and QUICKI-IS indexes and HDL cholesterol. Triglyceride levels were higher and the IGF-1 was lower in the SPE group than in the control group.

CONCLUSIONS

There were no differences in the insulin resitance indexes between the group with SPE and normal controls.

Is there evidence of separate inflammatory or metabolic forms of preeclampsia?

OBJECTIVES

To examine whether high insulin resistance versus high inflammation identifies subtypes of preeclampsia.

METHODS

A cytokine panel, glucose and insulin were measured in 37 preeclampsia plasma samples. Wilcoxon rank sum assessed median concentration of HOMA(IR) by pro-inflammatory:anti-inflammatory ratio. Regression stratifying by BMI and preterm birth was conducted.

RESULTS

There was no difference in median HOMA(IR) by the pro-inflammatory:anti-inflammatory ratio (p = 0.16). No subsets scatterplot clusters emerged. A positive correlation between HOMAlog and the ratio was significant (p = 0.04).

CONCLUSIONS

No dichotomous subsets of preeclampsia by inflammation versus insulin resistance were detected. Contrary to our hypothesis, insulin resistance was higher as inflammation increased in preeclampsia.

Hyperglycemia and Adverse Pregnancy Outcome (HAPO) study: preeclampsia

OBJECTIVE

The purpose of this study was to examine associations of fasting C-peptide, body mass index (BMI), and maternal glucose with the risk of preeclampsia in a multicenter multinational study.

STUDY DESIGN

We conducted a secondary analysis of a blinded observational cohort study. Subjects underwent a 75-g oral glucose tolerance test at 24-32 weeks' gestation. Associations of preeclampsia with fasting C-peptide, BMI, and maternal glucose were assessed with the use of multiple logistic regression analyses and adjustment for potential confounders.

RESULTS

Of 21,364 women who were included in the analyses, 5.2% had preeclampsia. Adjusted odds ratios for preeclampsia for 1 SD higher fasting C-peptide (0.87 ug/L), BMI (5.1 kg/m(2)), and fasting (6.9 mg/dL), 1-hour (30.9 mg/dL), and 2-hour plasma glucose (23.5 mg/dL) were 1.28 (95% confidence interval [CI], 1.20-1.36), 1.60 (95% CI, 1.60-1.71), 1.08 (95% CI, 1.00-1.16), 1.19 (95% CI, 1.11-1.28), and 1.21 (95% CI,1.13-1.30), respectively.

CONCLUSION

Results indicate strong, independent associations of fasting C-peptide and BMI with preeclampsia. Maternal glucose levels (below diabetes mellitus) had weaker associations with preeclampsia, particularly after adjustment for fasting C-peptide and BMI.

Increased plasma levels of inflammatory markers and upper airway resistance during sleep in pre-eclampsia

OBJECTIVES

To evaluate pregnancy-associated sleep disorders, pregnancy outcomes and inflammatory markers in pre-eclampsia and normal pregnancy (control).

PATIENTS AND METHODS

We studied 15 consecutive pre-eclamptic women and 14 controls. Pre-eclamptic women underwent overnight pulse oximetry and nasal pressure measurements at a university teaching hospital, and the sleep study for the controls was performed at home. Mean gestation was 31 weeks. Nasal airflow was carefully analyzed visually, and the time with flow limitation was calculated as a percentage of total recording time. At the time of the sleep study, the subjects were clinically evaluated, they answered sleep questionnaires, and fasting blood samples were drawn for tumor necrosis factor alpha TNF-alpha, interleukin 6 (IL-6) and sensitive C-reactive protein. Pregnancy outcomes were collected after delivery.

RESULTS

Pre-eclampsia patients spent significantly more time with flow limitation (mean+/-SD: 21+/-18% vs. 4+/-9%), had higher plasma levels of TNF-alpha (6.2+/-2.3 ng/l vs. 4.1+/-ng/l) and IL-6 (4.4+/-ng/l vs. 1.2+/-0.4 ng/l), had more generalized edema, had increased fatigue and snoring, and had poorer pregnancy outcomes than did controls. Age, gestational age, mean SpO2 and body mass index did not differ between the groups.

CONCLUSIONS

Pregnant women with pre-eclampsia showed significantly more nasal flow limitation during the night, higher fasting IL-6 and TNF-alpha plasma levels, more edema and worse pregnancy outcomes than did healthy pregnant women.

Insulin resistance in human preeclamptic placenta is mediated by serine phosphorylation of insulin receptor substrate-1 and -2

CONTEXT

Preeclampsia is a severe complication of human pregnancy often associated with maternal risk factors. Insulin resistance represents a major risk for developing preeclampsia during pregnancy.

OBJECTIVE

A putative second messenger of insulin, inositol phosphoglycan P type (P-IPG), was previously shown to be highly increased during active preeclampsia. Its association with insulin resistance was investigated.

DESIGN AND SETTING

A cross-sectional study was carried out in a referral center.

PATIENTS

Nine preeclamptic (PE) and 18 healthy women were recruited and matched for maternal age, body mass index, parity, and ethnicity in a 1:2 ratio. Placental specimens were collected immediately after delivery.

INTERVENTION

Placental tissue was incubated with insulin and P-IPG production assessed. Insulin signaling proteins were subsequently studied by immunoblotting.

RESULTS

P-IPG extracted from human term placentas upon incubation with insulin was found to be far lower in those with preeclampsia than controls (P < 0.001). Immunoblotting studies revealed serine phosphorylation of insulin receptor substrate-1 and -2 in PE placentas (P < 0.001) with downstream impairment of insulin signaling. The activation of the p85 regulatory subunit of phosphatidylinositol 3- kinase was markedly decreased in PE samples (P < 0.001).

CONCLUSIONS

These findings highlight the importance of P-IPG in active preeclampsia and demonstrate a substantially different response to the insulin stimulus of human PE placentas. Acquired alterations in activation of proteins involved in insulin signaling may play a role in the complex pathogenesis of preeclampsia, probably as a consequence of the immunological dysfunction that occurs in this syndrome. These results seem to confirm an insulin-resistant state in PE placenta and shed a different light on its role in the pathogenesis of this disease with potential therapeutic implications.