Urinary platelet-activating factor excretion is elevated in non-insulin dependent diabetes mellitus

Associations between healthy food groups and platelet-activating factor, lipoprotein-associated phospholipase A2 and C-reactive protein: a cross-sectional study

PURPOSE

To investigate the association between pro-inflammatory markers platelet-activating factor (PAF), lipoprotein-associated phospholipase A2 (Lp-PLA2), hsCRP, and intake of core food groups including fruit, cruciferous and other vegetables, grains, meat and poultry, fish and seafood, nuts and legumes, and dairy.

METHODS

A cross-sectional study was conducted. 100 adults (49 ± 13 years, 31% male) with variable cardiovascular disease risk were recruited. Data were collected in 2021 and 2022. Fasting PAF, Lp-PLA2 activity, hsCRP and usual dietary intake (via a validated food frequency questionnaire) were measured. Intake of foods were converted into serves and classified into food groups. Correlations and multiple regressions were performed with adjustment for confounders.

RESULTS

A one-serve increase in cruciferous vegetables per day was associated with 20-24% lower PAF levels. An increase of one serve per day of nuts and legumes was associated with 40% lower hsCRP levels. There were small correlations with PAF and Lp-PLA2 and cheese, however, these were not significant at the Bonferroni-adjusted P < 0.005 level.

CONCLUSION

The lack of associations between PAF and Lp-PLA2 and other healthy foods may be due to confounding by COVID-19 infection and vaccination programs which prevents any firm conclusion on the relationship between PAF, Lp-PLA2 and food groups. Future research should aim to examine the relationship with these novel markers and healthy food groups in a non-pandemic setting.

Interrelationships among platelet-activating factor and lipoprotein-associated phospholipase A2 activity and traditional cardiovascular risk factors

Traditionally cardiovascular disease (CVD) risk has been assessed through blood lipids and inflammatory marker C-reactive protein (hsCRP). Recent clinical interest in novel pro-inflammatory markers platelet-activating factor (PAF) and lipoprotein-associated phospholipase A₂ (Lp-PLA₂ ) recognizes that vascular damage can exist in the absence of traditional risk factors. This cross-sectional study investigated the potential relationship between circulating PAF, Lp-PLA₂ , hsCRP, and traditional risk factors for CVD. One hundred adults (49 ± 13 years, 31% male) with variable CVD risk were recruited. Fasting inflammatory markers PAF, Lp-PLA₂ and hsCRP and total, high-density lipoprotein (HDL), low-density lipoprotein (LDL) cholesterol, and triglycerides were measured. Blood pressure, body mass index, and waist circumference were measured. Medical and physical activity data were self-reported. Linear and multiple regressions were performed. PAF, Lp-PLA₂ , and hsCRP independently correlated with several CVD risk factors. PAF was correlated significantly with risk factors in an unexpected way; there was a medium positive correlation between PAF and HDL cholesterol (r = 0.394, p < 0.001) and medium negative correlations with Total:HDL cholesterol; (r = -0.436, p < 0.001) systolic blood pressure; (r = -0.307, p = 0.001); BMI (r = -0.381, p < 0.001); and waist circumference (r = -0.404, p < 0.001). There were large positive correlations between Lp-PLA₂ and LDL (r = 0.525, p < 0.001) and non-HDL cholesterol (r = 0.508, p < 0.001). There were large positive correlations between hsCRP and Total:HDL cholesterol (r = 0.524, p < 0.001); BMI (r = 0.668, p < 0.001); and waist circumference (r = 0.676, p < 0.001). PAF, Lp-PLA₂ , and hsCRP are implicated in the pathophysiology of inflammation in CVD; however, the relationships between each marker and traditional risk factors were different suggesting they may be involved in different atherogenic pathways.

The association between dietary patterns and the novel inflammatory markers platelet-activating factor and lipoprotein-associated phospholipase A2: a systematic review

CONTEXT

Atherosclerosis is a disease of chronic inflammation. Recent research has identified 2 novel inflammatory biomarkers: platelet-activating factor (PAF) and lipoprotein-associated phospholipase A2 (Lp-PLA2). Diet has been proposed as a mediator of inflammation, but to date, the focus for these novel biomarkers has been on individual foods and nutrients rather than overall dietary patterns.

OBJECTIVE

To systematically review the literature on the association between dietary patterns and PAF and Lp-PLA2.

DATA SOURCES

The PubMed, Embase, CINAHL, and Cochrane CENTRAL literature databases were searched.

DATA ANALYSIS

Study quality was evaluated using the Quality Criteria Checklist. Sixteen studies (n = 4 observational and n = 12 interventional) were included and assessed for associations between dietary patterns and PAF and Lp-PLA2.

CONCLUSION

Study quality varied from neutral (n = 10) to positive (n = 6). Mediterranean, heart healthy, and vegetarian dietary patterns were associated with improved levels of PAF and Lp-PLA2. Conversely, Western dietary patterns were less favorable. A range of well-established, healthier dietary patterns may lower inflammation and the risk of atherosclerosis. More well-designed studies are needed to confirm these findings and identify other dietary patterns that improve inflammation.

Inflammation, not Cholesterol, Is a Cause of Chronic Disease

Since the Seven Countries Study, dietary cholesterol and the levels of serum cholesterol in relation to the development of chronic diseases have been somewhat demonised. However, the principles of the Mediterranean diet and relevant data linked to the examples of people living in the five blue zones demonstrate that the key to longevity and the prevention of chronic disease development is not the reduction of dietary or serum cholesterol but the control of systemic inflammation. In this review, we present all the relevant data that supports the view that it is inflammation induced by several factors, such as platelet-activating factor (PAF), that leads to the onset of cardiovascular diseases (CVD) rather than serum cholesterol. The key to reducing the incidence of CVD is to control the activities of PAF and other inflammatory mediators via diet, exercise, and healthy lifestyle choices. The relevant studies and data supporting these views are discussed in this review.

Vascular Endothelial Growth Factor Activation of Intramembranous Absorption: A Critical Pathway for Amniotic Fluid Volume Regulation

OBJECTIVE

The purpose of this review is to propose a critical role for vascular endothelial growth factor (VEGF) in mediating the transfer of amniotic fluid from the amniotic compartment through the fetal membranes and fetal surface of the placenta into fetal blood.

METHODS

Experimental findings in humans and animal models on the action of VEGF in mediating fluid transfer are reviewed and interpreted in order to postulate a proposed mechanism for VEGF regulation of amniotic fluid absorption through the fetal membranes and placenta.

RESULTS

Recent scientific advances suggest that up-regulation of VEGF gene expression in the amnion and chorion is associated with increased transfer of amniotic fluid into fetal blood. The possible mechanisms of action for VEGF appear to involve regulation of intramembranous blood vessel proliferation and membrane transport via passive permeation as well as nonpassive transcytotic vesicular movement of fluid.

CONCLUSION

Currently evolving concepts suggest that amniotic fluid volume is regulated through modulation of the rate of intramembranous absorption of amniotic fluid by both passive and nonpassive mechanisms. The permeability factor VEGF appears to be a critical regulator of amniotic fluid transport in the fetal membranes.

Urothelial cell platelet-activating factor production mediated by calcium-independent phospholipase A2γ

OBJECTIVES

To determine the effect of phospholipase A(2) (PLA(2)) inhibitors on urothelial cell platelet-activating factor (PAF) production in response to tryptase stimulation.

METHODS

Urothelial cells isolated from normal human ureters were immortalized with the human papillomavirus type 16E6E7 cell line (TEU-2 cells). PLA(2) activity in TEU-2 cells was measured using (16:0, [(3)H]18:1) plasmenylcholine and phosphatidylcholine substrates in the presence and absence of calcium. [(3)H]PAF production was measured in TEU-2 cells prelabeled with [(3)H] acetic acid. PAF-acetylhydrolase activity was measured by determining the amount of [(3)H] acetate hydrolyzed from [(3)H]PAF incubated with TEU-2 cellular protein. Adherence of human polymorphonuclear leukocyte (PMN) to TEU-2 cells was assessed by measuring myeloperoxidase activity in adherent PMNs after incubation with TEU-2 cells.

RESULTS

Most PLA(2) activity measured in TEU-2 cells was determined to be membrane-associated, calcium-independent PLA(2) and selective for plasmenylcholine substrate. Stimulation of TEU-2 cells with tryptase results in increased production of PAF and increased PMN adherence that were inhibited completely by pretreatment with the membrane-associated, calcium-independent PLA(2)γ-selective inhibitor (R)-bromoenol lactone. Pretreatment with the cytosolic PLA(2) inhibitor methyl arachidonyl fluorophosphonate resulted in potentiation of tryptase-stimulated PAF production and PMN adherence to TEU-2 cells that is a result of PAF-acetylhydrolase inhibition.

CONCLUSIONS

Tryptase stimulation of TEU-2 cells results in activation of membrane-associated, calcium-independent PLA(2)γ, leading to an increase in PAF production and increased PMN adherence. Inhibition of TEU-2 cell PAF-acetylhydrolase activity with methyl arachidonyl fluorophosphonate potentiated tryptase-stimulated PAF production and PMN adherence.

Role of AKT-glycogen synthase kinase axis in monocyte activation in human beings with and without type 2 diabetes

Monocyte activation by chemokines is a vital trigger for initiation of atherosclerotic process. Circulating levels of platelet activating factor (PAF), a recognized chemokine, is known to be increased in type 2 diabetes that is linked to accelerated atherosclerosis. To explore the molecular basis we examined the signalling pathways involved in PAF induced monocyte activation. PAF increased migration in monocytes obtained from THP-1 cells, nondiabetic and diabetic subjects. This effect was blocked by AKT inhibition. It did so by phosphorylation of glycogen synthase kinase (GSK)-3βS⁹, which was completely blocked by AKT inhibition. Additionally, PAF induced GSK-3β phosphorylation was linked to Rac-1 activation and Rho-A inactivation leading to migration. Paradoxically, inhibition of GSK-3β phosphorylation also augmented monocyte migration in THP-1, ND and diabetic monocytes through phosphorylation of AKT and activation of Rho-A that was independent of GSK. This was validated when (i) overexpression of dominant negative mutants of Rho-A reversed GSK inhibitor induced monocyte migration and (ii) AKT inhibition blocked GSK inhibitor induced Rho-A activity. Constitutively active ARAP3 (Rho-GAP) appears to have a regulatory role in monocyte activity during GSK inhibition. Finally, inhibition of monocyte GSK-3β activity (by inhibitors and genetic manipulation) led to enhanced migration in diabetes compared to persons without diabetes. We conclude that diabetic monocytes show increased migratory capacity in response to GSK-3β inhibition. GSK inhibitors developed to treat the metabolic complications of diabetes should therefore be used with caution.

Effects of resistance versus aerobic training on coronary artery disease risk factors

Individuals exhibiting "the metabolic syndrome" have multiple coronary artery disease risk factors, including insulin resistance, hyperlipidemia, hypertension, and android obesity. We performed a randomized trial to compare the effects of aerobic and resistance training regimens on coronary risk factors. Twenty-six volunteers who exhibited android obesity and at least one other risk factor for coronary artery disease were randomized to aerobic or resistance training groups. Body mass index, waist-to-hip ratio, glucose, insulin, body composition, 24-hr urinary albumin, fibrinogen, blood pressure, and lipid profile were measured at baseline and after 10 weeks of exercise training. Both groups showed a significant reduction in waist-to-hip ratio and the resistance training group also showed a reduction in total body fat. There was no significant change in mean arterial blood pressure in either group. Fasting plasma glucose, insulin, total cholesterol, low-density lipoprotein (LDL) cholesterol, and triglycerides were unchanged in both groups. High-density lipoprotein (HDL) cholesterol increased (13%) with aerobic training only. Plasma fibrinogen was increased (28% and 34%, P < 0.02) in both groups and both groups showed a significant decrease (34% and 28%, P < 0.03) in microalbuminuria after their respective training regimen. In conclusion, resistance training was effective in improving body composition of middle-aged obese sedentary males. Only aerobic training was effective in raising HDL cholesterol. More studies are warranted to assess the effects of exercise on plasma fibrinogen and microalbuminuria.

The effect of 3-month ingestion of Ginkgo biloba extract (EGb 761) on pancreatic beta-cell function in response to glucose loading in individuals with non-insulin-dependent diabetes mellitus

In the first report (Journal of Clinical Pharmacology 2000; 40:647-654), it was shown that ingestion of 120 mg of Ginkgo biloba extract (EGb 761) daily for 3 months by normal glucose-tolerant individuals caused a significant increase in pancreatic beta-cell insulin and C-peptide response, measured as the area under the curve (AUC0-->120) during a 2-hour standard (75 g) oral glucose tolerance test (OGTT). This follow-up study was designed to determine the effect of the same Ginkgo biloba treatment on glucose-stimulated pancreatic beta-cell function in non-insulin-dependent diabetes mellitus (NIDDM) subjects. In diet-controlled subjects (fasting plasma glucose [FPG], 117 +/- 16 mg/dl; fasting plasma insulin [FPI], 29 +/- 8 microU/ml; n = 6), ingestion of Ginkgo biloba produced no significant effect on the insulin AUC0-->120 (193 +/- 53 vs. 182 +/- 58 microU/ml/h, before and after ingesting Ginkgo biloba, respectively). In hyperinsulinemic NIDDM subjects taking oral hypoglycemic medications (n = 6) (FPG 143 +/- 48 mg/dl; FPI 46 +/- 13 microU/ml), ingestion of Ginkgo biloba caused blunted plasma insulin levels from 30 to 120 minutes during the OGTT, leading to a reduction of the insulin AUC0-->120 (199 +/- 33 vs. 147 +/- 58 microU/ml/h, before and after Ginkgo biloba, respectively). The C-peptide levels increased, and so the AUC0-->120 did not parallel the insulin AUC0-->120, creating a dissimilar insulin/C-peptide ratio indicative of an enhanced hepatic extraction of insulin relative to C-peptide. Thus, in pancreatic beta-cells that are already maximally stimulated, ingestion of Ginkgo biloba may cause a reduction in plasma insulin levels. Only in NIDDM subjects with pancreatic exhaustion (FPG 152 +/- 46 mg/dl; FPI 16 +/- 8 microU/ml; n = 8), who also took oral hypoglycemic agents, did Ginkgo biloba ingestion significantly increase pancreatic beta-cell function in response to glucose loading (insulin AUC0-->120 increased from 51 +/- 29 to 98 +/- 20 microU/ml/h, p < 0.0001), paralleled by a C-peptide AUC0-->120 increase from 7.2 +/- 2.8 to 13.7 +/- 6.8 (p < 0.0001). Whether this increase is due to "resuscitation" of previously exhausted islets or increased activity of only the remaining functional islets is unclear. However, not even in this group did increased pancreatic beta-cell activity cause a reduction of blood glucose during the OGTT. It is concluded that ingestion of Ginkgo biloba extract by an NIDDM subject may increase the hepatic metabolic clearance rate of not only insulin but also the hypoglycemic agents. The result is reduced insulin-mediated glucose metabolism and elevated blood glucose.