Determination of retinoic acid in human serum and plasma by high-performance liquid chromatography

Lazy neutrophils - a lack of DGAT1 reduces the chemotactic activity of mouse neutrophils

BACKGROUND

Neutrophils are key players in the innate immune system, actively migrating to sites of inflammation in the highly energetic process of chemotaxis. In this study, we focus on the role of acyl-CoA: diacylglycerol acyltransferase 1 (DGAT1), an enzyme that catalyzes the synthesis of triglycerides, the major form of stored energy, in neutrophil chemotaxis.

METHODS AND RESULTS

Using a mouse model of psoriasis, we show that DGAT1-deficiency reduces energy-demanding neutrophil infiltration to the site of inflammation, but this inhibition is not caused by decreased glycolysis and reduced ATP production by neutrophils lacking DGAT1. Flow cytometry and immunohistochemistry analysis demonstrate that DGAT1 also does not influence lipid accumulation in lipid droplets during inflammation. Interestingly, as has been shown previously, a lack of DGAT1 leads to an increase in the concentration of retinoic acid, and here, using real-time PCR and publicly-available next-generation RNA sequencing datasets, we show the upregulation of retinoic acid-responsive genes in Dgat1KO neutrophils. Furthermore, supplementation of WT neutrophils with exogenous retinoic acid mimics DGAT1-deficiency in the inhibition of neutrophil chemotaxis in in vitro transwell assay.

CONCLUSIONS

These results suggest that impaired skin infiltration by neutrophils in Dgat1KO mice is a result of the inhibitory action of an increased concentration of retinoic acid, rather than impaired lipid metabolism in DGAT1-deficient mice.

Levels of retinol and retinoic acid in pancreatic cancer, type-2 diabetes and chronic pancreatitis

AIMS

Retinoids participate in multiple key processes in the human body e.g., vision, cell differentiation and embryonic development. There is growing evidence of the relationship between retinol, its active metabolite- all-trans retinoic acid (ATRA) - and several pancreatic disorders. Although low levels of ATRA in pancreatic ductal adenocarcinoma (PDAC) tissue have been reported, data on serum levels of ATRA in PDAC is still limited. The aim of our work was to determine serum concentrations of retinol and ATRA in patients with PDAC, type-2 diabetes mellitus (T2DM), chronic pancreatitis (CHP) and healthy controls.

METHODS

High performance liquid chromatography with UV detection (HPLC) was used to measure serum levels of retinol and ATRA in 246 patients with different stages of PDAC, T2DM, CHP and healthy controls.

RESULTS

We found a significant decrease in the retinol concentration in PDAC (0.44+/-0.18 mg/L) compared to T2DM (0.65+/-0.19 mg/L, P<0.001), CHP (0.60+/-0.18 mg/L, P< 0.001) and healthy controls (0.61+/-0.15 mg/L, P<0.001), significant decrease of ATRA levels in PDAC (1.14+/-0.49 ug/L) compared to T2DM (1.37+/-0.56 ug/L, P<0.001) and healthy controls(1.43+/-0.55 ug/L, P<0.001). Differences between early stages (I+II) of PDAC and non-carcinoma groups were not significant. We describe correlations between retinol, prealbumin and transferrin, and correlation of ATRA and IGFBP-2.

CONCLUSION

Significant decrease in retinol and ATRA levels in PDAC compared to T2DM, healthy individuals and/or CHP supports existing evidence of the role of retinoids in PDAC. However, neither ATRA nor retinol are suitable for detection of early PDAC. Correlation of ATRA levels and IGFBP-2 provides new information about a possible IGF and retinol relationship.

In vitro bioaccessibility and intestinal transport of retinoic acid in ethyl cellulose-based microparticles and impact of meal co-ingestion

The development of carrier-based delivery systems for oral administration of retinoic acid (RA), that provides its release and absorption at intestinal level, is of major relevance in the treatment of acute promyelocytic leukemia. The aim of this work was to evaluate RA bioaccessibility and intestinal transport on ethyl cellulose (EC)- and EC + polyethylene glycol (ECP)-based microparticles and to understand the impact of meal co-ingestion by applying in vitro assays. RA-loaded microparticles were produced by spray-drying with an encapsulation efficiency higher than 90 % for both formulations. The gastric bioaccessibility of RA (after in vitro static digestion of RA-loaded particles) was lower than 3 % for both types of microparticles, with and without meal co-ingestion. Whereas after intestinal digestion, RA bioaccessibility was significantly higher and affected by the type of microparticles and the presence of meal. The digestion of EC- and ECP-based microparticles without diet enabled a significantly higher bioaccessibility of RA when compared to the one recorded for the co-digestion of these microparticles with diet. Herein, RA bioaccessibility decreased from 84 ± 1 to 24 ± 6 % (p < 0.0001) for microparticles EC and 54 ± 4 to 25 ± 5 % (p < 0.001) for microparticles ECP. Moreover, comparing both types of microparticles, RA bioaccessibility was significantly higher for EC-based microparticles digested without diet (p < 0.0001). At last, the bioaccessibility of RA was similar among EC- and ECP-based microparticles when co-digested with diet. Intestinal transport experiments performed in Caco-2 monolayers evidenced that after 2 h of transport the amount of RA retained in the apical compartment was higher than the amount that reached the basolateral compartment evidencing a slow transport at intestinal level that was higher when RA is spiked in the blank of digestion and the meal digestion samples compared to RA dissolved in HBSS (44 ± 6 (p < 0.01) and 38 ± 1 (p < 0.05) vs 26 ± 2 %, respectively).

Fat-Soluble Vitamers: Parent-Child Concordance and Population Epidemiology in the Longitudinal Study of Australian Children

Fat-soluble vitamers (FSV) are a class of diverse organic substances important in a wide range of biological processes, including immune function, vision, bone health, and coagulation. Profiling FSV in parents and children enables insights into gene-environment contributions to their circulating levels, but no studies have reported on the population epidemiology of FSV in these groups as of yet. In this study, we report distributions of FSV, their parent-child concordance and variation by key characteristics for 2490 children (aged 11-12 years) and adults (aged 28-71 years) in the Child Health CheckPoint of the Longitudinal Study of Australian Children. Ten A, D, E and K vitamers were quantified using a novel automated LC-MS/MS method. All three K vitamers (i.e., K1, MK-4, MK-7) and 1-α-25(OH)₂D₃ were below the instrument detection limit and were removed from the present analysis. We observed a strong vitamer-specific parent-child concordance for the six quantifiable A, D and E FSVs. FSV concentrations all varied by age, BMI, and sex. We provide the first cross-sectional population values for multiple FSV. Future studies could examine relative genetic vs. environmental determinants of FSV, how FSV values change longitudinally, and how they contribute to future health and disease.