Gene expression profile following an oral unsaturated fat load in abdominal obese subjects

Systematic Review and Quantitative Data Synthesis of Peripheral Blood Mononuclear Cell Transcriptomics Reveals Consensus Gene Expression Changes in Response to a High Fat Meal

SCOPE

Metabolic flexibility is essential for a healthy response to a high fat meal, and is assessed by measuring postprandial changes in blood markers including peripheral blood mononuclear cells (PBMCs; lymphocytes and monocytes). However, there is no clear consensus on postprandial gene expression and protein changes in these cells.

METHOD AND RESULTS

The study systematically reviews the literature reporting transcriptional and proteomic changes in PBMCs after consumption of a high fat meal. After re-analysis of the raw data to ensure equivalence between studies, ≈85 genes are significantly changed (defined as in the same direction in ≥3 studies) with about half involved in four processes: inflammation/oxidative stress, GTP metabolism, apoptosis, and lipid localization/transport. For meals consisting predominantly of unsaturated fatty acids (UFA), notable additional processes are phosphorylation and glucocorticoid response. For saturated fatty acids (SFA), genes related to migration/angiogenesis and platelet aggregation are also changed.

CONCLUSION

Despite differences in study design, common gene changes are identified in PBMCs following a high fat meal. These common genes and processes will facilitate definition of the postprandial transcriptome as part of the overall postcibalome, linking all molecules and processes that change in the blood after a meal.

Dehydrogenase reductase 9 (SDR9C4) and related homologs recognize a broad spectrum of lipid mediator oxylipins as substrates

Bioactive oxylipins play multiple roles during inflammation and in the immune response, with termination of their actions partly dependent on the activity of yet-to-be characterized dehydrogenases. Here, we report that human microsomal dehydrogenase reductase 9 (DHRS9, also known as SDR9C4 of the short-chain dehydrogenase/reductase (SDR) superfamily) exhibits a robust oxidative activity toward oxylipins with hydroxyl groups located at carbons C9 and C13 of octadecanoids, C12 and C15 carbons of eicosanoids, and C14 carbon of docosanoids. DHRS9/SDR9C4 is also active toward lipid inflammatory mediator dihydroxylated Leukotriene B₄ and proresolving mediators such as tri-hydroxylated Resolvin D1 and Lipoxin A₄, although notably, with lack of activity on the 15-hydroxyl of prostaglandins. We also found that the SDR enzymes phylogenetically related to DHRS9, i.e., human SDR9C8 (or retinol dehydrogenase 16), the rat SDR9C family member known as retinol dehydrogenase 7, and the mouse ortholog of human DHRS9 display similar activity toward oxylipin substrates. Mice deficient in DHRS9 protein are viable, fertile, and display no apparent phenotype under normal conditions. However, the oxidative activity of microsomal membranes from the skin, lung, and trachea of Dhrs9^−/− mice toward 1 μM Leukotriene B₄ is 1.7- to 6-fold lower than that of microsomes from wild-type littermates. In addition, the oxidative activity toward 1 μM Resolvin D1 is reduced by about 2.5-fold with DHRS9-null microsomes from the skin and trachea. These results strongly suggest that DHRS9 might play an important role in the metabolism of a wide range of bioactive oxylipins in vivo.

Oral Unsaturated Fat Load Impairs Postprandial Systemic Inflammation in Primary Hypercholesterolemia Patients

Context: Primary hypercholesterolemia (PH) is a lipid disorder characterized by elevated levels of cholesterol and low-density lipoprotein (LDL). Low-grade systemic inflammation is associated with PH, which might explain the higher incidence of cardiovascular diseases in this setting.

Objective: To evaluate the effect of an oral unsaturated fat load (OUFL) on different immune parameters and functional consequences in patients with PH in postprandial state.

Design: A commercial liquid preparation of long-chain triglycerides (Supracal^®; ω6/ω3 ratio >20/1, OUFL) was administered to 20 patients and 10 age-matched controls. Whole blood was collected before (fasting state) and 4 h after administration (postprandial state). Flow cytometry was employed to determine platelet and leukocyte activation, and the levels of circulating platelet-leukocyte aggregates. Soluble markers were determined by ELISA, and the parallel-plate flow chamber was employed to study leukocyte adhesion to the dysfunctional arterial endothelium.

Results: The PH group had a lower percentage of activated platelets and circulating type 1 monocytes, and blunted neutrophil activation after the OUFL, accompanied by a significant increase in the percentage of regulatory T lymphocytes. In this group, the OUFL led to a significant impairment of leukocyte adhesion to the dysfunctional [tumor necrosis factor α (TNFα)-stimulated] endothelium and reduced the plasma levels of soluble P-selectin, platelet factor-4 (PF-4)/CXCL4, CXCL8, CCL2, CCL5, and TNFα.

Conclusion: The OUFL has a beneficial impact on the pro-thrombotic and pro-inflammatory state of PH patients and might be a promising macronutrient approach to dampen the systemic inflammation associated with PH and the development of further cardiovascular events.

Postprandial triglyceridaemia is modulated by insulin resistance but not by grade of obesity in abdominal and morbid obese subjects

BACKGROUND

Obesity is associated with high cardiovascular risk. Postprandial lipidaemia has been associated with cardiovascular disease risk. Our aim was to identify whether anthropometric parameters, insulin resistance (IR) and/or fasting plasma triglycerides may determine postprandial changes in lipoprotein concentrations in abdominal and morbid obese subjects.

METHODS

We have studied 20 non-diabetic, normolipidaemic subjects with abdominal obesity, 20 morbid obese subjects and 20 healthy individuals, that have similar age and gender. In all of them a standardised oral fat load test (OFLT) with unsaturated fat was performed.

RESULTS

During the OFLT, the postprandial triglycerides response was significantly higher in subjects with abdominal obesity compared with morbid obese subjects (4 hours triglycerides pick value and AUC of triglycerides). Both obese groups showed significantly higher postprandial triglycerides response compared with healthy subjects. Dividing the obesity group according to the presence of IR, we found that IR was an important factor related with postprandial lipaemia but not BMI or waist circumference. In addition, postprandial glycaemia and insulinaemia significantly decreased in all studied subjects, being the highest decrease in morbid obese subjects and in subjects with IR. Postprandial triglyceridaemia significantly correlated with IR parameters and not with anthropometric parameters in AO and MO subjects.

CONCLUSION

In subjects with AO and MO, postprandial triglycerides values are higher than healthy individuals and independently predicted by fasting IR parameters. Furthermore, unsaturated fat improved IR state.