Impact of oral lipid and glucose tolerance tests on the postprandial concentrations of angiopoietin-like proteins (Angptl) 3 and 4

Figures

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  Fig. 1. Circulating levels of Angptl3 and Angptl4 are differentially regulated upon lipid ingestion (OLTT) but not by glucose uptake (OGTT). OLTT participants orally received a lipid preparation (160 mL; 758.1 kcal; 75 g vegetable fat as triglycerides, 9.2 g fatty acids as pure vegetable oils) and venous blood was drawn at baseline (0 h) and after 2, 4, and 6 h (A, B). During OGTT, blood was sampled 0, 1, and 2 h after oral uptake of 75 g glucose (C, D). Raise of serum triglycerides during OLTT (A, B) and of blood glucose levels during OGTT (C, D) is illustrated by means ± standard deviation for the examined time-points. Angptl3 and Angptl4 concentrations in blood serum were measured by ELISA. Angptl3 angiopoietin-like protein3, Angptl4 angiopoietin-like protein4, ELISA enzyme-linked immunosorbent assay, OGTT oral glucose tolerance test, OLTT oral lipid tolerance test

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  Fig. 2. Angptl3 (A) and Angptl4 (B) gene expression is induced during adipocyte differentiation. During hormonally induced differentiation of murine 3T3-L1 fibroblast-like pre-adipocytes into mature adipocytes, mRNA levels of Angptl3 and Angptl4 were significantly upregulated during late stages of the differentiation process (day 0–3: undifferentiated, fibroblast-like pre-adipocytes; day 3–5: ongoing differentiation and lipid accumulation; day 7–9: late differentiation with fully differentiated and mature adipocytes showing a round shape and intensive lipid accumulation a day 7). Cellular phenotypes during differentiation were illustrated by representative light-microscopy images (magnification: × 200) and lipid accumulation in mature adipocytes was visualized by Oil Red O staining. Angptl3 mRNA expression was quantified by real-time PCR and expression levels were related to GAPDH expression (house-keeping gene). Angptl3 angiopoietin-like protein 3, Angptl4 angiopoietin-like protein 4, GAPDH glyceraldehyde-3-phosphate dehydrogenase

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  Fig. 3. Quantification of Angptl3 and Angptl4 mRNA expression in different adipose tissue compartments and cellular fractions. Gene expression of Angptl3 and Angptl4 is not different between total intra-abdominal (ia) and total subcutaneous (sc) adipose tissue (AT) resected from C57BL/6 wild-type mice (A, B). Angptl3 and Angptl4 expression is abundant in mature adipocytes but not in the stroma-vascular cell (SVC) fraction isolated from intra-abdominal (C, D) and subcutaneous (E, F) adipose tissue. Angptl3, angiopoietin-like protein 3; Angptl4, angiopoietin-like protein 4

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  Fig. 4. Effects of fatty acids on adipocytic Angptl3 and Angptl4 gene expression. 3T3-L1 adipocytes were treated with a broad panel of 11 saturated (lauric acid (LaA), 100 µM); margaric acid (MaA), 100 µM; myristic acid (MyA), 100 µM; palmitic acid (PA), 100 µM; stearic acid (SA), 100 µM) as well as monounsaturated (oleic acid (OA), 10 µM) and polyunsaturated fatty acids (arachidonic acid (ArA), 10 µM; docosahexaenoic acid (DHA), 10 µM; eicosapentaenoic acid (EPA), 10 µM; linoleic acid (LiA), 10 µM; palmitoleic acid (PoA), 10 µM) (A–D). Cells were incubated with free fatty acids for 18 h prior to RNA isolation and RT-PCR analysis. Angptl3 angiopoietin-like protein 3, Angptl4 angiopoietin-like protein 4, Ctrl control, n.s. not significant