Modulation of the biomarkers of inflammation and oxidative stress by ruminant trans fatty acids and dairy proteins in vascular endothelial cells (HUVEC).

This study aimed to determine whether dairy macronutrients alter markers of inflammation and oxidative stress in endothelial cells. Human endothelial cells (HUVEC) were treated with ruminant trans fatty acids (rTFA), either trans-vaccenic acid (tVA) or trans-palmitoleic acid (tPA), whey protein hydrolysate, leucine or combinations of rTFA and dairy protein compounds. Industrial TFA elaidic acid (EA) was also investigated and compared with rTFA. Inflammatory prostaglandins (PG) and F2-isoprostanes (F2-isoP) isomers, markers of oxidative stress, were assessed in cell supernatants by LC-MS/MS. Both tVA and tPA, as well as whey protein hydrolysate, decreased TNFα-induced PG excretion. Combinations of rTFA and dairy protein compounds decreased inflammation to a similar extent than rTFA alone. EA increased class VI F2-isoP isomers, whereas tVA mostly raised class III isomers. In summary, rTFA decreased inflammatory markers and increased oxidative stress markers in endothelial cells. Combinations of rTFA with whey proteins or leucine showed no additive effect.

Dairy Product Consumption Interacts with Glucokinase (GCK) Gene Polymorphisms Associated with Insulin Resistance.

Dairy product intake and a person's genetic background have been reported to be associated with the risk of type 2 diabetes (T2D). The objective of this study was to examine the interaction between dairy products and genes related to T2D on glucose-insulin homeostasis parameters. A validated food frequency questionnaire, fasting blood samples, and glucokinase (GCK) genotypes were analyzed in 210 healthy participants. An interaction between rs1799884 in GCK and dairy intake on the homeostasis model assessment of insulin resistance was identified. Secondly, human hepatocellular carcinoma cells (HepG2) were grown in a high-glucose medium and incubated with either 1-dairy proteins: whey, caseins, and a mixture of whey and casein; and 2-four amino acids (AA) or mixtures of AA. The expression of GCK-related genes insulin receptor substrate-1 (IRS-1) and fatty acid synthase (FASN) was increased with whey protein isolate or hydrolysate. Individually, leucine increased IRS-1 expression, whereas isoleucine and valine decreased FASN expression. A branched-chain AA mixture decreased IRS-1 and FASN expression. In conclusion, carriers of the A allele for rs1799884 in the GCK gene may benefit from a higher intake of dairy products to maintain optimal insulin sensitivity. Moreover, the results show that whey proteins affect the expression of genes related to glucose metabolism.

Whey protein hydrolysate and branched-chain amino acids downregulate inflammation-related genes in vascular endothelial cells.

A recent review of clinical studies reports that dairy products may improve inflammation, a key etiologic cardiovascular disease risk factor. Yet the impact of dairy proteins on inflammatory markers is controversial and could be mediated by a differential impact of whey proteins and caseins. In this study, we hypothesized that whey proteins may have a greater anti-inflammatory effect than caseins. A model of human umbilical vein endothelial cells, with or without TNF-α stimulation, was used to investigate the effect of several dairy protein compounds on inflammation. Specifically, the impact of whey proteins either isolate or hydrolysate, caseins, and their amino acids on expression of TNF, VCAM-1, SOD2, and eNOS was examined. After a 24-hour incubation period, whey protein hydrolysate, leucine, isoleucine, and valine attenuated the TNF-α-induced endothelial inflammation by normalizing TNF and eNOS gene expression. This effect was not observed in unstimulated cells. Oppositely, caseins, a whey protein/casein mixture (1:4 w/w), and glutamine aggravated the TNF-α-induced TNF and SOD2 gene expression. Yet caseins and whey protein/casein mixture decreased VCAM-1 expression in both unstimulated and stimulated human umbilical vein endothelial cells. Measurement of TNF-α in cell supernatants by immunoassay substantiates gene expression data without reaching statistical significance. Taken together, this study showed that whey proteins and their major amino acids normalize TNF-α-induced proinflammatory gene expression in endothelial cells.

Trans Fatty Acids Suppress TNF-α-Induced Inflammatory Gene Expression in Endothelial (HUVEC) and Hepatocellular Carcinoma (HepG2) Cells.

Trans fatty acids (TFA) intake has been linked to cardiovascular diseases and liver diseases; yet the effect of TFA on inflammation remains controversial. Accordingly, the objective of this paper was to determine the in vitro effects of TFA on inflammatory gene expression. Human umbilical vein endothelial cells (HUVEC) and human hepatocellular carcinoma (HepG2) cells were treated for 24 h with either trans-vaccenic acid (tVA), trans-palmitoleic acid (tPA) or elaidic acid (EA) at concentrations of 5-150 µM, or with a mixture of tVA and tPA (150/50 µM). All TFA were highly incorporated into cell membranes, as determined by gas chromatography, representing 15-20% of total fatty acids in HUVEC and 3-8% in HepG2 cells. Incorporation of EA, a common industrial TFA, increased the ratio of the stearoyl-CoA desaturase (SCD-1), a key enzyme involved in fatty acid metabolism. Ruminant TFA, including tVA, tPA and the mixture of tVA and tPA, significantly reduced the TNF-α-induced gene expression of TNF, VCAM-1 and SOD2 in HUVEC, as well as TNF and IL-8 in HepG2 cells. EA also decreased inflammatory gene expression in HUVEC, but not in HepG2 cells. The inhibition of peroxisome proliferator-activated receptor (PPAR)-γ did not influence the effects of TFA on gene expression. Overall, physiological and supraphysiological concentrations of TFA, especially tVA and tPA, prevented inflammatory gene expression in vitro. This effect is independent of PPAR-γ activation and may be due to an alteration of fatty acid metabolism in cell membranes caused by the high incorporation of TFA.