TABLE 4

Literature overview nutritional components and their effect on the immune system via TLRs

Receptor	Nutritional Activator	Concentration and Mode of Administration	Type of Study	Model	Stimulant/Disease Model	Effect	Reference
TLR2	Normal or Western-like rodent diet	Ad libitum	In vivo	WT and TLR2/4 double-KO C57BL6	Crossfostering and TLR4 specific inhibitor TAK-242	Maternal Western diet caused neonatal toxicity and inflammation, possibly related to long-chain fatty acids and SFAs in mother milk. TLR2/4 deletion rescues the neonatal toxicity	(Du et al., 2012)
	Free fatty acids	500 µM	In vitro/ex vivo	RAW264.7 cells and BMDC from WT and TLR2/4 double-KO C57BL/6 mice	RAW264.7 cells were treated with siRNA-TLR2/4	Increase in proinflammatory cytokines	(Nguyen et al., 2007)
	β2→1-fructan	1 or 100 µg/ml	In vitro	Human PBMC, THP-1 cells, and TLR2 reporter cell lines	—	Elevated IL-10/IL-12 protein levels	(Vogt et al., 2013)
	β2→1-fructan	100 mg/l	In vitro	T84 cells	Phorbol 12-myrestare 13-acetate and TLR2 blocking antibody	Improvement of intestinal epithelial barrier function	(Vogt et al., 2014)
TLR4	FOS, inulin, GOS, and goat milk oligosaccharides	0.005 –5 g/l	In vitro/ex vivo	Human peripheral blood monocytes, monocytes and lymphocytes from Wistar rats, and splenocytes from WT and TLR4^−/− C57BL/6J mice	LPS, concanavalin A, and MAPK inhibitors	NDOs generally evoked cytokine release by splenocytes and monocytes, possibly via activation of TLR4 and engagement of NF-ĸB and MAPK pathways NF-ĸB	(Capitán-Cañadas et al., 2014)
	Normal or Western-like rodent diet	Ad libitum	In vivo	WT and TLR2/4 double-KO C57BL6	Crossfostering and TLR4-specific inhibitor TAK-242	Maternal Western diet caused neonatal toxicity and inflammation, possibly related to long-chain fatty acids and SFAs in mother milk. TLR2/4 deletion rescues the neonatal toxicity	(Du et al., 2012)
	Sodium palmitate and laurate	100–500 µM	In vitro	RAW 264.7 cells, immortalized MyD88^−/− macrophages, and HEK293T cells	Bovine serum albumin and polymyxin B and TLR4-specific inhibitor TAK-242	Induction of COX-2 and TNF-α	(Huang et al., 2012)
	Sialyl(α2,3)lactose	25 mM in diet or 3 mg oral gavage	In vivo	St3gal4^−/−, IL10^−/−, St3gal4^−/−;IL10^−/− and TLR4^−/− C57BL/J6 mice	Crossfostering Spontaneous chronic intestinal inflammation	Early onset and exacerbation of colitis symptoms, increased proinflammatory cytokines, proinflammatory monocytes, Th1 and Th17 cells	(Kurakevich et al., 2013)
	Lauric acid	50, 75, or 100 µM	In vitro	RAW264.7 and 293T cells transfected with TLR4 and MD2	Dominant-negative mutant of TLR4, MyD88, IRAK-1, TRAF6, or IĸBα. I3K inhibitor (LY294002) or a dominant-negative mutant of PI3K or AKT	Activation of TLR4 and signaling pathways involving MyD88/IRAK/TRAF6 and PI3K/AKT	(Lee et al., 2003)
	Short-chain GOS/long-chain FOS	5 mg/ml	In vitro	Human monocyte–derived DCs	LPS, Bifidobacterium breve, and TLR4-specific antagonist	Induction of IL-10 secretion of (Bifidobacterium breve–stimulated) DCs	(Lehmann et al., 2015)
	Palmitic acid	50–300 µM	In vitro	Human monocyte–derived DCs and recombinant TLR4/MD2 HeLa cells	—	Upregulation of DC costimulatory factors CD86 and CD83 and expression of IL-1β by interacting with TLR4/MD-2	(Nicholas et al., 2017)
	Free fatty acids	500 µM	In vitro/ex vivo	RAW264.7 cells and BMDC from WT and TLR2/4 double-KO C57BL/6 mice	RAW264.7 cells were treated with siRNA-TLR2/4	Increase in proinflammatory cytokines	(Nguyen et al., 2007)
	Goat milk oligosaccharides, inulin, GOS, and FOS	5 mg/ml	In vitro/ex vivo	IEC18, HT29, Caco-2 and Caco‐2/TC7 cells and colon cells from WT and TLR4 KO C57BL/6J mice	Specific inhibitors of NF-κB and MAPK pathways, shRNA specific for MyD88 and TLR4 for gene knockdown	NDOs stimulated cytokine production in intestinal epithelial cells (e.g., CXCL-1 and MCP-1)	(Ortega-González et al., 2014)
	High-fat diet Palmitate and oleate	Not specified (diet) 200 or 400 µM (in vitro)	In vivo/in vitro	WT and TLR4^−/− C57BL6/J mice, ob/ob and db/db mice. RAW264.7 cells and 293T 3T3-L1 adipocytes, isolated mouse adipocytes, adipose tissue, and peritoneal macrophages from TLR4^−/− mice	Diet-induced obesity siRNA-TLR4	Diet-induced inflammation and insulin resistance, increased TLR4 expression in adipose tissue of obese/diabetic mice. Activation of TLR4 signaling, stimulation of cytokine expression (e.g., TNF-α, IL-6)	(Shi et al., 2006)
	Palmitate	100-200 µM	In vitro/ex vivo	Coculture of 3T3-L1 and RAW264.7, Ba/F3, or TLR4 mutant peritoneal macrophages of C3H/HeJ or C3H/HeN mice	TNF-α, LPS	Role of TLR4/NF-κB pathway in SFA-induced inflammatory changes	(Suganami et al., 2007)

HEK, Human Embryonic Kidney; IEC, intestinal epithelial cell line; MAPK = Mitogen-Activated Protein Kinase; shRNA, short hairpin RNA.