Table 2.

Concise summary of the effects of polyphenols from various sources on glucagon-like peptide-1 (GLP1), dipeptidyl peptidase-4 (DPP4) and insulin.

Polyphenol Source	Model	Effect on GLP1	Effect on DPP4	Effect on Insulin	Reference
Sweet potato ethanolic extract	Murine GLUTag cells	↑ secretion			[28]
Sweet potato ethanolic extract	Sprague–Dawley rats	↑ secretion			[28]
Coffee extract	Human NCI-H716 cells	Dose-related ↑ secretion			[29]
Coffee extract	C57BL/6J mice	↑ secretion			[29]
Cocoa products			Inhibit		[31]
Grape seed extract		↑ secretion	Inhibit	↑ secretion
Grape seed extract	STC-1 cells	↓ secretion			[33]
Grape seed extract	Wistar rats	↑ secretion		↑ secretion	[34]
Hibiscus sabdariffa	HK-2 cells		Inhibit		[36]
Hibiscus sabdariffa	Sprague–Dawley rats		Inhibit		[36]
Sorghum	Healthy adults	↑ GLP1 area under the curve			[37]
Cranberry extract	C57BL/6J mice			↓ fasting insulinemia	[38]
Cinnamon extract	Wistar rat enterocytes			↑ sensitivity	[40]
Procyanidin oligomers from cacao liquor	ICR mice	↑ secretion		↑ secretion	[41]
Cocoa flavanols	C57BL/6J mice			↓ fasting insulinemia	[42]
Syringic acid	Diabetic Wistar rats			Normalized glycemia and insulinemia	[43]
Mango	Overweight adults			↑ insulinemia in males	[44]
Apple polyphenol extract	Obese Zucker rats			No effect on postprandial insulinemia (acute effect)	[45]
Apple polyphenol extract	Obese Zucker rats			↑ postprandial insulin response (chronic effect)	[45]
Apple polyphenol extract	Murine L6-myocytes			Polyphenol/insulin synergy on glucose uptake	[45]
Blackcurrants, bilberries, cranberries, and strawberries	Healthy adults			Prevented insulin and glucose peaks	[46]
Olive leaf extract	Overweight men			↑ sensitivity	[47]
Dietary intervention with polyphenol-rich foods	Overweight adults			↑ secretion and sensitivity	[49]

↑: increases; ↓: decreases. STC: secretin tumor cells; ICR: Institute of Cancer Research.