TABLE 1.

Glucose-stimulated GLP-1 response (OGTT)

Author, (y), n	GLP-1 assay	Participant characteristics		GLP-1 values (pmol/L) at time points (min)											TTP (min)	Δ Peak (pmol/L)	GLP-1 AUC/iAUC	Results
				0	10	15	20	30	40	45	60	90	120	180
Theodorakis et al. 2006 [42] n = 53	RIALinco1	NGT (n = 36, BMI: 27 kg/m2)		6	15	21	22		21		16		11		20	16	120 min: AUC: 1874 (pmol/L∗min) #	↑ fasting values and AUC in T2DM compared with NGT
		T2DM (n = 17, BMI: 30 kg/m2)		12	19	28	31		33		32		12		40	21	120 min: AUC: 2866 (pmol/L∗min) #
Muscelli et al. 2008 [45] n = 51	RIA2	NGT (n = 24, BMI: 33.1 kg/m2)#		11	18		27	28	25		25	22	23	23	30	17	180 min: AUC: 4100 (pmol/L∗h) #	- ↓ GLP-1 response in T2DM compared with IGT and NGT - no significant differences between NGT and IGT - inverse relationship between GLP-1 response and BMI
		IGT (n = 17, BMI: 35.9 kg/m2)#		10	13		23	26	27		20	19	19	18	40	17	180 min: AUC: 3400 (pmol/L∗h)#
		T2DM (n = 10, BMI: 35.5 kg/m2)#		7	10		13	12	13		11	12	12	9	20 40	6	180 min: AUC: 2000 (pmol/L∗h)#
Vollmer et al. 2008 [49] n = 48	RIA2	NGT (n = 14, BMI: 27.5 kg/m2)		14				32			31	30	30	18	30	18	n.a.	- ↔ - positive relation between GLP-1 and age; negative association between GLP-1 concentrations and BMI - GLP-1 concentrations higher in females than in males
		IGT (n = 17, BMI: 29.5 kg/m2)		15				41			38	37	38	25	30	26
		T2DM (n = 17, BMI: 32.1 kg/m2)		16				35			33	39	28	23	90	23
Greenfield et al. 2009 [48] n = 24	RIA2	NW (n = 8, BMI: 22 kg/m2)		14		30		32		27	27	27	24		30	18	120 min: AUC: 3192 iAUC: 1242 (pmol/L∗120 min)#	↓ fasting values and AUC in T2DM/ IGT compared with NW/ OW ↔ iAUC
		OW (n = 8, BMI: 34.5 kg/m2)		13		22		24		22	23	21	18		30	11	120 min: AUC: 2550 iAUC:1082 (pmol/L∗ 120 min)#
		T2DM/IGT (n = 8, BMI: 38.5 kg/m2)		9		15		18		20	17	15	14		45	11	120 min: AUC: 1846 iAUC: 746 (pmol/L∗ 120 min)#
Bagger et al. 2011 [53] n = 16	RIA2	OW (n = 8, BMI: 29 kg/m2)		17	25		44	69		50	39		30	17	30	52	AUC: 7200#	↔ fasting/ peak values, AUC
		T2DM (n = 8, BMI: 29 kg/m2)		20	30		51	47		48	38		31	17	20	31	AUC: 6900# (4h∗ pmol/L)
Alssema et al. 2013 [44] n = 203	RIA2	NGT (n = 163, BMI: 26.7 kg/m2)		11		18		23			17	16	14		30	12	AUC: 18 iAUC: 7.3 (pmol/L per hour)	↑ fasting values and AUC per hour in T2DM compared with NGT
		IGT (n = 20, BMI: 28.5 kg/m2)		14		21		28			23	21	16		30	14	AUC: 21 iAUC: 6.7 (pmol/L per hour)
		T2DM (n = 20, 33.1 kg/m2)		17		29		37			26	23	16		30	20	AUC: 23 iAUC: 6.5 (pmol/L per hour)
Yabe et al. 2015 [47] n = 102	RIA2	NGT (n = 54, BMI: 21.3 kg/m2)		9		17	19	19			17		16		20 30	10	120 min: AUC: 2004 (pmol/L∗min)	↔
		IGT (n = 20, BMI: 22.5 kg/m2)		8		12	16	17			15		14		30	9	120 min: AUC: 1701 (pmol/L∗min)
		T2DM (n = 28, BMI: 23.5 kg/m2)		10		17	18	18			18		14		20 30 40	8	120 min: AUC: 1923 (pmol/L∗min)
Færch et al. 2015 [39] n = 1462	RIA2	NGT (n = 774, BMI: 26.0 kg/m2)#	F	9				31					23		30	22	120 min: AUC: 3124 (pmol/L∗min)#	- ↓GLP-1 response in IFG and T2DM (- up to25%) compared with NGT (females) - ↓120-min concentrations in IFG and T2DM (-16-21%) compared with NGT - ↓ GLP-1 response in persons with obesity (-20%) and OW (up to -8%) compared with NW participants
			M	10				26					18		30	16	120 min: AUC: 2612 (pmol/L∗min)#
		IGT (n = 525), 3 subgroups#
		i-IFG (BMI: 27.7 kg/m2)	F	11				29					22		30	18	120 min: AUC: 3029 (pmol/L∗min)#
			M	10				25					17		30	15	120 min: AUC: 2479 (pmol/L∗min)#
		i-IGT (BMI: 27.4 kg/m2)	F	11				31					22		30	20	120 min: AUC: 3131 (pmol/L∗min)#
			M	11				28					18		30	17	120 min: AUC: 2680 (pmol/L∗min)#
		IFG&IGT (BMI: 28.8 kg/m2)	F	10				26					18		30	16	120 min: AUC: 2591 (pmol/L∗min)#
			M	10				25					16		30	15	120 min: AUC: 2466 (pmol/L∗min)#
		T2DM (n = 163, BMI: 29.7 kg/m2)#	F	9				30					18		30	21	120 min: AUC: 2849 (pmol/L∗min)#
			M	11				27					16		30	16	120 min: AUC: 2582 (pmol/L∗min)#
Simon et al. 2015 [43] n = 21	RIA2	NW-NGT (n = 11, BMI: 23.6 kg/m2)#		6	14		17	21			22	21	22	14	60	16	n.a.	↓ GLP-1 response in OW-NGT compared with NW-NGT
		OW-NGT (n = 10, BMI: 35.5 kg/m2)#		7	13		18	15			15	14	12	8	20	11
Wang et al. 2016 [46] n = 80 (Han Chinese adults)	ELISA (Westang)3	NGT (n = 23, BMI: 25.6 kg/m2)		19				65			54		48	37	30	46	180 min: AUC: 192 (pmol/L∗min)	- ↓ fasting values in T2DM compared with NGT - ↓ peak values and AUC in T2DM compared with NGT/ IGT - no significant differences between NGT/ IGT
		IGT (n = 22, BMI: 26.0 kg/m2)		16				60			50		45	21	30	44	180 min: AUC: 182 (pmol/L∗min)
		T2DM (n = 35, BMI: 26.5 kg/m2)		15				42			38		35	26	30	27	180 min: AUC: 129 (pmol/L∗min)
Chia et al. 2017 [52] n = 40	ELISA (Alpco)4	NW (n = 20, BMI: 23.6 kg/m2)		3			14		11		10		9		20	11	120 min: AUC: 1150 (pmol/L∗min)#	↓ AUC in OW
		OW (n = 20, BMI: 35.6 kg/m2)		4			11		10		7		5		20	7	120 min: AUC: 831 (pmol/L∗min)#
Dybjer et al. 2020 [51] n = 3001	RIALinco1	NGT (n = 2453, BMI: 26.3 kg/m2)#		8									18		120	10	n.a.	- ↑ fasting levels in DM compared with NGT - ↓ postprandial levels in DM compared with NGT
		DM (n = 548, BMI: 28.7 kg/m2)#		9									16		120	7
Chong et al. 2022 [50] n = 174	ELISA (Millipore)5	NGT (n = 58, BMI: 24 kg/m2)#		16				31					24		30	15	120 min: AUC: 3266 (pmol/L∗min)#	- ↑ levels at fasting, after 30 min and AUC in T2DM compared with IGT and NGT - ↑ levels at fasting, after 30 min and AUC in IGT compared with NGT
		IGT (n = 54, BMI: 26.2 kg/m2)#		22				41					25		30	19	120 min: AUC: 3994 (pmol/L∗min)#
		T2DM (n = 62, BMI: 26.7 kg/m2)#		27				50					28		30	23	120 min: AUC: 4698 (pmol/L∗min)#

GLP-1 concentrations for selected time points of blood sampling, time-to-peak as well as peak (peak concentration – fasting concentration), and—if available—AUC or iAUC values are listed. Under “results,” only significant results are listed. Time point 0 describes fasting concentrations, and time points >0 are reporting postprandial concentrations.

^#original data, ↑ higher GLP-1 secretion in comparison to referred groups, ↓ lower GLP-1 secretion in comparison to referred groups, ↔ no differences of GLP-1 secretion between groups. Supplemental Table 2 shows GLP-1 values for all measured time points. Details on GLP-1 assays as stated in the publications or according to manufacturer instructions:

Abbreviations: AUC, the area under the curve; CV, coefficient of variation; DM, diabetes mellitus; F, female; GLP-1, glucagon-like peptide 1; IFG, impaired fasting glucose; i-IFG, isolated impaired fasting glucose; IGT, impaired glucose tolerance; i-IGT, isolated impaired glucose tolerance; LOD, limit of detection; M, male; n.a., not available; NGT, normal glucose tolerance; NW, normal weight; OGTT, oral glucose tolerance test; OW, overweight; RIA, radioimmunoassay; TTP, time-to-peak; T2DM, type 2 diabetes mellitus.

¹RIA_Linco (Linco Research), polyclonal antiserum no. 89390, LOD: 3 pM, intra-assay CV: 5%, inter-assay CV: 17%, specificity: 100% for GLP-1 (7–36) and GLP-1 (9–36);

²RIA: standardized assay (41), polyclonal antiserum no. 89390, LOD: 1 pM, intra-assay CV: 6%, specificity: 100% for GLP-1 (7–36) 89% for GLP-1 (9–36);

³ELISA (Westang Biological Technology), sensitivity: <0.1 pM, intra- and inter-assay CV: <10.3%;

⁴ELISA (Alpco Diagnostics), intra-assay CV: 3.7%–4.7%, inter-assay CV: 6.2–9.5%;

⁵ELISA (EMD Millipore), LOD: 1.5 pM, intra-assay CV: <2% inter-assay CV: <12%.