J Clin Med Res

Journal of Clinical Medicine Research, ISSN 1918-3003 print, 1918-3011 online, Open Access

Article copyright, the authors; Journal compilation copyright, J Clin Med Res and Elmer Press Inc

Journal website https://jocmr.elmerjournals.com

Original Article

Volume 16, Number 10, October 2024, pages 465-471

High Blood Glucose After Starch Loading in Young Women With Small Increase in Salivary Amylase: Another Crucial Role of Postprandial Salivary Amylase

Figure 1. Salivary amylase levels after starch loading according to SI- and LI-ΔSAA (means ± standard deviation). **P < 0.001, ***P < 0.0001 vs. SI-ΔSAA. LI-ΔSAA: ΔSAA at 60 min ≥ 28 IU/L (n = 29); SI-ΔSAA: ΔSAA at 60 min < 28 IU/L (n = 31). SAA: salivary α-amylase activity; LI-ΔSAA: large-increase in ΔSAA; SI-ΔSAA: small-increase in ΔSAA.

Figure 2. Blood glucose levels after starch loading according to SI- and LI-ΔSAA (means ± standard deviation). **P < 0.01, ***P < 0.001 vs. LI-ΔSAA. No significant difference in areas under the curve was observed between SI-ΔSAA (mean ± standard deviation: 53.1 ± 23.3 mg·min/dL) and LI-ΔSAA (43.5 ± 11.6 mg·min/dL) (P = 0.051). LI-ΔSAA: ΔSAA at 60 min ≥ 28 IU/L (n = 29); SI-ΔSAA: ΔSAA at 60 min < 28 IU/L (n = 31). SAA: salivary α-amylase activity; LI-ΔSAA: large-increase in ΔSAA; SI-ΔSAA: small-increase in ΔSAA.

**Table 1.** Characteristics of Participants
	Total (n = 60)	SI-ΔSAA (n = 31)	LI-ΔSAA (n = 29)	P values
Data are shown as mean ± SD or median (IQR). P values were calculated by t-test or Wilcoxon signed-rank test. SD: standard deviation; IQR: interquartile range.
Age (years old)	21.1 ± 0.8	21.0 ± 0.8	21.1 ± 0.8	0.61
BMI (kg/m²)	19.8 ± 2.0	20.0 ± 2.2	19.7 ± 1.7	0.53
Waist circumference (cm)	68.5 ± 5.0	69.0 ± 5.7	67.9 ± 4.2	0.42
Lean body mass (kg)	34.1 ± 3.3	34.7 ± 3.4	33.6 ± 3.0	0.19
Body fat (%)	26.3 ± 5.1	26.2 ± 5.4	26.4 ± 4.9	0.90
Blood glucose (mg/dL)
Baseline	94.4 ± 8.8	93.9 ± 10.6	95.0 ± 6.5	0.64
30 min	144 ± 19	144.1 ± 21.9	144.6 ± 16.0	0.92
60 min	145 ± 27	154.8 ± 28.3	133.7 ± 20.3	0.002
90 min	132 ± 26	142.3 ± 25.5	120.0 ± 21.3	0.0005
120 min	123 ± 18	129.2 ± 17.7	116.2 ± 16.1	0.004
Area under the curve	48.4 ± 19	53.1 ± 23.3	43.5 ± 11.6	0.051
ΔBG
30 - 0 min	49.9 ± 19.7	50.2 ± 24.0	49.6 ± 13.9	0.92
60 - 0 min	50.2 ± 28.6	60.9 ± 31.5	38.7 ± 19.8	0.002
90 - 0 min	37.1 ± 27.0	48.4 ± 27.7	25.0 ± 20.7	0.0005
120 - 0 min	28.8 ± 18.8	35.8 ± 19.6	21.3 ± 14.8	0.002
Unadjusted salivary amylase activity (U/mL)
Baseline	58.0 ± 30.3	54.9 ± 30.4	61.4 ± 30.3	0.41
60 min	96.4 ± 54.1	70.9 ± 32.9	123.6 ± 59.5	< 0.0001
120 min	99.9 ± 61.3	77.3 ± 46.1	124.1 ± 66.8	0.002
Unadjusted ΔSAA (U/mL)
60 - 0 min	40.5 ± 38.0	20.3 ± 16.4	62.2 ± 42.7	< 0.0001
120 - 0 min	41.9 ± 48.7	22.4 ± 41.0	62.7 ± 48.2	0.0009
Protein concentration in saliva (mg/mL)
Baseline	1.23 ± 0.35	1.17 ± 0.33	1.29 ± 0.37	0.18
60 min	1.22 ± 0.41	1.16 ± 0.37	1.29 ± 0.46	0.25
120 min	1.24 ± 0.50	1.13 ± 0.45	1.36 ± 0.53	0.078
Salivary amylase activity (U/mL)
Baseline	46.4 ± 20.2	46.3 ± 22.7	46.6 ± 17.4	0.95
60 min	76.8 ± 27.7	61.7 ± 23.5	93.0 ± 22.2	< 0.0001
120 min	76.7 ± 25.7	66.7 ± 26.0	87.3 ± 21.0	0.001
ΔSAA (U/mL)
60 - 0 min	31.2 ± 19.6	17.0 ± 7.8	46.4 ± 16.8	< 0.0001
120 - 0 min	30.3 ± 21.6	20.5 ± 20.9	40.7 ± 17.1	0.0001
Blood 3-hydroxybutyrate (mmol/dL)
Baseline	0.1 (0.0 - 0.3)	0.2 (0.0 - 0.4)	0.0 (0.0 - 0.1)	0.0008
120 min	0.0 (0.0 - 0.1)	0.0 (0.0 - 0.1)	0.0 (0.0 - 0.0)	0.86
Respiratory quotient	0.89 ± 0.04	0.88 ± 0.04	0.90 ± 0.04	0.19
Nutrition intake
Energy (kcal/day)	1,666 ± 33	1,663 ± 33	1,669 ± 33	0.54
Carbohydrate (g/day)	241.3 ± 5.6	240.8 ± 5.9	241.9 ± 5.3	0.43
Carbohydrate energy, % in total energy	59.7 ± 0.7	59.7 ± 0.8	59.7 ± 0.7	0.97
Lipid (g/day)	52.9 ± 2.0	52.9 ± 2.1	53.0 ± 2.1	0.84
Lipid energy, % in total energy	26.4 ± 0.6	26.4 ± 0.7	26.4 ± 0.6	0.81
Protein (g/day)	66.5 ± 1.8	66.4 ± 1.7	66.7 ± 1.9	0.43
Protein energy, % in total energy	13.9 ± 0.2	13.9 ± 0.2	13.9 ± 0.1	0.43

Table 1. Characteristics of Participants

Total (n = 60)

SI-ΔSAA (n = 31)

LI-ΔSAA (n = 29)

P values

Data are shown as mean ± SD or median (IQR). P values were calculated by t-test or Wilcoxon signed-rank test. SD: standard deviation; IQR: interquartile range.

Age (years old)

21.1 ± 0.8

21.0 ± 0.8

21.1 ± 0.8

0.61

BMI (kg/m²)

19.8 ± 2.0

20.0 ± 2.2

19.7 ± 1.7

0.53

Waist circumference (cm)

68.5 ± 5.0

69.0 ± 5.7

67.9 ± 4.2

0.42

Lean body mass (kg)

34.1 ± 3.3

34.7 ± 3.4

33.6 ± 3.0

0.19

Body fat (%)

26.3 ± 5.1

26.2 ± 5.4

26.4 ± 4.9

0.90

Blood glucose (mg/dL)

Baseline

94.4 ± 8.8

93.9 ± 10.6

95.0 ± 6.5

0.64

30 min

144 ± 19

144.1 ± 21.9

144.6 ± 16.0

0.92

60 min

145 ± 27

154.8 ± 28.3

133.7 ± 20.3

0.002

90 min

132 ± 26

142.3 ± 25.5

120.0 ± 21.3

0.0005

120 min

123 ± 18

129.2 ± 17.7

116.2 ± 16.1

0.004

Area under the curve

48.4 ± 19

53.1 ± 23.3

43.5 ± 11.6

0.051

ΔBG

30 - 0 min

49.9 ± 19.7

50.2 ± 24.0

49.6 ± 13.9

0.92

60 - 0 min

50.2 ± 28.6

60.9 ± 31.5

38.7 ± 19.8

0.002

90 - 0 min

37.1 ± 27.0

48.4 ± 27.7

25.0 ± 20.7

0.0005

120 - 0 min

28.8 ± 18.8

35.8 ± 19.6

21.3 ± 14.8

0.002

Unadjusted salivary amylase activity (U/mL)

Baseline

58.0 ± 30.3

54.9 ± 30.4

61.4 ± 30.3

0.41

60 min

96.4 ± 54.1

70.9 ± 32.9

123.6 ± 59.5

< 0.0001

120 min

99.9 ± 61.3

77.3 ± 46.1

124.1 ± 66.8

0.002

Unadjusted ΔSAA (U/mL)

60 - 0 min

40.5 ± 38.0

20.3 ± 16.4

62.2 ± 42.7

< 0.0001

120 - 0 min

41.9 ± 48.7

22.4 ± 41.0

62.7 ± 48.2

0.0009

Protein concentration in saliva (mg/mL)

Baseline

1.23 ± 0.35

1.17 ± 0.33

1.29 ± 0.37

0.18

60 min

1.22 ± 0.41

1.16 ± 0.37

1.29 ± 0.46

0.25

120 min

1.24 ± 0.50

1.13 ± 0.45

1.36 ± 0.53

0.078

Salivary amylase activity (U/mL)

Baseline

46.4 ± 20.2

46.3 ± 22.7

46.6 ± 17.4

0.95

60 min

76.8 ± 27.7

61.7 ± 23.5

93.0 ± 22.2

< 0.0001

120 min

76.7 ± 25.7

66.7 ± 26.0

87.3 ± 21.0

0.001

ΔSAA (U/mL)

60 - 0 min

31.2 ± 19.6

17.0 ± 7.8

46.4 ± 16.8

< 0.0001

120 - 0 min

30.3 ± 21.6

20.5 ± 20.9

40.7 ± 17.1

0.0001

Blood 3-hydroxybutyrate (mmol/dL)

Baseline

0.1 (0.0 - 0.3)

0.2 (0.0 - 0.4)

0.0 (0.0 - 0.1)

0.0008

120 min

0.0 (0.0 - 0.1)

0.0 (0.0 - 0.0)

0.86

Respiratory quotient

0.89 ± 0.04

0.88 ± 0.04

0.90 ± 0.04

0.19

Nutrition intake

Energy (kcal/day)

1,666 ± 33

1,663 ± 33

1,669 ± 33

0.54

Carbohydrate (g/day)

241.3 ± 5.6

240.8 ± 5.9

241.9 ± 5.3

0.43

Carbohydrate energy, % in total energy

59.7 ± 0.7

59.7 ± 0.8

59.7 ± 0.7

0.97

Lipid (g/day)

52.9 ± 2.0

52.9 ± 2.1

53.0 ± 2.1

0.84

Lipid energy, % in total energy

26.4 ± 0.6

26.4 ± 0.7

26.4 ± 0.6

0.81

Protein (g/day)

66.5 ± 1.8

66.4 ± 1.7

66.7 ± 1.9

0.43

Protein energy, % in total energy

13.9 ± 0.2

13.9 ± 0.1

0.43

**Table 2.** Correlations Between SAA, BG Concentrations, Their Changes From Baseline, and Blood 3HB Levels Across Participants
	SAA (U/mL)	ΔSAA (U/mL)	Blood 3HB (mmol/dL)
P < 0.05, P < 0.01, **P < 0.001 according to Spearman’s correlation coefficient. Δ: change from baseline; BG: blood glucose; BMI: body mass index; 3HB: 3-hydroxybutyrate; SAA: salivary amylase activity.
BMI (kg/m²)	0.002	-0.04	-0.03	-0.06	-0.01	0.09	0.13
BG (mg/dL)
0 min	0.23	0.20	0.13	0.09	-0.05	-0.19	0.21
30 min	0.04	-0.01	-0.04	-0.06	0.00	-0.14	0.05
60 min	0.04	-0.26*	-0.32*	-0.44**	-0.42**	0.30*	0.21
90 min	0.09	-0.30*	-0.30*	-0.53***	-0.46**	0.25	0.16
120 min	0.09	-0.25	-0.20	-0.42**	-0.31*	0.10	0.08
ΔBG
30 - 0 min	-0.02	-0.05	-0.06	-0.05	0.04	-0.06	0.01
60 - 0 min	-0.02	-0.28*	-0.33*	-0.42**	-0.37*	0.33*	0.14
90 - 0 min	0.06	-0.31*	-0.31*	-0.50***	-0.43**	0.27*	0.06
120 - 0 min	0.04	-0.30*	-0.24	-0.46**	-0.31*	0.20	0.02
Area under the curve	-0.07	-0.23	-0.24	-0.29*	-0.16	0.18	0.12
Blood 3HB (mmol/dL)
0 min	-0.07	-0.27*	-0.26*	-0.40**	-0.26	-	0.02
120 min	-0.34**	-0.16	-0.24	0.10	0.03	-	-

Table 2. Correlations Between SAA, BG Concentrations, Their Changes From Baseline, and Blood 3HB Levels Across Participants

SAA (U/mL)

ΔSAA (U/mL)

Blood 3HB (mmol/dL)

0 min

60 min

120 min

60 - 0 min

120 - 0 min

0 min

120 min

*P < 0.05, **P < 0.01, ***P < 0.001 according to Spearman’s correlation coefficient. Δ: change from baseline; BG: blood glucose; BMI: body mass index; 3HB: 3-hydroxybutyrate; SAA: salivary amylase activity.

BMI (kg/m²)

0.002

-0.04

-0.03

-0.06

-0.01

0.09

0.13

BG (mg/dL)

0 min

0.23

0.20

0.13

0.09

-0.05

-0.19

0.21

30 min

0.04

-0.01

-0.04

-0.06

0.00

-0.14

0.05

60 min

0.04

-0.26*

-0.32*

-0.44**

-0.42**

0.30*

0.21

90 min

0.09

-0.30*

-0.53***

-0.46**

0.25

0.16

120 min

0.09

-0.25

-0.20

-0.42**

-0.31*

0.10

0.08

ΔBG

30 - 0 min

-0.02

-0.05

-0.06

-0.05

0.04

-0.06

0.01

60 - 0 min

-0.02

-0.28*

-0.33*

-0.42**

-0.37*

0.33*

0.14

90 - 0 min

0.06

-0.31*

-0.50***

-0.43**

0.27*

0.06

120 - 0 min

0.04

-0.30*

-0.24

-0.46**

-0.31*

0.20

0.02

Area under the curve

-0.07

-0.23

-0.24

-0.29*

-0.16

0.18

0.12

Blood 3HB (mmol/dL)

0 min

-0.07

-0.27*

-0.26*

-0.40**

-0.26

0.02

120 min

-0.34**

-0.16

-0.24

0.10

0.03

**Table 3.** Generalized Liner Model of Variables for ΔBGs
Model and enrolled variables	ΔBG
P < 0.05, *P < 0.01. Each model includes relevant variables listed. Hormones, such as insulin, and serum lipids, such as triglyceride and high-density lipoprotein cholesterol, and glycated hemoglobin (HbA1c) were unavailable in this study. All variables were standardized before analysis. β regression and Wald Chi-square values were calculated using a generalized liner model. β: regression coefficient; Δ: change from baseline; BG: blood glucose; BMI: body mass index; 3HB: 3-hydroxybutyrate; SAA: salivary amylase activity.
Model 1
BMI	-0.16	1.63	-0.13	1.31	-0.15	1.64	0.10	0.68
ΔSAA 60 - 0 min	-0.06	0.21	-0.38**	10.5	-0.43**	13.8	-0.42**	12.7
Model 2
BMI	-0.07	0.24	-0.01	0.01	-0.05	0.20	0.25*	4.83
BG 0 min	-0.27*	4.02	-0.34**	7.69	-0.26*	4.73	-0.42**	13.4
SAA 0 min	0.05	0.14	0.04	0.14	0.09	0.62	0.05	0.21
ΔSAA 60 - 0 min	-0.04	0.12	-0.36**	10.6	-0.41**	13.3	-0.39**	13.7
Model 3
BMI	-0.03	0.07	-0.04	0.12	-0.08	0.46	0.25*	4.66
BG 0 min	-0.31*	5.23	-0.30*	6.10	-0.23	3.54	-0.42**	12.8
SAA 0 min	0.05	0.16	0.04	0.13	0.09	0.62	0.05	0.21
ΔSAA 60 - 0 min	-0.11	0.69	-0.31**	6.78	-0.35**	8.98	-0.39**	11.9
Blood 3HB 0 min	-0.19	2.03	0.17	2.05	0.16	1.90	0.01	0.00

Table 3. Generalized Liner Model of Variables for ΔBGs

Model and enrolled variables

ΔBG

Δ 30 - 0 min

Δ 60 - 0 min

Δ 90 - 0 min

Δ 120 - 0 min

Wald Chi-square value

*P < 0.05, **P < 0.01. Each model includes relevant variables listed. Hormones, such as insulin, and serum lipids, such as triglyceride and high-density lipoprotein cholesterol, and glycated hemoglobin (HbA1c) were unavailable in this study. All variables were standardized before analysis. β regression and Wald Chi-square values were calculated using a generalized liner model. β: regression coefficient; Δ: change from baseline; BG: blood glucose; BMI: body mass index; 3HB: 3-hydroxybutyrate; SAA: salivary amylase activity.

Model 1

BMI

-0.16

1.63

-0.13

1.31

-0.15

1.64

0.10

0.68

ΔSAA 60 - 0 min

-0.06

0.21

-0.38**

10.5

-0.43**

13.8

-0.42**

12.7

Model 2

BMI

-0.07

0.24

-0.01

0.01

-0.05

0.20

0.25*

4.83

BG 0 min

-0.27*

4.02

-0.34**

7.69

-0.26*

4.73

-0.42**

13.4

SAA 0 min

0.05

0.14

0.04

0.14

0.09

0.62

0.05

0.21

ΔSAA 60 - 0 min

-0.04

0.12

-0.36**

10.6

-0.41**

13.3

-0.39**

13.7

Model 3

BMI

-0.03

0.07

-0.04

0.12

-0.08

0.46

0.25*

4.66

BG 0 min

-0.31*

5.23

-0.30*

6.10

-0.23

3.54

-0.42**

12.8

SAA 0 min

0.05

0.16

0.04

0.13

0.09

0.62

0.05

0.21

ΔSAA 60 - 0 min

-0.11

0.69

-0.31**

6.78

-0.35**

8.98

-0.39**

11.9

Blood 3HB 0 min

-0.19

2.03

0.17

2.05

0.16

1.90

0.01

0.00