Masayuki Konishi

Short-term low carbohydrate/high-fat diet intake increases postprandial plasma glucose and glucagon-like peptide-1 levels during an oral glucose tolerance test in healthy men

Background/Objectives:Postprandial hyperglycemia increases the risks of development of type 2 diabetes and cardiovascular diseases. The purpose of this study was to determine whether a 3-day low-carbohydrate/high-fat diet (LC/HFD) alters postprandial plasma glucose and incretin levels during oral glucose tolerance test (OGTT) in healthy men.Subjects/Methods:Nine healthy young men (age (mean±s.e.), 27±1 years; body mass index, 22±1 kg/m2) consumed either a normal diet (ND: energy from ∼22% fat) or a LC/HFD (energy from ∼69% fat) for 3 days each. The total energy intake from each diet was similar. An OGTT was performed after each 3-day dietary intervention. Postprandial plasma glucose, insulin, free fatty acid and glucagon-like peptide-1 (GLP-1) levels were determined at rest and during the OGTT.Results:Plasma glucose levels and incremental area under the curve during the OGTT were significantly higher in the LC/HFD trial than in the ND trial (P=0.024). In addition, increase in GLP-1 levels was significantly higher in the LC/HFD trial than in the ND trial (P=0.025). The first-phase insulin secretion indexes were significantly lower in the LC/HFD trial than in the ND trial (P<0.041).Conclusions:These results demonstrate that even short-term LC/HFD increased postprandial plasma glucose and GLP-1 levels in healthy young men. A decrease in first-phase insulin secretion may partially contribute to the short-term LC/HFD-induced increase in postprandial plasma glucose levels.

Determination of the exercise intensity that elicits maximal fat oxidation in short-time testing

Abstract Maximal fat oxidation (MFO) rate and the exercise intensity that elicits MFO (FATmax-intensity) were designed to evaluate fat metabolism capacity and to provide individuals with a target exercise intensity during prolonged exercise. However, the previous methods of determining FATmax-intensity were time-consuming. The purpose of this study was to examine the validity of FATmax-intensity determined by short-time testing. Nine healthy young men performed ramp exercise, in a short-time test, until exhaustion and 5 constant-load exercises of 60 min each at individual FATmax-intensity determined by ramp protocol (FATmax-intensity(R)), FATmax-intensity(R) ± 5% of peak oxygen uptake (VO2peak) and FATmax-intensity(R) ± 10%VO2peak. FATmax-intensity was determined among 5 trials at points of early exercise (10 min) and prolonged exercise (60 min) to evaluate the validity of FATmax-intensity(R). Ten minutes after starting constant-load exercise, FATmax-intensity(R) showed the highest fat oxidation among 5 trials, even though MFO by ramp protocol was overestimated. Therefore, it may be useful for evaluation of fat metabolism to include the measurement of the FATmax-intensity in a routine ramp test. However, because FATmax-intensity(R) did not elicit the highest fat oxidation among 5 trials of 60 min each after starting constant-load exercise, FATmax-intensity(R) may not be effective for prolonged exercise training.

Effects of a single bout of aerobic exercise on short-term low-carbohydrate/high-fat intake-induced postprandial glucose metabolism during an oral glucose tolerance test

OBJECTIVE A single bout of exercise can improve acute postprandial glucose metabolism aggravated by short-term low-carbohydrate/high-fat diet (HFD). The purpose of this study was to investigate the effect of a single bout of aerobic exercise on short-term HFD-induced postprandial glucose and incretin metabolism during an oral glucose tolerance test (OGTT). MATERIALS/METHODS Eleven healthy young men (age [mean±SE] 27±1 years; body mass index, 22±1 kg/m(2)) performed three, 3-day interventions in randomized order: (1) a normal diet (ND: ~22% fat), (2) an HFD (~69% fat) and (3) an HFD with a single bout of aerobic exercise (HFDEx). The exercise (50% peak oxygen consumption; ~200 kcal) was performed on the third day in HFDEx. An OGTT was performed after each 3-day dietary intervention. RESULTS The incremental area under the curve (iAUC) of plasma glucose levels during the OGTT was significantly higher in the HFD and HFDEx trials than in the ND trial (P=0.001). In addition, the iAUC of glucagon-like peptide-1 (GLP-1) level was significantly higher in the HFD trial than in the ND and HFDEx trials (P=0.04). The first-phase insulin secretion indexes were significantly lower in the HFD (P=0.01 and 0.002) and HFDEx trials (P=0.05 and 0.008) than in the ND trial. CONCLUSION A single bout of aerobic exercise did not improve the short-term HFD-induced aggravation of postprandial glucose and insulin metabolism during the OGTT. However, it did normalize the increased postprandial GLP-1 level induced by HFD.

Effects of Acute Endurance Exercise Performed in the Morning and Evening on Inflammatory Cytokine and Metabolic Hormone Responses.

Purpose To compare the effects of endurance exercise performed in the morning and evening on inflammatory cytokine responses in young men. Methods Fourteen healthy male participants aged 24.3 ± 0.8 years (mean ± standard error) performed endurance exercise in the morning (0900–1000 h) on one day and then in the evening (1700–1800 h) on another day with an interval of at least 1 week between each trial. In both the morning and evening trials, the participants walked for 60 minutes at approximately 60% of the maximal oxygen uptake (V·O2max) on a treadmill. Blood samples were collected to determine hormones and inflammatory cytokines at pre-exercise, immediately post exercise, and 2 h post exercise. Results Plasma interleukin (IL)-6 and adrenaline concentrations were significantly higher immediately after exercise in the evening trial than in the morning trial (P < 0.01, both). Serum free fatty acids concentrations were significantly higher in the evening trial than in the morning trial at 2 h after exercise (P < 0.05). Furthermore, a significant correlation was observed between the levels of IL-6 immediately post-exercise and free fatty acids 2 h post-exercise in the evening (r = 0.68, P < 0.01). Conclusions These findings suggest that the effect of acute endurance exercise in the evening enhances the plasma IL-6 and adrenaline concentrations compared to that in the morning. In addition, IL-6 was involved in increasing free fatty acids, suggesting that the evening is more effective for exercise-induced lipolysis compared with the morning.

Short-term high-fat diet alters postprandial glucose metabolism and circulating vascular cell adhesion molecule-1 in healthy males

Short-term intake of a high-fat diet aggravates postprandial glucose metabolism; however, the dose-response relationship has not been investigated. We hypothesized that short-term intake of a eucaloric low-carbohydrate/high-fat diet (LCHF) would aggravate postprandial glucose metabolism and circulating adhesion molecules in healthy males. Seven healthy young males (mean ± SE; age: 26 ± 1 years) consumed either a eucaloric control diet (C, approximately 25% fats), a eucaloric intermediate-carbohydrate/intermediate-fat diet (ICIF, approximately 50% fats), or an LCHF (approximately 70% fats) for 3 days. An oral meal tolerance test (MTT) was performed after the 3-day dietary intervention. The concentrations of plasma glucose, insulin, glucagon-like peptide-1 (GLP-1), intercellular adhesion molecule-1, and vascular cell adhesion molecule-1 (VCAM-1) were determined at rest and during MTT. The incremental area under the curve (iAUC) of plasma glucose concentration during MTT was significantly higher in LCHF than in C (P = 0.009). The first-phase insulin secretion indexes were significantly lower in LCHF than in C (P = 0.04). Moreover, the iAUC of GLP-1 and VCAM-1 concentrations was significantly higher in LCHF than in C (P = 0.014 and P = 0.04, respectively). The metabolites from ICIF and C were not significantly different. In conclusion, short-term intake of eucaloric diet containing a high percentage of fats in healthy males excessively increased postprandial glucose and VCAM-1 concentrations and attenuated first-phase insulin release.

Mild Decrease in Skin Temperature Reduces the Heart Rate during Moderate Exercise

The purpose of this study was to investigate the effects of a mild decrease in skin temperature on the heart rate, substrate oxidation, and hormonal responses during exercise. Ten young men performed treadmill exercises approximately 65% of their maximal oxygen uptake for 60 min under two trials: (1) mild body cooling trial, and (2) control trial. Rectal and skin temperatures were recorded during and after exercise. Heart rate and oxygen uptake were monitored during exercise. Blood samples for catecholamine, cortisol, free fatty acid, insulin, and glucose concentrations were collected before, immediately after, and 1 h after exercise. In the mild body cooling trial, mean skin temperature decreased by 1.7 ± 0.7°C in the last minutes of exercise, compared with before exercise. No differences in rectal temperature were seen between the two trials. Although oxygen uptake during exercise and blood parameters did not differ between the trials, heart rate and subjective fatigue during exercise was lower in the mild body cooling trial than in the control trial. This study suggests that mild body cooling reduces the heart rate and subjective fatigue during moderate exercise, but does not affect substrate oxidation or hormonal responses to exercise.

P-56 Maximal fatmax oxidation and fatmax are not associated with endurance performance in trained runners

Objectives Substrate utilisation during exercise is an important factor for endurance performance. Higher availability of fatty acid extends endurance exercise time.1 Additionally, the anaerobic threshold (AT), which is the exercise intensity driven main energy substrate turning fat into carbohydrate, has shown a high correlation with endurance performance.2 Therefore, fat metabolism may be associated with endurance performance. Fatmax, defined as the exercise intensity that elicits the maximal fat oxidation (MFO) rate,3 and MFO are parameters relating to the ability of fat metabolism. Fatmax has been shown to be correlated with the AT4. The aim of current study was to investigate the correlations between MFO and Fatmax and endurance performance in trained runners. Methods Participants included 14 male endurance-trained runners. All participants performed a graded exercise test on a treadmill using a short-time testing protocol which increased 1 Mets per 1 min.5 The maximal oxygen consumption (VO2max), AT, MFO, and Fatmax were measured using indirect calorimetry. The time to exhaustion in the graded exercise test was defined as a measure of endurance performance. The linear relationships between endurance performance and the physiological parameters (VO2max, AT, MFO and Fatmax) were calculated using Pearson’s correlation coefficient. Results Table 1 shows physical characteristics of participants (Table 1). The VO2max and AT were significantly correlated with the time to exhaustion (Fig1 A, B). However, MFO and Fatmax were not significantly correlated with the time to exhaustion (Fig1C, D). Abstract P-56 Table 1 Physical characteristics of participants Conclusions MFO and Fatmax, parameters reflecting the ability for fat metabolism, were not associated with the time to exhaustion in the graded exercise test in trained runners. These findings suggest that fat metabolism may not determine endurance performance. Acknowledgment This study was supported by Grant-in-Aid from the Japan Society for the Promotion of Science Fellows (2016) and the research laboratory allowance of Waseda University. Abstract P-56 Figure 1 Relationship between time to exhaustion in the graded exercise test and physiological parameters (A) VO2 max, (B) AT, (C) MFO and (D) Fatmax- References Hickson RC, Rennie MJ, Conlee RK, Winder WW, Holloszy JO. Effects of increased plasma fatty acids on glycogen utilisation and endurance. Journal of Applied Physiology 1977 Nov:43(5):829–833. Kumagai S, Tanaka K, Matsuura Y, Matsuzaka A, Hirakoba K, Asano K. Relationships of the anaerobic threshold with the 5 km, 10 km, and 10 mile races. European journal of applied physiology and occupational physiology 1982 June:49(1):13–23. Achten J, Gleeson M, Jeukendrup AE. Determination of the exercise intensity that elicits maximal fat oxidation. Medicine and science in sports and exercise 2002 Jan:34(1):92–97. Venables MC, Achten J, Jeukendrup AE. Determinants of fat oxidation during exercise in healthy men and women: a cross-sectional study. Journal of applied physiology 2005 Jan:98(1):160–167. Takagi S, Sakamoto S, Midorikawa T, Konishi M, Katsumura T. Determination of the exercise intensity that elicits maximal fat oxidation in short-time testing. Journal of sports sciences 2014 Jan:32(2):175–182.

P-46 Effects of increased daily physical activity on blood lipids and blood pressure in older adults

Introduction Blood lipids and elevated blood pressure are associated with an increased risk of cardiovascular disease (CVD).1 Although several studies have shown that exercise training improves the risk factors for CVD,2 little is known about the effect of daily physical activity on the risk factors for CVD in older adults. This study aimed to examine the effects of increased daily physical activity during an 8-week intervention period on the levels of blood lipids and blood pressure in older adults. Methods In total, 24 postmenopausal women (age, 70.6 ± 0.7 years; height, 152.4 ± 0.9 cm) were assigned to control (C, n = 12) or physical activity (PA, n = 12) groups. Participants in the PA group were asked to increase their physical activities to more than their usual lifestyle levels for 8 weeks, while those in the control group were asked to maintain their usual lifestyle during the same period. The systolic and diastolic blood pressure of the participants was measured at the baseline and at the end of the intervention. All participants were asked to wear a triaxial accelerometer during the study. Blood samples were taken at the start (baseline) and end of the sessions. Results At the end of the 8-week intervention period, the step counts of the participants in the PA group had increased from 5972 ± 768 steps/day (at the baseline) to 8302 ± 1011 steps/day (P < 0.001). However, no change was observed in moderate to vigorous physical activity after intervention in either group. In addition, blood lipids (triglycerides, high-density lipoprotein cholesterol, and low-density lipoprotein cholesterol) and blood pressure did not differ between or within the groups at the baseline and at the end of the intervention. Abstract P-46 Table 1 The change of physical characteristics at base line and after 8 weeks Conclusion These findings indicate that promotion of daily physical activity in older adults is not sufficient to improve their blood lipids and blood pressure. Acknowledgment This work was supported by JSPS KAKENHI Grant Number 15K21434, Meiji Yasuda Life Foundation of Health and Welfare and a Grant-in-Aid from the Japan Society for the Promotion of Science Fellows (2015). References Mehta AK, Doshi RS, Chaudhry ZW, Jacobs DK, Vakil RM, Lee CJ, Bleich SN, Clark JM, Gudzune KA. Benefits of commercial weight-loss programs on blood pressure and lipids: a systematic review. Prev Med 2016 Sep;90:86–99. Fahlman MM1, Boardley D, Lambert CP, Flynn MG. Effects of endurance training and resistance training on plasma lipoprotein profiles in elderly women. J Gerontol A Biol Sci Med Sci 2002 Feb;57(2):B54–60