Prior meal enhances the plasma glucose lowering effect of exercise in type 2 diabetes

PURPOSE: To compare the changes in plasma glucose and insulin levels in response to 1 h of exercise performed at 60% of VO(2peak) either in the fasted state or 2 h after a standardized breakfast in subjects with type 2 diabetes. METHODS: Ten sedentary men with type 2 diabetes treated with oral agents and not under strict metabolic control were tested on two occasions (fasted and fed state) in a random order at a 1-wk interval. RESULTS: Plasma glucose was slightly but not significantly higher at the beginning of exercise performed in the fed state versus the fasted state (12.4 +/- 1.3 vs 11.1 +/- 1.1 mmol x L(-1) respectively; mean +/- SE, P = 0.06). However, after exercise, plasma glucose levels were much lower in the fed state (7.6 +/- 1.1 mmol x L(-1)) compared with the fasted state (10.0 +/- 1.0 mmol x L(-1); P = 0.009). Insulin levels were higher at the beginning of the exercise bout performed in the fed state (177 +/- 26 vs 108 +/- 19 pmol x L(-1); P < 0.05) and during exercise. Similar respiratory exchange ratio at identical workload indicated that the difference in glycemic response was not due to differences in whole body substrate utilization. Plasma concentrations of free fatty acids, glucagon, epinephrine, and norepinephrine were also similar during both experiments. CONCLUSIONS: One hour of aerobic exercise has a minimal impact on plasma glucose level when performed in fasted moderately hyperglycemic men with type 2 diabetes but induces an important decrease in plasma glucose level when performed 2 h after breakfast. Because glucose utilization increased similarly during exercise in both conditions, the higher insulin levels after the meal might have blunted glucose production, creating an imbalance between total glucose production and total peripheral utilization in the fed state in contrast to the fasted state.     

Metabolic responses to exercise after carbohydrate loads in healthy men and women

PURPOSE: This study aimed to investigate gender differences in i) pancreatic insulin secretory (beta-cell sensitivity) and whole body insulin sensitivity responses to an intravenous carbohydrate (CHO) load, and (ii) metabolic responses to exercise after both intravenous and oral CHO loads. METHODS: Seven untrained healthy men and seven age-, body mass-, and VO2max-matched women performed two trials. In one trial they cycled for 60 min at 50% VO2max, starting 60 min after ingestion of a carbohydrate-rich meal (ME trial). In the other trial, subjects were infused with 20% dextrose solution to maintain blood glucose concentration at approximately 8 mmol x L(-1) for 60 min (INF trial), then the infusion rate was maintained constant during the following 60 min while exercising at 50% VO2max. RESULTS: There was no gender effect on beta-cell sensitivity (serum insulin: 161 +/- 37 and 159 +/- 28 pmol x L(-1) for men and women, respectively) and whole body insulin sensitivity (155 +/- 24 and 135 +/- 29 mg x KgFFM(-1) x min(-1) per pmol x L(-1) x 100 for men and women, respectively). This may explain the similarity in glycemic, substrate oxidation and other metabolic responses to exercise after both intravenous and oral CHO loads in men and women. CONCLUSION: These results suggest that moderate exercise performed in the postprandial state presents a similar challenge to the ability of healthy, untrained men and women to perform exercise without a substantial decline in plasma glucose concentration below fasting values.     

补充巧克力对长时间中等度运动休闲跑步后恢复的影响

目的：研究运动前补充巧克力对运动引起的生理和代谢变化及恢复的影响。方法：１２名１８～２０岁男性休闲跑步自愿者作为受试实验对象,采用交叉设计,每名受试者参加两次试验,在跑步机上跑步１小时,运动中心率保持在１４８～１５０次／分。结果：运动前补充５６ｇ巧克力１５分钟后,血糖水平显著升高（５．４２±０．８３ｍｍｏｌ／Ｌ）并且在运动结束及其后的３０分钟仍保持在相当高的水平（４．９２±０．５７ｍｍｏｌ／Ｌ）,而补充安慰剂的对照组在运动后血糖水平低（３．９７±０．３７ｍｍｏｌ／Ｌ）,停止运动３０分钟后血糖低于正常水平（３．８４±０．３１ｍｍｏｌ／Ｌ）。血浆自由脂肪酸、血乳酸、血浆尿素氮水平以及自我感觉疲劳程度（ＲＰＥ）等结果均表明运动前补充巧克力提供运动和运动后恢复所必要的条件均有益。     

The effects of glucose polymer beverage ingestion during prolonged outdoor exercise in the heat

The aim of this study was to examine the effect of ingestion of a glucose polymer drink on fluid and metabolic balance during a 30 km outdoor march in the heat (ambient temperature, 26-31 degrees C; relative humidity, 53-34%). The subjects were randomly assigned to one of three groups: 7.2% glucose polymer-electrolyte beverage (GP) (N = 16), flavored sweetened placebo drink (SP) (N = 15), and tap water (TW) (N = 18). The subjects in the three groups consumed similar volumes of fluid, and no differences were found in sweat rate and percent dehydration. Changes in plasma volume were smaller, though not statistically significant, for GP than for SP and TW (-2.8%, -5.4%, -9.4%, respectively). Changes in sodium concentrations and serum osmolality were similar in the three groups. Subjects consuming GP maintained during exercise a significantly higher (P less than 0.001) blood glucose concentration (range: 6.5-7.4 mmol.l-1) than the SP and TW groups. They were also found to have increased levels of serum insulin (29.3 +/- 18.5 mU.l-1) and no change in serum free fatty acids (0.52 +/- 0.19 mmol.l-1). In contrast, subjects ingesting SP or TW had significantly elevated (P less than 0.001) concentrations of free fatty acids (range: 1.35-1.74 mmol.l-1) compared with subjects consuming GP (0.35-0.52 mmol.l-1), with no significant change in blood glucose and serum insulin levels over the exercise period. We conclude that highly trained endurance athletes may maintain a higher blood glucose level by consuming GP during prolonged exercise in the heat without impairing fluid replacement.     

钒盐补充与耐力训练干预对糖尿病大鼠代谢的影响

目的 :进一步探讨特殊营养和耐力运动因素对糖尿病实施非药物控制治疗的效果。方法 :本研究以糖尿病大鼠为对象 ,通过 6周耐力训练、硫酸钒盐补充、钒盐补充与运动组合的干预性治疗 ,运用对比分析 ,从血液生化、糖代谢、血乳酸代谢动力学等方面观察了糖尿病代谢紊乱的不同适应性变化。结果 :强化补充钒盐结合耐力训练 6周后 ,糖尿病大鼠空腹血糖降至 6 2 1± 1 4 1mmol/L (P <0 0 5 ) ,胰岛素恢复至 18 16± 2 17U/ml (P <0 0 5 ) ,提示耐力运动结合钒盐补充较大程度地改善了糖尿病大鼠糖和胰岛激素的代谢紊乱。实验中胰岛激素浓度有独立的适应性变化 ,提示钒盐补充在糖尿病治疗中的意义 ,以及结合耐力运动对胰岛细胞和血糖控制的整体干预作用与外周胰岛素敏感性变化的概念可能不同。本研究首次观察到与血糖动力学同步的OGTT血乳酸动力学过程的特点 ,这可能是反映糖尿病治疗和病情发展的新的诊断指标。钒盐补充用于控制糖尿病病程 ,仍需进一步探讨其可能机制。     

Effects of acute aerobic exercise on high-molecular-weight adiponectin

INTRODUCTION: Few studies have reported the response of high-molecular-weight (HMW) adiponectin to acute aerobic exercise. PURPOSE: The purpose of this study was to investigate the influence of acute aerobic exercise on HMW adiponectin in healthy men. METHODS: Eight healthy men (age, 24.9 +/- 1.8 yr; BMI, 21.9 +/- 0.5 kg x m) participated in this study. They performed two trials. Trial 1 [exercise trial (EX)] consisted of 60-min stationary cycle exercise (50% peak oxygen uptake) followed by 30-min rest. Trial 2 [control trial (CON)] was 90-min rest. Blood samples were drawn to assess hormones (catecholamine and insulin), metabolites (free fatty acid [FFA], glycerol, and glucose), and total and HMW adiponectin concentration. RESULTS: There were significant trial x group interactions in serum FFA and glycerol concentrations (P < 0.05). Serum FFA and glycerol concentrations were higher in EX than in CON (P < 0.05). There were significant trial x group interactions in plasma insulin and glucose concentration (P < 0.05). Plasma insulin and glucose concentrations were lower in EX than in CON (P < 0.05). Total adiponectin, HMW adiponectin concentration, and the ratio of HMW to total adiponectin concentration, however, were unchanged during aerobic exercise and postexercise. Also, those changes did not differ between EX and CON. CONCLUSION: Our results indicate that total adiponectin and HMW adiponectin concentrations are not regulated by the change of hormones or metabolites during acute moderate-intensity aerobic exercise and postexercise in healthy young men.     

Normalization of the metabolic profile in obese women by exercise and a low fat diet.

This study was performed to evaluate the additive effect of exercise and a low fat diet on body weight, body composition, and the metabolic profile in four obese women who were previously exercise-trained for 15 months. This study therefore included regular aerobic exercise for 15 months and a low fat diet plus exercise for an additional period of 14 months. After 15 months, mean body weight and fat losses corresponded to 6.4 and 8.4 kg, respectively. Significant reductions (P less than 0.05) in plasma insulin, cholesterol, apo B, and LDL-C were also observed. Following the second part of the study, mean cumulative body weight and fat losses were 11.0 and 11.3 kg, respectively. At this time, the subjects were still overweight, but their plasma glucose and insulin during an oral glucose tolerance test were essentially similar to values obtained in a sample of 22 nonobese women. With the exception of plasma apo B and HDL-C levels, plasma lipid and lipoprotein levels were also comparable to those observed in nonobese controls. These results thus indicate that aerobic exercise-training and a low fat diet can normalize the metabolic profile of obese women, even if their adiposity remains higher than that of lean women.     

Influence of liquid and solid meals on muscle glycogen resynthesis, plasma fuel hormone response, and maximal physical working capacity

The effect of forced liquid (L) or solid (S) carbohydrate (CHO)-rich feedings on plasma glucose, insulin, and glycogenesis after glycogen depletion was investigated. The relationship between glycogen restoration and maximal physical working capacity (MPWC) was studied as well. Eight males performed two experiments, with 2 weeks interval, on a bicycle ergometer. In each experiment, MPWC was determined in a graded test, which was immediately followed by interval work until exhaustion. After exercise cessation (EC), the subjects started to consume a standardized amount of concentrated L or CHO-rich food. Insulin and glucose concentration in blood were determined. Muscle glycogen was determined before, immediately after, 5 h after, and 22 h after EC. MPWC was determined again 22 h after EC. Four subjects performed a third experiment, in which solid food consumption was left ad libitum (AL). A rapid glycogen repletion was found 5 h after EC, i.e., from 72 +/- 40 to 198 +/- 38 mmol/kg in the S, and from 69 +/- 39 to 192 +/- 40 mmol/kg in the L experiment. The higher plasma glucose and insulin levels (P less than 0.05) during the 5 h after EC in the S experiments did not elicit a difference in glycogen repletion. Glycogen synthesis rate in the AL experiment was lower (P less than 0.05) than in the L and S experiments. Glycogen restoration in the L and S experiments was complete 22 h after depletion. However, despite repletion of glycogen, MPWC was decreased (P less than 0.05) in both experiments.(ABSTRACT TRUNCATED AT 250 WORDS)     

Normalization of diastolic dysfunction in type 2 diabetics after exercise training

PURPOSE: The purpose of this study was to evaluate the impact of aerobic exercise training on left ventricular diastolic dysfunction (LVDD) and exercise capacity in subjects with type 2 diabetes. METHODS: Twenty-three sedentary subjects with well-controlled type 2 diabetes, free of coronary disease and having different degrees of LVDD, participated in the study. Subjects were treated with oral hypoglycemic agents and/or diet. Eleven subjects (EX) (age: 58 +/- 5 yr; mean +/- SD) underwent a 3-month aerobic exercise training program using a cycle ergometer, whereas a control group (CONT) of 12 subjects (57 +/- 6 yr) maintained their activities of daily living. Exercise capacity and LVDD, using echocardiography, were evaluated before and after the 3-month exercise program. RESULTS: At baseline, anthropometric data were similar between the groups, except for body mass index (BMI), which was higher in CONT (31 +/- 3 vs 28+/- 3 kg x m(-2); P < 0.05). There were no significant differences in glycemic control (HbA1c: 6.4 +/- 1.2 vs 5.8 +/- 1.3%; P = 0.2) or maximal oxygen uptake (26.7 +/- 5.9 vs 28.6 +/- 3.9 mL x kg(-1) x min(-1); P = 0.4) between groups. Normalization of LVDD was observed in 5 of 11 EX subjects, (P < 0.0001) of whom four had grade 1 LVDD before exercise training. No change in diastolic function was observed in the CONT group. After exercise training, maximal oxygen uptake increased in the EX group (28.6 +/- 3.9 vs 32.7 +/- 5.7 mL x kg(-1) x min(-1); P < 0.05), whereas there was no change in the CONT group (26.7 +/- 5.9 vs 27.3 +/- 6.2 mL x kg(-1) x min(-1); P = 0.58). In both groups, there was no significant change in BMI. CONCLUSIONS: Along with an improvement in exercise capacity, aerobic exercise training has the potential to reverse LVDD in patients with well-controlled, uncomplicated type 2 diabetes.     

Effects of exercise training on glucose control, lipid metabolism, and insulin sensitivity in hypertriglyceridemia and non-insulin dependent diabetes mellitus

Exercise training has potential benefits for patients with hyperlipidemia and/or non-insulin dependent diabetes mellitus. In nondiabetic, nonobese subjects with hypertriglyceridemia, exercise training alone increased insulin sensitivity, improved glucose tolerance, and lowered serum triglyceride and cholesterol levels. These improvements did not occur when exercise training alone was given to similar patients with impaired glucose tolerance. In severely obese (X = 125 kg) subjects without diabetes melitus, a 600 calorie diet alone decreased glucose and insulin concentrations and improved glucose tolerance but did not increase insulin sensitivity. The addition of exercise training improved insulin sensitivity. Obese, non-insulin dependent diabetes mellitus subjects on sulfonylurea therapy alone increased insulin levels but failed to improve insulin sensitivity or glucose levels. In contrast, the addition of exercise training to this medication resulted in improved insulin sensitivity and lowered glucose levels. We conclude that exercise training has major effects on lowering triglyceride levels in hyperlipidemic subjects and can potentiate the effect of diet or drug therapy on glucose metabolism in patients with non-insulin dependent diabetes mellitus.     

Walking trials in postmenopausal women: effect of low doses of exercise and exercise fractionization on coronary risk factors

We studied the fractionization of walking training and searched for the minimum dose to affect coronary risk factors in two randomized controlled trials. Altogether 134 (Study I) and 121 (Study II) healthy, sedentary postmenopausal women started the trials, and 130 (Study I) and 116 (Study II) completed them. In Study I the exercise intensity was 65% of the maximal aerobic power (VO2max) and a total of 300 kcal was expended in one (Group W1) or two (Group W2) daily walking bouts. In Study II the exercise was continuous, and the exercise intensity (% of VO2max) and energy expenditure (kcal session(-1)) were 55% and 300 kcal (Group W3), 45% and 300 kcal (Group W4), 55% and 200 kcal (Group W5) and 45% and 200 kcal (Group W6). All the subjects walked 5 days a week. The outcome measures were blood pressure, serum lipoproteins and blood glucose and plasma insulin in fasting state and also during 2-h oral glucose tolerance test in Study I. There was no change in diastolic pressure in the original study groups, but in the combined exercise group (W1+W2) in Study I, the mean diastolic pressure declined by -3.0 mmHg (95% con-fidence interval (CI) -5.5 to -0.4) (P=0.025) in comparison with that of the controls. The mean blood glucose declined by -0.21 mmol L(-1) (CI -0.33 to -0.09) in Group W1 and -0.13 mmol L(-1) (CI -0.25 to -0.01) in Group W2 compared to controls (P=0.03). Also the 2-h glucose concentration decreased in Groups W1 and W2 compared to controls. Systolic blood pressure, serum lipoproteins and insulin levels did not change in Study I or Study II. We conclude that our training program with the greatest exercise dose, exercise intensity 65% of VO2max and weekly expenditure of 1500 kcal had a minimal, positive effect on diastolic pressure and blood glucose, and the effect was similar in one or two daily exercise session groups. This exercise dose is probably close to the minimum to affect coronary risk factors in healthy postmenopausal women. To get a more pronounced and clinically relevant effect, a greater exercise dose is needed.     

Effects of chromium supplementation on glycogen synthesis after high-intensity exercise

PURPOSE: Chromium enhances insulin signaling and insulin-mediated glucose uptake in cultured cells. We investigated the effect of chromium on glycogen synthesis and insulin signaling in humans. METHODS: Sixteen overweight men (BMI = 31.1 +/- 3.0 kg.m) were randomly assigned to supplement with 600 microg.d chromium as picolinate (Cr; N = 8) or a placebo (Pl; N = 8). After 4 wk of supplementation, subjects performed a supramaximal bout of cycling exercise to deplete muscle glycogen, which was followed by high-glycemic carbohydrate feedings for the next 24 h. Muscle biopsies were obtained at rest, immediately after exercise, and 2 and 24 h after exercise. RESULTS: Elevations in glucose and insulin during recovery were not different, but the lactate response was significantly higher in Cr. There was a significant depletion in glycogen immediately after exercise, an increase at 2 h, and a further increase above rest at 24 h (P < 0.05). The rate of glycogen synthesis during the 2 h after exercise was not different between groups (Cr: 25.8 +/- 8.0 and Pl: 17.1 +/- 4.7 mmol.kg.h). Glycogen synthase activity was significantly increased immediately after exercise in both groups. Muscle phosphatidylinositol 3-kinase (PI 3-kinase) activity decreased immediately after exercise and increased at 2 h (P < 0.05), with a trend for a lower PI 3-kinase response in Cr (P = 0.08). CONCLUSIONS: Chromium supplementation did not augment glycogen synthesis during recovery from high-intensity exercise and high-carbohydrate feeding, although there was a trend for lower PI 3-kinase activity.     

Training enhances ANP lipid-mobilizing action in adipose tissue of overweight men

PURPOSE: This study was designed to evaluate whether a 4-month endurance training program could improve ANP- as well as isoproterenol-mediated (beta-adrenergic receptor agonist) in situ lipolysis and adipose tissue blood flow (ATBF) in the subcutaneous adipose tissue (SCAT) of untrained overweight subjects. METHODS: Ten overweight men aged 26.0 +/- 1.4 yr with a mean body mass index of 27.6 +/- 0.2 kg.m(-2), performed aerobic exercise 5 d.wk(-1) for 4 months. Before and after the training period, SCAT responsiveness was investigated in situ during a 60-min infusion of 1 micromol.L(-1) isoproterenol and 10 micromol.L(-1) ANP through microdialysis probes. Plasma metabolic parameters and physical fitness variables were measured as well. RESULTS: Endurance training significantly increased fat-free mass and VO2max, while reducing plasma insulin, glucose, NEFA, low density lipoprotein (LDL)-C and the respiratory exchange ratio at rest. Training significantly lowered resting dialysate glycerol levels in SCAT. The lipid-mobilizing effect of ANP was markedly enhanced (by 191%, P < 0.05) after training as was that of isoproterenol (by 145%, P < 0.05). Resting adipose tissue blood flow as well as ANP- and isoproterenol-mediated rise in ATBF was increased after training. CONCLUSION: The present study shows that endurance training improves ANP- as well as beta-adrenergic-receptor-mediated lipid mobilization and ATBF in the SCAT of overweight subjects. The recovery of a higher lipolytic efficiency in adipose tissue is an important benefit of a training program in overweight subjects.     

The effect of a preexercise meal on time to fatigue during prolonged cycling exercise

PURPOSE AND METHODS: Seven subjects exercised to exhaustion on a bicycle ergometer at a workload corresponding to an intensity of 70% maximal oxygen uptake (VO2max). On one occasion (FED), subjects consumed a preexercise carbohydrate (CHO) containing breakfast (100 g CHO) 3 h before exercise. On the other occasion (FASTED), subjects exercised after an overnight fast. Exercise time to fatigue was significantly longer (P < 0.05) when subjects consumed the breakfast (136+/-14 min) compared with when they exercised in the fasted state (109+/-12 min). RESULTS: Pre- and post-exercise muscle glycogen concentrations, respiratory exchange ratio, carbohydrate and fat oxidation, and lactate and insulin concentrations were not significantly different between the two trials. Insulin concentrations decreased significantly (P < 0.05) from 4.7+/-0.05 microIU.mL(-1) to 2.8+/-0.4 microIU.mL(-1) in FED and from 6.6+/-0.6 microIU.mL(-1) to 3.7+/-0.6 microIU.mL(-1) in FASTED subjects and free fatty acid concentrations (FFA) increased significantly (P < 0.05) from 0.09+/-0.02 mmol.L(-1) to 1.4+/-0.6 mmol.L(-1) in FED and from 0.17+/-0.02 mmol.L(-) to 0.74+/-0.27 mmol.L(-1) in FASTED subjects over the duration of the trials. CONCLUSIONS: In conclusion, the important finding of this study is the increased time to fatigue when subjects ingested the CHO meal with no negative effects ascribed to increased insulin concentrations and decreased FFA concentrations after CHO ingestion.     

HDL atheroprotection by aerobic exercise training in type 2 diabetes mellitus

PURPOSE: In this study we analyzed the role played by aerobic exercise training in the plasma lipoprotein profile, prebeta 1-HDL concentration, and in the in vitro HDL3 ability to remove cholesterol from macrophages and inhibit LDL oxidation in type 2 diabetes mellitus (DM) patients and control subjects, in the fasting and postprandial states. METHODS: Healthy controls (HTC, N = 11; 1 M/10 F) and subjects with type 2 diabetes mellitus (DMT, N = 11; 3M/8F) were engaged in a 4-month aerobic training program, and compared with a group of sedentary subjects with type 2 diabetes mellitus (DMS, N = 10; 4 M/6 F). All groups were submitted to an oral fat load test to analyze all parameters, both at the beginning of the investigation protocol (basal) and at the end of the study period (final). RESULTS: Exercising did not modify body weight, BMI, plasma concentrations of total cholesterol, LDL cholesterol, HDL cholesterol, triglycerides (TG), glucose, insulin, or HOMA-IR, but it reduced the waist circumference. The HDL3 composition did not change, and its ability to remove cell cholesterol was unaltered by aerobic training. In DMT but not in HTC, aerobic training improved 15% the HDL3 protective effect against LDL maximal oxidation rate in the fasting state, and reduced 24% the plasma prebeta 1-HDL concentration in the postprandial state, suggesting an enhanced prebeta 1-HDL conversion into larger, more mature HDL particles. In this regard, regular aerobic exercise enriched HDL2 with TG in the fasting and postprandial states in HTC and in the fasting phase in DMT. CONCLUSION: Our results show that aerobic exercise training in diabetes mellitus improves the HDL efficiency against LDL oxidation and favors HDL maturation. These findings were independent of changes in insulin resistance and of the rise of plasma HDL cholesterol concentration.     

Oxidation and metabolic effects of fructose or glucose ingested before exercise

The aim of this study was to compare the effects of fructose (F) and glucose (G) intake before exercise on oxidation of the ingested substrate, glycogen utilization, work output, and metabolic changes. Ten trained subjects ingested F or G (1 g/kg), both of which were naturally enriched in 13C. After 1 h of rest, they exercised on an ergometer at 61% of their maximal oxygen uptake (VO2 max) for 45 min, which was immediately followed by 15 min at their maximal voluntary output. During the resting hour, blood insulin and glucose were lower (p less than 0.05) and respiratory quotient and blood lactate higher (p less than 0.01) after F. During exercise, the differences disappeared, apart from a transient but moderate (4.3 mmol/l) hypoglycemia after G compared to F. No difference between F and G was observed for uric acid, glycerol, FFA, and glucagon. Glycogen decrements in the vastus lateralis muscle were 67 +/- 9 (F) and 97 +/- 15 (G) mmol/kg, values not significantly different from each other (P greater than 0.05). The maximal voluntary work produced during the last 15 min did not differ between treatments. During the 2 h after sugar ingestion, 30 +/- 3 g of F and 26 +/- 3 g of G were oxidized to 13CO2. These findings indicate that fructose ingested before exercise was utilized at least as well as glucose, allowed a more stable glycemia, and did not modify performance.     

Oxidation of corn starch, glucose, and fructose ingested before exercise

The purpose of this study was to compare the metabolic and endocrine responses, and the amounts of exogenous carbohydrate oxidized, during prolonged moderate cycle ergometer exercise (120 min, 60% VO2max), preceded by ingestion of 13C enriched glucose (G), fructose (F), or pure corn starch (S) (1,592 kJ ingested with 400 ml of water, 60 min before the beginning of exercise) in six healthy young male subjects. Plasma glucose and insulin concentrations significantly increased in response to G and S feeding. The high plasma insulin values resulted in a significant transient reduction in plasma glucose concentration in the first hour of exercise and blunted the response of plasma free fatty acid and glycerol concentrations, when compared to the values observed with F ingestion, which did not modify plasma glucose or insulin concentrations. Over the 2 h exercise period, the percentages of exogenous G (67 +/- 9%) and S (73 +/- 8%) oxidized were not significantly different but were significantly higher than the percentage of exogenous F oxidized (54 +/- 6%). These results confirm that 1) exogenous F is less readily available for oxidation than G or S and 2) pure corn starch does not offer any advantage over glucose as a pre-exercise meal.     

Insulin sensitivity of protein and glucose metabolism in overweight female adolescents with type 1 diabetes mellitus: positive modulation by physical exercise

Abstract Impairment of insulin sensitivity of glucose metabolism, a prominent feature of type 1 diabetes (DM), is also well documented in adolescence and obesity. Overweight is frequently present during adolescence in females. Spurt in growth is significantly reduced during puberty in females with type 1 DM, while it is normal in males. In this study we assessed the effect of the coexistence of type 1 DM, adolescence, overweight, and their possible interference with growth. Moreover, we evaluated whether dietetic control associated with physical exercise improved insulin sensitivity in adolescence. The study enrolled 11 female adolescents and young adults (aged 18.5±0.6 years), affected by type 1 DM for 8.3±0.9 years, who were overweight (BMI, 27.3±0.8 kg/m²) and receiving conventional insulin therapy (0.78±0.10 U/kg day). We used the euglycemic hyperinsulinemic clamp technique coupled to [²H₂]glucose and [¹³C]leucine infusion. The results show a striking increase in insulin resistance of glucose metabolism: the suppression of endogenous glucose production (EGP) was 59% in comparison to 90%–100% recorded by others at similar insulin levels in subjects at different periods of life. Insulin resistance in type 1 DM overweight adolescents was also present on protein metabolism: the postabsorptive plasma leucine (146.9±10.1 M) and the endogenous leucine flux (ELF, 88.8±4.5 µmol/kg min) were higher than in healthy controls. The suppression of ELF during hyperinsulinemia was defective in diabetic adolescents (27%, p<0.001) with respect to controls (36%). Only three of the 11 overweight diabetic subjects completed the 6-month physical exercise and diet program, and showed improvement of insulin sensitivity at the final evaluation. The EGP suppression by insulin shifted from 41% to 79%; ELF suppression increased from 26% to 34%. All the parameters of glucose metabolism correlated with the weight loss (BMI reduction from 27.8±1.9 to 25.6±1.2 kg/m²). In conclusion, overweight female adolescents with type 1 DM have an impaired insulin action on glucose and protein metabolism. Physical exercise and correct dietary regimen positively influence insulin sensitivity. The present preliminary data are relevant for an improved control of glucose homeostasis and a normal growth in adolescence.     

4周运动减肥对肥胖青少年血浆致动脉粥样硬化指数和脂酰辅酶A胆固醇酰基转移酶2的影响

目的:观察运动减肥对肥胖青少年血浆致动脉粥样硬化指数和脂酰辅酶A胆固醇酰基转移酶等动脉粥样硬化致病相关因子的影响。方法:以参加2011年上海巅峰运动减肥夏令营的30名肥胖青少年为对象,进行4周中小强度有氧运动为主结合适当饮食控制的减肥运动训练。分别于入营第一天和出营前一天进行身体形态及血液指标测试。结果:经过夏令营4周有氧运动训练,肥胖青少年体重、体脂率、BMI与运动前相比显著下降,空腹血清胰岛素、血脂水平与运动前相比均明显改善,血浆致动脉粥样硬化指数、脂酰辅酶A胆固醇酰基转移酶2水平显著降低。结论:4周有氧运动明显降低了肥胖青少年的肥胖程度和胰岛素水平,改善血脂代谢,在一定程度上降低了动脉粥样硬化发病的风险。     

Effect of a two-week program of individually monitored physical activity on insulin resistance in obese non-insulin-dependent diabetics

It is well known that under the influence of regular, individually measured aerobic physical activity, it is possible to raise the biological efficiency of insulin by several mechanisms: by increasing the number of insulin receptors, their sensitivity and efficiency, as well as by increasing glucose transporters GLUT-4 on the level of cell membrane. The aim of this research was to examine whether decreased insulin resistance could be achieved under the influence of the program of individually measured aerobic physical activity in the 2-week period, in the obese type 2 diabetes patients with the increased aerobic capacity (VO2)max. In 10 type 2 diabetes patients 47.6 +/- 4.6 years of age (group E), in the 14-days period, program of aerobic training was applied (10 sessions--35 min session of walking on treadmill, intensity 60.8 +/- 5.7% (VO2)max, frequency 5 times a week), as well as 1,600 kcal diet. At the same time, other 10 type 2 diabetes patients 45.9 +/- 5.5 years of age (group C) were on 1,600 kcal diet. Before and after this period the following was measured in both groups: insulin sensitivity (M/I) by the method of hyperinsulin euglycemic clamp, and (VO2)max by Astrand test on ergocycle. In contrast to the group C, in the second testing of E group subjects a significant increase was obtained in M/I (1.23 +/- 0.78 vs. 2.42 +/- 0.95 mg/kg/min/mU p < 0.001, 96.75%) as well as the increase of (VO2)max (26.34 +/- 4.26 vs. 29.16 +/- 5.01 ml/kg/min p < 0.05, 10.7%). The results had shown that 2-week program of aerobic training had had significant influence on the increased aerobic capacity and insulin sensitivity in the tested patients.