Postprandial Plasma Insulin Research Articles

Sterilization in a Liquid of a Specific Starch Makes It Slowly Digestible In Vitro and Low Glycemic in Rats

Diabetics are recommended to eat a balanced diet containing normal amounts of carbohydrates, preferably those with a low glycemic index. For solid foods, this can be achieved by choosing whole-grain, fiber-rich products. For (sterilized) liquid products, such as meal replacers, the choices for carbohydrate sources are restricted due to technological limitations. Starches usually have a high glycemic index after sterilization in liquids, whereas low glycemic sugars and sugar replacers can only be used in limited amounts. Using an in vitro digestion assay, we identified a resistant starch (RS) source [modified high amylose starch (mHAS)] that might enable the production of a sterilized liquid product with a low glycemic index. Heating mHAS for 4–5 min in liquid increased the slowly digestible starch (SDS) fraction at the expense of the RS portion. The effect was temperature dependent and reached its maximum above 120°C. Heating at 130°C significantly reduced the RS fraction from 49 to 22%. The product remained stable for at least several months when stored at 4°C. To investigate whether a higher SDS fraction would result in a lower postprandial glycemic response, the sterilized mHAS solution was compared with rapidly digestible maltodextrin. Male Wistar rats received an i.g. bolus of 2.0 g available carbohydrate/kg body weight. Ingestion of heat-treated mHAS resulted in a significant attenuation of the postprandial plasma glucose and insulin responses compared with maltodextrin. mHAS appears to be a starch source which, after sterilization in a liquid product, acquires slow-release properties. The long-term stability of mHAS solutions indicates that this may provide a suitable carbohydrate source for low glycemic index liquid products for inclusion in a diabetes-specific diet.

Improved glucose metabolism in mice lacking α-tocopherol transfer protein

Conflicting evidence suggests a possible role for vitamin E in mammalian glucose metabolism and the protection from type 2 diabetes. The alpha-tocopherol transfer protein (alpha-TTP) mediates the transfer of alpha-tocopherol (alpha-TOH) from hepatocytes to very-low-density lipoproteins, thereby controlling plasma levels of alpha-TOH. The aim of this study was to investigate the putative impact of alpha-TTP knock-out on glucose metabolism in mice. Mice deficient for alpha-TTP and wild-type control littermates were fed a diet containing 200 mg alpha-tocopheryl acetate per kg to ameliorate alpha-TOH deficiency in knock-out mice. We investigated fasting and postprandial plasma glucose, insulin and triglyceride levels of both groups of mice at different ages. All genotypes and age groups were further subjected to glucose and insulin tolerance tests, and number of insulin-producing islets of Langerhans were determined. Plasma alpha-TOH levels of knock-out mice were 34% the levels of wild-type controls: Any signs of alpha-TOH deficiency were absent at any age. Unexpectedly, serum glucose levels both in the fasted and in the fed state were lower in alpha-TTP-deficient mice at any age. Removal rates for intraperitoneally injected glucose were found to be significantly increased in young alpha-TTP-deficient mice. This improved glucose tolerance was caused by increased insulin secretion in response to an intraperitoneal glucose challenge due to an increased number of pancreatic islets, as well as by increased sensitivity to intraperitoneally injected insulin, both significantly promoting glucose metabolism in alpha-TTP-deficient mice. Our findings suggest that alpha-TTP-deficiency in states of alpha-TOH supplementation unexpectedly promotes glucose tolerance in mice due to both increased insulin secretion and insulin action, suggesting differential roles of alpha-TTP and alpha-TOH in the pathogenesis of type 2 diabetes mellitus.

The effect of different protein hydrolysate/carbohydrate mixtures on postprandial glucagon and insulin responses in healthy subjects

To study the effect of four protein hydrolysates from vegetable (pea, gluten, rice and soy) and two protein hydrolysates from animal origin (whey and egg) on glucagon and insulin responses. Eight healthy normal-weight male subjects participated in this study. The study employed a repeated-measures design with Latin square randomization and single-blind trials. Protein hydrolysates used in this study (pea, rice, soy, gluten, whey and egg protein hydrolysate) consisted of 0.2 g hydrolysate per kg body weight (bw) and 0.2 g maltodextrin per kg bw and were compared to maltodextrin alone. Postprandial plasma glucose, glucagon, insulin and amino acids were determined over 2 h. All protein hydrolysates induced an enhanced insulin secretion compared to maltodextrin alone and a correspondingly low plasma glucose response. A significant difference was observed in area under the curve (AUC) for plasma glucagon between protein hydrolysates and the maltodextrin control drink (P<0.05). Gluten protein hydrolysate induced the lowest glucagon response. High amino-acid-induced glucagon response does not necessarily go together with low insulin response. Protein hydrolysate source affects AUC for glucagon more profoundly than for insulin, although the protein load used in this study seemed to be at lower level for significant physiological effects.

Metabolic and antihypertensive effects of moxonidine and moxonidine plus irbesartan in patients with type 2 diabetes mellitus and mild hypertension: A sequential, randomized, double-blind clinical trial

Background: The autonomic nervous system plays an important part in the homeostasis of blood pressure (BP), and sympathetic overactivity may contribute to metabolic conditions such as glycemic intolerance or insulin resistance. Objective: This study evaluated the anti-hypertensive and metabolic effects of moxonidine, a selective imidazoline II-receptor agonist that lowers BP by central inhibition of the sympathetic nervous system, and moxonidine plus the angiotensin II-receptor blocker irbesartan in patients with type 2 diabetes mellitus and mild hypertension. Methods: This was a study in patients with type 2 diabetes previously untreated with medication and untreated mild hypertension (diastolic blood pressure [DBP] >90 and <105 mm Hg). For the first 3 months of the study, all patients were treated for hypertension with moxonidine 0.2 mg once daily (M0.2) to establish a moxonidine baseline. After this single-arm period, patients were randomized to receive double-blind treatment with moxonidine 0.2 mg BID (M0.4) or moxonidine 0.2 mg plus irbesartan 150 mg (M0.2+1) once daily for 3 months. Changes in DBP, systolic blood pressure (SBP), body mass index (BMI), fasting and postprandial plasma glucose (FPG and PPG), fasting and postprandial plasma insulin (FPI and PPI), glycosylated hemoglobin (HbA 1c), Homeostasis Model Assessment of insulin sensitivity (HOMA-S), total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), and triglycerides (TG) were evaluated at baseline, 3 months (end of single arm period), and 6 months (end of randomized treatment period). Results: The study enrolled 99 patients (50 men, 49 women; mean [SD] age, 55 [7] years; mean BMI, 26.8 [0.9]). No significant changes in BMI, PPG, PPI, TC, or LDL-C were observed over the entire study period. At 3 months, treatment with M0.2 was associated with significant improvements from baseline in SBP and DBP ( P < 0.05), whereas there were no significant changes in HbA 1c, FPG, FPI, HOMA-S, HDL-C, or TG. At 6 months, significant decreases from baseline in HbA 1c, FPG, FPI, HOMA-S, and TG were observed in the M0.4 group (all, P < 0.05), but not in the M0.2+1 group. The M0.4 group also had a significant increase from baseline in HDL-C ( P < 0.05) that was not seen in the M0.2+1 group. The changes in FPI and HOMA-S were significantly greater in the M0.4 group compared with the M0.2+1 group ( P < 0.05). Significant decreases from baseline in SBP and DBP were observed in both the M0.4 and M0.2+1 groups ( P < 0.02 and P < 0.01, respectively). No patient withdrew from the study because of a drug-related adverse event, and there were no clinically significant drug-related changes in laboratory values during the study. Conclusion: In these patients with type 2 diabetes and mild hypertension, the M0.4 group had greater improvements in measures of glucose metabolism and the plasma lipid profile compared with those treated with M0.2+1.

Effect of simvastatin and/or pioglitazone on insulin resistance, insulin secretion, adiponectin, and proinsulin levels in nondiabetic patients at cardiovascular risk—the PIOSTAT Study

We investigated the effect of pioglitazone in comparison with and in combination with simvastatin on insulin resistance, plasma adiponectin, postprandial plasma glucose, insulin, and intact proinsulin levels in a nondiabetic population at cardiovascular risk. One hundred twenty-five nondiabetic patients at cardiovascular risk were randomized to pioglitazone (PIO), pioglitazone and simvastatin (PIO/SIM), or simvastatin (SIM) treatments. Blood samples were taken for the measurement of adiponectin and lipid levels. In addition, an oral glucose load with the measurements of glucose, insulin, and intact proinsulin levels was performed. Adiponectin levels increased from 14.0 ± 8.2 to 27.6 ± 14.5 μg/mL ( P < .0001) during PIO treatment and from 11.7 ± 10.0 to 26.7 ± 15.7 μg/mL ( P < .0001) during PIO/SIM treatment. A decrease in adiponectin levels from 15.5 ± 12.7 to 11.6 ± 7.0 μg/mL ( P < .05) was observed during SIM treatment. Although fasting intact proinsulin levels remained unchanged, the increase in postprandial intact proinsulin levels could be reduced from 29.5 ± 21.4 to 22.1 ± 17.5 pmol/L ( P < .01) during PIO treatment and from 24.3 ± 27.4 to 21.1 ± 16.5 mmol/L ( P < .05) during PIO/SIM treatment. Lipid parameters improved during SIM treatment but not during PIO treatment. Combined treatment with PIO/SIM was superior in improving overall cardiovascular risk profile than every single drug.

Nateglinide improves postprandial hyperglycemia and insulin secretion in renal transplant recipients

Postprandial hyperglycemia (PPHG) frequently occurs among renal transplant recipients (RTR). Reduced early insulin response (EIR) after a meal leads to impaired suppression of endogenous glucose production and subsequently PPHG, which is a risk factor for cardiovascular disease. Nateglinide is a rapid acting insulin secretagogue inducing an EIR after a meal. Our main objective was to investigate the safety and effect of nateglinide treatment on postprandial plasma glucose excursions and insulin secretion in RTR with PPHG. A total of 14 Caucasian RTR with new-onset diabetes mellitus (NODM; n = 6) or impaired glucose tolerance (IGT; n = 8) were included. The insulin response and glucose excursions were measured for 240 min after a standardized liquid meal at baseline and after two-wk treatment with nateglinide. Treatment with nateglinide was followed by a significant decrease in mean two-h plasma glucose from 10.5 mmol/L (3.1) to 7.6 mmol/L (2.1; p < 0.001) and a decline in total postprandial area under the curve (AUC) of glucose concentration (p < 0.001). Both estimated EIR and the late insulin response increased significantly (p = 0.008 and p = 0.003, respectively). No serious adverse event was observed during the study period. Treating RTR with nateglinide for two-wk significantly improved PPHG, increased the insulin response following a standardized meal and was well tolerated.

Metabolic effects of pioglitazone and rosiglitazone in patients with diabetes and metabolic syndrome treated with metformin

Metformin is considered the gold standard for type 2 diabetes treatment as monotherapy and in combination with sulphonylureas and insulin, whereas the combination of metformin with thiazolidinediones is relatively less studied. The aim of the present study was to assess the differential effect on glycaemic metabolism and lipid variables of the combination of metformin plus pioglitazone or metformin plus rosiglitazone in diabetic patients with metabolic syndrome. All patients began metformin and were randomized to receive pioglitazone or rosiglitazone for 12 months. We assessed body mass index, glycated haemoglobin, fasting plasma glucose, postprandial plasma glucose, fasting plasma insulin, postprandial plasma insulin, homeostasis model assessment index, total cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, triglycerides, apolipoprotein A-I, and apolipoprotein B. Significant decreases in glycated haemoglobin, fasting plasma glucose, postprandial plasma glucose, fasting plasma insulin, and postprandial plasma insulin were seen after 9 and 12 months in both groups. Homeostasis model assessment index improved at 12 months in both groups. Significant total cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, triglycerides, apolipoprotein A-I, and apolipoprotein B improvement was observed in pioglitazone group after 12 months, but not in the rosiglitazone group. These variations were significant between groups. The combination of metformin plus thiazolidinediones was able to improve glycaemic control compared with previous therapy. Pioglitazone was associated with a significant improvement in lipid and lipoprotein variables.

Effects of Nateglinide and Glibenclamide on Prothrombotic Factors in Naieve Type 2 Diabetic Patients Treated with Metformin: A 1-Year, Double-Blind, Randomized Clinical Trial

To evaluate the effect on coagulation and fibrinolysis parameters and on non-conventional cardiovascular risk factors of metformin plus nateglinide or glibenclamide in naïve type 2 diabetes patients. A total of 248 type 2 diabetic patients were enrolled and randomly assigned to receive nateglinide or glibenclamide, and metformin for 12 months. We assessed body mass index (BMI), glycated hemoglobin (HbA1c), fasting plasma glucose (FPG), postprandial plasma glucose (PPG), fasting plasma insulin (FPI), postprandial plasma insulin (PPI), homeostasis model assessment index (HOMA index), lipid profile with lipoprotein (a) [Lp(a)], fibrinogen (Fg), plasminogen activator inhibitor-1 (PAI-1), tissue plasminogen activator (t-PA), homocysteine (Hcy), systolic blood pressure (SBP), diastolic blood pressure (DBP). After 9 months of treatment, both tested drug combinations were similarly associated with a significant reduction in FPG (nateglinide, -17.2%; glibenclamide, -16.9%, both p<0.05) compared to the baseline, while HbA1c (-17.3%, p<0.05) and PPG (-15.2%, p<0.05) significantly decreased only in the nateglinide group. After one year of treatment, compared to the baseline the nateglinide group showed a significant reduction in HbA1c (-21%, p<0.01), FPG (-20.7%), p<0.01, PPG (-21.5%, p<0.05), HOMA index (-25.4%, p<0.05); the glibenclamide group, showed a significant reduction in HbA1c (-11%, p<0.05), FPG (-23.2%, p<0.05), PPG (-11.2%, p<0.05), and HOMA index (-23.9%, p<0.05) but to a minor extent. Moreover, the HbA1c difference value from baseline observed in the nateglinide-treated group was significantly higher than that observed in the glibenclamide group. Therefore the nateglinide-treated patients showed a significant reduction in some prothrombotic parameters (PAI-1=-19%, Lp(a)=-31%, and Hcy=-32.3%, all p<0.05), whereas the glibenclamide-treated patients did not. Nateglinide appears to improve glycemic control as well as the levels of some prothrombotic parameters compared to glibenclamide when administered in combination with metformin.

Blood Pressure Control and Inflammatory Markers in Type 2 Diabetic Patients Treated with Pioglitazone or Rosiglitazone and Metformin

The aim of the study was to assess the effects of the combination of metformin plus pioglitazone or rosiglitazone on glucose and blood pressure in type 2 diabetic patients with metabolic syndrome, as well as its tolerability in those patients. In this 12-month, multicentric, double-blind, randomized, controlled, parallel-group trial, all patients began with metformin. Patients were randomized for self-administration of either pioglitazone or rosiglitazone for 12 months. We assessed body mass index (BMI), glycemic control (glycosylated hemoglobin [HbA(1c)], fasting and postprandial plasma glucose and insulin levels [FPG, PPG, FPI and PPI, respectively] and homeostasis model assessment [HOMA] index) and systolic and diastolic blood pressure (SBP and DBP, respectively), at baseline and at 3, 6, 9 and 12 months of treatment, as well as high-sensitivity C-reactive protein (hs-CRP), nitrites/nitrates and adiponectin (ADN) at baseline and at 12 months of treatment. Significant HbA(1c) decreases were obtained after 9 (p<0.05) and 12 (p<0.01) months in both groups. After 9 and 12 months, mean FPG and PPG levels were decreased in both groups (p<0.05 and p<0.01, respectively). We observed decreases in FPI and PPI at 9 and 12 months (p<0.05 and p<0.01, respectively) compared to the baseline values in both groups. Furthermore, HOMA index improvement over the baseline value was obtained only at 12 months (p<0.05) in both groups. SBP and DBP improved significantly (p<0.05, for each) in both groups after 12 months. hs-CRP decreased significantly (p<0.05) in both groups after 12 months; nitrites/nitrates and ADN increased significantly (p<0.05, for each) in both groups after 12 months. The combination of thiazolinediones and metformin is associated with a slight but significant improvement in the long-term blood pressure control of these patients, and with an improvement in the anti-inflammatory state, both of which are related to a similar reduction in insulin-resistance.

Enhanced Wellbeing of Adults with Type 2 Diabetes following Multi-Vitamin and Mineral Supplementation for Three Months in a Randomised, Double-blind, Cross-over Pilot Study

Objective To investigate the effects of a daily multinutrient supplement on plasma indicators of glycemic and lipemic control and psychological wellbeing in type 2 diabetic patients. Design Double-blind, randomised, cross-over pilot intervention study. Subjects Twenty-nine subjects (15 males and 14 females) with non-insulin-dependent type 2 diabetes. Intervention Either a multinutrient supplement or placebo were provided daily during two intervention periods of 3 months separated by a 4 week washout. Results There were no significant changes of multinutrient treatment compared with placebo in HbA1c, fasting or postprandial plasma glucose and insulin concentrations and fasting plasma lipid concentrations. Using a validated wellbeing questionnaire (W-BQ 22) designed for diabetic subjects, the multinutrient supplement resulted in improvements in the secondary outcome of wellbeing of the volunteers in terms of anxiety (p = 0.020), vitality (p = 0.013) and general wellbeing (p = 0.021), relative to placebo. Conclusions Findings from this pilot study suggest that a multinutrient supplement may enhance the wellbeing of diabetic patients, even in the absence of a significant improvement in clinical parameters. If substantiated in a full clinical study the results would have important implications for the prevention of late complications of diabetes, as psychological factors can hinder successful management of the condition and adversely affect metabolic control.

Effects of a palatinose-based liquid diet (Inslow) on glycemic control and the second-meal effect in healthy men

Postprandial hyperglycemia induces prolonged hyperinsulinemia, which is a risk factor for type 2 diabetes mellitus. Foods with a low glycemic index blunt the rapid rise in postprandial plasma glucose and insulin levels. We herein investigated the effects of a novel, palatinose-based liquid diet (Inslow, Meiji Dairy Products, Tokyo, Japan) on postprandial plasma glucose and insulin levels and on the rate of substrate oxidation in 7 healthy men. Furthermore, to examine the effects of Inslow on the second-meal effect, we quantified our subjects' postprandial plasma glucose, insulin, and free fatty acid levels for up to 7 hours after they ingested a breakfast containing Inslow or control formula, followed by a standard lunch 5 hours later. Our results showed that peak plasma glucose and insulin levels 30 minutes after Inslow loading were lower than after control formula loading. Postprandial fat oxidation rates in the Inslow group were higher than in the control formula group ( P < .05). In the second-meal effect study, plasma glucose and insulin levels after lunch in the Inslow group were lower than in the control formula group ( P < .01), although the peak levels in these groups were not different. The free fatty acid concentration in the Inslow group immediately before lunch was significantly lower than in the control formula group ( P < .05). In conclusion, consumption of Inslow at breakfast appears to improve patient glycemic control by reducing their postprandial plasma glucose and insulin levels after lunch (second-meal effect).

Effects of Rosiglitazone and Pioglitazone Combined with Metformin on the Prothrombotic State of Patients with Type 2 Diabetes Mellitus and Metabolic Syndrome

In this multicentre, randomized, double-blind, controlled, parallel-group trial, 103 patients with type 2 diabetes mellitus and metabolic syndrome were randomized to receive one of two thiazolidinediones--pioglitazone or rosiglitazone--in combination with 1500 mg/day of metformin, increasing up to 3000 mg/day, for 12 months. Anthropometric, metabolic, coagulation and fibrinolysis parameters were assessed at baseline and after 3, 6, 9 and 12 months. Significant decreases in glycosylated haemoglobin, fasting plasma glucose and post-prandial plasma glucose levels were seen after 9 and 12 months in both groups, and significant decreases in fasting plasma insulin and post-prandial plasma insulin levels were seen after 12 months in both groups. In both groups, improvement in the homeostasis model assessment index compared with baseline was obtained only after 12 months. Plasminogen activator inhibitor-1 levels were significantly lower in both groups after 12 months compared with baseline values. In patients with type 2 diabetes mellitus and metabolic syndrome, the combination of metformin plus thiazolidinediones improved glycaemic control and produced a slight but significant reduction in plasminogen activator inhibitor-1 levels.

Metformin–pioglitazone and metformin–rosiglitazone effects on non-conventional cardiovascular risk factors plasma level in type 2 diabetic patients with metabolic syndrome

Metformin is considered the gold standard for type 2 diabetes treatment as monotherapy and in combination with sulphonylureas and insulin. The combination of metformin with thiazolidinediones is less well studied. The aim of the present study was to assess the differential effect, and tolerability, of metformin combined with pioglitazone or rosiglitazone on glucose, coagulation and fibrinolysis parameters in patients with type 2 diabetes mellitus and metabolic syndrome. This 12-month, multicentre, double-blind, randomized, controlled, parallel-group trial was conducted at three study sites in Italy. We assessed patients with type 2 diabetes mellitus (duration >or=6 months) and with metabolic syndrome. All patients were required to have poor glycaemic control with diet, or experienced adverse effects with diet and metformin, administered up to the maximum tolerated dose. Patients were randomized to receive either pioglitazone or rosiglitazone self-administered for 12 months. We assessed body mass index (BMI), glycaemic control [glycosylated haemoglobin (HbA(1c)), fasting and postprandial plasma glucose and insulin levels (FPG, PPG, FPI, and PPI respectively), homeostasis model assessment (HOMA) index], lipid profile [total cholesterol (TC), low-density lipoprotein-cholesterol (LDL-C), high-density lipoprotein-cholesterol (HDL-C) and triglycerides (TG)], lipoprotein (a) [Lp(a)] and homocysteine (HCT) at baseline and at 3, 6, 9 and 12 months of treatment. No BMI change was observed at 3, 6, 9 and 12 months in either group. Significant HbA(1c) decreases were observed at 9 and 12 months in both groups. After 9 and 12 months, mean FPG and PPG levels decreased in both groups. Decreases in FPI and PPI were observed at 9 and 12 months compared with the baseline in both groups. Furthermore, in both groups, the HOMA index improved but only at 12 months. Significant TC, LDL-C, HDL-C, TG improvement was present in the pioglitazone group at 12 months compared with the baseline values, and these variations were significantly different between groups. No TC, LDL-C, TG improvement was present in the rosiglitazone group after 12 months. Significant Lp(a) and HCT improvement was present in the pioglitazone group at 12 months compared with the baseline values, and Lp(a) change was significant compared with the rosiglitazone group. Significant HCT decrease was observed in the rosiglitazone group at the end of the study. In our type 2 diabetic patients, both drugs were safe and effective for glycaemic control and improving HCT plasma levels. However, long-term treatment with metformin plus pioglitazone significantly reduced Lp(a) plasma levels, whereas metformin + rosiglitazone did not. For patients with type 2 diabetes mellitus and metabolic syndrome, combined treatment with metformin and rosiglitazone or pioglitazone is safe and effective, However, the pioglitazone combination also reduced the plasma Lp(a) levels whereas the rosiglitazone combination did not.

Role of Low-Glycemic-Index Foods in Improving Overall Glycemic Control in Type 1 and Type 2 Diabetic Patients and Correcting Excessive Postprandial Hyperglycemia

Increasing postprandial plasma glucose and insulin excursions are assumed to increase severity of diabetes and to be independent predictors of risk for atherosclerotic diseases and adiposity. Many possible connections have been found between postprandial events and the development of diabetes complication [1]. Lowering postprandial plasma glucose and insulin responses is relevant in preventing and managing diabetes mellitus [2,3]. Therefore, intervention towards reducing postprandial plasma glucose and insulin spikes is an essential topic in therapeutic strategy for diabetic patients, and may reduce the risk of developing cardiovascular complications. There is growing recognition that the postprandial glycemic [4,5] and insulinemic [6] responses to different foods may vary despite equal amounts of total absorbable carbohydrates, thus favoring low-glycemic-index (GI) carbohydrates. The notion of glycemic index was proposed by David Jenkins and et al. [5] more than twenty years ago as a practical way of classifying carbohydrate-containing foods according to their effect on postprandial blood glucose rather than according to carbohydrate content alone. The Gl is defined as the incremental area under the blood-glucose response curve of a 50 carbohydrate test food portion expressed as the percentage of the response to the same amount of carbohydrate from standard food (glucose, or white bread) taken by the same subject [7]. In practice, the actual carbohydrate load from a normal portion size varies considerably. Both type and amount of carbohydrate have now widely accepted influences on glycemic response [8,9]. In order to address this problem, the concept of glycemic load (GL) was introduced. GL, calculated as the amount of carbohydrate in one serving multiplied by the GI of the food, allows comparisons between likely glycemic effects of different foods in realistic portions [10]. However, GL values should be considered with caution, as both a low-GI/high-CHO food and a high GI/low-CHO food can have the same GL with different metabolic effects on β-cell function and plasma lipids [8]. Separate use of GL may lead to habitual consumption of low-carbohydrate diets. While short-term beneficial effects could be induced by low-carbohydrate diet, the long-term effects might be harmful. All the centers over the world that have tested experimental and clinical use of low-GI foods are enthusiastic about diet counseling to diabetic or hyperlipidemic patients, and even normal subjects at risk of cardiovascular diseases. A large number of studies have indeed demonstrated the efficiency of diet counseling and the use of low glycemic index (low-GI) foods in these patients. More striking effects were noted in the improvement of postprandial blood glucose excursions and, consequently, in glycated hemoglobin, fasting plasma lipids - particularly triglyceride levels - and, marginally, total and LDL cholesterol. We will give some insights on a few of our clinical and experimental results on this topic. At this stage, we would like to point out that the use of low-GI foods is only part of a more general strategy to improve postprandial hyperglycemia, and thus overall blood glucose control.

Short-term and Long-term Effects of Guar on Postprandial Plasma Glucose, Insulin and Glucagon-like Peptide 1 Concentration in Healthy Rats

Ingestion of guar gum decreases postprandial glycemia and insulinemia and improves sensitivity to insulin in diabetic patients and several animal models of diabetes. The aim of the present study was to compare the short-term and long-term effects of guar on plasma insulin and glucagon-like peptide 1 concentration in healthy rats. In the short-term experiments, the concomitant intragastric administration of glucose and guar reduced the early increment in plasma glucose, insulin and glucagon-like peptide 1 concentration otherwise induced by glucose alone. Comparable findings were made after twelve days of meal training exposing the rats to either a control or guar-enriched diet for fifteen minutes. Mean plasma glucose concentrations were lower while mean insulin concentrations were higher in the guar group than in the controls according to intragastric glucose tolerance tests conducted in overnight fasted rats maintained for 19 to 36 days on either the control or guar-enriched diet. The intestinal content of glucagon-like peptide 1 at the end of the experiments was also lower in the guar group. Changes in body weight over 62 days of observation were comparable in the control and guar rats. Thus, long-term intake of guar improves glucose tolerance and insulin response to glucose absorption, without improving insulin sensitivity, in healthy rats.

Appetite Regulatory Hormone Responses to Various Dietary Proteins Differ by Body Mass Index Status Despite Similar Reductions inad LibitumEnergy Intake

Although dietary protein produces higher acute satiety relative to carbohydrate, the influence of protein source and body mass index (BMI) has not been clearly described. The objective of the study was to assess postprandial responses to different protein sources, compared with glucose, in males with normal and high BMI. This was a randomized, crossover study of four preloads followed by blood sampling (+15, 30, 45, 60, 90, 120, 180 min) and buffet meal. The study was conducted at an outpatient clinic. The study population included 72 men, with a BMI range 20.6-39.9 kg/m(2). Interventions consisted of liquid preloads (1.1 MJ, 450 ml) containing 50 g whey, soy, gluten, or glucose. Fasting and postprandial plasma glucose, insulin, ghrelin, glucagon-like peptide-1 (GLP-1) and cholecystokinin (n = 38), ad libitum energy intake, and appetite ratings were measured. Energy intake was 10% lower after all protein preloads, compared with the glucose treatment (P < 0.05), independent of BMI status and protein type. All protein loads prolonged the postprandial suppression of ghrelin (P < 0.01) and elevation of GLP-1 (P < 0.01) and cholecystokinin (P < 0.05). Fasting GLP-1 concentrations [overweight, 17.5 +/- 1.3; lean, 14.7 +/- 0.1 pg/ml (5.2 +/- 0.4 and 4.4 +/- 0.1 pmol/liter, respectively); P < 0.001] and postprandial responses (P = 0.038) were higher in overweight subjects. Whey, soy, and gluten similarly tend to reduce ad libitum food intake 3 h later in lean and overweight males relative to glucose. Postprandial ghrelin, GLP-1, insulin, and cholecystokinin may contribute to this higher satiety after protein consumption. GLP-1 concentrations are increased in overweight subjects, which may affect satiety responses in this group.

Co-Ingestion of a Protein Hydrolysate with or without Additional Leucine Effectively Reduces Postprandial Blood Glucose Excursions in Type 2 Diabetic Men

This study examined postprandial plasma insulin and glucose responses after co-ingestion of an insulinotropic protein (Pro) hydrolysate with and without additional free leucine with a single bolus of carbohydrate (Cho). Male patients with long-standing Type 2 diabetes (n = 10) and healthy controls (n = 10) participated in 3 trials in which plasma glucose, insulin, and amino acid responses were determined after the ingestion of beverages of different composition (Cho: 0.7 g/kg carbohydrate, Cho+Pro: 0.7 g/kg carbohydrate with 0.3 g/kg protein hydrolysate, or Cho+Pro+Leu: 0.7 g/kg carbohydrate, 0.3 g/kg protein hydrolysate and 0.1 g/kg free leucine). Plasma insulin responses [expressed as area under the curve (AUC)] were 141 and 204% greater in patients with Type 2 diabetes and 66 and 221% greater in the controls in the Cho+Pro and Cho+Pro+Leu trials, respectively, compared with those in the Cho trial (P < 0.05). The concomitant plasma glucose responses were 15 and 12% lower in the patients with Type 2 diabetes and 92 and 97% lower in the control group in the Cho+Pro and Cho+Pro+Leu trials, respectively, compared with those in the Cho trial (P < 0.05). Plasma leucine concentrations correlated with the insulin response in all subjects (r = 0.43, P < 0.001). We conclude that co-ingestion of a protein hydrolysate with or without additional free leucine strongly augments the insulin response after ingestion of a single bolus of carbohydrate, thereby significantly reducing postprandial blood glucose excursions in patients with long-standing Type 2 diabetes.

Consumption of Both Resistant Starch and -Glucan Improves Postprandial Plasma Glucose and Insulin in Women

Consumption of a meal high in resistant starch or soluble fiber (beta-glucan) decreases peak insulin and glucose concentrations and areas under the curve (AUCs). The objective was to determine whether the effects of soluble fiber and resistant starch on glycemic variables are additive. Ten normal-weight (43.5 years of age, BMI 22.0 kg/m2) and 10 overweight women (43.3 years of age, BMI 30.4 kg/m2) consumed 10 tolerance meals in a Latin square design. Meals (1 g carbohydrate/kg body wt) were glucose alone or muffins made with different levels of soluble fiber (0.26, 0.68, or 2.3 g beta-glucan/100 g muffin) and three levels of resistant starch (0.71, 2.57, or 5.06 g/100 g muffin). Overweight subjects had plasma insulin concentrations higher than those of normal-weight subjects but maintained similar plasma glucose levels. Compared with low beta-glucan-low resistant starch muffins, glucose and insulin AUC decreased when beta-glucan (17 and 33%, respectively) or resistant starch (24 and 38%, respectively) content was increased. The greatest AUC reduction occurred after meals containing both high beta-glucan-high resistant starch (33 and 59% lower AUC for glucose and insulin, respectively). Overweight women were somewhat more insulin resistant than control women. Soluble fiber appears to have a greater effect on postprandial insulin response while glucose reduction is greater after resistant starch from high-amylose cornstarch. The reduction in glycemic response was enhanced by combining resistant starch and soluble fiber. Consumption of foods containing moderate amounts of these fibers may improve glucose metabolism in both normal and overweight women.

Consumption of Both Resistant Starch and β-Glucan Improves Postprandial Plasma Glucose and Insulin in Women

OBJECTIVE—Consumption of a meal high in resistant starch or soluble fiber (β-glucan) decreases peak insulin and glucose concentrations and areas under the curve (AUCs). The objective was to determine whether the effects of soluble fiber and resistant starch on glycemic variables are additive. RESEARCH DESIGN AND METHODS—Ten normal-weight (43.5 years of age, BMI 22.0 kg/m2) and 10 overweight women (43.3 years of age, BMI 30.4 kg/m2) consumed 10 tolerance meals in a Latin square design. Meals (1 g carbohydrate/kg body wt) were glucose alone or muffins made with different levels of soluble fiber (0.26, 0.68, or 2.3 g β-glucan/100 g muffin) and three levels of resistant starch (0.71, 2.57, or 5.06 g/100 g muffin). RESULTS—Overweight subjects had plasma insulin concentrations higher than those of normal-weight subjects but maintained similar plasma glucose levels. Compared with low β-glucan–low resistant starch muffins, glucose and insulin AUC decreased when β-glucan (17 and 33%, respectively) or resistant starch (24 and 38%, respectively) content was increased. The greatest AUC reduction occurred after meals containing both high β-glucan–high resistant starch (33 and 59% lower AUC for glucose and insulin, respectively). Overweight women were somewhat more insulin resistant than control women. CONCLUSIONS—Soluble fiber appears to have a greater effect on postprandial insulin response while glucose reduction is greater after resistant starch from high-amylose cornstarch. The reduction in glycemic response was enhanced by combining resistant starch and soluble fiber. Consumption of foods containing moderate amounts of these fibers may improve glucose metabolism in both normal and overweight women.

Dietary amino acids fed in free form and as protein components do not differently affect postprandial plasma insulin, glucagon, growth hormone and corticosterone responses in rats

This study examined, whether the postprandial fate of dietary amino acids from different amino acid sources is regulated by the responses of insulin, glucagon, corticosterone and growth hormone (GH). Male Wistar rats were cannulated in the vena jugularis and assigned to dietary groups. The diets contained 21% casein or the same amino acids in free form. In the free amino acid diets, methionine level was varied between the groups. The feed was supplied in two distinct meals. In previous experiments it was established that oxidative amino acid losses of the free amino acid diets and protein diets were different. After 3 weeks on those diets, it appeared that the differences in postprandial oxidative losses had been diminished. GH was measured every 12 min, from 144 min before the start of the experimental meal over the following 144 min. Insulin and corticosterone were measured six times from the start of the meal until 270 min after the meal. No differences have been observed between the hormonal responses to both meals at day 5 and at day 26. In conclusion, it has been found that the differences in the oxidative losses between protein and free amino acid meals are not mediated by the combined action of the insulin, glucagon, corticosterone and GH. Postprandial catabolism of amino acids is most probably regulated by substrate induction.