High-fiber cereal reduces postprandial insulin responses in hyperinsulinemic but not normoinsulinemic subjects

Research Progress of α-Glucosidase Inhibitors Produced by Microorganisms and Their Applications

Based on the easy cultivation of microorganisms and their short cycle time, research on α-glucosidase inhibitors (α-GIs) of microbial origin is receiving extensive attention. Raw materials used in food production, such as cereals, dairy products, fruits, and vegetables, contain various bioactive components, like flavonoids, polyphenols, and alkaloids. Fermentation with specific bacterial strains enhances the nutritional value of these raw materials and enables the creation of hypoglycemic products rich in diverse active ingredients. Additionally, conventional food processing often results in significant byproduct generation, causing resource wastage and environmental issues. However, using bacterial strains to ferment these byproducts into α-GIs presents an innovative solution. This review describes the microbial-derived α-GIs that have been identified. Moreover, the production of α-GIs using industrial food raw materials and processing byproducts as a medium in fermentation is summarized. It is worth analyzing the selection of strains and raw materials, the separation and identification of key compounds, and fermentation broth research methods. Notably, the innovative ideas in this field are described as well. This review will provide theoretical guidance for the development of microbial-derived hypoglycemic foods.

Effects of a ready-to-eat cereal formula powder on glucose metabolism, inflammation, and gut microbiota in diabetic db/db mice

The cereal formula powder, Zhengda Jingshan (ZDJS), comprises dietary fiber, multivitamins, fine protein, and various cereal ingredients. The present study evaluated the effects of ZDJS on glucose metabolism and explored the corresponding mechanisms in terms of modulating gut microbiota and the fecal metabolome. Type 2 diabetic db/db mice were given ZDJS (1 g/kg) orally twice daily for 55 days, after which glucose metabolism, inflammation, gut microbiota, and fecal metabolomics were assayed. Repeated administration of ZDJS was associated with a trend toward decreasing fasting blood glucose and a 0.12% decrease in hemoglobin A1c (HbA1c), as well as statistically significant increases in the insulin sensitivity index and decreases in serum levels of tumor necrosis factor (TNF-α) and ileum expression of mucin-2. ZDJS also ameliorated the compensatory enlargement of islets and decreased the ratio of the α-cell area to total islet area; however, this amelioration of impaired oral glucose tolerance became less pronounced as treatment continued. In addition, ZDJS remarkably decreased the abundance of phylum Proteobacteria and the phylum ratio of Firmicutes to Bacteroidetes, as well as altered the fecal metabolic profile. Taken together, our findings demonstrate that ZDJS improved glucose metabolism and reduced inflammation in type 2 diabetic db/db mice, which may be associated with a reshaping of the gut microbiome and fecal metabolome in db/db mice. Thus, our study suggests that ZDJS may represent a complementary therapy for patients with type 2 diabetes.

Postprandial Glycemic and Insulinemic Effects of the Addition of Aqueous Extracts of Dried Corn Silk, Cumin Seed Powder or Tamarind Pulp, in Two Forms, Consumed with High Glycemic Index Rice

Several plant-based traditional ingredients in Asia are anecdotally used for preventing and/or treating type 2 diabetes. We investigated three such widely consumed ingredients, namely corn silk (CS), cumin (CU), and tamarind (TA). The aim of the study was to determine the effects of aqueous extracts of these ingredients consumed either as a drink (D) with high-glycemic-index rice or added to the same amount of rice during cooking (R) on postprandial glycemia (PPG), insulinemia (PPI), and blood pressure (BP), over a 3 h measurement period. Eighteen healthy Chinese men (aged 37.5 ± 12.5 years, BMI 21.8 ± 1.67 kg/m²) took part in a randomized crossover trial, each completing up to nine sessions. Compared to the control meal (plain rice + plain water), the addition of test extracts in either form did not modulate PPG, PPI, or BP. However, the extracts when added within rice while cooking gave rise to significantly lower PPI than when consumed as a drink (p < 0.01). Therefore, the form of consumption of phytochemical-rich ingredients can differentially modulate glucose homeostasis. This study also highlights the need for undertaking randomized controlled clinical trials with traditional foods/components before claims are made on their specific health effects.

Enzyme-treated orange pomace alters acute glycemic response to orange juice

The goal of the present study was to determine the impact of the addition of enzyme-treated orange pomace to orange juice on postprandial glycemic response. Ten healthy subjects (aged 27.9 ± 7.7 years, body mass index 22.1 ± 1.1 kg m-2) participated in a randomized, 2-arm, cross-over clinical trial to test the glycemic response to 100% orange juice (OJ) or 100% orange juice with 5 g of enzyme-treated orange pomace fiber (OPF). Blood samples were collected and glucose and insulin concentrations were measured at fasting (0 min) and every 15 min for 2 h after consuming the study juice products. Analysis of the 2 h incremental area under the curve (iAUC0-2h) indicated a significant reduction in blood glucose after ingesting the OPF juice compared to the OJ, p = 0.02. Peak glucose concentrations were also lowered after the OPF juice compared to the OJ, p < 0.05. No significant difference was observed in insulin responses between treatments, p > 0.05. Overall, this study demonstrated that adding 5 g of fiber from orange pomace into a serving of OJ attenuated the postprandial glucose response.

Effects of Higher Dietary Protein and Fiber Intakes at Breakfast on Postprandial Glucose, Insulin, and 24-h Interstitial Glucose in Overweight Adults

Dietary protein and fiber independently influence insulin-mediated glucose control. However, potential additive effects are not well-known. Men and women (n = 20; age: 26 ± 5 years; body mass index: 26.1 ± 0.2 kg/m²; mean ± standard deviation) consumed normal protein and fiber (NPNF; NP = 12.5 g, NF = 2 g), normal protein and high fiber (NPHF; NP = 12.5 g, HF = 8 g), high protein and normal fiber (HPNF; HP = 25 g, NF = 2 g), or high protein and fiber (HPHF; HP = 25 g, HF = 8 g) breakfast treatments during four 2-week interventions in a randomized crossover fashion. On the last day of each intervention, meal tolerance tests were completed to assess postprandial (every 60 min for 240 min) serum glucose and insulin concentrations. Continuous glucose monitoring was used to measure 24-h interstitial glucose during five days of the second week of each intervention. Repeated-measures ANOVA was applied for data analyses. The HPHF treatment did not affect postprandial glucose and insulin responses or 24-h glucose total area under the curve (AUC). Higher fiber intake reduced 240-min insulin AUC. Doubling the amount of protein from 12.5 g to 25 g/meal and quadrupling fiber from 2 to 8 g/meal at breakfast was not an effective strategy for modulating insulin-mediated glucose responses in these young, overweight adults.

Effects of Ready-to-Eat-Cereals on Key Nutritional and Health Outcomes: A Systematic Review

BACKGROUND

In many countries breakfast cereals are an important component of breakfast. This systematic review assesses the contribution of consumption of ready-to eat cereal (RTEC) to the recommended nutrient intake. Furthermore, the effects of RTEC consumption on key health parameters are investigated as well as health promoting properties of RTEC.

METHOD

The Cochrane Central Register of Controlled Trials, MEDLINE, EMBASE and CINAHL have been searched up till 16th of June 2015. Randomized controlled trials were excluded if RTEC were used during hypocaloric diets, if RTEC were eaten at other times than breakfast and if breakfasts included other products than RTEC, milk and fruit. Observational studies were excluded when "breakfast cereals" were not defined or their definition included cooked cereals. From cross-sectional studies only data concerning energy and nutrient intake as well as micronutrient status were used.

RESULTS

From 4727 identified citations 64 publications met the inclusion criteria of which 32 were cross-sectional studies, eight prospective studies and 24 randomized controlled trials. Consumption of RTEC is associated with a healthier dietary pattern, concerning intake of carbohydrates, dietary fiber, fat and micronutrients, however total sugar intake is higher. Persons consuming RTEC frequently (≥ 5 times/week) have a lower risk of inadequate micronutrient intake especially for vitamin A, calcium, folate, vitamin B 6, magnesium and zinc. Evidence from prospective studies suggests that whole grain RTEC may have beneficial effects on hypertension and type 2 diabetes. Consumption of RTEC with soluble fiber helps to reduce LDL cholesterol in hypercholesterolemic men and RTEC fortified with folate can reduce plasma homocysteine.

DISCUSSION

One of the review's strengths is its thorough ex/inclusion of studies. Limitations are that results of observational studies were based on self-reported data and that many studies were funded by food-industry.

CONCLUSION

Consumption of RTEC, especially of fiber-rich or whole grain RTEC, is implicated with several beneficial nutritional and health outcomes. The effect on body weight, intestinal health and cognitive function needs further evaluation. Of concern is the higher total sugar intake associated with frequent RTEC consumption.

Estimating the reliability of glycemic index values and potential sources of methodological and biological variability

BACKGROUND

The utility of glycemic index (GI) values for chronic disease risk management remains controversial. Although absolute GI value determinations for individual foods have been shown to vary significantly in individuals with diabetes, there is a dearth of data on the reliability of GI value determinations and potential sources of variability among healthy adults.

OBJECTIVE

We examined the intra- and inter-individual variability in glycemic response to a single food challenge and methodologic and biological factors that potentially mediate this response.

DESIGN

The GI value for white bread was determined by using standardized methodology in 63 volunteers free from chronic disease and recruited to differ by sex, age (18-85 y), and body mass index [BMI (in kg/m²): 20-35]. Volunteers randomly underwent 3 sets of food challenges involving glucose (reference) and white bread (test food), both providing 50 g available carbohydrates. Serum glucose and insulin were monitored for 5 h postingestion, and GI values were calculated by using different area under the curve (AUC) methods. Biochemical variables were measured by using standard assays and body composition by dual-energy X-ray absorptiometry.

RESULTS

The mean ± SD GI value for white bread was 62 ± 15 when calculated by using the recommended method. Mean intra- and interindividual CVs were 20% and 25%, respectively. Increasing sample size, replication of reference and test foods, and length of blood sampling, as well as AUC calculation method, did not improve the CVs. Among the biological factors assessed, insulin index and glycated hemoglobin values explained 15% and 16% of the variability in mean GI value for white bread, respectively.

CONCLUSIONS

These data indicate that there is substantial variability in individual responses to GI value determinations, demonstrating that it is unlikely to be a good approach to guiding food choices. Additionally, even in healthy individuals, glycemic status significantly contributes to the variability in GI value estimates. This trial was registered at clinicaltrials.gov as NCT01023646.

Ready-to-Eat Cereal Consumption with Total and Cause-Specific Mortality: Prospective Analysis of 367,442 Individuals

BACKGROUND

Intakes of ready-to-eat cereal (RTEC) have been inversely associated with risk factors of chronic diseases such as cardiovascular disease (CVD), type 2 diabetes, and certain cancers; however, their relations with total and cause-specific mortality remain unclear.

OBJECTIVE

To prospectively assess the associations of RTEC intakes with all causes and disease-specific mortality risk.

DESIGN

The study included 367,442 participants from the prospective National Institutes of Health (NIH)-AARP Diet and Health Study. Intakes of RTEC were assessed at baseline.

RESULTS

Over an average of 14 years of follow-up, 46,067 deaths were documented. Consumption of RTEC was significantly associated with reduced risk of mortality from all-cause mortality and death from CVD, diabetes, all cancer, and digestive cancer (all p for trend < 0.05). In multivariate models, compared to nonconsumers of RTEC, those in the highest intake of RTEC had a 15% lower risk of all-cause mortality and 10%-30% lower risk of disease-specific mortality. Within RTEC consumers, total fiber intakes were associated with reduced risk of mortality from all-cause mortality and deaths from CVD, all cancer, digestive cancer, and respiratory disease (all p for trend < 0.005).

CONCLUSIONS

Consumption of RTEC was associated with reduced risk of all-cause mortality and mortality from specific diseases such as CVD, diabetes, and cancer. This association may be mediated via greater fiber intake.

The benefits of breakfast cereal consumption: a systematic review of the evidence base

There have been no comprehensive reviews of the relation of breakfast cereal consumption to nutrition and health. This systematic review of all articles on breakfast cereals to October 2013 in the Scopus and Medline databases identified 232 articles with outcomes related to nutrient intake, weight, diabetes, cardiovascular disease, hypertension, digestive health, dental and mental health, and cognition. Sufficient evidence was available to develop 21 summary evidence statements, ranked from A (can be trusted to guide practice) to D (weak and must be applied with caution). Breakfast cereal consumption is associated with diets higher in vitamins and minerals and lower in fat (grade B) but is not associated with increased intakes of total energy or sodium (grade C) or risk of dental caries (grade B). Most studies on the nutritional impact are cross-sectional, with very few intervention studies, so breakfast cereal consumption may be a marker of an overall healthy lifestyle. Oat-, barley-, or psyllium-based cereals can help lower cholesterol concentrations (grade A), and high-fiber, wheat-based cereals can improve bowel function (grade A). Regular breakfast cereal consumption is associated with a lower body mass index and less risk of being overweight or obese (grade B). Presweetened breakfast cereals do not increase the risk of overweight and obesity in children (grade C). Whole-grain or high-fiber breakfast cereals are associated with a lower risk of diabetes (grade B) and cardiovascular disease (grade C). There is emerging evidence of associations with feelings of greater well-being and a lower risk of hypertension (grade D), but more research is required.

Hypoglycemic and hypolipidemic potential of a high fiber diet in healthy versus diabetic rabbits

The aim of this study was to investigate potential hypoglycaemic and hypolipidemic effects of Plantago ovata husk included in the diet, in healthy and diabetic rabbits. We also examined the effects of this fiber in other biochemical parameters. Two groups of 18 rabbits were used. The first group was fed with standard chow and the second with chow supplemented with Plantago ovata husk (3.5 mg/kg/day). On day 14 diabetes mellitus was induced by the intravenous administration of alloxan (80 mg/kg). After an oral glucose load (3 g), glucose, insulin, and other biochemical parameters were determined on day 14 (healthy rabbits) and on day 28 (diabetic rabbits). In healthy rabbits, fiber did not modify glucose or insulin levels but decreased significantly total cholesterol, LDL-cholesterol, atherogenic index, and glycosylated hemoglobin. In diabetic rabbits, fiber was more beneficial in mild diabetics than in severe diabetics with significant decreases in glucose levels and increases in insulin concentrations. In these animals fiber caused an important reduction in cholesterol, indicating a beneficial effect of Plantago ovata husk in diabetic rabbits. Although further studies in patients are necessary, we think that Plantago ovata husk offers interesting perspectives to be administered to patients with diabetes mellitus.

Glycaemic index methodology

The glycaemic index (GI) concept was originally introduced to classify different sources of carbohydrate (CHO)-rich foods, usually having an energy content of >80 % from CHO, to their effect on post-meal glycaemia. It was assumed to apply to foods that primarily deliver available CHO, causing hyperglycaemia. Low-GI foods were classified as being digested and absorbed slowly and high-GI foods as being rapidly digested and absorbed, resulting in different glycaemic responses. Low-GI foods were found to induce benefits on certain risk factors for CVD and diabetes. Accordingly it has been proposed that GI classification of foods and drinks could be useful to help consumers make 'healthy food choices' within specific food groups. Classification of foods according to their impact on blood glucose responses requires a standardised way of measuring such responses. The present review discusses the most relevant methodological considerations and highlights specific recommendations regarding number of subjects, sex, subject status, inclusion and exclusion criteria, pre-test conditions, CHO test dose, blood sampling procedures, sampling times, test randomisation and calculation of glycaemic response area under the curve. All together, these technical recommendations will help to implement or reinforce measurement of GI in laboratories and help to ensure quality of results. Since there is current international interest in alternative ways of expressing glycaemic responses to foods, some of these methods are discussed.

Effect of a Polyphenol-Rich Extract from Aloe vera Gel on Experimentally Induced Insulin Resistance in Mice

Insulin resistance, which precedes type 2 diabetes mellitus (T2DM), is a widespread pathology associated with the metabolic syndrome, myocardial ischemia, and hypertension. Finding an adequate treatment for this pathology is an important goal in medicine. The purpose of the present research was to investigate the effect of an extract from Aloe vera gel containing a high concentration of polyphenols on experimentally induced insulin resistance in mice. A polyphenol-rich Aloe vera extract (350 mg/kg) with known concentrations of aloin (181.7 mg/g) and aloe-emodin (3.6 mg/g) was administered orally for a period of 4 weeks to insulin resistant ICR mice. Pioglitazone (50 mg/kg) and bi-distilled water were used as positive and negative controls respectively. Body weight, food intake, and plasma concentrations of insulin and glucose were measured and insulin tolerance tests were performed. The insulin resistance value was calculated using the homeostasis model assessment for insulin resistance (HOMA-IR) formula. Results showed that the polyphenol-rich extract from Aloe vera was able to decrease significantly both body weight ( p < 0.008) and blood glucose levels ( p < 0.005) and to protect animals against unfavorable results on HOMA-IR, which was observed in the negative control group. The highest glucose levels during the insulin tolerance curve test were in the negative control group when compared to the Aloe vera extract and pioglitazone treated mice ( p < 0.05). In conclusion, Aloe vera gel could be effective for the control of insulin resistance.

Continuous glucose monitoring in gastroparesis

BACKGROUND

Delayed gastric emptying can alter glucose levels in diabetic patients; hyperglycemia can delay gastric emptying. Continuous glucose monitoring (CGM) may be useful to assess the relationship between gastric emptying and blood glucose levels.

AIMS

The aims of this study were to compare the postprandial blood glucose profile of patients with type 2 diabetes mellitus (T2DM) with and without gastroparesis, normal subjects, and patients with idiopathic gastroparesis (IG), and also to determine the effect of different meal compositions on glucose regulation in T2DM and normals.

METHODS

Seven patients with IG, seven T2DM with gastroparesis, ten non-gastroparetic T2DM, and ten normal subjects underwent CGM during a low fat (Eggbeaters) meal. Glucose profiles were also studied in T2DM and normal subjects after high fat, high fiber, spicy, and Ensure liquid nutrient meals.

RESULTS

After the Eggbeaters meal, the glucose profile of IGs and normals were similar. Diabetic patients with gastroparesis had similar peak postprandial blood glucose to nongastroparetic diabetics (231 ± 26 vs. 232 ± 18 mg/dl), but had a higher postprandial blood glucose at the end of the 4 h study (187 ± 26 mg/dl vs. 97 ± 10; P = 0.01). In contrast to normals, non-gastroparetic diabetics had higher mean postprandial blood sugar after the Eggbeaters meal (173 ± 5 mg/dl) compared to high fat (157 ± 3; P = 0.002), spicy (133 ± 2; P < 0.001) and Ensure meals (152 ± 1; P < 0.001).

CONCLUSIONS

Blood glucose monitoring provides insight to the presence of gastroparesis in diabetic patients: diabetic gastroparetics had prolonged postprandial hyperglycemic profile as compared to non-gastroparetic diabetics. Of the meals tested, the low fat (Eggbeaters) meal was associated with the highest mean postprandial glucose in diabetics.

Are the glycemic and insulinemic index values of carbohydrate foods similar in healthy control, hyperinsulinemic and type 2 diabetic patients?

BACKGROUND/OBJECTIVES

a criticism of glycemic index (GI) is that it does not indicate the insulin response of foods (insulinemic index, II). However, it is unknown if the GI and II values of foods are equivalent in all subjects, a necessary criterion for clinical utility. We compared GI and II values in non-diabetic subjects with fasting-serum-insulin (FSI) <40 pmol/l (healthy control) or with FSI ≥ 40 pmol/l (hyper[I]) and subjects with type 2 diabetes (T2DM), and to see whether GI and II were related to the serum-glucose concentrations, insulin sensitivity, β-cell function and hepatic insulin extraction (HIE) of the subjects.

SUBJECTS/METHODS

Serum-glucose, -insulin and -C-peptide responses after 50 g available-carbohydrate portions of glucose (tested three times by each subject), sucrose, instant mashed-potato, white-bread, polished-rice and pearled-barley were measured in healthy control (n=9), hyper[I] (n=12) and T2DM (n=10) subjects.

RESULTS

Food GI values did not differ significantly among the three subject groups, whereas II values were higher in T2DM (100±7) than healthy controls (78±5) and hyper[I] subjects (70±5) (mean±s.e.m., P=0.05). II was inversely associated with insulin sensitivity (r=-0.66, P<0.0001) and positively related to fasting- and postprandial-glucose (both r=0.68, P<0.0001) and HIE (r=0.62, P=0.0002). In contrast, GI was not related to any of the biomarkers (P>0.05).

CONCLUSION

The GI is a valid property of foods because its value is similar in healthy control, hyper [I] and T2DM subjects, and is independent of subjects' metabolic status. However, II may depend upon the glycaemic control, insulin sensitivity and HIE of the subjects.

Impact of overweight and glucose tolerance on postprandial responses to high- and low-glycaemic index meals

The beneficial effects of a low-glycaemic index (GI) meal on postprandial glucose and insulin levels have been demonstrated. However, limited data are available on the impact of overweight and glucose tolerance on postprandial responses to different GI meals. Our aim was to study the effects of physiological characteristics on postprandial glucose, insulin and lipid responses and the relative glycaemic response (RGR) of a low-GI (LGI) and a high-GI (HGI) meal. We recruited twenty-four normal-weight and twenty-four overweight subjects, twelve with normal glucose tolerance (NGT) and twelve with impaired glucose tolerance (IGT) in each group. Both test meals were consumed once and the glucose reference twice. Blood glucose and insulin were measured in the fasting state and over a 2 h period after each study meal, and TAG and NEFA were measured in the fasting state and over a 5 h period. The glucose responses of subjects with IGT differed significantly from those of subjects with NGT. The highest insulin responses to both meals were observed in overweight subjects with IGT. Physiological characteristics did not influence TAG or NEFA responses or the RGR of the meals. The LGI meal resulted in lower glucose (P < 0·001) and insulin (P < 0·001) responses, but higher TAG responses (P < 0·001), compared with the HGI meal. The GI of the meals did not affect the NEFA responses. In conclusion, the LGI meal causes lower glucose and insulin responses, but higher TAG responses, than the HGI meal. The RGR of the meals does not differ between normal-weight and overweight subjects with NGT or IGT.

Dietary intakes of fiber and magnesium and incidence of metabolic syndrome in first year after renal transplantation

OBJECTIVE

Considering the high prevalence of metabolic syndrome (MetS) and the associated cardiovascular disease mortality after renal transplant, and considering that the lack of prospective studies regarding the role of fiber and magnesium in MetS prevention after transplant precludes definitive recommendations, we prospectively evaluated the potential role of fiber and magnesium intake in the incidence of MetS at 1 year after renal transplantation.

DESIGN

This was a prospective cohort study.

SETTING, PARTICIPANTS, AND MEASUREMENTS

We included 160 recipients of kidney transplant (100 men and 60 women) aged over 18 years who were free of MetS or diabetes at time of transplant, and followed these patients for 1 year.

METHODS

The usual dietary intakes were assessed with a Willett-format 168-item food-frequency questionnaire. We defined MetS according to modified Adult Treatment Panel III guidelines. We categorized participants by tertiles of dietary fiber and magnesium. To determine associations of fiber and magnesium intake with MetS incidence 1 year posttransplant, we used multivariable logistic regression.

RESULTS

After controlling for potential confounders, including baseline body mass index and energy intake, subjects within the highest tertile of fiber intake had a lower odds ratio for incident MetS (odds ratio, 0.41; 95% confidence interval, 0.08 to 0.99; P < .05 for trend) than those in the lowest tertile. There was no significant overall association between magnesium intake and MetS.

CONCLUSIONS

These findings support current dietary recommendations to increase intakes of fiber-rich foods as a primary preventive approach against MetS and cardiovascular disease, which are very prevalent after renal transplant.

The influence of dietary fibre source and gender on the postprandial glucose and lipid response in healthy subjects

BACKGROUND

Consumption of soluble dietary fibre is correlated with decreased postprandial glucose and insulin responses and hence has beneficial effects on the metabolic syndrome.

AIM OF THE STUDY

To investigate the effects on postprandial glucose, insulin and triglyceride concentrations of meals enriched with soluble dietary fibres from oats, rye bran, sugar beet fibre or a mixture of these three fibres.

METHODS

Thirteen healthy human volunteers (6 men and 7 women, aged 20-28 years) were included in the study. The subjects came to the study centre once a week after an overnight fast to ingest test meals and a control meal in random order. The meals contained either oat powder (62 g, of which 2.7 soluble fibre), rye bran (31 g, of which 1.7 g soluble fibre), sugar beet fibre (19 g, of which 5 g soluble fibre), a mixture of these three fibres (74 g, of which 1.7 g soluble fibre from each source, giving 5 g soluble fibre) or no added fibre (control) and were all adjusted to contain the same total amount of available carbohydrates. Blood samples were drawn before and every 30 min up to 180 min after the meals.

RESULTS

Meals with rye bran gave a lower postprandial glucose peak when compared with the control meal, and this effect was more pronounced in women compared to men. Oat powder, containing a low amount of total fibre and a high amount of carbohydrates in liquid matrix, gave a higher incremental glucose peak concentration compared to rye bran and sugar beet fibre and higher insulin incremental area under curve compared to control. The oat powder also influenced the effects of the mixed meal, diminishing the glucose-lowering effects. Postprandial triglyceride levels tended to be higher after all fibre-rich meals, but only significant for oat powder and the mixed meal when compared with the control meal.

CONCLUSIONS

Postprandial glucose, insulin and triglyceride concentrations are influenced by dietary fibre-rich meals, depending on fibre source, dose of soluble and total fibre and possibly gender.

Reduced energy intake at breakfast is not compensated for at lunch if a high-insoluble-fiber cereal replaces a low-fiber cereal

BACKGROUND

In cohort studies, insoluble fiber has been associated with a reduced risk of obesity and diabetes; however, compared with soluble fiber, its role in the regulation of short-term food intake (FI) and satiety has received little attention.

OBJECTIVE

Our aim was to compare the effects of a high-insoluble-fiber (HF) cereal with a low-fiber (LF) cereal on FI, subjective appetite (SA), and plasma glucose (PG) in healthy individuals.

DESIGN

Males and females (n = 32) were randomly assigned to consume 60 g of either HF (26 g insoluble fiber, 120 kcal) or LF (1 g fiber, 217 kcal) breakfast cereal. Pre- and postlunch SA and PG were measured regularly for 4 h, and ad libitum FI was measured at 3 h.

RESULTS

The prelunch SA area under the curve did not differ between the 2 cereals, but when expressed as change in appetite per kilocalorie of cereal, HF suppressed SA more than did LF (-17.6 +/- 1.8 compared with -10.0 +/- 1.1 mm . min . kcal(-)(1), respectively; P < 0.01). Lunchtime FI did not differ between cereals, but cumulative energy intake (cereal + lunch) was lower after the HF than after the LF cereal (1330 +/- 57 compared with 1422 +/- 66 kcal, respectively; P = 0.01). The prelunch PG area under the curve (P < 0.0001) and the immediate postlunch PG (P = 0.01) were lower after HF cereal consumption.

CONCLUSIONS

An HF breakfast cereal contributes to a cumulative reduction in breakfast and lunch energy intake, possibly due to its high satiety value per kilocalorie. A short-term benefit of the HF cereal, compared with LF cereal, was lower PG concentration before and immediately after lunch.

Effect of mixing dietary fibre (purified lignocellulose or purified pectin) and a corn meal on glucose and insulin responses in healthy horses

The aim of this study was to investigate the effect of the addition of a purified soluble (pectin) and insoluble (lignocellulose) fibre to a starchy meal on post-prandial glucose and insulin responses in healthy horses. Four horses were fed in a randomized order three different diets: (i) cracked corn, (ii) cracked corn mixed with purified lignocellulose, and (iii) cracked corn mixed with purified pectin. Each diet was adjusted to a starch intake of 2 g/kg bodyweight (BW). Lignocellulose was aligned to an intake of 0.2 g/kg BW, and pectin was fed in a dosage of 0.1 g/kg BW. Each period consisted of a 10-day acclimatization to the diet (fed once per day); during this time, the horses were fed 1.2 kg hay/100 kg BW/day. Blood was collected after each acclimatization period before and after the test meal was fed, without any hay. The increase in plasma glucose and insulin, peak values, and area under the curves were similar for all diets. The present findings suggest that adding purified soluble or insoluble fibre to a corn meal does not affect post-prandial glucose and insulin responses in healthy horses. Feeding strategies for horses with a high energy requirement should include a starch reduction per meal, rather than the addition of purified fibre.

Enhanced food intake regulatory responses after a glucose drink in hyperinsulinemic men

OBJECTIVE

To determine the effect of hyperinsulinemia on food intake and plasma concentrations of glucose and food intake regulatory hormones in men after a glucose drink.

DESIGN

Cross-sectional clinical intervention study of the effect of a glucose drink on food intake regulation.

SUBJECTS

Thirty-three normoinsulinemic (NI) (body mass index (BMI)=25.3+/-0.6; age=41.4+/-2.4) and 32 hyperinsulinemic (HI) men (BMI=29.5+/-0.6; age=43.4+/-2.6).

MEASUREMENTS

Food intake was measured from a pizza meal 1 h after subjects consumed either a noncaloric sweetened drink or a glucose-containing drink (75 g/300 ml) in random order on two occasions. On another occasion, blood samples were taken every 30 min for 2 h after the glucose drink.

RESULTS

Fasting insulin in the HI and NI men was 65+/-3 (mean+/-s.e.m.) and 26+/-1.5 pmol/l, respectively. Food intake at the pizza meal was reduced by the glucose drink (P<0.01), but more so in HI (-9.7+/-4.1 %) than NI men (-5.4+/-3.4 %) (P=0.06). The increase in plasma insulin and cholecystokinin (CCK) after the glucose drink was greater and the plasma concentrations of leptin were higher, and ghrelin and adiponectin were lower in HI men than in NI men (P<0.05).

CONCLUSION

These results support epidemiological data suggesting that hyperinsulinemia, at least in the early stages, may provide resistance to weight gain, possibly through physiological mechanisms of food intake control.

The effects of fat and protein on glycemic responses in nondiabetic humans vary with waist circumference, fasting plasma insulin, and dietary fiber intake

The effects of protein and fat on glycemic responses have not been studied systematically. Therefore, our aim was to determine the dose-response effects of protein and fat on the glycemic response elicited by 50 g glucose in humans and whether subjects' fasting plasma insulin (FPI) and diet influenced the results. Nondiabetic humans, 10 with FPI < [corrected] or =40 pmol/L and 10 with FPI >40 pmol/L, were studied on 18 occasions after 10 14-h overnight fasts. Subjects consumed 50 g glucose dissolved in 250 mL water plus 0, 5, 10, or 30 g fat and/or 0, 5, 10, or 30 g protein. Each level of fat was tested with each level of protein. Dietary intake was measured using a 3-d food record. Gram per gram, protein reduced glucose responses approximately 2 times more than fat (P < 0.001) with no significant fat x protein interaction (P = 0.051). The effect of protein on glycemic responses was related to waist circumference (WC) (r = -0.56, P = 0.011) and intake of dietary fiber (r = -0.60, P = 0.005) but was unrelated to FPI or other nutrient intakes. The effect of fat on glycemic responses was related to FPI (r = 0.49, P = 0.029) but was unrelated to WC or diet. We conclude that, across the range of 0-30 g, protein and fat reduced glycemic responses independently from each other in a linear, dose-dependent fashion, with protein having approximately 3-times the effect of fat. A large protein effect was associated with high WC and high dietary-fiber intake, whereas a large fat effect was associated with low FPI. These conclusions may not apply to solid meals. Further studies are needed to determine the mechanisms for these effects.

Targeting postprandial hyperglycemia

In healthy individuals, blood glucose levels in the fasting state are maintained by the continuous basal-level insulin secretion. After a meal, the rise in postprandial glucose (PPG) is controlled by the rapid pancreatic release of insulin, stimulated by both glucose and the intestinal production of the incretins glucose-dependent insulinotropic polypeptide and glucagon-like peptide 1. In diabetic individuals, postprandial insulin secretion is insufficient to suppress an excessive rise in PPG. There is increasing evidence that elevated PPG exerts a more deleterious effect on the vascular system than elevation of fasting plasma glucose. In particular, individuals with normal fasting plasma glucose but impaired glucose tolerance have significantly increased risk of cardiovascular events. With the recognition of the importance of PPG and the availability of new pharmacologic options, management of diabetes will shift to greater attention to PPG levels. The prototype for such an approach is in the treatment of gestational diabetes and diabetic pregnancies where PPG is the primary target of efforts at glycemic control. These efforts have been extremely successful in improving the outlook for diabetic pregnant women. There are many approaches to reduction of PPG; dietary management and promotion of exercise are very effective. Sulfonylureas, meglitinides, metformin, thiazolidinediones, and disaccharidase inhibitors all counteract PPG elevation. The development of glucagon-like peptide 1 agonists such as exendin and dipeptidyl peptidase IV inhibitors such as vildagliptin offers a new approach to suppression of PPG elevation. New semisynthetic insulin analogues permit a more aggressive response to postprandial glucose elevation, with lower risk of hypoglycemia, than with regular insulin. Inhaled insulin also has a rapid onset of action and offers benefits in PPG control. It is proposed that an aggressive treatment approach focusing on PPG, similar to the current standards for diabetic pregancies, be directed at individuals with diabetes and impaired glucose tolerance.

Fiber and Cardiovascular Disease Risk

Dietary fiber consists of edible parts of plants or analogous carbohydrates that are resistant to digestion and absorption in the human small intestine. Fiber can be classified as a dietary source (eg, cereal, fruit, vegetable, or legume) or as a supplement. Based on chemical properties, fiber can be divided to water-soluble (eg, beta-glucans, pectin, and guar) and insoluble (eg, cellulose and lignin) forms. An increasing number of observational findings have reported a lower incidence of coronary heart disease in subjects who report consuming diets high in fiber. Dietary fiber is thought to affect several cardiovascular disease (CVD) risk factors. Soluble fiber decreases serum total and low-density lipoprotein cholesterol concentrations and improves insulin resistance. The effect of fiber on inflammatory markers and coagulation is not yet well established. While soluble, gel-forming fiber has beneficially affected CVD risk factors, food sources of mainly insoluble fibers, primarily contributed by cereal products, have been the most consistently associated with lower incidence rates of CVD. Despite this contradiction, the evidence promotes a food-based approach favoring increased intake of whole-grain cereals, fruit, and vegetables providing a mixture of different types of fibers for CVD prevention.