Improving Effect of the Acute Administration of Dietary Fiber-Enriched Cereals on Blood Glucose Levels and Gut Hormone Secretion

Effects of whole grain intake on glucagon-like peptide 1 and glucose-dependent insulinotropic peptide: a systematic review and meta-analysis

CONTEXT

Whole grain intake may control help glycemia and reduce food intake by affecting the secretion of glucagon-like peptide 1 (GLP-1) and glucose-dependent insulinotropic peptide (GIP).

OBJECTIVE

This systematic review and meta-analysis aimed to assess the postprandial and long-term effects of whole grains on GLP-1 and GIP levels.

DATA SOURCES

PubMed, Web of Science, and Scopus online databases were searched systematically to identify relevant randomized clinical trials (RCTs) published up to April 2021.

STUDY SELECTION

RCTs that evaluated the effects of whole grains, compared with refined grains, on the postprandial area under the curve (AUC) value, the postprandial serum concentration of incretins from 0 to 180 minutes, or the fasting level of incretins after at least 14 days of intervention were included.

RESULTS

Nineteen studies were included in the meta-analysis. The results showed that acute intake of whole grains could not significantly change the AUC value of GLP-1 or GIP. However, the AUC value of GIP was reduced more significantly in (1) unhealthy participants (standard mean difference [SMD] -1.08; 95%CI, -2.07 to -0.10; I2 = 75.9%) compared with healthy participants, and (2) those with a baseline fasting blood glucose of ≥99 mg/dL (SMD -0.71; 95%CI, -1.30 to -0.11; I2 = 74.4%) compared with those with a baseline value of < 99 mg/dL. On the other hand, the results of time-response evaluation during 0 to 180 minutes after the intake of test meals showed that serum concentrations of GIP decreased significantly from 0 to 30 minutes (coefficient = -44.72; P = 0.005), but increased from 60 to 180 minutes (coefficient = 27.03; P = 0.005). However, long-term studies found no significant effects of whole grains on fasting concentrations of GLP-1 or GIP.

CONCLUSION

Whole grain intake did not affect postprandial levels of GLP-1 but enhanced postprandial levels of GIP from 60 to 180 minutes. Further high-quality trials are required to assess the long-term effects of whole grain intake on serum levels of incretins.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO registration no. CRD42021256695.

The role of cereal soluble fiber in the beneficial modulation of glycometabolic gastrointestinal hormones

According to cohort studies, cereal fiber, and whole-grain products might decrease risk for type 2 diabetes (T2DM), inflammatory processes, cancer, and cardiovascular diseases. These associations, mainly affect insoluble, but not soluble cereal fiber. In intervention studies, soluble fiber elicit anti-hyperglycemic and anti-inflammatory short-term effects, partially explained by fermentation to short-chain fatty acids, which acutely counteract insulin resistance and inflammation. ß-glucans lower cholesterol levels and possibly reduce liver fat. Long-term benefits are not yet shown, maybe caused by T2DM heterogeneity, as insulin resistance and fatty liver disease - the glycometabolic points of action of soluble cereal fiber - are not present in every patient. Thus, only some patients might be susceptive to fiber. Also, incretin action in response to fiber could be a relevant factor for variable effects. Thus, this review aims to summarize the current knowledge from human studies on the impact of soluble cereal fiber on glycometabolic gastrointestinal hormones. Effects on GLP-1 appear to be highly contradictory, while these fibers might lower GIP and ghrelin, and increase PYY and CCK. Even though previous results of specific trials support a glycometabolic benefit of soluble fiber, larger acute, and long-term mechanistic studies are needed in order to corroborate the results.

Systematic literature review: should a bedtime snack be used to treat hyperglycemia in type 2 diabetes?

BACKGROUND

Consuming a bedtime snack is often recommended for people with type 2 diabetes.

OBJECTIVE

This systematic review aims to evaluate the evidence from intervention studies to determine whether consuming a bedtime snack improves fasting hyperglycemia and/or overall glycemic control in individuals with type 2 diabetes. Methods: PubMed, Medline (EBSCO), Cochrane Library and CINAHL Plus (EBSCO) databases were searched until July 20 2022. We included prospective studies in people with type 2 diabetes or prediabetes that included the intervention of a bedtime snack, consumed > 30 minutes after dinner and < 2 hours before bed and reported glycemic outcomes.

RESULTS

The systematic review included 16 studies. There was no consistent relationship between consumption of a bedtime snack and improved glycemic control, especially when a no snack control was included. Of the four studies that included the use of corn starch, a low dose seemed to have benefits over high dose corn starch in terms of improved nocturnal and fasting glucose levels.

CONCLUSIONS

Current advice to consume a bedtime snack is based on a limited number of intervention studies that often do not include a no snack control, nor have used a feasible bedtime snack option that could be translated into every day clinical practice. Further research is needed in type 2 diabetes patients treated with or without insulin.PROSPERO Registration Number: CRD42020182523.

Riceberry rice (Oryza sativa L.) slows gastric emptying and improves the postprandial glycaemic response

Postprandial glycaemia is a key determinant of overall glycaemic control. One mechanism by which dietary strategies can reduce postprandial glycaemic excursions is by slowing gastric emptying. This study aimed to evaluate the acute effect of ingesting riceberry rice (RR) compared with that of ingesting white rice (WR) on gastric emptying rate (GER), plasma glucose and glucose-regulating hormones, including insulin, glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide 1 (GLP-1), in healthy subjects. A randomised, open-label, within-subject, crossover study was performed in six healthy men. GER was measured by scintigraphy over 240 min, and plasma concentrations of glucose, insulin, GLP-1 and GIP were measured at multiple time points over 180 min. This study revealed that RR slows GER with a reduction in postprandial plasma glucose concentrations compared with WR. Plasma insulin and GLP-1 concentrations did not differ between RR and WR. However, plasma GIP concentrations were markedly increased after WR ingesting v. after RR ingestion. We conclude that RR attenuates postprandial glycaemia by slowing GER without altering plasma insulin or GLP-1. Plasma GIP concentrations are likely related to differences in GER and carbohydrate absorption. We propose that dietary fibre-enriched foods, including RR, could contribute to improvement in postprandial glycaemia via delayed gastric emptying.

A Review on the Main Phytoconstituents, Traditional Uses, Inventions, and Patent Literature of Gum Arabic Emphasizing Acacia seyal

Acacia seyal is an important source of gum Arabic. The availability, traditional, medicinal, pharmaceutical, nutritional, and cosmetic applications of gum acacia have pronounced its high economic value and attracted global attention. In addition to summarizing the inventions/patents applications related to gum A. seyal, the present review highlights recent updates regarding its phytoconstituents. Traditional, cosmetic, pharmaceutical, and medicinal uses with the possible mechanism of actions have been also reviewed. The patent search revealed the identification of 30 patents/patent applications of A. seyal. The first patent related to A. seyal was published in 1892, which was related to its use in the prophylaxis/treatment of kidney and bladder affections. The use of A. seyal to treat cancer and osteoporosis has also been patented. Some inventions provided compositions and formulations containing A. seyal or its ingredients for pharmaceutical and medical applications. The inventions related to agricultural applications, food industry, cosmetics, quality control of gum Arabic, and isolation of some chemical constituents (L-rhamnose and arabinose) from A. seyal have also been summarized. The identification of only 30 patents/patent applications from 1892 to 15 November 2021 indicates a steadily growing interest and encourages developing more inventions related to A. seyal. The authors recommend exploring these opportunities for the benefit of society.

Acacia Gum Is Well Tolerated While Increasing Satiety and Lowering Peak Blood Glucose Response in Healthy Human Subjects

Acacia gum (AG) is a non-viscous soluble fiber that is easily incorporated into beverages and foods. To determine its physiological effects in healthy human subjects, we fed 0, 20, and 40 g of acacia gum in orange juice along with a bagel and cream cheese after a 12 h fast and compared satiety, glycemic response, gastrointestinal tolerance, and food intake among treatments. Subjects (n = 48) reported less hunger and greater fullness at 15 min (p = 0.019 and 0.003, respectively) and 240 min (p = 0.036 and 0.05, respectively) after breakfast with the 40 g fiber treatment. They also reported being more satisfied at 15 min (p = 0.011) and less hungry with the 40 g fiber treatment at 30 min (p = 0.012). Subjects reported more bloating, flatulence, and GI rumbling on the 40 g fiber treatment compared to control, although values for GI tolerance were all low with AG treatment. No significant differences were found in area under the curve (AUC) or change from baseline for blood glucose response, although actual blood glucose with 20 g fiber at 30 min was significantly less than control. Individuals varied greatly in their postprandial glucose response to all treatments. AG improves satiety response and may lower peak glucose response at certain timepoints, and it is well tolerated in healthy human subjects. AG can be added to beverages and foods in doses that can help meet fiber recommendations.

Premeal Consumption of a Protein-Enriched, Dietary Fiber-Fortified Bar Decreases Total Energy Intake in Healthy Individuals

BACKGROUND

A premeal load of protein can increase satiety and reduce energy intake. Dietary fiber also conveys metabolic benefits by modulating energy intake. We made a protein-enriched, dietary fiber-fortified bar (PFB) and aimed to investigate its effects on food intake and gut hormone secretion in healthy individuals.

METHODS

Twenty subjects with normal glucose tolerance were enrolled. On three separate visits, the subjects received, in a randomized order, one of the following: a PFB containing 73 kcal with 10.7 g of protein and 12.7 g of dietary fiber; a usual bar (UB) containing the same calories as the PFB but only 0.9 g of protein and no dietary fiber; or water (control). After 15 minutes, the subjects had ad libitum intake of a test meal. Food consumption, appetite, and plasma gut hormone levels were measured.

RESULTS

Total energy intake, including the bar and the test meal, was significantly reduced with the PFB preload compared to the water (904.4±534.9 kcal vs. 1,075.0±508.0 kcal, P=0.016). With the UB preload, only the intake of the test meal was reduced (P=0.044) but not the total energy intake (P=0.471) than the water. Fullness was also significantly increased after the PFB. In addition, postprandial glucose levels decreased and glucagon-like peptide-1 levels increased with the PFB compared with both the UB and water.

CONCLUSION

In healthy individuals, a premeal supplementation of PFB reduced total energy intake and decreased postprandial glucose excursion. This finding necessitates long-term studies regarding clinical use in obesity.

Yacon syrup reduces postprandial glycemic response to breakfast: A randomized, crossover, double-blind clinical trial

Yacon is a root rich in fructooligosaccharides (FOS), which act as prebiotics. Numerous studies have shown promising results in the technological aspects of producing yacon syrup. However, uncertainties exist concerning whether yacon syrup can modulate postprandial glucose and lipid profiles. In order to assess the effect of yacon syrup on postprandial glucose, insulin and triglyceride (TG) responses, a randomized, crossover, double-blind clinical intervention with 40 women (20 normal weight and 20 grade I obese) was performed. Participants underwent two-arms of intervention with at least a one-week wash-out period between visits. On each intervention day, after 12 h of fasting, an aliquot of blood was collected. For intervention A, volunteers consumed breakfast +40 g of placebo, whereas for intervention B, participants consumed breakfast +40 g of yacon syrup (14 g of FOS). Blood samples were drawn at 15, 30, 45, 60, 90, and 120 min. Glucose and insulin concentrations were lowered after yacon syrup intake as compared to placebo at following times: 30 min for glucose and 15, 30 and 45 min for insulin. In conclusion, yacon syrup has a postprandial decreasing effect glucose and insulin concentrations in adult women. This effect was not evident for triglyceride concentration. Clinical trial registry: RBR-33wf46. Available in: http://www.ensaiosclinicos.gov.br/rg/RBR-33wf46/.

An 8-week diet high in cereal fiber and coffee but free of red meat does not improve beta-cell function in patients with type 2 diabetes mellitus: a randomized controlled trial

BACKGROUND

Higher dietary intake of fibers and coffee, but lower red meat intake is associated with reduced risk for type 2 diabetes in epidemiological studies. We hypothesized that a calorie-restricted diet, which is high in fiber and coffee, but free of red meat, improves beta-cell function in patients with T2D.

METHODS

In a randomized parallel-group pilot trial, obese type 2 diabetes patients were randomly allocated to consume either a diet high in cereal fiber and coffee, but free of red meat (n = 17) (L-RISK) or a diet low in fiber, free of coffee but high in red meat (n = 20) (H-RISK) for 8 weeks. Insulin secretion was assessed from glucagon stimulation tests (GST) and mixed-meal tolerance tests (MMTT) before and after dietary intervention.

RESULTS

Both diets resulted in comparable reduction of fasting concentrations of insulin (H-RISK -28% vs. L-RISK -32%, both p < 0.01), C-peptide (H-RISK -26% vs. L-RISK -30%, both p < 0.01) and blood glucose (H-RISK -6.8%, p < 0.05 vs. L-RISK -10%, p < 0.01). Gastric inhibitory peptide (GIP) secretion increased by 24% after 8 weeks in the L-RISK only (p < 0.01). However, GST and MMTT showed no differences in insulin secretion after intervention.

CONCLUSIONS

Calorie restriction independent of the intake of fiber, coffee or meat failed to improve beta-cell function, but improved GIP secretion in obese patients with type 2 diabetes.

TRIAL REGISTRATION

Registration at Clinicaltrials.gov, Identifier number: NCT01409330, Registered 4 August 2011 - Retrospectively registered.

Postprandial glucose-lowering effect of premeal consumption of protein-enriched, dietary fiber-fortified bar in individuals with type 2 diabetes mellitus or normal glucose tolerance

AIMS/INTRODUCTION

Protein preload improves postprandial glycemia by stimulating secretion of insulin and incretin hormones. However, it requires a large dose of protein to produce a significant effect. The present study was carried out to investigate the postprandial glucose-lowering effect of a premeal protein-enriched, dietary fiber-fortified bar (PFB), which contains moderate amounts of protein, in individuals with type 2 diabetes mellitus or normal glucose tolerance (NGT).

MATERIALS AND METHODS

The participants (15 type 2 diabetes mellitus and 15 NGT) were randomly assigned to either a premeal or postmeal PFB group and underwent two mixed meal tolerance tests, 1 week apart in reverse order. Plasma levels of glucose, insulin, glucagon-like peptide-1 and glucose-dependent insulinotropic polypeptide were measured.

RESULTS

During the mixed meal tolerance tests, the incremental area under the curve from 0 to 180 min of plasma glucose levels was lower with premeal PFB than with postmeal PFB in the type 2 diabetes mellitus (14,723 ± 1,310 mg min/dL vs 19,642 ± 1,367 mg min/dL; P = 0.0002) and NGT participants (3,943 ± 416 mg min/dL vs 4,827 ± 520 mg min/dL, P = 0.0296). In the type 2 diabetes mellitus participants, insulinogenic index and the incremental area under the curve from 0 to 180 min of plasma total glucagon-like peptide-1 levels were higher with premeal PFB than with postmeal PFB, but not in the NGT participants. There was no difference in postprandial glucose-dependent insulinotropic polypeptide levels between premeal and postmeal PFB in both groups.

CONCLUSIONS

Acute administration of premeal PFB decreased postprandial glucose excursion in both type 2 diabetes mellitus and NGT participants. In the type 2 diabetes mellitus participants, premeal PFB augmented the early-phase insulin secretion, possibly through enhancing glucagon-like peptide-1 secretion.