Role of resistant starch on diabetes risk factors in people with prediabetes: Design, conduct, and baseline results of the STARCH trial

The colloid and interface strategies to inhibit lipid digestion for designing low-calorie food

Although fat is one of the indispensable components of food flavor, excessive fat consumption could cause obesity, metabolism syndromes and an imbalance in the intestinal flora. In the pursuit of a healthy diet, designing fat reducing foods by inhibiting lipid digestion and calorie intake is a promising strategy. Altering the gastric emptying rates of lipids as well as acting on the lipase by suppressing the enzymatic activity or limiting lipase diffusion via interfacial modulation can effectively decrease lipolysis rates. In this review, we provide a comprehensive overview of colloid-based strategies that can be employed to retard lipid hydrolysis, including pancreatic lipase inhibitors, emulsion-based interfacial modulation and fat substitutes. Plants-/microorganisms-derived lipase inhibitors bind to catalytic active sites and change the enzymatic conformation to inhibit lipase activity. Introducing oil-in-water Pickering emulsions into the food can effectively delay lipolysis via steric hindrance of interfacial particulates. Regulating stability and physical states of emulsions can also affect the rate of hydrolysis by altering the active hydrolysis surface. 3D network structure assembled by fat substitutes with high viscosity can not only slow down the peristole and obstruct the diffusion of lipase to the oil droplets but also impede the transportation of lipolysis products to epithelial cells for adsorption. Their applications in low-calorie bakery, dairy and meat products were also discussed, emphasizing fat intake reduction, structure and flavor retention and potential health benefits. However, further application of these strategies in large-scale food production still requires more optimization on cost and lipid reducing effects. This review provides a comprehensive review on colloidal approaches, design, principles and applications of fat reducing strategies to meet the growing demand for healthier diet and offer practical insights for the low-calorie food industry.

The waxy mutation in sorghum and other cereal grains reshapes the gut microbiome by reducing levels of multiple beneficial species

Waxy starches from cereal grains contain >90% amylopectin due to naturally occurring mutations that block amylose biosynthesis. Waxy starches have unique organoleptic characteristics (e.g. sticky rice) as well as desirable physicochemical properties for food processing. Using isogenic pairs of wild type sorghum lines and their waxy derivatives, we studied the effects of waxy starches in the whole grain context on the human gut microbiome. In vitro fermentations with human stool microbiomes show that beneficial taxonomic and metabolic signatures driven by grain from wild type parental lines are lost in fermentations of grain from the waxy derivatives and the beneficial signatures can be restored by addition of resistant starch. These undesirable effects are conserved in fermentations of waxy maize, wheat, rice and millet. We also demonstrate that humanized gnotobiotic mice fed low fiber diets supplemented with 20% grain from isogenic pairs of waxy vs. wild type parental sorghum have significant differences in microbiome composition and show increased weight gain. We conclude that the benefits of waxy starches on food functionality can have unintended tradeoff effects on the gut microbiome and host physiology that could be particularly relevant in human populations consuming large amounts of waxy grains.

Dietary Nonstarch Polysaccharide Intake and Risk of Colorectal Cancer: Findings from the Singapore Chinese Health Study

Dietary fiber or non-starch polysaccharides (NSP) may provide protection from CRC development. Epidemiologic studies on the association between dietary fiber and CRC is inconsistent are limited on NSP as a modifiable risk factor. Using the Singapore Chinese Health Study, a population-based prospective cohort of 61,321 cancer-free middle-aged or older Chinese Singaporeans, we examined the association between dietary fiber and NSP intakes and CRC risk. Fiber and NSP intakes at baseline were obtained using a validated semi-quantitative food frequency questionnaire coupled with the Singapore Food Composition Database. Cox proportional hazard regression model was used to estimate the hazard ratios (HRs) and respective 95% confidence intervals (CIs) for CRC associated with dietary fiber and NSP intakes after adjusting for potential confounders. After an average of 17.5 years of follow-up, 2,140 participants developed CRC. NSP was inversely associated with the risk of CRC in a dose-dependent manner whereas dietary fiber was not associated with risk of CRC overall or histologic subtypes. The multivariable-adjusted HRs (95% CIs) of CRC for quartiles 2, 3 and 4 of dietary NSP intake were 0.99 (0.88-1.11), 0.98 (0.87-1.11) and 0.84 (0.73-0.95), respectively, compared with the lowest quartile (P _trend =0.006). This inverse association was more apparent for colon cancer (HR_{Q4 vs. Q1}=0.79, 95% CI: 0.67-0.93, P _trend =0.003) than rectal cancer (HR _{Q4 vs. Q1}=0.92, 95% CI: 0.74-1.13, P _trend =0.53). Our findings suggested that dietary NSP but not fiber is associated with a reduced risk of colon cancer in Chinese Singaporeans.

Significance

Non-starch polysaccharides may be beneficial for colorectal cancer primary prevention.

Prebiotics as a Tool for the Prevention and Treatment of Obesity and Diabetes: Classification and Ability to Modulate the Gut Microbiota

Diabetes and obesity are metabolic diseases that have become alarming conditions in recent decades. Their rate of increase is becoming a growing concern worldwide. Recent studies have established that the composition and dysfunction of the gut microbiota are associated with the development of diabetes. For this reason, strategies such as the use of prebiotics to improve intestinal microbial structure and function have become popular. Consumption of prebiotics for modulating the gut microbiota results in the production of microbial metabolites such as short-chain fatty acids that play essential roles in reducing blood glucose levels, mitigating insulin resistance, reducing inflammation, and promoting the secretion of glucagon-like peptide 1 in the host, and this accounts for the observed remission of metabolic diseases. Prebiotics can be either naturally extracted from non-digestible carbohydrate materials or synthetically produced. In this review, we discussed current findings on how the gut microbiota and microbial metabolites may influence host metabolism to promote health. We provided evidence from various studies that show the ability of prebiotic consumption to alter gut microbial profile, improve gut microbial metabolism and functions, and improve host physiology to alleviate diabetes and obesity. We conclude among other things that the application of systems biology coupled with bioinformatics could be essential in ascertaining the exact mechanisms behind the prebiotic–gut microbe–host interactions required for diabetes and obesity improvement.

Effects of high-amylose maize starch on the glycemic index of Chinese steamed buns (CSB)

The incorporation of resistant starch (RS) in food has gained importance to be a good replacement for digestible carbohydrate. This study examined the effect of compositing RS (high-amylose maize starch (HM)) as wheat flour substitute (30%) in Chinese steamed bun (CSB) formulation on postprandial glycemic response in healthy human subject. In this single-blind and cross-over experimental trial, a total of 15 female participants (mean age = 31.5 ± 3.9) were randomly assigned to receive CSB containing 30% HM (HM30) or control CSB (without HM) with their blood glucose were recorded throughout the test. The blood glucose concentrations recorded for HM30 were significantly lower than control CSB at 15 min (6.03 vs. 7.04 mmol/L, p = 0.041), 30 min (6.93 vs. 7.76 mmol/L, p = 0.021), 45 min (6.21 vs. 7.55 mmol/L, p = 0.032), 60 min (5.68 vs. 6.26 mmol/L, p = 0.038), and 90 min (5.08 vs. 5.73 mmol/L, p = 0.022). The 2-h postprandial glucose was significantly lower in HM30 (iAUC = 105.2 mmol x min/L) than the control (186.1 mmol x min/L). The low GI property of HM30 (GI = 39.11 ± 5.6) did not cause sudden rapid increase in blood glucose concentration as observed in medium-GI control CSB (GI = 69.18 ± 9.8). This study suggests that adding 30g of HM decreased the glycemic index of CSB in healthy female adult.

Ectopic fat deposition in populations of black African ancestry: A systematic review and meta-analysis

AIMS

In populations of black African ancestry (BA), a paradox exists whereby lower visceral adipose tissue is found despite their high risk for type 2 diabetes (T2D). This systematic review investigates ethnic differences in other ectopic fat depots (intrahepatic lipid: IHL; intramyocellular lipid: IMCL and intrapancreatic lipid; IPL) to help contextualise their potential contribution to T2D risk.

METHODS

A systematic literature search was performed in December 2020 to identify studies reporting at least one ectopic fat comparison between BA and one/more other ethnicity. For IHL, a meta-analysis was carried out with studies considered comparable based on the method of measurement.

RESULTS

Twenty-eight studies were included (IHL: n = 20; IMCL: n = 8; IPL: n = 4). Meta-analysis of 11 studies investigating IHL revealed that it was lower in BA populations vs pooled ethnic comparators (MD -1.35%, 95% CI -1.55 to -1.16, I² = 85%, P < 0.00001), white European ancestry (MD -0.94%, 95% CI -1.17 to -0.70, I² = 79%, P < 0.00001), Hispanic ancestry (MD -2.06%, 95% CI -2.49 to -1.63, I² = 81%, P < 0.00001) and South Asian ancestry comparators (MD -1.92%, 95% CI -3.26 to -0.57, I² = 78%, P = 0.005). However, heterogeneity was high in all analyses. Most studies found no significant differences in IMCL between BA and WE. Few studies investigated IPL, however, indicated that IPL is lower in BA compared to WE and HIS.

CONCLUSION

The discordance between ectopic fat and greater risk for T2D in BA populations raises questions around its contribution to T2D pathophysiology in BA.

Effects of Differences in Resistant Starch Content of Rice on Intestinal Microbial Composition

The aim of this study was to evaluate the effects of resistant starch (RS) and fat levels on the gut microbiome in C57BL/6 mice. Three levels of RS from three varieties of rice were the major source of carbohydrates and fat levels were low (10%) and high (39%). We confirmed that RS decreased the Firmicutes to Bacteroidetes ratio, increased SCFA production by higher Bacteroidaceae and S24-7 abundance, and enriched predicted gene families of glycosidases and functional pathways associated with carbohydrate and glycan metabolism. We also found correlations between microbial taxa and tissue gene expression related to carbohydrate and lipid metabolism. Moreover, increasing RS levels resulted in a molecular ecological network with enhanced modularity and interspecific synergy, which is less sensitive to high fat intervention. Overall, RS as low as 0.44% from cooked rice can modulate gut microbiome in mice, which correlated to a protective effect against deleterious effects of an obesogenic diet.

Effects of Rice with Different Amounts of Resistant Starch on Mice Fed a High-Fat Diet: Attenuation of Adipose Weight Gain

Increasing the amount of resistant starch (RS) in the diet may confer protective effects against chronic diseases. Rice, a good dietary source of carbohydrates, also contains RS. However, it remains unclear if RS at the amount consumed in cooked rice has a health benefit. To address the question, we examined the effects of cooked rice containing different levels of RS in a diet-induced obesity rodent model. Rice containing RS as low as 1.07% attenuated adipose weight and adipocyte size gain, induced by a moderately high-fat (HF) diet, which correlated with lower leptin levels in plasma and adipose tissue. Rice with 8.61% RS increased fecal short-chain fatty acid levels, modulated HF-diet-induced adipose triacylglycerol metabolism and inflammation-related gene expression, and increased fecal triglyceride excretion. Hence, including rice with RS level at ≥1.07% may attenuate risks associated with the consumption of a moderately HF diet.

Effects of potato resistant starch intake on insulin sensitivity, related metabolic markers and appetite ratings in men and women at risk for type 2 diabetes: a pilot cross-over randomised controlled trial

Background

The intake of certain types of resistant starch (RS) has been associated in some studies with increased whole‐body insulin sensitivity. This randomised, cross‐over pilot trial evaluated the effect of consuming cooked, then chilled potatoes, a source of RS, compared to isoenergetic, carbohydrate (CHO)‐containing control foods, on insulin sensitivity and related markers.

Methods

Nineteen adults with body mass index 27.0‐39.9 kg m⁻² consumed 300 g day⁻¹ RS‐enriched potatoes (approximately two potatoes; ~18 g RS) or CHO‐based control foods, as part of lunch, evening and snack meals, over a 24‐h period. After an overnight fast, insulin sensitivity, CHO metabolism markers, free fatty acids, breath hydrogen levels and appetite were assessed for up to 5 h after the intake of a standard breakfast. The primary endpoint was insulin sensitivity, assessed with the Matsuda index. P < 0.05 (one‐sided) was considered statistically significant.

Results

Insulin sensitivity was not significantly different between the potato and control conditions. The potato intervention resulted in higher postprandial breath hydrogen (P = 0.037), lower postprandial free fatty acid concentrations (P = 0.039) and lower fasting plasma glucose (P = 0.043) compared to the control condition. Fullness ratings were significantly lower after potato versus control (P = 0.002). No other significant effects were observed; however, there was a trend toward lower fasting insulin (P = 0.077) in the potato versus the control condition.

Conclusions

The results of this pilot study suggest RS‐enriched potatoes may have a favourable impact on carbohydrate metabolism and support the view that additional research in a larger study sample is warranted.

A P4 Medicine Perspective of Gut Microbiota and Prediabetes: Systems Analysis and Personalized Intervention

Type 2 diabetes (T2D) accounts for approximately 90% of diabetes worldwide and has become a global public health problem. Generally, individuals go to hospitals and get healthcare only when they have obvious T2D symptoms. While the underlying cause and mechanism of the disease are usually not well understood, treatment is for the symptoms, but not for the disease cause, and patients often continue to progress with more symptoms. Prediabetes is the early stage of diabetes and provides a good time window for intervention and prevention. However, with few symptoms, prediabetes is usually ignored without any treatment. Obviously, it is far from ideal to rely on the traditional medical system for diabetes healthcare. As a result, the medical system must be transformed from a reactive approach to a proactive approach. Root cause analysis and personalized intervention should be conducted for patients with prediabetes. Based on systems medicine, also known as P4 medicine, with a predictive, preventive, personalized, and participatory approach, new medical system is expected to significantly promote the prevention and treatment of chronic diseases such as prediabetes and diabetes. Many studies have shown that the occurrence and development of diabetes is closely related to gut microbiota. However, the relationship between diabetes and gut microbiota has not been fully elucidated. This review describes the research on the relationship between gut microbiota and diabetes and some exploratory trials on the interventions of prediabetes based on P4 medicine model. Furthermore, we also discussed how these findings might influence the diagnosis, prevention and treatment of diabetes in the future, thereby to improve the wellness of human beings.

Resistant Starch Content in Foods Commonly Consumed in the United States: A Narrative Review

Resistant starch (RS; types 1 to 5) cannot be digested in the small intestine and thus enters the colon intact, with some types capable of being fermented by gut microbes. As a fiber, types 1, 2, 3, and 5 are found naturally in foods, while types 2, 3, and 4 can be added to foods as a functional ingredient. This narrative review identifies RS content in whole foods commonly consumed in the United States. Scientific databases (n=3) were searched by two independent researchers. Ninety-four peer-reviewed articles published between 1982 and September 2018 were selected in which the RS was quantified and the food preparation method before analysis was suitable for consumption. The RS from each food item was adjusted for moisture if the RS value was provided as percent dry weight. Each food item was entered into a database according to food category, where the weighted mean±weighted standard deviation was calculated. The range of RS values and overall sample size for each food category were identified. Breads, breakfast cereals, snack foods, bananas and plantains, grains, pasta, rice, legumes, and potatoes contain RS. Foods that have been cooked then chilled have higher RS than cooked foods. Foods with higher amylose concentrations have higher RS than native varieties. The data from this database will serve as a resource for health practitioners to educate and support patients and clients interested in increasing their intake of RS-rich foods and for researchers to formulate dietary interventions with RS foods and examine associated health outcomes.

Resistant Starch Has No Effect on Appetite and Food Intake in Individuals with Prediabetes

BACKGROUND

Type 2 resistant starch (RS2) has been shown to improve metabolic health outcomes and may increase satiety and suppress appetite and food intake in humans.

OBJECTIVE

This study assessed whether 12 weeks of daily RS2 supplementation could influence appetite perception, food intake, and appetite-related gut hormones in adults with prediabetes, relative to the control (CTL) group.

DESIGN

The study was a randomized controlled trial and analysis of secondary study end points.

PARTICIPANTS/SETTING

Sixty-eight adults (body mass index ≥27) aged 35 to 75 years with prediabetes were enrolled in the study at Pennington Biomedical Research Center (2012 to 2016). Fifty-nine subjects were included in the analysis.

INTERVENTION

Participants were randomized to consume 45 g/day of high-amylose maize (RS2) or an isocaloric amount of the rapidly digestible starch amylopectin (CTL) for 12 weeks.

MAIN OUTCOME MEASURES

Subjective appetite measures were assessed via visual analogue scale and the Eating Inventory; appetite-related gut hormones (glucagon-like peptide 1, peptide YY, and ghrelin) were measured during a standard mixed-meal test; and energy and macronutrient intake were assessed by a laboratory food intake (buffet) test, the Remote Food Photography Method, and SmartIntake app.

STATISTICAL ANALYSES PERFORMED

Data were analyzed using linear mixed models, adjusting for treatment group and time as fixed effects, with a significance level of α=.05.

RESULTS

RS2 had no effect on subjective measures of appetite, as assessed by visual analogue scale (P>0.05) and the Eating Inventory (P≥0.24), relative to the CTL group. There were no effects of RS2 supplementation on appetite-related gut hormones, including glucagon-like peptide 1 (P=0.61), peptide YY (P=0.34), and both total (P=0.26) and active (P=0.47) ghrelin compared with the CTL. RS2 had no effect on total energy (P=0.30), carbohydrate (P=0.11), protein (P=0.64), or fat (P=0.37) consumption in response to a buffet meal test, relative to the CTL. In addition, total energy (P=0.40), carbohydrate (P=0.15), protein (P=0.46), and fat (P=0.53) intake, as quantified by the Remote Food Photography Method, were also unaffected by RS2, relative to the CTL.

CONCLUSIONS

RS2 supplementation did not increase satiety or reduce appetite and food intake in adults with prediabetes.

Preparation and characterization of resistant starch type III from enzymatically hydrolyzed maize flour

Polysaccharides including resistant starch are categorized as dietary fiber and are used as an important prebiotic. Similar to soluble fibers, resistant starch also has a number of physiological effects that have been shown to be beneficial for health. Starch hydrolyzing enzymes, most importantly amylases, play essential roles in the production of resistant starch. This study aimed to develop α-amylase-treated maize flour with slow digestibility and unique physicochemical characteristics compared to native maize flour. In the current study, resistant starch type III from maize flour was prepared using α-amylase obtained from indigenously isolated Bacillus licheniformis. The α-amylase gene from B. licheniformis was amplified and cloned into the pET-24(a) vector, expressed in E. coli BL21 (DE3) cells and purified by metal ion affinity chromatography. The purified enzyme enhanced the yield of resistant starch 16-fold in maize flour. Scanning electron microscopy revealed that the granular structure of maize flour was disrupted into a dense network with irregular structure, and X-ray diffractograms confirmed the transformation from an amorphous to a crystalline structure upon α-amylase treatment. Thermogravimetric analysis revealed increased amylose content of α-amylase-treated maize flour. Moreover, α-amylase-treated maize flour resulted in a significant enhancement of the desired properties of maize flour, such as resistant starch content, amylose, milk absorption capacity, and iodine and fatty acid complexing ability, and a reduction in swelling power, water binding, oil absorption capacity, and in vitro digestibility compared to untreated maize flour. Resistant starch type III showed low digestibility and increased complexing ability with iodine and fatty acid and therefore could be a safe and beneficial alternative as a coating material for the delivery of active, sensitive ingredients to the colon.

Effect of 12 wk of resistant starch supplementation on cardiometabolic risk factors in adults with prediabetes: a randomized controlled trial

Background

Type 2 resistant starch (RS2) has been shown to improve glycemic control and some cardiovascular endpoints in rodent and human studies.

Objective

The aim of this study was to perform one of the first randomized clinical trials in adults with prediabetes and one of the longest trials to test whether RS2 can improve cardiometabolic health.

Design

68 overweight [body mass index (BMI) ≥27 kg/m2] adults aged 35-75 y with prediabetes were randomized to consume 45 g/d of high-amylose maize (RS2) or an isocaloric amount of the rapidly digestible starch amylopectin (control) for 12 wk. At baseline and postintervention, ectopic fat depots (visceral adipose tissue, intrahepatic lipids, and intramyocellular lipids) were measured by magnetic resonance imaging/spectroscopy, energy metabolism by respiratory chamber, and carbohydrate metabolism by glycated hemoglobin (HbA1c), an intravenous glucose tolerance test, and a meal tolerance test. Cardiovascular risk factors-serum lipids, blood pressure, heart rate, and inflammatory markers (high-sensitivity C-reactive protein [hs-CRP], interleukin-6, and tumor necrosis factor [TNF]-α)-were also measured. The primary endpoints were insulin sensitivity, insulin secretion, ectopic fat, and markers of inflammation. Data were primarily analyzed as treatment effects via a linear mixed model both with and without the addition of covariates.

Results

Relative to the control group, RS2 lowered HbA1c by a clinically insignificant 0.1 ± 0.2% (Δ = -1 ± 2 mmol/mol; P = 0.05) but did not affect insulin secretion, insulin sensitivity, the disposition index, or glucose or insulin areas under the curve relative to baseline (P ≥ 0.23). RS2 decreased heart rate by 5 ± 9 beats/min (P = 0.02) and TNF-α concentrations by 2.1 ± 2.7 pg/mL (P = 0.004), relative to the control group. Ectopic fat, energy expenditure, substrate oxidation, and all other cardiovascular risk factors were unaffected (P ≥ 0.06).

Conclusions

12 wk of supplementation with resistant starch reduced the inflammatory marker TNF-α and heart rate, but it did not significantly improve glycemic control and other cardiovascular disease risk factors, in adults with prediabetes. This trial was registered at clinicaltrials.gov as NCT01708694.