Higher dietary flavonol intake is associated with lower incidence of type 2 diabetes

Higher dietary flavonol and isoflavonoid intakes are associated with lower incidence of type 2 diabetes

Background: Adequate evidence supports beneficial effects of plant-derived phytochemicals against type 2 diabetes (T2D). Among phytochemicals, dietary flavonoids is one of the superb candidates. The whole studies are carried out in Western populations, so it is needed to investigate the risk of T2D by dietary flavonoid intakes in ethnic origins and other regions to confirm these relations. This study was conducted to investigate whether the daily consumption of total flavonoid and its subclasses can affect the incidence of type 2 diabetes (T2D) in the Iranian population. Methods: Eligible adults (n=6547) were selected from among participants of the Tehran lipid and glucose study with an average follow-up of 3.0 years. Dietary intakes were assessed using a valid and reliable 168-item semi-quantitative food frequency questionnaire. Multivariate Cox proportional hazard regression models were used to estimate the development of T2D in relation to total intake of flavonoids. Results: This study was conducted on 2882 men and 3665 women, aged 41.3±14.6 and 39.0±13.4 years, respectively. After adjustment for several potential confounders (age, sex, diabetes risk score, physical activity, energy, fiber and total fat intakes), risk of T2D decreased from tertiles 1 to 3 for flavonols (HR (95% CI): 1.00, 0.86 (0.64-1.16), 0.87 (0.63-0.93), Ptrend=0.01) and isoflavonoids (HR (95% CI): 1.00, 0.84 (0.62-1.13), 0.64 (0.46-0.88), Ptrend=0.02), whereas non-significant results were found for total flavonoid and other subclasses of flavonoid. Conclusion: These results emphasize the potential protective role of flavonols and isoflavonoids rich food (e.g. apple, tea, soy, and dark chocolate) in the prevention of T2D.

The association of dietary total flavonoids and their subclasses with the risk of type 2 diabetes: a prospective cohort study

BACKGROUND

Data from mechanistic studies suggest flavonoids may benefit glucose metabolism, but their associations with type 2 diabetes (T2D) remain unclear. This study examined the prospective associations of dietary intake of total, classes, and individual flavonoids, as well as their source foods, with T2D in the CArdioVascular disease Association Study (CAVAS).

METHODS

A total of 16,666 Korean men and women were enrolled at baseline, and 953 were newly diagnosed with T2D over a median follow-up of 5.96 years. Intake of flavonoids was cumulatively averaged using all food frequency questionnaires before the censoring events. A Poisson regression model was used to estimate incidence rate ratios (IRRs) and 95% confidence intervals (CIs).

RESULTS

Women with higher total flavonoid, flavonol, isoflavone, and proanthocyanidin intake had a lower risk of T2D (fourth vs. first quartile, IRR 0.62; 95% CI 0.44-0.89; P for linearity and non-linearity < 0.05 for total flavonoids), while in men, flavanones, anthocyanins, and proanthocyanidins, but not total flavonoids, were inversely associated with T2D risk (all P interaction for sex > 0.05). The key source foods contributing to flavonoid intake were also different between men and women, except for apples: tangerines and strawberries in men and green leafy vegetables and soy products in women.

CONCLUSIONS

A higher intake of total flavonoids, particularly from vegetables, soybeans, and apples, may be associated with lower risk of T2D in women. However, flavonoids from fruits, rather than total flavonoids, may be inversely associated in men. The association between flavonoid intake and the risk of T2D may be contingent upon the dietary sources of flavonoids consumed.

Physiologic effects of the maqui berry (Aristotelia chilensis): a focus on metabolic homeostasis

The prevalence and socioeconomic impact of metabolic diseases is rapidly growing. The limited availability of effective and affordable treatments has fuelled interest in the therapeutic potential of natural compounds as they occur in selected food sources. These compounds might help to better manage the current problems of treatment availability, affordability, and adverse effects that, in combination, limit treatment duration and efficacy at present. Specifically, berries garnered interest given a strong epidemiological link between their consumption and improved metabolic functions, making the analysis of their phytochemical composition and the identification and characterization of biologically active ingredients an emerging area of research. In this regard, the present review focuses on the South American maqui berry Aristotelia chilensis, which has been extensively used by the indigenous Mapuche population for generations to treat a variety of disease conditions. An overview of the maqui plant composition precedes a review of pre-clinical and clinical studies that investigated the effects of maqui berries and their major components on metabolic homeostasis. The final part of the review highlights possible technologies to conserve maqui berry structural and functional integrity during passage through the small intestine, ultimately aiming to augment their systemic and luminal bioavailability and biological effects. The integration of the various aspects discussed herein can assist in the development of effective maqui-based therapies to benefit the growing population of metabolically compromised patients.

Flavonols as a Potential Pharmacological Intervention for Alleviating Cognitive Decline in Diabetes: Evidence from Preclinical Studies

Diabetes mellitus is a complex metabolic disease associated with reduced synaptic plasticity, atrophy of the hippocampus, and cognitive decline. Cognitive impairment results from several pathological mechanisms, including increased levels of advanced glycation end products (AGEs) and their receptors, prolonged oxidative stress and impaired activity of endogenous mechanisms of antioxidant defense, neuroinflammation driven by the nuclear factor kappa-light-chain enhancer of activated B cells (NF-κB), decreased expression of brain-derived neurotrophic factor (BDNF), and disturbance of signaling pathways involved in neuronal survival and cognitive functioning. There is increasing evidence that dietary interventions can reduce the risk of various diabetic complications. In this context, flavonols, a highly abundant class of flavonoids in the human diet, are appreciated as a potential pharmacological intervention against cognitive decline in diabetes. In preclinical studies, flavonols have shown neuroprotective, antioxidative, anti-inflammatory, and memory-enhancing properties based on their ability to regulate glucose levels, attenuate oxidative stress and inflammation, promote the expression of neurotrophic factors, and regulate signaling pathways. The present review gives an overview of the molecular mechanisms involved in diabetes-induced cognitive dysfunctions and the results of preclinical studies showing that flavonols have the ability to alleviate cognitive impairment. Although the results from animal studies are promising, clinical and epidemiological studies are still needed to advance our knowledge on the potential of flavonols to improve cognitive decline in diabetic patients.

Anthocyanins' effects on diabetes mellitus and islet transplantation

The incidence of diabetes mellitus is dramatically increasing every year, causing a huge global burden. Moreover, existing anti-diabetic drugs inevitably bring adverse reactions, and the application of islet transplantation is often limited by the damage caused by oxidative stress after transplantation. Thus, new approaches are needed to combat the growing burden of diabetes mellitus. Anthocyanins are of great nutritional interest and have been documented that have beneficial effects on chronic diseases, including diabetes mellitus. Here, we describe the health effects of anthocyanins on diabetes mellitus and islet transplantation. Epidemiological studies demonstrated that moderate intake of anthocyanins leading to a reduction in risk of diabetes mellitus. Numerous experiments both animal and clinical studies also showed positive effects of anthocyanins on prevention and treatment of diabetes and diabetic complications. These effects of anthocyanins may be related to mechanisms of improving glucose and lipid metabolism and insulin resistance, antioxidant, and anti-inflammatory activities. In addition, damage and function of pancreatic islets after transplantation are also improved by anthocyanins. These findings suggest that daily intake of anthocyanins may not only improve nutritional metabolism in healthy individuals to prevent from diabetes, but also as a supplementary treatment of diabetes mellitus and islet transplantation. Thus, more evidence is needed to better understand the potential health benefits of anthocyanins.

The associations between dietary flavonoid intake and the prevalence of diabetes mellitus: Data from the National Health and Nutrition Examination Survey 2007-2010 and 2017-2018

Background

Diabetes mellitus (DM) is a prominent health concern worldwide, leading to the high incidence of disability and mortality and bringing in heavy healthcare and social burden. Plant-based diets are reported associated with a reduction of DM risk. Plant-based diets are rich in flavonoids, which possess properties such as scavenging free radicals and exerting both anti-inflammatory and antioxidant effects.

Purpose

However, whether dietary flavonoids are associated with the prevalence of DM remains controversial. The potential reasons for contradictory epidemiological outcomes on the association between dietary flavonoids and DM prevalence have not been determined.

Methods

To address these limitations, we employed data from 22,481 participants in the National Health and Nutrition Examination Survey to explore the association between the intake of flavonoids and DM prevalence by weighted Logistic regression and weighted restricted cubic splines.

Results

We found that the prevalence of DM was inversely associated with the intake of total flavonoids in the second quartile [Odds Ratio (OR) 0.78 95% confidence interval (CI) (0.63, 0.97), p = 0.028], in the third quartile [0.76 (0.60, 0.97), p = 0.031], and in the fourth quartile [0.80 (0.65, 0.97), p = 0.027]. However, the p for trend was not significant [0.94 (0.88, 1.01), p = 0.096]. Moreover, the association between DM prevalence and the intake of total flavonoids was significantly influenced by race (p for interaction = 0.006). In Mexican Americans, there was a significant positive association between DM prevalence and total flavonoid intake within the third quartile [1.04 (1.02, 1.07), p = 0.003]. Total flavan-3-ol and subtotal catechin intake exhibited a non-linear U-shaped association with DM prevalence (p for non-linearity < 0.0001 and p for non-linearity < 0.0001, respectively). Compared to the first quartile of corresponding intakes, consumption within the third quartile of subtotal catechins [0.70 (0.55, 0.89), p = 0.005] and total flavan-3-ols [0.65 (0.50, 0.84), p = 0.002] was associated with a lower prevalence of DM.

Conclusion

Taken together, our study may provide preliminary research evidence for personalized improvement of dietary habits to reduce the prevalence of diabetes.

Apigenin Alleviates Endoplasmic Reticulum Stress-Mediated Apoptosis in INS-1 β-Cells

The improvement of type 2 diabetes mellitus induced by naturally occurring polyphenols, known as flavonoids, has received considerable attention. However, there is a dearth of information regarding the effect of the trihydroxyflavone apigenin on pancreatic β-cell function. In the present study, the anti-diabetic effect of apigenin on pancreatic β-cell insulin secretion, apoptosis, and the mechanism underlying its anti-diabetic effects, were investigated in the INS-ID β-cell line. The results showed that apigenin concentration-dependently facilitated 11.1-mM glucose-induced insulin secretion, which peaked at 30 µM. Apigenin also concentration-dependently inhibited the expression of endoplasmic reticulum (ER) stress signaling proteins, CCAAT/enhancer binding protein (C/EBP) homologous protein (CHOP) and cleaved caspase-3, which was elevated by thapsigargin in INS-1D cells, with peak suppression at 30 µM. This was strongly correlated with the results of flow cytometric analysis of annexin V/propidium iodide (PI) staining and DNA fragmentation analysis. Moreover, the increased expression of thioredoxin-interacting protein (TXNIP) induced by thapsigargin was remarkably reduced by apigenin in a concentration-dependent manner. These results suggest that apigenin is an attractive candidate with remarkable and potent anti-diabetic effects on β-cells, which are mediated by facilitating glucose-stimulated insulin secretion and preventing ER stress-mediated β-cell apoptosis, the latter of which may be possibly mediated by reduced expression of CHOP and TXNIP, thereby promoting β-cell survival and function.

In Vitro α-Amylase and α-Glucosidase Inhibitory Activity of Green Seaweed Halimeda tuna Extract from the Coast of Lhok Bubon, Aceh

Seaweed belongs to marine biota and contains nutrients and secondary metabolites beneficial for health. This study aimed to determine the antidiabetic activity of extracts and fractions of green seaweed Halimeda tuna. The H. tuna sample was extracted with the maceration method using methanol and then partitioned using ethyl acetate and water to obtain ethyl acetate and water fractions. The methanol extract, ethyl acetate fraction, and water fraction of H. tuna were tested for their inhibitory activity against α-amilase and α-glucosidase. The methanol extract and the fractions with the highest inhibitory activity were phytochemically tested and analyzed using gas chromatography-mass spectrometry (GC-MS). The results showed that the ethyl acetate fraction (IC50 = 0.88 ± 0.20 mg/mL) inhibited α-amylase relatively similar to acarbose (IC50 = 0.76 ± 0.04 mg/mL). The methanol extract (IC50 = 0.05 ± 0.01 mg/mL) and the ethyl acetate fraction (IC50 = 0.01 ± 0.00 mg/mL) demonstrated stronger inhibitory activity against α-glucosidase than acarbose (IC50 = 0.27 ± 0.13 mg/mL). Phytochemical testing showed that the methanol extract and the ethyl acetate fraction contained secondary metabolites: alkaloids, flavonoids, steroids, and phenol hydroquinone. The compounds in methanol extract predicted to have inhibitory activity against α-amylase and α-glucosidase were Docosanol, Neophytadiene, Stigmasta-7,22-dien-3-ol,acetate,(3.beta.,5.alpha.,22E), Octadecanoic acid,2-oxo-,methyl ester, and phytol, while those in the ethyl acetate fraction were n-Nonadecane, Phytol, Butyl ester, 14-.Beta.-H-pregna, Octadecenoic acid, and Oleic acid.

Total dietary flavonoid intake and risk of cardiometabolic diseases: A dose-response meta-analysis of prospective cohort studies

Several epidemiological studies have suggested that flavonoid intake is associated with a decreased risk of cardiometabolic disease. However, the results remained inconsistent and there is no dose-response meta-analysis for specific outcomes. We conducted a meta-analysis to synthesize the knowledge about their associations and to explore their dose-response relationships. We comprehensively searched the PubMed, Embase, and Web of Science databases for prospective cohort studies published up to December 1, 2021. Summary relative risks (RR) and 95% confidence intervals (CI) were pooled for the association between flavonoid intake and cardiometabolic disease. Evaluations of linear or nonlinear dose-response were presented by restricted cubic splines. We identified 47 articles, including 1,346 676 participants and 127,507 cases in this meta-analysis. The summary of RR per 500 mg/d increase in flavonoid intake was 0.93 (95% CI 0.88-0.98) for cardiovascular disease, 0.89 (95% CI 0.84-0.94) for diabetes, and 0.97 (95% CI 0.94-0.99) for hypertension, respectively. We also found a linearity dose-response association between total flavonoid intake and cardiovascular disease (p nonlinearity = 0.541), and diabetes (p nonlinearity = 0.077). Our finding based on quantitative data suggested that a higher level of flavonoid intake is beneficial for the prevention of cardiometabolic diseases.

Dietary antioxidant consumption and the risk of type 2 diabetes in South Korean adults: a prospective cohort study based on the Health Examinees study

OBJECTIVES

Antioxidants are common dietary compounds with multiple health benefits. This study aimed to identify the association between dietary antioxidant consumption and the incidence of type 2 diabetes (T2D) mellitus (defined using the Korean Diabetes Association criteria) in South Korean adults.

DESIGN

Baseline and follow-up data from the Health Examinees (HEXA) study, a large-scale community-based genomic cohort study conducted in South Korea SETTING: A South Korean community.

PARTICIPANTS

A total of 20 594 participants, aged 40-79 years, who participated in the baseline and follow-up surveys of the HEXA study were included. After an average of 5 years of follow-up, there were 332 men and 360 women with T2D.

RESULTS

Participants with the highest total flavonoid consumption (Q5) had a lower risk of T2D (men: HR 0.63; 95% CI 0.42 to 0.93; p value for trend=0.0169; and women: HR 0.54; 95% CI 0.438 to 0.78; p value for trend=0.0001) than those with the lowest consumption (Q1). Dietary total antioxidant capacity was significantly inversely associated with the development of T2D mellitus in women participants alone (HR 0.58; 95% CI 0.40 to 0.83; p value for trend=0.0004). Stratified analyses according to age and body mass index (BMI) showed that dietary total flavonoid consumption and total antioxidant capacity had a negative association with the development of T2D in women aged >52 years and women with BMI >25 kg/m².

CONCLUSIONS

Dietary flavonoid consumption and total antioxidant capacity were associated with a lower risk of T2D in South Korean adults, especially in women aged >52 years and overweight. The findings of this study may provide reference data for the modification of dietary guidelines for South Koreans.

Fruit and vegetable intake and risk of prediabetes and type 2 diabetes: results from a 20-year long prospective cohort study in Swedish men and women

Purpose

To investigate the association between fruit and vegetable intake (FVI) and the risk of developing prediabetes and type 2 diabetes (T2D) in a Swedish prospective cohort study.

Methods

Subjects were 6961 men and women aged 35–56 years old at baseline, participating in the Stockholm Diabetes Prevention Program cohort. By design, the cohort was enriched by 50% with subjects that had family history of diabetes. Anthropometric measurements, oral glucose tolerance tests and questionnaires on lifestyle and dietary factors were carried out at baseline and two follow-up occasions. Cox proportional hazard models were used to estimate hazard ratios with 95% CIs.

Results

During a mean follow-up time of 20 ± 4 years, 1024 subjects developed T2D and 870 prediabetes. After adjustments for confounders, the highest tertile of total FVI was associated with a lower risk of developing T2D in men (HR 0.76, 95% CI 0.60–0.96). There was also an inverse association between total fruit intake and prediabetes risk in men, with the HR for the highest tertile being 0.76 (95% CI 0.58–1.00). As for subtypes, higher intake of apples/pears was inversely associated with T2D risk in both sexes, whereas higher intakes of banana, cabbage and tomato were positively associated with T2D or prediabetes risk in either men or women.

Conclusion

We found an inverse association between higher total FVI and T2D risk and between higher fruit intake and prediabetes risk, in men but not in women. Certain fruit and vegetable subtypes showed varying results and require further investigation.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00394-022-02871-6.

Adopting a High-Polyphenolic Diet Is Associated with an Improved Glucose Profile: Prospective Analysis within the PREDIMED-Plus Trial

Previous studies suggested that dietary polyphenols could reduce the incidence and complications of type-2 diabetes (T2D); although the evidence is still limited and inconsistent. This work analyzes whether changing to a diet with a higher polyphenolic content is associated with an improved glucose profile. At baseline, and at 1 year of follow-up visits, 5921 participants (mean age 65.0 ± 4.9, 48.2% women) who had overweight/obesity and metabolic syndrome filled out a validated 143-item semi-quantitative food frequency questionnaire (FFQ), from which polyphenol intakes were calculated. Energy-adjusted total polyphenols and subclasses were categorized in tertiles of changes. Linear mixed-effect models with random intercepts (the recruitment centers) were used to assess associations between changes in polyphenol subclasses intake and 1-year plasma glucose or glycosylated hemoglobin (HbA1c) levels. Increments in total polyphenol intake and some classes were inversely associated with better glucose levels and HbA1c after one year of follow-up. These associations were modified when the analyses were run considering diabetes status separately. To our knowledge, this is the first study to assess the relationship between changes in the intake of all polyphenolic groups and T2D-related parameters in a senior population with T2D or at high-risk of developing T2D.

Lowering the predicted glycemic index of pasta using dried onions as functional ingredients

Pasta is a commonly consumed food; adding some ingredients, maybe turn it into a functional food with health benefits. These ingredients consist of dietary fiber, antioxidant molecules, and enzyme inhibitor compounds, related to a reduced risk for some diseases. Onion (Allium cepa L.) is a rich source of bioactive compounds rendering it a relevant candidate for the production of functional foods. The present study examines the in vitro starch digestibility of durum wheat pasta supplemented with 3% onion flour. The incorporation of onion flour attenuated the extent of starch digestion and accordingly the area under the curve of reducing sugars discharged during in vitro digestion. The predicted glycemic index (pGI) of pasta supplemented with onion flour (3%) was significantly lower (pGI = 54 ± 0.17) than the control pasta (pGI = 72 ± 0.14). These results indicate that 3% onion fortified pasta represents a food with potential healthy properties, showing glucose-lowering capabilities in vitro.

Fruit and vegetable consumption and the risk of type 2 diabetes: a systematic review and dose-response meta-analysis of prospective studies

BACKGROUND

The association between intake of fruit and vegetables and their subtypes, and the risk of type 2 diabetes has been investigated in several studies, but the results have been inconsistent.

OBJECTIVE

We conducted an updated systematic review and dose-response meta-analysis of prospective studies on intakes of fruit and vegetables and fruit and vegetable subtypes and the risk of type 2 diabetes.

DESIGN

PubMed and Embase databases were searched up to 20 October 2020. Prospective cohort studies of fruit and vegetable consumption and type 2 diabetes mellitus were included. Summary relative risks (RRs) and 95% CIs were estimated using a random effects model.

RESULTS

We included 23 cohort studies. The summary RR for high versus low intake and per 200 g/day were 0.93 (95% CI: 0.89 to 0.98, I²=0%, n=10 studies) and 0.98 (95% CI: 0.95 to 1.01, I²=37.8%, n=7) for fruit and vegetables combined, 0.93 (95% CI: 0.90 to 0.97, I²=9.3%, n=20) and 0.96 (95% CI: 0.92 to 1.00, I²=68.4%, n=19) for fruits and 0.95 (95% CI: 0.88 to 1.02, I²=60.4%, n=17) and 0.97 (95% CI: 0.94 to 1.01, I²=39.2%, n=16) for vegetables, respectively. Inverse associations were observed for apples, apples and pears, blueberries, grapefruit and grapes and raisins, while positive associations were observed for intakes of cantaloupe, fruit drinks, fruit juice, brussels sprouts, cauliflower and potatoes, however, most of these associations were based on few studies and need further investigation in additional studies.

CONCLUSIONS

This meta-analysis found a weak inverse association between fruit and vegetable intake and type 2 diabetes risk. There is indication of both inverse and positive associations between intake of several fruit and vegetables subtypes and type 2 diabetes risk, however, further studies are needed before firm conclusions can be made.

Higher Habitual Flavonoid Intakes Are Associated with a Lower Incidence of Diabetes

BACKGROUND

Higher flavonoid intakes are hypothesized to confer protection against type 2 diabetes mellitus.

OBJECTIVES

We aimed to 1) investigate associations between flavonoid intakes and diabetes, 2) examine the mediating impact of body fat, and 3) identify subpopulations that may receive the greatest benefit from higher flavonoid intakes in participants of the Danish Diet, Cancer, and Health Study followed up for 23 y.

METHODS

Cross-sectional associations between baseline flavonoid intake, estimated using FFQs and the Phenol Explorer database, and body fat, estimated by bioelectrical impedance, were assessed using multivariable-adjusted linear regression models. Nonlinear associations between flavonoid intake and incident diabetes were examined using restricted cubic splines with multivariable-adjusted Cox proportional hazards models.

RESULTS

Among 54,787 participants (median age: 56 y; IQR: 52-60 y; 47.3% men), 6700 individuals were diagnosed with diabetes. Participants in the highest total flavonoid intake quintile (median, 1202 mg/d) had a 1.52 kg lower body fat (95% CI: -1.74, -1.30 kg) and a 19% lower risk of diabetes (HR: 0.81; 95% CI: 0.75, 0.87) after multivariable adjustments and compared with participants in the lowest intake quintile (median: 174 mg/d). Body fat mediated 57% (95% CI: 42, 83%) of the association between flavonoid intake and incident diabetes. Of the flavonoid subclasses, moderate to high intakes of flavonols, flavanol monomers, flavanol oligo + polymers, and anthocyanins were significantly associated with a lower risk of diabetes. Although associations were not modified by sex, smoking status, BMI, or physical activity (Pinteraction > 0.05 for all), findings on an absolute scale suggest that those at a higher risk (those with obesity) may benefit the most from a higher flavonoid intake.

CONCLUSIONS

The findings reported in this study suggest that a diet abundant in flavonoid-rich foods may help ameliorate diabetes risk, in part through a reduction in body fat.

Mineral Composition, Phenolic Content, and In Vitro Antidiabetic and Antioxidant Properties of Aqueous and Organic Extracts of Haloxylon scoparium Aerial Parts

Haloxylon scoparium is a plant widely used in traditional medicine for the treatment of diabetes. Hence, this study focuses on the mineralogical and chemical composition and evaluation of the antidiabetic and antioxidant activities of the aerial part of this species. The mineralogical analysis was done by inductively coupled plasma atomic emission spectrometry (ICP-AES). The phytochemical study consisted in the preparation of different extracts from the aerial part by aqueous and organic extraction using Soxhlet and cold maceration. Then, phytochemical screening was performed on the plant powder and on the extracts, which is completed by spectrophotometric quantification of total polyphenols, flavonoids, and catechic tannins. The evaluation of antidiabetic activity was done by three enzymes: a-amylase, a-glucosidase, and ß-galactosidase, and that of antioxidant activity was done by five methods: H₂O₂, DPPH, ABTS, FRAP, and reducing power (RP). Mineralogical analysis revealed the presence of iron, potassium, magnesium, phosphorus, sodium, copper, calcium, strontium, selenium, and zinc. The studied part is rich in alkaloids, flavonoids, catechic tannins, and saponins. The methanolic extract is rich in total polyphenols (161.65 ± 1.52 Ug EAG/mg E), and the ethyl acetate extract has high levels of catechic tannins (23.69 ± 0.6 Ug EC/mg E). In addition, the decoctate expresses a high flavonoid content of 306.59 ± 4.35 Ug EQ/mg E. The in vitro evaluation of the antidiabetic activity showed that the decoctate has a higher inhibitory capacity on a-glucosidase (IC50 = 181.7 ± 21.15 ug/mL) than acarbose (IC50 = 195 ± 6.12 ug/mL). The results of the antioxidant activity showed that the methanolic extract and the decoctate present a percentage of hydrogen peroxide (H₂O₂) scavenging (20.91 ± 0.27 and 16.21 ± 0.39%) higher than that of ascorbic acid (14.35 ± 0.002%). Positive correlations obtained between the total polyphenol content and the antioxidant activity of the extracts were studied. A positive correlation of a-amylase inhibitory activity was also recorded with the antioxidant activity tests.

Systematic bioinformatic analysis of nutrigenomic data of flavanols in cell models of cardiometabolic disease

Flavanol intake positively influences several cardiometabolic risk factors in humans. However, the specific molecular mechanisms of action of flavanols, in terms of gene regulation, in the cell types relevant to cardiometabolic disease have never been systematically addressed. On this basis, we conducted a systematic literature review and a comprehensive bioinformatic analysis of genes whose expression is affected by flavanols in cells defining cardiometabolic health: hepatocytes, adipocytes, endothelial cells, smooth muscle cells and immune cells. A systematic literature search was performed using the following pre-defined criteria: treatment with pure compounds and metabolites (no extracts) at low concentrations that are close to their plasma concentrations. Differentially expressed genes were analyzed using bioinformatics tools to identify gene ontologies, networks, cellular pathways and interactions, as well as transcriptional and post-transcriptional regulators. The systematic literature search identified 54 differentially expressed genes at the mRNA level in in vitro models of cardiometabolic disease exposed to flavanols and their metabolites. Global bioinformatic analysis revealed that these genes are predominantly involved in inflammation, leukocyte adhesion and transendothelial migration, and lipid metabolism. We observed that, although the investigated cells responded differentially to flavanol exposure, the involvement of anti-inflammatory responses is a common mechanism of flavanol action. We also identified potential transcriptional regulators of gene expression: transcriptional factors, such as GATA2, NFKB1, FOXC1 or PPARG, and post-transcriptional regulators: miRNAs, such as mir-335-5p, let-7b-5p, mir-26b-5p or mir-16-5p. In parallel, we analyzed the nutrigenomic effects of flavanols in intestinal cells and demonstrated their predominant involvement in the metabolism of circulating lipoproteins. In conclusion, the results of this systematic analysis of the nutrigenomic effects of flavanols provide a more comprehensive picture of their molecular mechanisms of action and will support the future setup of genetic studies to pave the way for individualized dietary recommendations.

Dietary Blueberry and Soluble Fiber Supplementation Reduces Risk of Gestational Diabetes in Women with Obesity in a Randomized Controlled Trial

BACKGROUND

Gestational diabetes mellitus (GDM) is a growing public health concern and maternal obesity and poor dietary intakes could be implicated. Dietary polyphenols and fiber mitigate the risk of diabetes and its complications, but little is known about their efficacy in preventing GDM.

OBJECTIVES

We examined the effects of whole blueberry and soluble fiber supplementation on primary outcomes of cardiometabolic profiles in women at high risk of developing GDM.

METHODS

Women (n = 34; mean ± SD age: 27 ± 5 y; BMI: 35.5 ± 4.0 kg/m2; previous history of GDM ∼56%; Hispanic ∼79%) were recruited in early pregnancy (<20 weeks of gestation) and randomly assigned to 1 of the following 2 groups for 18 wk: intervention (280 g whole blueberries and 12 g soluble fiber per day) and standard prenatal care (control). Both groups received nutrition education and maintained 24-h food recalls throughout the study. Data on anthropometrics, blood pressure, and blood samples for biochemical analyses were collected at baseline (<20 weeks), midpoint (24-28 weeks), and end (32-36 weeks) of gestation. Diagnosis of GDM was based on a 2-step glucose challenge test (GCT). Data were analyzed using a mixed-model ANOVA.

RESULTS

Maternal weight gain was significantly lower in the dietary intervention than in the control group at the end of the trial (mean ± SD: 6.8 ± 3.2 kg compared with 12.0 ± 4.1 kg, P = 0.001). C-reactive protein was also lower in the intervention than in the control group (baseline: 6.1 ± 4.0 compared with 6.8 ± 7.2 mg/L; midpoint: 6.1 ± 3.7 compared with 7.5 ± 7.3 mg/L; end: 5.5 ± 2.2 compared with 9.5 ± 6.6 mg/L, respectively, P = 0.002). Blood glucose based on GCT was lower in the intervention than in the control (100 ± 33 mg/dL compared with 131 ± 40 mg/dL, P < 0.05). Conventional lipids (total, LDL, and HDL cholesterol and triglycerides) did not differ between groups over time. No differences were noted in infant birth weight.

CONCLUSIONS

Whole blueberry and soluble fiber supplementation may prevent excess gestational weight gain and improve glycemic control and inflammation in women with obesity.This trial was registered at clinicaltrials.gov as NCT03467503.

The Perspective of Croatian Old Apple Cultivars in Extensive Farming for the Production of Functional Foods

The Republic of Croatia has a long tradition of fruit growing due to its geographical location, climatic conditions, and high quality of fruit crops, especially apple fruits. Apples can be used for the formulation of functional foods either in processed form (e.g., juice), or as a by-product (e.g., apple pomace). However, there is a growing demand for functional foods derived from ancient and traditional plant sources as they are recognized as a very valuable source of health-promoting bioactive ingredients. Similarly, old apple cultivars (Malus domestica Borkh.) are characterized by good morphological and pomological properties, less need for chemicals during cultivation and the higher share of biologically active compounds (BACs) with better sensory acceptability compared to commercial cultivars. However, their nutritional and biological potential is underestimated, as is their ability to be processed into functional food. The importance in preserving old apple cultivars can also be seen in their significance for improving the nutritional composition of other apple cultivars through innovative cultivation strategies, and therefore old local apple cultivars could be of great importance in future breeding programs.

Health promoting properties and sensory characteristics of phytochemicals in berries and leaves of sea buckthorn (Hippophaë rhamnoides)

Sea buckthorn (Hippophaë rhamnoides L., SB), as a multi-functional plant, is widely grown in Asia, Europe and Canada. The berries and leaves of SB contain a diverse array of health-supporting phytochemicals, which are also related to the sensory qualities of berry and berry products. This review summarizes the biologically active key-compounds of the berries and leaves of SB, their health-promoting effects, as well as the contributions to the sensory quality of the berries. The target compounds consist of sugars, sugar derivatives, organic acids, phenolic compounds and lipophilic compounds (mainly carotenoids and tocopherols), which play an important role in anti-inflammatory and antioxidant functions, as well as in metabolic health. In addition, these compounds contribute to the orosensory qualities of SB berries, which are closely related to consumer acceptance and preference of the products. Studies regarding the bioavailability of the compounds and the influence of the processing conditions are also part of this review. Finally, the role of the sensory properties is emphasized in the development of SB products to increase utilization of the berry as a common meal component and to obtain value-added products to support human health.

Daily and Not Every-Other-Day Intake of Anthocyanin-Rich New Zealand Blackcurrant Extract Alters Substrate Oxidation during Moderate-Intensity Walking in Adult Males

Daily intake of anthocyanin-rich New Zealand blackcurrant (NZBC) extract can enhance exercise-induced fat oxidation. It is not known whether habitual dietary anthocyanin intake and body composition affects blackcurrant-induced fat oxidation or even if daily intake is required. We examined effects of daily and every-other-day intake of NZBC extract on metabolic and physiological responses during moderate-intensity walking. Sixteen physically active males (age: 24 ± 6 yr, body mass: 78 ± 16 kg, BMI: 24.7 ± 4.2 kg·m^-2, body fat: 15.2 ± 5.0%) volunteered. A randomized, cross-over design with a control condition was used and habitual dietary anthocyanin intake quantified. For intake conditions, participants consumed two capsules of NZBC extract (i.e. 210 mg of anthocyanins, CurraNZ™) with breakfast daily or every-other-day for 14 days (14-D and 14-EOD) with 14-days washout. Final two capsules were taken 2-hr before the walk (speed: 5.7 ± 0.7 km·hr^-1). There was a trend for lower respiratory exchange ratio and carbohydrate oxidation with changes only for 14-D. Fat oxidation was increased only for 14-D (p < 0.05) with 50% of the participants more than a 10% change. In 14-D, there was a positive correlation for BMI and body fat % with the absolute change in fat oxidation but not with habitual dietary anthocyanin intake. Daily intake of NZBC extract is required to enhance exercise-induced fat oxidation. Enhanced exercise-induced fat oxidation by daily intake of NZBC extract is related to body composition but not to habitual dietary anthocyanin intake in physically active males. Daily anthocyanin intake seems to be required to allow the gradual build-up and maintenance of anthocyanin-derived metabolites that are required to alter mechanisms for exercise-induced substrate oxidation.

Consumption of whole purple and regular wheat modestly improves metabolic markers in adults with elevated high-sensitivity C-reactive protein: a randomised, single-blind parallel-arm study

Whole-grain wheat, in particular coloured varieties, may have health benefits in adults with chronic metabolic disease risk factors. Twenty-nine overweight and obese adults with chronic inflammation (high-sensitivity C-reactive protein) > 1·0 mg/l) replaced four daily servings of refined grain food products with bran-enriched purple or regular whole-wheat convenience bars (approximately 41-45 g fibre, daily) for 8 weeks in a randomised, single-blind parallel-arm study where body weight was maintained. Anthropometrics, blood markers of inflammation, oxidative stress, and lipaemia and metabolites of anthocyanins and phenolic acids were compared at days 1, 29 and 57 using repeated-measures ANOVA within groups and ANCOVA between groups at day 57, with day 1 as a covariate. A significant reduction in IL-6 and increase in adiponectin were observed within the purple wheat (PW) group. TNF-α was lowered in both groups and ferulic acid concentration increased in the regular wheat (RW) group. Comparing between wheats, only plasma TNF-α and glucose differed significantly (P < 0·05), that is, TNF-α and glucose decreased with RW and PW, respectively. Consumption of PW or RW products showed potential to improve plasma markers of inflammation and oxidative stress in participants with evidence of chronic inflammation, with modest differences observed based on type of wheat.

Why is sea buckthorn (Hippophae rhamnoides L.) so exceptional? A review

Sea buckthorn (Hippophae L.) is a valuable, multipurpose plant extensively grown in Asia, Europe and Canada. In order to use it in the best way for products of human nutrition, it is necessary to recognize its positive aspects and to eliminate the negative ones. The exceptional value of sea buckthorn can be seen in the presence of both lipophilic antioxidants (mainly carotenoids and tocopherols) and hydrophilic antioxidants (flavonoids, tannins, phenolic acids, ascorbic acid) in remarkably high quantities. Some of the main nutrients, especially lipids of advantageous fatty acid composition, contribute to nutritional benefits of sea buckthorn products for a consumer as well. This review article focuses, besides the above mentioned compounds and vitamins, also on other important components, such as sugars, sugar derivatives, fibre, organic acids, proteins, amino acids and mineral elements. The article also deals with the effects of sea buckthorn components on the course of non-enzymatic browning of food and in vivo glycation. In addition, sensory perception of sea buckthorn and its constituents from the consumers point of view is discussed.

Recent Research on the Health Benefits of Blueberries and Their Anthocyanins

Awareness of the human health benefits of blueberries is underpinned by a growing body of positive scientific evidence from human observational and clinical research, plus mechanistic research using animal and in vitro models. Blueberries contain a large number of phytochemicals, including abundant anthocyanin pigments. Of their various phytochemicals, anthocyanins probably make the greatest impact on blueberry health functionality. Epidemiological studies associate regular, moderate intake of blueberries and/or anthocyanins with reduced risk of cardiovascular disease, death, and type 2 diabetes, and with improved weight maintenance and neuroprotection. These findings are supported by biomarker-based evidence from human clinical studies. Among the more important healthful aspects of blueberries are their anti-inflammatory and antioxidant actions and their beneficial effects on vascular and glucoregulatory function. Blueberry phytochemicals may affect gastrointestinal microflora and contribute to host health. These aspects have implications in degenerative diseases and conditions as well as the aging process. More evidence, and particularly human clinical evidence, is needed to better understand the potential for anthocyanin-rich blueberries to benefit public health. However, it is widely agreed that the regular consumption of tasty, ripe blueberries can be unconditionally recommended.

Dietary berries, insulin resistance and type 2 diabetes: an overview of human feeding trials

Dietary berries are a rich source of several nutrients and phytochemicals and in recent years, accumulating evidence suggests they can reduce risks of several chronic diseases, including type 2 diabetes (T2D). The objective of this review is to summarize and discuss the role of dietary berries (taken as fresh, frozen, or other processed forms) on insulin resistance and biomarkers of T2D in human feeding studies. Reported feeding trials involve different berries taken in different forms, and consequently differences in nutritional or polyphenol composition must be considered in their interpretation. Commonly consumed berries, especially cranberries, blueberries, raspberries and strawberries, ameliorate postprandial hyperglycemia and hyperinsulinemia in overweight or obese adults with insulin resistance, and in adults with the metabolic syndrome (MetS). In non-acute long-term studies, these berries either alone, or in combination with other functional foods or dietary interventions, can improve glycemic and lipid profiles, blood pressure and surrogate markers of atherosclerosis. Studies specifically in people with T2D are few, and more knowledge is needed. Nevertheless, existing evidence, although sparse, suggests that berries have an emerging role in dietary strategies for the prevention of diabetes and its complications in adults. Despite the beneficial effects of berries on diabetes prevention and management, they must be consumed as part of a healthy and balanced diet.

Effect of Rubus anatolicus Leaf Extract on Glucose Metabolism in HepG2, CRI-D2 and C2C12 Cell Lines

INTRODUCTION

The aim of this study was to assess the effects of Rubus anatolicus on glucose metabolism in HepG2, CRI-D2 and C2C12 cell lines.

MATERIALS AND METHODS

R. anatolicus was collected in Golestan province, Iran. Three different cell lines HepG2 (human liver cell), CRI-D2 (mice pancreatic cell) and C2C12 (rat myoblast) were used for cell culture experiments. Cell viability was measured using MTT assay. Cells were treated with various concentrations of the extract (6.25-400 μg/mL) and then the extracellular glucose level and intracellular glycogen content were measured using colorimetric methods. The insulin level of the culture medium was measured using the ELISA method.

RESULTS

Our findings showed that R. anatolicus extract enhances glucose uptake and consumption by all three cell lines. The R. anatolicus extract exposure also elevated cellular glycogen content in HepG2 and C2C12 cells (for 200 and 100 μg/mL) significantly. We found a significant increase in glucose uptake and consequently higher stimulation of insulin secretion in CRI-D2 cell pancreatic cells treated with R. anatolicus extract.

CONCLUSION

The R. anatolicus appears to activate glucose uptake and cellular glycogen synthesis probably by activating the glycogenesis or inhibition of glycogenolysis pathways. The extract enhances insulin secretion in the pancreatic cells by increased glucose uptake.

Adherence to UK dietary guidelines is associated with higher dietary intake of total and specific polyphenols compared with a traditional UK diet: further analysis of data from the Cardiovascular risk REduction Study: Supported by an Integrated Dietary Approach (CRESSIDA) randomised controlled trial

Adherence to dietary guidelines (DG) may result in higher intake of polyphenols via increased consumption of fruits, vegetables and whole grains. We compared polyphenol dietary intake and urinary excretion between two intervention groups in the Cardiovascular risk REduction Study: Supported by an Integrated Dietary Approach study: a 12-week parallel-arm, randomised controlled trial (n 161; sixty-four males, ninety-seven females; aged 40-70 years). One group adhered to UK DG, whereas the other group consumed a representative UK diet (control). We estimated polyphenol dietary intake, using a 4-d food diary (4-DFD) and FFQ, and analysed 24-h polyphenol urinary excretion by liquid chromatography-tandem MS on a subset of participants (n 46 control; n 45 DG). A polyphenol food composition database for 4-DFD analysis was generated using Phenol-Explorer and USDA databases. Total polyphenol intake by 4-DFD at endpoint (geometric means with 95 % CI, adjusted for baseline and sex) was significantly higher in the DG group (1279 mg/d per 10 MJ; 1158, 1412) compared with the control group (1084 mg/d per 10 MJ; 980, 1197). The greater total polyphenol intake in the DG group was attributed to higher intake of anthocyanins, proanthocyanidins and hydroxycinnamic acids, with the primary food sources being fruits, cereal products, nuts and seeds. FFQ estimates of flavonoid intake also detected greater intake in DG compared with the control group. 24-h urinary excretion showed consistency with 4-DFD in their ability to discriminate between dietary intervention groups for six out of ten selected, individual polyphenols. In conclusion, following UK DG increased total polyphenol intake by approximately 20 %, but not all polyphenol subclasses corresponded with this finding.

Enzymatically modified isoquercitrin improves endothelial function in volunteers at risk of cardiovascular disease

A higher intake of food rich in flavonoids such as quercetin can reduce the risk of CVD. Enzymatically modified isoquercitrin (EMIQ®) has a bioavailability 17-fold higher than quercetin aglycone and has shown potential CVD moderating effects in animal studies. The present study aimed to determine whether acute ingestion of EMIQ® improves endothelial function, blood pressure (BP) and cognitive function in human volunteers at risk of CVD. Twenty-five participants (twelve males and thirteen females) with at least one CVD risk factor completed this randomised, controlled, crossover study. In a random order, participants were given EMIQ® (2 mg aglycone equivalent)/kg body weight or placebo alongside a standard breakfast meal. Endothelial function, assessed by flow-mediated dilatation (FMD) of the brachial artery was measured before and 1·5 h after intervention. BP, arterial stiffness, cognitive function, BP during cognitive stress and measures of quercetin metabolites, oxidative stress and markers of nitric oxide (NO) production were assessed post-intervention. After adjustment for pre-treatment measurements and treatment order, EMIQ® treatment resulted in a significantly higher FMD response compared with the placebo (1·80 (95 % CI 0·23, 3·37) %; P = 0·025). Plasma concentrations of quercetin metabolites were significantly higher (P < 0·001) after EMIQ® treatment compared with the placebo. No changes in BP, arterial stiffness, cognitive function or biochemical parameters were observed. In this human intervention study, the acute administration of EMIQ® significantly increased circulating quercetin metabolites and improved endothelial function. Further clinical trials are required to assess whether health benefits are associated with long-term EMIQ® consumption.

Associations between Dietary Polyphenols and Type 2 Diabetes in a Cross-Sectional Analysis of the PREDIMED-Plus Trial: Role of Body Mass Index and Sex

Overweight and obesity are important risk factors for type 2 diabetes (T2D). Moving towards healthier diets, namely, diets rich in bioactive compounds, could decrease the odds of suffering T2D. However, those individuals with high body mass index (BMI) may have altered absorption or metabolism of some nutrients and dietary components, including polyphenols. Therefore, we aimed to assess whether high intakes of some classes of polyphenols are associated with T2D in a population with metabolic syndrome and how these associations depend on BMI and sex. This baseline cross-sectional analysis includes 6633 participants from the PREDIMED-Plus trial. Polyphenol intakes were calculated from food frequency questionnaires (FFQ). Cox regression models with constant time at risk and robust variance estimators were used to estimate the prevalence ratios (PRs) for polyphenol intake and T2D prevalence using the lowest quartile as the reference group. Analyses were stratified by sex and BMI groups (overweight and obese) to evaluate potential effect modification. Catechins, proanthocyanidins, hydroxybenzoic acids, and lignans were inversely associated with T2D. Hydroxycinnamic acids were directly related in men. These associations were different depending on sex and BMI, that is, women and overweight obtained stronger inverse associations.

Dietary intakes of flavan-3-ols and cardiometabolic health: systematic review and meta-analysis of randomized trials and prospective cohort studies

BACKGROUND

Although available data suggest that some dietary flavan-3-ol sources reduce cardiometabolic risk, to our knowledge no review has systematically synthesized their specific contribution.

OBJECTIVE

We aimed to examine, for the first time, if there is consistent evidence that higher flavan-3-ol intake, irrespective of dietary source, reduces cardiometabolic risk.

METHODS

MEDLINE, Cochrane Central, and Commonwealth Agricultural Bureau abstracts were searched for prospective cohorts and randomized controlled trials (RCTs) published from 1946 to March 2019 on flavan-3-ol intake and cardiovascular disease (CVD) risk. Random-effects models meta-analysis was used. The Grading of Recommendations Assessment, Development, and Evaluation (GRADE) approach assessed the strength of evidence.

RESULTS

Of 15 prospective cohorts (23 publications), 4 found highest compared with lowest habitual intakes of flavan-3-ols were associated with a 13% reduction in risk of CVD mortality and 2 found a 19% reduction in risk of chronic heart disease (CHD) incidence. Highest compared with lowest habitual intakes of monomers were associated with a reduction in risk of type 2 diabetes mellitus (T2DM) (n = 5) and stroke (n = 4) (10% and 18%, respectively). No association was found for hypertension. Of 156 RCTs, flavan-3-ol intervention resulted in significant improvements in acute/chronic flow-mediated dilation (FMD), systolic (SBP) and diastolic blood pressure (DBP), total cholesterol (TC), LDL and HDL cholesterol, triglycerides (TGs), hemoglobin A1c (HbA1c), and homeostasis model assessment of insulin resistance (HOMA-IR). All analyses, except HbA1c, were associated with moderate/high heterogeneity. When analyses were limited to good methodological quality studies, improvements in TC, HDL cholesterol, SBP, DBP, HOMA-IR, and acute/chronic FMD remained significant. In GRADE evaluations, there was moderate evidence in cohort studies that flavan-3-ol and monomer intakes were associated with reduced risk of CVD mortality, CHD, stroke, and T2DM, whereas RCTs reported improved TC, HDL cholesterol, SBP, and HOMA-IR.

CONCLUSIONS

Available evidence supports a beneficial effect of flavan-3-ol intake on cardiometabolic outcomes, but there was considerable heterogeneity in the meta-analysis. Future research should focus on an integrated intake/biomarker approach in cohorts and high-quality dose-response RCTs. This review was registered at www.crd.york.ac.uk/PROSPERO/ as CRD42018035782.

Antidiabetic Potential of Flavonoids from Traditional Chinese Medicine: A Review

Diabetes mellitus (DM) is a group of metabolic disorders in which high blood sugar levels occur over a prolonged period. Approximately 4% of the global population is affected by DM. Western medical treatment methods for diabetes including injection or oral hypoglycemic drugs have some toxic or side effects, economic pressures, and so on. Many researchers turn to discover new drugs from natural products or Traditional Chinese Medicine (TCM). Flavonoids are widely distributed in plants, and many studies have shown that flavonoids possess antidiabetic properties, exhibiting not only well-recognized antidiabetic and hypoglycemic activities but also activity in the treatment of diabetic complications. In this review, we systematically summarized anti-diabetic flavonoid compounds based on structure classification by examining the PubMed, Springer Link, Web of Science, and CNKI databases. There are 13 flavonoid compounds listed which have been studied extensively and have antidiabetic features respectively. Apigenin, baicalein, and catechin mainly reduces blood glucose via anti-oxidation; hesperidin is good for diabetic neuropathy; glycyrrhiza flavonoids have a significant effect on gestational DM; quercetin takes advantage of crossing the blood–brain barrier and improving renal function. Some compounds have protective and preventive effects on diabetic complications, such as kaempferol and puerarin which are beneficial to cardiomyopathy; myricetin has therapeutic potential in the treatment of DN; dihydromyricetin might improve CI. It is a pity or might be a pointcut that most studies remain in the animal experimental stage, and further investigation should be carried out.

Guava (Psidium guajava) Fruit Extract Prepared by Supercritical CO2 Extraction Inhibits Intestinal Glucose Resorption in a Double-Blind, Randomized Clinical Study

Inhibition of intestinal glucose resorption can serve as an effective strategy for the prevention of an increase in blood glucose levels. We have recently shown that various extracts prepared from guava (Psidium guajava) inhibit sodium-dependent glucose cotransporter 1 (SGLT1)- and glucose transporter 2 (GLUT2)-mediated glucose transport in vitro (Caco-2 cells) and in vivo (C57BL/6N mice). However, the efficacy in humans remains to be confirmed. For this purpose, we conducted a parallelized, randomized clinical study with young healthy adults. Thirty-one volunteers performed an oral glucose tolerance test (OGTT) in which the control group received a glucose solution and the intervention group received a glucose solution containing a guava fruit extract prepared by supercritical CO₂ extraction. The exact same extract was used for our previous in vitro and in vivo experiments. Blood samples were collected prior to and up to two hours after glucose consumption to quantitate blood glucose and insulin levels. Our results show that, in comparison to the control group, consumption of guava fruit extract resulted in a significantly reduced increase in postprandial glucose response over the basal fasting plasma glucose levels after 30 min (Δ control 2.60 ± 1.09 mmol/L versus Δ intervention 1.96 ± 0.96 mmol/L; p = 0.039) and 90 min (Δ control 0.44 ± 0.74 mmol/L versus Δ intervention -0.18 ± 0.88 mmol/L; p = 0.023). In addition, we observed a slightly reduced, but non-significant insulin secretion (Δ control 353.82 ± 183.31 pmol/L versus Δ intervention 288.43 ± 126.19 pmol/L, p = 0.302). Interestingly, storage time and repeated freeze-thawing operations appeared to negatively influence the efficacy of the applied extract. Several analytical methods (HPLC-MS, GC-MS, and NMR) were applied to identify putative bioactive compounds in the CO₂ extract used. We could assign several substances at relevant concentrations including kojic acid (0.33 mg/mL) and 5-hydroxymethylfurfural (2.76 mg/mL). Taken together, this clinical trial and previous in vitro and in vivo experiments confirm the efficacy of our guava fruit extract in inhibiting intestinal glucose resorption, possibly in combination with reduced insulin secretion. Based on these findings, the development of food supplements or functional foods containing this extract appears promising for patients with diabetes and for the prevention of insulin resistance. Trial registration: 415-E/2319/15-2018 (Ethics Commissions of Salzburg).

Systematic Review on Polyphenol Intake and Health Outcomes: Is there Sufficient Evidence to Define a Health-Promoting Polyphenol-Rich Dietary Pattern?

Growing evidence support association between polyphenol intake and reduced risk for chronic diseases, even if there is a broad debate about the effective amount of polyphenols able to exert such protective effect. The present systematic review provides an overview of the last 10-year literature on the evaluation of polyphenol intake and its association with specific disease markers and/or endpoints. An estimation of the mean total polyphenol intake has been performed despite the large heterogeneity of data reviewed. In addition, the contribution of dietary sources was considered, suggesting tea, coffee, red wine, fruit and vegetables as the main products providing polyphenols. Total flavonoids and specific subclasses, but not total polyphenols, have been apparently associated with a low risk of diabetes, cardiovascular events and all-cause mortality. However, large variability in terms of methods for the evaluation and quantification of polyphenol intake, markers and endpoints considered, makes it still difficult to establish an evidence-based reference intake for the whole class and subclass of compounds. Nevertheless, the critical mass of data available seem to strongly suggest the protective effect of a polyphenol-rich dietary pattern even if further well targeted and methodologically sound research should be encouraged in order to define specific recommendations.

Two Pairs of Isomerically New Phenylpropanoidated Epicatechin Gallates with Neuroprotective Effects on H2O2-Injured SH-SY5Y Cells from Zijuan Green Tea and Their Changes in Fresh Tea Leaves Collected from Different Months and Final Product

Zijuan tea ( Camellia sinensis var. assamica), an anthocyanin-rich cultivar with purple leaves, is a valuable material for manufacturing tea with unique color and flavor. In this paper, four new phenylpropanoid substituted epicatechin gallates (pECGs), Zijuanins A-D (1-4), were isolated from Zijuan green tea by different column chromatography. Their structures were identified by extensive high resolution mass spectroscopy (HR-MS), nuclear magnetic resonance (NMR), and experimental and calculated circular dichroism (CD) spectroscopic analyses. Detection of the changes in fresh tea leaves collected from April to September and the final processed product by high performance liquid chromatography (HPLC)-HRMS suggested that production of compounds 1 and 2 may be enhanced by the processing procedure of Zijuan green tea. Additionally, 1-4 were proposed to be synthesized through interaction between the abundant secondary metabolite ECG and phenolic acids from tea leaves by two key steps of phenol-dienone tautomerism. 1 and 2 showed impressive activity in protecting SH-SY5Y cells against H₂O₂-induced damage at the concentration of 1.0 μM.

A Selective Role of Dietary Anthocyanins and Flavan-3-ols in Reducing the Risk of Type 2 Diabetes Mellitus: A Review of Recent Evidence

Type 2 diabetes mellitus (T2DM) is the most common form of DM and its prevalence is increasing worldwide. Because it is a progressive disease, prevention, early detection and disease course modification are possible. Diet plays a critical role in reducing T2DM risk. Therapeutic dietary approaches routinely recommend diets high in plant foods (i.e., vegetables, fruits, whole-grains). In addition to essential micronutrients and fiber, plant-based diets contain a wide-variety of polyphenols, specifically flavonoid compounds. Evidence suggests that flavonoids may confer specific benefits for T2DM risk reduction through pathways influencing glucose absorption and insulin sensitivity and/or secretion. The present review assesses the relationship between dietary flavonoids and diabetes risk reduction reviewing current epidemiology and clinical research. Collectively, the research indicates that certain flavonoids, explicitly anthocyanins and flavan-3-ols and foods rich in these compounds, may have an important role in dietary algorithms aimed to address diabetes risk factors and the development of T2DM.

Plant phenolics as functional food ingredients

Phenolic compounds have attracted much attention in recent times as their dietary intake has been associated with the prevention of some chronic and degenerative diseases that constitute major causes of death and incapacity in developed countries, such as cardiovascular diseases, type II diabetes, some types of cancers or neurodegenerative disorders like Alzheimer's and Parkinson's diseases. Nowadays it is considered that these compounds contribute, at least in part, for the protective effects of fruit and vegetable-rich diets, so that the study of their role in human nutrition has become a central issue in food research. This chapter reviews the current knowledge on the phenolic compounds as food components, namely their occurrence in the diet, bioavailability and metabolism, biological activities and mechanisms of action. Besides, the approaches for their extraction from plant matrices and technological improvements regarding their preparation, stability and bioavailability in order to be used as functional food ingredients are also reviewed, as well as their legal situation regarding the possibility of making "health claims" based on their presence in food and beverages.

Hepatoprotective effects and structure-activity relationship of five flavonoids against lipopolysaccharide/d-galactosamine induced acute liver failure in mice

Acute liver failure (ALF) is a distinct clinical syndrome with high mortality and characterized by metabolic derangements, neurological complication, and multiple failures. Flavonoids exert great biological properties on anti-oxidation, anti-inflammation, and anti-apoptosis. After lipopolysaccharide (LPS)/d-galactosamine (d-GalN) administration, five flavonoids inhibited oxidative activities with reducing nitric oxide synthase (iNOS), malondialdehyde (MDA), and improving catalase (CAT), superoxide dismutase (SOD), total antioxidant capacity (T-AOC), nuclear factor erythroid-derived 2-related factor 2 (Nrf2) and heme oxygenase-1 (HO-1). They reduced the serum levels of alanine and aspartate aminotransferase (ALT, AST) and pro-inflammatory cytokines, prevented the phosphorylation of IKK, IκBα, and NF-κB/p65 in the NF-κB signaling pathway. Additionally five flavonoids inhibited hepatocyte apoptosis through increasing Bcl-2/Bax ratio and suppressing the Caspase family proteins. Chrysin, luteolin, apigenin, hesperetin and 3', 4'-dimethoxy hesperetin have apparently hepato-protective effects against ALF induced by LPS/d-GalN. The study found, the C2C3 double bond at A ring, and the hydroxyl group of C3' or C4' at B ring increased the protective activities, however, the effect of hydroxymethylation at C3' and C4' was reversed. In addition, apigenin has good hepatoprotective effects and potential as a promising therapeutic agent for ALF in clinical application.

Dietary intake of flavonoid subclasses and risk of type 2 diabetes in prospective cohort studies: A dose-response meta-analysis

Flavonoids intake has been linked to risk of type 2 diabetes theoretically, but the findings were conflicting from observational studies. Results from the recent meta-analysis suggested a moderate favorable effect of total dietary flavonoids consumption on type 2 diabetes risk. However, the relationship, if exists, between total dietary flavonoids consumption and type 2 diabetes risk is unclear, especially further in the association between flavonoid subclasses and risk of type 2 diabetes. Thus, the dose-response relationship was assessed by restricted cubic spline model and multivariate random-effect meta-regression. Among flavonoid subclasses, protective effects were obtained for intakes of flavonols, flavan-3-ols, isoflavones and anthocyanidins in high vs. low analysis and dose-response analysis.

Assessing the consumption of berries and associated factors in the United States using the National Health and Nutrition Examination Survey (NHANES), 2007-2012

Intake of berries was assessed relative to other fruit and fruit juices and total fruit intake in the U.S. population age 2 years and older using the National Health and Nutrition Examination Survey, 2007-2012. Average daily intake of total fruit was about 1 cup, and berries comprised approximately 10% of total fruit consumption. Only 18% of the population met the recommendation of at least 2 cups of fruit per day. Children ages 2 to 5 years consumed the most total fruit of which about half was juice and 4% of which was berries. Among adults, the highest berry consumption was by those who were 65 years and older, non-Hispanic White, and had the highest education and income levels. Use of the Nutrition Facts panel and ingredient labeling was associated with greater total fruit and berry intake. Those who were aware of an amount of fruit that is associated with good health and of dietary guidance in general and those who had fruit available in the home consumed about twice as much berries as others. Fruit intake remains below recommendations in the U.S.; berry intake is particularly low. Behavioral indicators provided insight on how fruit and berry consumption might be increased.

Polyphenol exposure and risk of type 2 diabetes: dose-response meta-analyses and systematic review of prospective cohort studies

Background

Type 2 diabetes is characterized by impaired glucose metabolism. Bioactive compounds in fruits and vegetables such as polyphenols have been suggested to influence glucose metabolism.

Objective

The aim of the current study was to systematically review the literature and conduct dose-response meta-analyses to summarize evidence of polyphenol exposure in association with incident type 2 diabetes.

Design

Prospective epidemiologic studies published before January 2018 were searched through 2 databases. Log-transformed multivariable adjusted hazard and odds ratios were combined in a random-effects model. Meta-analyses comparing extreme quantiles of polyphenol exposure were further explored with the use of linear and nonlinear dose-response meta-analyses.

Results

Eighteen studies investigated the association between polyphenols (51 different compounds in total) and type 2 diabetes. A comparison of extreme quantiles revealed inverse associations for intakes of polyphenols (HR: 0.56; 95% CI: 0.34, 0.93), flavonoids (HR: 0.88; 95% CI: 0.81, 0.96), flavonols (HR: 0.92; 95% CI: 0.85, 0.98), flavan-3-ols (HR: 0.89; 95% CI: 0.81, 0.99), catechins (HR: 0.86; 95% CI: 0.75, 0.97), anthocyanidins (HR: 0.86; 95% CI: 0.81, 0.91), isoflavones (HR: 0.92; 0.86, 0.97), daidzein (HR: 0.89; 95% CI: 0.83, 0.95), genistein (HR: 0.92; 95% CI: 0.86, 0.99), and stilbenes (HR: 0.44; 95% CI: 0.26, 0.72), and biomarkers of daidzein (HR: 0.81; 95% CI: 0.66, 0.99) and genistein (HR: 0.79; 95% CI: 0.62, 0.99). In the dose-response meta-analysis, nonlinear associations were observed for intakes of polyphenols, flavonoids, flavanones, anthocyanidins, anthocyanins, and biomarkers of genistein. A linear dose-response association was observed for phenolic acids.

Conclusions

This study adds to the evidence showing that diets rich in polyphenols, and particularly flavonoids, play a role in the prevention of type 2 diabetes. For most associations evidence for nonlinearity was found, suggesting a recommendable amount of intake associated with the lowest risk of type 2 diabetes. Therefore, future studies are warranted in which nonlinear associations are further explored.

Flavonoids intake and risk of type 2 diabetes mellitus: A meta-analysis of prospective cohort studies

Epidemiological studies exploring the role of flavonoids intake in preventing type 2 diabetes mellitus (T2DM) showed inconsistent results. Therefore, we performed a meta-analysis of relevant studies to examine the relationship between flavonoids intake and risk of T2DM. We hypothesized that flavonoids intake may decrease the risk of developing T2DM.A systematical search in PubMed and Embase until September 2017 was performed to identify eligible prospective cohort studies. The summary relative risks (RRs) and 95% confidence intervals (CIs) were calculated using random-effect models. Dose-response pattern between total flavonoids intake and T2DM risk was also estimated.Eight prospective studies were included with 312,015 participants, of whom 19,953 developed T2DM during the follow-up periods of 4 to 28 years. Compared with lower consumption, high intake of total flavonoids was associated with a decreased risk of T2DM (RR: 0.89, 95% CI: 0.82-0.96). Among flavonoid subclasses, inverse correlations with T2DM were achieved for intakes of anthocyanidins, flavan-3-ols, flavonols, and isoflavones. Dose-response meta-analysis indicated a curvilinear relationship between total flavonoids intake and incident T2DM (P for nonlinearity = .042), with a significant risk reduction at an intake of ≥550 mg/day. When assuming a linear pattern, the risk of T2DM was decreased by 5% for each 300-mg/day increment in total flavonoids intake (RR: 0.95, 95% CI: 0.93-0.97).Our study suggests that higher intakes of total flavonoids and subclasses (anthocyanidins, flavan-3-ols, flavonols, and isoflavones) are associated with lower risk of T2DM.

The safety of green tea and green tea extract consumption in adults - Results of a systematic review

A systematic review of published toxicology and human intervention studies was performed to characterize potential hazards associated with consumption of green tea and its preparations. A review of toxicological evidence from laboratory studies revealed the liver as the target organ and hepatotoxicity as the critical effect, which was strongly associated with certain dosing conditions (e.g. bolus dose via gavage, fasting), and positively correlated with total catechin and epigallocatechingallate (EGCG) content. A review of adverse event (AE) data from 159 human intervention studies yielded findings consistent with toxicological evidence in that a limited range of concentrated, catechin-rich green tea preparations resulted in hepatic AEs in a dose-dependent manner when ingested in large bolus doses, but not when consumed as brewed tea or extracts in beverages or as part of food. Toxico- and pharmacokinetic evidence further suggests internal dose of catechins is a key determinant in the occurrence and severity of hepatotoxicity. A safe intake level of 338 mg EGCG/day for adults was derived from toxicological and human safety data for tea preparations ingested as a solid bolus dose. An Observed Safe Level (OSL) of 704 mg EGCG/day might be considered for tea preparations in beverage form based on human AE data.

Dietary Behaviors and Glucose Metabolism in Young Adults at Risk for Type 2 Diabetes

Purpose The purpose of the study was to examine the associations between dietary behaviors and glucose metabolism in high-risk young adults to increase the precision of nutrition education to prevent early onset type 2 diabetes (T2D). Method Using a descriptive, cross-sectional study design, 106 overweight or obese sedentary young adults ages 18-29 years from the Atlanta metropolitan area were recruited to screen diabetes risk. Survey questionnaires, anthropometric assessment, blood pressure (BP), and laboratory data were collected in a clinical research unit. The Web-based HOMA2 calculator was used to calculate beta cell function and insulin sensitivity. Results The final sample included 103 participants. There were similar patterns of diet (caloric intake and dietary quality) between African Americans and non-African Americans, whereas African Americans showed hyperinsulinemia compared with non-African Americans. When young adults consumed a good quality diet (appropriate carbohydrate intakes; high fiber, low saturated fat but protein rich diet), their insulin resistance was decreased. There was a marginal interaction effect between insulin sensitivity and beta cell function by race. Systolic BP was higher in African Americans, and total cholesterol, triglycerides, and low-density lipoprotein cholesterol were higher in non-African Americans. Conclusion Findings are useful to develop age-specific nutrition guidelines to prevent early onset T2D in high-risk young adults.