Inhibition of human starch digesting enzymes and intestinal glucose transport by walnut polyphenols.

One approach to controlling type 2 diabetes (T2D) is to lower postprandialglucose spikesby slowing down the digestion of carbohydrates and the absorption of glucose in the small intestine. The consumption of walnuts is associated with a reduced risk of chronic diseases such as T2D, suggested to be partly due to the high content of (poly)phenols. This study evaluated, for the first time, the inhibitory effect of a (poly)phenol-rich walnut extract on human carbohydrate digesting enzymes (salivary and pancreatic α-amylases, brush border sucrase-isomaltase) and on glucose transport across fully differentiated human intestinal Caco-2/TC7 monolayers. The walnut extract was rich in multiple (poly)phenols (70 % w/w) as analysed by Folin-Ciocalteau and by LCMS. It exhibited potent inhibition of both human salivary (IC50: 32.2 ± 2.5 µg walnut (poly)phenols (WP)/mL) and pancreatic (IC50: 56.7 ± 1.7 µg WP/mL) α-amylases, with weaker effects on human sucrase (IC50: 990 ± 20 µg WP/mL), maltase (IC50: 1300 ± 80 µg WP/mL), and isomaltase (IC25: 830 ± 60 µg WP/mL) activities. Selected individual walnut (poly)phenols inhibited human salivary α-amylase in the order: 1,3,4,6-tetragalloylglucose > ellagic acid pentoside > 1,2,6-tri-O-galloyl-ß-D-glucopyranose, with no inhibition by ellagic acid, gallic acid and 4-O-methylgallic acid. The (poly)phenol-rich walnut extract also attenuated (up to 59 %) the transfer of 2-deoxy-D-glucose across differentiated Caco-2/TC7 cell monolayers. This is the first report on the effect of (poly)phenol-rich extracts from any commonly-consumed nut kernel on any human starch-digesting enzyme, and suggests a mechanism through which walnut consumption may lower postprandial glucose spikes and contribute to their proposed health benefits.

Inhibitory effect of extracts from edible parts of nuts on α-amylase activity: a systematic review.

Elevated blood glucose concentration is a risk factor for developing metabolic dysfunction and insulin resistance, leading to type 2 diabetes and cardiovascular diseases. Nuts have the potential to inhibit α-amylase activity, and so lower postprandial glucose, due to their content of polyphenols and other bioactive compounds. We conducted a systematic literature review to assess the ability of extracts from commonly consumed edible parts of nuts to inhibit α-amylase. Among the 31 included papers, only four utilised human α-amylases. These papers indicated that polyphenol-rich chestnut skin extracts exhibited strong inhibition of both human salivary and pancreatic α-amylases, and that a polyphenol-rich almond skin extract was a potent inhibitor of human salivary α-amylase. The majority of the reviewed studies utilised porcine pancreatic α-amylase, which has ∼86% sequence homology with the corresponding human enzyme but with some key amino acid variations located within the active site. Polyphenol-rich extracts from chestnut, almond, kola nut, pecan and walnut, and peptides isolated from cashew, inhibited porcine pancreatic α-amylase. Some studies used α-amylases sourced from fungi or bacteria, outcomes from which are entirely irrelevant to human health, as they have no sequence homology with the human enzyme. Given the limited research involving human α-amylases, and the differences in inhibition compared to porcine enzymes and especially enzymes from microorganisms, it is recommended that future in vitro experiments place greater emphasis on utilising enzymes sourced from humans to facilitate a reliable prediction of effects in intervention studies.

A systematic review of the inhibitory effect of extracts from edible parts of nuts on α-glucosidase activity.

An elevated postprandial glycaemic response is a risk factor for developing type 2 diabetes mellitus (T2DM). Inhibition of digestive enzymes, including membrane-bound brush-border α-glucosidases, leads to slowed carbohydrate digestion and absorption, and reduced postprandial glycaemia. Nuts are eaten widely around the world, and have the potential to inhibit α-glucosidases through their content of polyphenols and other bioactive compounds. We set out to conduct a systematic literature review exploring the inhibitory effect of extracts from edible parts of various nuts on α-glucosidase activity in vitro to ensure, as far as possible, that no papers were missed. After an initial screening, 38 studies were reviewed in full, of which 15 were suitable for the present systematic review. Notably, no studies were found which tested the inhibitory potential of nut extracts against human α-glucosidases. Two studies showed that extracts from almonds and hazelnuts inhibited rat α-glucosidase activity, but the remaining papers reported data on the yeast α-glucosidase enzyme. Where yeast and rat enzymes can be compared, it is clear that nut extracts inhibit yeast α-glucosidase more strongly than mammalian α-glucosidase, which may lead to over-estimation when predicting effects in vivo when using data from the yeast enzyme. In contrast, acarbose is a stronger inhibitor of mammalian α-glucosidase compared to the yeast enzyme. Thus, although the present review indicates that extracts from nuts inhibit yeast α-glucosidase, this cannot be extrapolated to humans in vivo. There is some evidence that extracts from almonds and hazelnuts inhibit rat α-glucosidase, but no information on human enzyme sources. Since most work has been published on the yeast enzyme, future work in vitro must utilise mammalian, and preferably human, α-glucosidases in order to be relevant to human health and disease. This systematic review was registered at INPLASY as INPLASY202280061.

Dietary inflammatory index and the risk of non-communicable chronic disease and mortality: an umbrella review of meta-analyses of observational studies.

We aimed to perform an umbrella review of systematic reviews and meta-analyses (SRMAs) of observational studies of the association of the dietary inflammatory index (DII) with the risk of non-communicable chronic disease and mortality in the general population. We searched PubMed, Scopus, and ISI Web of Science to November 2020. For each outcome, the summary effect sizes with the corresponding 95%CIs were recalculated using a random-effects model. The certainty of the evidence and the quality of conduct of published SRMAs were rated using the GRADE and ASMTAR 2 tools, respectively. A total of 11 SRMAs of observational studies, reporting pooled effect sizes for 29 outcomes obtain from 60 prospective cohort and 67 case-control studies, were included. Our results demonstrated evidence of moderate certainty for a positive relation between DII and the risk cardiovascular disease, all-cause mortality, and colorectal cancer. Higher DII was also associated with site-specific cancer risk, but for cancers at most sites, existing evidence is derived from case-control studies with the certainty of evidence being rated low or very low. Our findings suggested that adherence to a diet with high inflammatory features might be associated with a higher risk of colorectal cancer, cardiovascular disease, and all-cause mortality.

The interaction between rs 3,807,992 genotypes with the dietary inflammatory index on Leptin, Leptin resistance, and Galectin 3 in obese and overweight women.

OBJECTIVE: Obesity is related to increasing leptin and some inflammatory factors that are associated with low-grade inflammation. Moreover, several studies have shown Caveolin-1 (CAV1) genetic variations may be associated with dietary intake. The current study aimed to evaluate the interaction of CAV1 rs3807992 with types of the energy-adjusted dietary inflammatory index (EDII) in leptin, leptin resistance, and Galectin 3, as inflammatory factors. METHODS: This cross-sectional study was carried out on 363 overweight and obese females. Dietary intake and DII were obtained from a 147-item food frequency questionnaire (FFQ). The CAV-1 genotype was measured using the PCR-RFLP method. Anthropometric values and serum levels of leptin and Galectin 3 were measured by standard methods. RESULTS: Increased adherence to EDII in the interaction with CAV1 genotypes led to an increase in leptin level 79.15 (mg/l) (ß = 79.15, CI = - 1.23,163.94, P = 0.04) in model 3, after controlling for further potential confounders. By contrast, adherence to EDII in the interaction with the genotype including risk alleles showed no significant interaction, even after adjustment in model 3 (ß = 0.55, CI = - 0.99, 2.09, P = 0.48). Although, a marginal positive significant interaction was found between EDII and CAV1 genotypes on Galectin 3, after adjustment in model 3 (ß = 31.35, CI = 0.13, 77.13, P = 0.05). CONCLUSIONS: The present study indicates that a high adherence of EDII and CAV1 genotypes containing risk alleles may be a prognostic factor and increase both leptin and Galectin3. However, it seems that the presence of interaction was not on leptin resistance. Further functional studies are necessary to elucidate the exact mechanism.

Association of Dietary and Lifestyle Inflammation Score With Cardiorespiratory Fitness.

Objective: We aimed to assess the potential association of dietary (DIS) and lifestyle inflammation score (LIS) and their joint association (DLIS) with cardiorespiratory fitness (CRF) in Tehranian adults. Design: The present study was designed cross-sectional. Participants: A total of 265 males and females aged 18-70 years (mean ± SD: 36.9 ± 13.3) were entered in the present cross-sectional study. Eligible participants were healthy men and women who were free of medications and had no acute or chronic infection or inflammatory disease. Measures: The DIS was calculated by the use of data from 18 anti- and pro-inflammatory dietary components, and the LIS by three non-dietary components including physical activity, smoking status, and general adiposity, with higher scores indicating a more pro-inflammatory diet and lifestyle, respectively. The DLIS was calculated by summing the DIS and LIS. CRF was assessed by the Bruce protocol and VO2 max was measuredas the main variable of CRF. The odds ratio (OR) and 95% confidence interval (CI) of CRF across tertiles of the DIS, LIS, and DLIS were estimated by logistic regression analysis with considering age, gender, energy intake, marital and education status, and occupation as confounders. Results: The DLIS ranged from -2.10 to 0.38 (mean ± SD: -1.25 ± 0.64). In the model that controlled for all variables, the ORs of CRF for the second and third tertiles of the DLIS as compared to the first tertile were 0.42 (95%CI: 0.20, 0.90) and 0.12 (95%CI: 0.05, 0.32), respectively (P-trend < 0.001). There was a strong inverse association between the LIS and CRF (ORthirdvs.firsttertile: 0.12, 95%CI: 0.05, 0.32). There was no association between DIS and CRF. Conclusion: The present study examined the joint association of inflammation-related lifestyle behaviors with CRF and found a strong inverse association between a pro-inflammatory lifestyle with CRF. We did not find any association between dietary inflammatory properties with CRF. Future studies should address the relationship between the inflammatory potential of the diet and CRF.

The joint association of serum vitamin D status and cardiorespiratory fitness with obesity and metabolic syndrome in Tehranian adults.

We aimed to assess the individual and joint association of serum vitamin D and cardiorespiratory fitness (CRF) with obesity and metabolic syndrome (MetSyn). In this cross-sectional study 270 adults with an age range of 18 years and older were recruited from health centers from five districts in Tehran, Iran. CRF was assessed with Bruce protocol. MetSyn was defined based on International Diabetes Federation 2009. The odds ratio (OR) and 95 % confidence interval (CI) of obesity and MetSyn across tertiles of serum vitamin D and CRF were estimated with control for confounders. The results indicated that neither 25(OH)D nor 1,25(OH)D was associated with obesity and MetSyn. There was a strong inverse association between CRF and general (P-trend < 0.001) and abdominal adiposity (P-trend: 0.001). The joint association of vitamin D and CRF indicated that the inverse association of CRF with obesity was stronger in those with high serum vitamin D than those with low serum vitamin D and this joint association remained after considering age and diet quality. There was a significant inverse association for those with low serum 25(OH)D and high CRF (OR: 0.12, 95 % CI: 0.04-0.81; P = 0.02) compared to those with low serum 25(OH)D and low CRF in the crude model. Also, the OR of general obesity was 0.17 (95 % CI: 0.02-0.79; P = 0.03) for those with high CRF and low serum 1,25(OH)D compare with the reference group. Our findings indicated a strong inverse association between CRF and obesity, especially in those with high serum vitamin D.

Association of Oxidative Balance Score with the Metabolic Syndrome in a Sample of Iranian Adults.

OBJECTIVE: We aimed to assess the association of the oxidative balance score (OBS) with metabolic syndrome (MetS) in adults. DESIGN: A population-based cross-sectional study Setting. Health centers from five districts in Tehran, Iran. METHODS: We recruited 847 participants with an age range of 18-65 years. Dietary intake was assessed by a semiquantitative food frequency questionnaire with 168 items. The OBS was calculated by using the following 13 dietary and nondietary anti- and prooxidant components: dietary antioxidants (selenium, fiber, ß-carotene, vitamin D, vitamin C, vitamin E, and folate), dietary prooxidants (iron and saturated and polyunsaturated fatty acids), and nondietary anti- (physical activity) and prooxidants (smoking and obesity). The odds ratio (OR) and 95% confidence interval (CI) of the MetS and its components across tertiles of the OBS were calculated by logistic regression analysis, controlling for age, sex, energy intake, occupation, and educational level. RESULTS: The range of OBS was between 16 and 39. Being in the top versus the bottom tertile of the OBS was not associated with the MetS (OR = 0.71, 95% CI 0.48-1.03; P = 0.07), after controlling for potential confounders. Higher OBS score was associated with a lower likelihood of abdominal obesity (OR: 0.55, 95% CI: 0.38-0.81; P = 0.003) and increased diastolic blood pressure (OR: 0.64, 95% CI: 0.41-0.99; P = 0.04). Higher OBS was not associated with other components of the MetS. CONCLUSION: Overall, the present study showed that there was no significant relationship between OBS and MetS in Tehranian adults.

The Association of Dietary Phytochemical Index with Metabolic Syndrome in Adults.

In this study, we assessed the association between the dietary phytochemical index (DPI) and metabolic syndrome (MetS) among adults in a cross-sectional study. We enrolled 850 adult men and women aged 18-65 years who had been referred to health centers in Tehran, Iran. The DPI was calculated based on 8 components including fruits, vegetables, legumes, whole grains, soy products, nuts, seeds, olive, and olive oil. The odds ratio (OR) and 95% confidence interval (CI) of the MetS across quartiles of the DPI were calculated using the logistic regression analysis, adjusting for age, energy intake, marital status, education status, occupation, smoking status, physical activity, and body mass index. The mean age of participants was 44.7 ± 10.7, of whom 69% were women. The prevalence of MetS was 30.5%. The mean score of DPI in women and men was 36.2 ± 26.8 and 33.7 ± 24.7, respectively. There was no significant association between DPI and odds of MetS in men (ORfourth vs. first quartile,1.57; 95% CI, 0.64-3.84) and women (ORfourth vs. first quartile, 0.86; 95% CI, 0.50-1.49) in the fully adjusted model. There was an inverse association between DPI and increased risk of central obesity in women (ORfourth vs. first quartile, 0.54; 95% CI, 0.29-1.00; p trend = 0.03). There was no significant association between DPI and other components of the MetS in men and women. Finally, we observed no significant association between the DPI and the odds of MetS. However, the finding suggests that having a phytochemical-rich diet can be inversely associated with abdominal obesity.