Postprandial metabolic events and fruit-derived phenolics: a review of the science

Chronic supplementation of proanthocyanidins reduces postprandial lipemia and liver miR-33a and miR-122 levels in a dose-dependent manner in healthy rats

Elevated postprandial triglycerides are associated with an increased risk of cardiovascular disease. Acute proanthocyanidin supplementation improves postprandial lipemia. Therefore, in this study, we evaluated whether a chronic treatment (3 weeks) of grape seed proanthocyanidins (GSPE) improves tolerance to lipid overload and represses liver microRNA (miRNA)-33a and miRNA-122 and their target genes as a mechanism to soften the elevated postprandial triglycerides in healthy rats. Additionally, the minimal GSPE chronic dose required to alter miRNA levels was determined by means of a dose-response experiment using 5, 15, 25 or 50 mg of GSPE/kg body weight. GSPE repressed miR-33a and miR-122 liver expression and reduced postprandial lipemia in a dose-dependent manner. Significant effects were only observed at high levels of proanthocyanidin consumption, but moderate doses of proanthocyanidins were still able to modulate miRNA expression. Therefore, it can be suggested that a population with a normal intake of proanthocyanidin-rich foods can benefit from the modulation of miRNA expression. At the molecular level, this action can confer homeostatic robustness and will thus exert subtle changes in lipid metabolism, thereby reducing the risk associated with postprandial hyperlipemia.

Plant cell wall polysaccharides as potential resources for the development of novel prebiotics

Prebiotic oligosaccharides, with a degree of polymerization (DP) of mostly less than 10, exhibit diverse biological activities that contribute to human health. Currently available prebiotics are mostly derived from disaccharides and simple polysaccharides found in plants. Subtle differences in the structures of oligosaccharides can cause significant differences in their prebiotic proper-ties. Therefore, alternative substances supplying polysaccharides that have more diverse and complex structures are necessary for the development of novel oligosaccharides that have actions not present in existing prebiotics. In this review, we show that structural polysaccharides found in plant cell walls, such as xylans and pectins, are particularly potential resources supplying broadly diverse polysaccharides to produce new prebiotics.

Fruit juice drinks prevent endogenous antioxidant response to high-fat meal ingestion

High-fat meals (HFM) induce metabolic stress, leading to the activation of protective mechanisms, including inflammation and endogenous antioxidant defences. In the present study, we investigated the effects of antioxidant-rich fruit juice drinks on the endogenous antioxidant response induced by HFM. In a double-blind, cross-over design (10 d washout), fourteen overweight volunteers were randomly assigned to one of the following interventions: HFM+500 ml placebo beverage (HFM-PB, free from fruit); HFM+500 ml antioxidant beverage 1 (HFM-AB1; apple, grape, blueberry and pomegranate juices and grape skin, grape seed and green tea extracts); HFM+500 ml antioxidant beverage 2 (HFM-AB2; pineapple, black currant and plum juices). HFM-PB consumption increased the plasma levels of thiols (SH) (4 h, P< 0·001) and uric acid (UA) (2 h, P< 0·01) and total radical-trapping antioxidant parameter (TRAP) (4 h, P< 0·01). Following the consumption of drinks, UA production was significantly reduced with respect to placebo beverage consumption 8 h after HFM-AB2 consumption (P< 0·05). SH levels were reduced 0·5 (P< 0·05), 1 (P< 0·05) and 2 h (P< 0·01) after HFM-AB1 consumption and 2, 4 and 8 h (P< 0·05) after HFM-AB2 consumption. Plasma TRAP (2 h, P< 0·001) and urinary ferric reducing antioxidant power (0–8 h, P< 0·01) were increased by HFM-AB1 consumption, the drink with the highest in vitro antioxidant capacity, but not by HFM-AB2 consumption. In urine, UA levels were significantly increased from basal levels after the consumption of HFM-PB and HFM-AB2. However, neither of the beverages increased the urinary excretion of UA with respect to the placebo beverage. In conclusion, the increase in UA and SH levels induced by HFM as part of an endogenous antioxidant response to postprandial stress can be prevented by the concomitant ingestion of antioxidant-rich fruit juice drinks.

Evaluating and adapting the Mediterranean diet for non-Mediterranean populations: a critical appraisal

This review outlines the limitations of current techniques for evaluating the Mediterranean diet in Mediterranean versus non-Mediterranean populations. Differences between the two populations with regard to the foods that are available, food processing and preparation techniques, and eating and lifestyle habits may influence the implementation and effects of a Mediterranean diet in non-Mediterranean regions. For example, the composition of food groups may vary significantly, due to differences in the specific foods within a food group and to differences in aspects of food production and preparation. Notable differences between the diets of Mediterranean versus non-Mediterranean populations include the source of monounsaturated fatty acids (olive oil versus meat), the amount of vegetables consumed and their manner of preparation, the source of alcohol (wine versus other) and the pattern of intake, and the types of meat and dairy products consumed. Lifestyle factors such as meal patterns and exposure to sunlight may also act as confounding factors when the overall benefits of a Mediterranean diet are assessed. Improving the calculation of Mediterranean diet scores and measuring plasma nutrient levels may help mitigate the effects of confounders. These considerations could have important health implications when a Mediterranean diet is implemented by non-Mediterranean populations.

Functional foods and nutraceuticals as therapeutic tools for the treatment of diet-related diseases

In Western societies, the incidence of diet-related diseases is progressively increasing due to greater availability of hypercaloric food and a sedentary lifestyle. Obesity, diabetes, atherosclerosis, and neurodegeneration are major diet-related pathologies that share a common pathogenic denominator of low-grade inflammation. Functional foods and nutraceuticals may represent a novel therapeutic approach to prevent or attenuate diet-related disease in view of their ability to exert anti-inflammatory responses. In particular, activation of intestinal T regulatory cells and homeostatic regulation of the gut microbiota have the potential to reduce low-grade inflammation in diet-related diseases. In this review, clinical applications of polyphenol-rich functional foods and nutraceuticals in postprandial inflammation, obesity, and ageing will be discussed. We have placed special emphasis on polyphenols since they are broadly distributed in plants.

Different postprandial acute response in healthy subjects to three strawberry jams varying in carbohydrate and antioxidant content: a randomized, crossover trial

PURPOSE

Dietary food composition influences postprandial glucose homeostasis. Thus, the objective was to investigate the effects of an acute intake of three different types of strawberry jam, differing in carbohydrate and antioxidants content, on postprandial glucose metabolism, lipid profile, antioxidant status, and satiety.

METHODS

Sixteen healthy adults participated in a randomized, crossover, double-blind study with three arms, receiving 60 g of three different strawberry jams. Blood samples were collected at fasting and at 30, 60, 90, and 120 min after its intake. Blood analyses were performed with validated procedures and satiety was estimated with visual analogue scale (VAS).

RESULTS

Blood glucose concentrations were maintained at normal values and without peaks within the 2 h after consumption of low-sugar jams. However, blood glucose and insulin were significantly higher at 30 and 60 min after high-sugar (HS) jam intake versus both low-sugar jams. Furthermore, HS jam produced more satisfaction at short time, but decreased as soon as blood glucose concentration began to decrease. Moreover, HS ingestion produced lower free fatty acid levels (p < 0.05) throughout the trial with respect both the low-sugar jams. However, no additional benefits on oxidative status (malondialdehyde, glutathione peroxidase, total antioxidant capacity, and uric acid), glucose, lipid, and satiety variables were observed due to the inclusion of an antioxidant to low-sugar jam.

CONCLUSIONS

This study reinforces the idea that products without added sugars are appropriate for the management of glycemic alterations and provides further insight into the effect of natural antioxidants as a functional ingredient on oxidative status and related metabolic disturbances. Registered at www.clinicaltrials.gov as NCT01684332.

Effects of white rice, brown rice and germinated brown rice on antioxidant status of type 2 diabetic rats

Oxidative stress is implicated in the pathogenesis of diabetic complications, and can be increased by diet like white rice (WR). Though brown rice (BR) and germinated brown rice (GBR) have high antioxidant potentials as a result of their bioactive compounds, reports of their effects on oxidative stress-related conditions such as type 2 diabetes are lacking. We hypothesized therefore that if BR and GBR were to improve antioxidant status, they would be better for rice consuming populations instead of the commonly consumed WR that is known to promote oxidative stress. This will then provide further reasons why less consumption of WR should be encouraged. We studied the effects of GBR on antioxidant status in type 2 diabetic rats, induced using a high-fat diet and streptozotocin injection, and also evaluated the effects of WR, BR and GBR on catalase and superoxide dismutase genes. As dietary components, BR and GBR improved glycemia and kidney hydroxyl radical scavenging activities, and prevented the deterioration of total antioxidant status in type 2 diabetic rats. Similarly, GBR preserved liver enzymes, as well as serum creatinine. There seem to be evidence that upregulation of superoxide dismutase gene may likely be an underlying mechanism for antioxidant effects of BR and GBR. Our results provide insight into the effects of different rice types on antioxidant status in type 2 diabetes. The results also suggest that WR consumption, contrary to BR and GBR, may worsen antioxidant status that may lead to more damage by free radicals. From the data so far, the antioxidant effects of BR and GBR are worth studying further especially on a long term to determine their effects on development of oxidative stress-related problems, which WR consumption predisposes to.

Postprandial glucose, insulin, and free fatty acid responses to sucrose consumed with blackcurrants and lingonberries in healthy women

BACKGROUND

Sucrose induces high postprandial glucose and insulin responses. In vitro studies suggest that berries may reduce the digestion and absorption of sucrose and thereby suppress postprandial glycemia, but the evidence in humans is limited.

OBJECTIVE

We investigated the effects of sucrose ingested with blackcurrants (Ribes nigrum) and lingonberries (Vaccinium vitis-idaea) on postprandial glucose, insulin, and free fatty acid responses.

DESIGN

Twenty healthy women participated in a randomized, controlled, crossover meal study. They consumed whole blackcurrants or lingonberries (150 g served as purées) or blackcurrant or lingonberry nectars (300 mL), each with 35 g added sucrose. Sucrose alone (35 g in 300 mL water) was used as a reference. Blood samples were collected at 0, 15, 30, 45, 60, 90, and 120 min.

RESULTS

In comparison with sucrose alone, ingestion of sucrose with whole berries resulted in reduced glucose and insulin concentrations during the first 30 min and a slower decline during the second hour and a significantly improved glycemic profile. Berries prevented the sucrose-induced late postprandial hypoglycemic response and the compensatory free fatty acid rebound. Nearly similar effects were observed when sucrose was consumed with berry nectars. The improved responses were evident despite the higher content of available carbohydrate in the berry and nectar meals, because of the natural sugars present in berries.

CONCLUSIONS

Blackcurrants and lingonberries, as either whole berries or nectars, optimize the postprandial metabolic responses to sucrose. The responses are consistent with delayed digestion of sucrose and consequent slower absorption of glucose.

Spore-forming bacteria and their utilisation as probiotics

In this review article, the beneficial application of bacterial spore formers as probiotics in the food industry is discussed based on the knowledge gleaned from current publications. The summary of new scientific results provides evidence of the advantages of the utilisation of Bacillus or Clostridium strains in the food industry. Both bacteria are able to produce a very stable duration form: the endospore. Compared to the widely used lactic acid bacteria, bacterial spores offer the advantage of a higher survival rate during the acidic stomach passage and better stability during the processing and storage of the food product. In many food products, germination of the spores does not occur. Hence the product quality of the food is not affected because of their inactive metabolism. Besides the possible utilisation and functional properties, an overview of the fast-developing knowledge about the mechanisms of the beneficial health effects of spore-forming bacteria is provided.

Unraveling how probiotic yogurt works

No matter what the advertisements are, or are not, allowed to say, it would be good to know if probiotic yogurt, in addition to its nutritional value, has a beneficial effect on the gut. In this issue, McNulty, Gordon and their colleagues describe a parallel series of human and animal studies designed to uncover the effects of probiotic yogurt on the gut microbiota. The intake of yogurt supplemented with five bacterial species, including the probiotic Bifidobacterium animalis, did not appreciably alter the composition of the human or mouse gut microbiota, but it did induce transcriptional and metabolic changes that reflected host bacterial responses to the arrival of the new species. This elegant study provides a strategy to delineate the precise effects exerted by probiotic foods on the human gut.

Review article: fructose in non-alcoholic fatty liver disease

BACKGROUND

The role of excess fructose intake in the pathogenesis of non-alcoholic fatty liver disease (NAFLD) has recently received increasing attention, but the pathophysiology of this relationship has been only partly elucidated.

AIM

To provide an overview of the potential role played by fructose in the pathogenesis of NAFLD by focusing on both indirect and direct harmful effects.

METHODS

Experimental and clinical studies which investigated the relation of fructose with NAFLD are reviewed.

RESULTS

Several factors may potentially contribute to fructose-induced NAFLD, including the induction of the metabolic syndrome, copper deficiency, bacterial translocation from the gut to the liver, the formation of advanced glycation endproducts and a direct dysmetabolic effect on liver enzymes.

CONCLUSIONS

Experimentally-increased fructose intake recapitulates many of the pathophysiological characteristics of the metabolic syndrome in humans, which may in turn lead to NAFLD. However, the majority of experimental studies tend to involve feeding excessively high levels of fructose (60-70% of total energy intake) which is not reflective of average human intake. Hopefully, the combination of in vivo, in vitro and genetic research will provide substantial mechanistic evidence into the role of fructose in NAFLD development and its complications.

Soy protein based supplementation supports metabolic effects of resistance training in previously untrained middle aged males

OBJECTIVE

To determine changes in body composition, physical performance, metabolic and hormonal parameters induced by lifestyle counselling, resistance training and resistance training with soy protein based supplemention in middle aged males.

DESIGN

Randomised controlled study consisting of resistance training without (RT-G) or with (RTS-G) a soy protein based supplement and a control group with lifestyle education only (LE-G).

SUBJECTS

Forty healthy middle aged men (50-65 years, BMI 25-29.9 kg/m2).

MEASUREMENTS

Changes in body weight (BW) and waist circumference (WC) were measured and body composition (BC), fat mass (FM), lean body mass (LBM) were measured by skin fold anthropometry at baseline and after 12 weeks of intervention. In addition, changes in physical fitness, metabolic and hormonal parameters (lipids, glucose, fructosamines, insulin, insulin-like growth factor-1, Leptin, human growth hormone, dehydroepiandrosterone, testosterone, hs-CRP, Il-6) were evaluated.

RESULTS

Thirty-five participants completed the 12 week study. No significant changes in BW were noted although RM and WC dropped and LBM increased after training, particularly in the RTS group (FM 22.6 ± 5.5 kg to 21.2 ± 4.7 kg; LBM 68.5 ± 7.2 kg to 70.1 ± 7.4; p < 0.01). Subjects in the RTS group experienced more pronounced improvements in the strength measurements than the RT group. After the training intervention there were significant changes in hormonal and metabolic parameters as well as in glycemic control, particularly in the RTS group.

CONCLUSIONS

Our data suggest that resistance training, particularly in combination with a soy protein based supplement improves body composition and metabolic function in middle aged untrained and moderately overweight males.

Culinary plants and their potential impact on metabolic overload

Contemporary human behavior has led a large proportion of the population to metabolic overload and obesity. Postprandial hyperlipidemia and hyperglycemia evoke redox imbalance in the short term and lead to complex chronic disease in the long term with repeated occurrence. Complex diseases are best prevented with complex components of plants; thus, current nutrition research has begun to focus on the development of plant-based functional foods and dietary supplements for health and well-being. Furthermore, given the wide range of species, parts, and secondary metabolites, culinary plants can contribute significant variety and complexity to the human diet. Although understanding the health benefits of culinary plants has been one of the great challenges in nutritional science due to their inherent complexity, it is an advantageous pursuit. This review will address the challenges and opportunities relating to studies of the health benefits of culinary plants, with an emphasis on obesity attributed to metabolic overload.

The molecular basis of nutritional intervention in multiple sclerosis: a narrative review

It is commonly accepted that nutrition is one of the possible environmental factors involved in the pathogenesis of multiple sclerosis (MS), but its role as complementary MS treatment is unclear and largely disregarded. At present, MS therapy is not associated to a particular diet, probably due to lack of information on the effects of nutrition on the disease. To overcome the distrust of the usefulness of dietary control in MS and to encourage nutritional interventions in the course of the disease, it is necessary to assess the nature and the role of bioactive dietary molecules and their targets, and establish how a dietary control can influence cell metabolism and improve the wellness of MS patients. The aim of this review is to provide a rationale for a nutritional intervention in MS by evaluating at the molecular level the effects of dietary molecules on the inflammatory and autoimmune processes involved in the disease. Present data reveal that healthy dietary molecules have a pleiotropic role and are able to change cell metabolism from anabolism to catabolism and down-regulate inflammation by interacting with enzymes, nuclear receptors and transcriptional factors. The control of gut dysbiosis and the combination of hypo-caloric, low-fat diets with specific vitamins, oligoelements and dietary integrators, including fish oil and polyphenols, may slow-down the progression of the disease and ameliorate the wellness of MS patients.

Strawberry anthocyanin and its association with postprandial inflammation and insulin

The present study investigates the effect of strawberry antioxidants in beverage form on meal-induced postprandial inflammatory and insulin responses in human subjects. Overweight adults (n 24) consumed a high-carbohydrate, moderate-fat meal (HCFM) accompanied by either a strawberry or a placebo beverage in a cross-over design. Postprandial changes in plasma anthocyanins, their metabolites, insulin, glucose and inflammatory markers were assessed for 6 h. The postprandial concentrations of pelargonidin sulfate and pelargonidin-3-O-glucoside were significantly increased when the strawberry beverage was consumed concurrently with the HCFM compared with the placebo beverage (P < 0·001). The strawberry beverage significantly attenuated the postprandial inflammatory response as measured by high-sensitivity C-reactive protein and IL-6 (P < 0·05) induced by the HCFM. It was also associated with a reduction in postprandial insulin response (P < 0·05). Collectively, these data provide evidence for favourable effects of strawberry antioxidants on postprandial inflammation and insulin sensitivity.

Y2 and Y4 receptor signaling synergistically act on energy expenditure and physical activity

Neuropeptide Y receptors are critical regulators of energy homeostasis and are well known for their powerful influence on feeding, but their roles in other important aspects of energy homeostasis, such as energy expenditure and their functional interactions in these processes, are largely unknown. Here we show that mice lacking both Y2 and Y4 receptors exhibited a reduction in adiposity, more prominent in intra-abdominal vs. subcutaneous fat, and an increase in lean mass as determined by dual-energy X-ray absorptiometry. These changes were more pronounced than those seen in mice with Y2 or Y4 receptor single deletion, demonstrating the important roles and synergy of Y2 and Y4 signaling in the regulation of body composition. These changes in body composition occurred without significant changes in food intake, but energy expenditure and physical activity were significantly increased in Y4−/− and particularly in Y2−/−Y4−/− but not in Y2−/− mice, suggesting a critical role of Y4 signaling and synergistic interactions with Y2 signaling in the regulation of energy expenditure and physical activity. Y2−/− and Y4−/− mice also exhibited a decrease in respiratory exchange ratio with no further synergistic decrease in Y2−/−Y4−/− mice, suggesting that Y2 and Y4 signaling each play important and independent roles in the regulation of substrate utilization. The synergy between Y2 and Y4 signaling in regulating fat mass may be related to differences in mitochondrial oxidative capacity, since Y2−/−Y4−/− but not Y2−/− or Y4−/− mice showed significant increases in muscle protein levels of peroxisome proliferator-activated receptor (PPAR)γ coactivator (PGC)-1α, and mitochondrial respiratory chain complexes I and III. Taken together, this work demonstrates the critical roles of Y2 and Y4 receptors in the regulation of body composition and energy metabolism, highlighting dual antagonism of Y2 and Y4 receptors as a potentially effective anti-obesity treatment.