Britt Burton-Freeman

Dietary Fiber and Energy Regulation

Dietary fiber has many functions in diet, one of which may be to aid in energy intake control and reduced risk for development of obesity. The role of dietary fiber in energy intake regulation and obesity development is related to its unique physical and chemical properties that aid in early signals of satiation and enhanced or prolonged signals of satiety. Early signals of satiation may be induced through cephalic- and gastric-phase responses related to the bulking effects of dietary fiber on energy density and palatability, whereas the viscosity-producing effects of certain fibers may enhance satiety through intestinal-phase events related to modified gastrointestinal function and subsequent delay in fat absorption. The goal of this paper is to provide a brief overview of the role of dietary fiber in energy intake regulation, highlighting the relationship between fiber properties and physiologic action.

Strawberry Modulates LDL Oxidation and Postprandial Lipemia in Response to High-Fat Meal in Overweight Hyperlipidemic Men and Women

Background: Elevated levels of lipids, such as total cholesterol (TC), low-density lipoprotein cholesterol (LDL), and triglycerides (TG), are widely recognized as risk factors for cardiovascular disease (CVD). Oxidized LDL (OxLDL) is an emerging risk factor considered relevant in oxidative stress and endothelial dysfunction, which is implicated in the progression of CVD. Consumption of a diet rich in polyphenols may be cardioprotective through its impact on oxidative stress and protecting LDL from oxidation. Objectives: This study was designed to test the ability of strawberry phenolic compounds to mitigate the postprandial effects of a high-fat meal on OxLDL as well as investigate the effects of phenolic compounds on lipid metabolism. Methods: Twenty-four hyperlipidemic men and women (14 women, 10 men; mean age 50.9 ± SD 15 years) were recruited to participate in this randomized, single-blind, placebo-controlled, 12-wk crossover trial. After a 10-day run-in period, subjects consumed either an active strawberry beverage (Str; containing 10 g freeze-dried fruit) or a placebo (Pbo) beverage matched in energy and macronutrient composition for 6 weeks. Twice before randomization and once at the 6-week crossover point, subjects received either Str or Pbo with a high-fat challenge meal (HFM). TC, LDL, high-density lipoprotein cholesterol, TG, and OxLDL were measured at defined intervals for 6 h before and after HFM challenge. Fasting concentrations of blood variables at 0, 6, and 12 weeks were compared to assess chronic intake of Str or Pbo. Results: After the HFM during the run-in period, TG and OxLDL were lower after Str than Pbo (p  =  0.005, p  =  0.01, and p  =  0.0008, respectively). HFM responses after 6 weeks of Str versus Pbo resulted in decreased lipid levels and a sex by treatment interaction for OxLDL (p  = < 0.0001, and p  =  0.0002). Conclusion: The present results support a role for strawberry in mitigating fed-state oxidative stressors that may contribute to atherogenesis.

Berries: anti-inflammatory effects in humans.

A sustained pro-inflammatory state is a major contributing factor in chronic disease development, progression, and complication, including the most commonly known diseases: cardiovascular disease, Alzheimers, and type 2 diabetes. Fruits, such as berries, contain polyphenol compounds purported to have anti-inflammatory activity in humans. Among the most notable polyphenols in berries are anthocyanins, responsible for their distinctive colors of red, blue, and purple. Berries have been studied widely for their antioxidant properties; however, preclinical data suggest important effects on inflammatory pathways. Correspondingly, the effects of berries, including extracts and purified anthocyanins, have been the subject of a number of human trials. This review aims to evaluate the current state of the human science on berry (products) as a source of dietary polyphenols, particularly anthocyanins, to modulate inflammatory status. Identifying dietary strategies that manage the modern-day inflammatory burden has important implications for chronic disease risk reduction and informing dietary guidelines aimed at achieving and maintaining health.

Protective activity of processed tomato products on postprandial oxidation and inflammation: A clinical trial in healthy weight men and women

SCOPE This study was designed to evaluate the ability of tomato rich in lycopene to modify postprandial oxidative stress, inflammation, and endothelial function in healthy weight individuals. METHODS AND RESULTS Twelve women and 13 men (mean age = 27 ± 8 years; mean body mass index= 22 ± 2) consumed high-fat meals known to induce postprandial oxidative stress on two separate occasions containing either processed tomato product or non-tomato alternative. Blood samples were collected at 0, 30, 60, 90, 120 min, then hourly until 360 min. Flow-mediated dilation (FMD) was performed at 0 and 210 min. Endpoints included changes in glucose, insulin, lipids, oxidized low-density lipoprotein (OxLDL), inflammatory cytokines, and FMD. Both meals induced increases in plasma glucose, insulin, and lipid concentrations (p < 0.05). A trend for higher triglycerides at >240 min was observed after the tomato meal (p = 0.006). Tomato significantly attenuated high-fat meal-induced LDL oxidation (p < 0.05) and rise in interleukin-6 (p < 0.0001), a proinflammatory cytokine and inflammation marker. CONCLUSION The data indicate that consuming tomato products with a meal attenuates postprandial lipemia-induced oxidative stress and associated inflammatory response. The relevance of OxLDL and inflammation to vascular injury suggests a potentially important protective role of tomato in reducing cardiovascular disease risk. ClinicalTrials.gov Registration number - NCT00966550.

Glycomacropeptide (GMP) is not critical to whey-induced satiety, but may have a unique role in energy intake regulation through cholecystokinin (CCK)

BACKGROUND Whey protein is more satiating than other protein types, including casein. We hypothesized that enhanced satiety with whey protein is related to glycomacropeptide (GMP) content, a stimulator of cholecystokinin (CCK). OBJECTIVES To investigate the role of GMP in whey protein-induced satiety, as measured by subjective satiety, CCK release and food intake at a test meal in healthy weight men and women. DESIGN In a within-subjects design, twenty subjects (n=10 men, 10 women) consumed 1 of 4 preload shakes (300 mL, 1 MJ), 1 week apart. Preloads differed by protein source and content: Whey; whey protein isolate, Whey (-)GMP; whey protein without GMP, Control; low protein, GMP; GMP isolate. Protein energy of preloads was 44, 44, 2 and 3%, respectively. Subjective satiety and CCK were measured at 0, 15, 30, 45, 60, 75 and 105 min post-preload consumption. A lunch test meal was provided at 75 min. Food records were completed weekly. RESULTS Pre-meal satiety was greater after whey protein preloads compared to Control and GMP preloads in women, but no difference was evident in men (sex by preload, p<0.03). CCK concentrations followed a pattern that predicted the subjective satiety in women, but not in men. Test meal intake was not different by preload; however, compensation relative to usual daily intake was achieved after whey-containing- and GMP-containing preloads in women and after GMP and Control preloads in men. CONCLUSIONS GMP alone is not critical in pre-meal whey-induced satiety; however, it may have a unique role in compensatory intake regulation managing daily energy intake.

The effect of strawberries in a cholesterol-lowering dietary portfolio

Effective diets reduce blood lipids and oxidative damage, both of which have been linked to the complications of diabetes and coronary heart disease. Our objective was to assess the effect of adding strawberries, as a source of antioxidants, to improve the antioxidant effect of a cholesterol-lowering diet (dietary portfolio). To this end, 28 hyperlipidemic subjects who had followed the dietary portfolio consisting of soy, viscous fiber, plant sterol, and nuts for a mean of 2.5 years were randomized to receive supplements of strawberries (454 g/d, 112 kcal) or additional oat bran bread (65 g/d, 112 kcal, approximately 2 g beta-glucan) (control) in a randomized 1-month crossover study with a 2-week washout. Strawberry supplementation resulted in a greater reduction in oxidative damage to low-density lipoprotein (LDL) measured as thiobarbituric acid-reactive substances in the LDL fraction (P = .014). At the end of the strawberry period, reductions in LDL cholesterol and in the ratio of total to high-density lipoprotein cholesterol were maintained close to 1-year values at -13.4% +/- 2.1% and -15.2% +/- 1.7%, respectively (P < .001), and were similar to the post-oat bran bread values. Strawberries also improved the palatability of the diet. We conclude that strawberry supplementation reduced oxidative damage to LDL while maintaining reductions in blood lipids and enhancing diet palatability. Added fruit may improve the overall utility of diets designed to lower coronary heart disease risk.

Mechanism of the endothelium-dependent relaxation evoked by a grape seed extract

GSEs (grape seed extracts) which contain polyphenolic compounds cause an endothelium-dependent relaxation of blood vessels. The aim of the present study was to examine the mechanisms involved in this response. A well-characterized GSE was applied to rabbit aortic rings suspended in organ baths containing Krebs-Henseleit buffer maintained at 37 degrees C. In aortic rings pre-contacted with noradrenaline (norepinephrine), the extract produced a dose-dependent relaxation. The maximum relaxations elicited by the extract (71.9+/-1.0%) were similar to those elicited by acetylcholine (64.2+/-1.5%) (n=12 for each). As expected, the relaxations were abolished by removal of the endothelium and by prior incubation with L-NAME (N(G)-nitro-L-arginine methyl ester), confirming the essential role of eNOS (endothelial NO synthase) in the response. The responses to the GSE were also abolished by incubation with wortmannin and LY294002, which are inhibitors of PI3K (phosphoinositide 3-kinase). These compounds had no effect on the responses to acetylcholine. Using immunoblotting, we also demonstrated that the GSE induced the phosphorylation of both Akt and eNOS in HUVECs (human umbilical vein endothelial cells). Finally, the extract was modified by methylation of the hydroxy groups in the polyphenolic groups and was applied to the aortic rings. The modified extract failed to cause a relaxation. Taken together, these findings suggest that the endothelium-dependent relaxation induced by the GSE was mediated by activation of the PI3K/Akt signalling pathway through a redox-sensitive mechanism, resulting in phosphorylation of eNOS.

Effect of black currant anthocyanins on the activation of endothelial nitric oxide synthase (eNOS) in vitro in human endothelial cells.

Polyphenols are known to induce vasodilatory function via activation of the redox-sensitive phosphatidylinositol-3 (PI3)/protein kinase B (Akt) pathway. Black currant fruits have appreciable amounts of polyphenolic compounds including cyanidin-3-O-glucoside, cyanidin-3-O-rutinoside, delphinidin-3-O-glucoside, and delphinidin-3-O-rutinoside. It was hypothesized that black currant fruit extracts would cause activation of endothelial nitric oxide synthase (eNOS) through activation of redox-sensitive PI3 kinase/Akt signaling pathway. To test this hypothesis, human umbilical vein endothelial cells (HUVECs) were treated with different concentrations/times of black currant juice concentrates (Ben Gairn and Ben Hope) and the activation of Akt and eNOS was measured using immunoblotting. Vitamin C is also known to activate Akt and eNOS in in vitro models, and black currants are rich in vitamin C. Therefore, the effect of black currant extracts with and without coexisting vitamin C was investigated, using SPE columns to eliminate vitamin C content. The individual (and combined) effects of the major anthocyanins present in black currant juice samples with and without vitamin C were investigated and compared to the effects of the whole extract. Black currant juice samples (1 μL/mL) significantly increased the phosphorylation of Akt (p-Akt) and eNOS (p-eNOS) (P < 0.05). Activation of Akt and eNOS was abolished by incubation with wortmannin, a PI3K inhibitor, supporting the involvement of PI3K/Akt. Vitamin C alone significantly increased the p-Akt and p-eNOS (P < 0.05); however, removal of vitamin C from black currant did not significantly affect p-Akt and p-eNOS compared to black currant with vitamin C. Assessment of individual anthocyanins also showed significant effects on p-Akt and p-eNOS. In summary, in the present study data suggested that black currant concentrates, Ben Gairn and Ben Hope, activated eNOS via Akt/PI3 kinase pathway in vitro in HUVECs and that the effect was not dependent on vitamin C.

Cholecystokinin and serotonin receptors in the regulation of fat-induced satiety in rats

The present study investigated the relationship between endogenous CCK and serotonin (5-HT) in fat-induced satiety. Male Wistar rats with duodenal cannulas were adapted to eating 6 h/day along with receiving an infusion of saline or one of two isocaloric solutions (10 ml, 1 kcal/ml, 0.45 ml/min) varying in fat and carbohydrate content (20 or 80% energy from fat). Rats were infused 10 min after food presentation. The satiation/satiety response was determined from measures of meal size (MS), intermeal interval (IMI), and total food intake (TFI). Infusion with either fat solution reduced MS compared with saline; however, the 80% fat infusate reduced TFI and lengthened the IMI compared with saline and the 20% fat infusate. CCK and 5-HT involvement in fat-induced satiety was investigated by preceding the 80% fat infusate with CCK and/or 5-HT3 receptor antagonists Devazepide (Dev) and Tropisetron (Trop). A CCK releaser, trypsin inhibitor (TI), was added to the 20% fat infusate to enhance satiety. Pretreatment with Dev or Trop alone attenuated the inhibitory effects of the 80% solution on IMI, whereas reversal of the inhibitory effects on MS and TFI were sensitive only to Dev at the doses provided. Both antagonists together completely blocked the satiating effects of the 80% fat infusate on all feeding variables measured. Addition of TI to the 20% fat infusate lengthened the IMI but did not affect MS or TFI. These results provide evidence for the participation of both endogenous CCK and 5-HT in the satiety response to fat in the intestine.The present study investigated the relationship between endogenous CCK and serotonin (5-HT) in fat-induced satiety. Male Wistar rats with duodenal cannulas were adapted to eating 6 h/day along with receiving an infusion of saline or one of two isocaloric solutions (10 ml, 1 kcal/ml, 0.45 ml/min) varying in fat and carbohydrate content (20 or 80% energy from fat). Rats were infused 10 min after food presentation. The satiation/satiety response was determined from measures of meal size (MS), intermeal interval (IMI), and total food intake (TFI). Infusion with either fat solution reduced MS compared with saline; however, the 80% fat infusate reduced TFI and lengthened the IMI compared with saline and the 20% fat infusate. CCK and 5-HT involvement in fat-induced satiety was investigated by preceding the 80% fat infusate with CCK and/or 5-HT3 receptor antagonists Devazepide (Dev) and Tropisetron (Trop). A CCK releaser, trypsin inhibitor (TI), was added to the 20% fat infusate to enhance satiety. Pretreatment with Dev or Trop alone attenuated the inhibitory effects of the 80% solution on IMI, whereas reversal of the inhibitory effects on MS and TFI were sensitive only to Dev at the doses provided. Both antagonists together completely blocked the satiating effects of the 80% fat infusate on all feeding variables measured. Addition of TI to the 20% fat infusate lengthened the IMI but did not affect MS or TFI. These results provide evidence for the participation of both endogenous CCK and 5-HT in the satiety response to fat in the intestine.

Meal pattern analysis to investigate the satiating potential of fat, carbohydrate, and protein in rats

We examined meal patterns after isocaloric duodenal infusions of fat, carbohydrate (CHO), and protein by measuring meal size, intermeal interval (IMI) and total food intake (TFI). Wistar rats were adapted to normal feeding 6 h/day, with continuous computer monitoring of feeding patterns. One of five solutions (10 ml of 1 kcal/ml at 0.45 ml/min; 0, 20, 50, 80, or 100% of energy from fat) or saline (control) was infused 10 min after initiation of eating. Separate rats received casein or casein hydrolysate at 18.5 or 37% energy. Equivalent energy loads varying in fat, CHO, and protein content compared with saline resulted in similar reductions in first meal intakes. The second meal did not differ among fat and CHO treatments including saline; however, infusion with a protein-containing solution increased the size of meal 2. The IMI was doubled by protein infusion independently of dose or source but extended dose dependently by fat. TFI was lower after high fat and higher after protein than after saline infusion. The results indicate that the concentrations of fat, CHO, and protein differentially affect the qualitative and quantitative aspects of feeding in rats.We examined meal patterns after isocaloric duodenal infusions of fat, carbohydrate (CHO), and protein by measuring meal size, intermeal interval (IMI) and total food intake (TFI). Wistar rats were adapted to normal feeding 6 h/day, with continuous computer monitoring of feeding patterns. One of five solutions (10 ml of 1 kcal/ml at 0.45 ml/min; 0, 20, 50, 80, or 100% of energy from fat) or saline (control) was infused 10 min after initiation of eating. Separate rats received casein or casein hydrolysate at 18.5 or 37% energy. Equivalent energy loads varying in fat, CHO, and protein content compared with saline resulted in similar reductions in first meal intakes. The second meal did not differ among fat and CHO treatments including saline; however, infusion with a protein-containing solution increased the size of meal 2. The IMI was doubled by protein infusion independently of dose or source but extended dose dependently by fat. TFI was lower after high fat and higher after protein than after saline infusion. The results indicate that the concentrations of fat, CHO, and protein differentially affect the qualitative and quantitative aspects of feeding in rats.