Epicatechin ingested via cocoa products reduces blood pressure in humans: a nonlinear regression model with a Bayesian approach

Epicatechin-induced conformational changes in β-lactoglobulin B monitored by FT-IR spectroscopy

ABSTRACT

The interaction between whey carrier protein β-lactoglobulin B and (-)-epicatechin, a major dietary flavonoid with a wide range of health-promoting biological activities, was investigated by Fourier transform infrared spectroscopy in physiological conditions. Amide I spectra of epicatechin - β-lactoglobulin complexes, in D2O buffer solutions, pD= 6.8, at molar ratios from 0.5:1 to 15:1, were measured by using a cell device specifically created. Changes in secondary structure elements at increasing epicatechin concentrations were quantified. Two different trends were observed for the intensities of β-sheet, random coil, and side chain contributions. At molar ratios ≤2 the β-exposed strand contributions (1625 cm(-1)) increased at the expence of the β-antiparallel sheet band (1637 cm(-1)). At molar ratios >2 the intensities of both β structures slightly decreased. The same behaviour was observed for the side chain contributions (band around 1610 ÷ 1620 cm(-1)). In addition, a conformational transition to a slightly opened structure, followed by aggregate formation at the highest molar ratios, were revealed. The results suggest that binding of epicatechin to β-lactoglobulin in physiological conditions occurs at the surface of the protein molecule, resulting in protein dissociation at molar ratios ≤2 with minor changes in secondary structure. This finding provides further evidence for the possibility of successful use of the protein as a carrier of flavonoids, epicatechin included.

Nutrition and nutraceutical supplements for the treatment of hypertension: part III

Vascular biology, endothelial and vascular smooth muscle, and cardiac dysfunction play a primary role in the initiation and perpetuation of hypertension, cardiovascular disease, and target organ damage. Nutrient-gene interactions and epigenetics are predominant factors in promoting beneficial or detrimental effects in cardiovascular health and hypertension. Macronutrients and micronutrients can prevent, control, and treat hypertension through numerous mechanisms related to vascular biology. Oxidative stress, inflammation, and autoimmune dysfunction initiate and propagate hypertension and cardiovascular disease. There is a role for the selected use of single and component nutraceutical supplements, vitamins, antioxidants, and minerals in the treatment of hypertension based on scientifically controlled studies that complement optimal nutrition, coupled with other lifestyle modifications.

Tea and flavonoids: where we are, where to go next

There is a need to evaluate the evidence about the health effects of tea flavonoids and to provide valid, specific, and actionable tea consumption information to consumers. Emerging evidence suggests that the flavonoids in tea may be associated with beneficial health outcomes, whereas the benefits and risks of tea extracts and supplements are less well known. The next steps in developing tea science should include a focus on the most promising leads, such as reducing the risk of cardiovascular disease and stroke, rather than pursuing smaller, more diffuse studies of many different health outcomes. Future tea research should also include the use of common reference standards, better characterization of intervention products, and application of batteries of biomarkers of intakes and outcomes across studies, which will allow a common body of evidence to be developed. Mechanistic studies should determine which tea bioactive constituents have effects, whether they act alone or in combination, and how they influence health. Clinical studies should use well-characterized test products, better descriptions of baseline diets, and validated biomarkers of intake and disease risk reduction. There should be more attention to careful safety monitoring and adverse event reporting. Epidemiologic investigations should be of sufficient size and duration to detect small effects, involve populations most likely to benefit, use more complete tea exposure assessment, and include both intermediary markers of risk as well as morbidity and mortality outcomes. The construction of a strong foundation of scientific evidence on tea and health outcomes is essential for developing more specific and actionable messages on tea for consumers.

(-)-Epicatechin rich cocoa mediated modulation of oxidative stress regulators in skeletal muscle of heart failure and type 2 diabetes patients

BACKGROUND

Type 2 diabetes (T2D) and heart failure (HF) are associated with high levels of skeletal muscle (SkM) oxidative stress (OS). Health benefits attributed to flavonoids have been ascribed to antioxidation. However, for flavonoids with similar antioxidant potential, end-biological effects vary widely suggesting other mechanistic venues for reducing OS. Decreases in OS may follow the modulation of key regulatory pathways including antioxidant levels (e.g. glutathione) and enzymes such as mitochondrial superoxide dismutase (SOD2) and catalase.

METHODS

We examined OS-related alterations in SkM in T2D/HF patients (as compared vs. healthy controls) and evaluated the effects of three-month treatment with (-)-epicatechin (Epi) rich cocoa (ERC). To evidence Epi as the mediator of the improved OS profile we examined the effects of pure Epi (vs. water) on SkM OS regulatory systems in a mouse model of insulin resistance and contrasted results vs. normal mice.

RESULTS

There were severe alterations in OS regulatory systems in T2D/HF SkM as compared with healthy controls. Treatment with ERC induced recovery in glutathione levels and decreases in the nitrotyrosilation and carbonylation of proteins. With treatment, key transcriptional factors translocate into the nucleus leading to increases in SOD2 and catalase protein expression and activity levels. In insulin resistant mice, there were alterations in muscle OS and pure Epi replicated the beneficial effects of ERC found in humans.

CONCLUSIONS

Major perturbations in SkM OS can be reversed with ERC in T2D/HF patients. Epi likely mediates such effects and may provide an effective means to treat conditions associated with tissue OS.

(-)-Epicatechin reduces blood pressure and improves vasorelaxation in spontaneously hypertensive rats by NO-mediated mechanism

Studies in humans have found consumption of certain flavanoid-containing foods to be associated with improvement in endothelial function and with reduction of blood pressure (BP). (-)-Epicatechin is a compound representative of the flavanols (a subfamily of flavonoids), abundant in cocoa seeds, which is preserved during the industrialization process to chocolate. The antihypertensive effect of dietary (-)-epicatechin was investigated on spontaneously hypertensive rats (SHRs). Consumption of (-)-epicatechin-supplemented diet (3 g (-)-epicatechin/kg diet) decreased BP in SHR by 27 and 23 mm Hg on days 2 and 6, respectively. On day 6, a 173% increase of nitric oxide synthase (NOS) activity was observed in the aorta of EPI-SHR as compared to nonsupplemented SHR (P < 0.05). Responses to acetylcholine (ACh) were then examined in femoral arteries in the absence and the presence of L-NAME, a nonselective NOS inhibitor, to assess the ACh-mediated relaxation ascribed to NO-dependent and -independent mechanisms. Acetylcholine-induced endothelium-dependent relaxation in the femoral artery was significantly higher in EPI-SHR than in SHR, with a predominance of the NO-dependent component of this relaxation. The endothelium-independent relaxation, assayed by using the NO donor sodium nitroprusside, resulted in nonsignificant difference in the three experimental groups, demonstrating an unaffected function of vascular smooth muscle cells. These results give further support to the concept that (-)-epicatechin can modulate BP in hypertension by increasing NO levels in the vasculature.

Temperature influences epimerization and composition of flavanol monomers, dimers and trimers during cocoa bean roasting

Cocoa consumption is suggested to promote many health benefits, since cocoa is a rich source of flavanols; but amounts and profiles of flavanols depend strongly on the bean type, origin and manufacturing process. Roasting is known as a crucial step in technical treatment of cocoa, which leads to flavanol losses and modifications, especially the epimerization of (-)-epicatechin to (-)-catechin. This study monitors the influence of cocoa bean roasting on the composition of flavanol monomers to trimers, with special focus on epimerization, which was quantified for procyanidin dimers, and also observed for trimers for the first time. Five dimeric and two trimeric potential epimerization products were detected and the extent of epimerization during cocoa roasting was shown to be a function of temperature. The data also showed remarkable variations in the change of flavanol content. The quantified flavanols decreased about 50% in Java beans and increased about 30% in Ivory Coast beans, despite being roasted under equal conditions.

(-)-Epicatechin is associated with increased angiogenic and mitochondrial signalling in the hindlimb of rats selectively bred for innate low running capacity

Alternative approaches to reduce congenital muscle dysfunction are needed in cases where the ability to exercise is limited. (-)-Epicatechin is found in cocoa and may stimulate capillarity and mitochondrial proliferation in skeletal muscle. A total of 21 male rats bred for LCR (low running capacity) from generation 28 were randomized into three groups: vehicle for 30 days (control); (-)-epicatechin for 30 days; and (-)-epicatechin for 30 days followed by 15 days without (-)-epicatechin. Groups 2 and 3 received 1.0 mg of (-)-epicatechin/kg of body mass twice daily, whereas water was given to the control group. The plantaris muscle was harvested for protein and morphometric analyses. In addition, in vitro experiments were conducted to examine the role of (-)-epicatechin on mitochondrial respiratory kinetics at different incubation periods. Treatment for 30 days with (-)-epicatechin increased capillarity (P<0.001) and was associated with increases in protein expression of VEGF (vascular endothelial growth factor)-A with a concomitant decrease in TSP-1 (thrombospondin-1) and its receptor, which remained after 15 days of (-)-epicatechin cessation. Analyses of the p38 MAPK (mitogen-activated protein kinase) signalling pathway indicated an associated increase in phosphorylation of MKK3/6 (MAPK kinase 3/6) and p38 and increased protein expression of MEF2A (myocyte enhancer factor 2A). In addition, we observed significant increases in protein expression of PGC-1α (peroxisome-proliferator-activated receptor γ co-activator 1α), PGC-1β, Tfam and cristae abundance. Interestingly, these increases associated with (-)-epicatechin treatment remained after 15 days of cessation. Lastly, in vitro experiments indicated that acute exposure of LCR muscle to (-)-epicatechin incubation was not sufficient to increase mitochondrial respiration. The results suggest that increases in skeletal muscle capillarity and mitochondrial biogenesis are associated with 30 days of (-)-epicatechin treatment and sustained for 15 days following cessation of treatment. Clinically, the use of this natural compound may have potential application in populations that experience muscle fatigue and are unable to perform endurance exercise.

Chemical synthesis and characterization of epicatechin glucuronides and sulfates: bioanalytical standards for epicatechin metabolite identification

The monoglucuronides and sulfates of epicatechin, 3'-O-methylepicatechin, and 4'-O-methylepicatechin, respectively, were synthesized as authentic bioanalytical standards. Reversed-phase HPLC methods capable of baseline separation of the glucuronides and sulfates have been developed. Both the epicatechin glucuronides and sulfates were stable in the solid state when stored under ambient conditions and in aqueous solution when stored refrigerated. These results should prove invaluable to the research community as analytical standards as well as in future studies of the biological and pharmacological effects of epicatechin in humans.

The potential of flavanol and procyanidin intake to influence age-related vascular disease

Advancing age is an independent major risk factor for cardiovascular disease (CVD). Age-associated impairments in the control of inflammation, excessive oxidative stress, and reduced cellular repair can all contribute to the development and progression of CVD. Current recommendations for both the primary and secondary prevention of CVD promote lifestyle modifications that include the adoption of healthy dietary patterns, such as the consumption of diets rich in plant foods, as these have been associated with a lower lifetime risk for the development of CVD. The potential for a diet rich in plant foods to be cardiovascular protective is also supported by prospective studies that suggest the intake of foods providing high amounts of certain phytochemicals, in particular flavanols and procyanidins, reduce the risk for CVD. These observations are further supported by a number of dietary intervention trials that show improvements in vascular function and reduced platelet reactivity following the consumption of high flavanol foods. In the current article we review a selection of these studies, and comment on some of the potential mechanisms that have been postulated to underlie the health effects of flavanol and procyanidin-rich foods.

Blood pressure-lowering effect of dietary (-)-epicatechin administration in L-NAME-treated rats is associated with restored nitric oxide levels

Epidemiological and intervention studies have shown that the intake of certain chocolates or cocoa products decreases blood pressure (BP) in humans. (-)-Epicatechin is the most abundant flavanol present in cocoa seeds and its derived foods. This work investigates the effects of dietary (-)-epicatechin on BP in rats that received N(ω)-nitro-l-arginine methyl ester (L-NAME) for 4 days. (-)-Epicatechin administration prevented the 42mm Hg increase in BP associated with the inhibition of NO production in a dose-dependent manner (0.2-4.0g/kg diet). This BP effect was associated with a reduction in L-NAME-mediated increase in the indexes of oxidative stress (plasma TBARS and GSSG/GSH(2) ratio) and with a restoration of the NO concentration. At the vascular level, none of the treatments modified NOS expression, but (-)-epicatechin administration avoided the L-NAME-mediated decrease in eNOS activity and increase in both superoxide anion production and NOX subunit p47(phox) expression. In summary, (-)-epicatechin was able to prevent the increase in BP and in oxidative stress and restored NO bioavailability. The fact that (-)-epicatechin is present in several plants usually consumed by humans gives the possibility of developing diets rich in those plants or pharmacological strategies using that flavonoid to diminish BP in hypertensive subjects.

(-)-Epicatechin administration and exercising skeletal muscle vascular control and microvascular oxygenation in healthy rats

Consumption of the dietary flavanol (-)-epicatechin (EPI) is associated with enhanced endothelial function and augmented skeletal muscle capillarity and mitochondrial volume density. The potential for EPI to improve peripheral vascular function and muscle oxygenation during exercise is unknown. We tested the hypothesis that EPI administration in healthy rats would improve treadmill exercise performance secondary to elevated skeletal muscle blood flow and vascular conductance [VC, blood flow/mean arterial pressure (MAP)] and improved skeletal muscle microvascular oxygenation. Rats received water (control, n = 12) or 4 mg/kg EPI (n = 12) via oral gavage daily for 24 days. Exercise endurance capacity and peak O(2) uptake (Vo(2) peak) were measured via treadmill runs to exhaustion. MAP (arterial catheter) and blood flow (radiolabeled microspheres) were measured and VC was calculated during submaximal treadmill exercise (25 m/min, 5% grade). Spinotrapezius muscle microvascular O(2) pressure (Po(2mv)) was measured (phosphorescence quenching) during electrically induced twitch (1 Hz) contractions. In conscious rats, EPI administration resulted in lower (↓~5%) resting (P = 0.03) and exercising (P = 0.04) MAP. There were no differences in exercise endurance capacity, Vo(2) peak, total exercising hindlimb blood flow (control, 154 ± 13; and EPI, 159 ± 8 ml·min(-1)·100 g(-1), P = 0.68), or VC (control, 1.13 ± 0.10; and EPI, 1.24 ± 0.08 ml·min(-1)·100 g(-1)·mmHg(-1), P = 0.21) between groups. Following anesthesia, EPI resulted in lower MAP (↓~16%) but did not impact resting Po(2mv) or any kinetics parameters (P > 0.05 for all) during muscle contractions compared with control. EPI administration (4 mg·kg(-1)·day(-1)) improved modestly cardiovascular function (i.e., ↓MAP) with no impact on exercise performance, total exercising skeletal muscle blood flow and VC, or contracting muscle microvascular oxygenation in healthy rats.