High-calcium diet enhances vasorelaxation in nitric oxide-deficient hypertension

Flavonoids, Dairy Foods, and Cardiovascular and Metabolic Health: A Review of Emerging Biologic Pathways

A growing body of nutritional science highlights the complex mechanisms and pleiotropic pathways of cardiometabolic effects of different foods. Among these, some of the most exciting advances are occurring in the area of flavonoids, bioactive phytochemicals found in plant foods; and in the area of dairy, including milk, yogurt, and cheese. Many of the relevant ingredients and mechanistic pathways are now being clarified, shedding new light on both the ingredients and the pathways for how diet influences health and well-being. Flavonoids, for example, have effects on skeletal muscle, adipocytes, liver, and pancreas, and myocardial, renal, and immune cells, for instance, related to 5'-monophosphate-activated protein kinase phosphorylation, endothelial NO synthase activation, and suppression of NF-κB (nuclear factor-κB) and TLR4 (toll-like receptor 4). Effects of dairy are similarly complex and may be mediated by specific amino acids, medium-chain and odd-chain saturated fats, unsaturated fats, branched-chain fats, natural trans fats, probiotics, vitamin K1/K2, and calcium, as well as by processing such as fermentation and homogenization. These characteristics of dairy foods influence diverse pathways including related to mammalian target of rapamycin, silent information regulator transcript-1, angiotensin-converting enzyme, peroxisome proliferator-activated receptors, osteocalcin, matrix glutamate protein, hepatic de novo lipogenesis, hepatic and adipose fatty acid oxidation and inflammation, and gut microbiome interactions such as intestinal integrity and endotoxemia. The complexity of these emerging pathways and corresponding biological responses highlights the rapid advances in nutritional science and the continued need to generate robust empirical evidence on the mechanistic and clinical effects of specific foods.

Associations of dietary calcium intake with metabolic syndrome and bone mineral density among the Korean population: KNHANES 2008-2011

Excessive amount of calcium intake increased risk for metabolic syndrome in men. However, modest amount decreased the risk of metabolic syndrome and osteoporosis in postmenopausal women. Modest amount of calcium also increased bone mineral density (BMD) in both men and postmenopausal women.

INTRODUCTION

The present study aimed to evaluate the associations of dietary calcium intake with metabolic syndrome and bone mineral density (BMD) in Korean men and women, especially postmenopausal women.

METHODS

The study was performed using data from the Korean National Health and Nutrition Examination Survey (2008-2011) and included 14,705 participants (5953 men, 4258 premenopausal women, and 4494 postmenopausal women). Clinical and other objective characteristics, presence of metabolic syndrome, and the BMD of the femur neck and lumbar spine were evaluated according to dietary calcium intake.

RESULTS

There was a higher tendency for metabolic syndrome in men with a dietary calcium intake of >1200 mg/day than with ≤400 mg of calcium intake; >400 and ≤800 mg of calcium intake was helpful for postmenopausal women to decrease risk for metabolic syndrome. Overall, the group with calcium intake >400 and ≤800 mg daily had significantly increased BMD in both femoral neck and lumbar spine from both men and postmenopausal women. From both femoral neck and lumbar spine, the prevalence of osteoporosis in postmenopausal women significantly decreased in the group whose calcium intake was >400 and ≤800 mg daily.

CONCLUSION

Excessive dietary calcium may increase the prevalence of metabolic syndrome in men. For postmenopausal women, calcium intake does not increase the risk of metabolic syndrome, but modest amount decreases the risk. It may increase the BMD in men and postmenopausal women, and also reduce the prevalence of both osteoporosis and metabolic syndrome in postmenopausal women.

Controversy regarding the association of high calcium intake and increased risk for cardiovascular disease

Calcium intake has been shown to be associated with beneficial effects regarding hypertension, coronary heart disease (CHD), vascular disease, and stroke by several prospective cohort studies. However, recent studies have questioned the beneficial cardiovascular effects of calcium intake and instead have shown that high calcium intake is associated with an increased risk for CHD and stroke. These findings have created controversy and concern among physicians, because calcium is consumed by a large number of older men and women to prevent osteoporosis and bone fractures. Based on the methods of patient self-reporting of calcium intake and cardiovascular events, the conclusions drawn from the studies may not be entirely valid. Therefore, until more confirmatory data are available, physicians should not be dissuaded from prescribing calcium supplements to their patients. The best candidates are patients with low calcium intake, but their calcium supplementation should not exceed the recommended 1200 mg/d to 1500 mg/d.

The role of calcium in the prevention of cardiovascular disease--a review of observational studies and randomized clinical trials

Calcium is a mineral that is important for bone health and has also been suggested to play a role in the prevention of cardiovascular disease (CVD). Lately, the potential effects of both inadequate and excessive calcium intake have received growing attention. In this review, we summarize the evidence from experimental, epidemiologic, and clinical studies investigating the role of calcium intake, either from the diet or from supplements, as well as blood concentrations, in relation to the risk of CVD in adults. In vitro and in vivo laboratory studies suggest that calcium may be involved in CVD development through multiple pathways, including blood cholesterol, insulin secretion and sensitivity, vasodilation, inflammatory profile, thrombosis, obesity, and vascular calcification. Several prospective epidemiologic studies have examined how dietary or supplemental calcium intake is associated with CVD incidence or mortality in middle-aged and older adults, and the results are inconsistent. Prospective studies investigating blood concentrations of calcium have also reported mixed results. However, changes in blood calcium concentrations may reflect a disturbed calcium phosphate balance, which is associated with increased risk of CVD. To date there is no randomized clinical trial that has been designed specifically to test the effect of calcium supplementation on the risk of CVD as the primary end point. Existing trials have performed secondary analyses, and most of them have been conducted among postmenopausal women. These trials suggest that calcium supplementation has no effect on CVD development; however, they do not allow a definitive conclusion to be drawn. The average daily intake of calcium is low in many populations; however, the evidence for a potential role of dietary or supplemental calcium in the prevention of CVD remains insufficient and inconclusive. Only large-scale randomized trials designed to investigate the effects of calcium supplementation on CVD events as the primary end point, as well as short-term trials investigating the effect on coronary biomarkers, can provide a definitive answer.

Calcium intake and risk of cardiovascular disease: a review of prospective studies and randomized clinical trials

The potential effects of inadequate or excessive calcium supply on cardiovascular disease (CVD) are receiving growing attention. We review experimental, epidemiologic, and clinical evidence regarding the role of calcium intake in the development of CVD in adults. In vitro and in vivo laboratory studies have shown that calcium may affect the risk of developing CVD through multiple mechanisms including blood cholesterol, insulin secretion and sensitivity, vasodilation, inflammatory profile, thrombosis, obesity, and vascular calcification. A number of prospective epidemiologic studies have examined the relationship between dietary calcium intake and CVD incidence or mortality in middle-aged and older adults. The results were inconsistent, and the pooled data do not strongly support a significant effect of greater dietary calcium intake on the risk of coronary artery disease (CAD) or stroke. Only a few prospective studies have examined calcium supplement use in association with risk of CVD. The pooled data show no significant benefits of calcium supplement use in reducing the risk of CAD or stroke. No randomized clinical trial has specifically tested the effect of calcium supplementation on CVD as its primary endpoint. Secondary analyses in existing trials to date suggest a neutral effect of calcium (with or without vitamin D) supplements on CVD events, but do not allow for a definitive conclusion. A large percentage of Americans, particularly older adults, fail to meet the US recommendations for optimal calcium intake and are encouraged to increase daily calcium consumption. More prospective cohort studies and large-scale randomized trials are needed to further evaluate the risks or benefits of calcium supplementation on CVD endpoints as the primary pre-specified outcome.

Dietary calcium intake and renin angiotensin system polymorphisms alter the blood pressure response to aerobic exercise: a randomized control design

Background

Dietary calcium intake and the renin angiotensin system (RAS) regulate blood pressure (BP) by modulating calcium homeostasis. Despite similar BP regulatory effects, the influence of dietary calcium intake alone and combined with RAS polymorphisms on the BP response following acute aerobic exercise (i.e., postexercise hypotension) has not been studied. Thus, we examined the effect of dietary calcium intake and selected RAS polymorphisms on postexercise hypotension.

Methods

Subjects were men (n = 50, 43.8 ± 1.3 yr) with high BP (145.3 ± 1.5/85.9 ± 1.1 mm Hg). They completed three experiments: non-exercise control and two cycle bouts at 40% and 60% of maximal oxygen consumption (VO₂max). Subjects provided 3 d food records on five protocol-specific occasions. Dietary calcium intake was averaged and categorized as low (<880 mg/d = LowCa) or high (≥ 880 mg/d = HighCa). RAS polymorphisms (angiotensin converting enzyme insertion/deletion, ACE I/D; angiotensin II type 1 receptor, AT₁R A/C) were analyzed with molecular methods. Genotypes were reduced from three to two: ACE II/ID and ACE DD; or AT₁R AA and AT₁R CC/AC. Repeated measure ANCOVA tested if BP differed among experiments, dietary calcium intake level and RAS polymorphisms.

Results

Systolic BP (SBP) decreased 6 mm Hg after 40% and 60% VO₂max compared to non-exercise control for 10 h with LowCa (p < 0.01), but not with HighCa (p ≥ 0.05). Under these conditions, diastolic BP (DBP) did not differ between dietary calcium intake levels (p ≥ 0.05). With LowCa, SBP decreased after 60% VO₂max versus non-exercise control for 10 h among ACE II/ID (6 mm Hg) and AT₁R AA (8 mm Hg); and by 8 mm Hg after 40% VO₂max among ACE DD and AT₁R CC/CA (p < 0.01). With HighCa, SBP (8 mm Hg) and DBP (4 mm Hg) decreased after 60% VO₂max compared to non-exercise control for 10 h (p < 0.05), but not after 40% VO₂max (p ≥ 0.05).

Conclusion

SBP decreased after exercise compared to non-exercise control among men with low but not high dietary calcium intake. Dietary calcium intake interacted with the ACE I/D and AT₁R A/C polymorphisms to further modulate postexercise hypotension. Interactions among dietary calcium intake, exercise intensity and RAS polymorphisms account for some of the variability in the BP response to exercise.

Dietary Calcium as a Potential Modifier of the Relationship of Lead Burden to Blood Pressure

BACKGROUND

Cumulative lead burden and low dietary calcium have been independently associated with increased risk of hypertension. There is evidence of an interaction between these factors. We tested the hypothesis that dietary calcium intake modifies the relationship between lead burden and hypertension.

METHODS

A total of 471 men from the Normative Aging Study were evaluated. Bone lead was assessed using a K-x-ray fluorescence instrument, and information on dietary calcium intake was obtained with a self-administered semiquantitative food frequency questionnaire.

RESULTS

We categorized 259 subjects (55%) as having low calcium intake (< or =800 mg/d) and 212 subjects (45%) as having higher calcium intake. In logistic regression models stratified by dietary calcium intake, tibia lead had a weak association with hypertension among subjects with low dietary calcium (odds ratio for 1-standard deviation increase in tibia lead = 1.30; 95% confidence interval = 0.97-1.74) but not in subjects with higher dietary calcium intake. Similarly, blood lead was associated with hypertension only in subjects with low calcium intake. We also found evidence of an interaction between dietary calcium intake and body mass index.

CONCLUSIONS

High bone and blood lead increased the likelihood of hypertension, particularly among subjects with low dietary calcium intake. Dietary calcium may be helpful in prevention of hypertension induced by elevated lead burden.

Interaction of exercise training and chronic NOS inhibition on blood pressure, heart rate, NO and antioxidants in plasma of rats

Many individuals with cardiovascular diseases undergo periodic exercise conditioning with or without medication. Therefore, the purpose of this study was to examine the effect of exercise training on BP and HR under the condition of NOS inhibition and to clarify the mechanism of the effect in regard to oxidative stress, antioxidant enzyme activity, and NO production in the plasma of the rat. Fisher 344 rats were divided into four groups: (1) sedentary control, (2) exercise training for 8 weeks, (3) nitro-L-arginine methyl ester (L-NAME) (10mg/kg, s.c. for 8 weeks) and (4) ET + L-NAME. Blood pressure (BP) and heart rate (HR) were monitored weekly for 8 weeks. The animals were sacrificed 24h after last treatments, plasma isolated and analyzed. The results show that exercise conditioning resulted in enhanced NO production (120% of control), GSH levels (110% of control), GSH/GSSG ratio (124% of control) and the up-regulation of catalase (CAT) (225% of control), glutathione peroxidase (GSH-Px) (161% of control), glutathione reductase (GR) (142% of control) and glutathione-S-transferase (GST) (189% of control) and depression of malondialdehyde (MDA) (90% of control) and lactate (75% of control) in plasma of the rat. These biochemical changes were accompanied by no significant change in BP but slight increase in HR. Chronic L-NAME administration resulted in depression of NO (84% of control), GSH (90% of control), GSH/GSSG ratio (76% of control), the down-regulation of superoxide dismutase (SOD) (67% of control), GST (74% of control), and GR (90% of control). Plasma CAT and GSH-Px activities, MDA and lactate levels were significantly increased in L-NAME treated rats. The biochemical changes were accompanied by increase in blood pressure and heart rate. Interaction of exercise training and chronic NOS inhibitor treatment resulted in normalization of plasma NO levels, GSH/GSSG ratio, SOD and GST activities, and the up-regulation of, CAT, GSH-Px, and GR activities. The interaction resulted in depletion of plasma MDA levels compared to L-NAME treated group. The biochemical changes were accompanied by decrease in BP and HR compared to L-NAME treated group. The data suggest that the exercise training attenuated the oxidative injury caused by NOS inhibitor by increasing the plasma NO levels, GSH/GSSG ratio and up-regulating the antioxidant enzyme and lowering the BP and HR in the rat.

Dietary minerals and modification of cardiovascular risk factors

High serum cholesterol, hypertension and obesity are major risk factors for cardiovascular diseases, and together with insulin resistance form a deadly disorder referred to as the metabolic syndrome. All the aspects of this syndrome are strongly related to dietary and lifestyle factors; therefore, it would be reasonable to look for dietary approaches to their modification. Mineral nutrients, such as calcium, potassium and magnesium, lower blood pressure, and especially calcium has beneficial effects also on serum lipids. Recent evidence suggests that increased intake of calcium may help in weight control as well. This review summarizes previous literature on the effects and use of dietary minerals on serum lipids, blood pressure and obesity, with specific focus on the effects of calcium. Calcium and magnesium as divalent cations can form insoluble soaps with fatty acids in the intestine and thus prevent the absorption of part of the dietary fat. Decreased absorption of saturated fat leads to reduction in serum cholesterol level via decreased production of VLDL and increased intake of LDL in the liver. Dietary calcium may also bind bile acids, which increases the conversion of cholesterol to bile acids in the liver. Furthermore, calcium appears to enhance the cholesterol-lowering effect of plant sterols. Thus, dietary combination of the mineral nutrients and plant sterols provides a promising novel approach to the modification of cardiovascular risk factors.

Exercise conditioning attenuates the hypertensive effects of nitric oxide synthase inhibitor in rat

Many individuals with cardiovascular diseases undergo periodic exercise conditioning with or with out medication. Therefore, this study investigated the interaction of exercise training and chronic nitric oxide synthase (NOS) inhibitor (Nitro-L-Arginine Methyl Ester, L-NAME) treatment on blood pressure and its correlation with aortic nitric oxide (NO), antioxidant defense system and oxidative stress parameters in rats. Fisher 344 rats were divided into four groups: (1) sedentary control, (2) exercise training (ET) for 8 weeks, (3) L-NAME (10 mg/kg, subcutaneous for 8 weeks) and (4) ET + L-NAME. Blood pressure (BP) was monitored weekly for 8 weeks with tail-cuff method. The animals were sacrificed 24 h after last treatments and thoracic aortic rings were isolated and analyzed. Exercise conditioning resulted in a significant increase in respiratory exchange ratio (RER), aortic NO production, NO synthase activity and inducible iNOS protein expression. Training significantly enhanced aortic GSH levels, GSH/GSSG ratio and up-regulation of aortic CuZn-SOD, Mn-SOD, catalase (CAT), glutathione peroxidase (GSH-Px) activity and protein expression and significantly decreased aortic lipid peroxidation. Chronic L-NAME administration resulted in a significant depletion of aortic NO, NOS activity, endothelial (eNOS) and iNOS protein expression, GSH level, GSH/GSSG ratio, down-regulation of aortic antioxidant enzyme activities and protein expressions. Aortic xanthine oxidase (XO) activity significantly increased with increased lipid peroxidation and protein oxidation after L-NAME administration. The biochemical changes were accompanied by increased in BP. Interaction of training and chronic NOS inhibitor treatment resulted in normalization of BP and aortic antioxidant enzyme activity and protein expression, up-regulation of aortic GSH/GSSG ratio, NO levels, Mn-SOD protein expression, depletion of GSSG, protein oxidation and lipid peroxidation. The data suggest that training attenuated the oxidative injury caused by chronic NOS inhibitor treatment by up-regulating the NO and antioxidant systems and lowering the BP in rats.

Hypertension and impairment of endothelium-dependent relaxation of arteries from spontaneously hypertensive and L-NAME-treated Wistar rats

Effects of chronic treatment of normotensive Wistar rats with N(omega)-nitro-L-arginine methyl ester (L-NAME) on blood pressure and on endothelium-dependent relaxation of the aorta, carotid and iliac arteries were studied. The endothelium-dependent relaxation was compared in arteries from normotensive Wistar Kyoto rats (WKY) and genetically hypertensive rats (stroke-prone spontaneously hypertensive rats, SHRSP). Chronic treatment of normotensive Wistar rats with L-NAME caused an elevation of blood pressure. The elevated blood pressure at 15 weeks of age was significantly higher in these animals than that of untreated Wistar rats, but lower than that of SHRSP. Endothelium-dependent relaxation of the arteries induced by acetylcholine (ACh) was almost abolished by chronic treatment with L-NAME. The remaining small relaxation in arteries from L-NAME-treated rats was completely inhibited by application of L-NAME (10(-4) M). In such preparations, higher concentrations of ACh induced a contraction, which was abolished by removal of the endothelium or by an application of indomethacin (10(-5) M). Endothelium-independent relaxation induced by sodium nitroprusside was similar between preparations from untreated and L-NAME-treated Wistar rats. Endothelium-dependent relaxation was significantly impaired in preparations from SHRSP, when compared with that in those from WKY. However, the impairment was less prominent in preparations from SHRSP than in those from L-NAME-treated rats. These results suggest that the impairment of endothelium-dependent relaxation in the arteries from L-NAME-treated rats is not due to the elevated blood pressure resulting from the chronic treatment, and that impairment of NO synthesis by the endothelium does not play a major role in the initiation of hypertension in SHRSP.