Oral calcium supplementation reduces intraplatelet free calcium concentration and insulin resistance in essential hypertensive patients

Review Article on Molecular Mechanism of Regulation of Hypertension by Macro-elements (Na, K, Ca and Mg), Micro-elements/Trace Metals (Zn and Cu) and Toxic Elements (Pb and As)

Hypertension (HT) is a medical condition arising due to increase in blood pressure (BP) prevalent worldwide. The balanced dietary intakes of macro-elements and micro-elements including Na, K, Ca, Mg, Zn, and Cu have been described to maintain BP in humans by regulating the osmolarity of blood, cells/tissues, prevention of generation of oxidative and nitrosative stress (OANS), and endothelial damage through their functioning as important components of renin-angiotensin-aldosterone system (RAAS), antioxidant enzyme defense system, and maintenance of blood vascular-endothelial and vascular smooth muscle cell (VSMC) functions. However, inadequate/excess dietary intakes of Na/K, Ca/Mg, and Zn/Cu along with higher Pb and As exposures recognized to induce HT through common mechanisms including the followings: endothelial dysfunctions due to impairment of vasodilatation, increased vasoconstriction and arterial stiffness, blood clotting, inflammation, modification of sympathetic activity and higher catecholamine release, increased peripheral vascular resistance, and cardiac output; increased OANS due to reduced and elevated activities of extracellular superoxide dismutase and NAD(P)H oxidase, less nitric oxide bioavailability, decrease in cGMP and guanylate cyclase activity, increase in intracellular Ca2+ ions in VSMCs, and higher pro-inflammatory cytokines; higher parathyroid and calcitriol hormones; activation/suppression of RAAS resulting imbalance in blood Na+, K+, and water regulated by renin, angiotensin II, and aldosterone through affecting natriuresis/kaliuresis/diuresis; elevation in serum cholesterol and LDL cholesterol, decrease in HDL cholesterol due to defect in lipoprotein metabolism. The present study recommends the need to review simple dietary mineral intervention studies/supplementation trials before keeping their individual dietary excess intakes/exposures in consideration because their interactions lead to elevation and fall of their concentrations in body affecting onset of HT.

Adherence to the Dietary Approaches to Stop Hypertension (DASH) diet is associated with low levels of insulin resistance among heart failure patients

BACKGROUND AND AIMS

Heart failure (HF) patients are at risk of developing type 2 diabetes. This study examined the association between adherence to the Dietary Approaches to Stop Hypertension (DASH) diet and insulin resistance among U.S. adults with HF.

METHODS AND RESULTS

Using data from National Health and Nutrition Examination Survey 1999-2016 cycles, we included 348 individuals aged 20+ years with HF and no history of diabetes. DASH diet adherence index quartile 1 indicated the lowest and quartile 4 indicated the highest adherence. The highest level of insulin resistance was defined by the upper tertile of the Homeostatic Model Assessment of Insulin Resistance (HOMA-IR). Associations between level of insulin resistance and DASH diet adherence and its linear trends were examined using logistic regressions. Trend analyses showed that participants in upper DASH diet adherence index quartiles were more likely older, female, non-Hispanic White, of normal weight, and had lower levels of fasting insulin than those in lower quartiles. Median values of HOMA-IR from lowest to highest DASH diet adherence index quartiles were 3.1 (interquartile range, 1.8-5.5), 2.9 (1.7-5.6), 2.1 (1.1-3.7), and 2.1 (1.3-3.5). Multivariable logistic analyses indicated that participants with the highest compared to the lowest DASH adherence showed 77.1% lower odds of having the highest level of insulin resistance (0.229, 95% confidence interval: 0.073-0.716; p = 0.017 for linear trend).

CONCLUSION

Good adherence to the DASH diet was associated with lower insulin resistance among community-dwelling HF patients. Heart healthy dietary patterns likely protect HF patients from developing type 2 diabetes.

The Use and Effectiveness of Selected Alternative Markers for Insulin Sensitivity and Secretion Compared with Gold Standard Markers in Dietary Intervention Studies in Individuals without Diabetes: Results of a Systematic Review

Background: The gold-standard techniques for measuring insulin sensitivity and secretion are well established. However, they may be perceived as invasive and expensive for use in dietary intervention studies. Thus, surrogate markers have been proposed as alternative markers for insulin sensitivity and secretion. This systematic review aimed to identify markers of insulin sensitivity and secretion in response to dietary intervention and assess their suitability as surrogates for the gold-standard methodology. Methods: Three databases, PubMed, Scopus, and Cochrane were searched, intervention studies and randomised controlled trials reporting data on dietary intake, a gold standard of analysis of insulin sensitivity (either euglycaemic-hyperinsulinaemic clamp or intravenous glucose tolerance test and secretion (acute insulin response to glucose), as well as surrogate markers for insulin sensitivity (either fasting insulin, area under the curve oral glucose tolerance tests and HOMA-IR) and insulin secretion (disposition index), were selected. Results: We identified thirty-five studies that were eligible for inclusion. We found insufficient evidence to predict insulin sensitivity and secretion with surrogate markers when compared to gold standards in nutritional intervention studies. Conclusions: Future research is needed to investigate if surrogate measures of insulin sensitivity and secretion can be repeatable and reproducible in the same way as gold standards.

Dietary iron to total energy intake ratio and type 2 diabetes incidence in a longitudinal 12-year analysis of the Korean Genome and Epidemiology Cohort Study

PURPOSE

Recent study found iron consumption has been associated with an increased risk of type 2 diabetes (T2DM). Even though, high iron intake is correlated with total caloric intake, most studies have evaluated the individual effect of iron and total caloric intake. The aim of this study was to investigate the effect of iron intake, in conjunction with total energy intake, on developing T2DM. We also investigated the interactions between dietary iron and energy ratios (IERs) and iron-related single nucleotide polymorphisms (SNPs) in the development of T2DM.

METHODS

The study was carried out in Ansan and Ansung, Korea, between March 2001 and December 2014. A total of 6413 participants (3073 men and 3340 women), aged 40-69 years, were enrolled in this study. The mean follow-up period was 8.4 years. The study population was divided into quartiles based on IERs with cut-off points at 4.54, 5.41, and 6.29. The odds ratios (ORs) for new-onset T2DM were calculated across each quartile of IERs and a random forest model was constructed using the default settings to predict new-onset T2DM. To confirm the interaction among IERs, SNPs, and the incidence of T2DM, we measured the predictive power of new-onset T2DM using IER and six SNPs in genes related to iron metabolism [rs855791 (TPMRSS6), rs38116479 (TF), rs1799852 (TF), rs2280673, rs1799945 (HFT), rs180562 (HFE)].

RESULTS

The prevalence of T2DM was 762 (11.8%). IERs showed a positive association with T2DM. The ORs were 1.30 (95% CI 1.02-1.67), 1.20 (95% CI 0.94-1.56), and 1.43 (95% CI 1.11-1.86) across the IER quartiles after adjusting for non-dietary and dietary metabolic risk factors. When the IER was 1.89-fold higher than the reference group, the risk of developing T2DM increased by 43% (OR 1.43; 95% CI 1.11-1.86).

CONCLUSION

A higher IER was positively associated with developing T2DM independent of dietary or non-dietary risk factors. We also found the possible interactions between the identified SNPs and iron intake in relations to T2DM.

Calcium Intake Is Inversely Related to Risk of Obesity among American Young Adults over a 30-Year Follow-Up

BACKGROUND

Calcium (Ca) is an essential nutrient that may play an important role in weight maintenance through its involvement in energy or lipid metabolism. However, little is known about the long-term associations of Ca intake with obesity risk.

OBJECTIVES

We aimed to prospectively examine the association between cumulative Ca intake and the incidence of obesity among American young adults over 30 y of follow-up.

METHODS

Participants were from the CARDIA (Coronary Artery Risk Development in Young Adults) study. A total of 4097 of 5115 black and white individuals aged 18-30 y at baseline in 1985-1986 were included in the current analysis. Dietary and supplemental Ca intake was assessed by the validated interview-based CARDIA diet history at baseline and exam years 7 and 20. Incident cases of obesity were identified when BMI was ≥30 kg/m2 for the first time since baseline. A survival analysis was performed using Cox proportional hazards regression models to estimate the HRs and corresponding 95% CIs for obesity incidence during follow-up.

RESULTS

During a 30-y follow-up (mean ± SD: 20 ± 10 y), 1675 participants developed obesity. Cumulative total Ca intake (dietary plus supplemental Ca) was inversely associated with incidence of obesity in multivariable-adjusted analysis [quintile (Q)5 (highest intake) compared with Q1 (lowest intake): HR: 0.68; 95% CI: 0.56, 0.82; P-trend < 0.01]. This inverse association persisted among Ca supplement users (Q5 compared with Q1: HR: 0.53; 95% CI: 0.40, 0.70; P-trend < 0.01), but was not seen among nonusers.

CONCLUSIONS

Following a cohort of Americans from young adulthood to midlife, an inverse association between calcium intake and obesity incidence was observed. Further studies are needed to confirm our findings.

Calcium Intake and Serum Calcium Level in Relation to the Risk of Ischemic Stroke: Findings from the REGARDS Study

BACKGROUND AND PURPOSE

Data on the association between calcium (Ca) and ischemic stroke are sparse and inconsistent. This study aimed to examine Ca intake and serum Ca levels in relation to risk of ischemic stroke.

METHODS

The primary analysis included 19,553 participants from the Reasons for Geographic And Racial Differences in Stroke (REGARDS) study. A subcohort was randomly selected to create a case-cohort study (n=3,016), in which serum Ca levels were measured. Ischemic stroke cases were centrally adjudicated by physicians based on medical records. Cox proportional hazards regression for the cohort and weighted Cox proportional hazard regression with robust sandwich estimation method for the case-cohort analysis with adjustment for potential confounders were performed.

RESULTS

During a mean 8.3-year follow-up, 808 incident cases of ischemic stroke were documented. Comparing the highest quintile to the lowest, a statistically significant inverse association was observed between total Ca intake and risk of ischemic stroke (hazard ratio [HR], 0.72; 95% confidence interval [CI], 0.55 to 0.95; Plinear-trend=0.183); a restricted cubic spline analysis indicated a threshold effect like non-linear association of total Ca intake with ischemic stroke (Pnon-linear=0.006). In the case-cohort, serum Ca was inversely associated with the risk of ischemic stroke. Compared to the lowest, the highest quintile of serum Ca had a 27% lower risk of ischemic stroke (HR, 0.73; 95% CI, 0.53 to 0.99; Plinear-trend=0.013). Observed associations were mainly mediated by type 2 diabetes, hypertension, and cholesterol.

CONCLUSION

s These findings suggest that serum Ca has inverse and Ca intake has threshold effect like association with risk of ischemic stroke.

Youth and Long-Term Dietary Calcium Intake With Risk of Impaired Glucose Metabolism and Type 2 Diabetes in Adulthood

CONTEXT

To the best of our knowledge, no previous studies have examined the role of youth calcium intake in the development of impaired glucose metabolism, especially those with long-term high calcium intake.

OBJECTIVES

To examine whether youth and long-term (between youth and adulthood) dietary calcium intake is associated with adult impaired glucose metabolism and type 2 diabetes (T2D).

DESIGN, SETTING, AND PARTICIPANTS

The Cardiovascular Risk in Young Finns Study is a 31-year prospective cohort study (n = 1134; age, 3 to 18 years at baseline).

EXPOSURES

Dietary calcium intake was assessed at baseline (1980) and adult follow-up visits (2001, 2007, and 2011). Long-term (mean between youth and adulthood) dietary calcium intake was calculated.

MAIN OUTCOME MEASURES

Adult impaired fasting glucose (IFG) and T2D.

RESULTS

We found no evidence for nonlinear associations between calcium intake and IFG or T2D among females and males (all P for nonlinearity > 0.05). Higher youth and long-term dietary calcium intake was not associated with the risk of IFG or T2D among females or males after adjustment for confounders, including youth and adult body mass index.

CONCLUSIONS

Youth or long-term dietary calcium intake is not associated with adult risk of developing impaired glucose metabolism or T2D.

Mechanisms Involved in the Relationship between Low Calcium Intake and High Blood Pressure

There is increasing epidemiologic and animal evidence that a low calcium diet increases blood pressure. The aim of this review is to compile the information on the link between low calcium intake and blood pressure. Calcium intake may regulate blood pressure by modifying intracellular calcium in vascular smooth muscle cells and by varying vascular volume through the renin-angiotensin-aldosterone system. Low calcium intake produces a rise of parathyroid gland activity. The parathyroid hormone increases intracellular calcium in vascular smooth muscles resulting in vasoconstriction. Parathyroidectomized animals did not show an increase in blood pressure when fed a low calcium diet as did sham-operated animals. Low calcium intake also increases the synthesis of calcitriol in a direct manner or mediated by parathyroid hormone (PTH). Calcitriol increases intracellular calcium in vascular smooth muscle cells. Both low calcium intake and PTH may stimulate renin release and consequently angiotensin II and aldosterone synthesis. We are willing with this review to promote discussions and contributions to achieve a better understanding of these mechanisms, and if required, the design of future studies.

Salts and energy balance: A special role for dietary salts in metabolic syndrome

BACKGROUND

Dietary salts sodium (Na⁺), potassium (K⁺), magnesium (Mg2⁺), and calcium (Ca2⁺) are important in metabolic diseases. Yet, we do not have sufficient understanding on the salts global molecular network in these diseases. In this systematic review we have pooled information to identify the general effect of salts on obesity, insulin resistance and hypertension.

AIMS

To assess the roles of salts in metabolic disorders by focusing on their individual effect and the network effect among these salts.

METHODS

We searched articles in PubMed, EMBASE and Google Scholar. We selected original laboratory research, systematic reviews, clinical trials, observational studies and epidemiological data that focused on dietary salts and followed the preferred reporting items for systematic review in designing the present systematic review.

RESULTS

From the initial search of 2898 studies we selected a total of 199 articles that met our inclusion criteria and data extraction. Alterations in metabolic pathways associated with the sensitivity of sodium, potassium, magnesium and calcium may lead to obesity, hypertension, and insulin resistance. We found that the results of most laboratory research, animal studies and clinical trials are coherent but some research outcome are either inconsistent or inconclusive.

CONCLUSION

Important of salts in metabolic disorder is evident. In order to assess the effects of dietary salts in metablic diseases, environmental factors, dietary habits, physical activity, and the microbiome, should be considered in any study. Although interest in this area of research continues to grow, the challenge is to integrate the action of these salts in metabolic syndrom.

The effect of pre-pregnancy lifestyle counselling on food intakes and association between food intakes and gestational diabetes in high-risk women: results from a randomised controlled trial

BACKGROUND

Healthy diets before and during pregnancy have been suggested to reduce the risk of gestational diabetes (GDM). Several lifestyle intervention studies for pregnant women have reported dietary improvements after counselling. However, evidence concerning the effect of counselling initiated before pregnancy on diets is limited.

METHODS

This randomised controlled study explored whether pre-pregnancy lifestyle counselling influenced food intakes, as well as whether changes in food intakes were associated with GDM. The participants comprised 75 women with prior GDM and/or a body mass index ≥ 30 kg m^-2 . Women were randomised into a control or an intervention group, and their food intakes were followed from pre-pregnancy to early pregnancy using a food frequency questionnaire. The control and intervention groups were combined to assess the association between changes in food intakes and GDM. The diagnosis of GDM was based on a 75-g oral glucose tolerance test conducted in the first and second trimester of pregnancy.

RESULTS

Pre-pregnancy lifestyle counselling showed no major overall effect on food intakes. The intake of low-fat cheese increased significantly in women who did not develop GDM compared to women who did after adjusting for potential confounders (P = 0.028). This association was not observed for regular-fat cheese.

CONCLUSIONS

The findings obtained in the present study suggest that an increased intake of low-fat but not regular-fat cheese between pre-pregnancy and early pregnancy is associated with a lower risk of GDM in high-risk women.

The Effect of Improved Serum 25-Hydroxyvitamin D Status on Glycemic Control in Diabetic Patients: A Meta-Analysis

BACKGROUND

Type 2 diabetes is a global health concern, with an increased prevalence and high cost of treatment.

OBJECTIVE

The aim of this systematic review and meta-analysis was to determine the effect of vitamin D supplementation and improved vitamin D status on glycemia and insulin resistance in type 2 diabetic patients.

DATA SOURCE

We searched PUBMED/Medline, Cumulative Index to Nursing and Allied Health, and Cochrane Library (until January 2017).

STUDY SELECTION

Prospective clinical trials were selected evaluating the impact of vitamin D supplementation on glycosylated hemoglobin (HbA1c), serum fasting plasma glucose (FPG), and homeostatic model assessment of insulin resistance (HOMA-IR) in diabetic patients.

DATA EXTRACTION AND SYNTHESIS

We used a random-effects model to synthesize quantitative data, followed by a leave-one-out method for sensitivity analysis. The systematic review registration was CRD42017059555. From a total of 844 entries identified via literature search, 24 controlled trials (1528 individuals diagnosed with type 2 diabetes) were included. The meta-analysis indicated a significant reduction in HbA1c [mean difference: -0.30%; 95% confidence interval (CI): -0.45 to -0.15, P < 0.001], FPG [mean difference: -4.9 mg/dL (-0.27 mmol/L); 95% CI: -8.1 to -1.6 (-0.45 to -0.09 mmol/L), P = 0.003], and HOMA-IR (mean difference: -0.66; 95% CI: -1.06 to -0.26, P = 0.001) following vitamin D supplementation and significant increase in serum 25-hydroxyvitamin D levels [overall increase of 17 ± 2.4 ng/mL (42 ± 6 nmol/L)].

CONCLUSIONS

Vitamin D supplementation, a minimum dose of 100 µg/d (4000 IU/d), may significantly reduce serum FPG, HbA1c, and HOMA-IR index, and helps to control glycemic response and improve insulin sensitivity in type 2 diabetic patients.

A Mendelian randomization study of the effect of calcium on coronary artery disease, myocardial infarction and their risk factors

Meta-analyses of randomized controlled trials (RCTs) suggest calcium could have adverse effects on cardiovascular disease, although these findings are controversial. To clarify, we assessed whether people with genetically higher calcium had a higher risk of coronary artery disease (CAD), myocardial infarction (MI) and their risk factors. We used a two-sample Mendelian randomization study. We identified genetic variants (single nucleotide polymorphisms (SNPs)) that independently contributed to serum calcium at genome-wide significance which we applied to large extensively genotyped studies of CAD, MI, diabetes, lipids, glycaemic traits and adiposity to obtain unconfounded estimates, with body mass index (BMI) as a control outcome. Based on 4 SNPs each 1 mg/dl increase in calcium was positively associated with CAD (odds ratio (OR) 1.49, 95% confidence interval (CI) 1.02–2.17), MI (OR 1.58, 95% CI 1.06–2.35), LDL-cholesterol (0.21 standard deviations, 95% CI 0.01–0.4), total cholesterol (0.21 standard deviations, 95% CI 0.03-0.38) and possibly triglycerides (0.19 standard deviations, 95% CI −0.1–0.48), but was unlikely related to BMI although the estimate lacked precision. Sensitivity analysis using 13 SNPs showed a higher risk for CAD (OR 1.87, 95% CI 1.14–3.08). Our findings, largely consistent with the experimental evidence, suggest higher serum calcium may increase the risk of CAD.

A study of bone turnover markers in gestational diabetes mellitus

INTRODUCTION

Gestational diabetes is defined as carbohydrate intolerance resulting in hyperglycemia of variable severity with the first recognition during pregnancy. Established risk factors for gestational diabetes mellitus (GDM) are maternal age, obesity, family history of diabetes, etc. Vitamin D, parathyroid hormone (PTH), and various other hormones are known for their function in maintaining calcium and phosphorous homeostatic. Furthermore, Vitamin D, PTH serum ionized calcium, and alkaline phosphatase (ALP) have been reported to be altered with glucose homeostasis. The present study compares the bone markers in pregnant women with and without gestational diabetes.

MATERIALS AND METHODS

This cross-sectional study was conducted at outpatient antenatal check-up clinic and outpatient diabetic clinics at J. N. Medical College and Hospital, Aligarh. One hundred pregnant females, of which fifty with GDM and fifty without GDM, were included in the study from January 2014 to November 2015. Detailed history, physical examination, and anthropometric measurement were done. Bone turnover markers in the form of Vitamin D, parathyroid hormone, serum ionized calcium, and serum ALP were measured in pregnant women who had gestational diabetes which was compared with normal pregnant women.

RESULTS

In our study, the mean age of participate of GDM group was 28.2 ± 3 years, while the mean age group in non-GDM group was 25.44 ± 2.78 years. Ionized calcium in GDM was found to be 4.606 ± 0.354 mEq/L, while in non-GDM, it was 4.548 ± 0.384 mEq/L, P = 0.430. Vitamin D came out to be 21.80 ± 9.48 ng/ml, while it was 32.346 ± 8.37 ng/ml in non-GDM group. Serum PTH in GDM group was 71.436 ± 36.189 pg/ml and 37.168 ± 8.128 pg/ml in nondiabetic gestational group. Serum ALP in GDM group was 9.1 ± 4.56 KA U/dl and 6.98 ± 2.2 KA U/dl in nondiabetic gestational group, P - 0.0038. In GDM group, there was a significant negative linear correlation between PTH and 25-hydroxyvitamin D with research correlation coefficient r = -0.9073, P = 0; there was a significant positive linear correlation coefficient between PTH and ALP with Persian correlation coefficient r = 0.6597, P = 0; there was no statistically significant correlation between PTH and ionized calcium r = 0.1416, P = 0.3267.

CONCLUSION

All GDM subjects should ideally be screened for serum calcium, vitamin D, PTH, ALP. If found impaired should immediately be corrected in order to prevent its adverse effects on maternal and fetal outcome. Vitamin D supplementation should ideally be initiated in all GDM females even if the above parameters are not investigated in Indian setup.

Effect of vitamin D supplementation on insulin resistance and glycaemic control in prediabetes: a systematic review and meta-analysis

AIMS

To evaluate the effect of vitamin D on insulin resistance and glycaemic control in prediabetes.

METHODS

A literature search was conducted of MEDLINE, the Cochrane Library, Cumulative Index to Nursing and Allied Health Literature (CINAHL), Scopus, Web of Science and www.clinicaltrials.gov, together with a historical search through the reference lists of relevant articles until end of June 2014. Studies were included if they were randomized controlled trials of vitamin D or vitamin D analogues in prediabetes and if they reported homeostatic model assessment of insulin resistance or 2-h plasma glucose after oral glucose tolerance test. Treatment effect was estimated according to mean difference in the changes from baseline of homeostatic model assessment of insulin resistance, 2-h oral glucose tolerance test plasma glucose, fasting plasma glucose and HbA1c between vitamin D and control groups. Meta-analysis of eligible studies was performed.

RESULTS

A total of 10 randomized controlled trials were included. Vitamin D did not significantly improve homeostatic model assessment of insulin resistance and 2-h oral glucose tolerance test plasma glucose: the mean differences were -0.06 (95% CI -0.36 to 0.24) and -0.23 mmol/l (95% CI -0.65 to 0.19), respectively. Subgroup analysis suggested that vitamin D improved homeostatic model assessment of insulin resistance in a subgroup with baseline 25-hydroxyvitamin D ≥ 50 nmol/l [mean difference -0.59 (95% CI -1.14 to -0.04); P = 0.03] and improved 2-h oral glucose tolerance test plasma glucose in the subgroup with baseline 25-hydroxyvitamin D < 50 nmol/l [mean difference -0.68 mmol/l (95% CI -1.35 to -0.01); P = 0.05]. Vitamin D significantly reduced fasting plasma glucose and HbA1c levels. The mean differences were -0.10 mmol/l (95% CI -0.18 to -0.03), P = 0.006 and -1 mmol/mol (95% CI -2 to 0), P = 0.008, respectively.

CONCLUSIONS

No beneficial effect of vitamin D in improving insulin resistance was identified.

Differential expression of calcium transport genes caused by COMT inhibition in the duodenum, kidney and placenta of pregnant mice

Preeclampsia is a pregnancy-specific disease characterized by concurrent development of hypertension, proteinuria, and oxidative stress in the placenta. Preeclampsia-like genetic models were also developed by modification of preeclampsia-related genes, such as catechol-O-methyltranferase (COMT). In this study, we induced COMT inhibition in mice during pregnancy in order to reproduce physiological conditions associated with preeclampsia. Expression of the gene known as hypoxia biomarker, HIF-1α, was highly induced in the placenta of this model. The over-expression of HIF-1α demonstrates that our experimental conditions were similar to those of preeclampsia. We measured the expression of several calcium transport genes (CTGs; TRPV5, TRPV6, PMCA1 and CaBP-9k) in the placenta, duodenum and kidney after COMT inhibition on gestation day 17.5 (GD 17.5). In addition, we evaluated the calcium transporters in the kidney, duodenum of non-pregnant female mice. Placental TRPV5, TRPV6 and PMCA1 expressions were down-regulated by COMT inhibitor (ro41-0960). In addition, the reduced PMCA1 expression in the placenta was reversed by calcium supplementation. Duodenal expressions of TRPV5, TRPV6, and PMCA1 were decreased in COMT-inhibited mice, and recovered slightly after calcium supplementation. Renal expression of TRPV5, TRPV6, and PMCA1 was also decreased by COMT inhibition, while it was reversed by calcium supplementation to the level of control. Duodenal- and renal calcium transporting genes, TRPV5, TPRV6, PMCA1 and CaBP-9k, were down-regulated by COMT treatment in female mice. Taken together, these results indicate that physiological changes observed in COMT inhibition were similar to symptoms of preeclampsia, which may be related to disturbance of calcium metabolism during pregnancy.

Effects of combined vitamin D--calcium supplements on the cardiovascular system: should we be cautious?

Despite the growing body of evidence on the potential effects of calcium and vitamin D as monotherapies on different cardiovascular (CV) parameters, the combined supplementation with calcium and vitamin D (CaD), which is most frequently encountered in clinical practice, has not received the attention it deserves. A literature search was conducted via EMBASE and Medline and identified 14 randomised controlled trials (RCTs) and 2 meta-analyses reporting on effects of combined supplementation with CaD on CV events, CV death, blood pressure, lipids, glucose metabolism and weight. Overall, the existing evidence does not support beneficial properties of supplementation with CaD on the CV system, nor does it suggest that a re-appraisal of the use of CaD is necessary due to adverse effects, although increased risk of CV events has been reported by some authors. The guidelines for the use of CaD supplementation need not change until well-conducted RCTs that have CV effects as primary outcomes and adjust for major confounders indicate otherwise.

Calcium-vitamin D cosupplementation influences circulating inflammatory biomarkers and adipocytokines in vitamin D-insufficient diabetics: a randomized controlled clinical trial

CONTEXT

To the best of our knowledge, no study has examined the effects of vitamin D-calcium cosupplementation on inflammatory biomarkers and adipocytokines in vitamin D-insufficient type 2 diabetics.

OBJECTIVE

This study was performed to assess the effects of vitamin D and calcium supplementation on inflammatory biomarkers and adipocytokines in vitamin D-insufficient people with type 2 diabetes.

METHODS

Totally, 118 diabetic patients were enrolled in this randomized, placebo-controlled clinical trial. After matching for age, sex, body mass index, type and dose of hypoglycemic agents, and duration of diabetes, subjects were randomly assigned into 4 groups receiving the following: 1) 50000 IU/wk vitamin D + calcium placebo; 2) 1000 mg/d calcium + vitamin D placebo; 3) 50 000 IU/wk vitamin D + 1000 mg/d calcium; or 4) vitamin D placebo + calcium placebo for 8 weeks. Blood sampling was done for the quantification of inflammatory biomarkers and adipocytokines at the study baseline and after 8 weeks of intervention.

RESULTS

Calcium (changes from baseline: -75 ± 19 ng/ml, P = .01) and vitamin D alone (-56 ± 19 ng/mL, P = .01) and joint calcium-vitamin D supplementation (-92 ± 19 ng/mL, P = .01) resulted in a significant reduction in serum leptin levels compared with placebo (-9 ± 18 ng/mL). This was also the case for serum IL-6, such that calcium (-2 ± 1 pg/mL, P < .001) and vitamin D alone (-4 ± 1 pg/mL, P < .001) and their combination (-4 ± 1 pg/mL, P < .001) led to significant reductions compared with placebo (3 ± 1 pg/mL). After adjustment for potential confounders, individuals in the calcium (-3.1 ± 1.3, P < .05), vitamin D (-3.1 ± 1.3, P < .05), and joint calcium-vitamin D groups (-3.4 ± 1.3, P < .05) had greater reductions in serum TNF-α concentrations compared with placebo (0.1 ± 1.2). Individuals who received joint calcium-vitamin D supplements tended to have a decrease in serum high-sensitivity C-reactive protein levels compared with placebo after controlling for baseline levels (-1.14 ± 0.25 vs 0.02 ± 0.24 ng/mL, P = .09).

CONCLUSION

Joint calcium-vitamin D supplementation might improve systemic inflammation through decreasing IL-6 and TNF-α concentrations in vitamin D-insufficient people with type 2 diabetes.

Effects of calcium-vitamin D co-supplementation on metabolic profiles in vitamin D insufficient people with type 2 diabetes: a randomised controlled clinical trial

AIMS/HYPOTHESIS

This study was performed to assess the effects of vitamin D and calcium supplementation on the metabolic profiles of vitamin D insufficient persons with type 2 diabetes.

METHODS

In a parallel designed randomised placebo-controlled clinical trial, a total of 118 non-smoker individuals with type 2 diabetes and insufficient 25-hydroxyvitamin D, aged >30 years, were recruited from the Isfahan Endocrine and Metabolism Research Centre. Participants were randomly assigned to four groups receiving: (1) 50,000 U/week vitamin D + calcium placebo; (2) 1,000 mg/day calcium + vitamin D placebo; (3) 50,000 U/week vitamin D + 1,000 mg/day calcium; or (4) vitamin D placebo + calcium placebo for 8 weeks. A study technician carried out the random allocations using a random numbers table. All investigators, participants and laboratory technicians were blinded to the random assignments. All participants provided 3 days of dietary records and 3 days of physical activity records throughout the intervention. Blood samples were taken to quantify glycaemic and lipid profiles at study baseline and after 8 weeks of intervention.

RESULTS

30 participants were randomised in each group. During the intervention, one participant from the calcium group and one from the vitamin D group were excluded because of personal problems. Calcium-vitamin D co-supplementation resulted in reduced serum insulin (changes from baseline: -14.8 ± 3.9 pmol/l, p = 0.01), HbA1c [-0.70 ± 0.19% (-8.0 ± 0.4 mmol/mol), p = 0.02], HOMA-IR (-0.46 ± 0.20, p = 0.001), LDL-cholesterol (-10.36 ± 0.10 mmol/l, p = 0.04) and total/HDL-cholesterol levels (-0.91 ± 0.16, p = 0.03) compared with other groups. We found a significant increase in QUICKI (0.025 ± 0.01, p = 0.004), HOMA of beta cell function (HOMA-B; 11.8 ± 12.17, p = 0.001) and HDL-cholesterol (0.46 ± 0.05 mmol/l, p = 0.03) in the calcium-vitamin D group compared with others.

CONCLUSIONS/INTERPRETATION

Joint calcium and vitamin D supplementation might improve the glycaemic status and lipid profiles of vitamin D insufficient people with type 2 diabetes.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01662193 FUNDING: Clinical Research Council, Isfahan University of Medical Sciences, Isfahan, Iran.

Permethrin alters adipogenesis in 3T3-L1 adipocytes and causes insulin resistance in C2C12 myotubes

Pyrethroids are a class of insecticides structurally derived from the naturally occurring insecticides called pyrethrins. Along with emerging evidence that exposure to insecticides is linked to altered weight gain and glucose homeostasis, exposure to pyrethroids has been linked to altered blood glucose levels in humans. Thus, the purpose of this study was to determine the role of permethrin on lipid and glucose metabolisms. Permethrin was treated to 3T3-L1 adipocytes and C2C12 myoblasts to determine its role in lipid and glucose metabolisms, respectively. Permethrin treatment resulted in increased expression of key markers of adipogenesis and lipogenesis in adipocytes. Permethrin significantly reduced insulin-stimulated glucose uptake in myotubes. This is the first report on the role of permethrin in altered lipid metabolism in adipocytes and impaired glucose homeostasis in myotubes. These results may help elucidate fundamental underlying mechanisms between insecticide exposure, particularly permethrin, and potential risk of developing obesity and its comorbidities.

Vitamin D and type 2 diabetes mellitus (D2)

Based on increasing evidence from animal and human studies, vitamin D deficiency is now regarded as a potential risk factor for Type 2 diabetes mellitus (T2DM). Vitamin D is involved in the pathogenesis of pancreatic β-cell dysfunction, insulin resistance, and systemic inflammation, conditions that contribute to the development of T2DM. Vitamin D can affect the progress of this disease directly through the activation of its own receptor, and indirectly via the regulation of calcium homeostasis. Observational studies have revealed the association between vitamin D deficiency and incident T2DM. More double-blind randomized control studies that investigate the effects of vitamin D supplementation on insulin sensitivity, insulin secretion, and the occurrence of T2DM are needed.

Effect of Opuntia humifusa supplementation and acute exercise on insulin sensitivity and associations with PPAR-γ and PGC-1α protein expression in skeletal muscle of rats

This study examined whether Opuntia humifusa (O. humifusa), which is a member of the Cactaceae family, supplementation and acute swimming exercise affect insulin sensitivity and associations with PPAR-γ and PGC-1α protein expression in rats. Thirty-two rats were randomly divided into four groups (HS: high fat diet sedentary group, n = 8; HE: high fat diet acute exercise group, n = 8; OS: 5% O. humifusa supplemented high fat diet sedentary group, n = 8; OE: 5% O. humifusa supplemented high fat diet acute exercise group, n = 8). Rats in the HE and OE swam for 120 min. before being sacrificed. Our results indicated that serum glucose level, fasting insulin level and homeostasis model assessment of insulin resistance (HOMA-IR) in OS were significantly lower compared to those of the HS (p < 0.01, p < 0.05, p < 0.05). In addition, PPAR-γ protein expression in the OS and OE was significantly higher than that of the HS and HE, respectively (p < 0.05, p < 0.01). PGC-1α and GLUT-4 protein expressions in the OS were significantly higher compared to those of the HS (p < 0.05, p < 0.05). From these results, O. humifusa supplementation might play an important role for improving insulin sensitivity through elevation of PPAR-γ, PGC-1α, and GLUT-4 protein expression in rat skeletal muscle.

Change of genes in calcium transport channels caused by hypoxic stress in the placenta, duodenum, and kidney of pregnant rats

Preeclampsia is a pregnancy-specific disease characterized by concurrent development of hypertension, proteinuria, and oxidative stress in the placenta. In this study, we induced hypoxic stress in rats during pregnancy to reproduce physiological conditions associated with preeclampsia. The maternal weight of hypoxic pregnant rats was lower than that of normoxic animals. The level of calcium ions were also increased in urine collected from the hypoxic animals. In contrast, urinary concentrations of sodium, chloride, and potassium ions declined in hypoxic rats, and developed to proteinuria. The expression of genes known as two biomarkers, sFLT1 (for preeclampsia) and HIF-1alpha (for hypoxia), were highly induced in the placenta, duodenum, and kidney by hypoxic stress. The overexpression of sFLT1 and HIF-1alpha demonstrated that our experimental conditions closely mimicked ones that are associated with preeclampsia. In the present study, we measured the expression of calcium transporters (TRPV5, TRPV6, PMCA1, NCKX3, NCX1, and CaBP-9k) in the placenta, duodenum, and kidney under hypoxic conditions on Gestational Day 19.5 in rats. Placental TRPV5, TRPV6, and PMCA1 expression was up-regulated in the hypoxic rats, whereas the levels of NCX1 and CaBP-9k were unchanged. In addition, NCKX3 expression was increased in the placenta of hypoxic rats. Duodenal expression of CaBP-9k, TRPV5, TRPV 6, and PMCA1 was decreased in the hypoxic rats, whereas levels of NCXs were not altered. Renal expression of NCKX3 and TRPV6 was increased, whereas NCX1 was decreased in the hypoxic rats compared to the normoxic controls. Taken together, these results indicate that physiological changes observed in the hypoxic rats were similar to ones associated with preeclampsia. Expression of calcium transport genes in the placenta, duodenum, and kidney perturbed by hypoxic stress during pregnancy may cause calcium loss in the urine, and thereby induce calcium-deficient characteristics of preeclampsia.

Estimate of a predictive cut-off value for serum 25-hydroxyvitamin D reflecting abdominal obesity in Korean adolescents

Vitamin D deficiency is a serious global issue. Although the serum 25-hydroxyvitamin D [25(OH)D] test is generally the most accurate way to assess vitamin D levels, the optimal range of 25(OH)D has yet to be established. Moreover, the optimal level may vary according to race, region, and age. Suboptimal vitamin D status is associated with obesity and metabolic syndrome, which are the major risk factors for cardiovascular disorders; however, these relationships in children and adolescents have yet to be clearly determined. Therefore, we identified the best predictive cut-off value for reflecting abdominal obesity and, based on this value, we investigated the relationship between suboptimal 25(OH)D status and the risk for having abdominal obesity, being overweight or obese, and having metabolic syndrome in Korean adolescents. We performed a cross-sectional analysis of 713 Korean adolescents, between 12-19 years of age, and used data collected from the 2008 Korea National Health and Nutrition Examination Survey (KNHANES). Receiver operation characteristic curve analysis was used to identify the cut-off value that reflected abdominal obesity. The cut-off value of serum 25(OH)D that reflected abdominal obesity in Korean adolescents was 17.6 ng/mL. After making adjustments for gender, age, and regular physical exercise, the group that had lower levels of serum 25(OH)D compared to the cut-off value had a significantly higher risk for abdominal obesity, obesity, and metabolic syndrome than the group with 25(OH)D levels higher than the cut-off value. Suboptimal vitamin D status based on this value is associated with increased risk for abdominal obesity, obesity, and metabolic syndrome among Korean adolescents.

A critical analysis of the (near) legendary status of vitamin D

Labels such as food constituent, nutrient and supplement do not convey a sense of being essential. Yet these rather mundane descriptors, even if correct, belie the true significance of vitamin D. Long believed to be merely a functioning cofactor akin to vitamin C, deficiency of this secosteroid hormone is clearly associated with morbid complications of calcium and bone mineral metabolism, and because the hormonal effects are mediated by nuclear receptors that regulate the expression of many subordinate genes, the vitamin's pleiotropic mode of action can influence numerous metabolic pathways and, possibly, a number of different diseases. Although the vitamin is under intensive investigation, much still remains unknown, even in bone health, as the identity of osteoporosis susceptibility genes remains uncertain. This article focuses on various aspects of the basic science and molecular biology of the vitamin D endocrine system. The primary goal is to critically examine the evidence supporting its role in bone metabolism, diabetes and cancer.

Calcium supplementation reverts central adiposity, leptin, and insulin resistance in adult offspring programed by neonatal nicotine exposure

Obesity is a worldwide epidemic. Calcium influences energy metabolism regulation, causing body weight loss. Because maternal nicotine exposure during lactation programs for obesity, hyperleptinemia, insulin resistance (IR), and hypothyroidism, we decided to evaluate the possible effect of dietary calcium supplementation on these endocrine dysfunctions in this experimental model. Osmotic minipumps containing nicotine solution (N: 6 mg/kg per day for 14 days) or saline (C) were s.c. implanted in lactating rats 2 days after giving birth (P2). At P120, N and C offspring were subdivided into four groups: 1) C - standard diet; 2) C with calcium supplementation (CCa, 10 g calcium carbonate/kg rat chow); 3) N - standard diet; and 4) N with calcium supplementation (NCa). Rats were killed at P180. As expected, N offspring showed higher visceral and total body fat, hyperleptinemia, lower hypothalamus leptin receptor (OB-R) content, hyperinsulinemia, and higher IR index. Also, higher tyrosine hydroxylase (TH) expression (+51%), catecholamine content (+37%), and serum 25-hydroxyvitamin D(3) (+76%) were observed in N offspring. Dietary calcium supplementation reversed adiposity, hyperleptinemia, OB-R underexpression, IR, TH overexpression, and vitamin D. However, this supplementation did not reverse hypothyroidism. In NCa offspring, Sirt1 mRNA was lower in visceral fat (-37%) and higher in liver (+42%). In conclusion, dietary calcium supplementation seems to revert most of the metabolic syndrome parameters observed in adult offspring programed by maternal nicotine exposure during lactation. It is conceivable that the reduction in fat mass per se, induced by calcium therapy, is the main mechanism that leads to the increment of insulin action.

Dietary intake and serum and hair concentrations of minerals and their relationship with serum lipids and glucose levels in hypertensive and obese patients with insulin resistance

Inadequate minerals intake, as well as disruption of some metabolic processes in which microelements are cofactors, are suggested to lead to the development of hypertension. The role of minerals in the pathogenesis of hypertension still remains to be explained. In the present study, we sought to determine associations between serum and hair mineral concentrations and serum lipids and glucose levels. Forty obese hypertensive subjects with insulin resistance and 40 healthy volunteers were recruited in the study. Blood pressure, BMI, and insulin resistance were recorded in all subjects. Levels of lipids, glucose, sodium and potassium, iron, copper, zinc, magnesium, and calcium were assessed in serum. Iron, copper, zinc, magnesium, and calcium were assessed in hair. Dietary intake of the analyzed minerals was estimated. We found distinctly higher concentrations of serum iron and serum and hair calcium as well as markedly lower levels of hair zinc in the hypertensive subjects. The study group manifested also significantly lower daily intake of calcium, magnesium, and iron. We observed a relationship between the concentrations of iron, zinc, and copper in serum and hair and high and low range of cholesterol, triglycerides, and glucose serum levels in the studied patients. Moreover, this study demonstrated significant correlation between serum and hair concentrations of selected minerals and their dietary intake and levels of serum lipids and glucose and blood pressure in the study and the control groups. The obtained results seem to indicate the association between lipid and glucose metabolism and iron, copper, zinc, and calcium concentrations in blood and hair of hypertensive and obese patients with insulin resistance.

Multivitamins, individual vitamin and mineral supplements, and risk of diabetes among older U.S. adults

OBJECTIVE

Understanding the relationship between multivitamin use and diabetes risk is important given the wide use of multivitamin supplements among U.S. adults.

RESEARCH DESIGN AND METHODS

We prospectively examined supplemental use of multivitamins and individual vitamins and minerals assessed in 1995-1996 in relation to self-reported diabetes diagnosed after 2000 among 232,007 participants in the National Institutes of Health-American Association of Retired Persons Diet and Health Study. Multivitamin use was assessed by a food-frequency questionnaire at baseline. Odds ratios (ORs) and 95% CIs were calculated by logistic regression models, adjusted for potential confounders. In total, 14,130 cases of diabetes diagnosed after 2000 were included in the analysis.

RESULTS

Frequent use of any multivitamins was not associated with risk of diabetes after adjustment for potential confounders and uses of individual supplements. Compared with nonusers of any multivitamins, the multivariate ORs among users were 1.07 (95% CI 0.94-1.21) for taking vitamins less than once per week, 0.97 (0.88-1.06) for one to three times per week, 0.92 (0.84-1.00) for four to six times per week, and 1.02 (0.98-1.06) for seven or more times per week (P for trend = 0.64). Significantly lower risk of diabetes was associated with the use of vitamin C or calcium supplements. The multivariate ORs comparing daily users with nonusers were 0.91 (0.86-0.97) for vitamin C supplements and 0.85 (0.80-0.90) for calcium supplements. Use of vitamin E or other individual vitamin and mineral supplements were not associated with diabetes risk.

CONCLUSIONS

In this large cohort of U.S. older adults, multivitamin use was not associated with diabetes risk. The findings of lower diabetes risk among frequent users of vitamin C or calcium supplements warrant further evaluations.

Familial burden of hypertension and its effect on blood pressure levels, insulin resistance, and intracellular ions in Greek offspring

We examined the effect of familial burden of hypertension on blood pressure (BP) levels, insulin resistance (IR), and intracellular ions in healthy offspring of Greek families with one, two, or no hypertensive parents. A total of 118 adolescents and young adults were recruited. Three groups were formed: Group A, both parents were normotensive (N-N); Group B, one parent normotensive and one hypertensive (N-H); and Group C, both parents hypertensive (H-H). BP levels, homeostasis assessment model-IR (HOMA-IR) index, and intracellular Na(+), K(+), Ca(2+), and Mg(2+) were compared in the three groups. Also, multiple regression analyses were used to create models with BP parameters and HOMA-IR as dependent variables. Offspring of H-H parents had higher body mass index (BMI) (mean difference, 4.3 +/- 0.9 kg/m(2); 95% confidence interval [CI], 2.0-6.5), higher systolic blood pressure (SBP) (mean difference, 13.2 +/- 3.1 mm Hg; 95% CI, 5.8-20.7), increased levels of intraerythrocyte Ca(2+) (mean difference, 0.02 +/- 0.01 mmol/l; 95% CI, 0.05-0.1), and fasting blood glucose (mean difference, 0.31 +/- 0.10 mmol/l; 95% CI, 0.05-0.56) when compared with those with no parental history of hypertension. In the regression model, SBP was found to be significantly affected by BMI (beta = 0.43; P < .001), iK(+) (beta = -0.224; P < .01), and gender (beta = -0.298; P < .001). The addition of the parental history showed a significant independent association of H-H parental history with SBP (beta = 0.27; P < .05). HOMA-IR was significantly determined by BMI (beta = 0.511; P < .05), iNa(+) (beta = 0.211; P < .05), and iMg(2+) (beta = -0.205; P < .05). Parental history of hypertension did not influence the HOMA-IR index. This study highlights the relative importance and contribution of environmental and genetic influences on the development of high BP. Both these influences possibly alter the intracellular ionic environment. However, nurture rather than familial hypertension burden is the key factor of IR in Greek offspring.

Effects of calcium supplementation on glucose and insulin levels of athletes at rest and after exercise

This study was performed to determine how the calcium supplementation for a 4-week period affects the glucose and insulin levels at rest and at exhaustion in athletes. This is a 4-week study performed on 30 healthy subjects varying between 18 and 22 ages. Subjects were separated into three groups: first group (group supplemented with calcium, sedentary group), second group (calcium supplementations + exercise group), and third group (training group). Glucose and insulin parameters of the groups were measured four times, at rest and exhaustion in the beginning of the research and at rest and exhaustion after the end of 4 weeks application period. Exhaustion measurements both before and after the supplementations significantly decreased in compared to rest measurements in terms of insulin (p < 0.05). Significant difference was not determined in the glucose values of groups. In terms of glucose, values increased in all of the three groups occurred with exercise both before and after the supplementation by exercise and exhaustion (p < 0.05). The results of our study indicate that calcium gluconate supplementations for 4 weeks in sedentary subjects and athletes did not significantly affect plasma insulin levels at rest and exhaustion. However, glucose levels were affected by calcium supplementation and exhausting exercise in athletes.

Vitamin D status and impact of vitamin D3 and/or calcium supplementation in a randomized pilot study in the Southeastern United States

OBJECTIVE

Vitamin D supplementation may be required for certain subgroups in the United States in whom status and intake are inadequate, but the impact of various doses, and whether calcium administration jointly or independently influences vitamin D metabolite levels, is unclear.

METHODS

In a pilot chemoprevention trial of biomarkers of risk for colorectal adenoma, we measured the impact of vitamin D supplementation and/or calcium supplementation on plasma vitamin D metabolite concentrations. Ninety-two adult men and women living in the southeastern United States were randomized to 800 IU vitamin D(3), 2000 mg elemental calcium, both, or placebo daily for 6 months. We examined vitamin D status at baseline and postintervention and compared the change in plasma 25-hydroxyvitamin D (25(OH)D) and 1,25(OH)(2)D levels by intervention group using general linear models.

RESULTS

Eighty-two percent of the study population had insufficient plasma 25(OH)D concentrations (<75 nmol/L) at baseline, with the lowest levels observed among African American participants. Vitamin D supplements, with or without calcium supplementation, raised plasma 25(OH)D concentrations, on average, by 25 to 26 nmol/L. Half of the study participants were classified as having sufficient 25(OH)D status after 6 months of 800 IU of vitamin D(3) daily. Calcium alone did not influence 25(OH)D concentrations.

CONCLUSION

In this southeastern U.S. population, half of the study participants receiving 800 IU vitamin D(3) daily had blood 25(OH)D concentrations of Collapse

Key Words Collapse

MESH Headings

• Aged
• Alleles
• Analysis of Variance
• Calcium/administration & dosage
• Chi-Square Distribution
• Cholecalciferol/administration & dosage
• Dietary Supplements
• Double-Blind Method
• Female
• Genotype
• Georgia
• Humans
• Male
• Medication Adherence
• Middle Aged
• Pilot Projects
• Polymorphism, Single Nucleotide
• Receptors, Calcitriol/genetics
• Surveys and Questionnaires
• Treatment Outcome
• Vitamin D/analogs & derivatives
• Vitamin D/blood

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Grants

• R01 CA104637 NCI NIH HHS
• R03 CA121873 NCI NIH HHS

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Affiliation(s)

Marjorie L McCullough Epidemiology Research Program, American Cancer Society, Atlanta, Georgia 30303-1002, USA.
Roberd M Bostick
Carrie R Daniel
W Dana Flanders
Aasma Shaukat
Jill Davison
Udaya Rangaswamy
Bruce W Hollis

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Oral calcium supplementation ambulatory blood pressure and relation to changes in intracellular ions and sodium-hydrogen exchange

BACKGROUND

Calcium (Ca2+) supplementation has been shown paradoxically to reduce intracellular Ca2+ and induce vascular relaxation. The aim of the study was to assess 24-h blood pressure (BP) change after Ca2+ supplementation and to investigate its relation to changes in intracellular ions and the activity of the first isoform of sodium-hydrogen exchange (NHE-1) in subjects with hypertension and type 2 diabetes.

METHODS

This parallel, randomized controlled, single-blinded trial, consisted of 31 patients with type 2 diabetes, and hypertension who were allocated to receive 1,500 mg of Ca2+ per day (n = 15) or no treatment (n = 16) for 8 weeks.

RESULTS

In the Ca2+ group a decrease of 1.7 +/- 2.7 mm Hg (mean +/- SE) P = 0.52 for mean 24-h systolic BP (SBP) and 2.1 +/- 1.5 mm Hg, P = 0.19 for mean 24-h diastolic BP (DBP) was recorded. Whereas in the control group an increase of 1.4 +/- 2.7 mm Hg, P = 0.59 for mean 24-h SBP and 1.2 +/- 2.8 mm Hg, P = 0.83 for mean 24-h DBP was observed. Intraplatelet Ca2+ decreased whereas intraplatelet magnesium (Mg2+) and erythrocyte K+ increased in the intervention group. Change in mean 24-h SBP in the pooled group correlated with both change in intraplatelet Ca2+ (r = 0.49, P < 0.05) and NHE-1 activity (r = 0.6, P < 0.001). The contribution of intraplatelet Ca2+ was attenuated when both parameters were entered in a multivariate regression model.

CONCLUSIONS

The present study shows a weak, statistically nonsignificant trend towards association of Ca2+ supplementation on 24-h BP in hypertensive subjects with type 2 diabetes. However, our results indicated an interrelation of [Ca2+]i levels and NHE-1 activity on BP in patients with hypertension and type 2 diabetes.

Insulin sensitivity increase after calcium supplementation and change in intraplatelet calcium and sodium-hydrogen exchange in hypertensive patients with Type 2 diabetes

AIMS/HYPOTHESIS

To investigate the effect of oral calcium (Ca(2+)) supplementation on insulin sensitivity measured by the euglycaemic hyperinsulinaemic clamp, intraplatelet cationic concentration of Ca(2+) ([Ca(2+)](i)) and the transmembrane sodium-hydrogen exchanger (NHE) activity in erythrocytes in subjects with Type 2 diabetes and hypertension.

PATIENTS AND METHODS

In this parallel randomized controlled single-blinded trial, 31 patients were allocated to receive either 1500 mg of Ca(2+) orally, daily (n = 15) or no treatment (n = 16) for 8 weeks. At baseline and at the end of the 8-week period insulin sensitivity, [Ca(2+)](i) and the first isoform of NHE (NHE-1) activity were measured.

RESULTS

At the end of the study, subjects who received Ca(2+) supplementation showed higher insulin sensitivity (Delta M-value 0.32 +/- 0.5 mmol/min P < 0.05) and lower [Ca(2+)](i) (125.0 +/- 24.7 to 80.4 +/- 10.6 nmol/l, P < 0.05, mean +/- sem) and NHE-1 activity (79.5 +/- 10.0 to 52.1 +/- 6.4 mmol Na/l red cell/h, P < 0.05). None of the above parameters were changed in the control group. Simple regression analysis demonstrated the change in [Ca(2+)](i) significantly determined insulin sensitivity change (beta = -0.36, P < 0.05).

CONCLUSIONS/INTERPRETATION

Oral Ca(2+) supplementation improves insulin sensitivity in patients with Type 2 diabetes and hypertension. These changes are likely to be mediated by changes in intracellular ionic Ca(2+). NHE-1 activity was also reduced after Ca(2+) supplementation but its role in insulin sensitivity requires further investigation.

Inhibitory effect of deep-sea water on differentiation of 3T3-L1 adipocytes

Currently, the utilization of deep-sea water (DSW) is receiving much attention due to its high productivity, large quantity, and potential for biological application. The 3T3-L1 cell line is a well-established and commonly used in vitro model to assess adipocyte differentiation. Over the course of several days, confluent 3T3-L1 cells can be converted to adipocytes in the presence of an adipogenic cocktail. In this study, the effects of DSW on differentiation adipocyte 3T3-L1 cells were studied. DSW significantly decreased lipid accumulation, a marker of adipogenesis, in a dose-dependent manner. DSW of hardness 1,000 was the most effective for inhibiting adipocyte differentiation without any cytotoxicity. DSW significantly reduced expression mRNA levels of PPARgamma and C/EBPalpha and protein levels of fatty-acid-binding protein and adiponectin. Our results suggest a potential role for DSW as anti-obesity agents by inhibiting adipocyte differentiation mediated through the down-regulated expression of adipogenic transcription factors and adipocyte-specific proteins.

Plasma C-peptide is inversely associated with calcium intake in women and with plasma 25-hydroxy vitamin D in men

The consumption of calcium, vitamin D, and dairy products may be associated with a reduced risk of type 2 diabetes mellitus. However, whether this reduction is due to calcium, vitamin D, or other components of dairy products is not clear. We examined intakes of total calcium and vitamin D, and plasma concentrations of 25 hydroxyvitamin D [25(OH)D] in relation to fasting plasma concentrations of C-peptide in 2 cross-sectional studies among healthy men from the Health Professionals Follow-up Study and among healthy women from the Nurses' Health Study I. Intake of total calcium was modestly inversely associated with C-peptide concentration in women (P-trend = 0.05); however, the inverse association was not significant in men (P = 0.7). Concentrations of C-peptide were 20% lower among men who had plasma concentrations of 25(OH)D in the highest quartile compared with those in the lowest quartile (P-trend = 0.08); there was no association in women (P = 0.3). The inverse association between calcium intake and the plasma C-peptide concentration was stronger in hypertensive individuals of both sexes. The difference in the C-peptide concentrations between extreme quartiles of calcium intake was 17% in men and 20% in women. Plasma concentrations of C-peptide for the combination of the highest tertiles of calcium intake and plasma 25(OH)D compared with the opposite extreme were 35% lower (P = 0.03) in men and 12% lower (P = 0.01) in women. The results suggest that calcium intake or systemic vitamin D status, after adjustment for intake of dairy products, is associated with decreased insulin secretion.

Vitamin D and diabetes mellitus

Better understanding of the physiological role of the vitamin-D system, in particular its potential effects on inflammatory and autoimmune conditions as well as on insulin secretion and possibly also on insulin resistance, increased the interest in its potential role in prevention and control of the diabetic condition, both type-1 and -2 diabetes. Both these conditions are associated with inflammation and type-1 diabetes also with an autoimmune pathology. Indeed, animal and human studies support the notion that adequate vitamin-D supplementation may decrease the incidence of type-1 and possibly also of type-2 diabetes mellitus and may improve the metabolic control in the diabetes state. However, the exact mechanisms by which vitamin-D and calcium supplementation exert their beneficial effects are not clear and need further investigation.

Calcium supplementation does not alter lipid oxidation or lipolysis in overweight/obese women

Based on cell culture and studies in mice, increased dietary calcium appears to stimulate lipolysis and could possibly reduce body adiposity through hormonal influences on adipocyte calcium uptake. In this study, we investigated the effects of 1,500 mg supplemental calcium daily for 3 months on hormones regulating calcium and energy metabolism and rates of lipid oxidation and lipolysis in overweight women. Fifteen overweight (BMI > 25 kg/m(2)) premenopausal women were supplemented with 1,500 mg of calcium, as CaCO(3), per day for 3 months while maintaining their usual diets and activity levels. Baseline and endpoint measurements were obtained after the subjects consumed a standardized 25% fat diet for 4 days. Lipid oxidation was measured by indirect calorimetry, lipolysis by infusion of deuterated glycerol, and body fat by dual-energy X-ray absorptiometry. Urinary calcium, circulating levels of hormones involved in energy and lipid metabolism (insulin, leptin, and adiponectin) or calcium metabolism (25(OH)D, 1,25(OH)(2)D), and parathyroid hormone (PTH)) were also measured. Urinary levels of calcium (P = 0.005) increased and 1,25(OH)(2)D declined (P = 0.03). However other parameters, including body weight, body fat, PTH, insulin, leptin, adiponectin, 25(OH)D, as well as rates of lipid oxidation and lipolysis were not altered by calcium supplementation. Calcium supplementation for 3 months increased urinary calcium excretion, decreased circulating levels of 1,25(OH)(2)-D, but had no effect on rates of lipid oxidation or lipolysis, in these overweight women.

Vitamin D and calcium intake in relation to risk of endometrial cancer: a systematic review of the literature

OBJECTIVE

In response to a recent ecologic study of UV exposure and endometrial cancer incidence, we present the epidemiologic evidence on the relation between intake of vitamin D and its metabolically related nutrient, calcium, and the occurrence of endometrial cancer.

METHODS

We conducted a systematic literature review and meta-analysis of vitamin D and calcium in relation to endometrial cancer, including peer-reviewed manuscripts published up to May 2007. Random and fixed effects summary estimates were computed.

RESULTS

Pooled analyses of the three case-control studies of dietary vitamin D and endometrial cancer uncovered heterogeneous results that were not significant in random or fixed effects analyses. Cut-points for the highest vitamin D intakes ranged from >244 to >476 IU/day. Qualitatively similar findings were observed for dietary calcium. Only two studies provided estimates for calcium supplements (random effects OR=0.62, 95% CI 0.39-0.99; fixed effects OR=0.62, 95% CI 0.42-0.93, for top vs. bottom category, p for heterogeneity=0.25).

CONCLUSIONS

The limited epidemiological evidence suggests no relation between endometrial cancer in the ranges of dietary vitamin D examined, and suggests a possible inverse association for calcium from supplements. Prospective studies, ideally including plasma 25(OH) D to estimate vitamin D input from diet and sun exposure, are needed to further explore these hypotheses.

The role of vitamin D and calcium in type 2 diabetes. A systematic review and meta-analysis

CONTEXT

Altered vitamin D and calcium homeostasis may play a role in the development of type 2 diabetes mellitus (type 2 DM). EVIDENCE ACQUISITION AND ANALYSES: MEDLINE review was conducted through January 2007 for observational studies and clinical trials in adults with outcomes related to glucose homeostasis. When data were available to combine, meta-analyses were performed, and summary odds ratios (OR) are presented.

EVIDENCE SYNTHESIS

Observational studies show a relatively consistent association between low vitamin D status, calcium or dairy intake, and prevalent type 2 DM or metabolic syndrome [OR (95% confidence interval): type 2 DM prevalence, 0.36 (0.16-0.80) among nonblacks for highest vs. lowest 25-hydroxyvitamin D; metabolic syndrome prevalence, 0.71 (0.57-0.89) for highest vs. lowest dairy intake]. There are also inverse associations with incident type 2 DM or metabolic syndrome [OR (95% confidence interval): type 2 DM incidence, 0.82 (0.72-0.93) for highest vs. lowest combined vitamin D and calcium intake; 0.86 (0.79-0.93) for highest vs. lowest dairy intake]. Evidence from trials with vitamin D and/or calcium supplementation suggests that combined vitamin D and calcium supplementation may have a role in the prevention of type 2 DM only in populations at high risk (i.e. glucose intolerance). The available evidence is limited because most observational studies are cross-sectional and did not adjust for important confounders, whereas intervention studies were short in duration, included few subjects, used a variety of formulations of vitamin D and calcium, or did post hoc analyses.

CONCLUSIONS

Vitamin D and calcium insufficiency may negatively influence glycemia, whereas combined supplementation with both nutrients may be beneficial in optimizing glucose metabolism.

Dairy, magnesium, and calcium intake in relation to insulin sensitivity: approaches to modeling a dose-dependent association

Dairy intake has been inversely associated with insulin resistance, which may be partly due to the specific effects of calcium and magnesium. Data from the Insulin Resistance Atherosclerosis Study (1992-1999) for 1,036 US adults without diabetes at baseline were examined to evaluate the cross-sectional association of habitual dairy, magnesium, and calcium intake with insulin sensitivity at baseline and after 5 years of follow-up. Insulin sensitivity was directly measured with a validated, 12-sample, insulin-enhanced, intravenous glucose tolerance test with minimal model analysis. Dietary intake was assessed by a validated food frequency interview, and dietary supplement dose was confirmed by reviewing the supplement label. Several statistical approaches were used to ensure appropriate modeling of the dose-dependent association. No association was found between dairy intake and insulin sensitivity (p=0.41); however, associations were positive for magnesium and calcium intake (p=0.016) after adjusting for demographic, nondietary lifestyle and dietary factors, and food groups. Furthermore, magnesium intake was associated with insulin sensitivity in a threshold fashion, with a Bayesian method-estimated threshold (325 mg) (beta=0.0607/100 mg, p=0.0008 for <325 mg of magnesium/day; and beta=-0.001/100 mg, p=0.82 for >or=325 mg of magnesium/day). This study suggests that magnesium and calcium intake specifically, but not dairy intake, is associated with insulin sensitivity.

Iron intake and the risk of type 2 diabetes in women: a prospective cohort study

OBJECTIVE

Epidemiological studies suggest that high body iron stores are associated with insulin resistance and type 2 diabetes. The aim of this study was to evaluate the association between dietary intake of iron and the risk of type 2 diabetes.

RESEARCH DESIGN AND METHODS

We conducted a prospective cohort study within the Nurses' Health Study. We followed 85,031 healthy women aged 34-59 years from 1980 to 2000. Dietary data were collected every 4 years, and data on medical history and lifestyle factors were updated biennially.

RESULTS

During the 20 years of follow-up, we documented 4,599 incident cases of type 2 diabetes. We found no association between total, dietary, supplemental, or nonheme iron and the risk of type 2 diabetes. However, heme iron intake (derived from animal products) was positively associated with risk; relative risks (RRs) across increasing quintiles of cumulative intake were 1.00, 1.08 (95% CI 0.97-1.19), 1.20 (1.09-1.33), 1.27 (1.14-1.41), and 1.28 (1.14-1.45) (P(trend) < 0.0001) after controlling for age, BMI, and other nondietary and dietary risk factors. In addition, when we modeled heme iron in seven categories, the multivariate RR comparing women who consumed > or =2.25 mg/day and those with intake <0.75 mg/day was 1.52 (1.22-1.88). The association between heme iron and the risk of diabetes was significant in both overweight and lean women.

CONCLUSIONS

This large cohort study suggests that higher heme iron intake is associated with a significantly increased risk of type 2 diabetes.

Blood pressure response to calcium supplementation: a meta-analysis of randomized controlled trials

Calcium plays a role in blood pressure (BP) regulation, but the importance of supplemental calcium intake for the prevention of hypertension is still debated. We conducted a meta-analysis of randomized controlled trials to determine the effect of calcium supplementation on BP. A systematic search for randomized trials of calcium supplementation and BP in non-pregnant subjects was performed in Medline from 1966 to June 2003. Seventy-one trials were identified, 40 of which met the criteria for meta-analysis (total of 2492 subjects). Two persons independently extracted data from original publications on changes in calcium intake and BP. In addition, data were collected on subjects' characteristics, that is, age, gender, initial BP and initial calcium intake. A random effects model was used to obtain the effect of calcium supplementation on BP, overall and in predefined population subgroups. Calcium supplementation (mean daily dose: 1200 mg) reduced systolic BP by -1.86 mm Hg (95% confidence interval: -2.91 to -0.81) and diastolic BP by -0.99 mm Hg (-1.61 to -0.37). In people with a relatively low calcium intake (< or =800 mg per day) somewhat larger BP estimates were obtained, that is, -2.63 (-4.03 to -1.24) for systolic BP and -1.30 (-2.13 to -0.47) for diastolic BP. Our study suggests that an adequate intake of calcium should be recommended for the prevention of hypertension. More research on BP in people with calcium-deficient diets is warranted.

Dietary patterns and glucose tolerance abnormalities in Japanese men

The Western dietary pattern appears to confer diabetes risk, but the role of dietary patterns in Asian populations remains unclear. We investigated the association between major dietary patterns and the glucose tolerance status of Japanese men. Abnormalities included impaired fasting glucose, impaired glucose tolerance, and type 2 diabetes. Subjects were 2106 Japanese men who were administered a 75-g oral glucose tolerance test at their preretirement health check-ups. Information about diet was obtained using a 74-item FFQ before the test. Three dietary patterns were generated by factor analysis: 1) a high-dairy, high-fruit and -vegetable, high-starch, low-alcohol pattern; 2) an animal food pattern; and 3) a Japanese pattern. We used logistic regression analysis to estimate odds ratios (OR) with adjustment for potential confounding variables. A significant inverse association was found for the high-dairy, high-fruit and -vegetable, high-starch, low-alcohol pattern (P for trend < 0.0001); the OR of having a glucose tolerance abnormality (impaired fasting glucose, impaired glucose tolerance, or type 2 diabetes) for the 2nd, 3rd, and 4th quartiles were 0.80 (95% CI = 0.62-1.04), 0.71 (95% CI = 0.54-0.92), and 0.51 (95% CI = 0.38-0.67), respectively, compared with the lowest quartile. The inverse association was consistent for each glucose tolerance abnormality as well as across subgroups stratified by risk factors for diabetes. The Japanese dietary pattern was positively associated with impaired glucose tolerance (P for trend = 0.048). A dietary pattern characterized by frequent consumption of dairy products and fruits and vegetables but low alcohol intake may be associated with a decreased risk of developing a glucose tolerance abnormality.

Calcium supplementation for the management of primary hypertension in adults

BACKGROUND

Metabolic studies suggest calcium may have a role in the regulation of blood pressure. Some epidemiological studies have reported that people with a higher intake of calcium tend to have lower blood pressure. Previous systematic reviews and meta-analyses have reached conflicting conclusions about whether oral calcium supplementation can reduce blood pressure.

OBJECTIVES

To evaluate the effects of oral calcium supplementation as a treatment for primary hypertension in adults.

SEARCH STRATEGY

We searched the Cochrane Library, MEDLINE, EMBASE, Science Citation Index, ISI Proceedings, ClinicalTrials.gov, Current Controlled Trials, CAB abstracts, and reference lists of systematic reviews, meta-analyses and randomised controlled trials (RCTs) included in the review.

SELECTION CRITERIA

Inclusion criteria were: 1) RCTs comparing oral calcium supplementation with placebo, no treatment, or usual care; 2) treatment and follow-up >/=8 weeks; 3) participants over 18 years old, with raised systolic blood pressure (SBP) >/=140 mmHg or diastolic blood pressure (DBP) >/=85 mmHg; 4) SBP and DBP reported at end of follow-up. We excluded trials where: participants were pregnant; received antihypertensive medication which changed during the study; or calcium supplementation was combined with other interventions.

DATA COLLECTION AND ANALYSIS

Two reviewers independently abstracted data and assessed trial quality. Disagreements were resolved by discussion or a third reviewer. Random effects meta-analyses and sensitivity analyses were conducted.

MAIN RESULTS

We included 13 RCTs (n=485), with between eight and 15 weeks follow-up. The results of the individual trials were heterogeneous. Combining all trials, participants receiving calcium supplementation as compared to control had a statistically significant reduction in SBP (mean difference: -2.5 mmHg, 95% CI: -4.5 to -0.6, I(2 )= 42%), but not DBP (mean difference: -0.8 mmHg, 95% CI: -2.1 to 0.4, I(2) = 48%). Sub-group analyses indicated that heterogeneity between trials could not be explained by dose of calcium or baseline blood pressure. Heterogeneity was reduced when poor quality trials were excluded. The one trial reporting adequate concealment of allocation and the one trial reporting adequate blinding yielded results consistent with the primary meta-analysis.

AUTHORS' CONCLUSIONS

In view of the poor quality of included trials and the heterogeneity between trials, the evidence in favour of causal association between calcium supplementation and blood pressure reduction is weak and is probably due to bias. This is because poor quality studies generally tend to over-estimate the effects of treatment. Larger, longer duration and better quality double-blind placebo controlled trials are needed to assess the effect of calcium supplementation on blood pressure and cardiovascular outcomes.

Lifestyle interventions to reduce raised blood pressure: a systematic review of randomized controlled trials

PURPOSE

To quantify effectiveness of lifestyle interventions for hypertension.

DATA SOURCES

Electronic bibliographic databases from 1998 onwards, existing guidelines, systematic reviews.

STUDY SELECTION AND DATA ABSTRACTION

We included randomized, controlled trials with at least 8 weeks' follow-up, comparing lifestyle with control interventions, enrolling adults with blood pressure at least 140/85 mmHg. Primary outcome measures were systolic and diastolic blood pressure. Two independent reviewers selected trials and abstracted data; differences were resolved by discussion.

RESULTS

We categorized trials by type of intervention and used random effects meta-analysis to combine mean differences between endpoint blood pressure in treatment and control groups in 105 trials randomizing 6805 participants. Robust statistically significant effects were found for improved diet, aerobic exercise, alcohol and sodium restriction, and fish oil supplements: mean reductions in systolic blood pressure of 5.0 mmHg [95% confidence interval (CI): 3.1-7.0], 4.6 mmHg (95% CI: 2.0-7.1), 3.8 mmHg (95% CI: 1.4-6.1), 3.6 mmHg (95% CI: 2.5-4.6) and 2.3 mmHg (95% CI: 0.2-4.3), respectively, with corresponding reductions in diastolic blood pressure. Relaxation significantly reduced blood pressure only when compared with non-intervention controls. We found no robust evidence of any important effect on blood pressure of potassium, magnesium or calcium supplements.

CONCLUSIONS

Patients with elevated blood pressure should follow a weight-reducing diet, take regular exercise, and restrict alcohol and salt intake. Available evidence does not support relaxation therapies, calcium, magnesium or potassium supplements to reduce blood pressure.

PKC-mediated modulation of L-type calcium channels may contribute to fat-induced insulin resistance

Increased intracellular free calcium [Ca2+]i has been noted in adipocytes, platelets, and leukocytes of subjects with insulin resistance syndrome or allied disorders. In rodent studies, measures which increase [Ca2+]i in adipocytes and skeletal muscle are associated with impaired insulin signaling, attributable at least in part to diminished ability of insulin to activate phosphoserine phosphatase-1 (PP-1). In fat-fed insulin resistant rats, pre-treatment with a drug that selectively chelates intracellular calcium eliminates about half of the decrement in insulin-stimulated glucose uptake induced by fat feeding; since this chelator does not influence the insulin sensitivity of chow-fed rats, it is reasonable to suspect that fat feeding boosts [Ca2+]i in skeletal muscle, and that this effect is partially responsible for the associated reduction in insulin sensitivity. Clinical insulin resistance is associated with increased levels of triglycerides and other fatty acid metabolites in muscle fibers; this can give rise to diacylglycerol-mediated activation of PKC, which in turn compromises insulin signaling by triggering kinase cascades that phosphorylate IRS-1 on key serine residues. Yet there is also evidence that, in skeletal muscle, PKC activity up-regulates the function of L-type calcium channels, increasing their maximal conductance while left-shifting their voltage dependence. Thus, the PKC activation associated with fat overexposure might be expected to boost basal [Ca2+]i in skeletal muscle, potentially impeding insulin-mediated activation of PP-1. This hypothesis is consistent with several clinical studies demonstrating that long-acting inhibitors of L-type calcium channels can improve insulin sensitivity in overweight hypertensives; it should be readily testable in rodent models of fat-induced insulin resistance. Since parathyroid hormone can act on adipocytes and muscle to boost [Ca2+]i, mild secondary hyperparathyroidism associated with low calcium intakes and poor vitamin D status may contribute to insulin resistance, consistent with certain clinical and epidemiological findings. Magnesium, often thought of as a mild calcium antagonist, appears to have favorable effects on insulin sensitivity and risk for diabetes, and recent evidence indicates that increases of intracellular magnesium within the physiological range can diminish calcium influx through phosphorylated L-type calcium channels. It will be of interest to determine whether calcium antagonism does indeed underlie the favorable influence of good magnesium status on insulin function. A report that chromium picolinate can induce the plasmalemmal Ca2+-ATPase in smooth muscle cells, raises the possibility that modulation of calcium transport might play a role in the insulin-sensitizing efficacy of bioactive chromium.