A new "sunshine" in the vasculature?

Milk products, dietary patterns and blood pressure management

High blood pressure (BP) is a major risk factor for heart disease, stroke, congestive heart failure, and kidney disease. Inverse associations between dairy product consumption and systolic blood pressure (SBP) and diastolic blood pressure (DBP) have been observed in cross-sectional studies; some studies, however, have reported an inverse association with only one BP parameter, predominantly SBP. Randomized clinical trials examining the effect of calcium and the combination of calcium, potassium and magnesium provide evidence for causality. In these studies, reductions in BP were generally modest (-1.27 to -4.6 mmHg for SBP, and -0.24 to -3.8 mmHg for DBP). Dairy nutrients, most notably calcium, potassium and magnesium, have been shown to have a blood pressure lowering effect. A low calcium intake increases intracellular calcium concentrations which increases 1,25-dihydroxyvitamin D(3) and parathyroid hormone (PTH), causing calcium influx into vascular smooth muscle cells, resulting in greater vascular resistance. New research indicates that dairy peptides may act as angiotensin converting enzyme (ACE) inhibitors, thereby inhibiting the renin angiotensin system with consequent vasodilation. A growing evidence base shows that dairy product consumption is involved in the regulation of BP. Consequently, inclusion of dairy products in a heart healthy diet is an important focal point to attain BP benefits.

Serum vitamin D, parathyroid hormone levels, and carotid atherosclerosis

Evidence suggests low vitamin D and elevated parathyroid hormone (PTH) concentrations may increase risk for cardiovascular disease. However, little is known about the association between vitamin D or PTH and subclinical atherosclerosis. This cross-sectional study included 654 community-dwelling older adults aged 55-96 years (mean age, 75.5 years) without a history of coronary heart disease, revascularization, or stroke enrolled in the Rancho Bernardo Study who completed a clinic examination in 1997-1999 and provided a blood sample for determination of serum 25-hydroxyvitamin D [25(OH)D], 1,25-dihydroxyvitamin D [1,25(OH)(2)D], and PTH concentrations. Carotid artery intima-media wall thickness (IMT) was measured as an indicator of atherosclerosis at two sites with B-mode ultrasound. After adjusting for age, sex, smoking, alcohol intake, waist-to-hip ratio, exercise, season of blood draw, diabetes, and hypertension, geometric mean internal carotid IMT (p(trend) 0.022), but not common carotid IMT (p(trend) 0.834) decreased in a dose-dependent fashion with increasing concentration of 25(OH)D. There was no association of 1,25(OH)(2)D or PTH with either measure of carotid IMT. In subgroup analyses, 1,25(OH)(2)D was inversely associated with internal carotid IMT among those with hypertension (p for interaction 0.036). These findings from a population-based cohort of older adults suggest a potential role for vitamin D in the development of subclinical atherosclerosis. Additional research is needed to determine whether vitamin D may influence the progression of atherosclerosis, including the effects of supplementation on the atherosclerotic process.

Vitamin D, the renin-angiotensin system, and insulin resistance

Insulin resistance is characterized by the systemic impairment of insulin action and is usually the result of aging, obesity, chronic inflammation, or another factor that may contribute to the inhibition of the insulin signaling pathway. Insulin resistance is accompanied by defects in lipid metabolism and blood coagulation, hypertension, obesity, and vascular inflammation in a syndrome called syndrome X or metabolic syndrome. Metabolic syndrome is involved in the development of atherosclerosis with consequent cardiovascular complications including acute myocardial infarction, stroke, and vascular disease. Recent data have shown that vitamin D acts as a negative regulator of the renin gene and that vitamin D deficiency is followed by increased renin-angiotensin II expression. The link between the insulin signaling pathway/insulin resistance and the renin-angiotensin system has been well documented in previous studies. The present review focuses on disorders characterized by a reduction in vitamin D concentration or its receptor function and the development of insulin resistance or metabolic syndrome, and discusses also possible therapeutic interventions.