Diet, blood pressure and hypertension

Dietary cis-monounsaturated fatty acids and metabolic control in type 2 diabetes

Whether low-fat, high-carbohydrate (CHO) diets or moderately high-fat, high-monounsaturated fatty acid (MUFA) diets are preferable for the treatment and prevention of diabetes has been a matter of debate. High-fat diets based on MUFA-rich oils or whole foods have been compared with high-CHO diets for effects on several cardiovascular risk outcomes in diabetic subjects. Early studies using metabolic diets with wide differences in total fat content (15-25% of energy) generally found a beneficial effect of MUFA diets on glycemic control and serum lipids. Recent studies using prescribed diets with a difference of </= 15% of energy in total fat between low-fat and high-MUFA diets show similar effects on glycemic profiles but still favor MUFA diets for effects on triacylglycerols and HDL cholesterol. It is unclear whether postprandial fat clearance is impaired by CHO diets and improved by MUFA diets, independent of effects on fasting triacylglycerol concentrations. Unless one diet contains abundant antioxidants, the 2 dietary approaches appear to have similar effects on LDL oxidation. Low-fat diets, however, are associated with atherogenic, dense LDL particles, while normal, buoyant LDL predominate with high-fat diets irrespective of fatty acid composition. Limited experimental evidence suggests that MUFA diets favorably influence blood pressure, coagulation, endothelial activation, inflammation, and thermogenic capacity. Energy-controlled high-MUFA diets do not promote weight gain and are more acceptable than low-fat diets for weight loss in obese subjects. Thus, there is good scientific support for MUFA diets as an alternative to low-fat diets for medical nutrition therapy in diabetes.

Common gene polymorphisms and nutrition: emerging links with pathogenesis of multifactorial chronic diseases (review)

Rapid progress in human genome decoding has accelerated search for the role of gene polymorphisms in the pathogenesis of complex multifactorial diseases. This review summarizes the results of recent studies on the associations of common gene variants with multifactorial chronic conditions strongly affected by nutritional factors. Three main individual sections discuss genes related to energy homeostasis regulation and obesity, cardiovascular disease (CVD), and cancer. It is evident that several major chronic diseases are closely related (often through obesity) to deregulation of energy homeostasis. Multiple polymorphic genes encoding central and peripheral determinants of energy intake and expenditure have been revealed over the past decade. Food intake control may be affected by polymorphisms in the genes encoding taste receptors and a number of peripheral signaling peptides such as insulin, leptin, ghrelin, cholecystokinin, and corresponding receptors. Polymorphic central regulators of energy intake include hypothalamic neuropeptide Y, agouti-related protein, melanocortin pathway factors, CART (cocaine- and amphetamine-regulated transcript), some other neuropeptides, and receptors for these molecules. Potentially important polymorphisms in the genes encoding energy expenditure modulators (alpha- and beta- adrenoceptors, uncoupling proteins, and regulators of adipocyte growth and differentiation) are also discussed. CVD-related gene polymorphisms comprising those involved in the pathogenesis of atherosclerosis, blood pressure regulation, hemostasis control, and homocysteine metabolism are considered in a separate section with emphasis on multiple polymorphisms affecting lipid transport and metabolism and their interactions with diet. Cancer-associated polymorphisms are discussed for groups of genes encoding enzymes of xenobiotic metabolism, DNA repair enzymes, factors involved in the cell cycle control, hormonal regulation-associated proteins, enzymes related to DNA methylation through folate metabolism, and angiogenesis-related factors. There is an apparent progress in the field with hundreds of new gene polymorphisms discovered and characterized, however firm evidence consistently linking them with pathogenesis of complex chronic diseases is still limited. Ways of improving the efficiency of candidate gene approach-based studies are discussed in a short separate section. Successful unraveling of interaction between dietary factors, polymorphisms, and pathogenesis of several multifactorial diseases is exemplified by studies of folate metabolism in relation to CVD and cancer. It appears that several new directions emerge as targets of research on the role of genetic variation in relation to diet and complex chronic diseases. Regulation of energy homeostasis is a fundamental problem insufficiently investigated in this context so far. Impacts of genetic variation on systems controlling angiogenesis, inflammatory reactions, and cell growth and differentiation (comprising regulation of the cell cycle, DNA repair, and DNA methylation) are also largely unknown and need thorough analysis. These goals can be achieved by complex simultaneous analysis of multiple polymorphic genes controlling carefully defined and selected elements of relevant metabolic and regulatory pathways in meticulously designed large-scale studies.

Vegetable intake and long-term survival among middle-aged men in Italy

PURPOSE

To examine prospectively the relationship between vegetable consumption and long-term survival.

METHODS

In 1965, a total of 1536 Italian males from two Italian rural cohorts of the Seven Countries Study, aged 45-65 years, were examined. Information on lifestyle and food consumption collected at this visit, and total and cause-specific mortality data collected in 30 years of follow-up were analyzed for the present study.

RESULTS

During a period of 30 years, 1096 deaths occurred (308 from coronary heart disease, 325 from cancer, 158 from cerebrovascular disease and 305 from all other causes). The age-adjusted life expectancy for men consuming more than 60 g/day of vegetables was nearly 2 years longer than for men consuming less than 20 g/day. This increase in survival was more striking in smokers than nonsmokers (2.1 vs. a 1 year gain). The association also held for both geographic cohorts, although the pattern of vegetable consumption was very different in the two villages.

CONCLUSIONS

The results suggest a positive association between vegetable intake and life expectancy. Vegetable intake may be especially protective for smokers although the biological explanation for such an effect is unclear.

Association of blood pressure with intake of soy products and other food groups in Japanese men and women

BACKGROUND

Soy diet has been suggested to have antihypertensive effect in animal studies. The present study examined the cross-sectional relationship between blood pressure and intake of soy products and other food groups in Japanese men and women.

METHODS

Blood pressure was measured in Japanese 294 men and 330 women (246 premenopausal and 84 peri- and postmenopausal women) who participated in a health check-up program provided by a general hospital. Intake of various food groups and nutrients was estimated from a validated semiquantitative food frequency questionnaire.

RESULTS

In men, soy product intake was inversely significantly correlated with diastolic blood pressure (r = -0.12, P = 0.04) after controlling for age, total energy, smoking status, body mass index, and intake of alcohol, salt and seaweeds. The correlation of soy product intake with systolic blood pressure was of borderline significance (r = -0.10, P = 0.09). Systolic blood pressure was inversely correlated with intake of vegetables (r = -0.12, P = 0.04) and dairy products (r = -0.12, P = 0.05). There were no significant correlations between soy product intake and diastolic blood pressure in women.

CONCLUSIONS

These results indicate a mild effect of soy intake on blood pressure reduction in men.

Heart and blood pressure adaptations in Wistar rats fed with different high-fat diets for 18 months

OBJECTIVE

We investigated the effect of long-term administration of four different high-fat diets on systolic blood pressure (SBP), body and heart biometry, and left ventricular myocyte nuclei number (N[lvm]).

METHODS

Twenty-four Wistar rats were assigned to one of four groups from weaning to age 18 mo. The rats were fed experimental diets containing soybean oil (S group), canola oil (CA group), lard and egg yolk (LE group), and canola oil plus lard and egg yolk (CA + LE group). N(lvm) was measured with the disector method in isotropic uniform random sections of the left ventricular myocardium.

RESULTS

There were no significant differences across experimental groups in morphometric indices. SBP was higher in the LE group at all ages and lower in the 18-mo CA group. The myocardium structure analysis separated the animals in three major categories: the CA and LE groups as the extreme and the S and CA + LE groups as the intermediary. In the LE group the myocardium presented more important structural changes: cardiac myocytes were enlarged and surrounded with thick collagen bundles, and some regions exhibited myocardial necrosis.

CONCLUSION

Long-term intake of the CA diet was more efficient in maintaining normal N(lvm) and SBP than the S and LE diets. The CA + LE diet resulted in balanced levels of SBP and N(lvm) in rats, suggesting that canola oil reduces cardiovascular injury caused by intake of lard and egg yolk.

Soy product intake is inversely associated with serum homocysteine level in premenopausal Japanese women

Soybeans, which are an excellent source of folate, vitamin B-6 and minerals, may reduce serum homocysteine level. However, there is a possibility that dietary soy raises the serum homocysteine level because isoflavones, which are weak estrogens contained in soybeans, may exert antiestrogenic effects in a high estrogen environment, such as in premenopausal women. The present study examined a cross-sectional relationship between soy product intake and serum homocysteine level in 201 premenopausal Japanese women. Intakes of soy products, folate, methionine and vitamins B-6 and B-12 were estimated by a semiquantitative food frequency questionnaire. Folate status was also assessed by measuring serum folate. Soy product intake in terms of soy protein as well as soy isoflavone intake was modestly but significantly inversely associated with serum homocysteine level (r = -0.15, P = 0.04) after controlling for covariates. Soy product intake was also significantly positively correlated with serum folate (r = 0.15, P = 0.04). Although it is unclear the extent to which each component of soy, such as folate and isoflavones, is associated with the serum homocysteine concentration, this biochemical complex appears to have a favorable effect on homocysteine metabolism in premenopausal women.

The impact of fermentation and in vitro digestion on the formation of angiotensin-I-converting enzyme inhibitory activity from pea and whey protein

Pea and whey protein were fermented by Lactobacillus helveticus and Saccharomyces cerevisiae in monoculture and in combination at 28 and 37 degrees C in order to release angiotensin-I-converting enzyme (ACE) inhibitory peptides. The fermentation products were subjected to in vitro gastrointestinal digestion, and the digests of nonfermented samples served as controls. After fermentation, the ACE inhibitory activity (%) increased by 18 to 30% for all treatments, except for the fermentations of whey protein with Saccharomyces cerevisiae at 28 degrees C, where no significant change was observed. After digestion, however, both fermented and nonfermented samples reached maximum ACE inhibitory activity. The whey digests tended to have lower (50%) inhibitory concentrations (IC50; 0.14 to 0.07 mg/ml), hence, higher ACE inhibitory activity, than the pea digests (0.23 to 0.11 mg/ml). The nonfermented whey protein digest showed the highest ACE inhibitory activity of all. For pea protein, the nonfermented sample had the lowest IC50 value. These results suggest that in vitro gastrointestinal digestion was the predominant factor controlling the formation of ACE inhibitory activity, hence, indicating its importance in the bioavailability of ACE inhibitory peptides.

Therapeutic lifestyle changes for hypertension and cardiovascular risk reduction

Elevated blood pressure is the most common chronic illness in the United States, affecting more than 50 million people. Hypertension is an even greater problem in the African American community. Traditionally, management of hypertension and cardiovascular risk reduction has focused on drug therapy; however, several studies have shown the benefits of therapeutic lifestyle changes for blood pressure lowering and cardiovascular risk reduction. Therapeutic lifestyle changes to reduce blood pressure have enormous potential as a means for preventing and controlling hypertension and thereby reducing the risk of coronary heart disease. Although the reductions in blood pressure are relatively modest with these approaches, they could potentially have a beneficial impact on overall cardiovascular morbidity and mortality when applied to the whole population. Because of their high prevalence of certain cardiovascular risk factors (e.g., obesity, diabetes mellitus) and greater salt sensitivity, therapeutic lifestyle changes have particular relevance for African Americans.

The reno-protective role of AT(1)-receptor blockers

In the 1970s and 1980s it became evident that progression of renal disease and blood pressure are correlated. Subsequently, it was shown that antihypertensive treatment, especially with agents that block the renin-angiotensin system (RAS), could slow the progression of diabetic renal disease. Several studies, particularly with RAS blockers, have confirmed beneficial effects on urinary albumin excretion in patients with diabetes and microalbuminuria or proteinuria. There are good reasons to explore dual blockade of the RAS with an AT(1)-receptor blocker and an ACE inhibitor. Receptor blockers may block the effects of angiotensin II more effectively than ACE inhibitors; moreover, ACE inhibitors increase bradykinins which may have positive effects on blood pressure and renal function. Such combination treatment has been found to be well tolerated and more effective in reducing blood pressure than either monotherapy. Positive effects on microalbuminuria or proteinuria have also been noted. Studies have shown that treatment with AT(1)-receptor blockers postpones end-stage renal disease and reduces the rate of decline in glomerular filtration rate (GFR) in patients with type 2 diabetes and nephropathy. Moreover, albuminuria was reduced to a greater extent with AT(1)-receptor blockers than with conventional antihypertensive therapy producing the same blood pressure reductions. In summary, AT(1)-receptor blockers are effective in all stages of diabetic renal disease, and have an excellent tolerability profile. Usually the side-effect profile is comparable with placebo. In certain situations, there may be a slight, readily reversible, increase in serum potassium. There may also be a slight reduction in GFR, reflecting a decrease in glomerular filtration pressure.

Plasma vitamin C modifies the association between hypertension and risk of stroke

BACKGROUND AND PURPOSE

There are no prospective studies to determine whether plasma vitamin C modifies the risk of stroke among hypertensive and overweight individuals. We sought to examine whether plasma vitamin C modifies the association between overweight and hypertension and the risk of stroke in middle-aged men from eastern Finland.

METHODS

We conducted a 10.4-year prospective population-based cohort study of 2419 randomly selected middle-aged men (42 to 60 years) with no history of stroke at baseline examination. A total of 120 men developed a stroke, of which 96 were ischemic and 24 hemorrhagic strokes.

RESULTS

Men with the lowest levels of plasma vitamin C (<28.4 micromol/L, lowest quarter) had a 2.4-fold (95% CI, 1.4 to 4.3; P=0.002) risk of any stroke compared with men with highest levels of plasma vitamin C (>64.96 micromol/L, highest quarter) after adjustment for age and examination months. An additional adjustment for body mass index, systolic blood pressure, smoking, alcohol consumption, serum total cholesterol, diabetes, and exercise-induced myocardial ischemia attenuated the association marginally (relative risk, 2.1; 95% CI, 1.2 to 3.8; P=0.01). Adjustment for prevalent coronary heart disease and atrial fibrillation did not attenuate the association any further. Furthermore, hypertensive men with the lowest vitamin C levels (<28.4 micromol/L) had a 2.6-fold risk (95% CI, 1.52 to 4.48; P<0.001), and overweight men (> or =25 kg/m2) with low plasma vitamin C had a 2.7-fold risk (95% CI, 1.48 to 4.90; P=0.001) for any stroke after adjustment for age, examination months, and other risk factors.

CONCLUSIONS

Low plasma vitamin C was associated with increased risk of stroke, especially among hypertensive and overweight men.

The kidney in diabetes: how to control renal and related cardiovascular complications

The clear-cut and detailed pathogenesis of diabetic renal disease is not yet elucidated, but it is clear that both initiation and progression of renal disease in diabetes is related to glycemic control and blood pressure (BP) regulation, also seen in intervention studies. Consequently, optimal control of glycemia and antihypertensive treatment have become the cornerstones in the management of patients with diabetes. Naturally, modulating factors need to be discussed in further detail. The genetics of diabetes and its renal complications are still very complex issues that need to be explored further. Few and inconclusive data are available with respect to clinical management, for which genotyping is not required. Dietary protein content has long been an interesting avenue for possible treatment, but to date, data from patients with nondiabetic renal disease and with diabetes are not totally convincing, although further results may be published very soon. The issue is also complex because a low-protein diet may increase BP according to new studies, rendering the issue of low-protein content in the diet still more complex and controversial. Metabolic issues remain a key question, specifically with regard to glycemic control, in which data have accumulated over the past decade from epidemiological and interventional studies. There is no doubt that optimal glycemic control is crucial, but issues regarding specific glucose-related mechanisms and protein and lipid metabolism are still under investigation. The renin-angiotensin system has emerged as a key issue in diabetes, especially with regard to its inhibition by angiotensin-converting enzyme (ACE) inhibition and angiotensin-receptor blockade. New studies suggest that more complete inhibition of this system by dual blockade may be an avenue for further study according to positive results in patients with microalbuminuric type 2 diabetes, who are at great risk. Antihypertensive treatment still remains a fundamental component, although the metabolic effects of some antihypertensive agents may be important, especially with respect to diuretics, ss-blockers, and possibly alpha-blockers. The situation becomes complex with the frequent combination of various agents in the treatment of hypertension in patients with diabetes. Conversely, ACE inhibitors may have some diabetes-protective effect, but further studies are needed.