Refined carbohydrate increases blood pressure and catecholamine excretion in SHR and WKY

Diet-Induced Hyperinsulinemia as a Key Factor in the Etiology of Both Benign Prostatic Hyperplasia and Essential Hypertension?

Benign prostatic hyperplasia and hypertension are common age-related comorbidities. Although the etiology of benign prostatic hyperplasia (BPH) is still largely unresolved and poorly understood, a significant age-independent association was found between BPH and hypertension, indicating a common pathophysiological factor for both diseases. It has previously been suggested that the development of essential hypertension may be related to diet-induced hyperinsulinemia. This study follows the question, whether BPH may develop due to the same mechanism, thereby explaining the well-known comorbidity of these 2 disorders. The scientific evidence presented shows that BPH and hypertension share the same pathophysiological changes, with hyperinsulinemia as the driving force. It further shows that significant dietary changes during human history cause disruption of a finely tuned metabolic balance that has evolved over millions of years of evolution: high-insulinemic food, typical of current “Western” diets, has the potential to cause hyperinsulinemia and insulin resistance, as well as an abnormally increased activation of the sympathetic nervous system and the renin-angiotensin-aldosterone system, alterations that play a pivotal role in the pathogenesis of BPH and hypertension.

Sugar-sweetened beverage, sugar intake of individuals, and their blood pressure: international study of macro/micronutrients and blood pressure

The obesity epidemic has focused attention on relationships of sugars and sugar-sweetened beverages (SSBs) to cardiovascular risk factors. Here we report cross-sectional associations of SSBs, diet beverages, and sugars with blood pressure (BP) for United Kingdom and US participants of the International Study of Macro/Micronutrients and Blood Pressure. Data collected include four 24-hour dietary recalls, two 24-hour urine collections, 8 BP readings, and questionnaire data for 2696 people ages 40 to 59 years of age from 10 US/United Kingdom population samples. Associations of SSBs, diet beverages, and sugars (fructose, glucose, and sucrose) with BP were assessed by multiple linear regression. SSB intake related directly to BP, with P values of 0.005 to <0.001 (systolic BP) and 0.14 to <0.001 (diastolic BP). SSB intake higher by 1 serving per day (355 mL/24 hours) was associated with systolic/diastolic BP differences of +1.6/+0.8 mm Hg (both P<0.001) and +1.1/+0.4 mm Hg (P<0.001/<0.05) with adjustment for weight and height. Diet beverage intake was inversely associated with BP (P 0.41 to 0.003). Fructose- and glucose-BP associations were direct, with significant sugar-sodium interactions: for individuals with above-median 24-hour urinary sodium excretion, fructose intake higher by 2 SD (5.6% kcal) was associated with systolic/diastolic BP differences of +3.4/+2.2 mm Hg (both P<0.001) and +2.5/+1.7 mm Hg (both P=0.002) with adjustment for weight and height. Observed independent, direct associations of SSB intake and BP are consistent with recent trial data. These findings, plus adverse nutrient intakes among SSB consumers, and greater sugar-BP differences for persons with higher sodium excretion lend support to recommendations that intake of SSBs, sugars, and salt be substantially reduced.

Maitake mushroom extracts ameliorate progressive hypertension and other chronic metabolic perturbations in aging female rats

OBJECTIVE

We assessed the ability of two commercially-available fractions labeled SX and D derived from the edible maitake mushroom to overcome many age-associated metabolic perturbations such as progressive, age-related elevation of blood pressure, over activity of the renin-angiotensin system (RAS), decreased insulin sensitivity, and inflammation in an in vivo laboratory model.

DESIGN AND METHOD

We divided forty mature, female Sprague-Dawley rats (SD) into five groups of eight. SD ingested regular rat chow containing added sucrose (20% w/w). The groups received baseline diet alone (control) or baseline diet containing captopril, niacin-bound chromium, maitake fraction SX, or maitake fraction D. In addition to blood pressure readings, the following procedures were implemented: losartan and insulin challenges, evaluation of serum ACE activity, glucose tolerance testing, blood chemistries, LNAME challenge, and measurement of various circulating cytokines.

RESULTS

We found that implementation of all test conditions stopped the gradual elevation of systolic blood pressure (SBP) in the SD over the four months of study, even reversing some of the previous elevation that occurred over time. In general, the treatment groups showed decreased activity of the RAS estimated by less lowering of SBP after losartan challenge and decreased serum ACE activity and were more sensitive to exogenous insulin challenge. TNFa levels decreased in all four test groups suggesting a lessening of the inflammatory state.

CONCLUSIONS

We believe our data suggest that maitake mushroom fractions lessen age-related hypertension, at least in part, via effects on the RAS; enhance insulin sensitivity; and reduce some aspects of inflammation--actions that should lead to a longer, healthier life span.

Inhibition by natural dietary substances of gastrointestinal absorption of starch and sucrose in rats 2. Subchronic studies

Acute oral consumption of various natural inhibitors of amylase (bean and hibiscus extracts) and sucrase (L-arabinose) reduce absorption of starch and sucrose respectively in rats and pigs measured by lessened appearance of circulating glucose levels. The present subchronic study was designed to determine whether these selected inhibitors of gastrointestinal starch and sucrose absorption (so-called "carb blockers") remain effective with continued use and to assess their metabolic influences after prolonged intake. Sprague-Dawley rats were gavaged twice daily over nine weeks with either water or an equal volume of water containing a formula that included bean and hibiscus extracts and L-arabinose. To estimate CHO absorption, control and treated Sprague-Dawley rats were gavaged with either water alone or an equal volume of water containing glucose, rice starch, sucrose, or combined rice starch and sucrose. Circulating glucose was measured at timed intervals over four hours. The ability to decrease starch and sucrose absorption use. No toxic effects (hepatic, renal, hematologic) were evident. Blood chemistries revealed significantly lower circulating glucose levels and a trend toward decreased HbA1C in the nondiabetic rats receiving the natural formulation compared to control. Subchronic administration of enzyme inhibitors was also associated with many metabolic changes including lowered systolic blood pressure and altered fluid-electrolyte balance. We postulate that proper intake of natural amylase and sucrase inhibitors may be useful in the prevention and treatment of many chronic disorders associated with perturbations in glucose-insulin homeostasis secondary to the rapid absorption of refined CHO.

Effects of high-sucrose feeding on insulin resistance and hemodynamic responses to insulin in spontaneously hypertensive rats

This study was designed to investigate the effects of a sucrose diet on vascular and metabolic actions of insulin in spontaneously hypertensive rats (SHR). Male SHR were randomized to receive a sucrose or regular chow diet for 4 wk. Age-matched, chow-fed Wistar-Kyoto (WKY) rats were used as normotensive control. In a first series of experiments, the three groups of rats had pulsed Doppler flow probes and intravascular catheters implanted to determine blood pressure, heart rate, and blood flows. Insulin sensitivity was assessed during a euglycemic hyperinsulinemic clamp performed in conscious rats. In a second series of experiments, new groups of rats were used to examine glucose transport activity in isolated muscles and to determine endothelial nitric oxide synthase (eNOS) protein expression in muscles and endothelin content in vascular tissues. Sucrose feeding was shown to markedly enhance the pressor response to insulin and its hindquarter vasoconstrictor effect when compared with chow-fed SHR. A reduction in eNOS protein content in muscle, but no change in vascular endothelin-1 protein, was noted in sucrose-fed SHR when compared with WKY rats, but these changes were not different from those noted in chow-fed SHR. Similar reductions in insulin-stimulated glucose transport were observed in soleus muscles from both groups of SHR when compared with WKY rats. In extensor digitorum longus muscles, a significant reduction in insulin-stimulated glucose transport was only seen in sucrose-fed rats when compared with the other two groups. Environmental factors, that is, high intake of simple sugars, could possibly potentiate the genetic predisposition in SHR to endothelial dysfunction and insulin resistance.

Induction of insulin resistance by high-sucrose feeding does not raise mean arterial blood pressure but impairs haemodynamic responses to insulin in rats

1. This study was undertaken to further investigate the effects of a sucrose-enriched diet on vascular function and insulin sensitivity in rats. 2. Male Sprague-Dawley rats were randomized to receive a sucrose- or regular rat chow-diet for 4 weeks. A first group of sucrose- and chow-fed rats was instrumented with pulsed Doppler flow probes and intravascular catheters to determine blood pressure, heart rate, regional blood flows and insulin sensitivity in conscious rats. Insulin sensitivity was assessed by the euglycemic hyperinsulinemic clamp technique. Glucose transport activity was examined in isolated muscles by using the glucose analogue [(3)H]-2-deoxy-D-glucose. A second group of sucrose- and chow-fed rats was used to obtain information regarding nitric oxide synthase (NOS) isozymes protein expression in muscles, and determine endothelin content in vascular tissues isolated from both dietary groups. 3. Sucrose feeding was found to induce insulin resistance, but had no effect on resting blood pressure, heart rate, or regional haemodynamics. This insulin resistance was accompanied by alteration in the vascular responses to insulin. Insulin-mediated skeletal muscle vasodilation was impaired, whereas the mesenteric vasoconstrictor response was potentiated in sucrose-fed rats. A reduction in eNOS protein content in muscle and an increase in vascular endothelin peptide were noted in these animals. Moreover, a reduction in insulin-simulated glucose transport activity was also noted in muscles isolated from sucrose-fed rats. 4. Together these data suggest that a cluster of metabolic and haemodynamic abnormalities occur in response to the intake of simple sugars in rats.

Hyperinsulinemia produces both sympathetic neural activation and vasodilation in normal humans

Hyperinsulinemia may contribute to hypertension by increasing sympathetic activity and vascular resistance. We sought to determine if insulin increases central sympathetic neural outflow and vascular resistance in humans. We recorded muscle sympathetic nerve activity (MSNA; microneurography, peroneal nerve), forearm blood flow (plethysmography), heart rate, and blood pressure in 14 normotensive males during 1-h infusions of low (38 mU/m2/min) and high (76 mU/m2/min) doses of insulin while holding blood glucose constant. Plasma insulin rose from 8 +/- 1 microU/ml during control, to 72 +/- 8 and 144 +/- 13 microU/ml during the low and high insulin doses, respectively, and fell to 15 +/- 6 microU/ml 1 h after insulin infusion was stopped. MSNA, which averaged 21.5 +/- 1.5 bursts/min in control, increased significantly (P less than 0.001) during both the low and high doses of insulin (+/- 5.4 and +/- 9.3 bursts/min, respectively) and further increased during 1-h recovery (+15.2 bursts/min). Plasma norepinephrine levels (119 +/- 19 pg/ml during control) rose during both low (258 +/- 25; P less than 0.02) and high (285 +/- 95; P less than 0.01) doses of insulin and recovery (316 +/- 23; P less than 0.01). Plasma epinephrine levels did not change during insulin infusion. Despite the increased MSNA and plasma norepinephrine, there were significant (P less than 0.001) increases in forearm blood flow and decreases in forearm vascular resistance during both doses of insulin. Systolic pressure did not change significantly during infusion of insulin and diastolic pressure fell approximately 4-5 mmHg (P less than 0.01). This study suggests that acute increases in plasma insulin within the physiological range elevate sympathetic neural outflow but produce forearm vasodilation and do not elevate arterial pressure in normal humans.