Matching salt intake to physiological need in rats using foraging protocols

Several studies of the quantitative relationship between sodium need and sodium intake in rats are reviewed. Using acute diuretic treatment 24 h beforehand, intake matches need fairly accurately when intake is spread out in time by using a hypotonic solution of NaCl. In contrast, using a hypertonic solution, intake is typically double the need. Using the same diuretic treatment, although the natriuresis occurs within ~1 h, the appetite appears only slowly over 24 h. Increased plasma levels of aldosterone parallel the increased intake; however, treatment with metyrapone blocks the rise in aldosterone but has no effect on appetite. Satiation of sodium appetite was studied in rats using sodium loss induced by chronic diuretic treatment and daily salt consumption sessions. When a simulated foraging cost was imposed on NaCl access in the form of a progressive ratio lever press task, rats showed satiation for NaCl (break point) after consuming an amount close to their estimated deficit. The chronic diuretic regimen produced hypovolemia and large increases in plasma aldosterone concentration and renin activity. These parameters were reversed to or toward non-depleted control values at the time of behavioral satiation in the progressive ratio protocol. Satiation mechanisms for sodium appetite thus do appear to exist. However, they do not operate quantitatively when concentrated salt is available at no effort, but instead allow overconsumption. There are reasons to believe that such a bias toward overconsumption may have been beneficial over evolutionary time, but such biasing for salt and other commodities is maladaptive in a resource-rich environment.

Mineralocorticoid modulation of central angiotensin-induced neuronal activity, water intake and sodium appetite

Central angiotensin II (AngII) stimulates water and salt solution intake. Pretreatment with low-dose mineralocorticoid (DOCA) enhances this AngII-induced intake of salt solutions (the synergy theory) in Wistar and Sprague Dawley rats but not in Fischer rats. This response is mediated via the AT-1 receptor. Electrophysiological experiments using iontophoretic application of AngII and the AT-1 receptor-specific non-peptide antagonist losartan showed excitation of neurons in the preoptic/medial septum region of urethane-anesthetized male Wistar rats. DOCA pretreatment further enhances this neuronal excitation in response to AngII and reduces the responses to losartan. This generated the hypothesis that DOCA-enhanced AngII-induced neuronal excitation is the neural support for the synergy theory. AT-2 receptors modulate these intake responses depending on sodium in the diet, and diuretic-induced dehydration during pregnancy produces a higher salt intake in the offspring. AngII-induced salt and water intakes were tested in offspring from Sprague Dawley mothers with only 1.8% NaCl to drink in which half were treated with furosemide. The important observations were a) the AT-1 antagonist alone suppressed intakes in offspring from mothers not treated with furosemide, b) both AT-1 and AT-2 antagonists suppressed intakes in offspring from furosemide-treated mothers, and c) combined administration of AT-1 and AT-2 antagonists greatly suppressed water intake in offspring from mothers not treated with furosemide. These results suggest that AT-1 and AT-2 receptors have variable properties (receptor number and/or second messengers). Furthermore, the activity and function of these central AngII receptors depend on the background mineralocorticoid levels. The exact mechanism of this influence, however, remains to be determined.

Lesions of the commissural subnucleus of the nucleus of the solitary tract increase isoproterenol-induced water intake

The nucleus of the solitary tract (NTS) is the primary site of the cardiovascular afferent information about arterial blood pressure and volume. The NTS projects to areas in the central nervous system involved in cardiovascular regulation and hydroelectrolyte balance, such as the anteroventral third ventricle region and the lateral parabrachial nucleus. The aim of the present study was to investigate the effects of electrolytic lesion of the commissural NTS on water and 0.3 M NaCl intake and the cardiovascular responses to subcutaneous injection of isoproterenol. Male Holtzman rats weighing 280 to 320 g were submitted to sham lesion or electrolytic lesion of the commissural NTS (N = 6-15/group). The sham-lesioned rats had the electrode placed along the same coordinates, except that no current was passed. Water intake induced by subcutaneous isoproterenol (30 µg/kg body weight) significantly increased in chronic (15 days) commissural NTS-lesioned rats (to 2.4 ± 0.2 vs sham: 1.9 ± 0.2 mL 100 g body weight-1 60 min-1). Isoproterenol did not induce any sodium intake in sham or in commissural NTS-lesioned rats. The isoproterenol-induced hypotension (sham: -27 ± 4 vs commissural NTS-lesioned rats: -22 ± 4 mmHg/20 min) and tachycardia (sham: 168 ± 10 vs commissural NTS: 144 ± 24 bpm/20 min) were not different between groups. The present results suggest that the commissural NTS is part of an inhibitory neural pathway involved in the control of water intake induced by subcutaneous isoproterenol, and that the overdrinking observed in lesioned rats is not the result of a cardiovascular imbalance in these animals.

Salt and insulin sensitivity after short and prolonged high salt intake in elderly subjects

Salt sensitivity and insulin resistance are correlated with higher cardiovascular risk. There is no information about changes in salt sensitivity (SS) and insulin sensitivity (IS) after a chronic salt overload in humans. The aim of this study was to evaluate these parameters in the elderly. Seventeen volunteers aged 70.5 ± 5.9 years followed a low-salt diet (LSD) for 1 week and a high-salt diet (HSD) for 13 weeks. We evaluated SS after one week (HSD1) and after 13 weeks (HSD13), and subjects’ IS and lipids on their usual diet (UD) at HSD1, and at HSD13. Blood pressure (BP) was measured at each visit and ambulatory blood pressure monitoring (ABPM) was performed twice. SS was the same at HSD1 and HSD13. Systolic BP was lower on LSD than on UD (P = 0.01), HSD1 (P < 0.01) and HSD13 (P < 0.01). When systolic and diastolic BP were evaluated by ABPM, they were higher at HSD13 during the 24-h period (P = 0.03 and P < 0.01) and during the wakefulness period (P = 0.02 and P < 0.01) compared to the UD. Total cholesterol was higher (P = 0.04) at HSD13 than at HSD1. Glucose and homeostasis model assessment (HOMA) were lower at HSD1 (P = 0.02 and P = 0.01) than at HSD13. Concluding, the extension of HSD did not change the SS in an elderly group. The higher IS found at HSD1 did not persist after a longer HSD. A chronic HSD increased BP as assessed by ABPM.

Involvement of β3-adrenergic receptors in the control of food intake in rats

This study examined the food intake changes evoked by intracerebroventricular (icv) injection of a selective agonist (BRL37344, 2 and 20 nmol) or antagonist (SR59230A, 10 and 50 nmol) of β3-adrenergic receptors in 24-h fasted rats (adult male Wistar rats, 200-350 g, N = 6/treatment). The animals were also pretreated with saline icv (SAL) or SR59230A (50 nmol) followed by BRL37344 (20 nmol) or SAL in order to determine the selectivity of the effects evoked by BRL37344 on food intake or the selectivity of the effects evoked by SR59230A on risk assessment (RA) behavior. The highest dose of BRL37344 (N = 7) decreased food intake 1 h after the treatment (6.4 ± 0.5 g in SAL-treated vs 4.2 ± 0.8 g in drug-treated rats). While both doses of SR59230A failed to affect food intake (5.1 ± 1.1 g for 10 nmol and 6.0 ± 1.8 g for 50 nmol), this treatment reduced the RA frequency (number/30 min) (4 ± 2 for SAL-treated vs 1 ± 1 for 10 nmol and 0.5 ± 1 for 50 nmol SR59230A-treated rats), an ethological parameter related to anxiety. While pretreatment with SR59230A (7.0 ± 0.5 g) abolished the hypophagia induced by BRL37344 (3.6 ± 0.9 g), BRL37344 suppressed the reduction in RA frequency caused by SR59230A. These results show that the hypophagia caused by BRL37344 is selectively mediated by β3-adrenergic receptors within the central nervous system. Moreover, they suggest the involvement of these receptors in the control of anxiety.

Trans fatty acid intake is associated with insulin sensitivity but independently of inflammation

High saturated and trans fatty acid intake, the typical dietary pattern of Western populations, favors a proinflammatory status that contributes to generating insulin resistance (IR). We examined whether the consumption of these fatty acids was associated with IR and inflammatory markers. In this cross-sectional study, 127 non-diabetic individuals were allocated to a group without IR and 56 to another with IR, defined as homeostasis model assessment-IR (HOMA-IR) >2.71. Diet was assessed using 24-h food recalls. Multiple linear regression was employed to test independent associations with HOMA-IR. The IR group presented worse anthropometric, biochemical and inflammatory profiles. Energy intake was correlated with abdominal circumference and inversely with adiponectin concentrations (r = -0.227, P = 0.002), while saturated fat intake correlated with inflammatory markers and trans fat with HOMA-IR (r = 0.160, P = 0.030). Abdominal circumference was associated with HOMA-IR (r = 0.430, P < 0.001). In multiple analysis, HOMA-IR remained associated with trans fat intake (β = 1.416, P = 0.039) and body mass index (β = 0.390, P < 0.001), and was also inversely associated with adiponectin (β = -1.637, P = 0.004). Inclusion of other nutrients (saturated fat and added sugar) or other inflammatory markers (IL-6 and CRP) into the models did not modify these associations. Our study supports that trans fat intake impairs insulin sensitivity. The hypothesis that its effect could depend on transcription factors, resulting in expression of proinflammatory genes, was not corroborated. We speculate that trans fat interferes predominantly with insulin signaling via intracellular kinases, which alter insulin receptor substrates.

Correlations of circulating peptide YY and ghrelin with body weight, rate of weight gain, and time required to achieve the recommended daily intake in preterm infants

The objective was to elucidate the relationships between serum concentrations of the gut hormone peptide YY (PYY) and ghrelin and growth development in infants for potential application to the clinical observation index. Serum concentrations of PYY and ghrelin were measured using radioimmunoassay from samples collected at the clinic. For each patient, gestational age, birth weight, time required to return to birth weight, rate of weight gain, time required to achieve recommended daily intake (RDI) standards, time required for full-gastric feeding, duration of hospitalization, and time of administration of total parenteral nutrition were recorded. Serum PYY and ghrelin concentrations were significantly higher in the preterm group (N = 20) than in the full-term group (N = 20; P < 0.01). Within the preterm infant group, the serum concentrations of PYY and ghrelin on postnatal day (PND) 7 (ghrelin = 1485.38 ± 409.24; PYY = 812.37 ± 153.77 ng/L) were significantly higher than on PND 1 (ghrelin = 956.85 ± 223.09; PYY = 545.27 ± 204.51 ng/L) or PND 3 (ghrelin = 1108.44 ± 351.36; PYY = 628.96 ± 235.63 ng/L; P < 0.01). Both serum PYY and ghrelin concentrations were negatively correlated with body weight, and the degree of correlation varied with age. Serum ghrelin concentration correlated negatively with birth weight and positively with the time required to achieve RDI (P < 0.05). In conclusion, serum PYY and ghrelin concentrations reflect a negative energy balance, predict postnatal growth, and enable compensation. Further studies are required to elucidate the precise concentration and roles of PYY and ghrelin in newborns and to determine the usefulness of measuring these hormones in clinical practice.

Caffeine intake by patients with autosomal dominant polycystic kidney disease

Because caffeine may induce cyst and kidney enlargement in autosomal dominant polycystic kidney disease (ADPKD), we evaluated caffeine intake and renal volume using renal ultrasound in ADPKD patients. Caffeine intake was estimated by the average of 24-h dietary recalls obtained on 3 nonconsecutive days in 102 ADPKD patients (68 females, 34 males; 39 ± 12 years) and compared to that of 102 healthy volunteers (74 females, 28 males; 38 ± 14 years). The awareness of the need for caffeine restriction was assessed. Clinical and laboratory data were obtained from the medical records of the patients. Mean caffeine intake was significantly lower in ADPKD patients versus controls (86 vs 134 mg/day), and 63% of the ADPKD patients had been previously aware of caffeine restriction. Caffeine intake did not correlate with renal volume in ADPKD patients. There were no significant differences between the renal volumes of patients in the highest and lowest tertiles of caffeine consumption. Finally, age-adjusted multiple linear regression revealed that renal volume was associated with hypertension, chronic kidney disease stage 3 and the time since diagnosis, but not with caffeine intake. The present small cross-sectional study indicated a low level of caffeine consumption by ADPKD patients when compared to healthy volunteers, which was most likely due to prior awareness of the need for caffeine restriction. Within the range of caffeine intake observed by ADPKD patients in this study (0-471 mg/day), the renal volume was not directly associated with caffeine intake.

Acute effect of alcohol intake on sine-wave Cartesian and polar contrast sensitivity functions

The aim of this study was to assess contrast sensitivity for angular frequency stimuli as well as for sine-wave gratings in adults under the effect of acute ingestion of alcohol. We measured the contrast sensitivity function (CSF) for gratings of 0.25, 1.25, 2.5, 4, 10, and 20 cycles per degree of visual angle (cpd) as well as for angular frequency stimuli of 1, 2, 4, 24, 48, and 96 cycles/360°. Twenty adults free of ocular diseases, with normal or corrected-to-normal visual acuity, and no history of alcoholism were enrolled in two experimental groups: 1) no alcohol intake (control group) and 2) alcohol ingestion (experimental group). The average concentration of alcohol in the experimental group was set to about 0.08%. We used a paradigm involving a forced-choice method. Maximum sensitivity to contrast for sine-wave gratings in the two groups occurred at 4 cpd sine-wave gratings and at 24 and 48 cycles/360° for angular frequency stimuli. Significant changes in contrast sensitivity were observed after alcohol intake compared with the control condition at spatial frequency of 4 cpd and 1, 24, and 48 cycles/360° for angular frequency stimuli. Alcohol intake seems to affect the processing of sine-wave gratings at maximum sensitivity and at the low and high frequency ends for angular frequency stimuli, both under photopic luminance conditions.

Effect of salt intake and potassium supplementation on brachial-ankle pulse wave velocity in Chinese subjects: an interventional study

Accumulating evidence has suggested that high salt and potassium might be associated with vascular function. The aim of this study was to investigate the effect of salt intake and potassium supplementation on brachial-ankle pulse wave velocity (PWV) in Chinese subjects. Forty-nine subjects (28-65 years of age) were selected from a rural community of northern China. All subjects were sequentially maintained on a low-salt diet for 7 days (3.0 g/day NaCl), a high-salt diet for an additional 7 days (18.0 g/day NaCl), and a high-salt diet with potassium supplementation for a final 7 days (18.0 g/day NaCl+4.5 g/day KCl). Brachial-ankle PWV was measured at baseline and on the last day of each intervention. Blood pressure levels were significantly increased from the low-salt to high-salt diet, and decreased from the high-salt diet to high-salt plus potassium supplementation. Baseline brachial-ankle PWV in salt-sensitive subjects was significantly higher than in salt-resistant subjects. There was no significant change in brachial-ankle PWV among the 3 intervention periods in salt-sensitive, salt-resistant, or total subjects. No significant correlations were found between brachial-ankle PWV and 24-h sodium and potassium excretions. Our study indicates that dietary salt intake and potassium supplementation, at least in the short term, had no significant effect on brachial-ankle PWV in Chinese subjects.

Physical-chemical, caloric and sensory characterization of light jambolan (Syzygium cumini Lamarck) jelly

In Brazil, several little economically explored fruits have good potential as raw material for the agro-industry. This study aimed to produce and determine the physical-chemical and sensory characteristics of light jambolan jelly. This fruit has intense purple color, which gave the jellies - both standard and light - a quite attractive visual aspect. The light jellies exhibited similar physical-chemical characteristics to the ones developed through the conventional method and; with the proportion of sweeteners used, the caloric values of the formulations were reduced to the range of 41 to 53%, attending the requirements of the Brazilian legislation for this type of product. The sensory profile obtained for the 4 light formulations developed, clearly showed the tasters' preference for the jelly elaborated with the association of cyclamate and saccharin. Thus, the results revealed good perspectives for the application of this fruit in the food industry.

The effect of a diet education with six iso-caloric meals on the body weight and blood glucose of diabetes type 2 patients

The treatment of Diabetes should not only be sought through drug administration; diet is also a part of its treatment. The aim of this study was to determine the effect of a diet with six meals having equal calories on the body weight and blood glucose on diabetes type 2 patients. This research is an Experimental study conducted in 2009 on 181 patients with diabetes. The patients visited the IDSF (Iranian Diabetes Society of Fars) weekly and the patients to be studied were randomly divided into two groups of 85 and 96 patients, respectively. The participants were repeatedly requested to consume their calculated calorie in six equal parts. The average age in the Experimental and Control groups were 51.2 ± 13.3 and 53.1 ± 9.4, respectively. The mean body weight and fasting blood glucose at the beginning of the study in Experimental and Control groups were 66.3 ± 9.4 and 69.1 ± 11.1 kg, 198.9 ± 35.1, and 199.8 ± 39.1 mg.dL-1, respectively. At the end of the study, however, the values were 63.5 ± 7.5 and 66.98 ± 9 kg, 139.5 ± 34.6 and 164.2 ± 22.1 mg.dL-1, respectively. Only the mean fasting blood glucose at the end of the study revealed a significant difference (p-value = 0.001). The results show that educating those afflicted with Diabetes Type 2 aiming at changing their diet can greatly help them manage their blood glucose.

Stability of cassava flour-based food bars

The consumption of Brazilian cassava has been reduced due to a lack of adjustment to the modern lifestyle. To reverse this trend, new products could be developed specifically targeted to high-value niche markets. Cereal bars stand out as fast food high in nutritional value. A bar formula mimicking cereal bars was prepared using a mixture of Brazilian cassava flour, hydrogenated vegetable fat, dried bananas, ground cashew nuts, and glucose syrup. After being pressed, the bars were dried for 1 hour at 65 °C, packaged in films, and stored under ambient conditions. Its stability was continuously monitored for 210 days in order to ensure its safety and enable its introduction to the market. Texture loss was observed in the packed bars after 90 days of storage, but the sensory characteristics allowed the testers to perceive this tendency after only 30 days of storage. However, chemical, physical, and microbial analyses confirmed that the bars were safe for consumption for 180 days. The results showed that a 45 g cassava flour-based bar enriched with nuts and dried fruits can meet 6% of the recommended daily fiber intake with a caloric value between that of the common cereal bar and that of an energy bar. Adapting the formula with ingredients (fruits, nuts) from different regions of Brazil may add value to this traditional product as a fast food.

Estimate of dietary intake of chloropropanols (3-MCPD and 1,3-DCP) and health risk assessment

Chloropropanols, including 3-monochloropropane-1,2-diol (3-MCPD) and 1,3-dichloropropan-2-ol (1,3-DCP), comprise a group of chemical contaminants with carcinogenic and genotoxic properties. They have been found in a variety of processed foods and food ingredients, such as hydrolyzed vegetable protein, soy sauce, cereal-based products, malt-derived ingredients, and smoked foods. This study aimed to assess the dietary exposure to 3-MCPD and 1,3-DCP in Brazil and verify whether the presence of these substances in foods could represent health risks. The intake was calculated by combining data on food consumption, provided by the Consumer Expenditure Survey 2008-2009, with the levels of contaminant occurrence determined by gas chromatography-mass spectrometry. The exposure to 3-MCPD ranged from 0.06 to 0.51 µg.kg bw-1.day-1 considering average and high consumers, while the intake of 1,3-DCP was estimated to be 0.0036 µg.kg bw-1.day-1 in the worst case scenario evaluated. Based on these results, it was verified that the Brazilians' exposure to chloropropanols does not present a significant health risk. However, the consumption of specific foods containing high levels of 3-MCPD could exceed the provisional maximum tolerable daily intake of 2 µg.kg bw-1 established for this compound and, therefore, represent a potential concern.

Salt intake and blood pressure in the University of Asuncion-Paraguay youths: a preliminary study

INTRODUCTION: High salt intake is a major risk factor related to many cardiovascular and renal diseases. World Action on Salt and Health is a newly formed coalition of heath professionals whose goal is to implement changes in salt consumption in their respective countries for the goal of reducing blood pressure. In the same vein, we have decided to study the amount of salt intake in Paraguay to determine if a relationship exists between salt intake and blood pressure. OBJECTIVE: A preliminary study was undertaken to determine salt intake in Paraguay and its relationship with blood pressure, in order to implement a national program to combat hypertension. METHODS: Cross-sectional, observational study of 72 students from various universities in Asuncion (age range 22-30 years). Sodium excretion in 24-hour urine samples and blood pressure were measured. Assuming a steady state, urinary sodium excretion was converted into grams of salt ingested per day. RESULTS: Only 7% of the 72 participants had a salt intake less than the recommended maximum of 5 g/day. Forty-six percent had a blood pressure between 120-139 mmHg and 3% had stage 1 hypertension. There was no significant relationship between sodium excretion and blood pressure. CONCLUSION: Salt intake and blood pressure were found to be significantly elevated in young adults in Paraguay and argues for the importance of instituting a national campaign to reduce salt intake in this society.