This study was designed to investigate the brown adipose tissue (BAT) gene expression and some metabolic and hormonal parameters in monosodium glutamate (MSG) treated‐rats. Design and

ObjectiveTo study some factors related with the energy metabolism in adult offspring of dams fed low salt diet during pregnancy and lactation.MethodsFemale Wistar rats were fed low (LS 0.15%) or normal (NS 1.3% NaCl) salt diet since 8 weeks of age. At 12 weeks of age, they were mated. Offspring were fed NS from weaning and at 12 weeks of age, they were kept on 4oC or room temperature (RT) during 24 hours. Body weight (BW) and temperature (BT), blood glucose (GLU) plasma norepinephrine (NOR), and leptin (LEP) were measured. Gene expression (RT‐PCR) for uncoupling protein‐1 (UCP1), coenzyme Q1 (Q1) and Q2 (Q2) was evaluated in brown adipose tissue.Results(mean±SEM, n=5 to 8/group): No differences were observed in BW between adult offspring groups. UCP1, Q1 and Q2 were lower (p<0.05) in LS (UCP1 ‐ 1.5±0.1, Q1‐ 0.7±0.1, Q2 ‐ 1.0±0.1) than in NS (UCP1 ‐ 2.0±0.1, Q1 ‐ 1.1±0.1, Q2 ‐ 1.3±0.1) at RT but not at 4°C. At 4°C BT decreased (p<0.05) in NS but not in LS. NOR (pg/dL) was higher on 4°C (471±42) than on RT (206±28) in NS but not in LS. GLU did not change after exposure to 4°C in NS and LS. At 4°C, LEP decreased (p<0.05) in NS but not in LS.ConclusionsLow salt diet during pregnancy and lactation modifies expression of some genes involved in energy metabolism in adult female offspring. Supported by FAPESP.

The aim of this study was to evaluate blood pressure (BP), renal sympathetic nerve activity (rSNA), protein expression and activation of AT1R and AT2R in the RVLM of control (C, n=22), sucrose‐fed (20% sucrose solution, 30 days; SC, n=24) and sucrose‐fed rats treated with vitamin C (150 mg/Kg/day, last 7 days; SCvC, n=22). Thiobarbituric acid reactive substance (TBARS) was measured in serum. Insulin, Ang II and glucose were measured in plasma. Protein expression was evaluated by western blot and the receptors’ activation was evaluated by ELISA in tissue slices. BP, rSNA, insulin, Ang II and TBARS levels increased (P<0.05) in SC compared to C. In SCvC, Ang II and insulin levels were similar to SC although, BP, rSNA and TBARS were diminished. AT1R protein expression in the RVLM was similar in all groups while there was a 74% increase (P<0.05) in AT2R protein expression in SC compared to C. In relation to C, an intense (P<0.05) AT1R (116%) and AT2R activation (417%) were found in SC. In SCvC, AT2R protein expression levels were 43% lower than that of SC and were similar to those of C. AT1R and AT2R activation were also 39% and 29% lower in SCvC compared to SC. These results suggest that AT1R and AT2R activation in RVLM is involved in rSNA and hypertension in sucrose‐fed rats. Supported by FAPESP.

BACKGROUNDWe hypothesized that upregulation of angiotensin type 1 receptor (AT, R) and inducible nitric oxide (NO) synthase (iNOS) within the rostral ventrolateral medulla (RVLM) could contribute to two-kidney, one-clip (2K-1C) hypertension.METHODSThe experiments were performed in male Wistar rats, 6 weeks after the renal surgery. The animals were divided into control (SHAM, n = 18) and hypertensive groups (2K-1C, n = 18). Bilateral tissue punches were taken from sections containing the RVLM to perform iNOS gene expression analyses by the real-time PCR technique, and AT(1)R and iNOS protein expression analyses by western blotting. In addition, we injected losartan (1 nmol), an AT(1)R antagonist, and aminoguanidine (250 pmol), an iNOS inhibitor, bilaterally into the RVLM to analyze the mean arterial pressure (MAP) and renal sympathetic nerve activity (rSNA).RESULTSiNOS mRNA expression levels were greater (P < 0.05) in the 2K-1C group compared to the SHAM group. Furthermore, the AT(1)R and iNOS protein expression were significantly increased in the RVLM of 2K-1C rats compared to SHAM rats. Injection of losartan into the RVLM reduced the MAP (11%) and rSNA (18%) only in the 2K-1C rats, whereas injection of aminoguanidine in the same region decreased the MAP (31%) and rSNA (34%) in hypertensive rats.CONCLUSIONSThe present study suggests that upregulation of AT(1)R and iNOS in the RVLM is important in the maintenance of high blood pressure and renal sympathetic activation in 2K-1C hypertension.

Sucrose-fed rats, a model of metabolic syndrome, are characterized by insulin resistance, obesity, hypertension, and high plasma levels of triacylglycerols and angiotensin II (Ang II). However, whether tissue renin–angiotensin system (RAS) is altered in metabolic syndrome is unclear. To study this issue, food ad libitum and water (C) or 20% sucrose solution (SC) were given to adult male Wistar rats, for 30days. Body weight (BW), blood pressure (BP), epididymal adipose tissue (EPI) mass, rate of in vivo fatty acid (FA) synthesis in EPI, circulating glucose, insulin, leptin, angiotensins I and II, triacylglycerols, and plasma renin (PRA) and angiotensin-converting enzyme (ACE) activities were evaluated. In kidneys and EPI, gene and protein expression of type 1 (AT1) and 2 (AT2) Ang II receptors, ACE, angiotensinogen (AGT) as well as protein expression of angiotensin-converting enzyme 2 (ACE2) were determined. In both tissues, Ang I, Ang II and Ang-(1–7) contents were also measured by HPLC. In SC rats higher BP, EPI mass, circulating triacylglycerols, insulin, leptin, PRA and, Ang II were found. In EPI, the rate of in vivo FA synthesis was associated with increased Ang-(1–7), protein expression of AT1 and AT2 receptors, ACE2, AGT, and gene expression of AGT although a reduction in ACE activity and in adipose Ang I and Ang II contents was observed. In kidneys, AT1 and AT2, ACE and AGT gene and protein expression as well as protein expression of ACE2 were unaltered while Ang II, Ang-(1–7) and ACE activity increased. These RAS component changes seem to be tissue specific and possibly are related to enhancement of FA synthesis, EPI mass and hypertension.

In the present study we hypothesized that an increase of Ang II – via the AT-1 receptor – in the rostral ventrolateral medulla (RVLM) and the paraventricular nucleus of the hypothalamus (PVN) could activate NAD(P)H oxidase that will produce superoxides resulting in increased sympathetic activity and hypertension. The mRNA expression of AT-1 receptors, NAD(P)H oxidase subunits (p47phox and gp91phox) and CuZnSOD were analyzed in the RVLM and PVN of male Wistar rats (Goldblatt hypertension model – 2K-1C). Additionally, we administered Tempol-1 and 5 nmol into the RVLM, PVN. The mean arterial pressure (MAP) and renal sympathetic nerve activity (RSNA) were analyzed. The AT-1 mRNA expression and NAD(P)H oxidase subunits was greater in the RVLM and PVN in 2K-1C compared to the control group. However, the CuZnSOD expression was similar in both groups. Tempol-1 nmol into the RVLM reduced MAP (15±1%) and RSNA (11±2%) only in 2K-1C rats. Tempol (5 nmol) in the same region decreased the MAP (12±4%) and RSNA (20±7%) respectively, only in 2K-1C. In the PVN, Tempol-5 nmol resulted in a significant fall in the MAP (24±1%) and in the RSNA (7.9±2%) only in the 2K-1C. The data suggest that the hypertension and sympathoexcitation in 2K-1C rats were associated with an increase in oxidative stress in the sympathetic premotor neurons.

A number of studies conducted in humans and in animals have observed that events occurring early in life are associated with the development of diseases in adulthood. Salt overload and restriction during pregnancy and lactation are responsible for functional (hemodynamic and hormonal) and structural alterations in adult offspring. Our group observed that lower birth weight and insulin resistance in adulthood is associated with salt restriction during pregnancy. On the other hand, perinatal salt overload is associated with higher blood pressure and higher renal angiotensin II content in adult offspring. Therefore, we hypothesised that renin–angiotensin system (RAS) function is altered by changes in sodium intake during pregnancy. Such changes may influence fetoplacental blood flow and thereby fetal nutrient supply, with effects on growth in utero and, consequently, on birth weight. Female Wistar rats were fed low-salt (LS), normal-salt (NS), or high-salt (HS) diet, starting before conception and continuing until day 19 of pregnancy. Blood pressure, heart rate, fetuses and dams' body weight, placentae weight and litter size were measured on day 19 of pregnancy. Cardiac output, uterine and placental blood flow were also determined on day 19. Expressions of renin–angiotensin system components and of the TNF-alpha gene were evaluated in the placentae. Plasma renin activity (PRA) and plasma and tissue angiotensin-converting enzyme (ACE) activity, as well as plasma and placental levels of angiotensins I, II, and 1–7 were measured. Body weight and kidney mass were greater in HS than in NS and LS dams. Food intake did not differ among the maternal groups. Placental weight was lower in LS dams than in NS and HS dams. Fetal weight was lower in the LS group than in the NS and HS groups. The PRA was greater in LS dams than in NS and HS dams, although ACE activity (serum, cardiac, renal, and placental) was unaffected by the level of sodium intake. Placental levels of angiotensins I and II were lower in the HS group than in the NS and LS groups. Placental angiotensin receptor type 1 (AT1) gene expression and levels of thiobarbituric acid reactive substances (TBARS) were higher in HS dams, as were uterine blood flow and cardiac output. The degree of salt intake did not influence plasma sodium, potassium or creatinine. Although fractional sodium excretion was higher in HS dams than in NS and LS dams, fractional potassium excretion was unchanged. In conclusion, findings from this study indicate that the reduction in fetal weight in response to salt restriction during pregnancy does not involve alterations in uterine-placental perfusion or the RAS. Moreover, no change in fetal weight is observed in response to salt overload during pregnancy. However, salt overload did lead to an increase in placental weight and uterine blood flow associated with alterations in maternal plasma and placental RAS. Therefore, these findings indicate that changes in salt intake during pregnancy lead to alterations in uterine-placental perfusion and fetal growth.

Recently we showed that acute Vitamin C (Vit C) administration (intravenous or directly into the RVLM) caused a significant decrease in mean arterial pressure (MAP) and renal sympathetic nerve activity (RSNA) in 2K‐1C, but not in control rats. Moreover, we found that mRNA expression of NAD(P)H oxidase subunits (p47phox and gp91phox) was greater in 2K‐1C compared to the control group in the RVLM and CuZnSOD expression was similar in both groups. However, the chronic effects of Vitamin C (Vit C) in these parameters are unknown. Therefore, here we treated rats with Vit C (150 mg/kg/day) by gavage for 7 days and MAP, RSNA and mRNA expression of NAD(P)H oxidase subunits (p47phox and gp91phox) and CuZnSOD in the RVLM in the 2K‐1C rats was analyzed. The mRNA expression was analyzed by real‐time PCR. The Vit C resulted in a higher fall in MAP in 2K‐1C than in control group (2K‐1C, 22 ± 7%/C, 11 ± 3%) followed of a significant increase in RSNA (41± 2%) only in control group. The NAD(P)H oxidase subunits expression reduced significantly in both groups treated with Vit C in RVLM. In contrast, CuZnSOD expression was unchanged in all groups. The results support the idea that an increase in oxidative stress within the RVLM probably plays a major role in maintaining hypertension and sympathetic drive in 2K‐1C.Supported by FAPESP.

Sucrose feeding (SF) induces oxidative stress, metabolic abnormalities and high blood pressure (HBP). The aim of this study was to investigate if dietary supplementation with vitamin C ameliorates HBP, hyperinsulinaemia and the mRNA renal expression levels of AT1, NAD(P)H oxidase subunits (p47phox and gp91phox), CuZnSOD induced by SF. Wistar rats (150–180g) were treated, for 30 days, with 20% sucrose solution (SC, n=15) instead of drinking water (CC, n=24). Ascorbic acid (AA, 150 mg/kg) was given by gavage to sucrose‐fed (SAA; n=17) or control rats (CAA; n=25) for the last 7 days of SF. Mean arterial pressure (MAP) was recorded on a Power Lab System. The mRNA expression levels were analyzed in the cortical renal tissue by Real Time RT‐ PCR. An increase (P<0.05) in MAP was observed in SC compared to CC (136±3; 111±4 mmHg). AA supplementation decreases (P<0.05) MAP either in CAA or SAA (102±3; 105±1 mmHg) rats. Basal glucose levels were unchanged but plasma insulin increased (P<0.05) after SF; no alterations were observed after AA. SF increased (P<0.05) p47phox and gp91phox expression but did not change CuZnSOD or AT1 mRNA expression. However, AA reversed the increase of mRNA expression of NAD(P)H oxidase subunits and it reduced (P<0.05) AT1 expression. CuZnSOD expression was unchanged after AA administration. These findings suggest AA ameliorates HBP probably by decreasing oxidative stress induced by SF. Supported by FAPESP (06/58219‐4).

The present study was designed to evaluate, in Wistar rats, the effect of high- or low-salt diet on the hemodynamic parameters and on the renal and lumbar sympathetic nerve activity. The renal gene expression of the renin angiotensin system components was also evaluated, aiming to find some correlation between salt intake, sodium homeostasis and blood pressure increase. Male Wistar rats received low (0.06% Na, TD 92141-Harlan Teklad), a normal (0.5% Na, TD 92140), or a high-salt diet (3.12% Na, TD 92142) from weaning to adulthood. Hemodynamic parameters such as cardiac output and total peripheral resistance, and the renal and lumbar sympathetic nerve activity were determined (n=45). Plasma renin activity, plasma and renal content of angiotensin (ANG) I and II, and the renal mRNA expression of angiotensinogen, renin, AT1 and AT2 receptors were also measured (n=24). Compared to normal- and low-salt diet-, high-salt-treated rats were hypertensive and developed an increase (P<0.05) in total peripheral resistance and lumbar sympathetic nerve activity. A decrease in renal renin and angiotensinogen-mRNAs and in plasma ANG II and plasma renin activity was also found in salt overloaded animals. The renal sympathetic nerve activity was higher (P<0.05) in low- compared to high-salt-treated rats, and was associated with an increase (P<0.05) in renal ANG I and II and with a decrease (P<0.05) in AT2 renal mRNA. Plasma ANG I and II and plasma renin activity were higher in low- than in normal-salt rats. Our results show that increased blood pressure is associated with increases in lumbar sympathetic nerve activity and total peripheral resistance in high-salt-treated rats. However, in low-salt-treated rats an increase in the renal sympathetic nerve was correlated with an increase in the renal content of ANG I and II and with a decrease in AT2 renal mRNA. These changes are probably in favor of the antinatriuretic response and the sodium homeostasis in the low-salt group.

There is a relationship between sucrose feeding and arterial hypertension. Dysregulation of sodium and/or water reabsorption by the kidney may contribute to hypertension. The objective of this study was to investigate, in rats with overload of sucrose in diet, the effect on creatinine clearance (CCl), fractional excretion of Na+ (FENa), fractional excretion of K+ (FEK) and alterations in the mRNA expression levels of the kidney. Wistar rats (150–180g) were treated for 30 days with sucrose solution (20%) instead of drink water (SC; n=7), the control group (C; n=8) had tap water ad libitum. Mean arterial pressure (MAP), were recorded “on line” in a Power Lab system. The mRNA expression levels of epithelial sodium channel (ENaC) and water channel protein (AQP2) were analyzed in the cortical kidney tissue by Real Time RT-PCR technique. A significant (P<0.05) increase in MAP was observed in SC (128±1mmHg) compared with C (102±4 mmHg). The following values for renal function parameters were obtained for the sucrose and control groups: urinary sodium 77.6 ± 11.4 vs 144.7 ± 9.4 mEq/L (P<0.05); CCl 1.57 ± 0.22 vs 0.93 ± 0.07 ml/min−1 (P < 0.05); FENa 0.7 ± 0.10 vs 0.98 ± 0,07% (P < 0.05); FEK 36.4 ± 7.8 vs 31.4 ± 3.1%. The sucrose group showed significant increase in ENaC expression and AQP2 expression when compared with control group (SC: 1.95 vs. C: 1.03 and SC: 2.12 vs C: 1.07 respectively, P<0.05). Taken altogether, the results suggest that a decreased of FENa and an increased of mRNA expression level of ENaC and AQP2 may lead to arterial hypertension due to an augment of Na+and water reabsorption. Supported by FAPESP, CNPq-PRONEX.

There is a relationship between sucrose feeding and arterial hypertension. The objective of this study was to investigate, in rats with overload of sucrose in diet, the effect on cardiac output (CO) and total peripheral resistance (TPR). The effects of sucrose on sympathetic nervous system (SS) and renin-angiotensin system (RAS) were also evaluated. Wistar rats (150–220g) were treated for 30 days with sucrose solution (20%) instead of drink water (SC; n=10), the control group (C; n=9) had tap water ad libitum. Mean arterial pressure (MAP), CO and TPR were “on line” recorded in a Cardiomax system. The effects of sympathetic and angiotensinergic system blockade on hemodynamics parameters were evaluated by hexamethonium and captopril administration, respectively. Circulating levels of angiotensin I and II were determined by HPLC. An increase in MAP was observed in SC (128±1mmHg) compared with C (102±4 mmHg) meditated by a TPR increase (SC 1,39±0,03 and, C 0,93±0,11 mmHg/mL/min). The sympathetic blockade caused a larger fall in MAP in C (from 102±4 to 51±0,5 mmHg) than in SC (from 128±1 to 75±1 mmHg). However, the depressor response to captopril was larger in SC (from 97±2 to 58±2 mmHg) than in C (from 80±2 to 68±2 mmHg). There was a reduction in circulating AngioI levels in SC (80±10 ng/mL) in relation to C (193±27 ng/mL). However, AngioII was higher in SC (421±41 ng/mL) compared with C (302±10 ng/mL). Taken altogether, the results show that an overload of sucrose in the diet caused increase in MAP due to TPR. The hypertension was related to an increase in circulating AngioII. Supported by FAPESP; CNPq (PRONEX).

Objective: To get some additional insight on the mechanisms of the effect of salt intake on body weight.Design and methods: Rats were fed a tow (LSD), normal (NSD), or high (HSD) salt diet. In a first set, body weight, tail-cuff blood pressure, fasting plasma thyroid-stimulating hormone, triiodothyronine, L-thyroxine, glucose, insulin, and angiotensin II were measured. Angiotensin II content was determined in white and brown adipose tissues. Uncoupling protein 1 expression was measured in brown adipose tissue. In a second set, body weight, food intake, energy balance, and plasma leptin were determined. In a third set of rats, motor activity and body weight were evaluated.Results: Blood pressure increased on HSD. Body weight was similar among groups at weaning, but during adulthood it was tower on HSD and higher on LSD. Food intake, L-thyroxine concentration, uncoupling protein 1 expression and energy expenditure were higher in HSD rats, white non-fasting leptin concentration was lower in these groups compared to NSD and LSD animals. Plasma thyroid-stimulating hormone decreased on both HSD and LSD white plasma glucose and insulin were elevated only on LSD. A decrease in plasma angiotensin II was observed in HSD rats. On LSD, an increase in brown adipose tissue angiotensin II content was associated to decreased uncoupling protein 1 expression and energy expenditure. In this group, a low angiotensin II content in white adipose tissue was also found. Motor activity was not influenced by the dietary salt content.Conclusions: Chronic alteration in salt intake is associated with changes in body weight, food intake, hormonal profile, and energy expenditure and tissue angiotensin II content. (C) 2005 Elsevier B.V. All rights reserved.

In the present study, newborn male Wistar rats were injected, subcutaneously, five times, every other day, with monosodium glutamate (MSG, 4 g/kg bw) or saline (as control, C), during the neonatal period. MSG animals developed destruction of the arcuate nuclei (ARC) with absence of NPY-immunoreactive cell bodies, which impaired both the food intake (baseline) and the 2-deoxy-D-glucose (2DG) glucoprivic feeding response. Increases in the immunoreactivity of corticotropin-releasing hormone-cell bodies in the paraventricular nuclei might have developed to compensate for the atrophy of the pituitary in MSG-treated rats. After systemic 2DG injection, neither the C nor the MSG rats increased their food intake, but they showed similar hyperglycemic responses, whereas plasma free fatty acids (FFA) increased only in the C group. In other groups, 2DG, norepinephrine (NE), neostigmine (NEO) and saline were intracerebroventricularly (i.c.v.) administered. In this condition, impairment of the hyperglycemic and food intake responses, associated to a lower increase in plasma FFA levels, were observed. As opposed to this, the MSG treatment gives support to NE effects, enhancing food intake, as well as plasma glucose and FFA levels. After NEO, plasma glucose increased only in the MSG group, while plasma FFA levels were elevated in the C rats. Taken together, the results obtained after MSG treatment point to a separate neural control of the hyperglycemic response and of the lipid mobilization when stimulated by central 2DG, NE or NEO administration. It seems likely that the excitatory neural pathway that controls lipid metabolism and is present in C rats was destroyed by the MSG treatment.

Dietary salt restriction is associated with evidence of low insulin sensitivity. The current study was undertaken to investigate whether sympathetic nervous system and l-arginine-nitric oxide pathway activities are linked to insulin resistance in rats under chronic low salt intake. Male Wistar rats were fed a low (LSD) or normal (NSD) salt diet from weaning to adulthood. A euglycemic hyperinsulinemic clamp was performed in 4 sub-groups on each diet: (1) sympathetic nervous system blockade (propranolol and prazosin), (2) vehicle, (3) L-arginine, and (4) D-arginine. Blood pressure, heart rate and metabolic measurements were done before and 45 min after drug infusion and at the end of the clamp. At baseline conditions, body weight, hematocrit, blood glucose, plasma insulin, cholesterol, and triacylglycerols were higher in LSD than in NSD rats. Systolic blood pressure was lower and heart rate was higher in rats on LSD than on NSD. Glucose uptake was lower on LSD compared to NSD. Sympathetic nervous system blockade and L-arginine did, and vehicle and D-arginine did not improve glucose uptake in LSD rats. On NSD there was no effect of any of the infused drugs. A positive correlation between plasma nitrate and nitrite at the end of clamp and glucose uptake was observed in L-arginine--but not in D-arginine-infused LSD rats. These results provide evidence that the sympathetic nervous system and the L-arginine-nitric oxide pathway are involved in the glucose uptake impairment induced by chronic dietary salt restriction.