Effect of a neonatal low-protein diet on the morphology of myotubes in culture and the expression of key proteins that regulate myogenesis in young and adult rats

Aim  

To investigate the effects of a neonatal low-protein diet on the morphology of myotubes in culture and the expression of key proteins that regulate myogenesis in young and adult rats.     

Plasma proteins in growing analbuminaemic rats fed on a diet of low-protein content

1. Analbuminaemic and Sprague-Dawley (control) rats were fed on low- (60 g/kg) protein and control (200 g protein/kg) diets ad lib. from weaning. Males and females were studied separately. Body-weight and plasma protein concentrations were determined at 10 d intervals from 25 to 75 d of age. Electrophoresis of plasma proteins was performed in samples from day 75. Extracellular fluid volume was measured at 10 d intervals from day 45 onwards. Colloid osmotic pressure was measured in plasma and interstitial fluid (wick technique) at the start and end of the trial. 2. Body-weight increased much less on the low-protein diet than on the normal diet in both strains and sexes. The growth retardation was slightly more pronounced in the male analbuminaemic rats than in the male Sprague-Dawley controls. 3. Plasma protein concentration increased during normal growth in all groups, particularly in the female analbuminaemic rats. This increase was reduced by the 60 g protein/kg diet in all groups, with the exception of the male analbuminaemic rats. 4. Differences in plasma colloid osmotic pressure were similar to those seen in plasma protein concentration. Interstitial colloid osmotic pressure was higher in the control rats than in the analbuminaemic ones. The interstitial colloid osmotic pressure increased during growth in the control but not in the analbuminaemic rats. The difference in interstitial colloid osmotic pressure between the strains was maintained during low-protein intake, but at a lower level than during normal protein intake. 5. Subtracting interstitial from plasma colloid osmotic pressure, resulted in a rather similar transcapillary oncotic gradient in the various groups at 75 d, both on the control protein diet (11-14 mmHg), and on the low-protein diet (9-11 mmHg). 6. All protein fractions were reduced to a similar extent by the low-protein diet in the control rats, whereas in the analbuminaemic rats protein fractions produced in the liver were more severely depressed. 7. Extracellular fluid volume as a percentage of body-weight was similar in all groups, and decreased with increasing age. 8. In conclusion, the analbuminaemic rats were able to maintain the transcapillary oncotic gradient on both diets by reducing the interstitial colloid osmotic pressure. Oedema was not observed. 9. Despite the absence of albumin, the protein-malnourished analbuminaemic rat is no more susceptible to hypoproteinaemia and oedema than its normal counterpart.     

Effects of low-protein diet on the baroreflex and Bezold-Jarisch reflex in conscious rats

The present study evaluated the effects of a low-protein diet (LP, 6% protein) on cardiovascular reflexes of Male Fisher rats. Three experimental groups, and their respective controls (15% protein), were used: (1) Baroreceptor reflex (BAR); (2) Bezold-Jarisch reflex (BJR); and (3) Prazosin treated. Dietary restriction began after weaning (three weeks) and lasted for a period of five weeks, after which animals were subjected to the experimental protocols. The BAR group was evaluated through injections of phenylephrine (0.5-5.0 microgram/Kg, i.v.) and sodium nitroprusside (0.7-7.0 microgram/Kg, i.v.) while the BJR was evaluated through injections of serotonin (2.5-10 microgram/Kg, i.v.). Our results showed an increased baroreflex gain bradycardia for the LP group (-0.96+/-0.34 vs. -2.12+/-1.06 bpm/mmHg) and a larger bradycardia for the BJR the LP group (160+/-18% greater than controls). Basal cardiovascular parameters were not different between LP and control rats, however LP animals treated with prazosin resulted in a larger fall of blood pressure (-19+/-3 vs. -28+/-5 mmHg). In conclusion, LP rats present an increased responsiveness of BAR and BJR, which could contribute to their normal levels of cardiovascular parameters, in spite of the possible increase in the sympathetic vasomotor tonus observed with the prazosin protocol.     

Short- and long-term effects of calcium and exercise on bone mineral density in ovariectomized rats

At the level of prevention of bone mineral loss produced by ovariectomy, the aim of the present study was to determine the effect produced by supplementation of Ca in the diet and a moderate exercise programme (treadmill), simultaneously or separately, in ovariectomized rats, an experimental model of postmenopausal bone loss. Female Wistar rats (n 110, 15 weeks old) were divided into five groups: (1) OVX, rats ovariectomized at 15 weeks of age, fed a standard diet; (2) SHAM, rats sham operated at 15 weeks of age, fed a standard diet; (3) OVX-EX, ovariectomized rats, fed a standard diet and performing the established exercise programme; (4) OVX-Ca, ovariectomized rats fed a diet supplemented with Ca; (5) OVX-EXCa, ovariectomized rats with the exercise programme and diet supplemented with Ca. The different treatments were initiated 1 week after ovariectomy and were continued for 13 weeks for subgroup 1 and 28 weeks for subgroup 2, to look at the interaction of age and time passed from ovariectomy on the treatments. Bone mineral density (BMD) was determined, at the end of the study, in the lumbar spine (L2, L3 and L4) and in the left femur using a densitometer. Bone turnover was also estimated at the end of the study, measuring the serum formation marker total alkaline phosphatase (AP) and the resorption marker serum tartrate-resistant acid phosphatase (TRAP). As expected, OVX rats showed a significant decrease (P<0.05) in BMD, more pronounced in subgroup 2, and a significant increase in AP and TRAP with regard to their respective SHAM group. The simultaneous treatment with Ca and exercise produced the best effects on lumbar and femoral BMD of ovariectomized rats, partially avoiding bone loss produced by ovariectomy, although it was not able to fully maintain BMD levels of intact animals. This combined treatment produced a significant increase in AP, both in subgroups 1 and 2, and a decrease in TRAP in subgroup 1, with regard to OVX group. The exercise treatment alone was able to produce an increase in BMD with regard to OVX group only in subgroup 1 of rats (younger animals and less time from ovariectomy), but not in subgroup 2. In agreement with this, there was an increase of AP in both subgroups, lower than that observed in animals submitted to exercise plus Ca supplement, and a decrease of TRAP in subgroup 1, without significant changes in this marker in the older rats. Ca treatment did not produce any significant effect on BMD in OVX rats in both subgroups of animals, showing a decrease of AP and TRAP levels in the younger animals with no significant variations in markers of bone remodelling in the older female rats compared with their respective OVX group.     

Short- and long-term effects of acetaldehyde on plasma.

The effect of low concentrations of acetaldehyde on activated partial thromboplastin time (APTT) and prothrombin time (PT) of Accuclot coagulation plasmas was monitored over a prolonged time to mimic effects observed in alcoholism. A prolongation of the APTT from 31.9 +/- 0.7 s to 32.6 +/- 0.9 s (n = 8; P =.007) was observed after a 30-min preincubation time with 140 microM acetaldehyde. However, a minimum of 3.6 mM acetaldehyde was required to extend the APTT from 36.6 +/- 1.0 s to 41.2 +/- 0.8 s (P =.001) over an 18-h exposure time. Plasma acetaldehyde levels as low as 2.24 mM caused elevation of PTs from 12.5 +/- 0.5 s to 14.4 +/- 0.2 s (P =.005) after a 24-h preincubation time. These findings seem to indicate that short-term contact of acetaldehyde with plasma, probably yielding reversible interactions, may interfere with APTTs to a greater extent than long-term contact, which would presumably yield stable, irreversible interactions. In comparing the effects of 8.94, 17.9, 89.4, and 447 mM acetaldehyde on the PTs of Level I, II, and III plasma, the PTs were most increasingly prolonged in Level III plasma and least prolonged in Level I plasma at each acetaldehyde concentration, although the plasmas have comparable protein concentrations. These findings seem to indicate that coagulation factors are sensitive to inactivation by acetaldehyde.     

Fetal exposure to a maternal low-protein diet during mid-gestation results in muscle-specific effects on fibre type composition in young rats

This study assessed the impact of reduced dietary protein during specific periods of fetal life upon muscle fibre development in young rats. Pregnant rats were fed a control or low-protein (LP) diet at early (days 0-7 gestation, LPEarly), mid (days 8-14, LPMid), late (days 15-22, LPLate) or throughout gestation (days 0-22, LPAll). The muscle fibre number and composition in soleus and gastrocnemius muscles of the offspring were studied at 4 weeks of age. In the soleus muscle, both the total number and density of fast fibres were reduced in LPMid females (P = 0.004 for both, Diet x Sex x Fibre type interactions), while both the total number and density of glycolytic (non-oxidative) fibres were reduced in LPEarly, LPMid and LPLate (but not LPAll) offspring compared with controls (P < 0.001 for both, Diet x Fibre type interaction). In the gastrocnemius muscle, only the density of oxidative fibres was reduced in LPMid compared with control offspring (P = 0.019, Diet x Fibre type interaction), with the density of slow fibres being increased in LPAll males compared with control (P = 0.024, Diet x Sex x Fibre type interaction). There were little or no effects of maternal diet on fibre type diameters in the two muscles. In conclusion, a maternal low-protein diet mainly during mid-pregnancy reduced muscle fibre number and density in 4-week-old rats, but there were muscle-specific differences in the fibre types affected.     

Moderate physical training attenuates muscle-specific effects on fibre type composition in adult rats submitted to a perinatal maternal low-protein diet

Aim

To verify whether moderate physical training affects the muscle fibre composition of adult rats subjected to a low protein diet during the perinatal period.

Methods

Male Wistar rats were divided into two groups according to their mother’s diet during gestation and lactation: control (17% casein, C) and low-protein (8% casein, LP). On postnatal day 60, half of each group was submitted to moderate physical training (8?weeks, 5?days/week^?1, 60?min/day^?1, at 70% of VO_2max, T) or not. After the physical training period, soleus and extensor digitorum longus (EDL) muscles were removed. Myofibrillar ATPase staining was used to classify muscle fibres as type I, IIa, IIb, and intermediate.

Results

In the EDL muscle, LP rats showed no changes in the fibre type proportion. Both the C?+?T and LP?+?T groups showed a higher percentage of fibres of type IIa, and a lower proportion of fibres of type IIb. In the soleus muscle, LP animals showed a reduction in the proportion of fibre types I and intermediate. C?+?T rats showed an increase in the fibre type I and IIa. In the LP?+?T rats, the proportions of the fibre types remained similar to control rats.

Conclusions

Moderate physical training acts as a positive environmental stimulus that reverts the effects of a perinatal low-protein diet on the proportion of fibre types in skeletal muscle.     

Protein utilization in rats receiving a low-protein diet with various limiting amino acids

1. A study was made of protein utilization in rats given a variety of low-protein diets containing (g/kg) egg albumin 18, casein 49, gluten 50, or mixtures of either maize protein and gelatine 58, or casein and gelatin 37, each with supplemental methionine. The diets were limiting in leucine, tryptophan or lysine, or in both tryptophan and the sulphur-containing amino acids. 2. Values obtained for net protein utilization (NPU) at these low levels of nitrogen intake were markedly higher than the amino acid score calculated for the different test proteins, except with casein for which the two values were similar. The NPU values agreed more closely with chemical score values based on the content of S-amino acids or isoleucine in the dietary protein.     

The effects of berberine on hyperhomocysteinemia and hyperlipidemia in rats fed with a long-term high-fat diet

ABSTRACT: BACKGROUND: The study was undertaken to examine the effects of berberine (BBR) on serum homocysteine, lipids and the aortic lesion in Sprague-Dawley (SD) rats fed with a long-term high-fat diet (HFD). METHODS: Healthy male SD rats weighing 190-210 g received randomly standard diet or a high-fat diet for 24 weeks. After 8 weeks of feeding, rats fed with HFD were randomized to receive berberine (200 mg * kg-1 * day-1) or vehicle by gavage for 16 weeks. After overnight fasting, all rats were sacrificed and total blood samples were also collected for determinant of fasting serum homocysteine (Hcy), total cholesterol (TC) and low density lipoprotein cholesterol (LDL-c) levels. The aorta was stained with hematoxylin and eosin (HE) and Sudan Sha to evaluate aortic lesion. The livers were dissected out and snap-frozen in liquid nitrogen for hepatic TC content and molecular analysis. 3-hydroxy-3-methyl-glutaryl-CoA reductase (HMGR), Lipoprotein receptors and apolipoproteins gene expression in the liver were determined by real-time PCR. RESULTS: Intragastrical administration with berberine for 16 weeks lowered serum Hcy in rats fed with a high-fat diet. In parallel, it also decreased body weight and improved serum TC and LDL-c. Berberine also tended to decrease hepatic cholesterol. Consistently, berberine also upregulated LDL receptor (LDLR) mRNA level and suppressed HMGR gene expression. Meanwhile, upon berberine-treated rats, there was a significant increase in apolipoprotein E (apoE) mRNA, but no change in apoAI and scavenger receptor (SR) mRNA in the liver. Further, no atherosclerotic lesions were developed in berberine-treated rats for 16 weeks. CONCLUSION: Berberine can counteract HFD-elicited hyperhomocysteinemia and hyperlipidemia partially via upregulating LDLR and apoE mRNA levels and suppressing HMGR gene expression.     

Short- and long-term effects of changes in pleasantness on food intake

This study concerns the effects of pleasantness on ad libitum food intake, liking and appetite over 5 successive days. Pleasantness was manipulated by varying the salt level in bread. Thirty-five students consumed ad libitum sandwiches for lunch, made with bread individually perceived as low, medium or high in pleasantness, in a balanced cross-over design. Pleasantness and desire-to-eat the sandwich were rated at first bite, after the consumption of each sandwich and at the end of the lunch. Fullness was rated just before and at several intervals after lunch. On the first day, the students ate less of the least pleasant bread than of the medium and most pleasant bread. On the fifth day, however, consumption of all breads was similar. For the least pleasant bread, energy intake at lunch, desire-to-eat and fullness, all increased over days, whereas these variables remained constant for the medium and most pleasant bread. Mean pleasantness ratings for all breads remained unaltered across the days. We conclude that, with repeated exposure, the desire-to-eat, fullness and intake of a less preferred food can increase over time. Thus, the relationship between pleasantness and food intake changes over this period.     

Short- and long-term effects of bacterial gastrointestinal infections

During 1997-2004, microbiologically confirmed gastrointestinal infections were reported for 101,855 patients in Sweden. Among patients who had Salmonella infection (n = 34,664), we found an increased risk for aortic aneurysm (standardized incidence ratio [SIR] 6.4, 95% confidence interval [CI] 3.1-11.8) within 3 months after infection and an elevated risk for ulcerative colitis (SIR 3.2, 95% CI 2.2-4.6) within 1 year after infection. We also found this elevated risk for ulcerative colitis among Campylobacter infections (n = 57,425; SIR 2.8, 95% CI 2.0-3.8). Within 1 year, we found an increased risk for reactive arthritis among patients with Yersinia enteritis (n = 5,133; SIR 47.0, 95% CI 21.5-89.2), Salmonella infection (SIR 18.2, 95% CI 12.0-26.5), and Campylobacter infection (SIR 6.3, 95% CI 3.5-10.4). Acute gastroenteritis is sometimes associated with disease manifestations from several organ systems that may require hospitalization of patients.     

Effect of a low-protein diet during pregnancy on skeletal muscle mechanical properties of offspring rats

OBJECTIVE: The main goal of the present study was to investigate the effects of a low-protein diet during gestation on the biomechanical properties of skeletal muscle of offspring rats. METHODS: Male Wistar rats were divided into two groups according to their mothers' diet during pregnancy: a control group (mothers fed with 17% protein) and a low-protein group (mothers fed with 7.8% protein; UN). At birth, all mothers received a standardized meal ad libitum. When the rats were 25 and 90 d old, the soleus and extensor digitorum longus (EDL) muscles were removed from the pups. An analysis of the contractile and series elastic component properties was carried out on both muscles. Histochemical analysis was likewise performed. RESULTS: Group UN presented muscle wasting and diminution of maximum twitch and tetanic tension on the muscle at 25 and 90 d of life. There was an increase in maximal shortening velocity in the soleus and EDL muscles at 25 and 90 d in group UN. Series elastic component stiffness was increased in the soleus muscle, although a diminution of series elastic component stiffness was observed in the EDL at 25 d. With regard to the analysis of the muscle fiber proportions at 25 and 90 d, the UN group presented an increase in the IIa fibers in the soleus, whereas there was an increase in the IIb fibers and a diminution in the IIa fibers in the EDL. CONCLUSION: Low-protein intake during a critical period of development induces changes in the structure and function of skeletal muscle. Such changes may compromise an animal's posture and locomotion.     

Energy balance in predialysis patients on a low-protein diet.

OBJECTIVE: To determine if energy intake on a low-protein diet (0.6 g protein/kg ideal body weight (ibw)/d) with 70% animal protein (Diet A) or 30% animal protein (Diet B) meets energy expenditure derived from measured resting energy expenditure and activity levels. DESIGN: Patients already on a conventional low-protein diet with 70% animal protein kept a 5-day weighed dietary intake, with a 3-day activity diary, and had their resting metabolic rate (RMR) measured. Patients then switched to a diet with 30% animal protein for a minimum of 2 weeks (range, 2 to 16 weeks) and repeated the weighed intake and RMR measurement. SETTING: Predialysis hospital outpatients. PATIENTS: Seven patients were recruited, 5 male. Mean age, 56 years (range, 43 to 78 years); mean serum creatinine 300 micromol/L (range, 180 to 560 micromol/L). INTERVENTION: Indirect calorimetry used to measure RMR. MAIN OUTCOME MEASURE: RMR compared with standard formulae and total energy expenditure compared with dietary intake. RESULTS: Mean RMR was 5.76 MJ/d (1,385 kcal/d) or 84.9 kJ/kg ibw/d (20.3 kcal/kg ibw/d); which was 108% to 113% of that predicted by standard formulae. Total energy expenditure (RMR plus activity) was 8.35 MJ/d (1,996 kcal/d) or 123.3 kJ/kg/d (29.5 kcal/kg ibw/d). Mean energy intake was 116.3 (27.8 kcal/kg ibw/d) on Diet A and 131.2 (31.4 kcal/kg ibw/d) on Diet B (P = .096) with 3 of the 7 patients meeting their energy expenditure on Diet A and 4 on Diet B. CONCLUSION: RMR of patients with chronic renal failure is within expected range for healthy individuals, and the activity of these relatively fit patients similar to healthy individuals with light to moderate activity. Energy intake on the low-protein diets failed to meet energy expenditure in 4 patients on Diet A and 3 patients on Diet B. Low energy intake may contribute to the development of malnutrition in some patients.     

Beneficial effects of a low-protein diet on host resistance to Paracoccidioides brasiliensis in mice

ObjectiveAlthough protein malnutrition impairs immune functions, several studies have recently shown that protein restriction without malnutrition is beneficial to host defenses against invading pathogens and cancer. In an effort to establish the optimum diet for host resistance, we investigated the effect of different dietary protein levels on host resistance to Paracoccidioides brasiliensis.MethodsMice were fasted for 2 days and then infected with P. brasiliensis. Immediately after challenge with this fungus, mice were refed on diets with three different levels (0%, 1.5%, or 20%) of casein. On days 0–7 after infection, antifungal activity and levels of proinflammatory mediators in the spleen and liver were measured.ResultsMice refed on the 1.5% casein diet showed higher antifungal activity in the spleen and liver compared with mice on the 20% casein diet. The antifungal activity in the spleens of mice refed on the 0% casein diet was intermediate between the antifungal activities of those refed the 1.5% and 20% casein diets. After infection, increases in spleen and liver levels of interleukin-6 and interferon-γ, liver mRNA levels of antimicrobial proteins (myeloperoxidase, cathepsin-G, and elastase-2), and liver mRNA levels of proinflammatory mediators (interleukin-18, chemokine C-X-C motif ligand 10, nuclear factor-κB, inducible nitric oxide synthase, and granulocyte–macrophage colony-stimulating factor) were less profound in mice on the 1.5% or 0% casein diet compared with mice refed the 20% casein diet.ConclusionThe present results suggest that protein restriction without malnutrition could be beneficial to host resistance to P. brasiliensis.     

L-threonine supplementation increases the amplitude of the feed intake cycle of rats fed a low-protein zinc-deficient diet

Rats fed a Zn-deficient diet show characteristic variations in feed intake. These variations were followed by means of a personal computer. The specific feed intake patterns in rats fed a zinc-deficient diet before and after supplementation with protein and several essential amino acids were determined. The high-protein diet decreased the amplitude of feed intake under zinc deficiency, probably because of a decrease in sensitivity to the deficiency. Furthermore, the zinc-deficient diet was supplemented with essential amino acids, and of them L-threonine showed the most marked effect on the increased variability of feed intake.