Nutritional recovery with a soybean flour diet improves the insulin response to a glucose load without modifying glucose homeostasis

OBJECTIVE: We investigated the effect of nutritional recovery with a soybean flour diet on glucose tolerance, insulin response to a glucose load, and the action of insulin in adult rats exposed to a protein deficiency during intrauterine life and lactation. METHODS: Male Wistar rats from dams fed a normal- or low-protein diet during pregnancy and lactation were maintained after weaning by feeding them normal-protein isoenergetic diets containing soybean flour or casein and low-protein casein diet. RESULTS: Rats fed a soybean flour diet had a lower final body weight, epididymal fat pad, carcass fat content, and liver glycogen level. The serum glucose concentrations in the basal and fed states and the area under the glucose curves during the glucose tolerance test were not significantly different among the four groups. Their serum insulin levels during fasting were observed to be similar to those fed a casein diet. These rats also had a higher serum insulin levels in a fed state and total area under the insulin curves in response to a glucose load, but a lower ratio of area under the glucose/insulin curves during the glucose tolerance test than those fed a casein diet. CONCLUSION: These results indicate that nutritional recovery with a soybean flour diet improved the insulin response to a glucose load and decreased the sensitivity to insulin, at least in hepatic tissue.     

A soyabean diet does not modify the activity of brown adipose tissue but alters the rate of lipolysis in the retroperitoneal white adipose tissue of male rats recovering from early-life malnutrition

Nutritional recovery with a soyabean diet decreases body and fat weights when compared with a casein diet. We investigated whether the reduced adiposity observed in rats recovering from early-life malnutrition with a soyabean diet results from alterations in lipid metabolism in white adipose tissue (WAT) and/or brown adipose tissue (BAT). Male rats from mothers fed either 17 or 6?% protein during pregnancy and lactation were maintained on 17?% casein (CC and LC groups), 17?% soyabean (CS and LS groups) or 6?% casein (LL group) diets over 60?d. The rats maintained on a soyabean diet had similar relative food intakes, but lower body and retroperitoneal WAT weights and a reduced lipid content in the retroperitoneal WAT. The insulin levels were lower in the recovered rats and were elevated in those fed a soyabean diet. Serum T3 concentration and uncoupling protein 1 content in the BAT were decreased in the recovered rats. The thermogenic capacity of the BAT was not affected by the soyabean diet. The lipogenesis rate in the retroperitoneal WAT was similar in all of the groups except for the LL group, which had exacerbated lipogenesis. The enhancement of the lipolysis rate by isoproterenol was decreased in white adipocytes from the soyabean-recovered rats and was elevated in adipocytes from the soyabean-control rats. Thus, in animals maintained on a soyabean diet, the proportions of fat deposits are determined by the lipolysis rate, which differs depending on the previous nutritional status.     

Short- and long-term effects of a neonatal low-protein diet in rats on the morphology of the larynx

ObjectiveThe aim of this study was to investigate the short- and long-term effects of a maternal low-protein diet during lactation on offspring laryngeal morphology. Our hypothesis was that a neonatal low-protein diet during the critical period of development alters micro- and macroscopic structures of the larynx in adult rats.MethodsMale Wistar rats were assigned to a control (casein 17%, n = 24) or low-protein (casein 8%, n = 24) group according to their mother's diet during lactation. Body weight gain and growth rate were recorded throughout the experiment. The larynx was removed from offspring at days 22 and 60 of life. The anteroposterior and laterolateral lengths of the cartilages epiglottis, thyroid, and cricoid were measured by a digital caliper. The supraglottis, glottis, infraglottis, and vocal cords were stained by hematoxylin–eosin and their structures were analyzed by a Scion Image Beta 4.0.2 program.ResultsPups from mothers fed a low-protein diet showed a lower body weight gain. The laterolateral and anteroposterior lengths of the larynx were shorter in undernourished offspring at 22 d old. There were no differences in the structure of the supraglottis, glottis, and infraglottis between groups except for keratinization in pups from undernourished mothers. The microstructure of the vocal cords was changed only at 60 d old.ConclusionMacroscopic structures of the larynx are sensitive to short-term effects of a neonatal low-protein diet. Vocal cord development can be studied within the context of programming because their microscopic structures are sensitive to the long-term effects of a low-protein diet during lactation.     

Intake of trans fatty acid-rich hydrogenated fat during pregnancy and lactation inhibits the hypophagic effect of central insulin in the adult offspring

OBJECTIVE: Using rats we examined whether maternal intake of hydrogenated fat rich in trans fatty acids affects brain fatty acid profile, hypothalamic content of insulin receptor and insulin receptor substrate-1 proteins, and the hypophagic effect of centrally administered insulin in 3-mo-old male progeny. METHODS: Throughout pregnancy and lactation, Wistar rats ate isocaloric/normolipidic diets with soybean oil (control) or soybean oil-derived hydrogenated fat (trans diet) as a fat source. Upon weaning, the trans offspring continued on the trans diet (trans group) or were switched to a control diet (trans-control group). RESULTS: Compared with control rats, trans rats had lower brain levels of eicosapentaenoic acid. Compared with trans rats, trans-control rats had increased levels of total polyunsaturated fatty acids and arachidonic acid and decreased levels of trans fatty acids, saturated fatty acids, and monounsaturated fatty acids. Insulin receptor and insulin receptor substrate-1 levels were significantly lower (44% and 38%, respectively) in trans than in control rats. In trans-control rats, insulin receptor was 26% lower (P < 0.05), whereas insulin receptor substrate-1 was 50% lower, than in control rats. Insulin decreased 24-h feeding in control (27%) and trans (38%) rats but failed to do so in trans-control rats. The latter group had increased serum glucose levels. CONCLUSIONS: The data suggest that the early (intrauterine/perinatal) exposure to hydrogenated fat rich in trans fatty acids programmed the hypothalamic feeding control mechanisms. As young adults, only trans-control animals showed loss of insulin-induced hypophagia, indicating that the mismatch between early and later nutritional environments was relevant. However, the trans group also showed signs of altered appetite signaling mechanisms, suggesting that the early adaptations may have deleterious consequences later in life.     

Protein-energy malnutrition in pregnant rats improves the adaptation of the endocrine pancreas in malnourished offspring and induces insulin resistance after rehabilitation

1. In developing countries, malnutrition begins during pregnancy and lactation. Glucose intolerance is a problem of importance during protein-energy malnutrition (PEM). We therefore studied glucose homeostasis in rats weaned from undernourished mothers. 2. On weaning, 156 male Wistar rats, born from deprived mothers (75 g casein/kg diet), were fed ad lib on either a balanced diet (180 g casein/kg; group DR), or a protein-deficient diet (50 g casein/kg; group DD). At seven time intervals (weeks 0, 1, 3, 5, 8, 16 and 23) twelve rats were weighed, fasted overnight and then decapitated. Blood glucose, plasma insulin (IRI) and glucagon (IRG) levels and pancreatic insulin and glucagon contents were determined. 3. In DR and DD rats blood glucose, which was normal at weaning, dropped in the 1st week and then increased slowly. DR rats were hyperglycaemic from week 16. IRI continually increased during the experiment from near-normal values to hyperinsulinic levels in DR rats; in group DD, it remained stable until week 8 before increasing. IRG, which was very low at weaning, increased to normal levels in the 1st week in group DR; in group DD, it fell slightly during the study. Pancreatic hormone contents were much higher than after normal pregnancy and lactation. 4. We compared these results with those of a previous study with rats born from normal mothers: at weaning in the second experiment the rats were already well adapted to malnutrition. The plasma ratio IRI:IRG in DD rats showed two phases of adaptation: weeks 0-5 when glucose homeostasis did not change and weeks 5-23 when it became increasingly normal. At the end of the experiment DR rats still had a lower body-weight than normal rats but were insulin-resistant.     

Effect of feeding lysine and threonine fortified bread during gestation and lactation on growth of the offspring in rats.

White bread, bread fortified with lysine, or with lysine and threonine was fed to female rats as the sole source of protein (13% of diet) during two closely spaced gestation and lactation periods. Comparisons were made with diets containing 13% or 26% casein protein, and a stock diet. Weight changes and food consumption of the mothers were determined, as were birth weights and weaning weights of the offspring. Lysine fortification increased food consumption and decreased weight loss of the mothers during lactation. When threonine was added with the lysine, food consumption during lactation was further increased and maternal weight loss prevented. Average weaning weights for first litters as a function of diet were: bread 17.0 +/- 1.9 g, bread + lysine 26.8 +/- 1.0 g, bread + lysine + threonine 39.8 +/- 3.1 g, 13% casein 42.8 +/- 3.8 g, 26% casein 62.5 +/- 4.7 g, and stock diet 41.5 +/- 7.9 g. First and second litter weaning weights were closely similar for each. Although average birth weights were not greatly affected by dietary treatment, total offspring weight at birth of mothers fed unfortified bread was reduced 40% in the second, as compared to the first litter. This reduction in total offspring weight did not occur in mothers fed amino acid fortified bread.     

Interactions between protein and vegetable oils in the maternal diet determine the programming of the insulin axis in the rat

The available evidence suggests that metabolic control mechanisms are programmed early in life. Previous studies of pregnant rats fed low-protein diets have suggested that the vegetable oils used in the experimental diets influence the outcome. The present study investigated the offspring of female rats fed semi-synthetic diets containing either 180 or 90g casein/kg with 70 g/kg (w/w) of either corn oil or soya oil during gestation. During lactation, the dams received stock diet, and the offspring were subsequently weaned onto the stock diet. The offspring of dams fed the low-protein diets were smaller at birth. At 25 weeks of age, the offspring were subjected to an oral glucose tolerance test. In the offspring of dams fed the diet containing soya oil, the area under the insulin curve was affected by the protein content of the maternal diet. There was no effect of protein on the area under the insulin curve in the offspring of dams fed the diet prepared with corn oil. There were no differences in plasma glucose concentrations. The levels of mRNA for acetyl-CoA carboxylase- in the livers of female offspring were affected by the protein and oil content of the maternal diet. The level of carnitine palmitoyl transferase mRNA was affected by the protein content of the maternal diet. The present study suggests that PUFA in the maternal diet can interact with protein metabolism to influence the development of the offspring. This may involve the higher content of alpha-linolenic acid in soya oil compared with corn oil.     

Nutritional recovery with okara diet prevented hypercholesterolemia,hepatic steatosis and glucose intolerance

We assessed the biological value of an okara diet and its effects on the hormonal and metabolic profile of rats submitted to protein restriction during intra-uterine life and lactation and recovered after weaning. Male rats from mothers fed either 17% or 6% protein during pregnancy and lactation were maintained on 17% casein (CC, LC), 17% okara (CO, LO) or 6% casein (LL) diets over 60 d. The nutritional quality of the okara protein was similar to that of casein. The okara diet was effective in the nutritional recovery of rats in growing that were malnourished in early life. Furthermore, the okara diet reversed the hypercholesterolemia and the hepatic steatosis observed in the malnutrition and prevented glucose intolerance in an animal model prone to diabetes mellitus.     

Hydrogenated fat diet intake during pregnancy and lactation modifies the PAI-1 gene expression in white adipose tissue of offspring in adult life

We examine whether feeding pregnant and lactating rats hydrogenated fats rich in trans fatty acids modifies the plasma lipid profiles and the expression of adipokines involved with insulin resistance and cardiovascular disease in their 90-day-old offspring. Pregnant and lactating Wistar rats were fed with either a control diet (C group) or one enriched with hydrogenated vegetable fat (T group). Upon weaning, the male pups were sorted into four groups: CC, mothers were receiving C and pups were kept on C; CT, mothers were receiving C and pups were fed with T; TT, mothers were receiving T and pups were kept on T; TC, mothers were receiving T and pups were fed with C. Pups' food intake and body weight were quantified weekly and the pups were killed at day 90 of life by decapitation. Blood and carcass as well as retroperitoneal, epididymal, and subcutaneous white adipose tissues were collected. Food intake and body weight were lower in TC and TT, and metabolic efficiency was reduced in TT. Offspring of TT and TC rats had increased white adipose tissue PAI-1 gene expression. Insulin receptor was higher in TT than other groups. Ingestion of hydrogenated vegetable fat by the mother during gestation and lactation could promote deleterious consequences, even after the withdrawal of the causal factor.     

孕期补充二十二碳六烯酸对子代大鼠脂肪代谢及解偶联蛋白2基因表达的影响

目的探讨孕期补充二十二碳六烯酸(DHA)对子代脂肪代谢和解偶联蛋白2基因表达的影响。方法将SD雌鼠按体重随机分成A、B、C三组,孕期分别食用基础膳食(A)、补充低剂量DHA膳食(B)、补充高剂量DHA膳食(C)。所产雄性仔鼠均由A组母鼠哺乳,21d断乳,用基础膳食喂饲至出生后的第8w。将A组仔鼠按体重随机分为正常对照组A1、高脂对照组A2,A1组继续食用基础膳食至实验结束,A2、B、C三组给予高脂膳食喂饲7w,结束实验。在第8w、15w时各组随机选取8只仔鼠处死,观察体重、体脂含量、血脂和白色脂肪UCP2mRNA表达丰度变化。结果各组仔鼠出生体重和出生后第8w体重均无差异(P0.05)。第8w时B、C组仔鼠体脂含量、血清甘油三酯水平显著低于对照组(P0.05);第15w时,A2组体重、体脂含量、甘油三酯均显著高于A1组(P0.05),B、C两组体重和血清甘油三酯水平显著低于A2组(P0.05)。第8w时,B、C两组大鼠白色脂肪组织UCP2mRNA水平均高于A组;15w时,UCP2mRNA水平依次为C组高于B组、A1和A2组,A2组最低。结论孕期适量DHA补充可降低子代大鼠摄取高脂肪膳食时的体重、血清甘油三酯,即降低肥胖发生风险,改善脂肪代谢;其中对子代白色脂肪组织UCP2基因表达的上调作用可能是其潜在机制之一。     

Long-term effect of green tea extract during lactation on AMPK expression in rat offspring exposed to fetal malnutrition

ObjectiveThe fetal and neonatal environments are important determinants of disease risk in adult life. The aim of this study was to determine whether maternal green tea extract (GTE) intake during lactation affects the expression and activity of adenosine monophosphate-activated protein kinase (AMPK) in the kidneys of male offspring of protein-restricted dams during gestation.MethodsPregnant Wistar rats were fed control (C) or low-protein diets (LP) during gestation. Following delivery, dams received a control or GTE-containing control diet during lactation as follows: C on control diet (CC), LP on control diet (LPC), LP on 0.12% GTE-containing control diet (LPL), or LP on 0.24% GTE-containing control diet (LPH). Some of the male pups from each dam were sacrificed at week 3, and the remaining male pups were fed a standard diet and sacrificed at week 30. Blood chemistry and expression levels of AMPKα, mammalian target of rapamycin (mTOR), and Akt in the kidneys of the male offspring were examined.ResultsThe level of phosphorylated AMPKα in the LPH group at week 3 was higher than that in the LPC group. At week 30, the protein levels of total and phosphorylated AMPK in the LPL and LPH groups were lower than those in the LPC group. The protein levels of mTOR and Akt at week 30 in the LPL and LPH groups were lower than those in the LPC group.ConclusionGTE intake during lactation modulates AMPK, Akt, and mTOR expression in the kidneys of the adult male offspring of dams fed a protein-restricted diet and may induce long-term alterations in the expressions of these proteins in the kidneys.     

Wheat gluten-based diet retarded ethanol metabolism by altering alcohol dehydrogenase and not carnitine status in adult rats.

The objective of this study was to determine the effect of a lysine-deficient diet on carnitine status in adult rats and subsequently on ethanol metabolism. Adult male rats were fed either the AIN-76 diet (NS), the AIN-76 diet with wheat gluten (WG) replacing casein, the WG diet plus 0.8% L-lysine (LS), or the LS diet plus 0.5% L-carnitine (CS) for 30 days. On the 31st day the rats were given an oral dose of ethanol and blood-ethanol concentrations (BEC) were monitored for the next 8 hours. One week later the rats were given a second dose of ethanol and urine was collected until killed, 3 hours post-ethanol administration (PEA). Besides growth retardation and hypoproteinemia, BEC were significantly elevated in the WG group compared to the other group at hours 3-8 PEA. There were no significant differences in BEC between the LS and CS groups; however, their BEC were significantly higher than that of the NS group. The BEC were inversely related to liver alcohol dehydrogenase (ADH) activities which were significantly lower in WG, LS and CS groups than in the NS group. Plasma, liver and urine carnitine values were significantly higher in the CS group than in the NS, WG and LS groups, wherein the values were similar. It is concluded that the WG diet reduced ADH activity and attenuated ethanol metabolism without significantly altering blood, liver and urinary carnitines in the adult rat.     

Azuki bean polyphenols intake during lactation upregulate AMPK in male rat offspring exposed to fetal malnutrition

ObjectiveFetal malnutrition is an early-life inducer of dyslipidemia and glucose intolerance. The aim of this study was to examine whether maternal azuki bean (Vigna angularis) polyphenol (AP) intake during lactation affects the adenosine monophosphate–activated protein kinase (AMPK) pathway and lipid metabolism in offspring exposed to fetal malnutrition.MethodsPregnant Wistar rats were divided into three groups: a control diet offered during gestation and lactation (CC), a low-protein diet during gestation and a control diet during lactation (LPC); and a low-protein diet during gestation and a 1.0% AP-containing control diet during lactation (LPAP). Male pups were randomly selected for the study; half the pups were sacrificed at 3 wk of age and the other half were fed a standard diet and sacrificed at 23 wk. Hepatic triacylglycerol levels, phosphorylation levels of AMPK and acetyl-coenzyme A carboxylase (ACC), and mRNA levels of sterol regulatory element-binding protein-1c (SREBP-1c) were evaluated.ResultsSignificant decreases in body weights and hepatic triacylglycerol levels were found in the LPAP compared with the LPC group. Plasma adiponectin levels in the LPAP group were higher than those in the LPC group. AMPK phosphorylation was upregulated in the livers and skeletal muscles in young and adult LPAP compared with LPC rats. ACC phosphorylation was upregulated in skeletal muscles of LPAP rats. SREBP-1c mRNA expression was decreased in the livers of LPAP rats.ConclusionOur results suggest that maternal AP intake during lactation upregulates AMPK phosphorylation not only in young but also in adult offspring exposed to fetal malnutrition and may lead to decreased hepatic lipid accumulation by ACC phosphorylation and downregulation of SREBP-1c expression.     

Oxidative injuries induced by maternal low-protein diet in female brainstem

Many studies have shown that a maternal low-protein diet increases the susceptibility of offspring to cardiovascular disease in later-life. Moreover, a lower incidence of cardiovascular disease in females than in males is understood to be largely due to the protective effect of high levels of estrogens throughout a woman's reproductive life. However, to our knowledge, the role of estradiol in moderating the later-life susceptibility of offspring of nutrient-deprived mothers to cardiovascular disease is not fully understood. The present study is aimed at investigating whether oxidative stress in the brainstem caused by a maternal low-protein diet administered during a critical period of fetal/neonatal brain development (i.e during gestation and lactation) is affected by estradiol levels. Female Wistar rat offspring were divided into four groups according to their mothers’ diets and to the serum estradiol levels of the offspring at the time of testing: (1) 22 days of age/control diet: (2) 22 days of age/low-protein diet; (3) 122 days of age/control diet: (4) 122 days of age/low-protein diet. Undernutrition in the context of low serum estradiol compared to undernutrition in a higher estradiol context resulted in increased levels of oxidative stress biomarkers and a reduction in enzymatic and non-enzymatic antioxidant defenses. Total global oxy-score showed oxidative damage in 22-day-old rats whose mothers had received a low-protein diet. In the 122-day-old group, we observed a decrease in oxidative stress biomarkers, increased enzymatic antioxidant activity, and a positive oxy-score when compared to control. We conclude from these results that following a protein deficiency in the maternal diet during early development of the offspring, estrogens present at high levels at reproductive age may confer resistance to the oxidative damage in the brainstem that is very apparent in pre-pubertal rats.     

大豆蛋白对高血胆固醇模型大鼠胆固醇代谢的影响

目的:探讨膳食大豆蛋白对高胆固醇模型大鼠血浆胆固醇及其有关血脂指标的影响,并对其可能的作用机理加以研究。方法: 4周龄断乳雄性Wistar大鼠,经28d诱发高血胆固醇以后,按体重和血浆总胆固醇浓度将动物均衡分为两组,分别喂饲含酪蛋白和大豆蛋白的纯合成高脂饲料56d。结果:经28d诱导高脂模型后,高血胆固醇模型大鼠的TC浓度是阴性对照组的1 51倍。又经56d喂饲含有处理因素的饲料后,同酪蛋白组相比,大豆蛋白组动物TC,TG,apoB含量显著降低,而FT4水平显著高于酪蛋白组(P<0. 05)。膳食大豆蛋白摄入可降低高血胆固醇模型大鼠TC、TG、apoB浓度、使血浆FT4含量增高,但对HDL-C,apoA,FT3,TSH和胰岛素(INS)水平无影响。结论:大豆蛋白可影响血浆胆固醇水平,但其相应的作用机理还需进一步探讨。     

Immunohistochemical detection of changes in growth hormone cells in rat pituitaries in protein deficiency.

1. An immunohistochemical method was used to study the effect of a low-protein diet on growth hormone (GH) cells in the pituitaries of developing rats. The deficient diet (80 g protein/kg) was administered during gestation and lactation, or during the time after weaning until 90 d of age, or during both periods. 2. GH-cell changes were much more striking in males than in females. 3. In males, GH-producing cells were usually reduced in size and number in all treatments. The effect was most intense when protein deprivation occurred throughout gestation and sucking, and continued until 90 d of age, but it was also evident in animals given the low-protein diet only after weaning. Recuperation appeared to be almost complete when offspring of deprived dams were fed on a normal diet after weaning. 4. It is concluded that a low-protein diet reduces the amount of GH in the rat pituitary in a way similar to that with a protein-free diet.     

Soy protein- and casein-based weaning diets differ in effects on food intake and blood glucose regulation in male Wistar rats

The effect of weaning male Wistar rats to AIN-93G diets based on casein (C) and soy protein (S) on blood glucose and food intake (FI) regulation was determined. In experiment 1, male Wistar rats (n = 21 per group) received either C or S AIN-93G diets for 7 weeks. In experiment 2, 3 groups of rats were formed (n = 21 per group). The C followed by the S diet group (CS) was weaned to the C diet for 6 weeks followed by the S diet for another 7 weeks. Diet sequence was the reverse for the S followed by the C diet group (SC). The control group (CC) received the C diet throughout 13 weeks. Body weight and cumulative FI were not affected by diet in either experiment. In experiment 1, in fasted rats, S preloads reduced FI for 1 hour more in the C diet group (P < .05), but response to C preloads was not affected by diet. A cholecystokinin A receptor blocker prevented FI reduction by S in rats fed C but not S diet (P < .05). At week 7, rats fed the S diet had higher plasma insulin (67%) (P < .005), glucose (30%) (P < .05) and homeostatic model assessment of insulin resistance index (75%) (P < .005). In experiment 2, FI at weeks 6 and 12 was, again, suppressed most strongly by S preloads in rats fed the C diet (P < .05). At week 13, S and C preloads increased insulin and the insulin/glucose ratio (P < .05), but no differences were found due to preload or diet composition. In conclusion, differences in the effects of first diet exposure to the AIN-93G diets on blood glucose did not persist through either diet change or time. In contrast, protein composition of the most recent diet, but not time, affected FI regulation in response to protein preloads.