低钙饮食对雄性大鼠松质骨和密质骨影响的比较

目的　比较低钙饮食对大鼠胫骨上段松质骨和胫骨中段密质骨的影响。方法　实验用 3月龄SD雄性大鼠 2 0只 ,随机分为正常年龄对照组 (control)、极低钙组 (VLCD)、低钙组 (LDC)。Control组饲养正常饲料 ,VLCD组饲养 0 0 1%含钙饲料 ,LCD组饲养 0 3%含钙饲料。 3个月后取各组大鼠左侧胫骨近心端和中段 ,行不脱钙骨制片 ,进行骨组织形态计量学测量。结果　松质骨 :与对照组相比 ,VLCD组和LCD组的大鼠骨量减少 ,骨小粱面积百分率 (%Tb .Ar)分别减少 5 7% (P <0 0 1)和4 0 % (P <0 0 5 ) ,骨结构参数变差 ,代表骨形成指标荧光周长百分数 (L .Pm % )、矿化沉积率 (MAR)、骨形成率 (BFR/BV)有增加的趋势。VLCD组骨吸收参数骨小粱周长破骨细胞数量 (N .OC/Tb .Pm)有显著增加 ,呈现骨高转化的改变。密质骨 :与对照组相比 ,VLCD组和LCD组的骨量有减少的趋势 ,骨外膜面代表骨形成的参数增加 ,骨内膜代表骨形成的参数变化不大 ,骨内膜骨吸收增加。结论　低钙饮食使骨量减少 ,但不同的部位有不同的骨丢失速度     

Effect of dietary magnesium supplementation on bone loss in rats fed a high phosphorus diet.

The purpose of this study was to investigate the effect of dietary magnesium (Mg) supplementation on bone loss in rats fed a high phosphorus (P) diet. Weanling Wistar strain rats were randomly divided into four dietary groups of 6 rats each and fed their respective diets; a diet containing 0.3% P and 0.05% Mg (C), a diet containing 1.5% P and 0.05% Mg (HP), a diet containing 0.3% P and 0.15% Mg (HMg), or a diet containing 1.5% P and 0.15% Mg (HPMg), for 21 days. Compared to the C and HMg groups, serum parathyroid hormone (PTH) concentration was significantly higher in the HP and HPMg groups. Serum osteocalcin concentration and urinary excretion of C-terminal telopeptides of type I collagen (CTx), markers of bone turnover, were significantly higher in the HP and HPMg groups than in the C and HMg groups. Dietary Mg supplementation had no significant effects on serum PTH and osteocalcin concentrations, while urinary excretion of CTx was significantly lower in the HPMg group than in the HP group. These results suggested that dietary Mg supplementation suppressed bone resorption due to high P diet.     

Abdominal adiposity, insulin and bone quality in young male rats fed a high-fat diet containing soybean or canola oil

OBJECTIVES:

A low ratio of omega-6/omega-3 polyunsaturated fatty acids is associated with healthy bone properties. However, fatty diets can induce obesity. Our objective was to evaluate intra-abdominal adiposity, insulin, and bone growth in rats fed a high-fat diet containing low ratios of omega-6/omega-3 provided in canola oil.

METHODS:

After weaning, rats were grouped and fed either a control diet (7S), a high-fat diet containing soybean oil (19S) or a high-fat diet of canola oil (19C) until they were 60 days old. Differences were considered to be significant if p<0.05.

RESULTS:

After 60 days, the 19S and 19C groups showed more energy intake, body density growth and intra-abdominal fat mass. However, the 19S group had a higher area (200%) and a lower number (44%) of adipocytes, while the 7S and 19C groups did not differ. The serum concentrations of glucose and insulin and the insulin resistance index were significantly increased in the 19C group (15%, 56%, and 78%, respectively) compared to the 7S group. Bone measurements of the 19S and 19C groups showed a higher femur mass (25%) and a higher lumbar vertebrae mass (11%) and length (5%). Computed tomography analysis revealed more radiodensity in the proximal femoral epiphysis and lumbar vertebrae of 19C group compared to the 7S and 19S groups.

CONCLUSIONS:

Our results suggest that the amount and source of fat used in the diet after weaning increase body growth and fat depots and affect insulin resistance and, consequently, bone health.     

Induced biochemical and physiological changes in young and adult growing rats fed on a vegetable or animal protein diet

The influence of diets containing faba bean or casein as sources of protein were studied in rats at two stages of development. A significant impairment of growth rate, carcass, liver and skeletal muscle were found in young and adult rats fed for a period of 10 days on raw legume. Urinary urea output and the activities of three amino acid degrading enzymes: arginase, alanine aminotransferase and arginine succinate synthetase were all affected by the dietary protein and the stage of development. Urinary creatinine excretion was higher in the adult rats, while serum cholesterol was slightly increased in the young ones. Changes in plasma zinc may be attributed to a reduced zinc bioavailability to rats from the faba bean diet. Other biochemical parameters measured (glucose, triglycerides and plasma proteins) remained unchanged in all the experimental groups. Liver DNA and RNA content (mg/g tissue) decreased with age in both dietary groups, which were accompanied by an increase in tissue size. Furthermore, liver RNA concentration (primarily a measure of protein synthesis capacity) was enhanced in the adult legume fed rats. In this context, it is suggested that other organs (particularly muscle, with lower amino acid requirements for protein synthesis as a consequence of the stunting of growth) could contribute to increase the amino acid supply to liver in the animals fed on the faba bean diet.     

Effect of tea catechins on body fat accumulation in rats fed a normal diet

Although it is known that tea catechins exert potent effects in obese subjects, there is scant information concerning these effects on body weight gain and body fat accumulation in the non-obese. We studied normal rats fed a normal diet and water containing either 0.1% or 0.5% tea catechins to examine the effects on body fat content and serum cholesterol levels, as well as evaluating whether the effect is related to bile acids, which in recent years have emerged as an inducer of energy expenditure. The administration of 0.5% catechins decreased the accumulation of body fat and the serum levels of cholesterol and bile acids. These results indicate that tea catechins modulate lipid metabolism not only in obese subjects, but also in the non-obese.     

Ultrastructural changes in myocardial cells of rats fed a low protein diet

 Ultrastructural changes in the ventricular myocardial cells in rats fed a low protein diet were examined by electron microscopy. The most striking changes were observed in the I-band region of the sarcomeres, which occurred very occasionally in myofibrils. In the sarcomere affected the I-band region was often fractured and/or disintegrated on one side, leaving an extended space, while the opposing I-band region disappeared along with dislocation of the intact A-band toward the adjacent Z-line. This dislocation was presumably attributed to the elasticity of titins connecting between the end of thick filaments and the Z-line. Fractured I-band regions were often accompanied by the dilated sarcoplasmic reticulum in the close vicinity of them. In some myofibrils the streaming and/or disruption of the Z-line were occasionally observed where disarrangement of thick and thin myofilaments were usually present. The study suggests that the fracture of the I-band region, consisting of actin and titin filaments, and the streaming of the Z-line of myofibrils are due to a proteolytic action of calpain and/or cathepsin L, which are activated by leaked Ca²⁺ ion and/or by modification of internal circumstances of the cytoplasm induced by a low protein diet, thus resulting in a low cardiac output. Received: 22 April 1998 / Accepted: 7 September 1998     

Ultrastructural evaluation of the effects of 1,25-dihydroxyvitamin D3 on bone of thyroparathyroidectomized rats fed a low-calcium diet

Thyroparathyroidectomized rats fed a low-calcium-normal-phosphorus diet were administered 1 or 5 units of 1,25-dihydroxyvitamin D3-(1,25-[OH]2D3) or placebo daily for 7 days. 1,25-(OH)2D3 elevated serum and urine calcium and decreased serum phosphorus. Rats given 1 unit of 1,25-(OH)2D3 had increased numbers of osteoclasts in metaphyseal trabeculae, Ultrastructurally, osteoclasts, osteoblasts, and osteocytes in rats given 1 unit of 1,25-(OH)2D3, were similar to those in rats given placebo. In rats given 5 units of 1,25-(OH)2D3, osteoclasis was markedly increased. Osteoblasts were more numerous and interpreted to be active in matrix production and mineralization. Lamellated electron-dense bodies were observed adjacent to the plasma membranes of less active osteoblasts and were interpreted to be modified matrix. Most osteocytes in rats given 5 units of 1,25-(OH)2D3 were indistinguishable from osteocytes in rats given placebo. However,the pericellular space of some osteocytes in rats given 5 units of 1,25-(OH)2D3 contained electron-dense granular deposits that were interpreted to be calcium phosphate. It is concluded that 1,25-(OH)2D3 is able to significantly elevate serum calcium independent of dietary calcium, parathyroid hormone, and calcitonin primarily by increasing ostoeclasis with minimal dependence on osteocytic osteolysis.     

Impairment of cytokine production in mice fed a vitamin D3-deficient diet.

C57Bl/6 female mice fed a Vitamin D (VIT-D)-deficient diet had serum levels of 25-hydroxyvitamin D decreasing with the time of diet exposure (3 and 8 weeks). Cytokine production (IL-6, TNF and IL-1) by peritoneal macrophages cultured in vitro with a standard stimulus, LPS, evaluated in the supernatants as biological activity, was significantly reduced in VIT-D-deficient animals. The defect in monokine production was partial and was evident at suboptimal LPS concentrations and incubation times. I-A antigen expression, induced in macrophages by in vitro exposure to IFN-gamma, was not modified in VIT-D-deficient mice, but IFN-gamma-inducible macrophage cytotoxicity to tumour target cells was significantly decreased in VIT-D-deficient animals. Moreover, basal and Poly I:C-induced NK activity was not modified by VIT-D deficiency. Thus, macrophage functions, such as cytokine production and tumour cytotoxicity induction, are down-modulated in vitro by VIT-D deprivation. To give more support to the relevance of VIT-D availability for cytokine production, TNF and IL-6 have been evaluated in the sera of control and VIT-D-deficient mice given LPS as a model stimulus. Serum peak levels of both cytokines were at least halved in VIT-D-deprived mice. Thus, VIT-D deficiency may represent a model of partial defect of monokine production.     

Vitamin D status and bone density in steroid-treated children with glomerulopathies: effect of cholecalciferol and calcium supplementation

PurposeThe aim of this study was to assess vitamin D status and bone density in steroid-treated children with glomerulopathies and to evaluate the effect of prophylactic vitamin D and calcium supplementation.Material and MethodsRetrospective analysis was performed on 55 children aged 4–18 yrs with glomerulopathies. The following data were analyzed: antropometrical parameters, bone densitometries, parathormone, 25-hydroxyvitamin D (25-OHD), urinary calcium excretion and medications received for prevention of low bone mass.ResultsA significant number of children (38%) had decreased spinal bone mineral density (BMD z-score < ?2.0) and the majority of them (89%) had hypovitaminosis D (25-OHD < 30ng/ml), 75% were vitamin D insufficient (25-OHD < 20ng/ml) and 16% were vitamin D deficient (25-OHD < 10ng/ml). The mean serum 25-OHD concentration was comparable to that of controls (19.32±12.87 vs. 15.05±8.52 ng/ml). Nearly all patients (82%) were receiving preparations of calcium and/or vitamin D to improve bone health. Patients on cholecalciferol had higher mean concentration of 25-OHD compared to those who were not receiving it (p=0.027) and to the controls (p=0.047). In 23 children on vitamin D and calcium supplementation for an average 6-month time, we observed an increase in the mean BMD values (p=0.004), however, mean BMD z-score and 25-OHD concentrations did not significantly change over time.ConclusionsVitamin D and bone density deficits are remarkably common in steroid-treated children with glomerulopathies, despite vitamin D and calcium repletion. In order to enhance the effectiveness of vitamin D supplementation for improvement of bone density, we suggest regular assessment of serum concentration of 25-OHD that can guide subsequent dose adjustment of vitamin D.     

Effect of vitamin A supplemented diet on calcium oxalate renal stone formation in rats

ObjectivesTo study the effect of a vitamin A supplemented diet on calcium-oxalate stone formation in rats and to test its expected action in the dissolution of renal calculi.Material and methodsTwenty-four male Wistar rats were randomly divided into three groups of eight rats each. The first group (group A) received a normal diet for six weeks. The second group (group B) was fed a lithogenic diet by the addition of ethylene glycol 0.5% to drinking water for three weeks then a normal diet for three weeks. The third group (group C) received the same lithogenic diet for three weeks then a vitamin A supplemented diet 20 times the normal amount (5.1 mg/100 g of diet) at the three last weeks. One day before the end of treatment, each animal was placed for 24 h in metabolic cage in order to collect urine samples and determine the urinary parameters.ResultsThe glomerular filtration rate and the urinary excretion of citric acid which fell in group B have been restored in group C.ConclusionsThis study shows that a vitamin A supplemented diet at the rate of 20 times standard ration could improve the renal function by restoring the glomerular filtration rate and by increasing the urinary pH and excretion of citric acid.     

Release of hypothalamic norepinephrine during MSG intake in rats fed normal and nonprotein diet

Effects of monosodium L-glutamate (MSG) solution (0.06 M) on interstitial levels of norepinephrine (NE) were measured in the lateral hypothalamus (LH). Wistar male rats, housed in standard operant boxes, were fed either normal or nonprotein diet for 3 days. Beside a daily bar-mediated drinking session (75 min), animals were without access to fluids. Microdialysates, collected from the LH during the 75 min of drinking, were analyzed using high-pressure liquid chromatography. No significant responses of the LH NE to the drinking of distilled water, MSG, NaCl (0.06 M), and glucose solution (0.6 M) were found in normally fed rats. However, a specific decline in LH NE release was detected during MSG solution-drinking in rats fed nonprotein diet. As MSG preference indicates protein intake, it is possible that LH NE is, at least partially, one of the brain signals that relate MSG preference to dietary protein intake.     

Effect of vitamin K2 on cortical and cancellous bones in orchidectomized young rats

OBJECTIVES: The purpose of the present study was to compare the effect of vitamin K(2) on cortical and cancellous bones in orchidectomized young rats. METHODS: Forty male Sprague-Dawley rats, 6 weeks of age, were randomized by stratified weight method into four groups with 10 rats in each group: baseline controls (BLC), age-matched controls (AMC), orchidectomy (ORX), and ORX+vitamin K(2) administration (K). Vitamin K(2) (menatetrenone) was administered subcutaneously twice a week at dose of 30 mg/kg each. The experimental period was 8 weeks, and cortical and cancellous bone histomorphometry was performed on the tibial shaft and the proximal tibia, respectively. RESULTS: Cortical area (Ct Ar) and cancellous bone volume (BV/TV) were significantly greater in the AMC group than in the BLC group. Ct Ar was significantly lower in the ORX group than in the AMC group, and cancellous BV/TV was also significantly lower in the ORX group than in the AMC group as a result of significantly increased eroded surface (ES/BS). Although Ct Ar in the ORX+K group did not differ significantly from that in the ORX group, cancellous BV/TV was significantly greater in the ORX+K group than in the ORX group, but still significantly lower than in the AMC group. This protective effect of vitamin K(2) on cancellous bone was attributable to normalizing increased ES/BS. CONCLUSIONS: Vitamin K(2) appears to act more strongly on cancellous bone than on cortical bone in ORX young rats. High dose vitamin K(2) could partially prevent the reduction of cancellous bone gain by normalizing raised bone resorption in ORX young rats.     

维生素D受体基因起始密码子和CDX2多态性与钙剂补充对绝经后妇女骨密度作用的关系

目的了解维生素D受体（vitamin D receptor，VDR）基因（VDR）起始密码子（Fok Ⅰ位点）和启动子区CDX2结合位点多态性与绝经后妇女钙剂补充对骨密度（bone mineral density，BMD）和骨转换指标作用的关系。方法200名受试对象（均为上海市汉族无亲缘关系的绝经后妇女）分为两组：高钙组（日服元素钙1000mg和维生素D400IU）和低钙组（日服元素钙300mg和维生素D300IU）各100名，期限1年。检测治疗前后BMD和骨转换指标，以及VDR基因Fok Ⅰ位点和CDX2结合位点多态性。结果其中171名完成整个研究。研究人群础Ⅰ基因型频率分布依次为Ff（48．0％）、FF（31．0％）和ff（21．0％）；CDX2基因型频率分布依次为AG（56．7％）、GG（25．7％）和AA（17．6％），上述等位基因频率分布在整个人群或2亚组中均符合Hardy-Weinberg定律。无论在整个人群组、或是2亚组中，Fok Ⅰ或CDX2各基因型间各部位BMD和各骨转换指标的基线值差异均无统计学意义；钙剂补充1年时，各部位BMD和骨转换指标的终点值和变化的百分数与Fok Ⅰ或CDX2多态性均无相关性。结论高钙或低钙的补充对上海市汉族绝经后妇女BMD或骨转换指标的影响与VDR基因Fok Ⅰ或CDX2多态性无相关性。     

Effect of vitamin C deficiency and excess on the liver: a histopathological and biochemical study in guinea pigs fed normal or high cholesterol diet

When guinea pigs were kept on a restricted vitamin C intake of only 0.5 mg daily, their serum ascorbic acid fell to 0.16 +/- 0.06 mg/d1 in 16 weeks as compared to 0.73 +/- 0.11 in control. This was associated with significant increase in liver cholesterol and triglycerides. When they were simultaneously challenged with a high cholesterol load, this fat accumulation was markedly exaggerated. The weight of the liver now increased by almost two-and-half times. Liver cholesterol rose to 12.90 +/- 2.63 mg/gm as compared to 3.23 +/- 0.56 mg/gm with low vitamin C alone. Histopathology showed marked distension and vacuolation of hepatocytes, focal necrosis and fibroplasia. Administration of excess vitamin C (100 mg daily) significantly countered these changes. The vitamin C-lipid relationship has important clinical bearings and liver could be an important site of vitamin C action.     

Effect of a low magnesium diet on in vitro glucose uptake in sucrose fed rats.

Dietary magnesium deficiency and excess sucrose in the diet have been shown to play an important role in the development of insulin resistance. This study is an extension of a previously published experiment (Magnes Res 2004; 17: 293-300) and is focused on the effect of a low magnesium diet on in vitro glucose uptake in sucrose fed rats. For this purpose male Wistar rats were divided into four groups and fed control, high sucrose, low magnesium and high sucrose low magnesium diets for a period of three months. Serum and erythrocyte magnesium values demonstrated a significant drop in the low magnesium and high sucrose low magnesium groups. A significant increase was observed in the body weight of the high sucrose group, whereas the weights of animals in the high sucrose low magnesium group remained unchanged from controls. The biochemical analysis showed a significant decrease in in vitro glucose uptake in liver, muscle and diaphragm of rats consuming high sucrose, low magnesium and high sucrose low magnesium diets. The maximum reduction, however, was observed in the combined high sucrose low magnesium group. These findings seem to suggest the potential of a high sucrose low magnesium diet to cause insulin resistance by reducing glucose uptake in target tissues of rats.     

Ketogenic diet fed rats have low levels of S100B in cerebrospinal fluid

Ketogenic diets have been used to treat seizure disorders of children resistant to conventional anti-epileptic drug treatment. The mechanism of action of this diet, however, is unknown. Gliosis is a very common characteristic in tissues associated with epileptogenesis and glial cytokines may be involved in the pathology of seizure disorders. We investigate herein, whether ketogenic diet fed rats demonstrate changes in the immunocontent of S100B, an astrocyte-derived cytokine elevated in the temporal lobe of refractory epilepsy. Lower levels of S100B were observed in cerebrospinal fluid with no significant changes in S100B and GFAP content in brain tissue. Ketogenic fed rats presented a lower seizure severity induced by pentylenetetrazole and no change in cerebrospinal fluid S100B after pentylenetetrazole administration. These results support the concept that the ketogenic diet is neuroprotective in seizure disorders. Since S100B has an extracellular activity in neuronal excitability and synaptic plasticity, it would be reasonable to conceive that a decrease in the S100B could be involved in the mechanism of action of the ketogenic diet. However, it is not possible to establish a direct link between reduced CSF S100B and decreased severity of PTZ-induced attacks at present moment. Regardless of this, CSF S100B could be proposed as an index of efficacy of ketogenic diet for seizure disorders.