Dietary restriction reduces the incidence of 3-methylcholanthrene-induced tumors in mice: Close correlation with its potentiating effect on host T cell functions

Summary All mice treated with 3-methylcholanthrene (MC) suffered with tumor 114 days after treatment. However, 40% dietary restriction caused a great inhibition of tumor incidence. In order to understand the mechanisms by which dietary restriction decreased the occurrence of tumor in mice, we investigated the correlation between tumor incidence and host T cell immune responses. At 114 days after MC administration, the mice were sacrificed and their T cell immune responses were assessed. Flow cytometry studies demonstrated that dietary restriction caused a marked increase of the proportion of Thy1.2⁺, L3T4⁺ T cells in MC-treated diet-restricted mice. Consistent with this result, T cell responses against concanavalin A and interleukin-2 were also potentiated in spleen cells obtained from MC-treated diet-restricted mice, while spleen cells obtained from MC-treated unrestricted mice showed decreased T cell responses because of their tumor burden. Such potentiation of T cell functions by dietary restriction was also observed at earlier stages of MC-induced tumorigenesis. During the course of carcinogenesis, spleen cells obtained from diet-restricted mice showed decreased natural killer activity in vivo. However, in vitro induction of cytotoxic T cells was markedly augmented in MC-treated diet-restricted mice compared with unrestricted mice. These results strongly suggest that the increase of host T cell immune responses might be one of the major causes for the reduction of tumor occurrence by dietary restriction.     

Effects of long-term dietary restriction on body temperature are modified with increasing age

Effects of long-term dietary restriction on body temperature and its circadian changes were investigated in 3.5- and 14.5-month-old male Long-Evans rats. Animals were either fed and libitum or kept on a restricted diet for 8 weeks. Purina Lab Chow was constantly available to the ad libitum-fed groups, while half portions of their daily food consumption were given to age-matched diet-restricted groups every day. A highly significant lowering of body temperature in middle-aged diet-restricted (MR) rats was not observed until their food intake had been restricted for 5 weeks compared with that of the middle-aged ad libitum-fed (MA) group as well as that of the young diet-restricted (YR) rats. Eight weeks after diet restriction, both the circadian pattern of body temperature and its diurnal peak-trough difference remained almost unchanged in all four groups, while the average body temperature of MR rats was greatly lower than that of the YR group and that of MA animals. No significant difference in average body temperature was found between the young ad libitum-fed (YA) rats and the MA group. These data suggest that the average body temperature and its circadian changes in ad libitum-fed rats, at least before the age of 14.5 months, is not age-related, while the effect of dietary restriction on body temperature may be modified with increasing age.     

The emergence and maintenance of interdyad differences in the mother-infant relationships of rhesus macaques: A correlational study

The role of the mother in promoting infant independence, reflected in the time spent out of contact with her by the infant, was addressed with a simple correlational approach to scores of time out of contact (Off) and frequencies of acts of maternal rejection and restriction through the infants’ first 16 weeks of life. Correlations of the extents of age changes from week to week were also examined. Infants differed consistently in the times they spent off from their fourth through their eighth weeks, while rates of maternal restriction and rejection were consistent from week 4 until at least week 8 in both sexes and from week 2 in females. The correlations were consistent with the view that time off was set at its week-4 and possibly later levels by maternal rejection, while some further changes in time off, resulting in a loss of consistency from week to week, reflected the extents to which mothers of daughters decreased their restrictive behavior. Weeks in which individual differences in maternal restriction and rejection were correlated with differences in time spent off were generally weeks in which changes in group means of these mean measures were correlated. In daughters, age changes of individual dyad’s scores of time off and maternal rejection were correlated between week 2 and week 4, supporting the view that in these early weeks age changes and individual differences were produced by the same processes. Findings from comparative and experimental studies, and the limitations of correlational approaches now available, are discussed.     

Effects of time-based feed restriction on morbidity,mortality, performance and meat quality of growing rabbits housed in collective systems

In rabbit farms, quantitative feed restriction in the post-weaning period is widely used with the aim of reducing the impact of digestive diseases, whereas less information is available about feed restriction strategies based on the reduction of access time to feeders in different housing systems. This study compared morbidity, mortality, growth performance, carcass characteristics and meat quality of 368 crossbred rabbits fed ad libitum (L) or subjected to a time-based feed restriction programme (R) and housed from 31 to 73 days of age in cages or pens with different dimensions and group sizes, that is, eight conventional cages (0.33 m², six rabbits/cage), eight small open-top pens (0.50 m², eight rabbits/pen), eight medium open-top pens (1.00 m², 16 rabbits/pen) and four large open-top pens (2.00 m², 32 rabbits/pen). Feed restriction was attained by progressively reducing the access time to feeders in the 1st week from 14 to 8 h/day, maintaining 8 h in the 2nd week and then by increasing access time by 1 h/day during the 3rd and 4th week up to 24 h/day. In the first 2 weeks, R rabbits showed a lower (P ≤ 0.001) daily weight gain, feed intake and feed conversion as compared with L rabbits. During the 3rd and 4th weeks, R rabbits exhibited a greater daily weight gain and better feed conversion (P ≤ 0.001). In the last 2 weeks of trial, daily weight gain tended (P = 0.06) to be greater in the R than L rabbits. In the whole trial, R rabbits manifested a lower daily weight gain, feed intake and feed conversion, as well as lower final live weight and the carcass dressing percentage at slaughter (0.05 ≤ P ≤ 0.01). During feed restriction, R rabbits did not show digestive problems, which, however, appeared in the following 2 weeks of refeeding. Thus, R rabbits had a higher health risk index in the whole trial as compared with L rabbits (P ≤ 0.05). The housing system did not affect growth performance, characteristics at slaughter, and carcass and meat quality. Mortality tended to increase with group size (P = 0.06). In conclusion, the time-based feed restriction significantly improved feed efficiency of growing rabbits housed collectively but had somewhat negative effects on characteristics at slaughter and on morbidity and mortality rate.     

Prevention of mammary tumorigenesis by intermittent caloric restriction: does caloric intake during refeeding modulate the response?

Chronic caloric restriction (CCR) prevents mammary tumorigenesis in rodents, but a protective effect for intermittent caloric restriction (ICR) is less well documented. We recently reported that ICR reduced mammary tumor (MT) incidence of mouse mammary tumor virus-transforming growth factor (MMTV-TGF)-alpha mice to a greater extent than did CCR. Here, we repeated this protocol and obtained serum and tissue samples. Ad libitum (AL) MMTV-TGF-alpha mice were fed AIN-93M diet. Beginning at 10 weeks of age, ICR mice received isocaloric AIN-93M-mod diet (2-fold increases in protein, fat, vitamins, and minerals) at 50% of ad libitum for 3 weeks followed by 3 weeks refeeding with AIN-93M diet. CCR mice were pair-fed AIN-93M:AIN-93M-mod (2:1) matching intakes for restriction/refeeding cycles. Mice were sacrificed for MT size, at 79 (end of 12th restriction) or at 80 (1 week after 12th refeeding) weeks of age. AL and ICR-80 mice had heavier body weights than ICR-79 and CCR mice (P < 0.0001). Cumulative food intakes of ICR and CCR mice were reduced 12% and 15% versus AL mice (P < 0.0001). However, ICR mice consumed significantly (P < 0.0001) more food than did AL mice during refeeding. MT incidence was 84%, 13%, and 27% for AL, ICR, and CCR mice, respectively. MT weight (P < 0.0011) and number (P < 0.01) were higher for AL mice compared with ICR and CCR mice. AL and ICR-80 mice had similar serum IGF-I levels, but only AL values were higher than those of ICR-79 and CCR mice (P < 0.0017). ICR mice had more MT DNA breaks compared with AL and CCR mice, suggesting enhanced apoptosis (P < 0.02). AL mice had higher mammary fat pad ObR and ObRb leptin receptor mRNA expression than did ICR and CCR mice (P < 0.001), but there was no effect on MTs. These results confirm that ICR prevents development of MTs to a greater extent than does CCR, although "overeating" during refeeding may compromise this protection.     

Metabonomic investigations of aging and caloric restriction in a life-long dog study

Long-term restriction of energy intake without malnutrition is a robust intervention that has been shown to prolong life and delay age-related morbidity. A 1H NMR-based metabonomic strategy was used to monitor urinary metabolic profiles throughout the lifetimes of control-fed and diet-restricted dogs. Urinary metabolic trajectories were constructed for each dog, and metabolic variation was found to be predominantly influenced by age. Urinary excretion of creatinine increased with age, reaching a maximum between ages 5 and 9 years and declining thereafter. Excretion of mixed glycoproteins was noted at earlier ages, which may be a reflection of growth patterns. In addition, consistent metabolic variation related to diet was also characterized, and energy-associated metabolites, such as creatine, 1-methylnicotinamide, lactate, acetate, and succinate, were depleted in urine from diet-restricted dogs. Both aging and diet restriction altered activities of the gut microbiotia, manifested by variation of aromatic metabolites and aliphatic amine compounds. This analysis allowed the metabolic response to two different physiological processes to be monitored throughout the lifetime of the canine population and may form part of a strategy to monitor and reduce the impact of age related diseases in the dog, as well as providing more general insights into extension of longevity in higher mammals.     

Increased food intake and changes in metabolic hormones in response to chronic sleep restriction alternated with short periods of sleep allowance

Rodent models for sleep restriction have good face validity when examining food intake and related regulatory metabolic hormones. However, in contrast to epidemiological studies in which sleep restriction is associated with body weight gain, sleep-restricted rats show a decrease in body weight. This difference with the human situation might be caused by the alternation between periods of sleep restriction and sleep allowance that often occur in real life. Therefore, we assessed the metabolic consequences of a chronic sleep restriction protocol that modeled working weeks with restricted sleep time alternated by weekends with sleep allowance. We hypothesized that this protocol could lead to body weight gain. Male Wistar rats were divided into three groups: sleep restriction (SR), forced activity control (FA), and home cage control (HC). SR rats were subjected to chronic sleep restriction by keeping them awake for 20 h per day in slowly rotating drums. To model the human condition, rats were subjected to a 4-wk protocol, with each week consisting of a 5-day period of sleep restriction followed by a 2-day period of sleep allowance. During the first experimental week, SR caused a clear attenuation of growth. In subsequent weeks, two important processes occurred: 1) a remarkable increase in food intake during SR days, 2) an increase in weight gain during the weekends of sleep allowance, even though food intake during those days was comparable to controls. In conclusion, our data revealed that the alternation between periods of sleep restriction and sleep allowance leads to complex changes in food intake and body weight, that prevent the weight loss normally seen in continuous sleep-restricted rats. Therefore, this "week-weekend" protocol may be a better model to study the metabolic consequences of restricted sleep.     

Changes of lipid-carbohydrate metabolism during development of melanocortin obesity in the mice with the Agouti yellow mutation

Melanocortin obesity develops after puberty in mice with Agouti yellow mutation. The aim of the work was to study dynamics of the main characteristics oflipidcarbohydrate metabolism during the obesity development. We used female mice of C57BI/6J strain homozygous for recessive mutation nonagouti (a/a-mice) who were predisposed to the obesity, and heterozygous for dominant mutation Agouti yellow (Ay-mice) who were not predisposed to the obesity. Food consumption and body weights were measured from week 4 to week 22. Some animals were decapitated on 8, 11, 13, 15, 22 weeks. Hyperphagia (6 week) proceeds to body weight increasing (7 week) in the Ay-mice. In the Ay-mice compared to a/a-mice, adiposyte size and blood level of leptin were increased on the 11th week, blood levels of fatty acids and glucose--on the 13th week, blood level of insulin--on the 15th week. The hyperphagia seems to promote development ofmelanocortin obesity, stable disturbances of lipid metabolism appearing before those in glucose metabolism. Complete metabolic obesity syndrome was formed after the 15th week of life.     

Effects of germfree status and food restriction on longevity and growth of mice.

An investigation was undertaken to study the effects of germfree (GF) status and mild food restriction on life span in GF and specific pathogen-free (SPF) male ICR mice either full-fed (ad libitum) or on a restricted diet of 4.5 grams per day (equivalent to approximately 80% of full-fed intake) from five-week-old. The mean life span of the full-fed SPF and GF mice was 75.9 and 88.9 weeks respectively, while the mean life span of the food-restricted SPF and GF mice was 117.5 and 109.6 weeks, respectively. Mice in both GF and SPF food-restricted groups were characterized by lower body weight and increased survival. These findings suggest that the cessation of growth may be importantly and perhaps causally related to longevity. The GF mice survived longer than the SPF mice, but the combination of GF status with food restriction did not seem to extend life span more than food restriction alone.     

Effect of the energy density of non-purified diets on reproduction, obesity, alopecia and aging in mice.

Four diets with graded levels of energy at 24% crude protein were fed to C57BL/6J mice for approximately 3 years to develop pelleted non-purified diets. The nitrogen-corrected metabolizable energy (MEn) of the diets ranged from 2.86 to 3.73 kcal per g of dry matter (DM). Fifteen males and 30 females were assigned to each diet. The mice were housed together for 1 week at 7 week intervals, experiencing 5 matings. After the reproduction stage, they were allowed to complete their life span. Moribund mice after 60 weeks of age were subjected to histopathological examination. The highest energy diet showed the following results in comparison with the lowest energy diet: (1) weaning weight of pups increased by 31.6%; (2) males showed slight obesity even during the reproduction stage, but females did not; (3) both sexes developed remarkable obesity after 50 weeks of age with 41.2% (males) and 49.6% (females) increasing in maximum body weight; (4) although daily feed intake decreased by approximately 18%, the MEn was slightly over consumed; (5) females showed higher incidence of alopecia with age; (6) the survival rate after 50 weeks of age decreased earlier and life span was shortened; (7) histopathological changes associated with aging developed earlier. On the other hand, the early death rate of dams at parturition increased with a decrease in dietary energy. It was concluded that at least 2 types of diets are needed throughout the life span of C57BL/6J mice; a high energy diet with an MEn value of 3.73 kcal/g DM for maximum reproduction and a low energy diet with an MEn value of 2.86 kcal/g DM for the long term stage after reproduction to retard obesity and aging most effectively.     

阿霉素肾病小鼠的肾脏病理转变过程

目的观察不同时间点阿霉素肾病小鼠肾脏病理的转变过程。方法 48只雄性BALB/c小鼠,随机分成对照组和模型组,模型组经尾静脉一次性注射阿霉素10.5mg/kg,对照组给予等量的生理盐水。动态观察实验12周内小鼠24 h尿蛋白、血清生化指标、肾脏病理改变。结果模型小鼠蛋白尿于实验第2周出现,持续至第12周,第8周出现高峰(均P0.05);低蛋白血症、高脂血症分别于实验第4、8周出现,血肌酐于实验第12周明显高于正常组(均P0.05)。模型小鼠肾脏病理改变第4周表现为微小病变型;第8周病变较第4周加重,硬化不明显;第12周出现肾小球局灶节段性硬化、肾小球硬化指数(GSI)为(2.81±0.84)%,明显高于同一观测时间点对照组GSI(0.33±0.21)%(P0.01)。结论一次性尾静脉注射10.5 mg/kg阿霉素,能成功复制阿霉素肾病小鼠模型,该模型在早期表现为微小病变型肾病,晚期转变为局灶性节段性肾小球硬化。     

Life-long Dietary Restriction Modulates the Expression of Collagens and Collagen-binding Heat Shock Protein 47 in Aged Fischer 344 Rat Kidney

It has been shown that the expression of HSP47 and collagens is substantially increased in the sclerotic/fibrotic process in various organs, including kidney. However, the factors regulating the increased expression of HSP47 are not yet clear. In this study, we examined the effect of dietary restriction for the expression of collagens and collagen-binding HSP47 in the kidneys of 6- and 24-month-old male Fischer 344 (F 344) rats fed ad libitum or 30% diet-restricted. No significant histological alteration was found in the kidneys of 6-month-old fed or diet-restricted rats. Kidneys obtained from 24-month-old freely fed rats showed glomerulosclerosis with marked tubulointerstitial damage including interstitial fibrosis, while in the kidneys of 24-month-old diet-restricted rats, renal damage was remarkably less than those noted in 24-month-old freely fed rat kidneys. Immunohistochemical analysis showed an increased accumulation of type I, type III and type IV collagens in areas of glomerulosclerosis and interstitial fibrosis in old rat kidneys. Dietary restriction significantly reduces renal accumulation of collagens in old age. Aging enhanced expression of HSP47 in 24-month-old freely fed rat kidneys whereas dietary restriction suppressed its expression in 24-month-old diet-restricted rat kidneys. Also, phenotypic alterations of mesangial cells and interstitial cells (immunopositive for -smooth muscle actin), glomerular epithelial cells (immunopositive for desmin) and tubular epithelial cells (immunopositive for vimentin) were seen in 24-month-old freely fed rat kidneys and found to express HSP47. Dietary restriction significantly diminished phenotypically altered renal cells in 24-month-old rat kidneys. Our results suggest that increased expression of HSP47 is associated with age-related renal damage and that diet-restricted alteration of its expression is associated with the modulation of age-associated renal sclerosis/fibrosis.     

Body weight and some biometrical traits of ring-necked pheasants (Phasianus colchicus) at different ages

Although the growth of pheasants is an important issue, there are few publications providing information on body weight and morphometrics of pheasants at different ages. The aim of this study was to investigate body weight, tarsus length, wing length and wingspan in farmed pheasants aged 3-16 weeks. The study was carried out on 50 pheasants (31 females and 19 males). All one-day old birds were marked and kept until the 16th week of life. In the 3rd 8 h 12th and 16th weeks of life all pheasants were weighted and tarsus length, wing length and wingspan were measured. Male chicks appeared to be significantly heavier than females (P< or = 0.01) already in the third week of life. Also their wings were longer and their wingspan attained higher values (P < or = 0.05). Absolute gains of the majority of traits also differed between sexes (being larger in males) in all studied periods. Values of body weight, tarsus length and wingspan noted in the third week of life were significantly correlated with all later measurements. Thus body weight and some biometrical traits of pheasant chicks measured already at the 3rd week of life could be applied as predictors of future body weight and size.     

Behavioral effects of apomorphine during development of rats

The behavioral effects of apomorphine in a dose of 1.5 mg/kg i.p. were studied in male Wistar rats at the age of 3,4,6 weeks and 3,5,6 months. Behavioral features typical for apomorphine were observed in rats from the 6th week of life. It is concluded that maturation of central dopaminergic receptors in rats occurs at about 6th week of life.     

Cell size distribution in the thymus as a function of age

Although it is well known that thymus function changes with age, it is not known whether these changes are associated with specific thymocyte populations. Since one criterion of specificity is cell size, we studied the size distribution of thymocytes from mice 0.5 days to 30.5 months of age. Body weight, thymus weight, and thymocyte yield were also measured. The mean cell volume of thymocytes from 8.5 to 13 week old mice was 326 μ³, with two detectable subpopulations. Mean thymocyte size was found to change with age. During the first postnatal week, the mean cell volume of the whole thymocyte population increased from 200 to 350 μ³, and the percentage of large cells increased greatly and constituted 90% of the whole population at four days of age. A rather slow decline in mean cell volume with some fluctuation occurred throughout the remaining life span, and at 30.5 months the mean had dropped to about 190 μ³. We suggest on the basis of these data that large thymocytes are involved in the contribution of the thymus to early postnatal development of the immune system and that the age-related functional capacity of the thymus is related to the size of the thymocyte population.     

Immunological function of food-restricted germfree and specific pathogen-free mice.

The effects of food restriction on immune function was investigated in germfree (GF) and specific pathogen-free (SPF) mice. They were maintained from five weeks of age under either full-fed or food-restricted conditions to 4.5 grams per day (equivalent to approximately 80% of full-fed intake) of a commercial diet. Longest survival rate was attained in food-restricted SPF mice followed by food-restricted GF, full-fed GF, and full-fed SPF animals. Food-restricted GF mice showed shorter survival rate than their SPF counterparts. This result suggests that food restriction may be just as effective as GF status for extending life span. Immune function declined significantly with age in full-fed groups of GF and SPF mice. In both food-restricted GF and SPF mice, mitogenic response to concanavalin A or lipopolysaccharide and antibody response to sheep red blood cells were lower early in life and became higher later in life as compared with full-fed mice. Hence, the maintenance of effective immunological function until old age may be the reason for food-restricted groups to live slightly longer than full-fed groups.     

Time course of hepatic lipids accumulation in a strain of mice with an inherited deficiency of sphingomyelinase

Sphingomyelinosis (gene symbol, spm) is a recessive autosomal mutation in mice that causes a condition analogous to the human disease known as Niemann-Pick disease. The time course of hepatic lipids accumulation in this murine model was investigated. Hepatosplenomegaly in spm/ spm mice was noticeable as early as 4 weeks of age, and reached its maximum level at 6 weeks of age. Thereafter the weights of liver and spleen decreased in parallel with a decrease in body weight and an increase in severity of neurological symptoms. Hepatic concentrations of unesterified cholesterol and sphingomyelin were considerably elevated by 4 weeks of age, and further increased linearly to the terminal stages of the disorder. Sphingomyelinase activities in the livers of spm/ + and +/+ mice showed normal adult levels from as early as 4 weeks of age, whereas the activity in spm/ spm mice was consistently 30-40 percent of the normal level from 4 to 12 weeks of age.     

Exogenous hypercortisolism and epididymal fat cell count in young rats.

The influence of two different grades of exogenous hypercortisolism on body weight, epididymal fat pad weight and the total number of fat cells in epididymal fat pads was investigated in young, growing rats. Cortisol, 4-5 mg/kg/day orally from the 7th to the 9th week, reduced body weight gain, whereas epididymal fat pad weight and fat cell content did not differ from those of the control rats. Cortisone acetate, 2.5 mg per 100 g, given subcutaneously for 2 weeks to rats 4-11 week of age caused in the young rat (4-6 weeks) a partial inhibition of the normal increase in body weight, whereas in the young-adult rat (6 weeks and older) an actual decrease of body weight was seen. At both dose levels and - with respect to the higher dose level- in all age groups studied, the weight and fat cell content of the epididymal fat pad were not changed by the cortisone (cortisol) treatment.     

Placental restriction of fetal growth reduces size at birth and alters postnatal growth, feeding activity, and adiposity in the young lamb

Intrauterine growth restriction (IUGR) is associated with accelerated growth after birth. Together, IUGR and accelerated growth after birth predict reduced lean tissue mass and increased obesity in later life. Although placental insufficiency is a major cause of IUGR, whether it alters growth and adiposity in early postnatal life is not known. We hypothesized that placental restriction (PR) in the sheep would reduce size at birth and increase postnatal growth rate, fat mass, and feeding activity in the young lamb. PR reduced survival rate and size at birth, with soft tissues reduced to a greater extent than skeletal tissues and relative sparing of head width (P < 0.05 for all). PR did not alter absolute growth rates (i.e., the slope of the line of best fit for age vs. parameter size from birth to 45 days of age) but increased neonatal fractional growth rates (absolute growth rate relative to size at birth) for body weight (+24%), tibia (+15%) and metatarsal (+18%) lengths, hindlimb (+23%) and abdominal (+19%) circumferences, and fractional growth rates for current weight (P < 0.05) weekly throughout the first 45 days of life. PR and small size at birth reduced individual skeletal muscle weights and increased visceral adiposity in absolute and relative terms. PR also altered feeding activity, which increased with decreasing size at birth and was predictive of increased postnatal growth and adiposity. In conclusion, PR reduced size at birth and induced catch-up growth postnatally, normalizing weight and length but increasing adiposity in early postnatal life. Increased feeding activity may contribute to these alterations in growth and body composition following prenatal restraint and, if they persist, may lead to adverse metabolic and cardiovascular outcomes in later life.     

Some cellular immune reactions in infants. MIF,E-rosette formation and changes in nucleolar morphology

The cellular immune response (MIF, E-rosette formation and changes in nucleolar morphology of lymphocytes) was followed as related to age and antigenic stimulation. MIF in healthy infants increased from the 2nd to the 12th week of life as compared with the first week, probably due to BCG vaccination. The total and active E-rosette formation did not change during the whole period of investigation. Ring-shaped nucleoli increased gradually from the second week of life. Active nucleoli increased up to the 4th week,i.e. after BCG vaccination and then slowly decreased. Micronucleoli being high in the first week, decreased during 24 weeks of life. After artificial colonization of the intestine the production of MIF was slightly lower in colonized infants than in controls from the 2nd to the 12th week. The other parameters followed were not influenced by colonization.