Dietary vitamin A supplementation in rats: suppression of leptin and induction of UCP1 mRNA.
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All-trans-retinoic acid (RA), an active metabolite of vitamin A, induces the gene expression of uncoupling protein 1 (UCP1) in brown adipose tissue (BAT) and suppresses leptin gene expression in white adipose tissue (WAT) when given as an acute dose. These contrasting effects of RA leave in doubt the overall effect of chronic RA or vitamin A supplementation on energy homeostasis. To investigate the effects of dietary vitamin A supplementation on leptin and UCP1 gene expression, rats were fed either a normal diet (2.6 retinol/kg diet) or a vitamin A-supplemented diet (129 mg retinol/kg diet) for 8 weeks, and adiposity, serum leptin levels, leptin mRNA levels in perirenal WAT, UCP1 and UCP2 mRNA levels in BAT, and beta3-adrenergic receptor mRNA levels in BAT and WAT were examined. Rats on both diets gained a similar amount of weight, but there was a small 9% decrease in the adiposity index in the vitamin A-supplemented rats. Dietary vitamin A supplementation increased UCP1 gene expression in BAT by 31%, but suppressed leptin gene expression by 44% and serum leptin levels by 65%. UCP2 and beta3-adrenergic receptor gene expression in BAT and perirenal WAT were unchanged by the vitamin A diet. These data suggest that dietary vitamin A has a role in regulating energy homeostasis by enhancing UCP1 gene expression and decreasing serum leptin levels. (+info)
Role of adipocytokines on the pathogenesis of atherosclerosis in visceral obesity.
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Obesity which is defined as accumulation of excess body fat, is a major cause of atherosclerotic vascular disease in industrial countries. Recent advances in the biology of adipose tissue have revealed that adipose tissue is not simply an energy storage organ but it also secretes a variety of molecules which affect the metabolism of the whole body. Through a systematic search of active genes in adipose tissue, we found that adipose tissue, especially visceral fat expressed numerous genes for secretory proteins (about 30% of total genes analyzed). Among them, plasminogen activator-1 (PAI-1), which is a regulator of the fibrinolytic system, was overexpressed in the visceral fat in an animal model of obesity. Plasma levels of PAI-1 were closely correlated with visceral fat adiposity. Thus, PAI-1 secreted from visceral fat may play some role in thrombotic vascular disease in visceral obesity. Adiponectin, a novel adipose-specific gene product, which has a matrix-like structure, is abundantly present in the bloodstream. Dysregulated secretion of adiponectin may be related to vascular disease in obesity. Biologically active molecules secreted from adipose tissue (adipocytokines) may have important roles in the development of atherosclerotic disease in obesity. (+info)
Effects of castor oil on lipid metabolism in rats.
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Weanling rats were given diets contained castor oil (CAO-diet), coconut oil (CO-diet), or high-oleic safflower oil (HO-diet) each 10% (wt). No growth retardations were observed on the CAO-diets. The CAO-diet group showed significantly lower serum cholesterol and hepatic triacylglycerols than the HO-diet group. Ricinoleic acid was found at an extremely low level in perirenal adipose tissue. (+info)
Vascularisation in adipose depots surrounding immune-stimulated lymph nodes.
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We report a change in the vascularisation of the adipose depots surrounding the popliteal lymph node that has, and the contralateral node that has not, been exposed to a simulated immune challenge. The percentage of the depot that consists of vessels, as measured by image analysis, decreases over a period of 2 d after immune stimulus, then increases in a biphasic manner over the next 2-3 wk. By 1 mo after the stimulus, the vascularisation has returned to baseline values. The adipose tissue surrounding both the stimulated and the unstimulated lymph nodes shows a similar pattern, but the unstimulated depot lags by 3-6 d in reaching its maximum vascularisation. These data support the hypothesis that perinodal adipose tissue is involved in peripheral immune responses. (+info)
Relative development of subcutaneous, intermuscular, and kidney fat in growing pigs with different body compositions.
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A total of 94 pigs from seven groups considered as lean (boars from a synthetic line and the Pietrain breed), conventional (boars, gilts, and barrows from the Large White breed), fat (barrows from the Meishan x Large White cross), or obese (Meishan barrows) were serially slaughtered between 12 and 110 kg BW. Carcasses were dissected into muscle, bone, skin, and fat, which was further separated into subcutaneous, intermuscular, and kidney fats. Subcutaneous fat accounted for 60 to 70% of body fat and intermuscular fat for 20 to 35% of body fat. Relative to total fat, intermuscular fat grew more slowly (allometric growth coefficients generally < 1), subcutaneous fat at the same rate (b close to 1), and kidney fat more rapidly (1.12 < b < 1.33). The leaner the animals genetically, the higher the proportion of intermuscular fat in total fat. The ratio of intermuscular to subcutaneous fat varied from .31 in Meishan barrows to .66 in Pietrain boars. Overall, the ratio of intermuscular fat to muscle weight or body weight was positively related to the development of total fat. However, Pietrain pigs were unique in having a high development of intermuscular fat. The present results suggest that 1) the genetic controls of the development of intermuscular and subcutaneous fat are partially independent and 2) the development of intermuscular fat may be determined at an early stage, before 20 kg BW. (+info)
Postnatal development of stearoyl coenzyme A desaturase gene expression and adiposity in bovine subcutaneous adipose tissue.
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This investigation addressed the hypothesis that stearoyl coenzyme A desaturase (SCD) gene expression would serve as a postnatal marker of adipocyte differentiation in bovine s.c. adipose tissue. Samples of tailhead s.c. adipose tissue were obtained by biopsy from preweaning steer calves 2.5 wk, 5 mo, and 7.5 mo of age and from yearling steers 12 mo of age. Samples also were obtained at slaughter when the steers were 18 mo of age. The steers sampled as yearlings were fed native pasture from weaning until 12 mo of age, and the steers sampled at slaughter were fed a high-concentrate diet from 12 to 18 mo of age. Major peak adipocyte volumes for the 2.5-wk-, 5-mo-, and 7.5-mo-old steers were 14, 270, and 700 pL, respectively (P < .001). The steers did not gain weight during pasture feeding, and at 12 mo of age peak adipocyte volume had decreased (P = .009) to 270 pL. At this time, a second, smaller population of adipocytes had appeared with a peak volume of 115 pL. At slaughter, adjusted fat thickness of the steers was 1.60 +/- .13 cm, the USDA yield grade of the carcasses was 3.51 +/- .31, and peak adipocyte volume had increased (P = .01) to over 2,500 pL. The number of adipocytes per 100 mg of adipose tissue doubled (P = .006) between 2.5 wk and 5 mo of age, concurrent with the nearly 20-fold increase in peak adipocyte volume, indicating that this was a period of apparent adipocyte hyperplasia. Uncoupling protein mRNA was undetectable at all stages of postnatal growth, indicating that differentiating tailhead s.c. adipocytes do not acquire brown adipocyte characteristics postnatally. Lipogenesis expressed on a cellular basis was low in all preweaning samples and increased significantly above preweaning values only in the 18-mo-old steers. Stearoyl coenzyme A desaturase mRNA concentration also was low in all preweaning samples, but it peaked (P = .07) at 12 mo of age. Because the peak in SCD mRNA concentration preceded a significant rise in lipogenesis and lipid filling, we conclude that the level SCD gene expression may be indicative of the extent of terminal differentiation in bovine tailhead s.c. adipose tissue. (+info)
Reproductive, metabolic, and endocrine responses to feed restriction and GnRH treatment in primiparous, lactating sows.
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The current experiment was carried out to determine whether exogenous GnRH treatment in primiparous, lactating sows undergoing feed restriction would improve reproductive performance after weaning. Sows were allocated to one of three treatments: AA sows (n = 8) were fed to appetite throughout a 28-d lactation, AR (n = 12) and AR + GnRH (n = 12) sows were fed as AA sows from farrowing to d 21 of lactation, and feed intake was reduced to 50% of the ad libitum intakes from d 22 to 28. The AR + GnRH sows received 800 ng of GnRH i.v. every 6 h from d 22 to 28 of lactation, and AA and AR sows received saline. Sow weight, backfat, and litter weight were recorded weekly. Within 2 d after farrowing, litter size was standardized to 8 to 10. At d 17 of lactation, an indwelling jugular catheter was surgically implanted in each sow. Blood samples were taken for characterization of plasma LH, FSH, insulin, IGF-I, and leptin by RIA at d 21 and before and after weaning on d 28 of lactation. After weaning, all sows were given ad libitum access to feed, checked for onset of standing estrus twice daily with mature vasectomized boars, and inseminated 12 and 24 h after onset of standing estrus with pooled semen from the same fertile boars (3 x 10(9) sperm/AI). After breeding, feed allowance was reduced to NRC (1988) requirements for gestation. At d 28 +/- 3 of gestation, sows were killed and ovulation rate and embryo survival were determined. Restricted sows lost more weight during lactation than AA sows (P < .02). During the period of feed restriction, plasma IGF-I and postprandial insulin and leptin in AR and AR + GnRH sows, and LH pulse frequency in AR sows, were lower than those in AA sows (P < .04). Associations (P < .004) between plasma insulin and leptin and between leptin and mean LH concentrations were established. The LH pulse frequency in AR + GnRH sows did not differ from that in AA sows before weaning. After weaning, maximum, mean, and minimum LH concentrations in the AA and AR sows, and FSH concentrations in AR sows, increased (P < .05) in response to weaning. Paradoxically, GnRH treatment in lactation seemed to suppress the expected LH and FSH responses to weaning. Ovulation rate and embryo survival were not different among the three groups. In conclusion, although exogenous GnRH therapy restored LH secretion in feed-restricted sows, it did not improve overall reproductive performance. (+info)
Hydration of fat-free body mass: review and critique of a classic body-composition constant.
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The assumed "constancy" of fat-free body mass hydration is a cornerstone in the body-composition research field. Hydration, the observed ratio of total body water to fat-free body mass, is stable at approximately 0.73 in mammals and this constancy provides a means of estimating total body fat in vivo. This review examines both in vitro and in vivo data that support the hydration constancy hypothesis and provides a critique of applied methodology. Biological topics of interest are then examined and critical areas in need of future research are identified. These are important issues because water dilution is the only method currently available for estimating body fat in all mammals, which range in body mass by a factor of 10(4). (+info)