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The University of Sydney, School of Medical Sciences, Charles Perkins Centre, Sydney, New South Wales, Australia
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The University of Sydney, School of Medical Sciences, Charles Perkins Centre, Sydney, New South Wales, Australia
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al. 2016 , Tian et al. 2016 ). Because of the inconsistencies in the literature, the current study was conducted to investigate the effects of thermoneutral housing on energy balance and glucose metabolism at a whole-body and tissue level in
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Congenitally obese Zucker rats showed greater food intake, less running in activity wheels and greater body weight and fat content than the normal phenotype. Their food intake, running and body weight did not change significantly with the phase of the oestrous cycle. Ovariectomy had no effect on these variables or on body composition. Oestradiol replacement had little effect. Zucker rats of normal weight, however, showed a normal pattern of responses to the oestrous cycle, ovariectomy and oestradiol administration. The central regulation of energy balance and body weight appear to be insensitive to oestrogens in the obese Zucker rat.
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Dairy cows suffer from an intense energy deficit at parturition due to the onset of copious milk synthesis and depressed appetite. Despite this deficit, maternal metabolism is almost completely devoted to the support of mammary metabolism. Evidence from rodents suggests that, during periods of nutritional insufficiency, a reduction in plasma leptin serves to co-ordinate energy metabolism. As an initial step to determine if leptin plays this role in periparturient dairy cows, changes in the plasma concentration of leptin were measured during the period from 35 days before to 56 days after parturition. The plasma concentration of leptin was reduced by approximately 50% after parturition and remained depressed during lactation despite a gradual improvement in energy balance; corresponding changes occurred in the abundance of leptin mRNA in white adipose tissue. To determine whether negative energy balance caused this reduction in circulating leptin, cows were either milked or not milked after parturition. Absence of milk removal eliminated the energy deficit of early lactation, and doubled the plasma concentration of leptin. The plasma concentration of leptin was positively correlated with plasma concentrations of insulin and glucose, and negatively correlated with plasma concentrations of growth hormone and non-esterified fatty acids. In conclusion, the energy deficit of periparturient cows causes a sustained reduction in plasma leptin. This reduction could benefit early lactating dairy cows by promoting a faster increase in feed intake and by diverting energy from non-vital functions such as reproduction.
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-prandial energy expenditure was enhanced by prednisolone ( Fig. 3A ). The stimulation of energy expenditure could be interpreted as a beneficial effect on energy balance. However, this is not consistent with the obesogenic effects of glucocorticoids. Moreover, the
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evaluate potential endocrine alterations associated with GPRC6A deficiency and HFD feeding, we also analysed an array of plasma parameters. Lastly, mRNA levels of central hypothalamic markers known to integrate both short-term and long-term energy balance
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infusion, the present sheep were food restricted and therefore in negative energy balance. In seasonal species such as sheep, however, GnRH output is primarily under photoperiodic regulation, with short days being stimulatory and long days
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Abstract
Thyroid hormones have been implicated in the regulation of nuclear 3,5,3′-tri-iodothyronine (T3) receptor binding capacity (Bmax) but, despite numerous in vivo and in vitro studies, there is considerable controversy regarding their exact role. Since changes in thyroid status alter energy balance and hence may influence T3 receptor numbers, the effects of chronic hypothyroidism and T4 treatment have been studied in young pigs under conditions of controlled energy intake. Four groups of animals comprising a hypothyroid, a euthyroid and a hyperthyroid group, all on the same level of food intake, and a hyperthyroid group on twice the amount of food were used. After 3 weeks on the treatment regimes, both the hypothyroid animals on the same level of food intake and the hyperthyroid animals on twice the amount of food had significandy increased Bmax values (97% and 137% higher respectively) compared with euthyroid controls. However, there was no difference between controls and the hyperthyroid animals on the same level of food intake. In a second study, the effects of short-term treatment of euthyroid animals with T3 was investigated. Results showed that in two groups of controls that received intravenous saline, those on a higher food intake had higher Bmax values (76% increase). Intravenous T3 administration to animals on a low food intake did not change the receptor numbers. In none of the studies was there any change in the dissociation constant of the receptors as a result of different treatments. It is suggested that, at least in postnatal life, thyroid hormones per se have no significant effect on nuclear T3 receptor numbers in skeletal muscle. Instead, changes in Bmax in response to thyroid status may be secondary to alterations in energy balance induced by these hormones.
Journal of Endocrinology (1995) 144, 233–242
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amplify local chemerin concentration for CMKLR1 interaction ( Zabel et al . 2008 , De Henau et al . 2016 ). The role of chemerin in energy balance regulation and obesity Effect on whole body metabolism After the discovery of leptin
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ABSTRACT
Three experiments were conducted to compare the ability of different preparations of growth hormone-releasing factor (GRF) to stimulate GH secretion in sheep maintained in positive and negative energy balance.
In experiment 1 five sheep were injected (i.v.) with three preparations of human pancreatic GRF (hpGRF-44, hpGRF-40, hpGRF-29-NH2) and one preparation of rat hypothalamic GRF (rhGRF-29-NH2) all at 98·0 pmol/kg, or control vehicle, in a Latin square design when the animals either had free access to food or were fed half their maintenance requirements. Analysis of plasma samples, obtained before and for 150 min after injection, revealed that the reduced food intake resulted in the expected changes in body weight and circulating GH, insulin, glucose, urea and non-esterified fatty acids. The maximum post-injection concentrations of GH did not differ between either the two levels of feeding or the four GRF preparations but the mean post-injection concentration of GH was significantly higher for all GRF treatments on the restricted ration (P < 0·001). The mean post-injection response to rhGRF-29-NH2 was less than that obtained with hpGRF-44 for sheep with food available ad libitum (P < 0·05) and was clearly more persistent for all GRF treatments in animals fed the reduced diet (P < 0·001).
In experiment 2 the same five sheep were injected i.v. with rhGRF-29-NH2 (98·0 pmol/kg) when they had free access to food and after food had been withdrawn for 3 days. The peak concentrations of plasma GH and the speed of the response did not differ between feeding and food deprivation but the average post-injection concentration of GH was higher (P < 0·05) when the animals were deprived because the response was more persistent.
In experiment 3 the effects of i.v. injection of hpGRF-10-NH2, hpGRF-10-OH and hpGRF-10-OCH3 were examined at three different doses (8, 80 and 800 nmol/kg) each in three sheep. None of these treatments stimulated a significant increase in circulating GH.
J. Endocr. (1985) 105, 113–119
