Biomedical subjects

Johan Buyse

Publications and source records attributed to Johan Buyse.

18 recordsLinked to original sources

PubMed2007

The regulation of stearoyl-CoA desaturase gene expression is tissue specific in chickens.

Emerging evidence suggests a potential role of stearoyl-CoA desaturase (SCD)-1 in the control of body weight and energy homeostasis. The present study was conducted to investigate the effects of several energy balance-related factors (leptin, cerulenin, food deprivation, genotype, and gender) on SCD gene expression in chickens. In experiment 1, 6-week-old female and male broiler chickens were used. In experiment 2, two groups of 3-week-old broiler chickens were continuously infused with recombinant chicken leptin (8 micro g/kg/h) or vehicle for 6 h. In experiment 3, two groups of 2-week-old broiler chickens received i.v. injections of cerulenin (15 mg/kg) or vehicle. In experiment 4, two broiler chicken lines (fat and lean) were submitted to two nutritional states (food deprivation for 16 or 24 h and feeding ad libitum). At the end of each experiment, tissues were collected for analyzing SCD gene expression. Data from experiment 1 showed that SCD is ubiquitously expressed in chicken tissues with highest levels in the proventriculus followed by the ovary, hypothalamus, kidney, liver, and adipose tissue in female, and hypothalamus, leg muscle, pancreas, liver, and adipose tissue in male. Female chickens exhibited significantly higher SCD mRNA levels in kidney, breast muscle, proventriculus, and intestine than male chickens. However, hypothalamic SCD gene expression was higher in male than in female (P < 0.05). Leptin increased SCD gene expression in chicken liver (P < 0.05), whereas cerulenin decreased SCD mRNA levels in muscle. Both leptin and cerulenin significantly reduced food intake (P < 0.05). Food deprivation for either 16 or 24 h decreased the hepatic SCD gene expression in fat line and lean line chickens compared with their fed counterparts (P < 0.05). The hypothalamic SCD mRNA levels were decreased in both lines only after 24 h of food deprivation (P < 0.05). In conclusion, SCD is ubiquitously expressed in chickens and it is regulated by leptin, cerulenin, nutritional state, and gender in a tissue-specific manner.

Adipose Tissue↗

PubMed2007

Metabolism of stevioside by healthy subjects.

Stevioside (250-mg capsules) was given thrice daily for 3 days to 10 healthy subjects. Blood samples were collected and blood pressure measured after nocturnal fasting, before and at different time points during the third day of the administration of stevioside. No significant differences were found between the control and the stevioside condition for blood pressure and blood biochemical parameters. The 24-hr urinary volume and urinary excretion of electrolytes were not significantly different. Likewise, no significant difference was found for mean blood glucose and insulin between control and stevioside conditions. Thus, oral stevioside is not directly effective as a hypotensive or hypoglycemic agent in healthy subjects at the dose administered in this study. Stevioside, free steviol, and steviol metabolites were analyzed in blood, feces, and urine after 3 days of stevioside administration. No uptake was found of stevioside by the gastrointestinal tract or the amounts taken up were very low and below the detection limit of the UV detector. Stomach juice did not degrade stevioside. All the stevioside reaching the colon was degraded by micro-organisms into steviol, the only metabolite found in feces. In blood plasma, no stevioside, no free steviol or other free steviol metabolites were found. However, steviol glucuronide (SV glu) was found in maximum concentrations of 33 micro g/ml (21.3 micro g steviol equivalents/ml). In urine, no stevioside or free steviol were present, but SV glu was found in amounts of up to 318 mg/24-hr urine (205 mg steviol equivalents/24 hrs). No other steviol derivatives were detected. In feces, besides free steviol, no other steviol metabolites or conjugates were detected. Steviol was excreted as SV glu in urine.

Adult↗

PubMed2006

Identification of steviol glucuronide in human urine.

Stevioside (250 mg capsules) was given three times daily to 10 healthy subjects. Steviol glucuronide (steviol 19-O-beta-D-glucopyranosiduronic acid; MM, 494.58; melting point, 198-199 degrees C) was characterized in the 24 h urine as the only excretion product of oral stevioside by MS, NMR, IR, and UV spectroscopy. This is the first report on the unambiguous identification of steviol glucuronide in human urine.

Diterpenes, Kaurane↗

PubMed2006

Acute heat stress induces oxidative stress in broiler chickens.

The stress responses and possible oxidative damage in plasma, liver and heart were investigated in broiler chickens acutely exposed to high temperature. Eighty 5-week old broiler chickens were exposed to 32 degrees C for 6h. The extent of lipid peroxidation, activities of superoxide dismutase and total antioxidant power in plasma, liver and heart tissues were investigated. Meanwhile, the blood metabolites such as glucose, urate, triiodothyronine, thyroxine, corticosterone, ceruloplasmin and creatine kinase were measured before and after 3 and 6h of heat exposure. The results showed that oxidative stress could be induced in 5-week old broiler chickens by acute heat exposure (32 degrees C, 6h). The results suggest that the elevated body temperature can induce the metabolic changes that are involved in the induction of oxidative stress. The liver is more susceptible to oxidative stress than heart during acute heat exposure in broiler chickens. The oxidative stress should be considered as part of the stress response of broiler chickens to heat exposure.

Animals↗

PubMed2006

FAS inhibitor cerulenin reduces food intake and melanocortin receptor gene expression without modulating the other (an)orexigenic neuropeptides in chickens.

Cerulenin, a natural fatty acid synthase (FAS) inhibitor, and its synthetic analog C75 are hypothesized to alter the metabolism of neurons in the hypothalamus that regulate ingestive behavior to cause a profound decrease of food intake and an increase in metabolic rate, leading to body weight loss. The bulk of data exclusively originates from mammals (rodents); however, such effects are currently lacking in nonmammalian species. We have, therefore, addressed this issue in broiler chickens because this species is selected for high growth rate and high food intake and is prone to obesity. First, we demonstrate that FAS messenger and protein are expressed in the hypothalamus of chickens. FAS immunoreactivity was detected in a number of brain regions, including the nucleus paraventricularis magnocellularis and the nucleus infundibuli hypothalami, the avian equivalent of the mammalian arcuate nucleus, suggesting that FAS may be involved in the regulation of food intake. Second, we show that hypothalamic FAS gene expression was significantly (P < 0.05) decreased by overnight fasting similar to that in liver, indicating that hypothalamic FAS gene is regulated by energy status in chickens. Finally, to investigate the physiological consequences of in vivo inhibition of fatty acid synthesis on food intake, we administered cerulenin by intravenous injections (15 mg/kg) to 2-wk-old broiler chickens. Cerulenin administration significantly reduced food intake by 23 to 34% (P < 0.05 to P < 0.0001) and downregulated FAS and melanocortin receptors 1, 4, and 5 gene expression (P < 0.05). However, the known orexigenic (neuropeptide Y, agouti gene-related peptide, orexin, and orexin receptor) and anorexigenic (pro-opiomelanocortin and corticotropin-releasing hormone) neuropeptide mRNA levels remained unchanged after cerulenin treatment. These results suggest that the catabolic effect of cerulenin in chickens may be mediated through the melanocortin system rather than the other neuropeptides known to be involved in food intake regulation.

Animals↗

PubMed2005

Digestibility of a complete ration in horses fed once or three times a day and correlation with key blood parameters.

To determine the influence of feeding frequency on apparent digestibility and blood metabolites in horses, four geldings were fed a complete ration either once (at 08:00 h) or three times a day (at 08:00, 13:00 and 18:00 h). Horses were provided with a mixture of cereals and chopped alfalfa hay at maintenance level for energy supply, 344 kJ/kg BW(0.75) on a daily basis. After three weeks' adaptation, total amounts of faeces and urine were collected for five days, using collection harnesses. Serial blood samples were taken at -30, -15, 0, 5, 15, 30, 45, 60, 90, 120, 180, 240, 300, 360, 480 and 600 min after feeding and analysed for glucose, L-lactate, triglycerides (TG), non-esterified free fatty acids (NEFA) and triiodothyronine (T(3)). Apparent digestibility coefficients of dry matter (DM), crude protein (CP), ether extract (EE), crude fibre (CF), ash and nitrogen-free extract (NFE) were not significantly different (P>0.05) between the two feeding frequencies. Basal plasma glucose, plasma glucose curves and other plasma blood metabolites were not affected by meal frequency. The horses fed the whole ration in one morning feeding did not consume the entire meal at once, but spared feed for ingestion throughout the day, which may explain the lack of effect. Feeding frequency did not affect plasma glucose response (area under curve :AUC) (P=0.705), but AUC (glucose) was negatively correlated with CP (R(2)=0.76; P=0.005) and CF digestibility (R(2)=0.61; P=0.022). Further research is needed to clarify whether different endocrine responses or differences in passage rate can explain these correlations.

Animal Feed↗

PubMed2005

Mode of leptin action in chicken hypothalamus.

While there have been many studies in various species examining the mode of central leptin action on food intake, there is however a paucity of data in birds. We have, therefore, addressed this issue in broiler chickens because this strain was selected for high growth rate, hence high food intake. Continuous infusion of recombinant chicken leptin (8 microg/kg/h) during 6 h at a constant rate of 3 ml/h resulted in a significant reduction (49-57%) of food intake in 3-week-old broiler chickens (P < 0.05). The effect of leptin within the central nervous system (CNS) was mediated via selective hypothalamic neuropeptides. Leptin significantly decreased the expression of its receptor (Ob-R), neuropeptide Y (NPY), orexin (ORX), and orexin receptor (ORXR) (P < 0.05), but not that of agouti-related protein (AgRP) (anabolic/orexigenic effectors) in chicken hypothalamus. However, the catabolic/anorexigenic neuropeptides namely proopiomelanocortin (POMC) and corticotropin-releasing hormone (CRH) mRNA levels remained unchanged after leptin treatment. Despite the absence of leptin effect on AgRP (the antagonist of melanocortin receptor MCR) and POMC (the precursor of alpha-melanocyte stimulating hormone which is a potent agonist for MCR), leptin significantly decreased the expression of MCR-4/5 gene in chicken hypothalamus (P < 0.05) suggesting that leptin acts directly (as ligand) or indirectly (via other ligands) on MCRs to regulate food intake in birds. Additionally, leptin down-regulated the expression of fatty acid synthase (FAS) gene in chicken hypothalamus, indicating an additional pathway of leptin action on food intake such as described for FAS inhibitors. These findings provide new insight into the mechanism of leptin control of food intake in chickens.

Agouti-Related Protein↗

PubMed2005

Potential role of leptin in increase of fatty acid synthase gene expression in chicken liver.

Leptin is reported to have direct effects on lipogenesis in peripheral tissues that are independent of its central effects on food intake and body weight. These experiments have been mainly carried out in rodents (different models of obesity) in which lipogenesis occurs in both adipose tissue and liver. Such effects are unknown in birds in which lipogenesis occurs essentially in the liver. In this study, leptin gene expression and circulating leptin levels were examined in two chicken lines, selected for high (FL) or low (LL) abdominal fat pad size, at different nutritional states (fasted and fed state). In addition, effects of recombinant chicken leptin on liver metabolism were investigated. Hepatic leptin and fatty acid synthase (FAS) gene expression and plasma leptin levels were significantly higher in FL than in LL chickens (P < 0.05). In both lines, fasting significantly reduced hepatic leptin and FAS mRNA levels (P < 0.05). Continuous administration of recombinant chicken leptin (8 microg/kg/h) during 6 h significantly inhibited food intake (51%) and increased leptinemia (23-fold) compared to untreated group. Despite the decrease of food intake, leptin significantly induced the expression of FAS in chicken liver. These changes were accompanied by a significant down-regulation of leptin receptor gene expression, however SREBP-1, the main transcription factor of lipogenic genes, remained unchanged. This result suggests a local potential role of leptin in the regulation of avian hepatic lipogenesis, and explain, at least partly, the metabolic changes evolved during the divergent selection of FL and LL chickens.

Animals↗

PubMed2005

Potential involvement of mammalian and avian uncoupling proteins in the thermogenic effect of thyroid hormones.

Thyroid hormones (THs) have long been known to be involved in the control of thermoregulation in birds and mammals. In particular, they are reported to play a role in the regulation of heat production. The underlying mechanisms could be the stimulation of the nuclear and mitochondrial transcription of several genes involved in energy metabolism and/or a direct action on the activity of components of the mitochondrial respiratory chain. Attention has recently been focussed on a subfamily of mitochondrial anion carriers called uncoupling proteins (UCPs). These proteins are suspected to be involved in a partial dissipation of the mitochondrial proton electrochemical gradient that would uncouple phosphorylations from oxidations and hence produce heat. However, the involvement of uncoupling mechanisms in thermogenesis and particularly in the thermogenic effect of TH is still unclear. The thermogenic role of UCP1, specifically expressed in brown adipose tissue, and its regulation by TH in rodents is quite well recognised, but the involvement in heat production of its mammalian homologues UCP2, ubiquitously expressed, and UCP3, muscle and adipose tissue-specific, as well as the role of the muscular avian UCP (avUCP), are to be further investigated. The expression of the UCP2 and UCP3 genes was shown to be enhanced by TH in muscle of several rodent species, and to be increased in situations where thermogenesis is stimulated, whereas results are more contrasted in pig. There is now increasing evidence that the physiological role of the mammalian UCP3 and UCP2 is rather related to lipid oxidation and/or prevention of reactive oxygen species accumulation than to heat production by uncoupling. The expression of avUCP was also recently demonstrated to be strongly regulated by thyroid status in chicken, and overexpressed in experimental conditions favouring high triiodothyronine concentrations and thermogenesis. However, its real uncoupling activity and contribution to thermogenesis remain to be established.

Animals↗

PubMed2005

Anatomical parameters of cardiopulmonary system in three different lines of chickens: further evidence for involvement in ascites syndrome.

The present study was designed to compare the anatomical parameters of the cardiopulmonary system in three different lines of chickens with different susceptibility to ascites syndrome. Eggs from three different genetic lines-commercial broiler and layer lines and one native to Iran--were incubated and hatched, and 1-day-old chicks used. The relative heart and lung weights, the volumes of the heart, lung and thorax cavity, the incidence of ascites, and the related physiological parameters in these chickens were followed. Lung weight as a percentage of body weight, the relative lung and heart volume, and the volumes of the thorax cavity, before and after removing heart and lung tissues, were lower in fast-growing broiler chickens compared with the layer and native chickens. Additionally, most of these parameters (e.g. relative lung weight, lung volume and thorax cavity) were significantly decreased with age in broiler chickens but were increased in layer and native chickens, which was concomitant with the incidence of ascites in broiler chickens. Our data indicate that all cardiopulmonary parameters investigated are extremely unfavourable to broiler chickens and suggest a reduction in gas exchange area in broilers, and therefore higher susceptibility to pulmonary hypertension and ascites.

Aging↗

PubMed2004

Assessment of age-related glucose oxidation rates of broiler chickens by using stable isotopes.

During their relatively short commercial lifespan of six weeks, broiler chickens undergo very pronounced age- or body weight-related changes in metabolic rate and body composition. The present study was aimed to assess the age-related changes in glucose oxidation rate of broiler chickens by using 13C-labeled glucose. The methodology for this breath test needed to be established first. Broiler chickens aged from two to six weeks were placed in open-circuit respiration cells and received a single intubation of U-13C6-glucose, followed by breath sampling for 4 hours and mass spectrometric analysis of 13C: 12C ratio in the exhaled air. Simultaneously, CO2 concentration in the respiration cell air was continuously monitored in order to calculate the cumulative percentage dose recovery (CPDR). With respect to the methodology, an oral dose of 2 mg U-13C6-glucose per kg body weight while maintaining a CO2 in the concentration of 0.4 to 0.5% was considered to be optimal. The three-parameter Gompertz curve fitted the CPDR values very well. Pronounced age-related changes in exogenous glucose oxidation rates in rapidly growing meat-type chickens were assessed. Young broiler chickens spend only a relatively low percentage of ingested glucose for immediate oxidation. In contrast, broiler chickens approaching the age of maximal absolute growth rate oxidize a greater proportion of the recently ingested glucose relative to the non-oxidative disposal pathways. This shift in the exogenous partitioning is discussed in relation to age-dependent changes in glucose turnover, lipid oxidation and deposition and metabolic heat production.

Aging↗

PubMed2004

Gene expression, tissue distribution and potential physiological role of uncoupling protein in avian species.

Whole-body energy homeostasis and food intake control are essential for an economically sound selection for growth in poultry. The cellular and molecular mechanisms that regulate and link food intake, energy expenditure and energy balance are still poorly understood in poultry. Mitochondrial uncoupling protein-1 (UCP-1) is known to uncouple respiration from ATP synthesis by short circuiting the inward proton flow, resulting in heat production. Its role seems quite well established in adaptive thermogenesis and energy metabolism. However, uncertainty still surrounds the physiological function of the recently discovered UCP-1 homologues, UCP-2 and -3. Most of the functional characterization of these UCPs, to date, has been conducted in mammals. Recently, an avian UCP homologue, which was identified in chicken, hummingbird and king penguin, appears to play a key role in adaptative thermogenesis. Here, we review recent reports describing avian UCP (av-UCP) and discuss progress concerning the molecular mechanisms and potential role of the av-UCP in thermogenesis regulation in avian species.

Amino Acid Sequence↗

PubMed2004

Effect of chronic hypoxia during embryonic development on physiological functioning and on hatching and post-hatching parameters related to ascites syndrome in broiler chickens.

The present study was designed to investigate the effect of different atmospheric pressure on the endogenous functions of broiler chickens during embryonic, hatching and growing periods related to ascites. Eggs from a commercial broiler line were incubated in two similar commercial incubators at high and low altitudes. The effect on embryonic development and physiological functions including hatching parameters, incidence of ascites and growth performance were examined. Embryos incubated at high altitude had higher plasma tri-iodothyronine, thyroxine, corticosteroid and lactic acid levels, and hatched earlier than those incubated at low altitude. Embryonic mortality was higher at high altitude. Chickens that had been incubated at high altitude showed less right ventricular hypertrophy and ascites mortality than those incubated at low altitude. It was concluded that different atmospheric pressure during incubation interacts with the endocrine functions of the embryo and hence affects hatching parameters, thereby influencing ascites susceptibility.

Altitude↗

PubMed2004

Validation of a new test meal for a protein digestion breath test in humans.

Previously, overall protein assimilation after the ingestion of a pure protein meal was studied. In this study, the kinetics of protein assimilation in humans were investigated after the ingestion of a complex meal, which more closely represents a physiologically normal situation. Overall protein assimilation in humans after the ingestion of a pancake meal, containing 12 g of fat, 27 g of carbohydrate, and 19 g of protein, was evaluated in 26 normal volunteers. Both the egg white and yolk of L-[1-(13)C]-leucine-substituted eggs were used to make the batter. The labeled eggs were produced by feeding laying hens a standard chicken diet supplemented with 3 g/kg of L-[1-(13)C]-leucine (99%, mol:mol). High enrichment levels of protein with adequate labeling patterns were obtained in eggs from laying hens fed the L-[1-(13)C]-leucine-substituted diet. The isotopic enrichment of leucine at plateau was equal in egg white and yolk. The overall tracer recovery in egg proteins was 22.5%. The overall protein assimilation parameters in subjects that consumed the pancake meal did not differ from those obtained in subjects that consumed a single protein meal (mean cumulative (13)C recovery/6 h = 17.22 +/- 4.74%, with a maximal (13)C recovery/h of 5.65 +/- 1.48%, which was attained 145 +/- 25 min after ingestion of the meal). The pancake test meal prepared with eggs intrinsically labeled with L-[1-(13)C]-leucine is ideal for the study of protein assimilation. The incorporation of differently labeled substrates into a single test meal allows the assessment of different gastrointestinal processes in the overall assimilation of proteins.

Breath Tests↗

PubMed2003

Cold-induced enhancement of avian uncoupling protein expression, heat production, and triiodothyronine concentrations in broiler chicks.

The relationships among avian uncoupling protein (avUCP) mRNA expression, heat production, and thyroid hormone metabolism were investigated in 7-14-day-old broiler chicks (Gallus gallus) exposed to a low temperature (cold-exposed chicks, CE) or a thermoneutral temperature (TN). After 7 days of exposure, CE chicks exhibited higher heat production (+83%, P<0.01), avUCP mRNA expression (+20%, P<0.01), and circulating triiodothyronine (T(3)) levels (+104%, P=0.07) for non-statistically different body weights and feed intake between 3 and 7 days of exposure as compared to TN chicks. Plasma thyroxine (T(4)) concentration was clearly decreased in CE chicks (-33%, P=0.06). The lower hepatic inner-ring deiodination activity (-47%) and the higher renal outer-ring deiodination activity (+75%) measured in CE compared to TN chicks could partly account for their higher plasma T(3) concentrations. This study describes for the first time the induction of avUCP mRNA expression by low temperature in chickens, as it has been previously shown in ducklings, and supports the possible involvement of avUCP in avian thermogenesis.

Animals↗

PubMed2003

Effects of dietary macronutrient content on energy metabolism and uncoupling protein mRNA expression in broiler chickens.

The objective of the present study was to investigate the effects of dietary macronutrient ratio on energy metabolism and on skeletal muscle mRNA expression of avian uncoupling protein (UCP), thought to be implicated in thermogenesis in birds. Broiler chickens from 2 to 6 weeks of age received one of three isoenergetic diets containing different macronutrient ratios (low-lipid (LL) 30 v. 77 g lipid/kg; low-protein (LP) 125 v. 197 g crude protein (Nx6.25)/kg; low-carbohydrate (LC) 440 v. 520 g carbohydrate/kg). LP chickens were characterised by significantly lower body weights and food intakes compared with LL and LC chickens (-47 and -38 % respectively) but similar heat production/kg metabolic body weight, as measured by indirect calorimetry, in the three groups. However, heat production/g food ingested was higher in animals receiving the LP diet (+41 %, P<0.05). These chickens also deposited 57 % less energy as protein (P<0.05) and 33 % more as fat. No significant differences in energy and N balances were detected between LL and LC chickens. The diets with the higher fat contents (i.e. the LP and LC diets) induced slightly but significantly higher relative expressions of avian UCP mRNA in gastrocnemius muscle, measured by reverse transcription-polymerase chain reaction, than the LL diet (88 and 90 v. 78 % glyceraldehyde-3-phosphate dehydrogenase respectively, P<0.05). Our present results are consistent with the recent view that UCP homologues could be involved in the regulation of lipid utilisation as fuel substrate and provide evidence that the macronutrient content of the diet regulates energy metabolism and especially protein and fat deposition.

Animal Nutritional Physiological Phenomena↗

PubMed2002

Thyroid status, but not insulin status, affects expression of avian uncoupling protein mRNA in chicken.

The aim of this study was to investigate the hormonal regulation of the avian homolog of mammalian uncoupling protein (avUCP) by studying the impact of thyroid hormones and insulin on avUCP mRNA expression in chickens (Gallus gallus). For 3 wk, chicks received either a standard diet (control group), or a standard diet supplemented with triiodothyronine (T(3); T3 group) or with the thyroid gland inhibitor methimazole (MMI group). A fourth group received injections of the deiodinase inhibitor iopanoic acid (IOP group). During the 4th wk of age, all animals received two daily injections of either human insulin or saline solution. The results indicate a twofold overexpression of avUCP mRNA in gastrocnemius muscle of T3 birds and a clear downregulation (-74%) in MMI chickens compared with control chickens. Insulin injections had no significant effect on avUCP mRNA expression in chickens. This study describes for the first time induction of avUCP mRNA expression by the thermogenic hormone T(3) in chickens and supports a possible involvement of avUCP in avian thermogenesis.

Animals↗

PubMed2002

Pre- and postprandial changes in plasma hormone and metabolite levels and hepatic deiodinase activities in meal-fed broiler chickens.

The present study aimed to study the effects of food deprivation and subsequent postprandial changes in plasma somatotrophic and thyrotrophic hormone levels and focused on the inter-relationships between these hormonal axes and representative metabolites of the intermediary metabolism of meal-fed broiler chickens. Male broiler chickens (2 weeks old) were fed a meal of 40-45 g/bird per d for two consecutive weeks (food-restricted (FR) treatment). The daily allowance was consumed in about 30 min. At 4 weeks of age, FR chickens were killed at several time intervals (ten per sampling time) in relation to the daily food allowance: before feeding (about 23.5 h of food deprivation), and at 10, 20, 30 (end of feeding), 40, 50, 60, 90, 120 and 200 min after initiation of feeding. Birds fed ad libitum served as controls (ad-libitum (AL) treatment). Liver tissue was collected for deiodinase type I and type III activity measurements and blood samples for analysis of growth hormone (GH), insulin-like growth factor (IGF)-I, thyroxine (T4), 3,3',5-triiodothyronine (T3), glucose, non-esterified fatty acids (NEFA), uric acid, triacylglycerol (TG) and lactate levels. Food deprivation caused a shift from lipogenesis to lipolysis and increased fatty acid turnover, a reduction in protein anabolism and reduced metabolic rate. Food intake was followed immediately by a pronounced increase in metabolic rate, initially mainly based on anaerobic mechanisms. Refeeding gradually reversed the fasting-induced alterations in plasma hormone and metabolite levels, but the time course of changes differed between metabolites, which clearly preceded those of the hormones investigated. The order of responsiveness after food provision were glucose>uric acid>or=NEFA>lactate>TG for the plasma metabolites and for hormones. Based on these different postprandial time courses, several functional relationships are proposed. Glucose is believed to be the primary trigger for the normalisation of the effects of fasting on these plasma variables by restoring hepatic GH receptor capacity, as well as decreasing deiodinase type III activity.

Animals↗