Diurnal rhythms in plasma cortisol, insulin, glucose, lactate and urea in pigs fed identical meals at 12-hourly intervals

Circadian Regulation of the Lactate Metabolic Kinetics in Mice Using the [1H-13C]-NMR Technique

Lactate is not only the energy substrate of neural cells, but also an important signal molecule in brain. In modern societies, disturbed circadian rhythms pose a global challenge. Therefore, exploring the influence of circadian period on lactate and its metabolic kinetics is essential for the advancement of neuroscientific research. In the present study, the different groups of mice (L: 8:00 a.m.; D: 20:00 p.m.; SD: 20:00 p.m. with 12 h acute sleep deprivation) were infused with [3-13C] lactate through the lateral tail vein for a duration of 2 min. After 30-min lactate metabolism, the animals were euthanized and the tissues of brain and liver were obtained and extracted, and then, the [1H-13C] NMR technology was employed to investigate the kinetic information of lactate metabolism in different brain regions and liver to detect the enrichment of various metabolic kinetic information. Results revealed the fluctuating lactate concentrations in the brain throughout the day, with lower levels during light periods and higher levels during dark periods. Most metabolites displayed strong sensitivity to circadian rhythm, exhibiting significant day-night variations. Conversely, only a few metabolites showed changes after acute sleep deprivation, primarily in the temporal brain region. Interestingly, in contrast to brain lactate metabolism, liver lactate metabolism exhibited a significant increase following acute sleep deprivation. This study explored the kinetics of lactate metabolism, hinted at potential clinical implications for disorders involving circadian rhythm disturbances, and providing a new research basis for clinical exploration of brain and liver lactate metabolism.

Characterization of diet-dependent temporal changes in circulating short-chain fatty acid concentrations: A randomized crossover dietary trial

BACKGROUND

Production of SCFAs from food is a complex and dynamic saccharolytic fermentation process mediated by both human and gut microbial factors. Knowledge of SCFA production and of the relation between SCFA profiles and dietary patterns is lacking.

OBJECTIVES

Temporal changes in SCFA concentrations in response to 2 contrasting diets were investigated using a novel GC-MS method.

METHODS

Samples were obtained from a randomized, controlled, crossover trial designed to characterize the metabolic response to 4 diets. Participants (n = 19) undertook these diets during an inpatient stay (of 72 h). Serum samples were collected 2 h after breakfast (AB), after lunch (AL), and after dinner (AD) on day 3, and a fasting sample (FA) was obtained on day 4. The 24-h urine samples were collected on day 3. In this substudy, samples from the 2 extreme diets representing a diet with high adherence to WHO healthy eating recommendations and a typical Western diet were analyzed using a bespoke GC-MS method developed to detect and quantify 10 SCFAs and precursors in serum and urine samples.

RESULTS

Considerable interindividual variation in serum SCFA concentrations was observed across all time points, and temporal fluctuations were observed for both diets. Although the sample collection timing exerted a greater magnitude of effect on circulating SCFA concentrations, the unhealthy diet was associated with a lower concentration of acetic acid (FA: coefficient: -17.0; SE: 5.8; P-trend = 0.00615), 2-methylbutyric acid (AL: coefficient: -0.1; SE: 0.028; P-trend = 4.13 × 10-4 and AD: coefficient: -0.1; SE: 0.028; P-trend = 2.28 × 10-3), and 2-hydroxybutyric acid (FA: coefficient: -15.8; SE: 5.11; P-trend: 4.09 × 10-3). In contrast, lactic acid was significantly higher in the unhealthy diet (AL: coefficient: 750.2; SE: 315.2; P-trend = 0.024 and AD: coefficient: 1219.3; SE: 322.6; P-trend: 8.28 × 10-4).

CONCLUSIONS

The GC-MS method allowed robust mapping of diurnal patterns in SCFA concentrations, which were affected by diet, and highlighted the importance of standardizing the timing of SCFA measurements in dietary studies. This trial was registered on the NIHR UK clinical trial gateway and with ISRCTN as ISRCTN43087333.

Feeding behaviour and pre-prandial status affect post-prandial plasma energy metabolites and insulin kinetics in growing pigs fed diets differing in fibre concentration

Variations in feeding behaviour between animals result from individual variations in their metabolism as affected by diet composition. The study aimed to link the within-day dynamics of voluntary feed intake and those of blood metabolites and insulin in growing pigs having ad libitum access to feed and receiving diets differing in dietary fibre levels and aleurone supplementation. A total of forty pigs (body weight: 35 kg) had access to diets provided ad libitum, which differed by fibre content (13 or 18 % neutral-detergent fibre) and aleurone supplementation (0, 2 or 4 g/kg). Feeding behaviour was individually recorded for 1 week. The kinetic of plasma metabolites and insulin was followed for 1 h after a voluntary test meal. Dietary fibre level did not affect the daily feed intake but increased meal size and meal duration. Aleurone supplementation (4 g/kg) decreased the daily feed intake and number of meals. Dietary fibre level only decreased insulin concentration measured 15 min after meal beginning. Aleurone supplementation (4 g/kg) decreased glycaemia in the first hour after the meal and insulinaemia 15 min after the meal. Free access to feed led to high variability in pre-prandial metabolites and insulin concentrations, resulting in different test meal size irrespective of diet composition. Animals were then spread over different profiles combining feeding behaviour and fasted status to explain different profiles of regulation of feed intake. Plasma metabolites and insulin kinetics were affected by diet composition but also by animal characteristics. Individual variability should be considered when diet composition is used to modulate feeding behaviour.

Feeding-Induced Cortisol Response in Newborn Infants

CONTEXT

Understanding the biological rhythms and stress response in sick newborns is important to minimize the negative effects of intensive care. Salivary cortisol has been used as a noninvasive surrogate marker of adrenal function; however, understanding of its control variables is insufficient.

OBJECTIVE

To investigate the presence of feeding-induced cortisol response and its control variables in newborns.

DESIGN, SETTING, AND PATIENTS

Fifty-three newborn infants, who were between 30 and 40 weeks' corrected age and were on 3-hourly regular oral/enteral feeding, were recruited between January 2013 and June 2014.

MAIN OUTCOME MEASURE

Saliva samples were collected before and 1 hour after regular feeding. Dependence of cortisol levels (adjusted for postnatal age) and their feeding-related elevation on clinical variables was assessed by using generalized estimating equations.

RESULTS

Higher cortisol levels were associated with corrected age ≥37 weeks and saliva samples collected after feeding (both P < 0.001). Oral feeding was associated with a greater feeding-induced cortisol response compared with exclusive enteral feeding (P = 0.034), whereas a prolonged feeding duration (≥30 minutes) was associated with a reduced cortisol response compared with brief feeding (<30 minutes) (P < 0.001). Gestational age, corrected age, antenatal/postnatal glucocorticoids, type of milk, and daily feeding volume had no effect on cortisol response.

CONCLUSIONS

Feeding-induced cortisol response was observed in newborns. The cortisol response was more prominent following oral feeding and was reduced with prolonged feeding. Future studies may investigate whether feeding-induced cortisol response plays a role in the acquisition of adrenal ultradian and diurnal rhythms.

The importance of hormonal circadian rhythms in daily feeding patterns: An illustration with simulated pigs

The interaction between hormonal circadian rhythms and feeding behaviour is not well understood. This study aimed to deepen our understanding of mechanisms underlying circadian feeding behaviour in animals, using pigs, Sus scrofa, as a case study. Pigs show an alternans feeding pattern, that is, a small peak of feed intake at the beginning of the day and a larger peak at the end of the day. We simulated the feeding behaviour of pigs over a 24h period. The simulation model contained mechanisms that regulate feeding behaviour of animals, including: processing of feed in the gastrointestinal tract, fluctuation in energy balance, circadian rhythms of melatonin and cortisol and motivational decision-making. From the interactions between these various processes, feeding patterns (e.g. feed intake, meal frequency, feeding rate) emerge. These feeding patterns, as well as patterns for the underlying mechanisms (e.g. energy expenditure), fitted empirical data well, indicating that our model contains relevant mechanisms. The circadian rhythms of cortisol and melatonin explained the alternans pattern of feeding in pigs. Additionally, the timing and amplitude of cortisol peaks affected the diurnal and nocturnal peaks in feed intake. Furthermore, our results suggest that circadian rhythms of other hormones, such as leptin and ghrelin, are less important in circadian regulation of feeding behaviour than previously thought. These results are relevant to animal species with a metabolic and endocrine system similar to that of pigs, such as humans. Moreover, the modelling approach to understand feeding behaviour can be applied to other animal species.

Addition of crude glycerin to pig diets: sow and litter performance, and metabolic and feed intake regulating hormones

The continued growth in biofuel production has led to a search for alternative value-added applications of its main by-product, crude glycerin. The surplus glycerin production and a higher cost of feedstuffs have increased the emphasis on evaluating its nutritive value for animal feeding. The aim of this research was to evaluate the effect of the dietary addition of crude glycerin on sow and litter performance, and to determine the serum concentrations of hormones related to energy metabolism and feed intake in sows during gestation and lactation. A total of 63 sows were assigned randomly to one of three dietary treatments, containing 0, 3 or 6% crude glycerin (G0, G3 and G6, respectively) added to a barley-soybean meal-based diet. During gestation, none of the dietary treatments had an effect on performance, while during lactation, glycerin-fed sows consumed less feed than those fed the control diet (3.8 v. 4.2kg DM/day; P=0.007). Although lactating sows fed the G3 diet had a higher BW loss than those fed the control diet (���20.6 v. ���8.7 kg; P=0.002), this difference was not reflected in litter performance. In gestation, the inclusion of glycerin did not affect blood concentrations of insulin or cortisol. However, pregnant sows fed diets supplemented with glycerin showed lower concentrations of acyl-ghrelin and higher concentrations of leptin (���55 and +68%, respectively; P<0.001). In lactating sows, there were no differences between dietary treatments for any of the hormones measured. Pre-prandial acyl-ghrelin concentrations were positively correlated with cortisol concentrations during gestation (r=0.81; P=0.001) and lactation (r=0.61; P=0.015). In conclusion, the inclusion of up to 6% crude glycerin did not affect the performance of sows during the gestation period; however it had a negative effect on the feed intake and weight loss of lactating sows. Moreover, further research is needed to elucidate the potential relationship between glycerin inclusion levels in the diet and the serum concentrations of hormones related to feed intake and energy balance control.

Considerations on pig models for appetite, metabolic syndrome and obese type 2 diabetes: From food intake to metabolic disease

(Mini)pigs have proven to be a valuable animal model in nutritional, metabolic and cardiovascular research and in some other biomedical research areas (toxicology, neurobiology). The large resemblance of (neuro)anatomy, the gastro-intestinal tract, body size, body composition, and the omnivorous food choice and appetite of the pig are additional reasons to select this large animal species for (preclinical) nutritional and pharmacological studies. Both humans and pigs are prone to the development of obesity and related cardiovascular diseases such as hypertension and atherosclerosis. Bad cholesterol (LDL) is high and good cholesterol (HDL) is low in pigs, like in humans. Disease-relevant pig models fill the gap between rodent models and primate species including humans. Diet-induced obese pigs show a phenotype related to the metabolic syndrome including high amounts of visceral fat, fatty organs, insulin resistance and high blood pressure. However, overt hyperglycaemia does not develop within 6 months after initiation of high sugar-fat feeding. Therefore, to accelerate the induction of obese type 2 diabetes, obese pigs can be titrated with streptozotocin, a chemical agent which selectively damages the insulin-producing pancreatic beta-cells. However, insulin is required to maintain obesity. With proper titration of streptozotocin, insulin secretion can be restrained at such a level that hyperglycaemia will be induced but lipolysis is still inhibited due to the fact that inhibition of lipolysis is more sensitive to insulin compared to stimulation of glucose uptake. This strategy may lead to a stable hyperglycaemic, non-ketotic obese pig model which remains anabolic with time without the necessity of exogenous insulin treatment.

Effects of sequential feeding with low- and high-protein diets on growth performances and plasma metabolite levels in geese

This study was conducted by two trials to investigate effects of sequential feeding with low- and high-protein diets on growth traits and plasma metabolites in geese. In Trial I, the effect of sequential feeding under time-restricted feeding system was investigated. Seventy-two White Roman goslings were randomly allotted into either sequential feeding (S1) or control feeding (C1) group. All goslings were fed for 1 h at morning and at evening, respectively, from 2 to 8 weeks of age. S1 group was offered 13% CP diet at morning and 19% CP diet at evening. C1 group was offered the same diet (16% CP; mixed equally with the two diets mentioned above) at both morning and evening. Blood samples were hourly collected for 4 h after feeding at both morning and evening for the determination of the postprandial plasma levels of glucose, triacylglycerol and uric acid at the end of experiment. Results showed that BW, average daily gain (ADG), and daily feed intake (FI) were not different between groups, but the feed efficiency (FE) in S1 group was significantly higher than that in C1 group (P<0.05). The areas under curve (AUC) of plasma postprandial levels of glucose, triacylglycerol and uric acid were not affected by treatment, but the AUC of triacylglycerol and uric acid in morning were lower than those in evening (P<0.05). In Trial II, the effect of sequential feeding under ad libitum feeding system was investigated. Twenty-four goslings were randomly allotted into either sequential feeding (S2) or control feeding (C2) group. Diets were altered at 0600 and 1800 h, respectively, and geese were fed ad libitum from 4 to 8 weeks of age. S2 group was offered 14% CP diet at morning and 20% CP diet at evening. C2 group was supplied the same diet (mixed with the two diets according to the ratio of diets consumed by S2 group on the preceded day) at both morning and evening. Results showed that the ADG in S2 group was higher than those in C2 group (P<0.05). Summarized data from both trials showed that sequential feeding improves daily gain and FE in growing geese.

Insulin secretion, body composition and pig performance are altered by feeding pattern

Three studies investigated the effect of feeding strategy on production performance and endocrine status of growing pigs. For Experiment 1, 20 entire male pigs (70.0 ± 4.6 kg) were allocated randomly to individual pens in one of four climate-controlled rooms. Pigs were fed for 23 days either ad libitum or entrained to feed bi-phasically for two 90-min periods. For Experiment 2, 20 entire male pigs (41.2 ± 3.5 kg) were housed as per Experiment 1. Pigs were fed for 49 days either ad libitum or fed bi-phasically for two 60-min periods. For Experiment 3, 100 female pigs (66.1 ± 3.5 kg) were randomly allocated to individual pens within a commercial piggery and fed for 42 days either ad libitum or bi-phasically for two 60-min periods. Ear vein catheters were inserted into 10 pigs from each group and hourly blood samples were collected for 24 h in Experiments 1 and 2 and for 11 h in Experiment 3. Plasma insulin, non-esterified fatty acid and glucose concentrations were determined in Experiments 1 and 2, and glucose and insulin concentrations in Experiment 3. Feed intake and performance were recorded in all experiments and carcass composition was assessed by computed tomography for Experiment 2. There were no differences in final liveweight between the two treatment groups for all experiments. Pigs fed for two 90-min periods (Experiment 1) showed no difference in feed intake when compared with feeding ad libitum. Pigs in Experiment 2 fed for two 60-min intervals consumed 2.49 kg/pig.day compared with those fed ad libitum that consumed 2.68 kg/day (P = 0.057). In Experiment 3, pigs fed twice daily consumed 2.82 kg/pig.day compared with 2.91 kg/pig.day in ad libitum-fed pigs (P = 0.051). Bi-phasic fed pigs in Experiment 2 had improved (P < 0.05) feed conversion efficiency compared with pigs fed ad libitum. For all experiments, there was no difference in plasma glucose concentrations between the two treatments. In all three experiments, the circulating insulin concentrations for pigs fed ad libitum remained at a constant level throughout the sampling period. However, plasma insulin concentrations for the bi-phasic fed pigs significantly increased ~1 h after both feeding periods during all three experiments. Insulin secretion of pigs fed for two 90-min periods differed from that of pigs fed for two 60-min periods. Plasma insulin concentration increased five-fold following feeding for 60 min, compared with that in pigs fed for 90 min, which increased two-fold. Bi-phasic-fed pigs from Experiment 2 had reduced (P < 0.05) total carcass fat and significantly increased muscle when compared with pigs fed ad libitum. The data showed that feeding pigs at two succinct periods aligned insulin secretion to the time of feeding. Pigs fed for 60 min, unlike those fed for 90-min intervals, had reduced feed intake in comparison to those fed ad libitum. This may suggest that the duration of the feeding bout is important for this response and this may in turn influence both energy balance and the way energy is partitioned.

Unpredictable feeding impairs glucose tolerance in growing lambs

Irregular eating is associated with insulin resistance and metabolic disease in adults but may affect young, growing children differently. We investigated the metabolic effects of unpredictable feeding in female juvenile lambs randomly assigned to receive, for six weeks, maintenance feed given twice daily in equal portions (Control Group, C; n = 24) or the same weekly feed amount in aliquots of variable size at unpredictable times (Unpredictable Group, U; n = 21). Intravenous glucose tolerance tests (IVGTT), insulin tolerance tests (ITT), and measurement of diurnal plasma cortisol concentrations were performed pre and post the dietary intervention. Groups were compared using t test and RM ANOVA. Weight gain was similar in both groups (C 18±2%; U 16±2% of initial body weight). Glucose area under the curve (AUC) was unchanged in C (AUC pre 818±34, post 801±33 mmol.min.l⁻¹), but increased by 20% in U (pre 830±25, post 1010±19 mmol.min.l⁻¹; p<0.0001), with an inadequate insulin response to glucose load (log(AUC insulin first 40 minutes) post intervention C 1.49±0.04 vs U 1.36±0.04 ng.min.ml⁻¹; p = 0.03). Insulin tolerance and diurnal variation of plasma cortisol concentrations were not different between groups. Unpredictable feeding impairs insulin response to glucose in growing lambs despite high quality food and normal weight gain. Irregular eating warrants investigation as a potentially remediable risk factor for disordered glucose metabolism.

Insulin-stimulating diets during the weaning-to-estrus interval do not improve fetal and placental development and uniformity in high-prolific multiparous sows

Piglet birth weight and litter uniformity are important for piglet survival. Insulin-stimulating sow diets before mating may improve subsequent piglet birth weights and litter uniformity, but the physiological mechanisms involved are not clear. This study evaluated effects of different levels of insulin-stimulating feed components (dextrose plus starch; fed twice daily) during the weaning-to-estrus interval (WEI) on plasma insulin and IGF-1 concentrations, and on follicle development and subsequent luteal, fetal and placental development and uniformity at days 42 to 43 of pregnancy. During WEI, multiparous sows were isocalorically fed diets supplemented with 375 g/day dextrose plus 375 g/day corn starch (INS-H), with 172 g/day dextrose plus 172 g/day corn starch and 144 g/day animal fat (INS-L), or with 263 g/day animal fat (CON). Jugular vein catheters were inserted through the ear vein at 1.5 days before weaning to asses plasma insulin and IGF-1 concentrations. After estrus, all sows received a standard gestation diet until slaughter at days 42 to 43 of pregnancy. The dextrose plus starch-diets enhanced the postprandial insulin response in a dose-dependent manner (e.g. at day 2 insulin area under the curve was 4516 μU/444 min for CON, 8197 μU/444 min for INS-L and 10 894 μU/444 min for INS-H; s.e.m. = 694; P < 0.001), but did not affect plasma IGF-1 concentrations during the first 3 days of WEI. Follicle development and subsequent luteal, fetal and placental development and uniformity were not affected by the dietary treatments, nor related to plasma insulin and IGF-1 concentrations during WEI. Pre-weaning plasma insulin and IGF-1 concentrations were negatively related to sow body condition loss during lactation, but were not related to subsequent reproduction characteristics. This study shows that dietary dextrose plus starch are effective in stimulating insulin secretion (both postprandial peak and long-term concentration), but not IGF-1 secretion during the first 3 days after weaning in multiparous sows. The extreme insulin-stimulating diets during WEI did, however, not improve follicle development, or subsequent development and uniformity of fetuses and placentas in these high-prolific sows (27.0 ± 0.6 ovulations; 18.6 ± 0.6 vital fetuses).