Effect of postweaning feed intake on performance, intestinal morphology, and the probability of diarrhoea in piglets

Changes in gastrointestinal architecture, high incidence of diarrhoea, and low feed intake (FI) are commonly observed around weaning of pigs, but the relationship between postweaning FI and diarrhoea is unclear. This study aimed to determine the effect of low or high FI during the first days after weaning on growth performance, diarrhoea probability, intestinal permeability, and morphology in pigs until postweaning day (PWD) 28. A total of 120 pigs (7.20 ± 0.26 kg) weaned at 28 days of age (PWD 0) were randomly allocated to five diets and housed individually until PWD 28. Two diets differed in CP and three diets differed in threonine and tryptophan levels. At PWD 4, pigs with the 25% lowest accumulated FI (LOW; n = 30) and 25% highest accumulated FI (HIGH; n = 30) were selected for the study. Faecal consistency was evaluated daily using a 4-scale visual scoring system. Blood was collected at PWD 4, 14, 21 and 28, and small intestinal and colonic tissue was obtained at slaughter on PWD 28. Until PWD 4, LOW pigs consumed approximately 20% (35.7 ± 5.9 g/day) of the FI of HIGH pigs (181 ± 5.75 g/day; P < 0.05) and their average daily gain (ADG) was -103 ± 15.1 g/day. At PWD 28, average daily feed intake, ADG, and feed conversion ratio were still negatively affected by the FI level (P < 0.05) and pigs in the LOW group were on average 4.4 kg lighter than HIGH pigs. Pigs in the HIGH group showed a 55% higher probability of diarrhoea compared with LOW pigs during PWD 0-28. The number of antibiotic treatment days against diarrhoea was 2.38 days higher for HIGH compared with LOW pigs (P = 0.04). The intestinal permeability markers diamine oxidase and D-lactate in plasma were unaffected by the level of FI (P > 0.10). The systemic inflammatory markers haptoglobin and C-reactive protein were higher for HIGH pigs at PWD 4 (P = 0.005), but not affected in the following periods (P > 0.10). Pigs in the HIGH group had an increased area of acidic mucin-producing cells in the small intestine compared with LOW pigs (P < 0.05), but other intestinal morphology measurements at PWD 28 were unaffected by the level of FI. In conclusion, high FI just after weaning was associated with higher growth performance but also higher probability of diarrhoea and more frequent use of antibiotics until PWD 28.

The ileal and total tract digestibility fibre and nutrients in pigs fed high-fibre cereal-based diets provided without and with a carbohydrase complex

The effect of carbohydrase can be variable according to the complexity of cereal grains and co-products. Studies on the effect of carbohydrase on cereal diets varying in complexity are scarce. This study was conducted to investigate the apparent ileal (AID) and total tract digestibility (ATTD) of energy, fibre and nutrients in pigs fed diets based on cereal grains and co-products without and with supplementation with a carbohydrase complex in the form of xylanase, arabinofuranosidase and β-glucanase. The experiment was carried out as an 8 × 4 Youden Square design (eight diets and four periods by two blocks) using 16 growing pigs (33.3 ± 0.8 kg) surgically fitted with a T-cannula in the terminal ileum. The pigs were fed eight experimental diets based on either - maize, wheat, rye, or a wheat and rye mix that were provided with or without enzyme supplementation. The AID and ATTD of DM, organic matter, energy, CP, fat, starch, and soluble and insoluble non-starch polysaccharides (NSPs) were studied using titanium dioxide as an indigestible marker. There was a cereal type effect (P < 0.05) of the AID of most of the nutrients investigated but ash and NSP and some of its constituents but with no interactions between cereal types and carbohydrase supplementation (P > 0.05). The ATTD of nutrients in the large intestine was mainly influenced by the fibre composition and was significantly lower (P < 0.001) for NSP, protein and energy for the Maize than the other diets. Supplementation of the cereal diets with the carbohydrase complex partially degrades arabinoxylan (AX) and β-glucan giving rise to a generally higher AID of high-molecular weight arabinoxylan (P = 0.044), starch (P = 0.042), a tendency (P < 0.10) of higher AID of non-cellulosic polysaccharide glucose residue (β-glucan) and soluble arabinoxylan (AX) whereas none of the other components were affected (P > 0.05). Collectively, the results indicate that the carbohydrase complex degrades AX in the stomach and small intestine, leading to a higher AID but with no influence on the ATTD of fibres, nutrients, and energy.

Age-dependent development in protein digestibility and intestinal morphology in weaned pigs fed different protein sources

Today, weaner diets are optimised using digestibility coefficients obtained from grower-finisher pigs, which may overestimate the digestibility in weaners. The aim of this study was to evaluate the standardised ileal digestibility (SID) of CP and amino acids (AAs), and the intestinal morphology in pigs 0-4 weeks postweaning when fed different protein sources. The experiment included 128 pigs weaned at day 28 and the protein sources were wheat, soybean meal (SBM), enzyme-treated soybean meal (ESBM), hydrothermally treated rapeseed meal (HRSM) and casein. The experiment was conducted as a difference method study including wheat in all diets. Eight pigs were slaughtered on the day of weaning (day 0) and six pigs/treatment were slaughtered at days 7, 14, 21, and 28 postweaning. The SID of CP and AA, as average over the four weeks, was lowest for ESBM and highest for wheat and casein, with SBM and HRSM being intermediate. The SID of CP and AA increased (both linear and quadratic, P < 0.05) over time after weaning. The average SID of CP for all protein sources postweaning was 0.38, 0.59, 0.76, and 0.71 on days 7, 14, 21, and 28, respectively. These differences were significant (P < 0.05) between days 7 and 21, and between days 7 and 28 (P < 0.05), whereas there tended to be a difference between days 7 and 14 (P = 0.06). Protein source did not affect the small intestinal morphology response parameters, whereas time after weaning did. Villous height and villous height to crypt depth ratio differed (P < 0.05) between the days 0 and 7, with shorter villi and a higher ratio at day 7. Crypt depth was not altered between days 0 and 7, or between days 7 and 14. For villi density, crypt density and small intestinal length, a significant increase from days 7 to 14 was observed, but there was no further increase to or difference between days 21 and 28. In conclusion, the low SID of CP in casein on day 7 (0.50) illustrates the challenges related to protein digestion in weanling pigs. The SID of CP and AA is very low during the first two weeks postweaning and time after weaning is more important for protein digestibility, than the source of protein. Fewer mature epithelial cells and less absorptive area in the small intestine in the early postweaning period may partly explain the poor protein digestibility.

Lipolysis drives expression of the constitutively active receptor GPR3 to induce adipose thermogenesis

Thermogenic adipocytes possess a therapeutically appealing, energy-expending capacity, which is canonically cold-induced by ligand-dependent activation of β-adrenergic G protein-coupled receptors (GPCRs). Here, we uncover an alternate paradigm of GPCR-mediated adipose thermogenesis through the constitutively active receptor, GPR3. We show that the N terminus of GPR3 confers intrinsic signaling activity, resulting in continuous Gs-coupling and cAMP production without an exogenous ligand. Thus, transcriptional induction of Gpr3 represents the regulatory parallel to ligand-binding of conventional GPCRs. Consequently, increasing Gpr3 expression in thermogenic adipocytes is alone sufficient to drive energy expenditure and counteract metabolic disease in mice. Gpr3 transcription is cold-stimulated by a lipolytic signal, and dietary fat potentiates GPR3-dependent thermogenesis to amplify the response to caloric excess. Moreover, we find GPR3 to be an essential, adrenergic-independent regulator of human brown adipocytes. Taken together, our findings reveal a noncanonical mechanism of GPCR control and thermogenic activation through the lipolysis-induced expression of constitutively active GPR3.

Age-dependent transition from islet insulin hypersecretion to hyposecretion in mice with the long QT-syndrome loss-of-function mutation Kcnq1-A340V

Loss-of-function (LoF) mutations in KCNQ1, encoding the voltage-gated K⁺ channel K_v7.1, lead to long QT syndrome 1 (LQT1). LQT1 patients also present with post-prandial hyperinsulinemia and hypoglycaemia. In contrast, KCNQ1 polymorphisms are associated with diabetes, and LQTS patients have a higher prevalence of diabetes. We developed a mouse model with a LoF Kcnq1 mutation using CRISPR-Cas9 and hypothesized that this mouse model would display QT prolongation, increased glucose-stimulated insulin secretion and allow for interrogation of K_v7.1 function in islets. Mice were characterized by electrocardiography and oral glucose tolerance tests. Ex vivo, islet glucose-induced insulin release was measured, and beta-cell area quantified by immunohistochemistry. Homozygous mice had QT prolongation. Ex vivo, glucose-stimulated insulin release was increased in islets from homozygous mice at 12–14 weeks, while beta-cell area was reduced. Non-fasting blood glucose levels were decreased at this age. In follow-up studies 8–10 weeks later, beta-cell area was similar in all groups, while glucose-stimulated insulin secretion was now reduced in islets from hetero- and homozygous mice. Non-fasting blood glucose levels had normalized. These data suggest that K_v7.1 dysfunction is involved in a transition from hyper- to hyposecretion of insulin, potentially explaining the association with both hypoglycemia and hyperglycemia in LQT1 patients.

An abundant biliary metabolite derived from dietary omega-3 polyunsaturated fatty acids regulates triglycerides

Omega-3 fatty acids from fish oil reduce triglyceride levels in mammals, yet the mechanisms underlying this effect have not been fully clarified, despite the clinical use of omega-3 ethyl esters to treat severe hypertriglyceridemia and reduce cardiovascular disease risk in humans. Here, we identified in bile a class of hypotriglyceridemic omega-3 fatty acid-derived N-acyl taurines (NATs) that, after dietary omega-3 fatty acid supplementation, increased to concentrations similar to those of steroidal bile acids. The biliary docosahexaenoic acid-containing (DHA-containing) NAT C22:6 NAT was increased in human and mouse plasma after dietary omega-3 fatty acid supplementation and potently inhibited intestinal triacylglycerol hydrolysis and lipid absorption. Supporting this observation, genetic elevation of endogenous NAT levels in mice impaired lipid absorption, whereas selective augmentation of C22:6 NAT levels protected against hypertriglyceridemia and fatty liver. When administered pharmacologically, C22:6 NAT accumulated in bile and reduced high-fat diet-induced, but not sucrose-induced, hepatic lipid accumulation in mice, suggesting that C22:6 NAT is a negative feedback mediator that limits excess intestinal lipid absorption. Thus, biliary omega-3 NATs may contribute to the hypotriglyceridemic mechanism of action of fish oil and could influence the design of more potent omega-3 fatty acid-based therapeutics.

Effects of short-term prednisolone treatment on indices of lipolysis and lipase signaling in abdominal adipose tissue in healthy humans

BACKGROUND

Glucocorticoid (GC) excess increases lipolysis, circulating free fatty acid concentrations and lipid oxidation rates in humans. In vitro and animal studies have shown that GCs increase adipocyte ATGL and HSL mRNA contents and HSL phosphorylations, but the effects of GC on in vivo lipase signaling in humans are uncertain. Our study was designed to test how GC administration affects ATGL and HSL related signals in human adipose tissue.

MATERIAL AND METHODS

Nine healthy young men underwent 5 days administration of 37.5 mg prednisolone/d in a randomized, double-blinded, placebo-controlled crossover design. At the end of each 5 d period the subjects were studied after an overnight fast for 6.5 h including a basal period and a 2½ h hyperinsulinemic euglycemic clamp. Adipose tissue biopsies were sampled from the abdominal subcutaneous adipose tissue at the end of the basal period and the clamp.

RESULTS

GC treatment increased serum FFA concentrations and comparative gene identification-58 (CGI-58) mRNA - an ATGL activator - and decreased G0/G1 switch 2 gene (G0S2) mRNA - an ATGL inhibitor - in adipose tissue biopsies. In addition, pro-lipolytic ser⁵⁶³ HSL phosphorylations and protein kinase A (PKA) phosphorylation of PLIN1 (Perilipin-1) increased. The transcripts of ANGPTL4 (Angiopoietin-like 4) mRNA - a regulator of circulating triglycerides - were elevated by GC; as were CIDE (Cell-death Inducing DNA fragmentation factor-α-like Effector)-A and CIDE-C mRNA transcripts indicative of concurrent stimulation of lipolysis and lipogenesis. Finally GCs reduced insulin receptor phosphorylation, and Akt protein levels.

CONCLUSIONS

High dose GC administration to humans leads to pro-lipolytic alterations of CGI-58, G0S2 and ANGPTL4 mRNA transcripts, increases PKA signaling to lipolysis and inhibits the insulin signal in adipose tissue. The increased CIDE-A and CIDE-C mRNA levels suggest concomitant stimulation of lipolysis and lipid storage.

Assessment of mouse liver [1-13C]pyruvate metabolism by dynamic hyperpolarized MRS

Hyperpolarized [1-13C]pyruvate magnetic resonance (MR) spectroscopy has the unique ability to detect real-time metabolic changes in vivo owing to its high sensitivity compared with thermal MR and high specificity compared with other metabolic imaging methods. The aim of this study was to explore the potential of hyperpolarized MR spectroscopy for quantification of liver pyruvate metabolism during a hyperinsulinemic-isoglycemic clamp in mice. Hyperpolarized [1-13C]pyruvate was used for in vivo MR spectroscopy of liver pyruvate metabolism in mice. Mice were divided into two groups: (i) non-stimulated 5-h fasted mice and (ii) hyperinsulinemic-isoglycemic clamped mice. During clamp conditions, insulin and donor blood were administered at a constant rate, whereas glucose was infused to maintain isoglycemia. When steady state was reached, insulin-stimulated mice were rapidly infused with hyperpolarized [1-13C]pyruvate for real-time tracking of the dynamic distribution of metabolic derivatives from pyruvate, such as [1-13C]lactate, [1-13C]alanine and [13C]bicarbonate. Isotopomer analysis of plasma glucose confirmed 13C-incorporation from [1-13C]pyruvate into glucose was increased in fasted mice compared with insulin-stimulated mice, demonstrating an increased gluconeogenesis in fasted mice. The AUC ratios for [1-13C]alanine/[1-13C]pyruvate (38.2%), [1-13C]lactate/[1-13C]pyruvate (41.8%) and [13C]bicarbonate/[1-13C]pyruvate (169%) all increased significantly during insulin stimulation. Hyperpolarized [1-13C]pyruvate can be used for in vivo MR spectroscopy of liver pyruvate metabolism during hyperinsulinemic-isoglycemic clamp conditions. Under these conditions, insulin decreased gluconeogenesis and increased [1-13C]alanine, [1-13C]lactate and [13C]bicarbonate after a [1-13C]pyruvate bolus. This application of in vivo spectroscopy has the potential to identify impairments in specific metabolic pathways in the liver associated with obesity, insulin resistance and nonalcoholic fatty liver disease.

Differential regulation of lipid and protein metabolism in obese vs. lean subjects before and after a 72-h fast

Increased availability of lipids may conserve muscle protein during catabolic stress. Our study was designed to define 1) intracellular mechanisms leading to increased lipolysis and 2) whether this scenario is associated with decreased amino acid and urea fluxes, and decreased muscle amino acid release in obese subjects under basal and fasting conditions. We therefore studied nine lean and nine obese subjects twice, after 12 and 72 h of fasting, using measurements of mRNA and protein expression and phosphorylation of lipolytic and protein metabolic signaling molecules in fat and muscle together with whole body and forearm tracer techniques. Obese subjects displayed increased whole body lipolysis, decreased urea production rates, and decreased forearm muscle protein breakdown per 100 ml of forearm tissue, differences that persisted after 72 h of fasting. Lipolysis per fat mass unit was reduced in obese subjects and, correspondingly, adipose tissue hormone-sensitive lipase (HSL) phosphorylation and mRNA and protein levels of the adipose triglyceride lipase (ATGL) coactivator CGI58 were decreased. Fasting resulted in higher HSL phosphorylations and lower protein levels of the ATGL inhibitor G0S2. Muscle protein expressions of mammalian target of rapamycin (mTOR) and 4EBP1 were lower in obese subjects, and MuRf1 mRNA was higher with fasting in lean but not obese subjects. Phosphorylation and signaling of mTOR decreased with fasting in both groups, whereas ULK1 protein and mRNA levels increased. In summary, obese subjects exhibit increased lipolysis due to a large fat mass with blunted prolipolytic signaling, together with decreased urea and amino acid fluxes both in the basal and 72-h fasted state; this is compatible with preservation of muscle and whole body protein.

Dissecting adipose tissue lipolysis: molecular regulation and implications for metabolic disease

Lipolysis is the process by which triglycerides (TGs) are hydrolyzed to free fatty acids (FFAs) and glycerol. In adipocytes, this is achieved by sequential action of adipose TG lipase (ATGL), hormone-sensitive lipase (HSL), and monoglyceride lipase. The activity in the lipolytic pathway is tightly regulated by hormonal and nutritional factors. Under conditions of negative energy balance such as fasting and exercise, stimulation of lipolysis results in a profound increase in FFA release from adipose tissue (AT). This response is crucial in order to provide the organism with a sufficient supply of substrate for oxidative metabolism. However, failure to efficiently suppress lipolysis when FFA demands are low can have serious metabolic consequences and is believed to be a key mechanism in the development of type 2 diabetes in obesity. As the discovery of ATGL in 2004, substantial progress has been made in the delineation of the remarkable complexity of the regulatory network controlling adipocyte lipolysis. Notably, regulatory mechanisms have been identified on multiple levels of the lipolytic pathway, including gene transcription and translation, post-translational modifications, intracellular localization, protein-protein interactions, and protein stability/degradation. Here, we provide an overview of the recent advances in the field of AT lipolysis with particular focus on the molecular regulation of the two main lipases, ATGL and HSL, and the intracellular and extracellular signals affecting their activity.

GLUT4 and UBC9 protein expression is reduced in muscle from type 2 diabetic patients with severe insulin resistance

Aims

Subgroups of patients with type 2 diabetes mellitus demand large insulin doses to maintain euglycemia. These patients are characterized by severe skeletal muscle insulin resistance and the underlying pathology remains unclear. The purpose of this study was to examine protein expression of the principal glucose transporter, GLUT4, and associated proteins in skeletal muscle from type 2 diabetic patients characterized by severe insulin resistance.

Methods

Seven type 2 diabetic patients with severe insulin resistance (mean insulin dose 195 IU/day) were compared with seven age matched type 2 diabetic patients who did not require insulin treatment, and with an age matched healthy control group. Protein expression of GLUT4 and associated proteins was assessed in muscle and fat biopsies using standard western blotting techniques.

Results

GLUT4 protein expression was significantly reduced by ∼30 pct in skeletal muscle tissue from severely insulin resistant type 2 diabetic subjects, compared with both healthy controls and type 2 diabetic subjects that did not require insulin treatment. In fat tissue, GLUT4 protein expression was reduced in both diabetic groups. In skeletal muscle, the reduced GLUT4 expression in severe insulin resistance was associated with decreased ubiquitin-conjugating enzyme 9 (UBC9) expression while expression of GLUT1, TBC1D1 and AS160 was not significantly different among type 2 diabetic patients and matched controls.

Conclusions

Type 2 diabetic patients with severe insulin resistance have reduced expression of GLUT4 in skeletal muscle compared to patients treated with oral antidiabetic drugs alone. GLUT4 protein levels may therefore play a role in the pathology behind type 2 diabetes mellitus among subgroups of patients, and this may explain the heterogeneous response to insulin treatment. This new finding contributes to the understanding of the underlying mechanisms for the development of extreme insulin resistance.

Reduced cannabinoid receptor 1 protein in subcutaneous adipose tissue of obese

BACKGROUND

Cannabinoid 1 receptors are identified in various tissues involved in the internal metabolism including adipose tissue and the endocannabinoid system is claimed to be overactive in the obese state. To study the potential involvement of cannabinoid receptor 1 in the endocannabinoid system over-activity in adipose tissue in the obese state, we investigated the cannabinoid receptor 1 levels in adipose tissue from different fat depots in lean and obese humans.

MATERIALS AND METHODS

The adipose tissue samples were analysed by Western blot and by RT-PCR.

RESULTS

Both the gene expression and the protein of cannabinoid receptor 1 were lower in subcutaneous abdominal adipose tissue from obese subjects as compared with lean subjects (P < 0.01 and P = 0.058). Moreover, in lean subjects, the level of cannabinoid receptor 1 was significantly higher in subcutaneous adipose tissue compared with visceral adipose tissue (P < 0.05) for both gene expression and protein. The level of cannabinoid receptor 1 was similar between the two depots in obese subjects. The expression of cannabinoid receptor 1 was higher in subcutaneous gluteal adipose tissue as compared with subcutaneous abdominal adipose tissue (P < 0.05).

CONCLUSION

We found in lean subjects, a robust lower level of cannabinoid receptor 1 in visceral adipose tissue compared with subcutaneous adipose tissue (both RNA and protein levels), but similar levels of cannabinoid receptor 1 between the two depots in obese subjects. Our present findings do not indicate that cannabinoid receptor 1 is directly involved in the endocannabinoid system over-activity in adipose tissue in obesity.