Kjell Malmlöf

Effects of guar gum and cellulose on glucose absorption, hormonal release and hepatic metabolism in the pig

Six Large White pigs (mean body-weight 59 (SE 1.7) kg) were surgically fitted with permanent catheters in the portal vein, the brachiocephalic artery and the right hepatic vein, as well as with electromagnetic flow probes around the portal vein and the hepatic artery, and allowed to recover. The non-anaesthetized animals were given a basal non-fibre diet (diet A) alone or together with 60 g guar gum/kg (diet B) or 150 g purified cellulose/kg (diet C) by substitution for mica. The diets were given for weekly periods and according to a replicated 3 x 3 Latin square design. On the last day of each such adaptation period, test meals of 800 g were given before blood sampling. Sampling was continued for 8 h. Guar gum strongly reduced glucose apparent absorption without changing the absorption and the hepatic uptake profiles. Production rates of insulin, gastric inhibitory polypeptide and insulin-like growth factor-1 (IGF-1) were lowest after guar gum ingestion. However, the reductions in peripheral blood insulin levels caused by guar gum were not associated with a change in hepatic insulin extraction. IGF-1 appeared to be strongly secreted by the gut, whereas the liver had a net uptake of the peptide. Ingestion of guar gum increased the hepatic extraction coefficient of gut-produced IGF-1. Guar gum ingestion appeared also to decrease glucagon secretion. Cellulose at the level consumed had very few effects on the variables considered. It is suggested that the modulation of intestinal mechanisms by guar gum was sufficient to mediate the metabolic effects described.

Effect of the cannabinoid receptor-1 antagonist rimonabant on lipolysis in rats

The cannabinoid receptor 1 antagonist, rimonabant, reduces food intake and body weight, but contradictory findings have been reported as to whether the weight-reducing effect is fully accounted for by the reduced food intake or if rimonabant also mediates a lipolytic effect. In the present study, the effect on weight loss was studied in diet-induced obese rats after 3 days and 3 weeks of exposure to rimonabant, respectively. Induction of lipolysis was examined following acute administration and following 3 weeks of repeated dosing. Rimonabant-treated rats lost significantly more weight than their food-restricted controls. This effect was most pronounced in the beginning of the treatment period. No increase in lipolytic activity was found after 3 weeks of repeated dosing as measured by microdialysis in adipose tissue whereas acute administration of 10mg/kg produced a significant increase in microdialysate levels of glycerol illustrating an acute stimulation of lipolysis. No equivalent increase in glycerol was, however, observed in vitro following incubation of isolated rat adipocytes with rimonabant. This finding excludes a direct lipolytic action of rimonabant on tissue level. Instead, administration of 10mg/kg produced a significant increase in noradrenaline excretion in diet-induced obese rats, suggesting an increase in sympathoadrenal activity. In conclusion, the present study suggests an acute lipolytic effect of rimonabant mediated through activation of the sympathoadrenal system.

Protective effect of Actiniopteris radiata (Sw.) Link. against CCl4 induced oxidative stress in albino rats

ETHNOPHARMACOLOGICAL RELEVANCE Actiniopteris radiata is a herb with great medicinal value and is evaluated for hepatoprotective activity. To investigate the protective effect of ethanolic extract of Actiniopteris radiata (EEAR) on CCl₄ induced oxidative stress in male Wistar albino rats. MATERIALS AND METHODS EEAR were administered for 8 consecutive weeks to rats. Group I - control; Group II - toxin control (30% CCl₄); Group III and Group IV received EEAR (250 and 500 mg/kg respectively). Antioxidant status in liver were estimated by determining the activities of the antioxidant enzymes, superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx); as well as by determining the levels of lipid peroxidation (LPO) and reduced glutathione (GSH). In addition, isoenzyme pattern and mRNA expression of the antioxidants were studied. Partial characterization of EEAR was performed by Liquid chromatography-mass spectrometry (LC-MS). RESULTS CCl₄ induced oxidative stress as evidenced from increase in LPO along with reduction of SOD, CAT, GPx and GSH. Treatment with EEAR (250 and 500 mg/kg) mitigated the CCl₄ induced oxidative stress. An analysis of the isozyme pattern of these antioxidant enzymes revealed variations in SOD2, CAT, GPx2 and GPx3 in CCl₄ treated rats, which were normalized after EEAR treatment. Furthermore, expression of genes for the antioxidant enzymes, were down-regulated by CCl₄ treatment, which were reversed by EEAR. The results of partial characterization of EEAR by LC-MS revealed the presence of rutin and other 7 unknown phenolic derivatives. CONCLUSIONS These findings suggest the protective effect of EEAR against CCl₄ induced oxidative stress might be attributed to the presence of flavonoids and phenolic compounds.

Effects of guar gum on plasma urea, insulin and glucose in the growing pig

1. Six growing pigs fitted with portal and arterial blood cannulas were given a barley-fishmeal diet, either alone or supplemented with guar gum at 60 g/kg basal diet. Blood samples were taken during 8 h following test meals given at 08.00 hours. 2. Ingestion of the guar-gum-supplemented diet appeared to increase systematically portal and arterial levels of plasma urea. At peak values, 4 and 5 h after the test meal, this effect was statistically significant (P less than 0.05). 3. Irrespective of which diet was given, portal and arterial blood samples, withdrawn at the same time, were found to have about the same concentration of urea. This was found throughout the 8 h studied and implies that no net exchange of urea between the circulation and the gastrointestinal tract, as a whole, took place. 4. In the time-period 30-60 min following the test meal, guar gum significantly reduced the postprandial hyperglycaemia and hyperinsulinaemia in portal blood.

Porto-arterial plasma concentration differences of urea and ammonia-nitrogen in growing pigs given high- and low-fibre diets

The effects of a high- (HF) and a low- (LF) fibre diet on porto-arterial plasma concentration differences and plasma levels of urea ammonia-nitrogen were compared in six Swedish Landrace X Yorkshire pigs (30-52 kg). Portal and arterial blood samples were drawn during 8 h following two consecutive meals, given at 08.00 and 16.00 hours. The HF diet, in comparison with the LF diet, was found to produce significantly lower portal plasma urea levels. However, concomitant arterial plasma were equally depressed, consequently leaving the porto-arterial urea differences unchanged. In no instance during the 16 h studied could negative porto-arterial urea differences clearly be observed. It was thus concluded that none of the diets induced an important net flux of plasma urea directly from the circulation into the gastrointestinal tract. The significantly lower circulating plasma urea levels that were observed when the pigs received the HF diet were also associated with significantly lower urinary excretions of urea. The HF and LF diets had similar effects on portal and arterial plasma levels of ammonia-N. This was also true with regard to porto-arterial ammonia-N differences.

The Effects of Intravenous Urea Infusions on Portal and Arterial Plasma Ammonia and Urea Enrichment of Jejunal and Colonic Infusions: Acute Experiments with Growing Pigs

Six pigs (49-69 kg) were anaesthetized and fitted with cannulas in the brachiocephalic artery and portal and jugular veins. In addition, inlet-outlet perfusion cannulas were placed in segments of the small and large intestine. Intravenous infusion of urea for 2 h increased arterial plasma urea from a base-line level of 176 (SE, 51) mg/l up to 292 (SE, 67) mg/l after 5 h. During this rise portal ammonia levels remained fairly constant, with minimum and maximum values of 1.2 (SE, 0.3) and 1.7 (SE, 0.6) mg/l, respectively. The average amount of urea recovered in perfusates from small- and large-intestinal segments were 141.4 and 43.8, respectively (p less than 0.001), when expressed as micrograms/g tissue/30 min. It thus appears as if the portal blood is not an important carrier of ammonia liberated from the hydrolysis of urea and that the gastrointestinal tract is differentially permeable to urea at different levels.

Metabolic and Hormonal Response to a Feed‐challenge Test in Lean and Overweight Dogs

Background Obese dogs risk poor life quality, creating a need for increased knowledge of metabolism in overweight dogs. Objectives Investigate postprandial metabolic and hormonal responses to a high‐fat mixed‐meal in dogs and responses of lean versus overweight dogs. Animals Twenty‐eight healthy intact male Labrador Retrievers were included. Methods Prospective observational study. Twelve dogs were grouped as lean (body condition score (BCS 4–5), 10 as slightly overweight (BCS 6), and 6 as overweight (BCS 6.5–8) on a 9‐point scale. After an overnight fast, urine and blood samples were collected. Dogs were then fed a high‐fat mixed‐meal, and blood was collected hourly for 4 hours and urine after 3 hours. Results Postprandial concentrations of insulin and glucagon were increased at 1 hour (both P < 0.0001), triglycerides at 2 hours (P < 0.0001), and glucose at 3 hours (P = 0.004); and all remained increased throughout the feed‐challenge in all dogs. Postprandial urine cortisol/creatinine ratio was higher than fasting values (P = 0.001). Comparing between groups, there was an overall higher triglyceride response in overweight compared to lean (P = 0.001) and slightly overweight (P = 0.015) dogs. Overweight dogs also had higher fasting cortisol/creatinine ratio compared to lean dogs (P = 0.024). Conclusions and Clinical Importance Postprandial responses of dogs to a high‐fat mixed‐meal were similar to those previously reported in people. The higher postprandial triglyceride response and fasting cortisol/creatinine ratio in the overweight dogs could be early signs of metabolic imbalance. Thus, although overweight dogs often appear healthy, metabolic alterations might be present.

The urine metabolome differs between lean and overweight Labrador Retriever dogs during a feed-challenge

Obesity in dogs is an increasing problem and better knowledge of the metabolism of overweight dogs is needed. Identification of molecular changes related to overweight may lead to new methods to improve obesity prevention and treatment. The aim of the study was firstly to investigate whether Nuclear Magnetic Resonance (NMR) based metabolomics could be used to differentiate postprandial from fasting urine in dogs, and secondly to investigate whether metabolite profiles differ between lean and overweight dogs in fasting and postprandial urine, respectively. Twenty-eight healthy intact male Labrador Retrievers were included, 12 of which were classified as lean (body condition score (BCS) 4–5 on a 9-point scale) and 16 as overweight (BCS 6–8). After overnight fasting, a voided morning urine sample was collected. Dogs were then fed a high-fat mixed meal and postprandial urine was collected after 3 hours. Metabolic profiles were generated using NMR and 45 metabolites identified from the spectral data were evaluated using multivariate data analysis. The results revealed that fasting and postprandial urine differed in relative metabolite concentration (partial least-squares discriminant analysis (PLS-DA) 1 comp: R2Y = 0.4, Q2Y = 0.32; cross-validated ANOVA: P = 0.00006). Univariate analyses of discriminant metabolites showed that taurine and citrate concentrations were elevated in postprandial urine, while allantoin concentration had decreased. Interestingly, lean and overweight dogs differed in terms of relative metabolite concentrations in postprandial urine (PLS-DA 1 comp: R2Y = 0.5, Q2Y = 0.36, cross-validated ANOVA: P = 0.005) but not in fasting urine. Overweight dogs had lower postprandial taurine and a trend of higher allantoin concentrations compared with lean dogs. These findings demonstrate that metabolomics can differentiate 3-hour postprandial urine from fasting urine in dogs, and that postprandial urine metabolites may be more useful than fasting metabolites for identification of metabolic alterations linked to overweight. The lowered urinary taurine concentration in overweight dogs could indicate alterations in lipid metabolism and merits further investigation.

Nuclear Magnetic Resonance-Based Blood Metabolic Profiles of Rats Exposed to Short-Term Caloric Restriction

Caloric restriction increases the life-span of a number of organisms. The relationship between the increase in life-span and the extent of caloric restriction, however, varies among species. The underlying mechanisms are yet unknown, but appear to be related to changes in metabolism. In order to investigate the metabolic response of caloric restriction of rats, here is presented the first nuclear magnetic resonance (NMR) spectroscopy-based study of how blood metabolite profiles are influenced by graded levels of caloric restriction. The study involved three groups of obese rats exposed to 0, 20, and 40 percent caloric restriction for five days. Blood serum from each individual was analyzed by 1H NMR and the resulting spectra were subjected to multivariate analysis by unsupervised principal component analysis and supervised orthogonal-partial least square discriminant analysis. The analyses revealed that a response to caloric restriction was present at 20 percent caloric restriction. The metabolites that distinguished the profiles at 20 percent restriction deviated from those at 40 percent restriction. The changes induced by caloric restriction were most clearly observed as an increased level of 3-hydroxybutyrate, and decreased levels of lipids and pyruvate. The metabolic responses of rats exposed to caloric restriction are in good agreement with a switch in metabolism from anabolic pathways towards fatty acid catabolism and gluconeogenesis, which is consistent with previous observations for mice.

A note on the interactive influence of dietary lysine and threonine on plasma urea levels in the growing pig

A low protein diet (120 g CP kg−1) was divided and adjusted at two lysine levels, 8.0 and 10.0 g kg−1. At each of these levels l-threonine was included at four rates, producing diets with threonine contents of 4.4, 4.9, 5.4 and 5.9 g kg−1. Each of these eight test diets were given to eight growing pigs in a change-over experiment, which was designed as a 8 × 8 Latin square. After 3 days of adaptation to each diet the uraemic response to a morning meal was observed for 6 h. Over this time the mean urea plasma responses ranged between 148 and 123 mg urea 1−1. These two extreme values were statistically different (P < 0.01) and were associated with Diet A (4.4 g threonine and 8.0 g lysine kg−1) and Diet B (4.9 g threonine and 8.0 g lysine kg−1), respectively. Also on the 10.0 g lysine level the addition of 4.9 g kg−1 threonine of total diet (Diet F) appeared sufficient to produce maximum suppression of plasma urea. Since Diets B and F supplied very different threonine:lysine ratios, it is concluded that the relation between lysine and threonine was not the main determinant of plasma urea levels.