Gary Mitchell Davenport

Mannoheptulose has differential effects on fasting and postprandial energy expenditure and respiratory quotient in adult Beagle dogs fed diets of different macronutrient contents

The present study aimed to determine the effects of mannoheptulose (MH) (8 mg/kg) on energy expenditure (EE), respiratory quotient (RQ) and glycaemic response in healthy adult Beagle dogs (n 8; 9·62 (sem 0·31) kg; body condition score 4·5). The study was designed as replicated 4 × 4 Latin squares with a 2 × 2 factorial treatment structure. The dietary treatments were low carbohydrate (CHO) relative to fat diet (LC; 31 % CHO, 28 % fat) with placebo (0 mg/kg) or MH supplement and high CHO relative to fat diet (HC; 54 % CHO, 11 % fat) with placebo (0 mg/kg) or MH supplement. Dogs were fed to maintain body weight (HC and HC+MH 3625 (sem 295) kJ and LC and LC+MH 3542 (sem 284) kJ). Resting and postprandial (0–4 h; 5–10 h; 11–17 h; 18–23 h) EE and RQ were determined by indirect calorimetry (days 12 or 14). Glycaemic response to a meal (24 h) and plasma MH concentrations were determined on days 12 or 14. Plasma MH followed first-order kinetics, confirming that MH is absorbed and available to the animal. In the presence of high dietary CHO, MH increased postprandial EE (5–10 h only), suggesting MH increased dietary induced thermogenesis. In contrast to earlier reports, MH did not affect serum glucose or insulin in the present study. Irrespective of MH, dogs adapted RQ to diet composition and dogs consuming the LC diet had a greater incremental AUC for glucose, but not insulin, than dogs consuming the HC diet.

Dietary mannoheptulose has differential effects on fasting and post-prandial glucose oxidation in Labrador Retrievers

This study aimed to determine the effects of dietary mannoheptulose (MH; 2 mg kg−1), a glycolytic inhibitor, on glucose oxidation and biomarkers of energy metabolism in neutered, adult, male Labrador Retriever dogs (N = 6). Fasting and post-prandial respiratory quotient (RQ) and energy expenditure (EE) were determined by indirect calorimetry (d 16). Glucose turnover and oxidation were assessed during fasting and repeated meal feeding using indirect calorimetry and a constant intravenous infusion of U-13C-glucose (d 18). A sample from the biceps femoris was obtained to determine the muscle protein content of adenosine monophosphate-activated protein kinase (AMPK) and acetyl CoA carboxylase (ACC; total and phosphorylated forms; d 21). MH did not affect EE, serum glucose, insulin or free fatty acids or ACC protein content. In fasting, MH significantly increased the fasting RQ (p = 0.01) and glucose oxidation (p = 0.01) and tended to decrease the ratio of phosphorylated to total AMPK protein content (p = 0.16). In contrast, post-prandial glucose oxidation tended to be lower (p = 0.14) in dogs fed MH. These results suggest that MH has differential effects on fasting and post-prandial whole body glucose and fat oxidation. However, further research that uses a greater number of animals and/or higher dose of MH is required.

Oral and intravenous l-[1-13 C]phenylalanine delivery measure similar rates of elimination when gastric emptying and splanchnic extraction are accounted for in adult mixed hounds.

There are few reported estimates of amino acid (AA) kinetics in adult mammals and none exist in adult dogs. The study objectives were to evaluate the use of oral isotope delivery in contrast to the more commonly used intravenous (IV) delivery to estimate AA kinetics in adult dogs and to estimate splanchnic extraction and gastric emptying using a commonly accepted mathematical model. Dogs received 25 × 1/2-hourly meals (13 g/kg BW/day) and either an oral or IV bolus of l-[1-(13) C]Phe (12 mg/kg BW). Blood samples were taken immediately before each feeding. Concentrations of plasma Phe were measured using liquid chromatography-tandem mass spectrometry. There were no differences in baseline plasma Phe concentrations (34 μm ± 0.61), Phe distribution volume, Phe pool size and rate constants between dogs when the tracer was administered IV or orally (p > 0.25). Decay curve for plasma l-[1-(13) C]Phe differed between IV and oral dosing protocols with IV dosing fit best using a two-compartment model. Phe disappeared from plasma at a mean rate of 2.8%/min. Estimates of gastric emptying and splanchnic extraction did not differ based on oral or IV tracer dosing when the decay curves were fit with the two-compartment model (p > 0.40). The half-life for gastric emptying was 18 min, and first-pass Phe extraction by the splanchnic bed was 24% of the dietary Phe. These results suggest that oral isotope dosing can be used as an alternative to IV isotope dosing in studies that utilize a primed, constant dosing approach to measure protein and amino acid kinetics.

Dietary Mannoheptulose Increases Fasting Serum Glucagon Like Peptide-1 and Post-Prandial Serum Ghrelin Concentrations in Adult Beagle Dogs.

Simple Summary There is increased interest in the use of nutraceuticals for weight management in companion animals. A nutraceutical can broadly be considered a food (or a part of) that provides a health benefit. Mannoheptulose (MH), a sugar found in avocados, is being investigated as a nutraceutical for dogs. In this study, dogs fed a diet containing MH had increased concentrations of blood biomarkers related to energy intake. In addition, dogs fed MH were less physically active than dogs fed a control diet. These findings suggest that dietary MH has the ability to alter energy intake and lower daily energy expenditure. Abstract There is a growing interest in the use of nutraceuticals for weight management in companion animals. The purpose of this study was to determine the effects of mannoheptulose (MH), a sugar in avocados that inhibits glycolysis, on energy metabolism in adult Beagle dogs. The study was a double-blind, randomized controlled trial where dogs were allocated to a control (CON, n = 10, 10.1 ± 0.4 kg) or MH containing diet (168 mg/kg, n = 10, 10.3 ± 0.4 kg). Blood was collected after an overnight fast and 1 h post-feeding (week 12) to determine serum satiety related hormones and biochemistry. Resting and post-prandial energy expenditure and respiratory quotient were determined by indirect calorimetry (weeks 4 and 8). Physical activity was measured using an accelerometer (weeks 3, 7, 11). Body composition was assessed using dual X-ray absorptiometry (week 12). MH significantly (p < 0.05) increased fasting serum glucagon-like peptide-1 and post-prandial serum ghrelin. MH tended (p < 0.1) to increase fasting serum gastric inhibitory peptide and decrease physical activity. Together, these findings suggest that dietary MH has the ability to promote satiation and lowers daily energy expenditure.

Calibration and validation of a carbon oxidation system and determination of the bicarbonate retention factor and the dietary phenylalanine requirement, in the presence of excess tyrosine, of adult, female, mixed-breed dogs1,2,3

Carbon oxidation methods have been used as rapid and sensitive methods to determine whole-body AA requirements in multiple species. The objectives of the current studies were to validate complete CO recovery, determine the bicarbonate retention factor, and estimate the Phe requirement, in the presence of excess Tyr, in adult dogs using the direct oxidation technique. In this series of studies, 2 oxidation chambers were constructed and calibrated to ensure accurate collection of breath CO. First, 104.6 ± 7.1% CO was recovered from chambers and suggests that the chambers were appropriately designed for complete and efficient CO recovery. Second, we determined bicarbonate retention in 5 dogs using repeated oral dosing of a bicarbonate tracer (NaHCO) with small meals. At isotopic and physiological steady state, 102.5 ± 2.6% of the delivered NaHCO was recovered in breath. Third, the Phe requirement, when Tyr was supplied in excess, was determined by the rate of appearance of CO in the breath (CO). Dogs ( = 5) were fed test diets with different concentrations of Phe ranging from deficient to excessive for 2 d prior to conducting the tracer studies. The mean Phe requirement (when Tyr was supplied in excess) was 0.535% of diet (upper 95% confidence interval = 0.645% diet) on an as-fed basis or 0.575% of diet (upper 95% confidence interval = 0.694% of diet) on a DM basis and was based on a calculated (modified Atwater calculation) dietary ME density of 3.73 Mcal/kg DM. These data support the use of carbon oxidation methods and oral dosing of isotope to measure whole-body requirements of indispensable AA in adult dogs and suggest the current recommendations may be low.

Effect of graded inclusion of dietary soybean meal on nutrient digestibility, health, and metabolic indices of adult dogs.

Two studies were conducted using adult dogs to evaluate the effect of increasing the inclusion of soybean meal (SBM) in an adult dog food on body composition, hematological and biochemical blood analyses, and total tract nutrient digestibility. Nutritionally complete and balanced diets were formulated with commercial-grade SBM (48% CP) to replace 0, 10, 20, or 30% of the protein provided by dried chicken protein resulting in final SBM inclusion of 0, 6.0, 11.5, and 17.0% (as-fed basis), respectively. In study 1, diets were fed during a 24-wk feeding trial using 36 female (spayed), adult hounds to evaluate food intake, BW, body composition, and blood measurements. There were no diet-related differences in food intake or BW. Body composition responded in a quadratic manner to increased dietary SBM inclusion with the percentage (%) of lean mass responding positively (P < 0.05) and absolute amounts of fat mass and percent body fat responding negatively (P < 0.05). All diagnostic blood components remained within normal physiological ranges for healthy, adult dogs. Serum concentrations of C-reactive protein and IGF-1 were similar among diets. In study 2, diets were evaluated in a digestibility study using 12 adult dogs in a 4 × 4 Latin square design. Increased SBM inclusion was associated with linear increases in the digestibility of CP (P < 0.05) and fat (P < 0.05) and CP retention (P < 0.05). Linear reductions in fecal DM content (P < 0.01) and increased fecal output (P < 0.05) were noted with increased SBM inclusion. All diets were similar in DE and ME content, but a quadratic trend was noted with increased SBM inclusion when DE (P = 0.083) and ME (P = 0.062) were expressed per unit of metabolic body size. Overall, it can be inferred from these results that the partial replacement of dried chicken protein with SBM in a nutritionally complete and balanced diet does not compromise the nutritional status and long-term health of adult dogs.

Plasma Mannoheptulose Kinetics in Adult Domestic Short-Haired Felines

Mannoheptulose (MH), a sugar found in avocados that inhibits glycolysis, has been investigated as a functional feed ingredient for canines. However, no studies have sought to feed MH to felines. The purpose of this study was to assess whether ingested MH appears in peripheral circulation of adult domestic short-hair felines (N = 10, 4.1 ± 0.1 kg, 1.6 y) fed a MH containing diet. The study was designed as a randomized cross-over with each cat receiving dietary treatments, control and MH. Each study period lasted 28 d and a meal challenge was performed on d 28. Felines were fasted overnight, anaesthetized, and a catheter was inserted into the jugular vein for repeated blood sampling. A fasting blood sample was collected six hours after catheter placement. Subsequently, felines were offered their full daily ration of test diet and blood was collected every 2 h during the 24 h post-prandial period for analysis of plasma MH. Ingested MH appeared in the plasma within 2 h of ingestion confirming that dietary MH is absorbed and available for cellular uptake. Circulating MH was cleared from plasma within 24 h of ingestion. The differences in plasma MH kinetics between species are likely attributed to differences in feline carbohydrate metabolism relative to other mammals. No MH was detected in cats fed the control diet. These results suggest that MH is digested, absorbed and available from peripheral circulation in adult cats. Finally, MH remains in circulation longer than in dogs and may suggest that cats would only need a lower dose or fewer doses of MH per day.