Publications by authors named "Mark Tetrick"

8 Publications

  • Page 1 of 1

What Constitutes a Gluconeogenic Precursor?

J Nutr 2020 09;150(9):2239-2241

Department of Animal Science, North Carolina State University, Raleigh, NC, USA.

A gluconeogenic precursor is a biochemical compound acted on by a gluconeogenic pathway enabling the net synthesis of glucose. Recognized gluconeogenic precursors in fasting placental mammals include glycerol, lactate/pyruvate, certain amino acids, and odd-chain length fatty acids. Each of these precursors is capable of contributing net amounts of carbon to glucose synthesis via the tricarboxylic acid cycle (TCA cycle) because they are anaplerotic, that is, they are able to increase the pools of TCA cycle intermediates by the contribution of more carbon than is lost via carbon dioxide. The net synthesis of glucose from even-chain length fatty acids (ECFAs) in fasting placental mammals, via the TCA cycle alone, is not possible because equal amounts of carbon are lost via carbon dioxide as is contributed from fatty acid oxidation via acetyl-CoA. Therefore, ECFAs do not meet the criteria to be recognized as a gluconeogenic precursor via the TCA cycle alone. ECFAs are gluconeogenic precursors in organisms with a functioning glyoxylate cycle, which enables the net contribution of carbon to the intermediates of the TCA cycle from ECFAs and the net synthesis of glucose. The net conversion of ECFAs to glucose in fasting placental mammals via C3 metabolism of acetone may be a competent though inefficient metabolic path by which ECFA could be considered a gluconeogenic precursor. Defining a substrate as a gluconeogenic precursor requires careful articulation of the definition, organism, and physiologic conditions under consideration.
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September 2020

Octanoate and nonaoate oxidation increases 50-80% over the first two days of life in piglet triceps brachii and gracilis muscle strips.

J Nutr 2012 Jun 18;142(6):999-1003. Epub 2012 Apr 18.

Department of Nutritional Sciences, University of Wisconsin, Madison, WI, USA.

An in vitro muscle strip incubation system was developed to measure the rate of catabolism of 1 mmol/L [1-(14)C]octanoate, 1 mmol/L [1-(14)C]nonanoate, 1 mmol/L [9-(14)C]nonanoate, and 10 mmol/L [U-(14)C]glucose by measuring the recovery of (14)CO(2). Muscle strips (13 mm × 1.5 mm, ~50 mg) were isolated from triceps brachii and gracilis muscles of newborn and 2-d-old, small (<950 g) and large (>1450 g) piglets. The position of the (14)C label in the substrate affected the rate and amount of recovery in (14)CO(2). Therefore, comparisons were made between age groups (0 vs. 2 d old) within substrates but limited across substrates to comparisons of [1-(14)C]-labeled fatty acids. The medium-chain fatty acid (MCFA) oxidation rates [pmol/(h · mg)] in muscle strips isolated from piglets from the 2 weight groups (<950 and >1450 g) did not differ (P > 0.99), there was a trend towards a difference between triceps brachii and gracilis muscle (P = 0.09; data not shown), and there were no significant interactions involving pig weight or muscle type; therefore, results were pooled across these factors. During the first 2 d of life, MCFA oxidation [pmol/(h • · mg muscle strip)] increased (P < 0.05) 50-80%, but the glucose oxidation rate did not change (P > 0.82). By d 2, the oxidation rate of nonanoate as represented by the one carbon was 25% greater than for octanoate (P < 0.05). The conversion of [9-(14)C]nonanoate to (14)CO(2) indicated that muscle had the capacity to oxidize the propionyl-CoA produced by β-oxidation of nonanoate and that odd-chain C-9 MCFA provided anabolic carbon to the citric acid cycle.
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June 2012

Blood D-(-)-3-hydroxybutyrate concentrations after oral administration of trioctanoin, trinonanoin, or tridecanoin to newborn rhesus monkeys (Macaca mulatta).

Comp Med 2010 Dec;60(6):486-90

Department of Nutritional Sciences, University of Wisconsin, Madison, USA.

Premature newborn infants are born with limited stores of glycogen and fat. Energy, such as medium-chain triglycerides (MCT), which can spare the use of body protein as metabolic energy, may be beneficial. This study compares MCT containing C8, C9, or C10 fatty acids as oral sources of energy for newborn rhesus monkeys (Macaca mulatta). On day 1 of life, 4 groups of 5 monkeys were given a single dose of water or MCT by nasogastric tube. The dose provided approximately 80% of the expected energy requirement. Plasma C8:0, C9:0, and C10:0 fatty acids and whole-blood D-(-)-3-hydroxybutyrate (3HB) concentrations were measured at 0, 1, and 3 h after dosing. Concentrations of free fatty acids (C8, C9, or C10) and ketone (3HB) increased with time after the dose. At 1 and 3 h, concentrations of C8 and C9 did not differ, but C9 was greater than C10. At 1 h, blood 3HB concentrations due to C8 triglyceride were higher than C9 or C10 (503 versus 174 and 225 μmol/L respectively). As MCT chain length increased from C8 to C10, blood concentration of 3HB decreased. Odd-chain MCT (C9 versus C8) resulted in lower whole-blood ketone (3HB), perhaps due to C9 metabolism or the rate of release or uptake of fatty acids. These results have implications for the use of MCT in nutritional supplements for preterm infants.
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December 2010

Time trends and risk factors for diabetes mellitus in cats presented to veterinary teaching hospitals.

J Feline Med Surg 2007 Oct 20;9(5):351-8. Epub 2007 Apr 20.

Department of Veterinary Clinical Sciences, Purdue University, West Lafayette, IN 47907-2026, USA.

Veterinary Medical Data Base records of cats with diabetes mellitus (DM) from 1970 through 1999 were reviewed to identify trends in hospital prevalence of DM and potential host risk factors. Hospital prevalence increased from eight cases per 10,000 in 1970 to 124 per 10,000 in 1999 (P < 0.001). Case fatality percent at first visit decreased from 40% to 10% (P < 0.001). Hospital prevalence increased in all age groups (P < 0.002). There was no apparent seasonal pattern in hospital prevalence. Significant risk factors included male gender, increasing age for both genders (P < 0.001), increasing weight for males (P < 0.001), and mixed vs pure breed for females (P = 0.006).
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October 2007

Effects of caloric restriction and a moderate or intense physiotherapy program for treatment of lameness in overweight dogs with osteoarthritis.

J Am Vet Med Assoc 2006 Dec;229(11):1756-60

Institute of Nutrition, Movement Science Group Vienna (Project Group Dog), Veterinary University of Vienna, Veterinärplatz 1, A 1210 Vienna, Austria.

Objective: To evaluate the effects of a weight reduction program combined with a basic or more complex physical therapy program including transcutaneous electric nerve stimulation on lameness in overweight dogs with osteoarthritis.

Design: Nonblinded prospective randomized clinical trial. Animals-29 adult overweight or obese dogs with a body condition score of 4/5 or 5/5 and clinical and radiographic signs of osteoarthritis.

Procedures: A weight-loss program was initiated for all dogs. One group received caloric restriction and a home-based physical therapy program. The other group received the identical dietetic protocol and an intensive physical therapy program including transcutaneous electrical nerve stimulation. Lameness was assessed clinically and by kinetic gait analysis on a treadmill with 4 force plates to measure symmetry of ground reaction forces (GRFs) of the affected and contralateral limbs in bimonthly intervals for 6 months.

Results: Significant weight loss was achieved in both groups; however, greater weight reduction was attained by dogs treated with caloric restriction and intensive physiotherapy. Mobility and symmetry indices of GRFs were improved after 6 months; the best outcome was detected in the group receiving energy restriction combined with intensive physical therapy.

Conclusions And Clinical Relevance: Caloric restriction combined with intensive physical therapy improved mobility and facilitated weight loss in overweight dogs. The combination of dietetic and physical therapy may help to improve the health status more efficiently than dietetic treatment alone.
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December 2006

Comparison of various doses of carbon 13-labeled aminopyrine for a carbon 13-labeled aminopyrine demethylation blood test in healthy dogs.

Am J Vet Res 2006 Jul;67(7):1110-4

Gastrointestinal Laboratory, College of Veterinary Medicine, Texas A&M University, College Station, 77843, USA.

Objective: To determine an optimal dose of carbon 13 ((13)C)-labeled aminopyrine for use in a (13)C-aminopyrine demethylation blood test in healthy dogs.

Animals: 9 adult dogs.

Procedures: Food was withheld from each dog for 12 hours. A 2-mL baseline blood sample was obtained from each dog and placed into an evacuated tube containing sodium heparin. Carbon 13-labeled aminopyrine was administered IV at doses of 1, 2, 5, or 10 mg/kg. Additional blood samples (2 mL) were obtained and placed into evacuated tubes containing sodium heparin 30, 45, 60, and 75 minutes after (13)C-aminopyrine administration. Hydrochloric acid was used to extract CO(2) from blood samples. The extracted gas was analyzed by fractional mass spectrometry to determine the percentage dose of (13)C administered as (13)C-aminopyrine and recovered in extracted gas (PCD).

Results: Gross evidence of clinical adverse effects was not detected in any dog after administration of (13)C-aminopyrine. The mean coefficient of variation (CV) for PCD was significantly lower than the mean CV for the summation of PCD values up to a given sampling time (CUMPCD). Mean PCD values among the 4 doses for each sample time were not significantly different. Administration of (13)C-aminopyrine at a dose of 2 mg/kg resulted in the lowest interindividual variability.

Conclusions And Clinical Relevance: The PCD is superior to CUMPCD for the quantification of aminopyrine demethylation. Administration of (13)C-(13)C-aminopyrine at a dose of 2 mg/kg is appropriate for use in the (13)C-aminopyrine demethylation blood test in healthy dogs.
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July 2006

Kinetic analysis of demethylation of 13C-aminopyrine in healthy dogs.

Am J Vet Res 2004 Feb;65(2):159-62

Gastrointestinal Laboratory, College of Veterinary Medicine, Texas A&M University, College Station, TX 77843, USA.

Objective: To describe the kinetics of demethylation of 13C-aminopyrine in healthy dogs for use in determining the most appropriate time for collection of blood samples for a 13C-aminopyrine demethylation blood test for evaluation of hepatic function.

Animals: 9 healthy dogs.

Procedures: A 2-mL baseline blood sample was collected into an evacuated heparinized tube, and 13C-aminopyrine was administered to each dog (2 mg/kg, IV). Additional 2-mL blood samples were collected 15, 30, 45, 60, 75, 90, 105, 120, 135, 150, 180, 240, 300, and 360 minutes after 13C-aminopyrine administration. The CO2 was extracted from blood samples by addition of a strong acid, and the percentage dose of 13CO2 (PCD) in the extracted gas was determined by fractional mass spectrometry.

Results: No dogs had gross evidence of adverse effects, and all had an increase in PCD after IV administration of 13C-aminopyrine. The PCD had the least variability among 5 variables used to evaluate hepatic demethylating capacity. Peak PCD was detected at 30 minutes in 1 dog, 45 minutes in 5 dogs, 60 minutes in 2 dogs, and 75 minutes in 1 dog. The mean PCD for the 9 dogs peaked at 45 minutes after 13C-aminopyrine administration.

Conclusions And Clinical Relevance: PCD appears to be the preferable variable for evaluation of hepatic demethylating capacity. Intravenous administration of 13C-aminopyrine leads to a consistent increase in PCD. Mean PCD peaked 45 minutes after administration, suggesting that blood sample collection 45 minutes after 13C-aminopyrine administration may be appropriate for use in estimating hepatic demethylating capacity.
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February 2004

Estimation of iodine status in cats.

J Nutr 2002 06;132(6 Suppl 2):1751S-3S

Institute for Animal Physiology, Physiological Chemistry and Animal Nutrition, Ludwig-Maximilians-University Munich, Munich, Germany.

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June 2002