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  • Author or Editor: Joe D. Pagan x
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Abstract

Objective—To evaluate effects of fats with odd and even numbers of carbon atoms on muscle metabolism in exercising horses with polysaccharide storage myopathy (PSSM).

Animals—8 horses with PSSM (6 females and 2 males; mean ± SD age, 6.3 ± 3.9 years).

Procedures—Isocaloric diets (grain, triheptanoin, corn oil, and high-fat, low-starch [HFLS] feed) were fed for 3 weeks each; horses performed daily treadmill exercise. Grain was fed to establish an exercise target, and HFLS feed was fed as a negative control diet. Daily plasma samples were obtained. For each diet, a 15-minute exercise test was performed, and gluteus medius muscle specimens and blood samples were obtained before and after exercise.

Results—Feeding triheptanoin, compared with the corn oil diet, resulted in exercise intolerance; higher plasma creatine kinase (CK) activity and concentrations of C3:0- and C7:0-acylcarnitine and insulin; and lower concentrations of nonesterified fatty acids (NEFA) and C16:0-, C18:1-, and C18:2-acylcarnitine, without changes in concentrations of plasma glucose or resting muscle substrates and metabolites. Feeding grain induced higher CK activity and insulin concentrations and lower NEFA concentrations than did corn oil or HFLS feed. Feeding grain induced higher glucose concentrations than did triheptanoin and corn oil. In muscle, feeding grain resulted in lower glucose-6-phosphate, higher citrate, and higher postexercise lactate concentrations than did the other diets.

Conclusions and Clinical Relevance—Triheptanoin had detrimental effects, reflecting decreased availability of NEFA, increased insulin stimulation of glycogen synthesis, and potential inhibition of lipid oxidation. Long-chain fats are the best dietetic for PSSM.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To compare effects of corn oil or a 7-carbon fat (triheptanoin) on acylcarnitine, lipid, and carbohydrate metabolism in plasma or muscle of exercising horses.

Animals—8 Thoroughbred geldings.

Procedures—Horses received isocaloric diets containing 650 mL of oil (triheptanoin or corn oil)/d for 18 or 25 days in a crossover design with a 26-day washout period. On day 17 or 24 of each feeding period, the respective oil (217 mL) was nasogastrically administered; 120 minutes later, horses performed a 90-minute submaximal exercise test (SET). Blood and muscle samples were obtained before oil administration and immediately before (blood only), during (blood only), immediately after, and 24 hours after SETs.

Results—Compared with values before oil administration, triheptanoin administration increased plasma insulin and C7:0-, C5:0- and C3:0-acylcarnitine concentrations, whereas corn oil administration increased plasma NEFA concentrations. During SETs, plasma C7:0-, C5:0-, and C3:0-acylcarnitine concentrations were higher when triheptanoin, rather than corn oil, was administered to horses. Plasma glucose, NEFA, and C2:0-, C18:1-, and C18:2-acylcarnitine concentrations increased during SETs similarly for both oils. Respiratory quotient and muscle lactate, citrate, malate, glycogen, and ATP concentrations changed similarly from before to after SETs for both oils. Compared with muscle concentrations immediately after SETs, those for glucose-6-phosphate and citrate 24 hours after SETs were lower and for glycogen were similar to values before SETs.

Conclusions and Clinical Relevance—Fatigue was not associated with depletion of citric acid cycle intermediates for either oil. Triheptanoin induced a significantly higher insulin secretion and did not appear to enhance muscle glycogen repletion.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To determine daily variation in urinary clearance and fractional excretion (FE) of electrolytes and minerals within and between horses and to compare volumetric and single-sample urine collection for determining FE values of diets with a range of dietary cation-anion balance (DCAB).

Animals—5 Thoroughbred and 6 mixed-breed mares.

Procedure—3 isocaloric diets with low, medium, and high DCAB values (85, 190, and 380 mEq/kg of dry matter, respectively) were each fed for 14 days. Daily blood samples, single urine samples collected by using a urinary catheter (5 mares), and volumetric urine collections (6 mares) were obtained during the last 72 hours of each diet.

Results—Urine and plasma pH values, plasma concentrations, and FE values of sodium, chloride, potassium, magnesium, phosphorus, and calcium were altered by varying the DCAB. Noticeable variation in clearance and FE values was detected within horses from day-to-day on the same diet as well as between horses. Fractional excretion values were not significantly different between single-sample and volumetric methods, except for magnesium in the high DCAB diet. Volumetric and single-sample collections revealed similar patterns of change in urinary FE values with varying DCAB, except for calcium and magnesium.

Conclusions and Clinical Relevance—Substantial variation in clearance and FE of electrolytes and minerals are evident within horses between 24-hour periods as well as between horses fed a specific diet. Three daily urine samples provide similar information regarding dietary-induced changes in clearance and FE values (excluding calcium and magnesium) as that obtained by volumetric urine collection. (Am J Vet Res 2003;64:284–291)

Full access
in American Journal of Veterinary Research

Abstract

Objective—To determine whether plasma, urine, and fecal electrolyte and mineral concentrations differ between clinically normal horses and Thoroughbreds with recurrent exertional rhabdomyolysis (RER) after consumption of diets varying in cation-anion balance.

Animals—5 Thoroughbred mares with RER and 6 clinically normal mixed-breed mares.

Procedure—Each of 3 isocaloric diets designated as low, medium, and high on the basis of dietary cationanion balance (DCAB) values of 85, 190, and 380, respectively, were fed to horses for 14 days. During the last 72 hours, 3 horses with RER and 3 control horses had daily urine and fecal samples obtained by total 24-hour collection. Remaining horses had urine samples collected daily by single catheterization.

Results—For each diet, no differences existed between horses with RER and control horses in plasma pH, electrolyte concentrations, and creatine kinase activity or in urine pH and renal fractional excretion (FE) values. Plasma pH, strong ion difference, bicarbonate and total carbon dioxide concentrations, and base excess decreased and plasma chloride and ionized calcium concentrations increased with decreasing DCAB. Urine pH decreased with decreasing DCAB. The FE of chloride and phosphorus were greatest for horses fed the low diet. The FE values for all electrolytes exept magnesium did not differ between urine samples obtained by single catheterization and total 24-hour collection. Daily balance of calcium, phosphorus, sodium, chloride, and potassium did not differ significantly among horses fed the various diets.

Conclusions—In clinically normal horses and in horses with RER, the DCAB strongly affects plasma and urine pH and the FE of sodium, potassium, chloride, and phosphorus. (Am J Vet Res 2002;63:1053–1060)

Full access
in American Journal of Veterinary Research