Effect of Level of Intake and Physical Form of the Diet on Plasma Glucose Concentration and Volatile Fatty Acid Absorption in Ruminants

Plasma free fatty acid (FFA) concentration falls when an infusion of glucagon-free insulin is initiated in the normal unanesthetized dog in the postabsorptive state. Using C14 palmitate it was shown that the lowered FFA concentration is caused by decreased FFA production. This decreased FFA production accompanies increased glucose uptake by the tissues as demonstrated using C14 glucose. During slow insulin infusion, when plasma glucose concentration remains above 75 mg%, FFA production and concentration remain low. However, during more rapid insulin infusion, when plasma glucose concentration falls below 50 mg%, the initially lowered FFA production rebounds and FFA production and concentration exceed the preinsulin level. Glucose uptake always remains elevated during insulin infusion. Dibenzyline or guanethidine pretreatment blocks the rebound in FFA production. Thus decreased FFA production, due presumably to decreased FFA release by adipose tissue because of insulin-stimulated glucose uptake, can be overpowered by a sympatho-adrenal response to hypoglycemia during a continued infusion of insulin and a resulting continued increased glucose uptake.

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The effects of a ration change from a total mixed ration to pasture on rumen fermentation, volatile fatty acid absorption characteristics, and morphology of dairy cows

Journal of Dairy Science ◽

10.3168/jds.2015-10450 ◽

2016 ◽

Vol 99 (5) ◽

pp. 3549-3565 ◽

Cited By ~ 14

Author(s):

M. Schären ◽

G.M. Seyfang ◽

H. Steingass ◽

K. Dieho ◽

J. Dijkstra ◽

...

Keyword(s):

Fatty Acid ◽

Dairy Cows ◽

Volatile Fatty Acid ◽

Rumen Fermentation ◽

Total Mixed Ration ◽

Acid Absorption ◽

Fatty Acid Absorption ◽

Absorption Characteristics

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Influence of fasting on glycogen depletion in rats during exercise

Journal of Applied Physiology ◽

10.1152/jappl.1983.55.3.830 ◽

1983 ◽

Vol 55 (3) ◽

pp. 830-833 ◽

Cited By ~ 37

Author(s):

G. L. Dohm ◽

E. B. Tapscott ◽

H. A. Barakat ◽

G. J. Kasperek

Keyword(s):

Fatty Acid ◽

Free Fatty Acid ◽

Plasma Glucose ◽

Muscle Glycogen ◽

Glucose Concentration ◽

Plasma Glucose Concentration ◽

Control Group ◽

Glycogen Depletion ◽

Ad Libitum ◽

Beta Hydroxybutyrate

We recently observed that a 24-h fasted group of rats could run longer than an ad libitum fed control group before becoming exhausted. Because of the demonstrated importance of glycogen levels and free fatty acid availability during endurance exercise, we have investigated several parameters of carbohydrate and lipid metabolism in exercised and nonexercised rats that were either fed ad libitum or fasted for 24 h. A 24-h fast depleted liver glycogen, lowered plasma glucose concentration, decreased muscle glycogen levels, and increased free fatty acid and beta-hydroxybutyrate concentrations in plasma. During exercise the fasted group had lower plasma glucose concentration, higher plasma concentration of free fatty acids and beta-hydroxybutyrate, and a lower muscle glycogen depletion rate than did the ad libitum fed group. Since fasted rats were able to continue running even when plasma glucose had dropped to levels lower than those of fed-exhausted rats, it seems unlikely that blood glucose level, per se, is a factor in causing exhaustion. These results suggest that fasting increases fatty acid utilization during exercise and the resulting “glycogen sparing” effect may result in increased endurance.

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