Influence of prolonged fasting in the dog on glucose turnover and blood metabolites.

Glucose turnover and blood metabolites were measured in eight adult female beagles in the fed state, at 1 day of fasting, and at 7, 14, and 21 days of fasting. Glucose utilization decreased significantly from 1 to 7 days of fasting, but remained constant from 7 to 21 days, while blood ketones and plasma free fatty acids rose significantly during the same period. Plasma alanine, serine, and glycine fell with fasting, with the greatest decrease in alanine levels occurring between 7 to 14 days. Plasma branched chain amino acids rose significantly with fasting. It was concluded that the shifts in plasma metabolites and decreased glucose utilization could be indicative of decreased energy demands of the fasting dogs and/or a shift in substrate utilization with progressive fasting.