Role of FFA-glucose cycle in glucoregulation during exercise in total absence of insulin.
Muscle contraction in vitro increases glucose uptake (GU), independent of insulin, but in vivo, the exercise-induced increase in GU is impaired in insulin-deficient diabetic dogs. We wished to determine whether, in vivo, suppression of the free fatty acid (FFA)-glucose cycle with methylpalmoxirate (MP, inhibitor of FFA oxidation) alone or combined with propranolol (PRO, beta-blocker) could improve GU during exercise in the absence of insulin. We performed four groups of exercise experiments (6 km/h, 10% slope) in depancreatized insulin-deprived dogs: 1) control (n = 6); 2) MP treated (5 oral doses of 10 mg/kg, twice daily, n = 6); 3) treated with MP+octanoate (OCT; oxidation unaffected by MP, 27 mumol.kg-1.min-1 iv during exercise; n = 5); and 4) MP+PRO treated (5 micrograms.kg-1.min-1 iv during exercise, n = 6). MP abolished ketosis (inhibition of hepatic FFA oxidation), decreased basal glucose production (GP), and increased metabolic clearance of glucose (MCR). During exercise, MP attenuated the increment in GP (P < 0.01), which was reversed by OCT. MP did not affect the exercise-induced increase in GU and MCR. With MP+PRO, FFAs decreased and lactate did not rise during exercise. GP was not further suppressed, but GU and MCR were increased (P < 0.01) to 89 and 31% of normal, respectively. In insulin-deprived depancreatized dogs, glucose cycling was increased to a greater extent than GP, as in type II diabetes. By the end of exercise, glucose cycling increased (P < 0.05), but to a similar extent as GP.(ABSTRACT TRUNCATED AT 250 WORDS)
Yamatani
K
K
Department of Physiology, University of Toronto, Women's College Hospital, Ontario, Canada.
Shi
Z Q
ZQ
Giacca
A
A
Gupta
R
R
Fisher
S
S
Lickley
H L
HL
Vranic
M
M
D000818:Animals; D001786:Blood Glucose / Q000032:analysis; D004285:Dogs; D005230:Fatty Acids, Nonesterified / Q000378:metabolism*; D005947:Glucose / Q000378:metabolism*; D006728:Hormones / Q000097:blood; D007328:Insulin / Q000502:physiology*; D008297:Male; D010180:Pancreatectomy; D005082:Physical Exertion; D012146:Rest
D001786:Blood Glucose; D005230:Fatty Acids, Nonesterified; D006728:Hormones; D007328:Insulin; D005947:Glucose