Insulin and Ketone Responses to Ingestion of Medium and Long-chain Triglycerides in Man

A B S T R A C T The effects of a fat meal upon plasma insulin, glucagon, and glucagon-like immunoreactivity (GLI) have been studied in conscious dogs and in human volunteers. In dogs the intraduodenal instillation of 10 g/kg of peanut oil was accompanied by increases in the mean plasma levels of all three polypeptides that averaged 5 ytU/ml, 107 pg/ml, and 2.1 ng/ml, respectively.3 g/kg of peanut oil, when emulsified with egg yolk, elicited a much greater response of the three hormones, and a physiologic dose of 1 g/kg in emulsified form also caused a significant rise in glucagon and GLI. The islet cell hormone response was not ascribable to chylomicronemia since intravenous infusion of canine chyle failed to stimulate glucagon secretion; moreover, in dogs with a thoracic duct fistula in which chyle was excluded from the circulation, the intraduodenal administration of a fat meal elicited the normal islet cell hormone response, as well as a rise in GLI. 10 g/kg of mediumchain triglycerides failed to elicit these same responses.In six human volunteers the oral administration of 3 g/kg peanut oil was accompanied by increments of 2 AU/ml, 26 pg/ml, and 1.5 ng/ml in the mean levels of insulin, glucagon, and GLI. The changes in insulin and glucagon in man were neither statistically significant nor biologically impressive.It is concluded that in dogs fat absorption is accompanied by prompt and substantial increases in plasma glucagon and GLI and a small transient rise in insulin. The evidence favors an enterogenic signal to the islets of Langerhans rather than their stimulation by chylomi-

supporting

confidence: 82%

The Effects of Triglyceride Absorption upon Glucagon, Insulin, and Gut Glucagon-Like Immunoreactivity

Böttger¹,

Dobbs²,

Faloona³

et al. 1973

“…However, the curve appears to have the characteristics of a sigmoid relationship; further studies are required to define the association more definitively. The finding that the insulinotropic effect of ingested gltucose is absent during euglycemia is particularly intriguing in light of previous observations that fat ingestion, a potent stimuilus to GIP release (14), is accompanied by either no insulin release (24,37) or by a very small increase of about 4 AU/ml (15,23,(38)(39)(40), unless hyperglycemia is present. On the other hand, an insulinotropic effect of GIP independent of hyperglycemia has been reported in the dog (41).…”

Section: Discussionmentioning

confidence: 90%

Oral Glucose Augmentation of Insulin Secretion

Andersen¹,

Elahi²,

Brown³

et al. 1978

220

A B S T R A C T Gastric inhibitory polypeptide, or GIP, has been postulated as the major enteric hormonal mediator of insulin release. The release of immunoreactive GIP (IR-GIP) after oral glucose and its role in insulin release was studied in normal men by the glucose clamp technique. In 24 subjects studied with the hyperglycemic clamp, blood glucose was maintained at 125 mg/dl above basal for 2 h via a primedcontinuous IV glucose infusion coupled to a servo-controlled negative feedback system. 40 g glucose per m2 surface area was ingested at 60 min, and the blood glucose was maintained at the steady-state hyperglycemic level. Plasma IR-GIP and insulin (IRI) levels were measured throughout the 2-h period. IR-GIP levels changed little when IV glucose alone was given; the mean basal value was 305+±34 (SEM) pg/ml. After oral glucose, IR-GIP levels began to rise within 10 min and reached a peak within 40 min of 752±105 pg/ml. Plasma IRI responded initially to the square wave of hyperglycemia in the typical biphasic pattern. After oral glucose, plasma IRI levels rose strikingly above the elevated levels produced by hyperglycemia alone, reaching a peak of 170±15 ,tU/ml within 45 min. The time course of the rise in IR-GIP and IRI was nearly identical.To assess whether the maintenance of euglycemia would affect this process, the euglycemic clamp wasThis work was presented in part at the Eastern Section

“…High fasting triglyceride levels might then be expected to occur together with increased secretion of insulin, though the relationship need not be a causal one. Finally, there is the possibility that plasma triglyceride may stimulate insulin secretion; ingestion of triglycerides has been shown to stimulate insulin secretion in man (29).…”

Section: Discussionmentioning

confidence: 99%

Diurnal fluctuations in triglyceride, free fatty acids, and insulin during sucrose consumption and insulin infusion in man

Barter¹,

Carroll²,

Nestel³

1971

A B S T R A C T Serial changes in circulating triglyceride, free fatty acids (FFA), insulin, and glucose have been measured in human subjects fed sucrose as the sole source of calories for 2-or 3-day periods. The sucrose was given either during the day with overnight fasting (19 subjects) or as continual 3-hour meals during the day and night (seven subjects). Insulin was infused overnight in five additional subjects on the day-feeding regimen to determine the effect on triglyceride concentration.The concentration of triglyceride increased during the study in all subjects, but there was a clear diurnal pattern in the response which was present even in the continual feeding studies. The rise in triglyceride occurred mainly overnight, and during the day there was frequently a fall in the concentration. The overnight increase was significantly less when insulin was infused. There were also diurnal fluctuations in FFA and insulin in both daytime and continual feeding regimens. The plasma FFA, like triglyceride, rose during the night and fell during the day while the insulin rose during the day and fell overnight.Separate statistical analysis of the daytime and overnight changes revealed that the changes in triglyceride were significantly but negatively correlated with changes in insulin during both periods. The changes in triglyceride and FFA were positively correlated during the day but not significantly related during the night. The data show that when sucrose is eaten for 2 or 3 days, there is a general increase in triglyceride concentration upon which are superimposed major diurnal fluctuations in the concentrations of triglyceride, insulin, and FFA. It is suggested that the highly significant inverse relationship between changes in triglyceride and insulin may be mediated through an effect of insulin on triglyceride removal.