Metabolic response to a ketogenic breakfast in the healthy elderly.
OBJECTIVE
To determine whether the metabolism of glucose or ketones differs in the healthy elderly compared to young or middle-aged adults during mild, short-term ketosis induced by a ketogenic breakfast.


METHODS
Healthy subjects in three age groups (23 +/- 1, 50 +/- 1 and 76 +/- 2 y old) were given a ketogenic meal and plasma beta -hydroxybutyrate, glucose, insulin, triacylglycerols, total cholesterol, non-esterified fatty acids and breath acetone were measured over the subsequent 6 h. Each subject completed the protocol twice in order to determine the oxidation of a tracer dose of both carbon-13 (13C) glucose and 13C-beta-hydroxybutyrate. The tracers were given separately in random order. Apolipoprotein E genotype was also determined in all subjects.


RESULTS
Plasma glucose decreased and beta-hydroxybutyrate, acetone and insulin increased similarly over 6 h in all three groups after the ketogenic meal. There was no significant change in cholesterol, triacylglycerols or non-esterified fatty acids over the 6 h. 13C-glucose and 13C-beta-hydroxybutyrate oxidation peaked at 2-3 h postdose for all age groups. Cumulative 13C-glucose oxidation over 24 h was significantly higher in the elderly but only versus the middle-aged group. There was no difference in cumulative 13C-beta-hydroxybutyrate oxidation between the three groups. Apolipoprotein E (epsilon 4) was associated with elevated fasting cholesterol but was unrelated to the other plasma metabolites.


CONCLUSIONS
Elderly people in relatively good health have a similar capacity to produce ketones and to oxidize 13C-beta-hydroxybutyrate as middle-aged or young adults, but oxidize 13C-glucose a little more rapidly than healthy middle-aged adults.
Freemantle
E
E
Research Center on Aging, Health, and Social Services Center, Sherbrooke University Geriatrics Institute, 1036 Belvédère S., Sherbrooke, QC, Canada.
Vandal
M
M
Tremblay Mercier
J
J
Plourde
M
M
Poirier
J
J
Cunnane
S C
SC
D020155:3-Hydroxybutyric Acid / Q000378:metabolism*; D000096:Acetone / Q000097:blood; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology*; D053327:Apolipoprotein E4 / Q000097:blood*; D001053:Apolipoproteins; D001786:Blood Glucose / Q000378:metabolism*; D002247:Carbon Isotopes; D004032:Diet; D006801:Humans; D007328:Insulin / Q000097:blood; D007657:Ketone Bodies / Q000378:metabolism*; D007662:Ketosis / Q000378:metabolism*; D008875:Middle Aged; D010084:Oxidation-Reduction; D055815:Young Adult
D053327:Apolipoprotein E4; D001053:Apolipoproteins; D001786:Blood Glucose; D002247:Carbon Isotopes; D007328:Insulin; D007657:Ketone Bodies; D000096:Acetone; D020155:3-Hydroxybutyric Acid