Metabolic effects of diets differing in glycaemic index depend on age and endogenous glucose-dependent insulinotrophic polypeptide in mice.
OBJECTIVE
High- vs low-glycaemic index (GI) diets unfavourably affect body fat mass and metabolic markers in rodents. Different effects of these diets could be age-dependent, as well as mediated, in part, by carbohydrate-induced stimulation of glucose-dependent insulinotrophic polypeptide (GIP) signalling.


METHODS
Young-adult (16 weeks) and aged (44 weeks) male wild-type (C57BL/6J) and GIP-receptor knockout (Gipr ( -/- )) mice were exposed to otherwise identical high-carbohydrate diets differing only in GI (20-26 weeks of intervention, n = 8-10 per group). Diet-induced changes in body fat distribution, liver fat, locomotor activity, markers of insulin sensitivity and substrate oxidation were investigated, as well as changes in the gene expression of anorexigenic and orexigenic hypothalamic factors related to food intake.


RESULTS
Body weight significantly increased in young-adult high- vs low-GI fed mice (two-way ANOVA, p < 0.001), regardless of the Gipr genotype. The high-GI diet in young-adult mice also led to significantly increased fat mass and changes in metabolic markers that indicate reduced insulin sensitivity. Even though body fat mass also slightly increased in high- vs low-GI fed aged wild-type mice (p < 0.05), there were no significant changes in body weight and estimated insulin sensitivity in these animals. However, aged Gipr ( -/- ) vs wild-type mice on high-GI diet showed significantly lower cumulative net energy intake, increased locomotor activity and improved markers of insulin sensitivity.


CONCLUSIONS
The metabolic benefits of a low-GI diet appear to be more pronounced in younger animals, regardless of the Gipr genotype. Inactivation of GIP signalling in aged animals on a high-GI diet, however, could be beneficial.
Isken
F
F
Department of Clinical Nutrition, German Institute of Human Nutrition, Potsdam-Rehbruecke, Germany.
Weickert
M O
MO
Tschöp
M H
MH
Nogueiras
R
R
Möhlig
M
M
Abdelrahman
A
A
Klaus
S
S
Thorens
B
B
Pfeiffer
A F
AF
D000367:Age Factors; D000818:Animals; D001786:Blood Glucose / Q000032:analysis; D001823:Body Composition; D002151:Calorimetry; D004032:Diet; D002149:Energy Intake / Q000502:physiology; D005749:Gastric Inhibitory Polypeptide / Q000502:physiology*; D005951:Glucose Tolerance Test; D038321:Glycemic Index; D007328:Insulin / Q000097:blood; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D011964:Receptors, Gastrointestinal Hormone / Q000235:genetics / Q000502:physiology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014280:Triglycerides / Q000378:metabolism
D001786:Blood Glucose; D007328:Insulin; D011964:Receptors, Gastrointestinal Hormone; D014280:Triglycerides; D005749:Gastric Inhibitory Polypeptide; C041086:gastric inhibitory polypeptide receptor