Glucose tolerance, lipids, and GLP-1 secretion in JCR:LA-cp rats fed a high protein fiber diet.
BACKGROUND
We have shown that individually, dietary fiber and protein increase secretion of the anorexigenic and insulinotropic hormone, glucagon-like peptide-1 (GLP-1).


OBJECTIVE
Our objective was to combine, in one diet, high levels of fiber and protein to maximize GLP-1 secretion, improve glucose tolerance, and reduce weight gain.


METHODS
Lean (+/?) and obese (cp/cp) male James C Russell corpulent (JCR:LA-cp) rats lacking a functional leptin receptor were fed one of four experimental diets (control, high protein (HP), high fiber (HF, prebiotic fiber inulin), or combination (CB)) for 3 weeks. An oral glucose tolerance test (OGTT) was performed to evaluate plasma GLP-1, insulin and glucose. Plasma lipids and intestinal proglucagon mRNA expression were determined.


RESULTS
Energy intake was lower with the HF diet in lean and obese rats. Weight gain did not differ between diets. Higher colonic proglucagon mRNA in lean rats fed a CB diet was associated with higher GLP-1 secretion during OGTT. The HP diet significantly reduced plasma glucose area under the curve (AUC) during OGTT in obese rats, which reflected both an increased GLP-1 AUC and higher fasting insulin. Diets containing inulin resulted in the lowest plasma triglyceride and total cholesterol levels.


CONCLUSIONS
Overall, combining HP with HF in the diet increased GLP-1 secretion in response to oral glucose, but did not improve glucose tolerance or lipid profiles more than the HF diet alone did. We also suggest that glycemic and insulinemic response to prebiotics differ among rat models and future research work should examine their role in improving glucose tolerance in diet-induced vs. genetic obesity with overt hyperleptinemia.
Reimer
Raylene A
RA
Faculties of Kinesiology and Medicine, Department of Biochemistry and Molecular Biology, University of Calgary, Calgary, Alberta, Canada. reimer@ucalgary.ca
Russell
James C
JC
D000818:Animals; D001786:Blood Glucose / Q000378:metabolism*; D001835:Body Weight / Q000187:drug effects / Q000502:physiology; D004043:Dietary Fiber / Q000494:pharmacology*; D004044:Dietary Proteins / Q000494:pharmacology*; D004195:Disease Models, Animal; D004386:Duodenum / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D052216:Glucagon-Like Peptide 1 / Q000097:blood*; D005951:Glucose Tolerance Test; D007333:Insulin Resistance / Q000502:physiology; D007444:Inulin / Q000494:pharmacology*; D007583:Jejunum / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D008055:Lipids / Q000097:blood*; D008297:Male; D009765:Obesity / Q000378:metabolism*; D052336:Proglucagon / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D015430:Weight Gain / Q000187:drug effects / Q000502:physiology
D001786:Blood Glucose; D004043:Dietary Fiber; D004044:Dietary Proteins; D008055:Lipids; D012333:RNA, Messenger; D052336:Proglucagon; D052216:Glucagon-Like Peptide 1; D007444:Inulin