The guinea-pig is a poor animal model for studies of niacin deficiency and presents challenges in any study using purified diets.
The guinea-pig was previously reported as being sensitive to a niacin-deficient (ND), high-protein diet, suggesting that it is a suitable model for the low tryptophan to NAD+ conversion observed in human subjects. However, these studies were based on growth rates and mortality. The objective of the present study was to determine whether guinea-pigs are suitable for ND studies based on measurements of blood and bone marrow NAD+. Using a 20 % casein diet, ND decreased blood NAD+ after 4 weeks, but this parameter returned to normal after 9 weeks of feeding, while bone marrow was decreased by 35 % at this time point. Using a 15 % casein diet, 7 weeks of ND caused 44 and 42 % decreases in blood and bone marrow NAD+. Using a 10 % casein diet, ND decreased NAD+ by 32 % in blood and 62 % in bone marrow at 7 weeks. Growth rates were directly related to the dietary tryptophan content, with the lowest growth rates seen with the 10 % casein diet. Changes in guinea-pig NAD+ are comparable with the rat model at similar levels of dietary tryptophan, while mortality rates were dramatically higher in the guinea-pig model. The present study concludes that mortality in ND guinea-pigs is not indicative of poor tryptophan conversion, but is due to environmental stresses in guinea-pigs that are not observed with rats. We conclude that guinea-pigs are not suitable for research on niacin deficiency and they present challenges for any study requiring purified diets and wire-bottomed cages.
Thorn
Stephanie L
SL
Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada.
Young
Genevieve S
GS
Kirkland
James B
JB
D000818:Animals; D001853:Bone Marrow / Q000378:metabolism*; D002364:Caseins / Q000008:administration & dosage; D019587:Dietary Supplements; D004195:Disease Models, Animal; D005780:Gelatin / Q000008:administration & dosage; D006168:Guinea Pigs; D006801:Humans; D008297:Male; D009243:NAD / Q000032:analysis* / Q000097:blood; D009525:Niacin / Q000172:deficiency*; D016019:Survival Analysis; D014364:Tryptophan / Q000378:metabolism; D015430:Weight Gain / Q000502:physiology
D002364:Caseins; D009243:NAD; D009525:Niacin; D014364:Tryptophan; D005780:Gelatin