Effect of low or high glycemic load diets on experimentally induced mammary carcinogenesis in rats

Abstract

Scope High glycemic load diets have been associated with increased breast cancer risk in population-based studies, but the evidence is mixed. This investigation determined whether diets differing in glycemic load affected the carcinogenic process using a preclinical model. Methods and results Human diets, formulated to differ 2-fold in glycemic load, were evaluated in the 1-methyl-nitrosourea-induced (37.5 mg/kg) mammary carcinogenesis model. Cancer incidence (23.3 vs 50.0%, P = 0.032 ), multiplicity, (0.40 vs 1.03, P = 0.030) and burden, (0.62 vs 1.19 g/rat, P = 0.037) were reduced in the low versus high glycemic load diets, respectively. However, the low glycemic protective effect was attenuated when two purified diets that differed in resistant starch and simulated the glycemic effects of the human diets were fed. Protection was associated with alterations in markers of cell growth regulation. Conclusion Our findings show that human low or high glycemic load dietary patterns differentially affect the carcinogenic response in a non-diabetic rodent model for breast cancer. However, factors that are associated with these patterns, in addition to dietary carbohydrate availability, appear to account for the differences observed.

Metabolic Effects of High Glycaemic Index Diets: A Systematic Review and Meta-Analysis of Feeding Studies in Mice and Rats

“…The systematic search procedure with the number of articles included and excluded at each point is depicted in Figure 1 . The end result was 30 articles, with 15 [ 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 ] involving mice, 13 [ 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 ] involving rats and two [ 56 , 57 ] with experiments performed on both species. Of the articles that contained pertinent results, all contained information regarding the change or comparison of body weight or fat, and most examined some measure of glucose homeostasis.…”

“…The average score, out of 22, for each species was 13.3 and 12.2, respectively, to one decimal place. There was a small amount of variation in the quality of the articles, with the vast majority having a score between 11 and 16, inclusive [ 28 , 29 , 30 , 32 , 34 , 35 , 36 , 37 , 41 , 42 , 43 , 44 , 45 , 47 , 49 , 50 , 51 , 52 , 54 , 55 , 56 , 57 ], and a lowest score of 8 [ 38 ] and highest of 18 [ 31 ].…”

“…Three papers [ 33 , 37 , 50 ], with two of these from the same study, used a reference food, although one study used glucose in the diet frame as opposed to straight glucose and while the other did test straight glucose, it was compared to the carbohydrate source as opposed to the diet itself. Three provided the diets in terms of carbohydrate content [ 43 , 50 , 55 ], as is done in humans, as opposed to food weight. Only three papers used at least 10 animals for the test [ 33 , 37 , 45 ], and the time to eat ranged considerably with two as gavages [ 55 ], three eating for 15 min [ 33 , 37 , 45 ], and the remaining tests having the animals eat for 5 min [ 32 , 35 , 42 , 43 ].…”

“…Three provided the diets in terms of carbohydrate content [ 43 , 50 , 55 ], as is done in humans, as opposed to food weight. Only three papers used at least 10 animals for the test [ 33 , 37 , 45 ], and the time to eat ranged considerably with two as gavages [ 55 ], three eating for 15 min [ 33 , 37 , 45 ], and the remaining tests having the animals eat for 5 min [ 32 , 35 , 42 , 43 ]. Most studies did test the blood glucose over two hours [ 32 , 33 , 35 , 37 , 43 , 50 , 54 , 55 ].…”

“…In the meta-regression, there were considerable differences between the sexes. Of the 30 articles included, five papers detailed experiments on female animals, one of which used mice [ 34 ] and four used rats [ 46 , 54 , 55 , 57 ]. This makes it difficult to be sure that there is really a sex difference in response to HGI feeding as the data suggest.…”