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The effects of glycemic index on prostate cancer progression in a xenograft mouse model

ABSTRACT: Previously, we found low-carbohydrate diets slowed prostate cancer (PC) growth and increased survival vs. a Western diet in mice, by inhibiting the insulin/IGF-1 axis. Thus, we tested whether modifying carbohydrate quality to lower glycemic index (GI) without changing quantity results in similar benefits as with reduced quantity. Male SCID mice injected with LAPC-4 cells were single-housed and randomized when their tumors reached 200mm3 on average to a LoGI (48% carbohydrate kcal, from Hylon-VII) or HiGI Western diet (48% carbohydrate kcal, from sucrose). Body weight and tumor volume were measured weekly. Body composition was assessed 35 days after randomization. Blood glucose and serum insulin, IGF-1 and IGFBP3 were measured at study end when tumor volumes reached 800mm3. We analyzed gene expression of mice tumors by RNA-sequencing and human tumors using the Prostate Cancer Transcriptome Atlas. There were no significant differences in tumor volume (P>0.05), tumor proliferation (P=0.29), and overall survival (P=0.15) between groups. At 35 days after randomization, the LoGI group had 30% lower body fat (P=0.007) despite similar body weight (P=0.58). At sacrifice, LoGI mice had smaller livers (P<0.001) and lower glucose (P=0.15), insulin (P=0.11), IGF-1 (P=0.07) and IGF-1:IGFBP3 ratio (P=0.05), and higher IGFBP3 (P=0.09) vs. HiGI, although none of these metabolic differences reached statistical significance. We observed differential gene expression and pathway enrichment in mice tumors by diet. The most upregulated and downregulated gene in the LoGI group showed expression patterns more closely resembling expression in human benign prostate tissue vs. PC. In this single mouse xenograft model, consuming a low GI diet did not delay PC growth or survival vs. a high GI diet despite suggestions of decreased activation of the insulin/IGF-1 pathway. These data suggest that improving carbohydrate quality alone while consuming a high carbohydrate diet may not effectively slow PC growth.

ORGANISM(S): Mus musculus

PROVIDER: GSE246780 | GEO | 2024/01/01

REPOSITORIES: GEO

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Project description:We previously reported that a low versus high glycemic index (GI) diet on a high fat (30% kcal fat) background (LGI and HGI, respectively) significantly retarded adverse health effects in C57BL/6J male mice. The LGI diet enhanced whole body insulin sensitivity and repressed high fat diet-induced body and adipose tissue weight gain, resulting in reduced serum leptin and resistin levels (Faseb J 2009; 23: 1092-1101). How white adipose tissue (WAT) is effected is examined in the present study. We characterized the molecular mechanisms underlying the GI-mediated effects in WAT using whole genome transcriptomics technology. We show that a LGI vs. HGI diet mainly exerts its beneficial effects on substrate metabolism, especially insulin signaling of fatty acid metabolism. In addition, cell adhesion and cytoskeleton remodeling showed reduced expression in line with lower WAT mass, but it might also be due to altered insulin sensitivity. An important transcription factor showing enhanced expression is PPARgamma. Furthermore, serum levels of triglycerides, total cholesterol, HDL- and LDL-cholesterol were significantly reduced by a LGI vs. HGI diet, and muscle insulin sensitivity was significantly increased as analyzed by PKB/Akt phosphorylation. Cumulatively, even though these mice were fed a high fat diet, the low versus high GI induced significantly favorable changes in metabolism in WAT. These effects suggest a partial overlap with pharmacological approaches by thiazolidinediones (TZDs) to treat insulin resistance and statins and plantsterols/stanols for hypercholesterolemia. It is therefore tempting to speculate that such a dietary approach might beneficially support pharmacological treatment of insulin resistance or hypercholesterolemia in humans. We analyzed 19 epididymal whie adipose tissue (epiWAT) samples from a 13 week High fat diet, Low glycemic index dietary group (LGI, n=9) versus a High fat diet, High glycemic index dietary group (HGI, n=10) after 13 weeks of feeding wildtype C57BL/6J male adult mice. Of the 19 arrays, we excluded 2 arrays for downstream analysis based on quality control (total final set contains 8 LGI and 9 HGI samples).

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The effects of glycemic index on prostate cancer progression in a xenograft mouse model

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