Ketone ester supplementation of Atkins-type diet prolongs survival in an orthotopic xenograft model of glioblastoma

Abstract

Heavy reliance on glucose metabolism and a reduced capacity to use ketone bodies makes glioblastoma (GBM) a promising candidate for ketone-based therapies. Ketogenic diet (KD) is well-known for its promising effects in controlling tumor growth in GBM. Moreover, synthetic ketone ester (KE) has demonstrated to increase blood ketone levels and enhance animal survival in a metastatic VM-M3 murine tumor model. Here, we compared the efficacy of a KE-supplemented Atkins-type diet (ATD-KE) to a classic KD in controlling tumor progression and enhancing survival in a clinically relevant orthotopic patient-derived xenograft GBM model. Our findings demonstrate that ATD-KE preserves body weight (percent change from the baseline; 112±2.99 vs. 116.9±2.52 and 104.8±3.67), decreases blood glucose (80.55±0.86 vs. 118.6±9.51 and 52.35±3.89 mg/dl), and increases ketone bodies in blood (1.15±0.03 mM vs. 0.55±0.04 and 2.66±0.21 mM) and brain tumor tissue (3.35±0.30 mM vs. 2.04±0.3 and 4.25±0.25 mM) comparable to the KD (results presented for ATD-KE vs. standard diet [STD] and KD, respectively). Importantly, the ATD-KE treatment significantly enhanced survival compared to the STD and was indistinguishable from the KD (47 days in STD vs. 56 days in KD and ATD-KE), suggesting that a nutritionally balanced low carbohydrate ATD combined with KE may be as effective as the KD alone in reducing brain tumor progression. Overall, these data support the rationale for clinical testing of KE-supplemented low-carb diet as an adjunct treatment for brain tumor patients.

Keywords: Glioblastoma; Ketone bodies; Ketone ester; Survival; Tumor progression.

Fig. 1

Weight change, blood glucose, and ketone levels in NOD/SCID mice treated with different dietary interventions. (A) Body weight was presented as a percent of weight at the start of dietary intervention. Animals in KD and KE supplemented diet groups lost weight in the first week. KD remained unchanged over the rest of the study period but STD+KE and ATD+KE animals reached a plateau after decreasing KE from 20% to 10% in their food. (B, C) Three weeks after putting animals on the diets, the average blood glucose and β-hydroxybutyrate (β-HB) levels were measured over a course of 12 hours. (D) Blood acetoacetate (AcAc) was also measured only at the 12-hour time-point. Animals on the KD and ATD+KE had significantly lower glucose levels compared to the STD (control diet). Although the highest levels of β-HB were observed in the KD treated animals, the β-HB levels in the ATD+KE and STD+KE animals were significantly higher than the STD alone group. Additionally, AcAc in KD and ATD+KE and STD+KE were significantly higher than the STD alone group (*P<0.05, **P<0.0021, ***P<0.0002, ****P<0.0001; one-way ANOVA). KD, ketogenic diet; STD, standard diet; ATD, Atkins-type diet; KE, ketone ester.

Fig. 2

Weight change, blood glucose, and ketone levels in brain tumor bearing NOD/SCID mice under STD, ATD+KE, and KD dietary interventions. (A) Body weight was presented as a percent of weight at the start of dietary intervention. Compared to STD, no statistically significant changes occurred in animals’ body weight. (B) Both the KD and ATD+KE had significantly lower glucose compared to the STD group, and also glucose level in the KD group was significantly lower than the ATD+KE. (C) β-hydroxybutyrate (β-HB) was significantly higher in the KD as compared to the STD and ATD+KE groups. Moreover, β-HB level in ATD+KE was also significantly elevated relative to the STD alone group (**P<0.0021, ****P<0.0001; one-way ANOVA). KD, ketogenic diet; STD, standard diet; ATD, Atkins-type diet; KE, ketone ester.

Fig. 3

(A) Kaplan–Meier survival curve with stratified Max-Combo test demonstrated a significant survival benefit of both KD (***P=0.0003) and ATD+KE (**P=0.002) dietary interventions compared to STD in L0 tumor bearing NOD/SCID mice. (B) Measurements of β-hydroxybutyrate (β-HB) from tumor tissue demonstrated a significant increase of intra-tumoral β-HB under both dietary interventions. (C) Intra-tumoral AcAc levels were elevated but were not significantly different when compared to controls (*P<0.05, **P<0.0021; one-way ANOVA). KD, ketogenic diet; STD, standard diet; ATD, Atkins-type diet; KE, ketone ester; AcAc, acetoacetate.