The glucose ketone index calculator: a simple tool to monitor therapeutic efficacy for metabolic management of brain cancer.

BACKGROUND: Metabolic therapy using ketogenic diets (KD) is emerging as an alternative or complementary approach to the current standard of care for brain cancer management. This therapeutic strategy targets the aerobic fermentation of glucose (Warburg effect), which is the common metabolic malady of most cancers including brain tumors. The KD targets tumor energy metabolism by lowering blood glucose and elevating blood ketones (ß-hydroxybutyrate). Brain tumor cells, unlike normal brain cells, cannot use ketone bodies effectively for energy when glucose becomes limiting. Although plasma levels of glucose and ketone bodies have been used separately to predict the therapeutic success of metabolic therapy, daily glucose levels can fluctuate widely in brain cancer patients. This can create difficulty in linking changes in blood glucose and ketones to efficacy of metabolic therapy. METHODS: A program was developed (Glucose Ketone Index Calculator, GKIC) that tracks the ratio of blood glucose to ketones as a single value. We have termed this ratio the Glucose Ketone Index (GKI). RESULTS: The GKIC was used to compute the GKI for data published on blood glucose and ketone levels in humans and mice with brain tumors. The results showed a clear relationship between the GKI and therapeutic efficacy using ketogenic diets and calorie restriction. CONCLUSIONS: The GKIC is a simple tool that can help monitor the efficacy of metabolic therapy in preclinical animal models and in clinical trials for malignant brain cancer and possibly other cancers that express aerobic fermentation.

Reduced glucose utilization underlies seizure protection with dietary therapy in epileptic EL mice.

Dietary therapy has been used to treat many individuals with epilepsy whose seizures are refractory to antiepileptic drugs. The mechanisms for how dietary therapy confers seizure protection are currently not well understood. We evaluated the acute effects of glucose and ß-hydroxybutyrate (the major circulating ketone body) in conferring seizure protection to the EL mouse, a model of multifactorial idiopathic generalized epilepsy. EL mice were fed either an unrestricted standard diet or a calorie-restricted standard diet to achieve a body weight reduction of 20-23%. D-Glucose, 2-deoxy-D-glucose, and ß-hydroxybutyrate were supplemented in the drinking water of calorie-restricted mice for 2.5 h prior to seizure testing to simulate the effect of increased glucose availability, decreased glucose utilization, and increased ketone availability, respectively. Seizure susceptibility, body weight, plasma glucose, and ß-hydroxybutyrate were measured over a nine-week treatment period. Additionally, excitatory and inhibitory amino acids were measured in the brains of mice using (1)H NMR. Glutamate decarboxylase activity was also measured to evaluate the connection between dietary therapy and brain metabolism. We found that lowering of glucose utilization is necessary to confer seizure protection with long-term (>4 weeks) calorie restriction, whereas increased ketone availability did not affect seizure susceptibility. In the absence of long-term calorie restriction, however, reduced glucose utilization and increased ketone availability did not affect seizure susceptibility. Brain excitatory and inhibitory amino acid content did not change with treatment, and glutamate decarboxylase activity was not associated with seizure susceptibility. We demonstrated that reduced glucose utilization is necessary to confer seizure protection under long-term calorie restriction in EL mice, while acute ketone supplementation did not confer seizure protection. Further studies are needed to uncover the mechanisms by which glucose utilization influences seizure susceptibility.

Influence of a ketogenic diet, fish-oil, and calorie restriction on plasma metabolites and lipids in C57BL/6J mice.

BACKGROUND: Diet therapies including calorie restriction, ketogenic diets, and fish-oil supplementation have been used to improve health and to treat a variety of neurological and non-neurological diseases. METHODS: We investigated the effects of three diets on circulating plasma metabolites (glucose and ß-hydroxybutyrate), hormones (insulin and adiponectin), and lipids over a 32-day period in C57BL/6J mice. The diets evaluated included a standard rodent diet (SD), a ketogenic diet (KD), and a standard rodent diet supplemented with fish-oil (FO). Each diet was administered in either unrestricted (UR) or restricted (R) amounts to reduce body weight by 20%. RESULTS: The KD-UR increased body weight and glucose levels and promoted a hyperlipidemic profile, whereas the FO-UR decreased body weight and glucose levels and promoted a normolipidemic profile, compared to the SD-UR. When administered in restricted amounts, all three diets produced a similar plasma metabolite profile, which included decreased glucose levels and a normolipidemic profile. Linear regression analysis showed that circulating glucose most strongly predicted body weight and triglyceride levels, whereas calorie intake moderately predicted glucose levels and strongly predicted ketone body levels. CONCLUSIONS: These results suggest that biomarkers of health can be improved when diets are consumed in restricted amounts, regardless of macronutrient composition.

Glucose reduces the anticonvulsant effects of the ketogenic diet in EL mice.

The ketogenic diet (KD) is known to be anticonvulsant and anti-epileptogenic. While the mechanism behind this therapeutic benefit is unclear, a reduction of circulating glucose levels through calorie restriction (CR) has been implicated. Foods or drinks that elevate blood glucose are known to compromise the therapeutic benefit of the KD in some children with epilepsy. We therefore evaluated the effect of a calorie restricted KD (KD-R) with supplementation of glucose in the drinking water of EL mice, a natural model of idiopathic generalized epilepsy, prior to seizure testing to assess the effect of glucose on seizure generation. Mice were fed either a standard diet or the KD unrestricted (SD-UR and KD-UR, respectively), or the KD restricted (KD-R). d-Glucose (25 mM) was supplemented in the drinking water of KD-R fed mice for 0.5h or for 2.5h prior to seizure testing. Each restricted mouse served as its own body weight control to achieve a 15-18% body weight reduction. Seizure susceptibility, body weights, and plasma glucose and ß-hydroxybutyrate levels were measured over a nine-week treatment period. Body weights and glucose levels remained high over the testing period in both the SD-UR and the KD-UR groups, but were significantly reduced in all R-fed groups. A significant increase in ß-hydroxybutyrate levels was observed in all KD groups. Seizure susceptibility remained highest in the SD-UR group, was slightly reduced in the KD-UR group, and was significantly reduced after three weeks in all R-fed groups. Supplementation of glucose prior to seizure testing resulted in a decrease of seizure threshold for R-fed mice, but did not alter bodyweight or circulating glucose levels. The KD has both an anticonvulsant and antiepileptogenic effect in EL mice. Here we confirm that CR enhances the anticonvulsant action of the KD in EL mice. Additionally, we show for the first time that supplementation of glucose decreases the anticonvulsant action of the KD, which further supports the hypothesis that CR works through transitioning metabolism from glucose to ketone utilization for energy.

Dietary restriction promotes vessel maturation in a mouse astrocytoma.

Mature vasculature contains an endothelial cell lining with a surrounding sheath of pericytes/vascular smooth muscle cells (VSMCs). Tumor vessels are immature and lack a pericyte sheath. Colocalization of vascular endothelial growth factor receptor 2 (VEGFR-2) and platelet-derived growth factor receptor beta (PDGF-Rß) reduces pericyte ensheathment of tumor vessels. We found that a 30% dietary restriction (DR) enhanced vessel maturation in the mouse CT-2A astrocytoma. DR reduced microvessel density and VEGF expression in the astrocytoma, while increasing recruitment of pericytes, positive for alpha-smooth muscle actin (α-SMA). Moreover, DR reduced colocalization of VEGF-R2 and PDGF-Rß, but did not reduce total PDGF-Rß expression. These findings suggest that DR promoted vessel normalization by preventing VEGF-induced inhibition of the PDGF signaling axis in pericytes. DR appears to shift the tumor vasculature from a leaky immature state to a more mature state. We suggest that vessel normalization could improve delivery of therapeutic drugs to brain tumors.

The EL mouse: a natural model of autism and epilepsy.

PURPOSE: Autism is a multifactorial disorder that involves impairments in social interactions and communication, as well as restricted and repetitive behaviors. About 30% of individuals with autism develop epilepsy by adulthood. The EL mouse has long been studied as a natural model of multifactorial idiopathic generalized epilepsy with complex partial seizures. Because epilepsy is a comorbid trait of autism, we evaluated the EL mouse for behaviors associated with autism. METHODS: We compared the behavior of EL mice to age-matched control DDY mice, a genetically related nonepileptic strain. The mice were compared in the open field and in the light-dark compartment tests to measure activity, exploratory behavior, and restricted and repetitive behaviors. The social transmission of food preference test was employed to evaluate social communication. Home-cage behavior was also evaluated in EL and DDY mice as a measure of repetitive activity. KEY FINDINGS: We found that EL mice displayed several behavioral abnormalities characteristic of autism. Impairments in social interaction and restricted patterns of interest were evident in EL mice. Activity, exploratory behavior, and restricted behavior were significantly greater in EL mice than in DDY mice. EL mice exhibited impairment in the social transmission of food preference assay. In addition, a stereotypic myoclonic jumping behavior was observed in EL mice, but was not seen in DDY mice. It is of interest to note that seizure activity within 24 h of testing exacerbated the autistic behavioral abnormalities found in EL mice. SIGNIFICANCE: These findings suggest that the EL mouse expresses behavioral abnormalities similar to those seen in persons with autism. We propose that the EL mouse can be utilized as a natural model of autism and epilepsy.