Malignant brain tumors are a significant health problem in children and adults. Conventional therapeutic approaches have been largely unsuccessful in providing long-term management. As primarily a metabolic disease, malignant brain cancer can be managed through changes in metabolic environment. In contrast to normal neurons and glia, which readily transition to ketone bodies (β-hydroxybutyrate) for energy under reduced glucose, malignant brain tumors are strongly dependent on glycolysis for energy. The transition from glucose to ketone bodies as a major energy source is an evolutionary conserved adaptation to food deprivation that permits the survival of normal cells during extreme shifts in nutritional environment. Only those cells with a flexible genome and normal mitochondria can effectively transition from one energy state to another. Mutations restrict genomic and metabolic flexibility thus making tumor cells more vulnerable to energy stress than normal cells. We propose an alternative approach to brain cancer management that exploits the metabolic flexibility of normal cells at the expense of the genetically defective and metabolically challenged tumor cells. This approach to brain cancer management is supported from recent studies in mice and humans treated with calorie restriction and the ketogenic diet. Issues of implementation and use protocols are presented for the metabolic management of brain cancer.

Purpose: Malignant astrocytomas exhibit constitutive Akt phosphorylation due to reduced phosphatase and tensin homologue (PTEN) tumor suppressor expression or to increased growth factor receptor tyrosine kinase activation. Many astrocytomas are also tuberous sclerosis complex 2 (TSC2) protein deficient and exhibit constitutive mammalian target of rapamycin (mTOR) activity. Astrocytomas harboring PTEN/Akt/TSC2 pathway mutations are dependent on glycolysis to satisfy their bioenergetic requirements. Therapies that disrupt energy homeostasis can potentially manage astrocytoma growth and progression. Although dietary restriction (DR) reduces glycolysis and manages early-stage astrocytoma growth, no prior studies have identified the mechanisms involved or determined if DR can also manage late-stage tumor growth. Experimental Design: The effects of a late-onset intermittent DR feeding paradigm were examined in adult C57BL/6J mice bearing the syngeneic CT-2A malignant astrocytoma grown orthotopically or subcutaneously. Results: In contrast to contralateral normal brain, CT-2A was PTEN/TSC2 protein deficient; exhibited constitutive Akt, mTOR, and BAD phosphorylation; and overexpressed insulin-like growth factor-I (IGF-I), IGF-I receptor, hypoxia-inducible transcription factor-1a (HIF-1a), type 1 glucose transporter protein (GLUT1), and pyruvate kinase. DR initiated 10 to 14 days after tumor implantation (late onset) reduced CT-2A growth, delayed malignant progression, and significantly extended survival. DR suppressed phosphorylation of Akt and BAD while reducing expression of IGF-I, HIF-1a, and GLUT1. DR also enhanced procaspase-9/procaspase-3 cleavage but had no effect mTOR phosphorylation. Conclusions: Our findings indicate that IGF-I/Akt signaling is associated with the antiapoptotic and glycolytic phenotype of the CT-2A astrocytoma and that DR targets this pathway. Moreover, PTEN/TSC2 deficiency may impair adaptation to the DR-induced disruption of energy homeostasis, thus enhancing apoptosis. Our findings highlight the efficacy of late-onset DR in managing astrocytoma growth and suggest that DR may be an effective broad-spectrum inhibitor of Akt signaling in PTEN/TSC2^deficient astrocytomas.Malignant astrocytomas are the most common primary brain tumors and represent a leading cause of cancer-related deaths in children and the elderly (1 -4). The inability to effectively manage astrocytomas has been due, in part, to the unique anatomic and metabolic environment of the brain that prevents the complete resection of tumor tissue and impedes the delivery of therapeutic agents. Although glucose is the preferred metabolic fuel for healthy neurons and glia, these cells can transition to noncarbohydrate fuels (ketone bodies) for energy under low glucose conditions (5, 6). In contrast, astrocytomas lack metabolic flexibility and are more susceptible than normal brain tissues to cell death mediated by oxidative stress or ATP depletion in response to reduced glucose availability (7 -10). Hence, therapies that can ex...

Background: Astrocytomas are largely dependent on glycolysis to satisfy their bioenergetic requirements for growth and survival. Therapies that target glycolysis can potentially manage astrocytoma growth and progression. Dietary restriction of the high fat/low carbohydrate ketogenic diet (KD-R) reduces glycolysis and is effective in managing experimental mouse and human astrocytomas. The non-metabolizable glucose analogue, 2-deoxy-D-glucose (2-DG), is a potent glycolytic inhibitor that can mimic effects of energy restriction both in vitro and in vivo, but can also produce adverse effects when administered at doses greater than 200 mg/kg. The goal here was to determine if low doses of 2-DG could act synergistically with the KD-R to better manage growth of the CT-2A malignant mouse astrocytoma.

This study suggests that targeted short-course fluconazole prophylaxis in very low birth weight and ELBW infants may be efficacious and cost effective.

Background: AMP-activated protein kinase (AMPK) is a known physiological cellular energy sensor and becomes phosphorylated at Thr-172 in response to changes in cellular ATP levels. Activated AMPK acts as either an inducer or suppressor of apoptosis depending on the severity of energy stress and the presence or absence of certain functional tumor suppressor genes.