Puchowicz MA, Xu K, Sun X, Ivy A, Emancipator D, LaManna JC. Diet-induced ketosis increases capillary density without altered blood flow in rat brain. Am J Physiol Endocrinol Metab 292: E1607-E1615, 2007. First published February 6, 2007; doi:10.1152/ajpendo.00512.2006.-It is recognized that ketone bodies, such as R-␤-hydroxybutyrate (␤-HB) and acetoacetate, are energy sources for the brain. As with glucose metabolism, monocarboxylate uptake by the brain is dependent on the function and regulation of its own transporter system. We concurrently investigated ketone body influx, blood flow, and regulation of monocarboxylate transporter (MCT-1) and glucose transporter (GLUT-1) in diet-induced ketotic (KG) rat brain. Regional blood-to-brain ␤-HB influx (mol⅐g Ϫ1 ⅐min Ϫ1) increased 40-fold with ketosis (4.8 Ϯ 1.8 plasma␤-HB; mM) in all regions compared with the nonketotic groups (standard and no-fat diets); there were no changes in regional blood flow. Immunohistochemical staining revealed that GLUT-1 density (number/mm 2 ) in the cortex was significantly elevated (40%) in the ketotic group compared with the standard and no-fat diet groups. MCT-1 was also markedly (3-fold) upregulated in the ketotic group compared with the standard diet group. In the standard diet group, 40% of the brain capillaries stained positive for MCT-1; this amount doubled with the ketotic diet. Western blot analysis of isolated microvessels from ketotic rat brain showed an eightfold increase in GLUT-1 and a threefold increase in MCT-1 compared with the standard diet group. These data suggest that diet-induced ketosis results in increased vascular density at the blood-brain barrier without changes in blood flow. The increase in extraction fraction and capillary density with increased plasma ketone bodies indicates a significant flux of substrates available for brain energy metabolism. ketone bodies; monocarboxylate transporter-1; GLUT-1; ␤-hydroxybutyrate; brain metabolism; blood-brain barrier GLUCOSE IS THE MAJOR METABOLIC FUEL for the mammalian brain (37, 41), but alternate energy substrates such as ketone bodies, e.g., R-␤-hydroxybutyrate (␤-HB) and acetoacetate (6,19,29,39), serve as efficient metabolic fuel sources for the brain. This is especially important under certain nutritional conditions, such as fasting, starvation (28), feeding of a high-fat diet (24, 26), and early development and throughout the suckling period (2, 25, 42). Clinicians and investigators have been interested in ketone bodies as therapeutic agents for the treatment of hypoglycemia, seizure disorders, and Alzheimer's and Parkinson's diseases and as alternatives to high-lipid parenteral and enteral feedings (5,14,43).Similar in chemical structure to lactate and pyruvate (intermediates of glycolysis), ketones are metabolized by the brain, especially neonatal mammalian brain (1,2,20,40). These short-chain acids are referred to as monocarboxylates, and, as with glucose metabolism, systemic delivery of these substrates and availability for neuronal uptake are highly depe...

The propensity of uveal melanoma cells for invasion and metastasis is critical factor for the clinical outcome of this form of cancer, and the essential biology of its aggressiveness is not completely understood. In the present study we investigated the involvement of hypoxia-inducible factor 1 (HIF-1) in uveal melanoma migration, invasion and adhesion, the hallmarks of aggressive behavior of cancer cells. We demonstrate that exposure to hypoxia increased migration, invasion and adhesion of uveal melanoma cells in in vitro assays. The "silencing" of HIF-1alpha, the oxygen-regulated subunit of HIF-1, using RNA interference technology resulted in a marked decrease of the uveal melanoma cell migration, invasion and adhesion. GeneChip microarray analysis revealed that a number of genes which regulate cancer invasion and metabolism such as CXCR4, angiopoietin-related protein, pyruvate dehydrogenase kinase 1 (PDK1) are also activated by hypoxia in a HIF-1-dependent manner in Mum2B uveal melanoma cells. We further demonstrate that serum deprivation resulted in HIF-1 and CXCR4 activation, suggesting specific metabolic regulation of HIF-1 in these cells. Microarray analysis of serum-deprived cells identified among the upregulated genes a number of cancer invasion-related genes, some of them being known HIF-1-regulated targets. Taken together, these results suggest that the involvement of HIF-1 in uveal melanoma tumorigenesis is significant and complex, and that metabolic regulation of HIF-1 activation in Mum2B uveal melanoma cells has its specificities.

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