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Whole-animal liver retained substantial response after injected NR/NMN; the claim is not universal direct-uptake exclusion.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"nutrient_topic","value_text":"Niacin research collection; topical membership is not evidence of a direct dietary effect.","comparator":null,"unit":null,"notes":"","entity":{"slug":"niacin","display_name":"Niacin (vitamin B3)","entity_type_key":"nutrient_element"}},{"dimension":"organism","value_text":"Mus musculus","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"plain_language","value_text":"The precursor response required NRK1 in these isolated liver cells.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"primary_references","value_text":"[b3-pre-nmrk2016] NRK1 controls nicotinamide mononucleotide and nicotinamide riboside metabolism in mammalian cells. 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Whole-animal liver retained substantial response after injected NR/NMN; the claim is not universal direct-uptake exclusion.\nexposure: 0.5 mM NMN for 6 h (Fig. 5e)\nevidence_span: {\"source_cache\": \"artifacts/niacin-precursors-sources/nmrk2016.paragraphs.txt\", \"locator\": \"Normalized full-text paragraphs 14–14 (0-based)\", \"start_char\": 14813, \"end_char\": 16096, \"file_sha256\": \"fcbd5465aff51c9870d65fc9812edbad2cdf2af8bb16b6afb3170d7f0503178a\", \"text_sha256\": \"fcfc45b2ce45c05afffe5608ea3be48fe50bd17083c12f5b0993f3bc183da63f\"}\nsupporting_evidence_spans: [{\"source_cache\": \"artifacts/niacin-precursors-sources/nmrk2016.paragraphs.txt\", \"locator\": \"Normalized full-text paragraphs 52–52 (0-based)\", \"start_char\": 47696, \"end_char\": 48288, \"file_sha256\": \"fcbd5465aff51c9870d65fc9812edbad2cdf2af8bb16b6afb3170d7f0503178a\", \"text_sha256\": \"541856eddb8e5c1162040cb1e010a6d556de92ee36f223d0da751b4c53b06104\"}]\n[b3-pre-nmrk2016] NRK1 controls nicotinamide mononucleotide and nicotinamide riboside metabolism in mammalian cells. 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