Given an abstract from a research paper, your task is to identify and label relationships between chemical compounds and genes mentioned in the abstract.

The relationship type must be one of ['DOWNREGULATOR', 'SUBSTRATE', 'INDIRECT-REGULATOR', 'PART-OF', 'MODULATOR-ACTIVATOR', 'REGULATOR', 'INHIBITOR', 'COFACTOR', 'UPREGULATOR', 'ACTIVATOR', 'ANTAGONIST', 'NOT', 'INDIRECT-DOWNREGULATOR', 'SUBSTRATE_PRODUCT-OF', 'INDIRECT-UPREGULATOR', 'AGONIST', 'PRODUCT-OF', 'MODULATOR', 'DIRECT-REGULATOR', 'UNDEFINED', 'AGONIST-INHIBITOR', 'AGONIST-ACTIVATOR', 'MODULATOR-INHIBITOR'].

Please format your output as a JSON array. Each entry in the array should express a single relation, formatted as ["<Entity_A>", "<RELATION_A_B>", "<Entity_B>"]. If no relations can be found, please output an empty JSON array [].

Abstract:

Niacin mediates lipolysis in adipose tissue through its G-protein coupled receptor HM74A. A G-protein coupled receptor to niacin (nicotinic acid) was identified recently but the physiological/pharmacological role of the receptor remains poorly defined. We present our studies to demonstrate that HM74A, but not HM74, binds niacin at high affinities and effectively mediates Gi signaling events in human embryonic kidney HEK293 cells as well as in 3T3L1 adipocytes expressing HM74A. Furthermore, HM74A, but not HM74, expressed in differentiated 3T3L1 adipocytes effectively mediated inhibition of lipolysis by niacin. Our results provided direct evidence indicating that HM74A, but not HM74, was sufficient to mediate anti-lipolytic effect of niacin in adipose tissue.
[["nicotinic acid", "REGULATOR", "G-protein coupled receptor"], ["niacin", "DIRECT-REGULATOR", "HM74A"], ["niacin", "NOT", "HM74"], ["niacin", "REGULATOR", "HM74A"], ["niacin", "INDIRECT-UPREGULATOR", "Gi"], ["niacin", "REGULATOR", "G-protein coupled receptor"], ["Niacin", "REGULATOR", "G-protein coupled receptor HM74A"]]