Synthesis, radiosynthesis and in vitro evaluation of (18)F-Bodipy-C(16)/triglyceride as a dual modal imaging agent for brown adipose tissue

BACKGROUND: Brown adipose tissue research is in the focus in the field of endocrinology. We designed a dual-modal fluorescent/PET fatty acid based tracer on commercially available Bodipy-C(16), which can be synthesized to its corresponding triglyceride and which combines the benefits of fluorescent and PET imaging. METHODS: Bodipy-C(16) was coupled to 1,3-diolein resulting in Bodipy-triglyceride. Bodipy-C(16) and Bodipy-triglyceride compounds were radiolabeled with (18)F using an (18)F/(19)F exchange reaction to yield a dual-modal imaging molecule. Uptake of radiolabeled and non-labeled Bodipy-C(16) and Bodipy-triglyceride was analyzed by fluorescence imaging and radioactive uptake in cultured adipocytes derived from human brown adipose tissue and white adipose tissue. RESULTS: Bodipy-C(16) and Bodipy-triglyceride were successfully radiolabeled and Bodipy-C(16) showed high shelf life and blood plasma stability (99% from 0–4 h). The uptake of Bodipy-C(16) increased over time in cultured adipocytes, which was further enhanced after beta-adrenergic stimulation with norepinephrine. The uptake of Bodipy-C(16) was inhibited by oleic acid and CD36 inhibitor sulfosuccinimidyl-oleate. The poor solubility of Bodipy-triglyceride did not allow stability or in vitro experiments. CONCLUSION: The new developed dual modal fatty acid based tracers Bodipy-C(16) and Bodipy-triglyceride showed promising results to stimulate further in vivo evaluation and will help to understand brown adipose tissues role in whole body energy expenditure.