Lipid contributes greatly in cardiac metabolism to produce high energy ATPs, and is suggested to be related to the progression and deterioration of
heart disease. It is fortunate that the I-123-betamethyliodophenylpentadecanoic
acid (
BMIPP) imaging technique is now available in determining heart condition, but we must be cautious about the interpretation of images obtained with this new tracer. From the uptake of
BMIPP into the cell to breakdown and catabolism of it, there exist so many critical enzymatical pathways relating to the modification of
BMIPP imaging. In clinical evaluation, the image will be translated as the integral effects of these pathways. In other words, we must be aware of these critical pathways regulating lipid metabolism and modifying factors in order to correctly understand
BMIPP imaging.
Lipid transport is affected by the
albumin/FFA ratio in the blood, and extraction with
membrane transporter proteins.
Fatty acid binding protein (FABP) in the cytosole will play an important role in regulating
lipid flux and following metabolism.
Lipid will be utilized either for oxidation,
triglyceride or
phospholipid formation. For oxidation,
carnitine palmitoil
transferase is the key
enzyme for the entrance of
lipid into mitochondria, and oxidative
enzymes such as
acyl CoA dehydrogenase (MCAD, LCAD, HAD) will determine
lipid use for the TCA cycle. ATPs produced in the mitochondria again limit the TG store. It is well known that
BMIPP imaging completely changes in the ischemic condition, and is also shown that
lipid metabolical regulation completely differs from normal in the very early phase of
cardiac hypertrophy. In the process of deteriorating
heart failure, metabolical switching of
lipid with
glucose will take place. In such a different
heart disease conditions, it is clear that
lipid metabolical regulation, including many
lipid enzymes, works differently from in the healthy condition. These
lipid enzymes are regulated by nuclear factor
peroxisome proliferator-activated receptors (
PPAR) just like a conductor of an orchestra. Most of the regulating mechanisms of the
PPAR are still unknown, but reduction of this nuclear factor is shown in the process of decompensated
heart failure. This review is based by mostly on our fundamental and Japanese clinical data.
BMIPP has been used clinically in abundant cases in Japan. In such situations, further correct information on lipid metabolism, including
BMIPP, will contribute to the understanding of deteriorating
heart disease and its prognosis.