Chronic effects of dietary carbohydrate variation on [¹⁸F]-2- fluoro-2-deoxyglucose uptake in rodent heart

PURPOSE: Measured cardiac [F]-2-fluoro-2-deoxyglucose (FDG) activity in human PET scans is variable despite efforts to standardize patient preparation. Heart uptake can obscure chest disease, and is of physiologic interest. Short-term carbohydrate (CHO) restriction can reduce FDG uptake, although unreliably, whereas long-term restriction of CHO has not been systematically studied. It would be valuable to understand FDG hearts' chronic dietary dependence. METHODS: Fifteen Wistar rats (age 4 weeks) were randomized to three diet groups (n = 5) of low (0.1% of total energy), intermediate (52%), and high (78%) CHO content (LC, IC, and HC, respectively). After 4 weeks, blood for ketone bodies (KB), glucose, insulin, and glucagon was obtained, followed in 2 days by whole-body PET with 37 MBq FDG. Diet groups were switched every 4 weeks to control for the effects of dietary order. Heart maximal standardized uptake value was compared among animals. RESULTS: Heart mean maximal standardized uptake value was dramatically reduced for LC (3.4±0.4; P<0.001) compared with either IC (10.9±0.7) or HC (11.0±0.7) (P=NS, IC vs. HC). KB (μmol/l) differed widely (P<0.001) in LC (718.6±40.0) versus IC (120.3±34.0) and HC (99.2±32.1) (P=NS, IC vs. HC), whereas glucose, insulin, and glucagon did not differ among the groups. CONCLUSION: Sustained CHO-restriction results in marked, reproducibly reduced cardiac FDG uptake. Six-fold to seven-fold increased KB concentrations provide alternative substrate to glucose.