Background Fatty acids derived de novo or taken up from the extracellular space are an essential source of nutrient for cell growth and proliferation. Radiopharmaceuticals including 11 C-acetate, and 18 F-FAC (2-18 F-fluoroacetate), have previously been used to study short-chain fatty acid (SCFA) metabolism. We developed 18 F-fluoropivalate ( 18 F-FPIA; 3-18 F-fluoro-2,2dimethylpropionic acid) bearing a gem-dimethyl substituent to assert metabolic stability for studying SCFA metabolism. We report the safety, biodistribution, and internal radiation dosimetry profile of 18 F-FPIA in 24 healthy volunteers and the effect of dietary conditions. Materials and methods Healthy volunteer male and female subjects were enrolled (n = 24), and grouped into 12 fed and 12 fasted. Non-esterified fatty acids (NEFA) and carnitine blood measurements were assessed. Subjects received 159.48 MBq (range, 47.31-164.66 MBq) of 18 F-FPIA. Radiochemical purity was > 99%. Safety data were obtained during and 24 h after radiotracer administration. Subjects underwent detailed multiple whole-body PET/CT scanning with sampling of venous bloods for radioactivity and radioactive metabolite quantification. Regions of interest were defined to derive individual and mean organ residence times; effective dose was calculated using OLINDA 1.1. Results All subjects tolerated 18 F-FPIA with no adverse events. Over 90% of radiotracer was present in plasma at 60 min postinjection. The organs receiving highest absorbed dose (in mGy/MBq) were the liver (0.070 ± 0.023), kidneys (0.043 ± 0.013), gallbladder wall (0.026 ± 0.003), and urinary bladder (0.021 ± 0.004); otherwise there was low tissue uptake. The calculated effective dose using mean organ residence times over all 24 subjects was 0.0154 mSv/MBq (SD ± 0.0010). No differences in biodistribution or dosimetry were seen in fed and fasted subjects, though systemic NEFA and carnitine levels reflected fasted and fed states. Conclusion The favourable safety, imaging, and dosimetric profile makes 18 F-FPIA a promising candidate radiotracer for tracing SCFA metabolism.

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This paper analyzes how substantial fiscal policy stimulus in response to COVID-19, combined with the impact of the downturn on revenues, has severely weakened public finances in many developing Asian economies. Analysis drawing on newly compiled data shows that while tax revenues in developing Asia steadily rose in the 2 decades before the COVID–19 pandemic, they continued to lag well behind high-income economies and some developing peers. The region relies on indirect taxes, creating a relatively efficient but less progressive tax structure, while government expenditures on education and health were comparatively modest.

Individuals with antisocial behavior and psychopathic traits are characterized by deficits in processing facial expressions, which results in poor social adaptation and dysfunctional interpersonal relationships. However, it is not clear how individuals with varying levels of these traits differ in this emotional impairment and if these deficits are due to correctly identifying or reacting appropriately to facial expressions. The aim of the study was to examine how individuals with these traits recognized and responded to affective facial expressions by using FaceReader software (which analyses footage of faces) across different experimental conditions (imitation, suppression, and control). Imitating facial expressions was introduced to examine whether it could direct participants’ attention to the facial cues and improve participants’ performance on the facial task. A total of 643 individuals from the community were pre-screened and a sample (N = 107; M age = 21.08, SD = 1.55), differentiated on levels of antisocial personality disorder (APD) symptoms and psychopathic (PSY) traits, who were selected based on extreme scores (high/low), were invited to participate in the study. Individuals with higher levels of APD symptoms and PSY traits (APD + PSY) expressed more anger than other groups, while those in the APD-only group expressed more sadness, compared to other groups. Overall, participants were compliant in following the instructions to imitate facial expressions. However, only the group with predominantly APD symptoms and the group with combined symptoms (APD + PSY) showed improvement in their accuracy ratings specifically when instructed to imitate facial expressions, compared to when no instructions were provided. The study offers a promising direction for targeting deficits in facial emotion recognition, suggesting that the deficits found in individuals with behavioral problems (with and without psychopathic traits) can be improved by asking them to imitate facial expressions.