Evaluation of (2S,4S)-4-[18F]FEBGln as a Positron Emission Tomography Tracer for Tumor Imaging

Irruption of Network Analysis to Explain Dietary, Psychological and Nutritional Patterns and Metabolic Health Status in Metabolically Healthy and Unhealthy Overweight and Obese University Students: Ecuadorian Case

BACKGROUND

The association between dietary nutritional patterns, psychological factors, and metabolic health status has not been investigated in university students. There are studies that include numerous variables to test hypotheses from various theoretical bases, but due to their complexity, they have not been studied in combination. The scientific community recognizes the use of Gaussian graphical models (GGM) as a set of novel methods capable of addressing this.

OBJECTIVE

To apply GGMs to derive specific networks for groups of healthy and unhealthy obese individuals that represent nutritional, psychological, and metabolic patterns in an Ecuadorian population.

METHODOLOGY

This was a quantitative, non-experimental, cross-sectional, correlational study conducted on a sample of 230 obese/overweight university students, selected through a multi-stage random sampling method. To assess usual dietary intake, a Food Frequency Questionnaire (FFQ) was used; to evaluate psychological profiles (anxiety, depression, and stress), the DASS-21 scale was employed; blood pressure and anthropometric data were collected; and insulin levels, lipid profiles, and glucose levels were determined using fasting blood samples. The International Diabetes Federation (IDF) criteria were applied to identify metabolically healthy and unhealthy individuals. Statistical analysis relied on univariate methods (frequencies, measures of central tendency, and dispersion), and the relationships were analyzed through networks. The Mann-Whitney U test was used to analyze differences between groups.

RESULTS

In metabolically unhealthy obese individuals, GGMs identified a primary network consisting of the influence of waist circumference on blood pressure and insulin levels. In the healthy obese group, a different network was identified, incorporating stress and anxiety variables that influenced blood pressure, anthropometry, and insulin levels. Other identified networks show the dynamics of obesity and the effect of waist circumference on triglycerides, anxiety, and riboflavin intake.

CONCLUSIONS

GGMs are an exploratory method that can be used to construct networks that illustrate the behavior of obesity in the studied population. In the future, the identified networks could form the basis for updating obesity management protocols in Primary Care Units and supporting clinical interventions in Ecuador.

Design of Novel 18F-Labeled Amino Acid Tracers Using Sulfur 18F-Fluoride Exchange Click Chemistry

[18F]Gln-OSO2F, [18F]Arg-OSO2F, and [18F]FSY-OSO2F were designed by introducing sulfonyl 18F-fluoride onto glutamine, arginine, and tyrosine, respectively. [18F]FSY-OSO2F can be prepared directly by sulfur 18F-fluoride exchange, while [18F]Gln-OSO2F and [18F]Arg-OSO2F require a two-step labeling method. Those tracers retain their typical transport characteristics for unmodified amino acids. Both PET imaging and biodistribution confirmed that [18F]FSY-OSO2F visualized MCF-7 and 22Rv1 subcutaneous tumors with high contrast, and its tumor-to-muscle ratio was better than that of [18F]FET. However, [18F]Gln-OSO2F and [18F]Arg-OSO2F poorly image MCF-7 subcutaneous tumors, possibly due to differences in the types and amounts of transporters expressed in tumors. All three tracers can visualize the U87MG glioma. According to our biological evaluation, none of the tracers evaluated in this study exhibited obvious defluorination, and subtle structural changes led to different imaging characteristics, indicating that the application of sulfur 18F-fluoride exchange click chemistry in the design of radioactive sulfonyl fluoride amino acids is feasible and offers significant advantages.

Design, Synthesis, and Biological Evaluation of a Novel [18F]-Labeled Arginine Derivative for Tumor Imaging

To better diagnose and treat tumors related to arginine metabolism, (2S,4S)-2-amino-4-(4-(2-(fluoro-18F)ethoxy)benzyl)-5-guanidinopentanoic acid ([18F]7) was designed and prepared by introducing [18F]fluoroethoxy benzyl on carbon-4 of arginine. [18F]7 and 7 were successfully prepared using synthesis methods similar to those used for (2S,4S)-4-[18F]FEBGln and (2S,4S)-4-FEBGln, respectively. In vitro experiments on cell transport mechanisms showed that [18F]7 was similar to (2S,4S)4-[18F]FPArg and was transported into tumor cells by cationic amino acid transporters. However, [18F]7 can also enter MCF-7 cells via ASC and ASC2 amino acid transporters. Further microPET-CT imaging showed that the initial uptake and retention properties of [18F]7 in MCF-7 subcutaneous tumors were good (2.29 ± 0.09%ID/g at 2.5 min and 1.71 ± 0.09%ID/g at 60 min after administration), without significant defluorination in vivo. However, compared to (2S,4S)4-[18F]FPArg (3.06 ± 0.59%ID/g at 60 min after administration), [18F]7 exhibited lower tumor uptake and higher nonspecific uptake. When further applied to U87MG imaging, [18F]7 can quickly visualize brain gliomas (tumor-to-brain, 1.85 at 60 min after administration). Therefore, based on the above results, [18F]7 will likely be applied for the diagnosis of arginine nutrition-deficient tumors and efficacy evaluations.