Imaging individuals with obesity

Glutamate and obesity - what is the link?

PURPOSE OF REVIEW

Many studies using metabolomics have tried to unravel the metabolic signature of obesity and understand the pathophysiology of this complex and heterogeneous disease. Circulating levels of the amino acid glutamate have been consistently associated with obesity and more specifically with measurements of abdominal fat accumulation. The purpose of this narrative review is to highlight recent studies documenting this association.

RECENT FINDINGS

Circulating glutamate concentrations have been positively correlated with measurements of central fat accumulation such as waist circumference and visceral adipose tissue area. Moreover, elevated glutamate levels have been linked to a higher prevalence of type 2 diabetes, cardiovascular diseases and nonalcoholic fatty liver disease. The association with adiposity is detected in early life, and genetic predisposition does not appear as a major driver. Glutamate levels reflect in vivo synthesis rather than dietary intake. However, interventions generating metabolic improvements such as incretin receptor agonist treatment or dietary improvements may reduce plasma levels of this amino acid.

SUMMARY

Recent findings confirm the consistent association between circulating glutamate and abdominal obesity and its cardiometabolic complications. The pathophysiological pathways underlying this phenomenon are still unclear. Furthermore, studies are needed to establish the usefulness of this analyte as a biomarker of abdominal obesity.

Obesity and the risk of cardiometabolic diseases

The prevalence of obesity has reached pandemic proportions, and now approximately 25% of adults in Westernized countries have obesity. Recognized as a major health concern, obesity is associated with multiple comorbidities, particularly cardiometabolic disorders. In this Review, we present obesity as an evolutionarily novel condition, summarize the epidemiological evidence on its detrimental cardiometabolic consequences and discuss the major mechanisms involved in the association between obesity and the risk of cardiometabolic diseases. We also examine the role of potential moderators of this association, with evidence for and against the so-called 'metabolically healthy obesity phenotype', the 'fatness but fitness' paradox or the 'obesity paradox'. Although maintenance of optimal cardiometabolic status should be a primary goal in individuals with obesity, losing body weight and, particularly, excess visceral adiposity seems to be necessary to minimize the risk of cardiometabolic diseases.

Modification of [18F]-FDG PET/CT imaging protocols in obese oncology patients: A nationwide survey

INTRODUCTION

The use of medical imaging for diagnosis, staging and follow-up in Oncology context is incredibly important, being the use of [18F]-FDG PET/CT particularly advantageous in specific contexts like the case of obese patients. However, imaging the latter can be challenging sometimes, since their own body size may affect overall image quality and adds technical difficulties for the operator(s) performing the examination.

METHODS

This research project was developed with the aim of analysing the current personal practices of Portuguese Nuclear Medicine Technologists (NMTs) in the adaptation of ¹⁸F-FDG PET/CT oncological protocols for obese patients and comparing the results with parameters referenced in literature. A non-experimental research study was conducted using a survey delivered online to NMTs through social media platforms (Facebook® and LinkedIn®) and by sending the link directly to contacts within the research team professional and personal networks.

RESULTS

Answers from a total of 26 participants were obtained, with 88.5% of participants admitting modifying technical protocols in examinations for obese patients. Changes in PET protocols included an increase in the administered activity (60.9%), an increase in scan time per individual bed position (69.6%) and the use of Time-of-Flight (TOF) technology whenever available. Protocol changes in CT included increasing the mA (82.6%), raising the KVp (47.8%), the application of iterative reconstruction (69.6%) and the use of automatic exposure control (AEC) (52.2%). The remaining parameters (pitch, algorithm, slice thickness, display FOV, gantry rotation time and energy acceptance window) were claimed not to be modified by around 90% of professionals.

CONCLUSION

Portuguese NMTs tend to change the [18F]-FDG PET/CT protocols for obese patients. However, while some of the parameters appear to be contradictory or redundant, others require further optimisation, especially in the CT component.

IMPLICATIONS FOR PRACTICE

Efforts should be made to optimize acquisition protocols used in [18F]-FDG PET/CT scans for obese patients.