A 1-week extension of a ketogenic diet provides a further decrease in myocardial 18F-FDG uptake and a high detectability of myocarditis with FDG-PET

The active papillary muscle sign in 18F-FDG PET/CT cardiac sarcoidosis exams and its relationship with myocardial suppression

OBJECTIVE

Papillary muscle (PM) activity may demonstrate true active cardiac sarcoidosis (CS) or mimic CS in 18FDG-PET/CT if adequate myocardial suppression (MS) is not achieved. We aim to examine whether PM uptake can be used as a marker of failed MS and measure the rate of PM activity presence in active CS with different dietary preparations.

MATERIALS AND METHODS

We retrospectively reviewed PET/CTs obtained with three different dietary preparations. Diet-A: 24-h ketogenic diet with overnight fasting (n = 94); Diet-B: 18-h fasting (n = 44); and Diet-C: 72-h daytime ketogenic diet with 3-day overnight fasting (n = 98). Each case was evaluated regarding CS diagnosis (negative, positive, and indeterminant) and presence of PM activity. MaxSUV was measured from bloodpool, liver, and the most suppressed normal myocardium. Linear mixed-effects models were used to compare these factors between those with PM activity and those without.

RESULTS

PM activity was markedly lower in the Diet-C group compared with others: Diet-C: 6 (6.1%), Diet-A: 36 (38.3%), and Diet-B: 26 (59.1%) (p < 0.001). MyocardiumMaxSUV was higher, and MyocardiummaxSUV/BloodpoolmaxSUV, MyocardiummaxSUV/LivermaxSUV ratios were significantly higher in the cases with PM activity (p < 0.001). Among cases that used Diet-C and had PM activity, 66.7% were positive and 16.7% were indeterminate. If Diet-A or Diet-B was used, those with PM activity had a higher proportion of indeterminate cases (Diet-A: 61.1%, Diet-B: 61.5%) than positive cases (Diet-A: 36.1%, Diet-B: 38.5%).

CONCLUSION

Lack of PM activity can be a sign of appropriate MS. PM activity is less common with a specific dietary preparation (72-h daytime ketogenic diet with 3-day overnight fasting), and if it is present with this particular preparation, the likelihood that the case being true active CS might be higher than the other traditional dietary preparations.

Assessment of a one-week ketogenic diet on brain glycolytic metabolism and on the status epilepticus stage of a lithium-pilocarpine rat model

The ketogenic diet (KD) has been shown to be effective in refractory epilepsy after long-term administration. However, its interference with short-term brain metabolism and its involvement in the early process leading to epilepsy remain poorly understood. This study aimed to assess the effect of a short-term ketogenic diet on cerebral glucose metabolic changes, before and after status epilepticus (SE) in rats, by using [18F]-FDG PET. Thirty-nine rats were subjected to a one-week KD (KD-rats, n = 24) or to a standard diet (SD-rats, n = 15) before the induction of a status epilepticus (SE) by lithium-pilocarpine administrations. Brain [18F]-FDG PET scans were performed before and 4 h after this induction. Morphological MRIs were acquired and used to spatially normalize the PET images which were then analyzed voxel-wisely using a statistical parametric-based method. Twenty-six rats were analyzed (KD-rats, n = 15; SD-rats, n = 11). The 7 days of the KD were associated with significant increases in the plasma β-hydroxybutyrate level, but with an unchanged glycemia. The PET images, recorded after the KD and before SE induction, showed an increased metabolism within sites involved in the appetitive behaviors: hypothalamic areas and periaqueductal gray, whereas no area of decreased metabolism was observed. At the 4th hour following the SE induction, large metabolism increases were observed in the KD- and SD-rats in areas known to be involved in the epileptogenesis process late-i.e., the hippocampus, parahippocampic, thalamic and hypothalamic areas, the periaqueductal gray, and the limbic structures (and in the motor cortex for the KD-rats only). However, no statistically significant difference was observed when comparing SD and KD groups at the 4th hour following the SE induction. A one-week ketogenic diet does not prevent the status epilepticus (SE) and associated metabolic brain abnormalities in the lithium-pilocarpine rat model. Further explorations are needed to determine whether a significant prevention could be achieved by more prolonged ketogenic diets and by testing this diet in less severe experimental models, and moreover, to analyze the diet effects on the later and chronic stages leading to epileptogenesis.

Recent Advances in Cardiovascular Diseases Research Using Animal Models and PET Radioisotope Tracers

Cardiovascular diseases (CVD) is a collective term describing a range of conditions that affect the heart and blood vessels. Due to the varied nature of the disorders, distinguishing between their causes and monitoring their progress is crucial for finding an effective treatment. Molecular imaging enables non-invasive visualisation and quantification of biological pathways, even at the molecular and subcellular levels, what is essential for understanding the causes and development of CVD. Positron emission tomography imaging is so far recognized as the best method for in vivo studies of the CVD related phenomena. The imaging is based on the use of radioisotope-labelled markers, which have been successfully used in both pre-clinical research and clinical studies. Current research on CVD with the use of such radioconjugates constantly increases our knowledge and understanding of the causes, and brings us closer to effective monitoring and treatment. This review outlines recent advances in the use of the so-far available radioisotope markers in the research on cardiovascular diseases in rodent models, points out the problems and provides a perspective for future applications of PET imaging in CVD studies.

The detection of infectious endocarditis may be enhanced by a repeat FDG-PET while maintaining patients on a ketogenic diet

BACKGROUND

This study aims to determine whether the suppression of myocardial FDG uptake and detection of infectious endocarditis (IE) may be enhanced when FDG-PET is repeated on the next day while maintaining patients on a ketogenic diet in the interim.

METHODS

Seventeen patients with definite IE underwent FDG-PET investigations both after a conventional metabolic preparation (> 12-hour fast after a low-carbohydrate evening meal) and a subsequent 12-hour extension of the low-carbohydrate diet followed by an additional > 12-hour fast.

RESULTS

Plasma biomarkers showed increased ketogenic metabolism between the two FDG-PET scans. A myocardial FDG uptake persisted on the 1st PET in 9 patients (53%) for whom myocardial FDG uptake decreased significantly on the 2nd PET (SUVmax: 6.05 ± 3.25 vs 4.32 ± 3.47, P = 0.021), resulting in an enhancement in the diagnostic confidence of IE in 6 cases. These enhancements were not documented in the 8 patients exhibiting a total suppression of myocardial FDG uptake on the 1st PET.

CONCLUSIONS

Better suppression of myocardial uptake and enhanced detection of IE may be achieved when an FDG-PET, showing an incomplete suppression of the myocardial FDG uptake, is repeated as soon as the next day, while maintaining patients on a ketogenic diet in the interim.

18F-FDG PET imaging-monitored anti-inflammatory therapy for acute myocardial infarction: Exploring the role of MCC950 in murine model

BACKGROUND

MCC950 is a novel NLRP3 inflammasome inhibitor that possesses potent anti-inflammatory properties in acute myocardial infarction (AMI). However, the lack of noninvasive monitoring methods limits its potential clinical translation. Thus, we sought to investigate whether 18F-FDG PET imaging can monitor the therapeutic effects of MCC950 in an AMI murine model.

METHODS

C57BL/6 mice were used to generate an AMI model. MCC950 or sterile saline was intraperitoneally administered 1 hour after surgery and then daily for 7 consecutive days. 18F-FDG PET (inflammation) imaging was used to monitor inflammatory changes on days 3 and 5. Immunohistochemistry and Western blot were used to detect inflammatory markers and to confirm the PET imaging results. 18F-FDG PET (viability) imaging was used to quantitate the viability defect expansion on days 7 and 28. Cardiac ultrasound and survival analyses were performed to evaluate the cardiac function and survival rate. Adverse remodeling was determined by Wheat Germ Agglutinin (WGA) and Masson trichrome staining.

RESULTS

The FDG-PET (inflammation) imaging revealed that MCC950 treatment led to lower 18F-FDG inflammatory uptakes, at the infarct region, on days 3 and 5 when compared to the MI group. The decreased M1 macrophages and neutrophils infiltration and the remission of the NLRP3/IL-1β pathway, confirmed the FDG-PET (inflammation) imaging results. The FDG-PET (viability) imaging revealed that MCC950 significantly decreased the expansion of the viability defect, demonstrating its myocardial preservation effects. The acute FDG-PET (inflammation) signal positively correlated with the late viability defect and with the reduction in the left ventricular ejection fraction (LVEF). Additionally, the alleviated adverse remodeling and the improved survival rate further support the anti-inflammatory efficiency of MCC950 in AMI.

CONCLUSION

Using 18F-FDG PET imaging, we noninvasively demonstrated the therapeutic effects of MCC950 in AMI and showed that 18F-FDG PET imaging holds promising application potentials in MCC950's clinical translation.

COMPARISON OF THE EFFECT OF THREE DIFFERENT DIETARY MODIFICATIONS ON MYOCARDIAL SUPPRESSION IN 18F-FDG PET/CT EVALUATION OF PATIENTS FOR SUSPECTED CARDIAC SARCOIDOSIS

Rationale: A definitive dietary preparation recommendation is not possible based on literature in achievement of myocardial suppression for diagnosis of cardiac sarcoidosis (CS) with 18F-FDG PET/CT. Our goal is to compare three different dietary preparations in achievement of the best myocardial suppression and CS diagnosis. Methods: We retrospectively reviewed and compared three dietary preparations used at our institution. Three different diets were applied from 03/2014 to 12/2019. 24-h ketogenic diet with overnight fasting (n = 94); 18h-fasting (n = 44); 72-h daytime ketogenic diet with 3-day overnight fasting (n = 98). The interpretation of initial reports was recorded, and an independent radiologist (observer) retrospectively re-evaluated each case regarding CS diagnosis (Negative, Positive, Indeterminant) and myocardial suppression (Complete, Failed, Partial). Interobserver agreement was analyzed. We measured MaxSUV from bloodpool, liver, and the most suppressed normal myocardium. Results: We identified superior myocardial suppression with the 72-h preparation indicated by a higher bloodpool/myocardium and liver/myocardium ratios (P<0.001). Myocardial suppression rates for 72-h ketogenic diet, 24-h ketogenic diet and 18-h fasting preparations are as follows; Complete myocardial suppression: 96.9%/68.1%/52.3%, Failed myocardial suppression: 0%/23.4%/25%, Partial myocardial suppression: 3.1%/8.5%/22.7%) (P<0.001). The 72-hour preparation had significantly fewer "indeterminant" and "positive" exams. CS diagnosis rates for 72-h ketogenic diet, 24-h ketogenic diet and 18-h fasting preparations are as follows; Negative: 82.7%/52.1%/27.3%, Indeterminant: 2.0%/24.5%/40.9%, Positive: 15.3%/23.4%/31.8% (P<0.001). High agreement was present with the observer and the report (κ=0.88) Conclusion: A 72-h daytime ketogenic diet with 3-day overnight fasting, achieved substantially superior myocardial suppression versus 24-h ketogenic diet with overnight fasting and 18h-fasting using 18F-FDG PET/CT. This 72-h preparation results in significantly fewer "indeterminant" and potentially "false positive" CS results.