Atorvastatin lowers 68Ga-DOTATATE uptake in coronary arteries, bone marrow and spleen in individuals with type 2 diabetes

Aims/hypothesis Inflammation is a core component of residual cardiovascular risk in type 2 diabetes. With new anti-inflammatory therapeutics entering the field, accurate markers to evaluate their effectiveness in reducing cardiovascular disease are paramount. Gallium-68-labelled DOTATATE (68Ga-DOTATATE) has recently been proposed as a more specific marker of arterial wall inflammation than 18F-fluorodeoxyglucose (18F-FDG). This study set out to investigate whether 68Ga-DOTATATE uptake is amenable to therapeutic intervention in individuals with type 2 diabetes. Methods Individuals aged >50 years with type 2 diabetes underwent 68Ga-DOTATATE positron emission tomography (PET)/computed tomography (CT) at baseline and after 3 months treatment with atorvastatin 40 mg once daily. Primary outcome was the difference in coronary 68Ga-DOTATATE uptake, expressed as target-to-background ratio (TBR). The secondary outcome was difference in bone marrow and splenic uptake, expressed as the standardised uptake value (SUV). Results Twenty-two individuals with type 2 diabetes (mean age 63.2±6.4 years, 82% male, LDL-cholesterol 3.42±0.81 mmol/l, HbA1c 55±12 mmol/mol [7.2%±3.2%]) completed both 68Ga-DOTATATE PET/CT scans. The maximum TBR was −31% (95% CI −50, −12) lower in the coronary arteries, and bone marrow and splenic 68Ga-DOTATATE uptake was also significantly lower post statin treatment, with a mean percentage reduction of −15% (95% CI −27, −4) and −17% (95% CI −32, −2), respectively. Conclusions/interpretation 68Ga-DOTATATE uptake across the cardio–haematopoietic axis was lower after statin therapy in individuals with type 2 diabetes. Therefore, 68Ga-DOTATATE is promising as a metric for vascular and haematopoietic inflammation in intervention studies using anti-inflammatory therapeutics in individuals with type 2 diabetes. Trial registration ClinicalTrials.gov NCT05730634 Graphical Abstract Supplementary Information The online version contains peer-reviewed but unedited supplementary material available at 10.1007/s00125-023-05990-9.

written informed consent.Atorvastatin 40mg once daily would be initiated after the first 68 Ga-DOTATATE PET/CT, for a period of 12 weeks.After statin therapy was completed, the patients were subjected to a follow-up 68 Ga-DOTATATE PET/CT.The study protocol was approved by the local medical ethics committee and performed in accordance with the Declaration of Helsinki.

Laboratory measurements
Blood was collected at baseline and follow-up visits, to determine lipid, metabolic and inflammatory parameters.C-reactive protein (CRP), HbA1c, fasting glucose, total cholesterol, triglyceride, and high-density-lipoprotein cholesterol (HDL-C) and apolipoprotein B (ApoB) levels were measured.Low-density-lipoprotein cholesterol (LDL-C) was calculated using the Friedewald formula 1 .

Image acquisition and reconstruction
PET/CT image acquisition was performed 60 minutes after intravenous administration of approximately 100MBq 68 Ga-DOTATATE, a Biograph mCT Flow PET/CT scanner (Siemens, Germany) equipped with enhanced axial field of view (TrueV) was used.First, a low dose CT scan was performed from skull base to spleen followed by a PET scan continuous bed motion at 1mm/s.CT data was used for PET attenuation correction and PET data were reconstructed with TrueX algorithm 2 in 4mm×4mm×5mm voxels.
Then a sequential coronary artery calcium (CAC) scan was performed using an endinspiratory breath-hold with prospective electrocardiogram (ECG) gating, tube voltage 120kVp, and tube current 60mAs.Thereafter, a prospective ECG gated PET scan of the heart was performed for 20 minutes.PET Data were reconstructed in mid-diastolic phase, with a phase length of 25% using the same settings as described above, attenuation correction was performed using the first low dose CT.

Image analysis
Image analyses were performed on a dedicated workstation (FusionQuant) and analysed by an experienced observer (ET).Analyses of the follow-up scans were performed six weeks after the baseline analysis.To quantify uptake of 68 Ga-DOTATATE in coronary arteries, we used the maximum target to background ratio (TBRmax) due to extensive experience with this method of measuring tracer uptake within the arterial wall 3 .The administered activity always varies slightly between scans due to a multitude of factors, primarily the time delay between the labelling of the tracer and when the tracer is administered to the patient.Therefore, to correct for the difference in administered activity, it is standard practice to correct the uptake of tracer in the coronary arteries for the uptake in the blood pool.The TBRmax was calculated by dividing the standardized uptake value (SUV) of target tissue by background SUVmean.We measured the SUVmax in the coronary arteries by drawing volumes of interest (centrelines with 4mm diameter) across the main coronary arteries (left anterior descending (LAD), left circumflex (LCx) and right coronary artery (RCA)) starting from the ostium and then following the artery across the coronary groove.These encompass all the main epicardial coronary vessels and their immediate surroundings (4mm radius) facilitating per-vessel and per-patient uptake quantification.For this study we evaluated 68 Ga-DOTATATE activity along the entire course of the coronary arteries and we included the left main in the LAD volume of interest (VOI).Within such VOIs, we measured the whole vessel SUVmax, and used these to derive coronary TBR values after correction for blood pool.If scatter caused by the liver was identified near the RCA, the VOI would be adjusted to avoid these hotspots.We assessed the SUVmean 68 Ga-DOTATATE uptake in the left atrium by using a cylinder 10 mm in diameter and height.CAC measurements were performed according to the Agatston method 4 .Finally, ascending aorta uptake was calculated by drawing VOI starting from the sinotubular junction and finishing immediately proximal to the junction with the brachiocephalic artery 5 .The final diameter of the region of interest around the aorta was equal to the maximal luminal diameter of the aorta of that section plus 4mm (the approximate spatial resolution of PET).
SUVmax in bone marrow and spleen was assessed by drawing VOIs around each respective structure.For the spleen we used a cylinder of 10mm radius and 10mm height.We drew the VOI around the hottest point of the splenic uptake.For bone marrow uptake we drew VOI in the middle of the thoracic vertebrates and calculated the mean SUVmax value.SUVmean in the lung was assessed by drawing a sphere 15mm in diameter in the left lung at the level of the pulmonary artery bifurcation.For the SUVmean in muscle tissue we also drew a sphere 15mm in diameter in the left pectoral muscle at the level of the pulmonary artery bifurcation.We corrected these SUVmean values for the blood pool to derive the TBR values.

Statistical Analysis
Our sample size (n=24) was chosen to detect a ≥12% reduction in coronary TBRmax after atorvastatin treatment, with 80% power and a two-sided p value of <0.05.This was based on previous studies which evaluated changes in 18 F-FDG uptake after atorvastatin 40mg treatment, since Tarkin et al. found a strong correlation between the uptake of 68 Ga-DOTATATE and 18 F-FDG in the coronary arteries and aorta 6,7 .All data are expressed as mean ± standard deviation, median [interquartile range] or number (percentage), as appropriate.The primary outcome of this study was TBRmax reduction in the coronary arteries.Secondary outcomes were the reduction in bone marrow and spleen SUVmax.Changes in normally distributed data were assessed using a paired t-test, whereas those between non-normally distributed data were assessed using the Paired Samples Wilcoxon Signed-Rank test.All changes are expressed as the percentage difference between baseline and follow-up.Finally, we tested correlations between 68 Ga-DOTATATE uptake, CAC, glucose, LDL-C, and CRP using the Pearson correlation coefficient or Spearman's rank correlation coefficient for normally and non-normally distributed data, respectively.Statistical analyses were performed using R version 4.0.3.Graphical representations of the data were created using GraphPad Prism version 9.4.0.