Role of insulin resistance in heart and skeletal muscle F-18 fluorodeoxyglucose uptake in patients with noninsulin-dependent diabetes mellitus

BACKGROUND: Altered heart and skeletal glucose usage has been reported in patients with non-insulin-dependent diabetes mellitus (NIDDM). Although elevations in plasma free fatty acid (FFA) concentrations have been implicated in reduced myocardial 18fluorine-fluoro-2-deoxy-D-glucose uptake (MFU), the specific role of whole-body insulin resistance in MFU in patients with NIDDM compared with skeletal muscle metabolism remains controversial. PURPOSE: MFU and skeletal muscle 18fluorine-fluoro-2-deoxy-D-glucose uptake (SMFU) were compared with positron emission tomography and the whole-body glucose disposal rate (GDR) during hyperinsulinemic euglycemic clamping in 26 normotensive asymptomatic patients with NIDDM who were not taking medication. These factors were also compared in 12 age-matched control subjects to increase the knowledge of the influence of whole-body insulin resistance on MFU. In addition, independent factors for both SMFU and MFU were investigated. RESULTS: GDR in control subjects (10.0 +/- 2.97 mg/min per kilogram) was significantly higher than in patients with NIDDM (4.05 +/- 2.37 mg/min per kilogram, P < .01). SMFU in patients with NIDDM (0.826 +/- 0.604 mg/min per 100 g) was significantly lower than that in control subjects (1.86 +/- 1.06 mg/min per 100 g, P < .01). MFU in patients with NIDDM (5.35 +/- 2.10 mg/min per 100 g) was also significantly lower than that of control subjects (7.05 +/- 1.66 mg/min per 100 g, P = .0182). SMFU significantly correlated with GDR (r = .727, P < .01) and FFA (r = -.52, P < .01) in patients with NIDDM. MFU also correlated with GDR (r = .778, P < .01) and FFA (r = -.72, P < .01) in patients with NIDDM. Multivariate stepwise regression analysis showed that GDR (F = 36.8) was independently related to MFU (r = .85, P < .01) whereas FFA was not (F = 1.763), where F is the value for statistical analysis of multivariate stepwise regression analysis. CONCLUSION: Insulin resistance is the most essential factor for both heart and skeletal muscle FDG uptake in patients with NIDDM.     

Combined increased and decreased skeletal uptake of F-18 FDG

Increased uptake of F-18 FDG is the general mainstay of diagnosis, because it indicates hypermetabolic foci of pathology. This case, describing a patient with relapsing lymphoma, represents the diagnostic dilemmas of both locally decreased and diffusely increased uptake in the skeleton.     

Differentiation of mediastinal FDG uptake observed in patients with non-thoracic tumours

In regions with a high prevalence of granulomatous diseases, benign inflammatory fluorine-18 fluorodeoxyglucose (FDG) uptake in the mediastinum is frequently observed even in healthy subjects. We examined parameters of mediastinal FDG uptake to determine whether they can differentiate malignancy from benign lesions. Seventy patients with non-thoracic tumours who had mediastinal uptake on FDG positron emission tomography (PET) were included (33 males, 37 females; age 57.5±16.9 years; 168 lymph nodes). Determination of metastasis was confirmed by biopsy or computed tomography (CT) follow-up over 12 months (metastasis, 29; benign lesions, 41). No significant difference between the metastasis group and the benign group was found in terms of residual disease in the primary site (48% vs 46%), lung invasion (29% vs 20%), number of sites of uptake (2.3 vs 2.4), smoking history (30.3% vs 46.3%) or bilateral uptake (52% vs 54%). Maximal standardised uptake values (SUVs) in the mediastinal metastasis group were higher (4.9±1.8) than those in the benign group (2.5±0.9) (P<0.05). Using 3.4 as a cut-off value for maximal SUV, a sensitivity of 86% and a specificity of 85% were achieved (AUC=0.917). Maximal SUV showed better predictive value than lymph node size measured on chest CT (P<0.05). In 8 of 51 normal subjects who underwent FDG PET as a routine check-up, mediastinal FDG uptake was observed. Maximal SUV in normal subjects was 2.5±0.8, which was similar to that in the benign group. In conclusion, maximal SUV was identified as a significant parameter for determining whether mediastinal FDG uptake represents malignant metastasis. When maximal SUV exceeded 3.4, the metastasis rate was high regardless of lymph node size.     

Thymic enlargement and FDG uptake in three patients: CT and FDG positron emission tomography correlated with pathology

OBJECTIVE: Our purpose was to describe three adult patients in whom we found increased thymic uptake of FDG on positron emission tomography and thymic enlargement with convex lateral margins on CT. Subsequent biopsy or resection showed normal thymic tissue. CONCLUSION: In three adults, we found a physiologic uptake of FDG by the thymus with standardized uptake values in the range of thymic neoplasia.     

Diffuse bone marrow uptake on F-18 FDG PET in patients with myelodysplastic syndromes

It is well known that hematopoietic cytokine stimulation can cause diffuse increase of FDG accumulation in bone marrow on PET imaging, which simulates that seen in patients with bone marrow metastases. However, diffuse bone marrow FDG uptake can be caused by other etiologies. We report 2 patients who did not have a history of hematopoietic cytokine stimulation. The FDG PET images showed diffuse bone marrow FDG uptake, and the patients were diagnosed as having myelodysplastic syndromes. These cases demonstrate that diffuse FDG uptake by bone marrow can suggest neoplastic disease of the hematopoietic tissues.     

Evaluation of FDG uptake in pulmonary hila with FDG PET/CT and contrast-enhanced CT in patients with thoracic and non-thoracic tumors

Objective  

Fluorine-18 fluorodeoxyglucose (FDG) uptake is frequently observed in lung hilus. This finding causes difficulties during the interpretation. Our objective was to evaluate the features of FDG uptake in lung hilus associated with benign or malignant etiology in patients with thoracic and non-thoracic tumors.     

Patterns of FDG uptake in post-thoracotomy surgical scars in patients with lung cancer

Increased (18)F-fluorodeoxyglucose ((18)F-FDG) uptake can occur in surgical scars. This study assesses the incidence, patterns and natural history of (18)F-FDG uptake in post-thoracotomy scars of non-small cell lung cancer (NSCLC) patients. 73 (18)F-FDG-PET/CT studies performed after resection of NSCLC in 61 patients (49 men, 12 women; mean age, 66.7 years) were retrospectively reviewed for the presence, pattern and intensity (maximum standardized uptake value (SUV(max))) of (18)F-FDG uptake in sites of previous thoracotomy. Increased (18)F-FDG uptake in surgical scars was found in 61% of studies (43/70) (average SUV(max), 3.6); 3 patients with recurrence at the surgical scar were excluded from the analysis of the characteristics of physiological FDG uptake in scars over time. The average time from surgery was 14.4 months in patients with, and 43.8 months in patients without, scar uptake (p<0.0002). Increased uptake was seen in 14/14 studies (100%) at 1-3 months, in 12/13 studies (92%) at 3-12 months, and in 17/43 studies (40%) at more than 12 months after surgery in patients with no evidence of disease on follow-up. (18)F-FDG uptake was diffuse in 67% of studies (29/43). Tumour recurrence in the scar was found in three studies, showing focally increased uptake (average SUV(max), 9.1 ) at 3-8 months after thoracotomy. In conclusion, increased (18)F-FDG uptake in post-thoracotomy surgical scars is mainly diffuse, and decreases in incidence and intensity with time, with 60% of studies showing no scar uptake at more than 12 months after surgery. Focally intense scar uptake should be evaluated for suspected recurrence.     

FDG uptake in abdominal mesh implant on FDG PET/CT

A 50-year-old man with peritoneal angiosarcoma underwent total tumor excision along with removal of the total right rectus and medial part of the left rectus muscles 1 year earlier. F-18 fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) was performed for suspected recurrence. In the anterior abdominal wall extensive subcutaneous FDG uptake showing linear hypermetabolic zone on PET slices was noted. The patient had a history of a dual mesh implant, which consists of polypropylene and polyvinylidene fluoride for the reinforcement of the abdominal wall during the operation. PET/CT fusion image demonstrated that the finding was due to the dual mesh implant in the anterior abdominal wall most likely representing a foreign body reaction.     

Differential uptake of FDG and DG during post-ischaemic reperfusion in the isolated, perfused rat heart.

Fluorine-18 2-fluoro-2-deoxyglucose (FDG) and 2-deoxyglucose (DG) are widely used as tracers of glucose uptake in the myocardium. Although there is agreement that the two analogues behave similarly to glucose under control conditions, there is growing evidence that some interventions (e.g. insulin stimulation or ischaemia/reperfusion) cause differential changes in their behaviour. The addition of a two-surface coil nuclear magnetic resonance (NMR) probe and a dual-perfusion cannula to our recently developed PET and NMR dual-acquisition (PANDA) system allows us to collect PET (FDG) images and phosphorus-31 NMR (2-deoxyglucose-6-phosphate) spectra simultaneously from each independently perfused coronary bed of the heart. We have used this technique to study the effect of regional ischaemia/reperfusion on FDG and DG uptake in the isolated, perfused rat heart. During control perfusion, FDG uptake was almost identical in both coronary beds. When one coronary bed was made ischaemic, FDG uptake ceased on that side but continued on the control side. Reperfusion failed to restore FDG uptake. In contrast, NMR spectra showed that, during reperfusion, the uptake and phosphorylation of DG did not differ between the two coronary beds. The results thus demonstrate that regional myocardial ischaemia/reperfusion has different effects on the uptake of FDG and DG in the isolated, perfused rat heart.     

Resistance training improves insulin signaling and action in skeletal muscle

Resistance training can improve glucose transport in both normal and insulin-resistant skeletal muscle by enhancing the activation of the insulin signaling cascade and increasing GLUT-4 protein concentration. These training-induced alterations improve the quality of the skeletal muscle and can occur independent of significant increases in skeletal muscle mass.