A ketogenic diet lowers myocardial fatty acid oxidation but does not affect oxygen consumption: a study in overweight humans.

OBJECTIVE: A ketogenic diet (KD) characterized by very low carbohydrate intake and high fat consumption may simultaneously induce weight loss and be cardioprotective. The "thrifty substrate hypothesis" posits that ketone bodies are more energy efficient compared with other cardiac oxidative substrates such as fatty acids. This work aimed to study whether a KD with presumed increased myocardial ketone body utilization reduces cardiac fatty acid uptake and oxidation, resulting in decreased myocardial oxygen consumption (MVO2 ). METHODS: This randomized controlled crossover trial examined 11 individuals with overweight or obesity on two occasions: (1) after a KD and (2) after a standard diet. Myocardial free fatty acid (FFA) oxidation, uptake, and esterification rate were measured using dynamic [11 C]palmitate positron emission tomography (PET)/computed tomography, whereas MVO2 and myocardial external efficiency (MEE) were measured using dynamic [11 C]acetate PET. RESULTS: The KD increased plasma ß-hydroxybutyrate, reduced myocardial FFA oxidation (p < 0.01) and uptake (p = 0.03), and increased FFA esterification (p = 0.03). No changes were observed in MVO2 (p = 0.2) or MEE (p = 0.87). CONCLUSIONS: A KD significantly reduced myocardial FFA uptake and oxidation, presumably by increasing ketone body oxidation. However, this change in cardiac substrate utilization did not improve MVO2 , speaking against the thrifty substrate hypothesis.

Intravenous and oral whole body ketone dosimetry, biodistribution, metabolite correction and kinetics studied by (R)-[1-11C]ß-hydroxybutyrate ([11C]OHB) PET in healthy humans.

BACKGROUND: Ketones are increasingly recognized as an important and possibly oxygen sparing source of energy in vital organs such as the heart, the brain and the kidneys. Drug treatments, dietary regimens and oral ketone drinks designed to deliver ketones for organ and tissue energy production have therefore gained popularity. However, whether ingested ketones are taken up by various extra-cerebral tissues and to what extent is still largely unexplored. It was therefore the aim of this study to use positron emission tomography (PET) to explore the whole body dosimetry, biodistribution and kinetics of the ketone tracer (R)-[1-11C]ß-hydroxybutyrate ([11C]OHB). Six healthy subjects (3 women and 3 men) underwent dynamic PET studies after both intravenous (90 min) and oral (120 min) administration of [11C]OHB. Dosimetry estimates of [11C]OHB was calculated using OLINDA/EXM software, biodistribution was assessed visually and [11C]OHB tissue kinetics were obtained using an arterial input function and tissue time-activity curves. RESULTS: Radiation dosimetry yielded effective doses of 3.28 [Formula: see text]Sv/MBq (intravenous administration) and 12.51 [Formula: see text]Sv/MBq (oral administration). Intravenous administration of [11C]OHB resulted in avid radiotracer uptake in the heart, liver, and kidneys, whereas lesser uptake was observed in the salivary glands, pancreas, skeletal muscle and red marrow. Only minimal uptake was noted in the brain. Oral ingestion of the tracer resulted in rapid radiotracer appearance in the blood and radiotracer uptake in the heart, liver and kidneys. In general, [11C]OHB tissue kinetics after intravenous administration were best described by a reversible 2-tissue compartmental model. CONCLUSION: The PET radiotracer [11C]OHB shows promising potential in providing imaging data on ketone uptake in various physiologically relevant tissues. As a result, it may serve as a safe and non-invasive imaging tool for exploring ketone metabolism in organs and tissues of both patients and healthy individuals. Trial registration Clinical trials, NCT0523812, Registered February 10th 2022, https://clinicaltrials.gov/ct2/show/NCT05232812?cond=NCT05232812&draw=2&rank=1 .

Clinical use of cardiac 18 F-FDG viability PET: a retrospective study of 44 patients undergoing post-test revascularization.

The coupling between coronary artery disease and the development of ischemic heart failure is well-established. For these patients, assessment of potentially viable but dysfunctional myocardial tissue (hibernation) is considered critical to guide optimal surgical treatment. Assessment with positron emission tomography (PET) theoretically provides measurements of hibernating tissue and maximal myocardial glucose uptake (MGU) in all cardiac territories. However, the clinical benefits of these measures are not thoroughly studied. We therefore aimed to investigate whether cardiac viability testing with combined Rubidium-82 (82Rb) and 18F-fluorodeoxyglucose (18F-FDG) predicts post-intervention improvement in left ventricle ejection fraction (LVEF) and survival. This retrospective study consisted of 131 patients with ischemic heart failure referred for dynamic 82Rb/18F-FDG PET viability testing prior to revascularization. The FDG viability scan was done during a hyperinsulinemic-euglycemic clamp and included PET measures static FDG hibernation and absolute MGU as well as myocardial blood flow and coronary flow reserve. In total, 44/131 patients undergoing viability testing were subsequently revascularized. Following revascularization, 26 patients had LVEF improvement of at least 5% while 18 patients had no improvement. A poor correlation between areas of intervention and areas of hibernation was observed. Receiver operating characteristics for all PET metrics did not predict improvement in LVEF. Furthermore, hibernation failed to predict survival regardless of whether patients underwent subsequent revascularization. Dynamic viability PET metrics (hibernation and MGU) do not predict post-intervention improvement in LVEF or overall survival in ischemic heart failure patients undergoing revascularization. In a clinical setting, the value of these measurements may therefore be limited. Kindly check and confirm the Given names and Family names for all the authors.All names are correct!

Ketogenic Diet and Cardiac Substrate Metabolism.

The ketogenic diet (KD) entails a high intake of fat, moderate intake of protein, and a very limited intake of carbohydrates. Ketogenic dieting has been proposed as an effective intervention for type 2 diabetes and obesity since glycemic control is improved and sustained weight loss can be achieved. Interestingly, hyperketonemia is also associated with beneficial cardiovascular effects, possibly caused by improved cardiac energetics and reduced oxygen use. Therefore, the KD has the potential to both treat and prevent cardiovascular disease. However, the KD has some adverse effects that could counteract the beneficial cardiovascular properties. Of these, hyperlipidemia with elevation of triglycerides and LDL cholesterol levels are the most important. In addition, poor diet adherence and lack of knowledge regarding long-term effects may also reduce the broader applicability of the KD. The objective of this narrative review is to provide insights into the KD and its effects on myocardial ketone body utilization and, consequently, cardiovascular health.

Ischemic heart failure mortality is not predicted by cardiac insulin resistance but by diabetes per se and coronary flow reserve: A retrospective dynamic cardiac 18F-FDG PET study.

BACKGROUND & AIMS: The connection between peripheral insulin resistance (IR) and coronary artery disease is well-established. Both are major risk factors for the development of ischemic cardiomyopathy potentially leading to heart failure (HF). Whether cardiac IR also impacts overall survival and morbidity is still debated. We therefore aimed to test if cardiac IR predicts mortality and major cardiovascular events (MACE) in patients with HF scheduled for cardiac viability testing before revascularization. METHODS: This retrospective study included 131 patients with a clinical diagnosis of ischemic HF (114 (87%) male, 33 (25%) with diabetes) referred to a viability Rubidium-82 (perfusion) and dynamic 18F-Fluorodeoxyglucose (metabolism) positron emission tomography combined with computed tomography prior to a potential revascularization procedure. Cardiac IR was assessed by myocardial glucose uptake (MGU) in a remote (non-scarred) area of the left ventricle during a hyperinsulinemic-euglycemic clamp (1mIE/kg/min). RESULTS: MGU correlated with skeletal muscle glucose uptake (p < 0.001) and whole-body glucose uptake (M-value) (p < 0.001), whereas no association was observed for individuals with diabetes. MGU did not predict the risk of death or MACE. However, both overt diabetes and reduced coronary flow reserve predicted overall survival. CONCLUSION: Even though diabetes and related small-vessel disease is associated with increased mortality, cardiac IR per se does not predict cardiovascular morbidity and mortality.

18F-FDG Uptake in a Mesonephric Carcinoma.

We present the case of a 39-year-old woman with vaginal bleeding and abdominal pain. An F-FDG PET/CT showed high F-FDG uptake in a tumor in the pouch of Douglas, in 3 lymph nodes in the pelvis, and in the left tuber ischiadicum. Biopsies revealed a mesonephric carcinoma with metastases. Six series of empiric chemotherapy with carboplatin, paclitaxel, and bevacizumab were not sufficient to treat the cancer, and checkpoint immunotherapy with nivolumab and ipilimumab was initialized.

68Ga-Prostate-Specific Membrane Antigen Uptake in a Pancreatic Neuroendocrine Tumor.

We present a 60-year-old man with known prostate cancer treated with robot-assisted radical prostatectomy. Prostate-specific antigen levels did not decline accordingly, and a second Ga-PSMA PET/CT demonstrated a new focus with high Ga-PSMA uptake in the pancreatic tail. A subsequent CT scan did not display the lesion as a typical pancreatic tumor, and a spleen scintigraphy was also negative excluding an ectopic intrapancreatic accessory spleen. Ga-DOTATOC PET/CT showed uptake in the same area of the pancreatic tail consistent with a neuroendocrine tumor. This case illustrates that neuroendocrine tumors can be important pitfalls in Ga-PSMA PET/CT performed in prostate cancer patients.

Preoperative factors associated with prolonged postoperative in-hospital length of stay in patients with Crohn's disease undergoing intestinal resection or strictureplasty.

PURPOSE: To investigate factors that influence postoperative in-hospital length of stay (LOS) in patients with Crohn's disease (CD) undergoing bowel surgery. Furthermore, the study aimed to evaluate LOS as a surrogate for postoperative outcome. METHODS: This is a multicentre retrospective cohort study. Inclusion criteria were adult patients with CD who underwent bowel surgery with either anastomosis or stricturoplasty. All timings of surgeries were included regardless of the method of access to the abdominal cavities. Patients with stoma were excluded. Demographic data, preoperative medications, previous operations for CD, preoperative sepsis, and operation were recorded. Primary outcome was LOS while secondary outcome variable was postoperative complications. RESULTS: A total of 449 patients who underwent abdominal surgery for CD were included. Of the 449 patients, 265 were female (59%). Median age was 37 years (IQR = 20), median LOS was 7 days (IQR = 6). Patients with longer LOS had higher rates of re-laparotomy/re-laparoscopy (45/228 (19.7%) versus 9/219 (4.1%) p = 0.01). In multivariate analysis, age (OR = 1.024 [CI 95% 1.007-1.041], p = 0.005), preoperative intra-abdominal abscess (OR = 0.39 [CI 95% 0.185-0.821], p = 0.013), and previous laparotomy/laparoscopy (OR = 0.57 [CI 95% 0.334-0.918], p = 0.021) were associated with prolonged LOS. LOS correlated with postoperative complications after adjustment for age, gender, previous laparotomy/laparoscopy, and preoperative intra-abdominal abscesses (OR = 1.28 [CI 95% 1.199-1.366], p < 0.0001). CONCLUSION: Age, preoperative intra-abdominal abscess, and previous laparotomy/laparoscopy significantly prolonged LOS. LOS correlated with postoperative complications and can therefore be used in epidemiological or register-based studies as a surrogate for postoperative outcome.