Advanced Molecular Imaging (MRI/MRS/1H NMR) for Metabolic Information in Young Adults with Health Risk Obesity

Deuterium Metabolic Imaging of the Human Abdomen at Clinical Field Strength

OBJECTIVES

The aim of the study was to translate abdominal deuterium metabolic imaging (DMI) to clinical field strength by optimizing the radiofrequency coil setup, the administered dose of deuterium (2H)-labeled glucose, and the data processing pipeline for quantitative characterization of DMI signals over time. This was assessed in the kidney and liver to establish a basis for routine clinical studies in the future.

MATERIALS AND METHODS

5 healthy volunteers were recruited and imaged on 2 or 3 separate occasions, with varying doses of 2H-glucose: 0.75 g/kg (high dose), 0.50 g/kg (medium dose), and 0.25 g/kg (low dose), resulting in a total of 13 DMI scan sessions. DMI was performed at 3 T using a flexible 20 × 30 cm2 2H-tuned transmit-receive surface coil. For quantitative comparisons across scans, the 2H-glucose signal was normalized against the sum of 2H-glucose and 2H-water (GGW ratio). To quantify the time course of GGW, 3 novel metrics of metabolism were defined and compared between doses and organs: the maximum value across the time course (GGWmax), the sum over the whole time course (GGWAUC), and the average signal across a defined plateau (GGWmean plateau). The 2H-lipid signal overlaps with 2H-lactate; hence, the 2 signals were measured as the combined 2H-lipid+lactate signal.

RESULTS

The careful positioning of a dedicated surface coil minimized unwanted gastric signals while maintaining excellent hepatic and renal measurements. The time courses derived from the liver and kidney were reproducible and comparable across different doses, showing the potential for dose reduction. The signal from the liver plateaued at approximately 30 minutes, and that from the kidney at approximately 40 minutes. The liver exhibited higher quantitative values for 2H-glucose uptake compared to the kidney, a trend consistent across all 3 quantitative metrics and doses, for example, for the highest dose: GGWAUC liver = 31 ± 3; GGWAUC kidney = 27 ± 3; P = 0.05. A trend toward lower quantitative measurements with decreasing dose was observed: this was significant between the high and the low dose for all 3 parameters and between the medium and low dose for GGWmean plateau and GGWAUC, but was not significant between the high and the medium dose for any of the 3 parameters. The hepatic 2H-lipid+lactate signal increased over 70-90 minutes in 12/13 cases (mean: 39 ± 24%), while the renal lipid+lactate signal increased in only 8/13 cases (mean: 5 ± 17%). The hepatic 2H-water signal increased in all 13 cases (mean: 18 ± 10%), and the renal 2H-water signal increased in only 10/13 cases (mean: 10 ± 13%).

CONCLUSIONS

DMI of the human abdomen is feasible using a clinical magnetic resonance imaging system and the signal changes measured in the kidney and liver can serve as a reference for future clinical studies. The 2H-glucose dose can be reduced from 0.75 to 0.50 g/kg to minimize gastric signal without substantially affecting the reliability of organ quantification. The increase in 2H-lipid+lactate or 2H-water signal over time could serve as direct and indirect measures of metabolism, respectively.

Fatty acid composition evaluation of abdominal adipose tissue using chemical shiftencoded MRI: Association with diabetes

This study investigated the association between the fatty acid composition of abdominal adipose tissue in NAFLD patients using chemical shift-encoded MRI and the development of insulin resistance and T2DM. We enrolled 231 subjects with NAFLD who underwent both abdominal magnetic resonance spectroscopy and chemical shift-encoded MRI: comprising of 49 T2DM patients and 182 subjects without. MRI- and MRS-based liver fat fraction was measured from a circular region of interest on the right lobe of the liver. The abdominal fatty acid compositions were measured at the umbilical level with chemical shift-encoded MRI. Bland-Altman analysis, Student's t test, Mann-Whitney U test, and Spearman correlation analysis were performed. The logistic regression was applied to identify the independent factors for T2DM. Then, the predictive performance was assessed by Receiver operating characteristic curve analyses. An excellent agreement was found between liver fat fraction measured by MRS and MRI. (slope = 0.8; bias =-0.92%). In, patients with T2DM revealed lower fractions of mono-unsaturated fatty acid (Fmufa) (33.68 ± 10.62 vs 38.62 ± 12.21, P =.0089) and higher fractions of saturated fatty acid (Fsfa) (34.11 ± 9.746 vs 31.25 ± 8.66, P =.0351) of visceral fat tissue compared with patients without. BMI, HDL-c, Fmufa and Fsfa of visceral fat were independent factors for T2DM. Furthermore, Fsfa-S% was positively correlated with liver enzyme levels (P =.003 and 0.04). However, Fmufa-V% was negatively correlated with fasting blood glucose, HbA1c and HOMA-IR (P =.004, P =.001 and P =.03 respectively). Hence, the evaluation of fatty acid compositions of abdominal fat tissue using chemical shift-encoded MRI may have a predictive value for T2DM in patients with NAFLD.

Sarcosine, Trigonelline and Phenylalanine as Urinary Metabolites Related to Visceral Fat in Overweight and Obesity

The objective of the present study is to analyze the urinary metabolome profile of patients with obesity and overweight and relate it to different obesity profiles. This is a prospective, cross-sectional study in which patients with a body mass index (BMI) ≥25 kg/m were selected. Anthropometric data were assessed by physical examination and body composition was obtained by bioimpedance (basal metabolic rate, body fat percentile, skeletal muscle mass, gross fat mass and visceral fat). Urine was collected for metabolomic analysis. Patients were classified according to abdominal circumference measurements between 81 and 93, 94 and 104, and >104 cm; visceral fat up to 16 kilos and less than; and fat percentiles of <36%, 36-46% and >46%. Spectral alignment of urinary metabolite signals and bioinformatic analysis were carried out to select the metabolites that stood out. NMR spectrometry was used to detect and quantify the main urinary metabolites and to compare the groups. Seventy-five patients were included, with a mean age of 38.3 years, and 72% females. The urinary metabolomic profile showed no differences in BMI, abdominal circumference and percentage of body fat. Higher concentrations of trigonelline (p = 0.0488), sarcosine (p = 0.0350) and phenylalanine (p = 0.0488) were associated with patients with visceral fat over 16 kg. The cutoff points obtained by the ROC curves were able to accurately differentiate between patients according to the amount of visceral fat: sarcosine 0.043 mg/mL; trigonelline 0.068 mg/mL and phenylalanine 0.204 mg/mL. In conclusion, higher visceral fat was associated with urinary levels of metabolites such as sarcosine, related to insulin resistance; trigonelline, related to muscle mass and strength; and phenylalanine, related to glucose metabolism and abdominal fat. Trigonelline, sarcosine and phenylalanine play significant roles in regulating energy balance and metabolic pathways essential for controlling obesity. Our findings could represent an interesting option for the non-invasive estimation of visceral fat through biomarkers related to alterations in metabolic pathways involved in the pathophysiology of obesity.

Noninvasive NMR/MRS Metabolic Parameters to Evaluate Metabolic Syndrome in Rats

(1) Background: Ectopic fat deposition and its effects, metabolic syndrome, have been significantly correlated to lifestyle and caloric consumption. There is no specific noninvasive evaluation tool being used in order to establish clinical markers for tracing the metabolic pathway implicated in obesity-related abnormalities that occur in the body as a result of a high-fat diet (HFD). The purpose of this work is to investigate in vivo ectopic fat distribution and in vitro metabolite profiles given by HFDs, as well as how they are inter-related, in order to find surrogate metabolic biomarkers in the development of metabolic syndrome utilizing noninvasive approaches. (2) Methods: Male Wistar rats were divided into a standard normal chow diet, ND group, and HFD group. After 16 weeks of different diet administration, blood samples were collected for proton nuclear magnetic resonance (1H NMR) and biochemical analysis. Magnetic resonance imaging/proton magnetic resonance spectroscopy (MRI/1H MRS) was performed on the abdomen, liver, and psoas muscle of the rats. (3) Results: Visceral fat showed the strongest relationship with blood cholesterol. Although liver fat content (LFC) was not associated with any biophysical profiles, it had the highest correlation with metabolites such as (-CH2)n very-low-density lipoprotein/low-density lipoprotein (VLDL/LDL), lactate, and N-acetyl glycoprotein of serum 1H NMR. HFD showed no obvious influence on muscle fat accumulation. Acetoacetate, N-acetyl glycoprotein, lactate, (-CH2)n VLDL/LDL, and valine were the five possible metabolic biomarkers used to differentiate HFD from ND in the present study. (4) Conclusions: Our study has validated the influence of long-term HFD-induced ectopic fat on body metabolism as well as the metabolic profile deterioration both in vivo and in vitro.

Effects of one-year once-weekly high-intensity interval training on body adiposity and liver fat in adults with central obesity: Study protocol for a randomized controlled trial

Objective

This study aims to examine the effects of one-year, once-weekly high-intensity interval training (HIIT) on body adiposity and liver fat in adults with central obesity.

Methods

One-hundred and twenty adults aged 18–60 years with central obesity (body mass index ≥25, waist circumference ≥90 cm for men and ≥80 cm for women). This is an assessor-blinded randomized controlled trial. Participants will be randomly assigned to the HIIT group or the usual care control group. Each HIIT session will consist of 4 × 4-min bouts at 85%–95% maximal heart rate, interspersed with 3-min bouts at 50%–70% maximal heart rate. The HIIT group will complete one session per week for 12 months, whereas the usual care control group will receive health education. The primary outcomes of this study are total body adiposity and intrahepatic triglyceride content. The secondary outcomes include abdominal visceral adipose tissue, subcutaneous adipose tissue, body mass index, waist circumference, hip circumference, cardiorespiratory fitness, lean body mass, bone mineral density, blood pressure, fasting blood glucose, insulin, triglycerides, glycated hemoglobin, cholesterol profile, liver function enzymes, medications, adherence to exercise, adverse events, quality of life, and mental health. Outcome measure will be conducted at baseline, 12 months (post-intervention), and 24 months (one-year follow-up).

Impact of the project

This study will explore the benefits of long-term once-weekly HIIT with a follow-up period to assess its effectiveness, adherence, and sustainability. We expect this intervention will enhance the practical suitability of HIIT in inactive adults with central obesity, and provide insights on low-frequency HIIT as a novel exercise option for the management of patients with central obesity and liver fat.

Trial registration

ClinicalTrials.gov (NCT03912272) registered on 11 April 2019.