Distinct patterns of fat metabolism in skeletal muscle of normal-weight, overweight, and obese humans

Physiological Changes and Pathological Pain Associated with Sedentary Lifestyle-Induced Body Systems Fat Accumulation and Their Modulation by Physical Exercise

A sedentary lifestyle is associated with overweight/obesity, which involves excessive fat body accumulation, triggering structural and functional changes in tissues, organs, and body systems. Research shows that this fat accumulation is responsible for several comorbidities, including cardiovascular, gastrointestinal, and metabolic dysfunctions, as well as pathological pain behaviors. These health concerns are related to the crosstalk between adipose tissue and body systems, leading to pathophysiological changes to the latter. To deal with these health issues, it has been suggested that physical exercise may reverse part of these obesity-related pathologies by modulating the cross talk between the adipose tissue and body systems. In this context, this review was carried out to provide knowledge about (i) the structural and functional changes in tissues, organs, and body systems from accumulation of fat in obesity, emphasizing the crosstalk between fat and body tissues; (ii) the crosstalk between fat and body tissues triggering pain; and (iii) the effects of physical exercise on body tissues and organs in obese and non-obese subjects, and their impact on pathological pain. This information may help one to better understand this crosstalk and the factors involved, and it could be useful in designing more specific training interventions (according to the nature of the comorbidity).

Intramuscular fat in gluteus maximus for different levels of physical activity

We aimed to determine if gluteus maximus (GMAX) fat infiltration is associated with different levels of physical activity. Identifying and quantifying differences in the intramuscular fat content of GMAX in subjects with different levels of physical activity can provide a new tool to evaluate hip muscles health. This was a cross-sectional study involving seventy subjects that underwent Dixon MRI of the pelvis. The individuals were divided into four groups by levels of physical activity, from low to high: inactive patients due to hip pain; and low, medium and high physical activity groups of healthy subjects (HS) based on hours of exercise per week. We estimated the GMAX intramuscular fat content for each subject using automated measurements of fat fraction (FF) from Dixon images. The GMAX volume and lean volume were also measured and normalized by lean body mass. The effects of body mass index (BMI) and age were included in the statistical analysis. The patient group had a significantly higher FF than the three groups of HS (median values of 26.2%, 17.8%, 16.7% and 13.7% respectively, p < 0.001). The normalized lean volume was significantly larger in the high activity group compared to all the other groups (p < 0.001, p = 0.002 and p = 0.02). Employing a hierarchical linear regression analysis, we found that hip pain, low physical activity, female gender and high BMI were statistically significant predictors of increased GMAX fat infiltration.

Magnetic Resonance Spectroscopic Analysis of Multifidus Muscle Lipid Contents and Association with Nociceptive Pain in Chronic Low Back Pain

Study Design

Cross-sectional study.

Purpose

This study aimed to analyze the differences in the lipid contents in chronic low back pain (CLBP) patients with nociceptive pain (NocP) and neuropathic pain (NeP) using magnetic resonance spectroscopy (MRS) of the multifidus muscle (Mm).

Overview of Literature

Early identification of the pain characteristics with CLBP is important because specific treatment approaches are required, depending on NocP and NeP.

Methods

The participants were 50 patients with CLBP (23 men and 27 women; mean age, 63.1±17.8 years; range, 41–79 years). We compared the Visual Analog Scale (VAS) scores, intramyocellular lipids (IMCLs) and extramyocellular lipids (EMCLs) of the Mm in NocP and NeP groups, as evaluated with the Japanese NeP screening questionnaire.

Results

The patients were categorized into the NocP (n=32) and NeP (n=18) groups. The mean VAS score of the NocP group was 59.3±3.1 mm and that of the NeP group was 73.6±4.6 mm. The mean VAS score was significantly higher in the NeP group as compared to that in the NocP group (p<0.01). As per the analysis of covariance for the VAS score, the mean IMCL levels of the Mm in the NocP and NeP groups were 722.3 mmol/L (95% confidence interval [CI], 611.4–833.1) and 484.8 mmol/L (95% CI, 381.1–588.5), respectively. The mean IMCL level was significantly higher in the NocP group than in the NeP group (p<0.05). The mean EMCL levels of the Mm for the NocP and NeP groups were 6,022.9 mmol/L (95% CI, 4,510.6–7,535.2) and 5,558.1 mmol/L (95% CI, 4,298.3–6,817.9), respectively; however, the difference was not significant (p=0.72).

Conclusions

The results indicated an association between the IMCL level of the Mm and NocP. Our results suggest that MRS of the Mm might be beneficial for the assessment of CLBP as well as appropriate targeted analgesic therapies.

Multiomics Integrative Analysis for Discovering the Potential Mechanism of Dioscin against Hyperuricemia Mice

Hyperuricemia is a well-known key risk factor for gout and can cause a variety of metabolic diseases. Several studies have shown that dioscin could improve metabolic symptoms and reduce the uric acid level in blood. However, there is no comprehensive metabolomic study on the anti-hyperuricemia effects of dioscin. A total of 29 adult male Kunming mice were divided into three groups: Normal (blank), PO (potassium oxonate-administrated, 200 mg/kg/day), and Dioscin (potassium oxonate + dioscin, potassium oxonate 200 mg/kg/day, dioscin 50 mg/kg/day). All mice were treated for 42 days via oral gavage. This paper implemented an untargeted metabolomics study based on ¹H NMR and LC-MS to discover the comprehensive mechanism of dioscin. Furthermore, a targeted lipidomics was fulfilled to further analyze the lipid metabolism disorder. Finally, the metabolic pathway mediated by dioscin was verified at the gene level by means of transcriptomics. The results show 53 different metabolites were closely related to the improvement of dioscin in PO-induced hyperuricemia, and 19 of them were lipids. These metabolites are mainly involved in the tricarboxylic acid cycle, lipid metabolism, amino acid metabolism, and pyrimidine metabolism. According to the transcriptomics study, the levels of 89 genes were significantly changed in the PO group compared to the normal control. Among them, six gene levels were restored by the treatment of dioscin. The six changed genes (tx1b, Tsku, Tmem163, Psmc3ip, Tcap, Tbx15) are mainly involved in the cell cycle and energy metabolism. These metabolites and genes might provide useful information for further study of the therapeutic mechanism of dioscin.

Quantitative 1 H MRI and MRS of fatty acid composition

Adipose tissue as well as other depots of fat (triglycerides) are increasingly being recognized as active contributors to the human function and metabolism. In addition to the fat concentration, also the fatty acid chemical composition (FAC) of the triglyceride molecules may play an important part in diseases such as obesity, insulin resistance, hepatic steatosis, osteoporosis, and cancer. MR spectroscopy and chemical-shift-encoded imaging (CSE-MRI) are established methods for non-invasive quantification of fat concentration in tissue. More recently, similar techniques have been developed for assessment also of the FAC in terms of the number of double bonds, the fraction of saturated, monounsaturated, and polyunsaturated fatty acids, or semi-quantitative unsaturation indices. The number of papers focusing on especially CSE-MRI-based techniques has steadily increased during the past few years, introducing a range of acquisition protocols and reconstruction algorithms. However, a number of potential sources of bias have also been identified. Furthermore, the measures used to characterize the FAC using both MRI and MRS differ, making comparisons between different techniques difficult. The aim of this paper is to review MRS- and MRI-based methods for in vivo quantification of the FAC. We describe the chemical composition of triglycerides and discuss various potential FAC measures. Furthermore, we review acquisition and reconstruction methodology and finally, some existing and potential applications are summarized. We conclude that both MRI and MRS provide feasible non-invasive alternatives to the gold standard gas chromatography for in vivo measurements of the FAC. Although both are associated with gas chromatography, future studies are warranted.

Is the Lipid Content of the Psoas Major Correlated with Chronic Low Back Pain and Spinopelvic Alignment? A Magnetic Resonance Spectroscopic Study

Study Design

Cross-sectional observational study.

Purpose

This study aimed to analyze any potential associations of extramyocellular lipid (EMCL) and intramyocellular lipid (IMCL) contents with (1) the intensity of low back pain (LBP); (2) age, cross-sectional area (CSA), and fatty infiltration (FI) of the psoas major; and (3) spinopelvic parameters.

Overview of Literature

The psoas major has clinically relevant function; however, the association of this muscle with chronic LBP is controversial. Magnetic resonance spectroscopy enables a detailed analysis of the composition of muscular fat tissues such as its EMCL and IMCL contents.

Methods

The study population comprised 40 patients (19 males, 21 females; mean age, 61.7±2.4 years). Possible correlations of LBP Visual Analog Scale (VAS) scores, age, CSA, FI, and spinopelvic parameters with EMCL and IMCL contents of the psoas major were assessed.

Results

No association was identified between the EMCL and IMCL contents and LBP VAS scores (r=0.05, p=0.79 and r=0.06, p=0.75, respectively). The EMCL content correlated with age (r=0.47, p<0.01), body mass index (BMI) (r=0.44, p<0.01), CSA (r=−0.59, p<0.01), and FI (r=0.49, p<0.01). EMCL content showed a significant negative correlation with sacral slope (SS) (r=−0.43, p<0.05) and positive correlation with pelvic tilt (PT) (r=0.56, p<0.01).

Conclusions

EMCL content correlated with age, BMI, CSA, and FI of the psoas major, while IMCL content had no correlation. This study found correlations between SS and PT and EMCL content of the psoas major, but no correlations were found between spinopelvic parameters and IMCL content of the psoas major.

21st Century Advances in Multimodality Imaging of Obesity for Care of the Cardiovascular Patient

Although obesity is typically defined by body mass index criteria, this does not differentiate true body fatness, as this includes both body fat and muscle. Therefore, other fat depots may better define cardiometabolic and cardiovascular disease (CVD) risk imposed by obesity. Data from translational, epidemiological, and clinical studies over the past 3 decades have clearly demonstrated that accumulation of adiposity in the abdominal viscera and within tissue depots lacking physiological adipose tissue storage capacity (termed "ectopic fat") is strongly associated with the development of a clinical syndrome characterized by atherogenic dyslipidemia, hyperinsulinemia/glucose intolerance/type 2 diabetes mellitus, hypertension, atherosclerosis, and abnormal cardiac remodeling and heart failure. This state-of-the-art paper discusses the impact of various body fat depots on cardiometabolic parameters and CVD risk. Specifically, it reviews novel and emerging imaging techniques to evaluate adiposity and the risk of cardiometabolic diseases and CVD.

Quantitative Analysis Concerning Atrophy and Fat Infiltration of the Multifidus Muscle with Magnetic Resonance Spectroscopy in Chronic Low Back Pain

INTRODUCTION

Magnetic resonance spectroscopy (MRS) enables detailed analysis of the composition of muscular fat tissues such as intramyocellular lipids (IMCLs) and extramyocellular lipids (EMCLs). The aim of this study was to analyze the EMCL and IMCL of the multifidus muscle (Mm) using MRS in chronic low-back pain (CLBP) patients and identify their possible correlations with age, body mass index (BMI), low-back pain (LBP) visual analog scale (VAS) score, cross-sectional area (CSA), and fat infiltration of the Mm.

METHODS

Eighty patients (32 men and 48 women; mean age, 64.7 ± 1.3 years; range, 22-83 years) with VAS scores >30 mm for CLBP were included. We analyzed the gender difference and the possible correlations of age, BMI, LBP VAS, CSA, and fat infiltration of the Mm with the IMCL and EMCL of the Mm. The subjects were divided into five groups as per their age range: < 40s, 50s, 60s, 70s, and 80s. We also analyzed the EMCL and IMCL of the Mm as per the fat infiltration classification.

RESULTS

CSA was larger in the male group, EMCL was higher in the female group, and there was no significant difference in IMCL between the female and male groups. There was a significant positive correlation of EMCL with age (r = 0.33, p < 0.01) and BMI (r = 0.42, p < 0.01) and a significant negative correlation of EMCL with CSA (r = -0.61, p < 0.01). There was a significant positive correlation between IMCL and VAS (r = 0.43, p < 0.01). The EMCL and CSA of the Mm decreased with age, whereas fat infiltration increased with age.

CONCLUSIONS

These results suggest that EMCL could indicate Mm degeneration associated with aging, and IMCL could be an effective objective indicator of CLBP. The EMCL and IMCL of the Mm may be useful prognostic markers in rehabilitation strategies.

Multifidus Muscles Lipid Content Is Associated with Intervertebral Disc Degeneration: A Quantitative Magnetic Resonance Imaging Study

Study Design

Cross-sectional study.

Purpose

To determine the association between fatty degeneration of the multifidus muscle (Mm) and intervertebral disc degeneration (IVDD) using quantitative magnetic resonance imaging (MRI).

Overview of Literature

Few studies have reported on quantitative MRI analysis of the relation between the Mm and IVDD.

Methods

The subjects with chronic low back pain comprised 45 patients (19 males, 26 females; mean age, 63.8±2.0 years; range, 41-79 years). We analyzed the intramyocellular lipids (IMCL) and extramyocellular lipids (EMCL) of the Mm using magnetic resonance spectroscopy. The T2 values of the anterior annulus fibrosus (AF), nucleus pulposus (NP), and posterior AF were evaluated using MRI T2 mapping. We compared the possible correlations of IMCL and EMCL of the Mm with the T2 values of anterior AF, NP, and posterior AF.

Results

There was a significant negative correlation between IMCL and T2 values of the anterior AF (r=-0.65, p<0.01). There were no significant correlations between the IMCL and T2 values of NP (r=-0.16, p=0.30) and posterior AF (r=0.07, p=0.62). There were no significant correlations between the EMCL and T2 values of the anterior AF (r=-0.11, p=0.46), NP (r=0.15, p=0.32), and posterior AF (r=0.07, p=0.66). After adjustment for age and sex using multiple linear regression analysis, there was a significant negative correlation between the IMCL and T2 values of anterior AF (standardized partial regression coefficient=-0.65, p<0.01).

Conclusions

The results indicated that IMCL of the Mm might be accompanied with anterior AF degeneration. Therapeutic exercises using IMCL of the Mm as evaluation index might have the potential to identify novel targets for the treatment and prevention of IVDD.

Analysis of intra and extramyocellular lipids in the multifidus muscle in patients with chronic low back pain using MR spectroscopy

OBJECTIVE

To analyse the intra- (IMCL) and extramyocellular lipids (EMCL) concentration in the multifidus muscle (Mm) using MR spectroscopy (MRS) in patients with low back pain (LBP), and to evaluate the correlation between those lipid concentrations and age, obesity, atrophy of the Mm and LBP intensity.

METHODS

60 LBP patients underwent routine diagnostic MRI of the lumbar spine before undergoing imaging for the study. Body mass index, as an indicator of obesity and visual analogue scale, as an indicator of LBP were also measured. Proton MRS was acquired with a single-voxel point-resolved spectroscopy sequence. Furthermore, the MRS volume of interest for measuring the IMCL and EMCL concentration at L4/5 for the right Mm was determined, and we measured the cross-sectional area of Mm as an indicator of muscle atrophy.

RESULTS

Age showed correlation with EMCL concentration (r = 0.314, p = 0.008). The body mass index showed correlation with EMCL concentration (r = 0.358, p = 0.005). The cross-sectional area of Mm showed correlation with EMCL concentration (r = -0.543, p < 0.001). Moreover, the LBP visual analogue scale showed correlation with IMCL concentration (r = 0.367, p = 0.004).

CONCLUSION

There were correlations between age, obesity, muscle atrophy, and EMCL concentration in Mm. IMCL concentration in Mm showed a correlation with LBP intensity. This may suggest that IMCL concentration could become an effective objective indicator of chronic LBP intensity. Advances in knowledge: We investigated the characteristics of fat content in Mm with LBP patients. This study was demonstrated the association of the IMCL and EMCL concentration in Mm with various patient parameters.

Assessment of Lipid and Metabolite Changes in Obese Calf Muscle Using Multi-Echo Echo-planar Correlated Spectroscopic Imaging

Obesity-related conditions including heart disease, stroke, and type 2 diabetes are leading causes of preventable death. Recent evidence suggests that altered myocellular lipid metabolism in obesity may lead to increased insulin resistance (IR) that predisposes to these disorders. To test the hypothesis that muscles rich in type I vs. type II muscle fibers would exhibit similar changes in intramyocellular lipid (IMCL) and extramyocellular lipid (EMCL) content in obesity, we utilized a new four-dimensional multi echo echo-planar correlated spectroscopic imaging technique that allows separate determination of IMCL and EMCL content in individual calf muscles in obese vs. normal healthy human subjects. Calf muscles were scanned in 32 obese and 11 healthy subjects using a 3T MRI/MRS scanner, and IR in the obese subjects was documented by glucose tolerance testing. In obese subjects, elevation of both IMCL and EMCL content was observed in the gastrocnemius and tibialis anterior muscles (with mixed type I and II fiber content), while a significant increase in only IMCL content (+48%, p < 0.001) was observed in the soleus muscle (predominantly type I fibers). These observations indicate unexpected differences in changes in myolipid metabolism in type I vs. type II rich muscle regions in obesity, perhaps related to IR, and warrant further investigation.

Magnetic resonance spectroscopic analysis of multifidus muscles lipid content and association with spinopelvic malalignment in chronic low back pain

OBJECTIVE

To analyze intramyocellular lipids (IMCLs) and extramyocellular lipids (EMCLs) of the multifidus muscle (Mm) using MR spectroscopy in chronic low back pain (CLBP) and control groups and to identify correlations with spinopelvic alignment.

METHODS

40 patients (16 males, 24 females; mean age, 62.9 ± 1.9 years) whose visual analogue scale scores were >30 mm for CLBP were included. Furthermore, 40 control participants matched with the CLBP group subjects by sample size, gender and age (17 males, 23 females; mean age, 65.0 ± 1.2 years) were included. We compared the body mass index, physical workload, leisure time physical activity level, spinopelvic parameters, and IMCLs and EMCLs of the Mm between the groups. We also evaluated possible correlations of spinopelvic parameters with IMCLs and EMCLs of the Mm in the groups.

RESULTS

There were no statistically significant differences in body mass index, physical workload, exercise intensity level, spinopelvic parameters and EMCLs between the groups. The IMCLs were significantly higher in the CLBP group than in the control group (p < 0.01). In the CLBP group, there was a significantly negative correlation between IMCLs and lumbar lordosis (r = -0.64, p < 0.01) and a significantly positive correlation between IMCLs and sagittal vertical axis (r = 0.43, p < 0.01).

CONCLUSION

The measurement of IMCLs might be a characteristic finding of CLBP as well as a precursor to spinal deformity. Advances in knowledge: IMCLs of the Mm may be a useful prognostic marker in rehabilitation strategies for patients with CLBP.

Evaluation of intramyocellular and extramyocellular lipids in the paraspinal muscle in patients with chronic low back pain using MR spectroscopy: preliminary results

OBJECTIVE:

To analyze the intramyocellular lipids (IMCL) and extramyocellular lipids (EMCL) in the psoas muscle (Pm) and multifidus muscle (Mm) using MR spectroscopy (MRS) in patients with chronic low back pain (CLBP) and asymptomatic volunteers.

METHODS:

This prospective study had institutional review board approval, and written informed consent was obtained from all individual participants. 20 patients with CLBP (mean age, 49.8 ± 12.5 years; age range, 28-66 years) with low back pain (LBP) duration of ≥3 months and asymptomatic volunteers (mean age, 44.0 ± 12.8 years; age range, 28-65 years) underwent MRS for the quantification of IMCL and EMCL of the right Pm and Mm in a volume of interest at the intervertebral level of L4 through L5. We compared patients with CLBP and asymptomatic volunteers for age and body mass index (BMI), IMCL and EMCL of Pm and Mm. The Mann-Whitney U-test was used for significant difference testing, with p-value <0.05 indicating statistical significance.

RESULTS:

No statistically significant differences were observed in the age and BMI of patients with CLBP and asymptomatic volunteers. There was no statistically significant difference in the EMCL and IMCL in Pm between the two groups. EMCL in Mm was not statistically significantly different; the IMCL of patients with CLBP was significantly higher than that of asymptomatic volunteers (p < 0.05).

CONCLUSION:

MRS demonstrates that IMCL in the Mm of patients with CLBP is significantly higher than that of asymptomatic volunteers. The increase of IMCL in the Mm may be a characteristic finding in CLBP.

ADVANCES IN KNOWLEDGE:

We investigated the detail of the fat content in the paraspinal muscles in patients CLBP and asymptomatic volunteers. The increase of fat content in the Mm of patients with LBP on previous studies was demonstrated to be the increase of IMCL.

Bone marrow fat unsaturation in young adults is not affected by present or childhood obesity, but increases with age: A pilot study

OBJECTIVES

Obesity increases bone marrow fat (BMF) content. The association between early obesity and bone marrow fatty acid composition is unknown. We measured BMF unsaturation index (UI) in normal-weight and overweight young adults with a known weight status in early childhood and tested the relationship between BMF UI and exercise history, glycemic state, and other clinical characteristics.

METHODS

The study included 18 normal-weight (BMI <25 kg/m(2); 2 males, 16 females) and 17 overweight (BMI ≥25 kg/m(2); 9 males, 8 females) young adults aged 15-27 years. BMF UI was assessed with magnetic resonance proton spectroscopy optimized to reduce water interference. Exercise information was obtained with a pedometer accompanied with the history of recent physical activity. Blood samples (insulin, glucose, HbA1c) and body characteristics (BMI, waist-to-hip ratio, body fat composition) were assessed.

RESULTS

BMF UI was not affected by obesity at the time of study or before age 7 years. BMF UI increased with age in normal-weight and overweight subjects (R=0.408, p=0.015) but did not associate with gender, physical activity or body fat composition; a suggestive association was observed with glucose (R=-0.289, p=0.10).

CONCLUSIONS

The association of BMF UI with age in early adulthood may represent normal maturation of bone marrow. There was a trend toward an association with blood glucose, warranting further studies.

Fiber orientation measurements by diffusion tensor imaging improve hydrogen-1 magnetic resonance spectroscopy of intramyocellular lipids in human leg muscles

Twelve healthy subjects underwent hydrogen-1 magnetic resonance spectroscopy ([Formula: see text]) acquisition ([Formula: see text]), diffusion tensor imaging (DTI) with a [Formula: see text]-value of [Formula: see text], and fat-water magnetic resonance imaging (MRI) using the Dixon method. Subject-specific muscle fiber orientation, derived from DTI, was used to estimate the lipid proton spectral chemical shift. Pennation angles were measured as 23.78 deg in vastus lateralis (VL), 17.06 deg in soleus (SO), and 8.49 deg in tibialis anterior (TA) resulting in a chemical shift between extramyocellular lipids (EMCL) and intramyocellular lipids (IMCL) of 0.15, 0.17, and 0.19 ppm, respectively. IMCL concentrations were [Formula: see text], [Formula: see text], and [Formula: see text] in SO, VL, and TA, respectively. Significant differences were observed in IMCL and EMCL pairwise comparisons in SO, VL, and TA ([Formula: see text]). Strong correlations were observed between total fat fractions from [Formula: see text] and Dixon MRI for VL ([Formula: see text]), SO ([Formula: see text]), and TA ([Formula: see text]). Bland-Altman analysis between fat fractions (FFMRS and FFMRI) showed good agreement with small limits of agreement (LoA): [Formula: see text] (LoA: [Formula: see text] to 0.69%) in VL, [Formula: see text] (LoA: [Formula: see text] to 1.33%) in SO, and [Formula: see text] (LoA: [Formula: see text] to 0.47%) in TA. The results of this study demonstrate the variation in muscle fiber orientation and lipid concentrations in these three skeletal muscle types.

Investigation of Fat Metabolism during Antiobesity Interventions by Magnetic Resonance Imaging and Spectroscopy

The focus of current treatments for obesity is to reduce the body weight or visceral fat, which requires longer duration to show effect. In this study, we investigated the short-term changes in fat metabolism in liver, abdomen, and skeletal muscle during antiobesity interventions including Sibutra mine treatment and diet restriction in obese rats using magnetic resonance imaging, magnetic resonance spectroscopy, and blood chemistry. Sibutramine is an antiobesity drug that results in weight loss by increasing satiety and energy expenditure. The Sibutramine-treated rats showed reduction of liver fat and intramyocellular lipids on day 3. The triglycerides (TG) decreased on day 1 and 3 compared to baseline (day 0). The early response/nonresponse in different fat depots will permit optimization of treatment for better clinical outcome rather than staying with a drug for longer periods.

A pilot validation of multi-echo based echo-planar correlated spectroscopic imaging in human calf muscles

A current limitation of MR spectroscopic imaging of multiple skeletal muscles is prolonged scan duration. A significant reduction in the total scan duration using the echo-planar correlated spectroscopic imaging (EP-COSI) sequence was accomplished using two bipolar readout trains with different phase-encoded echoes for one of two spatial dimensions within a single repetition time (TR). The second bipolar readout was used for spatially encoding the outer k-space, whereas the first readout was used for the central k-space only. The performance of this novel sequence, called multi-echo based echo-planar correlated spectroscopic imaging (ME-EPCOSI), was demonstrated by localizing specific key features in calf muscles and bone marrow of 11 healthy volunteers and five subjects with type 2 diabetes (T2D). A 3 T MRI-MRS scanner equipped with a transmit-receive extremity coil was used. Localization of the ME-EPCOSI sequence was in good agreement with the earlier single-readout based EP-COSI sequence and the required scan time was reduced by a factor of two. In agreement with an earlier report using single-voxel based 2D MRS, significantly increased unsaturated pools of intramyocellular lipid (IMCL) and extramyocellular lipid (EMCL) and decreased IMCL and EMCL unsaturation indices (UIs) were observed in the soleus and tibialis anterior muscle regions of subjects with T2D compared with healthy controls. In addition, significantly decreased choline content was observed in the soleus of T2D subjects compared with healthy controls. Multi-voxel characterization of IMCL and EMCL ratios and UI in the calf muscle may be useful for the non-invasive assessment of altered lipid metabolism in the pathophysiology of T2D.

Marrow fat composition in anorexia nervosa

PURPOSE

Women with anorexia nervosa (AN) have increased marrow fat despite severe depletion of body fat. Recent studies have suggested that marrow fat composition may serve as a biomarker for bone quality. The purpose of our study was to investigate marrow fat composition of the femur using proton MR spectroscopy ((1)H MRS), and the relationship between measures of marrow fat composition and BMD and body composition in women with AN and normal-weight controls.

MATERIALS AND METHODS

14 women with AN (29.5±1.9years) and 12 age-matched normal-weight controls underwent (1)H MRS to determine total marrow fat content and marrow fat composition of the femoral diaphysis and soleus intramyocellular lipids und unsaturated muscle lipids. MRI was performed to quantify abdominal fat, thigh fat and muscle areas. Lumbar spine BMD, fat and lean mass were assessed by DXA.

RESULTS

Subjects with AN had higher marrow fat content (p<0.05), but similar marrow fat composition (p>0.05) compared to normal-weight controls. There was an inverse association between marrow methylene protons, an estimate of fatty acid (FA) saturated bonds, and lumbar spine BMD (r=-0.52, p=0.008) independent of %ideal body weight (%IBW). Olefinic protons at 5.3ppm, an estimate of FA unsaturated bonds, were inversely associated with body fat depots, independent of %IBW, and positively associated with soleus unsaturation (p≤0.05).

CONCLUSION

Women with AN have higher total femoral marrow fat but similar composition compared to normal-weight controls. The degree of marrow FA saturation correlates inversely with BMD, suggesting that saturated lipids may have negative effects on BMD. The degree of marrow FA unsaturation correlates positively with soleus unsaturation, suggesting that marrow fat composition may be influenced by the same factors as ectopic lipid composition in muscle.

Evaluation of dietary effects on hepatic lipids in high fat and placebo diet fed rats by in vivo MRS and LC-MS techniques

Background & Aims

Dietary saturated fatty acids contribute to the development of fatty liver and have pathogenic link to systemic inflammation. We investigated the effects of dietary fat towards the pathogenesis of non-alcoholic fatty liver disease by longitudinal in vivo magnetic resonance spectroscopy (MRS) and in vitro liquid chromatography coupled with mass spectrometry (LC-MS).

Methods

All measurements were performed on rats fed with high fat diet (HFD) and chow diet for twenty four weeks. Longitudinal MRS measurements were performed at the 12^th, 18^th and 24^th weeks. Liver tissues were analyzed by LC-MS, histology and gene transcription studies after terminal in vivo experiments.

Results

Liver fat content of HFD rats for all ages was significantly (P<0.05) higher compared to their respective chow diet fed rats. Unsaturation indices estimated from MRS and LC-MS data of chow diet fed rats were significantly higher (P<0.05) than HFD fed rats. The concentration of triglycerides 48∶1, 48∶2, 50∶1, 50∶2, 50∶3, 52∶1, 52∶2, 52∶3, 54∶3 and 54∶2 was significantly higher (P<0.05) in HFD rats. The concentration for some polyunsaturated triglycerides 54∶7, 56∶8, 56∶7, 58∶11, 58∶10, 58∶9, 58∶8 and 60∶10 was significantly higher (P<0.05) in chow diet fed rats compared to HFD rats. Lysophospholipid concentrations including LPC and LPE were higher in HFD rats at 24 weeks indicating the increased risk of diabetes. The expression of CD36, PPARα, SCD1, SREBF1 and UCP2 were significantly upregulated in HFD rats.

Conclusions

We demonstrated the early changes in saturated and unsaturated lipid composition in fatty liver by in vivo MRS and ex vivo LC-MS. The higher LPC concentration in HFD rats indicated a higher risk of developing diabetes. Early metabolic perturbations causing changes in lipid composition can be evaluated by the unsaturation index and correlated to the non alcoholic fatty liver disease.

Cardiac function and lipid distribution in rats fed a high-fat diet: in vivo magnetic resonance imaging and spectroscopy

Obesity is a major risk factor in the development of cardiovascular disease, type 2 diabetes, and its pathophysiological precondition insulin resistance. Very little is known about the metabolic changes that occur in the myocardium and consequent changes in cardiac function that are associated with high-fat accumulation. Therefore, cardiac function and metabolism were evaluated in control rats and those fed a high-fat diet, using magnetic resonance imaging, magnetic resonance spectroscopy, mRNA analysis, histology, and plasma biochemistry. Analysis of blood plasma from rats fed the high-fat diet showed that they were insulin resistant (P < 0.001). Our high-fat diet model had higher heart weight (P = 0.005) and also increasing trend in septal wall thickness (P = 0.07) compared with control diet rats. Our results from biochemistry, magnetic resonance imaging, and mRNA analysis confirmed that rats on the high-fat diet had moderate diabetes along with mild cardiac hypertrophy. The magnetic resonance spectroscopy results showed the extramyocellular lipid signal only in the spectra from high-fat diet rats, which was absent in the control diet rats. The intramyocellular lipids in high-fat diet rats was higher (8.7%) compared with rats on the control diet (6.1%). This was confirmed by electron microscope and light microscopy studies. Our results indicate that lipid accumulation in the myocardium might be an early indication of the cardiovascular pathophysiology associated with type 2 diabetes.

Characterization of Intra-myocellular Lipids using 2D Localized Correlated Spectroscopy and Abdominal Fat using MRI in Type 2 Diabetes

A major goal of this pilot study was to quantify intramyocellular lipids (IMCL), extramyocellular lipids (EMCL), unsaturation index (UI) and metabolites such as creatine (Cr), choline (Ch) and carnosine (Car), in the soleus muscle using two-dimensional (2D) localized correlated spectroscopy (L-COSY). Ten subjects with type 2 diabetes (T2D), controlled by lifestyle management alone, and 9 healthy control subjects, were studied. In T2D patients only, the following measurements were obtained: body mass index (BMI); waist circumference (WC); abdominal visceral and subcutaneous fat quantified using breath-held magnetic resonance imaging (MRI); a fasting blood draw for assessment of glucose, insulin, and estimation of homeostasis model assessment of insulin resistance (HOMA-IR), HbA_1c, and high-sensitivity c-reactive protein (hs-CRP). Analysis of the soleus muscle 2D L-COSY spectral data showed significantly elevated IMCL ratios with respect to Cr and decreased IMCL UI in T2D when compared to healthy subjects (P < 0.05). In T2D subjects, Pearson correlation analysis showed a positive correlation of IMCL/Cr with EMCL/Cr (0.679, P < 0.05) and HOMA-IR (0.633, P < 0.05), and a non-significant correlation of visceral and subcutaneous fat with magnetic resonance spectroscopy (MRS) and other metrics. Characterization of muscle IMCL and EMCL ratios, UI, and abdominal fat, may be useful for the noninvasive assessment of the role of altered lipid metabolism in the pathophysiology of T2D, and for assessment of the effects of future therapeutic interventions designed to alter metabolic dysfunction in T2D.

Nepeta japonica Maximowicz extract from natural products inhibits lipid accumulation

BACKGROUND

To develop novel and crude anti-obesity drugs from natural products is a promising field to approach the solution to a global health problem such as obesity. The aim of this study was to screen crude anti-obesity drugs from 400 natural products on lipase inhibition activity in vitro.

RESULTS

Among the natural products examined, 31 extracts showed significantly inhibition activity against porcine pancreatic lipase (triacylglycerol lipase, EC 3.1.1.3) by using spectrophotometry with 2,4-dinitrophenylbutyrate as a substrate. Furthermore, 31 natural products were investigated with regard to their lipid inhibition in 3T3-L1 cells. Among these, one of most promising was Nepeta japonica Maximowicz extract, which showed inhibition of triglyceride accumulation in 3T3-L1 adipocytes, suggesting anti-obesity activity. Also, the amount of glycerol released from cells into the medium was increased by treatment of Nepeta japonica Maximowicz extract at a concentration of 100 µg mL(-1) .

CONCLUSION

The present study suggests that a promising crude anti-obesity drug screened from 400 natural products might be of therapeutic interest with respect to the treatment of obesity.

Implementation of multi-echo-based correlated spectroscopic imaging and pilot findings in human brain and calf muscle

PURPOSE

To implement a spatially encoded correlated spectroscopic imaging (COSI) sequence on 3 Tesla (T) MRI/MR spectroscopy scanners incorporating four echoes to collect four phase-encoded acquisitions per repetition time (TR), and to evaluate the performance and reliability of this four-dimensional (4D) multi-echo COSI (ME-COSI) sequence in brain and calf muscle.

MATERIALS AND METHODS

Typical scan parameters for the 4D datasets were as follows: repetition time = 1500 ms, 2000 Hz bandwidth, 8 × 8 spatial encoding, one average, 64 Δt(1) increments and the scan duration was 25 min. The performance and test-retest reliability of ME-COSI were evaluated with phantoms and in the occipitoparietal brain tissues and calf of six healthy volunteers (mean age = 32 years old).

RESULTS

Regional differences in concentrations of lipids, creatine (Cr), choline (Ch), and carnosine (Car) were observed between spectra from voxels located in tibial marrow, tibialis anterior, and soleus muscle. Diagonal and cross-peak resonances were identified from several brain metabolites including N-acetyl aspartate (NAA), Ch, Cr, lactate (Lac), aspartate (Asp), glutathione (GSH), and glutamine\glutamate (Glx). Coefficients of variation (CV) in metabolite ratios across repeated measurements were <15% for diagonal and <25% for cross-peaks observed in vivo.

CONCLUSION

The ME-COSI sequence reliably acquired spatially resolved 2D Correlated Spectroscopy (COSY) spectra demonstrating the feasibility of differentiating spatial variation of metabolites in different tissues. Multi-echo acquisition shortens scan duration to clinically feasible times.

Rosiglitazone increases fatty acid Δ9-desaturation and decreases elongase activity index in human skeletal muscle in vivo

The ratio of unsaturated to saturated long-chain fatty acids (LC-FAs) in skeletal muscle has been associated with insulin resistance. Some animal data suggest a modulatory effect of peroxisome proliferator receptor γ (PPARγ) stimulation on stearoyl-CoA desaturase 1 (SCD1) and LC-FA composition in skeletal muscle, but human data are rare. We here investigate whether treatment with a PPARγ agonist affects myocellular SCD1 expression and modulates the intramyocellular fatty acid profile in individuals with impaired glucose tolerance. Muscle biopsies and hyperinsulinemic-euglycemic clamps were performed in 7 men before and after 8 weeks of rosiglitazone treatment. Intramyocellular saturated, monounsaturated, and polyunsaturated intramuscular fatty acid profiles were measured by gas chromatography. Effects on SCD1 messenger RNA expression were analyzed in C2C12 cells and in human biopsies before and after rosiglitazone treatment. As expected, treatment with the PPARγ activator rosiglitazone improved insulin sensitivity in humans. Myocellular SCD1 messenger RNA expression was increased in human biopsies and C2C12 cells. Although the total content of myocellular LC-FA was unchanged, a relative shift from saturated LC-FAs to unsaturated LC-FAs was observed in human biopsies. Particularly, the amount of stearate was reduced, whereas the amounts of palmitoleate as well as oleate and vaccenate were increased, after rosiglitazone therapy. These changes resulted in an increased fatty acid Δ9-desaturation index (16:1/16:0 and 18:1/18:0) in skeletal muscle and a decreased elongase activity index (18:0/16:0). The PPARγ associated phenotypes may be partially explained by an increased Δ9-desaturation and a decreased elongase activity of skeletal muscle.

Effect of J-coupling on lipid composition determination with localized proton magnetic resonance spectroscopy at 9.4 T

PURPOSE

To demonstrate, at 9.4 T, that J-coupling interactions exhibited by lipid protons affects lipid composition determination with a point resolved spectroscopy (PRESS) sequence.

MATERIALS AND METHODS

Experiments were conducted on four oils (almond, corn, sesame, and sunflower), on visceral adipose tissue of a euthanized mouse, and on pure linoleic acid at 9.4 T. The 2.1, 2.3, and 2.8 ppm resonances were measured at multiple echo times (TEs) by a standard PRESS sequence and by a PRESS sequence consisting of narrow-bandwidth refocusing pulses designed to rewind the J-coupling evolution of the target peak protons in the voxel of interest. T(2) corrections were performed on both groups of data for the three peaks and lipid compositions for the oils and for the mouse tissue were determined. Lipid compositions were also calculated from a short-TE standard PRESS spectrum.

RESULTS

A chemical analysis of the samples was not performed; however, the oil compositions calculated from resonance peaks acquired with the PRESS sequence designed to minimize J-coupling effects, following T(2) relaxation correction, closely agreed with values in the literature, which was not the case for all of the compositions determined from the regular PRESS spectra.

CONCLUSION

The presented work brings to attention the significance of J-coupling effects when calculating lipid compositions from localized proton spectra.

Investigation of adipose tissues in Zucker rats using in vivo and ex vivo magnetic resonance spectroscopy

In vivo single-voxel magnetic resonance spectroscopy (MRS) at 4.7T and ex vivo high-resolution proton magnetic resonance spectroscopy (HR-NMR) at 500 MHz were used to study the composition of adipose tissues in Zucker obese and Zucker lean rats. Lipid composition was characterized by unsaturation and polyunsaturation indexes and mean chain lengths. In vitro experiments were conducted in known mixtures of triglycerides and oils in order to validate the method. To avoid inaccuracies due to partial peak overlapping in MRS, peak quantification was performed after fitting of spectral peaks by using the QUEST algorithm. The intensity of different spectral lines was also corrected for T2 relaxation. Albeit with different sensitivity and accuracy, both techniques revealed that white adipose tissue is characterized by lower unsaturation and polyunsaturation indexes in obese rats compared with controls. HR-NMR revealed similar differences in brown adipose tissue. The present findings confirm the hypothesis that obese and lean Zucker rats have different adipose tissue composition.

T(2) determination of the J-coupled methyl protons of lipids: In vivo ilustration with tibial bone marrow at 3 T

PURPOSE

To demonstrate how J-coupling modulations of the CH(3) lipid resonance can be minimized enabling a representative T(2) to be measured.

MATERIALS AND METHODS

Experiments were conducted on canola oil and in vivo on tibial bone marrow of four volunteers at 3 T. The T(2) of the CH(2) protons was measured with a standard point resolved spectroscopy (PRESS) sequence, whereas the T(2) of the CH(3) protons was determined with a PRESS sequence composed of narrow bandwidth refocusing pulses designed to exploit the chemical shift displacement effect and rewind the J-coupling evolution of the CH(3) protons in the desired voxel. Spectra were acquired at five echo times.

RESULTS

The narrow bandwidth PRESS sequence rewound the J-evolution of the CH(3) protons resulting in a T(2) curve that was well described by a monoexponential function. The mean T(2) of the bone marrow CH(3) protons was calculated to be 132.6 msec. The mean T(2) of the bone marrow CH(2) protons was estimated with a regular PRESS sequence to be 88.0 msec. The mean CH(2):CH(3) tibial bone marrow composition was estimated to be 12.0:1.

CONCLUSION

The presented technique permits the T(2) of the methyl protons of lipids to be determined with more accuracy by minimizing contributions from J-coupling.

Imaging metabolic syndrome

Metabolic syndrome is a fast growing public health burden for almost all the developed countries and many developing nations. Despite intense efforts from both biomedical and clinical scientists, many fundamental questions regarding its aetiology and development remain unclear, partly due to the lack of suitable imaging technologies to visualize lipid composition and distribution, insulin secretion, β-cell mass and functions in vivo. Such technologies would not only impact on our understanding of the complexity of metabolic disorders such as obesity and diabetes, but also aid in their diagnosis, drug development and assessment of treatment efficacy. In this article we discuss and propose several strategies for visualization of physiological and pathological changes that affect pancreas and adipose tissue as a result of the development of metabolic diseases.

Assessment of lipids in skeletal muscle by LCModel and AMARES

PURPOSE

To process single voxel spectra of the human skeletal muscle by using an advanced method for accurate, robust, and efficient spectral fitting (AMARES) and by linear combination of model spectra (LCModel). To determine absolute concentrations of extra- (EMCL) and intramyocellular lipids (IMCL).

MATERIALS AND METHODS

Single-voxel proton magnetic resonance spectroscopy (PRESS) was used to obtain the spectra of the calf muscles. Unsuppressed water line was used as a concentration reference. A new prior knowledge for AMARES was proposed to estimate the concentrations of EMCL and IMCL. The prior knowledge was derived from the spectrum of vegetable oil. The results were compared with the values estimated by LCModel. Absolute concentrations of total lipid content in millimoles per kilogram wet weight were used for the comparisons.

RESULTS

Absolute concentrations of total lipid content in skeletal muscle were estimated by AMARES and LCModel. Very good correlation of the total fat (EMCL + IMCL) and IMCL concentrations was achieved between both data processing approaches.

CONCLUSION

Assessment the absolute concentrations of muscular lipids by AMARES and LCModel can be performed with comparable accuracy.