Proton magnetic resonance spectroscopy in skeletal muscle: Experts' consensus recommendations.

1 H-MR spectroscopy of skeletal muscle provides insight into metabolism that is not available noninvasively by other methods. The recommendations given in this article are intended to guide those who have basic experience in general MRS to the special application of 1 H-MRS in skeletal muscle. The highly organized structure of skeletal muscle leads to effects that change spectral features far beyond simple peak heights, depending on the type and orientation of the muscle. Specific recommendations are given for the acquisition of three particular metabolites (intramyocellular lipids, carnosine and acetylcarnitine) and for preconditioning of experiments and instructions to study volunteers.

Plasma metabolites reveal distinct profiles associating with different metabolic risk factors in monozygotic twin pairs.

BACKGROUND: Obesity is related to a myriad of cardiometabolic outcomes, each of which may have a specific metabolomic signature and a genetic basis. We identified plasma metabolites associating with different cardiometabolic risk factors (adiposity, cholesterol, insulin resistance, and inflammation) in monozygotic (MZ) twins. Additionally, we assessed if metabolite profiling can identify subgroups differing by cardiometabolic risk factors. METHODS: We quantified 111 plasma metabolites (Acquity UPLC-triple quadrupole mass spectrometry), and measured blood lipids, HOMA index, CRP, and adiposity (BMI, %bodyfat by DEXA, fat distribution by MRI) in 40 MZ twin pairs (mean BMI 27.9 kg/m2, age 30.7). We determined associations among individuals (via linear regression) between metabolites and clinical phenotypes, and assessed, with within-twin pair analysis, if these associations were free from genetic confounding. We also performed cluster analysis to identify distinct subgroups based on subjects' metabolite profiles. RESULTS: We identified 42 metabolite-phenotype associations (FDR < 0.05), 19 remained significant after controlling for shared factors within the twin pairs. Aspartate, propionylcarnitine, tyrosine hexanoylcarnitine, and deoxycytidine associated positively with two or more adiposity measures. HDL cholesterol (HDL-C) associated negatively and BMI positively with the most numbers of metabolites; 12 were unique for HDL-C and 3 for BMI. Metabolites associating with HDL-C had the strongest effect size. Metabolite profiling revealed two distinct subgroups of individuals, differing by 32 metabolites (p < 0.05), and by total and LDL cholesterol (LDL-C). Forty-two metabolites predicted subgroup membership in correlation with total cholesterol and 45 metabolites predicted subgroup membership in correlation with LDL-C. CONCLUSIONS: Different fat depots share metabolites associating with general adiposity. BMI and HDL-C associated with the most pronounced and specific metabolomic signature. Metabolomics profiling can be used to identify distinct subgroups of individuals that differ by cholesterol measures. Most of the observed metabolite-phenotype associations are free of confounding by genetics and environmental factors shared by the co-twins.

1H-MRS of femoral red and yellow bone marrow fat composition and water content in healthy young men and women at 3 T.

OBJECTIVES: There is a discrepancy between studies suggesting that higher bone marrow fat saturation is associated with impaired health, and studies suggesting that erythropoiesis increases red bone marrow (RBM) fat saturation in young healthy individuals. Here, we seeked to elucidate these discrepancies by using long TE magnetic resonance spectroscopy (MRS) to study both yellow bone marrow (YBM) and RBM in the femur of healthy volunteers. MATERIALS AND METHODS: Thirty-three young healthy volunteers (17 females), age range 20-31 years, underwent long TE 1H MRS at 3.0 T of RBM and YBM fat composition in the left femur. The water content of the bone marrow depots was measured using short TE MRS. RESULTS: The female participants displayed a lower unsaturation in the sampled RBM volume (RBMV) than the males (P < 0.01) without displaying a concomitant difference in YBM (P = 0.42). They also showed a higher water content and broader spectral linewidths in RBM (P = 0.04). The water content in RBM strongly associated with broader spectral linewidths (R = 0.887, P ≪ 0.01) and inversely with RBMV fat unsaturation (R = - 0.365, P = 0.04). DISCUSSION: These results partly support the notion that females display higher rate of erythropoiesis and lower fat unsaturation in RBM.

Personal model-assisted identification of NAD+ and glutathione metabolism as intervention target in NAFLD.

To elucidate the molecular mechanisms underlying non-alcoholic fatty liver disease (NAFLD), we recruited 86 subjects with varying degrees of hepatic steatosis (HS). We obtained experimental data on lipoprotein fluxes and used these individual measurements as personalized constraints of a hepatocyte genome-scale metabolic model to investigate metabolic differences in liver, taking into account its interactions with other tissues. Our systems level analysis predicted an altered demand for NAD+ and glutathione (GSH) in subjects with high HS Our analysis and metabolomic measurements showed that plasma levels of glycine, serine, and associated metabolites are negatively correlated with HS, suggesting that these GSH metabolism precursors might be limiting. Quantification of the hepatic expression levels of the associated enzymes further pointed to altered de novo GSH synthesis. To assess the effect of GSH and NAD+ repletion on the development of NAFLD, we added precursors for GSH and NAD+ biosynthesis to the Western diet and demonstrated that supplementation prevents HS in mice. In a proof-of-concept human study, we found improved liver function and decreased HS after supplementation with serine (a precursor to glycine) and hereby propose a strategy for NAFLD treatment.

Mitochondria-related transcriptional signature is downregulated in adipocytes in obesity: a study of young healthy MZ twins.

AIMS/HYPOTHESIS: Low mitochondrial activity in adipose tissue is suggested to be an underlying factor in obesity and its metabolic complications. We aimed to find out whether mitochondrial measures are downregulated in obesity also in isolated adipocytes. METHODS: We studied young adult monozygotic (MZ) twin pairs discordant (n = 14, intrapair difference ΔBMI ≥ 3 kg/m2) and concordant (n = 5, ΔBMI < 3 kg/m2) for BMI, identified from ten birth cohorts of 22- to 36-year-old Finnish twins. Abdominal body fat distribution (MRI), liver fat content (magnetic resonance spectroscopy), insulin sensitivity (OGTT), high-sensitivity C-reactive protein, serum lipids and adipokines were measured. Subcutaneous abdominal adipose tissue biopsies were obtained to analyse the transcriptomics patterns of the isolated adipocytes as well as of the whole adipose tissue. Mitochondrial DNA transcript levels in adipocytes were measured by quantitative real-time PCR. Western blots of oxidative phosphorylation (OXPHOS) protein levels in adipocytes were performed in obese and lean unrelated individuals. RESULTS: The heavier (BMI 29.9 ± 1.0 kg/m2) co-twins of the discordant twin pairs had more subcutaneous, intra-abdominal and liver fat and were more insulin resistant (p < 0.01 for all measures) than the lighter (24.1 ± 0.9 kg/m2) co-twins. Altogether, 2538 genes in adipocytes and 2135 in adipose tissue were significantly differentially expressed (nominal p < 0.05) between the co-twins. Pathway analysis of these transcripts in both isolated adipocytes and adipose tissue revealed that the heavier co-twins displayed reduced expression of genes relating to mitochondrial pathways, a result that was replicated when analysing the pathways behind the most consistently downregulated genes in the heavier co-twins (in at least 12 out of 14 pairs). Consistently upregulated genes in adipocytes were related to inflammation. We confirmed that mitochondrial DNA transcript levels (12S RNA, 16S RNA, COX1, ND5, CYTB), expression of mitochondrial ribosomal protein transcripts and a major mitochondrial regulator PGC-1α (also known as PPARGC1A) were reduced in the heavier co-twins' adipocytes (p < 0.05). OXPHOS protein levels of complexes I and III in adipocytes were lower in obese than in lean individuals. CONCLUSIONS/INTERPRETATION: Subcutaneous abdominal adipocytes in obesity show global expressional downregulation of oxidative pathways, mitochondrial transcripts and OXPHOS protein levels and upregulation of inflammatory pathways. DATA AVAILABILITY: The datasets analysed and generated during the current study are available in the figshare repository, https://dx.doi.org/10.6084/m9.figshare.3806286.v1.

Characterization of the peak at 2.06 ppm in (31) P magnetic resonance spectroscopy of human liver: phosphoenolpyruvate or phosphatidylcholine?

High field MR scanners can resolve a metabolite resonating at 2.06 ppm in the in vivo proton-decoupled liver (31) P MR spectrum. Traditionally this peak has been assigned to phosphoenolpyruvate (PEP), the key metabolite for gluconeogenesis. However, recent evidence supported the assignment to biliary phosphatidylcholine (PtdCh), which is produced in the liver and stored in the gall bladder. To elucidate the respective contributions of PtdCh and PEP to the in vivo resonance at 2.06 ppm (PEP-PtdCh), we made phantom measurements that confirmed that both biliary PtdCh and PEP resonate approximately at 2 ppm. The absolute quantification of PEP-PtdCh yielded concentrations ranging from 0.6 to 2.0 mmol/l, with mean coefficients of variation of 4.8% for intraday and 7.2% for interday reproducibility in healthy volunteers. The T1 relaxation time of PEP-PtdCh was 0.97 ± 0.30 s in the liver and 0.44 ± 0.11 s in the gallbladder. Ingestion of a mixed meal decreased the concentration of PtdCh-PEP by approximately 12%. In the retrospective analysis, PEP-PtdCh was 68% higher in the liver of subjects with gallbladder infiltration of the volume of interest (VOI) compared with those without gallbladder infiltration. PEP-PtdCh was also significantly higher in the liver of cholecystectomy patients compared with volunteers without gallbladder infiltration, which suggests increased intrahepatic bile fluid as a compensation for gall bladder removal. These results show that liver PtdCh is the major component of the resonance at 2.06 ppm and that careful VOI positioning is mandatory to avoid interference from the gallbladder.

Metabolome and fecal microbiota in monozygotic twin pairs discordant for weight: a Big Mac challenge.

Postprandial responses to food are complex, involving both genetic and environmental factors. We studied postprandial responses to a Big Mac meal challenge in monozygotic co-twins highly discordant for body weight. This unique design allows assessment of the contribution of obesity, independent of genetic liability. Comprehensive metabolic profiling using 3 analytical platforms was applied to fasting and postprandial serum samples from 16 healthy monozygotic twin pairs discordant for weight (body mass index difference >3 kg/m(2)). Nine concordant monozygotic pairs were examined as control pairs. Fecal samples were analyzed to assess diversity of the major bacterial groups by using 5 different validated bacterial group specific denaturing gradient gel electrophoresis methods. No differences in fecal bacterial diversity were detected when comparing co-twins discordant for weight (ANOVA, P<0.05). We found that within-pair similarity is a dominant factor in the metabolic postprandial response, independent of acquired obesity. Branched chain amino acids were increased in heavier as compared with leaner co-twins in the fasting state, but their levels converged postprandially (paired t tests, FDR q<0.05). We also found that specific bacterial groups were associated with postprandial changes of specific metabolites. Our findings underline important roles of genetic and early life factors in the regulation of postprandial metabolite levels.

Measuring short-term liver metabolism non-invasively: postprandial and post-exercise ¹H and ³¹P MR spectroscopy.

OBJECT: The objective of this study was to determine the effects of a standardized fat rich meal and subsequent exercise on liver fat content by ¹H MRS and on liver adenosine triphosphate (ATP) content by ³¹P MRS in healthy subjects. MATERIALS AND METHODS: Hepatic ¹H and proton decoupled ³¹P MRS were performed on nine healthy subjects on a clinical 3.0 T MR imager three times during a day: after (1) an overnight fast, (2) a following standardized fat rich meal and (3) a subsequent exercise session. Blood parameters were followed during the day to serve as a reference to MRS. RESULTS: Liver fat content increased gradually over the day (p = 0.0001) with an overall increase of 30 %. Also γ-NTP changed significantly over the day (p = 0.005). γ-NTP/tP decreased by 9 % (p = 0.019, post hoc) from the postprandial to the post-exercise state. CONCLUSION: Our study shows that in vivo MRS can depict short lived physiological changes; entering of fat into liver cells and consumption of ATP during exercise can be measured non-invasively in healthy subjects. The physiological state may have an impact on fat and energy metabolite levels. Hepatic ¹H and ³¹P MRS studies should be performed under standardized conditions.

Cardiac steatosis and left ventricular function in men with metabolic syndrome.

BACKGROUND: Ectopic accumulation of fat accompanies visceral obesity with detrimental effects. Lipid oversupply to cardiomyocytes leads to cardiac steatosis, and in animal studies lipotoxicity has been associated with impaired left ventricular (LV) function. In humans, studies have yielded inconclusive results. The aim of the study was to evaluate the role of epicardial, pericardial and myocardial fat depots on LV structure and function in male subjects with metabolic syndrome (MetS). METHODS: A study population of 37 men with MetS and 38 men without MetS underwent cardiovascular magnetic resonance and proton magnetic spectroscopy at 1.5 T to assess LV function, epicardial and pericardial fat area and myocardial triglyceride (TG) content. RESULTS: All three fat deposits were greater in the MetS than in the control group (p <0.001). LV diastolic dysfunction was associated with MetS as measured by absolute (471 mL/s vs. 667 mL/s, p = 0.002) and normalized (3.37 s⁻¹ vs. 3.75 s⁻¹, p = 0.02) LV early diastolic peak filling rate and the ratio of early diastole (68% vs. 78%, p = 0.001). The amount of epicardial and pericardial fat correlated inversely with LV diastolic function. However, myocardial TG content was not independently associated with LV diastolic dysfunction. CONCLUSIONS: In MetS, accumulation of epicardial and pericardial fat is linked to the severity of structural and functional alterations of the heart. The role of increased intramyocardial TG in MetS is more complex and merits further study.

Dual metabolic defects are required to produce hypertriglyceridemia in obese subjects.

OBJECTIVE: Obesity increases the risk of cardiovascular disease and premature death. However, not all obese subjects develop the metabolic abnormalities associated with obesity. The aim of this study was to clarify the mechanisms that induce dyslipidemia in obese subjects. METHODS AND RESULTS: Stable isotope tracers were used to elucidate the pathophysiology of the dyslipidemia in hypertriglyceridemic (n=14) and normotriglyceridemic (n=14) obese men (with comparable body mass index and visceral fat volume) and in normotriglyceridemic nonobese men (n=10). Liver fat was determined using proton magnetic resonance spectroscopy, and subcutaneous abdominal and visceral fat were measured by magnetic resonance imaging. Serum triglycerides in obese subjects were increased by the combination of increased secretion and severely impaired clearance of triglyceride-rich very-low-density lipoprotein(1) particles. Furthermore, increased liver and subcutaneous abdominal fat were linked to increased secretion of very-low-density lipoprotein 1 particles, whereas increased plasma levels of apolipoprotein C-III were associated with impaired clearance in obese hypertriglyceridemic subjects. CONCLUSIONS: Dual metabolic defects are required to produce hypertriglyceridemia in obese subjects with similar levels of visceral adiposity. The results emphasize the clinical importance of assessing hypertriglyceridemic waist in obese subjects to identify subjects at high cardiometabolic risk.

Abdominal adipose tissue and liver fat imaging in very low birth weight adults born preterm: birth cohort with sibling-controls.

Preterm birth at very low birth weight (VLBW, < 1500 g) is associated with an accumulation of cardiovascular and metabolic risk factors from childhood at least to middle age. Small-scale studies suggest that this could partly be explained by increased visceral or ectopic fat. We performed magnetic resonance imaging on 78 adults born preterm at VLBW in Finland between 1978 and 1990 and 72 term same-sex siblings as controls, with a mean age of 29 years. We collected T1-weighted images from the abdomen, and magnetic resonance spectra from the liver, subcutaneous abdominal adipose tissue, and tibia. The adipose tissue volumes of VLBW adults did not differ from their term siblings when adjusting for age, sex, and maternal and perinatal factors. The mean differences were as follows: subcutaneous - 0.48% (95% CI - 14.8%, 16.3%), visceral 7.96% (95% CI - 10.4%, 30.1%), and total abdominal fat quantity 1.05% (95% CI - 13.7%, 18.4%). Hepatic triglyceride content was also similar. VLBW individuals displayed less unsaturation in subcutaneous adipose tissue (- 4.74%, 95% CI - 9.2%, - 0.1%) but not in tibial bone marrow (1.68%, 95% CI - 1.86%, 5.35%). VLBW adults displayed similar adipose tissue volumes and hepatic triglyceride content as their term siblings. Previously reported differences could thus partly be due to genetic or environmental characteristics shared between siblings. The VLBW group displayed less unsaturation in subcutaneous abdominal adipose tissue, suggesting differences in its metabolic activity and energy storage.

Matrisome alterations in obesity - Adipose tissue transcriptome study on monozygotic weight-discordant twins.

Adipose tissue is a central regulator of metabolic health and its failure in obesity is a major cause of weight associated comorbidities, such as type 2 diabetes. Many extracellular matrix proteins, represented by matrisome, play a critical role in balancing adipose tissue health and dysfunction. Extracellular matrix components, produced by different cell types of adipose tissue, can modulate adipocyte function, tissue remodeling during expansion, angiogenesis, and inflammation and also form fibrotic lesions in the tissue. In this study, we investigated changes in matrisome of whole adipose tissue and adipocytes in human obesity. We investigated further the networks and biological pathways of the genes related to the changes and their association to development of metabolic dysfunction linked to type 2 diabetes. We used transcriptome data and clinical metabolic parameters from a rare weight-discordant MZ twin cohort. The Heavy-Lean differential matrisome gene expression (Δmatrisome) and differential metabolic parameters reflect changes in adipose tissue upon weight gain and changes in whole body glucose, insulin metabolism, as well as lipid status. We report that obesity Δmatrisome shows high specificity with 130 and 71 of the 1068 matrisome genes showing altered expression in the adipose tissue and adipocytes of heavier co-twin, respectively. The Δmatrisome differs considerably between adipose tissue vs adipocytes which reflects inflammation of hypertrophic adipocytes and the remodeling activity of the rest of the tissue resident cells. The obesity Δmatrisome is discussed extensively in the light of existing evidence and novel significant associations to obesity are reported to matrisome genes; cathepsin A, cathepsin O, FAM20B and N-glycanase1.

Long-TE 1H MRS suggests that liver fat is more saturated than subcutaneous and visceral fat.

Cross-talk between adipose tissue and liver is disturbed in the metabolic syndrome. Moreover, the relative fatty acid composition of adipose and liver fat is poorly characterized. Long-TE (1)H MRS can determine the unsaturation and polyunsaturation of adipose tissue. The aim of this study was to use long-TE (1)H MRS to determine the composition of liver fat and its relation to adipose tissue composition. Sixteen subjects with increased liver fat (>5%) were recruited for the study. Using TE = 200 ms, we were able to resolve the olefinic (=CH, 5.3 ppm) and water (H(2)O, 4.7 ppm) resonances in liver spectra and to obtain a repeatable estimate of liver fat unsaturation (coefficient of variation, 2.3%). With TE = 135 ms, the diallylic (=C-CH(2)-C=, 2.8 ppm) resonance was detectable in subjects with a liver fat content above 15%. Long-TE (1)H MRS was also used to determine the unsaturation in subcutaneous (n = 16) and visceral (n = 11) adipose tissue in the same subjects. Liver fat was more saturated (double bonds per fatty acid chain, 0.812 ± 0.022) than subcutaneous (double bonds per fatty acid chain, 0.862 ± 0.022, p < 0.0004) or visceral (double bonds per fatty acid chain, 0.865 ± 0.033, p < 0.0004) fat. Liver fat unsaturation correlated with subcutaneous unsaturation (R = 0.837, p < 0.0001) and visceral unsaturation (R = 0.879, p < 0.0004). The present study introduces a new noninvasive method for the assessment of the composition of liver fat. The results suggest that liver fat is more saturated than subcutaneous or visceral adipose tissue, which may be attributed to differences in de novo lipogenesis.

Body electrical loss analysis (BELA) in the assessment of visceral fat: a demonstration.

BACKGROUND: Body electrical loss analysis (BELA) is a new non-invasive way to assess visceral fat depot size through the use of electromagnetism. BELA has worked well in phantom measurements, but the technology is not yet fully validated. METHODS: Ten volunteers (5 men and 5 women, age: 22-60 y, BMI: 21-30 kg/m(2), waist circumference: 73-108 cm) were measured with the BELA instrument and with cross-sectional magnetic resonance imaging (MRI) at the navel level, navel +5 cm and navel -5 cm. The BELA signal was compared with visceral and subcutaneous fat areas calculated from the MR images. RESULTS: The BELA signal did not correlate with subcutaneous fat area at any level, but correlated significantly with visceral fat area at the navel level and navel +5 cm. The correlation was best at level of navel +5 cm (R(2) = 0.74, P < 0.005, SEE = 29.7 cm(2), LOOCV = 40.1 cm(2)), where SEE is the standard error of the estimate and LOOCV is the root mean squared error of leave-one-out style cross-validation. The average estimate of repeatability of the BELA signal observed through the study was ±9.6 %. One of the volunteers had an exceptionally large amount of visceral fat, which was underestimated by BELA. CONCLUSIONS: The correlation of the BELA signal with the visceral but not with the subcutaneous fat area as measured by MRI is promising. The lack of correlation with the subcutaneous fat suggests that subcutaneous fat has a minor influence to the BELA signal. Further research will show if it is possible to develop a reliable low-cost method for the assessment of visceral fat either using BELA only or combining it, for example, with bioelectrical impedance measurement. The combination of these measurements may help assessing visceral fat in a large scale of body composition. Before large-scale clinical testing and ROC analysis, the initial BELA instrumentation requires improvements. The accuracy of the present equipment is not sufficient for such new technology.

Liver Fat, Adipose Tissue, and Body Composition Changes After Switching from a Protease Inhibitor or Efavirenz to Raltegravir.

Integrase inhibitors appear to increase body weight, but paradoxically some data indicate that raltegravir (RAL) may decrease liver fat. Our objective was to study the effects of switching from a protease inhibitor (PI) or efavirenz (EFV) to RAL on liver fat, body composition, and metabolic parameters among people living with HIV (PLWH) with high risk for nonalcoholic fatty liver disease (NAFLD). We randomized overweight PLWH with signs of metabolic syndrome to switch a PI or EFV to RAL (n = 19) or to continue unchanged antiretroviral therapy (control, n = 24) for 24 weeks. Liver fat was measured by magnetic resonance spectroscopy (MRS), body composition by magnetic resonance imaging, and bioimpedance analysis; subcutaneous fat biopsies were obtained. Median (interquartile range) liver fat content was normal in RAL 2.3% (1.1-6.0) and control 3.1% (1.6-7.3) group at baseline. Liver fat and visceral adipose tissue remained unchanged during the study. Body weight [from 85.9 kg (76.1-97.7) to 89.3 (78.7-98.7), p = 0.019], body fat mass [from 20.3 kg (14.6-29.7) to 22.7 (17.0-29.7), p = 0.015], and subcutaneous adipose tissue (SAT) volume [from 3979 mL (2068-6468) to 4043 (2206-6433), p = 0.048] increased, yet, adipocyte size [from 564 pL (437-733) to 478 (423-587), p = 0.019] decreased in RAL but remained unchanged in control group. Circulating lipids and inflammatory markers improved in RAL compared to control group. The median liver fat measured by MRS was unexpectedly within normal range in this relatively small study population with presumably high risk for NAFLD contradicting high prevalence of NAFLD reported with other methods. Despite weight gain, increase in SAT together with decreased adipocyte size and reduced inflammation may reflect improved adipose tissue function. Clinical Trial Registration number: NCT03374358.

Molecular pathways behind acquired obesity: Adipose tissue and skeletal muscle multiomics in monozygotic twin pairs discordant for BMI.

Tissue-specific mechanisms prompting obesity-related development complications in humans remain unclear. We apply multiomics analyses of subcutaneous adipose tissue and skeletal muscle to examine the effects of acquired obesity among 49 BMI-discordant monozygotic twin pairs. Overall, adipose tissue appears to be more affected by excess body weight than skeletal muscle. In heavier co-twins, we observe a transcriptional pattern of downregulated mitochondrial pathways in both tissues and upregulated inflammatory pathways in adipose tissue. In adipose tissue, heavier co-twins exhibit lower creatine levels; in skeletal muscle, glycolysis- and redox stress-related protein and metabolite levels remain higher. Furthermore, metabolomics analyses in both tissues reveal that several proinflammatory lipids are higher and six of the same lipid derivatives are lower in acquired obesity. Finally, in adipose tissue, but not in skeletal muscle, mitochondrial downregulation and upregulated inflammation are associated with a fatty liver, insulin resistance, and dyslipidemia, suggesting that adipose tissue dominates in acquired obesity.

Nonalcoholic fatty liver disease: detection of elevated nicotinamide adenine dinucleotide phosphate with in vivo 3.0-T 31P MR spectroscopy with proton decoupling.

PURPOSE: To determine if 3.0-T proton-decoupled phosphorus 31 ((31)P) magnetic resonance (MR) spectroscopy can be used to differentiate between stages of nonalcoholic fatty liver disease (NAFLD) by resolving the components of phosphomonoester (PME) and phosphodiester (PDE) and enabling detection of a greater number of other phosphorus-containing compounds. MATERIALS AND METHODS: This study was approved by the ethics committee of Helsinki University Central Hospital, and written informed consent was obtained from all study subjects. A 3.0-T clinical imager was used to obtain proton-decoupled (31)P MR spectra in the liver of control subjects (n = 12), patients with biopsy-proved simple steatosis due to nonalcoholic causes (nonalcoholic fatty liver, n = 13; nonalcoholic steatohepatitis [NASH], n = 9), and patients with cirrhosis (n = 9) to determine PME, phosphoethanolamine (PE), phosphocholine, PDE, glycerophosphocholine (GPC), glycerophosphoryl ethanolamine, uridine diphosphoglucose, nicotinamide adenine dinucleotide phosphate (NADPH), inorganic phosphate, phosphoenolpyruvate, and alpha-, beta- and gamma-nucleotide triphosphate levels. Liver fat was determined with hydrogen 1 MR spectroscopy. Differences between the disease groups were analyzed with one-way analysis of variance. RESULTS: The PME/(PME + PDE), PME/PDE, and PE/(PME + PDE) ratios were higher and the GPC/(PME + PDE) ratio was lower in patients with cirrhosis than in the other study groups (P < or = .001, one-way analysis of variance). The NADPH/(PME + PDE) ratio was higher in patients with NASH and those with cirrhosis than in control subjects (P < .05, post hoc analyses) and correlated with disease severity (P = .007). CONCLUSION: NADPH, a marker of inflammation and fibrinogenic activity in the liver, is increased in patients with NASH and those with cirrhosis. Proton-decoupled (31)P 3.0-T MR spectroscopy shows promise in the differentiation of NAFLD stages.

Characterizing human adipose tissue lipids by long echo time 1H-MRS in vivo at 1.5 Tesla: validation by gas chromatography.

The aim of this study was to investigate the use of (1)H-MRS with various echo times to characterize subcutaneous human adipose tissue (SAT) triglyceride composition and to validate the findings with fatty acid (FA) analysis of SAT biopsies by gas chromatography (GC). (1)H-MRS spectra were acquired with a 1.5 Tesla clinical imager from the SAT of 17 healthy volunteers, with 10 undergoing SAT biopsy. Spectra were localized with PRESS and a series of echo times; 30, 50, 80, 135, 200, 300 and 540 ms were acquired with TR = 3000 ms. Prior knowledge from phantom measurements was used to construct AMARES fitting models for the lipid spectra. SAT FA composition were compared with serum lipid levels and subject characteristics in 17 subjects.Long TE (135, 200 ms) spectra corresponded better with the GC data than short TE (30, 50 ms) spectra. TE = 135 ms was found optimal for determining diallylic content (R = 0.952, p < 0.001) and TE = 200 ms was optimal for determining olefinic content (R = 0.800, p < 0.01). The improved performance of long TE spectra is a result of an improved baseline and better peak separation, due to J-modulation and suppression of water. The peak position of the diallylic resonance correlated with the average double bond content of polyunsatured fatty acids with R = 0.899 (p < 0.005). The apparent T(2) of the methylene resonance displayed relatively small inter-individual variation, 88.1 +/- 1.1 ms (mean +/- SD). The outer methyl triplet line of omega-3 PUFA at 1.08 ppm could be readily detected and quantitated from spectra obtained at TE = 540. The omega-3 resonance correlated with the omega-3 content determined by GC with R = 0.737 (p < 0.05, n = 8). Age correlated significantly with SAT diallylic content (R = 0.569, p = 0.017, n = 17), but serum lipid levels showed no apparent relation to SAT FA composition. We conclude that long TE (1)H-MRS provides a robust non-invasive method for characterizing adipose tissue triglycerides in vivo.

Expansion and Impaired Mitochondrial Efficiency of Deep Subcutaneous Adipose Tissue in Recent-Onset Type 2 Diabetes.

CONTEXT/OBJECTIVE: Impaired adipose tissue (AT) function might induce recent-onset type 2 diabetes (T2D). Understanding AT energy metabolism could yield novel targets for the treatment of T2D. DESIGN/PATIENTS: Male patients with recently-diagnosed T2D and healthy male controls (CON) of similar abdominal subcutaneous AT (SAT)-thickness, fat mass, and age (n = 14 each), underwent hyperinsulinemic-euglycemic clamps with [6,6-2H2]glucose and indirect calorimetry. We assessed mitochondrial efficiency (coupling: state 3/4o; proton leak: state 4o/u) via high-resolution respirometry in superficial (SSAT) and deep (DSAT) SAT-biopsies, hepatocellular lipids (HCL) and fat mass by proton-magnetic-resonance-spectroscopy and -imaging. RESULTS: T2D patients (known diabetes duration: 2.5 [0.1; 5.0] years) had 43%, 44%, and 63% lower muscle insulin sensitivity (IS), metabolic flexibility (P < 0.01) and AT IS (P < 0.05), 73% and 31% higher HCL (P < 0.05), and DSAT-thickness (P < 0.001), but similar hepatic IS compared with CON. Mitochondrial efficiency was ~22% lower in SSAT and DSAT of T2D patients (P < 0.001) and ~8% lower in SSAT vs DSAT (P < 0.05). In both fat depots, mitochondrial coupling correlated positively with muscle IS and metabolic flexibility (r ≥ 0.40; P < 0.05), proton leak correlated positively (r ≥ 0.51; P < 0.01) and oxidative capacity negatively (r ≤ -0.47; P < 0.05) with fasting free fatty acids (FFA). Metabolic flexibility correlated positively with SAT-oxidative capacity (r ≥ 0.48; P < 0.05) and negatively with DSAT-thickness (r = -0.48; P < 0.05). DSAT-thickness correlated negatively with mitochondrial coupling in both depots (r ≤ -0.50; P < 0.01) and muscle IS (r = -0.59; P < 0.01), positively with FFA during clamp (r = 0.63; P < 0.001) and HCL (r = 0.49; P < 0.01). CONCLUSIONS: Impaired mitochondrial function, insulin resistance, and DSAT expansion are AT abnormalities in recent-onset T2D that might promote whole-body insulin resistance and increased substrate flux to the liver.