Increased ATP synthesis might counteract hepatic lipid accumulation in acromegaly

Reproducibility of absolute quantification of adenosine triphosphate and inorganic phosphate in the liver with localized 31P-magnetic resonance spectroscopy at 3-T using different coils

Concentrations of the key metabolites of hepatic energy metabolism, adenosine triphosphate (ATP) and inorganic phosphate (Pi), can be altered in metabolic disorders such as diabetes mellitus. 31Phosphorus (31P)-magnetic resonance spectroscopy (MRS) is used to noninvasively measure hepatic metabolites, but measuring their absolute molar concentrations remains challenging. This study employed a 31P-MRS method based on the phantom replacement technique for quantifying hepatic 31P-metabolites on a 3-T clinical scanner. Two surface coils with different size and geometry were used to check for consistency in terms of repeatability and reproducibility and absolute concentrations of metabolites. Day-to-day (n = 8) and intra-day (n = 6) reproducibility was tested in healthy volunteers. In the day-to-day study, mean absolute concentrations of γ-ATP and Pi were 2.32 ± 0.24 and 1.73 ± 0.26 mM (coefficient of variation [CV]: 7.3% and 8.8%) for the single loop, and 2.32 ± 0.42 and 1.73 ± 0.27 mM (CVs 6.7% and 10.6%) for the quadrature coil, respectively. The intra-day study reproducibility using the quadrature coil yielded CVs of 4.7% and 6.8% for γ-ATP and Pi without repositioning, and 6.3% and 7.1% with full repositioning of the volunteer. The results of the day-to-day data did not differ between coils and visits. Both coils robustly yielded similar results for absolute concentrations of hepatic 31P-metabolites. The current method, applied with two different surface coils, can be readily utilized in long-term and interventional studies. In comparison with the single loop coil, the quadrature coil also allows measurements at a greater distance between the coil and liver, which is relevant for studying people with obesity.

Nonalcoholic Fatty Liver Disease, Liver Fibrosis, and Utility of Noninvasive Scores in Patients With Acromegaly

CONTEXT

Nonalcoholic fatty liver disease (NAFLD) is a metabolical disorder and can lead to liver fibrosis. Because it is commonly seen, several noninvasive scores (NS) have been validated to identify high-risk patients. Patients with NAFLD have been shown to have higher serum angiopoietin-like protein-8 (ANGPTL-8) levels.

OBJECTIVE

The risk of NAFLD is known insufficiently in acromegaly. Moreover, the utility of the NS and the link between NAFLD and ANGPTL-8 in acromegaly is unknown.

METHODS

Thirty-two patients with acromegaly (n = 15, active [AA] and n = 17, controlled acromegaly [CA]) and 19 healthy controls were included. Magnetic resonance imaging (MRI)-proton density fat fraction (PDFF) was used to evaluate hepatic steatosis, and magnetic resonance elastography to evaluate liver stiffness measurement. ANGPTL-8 levels were measured with ELISA.

RESULTS

Median liver MRI-PDFF and NAFLD prevalence in AA were lower than in CA (P = .026 and P < .001, respectively). Median magnetic resonance elastography-liver stiffness measurement were similar across groups. Of the NS, visceral adiposity index, fatty liver index, hepatic steatosis index, and triglyceride-glucose index (TyG) all showed positive correlation with the liver MRI-PDFF in the control group. However, only TyG significantly correlated with liver fat in the AA and CA groups. There was no correlation between traditional NAFLD risk factors (body mass index, waist circumference, C-reactive protein, homeostasis model assessment for insulin resistance, visceral adipose tissue) and liver MRI-PDFF in the AA and CA. Patients with acromegaly with NAFLD had lower GH, IGF-1, and ANGPTL-8 levels than in those without NAFLD (P = .025, P = .011, and P = .036, respectively).

CONCLUSION

Active acromegaly may protect from NAFLD because of high GH. In patients with acromegaly, NAFLD risk cannot be explained with classical risk factors; hence, additional risk factors must be identified. TyG is the best score to evaluate NAFLD risk. Lower ANGPTL-8 in patients with acromegaly and NAFLD implies this hormone may be raised because of insulin resistance rather than being a cause for NAFLD.

Endocrine aspects of metabolic dysfunction-associated steatotic liver disease (MASLD): Beyond insulin resistance

While the association of metabolic dysfunction-associated steatotic liver disease (MASLD) with obesity and insulin resistance is widely appreciated, there are a host of complex interactions between the liver and other endocrine axes. While it can be difficult to definitively distinguish direct causal relationships and those attributable to increased adipocyte mass, there is substantial evidence of the direct and indirect effects of endocrine dysregulation on the severity of MASLD, with strong evidence that low levels of growth hormone, sex hormones, and thyroid hormone promote the development and progression of disease. The impact of steroid hormones, e.g. cortisol and dehydroepiandrosterone, and adipokines is much more divergent. Thoughtful assessment, based on individual risk factors and findings, and management of non-insulin endocrine axes is essential in the evaluation and management of MASLD. Multiple therapeutic options have emerged that leverage various endocrine axes to reduce the fibroinflammatory cascade in MASH.

Effects of In Utero PFOS Exposure on Epigenetics and Metabolism in Mouse Fetal Livers

Prenatal exposure to perfluorooctanesulfonate (PFOS) increases fetus' metabolic risk; however, the investigation of the underlying mechanism is limited. In this study, pregnant mice in the gestational days (GD, 4.5-17.5) were exposed to PFOS (0.3 and 3 μg/g of body weight). At GD 17.5, PFOS perturbed maternal lipid metabolism and upregulated metabolism-regulating hepatokines (Angptl4, Angptl8, and Selenop). Mass-spectrometry imaging and whole-genome bisulfite sequencing revealed, respectively, selective PFOS localization and deregulation of gene methylation in fetal livers, involved in inflammation, glucose, and fatty acid metabolism. PCR and Western blot analysis of lipid-laden fetal livers showed activation of AMPK signaling, accompanied by significant increases in the expression of glucose transporters (Glut2/4), hexose-phosphate sensors (Retsat and ChREBP), and the key glycolytic enzyme, pyruvate kinase (Pk) for glucose catabolism. Additionally, PFOS modulated the expression levels of PPARα and PPARγ downstream target genes, which simultaneously stimulated fatty acid oxidation (Cyp4a14, Acot, and Acox) and lipogenesis (Srebp1c, Acaca, and Fasn). Using human normal hepatocyte (MIHA) cells, the underlying mechanism of PFOS-elicited nuclear translocation of ChREBP, associated with a fatty acid synthesizing pathway, was revealed. Our finding implies that in utero PFOS exposure altered the epigenetic landscape associated with dysregulation of fetal liver metabolism, predisposing postnatal susceptibility to metabolic challenges.

Increased GH/IGF-I Axis Activity Relates to Lower Hepatic Lipids and Phosphor Metabolism

CONTEXT

Non-alcoholic fatty liver disease (NAFLD) is a leading causes of liver-related morbidity and mortality. While data on acromegaly, a state of chronic growth hormone (GH)/insulin-like growth factor I (IGF-I) excess, suggest an inverse relationship with intrahepatic lipid (IHL) content, less is known about the impact of the GH/IGF-I axis on IHL, lipid composition, and phosphor metabolites in individuals without disorders of GH secretion.

OBJECTIVE

The aim was to investigate the relation between activity of the GH/IGF-I axis and IHL content and phosphor metabolism.

METHODS

We performed a cross-sectional study in 59 otherwise metabolically healthy individuals (30 females), of which 16 met the criteria of NAFLD with IHL of ≥5.6%. The GH/IGF-I axis was evaluated in a fasting state and during an oral glucose tolerance test (OGTT). Insulin sensitivity was estimated by validated indices. IHL, lipid composition (unsaturation index), and phosphate metabolites were analyzed by using 1H/31P magnetic resonance spectroscopy.

RESULTS

In the overall cohort (40.6 ± 15 years; body mass index: 24.5 ± 3 kg/m2; IGF-I: 68.0 ± 17% upper limit of normal), fasting GH (R = -0.31; P = .02), GH during oral glucose tolerance test (R = -0.51; P < .01), and IGF-I (R = -0.28; P = .03) inversely correlated with IHL. GH levels during OGTT were significantly lower in NAFLD than in controls (47.7 [22; 143] ng/mL/min vs 16.8 [7; 32] ng/mL/min; P = .003). GH/IGF-I axis activity correlated with lipid composition and with phosphor metabolites. In multiple regression analysis, the GH/IGF-I axis activity was a strong predictor for IHL and lipid composition independent from insulin sensitivity.

CONCLUSION

GH/IGF-I axis activity impacts hepatic lipid and phosphate metabolism in individuals without disorders in GH secretion. Lower GH axis activity is associated with higher IHL and an unfavorable lipid composition, probably mediated by changes in hepatic energy metabolism.

Growth hormone and nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is a prevalent cause of liver disease and metabolic comorbidities. Obesity is strongly associated with NAFLD and is also a state of relative deficiency of growth hormone (GH). Evidence supports a role of reduced GH and insulin-like growth factor-1 (IGF-1) in NAFLD pathogenesis. Physiological actions of GH in the liver include suppression of de novo lipogenesis (DNL) and promotion of lipid beta-oxidation, and GH also appears to have anti-inflammatory actions. Physiologic actions of IGF-1 include suppression of inflammatory and fibrogenic pathways important in the evolution from steatosis to steatohepatitis and fibrosis. Rodent models of impaired hepatic GH signaling show the development of steatosis, sometimes accompanied by inflammation, hepatocellular damage, and fibrosis, and these changes are ameliorated by treatment with GH and/or IGF-1. In humans, individuals with GH deficiency and GH resistance demonstrate an increased prevalence of NAFLD compared to controls, with improvement in hepatic lipid, steatohepatitis, and fibrosis following GH replacement. As a corollary, individuals with GH excess demonstrate lower hepatic lipid compared to controls along with increased hepatic lipid following treatment to normalize GH levels. Clinical trials demonstrate that augmentation of GH reduces hepatic lipid content in individuals with NAFLD and may also ameliorate steatohepatitis and fibrosis. Taken together, evidence supports an important role for perturbations in the GH/IGF-1 axis as one of the pathogenic mechanisms of NAFLD and suggests that further study is needed to assess whether augmentation of GH and/or IGF-1 may be a safe and effective therapeutic strategy for NAFLD.

Metabolomics in acromegaly: a systematic review

The therapeutic response heterogeneity in acromegaly persists, despite the medical-surgical advances of recent years. Thus, personalized medicine implementation, which focuses on each patient, is justified. Metabolomics would decipher the molecular mechanisms underlying the therapeutic response heterogeneity. Identification of altered metabolic pathways would open new horizons in the therapeutic management of acromegaly. This research aimed to evaluate the metabolomic profile in acromegaly and metabolomics' contributions to understanding disease pathogenesis. A systematic review was carried out by querying four electronic databases and evaluating patients with acromegaly through metabolomic techniques. In all, 21 studies containing 362 patients were eligible. Choline, the ubiquitous metabolite identified in growth hormone (GH)-secreting pituitary adenomas (Pas) by in vivo magnetic resonance spectroscopy (MRS), negatively correlated with somatostatin receptors type 2 expression and positively correlated with magnetic resonance imaging T2 signal and Ki-67 index. Moreover, elevated choline and choline/creatine ratio differentiated between sparsely and densely granulated GH-secreting PAs. MRS detected low hepatic lipid content in active acromegaly, which increased after disease control. The panel of metabolites of acromegaly deciphered by mass spectrometry (MS)-based techniques mainly included amino acids (especially branched-chain amino acids and taurine), glyceric acid, and lipids. The most altered pathways in acromegaly were the metabolism of glucose (particularly the downregulation of the pentose phosphate pathway), linoleic acid, sphingolipids, glycerophospholipids, arginine/proline, and taurine/hypotaurine. Matrix-assisted laser desorption/ionization coupled with MS imaging confirmed the functional nature of GH-secreting PAs and accurately discriminated PAs from healthy pituitary tissue.

Long-term Outcome of Body Composition, Ectopic Lipid, and Insulin Resistance Changes With Surgical Treatment of Acromegaly

Context

Acromegaly presents a unique pattern of lower adiposity and insulin resistance in active disease but reduction in insulin resistance despite a rise in adiposity after surgery. Depot-specific adipose tissue masses and ectopic lipid are important predictors of insulin resistance in other populations, but whether they are in acromegaly is unknown. Long-term persistence of body composition changes after surgery is unknown.

Objective

To determine how depot-specific body composition and ectopic lipid relate to insulin resistance in active acromegaly and whether their changes with surgery are sustained long-term.

Methods

Cross-sectional study in patients with active acromegaly and longitudinal study in newly diagnosed patients studied before and in long-term follow-up, 3 (1-8) years (median, range), after surgery. Seventy-one patients with active acromegaly studied cross-sectionally and 28 with newly diagnosed acromegaly studied longitudinally. Main outcome measures were visceral (VAT), subcutaneous (SAT), and intermuscular adipose tissue masses by whole-body magnetic resonance imaging; intrahepatic lipid (IHL) by proton magnetic resonance spectroscopy; insulin resistance measures derived from fasting; and oral glucose tolerance test insulin and glucose levels.

Results

SAT and insulin-like growth factor 1 level, but not VAT or IHL, were independent predictors of insulin resistance in active acromegaly. VAT, SAT, and IHL gains were sustained long-term after surgery. VAT mass rise with surgery correlated inversely with rise in QUICKI while SAT rise correlated with fall in the Homeostatic Model Assessment score.

Conclusion

SAT and disease activity are important predictors of insulin resistance in active acromegaly. Adiposity gains are sustained long-term after surgical treatment and impact on the accompanying improvement in insulin resistance.

Gene expression profiling of subcutaneous adipose tissue reveals new biomarkers in acromegaly

CONTEXT

Active acromegaly is characterized by lipolysis-induced insulin resistance, which suggests adipose tissue (AT) as a primary driver of metabolic aberrations.

OBJECTIVE

To study the gene expression landscape in AT in patients with acromegaly before and after disease control in order to understand the changes and to identify disease-specific biomarkers.

METHODS

RNA sequencing was performed on paired subcutaneous adipose tissue (SAT) biopsies from six patients with acromegaly at time of diagnosis and after curative surgery. Clustering and pathway analyses were performed in order to identify disease activity-dependent genes. In a larger patient cohort (n = 23), the corresponding proteins were measured in serum by immunoassay. Correlations between growth hormone (GH), insulin-like growth factor I (IGF-I), visceral AT (VAT), SAT, total AT, and serum proteins were analyzed.

RESULTS

743 genes were significantly differentially expressed (P-adjusted < .05) in SAT before and after disease control. The patients clustered according to disease activity. Pathways related to inflammation, cell adhesion and extracellular matrix, GH and insulin signaling, and fatty acid oxidation were differentially expressed.Serum levels of HTRA1, METRNL, S100A8/A9, and PDGFD significantly increased after disease control (P < .05). VAT correlated with HTRA1 (R = 0.73) and S100A8/A9 (R = 0.55) (P < .05 for both).

CONCLUSION

AT in active acromegaly is associated with a gene expression profile of fibrosis and inflammation, which may corroborate the hyper-metabolic state and provide a means for identifying novel biomarkers.

Ectopic lipid deposition and insulin resistance in patients with GH disorders before and after treatment

OBJECTIVES

Insulin resistance is associated with ectopic lipid deposition. Growth hormone (GH) status also modulates ectopic lipid accumulation, but how this associates with insulin resistance in patients with GH disorders is not well established.

DESIGN AND METHODS

Twenty-one patients diagnosed with acromegaly and 12 patients with adult GH deficiency (GHD) were studied at diagnosis and after treatment. A reference group of 12 subjects was included. Each study day comprised assessment of body composition with dual-energy X-ray absorptiometry, ectopic lipid deposition in the liver by MR spectroscopy, and Homeostatic Model Assessment for Insulin Resistance (HOMA-IR).

RESULTS

Disease control of acromegaly decreased lean body mass (LBM) (P < .000) and increased the percentage of total body fat (TBF) (P < .000). GH replacement increased LBM in the GHD patients (P = .007) and decreased the percentage of TBF (P = .010). The intrahepatic lipid (IHL) content increased after disease control in acromegaly (P = .004), whereas IHL did not change significantly after GH replacement in GHD (P = .34). Insulin resistance (HOMA-IR) improved after disease control of acromegaly (P < .000) and remained unaltered after GH replacement in the GHD patients (P = .829).

CONCLUSIONS

GH status is a significant modulator of body composition and insulin sensitivity.GH excess reduces total fat mass and intrahepatic lipid content together with induction of insulin resistance.The data support the notion that GH-induced insulin resistance is unassociated with hepatic lipid accumulation.

Ectopic lipid metabolism in anterior pituitary dysfunction

Over the past decades, adapted lifestyle and dietary habits in industrialized countries have led to a progress of obesity and associated metabolic disorders. Concomitant insulin resistance and derangements in lipid metabolism foster the deposition of excess lipids in organs and tissues with limited capacity of physiologic lipid storage. In organs pivotal for systemic metabolic homeostasis, this ectopic lipid content disturbs metabolic action, thereby promotes the progression of metabolic disease, and inherits a risk for cardiometabolic complications. Pituitary hormone syndromes are commonly associated with metabolic diseases. However, the impact on subcutaneous, visceral, and ectopic fat stores between disorders and their underlying hormonal axes is rather different, and the underlying pathophysiological pathways remain largely unknown. Pituitary disorders might influence ectopic lipid deposition indirectly by modulating lipid metabolism and insulin sensitivity, but also directly by organ specific hormonal effects on energy metabolism. In this review, we aim to I) provide information about the impact of pituitary disorders on ectopic fat stores, II) and to present up-to-date knowledge on potential pathophysiological mechanisms of hormone action in ectopic lipid metabolism.

The acromegaly lipodystrophy

Growth hormone (GH) and insulin-like growth factor 1 (IGF-1) are essential to normal growth, metabolism, and body composition, but in acromegaly, excesses of these hormones strikingly alter them. In recent years, the use of modern methodologies to assess body composition in patients with acromegaly has revealed novel aspects of the acromegaly phenotype. In particular, acromegaly presents a unique pattern of body composition changes in the setting of insulin resistance that we propose herein to be considered an acromegaly-specific lipodystrophy. The lipodystrophy, initiated by a distinctive GH-driven adipose tissue dysregulation, features insulin resistance in the setting of reduced visceral adipose tissue (VAT) mass and intra-hepatic lipid (IHL) but with lipid redistribution, resulting in ectopic lipid deposition in muscle. With recovery of the lipodystrophy, adipose tissue mass, especially that of VAT and IHL, rises, but insulin resistance is lessened. Abnormalities of adipose tissue adipokines may play a role in the disordered adipose tissue metabolism and insulin resistance of the lipodystrophy. The orexigenic hormone ghrelin and peptide Agouti-related peptide may also be affected by active acromegaly as well as variably by acromegaly therapies, which may contribute to the lipodystrophy. Understanding the pathophysiology of the lipodystrophy and how acromegaly therapies differentially reverse its features may be important to optimizing the long-term outcome for patients with this disease. This perspective describes evidence in support of this acromegaly lipodystrophy model and its relevance to acromegaly pathophysiology and the treatment of patients with acromegaly.

Growth Hormone and Insulin-Like Growth Factor 1 Regulation of Nonalcoholic Fatty Liver Disease

Patients with obesity have a high prevalence of nonalcoholic fatty liver disease (NAFLD), representing a spectrum of simple steatosis to nonalcoholic steatohepatitis (NASH), without and with fibrosis. Understanding the etiology of NAFLD is clinically relevant since NAFLD is an independent risk factor for diabetes and cardiovascular disease. In addition, NASH predisposes patients to the development of cirrhosis and hepatocellular carcinoma, and NASH cirrhosis represents the fastest growing indication for liver transplantation in the United States. It is appreciated that multiple factors are involved in the development and progression of NAFLD. Growth hormone (GH) and insulin-like growth factor 1 (IGF1) regulate metabolic, immune, and hepatic stellate cell function, and alterations in the production and function of GH is associated with obesity and NAFLD/NASH. Therefore, this review will focus on the potential role of GH and IGF1 in the regulation of hepatic steatosis, inflammation, and fibrosis.

The role of hepatic lipid composition in obesity-related metabolic disease

Obesity is a primary antecedent to non-alcoholic fatty liver disease whose cardinal feature is excessive hepatic lipid accumulation. Although total hepatic lipid content closely associates with hepatic and systemic metabolic dysfunction, accumulating evidence suggests that the composition of hepatic lipids may be more discriminatory. This review summarises cross-sectional human studies using liver biopsy/lipidomics and proton magnetic resonance spectroscopy to characterise hepatic lipid composition in people with obesity and related metabolic disease. A comprehensive literature search identified 26 relevant studies published up to 31st March 2021 which were included in the review. The available evidence provides a consistent picture showing that people with hepatic steatosis possess elevated saturated and/or monounsaturated hepatic lipids and a reduced proportion of polyunsaturated hepatic lipids. This altered hepatic lipid profile associates more directly with metabolic derangements, such as insulin resistance, and may be exacerbated in non-alcoholic steatohepatitis. Further evidence from lipidomic studies suggests that these deleterious changes may be related to defects in lipid desaturation and elongation, and an augmentation of the de novo lipogenic pathway. These observations are consistent with mechanistic studies implicating saturated fatty acids and associated bioactive lipid intermediates (ceramides, lysophosphatidylcholines and diacylglycerol) in the development of hepatic lipotoxicity and wider metabolic dysfunction, whilst monounsaturated fatty acids and polyunsaturated fatty acids may exhibit a protective role. Future studies are needed to prospectively determine the relevance of hepatic lipid composition for hepatic and non-hepatic morbidity and mortality; and to further evaluate the impact of therapeutic interventions such as pharmacotherapy and lifestyle interventions.

Towards Understanding the Direct and Indirect Actions of Growth Hormone in Controlling Hepatocyte Carbohydrate and Lipid Metabolism

Growth hormone (GH) is critical for achieving normal structural growth. In addition, GH plays an important role in regulating metabolic function. GH acts through its GH receptor (GHR) to modulate the production and function of insulin-like growth factor 1 (IGF1) and insulin. GH, IGF1, and insulin act on multiple tissues to coordinate metabolic control in a context-specific manner. This review will specifically focus on our current understanding of the direct and indirect actions of GH to control liver (hepatocyte) carbohydrate and lipid metabolism in the context of normal fasting (sleep) and feeding (wake) cycles and in response to prolonged nutrient deprivation and excess. Caveats and challenges related to the model systems used and areas that require further investigation towards a clearer understanding of the role GH plays in metabolic health and disease are discussed.

Serum metabolomic profiling reveals an increase in homocitrulline in Chinese patients with nonalcoholic fatty liver disease: a retrospective study

Backgrounds

Nonalcoholic fatty liver disease (NAFLD) has multiple causes, is triggered by individual genetic susceptibility, environmental factors, and metabolic disturbances, and may be triggered by acquired metabolic stress. The metabolic profiles of NAFLD show significant ethnic differences, and the metabolic characteristics of NAFLD in Chinese individuals are unclear. Our study aimed to identify the metabolites and pathways associated with NAFLD in a Chinese cohort.

Methods

One hundred participants, including 50 NAFLD patients and 50 healthy controls, were enrolled in this retrospective observational study at Jinling Hospital in Nanjing; serum samples were collected from the patients and healthy subjects. The metabolome was determined in all samples by liquid chromatography-hybrid quadrupole time-of-flight mass spectrometry (LC-Q/TOF-MS). Univariate and multivariate statistical analyses were used to compare the metabolic profiles between the two groups.

Results

The comparison indicated that the levels of 89 metabolites were different between the two groups. The glycerophospholipid family of metabolites was the most abundant family of metabolites that demonstrated significant differences. L-acetylcarnitine, L-homocitrulline, and glutamic acid were the top three metabolites ranked by VIP score and had favorable effective functions for diagnosis. Moreover, pathway enrichment analysis suggested 14 potentially different metabolic pathways between NAFLD patients and healthy controls based on their impact value. Biological modules involved in the lipid and carbohydrate metabolism had the highest relevance to the conditions of NAFLD. Glycerophospholipid metabolism had the strongest associations with the conditions of NAFLD.

Conclusions

Our data suggest that the serum metabolic profiles of NAFLD patients and healthy controls are different. L-Homocitrulline was remarkably increased in NAFLD patients.

Metabolite cycled liver 1 H MRS on a 7 T parallel transmit system

INTRODUCTION

Single-voxel ¹ H MRS in body applications often suffers from respiratory and other motion induced phase and frequency shifts, which lead to incoherent averaging and hence to suboptimal results.

METHODS

Here we show the application of metabolite cycling (MC) for liver STEAM-localized ¹ H MRS on a 7 T parallel transmit system, using eight transmit-receive fractionated dipole antennas with 16 additional, integrated receive loops. MC-STEAM measurements were made in six healthy, lean subjects and compared with STEAM measurements using VAPOR water suppression. Measurements were performed during free breathing and during synchronized breathing, for which the subjects did breathe in between the MRS acquisitions. Both intra-session repeatability and inter-session reproducibility of liver lipid quantification with MC-STEAM and VAPOR-STEAM were determined.

RESULTS

The preserved water signal in MC-STEAM allowed for robust phase and frequency correction of individual acquisitions before averaging, which resulted in in vivo liver spectra that were of equal quality when measurements were made with free breathing or synchronized breathing. Intra-session repeatability and inter-session reproducibility of liver lipid quantification were better for MC-STEAM than for VAPOR-STEAM. This may also be explained by the more robust phase and frequency correction of the individual MC-STEAM acquisitions as compared with the VAPOR-STEAM acquisitions, for which the low-signal-to-noise ratio lipid signals had to be used for the corrections.

CONCLUSION

Non-water-suppressed MC-STEAM on a 7 T system with parallel transmit is a promising approach for ¹ H MRS applications in the body that are affected by motion, such as in the liver, and yields better repeatability and reproducibility compared with water-suppressed measurements.