Human adipose and skeletal muscle tissue DNA, RNA, and protein content

Reduced plasma glycine concentration in healthy and chronically diseased older adults: a marker of visceral adiposity?

BACKGROUND

Previous studies have shown that a reduced plasma concentration of the amino acid glycine (Gly) is associated with intra-abdominal obesity, but the mechanism remains unclear.

OBJECTIVES

This study aimed to investigate whether lower plasma Gly concentrations in older adults are independently associated with (visceral) adiposity, age, sex, presence of chronic disease, and glucose intolerance, and whether they are caused by a reduced Gly whole-body production (WBP) and/or increased Gly disposal capacity.

METHODS

We studied 102 older adults (47 males/55 females, 68.5 ± standard deviation 6.4 y) without comorbidities and 125 older adults with chronic obstructive pulmonary disease (COPD) (58 males/67 females, 69.7 ± 8.6 y). We assessed body composition and visceral adipose tissue (VAT) by dual-energy x-ray absorptiometry and muscle function by dynamometry. We measured postabsorptive plasma amino acid profile and glucose, followed by pulse administration of stable isotope-labeled Gly ([2,2-2H2]), and blood sampling was performed to measure the WBP of Gly. Results are expressed as means and 95% confidence intervals (CIs).

RESULTS

We found a lower plasma Gly concentration in healthy males and males with COPD than in females (Healthy: 211; 95% CI: 193,230 compared with 248; 95% CI: 225,271; COPD: 200; 95% CI: 186,215 compared with 262: 95% CI: 241, 283; P < 0.0001, respectively), with no difference between healthy and COPD groups. A negative relationship was found between unadjusted plasma Gly and VAT mass (R2: 0.16; slope: -1.7; 95% CI: -2.4, -1.2; P < 0.0021), but not with total body fat or fasting glucose. The strong association between lower plasma Gly and increased VAT mass in older adults was independent of age, sex, body weight, lean mass or body mass index, and the presence of COPD. Inclusion of these covariates increased the R2 to 0.783. We found no relation between the VAT and WBP of Gly (P = 0.35) or Gly clearance (P = 0.187) when lean mass was considered.

CONCLUSIONS

Reduced plasma Gly in older adults can be considered a marker of visceral adiposity, independent of sex, age, body composition, presence of chronic disease, and whole-body Gly production or clearance. This study was registered on clinicaltrials.gov as NCT01787682, NCT02082418, NCT02157844, NCT02770092, NCT02780219, NCT03796455, and NCT04461236.

Adipocyte-released adipomes in Chagas cardiomyopathy: Impact on cardiac metabolic and immune regulation

Chronic Trypanosoma cruzi infection leads to Chagas cardiomyopathy (CCM), with varying manifestations such as inflammatory hypertrophic cardiomyopathy, arrhythmias, and dilated cardiomyopathy. The factors responsible for the increasing risk of progression to CCM are not fully understood. Previous studies link adipocyte loss to CCM progression, but the mechanism triggering CCM pathogenesis remains unexplored. Our study uncovers that T. cruzi infection triggers adipocyte apoptosis, leading to the release of extracellular vesicles named "adipomes". We developed an innovative method to isolate intact adipomes from infected mice's adipose tissue and plasma, showing they carry unique lipid cargoes. Large and Small adipomes, particularly plasma-derived infection-associated L-adipomes (P-ILA), regulate immunometabolic signaling and induce cardiomyopathy. P-ILA treatment induces hypertrophic cardiomyopathy in wild-type mice and worsens cardiomyopathy severity in post-acute-infected mice by regulating adipogenic/lipogenic and mitochondrial functions. These findings highlight adipomes' pivotal role in promoting inflammation and impairing myocardial function during cardiac remodeling in CD.

A comparison of five methods to maximize RNA and DNA isolation yield from adipose tissue

Adipose tissue in the human body occurs in various forms with different functions. It is an energy store, a complex endocrine organ, and a source of cells used in medicine. Many molecular analyses require the isolation of nucleic acids, which can cause some difficulties connected with the large amount of lipids in adipocytes. Ribonucleic acid isolation is particularly challenging due to its low stability and easy degradation by ribonucleases. The study aimed to compare and evaluate five RNA and DNA isolation methods from adipose tissue. The tested material was subcutaneous porcine adipose tissue subjected to different homogenization methods and RNA or DNA purification. A mortar and liquid nitrogen or ceramic beads were used for homogenization. The organic extraction (TriPure Reagent), spin columns with silica-membrane (RNeasy Mini Kit or High Pure PCR Template Preparation Kit), and the automatic MagNA Pure system were used for the purification. Five combinations were compared for RNA and DNA isolation. Obtained samples were evaluated for quantity and quality. The methods were compared in terms of yield (according to tissue mass), purity (A260/280 and A260/230), and nucleic acid degradation (RNA Integrity Number, RIN; DNA Integrity Number, DIN). The results were analyzed statistically. The average RNA yield was highest in method I, which used homogenization with ceramic beads and organic extraction. Low RNA concentration didn't allow us to measure degradation for all samples in method III (homogenization with ceramic beads and spin-column purification). The highest RNA quality was achieved with method IV using homogenization in liquid nitrogen and spin column purification, which makes it the most effective for RNA isolation from adipose tissue. Required values of DNA yield, purity, and integrity were achieved only with spin column-based methods (III and IV). The most effective method for DNA isolation from adipose tissue is method III, using spin-columns without additional homogenization.

Adipose biopsy techniques for studies in human exercise physiology

Adipose biopsy techniques are relatively undefined for exercise physiology research in individuals at or near normal weight. The purpose of this study was to compare the influence of two adipose biopsy techniques on tissue quality through measurements of adipocyte cell size, as well as mRNA and protein levels of select pro- and anti-inflammatory cytokines and adipokines. Thirteen participants (9 M, 4 W; 28 ± 4 yr; 27 ± 3 kg·m-2; V̇o2max: 3.3 ± 0.7 L·min-1) underwent subcutaneous adipose biopsies on either side of the umbilicus (incision: ∼8 cm lateral, sampling area: ∼5 cm lateral) using 1) a 6-mm Bergström biopsy needle and 2) a mini-liposuction approach with a 4-mm Mercedes biopsy needle that used prebiopsy tumescent delivery (∼30 mL 0.9% NaCl solution) into the sampling area (i.e., 'wet' technique). Tissue obtained was processed identically for analysis and both techniques returned high-quality tissue for histology (similar % intact adipocytes), mRNA (RNA integrity numbers >7.0), and protein. Adipocyte size was similar (P > 0.05) between both techniques (Bergström: 6,116 ± 1,652 μm2, 554-23,522 µm2; Mercedes: 6,517 ± 952 μm2, 926-21,969 µm2). There were also no differences (P > 0.05) between the two techniques for the measured cytokines (pro- and anti-inflammatory) and adipokines at the mRNA and protein levels. Adipocyte size was positively correlated with body mass index and body fat percentage, and negatively correlated with V̇o2max (P < 0.05). These results suggest both adipose biopsy techniques used in the current investigation are appropriate for histological, transcriptional, and translational level measurements in exercise physiology studies of nonobese women and men.NEW & NOTEWORTHY This study provides investigators with useful information related to adipose biopsy sampling approaches that can be used when planning studies that use measurements of adipose histology, as well as measurements at the mRNA and protein level. Adipose periumbilical sampling with the Bergström biopsy needle and the Mercedes wet mini-liposuction technique are both appropriate options for studies in exercise physiology and in nonobese individuals.

Exploration of macromolecular phenotype of human skeletal muscle in diabetes using infrared spectroscopy

Introduction

The global burden of diabetes mellitus is escalating, and more efficient investigative strategies are needed for a deeper understanding of underlying pathophysiological mechanisms. The crucial role of skeletal muscle in carbohydrate and lipid metabolism makes it one of the most susceptible tissues to diabetes-related metabolic disorders. In tissue studies, conventional histochemical methods have several technical limitations and have been shown to inadequately characterise the biomolecular phenotype of skeletal muscle to provide a holistic view of the pathologically altered proportions of macromolecular constituents.

Materials and methods

In this pilot study, we examined the composition of five different human skeletal muscles from male donors diagnosed with type 2 diabetes and non-diabetic controls. We analysed the lipid, glycogen, and collagen content in the muscles in a traditional manner with histochemical assays using different staining techniques. This served as a reference for comparison with the unconventional analysis of tissue composition using Fourier-transform infrared spectroscopy as an alternative methodological approach.

Results

A thorough chemometric post-processing of the infrared spectra using a multi-stage spectral decomposition allowed the simultaneous identification of various compositional details from a vibrational spectrum measured in a single experiment. We obtained multifaceted information about the proportions of the different macromolecular constituents of skeletal muscle, which even allowed us to distinguish protein constituents with different structural properties. The most important methodological steps for a comprehensive insight into muscle composition have thus been set and parameters identified that can be used for the comparison between healthy and diabetic muscles.

Conclusion

We have established a methodological framework based on vibrational spectroscopy for the detailed macromolecular analysis of human skeletal muscle that can effectively complement or may even serve as an alternative to histochemical assays. As this is a pilot study with relatively small sample sets, we remain cautious at this stage in drawing definitive conclusions about diabetes-related changes in skeletal muscle composition. However, the main focus and contribution of our work has been to provide an alternative, simple and efficient approach for this purpose. We are confident that we have achieved this goal and have brought our methodology to a level from which it can be successfully transferred to a large-scale study that allows the effects of diabetes on skeletal muscle composition and the interrelationships between the macromolecular tissue alterations due to diabetes to be investigated.

Low adipose tissue index as an indicator of hepatic encephalopathy in cirrhotic patients following transjugular intrahepatic portosystemic shunt

PURPOSE

We aimed to investigate the predictive value of body compositions measured by CT, including skeletal muscle and adipose tissue, for hepatic encephalopathy (HE) in cirrhotic patients following transjugular intrahepatic portosystemic shunt (TIPS).

METHODS

Patients who underwent TIPS between November 2015 and April 2021 were included in this retrospective study. CT images taken at L3 were quantified for three body composition indexes (cm²/m²), visceral fat area index (VFAI), subcutaneous fat area index (SFAI), and skeletal muscle index (SMI) at baseline. Multivariable logistic regression models were conducted to assess associations between post-TIPS HE and body compositions. Nomograms based on the multivariable logistic regression models were developed and were evaluated from Calibration curves.

RESULTS

Male patients had greater SMI, whereas SFAI and VFAI were higher in females (p < 0.001 for each). In sex stratified multivariate analyses after adjustment for other confounding variables, VFAI in males (p = 0.033) and SFAI in females (p = 0.003) were significant predictors of post-TIPS HE. Male patients with low VFAI (< 53.52 cm²/m²) (OR 6.44; 95% CI 1.72-23.59; p = 0.006) and female patients with low SFAI (< 70.05 cm²/m²) (OR 10.55; 95% CI 2.36-46.23; p = 0.002) had a higher risk of post-TIPS HE. Risk factors in the nomogram contributing to the male model included age, height, Child-Pugh score, and low VFAI; pre-albumin and low SFAI were contributed to female model.

CONCLUSION

Body compositions could not only be noninvasively used for nutritional assessment, but also be utilized to predict HE risk of cirrhotic patients after TIPS.

An optimized method for high-quality RNA extraction from distinctive intrinsic laryngeal muscles in the rat model

Challenges related to high-quality RNA extraction from post-mortem tissue have limited RNA-sequencing (RNA-seq) application in certain skeletal muscle groups, including the intrinsic laryngeal muscles (ILMs). The present study identified critical factors contributing to substandard RNA extraction from the ILMs and established a suitable method that permitted high-throughput analysis. Here, standard techniques for tissue processing were adapted, and an effective means to control confounding effects during specimen preparation was determined. The experimental procedure consistently provided sufficient intact total RNA (N = 68) and RIN ranging between 7.0 and 8.6, which was unprecedented using standard RNA purification protocols. This study confirmed the reproducibility of the workflow through repeated trials at different postnatal time points and across the distinctive ILMs. High-throughput diagnostics from 90 RNA samples indicated no sequencing alignment scores below 70%, validating the extraction strategy. Significant differences between the standard and experimental conditions suggest circumvented challenges and broad applicability to other skeletal muscles. This investigation remains ongoing given the prospect of therapeutic insights to voice, swallowing, and airway disorders. The present methodology supports pioneering global transcriptome investigations in the larynx previously unfounded in literature.

Extracellular vesicle secretion is tissue-dependent ex vivo and skeletal muscle myofiber extracellular vesicles reach the circulation in vivo

Extracellular vesicles (EVs) are biomarkers and modifiers of human disease. EVs secreted by insulin-responsive tissues like skeletal muscle (SkM) and white adipose tissue (WAT) contribute to metabolic health and disease but the relative abundance of EVs from these tissues has not been directly examined. Human Protein Atlas data and directly measuring EV secretion in mouse SkM and WAT using an ex vivo tissue explant model confirmed that SkM tissue secretes more EVs than WAT. Differences in EV secretion between SkM and WAT were not due to SkM contraction but may be explained by differences in tissue metabolic capacity. We next examined how many EVs secreted from SkM tissue ex vivo and in vivo are myofiber-derived. To do this, a SkM myofiber-specific dual fluorescent reporter mouse was created. Spectral flow cytometry revealed that SkM myofibers are a major source of SkM tissue-derived EVs ex vivo and EV immunocapture indicates that ∼5% of circulating tetraspanin-positive EVs are derived from SkM myofibers in vivo. Our findings demonstrate that 1) SkM secretes more EVs than WAT, 2) many SkM tissue EVs are derived from SkM myofibers, and 3) SkM myofiber-derived EVs reach the circulation in vivo. These findings advance our understanding of EV secretion between metabolically active tissues and provide direct evidence that SkM myofibers secrete EVs that can reach the circulation in vivo.