The Relationship between Intramuscular Adipose Tissue, Functional Mobility, and Strength in Postmenopausal Women with and without Type 2 Diabetes

Skeletal muscle density performance for screening frailty in older adults with cancer and the impact of diabetes: The CARE Registry

INTRODUCTION

Skeletal muscle density (SMD) measurements from imaging scans identify myosteatosis and could screen patients for geriatric assessment. We assessed SMD performance as a screening tool to identify older adults with cancer likely to be frail and who could benefit from in-depth assessment; we compared performance by sex and diabetes status.

MATERIALS AND METHODS

We analyzed patients in the Cancer & Aging Resilience Evaluation (CARE) Registry. Frailty and diabetes were captured using a patient-reported geriatric assessment (CARE tool). Frailty was defined using CARE frailty index (CARE-FI) based on principles of deficit accumulation. SMD was calculated from computed tomography scans (L3 vertebrae). Analyses were conducted by sex and diabetes status. Scatterplots and linear regression described crude associations between SMD and frailty score. Classification performance (frail vs. non-frail) was analyzed with (1) area under the receiver operating characteristic curves (AUC) and confidence intervals (CIs); and (2) sensitivity/specificity for sex-specific SMD quartile cut-offs (Q1, median, Q3). Performance was compared between patients with and without diabetes using differences and estimated CIs (2000 bootstrap replicates). We additionally calculated positive and negative likelihood ratios (LR+, LR-).

RESULTS

The analytic cohort included 872 patients (39% female, median age 68 years, 27% with diabetes) with predominately stage III/IV gastrointestinal cancer; >60% planning to initiate first-line chemotherapy. SMD was negatively associated with frailty score; models were best fit in male patients with diabetes. AUC estimates for female (range: 0.58-0.62) and male (0.58-0.68) patients were low. Q3 cut-offs had high sensitivity (range: 0.76-0.89), but poor specificity (0.25-0.34). Diabetes did not impact estimates for female patients. Male patients with diabetes had greater sensitivity estimates compared to those without (sensitivity differences: 0.23 [0.07, 0.38], 0.08 [-0.07, 0.24], and 0.11 [0.00, 0.22] for Q1, median, Q3, respectively). LR estimates were most notable for male patients with diabetes (LR+ = 2.92, Q1 cut-off; LR- = 0.46, Q3 cut-off).

DISCUSSION

Using SMD alone to screen older patients for geriatric assessment requires improvement. High-sensitivity cut-off points could miss 11-24% of patients with frailty, and many non-frail patients may be flagged. Screening with SMD is practical but work is needed to understand clinical andresource impacts of different cut-off points. Future research should evaluate performance with additional clinical data and in subgroups.

Sex-Specific Differences in Lower Body Fat Distribution and Association with Physical Performance among Healthy Community-Dwelling Older Adults: A Pilot Study

This study aims to examine sex-specific differences in body composition and lower extremity fat distribution and their association with physical performance among healthy older adults. The pilot study comprises 40 subjects (20 men and 20 women) matched by age and body mass index. The participants undergo dual-energy X-ray absorptiometry, magnetic resonance imaging, and proton magnetic resonance spectroscopy (¹H-MRS) to assess body composition and lower extremity fat distribution. ¹H-MRS is used to measure the extramyocellular lipid (EMCL) and intramyocellular lipid (IMCL) contents of the lower leg muscles (soleus and tibialis anterior) at the maximum circumference of the calf after overnight fasting. The tibialis anterior IMCL, as assessed by ¹H-MRS, is negatively associated with the five-times sit-to-stand test scores (r_s = 0.518, p = 0.023) in men, while the soleus IMCL content is negatively associated with the timed up-and-go test scores (r_s = 0.472, p = 0.048) in women. However, the soleus EMCL content is positively associated with the five-times sit-to-stand test scores (r_s = −0.488, p = 0.040) in women, but this association is not statistically significant in men. This study shows an inverse correlation between IMCL content and physical performance in healthy older individuals and lower leg muscle-specific IMCL based on sex differences. Furthermore, our results suggest that greater EMCL content in the soleus and calf subcutaneous fat might affect physical performance positively in women but not men.

Lipidomics of human adipose tissue reveals diversity between body areas

BACKGROUND AND AIMS

Adipose tissue plays a pivotal role in storing excess fat and its composition reflects the history of person's lifestyle and metabolic health. Broad profiling of lipids with mass spectrometry has potential for uncovering new knowledge on the pathology of obesity, metabolic syndrome, diabetes and other related conditions. Here, we developed a lipidomic method for analyzing human subcutaneous adipose biopsies. We applied the method to four body areas to understand the differences in lipid composition between these areas.

MATERIALS AND METHODS

Adipose tissue biopsies from 10 participants were analyzed using ultra-high-performance liquid chromatography coupled to quadrupole time-of-flight mass spectrometry. The sample preparation optimization included the optimization of the lipid extraction, the sample amount and the sample dilution factor to detect lipids in an appropriate concentration range. Lipidomic analyses were performed for adipose tissue collected from the abdomen, breast, thigh and lower back. Differences in lipid levels between tissues were visualized with heatmaps.

RESULTS

Lipidomic analysis on human adipose biopsies lead to the identification of 186lipids in 2 mg of sample. Technical variation of the lipid-class specific internal standards were below 5%, thus indicating acceptable repeatability. Triacylglycerols were highly represented in the adipose tissue samples, and lipids from 13 lipid classes were identified. Long polyunsaturated triacylglycerols in higher levels in thigh (q<0.05), when compared with the abdomen, breast and lower back, indicating that the lipidome was area-specific.

CONCLUSION

The method presented here is suitable for the analysis of lipid profiles in 2 mg of adipose tissue. The amount of fat across the body is important for health but we argue that also the distribution and the particular profile of the lipidome may be relevant for metabolic outcomes. We suggest that the method presented in this paper could be useful for detecting such aberrations.

Magnetic Resonance Imaging and Spectroscopy to Assess Leg Muscle Macrostructure and Microstructure in Healthy Older Women: A Feasibility Assessment

BACKGROUND

Advanced magnetic resonance (MR) scanning techniques, such as diffusion tensor imaging (DTI) and proton MR spectroscopy (¹H-MRS) permit microstructural evaluation of water diffusivity and intramyocellular lipid content, respectively. We aimed to determine the feasibility of performing advanced MR scanning (proton density [PD] weighted imaging, DTI, and ¹H-MRS) to evaluate properties of leg muscles in older women with respect to: (1) participant recruitment using three community-based strategies; (2) participant tolerance to the MRI scan acquisition protocol; and (3) scan acquisition and analyses protocols.

METHODS

Recruitment feasibility was evaluated based on the number of participants enrolled using various strategies. Participant tolerance was feasible if the scanning session was uninterrupted and image artifacts were absent. Optimal PD imaging, DTI, and ¹H-MRS acquisition and analyses protocols were established.

RESULTS

Nine women (mean age = 71 years) were recruited over four months. The acquisition protocol was well tolerated by all participants. Adaptations were required for women with short stature and vertebral fracture risk. PD-weighted image analyses were improved by using the phased array uniformity enhancement filter to increase tissue contrast.

CONCLUSIONS

It is feasible to use a combination of MR scanning methods to evaluate muscle macrostructure and microstructure in the leg of older women. Our findings suggest that advanced MR scanning methods can be used for future studies interested in quantifying components of muscle structure in older women, but prospective studies are needed to confirm whether change in microstructure can be detected in response to an intervention.

The role of adipose tissue in cancer-associated cachexia

Adipose tissue (fat) is a heterogeneous organ, both in function and histology, distributed throughout the body. White adipose tissue, responsible for energy storage and more recently found to have endocrine and inflammation-modulatory activities, was historically thought to be the only type of fat present in adult humans. The recent demonstration of functional brown adipose tissue in adults, which is highly metabolic, shifted this paradigm. Additionally, recent studies demonstrate the ability of white adipose tissue to be induced toward the brown adipose phenotype - "beige" or "brite" adipose tissue - in a process referred to as "browning." While these adipose tissue depots are under investigation in the context of obesity, new evidence suggests a maladaptive role in other metabolic disturbances including cancer-associated cachexia, which is the topic of this review. This syndrome is multifactorial in nature and is an independent factor associated with poor prognosis. Here, we review the contributions of all three adipose depots - white, brown, and beige - to the development and progression of cancer-associated cachexia. Specifically, we focus on the local and systemic processes involving these adipose tissues that lead to increased energy expenditure and sustained negative energy balance. We highlight key findings from both animal and human studies and discuss areas within the field that need further exploration. Impact statement Cancer-associated cachexia (CAC) is a complex, multifactorial syndrome that negatively impacts patient quality of live and prognosis. This work reviews a component of CAC that lacks prior discussion: adipose tissue contributions. Uniquely, it discusses all three types of adipose tissue, white, beige, and brown, their interactions, and their contributions to the development and progression of CAC. Summarizing key bench and clinical studies, it provides information that will be useful to both basic and clinical researchers in designing experiments, studies, and clinical trials.

The reliability of a segmentation methodology for assessing intramuscular adipose tissue and other soft-tissue compartments of lower leg MRI images

OBJECTIVE

Determine the reliability of a magnetic resonance (MR) image segmentation protocol for quantifying intramuscular adipose tissue (IntraMAT), subcutaneous adipose tissue, total muscle and intermuscular adipose tissue (InterMAT) of the lower leg.

MATERIALS AND METHODS

Ten axial lower leg MRI slices were obtained from 21 postmenopausal women using a 1 Tesla peripheral MRI system. Images were analyzed using sliceOmatic™ software. The average cross-sectional areas of the tissues were computed for the ten slices. Intra-rater and inter-rater reliability were determined and expressed as the standard error of measurement (SEM) (absolute reliability) and intraclass coefficient (ICC) (relative reliability).

RESULTS

Intra-rater and inter-rater reliability for IntraMAT were 0.991 (95% confidence interval [CI] 0.978-0.996, p < 0.05) and 0.983 (95% CI 0.958-9.993, p < 0.05), respectively. For the other soft tissue compartments, the ICCs were all >0.90 (p < 0.05). The absolute intra-rater and inter-rater reliability (expressed as SEM) for segmenting IntraMAT were 22.19 mm(2) (95% CI 16.97-32.04) and 78.89 mm(2) (95% CI 60.36-113.92), respectively.

CONCLUSION

This is a reliable segmentation protocol for quantifying IntraMAT and other soft-tissue compartments of the lower leg. A standard operating procedure manual is provided to assist users, and SEM values can be used to estimate sample size and determine confidence in repeated measurements in future research.