Differential Relationship between Intermuscular Adipose Depots with Indices of Cardiometabolic Health

Moderate resistance training reduces intermuscular adipose tissue and risk factors of atherosclerotic cardiovascular disease for elderly patients with type 2 diabetes

AIM

This study aimed to assess the impact of moderate resistance training on intermuscular adipose tissue (IMAT) in elderly patients with type 2 diabetes and the independent effect of IMAT reduction on metabolic outcomes.

METHODS

In this randomized controlled trial, 85 patients with type 2 diabetes were assigned to either the resistance training group (42 participants) or the control group (43 participants) for a 6-month intervention. The primary outcome was changes in IMAT measured by computed tomography scan and magnetic resonance imaging using the interactive decomposition of water and fat with echo asymmetry and least squares qualification sequence. Secondary outcomes included changes in metabolic parameters.

RESULTS

Thirty-seven participants in each group completed the study. The IMAT area (measured by a computed tomography scan) in the resistance group decreased from 5.176 ± 1.249 cm2 to 4.660 ± 1.147 cm2, which is a change of -0.512 ± 0.115 cm2, representing a 9.89% decrease from the least-squares adjusted mean at baseline, which was significantly different from that of the control group (a change of 0.587 ± 0.115 cm2, a 10.34% increase). The normal attenuation muscle area (representing normal muscle density) in the resistance group increased from 82.113 ± 8.776 cm2 to 83.054 ± 8.761 cm2, a change of 1.049 ± 0.416 cm2, a 1.3% increase, which was significantly different from that of the control group (a change of -1.113 ± 0.416 cm2, a 1.41% decrease). Homeostasis model assessment 2 of beta cell function (HOMA2-β; increased from 52.291 ± 24.765 to 56.368 ± 21.630, a change of 4.135 ± 1.910, a 7.91% increase from baseline) and ratio of insulin increase to blood glucose increase at 30 min after the oral glucose tolerance test (∆I30/∆G30; increased from 4.616 ± 1.653 to 5.302 ± 2.264, a change of 0.715 ± 0.262, a 15.49% increase) in the resistance group were significantly improved compared with those in the control group, which had a change of -3.457 ± 1.910, a 6.05% decrease in HOMA2-β, and a change of -0.195 ± 0.262, a 3.87% decrease in ∆I30/∆G30, respectively. Adjusting for sex, age, diabetes duration, baseline IMAT, and the dependent variable at baseline, linear regression showed that the change in IMAT area was not related to the change in HOMA2 insulin resistance (β = -0.178, p = .402) or the change in HOMA2-β (β = -1.891, p = .197), but was significantly related to the changes in ∆I30/∆G30 (β = -0.439, p = .047), 2-h postprandial glucose (β = 1.321, p = .026), diastolic blood pressure (β = 2.425, p = .018), normal attenuation muscle area (β = -0.907, p = .019) and 10-year risk of atherosclerotic cardiovascular disease (β = 0.976, p = .002).

CONCLUSION

Low-level, moderate resistance training reduces IMAT content. Even a small reduction in IMAT may be related to a decrease in risk factors for atherosclerotic cardiovascular disease, but this small reduction may not be sufficient to reduce insulin resistance.

Fibro-adipogenic progenitors in physiological adipogenesis and intermuscular adipose tissue remodeling

Excessive accumulation of intermuscular adipose tissue (IMAT) is a common pathological feature in various metabolic and health conditions and can cause muscle atrophy, reduced function, inflammation, insulin resistance, cardiovascular issues, and unhealthy aging. Although IMAT results from fat accumulation in muscle, the mechanisms underlying its onset, development, cellular components, and functions remain unclear. IMAT levels are influenced by several factors, such as changes in the tissue environment, muscle type and origin, extent and duration of trauma, and persistent activation of fibro-adipogenic progenitors (FAPs). FAPs are a diverse and transcriptionally heterogeneous population of stromal cells essential for tissue maintenance, neuromuscular stability, and tissue regeneration. However, in cases of chronic inflammation and pathological conditions, FAPs expand and differentiate into adipocytes, resulting in the development of abnormal and ectopic IMAT. This review discusses the role of FAPs in adipogenesis and how they remodel IMAT. It highlights evidence supporting FAPs and FAP-derived adipocytes as constituents of IMAT, emphasizing their significance in adipose tissue maintenance and development, as well as their involvement in metabolic disorders, chronic pathologies and diseases. We also investigated the intricate molecular pathways and cell interactions governing FAP behavior, adipogenesis, and IMAT accumulation in chronic diseases and muscle deconditioning. Finally, we hypothesize that impaired cellular metabolic flexibility in dysfunctional muscles impacts FAPs, leading to IMAT. A deeper understanding of the biology of IMAT accumulation and the mechanisms regulating FAP behavior and fate are essential for the development of new therapeutic strategies for several debilitating conditions.

The Important Role of Intermuscular Adipose Tissue on Metabolic Changes Interconnecting Obesity, Ageing and Exercise: A Systematic Review

As age increases, adipose tissue infiltrates muscle tissue and leads to sarcopenia. When excessive accumulation of adipose tissue accompanied progressive decrease in lean body mass especially visceral fat, termed as sarcopenic obesity (SO) and related metabolic intermuscular adipose tissue (IMAT) is an ectopic tissue found between muscle groups, and is distinct from subcutaneous adipose tissue. Until now, the association between IMAT and metabolic health was not understood. This study is the first systematic review assessing the association between IMAT and metabolic health. The PubMed, Science Direct and Cochrane databases were searched for studies reporting IMAT and metabolic risk. The descriptions of the extracted data are guided by the Preferred Reporting Items for Systematic Reviews (PRISMA) statement with a Grading of Recommendations Assessment, Development and Evaluation approach. This study is registered at PROSPERO (identifier: CRD42022337518). Six studies were pooled and reviewed using critical appraisal by the Newcastle Ottawa Scale and Centre for Evidence-Based Medicine checklist. Two clinical trials and four observational trials were included. Our results reveal that IMAT is associated with metabolic risk, especially in older adults and patients with obesity. However, in a person with abdominal obesity, VAT has a more significant role in metabolic risk than IMAT. The largest decrease in IMAT was achieved by combining aerobic with resistance training.

Sex Differences in Adiposity and Cardiovascular Diseases

Body fat distribution is a well-established predictor of adverse medical outcomes, independent of overall adiposity. Studying body fat distribution sheds insights into the causes of obesity and provides valuable information about the development of various comorbidities. Compared to total adiposity, body fat distribution is more closely associated with risks of cardiovascular diseases. The present review specifically focuses on the sexual dimorphism in body fat distribution, the biological clues, as well as the genetic traits that are distinct from overall obesity. Understanding the sex determinations on body fat distribution and adiposity will aid in the improvement of the prevention and treatment of cardiovascular diseases (CVD).

Keeping It Local in Metabolic Disease: Adipose Tissue Paracrine Signaling and Insulin Resistance

Alterations in adipose tissue composition and function are associated with obesity and contribute to the development of type 2 diabetes. While the significance of this relationship has been cemented, our understanding of the multifaceted role of adipose tissue in metabolic heath and disease continues to evolve and expand. Heterogenous populations of cells that make up adipose tissue throughout the body generate diverse secretomes containing a mosaic of bioactive compounds with vast structural and signaling capabilities. While there are many reports highlighting the important role of adipose tissue endocrine signaling in insulin resistance and type 2 diabetes, the direct, local, paracrine effect of adipose tissue has received less attention. Recent studies have begun to underscore the importance of considering anatomically discrete adipose depots for their specific impact on local microenvironments and metabolic function in neighboring tissues as well as regulation of whole-body physiology. This article highlights the important role of adipose tissue paracrine signaling on metabolic function and insulin sensitivity in nearby tissues and organs, specifically focusing on visceral, pancreatic, subcutaneous, intermuscular, and perivascular adipose tissue depots.

Investigation of the Relationship between the Mid_Thigh Adipose Tissue Distribution Measured by MRI and Serum Osteocalcin—A Sex-Based Approach

Osteocalcin, in its non-carboxylated form, has a positive effect on glucose metabolism. Additionally, osteocalcin levels are related to body composition, especially muscle mass. The relation to the distribution of different adipose tissue types, such as subcutaneous, intermuscular, and visceral adipose tissue, is unclear. This study aimed to investigate associations between serum osteocalcin and the distribution of subcutaneous and intermuscular adipose tissue of the mid-thigh. Furthermore, the influence of different training methods on osteocalcin levels was investigated. We performed adipose tissue quantification of subcutaneous adipose tissue (SAT) and intramuscular adipose tissue (IMAT) using MRI measurements of the mid-thigh in 128 volunteers (63 male/65 female). Laboratory analysis included blood lipid panel, serum insulin, adiponectin, and osteocalcin measurements. The main observation was a significant correlation of total serum osteocalcin (TOC) and the distribution of adipose tissue of the mid-thigh (SAT/(SAT + IMAT)) (cc = −0.29/p-value = 0.002), as well as the cross-sectional muscle area (MA), increasing with the weekly resistance training duration in males. Additionally, TOC (p-value = 0.01) and MA (p-value = 0.03) were negatively related to serum insulin. The significant relationship between TOC and SAT/(SAT + IMAT) is a new finding and confirms the negative influence of IMAT on glucose metabolism in a sex-specific approach. We could substantiate this by the negative relation of TOC with serum insulin.

Distribution of subcutaneous and intermuscular fatty tissue of the mid-thigh measured by MRI-A putative indicator of serum adiponectin level and individual factors of cardio-metabolic risk

Obesity and metabolic syndrome (MetS) are associated with hypoadiponectinemia. On the contrary, studies revealed correlations between the amount of subcutaneous adipose tissue (SAT) and higher serum adiponectin levels. Furthermore, independent association of intermuscular adipose tissue (IMAT) deposit in the thigh with cardiometabolic risk factors (including total blood cholesterol, low-density lipoprotein (LDL), and triglycerides), and decreased insulin sensitivity, as MetS components, are sufficiently described. The combined relationship of thigh IMAT and SAT with serum adiponectin, leptin levels, and cardiometabolic risk factors have not been investigated till date. Since both SAT and IMAT play a role in fat metabolism, we hypothesized that the distribution pattern of SAT and IMAT in the mid-thigh might be related to adiponectin, leptin levels, and serum lipid parameters. We performed adipose tissue quantification using magnetic resonance imaging (MRI) of the mid-thigh in 156 healthy volunteers (78 male/78 female). Laboratory measurements of lipid panel, serum adiponectin, and leptin levels were conducted. Total serum adiponectin level showed a significant correlation with the percentage of SAT of the total thigh adipose tissue (SAT/ (IMAT+SAT)) for the whole study population and in sex-specific analysis. Additionally, SAT/(IMAT+SAT) was negatively correlated with known cardiometabolic risk factors such as elevated total blood cholesterol, LDL, and triglycerides; but positively correlated with serum high-density lipoprotein. In multiple linear regression analysis, (SAT/(IMAT+SAT)) was the most strongly associated variable with adiponectin. Interestingly, leptin levels did not show a significant correlation with this ratio. Adipose tissue distribution in the mid-thigh is not only associated to serum adiponectin levels, independent of sex. This proposed quantitative parameter for adipose tissue distribution could be an indicator for individual factors of a person`s cardiometabolic risk and serve as additional non-invasive imaging marker to ensure the success of lifestyle interventions.

Effects of weight loss during a very low carbohydrate diet on specific adipose tissue depots and insulin sensitivity in older adults with obesity: a randomized clinical trial

Background

Insulin resistance and accumulation of visceral adipose tissue (VAT) and intermuscular adipose tissue (IMAT) place aging adults with obesity at high risk of cardio-metabolic disease. A very low carbohydrate diet (VLCD) may be a means of promoting fat loss from the visceral cavity and skeletal muscle, without compromising lean mass, and improve insulin sensitivity in aging adults with obesity.

Objective

To determine if a VLCD promotes a greater loss of fat (total, visceral and intermuscular), preserves lean mass, and improves insulin sensitivity compared to a standard CHO-based/low-fat diet (LFD) in older adults with obesity.

Design

Thirty-four men and women aged 60–75 years with obesity (body mass index [BMI] 30-40 kg/m²) were randomized to a diet prescription of either a VLCD (< 10:25:> 65% energy from CHO:protein:fat) or LFD diet (55:25:20) for 8 weeks. Body composition by dual-energy X-ray absorptiometry (DXA), fat distribution by magnetic resonance imaging (MRI), insulin sensitivity by euglycemic hyperinsulinemic clamp, and lipids by a fasting blood draw were assessed at baseline and after the intervention.

Results

Participants lost an average of 9.7 and 2.0% in total fat following the VLCD and LFD, respectively (p < 0.01). The VLCD group experienced ~ 3-fold greater loss in VAT compared to the LFD group (− 22.8% vs − 1.0%, p < 0.001) and a greater decrease in thigh-IMAT (− 24.4% vs − 1.0%, p < 0.01). The VLCD group also had significantly greater thigh skeletal muscle (SM) at 8 weeks following adjustment for change in total fat mass. Finally, the VLCD had greater increases in insulin sensitivity and HDL-C and decreases in fasting insulin and triglycerides compared to the LFD group.

Conclusions

Weight loss resulting from consumption of a diet lower in CHO and higher in fat may be beneficial for older adults with obesity by depleting adipose tissue depots most strongly implicated in poor metabolic and functional outcomes and by improving insulin sensitivity and the lipid profile.

Trial registration

NCT02760641. Registered 03 May 2016 - Retrospectively registered.

Neck circumference is associated with adipose tissue content in thigh skeletal muscle in overweight and obese premenopausal women

Neck circumference (NC) has been proposed as a simple and practical tool, independently associated with cardiometabolic risk factors. However, the association of NC with inter-muscular adipose tissue (IMAT) is still to be determined. We aimed to examine the association of NC with thigh IMAT, and visceral adipose tissue (VAT) measured with computed tomography (CT) in overweight/obese women. 142 premenopausal overweight and obese Caucasian women participated in this cross-sectional study. NC was measured with an inextensible metallic tape above the thyroid cartilage according to International Society for Advancement of Kinanthropometry protocol. Thigh IMAT and VAT volumes were measured with a single cross-sectional CT. Regarding the covariates, fat mass (FM) was assessed with dual-energy x-ray absorptiometry and physical activity was objectively measured with accelerometry. NC was positively associated with thigh IMAT and VAT volumes (standardized β coefficient: β = 0.45, P-value = ≤0.001, β = 0.60, P = ≤ 0.001; respectively), which persisted after adjusting for age, height, overall FM or moderate-to-vigorous physical activity. Our findings show that NC is associated with thigh IMAT volume in overweight and obese premenopausal Caucasian women, regardless of the amount of lower-body fatness. These results suggest underscoring the relevance of NC as a marker of adipose tissue content in thigh skeletal muscle.

Incorporating Milk Protein Isolate into an Energy-Restricted Western-Style Eating Pattern Augments Improvements in Blood Pressure and Triglycerides, but Not Body Composition Changes in Adults Classified as Overweight or Obese: A Randomized Controlled Trial

Unhealthy Western-style eating patterns (WSEP) predominate, adversely affecting health. Resistance to improving dietary patterns prompts interest to incorporate a potentially health-promoting ingredient into typical WSEP foods and beverages. We assessed the effect of incorporating isocalorically matched carbohydrates versus milk protein isolate (MPI) into a WSEP on weight loss-induced changes in cardiometabolic health and body composition. In a randomized, double-blind, parallel-design study, 44 participants (age 52 ± 1 years, body mass index (BMI) 31.4 ± 0.5 kg/m2, mean ± standard error) consumed a weight maintenance WSEP (0.8 g total protein/kg/day) for 3 weeks (baseline). After, participants consumed an energy-restricted (750 kcal/day below estimated requirement) WSEP for 16 weeks, randomly assigned to contain either an additional 0.7 g carbohydrate/kg/d (CON: n = 23, 0.8 g total protein/kg/day) or 0.7 g protein/kg/d from MPI (MPI: n = 21, 1.5 g total protein/kg/day) incorporated into foods and beverages. Compared to CON, the MPI favored reductions in average 24 h and sleeping systolic and diastolic blood pressures (BP), waking hours systolic BP, and fasting plasma triglyceride concentrations. Reductions in fasting plasma insulin, glucose, total cholesterol, and low-density lipoprotein cholesterol concentrations were not different between groups. Among all participants, whole body mass, lean mass, fat mass, and thigh muscle area, each decreased over time. For adults finding it difficult to deviate from a WSEP, replacing a portion of their carbohydrate with foods and beverages containing MPI may be an effective dietary strategy to reduce BP after weight loss.

Associations of Thigh and Abdominal Adipose Tissue Radiodensity with Glucose and Insulin in Nondiabetic African-Ancestry Men

OBJECTIVE

Decreased radiodensity of adipose tissue (AT) located in the visceral AT (VAT), subcutaneous AT (SAT), and intermuscular AT (IMAT) abdominal depots is associated with hyperglycemia, hyperinsulinemia, and insulin resistance independent of AT volumes. These associations were sought in African-ancestry men, who have higher risk for type 2 diabetes and have been underrepresented in previous studies.

METHODS

This cross-sectional analysis included 505 nondiabetic men of African-Caribbean ancestry (median age: 61 years; median BMI: 26.8 kg/m² ) from the Tobago Health Study. AT volumes and radiodensities were assessed using computed tomography, including abdominal (VAT and SAT) and thigh (IMAT) depots. Associations between AT radiodensities were assessed with fasting serum glucose and insulin and with insulin resistance (updated homeostatic model assessment of insulin resistance, HOMA2-IR).

RESULTS

Higher radiodensity in any AT depot was associated with lower log-insulin and log-HOMA2-IR (β range: -0.16 to -0.18 for each; all P < 0.0001). No AT radiodensity was associated with glucose. Thigh IMAT radiodensity associations were independent of, and similar in magnitude to, VAT radiodensities. Model fit statistics suggested that AT radiodensities were a better predictor for insulin and insulin resistance compared with AT volumes in individuals with overweight and obesity.

CONCLUSIONS

AT radiodensities at multiple depots are significantly associated with insulin and insulin resistance in African-ancestry men.