Greater Fat Infiltration Research Articles

Comparison of cross-sectional area and fat infiltration of suboccipital muscles between normal dogs and dogs with atlantoaxial instability

BackgroundAtlantoaxial instability (AAI) is primarily a congenital neurological disorder affecting young toy-breed dogs. So far, most studies have focused on bones and ligaments related to AAI, and there are no studies on the suboccipital muscles (SOMs) that occupy a large area from the occipital bone to C2 in dogs. This study evaluated the cross-sectional area (CSA) and fat infiltration of the SOMs using magnetic resonance imaging (MRI), specifically, T1-weighted images, in normal dogs (≤ 5 kg) and AAI dogs. The relationship between the severity of the neurological symptoms of AAI (group A and group B) and the values from MRI was also assessed.ResultsAAI dogs had significantly smaller CSA (P = 0.029) and greater fat infiltration (P = 0.044) of the SOMs compared to normal dogs. AAI dogs with mild neurological symptoms for a long period (group A) had greater fat infiltration than AAI dogs with severe neurological symptoms (group B) (P = 0.035).ConclusionsThe muscle changes are most likely due to spinal cord compression resulting from instability; however, the possibility that chronic changes of the muscle may play an additional role in maintaining stability in this region cannot be excluded. This study provides fundamental quantitative information of the SOMs in normal and AAI dogs.

Poorer Muscle Quality and Quantity With ART Initiation Is Associated With Greater Inflammation and Immune Activation.

We have previously shown that the initiation of antiretroviral therapy (ART) is associated with a decrease in skeletal muscle density (greater fat accumulation), suggesting that gains in lean body mass seen in many ART studies may reflect gains in low quality, fatty muscle. Here, we explore whether skeletal muscle density and area are associated with markers of inflammation and immune activation. ART-naïve people with HIV were randomized to raltegravir or ritonavir-boosted atazanavir or darunavir, each with tenofovir disoproxil fumarate/emtricitabine. Abdominal computed tomography scans from baseline and week 96 were reanalyzed for psoas density and area and correlations explored with inflammation [interleukin-6 (IL-6) and high-sensitivity C-reactive protein] and immune activation [soluble CD14 (sCD14), soluble CD163 (sCD163), and %CD38+HLADR+ on CD4+ or CD8+ T cells]. Two hundred twenty-two participants had available inflammation/immune activation markers and paired computed tomography scans. At baseline, lower psoas density (greater fat) correlated with higher IL-6 (r = -0.26, P < 0.001) and sCD163 (r -0.15, P = 0.03) and lower lean psoas area correlated with higher IL-6, high-sensitivity C-reactive protein, sCD14, sCD163, and %CD38+HLADR+ on CD4+ T cells (r = -0.30-0.13; all P ≤ 0.05). From baseline to week 96, greater percent decrease in total psoas density (more fat) correlated with greater increase in IL-6 (r = -0.14; P = 0.04); greater % decrease in lean psoas area correlated greater increases in IL-6, sCD14, sCD163, and %CD38+HLADR+ on CD8+ T cells (r = -0.15 to -0.18; all P < 0.04). Greater fat infiltration within the psoas muscle (lower density) and greater loss in lean psoas muscle area were associated with higher inflammation and immune activation, which may portend important effects on muscle function and cardiometabolic risk.

Association Between Sleep Duration and Mid-Thigh Muscle Composition

Age-related changes in sleep are broadly documented and complaints of sleep difficulties are more common among older adults. Although sleep disorders are viewed as a health threat in several physiological systems, it is unclear how thigh lean mass and muscle attenuation, markers of sarcopenia, are affected by sleep. PURPOSE: This study aimed to examine the association between 24-hour sleep duration and mid-thigh muscle composition. METHODS: 2,438 men and 3,326 women aged 66 to 96 years, residents in the Reykjavik area (Iceland), were included in this cross-sectional study. Mid-thigh muscle area (cm2) and muscle attenuation (Hounsfield units, HU) were assessed with a four-row detector computed tomography system. The muscle attenuation was used as an indicator of muscle fat infiltration; lower HU indicates greater fat infiltration. Sleep and nap habits were assessed using a questionnaire. Total 24-hour sleep duration was estimated as the sum of nighttime sleep hours and daytime nap hours. Statistical analysis was performed using multivariable linear regression. RESULTS: We found that after adjustment for age and body mass index (BMI) long sleep duration (>8 h/day) was negatively associated with thigh lean area in both men (B= −2.2, 95% confidence interval (CI) = −4.0, −0.4) and women (B=−2.9, 95% CI = −3.8, −1.0) and with muscle attenuation (B=−1.0, 95% CI = −1.5, −0.4) only in women. After adjustments for all relevant covariates (including age, BMI, health and lifestyle factors) the association between long sleep duration and thigh lean area was attenuated and became non-significant. In women, the associations between long sleep duration and muscle attenuation were significant in both the age and BMI- and the full-adjusted model. In men these associations were not significant. No associations were observed for short sleep duration (<6 h/day) and both muscle parameters. CONCLUSIONS: Long sleep duration, particularly in old women, is associated with thigh muscle attenuation. Whether optimization of sleep can ameliorate age-associated intramuscular adipose tissue warrants further studies. Supported by Intramural Research Program of the NIH, NIA; the AGES-Reykjavik Study is funded by NIH Grant N01-AG-12100, the NIA Intramural Research Program, Hjartavernd, and the Althingi.

Paraspinal muscle asymmetry and fat infiltration in patients with symptomatic disc herniation

To investigate asymmetry in size and composition of the multifidus and erector spinae in patients with posterolateral disc herniation and concordant radicular symptoms, and determine whether symptom duration is associated with degree of asymmetry. Thirty-three patients diagnosed with posterolateral disc herniation at L4-L5 verified on imaging and concordant leg pain were included. Multifidus and erector spinae cross-sectional area (CSA), functional cross-sectional area (FCSA, fat-free area), signal intensity and ratio of FCSA to total CSA were measured bilaterally from T 2-weighted axial magnetic resonance imaging (MRI) at L3-L4, L4-L5, L5-S1 and S1 levels. No side-to-side differences in multifidus CSA, FCSA, and ratio of FCSA/CSA reached statistical significance at any spinal level. The multifidus signal intensity at L5-S1 was significantly greater (more fatty infiltration) on the side of the disc herniation. The erector spinae FCSA (lean muscle mass) at L5-S1 was found to be significantly smaller on the side of the herniation and the ratio of FCSA/CSA was smaller (more fatty infiltration) on the side of the herniation at L4-L5 and L5-S1. The degree of muscle asymmetry was not associated with symptoms duration. There was no significant asymmetry of the multifidus at spinal level above, same or level below the disc herniation. Instead, variations in muscle composition were observed, with greater fat infiltration on the side and at spinal levels adjacent to the disc herniation. Muscle asymmetry was not correlated with symptom duration.

Canine chondrodystrophic intervertebral disc disease (Hansen type I disc disease)

Intervertebral disc disease (IVDD) is the most common spinal disease in dogs. Chondrodystrophic dogs, which have disproportionably short and curved limbs, are predisposed to Hansen type I IVDD and of these the miniature Dachshund is over represented [1,2], is more likely to be presented at an earlier age [3] and is at greater risk of a severe spinal cord injury [4]. The tendency for IVDD in Dachshunds is inherited [5,6] and a major locus on chromosome 12 harbours genetic variations affecting the development of intervertebral disc calcification [7]. Hansen type I disc degeneration is thought to occur because of loss of notochordal cells which produce proteoglycans which “hold water” in the disc. Chondrodystrophic dogs have a primary deficiency of notochordal cells, a study found that large notochordal cells in the nucleus pulposus of chondrodystrophoid dogs formed 13% of the cell population in young dogs and fell to 0.4% in adults, whereas they were the predominant cell type in the nonchondrodystrophoid dogs at all ages [8]. Thus chondrodystrophoid dogs suffer early degenerative changes in the disc and a concomitant reduction in proteoglycan content, increased collagen, and loss of water content making the discs likely to herniate [8]. Certain lifestyle factors may increase or decrease risk of IVDD and this is currently under investigation. There is a suggestion that exercise (including stair climbing) reduces the incidence of disc calcification [9]. By contrast it has been hypothesized that obesity/lack of postural muscle strength may increase risk. Dachshunds with intervertebral disc extrusion had significantly smaller cross sectional area and greater fat infiltration in the epaxial muscles (muscles which lie dorsal to the horizontal septum of the vertebrae which mobilize and globally stabilize the trunk [10]) compared to dogs presenting with fibrocartilagenous embolism (another acute onset intervertebral disc related spinal disease) [11]. In addition chondrodystrophic dogs may have increased risk of IVVD if they have a more extreme conformation e.g. Dachshunds that have a longer back and shorter limbs are more at risk [12] and breeds with a comparatively heavy head such as the Bassett Hound may be more at risk of cervical disc disease. Breeds with a tendency for kyphoscoliosis such as the French Bulldog may be more at risk of IVDD in the IVDs adjacent to a vertebral malformation [13,14]. This presentation details the pathogeneis, clinical presentation, diagnosis and treatment of IVDD in chondrodystrophic dogs.

Fat Infiltration in Muscle: New Evidence for Familial Clustering and Associations With Diabetes

Increased fat infiltration in skeletal muscle has been associated with diabetes. Quantitative computed tomography (QCT) can be used to measure muscle density, which reflects the lipid content of skeletal muscle such that greater fat infiltration in skeletal muscle is associated with lower muscle density. The relative contribution of genetic and environmental factors to fat infiltration in skeletal muscle has not been assessed. Therefore, our aim is to determine genetic and environmental contributions to measures of skeletal muscle composition, and describe their associations with type 2 diabetes in multigenerational families of African ancestry. Peripheral QCT (pQCT) measures of skeletal muscle density were obtained for the calf in 471 individuals (60% women; mean 43 years) belonging to eight large, multigenerational Afro-Caribbean families (mean family size 51 individuals; 3,535 relative pairs). The proportion of variance in muscle density due to additive genetic effects (residual heritability) was 35.0% (P < 0.001) and significant covariates (age, gender, BMI, and parity) explained 55.0% of the total phenotypic variation in muscle density. Muscle density was lower (P < 0.001) in 62 diabetics (69.5 mg/cm(3)) than in 339 nondiabetics (74.3 mg/cm(3)) and remained significant after adjusting for age, gender, and BMI (P = 0.005) or age, gender, and waist circumference (P = 0.01). Our results provide new evidence that ectopic lipid deposition in skeletal muscle is a heritable trait and is associated with diabetes, independent of overall and central obesity in families of African heritage. Genome-wide screens and candidate gene studies are warranted to identify the genetic factors contributing to ectopic deposition of skeletal muscle fat.

Muscle Mass, Muscle Strength, and Muscle Fat Infiltration as Predictors of Incident Mobility Limitations in Well-Functioning Older Persons

Lower muscle mass has been correlated with poor physical function; however, no studies have examined this relationship prospectively. This study aims to investigate whether low muscle mass, low muscle strength, and greater fat infiltration into the muscle predict incident mobility limitation. Our study cohort included 3075 well-functioning black and white men and women aged 70-79 years participating in the Health, Aging, and Body Composition study. Participants were followed for 2.5 years. Muscle cross-sectional area and muscle tissue attenuation (a measure of fat infiltration) were measured by computed tomography at the mid-thigh, and knee extensor strength by using a KinCom dynamometer. Incident mobility limitation was defined as two consecutive self-reports of any difficulty walking one-quarter mile or climbing 10 steps. Mobility limitations were developed by 22.3% of the men and by 31.8% of the women. Cox's proportional hazards models, adjusting for demographic, lifestyle, and health factors, showed a hazard ratio of 1.90 [95% confidence interval (CI), 1.27-2.84] in men and 1.68 (95% CI, 1.23-2.31) in women for the lowest compared to the highest quartile of muscle area (p <.01 for trend). Results for muscle strength were 2.02 (95% CI, 1.39-2.94) and 1.91 (95% CI, 1.41-2.58), p <.001 trend, and for muscle attenuation were 1.91 (95% CI, 1.31-2.83) and 1.68 (95% CI, 1.20-2.35), p <.01 for trend. When included in one model, only muscle attenuation and muscle strength independently predicted mobility limitation (p < .05). Among men and women, associations were similar for blacks and whites. Lower muscle mass (smaller cross-sectional thigh muscle area), greater fat infiltration into the muscle, and lower knee extensor muscle strength are associated with increased risk of mobility loss in older men and women. The association between low muscle mass and functional decline seems to be a function of underlying muscle strength.

Leg muscle mass and composition in relation to lower extremity performance in men and women aged 70 to 79: the health, aging and body composition study.

The loss of muscle mass with aging, or sarcopenia, is hypothesized to be associated with the deterioration of physical function. Our aim was to determine whether low leg muscle mass and greater fat infiltration in the muscle were associated with poor lower extremity performance (LEP). A cross-sectional study, using baseline data of the Health, Aging and Body Composition study (1997/98). Medicare beneficiaries residing in ZIP codes from the metropolitan areas surrounding Pittsburgh, Pennsylvania, and Memphis, Tennessee. Three thousand seventy-five well-functioning black and white men and women aged 70 to 79. Two timed tests (6-meter walk and repeated chair stands) were used to measure LEP. Muscle cross-sectional area and muscle tissue attenuation (indicative of fat infiltration) were obtained from computed tomography scans at the midthigh. Body fat was assessed using dual-energy x-ray absorptiometry. Blacks had greater muscle mass and poorer LEP than whites. Black women had greater fat infiltration into the muscle than white women. After adjustment for clinic site, age, height, and total body fat, smaller muscle area was associated with poorer LEP in all four race-gender groups. (Regression coefficients, expressed per standard deviation (+/-55 cm2) of muscle area, were 0.658 and 0.519 in white and black men and 0.547 and 0.435 in white and black women, respectively, P <.01.) In addition, reduced muscle attenuation-indicative of greater fat infiltration into the muscle-was associated with poorer LEP, independent of total body fat and muscle area. (Regression coefficients per standard deviation (= 7 Hounsfield Units) of muscle attenuation were 0.292 and 0.224 in white and black men, and 0.193 and 0.159 in white and black women, respectively, P <.05). The most important body composition components related to LEP were muscle area in men and total body fat in women. Results were similar after additional adjustment for lifestyle factors and health status. No interactions between race and muscle area (P>.7) or between race and muscle attenuation (P>.2) were observed. Smaller midthigh muscle area and greater fat infiltration in the muscle are associated with poorer LEP in well-functioning older men and women.