Quantification of adipose tissues by Dual-Energy X-Ray Absorptiometry and Computed Tomography in colorectal cancer patients.

BACKGROUND & AIMS: Excess adipose tissue may affect colorectal cancer (CRC) patients' disease progression and treatment. In contrast to the commonly used anthropometric measurements, Dual-Energy X-Ray Absorptiometry (DXA) and Computed Tomography (CT) can differentiate adipose tissues. However, these modalities are rarely used in the clinic despite providing high-quality estimates. This study aimed to compare DXA's measurement of abdominal visceral adipose tissue (VAT) and fat mass (FM) against a corresponding volume by CT in a CRC population. Secondly, we aimed to identify the best single lumbar CT slice for abdominal VAT. Lastly, we investigated the associations between anthropometric measurements and VAT estimated by DXA and CT. METHODS: Non-metastatic CRC patients between 50-80 years from the ongoing randomized controlled trial CRC-NORDIET were included in this cross-sectional study. Corresponding abdominal volumes were acquired by Lunar iDXA and from clinically acquired CT examinations. Also, single CT slices at L2-, L3-and L4-level were obtained. Agreement between the methods was investigated using univariate linear regression and Bland-Altman plots. RESULTS: Sixty-six CRC patients were included. Abdominal volumetric VAT and FM measured by DXA explained up to 91% and 96% of the variance in VAT and FM by CT, respectively. Bland-Altman plots demonstrated an overestimation of VAT by DXA compared to CT (mean difference of 76 cm3) concurrent with an underestimation of FM (mean difference of -319 cm3). A higher overestimation of VAT (p = 0.015) and underestimation of FM (p = 0.036) were observed in obese relative to normal weight subjects. VAT in a single slice at L3-level showed the highest explained variance against CT volume (R2 = 0.97), but a combination of three slices (L2, L3, L4) explained a significantly higher variance than L3 alone (R2 = 0.98, p < 0.006). The anthropometric measurements explained between 31-65% of the variance of volumetric VAT measured by DXA and CT. CONCLUSIONS: DXA and the combined use of three CT slices (L2-L4) are valid to predict abdominal volumetric VAT and FM in CRC patients when using volumetric CT as a reference method. Due to the poor performance of anthropometric measurements we recommend exploring the added value of advanced body composition by DXA and CT integrated into CRC care.

Insulin sensitivity, body composition and adipose depots following 12 w combined endurance and strength training in dysglycemic and normoglycemic sedentary men.

CONTEXT: Insulin resistance and dysglycemia are associated with physical inactivity and adiposity, and may be improved by exercise. OBJECTIVE: Investigate the effect of exercise on insulin sensitivity, body composition and adipose depots in sedentary men with (n = 11) or without (n = 11) overweight and dysglycemia. MATERIAL AND METHODS: Euglycemic-hyperinsulinemic clamp, ankle-to-neck MRI, MRS, muscle and adipose tissue biopsies before and after 12 weeks combined strength and endurance exercise. RESULTS: Insulin sensitivity, VO2max, strength, whole-body and muscle fat content, and abdominal adipose depots were improved without obvious differences between normo- and dysglycemic men. Hepatic fat, waist circumference and subcutaneous adipose tissue were reduced in the dysglycemic group. For both groups plasma adiponectin was reduced, whereas IL-6 was unchanged. Visceral fat was preferentially lost compared with other adipose depots. DISCUSSION AND CONCLUSION: Body composition, fat distribution and insulin sensitivity improved following training in sedentary middle-aged men with and without dysglycemia.

The effects of acute and chronic exercise on PGC-1α, irisin and browning of subcutaneous adipose tissue in humans.

Irisin was first identified as a peroxisome proliferator-activated receptor γ co-activator-1α (PGC-1α) dependent myokine with the potential to induce murine brown-fat-like development of white adipose tissue. In humans, the regulatory effect of training on muscle FNDC5 mRNA expression and subsequently irisin levels in plasma is more controversial. We recruited 26 inactive men (13 normoglycaemic and normal weight, controls; and 13 slightly hyperglycaemic and overweight, pre-diabetes group) aged 40-65 years for a 12-week intervention of combined endurance and strength training with four sessions of training per week. Before and after the 12-week intervention period, participants were exposed to an acute endurance workload of 45 min at 70% of VO(2max), and muscle biopsies were taken prior to and after exercise. Skeletal muscle mRNA for PGC1A and FNDC5 correlated and both PGC1A and FNDC5 mRNA levels increased after 12 weeks of training in both control and pre-diabetes subjects. Circulating irisin was reduced in response to 12 weeks of training, and was increased acutely (~1.2-fold) just after acute exercise. Plasma concentration of irisin was higher in pre-diabetes subjects compared with controls. There was little effect of 12 weeks of training on selected browning genes in subcutaneous adipose tissue. UCP1 mRNA did not correlate with FNDC5 expression in subcutaneous adipose tissue or skeletal muscle or with irisin levels in plasma. We observed no enhancing effect of long-term training on circulating irisin levels, and little or no effect of training on browning of subcutaneous white adipose tissue in humans.