Interleukin-18 Is a Potential Biomarker Linking Dietary Fatty Acid Quality and Insulin Resistance: Results from a Cross-Sectional Study in Northern Italy

Dietary lipids are pivotal in modulating metabolic inflammation. Among the inflammatory mediators characterizing metabolic inflammation, interleukin 18 (IL-18) has been consistently associated with obesity and insulin resistance. This study aims to evaluate whether the quality of lipid intake impacts upon IL-18 plasma levels and the implications on insulin resistance computed by the homeostatic model assessment for insulin resistance (HOMA-IR). Using a cross-sectional design, this study confirmed that IL-18 correlated positively with insulin resistance and individuals with a HOMA-IR ≥ 2.5 displayed higher circulating IL-18 levels compared with their insulin-sensitive counterparts. In terms of the effect of the quality of dietary lipids on IL-18 circulating levels, the ratio between monounsaturated, omega-3, polyunsaturated and saturated fatty acids as well as the intake of eicosapentaenoic and docosahexaenoic acids correlated negatively with IL-18. Despite this, IL-18 circulating levels, but not dietary fatty acid quality, predicted insulin resistance. Nevertheless, the ratio between omega 3 and saturated fatty acids was a predictor of IL-18 plasma levels. Thus, the downregulation of IL-18 may underpin, at least partially, the beneficial metabolic effects of substituting omega 3 for saturated fatty acids with this cytokine potentially representing a biomarker linking dietary lipids and metabolic outcomes

Irisin Attenuates Muscle Impairment during Bed Rest through Muscle-Adipose Tissue Crosstalk

The detrimental effect of physical inactivity on muscle characteristics are well known. Irisin, an exercise-induced myokine cleaved from membrane protein fibronectin type III domain-containing protein-5 (FNDC5), mediates at least partially the metabolic benefits of exercise. This study aimed to assess the interplay between prolonged inactivity, circulating irisin, muscle performance, muscle fibers characteristics, as well as the FNDC5 gene expression (FNDC5ge) in muscle and adipose tissue among healthy subjects. Twenty-three healthy volunteers were tested before and after 14 days of Bed Rest, (BR). Post-BR circulating levels of irisin significantly increased, whereas body composition, muscle performance, and muscle fiber characteristics deteriorated. Among the subjects achieving the highest post-BR increase of irisin, the lowest reduction in maximal voluntary contraction and specific force of Fiber Slow/1, the highest increase of FNDC5ge in adipose tissue, and no variation of FNDC5ge in skeletal muscle were recorded. Subjects who had the highest FNDC5ge in adipose tissue but not in muscle tissue showed the highest circulating irisin levels and could better withstand the harmful effect of BR

Tensiomyographic assessment of muscle contractile properties in 9- to 14-year old children

While there are numerous data on the skeletal muscle fibre type composition in adults, little is known about the changes in fibre type composition and contractile properties during maturational growth in children. Using noninvasive tensiomyography we measured contraction time, an indirect estimate of the myosin heavy chain I (MHC-I) proportion, to assess the longitudinal changes of the biceps brachii (BB), biceps femoris (BF), vastus lateralis (VL), and erector spinae (ES) muscles in 53 boys and 54 girls. The children were 9 years at the start of the study and returned for 5 follow-up measurements till the age of 14 years. The ES has the shortest and the BF has the longest Tc. The VL and ES of boys have shorter Tc than those from girls. When applying the relationship between proportion of MHC-I and Tc established in adults to the children TMG data, we found a slow-to-fast transition in the VL between at least the age of 6 and 10 years, when it had stabilized to adult proportions. Regular participation in sport was associated with a faster BF, but not in VL. Our data represents a first non-invasive indication of the developmental changes in muscle fiber type composition in children

Sarcopenia parameters in active older adults - an eight-year longitudinal study

BACKGROUD: Sarcopenia is a common skeletal muscle syndrome that is common in older adults but can be mitigated by adequate and regular physical activity. The development and severity of sarcopenia is favored by several factors, the most influential of which are a sedentary lifestyle and physical inactivity. The aim of this observational longitudinal cohort study was to evaluate changes in sarcopenia parameters, based on the EWGSOP2 definition in a population of active older adults after eight years. It was hypothesized that selected active older adults would perform better on sarcopenia tests than the average population. METHODS: The 52 active older adults (22 men and 30 women, mean age: 68.4 ± 5.6 years at the time of their first evaluation) participated in the study at two time points eight-years apart. Three sarcopenia parameters were assessed at both time points: Muscle strength (handgrip test), skeletal muscle mass index, and physical performance (gait speed), these parameters were used to diagnose sarcop0enia according to the EWGSOP2 definition. Additional motor tests were also performed at follow-up measurements to assess participants' overall fitness. Participants self-reported physical activity and sedentary behavior using General Physical Activity Questionnaire at baseline and at follow-up measurements. RESULTS: In the first measurements we did not detect signs of sarcopenia in any individual, but after 8 years, we detected signs of sarcopenia in 7 participants. After eight years, we detected decline in ; muscle strength (-10.2%; p < .001), muscle mass index (-5.4%; p < .001), and physical performance measured with gait speed (-28.6%; p < .001). Similarly, self-reported physical activity and sedentary behavior declined, too (-25.0%; p = .030 and - 48.5%; p < .001, respectively). CONCLUSIONS: Despite expected lower scores on tests of sarcopenia parameters due to age-related decline, participants performed better on motor tests than reported in similar studies. Nevertheless, the prevalence of sarcopenia was consistent with most of the published literature. TRIAL REGISTRATION: The clinical trial protocol was registered on ClinicalTrials.gov, identifier: NCT04899531

Positive energy balance is associated with accelerated muscle atrophy and increased erythrocyte glutathione turnover during 5 wk of bed rest

Background: Physical inactivity is often associated with positive energy balance and fat gain. Objective: We aimed to assess whether energy intake in excess of requirement activates systemic inflammation and antioxidant defenses and accelerates muscle atrophy induced by inactivity. Design: Nineteen healthy male volunteers were studied before and at the end of 5 wk of bed rest. Subjects were allowed to spontaneously adapt to decreased energy requirement (study A, n = 10) or were provided with an activity-matched diet (study B, n = 9). Groups with higher (HEB) or lower (LEB) energy balance were identified according to median values of inactivity-induced changes in fat mass (\u394FM, assessed by bioelectrical impedance analysis). Results: In pooled subjects (n = 19; median \u394FM: 1.4 kg), bed rest-mediated decreases in fat-free mass (bioelectrical impedance analysis) and vastus lateralis thickness (ultrasound imaging) were significantly greater (P &lt; 0.03) in HEBAB (-3.8 \ub1 0.4kg and -0.32 \ub1 0.04 cm, respectively) than in LEBab (-2.3 \ub1 0.5 kg and -0.09 \ub1 0.04 cm, respectively) subjects. In study A (median \u394FM: 1.8 kg), bed rest-mediated increases in plasma leptin, C-reactive protein, and myeloperoxidase were greater (P &lt; 0.04) in HEBA than in LEBA subjects. Bed rest-mediated changes of glutathione synthesis rate in eythrocytes (L-[3,3-2H2]cysteine incorporation) were greater (P = 0.03) in HEBA (from 70 \ub1 19 to 164 \ub1 29%/d) than in LEBA (from 103 \ub1 23 to 84 \ub1 27%/d) subjects. Conclusions: Positive energy balance during inactivity is associated with greater muscle atrophy and with activation of systemic inflammation and of antioxidant defenses. Optimizing caloric intake may be a useful strategy for mitigating muscle loss during period of chronic inactivity

Age-Related Declines in Lower Limb Muscle Function are Similar in Power and Endurance Athletes of Both Sexes: A Longitudinal Study of Master Athletes

The age-related decline in muscle function, particularly muscle power, is associated with increased risk of important clinical outcomes. Physical activity is an important determinant of muscle function, and different types of physical activity e.g. power-based versus endurance-based exercise appear to have differential effects on muscle power. Cross-sectional studies suggest that participation in power-based exercise is associated with greater muscle power across adulthood but this has not been investigated longitudinally. We recruited eighty-nine male and female power and endurance master athletes (sprint and distance runners respectively, baseline age 35–90y). Using jumping mechanography, we measured lower limb muscle function during a vertical jump including at least two testing sessions longitudinally over 4.5 ± 2.4y. We examined effects of time, discipline (power/endurance) and sex in addition to two- and three-way interactions using linear mixed-effects models. Peak relative power, relative force and jump height, but not Esslingen Fitness Index (indicating peak power relative to sex and age-matched reference data) declined with time. Peak power, force, height and EFI were greater in power than endurance athletes. There were no sex, discipline or sex*discipline interactions with time for any variable, suggesting that changes were similar over time for athletes of both sexes and disciplines. Advantages in lower limb muscle function in power athletes were maintained with time, in line with previous cross-sectional studies. These results suggest that improvements in lower limb function in less active older individuals following power-based training persist with continued adherence, although this requires further investigation in interventional studies

Greater maintenance of bone mineral content in male than female athletes, and in sprinting and jumping than endurance athletes: a longitudinal study of bone strength in elite masters athletes

Summary: We investigated longitudinal changes in tibia bone strength in master power (jumping and sprinting) and endurance (distance) athletes of both sexes. Bone mass but not cross‐sectional moment of inertia was better maintained in power than endurance athletes over time, particularly in men and independent of changes in performance. Objective: Assessment of effects of sex and athletic discipline (lower limb power events e.g. sprint running and jumping versus endurance running events) on longitudinal changes in bone strength in masters athletes. Methods: We examined tibia and fibula bone properties at distal (4% distal‐proximal tibia length) and proximal (66% length) sites using peripheral quantitative computed tomography (pQCT) in seventy‐one track and field masters athletes (30 male, 41 female, age at baseline 57.0±12.2y) in a longitudinal cohort study that included at least two testing sessions over a mean period of 4.2±3.1y. Effects of time, as well as time*sex and time*discipline interactions on bone parameters and calf muscle cross‐sectional area (CSA) were examined. Results: Effects of time were sex and discipline‐dependent, even following adjustment for enrolment age, sex, and changes in muscle CSA and athletic performance. Male sex and participation in power events was associated with better maintenance of tibia bone mineral content (BMC, an indicator of bone compressive strength) at 4% and 66% sites. In contrast, there was no strong evidence of sex or discipline effects on cross‐sectional moment of inertia (CSMI, an indicator of bone bending and torsional strength – P > 0.3 for interactions). Similar sex and discipline‐specific changes were also observed in the fibula. Conclusions: Results suggest that male athletes and those participating in lower limb power‐based rather than endurance‐based disciplines have better maintenance of bone compressive but not bending and torsional strength