RESUMEN

BACKGROUND: Physical inactivity triggers a rapid loss of muscle mass and function in older adults. Middle-aged adults show few phenotypic signs of aging yet may be more susceptible to inactivity than younger adults. OBJECTIVE: The aim was to determine whether leucine, a stimulator of translation initiation and skeletal muscle protein synthesis (MPS), can protect skeletal muscle health during bed rest. DESIGN: We used a randomized, double-blind, placebo-controlled trial to assess changes in skeletal MPS, cellular signaling, body composition, and skeletal muscle function in middle-aged adults (n = 19; age ± SEM: 52 ± 1 y) in response to leucine supplementation (LEU group: 0.06 g ∙ kg(-1) ∙ meal(-1)) or an alanine control (CON group) during 14 d of bed rest. RESULTS: Bed rest decreased postabsorptive MPS by 30% ± 9% (CON group) and by 10% ± 10% (LEU group) (main effect for time, P < 0.05), but no differences between groups with respect to pre-post changes (group × time interactions) were detected for MPS or cell signaling. Leucine protected knee extensor peak torque (CON compared with LEU group: -15% ± 2% and -7% ± 3%; group × time interaction, P < 0.05) and endurance (CON compared with LEU: -14% ± 3% and -2% ± 4%; group × time interaction, P < 0.05), prevented an increase in body fat percentage (group × time interaction, P < 0.05), and reduced whole-body lean mass loss after 7 d (CON compared with LEU: -1.5 ± 0.3 and -0.8 ± 0.3 kg; group × time interaction, P < 0.05) but not 14 d (CON compared with LEU: -1.5 ± 0.3 and -1.0 ± 0.3 kg) of bed rest. Leucine also maintained muscle quality (peak torque/kg leg lean mass) after 14 d of bed-rest inactivity (CON compared with LEU: -9% ± 2% and +1% ± 3%; group × time interaction, P < 0.05). CONCLUSIONS: Bed rest has a profoundly negative effect on muscle metabolism, mass, and function in middle-aged adults. Leucine supplementation may partially protect muscle health during relatively brief periods of physical inactivity. This trial was registered at clinicaltrials.gov as NCT00968344.

Asunto(s)

RESUMEN

The RDA for protein describes the quantity that should be consumed daily to meet population needs and to prevent deficiency. Protein consumption in many countries exceeds the RDA; however, intake is often skewed toward the evening meal, whereas breakfast is typically carbohydrate rich and low in protein. We examined the effects of protein distribution on 24-h skeletal muscle protein synthesis in healthy adult men and women (n = 8; age: 36.9 ± 3.1 y; BMI: 25.7 ± 0.8 kg/m2). By using a 7-d crossover feeding design with a 30-d washout period, we measured changes in muscle protein synthesis in response to isoenergetic and isonitrogenous diets with protein at breakfast, lunch, and dinner distributed evenly (EVEN; 31.5 ± 1.3, 29.9 ± 1.6, and 32.7 ± 1.6 g protein, respectively) or skewed (SKEW; 10.7 ± 0.8, 16.0 ± 0.5, and 63.4 ± 3.7 g protein, respectively). Over 24-h periods on days 1 and 7, venous blood samples and vastus lateralis muscle biopsy samples were obtained during primed (2.0 µmol/kg) constant infusion [0.06 µmol/(kg⋅min)] of l-[ring-(13)C6]phenylalanine. The 24-h mixed muscle protein fractional synthesis rate was 25% higher in the EVEN (0.075 ± 0.006%/h) vs. the SKEW (0.056 ± 0.006%/h) protein distribution groups (P = 0.003). This pattern was maintained after 7 d of habituation to each diet (EVEN vs. SKEW: 0.077 ± 0.006 vs. 0.056 ± 0.006%/h; P = 0.001). The consumption of a moderate amount of protein at each meal stimulated 24-h muscle protein synthesis more effectively than skewing protein intake toward the evening meal.

Asunto(s)

RESUMEN

PURPOSE: The purpose of this pilot study was to determine the feasibility of offering the authors' Diabetes Coaching Program (DCP), adapted for African Americans, in a sample of African American adults with type 2 diabetes. METHODS: The study used a 1-group, pretest-posttest design to test the acceptance and potential effectiveness of the DCP. Subjects were a convenience sample of 16 African Americans (8 women, 8 men) with type 2 diabetes; 12 subjects (6 women, 6 men) completed the program. The DCP included 4 weekly class sessions devoted to resilience education and diabetes self-management, followed by 8 biweekly support group meetings. Psychosocial process variables (resilience, coping strategies, diabetes empowerment) and proximal (perceived stress, depressive symptoms, diabetes self-management) and distal outcomes (body mass index [BMI], fasting blood glucose, HbA1C, lipidemia, blood pressure) were assessed at baseline and at 6 months after study entry. Qualitative data were collected at 8 months via a focus group conducted to examine the acceptability of the DCP. RESULTS: Preliminary paired t tests indicated statistically significant improvements in diabetes empowerment, diabetes self-management, BMI, HbA1c, total cholesterol, low-density lipoprotein cholesterol, and systolic and diastolic blood pressure. Medium to large effect sizes were reported. Resilience, perceived stress, fasting blood glucose, and high-density lipoprotein cholesterol improved, but changes were not statistically significant. Focus group data confirmed that participants held positive opinions regarding the DCP and follow-up support group sessions, although they suggested an increase in program length from 4 to 8 weeks. CONCLUSIONS: The pilot study documented the feasibility and potential effectiveness of the DCP to enhance diabetes empowerment, diabetes self-management, and reductions in the progression of obesity, type 2 diabetes, and cardiovascular disease in the African American community. Randomized experimental designs are needed to confirm these findings.

Asunto(s)

RESUMEN

BACKGROUND: Environmental tobacco smoke (ETS) exposure is recognized as a cardiovascular disease risk factor; however, the impact of prenatal ETS exposure on adult atherogenesis has not been examined. We hypothesized that in utero ETS exposure promotes adult atherosclerotic lesion formation and mitochondrial damage. METHODS AND RESULTS: Atherosclerotic lesion formation, mitochondrial DNA damage, antioxidant activity, and oxidant load were determined in cardiovascular tissues from adult apolipoprotein E-/- mice exposed to either filtered air or ETS in utero and fed a standard chow diet (4.5% fat) from weaning until euthanasia. All parameters were significantly altered in male mice exposed in utero to ETS. CONCLUSIONS: These data support the hypothesis that prenatal ETS exposure is sufficient to promote adult cardiovascular disease development.

Asunto(s)

RESUMEN

Hybrids between distinct Xiphophorus species have been utilized for over 70 years to study melanoma and other neoplasms that can develop spontaneously in hybrid offspring. Genetic linkage mapping has proven to be important in delineating genomic areas that harbor oncogenes and tumor suppressors. Within this report, two parallel backcrosses have been utilized to generate a genetic linkage map for Xiphophorus fishes. Isozyme/allozyme, RFLP and PCR-based mapping techniques, including AP-PCR/RAPDs and microsatellite loci were utilized. The derived linkage map provides a total of 403 mapped polymorphisms distributed among 24 linkage groups, representative of 24 acro- and telocentric chromosome pairs. Genomic coverage is approximately one marker per 5.8 cM. Detailed genotypic analysis of the utilized hybrids revealed two areas of the genome that show significant segregation distortion. Loci within the linkage group harboring the sex determining locus (LG 24) and an autosomal linkage group (LG 21) show highly significant deviations from Mendelian expectations. This phenomenon is not present in a hybrid cross that utilizes a different backcross hybrid progenitor species. The derived map with sequence-tagged markers provides a framework for physical map generation, large-scale genomic sequencing and will further enable cross-genome comparisons of vertebrate genomes.