Anabolic effects of testosterone are preserved during inhibition of 5α-reductase

2007 ◽  
Vol 293 (2) ◽  
pp. E507-E514 ◽  
Author(s):  
Stephen E. Borst ◽  
Christine F. Conover ◽  
Christy S. Carter ◽  
Chris M. Gregory ◽  
Emanuele Marzetti ◽  
...  
Keyword(s):  
Food Intake ◽  
Muscle Fibers ◽  
Hemoglobin Concentration ◽  
Male Rats ◽  
Type I ◽  
Mineral Density ◽  
Cross Sectional ◽  
Prostate Enlargement ◽  
Testosterone Administration ◽  
Novel Strategy

At replacement doses, testosterone produces only modest increases in muscle strength and bone mineral density in older hypogonadal men. Although higher doses of testosterone are more anabolic, there is concern over increased adverse effects, notably prostate enlargement. We tested a novel strategy for obtaining robust anabolic effects without prostate enlargement. Orchiectomized (ORX) male rats were treated for 56 days with 1.0 mg testosterone/day, with and without 0.75 mg/day of the 5α-reductase inhibitor MK-434. Testosterone administration elevated the prostate dihydrotestosterone concentration and caused prostate enlargement. Both effects were inhibited by MK-434. ORX produced a catabolic state manifested in reduced food intake, blunted weight gain, reduced hemoglobin concentration, decreased kidney mass, and increased bone resorption, and in the proximal tibia there was both decreased cancellous bone volume and a decreased number of trabeculae. In soleus and extensor digitorum longus muscles, ORX reduced both the percentage of type I muscle fibers and the cross-sectional area of type 1 and 2 fibers. Testosterone administration caused a number of anabolic effects, including increases in food intake, hemoglobin concentration, and grip strength, and reversed the catabolic effects of ORX on bone. Testosterone administration also partially reversed ORX-induced changes in muscle fibers. In contrast to the prostate effects of testosterone, the effects on muscle, bone, and hemoglobin concentration were not blocked by MK-434. Our study demonstrates that the effects of testosterone on muscle and bone can be separated from the prostate effects and provides a testable strategy for combating sarcopenia and osteopenia in older hypogonadal men.

scholarly journals Reduced Appendicular Lean Body Mass, Muscle Strength, and Size of Type II Muscle Fibers in Patients with Spondyloarthritis versus Healthy Controls: A Cross-Sectional Study

2016 ◽  
Vol 2016 ◽  
pp. 1-11 ◽  
Author(s):  
Kristine Røren Nordén ◽  
Hanne Dagfinrud ◽  
Amund Løvstad ◽  
Truls Raastad
Keyword(s):  
Body Composition ◽  
Muscle Strength ◽  
Lean Body Mass ◽  
Body Mass ◽  
Muscle Fibers ◽  
Type I ◽  
Healthy Controls ◽  
Type Ii ◽  
Mineral Density ◽  
Cross Sectional

Introduction. The purpose of this study was to investigate body composition, muscle function, and muscle morphology in patients with spondyloarthritis (SpA).Methods. Ten male SpA patients (mean ± SD age39±4.1years) were compared with ten healthy controls matched for sex, age, body mass index, and self-reported level of physical exercise. Body composition was measured by dual energy X-ray absorptiometry. Musculus quadriceps femoris (QF) strength was assessed by maximal isometric contractions prior to test of muscular endurance. Magnetic resonance imaging of QF was used to measure muscle size and calculate specific muscle strength. Percutaneous needle biopsy samples were taken fromm. vastus lateralis.Results. SpA patients presented with significantly lower appendicular lean body mass (LBM) (p=0.02), but there was no difference in bone mineral density, fat mass, or total LBM. Absolute QF strength was significantly lower in SpA patients (p=0.03) with a parallel trend for specific strength (p=0.08). Biopsy samples from the SpA patients revealed significantly smaller cross-sectional area (CSA) of type II muscle fibers (p=0.04), but no difference in CSA type I fibers.Conclusions. Results indicate that the presence of SpA disease is associated with reduced appendicular LBM, muscle strength, and type II fiber CSA.

Effects of Hypertrophy Exercise in Bone Turnover Markers and Structure in Growing Male Rats

2017 ◽  
Vol 38 (06) ◽  
pp. 418-425
Author(s):  
Elena Nebot ◽  
Virginia Aparicio ◽  
Peter Pietschmann ◽  
Daniel Camiletti-Moirón ◽  
Garyfallia Kapravelou ◽  
...  
Keyword(s):  
Bone Mineral ◽  
Volume Fraction ◽  
Bone Microarchitecture ◽  
Male Rats ◽  
Type I ◽  
Mineral Density ◽  
Plasma Parameters ◽  
Cross Sectional ◽  
Cortical Volume ◽  
Turnover Markers

AbstractThe benefits of exercise on bone density, structure and turnover markers are rather controversial. The present study aimed to examine the effects of hypertrophy exercise (HE) on bone. 20 male Wistar rats were randomly distributed in 2 experimental groups, one performing HE and the other untrained over 12 weeks. Plasma parameters, bone mineral content, bone mineral density (BMD), structure, and trabecular and cortical microarchitecture were measured. Femur Mg content was 12% higher (p<0.001), whereas femur length, dry weight, P content, and aminoterminal propeptides of type I procollagen were lower in the HE group (all, p<0.05). Total BMD and cortical/subcortical BMD were higher (both, p<0.01), whereas total cross-sectional and trabecular areas were lower (both, p<0.001), and cortical area and thickness were lower in the HE (both, p<0.05). Trabecular connectivity density, number, mean density of total and bone volume were higher in the HE (all, p<0.05). Cortical volume fraction and the mean density of total volume of the diaphysis were lower, whereas the cortical volume density was higher in the HE (all, p<0.05). This HE protocol may have beneficial effect on cancellous bone microarchitecture, but it induces low bone formation and is associated with hypogonadism in growing male rats. However, this type of training might be inefficient to maintain appropriate cortical thickness.

scholarly journals Different Short-Term Mild Exercise Modalities Lead to Differential Effects on Body Composition in Healthy Prepubertal Male Rats

2015 ◽  
Vol 2015 ◽  
pp. 1-9 ◽  
Author(s):  
D. M. Sontam ◽  
M. H. Vickers ◽  
J. M. O’Sullivan ◽  
M. Watson ◽  
E. C. Firth
Keyword(s):  
Body Composition ◽  
Food Intake ◽  
Vital Role ◽  
Voluntary Exercise ◽  
Bone Architecture ◽  
Male Rats ◽  
Short Term ◽  
Cross Sectional ◽  
Impact Exercise ◽  
Prepubertal Rats

Physical activity has a vital role in regulating and improving bone strength. Responsiveness of bone mass to exercise is age dependent with the prepubertal period suggested to be the most effective stage for interventions. There is a paucity of data on the effects of exercise on bone architecture and body composition when studied within the prepubertal period. We examined the effect of two forms of low-impact exercise on prepubertal changes in body composition and bone architecture. Weanling male rats were assigned to control (CON), bipedal stance (BPS), or wheel exercise (WEX) groups for 15 days until the onset of puberty. Distance travelled via WEX was recorded, food intake measured, and body composition quantified. Trabecular and cortical microarchitecture of the femur were determined by microcomputed tomography. WEX led to a higher lean mass and reduced fat mass compared to CON. WEX animals had greater femoral cortical cross-sectional thickness and closed porosity compared to CON. The different exercise modalities had no effect on body weight or food intake, but WEX significantly altered body composition and femoral microarchitecture. These data suggest that short-term mild voluntary exercise in normal prepubertal rats can alter body composition dependent upon the exercise modality.

Diaphragm muscle fatigue resistance during postnatal development

1991 ◽  
Vol 71 (2) ◽  
pp. 458-464 ◽  
Author(s):  
G. C. Sieck ◽  
M. Fournier ◽  
C. E. Blanco
Keyword(s):  
Postnatal Development ◽  
Fatigue Resistance ◽  
Muscle Fibers ◽  
Diaphragm Muscle ◽  
Fatigue Properties ◽  
Type I ◽  
Type Ii ◽  
Cross Sectional ◽  
Type I Fibers ◽  
Type Ii Fibers

postnatal development. Both twitch contraction time and half-relaxation time decreased progressively with age. Correspondingly, the force-frequency curve was shifted to the left early in development compared with adults. The ratio of peak twitch force to maximum tetanic force decreased with age. Fatigue resistance of the diaphragm was highest at birth and then progressively decreased with age. At birth, most diaphragm muscle fibers stained darkly for myofibrillar adenosinetriphosphatase after alkaline preincubation and thus would be classified histochemically as type II. During subsequent postnatal development, the proportion of type I fibers (lightly stained for adenosinetriphosphatase) increased while the number of type II fibers declined. At birth, type I fibers were larger than type II fibers. The size of both fiber types increased with age, but the increase in cross-sectional area was greater for type II fibers. On the basis of fiber type proportions and mean cross-sectional areas, type I fibers contributed 15% of total muscle mass at birth and 25% in adults. Thus postnatal changes in diaphragm contractile and fatigue properties cannot be attributed to changes in the relative contribution of histochemically classified type I and II fibers. However, the possibility that these developmental changes in diaphragm contractile and fatigue properties correlated with the varying contractile protein composition of muscle fibers was discussed.

Effect of acute nutritional deprivation on diaphragm structure and function

1990 ◽  
Vol 68 (5) ◽  
pp. 1938-1944 ◽  
Author(s):  
M. I. Lewis ◽  
G. C. Sieck
Keyword(s):  
Nerve Stimulation ◽  
Muscle Fibers ◽  
Medial Gastrocnemius ◽  
Fatigue Properties ◽  
Muscle Stimulation ◽  
Type I ◽  
Cross Sectional ◽  
Nutritional Deprivation ◽  
Nerve Muscle

The influence of 90 h of acute nutritional deprivation (ND) on the cross-sectional areas of muscle fibers and the contractile and fatigue properties of the adult rat diaphragm were determined. Isometric contractile properties and fatigue resistance of the diaphragm were measured by means of an in vitro nerve-muscle strip preparation. Contractions were evoked by using phrenic nerve stimulation (left hemidiaphragm) or direct muscle stimulation (right hemidiaphragm) in the presence of curare. Acute ND resulted in a 20% reduction in body weight. No significant decrements in diaphragm or soleus weights were noted in the ND animals compared with controls (CTL), whereas the weight of the medial gastrocnemius was reduced by 20% in the ND animals. Peak twitch and tetanic tensions (normalized for the weight of the diaphragm strip) were not reduced in ND compared with CTL animals after either nerve or muscle stimulation. The fatigue index of the diaphragm was significantly reduced in ND animals only after nerve stimulation. After the fatigue test, there was rapid recovery of the additional fatigue noted with nerve stimulation. The proportions of type I and II muscle fibers of the diaphragm were similar in the CTL and ND animals. No differences in diaphragm cross-sectional areas were noted for either type I or II muscle fibers in the CTL and ND animals. It is concluded that acute ND has no effect on diaphragm contractility or morphometry and only an inconsequential influence on diaphragm fatigue.

scholarly journals Effect of Intermittent Fasting on Glucose Homeostasis and Bone Remodeling in Glucocorticoid-Induced Osteoporosis Rat Model

2021 ◽  
Vol 28 (4) ◽  
pp. 307-316
Author(s):  
Majed G. Alrowaili ◽  
Abdelaziz M. Hussein ◽  
Elsayed A. Eid ◽  
Mohamed S. Serria ◽  
Hussein Abdellatif ◽  
...  
Keyword(s):  
Bone Remodeling ◽  
Bone Mineral ◽  
Serum Levels ◽  
Male Rats ◽  
Control Group ◽  
Intermittent Fasting ◽  
Tartrate Resistant Acid Phosphatase ◽  
Type I ◽  
Mineral Density ◽  
Trap 5B

Background: The present study examined the effect of intermittent fasting (IF) on bone mineral content (BMC) and bone mineral density (BMD) and the markers of bone remodeling in a glucocorticoid-induced osteoporosis (GIO) rat model.Methods: Forty male rats were allocated to 4 groups (N=10 per group): control group of normal rats; control+IF group (normal rats subjected to IF for 16-18 hr daily for 90 days); dexamethasone (DEX) group: (DEX [0.5 mg i.p.] for 90 days); and DEX+IF group (DEX and IF for 90 days). By the end of the experiment, BMD and BMC in the right tibia were measured. Serum levels of the following were measured: glucose; insulin; triglycerides (TGs); total cholesterol; parathyroid hormone (PTH); osteoprotegerin (OPG); receptor activator of nuclear factor-κB (RANK); bone-resorbing cytokines, including bone deoxypyridinoline (DPD), N-terminal telopeptide of collagen type I (NTX-1), and tartrate-resistant acid phosphatase 5b (TRAP-5b); and bone-forming cytokines, including alkaline phosphatase (ALP) and osteocalcin (OC).Results: DEX administration for 90 days resulted in significantly increased serum levels of glucose, insulin, TGs, cholesterol, PTH, OPG, DPD, NTX-1, and TRAP-5b and significantly decreased BMD, BMC, and serum levels of RANK, OC, and ALP (all P<0.05). IF for 90 days significantly improved all these parameters (all P<0.05).Conclusions: IF corrected GIO in rats by inhibiting osteoclastogenesis and PTH secretion and stimulating osteoblast activity.

Adaptations of the diaphragm in emphysema

1992 ◽  
Vol 72 (3) ◽  
pp. 934-943 ◽  
Author(s):  
M. I. Lewis ◽  
W. Z. Zhan ◽  
G. C. Sieck
Keyword(s):  
Muscle Fibers ◽  
Capillary Density ◽  
Histochemical Staining ◽  
Diaphragm Muscle ◽  
Fatigue Properties ◽  
Type I ◽  
Cross Sectional ◽  
Metabolic Properties ◽  
Type Ii Fibers

In adult male hamsters the influence of emphysema (EMP) on the in vitro contractile and fatigue properties and the histochemical, morphometric, and metabolic properties of muscle fibers in the costal diaphragm was determined 6 mo after the administration of either elastase or saline (controls, CTL). Isometric contractile properties were determined in vitro using supramaximal direct muscle stimulation. Optimal fiber length for force generation was significantly shorter in the EMP than in the CTL diaphragm. Maximum specific force (i.e., force per unit area) was 25% lower than CTL. Fatigue resistance was significantly improved in the EMP diaphragm compared with CTL. Diaphragm muscle fibers were classified as type I or II on the basis of histochemical staining for myofibrillar adenosinetriphosphatase after alkaline preincubation. The proportions of type I and II fibers were similar between the two groups. Cross-sectional areas of type II fibers were 30% larger in EMP than in CTL diaphragms. Succinate dehydrogenase activities of both type I and II fibers were higher in EMP than in CTL diaphragms. The number of capillaries surrounding both type I and II fibers increased with EMP, but in proportion to the hypertrophy of these fibers. Thus, capillary density (number of capillaries per fiber cross-sectional area) remained unchanged. We postulate that these contractile, morphometric, and metabolic adaptations reflect an increased activation of the diaphragm in response to the loads imposed by EMP.

Effects of starvation and refeeding on adult male rat diaphragm contractility, fatigue, and fiber types

1993 ◽  
Vol 74 (2) ◽  
pp. 742-749 ◽  
Author(s):  
D. J. Prezant ◽  
D. E. Valentine ◽  
H. H. Kim ◽  
E. I. Gentry
Keyword(s):  
Fatigue Resistance ◽  
Cross Sectional Area ◽  
Male Rats ◽  
Male Rat ◽  
Type I ◽  
Fiber Types ◽  
Type Ii ◽  
Sectional Area ◽  
Cross Sectional ◽  
Type Ii Fibers

The effects of 4.5 days of acute starvation, either alone or followed by refeeding (ad libitum), on diaphragm contractility, fatigue, and fiber types were studied in male rats. Contractility and fatigue resistance indexes were measured in an in vitro costal diaphragm strip preparation with direct stimulation at 37 degrees C. Compared with controls, starvation produced a 28 +/- 1% (P < 0.001) reduction in body weight and an 18 +/- 4% (P < 0.001) reduction in costal diaphragm weight. Twitch and tetanic tensions (normalized for weight or cross-sectional area) were not reduced by starvation. Starvation produced significant increases in fatigue resistance indexes after a 5-Hz stimulation paradigm but not after a 100-Hz paradigm, supporting the hypothesis that fatigue resistance is dependent on the energy demand of a given paradigm. The proportions of type I and type II fibers were similar between diaphragms of starved and control rats, but the cross-sectional area of type II fibers decreased significantly by 18 +/- 7% (P < 0.01). Thus, despite the significant decrease in diaphragm weight after starvation, contractility was preserved and fatigue resistance was increased (low-output paradigm). This is consistent with the decrease in type II fiber area. Refeeding restored all parameters so that there were no longer significant differences in body or diaphragm weight, contractility, fatigue, or fiber types.

Absence of regional differences in the size and oxidative capacity of diaphragm muscle fibers

1987 ◽  
Vol 63 (3) ◽  
pp. 1076-1082 ◽  
Author(s):  
G. C. Sieck ◽  
R. D. Sacks ◽  
C. E. Blanco
Keyword(s):  
Muscle Fibers ◽  
Continuous Distribution ◽  
Oxidative Capacity ◽  
Cross Sectional Area ◽  
Diaphragm Muscle ◽  
Type I ◽  
Fiber Types ◽  
Sectional Area ◽  
Cross Sectional ◽  
Fast Twitch

The oxidative capacity and cross-sectional area of muscle fibers were compared between the costal and crural regions of the cat diaphragm and across the abdominal-thoracic extent of the muscle. Succinate dehydrogenase (SDH) activity of individual fibers was quantified using a microphotometric procedure implemented on an image-processing system. In both costal and crural regions, population distributions of SDH activities were unimodal for both type I and II fibers. The continuous distribution of SDH activities for type II fibers indicated that no clear threshold exists for the subclassification of fibers based on differences in oxidative capacity (e.g., the classification of fast-twitch glycolytic and fast-twitch oxidative glycolytic fiber types). No differences in either SDH activity or cross-sectional area were noted between fiber populations of the costal and crural regions. Differences in SDH activity and cross-sectional area were noted, however, between fiber populations located on the abdominal and thoracic sides of the costal region. Both type I and II fibers on the abdominal side of the costal diaphragm were larger and more oxidative than comparable fibers on the thoracic side.

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