Revised contraindications for the use of non-medical WB-electromyostimulation. Evidence-based German consensus recommendations

Whole-body electromyostimulation has proven to be a highly effective alternative to conventional resistance-type exercise training. However, due to adverse effects in the past, very extensive contraindications have been put in place for the commercial, non-medical WB-EMS market. Considering recent positive innovations e.g., federal regulation, mandatory trainer education, revised guidelines, and new scientific studies on WB-EMS application, we believe that a careful revision of the very restrictive contraindications on WB-EMS is needed. This applies all the more because many cohorts with limited options for conventional exercise have so far been excluded. During a first meeting of an evidence-based consensus process, stakeholders from various backgrounds (e.g., research, education, application) set the priorities for revising the contraindications. We decided to focus on four categories of absolute contraindications: "Arteriosclerosis, arterial circulation disorders", "Diabetes mellitus" (DM), "Tumor and cancer" (TC), "Neurologic diseases, neuronal disorders, epilepsy". Based on scientific studies, quality criteria, safety aspects and benefit/risk assessment of the category, DM and TC were moved to the relative contraindication catalogue, while arteriosclerosis/arterial circulation disorders and neurologic diseases/neuronal disorders/epilepsy were still considered as absolute contraindications. While missing evidence suggests maintaining the status of neurologic diseases/neuronal disorders as an absolute contraindication, the risk/benefit-ratio does not support the application of WB-EMS in people with arteriosclerosis/arterial circulation diseases. Despite these very cautious modifications, countries with less restrictive structures for non-medical WB-EMS should consider our approach critically before implementing the present revisions. Considering further the largely increased amount of WB-EMS trials we advice regular updates of the present contraindication list.

Effects of different exercise intensity on bone mineral density in adults: a comparative systematic review and meta-analysis

PURPOSE

The primary objective of the present systematic review and meta-analysis was to determine the effect of differing exercise intensity on (areal) bone mineral density (BMD) at lumbar spine and hip in adults by a comparative meta-analysis.

METHODS

A systematic review of the literature according to the PRISMA statement included: (a) exercise trials, (b) with ≥two study arms that compared different exercise intensities, (c) intervention ≥6 months, (d) BMD assessments at lumbar spine (LS) or hip. Five electronic databases were scanned without language restrictions up to July 2021. The present analysis of exercise intensity was conducted as a mixed-effect meta-analysis and applied "type of exercise" and "study duration" as moderator in subgroup analyses. Outcome measures were standardized mean differences (SMD) for BMD changes at the LS, and hip.

RESULTS

Eleven exercise studies with 26 study arms were included. Although the effect of high-intensity exercise was more pronounced on LS-BMD (SMD: 0.19, 95%-CI: 0.61 to -0.23) and hip-ROI (0.17, 0.38 to -0.04), we did not observe significant differences between the groups (LS-BMD: p=0.373 and hip-BMD: p=0.109). We observed a substantial level of heterogeneity between the trials for LS- but not for hip-BMD. Applying "type of exercise" and "study duration" as moderators did not significantly modify the differences between low and high exercise intensity on BMD at LS or hip.

CONCLUSION

There is insufficient evidence for a superior effect of high-intensity exercise on areal BMD at lumbar spine and hip in people aged 50 years and older. Varying exercise intensity with periods of lower exercise intensity intermitted by higher intensity might be a promising option to address the issue of exercise intensities in intervention studies.

Effects of dynamic resistance exercise on bone mineral density in postmenopausal women: a systematic review and meta-analysis with special emphasis on exercise parameters

This systematic review and meta-analysis set out to determine the effect of dynamic resistance exercise (DRT) on areal bone mineral density (aBMD) in postmenopausal women and derive evidence-based recommendations for optimized training protocols. A systematic review of the literature according to the PRISMA statement included (a) controlled trials, (b) of isolated DRT with at least one exercise and one control group, (c) with intervention durations ≥ 6 months, (d) aBMD assessments at lumbar spine or proximal femur, (e) in cohorts of postmenopausal women. We searched eight electronic databases up to March 2019 without language restrictions. The meta-analysis was performed using a random-effects model. Standardized mean differences (SMD) for BMD changes at lumbar spine (LS), femoral neck (FN), and total hip (TH) were defined as outcome measures. Moderators of the exercise effects, i.e., "intervention length," "type of DRT," "training frequency," "exercise intensity," and "exercise volume," were addressed by sub-group analyses. The study was registered in the international prospective register of systematic reviews (PROSPERO) under ID: CRD42018095097. Seventeen articles with 20 exercise and 18 control groups were eligible. SMD average is 0.54 (95% CI 0.22-0.87) for LS-BMD, 0.22 (0.07-0.38) for FN-BMD, and 0.48 (0.22-0.75) for TH-BMD changes (all p ≤ 0.015). While sub-group analysis for FN-BMD revealed no differences within categories of moderators, lower training frequency (< 2 sessions/week) resulted in significantly higher BMD changes at LS and TH compared to higher training frequency (≥ 2 sessions/week). Additionally, free weight training was significantly superior to DRT devices for improving TH-BMD. This work provided further evidence for significant, albeit only low-moderate, effects of DRT on LS-, FN-, and TH-BMD. Unfortunately, sub-analysis results did not allow meaningful exercise recommendations to be derived. This systematic review and meta-analysis observed a significant low-moderate effect of dynamic resistance exercise on bone mineral density changes in postmenopausal women. However, sub-group analyses focusing on exercise characteristics found no results that enable the derivation of meaningful exercise recommendations in the area of exercise and osteoporosis prevention or therapy.

A Comparison between 6-point Dixon MRI and MR Spectroscopy to Quantify Muscle Fat in the Thigh of Subjects with Sarcopenia

BACKGROUND

Changes in muscle fat composition as for example observed in sarcopenia, affect physical performance and muscular function, like strength and power.

OBJECTIVES

The purpose of this study was to compare 6-point Dixon magnetic resonance imaging and multi-echo magnetic resonance spectroscopy sequences to quantify muscle fat. Setting, participants and measurements: Two groups were recruited (G1: 23 healthy young men (28 ± 4 years), G2: 56 men with sarcopenia (80 ± 5 years)). Proton density fat fraction was measured with a 6-point product and a 6-point prototype Dixon sequence in the left thigh muscle and with a high-speed multi-echo T2*-corrected H1 magnetic resonance spectroscopy sequence within the semitendinosus muscle of the left thigh. To evaluate the comparability among the different methods, Bland-Altman and linear regression analyses of the proton density fat fraction results were performed.

RESULTS

Mean differences ± 1.96 * standard deviation between spectroscopy and 6pt Dixon sequences were 1.9 ± 3.3% and 1.5 ± 3.6% for the product and prototype sequences, respectively. High correlations were measured between the proton density fat fraction results of the 6-point Dixon sequences and spectroscopy (R = 0.95 for the product sequence and R = 0.97 for the prototype sequence).

CONCLUSIONS

Dixon imaging and spectroscopy sequences show comparable accuracy for fat measurements in the thigh. Spectroscopy is a local measurement, whereas Dixon sequences provide maps of the fat distribution. The high correlations of the 6-point Dixon sequences with spectroscopy support their clinical use. They provide higher spatial resolution than spectroscopy, but are not suitable for a more complicated spectral analysis to separate extra- and intramyocellular lipids.

Longitudinal Changes in Muscle Mass and Function in Older Men at Increased Risk for Sarcopenia - The FrOST-Study

BACKGROUND

Declines in muscle mass and function are inevitable developments of the advanced aging process. Corresponding dimensions of longitudinal changes in at-risk populations are still scarce although clinically relevant. The present study monitored changes in morphologic and functional sarcopenia criteria related to sarcopenia in older men with low muscle mass over a period of 24 months.

OBJECTIVES

The main objective of the present study was to determine whether changes in muscle mass and function were comparable across the body. Our hypothesis was that both (1) fat free mass (FFM) and (2) function decline at a significantly higher rate in the lower versus the upper extremities.

DESIGN

We conducted an observational study of 24 months.

SETTING

Community dwelling men living in the area of Northern Bavaria were initially included in the Franconian Sarcopenic Obesity (FranSO) study by the Institute of Medical Physics University of Erlangen-Nürnberg, Germany.

PARTICIPANTS

One hundred and seventy-seven (177) men (77.5±4.5 years) within the lowest skeletal muscle mass index (SMI) quartile of the FranSO study were included in the present 24 month analysis.

MEASUREMENTS

Fat free mass (direct-segmental, multi-frequency Bio-Impedance-Analysis (DSM-BIA)), handgrip strength (hand-dynamometer) and 10-m habitual gait velocity (photo sensors) were assessed at baseline and 24-month follow-up.

RESULTS

Lower extremity fat free mass (LEFFM: -2.0±2.4%), handgrip strength (-12.8±11.0%) and gait velocity (-3.5±9.0%) declined significantly (p<.001) during the follow-up period, while upper extremity FFM was maintained unchanged (UEFFM: 0.1±3.1%). Changes in LEFFM were significantly higher (p<.001) compared with UEFFM, however contrary to our expectation the decline in handgrip strength representing upper extremity muscle function was 3.7-fold higher (p<.001) than the decline in gait velocity.

CONCLUSION

Medical experts involved in diagnosis, monitoring and management of sarcopenia should consider that parameters constituting morphologic and functional sarcopenia criteria feature different rates of decline during the aging process.

Exercise effects on bone mineral density in older men: a systematic review with special emphasis on study interventions

This systematic review detected only limited positive effects of exercise on bone mineral density in older men. Further, based on the present literature, we were unable to suggest dedicated exercise prescriptions for this male cohort that might differ from recommendations based on studies with postmenopausal women. The primary aim of this systematic review was to determine the effect of exercise on bone mineral density (BMD) in healthy older men. A systematic review of the literature according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement included only randomized or non-randomized controlled trials of exercise training ≥ 6 months with study groups of ≥ eight healthy men aged 50 years or older, not using bone-relevant pharmacological therapy, that determined BMD by dual-energy X-ray absorptiometry. We searched PubMed, Scopus, Web of Science, Cochrane, Science Direct, and Eric up to November 2016. Risk of bias was assessed using the PEDro scale. We identified eight trials with 789 participants (PEDro-score, mean value 6 of 10) which satisfied our eligibility criteria. Studies vary considerably with respect to type and composition of exercise. Study interventions of six trials were considered to be appropriate for successfully addressing BMD in this cohort. Between-group differences were not or not consistently reported by three studies. Three studies reported significant exercise effects on BMD for proximal femur; one of them determined significant differences between the exercise groups. None of the exercise trials determined significant BMD effects at the lumbar spine. Based on the present studies, there is only limited evidence for a favorable effect of exercise on BMD in men. More well-designed and sophisticated studies on BMD in healthy older men have to address this topic. Further, there is a need to define intervention quality standards and implement a universal scoring system that allows this pivotal determinant to be addressed much more intensively.

Körperliches Training, Fraktur und Knochendichte

Ziel der Untersuchung war es, den Einfluss eines langjährigen körperlichen Trainings auf die Inzidenz klinischer Fraktu-ren zu erfassen.

137 frühpostmenopausale Frauen mit Osteopenie wurden 1998 in die EFOPS-Studie eingeschlossen. 86 Personen wählten den durchgängig überwachten Trainingsarm der Studie (TG), 51 traten der Kontrollgruppe (KG) bei. Primärer Endpunkt waren Frakturrate und -risiko von nied-rigtraumatischen klinischen Frakturen, se-kundärer Endpunkt die Knochendichte.

105 Teilnehmer mit ca. 1650 Teilnehmerjahren wurden in die 16-Jahres-Messung eingeschlossen. Frakturrisiko (Relatives Risiko: 0,51; 95%-Konfidenzintervall: 0,23–0,97) und -rate (0,42; 0,20–0,86) lagen in der Trainingsgruppe signifikant niedriger als in der Kontrollgruppe. In beiden Gruppen sank die Knochendichte an Lendenwirbelsäu-le (TG: –1,5 ± 5,0 % vs. KG: 5,8 ± 6,4 %) und Schenkelhals (TG: –6,5 ± 4,6 % vs. KG: 9,6 ± 5,0 %) signifikant ab, die Reduktion der KG lag jedoch für beide Regionen signifikant (p ≤ 0,001) höher.

Die vorliegende Untersuchung bestätigt mit ausreichender statistischer Power den frakturpräventiven Effekt eines langjährigen körperlichen Trainings bei motivierten, post-menopausalen Frauen mit einem bewusst sportlich aktiven Lebensstil.

Prevalence of sarcopenia and sarcopenic obesity in older German men using recognized definitions: high accordance but low overlap!

The relevance of sarcopenia and sarcopenic Obesity (SO) is rising in our aging societies. Applying recognized definitions to 965 community-dwelling Bavarian men 70 years+ resulted in a prevalence for sarcopenia between 3.7 and 4.9 and between 2.1 and 4.1% for SO. Despite this high consistency, the overlap between the definitions/approaches was <50%.

INTRODUCTION

The relevance of sarcopenia and sarcopenic obesity (SO) is rising steadily in the aging societies of most developed nations. However, different definitions, components, and cutoff points hinder the evaluation of the prevalence of sarcopenia and SO. The purpose of this contribution was to determine the prevalence of sarcopenia and SO in a cohort of community-dwelling German men 70+ applying established sarcopenia (European Working Group on Sarcopenia in Older People, Foundation National Institute of Health, International Working Group on Sarcopenia) and obesity definitions. Further, we addressed the overlap between the definitions.

METHODS

Altogether, 965 community-dwelling men 70 years and older living in Northern Bavaria, Germany, were assessed during the screening phase of the Franconian Sarcopenic Obesity project. Segmental multi-frequency bio-impedance analysis (BIA) was applied to determine weight and body composition.

RESULTS

Applying the definitions of EWGSOP, IWGS, and FNIH, 4.9, 3.8, and 3.7% of the total cohort were classified as sarcopenic, respectively. When further applying body fat to diagnose obesity, SO prevalence in the total cohort ranged from 4.1% (EWGSOP + body fat >25%) to 2.1% (IWGS + body fat >30%). Despite the apparently high consistency of the approaches with respect to prevalence, the overlap in individual sarcopenia diagnosis between the sarcopenia definitions was rather low (<50%).

CONCLUSION

The prevalence of sarcopenia and SO in community-dwelling German men 70 years+ is relatively low (<5%) independently of the definition used. However, consistency of individual sarcopenia diagnosis varies considerably between the three definitions. Since sarcopenia is now recognized as an independent condition by the International Classification of Diseases, a mandatory definition must be stated.

TRIAL REGISTRATION NUMBER

ClinicalTrials.gov: NCT2857660.

Whole-body electromyostimulation to fight sarcopenic obesity in community-dwelling older women at risk. Resultsof the randomized controlled FORMOsA-sarcopenic obesity study

The effect of whole body-electromyostimulation in community-dwelling women ≥70 with sarcopenic obesity was heterogeneous, with high effects on muscle mass, moderate effects on functional parameters, and minor effects on fat mass. Further, we failed to determine a supportive effect of additional protein-enriched dietary supplementation in this albeit predominately well-nourished group.

INTRODUCTION

The aim of the study was to determine the effect of whole-body electromyostimulation (WB-EMS) on sarcopenic obesity (SO) in community-dwelling women more than 70 years with sarcopenic obesity.

METHODS

Seventy-five community-dwelling women ≥70 years with SO were randomly allocated to either a WB-EMS-application with (WB-EMS &P; 24.9 ± 1.9 kg/m²) or without (WB-EMS; 25.2 ± 1.8 kg/m²) dietary supplementation (150 kcal/day, 56 % protein) or a non-training control group (CG; 24.7 ± 1.4 kg/m²). WB-EMS consisted of one weekly session of 20 min (85 Hz, 350 μs, 4 s of strain-4 s of rest) performed with moderate to high intensity. Primary study endpoint was the Sarcopenia Z-Score constituted by skeletal muscle mass index (SMI, as assessed by dual energy X-ray absorptiometry), grip strength, and gait speed, and secondary study endpoint was body fat (%).

RESULTS

Sarcopenia Z-score comparably increases in the WB-EMS and the WB-EMS&P-group (p ≤ .046). Both groups differ significantly (p ≤ .001) from the CG which deteriorated significantly (p = .006). Although body fat changes were most pronounced in the WB-EMS (-0.9 ± 2.1; p = .125) and WB-EMS&P (-1.4 ± 2.5; p = .028), reductions did not statistically differ (p = .746) from the CG (-0.8 ± 2.7; p = .179). Looking behind the covariates, the most prominent changes were determined for SMI, with a significant increase in both EMS-groups (2.0-2.5 %; p ≤ .003) and a decrease in the CG (-1.2 ± 3.1 %; p = .050) with significant between-group differences (p = .001).

CONCLUSION

WB-EMS is a safe and attractive method for increasing muscle mass and functional capacity in this cohort of women 70+ with SO; however, the effect on body fat is minor. Protein-enriched supplements did not increase effects of WB-EMS alone.

Prevalence of sarcopenic obesity in Germany using established definitions: Baseline data of the FORMOsA study

The prevalence of sarcopenic obesity in community-dwelling women 70 years and older according to established sarcopenia and obesity definitions averaged between 0 and 2.3 % and can thus be considered as relatively low. However, the converse argument that sarcopenic obesity was incompatible with an independent life cannot be confirmed.

INTRODUCTION

The primary aim of the study was to determine the prevalence of sarcopenic obesity (SO) in community-dwelling (CD) older females in Germany. The secondary aim was to assess whether these females really live independently and autonomously.

METHODS

A total of 1325 CD females 70 years and older living in the area of Erlangen-Nürnberg, Germany were assessed. Sarcopenia as defined by (a) the European Working Group on Sarcopenia in older people (EWGSOP) and (b) the International working group on Sarcopenia (IWGS) combined with obesity defined as (a) BMI ≥ 30 kg/m(2) (NIH) or (b) body-fat ≥ 35 % (WHO) was determined. In participants with SO, Barthel Index, care level and social network were retrospectively evaluated via personal interview.

RESULTS

Based on anthropometric data, family, education and social status, lifestyle, number and distribution of diseases and medication, the present cohort is representative for the corresponding German population. Sarcopenia prevalence was 4.5 % according to EWGSOP and 3.3 % according to the IWGS criteria. Obesity prevalence in our cohort averaged 19.8 % (BMI, NIH) and 63.8 % (body fat, WHO). The overlap between both factors (i.e. SO) ranged from 0 % (EWGSOP + NIH criteria) to 2.3 % (EWGSOP + WHO criteria). Factors that may represent limited autonomy or independence were very rarely identified in this SO cohort.

CONCLUSION

The prevalence of sarcopenic obesity in the CD (female) German population 70 years + is relatively low. With respect to our second research aim, the hypothesis that SO was incompatible with independent life was rejected. However, the latter finding should be addressed with more dedicated study designs.

Exercise and fractures in postmenopausal women. Final results of the controlled Erlangen Fitness and Osteoporosis Prevention Study (EFOPS)

The EFOPS trial clearly established the positive effect of long-term exercise on clinical low-trauma fractures in postmenopausal women at risk. Bearing in mind that the complex anti-fracture exercise protocols also affect a large variety of diseases of increased age, we strongly encourage older adults to perform multipurpose exercise programs.

INTRODUCTION

Physical exercise may be an efficient option for autonomous fracture prevention during increasing age. The aim of the study was to evaluate the effect of exercise on clinical overall fracture incidence and bone mineral density (BMD) in elderly subjects at risk.

METHODS

In 1998 initially, 137 early-postmenopausal, osteopenic women living in Erlangen-Nuremberg, Germany, were included in the EFOPS trial. Subjects of the exercise group (EG; n = 86) conducted two supervised group and two home exercise sessions/week while the control group (CG; n = 51) was requested to maintain their physical activity. Primary study endpoints were clinical overall low-trauma fractures determined by questionnaires, structured interviews, and BMD at the lumbar spine and femoral neck assessed by dual-energy X-ray absorptiometry.

RESULTS

In 2014, 105 subjects (EG: n = 59 vs. CG: n = 46) representing 1680 participant-years were included in the 16-year follow-up analysis. Risk ratio in the EG for overall low-trauma fractures was 0.51 (95% confidence interval (95% CI) 0.23 to 0.97, p = .046), rate ratio was 0.42 (95% CI 0.20 to 0.86, p = .018). Based on comparable baseline values, lumbar spine (MV -1.5%, 95% CI -0.1 to -2.8 vs. -5.8%, -3.3 to -7.2%) and femoral neck (-6.5%, -5.2 to -7.7 vs. -9.6%, -8.2 to 11.1%) BMD decreased in both groups; however, the reduction was more pronounced in the CG (p ≤ .001).

CONCLUSION

This study clearly evidenced the high anti-fracture efficiency of multipurpose exercise programs. Considering furthermore the favorable effect of exercise on most other risk factors of increasing age, we strongly encourage older adults to perform multipurpose exercise programs.

Peak-bone-mass development in young adults: effects of study program related levels of occupational and leisure time physical activity and exercise. A prospective 5-year study

SUMMARY

Young adulthood is characterized by profound life-style changes. This study suggests that reduction of sport or exercise, induced by alteration of the occupational situation, negatively impacts generation/maintenance of peak bone mass. In order to compensate occupational-related reductions of physical activity, workplace exercise programs will be helpful.

INTRODUCTION

Only few studies have determined the effect of physical activity or physical exercise on bone mineral density (BMD) in the period of late skeletal maturation, i.e. around peak bone mass. The aim of this article was to determine the long-term effect of different levels of physical activity and exercise directly and indirectly derived by occupation during young adulthood.

METHODS

Sixty-one male and female dental students (DES) and 53 male and female sport students (SPS) 21±2 years old were accompanied over the course (4.8±0.5 years) of their study program. BMD at the lumbar spine (LS), hip, and whole body (WB) were determined using dual-energy X-ray absorptiometry.

RESULTS

Parameters of physical activity increased non-significantly in both groups with no relevant differences between the groups. Indices of exercise, however, increased significantly in the SPS group while a significant decrease was assessed for the DES group. Independent of gender, BMD of the SPS increased significantly (p≤0.007) at all skeletal sites (LS, 2.4±3.9%; hip, 1.6±3.5%; WB, 1.8±2.8%) while BMD of the DES remained unchanged at LS (-0.6±4.4%, p=0.432) and WB (0.5±1.9%, p=0.092) but decreased significantly at the hip (-1.9±4.3%, p=0.010). BMD-changes at LS, hip, and WB differ significantly between SPS and DES (p≤0.017). Results remained unchanged after adjusting for baseline BMD-values that differed (p=0.030 to p=0.082) in favor of the SPS group.

CONCLUSION

Changes of exercise levels directly or indirectly caused by occupational factors during young adulthood significantly affected generation and/or maintenance of peak bone mass. Compensatory exercise is thus highly relevant for bone health of young adults.

Effects of exercise on fracture reduction in older adults: a systematic review and meta-analysis

In this meta-analysis, we evaluated the effect of exercise on fracture reduction in the elderly. Our results determined a significantly positive effect on overall fractures, whereas the possibility of a publication bias indicates the need for well-designed (multi-center) trials that generate enough power to focus on osteoporotic fractures.

INTRODUCTION

The preventive effect of exercise on fracture incidence has not been clearly determined yet. Thus, the purpose of this study is to evaluate the effectiveness of exercise in preventing overall and vertebral fractures in older adults by meta-analyses technique.

METHODS

This study followed the PRISMA recommendations for systematic reviews and meta-analyses. A systematic review of English articles between 1980 and March 2012 was performed. Terms used were: "exercise", "fractures", "bone", "falls", "osteoporosis", "BMD", "BMC", "bone turnover", while the search was limited to "clinical trial" and "humans". Controlled exercise trials that reported fracture number as endpoint or observation in subjects 45 years and older were included.

RESULTS

Ten controlled exercise trials that reported overall fractures and three exercise trials that reported vertebral fractures met our inclusion criteria. Overall fracture number in the exercise group was 36 (n = 754) compared with 73 fractures in the CG (n = 670) (relative risk [RR] = 0.49; 95 % confidence interval [CI], 0.31-0.76). No significant heterogeneity of trial results (p = 0.28; I (2) = 17) was determined; however, there was some evidence to suggest a publication bias. The overall RR for vertebral fracture number (0.56; 95 % CI, 0.30-1.04) (EG: 19 fractures/103 subjects vs. CG: 31 fractures/102 subjects) was borderline non-significant while the heterogeneity of trial results also cannot be ruled out.

CONCLUSION

Although there is evidence that exercise reduces overall and, to a lesser degree, vertebral fractures in the elderly, the possibility of publication bias weakens our result and demonstrates the imperative for large exercise studies with dedicated exercise protocols that focus on fractures as a primary endpoint.

Exercise and fractures in postmenopausal women: 12-year results of the Erlangen Fitness and Osteoporosis Prevention Study (EFOPS)

This trial is the first exercise study that focuses on fracture incidence as a primary study endpoint. Although we marginally failed to determine significant effects on "overall" fracture risk (p = .074) or rate ratio (p = .095), our findings further increased the evidence that exercise relevantly prevents fractures in the elderly.

INTRODUCTION

The purpose of this study is to determine the effect of strictly supervised long-term exercise training on "overall" fracture incidence and bone mineral density (BMD) in postmenopausal osteopenic women.

METHODS

Eighty-five early postmenopausal (1-8 years), osteopenic women living in the area of Erlangen-Nuremberg, Germany without any medication or diseases affecting bone metabolism were assessed after 12 years of supervised exercise (EG) or unvarying lifestyle (control, CG). Exercisers were encouraged to perform two group sessions/week and two home training sessions/week. Calcium and vitamin D supplementation was provided for both groups. "Overall" fractures were determined by questionnaires and structured interviews. The BMD was assessed at lumbar spine and proximal femur by dual-energy X-ray absorptiometry.

RESULTS

"Overall" fracture risk ratio in the EG was 0.32 (95% confidence interval (CI), 0.08 to 1.05; p = .074), and the rate ratio for "overall" fractures was 0.38 (95% CI, 0.11 to 1.15; p = .095). BMD changes at lumbar spine (EG, -0.8%; 95% CI, 0.8% to -2.7% vs. CG, -4.0%; 95% CI, -2.4% to -5.7%; p = .011) and femoral neck (EG, -3.7%; 95% CI, -2.4% to -5.0% vs. CG, -6.7%; 95% CI, -5.3% to -8.2%; p = .003) significantly differed between both groups.

CONCLUSION

Although we marginally failed to determine significant effects on overall fracture risk or rate ratio, our study increased the body of evidence for the fracture prevention efficiency of exercise programs, with special regard on bone strength (as assessed by bone mineral density measurement). Future studies should focus on subjects more prone to fractures to generate enough statistical power to clearly determine this issue.

[Effects of two different types of whole body vibration on neuromuscular performance and body composition in postmenopausal women]

PURPOSE

The effects of different types of whole body vibration (WBV) training on neuromuscular performance and body composition were determined in postmenopausal women.

METHODS

In the Erlangen Longitudinal Vibration Study II (ELVIS-II-Study) 108 postmenopausal women between 60 and 75 years of age (average 65.8 ± 3.5 years) were randomly assigned to one of three groups: two WBV training-groups (n = 36 each), each performing an identical program thrice a week for 15 min on two different types of vibration plates for one year: 1. vertical vibrating, 35 Hz, 1.7 mm (VG); 2. rotational vibrating 12.5 Hz, 12 mm (RG). A control group (n = 36) conducted a low intensity gymnastic and relaxation program. Muscular strength and power were assessed, body composition was determined by Dual-energy X-ray absorptiometry (DXA), and pain intensity was assessed by a questionnaire.

RESULTS

Maximum leg strength (VG: 24.4 %; RG: 26.6 %; KG: 6.2 %; p < 0.001) and maximum trunk flexion strength (VG: 12.2 %; RG: 11.5 %; KG: -5.5 %; p = 0.01) significantly increased in both vibration groups. No changes were found for body composition parameters (lean body mass, appendicular muscle mass, fat mass). Pain intensity in the big joints (p < 0.05) decreased in both vibration groups, in the lumbar spine region this was not significant. There was no difference between vibration types. No vibration-related side effects were observed.

CONCLUSION

The study results suggest that WBV might be an alternative to classic training contents to increase maximum strength and reduce pain.

Effect of block-periodized exercise training on bone and coronary heart disease risk factors in early post-menopausal women: a randomized controlled study

The purpose of this 12 month randomized exercise intervention was to determine the effect of a block-periodized multipurpose exercise program on bone mineral density (BMD) and parameters of the metabolic syndrome (MetS) in early post-menopausal women. Eighty-five subjects (52.3 ± 2.4 years) living in the area of Erlangen (Germany) were randomly assigned into an exercise (EG, n=43) or a wellness-control group (CG: n=42). The EG performed a periodized multipurpose exercise program with 4-6-week blocks of high-intensity bone-specific exercise intermitted by 10-12 weeks of exercise dedicated to increase endurance and reduce cardiac and metabolic risk factors. The CG performed a low-volume/low-intensity "wellness" program to increase well-being. After 12 months, significant exercise effects were observed for the lumbar spine (LS) BMD as assessed by quantitative computed tomography [total BMD (EG: -0.3 ± 2.1% vs CG: -2.1 ± 2.2%, P=0.015); trabecular BMD (EG: -0.7 ± 3.4% vs CG: -4.7 ± 4.9%, P=0.001) and dual-energy x-ray absorptiometry (DXA) (EG: -0.1 ± 2.2% vs CG: -2.0 ± 2.0%, P=0.002)]. However, no significant effects were observed for total hip BMD as assessed by DXA (P=0.152). Although all MetS parameters were favorably affected among the EG, only the effect for waist circumference was significant. In summary, short periods of bone-specific intervention embedded in longer periods of exercises dedicated to improve cardiovascular and metabolic risk factors positively affected BMD at the LS.

Effects of whole body vibration on bone mineral density and falls: results of the randomized controlled ELVIS study with postmenopausal women

We determined whether the effect of exercise on bone mineral density (BMD) and falls can be enhanced by whole body vibration (WBV). In summary, the multi-purpose exercise training was effective to increase lumbar BMD but added WBV did not enhance this effect. However, falls were lowest in the exercise program combined with WBV.

INTRODUCTION

WBV is a new approach to reduce the risk of osteoporotic fractures. In the "Erlangen Longitudinal Vibration Study" (ELVIS), we investigated whether WBV enhances the effect of multifunctional exercise on BMD and falls.

METHODS

One hundred fifty-one postmenopausal women (68.5 ± 3.1 years) were randomly assigned to a: (1) conventional training group (TG); (2) conventional training group including vibration (TGV); and (3) wellness control group (CG). TG conducted an exercise program consisting of 20 min dancing aerobics, 5 min balance training, 20 min functional gymnastics, and 15 min dynamic leg-strength training on vibration plates (without vibration) twice a week. TGV performed an identical exercise regimen with vibration (25-35 Hz) during the leg-strengthening sequence. CG performed a low-intensity wellness program. BMD was measured at the hip and lumbar spine at baseline and follow-up using the DXA method. Falls were recorded daily via the calendar method.

RESULTS

After 18 months, an increase in BMD at the lumbar spine was observed in both training groups (TGV: +1.5% vs. TG: +2.1%). The difference between the TG and the CG (1.7%) was significant. At the hip no changes were determined in either group. The fall frequency was significantly lower in TGV (0.7 falls/person) compared with CG (1.5), whereas the difference between TG (0.96) and CG was not significant.

CONCLUSIONS

A multifunctional training program had a positive impact on lumbar BMD. The application of vibration did not enhance these effects. However, only the training including WBV affected the number of falls significantly.

Effect of whole-body vibration on neuromuscular performance and body composition for females 65 years and older: a randomized-controlled trial

We examined whether the effect of multipurpose exercise can be enhanced by whole-body vibration (WBV). One hundred and fifty-one post-menopausal women (68.5 ± 3.1 years) were randomly assigned to three groups: (1) a training group (TG); (2) training including vibration (VTG); and (3) a wellness control group (CG). TG and VTG performed the same training program twice weekly (60 min), consisting of aerobic and strength exercises, with the only difference that leg strength exercises (15 min) were performed with (VTG) or without (TG) vibration. CG performed a low-intensity "wellness" program. At baseline and after 18 months, body composition was determined using dual-X-ray-absorptiometry. Maximum isometric strength was determined for the legs and the trunk region. Leg power was measured by countermovement jumps using a force-measuring plate. In the TG lean body mass, total body fat, and abdominal fat were favorably affected, but no additive effects were generated by the vibration stimulus. However, concerning muscle strength and power, there was a tendency in favor of the VTG. Only vibration training resulted in a significant increase of leg and trunk flexion strength compared with CG. In summary, WBV embedded in a multipurpose exercise program showed minor additive effects on body composition and neuromuscular performance.

[Effect of whole body vibration on the neuromuscular performance of females 65 years and older. One-year results of the controlled randomized ELVIS study]

Sarcopenia is linked to an increased risk of morbidity and mortality in the aging. Whole body vibration (WBV) exercises are currently discussed as a "gentle" alternative to conventional exercises to improve muscle mass. The present study scrutinized whether a multipurpose (exercise) training program using WBV can improve muscle mass and neuromuscular capacity, while lowering fall risk. A total of 151 postmenopausal women were randomized into three groups: exercise group (TG), exercise group with vibration (VTG), and fitness control group (CG). The TG group participated in an exercise program including leg strengthening training twice a week over 12 months, while the VTG carried out an identical program with the leg exercises performed under WBV. Despite a positive trend regarding lean body mass in the two exercise groups, there was no difference between groups. Both exercise groups showed a significant increase (vs. KG) in trunk strength. An improvement in both exercise groups was also measured with respect to leg strength, but only the VTG showed significant differences compared to the CG. In addition, a significant lower risk of falls compared with the CG was evident only in VTG.

[Effect of whole body vibration exercise on osteoporotic risk factors]

BACKGROUND AND OBJECTIVE

Whole body vibration (WBV) training is a new approach which is currently discussed in the context of reducing the risk of osteoporotic fractures. The study was undertaken to determine the effect of one-year WBV exercise on bone mineral density (BMD) and the number of falls.

METHODS

151 postmenopausal women (68.5 +/- 3.1 years) were randomly assigned to three groups: (1) conventional (multifunctional) training (TG); (2) multifunctional training including WBV (VTG); (3) wellness-control group (CG). The training groups performed multifunctional training twice weekly (60 min; dancing aerobics, balance training, functional strength training). In the last 15 min of each session, leg strength exercises on vibration platforms were performed. The plates were switched on only in the VTG. The CG performed a low intensity gymnastic and relaxation programme (4 x 10 sessions of 60 min). BMD was measured at the hip and lumbar spine at baseline and after 12 months with the DXA method. Falls were recorded daily with the calendar method in a fall log.

RESULTS

An increase in BMD at the lumbar spine was measured after one year in both training groups (VTG: + 1.17 +/- 2.4 % vs. TG: + 1.73 +/- 2.4 %). The difference between the TG and the CG was significant (p < .05). Regarding the hip region a loss was noted in the CG (- 0.9 +/- 2.5), whereas the BMD stayed stable in the training groups (TG: - 0.3 %; VTG: + 0.1 %). The fall rate was significantly lower in VTG compared to CG (0.43 falls/person/year (VTG) vs. 1.14 (CG).

CONCLUSION

The multifunctional training resulted in a gain of BMD at the lumbar spine. Vibration training did not enhance the effect on bone but significantly reduced falls.

Plasma copper and bone mineral density in osteopenia: an indicator of bone mineral density in osteopenic females

Copper concentrations in blood plasma have been determined in 25 osteopenic females using inductively coupled plasma-mass spectrometry. A high degree of correlations has been demonstrated between the copper concentrations in plasma and the bone mineral density of the lumbar spine as measured using dual energy X-ray absorptiometry and quantitative computerized tomography. Results clearly indicate the involvement of copper in bone health and osteopenia. It is further suggested that plasma copper might be useful as a cheap and simple method indicative of bone mineral density in osteopenic postmenopausal females.

In healthy elderly postmenopausal women variations in BMD and BMC at various skeletal sites are associated with differences in weight and lean body mass rather than by variations in habitual physical activity, strength or VO2max

The objective of this study was an integrated cross-sectional investigation for answering the question whether differences in bone mineral density in elderly postmenopausal women are associated with differences in habitual physical activity and unspecific exercise levels. Two hundred and ninety nine elderly women (69-/+3 years), without diseases or medication affecting bone metabolism were investigated. The influence of weight, body composition and physical activity on BMD was measured at multiple sites using different techniques (DXA, QCT, and QUS). Physical activity and exercise level were assessed by questionnaire, maximum strength of the legs and aerobic capacity. Variations in physical activity or habitual exercise had no effect on bone. The only significant univariate relation between strength/VO(2)max and BMD/BMC that remained after adjusting for confounding variables was between arm BMD (DXA) and hand-grip strength. The most important variable for explaining BMD was weight and for cortical BMC of the femur (QCT) lean body mass. Weight and lean body mass emerge as predominant predictors of BMD in normal elderly women, whereas the isolated effect of habitual physical activity, unspecific exercise participation, and muscle strength on bone parameters is negligible. Thus, an increase in the amount of habitual physical activity will probably have no beneficial impact on bone.

Effect of exercise, body composition, and nutritional intake on bone parameters in male elite rock climbers

A low body mass index is considered essential for high performance in rock climbing; however its effect on bone may be negative. In this study we compared the BMD of competitive male rock climbers (n = 20) and age- and BMI-matched non-training controls (n = 11). Subjects with any medication or illness affecting bone metabolism or a family history of osteoporosis were not included in the analysis. Total body BMD was measured by dual-energy X-ray absorptiometry. Quantitative computed tomographic scans were made from the femoral neck and the lumbar spine. Dietary intake was assessed by a 5-day protocol. BMD of the TB-scan was significantly higher in the climbers group for all sub-regions except the skull (p = 0.191) and the lower extremities (p = 0.079). Trabecular and cortical BMD of the LS were significantly higher (p = 0.036 and p = 0.004) in the climbers. The same was true for total (p = 0.005) and cortical (p = 0.002) BMD of the FN. Trabecular BMD (p = 0.054), CSA (p < 0.343) and cortical thickness (p = 0.065) of the FN was non-significantly higher for the climbers. Our study indicates that the effect of climbing on bone parameters PER SE is not detrimental in elite male athletes. Contrarily climbers demonstrated significantly higher BMD values at all loaded regions without "steal effects" at skeletal sites with low mechanical impact. Although we determined a moderately negative effect of low BMI on BMD we could not decide whether a low BMI value should be used as an exclusion criterion in high level climbing competitions as practized by the Austrian Sportclimbing Organization.

Exercise maintains bone density at spine and hip EFOPS: a 3-year longitudinal study in early postmenopausal women

It is an important aim in the prevention of osteoporosis to stop or decelerate bone loss during the early postmenopausal years. Here we report on results of the 3-year EFOPS exercise trial in osteopenic women. The exercise strategy emphasized low-volume high-resistance strength training and high-impact aerobics. Forty-eight fully compliant women (55.1+/-3.3 years) with no medication or illness affecting bone metabolism participated in the exercise group (EG); 30 women (55.5+/-3.0 years) served as non-training controls (CG). At baseline there were no significant between-group differences with respect to physical fitness, bone mineral density, pain and nutritional status. The training consisted of two group training and two home training sessions per week. The study participants of both groups were individually supplemented with calcium and vitamin D (cholecalciferol). Bone mineral density (BMD) was measured by DXA at the lumbar spine, proximal femur and distal forearm and by QCT at the lumbar spine. Speed of sound and broadband ultrasound attenuation were determined at the calcaneus by quantitative ultrasound (QUS). Pain frequency and intensity at different skeletal sites were assessed via questionnaire. After 38 months, the following within-group changes were measured: DXA lumbar spine, EG: 0.8% n.s.; CG: -3.3% P<0.001; QCT trabecular ROI, EG: 1.1% n.s; CG: -7.7% P<0.001; QCT cortical ROI, EG: 5.3% P<0.001; CG: -2.6% P<0.001; DXA total hip: EG: -0.2% n.s; CG -1.9%, P<0.001; DXA distal forearm, EG: -2.8% P<0.001; CG: -3.8% P<0.001; BUA, EG: -0.3% n.s; CG -5.4% P<0.001; SOS, EG: 0.3% n.s; CG -1.0% P<0.001. At year 3 between-group differences relative to the exercise group were: DXA lumbar spine: 4.1% P<0.001; QCT trabecular ROI: 8.8% P<0.001; QCT cortical ROI: 7.9% P<0.001; DXA total hip: 2.1%, P<0.001; DXA distal forearm: 1.0% n.s.; BUA: 5.8% P<0.05; SOS: 1.3% P<0.001. Pain frequency and intensity in the spine significantly decreased in the exercise group and increased in the control group, while no between-group differences were detected in the main joints. In summary, over a period of 3 years our low-volume/high-intensity exercise program was successful to maintain bone mineral density at the spine, hip and calcaneus, but not at the forearm.

Power training is more effective than strength training for maintaining bone mineral density in postmenopausal women

Physical exercise has a favorable impact on bones, but optimum training strategies are still under discussion. In this study, we compared the effect of slow and fast resistance exercises on various osteodensitometric parameters. Fifty-three postmenopausal women were randomly assigned to a strength training (ST) or a power training group (PT). Both groups carried out a progressive resistance training, a gymnastics session, and a home training over a period of 12 mo. During the resistance training, the ST group used slow and the PT group fast movements; otherwise there were no training differences. All subjects were supplemented with Ca and vitamin D. At baseline and after 12 mo, bone mineral density (BMD) was measured at the lumbar spine, proximal femur, and distal forearm by dual-energy X-ray absorptiometry. We also measured anthropometric data and maximum static strength. Frequency and grade of pain were assessed by questionnaire. After 12 mo, significant between-group differences were observed for BMD at the lumbar spine (P < 0.05) and the total hip (P < 0.05). Whereas the PT group maintained BMD at the spine (+0.7 +/- 2.1%, not significant) and the total hip (0.0 +/- 1.7%, not significant), the ST group lost significantly at both sites (spine: -0.9 +/- 1.9%; P < 0.05; total hip: -1.2 +/- 1.5%; P < 0.01). No significant between-group differences were observed for anthropometric data, maximum strength, BMD of the forearm, or frequency and grade of pain. These findings suggest that power training is more effective than strength training in reducing bone loss in postmenopausal women.

The effect of habitual physical activity, non-athletic exercise, muscle strength, and VO2max on bone mineral density is rather low in early postmenopausal osteopenic women

CONTEXT

Although the positive effect of well-designed exercise regimes on bone mineral density (BMD) is established the osteo-anabolic relevance of habitual physical activity and non-athletic exercise is still under discussion.

OBJECTIVE

To determine the effects of habitual physical activity, non-athletic exercise muscle strength, VO2max and anthropometric parameters on BMD in early post-menopausal women.

DESIGN

Cross-sectional study.

METHODS

150 early postmenopausal women (55.5+/-3.4 years), which were free of diseases or medication affecting bone metabolism and had no athletic history were investigated. The influence of weight, body composition, physical activity, isometric strength, VO2max, and nutritional intake on BMD was measured at multiple sites using different techniques. Further bone markers (Osteocalcin, CTX) were determined. Activity and weight-bearing activity were assessed by questionnaire. Maximum strength was measured isometrically. Aerobic capacity was measured with an spirometric system in a stepwise treadmill test and dietary intake was monitored over 5 days.

RESULTS

Slight relationships between physical activity, exercise, muscle strength and VO2max with bone parameters were determined by univariate analysis. After adjusting for confounding variables in a stepwise regression analysis, significant relationships with BMD measured at the hip or the spine could no longer be detected for physical activity, exercise, and physical fitness (strength indices, VO2max). The same was true for osteocalcin and CTX. Arm strength explained 4.5% of the variation of forearm BMD (DXA). At the calcaneal site, osteogenic exercise was significantly related to the quantitative ultrasound index (r2 = 0.27).

CONCLUSION

The isolated effect of habitual physical activity, unspecific exercise participation, and muscle strength on bone parameters is rather low in (early-) postmenopausal women.

CLINICAL RELEVANCE

Women at risk should take specific exercise programs into consideration rather than to increasing the amount of habitual physical activity.

Acute hormonal responses of a high impact physical exercise session in early postmenopausal women

The effect of a single bout of exercise on hormones affecting bone metabolism was studied in 25 early postmenopausal women with osteopenia. The complex training session was performed between 8:00 a.m. and 9:05 a.m. Serum concentrations of dehydroepiandrosterone-sulfate (DHEA-S), total testosterone, free testosterone, 17beta-estradiol, cortisol, human growth hormone (hGH), insulin-like growth factor-I (IGF-I), and insulin-like growth factor binding protein-3 (IGFBP-3) were determined. Blood samples were obtained immediately before (baseline) and after exercise, as well as 2 h and 22 h post-exercise. DHEA-S increased by 10% immediately after exercise and remained increased 2 h later. Testosterone showed no increase immediately after exercise but fell by 21% 2 h post-exercise. Free testosterone was increased by almost 20% immediately after exercise and returned to baseline levels after 2 h. Two hours post-exercise a 20% increase in the estradiol level was measured. Cortisol decreased by 36% during exercise and a further 14% during the next 2 h, a loss higher than the normal diurnal decrease. hGH increased by 80% during exercise and fell 30% under baseline values after 2 h. Even though the assessment period was prolonged to 22 h no significant change could be demonstrated for IGF-I. Serum IGFBP-3 showed a biphasic increase. During the exercise session IGFBP-3 increased by 35%, returned to baseline values 2 h post-exercise and increased again by 40% 22 h post-exercise. In summary, this study showed that a single bout of exercise typically used in osteoporosis prevention programs could have an influence on hormones affecting bone metabolism.

Clinical utility of nonenzymatically glycosylated blood proteins as an index of glucose control

This study compares the utility of nonenzymatically glycosylated serum proteins (lys-GSP) to glycosylated hemoglobins (HbA1a-c) as control indices of glucose homeostasis in patients with IDDM. The diagnostic value of lys-GSP was also examined in patients with non-insulin-dependent diabetes mellitus, in subjects with impaired glucose tolerance, and in two patients with insulinoma. The intraindividual fluctuation of lys-GSP in normoglycemic subjects is very small, resulting in an interindividual range of 3.0 +/- 0.3 lysine-bound glucose/mg protein (means +/- SD, N = 52). HbA1a-c with a normal range of 6.4 +/- 0.9% (N = 52) shows greater variability. In IDDM there is no overlap of lys-GSP levels between the normal and the diabetic range at the 95% confidence level. In patients treated with an open-loop insulin delivery system failure of normalization of the glucose balance was clearly discernible by an elevation of GSP. In contrast, in about 40% of the patients with incomplete glycemic control the HbA1a-c levels fell within the normal range. The utility of lys-GSP for diagnosis of diabetes is compared with the results of 60 oral glucose tolerance tests. Two patients suffering from insulinoma displayed decreased lys-GSP values. From these results it appears that determination of lys-GSP represents a more sensitive parameter for long-term control than HbA1a-c and is suitable for monitoring even small fluctuations of blood glucose.

Extrapancreatic action of the sulphonylurea gliquidone: post-receptor effect on insulin-stimulated glycogen synthesis in rat hepatocytes in primary culture

The effects of a sulphonylurea, gliquidone, on insulin binding and the insulin induced rate of glycogen synthesis, were studied in rat hepatocytes in primary culture. Hepatocytes were cultured for 48 h. During the second 24 h of this period, the hepatocytes were incubated with or without gliquidone (5 mg/l). The binding of 125I-insulin and the insulin stimulation of glycogen synthesis from 14C-glucose were measured. Gliquidone influenced neither insulin binding nor the basal rate of glycogen synthesis, but it did enhance the effect of insulin on glycogen synthesis. Responsiveness was increased by gliquidone at all insulin concentrations used (10-10,000 mU/l); at 1000 mU/l the drug increased glycogen synthesis from 310 to 430% above the basal rate. Half-maximal stimulation was reached in control cells at an insulin concentration of 95 mU/l and in gliquidone-treated cells at 94 mU/l, which indicates unchanged insulin sensitivity. Based on these experiments with cultured rat hepatocytes it appears that the extrapancreatic action of gliquidone is not mediated by an effect on insulin binding.

Catecholamine-induced insulin resistance of glucose transport in isolated rat adipocytes

The effects of pre-incubation with isoprenaline and noradrenaline on insulin binding and insulin stimulation of D-glucose transport in isolated rat adipocytes are reported. (1) Pre-incubation of the cells with isoprenaline (0.1-10 microM) in Krebs-Ringer-Hepes [4-(2-hydroxyethyl)-1-piperazine-ethanesulphonic acid] buffer (30 min, 37 degrees C) at D-glucose concentrations of 16 mM, in which normal ATP levels were maintained, caused a rightward-shift in sensitivity of D-glucose transport to insulin stimulation by 50% and a decrease in maximal responsiveness by 30% (2) [A14-125I]insulin binding was reduced significantly by 35% at insulin concentrations less than 100 mu-units/ml and Scatchard analysis showed that this consisted mainly of a decrease in high-affinity binding. (3) Pre-incubation with catecholamines under the same conditions but at low glucose concentrations (0-5 mM) caused a fall in intracellular ATP levels of 65 and 45% respectively. (4) The fall in ATP additionally lowered insulin binding by 50% at all insulin concentrations and a parallel shift of the binding curves in the Scatchard plot showed that this was due to a decrease in the number of receptors. (5) At low and high ATP concentrations the insulin stimulation of D-glucose transport was inhibited to a similar extent. (6) Pre-incubation with catecholamines thus inhibited insulin stimulation of D-glucose transport in rat adipocytes mainly by a decrease in high-affinity binding of insulin, which was not mediated by low ATP levels. This mechanism may play a role in the pathogenesis of catecholamine-induced insulin resistance in vivo.

Cyclic AMP modulates insulin binding and induces post-receptor insulin resistance of glucose transport in isolated rat adipocytes

The effect of cAMP on insulin binding and insulin stimulation of glucose transport was investigated in isolated rat adipocytes. Preincubation for 30 min in medium containing 16 mmol/l glucose and either db-cAMP or bromo-cAMP in concentrations of 10(-4)-10(-3) M inhibited high affinity binding of insulin by 15 to 30% and glucose transport by 30 to 50%. Preincubation with IBMX (10(-4)-10(-3) M) reduced insulin binding by 25% and glucose transport by 70%. Closer analysis of these data indicated that preincubation with these compounds caused not only a decrease in insulin binding but also a post-receptor resistance. High intracellular cyclic AMP-levels seem therefore to induce insulin resistance at both receptor and post-receptor levels.

Insulin binding and action in antibody-induced diabetes in the rat

The influence of antibody-induced insulin deficiency in rats on the insulin binding and insulin sensitivity of adipocytes was studied. Rats were injected intraperitoneally with an insulin antibody preparation; the development of hyperglycaemia was followed and the animals were sacrificed 3 and 5 h after antibody injection. Up to 3 h, no significant change of insulin binding or sensitivity of the adipocytes occurred. At 5 h, cells of antibody-treated rats showed an approximately 40% increased binding capacity compared with untreated rats. The increased binding capacity was accompanied by an approximate two-fold increased sensitivity of the insulin effect on lipogenesis from glucose in these cells.

Relation of insulin receptor occupancy and deactivation of glucose transport

Kinetics of association and dissociation of 125I-insulin and of activation and deactivation of 3-O-methylglucose transport were determined in isolated rat fat cells. Equilibrium bound insulin (7.5, 25, 100 microunits/ml) dissociated with a t1/2 of 2 min (100 microunits/ml), 4 min (25 microunits/ml), and 16 min (7.5 microunits/ml). Consecutive deactivation of transport is observed only in the presence of glucose (1 mM); the t1/2 of deactivation is approximately 60 min (100 and 25 microunits/ml) and 20 min (7.5 microunits/ml). At 15 degrees C, the t1/2 of dissociation (7.5 microunits/ml) is 25 min, and deactivation is not observed. Addition of dithioerythritol (5 mM) during the association of insulin decreased the binding rapidly; however, a reduced insulin effect was only seen if the binding decreased during the early activation phase of transport. In conclusion, the maintenance of the insulin effect on transport does not require persistent receptor occupancy; dissociation and deactivation are, with respect to kinetics, temperature dependency and requirement of glucose, independent processes. Receptor occupancy probably only controls the activation of transport; deactivation seems to be controlled by postreceptor processes.

Coupling of insulin binding and insulin action on glucose transport in fat cells

The initial lag phase of insulin action on glucose transport in adipocytes reflects an unknown process that couples receptor binding and glucose transport activity. The influence of temperature, cellular ATP, cyclic AMP, and calcium on this process and a possible relation to internalization of insulin were studied. The Arrhenius plot of the coupling shows a break in slope at 30 degrees C; the activation energy below 30 degrees C is 17.5 kcal/mol. Reduction of cellular ATP by 70% prolongs the coupling process; initial binding and final maximal response of the glucose transport remain unaffected. Further reduction of ATP (greater than 90%) before addition of insulin abolishes the coupling completely. Reduction of ATP at different time points after addition of insulin blocks further activation; however, the actual state of activity is preserved. Calcium depletion by EDTA prolongs the coupling and decreases the maximal response. Internalization of insulin as determined in chloroquine-treated cells begins later than transport activation and is in contrast to transport activation not observable at 15 degrees C. In conclusion, the coupling is not related to internalization; it is ATP-dependent, whereas the initial binding and the activated transport system are ATP-independent. Calcium but not cyclic AMP might be second messenger or cofactor in the coupling process.

Insulin binding and insulin action in rat fat cells after adrenalectomy

Insulin binding and the effect of insulin on the transport of 3-O-methylglucose, lipogenesis from glucose, glucose oxidation and lipolysis was studied in fat cells of adrenalectomised rats and of a control group of sham-operated rats. The serum insulin level of the adrenalectomised rats (0.7 ng/ml) was lower than that of the controls (1.6 ng/ml). In adrenalectomised rats as compared to sham-operated rats the insulin concentrations causing half-maximal effect were reduced by 50% in lipogenesis and antilipolysis and by 30% in glucose transport. The increase in sensitivity to submaximal insulin concentrations was not observed in glucose oxidation. The maximal responsiveness was unchanged in all test systems. The increase in sensitivity in three of the four studied insulin effects may be related to the 37% increase in the binding capacity of fat cells from adrenalectomised compared with sham-operated rats. The unchanged sensitivity with respect to glucose oxidation indicates possible post-receptor modulation. When adrenalectomised rats were substituted with either insulin or cortisol serum insulin levels were elevated above normal; however, the changes in the receptor were prevented in the cortisol supplemented rats and only partially in the insulin supplemented rats. The observation suggests, that the insulin receptor is regulated not only by the serum insulin level but also by cortisol.

Free insulin, bound insulin, C-peptide and the metabolic control in juvenile onset diabetics: comparison of C-peptide secretors and non-secretors during 24 hours conventional insulin therapy

In two groups of juvenile onset diabetics similar in age, weight, diet and daily insulin dosage (eight without C-peptide, group I; eight with C-peptide, group II) the serum levels of free and antibody bound insulin, C-peptide, glucose, lactate, alanine and FFA were determined over 24 h. In addition the affinity and binding capacity of the insulin antibodies were determined in vitro. No correlation was found between free or bound insulin and glucose. This holds true for the individual profiles as well as for the averaged profiles of the two groups. Free insulin and lactate or alanine were positively correlated in the C-peptide secreting group. C-peptide secretion followed the flucturations of the glucose level during 24 h in each individual patient. As a group, C-peptide secretors were better controlled than non-secretors with respect to mean blood glucose, M-value and the lability index and showed higher free insulin levels despite a similar daily insulin dosage. The possible reasons for this fact are discussed. No correlation was found between the affinity characteristics of the insulin antibodies and the degree of metabolic control or the daily insulin dosage.