Function outperforms morphology in the assessment of muscular contribution to insulin sensitivity in premenopausal women

INTRODUCTION

Skeletal muscle contributes significantly to insulin sensitivity in humans. However, which non-invasive measurement best reflects this contribution remains unknown. Consequently, this paper compares morphologic and functional measurements.

RESEARCH METHODS AND DESIGN

We conducted a cross-sectional analysis of 144 premenopausal women enrolled in the "Prediction, Prevention, and Sub-classification of Type 2 Diabetes" (PPSDiab) cohort study. For the analysis, we quantified insulin sensitivity by oral glucose tolerance testing and, in a subgroup of 30 women, euglycemic clamp. To assess skeletal muscle, we measured volume by magnetic resonance imaging, intramyocellular lipid content by magnetic resonance spectroscopy, and physical fitness by cardiopulmonary exercise testing.

RESULTS

The mean age of the cohort was 35.7 ± 4.1 years and 94 participants (65%) had a history of gestational diabetes mellitus. Of the morphologic and functional muscle parameters, the maximum workload achieved during cardiopulmonary exercise testing associated most closely with insulin sensitivity (standardized beta = 0.39; p < .001). Peak oxygen uptake also demonstrated significant associations, whereas muscle volume and intramyocellular lipid content displayed none.

CONCLUSION

Functional measurements provided a better assessment of the muscular contribution to insulin sensitivity than morphologic measurements in premenopausal women. In particular, exercise testing rendered an easy and cost-effective method applicable in clinical settings and other human studies.

Association of Serum Myostatin with Body Weight, Visceral Fat Volume, and High Sensitivity C-Reactive Protein But Not With Muscle Mass and Physical Fitness in Premenopausal Women

BACKGROUND

The myokine myostatin regulates muscle mass and has been linked to insulin resistance and metabolic syndrome. However, data on its role in humans is still limited. We, therefore, investigated the associations of serum myostatin with muscle mass, physical fitness, and components of the metabolic syndrome in a cohort of premenopausal women.

METHODS

We undertook a cross-sectional analysis of 233 women from the monocenter study PPSDiab, conducted in Munich, Germany. Participants had recently completed a pregnancy with or without gestational diabetes. Our analysis included medical history, anthropometrics, oral glucose tolerance testing, laboratory chemistry, cardiopulmonary exercise testing, and magnetic resonance imaging (n=142) of visceral fat volume, left quadriceps muscle mass, and muscle fat content. Serum myostatin was quantified by a competitive enzyme-linked immunosorbent assay.

RESULTS

We observed positive correlations of serum myostatin with body mass index (ρ=0.235; p=0.0003), body fat percentage (ρ=0.166; p=0.011), waist circumference (ρ=0.206; p=0.002), intraabdominal fat volume (ρ=0.182; p=0.030) and high-sensitivity C-reactive protein (ρ=0.175; p=0.008). These correlations were reproduced in linear regression analyses with adjustment for age and time after delivery. We saw no correlations with muscle mass, physical fitness, insulin sensitivity, triglycerides, HDL cholesterol, and blood pressure.

CONCLUSIONS

Our observation of elevated serum myostatin in women with a higher body fat percentage, visceral obesity, and elevated c-reactive protein suggests that this myokine contributes to the altered muscle-adipose tissue crosstalk in metabolic syndrome. Elevated myostatin may advance this pathophysiologic process and could also impair the efficacy of exercise interventions. Further mechanistic studies, therefore, seem warranted.

A Pathophysiology of Type 2 Diabetes Unrelated to Metabolic Syndrome

OBJECTIVE

Clinically, type 2 diabetes mellitus (T2DM) is heterogeneous, but the prevailing pathophysiologic hypothesis nevertheless contends that components of metabolic syndrome are central to all cases of T2DM. Here, we re-evaluated this hypothesis.

RESEARCH DESIGN AND METHODS

We conducted a cross-sectional analysis of 138 women from the monocenter, post gestational diabetes study PPSDiab, 73 of which had incident prediabetes or T2DM. Additionally, we examined all the 412 incident cases of T2DM in phases 3 to 9 of the Whitehall II study in comparison to healthy controls. Our analysis included a medical history, anthropometrics, oral glucose tolerance testing, and laboratory chemistry in both studies. Additional analyses from the PPSDiab Study consisted of cardiopulmonary exercise testing, magnetic resonance imaging, auto-antibody testing, and the exclusion of glucokinase maturity-onset diabetes of the young.

RESULTS

We found that 33 (45%) of the women with prediabetes or T2DM in the PPSDiab study displayed no components of metabolic syndrome. They reached no point for metabolic syndrome in the National Cholesterol Education Program Adult Treatment Panel III score other than hyperglycemia and, moreover, had levels of liver fat content, plasma triglycerides, high-density lipoprotein cholesterol, c-reactive protein, and blood pressure that were comparable to healthy controls. In the Whitehall II study, 62 (15%) of the incident T2DM cases fulfilled the same criteria. In both studies, these cases without metabolic syndrome revealed insulin resistance and inadequately low insulin secretion.

CONCLUSIONS

Our results contradict the hypothesis that components of metabolic syndrome are central to all cases of T2DM. Instead, they suggest the common occurrence of a second, unrelated pathophysiology.

Efficacy and safety of azithromycin versus lymecyline in the treatment of genital chlamydial infections in women

To compare the clinical and microbiological efficacy of azithromycin in curing chlamydial infections in women with that of lymecycline, and with a view of the possibility of minimizing the problem of compliance by means of single-dose administration, 146 women with culture-positive Chlamydia trachomatis infections were randomly assigned to treatment with a 1 g bolus dose of azithromycin or a 10-day course of lymecycline 300 mg twice daily. Clinical and microbiological evaluations were performed and adverse effects monitored at check-ups after 15-35 and 40-65 days. Of the 146 patients enrolled in the study, 120 were evaluable. At the second check-up, C. trachomatis was found to have been eradicated in all patients in both treatment groups. Of the 51 patients who had clinical signs and symptoms of genital infection at enrolment, 96% (22/23) of those in the azithromycin group were considered cured (n = 18) or improved (n = 4), as compared with 100% (28/28) of those considered cured (n = 22) or improved (n = 6) in the lymecycline group. Adverse events related, or possibly related, to treatment were reported by 16 (21.6%) of the lymecycline group, but by only 6 (8.3%) of the azithromycin group. The 2 drugs were comparable with regard to microbiological and clinical efficacy in the treatment of genital chlamydial infection in women. The markedly lower rate of side-effects associated with azithromycin may be a feature conducive to patient compliance.

Fibronectin associated with infiltrating T lymphocytes. Evidence for in situ localization in biopsies and synthesis in vitro

Dermal and mucosal lymphocyte infiltrates in patients with lichen ruber planus and chronic graft-vs.-host disease exhibited reactivity with anti-fibronectin antibodies. This reactivity was associated with the lymphocytes and localized pericellularly. In contrast, biopsy areas outside lymphocyte accumulations were relatively devoid of reactivity with anti-fibronectin antibodies. Furthermore, the corresponding biopsies from healthy individuals or patients without lymphocyte infiltration showed negligible reactivity with anti-fibronectin antibodies. The fibronectin associated with infiltrating lymphocytes in biopsies may be exogenous of non-lymphoid origin. However, another possibility suggested by in vitro experiments is that this fibronectin is lymphocyte derived. Thus, during cultivation in vitro lymphocytes appear to synthesize a component with fibronectin-like properties. Furthermore, a prerequisite for detection of this synthesis was that the cells were cultured in the presence of serum depleted of fibronectin. These results point to the possibility that fibronectin may play a role for lymphocyte interactions with tissues during infiltrative processes.

Anchorage and lymphocyte function. Acquisition of spontaneous motile behaviour by human blood lymphocytes and its modulation by concanavalin A

The majority of splenic lymphocytes were motile, showing lamellipodial activity almost immediately after purification. In contrast, fresh blood lymphocytes were non-motile and maintained their spherical suspension morphology. The number of motile blood lymphocytes increased markedly during a 2-day in vitro culture period. This increase was enhanced by high cell density and required a metabolically active cell with protein synthesis but not exogenous mitogens. The spontaneous development of motility in different subpopulations of blood lymphocytes was analysed by means of monoclonal antibodies. The results indicated that cells which were motile immediately after purification were almost exclusively non-T lymphocytes. Lymphocytes which became motile during in vitro culture included both T and non-T cells. Substrate adhesion mediated by concanavalin A (Con A) changed the morphology of motile T lymphocytes and instead of being polar, the cells flattened over the substratum and acquired a non-polar shape. Furthermore, the morphogenetic response induced by Con A-mediated substrate adhesion appeared to distinguish T and non-T lymphocytes. Thus, the length of the cell perimeter showing lamellar activity was greater in T than in non-T lymphocytes, and the degree of polarity was greater in non-T (with and without B-cell markers) than in T lymphocytes.

Anchorage and lymphocyte function: pattern of spreading distinguishes T- and B-cell chronic lymphocytic leukaemia

T and B lymphocytes from normal individuals and patients with T and B chronic lymphocytic leukaemia (TCLL and BCLL) were induced to spread on a solid surface in the presence of Con A. The proportion of cell circumference exhibiting lamellar activity was considerably greater in T than in B cells. This difference also applied to T and B cells with a single leading lamellipodium. The different pattern of formation of active cell edges implied that the degree of polarity measured as the ratio between the largest and the shortest diameter (over the nucleus) was significantly greater in B than in T cells. This was also obvious when T and B cells, both with a single leading lamellipodium, were compared. The formation of active cell edges in T lymphocytes was generally accompanied by nuclear flattening, even in polar cells with a single leading lamellipodium. B cells, with the exception of one BCLL case, did not exhibit nuclear flattening. Thus, during the entire course of a contact-induced morphogenetic response, T- and B-cell leukaemias were easily distinguishable on the basis of the following criteria: (i) the proportion of the lymphocyte perimeter showing active cell edges, (ii) the degree of polarity and (iii) nuclear flattening.

Anchorage and lymphocyte function. Antibodies as adhesion and spreading factors for human T lymphocytes

When attached to a solid surface coated with protein A various antibodies reacting with lymphocyte membrane antigens (anti-beta 2m, OKT3, OKT8, Leu2, 3, 4 and certain patient sera) catalyse the formation of peripheral lamellar activity, i.e. an active spreading process in human T lymphocytes. In contrast, binding only of the same antibodies to the cells or allowing antibody-coated cells to settle and bind to a protein A-coated surface did not induce spreading although the number of cells attached to the solid surface was virtually the same as in the former case. The peripheral lamellar activity markedly facilitated short-range lymphocyte interactions and appeared to constitute the region of the lymphocyte that actively contacts other cells. These results show that antibodies can act as spreading factors, and indicate that this function is critically dependent on the presentation of the inducing ligand. The asymmetry in the induction of active cell edges may influence functional lymphocyte interactions with environmental surfaces.

Permissive effect of cytochalasin B on DNA synthesis in concanavalin-A-treated lymphocytes

Unfractionated or T-cell-enriched human lymphocytes can be stimulated to undergo DNA synthesis and mitosis by the addition of polyclonal cell activators such as the plant lectins phytohaemagglutinin and concanavalin A (ConA). Under conventional culture conditions stimulated cells cease proliferating only a few days after the first cells have initiated DNA synthesis. Cytochalasin B (CB), which is non-mitogenic per se, causes a prolongation of the period during which ConA stimulates DNA synthesis from normally 3–5 days to more than 3 weeks. The CB-induced prolongation of cell proliferation is clearly stage-specific in the sense that the CB effects are exerted after an initial period of 24 h and do not come into effect until 48 h after onset of ConA stimulation. In contrast, CB exerts a slight suppressive action on DNA synthesis between 24 h (when activated cells initiate DNA synthesis) and 48 h after onset of stimulation. These two separate effects of CB, i.e. augmentation of lymphocyte stimulation 48 h after stimulation, and suppression of stimulation before this point of time, are relatively independent of the concentration of CB.

Permissive effect of substratum contact on DNA synthesis in concanavalin A-treated lymphocytes

The effects of contact with a solid surface (in the form of adhesive microcarrier beads (Cytodex)) on the induction of proliferation of human blood lymphocytes after exposure to concanavalin A (Con A) were investigated. The duration of the lag phase preceding DNA synthesis was identical in the presence and absence of beads. The kinetic course of initiation of DNA synthesis was exponential but with different rate constants both in the presence and in the absence of beads during the first 4 days of the culture period. Cytodex exerted its effect by increasing the proportion of cells initiating DNA synthesis in response to Con A. To elucidate whether lymphocytes responded to Con A exposure in a dose-dependent manner, cells were seeded at different concentrations and exposed to Con A for different times. At 36 and 48 h after start of stimulation the proportion of cells synthesizing DNA increased with increasing cell number in the cultures. In contrast, the portion of cells synthesizing DNA was markedly decreased at high cell densities 60, 72 and 96 h after start of stimulation. In the presence of microcarrier beads, however, the proportion of cells synthesizing DNA was proportional to the cell number in the cultures also after 60, 72 and 96 h.

Cytochalasins distinguish by their action resting human T lymphocytes from activated T-cell blasts

In the majority of resting human peripheral T lymphocytes obtained from separate individuals cytochalasin B (CB) and D (CD) cause a disappearance of microvilli and induce a rapid formation of prominent sac and bleb-like projections with a length of 1-10 microns randomly distributed over the cell surface. During mitogen stimulation the cells lose the tendency to develop such projections when subsequently exposed to CB and CD. By contrast, in activated T lymphocytes the cytochalasins provoke an asymmetric localization of microvilli including cell surface antigens and actin to a prominent protuberance often separated from the cell body by a constriction. This protuberance is distinct from conventional spontaneous uropods formed by conA-stimulated lymphocytes in relation to contact with other cells and with non-cellular surfaces. The cytochalasins therefore in their action distinguish resting small lymphocytes from activated T-cell blasts.

Anchorage and lymphocyte function II. Contact with non-cellular surfaces, cell density and T-cell activation

Varying numbers of human blood lymphocytes were stimulated by concanavalin A (Con-A) in a constant medium volume. At 'low' cell densities DNA synthesis was proportional to the number of cells in the cultures whereas at 'high' densities DNA synthesis was considerably lower than expected. In the presence of non-mitogenic microcarrier beads, (diameter 195 micrometer) to which the cells attached, DNA synthesis was proportional or nearly proportional to the cell number in the cultures also at 'high' cell densities. The potentiating effect of beads on lymphocyte stimulation was particularly noteworthy in individuals showing a weak mitogen response. Another approach that yielded proportionality between DNA synthesis and cell number both at 'low' and 'high' cell densities was the use of culture vessels with a larger bottom area. Under such conditions the presence of beads did not augment DNA synthesis. These results suggest that the availability of non-cellular adhesive surface is a major limiting factor and cell density a major regulating factor in the control of lymphocyte activation. Anchorage of the cells to a surface may modulate the density dependent 'growth control mechanism' indirectly via an influence on cell-cell interaction. An alternative less-likely interpretation is that the contact with non-cellular surfaces directly gives rise to regulatory responses in lymphocytes or accessory cells.

Anchorage and lymphocyte function. Contact-induced augmentation of T-cell activation

Beads of polyacrylamide, latex or DEAE-Sephadex markedly augmented the stimulation of unfractionated or T-enriched lymphocytes by concanavalin A (Con A) or phytohaemagglutinin (PHA). The beads were not mitogenic in the absence of Con A or PHA. A prerequisite for the bead-induced augmentation was that the stimulated lymphocytes had been depleted of phagocytic and/or adherent accessory cells. The enhancing effect of beads was most pronounced during the initial 12 h after the beginning of lymphocyte stimulation, but not limited to this early phase of the growth period. The stimulation of lymphocytes in petri dishes of adhesive tissue culture plastic and non-adhesive bacterial plastic were compared. The magnitude of the stimulation on the non-adhesive surface was 10--50% lower than on the adhesive one, this difference being most pronounced at hyperoptimal mitogen concentrations. These results indicate that contact between some cell type and a solid surface can improve lymphocyte stimulation under experimental conditions when the number of phagocytic and adherent accessory cells is a limiting factor. The fact that cultivation on bacterial plastic, where adhesion and spreading were abolished, produced substantial stimulation (albeit reduced) demonstrates that substrate contact may be important, but is not a prerequisite, for lymphocyte activation.

Influence of specificity of reagents and of behaviour of cell surface Ig on the detection and enumeration of immunoglobulin-bearing lymphocytes in humans

Some parameters likely to influence detection and classification of human B-lymphocytes using anti-immunoglobulin (Ig) sera have been investigated. Of 20 separate mono- and polyspecific native or conjugated anti-Ig sera analysed by a passive haemagglutination technique, 13 exhibited non-specific reactivity. This technique showed no consistent correlation between the titre of individual sera against Fab2 and whole IgG respectively. The indirect immunofluorescence (IF) method applied to detect surface Ig on blood lymphocytes seemed to detect Fc-bearing rather than Ig-bearing cells. The direct method generally yielded fewer reacting cells (5%) than the indirect (10-25%), suggesting that Fc-bearing cells are more numerous than Ig-bearing cells. The Ig-bearing blood lymphocytes seemed to belong preferentially to the IgM class. Passively adsorbed Ig did not appear to contribute significantly to the number of Ig-bearing cells detected. Anti-Ig sera induced redistribution and some endocytosis of surface Ig but this did not markedly affect detection of Ig-bearing cells.

Erysipelas and necrotizing fasciitis

The clinical course of necrotizing fasciitis in 8 patients is compared with observations on 22 other patients with erysipelas. In necrotizing fasciitis the early erythematous areas turn into a dusky blue colour with later vesiculation and formation of bullae. An important finding is a non-pitting oedema extending outside the erythematous patches. The disease often progresses and involves further skin areas proximal to the initial ones. Gangrene tends to follow in multiple sites after the 1st week of illness. Group A streptococci in conjunction with widespread thrombosis and vascular necrosis of the involved skin are two major factors in the pathogenesis of the gangrene. Early debridement and excision of necrotic tissue in combination with large doses of penicillin and cloxacillin are confirmed as mandatory to remove toxaemia and inhibit further necrosis of the skin. In 3 of the 8 patients with necrotizing fasciitis the syndrome of disseminated intravascular coagulation complicated the course of the disease. A promising therapeutic result was seen in 2 further patients exhibiting alarming signs and symptoms of early necrotizing fasciitis; the combination of heparin, given intravenously in therapeutic doses guided by activated partial thromboplastin time studies, and of systemic antibiotics alleviated the symptoms, which vanished within 10 days of the start of treatment.

Treatment of trichomoniasis in females with and without gonorrhoea

46 women with trichomoniasis and gonorrhea were treated with nimorazole (300 mg twice daily for 7 days) and a trichomonal cure rate of 90-2 per cent. was noted. In addition, 53 of 112 patients with trichomoniasis but without gonorrhoea, were treated with metronidazole (200 mg three times a day for 7 days) and 59 with nimorazole (300 mg twice daily for 7 days) in a randomized trial. The cure rates were 96 and 90-5 per cent. respectively. There was no significant difference in the results noted in the two groups. Neither the trichomonal infection itself nor the result of antitrichomonal therapy was affected by antigonococcal therapy (one-day treatment with ampicillin or single-dose therapy with doxycycline). No increase was noted in the frequency of candidiasis after antitrichomonal therapy (in patients without gonorrhoea) or after antigonococcal therapy, but there was substantial variation between consecutive specimens in the prevalence of C. albicans.

Frequency of N. gonorrhoeae, T. vaginalis, and C. albicans in female venereological patients. A one-year study

The frequency of Neisseria gonorrhoeae, Trichomonas vaginalis, and Candida albicans has been studied over a period of one year in women attending a venereal diseases clinic. A total of 1,347 women were investigated, all coming from the same catchment area. Gonorrhoea was established at the first visit in 506 patients (38 per cent.), who constituted 97.5 per cent. of the total number of cases of gonorrhoea. Trichomonas vaginalis was found in 272 (20 per cent.) and Candida albicans in 233 (17 per cent.). 176 patients (13 per cent.) had more than one pathogen. Of the patients attending, 22 per cent. (292 women) were so-called "named contacts". The frequency of gonorrhoea established at the first visit in these patients (64 per cent.), was significantly higher, but the frequency of symptoms did not differ from that in other gonorrhoea patients. The number of asymptomatic cases was so large that a single compulsory examination is undoubtedly very useful from the epidemiological point of view, but the value of repeated specimen collections for gonorrhoea is debatable. Complications of gonorrhoea were observed in 29 patients (6 per cent.) at the first visit.