Stabilizing interactions between D666-S1787 and T657-Y1792 at the A2-A3 interface support factor VIIIa stability in the blood clotting pathway

Essentials Factor VIIIa (FVIIIa) is unstable due to loss of A2; D666 and Y1792 contribute to its stability. We conducted a study to identify the interactions made at these residues at the A2-A3 interface. We present evidence for stabilizing interactions between D666-S1787 and T657-Y1792 in FVIIIa. A D666C/S1788C variant with a disulfide A2-A3 linkage has a FVIIIa decay rate that is 1% of wild-type.

SUMMARY

Background Factor (F)VIIIa activity and stability depends on the non-covalent association of the A2 subunit with the A1/A3C1C2 dimer, but the interactions that contribute to A2 association are not well defined. Previous work had shown that D666A and Y1792F mutations at the A2-A3 interface resulted in increased FVIIIa decay, suggesting that the residues were involved in bonding interactions important for FVIIIa stability. Objectives Several potential hydrogen bonding partners of D666 and Y1792 across the A2-A3 interface were selected from the low-resolution FVIII crystal structure, and we used mutagenesis and biochemical analysis to examine the bonding interactions occurring at D666 and Y1792. Methods Using a series of stability and functional analyses, we analyzed FVIII variants in which D666 and Y1792 were each swapped with the residues of potential bonding partners. Results and conclusions We present evidence for hydrogen bonds between D666 and S1787 and between Y1792 and T657 that are important for FVIIIa stability. D666S/S1787D and T657Y/Y1792T variants each displayed wild-type (WT)-like FVIIIa stability and performed like WT FVIII in a series of functional analyses, whereas D666S, S1787D, and Y1792T single variants showed increased FVIIIa decay and a T657Y variant had little FVIIIa activity. These results suggest that WT hydrogen bonds are disrupted with the single mutations but maintained in the swap variants. Furthermore, mutation of D666 and S1788 to cysteine resulted in disulfide bond formation across the A2-A3 interface, confirming the close proximity of D666 and S1787, and this covalent attachment of the A2 subunit significantly increased FVIIIa stability.

Presbyphagia and Sarcopenic Dysphagia: Association between Aging, Sarcopenia, and Deglutition Disorders

Presbyphagia refers to age-related changes in the swallowing mechanism in the elderly associated with a frailty in swallowing. Presbyphagia is different from dysphagia. Sarcopenic dysphagia is difficulty swallowing due to sarcopenia of generalized skeletal muscles and swallowing muscles. Age-related loss of swallowing muscle mass becomes evident in the geniohyoid muscle and tongue. Elderly subjects with both sarcopenia and dysphagia may have not only disease-related dysphagia but also sarcopenic dysphagia. In cases of aspiration pneumonia, deterioration in activity-, disease-, and nutrition-related sarcopenia of generalized skeletal muscles and swallowing muscles may develop into sarcopenic dysphagia. Assessment of sarcopenic dysphagia includes evaluation of both dysphagia and sarcopenia. The 10-item Eating Assessment Tool (EAT-10) and a water test combined with pulse oximetry are useful for dysphagia screening. Assessment of the multi-factorial causes of sarcopenia including nutritional review is important, because rehabilitation of sarcopenic dysphagia differs depending on its etiology. Consensus diagnostic criteria for sarcopenic dysphagia were proposed at the 19th Annual Meeting of the Japanese Society of Dysphagia Rehabilitation. Rehabilitation for sarcopenic dysphagia includes treatment of both dysphagia and sarcopenia. The core components of dysphagia rehabilitation are oral health care, rehabilitative techniques, and food modification. The causes of adult malnutrition may also contribute to the etiology of secondary sarcopenia and sarcopenic dysphagia. Therefore, nutrition management is indispensable for sarcopenic dysphagia rehabilitation. In cases of sarcopenia with numerous complicating causes, treatment should include pharmaceutical therapies for age-related sarcopenia and comorbid chronic diseases, resistance training, early ambulation, nutrition management, protein and amino acid supplementation, and non-smoking.

Neck Circumference Is Not Associated with Dysphagia but with Undernutrition in Elderly Individuals Requiring Long-term Care

OBJECTIVES

The purpose was to assess the association between neck circumference, dysphagia, and undernutrition in elderly individuals requiring long-term care.

DESIGN

Cross-sectional study.

SETTING

Geriatric health services facilities, acute hospitals, and the community.

PARTICIPANTS

Elderly individuals ≥65 years of age with dysphagia or possible dysphagia (N=385).

MEASUREMENTS

Neck circumference, the Dysphagia Severity Scale (DSS) and the Mini Nutritional Assessment Short Form (MNA-SF).

RESULTS

Participants included 130 males and 255 females with a mean age (± standard deviation) of 83 ± 8.0 years. Sixty-six were in acute hospitals, 195 were in geriatric health services facilities, and 124 were community-dwelling. The mean neck circumference in males and females was 37.1 ± 3.0 cm and 33.3 ± 3.3 cm, respectively. Based on the DSS, 81 participants were within normal limits, 137 had dysphagia without aspiration, and 167 had dysphagia with aspiration. The MNA-SF revealed that 173 were malnourished, 172 were at risk of malnutrition, and 40 had a normal nutritional status. Neck circumference was not significantly correlated with the DSS (r=-0.080) but was significantly correlated with the MNA-SF (r=0.183) in the Spearman rank correlation analysis. In the logistic regression, neck circumference was not independently associated with the DSS after adjusting for the MNA-SF, the Barthel Index, age, sex, setting, and cerebrovascular disorders. However, the multiple regression analysis showed that neck circumference had an independent effect on the MNA-SF after adjusting for the Barthel Index, age, sex, setting and cerebrovascular disorders.

CONCLUSIONS

Neck circumference is not associated with dysphagia but with undernutrition in elderly individuals requiring long-term care.

Dysphagia Assessed by the 10-Item Eating Assessment Tool Is Associated with Nutritional Status and Activities of Daily Living in Elderly Individuals Requiring Long-Term Care

OBJECTIVES

The 10-item Eating Assessment Tool (EAT-10) is a self-administered questionnaire for dysphagia screening, with each item scored from 0 to 4. We assessed the associations among the EAT-10 score, nutritional status and activities of daily living (ADL) in elderly individuals requiring long-term care.

DESIGN

Cross-sectional study.

SETTING

Geriatric health services facilities, acute hospitals, and the community.

PARTICIPANTS

Elderly individuals ≥65 years of age with dysphagia or possible dysphagia (N=237).

MEASUREMENTS

The EAT-10, the Mini Nutritional Assessment Short Form (MNA-SF) and the Barthel Index.

RESULTS

There were 90 males and 147 females. Mean age was 82 ± 8 years. Eighty-nine were in geriatric health services facilities, 28 were in acute hospitals, and 120 were community-dwelling. The median Barthel Index score was 55 (interquartile range: 25, 80). The median EAT-10 score was 1 (interquartile range: 0, 9), and 101 respondents a score > 3, indicating the presence of dysphagia. The MNA-SF revealed that 81 were malnourished, 117 were at risk of malnutrition, and 39 had a normal nutritional status. The Barthel Index score and MNA-SF score were significantly lower in those with an EAT-10 score between 3 and 40, compared to those with an EAT-10 score between 0 and 2. The EAT-10 has an independent effect on the Barthel Index and the MNA-SF by adjusting for covariates such as age, gender, and setting in multiple regression analysis.

CONCLUSIONS

Dysphagia assessed by the EAT-10 is associated with nutritional status and ADL in elderly individuals requiring long-term care.

Skeletal muscle mass is associated with severe dysphagia in cancer patients

BACKGROUND

The purpose of this study was to assess the association between skeletal muscle mass, activities of daily living (ADLs) and severe dysphagia in cancer patients.

METHODS

A nested case-control study was performed in 111 consecutive cancer patients with dysphagia who were prescribed speech therapy. Skeletal muscle mass comprising the cross-sectional area of the left and right psoas muscles was assessed via abdominal computed tomography at the third lumbar vertebral level. ADLs were evaluated by the Barthel Index. The severity of dysphagia was assessed by the Food Intake Level Scale and was characterized by non-oral feeding or oral food intake at discharge. Univariate and logistic regression analyses were applied to examine the associations between dysphagia, skeletal muscle index (SMI) and ADLs.

RESULTS

There were 86 men and 25 women (mean age, 70 years). The mean SMI was 5.68 ± 1.74 cm(2)/m(2) in men and 4.43 ± 1.21 cm(2)/m(2) in women. The median Barthel Index score was 20. Thirty-three patients were on non-oral feeding at discharge. The mean SMI did not differ significantly between non-oral feeding and oral food intake groups in t-test. The median Barthel Index score was lower in the non-oral feeding group in Mann-Whitney U test. Logistic regression analysis of the severity of dysphagia adjusted for age, sex, SMI, Barthel Index score, serum albumin, cancer type and stage, and vocal cord paralysis showed that SMI was associated independently with oral food intake at discharge. Barthel Index score showed a tendency to be associated with oral food intake.

CONCLUSIONS

Skeletal muscle mass is associated with severe dysphagia in cancer patients. ADLs show a tendency to be associated with severe dysphagia in cancer patients.

Mild hemophilia A patient with novel Pro1809Leu mutation develops an anti-C2 antibody inhibiting allogeneic but not autologous factor VIII activity

BACKGROUND

In mild hemophilia A (MHA) patients, the risk of inhibitor development is generally low, but some factor VIII (FVIII) gene missense mutations are associated with a higher inhibitor incidence.

OBJECTIVE

To investigate the mechanism(s) of inhibitor development in MHA.

METHODS AND RESULTS

A patient, HA78, with MHA with a novel P1809L missense mutation in the A3 domain, exhibited significant residual FVIII activity (

FVIII

C ~10 IU dL(-1) ), despite the development of an inhibitor (5.6 BU mL(-1) ). Purified HA78-IgG significantly depressed

FVIII

C from normal plasma but not from patient's plasma without inhibitor, indicating that this IgG inhibited allogeneic but not autologous FVIII. The HA78-IgG blocked thrombin and FXa-catalyzed FVIII cleavage but had little effect on FVIII binding to von Willebrand factor and phospholipid. The IgG recognized a C2 epitope close or overlapping the previously described anti-C2 ESH8 epitope. Similarly, a recombinant FVIII-P1809L mutant was little inactivated by HA78-IgG. This mutant demonstrated ~3-fold lower binding affinities to von Willebrand factor and phospholipid compared with wild-type, while reactions with thrombin or FXa were not impaired. Reaction of FVIII-P1809L with the alternative anti-C2 ESH4 showed only an ~20% inhibition compared with wild-type FVIII but was similar to wild-type after incubation with ESH8. A surface plasmon resonance-based assay demonstrated that anti-C2 ESH4 bound to FVIII-P1809L with ~10(2) -fold lower affinity compared with ESH8.

CONCLUSION

These results indicated that the P1809L mutation in A3 induced the conformational change in the FVIII molecule that hampered antigenic determinant(s) located in the C2 domain and might result in the inhibitor development.

The efficacy of add-on tacrolimus for minor flare in patients with systemic lupus erythematosus: a retrospective study

Objective

We have assessed the effectiveness of tacrolimus for minor flares in systemic lupus erythematosus (SLE) patients.

Methods

The medical records of 313 patients were retrospectively reviewed over a period of seven years, from 2006 to 2013. We enrolled patients with minor flare treated with add-on tacrolimus, without glucocorticoid (GC) intensification (tacrolimus group). Minor flare was defined as a ≥1-point increase in a total score between 3 and 11 in the SLE Disease Activity Index (SLEDAI). We enrolled as controls patients who were administered increased doses of GC for minor flare (GC group). All patients were followed for one year. The primary outcome measure was the proportion of responders.

Results

There were 14 eligible patients in the tacrolimus group and 20 eligible patients in the GC group. The mean SLEDAI at flare tended to be higher in the tacrolimus group than in the GC group (7.5 vs. 6.2, p = 0.085). A mean dose of 1.6 mg tacrolimus/day was administered for flare, while the mean GC dose was 13.7 mg/day in the GC group. The proportion of responders was 86% (12/14) in the tacrolimus group and 75% (15/20) in the GC group ( p = 0.67). The mean dose of GC at 12 months was higher in the GC group than in the tacrolimus group (9.7 mg/day vs. 7.1 mg/day, p < 0.05). Only one patient discontinued tacrolimus because of fatigue after three months.

Conclusion

Adding tacrolimus without increasing the GC dose may provide an effective treatment option for minor flares in patients with SLE.

Effect of Bifidobacterium breve B-3 on skin photoaging induced by chronic UV irradiation in mice

Probiotics have been shown to have a preventative effect on skin photoaging induced by short term UV irradiation, however, the underlying mechanisms and the effect of probiotics on skin photoaging induced by chronic UV irradiation remain unclear. In this study, we investigated the effect of Bifidobacterium breve B-3 on skin photoaging induced by chronic UV irradiation in hairless mice. Mice were irradiated with UVB three times weekly and orally administered B. breve B-3 (2×109 cfu/mouse /day) for 7 weeks. Nonirradiated mice and UVB-irradiated mice without probiotic treatment were used as controls. B. breve B-3 significantly suppressed the changes of transepidermal water loss, skin hydration, epidermal thickening and attenuated the damage to the tight junction structure and basement membrane induced by chronic UVB irradiation. Administration of B. breve B-3 tended to suppress the UV-induced interleukin-1β production in skin (P=0.09). These results suggest that B. breve B-3 could potentially be used to prevent photoaging induced by chronic UV irradiation.