Predicting anterior cruciate ligament degeneration using magnetic resonance imaging: Insights from histological evaluation.

BACKGROUND: Mucoid degeneration of the anterior cruciate ligament is a pathological condition that may impair knee mechanics and contribute to the symptomatology of osteoarthritis. This study aimed to evaluate whether preoperative magnetic resonance imaging can predict anterior cruciate ligament degeneration, specifically mucoid degeneration, and to elucidate the histopathological characteristics of mucoid degeneration in knee osteoarthritis patients. METHODS: We evaluated a total of 95 knees of osteoarthritis patients (23 males, 72 females; mean age: 72.7 ± 7.5) scheduled for total knee arthroplasty. The relationship between preoperative magnetic resonance imaging findings and the histopathological evidence of anterior cruciate ligament mucoid degeneration was examined. Immunohistochemical analysis was employed for collagen types (COL-I, COL-II), chondrogenesis (SOX9), and vascularity (CD31). RESULTS: High signal intensity on magnetic resonance imaging showed a positive correlation with Alcian Blue staining areas (rs = 0.59, p < 0.01) and the swelling index (rs = 0.62, p < 0.01), indicating advanced mucoid degeneration. The absence of synovial lining around the anterior cruciate ligament was associated with more severe degeneration. In the histological evaluations, advanced degeneration was characterized by an increase in chondroid metaplasia and collagen disorientation. The Alcian Blue and SOX9 correlation was positive (rs = 0.69, p < 0.01), but negative with COL-I (rs = -0.38, p = 0.03) and vascularity (CD31) (rs = -0.60, p < 0.01). CONCLUSIONS: Preoperative magnetic resonance imaging is an effective tool in assessing the severity of anterior cruciate ligament degeneration; it influences surgical decisions. High signal intensity on magnetic resonance images denotes advanced mucoid degeneration. The absence of synovial lining around the anterior cruciate ligament is associated with more severe degeneration and may accelerate degenerative changes. Chondroid metaplasia and collagen disorientation mark advanced degeneration. Magnetic resonance imaging can be used to gauge the degree of anterior cruciate ligament degeneration in osteoarthritis.

Mass Spectrometry of Neutral Glycosphingolipids.

This chapter describes the protocols for mass spectrometry (MS) applied to the structural characterization of neutral glycosphingolipids (GSLs) and the determination of neutral GSL contents in biological materials. The structural characterization is performed by thin layer chromatography-matrix assisted laser desorption ionization/mass spectrometry (TLC-MALDI/MS) and liquid chromatography-electrospray ionization/mass spectrometry (LC-ESI/MS) with reversed phase separation. The content determination is carried out by LC-ESI/MS with multiple reaction monitoring (MRM). These protocols provide clues for the functions of neutral GSLs at the level of a single GSL molecular species.

Lower limb alignment in healthy Japanese adults.

BACKGROUND: Knowledge regarding the normal alignment of the lower limb is important when considering alignment for total knee arthroplasty. However, few studies have explored the lower limb alignment of healthy Japanese subjects. METHODS: Between July and October 2020, we performed whole leg standing radiography of 120 legs of 60 healthy adult Japanese volunteers aged <50 years in the closed-leg stance. The measurement parameters were hip knee ankle angle (positive for varus), percentage of constitutional varus (hip knee ankle angle ≥ 3°), mechanical axis deviation ratio, mechanical lateral distal femoral angle, medial proximal tibial angle, joint line convergence angle (positive for lateral opening), and tibial joint line angle (positive for medial inclination). RESULTS: The mean measured values for all volunteers, men and women, were as follows: hip knee ankle angle (°), 2.3, 2.6, and 2.0; mechanical axis deviation ratio, 35.8, 35.6, and 36.9; mechanical lateral distal femoral angle (°), 86.7, 87.0, and 86.7; medial proximal tibial angle (°), 85.6, 85.0, and 86.2; joint line convergence angle (°), 0.6, 0.3, and 0.8; and tibial joint line angle (°), -1.0, -0.7, -1.4, respectively. The percentage of constitutional varus was 35.8% overall, 35.8% in men and 35.3% in women. Only the medial proximal tibial angle was smaller in men than that in women (p = 0.003). CONCLUSIONS: The mechanical lateral distal femoral and medial proximal tibial angles were smaller, hip knee ankle angle was larger, and percentage of constitutional varus was higher in Japanese subjects than those reported for subjects in other countries. Our findings improve the understanding of Japanese-specific alignments when considering alignment for lower limb surgery, especially, total knee arthroplasty.

The Urinary Bladder is Rich in Glycosphingolipids Composed of Phytoceramides.

Glycosphingolipids (GSLs) are composed of a polar glycan chain and a hydrophobic tail known as ceramide. Together with variation in the glycan chain, ceramides exhibit tissue-specific structural variation in the long-chain base (LCB) and N-acyl chain moieties in terms of carbon chain length, degree of desaturation, and hydroxylation. Here, we report the structural variation in GSLs in the urinary bladders of mice and humans. Using TLC, we showed that the major GSLs are hexosylceramide, lactosylceramide, globotriaosylceramide, globotetraosylceramide, Neu5Ac-Gal-Glc-Ceramide, and Neu5Ac-Neu5Ac-Gal-Glc-Ceramide. Our LC-MS analysis indicated that phytoceramide structures with a 20-carbon LCB (4-hydroxyeicosasphinganine) and 2-hydroxy fatty acids are abundant in hexosylceramide and Neu5Ac-Gal-Glc-Ceramide in mice and humans. In addition, quantitative PCR demonstrated that DES2 and FA2H, which are responsible for the generation of 4-hydroxysphinganine and 2-hydroxy fatty acid, respectively, and SPTLC3 and SPTSSB, which are responsible for the generation of 20-carbon LCBs, showed significant expressions in the epithelial layer than in the subepithelial layer. Immunohistochemically, dihydroceramide:sphinganine C4-hydroxylase (DES2) was expressed exclusively in urothelial cells of the urinary bladder. Our findings suggest that these ceramide structures have an impact on membrane properties of the stretching and shrinking in transitional urothelial cells.

Evaluation of hindfoot and knee alignment by the hip-to-calcaneus view in patients with knee osteoarthritis and healthy individuals.

BACKGROUND: Hip-to-calcaneus (HC) view is a whole-leg standing view that can visualize the hindfoot in detail. The aim of this study was to investigate the reliability and validity of tibiocalcaneal angle in HC view (H-TCA) by comparing it with that in long axial view (L-TCA). We also verified whether periarticular knee alignment parameters, measured conventionally in whole-leg standing radiography, could be measured in HC view. METHOD: Sixty healthy volunteers and 61 patients with medial knee osteoarthritis were included. H-TCA was measured by two examiners in the healthy group, and intra-class correlation coefficients (ICCs) were evaluated. H-TCA and L-TCA were then measured in the healthy and osteoarthritis groups and correlated. Finally, we measured hip-knee-ankle angle, mechanical axis deviation ratio, mechanical lateral distal femoral angle, medial proximal tibial angle, and joint-line convergence angle in HC view and conventional whole-leg standing radiography to evaluate statistical differences and correlations. RESULTS: The intra-observer and inter-observer ICCs were 0.86 and 0.76, respectively. Correlation coefficients (r) between H-TCA and L-TCA were r = 0.87 in healthy group and r = 0.81 in osteoarthritis group, indicating a strong positive correlation in both groups. There was no significant difference in periarticular knee alignment parameters between HC view and conventional whole-leg radiography. CONCLUSIONS: Hindfoot evaluation in HC view showed high intra-observer and inter-observer reliabilities and strong positive correlation with TCA in long axial view. By using HC view before knee surgery, such as total knee arthroplasty, other necessary alignments can be evaluated simultaneously.

Effectiveness of Bone Marrow-Derived Platelet-Rich Fibrin on Rotator Cuff Healing in a Rabbit Degenerative Model.

BACKGROUND: Platelet-rich fibrin (PRF) is a second-generation platelet concentrate. Although peripheral blood-derived PRF (P-PRF) is commonly applied in biological augmentation, there is no report about the therapeutic effect of bone marrow-derived PRF (BM-PRF) for degenerative rotator cuff tears (RCTs). PURPOSE/HYPOTHESIS: To examine the effects of platelet-rich plasma (PRP), P-PRF, and BM-PRF during rotator cuff repair (RCR) in degenerative RCTs in rabbits. We hypothesized that BM-PRF would accelerate the bone-tendon healing after RCR. STUDY DESIGN: Controlled laboratory study. METHODS: Degenerative RCT models were created 2 weeks before beginning the study, and 68 juvenile rabbits were divided into 4 groups: the control, PRP, P-PRF, and BM-PRF groups. RCR without augmentation was done in the control group. PRP was prepared by centrifuging peripheral blood twice using a plastic tube. P-PRF and BM-PRF were prepared by centrifuging peripheral blood and bone marrow, respectively, using a glass tube. Rabbits from PRP, P-PRF, and BM-PRF groups were administered the augmentation in a similar fashion for RCR, between the rotator cuff and the footprint of the humerus. At 4, 8, and 12 weeks, rabbits were euthanized and histologically assessed using hematoxylin and eosin staining, Alcian blue staining, and immunohistochemical staining for type I and III collagen. The sections were also evaluated with immunofluorescence staining of vascular endothelial growth factor (VEGF) at 4 weeks. RESULTS: The continuity was significantly better in the BM-PRF group at 4 weeks (P < .05). Immunofluorescence staining demonstrated that VEGF-positive stained cells were significantly greater in the BM-PRF group than in the control group (P < .01). The modified tendon maturing score was significantly greater in the BM-PRF group than in the control and PRP groups at 12 weeks (P < .05). There was no significant difference in the modified tendon maturing score of the P-PRF group compared with the control group. CONCLUSION: The rabbit model of degenerative RCTs demonstrated that RCR combined with BM-PRF enhanced tendon-bone continuity and increased the VEGF-positive cells at 4 weeks and obtained preferable tendon-bone maturation at 12 weeks. CLINICAL RELEVANCE: RCR augmented with BM-PRF has the potential to improve clinical outcomes for RCTs.

Assessment of the severity of curly toe.

BACKGROUND: Curly/underlapping toe involves flexion, adduction, and varus deformity of the interphalangeal joints. There are no previous reports showing the relationship between physical examination and X-ray findings among patients with curly toe deformity. METHODS: We investigated the clinical findings of 116 consecutive patients associated with 239 underlapping toes. We compared the age and affected toes between patients whose deformities were pointed out at a pediatric medical examination (group 1) and those referred for medical treatment (group 2). The degree of curly toe deformity was graded by a physical examination and X-ray. RESULTS: The average age at presentation was 2.7 years. The affected toes were significantly different between groups 1 and 2 (p < .001). The morbidity of each toe differed significantly in group 2 (p < .005) but not in group 1. The correlation between the appearance grading and classification by X-ray was very strong using Spearman's rank correlation coefficient. The severity of curly toe was divided into mild in 104 toes, moderate in 105 toes, and severe in 17 toes. The methods of conservative treatment were observation only in 15 cases, manipulations in 30 cases, taping in 67 cases, and a brace in 9 cases. Surgery was performed in 8% of cases. CONCLUSION: Curly toe deformity of the third or fourth toes tend to be referred for medical treatment because of the abnormality. Our grading system using a physical examination and classification by X-ray was useful for assessing the severity of curly toe.

Forefoot Deformities in Patients with Rheumatoid Arthritis: Mid- to Long-Term Result of Joint-Preserving Surgery in Comparison with Resection Arthroplasty.

BACKGROUND: Joint-preserving surgery for the forefoot has been increasingly performed for rheumatoid arthritis (RA). We compared joint-preserving surgeries with resection arthroplasty for RA in the forefoot. METHODS: Forefoot surgeries were performed on 62 toes in 42 patients with RA (men: 2; women: 40) between 2002 and 2018. Three groups were compared: PP-31 toes treated with joint-preserving surgery involving the modified Mann method for the big toe and offset osteotomy for lesser toes, PR-15 toes treated with joint-preserving surgery for the big toe and resection arthroplasty for lesser toes, and RR-16 toes treated with resection arthroplasty for all the toes. RESULTS: The PP group had significantly higher mean scores on a scale for RA in the foot and ankle at the latest follow-up than the RR group (86 vs. 75 points; p < 0.05). Hallux valgus (angle > 20°) of the big toe at the latest follow-up recurred in 10 (32%), 9 (60%), and 16 (100%) patients in the PP, PR, and RR groups, respectively. A revision surgery was performed in one patient each in the PP and PR groups. CONCLUSIONS: Joint-preserving surgery is superior to resection arthroplasty in preventing function loss and the recurrence of hallux valgus.

Assessing an alpha-defensin lateral flow device for diagnosing septic arthritis: reporting on a false-negative case and a false-positive case.

Alpha-defensin (αD), an antimicrobial peptide released by neutrophils in response to bacterial pathogens, was proposed as a novel diagnostic biomarker in synovial fluid. Several reports have shown that αD can serve as a reliable biomarker in the diagnosis of periprosthetic joint infection (PJI). We assessed whether αD could also serve to diagnosis of septic arthritis, a similarly difficult to diagnose PJI. To our knowledge, besides PJI, few reports exist assessing the utility of αD for septic arthritis. We have attempted to diagnose several cases of suspected septic arthritis using the Synovasure® αD detection lateral flow device. We report a false-positive case and a false-negative case. The false-negative case we experienced was caused by Staphylococcus capitis, which is coagulase-negative, and possibly represents a low virulence micro-organism infection. The false-positive case was ultimately diagnosed as seronegative rheumatoid arthritis and possessed calcium pyrophosphate depositions. False positives have been suggested to occur in conditions where neutrophils are mobilised. As for PJI, in cases where diagnosis is difficult, αD can be an additional diagnostic indicator. However, making a definitive diagnosis using the αD lateral flow device alone was found to be difficult. The utility of αD in assessing septic arthritis is inconclusive; therefore, larger prospective clinical studies should be considered for a better assessment.

Homeostatic and pathogenic roles of GM3 ganglioside molecular species in TLR4 signaling in obesity.

Innate immune signaling via TLR4 plays critical roles in pathogenesis of metabolic disorders, but the contribution of different lipid species to metabolic disorders and inflammatory diseases is less clear. GM3 ganglioside in human serum is composed of a variety of fatty acids, including long-chain (LCFA) and very-long-chain (VLCFA). Analysis of circulating levels of human serum GM3 species from patients at different stages of insulin resistance and chronic inflammation reveals that levels of VLCFA-GM3 increase significantly in metabolic disorders, while LCFA-GM3 serum levels decrease. Specific GM3 species also correlates with disease symptoms. VLCFA-GM3 levels increase in the adipose tissue of obese mice, and this is blocked in TLR4-mutant mice. In cultured monocytes, GM3 by itself has no effect on TLR4 activation; however, VLCFA-GM3 synergistically and selectively enhances TLR4 activation by LPS/HMGB1, while LCFA-GM3 and unsaturated VLCFA-GM3 suppresses TLR4 activation. GM3 interacts with the extracellular region of TLR4/MD2 complex to modulate dimerization/oligomerization. Ligand-molecular docking analysis supports that VLCFA-GM3 and LCFA-GM3 act as agonist and antagonist of TLR4 activity, respectively, by differentially binding to the hydrophobic pocket of MD2. Our findings suggest that VLCFA-GM3 is a risk factor for TLR4-mediated disease progression.

Characterization of a novel glycolipid with a difucosylated H-antigen in human blood group O erythrocytes with monoclonal antibody HMMC-1 and its detection in human uterine cervical carcinoma tissues.

Humanized monoclonal antibody HMMC-1 established by immunizing transchromosomal mice with a human uterine endometrial cancer cell line has been found to react with the H-antigen carried on core l O-glycans through cotransfection of glycosyltransferases for O-glycans and inhibition of antibody-binding with synthetic oligosaccharides. However, direct binding analysis of an antibody against glycosphingolipids from human erythrocytes with different ABO blood groups revealed that it was able to bind selectively with polar glycolipids in blood group O, but not blood group A, B and AB erythrocytes. Unexpectedly, typical monofucosylated H-glycolipids, IV2Fucα-nLc4Cer and VI2Fucα-nLc6Cer, which are the precursors for A and B-glycolipids, and were present not only in blood group O, but also A, B and AB-erythrocytes, were not the antigens for the HMMC-1 antibody. The antigen comprised less than 0.001% of the total glycolipids in blood group O-erythrocytes, and was purified by conventional silica gel column chromatography. Structural determination by permethylation, GC-MS, and ESI-TOFMS demonstrated that the structure was a novel glycolipid with a difucosylated H-antigen, Fucα1-2Galß1-4GlcNAcß1-3Gal(2-1αFuc)ß1-4GlcNAcß1-3Galß1-4GlcNAcß1-3Galß1-4Glcß1-1'Cer, VI2,VIII2(Fucα)2-nLc8Cer, whose terminal difucosylated structure was the epitope of the HMMC-1 antibody. The HMMC-1 glycolipid was detected in five out of 29 tissues from patients suffering from uterine cervical carcinomas, irrespective of their ABO-blood groups.

Effects of Maternal Flaxseed Supplementation on Female Offspring of Diabetic Rats in Serum Concentration of Glucose, Insulin, and Thyroid Hormones.

Objective: This study aimed to evaluate the effect of maternal consumption of flaxseed flour and oil on serum concentrations of glucose, insulin, and thyroid hormones of the adult female offspring of diabetic rats. Methods: Wistar rats were induced to diabetes by a high-fat diet (60%) and streptozotocin (35 mg/kg). Rats were mated and once pregnancy was confirmed, were divided into the following groups: Control Group (CG): casein-based diet; High-fat Group (HG): high-fat diet (49%); High-fat Flaxseed Group (HFG): high-fat diet supplemented with 25% flaxseed flour; High-fat Flaxseed Oil group (HOG): high-fat diet, where soya oil was replaced with flaxseed oil. After weaning, female pups (n = 6) from each group were separated, received a commercial rat diet and were sacrificed after 180 days. Serum insulin concentrations were determined by ELISA, the levels of triiodothyronine (T3), thyroxine (T4) and thyroid-stimulating hormone (TSH) were determined by chemiluminescence. Results: There was a significant reduction in body weight at weaning in HG (-31%), HFG (-33%) and HOG (44%) compared to CG (p = 0.002), which became similar by the end of 180 days. Blood glucose levels were reduced in HFG (-10%, p = 0.044) when compared to CG, and there was no significant difference between groups in relation to insulin, T3, T4, and TSH after 180 days. Conclusions: Maternal severe hyperglycemia during pregnancy and lactation resulted in a microsomal offspring. Maternal consumption of flaxseed reduces blood glucose levels in adult offspring without significant effects on insulin levels and thyroid hormones.

Overexpression of HexCer and LacCer containing 2-hydroxylated fatty acids in cholangiocarcinoma and the association of the increase of LacCer (d18:1-h23:0) with shorter survival of the patients.

Alteration of glycosphingolipid (GSL) synthesis is observed in many types of cancer. In this study, we have analyzed the expression of sphingolipids and GSLs in cholangiocarcinoma (CCA) tissues and adjacent normal liver tissues. Neutral lipids were extracted from tissue samples using mild-alkaline treatment method followed by TLC and LC-MS analysis. The expression of ceramides, hexosylceramides (HexCer), and lactosylceramides (LacCer) was altered in CCA tissues, 61.1% (11/18) of them showing an increase whereas 38.9% (7/18) showing a decrease, compared with the adjacent normal tissue. Cers and GSLs containing 2-hydroxylated fatty acids except one LacCer molecular species were overexpressed in CCA tissues, and the increase of LacCer (d18:1-h23:0) was correlated with shorter survival of CCA patients, suggesting the involvement of GSL synthesis and fatty acid hydroxylation in progression of CCA. Taken together, we have demonstrated in this study the increase of GSL synthesis and fatty hydroxylation in CCA, which probably be used as a target for CCA treatment.

Globo-series glycosphingolipids enhance Toll-like receptor 4-mediated inflammation and play a pathophysiological role in diabetic nephropathy.

Alteration of glycosphingolipid (GSL) expression plays key roles in the pathogenesis and pathophysiology of many important human diseases, including cancer, diabetes and glycosphingolipidosis. Inflammatory processes are involved in development and progression of diabetic nephropathy, a major complication of type 2 diabetes mellitus. GSLs are known to play roles in inflammatory responses in various diseases, and levels of renal GSLs are elevated in mouse models of diabetic nephropathy; however, little is known regarding the pathophysiological role of these GSLs in this disease process. We studied proinflammatory activity of GSLs in diabetic nephropathy using spontaneously diabetic mouse strain KK. Mice were fed a high-fat diet (HFD) (60% kcal from fat) or normal diet (ND) (4.6% kcal from fat) for a period of 8 wk. HFD-feeding resulted in quantitative and qualitative changes of renal globo-series GSLs (particularly Gb3Cer), upregulation of TNF-α, and induction of renal inflammation. Gb3Cer/Gb4Cer treatment enhanced inflammatory responses via TLR4 in TLR4/MD-2 complex expressing cells, including HEK293T, mouse bone marrow-derived macrophages (BMDMs) and human monocytes. Our findings suggest that HFD-induced increase of Gb3Cer/Gb4Cer positively modulate TLR4-mediated inflammatory response, and that such GSLs play an important pathophysiological role in diabetic nephropathy.

Abnormal immunolabelling of SMAD4 in cell block specimens to distinguish malignant and benign pancreatic cells.

BACKGROUND: Accurate diagnosis of malignant and benign pancreatic lesions can be challenging, especially with endoscopic ultrasound-guided fine needle aspiration (EUS-FNA) samples that are small and/or degraded. In the present study, we determined how to best evaluate abnormal SMAD4 expression by immunohistochemical staining on cell block specimens from EUS-FNA samples. RESULTS: In surgically resected pancreas, when abnormal SMAD4 immunolabelling was evaluated as negative SMAD4 expression, the sensitivity was low (33%), but when it was evaluated as decreased SMAD4 expression, the sensitivity improved (53%). Specificity and positive predictive value were high for both evaluations. There were no false-positive cases. In cell block specimens, decreased SMAD4 expression showed 47% sensitivity and 72% specificity, while negative SMAD4 expression showed lower sensitivity (20%) and higher specificity (100%). Both evaluations in cell block specimens showed lower sensitivity and specificity compared to resected specimens. False-positive and -negative rates were higher for cell blocks than for resected specimens. CONCLUSIONS: Decreased SMAD4 immunolabelling provided improved sensitivity as compared to negative SMAD4 immunolabelling; therefore, it is important to compare SMAD4 expression in a sample to its expression in normal cells. Abnormal SMAD4 labelling showed low sensitivity and high specificity; therefore, SMAD4 staining using EUS-FNA samples might be helpful to detect malignancies that possess SMAD4 gene abnormalities.

The regulatory roles of glycosphingolipid-enriched lipid rafts in immune systems.

Lipid rafts formed by glycosphingolipids (GSLs) on cellular membranes play important roles in innate and adaptive immunity. Lactosylceramide (LacCer) forms lipid rafts on plasma and granular membranes of human neutrophils. These LacCer-enriched lipid rafts bind directly to pathogenic components, such as pathogenic fungi-derived ß-glucan and Mycobacteria-derived lipoarabinomannan via carbohydrate-carbohydrate interactions, and mediate innate immune responses to these pathogens. In contrast, a-series and o-series gangliosides form distinct rafts on CD4+ and CD8+ T cell subsets, respectively, contributing to the respective functions of these cells and stimulating adaptive immune responses through T cell receptors. These findings suggest that gangliosides play indispensable roles in T cell selection and activation. This Review introduces the involvement of GSL-enriched lipid rafts in innate and adaptive immunity.

Mass Spectrometry of Gangliosides.

This chapter describes protocols for mass spectrometry (MS) applied to the characterization of ganglioside structures and the determination of ganglioside contents. Matrix-assisted laser desorption/ionization (MALDI) and electrospray ionization (ESI) are often used to ionize biological materials and this chapter covers three protocols for atmospheric pressure MALDI MS (AP-MALDI MS), liquid chromatography-ESI MS (LC-ESI MS), and LC-ESI MS with multiple reaction monitoring (MRM). Purified gangliosides were used in AP-MALDI MS analyses while crude preparations of gangliosides were subjected to LC-ESI MS and LC-ESI MS with MRM. The LC protocol includes conditions for both reversed-phase and normal-phase column chromatography.

Biology of GM3 Ganglioside.

Since the successful molecular cloning in 1998 of GM3 synthase (GM3S, ST3GAL5), the enzyme responsible for initiating biosynthesis of all complex gangliosides, the efforts of our research group have been focused on clarifying the physiological and pathological implications of gangliosides, particularly GM3. We have identified isoforms of GM3S proteins having distinctive lengths of N-terminal cytoplasmic tails, and found that these cytoplasmic tails define subcellular localization, stability, and in vivo activity of GM3S isoforms. Our studies of the molecular pathogenesis of type 2 diabetes, focused on interaction between insulin receptor and GM3 in membrane microdomains, led to a novel concept: type 2 diabetes and certain other lifestyle-related diseases are membrane microdomain disorders resulting from aberrant expression of gangliosides. This concept has enhanced our understanding of the pathophysiological roles of GM3 and related gangliosides in various diseases involving chronic inflammation, such as insulin resistance, leptin resistance, and T-cell function and immune disorders (e.g., allergic asthma). We also demonstrated an essential role of GM3 in murine and human auditory systems; a common pathological feature of GM3S deficiency is deafness. This is the first direct link reported between gangliosides and auditory functions.

Induction of ganglioside synthesis in Drosophila brain accelerates assembly of amyloid ß protein.

The assembly and deposition of amyloid ß protein (Aß) is a fundamental event during the early stages of Alzheimer's disease (AD) and cerebral amyloid angiopathy. A growing body of evidence indicates that gangliosides form a pathological platform for the generation of ganglioside-bound Aß, which facilitates the assembly of soluble Aßs; however, the molecular mechanisms underlying the binding of Aß to gangliosides in the brain remain unclear due to the lack of an in vivo system that may address this issue. In insects, including the fruit fly Drosophila melanogaster, gangliosides are not intrinsically present at a detectable level. We herein demonstrate that ganglioside expression is inducible in Drosophila via the expression of transgenes of ganglioside synthesis enzymes and the feeding of exogenous sialic acid, and also that the induction of ganglioside synthesis significantly accelerates Aß assembly in vivo. Our results support the hypothesis that gangliosides are responsible for Aß assembly in vivo and also provide an opportunity to develop a valuable model for basic research as well as a therapeutic strategy for AD.