Mitochondrial Networking Protects ��-Cells From Nutrient-Induced Apoptosis

OBJECTIVE

Previous studies have reported that β-cell mitochondria exist as discrete organelles that exhibit heterogeneous bioenergetic capacity. To date, networking activity, and its role in mediating β-cell mitochondrial morphology and function, remains unclear. In this article, we investigate β-cell mitochondrial fusion and fission in detail and report alterations in response to various combinations of nutrients.

RESEARCH DESIGN AND METHODS

Using matrix-targeted photoactivatable green fluorescent protein, mitochondria were tagged and tracked in β-cells within intact islets, as isolated cells and as cell lines, revealing frequent fusion and fission events. Manipulations of key mitochondrial dynamics proteins OPA1, DRP1, and Fis1 were tested for their role in β-cell mitochondrial morphology. The combined effects of free fatty acid and glucose on β-cell survival, function, and mitochondrial morphology were explored with relation to alterations in fusion and fission capacity.

RESULTS

β-Cell mitochondria are constantly involved in fusion and fission activity that underlies the overall morphology of the organelle. We find that networking activity among mitochondria is capable of distributing a localized green fluorescent protein signal throughout an isolated β-cell, a β-cell within an islet, and an INS1 cell. Under noxious conditions, we find that β-cell mitochondria become fragmented and lose their ability to undergo fusion. Interestingly, manipulations that shift the dynamic balance to favor fusion are able to prevent mitochondrial fragmentation, maintain mitochondrial dynamics, and prevent apoptosis.

CONCLUSIONS

These data suggest that alterations in mitochondrial fusion and fission play a critical role in nutrient-induced β-cell apoptosis and may be involved in the pathophysiology of type 2 diabetes.Mitochondria mediate β-cell responses to extracellular glucose by generating ATP and initiating a cascade of events culminating in the release of insulin. It is not surprising that β-cell mitochondria have become an important target for investigations into the etiology of type 2 diabetes. Mitochondria are highly dynamic organelles whose morphology is regulated by cycles of fusion and fission, collectively termed mitochondrial dynamics (1,2). Networks are formed when mitochondria undergo fusion events that cause the compartments of participating mitochondria to become continuous. As a result, the constituents of each network share solutes, metabolites, and proteins (3–5) as well as a transmembrane electrochemical gradient (1,6). The disruption of such networks has been shown to have a profound effect on the progression of cells to apoptosis, particularly in cases where reactive oxygen species (ROS) are involved (7). As such, mitochondrial networking is thought to be a potential defense mechanism allowing for the buffering of mitochondrial ROS and calcium overload (8,9).Chronically elevated levels of glucose and fatty acid are thought to contribute to the progression of type 2 diabetes by adversely affecting β-cells and thereby causing a deterioration in insulin secretion (10). In vivo, a reduction in insulin gene expression due to reduced Pdx-1 binding has been observed in rats perifused with glucose and intralipids (11,12). In addition, exposure to high levels of glucose and/or free fatty acid has been shown to affect β-cell viability by inducing mitochondrial apoptosis and has been linked to ROS-induced mitochondrial calcium overload and damage (13). Recent studies indicate that nutrient-induced ROS increases subcellular mitochondrial membrane potential (ΔΨmt) heterogeneity and fragmentation of the mitochondrial architecture (14,15). These findings suggest that mitochondrial fragmentation-defragmentation might play a role in the effects of noxious stimuli. Although the functional significance of these changes has not been studied in β-cells, studies of mitochondrial morphology in other cells have demonstrated that the ability of mitochondria to form networks influences both ROS and calcium handling (7–9).Previous studies have reported that β-cell mitochondria form less elaborate network structures, compared with COS cells for example, and raise doubts on the existence of mitochondrial networking in these cells. Until now, technologies for examining and quantifying the ability of mitochondria to undergo fusion and fission were unavailable.In this work, we show that the densely packed appearance of mitochondria in the β-cell represents the existence of multiple juxtaposed units that do not share continuous matrix lumen but do go through frequent fusion and fission events. We further demonstrate that mitochondrial dynamics are disrupted by exposure to the combination of high fat and glucose, gradually leading to the arrest of fusion activity and complete fragmentation of the mitochondrial architecture. Inhibiting mitochondrial fission preserved mitochondrial morphology and dynamics and prevented β-cell apoptosis.     

Subacromial injection of autologous platelet-rich plasma versus corticosteroid for the treatment of symptomatic partial rotator cuff tears

Objective

Rotator cuff tears are one of the most common causes of chronic shoulder pain and disability. They significantly affect the quality of life. Reduced pain and improved function are the goals of conventional therapy, which includes relative rest, pain therapy, physical therapy, corticosteroid injections and surgical intervention. Tendons have a relative avascular nature; hence, their regenerative potential is limited. There is some clinical evidence that the application of autologous platelets may help to revascularize the area of injury in rotator cuff pathologies.

Patients and methods

This prospective randomized controlled study was done to evaluate the results of subacromial injection of platelet-rich plasma (PRP) versus corticosteroid injection therapy in 40 patients with symptomatic partial rotator cuff tears. All patients were assessed before injection, 6 weeks, 3 and 6 months after injection, using the American Shoulder and Elbow Surgeons Standardized Shoulder Assessment Form (ASES), the Constant–Murley Score (CMS), the Simple Shoulder Test (SST) and a Visual Analog Scale (VAS) for pain. An MRI was performed before and 6 months after the injection for all the included patients and was graded on 0–5 scale.

Results

Both injection groups showed statistically significantly better clinical outcomes over time compared with those before injection. There was a statistically significant difference between RPP group and corticosteroid group 12 weeks after injection, regarding VAS, ASES, CMS and SST in favor of the RPP group. MRI showed an overall slight nonsignificant improvement in grades of tendinopathy/tear in both groups, however, without statistically significant differences between the two groups.

Conclusion

PRP injections showed earlier better results as compared to corticosteroid injections, although statistically significant better results after 6 months could not be found. Therefore, subacromial RPP injection could be considered as a good alternative to corticosteroid injection, especially in patients with a contraindication to corticosteroid administration.

Level of evidence

II.

     

Comparison of bioengineered human bone construct from four sources of osteogenic cells

Osteoprogenitor cells have been reported to be present in periosteum, cancellous and cortical bone, and bone marrow; but no attempt to identify the best cell source for bone tissue engineering has yet been reported. In this study, we aimed to investigate the growth and differentiation pattern of cells derived from these four sources in terms of cell doubling time and expression of osteoblast-specific markers in both monolayer cells and three-dimensional cell constructs in vitro. In parallel, human plasma derived-fibrin was evaluated for use as biomaterial when forming three-dimensional bone constructs. Our findings showed osteoprogenitor cells derived from periosteum to be most proliferative followed by cortical bone, cancellous bone, and then bone marrow aspirate. Bone-forming activity was observed in constructs formed with cells derived from periosteum, whereas calcium deposition was seen throughout the constructs formed with cells derived from cancellous and cortical bones. Although no mineralization activity was seen in constructs formed with osteoprogenitor cells derived from bone marrow, well-organized lacunae as would appear in the early phase of bone reconstruction were noted. Scanning electron microscopy evaluation showed cell proliferation throughout the fibrin matrix, suggesting the possible application of human fibrin as the bioengineered tissue scaffold at non-load-bearing sites.     

Intestinal lymphangiectasia in children: A favorable response to dietary modifications

Intestinal lymphangiectasia (IL) is a rare disease characterized by dilatation of intestinal lymphatics. It can be classified as primary or secondary according to the underlying etiology. The clinical presentations of IL are pitting edema, chylous ascites, pleural effusion, acute appendicitis, diarrhea, lymphocytopenia, malabsorption, and intestinal obstruction. The diagnosis is made by intestinal endoscopy and biopsies. Dietary modification is the mainstay in the management of IL with a variable response. Here we report 2 patients with IL in Bahrain who showed positive response to dietary modification.Intestinal lymphangiectasia (IL) is a rare1-4 benign disease characterized by focal or diffuse dilation of the mucosal, submucosal, and subserosal lymphatics.2,5 In addition to being an important cause of protein losing enteropathy (PLE),6 IL is frequently associated with extraintestinal lymphatic abnormalities.5 Depending on the underlying pathology IL can be classified as primary or secondary disease.1,2,4,5 Primary IL (PIL) probably represents a congenital disorder of mesenteric lymphatics.1,3 The IL can be secondary to diseases like constrictive pericarditis, lymphoma, sarcoidosis, and scleroderma.1 A secondary disorder should always be ruled out before labeling IL as primary, this is by testing for proteinuria, rheumatic, neoplastic, and parasitic infection.1,3 Recently, a functional form of PIL with typical endoscopic and pathological findings but without clinical symptoms has been reported.3 The clinical presentations of IL are pitting edema, chylous ascites, pleural effusion, acute appendicitis, diarrhea, lymphocytopenia, malabsorption, and intestinal obstruction.1,2,4 Palliative treatment with lifelong dietary modification is the most effective and widely prescribed therapy.6 Limiting the dietary fat intake reduces chyle flow and therefore, protein loss.1 Once protein level is within the normal range, recurrence of enteric protein loss can be prevented by total parenteral nutrition (TPN) and medium chain triglycerides (MCT).1 In cases of secondary IL, treating the underlying primary disorder may be curative.2 Although the therapeutic approach for this disorder have gained a lot of attention lately, few studies have considered the therapeutic effects, nutritional condition, and long-term results in PIL patients.4 Here, we report 2 patients with PIL who were diagnosed by endoscopy and biopsy, and showed positive response to dietary modifications. We present these particular cases to highlight the effect of dietary modifications on the clinical status of patients with IL.     

Hyperlipidemia in Saudi Arabia

OBJECTIVE: To determine the prevalence of hyperlipidemia among Saudis of both genders in rural and urban communities. METHODS: Selected Saudis in the age group of 30-70 years were studied over a 5-year period between 1995 and 2000 in Saudi Arabia. Data were obtained from history, physical examination, and analysis of fasting plasma lipids. The data were analyzed to classify individuals with hypercholesterolemia (HC) (total cholesterol > or =5.2 mmol/l), and hypertriglyceridemia (HT) (total triglycerides > or =1.69 mmol/l). Logistic regression analysis was performed to provide a risk assessment model and correlation with other coronary artery disease (CAD) risk factors. RESULTS: The number of study samples included in the final analysis was 16,819. The prevalence of HC was 54% with mean cholesterol level of 5.4+/-1.52 mmol/l. Prevalence of HC among males was 54.9% and 53.2% for females, while 53.4% among urban Saudis and 55.3% for rural Saudis. Hypertriglycemia prevalence was 40.3% with mean triglycerides level of 1.8+/-1.29 mmol/l. Males had statistically significant higher HT prevalence of 47.6% compared to 33.7% in females (p<0.0001). CONCLUSION: Hyperlipedimia is reaching higher prevalence rates in KSA. This finding may suggest that CAD will soon be a major health problem. Reduction in obesity by adopting healthier eating habits, and increasing physical activity are of considerable importance to our community.     

Level IIb lymph nodes metastasis in elective supraomohyoid neck dissection for oral cavity squamous cell carcinoma: a molecular-based study

OBJECTIVES: To identify the incidence of level IIb lymph nodes metastasis in elective supraomohyoid neck dissection (SOHND) as a treatment for patients with squamous cell carcinoma (SCC) of the oral cavity. STUDY DESIGN: Prospective analysis of a case series. METHODS: Forty-eight patients with SCC of the oral cavity and with no palpable lymph nodes at the neck who underwent an elective SOHND were prospectively studied. The incidence of micrometastasis to level IIb lymph nodes after performing elective SOHND was evaluated by pathologic examination and molecular analysis. RESULTS: Of the 48 patients, 15 (31%) by pathologic analysis and 22 (46%) by molecular analysis had lymph nodes positive for metastatic SCC. By molecular analysis, 5 (10%) of the 48 patients had involvement of level IIb lymph nodes. All patients with metastasis to level IIb lymph nodes have their primary lesions in the tongue and constituted 22% of patients with tongue lesions. There was no instance of isolated metastasis to level IIb lymph nodes without involvement of other nodes in the SOHND specimens. CONCLUSIONS: In this study, level IIb lymph node metastasis was only found in association with tongue carcinoma. Although this region may be preserved in elective SOHND in patients with SCC of the oral cavity, it should be included whenever the tongue is the primary site.     

A STUDY COMPARING CHEMICAL PEELING USING MODIFIED JESSNER'S SOLUTION AND 15%TRICHLOROACETIC ACID VERSUS 15% TRICHLOROACETIC ACID IN THE TREATMENT OF MELASMA

Background:

Melasma is a symmetric progressive hyperpigmentation of the facial skin that occurs in all races but has a predilection for darker skin phenotypes. Depigmenting agents, laser and chemical peeling as classic Jessner''s solution, modified Jessner''s solution and trichloroacetic acid have been used alone and in combination in the treatment of melasma.

Objectives:

The aim of the study was to compare the therapeutic effect of combined 15% Trichloroacetic acid (TCA) and modified Jessner''s solution with 15% TCA on melasma.

Materials and Methods:

Twenty married females with melasma (epidermal type), with a mean age of 38.25 years, were included in this study. All were of skin type III or IV. Fifteen percent TCA was applied to the whole face, with the exception of the left malar area to which combined TCA 15% and modified Jessner''s solution was applied.

Results:

Our results revealed statistically highly significant difference between MASI Score (Melasma Area and Severity Index) between the right malar area and the left malar area.

Conclusion:

Modified Jessner''s solution proved to be useful as an adjuvant treatment with TCA in the treatment of melasma, improving the results and minimizing postinflammatory hyperpigmentation.     

使用OCT评估中心性浆液性脉络膜视网膜病变患者脉络膜厚度的变化

目的:使用光谱域光学相干断层成像(SD-OCT)技术研究中心性浆液性脉络膜视网膜病变(CSCR)3mo后脉络膜厚度的变化。方法:前瞻性研究。共纳入60眼,20眼(平均年龄:33.65±5.24岁)典型急性单侧中心性浆液性脉络膜视网膜病变以及对侧正常眼,20眼为健康对照组。进行荧光素血管造影和OCT检查。测量中心凹下脉络膜厚度(SFCT),黄斑中心凹视网膜厚度(CMT),到中央凹和视网膜下液1000μm处颞部和鼻部。结果:在三个不同的位置,三组间的SFCT差异有统计学意义。中心性浆液性脉络膜视网膜病变眼中心凹下脉络膜厚度(372.40±34.39μm)在基线和随访3mo后均显著大于对侧正常眼(302.10±8.9μm)和对照组眼(279.80±14.49μm)。CSCR眼平均CMT为317±141.86μm,并且SFCT与CMT呈显著正相关。结论:不同部位脉络膜厚度的增加,以及被称为“厚脉络膜”的过度扩张和高渗透血管,似乎在包括中心性浆液性脉络膜视网膜病变在内的广泛疾病中起着重要作用。