Perilipin 2 Improves Insulin Sensitivity in Skeletal Muscle Despite Elevated Intramuscular Lipid Levels

Type 2 diabetes is characterized by excessive lipid storage in skeletal muscle. Excessive intramyocellular lipid (IMCL) storage exceeds intracellular needs and induces lipotoxic events, ultimately contributing to the development of insulin resistance. Lipid droplet (LD)–coating proteins may control proper lipid storage in skeletal muscle. Perilipin 2 (PLIN2/adipose differentiation–related protein [ADRP]) is one of the most abundantly expressed LD-coating proteins in skeletal muscle. Here we examined the role of PLIN2 in myocellular lipid handling and insulin sensitivity by investigating the effects of in vitro PLIN2 knockdown and in vitro and in vivo overexpression. PLIN2 knockdown decreased LD formation and triacylglycerol (TAG) storage, marginally increased fatty-acid (FA) oxidation, and increased incorporation of palmitate into diacylglycerols and phospholipids. PLIN2 overexpression in vitro increased intramyocellular TAG storage paralleled with improved insulin sensitivity. In vivo muscle-specific PLIN2 overexpression resulted in increased LD accumulation and blunted the high-fat diet–induced increase in protein content of the subunits of the oxidative phosphorylation (OXPHOS) chain. Diacylglycerol levels were unchanged, whereas ceramide levels were increased. Despite the increased IMCL accumulation, PLIN2 overexpression improved skeletal muscle insulin sensitivity. We conclude that PLIN2 is essential for lipid storage in skeletal muscle by enhancing the partitioning of excess FAs toward TAG storage in LDs, thereby blunting lipotoxicity-associated insulin resistance.Lipid droplets (LDs) serve an essential function in eukaryotic cells. Accordingly, intracellular lipid levels need to be tightly controlled. Indeed, inappropriate intracellular lipid storage leads to impaired cellular function. In obesity, lipids will overflow into the circulation as a result of lack of storage capacity in adipose tissue, and, as a consequence, lipids may accumulate ectopically in tissues, including skeletal muscle (intramyocellular lipids [IMCLs]). This ectopic fat storage exceeds intracellular demand and may result in lipotoxic events, including the development of insulin resistance (1,2). Paradoxically, IMCL is increased in both endurance-trained athletes and type 2 diabetic patients (3,4), indicating that ectopic lipid accumulation per se does not induce insulin resistance.Thus far, explanations for this athlete’s paradox have focused on lipid turnover, oxidative capacity, and levels of lipid intermediates (5–8). Interestingly, one exercise session was shown to prevent lipid-induced insulin resistance by partitioning more fatty acids (FAs) toward triacylglycerol (TAG) synthesis in skeletal muscle (9). Therefore, increasing the depot for TAG storage might improve insulin sensitivity. Intracellular TAG is stored in LDs, which are increasingly recognized as dynamic organelles. They are composed of a neutral lipid core containing TAG, diacylglycerol (DAG), cholesterolesters, retinol esters, and free cholesterol (10) surrounded by a phospholipid monolayer (11) and a protein coat, composed of a variety of LD-coating proteins (12). Accumulating evidence suggests that LD-coating proteins mediate LD dynamics, including LD synthesis, growth and fusion, intracellular transport, organelle interactions, and breakdown and lipolysis (13,14).The best-characterized family of LD-coating proteins is the perilipin (PLIN) protein family, including PLIN1, PLIN2 (adipophilipin and adipose differentiation–related protein [ADRP]), PLIN3 (tail-interacting protein, 47 kDa [TIP47]), PLIN4 (adipocyte protein S3-12), and PLIN5 (OXPAT, lipid droplet storage protein 5 [LSDP5]). Whereas PLIN1 expression is restricted to adipose tissue, where it plays a crucial role in the control of storage and degradation of LDs (15,16), PLIN2 is expressed in several tissues, including liver, small intestine, and skeletal muscle (17,18). PLIN2 in skeletal muscle was previously shown to colocalize with IMCL (19). Interestingly, skeletal muscle Plin2 gene expression was shown to be lower in patients with type 2 diabetes versus obese control subjects (20). Furthermore, weight loss as well as metformin treatment, both resulting in lower IMCL levels (21,22), were demonstrated to increase skeletal muscle PLIN2 levels in parallel with improved insulin sensitivity (23). PLIN2 may be involved in the protection against lipotoxicity by facilitating efficient IMCL storage in the form of TAG. However, loss- and gain-of-function studies to characterize PLIN2 function in skeletal muscle, required to obtain more functional insight into the role of PLIN2 in muscle, have not been performed to date. Here, we aimed to examine the role of PLIN2 in myocellular fat accumulation, lipotoxicity, and insulin sensitivity.     

A Hospital-Based Work Support Intervention to Enhance the Return to Work of Cancer Patients: A Process Evaluation

Purpose To perform a process evaluation of a hospital-based work support intervention for cancer patients aimed at enhancing return to work and quality of life. The intervention involves the delivery of patient education and support at the hospital and involves the improvement of the communication between the treating physician and the occupational physician. In addition, the research team asked patient??s occupational physician to organise a meeting with the patient and the supervisor to make a concrete gradual return-to-work plan. Methods Eligible were cancer patients treated with curative intent and who have paid work. Data were collected from patients assigned to the intervention group (N?=?65) and from nurses who delivered the patient education and support at the hospital (N?=?4) by means of questionnaires, nurses?? reports, and checklists. Data were quantitatively and qualitatively analysed. Results A total of 47?% of all eligible patients participated. Nurses delivered the patient education and support in 85?% of the cases according to the protocol. In 100?% of the cases at least one letter was sent to the occupational physician. In 10?% of the cases the meeting with the patient, the occupational physician and the supervisor took place. Patients found the intervention in general very useful and nurses found the intervention feasible to deliver. Conclusions We found that a hospital- based work support intervention was easily accepted in usual psycho-oncological care but that it proved difficult to involve the occupational physician. Patients were highly satisfied and nurses found the intervention feasible.     

Identification and discrimination of voicing and place-of-articulation in developmental dyslexia

Problems in reading and spelling may arise from poor perception of speech sounds. To study the integrity of phonological access in children with developmental dyslexia (mean age 8 years, 9 months) as compared to two control groups of children (age-matched and matched on reading level), identification and discrimination functions of the features voicing and place-of-articulation were assessed. No differences were found between groups with respect to identification of place-of-articulation. With respect to identification of the voicing contrast, children with developmental dyslexia performed poorer than age-matched controls, but similar to reading-level controls. For the voicing as well as the place-of-articulation contrast, children with developmental dyslexia discriminated poorer than both control groups. This pattern of identification and discrimination performance is discussed relative to the multidimensionality of the speech perception system. The clinical relevance of these perception tasks could be demonstrated by significant negative correlations between performance on the perception tasks and reading and spelling ability. This provided additional support for a functional relation between speech perception and reading and spelling in developmental dyslexia.     

Coarticulation patterns in children with developmental apraxia of speech

The aim of this study was to enhance our insight into the underlying deficit in developmental apraxia of speech (DAS). In particular, the involvement of planning and/or programming of speech movements in context was tested by analysing coarticulatory cohesion. For this purpose, second formant frequency measurements were conducted in repetitions of nonsense utterances ([ CV]C=/s,x,b,d/; V=/i,a,u/), and compared across nine children with DAS, six normally speaking (NS) children and six adult women. The results showed both intra- and intersyllabic anticipatory coarticulation in NS children and adult women, in which the intersyllabic coarticulation was stronger in NS children than in adult women. The children with DAS showed more variability as compared to NS children, made, on average, less distinction between the vowels, and showed individually idiosyncratic coarticulation patterns. These results are discussed in the light of a delay as well as a deviance of speech development in children with DAS.     

Adenoviral transfer of murine oncostatin M elicits periosteal bone apposition in knee joints of mice,despite synovial inflammation and up-regulated expression of interleukin-6 and receptor activator of nuclear factor-kappa B ligand

Oncostatin M (OSM) has been described as a bone-remodeling factor either stimulating osteoblast activity or osteoclast formation in vitro. To elucidate the in vivo effect of OSM on bone remodeling, we injected an adenoviral vector encoding murine OSM in knee joints of mice. OSM strongly induced interleukin (IL)-6 gene expression, a known mediator of osteoclast development. We investigated the OSM effect in wild-type and IL-6-deficient mice and found a similar degree of OSM-induced joint inflammation. Within the first week of inflammation, the periosteum along the femur and tibia increased in cell number and stained positive for the osteoblast marker alkaline phosphatase. At these sites bone apposition occurred in both strains as demonstrated by Goldner and Von Kossa staining. In vitro OSM enhanced the effect of bone morphogenetic protein-2 on osteoblast differentiation. Immunohistochemistry demonstrated expression of receptor activator of nuclear factor-kappa B ligand (RANKL) and its receptor, receptor activator of nuclear factor-kappa B (RANK), in the periosteum but osteoclasts were not detected at sites of bone apposition. Induced mRNA expression for the receptor activator of nuclear factor-kappa B ligand inhibitor osteoprotegerin probably controlled osteoclast development during OSM overexpression. Our results show that OSM favors bone apposition at periosteal sites instead of resorption in vivo. This effect was not dependent on or inhibited by IL-6.     

ST-segment deviation on the admission electrocardiogram, treatment strategy, and outcome in non-ST-elevation acute coronary syndromes : A substudy of the Invasive versus Conservative Treatment in Unstable coronary Syndromes (ICTUS) Trial

Background

We assessed the prognostic significance of the presence of cumulative (∑) ST-segment deviation on the admission electrocardiogram (ECG) in patients with non-ST-elevation acute coronary syndrome and an elevated troponin T randomized to a selective invasive (SI) or an early invasive treatment strategy.

Methods

A 12-lead ECG obtained at admission was available for analysis from 1163 patients. The presence and magnitude of ST-segment deviation was measured in each lead, and absolute ST-segment deviation was summed. The effect of treatment strategy was assessed for patients with or without ∑ ST-segment deviation of at least 1 mm.

Results

The incidence of death or myocardial infarction (MI) by 1 year in patients with ∑ ST-segment deviation of at least 1 mm was 18.0% compared with 11.1% in patients with ∑ ST-segment deviation of less than 1 mm (P = .001). Among patients with ∑ ST-segment deviation of at least 1 mm, the incidence of death or MI was 21.9% in the early invasive group compared with 14.2% in SI group (P < .01). However, we observed a significantly higher rate of MI after hospital discharge among patients with ∑ ST-segment deviation of at least 1 mm randomized to SI who did not undergo angiography compared with patients who underwent angiography before discharge (10.9% vs 2.4%, P = .003). In a forward logistic regression analysis, the presence of ST-segment deviation was an independent predictor for failure of medical therapy (coronary angiography within 30 days after randomization in the SI group) (odds ratio, 1.56; 95% confidence interval, 1.12-2.18; P = .009).

Conclusion

Patients with non-ST-elevation acute coronary syndrome and an elevated troponin T and ∑ ST-segment deviation of at least 1 mm are at increased risk of death or MI, more often fail on medical therapy, and more often experience a spontaneous MI after discharge when angiography was not performed during initial hospitalization.     

Local interleukin‐12 gene transfer promotes conversion of an acute arthritis to a chronic destructive arthritis

Objective

To determine whether local overexpression of interleukin‐12 (IL‐12), a pleiotropic cytokine that promotes the development of naive T cells into Th1 cells, could aggravate murine streptococcal cell wall (SCW)‐induced arthritis, a model of acute arthritis.

Methods

C57BL/6 mice were injected intraarticularly with saline or with 10⁷ plaque‐forming units of control vector (Ad5del70‐3) or IL‐12 vector (AdmIL‐12.1) into the right knee joint 1 day before intraarticular injection of 25 μg of SCW fragments. The development of joint swelling, changes in chondrocyte proteoglycan (PG) synthesis, and joint destruction were examined thereafter.

Results

In normal joints, high levels of IL‐12 (20 ng/ml on day 1) could be detected after application of the AdmIL‐12.1 vector. After 14 days, expression of IL‐12 was still found locally, but IL‐12 alone did not induce protracted inflammation. Local expression of IL‐12, in combination with SCW, markedly aggravated SCW‐induced arthritis, as determined by enhanced joint swelling and prolonged inhibition of chondrocyte PG synthesis. Histologic examination on day 21 showed a chronic inflammatory process, with persistent cartilage PG depletion, cartilage erosion, and VDIPEN neoepitope expression (indicative of metalloproteinase activation). The mixture of IL‐12 with SCW fragments did not lead to a chronic destructive process in mice deficient for recombination‐activating gene 2, indicating the involvement of lymphocytes. In addition, systemic flare of smoldering SCW arthritis, produced by intravenous injection of SCW fragments, was only seen in the AdmIL‐12/SCW group.

Conclusion

These results indicate that local overexpression of IL‐12 promotes conversion of an acute arthritis to a chronic destructive immune‐mediated process, which is more susceptible to flares.