Ghrelin receptor agonist GHRP-2 prevents arthritis-induced increase in E3 ubiquitin-ligating enzymes MuRF1 and MAFbx gene expression in skeletal muscle

Time-Dependent Changes in Muscle IGF1-IGFBP5-PAPP System after Sciatic Denervation

Denervation-induced muscle atrophy is a frequent cause of skeletal muscle diseases. However, the role of the most important muscle growth factor, insulin-like growth factor (IGF-1), in this process is poorly understood. IGF-1 activity is controlled by six IGF-1 binding proteins (IGFBPs). In skeletal muscle, IGFBP-5 seems to have an important role in atrophic processes. Furthermore, pappalysins (PAPP-A) modulate muscle growth by increasing IGF-1 bioavailability through IGFBP cleavage. We aimed to study the time-dependent changes in the IGF1-IGFBP5-PAPP system and its regulators in gastrocnemius muscle after sciatic denervation. Gastrocnemius atrophy and overexpression of IGF-1 was observed from day 3 post-denervation. The proteolytic factors measured were elevated from day 1 post-denervation onwards. Expression of both IGFBP-5 and pappalysins were increased on days 1 and 3. Subsequently, on days 7 to 14 pappalysins returned to control levels while IGFBP-5 remained elevated. The ratio IGFBP-5/PAPP-A was correlated with the main proteolytic markers. All data suggest that the initial increase of pappalysins could facilitate the IGF-1 action on muscle growth, whereas their subsequent decrease could lead to further muscle wasting.

Potential Applications for Growth Hormone Secretagogues Treatment of Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) arises from neuronal death due to complex interactions of genetic, molecular, and environmental factors. Currently, only two drugs, riluzole and edaravone, have been approved to slow the progression of this disease. However, ghrelin and other ligands of the GHS-R1a receptor have demonstrated interesting neuroprotective activities that could be exploited in this pathology. Ghrelin, a 28-amino acid hormone, primarily synthesized and secreted by oxyntic cells in the stomach wall, binds to the pituitary GHS-R1a and stimulates GH secretion; in addition, ghrelin is endowed with multiple extra endocrine bioactivities. Native ghrelin requires esterification with octanoic acid for binding to the GHS-R1a receptor; however, this esterified form is very labile and represents less than 10% of circulating ghrelin. A large number of synthetic compounds, the growth hormone secretagogues (GHS) encompassing short peptides, peptoids, and non-peptidic moieties, are capable of mimicking several biological activities of ghrelin, including stimulation of GH release, appetite, and elevation of blood IGF-I levels. GHS have demonstrated neuroprotective and anticonvulsant effects in experimental models of pathologies both in vitro and in vivo. To illustrate, some GHS, currently under evaluation by regulatory agencies for the treatment of human cachexia, have a good safety profile and are safe for human use. Collectively, evidence suggests that ghrelin and cognate GHS may constitute potential therapies for ALS.

Clinical-Like Cryotherapy in Acute Knee Arthritis Protects Neuromuscular Junctions of Quadriceps and Reduces Joint Inflammation in Mice

Rheumatoid arthritis is an autoimmune and inflammatory disease that affects synovial joint tissues and skeletal muscle. Clinical-like cryotherapy benefits signs of joint inflammation in knee osteoarthritis after 60 days of anterior cruciate ligament transection surgery. However, it is unknown whether it also benefits acute knee arthritis (e.g., reduces inflammatory process and protects neuromuscular junction [NMJ] and muscle fibers). We aimed to analyze the effects of clinical-like cryotherapy on NMJ and quadriceps muscle fibers in a model of acute knee arthritis. Twenty-four male C57BL/6 mice (20 to 25 g) were randomly allocated into three groups: control (mice with no intervention), antigen-induced arthritis (AIA; mice sensitized and immunized with intra-articular [i.a.] injection of methylated bovine serum albumin [mBSA]), and AIA+cryotherapy (mice sensitized, immunized with i.a. injection of mBSA, and submitted to a clinical-like cryotherapy protocol). Twenty-one days after sensitization, arthritis was induced in immunized mice via i.a. injection of mBSA (100 μg/joint). Two clinical-like cryotherapy sessions (crushed ice pack for 20 min) were applied two hours apart. The first session was applied immediately after i.a. injection of mBSA. The quadriceps was removed two hours after the second clinical-like cryotherapy session for morphological analysis of muscle fibers (cross-sectional area), frequency distribution of muscle fiber area (%), and NMJ (area, perimeter, and maximum diameter). Gene expressions of mRNA involved in NMJ signaling (γ-nAChR, α1-nAChR, ε-nAChR, Agrin-MusK-Rapsyn, α-dystrobrevin, and utrophin) and atrophy (muscle RING-finger protein-1 and Atrogin-1) pathways were analyzed. Inflammatory signs were assessed in knee joint (swelling, articular surface temperature, and neutrophil migration in synovial fluid). Regarding morphological analysis of muscle fibers, 180 to 270 and >270 μm2 classes were higher in the AIA+cryotherapy than the AIA group. Area, perimeter, and maximum diameter of NMJ also increased in the AIA+cryotherapy compared with the control group. Agrin mRNA expression increased in the AIA+cryotherapy compared with the control and AIA groups. In the atrophy pathway, Atrogin-1 increased compared with the control and AIA groups. The AIA+cryotherapy group reduced knee swelling and neutrophil migration compared with the AIA group. In conclusion, clinical-like cryotherapy increased Agrin expression, contributing to NMJ maintenance and increased Atrogin-1 expression, thus protecting NMJ and muscle fiber. Furthermore, clinical-like cryotherapy reduced inflammatory signs (swelling and neutrophil migration) of acute knee arthritis.

Sesquiterpene lactones; Damsin and neoambrosin suppress cytokine-mediated inflammation in complete Freund's adjuvant rat model via shutting Akt/ERK1/2/STAT3 signaling

ETHNOPHARMACOLOGIAL RELEVANCE

Although Damsissa (Ambrosia maritima) is traditionally used as anti-inflammatory and diuretic, the biological activity and mechanism of action of its major constituents are to be elucidated.

AIM

to decipher the anti-arthritic potential of damsin (DMS) and neoambrosin (NMS) and to unfold their molecular signaling in complete Freund's adjuvant (CFA)-induced arthritis model.

MATERIALS AND METHODS

the right hind paw was inoculated with CFA (0.1 ml) at day 0 and 7 while treatments were started from the 14^th day and continued for 2 weeks. Rats were randomly assigned into 4 groups; normal group (NRML), CFA-induced arthritis group, CFA-induced arthritis treated with DMS and NMS (10 mg/kg/day) as 3^rd and 4^th group; respectively.

RESULTS

Throughout experimental period, treatments ameliorated the increase of paw volume, knee joint diameter and nociception tests as reflected in open field arena. Also, DSM and NMS suppressed phosphorylation of Akt, STAT-3, ERK1/2 which was further mirrored by inactivation of GSK3β and downregulation of MCP-1 together with CCN1 and NF-kβ in hind paw tissue. Concomitantly, inflammation markers; TNF-α, IL-6, -12 were lowered as confirmed microscopically during examination of hind paw tissue.

CONCLUSION

DSM and NMS-induced suppression of NF-kβ subdues clinical features of RA most probably through repression of Akt/ERK1/2/STAT3 pathway. Therefore, DMS and NMS can serve as safe and effective treatment for rheumatoid arthritis, one of the most disabling chronic, inflammatory and painful autoimmune disease.

Beneficial Effects of a Mixture of Algae and Extra Virgin Olive Oils on the Age-Induced Alterations of Rodent Skeletal Muscle: Role of HDAC-4

Aging is associated with a progressive decline in skeletal muscle mass, strength and function (sarcopenia). We have investigated whether a mixture of algae oil (25%) and extra virgin olive oil (75%) could exert beneficial effects on sarcopenia. Young (3 months) and old (24 months) male Wistar rats were treated with vehicle or with the oil mixture (OM) (2.5 mL/kg) for 21 days. Aging decreased gastrocnemius weight, total protein, and myosin heavy chain mRNA. Treatment with the OM prevented these effects. Concomitantly, OM administration decreased the inflammatory state in muscle; it prevented the increase of pro-inflammatory interleukin-6 (IL-6) and the decrease in anti-inflammatory interleukin-10 (IL-10) in aged rats. The OM was not able to prevent aging-induced alterations in either the insulin-like growth factor I/protein kinase B (IGF-I/Akt) pathway or in the increased expression of atrogenes in the gastrocnemius. However, the OM prevented decreased autophagy activity (ratio protein 1A/1B-light chain 3 (LC3b) II/I) induced by aging and increased expression of factors related with muscle senescence such as histone deacetylase 4 (HDAC-4), myogenin, and IGF-I binding protein 5 (IGFBP-5). These data suggest that the beneficial effects of the OM on muscle can be secondary to its anti-inflammatory effect and to the normalization of HDAC-4 and myogenin levels, making this treatment an alternative therapeutic tool for sarcopenia.

Lipid accumulation and mitochondrial abnormalities are associated with fiber atrophy in the skeletal muscle of rats with collagen-induced arthritis

Rheumatoid arthritis (RA) has a negative impact on muscle mass, and reduces patient's mobility and autonomy. Furthermore, RA is associated with metabolic comorbidities, notably in lipid homeostasis by unknown mechanisms. To understand the links between the loss in muscle mass and the metabolic abnormalities, arthritis was induced in male Sprague Dawley rats (n = 11) using the collagen-induced arthritis model. Rats immunized with bovine type II collagen were compared to a control group of animals (n = 11) injected with acetic acid and complete Freund's adjuvant. The clinical severity of the ensuing arthritis was evaluated weekly by a semi-quantitative score. Skeletal muscles from the hind limb were used for the histological analysis and exploration of mitochondrial activity, lipid accumulation, metabolism and regenerative capacities. A significant atrophy in tibialis anterior muscle fibers was observed in the arthritic rats despite a non-significant decrease in the weight of the muscles. Despite moderate inflammation, accumulation of triglycerides (P < 0.05), reduced mitochondrial DNA copy number (P < 0.05) and non-significant dysfunction in mitochondrial cytochrome c oxidase activity were found in the gastrocnemius muscle. Concomitantly, our results suggested an activation of the muscle specific E3 ubiquitin ligases MuRF-1 and MAFbx. Finally, the adipose tissue from the arthritic rats exhibited decreased PPARγ mRNA suggesting reduced adipogenic capacities. In conclusion, the reduced adipose tissue adipogenic capacity and skeletal muscle mitochondrial capacity are probably involved in the activation of protein catabolism, inhibition of myogenesis, accumulation of lipids and fiber atrophy in the skeletal muscle during RA.

Anti-Inflammatory, Anti-Arthritic and Anti-Nociceptive Activities of Nigella sativa Oil in a Rat Model of Arthritis

This study investigated the preventive efficacy of the crude oil extracted from Nigella sativa seeds in a rat model of arthritis induced by using complete Freund’s adjuvant (CFA). Nigella sativa oil at 1.82 mL/kg or 0.91 mL/kg (corresponding to 1596 and 798 mg/kg, respectively) was orally administered for 25 days from the day of immunization. One immunized group was treated orally with indomethacin (3 mg/kg) as a reference drug. Body weight growth rate, paw swelling, arthritis score, mechanical allodynia, locomotor activity and anxiety-like behavior were observed, and the levels of Interleukin 6 (IL-6), C-reactive protein, albumin and total cholesterol in plasma were measured on days 15 and 25. Nigella sativa oil showed anti-inflammatory, anti-arthritic and anti-nociceptive activities that were significant as compared to untreated arthritic rats but less than indomethacin. These results indicated that Nigella sativa oil significantly attenuated adjuvant-arthritis in rats and the higher dose (1.82 mL/kg) prevented the development of arthritis with an inhibition of 56%.

Effects of eldecalcitol and ibandronate on secondary osteoporosis and muscle wasting in rats with adjuvant-induced arthritis

Objectives

Rheumatoid arthritis (RA) is characterized by chronic inflammation of the synovium, progressive erosion of the articular cartilage, and joint destruction. RA also causes secondary osteoporosis and muscle wasting. We investigated the effects of ibandronate (IBN), a bisphosphonate; eldecalcitol (ELD), an active vitamin D3 derivative; and combination treatment with both agents on secondary osteoporosis and muscle wasting using adjuvant-induced arthritis rats.

Methods

Arthritis was induced in 8-week-old male Lewis rats. Rats were randomized into 4 treatment groups and an untreated normal control group: IBN (subcutaneously, once every 2 weeks, 10 μg/kg), ELD (orally, once daily, 30 ng/kg/day), IBN + ELD, vehicle, and control. Paw thickness measurements were performed for evaluation of arthritis. The femur was scanned using dual-energy X-ray absorptiometry. Cross-sectional areas of left tibialis and anterior muscle fibers and the expression of MuRF1, atrogin-1, MyoD, and myogenin in the gastrocnemius muscle were measured to evaluate muscle wasting.

Results

IBN and/or ELD increased bone mineral density (BMD) in the femur. In addition, there was an additive effect of combination treatment compared with single treatments for BMD. However, IBN and/or ELD did not inhibit muscle wasting in adjuvant-induced arthritis rats.

Conclusions

Combination treatment with IBN and ELD may be effective for secondary osteoporosis associated with RA. Other treatments are necessary for muscle wasting associated with RA. Studies in humans are needed to confirm these findings.

Enhanced activity of hormone sensitive lipase (HSL) in mesenteric but not epididymal fat correlates with higher production of epinephrine in mesenteric adipocytes in rat model of cachectic rheumatoid arthritis

Cachectic rheumatoid arthritis, the less frequent form of the disease, is associated with loss of fat mass and often more severe course of the disease. Its experimental model represents rat adjuvant arthritis (AA) characterized by edema, lack of appetite, sharp body weight and fat loss. As individual fat depots display functional differences, here we studied lipolytic activity and sensitivity to lipolytic stimuli of nodeless epididymal fat (eWAT) and perinodal mesenteric fat (mWAT) depots at the peak of AA. We also examined changes in catecholamine and cytokine levels involved in lipolysis in plasma and/or isolated adipocytes from both WATs to identify the contribution of local, adipocyte-based processes and/or systemic events to adiposity loss in cachectic rheumatoid arthritis. AA was induced to male Lewis rats by complete Freund's adjuvant. Groups of ad libitum-fed and pair-fed controls were used to distinguish the effects of food restriction from inflammation-induced cachexia. Adipose triglyceride lipase (ATGL), hormone-sensitive lipase (HSL) and its phosphorylated form (pHSL) were analyzed by western blot. CRP and catecholamine levels in plasma or adipocyte lysates were determined using ELISA kits. Cytokine-induced neutrophil chemoattractant-1 (CINC-1/CXCL1), monocyte chemoattractant protein-1 (MCP-1/CCL2), IL-1β, IL-6, IL-10 and leptin in adipocyte lysate were analyzed by quantitative protein microarray. Plasma glycerol and FFA were measured spectrophotometrically. AA rats developed severe cachexia, with lower adiposity in mWAT compared to normal and pair-fed controls, whereas in eWAT the adiposity was similarly reduced in AA and pair-fed groups. ATGL levels in both WATs were not affected by AA or pair feeding. AA upregulated levels of HSL, pHSL and pHSL/HSL ratio in mWAT, whereas none of these parameters has changed in eWAT of AA rats or in either WATs of pair-fed rats. In AA rats plasma glycerol was elevated, whereas FFA concentration was reduced. Plasma norepinephrine and epinephrine were increased in AA compared with both groups of controls. In eWAT adipocytes, AA but not pair feeding, upregulated norepinephrine levels. In mWAT adipocytes, AA rats showed higher epinephrine levels than pair-fed controls. Leptin levels in both WATs were depleted in AA animals in accordance with body weight loss. None of the measured cytokines in eWAT and mWAT was enhanced. Our results demonstrate augmented lipolytic activity in mWAT and not eWAT during cachectic arthritis. The adipocyte-derived cytokines do not seem to contribute to activated lipolysis. We first demonstrated enhanced presence of norepinephrine in perinodal adipocytes that may contribute to the regulation of local lipolytic activity by auto/paracrine fashion and thus provide independent fuel supply to activated lymph nodes.

The melanocortin receptor type 3 agonist d-Trp(8)-γMSH decreases inflammation and muscle wasting in arthritic rats

BACKGROUND

Chronic inflammatory diseases induce cachexia that increases mortality and morbidity of the illness. Adjuvant-induced arthritis is an experimental model of rheumatoid arthritis that is associated with body weight loss and muscle wasting. Alpha-melanocyte stimulating hormone has an anti-inflammatory effect in arthritic rats and decreases muscle wasting. The aim of this work was to elucidate whether the anti-cachectic action of alpha-melanocyte stimulating hormone is mediated by the melanocortin receptor type 3 pathway.

METHODS

Arthritis was induced in male Wistar rats by intradermal injection of Freund's adjuvant, and 6 days afterwards, arthritic rats were injected with the selective melanocortin receptor type 3 agonist d-Trp(8)-gammaMSH ( d-Trp(8)-γMSH) 500 µg/kg subcutaneously. or saline twice a day, for 10 days.

RESULTS

d-Trp(8)-γMSH decreased the external signs of inflammation and body weight loss, but it was not able to modify the anorexigenic effect of arthritis or the increase in hypothalamic cyclooxygenase-2 (COX-2) expression. In contrast, d-Trp(8)-γMSH prevented arthritis-induced increase in hypothalamic IL-1β and serum corticosterone levels and the decrease in serum IGF-I levels. d-Trp(8)-γMSH treatment also prevented arthritis-induced NF-kB(p65) phosphorylation and tumour necrosis factor-α mRNA increase in the gastrocnemius. d-Trp(8)-γMSH administration to arthritic rats increased gastrocnemius mass, its cross-sectional area, and mean fast fibre area. Those effects of d-Trp(8)-γMSH were associated with a decreased expression of atrogin-1 and muscle ring-finger protein-1 in the gastrocnemius. In rats treated with saline, arthritis increased the expression of autophagy marker genes LC3b, Bnip-3, and Gabarap1 as well as the conversion of LC3b I to LC3b II by lipidation in the gastrocnemius. d-Trp(8)-γMSH decreased gastrocnemius LC3b, Bnip-3, and Gabarap1 mRNA expression and prevented the increase in LC3b II in arthritic rats.

CONCLUSION

These data suggest that d-Trp(8)-γMSH administration prevents the effect of arthritis on corticosterone and insulin-like growth factor-I serum levels and decreases muscle wasting, by down-regulating atrogenes and autophagy through modifying the NF-kB(p65)/tumour necrosis factor-α signalling transduction pathway.

Effects of GHRP-2 and Cysteamine Administration on Growth Performance, Somatotropic Axis Hormone and Muscle Protein Deposition in Yaks (Bos grunniens) with Growth Retardation

The objective of this study was to investigate the effects of growth hormone-releasing peptide-2 (GHRP-2) and cysteamine (CS) administration on growth performance in yaks with growth retardation and try to elucidate its regulatory mechanisms. Trial 1, thirty-six 1-year-old Qinghai high plateau yaks (body weight 38–83.2 kg) were randomly chosen for body weight and jugular blood samples collection. The relationship between body weight and serum GHRH (P < 0.05, R = 0.45), GH (P < 0.05, R = 0.47), IGF-1 (P < 0.05, R = 0.62) was significantly correlated in yaks colonies with lighter body weights. Trial 2, fifteen 1-year-old Qinghai high plateau yaks with growth retardation (average body weight 54.8 ± 8.24 kg) were randomly selected and assigned to negative control group (NG), GHRP-2 injection group (GG) and cysteamine feeding group (CG), with 5 yaks per group. Another five 1-year-old Qinghai high plateau yaks with normal growth performance (average body weight 75.3 ± 2.43 kg) were selected as positive control group (PG). The average daily gain (ADG) of the GG and CG were significantly higher than those in the PG and NG (P < 0.05). Both GHRP-2 and CS administration significantly enhanced the myofiber diameter and area of skeletal muscle (P<0.05). GHRP-2 significantly enhanced the serum GH and IGF-1 levels (P < 0.05), and up-regulated GHR, IGF-1 and IGF-1R mRNA expression in the liver and skeletal muscle (P < 0.05), enhanced the mRNA expression of PI₃K, AKt and mTOR in the skeletal muscle (P<0.05). CS significantly reduced the serum SS levels and the hypothalamus SS mRNA expression (P < 0.05), and enhanced GHR and IGF-1 mRNA expression in the liver (P < 0.05), decreased the mRNA expression of muscle atrophy F-box (Atrogin-1) and muscle ring finger 1 (MuRF1) mRNA (P < 0.05). Conclusions: Growth retardation in yaks was primarily due to somatotropic axis hormones secretion deficiency. Both GHRP-2 and CS administration can accelerate growth performance and GH, IGF-1 secretion in yaks with growth retardation. GHRP-2 enhanced muscle protein deposition mainly by up-regulated the protein synthesis pathways, whereas CS worked mainly by down-regulated the ubiquitin-proteasome pathway.

Ghrelin prevents tumour- and cisplatin-induced muscle wasting: characterization of multiple mechanisms involved

BACKGROUND

Cachexia and muscle atrophy are common consequences of cancer and chemotherapy administration. The novel hormone ghrelin has been proposed as a treatment for this condition. Increases in food intake and direct effects on muscle proteolysis and protein synthesis are likely to mediate these effects, but the pathways leading to these events are not well understood.

METHODS

We characterized molecular pathways involved in muscle atrophy induced by Lewis lung carcinoma (LLC) tumour implantation in c57/bl6 adult male mice and by administration of the chemotherapeutic agent cisplatin in mice and in C2C12 myotubes. The effects of exogenous ghrelin administration and its mechanisms of action were examined in these settings.

RESULTS

Tumour implantation and cisplatin induced muscle atrophy by activating pro-inflammatory cytokines, p38-C/EBP-β, and myostatin, and by down-regulating Akt, myoD, and myogenin, leading to activation of ubiquitin-proteasome-mediated proteolysis and muscle weakness. Tumour implantation also increased mortality. In vitro, cisplatin up-regulated myostatin and atrogin-1 by activating C/EBP-β and FoxO1/3. Ghrelin prevented these changes in vivo and in vitro, significantly increasing muscle mass (P < 0.05 for LLC and P < 0.01 for cisplatin models) and grip strength (P = 0.038 for LLC and P = 0.001 for cisplatin models) and improving survival (P = 0.021 for LLC model).

CONCLUSION

Ghrelin prevents muscle atrophy by down-regulating inflammation, p38/C/EBP-β/myostatin, and activating Akt, myogenin, and myoD. These changes appear, at least in part, to target muscle cells directly. Ghrelin administration in this setting is associated with improved muscle strength and survival.

Skeletal muscle atrophy and the E3 ubiquitin ligases MuRF1 and MAFbx/atrogin-1

Muscle RING finger 1 (MuRF1) and muscle atrophy F-box (MAFbx)/atrogin-1 were identified more than 10 years ago as two muscle-specific E3 ubiquitin ligases that are increased transcriptionally in skeletal muscle under atrophy-inducing conditions, making them excellent markers of muscle atrophy. In the past 10 years much has been published about MuRF1 and MAFbx with respect to their mRNA expression patterns under atrophy-inducing conditions, their transcriptional regulation, and their putative substrates. However, much remains to be learned about the physiological role of both genes in the regulation of mass and other cellular functions in striated muscle. Although both MuRF1 and MAFbx are enriched in skeletal, cardiac, and smooth muscle, this review will focus on the current understanding of MuRF1 and MAFbx in skeletal muscle, highlighting the critical questions that remain to be answered.

Ghrelin induces apoptosis in colon adenocarcinoma cells via proteasome inhibition and autophagy induction

Ghrelin is a metabolism-regulating hormone recently investigated for its role in cancer survival and progression. Controversially, ghrelin may act as either anti-apoptotic or pro-apoptotic factor in different cancer cells, suggesting that the effects are cell type dependent. Limited data are currently available on the effects exerted by ghrelin on intracellular proteolytic pathways in cancer. Both the lysosomal and the proteasomal systems are fundamental in cellular proliferation and apoptosis regulation. With the aim of exploring if the proteasome and autophagy may be possible targets of ghrelin in cancer, we exposed human colorectal adenocarcinoma cells to ghrelin. Preliminary in vitro fluorimetric assays evidenced for the first time a direct inhibition of 20S proteasomes by ghrelin, particularly evident for the trypsin-like activity. Moreover, 1 μM ghrelin induced apoptosis in colorectal adenocarcinoma cells by inhibiting the ubiquitin-proteasome system and by activating autophagy, with p53 having an "interactive" role.

Evaluation of anti-inflammatory potential of the multidrug herbomineral formulation in male Wistar rats against rheumatoid arthritis

Background:

Immunological and inflammatory mechanisms, which may play a role in a number of disorders like rheumatoid arthritis (RA). Ancient ayurvedic physicians had developed certain dietary and therapeutic measures to arrest or prevent these disorders.

Objective:

Rheuma off gold (RG) is a herbomineral formulation recommended by ayurvedic medical practitioners for treatment of RA. This study was carried out to lend scientific evidence to the efficacy claim for RG in the management of RA in folklore medicine.

Materials and Methods:

Arthritis was induced by complete Freund's adjuvant. Treatment with formulation 100 mg/kg and dexamethasone 2 mg/kg was given to rats intragastrically once a day from day 1 to day 21 and after which estimation of physical, biochemical, and hematological parameters were carried out.

Results:

Treatment of formulation to adjuvant induced arthritic animal showed statistically significant (P < 0.05) improvement in physical parameters like arthritic index, paw edema, paw thickness as well as reduction of inflammatory markers like C-reactive protein, serum rheumatoid factor, erythrocyte sedimentation rate. The treatment also produced statistically significant (P < 0.05) increase in hemoglobin percent and improvement in splenomegaly and thymus index. In the histopathological examination, ameliorative effect of formulation was observed in hyperplasia of synovium, pannus formation, and destruction of the joint space.

Conclusion:

The results obtained in experiments indicated that the formulation significantly inhibited the adjuvant-induced arthritis which was comparable to dexamethasone and had preferable anti-inflammatory effect without significant side effect. Thus, the formulation may be a potential preventive or therapeutic candidate for the treatment of chronic inflammation and arthritis.

Systemic α-melanocyte-stimulating hormone administration decreases arthritis-induced anorexia and muscle wasting

Rheumatoid cachexia is associated with rheumatoid arthritis and it increases mortality and morbidity. Adjuvant-induced arthritis is an experimental model of rheumatoid arthritis that causes anorexia and muscle wasting. α-Melanocyte-stimulating hormone (α-MSH) has anti-inflammatory actions, and it is able to decrease inflammation in several inflammatory diseases including experimental arthritis. In this study we tested whether systemic α-MSH treatment is able to ameliorate cachexia in arthritic rats. On day 8 after adjuvant injection control and arthritic rats were treated with α-MSH (50 μg/rat ip) twice a day, until day 16 when all rats were euthanized. Arthritis decreased food intake, but it increased hypothalamic expression of neuropeptide Y (NPY) and Agouti-related peptides (AgRP) as well as interleukin-1β (IL-1β) and cyclooxygenase-2 (COX-2) mRNA. In arthritic rats, α-MSH decreased the external signs of arthritis and increased food intake (P < 0.01). In addition, α-MSH decreased hypothalamic expression of IL-1β, COX-2, proopiomelanocortin, and prohormone-converting (PC) enzymes PC1/3 and PC2 mRNA in arthritic rats. In control rats, α-MSH did not modify food intake or hypothalamic expression of aforementioned mRNA. α-MSH prevented arthritis-induced increase in gastrocnemius COX-2, muscle-specific RING-finger protein-1 (MuRF1), and atrogin-1 expression, and it increased fast myofiber size. In conclusion our data show that in arthritic rats peripheral α-MSH treatment has an anti-cachectic action increasing food intake and decreasing muscle wasting.

Molecular and cellular mechanisms of skeletal muscle atrophy: an update

Skeletal muscle atrophy is defined as a decrease in muscle mass and it occurs when protein degradation exceeds protein synthesis. Potential triggers of muscle wasting are long-term immobilization, malnutrition, severe burns, aging as well as various serious and often chronic diseases, such as chronic heart failure, obstructive lung disease, renal failure, AIDS, sepsis, immune disorders, cancer, and dystrophies. Interestingly, a cooperation between several pathophysiological factors, including inappropriately adapted anabolic (e.g., growth hormone, insulin-like growth factor 1) and catabolic proteins (e.g., tumor necrosis factor alpha, myostatin), may tip the balance towards muscle-specific protein degradation through activation of the proteasomal and autophagic systems or the apoptotic pathway. Based on the current literature, we present an overview of the molecular and cellular mechanisms that contribute to muscle wasting. We also focus on the multifacetted therapeutic approach that is currently employed to prevent the development of muscle wasting and to counteract its progression. This approach includes adequate nutritional support, implementation of exercise training, and possible pharmacological compounds.

Pharmacological characterization of the ghrelin receptor mediating its inhibitory action on inflammatory pain in rats

Recent research suggests a role for ghrelin in the modulation of inflammatory disorders. However, the type of ghrelin receptor (GHS-R) involved in both the anti-inflammatory and anti-hyperalgesic actions of ghrelin remains to be characterized. In this study, we examined whether the inhibitory effect of ghrelin in the development of hyperalgesia and edema induced by intraplantar carrageenan administration depends on an interaction with GHS-R1a. Both central (1 nmol/rat, i.c.v.) and peripheral (40 nmol/kg, i.p.) administration of the selective GHS-R1a agonist EP1572 had no effect on carrageenan-induced hyperalgesia measured by Randall-Selitto test and paw edema. Furthermore, pre-treatment with the selective GHS-R1a antagonist, D-lys(3)-GHRP-6 (3 nmol/rat, i.c.v.) failed to prevent the anti-hyperalgesic and anti-inflammatory effects exerted by central ghrelin administration (1 nmol/rat), thus indicating that the type 1a GHS-R is not involved in these peptide activities. Accordingly, both central (1 and 2 nmol/rat, i.c.v.) and peripheral (40 and 80 nmol/kg, i.p.) administration of desacyl-ghrelin (DAG), which did not bind GHS-R1a, induced a significant reduction of the hyperalgesic and edematous activities of carrageenan. In conclusion, we have shown for the first time that DAG shares with ghrelin an inhibitory role in the development of hyperalgesia, as well as the paw edema induced by carrageenan and that a ghrelin receptor different from type 1a is involved in the anti-inflammatory activities of the peptide.

Ghrelin - a pleiotropic hormone secreted from endocrine x/a-like cells of the stomach

The gastric X/A-like endocrine cell receives growing attention due to its peptide products with ghrelin being the best characterized. This peptide hormone was identified a decade ago as a stimulator of food intake and to date remains the only known peripherally produced and centrally acting orexigenic hormone. In addition, subsequent studies identified numerous other functions of this peptide including the stimulation of gastrointestinal motility, the maintenance of energy homeostasis and an impact on reproduction. Moreover, ghrelin is also involved in the response to stress and assumed to play a role in coping functions and exert a modulatory action on immune pathways. Our knowledge on the regulation of ghrelin has markedly advanced during the past years by the identification of the ghrelin acylating enzyme, ghrelin-O-acyltransferase, and by the description of changes in expression, activation, and release under different metabolic as well as physically and psychically challenging conditions. However, our insight on regulatory processes of ghrelin at the cellular and subcellular levels is still very limited and warrants further investigation.

Short-term growth hormone or IGF-I administration improves the IGF-IGFBP system in arthritic rats

OBJECTIVE

Adjuvant-induced arthritis is an experimental model of rheumatoid arthritis that inhibits the GH-IGF-I axis and decreases body weight gain and muscle mass. Although chronic GH or IGF-I treatment increases body weight gain in arthritic rats, muscle resistance to GH and IGF-I is a very common complication in inflammatory diseases. In this study we examine the effect of short-term administration of rhGH and rhIGF-I on liver and muscle IGF-I, IGFBP-3 and -5 as well as on the ubiquitin-ligases MuRF1 and atrogin-1 in the muscle of arthritic rats.

DESIGN

Arthritis was induced in adult male Wistar rats by an intradermal injection of 4 mg of Freund's adjuvant. Fifteen days after adjuvant injection, 300 μg/kg of rhGH or 200 μg/kg of rhIGF or saline was administrated 18 and 3h before decapitation. A pair-fed group injected with saline was included in order to discard a possible effect of decreased food intake. Gene expression of IGF-I, GHR, IGFBP-3, IGFBP-5, atrogin-1 and MuRF1 were quantified using RT-PCR. In serum, IGF-I was measured by radioimmunoassay (RIA) and IGFBP-3 by ligand blot.

RESULTS

Arthritis decreased serum IGF-I and IGF mRNA in liver (P<0.05), but not in skeletal muscle. In arthritic rats, rhGH increased serum IGF-I and liver IGF-I mRNA similar to the levels of pair-fed rats. Arthritis increased atrogin-1, MuRF1, IGFBP-3 and IGFBP-5 mRNA in muscle (P<0.01). IGFBP-3 mRNA was downregulated by rhIGF-I, but not by rhGH, administration in control and arthritic rats (P<0.05). Administration of rhGH and rhIGF-I increased IGFBP-5 in the gastrocnemius of arthritic rats.

CONCLUSIONS

Short-term rhGH and rhIGF-I administration was found to increase muscle IGFBP-5 mRNA, whereas only rhIGF-I administration decreased muscle IGFBP-3 mRNA in control and arthritic rats. These data suggest that arthritis does not induce GH or IGF-I resistance in skeletal muscle.

The effects of ghrelin on inflammation and the immune system

A number of hormones and metabolic mediators signal the brain of changes in the body's energy status and when an imbalance occurs; the brain coordinates the appropriate changes in energy intake and utilization via the control of appetite and food consumption. Under conditions of chronic inflammation and immune activation, there is often a significant loss of body mass and appetite suggesting the presence of shared ligands and signaling pathways mediating "crosstalk" between the immune and neuroendocrine systems. Ghrelin, the endogenous ligand for growth hormone secretagogue receptor (GHS-R), is produced primarily by cells in the stomach and serves as a potent circulating orexigenic hormone controlling food intake, energy expenditure, adiposity and GH secretion. The functional roles of ghrelin and other growth hormone secretagogues (GHS) within the immune system and under states of inflammatory stress and injury are only now coming to light. A number of reports over the past decade have described ghrelin to be a potent anti-inflammatory mediator both in vitro and in vivo and a promising therapeutic agent in the treatment of inflammatory diseases and injury. Moreover, ghrelin has also been shown to promote lymphocyte development in the primary lymphoid organs (bone marrow and thymus) and to ablate age-associated thymic involution. In the current report, we review the literature supporting a role for ghrelin as an anti-inflammatory agent and immunoregulatory hormone/cytokine and its potential use in the treatment of inflammatory diseases and injury.

Fenofibrate, a PPAR{alpha} agonist, decreases atrogenes and myostatin expression and improves arthritis-induced skeletal muscle atrophy

Arthritis is a chronic inflammatory illness that induces cachexia, which has a direct impact on morbidity and mortality. Fenofibrate, a selective PPARα activator prescribed to treat human dyslipidemia, has been reported to decrease inflammation in rheumatoid arthritis patients. The aim of this study was to elucidate whether fenofibrate is able to ameliorate skeletal muscle wasting in adjuvant-induced arthritis, an experimental model of rheumatoid arthritis. On day 4 after adjuvant injection, control and arthritic rats were treated with 300 mg/kg fenofibrate until day 15, when all rats were euthanized. Fenofibrate decreased external signs of arthritis and liver TNFα and blocked arthritis-induced decreased in PPARα expression in the gastrocnemius muscle. Arthritis decreased gastrocnemius weight, which results from a decrease in cross-section area and myofiber size, whereas fenofibrate administration to arthritic rats attenuated the decrease in both gastrocnemius weight and fast myofiber size. Fenofibrate treatment prevented arthritis-induced increase in atrogin-1 and MuRF1 expression in the gastrocnemius. Neither arthritis nor fenofibrate administration modify Akt-FoxO3 signaling. Myostatin expression was not modified by arthritis, but fenofibrate decreased myostatin expression in the gastrocnemius of arthritic rats. Arthritis increased muscle expression of MyoD, PCNA, and myogenin in the rats treated with vehicle but not in those treated with fenofibrate. The results indicate that, in experimental arthritis, fenofibrate decreases skeletal muscle atrophy through inhibition of the ubiquitin-proteasome system and myostatin.

Insulin and growth hormone-releasing peptide-6 (GHRP-6) have differential beneficial effects on cell turnover in the pituitary, hypothalamus and cerebellum of streptozotocin (STZ)-induced diabetic rats

Poorly controlled type1 diabetes is associated with hormonal imbalances and increased cell death in different tissues, including the pituitary, hypothalamus and cerebellum. In the pituitary, lactotrophs are the cell population with the greatest increase in cell death, whereas in the hypothalamus and cerebellum astrocytes are most highly affected. Insulin treatment can delay, but does not prevent, diabetic complications. As ghrelin and growth hormone (GH) secretagogues are reported to prevent apoptosis in different tissues, and to modulate glucose homeostasis, a combined hormonal treatment may be beneficial. Hence, we analyzed the effect of insulin and GH-releasing peptide 6 (GHRP-6) on diabetes-induced apoptosis in the pituitary, hypothalamus and cerebellum of diabetic rats. Adult male Wistar rats were made diabetic by streptozotocin injection (65 mg/kg ip) and divided into four groups from diabetes onset: those receiving a daily sc injection of saline (1 ml/kg/day), GHRP-6 (150 μg/kg/day), insulin (1-8U/day) or insulin plus GHRP-6 for 8 weeks. Control non-diabetic rats received saline (1 ml/kg/day). Diabetes increased cell death in the pituitary, hypothalamus and cerebellum (P<0.05). In the pituitary, insulin treatment prevented diabetes-induced apoptosis (P<0.01), as well as the decline in prolactin and GH mRNA levels (P<0.05). In the hypothalamus, neither insulin nor GHRP-6 decreased diabetes-induced cell death. However, the combined treatment of insulin+GHRP-6 prevented the diabetes induced-decrease in glial fibrillary acidic protein (GFAP) levels (P<0.05). In the cerebellum, although insulin treatment increased GFAP levels (P<0.01), only the combined treatment of insulin+ GHRP-6 decreased diabetes-induced apoptosis (P<0.05). In conclusion, insulin and GHRP-6 exert tissue specific effects in STZ-diabetic rats and act synergistically on some processes. Indeed, insulin treatment does not seem to be effective on preventing some of the diabetes-induced alterations in the central nervous system.

Current and potential roles of ghrelin in clinical practice

Ghrelin is a novel GH-releasing peptide, which has been identified as an endogenous ligand for GH-secretagogue receptor. Ghrelin is mainly secreted by the stomach and plays a critical role in a variety of physiological processes including endocrine, metabolic, cardiovascular, immunological, and other actions. Ghrelin stimulates food intake via hypothalamic neurons and causes a positive energy balance and body weight gain by decreasing fat utilization and promoting adiposity. Given the multiple effects of ghrelin, its potential clinical applications have been evaluated in various conditions. Preliminary trials have shown that it may prove valuable in the management of disease-induced cachexia. Ghrelin may improve the wasting syndrome through GH-dependent or GH-independent effects. Moreover, ghrelin may play a role in the management of disorders of gut motility and obesity. Finally, other potential clinical applications of ghrelin include the treatment of patients with diabetes mellitus, infections, rheumatological diseases or GH deficiency and the diagnosis of this hormonal disorder.

Pathogenesis of muscle wasting in cancer cachexia: targeted anabolic and anticatabolic therapies

PURPOSE OF REVIEW

Cancer-related muscle loss, or cachexia, is the cause of death for approximately 2 million people worldwide and severely reduces quality of life. The degree of cachexia is inversely correlated with survival time; however, the exact mechanisms behind cancer-induced muscle wasting remain under investigation.

RECENT FINDINGS

Cytokines such as tumor necrosis factor-alpha trigger degradatory pathways through nuclear factor-kappaB signaling that activate the ubiquitin-proteasome system and muscle proteolysis. Androgen treatment has been shown to reduce inflammatory cytokines and even stimulate anti-inflammatory cytokine production. Amino acid supplementation has been shown to induce muscle protein synthesis in ovarian cancer patients.

SUMMARY

Targeted anabolic therapies aimed at preventing or reversing cancer cachexia might involve the combined use of androgens and amino acids working concurrently to enhance muscle protein synthesis and reduce muscle protein breakdown. Additional focused clinical studies are needed to identify muscle-specific targets or biomarkers for defined therapeutic approaches to slow or prevent cancer cachexia. In this review, we summarize the pathogenesis of cancer-related muscle wasting and discuss potential interventions at reversing or preventing cancer-related muscle loss.

Systemic IGF-I administration attenuates the inhibitory effect of chronic arthritis on gastrocnemius mass and decreases atrogin-1 and IGFBP-3

Adjuvant arthritis is an animal model of rheumatoid arthritis that decreases liver and circulating IGF-I as well as skeletal muscle mass. The aim of this work was to elucidate whether IGF-I administration was able to prevent the effect of arthritis on body weight and on two skeletal muscles, gastrocnemius and soleus. On day 4 after adjuvant injection, control and arthritic rats were treated with IGF-I (100 microg/kg s.c.) two times a day, until day 15 when all rats were killed. Arthritis decreased body weight gain and gastrocnemius weight. In arthritic rats, IGF-I treatment increased body weight gain and gastrocnemius weight, without modifying food intake or the external signs of arthritis. Arthritis increased atrogin-1 and muscle ring finger 1 (MuRF1) gene expression in the gastrocnemius and to a lesser extent in the soleus muscle. IGF-I attenuated the arthritis-induced increase in atrogin-1 and MuRF1 expression in the gastrocnemius, whereas it did not modify the expression of these genes in the soleus muscle. Arthritis also increased IGF-binding protein (IGBP)-3 and IGFBP-5 gene expression in gastrocnemius and soleus, whereas IGF-I administration decreased IGFBP-3, but not IGFBP-5, gene expression in both muscles. In both groups of arthritic rats and in control rats treated with IGF-I, proliferating cell nuclear antigen and myogenic differentiation proteins were increased in the gastrocnemius. These data suggest that the inhibitory effect of chronic arthritis on skeletal muscle is higher in fast glycolytic than in slow oxidative muscle and that IGF-I administration attenuates this effect and decreases atrogin-1 and IGFBP-3 gene expression.

Ghrelin receptor agonist, GHRP-2, attenuates burn injury-induced MuRF-1 and MAFbx expression and muscle proteolysis in rats

Thermal injury results in hypermetabolism, loss of body weight, and skeletal muscle wasting in mice and rats. Our earlier studies have demonstrated that ghrelin injection stimulates food intake and growth hormone release and inhibits skeletal muscle proteolysis in rats with thermal injury. We sought to develop a lower molecular weight, stable and longer acting peptide to combat the catabolic responses caused by thermal injury. Towards this goal, we examined the role of the hexapeptide mimetic of ghrelin, growth hormone-releasing peptide-2 (GHRP-2), on expression of E3 ubiquitin ligases and breakdown of muscle protein in rats with thermal injury. Slow in vivo release of GHRP-2 through minipump for 24h attenuated the thermal injury-induced increase in mRNA expression of IL-6 and of the E3 ubiquitin ligases, MuRF-1 and MAFbx, in rat skeletal muscle. Furthermore, burn-induced increases in total and myofibrillar protein breakdown from rat EDL muscle were attenuated by GHRP-2. These findings suggest that catabolic responses resulting from thermal injury can be attenuated by GHRP-2.

Powerful signals for weak muscles

The aim of the present review is to summarise, evaluate and critique the different mechanisms involved in anabolic growth of skeletal muscle and the catabolic processes involved in cancer cachexia and sarcopenia of ageing. This is highly relevant, since they represent targets for future promising clinical investigations. Sarcopenia is an inevitable process associated with a gradual reduction in muscle mass and strength, associated with a reduction in motor unit number and atrophy of muscle fibres, especially the fast type IIa fibres. The loss of muscle mass with ageing is clinically important because it leads to diminished functional ability and associated complications. Cachexia is widely recognised as severe and rapid wasting accompanying disease states such as cancer or immunodeficiency disease. One of the main characteristics of cancer cachexia is asthenia or lack of strength, which is directly related to the muscle loss. Indeed, apart from the speed of loss, muscle wasting during cancer and ageing share many common metabolic pathways and mediators. In healthy young individuals, muscles maintain their mass and function because of a balance between protein synthesis and protein degradation associated with rates of anabolic and catabolic processes, respectively. Muscles grow (hypertrophy) when protein synthesis exceeds protein degradation. Conversely, muscles shrink (atrophy) when protein degradation dominates. These processes are not occurring independently of each other, but are finely coordinated by a web of intricate signalling networks. Such signalling networks are in charge of executing environmental and cellular cues that ultimately determine whether muscle proteins are synthesised or degraded. Increasing our understanding for the pathways involved in hypertrophy and atrophy and particularly the interaction of these pathways is essential in designing therapeutic strategies for both prevention and treatment of muscle wasting conditions with age and with disease.

Eicosapentaenoic acid attenuates arthritis-induced muscle wasting acting on atrogin-1 and on myogenic regulatory factors

Eicosapentaenoic acid (EPA) is an omega-3 polyunsaturated fatty acid that has anti-inflammatory and anticachectic actions. The aim of this work was to elucidate whether EPA administration is able to prevent an arthritis-induced decrease in body weight and muscle wasting in rats. Arthritis was induced by intradermal injection of Freund's adjuvant; 3 days later, nine rats received 1 g/kg EPA or coconut oil daily. All rats were killed 15 days after adjuvant injection. EPA administration decreased the external signs of arthritis and paw volume as well as liver TNF-alpha mRNA. EPA did not modify arthritis-induced decrease in food intake or body weight gain. However, EPA treatment prevented arthritis-induced increase in muscle TNF-alpha and atrogin-1, whereas it attenuated the decrease in gastrocnemius weight and the increase in MuRF1 mRNA. Arthritis not only decreased myogenic regulatory factors but also increased PCNA, MyoD, and myogenin mRNA in the gastrocnemius. Western blot analysis showed that changes in protein content followed the pattern seen with mRNA. In the control rats, EPA administration increased PCNA and MyoD mRNA and protein. In arthritic rats, EPA did not modify the stimulatory effect of arthritis on these myogenic regulatory factors. The results suggest that in experimental arthritis, in addition to its anti-inflammatory effect, EPA treatment attenuates muscle wasting by decreasing atrogin-1 and MuRF1 gene expression and increasing the transcription factors that regulate myogenesis.

Ghrelin inhibits skeletal muscle protein breakdown in rats with thermal injury through normalizing elevated expression of E3 ubiquitin ligases MuRF1 and MAFbx

We previously determined that ghrelin synthesis was downregulated after burn injury and that exogenous ghrelin retained its ability both to stimulate food intake and to restore plasma growth hormone levels in burned rats. These observations and the finding that anabolic hormones can attenuate skeletal muscle catabolism led us to investigate whether ghrelin could attenuate burn-induced skeletal muscle protein breakdown in rats. These studies were performed in young rats (50-60 g) 24 h after approximately 30% total body surface area burn injury. Burn injury increased total and myofibrillar protein breakdown in extensor digitorum longus (EDL) muscles assessed by in vitro tyrosine and 3-methyl-histidine release, respectively. Continuous 24-h administration of ghrelin (0.2 mg.kg(-1).h(-1)) significantly inhibited both total and myofibrillar protein breakdown in burned rats. Ghrelin significantly attenuated burn-induced changes in mRNA expression of IGFBP-1 and IGFBP-3 in liver. In EDL, ghrelin attenuated the increases in mRNA expression of the binding proteins, but had no significant effect on reduced expression of IGF-I. Ghrelin markedly reduced the elevated mRNA expression of TNF-alpha and IL-6 in EDL muscle that occurred after burn. Moreover, ghrelin normalized plasma glucocorticoid levels, which were elevated after burn. Expression of the muscle-specific ubiquitin-ligating enzyme (E3) ubiquitin ligases MuRF1 and MAFbx were markedly elevated in both EDL and gastrocnemius and were normalized by ghrelin. These results suggest that ghrelin is a powerful anticatabolic compound that reduces skeletal muscle protein breakdown through attenuating multiple burn-induced abnormalities.

The role of ghrelin and ghrelin analogues in wasting disease

PURPOSE OF REVIEW

The purpose of this review is to summarize recent studies that investigated the role of ghrelin and ghrelin analogs in wasting conditions.

RECENT FINDINGS

Numerous studies have demonstrated potential beneficial effects exerted by ghrelin in a number of diseases associated with wasting. Besides ghrelin's orexigenic effect, anabolic as well as anti-inflammatory activity mediated by ghrelin have been investigated in wasting conditions such as cancer, diabetes mellitus, malabsorptive diseases, chronic obstructive pulmonary disease, anorexia nervosa, renal failure, liver failure, and chronic heart failure. Encouraging results have been obtained from experimental studies and a few clinical trials using subcutaneous administration of ghrelin and ghrelin agonists in cachexia. In-vitro studies have shown ghrelin and des-acyl ghrelin biological activities on proliferation of tumor cells and abnormal tissues.

SUMMARY

The recent studies support the possible positive effects of ghrelin in therapeutic approaches and adjunct treatment of a number of diseases associated with wasting. Utilization of agonists of the ghrelin receptor growth hormone secretagogue-1a is a promising approach for clinical use. Randomized and placebo-controlled studies, including large number of patients are further required.

Effects of ghrelin on neuronal survival in cells derived from dorsal motor nucleus of the vagus

BACKGROUND

The effects of intestinal inflammation on the central neurons projecting to the enteric nervous system are unknown. The dorsal motor nucleus of the vagus signals to the gastrointestinal system. Ghrelin is elevated in patients with inflammatory bowel disease and has been implicated as an inflammatory mediator. The purpose of this study was to investigate the effects of gastrointestinal inflammation on the dorsal motor nucleus of the vagus in rats, as well as the effects of proinflammatory cytokines and ghrelin on neurons from the dorsal motor nucleus of the vagus in vitro.

METHODS

DiI was injected into the stomach wall of rats to retrogradely label neurons of the dorsal motor nucleus of the vagus. Intestinal inflammation was induced with indomethacin injection. Serial serum ghrelin measurements were performed. Tissue was examined under fluorescent microscopy. In vitro studies using primary culture of neurons from the dorsal motor nucleus of the vagus were performed. Reverse transcriptase-polymerase chain reaction for cytokine transcripts and immunohistochemistry for cytokine receptors were performed. Cell proliferation and apoptosis were measured by enzyme-linked immunosorbent assay.

RESULTS

A significant decrease of DiI labeling was demonstrated in the dorsal motor nucleus of the vagus of animals injected with indomethacin. Serum levels of ghrelin were significantly elevated 2 days after induction of inflammation. In vitro, apoptosis and cell proliferation were measured after 24-hour exposure to experimental conditions. Ghrelin alone had no effect on apoptosis. Exposure to interleukin (IL)-1 beta or tumor necrosis factor (TNF)-alpha increased apoptosis. The addition of ghrelin to cytokine resulted in significant decreases in apoptosis compared to cytokine alone. Ghrelin significantly increased neuronal proliferation. Exposure to IL-1 beta, IL-6, or TNF-alpha significantly decreased proliferation. The addition of ghrelin to TNF-alpha or IL-6 significantly increased cellular proliferation compared to cytokine alone.

CONCLUSIONS

Neurons from the dorsal motor nucleus of the vagus that project to the stomach are reduced in number after induction of colitis in rats. In vitro, proinflammatory cytokines increase apoptosis and decrease cell proliferation of neurons from the dorsal motor nucleus of the vagus. These effects are attenuated by ghrelin.

GH-releasing peptide-2 administration prevents liver inflammatory response in endotoxemia

It has been reported that growth hormone (GH)-releasing peptide-2 (GHRP-2), a ghrelin receptor agonist, has an anti-inflammatory effect. We investigated whether this GH secretagogue attenuates liver injury in LPS-treated rats. Wistar rats were simultaneously injected (ip) with LPS (1 mg/kg) and/or GHRP-2 (100 microg/kg). Serum levels of aspartate and alanine transaminases were measured as an index of liver damage. Circulating nitrites/nitrates and hepatic IGF-I and TNF-alpha were evaluated as possible mediators of GHRP-2 actions. LPS increased serum levels of transaminases and nitrites/nitrates. Moreover, LPS increased hepatic TNF-alpha and decreased hepatic IGF-I mRNAs. GHRP-2 administration attenuated the effects of LPS on transaminases, nitrites/nitrates, TNF-alpha, and IGF-I in vivo. This GHRP-2 effect does not seem to be due to modifications in food intake, since fasting did not modify serum levels of transaminases, serum nitrites/nitrates, and hepatic TNF-alpha mRNA both in vehicle rats and in LPS-injected rats. To elucidate whether GHRP-2 is acting directly on the liver, cocultures of hepatocytes and nonparenchymal cells and monocultures of isolated hepatocytes were incubated with LPS and GHRP-2. The ghrelin receptor agonist prevented an endotoxin-induced increase in transaminases and nitrite/nitrate release as well as in TNF-alpha mRNA and increased IGF-I mRNA from cocultures of hepatocytes and nonparenchymal cells, but not from monocultures. In summary, these data indicate that GHRP-2 has a protective effect on the liver in LPS-injected rats that seems to be mediated by IGF-I, TNF-alpha, and nitric oxide. Our data also suggest that the anti-inflammatory effect of GHRP-2 in the liver is exerted on nonparenchymal cells.

GHRP-2, a GHS-R agonist, directly acts on myocytes to attenuate the dexamethasone-induced expressions of muscle-specific ubiquitin ligases, Atrogin-1 and MuRF1

Recent reports suggest that Atrogin-1 and MuRF1, E3 ubiquitin ligases, play a pivotal role in muscle atrophy. In the present study, effect of Growth Hormone Releasing Peptide-2 (GHRP-2), a GH secretagogue receptor (GHS-R) agonist, on the expressions of Atrogin-1 and MuRF1 in vivo rat muscles was examined. Dexamethasone administration increased Atrogin-1 mRNA level in rat soleus muscle. The increased mRNA level of Atrogin-1 was significantly attenuated by GHRP-2. In addition, GHRP-2 decreased MuRF1 mRNA level irrespective of the presence of dexamethasone. Although IGF-I is a well-known protective factor for muscle atrophy, GHRP-2 did not influence plasma IGF-I levels and IGF-I mRNA levels in muscles. To clarify a direct effect of GHRP-2, differentiated C2C12 myocytes were used. Ten micrometer dexamethasone increased both Atrogin-1 and MuRF1 mRNA levels in C2C12 cells. GHRP-2 attenuated dexamethasone-induced expression of them dose-dependently and decreased the basal level of MuRF1 mRNA. The suppressive effect on the expressions of Atrogin-1 and MuRF1 by GHRP-2 was blocked by [D-Lys(3)]-GHRP-6, a GHS-R1a blocker, suggesting the effect of GHRP-2 was mediated through GHS-R1a. Taken together, GHRP-2 directly attenuates Atrogin-1 and MuRF1 mRNA levels through ghrelin receptors in myocytes.

Experimental arthritis inhibits the insulin-like growth factor-I axis and induces muscle wasting through cyclooxygenase-2 activation

Chronic arthritis induces cachexia associated with an inhibition of the growth hormone (GH)-insulin-like growth factor-I (IGF-I) system and an activation of the E3 ubiquitin-ligating enzymes muscle atrophy F-box (MAFbx) and muscle Ring finger 1 (MuRF1) in the skeletal muscle. The aim of this work was to study the role of cyclooxygenase (COX)-2 in chronic arthritis-induced cachexia. Arthritis was induced in rats by Freund's adjuvant injection, and the effects of two COX inhibitors (indomethacin, a nonspecific inhibitor, and meloxicam, a selective COX-2 inhibitor on pituitary GH and on liver and serum IGF-I levels) were tested. Arthritis decreased body weight gain and GH and liver IGF-I gene expression. In the arthritic rats, both inhibitors, indomethacin and meloxicam, prevented the inhibitory effect of arthritis on body weight gain. Indomethacin and meloxicam administration to arthritic rats increased pituitary GH and liver IGF-I mRNA as well as serum levels of IGF-I. These data suggest that induction of COX-2 during chronic inflammation is involved in the inhibition of the GH-IGF-I axis and in the body weight loss. In the gastrocnemius muscle, arthritis increased the gene expression of tumor necrosis factor (TNF)-alpha, the E3 ubiquitin-ligating enzymes MAFbx and MuRF1, as well as of IGF-I and IGF-binding protein-5 (IGFBP-5). Inhibition of COX-2 by meloxicam administration increased gastrocnemius weight and decreased MAFbx, MuRF1, TNF-alpha, and IGFBP-5 gene expression. In summary, our data indicate that chronic arthritis-induced cachexia and muscle wasting are mediated by the COX-2 pathway resulting in a decreased GH-IGF-I secretion and increased expression of MAFbx and MuRF1 mRNA.

Ghrelin and des-acyl ghrelin promote differentiation and fusion of C2C12 skeletal muscle cells

Ghrelin is an acylated peptidyl gastric hormone acting on the pituitary and hypothalamus to stimulate appetite, adiposity, and growth hormone release, through activation of growth hormone secretagogue receptor (GHSR)-1a receptor. Moreover, ghrelin features several activities such as inhibition of apoptosis, regulation of differentiation, and stimulation or inhibition of proliferation of several cell types. Ghrelin acylation is absolutely required for both GHSR-1a binding and its central endocrine activities. However, the unacylated ghrelin form, des-acyl ghrelin, which does not bind GHSR-1a and is devoid of any endocrine activity, is far more abundant than ghrelin in plasma, and it shares with ghrelin some of its cellular activities. In here we show that both ghrelin and des-acyl ghrelin stimulate proliferating C2C12 skeletal myoblasts to differentiate and to fuse into multinucleated myotubes in vitro through activation of p38. Consistently, both ghrelin and des-acyl ghrelin inhibit C2C12 proliferation in growth medium. Moreover, the ectopic expression of ghrelin in C2C12 enhances differentiation and fusion of these myoblasts in differentiation medium. Finally, we show that C2C12 cells do not express GHSR-1a, but they do contain a common high-affinity binding site recognized by both acylated and des-acylated ghrelin, suggesting that the described activities on C2C12 are likely mediated by this novel, yet unidentified receptor for both ghrelin forms.

Metabolic and immunologic derangements in cardiac cachexia: where to from here?

The onset of cardiac cachexia is characterized by a defined severe weight loss in patients with advanced chronic heart failure and it predicts an increased mortality in these patients. Recent studies with potential therapeutics investigated the effects and efficiency of beta-blockers, ghrelin, or ghrelin-agonists in cachexia. These and other new studies, like the influence of heart transplantation on cardiac cachexia, give prospect into potential therapeutic options in the future. General aim of the treatment strategy is to prevent the onset and retard the progress of cachexia. This could be achieved by modifying the metabolic, neurohormonal and immune system abnormalities, e.g. with beta-blockers and angiotensin-converting enzyme inhibitors. However, these alterations interact in a complex pathophysiological process, which is supposed to end in a vicious circle and thereby the wasting process is further promoted. To interrupt this, an early start of therapy is important to decelerate the development of cardiac cachexia. Many further investigations are needed to find out more about the pathophysiological pathways, to confirm the previous results, and to evaluate new therapeutics.

Ghrelin and immunity: a young player in an old field

There is increasing evidence of the coupling of immune status to the metabolic system. The communication between the state of systemic and cellular energy balance to immune compartment is mediated via a complex array of cytokines, hormones and neuropeptides. Ghrelin, a recently described orexigenic peptide hormone, is predominantly produced by the stomach and functions as a positive regulator of the somatotropic axis and a peripheral signal of negative energy balance. Apart from its well-studied metabolic effects, ghrelin also exerts multiple regulatory effects on several other organ systems including the cardiovascular, central nervous and immune systems. Here, we summarize the growing evidence of ghrelin as a significant player in the regulation of inflammation and the immune function and the potential therapeutic targeting of ghrelin or its receptor, the growth hormone secretagogue receptor (GHS-R), in various inflammatory and cachexic disease states.