Can Cytologic and Sonographic Features Help Prevent Overtreatment of Bethesda V Thyroid Nodules?

BACKGROUND: Although nearly half of thyroid nodules with Bethesda V cytology (suspicious for malignancy) may be benign or harbor low-grade neoplasms that can be sufficiently treated with lobectomy, many patients with Bethesda V cytology continue to be treated with total thyroidectomy. The objectives of this study were to establish whether cytomorphologic and ultrasonographic features can determine appropriate surgery for thyroid nodules with Bethesda V cytology and how often patients are overtreated with total instead of partial thyroidectomy. METHODS: Utilizing a 10-y prospective database starting January 1, 2004, cytomorphologic and ultrasonographic features of thyroid nodules with Bethesda V cytology were reviewed. Overtreatment was defined as total thyroidectomy when histopathology revealed benign nodule, noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) or a unilateral < 4 cm low risk cancer. RESULTS: Sixty-three patients were included in the study. Seventeen (27%) had benign, 14 (22%) NIFTP, and 32 (51%) malignant nodules. On cytology, nuclear pseudoinclusions, and on ultrasound, taller-than-wide configuration, were more common in malignant than benign or NIFTP nodules. Among 56 patients who underwent total thyroidectomy, 14 and 11 had a benign or NIFTP nodule, respectively, and 13 had a unilateral < 4 cm low risk cancer, suggesting that 68% (38/56) were overtreated. CONCLUSIONS: Total thyroidectomy for Bethesda V thyroid nodules may result in overtreatment in more than half of the patients. Although certain cytomorphologic and ultarsonographic features may be helpful in determining appropriate surgery for Bethesda V thyroid nodules, additional characteristics are needed to reduce overtreatment of these nodules.

The Smallpox Epidemics in America in the 1700s and the Role of the Surgeons: Lessons to be Learned During the Global Outbreak of COVID-19.

Today's COVID-19 pandemic offers many similarities with previous pandemics hitting our country. In particular, the smallpox epidemics during the 1700s threatened the lives of multitudes and created panic and fear in the society, similar to the situation caused by the coronavirus. Remedies that were instituted, especially inoculations, were met with opposition and even violence when first introduced. The newspapers were filled with headlines reflecting the disputes. There was a "six feet rule" during the smallpox epidemics, although it had a different meaning than today. Politicians and other leaders of the society were engaged in the war against the infection. Boston became involved in the fight against the smallpox by Dr. Zabdiel Boylston's and Rev. Cotton Mather's introduction of inoculations. When George Washington realized the benefits of the procedure and ordered mass inoculations of the Continental Army, it became an important factor in winning not only the fight against smallpox but the Revolutionary War as well. Looking back at history, realizing that we have survived previous outbreaks of devastating diseases, can provide hope during the current pandemic.

CaMKII activity is reduced in skeletal muscle during sepsis.

Exercise-induced muscle hypertrophy is associated with increased calcium/calmodulin-dependent protein kinase II (CaMKII) expression and activity. In contrast, the influence of muscle atrophy-related conditions on CaMKII is poorly understood. Here, we tested the hypothesis that sepsis-induced muscle wasting is associated with reduced CaMKII expression and activity. Sepsis, induced by cecal ligation and puncture in rats, and treatment of rats with TNFα, resulted in reduced total CaMKII activity in skeletal muscle whereas autonomous CaMKII activity was unaffected. The expression of CaMKIIδ, but not ß and γ, was reduced in septic muscle. In additional experiments, treatment of cultured myotubes with TNFα resulted in reduced total CaMKII activity and decreased levels of phosphorylated glycogen synthase kinase (GSK)-3ß, a downstream target of CaMKII. The present results suggest that sepsis-induced muscle wasting is associated with reduced CaMKII activity and that TNFα may be involved in the regulation of CaMKII activity in skeletal muscle. Decreased phosphorylation (consistent with activation) of GSK-3ß may be a consequence of reduced CaMKII activity, indicating that inhibited CaMKII activity may be involved in the catabolic response to sepsis.

Multiple muscle wasting-related transcription factors are acetylated in dexamethasone-treated muscle cells.

Recent studies suggest that the expression and activity of the histone acetyltransferase p300 are upregulated in catabolic muscle allowing for acetylation of cellular proteins. The function of transcription factors is influenced by posttranslational modifications, including acetylation. It is not known if transcription factors involved in the regulation of muscle mass are acetylated in atrophying muscle. We determined cellular levels of acetylated C/EBPß, C/EBPδ, FOXO1, FOXO3a, and NF-kB/p65 in dexamethasone-treated L6 muscle cells, a commonly used in vitro model of muscle wasting. The role of p300 in dexamethasone-induced transcription factor acetylation and myotube atrophy was examined by transfecting muscle cells with p300 siRNA. Treatment of L6 myotubes with dexamethasone resulted in increased cellular levels of acetylated C/EBPß and δ, FOXO1 and 3a, and p65. Downregulation of p300 with p300 siRNA reduced acetylation of transcription factors and decreased dexamethasone-induced myotube atrophy and expression of the ubiquitin ligase MuRF1. The results suggest that several muscle wasting-related transcription factors are acetylated supporting the concept that posttranslational modifications of proteins regulating gene transcription may be involved in the loss of muscle mass. The results also suggest that acetylation of the transcription factors is at least in part regulated by p300 and plays a role in glucocorticoid-induced muscle atrophy. Targeting molecules that regulate acetylation of transcription factors may help reduce the impact of muscle wasting.

Resveratrol prevents dexamethasone-induced expression of the muscle atrophy-related ubiquitin ligases atrogin-1 and MuRF1 in cultured myotubes through a SIRT1-dependent mechanism.

Resveratrol (3,5,4'-trihydroxystilbene) has been ascribed multiple beneficial biological effects but the influence of resveratrol on glucocorticoid-induced muscle atrophy is not known. We examined the effects of resveratrol on dexamethasone-induced atrogin-1 and MuRF1 expression, FOXO1 acetylation, protein degradation and atrophy in cultured L6 myotubes. In addition, the role of the deacetylase SIRT1 in the effects of resveratrol was determined by transfecting myotubes with SIRT1 siRNA. The catabolic effects of dexamethasone were prevented by resveratrol and the protective effects of resveratrol on dexamethasone-induced atrogin-1 and MuRF1 expression were abolished in myotubes transfected with SIRT1 siRNA. Results suggest that resveratrol can prevent glucocorticoid-induced muscle wasting and that this effect is at least in part SIRT1-dependent.

ß-Hydroxy-ß-methylbutyrate (HMB) prevents dexamethasone-induced myotube atrophy.

High levels of glucocorticoids result in muscle wasting and weakness. ß-hydroxy-ß-methylbutyrate (HMB) attenuates the loss of muscle mass in various catabolic conditions but the influence of HMB on glucocorticoid-induced muscle atrophy is not known. We tested the hypothesis that HMB prevents dexamethasone-induced atrophy in cultured myotubes. Treatment of cultured L6 myotubes with dexamethasone resulted in increased protein degradation and expression of atrogin-1 and MuRF1, decreased protein synthesis and reduced myotube size. All of these effects of dexamethasone were attenuated by HMB. Additional experiments provided evidence that the inhibitory effects of HMB on dexamethasone-induced increase in protein degradation and decrease in protein synthesis were regulated by p38/MAPK- and PI3K/Akt-dependent cell signaling, respectively. The present results suggest that glucocorticoid-induced muscle wasting can be prevented by HMB.

Loss of muscle strength during sepsis is in part regulated by glucocorticoids and is associated with reduced muscle fiber stiffness.

Sepsis is associated with impaired muscle function but the role of glucocorticoids in sepsis-induced muscle weakness is not known. We tested the role of glucocorticoids in sepsis-induced muscle weakness by treating septic rats with the glucocorticoid receptor antagonist RU38486. In addition, normal rats were treated with dexamethasone to further examine the role of glucocorticoids in the regulation of muscle strength. Sepsis was induced in rats by cecal ligation and puncture, and muscle force generation (peak twitch and tetanic tension) was determined in lower extremity muscles. In other experiments, absolute and specific force as well as stiffness (reflecting the function of actomyosin cross bridges) were determined in isolated skinned muscle fibers from control and septic rats. Sepsis and treatment with dexamethasone resulted in reduced maximal twitch and tetanic force in intact isolated extensor digitorum longus muscles. The absolute and specific maximal force in isolated muscle fibers was reduced during sepsis together with decreased fiber stiffness. These effects of sepsis were blunted (but not abolished) by RU38486. The results suggest that muscle weakness during sepsis is at least in part regulated by glucocorticoids and reflects loss of contractility at the cellular (individual muscle fiber) level. In addition, the results suggest that reduced function of the cross bridges between actin and myosin (documented as reduced muscle fiber stiffness) may be involved in sepsis-induced muscle weakness. An increased understanding of mechanisms involved in loss of muscle strength will be important for the development of new treatment strategies in patients with this debilitating consequence of sepsis.

Posttranslational Modifications in Thyroid Cancer: Implications for Pathogenesis, Diagnosis, Classification, and Treatment.

There is evidence that posttranslational modifications, including phosphorylation, acetylation, methylation, ubiquitination, sumoylation, glycosylation, and succinylation, may be involved in thyroid cancer. We review recent reports supporting a role of posttranslational modifications in the tumorigenesis of thyroid cancer, sensitivity to radioiodine and other types of treatment, the identification of molecular treatment targets, and the development of molecular markers that may become useful as diagnostic tools. An increased understanding of posttranslational modifications may be an important supplement to the determination of alterations in gene expression that has gained increasing prominence in recent years.

Molecules modulating gene transcription during muscle wasting in cancer, sepsis, and other critical illness.

Muscle wasting in patients with sepsis, severe injury, and cancer is associated with increased transcription of several genes regulating different proteolytic pathways. The involvement of gene activation in muscle wasting suggests that transcription factors and nuclear cofactors play important roles in the regulation of muscle mass. Among transcription factors, NF-κB, C/EBPß, and FOXO transcription factors are activated in atrophying muscle and stimulate the transcription of genes in the ubiquitin-proteasome proteolytic pathway, as well as genes regulating authophagy/lysosomal proteolysis. Changes in the expression and activity of several nuclear cofactors, including the histone acetyltransferase p300, histone deacetylases (HDACs), such as HDAC3, HDAC6, and SIRT1, as well as the nuclear cofactors PGC-1α and ß, contribute to loss of muscle mass in various catabolic conditions. The activity of transcription factors and nuclear cofactors involved in the regulation of muscle mass is influenced not only by their abundance, but also by posttranslational modifications as well, including ubiquitination, phosphorylation, and acetylation. Transcription factors and nuclear cofactors involved in muscle wasting interact with each other at multiple levels, supporting the concept that the molecular regulation of muscle mass in various catabolic conditions is complex. An increased understanding of molecules that modulate gene transcription in catabolic muscle may make it possible to develop treatments targeting transcription factors and nuclear cofactors in the prevention and treatment of muscle wasting.

C/EBPß regulates dexamethasone-induced muscle cell atrophy and expression of atrogin-1 and MuRF1.

Muscle wasting in catabolic patients is in part mediated by glucocorticoids and is associated with increased expression and activity of the transcription factor C/EBPß. It is not known, however, if C/EBPß is causally linked to glucocorticoid-induced muscle atrophy. We used dexamethasone-treated L6 myoblasts and myotubes to test the role of C/EBPß in glucocorticoid-induced expression of the muscle-specific ubiquitin ligases atrogin-1 and MuRF1, protein degradation, and muscle atrophy by transfecting cells with C/EBPß siRNA. In myoblasts, silencing C/EBPß expression with siRNA inhibited dexamethasone-induced increase in protein degradation, atrogin-1 and MuRF1 expression, and muscle cell atrophy. Similar effects of C/EBPß siRNA were seen in myotubes except that the dexamethasone-induced increase in MuRF1 expression was not affected by C/EBPß siRNA in myotubes. In additional experiments, overexpressing C/EBPß did not influence atrogin-1 or MuRF1 expression in myoblasts or myotubes. Taken together, our observations suggest that glucocorticoid-induced muscle wasting is at least in part regulated by C/EBPß. Increased C/EBPß expression alone, however, is not sufficient to upregulate atrogin-1 and MuRF1 expression.

Calpain activity is increased in skeletal muscle from gastric cancer patients with no or minimal weight loss.

The influence of cancer on skeletal muscle calpain expression and activity in humans is poorly understood. We tested the hypothesis that calpain activity is increased in skeletal muscle from gastric cancer patients with no or <5% weight loss. Muscle biopsies were obtained from rectus abdominis muscle in 15 patients who underwent surgery for gastric cancer and had <5% weight loss and also in 15 control patients. Calpain activity was determined using a calpain-specific substrate in the absence or presence of calcium. The expression of µ- and m-calpain, calpastatin, atrogin-1, and MuRF1 was determined by real-time polymerase chain reaction. Calpain activity was increased by 70% in cancer patients compared with controls. There were no differences in mRNA levels for µ- and m-calpain, calpastatin, atrogin-1, or MuRF1 between control and cancer patients. Calpain activity may be increased in muscle from gastric cancer patients even before changes in molecular markers of muscle wasting and significant weight loss occur.

Repeat Fine Needle Aspiration Cytology Refines the Selection of Thyroid Nodules for Afirma Gene Expression Classifier Testing.

Background: Molecular testing (MT) refines risk stratification for thyroid nodules that are indeterminate for cancer by fine needle aspiration (FNA) cytology. Criteria for selecting nodules for MT vary and remain largely untested, raising questions about the best strategy for maximizing the usefulness of MT while minimizing the harms of overtesting. We used a unique data set to examine the effects of repeat FNA cytology-based criteria for MT on management decisions and nodule outcomes. Methods: This was a study of adults (age 25-90 years; 281 women and 72 men) with cytologically indeterminate (Bethesda III/IV) thyroid nodules who underwent repeat FNA biopsy and Afirma Gene Expression Classifier (GEC) testing (N = 363 nodules from 353 patients) between June 2013 and October 2017 at a single institution, with follow-up data collected until December 2019. Subgroup analysis was performed based on classification of repeat FNA cytology. Outcomes of GEC testing, clinical/sonographic surveillance of unresected nodules, and histopathologic diagnoses of thyroidectomies were compared between three testing approaches: (i) Reflex (MT sent on the basis of the initial Bethesda III/IV FNA), (ii) SemiRestrictive (MT sent if repeat FNA is Bethesda I-IV), and (iii) Restrictive (MT sent only if repeat FNA is Bethesda III/IV) testing approaches. Results: Restricting MT to nodules that remain Bethesda III/IV on repeat FNA would have missed 4 low-risk cancers and 3 noninvasive follicular thyroid neoplasms with papillary-like nuclear features (NIFTP) (collectively 2% of the test population) but would have avoided diagnostic surgery for 42 benign nodules (12% of the test population). The Restrictive testing strategy was more specific (delta 0.126 confidence interval [CI 0.093 to 0.159] and 0.129 [CI 0.097 to 0.161], respectively) but less sensitive (delta -0.339 [CI -0.424 to -0.253] and -0.340 [CI -0.425 to -0.255], respectively) than the Reflex and SemiRestrictive approaches for detecting NIFTP or cancer. Conclusions: Repeat FNA cytology can guide the selection of cytologically indeterminate thyroid nodules that warrant MT. The Restrictive model of performing Afirma GEC only on nodules with two separate biopsies showing Bethesda III/IV cytology would reduce the rate of diagnostic surgery for histologically benign nodules while missing only rare low-risk tumors. Given the low but nontrivial risks of thyroidectomy, the higher specificity of the Restrictive testing approach disproportionately outweighs the potential harms.

Long-term voice changes after thyroidectomy: Results from a validated survey.

BACKGROUND: Long-term dysphonia may persist after thyroid surgery even in the absence of overt nerve injury. Therefore, we evaluated long-term dysphonia after thyroidectomy using a validated survey. METHODS: Patients undergoing thyroidectomy at a single institution from 1990 to 2018 were surveyed via telephone to complete the Voice Handicap Index-10 Survey. Individuals with documented nerve injury were excluded. RESULTS: In total, 308 patients completed the survey (mean age 51 ± 14 years, 78% female). Median time since surgery was 10.7 (interquartile range 2.3-17.5) years. The mean Voice Handicap Index-10 Survey score was 2.6 ± 5.2. Of the 113 (37%) patients who reported subjective dysphonia, the mean Voice Handicap Index-10 Survey score was 7.1 ± 6.5. Twenty-two (7.1%) patients had a Voice Handicap Index-10 Survey score above the empiric normative cutoff of 11, with a mean score of 17.6 ± 6.8. The most frequent complaints included "The clarity of my voice is unpredictable" (N = 71, 23%), "People have difficulty understanding me in a noisy room" (N = 70, 23%), and "I feel as though I have to strain to produce voice" (N = 65, 21%). CONCLUSION: Long-term follow-up of patients after thyroidectomy suggests that more than 30% without nerve injury report dysphonia. Research to further assess the etiology and impact of these changes on quality of life is needed.

Dexamethasone stimulates store-operated calcium entry and protein degradation in cultured L6 myotubes through a phospholipase A(2)-dependent mechanism.

Muscle wasting in various catabolic conditions is at least in part regulated by glucocorticoids. Increased calcium levels have been reported in atrophying muscle. Mechanisms regulating calcium homeostasis in muscle wasting, in particular the role of glucocorticoids, are poorly understood. Here we tested the hypothesis that glucocorticoids increase intracellular calcium concentrations in skeletal muscle and stimulate store-operated calcium entry (SOCE) and that these effects of glucocorticoids may at least in part be responsible for glucocorticoid-induced protein degradation. Treatment of cultured myotubes with dexamethasone, a frequently used in vitro model of muscle wasting, resulted in increased intracellular calcium concentrations determined by fura-2 AM fluorescence measurements. When SOCE was measured by using calcium "add-back" to muscle cells after depletion of intracellular calcium stores, results showed that SOCE was increased 15-25% by dexamethasone and that this response to dexamethasone was inhibited by the store-operated calcium channel blocker BTP2. Dexamethasone treatment stimulated the activity of calcium-independent phospholipase A(2) (iPLA(2)), and dexamethasone-induced increase in SOCE was reduced by the iPLA(2) inhibitor bromoenol lactone (BEL). In additional experiments, treatment of myotubes with the store-operated calcium channel inhibitor gadolinium ion or BEL reduced dexamethasone-induced increase in protein degradation. Taken together, the results suggest that glucocorticoids increase calcium concentrations in myocytes and stimulate iPLA(2)-dependent SOCE and that glucocorticoid-induced muscle protein degradation may at least in part be regulated by increased iPLA(2) activity, SOCE, and cellular calcium levels.

Sepsis downregulates myostatin mRNA levels without altering myostatin protein levels in skeletal muscle.

Myostatin is a negative regulator of muscle mass and has been reported to be upregulated in several conditions characterized by muscle atrophy. The influence of sepsis on myostatin expression and activity is poorly understood. Here, we tested the hypothesis that sepsis upregulates the expression and downstream signaling of myostatin in skeletal muscle. Because sepsis-induced muscle wasting is at least in part regulated by glucocorticoids, we also determined the influence of glucocorticoids on myostatin expression. Sepsis was induced in rats by cecal ligation and puncture and control rats were sham-operated. In other experiments, rats were injected intraperitoneally with dexamethasone (10 mg/kg) or corresponding volume of vehicle. Surprisingly, myostatin mRNA levels were reduced and myostatin protein levels were unchanged in muscles from septic rats. Muscle levels of activin A, follistatin, and total and phosphorylated Smad2 (p-Smad2) were not influenced by sepsis, suggesting that myostatin downstream signaling was not altered during sepsis. Interestingly, total and p-Smad3 levels were increased in septic muscle, possibly reflecting altered signaling through pathways other than myostatin. Similar to sepsis, treatment of rats with dexamethasone reduced myostatin mRNA levels and did not alter myostatin protein levels. Fasting, an additional condition characterized by muscle wasting, reduced myostatin mRNA and activin A protein levels, increased myostatin protein, and did not influence follistatin and p-Smad2 levels. Of note, total and p-Smad3 levels were reduced in muscle during fasting. The results suggest that sepsis and glucocorticoids do not upregulate the expression and activity of myostatin in skeletal muscle. The role of myostatin may vary between different conditions characterized by muscle wasting. Downstream signaling through Smad2 and 3 is probably regulated not only by myostatin but by other mechanisms as well.

Sepsis and glucocorticoids downregulate the expression of the nuclear cofactor PGC-1beta in skeletal muscle.

Muscle wasting during sepsis is at least in part regulated by glucocorticoids and is associated with increased transcription of genes encoding the ubiquitin ligases atrogin-1 and muscle-specific RING-finger protein-1 (MuRF1). Recent studies suggest that muscle atrophy caused by denervation is associated with reduced expression of the nuclear cofactor peroxisome proliferator-activated receptor-γ coactivator (PGC)-1ß and that PGC-1ß may be a repressor of the atrogin-1 and MuRF1 genes. The influence of other muscle-wasting conditions on the expression of PGC-1ß is not known. We tested the influence of sepsis and glucocorticoids on PGC-1ß and examined the potential link between downregulated PGC-1ß expression and upregulated atrogin-1 and MuRF1 expression in skeletal muscle. Sepsis in rats and mice and treatment with dexamethasone resulted in downregulated expression of PGC-1ß and increased expression of atrogin-1 and MuRF1 in the fast-twitch extensor digitorum longus muscle, with less pronounced changes in the slow-twitch soleus muscle. In additional experiments, adenoviral gene transfer of PGC-1ß into cultured C2C12 myotubes resulted in a dose-dependent decrease in atrogin-1 and MuRF1 mRNA levels. Treatment of cultured C2C12 myotubes with dexamethasone or PGC-1ß small interfering RNA (siRNA) resulted in downregulated PGC-1ß expression and increased protein degradation. Taken together, our results suggest that sepsis- and glucocorticoid-induced muscle wasting may, at least in part, be regulated by decreased expression of the nuclear cofactor PGC-1ß.

Sepsis and glucocorticoids upregulate p300 and downregulate HDAC6 expression and activity in skeletal muscle.

Muscle wasting during sepsis is in part regulated by glucocorticoids. In recent studies, treatment of cultured muscle cells in vitro with dexamethasone upregulated expression and activity of p300, a histone acetyl transferase (HAT), and reduced expression and activity of the histone deacetylases-3 (HDAC3) and -6, changes that favor hyperacetylation. Here, we tested the hypothesis that sepsis and glucocorticoids regulate p300 and HDAC3 and -6 in skeletal muscle in vivo. Because sepsis-induced metabolic changes are particularly pronounced in white, fast-twitch skeletal muscle, most experiments were performed in extensor digitorum longus muscles. Sepsis in rats upregulated p300 mRNA and protein levels, stimulated HAT activity, and reduced HDAC6 expression and HDAC activity. The sepsis-induced changes in p300 and HDAC expression were prevented by the glucocorticoid receptor antagonist RU38486. Treatment of rats with dexamethasone increased expression of p300 and HAT activity, reduced expression of HDAC3 and -6, and inhibited HDAC activity. Finally, treatment with the HDAC inhibitor trichostatin A resulted in increased muscle proteolysis and expression of the ubiquitin ligase atrogin-1. Taken together, our results suggest for the first time that sepsis-induced muscle wasting may be regulated by glucocorticoid-dependent hyperacetylation caused by increased p300 and reduced HDAC expression and activity. The recent development of pharmacological HDAC activators may provide a novel avenue to prevent and treat muscle wasting in sepsis and other catabolic conditions.

Corticosteroids and muscle wasting: role of transcription factors, nuclear cofactors, and hyperacetylation.

PURPOSE OF REVIEW: The purpose of this review is to discuss novel insight into mechanisms of glucocorticoid-regulated muscle wasting, in particular the role of transcription factors and nuclear cofactors. In addition, novel strategies that may become useful in the treatment or prevention of glucocorticoid-induced muscle wasting are reviewed. RECENT FINDINGS: Studies suggest that glucocorticoid-induced upregulation of the transcription factors Forkhead box O 1 and CCAAT/enhancer-binding protein beta and downregulation of MyoD and myogenin are involved in glucocorticoid-induced muscle wasting. In addition, glucocorticoid-induced hyperacetylation caused by increased expression of the nuclear cofactor p300 and its histone acetyl transferase activity and decreased expression and activity of histone deacetylases plays an important role in glucocorticoid-induced muscle proteolysis and wasting. Other mechanisms may also be involved in glucocorticoid-induced muscle wasting, including insulin resistance and store-operated calcium entry. Novel potential strategies to prevent or treat glucocorticoid-induced muscle wasting include the use of small molecule histone deacetylase activators, dissociated glucocorticoid receptor agonists, and 11beta-hydroxysteroid dehydrogenase type 1 inhibitors. SUMMARY: An increased understanding of molecular mechanisms regulating glucocorticoid-induced muscle wasting will help develop new strategies to prevent and treat this debilitating condition.

Experimental hyperthyroidism in rats increases the expression of the ubiquitin ligases atrogin-1 and MuRF1 and stimulates multiple proteolytic pathways in skeletal muscle.

Muscle wasting is commonly seen in patients with hyperthyroidism and is mainly caused by stimulated muscle proteolysis. Loss of muscle mass in several catabolic conditions is associated with increased expression of the muscle-specific ubiquitin ligases atrogin-1 and MuRF1 but it is not known if atrogin-1 and MuRF1 are upregulated in hyperthyroidism. In addition, it is not known if thyroid hormone increases the activity of proteolytic mechanisms other than the ubiquitin-proteasome pathway. We tested the hypotheses that experimental hyperthyroidism in rats, induced by daily intraperitoneal injections of 100 microg/100 g body weight of triiodothyronine (T3), upregulates the expression of atrogin-1 and MuRF1 in skeletal muscle and stimulates lysosomal, including cathepsin L, calpain-, and caspase-3-dependent protein breakdown in addition to proteasome-dependent protein breakdown. Treatment of rats with T3 for 3 days resulted in an approximately twofold increase in atrogin-1 and MuRF1 mRNA levels. The same treatment increased proteasome-, cathepsin L-, and calpain-dependent proteolytic rates by approximately 40% but did not influence caspase-3-dependent proteolysis. The expression of atrogin-1 and MuRF1 remained elevated during a more prolonged period (7 days) of T3 treatment. The results provide support for a role of the ubiquitin-proteasome pathway in muscle wasting during hyperthyroidism and suggest that other proteolytic pathways as well may be activated in the hyperthyroid state.

Curcumin and muscle wasting: a new role for an old drug?

Sepsis, severe injury, and cancer are associated with loss of muscle mass. Muscle wasting in these conditions is mainly caused by increased proteolysis, at least in part regulated by nuclear factor-kappaB. Despite recent progress in the understanding of mediators and mechanisms involved in muscle wasting, effective and universally accepted treatments by which muscle atrophy can be prevented or reversed are still lacking. We review recent evidence suggesting that curcumin (diferuloylmethane), a component of the spice turmeric, may prevent loss of muscle mass during sepsis and endotoxemia and may stimulate muscle regeneration after traumatic injury. Curcumin has been part of the traditional Asian medicine for centuries, mainly because of its anti-inflammatory properties. Studies suggest that inhibition of nuclear factor-kappaB is one of the mechanisms by which curcumin exerts its ant-inflammatory effects. Curcumin is easily accessible, inexpensive, and non-toxic even at high doses, and may therefore offer an important treatment modality in muscle wasting and injury. It should be noted, however, that the muscle-sparing effects of curcumin are not universally accepted, and more studies are therefore needed to further test the role of curcumin in the prevention and treatment of muscle wasting.