Adult expression of PGC-1α and -1ß in skeletal muscle is not required for endurance exercise-induced enhancement of exercise capacity.

Exercise has been shown to be the best intervention in the treatment of many diseases. Many of the benefits of exercise are mediated by adaptions induced in skeletal muscle. The peroxisome proliferator-activated receptor gamma coactivator-1 (PGC-1) family of transcriptional coactivators has emerged as being key mediators of the exercise response and is considered to be essential for many of the adaptions seen in skeletal muscle. However, the contribution of the PGC-1s in skeletal muscle has been evaluated by the use of either whole body or congenital skeletal muscle-specific deletion. In these models, PGC-1s were never present, thereby opening the possibility to developmental compensation. Therefore, we generated an inducible muscle-specific deletion of PGC-1α and -1ß (iMyo-PGC-1DKO), in which both PGC-1α and -ß can be deleted specifically in adult skeletal muscle. These iMyo-PGC-1DKO animals were used to assess the role of both PGC-1α and -1ß in adult skeletal muscle and their contribution to the exercise training response. Untrained iMyo-PGC-1DKO animals exhibited a time-dependent decrease in exercise performance 8 wk postdeletion, similar to what was observed in the congenital muscle-specific PGC-1DKOs. However, after 4 wk of voluntary training, the iMyo-PGC-1DKOs exhibited an increase in exercise performance with a similar adaptive response compared with control animals. This increase was associated with an increase in electron transport complex (ETC) expression and activity in the absence of PGC-1α and -1ß expression. Taken together these data suggest that PGC-1α and -1ß expression are not required for training-induced exercise performance, highlighting the contribution of PGC-1-independent mechanisms.

Comprehensive detection of structural variation and transposable element differences between wild type laboratory lineages of C. elegans.

Genomic structural variations (SVs) and transposable elements (TEs) can be significant contributors to genome evolution, altered gene expression, and risk of genetic diseases. Recent advancements in long-read sequencing have greatly improved the quality of de novo genome assemblies and enhanced the detection of sequence variants at the scale of hundreds or thousands of bases. Comparisons between two diverged wild isolates of Caenorhabditis elegans, the Bristol and Hawaiian strains, have been widely utilized in the analysis of small genetic variations. Genetic drift, including SVs and rearrangements of repeated sequences such as TEs, can occur over time from long-term maintenance of wild type isolates within the laboratory. To comprehensively detect both large and small structural variations as well as TEs due to genetic drift, we generated de novo genome assemblies and annotations for each strain from our lab collection using both long- and short-read sequencing and compared our assemblies and annotations with that of other lab wild type strains. Within our lab assemblies, we annotate over 3.1Mb of sequence divergence between the Bristol and Hawaiian isolates: 337,584 SNPs, 94,503 small insertion-deletions (<50bp), and 4,334 structural variations (>50bp). Further, we define the location and movement of specific DNA TEs between N2 Bristol and CB4856 Hawaiian wild type isolates. Specifically, we find the N2 Bristol genome has 20.6% more TEs from the Tc1/mariner family than the CB4856 Hawaiian genome. Moreover, we identified Zator elements as the most abundant and mobile TE family in the genome. Using specific TE sequences with unique SNPs, we also identify 38 TEs that moved intrachromosomally and 9 TEs that moved interchromosomally between the N2 Bristol and CB4856 Hawaiian genomes. By comparing the de novo genome assembly of our lab collection Bristol isolate to the VC2010 Bristol assembly, we also reveal that lab lineages display over 2 Mb of total variation: 1,162 SNPs, 1,528 indels, and 897 SVs with 95% of the variation due to SVs. Overall, our work demonstrates the unique contribution of SVs and TEs to variation and genetic drift between wild type laboratory strains assumed to be isogenic despite growing evidence of genetic drift and phenotypic variation.

Immunohistochemistry of COUP-TFI: an adjuvant diagnostic tool for the identification of corticotroph microadenomas.

Cushing's disease is caused by an ACTH-producing pituitary tumor, and accounts for 10-15% of pituitary tumors. The majority of corticotroph tumors are microadenomas (<10 mm), and accurate histologic identification of these tumors can be challenging because of their small size and the presence of nests of normal corticotroph cells in the anterior pituitary. Retinoic acid has been shown to inhibit ACTH production and induce apoptosis in corticotroph tumor cells. The expression of the orphan nuclear receptor COUP-TFI antagonizes retinoic acid signaling and has been shown to be expressed in normal corticotroph cells, but absent in corticotroph tumor cell lines. We analyzed 34 corticotroph tumor specimens by immunohistochemistry using a goat polyclonal IgG antibody with epitope mapping to the N-terminus of human COUP-TFI. Segments of normal pituitary in each of the 34 specimens demonstrate COUP-TFI immunoreactivity in normal corticotroph cells. Twenty-nine of 34 ACTH producing tumors were immunonegative for COUP-TFI. All of the tumors measuring less than 5 mm by preoperative MRI were COUP-TFI immunonegative. Two tumors, measuring 9 and 11 mm, showed consistent (>90%) expression of COUP-TFI, and three adenomas (5, 11, and 18 mm) showed heterogenous (20-80%) expression of COUP-TFI. Immunohistochemistry of COUP-TFI may be a useful adjuvant diagnostic tool in distinguishing corticotroph microadenomas from nests of normal corticotroph cells in the anterior pituitary. Furthermore, this study identifies two unique corticotroph tumor populations which differ in their expression of COUP-TFI, the presence of which occurs more frequently in macroadenomas.

Elevated Temperatures Cause Transposon-Associated DNA Damage in C. elegans Spermatocytes.

Sexually reproducing organisms use meiosis to generate haploid gametes and faithfully transmit their genome to the next generation. In comparison to oogenesis in many organisms, spermatogenesis is particularly sensitive to small temperature fluctuations, and spermatocytes must develop within a very narrow isotherm [1-4]. Although failure to thermoregulate spermatogenetic tissue and prolonged exposure to elevated temperatures are linked to male infertility in several organisms, the mechanisms of temperature-induced male infertility have not been fully elucidated [5]. Here, we show that upon exposure to a brief 2°C temperature increase, Caenorhabditis elegans spermatocytes exhibit up to a 25-fold increase in double-strand DNA breaks (DSBs) throughout meiotic prophase I and a concurrent reduction in male fertility. We demonstrate that these heat-induced DSBs in spermatocytes are independent of the endonuclease SPO-11. Further, we find that the production of these heat-induced DSBs in spermatocytes correlate with heat-induced mobilization of Tc1/mariner transposable elements, which are known to cause DSBs and alter genome integrity [6, 7]. Moreover, we define the specific sequences and regions of the male genome that preferentially experience these heat-induced de novo Tc1 insertions. In contrast, oocytes do not exhibit changes in DSB formation or Tc1 transposon mobility upon temperature increases. Taken together, our data suggest spermatocytes are less tolerant of higher temperatures because of an inability to effectively repress the movement of specific mobile DNA elements that cause excessive DNA damage and genome alterations, which can impair fertility.

Adult skeletal muscle deletion of Mitofusin 1 and 2 impedes exercise performance and training capacity.

Endurance exercise has been shown to be a positive regulator of skeletal muscle metabolic function. Changes in mitochondrial dynamics (fusion and fission) have been shown to influence mitochondrial oxidative capacity. We therefore tested whether genetic disruption of mitofusins (Mfns) affected exercise performance in adult skeletal muscle. We generated adult-inducible skeletal muscle-specific Mfn1 (iMS-Mfn1KO), Mfn2 (iMS-Mfn2KO), and Mfn1/2 (iMS-MfnDKO) knockout mice. We assessed exercise capacity by performing a treadmill time to exhaustion stress test before deletion and up to 8 wk after deletion. Analysis of either the iMS-Mfn1KO or the iMS-Mfn2KO did not reveal an effect on exercise capacity. However, analysis of iMS-MfnDKO animals revealed a progressive reduction in exercise performance. We measured individual electron transport chain (ETC) complex activity and observed a reduction in ETC activity in both the subsarcolemmal and intermyofibrillar mitochondrial fractions specifically for NADH dehydrogenase (complex I) and cytochrome- c oxidase (complex IV), which was associated with a decrease in ETC subunit expression for these complexes. We also tested whether voluntary exercise training would prevent the decrease in exercise capacity observed in iMS-MfnDKO animals ( n = 10/group). However, after 8 wk of training we did not observe any improvement in exercise capacity or ETC subunit parameters in iMS-MfnDKO animals. These data suggest that the decrease in exercise capacity observed in the iMS-MfnDKO animals is in part the result of impaired ETC subunit expression and ETC complex activity. Taken together, these results provide strong evidence that mitochondrial fusion in adult skeletal muscle is important for exercise performance. NEW & NOTEWORTHY This study is the first to utilize an adult-inducible skeletal muscle-specific knockout model for Mitofusin (Mfn)1 and Mfn2 to assess exercise capacity. Our findings reveal a progressive decrease in exercise performance with Mfn1 and Mfn2 deletion. The decrease in exercise capacity was accompanied by impaired oxidative phosphorylation specifically for complex I and complex IV. Furthermore, voluntary exercise training was unable to rescue the impairment, suggesting that normal fusion is essential for exercise-induced mitochondrial adaptations.

Temozolomide treatment for aggressive pituitary tumors: correlation of clinical outcome with O(6)-methylguanine methyltransferase (MGMT) promoter methylation and expression.

CONTEXT: The typically indolent behavior of pituitary tumors is juxtaposed with high rates of tumor cell invasion into adjacent dural structures, and occasional aggressive behavior. Although clinically significant invasion and malignant transformation remain uncommon, there are limited treatment options available for the management of these aggressive tumors. Recently, case reports have described efficacy of temozolomide for the treatment of aggressive pituitary tumors. DESIGN: Seven patients with aggressive pituitary tumors have been treated with temozolomide. We compared O(6)-methylguanine methyltransferase (MGMT) promoter methylation and MGMT expression in 14 surgical specimens from these seven patients and correlated these molecular features with the clinical response to temozolomide. RESULTS: Significant tumor regression was seen in two patients (29%), a 20% reduction in tumor volume with subsequent stable tumor size was noted in one patient, arrest of tumor growth occurred in three patients, and progressive metastatic disease developed during treatment in one patient. The DNA promoter site for MGMT was unmethylated in all 14 adequate specimens, and variable MGMT expression was seen in all 14 cases. There was no correlation between MGMT expression and clinical outcomes. CONCLUSIONS: We conclude that medical therapy with temozolomide can be helpful in the management of life-threatening pituitary tumors that have failed to respond to conventional treatments. The optimal duration of treatment in patients with stabilization or reduction of tumor size has not been established, and long-term follow up studies are needed.

Management of acromegaly: is there a role for primary medical therapy?

Acromegaly is a chronic, debilitating disease caused by chronic growth hormone (GH) hypersecretion which results in chronic medical comorbidities, poor quality of life and high mortality rates. Successful treatment can improve clinical signs and symptoms and normalize mortality rates. Over 95% of acromegaly is caused by a somatotroph adenoma of the pituitary, and the first-line treatment is generally transsphenoidal surgery, which can be curative in 50-60% of patients. Nonetheless, high rates of persistent acromegaly following surgery and the limited efficacy of radiation therapy necessitate chronic medical treatment for many patients. Somatostatin analogues have become the preferred first-line medical therapy for many practitioners, as they achieve better biochemical and direct tumor control than the dopamine agonists, and long-acting preparations make once monthly administration possible. Cabergoline, a dopamine agonist, offers a lower-cost option and may be effective in patients with a pituitary tumor that co-secretes GH and prolactin. Pegvisomant is a GH receptor antagonist that produces exceptional biochemical response rates but lacks any direct effects on the tumor, which may limit its effectiveness as life-long monotherapy. Combinations of these three drug classes have not been rigorously studied, and preliminary trials do not suggest improved clinical outcomes. While medical treatment options for acromegaly have significantly improved over the last 30 years, limitations remain, and a multi-specialty team approach is necessary for the effective long-term management of patients with acromegaly.

Acute pancreatitis in HIV-infected patients: are etiologies changing since the introduction of protease inhibitor therapy?

INTRODUCTION: Hypertriglyceridemia is a well-established cause of acute pancreatitis in the general population. Protease inhibitor (PI) therapy, introduced in 1996 for HIV infection, is associated with moderate to severe hypertriglyceridemia. AIMS: To determine whether the prevalence of hyperlipidemic pancreatitis in HIV-infected patients has increased since the introduction of PIs. METHODOLOGY: This was a retrospective study of patients with acute pancreatitis and HIV infection admitted to three local hospitals between 1990 and 2001. RESULTS: Before PIs became available (1990-1995), 30 index cases of acute pancreatitis in the setting of HIV infection were identified, and one of these cases (3.3%) was attributed to hypertriglyceridemia. After the introduction of PIs (1996-2001), 54 cases of acute pancreatitis in HIV-infected patients were identified, and two of these cases were attributed to hypertriglyceridemia (3.7%; p = 0.6). In both time periods, medication-induced pancreatitis was the most common cause of pancreatitis in HIV-infected patients. CONCLUSION: Despite the well-established association between PIs and hypertriglyceridemia, there was no significant increase in the prevalence of hyperlipidemic pancreatitis in this HIV-infected population after the introduction of PIs. Medication-associated pancreatitis remains the most common cause of acute pancreatitis in the era of potent antiretroviral therapy.