Aberrant anabolic activity is critical to tumor biology; however, much remains to be learned about the regulators of protein anabolism in cancer and how this regulation may affect cancer pathophysiology. MicroRNA (miRNA), a family of small nucleotide regulatory molecules, may serve as a potential source of proteostatic regulation. Here, we examined the ability of two co-transcribed miRNA species, miR15a and miR16 (jointly described as miR15a/16) to regulate protein handling and pathophysiology in non-small cell lung cancer (NSCLC). We found that miR15a/16 regulates genes in numerous metabolic and pathological pathways, including those related to protein metabolism. Transfection of cellular models of NSCLC with miR15a/16 mimetics caused reductions in both cell growth and protein synthesis rates. These findings indicate that miR15a/16 acts as regulators of protein anabolism in NSCLC, serving as novel metabolic regulators and potential clinical therapeutic targets for malignant lung cancer.

Abstract Dysregulated cellular protein metabolism is a key hallmark of pancreatic ductal adenocarcinoma (PDAC). However, much remains to be learned about how this process is regulated in cancerous cells. Here we investigated the role of two co‐transcribed microRNA (miRNA) species, miR‐15a/16, in regulating cellular protein translation, cell growth, metabolic processes, and clinical features in PDAC. Using cultured PDAC models, we show that overexpression of miR‐15a/16 in cancerous cells slows proliferation and attenuates protein synthesis rates. Bioinformatics analysis reveals that these miRNAs target a broad suite of pathophysiological and metabolic pathways, including numerous genes in cancer‐ and protein‐related processes. Finally, using publicly available patient data, we report that miR‐15a/16 expression is lower in PDAC tumors and in patients with pancreatitis than in healthy controls, and that high expression of miR‐15a/16 in tumors is associated with improved survival in patients. Our results indicate that miR‐15a/16 act as regulators of protein metabolism in PDAC, with potential clinical implications for the management of this devastating disease.

A high-fat diet (HFD) and metabolic disease can impair insulin signaling in skeletal muscle, including a reduction in IRS-1 and GLUT-4 at the cell membrane. Other sarcolemmal proteins (e.g. caveolin-3, nNOS) within the dystrophin-glycoprotein complex (DGC) are partially lost with Type II diabetes. Thus, we hypothesized that a HFD would cause a significant loss of sarcolemmal DGC proteins and GLUT4, and the anti-diabetic drug metformin would mitigate the disruption of the DGC and preserve sarcolemmal GLUT4 on the soleus muscle. Eight-week-old mice were fed a high-fat diet for 12 weeks. After 8 weeks, one-half of the HFD mice received metformin for the remaining 4 weeks. HFD caused a marked increase in soleus muscle mass and fiber cross-sectional area and elevated sarcolemmal GLUT4, even though systemic insulin resistance was greater. HFD-induced muscle hypertrophy and elevated membrane GLUT4 were unexpectedly attenuated by metformin. In addition, IRS-1 positive staining was not reduced by HFD but rather enhanced in the metformin mice fed a high-fat diet. Sarcolemmal staining of dystrophin and caveolin-3 was reduced by HFD but not in the metformin group, while nNOS intensity was unaffected by HFD and metformin. These findings suggest that skeletal muscles in young adult mice can compensate for a high-fat diet and insulin resistance, with a minor disruption of the DGC, by maintaining cell membrane nNOS and IRS-1 and elevating GLUT4. We postulate that a window of compensatory GLUT4 and nNOS signaling allows calorically dense food to enhance skeletal muscle fiber size when introduced in adolescence.

The hyperactivation of mTOR is a significant contributor to the development and progression of a number of human diseases, including a majority of human cancers. Although there have been many scientific and clinical efforts to reduce the impact of mTOR hyperactivation on downstream cellular metabolism, we aimed to mitigate this hyperactivation through a novel targeted gene edit of the intrinsic mTOR inhibitor, DEP domain containing MTOR interacting protein (DEPTOR), in MCF7 human breast cancer cells. Using publicly available bioinformatics tools, we demonstrate that DEPTOR gene expression is low in breast cancers compared with healthy tissues and that DEPTOR expression predicts overall survival, recurrence-free survival, and distant metastasis-free survival in breast cancer patients. We show that a directed overexpression of DEPTOR protein leads to significant alteration of downstream mTORC1 targets and subsequently reduces overall rates of protein synthesis. In addition, treatment of DEPTOR overexpressing cells with small-molecule DEPTOR inhibitor NSC126405 leads to a reversal of this effect, indicating a direct causal mechanism between DEPTOR protein levels and mTORC1 activation.NEW & NOTEWORTHY We identify DEPTOR as a predictor of mortality in breast cancer and show that precision gene editing to restore DEPTOR expression in breast cancer slows cell growth by inhibiting mTOR activity.

The complex interplay of metabolic signaling networks is critical to the pathophysiology of lung cancer. The anabolic mTORC1 kinase and catabolic process of autophagy are key among these regulatory pathways. While their relationship has long been viewed as a matter of simple inhibition, with mTORC1 as a negative regulator of autophagy, new evidence suggests that this relationship may be more nuanced than previously described. Here, we demonstrate that an autophagy-related, ATG4B, is required for mTORC1 activity and is associated with negative clinical outcomes in non-small cell lung cancer (NSCLC). Targeting ATG4B in vitro suppresses cell proliferation, protein synthesis rates, and mTORC1 signaling in a cellular model of NSCLC. In contrast, overexpressing the ATG4B protease in healthy models of lung tissue increased mTORC1 kinase activity in healthy lung cell models, indicating that an increase in ATG4B is sufficient to drive cellular anabolic signaling. Finally, we found that ATG4B expression is high in NSCLC patient tumors, is elevated in early-stage cancer, and predicts survival in lung adenocarcinoma patients. Taken together, our results demonstrate that ATG4B is required for anabolic behavior in NSCLC, indicating that the autophagic cascade may be a required input for mTORC1 activity and cellular anabolism in lung cancer. These results have implications for the field of cancer biology more broadly, as they indicate that the far from being a simple target of mTORC1, the autophagic cascade may serve as a requisite input for anabolic signaling, casting new light on the relationship between these processes in cancer pathophysiology. [Correction added on 25 February 2026, after first online publication: 9th sentence has been revised as "Targeting ATG4B in vitro suppresses cell proliferation, protein synthesis rates, and mTORC1 signaling in a cellular model of NSCLC"].

Background: Skeletal muscles adapt their mass (e.g., hypertrophy, atrophy) due to changes in loading, or mechanotransduction, as well as in response to nutrient and energy sensing. There are multiple load sensing pathways that could trigger unloading-induced muscle atrophy. Over the past 15 years, multiple laboratories have reported that post-translational translocation of neuronal nitric oxide synthase (nNOS) from the sarcolemma to the cytosol flips the role of nNOS from anabolic to catabolic. Loss of nNOS during mechanical unloading appears to be regulated by oxidative stress (e.g., NADPH oxidase-2, mitochondria), stress response proteins, and proteoglycans. In addition, Receptor Activator of Nuclear factor Kappa beta Ligand (RANKL), historically linked to osteoporosis in bone, could contribute to myopathies including unloading-induced atrophy. The NAD-dependent deacetylase sirtuin-1 (SIRT1) has numerous cell protective roles in metabolism, mitochondrial function, and stress protection. SIRT1 has recently been linked with muscle hypertrophy. Objective/Hypothesis: We hypothesized that a SIRT1 agonist (SRT2104) would significantly attenuate unloading-induced upregulation of Nox2 and RANKL, linked to preservation of sarcolemmal nNOS and muscle fibers cross-sectional area. Methods: In this experiment, 5-month-old F344 rats were divided into three groups (n=6 each): ambulatory controls (CON), hindlimb unloaded to 10 days (HU), and hindlimb unloaded + SIRT1 (25 mg/kg/day: HUS). Immunoblots, immunofluorescence (IF), and ELISA protein analysis was conducted on muscle samples. Results: We first confirmed that SRT2104 increased SIRT1 protein levels and activity in unloaded gastrocnemius muscle. The Nox2 subunit (p67phox), upstream regulators of Nox2 (e.g., cyclophilin A, acid sphingomyelinase), and RANKL were elevated by 2 - 4 fold by hindlimb unloading; however, unloading-induced elevation of Nox2-RANKL signaling was prevented by SRT2104. Further, loss of sarcolemmal nNOS was also found in HU muscle, while translocation of nNOS was largely prevented by SRT-2104 per both Western blotting and IFs. The sarcolemmal scaffolding protein dystrobrevin suffered loss of membrane localization with HU. In contrast, SRT2104 mitigated disruption of dystrobrevin. Sarcolemmal and blood serum Klotho levels were increased with unloading, which SRT2104 prevented. SRT2104 attenuated upregulation of Klotho and reduction in Akt phosphorylation (Ser308) in unloaded muscle. Conversely, p62 levels decreased with HU and was prevented with HU + SRT-2104. Conclusions: Our findings suggest that targeting SIRT1 could alleviate elevation in redox signaling (Nox2, RANKL), which appear to protect sarcolemmal nNOS. Furthermore, SRT2104 downregulated Klotho signaling and preserved anabolic/catabolic balance. A potential mechanism for SIRT1-induced protection could be through upstream regulators of nNOS and protection of the scaffolding protein dystrobrevin. Supported by NASA (80NSSC19K0432, NNX80NSSC17K0118, NNX13AE45G), NSBRI, Huffines Institute, Fight DMD This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.

Disuse muscle atrophy remains a major challenge in contexts such as prolonged bed rest or microgravity. Here, we investigated whether brief bouts of ambulatory reloading could attenuate skeletal muscle atrophy caused by five days of hindlimb unloading (HU) in rats. Using a deuterium oxide tracer, we measured integrative protein synthesis (fractional synthesis rate, FSR) in the soleus, plantaris, and gastrocnemius muscles, including distinct portions of the muscle that are composed mostly of red, white, and mixed fibers. HU significantly reduced both muscle mass and FSR in the predominantly slow-twitch soleus and in the predominantly fast gastrocnemius. Intermittent ambulatory reloading (HU + AR) partially restored FSR in the soleus and gastrocnemius but did not recover soleus or gastrocnemius mass to control levels. The plantaris muscle showed no differences in mass or FSR among groups, suggesting muscle-specific responses to unloading and reloading. Fiber-type analyses revealed that portions of the gastrocnemius that are mostly red fibers had higher baseline FSR than mixed or white portions, while HU consistently depressed protein synthesis across all fiber types. In conclusion, although intermittent ambulation increased protein synthesis during HU, it was not sufficient to prevent overall muscle mass loss. These findings emphasize the importance of both the duration and intensity of loading in preserving skeletal muscle during periods of disuse.

The mammalian target of rapamycin (mTOR), and specifically the mTOR complex 1 (mTORC1) is the central regulator of anabolism in skeletal muscle. Among the many functions of this kinase complex is the inhibition of the catabolic process of autophagy; however, less work has been done in investigating the role of autophagy in regulating mTORC1 signaling. Using an in vitro model to better understand the pathways involved, we activated mTORC1 by several different means (growth factors, leucine supplementation, or muscle contraction), alone or with the autophagy inhibitor NSC185058. We found that inhibiting autophagy with NSC185058 suppresses mTORC1 activity, preventing any increase in cellular protein anabolism. These decrements were the direct result of action on the mTORC1 kinase, which we demonstrate, for the first time, cannot function when autophagy is inhibited by NSC185058. Our results indicate that, far from being a matter of unidirectional action, the relationship between mTORC1 and the autophagic cascade is more nuanced, with autophagy serving as an mTORC1 input, and mTORC1 inhibition of autophagy as a form of homeostatic feedback to regulate anabolic signaling. Future studies of cellular metabolism will have to consider this fundamental intertwining of protein anabolism and catabolism, and how it ultimately serves to regulate muscle proteostasis.

Background: Rampant and unregulated cell growth is a key hallmark of cancer pathology; however, much remains to be discovered about the process that allow for pathological growth in cancerous cells. Recently, we demonstrated that the autophagy-related cysteine protease ATG4B is required for protein anabolism in skeletal muscle, indicating a previously undescribed mechanism by which autophagy directly acts as a recycling/remodeling system for cellular anabolism. Purpose: To investigate if ATG4B is responsible for growth in cancer, and if inhibition of ATG4B is a successful strategy to target cancer growth. Hypothesis: We hypothesized that ATG4B would be higher in cancerous tissues versus healthy ones, and that inhibition of ATG4B by NSC185058 would inhibit cell growth and reduce protein anabolism. Methods: We used the UALCAN web tool to analyze the TCGA data set for differences in ATG4B gene expression in lung adenocarcinoma, comparing healthy to cancerous tissues as well as across cancer stages. Separately, we used the A549 lung cancer cell line as a model to study the effects of ATG4B inhibition, treating cells with 100 μM NSC185058 or equimolar DMSO as a vehicle control, and analyzing treated cells for proliferation and protein synthesis rates. Welch’s t-test was used to calculate differences in TCGA data, while a two-tailed student’s t-test was used to determine differences in proliferation at indicated time points, with an α-level of 0.05. Results: ATG4B expression is 22% higher in cancerous tissues vs healthy controls (p<0.05), and also higher in stages 1-4 of lung adenocarcinoma (Healthy vs Stage 1: +25%, Healthy vs Stage 2: +23%, Healthy vs Stage 3: +13%, Healthy vs Stage 4: +30%, p<0.05). Treatment with NSC185058 suppresses cell growth across 72 hours (24 hour VC vs NSC: -59%, 48 hour VC vs NSC: -83%, 72 Hour VC vs NSC: -90%), and reduces 24-hour rates of protein synthesis by 56% (p<0.05) in cancer cells. Conclusions: ATG4B expression is increased in lung adenocarcinoma, including in early-stage cancer, and inhibition by NSC185058 drastically reduces anabolism in cancerous cells. We posit that autophagy, mediated by ATG4B is required for protein anabolism in lung cancer, and that targeting this process represents a novel strategy to combat cancer pathology. This work was generously funded by the Huffnes Institute and School of Education and Human Development at Texas A&M University. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

PURPOSE: Here, we set out to further elucidate the metabolic pathways by which autophagy may influence protein anabolism. METHODS: L6 myotubes received electrical pulse stimulation (EPS) to induce muscle contraction, and were then treated with NSC185058 (NSC, 100 μM, autophagy inhibitor) or DMSO as a vehicle control. After 24 hours, cells were lysed and prepared for Western blot analysis of phosphorylation status and content of several key signaling proteins. Differences in outcomes between VC and NSC treated groups were assessed by two-tailed t-test, while comparisons between VC, EPS, and EPS + NSC groups were made using ANOVA and SNK post-hoc test, with α levels set at 0.05. RESULTS: There was no difference in the ratio of phosphorylated to total P70S6K between VC and NSC treated groups. EPS induced a 97% increase in P70S6K phosphorylation (p < 0.05), with NSC treatment blunting this effect, consistent with our prior findings. EPS resulted in a 37% reduction in DEPTOR content (p < 0.05); however, NSC treatment alone produced a 166% decrease in DEPTOR level (p < 0.05), with EPS + NSC leading to a larger reduction (-766%) in DEPTOR than EPS. While not achieving the level of significance, NSC decreased (-85%) LC3II/I ratio relative to vehicle control, which was significantly reduced in both EPS (-68%) and EPS + NSC (-87%). P62 increased by 749% with EPS (p < 0.05), but there was no significant difference between VC and EPS + NSC, and NSC treatment alone led to a 61% decrease in P62. NSC did not change MAPK phosphorylation, and resulted in no significant difference in MAPK signaling when compared with EPS alone. Neither NSC nor EPS + NSC altered AMPK phosphorylation. CONCLUSION: Despite reductions of DEPTOR in the presence of NSC, P70S6K activity remained unaltered in quiescent cells and was unresponsive to EPS. This is particular to the mTOR pathway, as increase in MAPK phosphorylation post EPS was still observed in NSC treated cells. While the decrease in LC3II/I and the accumulation of P62 after EPS are due to autophagy inhibition by mTOR, our data seem to suggest that inhibition of the ATG4 enzyme by NSC leads to mTOR inhibition, as evidenced by loss of P62 protein in NSC treated cells. This DEPTOR-independent effect is likely not due to activation of the cellular energy sensor AMPK, as we found no increase in AMPK phosphorylation in any condition.

Choline plays many important roles, including the synthesis of acetylcholine, and may affect muscle responses to exercise. We previously observed correlations between low choline intake and reduced gains in strength and lean mass following a 12-week resistance exercise training (RET) program for older adults. To further explore these findings, we conducted a randomized controlled trial. Three groups of 50-to-69-year-old healthy adults underwent a 12-week RET program (3x/week, 3 sets, 8–12 reps, 70% of maximum strength (1RM)) and submitted >48 diet logs (>4x/week for 12 weeks). Participants’ diets were supplemented with 0.7 mg/kg lean/d (low, n = 13), 2.8 mg/kg lean/d (med, n = 11), or 7.5 mg/kg lean/d (high, n = 13) of choline from egg yolk and protein powder. The ANCOVA tests showed that low choline intake, compared with med or high choline intakes, resulted in significantly diminished gains in composite strength (leg press + chest press 1RM; low, 19.4 ± 8.2%; med, 46.8 ± 8.9%; high, 47.4 ± 8.1%; p = 0.034) and thigh-muscle quality (leg press 1RM/thigh lean mass; low, 12.3 ± 9.6%; med/high, 46.4 ± 7.0%; p = 0.010) after controlling for lean mass, protein, betaine, and vitamin B12. These data suggest that low choline intake may negatively affect strength gains with RET in older adults.

Unloading‐induced atrophy and exposure to space radiation are considered major physiological limitations to future space exploration. Muscle mass and muscle strength loss have been reported in models of hindlimb unloading and have been associated with fiber type changes and a shift toward more glycolytic activity. It is commonly purported that skeletal muscle is radio‐resistant due to its post mitotic state, but recent work has indicated changes in both protein synthesis rates and muscle morphometry with exposure to high‐charge high energy particles. While unloading‐induced atrophy has been widely studied in models of complete unloading, information on muscle atrophy in partial loading conditions is much less common, but there is indication that muscle anabolism is linked to gravitational load or lack thereof. It is clear that space exploration includes both space radiation‐ and unloading‐induced atrophy; however, the combined effects of these two environmental factors has limited investigation. The purpose of this study was to determine the impact of acute radiation exposure, with or without the addition of partial loading on skeletal muscle anabolic signaling.METHODSBALB/cByJ (4mo female) mice were assigned either to full weight bearing or partial weight bearing equal to 1/6th bodyweight groups. These groups were then further divided into either single 0.5 Gy of 300 MeV whole–body 28 Si radiation exposure (GCR) or sham. Radiation exposure occurred on Day 0 at Brookhaven National Laboratory and was followed by 21d of Earth (1G) or Lunar (G/6) loading. Muscles of the hind limb were examined for common markers of protein anabolism. Protein expression was measured in the quadriceps using western blot techniques and fiber type was measured using immunohistochemistry.RESULTSOur data indicate that neither GCR exposure nor Lunar loading alone altered mTORC1 dependent signaling. DEPTOR expression was significantly lower when lunar loading and radiation were combined, which may be an indication of bolstered repair response (P<0.05). Interestingly, radiation exposure had higher phosphorylation of ERK1/2 when compared to SHAM counterparts (CC 3.2 fold increase, and 5.6 fold increase in G/6 groups), and was associated with the preservation of muscle mass and the predominance of type 2 fiber composition in the irradiated animals of this experiment.CONCLUSIONThis study suggests that heavy ion exposure affects skeletal muscle and can lead to discrete and combined effects in anabolic signaling.Support or Funding InformationThis study was funded in part by National Space Biomedical Research Institute.

Objectives. - While resistance exercise increases plasma free fatty acids and mobilizes kinases activity, the direct effect of resistance exercise on skeletal muscle peroxisome proliferator-activated receptors delta (PPAR delta) remained unclear. The present study investigated the acute and training effects of resistance exercise on PPAR delta protein content and its association with serum lipid profile. Equipment and methods. - Seventeen young males (n = 8) and females (n = 9) performed a 10-week progressive resistance exercise-training regimen. Body composition was measured before, at the midpoint, and after the training. Vastus lateralis biopsies were obtained 24 hours before and after the first exercise and 24 hours after the last exercise to assess PPAR delta content. Blood samples were collected immediately before and after, and 24 hours after the first and the last exercises. Results. - PPAR delta content acutely increased 49.1 +/- 28.7% after exercise when adjusted for body fat percentage, and the increase was inversely proportional to body fat percentage (R = -0.877). The acute change in PPAR delta was associated with the initial lean mass (R = 0.789) before training. After training, PPAR delta content increased 114.7 +/- 31.9% and was inversely associated with resting serum total cholesterol (TC) (R = -0.731) and low-density lipoprotein cholesterol (LDL) (R =-0.746). Ten-week Lean mass gain was associated with greater changes in resting serum TC (R = 0.592), high-density lipoprotein cholesterol (HDL) (R = 0.616), and LDL (R = 0.587). Conclusion. - The associations among altered serum lipid profile, lean mass gain, and the increased PPAR delta protein content induced by resistance exercise suggest that resistance exercise may alter lipid metabolism and play a role in lean mass gain through PPAR delta. (c) 2023 Elsevier Masson SAS. All rights reserved.

Skeletal muscle is a highly dynamic organ that is essential for locomotion as well as endocrine regulation in all populations of horses. However, despite the importance of adequate muscle development and maintenance, the mechanisms underlying protein anabolism in horses on different diets, exercise programs, and at different life stages remain obscure. Mechanistic target of rapamycin (mTOR) is a key component of the protein synthesis pathway and is regulated by biological factors such as insulin and amino acid availability. Providing a diet ample in vital amino acids, such as leucine and glutamine, is essential in activating sensory pathways that recruit mTOR to the lysosome and assist in the translation of important downstream targets. When the diet is well balanced, mitochondrial biogenesis and protein synthesis are activated in response to increased exercise bouts in the performing athlete. It is important to note that the mTOR kinase pathways are multifaceted and very complex, with several binding partners and targets that lead to specific functions in protein turnover of the cell, and ultimately, the capacity to maintain or grow muscle mass. Further, these pathways are likely altered across the lifespan, with an emphasis of growth in young horses while decreases in musculature with aged horses appears to be attributable to degradation or other regulators of protein synthesis rather than alterations in the mTOR pathway. Previous work has begun to pinpoint ways in which the mTOR pathway is influenced by diet, exercise, and age; however, future research is warranted to quantify the functional outcomes related to changes in mTOR. Promisingly, this could provide direction on appropriate management techniques to support skeletal muscle growth and maximize athletic potential in differing equine populations.

Summary: There is strong evidence that physical activity has a profound protective effect against multiple types of cancer. Here, we show that this effect may be mediated by factors released from skeletal muscle during simulated exercise, in situ, which suppress canonical anabolic signaling in breast cancer. We report attenuated growth of MCF7 breast cancer cells in the presence of a rodent-derived exercise conditioned perfusate, independent of prior exercise training. This reduction was concomitant with increased levels of DEPTOR protein and reduced mTOR activity.

Objectives Choline is an essential micronutrient for many physiological processes related to exercise training including biosynthesis of acetylcholine. Though dietary choline intake has been studied in relation to endurance training and performance, none have studied it during resistance exercise training (RET) in older adults. The objective of the study was to examine the relationship between choline intake and muscle responses to RET in older adults. Methods Forty-six, 60–69-year-old individuals (M=19, F=27) underwent 12 weeks of RET (3x/week, 3 sets, 8–12 reps, 75% of maximum strength [1RM], 8 exercises). Body composition (DEXA) and 1RM tests were performed before and after training. After analyzing 1,656 diet logs (3x/week, 46 participants, 12 weeks), participants’ mean choline intakes were categorized into three groups: Low (2.9–5.5 mg/kg lean/d), Med-Low (5.6–8.0 mg/kg lean/d), or Adequate (8.1–10.6 mg/kg lean/d). These correspond to <50%, ∼63%, and ∼85% of Adequate Intake (AI) for choline, respectively. Results Gains in composite strength (leg press + chest press 1RM) were significantly lower in the Low group compared with the other groups (Low: 30.9 ± 15.1%, Med-Low: 70.3 ± 48.5%, Adequate: 81.9 ± 68.4%; p=0.004). ANCOVA with cholesterol, protein, or other nutrients did not alter this result. Reduced gains in lean mass were also observed in the Low group, compared with higher choline intake of 5.6–10.6 mg/kg lean/d (1.3 ± 0.6% vs. 3.2 ± 0.6%, p<0.05). Conclusion These data suggest that this population of older adults does not consume adequate choline and lower choline intake is negatively and independently associated with muscle responses to RET.

Exercise-Conditioned Perfusate Slows Growth in Cultured Pancreatic Cancer CellsPatrick J. Ryan, Steven Riechman (FACSM), James D. Fluckey Texas A&M UniversityBackground: Maintaining physical fitness or remaining physically active is associated with significant reductions in cancer incidence and mortality but the mechanism remains elusive. PURPOSE: To investigate the effect of contracting muscle perfusate on growth of cultured immortalized pancreatic cancer cells. METHODS: The inferior vasculature of three female Wistar rats was perfused with a physiological solution. Muscular contraction of the hindlimb was then elicited by electrical stimulation of the sciatic nerve, with perfusate from the hindlimb musculature collected before and during the stimulation period. Cultured immortalized pancreatic cancer cells (PANC-1) were then exposed to perfusate from contracting or quiescent (control) muscle from each animal. After 24 hours, cell proliferation was assessed using a water-soluble tetrazolium salt (WST-8) assay. A paired t-test (α < 0.05) was used to determine differences between groups. RESULTS: After 24 hours, cell proliferation in cells exposed to perfusate from contracting skeletal muscle was reduced by `20% (p < 0.05). CONCLUSION: Humoral factors released from contracting skeletal muscle slow the proliferation of cultured immortalized pancreatic cancer cells.

microRNAs (miRs) are linked to various human diseases including type 2 diabetes mellitus (T2DM) and emerging evidence suggests that miRs may serve as potential therapeutic targets. Lower miR-16 content is consistent across different models of T2DM; however, the role of miR-16 in muscle metabolic health is still elusive. Therefore, the purpose of this study was to investigate how deletion of miR-16 in mice affects skeletal muscle metabolic health and contractile function in both sexes. This study was conducted using both 1) in vitro and 2) in vivo experiments. In in vitro experiments, we used C2C12 myoblasts to test if inhibition or overexpression of miR-16 affected insulin-mediated glucose handling. In in vivo experiments, we generated muscle-specific miR-16 knockout (KO) mice fed a high-fat diet (HFD) to assess how miR-16 content impacts metabolic and contractile properties including glucose tolerance, insulin sensitivity, muscle contractile function, protein anabolism, and mitochondrial network health. In in vitro experiments, although inhibition of miR-16 induced impaired insulin signaling (P = 0.002) and glucose uptake (P = 0.014), overexpression of miR-16 did not attenuate lipid overload-induced insulin resistance using the diacylglycerol analog 1-oleoyl-2-acetyl-sn-glycerol. In in vivo experiments, miR-16 deletion induced both impaired muscle contractility (P = 0.031-0.033), and mitochondrial network health (P = 0.008-0.018) in both sexes. However, although males specifically exhibited impaired insulin sensitivity following miR-16 deletion (P = 0.030), female KO mice showed pronounced glucose intolerance (P = 0.046), corresponding with lower muscle weights (P = 0.015), and protein hyperanabolism (P = 0.023). Our findings suggest distinct sex differences in muscle adaptation in response to miR-16 deletion and miR-16 may serve as a key regulator for metabolic dysregulation in T2DM. NEW & NOTEWORTHY We set to investigate the role of miR-16 in skeletal muscle during diet-induced insulin resistance. Our data provide novel evidence that the lack of miR-16 induced multiple aberrations in insulin sensitivity, muscle contractility, mitochondrial network health, and protein turnover in a sex-dependent manner. Interestingly, miR-16 deletion leads to insulin resistance in males and exacerbated glucose intolerance in females, suggesting different mechanisms of metabolic dysregulation with a lack of miR-16 between sexes.

Risk factors for Nonalcoholic Fatty Liver Disease (NAFLD) include obesity, hypertension, dyslipidemia, and diabetes mellitus. While these risk markers are prevalent in the general US population, they are also present at high rates in a specific subset responsible for public safety - firefighters. PURPOSE: To use logistic regression to predict the likelihood of occurrence of NAFLD in firefighters using a subset of health-related factors associated with common cardiometabolic risk factors. METHODS: Data were collected on 136 firefighters (128 males, 8 females; 36.3 ± 9.0 yrs; 95.7 ± 17.0 kg; 178.9 ± 7.4 cm; 29.8 ± 4.2 kg/m2) participating in FITLIFE, a university-based fitness program at Texas A&M University. Nominal logistic regression with stepwise removal was used to estimate the best model to predict fatty liver disease. Stepwise removal identified resting systolic blood pressure (RSBP, mm HG), Body Mass Index (BMI, kg/m2), visceral adipose tissue (VAT, cm2), whether or not has hypertension or is on medication (HTNMED; 0 = No,1 = Yes), and plasma triglyceride concentrations (TG, mg/dL) as independent predictors (p < 0.05). Odds ratios (OR) were calculated to determine the change in the odds of NAFLD per unit increase in each predictor. RESULTS: Logistic regression yielded the following equation to predict the probability of developing NAFLD: Logit = -22.5176 + 0.0918(RSBP) + 0.2154(BMI) + 0.0065(TG) + 0.0161(VAT) + 1.830(HTNMED) (R2 = 0.4655, p > < 0.001). Of the predictors, the ORs from largest to smallest were 6.235, 1.240, 1.096, 1.016, and 1.002 for HTNMED, BMI, RSBP, VAT, and TG, respectively. CONCLUSIONS: Using RSBP, BMI, VAT, TG, and HTNMED as predictors, this study demonstrates that the probability of developing NAFLD in Texas firefighters can be reasonably predicted. This regression model and individual predictors may be used by health practitioners as a cost-effective screening tool to identify those at higher risk for NAFLD:

The orexigenic hormone ghrelin has multifaceted roles in health and disease. We have reported that ablation of the ghrelin receptor, growth hormone secretagogue receptor (GHS-R), protects against metabolic dysfunction of adipose tissues in aging. Our further observation interestingly revealed that GHS-R deficiency phenocopies the effects of myokine irisin. In this study, we aim to determine whether GHS-R affects the metabolic functions of aging skeletal muscle and whether GHS-R regulates the muscular functions via irisin. We first studied the expression of metabolic signature genes in gastrocnemius muscle of young, middle-aged and old mice. Then, old GHS-R knockout (Ghsr−/−) mice and their wild type counterparts were used to assess the impact of GHS-R ablation on the metabolic characteristics of gastrocnemius and soleus muscle. There was an increase of GHS-R expression in skeletal muscle during aging, inversely correlated with the decline of metabolic functions. Remarkedly the muscle of old GHS-R knockout (Ghsr−/−) mice exhibited a youthful metabolic profile and better maintenance of oxidative type 2 muscle fibers. Furthermore, old Ghsr−/− mice showed improved treadmill performance, supporting better functionality. Also intriguing to note was the fact that old GHS-R-ablated mice showed increased expression of the irisin precursor FNDC5 in the muscle and elevated plasma irisin levels in circulation, which supports a potential interrelationship between GHS-R and irisin. Overall, our work suggests that GHS-R has deleterious effects on the metabolism of aging muscle, which may be at least partially mediated by myokine irisin.