Epitrochlearis Muscles Research Articles

Genetic reduction of skeletal muscle glycogen synthase 1 abundance reveals that the refeeding-induced reversal of elevated insulin-stimulated glucose uptake after exercise is not attributable to achieving a high muscle glycogen concentration.

One exercise session can increase subsequent insulin-stimulated glucose uptake (ISGU) by skeletal muscle. Postexercise refeeding induces reversal of postexercise (PEX)-enhanced ISGU concomitant with attaining high muscle glycogen in rats. To test the relationship between high glycogen and reversal of PEX-ISGU, we injected one epitrochlearis muscle from each rat with adeno-associated virus (AAV) small hairpin RNA (shRNA) that targets glycogen synthase 1 (GS1) and injected contralateral muscles with AAV-shRNA-Scrambled (Scr). Muscles from PEX and sedentary rats were collected at 3-hour PEX (3hPEX) or 6-hour PEX (6hPEX). Rats were either not refed or refed rat-chow during the recovery period. Isolated muscles were incubated with [3H]-3-O-methylglucose, with or without insulin. The results revealed: (1) GS1 abundance was substantially lower for AAV-shRNA-GS1-treated versus AAV-shRNA-Scr-treated muscles; (2) reduced GS1 abundance in refed-rats induced much lower glycogen in AAV-shRNA-GS1-treated versus AAV-shRNA-Scr-treated muscles at 3hPEX or 6hPEX; (3) PEX-ISGU was elevated in not refed-rats at either 3hPEX or 6hPEX versus sedentary controls, regardless of GS1 abundance; (4) PEX-ISGU was not reversed by 3 h of refeeding, regardless of GS1 abundance; (5) despite substantially lower glycogen in AAV-shRNA-GS1-treated versus AAV-shRNA-Scr-treated muscles, elevated PEX-ISGU was eliminated at 6hPEX in both of the paired muscles of refed-rats; and (6) 3hPEX versus sedentary non-refed rats had greater AMP-activated protein kinase-γ3 activity in both paired muscles, but this exercise effect was eliminated in both paired muscles by 3 h of refeeding. In conclusion, the results provided compelling evidence that the reversal of exercise-enhanced ISGU by refeeding was not attributable to the accumulation of high muscle glycogen concentration.

A rare presentation of cubital tunnel syndrome by accessory anconeus muscle

Cubital tunnel syndrome (Cu TS) is the second most frequent upper extremity compressive neuropathy after carpal tunnel syndrome. Cu TS is idiopathic; however, it has been linked to ulnar nerve vulnerability and anconeus epitrochlearis (AE) muscle hypertrophy. Although there are few studies in the literature that reveal AE muscle as one of the causes of Cu TS, its prevalence is low. The goal of this case report is to raise awareness regarding the existence of AE muscle as a potential cause of Cu TS, as well as the imaging findings of Cu TS in magnetic resonance imaging (MRI). A 17-year-old male patient complained of intermittent pain in the medial aspect of the left elbow and paresthesia in the left hand. Examination revealed hyperextension of meta carpalphalangeal joints and flexion of proximal interphalangeal joints of the 4th and 5th digits, besides the sensory deficit along the ulnar border of the 5th digit. A nerve conduction study revealed non-stimulable sensory and motor components of the right ulnar nerve. MRI with T1-weighted fast spin echo, Fat sat proton density-weighted, and gradient echo T2*-weighted sequence showed AE - on the posteromedial aspect of the elbow. The ulnar nerve within the cubital tunnel appeared thickened and edematous with bright perineural fat signals with maintained fascicular architecture, secondary to compression by the anconeus muscle. This paper reviews imaging findings of ulnar neuropathy secondary to accessory anconeus muscle and explains the importance of MRI imaging for accurate diagnosis. Knowing MRI imaging is vital in the modern imaging era for accurate diagnosis.

Phosphorylation of AS160-serine 704 is not essential for exercise-increase in insulin-stimulated glucose uptake by skeletal muscles from female or male rats.

One exercise session can increase subsequent insulin-stimulated glucose uptake (ISGU) by skeletal muscle from rodents and humans of both sexes. We recently found that concurrent mutation of three key sites to prevent their phosphorylation (Ser588, Thr642, and Ser704) on Akt substrate of 160 kDa (AS160; also known as TBC1D4) reduced the magnitude of the enhancement of postexercise ISGU (PEX-ISGU) by muscle from male, but not female rats. However, we did not test the role of individual phosphorylation sites on PEX-ISGU. Accordingly, our current aim was to test whether AS160 Ser704 phosphorylation (pSer704) is required for elevated PEX-ISGU by muscle. AS160-knockout (AS160-KO) rats (female and male) were studied when either in sedentary or 3 h after acute exercise. Adeno-associated virus (AAV) vectors were used to enable muscle expression of wild-type AS160 (AAV-WT-AS160) or AS160 mutated Ser704 to alanine to prevent phosphorylation (AAV-1P-AS160). Paired epitrochlearis muscles from each rat were injected with AAV-WT-AS160 or AAV-1P-AS160. We discovered that regardless of sex 1) AS160 abundance in AS160-KO rats was similar in paired muscles expressing WT-AS160 versus 1P-AS160; 2) muscles from exercised versus sedentary rats had greater ISGU, and PEX-ISGU was slightly greater for muscles expressing 1P-AS160 versus contralateral muscles expressing WT-AS160; and 3) pAS160Thr642 was lower in muscles expressing 1P-AS160 versus paired muscles expressing WT-AS160. These results indicate that pAS160Ser704 was not essential for elevated PEX-ISGU by skeletal muscle from rats of either sex. Furthermore, elimination of the postexercise increase in pAS160Thr642 did not lessen the postexercise effect on ISGU.NEW & NOTEWORTHY The current study evaluated the role of Akt substrate of 160 kDa (AS160) phosphorylation on Ser704 in increased insulin-stimulated glucose uptake by skeletal muscle after exercise. Adeno-associated virus vectors were engineered to express either wild-type-AS160 or AS160 mutated so that it could not be phosphorylated on Ser704 in paired muscles from AS160-knockout rats. The results demonstrated that AS160 phosphorylation on Ser704 was not essential for exercise-induced elevation in insulin-stimulated glucose uptake by rats of either sex.

Sucrose-Enriched and Carbohydrate-Free High-Fat Diets Distinctly Affect Substrate Metabolism in Oxidative and Glycolytic Muscles of Rats.

Skeletal muscle substrate preference for fuel is largely influenced by dietary macronutrient availability. The abundance of dietary carbohydrates promotes the utilization of glucose as a substrate for energy production, whereas an abundant dietary fat supply elevates rates of fatty acid (FA) oxidation. The objective of this study was to determine whether an obesogenic, high-fat, sucrose-enriched (HFS) diet or a carbohydrate-free ketogenic diet (KD) exert distinct effects on fat, glucose, and ketone metabolism in oxidative and glycolytic skeletal muscles. Male Wistar rats were fed either a HFS diet or a KD for 16 weeks. Subsequently, the soleus (Sol), extensor digitorum longus (EDL), and epitrochlearis (Epit) muscles were extracted to measure palmitate oxidation, insulin-stimulated glucose metabolism, and markers of mitochondrial biogenesis, ketolytic capacity, and cataplerotic and anaplerotic machinery. Sol, EDL, and Epit muscles from KD-fed rats preserved their ability to elevate glycogen synthesis and lactate production in response to insulin, whereas all muscles from rats fed with the HFS diet displayed blunted responses to insulin. The maintenance of metabolic flexibility with the KD was accompanied by muscle-fiber-type-specific adaptive responses. This was characterized by the Sol muscle in KD-fed rats enhancing mitochondrial biogenesis and ketolytic capacity without elevating its rates of FA oxidation in comparison with that in HFS feeding. Conversely, in the Epit muscle, rates of FA oxidation were increased, whereas the ketolytic capacity was markedly reduced by the KD in comparison with that by HFS feeding. In the EDL muscle, the KD also increased rates of FA oxidation, although it did so without altering its ketolytic capacity when compared to HFS feeding. In conclusion, even though obesogenic and ketogenic diets have elevated contents of fat and alter whole-body substrate partitioning, these two dietary interventions are associated with opposite outcomes with respect to skeletal muscle metabolic flexibility.

The prevalence of the anconeus epitrochlearis muscle in a Central European population.

An anconeus epitrochlearis muscle (AE) is a common anatomical variant in the upper extremity, located at the medial aspect of the elbow. Its anatomical position contributes to the roof of the cubital tunnel. While it plays a role in protecting the ulnar nerve, it may also pose a risk for ulnar nerve compression. This study aimed to determine the true prevalence of AE in a Central European population. The presence of AE was evaluated in 115 cadaveric upper extremities from an undetermined number of subjects. The limbs for dissection were assumed to be healthy, and AE identification involved anatomical description and measurements. Data analysis aimed to determine the true prevalence, considering 95% confidence intervals. AE was present in 5 of the 115 cadaveric limbs (4.3%). Specimens lacking AE were observed, depicting normal cubital tunnel roof anatomy. When present, AE replaced the proximal part of the cubital tunnel roof, superficially coursing to the ulnar nerve. Morphological variations were noted. The true prevalence of AE was 4.3% (95% CI = 0.2%-8.4%), consistent with recent studies. Historical reports indicate varying true prevalence up to 26%, possibly linked to manual labor changes. Contrary to prior assumptions, our study did not find a significantly higher true prevalence in the European population. AE's association with cubital tunnel syndrome is complex, with both protective and potentially compressive roles.

Anconeus epitrochlearis muscle resulting in cubital nerve compressive neuropathy: Two case reports

Background: The anconeus epitrochlearis muscle is an anatomical variant prevalent in amphibians but unusual in humans. In favorable cases, this muscle provides protection to the cubital nerve but can result in neuropathy due to compression of the cubital nerve. Case Description: We present two cases with different clinical manifestations but both did not respond to conservative treatment. We opted for a surgical decompression where the anconeus epitrochlearis muscle was found intraoperatively, and the muscle fibers were dissected. Conclusion: Considering the presence of the muscle variant is the key point to intraoperatively achieve a complete dissection of the muscle fibers of the anconeus epitrochlearis muscle variant and obtain the decompression of the cubital nerve with satisfactory postoperative results.

Anconeus epitrochlearis muscle (epitrochlearisanconeus muscle; Musculus epitrochleoanconeus) with cubital tunnel syndrome – a rare but relevant clinical entity

BackgroundCompression of the ulnar nerve at the elbow within the cubital tunnel is related to the anatomical structures and is generally believed to be caused by Osborne's ligament (also known as the cubital retinaculum). However, in rare cases an anatomical variation of the developmental peculiarity of a remaining anconeus epitrochlearis muscle may be responsible for the disease. MethodsWe present a series of five cases in which an anconeus epitrochlearis muscle was found as the cause of illness. ResultsAll patients presented with typical symptoms of numbness and tingling in the hand and ulnar fingers, and recurring pain as well as weakness of the ulnar innervated muscles. With neurophysiologically confirmed diminished nerve conduction velocity and unsuccessful conservative treatment, surgical decompression revealed an anconeus epitrochlearis muscle as the reason of compression. Full symptom relief was achieved immediately after the procedure in all cases. ConclusionsThis article strives to call attention to this entity when diagnosing ulnar nerve compression. Myectomy and medial epicondylectomy is the preferred treatment option in such cases.

Insulin-resistant female rat skeletal muscles display diacylglycerol-mediated protein kinase C activation and inflammation without ceramide accumulation.

This study investigated the role of diacylglycerol (DAG)-mediated protein kinase C (PKC) activation, ceramide accumulation and inflammation in insulin-resistant female oxidative and glycolytic skeletal muscles induced by an obesogenic high-fat sucrose-enriched (HFS) diet. The HFS diet impaired insulin-stimulated AKTThr308 phosphorylation and glycogen synthesis, whereas rates of fatty acid oxidation and basal lactate production were significantly elevated in soleus (Sol), extensor digitorum longus (EDL) and epitrochlearis (Epit) muscles. Insulin resistance was accompanied by increases in triacylglycerol (TAG) and DAG contents in Sol and EDL, whereas in Epit muscles only TAG content and markers of inflammation were associated with HFS diet-induced insulin resistance. Analysis of membrane-bound/cytoplasmic PKC fractions revealed that the HFS diet promoted activation/translocation of PKCδ and θ isoforms in Sol, EDL and Epit muscles. However, none of these muscles displayed alterations in ceramide content in response to HFS feeding. This could be explained by a significant increase in Dgat2 mRNA expression in Sol, EDL and Epit muscles, which likely diverted most of the intramyocellular acyl-CoAs toward TAG synthesis instead of ceramides. Overall, this study helps elucidate the molecular mechanisms underlying insulin resistance caused by diet-induced obesity in female skeletal muscles with distinct fibre type compositions. KEY POINTS: Feeding female Wistar rats a high-fat sucrose-enriched diet (HFS) led to diacylglycerol (DAG)-induced PKC activation and insulin resistance in oxidative and glycolytic skeletal muscles. HFS diet-induced toll-like receptor 4 (Tlr4) expression did not lead to increased ceramide content in female skeletal muscles. In highly glycolytic female muscles, elevated TAG content and markers of inflammation underlay HFS diet-induced insulin resistance. The HFS diet suppressed glucose oxidation and increased lactate production in oxidative and glycolytic female muscles. Increased Dgat2 mRNA expression likely diverted most of the intramyocellular acyl-CoAs toward TAG synthesis and prevented ceramide formation in skeletal muscles of HFS-fed female rats.

Diffusion Tensor Imaging of Ulnar Neuropathy Caused by an Accessory Anconeus Muscle.

HomeRadiologyRecently Published PreviousNext Reviews and CommentaryFree AccessImages in RadiologyDiffusion Tensor Imaging of Ulnar Neuropathy Caused by an Accessory Anconeus MuscleTeodoro Martín-Noguerol , Antonio LunaTeodoro Martín-Noguerol , Antonio LunaAuthor AffiliationsFrom the Department of Radiology, MRI Unit, HT Médica, Clínica Las Nieves, Calle Carmelo Torres 2, 23007 Jaén, Spain.Address correspondence to T.M.N. (email: [email protected]).Teodoro Martín-Noguerol Antonio LunaPublished Online:Mar 21 2023https://doi.org/10.1148/radiol.221854MoreSectionsPDF ToolsImage ViewerAdd to favoritesCiteTrack CitationsPermissionsReprints ShareShare onFacebookTwitterLinked In A 29-year-old woman presented with complaints of progressive numbness in the left ulnar nerve territory. Physical examination demonstrated left ring and little finger weakness and hypoesthesia with positive flexion elbow test. MRI of the elbow with diffusion tensor imaging (DTI) neurography was performed and revealed extrinsic compression of the ulnar nerve by an accessory anconeus epitrochlearis muscle (Figure). DTI neurography scan showed deformity of the ulnar nerve with corresponding focal decrease in fractional anisotropy (FA) values at the compression site (0.3). FA values were also slightly decreased distally to the compression level (0.41), with normal appearance of the rest of the ulnar nerve (1).MRI scans show the left elbow in a 29-year-old woman with progressive numbness in the left ulnar nerve distribution. (A, B) Axial proton density–weighted images with spectral fat suppression show an accessory anconeus epitrochlearis muscle (arrow) with entrapment of the ulnar nerve (arrowhead). (C) Three-dimensional neurography reconstruction of diffusion tensor imaging with use of directional encoding color fused with proton density with spectral fat suppression shows deformity of the ulnar nerve at the site of extrinsic compression (arrowhead). A focal decrease in the fractional anisotropy values of the ulnar nerve (black arrow) is seen below the level of compression by the anconeus epitrochlearis muscle (white arrow).Download as PowerPointOpen in Image Viewer The anconeus epitrochlearis muscle is an accessory muscle located at the medial aspect of the elbow, originated at the inferior surface of medial epicondyle, and inserted at the medial cortex of the olecranon (2). The relationship between the accessory anconeus muscle and prevalence of ulnar neuropathy remains unknown (3). By providing quantitative information, DTI neurography allows detection of subtle changes in ulnar nerve morphologic conditions (4) and may prove helpful in diagnosis and treatment monitoring in ulnar neuropathy caused by accessory anconeus muscle. In the presented case, the patient was treated conservatively with a favorable clinical outcome.Disclosures of conflicts of interest: T.M.N. No relevant relationships. A.L. Royalties or licenses from Springer; fee to institution as lecturer from GE; Digital Oncology board member for Siemens Healthineers.

Akt substrate of 160kDa is essential for the calorie restriction-induced increase in insulin-stimulated glucose uptake by skeletal muscle of female rats.

We evaluated effects of calorie restriction (CR; consuming 65% of ad libitum (AL) intake) for 8 weeks on female wildtype (WT) and Akt substrate of 160kDa knockout (AS160-KO) rats. Insulin-stimulated glucose uptake (ISGU) was determined in isolated epitrochlearis muscles incubated with 0, 50, 100, or 500 µU/mL insulin. Phosphorylation of key insulin signaling proteins that control ISGU (Akt and AS160) was assessed by immunoblotting (Akt phosphorylation on Threonine-308, pAktThr308 and Serine-473, pAktSer473; AS160 phosphorylation on Serine-588, pAS160Ser588, and Threonine-642, pAS160Thr642). Abundance of proteins that regulate ISGU (GLUT4 glucose transporter protein and hexokinase II) was also determined by immunoblotting. The major results were as follows: (i) WT-CR versus WT-AL rats had greater ISGU with 100 and 500 µU/mL insulin; (ii) CR versus WT-AL rats had greater GLUT4 protein abundance; (iii) WT-CR versus WT-AL rats had greater pAktThr308 with 500 µU/mL insulin; (iv) WT-CR versus WT-AL rats did not differ for pAktSer473, pAS160Ser588, or pAS160Thr642 at any insulin concentration; (v) AS160-KO versus WT rats with each diet had lower ISGU at each insulin concentration, but not lower pAkt on either phosphosite; (vi) AS160-KO versus WT rats had lower muscle GLUT4 abundance regardless of diet; and (vii) AS160-KO-CR versus AS160-KO-AL rats did not differ for ISGU, GLUT4 abundance, pAkt on either phosphosite, or pAS160 on either phosphosite. These novel results demonstrated that AS160 expression, but not greater pAS160 on key phosphosites, was essential for the CR-induced increases in muscle ISGU and GLUT4 abundance of female rats.

Effect of caffeine on mitochondrial biogenesis in the skeletal muscle - A narrative review.

Caffeine is one of the most widely used substances as recreational drug for performance-enhancement in sport, underpinned by a strong evidence base. Although the effects of caffeine are widely investigated within the scope of performance physiology, the molecular effects of caffeine within skeletal muscle remain unclear. Evidence from invitro and invivo models suggest that caffeine regulates the glucose metabolism in the skeletal muscle. Moreover, caffeine seems to stimulate CaMKII, PPARδ/β, AMPK and PGC1α, classical markers of exercise-adaptations, including mitochondrial biogenesis and mitochondrial content. This review summarizes evidence to suggest caffeine-effects within skeletal muscle fibers, focusing on the putative role of caffeine on mitochondrial biogenesis to explore whether caffeine supplementation might be a strategy to enhance mitochondrial biogenesis.

The prevalence of the anatomical variation in a Turkish population: supernumerary muscle–anconeus epitrochlearis

The anconeus epitrochlearis (AE) muscle is an accessory muscle located between the medial cortex of the olecranon and the inferior surface of the medial epicondyle, posterior to the ulnar nerve. This muscle may compress the ulnar nerve causing a clinical neuropathy. We aimed to determine the gender and side characteristics of the AE muscle in patients who underwent elbow magnetic resonance imaging (MRI) and report its prevalence in a Turkish population. A total of 209 patients (210 elbows) who underwent elbow MRI between January and December 2020 were retrospectively evaluated. Cases with the AE muscle were included in the study. The craniocaudal (CC) dimension was examined from the coronal section, and the transverse (TR) and anteroposterior (AP) dimensions from the axial sections. Statistical analyses were performed to determine the relationship between the presence of the AE muscle and age, gender, and side (right/left). Differences between sexes and sides in terms of muscle sizes were evaluated using statistical tests. The AE muscle was detected in 17 patients (18 elbows) (8.1%). The mean age of the patients was 41.52 ± 14.63years. There was no statistically significant difference between the male and female patients in terms of age. This accessory muscle was found in nine female (9.8%) and eight male (6.3%) patients in total. There was one (0.5%) patient with the bilateral AE muscle, who was female. The accessory muscle was located in the right elbow in 13 patients (10.71%), and left elbow in five (4.10%). It was more common in the right elbow in both genders. The muscle was larger in the male patients and the right elbow, but this was not statistically significant. The prevalence of the AE muscle was determined to be 8.1% in a Turkish population, and this muscle was more common among the women and in the right elbow.

Ultrasound Diagnosis of Cubital Tunnel Syndrome in the Accessory Anconeus Epitrochlearis Muscle (Case Report)

Summary. A case of diagnosing the accessory anconeus epitrochlearis muscle, which caused compression of the ulnar nerve and was the cause of cubital tunnel syndrome, is presented. Ultrasound is an important diagnostic method, which allows preventing unnecessary medical manipulations and choosing the right treatment algorithm.

Prior AICAR induces elevated glucose uptake concomitant with greater γ3-AMPK activation and reduced membrane cholesterol in skeletal muscle from 26-month-old rats.

Attenuated skeletal muscle glucose uptake (GU) has been observed with advancing age. It is important to elucidate the mechanisms linked to interventions that oppose this detrimental outcome. Earlier research using young rodents and (or) cultured myocytes reported that treatment with 5-aminoimidazole-4-carboxamide-1-β-d-ribofuranoside (AICAR; an AMP-activated protein kinase (AMPK) activator) can increase γ3-AMPK activity and reduce membrane cholesterol content, each of which has been proposed to elevate GU. However, the effect of AICAR treatment on γ3-AMPK activity and membrane cholesterol in skeletal muscle of aged animals has not been reported. Our purpose was to evaluate the effects of AICAR treatment on these potential mechanisms for enhanced glucose uptake in the skeletal muscle of aged animals. Epitrochlearis muscles from 26-27-month-old male rats were isolated and incubated ± AICAR, followed by 3 h incubation without AICAR, and then incubation with 3-O-methyl-[3 H] glucose (to assess GU ± insulin). Muscles were also analyzed for γ3-AMPK activity and membrane cholesterol content. Prior AICAR treatment led to increased γ3-AMPK activity, reduced membrane cholesterol content, and enhanced glucose uptake in skeletal muscle from aged rats. These observations revealed that two potential mechanisms for greater GU previously observed in younger animals and (or) cell models are also potentially relevant for enhanced GU by muscles from older animals.

Exercise effects on γ3-AMPK activity, Akt substrate of 160 kDa phosphorylation, and glucose uptake in muscle of normal and insulin-resistant female rats.

Previous studies demonstrated that acute exercise can enhance glucose uptake (GU), γ3-AMP-activated protein kinase (AMPK) activity, and Akt substrate of 160 kDa (AS160) phosphorylation in skeletal muscles from low-fat diet (LFD)- and high-fat diet (HFD)-fed male rats. Because little is known about exercise effects on these outcomes in females, we assessed postexercise GU by muscles incubated ± insulin, delta-insulin GU (GU of muscles incubated with insulin minus GU uptake of paired muscles incubated without insulin), and muscle signaling proteins from female rats fed a LFD or a brief HFD (2 wk). Rats were sedentary (LFD-SED, HFD-SED) or swim exercised. Immediately postexercise (IPEX) or 3 h postexercise (3hPEX), epitrochlearis muscles were incubated (no insulin IPEX; ±insulin 3hPEX) to determine GU. Muscle γ3-AMPK activity (IPEX, 3hPEX) and phosphorylated AS160 (pAS160; 3hPEX) were also assessed. γ3-AMPK activity and insulin-independent GU of IPEX rats exceeded sedentary rats without diet-related differences in either outcome. At 3hPEX, both GU by insulin-stimulated muscles and delta-insulin GU exceeded their respective diet-matched sedentary controls. GU by insulin-stimulated muscles, but not delta-insulin GU for LFD-3hPEX, exceeded HFD-3hPEX. LFD-3hPEX versus LFD-SED had greater γ3-AMPK activity and greater pAS160. HFD-3hPEX exceeded HFD-SED for pAS160 but not for γ3-AMPK activity. pAS160 and γ3-AMPK at 3hPEX did not differ between diet groups. These results revealed that increased γ3-AMPK activity at 3hPEX was not essential for greater GU in insulin-stimulated muscle or greater delta-insulin GU in HFD female rats. Similarly elevated γ3-AMPK activity in LFD-IPEX versus HFD-IPEX and pAS160 in LFD-3hPEX versus HFD-3hPEX may contribute to the comparable delta-insulin GU at 3hPEX in both diet groups.NEW & NOTEWORTHY Glucose uptake (GU) and phosphorylated AS160 (pAS160) by insulin-stimulated muscles at 3 h postexercise (3hPEX) exceeded diet-matched controls in female low-fat diet-fed (LFD) or high-fat diet-fed (HFD) rats. GU with insulin for LFD-3hPEX exceeded HFD-3hPEX, whereas pAS160 was similar between these groups. γ3-AMPK immediately postexercise (IPEX) was similarly elevated in LFD and HFD, but only LFD-3hPEX had increased γ3-AMPK. These results suggest that greater γ3-AMPK at IPEX and pAS160 at 3hPEX may contribute to elevated GU with insulin, but greater γ3-AMPK at 3hPEX was dispensable for female HFD rats.

Distinct mechanisms involving diacylglycerol, ceramides, and inflammation underlie insulin resistance in oxidative and glycolytic muscles from high fat-fed rats

This study investigated whether oxidative and glycolytic rat skeletal muscles respond differently to a high-fat (HF) sucrose-enriched diet with respect to diacylglycerol (DAG) and ceramides accumulation, protein kinase C (PKC) activation, glucose metabolism, and the expression of inflammatory genes. HF diet (8 weeks) suppressed insulin-stimulated glycogen synthesis and glucose oxidation in soleus (Sol), extensor digitorum longus (EDL) and epitrochlearis (Epit) muscles. However, DAG and ceramides levels increased in Sol and EDL, but not in Epit muscles of HF-fed rats. Additionally, membrane-bound PKC-delta and PKC-theta increased in Sol and EDL, whereas in Epit muscles both PKC isoforms were reduced by HF diet. In Epit muscles, HF diet also increased the expression of tumor necrosis factor-α (TNF-α) receptors (CD40 and FAS), toll-like receptor 4 (TLR4), and nuclear factor kappa light polypeptide gene enhancer in B cells (NF-kB), whereas in Sol and EDL muscles the expression of these inflammatory genes remained unchanged upon HF feeding. In conclusion, HF diet caused DAG and ceramides accumulation, PKC activation, and the induction of inflammatory pathways in a fiber type-specific manner. These findings help explain why oxidative and glycolytic muscles similarly develop insulin resistance, despite major differences in their metabolic characteristics and responsiveness to dietary lipid abundance.

Anconeus Epitrochlearis Muscle and Cubital Tunnel Syndrome in a High School Volleyball Player

Please enjoy Volume 7, Issue 1 of the JSMAHS. In this issue, you will find Professional, Graduate, and Undergraduate research abstracts, and case reports. Thank you for viewing this 7th Annual OATA Special Edition.

29-LB: Exercise Effects on ?3-AMPK Activity, Akt Substrate of 160 kDa Phosphorylation, and Glucose Uptake in Muscle of Normal and Insulin-Resistant Female Rats

Background: Previous studies demonstrated that exercise can enhance insulin-stimulated glucose uptake (ISGU) concomitant with greater Akt Substrate of 160 kDa (AS160) phosphorylation in muscles from normal or insulin resistant, male rats. However, little is known about exercise effects on ISGU in insulin-resistant muscle from female rats. Our goal was to assess exercise effects on ISGU and key signaling proteins in muscles from female rats fed a low-fat or high-fat diet. Methods: Female rats were randomly assigned to 2 diet-groups: standard chow (low-fat diet, LFD: 14% kCal fat) or high-fat diet (HFD: 60% kCal fat). After 2 weeks, rats from each diet-group either remained sedentary (LFD-SED or HFD-SED) or exercised (2h duration swim). At 3h post-exercise (3hPEX), paired epitrochlearis muscles were isolated and incubated with [3H]-2-deoxyglucose ±insulin to measure GU. Muscles were also assessed for γ3-AMPK activity and phosphorylated AS160 (pAS160; Ser588 and Thr642). Results: HFD-SED vs. LFD-SED rats had lower ISGU. At 3hPEX in each diet group, ISGU exceeded their diet-matched, sedentary controls. ISGU for LFD-3hPEX was greater than HFD-3hPEX. LFD-3hPEX vs. LFD-SED had greater γ3-AMPK activity and insulin-stimulated pAS160 (Ser588 and Thr642). For HFD-3hPEX vs. HFD-SED, insulin-stimulated pAS160 Thr642 was increased. However, γ3-AMPK activity was not different between HFD-SED and 3hPEX. Insulin-stimulated pAS160 Ser588 and Thr642 at 3hPEX did not differ between diet-groups, but γ3-AMPK for LFD-3hPEX exceeded HFD-3hPEX. Conclusions: These results indicated that prior exercise can enhance ISGU for LFD and HFD female rats, and suggested that the exercise-increase in ISGU for each diet-group may be related to greater pAS160. The elevated γ3-AMPK activity for LFD-3hPEX vs. LFD-SED, but not HFD-3hPEX vs. HFD-SED, raises the possibility that this difference may be relevant for the greater ISGU in LFD-3hPEX vs. HFD-3hPEX. Disclosure H. Wang: None. E. B. Arias: None. A. Zheng: None. S. Kwak: None. J. Zhao: None. G. Dong: None. G. D. Cartee: None. Funding National Institutes of Health (DK71771)

Ulnar Neuropathy at the Elbow: From Ultrasound Scanning to Treatment.

Ulnar neuropathy at the elbow (UNE) is commonly encountered in clinical practice. It results from either static or dynamic compression of the ulnar nerve. While the retroepicondylar groove and its surrounding structures are quite superficial, the use of ultrasound (US) imaging is associated with the following advantages: (1) an excellent spatial resolution allows a detailed morphological assessment of the ulnar nerve and adjacent structures, (2) dynamic imaging represents the gold standard for assessing the ulnar nerve stability in the retroepicondylar groove during flexion/extension, and (3) US guidance bears the capability of increasing the accuracy and safety of injections. This review aims to illustrate the ulnar nerve's detailed anatomy at the elbow using cadaveric images to understand better both static and dynamic imaging of the ulnar nerve around the elbow. Pathologies covering ulnar nerve instability, idiopathic cubital tunnel syndrome, space-occupying lesions (e.g., ganglion, heterotopic ossification, aberrant veins, and anconeus epitrochlearis muscle) are presented. Additionally, the authors also exemplify the scientific evidence from the literature supporting the proposition that US guidance is beneficial in injection therapy of UNE. The non-surgical management description covers activity modifications, splinting, neuromobilization/gliding exercise, and physical agents. In the operative treatment description, an emphasis is put on two commonly used approaches—in situ decompression and anterior transpositions.

Ultrasound-Assisted Precise In Situ Decompression for Cubital Tunnel Syndrome.

ObjectiveTo explore the effect of locating the ulnar nerve compression sites and guiding the small incision so as to decompress the ulnar nerve in situ on the elbow by high‐frequency ultrasound before operation.MethodsA retrospective analysis was conducted on 56 patients who underwent ultrasound‐assisted in situ decompression for cubital tunnel syndrome from May 2018 to August 2019. The patients' average age was 51.13 ± 7.35 years, mean duration of symptoms was 6.51 ± 1.96 months, and mean postoperative follow‐up was 6.07 ± 0.82 months. Nine patients had Dellon's stage mild, 39 had stage moderate, and eight had stage severe. Ultrasound and electromyography were completed in all patients before operation. The presence of ulnar nerve compressive lesion, the specific location, and the reason and extent of compression were determined by ultrasound. A small incision in situ surgery was given to decompress the ulnar nerve according to the pre‐defined compressive sites.ResultsAll patients underwent in situ decompression. The compression sites around the elbow were as follows: two in the arcade of Struthers, one in the medial intermuscular septum, four in the anconeus epitrochlearis muscle, five beside the cyst of the proximal flexor carpi ulnaris (FCU), and the remaining 44 cases were all from the compression between Osborne's ligament to the two heads of the FCU. The compression localizations diagnosed by ultrasound were confirmed by operations. Preoperative ultrasound confirmed no ulnar nerve subluxation in all cases. The postoperative outcomes were satisfactory. There was no recurrence or aggravation of symptoms in this group of patients according to the modified Bishop scoring system; results showed that 43 cases were excellent, 10 were good, and three were fair.ConclusionsHigh‐frequency ultrasound can accurately and comprehensively evaluate the ulnar nerve compression and the surrounding tissues, thus providing significant guidance for the precise minimally invasive treatment of ulnar nerve compression.