bims-kimdis 2023-06-25 papers

bims-kimdis

Biomed News

on Ketones, inflammation and mitochondria in disease

Issue of 2023‒06‒25
sixteen papers selected by
Matías Javier Monsalves Álvarez

Dynamics of Glucose Concentration during the Initiation of Ketogenic Diet Treatment in Children with Refractory Epilepsy: Results of Continuous Glucose Monitoring.
Intermittent versus continuous ketogenic diet: impact on seizures, gut microbiota and mitochondrial metabolism.
Invasive and noninvasive markers of human skeletal muscle mitochondrial function.
Fasting ketone bodies and incident type 2 diabetes in the general population.
Oxidative stress: Roles in skeletal muscle atrophy.
Exercise testing and prescription in patients with inborn errors of muscle energy metabolism.
The life and times of cellular senescence in skeletal muscle: friend or foe for homeostasis and adaptation?
Mechanisms of dual modulatory effects of spermine on the mitochondrial calcium uniporter complex.
SIRT3 overexpression in rat muscle does not ameliorate peripheral insulin resistance.
Skeletal muscle protein turnover responses to parenteral nutrition in patients with alcoholic liver cirrhosis and sarcopenia.
Effect of early vs. late time-restricted high-fat feeding on circadian metabolism and weight loss in obese mice.
Low-carbohydrate diet in the treatment of type 2 diabetes mellitus (LoCaT): study protocol for a multicenter, randomized controlled trial.
Effects of high-intensity interval training (HIIT) on skeletal muscle atrophy, function, and myokine profile in diabetic myopathy.
Physical exercise volume, type, and intensity and risk of all-cause mortality and cardiovascular events in patients with cardiovascular disease: a mediation analysis.
miR-146a-5p regulates autophagy and NLRP3 inflammasome activation in epithelial barrier damage in the in vitro cell model of ulcerative colitis through the RNF8/Notch1/mTORC1 pathway.
L-Carnitine improves mechanical responses of cardiomyocytes and restores Ca2+ homeostasis during aging.

Epilepsia Open. 2023 Jun 22.

Dynamics of Glucose Concentration during the Initiation of Ketogenic Diet Treatment in Children with Refractory Epilepsy: Results of Continuous Glucose Monitoring.

Klára Brožová, Juraj Michalec, Marek Brabec, Petra Bořilová, Pavel Kohout, Jan Brož.

  OBJECTIVE: The ketogenic diet (KD) is a diet low in carbohydrates and rich in fats which has long been used to treat refractory epilepsy. The metabolic changes related to the KD may increase the risk of hypoglycemia, especially during the first days. The study focused on the impact of KD initiation on glycemia in non-diabetic patients with refractory epilepsy.METHODS: The subjects were 10 paediatric patients (6 boys, mean age 6,1±2,4 years), treated for intractable epilepsy. Blinded continuous glucose monitoring system (CGM) Dexcom G4 was used.. Patients started on their regular diet in the first 36 hours of monitoring, followed by an increase in lipids intake and a gradual reduction of carbohydrates (relations 1:1;2:1;3:1;3,5:1). We analysed changes in glycemia during fat: non fat ratio changes using a generalized linear model.
RESULTS: The mean monitored time per person was 6 days, 10 hours and 44 minutes. The mean±SD glycemia for the regular diet was 4.84±0.20 mmol/l, for the carbohydrates/fat ratio of 1:1 it was 4.03±0.16, for the ratio of 2:1 it was 3.57±0.10, for the ratio 3:1 it was 3.39±0.13 and for the final ratio of 3.5:1 it was 2.79±0,06 mmol/l (p< 0,001). The portions of time spent in glycemia ≤3.5 mmol/l (≤2.5 mmol/l respectively) were: on the normal diet 0.88% (0.31%) of the monitored period, during 1:1 KD ratio 1.92% (0.95%), during 2:1 ratio 3.18% (1.02%), and during 3:1 and 3.5:1 ratios 13.64% (2.36%) of the monitored time (p<0,05).
SIGNIFICANCE: CGM shows the dynamic of glucose concentration in ketogenic diet treatment initiation. It may be a useful tool to control the effects of this diet on glucose metabolism, especially in hypoglycemia detection.

Keywords:  censored data; continuous glucose monitoring; epilepsy; glucose concentration; ketogenic diet

DOI:  https://doi.org/10.1002/epi4.12778
Epilepsia. 2023 Jun 19.

Intermittent versus continuous ketogenic diet: impact on seizures, gut microbiota and mitochondrial metabolism.

Jane Shearer, Morris H Scantlebury, Jong M Rho, Thomas A Tompkins, Chunlong Mu.

  We have previously shown that the ketogenic diet (KD) is effective in reducing the seizures associated with infantile spasms syndrome (ISS) and that this benefit is related to alterations in the gut microbiota. However, it remains unclear whether the efficacy of the KD persists after switching to a normal diet. Employing a neonatal rat model of ISS, we tested the hypothesis that the impact of the KD would diminish when switched to a normal diet. Following epilepsy induction, neonatal rats were divided into two groups: continuous KD for 6 days; and a group fed with KD for 3 days, then a normal diet for 3 days. Spasms frequency, mitochondrial bioenergetics in the hippocampus, and fecal microbiota were evaluated as major readouts. We found that the antiepileptic effect of KD was reversible, as evidenced by the increased spasms frequency in rats that were switched from the KD to a normal diet. The spasms frequency was inversely correlated with mitochondrial bioenergetic function and a set of gut microbes, including Streptococcus thermophilus and Streptococcus azizii. These findings suggest that the antiepileptic and metabolic benefits of the KD decline rapidly in concert with gut microbial alterations in the ISS model.

Keywords:  Gut microbiota; Infantile spasms syndrome; Ketogenic diet; Mitochondrial bioenergetics; Seizures

DOI:  https://doi.org/10.1111/epi.17688
Physiol Rep. 2023 06;11(12): e15734

Invasive and noninvasive markers of human skeletal muscle mitochondrial function.

Rodrigo Mancilla, Diego Pava-Mejia, Nynke van Polanen, Vera de Wit, Maaike Bergman, Lotte Grevendonk, Johanna Jorgensen, Esther Kornips, Joris Hoeks, Matthijs K C Hesselink, Vera B Schrauwen-Hinderling.

  Mitochondria are organelles that fuel cellular energy requirements by ATP formation via aerobic metabolism. Given the wide variety of methods to assess skeletal muscle mitochondrial capacity, we tested how well different invasive and noninvasive markers of skeletal muscle mitochondrial capacity reflect mitochondrial respiration in permeabilized muscle fibers. Nineteen young men (mean age: 24 ± 4 years) were recruited, and a muscle biopsy was collected to determine mitochondrial respiration from permeabilized muscle fibers and to quantify markers of mitochondrial capacity, content such as citrate synthase (CS) activity, mitochondrial DNA copy number, TOMM20, VDAC, and protein content for complex I-V of the oxidative phosphorylation (OXPHOS) system. Additionally, all participants underwent noninvasive assessments of mitochondrial capacity: PCr recovery postexercise (by 31 P-MRS), maximal aerobic capacity, and gross exercise efficiency by cycling exercise. From the invasive markers, Complex V protein content and CS activity showed the strongest concordance (Rc = 0.50 to 0.72) with ADP-stimulated coupled mitochondrial respiration, fueled by various substrates. Complex V protein content showed the strongest concordance (Rc = 0.72) with maximally uncoupled mitochondrial respiration. From the noninvasive markers, gross exercise efficiency, VO2max , and PCr recovery exhibited concordance values between 0.50 and 0.77 with ADP-stimulated coupled mitochondrial respiration. Gross exercise efficiency showed the strongest concordance with maximally uncoupled mitochondrial respiration (Rc = 0.67). From the invasive markers, Complex V protein content and CS activity are surrogates that best reflect skeletal muscle mitochondrial respiratory capacity. From the noninvasive markers, exercise efficiency and PCr recovery postexercise most closely reflect skeletal muscle mitochondrial respiratory capacity.

Keywords:  human skeletal muscle; mitochondrial function; skeletal muscle mitochondrial respiration

DOI:  https://doi.org/10.14814/phy2.15734
Diabetes. 2023 Jun 23. pii: db220826. [Epub ahead of print]

Fasting ketone bodies and incident type 2 diabetes in the general population.

Tamas Szili-Torok, Martin H de Borst, Erwin Garcia, Ron T Gansevoort, Robin P F Dullaart, Margery A Connelly, Stephan J L Bakker, Uwe J F Tietge.

With rising incidence and prevalence of type 2 diabetes, prevention including identification of prospective biomarkers becomes increasingly relevant. Although ketone bodies recently received a renewed interest as potential biomarkers, data linking these metabolites to diabetes risk are scarce. Therefore, the present prospective study investigated a potential association between fasting ketone bodies and incident type 2 diabetes in the general population. This study from the PREVEND cohort included 3307 participants from the general population initially free of diabetes or impaired fasting glucose. Baseline fasting ketone body concentrations were measured by nuclear magnetic resonance spectroscopy. 126 participants (3.8%) developed type 2 diabetes during a median [IQR] follow-up of 7.3 [6.3-7.7] years. In Kaplan-Meier analysis sex-stratified ketone body levels strongly positively associated with incident type 2 diabetes, which was confirmed in Cox regression analyses adjusted for several potential confounders. There was no significant interaction by sex. Both, 3-beta-hydroxybutyrate and acetoacetate+acetone individually associated with incident type 2 diabetes. In conclusion, fasting plasma ketone body levels are strongly positively associated with incident type 2 diabetes in the general population independent of several other recognized risk factors. These results may have important implications for diabetes prevention including dietary strategies.

DOI: https://doi.org/10.2337/db22-0826
Biochem Pharmacol. 2023 Jun 16. pii: S0006-2952(23)00255-1. [Epub ahead of print]214 115664

Oxidative stress: Roles in skeletal muscle atrophy.

Han Zhang, Guangdong Qi, Kexin Wang, Jiawen Yang, Yuntian Shen, Xiaoming Yang, Xin Chen, Xinlei Yao, Xiaosong Gu, Lei Qi, Chun Zhou, Hualin Sun.

  Oxidative stress, inflammation, mitochondrial dysfunction, reduced protein synthesis, and increased proteolysis are all critical factors in the process of muscle atrophy. In particular, oxidative stress is the key factor that triggers skeletal muscle atrophy. It is activated in the early stages of muscle atrophy and can be regulated by various factors. The mechanisms of oxidative stress in the development of muscle atrophy have not been completely elucidated. This review provides an overview of the sources of oxidative stress in skeletal muscle and the correlation of oxidative stress with inflammation, mitochondrial dysfunction, autophagy, protein synthesis, proteolysis, and muscle regeneration in muscle atrophy. Additionally, the role of oxidative stress in skeletal muscle atrophy caused by several pathological conditions, including denervation, unloading, chronic inflammatory diseases (diabetes mellitus, chronic kidney disease, chronic heart failure, and chronic obstructive pulmonary disease), sarcopenia, hereditary neuromuscular diseases (spinal muscular atrophy, amyotrophic lateral sclerosis, and Duchenne muscular dystrophy), and cancer cachexia, have been discussed. Finally, this review proposes the alleviation oxidative stress using antioxidants, Chinese herbal extracts, stem cell and extracellular vesicles as a promising therapeutic strategy for muscle atrophy. This review will aid in the development of novel therapeutic strategies and drugs for muscle atrophy.

Keywords:  Antioxidant treatment; Muscle atrophy; Oxidative stress

DOI:  https://doi.org/10.1016/j.bcp.2023.115664
J Inherit Metab Dis. 2023 Jun 22.

Exercise testing and prescription in patients with inborn errors of muscle energy metabolism.

Kiera Batten, Kaustuv Bhattacharya, David Simar, Carolyn Broderick.

  Skeletal muscle is a dynamic organ requiring tight regulation of energy metabolism in order to provide bursts of energy for effective function. Several inborn errors of muscle energy metabolism (IEMEM) affect skeletal muscle function and therefore the ability to initiate and sustain physical activity. Exercise testing can be valuable in supporting diagnosis, however its use remains limited due to the inconsistency in data to inform its application in IEMEM populations. While exercise testing is often used in adults with IEMEM, its use in children is far more limited. Once a physiological limitation has been identified and the aetiology defined, habitual exercise can assist with improving functional capacity, with reports supporting favourable adaptations in adult patients with IEMEM. Despite the potential benefits of structured exercise programs, data in paediatric populations remain limited. This review will focus on the utilisation and limitations of exercise testing and prescription for both adults and children, in the management of McArdle Disease, long chain fatty acid oxidation disorders, and myopathic mitochondrial respiratory chain disorders. This article is protected by copyright. All rights reserved.

Keywords:  McArdle disease; cardiopulmonary exercise test; exercise; fatty acid oxidation disorder; inborn errors of metabolism; mitochondrial myopathy

DOI:  https://doi.org/10.1002/jimd.12644
Am J Physiol Cell Physiol. 2023 Jun 19.

The life and times of cellular senescence in skeletal muscle: friend or foe for homeostasis and adaptation?

Cory M Dungan, Jaden M Wells, Kevin A Murach.

  A gradual decline in skeletal muscle mass and function is closely tied to increased mortality and disease risk during organismal aging. Exercise training is the most effective way to enhance muscle health, but the adaptive response to exercise as well as muscle repair potential is blunted in older individuals. Numerous mechanisms contribute to the loss of muscle mass and plasticity as aging progresses. An emerging body of recent evidence implicates an accumulation of senescent ("zombie") cells in muscle as a contributing factor to the aging phenotype. Senescent cells cannot divide but can release inflammatory factors and create an unfavorable environment for homeostasis and adaptation. On balance, some evidence suggests that cells with senescent characteristics can be beneficial for the muscle adaptive process, specifically at younger ages. Emerging evidence also suggests multinuclear post-mitotic muscle fibers could become senescent. In this review, we summarize current literature on the prevalence of senescent cells in skeletal muscle and highlight the consequences of senescent cell removal on muscle mass, function, and adaptability. We examine key limitations in the field of senescence specifically in skeletal muscle and identify areas of research that require future investigation.

Keywords:  Exercise; Myonuclei; SA Beta Gal; p16; p21

DOI:  https://doi.org/10.1152/ajpcell.00553.2022
bioRxiv. 2023 Jun 06. pii: 2023.06.06.543936. [Epub ahead of print]

Mechanisms of dual modulatory effects of spermine on the mitochondrial calcium uniporter complex.

Yung-Chi Tu, Fan-Yi Chao, Ming-Feng Tsai.

The mitochondrial Ca 2+ uniporter mediates the crucial cellular process of mitochondrial Ca 2+ uptake, which regulates cell bioenergetics, intracellular Ca 2+ signaling, and cell death initiation. The uniporter contains the pore-forming MCU subunit, an EMRE protein that binds to MCU, and the regulatory MICU1 subunit, which can dimerize with MICU1 or MICU2 and under resting cellular [Ca 2+ ] occludes the MCU pore. It has been known for decades that spermine, which is ubiquitously present in animal cells, can enhance mitochondrial Ca 2+ uptake, but the underlying mechanisms remain unclear. Here, we show that spermine exerts dual modulatory effects on the uniporter. In physiological concentrations of spermine, it enhances uniporter activity by breaking the physical interactions between MCU and the MICU1-containing dimers to allow the uniporter to constitutively take up Ca 2+ even in low [Ca 2+ ] conditions. This potentiation effect does not require MICU2 or the EF-hand motifs in MICU1. When [spermine] rises to millimolar levels, it inhibits the uniporter by targeting the pore region in a MICU-independent manner. The MICU1-dependent spermine potentiation mechanism proposed here, along with our previous finding that cardiac mitochondria have very low MICU1, can explain the puzzling observation in the literature that mitochondria in the heart show no response to spermine.

DOI: https://doi.org/10.1101/2023.06.06.543936
J Endocrinol. 2023 Jun 01. pii: JOE-22-0101. [Epub ahead of print]

SIRT3 overexpression in rat muscle does not ameliorate peripheral insulin resistance.

Brenna Osborne, Lauren E Wright, Amanda E Brandon, Ella Stuart, Lewin Small, Joris Hoeks, Patrick Schrauwen, David A Sinclair, Magdalene K Montgomery, Gregory J Cooney, Nigel Turner.

Reduced expression of the NAD+-dependent deacetylase, SIRT3, has been associated with insulin resistance and metabolic dysfunction in humans and rodents. In this study we investigated whether specific overexpression of SIRT3 in vivo in skeletal muscle could prevent HFD-induced muscle insulin resistance. To address this we used a muscle-specific adeno-associated virus (AAV) to overexpress SIRT3 in rat tibialis and EDL muscles. Mitochondrial substrate oxidation, substrate switching and oxidative enzyme activity were assessed in skeletal muscle with and without SIRT3 overexpression. Muscle-specific insulin action was also assessed by hyperinsulinaemic-euglycaemic clamps in rats that underwent a 4-week HFD-feeding protocol. Ex vivo functional assays revealed elevated activity of selected SIRT3-target enzymes including hexokinase, isocitrate dehydrogenase and pyruvate dehydrogenase that was associated with an increase in the ability to switch between fatty acid and glucose-derived substrates in muscle with SIRT3 overexpression. However, during the clamp, muscle from rats fed a HFD with increased SIRT3 expression displayed equally impaired glucose uptake and insulin-stimulated glycogen synthesis as the contralateral control muscle. Intramuscular triglyceride content was similarly increased in muscle of high fat fed rats, regardless of SIRT3 status. Thus, despite SIRT3 KO mouse models indicating many beneficial metabolic roles for SIRT3, our findings show that muscle-specific overexpression of SIRT3 has only minor effects on the acute development of skeletal muscle insulin resistance in high fat fed rats.

DOI: https://doi.org/10.1530/JOE-22-0101
Am J Physiol Gastrointest Liver Physiol. 2023 Jun 20.

Skeletal muscle protein turnover responses to parenteral nutrition in patients with alcoholic liver cirrhosis and sarcopenia.

Ulrik Winning Iepsen, Anders Rasmussen Rinnov, Gregers Winding Munch, Mette Rugbjerg, Kamilla Munch Winding, Carsten Lauridsen, Ronan M G Berg, Bente Klarlund Pedersen, Lise Lotte Gluud, Gerrit van Hall.

  Alcoholic liver cirrhosis (ALC) is accompanied by sarcopenia. The aim of this study was to investigate the acute effects of balanced parenteral nutrition (PN) on skeletal muscle protein turnover in ALC. Eight male patients with ALC and seven age- and sex-matched healthy controls were studied for three hours of fasting followed by three hours of intravenous PN (SmofKabiven 1206 mL: Amino acid 38 g, carbohydrates 85 g, fat 34 g) 4 ml/kg/hour. We measured leg blood flow, sampled paired femoral arterio-venous concentrations and quadriceps muscle biopsies while providing a primed continuous infusion of [ring-2D5]-phenylalanine to quantify muscle protein synthesis and breakdown. Patients with ALC exhibited shorter 6-min walking distance (ALC: 487 ± 38 vs. controls: 722 ± 14 m, p<0.05), lower hand-grip strength (ALC: 34 ± 2 vs. controls: 52 ± 2 kg, p<0.05), and CT-verified leg muscle loss (ALC: 5922 ± 246 vs. controls: 8110 ± 345 mm2, p<0.05). Net leg muscle phenylalanine uptake changed from negative (muscle loss) during fasting to positive (muscle gain) in response to PN (ALC: -0.18 ± +0.01 vs. 0.24 ± 0.03 µmol/kg muscle*min-1; p <0.001 and controls: -0.15 ± 0.01 vs. 0.09 ± 0.01 µmol/kg muscle*min-1; p <0.001), but with higher net muscle phenylalanine uptake in ALC than controls (p <0.001). Insulin concentrations were substantially higher in ALC patients during PN. Our results suggest a higher net muscle phenylalanine uptake during a single infusion of PN in stable ALC patients with sarcopenia compared with healthy controls.

Keywords:  Isotope Labeling; Liver Cirrohsis; Muscular Atrophy; Nutrition Therapy; Sarcopenia

DOI:  https://doi.org/10.1152/ajpgi.00242.2022
Cell Mol Life Sci. 2023 Jun 17. 80(7): 180

Effect of early vs. late time-restricted high-fat feeding on circadian metabolism and weight loss in obese mice.

Shani Tsameret, Nava Chapnik, Oren Froy.

  Time-restricted feeding (TRF) limits the time and duration of food availability without calorie reduction. Although a high-fat (HF) diet leads to disrupted circadian rhythms, TRF can prevent metabolic diseases, emphasizing the importance of the timing component. However, the question of when to implement the feeding window and its metabolic effect remains unclear, specifically in obese and metabolically impaired animals. Our aim was to study the effect of early vs. late TRF-HF on diet-induced obese mice in an 8:16 light-dark cycle. C57BL male mice were fed ad libitum a high-fat diet for 14 weeks after which they were given the same food during the early (E-TRF-HF) or late (L-TRF-HF) 8 h of the dark phase for 5 weeks. The control groups were fed ad libitum either a high-fat (AL-HF) or a low-fat diet (AL-LF). Respiratory exchange ratio (RER) was highest for the AL-LF group and the lowest for the AL-HF group. E-TRF-HF led to lower body weight and fat depots, lower glucose, C-peptide, insulin, cholesterol, leptin, TNFα, and ALT levels compared with L-TRF-HF- and AL-HF-fed mice. TRF-HF regardless whether it was early or late led to reduced inflammation and fat accumulation compared with AL-HF-fed mice. E-TRF-HF led to advanced liver circadian rhythms with higher amplitudes and daily expression levels of clock proteins. In addition, TRF-HF led to improved metabolic state in muscle and adipose tissue. In summary, E-TRF-HF leads to increased insulin sensitivity and fat oxidation and decreased body weight, fat profile and inflammation contrary to AL-HF-fed, but comparable to AL-LF-fed mice. These results emphasize the importance of timed feeding compared to ad libitum feeding, specifically to the early hours of the activity period.

Keywords:  Circadian; Clock; Metabolism; RER; Restricted feeding; Time-restricted feeding; Timing

DOI:  https://doi.org/10.1007/s00018-023-04834-4
Trials. 2023 Jun 19. 24(1): 411

Low-carbohydrate diet in the treatment of type 2 diabetes mellitus (LoCaT): study protocol for a multicenter, randomized controlled trial.

Xinyi Xia, Miao Xu, Yunjie Gu, Yangxue Li, Li Li, Jun Yin.

  BACKGROUND: Low-carbohydrate diet (LCD) is an emerging therapy for type 2 diabetes mellitus (T2DM). Although its effect on glucose control has been confirmed in previous clinical trials, most of those studies have focused on comparing calorie-restricted LCD to iso-caloric low-fat diets. In this study, we aim to compare the effects of LCD and canagliflozin, a sodium-glucose cotransporter 2 inhibitor, in patients with T2DM.METHODS: This is a multicenter, randomized controlled trial. We will recruit 120 patients with poor-controlled T2DM. Participants will be randomly divided into canagliflozin and LCD groups in a 1:1 ratio. The primary outcome is the change in hemoglobin A1C levels after the 3-month intervention. The secondary outcomes are the time in range and cost of antihyperglycemic agents. Exploratory outcomes include physical examination, body composition, glucose variability, appetite, glycolipid metabolism, liver lipid content, and urine glucose threshold.
DISCUSSION: No previous study has compared an LCD with antihyperglycemic agents. In LoCaT, participants' metabolism will be assessed from multiple perspectives. It is believed that the finding obtained from this trial will optimize the treatments for patients with T2DM.
TRIAL REGISTRATION: Chinese Clinical Trial Registry ChiCTR1900027592. Registered on November 20, 2019.

Keywords:  Canagliflozin; Low-carbohydrate diet; Randomized controlled trial; Study protocol; Type 2 diabetes mellitus

DOI:  https://doi.org/10.1186/s13063-023-07427-5
Cytokine. 2023 Jun 15. pii: S1043-4666(23)00157-6. [Epub ahead of print]169 156279

Effects of high-intensity interval training (HIIT) on skeletal muscle atrophy, function, and myokine profile in diabetic myopathy.

Yeşim Özçatal, Fırat Akat, Yakup Tatar, Hakan Fıçıcılar, Bilge Serdaroğlu, Ferda Topal Çelikkan, Metin Baştuğ.

  PURPOSE: Diabetes is a metabolic disorder characterized by chronic hyperglycemia due to insulin deficiency and/or loss of its action. Diabetic myopathy causes functional limitations in diabetic patients. The beneficial effects of high-intensity interval training (HIIT) are widely reported. We have hypothesized that HIIT application would prevent the development of diabetic myopathy.METHODS: Male, Wistar albino rats (10 W) were randomly divided into four groups (1)Control(C), (2)Diabetes(DM), (3)Training(HIIT), and (4)Diabetes + Training(DM + HIIT). Streptozotocin(60 mg/kg) was injected for the induction of diabetes. The maximum exercise capacity(MEC) of animals was determined by an incremental load test. HIIT protocol (4 min 85-95 % MEC, 2 min 40-50 % MEC, 6 cycles, 5 days/week) was applied for 8 weeks. In the end, functional parameters, atrophy, and resistance to fatigue in soleus and EDL muscles were evaluated. IL-6, FNDC5, and myonectin levels were measured in EDL, soleus, and serum.
RESULTS: We observed atrophy, fatigue sensitivity, and proinflammatory alterations (IL-6 increase) in the EDL samples due to diabetic myopathy which were not observed in the soleus samples. HIIT application prevented the aforementioned detrimental alterations. Both force-frequency response and parallelly the twitch amplitude increased significantly in the DM + HIIT group. Half relaxation time (DT50) increased in both exercising and sedentary diabetics. FNDC5 was significantly higher in the exercising animals in soleus samples. Myonectin was significantly higher in the soleus muscle only in the DM + HIIT group.
CONCLUSION: Current findings show that diabetic myopathy develops earlier in glycolytic-fast-twitch fibers(EDL) than in oxidative-slow-twitch fibers(soleus). Furthermore, HIIT application prevents atrophy in skeletal muscle, increases resistance to fatigue, and has an anti-inflammatory effect.
NEW FINDINGS: The current study analyzes the myokine profile and skeletal muscle function under the effect of diabetes HIIT-type exercise. We also measured maximal exercise capacity and tailored the exercise program individually according to the result. Diabetic myopathy is an important complication of diabetes yet still, it is not understood completely. Our results show that HIIT-type training would be beneficial in diabetic myopathy but further investigation is needed to understand the whole molecular mechanism.

Keywords:  Diabetic myopathy; HIIT; Isolated skeletal muscle; Myokine

DOI:  https://doi.org/10.1016/j.cyto.2023.156279
Eur Heart J Open. 2023 May;3(3): oead057

Physical exercise volume, type, and intensity and risk of all-cause mortality and cardiovascular events in patients with cardiovascular disease: a mediation analysis.

Nadia E Bonekamp, Anne M May, Martin Halle, Jannick A N Dorresteijn, Manon G van der Meer, Ynte M Ruigrok, Gert J de Borst, Johanna M Geleijnse, Frank L J Visseren, Charlotte Koopal.

  Aims: To estimate the relation between physical exercise volume, type, and intensity with all-cause mortality and recurrent vascular events in patients with cardiovascular disease (CVD) and to quantify to what extent traditional cardiovascular risk factors mediate these relations.Methods and results: In the prospective UCC-SMART cohort (N = 8660), the associations of clinical endpoints and physical exercise volume (metabolic equivalent of task hours per week, METh/wk), type (endurance vs. endurance + resistance), and intensity (moderate vs. vigorous) were estimated using multivariable-adjusted Cox models. The proportion mediated effect (PME) through body mass index, systolic blood pressure, low-density lipoprotein cholesterol, insulin sensitivity, and systemic inflammation was assessed using structural equation models. Sixty-one percent of patients (73% male, age 61 ± 10 years, >70% receiving lipid-lowering and blood pressure-lowering medications) reported that they did not exercise. Over a median follow-up of 9.5 years [interquartile range (IQR) 5.1-14.0], 2256 deaths and 1828 recurrent vascular events occurred. The association between exercise volume had a reverse J-shape with a nadir at 29 (95% CI 24-29) METh/wk, corresponding with a HR 0.56 (95% CI 0.48-0.64) for all-cause mortality and HR 0.63 (95% CI 0.55-0.73) for recurrent vascular events compared with no exercise. Up to 38% (95% CI 24-61) of the association was mediated through the assessed risk factors of which insulin sensitivity (PME up to 12%, 95% CI 5-25) and systemic inflammation (PME up to 18%, 95% CI 9-37) were the most important.
Conclusion: Regular physical exercise is significantly related with reduced risks of all-cause mortality and recurrent vascular events in patients with CVD. In this population with high rates of lipid-lowering and blood pressure--lowering medication use, exercise benefits were mainly mediated through systemic inflammation and insulin resistance.

Keywords:  Cardiovascular disease; Endurance training; Low-grade inflammation; Mediation analysis; Physical exercise; Resistance training

DOI:  https://doi.org/10.1093/ehjopen/oead057
Immunobiology. 2023 Apr 14. pii: S0171-2985(23)00054-2. [Epub ahead of print]228(4): 152386

miR-146a-5p regulates autophagy and NLRP3 inflammasome activation in epithelial barrier damage in the in vitro cell model of ulcerative colitis through the RNF8/Notch1/mTORC1 pathway.

Zepeng Chen, Qinglong Gu, Ruichao Chen.

  Ulcerative colitis (UC) is a chronic inflammatory disease affecting the colon that can be influenced by microRNAs (miRNAs). This study aims to investigate the impact of miR-146a-5p on lipopolysaccharide (LPS)-induced Caco-2/HT-29 cell autophagy and NLRP3 inflammasome activation and the underlying mechanism, with the aim of identifying potential therapeutic targets. We used LPS to establish Caco-2/HT-29 cell models and measured cell viability by CCK-8. The levels of miR-146a-5p, RNF8, markers of NLRP3 inflammasome activation and autophagy, proteins involved in the Notch1/mTORC1 pathway, and inflammatory factors were assessed by RT-qPCR, Western blot, and ELISA. Intestinal epithelial barrier function was evaluated by measuring transepithelial electrical resistance. Autophagic flux was measured using tandem fluorescent-labeled LC3. miR-146a-5p was highly-expressed in LPS-induced Caco-2/HT-29 cells, and autophagy flux was blocked at the autolysosomal stage after LPS induction. Inhibition of miR-146a-5p suppressed NLRP3 inflammasome activation, reduced intestinal epithelial barrier damage, and facilitated autophagy inhibition in LPS-induced Caco-2/HT-29 cells. The autophagy inhibitor NH4Cl partially nullified the inhibitory effects of miR-146a-5p inhibition on NLRP3 inflammation activation. miR-146a-5p targeted RNF8, and silencing RNF8 partly abrogated the action of miR-146a-5p inhibition on promoting autophagy and inhibiting NLRP3 inflammasome activation. miR-146a-5p inhibition suppressed the Notch1/mTORC1 pathway activation by upregulating RNF8. Inhibition of the Notch1/mTORC1 pathway partially nullified the function of silencing RNF8 on inhibiting autophagy and bolstering NLRP3 inflammasome activation. In conclusion, miR-146a-5p inhibition may be a potential therapeutic approach for UC, as it facilitates autophagy of LPS-stimulated Caco-2/HT-29 cells, inhibits NLRP3 inflammasome activation, and reduces intestinal epithelial barrier damage by upregulating RNF8 and suppressing the Notch1/mTORC1 pathway.

Keywords:  Autophagy; Caco-2 cells; NLRP3 inflammasome; Notch1; RNF8; Ulcerative colitis; mTORC1; miR-146a-5p

DOI:  https://doi.org/10.1016/j.imbio.2023.152386
Histochem Cell Biol. 2023 Jun 17.

L-Carnitine improves mechanical responses of cardiomyocytes and restores Ca2+ homeostasis during aging.

Yasin Gökçe, Betul Danisman, Guven Akcay, Narin Derin, Nazmi Yaraş.

  L-Carnitine (β-hydroxy-γ-trimethylaminobutyric acid, LC) is a crucial molecule for the mitochondrial oxidation of fatty acids. It facilitates the transport of long-chain fatty acids into the mitochondrial matrix. The reduction in LC levels during the aging process has been linked to numerous cardiovascular disorders, including contractility dysfunction, and disrupted intracellular Ca2+ homeostasis. The aim of this study was to examine the effects of long-term (7 months) LC administration on cardiomyocyte contraction and intracellular Ca2+ transients ([Ca2+]i) in aging rats. Male albino Wistar rats were randomly assigned to either the control or LC-treated groups. LC (50 mg/kg body weight/day) was dissolved in distilled water and orally administered for a period of 7 months. The control group received distilled water alone. Subsequently, ventricular single cardiomyocytes were isolated, and the contractility and Ca2+ transients were recorded in aging (18 months) rats. This study demonstrates, for the first time, a novel inotropic effect of long-term LC treatment on rat ventricular cardiomyocyte contraction. LC increased cardiomyocyte cell shortening and resting sarcomere length. Furthermore, LC supplementation led to a reduction in resting [Ca2+]i level and an increase in the amplitude of [Ca2+]i transients, indicative of enhanced contraction. Consistent with these results, decay time of Ca2+ transients also decreased significantly in the LC-treated group. The long-term administration of LC may help restore the Ca2+ homeostasis altered during aging and could be used as a cardioprotective medication in cases where myocyte contractility is diminished.

Keywords:  Aging; Ca2+ transients; Cardiomyocyte; L-Carnitine; Shortening

DOI:  https://doi.org/10.1007/s00418-023-02215-3