Physical inactivity and aging cause significant impairment of skeletal muscle functionality and mechanical properties, as well as remodeling of the extracellular matrix (ECM). The purpose of this work was to study the effect of chronic decrease in physical activity and age on the biogenesis of ECM in skeletal muscle. Biopsy samples from m. vastus lateralis were taken for quantitative mass spectrometry-based proteomic analysis and RNA sequencing in 15 young healthy volunteers and 8 young and 37 elderly patients with long-term primary osteoarthritis of the knee/hip joint as a model to study the effects of chronic muscle motor decline. In total, 1022 mRNAs and 101 ECM proteins and ECM-associated proteins (matrisome) were detected. An increase in the expression of two dozen highly abundant matrisome proteins specific to elderly and young patients (relative to young healthy subjects) was identified; however, changes in the expression of mRNAs encoding matrisome regulators (enzymatic regulators and secreted proteins) were similar. Comparison with previous proteomic and transcriptomic data showed that the described matrisome changes were markedly different from those induced by aerobic physical training in young healthy individuals, in particular in the expression of dominant ECM proteins and, especially, in the expression of mRNAs of ECM enzymatic regulators and secreted proteins. Matching the expression profiles of these regulatory genes may be useful for finding pharmacological targets for preventing adverse changes/activation of ECM biogenesis in various pathological conditions/physical training.

The aim of the study was to investigate the dynamics of venous blood glucose, insulin, and C-peptide in response to an intake of a mixed meal normalized to body mass in obese patients without and with type 2 diabetes mellitus. Venous blood samples were taken from seven healthy subjects, nine obese patients, and ten obese patients with type 2 diabetes mellitus (mean duration of diabetes 7 years) before and 30, 60, 90, 120, and 180 min after a mixed meal (6 kcal/kg of body mass); additionally, nine patients with obesity and type 2 diabetes mellitus and three healthy volunteers completed the hyperinsulinemic-euglycemic clamp test. In patient groups the energy content of food did not differ but was 1.8 times higher than in the control. An increase in glucose level 1 h after a meal was maximal in patients with type 2 diabetes, and an increase in insulin and C-peptide was higher in obese patients, which is related to impairment of insulin-dependent glucose uptake by tissues and of the rate of insulin secretion (dysfunction of beta-cells) in patients. At the same time, an increase in the total area under the curve “C-peptide–time” demonstrates that the maximal secretory response of beta-cells is comparable in obese patients without and with type 2 diabetes mellitus. The absolute blood glucose level 90 min after a meal closely correlated with the M-index—the marker of systemic sensitivity to insulin (rs = –0.82, p = 0.002). Our results characterize the features in the regulation of carbohydrate metabolism after intake of a mixed meal, normalized to body mass, in people with varying severity of metabolic disorders, and open up prospects for a wider application of this test in practice.

ЦЕЛЬ: скелетные мышцы играют ключевую роль в регуляции углеводно-жирового обмена, а также в развитии метаболических нарушений в организме. При ожирении и особенно при сахарном диабете 2 типа (СД2Т) происходят выраженные изменение транскриптома скелетных мышц человека. Однако транс- криптомный ответ в скелетных мышцах на инсулин охарактеризован плохо, как и механизмы регуляции экспрессии инсулинозависимых генов. МАТЕРИАЛЫ И МЕТОДЫ: мы исследовали ранний транскриптомный ответ скелетных мышц людей на инсулин, индуцированный приемом смешанной пищи. В исследовании участвовали 8 здоровых людей и пациенты с ожирением с (n=8) и без СД2Т (n=8); биопсии из m. vastus lateralis были взяты до и через 1 ч после приема еды, нормированной на массу тела (Nestle Resource 2.0; 3 мл/кг массы тела). Пациенты были разделены на две группы: с сильным и слабым ответом С-пептида (и инсулина) на пищу. Как и ожидалось, вторая группа в основном состояла из людей с ожирением и СД2Т. Изменение транскриптомного профиля в мышце оценивали с помощью РНК секвенирования (NextSeq 550, Illumina). РЕЗУЛЬТАТЫ: анализ транскриптома показал, что у здоровых людей, несмотря на слабое повышение уровня С-пептида после приема пищи, несколько сотен генов изменили экспрессию. Используя метод позиционно-весовых матриц и наши данные по положению открытого хроматина вокруг стартов транс- крипции в скелетных мышцах человека (Makhnovskii et al. 2022), мы предсказали транскрипционные факторы, ассоциированные с генами, изменившими экспрессию. Примечательно, что пациенты со слабой реакцией С-пептида на прием пищи фактически не показали изменений в транскриптомном профиле, что указывает на наличие резистентности к инсулину с точки зрения экспрессии генов. Удивительно, но у паци- ентов с сильной реакцией С-пептида на прием пищи также было обнаружено лишь небольшое изменение транскриптомного профиля. Это означает, что резистентность к инсулину в регуляции экспрессии генов появляется на начальной стадии развития метаболических нарушений. ВЫВОДЫ: таким образом, наше исследование впервые показало, что развитие метаболических на- рушений у человека может быть связано с дефектом регуляции инсулин-зависимой генной экспрессии в скелетной мышце.

Skeletal muscle plasticity is the ability to change morphofunctional properties in response to changes in contractile activity. Strength training increases the size of muscle fibers and maximum strength with the activation of protein synthesis. Regulation of these changes at the gene level has not been investigated properly. This study aimed to identify transcription factors associated with changes in the transcriptome of the human skeletal muscle in the context of single and regular strength exercises. We assessed changes in the transcriptomic profile of m. vastus lateralis of 10 young men (mean age 23 (20.8 - 25.9) years) before and after 12-week leg extensor muscles strength training course, as well as before, 8 and 24 hours after a single exercise. Transcriptomic profiling involved RNA sequencing, search for binding motifs and the associated transcription factors. Bioinformatic methods of statistics, FastQC, GraphPad Prizm 8, DAVID, R enabled analysis of the data acquired. The strength training course resulted in the enrichment of the functional groups of genes "secreted proteins", "extracellular matrix" and "basal membrane" (p < 0.05). Transcriptomic responses and the associated transcription factors differed 8 and 24 hours after a single session as well as after regular training sessions. Transcription factors involved in adjustment to regular and one-time loads participate in myogenesis, angiogenesis, regulation of fiber phenotype, proteostasis and other processes. Thus, regulation of gene expression during adjustment to the resistance training loads is a complex process that involves many transcription factors with different functions. Investigation of the role played by these factors in the context of adjustment to exercising is a potentially rewarding task.

The aim of the study was to evaluate the possibility to predict the muscle fiber-type proportion in men of different sports specialization by testing the maximal torque production by knee extensors at different velocities. For this reason the proportion of fast- and slow-twitch muscle fibers (MFs) in m. vastus lateralis of 23 athletes (11 endurance and 12 power athletes), as well the maximal torque production of knee extensors at various angular velocities in isokinetic mode were determined. The group of strength trained athletes significantly exceeded the group of endurance trained athletes in body mass, body mass index, volume of the m. quadriceps femoris, maximum torque production, and specific force at angular velocities 30, 180 and 300 degrees per second. In contrast to cross-sectional area (CSA) of slow-twitch MFs, the average CSA of fast-twitch MFs and the proportion of fast-twitch MFs in the group of power athletes significantly exceeded those in the group of endurance athletes. In the combined group of volunteers (n = 23), the proportion of fast-twitch MFs significantly correlated with the torque production at high angular velocities (r = 0.51 and p = 0.01 at 180 deg/s; r = 0.47 and p = 0.02 at 300 deg/s). We did not find any correlation between these parameters in the separate groups of power and endurance athletes. The results indicate a low accuracy in predicting the proportion of fast-twitch MF in m. vastus lateralis in athletes using the maximal torque production of knee extensors at different angular velocities. Significant correlation between the proportion of fast-twitch MF and maximal torque at high angular velocities in the general group (n = 23) was due to the presence of two significantly different subgroups.

We tested the hypothesis that strength exercise after intermittent aerobic exercise might activate signaling pathways that regulate mitochondrial biogenesis (activation of the AMPK and p38 pathways; the expression of PGC-1α , NT-PGC-1α , TFAM , and VEGFA mRNA), protein synthesis (phosphorylation level of p70S6K1 Thr389 and eEF2 Thr56 ; the expression IGF-1Ea , IGF-1Ec (MGF) , and REDD1 mRNA) and proteolysis (phosphorylation level of FOXO1 Ser256 ; the expression of MURF1 , MAFbx , and Myostatin mRNA) in trained skeletal muscles. Nine amateur endurance-trained athletes performed an intermittent aerobic cycling (70 min), followed by one-leg strength exercise (ES: four sets of knee extensions till exhaustion), while the other leg was resting (E). Gene expression and protein level were evaluated in samples from m. vastus lateralis taken before the exercise, 40 min, 5 and 22 h after the aerobic exercise. The phosphorylation level of the АСС Ser79/222 (an endogenous marker of AMPK activity) and the expression of PGC-1α-related gene TFAM (a marker of mitochondrial biogenesis) were increased after E exercise and did not changed after ES exercise. The expression of PGC-1α and truncated isoform NT-PGC-1α was increased in both legs as well. Insulin concentration in blood was decreased significantly (7.5-fold) after aerobic exercise; the phosphorylation level of FOXO Ser256 (a regulator of ubiquitin-related proteolysis) was decreased in both legs, which means that it was activated in both types of exercises; at the same time, the expression of the E3-ubiquitin ligase gene MURF1 , its target, was only increased after E exercise. Neither aerobic or combined exercise had a significant effect on the regulation of protein synthesis: there were no changes in either expression of IGF-1Ea and IGF-1Ec(MGF) mRNA isoforms or the phosphorylation levels of markers of protein synthesis p70S6K1 Thr389 and eEF2 Thr56 . Thus, the performance of strength exercise immediately after aerobic one prevented the activation of mitochondrial biogenesis in endurance-trained muscles: activation of AMPK pathway and the expression of TFAM are decreased, while protein synthesis regulation is not affected. At the same time, the strength exercise inhibited the expression of MURF1 gene (a marker of ubiquitin proteasome system), which was induced by aerobic exercise. We suggest that strength exercise performed immediately after intense intermittent aerobic exercise may have a negative effect on aerobic performance if used chronically.