Efficacy of high-intensity interval- or continuous aerobic-training on insulin resistance and muscle function in adults with metabolic syndrome: a clinical trial

Efficacy of high-intensity interval training versus continuous training on serum myonectin and lipid outcomes in adults with metabolic syndrome: A post-hoc analysis of a clinical trial

BACKGROUND

Myonectin is a myokine with potential effects on the lipid metabolism; however, its regulation by exercise in humans remains unclear. We aimed to compare the efficacy of high-intensity interval training low-volume (HIIT) versus moderate-intensity continuous training (MICT) on serum myonectin, serum lipids, appendicular fat and lean mass, and intramuscular lipids in humans.

METHODS

Secondary analysis of a controlled, randomized, clinical trial in adults of both sexes with metabolic syndrome, who underwent a supervised, three-times/week, 12-week treadmill program. HIIT (n = 29) consisted of six intervals with one-minute, high-intensity phases at 90% of peak oxygen consumption (VO2peak) for a total of 22 min. MICT (n = 31) trained at 60% of VO2peak for 36 min. Serum myonectin was measured using a human enzyme-linked immunosorbent assay. Lipid profile was determined by enzymatic methods and free fatty acids (FFA) were measured by gas chromatography. Fat and lean mass were assessed by dual-energy X-ray absorptiometry. Intramuscular lipids were measured through proton magnetic resonance spectroscopy.

RESULTS

Subjects had a mean age of 50.8±6.0 years and body mass index of 30.6±4.0 kg/m2. Compared to MICT, HIIT was not superior at increasing serum myonectin (p = 0.661) or linoleic acid (p = 0.263), reducing palmitic (p = 0.286) or stearic acid (p = 0.350), or improving lipid profile (all p>0.05), appendicular fat mass index -AFMI- (p = 0.713) or appendicular lean mass percentage -ALM- (p = 0.810). Compared to baseline, only HIIT significantly increased myonectin (p = 0.042), with a large effect size, although both interventions reduced AFMI and increased ALM with a large effect size. Lipid profile, FFA and intramuscular lipids did not change in any intervention group (p>0.05).

CONCLUSIONS

Compared to MICT, HIIT low volume did not demonstrate superiority in improving serum lipids. The fact that both training types reduced AFMI without paralleled significant changes in serum myonectin suggests that this myokine may have a minor effect on short-middle-term exercise-induced fat mobilization.

Musclin Mitigates the Attachment of HUVECs to THP-1 Monocytes in Hyperlipidemic Conditions through PPARα/HO-1-Mediated Attenuation of Inflammation

Musclin, a myokine, undergoes modulation during exercise and has demonstrated anti-inflammatory effects in cardiomyocytes and glomeruli. However, its role in atherosclerotic responses remains unclear. This study aimed to explore the impact of musclin on inflammatory responses and the interaction between endothelial cells and monocytes under hyperlipidemic conditions. The attachment levels of THP-1 monocytes on cultured HUVECs were examined. Inflammation and the expression of cell adhesion molecules were also evaluated. To explore the molecular mechanisms of musclin, PPARα or heme oxygenase 1 (HO-1) siRNA transfection was performed in HUVECs. The results revealed that treatment with recombinant musclin effectively suppressed the attachment of palmitate-induced HUVECs to THP-1 cells and reduced the expression of cell adhesion proteins (ICAM-1, VCAM-1, and E-selectin) in HUVECs. Furthermore, musclin treatment ameliorated the expression of inflammation markers (phosphorylated NFκB and IκB) in both HUVECs and THP-1 monocytes, as well as the release of TNFα and MCP-1 from HUVECs and THP-1 monocytes. Notably, musclin treatment augmented the expression levels of PPARα and HO-1. However, when PPARα or HO-1 siRNA was employed, the beneficial effects of musclin on inflammation, cell attachment, and adhesion molecule expression were abolished. These findings indicate that musclin exerts anti-inflammatory effects via the PPARα/HO-1 pathway, thereby mitigating the interaction between endothelial cells and monocytes. This study provides evidence supporting the important role of musclin in ameliorating obesity-related arteriosclerosis and highlights its potential as a therapeutic agent for treating arteriosclerosis.

Serum Levels of Myonectin Are Lower in Adults with Metabolic Syndrome and Are Negatively Correlated with Android Fat Mass

Myonectin has shown beneficial effects on lipid regulation in murine models; therefore, it may have implications in the pathophysiology of metabolic syndrome (MS). We evaluated the relationship between serum myonectin and serum lipids, global and regional fat mass, intramuscular lipid content, and insulin resistance (IR) in adults with metabolic risk factors. This was a cross-sectional study in sedentary adults who were diagnosed with MS or without MS (NMS). Serum myonectin was quantified by enzyme-linked immunosorbent assay, lipid profile by conventional techniques, and free fatty acids (FFA) by gas chromatography. Body composition was assessed by dual-energy X-ray absorptiometry and intramuscular lipid content through proton nuclear magnetic resonance spectroscopy in the right vastus lateralis muscle. IR was estimated with the homeostatic model assessment (HOMA-IR). The MS (n = 61) and NMS (n = 29) groups were comparable in age (median (interquartile range): 51.0 (46.0-56.0) vs. 53.0 (45.5-57.5) years, p > 0.05) and sex (70.5% men vs. 72.4% women). MS subjects had lower serum levels of myonectin than NMS subjects (1.08 (0.87-1.35) vs. 1.09 (0.93-4.05) ng·mL^-1, p < 0.05). Multiple linear regression models adjusted for age, sex, fat mass index and lean mass index showed that serum myonectin was negatively correlated with the android/gynoid fat mass ratio (R² = 0.48, p < 0.01), but not with the lipid profile, FFA, intramuscular lipid content or HOMA-IR. In conclusion, serum myonectin is lower in subjects with MS. Myonectin negatively correlates with a component relevant to the pathophysiology of MS, such as the android/gynoid fat mass ratio, but not with other components such as FFA, intramuscular fat or IR.

In vivo absolute quantification of carnosine in the vastus lateralis muscle with 1H MRS using a surface coil and water as internal reference

OBJECTIVE

To standardize a method for ¹H MRS intramuscular absolute quantification of carnosine in the thigh, using a surface coil and water as internal reference.

MATERIALS AND METHODS

Carnosine spectra were acquired in phantoms (5, 10, and 15 mM) as well as in the right gastrocnemius medialis (GM) and right vastus lateralis (VLM) muscles of young team sports athletes, using volume (VC) and surface (SC) coils on a 3 T scanner, with the same receiver gain. Water spectra were used as internal reference for the absolute quantification of carnosine.

RESULTS

Phantom's experiments showed a maximum error of 7%, highlighting the validity of the measurements in the study setup. The carnosine concentrations (mmol/kg ww, mean ± SD) measured in the GM were 6.8 ± 2.2 with the VC (C_carVC) and 10.2 ± 3.0 with the SC (C_carSC) (P = 0.013; n = 9). Therefore, a correction was applied to these measurements (C_carVC = 0.6582*C_carSC), to make coils performance comparable (6.8 ± 2.2 for VC and 6.7 ± 2.0 for SC, P = 0.97). After that, only the SC was used to quantify carnosine in the VLM, where a concentration of 5.4 ± 1.5 (n = 30) was found, with significant differences between men (6.2 ± 1.3; n = 15) and women (4.6 ± 1.2; n = 15). The error in quantitation was 5.3-5.5% with both coils.

CONCLUSION

The method using the SC and water as internal reference can be used to quantify carnosine in voluminous muscles and regions of the body in humans, where the VC is not suitable, such as the VLM.

Epidemiological, mechanistic, and practical bases for assessment of cardiorespiratory fitness and muscle status in adults in healthcare settings

Given their importance in predicting clinical outcomes, cardiorespiratory fitness (CRF) and muscle status can be considered new vital signs. However, they are not routinely evaluated in healthcare settings. Here, we present a comprehensive review of the epidemiological, mechanistic, and practical bases of the evaluation of CRF and muscle status in adults in primary healthcare settings. We highlight the importance of CRF and muscle status as predictors of morbidity and mortality, focusing on their association with cardiovascular and metabolic outcomes. Notably, adults in the best quartile of CRF and muscle status have as low as one-fourth the risk of developing some of the most common chronic metabolic and cardiovascular diseases than those in the poorest quartile. The physiological mechanisms that underlie these epidemiological associations are addressed. These mechanisms include the fact that both CRF and muscle status reflect an integrative response to the body function. Indeed, muscle plays an active role in the development of many diseases by regulating the body's metabolic rate and releasing myokines, which modulate metabolic and cardiovascular functions. We also go over the most relevant techniques for assessing peak oxygen uptake as a surrogate of CRF and muscle strength, mass, and quality as surrogates of muscle status in adults. Finally, a clinical case of a middle-aged adult is discussed to integrate and summarize the practical aspects of the information presented throughout. Their clinical importance, the ease with which we can assess CRF and muscle status using affordable techniques, and the availability of reference values, justify their routine evaluation in adults across primary healthcare settings.

Moderate intensity continuous and interval training affect visceral fat and insulin resistance model in female rat exposed high calorie diet

Chronic high-calorie diet (HCD) combined with physical inactivity promotes obesity and insulin resistance (IR). This study aimed to analyse the comparable effect of moderate-intensity continuous training (MICT) and moderate-intensity interval training (MIIT) on visceral fat weight and IR in subjects exposed to HCD. This randomised post-test research used only a control group design with female rats (Wistar norvegicus), 8 weeks old and 100-200 g of bodyweight. They were randomly divided into four groups: standard diet group (C), HCD group (C1), HCD combined with MICT group (C2) and HCD combined with MIIT group (C3). Each group consisted of six rats. HCD consisted of ad libitum standard diet plus dextrose solution by oral gavage for 4 weeks. The MICT was conducted by swimming plus 6% load of body weight for 10 min in the first week, for 20 min in the second week and 30 min in the third and fourth week. The MIIT was conducted by swimming in a ratio between swimming and rest time at 2:1 plus 6% load of BW, performed 5×/week for 4 weeks, and increased progressively. The mean body weight pre-intervention was 152.79±13.280 g and 150.12±9.195 g post-intervention (P=0.115). The mean fasting blood glucose pre-intervention was 79±8.668 mg/dl, and post-intervention 86.29±12.142 mg/dl (P=0.142). The mean visceral fat weight between C (1.94±0.66 g), C1 (1.45±0.47 g), C2 (1.41±0.44 g), and C3 (1.22±0.59 g) was not significant (P=0.179). The mean triglyceride level for C (173.33±30.30 mg/dl), C1 (157.16±47.32 mg/dl), C2 (112.83±25.49 mg/dl), and C3 (80.33±23.47 mg/dl) was significant (P=0.000). The mean IR model for C (4.796±0.070), C1 (4.728±0.125), C2 (4.620±0.123), C3 (4.360±0.143) was significant (P=0.000). In conclusion, both MICT and MIIT have an effect to improve IR and TG. The MIIT was more effective to improve IR compared to MICT in the female rats exposed to an HCD.

Effects of two workload-matched high intensity interval training protocols on regulatory factors associated with mitochondrial biogenesis in the soleus muscle of diabetic rats

Aims: High intensity interval training (HIIT) improves mitochondrial characteristics. This study compared the impact of two workload-matched high intensity interval training (HIIT) protocols with different work:recovery ratios on regulatory factors related to mitochondrial biogenesis in the soleus muscle of diabetic rats.

Materials and methods: Twenty-four Wistar rats were randomly divided into four equal-sized groups: non-diabetic control, diabetic control (DC), diabetic with long recovery exercise [4–5 × 2-min running at 80%–90% of the maximum speed reached with 2-min of recovery at 40% of the maximum speed reached (DHIIT1:1)], and diabetic with short recovery exercise (5–6 × 2-min running at 80%–90% of the maximum speed reached with 1-min of recovery at 30% of the maximum speed reached [DHIIT2:1]). Both HIIT protocols were completed five times/week for 4 weeks while maintaining equal running distances in each session.

Results: Gene and protein expressions of PGC-1α, p53, and citrate synthase of the muscles increased significantly following DHIIT1:1 and DHIIT2:1 compared to DC (p ˂ 0.05). Most parameters, except for PGC-1α protein (p = 0.597), were significantly higher in DHIIT2:1 than in DHIIT1:1 (p ˂ 0.05). Both DHIIT groups showed significant increases in maximum speed with larger increases in DHIIT2:1 compared with DHIIT1:1.

Conclusion: Our findings indicate that both HIIT protocols can potently up-regulate gene and protein expression of PGC-1α, p53, and CS. However, DHIIT2:1 has superior effects compared with DHIIT1:1 in improving mitochondrial adaptive responses in diabetic rats.

Very Low-Carbohydrate High-Fat Diet Improves Risk Markers for Cardiometabolic Health More Than Exercise in Men and Women With Overfat Constitution: Secondary Analysis of a Randomized Controlled Clinical Trial

Purpose

This randomized controlled parallel-group study examined the effects of a very low-carbohydrate high-fat (VLCHF) diet and high-intensity interval training (HIIT) program over 12-weeks on cardiometabolic risk factors in individuals with overfat constitution.

Methods

Ninety-one participants out of 109 completed the study. The participants were randomly allocated to the HIIT (N = 22), VLCHF (N = 25), VLCHF+HIIT (N = 25), or control (N = 19) groups for 12 weeks. Fasting plasma samples were collected before the intervention and after 4 and 12 weeks. The analyzed outcomes included complete blood count, glucose, insulin, glycated hemoglobin, triglycerides (TG), cholesterol, high- and low-density lipoprotein (HDL-C and LDL-C), lipoprotein(a), adiponectin (Adpn), leptin (Lep), tumor necrosis factor α (TNF-α), other interleukins (hs-IL-6, IL-1β, and IL-10), and IL-1RA. The homeostasis model assessment of insulin resistance (HOMA-IR), Adpn/Lep ratio, TG/HDL-C ratio, and TyG index were calculated and analyzed. Blood pressure was measured before the intervention, after 4, 8, and 12 weeks (ClinicalTrials.gov: NCT03934476).

Results

Absolute changes in HOMA-IR, Adpn/Lep ratio, LDL-C, and diastolic blood pressure after 12 weeks differed by study groups (p < 0.05). The most pronounced changes were revealed in the VLCHF (ΔM [95% CI]; HOMA-IR: -0.75 [-1.13; -0.55]; Adpn/Lep: 9.34 [6.33; 37.39]; LDL-C: 0.06 [-0.12; 0.50] mmol/l) and VLCHF+HIIT (HOMA-IR: -0.44 [-1.14; 0.12]; Adpn/Lep: 4.26 [2.24; 13.16]; LDL-C: 0.25 [-0.04; 0.50] mmol/l) groups.

Conclusions

A 12-week VLCHF diet intervention in individuals with overfat constitution is effective for favorable changes in HOMA-IR (compared to HIIT), Adpn/Lep ratio, and diastolic blood pressure. HIIT, or HIIT combined with the VLCHF diet, had no additional benefits for the analyzed variables. No adverse side effects were observed.