Impact of Short-Term Continuous and Interval Exercise Training on Endothelial Function and Glucose Metabolism in Prediabetes

Tracking Biomarker Responses to Exercise in Hypertension

PURPOSE OF REVIEW

Strong evidence is evolving that physical exercise prevents hypertension and reduces blood pressure in patients with pre- and manifest HTN. Yet, identifying and confirming the effectiveness of exercise are challenging. Herein, we discuss conventional and novel biomarkers such as extracellular vesicles (EVs) which may track responses to HTN before and after exercise.

RECENT FINDINGS

Evolving data shows that improved aerobic fitness and vascular function as well as lowered oxidative stress, inflammation, and gluco-lipid toxicity are leading biomarkers considered to promote HTN, but they explain only about a half of the pathophysiology. Novel biomarkers such as EVs or microRNA are providing additional input to understand the complex mechanisms involved in exercise therapy for HTN patients. Conventional and novel biomarkers are needed to fully understand the integrative "cross-talk" between tissues to regulate vasculature physiology for blood pressure control. These biomarker studies will lead to more specific disease markers and the development of even more personalized therapy in this field. However, more systematic approaches and randomized controlled trials in larger cohorts are needed to assess exercise effectiveness across the day and with different exercise types.

Relation of Aortic Waveforms with Gut Hormones following Continuous and Interval Exercise among Older Adults with Prediabetes

Prediabetes raises cardiovascular disease risk, in part through elevated aortic waveforms. While insulin is a vasodilatory hormone, the gut hormone relation to aortic waveforms is less clear. We hypothesized that exercise, independent of intensity, would favor aortic waveforms in relation to gut hormones. Older adults (61.3 ± 1.5 yr; 33.2 ± 1.1 kg/m2) with prediabetes (ADA criteria) were randomized to undertake 60 min of work-matched continuous (CONT, n = 14) or interval (INT, n = 14) exercise for 2 wks. During a 180 min 75-g OGTT, a number of aortic waveforms (applanation tonometry) were assessed: the augmentation pressure (AP) and index (AIx75), brachial (bBP) and central blood pressure (cBP), pulse pressure (bPP and cPP), pulse pressure amplification (PPA), and forward (Pf) and backward pressure (Pb) waveforms. Acylated-ghrelin (AG), des-acylated ghrelin (dAG), GIP, and GLP-1active were measured, and correlations were co-varied for insulin. Independent of intensity, exercise increased VO2peak (p = 0.01) and PPA120min (p = 0.01) and reduced weight (p < 0.01), as well as AP120min (p = 0.02) and AIx75120min (p < 0.01). CONT lowered bSBP (p < 0.02) and bDBP (p < 0.02) tAUC180min more than INT. There were decreases dAG0min related to Pb120min (r = 0.47, p = 0.03), cPP120min (r = 0.48, p = 0.02), and AP120min (r = 0.46, p = 0.02). Declines in AG tAUC60min correlated with lower Pb120min (r = 0.47, p = 0.03) and cPP120min (r = 0.49, p = 0.02) were also found. GLP-1active 0min was reduced associated with lowered AP180min (r = 0.49, p = 0.02). Thus, while CONT exercise favored blood pressure, both intensities of exercise improved aortic waveforms in relation to gut hormones after controlling for insulin.

Addressing the Continuum of Dysglycaemia and Vascular Complications in Prediabetes and Type 2 Diabetes: Need for Early and Intensive Treatment

The onset of type 2 diabetes increases the risk of vascular complications and death. We know now that that this risk begins long before the diabetes diagnosis. Prediabetes and type 2 diabetes are not separate entities in practice and exist within a continuum of dysglycaemia and vascular risk that increases in severity over time. This excess risk requires early intervention with lifestyle therapy supported with pharmacologic antidiabetic therapy, intensified promptly where necessary throughout the duration of the diabetes continuum. Metformin is an evidence-based treatment for preventing prediabetes and improves cardiovascular outcomes in people with type 2 diabetes from diagnosis onwards. Newer agents (SGLT2 inhibitors and GLP-1 agonists) are appropriate for people presenting with type 2 diabetes and significant cardiovascular comorbidity. Additional therapies should be used without delay to achieve patients' individualised HbA1c goals and to minimise cardiovascular risk.

The impact of high-intensity interval training on vascular function in adults: A systematic review and meta-analysis

Aim

We performed a systematic review and meta-analysis to investigate the effects of high-intensity interval training (HIIT) compared with moderate-intensity continuous training (MICT) or with no exercise (CON) on vascular function in adults who were free of cardiometabolic diseases and those with cardiometabolic diseases.

Methods

A search across three electronic databases including Scopus, PubMed, and Web of Science was conducted through February 2022 to identify the randomized trials evaluating HIIT vs. MICT and/or CON on vascular function as measured using brachial artery flow-mediated dilation (FMD) in adults. Separate analyses were conducted for HIIT vs. MICT and/or CON to calculate weighted mean differences (WMD) and 95% confidence intervals (95% CIs) using random or fixed models.

Results

A total of 36 studies involving 1,437 participants who were either free of cardiometabolic diseases or had cardiometabolic diseases were included in the meta-analysis. HIIT effectively increased FMD when compared with MICT [1.59% (95% CI 0.87-2.31), p = 0.001] or CON [3.80% (95% CI 2.58-5.01), p = 0.001]. Subgroup analysis showed that HIIT increased FMD in participants with cardiovascular and metabolic diseases, but not in participants who were free of cardiometabolic diseases. In addition, HIIT effectively increased FMD regardless of age and body mass index.

Conclusion

We confirm that HIIT is effective for improving vascular function in individuals with metabolic disorders and cardiovascular diseases and has a superior effect compared to MICT, demonstrating time efficiency.

Systematic review registration

[https://www.crd.york.ac.uk/prospero], identifier [CRD42022320863].

Neural network methods for diagnosing patient conditions from cardiopulmonary exercise testing data

BACKGROUND

Cardiopulmonary exercise testing (CPET) provides a reliable and reproducible approach to measuring fitness in patients and diagnosing their health problems. However, the data from CPET consist of multiple time series that require training to interpret. Part of this training teaches the use of flow charts or nested decision trees to interpret the CPET results. This paper investigates the use of two machine learning techniques using neural networks to predict patient health conditions with CPET data in contrast to flow charts. The data for this investigation comes from a small sample of patients with known health problems and who had CPET results. The small size of the sample data also allows us to investigate the use and performance of deep learning neural networks on health care problems with limited amounts of labeled training and testing data.

METHODS

This paper compares the current standard for interpreting and classifying CPET data, flowcharts, to neural network techniques, autoencoders and convolutional neural networks (CNN). The study also investigated the performance of principal component analysis (PCA) with logistic regression to provide an additional baseline of comparison to the neural network techniques.

RESULTS

The patients in the sample had two primary diagnoses: heart failure and metabolic syndrome. All model-based testing was done with 5-fold cross-validation and metrics of precision, recall, F1 score, and accuracy. As a baseline for comparison to our models, the highest performing flow chart method achieved an accuracy of 77%. Both PCA regression and CNN achieved an average accuracy of 90% and outperformed the flow chart methods on all metrics. The autoencoder with logistic regression performed the best on each of the metrics and had an average accuracy of 94%.

CONCLUSIONS

This study suggests that machine learning and neural network techniques, in particular, can provide higher levels of accuracy with CPET data than traditional flowchart methods. Further, the CNN performed well with a small data set showing that these techniques can be designed to perform well on small data problems that are often found in health care and the life sciences. Further testing with larger data sets is needed to continue evaluating the use of machine learning to interpret CPET data.

The Problem of Wound Healing in Diabetes—From Molecular Pathways to the Design of an Animal Model

Chronic wounds are becoming an increasingly common clinical problem due to an aging population and an increased incidence of diabetes, atherosclerosis, and venous insufficiency, which are the conditions that impair and delay the healing process. Patients with diabetes constitute a group of subjects in whom the healing process is particularly prolonged regardless of its initial etiology. Circulatory dysfunction, both at the microvascular and macrovascular levels, is a leading factor in delaying or precluding wound healing in diabetes. The prolonged period of wound healing increases the risk of complications such as the development of infection, including sepsis and even amputation. Currently, many substances applied topically or systemically are supposed to accelerate the process of wound regeneration and finally wound closure. The role of clinical trials and preclinical studies, including research based on animal models, is to create safe medicinal products and ensure the fastest possible healing. To achieve this goal and minimize the wide-ranging burdens associated with conducting clinical trials, a correct animal model is needed to replicate the wound conditions in patients with diabetes as closely as possible. The aim of the paper is to summarize the most important molecular pathways which are impaired in the hyperglycemic state in the context of designing an animal model of diabetic chronic wounds. The authors focus on research optimization, including economic aspects and model reproducibility, as well as the ethical dimension of minimizing the suffering of research subjects according to the 3 Rs principle (Replacement, Reduction, Refinement).

Role of Blood Pressure Responses to Exercise and Vascular Insulin Sensitivity with Nocturnal Blood Pressure Dipping in Metabolic Syndrome

INTRODUCTION

Nocturnal systolic blood pressure (SBP) dipping is independently related to cardiovascular disease risk, but it is unclear if vascular insulin sensitivity associates with SBP dipping in patients with metabolic syndrome (MetS).

METHODS

Eighteen adults with MetS (ATP III criteria 3.3 ± 0.6; 53.2 ± 6.5 years; body mass index 35.8 ± 4.5 kg/m2) were categorized as "dippers" (≥10% change in SBP; n = 4 F/3 M) or "non-dippers" (<10%; n = 9 F/2 M). Twenty-four-hour ambulatory blood pressure was recorded to assess SBP dipping. A euglycemic-hyperinsulinemic clamp (40 mU/m2/min, 90 mg/dL) with ultrasound (flow mediated dilation) was performed to test vascular insulin sensitivity. A graded, incremental exercise test was conducted to estimate sympathetic activity. Heart rate (HR) recovery after exercise was then used to determine parasympathetic activity. Metabolic panels and body composition (DXA) were also tested.

RESULTS

Dippers had greater drops in SBP (16.63 ± 5.2 vs. 1.83 ± 5.6%, p < 0.01) and experienced an attenuated rise in both SBPslope (4.7 ± 2.3 vs. 7.2 ± 2.5 mm Hg/min, p = 0.05) and HRslope to the incremental exercise test compared to non-dippers (6.5 ± 0.9 vs. 8.2 ± 1.7 bpm/min, p = 0.03). SBP dipping correlated with higher insulin-stimulated flow-mediated dilation (r = 0.52, p = 0.03), although the relationship was no longer significant after covarying for HRslope (r = 0.42, p = 0.09).

CONCLUSION

Attenuated rises in blood pressure and HR to exercise appear to play a larger role than vascular insulin sensitivity in SBP dipping in adults with MetS.

Effects of indulgent food snacking, with and without exercise training, on body weight, fat mass, and cardiometabolic risk markers in overweight and obese men

We hypothesized that exercise training would prevent gains in body weight and body fat, and worsening of cardiometabolic risk markers, during a 4-week period of indulgent food snacking in overweight/obese men. Twenty-eight physically inactive men (ages 19-47 yr) with body mass index (BMI) ≥25 kg/m2 consumed 48 donuts (2/day, 6 days/week; ~14,500 kcal total) for 4 weeks while maintaining habitual diet. Men were randomly assigned to control (n = 9), moderate-intensity continuous training (MICT; n = 9), or high-intensity interval training (HIIT; n = 10). Exercise training occurred 4 days/week, ~250 kcal/session. Controls did not increase body weight, body fat, or visceral abdominal fat. This was partially explained by a decrease in self-reported habitual energy (-239 kcal/day, p = 0.05) and carbohydrate (-47 g/day; p = 0.02) intake. Large inter-individual variability in changes in body weight, fat, and fat-free mass was evident in all groups. Fasting blood pressure, and blood concentrations of glucose, insulin, and lipids were unchanged in all groups. Glucose incremental area under the curve during an oral glucose tolerance test was reduced by 25.6% in control (p = 0.001) and 32.8% in MICT (p = 0.01) groups. Flow-mediated dilation (FMD) was not changed in any group. VO2max increased (p ≤ 0.001) in MICT (9.2%) and HIIT (12.1%) groups. We conclude that in physically inactive men with BMI ≥25 kg/m2 , consuming ~14,500 kcal as donuts over 4 weeks did not adversely affect body weight and body fat, or several markers of cardiometabolic risk. Consumption of the donuts may have prevented the expected improvement in FMD with HIIT.

Diabetes pathogenesis and management: the endothelium comes of age

Endothelium, acting as a barrier, protects tissues against factors that provoke insulin resistance and type 2 diabetes and itself responds to the insult of insulin resistance inducers with altered function. Endothelial insulin resistance and vascular dysfunction occur early in the evolution of insulin resistance-related disease, can co-exist with and even contribute to the development of metabolic insulin resistance, and promote vascular complications in those affected. The impact of endothelial insulin resistance and vascular dysfunction varies depending on the blood vessel size and location, resulting in decreased arterial plasticity, increased atherosclerosis and vascular resistance, and decreased tissue perfusion. Women with insulin resistance and diabetes are disproportionately impacted by cardiovascular disease, likely related to differential sex-hormone endothelium effects. Thus, reducing endothelial insulin resistance and improving endothelial function in the conduit arteries may reduce atherosclerotic complications, in the resistance arteries lead to better blood pressure control, and in the microvasculature lead to less microvascular complications and more effective tissue perfusion. Multiple diabetes therapeutic modalities, including medications and exercise training, improve endothelial insulin action and vascular function. This action may delay the onset of type 2 diabetes and/or its complications, making the vascular endothelium an attractive therapeutic target for type 2 diabetes and potentially type 1 diabetes.

A single bout of exercise improves vascular insulin sensitivity in adults with obesity

OBJECTIVE

This crossover study explored the impact of a single bout of exercise on insulin-stimulated responses in conduit arteries and capillaries.

METHODS

Twelve sedentary adults (49.5 [7.8] years; maximal oxygen consumption [VO₂ max]: 23.7 [5.4] mL/kg/min) with obesity (BMI 34.5 [4.3] kg/m² ) completed a control and exercise bout (70% VO₂ max to expend 400 kcal). Sixteen hours later, participants underwent a 2-hour euglycemic-hyperinsulinemic clamp (90 mg/dL; 40 mU/m² /min) to determine vascular and metabolic insulin sensitivity. Endothelial and capillary functions were assessed by brachial artery flow-mediated dilation and contrast-enhanced ultrasound, respectively. Metabolized glucose infusion rate, substrate oxidation (indirect calorimetry), nonoxidative glucose disposal (NOGD), and inflammation were also determined.

RESULTS

Exercise increased insulin-stimulated preocclusion diameter (p = 0.01) and microvascular blood flow (condition effect: p = 0.04) compared with control. Furthermore, exercise improved metabolic insulin sensitivity by 21%, which paralleled rises in NOGD (p = 0.05) and decreases in soluble receptors for advanced glycation end products (condition effect: p = 0.01). Interestingly, changes in NOGD were related to increased insulin-stimulated microvascular blood flow (r = 0.57, p = 0.05).

CONCLUSIONS

A single bout of exercise increases vascular insulin sensitivity in adults with obesity. Additional work is needed to determine vascular responses following different doses of exercise in order to design lifestyle prescriptions for reducing chronic disease risk.

Considerations for Maximizing the Exercise "Drug" to Combat Insulin Resistance: Role of Nutrition, Sleep, and Alcohol

Insulin resistance is a key etiological factor in promoting not only type 2 diabetes mellitus but also cardiovascular disease (CVD). Exercise is a first-line therapy for combating chronic disease by improving insulin action through, in part, reducing hepatic glucose production and lipolysis as well as increasing skeletal muscle glucose uptake and vasodilation. Just like a pharmaceutical agent, exercise can be viewed as a "drug" such that identifying an optimal prescription requires a determination of mode, intensity, and timing as well as consideration of how much exercise is done relative to sitting for prolonged periods (e.g., desk job at work). Furthermore, proximal nutrition (nutrient timing, carbohydrate intake, etc.), sleep (or lack thereof), as well as alcohol consumption are likely important considerations for enhancing adaptations to exercise. Thus, identifying the maximal exercise "drug" for reducing insulin resistance will require a multi-health behavior approach to optimize type 2 diabetes and CVD care.

Cellular and Functional Effects of Insulin Based Therapies and Exercise on Endothelium

Endothelial dysfunction is a hallmark of type 2 diabetes that can have severe consequences on vascular function, including hypertension and changes in blood flow, as well as exercise performance. Because endothelium is also the barrier for insulin movement into tissues, it acts as a gatekeeper for transport and glucose uptake. For this reason, endothelial dysfunction is a tempting area for pharmacological and/or exercise intervention with insulin-based therapies. In this review, we describe the current state of drugs that can be used to treat endothelial dysfunction in type 2 diabetes and diabetes-related diseases (e.g., obesity) at the molecular levels, and also discuss their role in exercise.

Metformin May Contribute to Inter-individual Variability for Glycemic Responses to Exercise

Metformin and exercise independently improve glycemic control. Metformin traditionally is considered to reduce hepatic glucose production, while exercise training is thought to stimulate skeletal muscle glucose disposal. Collectively, combining treatments would lead to the anticipation for additive glucose regulatory effects. Herein, we discuss recent literature suggesting that metformin may inhibit, enhance or have no effect on exercise mediated benefits toward glucose regulation, with particular emphasis on insulin sensitivity. Importantly, we address issues surrounding the impact of metformin on exercise induced glycemic benefit across multiple insulin sensitive tissues (e.g., skeletal muscle, liver, adipose, vasculature, and the brain) in effort to illuminate potential sources of inter-individual glycemic variation. Therefore, the review identifies gaps in knowledge that require attention in order to optimize medical approaches that improve care of people with elevated blood glucose levels and are at risk of cardiovascular disease.