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

Road map for personalized exercise medicine in T2DM

The number of patients with type 2 diabetes mellitus (T2DM) is rising at an alarming rate. Regular physical activity and exercise are cornerstones in the therapy of T2DM. While a one-size-fits-all approach fails to account for many between-subject differences, the use of personalized exercise medicine has the potential of optimizing health outcomes. Here, a road map for personalized exercise therapy targeted at patients with T2DM is presented. It considers secondary complications, glucose management, response heterogeneity, and other relevant factors that might influence the effectiveness of exercise as medicine, taking exercise-medication-diet interactions, as well as feasibility and acceptance into account. Furthermore, the potential of artificial intelligence and machine learning-based applications in assisting sports therapists to find appropriate exercise programs is outlined.

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.

Early chronotype with metabolic syndrome favours resting and exercise fat oxidation in relation to insulin-stimulated non-oxidative glucose disposal

NEW FINDINGS

What is the central question of this study? Chronotype reflects differences in circadian-mediated metabolic and hormonal profiles. But, does resting and/or exercise fuel use differ in early versus late chronotype as it relates to insulin sensitivity? What are the main finding and its importance? Early chronotypes with metabolic syndrome utilized more fat during rest and exercise independent of aerobic fitness when compared with late chronotypes. Early chronotypes were also more physically active throughout the day. Greater fat use was related to non-oxidative glucose disposal. These findings suggest that early chronotypes have differences in fuel selection that associate with type 2 diabetes risk.

ABSTRACT

Early chronotypes (ECs) are often insulin-sensitive, in part, due to physical activity behaviour. It is unclear, however, if chronotypes differ in resting and/or exercise fuel oxidation in relation to insulin action. Using the Morningness-Eveningness Questionnaire (MEQ), adults with metabolic syndrome (ATP III criteria) were classified as EC (MEQ = 63.7 ± 0.9, n = 24 (19F), 54.2 ± 1.2 years) or late chronotype (LC; MEQ = 47.2 ± 1.4, n = 27 (23F), 55.3 ± 1.5 years). Carbohydrate (CHO) and fat oxidation (FOX, indirect calorimetry) were determined at rest, 55% and 85% V ̇ O 2 max ${\dot{V}}_{{{\rm{O}}}_{\rm{2}}{\rm{max}}}$ , along with heart rate and rating of perceived exertion. Physical activity patterns (accelerometers), body composition (DXA) and insulin sensitivity (clamp, 40 mU/m² /min, 90 mg/dl) with an indirect calorimetry for non-oxidative glucose disposal (NOGD) were also determined. While demographics were similar, ECs had higher V ̇ O 2 max ${\dot{V}}_{{{\rm{O}}}_{\rm{2}}{\rm{max}}}$ (P = 0.02), NOGD (P < 0.001) and resting FOX (P = 0.02) than LCs. Both groups increased CHO reliance during exercise at 55% and 85% V ̇ O 2 max ${\dot{V}}_{{{\rm{O}}}_{\rm{2}}{\rm{max}}}$ (test effect, P < 0.01) from rest, although ECs used more fat (group effect, P < 0.01). ECs had lower sedentary behaviour and more physical activity during morning/midday (both, P < 0.05). FOX at 55% V ̇ O 2 max ${\dot{V}}_{{{\rm{O}}}_{\rm{2}}{\rm{max}}}$ correlated with V ̇ O 2 max ${\dot{V}}_{{{\rm{O}}}_{\rm{2}}{\rm{max}}}$ (r = 0.425, P = 0.004) whereas FOX at 85% V ̇ O 2 max ${\dot{V}}_{{{\rm{O}}}_{\rm{2}}{\rm{max}}}$ related to NOGD (r = 0.392, P = 0.022). ECs with metabolic syndrome used more fat in relation to insulin-stimulated NOGD.

Localized Heat Therapy Improves Mitochondrial Respiratory Capacity but Not Fatty Acid Oxidation

AIM: Mild heat stress can improve mitochondrial respiratory capacity in skeletal muscle. However, long-term heat interventions are scarce, and the effects of heat therapy need to be understood in the context of the adaptations which follow the more complex combination of stimuli from exercise training. The purpose of this work was to compare the effects of 6 weeks of localized heat therapy on human skeletal muscle mitochondria to single-leg interval training. METHODS: Thirty-five subjects were assigned to receive sham therapy, short-wave diathermy heat therapy, or single-leg interval exercise training, localized to the quadriceps muscles of the right leg. All interventions took place 3 times per week. Muscle biopsies were performed at baseline, and after 3 and 6 weeks of intervention. Mitochondrial respiratory capacity was assessed on permeabilized muscle fibers via high-resolution respirometry. RESULTS: The primary finding of this work was that heat therapy and exercise training significantly improved mitochondrial respiratory capacity by 24.8 ± 6.2% and 27.9 ± 8.7%, respectively (p < 0.05). Fatty acid oxidation and citrate synthase activity were also increased following exercise training by 29.5 ± 6.8% and 19.0 ± 7.4%, respectively (p < 0.05). However, contrary to our hypothesis, heat therapy did not increase fatty acid oxidation or citrate synthase activity. CONCLUSION: Six weeks of muscle-localized heat therapy significantly improves mitochondrial respiratory capacity, comparable to exercise training. However, unlike exercise, heat does not improve fatty acid oxidation capacity.

Insulin Sensitivity and Metabolic Flexibility Parallel Plasma TCA Levels in Early Chronotype With Metabolic Syndrome

CONTEXT

People characterized as late chronotype have elevated type 2 diabetes and cardiovascular disease risk compared to early chronotype. It is unclear how chronotype is associated with insulin sensitivity, metabolic flexibility, or plasma TCA cycle intermediates concentration, amino acids (AA), and/or beta-oxidation.

OBJECTIVE

This study examined these metabolic associations with chronotype.

METHODS

The Morningness-Eveningness Questionnaire (MEQ) was used to classify adults with metabolic syndrome (ATP III criteria) as either early (n = 15 [13F], MEQ = 64.7 ± 1.4) or late (n = 19 [16F], MEQ = 45.5 ± 1.3) chronotype. Fasting bloods determined hepatic (HOMA-IR) and adipose insulin resistance (Adipose-IR) while a 120-minute euglycemic clamp (40 mU/m2/min, 5 mmoL/L) was performed to test peripheral insulin sensitivity (glucose infusion rate). Carbohydrate (CHOOX) and fat oxidation (FOX), as well as nonoxidative glucose disposal (NOGD), were also estimated (indirect calorimetry). Plasma tricarboxylic acid cycle (TCA) intermediates, AA, and acyl-carnitines were measured along with VO2max and body composition (DXA).

RESULTS

There were no statistical differences in age, BMI, fat-free mass, VO2max, or ATP III criteria between groups. Early chronotype, however, had higher peripheral insulin sensitivity (P = 0.009) and lower HOMA-IR (P = 0.02) and Adipose-IR (P = 0.05) compared with late chronotype. Further, early chronotype had higher NOGD (P = 0.008) and greater insulin-stimulated CHOOX (P = 0.02). While fasting lactate (P = 0.01), TCA intermediates (isocitrate, α-ketoglutarate, succinate, fumarate, malate; all P ≤ 0.04) and some AA (proline, isoleucine; P = 0.003-0.05) were lower in early chronotype, other AA (threonine, histidine, arginine; all P ≤ 0.05) and most acyl-carnitines were higher (P ≤ 0.05) compared with late chronotype.

CONCLUSION

Greater insulin sensitivity and metabolic flexibility relates to plasma TCA concentration in early chronotype.