Type 2 diabetic individuals have impaired leg blood flow responses to exercise: role of endothelium-dependent vasodilation

Transcapillary PO2 Gradients in Contracting Muscles of Type I Diabetic Rats

OBJECTIVE

This study aimed to clarify the effect of Type I diabetes (DIA) on transcapillary PO2 gradients, which are oxygen-driving factors between the blood and the interstitium, in the contracting muscle of rats.

METHODS

Wistar male rats were divided into the diabetic (streptozocin i.p.) and sham groups. Microvascular and interstitial PO2 were measured in the extensor digitorum longus muscle during electrical stimulation-induced muscle contraction, using the phosphorescence quenching method. Transcapillary PO2 gradient, ΔPO2, was calculated as microvascular minus interstitial PO2.

RESULTS

Resting microvascular PO2 was higher in the diabetic group than in the sham group (6.3 ± 1.7 vs. 4.7 ± 0.9 mmHg, p < 0.05) and remained for 180 s. Interstitial PO2 from rest to muscle contraction did not differ between the groups. The ΔPO2 was higher in the diabetic group than in the sham group at rest and during muscle contraction (4.03 ± 1.42 vs. 2.46 ± 0.90 mmHg at rest; 3.67 ± 1.51 vs. 2.22 ± 0.65 mmHg during muscle contraction, p < 0.05). Marked muscle atrophy was observed in the diabetic group.

CONCLUSION

DIA increased microvascular and transcapillary PO2 gradients in the skeletal muscle. The enhanced PO2 gradients were maintained from rest to muscle contraction in diabetic muscle.

Non-neuronal cell-derived acetylcholine, a key modulator of the vascular endothelial function in health and disease

Vascular endothelial cells play an important role in regulating peripheral circulation by modulating arterial tone in the microvasculature. Elevated intracellular Ca2+ levels are required in endothelial cells to induce smooth muscle relaxation via endothelium-dependent mechanisms such as nitric oxide production, prostacyclin, and endothelial cell hyperpolarization. It is well established that exogenous administration of acetylcholine can increase intracellular Ca2+ concentrations, followed by endothelium-dependent vasodilation. Although endogenous acetylcholine's regulation of vascular tone remains debatable, recent studies have reported that endogenously derived acetylcholine, but not neuronal cell-derived acetylcholine, is a key modulator of endothelial cell function. In this minireview, we summarize the current knowledge of the non-neuronal cholinergic system (NNCS) in vascular function, particularly vascular endothelial cell function, which contributes to blood pressure regulation. We also discuss the possible pathophysiological impact of endothelial NNCS, which may induce the development of vascular diseases due to endothelial dysfunction, and the potential of endothelial NNCS as a novel therapeutic target for endothelial dysfunction in the early stages of metabolic syndrome, diabetes, and hypertension.

Impaired muscle oxygenation despite normal pulmonary function in type 2 diabetes without complications

Long-term hyperglycemia in individuals with type 2 diabetes (T2D) can detrimentally impact pulmonary function and muscle oxygenation. As a result, these factors can impede the body's adaptation to physical exertion. We aimed to evaluate the oxygen pathway during maximal exercise among overweight/obese individuals with type 2 diabetes free from complications, in comparison with a group of matched overweight/obese individuals without diabetes, specifically concentrating on the effects on pulmonary function and muscle oxygenation. Fifteen overweight/obese adults with type 2 diabetes [glycated hemoglobin (HbA1c) = 8.3 ± 1.2%] and 15 matched overweight/obese adults without diabetes underwent pre- and post exercise lung function assessment. A maximal incremental exercise test was conducted, monitoring muscle oxygenation using near-infrared spectroscopy and collecting arterial blood gas samples. Both groups exhibited normal lung volumes at rest and after exercise. Spirometric lung function did not significantly differ pre- and post exercise in either group. During maximal exercise, the type 2 diabetes group showed significantly lower augmentation in total hemoglobin and deoxygenated hemoglobin compared with the control group. Despite comparable usual physical activity levels and comparable heart rates at exhaustion, the type 2 diabetes group had a lower peak oxygen consumption than controls. No significant differences were found in arterial blood gas analyses ([Formula: see text], [Formula: see text], [Formula: see text], and [Formula: see text]) between the groups. Individuals with type 2 diabetes free from complications displayed normal pulmonary function at rest and post exercise. However, impaired skeletal muscle oxygenation during exercise, resulting from reduced limb blood volume and altered muscle deoxygenation, may contribute to the lower V̇o2peak observed in this population.NEW & NOTEWORTHY Individuals with type 2 diabetes free from micro- and macrovascular complications have normal resting pulmonary function, but their V̇o2peak is impaired due to poor skeletal muscle oxygenation during exercise. Tailoring exercise regimes for this population should prioritize interventions aimed at enhancing muscle oxygenation and blood flow improvement.

Muscle deoxygenation during ramp incremental cycle exercise in older adults with type 2 diabetes

PURPOSE

To explore profiles of fractional O2 extraction (using near-infrared spectroscopy) during ramp incremental cycling in older individuals with type 2 diabetes (T2D).

METHODS

Twelve individuals with T2D (mean ± SD, age: 63 ± 3 years) and 12 healthy controls (mean age: 65 ± 3 years) completed a ramp cycling exercise. Rates of muscle deoxygenation (i.e., deoxygenated haemoglobin and myoglobin, Δ[HHb + Mb]) profiles of the vastus lateralis muscle were normalised to 100% of the response, plotted against absolute (W) and relative (%peak) power output (PO) and fitted with a double linear regression model.

RESULTS

Peak oxygen uptake (V̇O2peak) was significantly (P < 0.01) reduced in T2D (23.0 ± 4.2 ml.kg-1.min-1) compared with controls (28.3 ± 5.3 ml.kg-1.min-1). The slope of the first linear segment of the model was greater (median (interquartile range)) in T2D (1.06 (1.50)) than controls (0.79 (1.06)) when Δ%[HHb + Mb] was plotted as a function of PO. In addition, the onset of the second linear segment of the Δ%[HHb + Mb]/PO model occurred at a lower exercise intensity in T2D (101 ± 35 W) than controls (140 ± 34 W) and it displayed a near-plateau response in both groups. When the relationship of the Δ%[HHb + Mb] profile was expressed as a function of %PO no differences were observed in any parameters of the double linear model.

CONCLUSIONS

These findings suggest that older individuals with uncomplicated T2D demonstrate greater fractional oxygen extraction for a given absolute PO compared with older controls. Thus, the reductions in V̇O2peak in older people with T2D are likely influenced by impairments in microvascular O2 delivery.

Viewing life without labels under optical microscopes

Optical microscopes today have pushed the limits of speed, quality, and observable space in biological specimens revolutionizing how we view life today. Further, specific labeling of samples for imaging has provided insight into how life functions. This enabled label-based microscopy to percolate and integrate into mainstream life science research. However, the use of labelfree microscopy has been mostly limited, resulting in testing for bio-application but not bio-integration. To enable bio-integration, such microscopes need to be evaluated for their timeliness to answer biological questions uniquely and establish a long-term growth prospect. The article presents key label-free optical microscopes and discusses their integrative potential in life science research for the unperturbed analysis of biological samples.

Effects of comorbid type II diabetes mellitus and heart failure on rat hindlimb and respiratory muscle blood flow during treadmill exercise

In rats with type II diabetes mellitus (T2DM) compared with nondiabetic healthy controls, muscle blood flow (Q̇m) to primarily glycolytic hindlimb muscles and the diaphragm muscle are elevated during submaximal treadmill running consequent to lower skeletal muscle mass, a finding that held even when muscle mass was normalized to body mass. In rats with heart failure with reduced ejection fraction (HF-rEF) compared with healthy controls, hindlimb Q̇m was lower, whereas diaphragm Q̇m is elevated during submaximal treadmill running. Importantly, T2DM is the most common comorbidity present in patients with HF-rEF, but the effect of concurrent T2DM and HF-rEF on limb and respiratory Q̇m during exercise is unknown. We hypothesized that during treadmill running (20 m·min-1; 10% incline), hindlimb and diaphragm Q̇m would be higher in T2DM Goto-Kakizaki rats with HF-rEF (i.e., HF-rEF + T2DM) compared with nondiabetic Wistar rats with HF-rEF. Ejection fractions were not different between groups (HF-rEF: 30 ± 5; HF-rEF + T2DM: 28 ± 8%; P = 0.617), whereas blood glucose was higher in HF-rEF + T2DM (209 ± 150 mg/dL) compared with HF-rEF rats (113 ± 28 mg/dL; P = 0.040). Hindlimb muscle mass normalized to body mass was lower in rats with HF-rEF + T2DM (36.3 ± 1.6 mg/g) than in nondiabetic HF-rEF counterparts (40.3 ± 2.7 mg/g; P < 0.001). During exercise, Q̇m was elevated in rats with HF-rEF + T2DM compared with nondiabetic counterparts to the hindlimb (HF-rEF: 100 ± 28; HF-rEF + T2DM: 139 ± 23 mL·min-1·100 g-1; P < 0.001) and diaphragm (HF-rEF: 177 ± 66; HF-rEF + T2DM: 215 ± 93 mL·min-1·100g-1; P = 0.035). These data suggest that the pathophysiological consequences of T2DM on hindlimb and diaphragm Q̇m during treadmill running in the GK rat persist even in the presence of HF-rEF.NEW & NOTEWORTHY Herein, we demonstrate that rats comorbid with heart failure with reduced ejection fraction (HF-rEF) and type II diabetes mellitus (T2DM) have a higher hindlimb and respiratory muscle blood flow during submaximal treadmill running (20 m·min-1; 10% incline) compared with nondiabetic HF-rEF counterparts. These data may carry important clinical implications for roughly half of all patients with HF-rEF who present with T2DM.

The influence of simultaneous pancreas-kidney transplantation on the evolution of diabetic foot lesions and peripheral arterial disease

PURPOSE

Simultaneous pancreas-kidney transplantation (SPKT) remains the best treatment option in patients with type 1 diabetes and chronic kidney failure. There are only a few studies addressing the potential ischemic deterioration of peripheral arterial disease (PAD) due to blood diverting from the iliac artery to the kidney graft. We aimed to evaluate diabetic foot lesions and PAD evolution in SPKT recipients and investigate if they are more frequent in ipsilateral lower limb of kidney graft.

METHODS

We developed a retrospective cohort, including patients submitted to SPKT in our tertiary center, between 2000 and 2017. Diabetic foot lesions and PAD frequencies were compared in the period before and after transplantation.

RESULTS

Two hundred and eleven patients were included, 50.2% (n = 106) female, with a median age at transplantation of 35 years (IQR 9). After a median follow-up period of 10 years (IQR 7), patient, kidney, and pancreatic graft survival were 90.5% (n = 191), 83.4% (n = 176), and 74.9% (n = 158), respectively. Before transplant, 2.8% (n = 6) had PAD and 5.3% (n = 11) had history of foot lesions. In post-transplant period, 17.1% (n = 36) patients presented PAD and 25.6% (n = 54) developed diabetic foot ulcers, 47.6% (n = 35) of which in the ipsilateral and 53.3% (n = 40) in the contralateral lower limb of the kidney graft (p = 0.48). Nine patients (4.3%) underwent major lower limb amputation, 3 (30%) ipsilateral and 7 (70%) contralateral to the kidney graft (p = 0.29).

CONCLUSIONS

Diabetic foot lesions were not more frequent in the ipsilateral lower limb of the kidney graft, therefore downgrading the 'steal syndrome' role in these patients.

Eight weeks of inorganic nitrate/nitrite supplementation improves aerobic exercise capacity and the gas exchange threshold in patients with type 2 diabetes

Patients with type 2 diabetes mellitus (T2DM) have reduced exercise capacity, indexed by lower maximal oxygen consumption (V̇o2max) and achievement of the gas exchange threshold (GET) at a lower % V̇o2max. The ubiquitous signaling molecule nitric oxide (NO) plays a multifaceted role during exercise and, as patients with T2DM have poor endogenous NO production, we investigated if inorganic nitrate/nitrite supplementation (an exogenous source of NO) improves exercise capacity in patients with T2DM. Thirty-six patients with T2DM (10F, 59 ± 9 yr, 32.0 ± 5.1 kg/m2, HbA1c = 7.4 ± 1.4%) consumed beetroot juice containing either inorganic nitrate/nitrite (4.03 mmol/0.29 mmol) or a placebo (0.8 mmol/0.00 mmol) for 8 wk. A maximal exercise test was completed before and after both interventions. V̇o2max was determined by averaging 15-s data, whereas the GET was identified using the V-slope method and breath-by-breath data. Inorganic nitrate/nitrite increased both absolute (1.96 ± 0.67 to 2.07 ± 0.75 L/min) and relative (20.7 ± 7.0 to 21.9 ± 7.4 mL/kg/min, P < 0.05 for both) V̇o2max, whereas no changes were observed following placebo (1.94 ± 0.40 to 1.90 ± 0.39 L/min, P = 0.33; 20.0 ± 4.2 to 19.7 ± 4.6 mL/kg/min, P = 0.39). Maximal workload was also increased following inorganic nitrate/nitrite supplementation (134 ± 47 to 140 ± 51 W, P < 0.05) but not placebo (138 ± 32 to 138 ± 32 W, P = 0.98). V̇o2 at the GET (1.11 ± 0.27 to 1.27 ± 0.38L/min) and the %V̇o2max in which GET occurred (56 ± 8 to 61 ± 7%, P < 0.05 for both) increased following inorganic nitrate/nitrite supplementation but not placebo (1.10 ± 0.23 to 1.08 ± 0.21 L/min, P = 0.60; 57 ± 9 to 57 ± 8%, P = 0.90) although the workload at GET did not achieve statistical significance (group-by-time P = 0.06). Combined inorganic nitrate/nitrite consumption improves exercise capacity, maximal workload, and promotes a rightward shift in the GET in patients with T2DM. This manuscript reports data from a registered Clinical Trial at ClinicalTrials.gov ID: NCT02804932.NEW & NOTEWORTHY We report that increasing nitric oxide bioavailability via 8 wk of inorganic nitrate/nitrite supplementation improves maximal aerobic exercise capacity in patients with type 2 diabetes mellitus. Similarly, we observed a rightward shift in the gas exchange threshold. Taken together, these data indicate inorganic nitrate/nitrite may serve as a means to improve fitness in patients with type 2 diabetes mellitus.

Effects of Combined Inorganic Nitrate and Nitrite Supplementation on Cardiorespiratory Fitness and Skeletal Muscle Oxidative Capacity in Type 2 Diabetes: A Pilot Randomized Controlled Trial

Nitric oxide (NO) stimulates mitochondrial biogenesis in skeletal muscle. However, NO metabolism is disrupted in individuals with type 2 diabetes mellitus (T2DM) potentially contributing to their decreased cardiorespiratory fitness (i.e., VO2max) and skeletal muscle oxidative capacity. We used a randomized, double-blind, placebo-controlled, 8-week trial with beetroot juice containing nitrate (NO3−) and nitrite (NO2−) (250 mg and 20 mg/day) to test potential benefits on VO2max and skeletal muscle oxidative capacity in T2DM. T2DM (N = 36, Age = 59 ± 9 years; BMI = 31.9 ± 5.0 kg/m2) and age- and BMI-matched non-diabetic controls (N = 15, Age = 60 ± 9 years; BMI = 29.5 ± 4.6 kg/m2) were studied. Mitochondrial respiratory capacity was assessed in muscle biopsies from a subgroup of T2DM and controls (N = 19 and N = 10, respectively). At baseline, T2DM had higher plasma NO3− (100%; p < 0.001) and lower plasma NO2− levels (−46.8%; p < 0.0001) than controls. VO2max was lower in T2DM (−26.4%; p < 0.001), as was maximal carbohydrate- and fatty acid-supported oxygen consumption in permeabilized muscle fibers (−26.1% and −25.5%, respectively; p < 0.05). NO3−/NO2− supplementation increased VO2max (5.3%; p < 0.01). Further, circulating NO2−, but not NO3−, positively correlated with VO2max after supplementation (R2= 0.40; p < 0.05). Within the NO3−/NO2− group, 42% of subjects presented improvements in both carbohydrate- and fatty acid-supported oxygen consumption in skeletal muscle (vs. 0% in placebo; p < 0.05). VO2max improvements in these individuals tended to be larger than in the rest of the NO3−/NO2− group (1.21 ± 0.51 mL/(kg*min) vs. 0.31 ± 0.10 mL/(kg*min); p = 0.09). NO3−/NO2− supplementation increases VO2max in T2DM individuals and improvements in skeletal muscle oxidative capacity appear to occur in those with more pronounced increases in VO2max.

Type-2 Diabetes and the Clinical Importance of Exaggerated Exercise Blood Pressure

BACKGROUND

Exaggerated exercise blood pressure (EEBP) during clinical exercise testing is associated with poor blood pressure (BP) control and cardiovascular disease (CVD). Type-2 diabetes (T2DM) is thought to be associated with increased prevalence of EEBP, but this has never been definitively determined and was the aim of this study.

METHODS

Clinical exercise test records were analyzed from 13 268 people (aged 53±13 years, 59% male) who completed the Bruce treadmill protocol (stages 1-4, and peak) at 4 Australian public hospitals. Records (including BP) were linked to administrative health datasets (hospital and emergency admissions) to define clinical characteristics and classify T2DM (n=1199) versus no T2DM (n=12 069). EEBP was defined as systolic BP ≥90th percentile at each test stage. Exercise BP was regressed on T2DM history and adjusted for CVD and risk factors.

RESULTS

Prevalence of EEBP (age, sex, preexercise BP, hypertension history, CVD history and aerobic capacity adjusted) was 12% to 51% greater in T2DM versus no T2DM (prevalence ratio [95% CI], stage 1, 1.12 [1.02-1.24]; stage 2, 1.51 [1.41-1.61]; stage 3, 1.25 [1.10-1.42]; peak, 1.18 [1.09-1.29]). At stages 1 to 3, 8.6% to 15.8% (4.8%-9.7% T2DM versus 3.5% to 6.1% no-T2DM) of people with 'normal' preexercise BP (<140/90 mm Hg) were identified with EEBP. Exercise systolic BP relative to aerobic capacity (stages 1-4 and peak) was higher in T2DM with adjustment for all CVD risk factors.

CONCLUSIONS

People with T2DM have higher prevalence of EEBP and exercise systolic BP independent of CVD and many of its known risk factors. Clinicians supervising exercise testing should be alerted to increased likelihood of EEBP and thus poor BP control warranting follow-up care in people with T2DM.

Role of arterial stiffness and endothelial dysfunction on lower limb performance in older adults with type 2 diabetes: A cross-sectional study

AIM

To verify whether arterial stiffness and endothelial dysfunction influence lower limb muscle strength and gait speed in older adults with type 2 diabetes mellitus (T2DM).

METHODS

Cross-sectional study including seventy-eight older adults with T2DM (aged 67 ± 6 years and 42 % male). Arterial stiffness was assessed using pulse wave velocity (PWV), while endothelial function was measured by flow-mediated dilation (FMD). Lower limb muscle strength and gait speed were assessed using the 30-second chair stand test (30s-CST) and 10-Meter Walk Test, respectively.

RESULTS

Both PWV (m/s) and FMD (%) were univariately associated with number of repetitions in 30s-CST and gait speed (P < 0.05). After control for age, sex and body mass index, PWV remained associated with repetitions in 30s-CST (95 % CI: -0.494 to -0.054; P = 0.015) and gait speed (95 % CI: -0.039 to -0.002; P = 0.031). After adjustments for control variables, T2DM duration and glycemic control, FMD was associated with repetitions in 30s-CST (95 % CI: 0.008 to 0.324; P = 0.039) and gait speed (95 % CI: 0.011 to 0.038; P = 0.001).

CONCLUSION

In older adults with T2DM, both arterial stiffness and endothelial dysfunction are associated with decreased leg muscle strength and slower gait speed.

Characterization of Endothelium-Dependent Relaxation in the Saphenous Artery and Its Caudal Branches in Young and Old Adult Sprague Dawley Rats

Ageing is associated with reduced endothelium-derived nitric oxide (NO) production in the femoral artery of Sprague Dawley (SD) rats. In the current study, we examined endothelium-dependent relaxation (EDR) in the saphenous artery and its caudal branches. We used acetylcholine and the Proteinase-Activated receptor-2 (PAR2)-specific agonist (2fLIGRLO) with nitroarginine methylester (L-NAME) to assess EDR in two groups of male SD rats (age in weeks: young, 10–12; old, 27–29). Acetylcholine and 2fLIGRLO were potent NO-dependent relaxant agents in all arteries. For all arteries, EDR by acetylcholine decreased significantly in old compared to young SD rats. Interestingly, PAR2-induced EDR of proximal saphenous artery segments and caudal branches decreased significantly in old compared to young, but did not differ for the in-between middle and distal ends of the saphenous artery. L-NAME treatment increased subsequent contractions of proximal and middle segments of saphenous arteries by phenylephrine and U46619 in young, but not in old, SD rats. We conclude the SD saphenous artery and caudal branches exhibit regional characteristics that differ in response to specific EDR agonists, endothelial NO synthase inhibitor, and changes to endothelium function with increased age, which are, in part, attributed to decreased sensitivity of vascular smooth muscle to the gaseous transmitter NO.

The exercise pressor reflex: An update

The exercise pressor reflex is a feedback mechanism engaged upon stimulation of mechano- and metabosensitive skeletal muscle afferents. Activation of these afferents elicits a reflex increase in heart rate, blood pressure, and ventilation in an intensity-dependent manner. Consequently, the exercise pressor reflex has been postulated to be one of the principal mediators of the cardiorespiratory responses to exercise. In this updated review, we will discuss classical and recent advancements in our understating of the exercise pressor reflex function in both human and animal models. Particular attention will be paid to the afferent mechanisms and pathways involved during its activation, its effects on different target organs, its potential role in the abnormal cardiovascular response to exercise in diseased states, and the impact of age and biological sex on these responses. Finally, we will highlight some unanswered questions in the literature that may inspire future investigations in the field.

Muscle Microcirculatory Responses to Incremental Exercises Are Correlated with Peak Oxygen Uptake in Individuals With and Without Type 2 Diabetes Mellitus

Background: The role of impaired oxygen extraction on peak oxygen uptake (V̇O_2peak) has been extensively studied using noninvasive and indirect methods in both diabetic patients and healthy participants. Methods: A total of 22 participants with type 2 diabetes mellitus [T2DM; median (range) age: 60 (47-70) years] and 22 controls [58 (52-69) years] with no history of diabetes were recruited (reference no. 201812135RINB). Subjects performed an exhaustive incremental exercise and were evaluated using a gas analyzer and near-infrared spectroscopy (NIRS) to determine V̇O_2peak and changes in muscle oxygenation (SmO₂) in the vastus lateralis, respectively. Measurements were taken at rest, warm-up, a period during exercise when SmO₂ reached a minimum saturation plateau, and recovery. The microcirculatory responses of the vastus lateralis muscle during incremental exercise in patients with T2DM were compared with those in control individuals, and the correlation between changes in SmO₂ and V̇O_2peak was estimated. Results: The diabetic group demonstrated lower V̇O_2peak, peak workload, peak heart rate, peak minute ventilation (all P < 0.05), and lower SmO₂ during the rest, warm-up, and recovery phases (all P < 0.05) compared with the control group. A correlation was observed between the change in SmO₂ between the warm-up and plateau value and the V̇O_2peak (r = 0.608, P = 0.006). Conclusions: The results obtained in this study using NIRS support the feasibility of directly measuring changes in muscle SmO₂ magnitudes to estimate the contributions of peripheral active muscle to systemic O₂ uptake (V̇O₂) during incremental exercise.

The Impact of Obesity on the Regulation of Muscle Blood Flow during Exercise in Patients with Heart Failure with a Preserved Ejection Fraction

Obesity is now considered a primary comorbidity in heart failure with preserved ejection fraction (HFpEF) pathophysiology, mediated largely by systemic inflammation. While there is accumulating evidence for a disease-related dysregulation of blood flow during exercise in this patient group, the role of obesity in the hemodynamic response to exercise remain largely unknown. Small muscle mass handgrip (HG) exercise was utilized to evaluate exercising muscle blood flow in non-obese (BMI < 30 kg/m²,n=14) and obese (BMI > 30 kg/m²,n=40) patients with HFpEF. Heart rate (HR), stroke index (SI), cardiac index (CI), mean arterial pressure (MAP), forearm blood flow (FBF) and vascular conductance (FVC) were assessed during progressive intermittent HG exercise (15-30-45% maximal voluntary contraction, MVC). Blood biomarkers of inflammation (C-reactive protein (CRP) and Interleukin-6 (IL-6)) were also determined. Exercising FBF was reduced in obese patients with HFpEF at all work rates (15%: 304±42 vs. 229±15ml/min; 30%: 402±46 vs. 300±18ml/min; 45%: 484±55 vs. 380±23ml/min, non-obese vs. obese, p=0.025), and was negatively correlated with BMI (R=-.47, p<0.01). In contrast, no differences in central hemodynamics (HR, SI, CI, MAP) were found between groups. Proinflammatory biomarkers were markedly elevated in obese patients (CRP: 2133±418 vs. 4630±590ng/ml, p=0.02; IL-6: 2.9±0.3 vs. 5.2±0.7pg/ml, p = 0.04, non-obese vs. obese), and both biomarkers were positively correlated with BMI (CRP: R=0.40, p=0.03; IL-6: R=0.57, p<0.01). Together, these findings demonstrate the presence of obesity and an accompanying milieu of systemic inflammation as important factors in the dysregulation of exercising muscle blood flow in patients with HFpEF.

Combined inorganic nitrate/nitrite supplementation blunts α-mediated vasoconstriction during exercise in patients with type 2 diabetes

AIMS

Patients with type 2 diabetes mellitus (T2DM) have reduced vasodilatory responses during exercise partially attributable to low nitric oxide (NO) levels. Low NO contributes to greater α-adrenergic mediated vasoconstriction in contracting skeletal muscle. We hypothesized boosting NO bioavailability via 8wks of active beetroot juice (BR_A, 4.03 mmol nitrate, 0.29 mmol nitrite, n = 19) improves hyperemia, via reduced α-mediated vasoconstriction, during handgrip exercise relative to nitrate/nitrite-depleted beetroot juice (BR_P, n = 18) in patients with T2DM.

METHODS

Forearm blood flow (FBF) and vascular conductance (FVC) were calculated at rest and during handgrip exercise (20%max, 20contractions·min^-1). Phenylephrine (α₁-agonist) and dexmedetomidine (α₂-agonist) were infused intra-arterially during independent trials to determine the influence of α-mediated vasoconstriction on exercise hyperemia. Vasoconstriction was quantified as the percent-reduction in FVC during α-agonist infusion, relative to pre-infusion, as well as the absolute change in %FVC during exercise relative to the respective rest trial (magnitude of sympatholysis).

RESULTS

ΔFBF (156 ± 69 to 175 ± 73 ml min^-1) and ΔFVC (130 ± 54 to 156 ± 63 ml min^-1·100 mmHg^-1, both P < 0.05) during exercise were augmented following BR_A, but not BR_P (P = 0.96 and 0.51). Phenylephrine-induced vasoconstriction during exercise was blunted following BR_A (-17.1 ± 5.9 to -12.6 ± 3.1%, P < 0.01), but not BR_P (P = 0.58) supplementation; the magnitude of sympatholysis was unchanged by either (beverage-by-time P = 0.15). BR_A supplementation reduced dexmedetomidine-induced vasoconstriction during exercise (-23.3 ± 6.7 to -19.7 ± 5.2%) and improved the corresponding magnitude of sympatholysis (25.3 ± 11.4 to 34.4 ± 15.5%, both P < 0.05).

CONCLUSIONS

BR_A supplementation improves the hyperemic and vasodilatory responses to exercise in patients with T2DM which appears to be attributable to reduced α-adrenergic mediated vasoconstriction in contracting skeletal muscle.

Hemodynamic response during hyperbaric treatment on skeletal muscle in a type 2 diabetes rat model

Mild hyperbaric treatment prevents type 2 diabetes progression due to increased oxygen concentration and blood flow in skeletal muscle. However, it remains unknown whether this treatment is effective during all stages of type 2 diabetes. This study aimed to investigate the influences of hyperbaric treatment at 1.3 atmospheres absolute (ATA) on hemodynamic response in various stages of type 2 diabetes. Otsuka Long-Evans Tokushima fatty (OLETF) and Long-Evans Tokushima Otsuka (LETO) rats were used as models of type 2 diabetes and healthy controls, respectively. Glucose levels were significantly higher in OLETF rats than in LETO rats at all ages. Glucose intolerance gradually increased with age in OLETF rats. Insulin levels in OLETF rats were significantly higher at 20-week-old, however, were significantly lower at 60-week-old than in LETO rats. Oxy-Hb, total Hb, and StO₂ in skeletal muscle were increased during hyperbaric treatment in both rats. The hemodynamic changes were significantly higher in OLETF rats than LETO rats, and those changes were also pronounced at 8-week-old compared with other age in OLETF rats. These results suggest that hyperbaric treatment at 1.3 ATA acts on pathophysiological factors and the efficacy could be found only in the early stage of type 2 diabetes.

Current Review of Optical Neural Interfaces for Clinical Applications

Neural interfaces, which enable the recording and stimulation of living neurons, have emerged as valuable tools in understanding the brain in health and disease, as well as serving as neural prostheses. While neural interfaces are typically based on electrical transduction, alternative energy modalities have been explored to create safe and effective approaches. Among these approaches, optical methods of linking neurons to the outside world have gained attention because light offers high spatial selectivity and decreased invasiveness. Here, we review the current state-of-art of optical neural interfaces and their clinical applications. Optical neural interfaces can be categorized into optical control and optical readout, each of which can be divided into intrinsic and extrinsic approaches. We discuss the advantages and disadvantages of each of these methods and offer a comparison of relative performance. Future directions, including their clinical opportunities, are discussed with regard to the optical properties of biological tissue.

Microcirculatory Responses to Muscle and Tendon Exercises in Individuals With and Without Type 2 Diabetes Mellitus and the Association Between Microcirculatory and Exercise Performance

Background: This study aimed to measure and compare (1) the microcirculation and microcirculatory responses of the muscles and tendons at rest and during isometric muscle contractions in participants with and without diabetes mellitus (DM) and (2) to determine correlations between microcirculation and muscle strength. Methods: Sixty-three participants with type 2 DM and 42 physically matched controls were recruited. Baseline measurements of the microcirculation of the rectus femoris (RF) and medial gastrocnemius (MG) muscles and patellar (PT) and Achilles tendons (AT), as well as their microcirculatory changes during maximal isometric exercises, were performed and recorded by using near-infrared spectroscopy and a red laser. Data on various laboratory tests (including glycated hemoglobin, triglyceride, high-density cholesterol), the monofilament test, and the ankle-brachial index were also obtained. Results: The baseline measurements indicated that, compared with the controls, the diabetic participants had lower oxygen saturation (SpO₂) in their RF and MG muscles (both P < 0.001), and the total hemoglobin in the diabetic PT and AT was higher (P = 0.001 and P = 0.01). The minimal SpO₂ levels in the aforementioned muscles during isometric contractions were lower in the diabetes group than in the control group (P ≤ 0.001). Furthermore, there were correlations between the microcirculatory change of the RF muscle and the knee extension force. Conclusions: This study demonstrated the effects of diabetes on the microcirculation of skeletal muscles and tendons during baseline measurements and responses to maximal isometric exercises. The results support the need for preventive strategies for diabetic muscles to prevent adverse complications when performing resistance training.

Time course of changes in V̇o2peak and O2 extraction during ramp cycle exercise following HIIT versus moderate-intensity continuous training in type 2 diabetes

In the present study, we assessed the time course of adaptations in peak oxygen uptake (V̇o2peak) and muscle fractional oxygen (O2) extraction (using near-infrared spectroscopy) following 12 wk of low-volume high-intensity interval training (HIIT) versus moderate-intensity continuous endurance training (MICT) in adults with uncomplicated type 2 diabetes (T2D). Participants with T2D were randomly assigned to MICT ( n = 12, 50 min of moderate-intensity cycling) or HIIT ( n = 9, 10 × 1 min at ∼90% maximal heart rate) or to a nonexercising control group ( n = 9). Exercising groups trained three times per week and measurements were taken every 3 wk. The rate of muscle deoxygenation (i.e., deoxygenated hemoglobin and myoglobin concentration, Δ[HHb + Mb]) profiles of the vastus lateralis muscle were normalized to 100% of the response, plotted against % power output (PO), and fitted with a double linear regression model. V̇o2peak increased ( P < 0.05) by week 3 of MICT (+17%) and HIIT (+8%), with no further significant changes thereafter. Total increases in V̇o2peak posttraining ( P < 0.05) were 27% and 14%, respectively. The %Δ[HHb + Mb] versus %PO slope of the first linear segment ( slope1) was reduced ( P < 0.05) beyond 3 wk of HIIT and MICT, with no further significant changes thereafter. No changes in V̇o2peak or slope1 were observed in the control group. Low-volume HIIT and MICT induced improvements in V̇o2peak following a similar time course, and these improvements were likely, at least in part, due to an improved microvascular O2 delivery.

Neurovascular Dysregulation During Exercise in Type 2 Diabetes

Emerging evidence suggests that type 2 diabetes (T2D) may impair the ability to properly adjust the circulation during exercise with augmented blood pressure (BP) and an attenuated contracting skeletal muscle blood flow (BF) response being reported. This review provides a brief overview of the current understanding of these altered exercise responses in T2D and the potential underlying mechanisms, with an emphasis on the sympathetic nervous system and its regulation during exercise. The research presented support augmented sympathetic activation, heightened BP, reduced skeletal muscle BF, and impairment in the ability to attenuate sympathetically mediated vasoconstriction (i.e., functional sympatholysis) as potential drivers of neurovascular dysregulation during exercise in T2D. Furthermore, emerging evidence supporting a contribution of the exercise pressor reflex and central command is discussed along with proposed future directions for studies in this important area of research.

Time-course of V̇o2 kinetics responses during moderate-intensity exercise subsequent to HIIT versus moderate-intensity continuous training in type 2 diabetes

We assessed the time-course of changes in oxygen uptake (V̇o₂) and muscle deoxygenation (i.e., deoxygenated hemoglobin and myoglobin, [HHb + Mb]) kinetics during transitions to moderate-intensity cycling following 12 wk of low-volume high-intensity interval training (HIIT) vs. moderate-intensity continuous training (MICT) in adults with type 2 diabetes (T2D). Participants were randomly assigned to MICT (n = 10, 50 min of moderate-intensity cycling), HIIT (n = 9, 10 × 1 min at ∼90% maximal heart rate), or nonexercising control (n = 9) groups. Exercising groups trained three times per week, and measurements were taken every 3 wk. [HHb + Mb] kinetics were measured by near-infrared spectroscopy at the vastus lateralis muscle. The local matching of O₂ delivery to O₂ utilization was assessed by the Δ[HHb + Mb]/ΔV̇o₂ ratio. The pretraining time constant of the primary phase of V̇o₂ (τV̇o_2p) decreased (P < 0.05) at wk 3 of training in both MICT (from 44 ± 12 to 32 ± 5 s) and HIIT (from 42 ± 8 to 32 ± 4 s) with no further changes thereafter, whereas no changes were reported in controls. The pretraining overall dynamic response of muscle deoxygenation (τ'[HHb + Mb]) was faster than τV̇o_2p in all groups, resulting in Δ[HHb + Mb]/V̇o_2p showing a transient "overshoot" relative to the subsequent steady-state level. After 3 wk, the Δ[HHb + Mb]/V̇o_2p overshoot was eliminated only in the training groups, so that τ'[HHb + Mb] was not different to τV̇o_2p in MICT and HIIT. The enhanced V̇o₂ kinetics response consequent to both MICT and HIIT in T2D was likely attributed to a training-induced improvement in matching of O₂ delivery to utilization.NEW & NOTEWORTHY High-intensity interval training and moderate-intensity continuous training elicited faster pulmonary oxygen uptake (V̇o₂) kinetics during moderate-intensity cycling within 3 wk of training with no further changes thereafter in individuals with type 2 diabetes. These adaptations were accompanied by unaltered near-infrared spectroscopy-derived muscle deoxygenation (i.e. deoxygenated hemoglobin and myoglobin concentration, [HHb+Mb]) kinetics and transiently reduced Δ[HHb+Mb]-to-ΔV̇o₂ ratio, suggesting an enhanced blood flow distribution within the active muscles subsequent to both training interventions.

Combined mental task and metaboreflex impair cerebral oxygenation in patients with type 2 diabetes mellitus

Cardiovascular regulation is altered by type 2 diabetes mellitus (DM2), producing an abnormal response to muscle metaboreflex. During physical exercise, cerebral blood flow is impaired in patients with DM2, and this phenomenon may reduce cerebral oxygenation (COX). We hypothesized that the simultaneous execution of a mental task (MT) and metaboreflex activation would reduce COX in patients with DM2. Thirteen individuals suffering from DM2 (6 women) and 13 normal age-matched controls (CTL, 6 women) participated in this study. They underwent five different tests, each lasting 12 min: postexercise muscle ischemia (PEMI) to activate the metaboreflex, control exercise recovery (CER), PEMI + MT, CER + MT, and MT alone. COX was evaluated using near-infrared spectroscopy with sensors applied to the forehead. Central hemodynamics was assessed using impedance cardiography. We found that when MT was superimposed on the PEMI-induced metaboreflex, patients with DM2 could not increase COX to the same extent reached by the CTL group (101.13% ± 1.08% vs. 104.23% ± 2.51%, P < 0.05). Moreover, patients with DM2 had higher mean blood pressure and systemic vascular resistance as well as lower stroke volume and cardiac output levels compared with the CTL group, throughout our experiments. It was concluded that patients with DM2 had reduced capacity to enhance COX when undertaking an MT during metaboreflex. Results also confirm that patients with DM2 had dysregulated hemodynamics during metaboreflex, with exaggerated blood pressure response and vasoconstriction. This may have implications for these patients' lack of inclination to exercise.

Advancement of Sensor Integrated Organ-on-Chip Devices

Organ-on-chip devices have provided the pharmaceutical and tissue engineering worlds much hope since they arrived and began to grow in sophistication. However, limitations for their applicability were soon realized as they lacked real-time monitoring and sensing capabilities. The users of these devices relied solely on endpoint analysis for the results of their tests, which created a chasm in the understanding of life between the lab the natural world. However, this gap is being bridged with sensors that are integrated into organ-on-chip devices. This review goes in-depth on different sensing methods, giving examples for various research on mechanical, electrical resistance, and bead-based sensors, and the prospects of each. Furthermore, the review covers works conducted that use specific sensors for oxygen, and various metabolites to characterize cellular behavior and response in real-time. Together, the outline of these works gives a thorough analysis of the design methodology and sophistication of the current sensor integrated organ-on-chips.

Heart failure with preserved ejection fraction diminishes peripheral hemodynamics and accelerates exercise-induced neuromuscular fatigue

This study investigated the impact of HFpEF on neuromuscular fatigue and peripheral hemodynamics during small muscle mass exercise not limited by cardiac output. Eight HFpEF patients (NYHA II-III, ejection-fraction: 61 ± 2%) and eight healthy controls performed dynamic knee extension exercise (80% peak workload) to task failure and maximal intermittent quadriceps contractions (8 × 15 s). Controls repeated knee extension at the same absolute intensity as HFpEF. Leg blood flow (Q_L) was quantified using Doppler ultrasound. Pre/postexercise changes in quadriceps twitch torque (ΔQ_tw; peripheral fatigue), voluntary activation (ΔVA; central fatigue), and corticospinal excitability were quantified. At the same relative intensity, HFpEF (24 ± 5 W) and controls (42 ± 6 W) had a similar time-to-task failure (∼10 min), ΔQ_tw (∼50%), and ΔVA (∼6%). This resulted in a greater exercise-induced change in neuromuscular function per unit work in HFpEF, which was significantly correlated with a slower Q_L response time. Knee extension exercise at the same absolute intensity resulted in an ∼40% lower Q_L and greater ΔQ_tw and ΔVA in HFpEF than in controls. Corticospinal excitability remained unaltered during exercise in both groups. Finally, despite a similar ΔVA, ΔQ_tw was larger in HFpEF versus controls during isometric exercise. In conclusion, HFpEF patients are characterized by a similar development of central and peripheral fatigue as healthy controls when tested at the same relative intensity during exercise not limited by cardiac output. However, HFpEF patients have a greater susceptibility to neuromuscular fatigue during exercise at a given absolute intensity, and this impairs functional capacity. The patients' compromised Q_L response to exercise likely accounts, at least partly, for the patients' attenuated fatigue resistance.NEW & NOTEWORTHY The susceptibility to neuromuscular fatigue during exercise is substantially exaggerated in individuals with heart failure with a preserved ejection fraction. The faster rate of fatigue development is associated with the compromised peripheral hemodynamic response characterizing these patients during exercise. Given the role of neuromuscular fatigue as a factor limiting exercise, this impairment likely accounts for a significant portion of the exercise intolerance typical for this population.

Greater α1-adrenergic-mediated vasoconstriction in contracting skeletal muscle of patients with type 2 diabetes

Findings presented in this article are the first to show patients with type 2 diabetes mellitus have blunted hyperemic and vasodilatory responses to dynamic handgrip exercise. Moreover, we illustrate greater α1-adrenergic-mediated vasoconstriction may contribute to our initial observations. Collectively, these data suggest patients with type 2 diabetes may have impaired functional sympatholysis, which can contribute to their reduced exercise capacity.

Type 2 diabetes and reduced exercise tolerance: a review of the literature through an integrated physiology approach

The association between type 2 diabetes mellitus (T2DM) and heart failure (HF) is well established. Early in the course of the diabetic disease, some degree of impaired exercise capacity (a powerful marker of health status with prognostic value) can be frequently highlighted in otherwise asymptomatic T2DM subjects. However, the literature is quite heterogeneous, and the underlying pathophysiologic mechanisms are far from clear. Imaging-cardiopulmonary exercise testing (CPET) is a non-invasive, provocative test providing a multi-variable assessment of pulmonary, cardiovascular, muscular, and cellular oxidative systems during exercise, capable of offering unique integrated pathophysiological information. With this review we aimed at defying the cardiorespiratory alterations revealed through imaging-CPET that appear specific of T2DM subjects without overt cardiovascular or pulmonary disease. In synthesis, there is compelling evidence indicating a reduction of peak workload, peak oxygen assumption, oxygen pulse, as well as ventilatory efficiency. On the contrary, evidence remains inconclusive about reduced peripheral oxygen extraction, impaired heart rate adjustment, and lower anaerobic threshold, compared to non-diabetic subjects. Based on the multiparametric evaluation provided by imaging-CPET, a dissection and a hierarchy of the underlying mechanisms can be obtained. Here we propose four possible integrated pathophysiological mechanisms, namely myocardiogenic, myogenic, vasculogenic and neurogenic. While each hypothesis alone can potentially explain the majority of the CPET alterations observed, seemingly different combinations exist in any given subject. Finally, a discussion on the effects -and on the physiological mechanisms-of physical activity and exercise training on oxygen uptake in T2DM subjects is also offered. The understanding of the early alterations in the cardiopulmonary response that are specific of T2DM would allow the early identification of those at a higher risk of developing HF and possibly help to understand the pathophysiological link between T2DM and HF.

Recent advances in exercise pressor reflex function in health and disease

Autonomic alterations at the onset of exercise are critical to redistribute cardiac output towards the contracting muscles while preventing a fall in arterial pressure due to excessive vasodilation within the contracting muscles. Neural mechanisms responsible for these adjustments include central command, the exercise pressor reflex, and arterial and cardiopulmonary baroreflexes. The exercise pressor reflex evokes reflex increases in sympathetic activity to the heart and systemic vessels and decreases in parasympathetic activity to the heart, which increases blood pressure (BP), heart rate, and total peripheral resistance through vasoconstriction of systemic vessels. In this review, we discuss recent advancements in our understanding of exercise pressor reflex function in health and disease. Specifically, we discuss emerging evidence suggesting that sympathetic vasoconstrictor drive to the contracting and non-contracting skeletal muscle is differentially controlled by central command and the metaboreflex in healthy conditions. Further, we discuss evidence from animal and human studies showing that cardiovascular diseases, including hypertension, diabetes, and heart failure, lead to an altered exercise pressor reflex function. We also provide an update on the mechanisms thought to underlie this altered exercise pressor reflex function in each of these diseases. Although these mechanisms are complex, multifactorial, and dependent on the etiology of the disease, there is a clear consensus that several mechanisms are involved. Ultimately, approaches targeting these mechanisms are clinically significant as they provide alternative therapeutic strategies to prevent adverse cardiovascular events while also reducing symptoms of exercise intolerance.

Effects of exercise training and sex on dynamic responses of O2 uptake in type 2 diabetes

Effects of training and sex on oxygen uptake dynamics during exercise in type 2 diabetes mellitus (T2DM) are not well established. We tested the hypotheses that exercise training improves the time constant of the primary phase of oxygen uptake (τ_p oxygen uptake) and with greater effect in males than females. Forty-one subjects with T2DM were assigned to 2 training groups (T_male, T_female) and 2 control groups (C_male, C_female), and were assessed before and after a 12-week intervention period. Twelve weeks of aerobic/resistance training was performed 3 times per week, 60-90 min per session. Assessments included ventilatory threshold (VT), peak oxygen uptake, τ_p oxygen uptake (80%VT), and dynamic responses of cardiac output, mean arterial pressure and systemic vascular conductance (80%VT). Training significantly decreased τ_p oxygen uptake in males by a mean of 20% (T_male = 42.7 ± 6.2 to 34.3 ± 7.2 s) and females by a mean of 16% (T_female = 42.2 ± 9.3 to 35.4 ± 8.6 s); whereas τ_p oxygen uptake was not affected in controls (C_male = 41.6 ± 9.8 to 42.9 ± 7.6 s; C_female = 40.4 ± 12.2 to 40.6 ± 13.4 s). Training increased peak oxygen uptake in both sexes (12%-13%) but did not alter systemic cardiovascular dynamics in either sex. Training improved oxygen uptake dynamics to a similar extent in males and females in the absence of changes in systemic cardiovascular dynamics. Novelty Similar training improvements in oxygen uptake dynamics were observed in males and females with T2DM. In both sexes these improvements occurred without changes in systemic cardiovascular dynamics.

Augmented pressor and sympathoexcitatory responses to the onset of isometric handgrip in patients with type 2 diabetes

Patients with type 2 diabetes (T2D) exhibit greater daytime blood pressure (BP) variability, increasing their cardiovascular risk. Given the number of daily activities that incorporate short-duration isometric muscle contractions (e.g., carrying groceries), herein we investigated BP and muscle sympathetic nerve activity (MSNA) responses at the onset of isometric handgrip (HG). We tested the hypothesis that, relative to control subjects, patients with T2D would exhibit exaggerated pressor and MSNA responses to the immediate onset of HG. Mean arterial pressure (MAP) and MSNA were quantified during the first 30 s of isometric HG at 30% and 40% of maximal voluntary contraction (MVC) and during a cold pressor test (CPT), a nonexercise sympathoexcitatory stimulus. The onset of 30% MVC HG evoked similar increases in MAP between groups (P = 0.17); however, the increase in MSNA was significantly greater in patients with T2D versus control subjects with the largest group difference at 20 s (P < 0.001). At the onset of 40% MVC HG, patients with T2D demonstrated greater increases in MAP (e.g., 10 s, T2D: 9 ± 1 mmHg, controls: 5 ± 2 mmHg; P = 0.04). MSNA was also greater in patients with T2D at 40% MVC onset but differences were only significant at the 20-30 s timepoint (T2D: 15 ± 3 bursts/min, controls: -2 ± 4 bursts/min; P < 0.001). Similarly, MAP and MSNA responses were augmented during the onset of CPT in T2D patients. These findings demonstrate exaggerated pressor and MSNA reactivity in patients with T2D, with rapid and robust responses to both isometric contractions and cold stress. This hyper-responsiveness may contribute to daily surges in BP in patients with T2D, increasing their short-term and long-term cardiovascular risk.

Exaggerated exercise pressor reflex in type 2 diabetes: Potential role of oxidative stress

Type 2 diabetes mellitus (T2DM) leads to exaggerated cardiovascular responses to exercise, in part due to an exaggerated exercise pressor reflex. Accumulating data suggest excessive oxidative stress contributes to an exaggerated exercise pressor reflex in cardiovascular-related diseases. Excessive oxidative stress is also a primary underlying mechanism for the development and progression of T2DM. However, whether oxidative stress plays a role in mediating the exaggerated exercise pressor reflex in T2DM is not known. Therefore, this review explores the potential role of oxidative stress leading to increased activation of the afferent arm of the exercise pressor reflex. Several lines of evidence support direct and indirect effects of oxidative stress on the exercise pressor reflex. For example, intramuscular ROS may directly and indirectly (by attenuating contracting muscle blood flow) increase group III and IV afferent activity. Oxidative stress is a primary underlying mechanism for the development of neuropathic pain, which in turn is associated with increased group III and IV afferent activity. These are the same type of afferents that evoke muscle pain and the exercise pressor reflex. Furthermore, oxidative stress-induced release of inflammatory mediators may modulate afferent activity. Collectively, these alterations may result in a positive feedback loop that further amplifies the exercise pressor reflex. An exaggerated reflex increases the risk of adverse cardiovascular events. Thus, identifying the contribution of oxidative stress could provide a potential therapeutic target to reduce this risk in T2DM.

Influence of priming exercise on oxygen uptake and muscle deoxygenation kinetics during moderate-intensity cycling in type 2 diabetes

The pulmonary oxygen uptake (V̇o2) kinetics during the transition to moderate-intensity exercise is slowed in individuals with type 2 diabetes (T2D), at least in part because of limitations in O2 delivery. The present study tested the hypothesis that a prior heavy-intensity warm-up or “priming” exercise (PE) bout would accelerate V̇o2 kinetics in T2D, because of a better matching of O2 delivery to utilization. Twelve middle-aged individuals with T2D and 12 healthy controls (ND) completed moderate-intensity constant-load cycling bouts either without (Mod A) or with (Mod B) prior PE. The rates of muscle deoxygenation (i.e., deoxygenated hemoglobin and myoglobin concentration, [HHb+Mb]) and oxygenation (i.e., tissue oxygenation index) were continuously measured by near-infrared spectroscopy at the vastus lateralis muscle. The local matching of O2 delivery to O2 utilization was assessed by the Δ[HHb+Mb]-to-ΔV̇o2 ratio. Both groups demonstrated an accelerated V̇O2 kinetics response during Mod B compared with Mod A (T2D, 32 ± 9 vs. 42 ± 12 s; ND, 28 ± 9 vs. 34 ± 8 s; means ± SD) and an elevated muscle oxygenation throughout Mod B, whereas the [HHb+Mb] amplitude was greater during Mod B only in individuals with T2D. The [HHb+Mb] kinetics remained unchanged in both groups. In T2D, Mod B was associated with a decrease in the “overshoot” relative to steady state in the Δ[HHb+Mb]-to-ΔV̇o2 ratio (1.17 ± 0.17 vs. 1.05 ± 0.15), whereas no overshoot was observed in the control group before (1.04 ± 0.12) or after (1.01 ± 0.12) PE. Our findings support a favorable priming-induced acceleration of the V̇o2 kinetics response in middle-aged individuals with uncomplicated T2D attributed to an enhanced matching of microvascular O2 delivery to utilization.

NEW & NOTEWORTHY Heavy-intensity “priming” exercise (PE) elicited faster pulmonary oxygen uptake (V̇o2) kinetics during moderate-intensity cycling exercise in middle-aged individuals with type 2 diabetes (T2D). This was accompanied by greater near-infrared spectroscopy-derived muscle deoxygenation (i.e., deoxygenated hemoglobin and myoglobin concentration, [HHb+Mb]) responses and a reduced Δ[HHb+Mb]-to-ΔV̇o2 ratio. This suggests that the PE-induced acceleration in oxidative metabolism in T2D is a result of greater O2 extraction and better matching between O2 delivery and utilization.

Perfusion Assessment in Critical Limb Ischemia: Principles for Understanding and the Development of Evidence and Evaluation of Devices: A Scientific Statement From the American Heart Association

There are >12 million patients with peripheral artery disease in the United States. The most severe form of peripheral artery disease is critical limb ischemia (CLI). The diagnosis and management of CLI is often challenging. Ethnic differences in comorbidities and presentation of CLI exist. Compared with white patients, black and Hispanic patients have higher prevalence rates of diabetes mellitus and chronic renal disease and are more likely to present with gangrene, whereas white patients are more likely to present with ulcers and rest pain. A thorough evaluation of limb perfusion is important in the diagnosis of CLI because it can not only enable timely diagnosis but also reduce unnecessary invasive procedures in patients with adequate blood flow or among those with other causes for ulcers, including venous, neuropathic, or pressure changes. This scientific statement discusses the current tests and technologies for noninvasive assessment of limb perfusion, including the ankle-brachial index, toe-brachial index, and other perfusion technologies. In addition, limitations of the current technologies along with opportunities for improvement, research, and reducing disparities in health care for patients with CLI are discussed.

Influence of type 2 diabetes on muscle deoxygenation during ramp incremental cycle exercise

We tested the hypothesis that type 2 diabetes (T2D) alters the profile of muscle fractional oxygen (O₂) extraction (near-infrared spectroscopy) during incremental cycle exercise. Seventeen middle-aged individuals with uncomplicated T2D and 17 controls performed an upright ramp test to exhaustion. The rate of muscle deoxygenation (i.e. deoxygenated haemoglobin and myoglobin concentration, Δ[HHb+Mb]) profiles of the vastus lateralis muscle were normalised to 100% of the response, plotted against % power output (PO) and fitted with a double linear regression model. Peak oxygen uptake was significantly (P < 0.05) reduced in individuals with T2D. The %Δ[HHb+Mb]/%PO slope of the first linear segment of the double linear regression function was significantly (P < 0.05) steeper in T2D than controls (1.59 (1.14) vs 1.23 (0.51)). Both groups displayed a near-plateau in Δ[HHb+Mb] at an exercise intensity (%PO) not different amongst them. Such findings suggest that a reduced O₂ delivery to active muscles is an important underlying cause of exercise intolerance during a maximum graded test in middle-aged individuals with T2D.

Exaggerated cardiovascular responses to muscle contraction and tendon stretch in UCD type-2 diabetes mellitus rats

Patients with type-2 diabetes mellitus (T2DM) have exaggerated sympathetic activity and blood pressure responses to exercise. However, the underlying mechanisms for these responses, as well as how these responses change throughout disease progression, are not completely understood. For this study, we examined the effect of the progression of T2DM on the exercise pressor reflex, a critical neurocardiovascular mechanism that functions to increase sympathetic activity and blood pressure during exercise. We also aimed to examine the effect of T2DM on reflexive cardiovascular responses to static contraction, as well as those responses to tendon stretch when an exaggerated exercise pressor reflex was present. We evoked the exercise pressor reflex and mechanoreflex by statically contracting the hindlimb muscles and stretching the Achilles tendon, respectively, for 30 s. We then compared pressor and cardioaccelerator responses in unanesthetized, decerebrated University of California Davis (UCD)-T2DM rats at 21 and 31 wk following the onset of T2DM to responses in healthy nondiabetic rats. We found that the pressor response to static contraction was greater in the 31-wk T2DM [change in mean arterial pressure (∆MAP) = 39 ± 5 mmHg] but not in the 21-wk T2DM (∆MAP = 24 ± 5 mmHg) rats compared with nondiabetic rats (∆MAP = 18 ± 2 mmHg; P < 0.05). Similarly, the pressor and the cardioaccelerator responses to tendon stretch were significantly greater in the 31-wk T2DM rats [∆MAP = 69 ± 6 mmHg; change in heart rate (∆HR) = 28 ± 4 beats/min] compared with nondiabetic rats (∆MAP = 14 ± 2 mmHg; ∆HR = 5 ± 3 beats/min; P < 0.05). These findings suggest that the exercise pressor reflex changes as T2DM progresses and that a sensitized mechanoreflex may play a role in exaggerating these cardiovascular responses.NEW & NOTEWORTHY This is the first study to provide evidence that as type-2 diabetes mellitus (T2DM) progresses, the exercise pressor reflex becomes exaggerated, an effect that may be due to a sensitized mechanoreflex. Moreover, these findings provide compelling evidence suggesting that impairments in the reflexive control of circulation contribute to exaggerated blood pressure responses to exercise in T2DM.

Diagnostic methods for measurement of peripheral blood flow during exercise in patients with type 2 diabetes and peripheral artery disease: a systematic review

INTRODUCTION

Measurement of systolic ankle and to some extent toe pressure in patients suffering from combined type 2 diabetes mellitus (T2DM) and peripheral arterial disease (PAD) face several obstacles due to complex changes in the vascular bed. The aim of this review was to address the current literature on blood flow during exercise in patients with PAD and T2DM and assess the feasibility of these methods to diagnose and grade arterial insufficiency.

EVIDENCE ACQUISITION

A systematic review of the PubMed and EMBASE databases, supplemented by hand searching was performed according to PRISMA guidelines. Clinical studies evaluating methods to investigate peripheral blood flow in patients with PAD and T2DM during exercise were included.

EVIDENCE SYNTHESIS

In total nine eligible studies consisting of 1105 non-diabetic PAD patients, 336 diabetic PAD patients, 161 diabetic patients without PAD and 69 healthy controls were included in the review. Near-infrared spectroscopy (NIRS) was described in three studies, transcutaneous oxygen pressure measurement (TcpO2) in two and the following methods described in single studies: thermodilution, contrast enhanced ultrasound (CEUS), scintigraphy and TcpO2 in combination with ultrasound. These studies shows that patients with PAD and T2DM compared with patients with only PAD suffers different atherosclerotic lesions characterised by increased arterial stiffness and microcirculation abnormalities, not well differentiated by pressure measurement alone. Investigating patients with PAD and T2DM during exercise reveals that NIRS, TcpO2, CEUS, and scintigraphy have distinct advantages over ankle and toe-pressure.

CONCLUSIONS

Using methods like NIRS, TcpO2, CEUS and scintigraphy, peripheral blood flow during exercise can be measured at a detailed level and potentially improve future severity grading in patients with combined T2DM and PAD.

Reduced skeletal-muscle perfusion and impaired ATP release during hypoxia and exercise in individuals with type 2 diabetes

AIMS/HYPOTHESIS

Plasma ATP is a potent vasodilator and is thought to play a role in the local regulation of blood flow. Type 2 diabetes is associated with reduced tissue perfusion. We aimed to examine whether individuals with type 2 diabetes have reduced plasma ATP concentrations compared with healthy control participants (case-control design).

METHODS

We measured femoral arterial and venous plasma ATP levels with the intravascular microdialysis technique during normoxia, hypoxia and one-legged knee-extensor exercise (10 W and 30 W) in nine participants with type 2 diabetes and eight control participants. In addition, we infused acetylcholine (ACh), sodium nitroprusside (SNP) and ATP into the femoral artery to assess vascular function and ATP signalling.

RESULTS

Individuals with type 2 diabetes had a lower leg blood flow (LBF; 2.9 ± 0.1 l/min) compared with the control participants (3.2 ± 0.1 l/min) during exercise (p < 0.05), in parallel with lower venous plasma ATP concentration (205 ± 35 vs 431 ± 72 nmol/l; p < 0.05). During systemic hypoxia, LBF increased from 0.35 ± 0.04 to 0.54 ± 0.06 l/min in control individuals, whereas it did not increase (0.25 ± 0.04 vs 0.31 ± 0.03 l/min) in the those with type 2 diabetes and was lower than in the control individuals (p < 0.05). Hypoxia increased venous plasma ATP levels in both groups (p < 0.05), but the increase was higher in control individuals (90 ± 26 nmol/l) compared to those with type 2 diabetes (18 ± 5 nmol/l). LBF and vascular conductance were lower during ATP (0.15 and 0.4 μmol min^-1 [kg leg mass]^-1) and ACh (100 μg min^-1 [kg leg mass]^-1) infusion in individuals with type 2 diabetes compared with the control participants (p < 0.05), whereas there was no difference during SNP infusion.

CONCLUSIONS/INTERPRETATION

These findings demonstrate that individuals with type 2 diabetes have lower plasma ATP concentrations during exercise and hypoxia compared with control individuals, and this occurs in parallel with lower blood flow. Moreover, individuals with type 2 diabetes have a reduced vasodilatory response to infused ATP. These impairments in the ATP system are both likely to contribute to the reduced tissue perfusion associated with type 2 diabetes.

TRIAL REGISTRATION

ClinicalTrials.gov NCT02001766.

Hemodynamic abnormalities during muscle metaboreflex activation in patients with type 2 diabetes mellitus

Metaboreflex is a reflex triggered during exercise or postexercise muscle ischemia (PEMI) by metaboreceptor stimulation. Typical features of metaboreflex are increased cardiac output (CO) and blood pressure. Patients suffering from metabolic syndrome display hemodynamic abnormalities, with an exaggerated systemic vascular resistance (SVR) and reduced CO response during PEMI-induced metaboreflex. Whether patients with type 2 diabetes mellitus (DM2) have similar hemodynamic abnormalities is unknown. Here we contrast the hemodynamic response to PEMI in 14 patients suffering from DM2 (age 62.7 ± 8.3 yr) and in 15 age-matched controls (CTLs). All participants underwent a control exercise recovery reference test and a PEMI test to obtain the metaboreflex response. Central hemodynamics were evaluated by unbiased operator-independent impedance cardiography. Although the blood pressure response to PEMI was not significantly different between the groups, we found that the SVR and CO responses were reversed in patients with DM2 as compared with the CTLs (SVR: 392.5 ± 549.6 and -14.8 ± 258.9 dyn·s^-1·cm^-5; CO: -0.25 ± 0.63 and 0.46 ± 0.50 l/m, respectively, in DM2 and in CTL groups, respectively; P < 0.05 for both). Of note, stroke volume (SV) increased during PEMI in the CTL group only. Failure to increase SV and CO was the consequence of reduced venous return, impaired cardiac performance, and augmented afterload in patients with DM2. We conclude that patients with DM2 have an exaggerated vasoconstriction in response to metaboreflex activation not accompanied by a concomitant increase in heart performance. Therefore, in these patients, blood pressure response to the metaboreflex relies more on SVR increases rather than on increases in SV and CO. NEW & NOTEWORTHY The main new finding of the present investigation is that subjects with type 2 diabetes mellitus have an exaggerated vasoconstriction in response to metaboreflex activation. In these patients, blood pressure response to the metaboreflex relies more on systemic vascular resistance than on cardiac output increments.

Exercise intolerance in Type 2 diabetes: is there a cardiovascular contribution?

Physical activity is critically important for Type 2 diabetes management, yet adherence levels are poor. This might be partly due to disproportionate exercise intolerance. Submaximal exercise tolerance is highly sensitive to muscle oxygenation; impairments in exercising muscle oxygen delivery may contribute to exercise intolerance in Type 2 diabetes since there is considerable evidence for the existence of both cardiac and peripheral vascular dysfunction. While uncompromised cardiac output during submaximal exercise is consistently observed in Type 2 diabetes, it remains to be determined whether an elevated cardiac sympathetic afferent reflex could sympathetically restrain exercising muscle blood flow. Furthermore, while deficits in endothelial function are common in Type 2 diabetes and are often cited as impairing exercising muscle oxygen delivery, no direct evidence in exercise exists, and there are several other vasoregulatory mechanisms whose dysfunction could contribute. Finally, while there are findings of impaired oxygen delivery, conflicting evidence also exists. A definitive conclusion that Type 2 diabetes compromises exercising muscle oxygen delivery remains premature. We review these potentially dysfunctional mechanisms in terms of how they could impair oxygen delivery in exercise, evaluate the current literature on whether an oxygen delivery deficit is actually manifest, and correspondingly identify key directions for future research.

Laser application in neurosurgery

BACKGROUND

Technological innovations based on light amplification created by stimulated emission of radiation (LASER) have been used extensively in the field of neurosurgery.

METHODS

We reviewed the medical literature to identify current laser-based technological applications for surgical, diagnostic, and therapeutic uses in neurosurgery.

RESULTS

Surgical applications of laser technology reported in the literature include percutaneous laser ablation of brain tissue, the use of surgical lasers in open and endoscopic cranial surgeries, laser-assisted microanastomosis, and photodynamic therapy for brain tumors. Laser systems are also used for intervertebral disk degeneration treatment, therapeutic applications of laser energy for transcranial laser therapy and nerve regeneration, and novel diagnostic laser-based technologies (e.g., laser scanning endomicroscopy and Raman spectroscopy) that are used for interrogation of pathological tissue.

CONCLUSION

Despite controversy over the use of lasers for treatment, the surgical application of lasers for minimally invasive procedures shows promising results and merits further investigation. Laser-based microscopy imaging devices have been developed and miniaturized to be used intraoperatively for rapid pathological diagnosis. The multitude of ways that lasers are used in neurosurgery and in related neuroclinical situations is a testament to the technological advancements and practicality of laser science.

Consequences of Type 1 and 2 Diabetes Mellitus on the Cardiovascular Regulation During Exercise: A Brief Review

INTRODUCTION

One challenging problem in patients suffering from Diabetes Mellitus (DM) is the elevate incidence of cardiovascular events. Exercise has been proved useful in reducing cardiovascular risks in these patients. However, both type 1 and 2 DM significantly affect the cardiovascular response during exercise. Therefore, on one side exercise is considered to be a valid therapeutic tool for DM, whereas on the other side during exercise these patients may experience troubles in the cardiovascular regulation.

BACKGROUND

Several impairments at central and at peripheral level have been reported during exercise in both types of DM. For example, sympathetic dysfunctions have been demonstrated in type 1 and 2 DM. Furthermore, impairments in hemodynamics have been often reported. The purpose of the present paper is to briefly review the latest data on the role played by type 1 and 2 DM in the cardiovascular regulation during dynamic exercise.

CONCLUSION

Hemodynamic dysfunctions may develop in both type 1 and 2 DM during exercise. However, these cardiovascular dys-regulations are different between the two kinds of diabetes.

Dissociation of local and global skeletal muscle oxygen transport metrics in type 2 diabetes

AIMS

Exercise capacity is impaired in type 2 diabetes, and this impairment predicts excess morbidity and mortality. This defect appears to involve excess skeletal muscle deoxygenation, but the underlying mechanisms remain unclear. We hypothesized that reduced blood flow, reduced local recruitment of blood volume/hematocrit, or both contribute to excess skeletal muscle deoxygenation in type 2 diabetes.

METHODS

In patients with (n=23) and without (n=18) type 2 diabetes, we recorded maximal reactive hyperemic leg blood flow, peak oxygen utilization during cycling ergometer exercise (VO_2peak), and near-infrared spectroscopy-derived measures of exercise-induced changes in skeletal muscle oxygenation and blood volume/hematocrit.

RESULTS

We observed a significant increase (p<0.05) in skeletal muscle deoxygenation in type 2 diabetes despite similar blood flow and recruitment of local blood volume/hematocrit. Within the control group skeletal muscle deoxygenation, local recruitment of microvascular blood volume/hematocrit, blood flow, and VO_2peak are all mutually correlated. None of these correlations were preserved in type 2 diabetes.

CONCLUSIONS

These results suggest that in type 2 diabetes 1) skeletal muscle oxygenation is impaired, 2) this impairment may occur independently of bulk blood flow or local recruitment of blood volume/hematocrit, and 3) local and global metrics of oxygen transport are dissociated.

Intermittent hypoxia as a means to improve aerobic capacity in type 2 diabetes

Physical inactivity and a low maximal aerobic capacity (VO_2max) strongly predict morbidity and mortality in patients with type 2 diabetes (T2D). Patients with T2D have a reduced VO_2max when compared with healthy individuals of similar age, weight, and physical activity levels, and this lower aerobic capacity is usually attributed to a reduced oxygen delivery to the working muscles. The oxygen carrying capacity of the blood, as well as increases in cardiac output and blood flow, contribute to the delivery of oxygen to the active muscles during exercise. Hemoglobin mass (Hb mass), a key determinant of oxygen carrying capacity, is suggested to be reduced in patients with T2D following the observation of a lower blood volume (BV) in combination with normal hematocrit levels in this population. Therefore, a lower Hb mass, in addition to a reported lower BV and impaired cardiovascular response to exercise, likely contributes to the reduced oxygen delivery and VO_2max in patients with T2D. While exercise training increases Hb mass, BV, and consequently VO_2max, the majority of patients with T2D are not physically active, highlighting the need for alternative methods to improve VO_2max in this population. Exposure to hypoxia triggers the release of erythropoietin, the hormone regulating red blood cell production, which increases Hb mass and consequently BV. Exposure to mild intermittent hypoxia (IH), characterized by few and short episodes of hypoxia at a fraction of inspired oxygen ranging between 10 and 14% interspersed with cycles of normoxia, increased red blood cell volume, Hb mass, and plasma volume in patients with coronary artery disease or chronic obstructive pulmonary disease, which resulted in an improved VO_2max in both populations. We hypothesize that 12 exposures to mild IH over a period of 4weeks will increase Hb mass, BV, cardiac function, and VO_2max in patients with T2D. Therefore, exposures to mild IH may increase oxygen delivery and VO_2max without the need to perform exercise in patients with T2D.

Relationships among exercise capacity, dynamic balance and gait characteristics of Nigerian patients with type-2 diabetes: an indication for fall prevention

This study investigated the relationships among exercise capacity (EC), dynamic balance (DB), and gait characteristics (GCs) of patients with type-2 diabetes (T2D) and healthy controls (HCs). This observational controlled study involved 125 patients with T2D receiving treatment at a Nigerian university teaching hospital and 125 apparently healthy patients' relatives and hospital staff recruited as controls. EC maximum oxygen consumption (VO2max) was estimated following a 6-min walk test. DB and GC were assessed using the Time Up to Go Test and an accelerometer (BTS G-Walk) assessing gait speed, step length, stride length, and cadence respectively during a self-selected walk. Data were analyzed using descriptive and inferential statistics. Alpha level was set at P<0.05. The mean ages of patients with T2D and HCs were 57.6±6.6 and 60.0±7.0 years, respectively. All physical characteristics were comparable (P>0.05). There were significant differences in the VO2max and DB between patients with T2D and HCs; 7.6±0.6 mL/kg/min vs. 9.6±0.6 mL/kg/min (t=-16.6, P=0.001) and 14.2±2.1 sec vs. 10.4±1.5 sec (t=-6.37, P=0.001), respectively. Furthermore, significant differences were found in GC between patients with T2D and HCs; gait speed: 0.7±0.1 m/sec vs. 1.2±0.1 m/sec (t=-16.60, P=0.001), step length: 0.6±0.2 m vs. 0.9±0.3 m (t=-7.56, P=0.001) and stride length: 0.9±0.1 m vs. 1.1±0.5 m (t=-6.09, P=0.001). There were significant correlations between EC and gait speed in both groups (T2D: r=-0.26, P=0.032 and HCs: r=0.51, P=0.003). In conclusion, patients with T2D demonstrated lower EC, unstable DB, and altered GCs compared with HCs. Exercise interventions to improve EC and gait balance are recommended.

Obesity, type 2 diabetes, and impaired insulin-stimulated blood flow: role of skeletal muscle NO synthase and endothelin-1

Increased endothelin-1 (ET-1) and reduced endothelial nitric oxide phosphorylation (peNOS) are hypothesized to reduce insulin-stimulated blood flow in type 2 diabetes (T2D), but studies examining these links in humans are limited. We sought to assess basal and insulin-stimulated endothelial signaling proteins (ET-1 and peNOS) in skeletal muscle from T2D patients. Ten obese T2D [glucose disposal rate (GDR): 6.6 ± 1.6 mg·kg lean body mass (LBM)^-1·min^-1] and 11 lean insulin-sensitive subjects (Lean GDR: 12.9 ± 1.2 mg·kg LBM^-1·min^-1) underwent a hyperinsulinemic-euglycemic clamp with vastus lateralis biopsies taken before and 60 min into the clamp. Basal biopsies were also taken in 11 medication-naïve, obese, non-T2D subjects. ET-1, peNOS (Ser1177), and eNOS protein and mRNA were measured from skeletal muscle samples containing native microvessels. Femoral artery blood flow was assessed by duplex Doppler ultrasound. Insulin-stimulated blood flow was reduced in obese T2D (Lean: +50.7 ± 6.5% baseline, T2D: +20.8 ± 5.2% baseline, P < 0.05). peNOS/eNOS content was higher in Lean under basal conditions and, although not increased by insulin, remained higher in Lean during the insulin clamp than in obese T2D (P < 0.05). ET-1 mRNA and peptide were 2.25 ± 0.50- and 1.52 ± 0.11-fold higher in obese T2D compared with Lean at baseline, and ET-1 peptide remained 2.02 ± 1.9-fold elevated in obese T2D after insulin infusion (P < 0.05) but did not increase with insulin in either group (P > 0.05). Obese non-T2D subjects tended to also display elevated basal ET-1 (P = 0.06). In summary, higher basal skeletal muscle expression of ET-1 and reduced peNOS/eNOS may contribute to a reduced insulin-stimulated leg blood flow response in obese T2D patients.

NEW & NOTEWORTHY

Although impairments in endothelial signaling are hypothesized to reduce insulin-stimulated blood flow in type 2 diabetes (T2D), human studies examining these links are limited. We provide the first measures of nitric oxide synthase and endothelin-1 expression from skeletal muscle tissue containing native microvessels in individuals with and without T2D before and during insulin stimulation. Higher basal skeletal muscle expression of endothelin-1 and reduced endothelial nitric oxide phosphorylation (peNOS)/eNOS may contribute to reduced insulin-stimulated blood flow in obese T2D patients.

An acute bout of whole body passive hyperthermia increases plasma leptin, but does not alter glucose or insulin responses in obese type 2 diabetics and healthy adults

Acute and chronic hyperthermic treatments in diabetic animal models repeatedly improve insulin sensitivity and glycemic control. Therefore, the purpose of this study was to test the hypothesis that an acute 1h bout of hyperthermic treatment improves glucose, insulin, and leptin responses to an oral glucose challenge (OGTT) in obese type 2 diabetics and healthy humans. Nine obese (45±7.1% fat mass) type 2 diabetics (T2DM: 50.1±12y, 7.5±1.8% HbA1c) absent of insulin therapy and nine similar aged (41.1±13.7y) healthy non-obese controls (HC: 33.4±7.8% fat mass, P<0.01; 5.3±0.4% HbA1c, P<0.01) participated. Using a randomized design, subjects underwent either a whole body passive hyperthermia treatment via head-out hot water immersion (1h resting in 39.4±0.4°C water) that increased internal temperature above baseline by ∆1.6±0.4°C or a control resting condition. Twenty-four hours post treatments, a 75g OGTT was administered to evaluate changes in plasma glucose, insulin, C-peptide, and leptin concentrations. Hyperthermia itself did not alter area under the curve for plasma glucose, insulin, or C-peptide during the OGTT in either group. Fasting absolute and normalized (kg·fat mass) plasma leptin was significantly increased (P<0.01) only after the hyperthermic exposure by 17% in T2DM and 24% in HC groups (P<0.001) when compared to the control condition. These data indicate that an acute hyperthermic treatment does not improve glucose tolerance 24h post treatment in moderate metabolic controlled obese T2DM or HC individuals.

Knowledge, attitude and practice of exercise for plasma blood glucose control among patients with type-2 diabetes

AIMS

Exercise plays significant role in the health outcomes of patients with diabetes, however, little is known about patients' knowledge of exercise for plasma blood glucose control among patients with type-2 diabetes (T2D). This study investigated knowledge, attitude and practice (KAP) of exercise for plasma blood glucose control among patients with T2D.

MATERIALS AND METHODS

This cross-sectional study recruited 299 patients with T2D (male=105; female=194) from selected government hospitals in Osun State, Nigeria using purposive sampling technique. Validated questionnaires were used to assess of exercise for plasma blood glucose control and socioeconomic status (SES) of the patients. Data were analysed using descriptive and inferential statistics. Alpha level was set at <0.05.

RESULTS

The mean age of respondents was 51.9±9.8 years. A majority, 245(81.9%) were married individuals and more than half, 195(65.3%) were in the low SES. One hundred and forty-eight (49.5%) had good knowledge of exercise whilst 269(90.0%) had negative attitude to exercise practice. Less than a third, 82(27.4%) engaged in exercise practice for plasma blood glucose control. There was significant association between knowledge and practice of exercise ((2)=12.535; p=0.002). Furthermore, significant associations were found between knowledge and gender ((2)=11.453; p=0.003), and socioeconomic status ((2)=29.127, p=0.001) but not associated with attitude towards exercise (p>0.05).

CONCLUSION

Patients with demonstrated good knowledge of exercise for plasma blood glucose control but reported negative attitude and poor practice of exercise.