Regional cerebral hemodynamic response to incremental exercise is blunted in poorly controlled patients with uncomplicated type 1 diabetes

Blunted cerebral hemodynamic responses to incremental exercise in patients with end-stage renal disease

PURPOSE

The aims of this study were to compare cerebral hemodynamics and maximal oxygen uptake (VO2peak) in patients with end-stage renal disease (ESRD) vs. age-matched healthy controls during maximal exercise.

METHODS

Twelve patients with ESRD and twelve healthy adults (CTR group) performed exhaustive incremental exercise test. Throughout the exercise test, near-infrared spectroscopy allowed the investigation of changes in oxyhemoglobin (∆O2Hb), deoxyhemoglobin (∆HHb), and total hemoglobin (∆THb) in the prefrontal cortex.

RESULTS

Compared to CTR, VO2peak was significantly lower in ESRD group (P < 0.05). Increase in ∆THb (i.e., cerebral blood volume) was significantly blunted in ESRD (P < 0.05). ESRD patients also had impaired changes in cerebral ∆HHb and ∆O2Hb during high intensity of exercise (P < 0.05). Finally, no significant correlation was observed between VO2peak and changes in cerebral hemodynamics parameters in both groups (All P > 0.05).

CONCLUSION

Maximal exercise highlights subtle disorders of both hemodynamics and neuronal oxygenation in the prefrontal cortex in patients with ESRD. This may contribute to both impaired cognitive function and reduced exercise tolerance throughout the progression of the disease.

Muscle oxygen supply impairment during maximal exercise in patients undergoing dialysis therapy

This study aimed to investigate whether Chronic Kidney Disease (CKD) influences O2 supply including O2 delivery and release to the active muscles during maximal physical exercise. Twelve CKD patients undergoing dialysis therapy (HD group) and twelve healthy adults (CTR group) performed an incremental exercise test to determine maximal oxygen uptake (VO2peak). Throughout the exercise, near-infrared spectroscopy allowed the investigation of changes in oxyhemoglobin (∆O2Hb), deoxyhemoglobin (∆HHb), and total hemoglobin (∆THb) in the vastus lateralis muscle. VO2peak was significantly lower in HD group. In addition, HD patients had impaired changes in muscular oxygenation (∆HHb and ∆O2Hb) and blood volume (∆THb) during the exercise (p < 0.05). Moreover, a positive correlation was observed between VO2peak and muscle blood volume (∆THb) in both groups (p < 0.05). This study provides the first evidence that HD patients displayed lower VO2peak and blunted muscular deoxyhemoglobin increase during exercise. This result supports the hypothesis of an increase in oxygen affinity and/or mitochondrial dysfunction in this population.

Acute Effects of a Maximal Cardiopulmonary Exercise Test on Cardiac Hemodynamic and Cerebrovascular Response and Their Relationship with Cognitive Performance in Individuals with Type 2 Diabetes

Cardiovascular and cerebrovascular diseases are prevalent in individuals with type 2 diabetes (T2D). Among people with T2D aged over 70 years, up to 45% might have cognitive dysfunction. Cardiorespiratory fitness (V˙O₂max) correlates with cognitive performances in healthy younger and older adults, and individuals with cardiovascular diseases (CVD). The relationship between cognitive performances, V˙O₂max, cardiac output and cerebral oxygenation/perfusion responses during exercise has not been studied in patients with T2D. Studying cardiac hemodynamics and cerebrovascular responses during a maximal cardiopulmonary exercise test (CPET) and during the recovery phase, as well as studying their relationship with cognitive performances could be useful to detect patients at greater risk of future cognitive impairment. Purposes: (1) to compare cerebral oxygenation/perfusion during a CPET and during its post-exercise period (recovery); (2) to compare cognitive performances in patients with T2D to those in healthy controls; and (3) to examine if V˙O₂max, maximal cardiac output and cerebral oxygenation/perfusion are associated with cognitive function in individuals with T2D and healthy controls. Nineteen patients with T2D (61.9 ± 7 years old) and 22 healthy controls (HC) (61.8 ± 10 years old) were evaluated on the following: a CPET test with impedance cardiography and cerebral oxygenation/perfusion using a near-infrared spectroscopy. Prior to the CPET, the cognitive performance assessment was performed, targeting: short-term and working memory, processing speed, executive functions, and long-term verbal memory. Patients with T2D had lower V˙O₂max values compared to HC (34.5 ± 5.6 vs. 46.4 ± 7.6 mL/kg fat free mass/min; p < 0.001). Compared to HC, patients with T2D showed lower maximal cardiac index (6.27 ± 2.09 vs. 8.70 ± 1.09 L/min/m², p < 0.05) and higher values of systemic vascular resistance index (826.21 ± 308.21 vs. 583.35 ± 90.36 Dyn·s/cm⁵·m²) and systolic blood pressure at maximal exercise (204.94 ± 26.21 vs. 183.61 ± 19.09 mmHg, p = 0.005). Cerebral HHb during the 1st and 2nd min of recovery was significantly higher in HC compared to T2D (p < 0.05). Executive functions performance (Z score) was significantly lower in patients with T2D compared to HC (-0.18 ± 0.7 vs. -0.40 ± 0.60, p = 0.016). Processing speed, working and verbal memory performances were similar in both groups. Brain tHb during exercise and recovery (-0.50, -0.68, p < 0.05), and O₂Hb during recovery (-0.68, p < 0.05) only negatively correlated with executive functions performance in patients with T2D (lower tHb values associated with longer response times, indicating a lower performance). In addition to reduced V˙O₂max, cardiac index and elevated vascular resistance, patients with T2D showed reduced cerebral hemoglobin (O₂Hb and HHb) during early recovery (0-2 min) after the CPET, and lower performances in executive functions compared to healthy controls. Cerebrovascular responses to the CPET and during the recovery phase could be a biological marker of cognitive impairment in T2D.

Association of HbA1c with VO2max in Individuals with Type 1 Diabetes: A Systematic Review and Meta-Analysis

The aim of this systematic review and meta-analysis was to evaluate the association between glycemic control (HbA1c) and functional capacity (VO2max) in individuals with type 1 diabetes (T1DM). A systematic literature search was conducted in EMBASE, PubMed, Cochrane Central Register of Controlled Trials, and ISI Web of Knowledge for publications from January 1950 until July 2020. Randomized and observational controlled trials with a minimum number of three participants were included if cardio-pulmonary exercise tests to determine VO2max and HbA1c measurement has been performed. Pooled mean values were estimated for VO2max and HbA1c and weighted Pearson correlation and meta-regression were performed to assess the association between these parameters. We included 187 studies with a total of 3278 individuals with T1DM. The pooled mean HbA1c value was 8.1% (95%CI; 7.9−8.3%), and relative VO2max was 38.5 mL/min/kg (37.3−39.6). The pooled mean VO2max was significantly lower (36.9 vs. 40.7, p = 0.001) in studies reporting a mean HbA1c > 7.5% compared to studies with a mean HbA1c ≤ 7.5%. Weighted Pearson correlation coefficient was r = −0.19 (p < 0.001) between VO2max and HbA1c. Meta-regression adjusted for age and sex showed a significant decrease of −0.94 mL/min/kg in VO2max per HbA1c increase of 1% (p = 0.024). In conclusion, we were able to determine a statistically significant correlation between HbA1c and VO2max in individuals with T1DM. However, as the correlation was only weak, the association of HbA1c and VO2max might not be of clinical relevance in individuals with T1DM.

Early Endothelial Dysfunction in Type 1 Diabetes Is Accompanied by an Impairment of Vascular Smooth Muscle Function: A Meta-Analysis

Background: A large yet heterogeneous body of literature exists suggesting that endothelial dysfunction appears early in type 1 diabetes, due to hyperglycemia-induced oxidative stress. The latter may also affect vascular smooth muscles (VSM) function, a layer albeit less frequently considered in that pathology. This meta-analysis aims at evaluating the extent, and the contributing risk factors, of early endothelial dysfunction, and of the possible concomitant VSM dysfunction, in type 1 diabetes. Methods: PubMed, Web of Sciences, Cochrane Library databases were screened from their respective inceptions until October 2019. We included studies comparing vasodilatory capacity depending or not on endothelium (i.e., endothelial function or VSM function, respectively) in patients with uncomplicated type 1 diabetes and healthy controls. Results: Fifty-eight articles studying endothelium-dependent function, among which 21 studies also assessed VSM, were included. Global analyses revealed an impairment of standardized mean difference (SMD) (Cohen's d) of endothelial function: -0.61 (95% CI: -0.79, -0.44) but also of VSM SMD: -0.32 (95% CI: -0.57, -0.07). The type of stimuli used (i.e., exercise, occlusion-reperfusion, pharmacological substances, heat) did not influence the impairment of the vasodilatory capacity. Endothelial dysfunction appeared more pronounced within macrovascular than microvascular beds. The latter was particularly altered in cases of poor glycemic control [HbA_1c > 67 mmol/mol (8.3%)]. Conclusions: This meta-analysis not only corroborates the presence of an early impairment of endothelial function, even in response to physiological stimuli like exercise, but also highlights a VSM dysfunction in children and adults with type 1 diabetes. Endothelial dysfunction seems to be more pronounced in large than small vessels, fostering the debate on their relative temporal appearance.

Natural Alkaloids Intervening the Insulin Pathway: New Hopes for Anti-Diabetic Agents?

BACKGROUND

Accumulating experimental data supports the capacity of natural compounds to intervene in complicated molecular pathways underlying the pathogenesis of certain human morbidities. Among them, diabetes is now a world's epidemic associated with increased risk of death; thus, the detection of novel anti-diabetic agents and/or adjuvants is of vital importance. Alkaloids represent a diverse group of natural products with a range of therapeutic properties; during the last 20 years, published research on their anti-diabetic capacity has been tremendously increased.

PURPOSE

To discuss current concepts on the anti-diabetic impact of certain alkaloids, with special reference to their molecular targets throughout the insulin-signaling pathway.

METHODOLOGY

Upon in-depth search in the SCOPUS and PUBMED databases, the literature on alkaloids with insulin secretion/sensitization properties was critically reviewed.

RESULTS

In-vitro and in-vivo evidence supports the effect of berberine, trigonelline, piperine, oxymatrine, vindoneline, evodiamine and neferine on insulin-signaling and related cascades in beta-cells, myocytes, adipocytes, hepatocytes and other cells. Associated receptors, kinases, hormones and cytokines, are affected in terms of gene transcription, protein expression, activity and/or phosphorylation. Pathophysiological processes associated with insulin resistance, beta-cell failure, oxidative stress and inflammation, as well as clinical phenotype are also influenced.

DISCUSSION

Growing evidence suggests the ability of specific alkaloids to intervene in the insulin-signal transduction pathway, reverse molecular defects resulting in insulin resistance and glucose intolerance and improve disease complications, in-vitro and in-vivo. Future indepth molecular studies are expected to elucidate their exact mechanism of action, while large clinical trials are urgently needed to assess their potential as anti-diabetic agents.

Basal ganglia cerebral blood flow associates with psychomotor speed in adults with type 1 diabetes

Type 1 diabetes is associated with slower psychomotor speed, but the neural basis of this relationship is not yet understood. The basal ganglia are a set of structures that are vulnerable to small vessel disease, particularly in individuals with type 1 diabetes. Thus, we examined the relationship between psychomotor speed and resting state resting cerebral blood flow in a sample of adults with diabetes onset during childhood (≤ 17 years of age). The sample included 77 patients (39 M, 38 F) with a mean age of 47.43 ± 5.72 years, age of onset at 8.50 ± 4.26 years, and duration of disease of 38.92 ± 4.18 years. Resting cerebral blood flow was quantified using arterial spin labeling. After covarying for sex, years of education and normalized gray matter volume, slower psychomotor speed was associated with lower cerebral blood flow in bilateral caudate nucleus-thalamus and a region in the superior frontal gyrus. These results suggest that the basal ganglia and frontal cortex may underlie slower psychomotor speed in individuals with type 1 diabetes.

The presence of cerebral white matter lesions and lower skin microvascular perfusion predicts lower cognitive performance in type 1 diabetes patients with retinopathy but not in healthy controls-A longitudinal study

OBJECTIVE

Cognitive impairments in type 1 diabetes may result from hyperglycemia-associated cerebral microangiopathy. We aimed to identify cerebral microangiopathy and skin microvascular dysfunction-as a surrogate marker for generalized microvascular function-as predictors of cognitive performance over time.

METHODS

In this prospective cohort study, 25 type 1 diabetes patients with proliferative retinopathy and 25 matched healthy controls underwent neurocognitive testing at baseline and after follow-up (3.8 ± 0.8 years). At baseline, 1.5-T cerebral magnetic resonance imaging was used to detect WML and cerebral microbleeds. Skin capillary perfusion was assessed by means of capillary microscopy.

RESULTS

In type 1 diabetes patients, but not in healthy controls, the presence of WML (ß = -0.419; P = 0.037) as well as lower skin capillary perfusion (baseline: ß = 0.753; P < 0.001; peak hyperemia: ß = 0.743; P = 0.001; venous occlusion: ß = 0.675; P = 0.003; capillary recruitment: ß = 0.549; P = 0.022) at baseline was associated with lower cognitive performance over time, independent of age, sex, HbA1c, and severe hypoglycemia. The relationship between WML and lower cognitive performance was significantly reduced after adjusting for capillary perfusion.

CONCLUSIONS

These data fit the hypothesis that cerebral microangiopathy is a manifestation of generalized microvascular dysfunction, leading to lower cognitive performance.

Pregnancy and post-partum muscle and cerebral oxygenation during intermittent exercise in gestational diabetes: A pilot study

OBJECTIVE

This pilot, prospective, observational, cohort study aimed to examine, for the first time, the in vivo alterations in the oxygenation of the forearm skeletal muscles and the prefrontal lobes during intermittent exercise in women diagnosed with gestational diabetes mellitus (GDM), during and after pregnancy.

STUDY DESIGN

Nine pregnant women, diagnosed with GDM, performed a 3-min intermittent handgrip exercise protocol (at 35% of Maximal Voluntary Contraction) during pregnancy (mean 27th gestational week) and following labor (mean 71 weeks). During the protocol, muscle and cerebral oxygenation were assessed with near-infrared spectroscopy. Resting vascular parameters [carotid intima-media thickness (cIMT) and hemodynamic parameters (using rheocardiography)], and hematological/biochemical parameters during pregnancy and after delivery have been compared.

RESULTS

Although changes were observed in certain hematological parameters (p< 0.05), cIMT and hemodynamic parameters were not altered post-partum. In addition, both muscle and cerebral oxygenation parameters during handgrip were not significantly altered post-partum.

CONCLUSIONS

Despite significant changes in specific hematological parameters in women with GDM, impairments in muscle and cerebral oxygenation during exercise remained at one year after labor. These results indicate that alterations in vascular parameters and muscle/cerebral oxygenation associated with GDM do not entirely reverse post-partum. Future studies are needed to examine which interventions will lead to improvements in microvascular parameters and prevent type 2 diabetes.

Blunted cerebral oxygenation during exercise in women with gestational diabetes mellitus: associations with macrovascular function and cardiovascular risk factors

AIM/HYPOTHESIS

This cross-sectional, observational, controlled study examined cerebral oxygenation during exercise, an index of cerebrovascular function and cortical activation, in pregnancies complicated by gestational diabetes mellitus (GDM) and unaffected pregnancies. The association of cerebral oxygenation with macrovascular and cardiovascular function indices was also evaluated.

MATERIAL AND METHODS

Vascular function and structure [aortic pulse-wave-velocity (PWV), augmentation index (AI), carotid intima-media thickness], as well as 24-hour ambulatory blood pressure (BP) were assessed in women with GDM (n = 21) and uncomplicated pregnancies (n = 16), at 26-32 gestational weeks. Changes in cerebral oxygenation [oxy- (O₂Hb), deoxy- (HHb) and total- (tHb) hemoglobin] were continuously recorded by near-infrared spectroscopy (NIRS) during intermittent handgrip exercise. Beat-by-beat BP and systemic vascular resistance (SVR) were assessed (Finapres).

RESULTS

Women with GDM had higher AI than controls. During exercise, women with GDM maintained a smaller force (p < 0.05), despite similar ratings of perceived exertion. Despite similar increases in BP during exercise, the GDM group exhibited a lower average and total (AUC) increase in cerebral-O₂Hb than controls (p < 0.05). In addition, GDM exhibited a slower rate of cerebral-O₂Hb decay during recovery (p < 0.05). SVR was lower in GDM compared to controls throughout the protocol (p < 0.01). Cerebral oxygenation indices were correlated with PWV and AI (p < 0.05).

CONCLUSIONS

This study provided novel evidence for blunted cerebral oxygenation during exercise in women with GDM compared to uncomplicated pregnancies, suggesting a link between reduced cerebrovascular function with exercise intolerance in GDM. Cerebral oxygenation during physical stress was correlated with macrovascular function and cardiovascular risk factors. More studies are needed to examine whether this impaired cerebral oxygenation reflects early cerebrovascular disease.

Protein supplementation enhances cerebral oxygenation during exercise in elite basketball players

OBJECTIVE

The aim of the present study was to examine cerebral oxygenation during high-intensity exercise in elite basketball players who consumed supplements with different whey protein contents after a short postexercise recovery to determine whether changing whey protein content in carbohydrate-based supplementation influences cerebral hemodynamic response when the supplement was consumed during a 2-h recovery after a 1-h exercise challenge.

METHODS

This was a randomized, counterbalanced crossover study. Fifteen Division 1 collegiate basketball players (18-20 y) consumed 6.25 kcal/kg of either high-protein (36% protein in total calorie) or an isocaloric low-protein (12% protein in total calorie) control supplement in a carbohydrate-based drink immediately after a 1-h cycling (70% of maximal oxygen consumption [VO_2max]). After a 2-h rest, the athletes were challenged on a cycloergometer at 80% VO_2max. Blood perfusion (total hemoglobin) and oxygen saturation of frontal brain were continuously measured by near-infrared spectroscopy during the cycling.

RESULTS

Before the cycloergometer test, high-protein supplementation increased peak insulin response and lowered glucose increases during the recovery compared with the low-protein trial. High-protein supplementation enhanced increases in cerebral oxygen saturation (P < 0.01) and attenuated increases in cerebral blood perfusion (total hemoglobin; P < 0.01) during the cycloergometer exercise; and resulted in a 16% longer cycling time (from 474 ± 49 s to 553 ± 78 s, P < 0.05), compared with the low-protein trial.

CONCLUSION

Enhanced fatigue recovery after consumption of a high-protein supplement is associated with enhanced cerebral oxygenation against exercise challenge, which spares brain blood demand for periphery.

Berberine Ameliorates Diabetes-Associated Cognitive Decline through Modulation of Aberrant Inflammation Response and Insulin Signaling Pathway in DM Rats

Background: Memory-impairment was one of the common characteristics in patients with diabetes mellitus. The release of chronic inflammation mediators and insulin resistance in diabetic brain gave rise to the generation of toxic factor Aβ42 which was the marker of Alzheimer’s disease. In addition, the impairment of memory in diabetes mellitus was also correlated predominantly with uptake/metabolism of glucose in medial prefrontal cortex (mPFC). Previously, anti-inflammation and hypoglycemic effects of berberine (BBr) have been described in peripheral tissues. For better understanding the effects of BBr on cognitive action in diabetics, we investigated the functions of BBr involved in anti-inflammation and ameliorating insulin resistance in prefrontal cortex of diabetic rats.

Methods: Intragastric administration of BBr (187.5 mg/Kg/d) was used in diabetic rats. Fear-condition assay was applied for cognitive assessment, and relative protein expressions were detected by western-blot. The glucose uptake in prefrontal cortex of diabetic rats was tested by Positron-Emission Tomography imaging. The levels of inflammation mediators were determined by commercial ELISA kits.

Results: The inflammation mediator release and insulin resistance in the mPFC of diabetic rats was inhibited by BBr. The activation of PI3K/Akt/mTOR and MAPK signaling pathway, as well as two novel isoforms PKCη and PKC𝜀 and the translocation of NF-κB in neuron were also down-regulated by BBr; furthermore, the neuron specific glucose transporter GLUT3 was remarkably augmented by 2–3 times when compared with diabetic group; meanwhile, BBr also promoted glucose uptake in the brain. Additionally BBr decreased the expressions of amyloid precursor protein and BACE-1, and the production of oligomeric Aβ42. Finally, it accelerates the reinforcement of the information and ameliorates cognitive impairment.

Conclusion: BBr inhibited the activation of inflammation pathway and insulin resistance in the mPFC of diabetic rats. Finally, it improved the lesion of cognition in diabetic rats.