Exercise-mediated vasodilation in human obesity and metabolic syndrome: effect of acute ascorbic acid infusion

A Systematized Review of the Relationship Between Obesity and Vitamin C Requirements

Obesity rates have increased globally in recent decades. Body weight is used as a modifiable factor in determining vitamin requirements. Accordingly, vitamin C requirements are volumetrically scaled from data for healthy weight males to other age- and sex-based categories. Likewise, it is possible that increases in body weight due to obesity may affect vitamin C needs. A systematized literature review was performed to summarize evidence on whether obesity affects vitamin C intake or status. The literature was also scanned for potential mechanisms for the relationship. Many observational studies showed that vitamin C status is lower in overweight and obese children and adults; this may be explained by lower vitamin C intakes. Nevertheless, a reanalysis of carefully conducted intervention studies has demonstrated a lower vitamin C status in participants who were overweight or obese when given the same dose of vitamin C as subjects of normal weight. Several mechanisms have been proposed to potentially explain why vitamin C status is lower in people with obesity: changes in vitamin C partitioning between lean and adipose tissue, volumetric dilution, metabolic alterations due to obesity, and gut microbial dysbiosis. Depletion-repletion or pharmacokinetic studies that include individuals of diverse body weights and ages would be helpful to further investigate whether obesity increases requirements for vitamin C. The current evidence base supports a lower vitamin C status in people who are overweight or obese; however, the association may be attenuated by lower vitamin C intakes.

Rapid vasodilation within contracted skeletal muscle in humans: new insight from concurrent use of diffuse correlation spectroscopy and Doppler ultrasound

Previous studies showed that conduit artery blood flow rapidly increases after even a brief contraction of muscles within the dependent limb. Whether this rapid hyperemia occurs within contracted skeletal muscle in humans has yet to be confirmed, however. We therefore used diffuse correlation spectroscopy (DCS) to characterize the rapid hyperemia and vasodilatory responses within the muscle microvasculature induced by single muscle contractions in humans. Twenty-five healthy male volunteers performed single 1-s isometric handgrips at 20%, 40%, 60%, and 80% of maximum voluntary contraction. DCS probes were placed on the flexor digitorum superficialis muscle, and a skeletal muscle blood flow index (SMBFI) was derived continuously. At the same time, brachial artery blood flow (BABF) responses were measured using Doppler ultrasound. Single muscle contractions evoked rapid, monophasic increases in both SMBFI and BABF that occurred within 3 s after release of contraction. The initial and peak responses increased with increases in contraction intensity and were greater for BABF than for SMBFI at all intensities. BABF reached its peak within 5 to 8 s after the end of contraction. The SMBFI continued to increase after the BABF passed its peak and was decreasing toward the resting level and peaked about 10 to 15 s after completion of the contraction. We conclude that single muscle contractions induce rapid, intensity-dependent hyperemia within the contracted skeletal muscle microvasculature. Moreover, the characteristics of the rapid hyperemia and vasodilatory responses of skeletal muscle microvessels differ from those simultaneously evaluated in the upstream conduit artery.NEW & NOTEWORTHY Through the concurrent use of diffuse correlation spectroscopy and Doppler ultrasound, we provide the first evidence in humans that a single brief muscle contraction evokes rapid, intensity-dependent hyperemia within the contracted skeletal muscle microvasculature and the upstream conduit artery. We also show that the magnitude and time course of the contraction-induced rapid hyperemia and vasodilatory responses within skeletal muscle microvessels significantly differ from those in the conduit artery.

A New Treatment for Local Adiposity with Ascorbic Acid and Ascorbyl-Palmitate Solution: Clinical and Histological Study

Background

Localized adiposity (AL) is the accumulation of subcutaneous adipose tissue, placed in definite anatomic areas, building up an alteration of the body silhouette. The aim of the present clinical and histological study is to assess the effectiveness of an injectable solution containing sodium salt of ascorbic acid 0.24% and surfactant agent at 0.020% ascorbyl-palmitate (SAP) for treating local adiposity.

Methods

Eighty healthy female adult patients were selected, suffering from local adiposity in the abdominal region. The patients underwent a cycle of 6 sessions, with biweekly treatments, without the addition of any active ingredient. Direct infiltration of pharmacologically active SAP solutions into the adipose tissue with a long needle, very similar to the needles used for spinal anesthesia, was performed. This procedure is quick and painless (does not require any anesthesia) with moderate infiltration speed.

Results

All the patients treated showed good results with good satisfaction of the circumferential reductions. Before treatment: Waist (cm) 78.8 ± 10.6 and hip 93.6 ± 9.0 with WHR 0.84 ± 0.07. After treatment: Waist (cm) 70.8 ± 9.6 and hip 92.6 ± 8.0 with WHR 0.76 ± 0.06. Indeed, signs of adipocyte apoptosis were observed in subcutaneous skin after injection of SAP.

Conclusion

The results showed in the present study suggest that the SAP utilized induces apoptosis of adipocytes and could be of use as a safe and effective method with which to eliminate subcutaneous abdominal fat.

Level of Evidence IV

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Antioxidant supplements and endurance exercise: Current evidence and mechanistic insights

Antioxidant supplements are commonly consumed by endurance athletes to minimize exercise-induced oxidative stress, with the intention of enhancing recovery and improving performance. There are numerous commercially available nutritional supplements that are targeted to athletes and health enthusiasts that allegedly possess antioxidant properties. However, most of these compounds are poorly investigated with respect to their in vivo redox activity and efficacy in humans. Therefore, this review will firstly provide a background to endurance exercise-related redox signalling and the subsequent adaptations in skeletal muscle and vascular function. The review will then discuss commonly available compounds with purported antioxidant effects for use by athletes. N-acetyl cysteine may be of benefit over the days prior to an endurance event; while chronic intake of combined 1000 mg vitamin C + vitamin E is not recommended during periods of heavy training associated with adaptations in skeletal muscle. Melatonin, vitamin E and α-lipoic acid appear effective at decreasing markers of exercise-induced oxidative stress. However, evidence on their effects on endurance performance are either lacking or not supportive. Catechins, anthocyanins, coenzyme Q10 and vitamin C may improve vascular function, however, evidence is either limited to specific sub-populations and/or does not translate to improved performance. Finally, additional research should clarify the potential benefits of curcumin in improving muscle recovery post intensive exercise; and the potential hampering effects of astaxanthin, selenium and vitamin A on skeletal muscle adaptations to endurance training. Overall, we highlight the lack of supportive evidence for most antioxidant compounds to recommend to athletes.

Metabolic Syndrome-An Emerging Constellation of Risk Factors: Electrochemical Detection Strategies

Metabolic syndrome is a condition that results from dysfunction of different metabolic pathways leading to increased risk of disorders such as hyperglycemia, atherosclerosis, cardiovascular diseases, cancer, neurodegenerative disorders etc. As this condition cannot be diagnosed based on a single marker, multiple markers need to be detected and quantified to assess the risk facing an individual of metabolic syndrome. In this context, chemical- and bio-sensors capable of detecting multiple analytes may provide an appropriate diagnostic strategy. Research in this field has resulted in the evolution of sensors from the first generation to a fourth generation of 'smart' sensors. A shift in the sensing paradigm involving the sensing element and transduction strategy has also resulted in remarkable advancements in biomedical diagnostics particularly in terms of higher sensitivity and selectivity towards analyte molecule and rapid response time. This review encapsulates the significant advancements reported so far in the field of sensors developed for biomarkers of metabolic syndrome.

Phosphodiesterase-5 inhibition preserves exercise-onset vasodilator kinetics when NOS activity is reduced

Nitric oxide (NO)-mediated vasodilation contributes to the rapid rise in muscle blood flow at exercise onset. This occurs via increased cyclic guanosine monophosphate (cGMP), which is catabolized by phosphodiesterase-5 (PDE-5). Whether PDE-5 limits exercise vasodilation onset kinetics is unknown. We hypothesized the time course of exercise vasodilation would be 1) accelerated during PDE-5 inhibition (sildenafil citrate, SDF) and 2) decelerated during NO synthase inhibition ( N^G-monomethyl-l-arginine, l-NMMA), and 3) the effect of SDF on vasodilation onset kinetics would be attenuated with concurrent l-NMMA. Data from 29 healthy adults were analyzed. Individuals completed 5 min of moderate-intensity forearm exercise under control conditions and during 1) oral SDF ( n = 8), 2) intra-arterial l-NMMA ( n = 15), or 3) combined SDF + l-NMMA ( n = 6). Forearm blood flow (FBF; Doppler ultrasound of the brachial artery) and mean brachial artery blood pressure (MAP) were measured continuously. Forearm vascular conductance (FVC, FBF ÷ MAP) was curve-fit with a monoexponential model, and vasodilation onset kinetics were assessed by mean response time (MRT, time to achieve 63% of steady state). SDF had no effect on MRT ( P = 0.90). NOS inhibition increased MRT ( P = 0.01). MRT during SDF+l-NMMA was not different from control exercise ( P = 0.76). PDE-5 inhibition alone has no effect on rapid-onset vasodilation. Whereas NOS inhibition decelerates vasodilator kinetics, when combined with SDF, vasodilator kinetics do not differ from control. These data suggest NO-independent activation of cGMP occurs at exercise onset; thus PDE-5 inhibition may improve vasodilation in pathologies where NO bioavailability is impaired. NEW & NOTEWORTHY We show that when NO bioavailability is reduced, PDE-5 inhibition can restore vasodilation onset kinetics of exercise-mediated vasodilation via NO-independent cGMP pathways. These data suggest PDE-5 inhibition may improve exercise vasodilation onset kinetics in pathologies where NO bioavailability is impaired.

Cardiometabolic crosstalk in obesity-associated arterial hypertension

Abdominal obesity and elevated blood pressure commonly occur in the same patient and are key components of the metabolic syndrome. However, the association between obesity and increased blood pressure is variable. We review mechanisms linking cardiovascular and metabolic disease in such patients including altered systemic and regional hemodynamic control, neurohumoral activation, and relative natriuretic peptide deficiency. Moreover, we discuss recent results using omics techniques providing insight in molecular pathways linking adiposity, metabolic disease, and arterial hypertension. Recognition of the mechanisms orchestrating the crosstalk between cardiovascular and metabolic regulation in individual patients may lead to better and more precise treatments. It is reassuring that recently developed cardiovascular and metabolic medications may in fact ameliorate, both, cardiovascular and metabolic risks.

Hyperoxia increases arterial oxygen pressure during exercise in type 2 diabetes patients: a feasibility study

Objective

The study investigated the feasibility and potential outcome measures during acute hyperoxia in type 2 diabetes patients (DM2).

Methods

Eleven DM2 patients (7 men and 4 women) were included in the study. The patients cycled (30 min at 20 % W_max) whilst breathing three different supplemental oxygen flows (SOF, 5, 10, 15 L min⁻¹). During hyperoxic exercise, arterial blood gases and intra-arterial blood pressure measurements were obtained.

Results

Arterial pO₂ levels increased significantly (ANOVA, p < 0.05) with SOF: 13.9 ± 1.2 (0 L min⁻¹); 18.5 ± 1.5 (5 L min⁻¹); 21.7 ± 1.7 (10 L min⁻¹); 24.0 ± 2.3 (15 L min⁻¹). Heart rate (HR) and pH increased significantly after terminating administration of hyperoxic air.

Conclusions

An SOF of 15 L min⁻¹ appears to be more effective than 5 or 10 L min⁻¹. Moreover, HR, blood pressure, blood lactate and pH are not recommended as primary outcome measures.