Cerebral and muscle tissue oxygenation during exercise in healthy adults: A systematic review

Background:Near-infrared spectroscopy(NIRS)technology has allowed for the measurement of cerebral and skeletal muscle oxygenation simultaneously during exercise.Since this technology has been growing and is now successfully used in laboratory and sports settings,this systematic review aimed to synthesize the evidence and enhance an integrative understanding of bloodflow adjustments and oxygen(O_(2))changes(i.e.,the balance between O_(2) delivery and O_(2) consumption)within the cerebral and muscle systems during exercise.Methods:A systematic review was conducted using PubMed,Embase,Scopus,and Web of Science databases to search for relevant studies that simultaneously investigated cerebral and muscle hemodynamic changes using the near-infrared spectroscopy system during exercise.This review considered manuscripts written in English and available before February 9,2023.Each step of screening involved evaluation by 2 inde-pendent authors,with disagreements resolved by a third author.The Joanna Briggs Institute Critical Appraisal Checklist was used to assess the methodological quality of the studies.Results:Twenty studies were included,of which 80%had good methodological quality,and involved 290 young or middle-aged adults.Different types of exercises were used to assess cerebral and muscle hemodynamic changes,such as cycling(n=11),treadmill(n=1),knee extension(n=5),isometric contraction of biceps brachii(n=3),and duet swim routines(n=1).The cerebral hemodynamics anal-ysis was focused on the frontal cortex(n=20),while in the muscle,the analysis involved vastus lateralis(n=18),gastrocnemius(n=3),biceps brachii(n=5),deltoid(n=1),and intercostal muscle(n=1).Overall,muscle deoxygenation increases during exercise,reaching a plateau in voluntary exhaustion,while in the brain,oxyhemoglobin concentration increases with exercise intensity,reaching a plateau or declining at the exhaustion point.Conclusion:Muscle and cerebral oxygenation respond differently to exercise,with muscle increasing O_(2) utilization and cerebral tissue increasing O_(2) delivery during exercise.However,at the exhaustion point,both muscle and cerebral oxygenation become compromised.This is characterized by a reduction in bloodflow and a decrease in O_(2) extraction in the muscle,while in the brain,oxygenation reaches a plateau or decline,potentially resulting in motor failure during exercise.

Impact of Adrenaline or Cortisol Injection on Meat Quality Development of Merino Hoggets

Increased levels of stress hormones in the muscle could lead to post mortem metabolic/structural modiifcations that could be relfected on meat quality. The present study investigated the metabolic effect of either adrenaline or cortisol injected into lambs in order to obtain an animal model of acute stress. Results showed that adrenaline or cortisol injection lead to glucose metabolism and muscle temperature increase. Muscle pH immediately post mortem was affected by adrenaline treatment. Water holding capacity （WHC） of fresh muscle, ifnal muscle pH and temperature registered at 24 h post mortem were not affected by injected hormones. Hardness and adhesiveness of LD muscle evaluated 3 d post mortem tended to increase as a result of adrenaline or cortisol injection. Results demonstrated that injected hormones were able to affect the post mortem muscle biochemistry and the pH/T curve independently of ifnal muscle pH.

Small molecule conjugates with selective estrogen receptor β agonism promote anti-aging benefits in metabolism and skin recovery

Estrogen is imperative to mammalian reproductivity,metabolism,and aging.However,the hormone activating estrogen receptor(ERs)αcan cause major safety concerns due to the enrichment of ERαin female tissues and certain malignancies.In contrast,ERβis more broadly expressed in metabolic tissues and the skin.Thus,it is desirable to generate selective ERβagonist conjugates for maximizing the therapeutic effects of ERs while minimizing the risks of ERαactivation.Here,we report the design and production of small molecule conjugates containing selective non-steroid ERβagonists Gtx878 or genistein.Treatment of aged mice with our synthesized conjugates improved aging-associated declines in insulin sensitivity,visceral adipose integrity,skeletal muscle function,and skin health,with validation in vitro.We further uncovered the benefits of ERβconjugates in the skin using two inducible skin injury mouse models,showing increased skin basal cell proliferation,epidermal thickness,and wound healing.Therefore,our ERβ-selective agonist conjugates offer novel therapeutic potential to improve aging-associated conditions and aid in rejuvenating skin health.

Fat-to-muscle Ratio: A New Anthropometric Indicator for Predicting Metabolic Syndrome in the Han and Bouyei Populations from Guizhou Province, China

Objective To investigate the prevalence and possible factors influencing metabolic syndrome in people from Guizhou Province and to explore the predictive value of the fat-to-muscle ratio in diagnosing metabolic syndrome. Methods A multistage stratified sampling method was used in this cross-sectional study of 20-80 years old Han and Bouyei populations from Guizhou Province, southwestern China, from October-December 2012. The study included 4,553 cases of metabolic syndrome, that was defined according to 2005 International Diabetes Federation criteria. The receiver operating characteristic curve was used for determining the sensitivity, specificity, and predictive ability of the fat-to-muscle ratio for the diagnosis of metabolic syndrome. Results The age-standardized prevalence of metabolic syndrome was 11.38%（men： 9.76%; women： 12.72%） for Han and 4.78%（men： 4.43%; women： 5.30%） for Bouyei populations. In Guizhou Province, the cut-off value for the men fat-to-muscle ratio was 0.34, the area under the curve was 0.95, and the sensitivity and specificity were 0.94 and 0.85, respectively. The cut-off value for the women fat-to-muscle ratio was 0.55, the area under the curve was 0.91, and the sensitivity and specificity were 0.93 and 0.79, respectively. Conclusion The fat-to-muscle ratio is highly predictive of metabolic syndrome in Guizhou Province, and a useful reference indicator.

MUSCLE RESEARCH WORK WITH BRITTON CHANCE FROM IN VIVO MAGNETIC RESONANCE SPECTROSCOPY TO NEAR-INFRARED SPECTROSCOPY

Britton Chance has pioneered magnetic resonance spectroscopy(MRS)and near-infrared(NIR)spectroscopy(NIRS)as noninvasive methods for measuring muscle metabolism in vivo from the late 1970s.This review honoring Britton Chance will highlight the progress that has been made in developing and utilizing MRS and NIRS technologies for evaluating skeletal muscle O_(2) dynamics and energetics.Adaptation of MRS and NIRS technology has focused on the validity and reliability of the measurements and extending the methods in physiological and clinical research.Britton Chance has conducted MRS and NIRS research on elite athletes and a number of chronic health conditions,including patients with chronic heart failure,peripheral vascular disease,and neuromuscular myopathies.As MRS and NIRS technologies are practical and useful for measuring human muscle metabolism,we will strive to continue Chance's legacy by advancing muscle MRS and NIRS studies.

Premigratory fat metabolism in hummingbirds： A Rumsfeldian approach

Hummingbird migration is a remarkable feat, given the small body sizes of migratory species, their high metabolic rates during flight and the long distances traveled using fat to fuel the effort. Equally remarkable is the ability of premigratory hummingbirds in the wild to accumulate fat, synthesized from sugar, at rates as high as 10% of body mass per day. This paper summarizes, using Rumsfeldian terminology, ＂known knowns＂ concerning the energetics of hummingbird migration and premi- gratory fattening. Energy metabolism during hover-feeding on floral nectar is fueled directly by dietary sugar through the path- way recently named the ＂sugar oxidation cascade＂. However, flight without feeding for more than a few minutes requires shifting to fat as a fuel. It is proposed that behavior and metabolic fuel choice are coadapted to maximize the rate of fat deposition during premigratory fattening. The hummingbird liver appears to possess extraordinarily high capacities for fatty acid synthesis. The analysis of ＂known knowns＂ leads to identification of ＂known unknowns＂, e.g., the fates of dietary glucose and fructose, the regulation of fat metabolism and metabolic interactions between liver and adipose tissue. The history of science behooves recog- nition of ＂tmknown unknowns＂ that, when discovered serendipitously, might shed new light on fundamental mechanisms as well as human pathological conditions .

A novel function of CREG in metabolic disorders

Metabolic disorders are public health problems that require prevention and new efficient drugs for treatment.Cellular repressor of E1A-stimulated genes(CREG)is ubiquitously expressed in mature tissues and cells in mammals and plays a critical role in keeping cells or tissues in a mature,homeostatic state.Recently,CREG turns to be an important mediator in the development of metabolic disorders.Here in this review,we briefly discuss the structure and molecular regulation of CREG along with the therapeutic strategy to combat the metabolic disorders.