No effect of acute normobaric hypoxia on plasma triglyceride levels in fasting healthy men

Mahat, Bimit; Chassé, Étienne; Lindon, Clare; Mauger, Jean‐François; Imbeault, Pascal

doi:10.1139/apnm-2017-0505

Cited by 13 publications

(17 citation statements)

References 33 publications

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“…Because we thought that the postprandial rise in insulin might have inhibited adipose tissue lipolysis and suppressed hepatic very-low density lipoprotein (VLDL) production, we conducted another study in the fasting state under continuous (i.e., not intermittent) hypoxic conditions. Again, we observed no effect of hypoxia on circulating TG (Mahat et al, 2018). Interestingly, despite no changes in plasma TG concentrations, our previous studies reported significant increases (∼+35%) in circulating non-esterified fatty acids, which is an important contributor to hepatic lipogenesis and very-low density lipoprotein production (Nielsen and Karpe, 2012).…”

Section: Introductioncontrasting

confidence: 53%

“…While the regulation of VLDL and chylomicron remnants uptake is still poorly understood (Ramasamy, 2013), VLDL production is generally accepted to be reduced in the postprandial state, mainly because insulin inhibits adipose tissue lipolysis, thus reducing hepatic NEFA delivery, the main substrate for VLDL-TG production (Nielsen and Karpe, 2012). In our previous study conducted in the fasted state, the increase in circulating NEFA under hypoxia was not matched by an increase in plasma TG concentration, suggesting that in the fasted state, increased availability of NEFA alone may not acutely affect hepatic VLDL production (Mahat et al, 2018). In the present study, however, it could be suspected that the combination of chylomicron remnants delivery and elevated plasma NEFA may have provided enough lipid substrate to drive an increase in hepatic VLDL production.…”

Section: Discussionmentioning

confidence: 95%

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The Effect of Acute Continuous Hypoxia on Triglyceride Levels in Constantly Fed Healthy Men

et al. 2019

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Introduction Elevated plasma triglyceride (TG) concentrations are an important contributor to deleterious metabolic alterations. Evidence in animals suggest that acute exposure to an environment with reduced oxygen inhibits plasma TG clearance and causes important rise in plasma TG, especially in the postprandial state. The objective of this study was to characterize the effects of an acute exposure to normobaric hypoxia on prandial TG levels in 2 distinct lipoprotein subtypes in healthy humans: chylomicrons which are secreted by the intestine and carry dietary lipids, and denser TG carriers (mainly VLDL), which are secreted by the liver and carry endogenous lipids. Plasma lipolytic activity was also assessed. It was hypothesized that hypoxia would reduce prandial plasma lipolytic activity and raise prandial TG levels in both lipoprotein subtypes. Methods Using a randomized crossover design, 9 healthy young men were studied for 6 h in a constantly fed state while being exposed to either normobaric hypoxia (FiO 2 = 0.12) and normoxic conditions on two different days. Prandial glucose, TG, non-esterified fatty acid (NEFA), and post-heparin plasma lipolytic activity were measured during each session. Results Six hours of exposure to hypoxia marginally increase prandial glycemia (+5%, p = 0.06) while increasing insulinemia by 40% ( p = 0.04). Hypoxia induced a 30% rise in prandial NEFA levels and tended to slightly increased total prandial TG levels by 15% ( p = 0.11). No difference was observed in TG concentrations and metabolism of chylomicrons between conditions. However, TG in the VLDL containing fraction decreased significantly overtime under normoxia but not under hypoxia (time × condition interaction, p = 0.02). No difference was observed in post-heparin plasmatic lipolytic activity between conditions. Conclusion Acute hypoxia in healthy men tends to increase prandial VLDL-TG levels. These results lend support to the increased blood lipid levels reported in animals exposed acutely to lower partial pressures of oxygen.

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Section: Introductioncontrasting

confidence: 53%

Section: Discussionmentioning

confidence: 95%

The Effect of Acute Continuous Hypoxia on Triglyceride Levels in Constantly Fed Healthy Men

et al. 2019

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“…One possible explanation is that, under exposure to hypoxia, the upregulated HIF could increase the expression of the lipoprotein lipase gene through PPARc1 to prevent the loss of HDL-C [62]. Furthermore, we observed the higher magnitude of elevated serum FFA after LHTHL in the fasting state even with a decrease in serum TG, which is concordant with Mahat's report [63]. In previous studies, it has been demonstrated that the substrate shifts from carbohydrates to lipids for the energy source during the postexercise recovery period [64].…”

Section: Discussionsupporting

confidence: 92%

Effects of Living High‐Training Low and High on Body Composition and Metabolic Risk Markers in Overweight and Obese Females

Gao

Zhang

et al. 2020

BioMed Research International

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This study examined the effects of 4 weeks of living high-training low and high (LHTLH) under moderate hypoxia on body weight, body composition, and metabolic risk markers of overweight and obese females. Nineteen healthy overweight or obese females participated in this study. Participants were assigned to the normoxic training group (NG) or the LHTLH group (HG). The NG participants lived and trained at sea level. The HG participants stayed for approximately 10 hours in a simulated 2300 m normobaric state of hypoxia for six days a week and trained for 2 hours 3 times a week under the same simulated hypoxia. The interventions lasted for 4 weeks. All groups underwent dietary restriction based on resting metabolic rate. The heart rate of the participants was monitored every ten minutes during exercise to ensure that the intensity was in the aerobic range. Compared with the preintervention values, body weight decreased significantly in both the NG and the HG (−8.81 ± 2.09% and −9.09 ± 1.15%, respectively). The fat mass of the arm, leg, trunk, and whole body showed significant reductions in both the NG and the HG, but no significant interaction effect was observed. The percentage of lean soft tissue mass loss in the total body weight loss tended to be lower in the HG (27.61% versus 15.94%, P=0.085). Between the NG and the HG, significant interaction effects of serum total cholesterol (−12.66 ± 9.09% versus −0.05 ± 13.36%,) and apolipoprotein A1 (−13.66 ± 3.61% versus −5.32 ± 11.07%, P=0.042) were observed. A slight increase in serum high-density lipoprotein cholesterol (HDL-C) was observed in the HG (1.12 ± 12.34%) but a decrease was observed in the NG (−11.36 ± 18.91%). The interaction effect of HDL-C between NG and HG exhibited a significant trend (P=0.055). No added effects on serum triglycerides (TGs), low-density lipoprotein cholesterol (LDL-C), or APO-B were observed after 4 weeks of LHTLH. In conclusion, 4 weeks of LHTLH combined with dietary restriction could effectively reduce the body weight and body fat mass of overweight and obese females. Compared with training and sleeping under normoxia, no additive benefit of LHTLH on the loss of body weight and body fat mass was exhibited. However, LHTLH may help to relieve the loss of lean soft tissue mass and serum HDL-C.

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“…Two other findings pertain to reduced metabolic effects of acute hypoxia in the newborns of the present study. We did not see an increase in plasma triglycerides levels, akin to findings during acute hypoxia in humans (59). In addition, we did not see changes in plasma oxidative stress markers in response to acute hypoxia.…”

Section: Discussioncontrasting

confidence: 52%

Effects of Melatonin on the Defense to Acute Hypoxia in Newborn Lambs

et al. 2019

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Neonatal lambs, as other neonates, have physiologically a very low plasma melatonin concentration throughout 24 h. Previously, we found that melatonin given to neonates daily for 5 days decreased heart weight and changed plasma cortisol and gene expression in the adrenal and heart. Whether these changes could compromise the responses to life challenges is unknown. Therefore, firstly, we studied acute effects of melatonin on the defense mechanisms to acute hypoxia in the neonate. Eleven lambs, 2 weeks old, were instrumented and subjected to an episode of acute isocapnic hypoxia, consisting of four 30 min periods: normoxia (room air), normoxia after an i.v. bolus of melatonin (0.27 mg kg −1 , n = 6) or vehicle (ethanol 1:10 NaCl 0.9%, n = 5), hypoxia (PaO 2 : 30 ± 2 mmHg), and recovery (room air). Mean pulmonary and systemic blood pressures, heart rate, and cardiac output were measured, and systemic and pulmonary vascular resistance and stroke volume were calculated. Blood samples were taken every 30 min to measure plasma norepinephrine, cortisol, glucose, triglycerides, and redox markers (8-isoprostane and FRAP). Melatonin blunted the increase of pulmonary vascular resistance triggered by hypoxia, markedly exacerbated the heart rate response, decreased heart stroke volume, and lessened the magnitude of the increase of plasmatic norepinephrine and cortisol levels induced by hypoxia. No changes were observed in pulmonary blood pressure, systemic blood pressures and resistance, cardiac output, glucose, triglyceride plasma concentrations, or redox markers. Melatonin had no effect on cardiovascular, endocrine, or metabolic variables, under normoxia. Secondly, we examined whether acute melatonin administration under normoxia could have an effect in gene expression on the adrenal, lung, and heart. Lambs received a bolus of vehicle or melatonin and were euthanized 30 min later to collect tissues. We found that melatonin affected expression of the immediate early genes egr1 in adrenal, ctgf in lung, and nr3c1 , the glucocorticoid receptor, in adrenal and heart. We speculate that these early gene responses may contribute to the observed alterations of the newborn defense mechanisms to hypoxia. This could be particularly important since the use of melatonin is proposed for several diseases in the neonatal period in humans.

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No effect of acute normobaric hypoxia on plasma triglyceride levels in fasting healthy men

Cited by 13 publications

References 33 publications

The Effect of Acute Continuous Hypoxia on Triglyceride Levels in Constantly Fed Healthy Men

The Effect of Acute Continuous Hypoxia on Triglyceride Levels in Constantly Fed Healthy Men

Effects of Living High‐Training Low and High on Body Composition and Metabolic Risk Markers in Overweight and Obese Females

Effects of Melatonin on the Defense to Acute Hypoxia in Newborn Lambs

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