Hyperbaric exposure with high oxygen concentration inhibits growth-associated increase in the glucose level of diabetic Goto-Kakizaki rats

Mild Hyperbaric Oxygen Exposure Enhances Peripheral Circulatory Natural Killer Cells in Healthy Young Women

Mild hyperbaric oxygen (HBO) enhances oxygen absorption in blood, relieving fatigue without causing oxidative stress. The benefits of mild HBO have been recognized in the treatment of lifestyle-related diseases and hypertension, but no research has been conducted on its effects on immunity. The aim of the present study is to investigate the effect of mild HBO on natural killer (NK) cells and cytokines in healthy young women. This crossover randomized control trial was conducted with 16 healthy young women. Participants were randomly exposed to normobaric oxygen (NBO; 1.0 atmospheres absolute (ATA), 20.8% oxygen) and mild HBO conditions (1.4 ATA, 35-40% oxygen, injected 18L oxygen per minute) in a hyperbaric oxygen chamber for 70 min. Heart rate, parasympathetic activity, NK cell count, interleukin (IL)-6, IL-12p70 and derivatives of reactive oxygen metabolites (d-ROMs) were measured before and after both exposures. In the NBO condition, parasympathetic activity remained unchanged, whereas after mild HBO exposure, parasympathetic activity was significantly increased. NK cells remained unchanged after NBO exposure, while NK cells were increased after exposure to mild HBO. Exposure to mild HBO did not increase d-ROM values, IL-6 and IL-12p70 protein levels. These findings suggest that exposure to mild HBO can be a useful protocol to increase NK cells by regulating parasympathetic activity via increasing oxygen delivery.

Hyperbaric Normoxia Improved Glucose Metabolism and Decreased Inflammation in Obese Diabetic Rat

Hyperbaric treatment improves hyperglycemia and hyperinsulinemia in type 2 diabetes associated with obesity. However, its mode of action is unknown. The purpose of the present study was to investigate the influences of regular hyperbaric treatment with normal air at 1.3 atmospheres absolute (ATA) on glucose tolerance in type 2 diabetes with obesity. The focus was directed on inflammatory cytokines in the adipose tissue and skeletal muscle. Otsuka Long-Evans Tokushima Fatty (OLETF) rats were used as models of type 2 diabetes with obesity and Long-Evans Tokushima Otsuka (LETO) rats served as healthy controls. The rats were randomly assigned to untreated or hyperbaric treatment groups exposed to 1.3 ATA for 8 h d-1 and 5 d wk-1 for 16 wks. Glucose levels were significantly higher in the diabetic than in the healthy control rats. Nevertheless, glucose levels at 30 and 60 min after glucose administration were significantly lower in the diabetic rats treated with 1.3 ATA than in the untreated diabetic rats. Insulin levels at fasting and 120 min after glucose administration were significantly lower in the diabetic rats treated with 1.3 ATA than in the untreated diabetic rats. Hyperbaric treatment also increased interleukin-10 (IL-10) expression in the skeletal muscle and decreased tumor necrosis factor α (TNFα) expression in adipose tissue. These results suggested that TNFα downregulation and IL-10 upregulation in diabetic rats subjected to hyperbaric treatment participate in the crosstalk between the adipose and skeletal muscle tissues and improve glucose intolerance.

Mild hyperbaric oxygen: mechanisms and effects

Adequate oxygen supply by exposure to mild hyperbaric oxygen at appropriately high atmospheric pressure (1266-1317 hPa) and increased oxygen concentration (35-40% oxygen) has a possibility of improving the oxidative metabolism in cells and tissues without barotrauma and excessive production of reactive oxygen species. Therefore, metabolic syndrome and lifestyle-related diseases, including type 2 diabetes and hypertension, in rats were inhibited and/or improved by exposure to mild hyperbaric oxygen. It accelerated the growth-induced increase in oxidative capacity of the skeletal muscle in rats and inhibited the age-related decrease in oxidative capacity of the skeletal muscle in mice. A decrease in dopaminergic neurons in the substantia nigra of mice with Parkinson's disease was inhibited by exposure to mild hyperbaric oxygen. This review describes the beneficial effects of exposure to mild hyperbaric oxygen on some metabolic diseases and their perspectives.

Mild hyperbaric oxygen inhibits the growth-related decline in skeletal muscle oxidative capacity and prevents hyperglycemia in rats with type 2 diabetes mellitus

BACKGROUND

Humans and animals with type 2 diabetes mellitus (T2DM) exhibit low skeletal muscle oxidative capacity and impaired glucose metabolism. The aim of the present study was to investigate the effects of exposure to mild hyperbaric oxygen on these changes in obese rats with T2DM.

METHODS

Five-week-old non-diabetic Long-Evans Tokushima Otsuka (LETO) and diabetic Otsuka Long-Evans Tokushima Fatty (OLETF) rats were divided into normobaric (LETO-NB and OLETF-NB) and mild hyperbaric oxygen (LETO-MHO and OLETF-MHO) groups. The LETO-MHO and OLETF-MHO groups received 1266 hPa with 36% oxygen for 3 h daily for 22 weeks.

RESULTS

Fasting and non-fasting blood glucose, HbA1c, and triglyceride levels were lower in the OLETF-MHO group than in the OLETF-NB group (P < 0.05). In the soleus muscle, peroxisome proliferator-activated receptor δ/β (Pparδ/β), Pparγ, and PPARγ coactivator-1α (Pgc-1α) mRNA levels were lower in the OLETF-NB group than in all other groups (P < 0.05), whereas myogenin (Myog) and myogenic factor 5 (Myf5) mRNA levels were higher in the OLETF-MHO group than in the LETO-NB and OLETF-NB groups (P < 0.05). The soleus muscles in the OLETF-NB group contained only low-oxidative Type I fibers, whereas those in all other groups contained high-oxidative Type IIA and Type IIC fibers in addition to Type I fibers.

CONCLUSIONS

Exposure to mild hyperbaric oxygen inhibits the decline in skeletal muscle oxidative capacity and prevents the hyperglycemia associated with T2DM. Pgc-1α, Myog, and Myf5 mRNA levels appear to be closely associated with skeletal muscle oxidative capacity in rats with T2DM.

Unloading-induced atrophy and decreased oxidative capacity of the soleus muscle in rats are reversed by pre- and postconditioning with mild hyperbaric oxygen

Our aim was to determine the effects of pre- and/or postconditioning with mild hyperbaric oxygen (1.25 atmospheric pressure, 36% oxygen for 3 h/day) on the properties of the soleus muscle that was atrophied by hindlimb suspension-induced unloading. Twelve groups of 8-week-old rats were housed under normobaric conditions (1 atmospheric pressure, 20.9% oxygen) or exposed to mild hyperbaric oxygen for 2 weeks. Ten groups then were housed under normobaric conditions for 2 weeks with their hindlimbs either unloaded via suspension or not unloaded. Six groups subsequently were either housed under normobaric conditions or exposed to mild hyperbaric oxygen for 2 weeks: the suspended groups were allowed to recover under reloaded conditions (unrestricted normal cage activity). Muscle weights, cross-sectional areas of all fiber types, oxidative capacity (muscle succinate dehydrogenase activity and fiber succinate dehydrogenase staining intensity) decreased, and a shift of fibers from type I to type IIA and type IIC was observed after hindlimb unloading. In addition, mRNA levels of peroxisome proliferator-activated receptor γ coactivator-1α decreased, whereas those of forkhead box-containing protein O1 increased after hindlimb unloading. Muscle atrophy and decreased oxidative capacity were unaffected by either pre- or postconditioning with mild hyperbaric oxygen. In contrast, these changes were followed by a return to nearly normal levels after 2 weeks of reloading when pre- and postconditioning were combined. Therefore, a combination of pre- and postconditioning with mild hyperbaric oxygen can be effective against the atrophy and decreased oxidative capacity of skeletal muscles associated with hindlimb unloading.

Hyperbaric oxygen therapy reduces renal lactate production

Intrarenal hypoxia is an acknowledged factor contributing to the development of diabetic nephropathy. Hyperbaric oxygen (HBO) therapy is a well-known adjuvant treatment for several medical conditions, such as decompression sickness, infections, and wound healing. The underlying metabolic response of HBO is largely unknown. In this study, we investigated the effect of HBO on the intrarenal metabolic alteration in diabetes. Hyperpolarized [1-13C]pyruvate MRI was performed to assess intrarenal energy metabolism in normoglycemic controls and short-term (2 weeks) streptozotocin-induced diabetic rats with and without HBO for five consecutive days. HBO therapy blunted intrarenal lactate production, 3 days after the therapy, in both normoglycemic controls and diabetic rats without affecting either lactate dehydrogenase mRNA expression or activity. HBO therapy reduced lactate formation in both normoglycemic and hyperglycemic rats. These findings support hyperpolarized [1-13C]pyruvate MRI as a novel method for monitoring HBO therapy via the pyruvate to lactate conversion.

Mild Hyperbaric Oxygen Inhibits Growth-related Decrease in Muscle Oxidative Capacity of Rats with Metabolic Syndrome

Aim: We examined the effects of mild hyperbaric oxygen on the properties of the soleus muscle in rats with metabolic syndrome.

Methods: Five-week-old metabolic syndrome (SHR/NDmcr-cp, cp/cp) rats were divided into normobaric (CP) and mild hyperbaric oxygen (CP-H) groups (n = 5/group). In addition, 5-week-old Wistar rats were assigned as the normobaric control (WR) group (n = 5). The CP-H group was exposed to 1.25 atmospheres absolute with 36% oxygen for 3 h daily for 16 weeks. Succinate dehydrogenase (SDH) activity and mRNA levels of peroxisome proliferator-activated receptor γ coactivator-1α (Pgc-1α) in the soleus muscle were examined. The fiber type composition, cross-sectional areas, and SDH staining intensity in the soleus muscle were also examined.

Results: The CP-H group showed lower fasting and nonfasting blood glucose, glycated hemoglobin, total cholesterol, triglyceride, insulin, and systolic blood pressure levels; higher adiponectin levels; and higher SDH activity and mRNA levels of Pgc-1α in the muscle than the CP group. Compared with the CP group, the CP-H group had a lower percentage of type I fibers and observed type IIA fibers in the muscle. The CP-H group also had higher SDH staining intensity of type I and type IIC fibers in the muscle than the CP group. No differences in these values were observed in the muscles of the WR and CP-H groups.

Conclusion: Mild hyperbaric oxygen inhibited growth-related increase in blood glucose levels and decrease in muscle oxidative capacity of rats with metabolic syndrome because of improved oxidative metabolism.

Mild Hyperbaric Oxygen Improves Decreased Oxidative Capacity of Spinal Motoneurons Innervating the Soleus Muscle of Rats with Type 2 Diabetes

Rats with type 2 diabetes exhibit decreased oxidative capacity, such as reduced oxidative enzyme activity, low-intensity staining for oxidative enzymes in fibers, and no high-oxidative type IIA fibers, in the skeletal muscle, especially in the soleus muscle. In contrast, there are no data available concerning the oxidative capacity of spinal motoneurons innervating skeletal muscle of rats with type 2 diabetes. This study examined the oxidative capacity of motoneurons innervating the soleus muscle of non-obese rats with type 2 diabetes. In addition, this study examined the effects of mild hyperbaric oxygen at 1.25 atmospheres absolute with 36 % oxygen for 10 weeks on the oxidative capacity of motoneurons innervating the soleus muscle because mild hyperbaric oxygen improves the decreased oxidative capacity of the soleus muscle in non-obese rats with type 2 diabetes. Spinal motoneurons innervating the soleus muscle were identified using nuclear yellow, a retrograde fluorescent neuronal tracer. Thereafter, the cell body sizes and succinate dehydrogenase activity of identified motoneurons were analyzed. Decreased succinate dehydrogenase activity of small-sized alpha motoneurons innervating the soleus muscle was observed in rats with type 2 diabetes. The decreased succinate dehydrogenase activity of these motoneurons was improved by mild hyperbaric oxygen. Therefore, we concluded that rats with type 2 diabetes have decreased oxidative capacity in motoneurons innervating the soleus muscle and this decreased oxidative capacity is improved by mild hyperbaric oxygen.

Oxygen concentration-dependent oxidative stress levels in rats

Introduction. We determined derivatives of reactive oxygen metabolites (dROMs) as an index of oxidative stress level (oxidant capacity) and biochemical antioxidant potential (BAP) as an index of antioxidant capacity in rats exposed to different oxygen concentrations. Methods. Male Wistar rats were exposed to 14.4%, 20.9%, 35.5%, 39.8%, 62.5%, and 82.2% oxygen at 1 atmosphere absolute for 24 h. Serum levels of dROMs and BAP were examined by using a free radical and antioxidant potential determination device. The morphological characteristics of red blood cells were examined by phase contrast microscopy. Results. There were no differences in the levels of dROMs in rats exposed to 14.4%, 20.9%, and 35.5% oxygen. However, the levels of dROMs increased in the rats exposed to 39.8% and 62.5% oxygen. The levels of dROMs were the highest in the rats exposed to 82.2% oxygen. There were no differences in the levels of BAP with respect to the oxygen concentration. Morphological changes in the red blood cells induced by oxidative attack from reactive oxygen species were observed in the rats exposed to 39.8%, 62.5%, and 82.2% oxygen. Conclusion. Our results suggest that exposure to oxygen concentrations higher than 40% for 24 h induces excessive levels of oxidative stress in rats.

Effects of hyperbaric oxygen on metabolic capacity of the skeletal muscle in type 2 diabetic rats with obesity

We investigated whether hyperbaric oxygen enhances the oxidative metabolic capacity of the skeletal muscle and attenuates adipocyte hypertrophy in type 2 diabetic rats with obesity. Five-week-old male Otsuka Long-Evans Tokushima fatty (OLETF) and Long-Evans Tokushima Otsuka (LETO) rats were used as diabetic animals and nondiabetic controls, respectively, and assigned to control and hyperbaric oxygen groups. Animals in the hyperbaric oxygen group were exposed to an atmospheric pressure of 1.25 with an oxygen concentration of 36% for 3 h daily. The glucose level at 27 weeks of age was significantly higher in OLETF rats than in LETO rats, but the elevation was inhibited in OLETF rats exposed to hyperbaric oxygen. The slow-to-fast fiber transition in the skeletal muscle was observed in OLETF rats, but the shift was inhibited in OLETF rats exposed to hyperbaric oxygen. Additionally, the oxidative enzyme activity of muscle fibers was increased by hyperbaric oxygen. The adipocyte size was larger in OLETF rats than in LETO rats, but hypertrophied adipocytes were not observed in OLETF rats exposed to hyperbaric oxygen. Hyperbaric oxygen enhances glucose and lipid metabolism in the skeletal muscle, indicating that hyperbaric oxygen can prevent elevation of glucose and adipocyte hypertrophy in diabetic rats with obesity.

Effect of exposure to hyperbaric oxygen on diabetes-induced cataracts in mice

BACKGROUND

The growth-associated increase in the blood glucose level of animals with Type 2 diabetes is inhibited by moderate hyperbaric exposure at 1.25 atmospheres absolute (ata) with 36% oxygen, presumably due to an increase in oxidative metabolism. However, there are no data available regarding the effect of moderate hyperbaric oxygen (HBO) on diabetes-induced cataracts.

METHODS

Four-week-old mice with Type 2 diabetes and cataracts were exposed to 1.25 ata with 36% oxygen, 6 h daily, for 12 weeks, followed by normal conditions at 1 ata with 21% oxygen for 16 weeks (cataract + hyperbaric group). Levels of blood glucose and derivatives of reactive oxygen metabolites (dROMs), used as an index of oxidative stress, and the turbidities of the lenses from these mice at 4, 8, 12, 16, and 32 weeks of age were compared with those of control and diabetic (cataract group) mice not exposed to HBO.

RESULTS

Non-fasting and fasting blood glucose levels were lower in the cataract + hyperbaric group at 12, 16, and 32 weeks of age than in the age-matched cataract group. The levels of dROMs were lower in the cataract + hyperbaric group at 16 and 32 weeks of age than in the age-matched cataract group. The turbidities of the peripheral and central regions of the lenses were lower in the cataract + hyperbaric group at 12, 16, and 32 weeks of age than in the age-matched cataract group.

CONCLUSIONS

Hyperbaric exposure at 1.25 ata with 36% oxygen delays cataract development and progression in mice with Type 2 diabetes.

Advantages and disadvantages of hyperbaric oxygen treatment in mice with obesity hyperlipidemia and steatohepatitis

The effect of hyperbaric oxygen treatment (HBOT) was examined using MSG mice, which are an animal model of obesity, hyperlipidemia, diabetes, and nonalcoholic fatty liver disease. Nineteen MSG male mice were divided into HBOT treated and control groups at 12 weeks of ages. The HBOT group was treated with hyperbaric oxygen from 12 to 14 weeks (first phase) and then from 16 to 18 weeks (second phase). Interestingly, the body weight of the HBOT group was significantly lower (P < 0.01) than that of the control group. In contrast, the serum lipid level did not show significant changes between the two groups. As for the effects of increasing oxidative stress, the liver histology of the HBOT group showed severer cellular damage and aberrant TNF-α expression. HBOT has the advantage of improving obesity in patients with metabolic syndrome, but the fault of causing organ damage by increasing oxidative stress.

Hyperbaric oxygen improves ultraviolet B irradiation-induced melanin pigmentation and diminishes senile spot size

BACKGROUND

The effects of exposure to hyperbaric oxygen on ultraviolet B (UVB) irradiation-induced melanin pigmentations of skins and on senile spot sizes of faces were investigated.

METHODS

In the first experiment, male subjects were irradiated with UVB on their upper arms for inducing erythema and the subsequent melanin pigmentation. They were exposed to a hyperbaric environment at 1.25 atmospheres absolute (ATA) with 32% oxygen for 1 h/day, three times per week. In the second experiment, female subjects were exposed to a hyperbaric environment at 1.25 ATA with 32% oxygen for 1 h/day, two times per week.

RESULTS

In the first experiment, melanin pigmentations lightened after 4 weeks of exposure to hyperbaric oxygen. In the second experiment, senile spot sizes became small after 12 weeks of exposure to hyperbaric oxygen.

CONCLUSION

We concluded that exposure to hyperbaric oxygen used in this study accelerates both the fading in melanin pigmentation and the decrease in senile spot size.

Long-term treatment with hyperbaric air improves hyperlipidemia of db/db mice

Hyperbaric air (HBA) is used to improve healing of wounds including diabetic ulcer. The aim of this study was to clarify the effects of HBA exposure on lipid and glucose metabolism in db/db mice. HBA did not influence the weight of db/db mice. Serum levels of free fatty acid and triglyceride, but not glucose and insulin, were significantly decreased after 6 weeks of treatment with HBA. The mRNA expressions of CPT-1, PPARα and PGC-1α genes, which are related to lipid metabolism, were significantly up-regulated in the muscle and liver. Increases in TNFα and MCP1 mRNA, which impaired lipid metabolism, were also attenuated by HBA treatment. These results suggest that exposure of HBA could have beneficial effects on lipid metabolism in patients with type 2 diabetes mellitus.

Hyperbaric oxygen exposure improves blood glucose level and muscle oxidative capacity in rats with type 2 diabetes

BACKGROUND

The effects of exposure to hyperbaric oxygen on blood glucose level and muscle oxidative capacity in rats with type 2 diabetes were investigated.

METHODS

Five-week-old male Goto-Kakizaki rats were divided into four groups: normobaric (NN; exposed to 21% oxygen at 760 mm Hg for 8 weeks), hyperbaric to normobaric (HN; exposed to 36% oxygen at 950 mm Hg for 4 weeks, followed by 21% oxygen at 760 mm Hg for 4 weeks), normobaric to hyperbaric (NH; exposed to 21% oxygen at 760 mm Hg for 4 weeks, followed by 36% oxygen at 950 mm Hg for 4 weeks), and hyperbaric (HH; exposed to 36% oxygen at 950 mm Hg for 8 weeks).

RESULTS

Blood glucose levels were lower in the HN, NH, and HH groups than in the NN group. Up-regulated mRNA expression levels of peroxisome proliferator-activated receptor-gamma co-activator-1alpha were observed in the soleus muscles of the HN, NH, and HH groups and in the plantaris muscles of the HN and HH groups. The soleus muscles of the NN group contained only type I fibers, whereas those of the HN, NH, and HH groups contained type I, type IIA, and type IIC fibers. An increased percentage of type I fibers and a decreased percentage of type IIB fibers were observed in the plantaris muscles of the NH, HN, and HH groups.

CONCLUSIONS

Exposure to hyperbaric oxygen reduces high blood glucose levels and improves oxidative capacities in the skeletal muscles of rats with diabetes, and these effects are maintained under normobaric conditions even after exposure to hyperbaric oxygen.

Hyperbaric oxygen exposure reduces age-related decrease in oxidative capacity of the tibialis anterior muscle in mice

The effects of exposure to hyperbaric oxygen on the oxidative capacity of the skeletal muscles in mice at different ages were investigated. We exposed 5-, 34-, 55-, and 88-week-old mice to 36% oxygen at 950 mmHg for 6 hours per day for 2 weeks. The activities of succinate dehydrogenase (SDH), which is a mitochondrial marker enzyme, of the tibialis anterior muscle in hyperbaric mice were compared with those in age-matched mice under normobaric conditions (21% oxygen at 760 mmHg). Furthermore, the SDH activities of type IIA and type IIB fibers in the muscle were determined using quantitative histochemical analysis. The SDH activity of the muscle in normobaric mice decreased with age. Similar results were observed in both type IIA and type IIB fibers in the muscle. The decrease in the SDH activity of the muscle was reduced in hyperbaric mice at 57 and 90 weeks. The decreased SDH activities of type IIA and type IIB fibers were reduced in hyperbaric mice at 90 weeks and at 57 and 90 weeks, respectively. We conclude that exposure to hyperbaric oxygen used in this study reduces the age-related decrease in the oxidative capacity of skeletal muscles.

Effects of exposure to hyperbaric oxygen on oxidative stress in rats with type II collagen-induced arthritis

Arthritis was induced in 9-week-old female Dark Agouti rats by injecting type II collagen. Serum levels of the derivatives of reactive oxygen metabolites (dROMs), which are oxidative stress markers, and C-reactive protein (CRP) in arthritic rats that were exposed to a pressure of 1.25 atmospheres absolute and an oxygen concentration of 36% for 3 weeks (arthritis + HBO group) were compared to those of control rats (control group) and arthritic rats that were not exposed to hyperbaric oxygen (arthritis group). The body weights of the arthritis and arthritis + HBO groups were lower than that of the control group, whereas no difference in the body weight was observed between the arthritis and arthritis + HBO groups. The serum levels of dROMs and CRP in the arthritis group were higher than those in the control and arthritis + HBO groups. No difference in the serum level of CRP was observed between the control and arthritis + HBO groups. These results indicate that the conditions of hyperbaric oxygen exposure used in this study are effective for reducing the levels of reactive oxygen species, which are overproduced during arthritis.

Hyperbaric Exposure with High Oxygen Concentration Improves Altered Fiber Types in the Plantaris Muscle of Diabetic Goto-Kakizaki Rats

Hyperbaric exposure with high oxygen concentration inhibits a growth-related increase in the glucose and insulin of diabetic rats. In this study, 5-week-old diabetic Goto-Kakizaki rats were exposed to a hyperbaric environment (1.25 atmospheric pressure) with a high oxygen concentration (36%) for 6 h daily. Fiber type distributions and oxidative enzyme activities in the fast-twitch plantaris muscle of Goto-Kakizaki rats were examined after hyperbaric exposure for 4 weeks. The percentages of high-oxidative type I and type IIA fibers increased and that of low-oxidative type IIB fibers decreased after hyperbaric exposure. Furthermore, the fiber oxidative enzyme activity increased after hyperbaric exposure, regardless of fiber type. It is concluded that altered patterns of fiber types in the plantaris muscle of diabetic rats shift toward normal, which is observed in nondiabetic rats, following hyperbaric exposure with high oxygen concentration.