Subcutaneous injection of hydrogen gas is a novel effective treatment for type 2 diabetes

A comprehensive review of molecular hydrogen as a novel nutrition therapy in relieving oxidative stress and diseases: Mechanisms and perspectives

Oxidative stress is responsible for the pathogenesis of many diseases, and antioxidants are commonly included in their treatment protocols. Over the past two decades, numerous biomedical reports have revealed the therapeutic benefits of molecular hydrogen (H2) in relieving oxidation-related diseases. H2 has been found to have selective antioxidant properties against the most dangerous oxidants (hydroxyl radicals and peroxynitrite). H2 demonstrates numerous biologically therapeutic properties, including anti-inflammatory, antioxidant, anti-cancer, anti-stress, anti-apoptotic, anti-allergic effects, signaling molecule functions, regulation of redox balance, modulation of antioxidant enzyme gene expression, improvement of blood vessel function, down-regulation of pro-inflammatory cytokines, stimulation of energy metabolism, and protection of the nervous system. Experimental and clinical studies have shown the potential use of hydrogen nutrition therapy for ameliorating various diseases, including cardiovascular, respiratory, and metabolic disorders, as well as obesity, gastrointestinal disorders, and brain and nervous system disorders. The administration methods of hydrogen include inhalation, hydrogen-rich water, hydrogen-rich saline, hydrogen-rich eye drops, and hydrogen-rich bathing. Hydrogen nutritional therapy can be applied to different diseases, and it offers a natural alternative to chemical and radiation therapies. This review covers the different administration methods and the latest experimental and clinical research on the potential applications of H2 in nutritional therapy for different diseases.

Hydrogen therapy: recent advances and emerging materials

Hydrogen therapy, leveraging its selective attenuation of hydroxyl radicals (˙OH) and ONOO-, has emerged as a pivotal pathophysiological modulator with antioxidant, anti-inflammatory, and antiapoptotic attributes. Hydrogen therapy has been extensively studied both preclinically and clinically, especially in diseases with an inflammatory nature. Despite the substantial progress, challenges persist in achieving high hydrogen concentrations in target lesions, especially in cancer treatment. A notable breakthrough lies in water/acid reactive materials, offering enhanced hydrogen generation and sustained release potential. However, limitations include hydrogen termination upon material depletion and reduced bioavailability at targeted lesions. To overcome these challenges, catalytic materials like photocatalytic and sonocatalytic materials have surfaced as promising solutions. With enhanced permeability and retention effects, these materials exhibit targeted delivery and sustained stimuli-reactive hydrogen release. The future of hydrogen therapy hinges on continuous exploration and modification of catalytic materials. Researchers are urged to prioritize improved catalytic efficiency, enhanced lesion targeting effects, and heightened biosafety and biocompatibility in future development.

Real-World Effectiveness and Safety of Hydrogen Inhalation in Chinese Patients with Type 2 Diabetes: A Single-Arm, Retrospective Study

Aim

To evaluate the real-life effectiveness and safety of Chinese patients with type 2 diabetes mellitus (T2DM) receiving hydrogen inhalation (HI) treatment as a supplementary treatment.

Methods

This retrospective, multicenter, observational 6-months clinical study included T2DM patients maintaining HI, visited at 4 time points. The primary outcome is the mean change in glycated hemoglobin (HbA1c) at the end of the study compared to baseline. The secondary outcome is analyzing the mean change of fasting plasma glucose (FPG), weight, lipid profile, insulin dose and homeostasis model assessment. Linear regression and logistics regression are applied to evaluate the effect of HI after the treatment.

Results

Of the 431 patients comprised, it is observed a significant decrease in HbA1c level (9.04±0.82% at baseline to 8.30±0.99% and 8.00±0.80% at the end, p<0.001), FPG (165.6±40.2 mg/dL at baseline to 157.1±36.3mg/dL and 143.6±32.3mg/dL at the end, p<0.001), weight (74.7±7.1kg at baseline to 74.8±10.0kg and 73.6±8.1kg at the end, p<0.001), insulin dose (49.3±10.8U/d at baseline to 46.7±8.0U/d and 45.2±8.7U/d, p<0.001). The individuals in subgroup with higher baseline HbA1c and longer daily HI time duration gain greater HbA1c decrease after 6 months. Linear regression shows that higher baseline HbA1c level and shorter diabetes duration are significantly in relation to greater HbA1c reduction. Logistics regression reveals that lower weight is associated with a higher possibility of reaching HbA1c<7%. The most common adverse event is hypoglycemia.

Conclusion

HI therapy significantly improves glycemic control, weight, insulin dose, lipid metabolism, β-cell function and insulin resistance of patients with type 2 diabetes after 6 months. Higher baseline HbA1c level and shorter diabetes duration is related to greater clinical response to HI.

Therapeutic Potential of Molecular Hydrogen in Metabolic Diseases from Bench to Bedside

Oxidative stress and chronic inflammation have been implicated in the pathophysiology of metabolic diseases, including diabetes mellitus (DM), metabolic syndrome (MS), fatty liver (FL), atherosclerosis (AS), and obesity. Molecular hydrogen (H₂) has long been considered a physiologically inert gas. In the last two decades, accumulating evidence from pre-clinical and clinical studies has indicated that H₂ may act as an antioxidant to exert therapeutic and preventive effects on various disorders, including metabolic diseases. However, the mechanisms underlying the action of H₂ remain unclear. The purpose of this review was to (1) provide an overview of the current research on the potential effects of H₂ on metabolic diseases; (2) discuss the possible mechanisms underlying these effects, including the canonical anti-oxidative, anti-inflammatory, and anti-apoptotic effects, as well as suppression of ER stress, activation of autophagy, improvement of mitochondrial function, regulation of gut microbiota, and other possible mechanisms. The potential target molecules of H₂ will also be discussed. With more high-quality clinical trials and in-depth mechanism research, it is believed that H₂ will eventually be applied to clinical practice in the future, to benefit more patients with metabolic disease.

Effectiveness and safety of hydrogen inhalation as an adjunct treatment in Chinese type 2 diabetes patients: A retrospective, observational, double-arm, real-life clinical study

Aim

To analyze the effectiveness and safety of hydrogen inhalation (HI) therapy as an adjunct treatment in Chinese type 2 diabetes mellitus (T2DM) patients in a real-life clinical setting.

Methods

This observational, non-interventional, retrospective, double-arm, 6-month clinical study included T2DM patients receiving conventional anti-diabetes medication with or without HI initiation from 2018 to 2021. Patients were assigned to the HI group or non-HI group (control group) after 1:1 propensity score matching (PSM). The mean change in glycated hemoglobin (HbA1c) after 6 months in different groups was evaluated primarily. The secondary outcome was composed of the mean change of fasting plasma glucose (FPG), weight, lipid profile, and homeostasis model assessment. Logistics regression was performed to evaluate the likelihood of reaching different HbA1c levels after 6-month treatment between the groups. Adverse event (AE) was also evaluated in patients of both groups.

Results

In total, 1088 patients were selected into the analysis. Compared to the control group, subjects in HI group maintained greater improvement in the level of HbA1c (-0.94% vs -0.46%), FPG (-22.7 mg/dL vs -11.7 mg/dL), total cholesterol (-12.9 mg/dL vs -4.4 mg/dL), HOMA-IR (-0.76 vs -0.17) and HOMA-β (8.2% vs 1.98%) with all p< 0.001 post the treatment. Logistics regression revealed that the likelihood of reaching HbA1c< 7%, ≥ 7% to< 8% and > 1% reduction at the follow-up period was higher in the HI group, while patients in the control group were more likely to attain HbA1c ≥ 9%. Patients in HI group was observed a lower incidence of several AEs including hypoglycemia (2.0% vs 6.8%), vomiting (2.6% vs 7.4%), constipation (1.7% vs 4.4%) and giddiness (3.3% vs 6.3%) with significance in comparison to the control group.

Conclusion

HI as an adjunct therapy ameliorates glycemic control, lipid metabolism, insulin resistance and AE incidence of T2DM patients after 6-month treatment, presenting a noteworthy inspiration to existing clinical diabetic treatment.

Evaluation of the hydrogen-rich water alleviation potential on mercury toxicity in earthworms using ATR-FTIR and LC-ESI-MS/MS spectroscopy

The toxic effects of mercury in earthworms and the potential alleviation effect of hydrogen-rich water (HRW) using ATR-FTIR and LC-MS analysis methods were investigated. Different concentrations of mercury chloride (H1: 5 µg/mL, H2: 10 µg/mL, H3: 20 µg/mL, H4: 40 µg/mL, and C1: control) and mercury chloride prepared in hydrogen-rich water (H5: 5 µg/mL, H6: 10 µg/mL, H7: 20 µg/mL, H8: 40 µg/mL, and C2: control) were injected into earthworms. The changes and reductions in some bands representing proteins, lipids, and polysaccharides (3280 cm^-1, 2922 cm^-1, 2855 cm^-1, 1170 cm^-1, and 1047 cm^-1) showed that protective effects could occur in groups prepared with hydrogen-rich water. In the FTIR results, it was found that these bands in the H3 group were more affected and decreased by the influence of mercury on earthworms than the H7 group prepared with hydrogen. LC-MS analysis showed that the changes in some ions of the highest dose groups (H4 and H8) were different, and mercury caused oxidative DNA damage in earthworms. When the high-level application groups of mercury, i.e., H4 and H8 were compared with the controls, the ion exchange ([M + H] + ; m/z 283.1) representing the 8-Oxo-dG level in earthworms was higher in the H4 group than the H8 group. This reveals that HRW exhibited the potential ability to alleviate the toxic effects of mercury; however, a longer period of HRW treatment may be necessary to distinguish an obvious effect. The ATR-FTIR spectroscopy provided a rapid and precise method for monitoring the changes in biological tissues caused by a toxic compound at the molecular level.

A Preliminary Study on the Effect of Hydrogen Gas on Alleviating Early CCl4-Induced Chronic Liver Injury in Rats

As a small-molecule reductant substance, hydrogen gas has an obvious antioxidant function. It can selectively neutralize hydroxyl radicals (^•OH) and peroxynitrite (ONOO^•) in cells, reducing oxidative stress damage. The purpose of this study was to investigate the effect of hydrogen gas (3%) on early chronic liver injury (CLI) induced by CCl₄ and to preliminarily explore the protective mechanism of hydrogen gas on hepatocytes by observing the expression of uncoupling protein 2 (UCP2) in liver tissue. Here, 32 rats were divided into four groups: the control group, CCl₄ group, H₂ (hydrogen gas) group, and CCl₄ + H₂ group. The effect of hydrogen gas on early CLI was observed by serological tests, ELISA, hematoxylin and eosin staining, and oil red O staining. Immunohistochemical staining and Western blotting were used to observe the expression of UCP2 in liver tissues. We found that CCl₄ can induce significant steatosis in hepatocytes. When the hydrogen gas was inhaled, hepatocyte steatosis was reduced, and the UCP2 expression level in liver tissue was increased. These results suggest that hydrogen gas might upregulate UCP2 expression levels, reduce the generation of intracellular oxygen free radicals, affect lipid metabolism in liver cells, and play a protective role in liver cells.

Hydrogen gas inhalation ameliorates cardiac remodelling and fibrosis by regulating NLRP3 inflammasome in myocardial infarction rats

It is noteworthy that prolonged cardiac structural changes and excessive fibrosis caused by myocardial infarction (MI) seriously interfere with the treatment of heart failure in clinical practice. Currently, there are no effective and practical means of either prevention or treatment. Thus, novel therapeutic approaches are critical for the long‐term quality of life of individuals with myocardial ischaemia. Herein, we aimed to explore the protective effect of H₂, a novel gas signal molecule with anti‐oxidative stress and anti‐inflammatory effects, on cardiac remodelling and fibrosis in MI rats, and to explore its possible mechanism. First, we successfully established MI model rats, which were then exposed to H₂ inhalation with 2% concentration for 28 days (3 hours/day). The results showed that hydrogen gas can significantly improve cardiac function and reduce the area of cardiac fibrosis. In vitro experiments further proved that H₂ can reduce the hypoxia‐induced damage to cardiomyocytes and alleviate angiotensin II‐induced migration and activation of cardiac fibroblasts. In conclusion, herein, we illustrated for the first time that inhalation of H₂ ameliorates myocardial infarction‐induced cardiac remodelling and fibrosis in MI rats and exert its protective effect mainly through inhibiting NLRP3‐mediated pyroptosis.

Molecular Hydrogen as a Potential Clinically Applicable Radioprotective Agent

Although ionizing radiation (radiation) is commonly used for medical diagnosis and cancer treatment, radiation-induced damages cannot be avoided. Such damages can be classified into direct and indirect damages, caused by the direct absorption of radiation energy into DNA and by free radicals, such as hydroxyl radicals (•OH), generated in the process of water radiolysis. More specifically, radiation damage concerns not only direct damages to DNA, but also secondary damages to non-DNA targets, because low-dose radiation damage is mainly caused by these indirect effects. Molecular hydrogen (H₂) has the potential to be a radioprotective agent because it can selectively scavenge •OH, a reactive oxygen species with strong oxidizing power. Animal experiments and clinical trials have reported that H₂ exhibits a highly safe radioprotective effect. This paper reviews previously reported radioprotective effects of H₂ and discusses the mechanisms of H₂, not only as an antioxidant, but also in intracellular responses including anti-inflammation, anti-apoptosis, and the regulation of gene expression. In doing so, we demonstrate the prospects of H₂ as a novel and clinically applicable radioprotective agent.

Role of Hydrogen in Atherosclerotic Disease: From Bench to Bedside

Atherosclerotic cardiovascular and cerebrovascular diseases are among the leading causes of morbidity and mortality worldwide. Given our recent understanding of its role as a small-molecule antioxidant and anti- inflammatory agent, hydrogen may play an important role in preventing and treating atherosclerotic cardiovascular and cerebrovascular disease. In the past decade, more than 50 publications in the English language literature considered the role of hydrogen as an anti-atherosclerotic agent. In this review, we summarized the pathophysiological characteristics and risk factors associated with atherosclerosis (AS) and the laboratory research data that focuses on hydrogen to prevent and treat this condition, including the responses observed in both animal models and human studies. We will also consider the molecular mechanisms underlying the efficacy of hydrogen molecules with respect to atherosclerotic disease. Future studies might include clinical trials with larger sample populations as well as experiments designed to explore the molecular mechanisms associated with hydrogen treatment in greater depth.

ESRα Promoter Methylation May Modify the Association Between Lipid Metabolism and Type 2 Diabetes in Chinese Farmers

Objective: This study is aimed to explore the potential association among the estrogen receptor alpha (ESRα) promoter methylation, lipid metabolism and the risk of type 2 diabetes mellitus (T2DM). Methods: A total of 1143 rural residents were recruited randomly from Henan Province, China. The circulating methylation levels in ESRα promoter region were determined by quantitative methylation-specific polymerase chain reaction. Serum high density lipoprotein cholesterol (HDL-C), low density lipoprotein cholesterol (LDL-C), triglyceride (TG), total cholesterol (TC) and fasting plasma-glucose (FPG) were measured. Results: The ESRα promoter methylation levels were negatively associated with HDL-C levels whether gender stratification was performed (P < 0.05) and positively correlated with LDL-C in men (P < 0.05). Each unit standard deviation (SD) increment in TG was associated with a 43% increase (95% CI: 1.25, 1.64) in the risks of T2DM in all participants, a 36% increase (95% CI: 1.13, 1.64) in the risks of T2DM in men and a 49% increase (95% CI: 1.21, 1.83) in the risks of T2DM in women. Furthermore, each SD increment in HDL-C was associated with a reduction of 25% (OR = 0.75, 95% CI: 0.58, 0.97) in the risks of T2DM in men, and the risk of T2DM in men may be more susceptible to HDL-C than that in women (P for interaction < 0.05). Additionally, we found that the risk of T2DM in participants with lower methylation levels (≤4.07%) were more susceptible to HDL-C (P for interaction < 0.05). Conclusions: These findings suggested that lipid metabolism was associated with ESRα promoter methylation levels and the risk of T2DM. Besides, the levels of ESRα promoter methylation and gender can modify the association of HDL-C and T2DM.

Potential Therapeutic Applications of Hydrogen in Chronic Inflammatory Diseases: Possible Inhibiting Role on Mitochondrial Stress

Mitochondria are the largest source of reactive oxygen species (ROS) and are intracellular organelles that produce large amounts of the most potent hydroxyl radical (·OH). Molecular hydrogen (H₂) can selectively eliminate ·OH generated inside of the mitochondria. Inflammation is induced by the release of proinflammatory cytokines produced by macrophages and neutrophils. However, an uncontrolled or exaggerated response often occurs, resulting in severe inflammation that can lead to acute or chronic inflammatory diseases. Recent studies have reported that ROS activate NLRP3 inflammasomes, and that this stimulation triggers the production of proinflammatory cytokines. It has been shown in literature that H₂ can be based on the mechanisms that inhibit mitochondrial ROS. However, the ability for H₂ to inhibit NLRP3 inflammasome activation via mitochondrial oxidation is poorly understood. In this review, we hypothesize a possible mechanism by which H₂ inhibits mitochondrial oxidation. Medical applications of H₂ may solve the problem of many chronic inflammation-based diseases, including coronavirus disease 2019 (COVID-19).

Hydrogen Is Promising for Medical Applications

Hydrogen (H2) is promising as an energy source for the next generation. Medical applications using H2 gas can be also considered as a clean and economical technology. Since the H2 gas based on electrolysis of water production has potential to expand the medical applications, the technology has been developed in order to safely dilute it and to supply it to the living body by inhalation, respectively. H2 is an inert molecule which can scavenge the highly active oxidants including hydroxyl radical (·OH) and peroxynitrite (ONOO−), and which can convert them into water. H2 is clean and causes no adverse effects in the body. The mechanism of H2 is different from that of traditional drugs because it works on the root of many diseases. Since H2 has extensive and various effects, it may be called a “wide spectrum molecule” on diseases. In this paper, we reviewed the current medical applications of H2 including its initiation and development, and we also proposed its prospective medical applications. Due to its marked efficacy and no adverse effects, H2 will be a next generation therapy candidate for medical applications.

Effects of long-term hydrogen intervention on the physiological function of rats

The potential therapeutic effects of molecular hydrogen (H₂) have now been confirmed in various human and animal-disease models. However, the effects of H₂ on the physiological function in a normal state have been largely neglected. Hydrogen-rich water (HRW) intake and hydrogen inhalation (HI) are the most common used methods for hydrogen administration, the difference in the effects between HRW intake and HI remains elusive. In the present study, the body weight and 13 serum biochemical parameters were monitored during the six-month hydrogen intervention, all these parameters were significantly altered by oral intake of HRW or HI. Among the 13 parameters, the most striking alterations induced by hydrogen treatment were observed in serum myocardial enzymes spectrum. The results also showed that the changes in these parameters occurred at different time points, and the alterations in most of the parameters were much more significant in HI than HRW. The results of this study provides the basic data for the mechanism research and application of molecular hydrogen in the future.

Hydrogen: A Novel Option in Human Disease Treatment

H₂ has shown anti-inflammatory and antioxidant ability in many clinical trials, and its application is recommended in the latest Chinese novel coronavirus pneumonia (NCP) treatment guidelines. Clinical experiments have revealed the surprising finding that H₂ gas may protect the lungs and extrapulmonary organs from pathological stimuli in NCP patients. The potential mechanisms underlying the action of H₂ gas are not clear. H₂ gas may regulate the anti-inflammatory and antioxidant activity, mitochondrial energy metabolism, endoplasmic reticulum stress, the immune system, and cell death (apoptosis, autophagy, pyroptosis, ferroptosis, and circadian clock, among others) and has therapeutic potential for many systemic diseases. This paper reviews the basic research and the latest clinical applications of H₂ gas in multiorgan system diseases to establish strategies for the clinical treatment for various diseases.

Hydrogen gas protects against ovariectomy-induced osteoporosis by inhibiting NF-κB activation

OBJECTIVES

Osteoporosis is a prevalent condition among postmenopausal women, and lacks satisfactory therapeutic options. Hydrogen (H2) has been shown to be effective in alleviating many diseases. This study aimed to investigate the effects of H2 on inhibiting osteoclastogenesis and bone loss in ovariectomized mice.

METHODS

Osteoclast differentiation from Raw264.7 cells was induced with receptor activator NF-κB ligand (RANKL) with or without 60% H2. The number and resorption activity of osteocalsts were assessed by tartrate-resistant acid phosphatase staining and pit formation assay, respectively. The expression of osteoclast markers and NF-κB phosphorylation were detected by western blot. NF-κB nuclear translocation was assessed by immunofluorescence. NF-κB transcriptional activity was analyzed by luciferase assay. Bone loss in mice was induced by ovariectomy (OVX). OVX mice were given either regular air or 60% H2. Bone structure was analyzed by micro-computed tomography and hematoxylin and eosin staining. Cytokine levels were measured by enzyme-linked immunosorbent assay. The data were analyzed with one-way or two-way ANOVA followed by Bonferroni post hoc tests.

RESULTS

H2 did not have any measurable effect on the proliferation of Raw264.7 cells. The number of osteoclasts and size of resorption pits of RANKL+H2-treated cells were 3 to 4 times less than RANKL treated cells. The expression of osteoclast marker genes of RANKL+H2-treated cells was 30% to 60% lower than RANKL-treated cells (P < 0.05). H2 markedly inhibited RANKL-induced activation, nuclear translocation, and transcriptional activity of NF-κB (P < 0.05, RANKL+H2 vs RANKL). The amount and density of trabecular bone and bone mineral density of ovariectomized mice were significantly less than sham-operated mice (P < 0.05 OVX vs sham). The amount of trabecular bone and bone mineral density of OVX mice that inhaled H2 were more than 40% higher, whereas the levels of serum proinflammatory cytokine interleukin 1β, IL-6, and tumor necrosis factor-α were more than 50% lower than those of OVX mice (P < 0.05).

CONCLUSIONS

These results demonstrated that H2 could be an effective therapeutic agent of postmenopausal osteoporosis.

Hydrogen Attenuates Allergic Inflammation by Reversing Energy Metabolic Pathway Switch

Mechanisms mediating the protective effects of molecular hydrogen (H₂) are not well understood. This study explored the possibility that H₂ exerts its anti-inflammatory effect by modulating energy metabolic pathway switch. Activities of glycolytic and mitochondrial oxidative phosphorylation systems were assessed in asthmatic patients and in mouse model of allergic airway inflammation. The effects of hydrogen treatment on airway inflammation and on changes in activities of these two pathways were evaluated. Monocytes from asthmatic patients and lungs from ovalbumin-sensitized and challenged mice had increased lactate production and glycolytic enzyme activities (enhanced glycolysis), accompanied by decreased ATP production and mitochondrial respiratory chain complex I and III activities (suppressed mitochondrial oxidative phosphorylation), indicating an energy metabolic pathway switch. Treatment of ovalbumin-sensitized and challenged mice with hydrogen reversed the energy metabolic pathway switch, and mitigated airway inflammation. Hydrogen abrogated ovalbumin sensitization and challenge-induced upregulation of glycolytic enzymes and hypoxia-inducible factor-1α, and downregulation of mitochondrial respiratory chain complexes and peroxisome proliferator activated receptor-γ coactivator-1α. Hydrogen abrogated ovalbumin sensitization and challenge-induced sirtuins 1, 3, 5 and 6 downregulation. Our data demonstrates that allergic airway inflammation is associated with an energy metabolic pathway switch from oxidative phosphorylation to aerobic glycolysis. Hydrogen inhibits airway inflammation by reversing this switch. Hydrogen regulates energy metabolic reprogramming by acting at multiple levels in the energy metabolism regulation pathways.

Hydrogen Gas in Cancer Treatment

Gas signaling molecules (GSMs), composed of oxygen, carbon monoxide, nitric oxide, hydrogen sulfide, etc., play critical roles in regulating signal transduction and cellular homeostasis. Interestingly, through various administrations, these molecules also exhibit potential in cancer treatment. Recently, hydrogen gas (formula: H₂) emerges as another GSM which possesses multiple bioactivities, including anti-inflammation, anti-reactive oxygen species, and anti-cancer. Growing evidence has shown that hydrogen gas can either alleviate the side effects caused by conventional chemotherapeutics, or suppress the growth of cancer cells and xenograft tumor, suggesting its broad potent application in clinical therapy. In the current review, we summarize these studies and discuss the underlying mechanisms. The application of hydrogen gas in cancer treatment is still in its nascent stage, further mechanistic study and the development of portable instruments are warranted.

Hydrogen molecules (H2) improve perfusion recovery via antioxidant effects in experimental peripheral arterial disease

Reactive oxygen species (ROS) impair neovascularization and perfusion recovery following limb ischemia in patients with peripheral arterial disease (PAD). Hydrogen molecules (H₂) comprise an antioxidant gas that has been reported to neutralize cytotoxic ROS. The present study investigated whether H₂ may serve as a novel therapeutic strategy for PAD. H₂-saturated water or dehydrogenized water was supplied to mice with experimental PAD. Laser Doppler perfusion imaging demonstrated that H₂-saturated water improved perfusion recovery, decreased the rate of necrosis, increased the capillary density in the gastrocnemius muscle and increased the artery density in the abductor muscle in the ischemic limbs, at 14 and 21 days post-hindlimb ischemia. Ischemic muscle tissue was harvested 7 days after experimental PAD for biochemical testing and H₂ was observed to reduce the levels of malondialdehyde and increase the levels of cyclic guanine monophosphate (cGMP). In cultured endothelial cells, H₂-saturated culture medium resulted in reduced ROS levels, increased tube formation and increased cGMP levels. In macrophages, H₂ decreased cellular ROS levels and promoted M2 polarization. H₂-saturated water increases angiogenesis and arteriogenesis and subsequently improves perfusion recovery in a mouse PAD model via reduction of ROS levels.

The transfer of hydrogen from inert gas to therapeutic gas

Hydrogen is the most abundant chemical element in the universe, and has been used as an inert gas for a long time. More recent studies have shown that molecular hydrogen as a kind of antioxidant, anti-inflammatory, anti-apoptosis, gene expression and signal modulation molecule, can be used for the treatment of many diseases. This review mainly focuses on the research progresses of hydrogen in various medical fields and the possible action mechanisms.

Subcutaneous injection of hydrogen gas is a novel effective treatment for type 2 diabetes

Aims/Introduction

In previous studies, hydrogen gas (H₂₎ administration has clearly shown effectiveness in inhibiting diabetes. Here, we evaluated whether subcutaneous injection of H₂ shows enhanced efficacy against type 2 diabetes mellitus induced in mice by a high‐fat diet and low‐dose streptozotocin treatment.

Material and Methods

H₂ was injected subcutaneously at a dose of 1 mL/mouse/week for 4 weeks. Type 2 diabetes mellitus‐associated parameters were then evaluated to determine the effectiveness of subcutaneous H₂ administration.

Results

The bodyweight of H₂‐treated mice did not change over the course of the experiment. Compared with the untreated control animals, glucose, insulin, low‐density lipoprotein and triglyceride levels in the serum were significantly lower in treated mice, whereas high‐density lipoprotein cholesterol in the serum was significantly higher. Glucose tolerance and insulin sensitivity were both improved in H₂‐treated mice. Diabetic nephropathy analysis showed significant reductions in urine volume, urinary total protein and β2‐microglobulin, kidney/bodyweight ratio, and kidney fibrosis associated with subcutaneous injection of H₂.

Conclusions

Subcutaneous injection of H₂ significantly improves type 2 diabetes mellitus and diabetic nephropathy‐related outcomes in a mouse model, supporting further consideration of subcutaneous injection as a novel and effective route of clinical H₂ administration.