Hyperbaric oxygen therapy attenuates D-galactose-induced-age-related cardiac dysfunction through mitigating cardiac mitochondrial dysfunction in pre-diabetic rats
Authors: Bo-Htay C , Shwe T , Palee S , Pattarasakulchai T , Shinlapawittayatorn K , Chattipakorn S , Chattipakorn N 
Published: November 2020

Abstract

Background
D-galactose (D-gal) induced ageing has been shown to exacerbate left ventricular (LV) dysfunction via worsening of apoptosis and mitochondrial dysfunction in the heart of obese rats. Hyperbaric oxygen therapy (HBOT) has been demonstrated to exert anti-inflammatory and anti-apoptotic effects in multiple neurological disorders. However, the cardioprotective effect of HBOT on inflammation, apoptosis, LV and mitochondrial functions in D-gal induced ageing rats in the presence of obese-insulin resistant condition has never been investigated.

Purpose
We sought to determine the effect of HBOT on inflammation, apoptosis, mitochondrial functions and LV function in pre-diabetic rats with D-gal induced ageing. We hypothesized that HBOT attenuates D-gal induced cardiac mitochondrial dysfunctions and reduces inflammation and apoptosis, leading to improved LV function in pre-diabetic rats.

Methods
Forty-eight male Wistar rats were fed with either normal diet or high-fat diet for 12 weeks. Then, rats were treated with either vehicle groups (0.9% NSS, subcutaneous injection (SC)) or D-gal groups (150 mg/kg/day, SC) for 8 weeks. At week 21, rats in each group were equally divided into 6 sub-groups: normal diet fed rats treated with vehicle (NDV) sham, normal diet fed rats treated with D-gal (NDDg) sham, high fat diet fed rats treated with D-gal (HFDg) sham, high fat diet fed rats treated with vehicle (HFV) + HBOT, NDDg + HBOT and HFDg + HBOT. Sham treated rats were given normal concentration of O2 (flow rate of 80 L/min, 1 ATA for 60 minutes), whereas HBOT treated rats were subjected to 100% O2 (flow rate of 250 L/min, 2 ATA for 60 minutes), given once daily for 2 weeks.

Results
Under obese-insulin resistant condition, D-gal-induced ageing aggravated LV dysfunction (Fig 1A) and impaired cardiac mitochondrial function, increased cardiac inflammatory and apoptotic markers (Fig 1B). HBOT markedly reduced cardiac TNF-α level and TUNEL positive apoptotic cells, and improved cardiac mitochondrial function as indicated by decreased mitochondrial ROS production, mitochondrial depolarization and mitochondrial swelling, resulting in the restoration of the normal LV function in HFV and NDDg rats, compared to sham NDDg rats. In addition, in HFDg treated rats, HBOT attenuated cardiac TNF-α level, TUNEL positive apoptotic cells and cardiac mitochondrial dysfunction, compared to sham HFDg rats, leading to improved cardiac function as indicated by increased %LV ejection fraction (LVEF) (Figure 1).

Conclusion
HBOT efficiently alleviates D-gal-induced-age-related LV dysfunction through mitigating inflammation, apoptosis and mitochondrial dysfunction in pre-diabetic rats.
Figure 1

Funding Acknowledgement
Type of funding source: Public grant(s) – National budget only. Main funding source(s): 1. The National Science and Technology Development Agency Thailand, 2. Thailand Research Fund Grants