Impact of 8-week cold-and warm water swimming training combined with cinnamon consumption on serum METRNL, HDAC5, and insulin resistance levels in diabetic male rats.

OBJECTIVE: Numerous studies have reported the beneficial effects of exercise and the use of herbal supplements in improving type 2 diabetes and insulin resistance. However, there are still many unanswered questions about the effects of cold and hot water, exercise, and herbal supplements on meteorine-like protein (METRNL), which is considered one of the key factors influencing insulin resistance improvement in this condition. Hence, the current study aimed to address these knowledge gaps and investigate the effects of 8 weeks of warm and cold-water swimming exercise with cinnamon consumption on serum levels of METRNL, histone deacetylase-5 (HDAC5), and insulin resistance in diabetic male rats.

METHODS: For this purpose, 70 diabetic male rats were randomly divided into seven groups (10 rats in each group) H ealthy control (HC) , Diabetic control , swimming training in cold water (temperature 5 °C) , swimming training at 5‌‌ °C + cinnamon consumption (200 mg/kg body weight) , swimming training in warm water (temperature 36-35 °C) , swimming training in warm water (temperature 36-35 °C) + consumption of cinnamon, and consumption of cinnamon only.

RESULTS: The present study revealed a significant increase in serum METRNL concentration in the cold-water swimming + cinnamon consumption group (p < 0.05). However, no significant changes were observed in insulin levels and HOMA-IR across the different groups (p > 0.05). Additionally, noteworthy findings included a significant reduction in HDAC5 levels in both the cold-water swimming group and the cold-water swimming + cinnamon consumption group, as well as a significant decrease in fasting blood sugar (FBS) levels in all groups compared to the HC group (p < 0.05).

CONCLUSIONS: The results of the present study demonstrate that the combination of cold-water swimming exercises and cinnamon extract consumption led to notable increases in serum METRNL concentration. Additionally, significant reductions were observed in HDAC5 and FBS levels. These findings highlight the potential effectiveness and benefits of the combination of cold-water swimming exercises and cinnamon extract consumption as an approach to improve diabetes-related indices.