Effects of swimming training in hot and cold temperatures combined with cinnamon supplementation on HbA1C levels, TBC1D1, and TBC1D4 in diabetic rats

Diabetes is a global health crisis, with prevalence projected to increase dramatically. Current treatments often fall short, highlighting the need for non-pharmacological interventions. This study focuses on the potential benefits of combining exercise and herbal supplements. Previous research indicated that resistance training can improve glucose levels and insulin resistance, potentially through the modulation of meteorin-like protein (METRNL) and its effects on TBC1D1 and TBC1D4 phosphorylation. TBC1D1 and TBC1D4 are crucial regulators of glucose transport via GLUT4 translocation, influenced by insulin, muscle contraction, and AMPK. Their activity is intricately linked to insulin signaling pathways and glucose homeostasis. Glycated hemoglobin (HbA1c) levels serve as a key indicator of long-term blood glucose control. Insulin and exercise both promote glucose transport by increasing GLUT4 translocation to the cell membrane; however, the precise mechanisms remain an area of ongoing research. Cold water immersion and cinnamon supplementation have also shown promise in improving glucose tolerance and insulin sensitivity; cold exposure activates thermogenesis and improves metabolic responses while cinnamon modulates insulin receptor activity. Therefore, this study hypothesized that combining cold-water swimming and cinnamon supplementation would synergistically improve glucose control in diabetic rats by affecting TBC1D1, TBC1D4, and HbA1c levels.

The literature review extensively examined the individual effects of exercise training, cold water immersion, and cinnamon supplementation on glucose metabolism. Studies on resistance training demonstrated its efficacy in reducing glucose levels and improving insulin sensitivity. The role of METRNL, TBC1D1, and TBC1D4 in mediating these effects was explored. The existing literature on cold water immersion highlighted its potential in improving glucose tolerance and insulin sensitivity. Additionally, studies reviewed the mechanisms by which cinnamon supplementation enhances insulin sensitivity by affecting insulin receptor activity. However, the combined effects of these interventions remained largely unexplored, especially concerning their effects on TBC1D1 and TBC1D4, prompting this investigation.

Ninety-one rats (13 healthy controls, 78 diabetic rats induced by streptozotocin injection) were randomly assigned to seven groups (n=13 per group): healthy control (HC), diabetic control (DC), cold water swimming (5°C) (S5), cold water swimming (5°C) + cinnamon (200 mg/kg) (S5+Ci), warm water swimming (35-36°C) (S35), warm water swimming (35-36°C) + cinnamon (S35+Ci), and cinnamon supplementation only (Ci). Rats underwent an acclimation period to cold water, followed by 8 weeks of swimming training (4 minutes, 5 days/week). Cinnamon supplementation was delivered via drinking water. After 8 weeks, blood samples were collected to measure HbA1c, TBC1D1, and TBC1D4 using ELISA kits. Data were analyzed using one-way ANOVA and Tukey's post hoc test. Effect sizes were also calculated.

The study revealed significant group differences in TBC1D4 (F(6,84)=5.92, p<0.001, η² = 0.297), TBC1D1 (F(6,84)=8.51, p<0.001, η² = 0.378), and HbA1c (F(6,84) 6.25, p<0.001, η² = 0.309). Post-hoc analysis showed that TBC1D4 and TBC1D1 levels were significantly higher in the diabetic control and warm water swimming groups compared to the healthy control group (p<0.001). Crucially, the S5+Ci group (cold water swimming + cinnamon) exhibited significantly lower levels of TBC1D1, TBC1D4, HbA1c, and glucose compared to all other groups (p<0.05). The effect sizes were substantial, indicating strong effects of the intervention. Specifically, the cold water swimming group (S5) showed significantly lower HbA1c compared to the diabetic control group (p=0.018). The cinnamon supplementation alone group also showed significantly lower HbA1c compared to the diabetic control group (p<0.001).

The findings support the hypothesis that combining cold water swimming training and cinnamon supplementation effectively reduces markers of diabetes. The lower TBC1D1 and TBC1D4 levels in the S5+Ci group suggest improved insulin sensitivity and glucose uptake. This aligns with previous research demonstrating the benefits of cold exposure and cinnamon on glucose homeostasis. The significant reduction in HbA1c further validates the efficacy of the combined intervention. The study also contributes new data by comparing the effects of cold versus warm water swimming, highlighting the superior effects of cold water. This suggests that cold exposure may activate mechanisms beyond simple caloric expenditure, potentially involving brown adipose tissue and other thermogenic processes that benefit glucose metabolism. While cinnamon supplementation alone reduced HbA1c, its combined effect with cold water swimming was markedly more significant.

This study demonstrated that eight weeks of cold water swimming combined with cinnamon supplementation significantly reduced TBC1D1, TBC1D4, and HbA1c levels in diabetic rats. This non-traditional exercise approach coupled with cinnamon supplementation represents a potentially effective and accessible strategy to improve glucose control and insulin sensitivity. Future research could explore the underlying mechanisms, optimize the intervention parameters, and evaluate its efficacy in humans with type 2 diabetes.

The study utilized a rat model, which may limit the generalizability to humans. The sample size, while sufficient for statistical analysis, could be increased for enhanced power. Further research is needed to elucidate the specific mechanisms through which cold water immersion and cinnamon synergistically improve glucose metabolism. Long-term effects and potential adverse effects of the combined intervention also warrant investigation.