Effects of short-term thiamine supplementation on glucose balance and glucagon-like peptide-1 levels in diabetic rats

As a prominent global metabolic condition, Diabetes mellitus (DM) is primarily identified by chronic elevations in blood glucose levels. Studies indicate that vitamin B1 (thiamine) possesses the capacity to enhance glucose tolerance and offers therapeutic potential for managing diabetes. This investigation was designed to explore the effects of thiamine supplementation on glucagon-like peptide-1 (GLP-1) concentrations and glucose homeostasis within an experimental diabetic model. The study utilized twenty-eight male adult Sprague-Dawley rats partitioned into four distinct cohorts (n=7 each): control, thiamine-supplemented control, diabetes (DM), and thiamine-supplemented diabetes. Diabetes was created via an intraperitoneal injection of streptozotocin (STZ; 70 mg/kg); subjects displaying blood glucose levels above 200 mg/dL after three days were categorized as diabetic. Over the 15-day trial, thiamine was provided through drinking water at a 0.2% concentration. Assessments included glucose (GTT) and insulin (ITT) tolerance tests, along with analysis of serum biochemistry, insulin, and GLP-1 levels. Furthermore, insulin resistance, beta-cell performance were evaluated using homeostatic model assessment of insulin resistance (HOMA-IR), homeostatic model assessment of beta-cell function (HOMA-B), and quantitative insulin sensitivity check index (QUICKI) indices. Diabetic rats exhibited significantly increased serum triglyceride, glucose, and HDL-C levels relative to the controls ( p < 0.05). Insulin ( p <0.01) and GLP-1 levels ( p < 0.001) were markedly elevated in DM group, whereas GLP-1 levels were markedly reduced in the control + thiamine group ( p < 0.001). HOMA-IR was increased ( p < 0.01), while HOMA-B and QUICKI indices were decreased ( p < 0.05) in diabetic rats. Thiamine supplementation significantly improved glucose and insulin tolerance and reduced glucose and insulin area under the curve (AUC) values ​​in diabetic rats. These findings suggest that while thiamine supplementation may potentially offer therapeutic benefits in the management of diabetes, longer-term administration of thiamine supplementation is required for more effective results.