Yiqi Yangyin and Huatan Quyu granule can improve skeletal muscle energy metabolism in a type 2 diabetic rat model by promoting the AMPK/SIRT/PGC-1α signalling pathway

To investigate how Yiqi Yangyin and Huatan Quyu granule (YYHQ) improves skeletal muscle insulin resistance in a type 2 diabetic rat model and to discover whether the molecular mechanism is related to the promotion of the AMPK/SIRT/PGC-1α signalling pathway.

Rats were randomly divided into 4 groups: the normal group, the model group, the YYHQ granule group, and the pioglitazone group. The type 2 diabetic rat model was established by feeding a high-fat diet for 5 weeks along with a single intraperitoneal injection of 30 mg/kg streptozotocin (STZ). After modelling successfully, the appropriate drug was intragastrically administered to diabetic rats for 2 weeks, once per day. The YYHQ granule group was given a dose of 4.8 g/kg body weight per day, the pioglitazone group was given a dose of 1.35 mg/kg body weight per day. The doses for both groups were equivalent to the clinical equivalent dose based on a previous study. Other groups were gavaged with the same amount of saline water. Body weight, food intake, water intake, urine volume and grip strength were recorded weekly. The fasting blood glucose(FBG) was determined weekly using blood glucose test strips. The related glucose and lipid metabolism indexes, e.g., fasting insulin (Fins), glycated haemoglobin (GHb), HOMA-IR, ISI, triglycerides (TG), total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C) and free fatty acid (FFA), were determined using biochemical method. The mRNA expression levels of adenosine monophosphate-activated protein kinase (AMPK), peroxisome proliferator-activated receptor gamma coactivator-1 alpha (PGC-1α), carnitine palmitoyl transterase-1 (CPT-1), Sirtuin 1 (SIRT1), and Sirtuin 3 (SIRT3) were assessed using quantitative real-time PCR (qRT-PCR). The protein expression levels of creatine kinase (CK), Ca²⁺ ATPase, α-Actin, AMPK, PGC-1α and CPT-1 were determined using enzyme-linked immunosorbent assay method (ELISA).

Body weight decreased significantly (P < .01), food intake, water intake and urine volume increased significantly (P < .01), and grip strength decreased significantly (P < .01) in the model group compared with the normal group. The levels of FBG, Fins, GHb and HOMA-IR increased significantly (P < .01), and the ISI decreased significantly (P < .01) in the model group. The levels of TG, TC, LDL-C and FFA increased significantly (P < .05 or P < .01), and the level of HDL-C decreased significantly (P < .05) in the model group. These changes were reversed after treatment with YYHQ granule or pioglitazone. Compared with the model group, the YYHQ granule and pioglitazone groups significantly improve body weight, water intake and urine volume (P < .05 or P < .01), however, both treatments had no significant effect on food intake (P > .05). The levels of FBG, Fins, GHb, HOMA-IR and ISI were improved significantly (P < .01) and the levels of TG, TC and LDL-C were improved significantly (P < .05 or P < .01), however, both treatments had no significant effect on the levels of HDL-C and FFA (P > .05). Further results indicated that YYHQ granule significantly decreased the mRNA expression of AMPK, PGC-1α, CPT-1, SIRT1 and SIRT3 in skeletal muscle (P < .01) and the pioglitazone group showed similar effects; moreover, the protein expression levels of CK, Ca²⁺ATPase, α-Actin, AMPK, PGC-1α and CPT-1 in skeletal muscle significantly decreased (P < .01), however, pioglitazone had no significant effect on CK and α-Actin (P > .05).

The possible molecular mechanism of YYHQ granule improving skeletal muscle insulin resistance in a type 2 diabetic rat model may be related to the stimulation of energy metabolism in skeletal muscle via the AMPK/SIRT/PGC-1α signalling pathway.