Objective

2

To observe the effect and possible mechanism of

Tangbikang

（糖痹康） on diabetic sciatic neuropathy in diabetes.

Methods

2

Sixty male SD rats were randomly divided into normal group， model group， lipoic acid group and

Tangbikang

high-， medium- and low-dose groups， with 10 rats in each group. Except for the normal group， rats were fed with high-fat and high-sugar diet plus intraperitoneal injection of streptozotocin to establish diabetes model. After successful modeling， corresponding interventions including 0.0268 g/（kg·d） of lipoic acid injection intraperitoneally injected， 2.5， 1.25， and 0.625 g/d of

Tanbikang

granules by gavage， and 10 ml/kg of normal saline by gavage were respectively taken in lipoic acid group，

Tangbikang

high-， medium- and low-dose groups， normal group and model group. All interventions continued for 12 weeks. Before medication and after 4， 8 and 12 weeks of treatment， the blood glucose and body weight of each group were measured. After 12 weeks， the thermal pain threshold and sciatic nerve motor nerve conduction velocity （MNCV） were measured. The sciatic nerves of rats were taken， and the oxidative stress indicators including superoxide dismutase （SOD） and Malondialdehyde （MDA）， the inflammatory factors including interleukin-1β （IL-1β） and tumor necrosis factor-α （TNF-α）， and mitochondrial energy metabolism indicators including nicotinamide adenine dinucleotide （NAD

+

）， reduced coenzyme （NADH

+

） and adenosine triphosphate （ATP） were detected. Hematoxylin eosin （HE） staining was used to detect the histological morphology of the sciatic nerve sections， and the ultrastructure of the sciatic nerve was observed by electron microscopy. The expression of adenylate-activated protein kinase （AMPK）/ sirtuin 3 （SIRT3） pathway-related proteins in sciatic nerve were detected including phosphorylated AMP-activated protein kinase （p-AMPK）， AMPK， peroxisome proliferator-activated receptor coactivator 1α （PGC-1α）， SIRT3， neuronal nitric oxide synthase （nNOS） and mitochondrial transcription factor A （TFAM）.

Results

2

After 4， 8 and 12 weeks of treatment， the blood glucose of

Tangbikang

high- and medium-groups were significantly lower than that of the model group （

P

＜0.05 or

P

＜0.01）. There was no signi-ficant difference in body weight between all the intervention groups and the model group at each timepoint （

P

＞0.05）. After 12 weeks of treatment， the model group had increased thermal pain threshold， MDA， IL-1β， TNF-α and NADH

+

， as well as decreased MNCV， SOD， NAD

+

， NAD

+

/NADH

+

， ATP levels and protein expressions of PGC-1α， SIRT3， TFAM and nNOS as compared to the normal group （

P

＜0.05 or

P

＜0.01）. Compared to those in the model group， the thermal pain threshold， MDA， IL-1β and TNF-α levels decreased， while MNCA and SOD levels increased in all

Tangbikang

groups and the lipoic acid group， and

Tangbikang

high-dose group was superior to the medium- and low-dose groups （

P

＜0.05 or

P

＜0.01） in the above-mentioned indicators but MDA. Compared to those in the model group， the NAD

+

， NAD

+

/NADH

+

and

ATP in all intervention groups increased； the protein expressions of PGC-1α， SIRT3， TFAM and nNOS in lipoic acid group and

Tangbikang

high- and medium-dose groups increased （

P

＜0.05 or

P

＜0.01）； the

Tangbikang

high-dose group was superior to the lipoic acid group in increasing NAD

+

/NADH

+

and ATP， and was superior to the medium- and low-dose groups （

P

＜0.05） in increasing PGC-1α and TFAM.Light and electron microscopy showed that in the model group， the structure of the sciatic nerve fibers was damaged， and the mitochondrial structure was disordered， with severly destroyed myelin sheath lamellar structure， cracks and vacuoles appearing in the myelin sheath， and obvious demyelinating lesions； the pathogenic damage of sciatic nerve fibers in all intervention groups was improved to varying degrees， and the lipoic acid group and

Tangbikang

high-dose group improved more significantly.

Conclusion

2

Tangbikang

may play repairing and neuro-protecting role in diabetes peripheral neuropathy by regulating the sciatic nerve AMPK/SIRT3 pathway， inhibiting mitochondrial oxidative stress， reducing inflammatory response， and improving mitochondrial energy metabolism.