Objective:

2

To investigate the effect of sennoside A (SA) on atherosclerosis (AS) in type 2 diabetes mellitus (T2DM) mice and its underlying mechanisms.

Methods:

2

Sixty-one 9-week-old AopE

-/-

mice were randomly divided into 6 groups using the random number table: control

model (fed a high-fat diet for 4 weeks

followed by intraperitoneal injection of streptozotocin)

SA low-

medium-

high-doses (15

30

and 45 mg/kg per day

respectively for 8 weeks)

and positive control groups (100 mg/kg metformin per day

for 8 weeks

10 or 11 per group). The body weight and blood glucose levels of the mice were monitored regularly. Serum lipid content was measured using biochemical kits

and fasting insulin levels were qualified using ELIS

A kits. Aortic tissue was examined using Oil Red O

HE

Masson

and Picrosirius red stainings to observe the pathological changes. The mRNA expressions of CD31

VE-cadherin

α-smooth muscle actin (α-SMA) and vimentin were detected by RT-qPCR. The relative protein expressions of organic solute carrier partner (OSCP1)

matrix metalloproteinase 9 (MMP9)

vascular endothelial growth factor A (VEGFA) and p-ERK1/2 proteins were analyzed using Western blot.

In vitro

endothelial cell dysfunction was induced using high glucose combined with oxidized low-density lipoprotein (ox-LDL). These cell groups included the blank control

model

different concentrations of SA (1

30

100 μmol/L)

metformin (Met)

OSCP1 knockdown

SA combined with OSCP1 knockdown

and OSCP1 overexpressing combined with SA groups. Cell morphology was observed under a microscope. Cell proliferation was assessed utilizing cell count kit (CCK)-8 assay

migration was evaluated with scratch test

and invasion ability was determined using transwell assay. The methods for mRNA and protein detection were the same as

in vivo

.

Results:

2

Animal experiments demonstrated that SA and Met improved blood glucose

lipid levels

and insulin sensitivity in T2DM mice

delayed AS progression

and reduced plaque area (

P

<

0.05 or

P

<

0.01). Compared with the model group

SA and Met treatment increased the expressions of CD31 and VE-cadherin

decreased the mRNA expressions of α-SMA and vimentin

and reduced the relative protein levels of OSCP1

MMP9

VEGFA and p-ERK1/2 (

P

<

0.05 or

P

<

0.01). Cell experiments showed that SA and Met can inhibit the morphological changes

excessive proliferation

migration

and invasion of endothelial cells induced by high glucose and ox-LDL (

P

<

0.05 or

P

<

0.01). The trends of mRNA and protein expression were consistent with the results of the animal experiments. In the

si-OSCP1 and si-OSCP1+SA groups

mRNA levels of CD31 and VE-cadherin were increased

while α-SMA and vimentin mRNA levels were reduced (

P

<

0.05 or

P

<

0.01). Additionally

the relative expression levels of these proteins were downregulated (

P

<

0.05 or

P

<

0.01)

and cellular morphological changes and excessive proliferation were reversed (

P

<

0.01). However

OSCP1 overexpression resulted in the opposite effects (

P

<

0.05 or

P

<

0.01).

Conclusions:

2

SA reduces plaque area and stabilizes plaque in T2DM mice. Its anti-AS effects may be mediated through the downregulation of OSCP1/ERK1/2 signaling pathway

which helps reverse endothelial-to-mesenchymal transition.