This study investigated the effects of long-term high fat diet-induced hyperlipidemia and oxidative stress on placenta growth factor (PLGF) expression in mouse heart. The high fat diet significantly reduced PLGF protein levels in all treatment groups, with the greatest decrease observed in mice with extreme hyperlipidemia. PLGF expression correlated with plasma cholesterol and oxidative stress levels but not glucose or insulin levels. In contrast, levels of vascular endothelial growth factor A and its receptor VEGFR1 were unaffected by diet. The results support the hypothesis that hyperlipidemia inhibits PLGF expression, potentially through increased oxidative stress.

1. Placenta Growth Factor Expression in Mouse Heart Correlates
with Long Term Diet Induced Hyperlipidemia and Oxidative Stress
Asitha T Silva, Pamela G Lloyd
Department of Physiological Sciences, Oklahoma State University, Stillwater OK 74078
Funding : NIH R01 HL084494 (PL)
Figure 2 (above left): Feeding of a high fat diet for 6 mo increased plasma insulin in all groups
(dark bars) compared to the low fat diet (light bars). Figure 3 (above right): All HF fed groups
showed significantly high HOMA IR. (Legend applies to all figures).
Figure 7 (above left): The HF diet significantly reduced PLGF protein expression in heart in all
treatment groups. Figure 8: PLGF protein in mouse heart is well correlated with plasma
cholesterol and plasma isoprostane (above right), but not with glucose during IPGTT (120 min),
fasting insulin or HOMA-IR (above center). N=64
Conclusions
• These data shows that PLGF expression is significantly
decreased in mouse heart by a high fat diet. The
decrease is correlated with cholesterol and isoprostane,
providing strong support for our hypothesis that PLGF
expression is inhibited by hyperlipidemia.
• The mechanism of inhibition may involve oxidative
stress, consistent with the previously described negative
influence of oxidative stress on collateral enlargement.
Figure 1: IPGTT in C57BL/6 mice (above left) and ApoE-/-
mice (above right). *, p<0.05 for males vs low fat fed
group of the same strain at the same time point; +,
p<0.05 for females vs low fat fed group of the same strain
at the same time point. See Figure 2 for legend.
Figure 9 (above left): The high fat diet did not affect VEGF-A
protein levels. Figure 10 (above right): The high fat diet did not
affect VEGFR1 protein level.
Figure 4 (above left): Feeding of a high fat diet increased plasma cholesterol in all the
treatment groups. Figure 5 (above center): High fat fed ApoE-/- mice had elevated plasma
triglycerides compared to the low fat fed ApoE -/- mice, as well as all C57BL/6 groups. Figure 6
(above right): Plasma 8-isoprostane was measured as a biomarker for oxidative stress. High fat
fed mice showed increased oxidative stress, compared to low fat fed groups.
ApoE -/-
C57BL/6J
M F M F
ApoE -/-
C57BL/6J
M F M F
ApoE -/-
C57BL/6J
M F M F
ApoE -/-
C57BL/6J
M F M F
ApoE -/-
C57BL/6J
M F M F
• Arteriogenesis (collateral artery remodeling) is a
vital adaptation of the vasculature in response to
occlusion which serves to improve O2 and nutrient
delivery to distal tissue decreasing ischemic injury.
• Stimulation of arteriogenesis would be highly
beneficial in diabetics, who are especially prone to
develop ischemic cardiovascular disease. However,
arteriogenesis is suppressed in diabetes by an
undefined mechanism.
• Placenta growth factor (PLGF) is a key arteriogenic
factor; thus, we hypothesized that decreased PLGF
levels might contribute to impaired
arteriogenesis in diabetes.
Introduction
• Three mouse models of long term (6 mo) diet-
induced metabolic dysfunction in both genders:
• Hyperglycemic + hypercholesterolemic
(high fat fed C57BL/6; HG/HL, n=18)
• Moderately hyperlipidemic (low fat fed
ApoE-/-; HL, n=12)
• Extremely hyperlipidemic (high fat fed
ApoE-/-; EXHL, n=15)
• Normoglycemic + normolipidemic control
group (low fat fed C57BL/6; CONT, n=18)
• Metabolic phenotype was confirmed by
measuring plasma cholesterol, triglycerides,
insulin, and isoprostane; and by intraperitoneal
glucose tolerance testing (IPGTT).
• Cardiac PLGF, VEGF, and PLGF receptor (VEGFR1)
protein levels were measured by ELISA.
• Regression analysis of PLGF protein levels vs
metabolic parameters was performed.
Methods
Results
• C57BL/6 mice fed the high fat diet showed profound
hyperglycemia, hyperinsulinimia, and high HOMA IR. In
contrast, blood glucose levels were only slightly affected
by the high fat diet in ApoE-/- mice, but these animals
showed hyperinsulinemia.
• Feeding of a high fat diet increased plasma cholesterol in
both male and female C57BL/6 relative to low fat fed
C57BL/6 mice, but cholesterol levels in the high fat fed
group were still lower than those in ApoE-/- male and
female mice on either a low or high fat diet.
• All C57BL/6 mice showed normal triglyceride levels,
regardless of diet. ApoE-/- mice fed a high fat diet
displayed high triglyceride levels.
• The high fat diet significantly reduced PLGF protein in
cardiac tissue from all groups.
• The greatest diet-induced decrease in PLGF expression
was observed in ApoE-/- mice (both males and females).
This finding suggests that the combination of extreme
hyperlipidemia and hyperinsulinemia may have a greater
inhibitory effect on PLGF expression than moderate
hyperlipidemia or hyperglycemia/hyperinsulenimia
alone.
• Oxidative stress was highest in the extremely
hyperlipidemic groups, suggesting a potential
mechanism for inhibition of PLGF expression in these
groups.
• Expression of VEGFA and VEGFR1 were not affected by
diet.
Discussion
Conclusions