Early Methylglyoxal Exposure Leads to Worsened Cardiovascular Function in Young Rats

Abstract

Background: Though maternal diabetes effects are well described in the literature, the effects of maternal diabetes in postnatal phases are often overlooked. Diabetic individuals have higher levels of circulating glycotoxins, and there is a positive correlation between maternal-derived glycotoxins and circulating glycotoxins in their progeny. Previous studies evaluated the metabolic effects of high glycotoxin exposure during lactation in adult animals. However, here we focus on the cardiovascular system of juvenile rats.

Methods: For this, we used two experimental models: 1. High Methylglyoxal (MG) environment: pregnant Wistar rats were injected with PBS (VEH group) or Methylglyoxal (MG group; 60 mg/kg/day; orally, postnatal day (PND) 3 to PND14). 2. GLO-1 inhibition: pregnant Wistar rats were injected with dimethyl sulfoxide (VEH group) or a GLO-1 inhibitor (BBGC group; 5 mg/kg/day; subcutaneously, PND1-PND5). The offspring were evaluated at PND45.

Results: MG offspring presented cardiac dysfunction and subtly worsened vasomotor responses in the presence of perivascular adipose tissue, without morphological alterations. In addition, an endogenous increase in maternal glycotoxins impacts offspring vasomotricity due to impaired redox status.

Conclusions: Our data suggest that early glycotoxin exposure led to cardiac and vascular impairments, which may increase the risk for developing cardiovascular diseases later in life.

Keywords: BBGC; glycotoxins; lactation; left ventricular dysfunction; methylglyoxal.

Figure 1

Effects of early methylglyoxal exposure during lactation on the phenotype of young offspring. Experimental design (A). Body weight of VEH and MG offspring remains the same before (B) and after weaning (C). The weight of the most affected tissue, the liver, in MG-injected animals was the same in MG and VEH animals (D). Early MG exposure was not able to impact plasma biochemical parameters, namely blood glucose (E), fructosamine (F), total (G) and HDL (H) cholesterol, and triglycerides (I). The weight of mesenteric (J), retroperitoneal (K), and inguinal (L) white adipose tissues was the same between the groups. In the same sense, the weight of interscapular brown adipose tissue (M) was similar between the groups. Two-way ANOVA followed by Sidak’s post hoc test was used for the analysis of time-dependent parameters. Student’s t-test was used for the analysis of time-independent parameters.

Figure 2

Effects of early methylglyoxal exposure during lactation on left ventricular cardiac function. During ex vivo assessment of basal left ventricular intraventricular pressure, MG offspring developed lower systolic pressure (A,B), despite no changes in diastolic pressure (C,D). However, MG hearts also developed lower positive (E,F) and negative (G,H) dP/dt. No changes were observed in all evaluated parameters in response to local ischemia promoted by circumflex artery ligature. Two-way ANOVA followed by Sidak’s post hoc test was used for the analysis of pre-/post-ischaemia data. * p < 0.05 vs. VEH.

Figure 3

Effects of early exposure to methylglyoxal during lactation on vasomotricity. During the vasomotricity experiments, MG animals presented similar responses to the VEH group in the absence of PVAT for ACh (A,C) or SNP (D,F) mediated relaxation, and in PHE (G,I) mediated constriction. However, in the presence of PVAT, the responses were altered in the vessels of MG animals for ACh (B,C) or SNP (E,F) mediated relaxation and in PHE (H,I) mediated constriction. Two-way ANOVA followed by Sidak’s post hoc test was used for the analysis of the influence of PVAT on vasomotricity. * p < 0.05, ** p < 0.01, *** p < 0.001, **** p < 0.0001 vs. VEH.

Figure 4

Effects of early exposure to methylglyoxal during lactation on cardiac and aorta morphology. Despite functional impairments, the morphology of MG hearts and aorta remained similar to the hearts of VEH offspring, evidenced by the similar heart weight (A), cardiomyocyte diameter (B), perivascular (C) and interstitial (D) fibrosis, and aorta thickness (E). Representative images of each parameter are positioned at the right side of the respective graph. Black lines represent, from top to bottom, 2 mm, 25 μm, 40 μm, 100 μm, and 25 μm. Student’s t-test was used.

Figure 5

Effects of early exposure to endogenous glycotoxins during lactation on offspring development and vasomotricity. Experimental design (A). Body weight of VEH and BBGC offspring remains the same before (B) and after weaning (C). Early glycotoxin exposure due to maternal GLO-1 inhibition did not affect liver or heart weight (D,E). No overall differences were observed during the acetylcholine-induced relaxation before (F) or after (G) ascorbic acid incubation. However, comparing the two curves of BBGC offspring before and after ascorbic acid incubation (H), there is an increase in EC₅₀ in BBGC offspring both in basal conditions and after the incubation with ascorbic acid (I). Student’s t-test was used for the analysis of time-independent parameters. Two-way ANOVA followed by Sidak’s post hoc test was used for the analysis of time-dependent parameters and ascorbic acid incubation influence on vasomotricity. * p < 0.05 and *** p < 0.001 vs. VEH.