Maternal high fat diet compromises survival and modulates lung development of offspring, and impairs lung function of dams (female mice)

Abstract

Background: Epidemiological studies have identified strong relationships between maternal obesity and offspring respiratory dysfunction; however, the causal direction is not known. We tested whether maternal obesity alters respiratory function of offspring in early life.

Methods: Female C57Bl/6 J mice were fed a high or low fat diet prior to and during two rounds of mating and resulting pregnancies with offspring lung function assessed at 2 weeks of age. The lung function of dams was measured at 33 weeks of age.

Results: A high fat diet caused significant weight gain prior to conception with dams exhibiting elevated fasting glucose, and glucose intolerance. The number of surviving litters was significantly less for dams fed a high fat diet, and surviving offspring weighed more, were longer and had larger lung volumes than those born to dams fed a low fat diet. The larger lung volumes significantly correlated in a linear fashion with body length. Pups born from the second pregnancy had reduced tissue elastance compared to pups born from the first pregnancy, regardless of the dam's diet. As there was reduced offspring survival born to dams fed a high fat diet, the statistical power of lung function measures of offspring was limited. There were signs of increased inflammation in the bronchoalveolar lavage fluid of dams (but not offspring) fed a high fat diet, with more tumour necrosis factor-α, interleukin(IL)-5, IL-33 and leptin detected. Dams that were fed a high fat diet and became pregnant twice had reduced fasting glucose immediately prior to the second mating, and lower levels of IL-33 and leptin in bronchoalveolar lavage fluid.

Conclusions: While maternal high fat diet compromised litter survival, it also promoted somatic and lung growth (increased lung volume) in the offspring. Further studies are required to examine downstream effects of this enhanced lung volume on respiratory function in disease settings.

Keywords: Immune training; Inflammation; Lung development; Lung function; Maternal obesity.

Fig. 1

Overview of the experiment. From 4 weeks of age, C57Bl/6 J female mice (n = 28) were separated into 2 treatment groups and fed either a low fat diet (LFD, n = 14) or high fat diet (HFD, n = 14). Fasting glucose and insulin levels were determined in these female mice after being fed the diets for 5, 7, 9, 11 and 18 (glucose only) weeks. A glucose tolerance test (GTT) was performed after female mice had been fed either diet for 11 weeks. Female mice were first mated with C57Bl/6 J male mice, after dams had been fed either diet for 12 weeks. Three weeks later, offspring were born. Dams were re-mated 1 week after their first litters were removed at 2 weeks of age. The lung function of all surviving offspring (of both pregnancies) was measured when these mice reached 2 weeks of age. After lung function assessments were completed, BALF was collected from most neonates to determine the proportions of major cell types, and levels of cytokines and adipokines. In a small subset of the neonates, lungs were fixed for structural assessment. After eating the LFD or HFD for 29 weeks, the dams had their lung function and responsiveness to methacholine measured, with BALF also collected to determine the proportions of major cell types, and levels of cytokines and adipokines

Fig. 2

Female C57Bl/6 J gained more weight when fed a high fat diet. From 4 weeks of age, female mice were fed either a low fat diet (LFD, n = 14) or high fat diet (HFD, n = 14). Female mice were mated with male mice, first after dams were fed either diet for 12 weeks, and secondly 1 week after the first litter of 2 week-old offspring were tested for lung function. Dams were weighed on a weekly basis until mice were mated for the first time, with a further weighing immediately prior to the second mating. Data are shown as mean ± SEM for n = 14 mice/treatment. In (a), body weights and in (b) percentage weight gain are shown (*p < 0.05)

Fig. 3

Female C57Bl/6 J mice fed a high fat diet developed metabolic dysfunction. From 4 weeks of age, female mice were fed either a low fat diet (LFD, n = 14) or high fat diet (HFD, n = 14). Female mice were mated with male mice, firstly after dams were fed either diet for 12 weeks, and secondly 1 week after the first litter of 2 week-old offspring were tested for lung function. In (a), fasting glucose at 5, 7, 9, 11 and 18 weeks after consuming either diet. In (b), fasting insulin at 7, 9, and 11 weeks after consuming either diet. In (c), results of glucose tolerance tests are shown for dams tested 11 weeks after consuming either diet, with glucose levels at various times post-injection of mice with glucose (1 g glucose/kg body weight), and (d), the area under the curve for these tests. Data are shown as mean ± SEM for n = 14 mice/treatment (*p < 0.05)

Fig. 4

The lung volume of offspring and dams was increased by maternal consumption of a high fat diet. From 4 weeks of age, female mice were fed either a low fat diet (LFD, n = 14) or high fat diet (HFD, n = 14). Female mice were mated with male mice, first after dams were fed either diet for 12 weeks, and secondly 1 week after the first litter of offspring was tested for lung function. Offspring of both pregnancies had their lung function measured at 2 weeks of age. The dams had their lung function measured after eating the LFD or HFD for 29 weeks. In (a), thoracic lung volume; (b), specific airway resistance (SR_aw); (c), specific tissue damping (SG); (d), specific tissue elastance (SH); and (e), hysteresivity (G/H) measured for offspring born to the first and second matings, and dams (respectively). Data are shown as mean + SEM, with number of mice (n)/treatment shown (*p < 0.05)

Fig. 5

Dams fed a high fat diet for 29 weeks were more responsive to methacholine. From 4 weeks of age, female mice were fed either a low fat diet (LFD, n = 14) or high fat diet (HFD, n = 13). Female mice were mated with male mice, first after dams were fed either diet for 12 weeks, and secondly 1 week after the first litter of 2 week-old offspring were tested for lung function. After eating the LFD or HFD for 29 weeks, the dams had their lung function measured following an initial challenge with saline and then increasing doses of methacholine. In (a), airway resistance; in (b), tissue damping; and, in (c), tissue elastance are shown. Data are shown as mean ± SEM (*p < 0.05)

Fig. 6

Increased TNF, IL-5 and IL-33 are observed in the lungs of dams fed a high fat diet, but not their offspring. From 4 weeks of age, female mice were fed either a low fat diet (LFD, n = 14) or high fat diet (HFD, n = 13). Female mice were mated with male mice, first after mice were fed either diet for 12 weeks, and secondly 1 week after the first litter of 2 week-old offspring were tested for lung function. The proportions of: (a) major cell types; (b) levels of TNF, IL-5, and IL-33; and, (c) adiponectin and leptin were measured in the BALF of offspring (2 week-old, n ≥ 5) and dams fed a LFD or HFD for 29 weeks. Data are shown as mean ± SEM (*p < 0.05), with some data points overlapping (particularly for part (A) dams)

Fig. 7

Dams fed a high fat diet had reduced fasting glucose levels prior to a second pregnancy, and BALF levels of IL-33 and leptin at the experimental endpoint. From 4 weeks of age, female mice were fed either a low fat diet (LFD, n = 14) or high fat diet (HFD, n = 13). Female mice were mated with male mice twice, after mice were fed either diet for 12 and then 18 weeks, with (a) fasting glucose measured immediately prior to second mating. BALF levels of (b) IL-33 and (c) leptin, from dams fed a LFD or HFD for 29 weeks, were measured. Data are shown as mean ± SEM (*p < 0.05)