Respective contributions of maternal insulin resistance and diet to metabolic and hypothalamic phenotypes of progeny

Abstract

Maternal obesity can influence susceptibility to obesity and type 2 diabetes in progeny. We examined the relationship of maternal insulin resistance (IR), a metabolically important consequence of increased adiposity, to adverse consequences of obesity for fetal development. We used mice heterozygous for a null allele of the insulin receptor (Insr) to study the contributions of maternal IR to offspring phenotype without the potential confound of obesity per se, and how maternal consumption of high-fat diet (HFD) may, independently and interactively, affect progeny. In progeny fed a 60% HFD, body weight and adiposity were transiently (5-7 weeks) increased in wild-type (+/+) offspring of Insr(+/-) HFD-fed dams compared to offspring of wild-type HFD-fed dams. Offspring of HFD-fed wild-type dams had increased body weight, blood glucose, and plasma insulin concentrations compared to offspring of chow-fed wild-type dams. Quantification of proopiomelanocortin (POMC) and neuropeptide-Y (NPY) populations in the arcuate nucleus of the hypothalamus (ARH) of offspring of wild-type vs. Insr(+/-) dams was performed to determine whether maternal IR affects the formation of central feeding circuits. We found a 20% increase in the number of Pomc-expressing cells at postnatal day 9 in offspring of Insr(+/-) dams. In conclusion, maternal HFD consumption-distinct from overt obesity per se-was a major contributor to increased body weight, adiposity, IR, and liver triglyceride (TG) phenotypes in progeny. Maternal IR played a minor role in predisposing progeny to obesity and IR, though it acted synergistically with maternal HFD to exacerbate early obesity in progeny.

Figure 1

Breeding strategy. Female Insr^+/− mice were crossed to wild-type (+/+) males to produce an anticipated 1:1 ratio of Insr^+/+ (wild-type) to Insr^+/− offspring. A reciprocal cross of female +/+ and male Insr^+/− mice was used to generate control animals. Wild-type (+/+) offspring from the crosses were studied. Insr, insulin receptor.

Figure 2

Dam phenotype. Wild-type dams did not differ in prebreeding body weight or weight gain during gestation compared to Insr^+/− dams in diet-matched groups. Ingesting a high-fat diet (HFD), +/+ and Insr^+/− dams did not have different fractional body fat content. Insr^+/− dams showed increased circulating insulin concentrations at gestational day E17–E19, but not increased blood glucose. Gray bars: chow wild-type dams; hatched bars: chow Insr^+/− dams; white bars: HFD wild-type dams; black bars: HFD Insr^+/− dams. Data are expressed as mean ± s.e.m (*P < 0.01).

Figure 3

Wild-type offspring body weight. (a) Males. Male offspring of high-fat diet (HFD)-fed Insr^+/− dams (n = 13) weighed more than male offspring of HFD-fed wild-type dams (n = 11) at 4 – 8 weeks of age (*P < 0.05). Male offspring of HFD-fed wild-type dams weighed more than male offspring of chow-fed wild-type dams at 3–16 weeks of age (n = 15). All offspring fed HFD (^†P < 0.05). Open circles: wild-type male progeny of chow wild-type dams; filled circles: wild-type males of chow Insr^+/− dams; open squares: wild-type males of HFD wild-type dams; filled squares: wild-type males of HFD Insr^+/− dams. (b) Comparison of male and female offspring. Similar to males, female offspring of HFD-fed Insr^+/− dams (n = 19) weighed more than females of HFD-fed wild-type dams (n = 10) at 4–9 weeks of age. All offspring fed HFD (*P < 0.05). Mean ± s.e.m. Open triangles: wild-type females of HFD wild-type dams; filled triangles: wild-type females of HFD Insr^+/− dams; open squares: wild-type males of HFD wild-type dams; filled squares: wild-type males of HFD Insr^+/− dams.

Figure 4

Male wild-type offspring body composition. Male offspring from high-fat diet (HFD)-fed Insr^+/− dams had higher % body fat than males from HFD-fed wild-type dams (white bars) at 5 and 7 weeks of age, but not at later 12- and 16-week time points (*P < 0.05). Mean ± s.e.m. White bars: wild-type males of HFD wild-type dams; black bars: wild-type males of HFD Insr^+/− dams.

Figure 5

Male wild-type offspring plasma insulin and blood glucose concentrations. (a) Plasma insulin. Plasma insulin concentrations did not differ between male offspring from high-fat diet (HFD)-fed wild-type and Insr^+/− dams. Males from chow-fed Insr^+/− dams had increased random-fed plasma insulin concentrations at 8 weeks of age, but these concentrations did not differ significantly at later time points (*P < 0.05). Plasma insulin concentrations were higher in males from HFD-fed wild-type dams at 8, 12, and 16 weeks compared to male progeny chow-fed wild-type dams. All offspring fed HFD (^†P < 0.05). (b) Blood glucose. Blood glucose concentrations did not differ in male progeny of HFD-fed wild-type and Insr^+/− dams. Male progeny of chow-fed Insr^+/− dams had increased random fed blood glucose concentrations at 4 weeks of age compared to males from chow-fed wild-type dams (*P < 0.05). Blood glucose concentrations in male progeny of HFD-fed wild-type dams were increased at 8 and 16 weeks compared to males from chow-fed wild-type dams. All offspring fed HFD (^†P < 0.05). Mean ± s.e.m. Gray bars: wild-type males of chow wild-type dams; hatched bars: wild-type males of chow Insr^+/− dams; white bars: wild-type males of HFD wild-type dams; black bars: wild-type males of HFD Insr^+/− dams.

Figure 6

Liver triglyceride (TG) concentration of male wild-type progeny. Liver TG concentration was higher in wild-type male progeny of wild-type dams fed a high-fat diet compared to progeny of wild-type dams fed a chow diet (^†P < 0.05). Liver TG concentration was decreased in males born to HFD-fed Insr^+/− dams vs. progeny of the HFD-fed wild-type dams (*P < 0.05). All offspring fed HFD. Mean ± s.e.m. Gray bars: wild-type males of chow wild-type dams; hatched bars: wild-type males of chow Insr^+/− dams; white bars: wild-type males of HFD wild-type dams; black bars: wild-type males of HFD Insr^+/− dams.

Figure 7

Pomc and Npy cell counts in the arcuate nucleus of the hypothalamus of offspring. There were no differences in the number of Pomc+ cells in the ARH at E14 in offspring born to wild-type vs. Insr^+/− dams (n = 6). There was an increase in the number of Pomc-expressing cells at P9 in offspring born to Insr^+/− dams, and a trend of an increase of Pomc+ cells at P0 and P35 (P0: P = 0.11, n = 9; P9: P = 0.007, n = 11; P35: P = 0.11, n = 9). P35 pups fed chow postweaning (*P < 0.05). Each group represents the average counts of at least 6 coronal hemisections sections per animal spanning the rostrocaudal extent of the presumptive ARH with error bars representing mean ± s.e.m. White bars: wild-type offspring of chow wild-type dams; black bars: wild-type offspring of chow Insr^+/− dams.