GDF15 knockout does not substantially impact perinatal body weight or neonatal outcomes in mice

Abstract

Growth differentiation factor-15 (GDF15) increases in circulation during pregnancy and has been implicated in food intake, weight loss, complications of pregnancy, and metabolic illness. We used a Gdf15 knockout mouse model (Gdf15^{-/- )} to assess the role of GDF15 in body weight regulation and food intake during pregnancy. We found that Gdf15^-/- dams consumed a similar amount of food and gained comparable weight during the course of pregnancy compared to Gdf15^+/+ dams. Insulin sensitivity on gestational day 16.5 was also similar between genotypes. In the postnatal period, litter size, and survival rates were similar between genotypes. There was a modest reduction in birth weight of Gdf15^-/- pups, but this difference was no longer evident postnatal day 3.5 to 14.5. We observed no detectable differences in milk volume production or milk fat percentage. These data suggest that GDF15 is dispensable for changes in food intake, and body weight as well as insulin sensitivity during pregnancy in a mouse model.

Keywords: GDF15; pregnancy; stress; weight gain.

Figure 1:. Schematic of Experimental Manipulations

A) Insulin resistance of pregnancy study, comparing age-matched females in 3 groups; non-pregnant females (n=7), pregnant females given plain drinking water (n=7), pregnant females given 1.0 mg/kg dexamethasone in drinking water (n=7). B) Gdf15 Knockout study in pregnancy. Gdf15^+/+ females (n=6) were mated with Gdf15^+/+ males. Gdf15^−/− females (n=7) were mated with Gdf15^−/− males. Food intake and body weight was measured weekly from one week before mating until 14–16 days after pups were born.

Figure 2:. Insulin Resistance of Pregnancy Co-occurs with Elevations in GDF15

A) Intraperitoneal insulin tolerance testing on E16.5 in pregnant C57BL/6J mice given plain water and age-matched non-pregnant females. Values are relative to fasting blood glucose and were assessed using a linear mixed effect model. B) Fasting blood glucose values in pregnant dams given water and non-pregnant females, assessed using student’s T test. C) GDF15 levels at ZT1 in pregnant and non-pregnant females, assessed as paired t tests. D) Intraperitoneal insulin tolerance testing on E16.5 in pregnant dams given water or 1mg/kg dexamethasone in drinking water, assessed via linear mixed effect modeling. Values are relative to fasting blood glucose levels. E) Fasting blood glucose values in pregnant dams given plain drinking water or dexamethasone in drinking water, assessed via student’s t test. F) GDF15 ELISA evaluating serum levels at ZT1 and ZT13 in pregnant dams given plain drinking water, pregnant dams given dexamethasone in drinking water, assessed as paired t tests. * indicates p<0.05

Figure 3:. Gdf15 Knockout Does Not Impact Food Intake or Body Weight During Mouse Pregnancy

A) Cumulative food intake during the prenatal period (pre-mating through final measurement before birth), assessed via Student’s t test. B) Weight gained during prenatal period, assessed via student’s t test. C)Postnatal cumulative food intake (after birth of pups-end of experiment), assessed via Student’s t test. D) Weight lost in the postnatal period, assessed via Students’ t test. E) Plot of the weekly food intake in both genotypes from 1 week before mating until end of the experiment. F) Plot of maternal body weight throughout the experimental period.

Figure 4:. Gdf15 Knockout Has No Effect on Gestational Insulin Tolerance

A) Intraperitoneal insulin tolerance test in Gdf15^+/+ and Gdf15^−/− dams at E16.5. Values are relative to fasting blood glucose levels. Assessed via linear mixed effects modeling. B) Fasting Blood glucose levels in dams, assessed by students t test. C) Area under the curve defined as sum of all glucose values for each animal, assessed by Student’s t test. D) Rate of drop in blood glucose in the first hour of the insulin tolerance test, assessed by Student’s t test.

Figure 5:. Offspring Birth Weight is Reduced in Gdf15 Knockout Pregnancies

A) Latency to copulatory plug (time from introduction of male into cage until copulatory plug is discovered), assessed via student’s t test. B) Gestational age in days, calculated as the number of days from appearance of copulatory plug until birth of the litter. Assessed via Mann-Whitney test. C) Average birth weight of pups, calculated as the average birth weight for each dam, then averaged by genotype. Assessed by Student’s t test. D) Total litter size (including those born dead), assessed via student’s t test. E) Number of live pups born per litter, assessed via student’s t test. F) Percentage of pups in each litter who were dead by postnatal day 3.5, assessed by Mann Whitney test. * indicates p<0.05

Figure 6:. Milk volume and Milkfat Percentage Are not Changed in Gdf15 Knockout Dams

A) Total mass (in grams) lost by dam during the suckling period of the weigh-suckle-weigh test on PND10.5, assessed by student’s t test. B) Total mass (in grams) gained cumulatively between all pups in the litter during suckling period during weigh-suckle-weigh test, assessed by Mann Whitney test. C) Percentage of fat found in mouse milk collected PND 14–16.5, assessed by student’s t test.

Figure 7:. Offspring Postnatal Growth is Normal in Gdf15 Knockout Litters

A) Postnatal bodyweight measurements from birth through PND14.5 in male and female pups, assessed via linear mixed effect models.