Suboptimal maternal diets alter mu opioid receptor and dopamine type 1 receptor binding but exert no effect on dopamine transporters in the offspring brain

Abstract

Birthweight is a marker for suboptimal fetal growth and development in utero. Offspring can be born large for gestational age (LGA), which is linked to maternal obesity or excessive gestational weight gain, as well as small for gestational age (SGA), arising from nutrient or calorie deficiency, placental dysfunction, or other maternal conditions (hypertension, infection). In humans, LGA and SGA babies are at an increased risk for certain neurodevelopmental disorders, including Attention Deficit/Hyperactivity Disorder, schizophrenia, and social and mood disorders. Using mouse models of LGA (maternal high fat (HF) diet) and SGA (maternal low protein (LP) diet) offspring, our lab has previously shown that these offspring display alterations in the expression of mesocorticolimbic genes that regulate dopamine and opioid function, thus indicating that these brain regions and neurotransmitter systems are vulnerable to gestational insults. Interestingly, these two maternal diets affected dopamine and opioid systems in somewhat opposing directions (e.g., LP offspring are generally hyperdopaminergic with reduced opioid expression, and the reverse is found for the HF offspring). These data largely involved evaluation at the transcriptional level, so the present experiment was designed to extend these analyses through an assessment of receptor binding. In this study, control, SGA and LGA offspring were generated from dams fed control, low protein or high fat diet, respectively, throughout pregnancy and lactation. At weaning, mice were placed on the control diet and sacrificed at 12 weeks of age. In vitro autoradiography was used to measure mu-opioid receptor (MOR), dopamine type 1 receptor (D1R), and dopamine transporter (DAT) binding level in mesolimbic brain regions. Results showed that the LP offspring (males and females) had significantly higher MOR and D1R binding than the control animals in the regions associated with reward. In HF offspring there were no differences in MOR binding, and limited increases in D1R binding, seen only in females in the nucleus accumbens core and the dorsomedial caudate/putamen. DAT binding revealed no differences in either models. In conclusion, LP but not HF offspring show significantly elevated MOR and D1R binding in the brain thus affecting DA and opioid signaling. These findings advance the current understanding of how suboptimal gestational diets can adversely impact neurodevelopment and increase the risk for disorders such as ADHD, obesity and addiction.

Keywords: Dopamine; Maternal high fat diet; Maternal low protein diet; Opioid; Reward.

Figure 1

Qualitative and quantitative autoradiographic binding of MOR in HF and LP offspring. Representative images show binding of [³H] DAMGO in the offspring fed from SC (a), HF (b), and LP (c) diet dams. Schematic delineations of [³H] DAMGO binding to MORs from rostral to caudal positions in coronal brain sections showing ROIs, including fontal-parietal cortex (frp), caudate putaman (cp) (dorsal medial (DM), dorsal lateral, ventral medial (VM), and ventral lateral (VL)), nucleus accumbens core (AcbC), Acb shell (AcbSh), endopiriform nucleus(en), olfactory tubercle (Tu), hippocampus (hpc), habenula (hb), thalamus (thl), amygdala (amg), hypothalamus (hyp), superior colliculus (SCo), medial geniculate (mg), substantia nigra (SNr), red nucleus (rn), ventral tegmental area (VTA), and interpeduncular complex (ip) (d). [³H] DAMGO standards ranging from 0 to 18.4 uCi/g were counted (e). Freehand drawings are according to the mouse atlas of Franklin and Paxinos (2007). In HF diet fed mice, none of the brain ROIs show treatment, or sex significance, but increasing trend of MOR binding is noticed in female HF diet compared to SC mice (f). In offspring fed from LP diet, significant treatment difference was shown compared to SC mice, and within females, significant treatment difference was also displayed (g). Values are mean +SEM of five animals per diet group.*p<0.05, LPSC>SCSC; **p<0.01, LPSC>SCSC; ^$p<0.05, LPSC Female> SCSC Female; ^$$p<0.01, LPSC Female> SCSC Female.

Figure 2

Qualitative and quantitative autoradiographic binding of D1R in in HF and LP offspring. Representative images show binding of [³H] SCH 23390 in the offspring fed from SC (a), HF (b), and LP (c) diet dams. Schematic delineations of [³H] SCH 23390 binding to D1Rs from rostral to caudal positions in coronal brain sections showing ROIs, including Tu, Acb AcbSh, AcbC, DM CPu, DL CPu, VM CPu, VL CPu, DL CPu Tail, VL CPu Tail, VTA and SNr (d). [³H] SCH 23390 standards ranging from 0 to 0.4871 uCi/g were counted (e). Freehand drawings are according to the mouse atlas of Franklin and Paxinos (2007). In HF diet fed mice, only AcbC and DM CPu show treatment significance within females compared to SC mice (f). In offspring fed from LP diet, significant treatment difference was shown compared to SC mice, and within females, significant treatment difference was also displayed (g). Values are mean+SEM of five animals per diet group. ^!p<0.05, HFSC Female > SCSC Female; *p<0.05, LPSC>SCSC; **p<0.01, LPSC>SCSC; ^$p<0.05, LPSC Female> SCSC Female; ^$$p<0.01, LPSC Female> SCSC Female.

Figure 3

Qualitative and quantitative autoradiographic binding of DAT in in HF and LP offspring. Representative images show binding of [³H] WIN 35,428 in the offspring fed from SC (a), HF (b), and LP (c) diet dams. Schematic delineations of [³H] WIN 35,428 binding to DAT from rostral to caudal positions in coronal brain sections showing ROIs, including Tu, AcbSh, AcbC, DM Cpu, DL Cpu, VM Cpu, VL CPu, DL CPu Tail, VL CPu Tail, VTA and SNr (d). [³H] WIN 35,428 standards ranging from 0 to 18.4 uCi/g were counted (e). Freehand drawings are according to the mouse atlas of Franklin and Paxinos (2007). In both HF and LP diet fed mice, none of the brain ROIs show treatment, or sex significance compared to SC mice (f) (g).