Maternal high-fat diet induces obesity and adrenal and thyroid dysfunction in male rat offspring at weaning

Abstract

Maternal nutritional status affects the future development of offspring. Both undernutrition and overnutrition in critical periods of life (gestation or lactation) may cause several hormonal changes in the pups and programme obesity in the adult offspring. We have shown that hyperleptinaemia during lactation results in central leptin resistance, higher adrenal catecholamine secretion, hyperthyroidism, and higher blood pressure and heart rate in the adult rats. Here, we evaluated the effect of a maternal isocaloric high-fat diet on breast milk composition and its impact on leptinaemia, energy metabolism, and adrenal and thyroid function of the offspring at weaning. We hypothesised that the altered source of fat in the maternal diet even under normal calorie intake would disturb the metabolism of the offspring. Female Wistar rats were fed a normal (9% fat; C group) or high-fat diet (29% fat as lard; HF group) for 8 weeks before mating and during pregnancy and lactation. HF mothers presented increased total body fat content after 8 weeks (+27%, P < 0.05) and a similar fat content at the end of lactation. In consequence, the breast milk from the HF group had higher concentration of protein (+18%, P < 0.05), cholesterol (+52%, P < 0.05) and triglycerides (+86%, P < 0.05). At weaning, HF offspring had increased body weight (+53%, P < 0.05) and adiposity (2 fold, P < 0.05), which was associated with lower β3-adrenoreceptor content in adipose tissue (-40%, P < 0.05). The offspring also presented hyperglycaemia (+30%, P < 0.05) and hyperleptinaemia (+62%, P < 0.05). In the leptin signalling pathway in the hypothalamus, we found lower p-STAT3/STAT3 (-40%, P < 0.05) and SOCS3 (-55%, P < 0.05) content in the arcuate nucleus, suggesting leptin resistance. HF offspring also had higher adrenal catecholamine content (+17%, P < 0.05), liver glycogen content (+50%, P < 0.05) and hyperactivity of the thyroid axis at weaning. Our results suggest that a high fat diet increases maternal body fat and this additional energy is transferred to the offspring during lactation, since at weaning the dams had normal fat and the pups were obese. The higher fat and protein concentrations in the breast milk seemed to induce early overnutrition in the HF offspring. In addition to storing energy as fat, the HF offspring had a larger reserve of glycogen and hyperglycaemia that may have resulted from increased gluconeogenesis. Hyperleptinaemia may stimulate both adrenal medullary and thyroid function, which may contribute to the development of cardiovascular diseases. These early changes induced by the maternal high-fat diet may contribute to development of metabolic syndrome.

Figure 1. Maternal body weight and adiposity

Body mass evolution and fat content/DEXA of control (filled bars; n= 6) and high-fat (open bars; n= 9) dams before gestation (A and B, respectively), and body mass and fat content at weaning (C and D, respectively). Results are expressed as means ± SEM; *P < 0.05.

Figure 2. Breast milk composition

Milk content of protein (A), lactose (B), triglycerides (C), cholesterol (D) and leptin (E) of control (filled bars; n= 6) and high-fat (open bars; n= 6) dams at the 11th day of lactation (middle lactation) and at weaning. Results are expressed as means ± SEM; *P < 0.05.

Figure 3. Effect of maternal HF diet on the offspring body mass

Birth weight (A) and body mass at weaning (B) of the control (C; n= 9) and high-fat (HF; n= 10) offspring. Results are expressed as means ± SEM; *P < 0.05.

Figure 4. Effect of maternal HF diet on the offspring adiposity and leptin production

Fat mass of retroperitoneal, epididymal and inguinal compartments (A), leptin RNAm expression in inguinal fat pad (B) and leptinaemia (C) of the control (C; n= 9) and high-fat (HF; n= 10) offspring at weaning. Results are expressed as means ± SEM; *P < 0.05.

Figure 5. Effect of maternal HF diet on leptin signalling pathway in the arcuate nucleus of the offspring

Content of OBRb (A), JAK2 (B), p-STAT3 (C) and SOCS3 (D) in samples of arcuate hypothalamic nuclei of control (C; n= 6) and high-fat (HF; n= 6) offspring at weaning. Representative blots of leptin pathway proteins and cyclophilin (control load) are shown (E). Results are expressed as means ± SEM; *P < 0.05.

Figure 6. Effect of maternal HF diet on adrenal function of the offspring

Adrenal content of catecholamines (A), serum corticosterone (B), adrenal content of tyrosine hydroxylase (TH; C) and phenylethanolamine n-methyl transferase (PNMT; D) of control (C; n= 7–9) and high-fat (HF; n= 7–10) offspring at weaning. Representative blots of catecholamine synthesising enzymes and cyclophilin (control load) are shown (E). Results are expressed as means ± SEM; *P < 0.05.

Figure 7. Effect of maternal HF diet on content of adrenoreceptors in adipose tissue of the offspring

Content of β2 (A) and β3 (B) adrenoreceptors in the inguinal adipose tissue of control (C; n= 7) and high-fat (HF; n= 7) offspring at weaning. Representative blots of ARs and Ponceau staining (control load) are shown (C). Results are expressed as means ± SEM; *P < 0.05.

Figure 8. Effect of maternal HF diet on glucose homeostasis of the offspring

Glycaemia (A), insulinaemia (B), adiponectinaemia (C) and serum free fatty acids (D) of control (C; n= 9) and high-fat (HF; n= 10) offspring at weaning. Results are expressed as means ± SEM; *P < 0.05.

Figure 9. Effect of maternal HF diet on the liver content of glycogen and adrenoreceptor of the offspring

Liver weight (A), glycogen content (B) and content of β2 adrenoreceptor (C) in the liver of control (C; n= 7–9) and high-fat (HF; n= 7–10) offspring at weaning. Representative blots of β2AR and cyclophilin (control load) are shown (C). Results are expressed as means ± SEM; *P < 0.05.

Figure 10. Effect of maternal HF diet on the thyroid function of the offspring

Serum total T3 (A), free T4 (B), TSH (C) and pro-TRH content in the hypothalamic paraventricular nucleus (D) of control (C; n= 5–9) and high-fat (HF; n= 5–10) offspring at weaning. Representative blots of pro-TRH and cyclophilin (control load) are shown (D). Results are expressed as means ± SEM; *P < 0.05.