Effects of Aging on the Energy Balance of Pregnant Rats

Abstract

In pregnant and non-pregnant female rats at various ages the energy balance was determined to study the age-induced alterations in the mother and conceptus. The animals were anesthetized and the conceptus removed and separated into male, female, and placental tissues. The animals were then killed and the carcasses prepared for energy balance determination. The results obtained showed that the older animals gained less energy in the body and had lower gross food efficiency than the younger animals. The number, energy and weight of the offspring were not affected by the mother’s age. Nevertheless, due to its constant growth during life, the rat is not the best model to study age-related processes.

Energy balance of pregnant diabetic rats

“…Impairment of gross food efficiency is probably due to higher costs of protein synthesis (Nair et al 1984) and gluconeogenesis (Nair et al 1984) present in diabetic subjects. It is interesting to notice that DM even led to an inhibition of the characteristic increase of gross food efficiency during pregnancy as previously reported (Luz & Griggio, 1990). DM can lead to gastrointestinal alterations such as dysphagia, abdominal pain, nausea, Mean values with unlike superscript letters were significantly different (P,0·05).…”

“…All of our diabetic animals were treated daily with insulin in order to avoid large differences in the individual glycaemia values among diabetic animals, as well as to keep the glycaemia levels into a range that allowed the animals survival. The pregnancy, as expected, increased the energy expenditure as a consequence development of conceptuses and placentas (Rosso, 1975;Luz & Griggio, 1990;Hay, 1991). In order to compensate for this increased energy expenditure, the animals enhanced their metabolizable energy intake and showed increase in the net bodyweight gain (Luz & Griggio, 1992, 1998.…”

“…Considering that pregnancy leads to uterus hypertrophy, an increase in the weight and energy content in this tissue is expected during this period (Luz & Griggio, 1998). On the other hand, a reduction in uterus weight could be expected in diabetic animals since DM can alter the hypothalamus-hypophysis -ovary axis leading to a reduction in plasma concentrations of the luteinizing hormone, folliclestimulating hormone, prolactin and oestrogen (La Marca et al 1999), and it is reported that a decrease in oestrogen levels can reduce uterus size (Merry & Holehan, 1994).…”

“…During pregnancy, most animals increase their food intake (Chaves & Herrera, 1980;Luz & Griggio, 1990;Murphy & Abrams, 1993) as well as the gross food efficiency (Naismith & Brookes, 1983;Luz & Griggio, 1990). Part of the extra energy ingested is used to form the uterine contents and for uterus growth (Rosso, 1975;Hay, 1991;Luz & Griggio, 1992), and part is spent as heat as a consequence of the increased energy expenditure (Richard & Trayhurn 1985;Lux & Griggio, 1990).…”

Low reproductive success in Per1 and Per2 mutant mouse females due to accelerated ageing?

“…Generally, the periods of pregnancy and lactation are characterised by an increased metabolic rate and a preference for high protein food (Trojan & Wojciechowska 1968, Lewis et al 2001, Kasparian & Millar 2004. Thus, energy expenditure is an important factor during reproductive stages and decreases in ageing females (Luz & Griggio 1998). Since recent studies on Clock and Bmal1 mutants have revealed that clock genes play a role in the regulation of metabolic rate (Shimba et al 2005, Turek et al 2005, Kornmann et al 2007, it is likely to assume that also Per genes may be involved in metabolic regulation.…”