Adaptive changes in thyroid function of female rats fed a high-fat and low-protein diet during gestation and lactation

The percent of lipids in the western diet has been continuously increasing in the last decades and is associated with a decrease in the proportion of protein intake. Recently, we demonstrated that protein malnutrition during lactation is associated with lower body weight and thyroid hypofunction in female rats and their offspring. Our objective in the present study was to determine if a high-fat and low-protein diet was associated with similar changes. Three-month-old female Wistar rats were randomly assigned to one of the following groups with 8 animals each: high-fat and low-protein (40% lipid, 5% protein, and 55% carbohydrate of the total energy content) from the 3rd week of gestation to the end of lactation; control group - standard diet (11% lipid, 23% protein, and 66% carbohydrate of the total energy content). Food consumption and body weight were monitored daily. Serum thyrotropin and thyroid hormone concentrations were determined by specific radioimmunoassay at the end of lactation. Animals receiving high-fat and low-protein diet had a significantly lower body weight (13.9% at weaning, P < 0.05) and serum albumin (25%, P < 0.05) and thyrotropin (26.2%, P < 0.01) concentrations, and a higher serum triiodothyronine concentration (74%, P < 0.005) and 131I-thyroid uptake (77%, P < 0.005). These data show that a high-fat and low-protein diet can promote maternal thyroid hyperfunction that differs from the thyroid hypofunction observed in dams fed a low-protein diet, a phenomenon that can be of adaptive importance for pup nurturing.

Thyroid function in post-weaning rats whose dams were fed a low-protein diet during suckling

This study was designed to evaluate the thyroid and pituitary hormone levels in post-weaning rats whose dams were fed a low-protein diet during suckling (21 days). The dams and pups were divided into 2 groups:a control group fed a diet containing 22 per cent protein that supplies the necessary amount of protein for the rat and is the usual content of protein in most commercial rat chow, and a diet group fed a lowprotein (8 per cent) diet in which the protein was substituted by an isocaloric amount of starch. After weaning all dams and pups received the 22 per cent protein diet. Two hours before sacrifice of pups aged 21, 30 and 60 days, a tracer dose (0.6 mui) ofl25I was injected (ip) into each animal. Blood and thyroid glands of pups were collected for the determination of serum T4, T3 and TSH and radioiodine uptake. Low protein diet caused a slight decrease in radioiodine uptake at 21 days, and a significant decrease in T3 levels (l28 ñ 14 vs 74 ñ 9 ng/dl, P<0.05), while T4 levels did not change and TSH was increased slightly. At 30 days, T3 and TSH did not change while there was a significant increase in both T4 levels (4.8 ñ 0.3 vs 6.1 ñ 0.2 mug/dl, P<0.05) and in radioiodine uptake levels (0.34 ñ 0.02 vs 0.50 ñ 0.030 per cent/mg thyroid, P<0.05). At 60 days serum T3, T4 and TSH levels were normal, but radioiodine uptake was still significantly increased (0.33 ñ 0.02 vs 0.41 ñ 0.03 per cent/mg thyroid, P<0.05). Thus, it seems that protein malnutrition of the dams during suckling causes hypothyroidism in the pups at 21 days that has a compensatory mechanism increasing thyroid function after refeeding with a 22 per cent protein diet. The radioiodine uptake still remained altered at 60 days, when all the hormonal serum levels returned to the normal values, suggesting a permanent change in the thyroid function.

Use of y-chromosome-specific DNA probes to evaluate an XX male

The function of a Y human chromosomal DNA sequence was evaluated. The Y-5 probe was isolated from a flow-sorted chromosome library and detects Y-specific sequences. The Y-5 probe and other T-specific probes were used to analyze an XX male patient without ambiguous genitalia. DNA sequences from the short arm of the chromosome Y that were detected with pDP1007 and DP105 in the patient's genome explain the testis differentation observed in this case. Failure of the patient's DNA to hybridize to the Y-5 probe shows that the primitive gonads can differentiate into testes even in the absence of this chromosome region. In contrast, a gene controlling spermatogenesis may exist in this region because the patient azoospermic

A technical improvement for the thyroid peroxidase iodination assay

Thyroid peroxidase (TPO) iodination activity is generally evaluated in vitro by the iodination of poorly iodinated thyroglobulin or bovine serum albumin, followed by separation of protein-bound and inorganic iodide by paper chromatography,. Precipitation of protein-bound iodine by trichloroacetic acid (TCA) was evaluated as an alternative to the time-consuming paper chromatographic separation (PC) in normal rat TPO preparations. The protein-bound iodine estimates as well as the iodination activities determined by these two procedures were significantly correlated (r = 0.95 and 0.98, respectively, P<0.001), and the iodination activities regression line slope (b = 0.97 + or - 0.11) was not different from 1. The protein-bound iodine separation by TCA is simpler and faster, without loss of precision. Thus, it can be a useful alternative step in the thyroid peroxidase iodination assay