Effect of age, sex, and site on the cellularity of the adipose tissue in mice and rats rendered obese by a high-fat diet

Abstract

A B S T R A C T Cell size and number of parametrial fat pads were determined in Swiss mice made obese by means of a high-fat diet (40% lard w/w) given ad lib.This diet and a control were introduced to two groups of mothers during gestation and lactation, and sucklings were given the same diets as their mothers at weaning and throughout life.2-wk old mice suckled by mothers fed a high-fat diet have fatter parametrial pads. This difference is due solely to an increase in fat cell size. After weaning, until the 18th wk, the two groups differed with a striking fat cell enlargement seen in the obese group. Later on, whereas cell numbers did not change in the control group, a constant and uninterrupted increase in number is shown in those of obese mice until the 52nd wk. Hyperplasia was observed only in adults. When the highfat diet was introduced to adult rats it also triggered an increase in fat cell number.Three sites of fat pads were compared in both sexes at 32 wk of age. All sites increased in weight in the high-fat fed group. This was due to: hyperplasia in perirenal site, hypertrophy in epididymal and subcutaneous sites, and hyperplasia plus hypertrophy in the parametrial one. So, in each sex, adipose sites in the obese mice reacted to the diet in a site-specific way. It was concluded that the level of fat in a diet is involved in both formation and maturation of new fat cells and in the regulation of fat cell lipid content. The two processes may be separated or may act together according to the adipose tissue site.

Effects of diet and progesterone on the cellularity of parametrial adipose tissue in mice

“…This overweight could be attributed to an increase in adipose mass as shown by the weight of the three fat pad depots. A marked sensitivity to high-fat diet has already been found in the parametrial adipose tissue of these mice : the fat cells of that fat pad showed hypertrophy and hyperplasia (Lemonnier, 1972). This type of obesity could not be related to hyperphagia : the food intake was reduced in weight, but expressed in terms of calories, it was slightly higher.…”

“…These cells did not approach their maximal size (Lemonnier, 1972) ; only a slight increase in their number was observed. Progesterone therefore had the same effect on the cellularity of the control and the obese mice.…”

“…They were then divided into four groups and fed ad libitum either a control diet T with 9 p. 100 fat (in calorie) or a high-fat diet L (Lard) containing 72 p. 100 fat (in cal) (Lemonnier, 1972) Spontaneous exploratory activity (measured by the number of squares the mouse entered over a 9-min period) (table 2) was significantly decreased (P < 0.05) in mice fed the progesterone-enriched diet. However, the number of times the mice reared on their hind legs was the same in the control animals and in those fed the progesterone-enriched diets.…”

“…Indeed, the same obese animal may show an hypertrophy and/or an hyperplasia according to adipose localization. Female mice frequently show hyperplasia and hypertrophy of the fat cells of the parametrial adipose tissue, while the epididymal fat pad in the males rarely shows any signs of hyperplasia (Lemonnier, 1972 ;Lemonnier and Alexiu, 1973). The present experiment was conducted to determine how progesterone interferes with parametrial adipose tissue cellularity in both the control mice and in those rendered obese by a high-fat diet.…”

Adipose tissue growth, distribution and cellularity in steers of two biological types

“…An early report by Lemonnier (1972) concluded that the cell number in the perirenal and parametrial fat depots in adult rats could be affected by dietary manipulations. It was not clear, however, if the hyperplasia reported was due to the appearance of new cells or to the filling of preadipocytes.…”