Figure 1.
Average daily caloric intake and average weekly body weights.
There were 10 mice in each diet group. (A) *, stearic acid vs. all other diets, p<0.01. #, low fat vs. all other diet groups, p<0.007. (B) There were no significant changes in body weight among the four experimental groups throughout the study. The average initial body weight was 15.3±2.6 g (p = 0.277) and the final body weight was 25.0±2.3 g (p = 0.203).
Figure 2.
Body composition measured by DXA and QMR at week 18.
Total body fat (TBF) and total body lean mass (TBLM) were assessed by DXA (A, B) and QMR (C, D), n = 10 per diet group. Mice on the stearic acid diet had a 25% decrease in TBF by DXA and 15% by QMR as compared to the low fat diet fed mice (*, p<0.009) and a 12% decrease as compared to mice on the corn oil diet by QMR **, p<0.008). Mice on the stearic acid diet also had a 4% increase in TBLM measured by DXA when compared to when compared to the other diet groups (*, p<0.01) and to the low fat diet fed mice when measured by QMR (*, p = 0.047).
Figure 3.
Abdominal fat and organ weight.
(A) Abdominal fat images are representative of each experimental group. (B) Mice on the stearic acid diet had significantly less abdominal fat when compared to the low fat and corn oil groups (*, p<0.01, n = 10 per diet group). (C) There was no difference in the weight of heart/lungs, liver, kidney or brain between any of the dietary groups.
Figure 4.
The size of abdominal adipocytes in dietary groups.
Representative images of histopathologic sections of abdominal fat from mice fed: a low fat diet (A), corn oil diet (B), safflower oil diet (C) or stearic acid diet (D) All images are at the same low power (25x) magnification. (E) Mice on the low fat diet had significantly larger adipocytes as compared to all other groups (*, p<0.01).
Figure 5.
N = 10 per diet group. (A) Mice on the stearic acid diet had significantly reduced serum glucose compared to all other experimental groups (*, stearic acid vs. low fat, p = 0.006; corn oil, p = 0.039; safflower oil, p<0.001). Mice on the corn oil diet also had a significantly reduced level of glucose as compared to the safflower group (#, p = 0.034). (B) Mice on the high fat diets had significantly reduced levels of leptin as compared to the low fat group (*, low fat vs. stearic acid, p<0.001; corn oil, p = 0.014; safflower oil, p<0.001). Mice on the stearic acid and safflower oil diets also had a significantly lower level of leptin when compared to the corn oil group (#, p = 0.015 and 0.003, respectively). (C) Mice on the stearic acid diet had a significantly increased level of MCP-1 when compared to the low fat and safflower oil groups (*, p = 0.003 and 0.019, respectively). Mice on the low fat diet also had a significantly reduced level of MCP-1 when compared to the corn oil group (#, p = 0.032).
Figure 6.
Effects of 50 µM stearic acid, oleic acid and linoleic acid on cell death and apoptosis of 3T3L1 preadipocytes.
(A) Trypan blue staining showed that the percentage of dead cells was significantly increased after a 48 hour treatment with stearic acid (*, p<0.01, compared to control, n = 3). In contrast, oleic acid or linoleic acid had no significant changes over time (p>0.05, n = 3). (B) Cytotoxicity was significantly increased after 24 hours of treatment with stearic acid (*, p<0.01, compared to control, n = 5). However, it was significantly decreased with 24 hours of oleic acid treatment (#, p<0.01, compared to control, n = 4). Cytotoxicity did not change significantly with linoleic acid treatment (p>0.05, n = 4). (C) Flow cytometry revealed an increase in dead cells after 48 hours of treatment with stearic acid (*, p<0.01, compared to control, n = 4), while oleic acid significantly decreased the number of dead cells at 48 hours (#, p<0.01, compared to control, n = 4). In contrast, linoleic acid had no significant effects over time (n = 4). (D) Apoptotic cells were significantly increased with stearic acid treatment (*, p<0.01, compared to control, n = 4) and decreased with oleic acid (#, p<0.01, compared to control, n = 4). No significant changes were observed with linoleic acid treatment (p>0.05, n = 4).
Figure 7.
Cytotoxicity effect of stearic acid on 3T3L1 preadipocytes.
(A) Lactate dehydrogenase concentrations increased significantly when the dose of stearic acid was over 35 µM after 48 hours of treatment, and peaked at 100–200 µM (*, p<0.01, compared with the control group, n = 4). (B) Measurement of caspase-3 activity showed stearic acid (50 µM) increased caspase-3 activity of the cultured preadipocytes after 48 hours' treatment (*, p<0.05, compared to control, n = 4). (C). When preadipocytes were pretreated with a specific caspase-3 inhibitor for 4 hours, and then treated with stearic acid (50 µM), the stearic acid induced cytotoxicity was partially inhibited (*, p<0.01, compared with the control group; #, p<0.01, n = 3).
Figure 8.
Effects of 50 µM stearic acid, oleic acid or linoleic acid on gene expression in 3T3L1 preadipocytes; Control cells were treated the same as fatty acid treated cells except they were treated with fatty acid free BSA.
Cells were treated for 48 hours. These data showed that stearic acid decreased the expression of cIAP2 and Bcl2 (although only cIAP2 was significant, n = 6 replicates * p<0.01), which encodes antiapoptotic proteins, and increased Bax gene expression, which encodes for a proapoptotic protein, when compared to control cells n = 6 replicates, (* p<0.01). Linoleic acid also increased expression of Bax compared to control cells (n = 6 replicates, * p<0.01).