Figure 5. Lower insulin release in INS-1 832/13 cell lines is proportional to knockdown of fatty acid synthase (FAS) enzyme activity and lowered lipid synthesis.

Insulin release is the average ± SE of 12–24 replicate incubations (in the presence of 11.1 mM glucose for 1 h). mRNA levels were estimated by qPCR on 6–9 replicate plates of each cell line and FAS protein levels were estimated by western analysis and densitometry and are the average ± SE of measurements on 4–5 separate cell preparations. Except for the insulin release values, results are expressed as a percent ± SE of the CHS cell line set at 100%. The values for incorporation of ¹⁴C into lipid, CO₂ or anaplerotic products (¹⁴C anaplerosis) from incubating cells (Passage numbers 4–13) in the presence of 16.7 mM glucose [U-¹⁴C]glucose (specific radioactivity 0.2 µCi/mmol) for 1 h and are the averages of three experiments with 4–6 replicate incubations for each cell line per experiment. The average glucose incorporation into lipid, CO₂ and the anaplerotic products for the CHS control cell line were 2.3 ± 0.3, 10.8 ± 0.7 and 3.5 ± 0.5 nmol glucose/mg whole cell protein, respectively. The insulin contents are expressed as a percent of the control CHS cell line (70 ± 4 mUnits insulin/mg whole cell protein) set at 100%. The incorporation of ¹⁴C into lipid was lower in the cell lines with targeted FAS expression, but the ¹⁴C incorporation into CO₂ or anaplerotic products, which indicate glucose oxidation and anaplerosis, respectively, were not lower. This pattern is consistent with knockdown of FAS exerting a specific, and not generalized, effect on cell metabolism.