Periodic 48h feed withdrawal improves glucose tolerance in growing pigs by enhancing adipogenesis and lipogenesis

Background: Adipocyte numbers and peroxisome proliferators activated receptorgamma (PPARgamma) expression of retroperitoneal tissue increased while area under the curve (AUC) during the glucose tolerance test (GTT) was reduced in rats subjected to certain feed withdrawal (FW) regimens. Thus, using pigs as the experimental model, the hypothesis that FW regimens influence glucose tolerance by influencing fat cell function was evaluated with the objective of determining the effect of a single (FWx1; at age of 19 wk for 48 h) or periodic, multiple (FWx4; 24 h FW at 7 and 11 wk of age and 48 h FW at 15 and 19 wk of age) FW on AUC of glucose and insulin during the GTT relative to pigs that did not experience FW (Control). Methods: Growth, body composition, adipocyte numbers, PPARgamma expression, lipogenic potential as glucose uptake into fat of adipocytes of varying diameter in omental (OM) and subcutaneous (SQ) fat as affected by FW regimens were determined in pigs initiated into the study at 5 wk of age and fed the same diet, ad libitum. Results: Blood glucose concentrations for prior to and 120 min post glucose meal tended to be lower (p=0.105 and 0.097, respectively) in pigs in FW treatments. In OM fat; cell numbers, glucose Universal14C [U14C] incorporation into fat and rate of incorporation per 104 cells was greatest for cells with diameters of 90-119 um. Pigs undergoing FWx4 tended to have greater (p=0.0685; by 191 %) number of adipocytes, increased (p=0.0234) glucose U-C14 incorporation into adipocytes and greater (p=0.0872) rate of glucose uptake into cells of 119-150 um diameter than of cells from control or FWx1 pigs. Subcutaneous adipocyte numbers in 22-60 and 61-90 um diameter ranges from pigs in FWx1 tended to be greater (p=0.08 and 0.06, respectively) than for those in FWx4 treatment, yet PPARgamma expression and total cell number were not affected by treatment. Conclusions: Results suggest that FW regimens influence fat cell function or lipogenesis rather than number, affecting glucose metabolism and may have implications in drug-free control of metabolic syndrome symptoms.