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

BACKGROUND: Adipocyte numbers and peroxisome proliferators activated receptorγ (PPARγ) 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, PPARγ 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 µm. Pigs undergoing FWx4 tended to have greater (p = 0.0685; by 191%) number of adipocytes, increased (p = 0.0234) glucose U14C incorporation into adipocytes and greater (p = 0.0872) rate of glucose uptake into cells of 119-150 µm diameter than of cells from control or FWx1 pigs. Subcutaneous adipocyte numbers in 22-60 and 61-90 µm diameter ranges from pigs in FWx1 tended to be greater (p = 0.08 and 0.06, respectively) than for those in FWx4 treatment, yet PPARγ 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.

Feed withdrawal abate regimens lipodystrophy and metabolic syndrome symptoms, such as glucose tolerance, are associated with the diameter of retroperitoneal adipocytes in rats.

Adipocyte numbers were increased by feed withdrawal (FW) regimens in cattle; thus, the effect of FW regimens was studied in male Wistar and fa/fa obese rats, as models for humans, in 2 completely randomized design experiments to abate lipodystrophy and progression of metabolic syndrome symptoms. The hypothesis was that application of FW regimens could alter adipose tissue cellularity, adipocyte size, and affect area under the curve (AUC) during glucose tolerance tests. Objectives were to determine associations among retroperitoneal and inguinal adipose tissue adipocyte number, diameter, and AUC, as affected by fortnightly or a single (at age 50 days) 24-hour FW regimen. Adipocyte marker peroxisome proliferator-activated receptor gamma expression was elevated (P = .054) in the retroperitoneal tissue of fa/fa obese rats in the fortnightly FW treatment because of a 13% increase in tissue cell density (cells per gram; P = .13). Average cell diameter in retroperitoneal adipose and AUC were negatively corelated. Regression analyses after including the square of average cell diameter indicated that average retroperitoneal adipocyte diameter (between 65 and 135 mum) and the AUC were related in a quadratic manner (R(2) = 0.14; n = 49; P = .03) for Wistar rats. Cell number of the inguinal and retroperitoneal adipocytes tended to be positively corelated (r = 0.24; P = .09 and r = 0.26; P = .07, n = 49, respectively) to the AUC and are indexes of adiposity. Results suggest that maintenance of retroperitoneal adipocytes at appropriate diameters may control progression of metabolic syndrome symptoms such as glucose tolerance.

Effect of conjugated linoleic acids from beef or industrial hydrogenation on growth and adipose tissue characteristics of rats.

BACKGROUND: The conjugated linoleic acid (CLA) content of beef can be increased by supplementing appropriate beef cattle diets with vegetable oil or oil seed. Yet the effect of consumption of such beef on adipose tissue characteristics is unclear, thus the study was conducted to compare adipose tissue responses of rats to diets containing beef from steers either not provided or provided the oil supplements to alter CLA composition of the fat in muscle. METHODS: Effects of feeding synthetic (industrial hydrogenation) CLA or CLA from beef on growth and adipose tissue responses of weanling, male, Wistar rats (n = 56; 14 per treatment diet) were investigated in a completely randomized design experiment. Diets were: control (CON) diet containing casein and soybean oil, synthetic CLA (SCLA) diet; where 1.69% synthetic CLA replaced soybean oil, two beef-diets; CONM and CLAM, containing freeze dried beef from steers either not fed or fed 14% sunflower seeds to increase CLA content of beef. Diets were isonitrogenous (20% protein) and isocaloric. Rat weights and ad libitum intakes were recorded every 2 wk. After 9 wk, rats were fasted for 24 h, blood sampled by heart puncture, sacrificed, tissue and organs were harvested and weights recorded. The adipose tissue responses with regard to cellularity and fatty acid compositions of retroperitoneal and inguinal adipose tissue were determined. RESULTS: Body weights and gains were comparable, but organ weights as percent of body weight were greater for rats fed SCLA than CONM. Fasting blood glucose concentration was lower (p < 0.01) in rats fed SCLA than those fed CONM or CLAM. Retroperitoneal and inguinal fat weights, as percent of body weight were greater (p < 0.01) in rats fed CONM or CLAM than those fed CON or SCLA diets. Adipocyte numbers were least in retroperitoneal tissue of rats fed SCLA, while inguinal tissue cell density and total number were lower (p = 0.02) in rats fed CLAM (7.26 x 107 cells/g and 8.03 x 108 cells) than those fed CONM (28.88 x 107 cells/g and 32.05 x 108 cells, respectively). CONCLUSION: Study suggests that dietary CLA either as synthetic or high CLA-beef may alter adipose tissue characteristics by decreasing the number of adipocytes and by decreasing the size of the tissue.