The effects of sex, genotype, and adipose depot on lipogenic enzyme activity have been investigated in Holstein and Pirenaican bulls and heifers, taking into account differences in adipocyte size. Fifteen Pirenaican bulls and 15 heifers and 15 Holstein bulls and 13 heifers were fattened until slaughter (12 to 13 mo old and 450 to 500 kg of body weight). During the fattening period, animals had ad libitum access to commercial concentrates and straw. The 10th rib was dissected to determine the fat content. Adipocyte size and activities of the following lipogenic enzymes were determined: glycerol 3-phosphate dehydrogenase, fatty acid synthase, nicotinamide adenine dinucleotide phosphate (NADP)-malate dehydrogenase, glucose 6-phosphate dehydrogenase, and NADP-isocitrate dehydrogenase, in the omental, perirenal, subcutaneous, and intermuscular adipose depots, respectively. Because adipocyte mean cell volume varied with sex, breed, and depot, regression analyses of log(e) activity per cell and log(e) cell volume were used to compare activities per unit volume. Sex, breed and depot had no effect (P > 0.05) on the gradients of regressions, which did not differ significantly from 1. Thus, activity per unit volume did not vary with cell size. Consequently, sex, breed, and depot effects on the regression analyses were equivalent to effects on activity per unit volume. Females had greater amounts of fat in the 10th rib (P < 0.001), larger adipocytes (P < 0.001) and, in general, greater (P < 0.05) lipogenic activity per cell, even when adjusted for cell size, than males. These findings suggest that differences in adiposity between sexes are mainly due to females having a greater capacity for lipid synthesis, and hence, hypertrophy, than males. When adjusted for differences in carcass weight, Holsteins had larger adipocytes than Pirenaicans. The abdominal depots, omental and perirenal, had a greater adipocyte size (P < 0.001) and, in general, greater lipogenic enzyme activities per cell (P < 0.05) than the subcutaneous and intermuscular carcass depots. However, when activity per cell was adjusted for cell size, subcutaneous depots had greater fatty acid synthae, glucose 6-phosphate dehydrogenase, and NADP-malate dehydrogenase activities than omental and perirenal, indicating that other factors such as nutrient supply may restrict hypertrophy of carcass adipocytes.

Mendizabal, J. A., Delfa, R., Arana, A., Eguinoa, P., González, C., Treacher, T. and Purroy, A. 2003. Estimating fat reserves in Rasa Aragonesa ewes: A comparison of different methods. Can. J. Anim. Sci. 83: 695-701. Four pre-slaughter measurements, liveweight (LW), body condition score (BCS) and fat thickness, measured by ultrasound, in the lumbar (FTL) and sternal regions (FTS), and four post-slaughter measurements, empty liveweight (ELW), hot carcass weight (HCW) and diameter of adipocytes in subcutaneous (DSC) and omental (DOM) fat depots¸ were used to predict the weight of fat in the omental (OM), mesenteric (MES), perirenal (PR), subcutaneous (SC) and intermuscular (IM) depots of ewes. Linear and multiple regressions were fitted to data from 42 adult, non-pregnant and non-lactating Rasa Aragonesa ewes, with liveweights between 29.8 and 79.2 kg and body condition scores between 0.75 and 4.5. Using a single parameter, ELW and HCW gave the most accurate predictions of the total depot fat (R 2 = 0.88 and 0.90, RSD = 1.571 and 1.484 kg, respectively). Multiple regressions predicted total weight of fat depots from the pre-slaughter variables LW, BCS and FTS with an R 2 value of 0.92 (RSD=1.317 kg). This result confirms the utility of using in vivo measures as fat reserve predictors in Rasa Aragonesa ewes.

The effect of genotype on the size of adipocytes and on the lipogenic enzyme activities in different fat depots in Asturiana, Avilena, Morucha, Parda Alpina, Pirenaica, Retinta and Rubia Gallega steers was studied (six animals per breed). Steers were weaned at about 6 to 8 months of age and 220 to 260 kg live weight (LW). During the fattening period the steers were given commercial concentrates and straw, both ad libitum, until slaughter at 470 kg average LW. Adipocyte size and activity of the following lipogenic enzymes were studied: glycerol 3-phosphate dehydrogenase (G 3-PDH); fatty acid synthase (FAS); NADP-malate dehydrogenase (MD), glucose 6-phosphate dehydrogenase (G 6-PDH) and NADP-isocitrate dehydrogenase (ICDH) in the omental, perirenal, subcutaneous and intermuscular adipose depots. Also the perirenal fat depot was removed and weighed and the 10th rib was dissected. Differences between breeds were significant for the amount of fat in the different adipose depots (P < 0·001), for adipocyte size (except in intermuscular depot) and for G 3-PDH, FAS, MD, ICDH (P < 0·001) and G 6-PDH (P < 0·01). In general, steers of breeds that had more fat also had bigger adipocytes and higher lipogenic enzyme activities. In this way, Asturiana breed (lean breed) had smaller adipocytes and lower lipogenic enzyme activities than Morucha breed (fatter breed). Finally, adipocytes from the perirenal depot were the biggest and showed the highest G 3-PDH and FAS activities while adipocytes from the intermuscular depot had the smallest size and the lowest lipogenic activities.

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. 2005. Lipogenic activity in Rasa Aragonesa ewes of different body condition score. Can. J. Anim. Sci. 85: 101-105. The aim of the study was to assess the effect of body condition score on tissue and metabolic characteristics of the adipose depots in sheep of Rasa Aragonesa breed. Ewes were uniformly assigned according to their body condition score (BCS) (scale 0 to 5), to four groups: 0.75-1.75, 2-2.75, 3-3.75, and 4-4.5. The amount of fat and the adipocyte size in the different adipose depots increased as BCS did (P < 0.001) while the number of adipocytes did not change. The greatest ability to accumulate or mobilize fat was the subcutaneous depot (slope of the regression between amount of fat and BCS, b = 1.92; P < 0.001). Fatty acid synthase (FAS) lipogenic enzyme activity was affected by BCS, while G3-PDH and G6-PDH activities were not.Key words: Adipose tissue, body condition score, adipocyte size, lipogenic enzyme activity, ewes Arana, A., Mendizabal, J. A., Delfa, R., Eguinoa, P., Soret, B., Alzon, M. et Purroy, A. 2005. Activité lipogénique des brebis Rasa Aragonesa avec différent note d'état corporel. Can. J. Anim. Sci. 85: 101-105. On a etudié l'effet de la note d'état corporel (nCC) sur le metabolisme des differentes dépots adipeux dans les brebis de race Rasa Aragonesa, distribuées dans quatre groups de nCC (échelle 0-5): 0,75-1,75, 2-2,75, 3-3,75, et 4-4,5. La quantité de tissu adipeux et le diamètre des adipocytes des differentes dépots ont augmenté avec la nCC des brebis (P < 0,001) mais il n'a pas eu de variation du nombre des adipocytes. Le tissu adipeux sous-cutané a montré la plus grande capacité d'acumulation/mobilisation (pente de la regression entre la quantité de tissu adipeux et la nCC, b = 1,92; P < 0,001). En ce qui concerne à l'activité des enzymes lipogéniques, uniquement on a trouvé variation de l'activité de l'enzyme FAS Mots clés: Tissu adipeux, note d'état corporel, taille des adipocytes, activité enzymatique lipogénique, brebis Sheep accumulate fat reserves when feed is available in excess and mobilize it when feed is limiting. Fat mobilization occurs mainly over the first period of lactation and the total loss of fat reserves can reach 70% (Cowan et al. 1979). Depending on the production system used, recovery of fat reserves is initiated either after weaning or during the final stage of lactation. Fat accumulation will then take place until mating or even during early gestation. The activity of different lipogenic and lipolytic enzymes is involved in the fat accumulation and mobilization processes. Furthermore, there are changes in adipose tissue cellularity, mainly in adipocyte size, which are achieved by changes in enzyme activity (Vernon 1986).There are different studies of adipose tissue metabolism in sheep either in periods of negative energy balance when fat mobilization occurs (Vernon et al. 1981) or in periods of positive energy balance when fat accretion exists (Sebastian et al. 1993). Nevertheless, the body condition score (range from 0 to 5; Russel et al. 1969) of t...

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Changes during growth and fattening in the number and size of adipocytes and in the activity of the lipogenic enzymes glycerol 3-phosphate dehydrogenase (G3PDH), fatty acid synthetase (FAS) and lipoprotein lipase (LPL) were studied in perirenal (PR) and subcutaneous (SO adipose depots of 28 male lambs of Rasa Aragonesa Spanish breed. Three groups of animals were slaughtered at: 32 (s.d. 6) (no. = 10), 89 (s.d. 8) (no. = 10) and 120 (s.d. 8) (no. = 8) days of age. A significant increase in the quantity of fat was observed as the age of the lambs increased (P < 0-001). Fat deposition was higher between 89 and 120 days of age. The number of adipocytes in the PR depot did not change but hypertrophy in this depot continued during the whole period studied (P < 0-001). In the SC depot a significant increase in adipocyte volume was only found between 89 and 120 days of age (P < 0-001). The increase in G3PDH activity (which estimates fatty acid esterification) and FAS activity (which estimates fatty acid synthesis) was greater in the final phase of the study. Besides, LPL enzyme activity (which estimates the uptake of plasma fatty acids) increased between 32 and 89 days of age in both depots and between 89 and 120 days in PR depot (P < 0-001).