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Home » Archive » 2014

TDK conference 2014

Dynamics of adipose tissue morphology in periparturient dairy cows
Kluge Franziska - year 4
SZIU Faculty of Veterinary Science, Department of Physiology and Biochemistry
Supervisors: Dr. Ákos Kenéz, Dr. Gábor Mátis, Dr. Korinna Huber

Abstract:

During the peripartal period the dairy cow undergoes enormous metabolic changes switching from the anabolic to the catabolic status due to the onset of lactation. In early lactation the cow is in a negative energy balance, in which the feed intake cannot cover the energy requirements. Therefore, cows mobilize the body’s own energy reserves. The adipose tissue is the major site of energy storage and through lipolysis it liberates fatty acids and glycerol into the blood, providing metabolic energy. Due to the lipid mobilization, the morphology of adipose tissue has to be dynamically modified, e.g. by reducing cell size due to decreased lipid droplet size.

The aim of this study was to investigate the morphological changes in adipose tissue during the periparturient period. As other studies provided evidence for possible differences between adipose tissue depots within the same animal, both the subcutaneous (SCAT) and retroperitoneal adipose tissue (RPAT) were examined.

The study included 13 dairy cows of which biopsy samples of SCAT and RPAT were collected -42d, +1d, +21d, +100d relative to parturition. The histomorphometric analysis of the adipose tissue was performed using cryostat-cut tissue slices stained with hematoxylin eosin. Cell size was determined in both SCAT and RPAT for all four time points. Triglyceride (TG) content of the adipose tissue as well as the genomic DNA of the samples were also measured.

The adipocytes of the SCAT constantly decreased in cell size within the peripartal period, whereas the RPAT had the largest cells on d+1 and subsequently decreased in cell size more drastically. Larger numbers of small adipocytes on d+100 in both tissue depots reflected a depletion of adipocyte lipid droplets due to the higher rate of lipolysis in times of a negative energy balance. However, this seemed to be more pronounced in the RPAT indicated by left sided shift of the frequency distribution of cell size. This was also confirmed by the observation that abdominal adipose depots decreased faster during early lactation than subcutaneous depots (Raschka et al., unpublished data). Hypothetically, a decrease in cell size should be associated with a decreased TG storage and an increased DNA concentration. Interestingly, the TG and DNA content of the adipose tissue barely correlated with the cell size, which indicates that the decrease in cell size is not simply due to a decrease in TG. Furthermore, TG concentrations differed among depots with higher concentrations in the SCAT.

Based on our results, it can be stated that the dynamic changes within the adipose tissue are determined not only by the increased lipolysis during early lactation. There are many other factors such as lipogenesis, cell death and adipocyte differentiation which substantially contribute to differences in morphology.



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