ponies and horses. Obesity, regional adiposity and insulin resistance are key characteristics of EMS.
Recent studies have confirmed the association between EMS and laminitis. Especially systemic
insulin resistance is linked to laminitis risk in EMS affected ponies and horses. Fat deposition is
suggested to be important contributor to insulin resistance.
Adipose tissue is known to secrete adipokines (e.g. adiponectin, leptin, retinol binding protein 4).
Macrophages may reside in excess adipose tissue and they synthesize chemokines (e.g. monocyte
chemoattractant protein 1). Gene expression profiles of adipokines and chemokines have been used
to determine insulin sensitivity or insulin resistance. In addition, lipogenesis related genes (e.g.
stearoyl-CoA desaturase) and insulin signalling pathway genes (e.g. insulin receptor substrate) can
be used as indicators of insulin resistance.
Our first objective was to study effects of two different pasture types on changes in live weight and
fatness measurements in Finnhorse mares during grazing season. Eleven barren mares were grazing
either on cultivated pasture (CG) or on semi-natural grassland (NG) from the end of May to the
beginning of September. Sixteen mares (6 to 19 years old) were selected to gene expression
profiling from a total of 22 mares included in the grazing experiment. Biopsies were collected from
neck and tail head adipose tissue depots both in May and September. Biopsies were snap-frozen in
liquid nitrogen and stored at -80° C until total RNA was extracted. Gene expression was measured
as mRNA abundances using quantitative real-time PCR (qPCR). QPCR analyses were conducted
using mitochondrial-like 39S ribosomal protein L39 (MRPL39) as an internal control gene. The
following genes were examined: adiponectin, adiponectin receptor 1, adiponectin receptor 2, insulin
receptor substrate 1, leptin, monocyte chemoattractant protein 1 (chemokine C-C motif ligand 2),
retinol binding protein 4 and stearoyl-CoA desaturase. Statistical analyses were based on ΔCt and
10-ΔCt values and mixed models.
Our results showed that at the end of grazing season, the mares on CG were 71 kg heavier and had
1.35 points higher body condition score than mares grazing on NG. In addition, mares on CG had
significantly more fat deposition in the shoulder and tailhead areas than mares on NG. According to
our preliminary results, it is suggested that differences in pasture-associated fat deposition did not
affect expression of studied genes. However, suggestive pasture-associated effects were detected in
expression of monocyte chemoattractant protein 1 (P=0.07) in tail head and in adiponectin receptor
1 (P=0.08) in neck. All studied genes had significant (P<0.05) changes in expression from May to
September. These changes are interpreted to indicate normal response to weight gain and fat
deposition during grazing season. We concluded that based on changes in gene expression in
adipose tissue, there were no signs of increased insulin resistance that could be related to nutritional
status during grazing in studied mares.
In this study, our main objective was to investigate the relationship between weight gain of mares
grazing on two pastures and gene expression profiles in their adipose tissues. However, our
intention is to integrate the data of this study to the data of glucose tolerance tests to further
examine factors associated to insulin resistance and weight gain in horses.
|Otsikko||Proceedings of the 4th Nordic Feed Science Conference, Uppsala, Sweden, 12-13 June 2013|
|Toimittajat||P. Udén, T. Eriksson, B-O. Rustas, C. E. Müller, R. Spörndly, T. Pauly, M. Emanuelson|
|Kustantaja||Organising committee of the 4th Nordic Feed Science Conference|
|Tila||Julkaistu - 2013|
|OKM-julkaisutyyppi||A4 Artikkeli konferenssijulkaisuussa|
|Tapahtuma||Nordic Feed Science Conference - Uppsala, Ruotsi|
Kesto: 12 kesäkuuta 2013 → 13 kesäkuuta 2013
|Kustantaja||Swedish University of Agricultural Sciences Uppsala, Department of Animal Nutrition and Management|
- 412 Kotieläintiede, maitotaloustiede
- body condition score
- metabolic syndrome
- insulin resistance
- Adipose tissue