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Hepatic and adipose mRNA expression of genes related to FGF21 in response to conjugated linoleic acid (CLA) supplementation in dairy cows during early lactation
The hepatokine fibroblast growth factor 21 (FGF21), a member of the FGF super-family, is emerging as an important regulator of metabolism. It is induced by fasting, ketogenic diets, and by peroxisome proliferator-activated receptor (PPAR) agonists. The glycemic and insulin sensitizing effects of FGF21 are mediated through the adipokine adiponectin that is induced by FGF21. We recently reported that the postpartal increase of adiponectin is attenuated in dairy cows receiving the PPAR-agonistic CLA and thus hypothesized that supplementation of cows with CLA in early lactation will affect the expression of FGF21, of the FGF receptor (FGFR) isotopes FGFR1c and FGFR2c, and of the essential co-receptor b-Klotho in liver and adipose tissue. German Holstein cows receiving 100 g/d CLA (n = 11; Lutrell pure, BASF, Germany; each 12% of trans-10, cis-12 and cis-9, trans-11 CLA) or a control fat supplement (Silafat, BASF; CTR; n = 10) from DIM 1 to 182 were biopsied (liver and subcutaneous fat) on d -21, 1, 21, 70, and 105 relative to calving. The target mRNAs were quantified by real-time RT-PCR. Data were analyzed by the MIXED procedure of SAS 9.2. Hepatic FGF21 and FGFFR2c mRNA abundance were affected by time (P < 0.05) and by treatment (FGF21: P = 0.08; FGFR2c: P < 0.01). In CTR cows, a 4.5 fold increase in FGF21 mRNA was observed from d -21 to d 21, followed by a decline to nearly prepartum values by d 105. The CLA cows had less FGF21 mRNA than the CTR cows. The mRNA abundance of FGFR2c increased during lactation in CTR but not in CLA; the greatest difference (1.5 fold) between the CLA and the CTR group was observed on d 70. The mRNA abundance of b-Klotho in the liver and adipose tissue changed over time (P < 0.05), while CLA had no effect. Expression of FGFR1c mRNAin adipose tissue was neither affected by time nor by treatment. The observed upregulation of hepatic FGF21 expression during the first 3 wk in liver supports a role of FGF21 in metabolic regulation and nutrient partitioning during early lactation. The inhibiting effects of CLA supplementation on hepatic mRNA expression of FGF21 and its receptor might promote glucose availability for the mammary gland by reducing peripheral insulin sensitivity.
Keywords:
FGF21, CLA, liver and fat tissues, dairy cow