The impact of the chromium supplementation on insulin signalling pathway in different tissues and milk yield in dairy cows.

Thirty days before expected time of parturition, 20 Holstein cows were divided into -Cr and +Cr groups. From day 25 before parturition (BP) up to day 30 after parturition (AP), +Cr cows received 10 mg of Cr (chromium-enriched yeast) daily. Muscle and adipose tissue samples were taken at days -30, -10, +7 and +10 related to parturition, when body condition score (BCS) was also determined. Hepatic tissue samples were taken at days -10 and +7. Tissue samples were used for determination of the insulin signalling pathway protein expressions. Intravenous glucose tolerance test (IVGTT) was performed at days -28, -7, +10 and +30. Milk yield was recorded during first 14 weeks AP. Milk composition was obtained at days 7 and 28 AP. At day 10 BP, protein content of ß-subunit of insulin receptor (IRß) was significantly higher (p Ë‚ 0.05) in muscle, and phosphorylation of insulin receptor substrate 1 at serine 307 (pIRS-1 Ser307 ) was significantly lower (p Ë‚ 0.05) in hepatic tissue of +Cr group. After parturition, pIRS-1 Ser307 was significantly lower in muscle tissue at days 7 and 28 (p Ë‚ 0.05 and p Ë‚ 0.001, respectively), while phosphorylation of Akt at serine 473 (pAkt Ser473 ) was significantly higher (p Ë‚ 0.01) in hepatic tissue at day 7 AP in +Cr group. Chromium had opposite effect on insulin kinetics during IVGTTs obtained BP and AP. Insulin secretion was significantly reduced at day 7 BP and significantly enhanced at day 10 AP, when NEFA concentration was also significantly increased. Milk yield and ECM value were depressed in +Cr group. DMI and BCS were significantly enhanced in +Cr group at day 7 BP. In conclusion, chromium modulates insulin signalling pathway in dairy cows, but targeted signalling molecules are different in antepartal then post-partal period, probably due to duration of exposure to chromium and different energy status between those periods.

Fructose-Rich Diet-Induced Changes in the Expression of the Renin Angiotensin System Molecules in the Heart of Ovariectomized Female Rats Could be Reversed by Estradiol.

The renin-angiotensin system has been implicated in the development of metabolic syndrome and appears to be a key in the local tissue control of normal cardiac functions. Physiological concentrations of estrogens have been shown to be cardioprotective, especially against the damaging effects of fructose-rich diet. The aim of the study was to investigate the expression of the renin-angiotensin system molecules with potentially deleterious effect on the heart (angiotensin-converting enzyme and angiotensin II type 1 receptor) and those with potentially protective effects, (angiotensin-converting enzyme 2 and angiotensin II type 2 receptor), in ovariectomized fructose fed female rats with 17ß-estradiol replacement. Real-time PCR and Western blot analysis were used for quantification of gene and protein expression in the heart. Fructose diet increased the expression of angiotensin-converting enzyme and angiotensin II type 1 receptor and decreased the expression of angiotensin-converting enzyme 2 and angiotensin II type 2 receptor. On the other hand, estradiol replacement seems to undo fructose diet effects on cardiac renin-angiotensin system. Downregulation of angiotensin-converting enzyme and angiotensin II type 1 receptor, and reversion of expression of both potentially protective molecules, angiotensin-converting enzyme 2 and angiotensin II type 2 receptor, to the control level in cardiac tissue took place. Obtained results suggest that estradiol may reverse the harmful effect of fructose-rich diet on the expression of renin-angiotensin system molecules. These findings may also be important in further research of phenotypes like insulin resistance, metabolic syndrome, and following cardiovascular pathology in females.

Oestradiol Treatment Counteracts the Effect of Fructose-Rich Diet on Matrix Metalloproteinase 9 Expression and NFκB Activation.

Fructose-rich diet induces metabolic changes similar to those observed in metabolic syndrome. Among other matrix metalloproteinases, MMP-9 has an important role in adverse cardiac remodelling and might have a role in the development of cardiovascular disorders associated with metabolic syndrome. The changes of MMP-9 expression could be mediated via the NFκB pathway. In this study we investigated the effect of fructose-rich diet on MMP-9 expression in the heart of male and female rats, along with the effect of fructose-rich diet and oestradiol on MMP-9 expression in ovariectomized females. We further assessed the effect of fructose-rich diet and oestradiol on NFκB activation, measured as the level of p65 phosphorylation at Ser 276. The results showed that the diet regime did not affect the heart mass. Higher MMP-9 gene expression was found in cardiac tissue of male rats fed the fructose-rich diet than in females on the same diet regime. In ovariectomized females, fructose-rich diet upregulated MMP-9 protein and mRNA expression in the heart, as well as phosphorylation of the p65 subunit of NFκB at Ser 276. Oestradiol replacement therapy reverted these changes in the heart of ovariectomized females. This study has shown that oestradiol could revert the early molecular changes in MMP-9 expression induced by fructose-rich diet that occurred before cardiac hypertrophy development by decreasing phosphorylation of the NFκB p65 subunit at Ser 276.