Induced hypoglycemia for 48 hours indicates differential glucose and insulin effects on liver metabolism in dairy cows

Kreipe, L.; Vernay, M.C.; Oppliger, A.; Wellnitz, O.; Bruckmaier, R.M.; van Dorland, H.A. (2011). Induced hypoglycemia for 48 hours indicates differential glucose and insulin effects on liver metabolism in dairy cows. Journal of dairy science, 94(11), pp. 5435-48. Savoy, Ill.: American Dairy Science Association 10.3168/jds.2011-4208

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Hypoglycemia is a characteristic condition of early lactation dairy cows and is subsequently dependent on, and may affect, metabolism in the liver. The objective of the present study was to investigate the effects of induced hypoglycemia, maintained for 48 h, on metabolic parameters in plasma and liver of mid-lactation dairy cows. The experiment involved 3 treatments, including a hyperinsulinemic hypoglycemic clamp (HypoG, n=6) to obtain a glucose concentration of 2.5 mmol/L, a hyperinsulinemic euglycemic clamp (EuG, n=6) in which the effect of insulin was studied, and a control treatment with a 0.9% saline solution (NaCl, n=6). Blood samples for measurements of insulin, metabolites, and enzymes were taken at least once per hour. Milk yield was recorded and milk samples were collected before and after treatment. Liver biopsies were obtained before and after treatment to measure mRNA abundance by real-time, quantitative reverse transcription-PCR of 12 candidate genes involved in the main metabolic pathways. Milk yield decreased in HypoG and NaCl cows, whereas it remained unaffected in EuG cows. Energy-corrected milk yield (kg/d) was only decreased in HypoG cows. In plasma, concentration of beta-hydroxybutyrate decreased in response to treatment in EuG cows and was lower (0.41+/-0.04 mmol/L) on d 2 of the treatment compared with that in HypoG and NaCl cows (on average 0.61+/-0.03 mmol/L, respectively). Nonesterified fatty acids remained unaffected in all treatments. In the liver, differences between treatments for their effects were only observed in case of mitochondrial phosphoenolpyruvate carboxykinase (PEPCKm) and glucose-6-phosphatase (G6PC). In HypoG, mRNA abundance of PEPCKm was upregulated, whereas in EuG and NaCl cows, it was downregulated. The EuG treatment downregulated mRNA expression of G6PC, a marked effect compared with the unchanged transcript expression in NaCl. The mRNA abundance of the insulin receptor remained unaffected in all treatments, and no significant treatment differences were observed for genes related to lipid metabolism. In conclusion, low glucose concentrations in dairy cows affect liver metabolism at a molecular level through upregulation of PEPCKm mRNA abundance. Metabolic regulatory events in the liver are directed, apart from hormones, by the level of metabolites, either in excess (e.g., free fatty acids) or in shortage (e.g., glucose).

Item Type:	Journal Article (Original Article)
Division/Institute:	05 Veterinary Medicine > Department of Clinical Research and Veterinary Public Health (DCR-VPH) > Veterinary Physiology
UniBE Contributor:	Kreipe, Linda, Vernay, Martin César, Oppliger, Alexa, Wellnitz, Olga, Bruckmaier, Rupert, van Dorland, Hendrika Anette
ISSN:	0022-0302
Publisher:	American Dairy Science Association
Language:	English
Submitter:	Factscience Import
Date Deposited:	04 Oct 2013 14:32
Last Modified:	02 Mar 2023 23:21
Publisher DOI:	10.3168/jds.2011-4208
Web of Science ID:	000296264600019
URI:	https://boris.unibe.ch/id/eprint/12243 (FactScience: 218555)