Carnivorous fish species such as the rainbow trout (Oncorhynchus mykiss) are traditionally considered to be "glucose intolerant" due to the prolonged hyperglycemia experienced after intake of a carbohydrate-enriched meal. In the present study we use this species to study glucose homeostasis in fish chronically infused with the hypoglycemic agents, insulin and metformin, and fed with a high proportion of carbohydrates (30%). We analyzed liver, skeletal muscle and white adipose tissue (WAT) insulin and metformin specific targets at both biochemical and molecular levels. Trout infused with insulin and metformin can effectively utilize dietary glucose at the liver, resulting in lowered glycemia, increased insulin sensitivity and glucose storage capacity, combined with reduced glucose output. However, in both WAT and skeletal muscle we observed decreased insulin sensitivity with the combined insulin + metformin treatment, resulting in the absence of changes at the metabolic level in the skeletal muscle and an increased potential for glucose uptake and storage in the WAT. We can, therefore suggest that the poor utilization of a diet with a high proportion of carbohydrate by the rainbow trout could at least be partially improved by a combination of insulin and metformin, and that the glucose intolerance observed in this species could be in part due to some of the downstream components of the insulin and metformin signaling pathways. However, the predominant effects of metformin treatment on insulin actions in these three tissues thought to be involved in glucose homeostasis remains exclusive in this species.
- glucose homeostasis
- Copyright © 2010, American Journal of Physiology - Regulatory, Integrative and Comparative Physiology