Hormonal
Local thyroid hormone activation in skeletal muscle via D2 drives a shift from slow-twitch (Type I) to fast-twitch (Type II) fibers, increasing energy expenditure and influencing insulin sensitivity.
Skeletal muscle uses local thyroid hormone activation to adjust its metabolic profile. Higher local T3 levels promote fast-twitch fibers and increase energy expenditure through heat production and glucose uptake. This suggests that muscle-specific thyroid regulation plays a key role in metabolic flexibility and insulin sensitivity.
High TH levels induce a shift from type I fibers (slow) to type II fibers (fast), which results in up-regulation of sarcoendoplasmic reticulum Ca2+ATPase, of glucose transporter 4 (GLUT4) and of uncoupling protein 3 (UCP3) thereby producing heat and increasing energy expenditure.
Why this rating
Supported by D2KO mouse models showing insulin resistance and fiber type shifts.
Source
Metabolic Effects of the Intracellular Regulation of Thyroid Hormone: Old Players, New Concepts
Annunziata Gaetana Cicatiello et al. · Frontiers in Endocrinology · 2018
DOI 10.3389/fendo.2018.00474
More from this paper
- Intracellular regulation of thyroid hormone by deiodinases (D1, D2, D3) dictates tissue-specific metabolic outcomes, where local T3 activation promotes energy expenditure and lipid mobilization, while inactivation preserves energy stores.Good
- Brown Adipose Tissue (BAT) activity and adaptive thermogenesis are critically dependent on local Type 2 Deiodinase (D2) activity converting T4 to T3, particularly in response to cold exposure.Good
- Type 3 Deiodinase (D3) inactivation of thyroid hormone is essential for pancreatic beta-cell maturation and insulin secretion; D3 deficiency leads to glucose intolerance and impaired insulin secretion.Good
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