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  • 1
    In: Diabetes, American Diabetes Association, Vol. 71, No. 11 ( 2022-11-01), p. 2237-2250
    Abstract: Exercise profoundly influences glycemic control by enhancing muscle insulin sensitivity, thus promoting glucometabolic health. While prior glycogen breakdown so far has been deemed integral for muscle insulin sensitivity to be potentiated by exercise, the mechanisms underlying this phenomenon remain enigmatic. We have combined original data from 13 of our studies that investigated insulin action in skeletal muscle either under rested conditions or following a bout of one-legged knee extensor exercise in healthy young male individuals (n = 106). Insulin-stimulated glucose uptake was potentiated and occurred substantially faster in the prior contracted muscles. In this otherwise homogenous group of individuals, a remarkable biological diversity in the glucometabolic responses to insulin is apparent both in skeletal muscle and at the whole-body level. In contrast to the prevailing concept, our analyses reveal that insulin-stimulated muscle glucose uptake and the potentiation thereof by exercise are not associated with muscle glycogen synthase activity, muscle glycogen content, or degree of glycogen utilization during the preceding exercise bout. Our data further suggest that the phenomenon of improved insulin sensitivity in prior contracted muscle is not regulated in a homeostatic feedback manner from glycogen. Instead, we put forward the idea that this phenomenon is regulated by cellular allostatic mechanisms that elevate the muscle glycogen storage set point and enhance insulin sensitivity to promote the uptake of glucose toward faster glycogen resynthesis without development of glucose overload/toxicity or feedback inhibition.
    Type of Medium: Online Resource
    ISSN: 0012-1797
    Language: English
    Publisher: American Diabetes Association
    Publication Date: 2022
    detail.hit.zdb_id: 1501252-9
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  • 2
    In: Diabetes, American Diabetes Association, Vol. 70, No. Supplement_1 ( 2021-06-01)
    Abstract: In the Greenlandic Inuit population a common nonsense TBC1D4 p.Arg684Ter variant in muscle is found with an allele frequency of 17%. Homozygous carriers of this variant have impaired glucose tolerance, and a 10-fold increased risk of type 2 diabetes. Here we investigate whether the TBC1D4 p.Arg684Ter affects regulation of skeletal muscle glucose uptake during exercise and during insulin stimulation in the post exercise period. Inuits carrying zero (n=8) or two (n=8) alleles of TBC1D4 p.Arg684Ter were recruited from population surveys in Greenland. Glucose tolerance was measured during a 6 hour oral glucose tolerance test (OGTT). Skeletal muscle glucose uptake was measured by applying arterial-venous balance technique across the legs during one-legged exercise and during subsequent euglycemic hyperinsulinemic clamp. Glucose uptake was measured in both the rested and the exercised leg. During the OGTT blood glucose was similar at fasting but markedly elevated (by 4.4 mM) in TBC1D4 p.Arg684Ter carriers compared to matched controls at 2 hours, and variants became hypoglycemic at 4 hours (3.3 vs. 4.7 mM) and similar to controls at 6 hours. During exercise, TBC1D4 variant carriers and controls displayed similar glucose uptake in skeletal muscle. During insulin clamp, glucose uptake in the previously rested leg was lower (~50%) in TBC1D4 variant carriers compared to controls. In the prior exercised leg, glucose uptake during the insulin clamp was higher in both groups compared to the rested leg. However, glucose uptake in the previously exercised leg from TBC1D4 variant carriers was comparable to the previously rested leg in controls and thus still markedly lower than controls. In conclusion: TBC1D4 p.Arg684Ter carriers have impaired insulin stimulated but normal exercise stimulated glucose uptake in skeletal muscle. A single bout of exercise improves muscle glucose uptake in carriers to levels seen in non-exercise muscle of controls. Disclosure J. M. Kristensen: None. T. Hansen: None. M. E. Jørgensen: Research Support; Self; Boehringer Ingelheim International GmbH, Sanofi-Aventis, Stock/Shareholder; Self; Novo Nordisk A/S. J. F. P. Wojtaszewski: None. T. L. J. Larsen: None. C. S. Carl: None. A. Thorup: None. J. Hingst: None. J. Onslev: None. J. S. Olesen: None. M. L. Pedersen: None. E. A. Richter: None. Funding Novo Nordisk Foundation (NNF14OC0013057, NNF17OC0028136); Independent Research Fund Denmark (FSS802000288B5855628)
    Type of Medium: Online Resource
    ISSN: 0012-1797 , 1939-327X
    Language: English
    Publisher: American Diabetes Association
    Publication Date: 2021
    detail.hit.zdb_id: 1501252-9
    Location Call Number Limitation Availability
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