Long term effects of high fat or high carbohydrate diets on glucose tolerance in mice with heterozygous carnitine palmitoyltransferase-1a (CPT-1a) deficiency: Diet influences on CPT1a deficient mice.
Nutr Diabetes 2011;
1:e14. [PMID:
22229081 PMCID:
PMC3251273 DOI:
10.1038/nutd.2011.11]
[Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
Background: Abnormal fatty acid metabolism is an important feature in the mechanisms of insulin resistance and β-cell dysfunction. Carnitine palmitoyltransferase-1a (CPT-1a, liver isoform) has a pivotal role in the regulation of mitochondrial fatty acid oxidation. We investigated the role of CPT-1a in the development of impaired glucose tolerance using a mouse model for CPT-1a deficiency when challenged by either a high-carbohydrate (HCD) or a high-fat diet (HFD) for a total duration of up to 46 weeks.
Methods: Insulin sensitivity and glucose tolerance were assessed in heterozygous CPT-1a-deficient (CPT-1a+/−) male mice after being fed either a HCD or a HFD for durations of 28 weeks and 46 weeks. Both glucose and insulin tolerance tests were used to investigate β-cell function and insulin sensitivity. Differences in islet insulin content and hepatic steatosis were evaluated by morphological analysis.
Results: CPT-1a+/− mice were more insulin-sensitive than CPT-1a+/+ mice when fed either HCD or HFD. The increased insulin sensitivity was associated with an increased expression of Cpt-1b (muscle isoform) in liver, as well as increased microvesicular hepatic steatosis compared with CPT-1a+/+ mice. CPT-1a+/− mice were more glucose tolerant than CPT-1a+/+ mice when fed the HCD, but there was no significant difference when fed HFD. Moreover, CPT-1a+/− mice fed HFD or HCD had fewer and smaller pancreatic islets than CPT-1a+/+ mice.
Conclusions: CPT-1a deficiency preserved insulin sensitivity when challenged by long-term feeding of either diet. Furthermore, CPT-1a-deficient mice had distinct phenotypes dependent on the diet fed demonstrating that both diet and genetics collectively have a role in the development of impaired glucose tolerance.
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