Key result
Acute fat challenge increases cardiac glutathione AUC ~16% in early diabetes, but effect wanes with disease progression.
Why the study?
Insulin resistance shifts cardiac fuel preference toward fatty acid beta-oxidation, which generates more mitochondrial oxidants than glucose oxidation, raising the possibility that an acute fat bolus places a disproportionate redox burden on the diabetic heart.
Does a fat tolerance test via cottonseed oil gavage alter cardiac glutathione exposure and plasma triacylglycerol clearance in insulin-resistant (OLETF) rats compared to lean (LETO) rats at pre-diabetic and frank type 2 diabetic stages?
Does a fat tolerance test via cottonseed oil gavage alter cardiac glutathione exposure and plasma triacylglycerol clearance in insulin-resistant (OLETF) rats compared to lean (LETO) rats at pre-diabetic and frank type 2 diabetic stages?
In a rat model of type 2 diabetes, the heart's compensatory increase in glutathione mobilization during an acute lipid load is lost as the disease progresses to frank diabetes, despite worsening triglyceride intolerance, ventricular hypertrophy, and hypertension.
Highlights potential antioxidant vulnerability in advanced diabetes under lipid stress; hypothesis-generating for redox interventions pending human trials.
Type 2 diabetes (T2DM) imposes chronic metabolic and oxidative stress on the heart, and glutathione (GSH), the most abundant non-enzymatic antioxidant in the myocardium, is central to its defense against this stress. Insulin resistance shifts the heart's fuel preference toward fatty acid β-oxidation, a pathway that generates more mitochondrial oxidants than glucose oxidation, raising the possibility that an acute fat bolus places a disproportionate redox burden on the diabetic heart. We used a fat tolerance test (FTT; cottonseed oil gavage) to measure cardiac GSH and plasma triacylglycerol (TAG) clearance in lean (LETO) and insulin resistant (OLETF) rats at 14 weeks (pre-diabetic) and 28 weeks (frank T2DM) of age. At 14 weeks, cardiac GSH exposure across the FTT (AUC) was 16% greater in OLETF than LETO. By 28 weeks, this elevation was no longer present and was reversed at two individual timepoints, despite OLETF plasma TAG clearance being substantially more impaired relative to LETO at this age (TAG AUC 77% greater than LETO at 14 weeks vs. 113% greater at 28 weeks). Ventricular mass did not differ between strains at 14 weeks but was 10% greater in OLETF by 28 weeks, and systolic blood pressure was similarly unchanged at 13 weeks but 27% greater in OLETF by week 27. These findings reveal a dissociation between the cardiac GSH response to an acute fat challenge and the severity of triglyceride intolerance, indicating that a metabolically impaired heart's capacity to mobilize GSH in response to lipid overload is not sustained as T2DM progresses.
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Thorwald et al. (2026) studied Type 2 diabetes and insulin resistance (rat model). Fat tolerance test (cottonseed oil gavage) in insulin-resistant OLETF rats vs. Lean (LETO) control rats was evaluated on Cardiac glutathione (GSH) exposure (AUC) and plasma triacylglycerol (TAG) clearance across the fat tolerance test (Cardiac GSH AUC +16% at 14 weeks; TAG AUC +77% at 14 weeks and +113% at 28 weeks in OLETF vs LETO). Acute fat challenge in diabetic OLETF rats increased cardiac GSH AUC by 16% at 14 weeks vs LETO, an effect lost by 28 weeks despite TAG AUC worsening from 77% to 113% higher.
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