Association of the triglyceride-glucose index with subclinical left ventricular dysfunction in type 2 diabetes mellitus: mediation by myocardial energetic efficiency and resting perfusion.

BACKGROUND: The triglyceride-glucose(TyG) index, a surrogate marker of insulin resistance, has been linked to cardiac dysfunction; however, its underlying associated pathways in patients with type 2 diabetes mellitus(T2DM) remain unclear. This study used cardiac magnetic resonance(CMR) to explore the association of TyG index with subclinical left ventricular(LV) myocardial dysfunction and whether imaging indicators statistically mediate this relationship.

METHODS: In this retrospective cross-sectional study, a total of 235 T2DM patients who underwent CMR examination were included and assigned to three groups based on the tertiles of their TyG indexes as follows: low(< 8.73, n = 78), moderate(8.73-9.36, n = 79), and high TyG index(≥ 9.36, n = 78) groups. LV geometry, function, myocardial energetic efficiency index (MEEi), resting first-pass perfusion, and global peak strain in radial(GRPS), circumferential(GCPS), and longitudinal(GLPS) directions were measured. Univariate and multivariate linear regression models and exploratory mediation analysis were used to analyze the associations of TyG index on LV global strain.

RESULTS: Compared with the low and moderate TyG index groups, the high TyG index group had significantly higher LV remodeling index, lower LV global function index, lower MEEi, impaired resting myocardial perfusion, and reduced LV global peak strain (all p ≤ 0.002). Multivariate analysis showed that TyG index remained independently associated with reduced LV strain after adjusting for confounders (GRPS β = -0.261; GCPS β = 0.271; GLPS β = 0.381; all p < 0.001). And MEEi and upslope were also independently associated with reduced LV GRPS and GLPS (all p < 0.05). Further mediation analysis revealed the statistically mediated proportions of the association between the TyG index and LV global strain were 8.2-8.6% for MEEi and 4.3% to 12.5% for upslope. In model comparison analyses, the TyG index demonstrated substantially better model fit than either component alone across all strain directions (all Akaike Information Criterion difference > 150).

CONCLUSIONS: In patients with T2DM, a higher TyG index is independently associated with decreased LV global strain, and this relationship is statistically mediated by reduced MEEi and impaired resting perfusion upslope. These findings generate hypotheses regarding myocardial energetics and resting perfusion as potential pathways associated with diabetic myocardial dysfunction that warrant prospective investigation.