Predictive value of 1-hour postprandial SPARC levels on metabolic outcomes from Mediterranean diet adherence: results from a randomized controlled feeding study

Precision nutrition is pivotal to preventing cardiometabolic diseases. However, almost no single blood biomarker capable of predicting the metabolic benefits of specific dietary patterns has yet been identified. Here, we revealed the associations of plasma levels of the secreted protein acidic and rich in cysteine (SPARC), an inflammatory factor highly expressed in fat tissues, and insulin sensitivity improvement in a 6-month randomized controlled, calorie-restricted feeding trial recruiting 235 Chinese adults with overweight/obesity and prediabetes: the Mediterranean diet (MD) group (n = 81), the traditional Jiangnan diet (TJD) group (n = 81), and the control diet (CD) group (n = 73). The 1-h post-glucose loading plasma SPARC levels (SPARC-1H) decreased significantly from baseline to 3 months and 6 months in the MD group, whereas no significant changes were observed in the TJD or CD groups. Further analyses revealed that the individuals with higher baseline SPARC-1H levels were associated with fewer improvements in fasting insulin (β ± SE: 1.54 ± 0.43; P = 0.002), fasting glucose (0.10 ± 0.04; P = 0.049), the homeostasis model assessment of insulin resistance (HOMA-IR, 0.47 ± 0.12; P = 0.0005), and the homeostasis model assessment of β-cell function (HOMA-β, 7.63 ± 3.27; P = 0.047) after 6 months in the MD group. Moreover, baseline SPARC-1H levels were positively correlated with changes in lipidomic profiles, including three alkenylphosphatidylethanolamines, which potentially mediate the cardiometabolic benefits of MD. No significant associations were observed in the other two diet groups. Our findings suggest postprandial SPARC as a predictor for the metabolic benefits of MD, offering a potential biomarker for individualized nutrition intervention against cardiometabolic diseases.