Endocrine Abstracts

Introduction: Leptin is a well-known adipokine which has a critical role in the regulation of body weight, body fat mass, appetite, and food intakes. Energy-supplying nutrients such as carbohydrates is a dietary-related factor which has potential effects on plasma leptin levels. The effect of habitual carbohydrates intake on leptin gene expression was limited only in animal studies. The current study aimed to investigate the association of habitual carbohydrate intake with leptin gene expression in visceral and subcutaneous adipose tissue of non-diabetic adults.

Methods: In this cross-sectional study, visceral and subcutaneous adipose tissues were gathered from 102 participants aged≥20, who had undergone elective abdominal surgery with minimal impact on dietary intake. All of the subjects were free of diabetes and cancers and without using anti-lipid medication. Habitual dietary intake of participants was collected before surgery using a reliable validated semi-quantitative food frequency questionnaire, and daily intake of carbohydrates including total carbohydrates, fiber, glucose, fructose, and total sugar were calculated. To adjust energy intake for dietary exposures, the residual method was used. The mRNA expressions of leptin gene in visceral and subcutaneous adipose tissues were measured by real-time quantitative PCR. Linear regression models were used to estimate dietary carbohydrate intake and leptin gene expression after adjustment for potential confounding variables.

Results: The mean age and body mass index (BMI) of participants was 41.7 years and 25.6 kg/m², respectively. Leptin mRNA expression in visceral was higher than subcutaneous adipose tissue (0.375 vs. -1.210, P=0.891). After adjusting for age, BMI, and insulin level, total carbohydrate intake was positively associated with leptin gene expression in visceral and subcutaneous adipose tissue (β=0.484 and 0.522, respectively). Usual intake of sugar (β=0.425, P<0.001), glucose (β=0.323, P=0.004), and fructose (β=0.336, P=0.003) was directly associated with leptin gene expression in subcutaneous fat depots, additionally, we found significant positive association between leptin expression in visceral adipose tissue and sugar (β=0.377, P=0.001), fructose (β=0.263, P=0.018), and glucose (β=0.242, P=0.034). However, dietary intake fiber was negatively associated with leptin mRNA expression in both subcutaneous (β=−0.391, P=0.001) and visceral (β=-0.330, P=0.007) adipose tissues.

Conclusions: There was the significant positive association of total carbohydrate, sugar, fructose, and glucose and inverse association of fiber on leptin gene expression in subcutaneous and visceral fat mass, independent of BMI, age and insulin level. This might provide an initial step towards understanding nutrient effects on energy homeostatic pathways to consider future clinical approaches to dietary weight loss interventions.