The Influence of Subcutaneous and Visceral Adipocyte Geometries on Metabolic Parameters and Metabolic Regulating Hormones in Obese and Non-Obese Subjects

Abstract

Adipose tissue plays a pivotal role in endocrine and metabolic homeostasis. This study aimed to compare subcutaneous and visceral adipocyte measurements, including area, shortest diameter, longest diameter, and perimeter, between groups of different metabolic profiles; and to determine correlations of adipocyte geometries with metabolic parameters and hormones in obese (n=20) and non-obese subjects (n=14). We hypothesized that geometries of subcutaneous and visceral adipocytes differ between groups with distinct metabolic conditions, and that their measurements correlate with obesity parameters, metabolic profiles, and hormones differently within subcutaneous and visceral adipocyte parameters as well as between obese and non-obese subjects. A total of 34 subjects were classified based on insulin resistance, using the Homeostatic Model Assessment for Insulin Resistance (HOMA-IR) >2.3, and the presence of hypertension (HT), defined as systolic blood pressure (SBP)/diastolic blood pressure (DBP) ≥130/80 mmHg. These subjects underwent open abdominal surgery, with blood sample collection in a fasting state before the operation, and abdominal subcutaneous and omental (visceral) adipose tissue collection during the operation. Subjects with insulin resistance (n=6) and those with HT (n=15) both had a greater size of visceral adipocytes compared to those without insulin resistance (n=28) or HT (n=19), respectively; however, there were no significant differences in subcutaneous adipocyte size between the groups. For correlation analyses in obese subjects, subcutaneous adipocyte measurements exhibited significant positive correlations with visceral adipocyte measurements (R=0.592-0.630); while they showed significant negative correlations with cholesterol (R=-0.573) and serum visfatin (R=-0.610), all with p<0.05. Furthermore, in obese subjects, visceral adipocytes geometries were positively correlated with body weight, waist circumference, and hip circumference (R=0.575-R=0.607), all with p<0.05. In non-obese subjects, geometries of subcutaneous adipocytes were significantly positively correlated with body weight, BMI, waist circumference, and visceral adipocyte size (R=0.555-0.642); while were negatively correlated with serum adiponectin (R=(-0.608)-(-0.676)), all with p<0.05. Furthermore, in non-obese subjects, the measurements of visceral adipocytes were significantly positively correlated with body weight, BMI, serum leptin levels, serum leptin/adiponectin ratio, waist circumference, and DBP (R=0.555-0.836); while were negatively correlated with serum adiponectin (R=(-0.608)-(-0.647), all with p<0.05. These results suggest that hypertrophy of visceral adipocytes, rather than subcutaneous adipocytes, could contribute to insulin resistance and hypertension. Subcutaneous adipocyte size in obese subjects was not correlated with obesity parameters but was negatively correlated with cholesterol and visfatin levels potentially reflecting a protective effect or a compensatory mechanism in which an increase in subcutaneous fat might be a response to store excess lipids more safely when visceral fat capacity is limited. In non-obese subjects, visceral adipocyte geometries were positively correlated with DBP but inversely related to serum levels of adiponectin, an anti-inflammatory adipokine, indicating that larger adipocytes in non-obese individuals are not benign but indicative of early metabolic derangement. In conclusion, subcutaneous fat in obese individuals may represent a potentially protective effect or compensatory response to metabolic disturbance induced by excess visceral fat. In non-obese individuals, a larger visceral adipocyte size could signal early metabolic alterations, even in the absence of obesity. The research was funded by the Faculty of Medicine Siriraj Hospital Research Fund ((IO) R015332009). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.