Sex influenced association of directly measured insulin sensitivity and serum transaminase levels: Why alanine aminotransferase only predicts cardiovascular risk in men?

BACKGROUND: Non alcoholic fatty liver disease (NAFLD) is an independent cardiovascular (CV) risk factor which is closely associated with insulin resistance measured by both direct or indirect methods. Gender specific findings in the relationship between alanine aminotransferase (ALT) and CV disease, the prevalence of NAFLD and type 2 diabetes (T2DM) have been published recently. The aim of the present study was to explore the gender aspects of the association between insulin sensitivity, liver markers and other metabolic biomarkers in order to elucidate the background behind the sex influenced difference in both NAFLD, T2DM and their association with CV risk. PATIENTS AND METHODS: 158 female (47 normal and 111 impaired glucose intolerant) and 148 male (74 normal and 74 impaired glucose tolerant) subjects were included (mean age: 46.5 ± 8.31 vs. 41.6 ± 11.3, average Hba1c < 6.1 %, i.e. prediabetic population, drug naive at the time of the study). Subjects underwent a hyperinsulinemic normoglycemic clamp to determine muscle glucose uptake (M3), besides liver function tests and other fasting metabolic and anthropometric parameters were determined. RESULTS: Significant bivariate correlations were found between clamp measured M3 and all three liver enzymes (ALT, aspartate aminotransferase and gamma-glutamyl transferase) in both sexes. When data were adjusted for possible metabolic confounding factors correlations ceased in the male population but stayed significant in the female group. Feature selection analysis showed that ALT is an important attribute for M3 in the female but not in male group (mean Z: 3.85 vs. 0.107). Multiple regression analysis confirmed that BMI (p < 0.0001) and ALT (p = 0.00991) significantly and independently predicted clamp measured muscle glucose uptake in women (R(2) = 0.5259), while in men serum fasting insulin (p = 0.0210) and leptin levels (p = 0.0294) but none of the liver enzymes were confirmed as significant independent predictors of M3 (R(2) = 0.4989). CONCLUSION: There is a gender specific association between insulin sensitivity, metabolic risk factors and liver transaminase levels. This might explain the sex difference in the predictive role of ALT elevation for CV disease. Moreover, ALT may be used as a simple diagnostic tool to identify insulin resistant subjects only in the female population according to our results.

[The effect of genetic risk of diabetes on the correlations in bone and energy homeostasis]. / A genetikai diabeteskockázat hatása a csontanyagcsere-energia-háztartás kapcsolatokra.

INTRODUCTION: Type 2 diabetes is associated with increased risk of bone fractures, and the connection between bone remodeling and carbohydrate homeostasis is decoupled. It is not known whether these phenomena are the consequence of the deteriorating glucose metabolism, and the increasing insulin resistance or they belong to the genetic risk of type 2 diabetes. AIM: The aim of the authors was to clarify the impact of genetic risk on bone and carbohydrate homeostasis connections. METHOD: Hyperinsulinemic-normoglycemic clamps, and oral and iv. glucose loads were done to select 18 metabolically healthy females with first degree type 2 diabetic relatives -and 26 without diabetic relatives. RESULTS: The connections between total body glucose utilization and the activity of the bone metabolic unit were missing in healthy females with the genetic risk of type 2 diabetes, like in those with manifest diabetes. In this risk group the level of low-density-large molecular sized LDL lipids were decreased, while the high-density LDL group with low molecular size was increased. The latter change was in significant connection with increased interleukin-6 levels and increased bone resorption within the bone metabolic unit. CONCLUSIONS: These data suggest that the missing connection between glucose and bone metabolism is not the consequence of the developing insulin resistance and deteriorating glucose metabolism, but rather it belongs to the inherited diabetes risk. The etiology of this early alteration, which develops prior to glucose intolerance and insulin resistance is unknown and needs further investigations.

Serum osteocalcin is associated with improved metabolic state via adiponectin in females versus testosterone in males. Gender specific nature of the bone-energy homeostasis axis.

OBJECTIVE: The osteoblast-derived protein osteocalcin (OCN) is known to be involved in glucose metabolism by increasing adiponectin secretion from adipocytes. Recently, OCN was also found to enhance testosterone production in mouse testes, suggesting that OCN effects on energy metabolism may be mediated through testosterone. Our aim was to assess a possible gender difference in the metabolic effect of OCN in humans. METHODS: We included 135 women and 155 men exhibiting changes in glucose tolerance in our study. Oral and intravenous glucose tolerance tests (OGTT and IVGTT, respectively) and a hyperinsulinemic normoglycemic clamp were performed. For clamp indices, whole body (M1) and muscle (M2) glucose uptake values were used. Leptin, adiponectin serum lipid, lipoprotein, total serum OCN and testosterone levels, and body composition were determined. RESULTS: Higher OCN values were associated with improving metabolic state in both genders. Adiponectin and OCN correlated significantly only in females (r=+0.254, p=0.0029), while in men, testosterone and OCN values showed a significant positive correlation (r=+0.243, p=0.0023), independent of age, BMI, HbA1c and body composition. In women, adiponectin was confirmed by feature selection analysis as being an independent determinant of OCN, in addition to age and three of the IVGTT glucose values. In men, besides M1, BMI, M2, leptin, body fat percent, and the 90-minute OGTT glucose reading testosterone, but not adiponectin were identified as independent contributors for OCN. CONCLUSION: We confirmed the 'classic' adiponectin-mediated insulin-sensitising effect of OCN only in females. In men, a testosterone-mediated OCN metabolic effect is more likely.