Circulating apelin is increased in patients with type 1 or type 2 diabetes and is associated with better glycaemic control

CONTEXT

Apelin is an adipokine expressed in several tissues and it appears to be involved in energy metabolism.

OBJECTIVE

The aim of this study was to determine serum apelin levels in a large cohort of patients with type 1 and type 2 diabetes and control subjects and to correlate the results with glycaemic control.

DESIGN AND PARTICIPANTS

One hundred and thirty patients with type 1 diabetes, 98 patients with type 2 diabetes and 162 controls were enrolled in the study. Apelin levels were measured by enzyme-linked immunosorbent assay.

RESULTS

Serum apelin levels were significantly higher in type 1 and type 2 diabetic patients than in controls (P < 0·0001). Serum apelin levels were higher in type 1 than in type 2 diabetic patients (P = 0·02). In multivariate analysis, serum apelin levels were higher in patients with type 1 diabetes and in patients with type 2 diabetes versus controls. We found a negative correlation between glycosylated haemoglobin and serum apelin levels in all diabetic patients (r = -0·17, P = 0·008) and in patients with type 2 diabetes (r = -0·24 P = 0·01). No correlation was found in type 1 diabetic patients.

CONCLUSION

Our study showed that apelin concentrations were increased in diabetic patients. This rise, which was greater in type 1 than in type 2 diabetic patients, suggests that obesity is not the main determinant of plasma apelin levels. The negative correlation with glycosylated haemoglobin in patients with type 2 diabetes could indicate that apelin plays a role in glycaemic balance and even insulin sensitivity.

Liver fat content is associated with an increase in cholesterol synthesis independent of statin therapy use in patients with type 2 diabetes

We investigated how liver fat content (LFC) influences cholesterol metabolism by quantifying liver fat using proton magnetic resonance spectroscopy and by measuring the serum concentrations of lathosterol, a marker of cholesterol synthesis, and sitosterol and campesterol, two markers of cholesterol absorption. We also evaluated whether this relationship could be modified by statin therapy. The study was conducted in 263 patients with type 2 diabetes, 137 of whom (52.0%) received statin therapy.

RESULTS

One hundred and sixty-five patients (62.7%) had steatosis (LFC>5.5%). We performed specific analyses in patients without statin therapy and in patients treated with statin therapy. In both groups, the lathosterol to cholesterol ratio correlated positively with LFC, and in multivariate analysis, the lathosterol to cholesterol ratio was associated with LFC independently of age, gender and BMI. Sitosterol and campesterol concentrations were not associated with LFC.

CONCLUSIONS

Our study suggests that in patients with type 2 diabetes, LFC is associated with an increase in cholesterol synthesis that is independent of obesity or diabetes mellitus. Statin therapy does not modify this relationship.