Isolated hyperglycaemia does not increase VLDL-triacylglycerol secretion in type 1 diabetic men

Attenuated suppression of lipolysis explains the increases in triglyceride secretion and concentration associated with basal insulin peglispro relative to insulin glargine treatment in patients with type 1 diabetes

AIMS

To test the hypothesis that, as well as lowering weight and increasing plasma triglyceride (TG) levels and hepatic fat compared with insulin glargine (GL) in patients with type 1 diabetes, the attenuated peripheral effects of basal insulin peglispro (BIL) may include increased free fatty acid flux to the liver, causing increased very-low-density lipoprotein (VLDL)-TG secretion and lipid oxidation, and decreased TG adipose tissue deposition.

METHODS

In this open-label, randomized, 2-period crossover study, 14 patients with type 1 diabetes received once-daily, individualized, stable BIL or GL doses for 3 weeks. Palmitate flux was assessed using [9,10-³ H]palmitate infusion. VLDL-TG secretion, clearance and oxidation rate were assessed using primed-constant infusion of ex vivo labelled [1-¹⁴ C]VLDL-TG, while VLDL-TG storage rate was assessed using [9,10-³ H]VLDL-TG bolus injection.

RESULTS

The VLDL-TG concentration and secretion rate, and palmitate flux were statistically significantly higher during BIL than during GL treatment (58%, 51% and 35%, respectively). The ratios of least squares (LS) geometric means for VLDL-TG clearance and oxidation were 0.92 (95% confidence interval [CI] 0.72, 1.17) and 1.31 (95% CI 0.91, 1.90), respectively. The difference in LS means for VLDL-TG storage rate was -0.36 (95% CI -0.83, 0.12).

CONCLUSIONS

BIL-treated patients had higher effective lipolysis, VLDL-TG secretion and VLDL-TG concentration compared with GL-treated patients, explaining the increased plasma TG concentrations reported previously. Data support attenuated effects of BIL on lipolysis, in addition to the recently described hepato-preferential glucodynamic effects.

Kinetics of plasma triglycerides in abdominal obesity

PURPOSE OF REVIEW

Abdominal obesity is associated with a number of important metabolic abnormalities including liver steatosis, insulin resistance and an atherogenic lipoprotein profile (termed dyslipidemia). The purpose of this review is to highlight recent progress in understanding the pathogenesis of this dyslipidemia.

RECENT FINDINGS

Recent results from kinetic studies using stable isotopes indicate that the hypertriglyceridemia associated with abdominal obesity stems from dual mechanisms: (1) enhanced secretion of triglyceride-rich lipoproteins and (2) impaired clearance of these lipoproteins. The over-secretion of large triglyceride-rich VLDLs from the liver is linked to hepatic steatosis and increased visceral adiposity. The impaired clearance of triglyceride-rich lipoproteins is linked to increased levels of apolipoprotein C-III, a key regulator of triglyceride metabolism.

SUMMARY

Elucidation of the pathogenesis of the atherogenic dyslipidemia in abdominal obesity combined with the development of novel treatments based on apolipoprotein C-III may in the future lead to better prevention, diagnosis and treatment of the atherogenic dyslipidemia in abdominal obesity.