Hyperinsulinemic clamp modulates milk fat globule lipid composition in goats

Abstract

We determined the effect of insulin on milk fatty acid (FA) and lipid composition in goats. Four dairy goats, 150 d in milk, were subjected to hyperinsulinemic clamp (treatment) or saline (control) infusion for 4d in a crossover design study. Composition and concentration of plasma and milk FA, triglycerides, phospholipids, sphingolipids, and cholesterol were determined. Mammary gland biopsies were taken at the end of each experimental period and lipogenic gene expression was determined. Plasma insulin was elevated 3.5-fold, whereas plasma glucose remained constant during the treatment period. Feed intake decreased by 26% and fat yield decreased by 17% relative to controls. No change in nonesterified FA concentration was found between controls and treatment. Compared with controls, insulin decreased yield of long-chain saturated FA by 14%. Milk concentration of long-chain FA was reduced by 3%, whereas that of medium-chain FA increased by 5% during the treatment compared with controls. Hyperinsulinemic clamps increased the yields of milk phospholipids by 9% and cholesterol by 16%, whereas it only tended to decrease triglyceride yields (by 11%). Hyperinsulinemic treatment resulted in compositional changes in the milk fat globule membrane, as reflected by 15 and 9% decreases in phosphatidylethanolamine and phosphatidylcholine concentrations, respectively. Lipogenic gene expression of acyl coenzyme A carboxylase, stearoyl coenzyme A desaturase, and FA synthase did not change, whereas lipoprotein lipase gene expression tended toward an increase in the treatment period compared with controls. Hyperinsulinemic clamps reduce the availability of long-chain FA, which are considered to originate from the diet and adipose lipolysis for milk lipid synthesis by the mammary gland of goats. Under these conditions, long-chain FA might be preferentially channeled to phospholipid rather than triglyceride synthesis, hence increasing phospholipid yields. Mechanisms determining FA distribution among milk lipid components and the consequences of altered milk fat globule membrane lipid composition remained to be elucidated.

Influence of glucogenic dietary supplementation and reproductive state of dairy cows on the composition of lipids in milk

“…The fact that no differences were found in the morning samples might be attributed to the proximity of blood sampling time to the propylene glycol drenching, because plasma insulin concentration is expected to peak ∼2 h after propylene glycol administration (Studer et al, 1993;Grummer et al, 1994). In a previous study, following alteration of lipid metabolism in the mammary gland by hyperinsulinogenic clamp, PS was the main MFG membrane constituent to show changes in concentration (Argov-Argaman et al, 2012). Similarly, in the present study, the combined effect of treatment and cycle day affected PS.…”

“…Extraction of total lipids and fatty acid methyl ester (FAME) preparation Total lipids were extracted from the milk using the coldextraction procedure (Folch et al, 1957) with minor adaptations as previously described (Argov-Argaman et al, 2012). Each sample was divided into two equal portions: one was used for lipid analysis by normal-phase liquid chromatography and the other was used for fatty acid analysis by gas chromatography.…”

“…The analysis was performed in a gas chromatograph (Agilent Technologies, Santa Clara, CA, USA) equipped with a fusedsilica capillary column (60 m × 0.25 mm ID, DB-23, Agilent Technologies) as previously described (Argov-Argaman et al, 2012). Briefly, oven temperature was programmed from 130°C to 170°C at a rate of 27°C/min, from 170°C to 215°C at 2°C/min, holding at 215°C for 8 min, from 215°C to 250°C at 40°C/min, holding at 250°C for 5 min.…”

“…Analysis of polar and neutral lipids Polar and neutral lipids were identified and quantified by HPLC (HP 1200, Agilent Technologies) combined with an evaporative light-scattering detector (ELSD; Agilent Technologies) as previously described (Argov-Argaman et al, 2012). The separation process was managed by ChemStation software, which permitted data acquisition from the ELSD.…”

“…Milk polar lipid composition and concentration are closely associated with lactation stage (Bitman and Wood, 1990), genetic predisposition (Argov-Argaman et al, 2013), plasma insulin concentration (Argov-Argaman et al, 2012) and diet (Lopez et al, 2008). In general, milk polar lipid composition and concentration are altered when systemic or local -within the mammary gland -changes in lipid metabolism are induced.…”