Insights into Manipulating Postprandial Energy Expenditure to Manage Weight Gain in Polycystic Ovary Syndrome

Abstract

Women with polycystic ovary syndrome (PCOS) are more likely to be obese and have difficulty in losing weight. They demonstrate an obesity-independent deficit in adaptive energy expenditure. We used a clinically realistic preclinical model to investigate the molecular basis for the reduced postprandial thermogenesis (PPT) and develop a therapeutic strategy to normalize this deficit. Sheep exposed to increased androgens before birth develop the clinical features of PCOS. In adulthood they develop obesity and demonstrate an obesity-independent reduction in PPT. This is associated with reduced adipose tissue uncoupling protein expression and adipose tissue noradrenaline concentrations. These sheep are insulin resistant with reduced insulin signaling in the brain. Increasing brain insulin concentrations using intranasal insulin administration increased PPT in PCOS sheep without any effects on blood glucose concentrations. Intranasal insulin administration with food is a potential novel strategy to improve adaptive energy expenditure and normalize the responses to weight loss strategies in women with PCOS.

Keywords: Biological Sciences; Pathophysiology; Sheep Physiology.

Graphical abstract

Figure 1

Postprandial Thermogenesis and Weight (A) Weight of C-sheep (n = 11) and PCOS-sheep (n = 4) from birth to 30 months. Adulthood is indicated by the dotted line. (B) Two subsets of C-sheep showing the obese (O) (n = 4) and normal (N) (n = 4) controls and the PCOS-sheep (n = 4). (C) The basal body temperature in the normal (N) C-sheep, the obese (O) C-sheep, and the PCOS-sheep. (D) The temperature increase after feeding as a function of time in PCOS-sheep and C-sheep at 30 months of age. (E) The maximal minus the minimum temperature after feeding in the (N) C-sheep, the (O) C-sheep, and the PCOS-sheep. (F) The time to maximum temperature in the (N) C-sheep, the (O) C-sheep, and the PCOS-sheep. Data are represented as mean ± SEM. ∗p < 0.05, ∗∗p < 0.01, ∗∗∗p < 0.005, ∗∗∗∗p < 0.001.

Figure 2

Insulin Resistance (A and B) (A) Plasma glucose and (B) insulin in the 45 min after an IV GTT in C-sheep and PCOS-sheep at 24 months of age. (C and D) (C) Fasting insulin concentrations at 24 months and (D) 30 months in C-sheep and PCOS-sheep. (E) Fasting glucose to insulin ratio in C-sheep and PCOS-sheep at 30 months of age. (F) Correlation between postprandial temperature difference and fasting insulin concentrations (p < 0.05). (G) Correlation between fasting insulin concentrations and time to maximal postprandial temperature (p < 0.05). Data are represented as mean ± SEM. ∗p < 0.05.

Figure 3

Expression of UCPs (A) Relative mean gene expression ± SEM measured by RT-PCR in skeletal muscle for uncoupling proteins and genes involved in futile calcium cycling. (B–J) (B) Diagram highlighting the adipose tissue depots studied: the neck (N) fat, inter-scapular back (B) fat, visceral (V) fat, and subcutaneous groin (G) fat. Relative expression of (C) UCP1, (D) UCP2, and (E) UCP3 in the four adipose tissue depots. Immunohistochemistry for UCP1 (brown) in G fat from (F) C-sheep and (G) PCOS-sheep. (H) Correlation between UCP1 expression in G fat and postprandial temperature increase (p < 0.05). Immunohistochemistry for UCP3 (brown) in B fat from (I) C-sheep and (J) PCOS-sheep. (K) Correlation between UCP3 expression in B fat and postprandial temperature increase (p < 0.05). All immunochemistry taken at the same magnification. Scale bar, 100 μm. NS is not significant. Data are represented as mean ± SEM. ∗p < 0.05, ∗∗p < 0.01).

Figure 4

Sympathetic Activity (A) Relative mean gene expression ± SEM for β-adrenergic receptors, measured by RT-PCR, in the neck (N), inter-scapular back (B), visceral (V), and subcutaneous groin (G) adipose tissue depots in C-sheep and PCOS-sheep. (B) NA concentrations in the four adipose tissue depots in C-sheep and PCOS-sheep. (C–E) (C) Four-site average NA concentrations in adipose tissue in C-sheep and PCOS-sheep. Correlation of adipose tissue NA concentrations and (D) postprandial temperature increase (p < 0.05) and (E) body weight at 30 months of age (p < 0.05). NS, not significant; ND, not detected. Data are represented as mean ± SEM. ∗p < 0.05.

Figure 5

Central Insulin Signaling (A–D) (A) Immunohistochemistry for pERK (brown) in the hypothalamus of C-sheep. Inset is negative control serial section. Relative mean gene expression ± SEM for (B) INSR (IR), (C) IRS1, and (D) IRS2 in the frontal cortex of C-sheep and PCOS sheep. (E) Representative western blot of AKT, phospho-AKT (pAKT), ERK, and phospho-ERK (pERK) in the frontal cortex of C-sheep and PCOS-sheep with α-tubulin as a loading control. The size representation in kDa, determined by a molecular weight marker ladder, is shown to the left. Sheep were sacrificed 15 min after an intravenous glucose bolus. (F) Quantification of pAKT to ATK ratio in the frontal cortex in C-sheep and PCOS-sheep. (G) Quantification of pERK to ERK ratio in the frontal cortex in C-sheep and PCOS-sheep. Scale bar, 50 μm. Data are represented as mean ± SEM. ∗p < 0.05.

Figure 6

Intranasal Insulin Administration (A) Assessment of plasma insulin concentrations before and up to 45 min after intravenous (i.v.) GTT in the second cohort of PCOS-sheep (n = 12) at 9, 11, 17, and 20 months of age. (B) Plasma insulin concentrations after i.v. GTT at 20 months of age (black) showing the mean ± SEM of historical age-matched C-sheep (gray). (C) The fasting glucose to insulin ratio in these PCOS-sheep with the mean ± SEM of historical age-matched C-sheep (gray). (D–H) (D) The effect of 10 IU intranasal administration over 60 min of plasma glucose concentration in a single PCOS-sheep. The effect of 10 IU insulin 10 min after administration on plasma glucose in PCOS-sheep (n = 12) in the absence (E) or presence (F) of feeding. The effect of 10 IU insulin 10 min after administration on plasma insulin in PCOS-sheep (n = 12) in the absence (G) or presence (H) of feeding. (I) Temperature increase in PCOS-sheep at 20 months of age as a function of time from feeding (black), after feeding with 10 IU intranasal insulin (gray) and after 10 IU intranasal insulin without feeding (gray dashed line). Data are represented as mean ± SEM. ∗p < 0.05.