Hepatic steatosis is strongly associated with chronic liver disease and systemic metabolic disorder. Adipose lipolysis is a recognized principal source of intrahepatic fat in various metabolic disorders, including non-alcoholic fatty liver disease. We hypothesized that, in the premorbid state, hepatic de novo lipogenesis (DNL) driven by excess carbohydrates abundance might play a more significant role. We employed a novel nutritional model in sheep of two distinct carbohydrates abundances. During 4 months of the dietary treatment, lambs were monitored for metabolic and terminal liver parameters. Lambs grown on the high-calorie (Hc) diet were consistently more hyperglycemic and hyperinsulinemic than lambs grown on the lower-calorie (Lc) diet (P < 0.0001). As a result, the HC lambs developed systemic-(HOMA-IR of 7.3 vs. 3.1; P < 0.0001), and adipose-(ADIPO-IR of 342.7 vs. 74.4; P < 0.0001) insulin resistance, significant adiposity (P < 0.0001), and higher plasma triglycerides (P < 0.05). Circulating leukocytes in the HC lambs had higher mRNA expression levels of the proinflammatory markers CCL2 (P < 0.01) and TNF-alpha (P < 0.04), and IL1B trended higher (P < 0.1). Remarkably, lambs on the HC diet developed substantial liver steatosis (mean fat content of 8.1 vs. 5.3% in the LC group; P < 0.0001) with a higher histological steatosis score (2.1 vs. 0.4; P < 0.0002). Hepatic steatosis was most-strongly associated with blood glucose and insulin levels but negatively correlated with circulating fatty acids-indicating a more significant contribution from hepatic DNL than from adipose lipolysis. Sheep may prove an attractive large-animal model of fatty liver and metabolic comorbidities resulting from excess carbohydrate-based energy early in life.

Simple SummaryPropylene glycol (PG) and glycerol are common energy substances used to supplement the feed of transitioning ruminants in order to minimize the development of metabolic disorders related to energy deficiency. Their effects on the energetic status of the animal have been, thus far, studied mostly by oral administration, which exposes them to substantial microbial metabolism in the rumen. This study compared the direct metabolic effects of these substances following their intravenous (IV) infusion. We found that glycerol was highly glucogenic and insulinotropic, as expected. However, surprisingly, PG had no significant effect on the circulating levels of glucose or insulin. Unlike glycerol, PG significantly raised circulating lactate levels and showed some potential tissue damage activity. Our study points to glycerol, rather than PG, as a potential IV treatment for efficient relief of hypoglycemia and hyperketonemia.AbstractNegative energy balance (NEB) is a state of insufficient dietary-energy consumption, characterized by the breakdown of adipose fat to meet the physiological energy expenditure. Extensive NEB, as common in high-yielding transitioning ruminants, drives significant metabolic disturbance and pathologies such as pregnancy toxemia and ketosis. Strategies to minimize the severity of NEB include the use of energy-dense feed supplements, like glycerol and propylene glycol (PG), or IV glucose infusion during severe hypoglycemia. PG and glycerol have been studied mainly by oral or ruminal administration, which exposes them to substantial metabolism in the digestive system. To investigate their direct benefits to mitigating NEB, we intravenously infused them into sheep induced into NEB by feed restriction. Sixteen 5-month-old ewe lambs at NEB were IV-treated with 170 mL isotonic saline containing 15% glycerol or 15% PG. Both PG and glycerol effectively reduced hyperketonemia by 57% and 61%, and inhibited adipose lipolysis by 73.6% and 73.3%, respectively. Surprisingly, only glycerol was glucogenic (p < 0.0001) and insulinotropic (p < 0.0075), while PG was primarily utilized for production of lactate (p < 0.0001). Tissue-damage biomarkers indicated hemolytic activity for PG. This study revealed glycerol as a superior IV treatment for effective relief of NEB. Since it carries no risk of glucose overloading, glycerol IV infusion may also have clinical advantages over glucose for treatment of pregnancy toxemia and ketosis.

This research determined effects of dietary supplementation with rumen protected arginine on metabolites and amino acids in maternal plasma and lamb survival rate at birth (LSRAB) in prolific Afec-Assaf ewes. The hypothesis was that rumen protected arginine, the precursor for nitric oxide and polyamines, would increase placental development and vascularity, utero-placental blood flow and nutrient transport, and reduce oxidative stress to increase LSRAB. Ewes were fed either their basal diet, basal diet with rumen protected arginine or basal diet with unprotected arginine (18g/head/d). The supplemental arginine was about 1% of the dry matter intake from d 40 or d 60 of gestation until parturition. Ninety-two of 98 ewes produced live lambs. Ewes fed protected arginine had greater (P=0.002) concentrations of arginine and other amino acids in plasma, whereas unprotected arginine did not affect concentrations of arginine, but decreased (P&0.05) concentrations of some amino acids. There was no effect of treatments on gestation length (144±2d), prolificacy (2.65 lambs born/ewe), LSRAB (0.80), body weight (88.8±10.8 kg) and body condition score (2.8±0.6) of ewes, or birth weight and crown-rump length of lambs. The GI was affected by sex of lamb (P=0.008), parity of ewe (P=0.002), litter size (P=0.0001) and lamb status (P=0.003). Of 229 lambs born, 32 were dead and 16 died before 5 mo of age, leaving 181 lambs with records on weights at birth and 5 mo of age. Interestingly, lambs born to ewes fed the unprotected and protected arginine weighed 3.6 kg less at postnatal d 150 than lambs from control ewes.