We have developed a sheep model to facilitate studies of the fetal programming effects of mismatched perinatal and postnatal nutrition. During the last trimester of gestation, twenty-one twin-bearing ewes were fed a normal diet fulfilling norms for energy and protein (NORM) or 50 % of a normal diet (LOW). From day 3 postpartum to 6 months (around puberty) of age, one twin lamb was fed a conventional (CONV) diet and the other a high-carbohydrate -high-fat (HCHF) diet, resulting in four groups of offspring: NORM-CONV; NORM-HCHF; LOW-CONV; LOW-HCHF. At 6 months of age, half of the lambs (all males and three females) were slaughtered for further examination and the other half (females only) were transferred to a moderate sheep diet until slaughtered at 24 months of age (adulthood). Maternal undernutrition during late gestation reduced the birth weight of LOW offspring (P, 0·05), and its long-term effects were increased adrenal size in male lambs and adult females (P, 0·05), increased neonatal appetite for fat-(P¼0·004) rather than carbohydrate-rich feeds (P,0·001) and reduced deposition of subcutaneous fat in both sexes (P,0·05). Furthermore, LOW-HCHF female lambs had markedly higher visceral:subcutaneous fat ratios compared with the other groups (P, 0·001). Postnatal overfeeding (HCHF) resulted in obesity (. 30 % fat in soft tissue) and widespread ectopic lipid deposition. In conclusion, our sheep model revealed strong pre-and postnatal impacts on growth, food preferences and fat deposition patterns. The present findings support a role for subcutaneous adipose tissue in the development of visceral adiposity, which in humans is known to precede the development of the metabolic syndrome in human adults.

Impaired mitochondrial function is implicated in the development of type 2 diabetes mellitus (T2DM). This was investigated in mitochondria from skeletal muscle and liver of the Goto-Kakizaki (GK) rat, which spontaneously develops T2DM with age. The early and the manifest stage of T2DM was studied in 6- and 16-wk-old GK rats, respectively. In GK16 compared with GK6 animals, a decrease in state 3 respiration with palmitoyl carnitine (PC) as substrate was observed in muscle. Yet an increase was seen in liver. To test the complex II contribution to the state 3 respiration, succinate was added together with PC. In liver mitochondria, this resulted in an ∼50% smaller respiratory increase in the GK6 group compared with control and no respiratory increase at all in the GK16 animals. Yet no difference between groups was seen in muscle mitochondria. RCR and P/O ratio was increased (P < 0.05) in liver but unchanged in muscle in both GK groups. We observed increased lipid peroxidation and decreased Akt phosphorylation in liver with the progression of T2DM but no change in muscle. We conclude that, during the progression of T2DM in GK rats, liver mitochondria are affected earlier and/or more severely than muscle mitochondria. Succinate dehydrogenase flux in the presence of fatty acids was reduced severely in liver but not in muscle mitochondria during manifest T2DM. The observations support the notion that T2DM pathogenesis is initiated in the liver and that only later are muscle mitochondria affected.

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Extreme diets consisting of either high fat (HF) or high sucrose (HS) may lead to insulin resistance in skeletal muscle, often associated with mitochondrial dysfunction. However, it is not known if these diets alter normal interactions of pyruvate and fatty acid oxidation at the level of the mitochondria. Here, we report that rat muscle mitochondria does show the normal Randle‐type fat‐carbohydrate interaction seen in vivo. The mechanism behind this metabolic flexibility at the level of the isolated mitochondria is a regulation of the flux‐ratio: pyruvate dehydrogenase (PDH)/β‐oxidation to suit the actual substrate availability, with the PDH flux as the major point of regulation. We further report that this regulatory mechanism of carbohydrate‐fat metabolic interaction surprisingly is lost in mitochondria obtained from animals exposed for 12 weeks to a HF‐ or a HS diet as compared to rats given a normal chow diet. The mechanism seems to be a loss of the PDH flux decrease seen in controls, when fatty acid is supplied as substrate in addition to pyruvate, and vice versa for the supply of pyruvate as substrate to mitochondria oxidizing fatty acid. Finally, we report that the calculated TCA flux in the isolated mitochondria under these circumstances shows a significant reduction (~50%) after the HF diet and an even larger reduction (~75%) after the HS diet, compared with the chow group. Thus, it appears that obesogenic diets as those applied here have major influence on key metabolic performance of skeletal muscle mitochondria.

In a sheep model, we investigated diet effects on skeletal muscle mitochondria to look for fetal programming. During pregnancy, ewes were fed normally (N) or were 50% food restricted (L) during the last trimester, and lambs born to these ewes received a normal (N) or a high-fat diet (H) for the first 6 mo of life. We examined mitochondrial function in permeabilized muscle fibers from the lambs at 6 mo of age (adolescence) and after 24 mo of age (adulthood). The postpartum H diet for the lambs induced an ϳ30% increase (P Ͻ 0.05) of mitochondrial V O2max and an ϳ50% increase (P Ͻ 0.05) of the respiratory coupling ratio (RCR) combined with lower levels of UCP3 and PGC-1␣ mRNA levels (P Ͻ 0.05). These effects proved to be reversible by a normal diet from 6 to 24 mo of age. However, at 24 mo, a long-term effect of the maternal gestational diet restriction (fetal programming) became evident as a lower V O2max (ϳ40%, P Ͻ 0.05), a lower state 4 respiration (ϳ40%, P Ͻ 0.05), and lower RCR (ϳ15%, P Ͻ 0.05). Both PGC-1␣ and UCP3 mRNA levels were increased (P Ͻ 0.05). Two analyzed muscles were affected differently, and muscle rich in type I fibers was more susceptible to fetal programming. We conclude that fetal programming, seen as a reduced V O2max in adulthood, results from gestational undernutrition. Postnatal high-fat diet results in a pronounced RCR and V O2max increase in adolescence. However, these effects are reversible by diet correction and are not maintained in adulthood. metabolic syndrome; high-fat diet; nutrient restriction; maternal diet; respiratory coupling ratio EPIDEMIOLOGICAL STUDIES IN HUMANS since the 1980s and subsequent clinical studies have revealed that small size or thinness at birth is associated with increased risk of developing metabolic dysfunctions like obesity, type 2 diabetes, and abnormal lipid and carbohydrate metabolism, leading to coronary heart disease and elevated blood pressure in adulthood (2, 21). This has spurred an increasing interest in the long-term consequences of maternal nutrition during pregnancy and early postnatal nutrition, a phenomenon first described by Hales and Barker (22) and termed metabolic programming. Although this concept is now widely accepted, the mechanisms behind it remain poorly understood. The observed effects reflect phenotypical alterations, probably established through epigenetic mechanisms, which occur as a result of fetal adaptations to intrauterine and probably early postnatal influences (23, 38). Maternal low-protein diet during pregnancy in rats may in adulthood result in reduced glucose tolerance and high blood pressure, evidently due to a prenatally programmed tendency to dysfunction of small arteries and abnormal pancreatic development (9, 17, 25). Likewise, maternal low-protein diets may result in very significantly shortened life span in mice offspring (44). Thus, both the type of malnutrition and the time of exposure during pregnancy appear to influence the programming effects observed later in life (21, 23). Furthermore, the potentially de...