Influence of low- and high-protein diets on insulin and insulin-like growth factor-1 binding to skeletal muscle and liver in the growing rat

Dietary protein levels changed the hardness of muscle by acting on muscle fiber growth and the metabolism of collagen in sub-adult grass carp (Ctenopharyngodon idella)

Background

Nutrient regulation has been proven to be an effective way to improve the flesh quality in fish. As a necessary nutrient for fish growth, protein accounts for the highest proportion in the fish diet and is expensive. Although our team found that the effect of protein on the muscle hardness of grass carp was probably related to an increased collagen content, the mechanism for this effect has not been deeply explored. Moreover, few studies have explored the protein requirements of sub-adult grass crap (Ctenopharyngodon idella). Therefore, the effects of different dietary protein levels on the growth performance, nutritional value, muscle hardness, muscle fiber growth, collagen metabolism and related molecule expression in grass carp were investigated.

Methods

A total of 450 healthy grass carp (721.16 ± 1.98 g) were selected and assigned randomly to six experimental groups with three replicates each (n = 25/replicate), and were fed six diets with 15.91%, 19.39%, 22.10%, 25.59%, 28.53% and 31.42% protein for 60 d.

Results

Appropriate levels of dietary protein increased the feed intake, percentage weight gain, specific growth rate, body composition, unsaturated fatty acid content in muscle, partial free amino acid content in muscle, and muscle hardness of grass carp. These protein levels also increased the muscle fiber density, the frequency of new muscle fibers, the contents of collagen and IGF-1, and the enzyme activities of prolyl 4-hydroxylases and lysyloxidase, and decreased the activity of matrix metalloproteinase-2. At the molecular level, the optimal dietary protein increased collagen type I α1 (Colα1), Colα2, PI3K, Akt, S6K1, La ribonucleoprotein domain family member 6a (LARP6a), TGF-β1, Smad2, Smad4, Smad3, tissue inhibitor of metalloproteinase-2, MyoD, Myf5, MyoG and MyHC relative mRNA levels. The levels of the myostatin-1 and myostatin-2 genes were downregulated, and the protein expression levels of p-Smad2, Smad2, Smad4, p-Akt, Akt, LARP6 and Smad3 were increased.

Conclusions

The appropriate levels of dietary protein promoted the growth of sub-adult grass carp and improved muscle hardness by promoting the growth of muscle fibers, improving collagen synthesis and depressing collagen degradation. In addition, the dietary protein requirements of sub-adult grass carp were 26.21% and 24.85% according to the quadratic regression analysis of growth performance (SGR) and the muscle hardness (collagen content), respectively.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40104-022-00747-7.

The association of breastfeeding with insulin resistance at 17 years: Prospective observations from Hong Kong's "Children of 1997" birth cohort

Breastfeeding has many benefits for mother and infant. Whether breastfeeding also protects against type 2 diabetes is unclear. To clarify the role of breastfeeding in type 2 diabetes, we assessed the association of breastfeeding with insulin resistance in late adolescence in a birth cohort from a non-Western setting where breastfeeding was not associated with higher socio-economic position. We used multivariable linear regression, with multiple imputation and inverse probability weighting, to examine the adjusted associations of contemporaneously reported feeding in the first 3 months of life (exclusively breastfed, mixed feeding, or always formula-fed) with fasting glucose, fasting insulin, and homeostasis model assessment of insulin resistance (HOMA-IR) at 17 years in a subset (n = 710, 8.6% of entire cohort) of the Hong Kong Chinese birth cohort "Children of 1997." We found a graded association of breastfeeding exclusivity in the first 3 months of life with lower fasting insulin and HOMA-IR (p-for-trend < .05), but not fasting glucose, at 17 years. Exclusively breastfed adolescents (7%) had nonsignificantly lowest fasting insulin and HOMA-IR, adjusted for sex, birth weight, parity, length of gestation, pregnancy characteristics, parents' education, and mother's place of birth. Exclusively breastfeeding for 3 months may be causally associated with lower insulin resistance in late adolescence. Further follow-up studies into adulthood are required to clarify the long-term protection of breastfeeding from type 2 diabetes.

How growth due to infant nutrition influences obesity and later disease risk

Infant nutrition has a major impact on immediate outcomes and long-term health and later disease risks, such as obesity and related disorders, a phenomenon referred to as 'metabolic programming'. This review discusses the currently postulated hypotheses and mechanisms investigated by the EarlyNutrition project.

CONCLUSION

Rapid weight gain in the first 2 years of life, most notably mediated by diary protein, affects the insulin-like growth factor metabolic pathways. Epigenetic processes seem to play a role.

Early nutrition impact on the insulin-like growth factor axis and later health consequences

PURPOSE OF REVIEW

There is increasing interest in the role of insulin-like growth factor-I (IGF-I) in the relation between early growth and later risk of noncommunicable diseases (NCDs). This review presents and discusses a selection of recent publications on this topic.

RECENT FINDINGS

Nutrition during pregnancy and in preterm infants has an influence on IGF-I. Breastfeeding is associated with lower IGF-I values and the effect of early protein intake was confirmed in a large intervention study. IGF-I levels are associated with early obesity, but the relation is complex and differs with age. Further studies and reviews support that there is a programming of the IGF axis, with higher levels during early life being associated with lower levels in adulthood, which is likely to influence the risk of NCDs later in life.

SUMMARY

Recent studies support that IGF-I plays an important role in the complex association between early diet, growth and later health, but more studies are needed to better understand the role of IGF-I, especially in the early development of obesity. Studies with data on how IGF-I is influenced by early diet in studies of preterm infants and young children with undernutrition from low-income countries will be helpful in recommending optimal diets.

Increased protein intake augments kidney volume and function in healthy infants

Protein intake has been directly associated with kidney growth and function in animal and human observational studies. Protein supply can vary widely during the first months of life, thus promoting different kidney growth patterns and possibly affecting kidney and cardiovascular health in the long term. To explore this further, we examined 601 healthy 6-month-old formula-fed infants who had been randomly assigned within the first 8 weeks of life to a 1-year program of formula with low-protein (LP) or high-protein (HP) contents and compared them with 204 breastfed (BF) infants. At 6 months, infants receiving the HP formula had significantly higher kidney volume (determined by ultrasonography) and ratios of kidney volume to body length and kidney volume to body surface area than did infants receiving the LP formula. BF infants did not differ from those receiving the LP formula in any of these parameters. Infants receiving the HP formula had significantly higher serum urea and urea to creatinine ratios than did LP formula and BF infants. Hence, in this European multicenter clinical trial, we found that a higher protein content of the infant formula increases kidney size at 6 months of life, whereas a lower protein supply achieves kidney size indistinguishable from that of healthy BF infants. The potential long-term effects of a higher early protein intake on long-term kidney function needs to be determined.

Additive effect of diets and training on total insulin-like growth factor-1 (IGF-1) in rats

OBJECTIVES

Although it is known that circulating levels of insulin-like growth factor-1 (IGF-1) are influenced by both physical exercise and dietary intake separately, there is little information regarding the additive effect of diets and training on IGF-1 regulation. To test this, we examined the combined effect of 30 days of two different diets (high-protein and high-carbohydrate) and exercise training on total IGF-1.

MATERIALS AND METHODS

The study was carried out with four groups of rats; the sedentary group with standard diet (SS) (control group), standard diet with exercise (SE), high-protein diet with exercise (PE) and high-carbohydrate diet with exercise (CE). Serum IGF-1, insulin, corticosterone were analyzed.

RESULTS

IGF-1 concentrations were decreased by exercise training (p<0.001) and only with protein diet (p<0.05). Physical training, with and without diet, decreased body weight and food intake (p<0.01) and increased corticosterone levels (p<0.05). Carbohydrate diet did not cause major hormonal and metabolic alterations.

CONCLUSION

The main result of this study was the decreased levels of IGF-1 in spite of high-protein diet, which is known to enhance IGF-1 secretion, and the little changes with carbohydrate diet. This may be related to the negative energy balance as a result of the catabolic state induced by exercise training and decreased calorie intake in protein diet. Thus, it can be concluded that the caloric restriction, regardless of dietary composition, decreased IGF-1 secretion.

High intakes of skimmed milk, but not meat, increase serum IGF-I and IGFBP-3 in eight-year-old boys

OBJECTIVE

To examine whether a high protein intake (PI) from either milk or meat, at a level often seen in late infancy, could increase s-IGF-I and s-IGF-I/s-IGFBP-3 in healthy, prepubertal children. IGF-I levels are positively associated with growth velocity in children and some studies suggest that a high animal PI can stimulate growth. During protein deprivation IGF-I decrease, but it is unknown whether a high PI can increase s-IGF-I in well-nourished children.

DESIGN

In all, 24 8-y-old boys were asked to take either 1.5 l of skimmed milk (n = 12) or the same amount of protein as 250 g low fat meat (n = 12) daily for 7 days. The remaining diet they could choose freely. At baseline and after 7 days, anthropometrical variables were measured, diet was registered (3-day weighed records), and s-IGF-I and s-IGFBP-3 (RIA) were determined after fast.

RESULTS

PI increased by 61% in the milk group to 4.0 g/kg/day (P < 0.0001) and by 54% in the meat group to 3.8 g/kg/day (P = 0.001). The high milk intake increased s-IGF-I by 19% (P = 0.001) and s-IGF-I/s-IGFBP-3 by 13% (P < 0.0001). There were no increases in the meat group.

CONCLUSIONS

High intake of milk and not meat, increased concentrations of s-IGF-I and s-IGF-I/s-IGFBP-3 significantly. Compounds in milk and not a high PI as such seem to stimulate IGF-I. This might explain the positive effect of milk intake on growth seen in some studies.

Enriched protein diet-modified ghrelin expression and secretion in rats

Gastrointestinal (GI) integrity and function are regulated by nutrition and growth factors. The discovery of ghrelin, a natural growth hormone (GH) secretagogue produced by the gastrointestinal (GI) tract, is a potential link between diet and growth signals. The aim of this study was to evaluate macronutrient effect on ghrelin expression and secretion in addition to some possible function in intestinal trophic status. Wistar rats were fed a high-carbohydrate, high-protein (HP), high-fat or standard (St) diet. Animals received the same daily food volume and caloric intake. After 7 days, animals were fasted for 24 h and blood and tissue samples were obtained just before feeding or at 2 or 6 h after feeding. Fasting high-protein-fed rats had higher ghrelin plasma levels than with rats fed the high-carbohydrate, high-fat or standard diets. Two-hours after refeeding, ghrelin plasma levels had decreased in all groups with a slight recovery at 6 h after refeeding, except in the high-protein group. Ghrelin plasma levels in rats fed with the high-protein diet correlated negatively with their GH and insulin-like growth factor 1 (IGF-1) plasma concentrations which were also the lowest among the study groups. In conclusion, ghrelin secretion was nutritionally manipulated because a protein-enriched diet increased its levels.

Protein intake at 9 mo of age is associated with body size but not with body fat in 10-y-old Danish children

BACKGROUND

During the complementary feeding period, infants shift from a daily protein intake (PI) of approximately 1 g/kg body wt to an intake 3-4 times as high. A high PI probably has both endocrine and physiologic effects and may increase the risk of obesity.

OBJECTIVE

We examined the associations between PI in infancy and body size and composition in late childhood.

DESIGN

We conducted an observational cohort study of 142 Danish healthy term infants (63 boys) born during 1987-1988. At 9 mo of age, diet, weight, length, skinfold thicknesses, insulin-like growth factor I, and serum urea nitrogen were determined. At 10 y of age, 105 children (51 boys) participated in a follow-up study. Diet, weight, height, skinfold thicknesses, percentage of body fat (dual-energy X-ray absorptiometry), insulin-like growth factor I, and serum urea nitrogen were determined.

RESULTS

At 9 mo of age, PI (in g/d and percentage of energy) was strongly correlated with body size (length and weight) but not with measures of adiposity. PI at 9 mo of age was positively associated with height and weight but not with percentage of body fat at 10 y of age. Inclusion of parental body size in the models did not change the associations, but the significant associations were attenuated when body size at 9 mo of age was included.

CONCLUSIONS

PI in infancy seems to stimulate early growth. This might explain part of the association between early PI and body size at 10 y of age, but a continuous effect of protein on growth during childhood cannot be excluded. PI in infancy was not associated with any measure of body fat at 10 y of age.

Effects of growth hormone and feeding level on endocrine measurements, hormone receptors, muscle growth and performance of prepubertal heifers

Prepubertal Friesian heifer calves (n = 24, initial BW = 195 +/- 5 kg) were assigned to a 2 x 2 factorial block design and used to evaluate the effects of daily GH treatment (0 or 15 mg/d) at either a low or a high feeding level in a 5-wk treatment period on endocrine measurements, hormone receptors, muscle growth, and overall performance. In the pretreatment period, a low feeding level was employed for all calves. During the treatment period, animals at the low feeding level had free access to a roughage-based mixture, whereas animals at the high feeding level had free access to a concentrate mixture and were offered 2 kg/d of the roughage-based mixture. Blood samples were collected weekly starting 3 wk before treatment. Longissimus (LM) and supraspinatus (SS) muscles were obtained at slaughter. Metabolizable energy intake was 81% higher, digestible CP intake was 140% higher, and ADG was 115% higher (all P < 0.001) at the high vs. low feeding level. Feed (DMI, ME, and protein) intake was not affected by GH treatment, but ADG was 18% higher (P < 0.13) in GH-treated than in control heifers at both feeding levels. Although of different magnitudes, the muscle anabolic effects of GH treatment and high vs. low feeding level were additive, and both treatments increased carcass weights (P < 0.02 and P < 0.001, respectively), LM (P < 0.05 and P < 0.001), and SS (P < 0.06 and P < 0.003). The anabolic effect of GH treatment was similar in both muscles, whereas the effect of feeding level was most pronounced in LM. Overall, GH treatment increased plasma GH, IGF-I (both P < 0.001), and IGFBP-3 (P < 0.02); however, GH treatment increased total IGF-I, free IGF-I, and IGFBP-3, and decreased IGFBP-2 mainly at the high feeding level (GH x feeding level interaction; P < 0.02, 0.01, 0.03, and 0.10, respectively). The high feeding level increased insulin, free and total IGF-I, and IGFBP-3 (all P < 0.001), but decreased GH and IGFBP-2 (both P < 0.001). High feeding increased type-1 IGF receptor density (P < 0.02), mainly in LM, in accordance with the largest anabolic response in this muscle, whereas GH treatment had no effect on type-1 IGF receptors. The results suggest that in skeletal muscle, the anabolic effects of exogenous GH are related to endocrine changes in the GH-IGF axis, whereas the effects of feeding level also seem to rely on IGF receptor density in the muscles.

Growth, hormonal status and protein turnover in rats fed on a diet containing peas (Pisum sativum L.) as the source of protein

The inclusion of peas (Pisum sativum L.) as the source of protein in the diet of growing rats brings about a reduction in growth rate as well as the impairment in the liver, muscle and spleen weights as compared with casein fed controls. Also, a fall in plasma glucose, triglycerides and protein was observed in the legume fed animals, while no changes in cholesterol levels were found. Furthermore, the rats fed on the diet containing peas showed lower levels of plasma insulin, corticosterone, IGF-I and T4 as compared with casein controls. Liver and muscle total protein (mg) and total DNA (mg) were markedly decreased in the legume fed animals, but DNA/g, protein/DNA and RNA/protein ratios were similar in both dietary groups. Likewise, liver and muscle fractional synthesis rates were similar in the casein and legume groups, while the whole body protein synthesis is assumed to be lower in the legume fed animals due to differences in body weights. It is concluded that animals fed on a diet containing peas (Pisum sativum L.) as the only source of protein showed less adverse effects than those found with other legumes such as Vicia faba L. or Phaseolus vulgaris L., in which protein quality, antinutritional factors and nutrient availability could be involved.

Supplementation of a restricted maternal diet with protein or carbohydrate alone prevents a reduction in fetal muscle fibre number in the guinea-pig

A 60% reduction in maternal feed intake is known to cause a reduction of approximately 20% in biceps brachii fibre number in the guinea-pig fetus. This investigation was designed to isolate the dietary component responsible by reducing all dietary components to 60% of the ad lib. level and supplementing the protein, carbohydrate or fat component to the level of the ad lib. intake. Fetal muscles were examined at 50 d gestation to determine numbers of primary and secondary fibres, and at term to determine total fibre number. Fetal and neonatal weights were reduced in all restricted groups (P < 0.05) when compared with ad lib. controls. At term this reduction was significantly less (P < 0.05) in the protein-supplemented group (20%) than in the 60%-restricted and fat-supplemented groups (43%) and the carbohydrate-supplemented group (34%). Biceps brachii fibre numbers were reduced in the 60%-restricted fat-supplemented groups by 14-16%, but fibre numbers were similar in control, protein-supplemented and carbohydrate-supplemented groups. Any reduction in fibre number was in the secondary fibre component of total fibre number. Therefore, biceps brachii fibre numbers were reduced only when maternal diets were deficient in both protein and carbohydrate.

Age-related plasma concentrations of growth hormone (GH) and insulin-like growth factor I(IGF-I) in Great Dane pups fed different dietary levels of protein

During a 20-week study, 17 Great Dane dogs, 7 weeks of age, were used to study the influence of 3 isoenergetic diets differing in dietary protein levels (i.e., 31.6%, 23.1%, and 14.6% on a dry matter basis) on body weight, growth in length, and age-related plasma GH and IGF levels. Significant differences occurred in weekly body weight gain of the high- and low- protein groups only in the fourth week of the study. There was a significant decrease in mean basal plasma GH values with time from 14.8 +/- 2.2, 13.7 +/- 2.2, and 14.3 +/- 2.2 micrograms/l in the second week to 2.3 +/- 1, 0.7 +/- 0.4, and 1.8 +/- 0.7 microgram/l in the last week of the study for the high-, normal- and low-protein groups, respectively. Differences among groups were not significant. There was a positive correlation between the decrease in weekly body weight gain and plasma GH concentration in all 3 groups. IGF-I concentrations in plasma did not change consistently with age and were not correlated with plasma GH values. Significant differences in plasma IGF-I concentrations were found between groups at 15 weeks of age. Preliminary results of measurements of IGF receptors in the membranes of growth plate cartilage of long bones of 5 dogs revealed that homologous displacement of 125I-labeled IGF-I binding resulted in similar curves. A single binding site for IGF-I was assumed. The large number of type II IGF receptors in 7 dogs suggests a key role for IGF-II in postnatal skeletal growth. The results of this study demonstrate for the first time that in Great Dane pups basal GH concentrations in plasma decrease between 7 and 27 weeks of age, parallel to the decrease in growth velocity, whereas the plasma IGF-I concentrations remain relatively high and unchanged. The slight but statistically significant effects of low-protein feeding on growth velocity and circulating concentrations of IGF-I indicate that a diet containing 14.6% protein on a dry matter basis (13% protein as metabolizable energy) is marginal for growing Great Dane pups between 7 and 17 weeks of age.

IGF-I binding and IGF-I expression in regenerating muscle of normal and hypophysectomized rats

Binding of iodinated IGF-I to tissue sections from regenerating muscle was studied by autoradiography in normal and in hypophysectomized rats. Binding of IGF-I was low in control muscle in both groups of animals, but increased transiently about 10-fold during regeneration after injury. Maximal binding occurred later in hypophysectomized rats than in control rats, and there was also a slower regeneration process in these animals. IGF-I, as demonstrated by immunohistochemistry, and IGF-I mRNA, as demonstrated by in situ hybridization, were expressed by the regenerating muscle cells in both groups of animals. It is concluded that locally produced IGF-I is the most likely ligand for IGF-I receptors during muscle regeneration.

Protein energy malnutrition and the nervous system

Protein-energy malnutrition (PEM), a natural ramification of poverty, continues to be a perennial source of concern to a large segment of the world population. The developing nervous system of a child is specially vulnerable to deprivations in nurture. Peripheral nerve and muscle derangements are clinically evident by weakness, hypotonia and hyporeflexia in accordance with severity and duration of PEM. Motor and sensory nerve conduction studies exhibit significant abnormalities and often furnish useful and ominous correlation with grades of PEM. The human sural nerve histology in cases of severe PEM is characterized by persistence of small myelinated fibres, striking failure of internodal elongation and significant segmental demyelination. Young rhesus monkeys are ideal experimental PEM models and they show myopathic EMG changes amenable to rehabilitation. Muscle pathology comprises obliteration of cross-striations, streaming of Z bands, increased interfibrillary spaces, mitochondriomegaly and small-for-age fibres. Radioisotope assays reveal anomalous incorporation into various nerve and muscle constituents. Central nervous system, specially the neuropsychological functions are affected in a lasting manner. Learning deficits, behavioural problems and manual indexterity are most obtrusive features.

Insulin receptor binding and kinase activity in liver and skeletal muscles of lactating goats

Lactation in goats has been shown to modify in vivo insulin action. [Debras, E., J. Grizard, E. Aina, S. Tesseraud, C. Champredon, and M. Arnal. Am. J. Physiol. 256 (Endocrinol. Metab. 19): E295-E302, 1989]. To further elucidate the mechanism of insulin action, we studied insulin binding and insulin receptor tyrosine kinase activity in solubilized and partially purified receptor preparations from liver and skeletal muscles (longissimus dorsi, tensor fascia lata, diaphragm, and masseter) from lactating and nonlactating goats. Lactation did not alter insulin receptors in the various skeletal muscles and had a minor influence on liver receptors (where only a 20% increase in receptor number was visible, P less than 0.05). Insulin-stimulated autophosphorylation and the kinase activity against polyglutamyltyrosine (4:1) were not significantly modified in skeletal muscle receptor preparations from lactating goats when compared with nonlactating animals. They tended to decrease in liver preparations, but not significantly. Thus the changes in insulin action in vivo during lactation in goats were not related to modifications in insulin kinase activity but were probably localized at a postreceptor level.