Blood Insulin Levels

This invention relates to methods and means for treating very low birthweight (VLBW) infants to reduce the risks of associated medical problems .

In all human newborns , the disruption of the intrauterine delivery of nutrients via the placenta results in an acute phase of profound catabolism with a weight loss that is restored only after the establishment of regular postnatal feeding . Although data from human infants are sparse , data from animal studies indicate that this catabolism relates to beta cell apoptosis immediately after birth, which is followed by renewal of beta cells , reflecting the change from a prenatal state of continuous and parenteral delivery of nutrients to a postnatal state of discontinuous and enteral delivery. Thus , this catabolic phase reflects transient insulin deficiency followed by restoration of normal insulin secretion related to enteral feeds .

In the term neonate, the catabolic phase is transient and may be considered to be physiological , given that term human newborns have large fat stores (on average , 12% of the body weight of a term human newborn is fat) and lipolysis can be readily activated . In very low birthweight (VLBW) neonates , however, the catabolic phase may be prolonged, for example because of delay in instituting normal enteral feeding or because of the immaturity of the gut and pancreas . The prolonged catabolism which occurs in these infants results in insulin resistance and hyperglycaemia that, in turn, enhances the risk of infection . Overall , prolonged catabolism leads to poor weight gain and brain growth, and low levels of IGF- 1 , which have been implicated in the pathogenesis of retinopathy of prematurity (ROP) .

Longitudinal data from VLBW and/or SGA infants suggest that an early failure to provide the anabolic drive for catch-up growth has long-term consequences in terms of brain growth, height gain, and body composition in early childhood, and may thereby affect intellectual performance and disease risk in adult life .

The present inventors have discovered that early continuous insulin intervention improves glucose control during the first week of life and prevents the pronounced hyperglycaemia that may be evident in some babies , particularly on day 2 through 3. This intervention prior to hyperglycemia is more efficient than intermittent or continuous insulin therapy in response to hyperglycemia and may lead to improved weight gain and overall improvement in outcome of this high-risk population .

An aspect of the invention provides a method of treating a very low birth weight (VLBW) infant or preventing or attenuating neonatal catabolism in a VLBW infant or preventing or attenuating the development of hyperglycemic insulin resistance in a VLBW infant or reducing the risk of mortality and morbidity in a VLBW infant, the method comprising; increasing blood insulin levels in said infant and maintaining said increased levels for an extended period.

Insulin levels may be increased or elevated in said infant from within 24 hours of birth, more preferably from within 4 , 8 or 12 hours of birth. Insulin levels may be increased relative to levels in the untreated infant .

Increased blood insulin levels are preferably maintained for up to 7 days after birth. For example, increased blood insulin

levels may be maintained for 3 or more, 4 or more, 5 or more or 6 or more days up to about 7 days .

Preferably, the infant is treated in accordance with the present methods until the end of the neonatal catabolic phase and the establishment of enteral feeding .

A VLBW infant is an infant weighing less than 150Og at birth. A VLBW infant may be premature or may be a full term infant who is small for gestational age (SGA) .

In some preferred embodiments , a VLBW infant suitable for treatment as described herein is non-hyperglycaemic . In other words , the VBLW infant has blood glucose levels of less than 10 mmol/1.

Methods described herein may be useful in preventing or attenuating neonatal catabolism and the development of hyperglycemic insulin resistance , and may therefore be useful in reducing the risk of mortality and morbidity in VLBW infants , in particular the risk of infection, retinopathy of prematurity (ROP) , intracranial haemorrhage and/or necrotising enterocolitis . A method of reducing the risk of retinopathy of prematurity in a VLBW infant may comprise ; increasing blood insulin levels in said infant and maintaining said increased levels for an extended period, as described herein.

Methods described herein may facilitate induction of anabolism and may have beneficial effects on long-term growth, brain development and neuropsychological outcomes as well as reducing the risk of long-term disease associated with being born premature and/or small for gestational age (SGA) .

Blood insulin levels may be increased by introducing exogenous insulin to the infant (i . e . insulin not produced by the

infant) or by stimulating an increase in the production of endogenous insulin by the infant .

In some embodiments , insulin levels may be increased by administering insulin to the infant . Aspects of the invention provide insulin for use in the treatment of a VLBW infant as described herein and the use of insulin in the manufacture of a medicament for use in a method of treating a VLBW infant . Preferably, the VLBW infant is a non-hyperglycaemic VLBW infant .

As is well known in the art , insulin is a 51 amino acid polypeptide hormone of 5.7 kD which is secreted by islet cells within the pancreas and is an important regulator of carbohydrate metabolism.

Insulin may include animal-derived insulin, for example pork, fish or beef insulin, or, more preferably, recombinant human insulin or derivatives and analogues thereof . A human insulin analogue or derivative may have an amino acid sequence that differs from the human insulin by the addition, substitution or deletion of 1 , 2 , 3 , 4 or 5 amino acids and may have improved properties such as onset , peak, and duration of action relative to wild-type human insulin .

Many clinically approved insulins are commercially available and may be used in accordance with the invention, including, for example , short acting insulins such as soluble insulin (Actrapid ^® , Humulin ^® ) and insulin analogues (Humalog ^® (Lispro) , Novolog ^® (Aspart) .

In some preferred embodiments , insulin is continuously administered to the VLBW infant to increase insulin levels and maintain the increased levels . Continuous administration may be especially suitable for short-acting insulins .

Methods and means of continuous administration of therapeutic agents are well known in the art . Insulin may, for example , be administered continuously by infusion, in particular intravenous infusion .

Medical practitioners are familiar with the administration of insulin, which is preferably in a "therapeutically effective amount " , this being sufficient to show benefit to the individual without elicited undesirable side effects . The actual amount of insulin administered, and rate and time- course of administration, will depend on the particular circumstances and is within the responsibility of medical practitioners .

In some embodiments , 0.01 units/kg/hour to 0.1 units/kg/hr of insulin may be administered, more preferably 0.02 units/kg/hr to 0.075 units/kg/hr . For example, doses of about 0.025 units/kg/hr or about 0.05 units/kg/hr may be administered.

In other embodiments , blood insulin levels may be increased by stimulating an increase in the production and secretion of endogenous insulin by the infant . This may be achieved, for example , by administering an insulinotropic agent to the infant .

Insulinotropic agents include peptides such as incretins, which promote insulin secretion and beta cell development . Incretins include glucagon-like peptide-1 (GLP-I) (P01275 GI : 45644939 residues 7 to 36 or 37) , glucose-dependent insulinotropic polypeptide (GIP) (P09681 GI : 121194 residues 52 to 93 ) and derivatives or agonists of these peptides , including exendin 3 (P20394 GI : 119677) , exendin 4 (AAB22006.1 GI : 248418) (Xu G et al 1999 ; Tourrel et al 2001) NN2211 (Rolin B et al 2002 ) .

Commercially available GLP-I agonists include Extendin (Lilly) , GLP-I I .N . T . (Transistion Therapeutics) , Byetta (Amylin) , Liraglutide (Novo) and AVEOOlO (Aventis) .

Other insulinotropic agents include DPP-IV inhibitors . Commercially available DPP-IV inhibitors include Vildagliptin (Lilly) , Saxagliptin (BMS) and Sitagliptin (Merck) .

Insulinotropic peptides may be synthesized by conventional means as detailed below, such as solid-phase peptide synthesis . Solid phase peptide synthesis is described in J . M . Stewart and J . D . Young, Solid Phase Peptide Synthesis , W. H . Freeman Co . (San Francisco) , 1963 and J . Meienhofer, Hormonal Proteins and Peptides , vol . 2 , p . 46 , Academic Press (New York) , 1973.

Insulinotropic peptides may also be produced through the use of recombinant DNA technology (for example , see Sambrook "Molecular Cloning, A Laboratory Manual , Cold Spring Harbor Laboratory Press 3 ^rd Edition (2001) , and Ausubel et al . , Current Protocols in Molecular Biology, John Wiley and Sons , (1994 ) ) .

The insulinotropic activity of an agent may be determined by providing a compound to animal cells , or injecting a compound into animals and monitoring the release of immunoreactive insulin (IRI) into the media or circulatory system of the animal , respectively . The presence of IRI may be detected, for example, through the use of a radioimmunoassay which specifically detects insulin.

Administration of an insulinotropic agent may be continuous or periodical . The frequency of administration may depend on the active half-life of the agent . For example , a short acting

agent may be administered continuously, while a long acting agent may be administered periodically, for example daily.

In some embodiments , the insulinotropic agent is continuously administered to the infant to increase production and secretion of insulin, thereby increasing blood insulin levels and maintaining the increased levels . Methods and means of continuous administration of therapeutic agents are well known in the art and are described in more detail above . An insulinotropic agent may be administered continuously by infusion, for example intravenous infusion

In other embodiments , long-acting insulinotropic agents may be administered periodically, for example daily, to increase blood insulin levels in the VLBW infant and maintain these increased levels .

Other aspects of the invention provide an insulinotropic agent for use in the treatment of a VLBW infant as described herein and the use of an insulinotropic agent in the manufacture of a medicament for use in a method of treating a VLBW infant .

The insulinotropic agent may be administered from within 24 hours of the birth of said infant and may be administered for up to seven days after birth .

In some embodiments , a method of treating a VLBW infant may comprise administering insulin and an insulinotropic agent to said infant .

Related aspects of the invention relate to the combination of insulin and an insulinotropic agent in the treatment of a VLBW infant and the use of insulin and an insulinotropic agent in the manufacture of a medicament for use in the treatment of a VLBW infant .

Insulin and insulinotropic agents are described in more detail above .

Blood glucose levels may be measured and/or monitored in the VLBW infant during the treatment described herein. Preferably, blood glucose levels in the infant remain between 4 and 8 τnmol/1 when the blood insulin level is increased in accordance the methods described herein .

In cases in which the blood glucose level drops below a threshold value, typically 4.0 mmol/1 , during the treatment (hypoglycaemia) , glucose may be administered to the infant . For example, glucose , conveniently in the form of a solution comprising up to about 20% dextrose, may be administered by infusion .

Techniques for monitoring blood glucose levels are well-known in the art and include , for example , the use of a glucose sensor, such as the MiniMed Glucose Sensor .

Various further aspects and embodiments of the present invention will be apparent to those skilled in the art in view of the present disclosure . All documents mentioned in this specification are incorporated herein by reference in their entirety .

The invention encompasses each and every combination and sub- combination of the features that are described above .

Certain aspects and embodiments of the invention will now be illustrated by way of example and with reference to the figures described above and tables described below.

Figure 1 shows blood glucose levels in VLBW infants treated within the first 24 hours with insulin as described relative to controls .

Figure 2 shows the proportion of time spent in normo-glycaemic condition by VLBW babies subj ected to insulin treatment in the first 24 hours relative to controls .

Figure 3 shows the timing of hyperglycaemia in VLBW babies subj ected to early insulin treatment relative to controls .

Figure 4 shows the ratio of glucose to insulin in VLBW babies subj ected to early insulin treatment relative to controls .

Figure 5 shows the amount of IGF-I in VLBW babies subj ected to early insulin treatment relative to controls .

Figure 6 shows the amount of IGFBP-I in VLBW babies subjected to early insulin treatment relative to controls .

Table 1 shows patient demographics of VLBW infants randomised to receive either a continuous insulin infusion over the first seven days of life or intermittent insulin therapy as dictated by blood glucose levels (i . e . more than 10 mmol/1) .

Table 2 shows growth and hormone data during the whole 7-day study period by treatment group . Median (IQ Range) .

Table 3 shows pilot data from neo-natal insulin replacement studies on numbers with retinopathy of Prematurity (RoP) (Chi- square p 0.03 ) .

Examples

Sixteen very low birth weight infants (less than 1500 g) were randomised to receive either a continuous insulin

infusion over the first seven days of life or intermittent insulin therapy as dictated by blood glucose levels (i . e . more than 10 mmol/1) . Details of the infants studied are summarised in Table 1.

The early introduction of insulin therapy was observed to result in more stable blood glucose control over the seven- day period, as illustrated by data collected with the MiniMed Glucose Sensor shown in Figure 1. Normal blood glucose levels were achieved in the active treatment group by additional infusions of glucose and, overall , the babies treated with continuous insulin infusion spent a much longer part of the first week with normal glucose levels than those treated with intermittent insulin therapy dictated by blood glucose levels (Figure 2) .

The hyperglycaemia that was evident in many of the control babies over the first week of life was abolished in those babies given continuous insulin therapy from day one (Figure 3 ) . Infants in the control arm received insulin therapy because of the high blood sugars and, in fact, the amount of insulin given over the seven days in the two groups was not significantly different . However, in the control babies the insulin failed to prevent further episodes of hyperglycaemia, probably because of the development of insulin resistance . The glucose-insulin ratios based on daily measurements in the two groups of babies are illustrated in Figure 4 and suggest an altered relationship between insulin and glucose between the groups . The early introduction of continuous insulin therapy was shown to attenuate or prevent the catabolism and insulin resistance which was evident in the control babies .

Early continuous insulin delivery was also observed to result in higher IGF-I and lower IGFBP-I levels (Fig 5 , 6) : IGF-I bioavailability was thus increased by the treatment .

Insulin-like growth factor (IGF-I) bioactivity provides the best assessment of bioavailability of IGF-I in the newborn. The IGF-I Kinase receptor activation assay (KIRA) based on cells transfected with the human IGFlR gene was used to determine the effect of early continuous insulin delivery. The bioassay has been validated and is highly sensitive and specific (Chen et al 2003) .

Infants treated with insulin from day 1-7 were observed to have a 2.4 fold increase in IGF-I bioactivity compared with controls (P 0.005 Table 2 , Fig 7) .

Since low IGF-I in VLBW infants has been associated with the development of ROP (Hellstrom et al 2001, Hellstrom et al 2002 , Hikino et al 2001) , these results are indicative that early insulin treatment may prevent or reduce this complication in the newborn.

The incidence of RoP in infants treated with insulin from day 1-7 was assessed in relation to a control group . Early continuous insulin delivery was observed to result in a reduced incidence of RoP in VLBW infants (Table 3 ) .

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Table 1

Table 2

Table 3