Effects of quality of energy intake on growth and metabolic response of enterally fed low-birth-weight infants

Carbohydrate and fat may vary in their ability to support protein accretion and growth. If so, variations in the source of nonprotein energy might be used to therapeutic advantage in enterally fed low-birth-weight infants. To test the hypothesis that high-carbohydrate diets are more effective than isocaloric high-fat diets in promoting growth and protein accretion, low-birth-weight infants weighing 750-1600 g at birth were randomized in a double blind study to receive one of five formulas differing only in the quantity and quality of nonprotein energy. Groups 1, 2, and control received 130 kcal x kg(-1) x d(-1) with 35, 65, and 50% of the nonprotein energy as carbohydrate. Groups 3 and 4 received energy intake of 155 kcal x kg(-1) x d(-1) with 35 and 65% of the nonprotein energy as carbohydrate. Protein intake of all groups was 4 g x kg(-1) x d(-1). Growth and metabolic responses were followed weekly, and macronutrient balances including 6-h indirect calorimetry were performed biweekly. Greater rates of weight gain and nitrogen retention were observed at high-carbohydrate intake compared with high-fat intake at both gross energy intakes. Greater rates of energy storage and an increase in skinfold thickness were observed in group 4 (high-energy high-carbohydrate diet) despite higher rates of energy expenditure. These data support the hypothesis that at isocaloric intakes, carbohydrate is more effective than fat in enhancing growth and protein accretion in enterally fed low-birth-weight infants. However, a diet with high-energy and high-carbohydrate content also results in increased fat deposition.

Effects of quality of energy on substrate oxidation in enterally fed, low-birth-weight infants

BACKGROUND

Carbohydrate and fat may differ in their ability to support energy-requiring physiologic processes, such as protein synthesis and growth. If so, varying the constituents of infant formula might be therapeutically advantageous.

OBJECTIVE

We tested the hypothesis that low-birth-weight infants fed a diet containing 65% of nonprotein energy as carbohydrate oxidize relatively more carbohydrate and relatively less protein than do infants fed an isoenergetic, isonitrogenous diet containing 35% of nonprotein energy as carbohydrate.

DESIGN

Sixty-two low-birth-weight infants weighing from 750 to 1600 g at birth were assigned randomly and blindly to receive 1 of 5 formulas that differed only in the quantity and quality of nonprotein energy. Formula containing 544 kJ x kg(-1) x d(-1) with either 50%, 35%, or 65% of nonprotein energy as carbohydrate was administered to control subjects, group 1, and group 2, respectively. Groups 3 and 4 received gross energy intakes of 648 kJ x kg(-1) x d(-1) with 35% and 65% of nonprotein energy as carbohydrate. Protein intake was targeted at 4 g x kg(-1) x d(-1). Substrate oxidation was estimated from biweekly, 6-h measurements of gas exchange and 24-h urinary nitrogen excretion.

RESULTS

Carbohydrate oxidation was positively (r = 0.71, P < 0.0001) and fat oxidation was negatively (r = -0.46, P < 0.001) correlated with carbohydrate intake. Protein oxidation was negatively correlated with carbohydrate oxidation (r = -0.42, P < 0.001). Fat oxidation was not correlated with protein oxidation. Protein oxidation was less in infants receiving 65% of nonprotein energy as carbohydrate than in groups receiving 35% nonprotein energy as carbohydrate.

CONCLUSION

These data support the hypothesis that energy supplied as carbohydrate is more effective than energy supplied as fat in sparing protein oxidation in enterally fed low-birth-weight infants.

Mesenchymal chondrosarcoma of the orbit: a clinicopathological study

Extraskeletal mesenchymal chondrosarcoma of the orbit is a rare tumour and generally presents in young females. We report the clinical presentation and histopathological features of a case of orbital mesenchymal chondrosarcoma in a middle-aged man. The prognosis of this tumour is poor and though rare it should be kept in the differential diagnosis of orbital masses.

Polycystic ovary disease and the risk of pregnancy-induced hypertension

OBJECTIVE

To compare the incidence of pregnancy-induced hypertension in patients with and without polycystic ovary disease (PCOD).

STUDY DESIGN

We conducted a retrospective, case-control analysis of patients who achieved singleton pregnancies with human menopausal gonadotropin (hMG) therapy. Twenty-two PCOD patients were compared to 27 infertility patients without PCOD who were pregnant after hMG therapy. Non-PCOD patients received hMG for superovulation as part of superovulation/intrauterine insemination or in vitro fertilization/embryo transfer. PCOD patients were receiving hMG for simple ovulation induction. Pregnancy-induced hypertension was defined as late pregnancy blood pressure > 140/90 mm Hg on two readings six hours apart and return to normal blood pressure by four to six weeks postpartum.

RESULTS

There were no differences between PCOD and non-PCOD patients with reference to age, body mass index, parity or other pregnancy-induced hypertension risk factors (i.e., chronic hypertension, diabetes or chronic renal disease). Pregnant PCOD patients had a much higher incidence of pregnancy-induced hypertension, 31.8% (7/22), versus non-PCOD patients, who only had a pregnancy-induced hypertension incidence of 3.7% (1/27) (P = .016, OR = 12.1, 95% CI = 1.3-566.8).

CONCLUSION

PCOD patients are at very high risk of pregnancy-induced hypertension when pregnant after ovulation induction.

Case of the month

Each month, we will present a challenging Case of the Month for Green Journal readers, who must use their clinical acumen to arrive at the correct answer. We will also post the case each month on the Journal's web site (http://www.ajmselect.com). Several possible answers may be consistent with the case presentation; use your best judgment. Please send your answer (one per respondent) to The Green Journal at editors@amjmed.org or via Fax to (415) 447-2799. Indicate the case to which you are responding, and include your complete address. The correct answer will appear in the next issue of the Journal. The first five persons who submit correct answers will receive a free one-year subscription to the Journal. Colleagues of Drs. Kashyap in Pune, India are not eligible for this month's case. If you would like to contribute a case, please submit a brief synopsis (<250 words) to the editorial office.

Dermatofibroma of the eyelid: a case report

A 5-year-old girl presented with a large swelling measuring 50 x 35 mm in the left upper lid. The mass was firm to hard in consistency. Fine-needle aspiration showed a few spindle-shaped cells arranged in clusters. The mass was excised in toto and the histopathological examination revealed dermatofibroma, which is an extremely rare condition affecting the eyelid.

Maturational changes in heart rate and heart rate variability in low birth weight infants

To provide insight into the maturation of neural mechanisms responsible for variability in heart rate during quiet and active sleep, 6-hour continuous electrocardiographic recordings and simultaneous minute-by-minute behavioral activity state assignments were performed in 61 healthy, growing low birth weight infants. The infants weighed 795-1600 g at birth and ranged between 31-38 weeks in postconceptional age. During this age interval there was a decrease in heart rate during quiet sleep and an increase in both time domain and frequency domain measures of the variability in cardiac interbeat intervals. In quiet sleep, global variability, measured as SD of R-R intervals, increased in relation to age, as did higher frequency variability, measured as the square root of the mean of squared successive differences in R-R intervals. Developmental changes in the 0.5-2.0 Hz spectral power band of RR-interval variability, another measure of high frequency variability, paralleled the changes seen in the time domain measure. Evaluation of patterns of changes in the magnitude and direction of successive interbeat intervals provided evidence that the incidence of sustained accelerations or decelerations increased whereas the incidence of no change in consecutive RR-intervals decreased as infants matured. Among the various measures of heart rate variability, the incidence of sustained change and no change in successive interbeat intervals were most closely related to postconceptional age in both sleep states. The overall decrease in heart rate, increase in heart rate variability, and increase in the pattern of changes in interbeat interval with postconceptional age are consistent with the maturation of the autonomic cardio-regulatory activity from 31-38 weeks age.

Hypoparathyroidism unmasked by alendronate

The case of an elderly woman is reported in whom alendronate, given for osteoporosis, led to severe hypocalcaemia a few days after starting the drug treatment. This was caused by the unmasking of previously unrecognised hypoparathyroidism.