Plasma glucose, free amino acids, free amino acid fractions, total free fatty acids (FFAs), long chain tatty acids (LCFAs) and volatile tatty acids (VFAs) have been investigated following different doses and duration of long acting zinc protamine bovine insulin and bovine glucagon, and also during a long phase of diabetes mellitus. The target metabolites were also observed in the diabetic state following the treatments' with various factors; including bioactive peptides, thyroid hormone, corticosteroid, sulfonylurea, starvation and exercise. The major work thus investigates the roles of endocrine pancreatic hormones in nutrient metabolism in ruminants using dwarf goat as a model.
The experiments were performed, for ill vivo studies, with single and repeated low (0.2U/kg body weight) and high (3U/kg body weight) dose/s of insulin in maintained animal house conditions. In a similar plan, low (50ng/kg body weight) and high (5µg/kg body weight) dose/s glucagon were employed. Repeated sampling was done prior to and after the administrations. Separate batches of goats at farm and / or slaughter house were treated for tissue sample studies following their slaughter. The goats were rendered diabetic with streptozotocin with two successive doses of 33 and 40 mg/kg body weight. A separate control group was used for the diabetic goats. Glucose, total amino acids and total free fatty acids were estimated by modified reproducible colorimetric methods. The fractions of VF As and LCF As were determined by modified gas chromatography method and fractions of free amino acids by thin layer chromatography.
Insulin is found an undisputed potent hypoglycemic and hypoaminoacidemic agent in dwarf goat with low and high doses of the hormone. Long acting zinc protamine insulin resulted in insulin shock in goats between 6-7 hours after the hormone administration; this response reported is unlike the findings of many workers in other models of the ruminants. The pertinent results of these metabolites interaction has revealed that consistent low glycemia due to prolonged and high doses of insulin enhances FF A levels in circulation; most likely, due to low availability of glucose. As dextrose infusion in excessive hypoglycemia in insulin shock promptly reduces the enhanced plasma FF A.
Analysis of plasma free fatty acids fractions has revealed that ten fractions of volatile fatty acids (VFAs) and six fractions of long chain fatty .acids (LCFAs) are most prevalent in the goat. Among VF As acetic acid constitutes the overwhelming proportion. The increase in FFAs after hypoinsulinemia involved increases in both categories of LCF As and VF As.
Free fatty acids contents in liver tissue were elevated after low and high dose of insulin. These were decreased in muscle tissue and were raised in the adipose tissue with the high dose of insulin. The low dose insulin decreased liver amino acids. Liver glycogen was increased, significantly, after high dose insulin.
Glucagon is an effective and dose response related hyperglycemic agent and a hypoaminoacidemic, even in low doses and more potent that insulin, in character; which persisted for hours even after the restoration of euglycemia, probably due to their use in gluconeogenesis. FFA increase accompanied glycemic elevation and amino acids reduction but soon was restored to pre-administration levels. Glucagon permits enormous presence of glycogen and enough of gluc08e in muscle tissue. The content of liver FF As was significantly elevated after low dose glucagon. Adipose tissue FF As increased and muscle FFAs decreased markedly following 5µg/kg body weight glucagon. Profound decrement in liver tree amino acids, glucose and glycogen and appreciable increment in muscle was observed post hormonal treatment.
Insulin in low doses and glucagon in high doses decrease and insulin absence increases hepatic free amino acids. This exhibits that glucagon utilizes free amino acids for gluconeogenesis and insulin inhibits this process in liver. Insulin absence increased only specific types of amino acid fractions, Tyr, Pro, and Ala; whereas the glucagon and insulin decreased most of the tractions of amino acid in the circulation. Amino acids in muscle tissue seem independent of pancreatic hormones in the goat.
Diabetes mellitus was successfully induced in the goats with two administrations of streptozotocin. The goats were maintained in diabetic state for about hundred days, a series of different experiments were performed in the hypoinsulinemic state while obtaining blood samples repeatedly, and those were eventually slaughtered to obtain tissues. A comparable group of control goats was also maintained on similar feeding regime and other experimental conditions.
Diabetes induction accompanied marked hyperglycemia, initial hypoaminoacidemia, later followed by hyperaminoacidemia and elevated total tree fatty acids, LCF As and VF As were observed. The content of FF As decreased appreciably in adipose tissue, increased markedly in liver while enhanced non significantly in muscle in diabetic compare to intact goats. In similar comparison insulin deficient group exhibited marked elevation in liver and considerable reduction in muscle free amino acids. Remarkably lower liver and muscle glucose contents were observed in hypoinsulinemic goats. Liver glycogen remained unaffected, however, the reduction in muscle glycogen was noteworthy in hypoinsulinemic compare to control goats.
Glucose loading in fasted intact goats brought profound hyperglycemia and hyperaminoacidemia, however, hyperglycemia accompanied hypoaminoacidemia only in intact goats. Significant reduction in total FF As in both intact and diabetic goats and declined LCF As fractions in hypoinsulinemic goats only was observed in post glucagon infusion experiments. Refeeding provoked hyperglycemia, hypoaminoacidemia and lowered VF As in circulation of hypoinsulinemic goats.
Therapeutic insulin treatment reduced glycemia within the normal pre diabetic range and also glycosuria disappeared while plasma free amino acids exhibited inconsistent trend. Plasma total FFA were significantly decreased during insulin therapy, however, no change was found in it soon after the hormonal withdrawal. Remarkable reduction in all LCF As fractions were observed during insulin treatment, and following its withdrawal except lauric and myristic acid rest of the fractions were decreased. Most of the VF As fractions were found to be decreased during insulin therapy and on its withdrawal almost all the fractions were enhanced in concentration.
Thyrotropin releasing hormone is observed adequate hyperglycemic in intact goats, its infusion significantly enhanced plasma FFAs and LCF As in intact as well as in hypoinsulinemic group, while VF As were decreased in intact and increased in insulin deficient group. All the fractions of LCF As were significantly affected by thyrotropin treatment in intact and hypoinsulinemic groups. The hypoinsulinemic goats maintained euglycemic with exogenous insulin, exhibited pronounce reduction in the concentration of all LCF As fractions in plasma. In intact and hypoinsulinemic group most of the LCF As were enhanced appreciably.
Growth hormone releasing hormone induced hyperglycemic response in intact goats and invariably different fractions of VF As were affected in both the hypoinsulinemic untreated and insulin treated groups.
Somatostatin failed to elicit any variation, in blood glucose and in VF As fractions, however, enormous reductions, in the fractions of LCF As were observed in both diabetic and intact goats.
Glycemia remained unaffected by GH, while hypoaminoacidemia developed in both diabetic and control groups, it was however, more intense and prolonged in insulin deficient goats. Plasma FF As were not affected after GH administration in intact as well as hypoinsulinemic goats. Almost all the fractions of LCF As disappeared in insulin deficient group after GH treatment, whereas VF As fractions exhibited a decreasing trend in intact and an elevated tendency in hypoinsulinemic goats following GH treatment.
Thyroxine (T4) administration caused marked hypoglycemia in hypoinsulinemic goats, however, in intact goats the glycemia remained, almost, unaffected. Profound hypoaminoacidemia was observed following first T4 infusion in both control and diabetic groups, however in intact group the hypoaminoacidemic state persisted for longer duration. Plasma total free fatty acids were found to be appreciably elevated after subsequent T4 treatment in both the groups, however, marked enhancement Cement was exhibited in intact group.
Marked hyperglycemia in intact and non significant hyperglycemia in hypoinsulinemic group was observed following uninterrupted walk of the goats. Insulin deficient group shows profound hyperaminoacidemia and intact group exhibited marked hypoaminoacidemia following this exercise. It enhanced plasma FFA levels in both groups. Enhanced levels of LCF As were found after walk in the intact goats and most of the fractions of VF As were increased after walk exercise in insulin deficient group.
Glibenclamide, administration evoked marked hypoglycemia and hypoaminoacidemia in intact goats,
Cortisone treatment caused hypoaminoacidemia, reduced total FFA and lower LCFAs in both intact and insulin deficient animals In insulin deficient group, cortisone treatment enhanced most of the VF As compare to pretreatment control concentrations.
Glucagon administration in hypoinsulinemic goats elevated blood glucose, showed profound hyperaminoacidemia decreased plasma FF As and a trend of increase was observed in the fractions of LCFAs and VFAs following the hormone treatment.
The results of present study explicate that unlike the general view about ruminants being insulin resistant, this characteristic is limited, at least, in goat. The mechanism of VFAs mobilization, in insulin presence, fails to compensate the glucose demand by gluconeogenesis. Instead it promotes glycogenesis, Glucagon is found glycogenic and promotes high free amino acids in muscle. A characteristic understood to be peculiar to ruminants and / or the goat. The counter-regulatory role of insulin and glucagon is also found unlike the non ruminant model. The hypoinsulinemic model of the goat has clearly exhibited that regulation of nutrient metabolites is not merely the role of a few hormones. These are regulated by complex interaction of various hormones and insulin is an indispensable factor. The present study has indicated the various avenues to be investigated in this regard.