γ‐(D,L)‐Polyglutamic acid [γ‐(D,L)‐PGA, or γ‐PGA] produced by Bacillus subtilis (natto) both on laboratory and pilot scale fermenter systems has been characterized. γ‐PGA in its free acid form (H+) is insoluble in water. The salt forms of K+, Na+, NH4+, Ca2+, and Mg2+ of γ‐polyglutamates are fully soluble in water. The structural characteristics of the salts of γ‐Polyglutamates (Na+, K+, NH4+, Ca2+, and Mg2+) were determined with 1H‐ and 13C‐NMR spectroscopy and FT‐IR spectroscopy. The thermal properties were determined with thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The typical physical and chemical properties including pH‐titration curve, concentration‐dependent viscosity temperature‐dependent viscosity, and heavy metal binding properties with Pb2+, Cd2+, and Cu2+ were also determined. The biological functionalities were partially characterized with in vivo feeding studies with broilers and egg‐layers, and activation of GTF (Glucose tolerance factor) activity with rat 3T3‐L1 cell culture studies. γ‐(D,L)‐Polyglutamic acid [γ‐(D,L)‐PGA] appears to have five different conformations depending on the environmental conditions. They are the α‐helix, β‐sheet, helix‐to‐random coil transition, random‐coil and enveloped aggregate. The conformational states, hydrogen bonding and polyanionic nature make γ‐PGA a versatile multi‐functional biopolymer possessing many useful biological functionalities.

The effects of zinc supplementation (20 mM ZnCl2 from the drinking water for eight weeks) on plasma glucose and insulin levels, as well as its in vitro effect on lipogenesis and lipolysis in adipocytes were studied in genetically obese (ob/ob) mice and their lean controls (+/?). Zinc supplementation reduced the fasting plasma glucose levels in both obese and lean mice by 21 and 25%, respectively (p < 0.05). Fasting plasma insulin levels were significantly decreased by 42% in obese mice after zinc treatment. In obese mice, zinc supplementation also attenuated the glycemic response by 34% after the glucose load. The insulin-like effect of zinc on lipogenesis in adipocytes was significantly increased by 80% in lean mice. However, the increment of 74% on lipogenesis in obese mice was observed only when the zinc plus insulin treatment was given. This study reveals that zinc supplementation alleviated the hyperglycemia of ob/ob mice, which may be related to its effect on the enhancement of insulin activity.

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In order to investigate the relationships between metals zinc [Zn], copper [Cu], magnesium [Mg], or Calcium [Ca] and noninsulin-dependent diabetes mellitus, 65 patients of newly diagnosed noninsulin-dependent diabetes mellitus and 54 nondiabetic healthy controls were studied. The concentrations of selected metals in fasting blood samples and 24-h urine collections were determined. Hyperzincuria and hypermagnesuria were detected in diabetic patients (p < 0.01). The diabetics also had lower Zn and Mg, and higher Cu, and Ca levels in their plasma than those of the controls, but the statistical differences in Ca and Mg were not significant. Significantly lower Zn and higher Ca levels in erythrocytes were found in diabetic patients (p < 0.01). There is evidence of a significant difference in metals status between diabetic patients with or without the specific complications. This study further indicates that patients with NIDDM on Taiwan also have distinct changes in their metals status, and these perturbations are associated with some diabetic complications.